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iThemba LABS Annual Report 2008


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iThemba LABS

Annual Report

March 2008

This report covers the period 1 April 2007 to 31 March 2008

Some of the results presented in this report are in part preliminary and should not be

quoted without the approval of the authors

Editor: Kobus Lawrie Associate Editors

Yunus Manjoo Simon Mullins

Mark Swanepoel Gillian Arendse

Published in 2008 iThemba LABS

P O Box 722 Somerset West

7129 South Africa

Design and Layout by iThemba LABS

Printed in the Republic of South Africa by iThemba LABS, Faure

Copyright of this report is the property of the National Research Foundation


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Members of the Director’s Council

Dr Trevor Mdaka Chairman

Prof. David Aschman

University of Cape Town

Prof. Joao Rodrigues University of the Witwatersrand

Prof. Mike Sathekge University of Pretoria

Prof. Hendrik Geyer

University of Stellenbosch

Prof. Fred Vernimmen University of Stellenbosch

iThemba LABS

Telephone: International +27-21-843-1000

National: 021-843-1000

Fax: International +27-21-843-3525 National: 021-843-3525

e-mail: [email protected]

world-wide web: http://www.tlabs.ac.za

mailto:[email protected]

http://www.tlabs.ac.za


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FOREWORD: This year was characterised by a few challenges that iThemba LABS had to contend with; ranging from the power crisis to a tighter financial regime and many human resources concerns. That notwithstanding, I would – once again – make mention of a few successes that many in our organisation should take pride in. During this period, beam delivery uptime on a year-to-date basis hovered around 63%; which if viewed in the context of the ageing equipment is something that again points to the fact that we were able to deliver services to our clients and realise our targets in spite of all these challenges. The highlight of the year was the inauguration of the Gauteng facilities at the annual South African Institute of Physics (SAIP) conference. The event marked the completion of the refurbishment process that began with the acquisition of the erstwhile Schonland Institute of the University of the Witwatersrand and culminated into its conversion into a national facility whose primary goal would be that of the establishment of the first Accelerator Mass Spectrometry (AMS) facility on the African continent. To this end, we have received generous support from the community of potential users who see the development of this facility as long overdue. Furthermore, the technical and financial support from the International Atomic Energy Agency (IAEA), International Centre for Theoretical Physics (ICTP) and colleagues at the Lawrence Livermore National Laboratory (LLNL) has proven to be most invaluable. We will pull no stops in ensuring that the Accelerator Mass Spectroscopy (AMS) is realised within a reasonable time scale.

Revenue on sales of radioisotopes reached an all time high of R12,5m. This feat has been realised due largely to sterling efforts of very dedicated members of the radioisotope group working in concert with the Accelerator team. It is hoped that the recent upgrades of the newly commissioned Vertical Beam Target Station (VBTS) and increased beam current will allow for all capacity for the VBTS to be utilised for export orders of 82Sr to Nordion, Canada. It is with these considerations in mind that we still hope to raise (or maintain) this new revenue baseline despite the current climate of constraints posed by the energy crisis. The R15m Innovation Fund project – which, among others, was for the production of 18F and 68Ge for 18F-FDG and 68Ge/68Ga generators, respectively (and the production of ultra-pure 67Ga for peptide labelling) has now run its full funding cycle. This project, which was approved in 2004, has delivered on all the objectives as prescribed by the Innovation Fund proposal with the exception of the completion of the Beam Splitter (which has been delayed to April 2009) for reasons of non-availability of human resources due to the Gauteng refurbishment operation.


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The therapy programme has also been adversely affected by the erratic beam supply, especially Proton Therapy which receives only – as per the previous schedule – two beam days per week. Neutron patient numbers are, at year-end reporting, marginally higher than last year’s 50 while numbers for proton patients averaged around nine. On the accelerator front, the new ion source will only be commissioned during the second half of 2008, as a result of the need to upgrade the electrical infrastructure (which is scheduled for May 2008). Other developments that warrant mentioning include the establishment of the SA-CERN programme, whose purpose is to actively foster research activities (in a co-ordinated way) between national institutions and CERN. The consortium members include iThemba LABS and the Universities of Cape Town, the Witwatersrand, Rhodes, KwaZulu-Natal and Johannesburg. This will be a long-term (ten-year) project whose primary goals include inter alia:

• To develop high quality human resources in frontier-level research: This is very much in line with the over-arching NRF mission and mandate of skills development and redress. Moreover, the expectation is that of retention (and recruitment) of talent in the SA science system.

• Technology transfer process through access to frontier level research endeavours.

It has to be noted that such endeavours form part of the key strategic objectives of iThemba LABS; namely, the acquisition of the capacity to technically and scientifically service University research groups that need to use international facilities. Finally, iThemba LABS’ role in the National System of Innovation can only be manifest in showcasing the centrality of our role in a variety of ways. These include the hosting of workshops, conferences and schools; involvement in multi-stakeholder forums such as the Nuclear Industries Association (NIASA) and others. Mulling through the report, the reader will be left with no doubt about the crucial role iThemba LABS plays in ensuring that South Africa (and the African continent) maintain a foothold in the global arena of advancement of accelerator based sciences and their applications to human health, fundamental research and high-level skills development.

Dr Z Z Vilakazi

Director


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Contents 1. Performance Summary 7

1.1 Highlights 8 1.2 Directorate Level Organisation 14 1.3 Financial Performance 15 1.4 Key Performance Indicators 17 1.5 Human Resources 18

2. Group Operational Highlights 21

2.1 Accelerator Group 22 2.2 Medical Radiation Group 27 2.3 Hospital Services Group 31 2.4 Radionuclide Production Group 32 2.5 Materials Research Group 37 2.6 Physics Group 40 2.7 iThemba LABS (Gauteng) 43 2.8 Radiation Biophysics 46 2.9 Electronics and Information Technology (EIT) 48 2.10 Technical Support Services Group 52 2.11 Safety, Health & Environmental Group 56 2.12 Science and Technology Awareness Programme 63

3. Scientific and Technical Reports 65

3.1 Medical Radiation Group 66 3.2 Radionuclide Production Group 74 3.3 Physics Group 94 3.4 Radiation Biophysics 123 3.5 Materials Research Group 146 3.6 iThemba LABS (Gauteng) 194


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4. Appendices 196

4.1 Publications in Refereed Journals 197 4.2 Conference Proceedings 200 4.3 Conference Contributions 202 4.4 Colloquia and Talks 210 4.5 Post Graduate Training 211 4.6 Users and Collaborators 216 4.7 Staff List 225


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1. PERFORMANCE SUMMARY


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1.1 Highlights 2007/08 Record Radionuclide Sales Revenue for radionuclides and radiopharmaceuticals year on year has increased by 120%, from R5,6m to R12,5m. International sales accounted for ~R9,5m of the revenue. Overall service delivery (first time on time) of radionuclides and radiopharmaceuticals for the period was >93%. In March 2008 iThemba LABS produced its first 68Ge/68Ga generator for commercial use in Europe. The 68Ge/68Ga generator provides an excellent source of a positron-emitting 68Ga that is used to label various types of peptides that are mainly used to localise neuroendocrine tumours (brain tumours). In February 2008 iThemba LABS concluded a distributorship agreement with a company in the Netherlands, IDB-Holland, for them to serve as the exclusive sales and marketing agents of the iThemba LABS 68Ge/68Ga generator in Europe.

68Ge/68Ga generator Completion of iThemba LABS (Gauteng) Refurbishment Programme A two and a half year refurbishment project of the tandem accelerator facility started early in 2005 and the first phase of the project drew to a close with the first beam on target produced on 31 May 2007. The official opening of the new iThemba LABS (Gauteng) EN tandem accelerator facility took place on 2 July 2007. The event coincided with the official opening of the 2007 SAIP conference, which took place at WITS University. The facility was transferred from WITS to the NRF on 1 January 2005 and the DST provided funding of R16m for the refurbishment. Total actual cost for the project was (R16,5m).


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iThemba LABS staff and SAIP delegates at the official opening of the Tandem Van de Graaff Accelerator in iThemba LABS (Gauteng).

The refurbished tandem accelerator.


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First Cryo-Measurement of Biological Tissues Using Protons The nuclear microprobe at Materials Research Group of iThemba LABS became the first such facility in the world with proven capabilities of PIXE microanalysis of biological material in the frozen-hydrated state. The necessary modifications of the commercially available cryotransfer system coupled to the experimental chamber of the microprobe were done by Dr G. Tylko who spent three years working as post-doctoral fellow, collaborating with Dr J. Mesjasz-Przybylowicz and Dr W. Przybylowicz. Thorough testing using thick sections of selected plant and animal material has been performed. While other groups worldwide attempted to perform similar modifications, none reported quantitative results from their trials. The importance of this achievement lies in the fact that microanalysis using protons is typically 100 to 1000 times more sensitive than with electrons, thus making possible studies of distributions and transport of trace elements in living organisms – sometimes toxic, sometimes beneficial. Until now, such analyses were done on freeze-dried materials following special procedures tailored to microanalysis. However, it was never exactly confirmed whether the obtained concentrations and distribution of elements present in bound or diffusible forms reflected correctly the true situation in living organisms. The obtained results were presented at international conferences and published in 2007. This time the technology transfer would take place not to Africa but from Africa, and the first research group to learn from the South African team would be their Swedish colleagues from Lund Institute of Technology, under a planned bilateral collaboration.

Dr Grzegorz Tylko operates the cryotransfer system at the nuclear microprobe of iThemba LABS.


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Masters School in the Western Cape an Unparalleled Success To drastically increase the throughput of Masters postgraduates, iThemba LABS, in collaboration with the Universities of Western Cape (UWC) and Zululand (UZ), launched a two-year Masters School in 2004. The UWC agreed to offer the course at its campus with laboratory work being done at iThemba LABS. Lecture contributions are from all three institutions. Students from all universities in South Africa have been enrolled in the course, which offers a first year taught lecture programme, and a mini-thesis in the second year; either at one of the three institutions or at organisations such as Necsa, CSIR, Eskom, PBMR and Mintek. The student intake is not restrictive, as applicants have degrees in physics, mathematics, computer science and chemistry. The success of the course can be gauged by the number of graduates in the four years of its existence. Currently, some forty have graduated with M.Sc’s with another twenty scheduled to complete by end 2008. The total intake over the four years has been 86; over 95% are South African and black and 20% female! Ph.D. enrolment is currently at nine. Prior to the introduction of the course, UZ had only six Masters and one Ph.D. graduates since 1960. The Masters School has realised twenty UZ graduates in four years, whilst there are now three Ph.D. enrolments. The degree is offered in two streams; a Masters in Accelerator and Nuclear Science (MANUS) and a Masters in Materials Science (MATSCI). All graduates have been readily employed in industry and the courses provide the requisite skills base for both the nuclear industry and the nanotechnology fields. Student funding has been a novel approach, a monthly stipend is paid to each student for living and accommodation expenses and all university fees are also paid by the Course Administration which is the responsibility of iThemba LABS. This is financed mainly from the Scarce Skills Scholarship which is administered by the NRF on behalf of the Department of Labour. Any shortfall in funding is shared equally by the three participating institutions. 2008 is the fifth year of the course, its popularity remains high; 19 have enrolled for the first year, whilst 13 are completing their second and final year.


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iThemba Summer School in Nuclear and Particle Physics Among several activities at iThemba LABS (Gauteng) in the year 2007/08, the most important event was the successful iThemba School 2008 that took place from the 27 January 2008 to the 3 February 2008 in Skukuza, in the Kruger National Park. Presentations by a carefully selected group of lecturers, consisting of several well known local scientists and international scholars, namely Dr Tom Brown (USA), Prof. Yoshi Fujita (from Japan), Prof. Neil Rowley (from France), were of the highest quality.

Interest shown by delegates, especially students, was beyond expectation of the organisers and about 71 students from various institutions, as indicated in the chart below, attended.

The programme for the school was packed with six hour-long lectures each day, for the first four days, while seven lectures were presented on Friday and Saturday. The programme of the school spanned scientific fields that appear below.

• Introduction to Particle Physics,

• Introduction to Nuclear Physics,

• Nuclear Reactions,

• Field Theory,

• Nuclear Experimental Methods and Particle Detectors,

• Nuclear Techniques, applied in Material Sciences, Environment and Industry,

UNIVERSITY REPRESENTATIONS

iThemba LABS & UWC24

NECSA, 5 Trans Africa Projects, 1

N-WU, 4UCT, 7

UKZN, 1

Fort Hare, 1 Pretoria, 3

Stellenbosch, 6

Zululand, 10

Wits, 8

Prof. N Rowley, IRIS Prof. Y Fujita Dr T Brown Strasbourg - France Osaka – Japan Lawrence Livermore


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• Experimental Nuclear Structure,

• High Energy Heavy Ion Collisions,

• Physics and Technology of the Pebble Bed Modular Reactor,

• Accelerator Mass Spectrometry. The School was funded by SANHARP, PBMR and iThemba LABS. The picture below is testimony to the well attended iThemba School 2008.


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Director

Business Admin

Finance

Human Resources

Directorate Level Organisation

Deputy Director

Laboratory Director’s officeDirector’s Council

Relations with …

Government

Higher Education

International Orgs.

User groups

Scientific Committees

“iTPTC”

Project Management

Groups/Departments

Radio Active Beams …

…

NRF

Secretariat

Accelerators Gauteng TechnicalSupport

Medical Radiation

MaterialsResearch Physics Information

Technology Radionuclides Science Awareness

1.2


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1.3 Financial Performance

The table below summarizes the financial performance for 2007/08.

Budget R’000’s

Actuals R’000’s

Latest Forecast R’000’s

Income 124104 127734 133697 Core Grants 104285 103732 105277 Other Internal Grants 4898 7699 8581 Radionuclide Revenue 12930 12521 12850 Other 1991 3782 6989 Expenditure (125802) (129989) (134020) Net operating expenses (36432) (41271) (42861) Salaries (78347) (76729) (77634) Capital Expenditure (11023) (11989) (13525) Net Funding/(Deficit) (1698) (2255) (323) Cumulative Funding/(Deficit) (491) (2350) (418)

1.3.1 The closing deficit of R2,35m translates to break-even for core operations with some R4,5m outstanding

in revenue. The Gauteng 2005 costs of R1,5m remains unresolved whilst R2m is outstanding from the NRF for the new ECR Ion Source Components which has been pre-funded by iThemba LABS. The hosting of several conferences and workshops during the past year has realised unrecovered expenses of (R1m). Donor grant money remains outstanding for the Nano College, iThemba Summer School and EBASI. The net unspent funds of R2m is for the SA-CERN collaboration, a new research initiative involving UCT, WITS, UKZN, Rhodes and iThemba LABS.

1.3.2 The higher revenue in comparison to the original budget arises mainly from conference income of R1,5m

and the grant for the SA-CERN collaboration. Net operating costs for the year are R4,8m or 13,3% above budget, the major variances being:

R’000’s Conference costs (2200) Repairs & Maintenance (1400) Travel (800) Rates (500) (4900)


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1.3.3 The higher travel costs are mainly for new collaborations in Africa and Europe, the majority of which has been financed by travel grants from the African Laser Centre. The City of Cape Town has revalued the site at R80m compared to the current market value of R30m, an appeal has been lodged and this will only be resolved mid-2008, however, the additional rates have been paid as per municipal policy.

1.3.4 The frequent power outages of last year as a result of load shedding, as well as Eskom equipment

failures, have resulted in equipment failures across all groups, and in particular, an additional R0,5m has been spent on the cyclotron to resolve water leaks, RF vacuum systems and component failures. An additional R0,4m was spent on damages to research equipment in Cape Town and Gauteng.

1.3.5 Salaries benefit from the average 17 vacancies throughout the year, the staff turnover is 12%. In addition,

some non-key posts have been frozen in the short-term due to funding constraints in 2008/09. (Driver, Fitter & Turner, Hospital Receptionist). iThemba LABS continues to experience difficulty in recruiting programmers and electronics personnel, especially in Gauteng. The lack of funds for the AMS has delayed the recruitment of researchers in Gauteng as well.

1.3.6 Although Radionuclide revenue of R12,5m is broadly in line with the budget, this is a record achievement

and represents an increase of over 100% relative to the previous year. This revenue stream, which now includes some R3m for national sales, is virtually assured in the medium term due to contractual obligations. Achievement of higher sales in the short-term is restricted by lack of capacity which will be resolved with the installation and commissioning of the beam splitter in 2009.


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1.4 Key Performance Indicators (KPI’s) iThemba LABS Listed below are the major KPI’s used to manage the operations of iThemba LABS. MAJOR KPI’S

Actual 2006/07

Target

2007/08

Actual 2007/08

Target

2008/09

% Useful Beam Time (SSC) 70,0 75,0 63,0 70,0

% Useful Beam Time: Van de Graaff 73,1 70,0 59,9 68,0

% Usage Van de Graaff 40,1 45,0 30,9 45,0

% Useful Beam Time (Gauteng) 0 60,0 0 50,0 Patient Income: Proton/Neutron Therapy & LINAC (R’000’s) 75 300 311 325

Hospital Income (R’000’s) 449 425 473 500

Radionuclide Income (R’000’s) 5 896 11 200 12 521 14 250

iThemba LABS Research Papers 78 55 73 80 Presentations at International Conferences 81 85 56 85

Number of Collaborators 411 425 538 450

% Black SA Users & Collaborators 35 35 35 35

Total Number of Postgraduate Students 211 210 199 205

% Black Postgraduate Students 86,7 85,0 84,9 86,0 Number of M.Sc. & Ph.D. Degrees obtained 35 30 40 52

Number of African Collaborations 18 22 44 22

International Users & Collaborators 243 225 281 250

Number of International Collaborative Projects 82 80 90 85 Scientists from African Countries using iThemba LABS 63 50 53 70

Other Income as % of Core State Grant 23,0 18,3 23,1 22,5

IT Costs as % of Total Costs 10,6 12,0 12,3 11,6

Capital Expenditure as % of Annual Depreciation Charge 127,3 51,6 54,4 73,2

Number of Visitors 6 000 8 000 6 746 9 000


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1.5 Human Resources The 2007/2008 financial year has had its fair share of successes amidst ongoing HR challenges. Although some successful key appointments were made, we also experienced a somewhat raised staff turnover during the year. Although this does raise some anxieties, in particular in the technical and professional skills categories, we do see the new financial year as an opportunity to meet the challenge of an improved succession management plan and more effective way of managing our current talent. We have seen the start of a major job evaluation exercise where some 130 positions were graded, with the first phase of implementation effective at the start of the new financial year. This has certainly led to the clear identification of skills in our organisation that now, to a greater extent, informs a Succession Management Plan and related career development opportunities for staff. There has also been a strong focus on Employment Equity compliance with an ongoing effort to ensure that our goals are being met.

1.5.1 Staff Representation Employment Equity representation achieved for the said financial year was 66% with females representing 29% of our workforce. The Employment Equity & Skills Development Committee plays an active role in the selection committee to ensure achievement of Employment Equity targets as per the 2005-2010 Employment Equity Plan. This plan was revised during 2007 with special attention given to specific objectives and numerical goals to be achieved.

The table below displays a detailed staff profile for 2007/08:

Occupational Level

Designated Non - Designated

Gran

d To

tal

Male Female White Male

Foreign Nationals

Afric

an

Colou

red

Indian

Tota

l

Afric

an

Colou

red

Indian

Whit

e

Tota

l

Whit

e

Male

Fema

le

Senior management 2 2 2 6 0 4 10

Professionally qualified and experienced specialists and

mid-management 8 9 2 19 2 8 11 21 43 11 4 98

Skilled technical and academically qualified workers,

junior management, supervisors, foremen and

superintendents

19 36 2 57 6 6 1 13 21 1 92

Semi-skilled and discretionary decision-making 10 29 39 14 26 5 45 84

Unskilled and defined decision-making 2 5 7 7

TOTAL 41 81 6 128 22 40 0 17 79 68 12 4 291


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Proportion of researchers to total staff

Researchers Staff Percentage

iThemba LABS 2006/07 44 278 15.83%

2007/08 49 291 16.8% 1.5.2 Staff Movements Of the eleven internal staff movements that took place, five were internal promotions to facilitate and give effect to internal career development opportunities. There were more appointments made during 2007/08 than in the previous year, with 29 positions still remaining vacant.

The following table displays the staff movements as at 31 March 2008:


Gran

d To

tal


Foreign Nationals

Afric

an

Colou

red

Indian

Tota

l

Afica

nr

Colou

red

Indian

Whit

e

Tota

l

Whit

e

Male

Fema

le

Recruits 2006/07 14 5 1 20 4 5 9 8 1 1 39 2007/08 20 9 1 30 9 7 1 17 2 1 2 52

1.5.3 Training and Skills Development The number of staff currently registered for part-time studies increased to 32 during the last year, and over 60 staff members attended various training courses during the year.

Training of post-graduate students and trainees coordinated by iThemba LABS has also increased in some categories:

TRAINING CATEGORY NUMBER 2006/07

NUMBER 2007/08

Post-graduate students 102 110 MARST 23 11 MANUS 67 46 Trainees 34 29 Apprentices 3 4 Vacation students 1 32


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Staff Profile in terms of post-graduate qualifications:

BUSINESS UNIT


Gran

d To

tal


Foreign Nationals

Afric

an

Colo

ured

Indi

an

Tota

l

Afric

an

Colo

ured

Indi

an

Whi

te

Tota

l

Whi

te

Male

Fem

ale

iTHE

MBA

LABS

Staff with Ph.D.

2006/07 4 1 1 6 1 4 5 25 9 3 48

2007/08 3 2 3 8 1 3 4 21 7 3 43

Staff enrolled for Ph.D.

2006/07 2 2 0 3 1 6

2007/08 3 3 3 6

Staff with Masters

2006/07 2 2 1 1 4 1 8

2007/08 2 2 1 1 3 1 7

Staff enrolled for Masters

2006/07 1 1 2 0 2 4

2007/08 1 1 1 3 3

Total 2006/07 9 2 1 12 2 0 0 4 6 34 11 3 66

Total 2007/08 8 2 3 13 3 1 0 4 8 27 8 3 59

1.5.4 Key Human Resources Challenges

The major HR challenge is the development of an organisational / management culture conducive to achieving both staff and overall organisational objectives by having:

• A ongoing focus on Employment Equity and Transformation strategies

• A Talent Management Strategy that includes an effective Succession Management Plan to ensure that key positions and scarce skills are addressed to meet current and future organizational demands

• Continuous organisational improvement and development by effective use of the NRF performance management system and linked training and development interventions


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2. GROUP OPERATIONAL HIGHLIGHTS

iThemba LABS Annual Report 2008 Accelerator Group

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2.1 Accelerator Group Introduction This report summarizes some of the current major projects in which the accelerator group is involved. They include the design and construction of the beam splitter system, the development of non-destructive beam position and profile measurement techniques together with one of our international collaboration partners, the assembling of the Hahn Meitner ECR source and the development of a small microwave ion source for the Van de Graaff accelerator. The status of the refurbishment of the Tandem Accelerator facility in Gauteng is reviewed. The accelerator performance (beam supplied 81,6% of scheduled beam time) is slightly better than in 2006/07.

2.1.1 Beam Splitter The increase in beam current from 100 µA to 265 µA using the newly installed flat-top systems in SPC1 and the SSC makes it possible to increase the production of radioisotopes. Because each target can handle only a limited beam current, the isotope beam lines will be modified to allow irradiation of targets in two vaults simultaneously. This will be achieved with an electrostatic channel and a septum magnet, which will peel off a portion of the beam, and thus split the beam into two separate beams.

The electrostatic channel will operate at a voltage of 100 kV across a gap of 30 mm. The septum will deflect the

beam by 16°. The calculations for the septum magnet and beam position were made using the program TOSCA.

The beam loss on the electrostatic channel septum will be approximately 0,3% of a total beam current of 350 µA, according to calculations with the program TURTLE.

Figure 1a. The partially assembled electrostatic channel, Figure 1b. A drawing of the magnetic septum magnet, which will be used for the initial separation of the beam. also indicating the position of the two separated beams


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2.1.2 Beam Position Monitors based on Beam Induced Fluorescence Figure 2: A proton beam profile measured using beam induced fluorescence. An experimental apparatus making use of a non-destructive method of beam position and profile measurement based on light emitted by atoms exited by beam particles, has been installed in the J-line between the SPC1 and the SSC. The light emitted by the residual gas atoms is focused through a lens onto a multi-channel photomultiplier tube (PMT) array with 32 photo-cathodes. A multi-core cable was installed to the electronics area to monitor the 32 channels on a 48-channel current measurement module. Prototype software enabled the measurement and display of the beam profile on a computer screen. The preliminary results (Figure 2) are encouraging and compare very well with measurements made with a capacitive beam position monitor (BMP) and a beam profile grid. Further improvements have been suggested to the mechanical installation, which will be implemented during the next phase of the development. 2.1.3 Upgrading of iThemba LABS (Gauteng) Figure 3: The refurbished tandem accelerator at iThemba LABS, Gauteng The refurbishment of the tandem accelerator facility (Figure 3) started early in 2005 and the first beam was on target on 31 May 2007. The official opening of the new iThemba LABS (Gauteng) EN tandem accelerator facility


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took place on 2 July 2007. The event coincided with the official opening of the 2007 SAIP conference, which took place at WITS University. Since then several improvements were made: A multiplexer system was developed to automatically select, measure and display the beam current on the Faraday cup, on a screen at the control desk. Anti-suckback valves for fore-pumps were installed to limit back-streaming of oil under certain operating conditions, especially at the ion source and accelerator tubes. Scanner (BPM) control and display software, which runs on the Experimental Physics and Industrial Control System (EPICS), was developed to display beam profiles on a computer screen instead of an oscilloscope. A calibrated Hall probe was installed in the analyzing magnet. Software monitors the Hall probe voltage to calculate and display the energy of the accelerated particles. X-ray monitors alongside the accelerator tank monitor X-ray activity, and is also used as a diagnostic tool during tube conditioning, since X-ray activity provides an early warning of imminent sparking in the tubes as the terminal voltage increases. 2.1.4 Electron Cyclotron Resonance (ECR) Ion Source. The ECR source with its beam line (Figure 4), that was originally built by GANIL for the Hahn Meitner Institute (HMI), was recently installed at iThemba LABS and linked up to the existing Q-line. Beams from this source for acceleration with the separated-sector cyclotron will be available during the course of 2008, when sufficient cooling water from other resources has been made available. With the ECR source the maximum beam energy for Xenon ions will be about 40% higher than at present and the intensities of beam currents at lower energies will increase dramatically.

Figure 4: The ECR source installed and connected to the existing beam line. 2.1.5 Microwave Ion Source. A small microwave ion source for the Van de Graaff accelerator at Faure, was developed during 2006 as a project for a Masters degree thesis. This work was continued and very exciting results were achieved. The ion

source, connected to a 15 Watt solid state microwave generator produces up to 70 µA protons from a 0.8 mm

diameter outlet hole, or 20 µA with a 0.33 mm hole. The proton percentage is normally above 85% with the

remainder being H2+. Four small permanent magnets are used to provide the required magnetic field and once


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the source parameters have been optimized, no further adjustments are required to start and operate the source. It is only necessary to switch on the microwave generator and then adjust the gas flow for the required current intensity. If maximum current is not required, the intensity can be lowered by as much as a factor ten, simply by reducing the hydrogen gas flow. No forced cooling is required and a life-time of 1000 hours has been obtained.

2.1.6 Beam Statistics The performance of the cyclotrons for the last 13 years is shown in the Table 1 below. Beam on target time has remained roughly constant during these years. The scheduled beam time for the past calendar year is slightly more than 80%. Traditionally the RF systems have been the main source of interruptions. This situation has changed this past calendar year with interruptions from water leaks in the SPM1 septum magnet contributing 8,8% of the total beam time lost. This is followed by RF interruptions causing a total loss in beam time of 6,7%. The persistent power failures and load shedding (both scheduled and unscheduled) caused 5,8% to the total beam time lost.

Table 1: Beam delivery statistics for the period from 1995 to 2007.

Year Beam Supplied as: % of Scheduled beam time for: % of Total time % of Scheduled* time Energy Changes Interruptions

1995 72.95 82.91 5.67 8.46 1996 69.69 78.21 9.30 8.92 1997 67.63 77.31 11.02 10.60 1998 66.93 75.55 13.20 9.73 1999 69.12 78.82 9.99 10.81 2000 58.51 73.07 9.36 15.50 2001 66.13 78.70 6.30 12.61 2002 72.29 82.69 7.50 7.28 2003 70.93 82.79 6.87 8.08 2004 72.0 84.9 6.7 5.9 2005 71.3 83.6 5.5 6.4 2006 66.1 80.3 5.5 7.9 2007 67.1 81.6 5.4 10.4

* Scheduled time is total calendar time minus scheduled maintenance time and the time that the laboratory is officially closed during December.

2.1.7 The Van de Graaff Accelerator The controls for the power supplies and the beam profile monitors are currently being modified so that they can be controlled and displayed on a computer. It will then be possible to see a deviation of the beam from the centre of the beam line.


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The gas transfer pipes between the storage tank and the building had to be replaced. The gas will also be dried while it is in the storage tank. A new fully automated chiller plant with a de-ionizer is being constructed. This project is nearing completion. Table 2 below shows the beam time statistics.

Table 2: Beam statistics

Year Beam on target (Hours)

Maintenance/Conditioning (Hours)

Development (Hours)

Interruptions

2000 4016 2457 15.50 2001 3381 479 12.61 2002 3560 3212 7.28 2003 1635 2331 88 8.08 2004 4700 2329 38 5.9 2005 4527 2360 1886 6.4 2006 6404 1457 776 7.9 2007 5794 1961 554 10.4

iThemba LABS Annual Report 2008 Medical Radiation Group

28

2.2 Medical Radiation Group 2.2.1 Equipment Upgrades The core function of the Medical Radiation Group is the provision of proton and neutron therapy. All projects completed during 2007/08 were designed to increase the accuracy and efficiency of treatment planning and delivery, so as to give patients the best possible care. 2.2.2 Neutron Therapy Projects completed for neutron therapy include:

1. Replacement electronics for the couch rotation motor drive. 2. Replacement of the Programmable Logic Controller (PLC) used for the beam safety interlock system by

a PLC built in-house. 3. Reconstruction of a spare neutron dose-monitor chamber. 4. Replacement of the bearings of the wedge carousel used for beam shaping. This intricate work took

place in a highly activated section of the neutron gantry. 2.2.3 Proton Therapy During the year the Medical Radiation Group treated its 500th patient since the founding of the South African proton therapy facility. In 2007/08, an average of one fraction was delivered per treatment day. Capacity has been increased by improvements to the equipment used for treatment planning and therapy. New equipment and immobilization techniques were developed within the Group to improve the accuracy and reproducibility of patient-positioning, significantly reducing the time spent by patients in the treatment vault. In particular the use of reflective markers mounted on patient-specific bite-blocks has proven to be better than the use of markers mounted on head masks. It is hoped that the accuracy of patient positioning will further improve when a new digital X-ray flat-panel detector comes into operation within the next two years. The following projects related to proton therapy were completed during 2007/08:

1. The chair control system hardware and software have been upgraded (currently being tested). 2. The bite-block system for patient immobilization has obtained ethical approval from Groote Schuur

Hospital. We are now awaiting ethical approval from the University of Stellenbosch for Tygerberg Hospital patients and from the South African Medical Association for private patients.

3. A new X-ray unit for verifying patient position has replaced the obsolete mobile unit. 4. The stereophotogrammetric patient-positioning system in the proton treatment vault has been

upgraded. 5. A hoist mechanism for a flat panel X-ray detector has been installed in the treatment vault. 6. Monte Carlo simulations for the scattering system of the proposed second beam line have been

completed.


29

2.2.4 Computed Tomography Scanner During 2007/08, 46 patients were scanned. The year saw a number of other milestones:

1. The CT scanner was connected to the UPS and emergency back-up generator. 2. The present treatment planning system was upgraded to allow for the import of DICOM images and to

support the fusion of CT and MR images. 3. The electronics for the interface to transmit data from the CT scanner to the SPG system were

completed.

2.2.5 Workshop: iThemba LABS Particle Therapy Centre (iTPTC) A proton therapy workshop took place in July 2007 to discuss possible expansion of the facility. It was attended by representatives of the radiation oncology community, DoH, NRF, DST, and iThemba LABS. A report on the pathologies and numbers of patients likely to be treated at a proton therapy facility incorporating new technology was submitted by Dr V. Levin to the iTPTC Steering Committee. The report is under consideration. 2.2.6 Training A number of M.Sc. students obtained their degrees, one cum laude (see section 4.2.1.). Four bursaries were allocated to Medical Physics interns, two of these being under the joint collaboration agreement with the University of the Free State (UFS) to alleviate the scarce skills situation.

2.2.7 Treatment Planning In an agreement with Varian Medical Systems the Medical Radiation Group is investigating the suitability of the new “Varian Eclipse” treatment planning system for use with iThemba LABS’ beam delivery system. A similar offer has been made by Philips Medical Systems on behalf of Computerized Medical Systems. 2.2.8 Donations The Group has been offered a life-time donation of R550 per month from a cancer patient who stipulated that the funds be used exclusively for cancer-related research purposes. 2.2.9 Radiotherapy and Research in Biomedical Sciences Fifty-nine patients were treated on the p(66)/Be isocentric neutron unit during the year. Neutron therapy statistics are given in Table 3 and Figure 5 – Figure 7. Seventy-seven of 790 treatments (9,7%) had to be rescheduled. Problems that caused rescheduling are listed in Table 4. Just nine patients were treated on the 200 MeV horizontal beam proton therapy facility during the year. Proton therapy statistics are listed in Table 3 and Figure 8 – Figure 10. Thirteen of 40 treatments (32,5%) had to be rescheduled. Problems that caused rescheduling are listed in Table 5.


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Neutron therapy Proton therapy 2007/2008 To date 2007/2008 To date Treatments per day 5.5 6.7 0.9 2.7 Fields per day 17.2 18.6 2.9 7.7 Fields per treatment 3.1 2.8 3.3 2.9 Time per field (min) 9.4 11.2 24.7 17.8 Time per day (min) 161 208 72 138

Table 3: Hadron therapy statistics

Cause Number of treatments rescheduled

Repairs to wedge carousel 49 Power failures 18 Water leak in gantry 7 Beamline vacuum leak 2 SPC1 water leak 1

Table 4: Neutron therapy rescheduled treatments – causes

Cause Number of treatments rescheduled

Ion source 8 Problems fitting mask to patient 3 Portal X-ray unit 2

Table 5: Proton therapy rescheduled treatments – causes


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iThemba LABS Annual Report 2008 Hospital Group

32

2.3 Hospital Services 2.3.1 Overview of Group The staff component of the hospital group currently consists of: Nursing staff 8 (complemented by 2 carers funded by Tygerberg hospice), Housekeeping 6, Dietician 1, Canteen staff 5, and Administrative staff 2. To supplement the nursing staff at the hospital, agency-nursing staff is used. One registered nurse post is currently full time provided by the nurse agencies. Complementary services to the hospital are rendered by an Aromatherapist (twice a week) and a Counsellor (once a week).

2.3.2 Highlights of the Year

The average bed occupancy for 2007/08 was 31%, compared to 36% in the previous financial year, excluding January, as the hospital was closed during that period. The minimum bed occupancy was during February 8,81%, and was mainly due to reduction in patient admissions due to measures taken to accommodate the power failures during that period. The maximum bed occupancy was 43% during April 2007 compared to the maximum of the previous year of 56%. Both therapy patients and step down care patients are currently being managed in the hospital. No foreign patients were admitted during this period. 60 Therapy patients were managed in the hospital as opposed to 77 step-down care patients. The step down care patients admitted during the year totalled 77 compared to 101 for the previous year and 169 the year before. There is a steady decline in step-down care patients, mainly due to restructuring of the hospice boundaries and an added facility in Mitchells Plain for HIV/AIDS step down. Demographically, 37% African patients were admitted, 50% Coloured and 13% White. Patient revenue decreased during the past financial year due to a limited number of private patients being admitted. The total patient related revenue for the hospital was R57 000, whilst the canteen revenue was R412 000. A total of 20 240 meals were prepared by the hospital canteen during the year compared to 18 135 the previous year. Hospital overtime cost for the financial year comprised of 35% cost to work on Sundays, 23% cost to work on Public holidays and 42% cost to actual overtime. Petra Fördelmann, the Nursing Services Manager, lectures the B Tech Oncology Nursing course at the Cape Peninsula University of Technology. Nine students enrolled for the course during this financial year. The students did experiential training and the examinations were done at iThemba LABS.

Number of in patients Hospital days In patient totals

Year Therapy patients

Step down care Therapy patients Step down

care Total number of hospital days

% Utilization

2007/2008 60 77 18043 723 2587 30.59% 2006/2007 72 101 2219 988 3204 36.14% 2005/2006 82 101 2107 1058 3164 42.46%

iThemba LABS Annual Report 2008 Radionuclide Production Group

33

2.4 Radionuclide Production 2.4.1 Overview The mission of the Radionuclide Production Group (RPG) of iThemba LABS is to develop methods to produce high-grade radionuclides with the 66 MeV proton beam and to apply these methods to produce regularly, on a weekly basis, radionuclides and radiopharmaceuticals for nuclear medicine in South Africa, and also to produce longer-lived radionuclides for the export market to aid cost recovery. It includes the objective to sustain and upgrade the production facilities, to increase the production yield while simultaneously reducing radiation exposure to staff. As such, and in compliance with the mission of iThemba LABS, the group strives to pursue active and internationally competitive in-house research, development and training programmes. Relative to the previous financial year, the income generated from the sales of radiopharmaceuticals and radionuclides has shown substantial growth of more than 120% (see Table 6). Income revenue peaked at a record R12,5m.

2006-7 2007-8 Activity

(mCi) Consignments Total

Income (R)

Activity (mCi)

Consignments Total Income

(R) Radionuclide 22Na 664 25 1 956 397 263 19 819 891 68Ge, 68Ge/68Ga 0 0 0 276 10 547 571 82Sr 7073 3 1 627 154 24744 11 8 183 278 109Cd 0 0 0 2 1 11 486 88Y 7 1 0 10 1 8 439 Radiopharmaceuticals 123I (Solution, Capsule & mIBG)

4034 458 770 384 3948 422 795 233

67Ga Citrate 6711 420 951 975 6147 390 904 825 67Ga Resin 13 12 2 190 5 5 1 003 81Rb/81mKr generator

2925 203 156 897 2430 169 138 697

18F-FDG 570 35 154 349 3210 149 993 313 SUB-TOTAL 19870 1158 5 619 346 41035 1178 12 403 740 Less Credits -3 340 -35 018

TOTALS 5 616 006 12 368 722

Table 6 : Radiopharmaceuticals and radionuclides sales figures

The increase in sales is mainly attributable to a) the increased supply of irradiated 82Sr targets to MDS Nordion in Canada, b) the increased demand for 18F-FDG by the local market, and c) the introduction of a new product, 68Ge/68Ga generator. In February 2008, iThemba LABS concluded a supply agreement with IDB-Holland to serve


34

as an exclusive European distributor of the iThemba LABS 68Ge/68Ga generator. iThemba LABS continues to supply radiopharmaceuticals to the local public hospitals at a 40% discounted price, and continues to provide a free supply of 81Rb/81mKr generators (used for lung ventilation studies) to Groote Schuur Hospital on a weekly basis because of their severe budget constraints. For the review period, more than 1100 consignments were dispatched to over 120 clients worldwide and the delivery of consignments correctly and punctually peaked at more than 93%. Non-delivery or delayed delivery was mainly attributable to a) unscheduled power outages, b) cyclotron downtime, c) breakdown of ageing equipment and infrastructure related to targetry and chemistry. The RPG operates three bombardment stations for the production of radiopharmaceuticals and radionuclides. Figures 11 and 12 show the beam time allocation to the various targets for both the horizontal and vertical beams.

Figure 11: Percentage of total accumulated charge per production type for horizontal beams.

Figure 12: Percentage of total accumulated charge by bombardment for vertical beams.

IL 0705-01-Rb0311%

IL 0706-01-Rb0411%

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Rb-81/Kr-814%

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2.4.2 Major Achievements Ø Revenue for the sales of radiopharmaceuticals and radionuclides peaked at a record R12,5m. Ø The service delivery of radiopharmaceuticals such as 18F-FDG, 123I, 67Ga and 81Rb/81mKr generators to over 60

clients nationwide was performed with more than 93% efficiency (first time on time), however, the overall successful radiopharmaceutical productions (processes within the control of the group) improved from 93% to 98%.

Ø In March 2008, the Radionuclide Production Group introduced for the first time a commercial 68Ge/68Ga generator compliant to current Good Manufacturing Practice (cGMP).

Ø In February 2008, iThemba LABS concluded a Supply Agreement with IDB-Holland, to serve as an exclusive European distributor of the iThemba LABS 68Ge/68Ga generator.

Ø For the review period, the RPG staff authored and co-authored 7 scientific papers in international journals (RPG personnel were the first authors in 4 publications).

Ø RPG collaborations with Hungary continued and new bilaterals with South Korea and African countries such as Algeria and Lesotho were pursued.

2.4.3 Innovation Fund Project In December 2004 the Radionuclide Production Group was awarded a NRF Innovation Fund Grant of R15m over 3 years to develop critical radionuclides for medical diagnosis and therapy. The primary objectives at that time were as follows: 1) To develop an innovative method to produce 18F-FDG so that hospitals within four hours’ delivery time may

be reliably provided with this currently unavailable, but diagnostically essential, radiopharmaceutical. 2) To upgrade current dual-headed gamma-cameras in partner State hospitals to utilize the [18F]FDG, so that

they may gain clinical experience in its use and to pave the way for realization of state-of-the-art PET (positron emission tomography) in Southern Africa.

3) To develop a prototype 68Ge/68Ga generator for the radio-labelling of peptides for subsequent use in PET. This included development of facilities such as the hot cells customisation and the beam splitter. Most of these generators will be exported to serve a worldwide market of over 1200 PET cameras.

4) To develop a commercial process to prepare ultra pure 67Ga that is needed to label peptides for cancer therapy.

By 31 March 2008 (project termination date), all the above objectives were successfully achieved with the exception of the delayed completion of the hot cells customisation and the beam splitter. Due to budget constraints and the lack of the human resources, the envisaged completion date for the hot cells is July 2008 and that of the beam splitter 31 March 2009. This however, has not had an impact on the delivery of the Innovation Fund radiopharmaceuticals, namely 18F-FDG, 68Ge/68Ga generators and ultrapure 67Ga, as serving the existing market demand has been achieved by adapting existing production facilities.


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2.4.4 Radiopharmaceutical Manufacturing In the past year we’ve seen an improvement of the overall successful radiopharmaceutical productions from 93,3% (in the previous review period) to 97,5%. There were no 67Ga production failures! This achievement can largely be attributed to a dedicated team, the improvement of production processes and either replacement or improvement of equipment. The 68Ge/68Ga generator was the latest product to be added to iThemba LABS’ radiopharmaceutical portfolio and is mainly exported to Europe for PET applications. The following radiopharmaceuticals were routinely produced in compliance with current Good Manufacturing Practices (cGMP) and delivered to over 60 Nuclear Medicine departments at private and public healthcare facilities throughout South Africa:

• 18F-FDG for oncology, cardiac and neurological applications;

• 123I capsules, 123I oral solution/injection and 123I-mIBG injection for tumour localisation and for observing heart, kidney, thyroid and brain function;

• 67Ga-citrate injection for inflammatory lesions and tumour localisation;

• 67Ga oral resin used as a radioactive solid food tracer; and

• 81Rb/81mKr generators for lung studies. A special 123I–solution was also produced for the University of Stellenbosch (Tygerberg Hospital) for the synthesis of radio-iodinated brain receptor ligands.

18F-FDG (Gluscan) is still awaiting registration by the South African Medicines Control Council and is supplied in terms of Section 21 of the Medicines and Related Substances Control Act to Tygerberg Hospital, Red Cross Hospital, Groote Schuur Hospital and Cape Pet to perform diagnostic PET studies.

Figure 13: Preparation of Radiopharmaceuticals in compliance with current Good Manufacturing Practices


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2.4.5 Long-lived Radionuclides Production of 22Na and positron sources iThemba LABS still remains the only supplier of 22Na positron sources worldwide. Positron sources are being produced according to purchase orders received. Sources made during this period were done using 22Na produced in the last review period. During the present review period, no 22Na was produced because a large percentage of beam time had to be allocated to the irradiation of Rb targets in the VBTS for the production of 82Sr. Unfortunately, both 22Na and 82Sr are produced in the same energy window, thus they cannot be produced simultaneously in a tandem target geometry and consequently they compete for beam. Only one Mg target for 22Na production received beam in 2007 but that production failed as a result of a target failure. Due to the limited beam time available, that bombardment could not be repeated. Our next 22Na production is earmarked for July 2008. In the meantime, due to the hazardous nature of the current methodology used to manufacture sources, a so-called drop-on-demand technique, based on the inkjet printing principle, has been proposed to manufacture sources. A microdispensing device and piezoelectric actuating electronic driver [MicroFab, USA] with a XY micro-stepping stage and control system [Newmark Systems, USA] was acquired. The XY stage has been thoroughly tested using LabVIEW test programs and using a Monte Carlo moving strategy. Pattern construction algorithms for droplet formation across the entire source area have been studied. This represents the first steps in this project. The microdispensing unit will subsequently be tested. The development work is in progress. Other long-lived radionuclides In addition to the regular production of 22Na, 68Ge and 82Sr, iThemba LABS can also produce 88Y, 139Ce, 57Co, 55Fe and 65Zn on request.

iThemba LABS Annual Report 2008 Materials Research Group

38

2.5 Materials Research Group The Materials Research Group (MRG) is a multi-disciplinary research group at iThemba LABS which conducts both basic and applied research by probing various aspects of matter using a wide range of research techniques in ion beam analysis (NMP, RBS, HI-ERDA, etc.), X-ray diffraction, pulsed laser deposition, scanning probe microscopy, Mössbauer spectroscopy, materials engineering and biological sciences. Accordingly, with such a range of materials research techniques at our disposal, the MRG is fully committed to research capacity development and post-graduate student training programmes.

2.5.1 Highlights For the period under review, the overall activities of our group have proved as challenging as they have been exciting. The following are some of the MRG highlights for the year 2007/08. 1. The MRG successfully hosted a nanotechnology conference event, the African Regional College on Science

at the Nanoscale, on 19-30 November 2007. Organised jointly with the International Center for Theoretical Physics (ICTP), the event drew active participation from eminent scientists and international experts in nanotechnology, with a sizable pool of student participation coming from the SADC region.

2. An equipment grant proposal of R1,9m was submitted to the NEP programme of the NRF in June 2007 for the upgrade of the X-ray diffraction (XRD) laboratory. The proposal was successful with a grant of R1,1m awarded by the NRF. iThemba LABS subsequently committed to supplement the NRF grant with R700k. The current phase of the XRD upgrade consists of the following four key items: (a) A heating stage with a position sensitive detector for in-situ measurements of phase transformations

and reaction kinetics up to temperatures of 800°C. (b) Grazing incidence upgrade for a significant increase in detection sensitivity of thin layers and coatings. (c) In-situ reflectometry upgrade to characterize the properties of thin layers, such as layer thickness,

composition, surface and inter-layer corrugation. (d) Software upgrade for quantitative analysis and structure refinement.

3. During the year under review, the MRG has also concluded the design, construction and ultimately the physical delivery to Nigeria of a data acquisition end-station which is currently being used for Ion Beam

Analysis on the 15° beam line of the newly acquired 1.7 MV Tandem Accelerator at the Center for Energy Research and Development (CERD) of the University of Ile Ife, Nigeria. This project was initiated in 2007 with the signing by iThemba LABS and the CERD of a memorandum of understanding according to which the MRG committed its technical expertise to order equipment and assemble hardware and software components of the IBA End-Station. After completion, the End-Station was successfully tested for RBS, PIXE and HI-ERDA techniques. All costs associated with the project were borne by the CERD, including transportation of the End-Station to Nigeria. The successful completion of this project has consolidated our


39

well established collaboration with the CERD and accordingly broadens the scope of our joint scientific projects with more opportunities for researchers and post-graduate student exchange.

4. Our nuclear microprobe is now the first such facility in the world with proven capabilities of PIXE microanalysis of biological material in the frozen-hydrated state. The necessary modifications of the commercially available cryotransfer system coupled to the experimental chamber of the microprobe had been completed in 2005/06, followed by thorough testing using thick sections of selected plant and animal material. While other groups worldwide attempted to perform similar modifications, none reported quantitative results from their trials. The obtained results were published in 2007. The total cost of these modifications was minimal due to the donation of a second-hand cryo-transfer system by Dr Rosemary White from the Microscopy Centre of the CSIRO Plant Industry in Canberra, Australia.

5. A research project on micronutrient localization in plant seeds using our cryo-laboratory and the nuclear microprobe was initiated in 2007. This is part of a bigger project related to isolation and characterization of Lotus japonicus genes involved in zinc and iron homeostasis, started in 2007 in collaboration with scientists from Denmark (see 3.5.23.). Technically relatively simple, micro-PIXE analyses make an important contribution to studies on iron deficiency with the goal of fighting anaemia, which affects 30% of the world’s population leading to premature death, poor health, and lost earnings. Plant products are major sources of mineral nutrients in human diets, in particular in resource-poor populations where anaemia is more prevalent.

6. One of the main achievements of our group in 2007/08 has been the successful synthesis and

characterization of a novel photo-active nano-composite material, appropriate for ultrafast nonlinear laser χ3 applications. Thin films of vanadium oxide with clear nano-particles were deposited on glass substrates using the sputtering unit at the MRG. Compared to standard noble metal particles, which exhibit an

enhanced χ3 caused by the electromagnetic local electric field’s enhancement, this new class of Au-VO2 nano-composites displays an additional reversible and tunable surface plasmon frequency under external temperature stimuli correlated to the Mott type semiconducting-metallic 1st order transition of the host VO2 matrix. The results of this experiment represent the first direct observation of Mott phase transition on a single VO2 nano-particle. The experiment received international acclaim from the International Photonics Society, and a special award by the Cambridge International Biography Council in the UK.

7. Following the successful commissioning of the AFM, a new Nanoman V scanner was fitted to replace the original scanner which was diagnosed as the source of intermittent software glitches experienced during imaging. Furthermore, a manually operated humidity control mechanism was designed to control ambient humidity in the AFM chamber during lithography. This has paved the way for a number of research projects which require the generation of oxide patterns using conducting AFM probes in a humidity-mediated local anodic oxidation process.


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8. Research projects on platinum coatings and alloys have been initiated between the MRG and Le Mans University (Prof. A Gibaud), France. Results of this collaborative work are expected to culminate in the preparation of a patent for a technique to precisely determine the chemical composition of platinum alloys. This patent will be of significant importance in the application of platinum in the jewellery industry. According to the international convention, the minimum platinum content in jewellery must be 95wt % in order for it to be classified as precious jewellery. Developing more accurate methods of determining the precise platinum content is therefore crucial for platinum jewellery producers. A memorandum of understanding has been signed between iThemba LABS and Le Mans University as the main collaborators on the project, with MINTEK as a potential beneficiary.

9. Over the past year the Heavy Ion – Elastic Recoil Detection Analysis (HI-ERDA) set up was installed on the

K1 line in the SPC2 vault. Initial characterisation tests of the Time of Flight – Energy (ToF – E) detector system, performed using a 252Cf radioactive source, demonstrated the functionality of the data acquisition system. Subsequent tests using a 3 MeV Oxygen beam pointed to a need for better beam focusing and target alignment. Latest test results using a 3.3 MeV He2+ beam after improvements in beam focusing and target alignment, indicate that the performance of the ToF-E coincidence spectrometer was up to expectation. The HI-ERDA project forms part of the IAEA’s Coordinated Research Project CRP F1 1013, titled “Improvement of the reliability and accuracy of heavy ion beam nuclear analytical techniques”, and is carried out in collaboration with Prof. Günther Dollinger’s group at the Universität der Bundeswehr München, Garching, Germany.

iThemba LABS Annual Report 2008 Physics Group

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2.6 Physics Group

2.6.1 Overview The main activities in the Physics Group at iThemba LABS are research and training (mainly at post-graduate level) in basic and applied nuclear physics. The basic research being conducted is aimed at expanding knowledge about nuclear reaction mechanisms and nuclear structure. The major facilities include a K600 magnetic spectrometer, the AFRODITE gamma-ray detector array and the large A-line scattering chamber. In order to produce and store targets needed for SSC-related research, a target laboratory with a dedicated target maker is operated by the group. The group also conducts research on theoretical nuclear physics. In this regard we have maintained a focus on clustering phenomena in nuclei and the modelling of rapidly rotating nuclei. During the year covered by this report the group also initiated a research programme around physics that can be studied using the ALICE detector at the Large Hadron Collider at CERN. Applied research is conducted in the Environmental Radioactivity Laboratory (ERL) which is operated by our group, and by means of secondary neutron beams produced via protons (from the SSC). In the ERL research is conducted into natural and anthropogenic radioactivity in the environment (mainly soils, sediment, water). The neutron-related studies are aimed at studying biological effects of ionizing radiation and the intercomparison of dosimetry systems. In order to complement mainly the applied research we also conduct research around the use of Monte Carlo simulation techniques to model the interaction of radiation with materials. A significant change during the period covered by this report was the appointment of R.T. Newman as an interim head of the group in the light of the promotion of J.J. Lawrie to interim deputy director. The Physics Group employed 8 research physicists (permanent staff, including the interim head of the group), 1 junior research physicist and 3 post-doctoral researchers. One of these research physicists is also responsible for managing the ERL. In addition we employ a mechanical technician, a technical officer (ERL), a target maker and two research associates. We also have an honorary research physicist in our group who is mainly assisting with research done with the AFRODITE array. In this year there were 22 post-graduate students (12 and 10, at masters and doctoral level, respectively) registered at South African universities who made use of our group resources to conduct their research. Of these 15 were black students (as classified by the Employment Equity Act), 5 were female and 5 were foreign students (from the African continent). During the year 9 masters level students were awarded their degrees. Seven group staff members are also lecturing and organising practicals for students in the Masters in Accelerator and Nuclear Science (MANUS) programme which is jointly organised by iThemba LABS and the Universities of the Western Cape and Zululand.


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The group was associated with 16 and 21 contributions at local and international conferences, respectively. During the year covered by this report 17 research articles (13 peer reviewed) were published from research conducted by the group.

2.6.2 Highlights • The group was successful in acquiring funding to the tune of R1,8m via the NRF National Equipment

Programme to upgrade a large fraction of our data acquisition electronics from conventional to digital signal processing (DSP) electronics. This project will revolutionize the way data are acquired and processed from experiments (especially with the AFRODITE array) conducted using ions accelerated with the SSC. It is envisaged that the commissioning of the new data acquisition system will be completed during 2009, with the arrival of the electronics (XIA Corporation, USA) expected at the end of 2008. The new system is furthermore a prerequisite to the envisaged implementation of gamma-ray tracking with highly segmented germanium detectors.

• Significant progress was made with the commissioning of the two recently acquired evaporators (e-gun and filament heating) used in the Physics Target Laboratory (PTL). The PTL makes targets for users of iThemba LABS who utilize SSC beam time to perform nuclear physics experiments. Furthermore the glove box which is used to prepare sensitive targets was upgraded by installing a roughing pump and piping system in order to achieve a controlled, inert environment that allows for the working with air reactive materials without oxidation. Encouraging results were obtained from first tests made with a target-thickness measurement setup that uses an alpha source.

• The AFRODITE detector array is used to perform studies of atomic nuclei using mainly in-beam gamma-ray spectrometry. The array comprises clover and LEPS germanium detectors. With time some detectors deteriorate and need repair. Before these repairs entailed shipping detectors back to the supplier in France. We embarked on a programme to do in-house repair of our detectors. We sent a staff member to receive training in France on detector repair. This strategy has resulted in significant savings (money and time) and improved data quality from AFRODITE.

• Our group has formally become involved in the physics programme around the ALICE detector at the Large Hadron Collider at CERN (Geneva, Switzerland). One group member will spend close to 100% of his time on ALICE physics while a second will spend about 50% of her time. Our involvement will initially focus on the muon spectrometer of the ALICE detector.

• One key project in our group is related to the EARTH (Earth AntineutRino TomograpHy) project. This project’s ultimate aim is to map the heat sources of the earth using an array of geoneutrino detectors. Our group is playing a vital role in developing the detectors for the geoneutrinos. A successful mini-symposium on topics related to the EARTH project was held at iThemba LABS on 29 February 2008. Fifty persons


43

attended, including delegates from UCT, UWC and SU. Dr P. Kotze from the Hermanus Magnetic Observatory presented an invited lecture on the earth’s changing magnetic field. The feedback received from participants was very positive.

• Ms I. Usman (Ph.D. student, University of the Witwatersrand) won the prize for the best oral presentation by a doctoral student in the Nuclear, Particle and Radiation Physics section at the 2007 South African Institute of Physics conference which was held at the University of the Witwatersrand. The title of her talk was ‘A global investigation of the fine structure of the Isoscalar Giant Quadrupole Resonance’. Ms Usman’s research was conducted using the K600 magnetic spectrometer (see 3.3.9).

iThemba LABS Annual Report 2008 iThemba LABS (Gauteng)

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2.7 iThemba LABS (Gauteng) 2.7.1 Highlights Major Highlights involve construction of the microprobe beam-line, and advancement towards the realization of the Accelerator Mass Spectrometer (AMS) facility. The micro-probe beam line is the second, after the completion of the nuclear physics beam-line early in the year 2007. It is envisaged that the micro-probe beam-line will be the most important and most used facility, after completion of AMS facility. There is no doubt that both the AMS and micro-probe beam lines will be the best in the African continent and will result in experiments that will be competitive at international level. This optimistic expression is affirmed by the fact that beams that will be transported in these facilities (AMS and micro-probe) will be produced by an already completed state-of-the-art 6MV Tandem Van de Graaff accelerator. A closer look at the recently refurbished 6MV Tandem Van de Graaff accelerator, AMS and the micro-probe beam lines appear below. Refurbished 6MV Tandem Van de Graaff Accelerator, with AMS central to all activities; More than R10m was spent in refurbishing the accelerator (see figure below) of which a significant portion went into replacement of the old tubes (in the accelerator tank) and replacement of the charging belt with a Pelletron chain. The obvious intended outcome of the refurbishment exercise was to achieve the most stable beam, given that the refurbished accelerator is earmarked for production of stable beams for the AMS facility, and that experimental results will have to be competitive with the best in the world, as the facility will be used for both fundamental research and for commercial purposes. The latter also takes into consideration immense interest that had been expressed by industry in the AMS facility, which will be the only one in the entire African continent. Currently, the construction of the AMS Ion Source, based on the design of Lawrence Livermore (in USA), which is one of the best in the world, is at an advanced stage and is due for completion within the first quarter of the year 2009. The Ion Source, which is funded by the IAEA, is estimated to cost between two and three million Rand. This is in addition to funding of scientific visits (estimated at R1m) provided by the IAEA, as part of knowledge exchange in the field of AMS. The challenge towards the completion of AMS is securing of additional seven million Rand (approximately) to construct the high energy system of AMS. Current expectations hinge on a funding application that was submitted to the National Equipment Programme (NEP) of the NRF.


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0

20

40

60

80

100

120

140

160

180

200

May-07

Jun-07

Jul-07Aug-07

Sep-07

Oct-07Nov-07

Dec-07

Jan-08Feb-08

Mar-08

Apr-08

Stable IsotopesTritiumRadiocarbonRadon

Construction of the state-of-the-art micro-probe facility; The complete hardware section of the micro-probe beam-line is as shown in the figure below (the beam-line on the right). The latest version of the data acquisition program OMDAQ 2007, and associated NIM modules (e.g. ADC) is due for shipment during September – October 2008 , and is supplied by Oxford Micro-beams in the United Kingdom. The equipment boasts the latest state-of-the-art innovations in micro-probe measurements as stated below. The chamber will have a motorized XYZ stage (where samples will be mounted), comprising three axis stepper motors with encoded shafts that allows better than two micron repeatability. In addition to the three axis stepper motors, there will be an integrated manual rotation stage allowing 360 degree rotation about the z-axis (vertical), which will allow channelling experiments to be conducted with a high degree of accuracy. The micro-probe will be used in the areas of Rutherford Back Scattering (RBS), Elastic Recoil Detection Analysis (ERDA), Channelling and PIXE experiments. Scientists will span a broad spectrum of science fields. Additional Activities (Gauteng) in the year 2007/2008 In addition to the above developments, which are core to iThemba LABS (Gauteng), advances were made in other sections of the laboratory which included the analytical divisions of the Environmental Isotope Laboratory (EIL) and Geology, respectively. In addition to research, hundreds of samples (generating income of the order of R500k, annually) are being analyzed in EIL (see attached statistical diagram, which incorporates both uncharged and charged results). Various research projects associated with the EIL are listed below. These projects are in addition to analysis of commercial samples from various institutions such as the Department of Water Affairs (DWAF) and the IAEA, to mention a few.


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Research Projects in EIL

• Recharge mechanisms and geochemical processes in the Johannesburg-Pretoria area: hydrochemical and isotope approach.

• Hydrological processes in the Thukela Basin, South Africa. This national project was initiated by Prof. S. Lorentz of the UKZN School of Bioresources and Environmental Hydrology, in collaboration with the Department of Technical Co-operation of the International Atomic Energy Agency.

• Environmental isotope studies as part of a rural ground water supply development: Taaibosch area, Limpopo Province, South Africa. This is an ongoing study in conjunction with Mr E. van Wyk of the Department of Water Affairs and Forestry.

The research activities in Geology have been largely conducted off site, and are driven by Dr Rodger Hart. The work has mainly centred on collaborative projects with scientists from the Institut de Physique du Globe, in Paris. The major project in this field is entitled “Super Magnetic rock from the Vredefort meteorite crater, South Africa”. The project aims at understanding the development of both crystal magnetization and gravity features in the crust. This is essential in interpreting continental scale terrain boundaries which manifest themselves either as major magnetic or gravity anomalies.

iThemba LABS Annual Report 2008 Radiation Biophysics Group

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2.8 Radiation Biophysics 2.8.1 New Flow Cytometer Modern molecular research methods have been implemented in the Radiobiology Laboratory during the last year. These include the installation of a flow cytometer equipped with 3-colour laser optics. The cell analyser was made available by the Faculty of Health and Wellness of the Cape Peninsula University of Technology. It is being used to measure radiation-induced apoptosis in different subsets of human lymphocytes identified by cell surface markers and light scatter parameters. Also, the rates of division by different types of cancer cells can now be followed using fluorescence signals from a molecular marker and DNA staining.

2.8.2 Enhanced Radiosensitivity from Lentivirus-mediated RNA Interference The collaborative research project between iThemba LABS and the Universities of Ghent (Belgium) and Insubria (Italy) to investigate molecular mechanisms in radiobiology has demonstrated the enhancement of cellular radiosensitivity following lentivirus-mediated RNA interference.

2.8.3 Measurement of RBE Variation in the Proton Beam SOBP A bespoke jig made by the University of Louvain, Belgium, has allowed murine jejunum segments to be irradiated in the last 3 mm of a proton beam spread-out Bragg peak (SOBP). This novel approach has allowed in vivo measurement of the post-irradiation regeneration of crypt stem cells, so revealing important position-dependent changes in the RBE of the SOBP.

2.8.4 Estimate of α/β ratio for Acoustic Neuromas A very low estimate of the α/β ratio for acoustic neuromas has been determined (1.3 CGyE) from a radiobiological analysis of proton therapy patient data, suggesting that a strict radiosurgery treatment protocol is beneficial.

2.8.5 Radiosensitivity of Prostate Cancer Cells to X-ray and Neutron Radiation Much larger than expected variations in the radiosensitivity of different prostate cancer cell lines have been noted for both X-rays and neutrons. Also, a substantial increase in the inherent radiosensitivity of lymphocytes from HIV-positive individuals has now been confirmed using a large number of donors. Z-score analysis of radiation-induced apoptosis in CD4 and CD8 lymphocytes showed that about 10% of a very large donor population is likely to be very sensitive to radiotherapy treatments.

2.8.6 Low Dose-limiting RBE for 100 MeV Neutrons The dose-limiting RBE for 100 MeV neutrons measured using dicentric aberrations in white blood cells is much lower than previously reported. This confirms observations made earlier at iThemba LABS with a 200 MeV neutron beam.


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2.8.7 Automated Identification of Micronuclei Induced in Binucleated Lymphocytes Radiation protection radiobiology was improved during the past year with the installation of an automated image analysis system at Ghent University, Belgium. Work has started at Ghent University to ensure that the system accurately identifies micronuclei induced in binucleated lymphocytes, before the equipment is transferred to iThemba LABS. First results are promising, and more than 1000 lymphocytes can be analysed in a few minutes.

2.8.8 Postgraduate Training in Radiobiology Training of postgraduates in basic radiobiology is ongoing for Honours Students in Applied Radiation and Technology. Teaching in clinical radiobiology has also been offered to M. Med. Registrars (Radiotherapy), and radiobiology for radiosurgery to practicing clinicians. A course in practical radiobiology to observe cellular radiation damage proved to be very popular with 20 students in radiation protection. Postgraduates from 10 different countries in Africa attended the week long IAEA – WITS radiation protection course.

Figure 14: Prof. Leo de Ridder from Ghent University, Belgium, was funded by the Flemish Inter-university Council (VLIR) to travel to iThemba LABS tohelp with lectures and practicals for postgraduates in radiation protection.

iThemba LABS Annual Report 2008 Electronics and Information Technology Group

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2.9 Electronics and Information Technology A significant increase in power outages due to the ongoing national electricity supply crisis has been the source of numerous problems (exacerbated by ageing equipment). The laboratory has continued to lose components in the form of hard drives, PC power supplies, monitors, etc. as a result of the outages. As a preventative measure, a larger 10 kVA uninterruptible power supply (UPS) was installed in the main server room, and power to this UPS was sourced by a circuit which switches to a standby generator in the event of a general utility power failure. Additional smaller UPSs have been installed on the network backbone switches which provide connectivity to both the campus and control networks. Extra air conditioning has been installed in the dataroom to reduce the risk of overheating following failure of the main air-handling system after an unexpected power outage. Development of the software for the new distributed control system of the tandem electrostatic accelerator at iThemba LABS (Gauteng) has continued during the past year, and the first operational system was successfully commissioned. Additional control and monitoring subsystems continue to be developed. A project to evaluate the use of EPICS as the platform on which future accelerator control software will be developed at the laboratory was begun. EPICS (Experimental Physics and Industrial Control System) is a distributed computer control system collaboratively developed at a number of accelerator-based laboratories around the world over a number of years. The initial task was to develop a subsystem to control, and acquire and monitor data from beam scanners installed in the beam lines of the electrostatic accelerators. This was successfully completed, and the subsystem is currently being deployed. Subsequent EPICS-based developments have included the implementation of two channel access servers currently being tested, a channel access client based on .NET technology, and software to bridge between the EPICS database and the old control system’s variable table environments. iThemba LABS is a member (together with partners in the physics community based in some local universities) of the SA Nuclear Grid Consortium project, which will create an infrastructure of many cooperative computer systems providing the ability to perform sorting and analysis of large amounts of data and complex computer simulations. The laboratory is also a member of the SA-CERN consortium, and in particular, is actively participating in the area of the high-performance computing for physics applications component of this partnership. The success of these projects is critically dependent on the provision of significantly higher Internet bandwidth between the participating institutions. It is hoped that the current implementation of the SANReN infrastructure (an upgraded national research and education network, partially funded by the South African Department of Science and Technology) will go a long way to meeting these needs within South Africa. Developments in the provision of significantly enhanced affordable international Internet bandwidth are also promising and should bear fruit during 2009. The two electronics divisions within the EIT Group provided support and assistance in several major lab projects such as the Vertical Beam Target Station (VBTS) and beam splitter for radionuclide production, the Van de Graaff


50

control system for the Materials Research Group, the redesign (based on new technology) of the cyclotron’s multi-wire harp current measurement and readout subsystem, and the refurbishment of the iThemba LABS (Gauteng) tandem accelerator. For these projects many new electronics hardware modules were designed, constructed and debugged. An example is shown in Figure 15.

Figure 15: A 48-channel picoamp current measurement module

The ECR ion source donated to iThemba LABS by the Hahn-Meitner Institute (HMI) in Berlin was installed during the year. Staff from HMI assisted with the installation of the control system CODIAN30 which runs under LabVIEW, and the control system was then customized for local use. Work has continued on the design and implementation of several electronics subsystems required for the upgrade of the current proton therapy programme for the Medical Radiation Group. These have included the proton therapy chair control system, where the old X286 PC (with ISA digital I/O Card) will be replaced by an ETX single board computer that fits into a standard SABUS crate together with 5 stepper motor controller cards. The new system allows for simultaneous movement of the 5 axes. The stepper motor drive electronics is interchangeable between the old and new chair control system which allows for the testing of the new design without causing long interruptions to the working system.

An automated liquid nitrogen filling system was developed using LabVIEW to control the filling process of up to 32 cryostats in the Afrodite detector array (Figure 16). Many features such as detailed monitoring, logging and alarm notification were built into the program. This system has undergone extensive testing and is currently in use.


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Figure 16: One of the user interface pages of the liquid nitrogen filling system

EIT Group staff members were involved in teaching the electronics modules in the MANUS and MATSCI courses at the University of the Western Cape. Topics included basic analogue and digital electronics, control systems and electronic interfaces used in accelerator control systems, and experimental physics instrumentation. Practical sessions were held at iThemba LABS on analogue, digital and control electronics using National Instruments NI-Elvis training stations. A post-graduate student working on an iThemba LABS-based project and co-supervised by a member of the EIT group graduated with an M.Sc. from the University of Stellenbosch. Two collaboration students form the National University of Lesotho worked on EIT projects in the Medical Radiation Group. Four electrical engineering national diploma students studying at Cape Peninsula University of Technology (CPUT) were placed in the EIT Group for their 12-month in-service training. Six Office Management and Technology students spent 6 months each of their experiential training in the library. In the iThemba LABS’ International Computer Driving Licence (ICDL) teacher training programme, 168 teachers and 15 Khanya facilitators were trained. For the first time 6 Edunova facilitators were also trained. Edunova is a local organisation that assists Khanya in the local township schools. The ICDL testing centre switched over to Electric Paper’s automated testing software and, for the first time not a single test software failure occurred the whole year. In order to promote computer literacy, schools are allowed to use the iThemba LABS’ training


52

materials free of charge. To date 33 schools and community centres have signed the “Use Of Training Materials” agreement. The library staff managed the organisation and logistics for numerous conferences and meetings during the year, including

• The IAEA AFRA Workshop on Integrated Management Systems, 7-11 May 2007;

• Esteq Product training, July 2007;

• A two week ICTP African Regional College on Science at the Nanoscale, held from 19-30 November 2007 (150 participants)

The head of the library visited CERN laboratory during the period 1-15 December 2007. The trip was fully funded by CERN. She met with the CERN Information Services and scientific staff to discuss collaboration possibilities between the two library services. It is planned to set up a mirror site of the CERN Document Server (CDS) at iThemba LABS. She made a presentation to the CERN Library Group during her visit. iThemba LABS organised and ran a Training Course in Quality Management on behalf of the IAEA from 7 – 11 May 2007. The course was attended by 21 participants from the rest of Africa including one candidate from the Republic of South Africa. iThemba LABS was given 6 places on the training course. Members of staff of iThemba LABS also delivered lectures at this course. A presentation on the implementation of an Integrated Management System (IMS) was made to senior management during May 2007. It covered: • A report back on the IAEA Technical Meeting on Integrated Management Systems held in Vienna from 19 to

23 March 2007. • The status of IMS at iThemba LABS and the way forward. The strategic decision was taken to:

o Perform an initial assessment of radionuclide production in preparation for an application for ISO9001:2000 certification.

o Draw up an implementation plan for certification and accreditation of relevant functions within the laboratory.

o Pursue software tools to aid in IMS implementation and operation. o Confirm that Health and Safety and Radiation Protection are central to the IMS initiatives of iThemba

LABS.

iThemba LABS Annual Report 2008 Technical Support Services Group

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2.10 Technical Support Services Group The Technical Support Services Group (TSS) plays a major role in the provision of high quality technical support to ensure that iThemba LABS’ core functions are realized with minimal interruptions. To a large extent we have managed to successfully deliver on our Group’s key objectives and hope to further progress on the sustainable delivery of core services to the user groups. In this regard operational sustainable efficiency and reliability are considered as the most important determinants of success. A further important success factor is the adoption of best-practice in the sectors of design, manufacturing, operating and maintenance of our critical plant.

2.10.1 Electrical Distribution During the past year, the power crisis which faces the country stood out as a critical factor affecting all operations at iThemba LABS. The lack of capacity in the current national electrical power infrastructure resulted in unplanned blackouts, 24-hour load-sheddings, power dips/surges, power rationing and conservation, throughout the country. This trend is likely to continue for the next 3 years until such time as the proposed power-stations are commissioned or the mothballed stations returned to service. It is therefore imperative that back-up power supply be available and reliable to ensure that critical equipment is kept “on-line”. Although iThemba LABS is equipped with an Uninterruptible Power Supply System (UPS) which provides essential back-up (10-15 minutes at full load), the equipment is unlikely to sustain reliability during repeated and successive power incidences. Power incidences during the past year are listed in Table 7 below.

TYPE OF DISTURBANCE TOTAL NO. OF DAYS (HOURS)

Planned/unplanned (emergency) load-shedding 11 (20 hrs)

Dips/surges 83

Total power failures due to external causes 5 (48 hrs)

Partial failures due to internal causes 4

The above-mentioned interruptions have had an adverse effect on the UPS motor/generator sets and standby battery banks. UPS 1 motor/generator sustained severe damage due to electro-mechanical and thermal stresses. All four UPS battery banks also suffered severe stresses during the recent planned/unplanned load-sheddings. As a result, and due to the decreased life expectancy of the battery banks, the reliability factor decreased to below 40% which is unsuitable to sustain the electrical loading during interruptions. The battery banks will be replaced during July 2008. Additional consequences of power interruptions are: (i) Damage to critical electronic equipment that had to be replaced at considerable cost.

Table 7: Electrical power interuption statistics: April 2007 – March 2008


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(ii) Loss of beam time. It takes in excess of 5 hours to restore the cyclotron magnets to full operation with sufficient stability to extract useable particle beams. The beam interruptions due to power outages increased from 0,7% (of calendar time) in April 2007 to 2,5% in March 2008.

(iii) Patient treatment was severely interrupted resulting in the rescheduling of treatment days. (iv) Production of scheduled assignments of short-lived radio-isotopes for Nuclear Medicine was affected,

and some consignments had to be delayed or cancelled. Planned load-shedding and demand side management. As part of Eskom’s plans to manage and minimise interruptions large power users including iThemba LABS with an average consumption of 2,5 million kWh/month, were requested to reduce electrical power consumption by 10% and sustain this level. Some innovative thinking by one of our staff members resulted in an agreement with Eskom that iThemba LABS be allowed to carry out 90% load-shedding internally, on Mondays for a duration of six hours continuously. This would then constitute our share of load-shedding for the entire week, allowing normal operations to continue for the rest of the week. However, this would only contribute 3 – 4% towards our reduction in electrical consumption. Further initiatives include the allocation of beam time for patient treatment for only one weekend and physics research for three weekends per month. Further reduction in power consumption is obtained by: (i) Disabling some lighting circuits without compromising the safety of employees. (ii) Disabling of all geyser and water-heating circuits, except those required for cleaning purposes. (iii) Disabling of all air-conditioners in offices and non-critical areas. (iv) Staff awareness of the importance of energy conservation i.e. making use of natural lighting etc. The table below shows the actual consumption comparisons during the last three months.

MONTH CONSUMPTION (kWh) % DECREASE AVE % DECREASE

2007 2008 13,6 %

Feb 2 662 755 2 138 207 19,7 %

March 2 525 420 2 185 144 13,5 %

April 2 431 219 2 155 795 11,3 %

The significant decrease of 19,7% in February 2008 was largely due to a transformer cable fault at the Eskom Cyclotron sub-station which resulted in an additional 22 hours complete shutdown of the facility.

Upgrade of Electrical Infrastructure The installation of the new Berlin and Grenoble Ion-sources necessitated the upgrade of the electrical infrastructure from a Notified Maximum Demand (NMD) of 5 MVA to 7.5 MVA. Although the infrastructure upgrade will be completed end May 2008, Eskom still has to approve the additional capacity demand as a result of power supply constraints being experienced.


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Figure 17

Figure 18

Figure 20

Figure 19

2.10.2 Mechanical Engineering The Mechanical Engineering Division, consisting of the mechanical design office and the manufacturing workshop, offers technical service to all of the groups as our end-users. A substantial amount of design and mechanical manufacturing was carried out in-house with urgent manufacturing works being outsourced due to the lack of the necessary resources. Major projects that were completed and some which are still in progress are highlighted below: § Hot Cell Upgrade The engineering department designed, built and tested 2 new sample cells and 2 new production hot cells. These hot cells were installed in the isotope production area (see Figure 17). The lead glass windows still need to be fitted by RPG. The project is 95% complete. § IAEA Robot Project The 1st hoist mechanism, for the portal X-ray imaging device, and the 2nd Hoist Mechanism, for the second X-ray imaging device needed for the stereo X-ray imaging system, was assembled, tested and installed in the second proton therapy beam line vault BG3 (see Figure 18). § Beam Splitter Line

The Electrostatic Channel for the beam splitter was manufactured and assembled (see Figure 19). The Accelerator Group will finalise the design of the Magnetic Channel prior to manufacture by the workshop. Seven ‘short’ quadropole magnets for the beam splitter line were manufactured, assembled and tested. It is planned to install all components for the Beam Splitter line during the 2008 year-end shutdown. This project is roughly 80% complete. § The New SPM2 70% of the SPM2 components are being manufactured in-house to save costs, given our current financial constraints. 80% of the stock items required have been purchased and orders have already been placed for all the outstanding items. The SPM2 Magnet Coil was manufactured (Figure 20) and is being prepared to be cast in resin. A spare SPM2 Magnet Coil will also be manufactured. The manufacture of some bigger components was outsourced. It is planned to have the SPM2 built and tested by October 2008. It is currently about 40% complete.


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2.10.3 Site Services The Site Services section is responsible for the site mechanical (cooling system, air-conditioning and ventilation system, compressed air systems etc.) and building (electrical installation, sewage system, water reticulation system, plumbing, painting etc.) and grounds maintenance. Some of the projects successfully completed by the Site Services division ahead of deadlines and with the satisfaction of the end-user are listed below. § New ECRIS Power Supply Room Design and construction of the new ECRIS power supply and control room to accommodate the Berlin and Grenoble Ion-source power supplies were completed ahead of schedule over a period of seven months (Figure 21). The project required the installation of an upper level of the existing Ion-source room using pre-cast reinforced modular floors with a load capability of 1500 kg/m2. In addition, removable galvanized chequered plates were installed in the floor centre to accommodate removal of equipment from the lower level. The existing removable wooden roof was retained in the upper floor to allow easy installation/removal of equipment. Wooden partitioning separates the power supply equipment room from the control room on the same level. New electrical distribution boards were installed in this area close to the equipment. § Repairs to Chiller no. 1 The chiller motor was completely refurbished due to damage caused by and internal short-circuit of the main windings. The motor was repaired and assembled with the chiller compressor. New bearings and seals were also fitted to the compressor after which full commissioning of the system was carried out (Figure 22).

2.10.4 Human Resources Staff Training and Development Throughout the year several staff members engaged in further studies (part-time) including studies towards MBA, Project Management, International Computer Drivers’ Licence (ICDL Computer Literacy), Engineering Studies, Supervisory Skills Training, Structural Welding, Forklift and Crane Operator refresher training, Basic Pneumatics etc. In-house development of staff with the aid of predetermined Personal Development Plans proved to be highly successful and has become a standard when further training and development of technical staff is undertaken. Two electrical apprentices, employed in 2006, have completed their three levels of modular training and will be doing a voluntary trade test in July 2008. Technikon Trainees are recruited each year on a one-year contract for in-service training and follow a predetermined training schedule as prescribed by the Technikons. During the last five years, all Trainees were successfully recruited by outside companies.

Figure 22

Figure 21

iThemba LABS Annual Report 2008 Safety, Health and Environmental Group

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2.11 Safety, Health and Environmental Management

Highlights • A Substance and Alcohol Abuse Policy was accepted by management and staff for implementation.

• A customised Fire Fighting Course for staff was designed and included in the Induction Training.

• An integrated burglar alarm system was installed in all high risk areas.

• The Access Control System was replaced.

• A Risk Officer was appointed at iThemba LABS (Gauteng) to oversee all S.H.E.Q. and radiation protection functions.

2.11.1 Safety Management Safety, Health and Environmental Committee The S.H.E. Committee Meetings were held every second month. The committee comprises of management, nominated members, co-opted members and employee elected S.H.E. representatives as required by legislation. This forum discussed incidents/accidents which occurred on-site and made appropriate recommendations as necessary. 135 S.H.E. non-conformances were reported to and discussed by the committee.

Hazardous Chemical Substance Control Material Safety Data Sheets (MSDS) were reviewed and distributed to critical areas. Procedures to collect hazardous chemical substance waste were updated and implemented. Fire Prevention and Disaster Management All firefighting equipment was serviced as required by legislation. The replacement of the ageing Halon Fire Suppression system was considered. Additional CO2 fire extinguishers will be placed in the areas where Halon tanks are present. Basic Fire Safety and Fire Emergency Response have been incorporated into the Occupational Health and Safety Induction programme. First-aid There were 12 first aid injuries during the year. 13 First aiders were re-appointed and 20 additional first aiders were trained and appointed. Occupational Injuries 4 Disabling occupational injuries were reported to the Compensation Commission. During the 2007/08 period 1 serious/non-disabling occupational injury and 12 minor/first-aid injuries were reported to the S.H.E. Department. The reporting of all minor injuries attended to by the first aider has not taken place as required. The reporting system is in the process of being revised. Any employee involved in disabling injuries or who shows an increasing trend in minor and/or serious injuries is required to attend a meeting with the directorate to review the injuries/incidents and agree to an action plan to eliminate these.


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The Disabling Injury Frequency Rate (DIFR) is an internationally accepted formula used to assess the frequency of disabling injuries, and is defined as DIFR = Disabling Injuries X 200 000 / Work Hours. 4 Disabling Injuries occurred during this period, resulting in 21 days lost. The DIFR for 2007/2008 is 1.48. The DIFR increased due to 4 disabling injuries occurring during 2007/08. The trend over the last 6 years is shown in Figure 23 below. Similarly the Minor Injury Frequency Rate (MIFR) is used to assess the frequency of minor injuries, and is defined as MIFR = Minor Injuries X 200 000 / Work Hours. 12 Minor injuries occurred during this period. The MIFR for 2007/08 is 3.60 showing a decrease in minor injuries over a 6-year period as indicated in Figure 24.

2.11.2 Occupational Health and Hygiene The Occupational Health Clinic in collaboration with the S.H.E. Department continued to have monthly first aid update and training sessions throughout the year. All injuries attended to by the Occupational Health Clinic are progressed by the S.H.E. Department for investigation. As per the report of the Occupational Hygiene survey conducted by an approved inspection authority in 2006/2007, all non-conformances were attended to and the interventions discussed at the S.H.E. Committee Meetings.

2.11.3 Environmental Management Water Sampling Water samples, collected monthly from bore holes, the sewerage treatment plant, the main water holding tank and sampling spots around the dams are sent for chemical (pH, toxic ammonia and free chlorine) and biological analysis (coliform, faecal coliform and Escherichia Coli). All results are compared to the relevant legislation and S.A.B.S. standards (S.A.B.S. 241), and any deviations are acted upon immediately. Results of water samples collected in February 2008, shown below, necessitated the need to increase chlorine used to treat effluent water which, after treatment, enters the dams and is finally used for irrigation purposes.

DIFR Rate

0.592897386

0.32644587

0

0.867448003 0.881851064

1.478024

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2002/2003 2003/2004 20 04/2005 2005/2 006 2006/2 007 2007/2008

Year

DIF

R C

ount

MIFR Rate

10.67215294

8.487592609

5.956187538

4.528140402 4.1672165083.604178074

0

2

4

6

8

10

12

2002/2003 2003/2004 2004/2005 2005/2006 2006/2007 2007/2008

Year

MIFR

Cou

nt

Figure 23: The DIFR for the past 6 years Figure 24: The MIFR for the past 6 years


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Samples Sample Type Tested for Results (PPM)

Standard (PPM)

First Dam (Entry Point)

Effluent Total Coliforms (per 100ml) E-Coli (per 100ml) Faecal Coliforms (per 100ml)

> 1100 15 15

10 0 0

Second Dam (Exit on boundary fence)


240 93 93

10 0 0

Ground water next to Sewage plant

Environmental Total Coliforms (per 100ml) E-Coli (per 100ml) Faecal Coliforms (per 100ml)

21 11 11

10 0 0

Pump Station next to Sewage plant


4 4 4

10 0 0

Tap water next to Sewage plant

Potable Total Coliforms (per 100ml) E-Coli (per 100ml) Faecal Coliforms (per 100ml)

ND ND ND

10 0 0

Sewage plant (Tank 4)


> 1100 29 29

10 0 0

A-Block Basement Potable Total Coliforms (per 100ml) E-Coli (per 100ml) Faecal Coliforms (per 100ml)

ND ND ND

10 0 0

Water Reservoir overflow

Potable Total Coliforms (per 100ml) E-Coli (per 100ml) Faecal Coliforms (per 100ml)

9 ND ND

10 0 0

Waste Management Biological wastes and superfluous hazardous chemical substances were successfully disposed of.used machine oil is stored in an oil storage tank for removal from site by the R.O.S.E. (Recycle Oil Save Environment) Foundation for recycling (Figure 25). Redundant equipment e.g. e-waste, old machinery, etc. was collected and disposed of in a controlled manner.

Figure 25: Used oil storage tank acquired from the R.O.S.E. Foundation situated in same storage area for safer storage of used machine oil.


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2.11.4 Loss Control Management Loss Control Loss control incidents are as follows:

2005 2006 2007 Totals Motor-Vehicle Accidents 1 3 5 9 Theft / Break-in 0 0 9 9 Property Damage 0 1 4 5 Totals 1 4 18 23

Security Management A security plan is in place which requires a security presence 24 hours a day, 7 days a week. An armed response company has been contracted to assist with security emergencies as they arise.

2.11.5 Quality Management Systems The assembly of the S.H.E.Q. Manual is an on-going process. The policies, procedures and standards for all activities are revised on a regular basis and incorporated into the manual. Documentation is continually converted to be in-line with ISO 9001 and ISO 14001 requirements. OHASAS 18001 has been accepted as the guideline for the S.H.E. Departments O.H.S. programme.

2.11.6 Training Departmental Development training for 2007/2008 is as follows:

ISO 9001 Security Level E

Admin Skills for Office Administration

Substance Abuse Management

Modern S.H.E.Q. Management Totals

2 4 3 3 1 13

Safety Management training for 2007/2008 is as follows:

Staff O.H. Induction Training

HAZCHEM Safety

S.H.E. Inspection

Level 1 First Aid Training

S.H.E.Q. Training

Evacuation Marshal Training

Totals

Totals 131 5 1 20 1 5 163


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2.11.7 Radiation Protection The purpose of the iThemba LABS Radiation Protection Policy is to minimize the risk of worker and public exposure to the harmful effects of radiation employed at the laboratory. The main aims of the policy are: 1. To contribute to the development of a sound culture of risk management including occupational safety and

environmental conservation. 2. In particular, to provide appropriate radiation management systems that will enable compliance with

national regulatory requirements and best international practices. To comply with these aims, the Radiation Protection division continuously monitors the effects of potentially harmful ionising radiation on the public, staff and environment in and around iThemba LABS. Regular environmental samples are taken and measured to ensure iThemba LABS complies with the regulatory requirements of the Department of Health. Personal dosimetry is issued to all staff that may be occupationally exposed to ionising radiation and all radioactive waste is packaged and stored in accordance with the National Nuclear Regulatory guidelines and Waste Acceptance Criteria. At present, iThemba LABS has managed to contain all its waste products on-site. A programme is in place to eventually dispose of this waste at the National Waste Repository at Vaalputs in the Northern Cape.

Leak Test Service In terms of Article 3A of the Hazardous Substances Act of 1973, holders of radioactive sources must have their radioactive sources leak-tested annually to ensure that they are not damaged or leaking and causing a potential threat to the users or the public. The Radiation Protection Division of iThemba LABS provides a leak-test service for all radioactive source holders in the Western Cape. During the period April 2007 – March 2008 iThemba LABS performed 154 leak tests and generated 154 leak-test certificates. To ensure responsible disposal of old radioactive sources, the RP Division has also taken ownership of several small sources which will be absorbed into our radioactive waste programme.

Assistance for External Companies Part of being a centre of excellence entails providing specialized services for other radioactive source holders. In the last year, technical expertise and advice were dispensed to the following organisations:

• The Citrusdal Irradiator. The production of citrus fruit in the Citrusdal valley has been hampered by the presence of the False Codling Moth. The False Codling Moth lays its eggs in the citrus fruit which makes the fruit unsuitable for local consumption or export. As the use of pesticides is slowly being eradicated due to the harmful side effects of the chemicals a new method of reducing the Codling Moth population had to be introduced. Buoyed by the success of the SIT (Sterile Insect Technique) that is in use in the Hex River Valley, a company called XSIT has been formed. Using a large radioactive source, male moths are sterilised using high energy radiation. They are released into the Citrusdal Valley at a rate of 25 million per week.


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iThemba LABS’ involvement is to provide radiological expertise and training to the management and staff, and to provide an accurate dose-measuring system using chemical dosimeters to ensure that the correct amount of radiation is administered to the moths to ensure that they are sterilised.

• Cape Peninsula University of Technology (CPUT), Engineering Department. The Engineering department at CPUT has several in-line density and flow monitors that incorporate radioactive sources as part of their function. iThemba LABS was requested to perform leak-tests and give a brief talk on radioactivity, its uses and hazards to the lecturers at CPUT.

• Kirstenbosch Gardens The research facility at Kirstenbosch Botanical Gardens purchased a Troxler Soil Density / Moisture meter, containing Am/Be and 137Cs sources, for use in some experiments. The unit is no longer in use and presented a potential radiological hazard, and thus had to be disposed of. iThemba LABS offered to purchase the unit from Kirstenbosch Botanical gardens to be used as a training unit at iThemba LABS.

• University of Cape Town (UCT) [Health Sciences] The co-ordinator of Health Sciences students at UCT contacted iThemba LABS to present a course on radiation awareness, legal requirements and safe working methods with sealed and unsealed sources. The course was scheduled to be presented at iThemba LABS in early April.

• Stellenbosch University (US) [Health Sciences] Several Physics students requested RP Officer training from iThemba LABS to equip them for their eventual employment in the Radiation Protection field. The training is scheduled to be presented in April 2008.

Radioactive Waste Programme iThemba LABS has been a producer of low-level radioactive waste for many years. Due to various factors, none of the waste has been shipped to the National Waste Repository at Vaalputs, resulting in a 20-year backlog in the temporary holding area in the D Block basement. To relieve the pressure on the basement, two storage containers were purchased to store the sealed drums of radioactive waste until the application to finally dispose of it is approved. At present, 121 drums of Low Level waste have been processed and are awaiting shipment. Two additional containers have been purchased to store the subsequent waste produced during 2007/08. Negotiations have started regarding the disposal of two large 60Co sources. The IAEA has offered to remove and assist with disposal of all large radioactive sources in South Africa that are not in use. iThemba LABS identified two such sources, one in Cape Town and one in Gauteng.


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Radiation Exposure of iThemba LABS Personnel International guidelines have been developed to limit and control the amount of radiation that any individual worker may be exposed to. At iThemba LABS all personnel who may be exposed to radiation during the course of their employment are issued with a personal dosimeter. In addition, several members of staff who work with small amounts of high-activity liquids, particularly during the manufacture and dispensing of nuclear medicines, are issued with extremity dosimeters, usually worn on the finger. The doses accrued by these dosimeters are monitored on a monthly basis to ensure nobody exceeds the recommended limits. Highest Individual Dose – This graph displays the highest total body dose received by a member of staff in any single calendar month. The high peak in October 2006 is due to the production of 22Na. Any individual monthly dose above 4 mSv must be reported to the Regulator (DoH). Highest Individual Extremity Dose – This graph displays the highest total extremity or hand-dose received by a member of staff in any single calendar month. The high reading in April was a once-off exposure of a member of the Radionuclide Production Group, exposures above 40 mSv must be reported to the Regulator (DoH). Worker Monthly Dose – This graph displays the total dose to all staff on a monthly basis. The graph does not take into account the fluctuating number of radiation workers, which has steadily increased during this period. The peaks in June and the Aug-Sep period are due to maintenance on the Vertical Beam Target Station and the production of 22Na sources for export.

Training Mr I Bapela from the North West University is doing Honours in Applied Radiation Science and Technology and was supervised by Mr T Modisane for a one-week project. The project was titled: “Radiometry of water from iThemba LABS dams”.

02468

101214

Apr Jun Aug Oct Dec Feb

Dos

e (m

Sv)

05

1015202530

Apr Jun Aug Oct Dec Feb

Dos

e (m

Sv)

0

0.5

1

1.5

2

Apr Jun Aug Oct Dec FebD

ose

(mSv

)

iThemba LABS Annual Report 2008 Science and Technology Awareness Group

64

2.12 Science and Technology Awareness Programme The strategic objective of the Science and Technology Awareness Programme (STAP) at iThemba LABS is to create the required perceptions related to iThemba LABS’ Vision amongst the various target groups with which we want to interact, as illustrated in the accompanying diagram.

iThemba LABS wants to be the primary centre for research, training and service expertise in radiation medicine and accelerator-based science and technology. The STAP will assist in the attainment of these visionary goals by:

1. Making learners aware of the importance of science and technology in their everyday lives through science shows, workshops, career days and job-shadowing.

2. Exposing undergraduate students enrolled in science programmes to the research opportunities at iThemba LABS through public lectures, vacation jobs, and research days.

3. Developing the content knowledge of teachers through workshops organised by the education department.

4. Creating an environment within which postgraduate students can develop to their full potential. 5. Equipping staff with the necessary skills and content knowledge to effectively interact with learners,

students, teachers and the general public. 6. Effectively communicating with the general public through printed media, radio, and television. 7. Promoting the activities within the facility through public lectures and site-tours.

The activities can be broadly grouped as science engagement and science education. The STAP-group currently consists of three permanent members of staff with a dedicated cost centre from which all activities are financed. Postgraduate students are involved on a contract basis to assist with the management of a tutor

STAP

Learners

Students

StaffTeachers

Public

iThemba LABS Annual Report 2008 Science and Technology Awareness Group

65

programme amongst learners from local high schools. The accompanying table gives an overview of the activities that have been undertaken since January 2008 as well as activities that are planned for the not too distant future.

Activity Description Staff development There is a real need to continuously invest in the development of staff at

iThemba LABS. It is for this reason that opportunities need to be created/sought that will address the skills shortage, but also develop staff to a higher level of competency. Staff members have been involved in various teacher training courses, and have also participated in various seminars and conferences (both locally and abroad).

Site-visits Learners and teachers from local high schools are encouraged to visit the facility.

What’s up at iThemba LABS

This intervention is intended to expose undergraduate students to the activities at iThemba LABS through public lectures, site-tours and research days.

Holiday programme An intervention aimed at interacting with learners (grades 1-11) during school holidays. The activities will include workshops, Olympiads and competitions, as well as design and manufacturing.

Summer/Winter Schools An intervention aimed at addressing the academic needs (mathematics and physical science) of grade-12 learners during school holidays. This provides postgraduates with a wonderful opportunity to “give to the community” (social responsibility).

Career days An intervention aimed at exposing learners to different careers associated with science, mathematics and engineering. Members of staff will be targeted to showcase various careers during these days. Learners will get an opportunity to complete a questionnaire indicating possible “high-interest” fields.

Teachers’ day An intervention (at least twice a year) aimed at developing teachers in terms of their content and pedagogical knowledge. Teachers will be exposed to best practice associated with current topics included in the National Curriculum Statement (NCS).

Women’s Day A one-day intervention aimed at creating an awareness of science amongst female learners.

Public lectures Creating a forum where the general public are exposed to current science through informative plenary lectures once every month.

Science communication Making use of the media (web, printed, TV, radio) to make the general public aware of the activities at iThemba LABS. Accepting invitations as invited speakers and judges at science Expo’s.

Science shows and workshops

A concerted effort to take science to the “people” by presenting science shows and workshops at schools in the Western Cape and Gauteng. Staff should be encouraged to take part in national and international events such as National Science Week, the annual science festival in Grahamstown (Scifest), the Namibian National Science Week (NAM.SC.I), and other similar events.

Exhibitions Interactive exhibitions are needed to expose visitors to the activities at iThemba LABS (Western Cape and Gauteng). Branded items (brochures, clothing, stationary).

Job-shadowing An intervention aimed at providing learners and students with the opportunity to spend time within a scientific environment – a day (or more) in the life of a scientist.

Training centre Creating an environment within which learners and students can be exposed to “real science”.


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3. SCIENTIFIC AND TECHNICAL REPORTS


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3.1 Medical Radiation Group

3.1.1 Proton Therapy Clinical Programme Nine patients were treated on the 200 MeV horizontal beam proton therapy facility during the 2007/08 financial year (Table 8). We were hoping to treat more patients, but the clinical programme was suspended from January until April 2008 due to Eskom’s failure to provide a reliable power supply. To avoid unexpected power cuts iThemba LABS concluded an agreement with Eskom, whereby the cyclotron is shut down each Monday morning. This has reduced proton therapy to just three days per month, nominally on the third weekend of each month, excluding the scheduled shutdown months of July, December, and January.

1993 - 2008 April 06 - March 07 April 07 - March 08 Arteriovenous malformation 81 1 2 Angioma 15 Acoustic neuroma 64 3 3 Pituitary adenoma 62 1 Meningioma 41 Brain tumour 60 Brain metastasis 33 Paranasal sinus tumour 23 Skull base tumour 28 1 Orbital & eye tumour 33 1 3 Craniopharyngioma 14 Head & neck tumour 11 Prostate tumour 4 Other 31 Patient total 500 6 9

Table 8: Patients undergoing proton therapy, by diagnosis

3.1.2 Benign Intracranial Lesions Treated with Proton Therapy

There are many risks associated with surgery for benign intracranial lesions. Radiotherapy is often used for these lesions, particularly if surgery is incomplete or the lesion recurs post-surgery. Conventional photon radiotherapy is often not suitable for these lesions due to the high dose to normal brain tissue and resulting late effects of radiotherapy. This is particularly important if the lesion is close to critical structures such as the brainstem or cranial nerves, or if one is treating a young patient with a good prognosis. Proton beam radiotherapy is highly conformal with no dose distal to the proton range. Another significant advantage for proton beam therapy is that the integral dose is approximately half that of photon therapy (H. Suit, Int. J. Rad. Oncol. Biol., Phys. 2002). These factors make proton therapy ideal for benign intracranial lesions.


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The iThemba LABS results for the treatment of meningiomas, arteriovenous malformations, acoustic neuromas and cavernous angiomas are given below. [The proton doses are presented as single-fraction equivalent cobalt Gray equivalent doses (SFEcGyE).] The results compare favourably with those achieved at other institutions using radiosurgery or stereotactic radiotherapy, despite the fact that we generally treat larger lesions.

3.1.3 Clinical Results of Proton Therapy ARTERIOVENOUS MALFORMATIONS (AVM) [1, 2] Since 1993 a total of 96 patients with vascular lesions have been treated. Of those, 72 patients treated for an arteriovenous malformation were followed for long enough to merit inclusion in the study. The median follow-up was 4.8 years. The AVMs were grouped by volume: <14 cm3 (31 patients) and ≥14 cm3 (41 patients). Median volume treated was 15.6 cm3. The majority of patients were hypofractionated (2 or 3 fractions) and the median minimum target volume dose was 17.3 SFEcGyE. Analysis by volume group showed obliteration in 75% for volumes of 10-13.9 cm3 and 46% for volumes ≥14 cm3. Grade IV acute complications were observed in 3%. Transient delayed effects were seen in 15 patients (21%), becoming permanent in 3 patients. One patient also developed a cyst 8 years after therapy. Stereotactic proton beam therapy applied in a hypofractionated schedule allows for the safe treatment of large AVMs, with acceptable results. It is an alternative to other treatment strategies for large AVMs. [1, 2]

SKULL BASE MENINGIOMAS [2, 3] 28 patients with skull base meningiomas were treated stereotactically with protons. Both stereotactic radiotherapy (SRT, 16 or more fractions) and hypofractionated stereotactic radiotherapy (HSRT, 3 fractions) were used. 20 patients underwent proton HSRT, while 8 patients were treated with SRT. The median follow-up was 6.8 years. The median target volume for the HSRT group was 8.4 cm3 and the median minimum planning target dose was 17.2 SFEcGyE. The mean volume in the SRT group was 43.7 cm3, with ICRU reference doses ranging from 54 CGyE in 27 fractions to 61.6 CGyE in 16 fractions. In the HSRT group 90% of patients remained clinically stable or improved, while the remaining 2 patients deteriorated. Of the 8 SRT patients, 5 were clinically better and 3 remained stable. Thus all SRT patients achieved radiological control. Overall the proton therapy was well tolerated. Two patients (10%) developed late neurological sequelae. One patient had an anticipated neurological deficit secondary to tumour involvement, and another patient’s previous surgery was an additional risk factor. In conclusion, proton irradiation is effective and safe in controlling large and complex shaped skull base meningiomas. ACOUSTIC NEUROMAS [4] A total of 64 patients with acoustic neuromas have been treated with hypofractionated (3 fractions) proton therapy. Of those, 48 were evaluable and the median follow-up was 5.3 years. The mean tumour volume was


69

7.0 cm³ and the mean minimum planning target dose was 13.5 SFEcGyE. Radiological control at 5 years was 93%. 61% of patients had preservation of hearing at 5 years. Facial nerve function preservation was 87% at 5 years and trigeminal nerve function preservation was 91% at 5 years. Stereotactic proton beam radiotherapy achieved radiological control similar to that in most radiosurgical series, with comparable long-term preservation of cranial nerve function, despite somewhat larger volumes having been treated. CAVERNOUS ANGIOMAS [5] A total of 96 patients with vascular lesions have been treated. Of those, 13 patients suffered from a cavernous angioma and were followed sufficiently long after treatment for research purposes. The median follow-up was 36 months. Median volume treated was 3.4 cm3. Most patients were treated with 2 or 3 fractions and the median minimum target volume dose was 15.1 SFEcGyE. Treatment was well-tolerated with no acute side-effects. 89% of patients had no further bleeds and the angioma occluded in 31% of patients. Two patients had late neurological complications. The role of radiosurgery for angiomas is still developing. This limited series shows that proton therapy can be of value in the non-surgical management of cavernous angiomas.

3.1.4 Neutron Therapy Clinical Programme

1988 – 2008 April 06 - March 07 April 07 - March 08 Head & Neck carcinoma 211 3 3 Salivary gland carcinoma 499 18 16 Soft tissue sarcoma 131 2 4 Breast carcinoma 266 41 32 Cervical carcinoma 5 Bronchus carcinoma 6 Uterine sarcoma 93 Mesothelioma 21 Paranasal sinus carcinoma 63 6 3 Bone sarcoma 110 1 Malignant Melanoma 64 Other 55 Patient total 1524 70 59

Table 9: Patients undergoing neutron therapy, by diagnosis


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Neutrons are produced by the reaction of 66 MeV protons on a beryllium target in the head of the neutron therapy gantry. The beam is collimated and further shaped, initially by tungsten blocks and subsequently by a multiblade trimmer. The beam characteristics are similar to those of an 8 MV photon beam. The advantage of neutron therapy is in its biological effects. Tumour cells in the resting phase of the cell cycle (G0) are less sensitive to photons, whereas with neutron therapy there is less variation in sensitivity during the different phases of the cell cycle. Therefore neutron therapy would be the preferred treatment for slowly growing tumours having a large number of cells in G0. Only 59 patients were treated on the isocentric neutron unit during the year (Table 9). There has been a significant drop in patient numbers, which is attributable to the unreliable power supply, as mentioned earlier. Therapy started a month after the completion of shutdown. Neutron therapy is given in 3 fractions a week, Tuesdays to Thursdays. 3.1.5 Clinical Results of Neutron Therapy The results achieved for neutron treatment of salivary gland tumours, cervical squamous carcinoma lymphadenopathy, maxillary antrum tumours, inoperable breast cancer, chordoma, mesothelioma, uterine sarcoma, and soft tissue sarcoma were reviewed in iThemba LABS Annual Report 2006/07. More detailed information may be found in references 6-14, below. References 1. F.J.A.I. Vernimmen, J.A. Wilson, R. Melvill, et al. Stereotactic proton beam therapy for intracranial

arteriovenous malformations. Int. J. Rad. Oncol. Biol. Phys. 62, No. 1 (2005) 44. 2. S.M. de Canha et al. Particle therapy in South Africa - iThemba LABS – updated data presented at ESTRO

(European Society for Therapeutic Radiology & Oncology) Meeting on Physics & Radiation Technology for

Clinical Radiotherapy, Barcelona, Spain, Sept 2007.

3. F.J.A.I. Vernimmen, J.K. Harris, J.A. Wilson, R. Melvill, et al. Stereotactic proton beam therapy of skull base meningiomas. Int. J. Rad. Oncol. Biol. Phys. 49, No. 1 (2001) 99.

4. F.J.A.I. Vernimmen, D. Eedes. The role of stereotactic radiosurgery in the management of acoustic neuromas. Ear, Nose and Throat Congress, Sun City, Nov 2007.

5. F.J.A.I. Vernimmen, J.A. Wilson, S. Fredericks. Stereotactic protonbeam therapy for intracranial cavernous angiomas. PTCOG 45 (Particle Therapy Co-operative Group), M.D. Anderson Cancer Centre, Houston,

Texas, USA, Oct 2006. 6. C.E. Stannard et al. Salivary gland tumours treated with fast Neutron therapy at iThemba LABS.

International Workshop on Fast Neutron Therapy, Essen, Germany, 14-16 September 2006.

7. C.E. Stannard et al. Salivary gland tumours treated with fast Neutron therapy at iThemba LABS. 13th National Congress of the SA Society of Clinical & Radiation Oncology & SA Society of Medical

Oncology, Drakensberg, South Africa, 27 April – 1 May 2007.

8. J.J.P. Maurel, C.E. Stannard, et al. Fast Neutron radiotherapy for the treatment of inoperable N3 cervical adenopathy in patients with squamous carcinoma of the head and neck. 13th National Congress of the SA


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Society of Clinical & Radiation Oncology & SA Society of Medical Oncology, Drakensberg, South Africa,

27 April – 1 May 2007. 9. P. Kraus, C.E. Stannard, et al. Retrospective review of locally advanced maxillary antrum tumours treated

with fast neutrons. 13th National Congress of the SA Society of Clinical & Radiation Oncology & SA Society

of Medical Oncology, Drakensberg, South Africa, 27 April – 1 May 2007.

10. E.M. Murray, G. Schmitt, et al. Neutron vs photon radiotherapy for local control in inoperable breast cancer. Strahlentherapie und Onkologie 181 (2005) 77.

11. E.M. Murray, G. Schmitt, S.M. de Canha, et al. Neutron vs photon radiotherapy in locally advanced breast cancer with or without metastases. International Workshop on Fast Neutron Therapy, Essen, Germany,

14-16 September 2006.

12. S.M. de Canha, F.J.A.I. Vernimmen, C.E. Stannard et al. Neutron radiotherapy for chordomas. International

Workshop on Fast Neutron Therapy, Essen, Germany, 14-16 September 2006. 13. K. Marszalek, S.M. de Canha, F.J.A.I. Vernimmen. Neutron radiotherapy for mesothelioma – a pilot study.

International Workshop on Fast Neutron Therapy, Essen, Germany,14-16 September 2006. 14. A.L. van Wijk, C.E. Stannard, et al. The neutron therapy clinical programme at the National Accelerator

Centre (NAC). Bull. Cancer / Radiotherapy, Vol. 83 (Suppl 1) (1996) 87s.

3.1.6 Monte Carlo Simulations Second proton therapy nozzle MCNPX simulations of the scattering system of the second proton therapy nozzle were completed in June 2007. In the final design (Figure 26) the carousel of contoured bimaterial scatterers (CBSs) was shifted 50 cm further upstream of the isocentre and a cassette of pop-up scattering foils was designed for use 46 cm upstream of the carousel. MCNPX simulations indicated that the thicknesses of the thin foils and/or lead parts of the CBSs require adjustment, but no major problem was encountered across the range of specified fields. Ideally 11 pop-up foils having a binary thickness series would be used, the minimum having a scattering power equivalent to a layer of

lead 4 µm thick. Such thin foils can be made from a polymer. A set of occluding rings can be designed for treatment depths > 24 cm.

Figure 26: The final scattering system, August 2007


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MCNPX simulations to assess shielding were continued for research purposes, as the secondary dose delivered by scattering systems is debated. It was found that a limonite concrete wall 25 cm thick protects radiation-sensitive items that are far off-axis better than a polyethylene wall of the same thickness, whereas the opposite is true for non-targeted regions of the patient’s body, close to the beam axis. The difference is due to the RBE of 3.0 for neutron radiation. A limonite concrete wall with a boronated polyethylene collar around the beam axis is to be investigated. Comparison of MCNPX, GEANT4, and real measurements of Coulombic scattering Over the years the Medical Radiation Group (Med Rad) has used the MCNPX Monte Carlo code [1,2] to aid the modification of existing equipment and develop new items. During 2007 GEANT4 [3] was installed on several computers by a postgraduate student, Mr Jonathan Mbewe. He is investigating how the water phantom dose distributions predicted by GEANT4 and MCNPX simulations differ for a range of scattering foils of different thicknesses and atomic numbers, interposed in the current proton therapy nozzle over a range of degraded beam energies. During the year dose distributions were measured for steel, lead, and aluminium foils, using the thimble chamber used for proton therapy quality assurance. Dose distributions for polycarbonate and brass foils have yet to be measured. An existing GEANT4 simulation of a proton therapy nozzle [4] is also being converted to model Med Rad’s nozzle. It is hoped that the work will explain differences between simulated and measured dose distributions in terms of the different Coulombic scattering models of MCNPX [5] and GEANT4 [6], as well as their range straggling models. This work should make it easier to select GEANT4 or MCNPX for specific simulations. Improvements to MCNPX simulations of the current proton therapy nozzle At the start of 2007 it was discovered that the Annular Multilayer Faraday Cup (AMFC) between the carbon wedge degrader and range modulator, causes the lateral shoulders of MCNPX dose distributions to droop, as evidenced by thimble chamber measurements. The AMFC was intended to monitor the range of the proton beam during dose delivery, but is defunct due to the problem of housing it in a vacuum. Simulations suggest that lateral dose distributions would be improved by removing it. This change would require recommissioning of the Treatment Planning System, a major task. MCNPX simulations for the Varian Eclipse Treatment Planning System Accurate dose distributions were required for beta-testing of the Varian Eclipse Proton Therapy TPS, prompting a detailed review of the geometry and materials of the current nozzle. MCNPX simulations were updated accordingly and 43 simulations were undertaken in support of the TPS beta-testing. One set of simulations was performed without the AMFC (see above), but including the current occluding ring scattering system and axially-retractable range monitor. New proton therapy range monitor Fourteen simulations were conducted to test configurations of a new range monitor to replace the AMFC (see above). Ideally, data would be sampled simultaneously from all the channels connected to an axially-arranged set


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of thin energy-degrading plates; the penetration of the proton beam through such a Faraday Cup produces a charge upon each plate corresponding with its axial position in a depth-dose curve. Optimal range measurement demands a 48-channel AMFC, but the axial space created by removing the current AMFC is too short for such a device. MCNPX simulations suggested that a 32-channel solution may be feasible. This solution would require a wider central aperture than that of the defunct AMFC, to prevent interference with dose distributions. A look-up table would be essential to compensate for variable scatter from the double wedge energy degrader, and for range interpolation between the foils. It would be difficult to house this device inside a vacuum at the existing position of the AMFC. Thus an alternative solution was investigated: that of replacing the existing occluding ring with a 48-channel AMFC having annular foils with the same internal and external diameters as the ring. MCNPX simulations confirmed that a 48-channel device would produce acceptable dose distributions, despite having an axial length 28 mm longer than the ring it replaces. (The central occluding rod would also be lengthened.) There is enough space at this position to house such an AMFC in a vacuum can with Havar entry and exit windows. Investigation of dose deposition in neutron therapy Extensive use has been made of the cross-section libraries of MCNPX [2] to study the major interactions of neutrons in a four isotope model of human tissue. This was immensely rewarding from an educational point of view. A research paper was written based upon this work. It is to be subdivided and rearranged for publication. References 1. J.F. Briesmeister. MCNP: A general Monte Carlo N-Particle Transport Code. Los Alamos National

Laboratory Report LA-13709 (2000).

2. M.B. Chadwick, P.G. Young, S. Chiba, S.C. Frankle, G.M. Hale, H.G. Hughes, A.J. Koning, R.C. Little, R.E. MacFarlane, R.E. Prael, L.S. Waters. Cross Section Evaluations to 150 MeV for Accelerator-Driven Systems and Implementation in MCNPX. Nuclear Science and Engineering 131(3) (1999) 293.

3. S. Agostinelli et al. GEANT4 – A simulation toolkit. Nuclear Instruments and Methods in Nuclear Research

A 506 (2003) 250. 4. G.A.P. Cirrone. GEANT4 simulation of an ocular proton therapy beamline. International Conference on

Advanced Technology and Particle Physics; Como, Italy; 6–11 Oct 2003.

5. B. Rossi and K. Greisen. Cosmic-Ray Theory. Reviews of Modern Physics 13 (1941) 262. 6. H.W. Lewis. Multiple scattering in an infinite medium. Physics Review 78 (1950) 526.


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3.1.7 Proton Therapy Projects 2007/2008 Replacement SPG System for the old vault Several new features have been added to the replacement SPG system over the course of the year. We have significantly improved the distortion model, made improvements to the calibration code, improved the outlier detection and recovery used in the SVD routine, and replaced the serial interface to the old chair control system with a more flexible network-based system that can talk to both the new chair control system and the robot control system. New Chair Control System The new chair control system has been fully implemented. Various hardware issues with the chair have been resolved during the course of its development as well. The new system is more accurate than the old system, due to the improved calibration procedure and the improved motor electronics, and is also much smoother, as it implements more controlled accelerations and decelerations. The new system also allows multiple axes to be used simultaneously, which significantly speeds up the time taken to do large movements. Robot Positioning System Much of the work has focused on the network communication requirements for the robot system. The robot presents the same interface to the SPG system as the chair control system, so there is no need for special logic on the SPG side. The SPG system can successfully communicate with the robot control system. Work is progressing on integrating the previous work on the safety system with the robot control system. The robot cover had to be adjusted to accommodate the robot’s range of motion, but it is now properly installed. Digital X-ray System There has been considerable work on the hardware side. The hoist mechanisms required have been installed in both vaults, and the electronics required to ensure that the X-ray acquisition is properly synchronized with the X-ray generator have been completed. Since the digital X-ray system requires generating numerous digitally reconstructed radiographs (DRR), which are computationally expensive, Cobus Carstens has been looking at the different algorithms and ways of implementing them efficiently as part of his M.Sc. thesis. By using a parallel implementation of the light field method, the DRRs can be computed fast enough for our requirements.


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3.2 Radionuclide Production 3.2.1 Radio-iodine Labelling of a Small Chemotactic Peptide, Utilizing Two Different

Prosthetic Groups: A Comparative Study D.D. Rossouw iThemba LABS, P.O. Box 722, Somerset West, South Africa The use of radio-iodinated succinimidyl-iodobenzoates as pre-labelled prosthetic groups in the radio-iodination of antibodies and peptides is becoming increasingly popular [1,2]. In this study the utilization of a radio-iodinated iodovinyl ester unit as an alternative conjugation agent for the preparation of a radio-iodinated peptide conjugate (peptide-[123I]I-PEA), was investigated. This conjugation agent was previously used to prepare an iodovinyl-antibody conjugate [3]. A pre-synthesized precursor of this agent was radio-iodinated and purified on a small column containing C18 silica gel chromatographic material. The labelled product was eluted with dimethylformamide and the eluate used directly in the conjugation step. Similar methodology was applied to a comparative radiosynthesis of an iodobenzoate analogue (peptide-[123I]IB). The influences of various reaction parameters on conjugation yields were investigated while maintaining a fixed amount of peptide. At high activity levels (more than 200 MBq) the conjugation yield of peptide-[123I]I-PEA was very sensitive to relatively large reaction volumes and increased amount of base. By optimising these parameters, the formation of radiochemical impurities was minimized. Under similar conditions, peptide-[123I]I-PEA formed much faster than peptide-[123I]IB. Sep-Pak C18 purification afforded both conjugates with radiochemical purities in excess of 98% and free from un-reacted peptide. Recovered conjugation yields of peptide-[123I]I-PEA in 50% ethanol were in excess of 60%, while those for peptide-[123I]IB were less than 40%. These features could make a radiolabelled iodovinyl unit an attractive alternative for the preparation of radiolabelled peptide conjugates, provided that the latter’s biological properties remain intact. References

1. I. Al-Jammaz, B. Al-Otaibi and J.K. Amartey. Appl. Radiat. Isot. 60 (2002) 743. 2. O.R. Pozzi, E.O. Sajarof and M.M. Edreira. Appl. Radiat. Isot. 64 (2006) 668. 3. S.W. Hadley and D.S. Wilbur. Bioconjugate Chem. (1990) 154.


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3.2.2 Influence of Carrier Iodide on Radiolabelling Efficiencies of Various Organic

Compounds D.D. Rossouw1 and L. Taleli1,2 1iThemba LABS, P.O. Box 722, Somerset West, South Africa 2University of Lesotho, Maseru, South Africa Radioisotope exchange is one of the most common labelling techniques to produce radiopharmaceuticals due to its simplicity. At iThemba LABS this technique is used to produce [123I]mIBG on a routine basis. Other radiopharmaceuticals, such as o-[123I]iodohippuran ([123I]oIHA) and p-[123I] iodophenylpentadecanoic acid ([123I]pIPPA), previously produced at iThemba on a non-routine basis, are also produced via this route. For isotope exchange labelling it is crucial that radio-iodine should be no-carrier-added to ensure optimal labelling yields. Due to the utilization of a sodium iodide target to produce 123I at iThemba LABS, recovered radio-iodide solutions have in the past occasionally been contaminated with traces of stable carrier iodide. This problem has been rectified over the years, but could still pose a threat. It is important to know how much carrier iodide can be tolerated to still ensure satisfactory labelling efficiencies. A project was therefore initiated in order to establish this experimentally, as experimental results often differ from theoretically calculated values. The mentioned three organic compounds were used as model compound precursors for the investigation. The labelling methods used were roughly based on the methods of Verbruggen [1-3]. Various amounts of stable iodide were deliberately included in reaction mixtures and labelling yields were analytically determined by means of high performance liquid chromatography. Experiments were repeated in order to add adequate statistical value to the results obtained. The results in Figure 27 show that the labelling efficiencies of [123I]mIBG and [123I]oIHA start decreasing at a carrier iodide:precursor molar ratio of between 0.01 and 0.02, while that for [123I]pIPPA

started decreasing between 0.03 and 0.05. The labelling efficiency of [123I]mIBG also decreases faster than that of the other two. The exact reason for the different tendencies is not entirely clear but the latter could be ascribed to chemical structure variation as well as solvent effects. The results nevertheless enable one to predict labelling efficiencies more accurately should radio-iodine solutions be contaminated with traces of carrier iodide, and the latter be accurately quantified.

References

1. R.F. Verbruggen. Appl. Radiat. Isot. 37 (1986) 1249. 2. R.F. Verbruggen. Appl. Radiat. Isot. 38 (1987) 303.

3. R.F. Verbruggen. Appl. Radiat. Isot. 39 (1988) 1097.

Figure 27: Radiochemical yields of [123I]mIBG, [123I]oIHA and [123I]pIPPA as a function of carrier iodide: precursor molar ratios.


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3.2.3 Evaluation of iThemba LABS 68Ge/68Ga Generator for Radiolabelling W.A.P. Breeman1, D.D. Rossouw2 and C. Naidoo2 1Erasmus Medical Centre, Rotterdam, The Netherlands 2iThemba LABS, P.O. Box 722, Somerset West, South Africa The 68Ge/68Ga generator provides an excellent source of the positron-emitting 68Ga [1]. One of its applications is in the radiolabelling of suitably derivatised peptides, the so-called DOTATOC and DOTATATE, which are used in positron emission tomography (PET) imaging of various tumours [2]. The radiometal is incorporated into the DOTA “cage”, a cyclic structure containing four nitrogen donor atoms that hold the metal in position by means of dative covalent bonds. Today, the most common commercially available generator of this type is based on a titanium dioxide solid phase [3]. iThemba LABS has recently developed a tin dioxide based generator in which there is already commercial interest. For peptide labelling trace amounts of other metal cations should be excluded in order to ensure maximal radiochemical yields [4]. For this and other reasons generator eluates need to be properly evaluated for their suitability for radiolabelling. During March 2008 a scientist from the Netherlands visited iThemba Labs to do an on-site evaluation of our generator. The generator was eluted with 0.6 M hydrochloric acid on a daily basis, and labelling experiments were performed with the eluates, using DOTATATE as the labelling precursor and sodium acetate as the buffer system. The pH of the mixture was approximately 3.5-4.0. Quality control (QC) of the labelled product was done by means of Instant Thin Layer Chromatography (ITLC) as well as radio-High Performance Liquid Chromatography (radio-HPLC). Initial QC results with ITLC showed poor labelling efficiency, but it was soon discovered that these results were false due to a too high moisture content of the ITLC silica gel-containing strips. This had resulted in a poor separation of labelled peptide from free radiogallium on the strip. After drying the strips, the results were good. This was also confirmed by HPLC. To conclude, the iThemba generator appears to be suitable with respect to the labelling efficiency of its eluate. Further experiments will be pursued at iThemba LABS in order to explore various other reaction parameters. References: 1. K.P. Zhernosekov, D.V. Filosofov, R.P. Baum, P. Aschoff, H. Bihl, A.A. Razbash, M. Jahn, M. Jennewein

and F. Rösc. J. Nucl. Med. 47 (2007) 1741.

2. W.A.P. Breeman, M. de Jong, E. de Blois, B.F. Bernard, M. Konijnenberg, E.P. Krenning. Eur. J. Nucl. Med.

Mol. Imaging 32 (2005) 478.

3. A.A. Razbash, Yu. G. Sevastianov, N.N. Krasnov, A.I. Leonov, V.E. Pavlikhin. Proceedings of the

5th International Conference on Isotopes, 5ICI, Brussels, Belgium (2005). Bologna, Italy: Medimond;

(2005) 47. 4. G. J. Meyer, H. Mäcke, J. Schuhmacher, W. H. Knapp and M. Hofmann. Eur. J. Nucl. Med. Mol. Imaging 31

(2004) 1097.


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3.2.4 Tandem Targetry Development for the Vertical Beam Target Station (VBTS)

G.F. Steyn1, C. Vermeulen1, E. Isaacs1, S. DeWindt1, D. Saal1, H.P. Burger2, C. van Rooyen2, F.C. de Beer3 and H. Knox4 1 iThemba LABS, P. O. Box 722, Somerset West 7129, South Africa 2 National Laser Centre, CSIR, P. O. Box 395, Pretoria, 0001, South Africa 3 Nuclear Technology Division, Necsa, P. O. Box 582, Pretoria, 0001 4 EB Welding CC, Pelindaba, P. O. Box 582, Pretoria, 0001 Two kinds of tandem targetry are currently in routine use on the Vertical Beam Target Station (VBTS) at iThemba LABS. A Mg/Ga tandem target was developed for the simultaneous production of 22Na/68Ge and a Rb/Ga tandem target for the simultaneous production of 82Sr/68Ge. All materials are natural (i.e. not enriched). The Mg and Ga are encapsulated in Nb and the Rb in stainless steel. Both Ga and Rb are metals with a low melting point, near room temperature (Ga: 29.8°C; Rb 38.9°C) thus they are always in a liquid state during bombardment. In contrast, the encapsulation metals have relatively high melting points (Nb: 2468°C; SS: nominally 1375°C for the grade used) to effectively contain the target material and to provide a barrier between the target material and the fast-flowing cooling water. Ga and Rb have other favourable properties for targetry. In contrast to their melting points, their boiling points are relatively high (Ga: 2403°C; Rb: 686°C). Their volume changes during solid to liquid phase transitions are minimal (Ga: -1.094%; Rb: +1.038%), thus the capsules can be filled completely without risk of stress-induced failure, a well-known phenomenon when using salts of these metals as target materials. The heat transfer between the liquid metal target material and capsule walls is excellent, thus these targets can withstand bombardments with high intensity proton beams over prolonged periods of time. In the case of Mg, encapsulation with an inert metal is essential, even though it has a relatively high melting point (648.8°C). Open Mg reacts with the cooling water at elevated temperatures and the target loses mass. Figure 28 shows a photograph of the tandem targets as one would see them when removed from their respective target holders. Bombardments are performed with beams of 66 MeV protons at nominally

250 µA intensity. The beam is stopped in the second target, thus 16.5 kW is deposited in only a few cubic

cm of material and the available surface to cool from

is very limited. Water cooling is provided in a 4π geometry in the form of 1 mm thick layers flowing over the major outer surfaces of the capsules, with a linear velocity of 30 to 35 m/s. The relatively high flow rate, at a pressure of 10 bar, is required to obtain a sufficient forced convection heat-transfer coefficient and to suppress surface boiling. (Note that the formation of a steam layer on a target surface can lead to the heat flux becoming critical, leading to sudden and catastrophic target failure.)

Figure 28: LEFT: Encapsulated Mg/Ga targets for the simultaneous production of 22Na/68Ge in the VBTS. RIGHT: Encapsulated Rb/Ga targets for the simultaneous production of 82Sr/68Ga in the VBTS. Note that these “inner assemblies” have been removed from their respective target holders. The beam direction is vertical and downwards. The inner diameter of the capsules is 40 mm.


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Figure 29 shows the relevant excitation functions and production energy windows. Not all the energy from the beam is available for radionuclide production as the target-holder entrance window, capsule walls and cooling water all constitute “dead” layers. A smaller energy window for 68Ge production in the Rb/Ga target maximizes the 82Sr yield. Production rates of nominally 9.3 MBq/μAh (82Sr) and 1.1 MBq/μAh (68Ge) are obtained with the Rb/Ga target, while the values for the Mg/Ga target are 2.9 kBq/μAh (22Na) and 1.7 MBq/μAh (68Ge), respectively.

Most of the technology needed to manufacture these high-performance targets does not exist at iThemba LABS. The individual components of the capsules are pressed from sheet (of 0.5 mm thickness) and/or machined at iThemba LABS. The welding of the capsules for the Rb targets is done by the National Laser Centre (NLC) of the CSIR in Pretoria [1], using state-of-the-art YAG-laser based welding equipment in combination with an advanced robotic positioning system. Note that a very high demand is put on the integrity of the welded joints, which should be even and fault-free. That quality was only achieved once the CSIR was consulted. Empty capsules are shipped to MDS Nordion in Vancouver, Canada, for filling with the Rb metal, then shipped back to iThemba LABS, ready for bombardment. Note that these capsules are provided with Swagelok fittings (having screw-on caps) through which the highly reactive Rb metal is injected in an inert argon atmosphere. For the manufacture of the capsules for the Mg and Ga targets, other requirements make electron-beam (EB) welding the technology of choice: These capsules are not provided with Swagelok fittings as the target material cannot be introduced at a later stage into “empty” capsules. Instead, the target material is sealed into the capsule at the time it is welded together. Since EB welding is done in vacuum, air from the atmosphere is effectively removed from the capsule. This is important, as trapped air can expand when targets reach elevated temperatures during bombardment, which can lead to pressure-induced capsule rupture. The EB welding of capsules for iThemba LABS is done by EB Welding CC, Pelindaba. Both X-ray and neutron radiography techniques have been investigated for purposes of non-destructive evaluation of the integrity of welded seams on target capsules. While not much success was obtained with X-ray radiography, neutron radiography shows tremendous promise. Figure 30 shows a few results from an evaluation

Figure 29: Excitation functions (a) for the production of 68Ge and 82Sr and (b) for the production of 68Ge and 22Na. The production energy windows as implemented for VBTS targetry are indicated by the arrows.


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done by means of 3D thermal neutron tomography on a Rb-target capsule, performed by the South African Radiography (SANRAD) facility at the SAFARI-I nuclear reactor [2]. By obtaining images of an object by neutron transmission from many angles, an image can be reconstructed from its various projections. Figure 30 (a) shows such a reconstruction, while (b) and (c) shows various cuts made in the frontal and axial directions, respectively. Slices in the axial, frontal and sagittal directions are shown in (d), (e) and (f), respectively. In this particular study, 247 frontal, 538 axial and 468 sagittal slices were generated, making it possible to investigate the welded seams extensively. In practice, these images can be enlarged to fill an entire computer screen.

References

1. African Fusion (Ed. J. Warwick), the official magazine of the South African Institute of Welding, Crown Publications, February 2008 edition, p. 31. Available from URL: http://www.crown.co.za/africanfusion.html.

2. F.C. de Beer. Nucl. Instrum. and Meth. A 542 (2005) 1.

Figure 30: Reconstructed image (a) and reconstructed images showing selected cuts (b and c) of a target capsule, obtained by means of thermal neutron tomography. Axial, frontal and sagittal cuts are shown in (d), (e) and (f), respectively.

http://www.crown.co.za/africanfusion.html


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3.2.5 Matching a 66 MeV Proton Beam to 18 MeV Targetry for the Production of 18F C. Vermeulen, G.F. Steyn, C. Naidoo, D. Saal and J. Crafford iThemba LABS, PO Box 722, Somerset West 7129, South Africa The 18F-FDG production facility at iThemba LABS utilizes an enriched water target (H218O) which was purchased commercially. The IBA standalone target (SAT) system was selected, since this was considered to be the most compatible to incorporate into an existing bombardment station (Babe) which was originally built for semi-permanent targets and was at one time used to accommodate an experimental Ne gas target for 18F production. A complication, however, was that the water target was designed to accept an external proton beam of 18 MeV. Although the separated sector cyclotron can indeed deliver primary proton beams of 18 MeV, the rather long duration of such additional energy changes would have negatively affected the routine production of other radioisotopes, which is exclusively based on the 66 MeV proton beam shared with neutron therapy. The only feasible option was to degrade and reshape the 66 MeV beam. The first approach was to mount a water-cooled, solid aluminium degrader directly upstream from an unmodified IBA target. Since the IBA target was supplied with an integral entrance collimator, it seemed reasonable to retain it but to keep the distance between the degrader and collimator as short as possible, as it was known that the degraded beam would obtain a significant radial spread due to Coulomb interactions. Tests with first beam immediately indicated that the radial spread was too severe for such a configuration, as only nominally 20% of a well-focused beam entered the enriched water cavity, a fact later confirmed by performing beam spread calculations with the computer code SRIM [1]. It was clear that modifications to the original IBA target system were unavoidable. It was also realized that the IBA collimator had to be permanently removed in order to effectively reduce the distance between the enriched water cavity and the degrader.

Several ideas were considered in the design of an integrated degrader/collimator unit which could be mounted in very close proximity to the enriched water cavity. It was also important that the degrader/collimator unit had to be electrically insulated from the target body, as beam current had to be measured independently on these components to establish the percentage of beam entering the enriched water cavity. A novel idea was pursued to

Figure 31: LEFT: Design of the initial degrader/collimator unit coupled to the IBA entrance collimator and target. RIGHT: Design of the final degrader/collimator unit. Note that the original IBA entrance collimator had been discarded.


82

obtain the bulk of the energy degradation with the cooling water. This led to a marked reduction in the radial beam spread. An added bonus of the new design was that the residual activation of the unit would be much less, as the cooling water could be drained away using compressed air, thus reducing the dose to the operator who has to service the target. Figure 31 shows the details of the initial and final degrader/collimator and target configurations and Figure 32 shows the corresponding calculated beam profiles. With the final design, >80% of the beam enters to the enriched water cavity.

To measure the energy of the beam entering the target cavity, a stack of Cu monitor foils [2] was activated with the degraded beam. By placing the foils in the beam stop provided by IBA for setting up the target, it was possible to measure the energy in the exact location of the enriched water cavity. The results are shown in Figure 33. It is clear that the mean energy of the degraded beam has the desired value of 18 MeV. The pressure inside the enriched water cavity is a sensitive diagnostic of the condition of the target during bombardment and is monitored continuously. The pressure-versus-current curve provided by IBA for normal operation is shown in Figure 34, together with values measured at iThemba LABS. The good agreement is an indication that the target behaves as it should, thus acceptable matching with the degraded beam was achieved. References 1. J. Ziegler, SRIM-The Stopping and Range of Ions in Matter. Available from URL: http://www.srim.org. 2. K. Gul et al. IAEA-TECDOC-1211, IAEA, Vienna, May 2001. Available from URL:

http://www-nds.iaea.org/medical/. (last updated 2005).

Figure 34: The solid line is the pressure-versus-current curve provided by IBA. The square symbols are the values measured at iThemba LABS.

Figure 33: Stacked-foil activation measurements performed to obtain the mean beam energy at the entrance to the enriched water cavity. The curve is a standard 65Zn monitor excitation function [2] recommended by the IAEA, while the symbols are values measured at iThemba LABS.

F-18 SAT Pressure Graph

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Figure 32: The beam profile at the entrance of the target cavity, as calculated using the SRIM code for (a) the initial degrader/collimator design and (b), the final degrader/collimator design.

http://www.srim.org

http://www-nds.iaea.org/medical/


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3.2.6 New Cross Section Measurements for the Production of the Medically Interesting

Radionuclides 75, 76, 77, 80mBr I. Spahn1, G.F. Steyn2, C. Vermeulen2, Z. Kovács3, F. Szelecsényi3, M.M. Shehata1, S. Spellerberg1, B. Scholten1, H.H. Coenen1 and S.M. Qaim1

1 Institut für Neurowissenschaften und Biophysik: Nuklearchemie (INB 4), Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany 2 iThemba LABS, P.O. Box 722, Somerset West 7129, South Africa 3 Cyclotron Department, ATOMKI, H-4026, Bem tér 18/C, Debrecen, Hungary There is a longstanding interest in the application of radioisotopes of bromine in nuclear medicine. Whereas the two lighter isotopes 75Br (T½ = 1.6 h) and 76Br (T½ = 16.0 h) are useful for Positron Emission Tomography (PET), the Auger electron emitting radionuclides 77Br (T½ = 57.0 h) and 80mBr (T½ = 4.4 h) can be applied in internal radiotherapy [1, 2]. In particular, 76Br already finds application in radiolabelling of antibodies for tumour imaging [1]. The radionuclide 77Br is discussed as a possible subject for diagnosis and therapy [3]. The potential of 80mBr has as not yet been explored.

The cross section data for the production of 76Br and 77Br via low energy (p,n) reactions have been well determined [4]. Measurements on those two radionuclides as well as on 75Br have also been done up to proton energies of about 35 MeV [5]. In this work, those measurements were extended and seven other nuclear processes, namely 80Se(p,xn)75,76,77,80mBr and 78Se(p,xn)75,76,77Br were studied, using enriched target materials. The preparation of the highly enriched Se targets was done by sedimentation of fine Se metal powder onto thin Al backings [4, 6]. The samples were irradiated in a stacked-foil arrangement together with Ni and Cu monitor foils. The irradiations were done at the compact cyclotron CV 28 and the injector cyclotron of COSY of the Forschungszentrum Jülich, Germany, at up to 45 MeV. Irradiations in the higher energy region were done at the Separate Sector Cyclotron (SSC) of iThemba LABS. The proton energy range covered by the irradiations was

from 5 to 80 MeV. The produced radioactivity was measured non-destructively using HPGe detector γ-ray

spectrometry. For measurements on 80mBr, which emits only a low-energy γ-ray of 37 keV, a special low-energy solid state detector was used.

Extended experimental cross section data for the formation of 75,76,77Br via proton induced reactions on enriched 76Se and 77Se are now available for proton energies up to 80 MeV. The full excitation function for the 80Se(p,n)80mBr reaction has been determined systematically for the first time up to 20 MeV and cross sections have also been measured for the first time for the reactions 80Se(p,xn)75,76,77Br and 78Se(p,xn)75,76,77Br between 34.5 and 80.0 MeV. Thus the cross section databases have been significantly improved. The experimental results on the formation of 75,76,77Br were fitted with cublic spline curves and integrated in order to obtain the thick-target production rates of the above mentioned four radionuclides. Some of the results for 76Br and 77Br are shown in Figures 35 and 36, respectively.


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References

1. M.R. Zalutski. in Radiolabelled monoclonal antibodies for imaging and therapy (Ed: S. C. Srivastava), Plenum Press, New York, USA, (1988) p. 195

2. R.C. Mease, O.T. DeJesus, S.J. Gatley, P.V. Harper, E.R. Desombre and A.M. Friedman. Appl. Radiat. Isot. 42 (1990) 57.

3. B. Maziere and C. Loch. Appl. Radiat. Isot. 37 (1986) 703.

4. H.E. Hassan, S.M. Qaim, Yu Shubin, A. Azzam, M. Morsy and H.H. Coenen. Appl. Radiat. Isot. 60 (2004)

899.

5. Z. Kovács, G. Blessing, S. M. Qaim and G. Stöcklin. Appl. Radiat. Isot. 36 (1985) 635.

6. I. Spahn, G.F. Steyn, F.M. Nortier, H.H. Coenen and S.M. Qaim. Appl. Radiat. Isot. 65 (2007) 1057.

0200400600800

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Figure 35: Production rate of 76Br derived from measured excitation functions of the reactions as indicated, in the proton bombardment of the relevant enriched Se targets.

050

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Figure 36: Production rate of 77Br derived from measured excitation functions of the reactions as indicated, in the proton bombardment of the relevant enriched Se targets.


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3.2.7 The Production of 82Sr Using Larger Format RbCl Targets. N.P. van der Meulen1, T.N. van der Walt2, G.F. Steyn1, H.G. Raubenheimer3. 1 iThemba LABS, P.O. Box 722, Somerset West 7129, South Africa. 2 Faculty of Applied Sciences, Cape Peninsula University of Technology, P.O. Box 1906, Bellville, South Africa 3 Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602 82Sr (T1/2 = 25.55 d), which can be produced by means of a cyclotron, is currently a sought after commodity for use in medical generators, with a growing world demand driven, particularly, by cardiologists in North America. It decays purely by electron capture [1] into its daughter, 82Rb (t1/2 = 75 s), which behaves physiologically like potassium and is effective for myocardial infusion imaging studies of patients with the use of Positron Emission Tomography (PET) [2,3]. 82Rb is also used in the measurement of blood-brain barrier permeability [4]. A chemical separation method was developed for its separation from larger format targets, activated in the Vertical Beam Target Station (VBTS). The bombarded RbCl target (30 g) was dissolved in 0.5 M ammonium chloride, containing 5% methanol and 0.1 g o-phenanthroline monohydrate (to increase the distribution coefficient of Sr for a more effective retention on the resin). The resultant solution was loaded on to a column (1.0 cm internal diameter) filled to 9 cm3 with Purolite S950, lightly crushed to decrease the particle size, and equilibrated with 0.5 M ammonium chloride at a pH of 8. The elements were washed onto the resin using 0.5 M ammonium chloride. The Rb was eluted from the resin column using 0.5 M ammonium chloride, before the column was rinsed with water to remove any traces of ammonium chloride. The 85Sr was eluted with 2 M HCl (see Figure 37 for elution curve). The activity of 82Sr was determined using the 776.5 keV γ-ray peak of the 82Rb daughter, which is in equilibrium with the parent after about three days from EOB. It was determined that the yield of 82Sr was over 94% and of high purity, suitable for use in 82Sr/82Rb generators. References 1. S.M. Qaim, G.F. Steyn, I. Spahn, S. Spellerberg, T.N. van der Walt and H.H. Coenen. Appl. Radiat. Isot. 65

(2007) 247.

2. N.A. Mullani, R.A. Goldstein, K.L. Gould, S.K. Marani, D.J. Fisher, H.A. O’Brian Jr and M.D. Loberg. J. Nucl.

Med. 24 (1983) 898. 3. G.B. Saha, R.T. Go, W.J. MacIntyre, T.H. Marwick, A. Beachler, L.L. King and D.R. Neumann. Int. J. Rad.

Appl. Instrum. B 17 (1990) 763.

4. D.J. Brooks, R.P. Beaney, A.A. Lammertsma, K.L. Leenders, P.L. Horlock, M.J. Kensett, J. Marshall, D.G. Thomas and T. Jones. 1984. J. Cereb. Blood Flow Metab. 4 (1984) 535.

Elution Curve for Rb/Sr separation in 0.5 M NH4Cl/2.0 M HCl on Purolite S950 resin

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Figure 37: Elution curves of 82Sr and 84Rb from Purolite S950 using 0.5 M NH4Cl and 2.0 M HCl, respectively.


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3.2.8 The Production of 133Ba in the Proton Bombardment of Cs T.N. van der Walt1, N.P. van der Meulen2,4, G.F. Steyn2, F. Szelecsényi3, Z. Kovács3, H.G. Raubenheimer4 1 Faculty of Applied Sciences, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535 2 iThemba LABS, P.O. Box 722, Somerset West, 7129, South Africa 3 Cyclotron Department, ATOMKI, H-4026, Bem tér 181C, Debrecen, Hungary 4 Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602 133B (T½= 10.54 years) is mainly used as a calibration source for γ-rays in the energy region 81 to 356 keV as it

has several strong γ-emitting transitions in this region. It is generally obtained from the bombardment of Cs-based materials via the 133Cs(p,n)133Ba nuclear reaction. Other applications include studies of perturbed angular correlation [1,2] as well as investigations of the attachment of cryptates containing radioactive metal ions to proteins [3]. 133B has also been used as tracer for predicting 226Ra in soil-plant transfer studies [4] as it is a good analogue of the environmental behaviour of Ra. It is an expensive radionuclide to produce due to its long half-life and only a few accelerator facilities consider it financially viable to produce it routinely. Production of this radionuclide using reactor facilities has been reported [5] but that product is not carrier free. Due to its long half-life, it can take a very long time to produce a reasonable quantity of the product at an accelerator facility. Even though its production rate may be quite low, the price per unit activity that the market offers is relatively high, making it worthwhile to consider its production as a “by-product” of the regular 22Na and 82Sr productions at iThemba LABS, making use of tandem targetry. As no excitation function data for the nuclear reaction 133Cs(p,n)133Ba could be found in the literature, new measurements were performed in collaboration with Hungarian Scientists at ATOMKI, Debrecen, Hungary. The targets were prepared by powder compaction of fully anhydrous CsF salt (99.9 %, Alfa Aesar) in a punch-and-die set with a hydraulic press. All the targets irradiated had a nominal thickness of 1000 mg/cm2, thus, thick enough to stop the beam. Activations were performed using degraders of various thicknesses to cover the energy region from threshold up to ~17.5 MeV, the maximum energy which could be obtained from the ATOMKI cyclotron. Due to its long half-life, the bombardment time per target activation also had to be relatively long, thus the number of individual points measured was limited within the allocated beamtime on the ATOMKI cyclotron. The measured 133Ba thick-target production rate curve for CsF + p is shown in Figure 38a. Since only four data points were measured, not enough information was available to uniquely fit a polynomial function. It was, therefore, necessary to fit a nuclear model-generated function to the measured values. For this purpose, the Geometry Dependent Hybrid (GDH) model as implemented in the ALICE-IPPE code was used. The solid curve shown in Figure 38a was calculated from the ALICE-IPPE predicted excitation function for the 133Cs(p,n)133Ba reaction. The dashed curve is the same information but renormalized to the data. The expected production rate for the proton energy window 4 – 20 MeV is about 25.6 kBq/µAh. The corresponding excitation function curves are shown in Figure 38b. It has the typical shape for a (p,n) reaction and reaches a maximum of about 550 mb at a proton energy of 10.2 MeV. An energy window of 4 – 20 MeV should, therefore, be ideal for 133Ba production.


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Ion exchange methods to separate Ba from Cs have been reported in several studies [6-9]. In this work, organic cation exchange resins were investigated to separate 133Ba from activated Cs compounds. Two new methods, using the cation exchange resins AG 50W-X4 and AG MP-50, respectively, were compared. In both cases 133Ba could be quantitatively separated from Cs. Details of the methods will be published elsewhere, thus only the results, summarized in Table 10, will be discussed here. Note that 131Ba and 132Cs were used as tracers to follow the efficacy of the various steps of the separation procedures.

Eluates AG 50W–X4 AG MP-50 131Ba(496 keV) 132Cs(667 keV) 131Ba(496 keV) 132Cs(667 keV)

E1 npf npf 1753(3.3%) 73703(74.2%)

E2 npf npf 2182(4.1%) 17138(17.3%)

E3 npf 9352(100%) 1056(2.0%) 8433(8.5%)

E4 370(0.4%) npf npf npf

E5 98443(98.2%) npf 455(0.8%) npf

E6 1422(1.4%) npf 47181(89.0%) npf

E7 - - 387(0.7%) npf

E8 - - npf npf

Column(after) npf npf npf npf

Total Activity 100235 9352 53014 99274

Table 10: Separation of 131Ba from Cs by ion exchange chromatography on AG 50W–X4 cation exchange resin and on AG MP-50 macroporous cation exchange resin Table 10 shows that with the AG 50W-X4 cation exchanger there was no breakthrough of the 131Ba through the resin column during the loading step (E1), the wash step (E2) and the subsequent 132Cs elution steps and no 132Cs was found in the Ba eluates. The column contained no radionuclides after the separation was done. The

(a) (b)(a) (b)

Figure 38: (a) Thick-target production rates of 133Ba produced in the proton bombardment of CsF. The solid symbols are the measured values of this work while the solid curve is a prediction based on the Geometry Dependent Hybrid (GDH) model. The dashed curve is the same GDH prediction but normalized to the measured data. Error bars are shown when they exceed the symbol size. (b) Excitation function of 133Ba formed in the reaction of protons with 133Cs. The solid curve is the ALICE-IPPE prediction while the dashed curve represents the renormalized excitation function according to the integral yield measurements of this study.


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results show that a good separation of Ba from the Cs target material can be obtained with the AG 50W-X4 cation exchanger. Table 10 also shows that, using the macroporous cation exchanger AG MP-50, a breakthrough of 131Ba occurred during the loading step (E1), wash step (E2) and the first 132Cs elution step (E3) adding up to a total amount 9,4%. However, the 132Cs was completely removed before the final elution of 131Ba. It is clear, from the results of the two experiments, that a better separation of 131Ba from 132Cs was obtained with the AG 50W-X4 resin and for this reason this resin is proposed for the routine separation of 133Ba from the target material.

References 1. J.N. Rimbert, C. Kellershohn, F. Dumas and C. Hubert. Phys. Med. Biol. 26 (1981) 221. 2. H. Singh, H.S. Binarh, S.S. Ghumman and H.S. Sahota. Int. J. Rad. Appl. Instrum. A 41 (1990) 797.

3. W.A. Pettit and B.K. Swailes. J. Label Compd. Radiopharm. 33 (1993) 305.

4. H. Vandenhove, T. Eyckmans and M. Van Hees. J. Environ. Radioact. 81 (2005) 255. 5. Y.A. Karelin, Y.N. Gordeev, V.T. Filimonov, Y.G. Toporov, A.A. Yadovin, V.I. Karasev, V.M. Lebedev,

V.M. Radchenko and R.A. Kuznetsov. Appl. Radiat. Isot. 48 (1997) 1585. 6. M.M. Ferraris. Health Phys. 10 (1964) 833. 7. P. Groll, F. Gran and K. Buchtella. Radiochim. Acta 12 (1969) 152.

8. K. Roy, D. K. Pal, S. Basu, D. Nayak and S. Lahiri. Appl. Radiat. Isot. 57 (2002) 471.

9. S. Dhara, S. Dey, S. Basu, M.G.B. Drew and P. Chattopadhyay. Radiochim. Acta 95 (2007) 297.

3.2.9 The Production of Ultra-pure 67Ga

N.P. van der Meulen1 and T.N. van der Walt2

1 iThemba LABS, P.O. Box 722, Somerset West, South Africa 2 Faculty of Applied Sciences, Cape Peninsula University of Technology, P.O. Box 1906, Bellville, 7535 67Ga (t1/2 = 78.3 h), which is produced in a cyclotron by the reaction natZn(p,x)67Ga, and decays to stable 67Zn, is

extensively used in nuclear medicine [1]. Its main decay emission γ-rays are 93.3 keV (37 % abundance), 184.6 keV (20.4 % abundance) and 300.2 keV (16.6 % abundance). It is usually separated from Zn by means of ion exchange chromatography [2,3] or by liquid extraction [2,4]. The product is predominantly supplied in the citrate form and used for imaging soft tissue tumours and abscesses. The current production method for ultra-pure 67Ga at iThemba LABS involves the bombardment of two natZn targets in tandem with a 66 MeV proton beam. The two bombarded Zn targets are dissolved in 60 ml concentrated Suprapur HCl, after which a further 60 ml (containing 3 ml purified TiCl3) is added. The resultant solution is loaded on to a 2.5 ml column containing Amberchrom CG161M resin (equilibrated with 50 ml 7.0 M Suprapur HCl). Any remaining Zn and Fe impurities are eluted with 150 ml 7.0 M Suprapur HCl, before the 67Ga is eluted from the resin column using 30 ml 0.1 M HCl (see Figure 39 for elution curve).


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When using purified TiCl3 as a reducing agent in the process and applying an Amberchrom CG-161M resin column, the results produced are excellent, with a removal of > 99 % of Fe and > 99,9% of Zn from the final product. This ultra-pure form of the product is required for the labelling of peptides, as citrate would interfere with the labelling process. The main reason that this method would not be adopted for all the routine production of 67Ga is the substantial increase in cost, which would imply an increase in price for the consumers. References 1. M.A. Green and M.J. Welch. J. Nucl. Med. Biol. 16 (1989) 435. 2. F. Helus and W. Maier-Borst. J. Label. Compd. Radiopharm. (1973) 317. 3. T.N. van der Walt and F.W.E. Strelow. Anal. Chem. 55 (1983) 212. 4. H.B. Hupf and J.E. Beaver. Int. J. Appl. Radiat. Isot. 27 (1970) 1.

3.2.10 The Production of 88Y in the Proton Bombardment of natSr N.P. van der Meulen1,2, T.N. van der Walt3, G.F. Steyn1, F. Szelecsényi4, Z. Kovács4, C.M. Perrang1 and H.G. Raubenheimer2. 1 iThemba LABS, PO Box 722, Somerset West 7129, South Africa 2 Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 3 Faculty of Applied Sciences, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535 4 Cyclotron Department, ATOMKI, H-4026, Bem tér 18/C, Debrecen, Hungary

88Y (T1/2 = 106.6 d) can be effectively produced by means of a cyclotron. Its mode of decay is predominantly by

means of electron capture and the decay emissions include the strong γ-rays of 898.0 keV (93,7%) and

1836.1 keV (99,2%). It is formed in proton-induced reactions, using natSr as target material, only via the 88Sr(p,n)88Y reaction [1], while productions via the 87Rb(3He,2n)88Y and 85Rb(4He,n)88Y reactions have also been reported [2,3]. In recent years, 88Y has become important as a substitute for 90Y (a β- emitter used in radiotherapy) to quantify the bio-distribution of Y-pharmaceuticals and it is also used effectively as a tracer for the chemical yield determination of 90Y [4,5]. Small 88Y point sources are also used in the calibration of instruments. It was found that rather large discrepancies existed between the relevant excitation function data sets, even between the most recent studies. New measurements for the 88Sr(p,n)88Y reaction have therefore been performed up to an energy of nominally 20 MeV. In metallic form, Sr reacts rapidly with oxygen in the atmosphere, while the available compounds of Sr are brittle. As a result, it proved to be difficult to prepare thin self-supporting samples of a compound containing Sr, a

Ga-67 on Amberchrom CG-161M

0

20

40

60

80

100

0 5 10 15 20 25 30

Eluant Volume (mL)

% A

ctiv

ity in

Elu

ant

Figure 39: Elution of 67Ga from Amberchrom CG-161M using 0.1 M HCl.


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necessary requirement to exploit the conventional stacked-foil activation technique. Although methods exist for preparing thin samples of brittle substances on backing foils, such methods also have their disadvantages. As an alternative, the integral thick-target production rate curve was first determined experimentally, by activating targets thick enough to stop the beam. The excitation function was then deduced using a differentiation method. The incident proton energy was adjusted by using various thicknesses of Al degraders. Further details on the method can be found in ref. [6]. The measured 88Y thick-target production rate curve for SrCl2 + p is shown in Figure 40a. A standard polynomial function was fitted through the measured data using the code TABLECURVE 2D [7]. The polynomial could be differentiated analytically, allowing the derivation of the 88Y excitation function for 88Sr + p, shown in Figure 40b. The data of Kettern et al. [1] and Levkovskii [8] are also shown. Interestingly, the values of this work are lower than those of Levkovskii but higher than those of Kettern et al., falling just about half-way between those two data sets. The maximum of the excitation function is at about 12.5 MeV, thus, the energy region 4 – 20 MeV is ideal for the routine production of 88Y.

Both ion exchange chromatography and liquid extraction methods have been described in the literature for the separation of Y from Sr (see e.g. [9,10]). Experiments have also been performed at iThemba LABS and two new methods have been developed, both based on ion-exchange chromatography. The salient steps of the first method are as follows: A bombarded SrCl2 target is dissolved in water and the Y precipitated by adding ammonium carbonate to the solution. This precipitate is then isolated, dissolved in 2.0 M HCl and evaporated to dryness, whereafter the resulting Y salt is again dissolved in water. An AG MP-1 resin column is then used to retain the Y while removing the Sr by passing the solution through and further rinsing with water. The Y is then eluted from the column using 6.0 M HCL. Finally, the elution is brought to a 0.1 M HCl solution. In the second method, the target is dissolved in 0.5 M HCl and an AG 50W-X4 resin column is used instead. The Sr is removed by rinsing the column with 1.2 M HNO3, whereafter the Y is eluted using a 4.0 M

Figure 40: (a) Thick-target production rate curve of 88Y produced in the proton bombardment of SrCl2. The solid symbols are the measured values of this work while the solid curve is a polynomial fit. Error bars are shown when they exceed the symbol size. (b) The curve is the excitation function derived from the polynomial in (a). The open triangles are the data of Levkovskii [8] and the open circles the data of Kettern et al. [1].


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HNO3 solution. The Y is finally picked up in 0.1 M HCl as before. The elution curves, demonstrating the separation of Y from Sr in the two methods described, are shown in Figure 41.

An effective separation between 88Y from the Sr target material could be successfully obtained by using AG MP-1 macroporous anion exchange resin at a pH > 7 or when performing a production using AG 50W-X4 cation exchange resin. The use of a co-precipitation step, using ammonium carbonate, proved to be very effective in the removal of the bulk of the strontium from the yttrium and can be used in both chromatographic methods. References 1. K. Kettern, K.-H. Linse, S. Spellerberg, H.H. Coenen and S.M. Qaim. Radiochim. Acta 90 (2002) 845. 2. D.R. Sachdev, N.T. Porile, L. Yaffe. Can. J. Chem. 45 (1967) 1149. 3. Y. Homma, M. Ishii and Y. Murase. Int. J. Appl. Radiat. Isotopes 31 (1980) 399. 4. G.L. Griffiths, S.V. Govindan, R.M. Sharkey, D.R. Fischer, D.M. Goldenberg. J. Nucl. Med. 44 (2003) 77.

5. A. Arzumanov, V. Batischev, N. Berdinova, A. Borissenko, G. Chumikov, S. Lukashenko, S. Lysukhin, Yu Popov and G. Sychikov. In Cyclotrons and Their Applications, Sixteenth International Conference, East Lansing, Michigan (Ed: F. Marti) 2001, p 34.

6. C. Vermeulen, G.F. Steyn, F.M. Nortier, F. Szelecsényi, Z. Kováks and S.M. Qaim. Nucl. Instrum. Meth.

B 255 (2007) 331.

7. TABLECURVE 2D, Automated Curve Fitting & Equation Discovery, Jandel Scientific, San Rafael, California, 1996.

8. V.N. Levkovskii. Cross-sections of medium mass nuclide activation (A=40-100) by medium energy protons

and alpha particles (E=10-50) (Experiment and Systematics), Inter-Vesi, Moscow, 1991, p. 147. 9. Z. Grahek, I. Eskinja, K. Kosutic and S. Cerjan-Stefanovic. Croatica Chemica Acta 73 (2000) 795, and

references therein. 10. K. Shikano, M. Katoh, T. Shigematsu and H. Yonezawa. J. Radioanal. Nuclear Chem. 119 (1987) 433, and

references therein.

Figure 41: LEFT: Elution of 85Sr and 88Y from AG MP-1 resin using water and 6.0 M HCl, respectively. RIGHT: Elution of 85Sr and 88Y from AG 50W-X4 resin using 1.2 M HNO3 and 4.0 M HNO3, respectively.


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3.2.11 The Production of 68Ge using Larger VBTS format Ga Targets

N.P. van der Meulen1, S.G. Dolley1, G.F. Steyn1, T.N. van der Walt2 and H.G. Raubenheimer3 1 iThemba LABS, P.O. Box 722, Somerset West 7129, South Africa. 2 Faculty of Applied Sciences, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535 3 Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602 68Ga, which has physical characteristics desirable for PET, is obtained via the decay of 68Ge, making the production of 68Ge an important product for iThemba LABS. 68Ge, having a half-life of 288 days, decays entirely by electron capture [1] to produce 68Ga (T1/2 = 68 m), which disintegrates mainly by positron emission (90,5%) [2]. The daughter (68Ga) is obtained from 68Ge when in secular equilibrium with the mother. 68Ge has been used as a positron source in positron annihilation studies in nuclear physics and in metal radiography in industry [3]. The most recent application of this radionuclide, however, is as a 68Ge/68Ga generator for PET in nuclear medicine [4,5], with the use of 68Ga as a PET tracer. The greater demand for 68Ge is as a result of the increased use of 68Ge/68Ga generators for radiopharmaceutical purposes [6].

Two nuclear reactions have been utilized to produce 68Ge routinely, namely, by 66Zn(α,2n)68Ge (66Zn natural

abundance being 27,8%) giving a yield of up to 2 µCi/µAh, or by 69Ga(p, 2n)68Ge (69Ga natural abundance being

60%) giving a yield of up to 20 µCi/µAh. The latter reaction is regarded as the reaction of choice for medical cyclotrons due to the higher yields obtained. Ga targets are therefore used at iThemba LABS for 68Ge production. An in-house chemical process has been developed for its separation from the Ga target material, irradiated in the larger format Nb capsules used in Vertical Beam Target Station (VBTS) targetry. The 32 g of Ga was removed from its niobium encapsulation by puncturing it and placing it in hot water and letting the Ga flow out, sans water and capsule, into the reaction vessel containing concentrated HCl. Concentrated HNO3 was added to the vessel and the reaction solution heated to 70ºC for 30 minutes, such that the target material can react vigorously. This was followed by the addition of a further aliquot of HNO3. Once the HCl was depleted, the additional HCl was added, before concentrated HNO3 was added to the reaction and the process repeated. Once the reaction was depleted, this process was performed a final time. Once the reaction was completed, the scrubber solution, consisting of 1.0 M NaOH containing Na2SO3 and the 68Ge activity, was pumped to a bottle containing water and concentrated HF. The resultant solution was stirred for 10 minutes, before being pumped through a column containing 10 ml AG MP-1 macroporous anion exchange resin (equilibrated with 0.2 M HF). Any impurities, such as Na+ ions, were removed by rinsing the column with 0.05 M HF, before acetic acid was pumped through the resin column to assist in the elution of the final product. The final product, 68Ge, was eluted from the resin using 0.1 M HCl, in 10 ml fractions. A radiochemically pure product is obtained with the use of what can be described as an elegant radiochemical method, obtaining a yield of 90%, with the remaining 10% found in the catcher system also available for use.


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References 1. R.B. Firestone and L.P. Eckström. www Table of radioactive isotopes, Version 2.1 (2004). Available from

URL: <http://ie.lbl.gov/toi>. 2. Y. Iwata, M. Kawamoto and Y. Yoshizawa. Int. J. Appl. Radiat. Isot. 31 (1983) 1537. 3. E. Hughes. Mat. Eng., 2 (1980) 34. 4. R.M. Lambrecht and M. Sajjad. Radiochim. Acta 43 (1988) 171. 5. R.M. Lambrecht. Radiochim. Acta 34 (1988) 9.

6. D.J. Hnatowich. Int. J. Appl. Radiat. Isot. 28 (1977) 169.

3.2.12 The Production of 28Mg in the Proton Bombardment of natCl N.P. van der Meulen1, G.F. Steyn1, T.N. van der Walt2, C. Vermeulen1, H.G. Raubenheimer3 1 iThemba LABS, P.O. Box 722, Somerset West 7129, South Africa. 2 Faculty of Applied Sciences, Cape Peninsula University of Technology, P.O. Box 1906, Bellville 7535 3 Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602 28Mg was discovered in 1953 [1] and has a half-life of 20.9 h. Its mode of decay [2,3] is 100% by β- emission to 28Al. Interest was shown in this radionuclide for mineral uptake studies by the local Fruit and Fruit Technology Research Institute (FFTRI) of South Africa in the early 1990’s. A project was started at iThemba LABS at that time to investigate its production, however, that project was never completed because priorities had changed. Recently, however, interest has been rekindled and a project to produce 28Mg reopened. The options available for 28Mg production in the proton energy region 50 - 200 MeV has been revisited at iThemba LABS. Extensive new production rate and excitation function data have also been measured for the natCl(p,6pxn)28Mg nuclear process [4]. The thick-target production rate curve was measured using primary beams of 66, 100 and 200 MeV to get data from the reaction threshold up to 200 MeV (see Figure 42). LiCl was determined to be the target material of choice, as it has excellent thermal stability as well as a yield of about 80% of the natCl + p theoretical maximum, however, a production energy window of 50 - 200 MeV will result in a very thick LiCl target (about 32 g/cm2). Such a thick target would be virtually impossible to cool sufficiently during high-intensity irradiation. A practical solution was to place several thinner

targets (properly encapsulated) in series and to provide fast flowing cooling water around them in a 4π geometry [5]. A diagram of the target is shown in Figure 43. Ten thinner targets, therefore, were bombarded in series with a primary proton beam of 200 MeV (see Figure 44), utilising the energy window 50 – 200 MeV as the reaction

Figure 42 Thick-target production rate curve of 28Mg produced in the proton bombardment of NaCl. The solid symbols are the measured values of this work while the solid curve is a polynomial fit. Error bars are shown when they exceed the symbol size.

http://ie.lbl.gov/toi>


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threshold is just below 50 MeV. A LiCl target (8.6 g) was dissolved in 1.0 M ammonium chloride solution, at a pH of 8, to which o-phenanthroline monohydrate was added. The resultant solution was pumped through a column of 12.5 cm in length and a diameter of 1 cm, packed with Purolite S950 chelating resin (the resin lightly ground to create finer particles for greater surface area), equilibrated with 1.0 M ammonium chloride. The elements were washed onto the column with 1.0 M ammonium chloride (pH 8), before the Li was eluted from the resin column with a further aliquot of 1.0 M ammonium chloride (pH 8). The 28Mg final product was eluted from the resin column using 2.0 M HCl.

The chemical separation produced a 100% yield of the final product. There was some 7Be found in the final product, as a result of the Li(p,n)7Be reaction. In most applications this would not be a problem. Should this be a problem for potential users, however, NaCl targets can be used instead, although the yield of 28Mg will not be as high as when LiCl target material is used. References 1. R.K. Sheline and N.R. Johnson. Phys. Rev. 89 (1953) 520. 2. S.M. Qaim. Radiochim. Acta 89 (2001) 223.

3. R.B. Firestone and L.P. Eckström www Table of radioactive isotopes, Version 2.1 (2004). Available from URL: http://ie.lbl.gov/toi.

4. G.F. Steyn, N.P. van der Meulen, T.N. van der Walt and C. Vermeulen. In Proceedings of the International

Conference on Nuclear Data for Science and Technology (2007, Nice, France). In press. 5. F.M. Nortier, F.J. Haasbroek, S.J. Mills, H.A. Smit, G.F. Steyn, C.J. Stevens, T.F.H.F. van Elst and

E. Vorster. In Proceedings of the 4th Int. Workshop on Targetry and Target Chemistry, PSI-Proceedings 92-01, Villigen, Switzerland (1992) p60.

Figure 43: An exploded view of the LiCl target holder, showing the 10 encapsulated LiCl targets, an entrance window at one end and a beam stop at the other end. A rack was designed to keep the targets in position inside an aluminium sleeve while simultaneously providing cooling channels for cooling water. The cooling-water layers between targets had a thickness of 1 mm.

Figure 44: The ratio of the measured 28Mg activity and the corresponding predicted value based on the nuclear data measurements, plotted as a function of the target number. Note that the target number increases as the penetration depth into the target stack increases.

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3.3 Physics Group 3.3.1 Possible Chirality in the Doubly-odd 198Tl E.A. Lawrie1, P.A. Vymers1,2, J.J. Lawrie1, Ch. Vieu3, R.A. Bark1, R. Lindsay2, G.K. Mabala1,4, S.M. Maliage1,2, P.L. Masiteng1,2, S.M. Mullins1, S.H.T. Murray1, I. Ragnarsson5, J.F. Sharpey-Schafer1,2, O. Shirinda1,2 1iThemba LABS, PO Box 722, Somerset West 7129, South Africa 2University of the Western Cape, Private Bag X17, 7535 Bellville, South Africa 3Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, IN2P3, 91405 Orsay, France 4Physics Department, University of Cape Town, Rondebosch 7700, South Africa 5Division of Mathematical Physics, LTH, Lund University, SE-221 00 Lund, Sweden Nuclear chiral systems occur if the total angular momentum of the nucleus has an aplanar orientation, i.e. it is pointed out of the planes defined by the major nuclear axes [1,2]. For odd-odd nuclei this can happen for a particle-hole configuration, because the angular momentum of the particle (hole) tends to align along the short (long) nuclear axes. Provided the nuclear shape is triaxial, the angular momentum of the collective rotation aligns along the intermediate axis, and thus a chiral system might be formed. The three angular momenta can be arranged either in a left- or in a right-handed system, both of which are equivalent except for their chirality. In the laboratory frame the two chiral systems exhibit two ΔI = 1 degenerate bands [1,2], i.e. bands with the same excitation energy, B(M1) and B(E2) transition probabilities, alignments, moments of inertia, etc. In addition vanishing energy staggering might be expected for these bands [1,2,3], while they may also show staggering in the B(M1) transition probabilities [4]. Several partner bands were suggested as chiral candidates in the A=130 and A=100 mass regions, but there is still no case when the partner bands are truly degenerate. It is however unclear, whether the differences in the partner bands prove non-chirality of the nucleus, or whether they are caused by other effects. Thus, it is important to investigate more nuclei where chirality might be present, and in particular in different mass regions and for different nuclear configurations. In this work the previously known level scheme of 198Tl [5] was considerably extended and a partner to the yrast band was observed [6]. These

bands were assigned the same πh9/2 ⊗ νi13/2-1 particle-hole configuration, which is suitable for a chiral system. This work indicates a new region where chirality can be studied. The partner bands in 198Tl do not show true degeneracy. They have the same alignments, moments of inertia and B(M1)/B(E2) ratios, but the side band lies at an excitation energy of about 500 keV higher than that of the yrast band, (see Figures 45 and 46). In order to study these bands we have performed two-quasiparticle-plus-triaxial-

rotor model calculations [7]. A quadrupole deformation of ε2 = 0.15 and a variable moment of inertia were used. Five single particle configurations around the Fermi levels for protons and neutrons were included in the single particle basis. No Coriolis attenuation factor and standard parameters for the pairing and the Nilsson Hamiltonian

were used. These calculations were performed for different values of the non-axiality parameter γ and with or without a residual proton-neutron interaction (see Figure 47). It is clear that the residual proton-neutron interaction has a very strong effect on the staggering in the bands. Indeed, it is impossible to reproduce the signature

inversion in the yrast band of 198Tl (for any value of γ), unless the residual proton-neutron interaction is considered. The magnitude of the divergence from axiality strongly affects all characteristics of the bands. The


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excellent agreement that is observed between the experimental data and the calculations obtained with γ = 44° is worth noting. Not only the nearly constant relative excitation energy in the spin range of I = 10 ћ up to I = 14 ћ and the smooth dependence of the B(M1)/B(E2) ratios with spin, but also the signature inversion in the yrast band and the absence of signature staggering in the side band are all well reproduced by the calculations.

Figure 45: Excitation energy (left panel) and staggering, S(I) = [E(I) – E(I-1)]/2I, (right panel) in the yrast and side bands in 198Tl.

This indicates that the nuclear shape in 198Tl is unlikely to be axially symmetric with γ = 44°. It is worth noting that

for γ = 30°, where the best conditions for chirality occur, a large energy staggering is calculated for both partner bands. This contradicts previous suggestion [5] that vanishing staggering is a fingerprint of chirality. In order to check whether the partner bands in 198Tl are chiral we studied the orientation of the angular momenta. The calculations showed that the proton, neutron and the rotation angular momenta have major components along the short, long and intermediate nuclear axes, respectively, within the observed spin range, which indicates an aplanar orientation of the total angular momentum and thus possibly a chiral system. This work was submitted for publication [8].

Figure 46: Experimental quasiparticle alignments (a), Routhians (b), kinematic moment of inertia (c), and B(M1)/B(E2) transition probabilities ratios (d), for the yrast and side bands in 198Tl.


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References 1. S. Frauendorf and J. Meng, Nucl. Phys. A 617 (1997) 131. 2. S. Frauendorf, Rev. Mod. Phys. 73 (2001) 463.

3. C. Vaman et al., Phys. Rev. Lett. 92 (2004) 032501.

4. T. Koike, K. Starosta, and I. Hamamoto, Phys. Rev. Lett. 93 (2004) 172502. 5. A.J. Kreiner, M.Fenzl, S. Lunardi, M.A.J. Mariscotti, Nucl. Phys. A282 (1977) 243.

6. E.A. Lawrie et al., iThemba LABS Annual Report (2007) 112.

7. P.B. Semmes and I. Ragnarsson in Proc. Int. Conf. on High-Spin Physics and Gamma-Soft nuclei, Pittsburg,

1990, eds. J.X. Saladin, R.A. Sorenson and C.M. Vincent (World Scientific, 1991), p. 500.

8. E.A. Lawrie et al., submitted to Phys. Rev. Lett.

Figure 47: Calculated excitation energies, staggering S(I) = [E(I) – E(I-1)]/2I, and B(M1)/B(E2) transition probability ratios for the yrast and side bands in 198Tl at different γ deformations and with or without residual proton-neutron interaction.


98

3.3.2 Investigation of Lifetimes in 134 Nd with AFRODITE using DSAM E.O. Lieder1,2, R.M. Lieder1, A.A. Pasternak2, A. Efimov2, R.A. Bark1, E.A. Lawrie1, J.J. Lawrie1, S.M. Mullins1, P. Papka1, Y. Kheswa1, J. Sharpey-Schafer3 and K.O. Zell4 1 iThemba Laboratory for Accelerator Based Sciences, Somerset West 7129, South Africa 2 A.F. Ioffe Physico-Technical Institute RAS, RU-194021 St. Petersburg, Russia 3 Dept. of Physics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa 4 Institut für Kernphysik, Universität zu Köln, Köln, Germany Lifetime measurements using the Doppler Shift Attenuation Method (DSAM) have been carried out with the AFRODITE array at iThemba LABS which allowed the determination of B(E2) values for quadrupole bands in 134Nd. In the investigation, a 12.8 mg/cm2 thick 114Cd target was bombarded with 155 MeV 28Si projectiles. The

final nucleus 134Nd was produced through the (α, 4n) channel. In the AFRODITE array four CLOVER detectors

each were mounted at 45° and 135° (w.r.t. to the beam direction), respectively. The initial recoil velocity is v/c=2,15% for this reaction. The stopping power parameters required for the analysis were determined in a separate measurement using the “semi-thick target method” [1], applied to a target with a thickness of 3.65 mg/cm2 [2].

A partial level scheme of 134Nd [3] is shown in Figure 48. The heads of the (+,0)0 and (+,0)1 bands were assigned

configurations of νh11/2-2 and πh11/22 respectively by Petrache et al. [3] , and of (νf7/2/h9/2)-2 and νh11/2-2 respectively by Klemme et al. [4]. The new lifetime results may help to clarify the configuration assignments. A plot of the spin

vs. γ-ray energy for the ground, (+,0)0 and (+,0)1 bands is shown in Figure 49 indicating a crossing of the ground band with the (+,0)0 band and two crossings in the (+,0)1 band. Lifetimes for high-spin states from 10+ to 22+ of the (+,0)0 band of 134Nd have been determined by means of lineshape analysis with the computer codes COMPA, GAMMA and SHAPE [5] using Monte-Carlo simulation calculations. To extract lifetimes, single-gated coincidence spectra have been used. The data have been sorted into γ-γ matrices for which the γ-ray energies from any detector were stored along the first axis, and the energies from detectors placed at a certain angle with respect to

Figure 48: Partial level scheme of 134Nd [3]. Lifetimes obtained by RDM [4] and in the present DSAM experiment are indicated.


99

the beam direction along the second axis (45° and

135°, respectively). For the analysis, spectra obtained for the two detector angles as well as for the sum of

the 45° and 135° spectra were used to increase the

statistics. In the latter case the γ-lineshapes are fully symmetric showing Doppler-shifted components on the low- and high-energy sides of the peak. Examples of such spectra, obtained by summing of several individually gated spectra are shown in Figure 50a-c for the 836 keV 18+→16+ transition. The experimental

lineshapes (circles) are compared with calculated γ-line shapes for which the best fits were obtained. The

lifetimes deduced from these three spectra are the same within uncertainties. The χ2 analysis of the spectrum

obtained by summing the 45° and 135° spectra (Figure 50c) is shown in Figure 50d.

Reduced transition probabilities B(E2) were extracted from the lifetimes deduced for the 10+ to the 22+ levels and are shown in Figure 51. The experimental B(E2) values are compared with theoretical calculations. The calculations were carried out in the framework of a phenomenological IBM model using the Hamiltonian

H = H(0)IBM1 for I < 10 and H = E(1) + H(1)IBM1 for I ≥ 10, where I = 10 is the band-head spin of the (+,0)0 band and

E(1) a correction energy. In these calculations, the γ-ray energy as function of spin can be well reproduced

Figure 49. Spin vs. γ-ray energy for bands in 134Nd. For the (+,0)0 band, the results of IBM calculations are also shown.

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60

10

20

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)

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134Nd

Figure 50: DSAM lineshape analysis for the 836 keV 18+ →16+ transition of the (+,0)0 band: (a,b) for the 450 and 1350 spectra and (c) for a sum of 450 and 1350 spectra, obtained by different gatings. (d) The lifetime of the level was extracted by means of a χ2 analysis.


100

(Figure 49). In the present phenomenological IBM model, the (+,0)0 band appears to be a continuation of the ground band and the observed anomaly at I=10 is not caused by quasi-particle excitations. The present description allows one to also understand the absence of a noticeable change in the B(E2) values in the region of the band anomaly. A comparison of the experimental and theoretical B(E2) values for these bands shows excellent agreement (Figure 51). References 1. Kh. Lemberg and A.A. Pasternak, Nucl. Instrum. Meth. A140 (1977) 71. 2. E.O. Lieder, R.M. Lieder, A.A. Pasternak, R.A. Bark, E. Gueorguieva, J.J. Lawrie, S.M. Mullins, P. Papka,

Y. Kheswa, W. Przybylowicz and W. Gast, iThemba LABS Annual Report 2007, p115.

3. C.M. Petrache, D. Bazzacco, S. Lunardi, C. Rossi Alvarez, R. Venturelli, R. Burch, P. Pavan, G. Maron, D.R. Napoli, L.H. Zhu and R. Wyss, Phys. Lett. B387 (1996) 31.

4. T. Klemme, A. Fitzler, A. Dewald, S. Schell, S. Kasemann, R. Kuhn, O. Stuch, H. Tiesler, K.O. Zell, P. von Bretano, D. Bazzacco, F. Brandolini, S. Lunardi, C.M. Petrache, C. Rossi Alvarez, G. De Angelis, P. Petkov and R. Wyss, Phys. Rev. C60 (1999) 034301.

5. E.O. Lieder, A.A. Pasternak, R.M. Lieder, A.D. Efimov, V.M. Mikhajlov, B.G. Carlsson, I. Ragnarsson, W. Gast, Ts. Venkova, T. Morek, S. Chmel, G. de Angelis, D.R. Napoli, A. Gadea, D. Bazzacco, R. Menegazzo, S. Lunardi, W. Urban, Ch. Droste, T. Rząca-Urban, G. Duchêne and A. Dewald, Eur. Phys. J.

A21 (2008) 37.

3.3.3 Investigation of Lifetimes in 143Gd with EUROBALL using DSAM E.O. Lieder1,2, R.M. Lieder1, A.A. Pasternak2 and W. Gast3 1 iThemba Laboratory for Accelerator Based Sciences, Somerset West 7129, South Africa 2 A.F. Ioffe Physico-Technical Institute RAS, RU-194021 St. Petersburg, Russia 3 Institute für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich, Germany A lifetime measurement for 143Gd using the Doppler-shift attenuation method (DSAM) has been carried out by means of the 114Sn(32S,2pn) reaction at a beam energy of 160 MeV with the γ-detector array EUROBALL. The target consisted of a self-supporting metallic 114Sn foil of 8 mg/cm2 thickness with an enrichment of 71,1%. The initial recoil velocity of the compound nuclei is v/c=2.2% for this reaction. The γ-detector array EUROBALL consisted of 14 CLUSTER, 26 CLOVER and 30 individual Compton-suppressed Ge detectors. Approximately 4.3x109 γ-events with fold ≥ 5 were collected.

0 2 4 6 8 10 12 14 16 18 20 22 24 26 280.1

1

IBM

(+,0)0

gb

B(E

2 I g

I-2)

, (eb

)2

Spin

134Nd RDM [Klemme et al] DSAM [present exp.]

Figure 51. Comparison of experimental B(E2) values for the (+,0)0 band in 134Nd with theoretical calculations in the framework of the Interacting Boson Model (IBM). The present DSAM results are shown by open and the previous RDM results [4] by full symbols.


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To extract lifetimes, the data were sorted into γ-γ-γ cubes for which the γ-ray energies from any detector were stored along the first two axes and the energies from detectors placed at a certain angle with respect to the beam

direction along the third axis (77°, 103° and 133°, respectively). In the analysis doubly-gated coincidence spectra were used. The lineshape analysis was carried out with the computer codes COMPA, GAMMA and SHAPE [1] using Monte-Carlo simulation calculations. This software includes the Monte-Carlo simulation of the production, slowing down of the recoils, the γ-ray emission and registration in the Ge detectors as well as the line-shape fit. Spectra for the lineshape analysis were produced by placing gates below the transition under investigation. For the analysis of the 629.6 keV transition de-exciting the 49/2 level a gate was furthermore set on the shifted component of the feeding 811.1 keV transition, to avoid systematic errors caused by cascade and side feedings.

Lifetimes have been deduced for the 33/2+ to 69/2+ levels of the strongly populated quadrupole band in 143Gd [2]. The resulting B(E2) values are shown in Figure 52. For an interpretation of the experimental B(E2) values, theoretical calculations in the framework of the cranked Nilsson-Strutinski model [3] are presently being carried out. References 1. E.O. Lieder, A.A. Pasternak, R.M. Lieder, A.D. Efimov, V.M. Mikhajlov, B.G. Carlsson, I. Ragnarsson,

W. Gast, Ts. Venkova, T. Morek, S. Chmel, G. de Angelis, D.R. Napoli, A. Gadea, D. Bazzacco, R. Menegazzo, S. Lunardi, W. Urban, Ch. Droste, T. Rząca-Urban, G. Duchêne and A. Dewald, Eur. Phys. J.

A35 (2008) 135. 2. R.M. Lieder, T. Rząca-Urban, H.J. Jensen, W. Gast, A. Georgiev, H. Jäger, E. van der Meer, Ch. Droste,

T. Morek, D. Bazzacco, S. Lunardi, R. Menegazzo, C.M. Petrache, C. Rossi Alvarez, C. Ur, G. de Angelis, D.R. Napoli, Ts. Venkova and R. Wyss, Nucl. Phys. A671 (2000) 52.

3. B.G. Carlsson, I. Ragnarsson, R. Bengtsson, E.O. Lieder, R.M. Lieder, A.A. Pasternak, submitted to Phys.

Rev. C (2008).

2 5 /2 3 3 / 2 4 1 / 2 4 9 /2 5 7 / 2 6 5 /2 7 3 / 20 . 10 . 1

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2) [W

.U.]

B(E

2) [e

2 b2 ]

S p in

1 4 3 G d , B a n d 1

Figure 52: Experimental B(E2) values for the 33/2+ to 69/2+ levels of the strongly populated quadrupole band in 143Gd [2].


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Figure 53: Experimental fold distributions for 140-144Eu obtained for the αxn and 2pxn channels in the 97Mo + 51V reaction at 238 MeV are shown as histograms. Monte-Carlo simulations of the fold distributions calculated assuming a complete fusion reaction mechanism are shown as lines.

3.3.4 Observation of a Double-humped γ-ray Fold Distribution in 142Eu R.M. Lieder1, A.A. Pasternak2, E.O. Lieder1,2, W. Gast3, G. de Angelis4 and D. Bazzacco5 1 iThemba Laboratory for Accelerator Based Sciences, Somerset West 7129, South Africa 2 A.F. Ioffe Physico-Technical Institute RAS, RU-194021 St. Petersburg, Russia 3 Institute für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich, Germany 4 INFN, Laboratori Nazionali di Legnaro, I-35020 Legnaro, Italy 5 Dipartimento di Fisica dell’Università and INFN Sezione di Padova, I-35131 Padova, Italy In heavy-ion induced reactions high excitation energies and large angular momenta are transferred to the produced nuclei. The highly-excited nuclei de-excite by long cascades of γ-ray transitions to the ground state. The number of γ-rays in each cascade is referred to as γ-ray multiplicity Mγ. The multiplicity distribution can be measured with γ-detector arrays equipped with an inner scintillator ball. The number of detectors responding to a γ-ray cascade of multiplicity Mγ is called the fold K. Fold distributions for the population of specific final nuclei around 142Eu were deduced from high-spin γ-spectroscopy data obtained with the γ-detector array GASP of the Laboratori Nazionali di Legnaro, Italy. In this investigation a 97Mo target was bombarded with 238 MeV 51V projectiles. The self-supporting 97Mo target (enrichment 94,2%) was ≈1.0 mg/cm2 thick. The GASP array, consisting of 40 bismuth-germanate (BGO) suppressed Ge detectors and an 80 element BGO ball, was equipped with the charged-particle detector array ISIS, consisting of 40 Si particle telescopes with thicknesses of ≈140 µm and ≈1 mm for the ΔE and E detectors, respectively. Coincidence events were recorded when ≥ 3 escape-suppressed Ge detectors and ≥ 3 BGO scintillators detected γ-rays in coincidence. In total 2 ∙ 109 coincidence events were collected.


103

Fold distributions for the 97Mo(51V,2pxn) and αxn reaction channels leading to 141-144Eu were produced by the analysis of p- and α-gated matrices and are shown in Figure 53. The centroids of the 2pxn fold distributions are gradually shifting to lower folds with an increasing number of emitted neutrons as expected for complete-fusion reactions. However, a completely different picture is found for the αxn channels leading to the nuclei 140-143Eu, as can be seen in Figure 53. The centroids of the fold distributions change irregularly with the number of emitted neutrons (α4n: <F>= 11; α3n: <F>= 16; αn: <F>= 15) and the fold distribution of the α2n channel leading to 142Eu shows a double-humped structure with maxima at <F>= 11 and 17. For the interpretation of the observed fold distributions Monte-Carlo simulation calculations were carried out using the codes COMPA and GAMMA [1]. A new approach was developed, based on Monte-Carlo simulations of entry-state population distributions as well as of the depopulation to known levels. In the first step the input angular momentum is calculated taking into account the dependence of the fission barrier on the angular momentum L. In the second step, for complete fusion reactions, the light-particle evaporation is simulated with Monte-Carlo methods based on a statistical theory of nuclear reactions. The competition between particle evaporation and fission mainly defines the locations of the entry-state population distributions of the various final nuclei in a plot of the excitation energy E* vs. angular momentum I. In the third step the de-excitation of the entry states is simulated taking into account statistical E1, M1 and E2 transitions, stretched E2 bands, superdeformed bands in the continuum and the existence of a large amount of particle-hole excitations which generate cascades of stretched magnetic dipole transitions. Parameters for the calculation of statistical transitions were chosen in accordance with systematics of γ-ray strength functions for E1, M1 and E2 multipolarities, respectively [2]. In this way for each cascade the number of emitted γ-rays Mγ is determined giving the multiplicity distribution considering a large number of cascades. A comparison of the experimental fold distributions with the simulated multiplicity distributions is not carried out by an unfolding procedure applied to the fold distributions. Instead, the simulated γ-ray multiplicity distributions are transformed into fold distributions by Monte-Carlo methods. The response of the BGO ball is simulated for each γ-ray transition separately, using detection probabilities for γ-quanta of given energy which has been extracted from fold-multiplicity calibrations of the BGO ball. In Figure 53 the experimental fold distributions are compared with simulations assuming a complete fusion reaction mechanism. It can be seen that for the 2pxn, α3n and α4n reaction channels the experimental fold distributions are described rather well, indicating that these reactions proceed through a complete fusion reaction mechanism. However, the fold distributions for 142,143Eu nuclei populated in the α2n and αn reaction channels, respectively, cannot be described. Furthermore, the complete-fusion calculations predict very small cross sections for these channels contradictory to the experimental observation. Both facts indicate that an incomplete-fusion reaction mechanism may play a role.

References 1. E.O. Lieder, A.A. Pasternak, R.M. Lieder, A.D. Efimov, V.M. Mikhajlov, B.G. Carlsson, I. Ragnarsson,

W. Gast, Ts. Venkova, T. Morek, S. Chmel, G. de Angelis, D.R. Napoli, A. Gadea, D. Bazzacco, R. Menegazzo, S. Lunardi, W. Urban, Ch. Droste, T. Rząca-Urban, G. Duchêne and A. Dewald, Eur. Phys. J.

A21 (2008) 37. 2. Handbook for Calculations of Nuclear Reaction Data, RIPL-2, IAEA-TECDOC-1506 IAEA, Vienna (2006).


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3.3.5 Level Structure of 195,196,197Po S.S. Ntshangase1 , A.N. Wilson2, R.A. Bark1, P.M. Davidson2, P. Nieminen2, E.A. Lawrie1, J.J. Lawrie1, S.M. Mullins1, P. Papka1, E.O. Lieder1,4, R.M. Lieder1, P.L. Masiteng1,3 and J. Sharpey-Schafer3 1 iThemba LABS, Somerset West, 7129, South Africa 2 Department of Nuclear Physics, Australian National University 3 Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa 4 A.F. Ioffe Physico-Technical Institute RAS, RU-194021 St. Petersburg, Russia The study, reported last year, of 196Po, using the new Microchannel Plate (MCP) -based recoil detector, has been extended to the study of the odd-neutron neighbours 195-197Po. Due to a lack of success in identifying any superdeformed or magnetic rotational bands in the 196Po experiment, the emphasis has shifted to studying the onset of collectivity at low spins in Po isotopes. These states have been understood in terms of mixing between near spherical, or vibrational states, with deformed oblate structures [1,2]. The experiments to populate 195-197Po are presently in progress. The same reaction, 180W + 20Ne and experimental set-up used for the 196Po study, was used to populate 195Po, with a beam energy of 118 MeV. The cross-section to populate 195Po is a few percent of the fission cross-section, necessitating the use of the recoil detector. To study 197Po, the reaction 180W(22Ne,5n) at a beam energy of 116 MeV was employed. The data acquired to date for both 195Po and 197Po have been sorted into matrices and the level schemes have been constructed. Due to statistics our 195Po data presently only confirms the known level scheme, while the level scheme of 197Po has already been extended. Further data analysis is in progress. The bands identified in 196Po are shown in Figure 54. At low spins the ground band has an irregular structure suggesting mixing with spherical states. The ground band develops into a regular structure at higher spins, indicating the development of collectivity. It is crossed by several bands having aligned angular momenta in the

region of 7 - 9h. Suggested configurations are given.

References 1. L.A. Bernstein et al., Phys. Rev. C52 (1995) 621. 2. M. Leino, Acta Phys. Pol. B32 (2001) 2365.

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Figure 54: The bands identified in 196Po and suggested configurations.


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3.3.6 High Spin States in 194Tl P.L. Masiteng1,2, E.A. Lawrie1,T.M. Ramashidzha1,2, Y. Zhang1,3, J.J. Lawrie1, R.A. Bark1, J. Kau1,4, F. Komati1,4, S.M. Maliage1,2, I. Matamba5, S.M. Mullins1, S.H.T. Murray1,3, K.P. Mutshena1,5, J.F. Sharpey-Schafer1, P. Vymers1,2 1 iThemba LABS, PO Box 722, 7129 Somerset West, South Africa 2 University of the Western Cape, Private Bag X17, 7535 Bellville, South Africa 3 University of Cape Town, Private Bag, 7701, Rondebosch, South Africa 4 University of North West, Private Bag X2046, 2735 Mmabatho, South Africa 5 University of Venda for science and technology, Thohoyandou, South Africa High spin states in 194Tl, excited through the 181Ta (18O, 5n) heavy-ion fusion evaporation reaction at beam

energies of 91 and 93 MeV were studied using in-beam γ-ray spectroscopic techniques. A stack of two thin

metallic tantalum targets with thickness of 0.5 mg/cm2 each were used in this measurement. The AFRODITE array consisted of 8 clover detectors and 6 LEPS with the trigger logic set to accept events when at least two clover detectors fired in coincidence. Data were collected during two weekends of beam time.

Data analysis of the second weekend consisting of a γ-γ coincidence study and directional correlation (DCO)

ratio measurements resulted in a considerable extension [2] of the previously reported level scheme of 194Tl [1]. Spin assignments for many new levels were based on results from measurements of DCO ratios [2]. The complete data set was used to perform linear polarization measurements and to assign parities to the new states [3] and also to search for isomeric states using the Recoil Shadow Anisotropy Method (RSAM). Only one isomeric state, the 8- level, was found [3]. Lifetime measurements resulting in a half-life of 85 ± 4 ns for the 8- isomeric level, were done using the time spectra for the clover detectors [4]. Further improvements to the level scheme

were made when studying the γ-γ coincidences using the whole data set.

The previous level scheme from Kreiner et al. [1] consisted of a single band of 14 transitions and 11 levels and our data are in agreement with most of the placements of the transitions from this study. In this work Band 1 was

extended up to the Iπ = 24- level at 4.817 MeV and four new bands were observed. Band 1 levels and transitions were previously reported in Ref. [1] up to spin 15. A few changes were made in this work such as the placement

of the 289 keV transition in the new band 2 (18+→17+), the 741.3 keV γ-ray was moved to higher excitation

energies (24-→22) and the 458.6 keV transition was assigned to the new structure A. Our data could not confirm the placement of the previously suggested tentative 748.6 keV transition and it was removed from the level

scheme. Band 2 was observed for the first time in the present data and extends up to Iπ = 28+ and excitation energy of 6.32 MeV. It is linked by four transitions to Band 1. A 25 keV (13+→12+) transition was not observed in

the γ-ray spectra, but it was introduced in Band 2 based on the observed coincidence relationships.

Band 3 was also not known before the present experiment. This band extends up to Iπ = 24- at 4.771 MeV and it

has several linking transitions to bands 1 and 4. Band 4 is also new. This band extends up to Iπ = 23- at 4.556 MeV excitation energy. It is linked to band 1 by several transitions. Band 5 is also observed for the first time in the present experiment and extends up to I = 19 and 3.632 MeV excitation energy. This band de-excites


106

to the 13+ state of Band 1. The γ-γ coincidence spectra showing the bands in 194Tl can be seen in Figure 55. The

DCO and linear polarization measurements allowed us to assign spins and parities to most of the new levels. Data analysis is still in progress.

References 1. A.J. Kreiner, et al., Phys. Rev. C 20 (1979) 2205. 2. T. M. Ramashidzha, M.Sc. thesis, University of the Western Cape, 2006. 3. P. L. Masiteng, M.Sc. thesis, University of the Western Cape, 2007. 4. Y. Zhang, Vacation Project report , iThemba LABS, 2006.

Figure 55: γ-γ coincidence spectra gated on: the 278 γ-ray (upper panel) where transitions from band 1 are marked with stars and transitions from band 3 are marked with double stars; the 388 keV transition (middle panel) where the transitions from band 4 are marked with stars; and the 1058 keV γ-ray (lower panel) where the transitions from band 2 are marked with stars and those from band 5 are marked with double stars.


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3.3.7 Cluster States in 6Be P. Papka1, R.A. Bark1, S.P. Fox2, B.R. Fulton2, A. Krashnahorkay3, J. Gál3, E.A. Lawrie1, G. Kalinka3, J.J. Lawrie1, E. Lieder1, R. Lieder1, J. Molnár3, S.M. Mullins1, B.M. Nyakó3 , J. Timár3, L. Zolnai3

1iThemba LABS, PO Box 722, Somerset West 7129, South Africa 2Department of Physics, University of York, Heslington, United Kingdom 3ATOMKI, Institute of nuclear research, Debrecen, Hungary The study of three body breakup relies on complete kinematic measurement in order to identify the correlations between observables. In this work, we are investigating the structure of 6Be, a strong candidate for direct three body break-up [1,2] with a di-proton width calculated to be rather low [3]. We used the 6Li(3He,t) reaction at Elab = 50 MeV to populate 6Be. The experimental data of the ground and first excited states are compared with the simulation of the sequential decay, namely 6Be → 5Li + p and 6Be → 4He + 2He. The decay via the direct breakup channel is discussed. A broad component, observed in the Ex = 3-20 MeV excitation energy region, indicates the existence of a broad resonance in 6Be around the 3He-3He threshold. This experiment was designed to cover a large solid angle to detect 3-4 particles in coincidence with a rather high

efficiency and large angular coverage. Two E-∆E telescopes made of a 300 µm thick (16 strip 50x50 mm2)

DSSSDs, backed with a CsI(Tl) crystal divided in 4 segments, were placed at θlab = 45o opposite to each other

with respect to the beam. The distance of d = 6 cm from the front of the detector to the target made the solid

angle of each detector of approximately dΩ = 1 sr allowing three particles to be detected and identified in the

same telescope. The α particles are assumed to be detected when any particle with E > 10 MeV is stopped in the silicon detector without Particle Identification (PID) while the punch through energy for t is E > 9 MeV and for p

E > 6 MeV allowing E- ∆E PID. The beam energy was Elab = 50 MeV and the thickness of the target was 5 mg/cm2. The excitation energy spectrum of 6Be, shown in Figure 56, is extracted from the four-fold events with t-6Be in-plane condition and a selection on the Total final state Kinetic Energy to be 46 < ETKE < 48 MeV. The ground and second excited states, known since early studies [4], are clearly visible and a broad component spans from Ex ~ 3.0-20 MeV. The excited states above Ex = 20 MeV do not show in the spectrum most probably due to the relatively low beam energy and low efficiency at high excitation energy.

Figure 56: Excitation energy spectrum of 6Be


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The decay of the low lying states of 6Be was simulated using the 2He-4He and 5Li-p sequential decay paths. The relative energy profiles were calculated including the Coulomb and centrifugal barriers, due to the relative angular momenta in the two decay paths, folded with the Lorentzian tail of the 2He and 5Li resonances [5]. The width and position of the peaks are very well reproduced using both exit channels. The experimental energy spectrum for Ex < 3 MeV is compared with the simulated profile for the 2He-4He channel in Figure 57. However, the angular

correlation of Figure 58 cannot be reproduced using any sequential decay. θ1 is the angle between the direction of the first and second step decay when reconstructing the 2He-4He break-up channel as showed in the insert of Figure 58. The angular correlation parameters are calculated using the Bidenharn and Rose formalism and

introduced in the simulation [6]. Concerning the ground state, Jπ = 0+, any correlation should not be exhibited in

the 2He-4He break-up channel. Concerning the 5Li-p decay, θ1 is obtained from the mis-reconstruction of the 2He-4He events. This is achieved using both experimental and simulated data and the angular distributions can be compared.

In both cases the simulated θ1 angular distributions exhibit a double-humped structure as seen in Figure 58. From

the theoretical point of view, any pure or mixed decay channels do not compare at all with the experimental angular correlation spectrum. Though, parameters can be artificially adjusted for the di-proton emission to mimic the experimental data while no set of parameters can be found for the sequential proton emission. We are now investigating if the angular correlation can be better reproduced in the framework of a direct breakup using the formalism detailed in [7]. A broad component in the excitation energy spectrum, seen in Figure 56, is characterized by a double-humped structure but it is not yet clear if this is purely an effect of the acceptance of the detectors or if two states can be resolved. The analysis of the relative energy between the three break-up particles indicates that most of the

strength decays via the 5Li-p break-up channel. Nearly half of the events in the α-p relative energy spectrum of

Figure 59 are centred on Erel = 1.4 MeV, FWHM = 1.76 MeV corresponding to the 5Li decay. The higher α-p

relative energies are associated with the first step p emitted which has a much higher relative energy than the

Figure 57: Experimental (black) and simulated (red) data of the ground and first excited states of 6Be

Figure 58: Angular distribution measured between the direction of the “di-proton” emitted in the first step decay and the direction of the subsequent two individual protons emitted in the second step decay


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α−particle emitted in the 5Li decay. The position of the 5Li peak differs from the expected relative energy

(Erel = 1.968 MeV, Γ = 1.23 MeV). The red histogram of Figure 59 indicates that the lower position of the peak is consistent with the simulation.

The structure of the two low lying states of 6Be cannot be interpreted in terms of 2He-4He and/or 5Li-p two-body cluster configurations as expected from theoretical calculations [1,2]. Those states are most probably decaying via direct breakup. Three body calculations are now being performed and introduced into simulations. The events with an excitation energy between Ex = 1.67-20 MeV decay via 6Be → 5Li-p but the structure of 6Be is not yet very well understood. References 1. E. Garrido, D.V. Fedorov, A.S. Jensen, Nucl. Phys. A790 (2007) 96c. 2. L.V. Grigorenko, R.C. Johnson, I.G. Mukha, I.J. Thompson, M.V. Zhukov, Phys. Rev. Lett. 85 (2000) 22. 3. O.V. Bochkarev, L.V. Chulkov, A.A. Korsheninnikov, E.A. Kuzmin, I.G. Mukha, G.B. Yankov, Nucl. Phys.

A505 (1989) 215. 4. G.F. Bogdanov, N.A. Vlasov, S.P. Kalinin, B.V. Rybakov, V.A. Sidorov, Soviet. J. Atomic Energy

3 (1957) 987, J.Nuclear Energy 8 (1958) 148. 5. F. Barker, private communication. 6. L.C. Biedenharn and M.E. Rose, Rev. Mod. Phys. 25 (1953) 729. 7. R. Alvarez-Rodriguez, H.O.U. Fynbo, A.S. Jensen, and E. Garrido, Phys. Rev. Lett. 100 (2008) 192501.

Figure 59: α-p relative energy for those events with 3.0 < Ex < 20.0 MeV.


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3.3.8 The K600 Zero Degree Facility R. Neveling1, H. Fujita1,2, F.D. Smit1, Z. Buthelezi1, G.P.A. Berg3, J. Carter2, L. Conradie1, R.W. Fearick4, S.V. Förtsch1, D. Fourie1, Y. Fujita5, K. Hatanaka6, S. Jones4, S.H.T. Murray1, S. O'Brien3, A. Richter7, A. Tamii6, I. Usman2, P. von Neumann-Cosel7 and S. Walton4

1 iThemba Laboratory for Accelerator Based Sciences, Somerset West 7129, South Africa. 2 School of Physics, University of Witwatersrand, Johannesburg 2050, South Africa. 3 Department of Physics, University of Notre Dame, Indiana 46556, USA. 4 Physics Department, University of Cape Town, Rondebosch 7700, South Africa. 5 Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan. 6 Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan. 7 Institut für Kernphysik, TU Darmstadt, Darmstadt 64829, Germany. The motivation for the development of a zero-degree facility at the K600 Magnetic Spectrometer follows the

impressive progress witnessed during the last few years towards a combination of 0° experiments for medium-energy hadron scattering with high energy resolution [1,2]. Such measurements can address a number of important questions concerning, amongst other, the properties of the isoscalar giant monopole and dipole resonances and their relation to the nuclear equation of state [3] or the mapping of Gamow-Teller (GT) strength distributions relevant for the understanding of supernova dynamics [4]. A particular advantage of

0° measurements is the selectivity to low angular momentum transfer (∆L = 0 or 1) simplifying the analysis of the

many contributions to the spectra due to the complex nature of the nuclear interaction. The establishment of such a facility at iThemba LABS was first envisioned during 2003. The project started towards the end of 2005 when financial support was received from the Deutsche Forschungsgemeinschaft (DFG) (funding code NE 679/2-2) under a DFG/BMZ (the German Federal Ministry of Economic Co-operation and Development) programme in the framework of Research Co-operation with Developing Countries. This was subsequently followed by the allocation of funds from the NRF in April 2006 as part of a DFG/NRF agreement. The goal is to build a facility which permits the measurement of proton and other light ion scattering reactions at

0° with an extremely high energy resolution ∆E / E ≈ 104. The "Faint Beam" technique [5] for dispersion matching of the beams necessary to achieve such values and maintain them over longer measuring periods has been

implemented and successfully tested at finite angles at iThemba LABS. However, in order to measure at 0° an upgraded detection system, positioned in the high dispersion focal plane, and associated electronics, as well as a new beamstop, was required. Furthermore, as both the primary beam and scattered particles pass through the spectrometer, stable beam conditions and the minimization of beam halo becomes critical.

Accurate determination of the scattering angle in 0° measurements requires the accurate determination of both

the horizontal and the vertical components of particle tracks in the focal plane. Since the vertical resolution of the existing Vertical Drift Chambers (VDCs) was found to be inadequate, new VDCs were designed and manufactured at iThemba LABS, as shown in Figure 60. Additionally, new trigger scintillators with improved geometric efficiency in the high dispersion focal plane were designed and manufactured. Figure 61 illustrates the vastly improved vertical resolution achieved by the new VDCs. The previous detection system divided the


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Figure 60: One of the two new Vertical Drift Chambers, situated along the medium dispersion focal plane for beam testing

100 mm vertical distance (indicated on the x-axis of the figure) in only 16 bins. Note that this test was conducted with the old electronics and DAQ system coupled to a new VDC.

The number of preamp and TDC channels required to instrument the two new drift chambers increased from the original 412 to 682 as a result of the improved vertical position resolution capabilities. The available preamplifiers and CAMAC TDC electronics did not have the spare capacity and additions were no longer commercially available. This prompted the complete upgrade of the TDC electronics from CAMAC to VME. Additional LeCroy compatible preamp cards, were sourced from the Japanese company Technoland. Likewise the data acquisition (DAQ) system was changed from the XSYS software package running on a

VAX workstation [6] to PSI MIDAS [7] running on a Linux desktop. Figure 62 illustrates a position spectrum of the 12C(p,p) reaction at 66 MeV which was acquired at 7o with the new electronics and DAQ system coupled to an old VDC.

In addition to the above mentioned work on the new detectors and DAQ system, the Zero Degrees project entailed a host of smaller projects such as the installation of a dedicated zero degree beamstop between the K600 and AFRODITE experimental vaults, the installation of bigger entrance and exit beampipe elements to and from the K600 scattering chamber and the slight realignment of beamline elements. Hall probes are being installed to monitor the magnetic fields of the various bending magnets involved in the transportation of the proton beam from the SSC to the K600 in an effort to have better beam diagnostics and improve beam stability. Also, thinner object slits were installed in the X-line to minimize beam halo that is caused by small angle slit scattering.

Figure 61. Online spectrum of the vertical position in the focal plane for the "pepperpot" collimator representing mostly elastic 12C(p,p) data at 200 MeV for the K600 at 7° and in under focus mode. The data were acquired with the old electronics and DAQ system coupled to a new VDC. The five peaks represent five vertical rows of holes in the "pepperpot" collimator.

Figure 62: The focal plane position spectrum of the 12C(p,p) reaction at 66 MeV as acquired at 7° with the new electronics and DAQ system coupled to the old VDCs. The elastic peak and first excited state of 12C are clearly visible.


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Newly installed current reading on these slits can also be instrumental in achieving better focussing and stable beam conditions.

There are a few remaining challenges before the K600 Zero Degree Facility can be routinely used in experiments. The new VDCs in combination with the new DAQ system are still to be commissioned as these systems were only individually tested with respectively the old DAQ system and old VDCs. Finally, work in understanding the beam setup may still be required in order to sustain low beam halo conditions, absolutely essential for successful

0° measurements, over long periods of time. References 1. Y. Fujita, B.A. Brown, H. Ejiri, K. Katori, S. Mizutori and H. Ueno, Phys. Rev. C 62 (2000) 044314.

2. C. Bäumer, A.M. van den Berg, B. Davids, D. Frekers, D. De Frenne, E.W. Grewe, P. Haefner, M.N. Harakeh, F. Hofmann, M. Hunyadi, E. Jacobs, B.C. Junk, A. Korff, K. Langanke, G. Martinez-Pinedo, A. Negret, P. von Neumann-Cosel, L. Popescu, S. Rakers, A. Richter and H.J. Wörtche, Phys. Rev. C 68

(2003) 031303(R). 3. Proceedings of COMEX1, Paris, 2003, Nucl. Phys. A 731 (2004). 4. K. Langanke and G. Martinez-Pinedo, Rev. Mod. Phys. 75 (2003) 819. 5. H. Fujita, Y. Fujita, G.P.A. Berg, A.D. Bacher, C.C. Foster, K. Hara, K. Hatanaka, T. Kawabata, T. Noro,

H. Sakaguchi, Y. Shimbara, T. Shinada, E.J. Stephenson, H. Ueno and M. Yosoi, Nuclear Instrument and

Meth. A 484 (2002) 17. 6. J.V. Pilcher, The NAC MBD to VME Conversion Guide, National Accelerator Center (1996), unpublished. 7. PSI MIDAS, https://midas.psi.ch/.

https://midas.psi.ch/


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3.3.9 A Global Investigation of the Fine Structure of the Isoscalar Giant Quadrupole

Resonance: The Low-Mass Region 12 ≤ A ≤ 40 I. Usman1,2, J. Carter1, R. Neveling2, Z. Buthelezi2, S.V. Förtsch2, H. Fujita1, 2, F.D. Smit2, R. Fearick3, G.R.J. Cooper4, E. Sideras-Haddad1, P. von Neumann-Cosel5, A. Richter5, A. Shevchenko5, J. Wambach5 and Y. Fujita6

1 School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa 2 iThemba Laboratory for Accelerator Based Sciences, Somerset West 7129, South Africa 3 Department of Physics, University of Cape Town, Rondebosch 7700, South Africa 4 School of Geophysics, University of the Witwatersrand, Johannesburg 2050, South Africa 5 Institut fϋr Kernphysik, TU Darmstadt, Darmstadt 64829, Germany 6 Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan Inelastic hadron scattering is a powerful tool for the investigation of nuclear giant resonances across the periodic table, and especially so for the isoscalar giant quadrupole resonance (ISGQR). High energy resolution inelastic proton scattering experiments were performed for medium to heavy-mass nuclei at iThemba LABS in 2003 [1], which revealed that the ISGQR carries fine structure. As a result of this success the investigations continued in early 2007 with high energy-resolution experiments on the light nuclei 12C, 28Si, 27Al, and 40Ca. Experiments were carried out using the K600 Magnetic Spectrometer with a proton beam at incident energy of 200 MeV. The inelastically scattered protons were momentum analysed by the K600 Magnetic Spectrometer and were detected in the focal-plane detection system designed and manufactured at iThemba LABS [2]. This detection system consists of three multiwire drift chambers for position analysis and a pair of plastic scintillation detectors for particle identification and trigger purposes. Experimental data were analysed offline using the C software developed at iThemba LABS which utilises the CERN Library’s Physics analysis Workstation (PAW) interface. The energy resolution obtained was in the range of 25-30 keV (FWHM). Shown in Figure 63 are the resulting excitation energy spectra for three of the low mass nuclei investigated at the maximum of the ISGQR. Fine structure, similar to that seen for heavier targets, is visible in all nuclei under investigation, thus confirming it to be a global phenomenon. Since the main aim of this experiment was to investigate the fine structure and characteristic energy scales in light nuclei, extraction of characteristic energy scales were carefully carried out using Matlab software with specific emphasis on Wavelet transform and Fourier analysis techniques [3]. A critical comparison of the different energy scales analysis techniques is discussed in reference [4]. Level densities represent additional information which can be retrieved from the fine structure of the giant resonances by means of a fluctuation analysis. It has been shown in recent work [5] that the high energy-resolution data obtained at iThemba LABS is a good

Figure 63: Energy spectra showing the region of the ISGQR measured for different nuclei.


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candidate for an autocorrelation function approach of extracting level densities in nuclei. This is essential for an application of the fluctuation analysis technique and has been applied to the 40Ca(p,p´) data.

The characteristic energy scales of experimental and theoretical 40Ca(p,p´) E2 results are compared in Figure 64. Theoretical predictions of the excitation energy spectrum were performed within the framework of the Second Random Phase Approximation (SRPA) [6]. It was found that the theoretical calculation is quite insensitive to the details of the E2 strength functions of the fragmented segment about 14 MeV. This is not too surprising as it is known that beyond mean-field theory, coupling to low-lying states plays an essential role in the damping of the isoscalar quadrupole resonance. Certain features of the intermediate energy scales are shared by the experimental data and theoretical predictions, as seen from the Figure 65. In conclusion, these results confirmed that fine structure is truly a global phenomenon found in all nuclei across the periodic table. By comparison of experimental data with a SRPA calculation it is possible to comment on the dominance of the escape width in the damping mechanisms of light nuclei. References 1. A. Shevchenko, J. Carter, R.W. Fearick, S.V. Förtsch, H. Fujita, Y. Fujita, Y. Kalmykov, D. Lacroix, J.J. Lawrie,

P. von Neumann-Cosel, R. Neveling, V.Yu. Ponomarev, A. Richter, E. Sideras-Haddad, F.D. Smit and J. Wambach, Phys. Rev. Lett. 93 (2004) 122501.

2. R. Neveling, F.D. Smit, H. Fujita, and R.T. Newman, Guide to the K600 Magnetic Spectrometer, pg. 12, 2007. 3. M. Misiti, Y. Misiti, G. Oppenheim, and J.M. Poggi, Wavelet toolbox, User’s Guide (The mathworks, Inc. 1996-

1997). 4. A. Shevchenko, J. Carter, G.R.J. Cooper, R.W. Fearick, Y. Kalmykov, P. von Neumann-Cosel,

V.Yu. Ponomarev, A. Richter, I. Usman and J. Wambach, Phys. Rev. C 77 (2007) 024302. 5. Y. Kalmykov, C. Ozen, K. Langanke, G. Martinez-Pinedo, P. von Neumann-Cosel and A. Richter, Phys. Rev.

Lett. 99 (2007) 202502. 6. P. Papaconstantino and R. Roth, IKP TU Darmstadt (2008) private communication: J. Wambach, Rep. Prog.

Phys. 51 (1988) 989.

Figure 65: Characteristic scales extracted from the Second Random Phase Approximation calculation for the 40Ca ISGQR using the Complex Morlet wavelet analysis technique.

Figure 64: Characteristic energy scales extracted from the experimental 40Ca data using the Complex Morlet wavelet analysis technique.


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3.3.10 A Search for the Excited Hoyle States

H. Fujita1,2, M. Freer3, Z. Buthelezi1, J. Carter2, S.V. Förtsch1, R. Neveling1, S.M. Perez1,4, F.D. Smit1, I. Usman1,2

1iThemba LABS, PO Box 722, Somerset West 7129, South Africa 2School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa 3School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom 4Physics Department, University of Cape Town, Rondebosch 7700, South Africa One of the most significant states in all nuclei is the 7.654 MeV excited state in 12C, the so called Hoyle state. In the stellar production of nuclei, virtually all matter from 12C and heavier pass through this state. This second 0+ state is thought to have a triple alpha cluster nature. Recently electron scattering measurements on 12C were consistent with the Hoyle state having a rms radius of about 1.5 times that of the ground state [1]. Ever since the state was discovered, there has been interest in finding the excited states built on this second 0+ state. An investigation using the 11B (3He, d) 12C reaction suggested that the state found at 11.16 MeV [2] may be the 2+ state related to the Hoyle state, but this has not yet been confirmed. Recent measurements of the breakup of 12C into three alpha particles [3] suggest that the very broad structure around 10.3 MeV also has some 2+ character. At iThemba LABS inelastic proton scattering data were taken on 12C at an incident proton energy of 200 MeV. The inelastically scattered protons in the range 7 – 20 degrees were momentum analyzed using the high energy resolution K600 magnetic spectrometer. Interest was initially focused on a small peak around 11.2 MeV seen at 13 degrees in data from a previous experiment, but this was identified as having come from 16O contamination in the target. It was noticed that the 9.641 MeV peak had a tail. A fit to the 9.641 MeV peak was done taking the peak shape of a single state from the 12.71 MeV peak and setting the width of the 9.641 MeV peak to the accepted literature value of 34 keV. It revealed a possible weak state at 9.7 MeV. This situation repeated itself at the other angles. Rough cluster calculations support this finding and predict the 4+ state at around 14 MeV. More work is underway to prove the existence of this peak. References 1. M. Chernykh, H. Feldmeier, T. Neff, P. von Neumann-Cosel, and A. Richter, Phys. Rev. Lett. 98 (2007)

032501.

2. G.M. Reynolds, D.E. Rundquist and R.M. Poichar, Phys. Rev. C 3 (1971) 442. 3. H.O.U. Fynbo, G. Ciangaru, F. Khazaie, D.J. Mack, A. Nadasen, S.J. Mills, R.E. Warner, E. Norbeck,

F.D. Becchetti, J.W. Janecke, and P.M. Lister, Phys. Rev. Lett. 91 (2004) 082502.


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3.3.11 The Role of a Direct Knockout Mechanism in the Inclusive (p,α) Reaction J.J. van Zyl1, J. Bezuidenhout1, E.Z. Buthelezi2, A.A. Cowley1,2, S.V. Förtsch2, G.C. Hillhouse1, P.E. Hodgson3, R. Neveling2, F.D. Smit2, J.A .Stander1, G.F. Steyn2 1Department of Physics, University of Stellenbosch, Stellenbosch, South Africa 2iThemba LABS, PO Box 722, Somerset West 7129, South Africa 3Particle Physics Laboratory, Department of Physics, University of Oxford , United Kingdom Whereas nucleon emission into the continuum induced by medium energy protons is described reasonably well in terms of formulations based on statistical multistep theories, the processes involved in complex particle emission,

such as helions and α-particles, are not understood to the same extent.

Based on simple arguments one expects a two-nucleon pickup mechanism to dominate the (p,3He) reaction. The

(p,α) reaction, on the other hand, is more likely to involve the knockout of an α-cluster. Studies at incident

energies between 100 and 200 MeV show that calculations based on a statistical multistep mechanism preceding the final pickup or knockout step respectively, describe the observed cross section distributions reasonably well [1,2]. Of course, analyzing power distributions are even more sensitive to the details of the reaction mechanism than cross sections. Consequently this was exploited to confirm the interpretation of the details of the basic process for the (p,3He) reaction [3], and to track the incident energy dependence of the observables [4].

An understanding of the mechanism of the (p,α) reaction needs to be developed to the same extent as that of the (p,3He) reaction. Although the qualitative similarities between the two sets of experimental cross section and analyzing power distributions suggest that they share a common multistep component, the knockout process that

is expected to dominate in the case of the (p,α) reaction needs to be confirmed.

In this work we investigated the cross section and analyzing power distributions for the (p,α) reaction on targets of 59Co and 93Nb in terms of a simplistic single step cluster knockout model. Calculations were based on a distorted wave impulse approximation. Experimental data to compare with the predicted distributions are available at incident energies of 100, 130 and 160 MeV. Of course, due to the extreme simplicity of our present model, even if basically correct, one would expect fair agreement with the experimental data only under certain kinematic conditions, such as high emission energies and small scattering angles. As shown in Figure 66 this expectation is realised, which suggests that the reaction

process which leads to the eventual emission of an α-particle is identified correctly.


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References 1. A.A. Cowley, G.J. Arendse, G.F. Steyn, J.A. Stander, W.A. Richter, S.S. Dimitrova, P. Demetriou, and

P.E. Hodgson. Phys. Rev. C 55 (1997) 1843. 2. A.A. Cowley, G.J. Arendse, J.W. Koen, W.A. Richter, J.A. Stander, G.F. Steyn, P. Demetriou,

P.E. Hodgson, and Y. Watanabe. Phys. Rev. C 54 (1996) 778. 3. A.A. Cowley, G.F. Steyn, S.S. Dimitrova, P.E. Hodgson, G.J. Arendse, S.V. Förtsch, G.C. Hillhouse,

J.J. Lawrie, R. Neveling, W.A. Richter, J.A. Stander, and S.M. Wyngaardt. Phys. Rev. C 62 (2000) 064605. 4. A.A. Cowley, J. Bezuidenhout, S.S. Dimitrova, P.E. Hodgson, S.V. Förtsch, G.C. Hillhouse, N.M. Jacobs,

R. Neveling, F.D. Smit, J.A. Stander, G.F. Steyn, and J.J. van Zyl. Phys. Rev. C 75 (2007) 054617.

Figure 66: Double differential cross section (top) and analyzing power (bottom) as a function of scattering angle for 56Co(p,α) and 93Nb(p,α) at 100 MeV incident proton energy for an out-going α-particle of 82 MeV.


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3.3.12 Complete and Incomplete Fusion Processes in the 12C +12C System at an Energy

of 16.7 MeV/nucleon S.V. Förtsch1, A. Mairani2, J. Mira1,3, F. Cerutti4, E. Gadioli5,6, E.Z. Buthelezi1, S.H. Connell7, H. Fujita1,7, R. Neveling1, F.D. Smit1, A. A. Cowley1,8, J. Dlamini1,9 1iThemba LABS, Somerset West, 7129, South Africa 2Dipartimento di Fisica Nucleare e Teorica, Università di Pavia and INFN, Pavia, Italy 3Department of Physics, University of the Western Cape, Bellville, South Africa 4CERN, Geneva, Switzerland 5INFN, Sezione di Milano, Italy 6Dipartimento di Fisica, Università di Milano, Italy 7School of Physics, University of the Witwatersrand, Johannesburg, South Africa 8Department of Physics, University of Stellenbosch, South Africa 9Department of Physics, University of Zululand, South Africa

The role of target and projectile fragmentation in the production of Intermediate Mass Fragments (IMF) in very light projectile-target systems is extended in the present project to study, in particular, also those IMFs which are emitted with a mass heavier than the target or the projectile. At relatively high incident energies, nucleon transfer is known to dominate the spectra of fragments emitted especially around near-target or near-projectile masses. However, recent results [1] of similar light systems have shown that such IMFs might also be produced as evaporation residues in complete fusion and/or break-up-fusion reactions. In order to ascertain whether these

mechanisms also play an important role in the present study complete energy spectra of the IMFs (Z ≥ 5 ) emitted in the 12C + 12C interaction were measured at an incident energy of 200 MeV and over a range of emission angles between 10° and 60°. The same reaction mechanisms were considered in the present calculations as in the theoretical analysis of our previous study [1] of the relatively light 12C + 27Al system. These are the complete fusion and break-up-fusion reactions involving, in this case, both projectile and target nucleus fragmentation. In a complete fusion reaction, the IMFs should mainly be produced either by nucleon coalescence during the thermalization of the excited nuclei or as evaporation residues. Both the thermalization mechanism and nucleon coalescence are described in detail in our previous papers (see for instance [1, 2] and references therein). The fusion of the projectile with the target nucleus (or, in break-up-fusion reactions, the fusion of a nucleus fragment with the other nucleus) creates a non equilibrated excited nucleus. Statistical equilibrium is reached through a cascade of nucleon-nucleon (N-N) interactions during which nucleons or clusters of nucleons may be emitted with emission energies higher than those expected from evaporation of an equilibrated system, and, in the case of IMF, with a much higher yield. We simulate the cascade of N-N interactions by means of the Boltzmann Master Equation (BME) theory [2]. As we have found in [1], the IMF may also be produced as evaporation residues at the end of a cascade of particle emissions which occur during both thermalization and the subsequent evaporation from the equilibrated nuclei. In our approach, the production cross sections are either obtained from the measured spectra or are evaluated by a Monte Carlo procedure described in [3,4] for those cases not detected experimentally.


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In a break-up-fusion reaction, one of the IMFs which is produced in the binary fragmentation of the projectile is assumed to escape without further interactions and contributes, at the most forward angles, mainly to the highest energy part of the IMF spectra. We refer to these fragments as the projectile break-up spectator fragments. The other fragment is assumed to fuse with the partner ion. During the ensuing thermalization of the excited composite nucleus, IMFs can still be produced by nucleon coalescence. While light particles are being emitted during both the thermalization and the subsequent evaporation, IMFs eventually may also remain as evaporation residues. Similarly, target break-up spectator fragments are produced with lower energies and at larger emission angles by break-up-fusion reactions in target-nucleus-fragmentation. The energy and angular distributions of evaporation residues produced by the incomplete fusion of target fragments with the projectile differ, mainly for kinematical reasons, from the distributions of residues produced by the incomplete fusion of the projectile fragments with the target. The binary fragmentation (break–up) of 12C is reasonably well described by the local plane wave approximation (LPWA) theory and was calculated as described in [1]. Selected results of the calculations of complete fusion (CF) and break-up fusion (BF) processes obtained for the energy spectra of the positron emitters 15O, 13N and 11C are shown in Figure 67. The one-nucleon transfer in the 12C(12C, 11C)13C* and 12C(12C, 13N)11B* reaction paths was obtained by break-up followed by absorption of the

nucleon by the 12C partner. These calculations reveal that even at forward emission angles, processes of complete fusion followed by the emission of nucleons and light clusters during the thermalization of the excited composite system and the eventual evaporation stage, are playing a significant role in the description of the complete energy spectra of IMFs. The contributions from these complete fusion processes to the measured cross

Figure 67: Laboratory double differential energy spectra of 11C, 13N and 15O shown at emission angles as indicated. Experimental data (full circles with error bars) are compared with the theoretical predictions (black lines) given by the sum of two contributions: fragments produced in complete fusion CF (red lines) and break-up fusion BF (blue lines) reactions. The green lines refer to the 12C(12C, 11C)13C* and 12C(12C, 13N) 11B* reaction paths, respectively.


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sections increase as function of the IMF mass as well as the emission angle. In contrast to this observation the contributions of binary break-up and break-up-fusion processes to the spectra, at the higher emission energies, decrease as the IMF mass and emission angle increase. This study has therefore shown that complete as well as incomplete fusion processes seem to be necessary ingredients of the reaction mechanisms which complement the dominant direct transfer reactions in describing the complete energy spectra of near target/projectile fragments at forward angles. Similar calculations are being performed to interpret the energy spectra measured at the larger emission angles. References 1. S.V. Förtsch, F. Cerutti, P. Colleoni, E. Gadioli, E. Gadioli Erba, A. Mairani, G.F. Steyn, J.J. Lawrie,

F.D. Smit, S.H. Connell, R.W. Fearick, T. Thovhogi, Nucl. Phys. A79 (2007) 1 and references therein. 2. M. Cavinato, E. Fabrici, E. Gadioli, E. Gadioli Erba, E. Risi, Nucl. Phys. A643 (1998) 15. 3. M. Cavinato, E. Fabrici, E. Gadioli, E. Gadioli Erba, G. Riva, Nucl. Phys. A679 (2001) 753.

4. P. Vergani, E. Gadioli, E. Vaciago, E. Fabrici, E. Gadioli Erba, M. Galmarini, Phys. Rev. C 48 (1993) 1815.

3.3.13 Cluster Models of Heavy Nuclei B. Buck1, A.C. Merchant1, S.M. Perez2,3 and H.E. Seals3

1Theoretical Physics, University of Oxford, Oxford OX1 3NP, U.K. 2iThemba LABS, PO Box 722, Somerset West 7129, South Africa. 3Department of Physics, University of Cape Town, Rondebosch 7700, South Africa. Cluster models of the nucleus have a long history of applications to light nuclei. More recently attention has shifted to heavier nuclei, where both the nature and the amount of clustering are open to debate.

The cluster model we have proposed offers the most straightforward calculation of nuclear properties, because it consists of just two spinless bodies interacting through a central potential whose parameters (other than the nuclear radius) are fixed by a simple scaling procedure. For a given nucleus the optimal nuclear radius and the corresponding core-cluster partition can be obtained by optimising the cluster model fit to the observed energy spectrum. Thus the total mass AT and charge ZT of a nucleus can be split into their components (A1, Z1) and (A2, Z2) for the core and cluster respectively [1,2,3]. In the present analysis we have confined ourselves

Figure 68: Plot of B(E2 ; 2+ -> 0+)1/2AT-2/3 with B(E2) in e2fm4 vs the charge product Z1Z2/ZT for the selected nuclei. AT and ZT are the total nuclear mass and charge, and Z1 and Z2 the core and cluster charges respectively.


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to nuclei in the first half of each shell to minimise the effects of deformed cores [1]. With this proviso we have included all even-even nuclei with AT > 100 for which the excitation energies of the JP=0+, 2+, 4+, …, 10+ members of the ground state bands and the corresponding B(E2) values are known. The latter provide a good test of the reliability of the analysis with the cluster model predicting a linear relationship between the observed values of B(E2)1/2AT-2/3 and the charge products Z1Z2/ZT obtained from the partitioning exercise described above. Further, if R = r0AT1/3 is the cluster orbit rms radius, then r0 is simply related to the slope of the line [1]. Figure 68 shows the result, with r0 = 1.09 ± 0.02 fm, in clear agreement with expectations. References 1. B. Buck, A.C. Merchant, S.M. Perez and H.E. Seals, Phys. Rev. C76 (2007) 014310. 2. B. Buck, A.C. Merchant and S.M. Perez, Phys. Rev. C77 (2008) 017301. 3. B. Buck, A.C. Merchant and S.M. Perez (In preparation).

3.3.14 Characterisation of (Vineyard) Soils in Terms of Radioactivity Levels using

Gamma- Ray Spectrometry

N.A. Mlwilo1,2 , R.T. Newman2, R. Lindsay1, R.J. de Meijer1,3 and A.K. Mohanty2 1Department of Physics, University of Western Cape, Private Bag X17, Belville 7535, South Africa 2 Physics Group, iThemba LABS, P.O. Box 722, Somerset West, 7129, South Africa. 3Stichting EARTH, 9321 XS Peize, the Netherlands

The main objective of this project is the classification of vineyard soils based on its natural radioactivity content and to study its relation with various soil parameters [1]. The study was conducted on the Simonsig wine estate in the Stellenbosch district, 45 km from Cape Town. Three vineyard blocks namely Pomphuis (6.4 ha), Nuweland (5.7 ha) and Block 2 (9.2 ha) were studied. The experimental methods involved in-situ and ex-situ measurements with the MEDUSA and HPGe gamma detectors, respectively. Rapid in-situ gamma-ray spectroscopy was used to measure the activity concentrations of the natural (primordial) radionuclides, namely the 238U series, the 232Th series and 40K, in the soil. The MEDUSA detector, which comprises a CsI(Na) crystal (length 15 cm, diameter 7 cm) and associated electronics for amplification and digitization of pulses, was mounted in a watertight casing and placed on a rack 0.6 m off the ground on the portable trolley. The land surface was traversed in a grid-like pattern (with a spacing of 5 m) at a speed of ~0.8 m.s-1 while spatial data (from a GPS signal receiver mounted on the vehicle) and gamma-ray spectra (0 – 3 MeV) were recorded onto a laptop computer every 1 s and 2 s, respectively. The values of the detector total count rate and absolute 238U, 232Th and 40K activity concentrations were then interpolated using the Surfer8 software package [2] to generate 238U series, 232Th series and 40K activity concentration maps and count rate maps for the three blocks. Locations in red are “hot spots” and those in blue are “cold spots”.


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Soil sampling was performed at 0 - 30 cm depth intervals basing on the hot and cold spot locations. A total of 76 samples were collected from the three blocks (35 samples from Pomphuis block, 24 samples from Nuweland block and 17 from Block 2). The samples were taken for radiometric, mineralogy and chemical analyses (exchangeable cations, major elements, trace elements). Radiometric analysis was done in the iThemba LABS Environmental Radioactivity Laboratory (ERL) using high-resolution gamma-ray spectrometry. Soil mineralogy analysis was performed at Material Science Research Group at iThemba LABS whereas, chemical analyses was done by BEMLAB laboratory, Somerset West. At the ERL all the samples were oven-dried (at 105°C), sieved through 2 mm mesh size, sealed into Marinelli beakers, and then measured (after a minimum of 21 days) using the lead-shielded HPGe detector (Canberra p-type model with built-in pre-amplifier, crystal diameter 62.5 mm, length 59.9 mm) with relative efficiency 45% and energy resolution 2 keV at 1.33MeV [4]. The absolute full-energy peak (FEP) detection efficiency was measured using gamma-ray lines associated with the decay of 238U series and 232Th series radionuclides present in soil samples, and the 1460.8 keV 40K line as measured with a KCl standard, as described in previous work [3]. Significant correlations between radiometric results and chemical data (exchangeable cations) were found for the three blocks. It was found that the 238U and 232Th series radionuclide activity concentrations are strongly correlated with soil Mg and Na content, while 40K activity concentration is strongly correlated with Mg content. Further analyses of correlations are in progress. References

1. N.A. Mlwilo et al., iThemba LABS Annual Report 2007. 2. Golden Software, Inc., Surfer8 software package, www.goldensoftware.com. 3. S. Croft, I. G. Hutchinson. Appl. Rad. Isot. 51 (1999) 483.

http://www.goldensoftware.com


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3.3.15 Report on the Physics Target Laboratory

N.Y. Kheswa1, P. Papka1, R.T. Newman1

1 iThemba LABS, PO Box 722, Somerset West, 7129, South Africa The Physics Target Laboratory (PTL) at iThemba LABS was established in January 2006. Two vacuum evaporators obtained from the University of Stellenbosch are now in full operation. In order to commission the evaporators the following steps were taken:

• cooling water system feedthroughs were fitted; • a new electron-beam gun with copper crucible was installed; • design and manufacture of a substrate that was compatible with an existing transfer chamber; and • a quartz crystal monitor was installed to monitor deposition rate and evaporant thickness during evaporation

of target material. Furthermore a glove box was upgraded by installing a roughing pump and piping system in order to achieve a controlled, inert environment that allows for the working with air reactive materials without oxidation. Target thickness measurement capability is being developed. The thickness measurements are made using an alpha source. A list of targets prepared in the PTL during the period covered by this report is given in Table 11 below.

Target Thickness Method 7Li 6 mm – 8 mm Pressing 232Th 150 µg/cm2 Vacuum evaporation 114Cd 12.8 mg/cm2 Mechanical rolling 120Sn 1 mg/cm2 Vacuum deposition 97Mo Vacuum deposition and rolling 181Ta 0.5 mg/cm2

0.25 mg/cm2 Rolling

40Ca 1 mg/cm2 Vacuum evaporation 6Li 5 mg/cm2 Rolling 18O onto Ta Electrolysis

Table 11: List of targets prepared in the Physics Target Laboratory during 2007-2008.

A notable achievement during the year was the successful mounting of 4 µg.cm-2 carbon foils onto frames which were used in a recoil detector based on micro-channel plate technology. The recoil detector was used in conjunction with the AFRODITE array (see 3.3.5) .


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3.4 Radiation Biophysics Group 3.4.1 Molecular Neutron Radiobiology – enhanced Radiosensitivity of Cells by

Lentivirus-mediated RNA Interference A. Vral1, P. Perletti2 and J.P. Slabbert3 1Department of Histology, Embryology and Medical Physics, University of Ghent, Belgium 2Department of Structural and Functional Biology, University of Insubria, Milan, Italy 3iThemba LABS, Somerset West, South Africa This collaborative research project between iThemba LABS and the Universities of Ghent (Belgium) and Insubria (Italy) continues. The principal aim is to investigate molecular mechanisms in radiobiology that can improve the outcome of neutron radiotherapy, in particular to increase the radiosensitivity of cancer cells to neutrons, as a need to do so for the p(66)/Be beam generated at iThemba LABS has been established [1]. The emphasis during the last year was to demonstrate an enhancement in radiosensitivity following the silencing of the expression of the DNA repair proteins KU70 and KU80 by lentivirus-mediated RNA interference. The latter was generated using a three-plasmid system containing a siRNA expression cassette, a pLVTHM lentiviral construct and a pCMV-dR8.74 vector.

Immortalised MCF10 human mammary epithelial cells were used as target cells for RNA interference to study the silencing of repair proteins Ku70 and Ku80. Western Blot analysis during the last year again showed that the lentiviral vectors are very effective in silencing the expression of both Ku70 and Ku80 (Figure 69, below). Protein levels shown in Figure 69 are compared to those of mock-infected cells (pLV). These readings also demonstrated that when the vector targeting Ku70 is used to infect cells, Ku80 was concomitantly down-regulated compared with either wild-type or mock-infected cells. This shows that the Ku70-targeting vector can concomitantly suppress Ku70 and Ku80. In the second phase of this study, the radiosensitising effect of Ku70/80 knockdown is studied by using lentiviral vectors for siRNA of Ku70 in MCF10 cell lines. Several endpoints are measured to quantify radiosensitivity and this includes micronucleus formations in cytokinesis block cells, cell survival, apoptosis, and senescence. It is now possible to estimate the percentage of transfected cells by fluorescence microscopy, as the lentiviral vectors harbour cDNA encoding the fluorescent molecule GFP (green fluorescent protein), Figure 70. This is done after each infection, and only when a satisfactory knockdown is obtained in more than 75% of cells are the cultures used to perform radiation experiments.

Radiosensitivity readings for cell exposed to 60Co γ-rays are shown in Figure 71. Cell survival for doses ranging

between 0 and 8 Gy are quantified in multiwell dishes 5 days after irradiations using a crystal violet cell stain. This is read at 590 nm with a plate reader. Reduced survival of Ku70/80 knockdown cells is evident compared with MCF 10 cells mock-infected with lentiviral vectors.


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More tests are needed to confirm the radiosensitisation effect of Ku70/80 in knockdown cells. Also, a differential involvement of Ku70/80 in the repair of DNA lesions induced by neutrons and X-rays needs to be investigated. Nevertheless it is concluded that knockdown by RNAi results in an increased radiosensitivity of immortalised MCF10 human mammary cells. Thus RNA interference of Ku70/80 in tumour cells could well be a mechanism to increase the therapeutic benefits of neutron treatments.

Reference J.P. Slabbert, T. Theron, F. Zölzer, C. Streffer and L. Böhm. Int. J. Radiat. Oncol. Biol. Phys. 47 (2000)1059.

Plv Ku70 Plv Ku70 cell lines

Ku70 antibody

Ku80 antibody

Plv Ku70 Plv Ku70 cell lines

Figure 69: Silencing of Ku70 / Ku80 expression in MCF10 cells as monitored at the protein level by Western Blot analysis. Blots shown are for MCF 10 cells infected with the lentiviral vectors for Ku70 (left) and Ku80 (right), and are compared with blots of pLV cells transduced with an empty vector (mock-infected control cells).

Figure 71: Survival of MCF10 human mammary cells following graded doses of radiation: Observations for cells mock-infected with an empty vector are shown on the left. Cells with Ku70/80 knockdown by lentiviral vectors for siRNA are shown on the right.

Figure 70: An infection efficiency of more than 90% is shown for MCF10 cells transfected with lentiviral vectors. Fluorescence microscopy reveals the green fluorescence protein (GFP).


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3.4.2 The RBE of a 200 MeV Proton Beam in the Distal Part of a Spread out Bragg

Peak

J. Gueulette1, J.P. Slabbert2, J. Martinez1, B. de Coster1, J. Symons2, J. Nieto-Camero2, and C. Trauernicht2 1Molecular Imaging and Experimental Radiotherapy, Catholic University of Louvain, Belgium 2iThemba LABS, Somerset West, South Africa Studies to quantify the relative biological effectiveness (RBE) of the 200 MeV proton beam at different positions in the Spread Out Bragg Peak (SOBP) continue. A substantial increase in proton RBE is expected in the distal part of the SOBP, where proton energies are lower than those in the plateau region and proximal part of the SOBP. Such a change raises concerns about the radiotoxicity in different parts of proton therapy target volumes, as well as the involvement of critical structures close to these volumes.

An increase in proton RBE in the distal SOBP is expected from biophysical considerations and on the basis of cell survival data obtained in vitro. For RBE estimates to be of clinical relevance in vivo measurements are needed. To obtain these a novel jig was designed that allows specific segments of murine jejunum to be irradiated, from which crypt cell survival readings can then be obtained [1]. Such readings are important as a change in radiation RBE is best quantified in tissue that has a large repair capacity. The jig makes it possible to position a small segment of intestine perpendicularly to the beam axis, and adjust its position such that it is irradiated close to the distal edge of the SOBP. The width of the biological target along the beam’s axis is restricted to its smallest dimension, i.e. the intestinal diameter of 3 mm.

The first set of results obtained with this specialised irradiation set-up is shown in Figure 72. Regeneration of crypt stem cells could be measured with great accuracy over a wide range of doses. Data for jejunum segments irradiated in the middle and distal part of a 7 cm SOBP are shown. Irradiations at the end of the SOBP are about

Figure 72: Left: Dose-effect relationships for crypt regeneration in mice after irradiations in the middle or very end of the SOBP. Right: Profile of the proton depth-dose curve showing the respective positions of the intestines. The egg-shaped area on the right corresponds to the space occupied by tissue when doing whole-body irradiations using a previous method. The new jig allows selective irradiations in the very end of the SOBP (red point) and variations in proton RBE larger than previously thought can now be detected.


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10% more effective than those in the middle. These results are consistent with what had been expected on the basis of biophysical principles, and confirm the increase in RBE of a proton beam at the very end of the SOBP, noted before from cell survival readings obtained with in vitro methods. This increase is also in general agreement with whole-body irradiations carried out in the SOBP [2]. However, increases in the RBE noted in these earlier experiments, which were also performed using a 7 cm SOBP, were somewhat less, at 7%. The greater increases obtained with the specialised set-up confirm the need to perform the more complex irradiation of externalised intestinal tissue, and it is currently the only possible way to map RBE variations in the critical SOBP dose zone. Additional readings are needed, especially for shorter SOBPs in which RBE variation could well exceed that noted for the 7 cm SOBP. As the externalisation technique works well, other as yet unstudied radiobiological phenomena associated with proton beam irradiation can be investigated, e.g. dose volume effects in which the tolerance of healthy tissues depends on the volume irradiated. The influence of the volume irradiated in turn depends partly upon the structural organisation of the irradiated tissue. For this reason the use of intestine for such studies is appropriate; in many aspects it is analogous to spinal chord. Irradiating intestine with the specialised jig is useful to understand how proton irradiation of small tissue volumes interrupts its serial organisation and inactivates organ function. The volume effect deserves to be "revisited" as protons produce dose distributions with steep lateral and distal fall-offs, such that there is a risk of the unplanned exposure of healthy tissue near a radiotherapy target volume to unacceptably high doses due to minor misalignment, e.g. due to patient motion. References 1. J. Gueulette, J.P. Slabbert, J. Martinez, B. de Coster, J. Symons, J. Nieto-Camero, and C. Trauernicht.

iThemba LABS Annual Report 2006/07, p158. 2. J. Gueulette, J.P. Slabbert, L. Bohm, B.M. de Coster, J.-F. Rosiera, M. Octave-Prignot, A. Ruifrok,

A.N. Schreuder, P. Scalliet, D.T.L. Jones. Radiotherapy and Oncology 61 (2001) 177. 3. J. Gueulette. Journées de Radiobiologie Appliquée, Centre de Recherche Nucléaire d’Alger (Algeria),

February 27-28, 2007. 4. J. Gueulette, J.P. Slabbert, D.T.L. Jones and A. Wambersie. Istituto Nazionale di Fisica Nucleare

Laboratori Nazionali di Legnaro (Padova, Italy), April 17, 2007. 5. J. Gueulette, J.P. Slabbert, B.M. de Coster, D.T.L. Jones and A. Wambersie. Protons, Ions and Neutrons

in Radiation Oncology International Symposium, Munich (Germany), July 6-7, 2007. 6. J. Gueulette, J. Martinez, B.M. de Coster and J.P. Slabbert. Groupe de travail "Biologie des Radiations"

MELUSYN ; workshop on "Activation d'éléments lourds et amplifications des altérations radiobiologiques", ENGREF, Amphi B 208 (Paris, France), March 12, 2008.

7. J. Gueulette and V. Grégoire. Joint meeting UCL (Brussels) CEN/SCK (Mol), Halles Universitaires de Louvain-la-Neuve (Belgique), April 11, 2008.


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3.4.3 Estimating the α/β Ratio for Acoustic Neuromas

F.J. Vernimmen1, Z. Mohamed2, J.P. Slabbert3, J. Wilson4, S. Fredericks3 1Department of Medical Imaging and Clinical Oncology, University of Stellenbosch 2Department of Radiation Oncology, Groote Schuur Hospital 3iThemba LABS, Somerset West 4Department of Radiation Oncology, University of Pretoria Radiobiological modelling of the repair characteristics of different tissues is important for proton therapy. The principal aims of such investigations are to elucidate possible therapeutic gains using proton therapy and to derive parameters that can help in calculating treatment doses for different fractionation schedules. In particular,

the estimation of the α/β ratios for radiosurgery target tissues is paramount. In this work clinical data for a series of proton therapy patients treated for acoustic neuromas were examined. These patients were treated according to different protocols but most received 3 fractions (hypo-fractionated stereotactic proton therapy). Following treatment the patients were followed for at least two years (mean 69 months). The iso-effect examined was long term (2-10 years) radiological control with a complication rate of ≤10% and a hearing preservation of 30% or more. The fractionated equivalent data are plotted in Figure 73. In this the proton doses are expressed in terms of a cobalt gray equivalent (CGyE). For this an RBE of 1.1 was used and the dose per fraction administered is compared to the inverse of the total dose given in each treatment.

0 3 6 9 12 150.00

0.05

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Acoustic NeuromasLocal Control > 90 %

Dose per fraction (CGyE)

1 / T

otal

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e (C

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-1)

For the most part treatments given with different treatment protocols are iso-effective. However, some treatments

in the 3 fraction protocol appear to be somewhat more than iso-effective. The analysis yields an α/β ratio of 1.3 CGyE with a 95% confidence interval of 1 to 1.6 CGyE. This value is very low even for late responding tissue, but

Figure 73: The reciprocal of the total dose received by a series of proton therapy patients plotted as a function of the dose per fraction administered during each treatment. Doses are Cobalt Gray Equivalent (CGyE) values. The number of fractions used in each group of treatments is shown. Dashed curves are the 95% confidence limits for the fitted line.


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can be expected as Schwannoma tissue falls within this category. It is concluded that acoustic neuromas comprise tissue with a very high capacity to repair radiation damage. As such, the use of radiosurgery is indicated

to ensure therapeutic gain with respect to surrounding normal tissue. Assuming an α/β ratio of about 3 Gy for normal brain, fractionated treatment protocols may well result in less sparing of normal tissue around target volumes, than radiosurgery. More analysis using different radiobiological models is needed to confirm these results. Verification of the very

low α/β ratio is needed as it implies that relatively large corrections should be made to the total dose to obtain the same iso-effect as radiosurgery when planning fractionated and even hypo-fractionated treatment protocols. Dose calculations for proton treatments using 3 fractions are particularly affected by the 1.3 CGyE estimate. Currently it is concluded that based on radiobiological principles a radiosurgery protocol appears to be suitable when treating acoustic neuromas using protons.

3.4.4 Mean Inactivation Doses for Prostate Cancer Cells exposed to Neutrons and

X-rays

J.P. Slabbert1, A.M. Serafin2, T.T. Sebeela3, J. Symons1 1iThemba LABS, Somerset West 2Department of Medical Imaging and Radiation Oncology, University of Stellenbosch 3Department of Physics, University of Pretoria Studies that compare the radiosensitivity of different tumour cell types to neutrons and X-rays are important as they provide information about the therapeutic gain that can be expected from particle therapy. This is of particular relevance to the relatively high energy neutrons used in the therapeutic beam at iThemba LABS, as these have advantages in terms of the depthwise dose distribution in tissue, but have radiobiological characteristics that limit the therapeutic gains to be expected relative to photons. Studies in the past have shown a limited increase in the relative biological effectiveness (RBE) of p(66)/Be neutrons for cells radio-resistant to photons [1]. As neutrons have been identified in recent years as being beneficial for the treatment of advanced prostate cancer, experiments are being conducted to determine the radiosensitivity of different prostate cancer cell types to neutrons and X-rays [2]. Data obtained thus far for cell lines resistant to X-ray treatment are inconsistent, and only the mean inactivation doses for a BPH-1 human prostate cell type can be added to those determined

previously [3]. The mean inactivation doses ( D ) measured for this cell type are 1.54 Gy for X-rays and 0.72 Gy for neutrons. As a result this prostate cancer cell type is relatively sensitive compared to PNT-1a, PNT-2C,

1542N, and 1542T cell lines. The additional data make it possible to compare variations in D values observed for different cell types following exposure to 6 MV X-rays and neutrons (Figure 74). A strong correlation in the variation in radiosensitivity of prostate cancer cells to the two treatment modalities is evident.


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The increase in resistance of cells to neutrons correlates with their resistance to photons to a high degree of statistical significance (p = 0.0116). Therefore it is unlikely that an increase in neutron RBE will be seen for cells resistant to X-rays. This has not yet been demonstrated because most of the cell types used thus far in the study are radiosensitive. Currently cells radioresistant to X-rays are being identified. Final conclusions about a potential therapeutic gain for neutrons versus X-rays in the treatment of prostate cancer can only be made once such radioresistant cell types have been investigated.

References 1. J.P. Slabbert, T. Theron, F. Zölzer, C. Streffer and L. Böhm. Int. J. Radiat. Oncol. Biol. Phys. 47 (2000)

1059.

2. L. Santanam, T. He, M. Yudelev, J. D. Forman, C.G. Orton, F. van den Heuvel, R.L. Maughan, J. Burmeister. Int. J. Radiat. Oncol. Biol. Phys. 68 (2007) 1546.

3. T.T. Sebeela, J.P. Slabbert, A.M. Serafin and J. Symons. iThemba LABS Annual Report 2006/07, p161.

0 2 4 6 8 10 12 140.001

0.01

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1BPH-1

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=γD 1.54=nD 0.72

RBE = 2.1

Dose (Gy)

Surv

ivin

g Fr

actio

n

Figure 74: Cell survival data obtained for a BPH-1 human prostate cancer line. Observations are for cells exposed to graded doses of 6 MV X-rays and p(66)/Be neutrons, clonogenic capacity tested using conventional methods.

0 1 2 3 40.6

0.7

0.8

0.9

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1.4

R2 = 0.91p = 0.0116

Mean Inactivation Dose X-rays (Gy)Mean

Inac

tivat

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Dose

Neu

trons

(Gy)

Figure 75: The mean inactivation doses calculated from inactivation parameters measured for a series of human prostate cancer cell types.


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3.4.5 Response of T-lymphocytes from HIV-positive Individuals to Acute and

Fractionated X-ray Treatments A. Baeyens1, J.P. Slabbert1, P. Willem2, S. Josela3, A. Vral4

1iThemba LABS, Somerset West 2Department of Haematology and Molecular Medicine, WITS Medical School 3Department of Radiation Oncology, WITS Medical School, 4Department of Anatomy, Embryology, Histology, and Medical Physics, University of Ghent, Belgium The radiosensitivity of human lymphocytes in response to HIV status continues to be studied, as it is of special importance to both radiation workers and cancer therapy patients in South Africa, where the prevalence of HIV infection is high. The principal aim of this investigation is to determine the radiosensitivity of white blood cells of individuals who are HIV-positive, and compare it with that of blood cells obtained from a group of HIV-negative donors. The study is conducted in the Dept. of Human Genetics at WITS Medical School in Johannesburg, as it is equipped to handle HIV-infected blood cultures. Irradiations with X-rays are performed using a linear accelerator in the Dept. of Radiation Oncology. Samples are collected at the Helen Joseph Hospital from patients who are informed about the project’s objectives, and blood samples are drawn before the start of ARV treatment. The study has ethical clearance. Some changes in the radiosensitivity of HIV donors to X-rays have already been reported [1]. In this work additional samples have been processed to count the number of micronuclei formed in response to graded doses of 6 MV X-rays. This is to obtain dose response curves that can be used to establish a dose modifying factor suitable for use in radiotherapy treatments, and to quantify the change in the radiosensitivity of HIV-positive radiation workers. The use of T-lymphocytes to quantify the radiosensitivity of different individuals offers advantages. However, working with non-dividing cells requires lymphoblasts to be cultivated in vitro by selectively stimulating T-lymphocytes with phytohaemagglutinin (PHA). A poor yield of binucleated cells suitable for micronuclei scoring is a constant difficulty of working with HIV-positive blood samples. In a large number of cultures T-lymphocytes are not stimulated from their usual G0 status into dividing cells (Table 12). By contrast cultures from blood samples of HIV-negative donors are mostly successful. Reasons for this are not clear, but as a result the study has now been limited to samples from HIV-positive donors with a CD4 count not less than 300.

HIV-positive

individuals HIV-negative individuals

No of blood samples collected 24 17 No of cultures successful stimulated 14 15

Table 12: Number of blood samples collected and number of T-lymphocyte cultures successfully stimulated using PHA. No or very poor yields of binucleated cells are obtained from samples from HIV-positive donors with a CD4 count smaller than 300.


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Whole-blood samples are exposed in vitro to doses of 6 MV X-rays ranging from 0 to 4 Gy. For this radiation dosimetry and sample exposures take place in test tubes placed in a water phantom. Whole-blood samples are cultivated in RPMI medium and Cytochalasin B is added at 24 hours. After 3 days the yields of binucleated T-type lymphoblasts and micronuclei are counted using fluorescence microscopy. Micronuclei frequency is a measure of chromosomal damage and is quantified in at least 500 binucleated cells per sample. Un-irradiated control samples from each donor are also analysed. Micronuclei frequencies are consistently higher in T-lymphocytes of HIV-positive individuals (n = 14) than those observed in blood cells from HIV-negative donors (n = 15), Figure 76. The dose response curves for both sets of donors are linear-quadratic, indicating that the formation of residual radiation damage in both HIV-positive and control samples is consistent with standard biophysical modelling.

α- and β-values that describe the dose response curves in classical linear-quadratic terms were calculated, as well as the 95% confidence ellipses around these co-variant parameters (Figure 77). This shows a substantial increase in the inherent radiosensitivity of lymphocytes obtained from HIV-positive donors, which is significant at the 95% level. A significant increase in the inherent radiosensitivity of T-lymphocytes from HIV-positive individuals is now confirmed. The underlying molecular mechanisms are not clear. One of several possibilities is that the repair of DNA damage after irradiation could be impaired. For this reason blood samples from some donors were treated with fractionated doses of radiation as well as acute exposures. Fractionated irradiations were limited to a split-dose regime of 2 Gy X-rays followed by 2 hours incubation at 37°C followed by another dose of 2 Gy X-rays. The 2 hours at 37°C is to allow for the repair of sublethal damage (Elkind repair). Micronuclei data noted for this split-

0 1 2 3 4 50

100

200

300

400

500

600

HIV Positive (n=14)

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0 20 40 60 80 100 1200

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HIV Negative

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α (Gy-1)

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y-2)

Figure 76: Micronuclei frequencies noted in T-lymphocytes for HIV-positive and HIV-negative donors after exposure to 6 MV X-rays. Error bars indicate standard error of the mean. A clear increase in radiosensitivity is evident for HIV-positive individuals.

Figure 77: 95% confidence ellipses for the covariant linear-quadratic parameters α and β that describe the dose response curves for micronuclei formations in T-lymphocytes of HIV-positive and negative donors.


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dose are compared to those for lymphocytes from the same donor, but exposed to a single dose of 4 Gy X-rays. The aim is to quantify the repair of sublethal damage and establish whether it differs for HIV-positive and -negative donors. Figure 78 summarises the data obtained thus far.

Similar lymphocyte micronuclei frequencies are noted for the different treatment protocols in two of the HIV-positive donors. This suggests no or a reduced DNA repair capacity following exposure to ionising radiation. Some repair of sublethal damage is however noted in the lymphocytes for a third HIV-positive donor. Normal repair of sublethal damage is demonstrated with lymphocytes from all HIV-negative donors. It is unclear if the capacity for DNA repair in cellular systems is compromised by HIV infection. As the influence of the virus could well be affecting DNA repair at a molecular level it is essential to clarify the mechanism of increased radiosensitivity noted for HIV-positive donors. For this reason additional samples need to be analysed. Reference

1. A. Baeyens, J.P. Slabbert, P. Willem, S. Josela, D. van der Merwe, A. Vral. iThemba LABS Annual Report

2006/07, p 163.

comparison between 2+2Gy and 4Gy

0

100

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300

400

500

600

700

800

2Gy+2h+2Gy 4 GyDose

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Figure 78: The number of micronuclei observed in lymphocytes obtained from HIV-positive and -negative donors. One whole-blood sample from each donor was exposed to 4 Gy X-rays, and another to 2 Gy X-rays followed by a 2 hour incubation at 37°C, and then another 2 Gy X-rays.


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3.4.6 Radiation-induced Apoptosis of Lymphocytes as Measured by the Leukocyte

Apoptosis Assay W. Solomon1, K. Meehan2, J.P. Slabbert3, N.E.A. Crompton4, D. Gihwala1 1Cape Peninsula University of Technology 2Centre of Excellence for Applied Research and Training, Abu Dhabi, UAE 3iThemba LABS, Somerset West 4Cornerstone University, Michigan, USA Crompton and Ozsahin developed the leukocyte apoptosis assay (LAA) to predict intrinsic radiosensitivity of normal tissue based on the radiation-induced apoptotic response of CD4+ and CD8+ T-lymphocytes [1]. Of significance is that radiosensitive individuals have an abnormality in their ability to recognise or repair DNA double-strand breaks induced by ionising radiation, leading to enhanced toxicity and a predisposition to cancer [2]. Studies have shown that approximately 6-10% of patients receiving radiotherapy show signs of late toxicity (RTOG/EORTC scale) many months after therapy has been completed. Our first results, which yielded a standard curve for this assay, have been reported [3]. In this study the distribution of radiation-induced apoptosis in 100 healthy South African donors was investigated. Z-score data were later obtained from that study and approximately 10% of the donors had a low apoptotic response in both CD4 and CD8 lymphocytes (Figure 79). This agrees with what is to be expected using flow cytometer type readings. Additional radiation-induced apoptosis readings in a total of 300 healthy South African donors have now been investigated.

Late effects of radiation treatment are particularly important in neutron therapy. For this reason the radiosensitivities of lymphocytes exposed in vitro to X-ray (low–LET) and neutron (high–LET) radiation have been compared (Figure 80).

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(a) (b) Figure 79: Z scores showing apoptotic response of CD4 versus CD8 T-lymphocytes: (a) Crompton et al. 2001: + symbols = normal responders; filled circles inside the red ring = enhanced radiosensitivity patients;

X symbols = ataxia telangiectasia homozygotes. (b) The standard curve study of 2007 in which approximately 10% of donors exhibited enhanced radiosensitivity (red ring).


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A clear dose response curve was observed following neutron radiation, indicating an increase in apoptotic response with increasing doses of neutron radiation. When comparing the apoptotic response to X-ray and neutron radiation, increased damage by neutron radiation was observed (Figure 81 and Table 13).

The observed RBE of about 2 indicates that the leukocyte apoptosis assay (LAA) can detect the increased damage caused by neutron therapy. The LAA assay can thus be helpful for patients suffering from advanced cancers not easily treated with X-ray radiation, e.g. salivary gland tumours and soft tissue sarcomas.

(a) (b)

Figure 80: Flow cytometry dot plots showing: (a) selection of lymphocytes at gated region R1 and apoptotic lymphocytes; (b) PI versus FSC after 2 Gy neutron irradiation at region R3.

Figure 81: Dose response curves showing an increase in apoptotic response with increasing doses of neutron and X-ray radiation.

Dose Response Curve: Neutron vs X-rays

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Table 13: Percentage apoptosis of CD4 and CD8 lymphocytes after X-ray and neutron irradiation

References 1. N.E.A. Crompton, M. Ozsahin. Radiation Research 147 (1997) 55. 2. N.E.A. Crompton, Y. Shi, G.C. Emery, L. Wisser, H. Blattmann, A. Maier, L. Li, D. Schindler, H. Oszahin,

M. Oszahin. Int. J. Rad. Oncol. Biol. Phys. 49 (2001) 547. 3. W. Solomon, K. Meehan, J.P. Slabbert, N.E.A. Crompton, D. Gihwala. iThemba LABS Annual Report

2006/07, p165.

3.4.7 Cell Kinetic Parameters in Relation to Radiosensitivity

Z. Dashi1, M. de Kock1, J.P. Slabbert2

1Department of Biosciences, University of the Western Cape, Bellville 2iThemba LABS, Somerset West Cellular radiosensitivity is an indicator of tumour response to treatment with ionising radiation, which is influenced by many factors including inherent cell kinetics and lengthening of the cell cycle in response to the radiation treatment. Synchronization of populations can leave cells in a resistant phase of the cycle. Thus it is important to follow cellular radiation sensitivity in relation to cellular kinetics, and in particular to identify the late S-phase population as these cells are very resistant to treatment with most types of ionising radiation. A project has been started to determine how many cells in exponentially growing cancer cell cultures are in the S-phase at any given time. This investigation has been made possible by the installation of a flow cytometer in the radiobiology laboratory at iThemba LABS. The first aim of the study is to be able to quantify S-phase cell fractions accurately using light scatter and fluorescent signals from the laser beam of the flow cytometer. Data are generated relating S-phase fractions to cellular radiosensitivity. The latter is quantified using clonogenic survival.

X-rays Neutrons Dose % Apoptosis Dose % Apoptosis

Gy CD4 CD8 Gy CD4 CD8 0 2.74 3.40 0 2.74 3.40 2 15.47 16.58 1 14.15 17.75 4 21.45 30.61 2 17.44 22.04 6 23.99 36.53 3 21.52 30.95 8 26.17 37.86 4 23.46 35.86


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The S-phase fraction of an exponentially growing culture is determined by pulse labelling the cells with

5-bromodeoxyuridine (BrdU). At present 2 to 4 × 106 cells are exposed for one hour to BrdU at a final

concentration of 20 μM while being incubated at 37°C / 5% CO2. The cells are then trypsinised and prepared for

flow cytometry. For this various protocols were investigated. The approach is to detect the BrdU incorporated into

the DNA of S-phase cells by labelling it with a FITC fluorescent marker attached to antibodies raised to BrdU. Total cellular DNA is detected with the fluorescent dye 7-AAD (7-amino-actinomycin-D). The aim is to use a combination two-colour flow-cytometric analysis that permits an accurate enumeration and characterisation of cells that have actively synthesized DNA (i.e. incorporated BrdU), cells in the G1 and G2/M phases, and also apoptotic cells that may be present. For this the use of a standard BrdU Flow Kit that is commercially available proved to be problematic. Reliable readings are now possible using a method described by Gillet et al. [1]. An example of a two-colour flow-cytometric analysis is shown in Figure 82 , above. The next phase of the study is to measure the inherent radiosensitivity of different human cell lines that can be cultivated in vitro. Then an attempt will be made to relate S-phase fraction readings to radioresistance.

Reference 1. L. Gillet, F. Minner, B. Detry, F. Farnir, L. Willems, M. Lambot, E. Thiry, P. Pastoret, F. Schynts and

A. Vanderplasschen. Journal of Virology 78:5 (2004) 2336.

Figure 82: Dot plot of events detected using two-colour flow cytometry. Total DNA content is shown with 7-AAD fluorescent signals. S-phase cells in a PC3 prostate cancer cell culture are detected with the FITC signal from an antibody against BrdU and are clearly distinguishable (R5) from cells in the G1 phase (R3) and G2/M phase (R4). Apoptotic bodies are also visible (R2).


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3.4.8 The Relative Biological Effectiveness of a 100 MeV quasi-mono-energetic Neutron

Beam measured by the Induction of Dicentric Chromosomes in Human

Lymphocytes R. Nolte1, V. Dangendorf1, E. Schmid2, J.P. Slabbert3, G. Stephan4, M. Haney2 and F.D. Smit3

1Physikalisch-Technische Bundesanstalt Braunschweig, Germany 2Institute of Radiobiology, GSF - National Research Center for Environment and Health, Neuherberg Germany 3 iThemba LABS, Somerset West 4Federal Office for Radiation Protection, Oberschleissheim Germany. A series of experiments are ongoing to assess the risk to personnel from exposure to cosmic radiation during travel in civilian aircraft. At the typical cruising altitudes of commercial jet airliners neutrons having energies of about 100 MeV are particularly important, and information about the relative biological effectiveness of high energy neutrons at low dose (RBEM) is required. Data for 200 MeV neutrons have been already been reported [1,2]. In this work the induction of dicentric chromosomes in human lymphocytes was studied following their exposure to graded doses of 100 MeV neutrons. The formation of dicentric chromosomes by ionising radiation is a classical endpoint and a suitable measure for radiation risk. A comprehensive set of RBEM data for this endpoint is available for neutron energies below 14.8 MeV [3] as well as for 60 MeV quasi-mono-energetic neutrons [4]. As in the earlier experiments, blood from the same donor was used for the current measurements so as to yield a consistent data set for a full range of neutron energies that would allow collective analysis. The quasi-mono-energetic neutron beam was produced by 100 MeV protons incident on a 9Be target. An iron collimator was used to provide neutron beams at emission angles of 0° and 16°. The reference radiation for this test series was 60Co γ-rays. During irradiation the blood samples were contained

in syringes kept at room temperature (20-22°C). The syringes were inserted into two lucite mini-phantoms positioned at a distance of 5.5 m from the Be target at neutron emission angles of 0° and 16°. The phantoms provide a build-up layer of 85 mm in front of the blood samples to ensure charged particle equilibrium. The dose rate was about 20 mGy/hour. The available beam time in one weekend was divided into intervals so that five sets of blood samples could be irradiated to 20%, 40%, 60%, 80% and 100% of the total dose. Then whole-blood cultures were set up as previously described and metaphase preparations were made to examine dicentric chromosomes [4]. The distribution of dicentric chromosomes observed for irradiations at 0° and 16° are listed in Table 14.

Significant over-dispersion (µ > 1.96) is noted for most samples. This is consistent with irradiating cells with high-

LET radiation. The data were fitted to a yield curve y = c + αD + βD2 where y denotes the number of dicentric chromosomes per cell and c is the background frequency observed in the absence of radiation. Figure 83 shows the present data and the results of the earlier measurements. Reciprocals of the estimated variances were used as weights. The RBE at low dose was calculated from the linear yield coefficient as

RBEM = α(neutron)/α(reference). Table 15 shows these linear yield coefficients and their type-A uncertainties,

as well as the resulting RBEM values.


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Similar lymphocyte micronuclei frequencies are noted for the different treatment protocols in two of the HIV-positive donors. This suggests no or a reduced DNA repair capacity following exposure to ionising radiation. Some repair of sublethal damage is however noted in the lymphocytes for a third HIV-positive donor. Normal repair of sublethal damage is demonstrated with lymphocytes from all HIV-negative donors. It is unclear if the capacity for DNA repair in cellular systems is compromised by HIV infection. As the influence of the virus could well be affecting DNA repair at a molecular level it is essential to clarify the mechanism of increased radiosensitivity noted for HIV-positive donors. For this reason additional samples need to be analysed. An RBEM value of 6.7 is calculated from the data for lymphocytes irradiated with 100 MeV neutrons. This result from the latest set of measurements supports the earlier observations for 200 MeV neutrons. For energies above 20 MeV the RBEM for the production of dicentric chromosomes by fast neutrons is almost independent of energy. This is shown in Figure 84 where the initial slope of the dicentric yield curve varies little with neutron energy. As noted previously with 200 MeV neutrons, the findings made here are at variance with the reported RBEM values of about 100 for simulated neutron spectra at airliner cruising altitudes [5].

0° irradiation position Dose (mGy) Analysed cells Dicentrics per cell Intercellular distribution of dicentrics

0 1 2 σ2 / y µ-value 0* 18000 0.00028 17995 5 - 1.0 0 0 3000 0.00033 2999 1 - 1.0 0

111.3 1312 0.0135 1312 18 0.99 -0.27 213.7 1136 0.0273 1107 27 2 1.10 2.47 291.5 1027 0.0370 992 32 3 1.12 2.80 393.9 Data being analysed 505.2 1000 0.0560 947 51 1

1 with 3 1.09 1.99

16° irradiation position Dose (mGy) Analysed cells Dicentrics per cell Intercellular distribution of dicentrics

0 1 2 σ2 / y µ-value 0* 3000 0.00033 2999 1 - 1.0 0

67.1 1328 0.0053 1321 7 0.99 -0.28 128.8 1044 0.0115 1033 10 1.16 3.27 175.7 1071 0.0149 1055 16 1 0.99 -0.26 237.3 Data being analysed 304.4 919 0.0229 899 19 1 1.07 1.56

Table 14: Intercellular distribution of dicentric chromosomes in human lymphocytes induced by quasi-mono-energetic 100 MeV neutrons at the 0° and 16° irradiation positions. *The asterisk denotes the background frequency from the same donor examined earlier.


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References 1. R. Nolte, V. Dangendorf, A. Buffler, F.D. Brooks, J.P. Slabbert, F.D. Smit, M. Haney, E. Schmid,

G. Stephan. Proceedings of Science http://pos.sissa.it (2007) p1. 2. R. Nolte, V. Dangendorf, E. Schmid, J.P. Slabbert, G. Stephan, M. Haney and F.D. Smit. 2007. iThemba

LABS Annual Report 2006/07, p 167.

3. E. Schmid, D. Schlegel, S. Guldbakke, R.P. Kapsch, and D. Regulla. Radiat. Environ. Biophys. 42 (2003)

87.

4. R. Nolte, K.-H. Mühlbradt, J.P. Meulders, G. Stephan, M. Haney, and E. Schmid. Radiat. Environ. Biophys.

44 (2005) 201.

5. A. Heimers. Int. J. Radiat. Biol. 75 (1999) 691.

α (Gy-1) ( ) (Gy-1) RBEM

0° 0.107 0.015 10.1 16° 0.086 0.021 8.1

Table 15: Linear yield coefficients (α) for the irradiations at 0° and 16° for lymphocytes irradiated with 100 MeV neutrons. The type-A uncertainties ( ) are also listed. The linear yield coefficient for 60Co γ-radiation is αref = (0.0106±0.003) Gy-1.

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Figure 83: (Top) Yield of dicentric chromosomes (y) observed in lymphocytes after irradiating whole-blood at 0° (squares) and 16° (circles) with neutron beams of 100 MeV. (Bottom) Data for 200 MeV neutron irradiations are shown for compariso

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3.4.9 Cellular Uptake of a Radioactive Labelled Compound J.P. Slabbert1, N. Rossouw1, M.T. Madziwa2, N. Ramluckan1 1iThemba LABS, Somerset West 2Institute of Infectious Disease and Molecular Medicine, University of Cape Town An accurate, yet convenient method to quantify cellular uptake of radioactive labelled compounds is needed for both radiobiological studies and tests of the suitability of radio-pharmaceuticals. As a liquid scintillation detection system is not available at iThemba LABS, the precision of a multi-well plate method has been investigated to obtain radioactive count readings in response to cell numbers. In this work the halogenated pyrimidine [123I]-deoxyuridine was prepared and 1 micro-curie added to cultures of a fast dividing epithelial cell type (CHO-K1) with a doubling time of about 11 hours. The fast doubling time is expected to result in high levels of cells in the S-phase that specifically incorporate [123I]-deoxyuridine during DNA synthesis, because the labelled structure is almost identical to deoxythymidine (Figure 85).

A major advantage in using a multi-well plate is that cell monolayers attached to the bottom of each well can easily be washed repeatedly to remove unbound radioactivity. The 123I incorporated into cellular DNA is then released by treating the monolayers for 10 min with 1N NaOH. Aliquots of this were read using a bore hole type detector (Figure 86). Accurate counts for cell cultures pulse treated for both 1 hour and 21 hours with [123I]-deoxyuridine are evident. Relatively high counts are observed for the 21 hour cultures notwithstanding the fact that samples intended for the longer culture time were initially seeded with many fewer cells. This reflects the greater cell numbers that have passed through the S-phase stage of the cell cycle during the 21 hours of incubation, and proves that the [123I]-deoxyuridine preparation is free of any contaminants that hinder cell division. The method appears to be suitable to count radioactivity in cultures where cells have been plated for only a few hours. This allows one to define more accurately the cell numbers associated with radioactive counts.

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Figure 86: Radioactivity counts in cell samples exposed to 5-[123I]iodo-2´-deoxyuridine (IUdR) reflecting S-phase status

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3.4.10 The Role of Mitochondria-Mediated Apoptosis in the Radiation Response of

Prostate Cancer and Normal Cells

J.M. Akudugu, J.P. Slabbert, J. Symons, J. Nieto-Camero 1iThemba LABS In the radiotherapy of localised cancers a number of factors can influence the response of tumours and surrounding normal tissues. Some factors are patient-specific while others depend on the tumours or normal tissues concerned. One such prognostic factor is the susceptibility of different cell types to undergo programmed cell death (apoptosis) after irradiation. Apoptosis occurs via three major pathways: (1) the apoptosis trigger that is initiated by the translocation of bax (a pro-apoptotic protein) to mitochondrial membranes, and mediated by the release of cytochrome c from mitochondria and the activation of caspase-9; (2) the death ligand that leads to the activation of caspase-8; and (3) the endoplasmic reticulum stress that activates caspase-12. This study was designed to investigate whether human prostate cancer cells (DU 145) and normal Chinese hamster ovarian (CHO-K1) epithelial cells would preferentially undergo apoptosis via the mitochondria-mediated pathway after photon and neutron irradiation.

DU 145 cell cultures were variously treated with neutron or γ radiation, and P5, a cell-permeating synthetic peptide inhibitor of bax translocation to mitochondria (Tocris, Bristol, UK). Apoptosis was determined on the basis of changes in mitochondrial membrane potential using the DePsipher Kit (Assay Designs, MI, USA). In healthy cells the mitochondria appear red due to aggregation of the DePsipher dye. Apoptotic cells having disrupted mitochondrial membranes appear green, as the dye remains in its monomeric form in the cytoplasm. The data in Figure 87 show a clear LET-dependent dose response for mitochondria-mediated apoptosis in DU 145 cells. The presence of P5 in cultures during irradiation almost completely abolished this mode of cell death, irrespective of the type of radiation. The results indicate a significant role for mitochondria-mediated apoptosis in DU 145 cell demise after exposure to both photons and neutrons. This phenomenon is reflected in enhanced radioresistance following P5 treatment (Figure 88). In these cells the radioprotection factors produced by P5, based on the mean inactivation doses, were found to be 1.32 ± 0.04 and 1.24 ± 0.05 for photon and neutron irradiation respectively, and were not significantly different (P = 0.40). Therefore, on average, the DU 145 cells were rendered 30% more radioresistant by P5, irrespective of the type of radiation. Interestingly, P5 did not seem to have an effect on radiation-induced cell death in the normal CHO-K1 cells (Figure 88). Only a marginal radioprotection factor of 1.05 ± 0.05 was observed when CHO-K1 cells were irradiated in the presence of P5, indicating a minor role for bax-mediated cell death in this cell line.


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Although the p53 gene is known to be mutant and dysfunctional in DU 145 [1] and CHO-K1 [2] cells respectively, there is sufficient evidence to suggest that a wild-type or functional p53 is not required for cells to undergo apoptosis [3, 4]. In fact the translocation of bax to mitochondria in response to exposure to cytotoxic agents has been demonstrated in cells lacking functional p53 [5, 6]. The cell survival data in Figure 88 seem to indicate that manipulation of bax availability during irradiation may lead to significant changes in the radiosensitivity of the prostatic cancer cell line but not of the normal cell line, and result in an enhanced therapeutic gain.

References 1. A.G. Carroll, H.J. Voeller, L. Sugars and E. Gelmann. Prostate 23 (1993) 123. 2. H. Lee, J.M. Larner and J.L. Hamlin. Gene 184 (1997) 177. 3. J.R. Chapman, H. Tazaki, C. Mallough and S. Konno. BJU International. 83 (1999) 703. 4. Z. Han, D. Chatterjee, D.M. He, J. Early, P. Pantazis, J.H. Wyche and E.A. Hendrickson. Mol. Cell. Biol. 15

(1995) 5849. 5. T. Strobel, L. Swanson, S. Korsmeyer and S.A. Cannistra. Proc. Natl. Acad. Sci. USA 93 (1996) 14094. 6. Y.-J. Lee, D.Y. Chung, S.-J. Lee, G.J. Jhon and Y.-S. Lee. Int. J. Radiat. Oncol. Biol. Phys. 64 (2006) 1466.

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Figure 87: Solid squares, solid line: % of apoptotic cells in DU 145 cultures after irradiation with p(66)/Be neutrons. Solid circles, dashed line: % of apoptotic cells in DU 145 cultures after irradiation with 60Co γ-rays. Open square: % of apoptotic cells in DU 145 cultures treated with P5, following a 6 Gy γ-ray dose. Open circle: % of apoptotic cells in DU 145 cultures treated with P5, following a 2.5 Gy neutron dose. Each data point represents the mean ± SE of three independent experiments.

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3.4.11 Commissioning of an Automated Microscope with Real Time Image Analysis to

Detect Radiation Induced Cellular Damage M.S. Rossouw1, A. Vral2, P. Willems2, B. Thierens2, J.P. Slabbert3

1Radiation Oncology, Tygerberg Hospital 2Department of Human Anatomy, Embryology, Histology and Medical Physics, Ghent University, Belgium 3iThemba LABS An automated microscope that is equipped with a real time image analysis system has been installed at the Department of Human Anatomy, Embryology, Histology and Medical Physics at Ghent University, Belgium. The acquisition of this instrument is part of the activities funded by a grant from the Flemish Inter-University Council (VLIR) to help South Africa implement a routine bio-monitoring service for radiation workers. The induction of micronuclei in T-lymphocytes is well established as a biomarker of radiation damage, but the tedium of the assay makes it unsuitable for large scale bio-dosimetry. To eliminate the need for manual scoring of white blood cell preparations, a project has been launched to automate microscopy analysis with an image analysis system developed by Meta Systems. It consists of a Zeiss Axiolmager microscope equipped with a Märzhäuzer motorised scanning stage driven by Metafer4 scanning software. The microscope is controlled by a central PC unit, which also processes the images obtained by its CCD camera. A total of 8 slides can be set up for automatic screening in a single session (Figure 89). Before using such a system, the cell classifiers need to be optimised for a specific radiobiological endpoint using laboratory-specific cell preparation techniques. The parameters that make up the classifier system to detect binucleated cells and micronuclei within such structures are listed in Table 16. An example of how the system scans a microscope slide and process images is shown in Figure 90. In the first of a series of tests the accuracies with which the system detects binucleated cells and micronuclei in slide preparations of cultured lymphocytes were evaluated. Whole-blood cultures were prepared for this, as the method for preparing such cultures is best suited to the processing of large numbers of blood samples simultaneously. Blood collected with the anti-coagulant Li-heparin was used. At the end of the cultures Giemsa-stained slides were prepared for both manual and automated screening, so allowing the accuracy of cell classification to be determined. In this first set of readings using whole-blood cultures and a passive staining technique, incorrectly classified cells ranged from 6% for binucleated cells with no micronuclei, to 18% for two micronuclei in a binucleated cell. The origins of misclassifications are currently being investigated to help optimise the variables that are needed to ensure accurate analysis. Also, the use of different cell fixation methods is followed to improve classification. Notwithstanding the inaccuracies noted in these first runs, clear advantages in using automated detection to identify binucleated cells and count micronuclei are evident. This includes speed and consistency.

Figure 89: Co-workers at Ghent University setting up the automated image analysis system.


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Table 16: Cell classifier parameters that need optimisation to accurately detect and count binucleated cells and micronuclei

Binucleated lymphoblasts Characteristic Explanation 1. Object threshold Defines the object threshold used to segment cell nuclei 2. Minimum area (µm2) Min area for a single nucleus to be accepted for analysis 3. Maximum area (µm2) Max area for a single nucleus to be accepted for analysis 4. Maximum relative concavity depth To discriminate single nuclei from nucleus clusters 5. Maximum aspect ratio To discriminate round objects from elongated ones 6. Maximum distance (µm) Max distance between two nuclei 7. Maximum area asymmetry Max relative size difference between two nuclei 8. Region of interest radius (µm) Defines area around nuclei that is checked for other objects

9. Maximum object area in ROI (µm2) Max area of all other objects in ROI Micronuclei Characteristic Explanation 1. Object threshold Defines the object threshold used to segment micronuclei 2. Minimum area (µm2) Min area for a single micronucleus to be accepted for analysis

3. Maximum area (µm2) Max area for a single micronucleus to be accepted for analysis 4. Maximum relative concavity depth To define shape of micronucleus 5. Maximum aspect ratio To discriminate round objects from elongated ones 6. Maximum distance (µm) Max distance a MN may have from centre of ROI 7. Object threshold Defines the object threshold used to segment micronuclei 8. Minimum area (µm2) Min area for a single micronucleus to be accepted for analysis

9. Maximum area (µm2) Max area for a single micronucleus to be accepted for analysis 10. Maximum relative concavity depth To define shape of micronucleus 11. Maximum aspect ratio To discriminate round objects from elongated ones 12. Maximum distance (µm) Max distance a MN may have from centre of ROI

Figure 90: A gallery of binucleated lymphoblasts identified in a culture of whole-blood by the Metafer system. This is based on the initial set of image classifier parameters. In this example more than 1000 images have been processed in less than 2 minutes. Also shown are the positions of cells on a microscope slide as well as the number of micronuclei detected.


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3.4.12 Chemical Dosimetry B. Adam1, T. Kupi2, Z. Buthelezi2, H. Hofmeyr3, T.L. Blomefield4, J.P. Slabbert2

1African Institute for Mathematical Sciences (AIMS), Muizenberg 2iThemba LABS 3Citrus Research International, Citrusdal 4ARC Infruitec-Nietvoorbij, Stellenbosch Industrial demand for chemical dosimetry continues, mainly for high dose irradiation of electronic products and applications in Sterile Insect Techniques (SIT). During the last year new SIT projects have begun at Citrus Research International, Citrusdal, and at the Agricultural Research Council’s facility at Stellenbosch. These projects focus on the release of sterile codling moths to disinfest stone fruit orchards, and sterile false codling moths to disinfest citrus farms. Most chemical dosimetry is performed using 1mM Fe(HN4)2(SO4)2. This solution is most appropriate for spectrophotometric readings of molecular yield following doses of 80 to 200 Gy. All SIT applications for which it is used fall within this range. Small volumes of dosimetric solutions (1.5 ml) are placed within irradiated volumes of several litres. The use of chemical dosimeters for SIT applications is convenient, as up to eight irradiated volumes rotate around their own central axes and simultaneously around the source, during routine production. During the development of a new SIT programme several changes are made to the radiation set-up. Dose calculation methods are being implemented to understand the effects of changing the sample volume and geometry. To date these have aided the prediction of changes in radiation dose with depth.

Figure 91: Ms Buthaina Adam, a Sudanese citizen, completed her studies at the African Institute for Mathematical Sciences with a project in chemical dosimetry


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3.5 Materials Research Group 3.5.1 RBS Study of Metal Diffusion into Polyethylene Terephthalate Foils influenced by

Surface Treatment M.M. Nkosi1, C.C. Theron1,2, and R. Nemutudi1 1iThemba Labs, Materials Research Group 2Element Six There is a wide range of applications for metallized polymers [1]. Mechanical and electrical properties of a metal/polymer interface are strongly affected by the degree of metal/polymer diffusion and intermixing [2]. With such widespread technological impact, there is a basic need to understand the mechanism of metal diffusion in polymers and its effects on the structure and formation of the metal/polymer interface. In this investigation we considered metal/polymer interfaces prepared by the evaporation of gold (Au) and silver (Ag) onto PET membranes. Gold was preferred because it is known to be the most inert metal and therefore minimizes the chemical effects superposed on the measurements. The samples were prepared by the deposition of thin Au and Ag layers on biaxially orientated polyethylene

terephthalate (PET ~ 100µm thick, C10H8O4, ρ = 1.397 g.cm-3) films. Au and Ag layers with typical thickness of approximately 10 nm were deposited using a High Vacuum Electron Gun Evaporator system on polymer substrates. The base pressure in the HV electron beam system was better than 4x10-6 torr and increased only by an order of magnitude during metal evaporation. The annealing was performed in air atmosphere in a small annealing furnace up to 150°C at different annealing times. RBS was used to follow the formation of the Au/PET and Ag/PET interfaces at room temperature. The kinematic factors for C, N, O, Ag and Au are indicated by dotted lines. The position of the as deposited Ag and Au RBS peaks in Figures 92 and 93 (solid lines) indicate that the metal lies on top of the PET surface. There was no evidence of Au or Ag diffusion into the polymer matrix during adsorption within the depth resolution limit of our apparatus. Even upon thermal exposure under vacuum after

100 200 300 400Channel

0

10

20

30

40

50

Nor

mal

ized

Yie

ld

0.5 1.0 1.5Energy (MeV)

PET/Ag As depositedPET/Ag Annealed 120oC 1hr

Ag

0 50 100 150 200Ch an nel

0

5

10

15

Nor

mal

ized

Yie

ld

0.2 0.4 0.6 0.8

E nergy (M eV)

N OC OC N

400 410 420 430 440 450Channel

0

10

20

30

40

50

Nor

mal

ized

Yie

ld

1.65 1.70 1.75 1.80Energy (MeV)

A g

0 50 100 150 200Channel

0

5

10

15

Nor

mal

ized

Yie

ld

0.2 0.4 0.6 0.8Energy (MeV)

N OC OC N

430 440 450 460 470 480Channel

0

50

100

150

200

Nor

mal

ized

Yie

ld

1.75 1.80 1.85 1.90Energy (MeV)

A u

100 200 300 400Channel

0

50

100

150

200

250

Nor

mal

ized

Yie

ld

0.5 1.0 1.5Energy (MeV)

PET/Au As deposited

Au

PET/Au Annealed 120oC 3hrs

Figure 92: RBS spectrum of Ag (10nm) deposited on PET foils (a) as deposited (solid line), and (b) after annealing at 120°C for 1 hour.

Figure 93: RBS spectrum of Au (10nm) deposited on PET membrane (a) as deposited, and (b) after annealing at 120°C for 3 hours.


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deposition, Au and Ag do not significantly diffuse into the PET. The total Au and Ag coverage stays constant upon annealing. As the deposition was carried out at room temperature clusters were formed at the surface. Upon annealing, the clusters agglomerate into larger clusters, and even prolonged annealing at elevated temperatures does not lead to significant diffusion into the polymer. This result can be explained by the difference in cohesive energy, which, for metals, is typically two orders of magnitude higher than for polymers. One expects that metals will agglomerate at the polymer surface rather than diffuse into polymers.

Reference: 1. C. v. Bechtolsheim, V. Zaporojtchnko, and F. Faupel. J. Mater. Res., Vol. 14, No. 9, (1999).

2. P.S. Ho, R. Haight, R.C. White, B.D. Silverman and F. Faupel. In Fundamentals of Adhesion, Plenum Press,

New York 1991, p. 383.

3.5.2 Real-time Rutherford Backscattering Spectrometry Study of Diffusing Species

during the Formation of Germanides of Nickel C.M. Comrie1

1 Department of Physics, University of Cape Town. The scaling of micro-electronic devices to ever smaller dimensions and ever better performance has pushed the Si based materials to its physical limits. Currently, a lot of effort is invested in research on high mobility semiconductors such as Ge, in order to replace the Si channel in future high performance metal-oxide-semiconductor (MOS) -devices. However, before germanium can be adopted by the industry, a suitable contact material must be identified to make electrical contact to the active areas (source, drain and gate) of a transistor. The use of metal-germanides, similar to metal-silicides used in silicon-technology, is proposed for this purpose. Such metal-germanides, compounds of Ge with a suitable metal, can be formed in a self-limited way. As was the case for silicides, a thorough, fundamental understanding of germanide formation will be essential for the successful implementation of germanides in Ge-based transistors. The controlled and self-limited growth of germanide thin films with the desired structural and electrical properties is based upon a proper knowledge of the germanide formation process. A key to the understanding of the basic kinetic processes involved in germanide formation is the identification of the dominating diffusing species during germanide growth. Furthermore, not only is there a fundamental interest in the identification of the diffusing species, it is also relevant for the possible implementation of germanides in microelectronic devices. During device manufacturing processes it is often found that when the substrate element (Si or Ge) is the dominant diffusing species, this results in overgrowth and bridging in devices, which in turn has a detrimental effect on their performance. Recent research has shown that NiGe and PdGe are the most promising candidates for contact materials with germanium. However, little is known about the kinetics of germanide formation and reports about the diffusing species during NiGe or PdGe formation are missing in literature.


149

The diffusing species during germanide growth is best determined by use of an inert marker. The UCT group has considerable experience in the use of inert markers while studying metal silicide growth, and real-time Rutherford backscattering spectrometry is ideally suited for monitoring the movement of the marker during germanide formation. With real-time RBS the sample is continuously analysed by an ion beam while it is simultaneously subjected to a thermal anneal to induce phase formation. By determining the movement of the marker as a function of growth it is possible to determine which species diffuses at every stage of the germanide growth. We have undertaken some preliminary research on the Ge/Ni system. For the investigation, samples were prepared in which a very thin layer of an Au was sandwiched between the germanium substrate and the overlying Ni film. During the real-time RBS analysis the sample was ramped from 140°C to 300°C at a rate of 1°C/minute, and RBS spectra were captured every 30 s. To improve statistics four 30-s spectra were combined into a single 2-min spectrum, which was therefore representative of a 2°C temperature interval. A 2-D plot of the spectra obtained from one of the runs is shown in Figure 94.

In the RBS spectra shown in Figure 94 the signal in the region 340-370 is from the Ni signal superimposed on the broad Ge background. The small signal at channel 420 is from the Au marker. It is clear from the data that the marker moves towards the surface of the sample as the reaction proceeds indicating that Ni is the diffusing species during the initial stages of the reaction. It should be noted that gold is not ideal as an inert marker as it forms a eutectic with germanium but it was all that was available at the time and it was hoped that providing the temperature of the ramp was kept well below the eutectic temperature, Au would act as inert. It is interesting to note, however, that in the data shown in Figure 94 the height of the Au signal suddenly drops towards the end of the reaction. It is believed that this is associated with the formation of voids deep in the sample followed by diffusion of Au into the voids to decorate the surfaces of the voids. In the next set of experiments Ta will be used as marker.

Figure 94: Real-time RBS spectra obtained from Ge/Ni containing an Au marker


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3.5.3 A Time of Flight – Energy Spectrometer for Stopping Power Measurements at iThemba LABS

M. Msimanga1, 2, C.M. Comrie2, C. Pineda-Vargas1, S. Murray1. 1iThemba LABS, P O Box 722, Somerset West 7129, Cape Town, South Africa. 2 University of Cape Town, Rondebosch 7701, South Africa The quantitative analysis of thin layers using Heavy Ion – Elastic Recoil Detection Analysis (HI – ERDA) can be reliably performed if the stopping powers of the probing ions and recoils in a given target matrix are accurately known. Unfortunately for many projectile/target combinations experimental data on stopping powers is limited and where available, deviations of up to 50% between experiment and semi-empirical predictions have been reported [1]. A Time of Flight – Energy (ToF – E) spectrometer has been developed and assembled for stopping power measurements at iThemba LABS. The HI-ERDA set up is located in the SPC2 vault on the K1 line, where a range of low energy (< 0.34 MeV/amu) light and heavy ions is available. The ToF-E spectrometer consists of a time of flight detector, built from two timing detectors, T1 and T2, a flight distance of 0.58 m apart and a silicon surface barrier detector (SBD) positioned 6.5 cm behind the second time detector for energy measurement. Each timing detector consists of a thin carbon foil mounted about 5 cm from a microchannel plate (MCP). Probing ions incident on a target sample either produce recoils or are scattered off the target to the detector system, depending on the mass of the target species. Recoils or scattered ions passing through the carbon foil eject electrons from the foil and an electric field applied between the carbon foil and a grid accelerates and guides the electrons to the MCP assembly where the electron signal is multiplied to give a fast (< 1.0 ns rise time) timing signal. For stopping power measurements thin stopper foils are inserted between the second timing detector and the Si SBD. A recoiled/scattered ion passing through the detector system is detected by the two timing detectors to give the time of flight and by the SBD to give the residual energy. The time of flight (ToF) and the energy of each particle are measured in coincidence and this allows for measurement of the particle energy before and after passing through the target stopper foil. The energy of the incident ion before hitting the stopper foil is determined from the ToF measurement and the exit energy, for the lightest ions - hydrogen and helium, is measured using the SBD. For heavier ions the exit energy is determined from a ToF – E measurement without any stopper foil between T2 and the Si SBD (see description below). This method facilitates simultaneous energy loss measurement over a continuous range of incident energies as opposed to the traditional transmission measurements at a single incident energy at a time [2]. In this work measurements were performed to demonstrate the possibility of using the spectrometer to determine stopping powers of thin film materials for incident ions heavier than helium. Owing to beam time constraints the only ion beam available for the tests was 3.33 MeV He2+ and so this was a proof-of-principle measurement for the

spectrometer. Incident projectiles were scattered 30o from a 100nm Au-on-Si target towards the spectrometer.


151

Figure 95 shows the raw ToF – E coincidence spectra acquired with (left) and without (right) a 2500 μg/cm2 Ta foil placed in front of the SBD. The axes scales and ranges are the same in both plots. The shift in the high-energy edge when the Ta stopper foil is inserted between T2 and the SBD indicates a loss of energy as the scattered helium ions pass through the foil. The time of flight is unchanged since the energy between T1 and T2 remains unchanged. The ToF – E curve with the stopper foil in place is shifted to the left by an amount equal to the energy loss at any given energy along the energy axis. Plotted on the same axes, the two curves in Figure 95 would run parallel to each other with the upper one displaced in energy to the left.

For ions in the range Z ≥ 3 the energy determined from the ToF measurement is expected to be of a much better resolution than that measured by the SBD because the timing resolution improves with mass, whereas the converse is true for the SBD energy resolution. Therefore the energy signal from the SBD is only used to tag events of a similar energy on the two ToF curves, before and after the stopper foil is inserted, and the corresponding ToF then used to calculate the energy in each instance. In other words the energy loss is determined by selecting a single energy point along the energy axis and reading off the corresponding ToF, from each of the 2D ToF – E curves, and using these times of flight to calculate the energy difference. The procedure is then repeated for a series of different energies along the energy axis to generate a continuous stopping power

curve. Work is currently in progress to fully implement the data analysis procedure.

References. 1. G. Dollinger, High resolution stopping force and straggling measurements for heavy ions. IAEA Proposal

Research Agreement CRP F11013, August 2007. 2. Y. Zhang and G. Possnert, Nucl. Instr. Meth. B 190 (2002) 69.

Figure 95: Raw 2D ToF-E spectra of ~3.3 MeV helium ions with (left) and without (right) a Ta stopper foil.


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3.5.4 Ginzburg-Landau Treatment for a Two-band Superconductor T. B. Doyle1 and R Labusch2

1 iThemba LABS, PO Box 722, Somerset West 7129, South Africa 2Department of Applied Physics, Technical University of Clausthal, Clausthal-Zellerfeld, Germany.

In a two-band superconductor, described by two order parameters ψ 1 and ψ 2 , the Ginzburg - Landau free

energy functional is given by the free energies of the two conduction bands and additional terms containing

products of ψ 1 and ψ 2 . The most obvious ‘interaction’ term is proportional to ψ ψ12

22⋅ . Additional terms,

proportional to the real part of ψ ψ1 2⋅ * and characterized as due to ‘Josephson inter-band tunnelling’, have

been proposed, but have yet to be shown to be significant. In view of the fact that the wave functions of the two bands are orthogonal and that scattering of superconducting states is not allowed, it could be justified to omit these terms altogether. Moreover, it turns out that the experimental results obtained for MgB2 (the most prominent

two-band superconductor) are quite well accounted for with the ψ ψ12

22⋅ -term alone. We therefore confine

our treatment to neglect other possible interaction terms which has the advantage that the number of adjustable material parameters stays reasonably low. The Ginzburg-Landau free energy per unit volume in the mixed state can then be written as

( ) ( )∫

∑

+

−∇⋅+

−∇⋅+

−⋅−⋅

=∆=

cell

jiij

ArdrBAe

imnAe

imn

a

F /''

22

22

2

11

2 2

0

22

22

22

11

1

22

21

2

1,

µψψ

ψψ

πrhrh

Here ∆F is the free energy relative to the superconducting state in zero magnetic field; the integral is taken over

the cross section of the unit cell of the vortex lattice. B r( )r is the local flux density inside the specimen and r rA r( ) its vector potential. n1 , n2 , m1 , m2 are the superfluid densities and the effective masses in the two

conduction bands, respectively. ψ 1 and ψ 2 have been normalized to unity in the ground state (i.e. at zero field

and at the minimum of F∆ . For symmetry reasons a a12 21= . If B = 0 and both order parameters are zero,

∆F is the total condensation energy which is associated with the thermodynamic critical field Hc or Bc , so that

a Bij

c

i j

==

∑2

01

2

2µ,

.

After suitable normalization and re-arrangement of the above equation for ∆F , the application of boundary

conditions for a unit cell in the vortex lattice and minimization with respect to ψ 1 , ψ 2 , and A, three highly

inhomogeneous, differential equations are obtained. These are solved simultaneously using numerical

techniques, and yield the normalized radial profiles )(1 rψ and )(2 rψ , and the local field intensity h(r) in the

unit cell, which contains a single flux quantum. Integration of these profiles over a unit cell, and the use of


153

standard relations, gives values for the electronic specific heat Ce(H) and for the magnetization M(H), as a function of the local thermodynamic field H, for the system. The physics of the problem unavoidably requires four material parameters that can be obtained only by fitting to experimental data. These are the Ginzburg Landau

parameter κ, and parameters relating to for the zero field super-fluid densities in each band and for their cross term. Fits of the theory to experiment for the two-band MgB2 system are given in Figure 96 below.

Figure 96(a): Electronic specific heat Ce as a function of reduced field H/Hc2 at T = 5K. Experimental data (circles) from [1], solid line from theory.

Figure 96(b) . Equilibrium magnetization as a function of reduced field H/Hc1 at T = 12K. Experimental data (circles) from [2], solid line from theory.

References 1. A.Y. Liu, I.I. Mazin, and J. Kortus, Phys. Rev. Lett. 87 (2001) 087005. 2. F. Bouquet et al., Phys. Rev. Lett. 89 (2001) 257001. 3. T.B. Doyle, A. Wisniewski, M. Zehetmayer, H.W. Weber, and J. Karpinski, Physica C408-410 (2004) 526.


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3.5.5 Influence of Low-level Pr Substitution on the Superconducting Properties of

YBa2Cu3O7-δ Single Crystals A. Kortyka1,2, R. Puzniak1, A. Wisniewski1, H. W. Weber2, T. B. Doyle3, Y. Q. Cai4, X. Yao4 1Institute of Physics, Polish Academy of Sciences, PL 02-668 Warsaw, Poland 2TU Vienna, Atomic Institute of the Austrian Universities, A-1020 Vienna, Austria 3School of Physics, University of KwaZulu-Natal, Durban 4001, and Materials Science Group, iThemba LABS, Somerset West 7129, South Africa 4Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, P. R. China Isothermal magnetization M(H) measurements have been made on the single-phase monocrystals of the Y1-xPrxBa2Cu3O7-δ system. Fits to the isothermal M(H) data, using model calculations for the equilibrium and irreversible/vortex pinning behaviour [4,5,6,7], allows for the approximate determination of the lower and upper critical fields, Hc1(T) and Hc2(T), respectively, and the thermodynamic critical field, Hc(T), the critical current

density Jc(B,T), coherence length, ξ(T), penetration depth, λ(T), and the Ginzburg-Landau parameter, κ = λ/ξ, for various temperatures (and, by extrapolation, the zero temperature values of these parameters) and values of x in the range 0 < x < 0.024. The crystals used in this work were plate-like, with dimensions 4.3 × 4.1 × 1 mm3, 5.2 × 3.7 × 1.2 mm3, and 4.7 × 3.35 × 2.1 mm3, for x = 0, 0.013, and 0.024, respectively. Isothermal M(H) data was obtained with the magnetic field applied parallel to the crystal c axis (corresponding to the smallest dimension) of the crystals.

The bulk equilibrium properties, Hc1(T), Hc2(T), and the G-L parameter κ for the specimens are obtained by fitting the mean value (i.e. for H increasing and H decreasing) of the M(H) isotherms to model predictions using an algorithm based on a theoretical treatment for the magnetization behaviour in a platelet specimen [1,2]. This treatment includes an explicit formula for B(H), which in the present work is derived from a numerical solution of the Ginzburg-Landau equation and is based on a modification [3] of the Hao-Clem [4] approach. In this treatment

magnetic properties are normalized by Hc1, which together with the G-L parameter κ, is treated as a free fitting

parameter. The illustrative example of results of these fits is shown in Figure 97, and the obtained parameters are given in the table below. The model algorithm also contains an explicit expression for the critical current density Jc(B). A representative fit of the model calculations to the full hysteretic M(H) data, using a well known expression for the form of Jc(B) in the so-called “fish-tail” regime (where Jc(B) scales with temperature) is given in Figure 98, and the values for Jc(0,80K) are included in the table below.

Pr Content

Tc (K) µ0Hc1c(0)

(mT) µ0Hc2c(0) (T) µ0Hcc(0)

(T) ξab(0) (Å)

λab(0)

(Å) κc Jc(0,80K)

Am-2

0 90.1 96.6 119.2 1.33 16.6 815 49 6.5 107 0.013 89.9 102 130.5 1.38 15.9 794 50 9.5 107 0.024 90.2 103 136.8 1.44 15.5 791 51 1.0 108


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References 1. R. Labusch, T.B. Doyle, Physica C 290 (1997) 143. 2. T.B. Doyle, R. Labusch, R.A. Doyle, Physica C 290 (1997) 148.

3. R. Labusch and T.B. Doyle, European Conference on Applied Superconductivity EUCAS2003, Sorrento, Italy, 14-19 September 2003.

4. Z. Hao et al., Phys. Rev. B 43 (1991) 2844.

Figure 98: Magnetization data for Y0.82Pr0.018Ba2Cu3O7-δ. Manifesting the “fish-tail” effect and shown by the coloured points. The solid line is the theoretical fit.

Figure 97: Mean magnetization data for Y0.82Pr0.018Ba2Cu3O7-δ. Shown by the coloured points. The solid line is the theoretical fit (the error on κ is better than ± 2).


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3.5.6 Electroless Deposition of Palladium Layers on Rare Earth Metal Hydride Alloy for

the Enhancement of Hydrogen Sorption Kinetic

M. Williams1, M. Lototsky1, A. Nechaev1, V. Yartys2, J. Solberg3, C.A. Pineda-Vargas4, Q. Li5 and V. Linkov1

1 South African Institute for Advanced Materials Chemistry, Department of Chemistry, University of the Western Cape, Private Bag X17, Bellville, 7535, South Africa 2 Institute for Energy Technology, P.O. Box 40, Kjeller NO-2027, Norway 3 Norwegian University of Science and Technology, NO-7491 Trondheim, Norway 4 Materials Research Group, iThemba Labs, P.O. Box 722, Somerset West, 7129, South Africa 5 Guangzhou Research Institute of Non-Ferrous Metals, Guangzhou, Guangdong, China Dynamic analysis in PIXE was conducted to qualitatively study the dispersion of palladium metal, deposited by electroless plating, on the surface of metal hydride ([La,Ce,Pr,Nd][Ni,Co,Al,Mn]5) alloy powders, and to determine whether continuous or discontinuous films were attained on the surface of the alloy. Irradiation was done using the nuclear microprobe (NMP) facility at iThemba LABS. PIXE confirmed that a thin layer of palladium was deposited onto the surface of the sample material, for the metal hydride alloy surface-modified without pre-

treatment and surface-modified after 1vol% γ-APTES pre-treatment, respectively. The elemental maps reconstructed by DA are shown in Figure 99.

It was observed that the metal hydride alloy surface-modified without pre-treatment did not facilitate the surface deposition of continuous layers of palladium, and the palladium particles were randomly distributed on the surface of the metal hydride alloy particle. At the same time, for the metal hydride alloy surface-modified after pre-

treatment in 1vol% γ-APTES, the deposition of continuous layers of palladium on the surface was observed.

Figure 99. Elemental maps obtained by PIXE of metal hydride ([La,Ce,Pr,Nd][Ni,Co,Al,Mn]5) alloy surface-modified with palladium: (a) no surface pre-treatment; (b) 1vol% γ-APTES surface pre-treatment.


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3.5.7 Non-destructive Analysis of Roman Coins by Micro-PIXE and RBS

A. Denker1, C.A. Pineda-Vargas2

1 Hahn-Meitner Institute, Berlin, Germany 2 Materials Research Group, iThemba Labs, P.O. Box 722, Somerset West, 7129, South Africa

A set of Roman coins of defined origin and epoch with sizes of between 1 - 3 cm in diameter were analysed at the NMP facility at the MRG using micro-PIXE and RBS to determine the trace elemental profile and patina layer thickness of the coins. Polished and non-polished sections that have a strong corrosion/patina layer were analysed previously by High Energy PIXE at the HMI cyclotron in Berlin. Since the penetration of the high energy protons in the coins is much larger, covering the patina and sub-patina layers in the coins, it was of interest to analyse these specimens with low energy protons to characterize the near surface spatial elemental distribution on the patina and on the polished area separately. Therefore a 3 MeV proton beam of 3 x 3 microns lateral resolution with currents of the order of 200 pA was used. Elemental maps were reconstructed using the technique of Dynamic Analysis and single point analyzers were extracted from the maps data using the software program GeoPIXE. Evaluation of the qualitative maps shows that in general there are no relative differences between the spatial distribution of Cu and Zn in the polished area. On the other hand there appears to be a negative correlation between Cu and Zn in the patina layer (see Figure 100). This may be due to the chemical bounding of these metals with different ions, particularly oxygen and hydrogen.

Figure 100: Micrograph of a real Roman coin showing the areas 1 (polished), and 2, 3 (unpolished) selected for analysis. A smaller micro-region of about 500 µm was selected on each area. The maps for major components in the bulk of the coins (Cu and Zn) show a negative correlation.


158

3.5.8 Nuclear Microprobe Ion Beam Facility and the PIXE Technique as a Probe of

Chemical Composition of AFM-induced Oxide Layers

R. Nemutudi1, M. Nkosi1, C. Pineda-Vargas1 and W. Przybylowicz1 1 Materials Research Group, iThemba LABS, P O Box 722, Somerset West, South Africa Local Anodic Oxidation with an atomic force microscope (AFM) [1-5] is a relatively new nano-lithographic fabrication technique. With the continued miniaturization of lateral dimensions of electronic devices, the ability of the AFM nano-probes to generate oxide patterns on a surface at nanometric scale presents AFM lithography as a preferred technique to fabricate low dimensional nano-electronic devices such as quantum dots, quantum channels and quantum detectors. The oxide patterns generated by the AFM probe exhibit special electrical characteristics, both at room and cryogenic temperatures, that make them suitable candidates to define in-plane side-gates and non-conducting regions on the plane of the two dimensional electron gas (2DEG) [2]. Although AFM-induced oxide lines are increasingly being used in the fabrication of devices, there is currently a conspicuous absence in the literature of data on the chemical composition of such oxides. We present preliminary results of our attempt to use the Nuclear Microprobe facility at the Materials Research Group (MRG) to gain insight in the chemical composition of the AFM induced oxide layers. The sample we use is an MBE-grown GaAs/AlGaAs heterostucture, with a quantum well buried 27Å beneath the GaAs capping layer [6]. The MBE-grown sample is first chemically etched to define a mesa structure as shown on the optical image in Figure 101(a). The AFM lithography technique is subsequently applied to write oxide patterns in the centre and most narrow part of the mesa. At appropriate magnification, such AFM-induced oxide patterns are optically resolved as dark lines, see Figure 101(b). The sample is then loaded in the Microprobe chamber and subjected to irradiation by a beam of alpha particles at an incident energy of 2 MeV. First a large area is scanned, which incorporates ohmic contacts that serve as alignment marks as shown in Figure 101(a). The scanned area is subsequently reduced to focus most of the beam into the area of interest where the AFM oxide lines were drawn. PIXE maps are recorded for Ga, Al, As, Si, and Au concentrations. The PIXE Al map shown in Figure 101(c) reveals an almost direct correspondence with the optical image in Figure 101(b). The PIXE Al concentration map is the most appropriate guide to the central region of interest as Al is more concentrated only on the mesa while

(a) (b) (c) Figure. 101: (a) An optical image of a mesa wet-etched on an MBE-grown GaAs/AlGaAs heterostructure showing AuNiGe ohmic contacts that serve as alignment marks during PIXE scans. The dark rectangular shadow is the region irradiated with 2MeV alpha particles.(b) A magnified optical image showing, in dark in the middle, AFM-induced lines. (c) A PIXE map of aluminium concentration corresponding to the irradiated region in (a).


159

elsewhere it has been chemically etched. The colour bar on the PIXE map reflects the intensity of the aluminium signal and not the quantitative concentration of the element. The experiment was performed with the alpha beam resolution of 2 x 2 (xy) µm2. Our ability in this experiment to generate such a visible Al PIXE map is a critical step and opens for us the possibility, with a more stable beam at an optimized lateral resolution of 1 x 1 µm2, to probe the central region of the device and extract a series of RBS spectra from AFM-oxidized regions. Such RBS spectra should ultimately allow us to quantify both the thickness and the phase of the AFM-induced oxides. References: 1. E.S. Snow and P.M. Campbell, Science 270 (1995) 1639. 2. R. Held et al., Appl. Phys. Lett. 71 (1997) 2689. 3. R. Weisendanger, Cambridge University Press. 4. C.J. Chen, Introduction to Scanning Tunneling Microscopy, Oxford University Press 1993. 5. M.A. Herman and H. Sitter, Molecular Beam Epitaxy, Springer Series Materials Science 7.

6. N. Curson, R. Nemutudi et al., Appl. Phys. Lett. 78 (2001) 3466.

3.5.9 Using PIXE to Analyze the Association between Hydrocarbons and Mineralization

in the Witwatersrand Basin G.R. Drennan1, S.M. Mashego1, S. Ntshangase1, M. Msimanga2, T.P. Sechogela2, W.J. Przybylowicz2 1 School of Geociences, University of the Witwatersrand, Private Bag 3, WITS 2050, Johannesburg 2 iThemba LABS, PO Box 722, Somerset West 7129, South Africa The presence of carbonaceous matter in the gold- and uranium-bearing conglomerates of the Witwatersrand Basin is one of the more intriguing and controversial aspects of the genesis of these deposits. Its occurrence is particularly relevant to mining operations since it is usually an indication of high grades of both gold and uranium. Values of up to 4,7% gold and 11,5% uranium have been reported from analyses of separated carbonaceous matter [1-7] and, consequently an understanding of its origins, distribution, and relationship to gold and uranium is pertinent to the economic evaluation of individual reef horizons. Micro-PIXE analyses on the Carbon Leader Reef and South Reef were undertaken using the nuclear microprobe. Elemental concentrations and maps were obtained using GeoPIXE II software. Preliminary results reveal that the Carbon Leader Reef has both filamentous seam and “fly-speck” carbon. Elemental mapping of the cabonatious material reveals that the seam carbon at Tau Tona and Savuka Mines is enriched in places in K, Al, Ca, Ti, Cr, S, Fe, Y, Zr, Ag, Au, Pb, Th and U (e.g. Sample T3.6E & F). Potassium and aluminium occur as concentrations rimming silica inclusions suggesting that sericite has formed around quartz grains. Calcium exhibits a similar relationship.


160

Titanium concentrations are associated with rutile inclusions within the seam. Chrome and iron concentrations suggest the presence of detrital chromite and iron and sulphur concentrations point to the presence of detrital pyrite. Detrital zircon grains account for the Zr and Y concentrations. Lead, thorium and uranium are associated with the occurrence of uraninite grains that exhibit replacement along fractures by carbon and the production of galena. Gold shows two associations: one with sulphur and lesser copper suggesting that it is associated with sulphides (pyrite and chalcopyrite), and the other with lead, thorium and uranium, suggesting association with the carbonaceous material that is replacing detrital uraninite. Recrystallized pyrite occurring within the Carbon Leader Reef at Savuka Mine shows evidence of zonation with higher concentrations of arsenic and nickel towards grain centres and iron at grain boundaries (e.g. Sample P2BBA & B). Chromium occurs interstitially to these recrystallized grains. Elemental concentrations for South Reef at the Doornkop Section also exhibit strong associations between sulphur, iron and chromium indicating the presence of pyrite and chromite mineralization. Silica and potassium concentrations interstitial to the sulphide mineralization suggest the abundance of phyllosilicates within the matrix of this reef. Gold, lead, thorium and uranium indicate the presence of remobilized mineralization associated with detrital uraninite grains undergoing replacement by carbonaceous matter in some samples (e.g. DK1507_15 and DK1507_22), however, gold also appears to be particulate and unrelated to sulphides or uraninite in other samples (e.g. DK1507_20) although the gold is in close proximity to uraninite grains. In conclusion, sediment-hosted bitumen occurs in seams and as "fly-speck" nodules within the sediment matrix. This organic material is heterogeneous and its chemical structure is a function of proximity to uraninite grains and uranium content. Radiolytic polymerization, during catagenesis within the Witwatersrand Basin, resulted in the precipitation of heavy hydrocarbons around detrital uraninite (giving rise to reef- and "fly-speck" bitumen as seen in the Carbon Leader Reef and South Reef) and the liberation of light hydrocarbons (CH4, C2H6, C3H8, etc.) into circulating basinal fluids.

Figure 102: PIXE maps showing concentrations of elements in sample T 3.6.

Figure 103: Complete scan of sample DK1507_19


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References 1. G.L. England, B. Rasmussen, B. Krapež, and D.I. Groves, Economic Geology, 96 (2001) 1907. 2. H.E. Frimmel, Earth-Science Reviews, 70 (2005) 1. 3. G.J. Gray, R. Lawrence, K. Kenyon, and C. Cornford. Journal of the Geological Society, London, 155

(1998) 39. 4. D.K. Hallbauer, In: Anhaeusser, C.R. and Maske, S. (eds.). Mineral deposits of Southern Africa, 1 (1986)

731.

5. P. Landais, J. Dubessy, B. Poty and L.J. Robb. Organic Geochemistry, 16 (1990) 601. 6. L.J. Robb, P. Landais, G.R. Drennan and J. Dubessy. In: J.P. Hendry, P.F. Garey, Parnell, J., Ruffell,

A.H. and R.H. Warden (eds.). GEOFLUIDS II ’97, Contributions to the Second International Conference on Fluid Evolution, Migration and Integration in Sedimentary Basins and Orogenic Belts, Belfast, Ireland, 10-14

March 1997, 452. 7. L.J. Robb, P. Landais, G.R. Drennan and J. Dubessy. Economic Geology Research Unit Information

Circular, 312 (1997) 34.

3.5.10 Micro PIXE analyses of Furnace and Converter Mattes for the Determination of

Trace Element Distribution and Concentrations S. Govender1, W. Przybylowicz2, O.M. Ndwandwe1, J. Nell3 1Department of Physics and Engineering, University of Zululand, Kwa-Zulu Natal, South Africa 2iThemba LABS, PO Box 722, Somerset West 7129, South Africa 3Mintek, Randburg, Johannesburg, South Africa South Africa is the world’s foremost primary producer of platinum. The Platinum Group Elements (PGE) are almost exclusively extracted from three mineralized horizons within the Bushveld Complex (BC) which is the repository for 75% to 80% of the world’s reserves of PGE [1, 2]. PGEs consist of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os). In the earth’s crust, the PGEs have abundance of the order of 10-6 % to 10-7 % [3]. PGEs fall into two categories. The first group is known as the platinum group minerals (PGMs), where the PGEs occur as impurities within other minerals. The second group consists of those minerals in which the PGEs occur as trace elements i.e. at concentrations of less than 500 ppm. The trace elements can significantly influence product quality and impact substantially on the environmental and economic sustainability of an operation. The most common PGMs found are sulphides, tellurides, arsenides and alloys [4]. The following sulphides from the Merensky Reef are major repositories of PGEs and trace PGEs: pentlandite ((Fe, Ni)9S8), pyrrhotite (Fe1-xS), pyrite (FeS2) and chalcopyrite (CuFeS2). Tentative analysis has shown that pyrrhotite and pentlandite are important PGE repositories. They both host platinum; Au and Pd are favoured more by pentlandite [5]. X-ray emission spectrography was earlier used to


162

analyze pure base metal sulphide concentrations from various localities (Rustenburg, Union and Amandebult sections of RPM) and the results showed that pyrrhotite contains 11-47 ppm Pt and 3 ppm Rh; pentlandite contains 11-13 ppm Pt, 142-415 ppm Pd and 23-74 ppm Rh; pyrite contains 15 ppm Pt, < 34 ppm Pd and < 9 ppm Rh; and no PGEs were detected in chalcopyrite [6, 7]. It is clear from these and other publications that base metal sulphides host PGEs, and pyrrhotite is the main repository for Pt and pentlandite for Pd. The treatment of the ore requires four processes - beneficiation, smelting and converting, base metal extraction and PGE refining. Smelting and converting is a pyrometallurgical concentration process which produces a PGE enriched Ni-Cu sulphide matte. A product of smelting is called furnace matte, while converter matte is produced in the converting process. Furnace and converter matte samples were used for the analysis of trace element concentration and distributions. The initial part of the study involved the identification of phases which were produced during the processing stages, and this was carried out at Mintek, Randburg, South Africa. Scanning electron microscopy and optical microscopy were used for the phase identification. The major part of study was carried out using the nuclear microprobe and particle induced X-ray emission (PIXE) to determine the trace elements concentrations and distribution in the different phases. Selenium was found in all the converter matte phases. Traces of Se were found in the chlorite region in which it was at concentrations around 35 ppm, followed by heazlewoodite (Figure 104). The lowest Se concentration was found in the Ni-Cu alloy (21 ppm), this was common in all the Ni-Cu alloy phases. Converter matte mostly consists of heazlewoodite, chalcocite and small quantities of Ni-Cu alloys and trevorite. A relative increase in the heazlewoodite concentration has lead

to an increase in the Ni and S content, and an increase in Cu-sulphides has resulted in an increase of the Cu content. The loss of Fe from the matte by oxidation during the converting process has resulted in an increase of the PGE content in the alloy. The highest amounts of trace elements were found in chalcocite followed by trevorite; the alloy phases had the lowest amount of trace elements. Trevorite and chalcocite contained traces of PGEs and Au and the alloys contained the highest concentration of Au and PGEs. As, Se, Co, Ag, Pb and Bi concentrations have decreased to trace quantities in most of the phases, traces of Se were evenly distributed in the chalcocite phase [8]. The results show that Co has an affinity for Fe, with trevorite containing the highest concentration of Fe. The Co concentration decreased in regions where the Fe content was low, so the reduction of Co may be due the low Fe content or it has been oxidised along with Fe [8].

Figure 104: PIXE maps of converter matte showing the distribution of Se in heazlewoodite (region 1), Ni-Cu alloy (region 2), and chalcocite (region 3).


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References 1. R.T. Jones. South African Journal of Science, (1999) 525.

2. R.G. Cawthorn and R.C. Hochreiter. Global Platinum and Palladium Deposits. In Proceedings, 2nd Bi-Annual

World Platinum Congress 2000, pp. 20. 3. F.A. Cotton and G. Wilkinson. Advanced inorganic chemistry 4th Edition. Wiley-Interscience Publication.

(1980) pp. 1396.

4. L.J. Cabri (editor). Platinum-group elements. mineralogy, geology and recovery. Can. Inst. Min. Metal. Spec.

Vol. 23. (1981a)

5. N.M. Lindsay. The processing and recovery of the platinum-group elements, M.Sc thesis, University of the Witwatersrand, Johannesburg (1988).

6. E.D. Kinloch. Regional trends in the platinum group mineralogy of the Critical Zone of the Bushveld Complex, South Africa. Economic Geology. 77 (1982) 1328.

7. W. Peyerl. The metallurgical implications of the mode of occurrence of platinum-group metals in the Merensky reef and UG-2 chromitite of the Bushveld complex. Geol. Soc. S. Afr. Spec. Publ. 7 (1983) 295.

8. S. Govender. Micro PIXE analyses of Furnace and Converter Mattes for the Determination of Trace Element Distribution and Concentrations, M.Sc. thesis, University of Zululand, Kwa-Zulu Natal, South Africa (2005)

pp. 1-16, 68-81.

3.5.11 Heavy Metal Binding using Surfactant Modified Membranes S. Govender1,2, W.J. Przybylowicz3, and P. Swart1, 1Department of Biochemistry, University of Stellenbosch, Stellenbosch, South Africa 2CSIR Built Environment (RIS), PO BOX 395, Pretoria, 0001, South Africa 3iThemba LABS, PO Box 722, Somerset West 7129, South Africa Heavy metal pollution is becoming an increasing environmental concern exacerbated by the unprecedented increase in urbanisation and industrialisation. Toxic pollutants such as cadmium, lead, mercury, nickel, zinc and copper enter aquatic systems naturally via weathering and also through mining, air-pollution and processing. Removal strategies are therefore of both environmental and industrial significance with human and animal health as a driving force [1]. Membrane technology is a widely accepted and a relatively low-cost (e.g. ultrafiltration and microfiltration) large scale technology for water treatment and potable water production [2]. Metal ion removal however, is not so trivial, necessitating higher process costs associated with nanofiltration and reverse osmosis. Well-characterised, hydrophobic, piezoelectric PVDF membranes and a physisorbed amphiphillic surfactant as an affinity linker with covalently attached bio-specific ligands to demonstrate metal binding, regeneration and re-use are described. It also has two pendent hydroxyl groups per molecule that can be derivatised to attach functional groups or ligands [3]. This work details the fabrication of non-porous, hydrophobic PVDF membranes for the attachment of a novel EDTA type metal chelating ligand (coupled to Pluronic F108) in order to specifically remove divalent cations (Cd2+, Ni2+, Zn2+, Fe2+) from solution. Specifically this report focuses on the ability of said functionalised polymer to bind and remove Cd from solution. Specific binding is shown to occur in Figure 105.


164

What separates this membrane-based technology from other reports is that it is scalable (due to the multi-variant membrane module design), able to resist non-specific surface fouling and can be regenerated and re-used (up to five times) with a simple anionic surfactant treatment [4]. Following the proof of concept demonstrated above, future work will involve investigating the robustness of this technology subject to pH and ionic strength variations. The scalability proposed by the membrane technology, can now be more effectively exploited based on the ability of accurate solid-state quantification of Cd binding using PIXE.

References 1. A. Nastasovic, S. Jovanovic, D. Dordevic, A. Onija, D. Jakovlejevic, T. Novakovic, Reactive and Functional

Polymers. 58 (2003) 139.

2. S-Y. Suen. Y-C. Liu, C-S. Chang, J. Chromat. B. 797 (2003) 305. 3. S. Govender, E.P. Jacobs, M.W. Bredenkamp, P. Swart, J. Colloid Int. Sci. 282 (2005) 306. 4. S. Govender, W.J. Przybylowicz, E.P. Jacobs, M.W. Bredenkamp, L. van Kralingen, P. Swart, J. Mem. Sci.

279 (2006) 120.

Figure 105: PIXE spectra showing specific divalent Cd binding on ligand modified PVDF membranes compared with native unmodified membranes.

ZnFe

Ca

Cd-KαCd-Kβ

Zn

Cd-LCl


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3.5.12 Determination of Boron using the 11B(p, α)8Be Nuclear Reaction

A.I Mabuda,1,2 and W. Przybylowicz1

1 MRG, iThemba LABS, PO Box 722, Somerset West 7129, South Africa 2 Department of Physics, University of the Western Cape, Private Bag X17, Bellville, 7535 Determination of trace quantities of boron is required in various studies of materials and in geology. Using the 11B(p,α)8Be nuclear reaction with a focused proton beam of 670 keV energy is one of the few microanalytical

techniques capable of achieving detection limits in the 5-10 ppm range. The set-up for the determination of boron was developed at the iThemba LABS nuclear microprobe facility, in which high sensitivity is achieved by using a detector consisting of four photodiodes mounted in a half-spherical geometry. This project aims at performing micro-analysis of boron by the NRA method and reaching the development phase in which routine, non-destructive boron analyses would be possible at detection limits below 5 ppm.

Yield curve measurements were performed on NIST 611, NIST 612, pure boron, BN and tourmaline standards. Before performing nuclear microprobe measurements Scanning Electron Microscopy (SEM) images (see Figure 106) of Mts+Tu 950 glass samples were taken to find the position of the sample when adjusting the beam in the experimental chamber. The maps of samples were obtained to extract the region of boron within the samples (see Figure 107). The concentrations of boron from the measured Mts+Tu 950 glass samples were ranging between 0.2 - 1.5 wt % and the detection limit of 8.44 ppm for the minimum counts of 100 was obtained from the yield curve.

Figure 106: SEM image from Mts+Tu 950 (glass) sample

Figure 107: The distribution of oxygen (O) and boron (B) maps from Mts+Tu 950 (glass) sample. The scalebar is in microns.


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3.5.13 PIXE Microanalysis Of Biological Materials in Frozen-hydrated State W.J. Przybylowicz1, G. Tylko2, J. Mesjasz-Przybylowicz1 and A. Barnabas1

1 Materials Research Group, iThemba LABS, Somerset West 7129, South Africa 2 Department of Cytology and Histology, Institute of Zoology, Jagiellonian University, 30-059 Kraków, Poland There is a growing need for elemental microanalysis with good spatial resolution and high sensitivity, to study metal ions utilized by biological systems in fundamental processes such as signalling, gene expression, and catalysis [1]. Preservation of analyzed specimens in their natural hydrated state is the best way to ensure that the measured elemental distribution reflects the true location and concentration of elements in living tissues and cells. Micro-PIXE is one of the few methods meeting the demands of trace element microanalysis at the spatial resolution required for single cell analysis, with easy quantification. While numerous examples of PIXE microanalysis of freeze-dried specimens can be found, in-vacuum analysis of frozen-hydrated biological material has been reported only recently [2, 3]. An example of such analysis is shown, and the results obtained for frozen-hydrated and freeze-dried specimens are compared. The commercially available cryotransfer system has been attached to the experimental chamber of the nuclear microprobe, after necessary adaptation. Normalization of results was obtained by direct measurement of integrated charge deposited by protons, with proton current measured simultaneously from the insulated sample holder. The temperature of the cold stage during measurements was maintained at 90 - 100 K. A proton beam of

3.0 MeV energy and current kept at ca. 120 pA was focused to a 2 µm x 3 µm spot and scanned over the sample areas. GeoPIXE II software [4] was used for data processing. Quantitative elemental maps were generated using the dynamic analysis method. In addition, PIXE and BS spectra were extracted from the areas of interest defined in relation to anatomy of biological material and features visible from elemental maps. Average concentrations of elements and their minimum detection limits for these areas were obtained using the non-linear least square fit of respective PIXE spectra. The matrix composition and areal density were obtained from the analysis of corresponding BS spectra. Before measurements of frozen-hydrated specimens, the experimental setup was calibrated using synthetic glasses (internal standards). Verification of results was further done by measurements of frozen-hydrated standards made from a 20% gelatine solution with added known concentrations of PbCl2 or KI. Senecio coronatus (Thunb.) Harv. Asteraceae is a widespread South African grassland plant species. Two types of its adaptation on ultramafic sites have been identified: nickel hyperaccumulating and non-hyperaccumulating genotypes. Recent studies [5] showed the occurrence of specialized cellular structures in the inner cortical zone of roots in the Ni-hyperaccumulating genotype of this plant (Figure 108), probably related to hyperaccumulation phenomena. The distribution of elements therein might explain their role. Small root pieces of hyperaccumulating genotype of S. coronatus collected from ultramafic outcrop in Agnes Mine (Mpumalanga Province, South Africa) were cryofixed in liquid propane using the Leica CPC-cryoworkstation.


167

Frozen specimens were next fractured and their newly opened surfaces were polished using cryo-ultramicrotome, and transferred to the microprobe chamber at liquid nitrogen temperature. Measurements of specialized cellular structures were first performed in the frozen-hydrated state. Subsequent analyses of the same areas were performed after freeze-drying the specimens overnight in the NMP chamber.

The same set of elements could be measured in both

cases, at comparable detection limits in the few µg g-1 range (Table 17, Figure 109). The loss of water was evaluated from BS spectra (Figure 110, Table 17). Elemental maps showed good preservation of structure, with single cells well visible in Ca maps (Figure 111). Specialized cells present in the inner cortex demonstrated significant relative Ni depletion in comparison with the adjacent inner cortex and phloem.

Frozen hydrated Freeze dried P 743 + 54 (8.7) 2060 + 72 (9.5) S 1325 + 26 (5) 4815 + 79 (5.2)

Cl 270 + 9 (3.5) 893 + 48 (4.1) K 1749 + 11 (1.8) 7581 + 38 (1.9)

Ca 301 + 8 (1.4) 1296 + 20 (1.5) Mn 4.3 + 0.4 (0.55) 23.8 + 0.7 (0.59) Fe 12.8 + 0.4 (0.44) 48 + 1 (0.5) Co < 0.4 < 1 Ni 164 + 3 (0.56) 753 + 13 (0.76)

Cu 4.7 + 0.3 (0.56) 10.1 + 0.8 (0.83) Zn 10.1 + 0.5 (0.5) 29.9 + 0.9 (0.69) Se 0.7 + 0.3 (0.5) < 0.6 Br < 0.6 1.2 + 0.4 (0.62) Rb 3.7 + 0.5 (0.74) 12 + 1 (1) Sr 5.3 + 0.7 (0.95) 19 + 1(1.2) Au 10.6 + 0.7 (0.8) 14 + 0.8 (1.1)

C7.3 O33H59N0.7S0.15 C31O15H51N2S0.8

Figure 108: Light micrograph of hand-cut fresh root cross-section stained with aniline blue, showing groups of specialized cells.

Figure 109: PIXE spectra showing the same background pattern for frozen-hydrated and freeze dried specimens.

Table 17: Comparison of concentrations and minimum detection limits (99% confidence level) for frozen-hydrated and freeze-dried specimens. Accumulated charge 1 µC. All values in µg g-1. Matrix composition (atomic ratios) is shown in the last row.


168

References 1. J. Szpunar, Anal. Bioanal. Chem. 378 (2004) 54. 2. G. Tylko, J. Mesjasz-Przybylowicz, W.J. Przybylowicz, Microsc. Res. Tech. 70 (2007) 55. 3. G. Tylko, J. Mesjasz-Przybylowicz, W.J. Przybylowicz, Nucl. Instr. and Meth. B 260 (2007) 141;

doi:10.1016/j.nimb.2007.02.017. 4. C.G. Ryan, Int. J. Imaging Syst. Technol. 11 (2000) 219. 5. J. Mesjasz-Przybylowicz, A. Barnabas, W. Przybylowicz, Plant and Soil 293 (2007) 61. doi 10.1007/s11104-

007-9237-1.

3.5.14 Transfer of Selected Metals along Simplified Food Chains of Ultramafic

Ecosystem in Mpumalanga Province, South Africa J. Mesjasz-Przybylowicz1, P. Migula2, W.J. Przybylowicz1, M. Augustyniak2, M. Nakonieczny2, and E. Orlowska1 1 Materials Research Group, iThemba LABS, P.O. Box 722, Somerset West 7129, South Africa 2 Department of Animal Physiology and Ecotoxicology, University of Silesia, Bankowa 9, 40-007 Katowice, Poland Transfer of selected metals was studied along the food chains: soil; Ni-hyperaccumulating plant Berkheya coddii

(Asteraceae); herbivores: chewing beetle Chrysolina pardalina (Chrysomelidae) and Holcolaccus sp. (Curculionidae); a sap feeder Protaphis pseudocardui (Aphididae). Predators were the bug Rhynocoris navii (Reduviidae) and the jumping spider Pachyballus sp. (Salticidae). Metal balances were based on ICP and AAS measurements. Micro-PIXE was used for construction of quantitative elemental maps of the bodies. Herbivores coped well with the excess of Ni and the bioaccumulation factor (BAF) for Ni was the lowest in the aphid, followed by C. pardalina. The BAF of metals in predators was prey-dependent, except for Mn. The average levels of metals in both herbivores and predators were maintained within physiological limits typical for species inhabiting non-ultramafic ecosystems, thus demonstrating adaptive strategies to utilize Ni hyperaccumulating plant species in their food chains. This observation was confirmed by micro-PIXE elemental mapping.

Figure 110: BS spectra illustrating changes of C/O ratio during freeze-drying.

0

2000

4000

6000

8000

0 100 200 300 400

Channel

Cou

nts

Freeze dried Frozen hydrated

O

C

Figure 111: Quantitative micro-PIXE maps of Ca and Ni in special cellular structures of S. coronatus roots for the frozen-hydrated and freeze-dried state. The concentration scale is in µg g-1.


169

Ultramafic rocks and soils create a specific biological resource with distinctive vegetation and associated fauna due to unique chemical composition - rich in Mg, Ni, Fe, low in Ca and other nutrients. Berkheya coddii Roessler (Asteraceae) is one out of five Ni-hyperaccumulating endemic plant species of the serpentine formations in Mpumalanga Province, South Africa, with the highest measured concentration of Ni [1]. Ecophysiology of insects associated with B. coddii and functional effects of excessive Ni have been intensively studied [2, 3, 4]. Ni is reported to be toxic at concentrations above 50 mg kg-1. In this study we searched for any evidence of Ni biomagnification in two simple food chains, with insects or spiders as predators. Elemental maps of selected body parts in herbivores and a predator were constructed with the aim to identify target organs where Ni toxicity played the most significant role.

Ni Zn Cr Cu Pb Mn Fe Soil total

398 (7.4)

39.5 (19)

544 (196)

94 (8.5)

4.1 (0.5)

1328 451

23725 (390)

Soil – ext. DTPA 217 (255)

1.6 (1.0)

0.1 (<0.1)

3.6 (0.2)

1.1 (0.1)

27.9 (5.5)

48.7 (8.1)

B. coddii Leaf 8023

(3810) 67 (35.5)

13 (7.7)

19.1 (16.7)

1.3 (0.8)

180 (93.1)

705 (893)

Stem 9004 (5556)

111.6 (45.6)

26.9 (8.1)

25.7 (22.1)

2.2 (1.0)

91.4 (107)

439 (246)

Tip of stem 10547 (3736)

131.4 (35)

32.7 (18.3)

27 (9.5)

2.3 (0.7)

158.2 (51.2)

719 (140)

C. pardalina 363 (236)

99 (25)

16 (7)

122 (74)

1.1 (0.1)

130 (43)

336 (313)

Holcolaccus sp. 1217 (97)

173 (29)

1.7 (0.9)

99.4 (0.45)

3.0 (0.3)

112 (34)

370 (104)

P. pseudo-cardui 92 4.6

92 (4.6)

8.3 (3.4)

15.2 (3.6)

1.2 (1.4)

110 (71)

919 (480)

Pachyballus sp. 306 (241)

454 (42.2)

24.4 (5.4)

114.5 (38.7)

2.8 (1.1)

125 (52)

1279 (1541)

R. navii 516 (353)

362 (249)

34.8 (22.7)

61.7 (24.2)

3.2 (2.1)

145 (65)

521 (283)

Material was collected from natural stands on ultramafic outcrops at Agnes Mine near Barberton (South Africa). Soil samples were taken below the plants. A primary producer was B. coddii. Leaves, stems and tips of the stem were used for further analysis. Phytophages were: folivorous beetle Chrysolina pardalina (Chrysomelidae); a folivore and tip of stem feeder Holcolaccus sp. (Curculionidae), and a sap-feeding aphid Protaphis pseudocardui (Aphididae). The predators were assassin bugs Rhynocoris navii (Reduviidae), hunting on C. pardalina and a jumping spider Pachyballus sp. (Salticidae). Determination of metal concentrations (Ni, Zn, Cr, Cu, Pb, Fe, Mn) was done using standard ICP-OES and AAS techniques. Metal availability from the soil was measured using DTPA extracts. Moreover, elemental maps of cryofixed and freeze-dried material of whole bodies or dissected organs of insects and a spider were obtained using a nuclear microprobe. Maps were complemented by average elemental concentrations obtained for selected regions of bodies or organs [4].

Table 18. Concentration of metals in consecutive links of the food chain. Means and SD in ppm.


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Ni concentration in above-ground parts of B. coddii exceeded nearly 40 times its bioavailable level. Cr and Zn were also accumulated in relation to the bioavailable pool in the soil but their average levels were significantly lower than total soil levels (Table 18). Mn and Fe were depleted in the plant; their contents were much higher in the soil. Bioavailability of Ca to plants was also highly reduced but in leaves of B. coddii it often exceeded 1% of the dry mass. All studied herbivores easily coped with Ni excess; the BAF was the lowest in the aphid, followed by the respective value in C. pardalina (Table 19). Their Zn body burdens were slightly above the dietary levels. Both folivore chewers accumulated Cu while the sap-feeder maintained similar level as in leaves. The predatory spider was the accumulator of all measured metals except Mn. The BAF for the assassin bug was prey-dependent and differed significantly for Ni, Zn and Pb. Fe contents in this species was about 50% higher than in the prey bodies.

Quantitative micro-PIXE maps identified areas where metals were predominantly accumulated and quantitative relationships between metals within and between these parts of the organism. Positive correlation between Ni contents and Ca, Zn was noted as characteristic feature. Ni concentration in leaves varied considerably, reaching 7,6% of dry mass [1]. Analyses of the fate of metals along the food chains in case of ultramafic ecosystems clearly demonstrate evolutionary traits of both, the plant species that hyperaccumulate Ni as a part of their defence against consumers [5], and herbivores that undergo a route where development of various mechanisms takes place in order to support them in bio-elimination of toxic substances [4]. The beetles C. pardalina and Holcolaccus sp. are perfect Ni bioeliminators with many physiological adaptations. Quantitative maps of metal distribution in the body of preys and predators clearly showed their ability to maintain metal levels within the same physiological ranges as in species from non- metaliferous ecosystems.

Ni Zn Cr Cu Pb Mn Fe B. coddii leaves / Soil 20.2 1.7 0.02 0.2 0.31 0.13 0.03 B. coddii leaves / DTPA soil

36.9 41.8 130 5.3 1.18 6.45 14.4

C. pardalina / B. coddii leaves 0.045 1.47 1.23 6.4 0.84 0.72 0.47 Holcolaccus sp./ B. c. stem tips

0.115 1.32 0.52 3.68 1.3 0.71 0.51

P. pseudocardui./ B. c. leaves

0.011 1.37 0.64 0.81 0.92 0.61 1.3

Pachyballus sp. / P. pseudocardui

3.32 4.59 2.93 7.54 2.33 1.13 1.39

R. navii / Holcolaccus sp. 0.42 2.09 1.42 0.62 1.14 1.16 1.41 R. navii / C. pardalina 1.42 3.65 2.17 0.51 2.9 1.11 1.55

Table 19. Bioaccumulation factors (BAF) for selected metals between consecutive links of the food chain


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References 1. J. Mesjasz-Przybylowicz, M. Nakonieczny, P. Migula, M. Augustyniak, M. Tarnawska, W. Reimold,

C. Koeberl, W. Przybyłowicz and E. Głowacka Acta Biol. Cracoviensia Series Botanica 46 (2004) 75.

2. R.S. Boyd, M.A. Davis, M.A. Wall and K. Balkwill, Insect Science 13 (2006) 85. 3. J. Mesjasz-Przybylowicz, W. Przybylowicz, B. Ostachowicz, M. Augustyniak, M. Nakonieczny and P. Migula

Fresenius Env. Bull. 11 (2002) 78. 4. W.J. Przybylowicz, J. Mesjasz-Przybyłowicz, P. Migula, E. Glowacka, M. Nakonieczny, M. Nucl. Instr. and

Meth. B 210 (2003) 343. 5. M.J. Ihee, R.S. Boyd and M.D. Eubanks, New Phytologist 168 (2005) 331.

3.5.15 Ultrastructural Features of Root Tissues of Ni-hyperaccumulating and Non-

accumulating Genotypes of Senecio Coronatus J. Mesjasz-Przybylowicz1, A.Barnabas1, and W.J. Przybylowicz1

1Materials Research Group, iThemba LABS, P O Box 722, Somerset West 7129, South Africa

In a previous study [1], root cytology at the light microscope level as well as elemental distribution using a nuclear microprobe, were examined in two genotypes of Senecio coronatus growing on ultramafic outcrops. Cytological differences were found in inner cortical cells and exodermis and a higher concentration of Ni was present in root tissues of the hyperaccumulator. The present investigation extends the previous study and focuses on ultrastructural features of root tissues of both genotypes since little is known about the ultrastructural morphology of plants growing on ultramafic soil. Root samples were processed for electron microscopy using standard preparation procedures. For light microscopy, sections of roots were stained with Aniline blue. Distinct groups of inner cortical cells of the Ni-hyperaccumulator (Figure 112d, double arrows) were characterized by the presence of large nuclei and an organelle-rich cytoplasm (Figure 112e). An extensive network of endoplasmic reticulum (ER) cisternae, numerous ribosomes, microbodies with crystalline inclusions, mitochondria, Golgi bodies, membranous vesicles and lipid-like spherical bodies were present (Figures 112d – 112h). Distinct cell groups were not found in the inner cortex of the non-accumulator (Figure 112a, arrows) and cells here had generally smaller nuclei, a thin parietal cytoplasmic layer and few of the organelles present in the hyperaccumulator (Figure 112b). Various cytoplasmic organelles appear to be implicated in the formation of the secondary metabolites reported previously [1]. Significantly larger amounts of secondary metabolites accumulate in the hyperaccumulator compared to the non-accumulator (Figures 112c, 112d). Genesis of these secondary metabolites seems to begin in the spherical lipid-like bodies within the cytoplasm, which are closely associated with the ER (Figure 112g).


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Continual fusion of vesicles, derived from the ER and Golgi bodies, lead to an increase in size of the spherical bodies and their contents (Figure 112h). Microbodies and mitochondria are also closely associated with the developing spherical bodies (Figures 112g, 112h). As the spherical bodies continue to increase in size, they are gradually extruded from the cytoplasm into the vacuoles (Figure 112h) and intercellular air spaces of the inner cortical cells where they coalesce to form larger deposits (Figures 112c, 112f). Exodermal Casparian bands of the non-accumulator were better defined at the ultrastructural level compared to those of the hyperaccumulator giving further support to the earlier finding [1] that the bands may be functionally different from those of the hyperaccumulator and may limit the entry of Ni into roots of the non-accumulator. The present study highlights the value of ultrastructural research in understanding plants growing on ultramafic soil.

Reference 1. J. Mesjasz-Przybylowicz, A. Barnabas, and W. Przybylowicz, Plant Soil 293 (2007) 61.

Figures 112: a) – c) NON-ACCUMULATOR. d) – h): NICKEL HYPERACCUMULATOR ER, endoplasmic reticulum; M, mitochondria;MB, microbody with crystalline inclusion; N, nucleus; PC, thin parietal cytoplasm; R, ribosomes; SB, spherical bodies;SM, secondary metabolites; V, vacuole; Vs, membranous vesicles.

a b c

d e f

g h


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3.5.16 Micro-PIXE Mapping of Elemental Distribute in Roots of a Medicinal Plant,

Agathosma Betulina (Buchu), Colonized by a Yeast, Cryptococcus sp. K.J. Cloete1, W.J. Przybylowicz2, J. Mesjasz-Przybylowicz2, A.J. Valentine3, A. Botha1

1Department of Microbiology, Faculty of Science, University of Stellenbosch, Private Bag X1, MATIELAND, 7602, South Africa 2Materials Research Group, iThemba LABS, P.O. Box 722, Somerset West 7129, South Africa 3Plant Physiology Group, South African Herbal Science and Medicine Institute, Faculty of Science, University of the Western Cape, Private Bag X17, Bellville, 7535, South Africa Buchu (Agathosma betulina, Rutaceae) is a Fynbos plant of enormous medicinal and ethnobotanical value to South Africa [1]. Plantations of A. betulina are obtained by the transplantation of five-month old nursery seedlings to its natural habitat, which is characterized by leached soils with a low nutrient status. Seedling survival is however less than 10% [2]. Since it is known that yeast have a beneficial effect on plant performance [3], it was postulated that inoculation of nursery seedlings with yeast indigenous to the plant’s rhizosphere, would increase plant nutrition and fitness. A. betulina plants inoculated with Cryptococcus laurentii, a yeast indigenous to the plant’s rhizosphere, and un-inoculated controls were grown under low-nutrient conditions and harvested after five months. Root material was immediately cryofixed in liquid propane using a Leica EM CFC Cryoworkstation and freeze-dried in a Leica EM CFD Cryosorption Freeze Dryer. Thin cross sections of the material were subsequently mounted between two layers of formvar, one of which was carbon-coated. Elemental distribution in inoculated and control A. betulina plants was characterized using micro-PIXE spectrometry in combination with Rutherford backscattering spectrometry. Preliminary results indicated that the elemental distribution pattern in roots of colonized plants and controls differed significantly. It was found that a positive correlation existed between phosphorus and iron distribution in plants colonized with the yeast in comparison to the control plants (Figure 113). This indicated that the yeast might have a positive effect on phosphorus and iron nutrition of this plant. References 1. K.J. Cloete, A.J. Valentine, L.M. Blomerus, A. Botha and M.A. Pèrez-Fernández. Nutritional effects of

indigenous arbuscular mycorrhizal associations on the sclerophyllous species Agathosma betulina. Web Ecol. 77 (2007) 77.

2. M. De Ponte Machado. 2003. Is buchu (Agathosma betulina) harvesting sustainable? Effects of current harvesting practices on biomass, reproduction and mortality. Master of Science in Conservation Biology Dissertation, University of Cape Town, S.A.

3. K.A. El-Tarabily and K. Sivasithamparam. Potential of yeasts as biocontrol agents of soil-borne fungal plant pathogens and as plant growth promoters. Mycoscience, 47 (2006 ) 25.

Figure 113: Quantitative elemental PIXE maps of iron and phosphorus distribution in Agathosma betulina root cross sections colonized by Cryptococcus laurentii (A) and control plants (B). Concentrations are presented in wt%.

A B


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3.5.17 Structural Organization of Psoralea pinnata Root nodules using Chemical and

Cryo-fixation/freeze-substitution, using Light Microscopy (LM) and Transmission

Electron Microscopy (TEM) S. Kanu1, M. Jaffer2, J. Mesjasz-Przybylowicz3, and F. D. Dakora1 1Faculty of Science, Tshwane University of Technology, Pretoria 0001, South Africa 2Electron Microscopy Unit, University of Cape Town, Rondebosch 7700, South Africa 3Materials Research Group iThemba LABS, PO Box 722, Somerset West 7129, South Africa A typical member of the tribe Psoraleae, Psoralea pinnata L. (Leguminoseae), is an indigenous legume endemic to the Cape Floristic Region in South Africa and grows largely in acidic soils notoriously devoid of nutrients. The complex interaction between legumes with their associated rhizobia results in the formation of symbiotic root nodules capable of reducing atmospheric nitrogen to ammonia which can be made available in other forms as a source of nitrogen to both the plant and ecosystem. The aim of the work was to study the internal structural organization of the root nodule of P. pinnata. Root nodules of P. pinnata were collected from two contrasting habitats (well drained upland and wetland conditions) in the fynbos vegetation in the Western Cape: Harold Porter Botanical Gardens, Betty’s Bay and Rock View Dam. We report here preliminary observations made on the general internal structure of the round determinate root nodule found in P. pinnata, based on the conventional chemical fixation and cryo-fixation (High-pressure freezing and Plunge freezing)/freeze-substitution techniques, using Light Microscopy (LM) and Transmission Electron Microscopy (TEM). A transverse section of the fresh mature root nodule of P. pinnata under the light microscope shows five zones (Figures 114, 115) as was identified for other legumes by [1, 2]. Our micrographs show that about 2-3 layers of tightly packed convoluted cells (the periderm with lenticels in wetland nodules) surround the outer cortex of the

Figure 114: Free-hand section of a fresh mature Psoralea pinnata root nodule from wetland condition showing tissue components: IC = inner cortex, M = medulla (central infected zone), MC = middle cortex, OC = outer cortex (x 100).

Figure 115: Light micrograph of a transverse section of Psoralea pinnata root nodule from dry upland condition showing tissue components: OC = outer cortex, MC = middle cortex, IC = inner cortex, M = medulla (x 400).


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nodule (Figure 114). The outer cortex is composed of about 3-4 layers of loosely packed cells with intercellular spaces. The middle cortex has several layers of relatively small round cells with or without airspaces between them. There is also present a layer of thick walled scleroid cells (Scleroid layer) with intercellular spaces, that is between the outer and inner cortex (Figure 115). The inner cortex is composed of about 2-4 layers of relatively large elongated cells with thick walls and contains intercellular spaces some of which are occluded. Also present

is a single layer of tightly packed cells without any intercellular air spaces, which marks one end of the inner cortex towards the medulla or central infected zone. Next to this layer of interlocking cells, are present 2-3 layers of uninfected cells with lots of intercellular airspaces (Figure 115). The medulla/central infected zone is made up of infected and uninfected cells and their numbers and volumes were observed to be different in the two types of nodules studied (data not shown). In general, the cells of the nodule tissue that were cryo-fixed and dehydrated by freeze-substitution were better preserved than cells that had been chemically fixed (Figures 116, 117), which not only confirms but also highlights the advantages of cryo-fixation techniques for structural studies of cells and tissues. Our micrographs of plunge and high-pressure frozen samples largely confirm what has been reported by others [3, 4], that all the membrane-bound organelles were turgid in appearance and easily identifiable and typically, the membrane contours were smooth and not wavy or rippled (Figure 116b). Also the peribacteroidal spaces within the symbiosomes inside the infected cells are quite reduced in cryo-fixed tissues compared to those chemically fixed (Figure 117a, b & c). However, possible artifacts like holes in the cytosol were identified especially with the plunge frozen samples, which may be due to the “airspace collapse” theory proposed by [3]. Interestingly, preliminary observations show that there are structural differences, especially in cell geometry in the inner cortex, between root nodules growing in waterlogged soils and well drained uplands as has been reported by [5] (data not shown).

(A) (B) (C) Figure 117: High magnification of symbiosomes in the medulla of Psoralea pinnata root nodules from wetland conditions: (A) cryo-fixed (Plunge frozen) (x5000), (B) cryo-fixed (High-pressure frozen) (x10, 000) and (C) chemically fixed (x4000). Note the differences in the peribacteroid spaces (arrow) between the peribacteroid membrane and bacteroid.

Figure 116: Light micrographs of the medulla of a transverse section of Psoralea pinnata root nodules from upland (A & B) and wetland (C) conditions: (A) cryo-fixed (Plunge freezing)(x 400), (B) chemically fixed (x 400) and (C) cryo-fixed (High-pressure frozen) (x 400). Note the smoothness and turgidity of the cell membranes in the cryo-fixed samples


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Future work will include micro-PIXE (Particle Induced X-ray Emission) analysis for nutrient content and localization in root nodules of P. pinnata plants growing in those poor nutrient environment, of course it will be complimented by BS spectrometry (Proton Backscattering) for matrix assessment using the nuclear microprobe at the Materials Research Group, iThemba LABS.

References 1. J.M. Sutherland and J.I. Sprent, Planta 161(1984) 193. 2. R. Parsons and D.A. Day, Plant, Cell and Environment 13 (1990) 501.

3. S. Graig and L.A. Staehelia, European Journal of Cell Biology 46 (1988) 80.

4. D. Studer, H. Hennecke and M. Muller, Planta 188 (1992) 155. 5. F.D. Dakora and C.A. Atkins, Planta 182 (1990a) 572.

3.5.18 Distribution of Metals in the leaves of Metallophytes Helichrysum candolleanum

(HC), Blepharis diversispinia (BD), Blepharis aspera (BA) from Mineralized sites in

Botswana P. Koosaletse-Mswela1, J. Mesjasz-Przybylowicz2, A. Barnabas2, W. Przybylowicz2, N. Torto3, O. Totolo1, G.Wibetoe4 1Department of Environmental Science, P/Bag UB 00704, Gaborone, Botswana

2iThemba LABS, PO Box 722, Somerset West 7129, South Africa 2Department of Chemistry, P/Bag UB 00704 Gaborone, Botswana 4Department of Chemistry, University of Oslo, Oslo, Norway

According to Baker [1], plants that accumulate metals in their roots, leaves, or stem can be classified into three categories, depending on the concentration of the metals in the soil; namely excluder, indicator and accumulator. In most studies conducted to establish the classification, only methods of analysis such as AAS and ICP-AES/OES/MS that introduce a homogenized solid or liquid sample, have been employed. For several years there have been efforts in identifying plants that tolerate high Cu and Ni content in the North-East of Botswana [2]. Our group employed spectrometric techniques for multi-elemental determination in leaves, stems and roots of plants growing in mineralized zones. Accumulation patterns of Cu and Ni were investigated in Helichrysum candolleanum (HC) and Blepharis divisispina (BD) by analyzing the roots, stem, leaves and flowers of these plants using electrothermal atomic absorption spectrometry (ETAAS). The plant HC was found to be a potential Cu hyperaccumulator and Ni indicator [3]. The information obtained after analysis of plant components only reflects the concentration of the homogenized sample without necessarily indicating the exact location of the metals in the plant sample. Therefore further studies are conducted using micro-PIXE and proton backscattering spectrometry (BS) to find the distribution of metals in plant leaves to further understand the classification of plants as accumulators.


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Whole Helichrysum candolleanum (HC), Blepharis diversispinia (BD), Blepharis aspera (BA) samples were collected from an active Cu-Ni mine in Botswana. At iThemba LABS they were prepared for elemental microanalysis using cryotechniques, and parallel thin sections embedded in resin for microscopic examinations. The distribution and concentration of Cu, Ni and other elements in leaf tissues was obtained using a nuclear microprobe at the Materials Research Group. Elemental concentrations were obtained using GeoPIXE II software and reported in µg/g dry weight. The first results show that Ni in BA and HC is highly concentrated in the epidermis but also in vascular bundle and mid-vein, one of the most metabolically active areas. This behaviour is surprising since toxic levels of metals are always kept away from the metabolically active regions of plants. Another interesting observation is that Mn in the leaves of Blepharis aspera seems to be compartmentalized in specific regions of the mid-rib. Leaves of all three plants under investigation show an inverse relationship between Ca and K. References 1. A.J.M. Baker, Journal of Plant Nutrition Vol. 3 (1981) 643. 2. D.T. Takuwa, G. Sawula, G. Wibetoe and W. Lund, J. Anal. At. Spectrom. 12 (1997) 849. 3. B.B.N. Nkoane, G.M. Sawula, G. Wibetoe and W. Lund, J. Geochem. Explor. 86 (2005) 130.

Figure 118: Distribution of Cu and Ni in leaves of Blepharis aspera


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3.5.19 Digestive Enzymes and Metal Distribution in the Gut of Grasshopper Stenoscepa

sp. associated with Ni Hyperaccumulators M. Augustyniak1 , K. Michalczyk1, W. Przybylowicz2 , A. Babczynska1, M. Tarnawska1, P. Migula1, and J.Mesjasz-Przybylowicz2

1Department of Animal Physiology and Ecotoxicology, University of Silesia, Katowice, Poland 2Materials Research Group, iThemba LABS, PO Box 722, Somerset West 7129, South Africa Stenoscepa sp. (Orthoptera), South African grasshopper lives on Ni-hyperaccumulating plants (e.g. Berkheya coddii). Our previous observations proved that their proper development and growing process depend on nickel in their food. This phenomenon made us to analyze the activity of digestive enzymes (photometrical methods), the distribution of nickel and other metals (micro-PIXE assay), and nickel concentration (AAS method) in the gut of II nd-instar larvae and adult individuals of Stenoscepa sp. We found very high amylase activity, especially in larvae (95 µmol maltose/min/mg protein). Among the disaccharidases, high saccharase, maltase and cellobiase activity, especially in adult males, was measured, as opposed to the activity of lactase and trehalase that was low. Total proteolytic activity oscillated around 100 JA/min/mg protein/ml and did not differ between developmental stages, although tripsine activity was higher in larvae than in adults. The analysis of Ni concentration in Stenoscepa sp. larvae performed by the micro-PIXE method showed the highest Ni level in the gut (in the peritrophic membrane areas and in the pyloric valves), over 1000 µg/g, while in females the value was lower (4251 µg/g). Nickel concentration in gonads, body walls and brains was about ten times lower than in the gut, and in faeces it reached 11 280 µg/g. Our results show that the grasshoppers feeding on nickel hyperaccumulators excrete toxic metal. This is probably connected with ineffective food assimilation, which was suggested by the pattern of digestive enzymes activity, revealed in our study, and increased food intake. This question still needs investigation.

3.5.20 Strategies of Ni-elimination in Epilachna cf. Nylanderi (coccinellidae) Feeder of

South African Ni-hyperaccumator Berkheya coddii (Asteraceae)

P. Migula1, W.J. Przybyłowicz2, J. Mesjasz-Przybyłowicz2, M. Rost-Roszkowska1, M. Augustyniak1, J. Klag1, E. Głowacka1, and M. Tarnawska1 1Faculty of Biology and Environment Protection, University of Silesia, Katowice, Poland 2Materials Research Group, iThemba LABS, Somerset West, South Africa Plants that accumulate metals may use them in protective mechanisms against their consumers. However, the case of B. coddii demonstrated that despite its high Ni content some insect species are well adapted to exploit it as a good dietary resource. Such species have to prevent, decrease or repair effects of metals that have entered the body. Among physiological strategies this can be intensified metal excretion, their binding to metallothioneins or a sequestration in intracellular granular structures. In former studies we successfully applied micro-PIXE in investigating the distribution of various elements in different organs of a chrysomelid beetle Chrysolina pardalina, and to prove our hypothesis that Ni might replace Zn in the tubular space, bound to sulphur- and nitrogen-bearing ligands in the Malpighian tubules. We recently found another beetle species, Epilachna cf nylanderi, known hitherto from only one site in ultramafic ecosystems of Mpumalanga, South Africa. This species can fully develop on B. coddii, B. zeyherii or Senecio coronatus (other Ni-hyperaccumulators), despite its systematic position,


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which is the same as predatory lady birds (Coccinellidae). Insects must balance between two properties of their ionic forms, an essential nutrient and a potent toxin. In this study we checked whether Ni transfer from plant to E. nylanderi may influence elemental distributions within their body by combining micro-PIXE quantitative elemental mapping in organs of the same organism responsible for metal transfer bioaccumulation or bioelimination (parts of the digestive tract and Malpighian tubules) with TEM morphological studies. Such an approach made possible a comparison of adaptive mechanisms against Ni used by this species with the mechanisms used by C. pardalina. Functional comparisons and quantification of data extracted from selected micro-areas in analysed organs demonstrated a similarity of detoxification mechanisms used against metals through spheric granules, which in E. nylanderi are in the mid-intestine, while in C. pardalina are mainly formed in Malpighian tubules. A series of changes were identified in the midgut of E. nylanderi such as formation of extracellular vacuoles between degenerating and newly formed epithelial cells, which possibly contain excess of metals. Single regenerative cells in each regenerative nest do not differentiate and will function as the midgut stem cells. Regenerative cells proliferation and their differentiation proceed accidentally in all regions of the midgut epithelium. The role of Malpighian tubule in this species seems to be less important than in the chrysomelid beetle. True maps of Ni and Zn in Malpighian tubules showed their positive correlation while quantitative relations between K+ and Clˉ indicated higher osmotic pressure allowing reabsorption of water which can be used for Ni transportation back to the lumen of the gut. 3.5.21 Glutathione Level, Metal Mapping and Ultrastructural Changes in the

Hepatopancreas of the Isopod Porcellio scaber (Oniscidea) after Nickel Exposure

M. Tarnawska1, P. Migula1, W. Przybyłowicz2, J. Mesjasz-Przybyłowicz2, and M. Augustyniak1 1Department of Animal Physiology and Ecotoxicology, University of Silesia, Katowice, Poland 2Materials Research Group, iThemba LABS, Somerset West, South Africa Metal bioaccumulation depends on detoxifying mechanisms, which in isopods include lysosome-derived granules documented for Pb, Cd and Cu or binding to short peptide metal chelators, containing reactive sulphydryl groups, such as glutathione. Ni burden, glutathione levels and metal distribution in the hepatopancreas of Porcellio scaber were compared on the basis of the set-up of four experimental groups of woodlice kept for 24 weeks on a Ni enriched diet (dried senescent maple leaves) with the resulting concentrations of Ni0=0.1; Ni1=8.0; Ni2=75; Ni3=270 µg g-1. Correlations between GSH contents and Ni concentration (AAS measurements) in the hepatopancreas were calculated. The micro-PIXE method was applied for mapping potent differences of elemental distribution caused by dietary Ni toxicity. Transmission electron microscopy (TEM) was used to identify ultrastructural changes in the hepatopancreatic cells variously affected by Ni. The glutathione concentrations appeared to be Ni-dependent. A significant correlation between Ni concentration and GSH level was observed in the hepatopancreas of the isopods from different groups (r = 0.37, p < 0.05). Elemental mapping showed a dose-related nickel bioaccumulation in the hepatopancreas at concentrations from 3 µg/g (control animals) to nearly 840 µg/g (Ni3 group). Generally, the Ni distribution pattern of the hepatopancreatic cells demonstrates that they are formed as small aggregations. A combined analysis of elemental maps and electronograms taken from similarly treated woodlice showed that most of the Ni observed as concentrated regions in selected micro-areas of PIXE maps correspond well with the granular structures observed in TEM electronograms.


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3.5.22 Ni Mapping in Berkheya coddii by Micro-PIXE and NEXAFS W.J. Przybylowicz1, T. Tyliszczak2, A. Barnabas1 and J. Mesjasz-Przybylowicz1 1Materials Research Group, iThemba LABS, PO Box 722, Somerset West 7129, South Africa 2Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA Near Edge X-ray Absorption Spectroscopy (NEXAFS) and the Scanning Transmission X-ray Microscopy (STXM), performed at the 11.0.2 line of the Advanced Light Source of Lawrence Berkeley National Laboratory, have been used for quantitative elemental mapping in leaves of Berkheya coddii, a Ni-hyperaccumulating plant from South Africa. Specimens were prepared using cryofixation in a high-pressure freezer and freeze-substitution with diethyl ether, followed by sectioning with an ultramicrotome. Spectra and maps were processed using AXIS2000 software.

Comparative studies of the same specimens were performed with micro-PIXE and proton backscattering spectrometry (BS) using the nuclear microprobe at the Materials Research Group, iThemba LABS. Quantitative maps of Ni (Figure 119) and other elements as well as concentrations of elements from selected areas within maps were obtained using GeoPIXE II software. The thickness of specimens and composition of major elements obtained from the BS method were used for matrix corrections in PIXE maps and spectra. STXM offers excellent lateral resolution of the order of 30 nm. The available energy range is 80 – 2100 eV with E/ΔE > 7500. Ni mapping was performed using the Ni L3 absorption edge (Figure 120). Predictably, the requirement of X-ray transmission through the specimen introduces strict limits on specimen thickness. This is a serious practical limitation in multi-elemental analysis where various X-ray energies must be used.

Micro-PIXE has inferior lateral resolution (3 µm x 3 µm) but is much more flexible as far as specimen thickness is

concerned. Multi-elemental analysis and easy quantification make it a method of choice for study of elemental distributions in plants. However, STXM is needed for studies of the details of elemental distribution at intracellular level, and for chemical mapping.

0

7

14

Figure. 119: Micro-PIXE quantitative image of Ni distribution

Figure 120 : NEXAFS quantitative image of Ni distribution

Νι µg/cm2


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3.5.23 Isolation and Characterization of Lotus japonicus genes involved in Zinc and Iron

Homeostasis

C. Cvitanich2, W. J. Przybyłowicz1, E. Orłowska1,2, J. Mesjasz-Przybyłowicz1, J. Stougaard2, and E. Ø. Jensen2 1Materials Research Group, iThemba LABS, Somerset West, South Africa 2Laboratory of Gene Expression, Institute of Molecular Biology, University of Aarhus, Denmark

The goal of the project is to find ways to improve the nutritional value of legumes by identifying genes and proteins important for iron and zinc regulation in the model legume Lotus japonicus. Iron deficiency is the most widespread nutritional disorder in the world (www.who.int). Anaemia affects 30% of the world’s population leading to premature death, ill-health, and lost earnings. This condition is in many cases caused by iron deficiency and is frequently exacerbated by infectious diseases. Plant products are major sources of mineral nutrients in human diets, in particular in resource-poor populations where anaemia is more prevalent. Legumes are important staples in the developing world, they provide calories as well as protein, minerals, and vitamins to its consumers. They are frequently grown in soil with limited nutrient availability in resource-poor areas, reaching the most affected population. Legume seeds contain relatively high amounts of micronutrients but there is a significant variation even within legumes of the same species. Based on this variation, a biofortification project to improve the concentration of iron in common beans, Phaseolus vulgaris, is being sponsored by HarvestPlus. It has been shown that the iron concentration and distribution varies among bean genotypes and the genotypic variation for common bean micronutrient content and for iron bioavailability have been studied [1,2]. Plants use finely tuned mechanisms to regulate levels of iron and zinc in different tissues. Several genes involved in iron and zinc homeostasis have been described in yeast, and great progress in the knowledge about plant genes regulating these processes has been achieved during the last decade (Reviewed by [3, 4, 5]). In spite of the great advances on the information about genes that regulate iron and zinc metabolism in plants, there are still several open questions. If we want to apply the concept of iron biofortification for improving human nutrition, our knowledge about the mechanisms behind iron loading and storage in seeds needs to be significantly improved and this project has been a step in the right direction.

Studies of micronutrient localization in seeds: Because we wish to extrapolate our results from a model legume to crop legumes, it was important to analyze whether the distribution of nutritional important elements in their seeds was similar. The literature about iron distribution within seeds is very limited. It has been shown that soybean seed coats accounts for 7% of the seed dry weight and contain five times higher concentrations of iron than the embryo [6]. Recently the distribution of iron and phytate in different tissues of eight Phaseolus vulgaris (common bean) accessions has been investigated [1]. It was shown that the iron distribution within the seeds was significantly different among genotypes. Seed coats contained between 4 and 26% of the total iron depending on the analyzed accession, while cotyledons contained the majority of the iron and their content varied between 71 and 94% of the total iron.

http://www.who.int)


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The distribution of nutritional important elements in untreated dry seeds of the Lotus japonicus and L. filicaulis, P. vulgaris, Phaseolus coccineus, and Glycine max (soybean) has been studied by the nuclear microprobe. Micro-PIXE and proton backscattering were simultaneously used. Elemental maps were obtained by the Dynamic Analysis method. Information from maps was complemented by average concentrations of elements from areas selected within seeds. Additionally the localization of iron has been studied using biochemical stains [7], tissue sectioning, and microscopy. Our results show that there are significant differences in the distribution of iron between the analyzed legumes. We observed accumulation of iron in the endosperm layer of L. japonicus GIFU, while provascular tissue of L. filicaulis was rich in iron. These results indicate that iron is transported into the embryo of the iron rich seeds of L. filicaulis, while this transport is less efficient in the seeds of L. japonicus GIFU which contain less iron. Studies of P. vulgaris and P. coccineus showed a distinct pattern of the distribution of iron in the cotyledonary parts of the embryo. These patterns were shown to be formed by iron rich cells that surround the provascular tissue of cotyledons. These cells seem to be important for iron storage in the embryo. In comparison, a large proportion of the iron stored in G. max seeds accumulates in the cuticular region of their seed coats. ICP-AES analysis show that between 25 and 45% of the total iron in soybean seeds can be found in the seed coats that made up approximately 7% of the total seed weight. As previously described [1] we found significant differences in the total iron content and distribution in seeds of different P. vulgaris genotypes. In all the analyzed seeds, the radicles were rich in both iron and zinc, but because radicles constituted less than 3% of the total seed dry weight, their contribution to the total nutritional value of the legume is relatively low. In all the analyzed bean accessions the cotyledons contributed with 71 to 98% of the total iron content in the bean seeds. References 1. M. Ariza-Nieto, M.W. Blair, R. M. Welch, and R.P. Glahn, Journal of Agricultural and Food Chemistry (2007)

7950.

2. R.M. Welch, W.A. House, S. Beebe, and Z. Cheng, Journal of Agricultural and Food Chemistry 48 (2000)

3576.

3. J.-F Briat, Advances in Botanical Research 46 (2008) 137. 4. E.L. Connolly and M.L. Guerinot, Genome Biology 3(8) ( 2002) reviews 1024.1-1024.3. 5. N. Grotz and M.L. Guerinot, Biochimica et Biophysica Acta 1763 (2006) 595. 6. L.O. Tiffin and R.L. Chaney, Plant Physiology 52 (1973) 393. 7. E.Y. Choi, R. Graham and J. Stangoulis, Journal of Food Composition and Analysis 20 (2007) 496.


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3.5.24 Molecular Biomarkers of Stress in The Terrestrial Pulmonates Cepea Nemoralis

and Slug Arion luisitanicus Exposed Jointly or Separately to Cadmium, Nickel and

Pesticide

D. Drożdż-Gaj1, P. Migula 1, W.J. Przybylowicz2, and J. Mesjasz-Przybyłowicz2

1Department of Animal Physiology and Ecotoxicology, University of Silesia, Katowice, Poland 2Materials Research Group, iThemba LABS, Somerset West, South Africa Stress biomarkers (metalothioneins, hsp70, ubiquitins and enzyme activities – mannitol oxidase, carboxylesterase, acetylcholinesterase and glutathione-S-transferase) were compared in the digestive glands of two common terrestrial pulmonate species, a snail and a slug, from a metal polluted and a reference site. The same biomarkers were assayed after laboratory exposure to dietary Cd and/or Ni in two concentrations and a limacide (carbamate - methiocarb). Elemental mapping and metal concentrations in the midgut glands analyzed with particle-induced X-ray emission techniques (micro-PIXE) enabled the analysis of quantitative relationships between metals and biomarkers. In both species GST and MT cooperated in diminishing toxic effects of metals. Detoxifying systems were more efficient in the slug but joint action of used stressors exceeded compensatory capabilities in both species. Hsp70 was upregulated at lower concentrations of stressors but downregulated with its increase. MT expression was positively correlated with Cd or Ni levels. An increase of H2O2-generating mannitol oxidase activity was parallel to Hsp70 induction. D-mannose produced in C. nemoralis under metals stress might be an additional energy resource supporting detoxication processes.

3.5.25 The Characterisation of Pt-Al Coatings M. Topić1, C. Freemantle2, N. Abbas2, T.P. Ntsoane1, CA Pineda-Vargas1, C.I. Lang2 1 iThemba LABS (MRG), PO Box 722, Somerset West 7129, South Africa 2 Centre for Materials Engineering, University of Cape Town, South Africa The phase formation sequence of intermetallic phases in Pt-Al coatings has been investigated. Platinum coatings

of 0.5 µm and 1.0 µm thicknesses have been deposited onto 1 mm thick aluminium substrates using electron

beam physical vapour deposition. The quality of the subsequent Pt-Al coatings was found to be sensitive to the washing techniques employed before deposition. Washing methods that remove or minimise the oxide layer of the aluminium substrate have proven to be most effective in producing better quality substrate-coating adhesion. Intermetallic phase formation has been investigated for annealing temperatures of 400°C and 500°C and annealing times of 1, 2 and 4 hours as well as a 24 hour annealing process. X-ray diffraction studies have been used to determine the phase formation sequence (and intermetallic phases present) for the various annealing treatments and the coating thicknesses.

Proton induced X-ray emission has been used to identify the elemental composition of 0.5 µm platinum coatings

on aluminium substrates exposed to an annealing temperature of 500°C for two hours. The same technique detected the active diffusion of iron from the substrate in response to prolonged annealing.


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Scanning electron microscopy was used to obtain photomicrographs of the surfaces of the Pt-Al coatings in the as-deposited state as well as in response to the 1, 2 and 4 hour heat treatment practices. Pt-Al coatings have been determined to exhibit surface quality degradation and substrate adhesion with increasing time at temperature when annealed. This fact has important and negative ramifications for the potential uses of such coatings in high temperature applications unless this behaviour can be compensated for. Coating thickness differences do not appear to significantly alter coating degradation with increased time at temperature during annealing. The formation sequence of the intermetallic phases in aluminium rich environments have been successfully compared with the phases predicted by the effective heat of formation model.

3.5.26 Mechanical Properties of Pt-Al Coatings M. Topić1, N. Abbas2, R Bucher1, CA Pineda-Vargas1, C.I. Lang2 1 iThemba LABS (MRG), PO Box 722, Somerset West 7129, South Africa 2 Centre for Materials Engineering, University of Cape Town, PO Box 5500 Rondebosch, South Africa This study is an initiative undertaken by the University of Cape Town and iThemba LABS in order to investigate the mechanical properties of the Pt-Al coating system (aluminium substrate coated with platinum). The motivation of this research was a previous study of the mechanical properties of the Al-Pt (platinum substrate with aluminium coating) by iThemba LABS. This system offers a promising field of research since mechanical properties such as hardness can be altered by subjecting the coating/substrate system to elevated heat treatments. The Pt-Al project therefore serves as a comparative study to the Al-Pt system, and could lead to a conclusion whether the mechanical properties of the Al substrate will improve after coating with platinum and subsequent heat treatments.

The samples are firstly prepared by machining to the correct dimensions for the various mechanical testing and microscopy analysis. The samples were polished to a mirror shine and were then coated with platinum using the Electron beam vapour deposition technique. Heat treatments were then performed on the samples in order to form intermetallic compounds. Microtensile testing, Atomic Force microscopy (AFM), Proton induced X-ray emission spectroscopy (PIXE), scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were the techniques then used in order to analyse the intermetallic phase formation and the mechanical properties of the coating and the coating/substrate system. Microtensile testing showed that the coating had no significant influence on the overall mechanical properties of the aluminium substrate, since the coating (with intermetallic compounds after heat treatments) was extremely brittle and “flaky” with poor adhesion to the aluminium substrate. The poor adhesion was attributed to the fact that the brittle phases Al6Pt, Al2Pt, and Pt2Al were formed after heat treatments, according to XRD, as well as differing


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thermal expansion coefficients of the intermetallic compounds and the aluminum substrate. Increasing the heating time of the samples also resulted in an increase of the brittleness of the coating, since a delamination (“rumpling”), then “thickened skin” with cracks and eventually flaky, brittle behaviour was observed with an increase in heating time. The mechanical properties of the Al-Pt system were far superior to the Pt-Al system due to its increase in hardness after heat treatments as a result of more intermetallic compounds which formed during these heat treatments. Further studies of the Al-Pt system should thus be undertaken in order to perform a full phase analysis of the intermetallic compounds which are formed in order to understand how these various phases contribute to the increased strength of the system.

3.5.27 Neutron Strain Investigations of Laser Bent Samples

A.M. Venter1, M.W. van der Watt1, R.C. Wimpory2, R. Schneider2, P.J. McGrath3, M. Topic4

1Research and Development Division, Necsa Ltd, PO Box 582 Pretoria 0001, South Africa 2 Hahn-Meitner-Institute, Berlin, Germany 3 Mechanical and Industrial Engineering, UNISA, South Africa 4 Materials Research Group, iThemba LABS, PO Box 722 Somerset West 7129, South Africa Forming of metal plates with high-energy laser beams presents a non-contact method for shaping into components. Initial application was in the mid-1980s in the shipbuilding industry for the controlled shaping of ship hulls. Today with improved processing and understanding of the mechanisms of laser forming, virtually any shape can be produced with applications extending to the aircraft, motor and materials industries [1]. The major advantages lie in that any sheet metal material up to 10 mm in thickness, as well as tubes, can be bent without hard tooling or application of external forces. By exploiting the combined effect of incremental bends axially, bend angles in excess of 90° can be achieved. The aim of this study is the systematic elucidation of the residual stress states resulting from the repeated application of a laser beam along the same line across the plate width. This is done through non destructive 3D strain mapping straddling the laser path, and as a function of depth below the laser path. The prevailing strains were measured without any sectioning. This is an extension of XRD and synchrotron studies on slices sectioned from the bulk material to overcome the limited penetration depths of these techniques into steel [2,3]. Specific attention has also been paid to determine the absolute residual strain values in the neutron diffraction study by using d0 reference cubes. Neutron diffraction strain measurements have been performed on the E3 instrument at HMI using the (211) Bragg reflection observed at scattering angles of ~72° with a neutron wavelength of 1.37 Å. A gauge volume of 2x2x2 mm3 was employed. The strain components, longitudinal (parallel to the laser path), transverse (in-plate normal to the laser path) and normal (perpendicular to plate surface, i.e. parallel to the laser direction) were measured in the centre of the sample width, along lines straddling the laser path, at depths of 1.5, 2.75, 4, 5.25


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and 6.5 mm. Guided by the results from the microstructural analysis and the neutron gauge volume employed, representative d0 cubes were EDM wire cut from the edge of each sample using a 0.1 mm diameter wire to be representative of the material microstructure at different distances from the laser path as well as at different depths. Material loss was limited to within 0.2 mm to provide cubes with approximate sides slightly less than 2 mm. Each cube in the representative d0 ribbon was measured individually (approached as a complex geometrical shape with the centre of each cube aligned to within 0.1 mm within the gauge volume) fully bathed within the neutron probe volume. The cube ribbons represent the region from the laser path centre line (0 mm) to 30 mm from the laser path (16 cubes) with 4 cubes through the plate thickness (centerlines 1, 3, 5 and 7 mm). With the cubes being smaller than the HAZs the influence of chemical changes on the lattice-plane spacings could be verified. An average d-value was determined independently for each strain component by retaining their orientations relative to the bulk samples. Residual strains from samples LS1 and LS3 are summarised in Figures 121 and 122. The graphs show the comparative trends for the individual strain components as function of depth below the sample surface. Also shown are the residual strains measured in the representative d0 cubes for each bulk sample.

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Figure 121: Residual strains in mild steel plate LS1 from the application of one laser pass across the sample width. Curve sets (a) depict the trends for the individual strain components (from left to right L: longitudinal; N: normal; T: transverse) in the bulk sample as function of depth through the sample thickness: 1.5 mm; 2.75 mm; Δ 4 mm; ◊ 5.25 mm; 6.5 mm. Curve sets (b) depict the residual strains in the d0 cubes for the individual strain components L, N, T (moving from the top to the bottom) at depths (cube centres) 1 mm; 3 mm; Δ 5 mm; ◊ 7 mm.

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Figure 122: Residual strains in mild steel plate LS3 from the application of three laser passes across the sample width. Curve sets (a) depict the trends for the individual strain components (from left to right L: longitudinal; N: normal; T: transverse) in the bulk sample as function of depth through the sample thickness: 1.5 mm; 2.75 mm; Δ 4 mm; ◊ 5.25 mm; 6.5 mm. Curve sets (b) depict the residual strains in the d0 cubes for the individual strain components L, N, T (moving from the top to the bottom) at depths (cube centres) 1 mm; 3 mm; Δ 5 mm; ◊ 7 mm.


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The transverse and normal components of strain measured by neutron diffraction qualitatively have similar trends to the synchrotron results performed on a 3 mm thick transverse slice cut from LS3 [3]. Quantitatively though the values are at least 50% larger in the neutron study indicating that strain relaxation had taken place. This observation is reinforced by the d0 values of the neutron study. The neutron study shows the longitudinal component to be dominant. Measurement of the longitudinal strains was not performed in the synchrotron study due to its relaxation.

The first laser pass induces extensive residual stresses. The longitudinal component is tensile below the laser path with a ”saturation” type dependence extending over at least 60% of the laser beam spot size. The width is similar to the width of the HAZ observed in the microstructural analysis. A symmetrical residual stress field is induced around the laser path that decreases with depth as well as with increased number of laser passes. The normal stresses are compressive below the laser path. Cubes EDM wire cut to sizes similar to the gauge volume employed have no observable residual strains therefore presenting accurate strain-free references for studies of laser treated samples where no melting is induced.

References: 1. M. Geiger, F. Vollertsen, CIRP Ananlysis 42 (1993) 304.

2. M. Topic, R. Bucher, W. Vorster, S.Y. Zhang, P. McGrath, A.M. Korsunsky, Materials Science Forum,

Vols.524-525 (2006) 299. 3. M. Topic, P. McGrath, W.J. Vorster, S.Y. Zhang, R. Bucher, A.M. Venter, A.M. Korsunsky, J. Strain Analysis

IMechE 42 (2007) 497.

Figure 123: 2D contour mapping of the longitudinal residual stresses in samples LS1 (top), LS2 (middle), LS3 (bottom). Positions 0 are coincident with the laser pass location.


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3.5.28 The Effect of e-Beam Deposition and Annealing on Coating Morphology, Phase

Formation and Residual Stress of Pt-Al Coating Systems

Ch. Genzel1, M. Klaus1, C. I. Lang2, M. Topić3 1Hahn-Meitner-Institute Berlin GmbH c/o BESSY II, Germany. 2 Mechanical Engineering Department, University of Cape Town, South Africa. 3 iThemba LABS (Materials Research Group), South Africa The residual elastic stress in the samples used in this study was determined using sin2ψ-method. One of the most important advantages of this method is its numerical stability and insensitivity to experimental uncertainties. So the exact knowledge of the strain-free lattice spacing d0(hkl), which is often very difficult to obtain, is only of minor importance in this case, because the stress evaluation is based on a relative comparison of lattice parameters.

Since the sin²ψ-method assumes a uniform biaxial residual stress state within the information depth τ of the

X- rays it gives only an average value for the in-plane stress component σφ in the respective azimuth direction ϕ. The experimental data obtained by means of this measuring technique can also be used to get more detailed information on the stress depth distribution. For this purpose, use is made of the exponential attenuation of the X-rays within the material, which acts as a weighting factor. Therefore, X-ray diffraction always yields the Laplace transform of the actual depth profile of any physical quantity (in the present case the lattice strains and stresses)

with respect to 1/τ:

dze

dze),(),( D

0

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0

∫

∫−

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=

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ετε

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∫

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−

=

Dz

ij

ij

ez τστσ (1)

where D stands for the sample thickness, which can be replaced by infinity in the case of compact (bulk)

specimens. If the in-plane residual stress state is of rotational symmetry, i. e. σ11=σ22= σII then σII takes a very simple form and can be solved directly with respect to the unknown stress. Regarding the depth dependence of the residual stress state one obtains:

)(2sin)(

21

),()(

12

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||

hklshkls

hkl

+=

ψ

τετσ ψ (2)

This equation is of ‘universal’ nature and all experimental data, independently of used radiation and reflections

can be plotted versus the corresponding penetration depth, τ, into one curve. In order to get an idea of the actual

stress depth profile in the real or z-space, σII(z), the experimentally obtained Laplace stress distribution σII(τ) given by eq.(5) is usually fitted by simple polynomial or exponential functions, which can be easily transformed into the Laplace space by means of eq.(1).


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The X-ray analyses have been performed in two steps: (a) identification of phases and (b) determination of

residual stresses in the Pt-Al system before and after heat treatment. In the first step (a), diffractograms for ψ=0°

(scattering vector parallel to the surface normal) and for ψ=70° (inclination angle between scattering vector and

surface normal) were recorded within a wide 2θ range. However, in the second step (b), which considers the residual stress determination, our attention has been placed onto both analysis of the in-plane stress as well as on the in-plane residual stress distribution within near-surface region of the substrate. The phase analysis results

of as-deposited sample show clearly separated diffraction lines for Pt and Al at both inclination angles ψ=0° and

ψ=70°. In comparison to the X-ray diffraction pattern of the heat treated Pt-Al sample, the diffraction lines strongly overlap and consequently only two phases, Al6Pt and AlPt3, have been identified. For the residual stress analysis of as-deposited sample, (220) reflections for Pt and Al were used. It is clearly visible that there is a significant peak shift for the Pt-220 reflection and therefore it has been used for the residual stress evaluation. On the other hand, only a small shift is observed for the Al-220 reflection. The lattice spacing

d (220) versus sin2ψ plots for Pt substrate and Al coating in the as-deposited system are shown in Figure 124.

The diagrams revealed that the residual stress states are completely different in substrate and coating. A slightly

negative slope is observed up to approximately sin2ψ=0.7 for the substrate (upper graph on Figure 124).

At high ψ-tilt angles, the d (220)-sin2ψ shows a strongly non-linear behaviour in the form of a concave curvature, which indicates the occurrence of a steep stress gradient in the near-surface region. The average in-plain

residual stress (σII) which is calculated from the slope of the regression line (despite the curvature) is of the order of -150 MPa, i.e. there are compressive stresses in the near-surface substrate region. The presence of high compressive stresses is expected since the Pt substrate was formed by a cold rolling process consisting of more

Figure 124: d vs sin2 ψ graphs for as-deposited Pt-Al system: a) Pt-substrate, b) Al-coating.

Figure 125: Residual stress gradient in the substrate (Pt) of the as-deposited Pt-Al system.


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than six consecutive passes without intermediate heat treatment. Contrary, the d vs sin2ψ plot for the Al coating

(lower graph on Figure 124) shows a slight positive slope which corresponds to in-plane coating stress (σII) of

about +20 MPa. It indicates that the e-beam deposition parameters used in our experiments were correctly

optimised leading to minimal intrinsic stresses in coating. The large error bars for small ψ angles are due to the weak diffraction line intensity (small coating thickness) at steep incidence. It is also interesting to determine the residual stress depth profile in the substrate near-surface region. Materials processing such as cold rolling is well known to give rise to a complex residual stress fields in the near-surface region of polycrystalline materials, which may vary strongly with depth. For this reason the so-called ‘universal

plot’ method based on the eqs. (1) and (2), which yields residual stress depth profiles σII (τ) in the Laplace space

was applied. An exponentially applied polynomial function of first degree, σII (z) = (a0 + a1z) e-az, was used to describe the stress depth profile in the z-space. Its Laplace transform as calculated by eq. (1) was then tilted to the discrete stress data using eq. (2). The results are summarised in Figure 125. The upper diagram shows the

discrete stress depth distribution σII (τk) evaluated from the experimental data as well as the fitted σII (τ)- function

and the corresponding σII (z)-profile. The recalculated d (220)-sin2 ψ-distribution is shown in the lower chart of

Figure 125. The results give clear evidence that there is a steep residual stress gradient in the substrate near-surface (i.e. interface) region. The stress information was obtained up to a depth of approximately 0.5 µm due to

very large absorption of the Co Kα radiation by Pt. However, it is interesting to note that the in-plane residual

stress is balanced within the very small surface zone being accessible by the X-ray beam. Therefore, the high compressive surface stresses are compensated by small tensile stresses in “deeper” material regions. Different techniques such as microscopy and X-ray diffraction have been used to study the effects of deposition and annealing processes on morphology, phase formation and residual stress of Pt-Al coated system. The following conclusions could be drawn from this study:

• The residual stress analysis of the as-deposited system revealed that only small tensile residual stresses

were found within the Al coating (+21 ± 7 MPa) while large compressive stresses of − 157 ± 21 MPa were determined in Pt substrate. The compressive stresses are the result of severe plastic deformation caused by the cold rolling process applied during substrate manufacturing.

• The residual stress depth distribution analysis of the as-deposited system however, showed that the in-plane stress in the substrate is not uniform; it occurs in the form of a steep gradient with compressive stresses at the surface which are compensated by tensile stresses beneath.

• The experimental results showed that the annealing process has crucial effect on coating morphology, phase transformation and hardness of the studied Pt-Al coating system.


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3.5.29 High Temperature Study of Thin Aluminum Coatings Deposited onto Thick

Platinum Substrates

M. Topić1, C.A. Pineda-Vargas1, E. du Plessis2, B. Breedt2, R. Bucher1, V. Pischedda3, S. Nxumalo4, C.I. Lang4

1 Materials Research Group, iThemba Labs, P.O. Box 722, Somerset West, 7129, South Africa 2SASOL 3Physics Department, University of Witwatersrand, Johannesburg, South Africa; 4Centre for Materials Engineering, Department of Mechanical Engineering, University of Cape Town, South Africa The intermetallic phase formation sequence reported previously [1] showed that the most Pt-rich phase (Pt3Al) was observed at 500°C. On the other hand there was an indication that the Al was consumed by the Pt substrate during formation of Pt-rich phases. Interdiffusion and intermetallic formation in the Pt-Al binary system at temperatures in the range of 200-550°C were investigated by studying thin aluminium coatings on thick platinum substrates. X-ray diffraction (XRD), microhardness, proton-induced X-ray emission (PIXE) and scanning electron microscopy (SEM) were used to monitor the phase transformation process. High temperature X-ray diffraction analysis showed that the first phase to be formed on heat treatment of the coating/substrate couple was Pt2Al3, followed by the PtAl and Pt3Al phases. The sequence of phase formation observed in our study is in good agreement with the effective heat of formation (EHF) model [2]. Furthermore, the formation of intermetallic compounds increased the hardness to a greater depth than the thickness of the initially deposited Al coating.

Furthermore Pt-Al intermetallics increased the surface hardness. AFM microscopy revealed that the morphology of deposited coatings have a grain size of 375-480 nm (see Figure 126), and the surface roughness was measured at Ra=17-22 nm. However the coating morphology changed significantly during the annealing process; the Pt layer became rough and irregular. A scanning electron micrograph of the coating morphology (annealed up to 600°C and cooled down to room temperature during in-situ XRD) clearly showed the presence of “islands” which indicates localized coating consumption of the Al coating by the Pt substrate (Figure 127). No differences in coating morphology were observed between samples annealed in air or argon. References 1. M. Topic et al. iThemba LABS, Annual Report 2006/07, page 186. 2. R. Pretorius, R. de Reus, A.M. Vredenberg, F.W. Saris, Mat. Lett. 9 (1990) 494.

Figure 126: AFM image showing the surface morphology of deposited Al coating

Figure 127: Scanning electron micrograph shows the changes in coating morphology over regions 1 and 2 (annealing up to 600°C and cooled down to room temperature).


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3.5.30 Design and Construction of an End-Station for Nigerian 1.7 MV Tandem

Accelerator C.A. Pineda-Vargas1, K. Springhorn1, L. Ashworth1, R. Nemutudi1, G.A. Osinkolu2

1 Materials Research Group, iThemba Labs, P.O. Box 722, Somerset West, 7129, South Africa 2 Centre for Energy Research & Development, CERD, Ile-Ife, Nigeria A Memorandum of understanding (MoU) between the Centre for Energy Research and Development (CERD) at Ile-Ife, Nigeria and the iThemba LABS was signed in May 2007 to established a cooperation with the main objective to assist the CERD in the design and construction of an End-Station (ES) to be used for Ion Beam

Analysis (IBA) at the -15° line of the newly acquired 1.7 Tandem accelerator by the Nigerian Government.

During April to December 2007 construction and assembly of the ES was accomplished in the D line at the Van de Graaff accelerator. The ES was constructed based on the design of a scattering chamber used previously at the Materials Research Group, with some modification. The aluminium scattering chamber was fitted with a

vertical pedestal for ground support, a vesconite insulating coupling to the experimental line, one port at 45° for a Si(Li) detector for PIXE (including a wheel to position up to 8 filters used to cut down low energy X-ray signals),

two ports at -150° and +165° respectively for positioning of PIPS detectors for RBS and ERDA techniques, one

exit window with a quartz viewer and chatter at 180°, an additional port at -90° for future use of Ge detectors, a

ladder fitted with a manual sample changer mechanism with possibility to position up to 10 specimens, and an adjustable dual platform for positioning of Si(Li) and/or Ge detectors. The detection system for all techniques available consisted of a NIMBIN power supply, a Multi-port MCA with two ADC channels, two high voltage power supplies, a Si(Li) detector for PIXE, two PIPS detectors for RBS and ERDA working with two Canberra semiconductor preamplifiers, one dual counter for preset charge integration, and two Canberra spectroscopy amplifiers. The data acquisition PC was designed to be compatible with the Canberra GENIE-2K software. In addition a Pfeiffer turbo pumping station was implemented to obtain vacuum levels of the order of 10-7 Torr. Figure 128 shows a photograph of the assembled ES at the D-line of the Van de Graaff accelerator. During a visit by a Nigerian team in February 2008 a set of experiments were conducted to evaluate all possible analytical techniques implemented in the ES: Proton Induced X-ray Emission (PIXE), proton and alpha Backscattering Spectrometry (RBS), Energy Recoil Detection Analysis (ERDA) and Proton Induced Gamma-ray Emission Spectrometry (PIGE). The operation of the Canberra electronics and data acquisition system was optimal and the Nigerian team was satisfied with the operation of the system.

In April 2008 a team of iThemba LABS personnel successfully installed the IBA End-Station on the -15° line at the Tandem accelerator in Nigeria. All the equipment including beam line, detection system and data acquisition performed according to specifications. Four techniques are currently implemented: PIXE, RBS, ERDA and PIGE.


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At present only a Si(Li) detector is available with a resolution of 148 eV measured at 5.9 KeV. In addition two PIPS detectors to be used for RBS and ERDA, with a resolution of 11 KeV, are fitted in the scattering chamber. An additional HPGe detector for low energy gamma spectrometry will also be available shortly. A critical part of the installation process was the calibration of the instrumentation,

particularly for RBS and PIXE. This required the precise determination and quantification of detector parameters as well as geometrical factors such as solid angle. During 17-26 April several calibration

experiments were done by performing PIXE and RBS with 2.2 MeV alpha particles as well as with 3 MeV protons. There are already a dozen of potential M.Sc. and Ph.D. students interested in following research at the new facility. This activity completes the main objective of the MoU between iThemba LABS and the CERD in Nigeria signed in May 2007.

Ge(Li)

Si(Li)

SampleChanger

PumpingStation

Insulation

RBS-PIPS

ERDA-PIPS

18/02/2008 Figure 128: A whole view of the End-Station assembled at the D-line of the Van de Graaff accelerator showing the Si(Li) detector; two PIPS detectors for RBS and ERDA techniques; an additional port at -900 for use of Ge detectors; a ladder fitted with a manual sample changer mechanism and an adjustable dual platform for positioning of Si(Li) and/or Ge detectors.


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3.5.31 Characterization of Ambient Atmospheric Aerosol using Accelerator Based

Techniques K.G. Sekonya1,2, E. Sideras-Haddad1,3, S.J. Piketh2, W.J. Przybylowicz4, P. Sechogela4

1iThemba LABS (Gauteng), Johannesburg, South Africa 2Climatology Research Group, University of the Witwatersrand, WITS 2050 3Physics Department, University of the Witwatersrand, WITS 2050 4Material Research Group, iThemba LABS, Somerset West 7129 The aim of the study was to determine the elemental composition of particulate matter at the urban site of Khayelitsha and the industrial site of Witbank. Samples were collected over continuous periods of 12 hours using partisol-plus dichotomous samplers and over 24-hour periods using Tapered Element Oscillating Microbalance (TEOM). The aerosol samples were analyzed using Particle-Induced X-ray Emission (PIXE) technique at iThemba LABS [1] and 16 different elements (Al, Si, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, As, Br, Sn, and Pb) were detected at µg/m3 levels. The measurements were performed with a 3 MeV proton beam with an average current of 200 pA. The beam spot at the target position was about 7 x 4 μm and the beam was scanned over a 2 mm x 2 mm area on the sample in order to avoid beam damage to filters and reduce elemental loses. The integrated charge was 300 nC. The standardization procedures as well as data analysis were performed using GUPIX code in the thin target approximation [2]. Enrichment factors (EF) for each element of the PM10 samples were calculated to identify the sources [3]. Calculation of EF values helps decide whether a certain element has additional sources other than its major natural source. S, K, Cl, Cu, and Br were the reference elements chosen for soil, wood combustion, sea salt, diesel, and petrol, respectively. S, Cl, Cr, As, Pb, and Br were highly enriched with respect to soil at Witbank. Cr is also detected in high concentrations and is attributed to the activities of the Ferrochrome plant in the area while the high concentrations of As, Pb and Br are related to the activities of the petrochemical company in the vicinity of the sampling site. S, Cl, Cu, Zn, As, Br and Pb were enriched with respect to soil at Khayelitsha and the detected concentrations of S, Cu and Zn are attributed to the local iron industry, while As, Pb and Br are related to the local petrochemical industry. References 1. S.A.E. Johansson and J.L. Campbell. PIXE: A novel technique for elemental analysis. John Wiley and Sons,

Chichester (1988). 2. J.A. Maxwell, T.L. Hopman, J.L. Campbell, and Z. Nejedly. Nuclear Instruments and Methods in Physics

Research B95 (1995) 407. 3. I. Senaratne and D. Shooter. Atmospheric Enviroment 38 (2004) 3049.

Figure 129: Median elemental composition of PM10 deduced by PIXE analysis of Partisol-plus.


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3.6 iThemba LABS (Gauteng) 3.6.1 The Tectonic Framework of Southern Africa as Interpreted from Regional Gravity

and Aeromagnetic Data.

R. Hart1, S. Webb2, M. Doucouré2, A. Galdeano3, L. Gaya-Piqué3, J-L. Le Mouël3, E. Thébault3, S. Gilder4, V. Mikhailov3 1 iThemba Labs (Gauteng), P. Bag 3, Wits 2050, South Africa, 2School of Geoscience, University of the Witwatersrand, P. Bag 3 Wits 2050, Johannesburg, South Africa 3Institut de Physique du Globe, Laboratoire de Paléomagnétisme, 75252 Paris Cedex 05 France 4Now at: Ludwig Maximilians University, Department of Earth and Environmental Sciences, Geophysics

An understanding of the development of both crustal magnetization and gravity features in the crust is essential in interpreting continental scale terrain boundaries which manifest themselves either as major magnetic or gravity anomalies. In order to determine the major gravity and magnetic features in the upper 30 km of Southern Africa, we intend to apply a number of transformations e.g. block levelling and low pass filtering of the gravity and aeromagnetic data of Southern Africa. These crustal features include kimberlites resulting from magmatic events. The distribution of kimberlites will be analysed through anisotropy associated with magnetization directions. Aeromagnetic Data Set Aeromagnetic surveys over Southern Africa were flown by the Geological survey of South Africa during the period from 1966 to 1981 [1]. Total field data were collected along north–south flight lines at a nominal terrain clearance of 150 m, flying at 240 km/h with a sampling interval of two seconds. Flight line spacing was 1 km and perpendicular tie-lines were flown every 10 km. In order to facilitate digital transformation, the data were flight line levelled and block levelled, thus establishing a common datum for all aeromagnetic surveys across South Africa. The interpolation of the aeromagnetic map was done with a grid lattice of 250 x 250 m (Figure 130). It should be noted that the post-acquisition treatment of the data has not been published and is unknown. Because of the way the magnetic data set was collected and levelled, the longest wavelength anomalies do not match up across the subcontinent. We want to develop a procedure to do large scale block corrections in order to obtain unity in the data across the subcontinent. One possible way to achieve unity across the different survey areas is to compare aeromagnetic data with satellite data by upward continuing the aeromagnetic data. Finally once the data is corrected we plan to do an interpretative study that will include structures and geometry definition, source depth clustering and separation of crustal/mantle features.

Figure 130: Magnetic map of Southern Africa


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Bouguer Gravity Data Set The gravity data were collected from a number of regional and detailed surveys conducted by the University of the Witwatersrand, the Geological Survey of South Africa, the institute of Geological Sciences of Great Britain and various mining and exploration companies. Most of the data were gathered along roads with maximum station intervals of approximately 3 km. The majority of station elevations were determined barometrically and the measurements reduced using the geodetic reference system 1967 formula. A total of 13 500 stations were finally accepted for the compiled data set with an average error of ~1,62 mgal [1]. The data set was gridded at 100 m intervals and the UTM projection utilized. The gravity data will be used to identify large (>100 km) crustal anomalies (dense rocks). To do this we have to devise techniques to effectively remove topographic and mantle contributions to the gravity field. One example of the processing we can perform across Southern Africa is to correlate the gravity map and the pseudo-gravimetric map (derived from the magnetic map). This can be computed in a moving window of a few kilometers (Gilbert and Galdeano 1992). The resulting map will give us the distribution of the coherence (or the “anti-coherence”) between the 2 anomaly fields (gravity and magnetic) which in turn will provide information about the nature of responsible sources. Mode of co-operation between the French and South African research teams. The project will involve bilateral travel between France and South Africa for both research teams, including post-graduate students, for the exchanges of ideas, the interpretation and publication of results. Both South African and French research teams will serve as supervisors of the post-graduate students. Tangible items to be shared between France and South African research teams, to the benefit of both countries, will include digital data (including databases), computer programs and other software, maps, and written works including scientific publications, reports and theses. Capitalizing on other geophysical studies 1. Magnetotelluric data have recently been collected in the region that has the potential to image to upper

mantle depths. 2. Deep (16 sec) seismic data of the region collected during the Kaapvaal seismic program is also available. 3. Recent basic 3D model of the Wits basin has been developed in gOcad which can be used in modelling

programs to test ideas. References 1. B. Corner and W.A. Wilsher, Exploration ’87. Geol. Surv. Can. Spec. 3 (1989) 523.

2. D. Gibert and A. Galdeano, Comp. and Geosciences 11 (1992) 553.

iThemba LABS Annual Report 2008 Appendices

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4 APPENDICES


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4.1 Publications and Reports* *(Publications and reports on research done (fully or in part) at iThemba LABS by external users and/or members of staff, as well as work done elsewhere in which members of staff participated) Publications in Refereed Journals iThemba LABS (Gauteng) 1. M Muundjua, R J Hart, S A Gilder, L Carporzen

and A Galdeano. Magnetic imaging of the Vredefort impact crater, South Africa. Earth and Planetary Science Letters 261 (2007) 456-468.

Materials Research Group

1. A Y Fasasi, M Maaza, C Theron, P Neethling, U Buttner, A Leitch, A K Chaudhary. Non-liner absorption and second harmonic imaging of Zn-BaTiO3 thin films prepared by laser ablation. Thin Solid Films 516 (2008) 6233-6239.

2. G Tylko, J Mesjasz-Przybylowicz, W J Przybylowicz. In-vacuum micro-PIXE analysis of biological specimens in frozen-hydrated state. Nucl. Instr. Meth. Phys. Res. B 260 (2007) 141-148.

3. A Y Fasasi, M Maaza, E G Rohwer, D Knoessen, C Theron, A Leitch, U Buttner. Effect of Zn-doping on the structural and optical properties of BaTiO3 thin films grown by pulsed laser deposition. Thin Solid Films 516 (2008) 6226-6232.

4. A C Beye, M Maaza. Themochromic VO2 thin films synthesized by rf-inverted cylindrical magnetron sputtering. Applied Surface Science 16239 (2008) 1-5.

5. A M Korsunsky, W J Vorster, S Y Zhang, M Topić, A Venter. A beam-bending eigenstrain analysis of residual elastic strains in multi-scan laser-formed steel samples. Journal of Engineering Science, (2008) (in press).

6. E Orlowska, J Mesjasz-Przybylowicz, W Przybylowicz and Turnau, Nuclear microprobe studies of elemental distribution in mycorrhizal and non-mycorrhizal roots of Ni-hyperaccumulator Berkheya coddii. X-ray Spectrometry 37 (2008) 129-132.

7. M Augustyniak, W Przybylowicz, J Mesjasz-Przybylowicz, M Tarnawska, P Migula, E Glowacka and A Babczynska. Nuclear microprobe studies of grasshopper feeding on nickel hyperaccumulating plants. X-ray Spectrometry 37 (2008) 142-145.

8. M Topić, R Heimann, C A Pineda-Vargas, T Ntsoane, Biomimetic formation of hydroxy-apatite investigated by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and proton-induced X-ray emission (PIXE). Mater Sci Med (2008) (in press).

9. A M Venter, M W van der Watt, R C Wimpory, R Schneider, P McGrath, M Topić. Neutron strain investigations of laser bent samples. Materials Science Forum 571-572 (2008) 63-68.

10. M Williams, C A Pineda-Vargas, E V Khataibe, B J Bladergroen, A N Nechaev, V M Linkov. Surface functionalization of porous ZrO2-TiO2 membranes using γ-aminopropyltriethoxysilane in palladium electroless deposition. Applied Surface Science 254 Issue 10 (2008) 3211-3219.

11. C A Pineda-Vargas, M E M Eisa, A L Rodgers. Characterization of human kidney stones using micro-PIXE and RBS: A comparison study between two different populations. Journal of Applied Radiation and Isotopes (2008) (in press).

12. R B Heimann, T P Ntsoane, C A Pineda-Vargas, W J Przybylowicz, M Topic. Biomimetic formation of hydroxyapatite investigated by analytical techniques with high resolution Journal of Materials Science: Materials in Medicine (2008) (in press).

13. M Tarnawska, P Migula, W Przybyłowicz, J Mesjasz-Przybyłowicz, M Augustyniak. Nickel Toxicity in the Hindgut of an Isopod Porcellio scaber (Oniscidea). Nucl Instr Meth Phys Res B 260, (2007) 222-226.

14. M Tarnawska, P Migula, W Przybyłowicz, J Mesjasz-Przybyłowicz, M Augustyniak. Nickel Toxicity in the Hepatopancreas of an Isopod Porcellio scaber (Oniscidea). Nucl Instr Meth Phys Res B 260, (2007) 213-217.

15. R Maleri, S A Reinecke, J Mesjasz-Przybylowicz, A J Reinecke. Growth and reproduction of earthworms in ultramafic soils. Archives of Environmental Contamination and Toxicology 52 (2007) 363-370.

16. G Reama, G O Egharevba and M Maaza. Effect of heat on the morphology and optical properties of nano-structured porphyrins, Sensors and Actuators B (2007) (in press).


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17. M Maaza, H Chambalo, S Ekambaram, B D Ngom, O Nemraoui & N Manyala Pulsed laser liquid solid interaction of Pt, Au, Ag and Cu nano-suspensions and their stability. International Journal of Nano-Manufacturing. (2007) (in press).

Medical Radiation Group

1. M W Swanepoel and D T L Jones. Use of Monte-Carlo software to aid design of a proton therapy nozzle. Nucl. Instr. Meth. Phys. Res. A580 (2007) 145-148.

2. D T L Jones and A Wambersie. Radiation therapy with fast neutrons – a review. Nucl. Instr. Meth. Phys. Res. A580 (2007) 522-525.

3. J Blomgren, L Lindborg, N Golnik, D T L Jones, H Schuhmacher, F Spurny, and B Stenerlöw. Progress in dosimetry of neutrons and light nuclei. Radiat. Prot. Dosim. 26 (2007) 1-2.

4. F D Brooks, A Buffler, M S Allie, M S Herbert, M R Nchodu, D T L Jones, F D Smit, R Nolte, and V Dangendorf. A compact high-energy neutron spectrometer. Radiat. Prot. Dosim. 126 (2007) 218-222.

5. M S Herbert, F D Brooks, M S Allie, A Buffler, M R Nchodu, S A Makupula, D T L Jones, and K M Langen. Determination of neutron energy spectra inside a water phantom irradiated by 64 MeV neutrons. Radiat. Prot. Dosim. 126 (2007) 346-349.

6. D T L Jones, H D Suit et al. Prescribing, recording, and reporting proton-beam therapy. J ICRU 7/2 (2007).

7. A Wambersie, D T L Jones, and H D Suit. Presentation of the ICRU-IAEA joint report: Prescribing, recording, and reporting proton-beam therapy. Strahlenther. Onkol. 183 Suppl. 2 (2007) 87-89.

Physics Group

1. S S Ntshangase, N Rowley, R A Bark, S V Förtsch, J J Lawrie, E A Gueorguieva, R Lindsay, M Lipoglavšek, S M Maliage, L J Mudau, S M Mullins, O M Ndwandwe, R Neveling, G Sletten, F D Smit, C Theron. Barrier distribution for a ‘Superheavy’ Nucleus-Nucleus collision, Phys. Lett. B 651 (2007) 27–32.

2. B Buck, A C Merchant, S M Perez and H E Seals. Core-cluster partitions of Actinide Nuclei. Phys. Rev. C 76, (2007) 014310.

3. B Buck, A C Merchant and S M Perez. Negative parity bands in 238U. J. Phys. G34 (2007) 1985.

4. B Buck, A C Merchant and S M Perez. Parameter-free characterization of nuclear band spectra. Phys. Rev. C76 (2007) 034326.

5. B Buck, A C Merchant and S M Perez. Core-cluster partitions of rare-earth nuclei. Phys. Rev. C 77 (2008) 017301.

6. A A Cowley, J Bezuidenhout, S S Dimitrova, P E Hodgson, S V Förtsch, G C Hillhouse, N M Jacobs, R Neveling, F D Smit, J A Stander, G F Steyn, and J J van Zyl. Multistep direct mechanism in the (p,3He) inclusive reaction on 59Co and 93Nb at incident energies between 100 and 160 MeV. Phys. Rev. C 75 (2007) 054617.

7. S V Förtsch, F Cerutti, P Colleoni, E Gadioli, E Gadioli Erba, A Mairani, G F Steyn, J J Lawrie, F D Smit, S H Connell, R W Fearick, T Thovhogi. Contributions of complete fusion and break-up fusion to intermediate mass fragment production in the low energy interaction of 12C and 27Al. Nucl. Phys. A 797 (2007) 1-32.

8. O Burda, N Botha, J Carter, R W Fearick, S V Förtsch, C Fransen, H Fujita, J D Holt, M Kuhar, A Lenhardt, P von Neumann-Cosel, R Neveling, N Pietralla, V Yu Ponomarev, A Richter, O Scholten, E Sideras-Haddad, F D Smit, and J Wambach. High Energy-Resolution Inelastic Electron and Proton Scattering and the Nature of Mixed-Symmetry 2+ States in 94Mo. Phys. Rev. Lett. 99, (2007) 092503.

9. E-W Grewe et. al. (3He,t) reaction on the double beta decay nucleus 48Ca and the importance of nuclear matrix elements. Phys Rev C 76, (2007) 054307.

10. D S Armstrong et al. Transverse beam spin asymmetries in forward-angle elastic electron-proton scattering (G0 Collaboration) Phys Rev Lett 99, (2007) 092301.

11. R Neveling, A A Cowley, Z Buthelezi, S V Förtsch, G C Hillhouse, J J Lawrie, G F Steyn, F D Smit, S M Wyngaardt, N T Botha, L Mudau, S S Ntshangase. Analysing power of the


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40Ca(p, px) reaction at 100 meV. Phys Rev C 77 (2008) 037601.

12. E O Lieder et al. Investigation of lifetimes in quadrupole bands of 142Gd. Eur. Phys. J. A, DOI 101140/epja/i2007-10533-0.

Radioisotope Production Group 1. K Aardeneh, D Saal, G Swart, S C de Windt.

TBP and TBP impregnated Amberlite XAD-4 resin for radiochemical separation of 88Y from Sr and Al. J. Radioanal Nucl. Chem. 275 (2008) 665

2. K Aardeneh, C Naidoo, G F Steyn.

Radiochemical separation of 109Cd from a silver target. J. Radioanal & Nucl. Chem. 276 (2008) 831.

3. I Spahn, G F Steyn, F M Nortier, H H Coenen,

S M Qaim. Excitation functions of natGe(p,xn)71,72,73,74As reactions up to 100 MeV with a focus on the production of 72As for medical and 73As for environmental studies. Appl Radiat Isot 65 (2007) 1057.

4. D D Rossouw. Radio-iodine labelling of a small

chemotactic peptide, utilising two different prosthetic groups: A comparative study. J Label Compd Radiopharm 51 (2008) 48 .

Radiation Biophysics Group 1. J M Akudugu, J P Slabbert. Modulation of

radiosensitivity in Chinese hamster lung fibroblasts by cisplatin. Canadian Journal of Physiology and Pharmacology 86 (2008) 257-263.


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4.2 Conference Proceedings Accelerator Group 1. J L Conradie, P J Celliers, J G de Villiers, J L G

Delsink, H du Plessis, J H du Toit, R E F Fenemore, D T Fourie, I H Kohler, C Lussi, P T Mansfield, H Mostert, G S Muller, G S Price, P F Rohwer, M Sakildien, R W Thomae, M J van Niekerk, P A van Schalkwyk, Z Kormány, J Dietrich, T Weis, S Adam, D Goetz, PA Schmelzbach. Improvements to the iThemba LABS Cyclotron Facilities. 18th International Conference on Cyclotrons and their Applications, Giardini Naxos Messina, 30 September- 5 October 2007.

2. J Dietrich, C Boehme, T Weis, A H Botha, J L

Conradie, P F Rohwer. Beam Profile Measurements based on light radiation of atoms excited by the particle beam. Proceedings of 22nd Particle Accelerator Conference 07, Albuquerque, New Mexico, USA, 25-29 June 2007.

Materials Research Group 1. S Kortyka, R Puzniak, A Wisniewski, H W

Weber, T B Doyle, T Q Cai and X Yao. Influence of low-level Pr substitution on the superconducting properties of YBa2Cu3O7-d single crystals. Journal of Physics: Conference Series (JPCS) (in press).

2. C Pineda-Vargas, M Topić, T Ntsoane. Micro-PIXE analysis of bioconductive hydroxyapatite coatings on titanium alloys. Conference Proceedings of the XI Inter Conf on PIXE and its Analytical Applications, Puebla, Mexico (2007).

3. C A Pineda-Vargas, M E M Eisa, U M E Chikte, A L Rodgers, S Naidoo, J L Conradie. Applications of micro-PIXE and dynamic analysis for the characterization of human hard tissues. eProceedings of the 11th International Conference on PIXE and its Analytical Applications (PIXE-2007), Puebla, Mexico, 25-29 May 2007.

4. M Augustyniak, W Przybyłowicz, J Mesjasz-Przybyłowicz, M Tarnawska, P Migula, E Głowacka, A Babczyńska. Nuclear microprobe studies of grasshopper feeding on nickel hyperaccumulating plants. Proceedings of the 11th International Conference on Particle-

Induced X-ray Emission and its Analytical Applications, 25-29 May 2007, Puebla, Mexico ISBN 978-970-32-5115-5, pp D4-1 – D4-4 (2007).

5. E Orłowska, J Mesjasz-Przybyłowicz, W

Przybyłowicz, K Turnau. Micro-PIXE studies of elemental distribution in mycorrhizal and nonmycorrhizal roots of Ni-hyperaccumulator Berkheya coddii. Proceedings of the 11th International Conference on Particle-Induced X-ray Emission and its Analytical Applications, 25-29 May 2007, Puebla, Mexico. ISBN 978-970-32-5115-5, pp C3-1 – C3-4 (2007).

6. W J Przybylowicz, G Tylko, J Mesjasz-Przybylowicz, A Barnabas. PIXE microanalysis of biological materials in frozen-hydrated state. Biochemistry of Trace Elements: Environmental Protection, Remediation and Human Health Yongguan Zhu, Nicholas Lepp and Ravi Naidu (Editors), Tsinghua University Press, Beijing 2007, ISBN 978-7-302-15627-7, pp 338-339 (2007).

7. P Migula, J Mesjasz-Przybylowicz, W J Przybylowicz, M Augustyniak, M Nakonieczny, E Orlowska. Transfer of selected metals along simplified food chains of ultramafic ecosystem in Mpumalanga Province, South Africa. Biochemistry of Trace Elements: Environmental Protection, Remediation and Human Health Yongguan Zhu, Nicholas Lepp and Ravi Naidu (Editors), Tsinghua University Press, Bei Jing, ISBN 978-7-302-15627-7, pp 1020-1021 (2007).

8. M Augustyniak, K Michalczyk, W Przybylowicz, A Babczynska, M Tarnawska, P Migula, J Mesjasz-Przybylowicz. Digestive enzymes and metal distribution in the gut of grasshopper Stenoscepa sp associated with Ni hyperaccumulators. Toxicology Letters 172 Supplement 7 October 2007 pp S156 DOI 101016/jtoxlet200705401 (2007).

9. H J Hawkins, H Hettasch, J Mesjasz-Przybylowicz, W Przybylowicz, M D Cramer. Micro-location of elements in leaves of Leucadendron ‘Safari Sunset’ (Proteaceae) with phosphorus toxicity. South African Journal of Botany 73 (2007) 290.

10. J Mesjasz-Przybylowicz, W J Przybylowicz. Nuclear microprobe in plant sciences – present status and challenges. South African Journal of Botany 73 (2007) 302.


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11. E Orłowska, T Anielska, B Godzik, K Turnau. Influence of different arbuscular mycorrhizal fungal strains on heavy metal uptake by Plantago lanceolata L. South African Journal of Botany 73(2) (2007) 333.

Physics Group 1. E A Lawrie, P Vymers, Ch Vieu, J J Lawrie, C

Schuck, R A Bark, R Lindsay, S M Maliage, S M Mullins, S H T Murray, T M Ramashidzha, and J F Sharpey-Schafer. Pair of bands in the oblate doubly-odd 198Tl nucleus. Acta Physica Polonica B 38 (2007) 1417-1420.

2. E A Lawrie, P A Vymers, Ch Vieu, J J Lawrie, R A Bark, R Lindsay, S M Maliage, S M Mullins, S H T Murray, T M Ramashidzha, C Schück, J F Sharpey-Schafer. Possible chirality in the doubly-odd 198Tl nucleus. Proceedings of the 26th International Workshop on Nuclear Theory (Rila Mountain, Bulgaria) (2007) pp 109-118.

3. S M Mullins, B M Nyakó, J Timár, J Gál, G

Kalinka, J Molnár, R A Bark, G Berek, E A Gueorguieva, K Juhász, F S Komati, A Krasznahorkay, T T Hlatshwayo, J J Lawrie, M Lipoglavšek, S M Maliage, T Malwela, S H T Murray, S S Ntshangase, T M Ramashidzha, J N Scheurer, J F Sharpey-Schafer, O Shirinda, P A Vymers. Probing a variety of nuclear phenomena with DIAMANT and AFRODITE. Proceedings of the 26th International Workshop on Nuclear Theory (Rila Mountain, Bulgaria) (2007), pp 119-128.

4. J J Lawrie, R A Bark, N T Botha, O Burda, J Carter, R W Fearick, S V Förtsch, C Fransen, H Fujita, M Kuhar, E A Lawrie, A Lenhardt, R Lindsay, M Lipoglavšek, A M Maliage, B M Msesane, L J Mudau, S M Mullins, P Mutshena, O M Ndwandwe, R Neveling, S S Ntshangase, N Pietralla, V Yu Ponomarev, A Richter, N Rowley, O Scholten, JF Sharpey-Schafer, E Sideras-Haddad, G Sletten, FD Smit, C Theron, P von Neumann-Cosel, J Wambach. Recent results from the experimental nuclear structure program at iThemba LABS. Proceedings of the 26th International Workshop on Nuclear Theory (Rila Mountain, Bulgaria) (2007) pp 3-12.

5. G Deyanova, D Balabanski, B Akkus, L Atanasova, P Can, P Detistov, K Gladnishki, M N Erduran, EA Lawrie, J J Lawrie, A Minkova, S M Mullins, J Ncapayi, G Rainovski, J F Sharpey-Schafer. High spin states in 136La.

Proceedings of the 26th International Workshop on Nuclear Theory (Rila Mountain, Bulgaria) (2007), pp 149-157.

Radioisotope Production Group 1. F Szelecsényi, G F Steyn, K Suzuki, Z Kovács,

T N van der Walt, C Vermeulen, N P van der Meulen, S G Dolley, K Mukai. Applications of Zn + p reactions for production of copper radioisotopes for medical studies. Presented at the International Conference on Nuclear Data for Science and Technology, Nice, France, April 22-27, 2007, Journal of Nuclear Science and Technology, (in press).

2. G F Steyn, N P van der Meulen, T N van der

Walt, C Vermeulen. Production of carrier-free 28Mg by 50 – 200 MeV protons on natCl: Excitation function and target optimization. Presented at the International Conference on Nuclear Data for Science and Technology, Nice, France, April 22-27, 2007, Journal of Nuclear Science and Technology, (in press).

3. F Szelecsényi, G F Steyn, Z Kovács, T N van

der Walt. Application of Au + p nuclear reactions for proton beam monitoring up to 70 MeV. Presented at the International Conference on Nuclear Data for Science and Technology, Nice, France, April 22-27, 2007, Journal of Nuclear Science and Technology, (in press).

4. A Guglielmetti, D Faccio, R Bonetti, S V

Shishkin, S P Tretyakova, S V Dmitriev, A A Ogloblin, G A Pik-Pichak, N P van der Meulen, G F Steyn, T N van der Walt, C Vermeulen, D McGee. Carbon radioactivity of 223Ac and a search for nitrogen emission. Presented at the 9th International Cluster Conference, Stratford-upon-Avon, UK, November 2007, Journal of Physics: Conference Series 111 (2008) 012050.

Radiation Biophysics Group 1. J M Akudugu, J P Slabbert. Exposure time and

concentration dependence of cisplatin toxicity in vitro: implications for radiotoxicity modification Proceedings of the Association for Radiation Research (ARR 2007), Belfast, UK, 3-5 April 2007.


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4.3 Conference Contributions 1st North South workshop on Research & Education, Oudja-Morocco, 9-13 April 2007 M Maaza et al., Les nanosciences: vehicule interfacial……Le cas de l’Afrique du Sud. International Meeting on Materials for Electronic Applications - IMMEA 2007, Marrakech, Morocco, 30 April – 2 May 2007 1. G Hailu, G Tessema, R Bucher, A C Beye and

M Maaza. Nano-structured porphyrins confined in inert host matrix: optical properties.

2. J B Kana Kana, J M Ndjaka, O Nemraoui, C

Theron, R Bucher, A Beye and M Maaza. MIT Mott’s VO2 nanostructures for infrared modulation and ultrafast photonic switching.

3. P Sibuyi, D Knoessen, C Theron, R Bucher, B D Ngom and M Maaza. Nano-rods of WO3- for electrochromic smart windows and visible modulation.

4. P S Sibiya, O M Ndwandwe, T Kerdja, U Buttner, M Moodley, T Baisetse, S Halindintwali and M Maaza. Diamond-like carbon nano-structures by double pulsed gas feeding-pulsed laser deposition.

5. T Mphahane, B Ngom, D Knoessen, C Theron, U Buttner, A C Beye and M Maaza. Optical properties of pulsed laser deposited Al:ZnO nano-structures.

6. Th. Mhlungu, M Ndwandwe, N Cingo, A C

Beye, C N R Rao and M Maaza. IR attenuated total reflection in CNTS: Anderson localization phenomenon.

7. G H Mhlongo, M Ndwandwe, O Nemraoui, R Bucher, H Haneda, L Vayssieres and M Maaza. Nano-rods of TiO2 for Gratzel type dye solar cells.

8. R George, G Egharevba, S O Paul, I Adraoui

and M Maaza. Nano-rods of porphyrins by molecular recognition and self-assembly.

9. C Mtshali, M Ndwandwe, R Bucher, S O Paul,

P Buah Bassuah, K Miyazawa and M Maaza. C60 nano-rods by self assembly: growth mechanism and growth conditions.

10. N Ntshangase, M O Ndwandwe, R Bucher, T Ntsoane, C Theron and M Maaza. Room temperature solid nano-mercury: surface tension and phase transition.

SETAC (Society of Environmental Toxicology and Chemistry) Europe, 17th Annual Meeting, Porto, Portugal, 20-24 May 2007 R A Maleri, J Mesjasz-Przybylowicz, W J Przybylowicz, A J Reinecke, S A Reinecke. Availability and uptake of metals of geogenic origin in two ecophysiologically different earthworm species. Meeting on the progress of Coordinated Research Project F12019 “Development of nuclear microprobe techniques for the quantitative analysis of individual microparticles”, IAEA, Vienna, Austria, 24-26 April 2007 W Przybylowicz. Run report on the progress of Research Contract No 13263 entitled “Quantitative studies of cells and tissues by nuclear microprobe techniques” . 11th International Conference on Particle-Induced X-ray Emission and its Analytical Applications, Puebla, Mexico, 25-29 May 2007 1. C A Pineda-Vargas, M E M Eisa, U M E Chikte,

A L Rodgers, S Naidoo, J L Conradie Applications of micro-PIXE and dynamic analysis for the characterization of human hard tissues.

2. C A Pineda-Vargas, M Topic, T P Ntsoane.

Micro-PIXE analysis of bioconductive hydroxyapatite coatings on titanium alloy.

3. M Augustyniak, W Przybyłowicz, J Mesjasz-

Przybyłowicz, M Tarnawska, P Migula, E Głowacka, A Babczyńska. Nuclear microprobe studies of grasshopper feeding on nickel hyperaccumulating plants.

4. E Orłowska, J Mesjasz-Przybyłowicz, W

Przybyłowicz, K Turnau. Micro-PIXE studies of elemental distribution in mycorrhizal and nonmycorrhizal roots of Ni-hyperaccumulator Berkheya coddii.


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Africa Day, Trieste, Italy, 30 May 2007, Spring Meeting of the European Materials Research Society, Strasbourg, France, 28 May – 1 June 2007 M Maaza. Nanophotonics within the Nanosciences African Network. Spring Meeting of the European Materials Research Society, Strasbourg, France, 28th May – 1st June 2007 M Topic, S Nxumalo, R Bucher, C A Pineda-Vargas, V Pischedda. C I Land. Phase transformation in platinum-aluminium coatings.

3rd African Laser Centre General Meeting, Lusaka, Zambia, June 2007 M Maaza. Multifunctional nanophotonics & laser processing for photonics.

52nd Annual SAIP (South African Institute of Physics) Conference, Johannesburg, South Africa, 3-6 July 2007 1. M Topic, R Bucher, C A Pineda-Vargas, V

Pischedda, S Nxumalo. C I Land Phase transformation in platinum-aluminium coatings.

2. I Mabuda, W J Przybylowicz. The determination of boron by 11B(p,α)8Be nuclear reaction.

3. M Msimanga, C C Theron, C M Comrie and S

Murray. Performance characterization of a TOF – E spectrometer designed for heavy ion elastic recoil detection thin film analysis: mass separation of 252Cf fission fragments.

4. B Ngom Diop, A C Beye, N Manyala, C Theron

and M Maaza. Infra-red active Sm1-xNdxNiO3 based nano-switching for high powered lasers.

5. J B Kana Kana, O Nemoraoui, J M Ndjaka, A C

Beye and M Maaza. Synthesis and characterization of the thermionic VO2 films fabricated by reactive RF magnetron sputtering.

6. M Nkosi and C C Theron. Phase stability of Pt-

Cr-Ru Binary alloys. 7. P S Sibiya, M Moodley, D Knoesen, D Motaung

and M Maaza. Synthesis and characterization of hard materials by pulsed laser deposition.

8. C B Mtshali, M Ndwandwe, O Nemraoui, K Miyazawa, S O Paul, P Buah-Bassuah and M Maaza. Nano-rods of C-60 by self assembly growth mechanism and growth conditions.

9. P Sibuyi, D Knoesen and M Maaza. Nano-rods

of WO3 for electrochromic smart windows applications.

10. S Lafane, T Kerdja, S Messaci, S Malek and M

Maaza. Dynamic expansion of Sm1-xNdxNiO3 lasers ablation plume in oxygen gas.

11. O Nemraoui and J Shepperd. Structural and

optical properties of ZnO:Al thin films deposited in dynamic mode by RF magnetron sputtering.

12. B Masina et al. An all-optical system for the

heating.

13. H Ahmed, J Demeulemeester, D Smeets, C C Theron and C M Comrie. Controlling CoSi2 formation temperature by reactive deposition.

14. S M Wyngaardt et al. An investigation into

exotic clustering in nuclei. 15. T T Ibrahim et al. An investigation of nuclear

clustering in heavy nuclei. 16. S V Förtsch et al. Complete and incomplete

fusion processes in the 12C + 12C system at an Energy og 167 MeV/nucleon .

17. J Mira et al. Production of Li, Be and B in the

interaction of 12C with 12C at incident energies of 200 MeV and 400 MeV.

18. T E Madiba et al. Directional correlations from

oriented states (DCO) and linear polarization measurements of 190Tl.

19. S S Ntshangase et al. Development of a recoil

detector to study exotic nuclear shapes. 20. L P Masiteng et al. Linear polarization and

lifetime measurements in 194Tl .

21. O Shirinda et al. Signature splitting and inversion on the 186-194Au nuclei predicted by the total Routhian surface (TRS) and Cranked Shell Model (CSM) calculations.


205

22. F D Smit et al. The status of the development of a high energy-resolution zero degree facility at the iTL K600 magnetic.

23. Burda et al. One- and two-phonon mixed-

symmetry states in 94Mo in high-resolution electron and proton scattering.

24. J Carter et al. Cross-correlations using wavelet

semblance techniques between experimental and theoretical energy spectra in the region of the nuclear ISGQR.

25. I Usman et al. A global investigation of the fine

structure of the isoscalar giant quadrupole resonance.

26. E Schmid et al. Determination of the relative

biological effectiveness of the quasi-monoenergetic 200 MeV and 100 MeV neutron radiation.

27. R A Bark. A survey of radioactive beam

facilities: possibilities for iThemba LABS. 28. A K Mohanty et al. Applications of gamma-ray

spectrometry of beach sands on the west coast of South Africa.

29. I N Hlatshwayo et al. In-situ gamma-ray

mapping of environmental radioactivity at iThemba LABS and associated risk assessment.

30. R Lindsay et al. A study of airborne radon

levels in Paarl houses (Western Cape) and associated source terms, using electrets ion-chambers and gamma-ray spectrometry.

31. N A Mlwilo et al. Systematic effects associated

with primordial activity concentration measurements with the MEDUSA in-situ gamma-ray detector.

The 9th International Conference on the Biogeochemistry of Trace Elements (ICOBTE), Beijing, China, 15-19 July 2007 1. WJ Przybylowicz, G Tylko, J Mesjasz-

Przybylowicz, A Barnabas. PIXE microanalysis of biological materials in frozen-hydrated state.

2. P Migula, J Mesjasz-Przybylowicz, W J

Przybylowicz, M Augustyniak, M Nakonieczny, E Orlowska. Transfer of selected metals along simplified food chains of ultramafic ecosystem in Mpumalanga Province, South Africa.

International Conference on Biomedical Applications of High Energy Ion Beam, University of Surrey, UK, 20 July-2 August 2007

C A Pineda-Vargas. M E M Eisa, A L Rodgers. Characterization of human kidney stones using micro-PIXE and RBS: A comparison study between two different populations. 2nd International Conference “Rhizosphere” Montpellier, France, 26-31 August 2007 E Orłowska, D Orłowski, J Mesjasz-Przybylowicz, W Przybylowicz, K Turnau. Role of mycorrhiza in Ni-hyperaccumulator Berkheya coddii Roessler. Electron Microscopy and Microanalysis Conference, Jagiellonian University, Krakow, Poland, 17-18 September 2007 1. W J Przybylowicz. Micro-PIXE in Biological

Sciences. 2. M M Rost-Roszkowska, I Poprawa, J Klag, P

Migula, J Mesjasz-Przybylowicz, W Przybylowicz. Differentiation of the midgut epithelium of Epilachna cf nylanderi (Insecta, Coccinellidae) a feeder of Ni-hyper-accumulating Berkheya sp (Asteraceae).

3. M Tarnawska, P Migula, WJ Przybylowicz, J

Mesjasz-Przybylowicz, M Augustyniak. Glutathione level, metal mapping and ultrastructural changes in the hepatopancreas of the isopod Porcellio scaber (Oniscidea) after nickel exposure.


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Vth International Conference on Arthropods: Chemical, Physiological and Environmental Aspects, Stefan Kopeć Memorial Conference, Białka Tatrzańska, Poland, 16-21 September 2007

P Migula, W J Przybyłowicz, J Mesjasz-Przybyłowicz, M Rost-Roszkowska, M Augustyniak, J Klag, E Głowacka, M Tarnawska. Strategies of Ni-elimination in Epilachna cf nylanderi (Coccinellidae), feeder of South-African Ni-hyperaccumator Berkheya coddii (Asteraceae).

44th Congress of the European Societies of Toxicology, Amsterdam, The Netherlands, 7-10 October 2007 M Augustyniak, K Michalczyk, W Przybylowicz, A Babczynska, M Tarnawska, P Migula, J Mesjasz-Przybylowicz. Digestive enzymes and metal distribution in the gut of grasshopper Stenoscepa sp associated with Ni hyperaccumulators.

1st IAEA Research Co-ordination Meeting, Lisbon, Portugal 10 – 15 November 2007

M Msimanga et al. Measurement of the stopping power of 0.1 – 1.0 MeV/amu heavy ion beams in selected elemental and oxide thin films.

African Regional College on Science at the Nanoscale, iThemba LABS, 19-30 November 2007

1. C A Pineda-Vargas, W J Przybylowicz, P Sechogela. Characterisation of materials by ion beam analytical techniques.

2. M Maaza et al. Size effects in nano-structured systems.

3. R Nemutudi, M Kataoka, C T Liang, M Pepper, D A Ritchie and G A C Jones. Nano-electronic devices patterned using proximal probe technique.

4th African Materials Research Symposium, Dar es Salaam, Tanzania, 10-14 December 2007

1. G Hailu, G Tessema, R Bucher, A C Beye and M. Maaza. Nano-structured porphyrins confined in inert host matrix: optical properties.

2. J B Kana Kana, J M Ndjaka, O Nemraoui, C Theron, R Bucher, A Beye and M Maaza. MIT Mott’s VO2 nanostructures for infrared modulation and ultrafast photonic switching.

3. P Sibuyi, D Knoessen, C Theron, R Bucher, B D Ngom and M Maaza. Nano-rods of WO3 for electrochromic smart windows and visible modulation

4. P S Sibiya, O M Ndwandwe, T Kerdja, U Buttner, M Moodley, T Baisetse, S Halindintwali and M. Maaza. Diamond-like carbon nano-structures by double pulsed gas feeding-pulsed laser deposition.

5. T Mphahane, B Ngom, D Knoessen, C Theron, U Buttner, A C Beye and M Maaza. Optical properties of pulsed laser deposited Al:ZnO nano-structures.

6. Th Mhlungu, M Ndwandwe, N Cingo, A C Beye,

CNR Rao and M Maaza. IR attenuated total reflection in CNTS: Anderson localization phenomenon.

7. G H Mhlongo, M Ndwandwe, O Nemraoui, R Bucher, H Haneda, L Vayssieres and M Maaza. Nano-rods of TiO2 for Gratzel type dye solar cells.

8. R George, G Egharevba, S O Paul, I Adraoui

and M Maaza. Nano-rods of porphyrins by molecular recognition and self-assembly.

9. C Mtshali, M Ndwandwe, R Bucher, S O Paul, P

Buah Bassuah, K Miyazawa and M Maaza. C60 nano-rods by self assembly: growth mechanism and growth conditions.

10. C Mtshali, M Ndwandwe, O Nemraoui, S Paul ,

A Beye, K Miyazawa and M Maaza. Nano-rods of C60: synthesis and physical investigations.

11. N Ntshangase, M O Ndwandwe, R Bucher, T

Ntsoane, C Theron and M Maaza. Room temperature solid nano-mercury: surface tension and phase transition.

12. P S Sibiya, O M Ndwandwe, S O Paul, T

Kerdja, U Buttner and M Maaza. Diamond-like carbon nano-structures by double pulsed gas feeding-pulsed lased deposition.


207

Gulf Middle East Regional Workshop on Nanotechnology, Muscatt, Oman, 11-14 January 2008

M Maaza et al. Properties of Materials at the nanoscale.

Workshop on Environmental and Biological Applications of Lasers, Cairo, Egypt, 19-28 January 2008

1. M Maaza et al. Effect of heat on the morphological and optical properties of porphyrins nanostructures.

2. M Maaza et al. Effect of laser energy on the

structural and optical properties of nano-structured W-ZnO.

International Symposium on Protons, Ions and Neutrons in Radiation Oncology, Munich, Germany, 6-7 July 2007 1. D T L Jones. Clinical hadron therapy units: a

global perspective. 2. D T L Jones and the Medical Radiation Group,

iThemba LABS. The only centre for proton and neutron therapy

3. J Gueulette, J P Slabbert, B-M de Coster, D T L

Jones, and A Wambersie. Variation of the proton RBE in the SOBP shown with in-vivo systems.

4. D T L Jones. The ICRU and its current

activities.

Workshop on Nuclear Data in Science and Technology: Medical Applications, Trieste, Italy, 13-24 November 2007 1. D T L Jones. Review of neutron and proton

therapy. 2. D T L Jones. Dosimetry for fast neutron and

proton therapy. ESTRO Meeting on Physics & Radiation Technology for Clinical Radiotherapy, Barcelona, Spain, 8-13 September 2007 S M de Canha. Particle therapy in South Africa - iThemba LABS.

National Nuclear Technical Cooperation Conference Midrand, South Africa, 14–15 March 2007 D T L Jones. Development of a patient positioning system for high-precision radiotherapy. 13th National Congress of the SA Society of Clinical & Radiation Oncology and SA Society of Medical Oncology, Drakensberg, South Africa, 27 April – 1 May 2007 1. D T L Jones. The status of proton therapy. 2. D T L Jones and the Medical Radiation Group.

The hadron therapy facilities at iThemba LABS. 3. D T L Jones. The ICRU and its current

activities. 4. C E Stannard, F J A Vernimmen, D T L Jones,

E A de Kock, E E D Mills, C V Levin, S Fredericks and J J Hille. Salivary gland tumours treated with fast neutron therapy at iThemba LABS, Faure, South Africa.

5. J J P Maurel, C E Stannard, et al. Fast Neutron

radiotherapy for the treatment of inoperable N3 cervical adenopathy in patients with squamous carcinoma of the head and neck.

6. P Kraus, C E Stannard, et al. Retrospective

review of locally advanced maxillary antrum tumours treated with fast neutrons.

Future Path for Particle Therapy in South Africa Workshop, iThemba LABS, 28-29 July 2007 1. D T L Jones. Introduction to proton therapy

and the iThemba LABS facility.

2. C J Trauernicht. Latest proton therapy developments at iThemba LABS.

3. S M de Canha. Proton therapy in a South African context.

Annual Congress of the Pattern Recognition Association of South Africa, Pietermaritzburg, 28-30 November 2007 1. B M van Wyk and N Muller, and K M Hunter.

Improving UKF performance.

2. C Carstens and N Muller. Fast calculation of digitally reconstructed radiographs using parallelism.


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Society of Radiographers of South Africa AGM, iThemba LABS, 26 January 2008 1. S Rhoda. Overview of particle therapy at

iThemba LABS.

2. S Schroeder. Neutron therapy at iThemba LABS.

3. D E Commin. Proton therapy at iThemba

LABS. Annual German Nuclear Physics Spring Conference (Deutsche Physikalische Gesellschaft), Darmstadt, Germany 10-14 March 2008 I Usman, E Z Buthelezi, J Carter, G R J Cooper, R W Fearick, S V Förtsch, H Fujita, Y Fujita, Y Kalmykov, P von Neumann-Cosel, R Neveling, V Yu Ponomarev, A Richter, A Shevchenko, E Sideras-Haddad, F D Smit and J Wambach. Damping mechanisms of the Isoscalar Giant Quadrupole Resonance in Light nuclei . IAEA International Conference on Environmental Radioactivity, Vienna, Austria, 23-27 April 2007 1. R Lindsay, R T Newman, W J Speelman. A

study of airborne radon levels in Paarl houses (South Africa) and associated source terms, using electrets ion-chambers and gamma-ray spectrometry.

2. S A Talha, R Lindsay, R T Newman, R J de

Meijer, I N Hlatshwayo, and A K Mohanty. Gamma-ray spectrometry of radon in water and the role of radon to representatively sample aquifers.

7th International Symposium on Applied Isotope Geochemistry, Stellenbosch, 10-14 September 2007

A K Mohanty, R T Newman, N B Mbatha, I N Hlatshwayo, R Lindsay, and R J de Meijer. Radiometric study of beach sands on the west coast of South Africa.

16th International Conference on Radionuclide Metrology and its Applications, Cape Town, 3 – 7 September 2007 1. R T Newman, R Lindsay, K P Maphoto, N A

Mlwilo, A K Mohanty, D G Roux, R J de Meijer and I N Hlatshwayo. Determination of soil primordial radionuclide concentrations by full-spectrum analyses of high-purity germanium detector spectra.

2. S A Talha, R Lindsay, R T Newman, R J de

Meijer, I N Hlatshwayo, N A Mlwilo, A K Mohanty. Measurement of water radon-222 concentrations in the field using gamma-ray spectrometry.

XXVI International Workshop on Nuclear Theory, Rila Mountain, Bulgaria, 25 – 30 June 2007

1. E A Lawrie, P A Vymers, Ch Vieu, J J Lawrie, R

A Bark, R Lindsay, S M Maliage, S M Mullins, S H T Murray, T M Ramashidzha, C Schück, J F Sharpey-Schafer. Possible chirality in the odd-odd 198Tl nucleus.

2. J J Lawrie, R A Bark, N T Botha, O Burda, J

Carter, R W Fearick, S V Förtsch, C Fransen, H Fujita, M Kuhar, E A Lawrie, A Lenhardt, R Lindsay, M Lipoglavšek, A M Maliage, B M Msesane, L J Mudau, S M Mullins, P Mutshena, O M Ndwandwe, R Neveling, S S Ntshangase, N Pietralla, V Yu Ponomarev, A Richter, N Rowley, O Scholten, J F Sharpey-Schafer, E Sideras-Haddad, G Sletten, F D Smit, C Theron, P von Neumann-Cosel, J Wambach. Recent Results from the Experimental Nuclear Structure Programme at iThemba LABS.

3. G Deyanova, D Balabanski, B Akkus, L

Atanasova, P Can, P Detistov, K Gladnishki, MN Erduran, EA Lawrie, J J Lawrie, A Minkova, S M Mullins, J Ncapayi, G Rainovski, J F Sharpey-Schafer. High-spin states in 136La.

4. S M Mullins, B M Nyakó, J Timár, J Gál, G

Kalinka, J Molnár, R A Bark, G Berek, E A Gueorguieva, K Juhász, F S Komati, A


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Krasznahorkay, T T Hlatshwayo, J J Lawrie, M Lipoglavšek, S M Maliage, T Malwela, S H T Murray, S S Ntshangase, T M Ramashidzha, J N Scheurer, J F Sharpey-Schafer, O Shirinda, P A Vymers. Probing a Variety of Nuclear Phenomena with DIAMANT and AFRODITE.

International Nuclear Physics Conference, Tokyo, Japan, 3-8 June 2007 1. S V Förtsch, E Z Buthelezi, H Fujita, R

Neveling, F D Smit, F Cerutti, E Gadioli, A Mairani, A A Cowley, S H Connell, J Dlamini. Complete and Incomplete Fusion Processes in the 12C+12C System at an Incident Energy of 167 MeV/nucleon.

2. A A Cowley, J Bezuidenhout, E Z Buthelezi, S

S Dimitrova, S V Förtsch, G C Hillhouse, P E Hodgson, N M Jacobs, R Neveling, F D Smit, J A Stander, G F Steyn, and J J van Zyl. Reaction mechanism for proton-induced alpha and 3He emission into the continuum at incident energies between 100 and 200 MeV.

3. I Usman, J Carter, H Fujita, F Makayi, E Sideras-Haddad, P Von Neumann-Cosel, I Poltoratska, A Richter, A Shevchenko, Z Buthelezi, J Dlamini, S V Förtsch, MZ Mazibuko, R Neveling, F D Smit, R W Fearick, S Jones, S Walton, and Y Fujita. A Global Investigation of the Fine Structure of the Isoscalar Giant Quadrupole Resonance: The Low-Mass Region 12 ≤ A ≤ 40.

Turkish Physical Society 24th International Congress, Inonu University, Malatya, Turkey, 28-31 August 2007

S M Mullins. Accelerator Based Sciences at the Fairest Cape of Storms and Good Hope. Clusters 07 International Conference, Stratford-upon-Avon, United Kingdom, 3-7 September 2007 1. B Buck, A C Merchant and S M Perez.

Octupole bands in even isotopes of Ra, Th, U and Pu.

2. B Buck, A C Merchant and S M Perez. Recurring nuclear band spectra.

2nd International Conference on Frontiers in Nuclear Structure, Astrophysics and Reactions (FINUSTAR2) , Crete, Greece, 10 – 14 September 2007 1. J F Sharpey-Schafer et al. Shape Transitional

Nuclei: What can we learn from the Yrare States?

2. R M Lieder, A A Pasternak, E O Lieder, W Gast,

G De Angelis, D Bazzacco. Observation of a Double-humped gamma-ray fold distribution in 142Eu.

3. M Lipoglavšek, R A Bark, E A Gueorguieva, J J

Lawrie, E Lieder, R Lieder, S M Mullins, S S Ntshangase, P Papka, M Vencelj. Study of neutron-rich nuclei produced in collisions of very heavy ions.

4. E O Lieder, R M Lieder, A A Pasternak, B G

Carlsson, I Ragnarsson, R A Bark, E Gueorguieva, J J Lawrie, S M Mullins, P Papka, W Gast, G Duchêne. DSAM Lifetime Studies for Gd-Nd nuclei with EUROBALL and AFRODITE.

5. S M Mullins, B M Nyakó, J Timár, G Berek, J

Gál, G Kalinka, J Molnár, S H T Murray, R A Bark, E A Gueorguieva, K Juhász, A Krasznahorkay, J J Lawrie, E O Lieder, R M Lieder, M Lipoglavšek, S S Ntshangase, P Papka, J N Schreuder, J F Sharpey-Schafer, O Shirinda, L Zolnai. A DIAMANT wedding for AFRODITE: probing structure and characterizing reaction properties via charged-particle-gamma correlations.

The XLVI International Winter Meeting on Nuclear Physics, Bormio (Italy), 21 – 25 January 2008 J F Sharpey-Schafer, S M Mullins, R A Bark, J Kau, F Komati, E A Lawrie, J J Lawrie, P Maine, A Minkova, S H T Murray, N J Ncapayi, P Vymers. The Double Vacuum in Rare Earth Transitional


210

Nuclei, Lack of β-Vibrations and Consequences for Phonon Interpretations. 17th International Symposium on Radiopharma-ceutical Sciences, Aachen, Germany, 30 April - 4 May 2007 D D Rossouw. Utilization of an iodovinyl unit in the radioiodination of a small peptide. International Conference on Nuclear Data for Science and Technology, Nice, France, 20 April 2007 1. F Szelecsényi, G F Steyn, Z Kovács and T N

van der Walt. Application of Au + p nuclear reactions for proton beam monitoring up to 70 MeV.

2. F Szelecsényi, G F Steyn, K Suzuki, Z Kovács,

T N van der Walt, C Vermeulen, N P van der Meulen, S G Dolley and K Mukai. Application of Zn + p reactions for production of copper radioisotopes for medical studies.

3. G F Steyn, N P van der Meulen, T N van der

Walt and C Vermeulen. Production of carrier-free 28Mg by 50 - 200 MeV protons on natCl: Excitation function and target optimization.

4. I Spahn, G F Steyn, H H Coenen and S M Qaim.

New nuclear data for production of 73As, 88Y and 153Sm: important radionuclides for environmental and medical applications.

SAAPMB Conference, Pretoria, 6-8 June 2007 1. A Baeyens, J P Slabbert, P Willem, S Jozela, D

van der Merve, A Vral. Radiosensitivity of lymphocytes in HIV-positive individuals.

2. W Groenewald, B de Villiers, A Rossouw, J P

Slabbert. Medical response to radiation emergencies: Establishing a Radiation Emergency Medical Advisory Centre of Southern Africa (REMACSA).

South African Young Nuclear Professionals Regional Conference, Midrand, Gauteng, 3-7 November 2007 T T Sebeela, J P Slabbert, A M Serafin, J Symons. Variations in the radiosensitivity of prostate cell lines to neutrons and X-rays. Journées de Radiobiologie Appliquée, Centre de Recherche Nucléaire d’Alger (Algeria), February 27-28, 2007 J Gueulette. Bases radiobiologiques de la radiothérapie: état de l'art. Workshop on "Activation d'éléments lourds et amplifications des altérations radiobiologiques", ENGREF, Amphi B 208, Paris, France, 12 March 2008 J Gueulette, J Martinez, B M de Coster, J P Slabbert. Expériences radiobiologiques dans un faisceau clinique de protons Groupe de travail "Biologie des Radiations" MELUSYN.


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4.4 Colloquia and Talks Materials Research Group 1. B Ngom Diop. Optical and structural properties

of PLD ZnO:m Nanostructures, University of Cheikh Anta Diop-Dakar, Senegal and University of the Western Cape, 22 May 2007.

2. T Ntsoane. Optical and structural properties of PLD ZnO:m Nanostructures, University of Cape Town and iThemba LABS, MRG, 30 May 2007.

3. M Ntwaeaborwa. Sol-gel synthesis and

luminescent properties of nanomaterials, University of the Free State, 06 June 2007

4. E Sideras-Haddad. Nanotechnology and

quantum information system using the EBIT facility at Berkeley, University of the Witwatersrand, 27 September 2007.

5. C Theron. Materials research program at De-

Beers Element Six, Element Six, October 2007. 6. S Halindintwali. Thin Films and Nano-catalysts:

Electrical Properties of Semiconductors, nano-crystalline and armorphous silicon, University of the Western Cape, 17 October 2007.

7. N Ostrovski. Electrical Transport Measurement

Capability of Keithly Products, World Test Systems, 20 February 2008.

8. B Ngom Diop. W doped ZnO Nano-coating by PLD, University of the Western Cape and iThemba LABS, MRG, 05 March 2008.

9. C B Mtshali. C60 based nano-structures by molecular recognition and self-assembly, University of Zululand, 12 March 2008.

10. M Msimanga. Progress in the development of a

Time of flight-Energy (TOF-E) spectrometer for applications in Heavy Ion – Elastic Recoil Detection (HI-ERD) thin film analysis.

11. J Jacobson. IBA Techniques in Archeometry

McGregor Museum, Kimberley, 26 March 2007.

12. J Sithole. Synthesis of size/shape and their effects on linear optical properties of ZnO nanoparticles using aqueous solution method, University of the Western Cape, 31 March 2008.

Radiation Biophysics Group 1. M S Rossouw, A Vral, P Willems, H Thierens, J

P Slabbert. Automated image analysis of lymphocytes to detect radiation-induced micronuclei University of Stellenbosch Academic Year Day, Tygerberg, South Africa, 15-16 August 2007.

2. W Groenewald, B de Villiers, A Rossouw, J P Slabbert. Medical response to radiation emergencies: Establishing a Radiation Emergency Medical Advisory Centre of Southern Africa (REMACSA) University of Stellenbosch Academic Year Day, Tygerberg, South Africa, 15-16 August 2007.

3. A Baeyens, J P Slabbert, P Willem, D van der

Merwe, S Jozela, P MacPhail. Radiosensitivity of lymphocytes in HIV-positive individuals University of Stellenbosch Academic Year Day, Tygerberg, South Africa, 15-16 August 2007.

4. P Willem. Stable radiation damage in air crew and genetic instability in the eye of molecular cytogenetics iThemba LABS, 16 May 2007.


212

4.5 Post Graduate Training Degrees Awarded iThemba LABS (Gauteng) MSc M Muundjua PhD A da Costa M Madhuku Materials Research Group BSc (Honours)

1. S M Mashego: The association of hydrocarbons and mineralization in the South Reef at Doornkop Section, Witwatersrand Basin, South Africa. University of the Witwatersrand

2. S. Ntshangase: Association between

hydrocarbons and mineralization in the “Carbon Leader Reef”, Witwatersrand Basin. University of the Witwatersrand

MSc 1. C Freeman: A Single Photon Source, University

of KwaZulu-Natal, April 2007. 2. C Durrheim: Photometry and characteristics of

tubular fluorescent lamps, University of KwaZulu-Natal, April 2007.

3. K Mbela: The geometry effect and vortex pinning in high-Tc superconductors, University of KwaZulu-Natal, March 2008.

4. G G Hailu, The study of porphyrins confinement in nafion membranes, Addis Ababa University, Ethiopia, April 2007

5. S Lafane: Plasma studies of laser ablated SmNdNiO3, University of Bab Ezzouar-Algeria, Algeria, March 2007.

6. S Mundenda: Development and

Characterization of bio-ceramics for Medical and Dental Applications, University of the Western Cape, June 2007.

7. H Ahmed: Controlling CoSi2 Formation

Temperature by Reaction Deposition, University of Cape Town, December 2007.

8. S Govender: Micro PIXE analyses of furnace and converter mattes for the determination of trace element distribution and concentrations University of Zululand.

PhD 1. A S Didi: Magnetooptical properties of quantum

dots, Morocco University of dhar El Mehrez-Morocco (2007).

2. L Jarvis: The granularity problem in ceramic oxide superconductors, University of KwaZulu-Natal, April 2007.

3. J Msomi: The magnetic properties of mixed ferrites, University of KwaZulu-Natal, March 2008.

Physics Group MSc 1. M J Dlamini, Production of C, N and O

fragments in the interaction of 12C with 12C at an incident energy of 200 MeV, University of Zululand, 2007.

2. O Shirinda, Signature inversion in the 186-194Au nuclei predicted by the TRS and CSM calculations, University of the Western Cape, 2007.

3. A D Joseph, Radiometry of soil – The

systematic effects, University of the Western Cape, 2007.

4. R F Manavhela, In-situ measurements of

radon concentrations in soil gas at a site on the Cape flats, University of the Western Cape, 2007.

5. N B Mbatha, Radiometric study of beach sand deposits along the coast of Western Cape Province, South Africa, University of the Western Cape, 2007.

6. B M Msezane, DCO ratios and linear polarization measurements in 196Hg, University of the Western Cape, 2007.


213

7. I N Hlatshwayo , In situ gamma-ray mapping at iThemba LABS, University of the Zululand, 2007.

8. T M Masikhwa, Inclusive (p, α) and (p,3He)

cross sections induced by 100 MeV protons on 40Ca, University of the Western Cape, 2007.

9. J J van Zyl, The role of a knockout mechanism in the (p,3He) reaction, University of Stellenbosch, 2008.

Medical Radiation MSc B-M van Wyk: Verifying Stereo Vision Using Structure from Motion. Radiation Biophysics Group MSc 1. E Seane: Radiobiology of neutrons and

protons, Cape Peninsula University of Technology.

Radioisotope Production MSc 1. C Vermeulen, Production of 139Pr and 139Ce in

proton induced reactions on natPr and natLa targets, University of Stellenbosch.

PhD 1. N P van der Meulen, The Cyclotron Production

of Selected Radionuclides using Medium Energy Protons. University of Stellenbosch, March 2008.

Postgraduate Students Medical Radiation MSc R Mlambo L van der Bijl B-M van Wyk S Tsoeu K Peko M Seotsanyana C Trauernicht

PhD M A Herbert iThemba LABS (Gauteng) MSc KG Sekonya Feleke Mekiso FN Shangase M C S Muthejwara N Mlambo K Buthelezi M Jingo O Kureba T Tjebane PhD T Jili D Gxawu M Butler D Mavunda Materials Research Group BSc (Hons.) 1. M. Naude, University of Stellenbosch 2. S. Mashego, The association of hydrocarbons

and mineralization in the South Reef at Doornkop Section, Witwatersrand Basin, South Africa. University of the Witwatersrand.

3. S. Ntshangase, Association between hydrocarbons and mineralization in the “Carbon Leader Reef”, Witwatersrand Basin. University of the Witwatersrand.

MSc 1. I Mabuda, Determination of boron by 11B (p,

α)8Be nuclear reaction, University of the Western Cape.

2. Z M Khumalo, Nano structured of undoped and

dopers ZNO University of Zululand.

3. H M Cele, Photometry and characteristics of tubular fluorescent lamps, University of Zululand.

4. B Zulu, The geometry effect and vortex pinning in high-Tc superconductors, University of Zululand.


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5. C Masina, Phase transformation in aluminum-platinum single and multilayer structures, University of Zululand.

6. N P Mongwaketsi: Micro-Pixe Study of Arbuscular

Mycorrhiza Influence on Elemental uptake by Berkheya Coddii, University of North West

7. M Makgale: Nuclear Microprobe study of the exoskeleton role in metal elimination in insect, Epilachna cf nylanderi, University of North West.

8. P Mkwae, Fabrication and Characterization of

Zinc Oxide thin film diodes, University of Zululand.

9. S Nkosi, Effect of stress on properties of VO2

thin films, University of Zululand. 10. V Msomi, Vanadium dioxide thermochromic thin

film correlation between microstructure, electrical and optical properties, University of Zululand.

11. S G Sekonya, Characterization of Atmospheric aerosols at Khayelitsha using PIXE, University of the Witwatersrand.

12. A Pajor, Effects of nickel on reproductive

activity of the house cricket, Acheta domesticus (Orthoptera), University of Silesia, Poland.

13. B Moore, Fungal treatment of heavy metal

contaminated wastewater, Rhodes University.

14. Berkan Ozturk, Outgasing Analysis of Capsules containing Diamond Powder, Middle East Technical University.

15. M Modise, Application of X-ray microanalysis to study the influence of heavy metals on cellular processes in selected insects, University of North West.

16. J Chamier, Electrochemical evaluation of composite carbon membranes for desalination processes, University of Stellenbosch.

17. O Adegbite, Elemental impurities in pulverized metallurgical silicon, University of Cape Town.

18. M. Desai, University of KwaZulu-Natal

19. S. Govender, Micro PIXE analyses of furnace

and converter mattes for the determination of trace element distribution and concentrations. University of Zululand.

PhD 1. M Msimanga, Development of a Heavy Ion-

Elastic Recoil Detection (HI-ERD) system for applications in thin film analysis, University of Cape Town.

2. T Ntsoane, Influence of simulated-body fluids on the residual stress behavior of plasma-sprayed hydroxyapatite coatings, University of Cape Town.

3. P Sechogela, Synthesis and characterization of

VO2 implanted in ZnO by ion implantation, University of the Western Cape.

4. J B Kana Kana, Novel class of tunable and

reversible AuVO2 and AgVO2 based ultra-fast nano-plasmonics, University of the Western Cape.

5. B Ngom Diop, Infra-red Active nicolate-based

nano-switching for ultra-fast laser source, University of the Western Cape.

6. J Sithole, The Study of Physical Properties of

doped Zinc-Oxides, University of the Western Cape.

7. P Sibuyi, Study of the behavior of TRISO coated

fuel particles & thermal Induced interfacial diffusion Phenomena in PBMR, University of Zululand.

8. C B Mtshali, C60-based nanostructures by

molecular recognition of self assembly, University of Zululand.

9. C Ndlangamandla, The design of advanced

metal oxide of Iron oxide nanomaterials, thin films coating for production of hydrogen gas and its storage devices, University of Zululand.

10. K Saleh, Nanostructures Photonics Applications,

Hassan II Mohammedia University, Morocco.

11. M Williams, Palladium-composite membranes for the separation of hydrogen from gas mixtures, University of the Western Cape.

12. H Ahmed, The role of reactive deposition in

determining the physical properties of thin films, University of Cape Town, March 2008.

13. N Ntshangase, The effects of irradiation of hot

and cold neutrons for PBMR fuel studies by synchrotron radiation, University of Zululand.


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14. K Cloete, Effect of a soil yeast, Cryptococcus laurentii, on growth and nutrition of Agathosma betulina, University of Stellenbosch.

15. T Nqcabaza, AFM study of polymer phase

separation, Center for Scientific and Industrial Research (CSIR).

16. P Koosaletse-Meswela, Profiling metal ions in

leaves of plants grown in the mineralized northern zones of Botswana, University of Botswana, Gaborone, Botswana.

17. S J Moloi, Semiconductor devices on defect

engineered crystalline silicon, University of North West.

18. C Mshumi, Effects of crystallographic ordering

on mechanical properties of Pt alloys, University of the Western Cape.

19. T Muller, XRD-Phase analysis of aluminium and

nickel silicides on armorphous silicon and glass substrates, University of the Western Cape.

20. L Jarvis, The granularity problem in ceramic

oxide superconductors, University of KwaZulu-Natal.

21. J Msomi, The magnetic properties of mixed

ferrites, University of KwaZulu-Natal.

22. S Kanu, Studies of nodule formation and N2 fixation in the tribe Psoraleae, Tshwane University of Technology

23. J Martinovac, Investigation of using cobalt dendrimer as a redox mediator in impedimetric ELC DNA biosensors, University of the Western Cape.

24. F Dhlamini, CuInSe2 thin film modules,

University of Johannesburg.

25. D Drozdz-Gaj, Biomarkers of exposure to heavy metals and a pesticide (merthiocarb) in selected organs of terrestrial snails, University of Silesia, Poland .

26. Ms K. Michalczyk, University of Silesia, Poland

27. Mr T. Sawczyn, University of Silesia, Poland 28. P Raath, University of Stellenbosch

29. G Wojtczak, Jagiellonian University, Krakow,

Poland 30. I Jerzykowska, Jagiellonian University, Krakow,

Poland Physics Group MSc 1. A D Joseph, Radiometric study of soils, University of the Western Cape. 2. I N Hlatshwayo, In situ gamma-ray mapping at iThemba LABS, University of Zululand. 3. R F Manavela, Systematic effects affecting radon in soil gas: measurements and modelling, University of the Western Cape. 4. T M Masikhwa, Inclusive (p,α) and (p,3He) cross sections induced by 100 MeV protons on 40Ca, University of the Western Cape. 5. N B Mbatha Radiometric study of beach sand deposits along the coast of Western Cape Province, South Africa, University of the Western Cape 6. O Shirinda, Signature inversion in the odd-odd Au nuclei predicted by the TRS and CSM calculations, University of the Western Cape. 7. T D Singo, Non-yrast states in 160Yb, University of Cape Town 8. B Adam Monte Carlo simulations of the D-line vault, University of Cape Town 9. T E Madiba, DCO and linear polarization measurements in 190Tl , University of the Western Cape. 10. S Bvumbi Nuclear structure of 152Gd, University of the Western Cape 11. J P Mira, Production of Li, Be and B in the interaction of 12C and 12C at incident energies of 200 and 400 MeV, University of the Western Cape.


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12. M J Dlamini, Production of C, N and O fragments in the interaction of 12C with 12C at an incident energy of 200 MeV, University of Zululand.

13. B M Msezane DCO ratios and linear

polarization measurements in 196Hg, University of Zululand

PhD 1. N Botha, M1 states in 56Fe and Gamow-

Teller states in its neighbouring nuclei in the A = 56 mass region, University of the Cape Town (part-time).

2. N Mlwilo, Radiometric characterization of

soil, University of the Western Cape. 3. S S Ntshangase, Development and

application of a recoil detector to study levels in 195-197Po nuclei, University of Cape Town.

4. S A Talha, Uses of radon in water resource

management, University of the Western Cape.

5. D de Villiers, The application of naturally

occurring radioactivity in the mining industry, University of Stellenbosch (part-time).

6. P A Vymers, Complementary electron and

gamma studies in the 197,198Tl nuclei, University of the Western Cape (part-time).

7. I Usman, Fine structure of the isoscalar

GQR for the low mass region 12 < A < 40, University of the Witwatersrand.

8. MA Stankiewicz Nuclear structure and

reaction dynamics with AFRODITE and DIAMANT, University of Cape Town

9. T T Ibrahim, Studies of clustering phenomena in nuclei, University of Stellenbosch.

10. P L Masiteng, Gamma spectroscopy of

oblate nuclei in A=190 mass region, University of the Western Cape .

Radiation Biophysics MSc/Mtech/MMed 1. Z Dashti, DNA labelling for the assessment of

cellular kinetics in different cancer cell types, University of the Western Cape.

2. R Swanson, Use of molecular markers for microscopic detection of centromeric regions of chromosomes, University of the Witwatersrand.

3. W Solomon, Flow cytometric and microscopic analysis of radiation-induced apoptosis in T-lymphocytes, Cape Peninsula University of Technology.

4. D Narinesingh, Use of Neutrons in Treatment

of Prostate Cancer, University of Stellenbosch. Radioisotope Production Group MTech 1. C Perrang, Separation of 88Y from 88Zr and Nb

target material, Cape Peninsula University of Technology.

2. M van Ryhn, The possible separation of

radioactive contaminants from waste water, Cape Peninsula University of Technology.

3. S G Dolley, Radiochemical Aspects to resolve a

problem in the determination of the cross section 68Zn(p,xn)64Cu, Cape Peninsula University of Technology.

4. L Taleli, Radiosynthesis of various

radioiodinated pyrimidine nucleoside derivatives and determining their uptakes into cells, Cape Peninsula University of Technology.

PhD 1. C Vermeulen, Development and modelling of

bombardment facilities at iThemba LABS, University of Stellenbosch.

2. S Mutsamwira, Separation of some elements by ion exchange chromatography using a synthesised ion exchange resin, Cape Peninsula University of Technology.


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4.6 Users and Collaborators

International Users and Collaborators Auburn University, Auburn, USA R Boyd

Addis-Ababa University, Addis-Ababa, Ethiopia G Tessema G Hailu

AF Ioffe Physico-Technical Institute RAS, St. Petersburg, Russia A A Pasternak A Efimov ATOMKI (Institute for Nuclear Research), Debrecen, Hungary B M Nyakó J Molnár J Timar J Gál G Berek G Kalinka A Krasznahorkay F Szelecsenyi Z Kovacs L Zolnai Australian National University, Canberra, Australia A Wilson P Davidson P Nieminen Brookhaven National Laboratory, The National Synchrotron Light Source, New York, USA K Evans-Lutterodt Bubble Technology Industries, Chalk River, Canada K Garrow

Catholic University Louvin, Brussels, Belgium J Gueulette A Wambersie B M de Coster A Vantomme J Demeulemister

D Smeets J Martinez V Grégoir Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria G Egharevba G Osinkolu S O Olabanji O O Akinwunmi A A Oladipo F I Ibitoye E I Obiajunwa A Fasasi Centre de Development des Technologies Avancees-Algiers, Algeria T Kerdja

CERN, Switzerland F Cerutti CSI, Switzerland G Fabaro

Cornerstone University, Michigan, USA N Crompton Deutches Krebsforschungzentrum, Heidelberg, Germany W Schlegel A Höss Deutsches Institut für Luft- und Raumfahrtmedizin, Köln, Germany G Reitz T Berger Dipartimento di Scienze Ambientali 'G Sarfatti', Università degli Studi di Siena, Italy A Chiarucci

EARTH Foundation, The Netherlands R J De Meijer Eduardo Mondlane University, Maputo, Mozambique JF Guambe


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Erasmus Hospital, Rotterdam, The Netherlands W A P Breeman Federal Office for Radiation Protection, Germany G Stephan Forschungszentrum Jülich GmbH, Jülich, Germany H Machner F Goldenbaum W Gast S Qaim I Spahn GSI, Germany T Radon HMI (Hahn-Meitner Institute), Berlin, Germany A Denker

Indian Institute of Sciences (IISc), Bangalore, India A Gosh

Insubria University, Milan, Italy P Perletti International Atomic Energy Agency, Vienna, Austria N Dytlewski IPN Orsay, Paris, France C Schück Ch Vieu E Khan Y Blumenfeld M Assie D Beaumel C Monrozau S Franchoo A Ramus J A Scarpaci F Azaiez Institut de Recherches Subatomique, France G Duchêne Jagiellonian University, Krakow , Poland M Michalik

K Turnau P Ryszka G Wojtczak E Kuta A Siuta G Tylko E Pyza I Jerzykowska Jawaharal Nehru Center for Advanced Scientific Research, Bangalore, India C N R Rao A Govindaraj

Joint Institute for Nuclear Research, Dubna, Russia O Meshkov S Yakovenko A Ogloblin S Shishkin Josef Stefan Institute, Ljubljana, Slovenia M Lipoglavšek A Likar M Vencelj T Vidmar J. Simčič P. Pelicon M. Budnar Korea Atomic Energy Research Institute, Jeongup-si, Daejeon, South Korea J S Chai S D Yang KTI, Stockholm, Sweden R Wyss Laboratori Nazionali di Legnaro, Instituto Nazionale di Fisca Nucleare,Legnaro, Italy A Dainelli,

Lawrence Berkeley National Laboratory Advanced Light Source, Berkeley, USA T Tyliszczak Los Alamos National Laboratory, Dept of Energy, Los Alamos USA M Nortier


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Lund Institute of Technology, Lund, Sweden BG Carlsson I Ragnarsson M D Anderson Cancer Center, Orlando, USA Dept of Radiation Physics K M Langen Medical College of Jaipur, India A Chougule MEDUSA Exploration BV, The Netherlands J Limburg R Koomans Michigan State University,East Lansing, USA B A Brown Museum of Natural History, Berlin, Germany U Reimold National Centre for Health and Environment, Neuherberg, Germany E Schmid Niels Bohr Institute, Copenhagen, Denmark G Sletten Nuclear Research Centre of Draria, Algiers, Algeria M Baalioumer B Meftah Institute of Physics, Polish Academy of Sciences, PL 02-668 Warsaw, Poland Prof Andrzej A Kortyka,,

Physikalisch-Technische Bundesanstalt, Braunschweig, Germany R Nolte B Wiegel, M Luszik-Bhadra S Röttger V Dangendorf RCNP, Osaka, Japan K Hatanaka A Tamii T Adachi M Matsubara

Royal Military College of Canada, Kingston, Canada L Bennet M Boudreau B Lewis Sudan University of Science & Technology, Department of Physics, Khartoum, Sudan M Eisa Sultan Qaboos University, College of Science, Oman K Bouziane S El Harthi

Sunnybrook Health Sciences Centre, Toronto, Canada J-P Pignol R Reilly The Synchrotron SOLEIL, France P Dumas V Briois Synchrotron Radiation Source (SRS), Surrey, United Kingdom A Korsunsky Technische Universität Darmstadt, Germany P von Neumann-Cosel, A Richter A Shevchenko V Yu Ponomarev J Wambach Y Kalmykov L Popescu I Poltoratska O Burda M Kuhar A Lenhardt Technical University of Clausthal, Clausthal-Zellerfeld, Germany R Labusch Molecular Biology Institute, University of Aarhus, Aarhus, Denmark C Cvitanich A Jurkiewicz J Stougaard


220

E Østergaard Jensen S Dam D Urbanski E Orłowska N Sandal UAE University, Abu Dahbi, United Arab Emirates K Meehan University of Baroda, India S Mukherjee K Kumar University of Birmingham, United Kingdom M Freer University of Burdan, West Bengal, India A Chaundhary University of Borbeaux, France J N Sheurer University of Botswana, Gaborone N Torto B Abegaz O Tortolo MP Setshogo University of Cambridge, Department of Physics, Cavendish Laboratory, United Kingdom M Pepper C Smith GAC Jones CB Ford I Farrer M Kataoka University of Camerino, Italy C Petrache M Fantuzi D Mengoni D Petrache University of Cape Coast, Ghana YS Mensah University Center of Medical Technology (UZMT), Ruhr-Universität Bochum, Germany Prof R B Heimann

University of Coimbra, Portugal Prof Cavaliero T Polchar

University of Cologne, Germany C Fransen N Pietralla KO Zell University of Copenhagen, Denmark S Husted University of Debrechen (Institute of Informatics), Hungary K Juhász University of Edinburgh, United Kingdom A Murphy University of Ghent, Ghent, Belgium A Vral P Willems B Thierens L de Ridder University of Groningen (Kernfysisch Versneller Instituut), The Netherlands H Wörtche University of Ibadan, Nigeria I Farai University of Istanbul, Turkey N Erduran B Akkus I Izgur University of Le Mans, France A Gibaud University of Lesotho, Maseru, Lesotho MC Matoetoe L Taleli L Machel N Manyala M Sekota


221

University of Ljubljana, Ljubljana, Slovenia M Regvar K Vogel-Mikuš P Pongrac University of Madrid, Spain N Schunk Université Cheikh Anta DIOP de Dakar, Senegal Département Physique/Faculté Sciences & Techniques S Ndiaye SC Beye University of Milan, Italy E Gadioli A Guglielmetti R Bassini E Gadioli-Erba P Colleoni University of Namibia, Windhoek, Namibia F Kavishe University of Notre Dame, USA G Berg M Wiescher S O’brien University of Osaka, Japan Y Fujita University of Oslo, Department of Chemistry, Norway G Wibetoe University of Oxford, United Kingdom B Buck AC Merchant P Hodgson University of Pavia, Italy A Mairani University of Silesia, Katowice, Poland P Migula M Augustyniak M Augustyniak M Nakonieczny M Tarnawska

J Juchimiuk A Babczyńska A Kafel T Sawczyn D Drozdz-Gaj K Michalczyk I Pajor E Głowacka J Klag M Rost-Roszkowska I Poprawa University of Sofia, Bulgaria D Balabanski A Minkova University of Surrey, Ion Beam Analysis, Surrey, United Kingdom C Jeynes University of Vienna, Department of Geology, Vienna, Austria C Koeberl University of Taiiwan, Department of Physics, Taiwan C T Liang University of Yaounde, Department of Physics, Cameroon J M Ndjaka University of York, United Kingdom B R Fulton S P Fox A Laird P Joshi D G Jenkins, F Johnson-Theasby R Wadsworth National University of Zambia, Zambia K Chinyama


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South African Users and Collaborators ARC-Infruitec, Stellenbosch T Blomefield Arnelia Farms, Hopefield, South Africa H Hettasch Cape Peninsula University of Technology W Solomons M Zerabruk B Mokaleng Z Jalali B Wyrley-Birch M von Aulock C le Roux D Gihwala T N van der Walt M R van Heerden C Liu Citrus Research International H Hofmeyr M Hofmeyr S Groenewald Constantiaberg Mediclinic, Cape Town R Mellvill CSIR (National Metrology Laboratory) – Cape Town B Simpson F Van Wyngaardt CSIR, Pretoria C Arendse S Sinha Ray T Hillie S Thema C Colvin P Hobbs A Maherry G Tredoux

The Deciduous Fruit Trust, South Africa P Raath

Department of Health S Olivier

Eskom P Frampton ISS International, Stellenbosch R van Rooyen Kimberley Museum, Kimberley, South Africa L Jacobson MINTEK, Advanced Materials Division, Randburg E van der Linden R Suss J Nell National Nuclear Regulator J Pule Necsa (Nuclear Energy Corporation of South Africa) J Nell P Segonyane C Franklyn F de Beer G K Mabala K P Maphoto North West University, Centre of Applied Radiation Science and Technology N. Mongwaketsi M. Modise M. Makgale Pretoria Academic Hospital, Pretoria M Sathekga Red Cross Children’s Hospital, Dept of Nuclear Medicine M M Mann Rhodes University J Burgess BA Moore South African National Accreditation System N Tayler Simonsig Wine Estate F Malan


223

Sun Space and Information Systems (Pty) Ltd N Steenkamp E Jansen K B Mathapo Tswane University of Technology N Cingo F Dakora S Kanu Tygerberg Hospital, Dept of Nuclear Medicine S Rubow J M Warwick University of Cape Town, Cape Town, South Africa M Cerf M. Cramer H Hawkins A Rodgers C Lang R Knutsen A Rodgers C Lang M Madziva J Visser A Hunter A Hendricks University of Cape Town, Dept of Physics D G Aschman M S Allie F D Brooks A Buffler, R W Fearick M Herbert M R Nchodu S M Perez S Wyngaardt S Jones S Walton I Govender T Volkwyn J Cleymans C Comrie D Britton M Harting H E Seals

University of Cape Town, Dept of Clinical Pathology J J Hille University of Cape Town, Dept of Radiation Oncology R Abratt E A Murray C E Stannard A L van Wijk K Marszalek J J P Maurel P Kraus University of Cape Town, Dept of Electrical Engineering and Instrumentation J Tapson University of Cape Town, Department of Astronomy M Inggs University of Cape Town, Dept of Medical Physics E Hering J K Hough University of the Free State, Dept of Radiation Oncology L Goedhals University of the Free State, Dept of Medical Physics A van Aswegen University of Free State M Ntwaeborwa D Ben R Luyt University of Johannesburg, Department of Geography, Environmental Management and Energy Studies H Annegarn University of Kwazulu Natal A J Smit M Desai


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University of Pretoria, Department of Radiation Oncology J A G Wilson University of Pretoria C Medlin University of Stellenbosch C Wright A Serafin W Groenewald B de Villiers EP Jacobs M W Bredenkamp P Swart S Govender U Buttner L Lorenzen Y Muntingh P Raath M Naude B du Plessis J Symons A Reinecke S Reinecke R Maleri A Botha K Cloete G Stevens R Rossow University of Stellenbosch, Dept of Physics A A Cowley D Heiss G C Hillhouse A Stander J J van Zyl J Bezuidenhout N M Jacobs University of Stellenbosch, Dept of Chemistry HG Raubenheimer University of Stellenbosch, Dept of Geology A Rozendaal University of Stellenbosch, Dept of Radiation Oncology and Tygerberg Hospital F J Vernimmen J K Harris

G Georgiev L Dupper P C van Eeden University of Stellenbosch, Dept of Applied Mathematics B Herbst University of the Western Cape K Streib M Tchokonte S Halindintwali J N Mugo G Balfour P Ndugu L Petric S Naidoo U Chikte M Williams J Mars S Naidoo L Petrik A Valentine M de Kock L August University of the Western Cape, Dept of Physics R Lindsay I Schroeder DG Roux J F Sharpey-Schafer D Knoesen R Majoe C. Kotsedi University of the Western Cape, Dept of Earth Sciences U Saeze University of the Western Cape, Dept of Radiobiology L August University of the Witwatersrand K Sekonya S Piketh J Sagalas P Willem D vd Merwe


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University of the Witwatersrand (School of Geophysics) G R J Cooper

University of the Witwatersrand, Dept of Physics J Carter S H Connell E Berdermann E Sideras-Haddad H Fujita F Makayi B Verhagen University of the Witwatersrand, Dept of Radiation Oncology, and Johannesburg General Hospital B Donde University of the Witwatersrand, Dept of Biomedical Engineering R Mlambo University of Venda, Dept of Physics I Matamba K P Mutshena University of Zululand, Dept of Physics and Engineering OM Ndwandwe O Nemraoui S Govender J Dlamini Unaffiliated CV Levin


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4.7 Staff List (as on 31 March 2008) DIRECTORATE Z Vilakazi (Managing Director) J Lawrie (Interim Deputy Director) E Hudson (Personal Assistant)

ACCELERATOR L Conradie (Group Head) P Celliers (Deputy Group Head) A Raman (Secretary)

Cyclotron & Beam Transport G de Villiers D de Villiers J Delsink

Cyclotron Operation D Fourie (Division Head) M Sakildien (Supervisor: Operations) L Anthony B Greyling S Eloff N Khumalo E van Oordt K Fortuin C Williams E Sauls H Anderson K Springhorn S Marsh C Doyle M Dire

Radio-Frequency J van Niekerk (Division Head) D April G Price H du Plessis

Diagnostic & Vacuum P Rohwer (Division Head) C Antonie R McAlister H du Toit G Pfeiffer P van Schalkwyk R Thomae A Botha M Smith

ELECTRONICS & INFORMATION TECHNOLOGY J Pilcher (Group Head) L Serutla (Deputy Group Head) S Watts (Secretary) N Rabe

Library & Information Systems N Haasbroek (Division Head) A Sauls W Zaal

Software Engineering M Hogan (Division Head) C Oliva C Pieters S Murray MA Crombie A Sook M Mvungi

Electronic Engineering (R & D) N Stodart (Division Head) H Mostert J van der Merwe P Petev S Stefanov P Cronje

Electronic Engineering (I & M) S du Toit (Division Head) H Gargan C Lussi M Klop J Solomons O Smith C Baartman H Klink P Davids R Pylman T Boloyi P Sheodass H Raman N Klaasen

Information Technology Support I Kohler (Division Head) J Krijt A Phillips R Michau M Robertson M van der Ventel


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FINANCE A Tyhali C Saaiman D Smith F Wallace L Sabsana

GENERAL ADMINISTRATION Y Manjoo (Business Manager) N Oliver (Secretary) E Mraqisa L Davids R Hendricks G Christians E Theunissen

Stores I Antonie (Supervisor) A Ntunzi

Safety, Health & Environment F Daniels (Division Head) J Fredericks I Stephanus B du Preez R Masiza A Lombard M Lots F September L Sidukwana ED Knoop (Supervisor: Housekeeping) J Aron S Klaaste D Theunissen E Sono S Silwanyane E Matoshwa S Magwa Z Diba T Tocke J Mncube

HOSPITAL P Fördelmann (Division Head) L Faviers A Lawrence E Booysen S February J Fuller S Rose L Nigrini L Arendorff E van Zyl S Daniels (Supervisor: Kitchen) J de Morney M Bond E Knoop O Lewis J Petro A Rhoda A Steyn M Turner F Fredericks (Supervisor: Housekeeping) S Daniels

HUMAN RESOURCES N Africa (Division Head) M Plaatjies S Mapela M van der Meulen B Msiza


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iTHEMBA LABS (GAUTENG) I Machi (Group Head) D Monyamane (Secretary) R Hart K Radebe N Hadebe M Lunga V Govender (Supervisor: Workshop) T Sibanyoni M Rebak T Mashego E Sideras-Haddad M Maine T Matsibiso K Balzun M Mthembu R Chirwa A Kwelilanga M Labuschagne N Makhathini P Chuma O Pekar

Environmental Isotopes Laboratory M Butler (Division Head) M Mabitsela O Malinga

MATERIALS RESEARCH R Nemutudi (Interim Group Head) L Cuba (Secretary) J Crafford L Ashworth J Mesjasz-Przybylowicz T Ntsoane M Maaza W Przybylowicz M Topic M Nkosi M Msimanga R Bucher P Sechogela J Sithole R Minnis A Barnabas (Research Associate) T Doyle (Research Associate)

MEDICAL RADIATION J Nieto-Camero (Interim Group Head) E van Ster (Secretary) D Jones

Operations & Treatment S Schroeder (Supervisor) S Rhoda M Loubser PC du Plessis

Treatment Planning & Development E de Kock (Division Head) J Symons M Swanepoel N Muller B Martin M Davids C van Tubbergh C Callaghan J Carstens

Clinical Research S de Canha (Division Head) D Commin (Supervisor) S Fredericks

PHYSICS R Newman (Interim Group Head) S Förtsch E Lawrie S Mullins F Gonglach R Smit R Bark R Neveling P Masiteng Z Buthelezi Y Kheswa I Hlatshwayo A Mohanty (Post-doc) E Lieder (Post-doc) P Papka (Post-doc) S Perez (Research Associate) A Cowley (Research Associate)


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RADIATION BIOPHYSICS K Slabbert (Division Head) A Baeyens (Post-Doc) J Akudugu (Post-Doc)

Radiation Protection D McGee (Division Head) T Kupi T Modisane E Mzuzu W Fredericks J Otto S Sam

RADIONUCLIDE PRODUCTION C Naidoo (Group Head) D Opperman (Secretary)

Radiopharmacy D Prince (Division Head) R de Wee C Davids X Mncedane G Sedres S Dyushu S Dolley A Pakati E Hlatshawyo M van Rhyn C Perrang

Physics & Targetry G Steyn (Division Head) E Isaacs N Dwane P Louw S Losper C Vermeulen S de Windt G Swarts D Saal

Radiochemistry N Rossouw (Division Head) N Van Der Meulen

SCIENCE & TECHNOLOGY AWARENESS G Arendse (Division Head) A Yaga R Linden

TECHNICAL SUPPORT SERVICES M Jakoet (Group Head)

Mechanical Engineering D Wyngaard (Division Head) P Paulsen (Supervisor: Workshop) S Bizwaphi L Adams M Williams D de Kock J van der Walt N Ndyalvane A du Plessis M Adams W Kearns E Ndyalvane J Augustine C Alexander

Site Services P Gardiner (Division Head) G September (Supervisor) J Pietersen J Petersen W Escourt A Daniels P Visagie R Adams J Jacobs D Arendse J Carelse V Nkhalashe P Naidoo I Joseph R Adams R Hendricks L Swartz Z Nogqala M Isaacs J Makhasi E Kanow L Ntuma (Apprentice) N Xhelo (Apprentice) N Mngqibisa (Apprentice) D Payn (Apprentice)

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