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Applied Radiation and Isotopes 67 (2009) 1348–1354

Contents lists available at ScienceDirect

Applied Radiation and Isotopes

0969-80

doi:10.1

� Corr

E-m

journal homepage: www.elsevier.com/locate/apradiso

Investigations of the natTi(p,x)43,44m,44g,46,47,48Sc,48V nuclearprocesses up to 40 MeV

M.U. Khandaker a,b, K. Kim a, M.W. Lee a, K.S. Kim a, G.N. Kim a,�, Y.S. Cho b, Y.O. Lee b

a Department of Physics, Kyungpook National University, Daegu 702-701, Republic of Koreab Nuclear Data Evaluation Laboratory, Korea Atomic Energy Research Institute, Daejeon 305-353, Republic of Korea

a r t i c l e i n f o

Keywords:

Natural titanium

Stacked target technique

40 MeV proton

Cyclotron

Vanadium

Scandium radionuclides

43/$ - see front matter & 2009 Elsevier Ltd. A

016/j.apradiso.2009.02.030

esponding author. Tel.: +82 539505320; fax:

ail address: gnkim@knu.ac.kr (G.N. Kim).

a b s t r a c t

Independent and cumulative production cross-sections for the natTi(p,x)48V, 43,44m,44g,46,47,48Sc nuclear

processes are reported here, for the energy region of 4–38 MeV by using a stacked-foil activation

technique. Measured data were critically compared with the earlier reported values, and also with the

theoretical data from the TALYS and ALICE-IPPE codes. The measured natTi(p,x)48V reaction is important

for charged particle beam monitoring purposes, whereas the 43,44,47Sc radionuclide have various

practical applications in nuclear medicine.

& 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Nuclear data relevant to important medical radionuclide canbe divided into two main categories: the decay data andthe nuclear reaction cross-sections. The suitability of a radio-nuclide for medical applications largely depends on the decaydata, whereas the production and radionuclidic quality controldepends on accurate data for the reaction cross-sections.In general, the decay data are known with sufficient accuracy,but the reaction cross-sections, especially the charged particleinduced ones, need more attention for the optimization of theestablished production routes and the development of new routes.In particular, the optimum production parameters for importantmedical radionuclide can be determined easily from measuredcross-sections and/or excitation functions. Conversely, the accu-racy of the measured excitation functions largely depends on theaccurate cross-sections of the monitor reactions. The natTi(p,x)48Vreaction is an ideal reaction for monitoring charged particle beamenergy and intensity for a low energy particle accelerator and/or amedical cyclotron (Tarkanyi et al., 2001). Therefore, precisemeasurements of the natTi(p,x)48V processes are required forvarious practical applications including charged particle activa-tion analysis.

Titanium (Ti), a light, strong, non-toxic, lustrous, white metal,has a wide array of practical applications in the industrial,aerospace (high strength-to-weight ratio), recreational, andemerging markets. It is widely used as a refractory and corrosionresistant metal. Moreover, this metal is a potential candidate for

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the production of medical radionuclides, such as 43Sc, 44Sc, 47Sc,and so on. The positron emitting radionuclide 43Sc (T1/2 ¼ 3.89 h;Eg ¼ 372.8 keV, Ig ¼ 22.5%; Ebþ ¼ 1198:5 keV, Ibþ ¼ 70:9%) couldbe used for an in vivo dosimetry. Grignon et al. (2007) reportedthat 44Sc (T1/2 ¼ 3.93 h; Eg ¼ 511 keV, Ig ¼ 188.68%; Ebþ ¼

1475:3 keV, Ibþ ¼ 94:34%) is the most interesting radionuclidefor nuclear medical imaging using b+g coincidences. Moreover,when it is associated with 47Sc, it could be used for a pre-therapeutic imaging. Furthermore, the 47Sc (T1/2 ¼ 3.35 d) radio-nuclide shows promising interest in radio-immunotherapy(Masuner et al., 1998) due to its suitable b� emission(Eb� ¼ 440:7 keV, Ib� ¼ 68:4%; Eb� ¼ 600:1 keV, Ib� ¼ 31:6%). Baeret al. (1984) used the 46Sc radionuclide as a labeled microspherefor an investigation of an increased number of myocardial bloodflow measurements, whereas this (46Sc) radionuclide was used asa radiotracer to analyze Lungs by Wehner et al. (1984). On theother hand, Mutsuo and Kazuhisa (2001) demonstrated thepotential use of 46Sc as a cosmogenic radionuclide for aninvestigation into the evolution history of chondrites afterseparation from their parent body. Moreover, Hichwa et al.(1995) investigated 48V (T1/2 ¼ 15.98 d) as an alternative to 68Gefor a routine transmission scanning in PET. Therefore, an accuratedetermination of the natTi(p,x)48V, 43,44m,44g,46,47,48Sc nuclearprocesses has great importance in the field of nuclear medicine,trace element analysis, radiation protection in space and onearth etc.

A detailed study has shown that various production pathways(such as, 43Sc from 43Ca(p,n), 44Ca(p,2n); 44Sc from 44Ti decay/generator, V, Ti(p,spallation) etc.) for the mentioned radionuclidesare available in the literature. Moreover, several authors(Barrandon et al., 1975; Brodzinski et al., 1971; Fink et al., 1990;Jung, 1991; Kopecky et al., 1993; Michel et al., 1978, 1997; Michel

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and Brinkmann, 1980; Szelecsenyi et al., 2001; Tarkanyi et al.,1991; Takacs et al., 2002; Walton et al., 1973, 1976) haveinvestigated the (p,x) processes using natural or enriched Titargets, but considerable discrepancies are found amongthem. Therefore, the aim of the present study was to reduce theexisting discrepancies among the various literature data, tovalidate the existing data for the important monitor reactionnatTi(p,x)48V, and finally, to report on a new data set for thenatTi(p,x)43,44m,44g,46,47,48Sc processes leading to various practicalapplications.

2. Experimental procedures

The experimental technique and the data evaluation procedurewere similar as described in our previous works (Khandaker et al.,2007; Uddin et al., 2008). Some important features relevant tothe present experiment are discussed as follows. The wellestablished stacked-foil activation technique combined with ahigh-resolution g-ray spectroscopy was employed to determinethe production cross-sections of the residual radionuclidesfrom a proton irradiation on natural Ti. A high-purity (99.98%)Ti foil (50-mm thickness, Nilaco Corp., Japan) with a naturalisotopic composition (46Ti 8.0%, 47Ti 7.3%, 48Ti 73.8%, 49Ti 5.5%, 50Ti5.4%) was used as the target for the irradiation. Monitor foils ofcopper (499.98% purity and 50-mm thickness, Nilaco Corp., Japan)and energy degrader foils of Al (99.999% purity and 100-mmthickness, Nilaco Corp., Japan) with known cross-sectionswere also included in the stack. In order to accurately measurethe beam flux and energy, two Cu foils (200-mm thickness)and an Al foil (200-mm thickness) were placed at the frontof the stack which consists of 10 groups of foils (Ti–Cu–Al–Ti–Al)and 2 groups of foils (Ti–Ti–Al–Ti–Al). The stacked-foils wereirradiated for 1.0 h with proton energy of 42.1 MeV and with abeam current of about 100 nA from an external beam lineof the MC-50 cyclotron at the KIRAMS. The beam intensitywas kept constant during the irradiation. It was necessary toensure that equal areas of the monitor and target foils interceptedthe beam.

Table 1Decay data of the residual radionuclides from proton activated titanium.

Radio nuclide Half-life (T1/2) Decay mode (%) g-energy, Eg (keV) g-int

48V 15.97 d EC (100) 944.13 7.

983.52 100

1312.1 97.

43Sc 3.89 h EC (100) 372.8 22.

44mSc 2.44 d IT (98.8) 271.1 86.

EC (1.2) 1002 1.44gSc 3.93 h EC (100) 1157.0 99.

46gSc 83.79 d b� (100) 889.28 99.

1120.55 99.

47Sc 3.35 d b� (100) 159.38 68.

48Sc 1.82 d b� (100) 175.36 7.

1037.52 97.

After the irradiations the targets and the monitor foils weremeasured by using a high-resolution (1.90 keV at FWHM for the1332.5-keV) g-ray spectrometer based on HpGe detector. TheHpGe-detector was coupled to a 4096 multi-channel analyzerwith the associated electronics to determine the photo-peak areaof the gamma-ray spectrum. The spectrum analysis was doneusing the Gamma Vision 5.0 (EG&G Ortec) program. The photo-peak efficiency curve of the g-spectrometer was calibrated with aset of standard point sources. The detection efficiencies as afunction of the photon energy were measured at 5–20 cmdistances from the end-cap of the detector to avoid coincidencelosses, and to assure a low dead time (o10%) and a point likegeometry. The measurements were repeated 3–4 times to followthe decay of the radionuclides and thereby to identify the possibleinterfering nuclides. The activity measurements of the irradiatedsamples were started at about 2.0 h after the end of thebombardment (EOB). This cooling time was enough to separatethe complex g-lines from the decay of the undesired short-livednuclides.

The proton beam intensity was determined by using themonitor reactions, 27Al(p,x)24Na and natCu(p,x)62Zn with knowncross-sections from the Tarkanyi et al. (2001). The use of multiplemonitor foils decreases the probability of introducing unknownsystematic uncertainties during an activity determination. Thebeam intensity was considered to be constant to deduce the cross-sections for each foil in the stack. The proton energy degradationalong the stack foils was calculated by using the computerprogram SRIM-2003 (Ziegler et al., 2003).

The cross-sections were determined with the well-knownactivation formula. The cross-sections include cumulative con-tributions from direct production on the different target isotopesand from complete decay of the short half-life parent radio-isotopes. The decay data of the radioactive products, such as thehalf-life (T1/2), the g-ray energy (Eg), and the g-ray emissionprobability (Ig) were taken from the NUDAT database (Kinseyet al., 1997) and are presented in Table 1. The threshold energiesgiven in Table 1 were taken from the Los Alamos NationalLaboratory, T-2 Nuclear Information Service on the Internet(http://t2.lanl.gov/data/qtool.html).

ensity, Ig (%) Contributing reactions Q-value (MeV) Threshold (MeV)

87 47Ti(p,g) 6.83 0.048Ti(p,n) �4.79 4.89

5 49Ti(p,2n) �12.93 13.2050Ti(p,3n) �23.88 24.36

5 46Ti(p,a) �3.07 3.1447Ti(p,na) �11.95 12.2148Ti(p,2na) �23.58 24.0749Ti(p,3na) �31.72 32.37

7 47Ti(p,a) �2.25 2.30

2 48Ti(p,na) �13.88 14.17

9 49Ti(p,2na) �22.02 22.4750Ti(p,3na) �32.96 33.63

98 47Ti(p,2p) �10.46 10.69

99 48Ti(p,3He) �14.37 14.6749Ti(p,a) �1.94 1.9850Ti(p,na) �12.87 13.13

3 48Ti(p,2p) �11.44 11.6849Ti(p,3He) �11.87 12.1150Ti(p,a) �2.23 2.28

48 49Ti(p,2p) �11.35 11.59

6 50Ti(p,3He) �14.58 14.87

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In the present experiment, all the uncertainties were con-sidered as independent. Consequently, they were quadraticallyadded according to the laws of an error propagation to obtain thetotal uncertainties. The uncertainty of the proton energy for eachfoil in the stack depends on the irradiation circumstances and theposition of the foil in the stack. Particularly, the uncertaintyrelevant to the proton energy was calculated from the uncertain-ties for the incident beam energy, the target thickness andhomogeneity, and the beam straggling. The estimated uncertaintyfor a representative point in the excitation function ranges from70.3 to 71.0 MeV. On the other hand, the combined uncertaintyin each cross-section was estimated by considering the followinguncertainties; statistical uncertainty of the g-ray counting(0.5–10%), uncertainty in the monitor flux (�7%), uncertainty inthe efficiency calibration of the detector (�4%) and so on. Theoverall uncertainties of the cross-sections measurements were inthe range of 8–16%.

Fig. 1. Excitation function for the natTi(p,x)48V processes.

3. Theoretical calculations

The measured excitation functions from the natTi(p,x) pro-cesses were fitted using the model calculations by the TALYS andALICE-IPPE codes. An overview relevant those are as follows:

The TALYS (Koning et al., 2005) is a computer code systemwhich can basically simulate all types of nuclear reactions in theenergy region of 1 keV–200 MeV. The accuracy of the computersimulations for nucleon-induced reactions largely depends on theemployed nuclear models and their parameters, which canbe taken from the literature or a comprehensive database, suchas the Reference Input Parameter Library (RIPL). With a fewexceptions, the TALYS database is based on the RIPL-2 (http://www-nds.iaea.org/RIPL-2/). In TALYS, the coupled-channel code,Sequential Iteration for Coupled Equations (ECIS-97) (Raynal,1994) is used as a subroutine for all the optical models and directreaction calculations. The default optical-model potentials (OMP)used in TALYS are the local and global parameterizations forneutrons and protons (Koning and Delaroche, 2003) but we canadjust the parameters on demand. All types of compound nucleusreaction mechanisms are included in this code where thecalculations are mostly based on the Hauser and Feshbach(1952) formalism including width fluctuation corrections (WFC).In TALYS, several models for the level densities are introduced;whereas Gilbert and Cameron (1965) model for level density isused as default. For nucleon reactions, a two-component excitonmodel with a new form of the internal transition rates based onthe OMP is implemented, which yields an improved description ofthe pre-equilibrium processes over the whole energy range. Themultiple pre-equilibrium processes are accomplished by keepingtrack of all the successive particle-hole excitations for eitherprotons or neutrons. For a nuclear reaction mechanism involvingprojectiles and ejectiles with different particle numbers like thestripping, pick-up, and knock-out processes, and for a predictionof the pre-equilibrium angular distributions, the newly developedKalbach (1988, 2005) phenomenological systematics are includedin this code. An independent treatment of an isomeric statecross-section is the main advantage of this code. The presentresults for the p+natTi processes were mostly evaluated using thedefault values of various models (such as pre-equilibrium model,level density model, etc.) of this code.

Furthermore, the measured data was also compared with thetheoretical data taken from the MENDL-2P database (Dityuk et al.,1998) calculated by using the ALICE-IPPE code. The ALICE-IPPEcode is a modified version of ALICE-91 proposed by the Obninskgroup (Dityuk et al., 1998). The calculation of a cross-section usingthis code was based on the Weisskopf–Ewing evaporation model

and a geometry dependent hybrid exciton model (Blann andVonach, 1983). Pre-equilibrium cluster emission calculation isincluded in this code. The lack of angular momentum and paritytreatments in the Weisskopf–Ewing formalism used in thesecodes makes an independent treatment of isomeric statesimpossible, thus only the total production cross-sections werecalculated. The individual results of the present reactions ofinterest were weighted and summed according to the abundanceof the target isotopes.

4. Results and discussions

The proton irradiation on natural Ti resulted in the productionof vanadium (V) and scandium (Sc) radionuclide through the(p,xn) and (p,axn) processes, respectively. A new data set for theformation of the 48V and 43,44m,44g,46,47,48Sc radionuclide throughthe natTi(p,xn) processes were measured in the energy region of4–40 MeV. In some cases, two or more g-rays were used for themeasurement of each reaction cross-section, and the averagevalue is presented. Some of the radionuclides are formed as aresult of the cumulative processes through mostly an IT decay ofthe metastable states and/or a contribution of the parent nuclidesin the production process. The excitation functions of theinvestigated radioactive products 48V and 43,44m,44g,46,47,48Scare shown in Figs. 1–7 together with the available literature data,the evaluated data by the computer code TALYS, and thetheoretical data taken from the calculations based on the ALICE-IPPE code. The numerical data with errors are presented in Table 2.The integral yields were deduced using the measured cross-sections by taking into account that the total energy is absorbed inthe targets, and they are shown in Figs. 8–10.

4.1. Production of 48V

The long-lived radionuclide 48V (T1/2 ¼ 15.97 d) completelydecays to the stable 48Ti nuclide by 100% EC process. Theformation of the 48V radionuclide is only contributed to by severaldirect reactions: 47Ti(p,g) (Q ¼ 6.83 MeV), 48Ti(p,n) (Q ¼ �4.79 MeV),49Ti(p,2n) (Q ¼ �12.93 MeV), and 50Ti(p,3n) (Q ¼ �23.88 MeV).The radionuclide 48V was identified by using the independentgamma lines of 983.52 and 1312.1 keV, and the average value ispresented. The measured excitation function of 48V is shown inFig. 1 together with the data available in the literature, thetheoretical data from the model calculations by the TALYS and theALICE-IPPE codes. A good overall agreement is found with most ofthe literature data mentioned in Fig. 1 except for few points

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Fig. 2. Excitation function for the natTi(p,x)43Sc processes.

Fig. 3. Excitation function for the natTi(p,x)44mSc processes.

Fig. 4. Excitation function for the natTi(p,x)44gSc processes.Fig. 7. Excitation function for the natTi(p,x)48Sc processes.

Fig. 6. Excitation function for the natTi(p,x)47Sc processes.

Fig. 5. Excitation function for the natTi(p,x)46gSc processes.

M.U. Khandaker et al. / Applied Radiation and Isotopes 67 (2009) 1348–1354 1351

reported by Brodzinski et al. (1971), Walton et al. (1973), Tarkanyiet al. (1991), and Kopecky et al. (1993). We found an excellentagreement with the IAEA recommended data for the wholeinvestigated energy region. The model code TALYS produce abetter fitted excitation function with the measured data compareto the ALICE-IPPE code predicted ones. An analysis of thecontributing reactions signify that the maximum around 12 MeVis highly contributed to by the 48Ti(p,n) (Q ¼ �4.79 MeV) reaction.Numerous authors investigated natTi(p,x)48V processes due to the

importance of this reaction for the charged particle beammonitoring applications.

4.2. Production of 43Sc

The short-lived radionuclide 43Sc (T1/2 ¼ 3.89 h) was identifiedthrough an analysis of the 372.8 keV g-line. The population of thisradionuclide is only contributed to by the direct nuclear reactions

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Table 2Measured cross-sections for the 43,44m,44g,46g,47,48Sc and 48V radionuclides.

Energy Cross-sections (mb) with uncertainties

MeV 48V 43Sc 44mSc 44gSc 46gSc 47Sc 48Sc

37.870.3 44.073.7 9.271.8 16.771.2 43.373.4 48.274.9 22.771.7 1.0070.21

36.170.3 45.574.0 7.171.4 17.271.3 46.173.6 42.474.5 23.771.8 0.9570.2

35.570.3 40.674.4 6.071.4 17.371.6 49.474.7 33.474.5 24.272.3 0.9970.18

33.870.4 43.773.8 4.871.3 17.171.3 52.374.0 24.273.6 24.571.8 0.7770.17

33.070.4 41.973.7 2.971.0 17.071.3 51.574.0 24.173.5 24.271.8 0.8970.19

31.270.4 41.073.8 3.171.0 15.071.1 51.173.9 15.973.1 22.971.7 0.7370.16

30.670.4 46.774.0 3.771.1 14.871.1 48.873.8 16.173.1 22.171.6 0.8270.16

28.670.5 50.474.2 4.371.3 12.170.9 47.073.7 15.573.0 19.371.4 0.6670.13

27.870.5 50.375.5 4.471.5 11.371.1 44.174.3 10.971.9 18.371.7 0.5270.13

25.870.5 56.476.0 3.371.1 8.670.8 34.673.4 12.272.1 14.871.4 0.3170.12

25.170.5 57.776.2 2.871.1 7.170.7 26.972.7 9.672.9 13.571.3 0.3070.10

22.970.6 68.677.3 2.571.1 3.070.3 11.171.3 9.471.8 9.470.9 0.2070.10

22.070.6 76.078.3 3.171.0 2.170.2 6.370.9 9.271.9 8.670.8 0.2870.10

19.670.6 110.7711.9 3.771.1 1.570.2 4.070.8 8.672.5 4.770.5 0.2070.09

18.770.7 144.2714.6 3.771.3 1.270.2 4.370.9 8.172.2 3.370.4 0.1370.07

16.170.7 268.5727.4 3.571.6 1.270.2 2.071.0 5.772.7 1.170.3

14.970.7 330.5733.3 3.471.8 0.870.2 4.771.0 3.772.3 0.970.3

11.970.8 383.8735.7 2.571.8 0.470.2 1.870.6 2.271.0 0.770.2

10.670.8 361.8732.5 2.271.4 0.370.1 1.570.7 2.071.5 0.670.3

6.770.9 62.575.4 0.870.5 0.1370.07 0.270.1 1.970.9 0.3970.14

5.870.9 23.172.5 0.1370.06 1.771.0 0.2570.1

3.971.0 4.370.9 0.1170.06 1.770.7 0.1570.08

Fig. 8. Integral yields for the 48V, 47Sc, and 44mSc radionuclides.

Fig. 9. Integral yields for the 46gSc and 48Sc radionuclides.

Fig. 10. Integral yields for the 44gSc and 43Sc radionuclides.

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presented in Table 1. The measured excitation function of thisradionuclide formation is shown in Fig. 2 together with theavailable literature data and the theoretical data from the model

code calculations. We found a good agreement with the datareported by Michel et al. (1978) and Kopecky et al. (1993). Theflat maximum around 15 MeV is from the contribution bythe 47Ti(p,na) (Q ¼ �11.95 MeV) reaction, whereas the secondmaximum around 28 MeV is mostly contributed to by the48Ti(p,2na)(Q ¼ �23.58 MeV) reaction. Both the codes TALYS andALICE-IPPE were unable to produce a reliable excitation functionfor this (43Sc) radionuclide production by natTi(p,x)43Sc processes.

4.3. Production of 44mSc

The radionuclide 44mSc (T1/2 ¼ 2.44 d) decays to it’s groundstate 44gSc by 98.8% IT process and to 44Ca by 1.2% EC process. Themoderate half-life of this radionuclide allows us to measure itproperly within the frame of the present experimental conditions.The strong and independent characteristic g-line 271.1 keV wasused to identify this radionuclide. The population of 44mSc is onlycontributed to by the direct nuclear reactions presented in Table 1.The measured excitation function of this radionuclide formation isshown in Fig. 3 together with the available literature data and thetheoretical data from the model code calculations. We found a

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very good agreement with all of the literature data mentioned inFig. 3 except only one point reported by Michel et al. (1997) at27 MeV. The model code TALYS produces a better fitted excitationfunction with this measurement compared to the ALICE-IPPEpredicted one.

4.4. Production of 44gSc

44Sc has a short-lived ground state radionuclide 44gSc(T1/2 ¼ 3.93 h) and a long-lived isomeric state 44mSc (T1/2 ¼ 2.44 d),whereas the isomeric state radionuclide decays to the groundstate by 98.8% IT process. The formation of the 44gSc radionuclideis also contributed to by the direct reaction channels 47Ti(p,a)(Q ¼ �2.25 MeV), 48Ti(p,na) (Q ¼ �13.88 MeV), 49Ti(p,2na)(Q ¼ �22.02 MeV) and 50Ti(p,3na) (Q ¼ �32.96 MeV). The mea-sured excitation function of 44gSc is shown in Fig. 4 together withthe available literature values and the data from the model codecalculations. The sharp maximum around 32 MeV is mostlycontributed to by the 48Ti(p,na) (Q ¼ �13.88 MeV) and 49Ti(p,2na)(Q ¼ �22.02 MeV) direct channels. We found a good agreementwith the literature data reported by Michel et al. (1978) andKopecky et al. (1993) for the whole investigated energy region.The theoretical calculations by the model code ALICE-IPPEproduce a better fitting in both the shape and absolute values ofthe excitation function with our measurements than the TALYScode predicted one. In fact, the TALYS code predicted theformation of 44gSc, whereas the ALICE-IPPE code predicted theformation of 44m+gSc. It is already mentioned that the isomericstate 44mSc has some IT contribution to the formation of theground state 44gSc, and the present measured cross-sectionsproved this fact.

4.5. Production of 46gSc

46Sc has a long-lived ground state radionuclide 46gSc(T1/2 ¼ 83.79 d) and a short-lived isomeric state 46mSc(T1/2 ¼ 18.75 s), whereas the isomeric state radionuclide comple-tely decays to the ground state by an IT process. Therefore,the measured cross-section of the 46gSc radionuclide is acumulative type. It was not possible for us to measure the 46mScradionuclide under the present experimental conditions. Themeasured excitation function of 46gSc is shown in Fig. 5 togetherwith the available literature values and the data from the modelcalculations. The formation of the 46gSc radionuclide is alsocontributed by the direct reaction channels presented in Table 1.The present results are in good agreement with the measured datareported by the authors Michel et al. (1978, 1997), Michel andBrinkmann (1980), Brodzinski et al. (1971), and Fink et al. (1990).The data calculated by the TALYS and ALICE-IPPE codes revealed agood agreement in the shape of the excitation function butslightly underestimated in magnitudes.

4.6. Production of 47Sc

The radionuclide 47Sc (T1/2 ¼ 3.35 d) decays to the stable 47Tiby b� (100%) emission. The moderate half-life of this radionuclideallows us to measure it properly within the frame of the presentexperimental conditions. The strong and independent character-istic g-line 159.38 keV was used to identify this radionuclide. Thepopulation of 47Sc is only contributed to by the direct nuclearreactions presented in Table 1. The measured excitation functionof this radionuclide formation is shown in Fig. 6 together with theavailable literature data and the theoretical data from the modelcode calculations. We found a good general agreement with thedata reported by several authors (Michel et al., 1978, 1997; Michel

and Brinkmann, 1980; Brodzinski et al., 1971; Fink et al., 1990;Kopecky et al., 1993) for the whole investigated energy region.Both the model code TALYS and ALICE-IPPE produced similarshape of excitation functions with the measured one butoverestimated and underestimated in magnitudes, respectively.

4.7. Production of 48Sc

The radionuclide 48Sc (T1/2 ¼ 1.82 d) has no isomeric state, anddecays to the stable 48Ti by b� (100%) emission. The moderatehalf-life of this radionuclide allows us to measure it properlywithin the frame of the present experimental conditions. Thestrong and independent g-lines of 983.53, 1037.52, and1312.12 keV were used to identify this radionuclide, and theaverage value is presented here. The population of 47Sc is onlycontributed to by the direct nuclear reactions presented in Table 1.The measured excitation function of this radionuclide formation isshown in Fig. 7 together with the available literature data and thetheoretical data from the model code calculations. No clearstructure and/or peak are found for this radionuclide productionwithin the present investigated energy region. We found a goodgeneral agreement with the data reported by the authors Michelet al. (1978, 1997) and Fink et al. (1990). The data reported byBrodzinski et al. (1971) showed quite discrepant value with allother measurements including this work. Both the model codeTALYS and ALICE-IPPE produced similar excitation functions inshape and magnitudes.

5. Integral yield

The integral yields for all investigated radionuclide werededuced using their measured cross-sections and the electronicstopping power of natTi over the energy range from a threshold to38 MeV by taking into account that the total energy is absorbed inthe targets. The deduced yield is expressed as MBq/mA h, i.e. theactivity at the EOB performed at a constant 1-mA beam current ona target during 1 h. The deduced yields are given in Figs. 8–10 as afunction of the proton energy with the directly measured thicktarget yield found in the literature. Dmitriev and Molin (1981)reported thick target integral yields for the 48V and 47,46Scradionuclide measured by irradiating thick natural Ti target with22.4 MeV proton beam. The used target was thick enough to coverthe energy ranges from threshold to 22.4 MeV. Furthermore,Sabbioni et al. (1977) measured thick target yield for the 47Sc and46gSc radionuclide from 44 MeV to down to the threshold values.The present results deduced from the measured excitationfunction revealed a general agreement with the directly measuredvalues by Dmitriev and Molin (1981) and Sabbioni et al. (1977).

6. Conclusions

Excitation functions for the formation of the 43,44m,44g,46,47,48Scand 48V radionuclides through the natTi(p,x) nuclear processeswere measured over the energy range 4–38 MeV using a stacked-foil activation technique with an overall uncertainty of about 16%.Measured data were critically compared with the availableliterature data and also with the theoretical data from the TALYSand ALICE-IPPE codes. The integral yields were also deduced byusing the measured cross-sections. It was possible to select thesuitable irradiation parameters for the optimum production of themedically important 47Sc radionuclide with minimum impuritylevel. Optimum production for the 47Sc radionuclide from thenatural titanium target was found as 12 MBq/mA h over the energyrange 33-22 MeV with �3% impurity from 46,48Sc. Therefore, a

ARTICLE IN PRESS

M.U. Khandaker et al. / Applied Radiation and Isotopes 67 (2009) 1348–13541354

low energy (o33 MeV) cyclotron and enriched 50Ti target could beused to produce large amount of 47Sc with minimum impurityfrom the simultaneously produced 46,48Sc radionuclides. On theother hand, the natTi(p,x)48V reaction can be advantageouslyutilized for monitoring the proton beam parameters under40 MeV. The IAEA recommended values for the natTi(p,x)48Vnuclear process was verified by the present investigations. Finally,the measured data for the natTi(p,x)48V, 43,44m,44g,46,47,48Sc nuclearprocesses could play an important role to enrich the literaturedata base leading to various practical applications.

Acknowledgments

This work was partly supported by the Korea Scienceand Engineering Foundation (KOSEF) through a Grant providedby the Korean Ministry of Education, Science and Technology(MEST) in 2007 and 2008 (Project nos. M207B020000810,M207M040001110, and M208M040001110). One of authors(G.N.K.) is partly supported by the KOSEF through theCenter for High Energy Physics (CHEP), Kyungpook NationalUniversity.

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