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Fusion Plasma Physics Annual Report 2005

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Fusion Plasma Physics

Annual Report 2005

Division of Fusion Plasma Physics Alfvén Laboratory

School of Electrical Engineering KTH

Stockholm, May 2006


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Division of Fusion Plasma Physics, Alfvén Laboratory, School of Electrical Engineering, KTH, 100 44 Stockholm, Sweden


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Contents 1. Highlights...................................................................................................................5 2. Introduction................................................................................................................6 3. Summary of research results......................................................................................8

3.1. EXTRAP T2R experiment................................................................................12 3.1.1. Active resistive wall mode control ............................................................13 3.1.2. Tearing mode dynamics.............................................................................19 3.1.3. Edge turbulence .........................................................................................20 3.1.4. Confinement...............................................................................................24 3.1.5. EFDA activity ............................................................................................25

3.2. Plasma-wall interactions ...................................................................................26 3.2.1. Material migration in operation with the MkII-SRP divertor....................26 3.2.2. Deposition and fuel inventory in C and Be MkI divertors.........................28 3.2.3. Characterisation of components after flash-light cleaning ........................29 3.2.4. First mirror test ..........................................................................................30 3.2.5. Fuel removal by helium-oxygen glow .......................................................31 3.2.6. Tungsten under plasma load: melt layer and droplet formation ................33 3.2.7. Deposition and fuel inventory in castellated tungsten limiter ...................34

3.3. Theoretical fusion plasma physics ....................................................................37 3.3.1. Fast particle excitation of global Alfvén eigenmodes................................37 3.3.2. FWCD experiments in JET ITB plasmas...................................................38 3.3.3. Parasitic absorption in FWCD experiments in JET ITB plasmas..............39 3.3.4. Minority ion cyclotron current drive in ITER............................................40 3.3.5. Ion cyclotron emission in toroidal plasmas ...............................................41 3.3.6. Analysis of JET experiments .....................................................................42 3.3.7. High- frequency TAE modes in the RFP device EXTRAP T2R...............43

3.4. Computational methods for fusion plasmas......................................................44 3.4.1. Numerical confinement scaling in the advanced RFP ...............................44 3.4.2. Semi-analytical solution of initial-value problems ....................................44

3.5. Chaos and self-organisation..............................................................................46 4. EFDA activity ..........................................................................................................47 5. International collaborations .....................................................................................49 6. Education and research training...............................................................................51

6.1. Undergraduate education ..................................................................................51 6.2. Graduate education ...........................................................................................53

7. Publications..............................................................................................................54 7.1. Peer-reviewed journal publications...................................................................54 7.2. Invited talks at international conferences .........................................................57 7.3. International conference contributions .............................................................59 7.4. Other publications.............................................................................................63

8. Staff..........................................................................................................................64 9. Professional activity.................................................................................................65 10. Economy ................................................................................................................68


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1. Highlights High scientific output The year 2005 has been very productive in terms of scientific output. Researchers at the Division of Fusion Plasma Physics have published 32 peer-reviewed journal articles, have been awarded 15 invited talks at international conferences and workshops, and have contributed 39 papers to international conference and workshop proceedings (orals and posters). ITER An important milestone in the ITER project was the signing of the agreement in June 2005 to site ITER in France. One researcher at the department is seconded to EFDA-CSU in Garching as liaison officer in the area of plasma diagnostics for ITER. EFDA-JET The Division is active at the European fusion research facility EFDA-JET, and three researchers have been seconded to EFDA-JET during 2005, participating in operations, experimental programme planning, and experiment modeling. Excellent research results • Very positive research results have been obtained at EXTRAP-T2R in

experiments with feedback control of MHD instabilities. The results, which are relevant for ITER, have received high attention in the fusion community. They have been published in Physical Review Letters and presented at the annual plasma physics conference organized by European Physical Society.

• Successful fast wave current drive experiments have been carried out at EFDA-JET in high temperature plasmas with enhanced confinement caused by internal transport barriers.

Graduate eduation • Martin Laxåback presented in February his PhD thesis "Fast wave heating and

current drive in tokamaks". The thesis subject is heating and current drive in tokamak plasmas using the fast magnetosonic wave in the ion cyclotron range of frequencies.

• Dmitriy Yadikin presented his Licentiate thesis "Feedback control of resistive wall modes in the reversed field pinch". The thesis deals with magnetohydrodynamic (MHD) instabilities and active feedback control methods.

Undergraduate education • The Division participates in the Erasmus Mundus European Master Programme in

Nuclear Fusion Science and Engineering Physics (FUSION-EP). The programme was granted during 2005 in competition with many other master programmes in the EU. The programme will start 2006.


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2. Introduction The European magnetic fusion research programme is based on the Euratom treaty and co-ordinated through Contracts of Associations with national research organisations (VR is the partner on the Swedish side). The European Fusion Development Agreement (EFDA) provides for fusion technology development, use of the Joint European Torus (JET) facility, establishment of European Task Forces (TF) and ITER activity. In addition, there are agreements for mobility of researchers and fellowships. The Contract of Association establishes a Research Unit (RU) within Sweden, which includes the Division of Fusion Plasma Physics. Decisions on activities are made by a Steering Committee with representation from the European Commission. The EU funding to the Division is based on cost sharing at various percentages where support from Swedish sources is necessary. Sweden participates in the European EFDA-JET project. The EFDA Work programme is the basis for the research at JET, which is organised in nine Task Forces. The Division is contributing by providing competence in Task Force “Heating” (TFH) with specialists in Ion Cyclotron Resonance Heating, in Task Force “Exhaust” (TFE) and Task Force “Fusion Technology” (TFFT) with expertise in Plasma -Wall Interaction and in Task Force “Diagnostics and Systems” (TFD) in Spectroscopy Diagnostics and Diagnostics development. Additionally our Division is starting involvement in the work of Task Force “MHD” (TFM) with expertise in Resistive Wall Modes. Fusion research conducted in the EU countries in certain strategic areas has recently been integrated into European Task Forces (TF). Two TFs have been formed so far: the “Integrated Tokamak Modelling” TF (ITM) and the “Plasma-Wall Interaction” TF (PWI). The Division is active in both these TFs. The Division leads a project for developing codes for “heating, current drive and fast particle phenomena”, one of seven projects within the ITM TF. It also co-ordinates several activities within the PWI TF related to the JET “ITER-like Wall Project”. The Division of Fusion Plasma Physics contributes directly to the European ITER programme with the secondment of one scientist at the EFDA Close Support Unit (CSU) in Garching bei München, Germany in the field of “Physics Integration” as liaison officer for ITER diagnostics. The Division is also involved in the EFDA Technology Programme within “Physics Integration” with specific tasks in the area “Plasma-Wall Interactions” and is involved in the development of RF heating through the ITER coordination committee for “Fast Wave Heating and Current Drive”. In addition, there are indirect contributions to ITER by participation in scientific programmes at JET that are dedicated to support ITER, including JET diagnostic upgrades. The experimental research is mainly carried out at the EXTRAP-T2R device located at Division of Fusion Plasma Physics, at the EFDA-JET facility at the Culham Science Centre, UK and at the TEXTOR tokamak in the Forschungszentrum Jülich (FZJ), Germany.


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The Division is host for one of the European priority experiments, the EXTRAP-T2R reversed field pinch device. About 42 Mkr has been invested between 1990 and 2001 with priority funding; 45% paid by Euratom and 55% by Swedish sources (FRN, NFR, VR, Wallenberg). EXTRAP-T2R has been upgraded during 2004-2005. A system for active control of resistive wall mode instabilities has been developed and installed on the device, in collaboration with Consorzio RFX at Padova, Italy. The EFDA work programme is the basis for the collective utilisation of the large JET tokamak facility at Culham Science Centre, UK. The Division of Fusion Plasma Physics is actively involved in EFDA-JET, mainly in the areas of “Plasma-wall interactions”, “RF Heating and current drive”, “RWM physics” and “Diagnostics development”. The Division is co-ordinating several activities within the “ITER-like Wall Project”. The Division contributes to the JET Operator (UKAEA) tasks by supplying competence of Session Leader. A scientist seconded from the Division is contributing as Deputy Leader for Task Force Diagnostics with the opportunity to define and execute the EFDA-JET Work programme within the competence of Task Force D and as Manager for one of the “Spectroscopy Enhancement” projects. Other staff is seconded to the EFDA Close Support Unit (CSU) Culham as a responsible officer within the Programme Department, with special responsibilities for the “Heating” Task Force, and under a JET Operation Contract (JOC) with responsibilities for developing integrated tools and performing numerical analysis of JET plasma discharges, particularly with respect to ion cyclotron heating and in relation to the installation of the new ITER-like RF antenna. Under a tri-lateral agreement between Germany, Belgium and the Netherlands, the TEXTOR tokamak is operated at Forschungszentrum Jülich (FZJ), Germany. The experimental programme of the medium sized device focuses on studies of plasma-wall interaction. A large part of the work involves ex-situ studies of probes that have been exposed to plasma discharge. Analysis of the surface provides information on erosion, deposition and co-deposition of fuel species.


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3. Summary of research results The research at the Division of Fusion Plasma Physics is well integrated into the European fusion programme. The research carried out at the Division during 2005 has been focused on projects that are within areas identified as having strategic importance for the EU programme, including projects on

• Tokamak modelling • MHD instability control • Plasma – wall interactions

The Division has contributed directly to the major EU project JET and the international ITER project by staff secondments, mainly in the fields of plasma diagnostics and tokamak modelling. The Division is maintaining a strong involvement in basic fusion plasma physics research, with emphasis on topics that are important also for the broader plasma physics community, such as studies of

• Plasma turbulence • Chaos and self-organisation • Computational methods for fusion plasmas

The main mile stones achieved during 2005 are listed below: EXTRAP T2R experimental studies on MHD mode control Main scientific results published in 2005: • Demonstration of feedback suppression of multiple RWMs. During the step-

wise installation of active coils on the device, experiments with partial coil arrays were carried out. The results have been very encouraging and are the first demonstration of simultaneous feedback stabilization of multiple resistive wall modes.

• Suppression of two linearly coupled modes with mode control feedback scheme. A feature of a control system using an array of coils is a linear mode coupling of side band modes. With the intelligent shell feedback scheme, the coupled modes are generally not controlled. Different layouts of coil arrays were used for a detailed study of the coupling effect, confirming the theoretical predictions.

• First demonstration of stabilization of the full range of unstable RWMs. With the full array of coils, a significant improvement of the efficiency of the control system is obtained, and control of the full range of unstable RWMs in the RFP has for the first time been demonstrated. The results have been presented at an invited talk at the EPS Plasma Physics Conference 2005.

• Response of resistive wall modes to applied perturbations. The use of pre-programmed non-axisymmetric external fields has allowed for the separation of the effects of intrinsic field errors from the natural plasma behavior. For the first time also the damping rates for stable RWMs have been estimated. The results


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have been compared with the linear cylindrical MHD model, and the agreement is satisfactory.

• Electromagnetic model for advanced active control methods. An electromagnetic model including the plasma, conducting structures, sensors and active control coils has been developed for EXTRAP T2R in collaboration with researchers at Consorzio RFX.

• Finite Element electromagnetic analysis of the conducting wall and control system. The electromagnetic characteristics of the control system are studied by means of a FE model.

MHD mode control system enhancements during 2005: • Active coil array: The 2004 configuration of 16x4=64coils (32 controlled output

signals) has been increased during 2005 to 32x4=128 coils (64 controlled output signals) corresponding to 100% coverage of the plasma surface.

• Power amplifiers: The system is based on broadband commercial audio amplifiers. The number of amplifier units has been increased from 16 to 32 giving a total of 64 output channels.

• Integrated digital control module: The integrated digital control module has been upgraded to include support for 64 controlled output signals. 1) ADC for analog input: 64 sensor signals, 64 coil current signals, 2) DAC for analog output: 64 amplifier control voltages. 4) Software for the following feedback control schemes:”Intelligent shell”: 64 independent PID-feedback control systems. ”Mode control”: FFT of 64 sensor signals, independent P-feedback control for individual Fourier modes, inverse FFT, output 64 control signals.

EXTRAP T2R experiments on edge turbulence and confinement Main scientific results: • Self-regulation of ExB flow shear via plasma turbulence. The momentum

balance has been applied to the ExB flow in the edge region. All terms, including those involving fluctuations, have been measured in EXTRAP T2R. It is found that the component of the Reynolds stress driven by electrostatic fluctuations is the term playing the major role in driving the shear of the ExB flow to a value marginal for turbulent suppression, so that the results are in favor of a turbulence self-regulating mechanism underlying the momentum balance at the edge.

• Reynolds and Maxwell stress measurements. The Reynolds stress exhibits a strong gradient in the region where a high ExB shear takes place. This has been interpreted as experimental evidence of flow generation via turbulence mechanism. The scales involved in flow generation are deduced from the frequency decomposition of the Reynolds stress tensor. They are found related to magnetohydrodynamic activity but are different with respect to the scales responsible for turbulent transport.

• Toroidal Alfvén Eigenmodes. The first clear observation of TAE in a RFP device has been obtained in measurements in the edge region with high frequency magnetic probes in EXTRAP T2R. A high frequency and high-n mode, which shows the proper time scaling, polarization, and phase properties of an edge resonant TAE has been observed. The model developed has a general validity. An important role is played by the local mass density.


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Plasma-wall interactions Scientific Achievements: • Detailed characterisation of erosion and deposition scenario in JET operated with

the MkII-SRP Septum Replacement Plate has been performed and the distribution of the injected carbon-13 (13CH4) transport marker has been quantified.

• Long-term fuel inventory and co-deposition in gaps and grooves separating PFC tiles has been quantified for the carbon and beryllium MkI divertors at JET. The impact of the gap width on the inventory was identified.

• Deposition and fuel inventory in the tungsten castellated limiters exposed at TEXTOR has been determined.

• Efficacy of fuel removal and surface state after cleaning have been determined for three techniques being developed for detritiation: photonic cleaning by flash lamp, laser-induced detritiation and oxygen-assisted desorption.

• Plasma impact on melt layer behaviour and dust formation was determined for tungsten exposed at TEXTOR.

• Beryllium coatings on inconel (for ILW) were developed and tested. Development of Research Facilities: New and Upgraded Equipment. • Ion microprobe has been brought to operation and used for studies of co-deposits

from JET. The facility is located at the Ångström Laboratory, Uppsala University. • The First Mirror Test for ITER is carried out at JET. All components were

installed in the torus. Photo-spectrometric equipment was procured and installed to enable studies of mirrors after their retrieval from the torus.

• Fast reciprocating probe system at TEXTOR has recently been upgraded by adding a specially designed transition piece between the transfer system and a head of the collector probe.

• Preparation of erosion-deposition diagnostic for ILW is under way. Theoretical fusion plasma physics • Non-linear study of fast particle excitation of global Alfvén eigenmodes. We

have simulated the dynamics of TAE excitation during ICRH and explained both the appearance of side bands by the decorrelation of the interactions between the fast ions and the renewal of the distribution function by cyclotron heating and the fast termination of the TAEs after the ICRH power was switched off.

• FWCD experiments in JET ITB plasmas. We have demonstrated FWCD on JET. FWCD had earlier been demonstrated on other machines, but not on JET, because of the frequency range of the JET generators and the good confinement of high-energy ions that parasitically absorb the wave due to the weak electron damping. FWCD was demonstrated in high temperature plasmas with internal transport barriers, ITBs, with strongly reversed magnetic shear with a low current density at the centre.

• Parasitic absorption in FWCD experiments in JET ITB plasmas. Evidences of large fractions of the lost power were found during the FWCD experiments from the energy balance between the energy coupled by the heating system and the sum


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of the radiated energy and the energy conducted to the divertor. Evidences of the lost power were also obtained from the strong Be-line radiation at the edge and the performance of discharges for similar heating power.

• Minority ion cyclotron current drive in ITER. Helium-3 minority ion cyclotron current drive (MICCD) at the low field side (LFS) q=1 flux surface is therefore considered for sawtooth destabilisation in ITER by locally increasing the magnetic shear.

• Ion cyclotron emission in toroidal plasmas. Emission in the ion cyclotron frequency range in tokamak plasmas is of interest because of its potential of using it for diagnostic purpose. The effect of the orbit topology on ion cyclotron emission, ICE, has also been studied.

Chaos and self-organisation • Transport barriers. The concept of ExB flow velocity shear suppression is

utterly fundamental in modern fusion research. It is asserted that there are models enabling to understand the physics involved in LH transitions. To improve the understanding of the mechanisms leading to formation of Transport Barriers, especially the relation between Internal and Edge barriers it is necessary to invoke the issue of electric fields. Edge transport barriers are the feature of the H-mode, the baseline regime of ITER, whereas Internal Transport Barriers are used to develop regimes that might be employed for steady state operation of ITER, definitely beneficial for design and operation of fusion power plants in the future. Their synergy is addressed.

Computational methods for fusion plasmas • Numerical computation of confinement scaling in the advanced RFP. In the

advanced RFP, tearing modes are diminished by the use of current profile control. In this theoretical study, the advanced RFP is examined by the use of numerical simulations, and scaling laws are derived for confinement parameters. The model is nonlinear MHD in 3D including finite resistivity and pressure. It is observed that the configuration spontaneously develops into a quasi single helicity (QSH) state. The current profile control scheme is designed to eliminate the fluctuating electric dynamo field Ef = - <vxB>, using feedback of an externally imposed electric field.


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3.1. EXTRAP T2R experiment H. Bergsåker, P. Brunsell, J. Brzozowski, M. Cecconello, J. R. Drake, E. Tennfors, D. Yadikin (PhD student), P. Ronquist (MSc student), O. Danielson (MSc student), P. Oen (MSc student) In collaboration with: E. Rachlew, M. Kuldkepp, S. Menmuir, Dept. Physics, KTH Y. Q. Liu, D. Gregoratto, Dept. Appl. Mechanics, Chalmers The EXTRAP T2R reversed field pinch (RFP) device at the Alfvén Laboratory received approval as a priority project in 1990. The experiment was operated through 1999 at which time the experiment was rebuilt and operation resumed in 2001. The goal of the modifications was to establish an experiment that can be used for the study of long-pulse operation with a resistive wall. EXTRAP T2R has been upgraded during 2004-2005. A system for active control of non-axisymmetric MHD instabilities has been developed and installed on the device, in collaboration with Consorzio RFX. Very positive initial results on active feedback control of Resistive Wall Modes (RWM) have been obtained during 2005 using the new system.

Figure 3.1.1. EXTRAP T2R vessel and shell during assembly at the Alfvén Laboratory, KTH during 2000. An extensive set of magnetic diagnostics are mounted directly on the outer surface of the vacuum vessel. Two-dimensional arrays of magnetic sensors at 4 poloidal and 64 toroidal positions measuring the three vector components are available.

Figure 3.1.2. Section of copper shell. Each layer is 0.5 mm thick. There are two layers with gaps displaced approximately 180 degrees to achieve passive shielding of field errors.

The scientific programme of the EXTRAP T2R device for 2005 includes three main areas:

• MHD mode control. Active mode control work primarily focuses on control of resistive wall mode instabilities. Real-time feedback systems will be further developed and studied using magnetic pick-up coil sensors for mode detection and arrays of saddle coils acting as actuators to control the growth of the unstable modes.


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• Edge turbulence. The edge turbulence studies focus on the statistical properties of electrostatic and magnetic turbulence in the plasma edge region based on measurements using electric and magnetic probes.

• Confinement. Improvement of confinement requires reduction of magnetic turbulence. Two methods studied are the use of pulsed poloidal current drive (PPCD) and achievement of quasi-single helicity (QSH) equilibria.

The RFP, like the Tokamak, is a toroidal configuration characterised by nested flux surfaces defined by a magnetic field with both toroidal and poloidal components. However, the RFP configuration is dependent on a close-fitting conducting wall for MHD stability. For a tokamak the stabilising effects of a conducting wall are not vital, but they can improve stability for pressure driven modes and thereby enhance confinement performance. The main parameters of the EXTRAP T2R device and the plasma parameters during experiments in 2005 were as follows:

• Major radius R=1.24 m. • Minor radius a=0.183 m. • Shell time constant τ=6.3 ms. • Plasma current Ip=80-120 kA. • Electron temperature Te=200-300 eV. • Pulse length up to 45 ms.

3.1.1. Active resistive wall mode control Background A major part of the experimental research programme at EXTRAP T2R is focussed on the development of methods for active control of resistive wall modes (RWM), a research area that is relevant for ITER. Active feedback suppression of resistive wall modes is of common interest for several fusion concepts relying on close conducting walls for stabilisation of ideal MHD modes, such the advanced tokamak, the RFP, the spherical torus and the spheromak. The research area is currently very active and the interest in the subject is boosted by the current view that plasma rotation in large tokamaks (such as ITER) will not be sufficient for passive stabilisation of the RWMs, and therefore studies of feedback methods are vital. The research at EXTRAP T2R addresses for example the critical issue of side band generation by the active coil array and the accompanying coupling of different unstable or weakly stable plasma modes through the feedback action. The obtained results, which are in basic agreement with the present theory models, are of interest for the broader magnetic fusion community, and provide a significant input to the understanding of the physics of RWM active feedback in various configurations. The main important features of the RWM studies at EXTRAP T2R that motivates the current research programme are, in summary:


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• EXTRAP T2R has a resistive wall and extensive magnetic diagnostics to measure mode spectra and growth rates. RWMs are observed and their growth rates are compared with theory.

• The research project is carried out in collaboration with the theory group at Dept. Appl. Mechanics, CTH and Consorzio RFX, Padova (developing advanced systems for real-time magnetic control).

• Studies of RWM feedback stabilisation in the RFP complement studies in tokamaks in several ways, e. g. as test bed for real-time active control hardware and software.

• Emphasis is on comparison of theory and experiment. Areas of research are evaluation of requirements for feedback laws based on harmonics and studies of the role of field error amplification.

The present programme is based on the results of initial studies of RWM feedback control on EXTRAP T2R: • Quantitative agreement between experimental and MHD growth rates is observed

for the RWMs that are intrinsically unstable in the magnetic configuration. • In addition, other modes are seen experimentally that grow from field errors

through ”field error amplification”. • Initial experiments on EXTRAP T2R with partial coverage of the plasma surface

with active coils demonstrated successfully the first simultaneous magnetic feedback suppression of several RWMs using an intelligent-shell type system (Published in Physical Review Letters 2004)

• The theoretical modelling done by the groups at CTH and RFX using the EXTRAP T2R experimental coil layout and measured RWM growth rates as input are in basic agreement with the experimental data.

Technical The MHD mode control system installed on EXTRAP T2R has been upgraded during 2005 and has now an excellent capability for mode control studies: • Sensor coils array: A two-dimensional sensor array at 4 poloidal and 64 toroidal

positions. Each sensor coil is a one-turn flux loop spanning 90° poloidally and 5.625° toroidally, measuring the radial magnetic flux at a radial position just inside the resisitve wall.

• Active saddle coil array: The number of active coils has been increased by a factor of two during 2005 and cover now fully the toroidal surface. It consists of a two-dimensional active coil array at 4 poloidal and 32 toroidal positions outside the resistive wall, with a total of 4x32=128 coils. The coil spans 90° poloidally and 11.25° toroidally. Saddle coils are m=1 pair-connected to form 2x32=64 independent coils. The L/R time constant of the coil is 1.0 ms. Each saddle coil has 40 turns of 1 mm diameter insulated copper wire.

• Power amplifiers: The number of power amplifiers has been increased by a factor of two during 2005, to a total of 32 amplifier units with 2 channels each, providing 64 amplifier channels in total. Professional audio amplifiers are used with output power of 800-1200 Watt and bandwidth 1 Hz to 25 kHz. Maximum saddle coil current is 20 A. Maximum magnetic field at plasma boundary is 3 mT.


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• Analog feedback controllers: A set of analog PID-type feedback controllers is available for optional use with the intelligent shell feedback control scheme.

• Digital controller: A digital controller that has been developed for the RFX experiment has been installed at EXTRAP T2R. The system is contained in a VME bus crate installed at EXTRAP T2R. The system has been upgraded 2005 to include support for the increase in the number of output channels from 32 to 64. 1) ADC for analog input: 64 sensor signals at 32 evenly spaced toroidal positions, 64 coil current signals, 2) CPU for real-time control: PPC, 500 MHz, 512 MB RAM, 3) DAC for analog output: 64 amplifier control voltages. Software for the following feedback control schemes is installed:”Intelligent shell” (SISO control): 64 independent PID-feedback control systems. ”Mode control” : FFT of 64 sensor signals, independent P-feedback control for individual Fourier modes, inverse FFT, output 64 control signals. Measured latency time for the system is < 50 microseconds. The digital controller is also operated in "open loop" mode for various studies involving application of external controlled fields.

Figure 3.1.3. Active coil layout used up to April 2005. Two-dimensional array at 4 poloidal and 16 toroidal positions (4x16=64 coils). Coils are m=1 series connected to form 32 independent cosine and sine coils.

Figure 3.1.4. Active coil layout used from May 2005. Two-dimensional array at 4 poloidal and 32 toroidal positions (4x32=128 coils). Coils are m=1 series connected to form 64 independent cosine and sine coils.

Research objectives Multiple RWM feedback control. The studies include a comparison of model predictions for RWM feedback with experimental data. An array with a limited number of active coils has several consequences that have been analyzed theoretically. The theoretical modelling predicts that in the case of only 16 toroidal positions of coils, several unstable m=1 modes are coupled by the active coils preventing stabilisation of all modes. Thirty-two toroidal modes (m=1, -16 < n < 15) are considered in the model. There are 16 toroidal positions with active coils and 32/16 = 2 modes are coupled in one set. While the dominant mode in the set decreases its amplitude the other coupled mode in the set can grow. The mode n-spacing” of the side-band” is given by the number toroidal positions (16) for the active coils: one set of coupled modes is m=1, n= -10, +6, and another possible set is m= 1, n= -14, +2. The studies investigate the stabilization of targeted modes and coupled "side-band" modes: • Experiments using different sets of active coils, giving different combinations of

coupled sets. With a 2x32 system (instead of 4x16) different pairs of modes are


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coupled by the coils. It is possible to interact with unstable RWM without disturbing internally resonant tearing modes.

• Experiments using different feedback schemes comparing proportional feedback with real gains (that suppress modes) and complex gains (that drive mode rotation). The main purpose is to test the effectiveness of complex gains in stabilization the modes. This is motivated by numerical simulations using the DEBS code (modified for feedback).

Response of RWMs to applied perturbations. The applicability of the RWM linear model is studied and parameters evaluated using open loop experiments: A study of vacuum shots with programmed external fields will be used to estimate characteristic diffusion times of helical magnetic field with poloidal mode number m=1, and different toroidal mode number n. A model of the system is used to fit the time evolution of the magnetic field harmonics. Using the data and information obtained will allows the estimation of: • The amplitude and phase of some of the external error fields present on the

machine. • Damping rates of stable RWMs. • The plasma response or the so-called resonant field amplification. The phenomenon of resonant field amplification is studied in experiments with the aim of direct comparison with linear theory. The observed response of the mode growth to the external field is compared with the thin-wall model including the externally produced control harmonic. The RFX digital controller is used in the”open-loop” mode. Actively driven field perturbations are produced with the saddle coil array. The following operation modes are currently used: • Individual coil perturbations. The wave form of a coil is set individually

(amplitude, frequency and phase). • Stationary or rotating Fourier mode perturbations. The wave form of a Fourier

mode is set individually (amplitude, frequency and phase) and also the toroidal rotation of the mode is set (angular frequency and phase).

The studies are aimed at investigating the amplitude reduction or amplification of intrinsic RWM for external fields with varying amplitudes and phases. Tearing mode dynamics. Another research area at EXTRAP T2R is the non-linear mode interactions involving tearing modes that is observed in the RFP. Tearing modes form island chains localised on resonant surfaces and experiences viscous forces from the plasma fluid such that the island chain tend to follow the plasma flow. There are electromagnetic torques on the rational surfaces where the modes interact with e. g. external non-axisymmetric fields that can be produced by the saddle coil system. The physics of these processes will be studied using magnetic diagnostics and spectroscopic measurements of plasma flow. Scientific results Demonstration of feedback suppression of multiple RWMs. Spontaneous growth of a range of RWMs is observed in EXTRAP T2R. Measurements of RWM growth rates are in good qualitative agreement with linear MHD stability calculations.


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difference due to field error

γτ=+1.3

γτ=+0.25

γτ=+0.47

difference due to field error

γτ=+1.3

γτ=+0.25

γτ=+0.47

Figure 3.1.5. Spontaneous growth of RWMs is observed in EXTRAP T2R. From top: Plasma current, mode amplitude for m=1, n=-10, n=+2 and n=+5. Measured mode amplitude (black), MHD model predicted exponential growth (blue). Experimental and MHD growth rates are in agreement for n=-10, +5. Disagreement for n=+2 can be explained by resonant field amplification of intrinsic error fields. Assuming the theoretical MHD growth rate, the field error is estimated from the model (red).

Preliminary results from RWM feedback control experiments on EXTRAP T2R are very encouraging. The basic feasibility of multi-mode RWM control has already been shown. This is the first demonstration of multiple RWM feedback suppression (Published in Physical Review Letters in November 2004). During the step-wise installation of active coils on the device, experiments with partial coil arrays were carried out. A feature of a control system using an array of coils is a linear mode coupling of side band modes. With a system of 16 toroidal positions, the sideband mode spacing is 16, resulting in coupling of pairs of unstable RWMs. The vacuum toroidal mode spectrum for this case is plotted in the figure below, for the 4x16 coil array (left) and the 4x32 coil array (right). The coil currents are pre-programmed for an m=1, n=6 harmonic. With 4x16 coils, the main side band modes in the magnetic field spectrum are n=-26, -10, +6, +22.

n=-26

n=+6n=-26 n=+6n=-10

n=+22

Figure 3.1.6. Vacuum m=1 mode spectrum with different coil arrays. The coil currents are pre-programmed for an m=1, n=6 harmonic. Left: Array with 4x16 coils, side-band harmonic spacing is 16. The main side band modes in the magnetic field spectrum are n=-26, -10, +6, +22. Pairs of coupled unstable RWMs with feedback control. Right: Array with 4x32 coils, side band spacing is 32. There are no coupled unstable RWMs in this case.

With the intelligent shell feedback scheme, the coupled modes are generally not controlled. Different layouts of coil arrays were used for a detailed study of the coupling effect, confirming the theoretical predictions.


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Suppression of two coupled rotating modes with mode control feedback. With the mode control feedback scheme, a real-time spatial FFT is used in the controller algorithm in order individually select the feedback gain for Fourier modes. Suppression of the dominant mode in a set of coupled modes has been demonstrated using real feedback gains. Experiments with complex feedback gains have demonstrated simultaneous suppression and rotation of both modes, in agreement with the theory prediction.

First demonstration of stabilization of the full range of unstable RWMs. Starting from May 2005 experiments using the full array with 4x32=128 coils have been carried out. A significant improvement of the efficiency of the control system is obtained, compared to experiments with partial arrays, and control of the full range of unstable RWMs in the RFP has for the first time been demonstrated.

Figure 3.1.8. Feedback control experiments with the full coil array. Shot with intelligent shell feedback (black), and a reference shot without feedback (red). From top a) plasma current, b) amplitude of the main RWMs m= 1, n=-11, c) n=-10, d) n=-9, e) n=-8, f) n=+2, g) n=+5, h) n=+6. The two discharges have the same programming. There is a significant effect of the mode control: The pulse length is two-folded reaching 7-8 wall times.

The initial results have been presented at an invited talk at the EPS Plasma Physics Conference 2005. As a result of the feedback control, a two-fold extension of the pulse length is observed in these preliminary experiments. With feedback control, the

Phases computed at an active coil position

Mode amplitudes Mode phases

w/o fb

intelligent shell

mode control π diff

fb induced rotation

Phases computed at an active coil position

Mode amplitudes Mode phases

w/o fb

intelligent shell

mode control π diff

fb induced rotation

Figure 3.1.7. Comparison of intelligent shell and mode control feedback for coupled modes n=+5,-11 with 4x16 coil array. Left: Mode amplitudes, Right: Mode phases, Top: n=-11, Bottom: n=+5. Reference shot without feedback (red), Shot with intelligent shell feedback (blue), shot with mode control feedback using complex gains (black). Intelligent shell is ineffective for coupled modes. Mode control feedback suppresses coupled modes and induces mode rotation.


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discharge duration is around 7-8 wall times, limited by the vertical field power supply. Response of resistive wall modes to applied perturbations. The use of pre-programmed non-axisymmetric external fields has allowed for the separation of the effects of intrinsic field errors from the natural plasma behaviour. Experiments have been conducted to determine the shell diffusion times for different harmonics and the growth rates for unstable RWMs. For the first time also the damping rates for stable RWMs have been estimated. The results have been compared with the linear cylindrical MHD model, and the agreement is satisfactory.

stable

marg.unstable

unstable

Figure 3.1.9. Measurement of the plasma response to an externally applied field. From top: coil current, radial magnetic field of m=1, n=-8 (unstable mode), n=-4 (marginally unstable mode), n=+12 (robustly stable mode) Measured mode amplitudes (black), Computed mode amplitudes using the cylindrical MHD model (red), and vacuum magnetic field (black).

Electromagnetic model for advanced active control methods. An electromagnetic model including the plasma, conducting structures, sensors and active control coils has been developed for EXTRAP T2R in collaboration with researchers at Consorzio RFX. Finite element electromagnetic analysis of the conducting wall and control system. The electromagnetic characteristics of the control system are studied by means of a FE model.

Figure 3.1.10. The control system at EXTRAP T2R includes a two-dimensional array of MxN=4x32=128 rectangular active coils. The drawing shows an electromagnetic model of one toroidal sector of the copper shell with one poloidal array of M= 4 coils. There is a total of N=32 arrays fully covering the torus surface.

3.1.2. Tearing mode dynamics TMs remain at a constant, non-linearly saturated level, spontaneously rotating at high velocities for a large fraction of the discharge duration. They behave qualitatively as if the shell were ideally conducting. This feature of the EXTRAP T2R device is unique


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for a thin shell RFP and gives a clear separation of TM and RWM temporal behavior. However, in standard discharges without feedback, the TM rotation slows down prior to the discharge end, and the modes lock to the wall. With feedback control on RWMs, a significant extension of the pulse length is obtained, and the wall locking of the TMs is delayed.

3.1.3. Edge turbulence Background Turbulence in fusion plasmas refers to the presence of fluctuations in the fluid parameters in time and space that have characteristic statistical averages. An implication of turbulence is that the associated local convective transport is large compared to classical cross-field transport in laminar plasma. The edge region of the RFP is of particular interest because, as is the case in a tokamak, the transport is dominated by electrostatic turbulence. Turbulence and anomalous transport have been studied in the EXTRAP T2R device in a collaborative study with Consorzio RFX in Padua. Plasma momentum balance. Plasma turbulence is a key subject in fusion research as it is believed to drive anomalous particle and energy transport. Regimes of improved confinement has been discovered in which turbulent transport is greatly reduced and the setting up of a layer of highly sheared plasma flow is observed. This effect has been interpreted as turbulence suppression occurring when the gradient of ExB velocity drift exceeds a critical value related to broadband turbulence frequency and spatial scales. Spontaneous sheared flows due to ExB drift have been observed in the edge regions of tokamaks and stellarators that is marginal for turbulence suppression. A dynamical link has been proposed between ExB flows and turbulent transport which eventually leads to a self-regulation process for turbulence. Despite the rich magnetic activity that characterizes the RFP configuration, the edge region is found to share several features with other magnetic configurations, among which is a particle

TM wall locksTM wall locks

Figure 3.1.11. Effect of RWM feedback on plasma rotation and resonant tearing modes. From top: plasma current, m=1 RMS amplitude, m=1,n=-12 tearing mode amplitude, mode phase velocity, plasma toroidal flow velocity. Two discharges are compared, without feedback control (red) and with intelligent shell feedback control (black). With feedback control, tearing mode rotation and plasma rotation is sustained.


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transport mainly driven by electrostatic turbulence and a highly sheared ExB flow, with a shear value close to turbulence suppression. Toroidal Alfvén eigenmodes. Observations Alfvén eigenmodes (AE) and toroidicity-induced Alfvén eigenmodes (TAE) have been reported in the literature for tokamaks. However, there are almost no studies yet of TAE in a RFP device. In an axi-symmetric cylindrical single-ion species plasma, shear Alfvén waves have a continuous spectrum. All perturbations belonging to the Alfvén continuum suffer strong damping due to wave phase mixing. Toroidicity effects create a gap in the spectrum. Inside the gap, Alfvén waves cannot exist except for a discrete frequency TAE. Such a mode does not experience continuum damping and is observed at a frequency with Alfvénic scaling. Technical In order to measure all terms in the momentum balance, a new probe array which combines electrostatic and magnetic measurements have been developed. The probe array consists of a boron nitride (BN) case where 17 molybdenum pins and 2 three-axial magnetic probes are housed. The five pins on the top of the BN case are used as a five-pin triple balanced probe, whereas the remaining ones measure floating potential. The 2 three-axial magnetic probes, 13 mm toroidally spaced, measure the time derivative of the three components of the magnetic field.

Figure 3.1.12. Probe array used in edge turbulence measurements in EXTRAP T2R. The molybdenum pins protrude 1 mm from the BN case surface.

As is commonly done in tokamaks and stellarators, fluctuating perpendicular velocities have been approximated by ExB drift velocity fluctuations. The electric field fluctuations have been derived from the gradient of the floating potential fluctuations. A second probe, separated poloidally from the complex probe, with three-axial high bandwidth magnetic pick-up coils, is used for the TAE study. Research objectives Plasma momentum balance. The aim is to measure simultaneously in the same location the toroidal and radial mean velocity, their radial derivatives, and the fluctuations of velocity and magnetic field. This allows, for the first time for a RFP configuration, the main terms entering in the momentum balance to be measured, among which are the complete Reynolds stress and the triple correlation product. Toroidal Alfvén eigenmodes. To obtain information of the magnetic fluctuations frequency and wavenumber spectra, and the polarization of the fluctuating field, all three components of the magenetic field vector is measured by insertable probes separated toroidally and poloidally. Langmuir probes have been used to estimate the local plasma density.


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Scientific results Self-regulation of ExB flow shear via plasma turbulence. The momentum balance has been applied to the ExB flow in the edge region. All terms, including those involving fluctuations, have been measured in EXTRAP T2R. It is found that the component of the Reynolds stress driven by electrostatic fluctuations is the term playing the major role in driving the shear of the ExB flow. The shear has a value marginal for turbulent suppression. The results are in favor of a turbulence self-regulating mechanism underlying the momentum balance at the edge. In the figure below is shown the radial profile of the toroidal ExB mean velocity and the components of the measured Reynolds Stress (RS) tensor.

Figure 3.1.13. Radial profile of ExB velocity, mainly toroidal (top) and terms in the Reynolds stress tensor (bottom). The electrostatic and the magnetic components are shown.

The two components have comparable magnitudes, contrary to what is observed in tokamaks, but different radial behavior as the velocity contribution increases inside the plasma while the magnetic one has a less pronounced dependence. The present experimental results have been obtained during discharges without sawtooth crashes. The radial variation of the complete RS consequently depends almost entirely on the electrostatic part, in analogy to what is observed in other devices. In particular, a change of sign in the RS gradient is observed crossing the limiter surface, as is also seen in tokamaks and stellarators. The radial derivatives of Reynolds stress tensor can either oppose or favor the viscous force, it represents the radial flux of momentum perpendicular to the magnetic field. In general it is related to the degree of anisotropy in the structure of the turbulence. Kinematic viscosity is anomalous and consistent with anomalous diffusity due to turbulent transport. It is found that the Reynolds stress drives the ExB shear opposing the flattening action of the viscous damping.


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Figure 3.1.14. The radial derivative of the total Reynolds stress tensor driving the ExB shear (black) and the viscous damping acting to flatten the velocity profile (red).

The self-regulation model for edge turbulence can be described as follows: Electrostatic turbulence drives most of the mean flow through the velocity coupling term in the Reynolds stress tensor. ExB sheared flow is the result of the counteracting action of turbulence driving and viscous damping, where viscosity is anomalous occurring through electrostatic turbulence. The ExB flow shear is effective in reducing the coupling between density and velocity fluctuations, and it may modify the turbulence anisotropy and thereby the Reynolds stress Reynolds and Maxwell stress frequency resolved measurements. The Reynolds stress exhibits a strong gradient in the region where a high ExB shear takes place. This has been interpreted as experimental evidence of flow generation via turbulence mechanism. The scales involved in flow generation are deduced from the frequency decomposition of the Reynolds stress tensor. They are found related to magnetohydrodynamic activity but are different with respect to the scales responsible for turbulent transport. Some general conclusions can be drawn from this study: 1) In many devices the ExB flow shear is marginal for turbulence suppression. 2) The Reynolds stress tensor is a driving term implying non-isotropic turbulence. 3) Reynolds stress is mainly driven by electrostatic turbulence. 4) There is experimental support for a turbulenced self-regulation process at the edge by which turbulence drives the ExB flow shear marginal. Observation of toroidal Alfvén eigenmodes (TAE). Observations Alfvén eigenmodes (AE) and toroidicity-induced Alfvén eigenmodes (TAE) have been reported in the literature for tokamaks. This is the first clear observation of TAE in a RFP device. A high frequency, high-n mode with the proper time scaling, polarization, and phase properties of an edge resonant TAE has been observed in EXTRAP T2R. A model has been developed that has general validity, and the same phenomenon is expected also in other RFP devices. An important role is played by the local mass density. Gas puffing fuelling experiments that change the edge density have been used to resolve this issue. The Alfvénic nature of high frequency magnetic fluctuations may be important for the edge transport phenomena in the RFP.


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Figure 3.1.15. Magnetic field fluctuation spectrogram. From top: a) time evolution of edge density measured by Langmuir probe, b) H�emissivity signal measured at the edge near the magnetic probe, c) spectrogram magnetic field fluctuation and the model prediction for the TAE frequency evolution superimposed as white full line. The density dependence of the TAE frequency was studied by using gas puff fuelling. The decrease of the frequency is consistent with the increase in density (during time 7-10 ms).

3.1.4. Confinement In the core of the RFP plasma, magnetic turbulence plays an important role in driving transport. The turbulence is connected with the RFP dynamo mechanism which drives the poloidal electric current in the plasma through velocity and magnetic field fluctuations. Confinement studies are of importance for two reasons. First, it is important to develop methods to improve confinement and several methods to improve confinement in the RFP are being studied. However the confinement studies also provide insight into the processes responsible for transport. Comparison studies between the RFP and tokamak are valuable in order to identify the fundamental physics issues behind anomalous transport. Pulsed poloidal current drive (PPCD). In order to improve the core confinement, an alternative way of driving the poloidal current is needed. A strong transient reduction of magnetic turbulence has been obtained by a applying a poloidal electric field to the plasma edge, the so-called Pulse Poloidal Current Drive (PPCD) technique, first used on the MST reversed field pinch device, and later also on EXTRAP T2R. As a consequence of PPCD, confinement does indeed improve. On EXTRAP T2R the confinement time and the electron temperature is approximately doubled during the PPCD. The physics of PPCD is studied using the extensive set magnetic diagnostics available on EXTRAP T2R. Quasi-single helicity. An interesting MHD regime found first in the RFX device, and later also in other RFP machines including EXTRAP T2R is the quasi-single helicity state (QSH). It is based on the theoretical prediction that the RFP plasma can spontaneously access, through a self-organisation process, the single-helicity (SH) regime. In this condition the dynamo needed to sustain the RFP configuration is driven by an individual m=1 instability. The SH state would naturally be resilient to the magnetic chaos implicit in the standard multi-mode dynamo. Soft x-ray (SXR) tomographic imaging in RFX and MST devices reveals that the dominant mode produces a hotter helical structure with closed helical flux surfaces.


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An SXR camera on loan from RFX is installed on EXTRAP T2R in order to study the physics of QSH states on EXTRAP T2R. Also bolometric profile measurements are used. The aim is to actively induce QSH through the application of external helical field using the saddle coil system. Analysis of the magnetic data with the ORBIT code will be used to reconstruct the magnetic surfaces starting from experimental measurements of mode amplitudes. (The ORBIT code is a guiding centre Monte-Carlo code in which field line equation are cast in Hamiltonian form and integrated over long distances to reconstruct magnetic surfaces.)

3.1.5. EFDA activity The studies of RWM feedback stabilisation carried out in collaboration with Chalmers and the Consorzio RFX contribute to the work being done in the European programme by the Chalmers group in the area of RWM control for ITER. Aspects of both the experimental and theoretical work for RFPs provide bench marking and verification for RWM feedback control studies for tokamaks. The RWM control work should provide the persons that are proposed for collaboration on RWM task areas for ITER with valuable experience.


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3.2. Plasma-wall interactions Marek Rubel, Henric Bergsåker In collaboration with Birger Emmoth, IMIT, KTH Plasma-wall interactions (PWI) comprise all processes involved in the exchange of mass and energy between the plasma and the surrounding wall. Two inter-related aspects of fusion reactor operation - economy and safety - are the driving forces for studies of PWI. The major issues to be tackeled are: (i) lifetime of plasma-facing materials (PFM) and components (PFC), (ii) accumulation of hydrogen isotopes in PFC, i.e. tritium inventory; (iii) carbon and metal (Be, W) dust formation. PWI is one of the primary areas where integration of the Physics and Technology programmes is being achieved. The work at KTH in the field of PWI and fusion-related material physics has been fully integrated with the international fusion programme: (i) EU Fusion Programme, (ii) International Tokamak Fusion Activity (ITPA), (iii) Implementing Agreements of International Energy Agency (IEA). It is demonstrated by the participation in: • European Task Force on Plasma – Wall Interactions (EU-TF-PWI), • EFDA Technology Programme, • EFDA-JET Work Programme: Task Forces “E” (Divertor Physics), “FT” (Fusion

Technology), “D” (Diagnostics) and JET Enhancements (Phase 1 and Phase 2) including the ambitious ITER-Like Wall (ILW) Project, i.e. full metal wall at JET;

• ITPA and IEA activities. The research programme is concentrated on: • Material erosion, migration and re-deposition including: • Fuel retention studies and fuel removal techniques • Characterisation of plasma-facing materials and components including testing of

high-Z metals • Development and characterization of wall materials for ILW at JET • Development of diagnostic tools for PWI studies Experimental work is carried out at home laboratory, JET and TEXTOR. EFDA-JET activity

3.2.1. Material migration in operation with the MkII-SRP divertor Studies were performed by means of tracer techniques. The aim was to determine the flow direction in the SOL and the mechanism of carbon transport to the shadowed region in the inner divertor. The experiment was done on the last operation day with the MkII-SRP divertor. Three tracers were introduced during thirty two H-mode discharges with strike points on the vertical target: 13CH4 injected from the outer vertical target and tri-methyl borine (TBM) from the outer divertor base (private region). The injection of both gases was toroidally symmetric. In addition, hafnium was laser ablated from the single location in the outer midplane. The injection scenario is shown in Fig. 3.2.1.The experiment was followed by retrieval of several limiter and divertor (a full poloidal cross-section) tiles for ex-situ examination using accelerator-based ion beam analysis (IBA).


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Figure 3.2.1. (a) JET with the Mk-IISRP divertor. Injection points of tracers are indicated: 13CH4 from the outer divertor ring; B(CH3)3 [TMB] from the outer divertor base; Hf from the outer midplane; (b) divertor cross-section with indicated strike point position during the experiment. The essential results from the examination of the inner divertor tiles are: (i) the tracer is found on the vertical target; (ii) significant C-13 deposition has occurred on the plasma facing-surface of the base tile; (iii) no ablated Hf and injected boron has been identified on the analysed surfaces; (iv) no tracer has been detected in the shadowed region. The latter result is the same as obtained in the previous tracer experiment (end of C4 in 2001), but there are also significant differences between the two experiments. They are summarised in Table 3.2.1. Table 3.2.1:Comparison of two C-13 tracer experiments at JET. End of C-4 campaign: Mk-IIGB End of C-14 campaign: Mk-IISRP Localised 13CH4 source from top: 1.3x1023 C

Toroidally symmetric 13CH4 injection from the outer divertor: 4.3 x1023 C

L-mode ELMy H-mode 13C integrated amount on Tile 4: 1.1x1021, i.e. 0.8% of the input (SIMS)

13C integrated amount on Tile 4: 2.8x 1022, i.e. 6.5% of the input.

Total amount detected in the divertor: 45 % in the inner (Tile 1 & 3) and < 0.5 % in the outer.

Total amount found on the tiles analysed until now: 9 % and 13 % in the inner and outer divertor channels, respectively .

The results indicate that material can indeed be transported from the outer to inner divertor following a pathway through the SOL plasma. No indication of the tracer migration to the inner divertor shadowed region, supports the current idea that carbon transport to that area is a multi-step process. There is no immediate C-D film formation in the shadow during operation with strike points on the vertical targets. The presence of C-13 on the base Tile 4 may suggest a significant role of ELMs in re-

Probe

1.4x1017 Hf at

4.29x1023 13C at

4.5x1021 B at

Injection and Main Plasma Parameters:Ip = 1.2 MA Bt = 1.2 T ne = 7.8 x 1019 m-3 H-mode ELMy discharges 32 good shots, DOC-L

13 GIM 10

GIM 9

13CH3

TMB

KT3B

12 1

separatrix


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erosion and re-distribution of carbon from vertical tiles of the inner divertor. This issue will be addressed when the analyses of all tiles from the full poloidal cross section of divertor have been completed (Tile 5 is still to be examined).

3.2.2. Deposition and fuel inventory in C and Be MkI divertors The use of castellated structures for plasma-facing components (PFCs: divertor and the main chamber wall) in ITER is thought to be the best solution to ensure the thermo-mechanical durability and integrity of materials under high heat flux loads, especially when considering the use of metals (tungsten and beryllium). It is known, however, that eroded material may be transported and co-deposited together with fuel species in areas shadowed from the direct plasma impact. As a consequence, re-deposition may occur in grooves of castellation and in gaps separating PFCs. An enormous number of such grooves (around 1 million) will be present in structures currently foreseen for ITER. The low level of tritium retention (350 g) that can be tolerated means that quantifying these processes in today’s experiments becomes an urgent priority. Until recently in fusion experiments the only large-scale castellated structures were used at JET: (i) beryllium belt limiters protecting the main chamber wall (castellation 14 mm deep and 1 mm wide) operated for 56000 s and (ii) the Mk-I divertor. This water-cooled structure was composed of small roof-shaped tiles, separated by 6-10 mm wide gaps shadowed from direct plasma impact by the roof-shaped geometry. The divertor was first employed with carbon fibre composite tiles (CFC) for about 60000 s of plasma operation with 25600 s in X-point phases. Subsequently, the CFC was replaced by castellated (6x6 mm with 0.6 mm deep groove) beryllium blocks and exposed for a further ~20000 s of plasma with 9150 s in X-point phases. CFC and Be tiles are shown in Fig. 3.3.2.

The most important results may be summarised by the following: (i) significant co-deposition of carbon and deuterium has been observed up to a few cm deep in the gaps between the tiles, in both the CFC and Be divertors; (ii) in the gaps between inner divertor CFC tiles, the fuel inventory exceeds that on plasma-facing surfaces by up to a factor of 2; (iii) in the gaps between the inner divertor Be tiles the fuel inventory reaches 30% of that on plasma-facing surfaces; (iv) in the narrow castellated grooves the co-deposited fuel is only around 2% of that found on top surfaces; (v) the deposition profile of deuterium found in the grooves has a short e-folding length of ~1.5 mm; (vi) the presence of fuel is always associated with the co-deposition of carbon.


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Fig. 3.2.2. (a) CFC and (b) castellated beryllium tiles employed in the Mk-I divertors. Segments of the Be tiles shown in Fig. 1b were cut to enable the analysis in the castellated grooves; the results for surfaces in the gaps between tiles and in the castellation are included. This last point constitutes an extremely important observation, particularly with regard to the current ITER first wall material mix which still envisages carbon at the divertor targets. The difference in the fraction of fuel content in the gaps between tiles (less in the case of Be than for CFC) also indicates that co-deposition in the divertor and in the gaps may be attributed to two factors: (i) transport of species eroded from the main chamber wall; (ii) transport from a local carbon source in the divertor itself. The small inventory in the castellated grooves of Be tiles points to the influence of the gap width on the overall in-vessel fuel retention. This is also an important consideration when choosing the optimum groove width (particularly in regions of glancing magnetic field line impact where Debye sheath effects must be accounted for) and modeling efforts will be reported both for ion and neutral (CxHy) transport into the gaps. These results from JET operated with the carbon wall and beryllium limiters or evaporated Be coating in the main chamber should not be immediately translated into conclusions and quantitative predictions regarding the material migration and fuel inventory in ITER. The planned material configuration in the divertor (W and CFC) and on the main chamber wall (Be) will be different than in any present-day device. This will change both the scenario of material erosion and will influence fuel co-deposition. These are critical issues that the ITER-like Wall Project being in preparation at JET is intended to address. Nevertheless, results presented here strongly imply that the material transport and resulting fuel inventory would be strongly reduced in a machine with all-metal walls in the main chamber. It is unreasonable to expect, however, that the deposition in the castellation grooves will be completely eliminated. The development of efficient techniques of fuel removal from all in-vessel components remains, therefore, crucial for the operation of a reactor-class device.

3.2.3. Characterisation of components after flash-light cleaning After C14 campaign a number of tiles was retrieved from the torus and cleaned by flash-light in order to reduce the amount of fuel and to remove the co-deposited layer. The thickest (several tens of micrometers) deposits are on Tile 4 (inner divertor) in the region shadowed from the direct plasma impact. Comparative studies performed by means of ion beam analysis for a treated and not treated tiles have shown that only

Plasma facing


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thin surface layer (approx. 0.25 micron) was removed from the co-deposits. This result was inferred from comparison of the Carbon -13 distribution on the tiles: the tracer was removed from the cleaned part of the tile.

3.2.4. First mirror test JET Enhancements (JW5-OES-TRS-VR18) First Mirror Test (FMT) project was initiated at JET in year 2002 within the Project on Tritium Retention Studies (TRS). The origin of this programme is related to the fact that first mirrors will be plasma facing components of all optical diagnostic systems in ITER. Mirror surfaces will undergo modification caused by erosion and re-deposition processes influencing reflectivity of mirrors and thus affecting the spectroscopy signals. The limited access to in-vessel components of ITER calls for testing the mirror materials in present day devices in order to gather information on the material damage and degradation of mirror performance, i.e. reflectivity. Therefore, the ITER Team requested the FMT experiment to be carried out. The Swedish EURATOM Association (Responsible officer: Marek Rubel) in co-operation with UKAEA carried out the project aiming at the manufacturing, delivery and installation of mirror samples and their carriers in several locations inside the JET vacuum vessel. All items were produced (see 2004 Report) and installed in the torus in 2005. Figure 3.2.3 shows cassettes installed below the load bearing plate (LBP) of the MkII-SRP-LBP divertor, whereas in Figure 3.2.4 a wall bracket (for the main chamber) is depicted. Figure 3.2.3. Cassettes with mirrors in the divertor base modules.

Figure 3.2.4. Bracket assembly for installation on the main chamber wall: holder (1); cassette with mirrors (2); magnetic shutter (3); rotating deposition monitor (4).


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After the C15-C17 campaigns some of the mirrors will be removed and examined ex-situ in order to determine their optical properties after the long-term exposure. To enable studies of materials contaminated by beryllium and tritium a special spetro-photometic equipment was procured and installed at JET. The measuring unit (integrating sphere) is encased in a glove box, as shown in Figure 3.2.5.

EFDA technology

3.2.5. Fuel removal by helium-oxygen glow (EFDA Technology TASK TW5-TPP-TILCAR) The aim was to determine the morphology of plasma-facing materials following the oxygen-assisted removal of fuel and co-deposited layers. The oxidation experiment was carried out in the TEXTOR tokamak. The comparison to experiments performed under laboratory conditions has also been done. The essential results are summarised by the following: • During the oxygen glow at wall temperature ~200 C, the laboratory-prepared

carbonised layers are decomposed very efficiently: D and C contents are decreased by a factor of 150-180 and 30-60, respectively.

• The same treatment of the in-situ boronised films leads to a much less effective release of D (factor of 6-25) and no removal of carbon occurs, but also the initial C concentrations are low.

• The oxidation (1-2 h in air at 300 C, in laboratory) of co-deposits on PFC and probes exposed to the SOL reduces the D content by a factor of 4-5, but no significant changes in the structure of co-deposits are associated with this process.

• The content of elements not transferred to volatile compounds (e.g. B, Si, metals) remains unchanged, as expected.

Samples of laboratory-prepared amorphous carbon films and pre-boronised layers were inserted to TEXTOR for the oxidation experiment by the He-oxygen glow plasma. Fig. 3.2.6 shows the holder with samples before and after oxidation.

Fig. 3.2.5. Final set-up of the equipment: photo-spectrometers and the light source (1), glove box (2), integrating sphere (3), holder for mirrors (4) and holder for windows (5).


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Figure 3.2.6. Carbonised and boronised Si substrates before (a) and after (b) exposure to the oxygen-helium glow discharge. The boronised sample is marked with an arrow. Following the exposure the content of deuterium, carbon and boron was measured with accelerator-based ion beam analysis methods. The study has shown that oxidation – as expected – reduces the amount of deuterium retained in the layers. However, only for laboratory-prepared thin pure carbonised layers on Si the release of deuterium is accompanied by the removal of the carbon film. In case of real co-deposits – either thin or thick – the co-deposited layer is not fully decomposed, showing that the recession rate of carbon from the mixed layer is much slower than from the pure a-C:D film. The fuel removal efficiency may be dependent on the overall composition of mixed layer. The content of elements not transferred to volatile compounds (e.g. B, Si, metals) remains unchanged. There are two reasons that may be considered: (i) the presence of admixtures slows the process by inhibiting the penetration of oxygen into the depth of co-deposits and the diffusion of volatile reaction products to the surface; (ii) carbon is partly bonded to Si or B in the form of carbides. The presence of other carbides, silicides and borides or oxides (in all cases with metal impurities) cannot be excluded. Similar effects influencing the fuel release rate (efficiency) may probably be foreseen in case of Be-containing films. From the measurements performed with techniques used in this study, one cannot directly prove the presence of carbides and other compounds on surfaces of probes or PFC. However, the analysis performed recently with X-ray diffraction on VPS W-coated graphite limiters from TEXTOR has clearly identified the presence of tungsten carbides, borides and silicides on tungsten. One may propose that such type of measurements are also carried out for carbon PFC from carbon-wall machines like TEXTOR The results indicate that the fuel and carbon can be removed quite efficiently from the test films prepared in laboratory, but the removal of real co-deposits (“tokamakium”) remains an issue. The other point that deserves studies and deep insight is the uptake of fuel by the depleted layers. There is no enough data base to judge the extent of this effect which may be of particular importance for thick layers.

a b


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3.2.6. Tungsten under plasma load: melt layer and droplet formation An important issue for ITER is the choice of materials for plasma-facing components. Bulk tungsten (W) is the most promising candidate to replace carbon fibre composites on the divertor targets of ITER. It will also be used during the full metal operation of JET. Low sputter erosion and low tritium retention are the most attractive features of tungsten, whereas the major problem is related to melting and melt-layer loss under high-power transient events. Melt layer motion would strongly enhance the local erosion of tiles eventually leading to the surface irregularity and formation of tungsten dust or larger droplets. The investigation of the melt layer behaviour in a strong magnetic field is, therefore, a necessary step to understand the consequences of erosion phenomena of high-Z refractory metals in fusion devices. In the experiment performed at TEXTOR a thermally insulated solid W plate (2 mm thick) fixed on a graphite roof-like limiter heated up by the plasma to the melting point. The main objectives were to determine the metal damage, the formation melt layer and its motion in a strong magnetic field. Fig. 3.2.7 shows the plate before and after exposure to the plasma.

Figure 3.2.7. Tungsten plate on a roof-like limiter: (a) before and (b) after exposure. Images in Fig. 3.2.8 show the details of the melt zone. In small black spots (8a) carbon inclusions have been identified with EDS. The formation of W droplets has also been observed (8b).


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Figure 3.2.8. Surface topography of melt zone on the tungsten plate. Specific features are marked with arrows and circles: (a) carbon inclusions; (b) small droplets.

3.2.7. Deposition and fuel inventory in castellated tungsten limiter (EFDA Technology TASK TW3-TPP-ERTUBE, in co-operation with the TEXTOR Team). The aim was to determine the amount of deuterium and carbon co-deposited in the narrow gaps of the tungsten macro-brush limiter exposed at the TEXTOR tokamak. The limiter was composed of twelve slices and could be dismantled following the exposure thus enabling morphology studies in the poloidal gaps. The tungsten part was brazed to a copper base as shown in Fig. 3.2.9. Deposition in castellated grooves is depicted in Fig. 10.The essential results are summarised by the following:

a

b


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• deuterium retention in the narrow castellated gaps of metal PFC is strongly related to the co-deposition with carbon;

• both carbon and deuterium are detected a few mm down the gap with the decay length l~1 -1.5 mm;

• the formation of copper droplets (originating probably from the limiter base) and W-O compound has been detected in the gaps of the W macro-brush limiter.

Fig. 11 shows the deposits on the surface of one segment. One can distinguish films of different hue (blackish and reddish) present deep in the gaps. SEM images recorded with back-scattered electrons (mass contrast) reflect the presence of lighter and heavier elements, respectively. As identified with energy dispersive X-ray spectroscopy (EDS), blackish deposit in (a) and (c) contains tungsten and oxygen, whereas the presence of copper droplets has been proven in (b).

Fig. 3.2.9. Castellated tungsten limiter after exposure to the TEXTOR plasma

Figure 3.2.10. Deposition pattern on two sides of the limiter segment


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Figure 3.2.11. Back-scattered electron images in three regions in the gap. High-resolution image of W-O deposit is shown in Fig. 3.2.12. The possibility of the W-O formation in tokamaks has been discussed earlier as a potentially dangerous mechanism of tungsten transport. However, no evidence has been demonstrated before. From the detailed SEM image in Fig. 12 one may suggest that the islands of the W-O compound have been formed by deposition from the gas phase. They seem to be loosely bound to the tungsten substrate. To understand the processes underlying the formation of the detected W-O system the source of oxygen must be found. Two potential candidate sources are considered: (i) plasma impurities and (ii) oxygen released under high temperature from the copper containing oxygen (non-oxygen free Cu was used for manufacturing the limiter base). Further studies are needed to clarify this issue and also to better diagnose the W-O deposit.

Figure 3.2.12. High resolution SEM image of the deposit containing W-O compound.


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3.3. Theoretical fusion plasma physics T. Hellsten, E. Tennfors, T. Bergkvist, K. Holmström, T. Johnson, and M. Laxåback The research is focused on studying wave-particle interactions relevant for fusion experiments, in particular for heating, current drive and excitation of waves by fast particles. Codes to predict the effects of ICRH are developed, and validated against experiments. The studies are well integrated in the European program by participating in the Integrated Modeling Task Force and through participation in the exploitation of the JET facility. The two main codes used by the group are FIDO and SELFO. The Monte Carlo code FIDO calculates the distribution functions of the resonant ion species taking into account effects caused by finite orbit width and RF-induced spatial transport due to absorption of the momentum of the wave. The SELFO code calculates the wave field, using the LION code, and the distribution function, using the FIDO code, self-consistency is obtained by means of iterations. The FIDO code is being upgraded to include interaction with MHD waves allowing self-consistent studies MHD modes during ICRH; at the moment by using simple models of the MHD-modes.

3.3.1. Fast particle excitation of global Alfvén eigenmodes The dynamics of AEs excited by high-energy thermonuclear alpha particles are experimentally often simulated by ICRH due to the lack of thermonuclear alpha particles. We have found that the dynamics of AEs excited by thermonuclear alpha particles differ considerably from AEs excited during ICRH because of the decorrelation of the AE interactions by the ICRH. We have simulated the dynamics of TAE excitation during ICRH and explained both the appearance of side bands by the decorrelation of the interactions between the fast ions and the renewal of the distribution function by cyclotron heating and the fast termination of the TAEs after the ICRH power was switched off.


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Figure 3.3.1. Top left TAE modes excited in JET with side bands. Simulation of a TAE mode including ICRH and Coulomb collisions (red) without ICRH (blue) (middle figure). Fourier transforms of the amplitude variation (right). The peak at 2kHz is consistent with frequency side bands. .

Figure 3.3.2. The fast damping is illustrated in the figure above as the ICRH power is switched off at t =10ms, caused by ion-Landau damping of high-energy resonant ions

3.3.2. FWCD experiments in JET ITB plasmas We have demonstrated FWCD on JET. FWCD had earlier been demonstrated on other machines, but not on JET, because of the frequency range of the JET generators and the good confinement of high-energy ions that parasitically absorb the wave due to the weak electron damping. FWCD was demonstrated in high temperature plasmas with internal transport barriers, ITBs, with strongly reversed magnetic shear with a low current density at the centre. Such plasmas are also the most interesting ones for current profile control, since the performance of ITB plasmas are sensitive to profiles of the current. Although the current efficiency for the power absorbed on the electrons was fairly high, it was nevertheless difficult to affect the plasma current due to the strongly inductive nature of the plasma (large inductance and low resistivity), the interplay between the bootstrap current and driven current (when the central plasma current increases the bootstrap current in the barrier decreases and vice versa), and the strong parasitic absorption. Even though it was difficult to affect the current profile with FWCD the change in current was larger than expected, when calculating


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the driven current profile from the measured direct electron heating profiles, which suggests an anomalous fast current penetration compared to neoclassical theory, polarimetric measurement of the time evolution of the central current also demonstrated rapid changes in the central current in connection with tearing modes in the reversed magnetic shear region.

Figure 3.3.3. Comparison of the evolution of the central current density for co (#60664) and counter (#60063) current drive.

3.3.3. Parasitic absorption in FWCD experiments in JET ITB plasmas Evidences of large fractions of the lost power were found during the FWCD experiments from the energy balance between the energy coupled by the heating system and the sum of the radiated energy and the energy conducted to the divertor. Evidences of the lost power were also obtained from the strong Be-line radiation at the edge and the performance of discharges for similar heating power. Clear degradation of the heating with respect and phasing and single pass damping were seen; the efficiency of the dipole phasing was twice that for the current drive phasings, both for single pass damping of a few percent. Direct electron heating using dipole phasing proved to be an effective heating scenario for electrons with ITBs and had a heating efficiency similar to the standard minority heating scenarios even for single pass damping of a few percent.


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Figure 3.3.4. Top left BeII- line radiationfor different phasings #60673 with dipole, #60664 -90o and #60663 + 90 o (check). Lower left curve electron temperature for the same discharges. Righthand figure demonstrates the heating degradation: top curveelectrin temperature and bottom curveplasma energy measured with a diamagnetic loop #60673 with dipole and #58662 with H-minority heating + 90 o both with 4.5MW, #60675 +90o and #60676 - 90 o both with 6MW. The effect on the weak single pass damping on the coupling of RF-power was studied theoretically in order to understand the cause of the parasitic damping during the FWCD experiments. The losses at the rectified RF sheath potentials were found to increase strongly as the single pass damping decreased. It was also possible to explain the differences in the efficiency between the monopole phasing of the old A1 antennas and the newer A2 antennas with lower efficiency (a long unexplained issue). The losses increases for current drive phasings as the single pass damping decreases below a few percent, whereas for monopole phasing they become significant already below 20-30%.

Figure 3.3.5. Losses caused by dissipation of rectified RF-sheath potentials versus single pass damping.

3.3.4. Minority ion cyclotron current drive in ITER The achievable plasma in the next-generation of Tokamaks is expected to be limited by neoclassical tearing modes (NTMs) triggered by long-period, large-amplitude,


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sawtooth crashes. Helium-3 minority ion cyclotron current drive (MICCD) at the low field side (LFS) q=1 flux surface is therefore considered for sawtooth destabilisation in ITER by locally increasing the magnetic shear. Comprehensive integrated MICCD simulations using the SELFO code for the ITER PFUS=400MW reference plasma however indicate that the driven current densities will be insufficient (Figure 3.3.6) for any significant increase in the magnetic shear (Figure 3.3.7) even for RF powers greatly exceeding the total power to be installed. Hydrogen MICCD, having a much smaller electron back-current and larger high-energy ion distribution function component, is found to be a significantly more efficient alternative (Figures 3.3.8 & 3.3.9). [M. Laxåback and T. Hellsten, Nucl. Fusion (2005) 1510-1523].

Figure 3.3.6. Driven currents with the 3He cyclotron resonance on the LFS. (a) -90º and (b) +90º phasing. Full, dotted and dashed lines indicate the currents driven with powers corresponding to 20MW, 40MW and 60MW in ITER. The vertical dashed line indicates the un-shifted cyclotron resonance.

Figure 3.3.7. Magnetic shear modification with the 3He cyclotron resonance on the LFS. (a) -90º and (b) +90º phasing. Full, dotted and dashed lines indicate the currents driven with powers of 20MW, 40MW and 60MW. The vertical dashed line indicates the un-shifted cyclotron resonance.

Figure 3.3.8. Driven currents with the H cyclotron resonance on the LFS and 20MW of power. (a) -90º and (b) +90º phasing. Dashed and dotted lines indicate the currents driven by respectively ions in passing and trapped orbits. The vertical dashed line indicates the un-shifted cyclotron resonance.

Figure 3.3.9. Magnetic shear modification with the H cyclotron resonance on the LFS at 20MW of power. (a) -90º and (b) +90º phasing. The dashed line indicates the unperturbed magnetic shear. The vertical dashed line indicates the un-shifted cyclotron resonance.

3.3.5. Ion cyclotron emission in toroidal plasmas Emission in the ion cyclotron frequency range in tokamak plasmas is of interest because of its potential of using it for diagnostic purpose. The effect of the orbit topology on ion cyclotron emission, ICE, has also been studied. Emission can appear for collisionally relaxed distribution functions due to interactions with barely trapped co-passing drift orbits and marginally trapped drift orbits. Stimulated emission of edge localised magnetosonic modes by neoclassical effects such as detrapping of ions with trapped orbits into co-current passing orbits can appear even in absence of a poloidal localisation of the modes.


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Figure 3.3.10. The anti-hermitian part of the susceptibility tensor element, versus frequency in a cross section of a tokamak plasma. Left waves propagating anti-parallel to the plasma current and to the right waves propagating parallel with the plasma current. The vertical lines indicate the position of the harmonics of alpha particle cyclotron resonances. The blue part determines region with negative anti-hermitian part that can give rise to stimulated emission of waves and the red and yellow parts to absorption.

3.3.6. Analysis of JET experiments The group has participated in analysing various ICRH effects on JET using the SELFO code, such as RF-induced rotation, avoidance of neo-classical tearing modes by control of the sawtooth period, reducing the number of high-energy ions created with ICRH by using polychromatic spectra and studies of so called inverted minority scenarii, scenario with the charge to mass ratio of the heated minority ions lower than the majority ions.


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3.3.7. High- frequency TAE modes in the RFP device EXTRAP T2R The first clear observation of high- frequency TAE modes in a RFP device EXTRAP T2R has been reported, in collaboration with, Regnoli from the RFX team in Padua. When the mode is not destabilised, the typical power law scaling of fully developed turbulence power spectra are observed, otherwise the spectra are characterised by a high frequency peak. This observation has given new insights on the investigation of RFP edge turbulence and is expected to contribute to a better understanding of related transport phenomena. The first observations in the RFX device of an Alfvénic high-frequency activity have been reported in 2005.

Figure 3.3.11. Frequency spectrum showing TAE mode activity


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3.4. Computational methods for fusion plasmas J. Scheffel, J.-E. Dahlin (PhD student)

3.4.1. Numerical confinement scaling in the advanced RFP In the advanced RFP, tearing modes are diminished by the use of current profile control. In this theoretical study, the advanced RFP is examined by the use of numerical simulations, and scaling laws are derived for confinement parameters. The model is nonlinear MHD in 3D including finite resistivity and pressure. It is observed that the configuration spontaneously develops into a quasi single helicity (QSH) state. The current profile control scheme is designed to eliminate the fluctuating electric dynamo field Ef = - <vxB>, using feedback of an externally imposed electric field. A linear regression analysis is performed on simulation data from a series of computer runs for a set of initial parameter values. Scaling laws are determined for radial magnetic field, energy confinement time, poloidal beta and temperature. Confinement is improved substantially as compared to the conventional RFP. It is found that poloidal beta degrades only weakly, as [I(I/N)]-0.12, at higher plasma current I and I/N ratios, where N is the line density. On-axis ion temperature scales as [I(I/N)]0.74 to reactor relevant levels, and energy confinement time scales as [I(I/N)]0.50.

3.4.2. Semi-analytical solution of initial-value problems A new spectral method has been developed to obtain semi-analytical solutions of initial-value partial differential equations, the so-called time- and parameter generalized weighted residual method (TP-WRM). The purpose is primarily to produce suitable computational tools for determining operational limits, in terms of scaling laws for fluctuations and confinement, for the RFP confinement scheme. Important two-fluid effects, like the Hall and diamagnetic contributions to Ohm’s law, will be included for the first time. The method is also suitable for applications in fluid mechanics and other problems within magnetohydrodynamics. By ”semi-analytical” is meant that an analytical, spectral solution ansatz in certain defined basis functions (polynomials, Chebyshev polynomials) is assumed, and that the coefficients of the ansatz are determined numerically. As a result, analytical solutions in all time, space and physical parameters are obtained as spectral expansions with numerical coefficients. A fully spectral algorithm is used. All time, spatial and physical parameter domains are represented by multivariate, shifted Chebyshev series. The algorithm is fully implicit in the sense that time step limitations are completely avoided. The spectral coefficients are determined by iterative solution of a linear or nonlinear system of algebraic equations, obtained by use of the method of weighted residuals (Galerkin method) for Chebyshev polynomials. Several effective algorithms have been developed for differentiation, integration and multiplication of multivariate, shifted Chebyshev polynomials in spectral space. During 2005, a new iterative real root solver for nonlinear systems of algebraic equations has been developed by us. It features global, monotonous and superlinear


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convergence and is thus more robust than Newton’s method for solving problems where the initial ”guess” solution strongly deviates from the exact solution. The root solver SIR (semi-implicit root solver) is derived using principles from semi-implicit solution of partial differential equations. It generalizes Newton’s method and essentially requires a similar amount of numerical work. The TP-WRM has been successfully benchmarked against the nonlinear, viscous Burger equation (for which exact solutions exist) and the linearized, resistive MHD equations. It is presently applied to a Rayleigh-Taylor instability problem formulated within the compressible 2D Navier-Stokes equations.


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3.5. Chaos and self-organisation M. Tendler The concept of ExB flow velocity shear suppression is utterly fundamental in modern fusion research. It is asserted that there are models enabling to understand the physics involved in LH transitions. To improve the understanding of the mechanisms leading to formation of Transport Barriers, especially the relation between Internal and Edge barriers it is necessary to invoke the issue of electric fields. Edge transport barriers are the feature of the H-mode, the baseline regime of ITER, whereas Internal Transport Barriers are used to develop regimes that might be employed for steady state operation of ITER, definitely beneficial for design and operation of fusion power plants in the future. Their synergy is addressed. Plasma flows are closely connected to electric fields. Therefore, their role is crucial for understanding of tokamaks aimed at the achievement of fusion energy. This appears in the well known neoclassical theory as the most accomplished and selfconsistent basis for understanding of fusion plasmas. It pertains to the novel concept of ”zonal flows” emerging from the recent development of gyro-kinetic transport codes. The equilibrium poloidal and toroidal flows are also crucial for the concept of the electric field shear suppression of plasma turbulence in tokamaks. Yet, this timely and topical issue has remained largely unaddressed experimentally because of great difficulties of measuring flows in plasmas. Moreover, the concept of “ zonal flows “ does not fully account for the impact of toroidicity. Therefore, to reconcile the neoclassical theory with anomalous momentum transport invoking effective viscosity due to “ zonal flows “ appears mandatory. The impact of sheared radial electric fields on turbulent structures and flows at the plasma edge is investigated. A non-intrusive biasing scheme called ″separatrix biasing″ whereby the electrode is located in the scrape-off layer (SOL) with its tip just touching the LCFS was found to be efficient, as predicted by our theory. There is evidence of a strongly sheared radial electric field and ExB flow, resulting in the formation of a transport barrier at the separatrix. Advanced probe diagnosis of the edge region has shown that the EXB shear rate that arises during separatrix biasing is larger than for standard edge plasma biasing (with the electrode inserted inside the LCFS as in TEXTOR). The plasma flows, especially the poloidal ExB drift velocity, are strongly modified in the sheared region, reaching Mach numbers as high as half the sound speed. The corresponding shear rates (~5x106 s-1) derived from both the flow and electric field profiles are in excellent agreement and are at least an order of magnitude higher than the growth rate of unstable turbulent modes as estimated from fluctuation measurements. It is demonstrated that the radial electric field shows no bifurcation and the origin of the strong electric field in the H – mode, the base line regime of ITER might be explained by the self-consistent change of the plasma profiles.


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4. EFDA activity EFDA - JET J. Brzozozowki works at EFDA-JET under a JET Operation Contract (JOC) with UKAEA where duties are divided between tasks as Session Leader and as Spectroscopy Diagnostician. The work as Spectroscopy Diagnostician is mainly on upgrading a VUV spectrometer system. Appointments include Deputy Task Force Leader for Diagnostics and Project Manager of one of the JET-EP2 Spectroscopy Enhancement Projects. M. Laxåback holds position as Responsible Officer for Task Force H within the Programme Department of the EFDA-JET Close Support Unit Also performed and reported on a study to assess the impact of the fast ion population accelerated by ion cyclotron resonance heating on collective Thomson scattering diagnostics. T. Johnson is responsible for the ICRH modelling codes PION, FIDO, SELFO and ORBIT-RF at JET. T. Johnson has been linking the PION code with the transport code JETTO under the JAMS modelling environment. This work has been supported by ST-orders under the project “Integration of Transport and MHD Codes at JET”. EFDA - ITER Since September 2005, the Alfvén Laboratory is contributing directly to the ITER programme with the secondment of M Cecconello at the EFDA Close Support Unit (CSU) in Garching (Munich) in the field of Physics Integration. The Physics Integration field coordinates the EU activities in the field of physics technology for control, heating systems and diagnostics for ITER, collaborates with the ITER International Team in the definition of the physics for the “next step” devices and addresses plasma physics issues in support of the JET scientific programme by helping to define a scientific programme for JET in support of the needs of ITER (including JET diagnostic upgrades). In addition, the Physics Integration field is also responsible for the EFDA Ceramic Irradiation Programme, which consists of an extensive research of irradiation effects on ceramic materials and components for Diagnostics and Heating and Current Drive system for ITER and “next step” devices. Within the general activity of the Physics Integration field, M Cecconello is involved in the coordination and management of different projects in quality of diagnostic physicist and liaison officer (in this role, M Cecconello defines the contracts technical specifications and follows the contracts as far as scientific and technical matters are concerned). In particular, M Cecconello is liason officer for: • the contract “Diagnostic design for ITER – Pressure gauges and divertor

thermography” between the European Atomic Energy Community and the IPP (Germany),

• the contract “Diagnostic design for ITER – Development of a prototype silicon-nitride resistive bolometer” between the European Atomic Energy Community and IPP (Germany),


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• tasks of the EFDA Ceramic Irradiation Programme were he acts also as responsible officer,

• the contract “Diagnostic design for ITER – Port Integration, Radial Neutron Camera and Diagnostic shutters” between the European Atomic Energy Community and ENEA (Italy),

• the contract “Diagnostic design for ITER – Diagnostic Port Integration, Magnetics and Thermocouples” between the European Atomic Energy Community and CEA (France),

• the EU/RF (Russian Federation) collaborative tasks on ITER diagnostics in the areas of optical fibres development, performance assessment and design of the ITER Hα spectroscopy diagnostic, development and testing of radiation-hard neutron detector and in the assessment of laser and detector requirement for ITER Thomson-scattering diagnostic.


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5. International collaborations EXTRAP T2R Consorzio RFX , Padova: • Collaboration with RFX on MHD mode control in EXTRAP T2R: The areas of

collaboration and key persons involved are as follows: 1) Theoretical assessment of RWM feedback control schemes and feedback experiments on EXTRAP T2R (R. Paccagnella, D. Gregoratto, G. Marchiori, S. Ortolani), 2) Finite Element Electromagnetic analysis for mode control in EXTRAP T2R (A. Masiello), 3) Development of electromagnetic model for advanced feedback schemes (M. Cavinato), 4) Development and test of integrated control module (A. Luchetta, G. Manduchi), 5) Active MHD mode control experiments (P. Zanca, T. Bolzonella) , 6) QSH experiments and SXR tomography diagnostic development (P. Martin, L. Marrelli, G. Spizzo, P. Franz)

• Collaboration with RFX on Edge Turbulence in EXTRAP T2R: The collaboration involves edge plasma measurements in EXTRAP T2R with insertable complex probe systems and data analysis. (N. Vianello, M. Zuin, V. Antoni, G. Serianni, M. Spolaore, G. Regnoli).

• Remote access to EXTRAP T2R data from the RFX site: Remote access to EXTRAP T2R data at the RFX site has been simplified in 2005 through installation of software which links the MDS data acquisition system at EXTRAP T2R with the MDS-Plus system at RFX.

• MHD mode control system equipment installed at EXTRAP T2R on loan from RFX: Integrated digital control module. The module has been developed for RFX and is a prototype for the system used at RFX. This work is in part support for the RFX experiments with active control. The module has been upgraded in 2005 for increase of the number of output control signals from 32 to 64.

• Diagnostic equipment installed at EXTRAP T2R on loan from RFX: Diagnostics installed at EXTRAP T2R on loan from RFX include: 1) Neutral Particle Time-of-flight diagnostic, 2) Interferometer components, 3) Thomson Scattering components, 4) Multi-chord Bolometer, 4) 20-chord Soft-X Ray Camera, 5) Probe equipment for edge turbulence studies.

EFDA-JET. Scientists from the group (P. Brunsell, D. Yadikin) are starting involvement in Task Force MHD, in the area of RWMs. There is an on-going collaboration with the Chalmers group in this area (Y. Q. Liu), which involves scientists at MAST, UKAEA (T. Hender, M. Gryaznevich). Participation in experimental campaigns at JET on RWM physics is planned. Areas of work are: 1) studies of the RWM rotational stabilization effect. 2) active MHD spectroscopy. IEA Implementing Agreement on Reversed Field Pinches: This agreement is between Japan, USA and Europe and enables the exchange of personnel and equipment. The EXTRAP group collaborates with the MST group at Univ. Wisconsin in the areas of Pulsed Poloidal Current Drive (PPCD) and Probe Diagnostics.


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MHD mode control: The EXTRAP T2R group is active in the international MHD mode control community, with collaboration with the group at Columbia Univ. (G. Navratil). The group participates in the annual MHD Mode Control Workshop held in the US. Plasma-wall interactions Major collaborations and involvement in the EFDA Work Programme • EFDA-JET including JET EP Programme, • FZJ, Institute of Plasma Physics, TEXTOR Team (Germany), • EFDA-Technology Tasks within Physics Integration Other collaborations with EURATOM Associations • TCV in Lausanne (Switzerland) and Basel University (Switzerland): First Mirrors • TEKES, Finland: studies of plasma-facing components from JET • IPPLM, Poland: structure & composition of dust, laser-induced detritiation, high-

Z metals • MEdC, Romania: development of beryllium coatings for JET • Josef Stefan Institute, Slovenia: fuel retention studies. • CEA Cadarache, ToreSupra, France: structure and composition of co-deposits Collaborations with laboratories outside EFDA: • University of California in San Diego (UCSD), PISCES Team: development of Be

layers; • Nagoya University and Kyushu University (Japan): tritium inventory and high-Z

metals; • Team of the DIII-D tokamak in San Diego(USA): tracer techniques in material

migration; Theoretical fusion plasma physics • General Atomics, San Diego. The Orbit-RF code was transferred and installed on

the JET analysis cluster. Computational methods • SAIC, CA, USA, Daltron Schnack, collaboration on numerical MHD simulations

using the DEBS code


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6. Education and research training The number of students attending undergraduate education at the Division of Fusion Plasma Physics have substantially increased during later years. The main reasons for this is that a number of new courses have been established and the association with TET (Division for Electromagnetic field Theory), which have been a division within the Alfvén Laboratory during 2000-2005. Course development, primarily through course analysis, is emphasized at the Alfvén Laboratory. The aim of course analysis is primarily to help the teacher reflect on how the quality of each course can be improved from one year to the next. Regular discussions with the director of studies is part of this process. Course analysis is now carried out for all courses given. A special form has been developed to support this work. An earlier version of this form was designed by us, and the extended version has now become standard for all course analysis at KTH. Training in pedagogic, both for senior teachers and graduate students, has been emphasized during the later years in collaboration with KTH Learning Lab. The course 2A1500 Engineering Science (Ingenjörsvetenskap), which is given at the CL programme, has been further developed. This course, with its core in mathematical modelling, estimations, dimensional analysis and history of engineering, aims at providing basic engineering skills for further studies of natural science and engineering at KTH, and is now given in a similar form for the OPEN education at KTH by the Division for Space- and Lab Plasma Physics. Researchers at the Division of Fusion Plasma Physics have collaborated with students and teachers at upper secondary schools (see www.alfvenlab.kth.se/edu/gymsam.html) during 2005. This is part of the Alfvén laboratory effort to strengthen connections with Stockholm schools in the fields of mathematics and physics with the aim of improving student interest in these subjects. The Alfvén laboratory is one of the leading KTH departments in this work. 6.1. Undergraduate education The Division of Fusion Plasma Physics participates in the Erasmus Mundus European Master Programme in Nuclear Fusion Science and Engineering Physics (FUSION-EP). The programme was granted in competition with many other master programmes in the EU during 2005. The programme is scheduled to start in 2006. M. Tendler co-ordinates the participation by the Division of Fusion Plasma Physics. Other participants are Ghent University (Gent), Universidad Carlos III (Madrid), Universidad Complutense de Madrid, Université Henri Poincaré (Nancy), and Universität Stuttgart.

http://www.alfvenlab.kth.se/edu/gymsam.html


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Undergraduate level courses The Division for Fusion Plasma Physics offered or co-offered 8 undergraduate courses during 2005. An overview of the courses follows: Compulsory courses: 2A1500, Engineering Science, 5 p CL, J. Scheffel. The progress of technology. Development in the physics, chemistry and computer sciences. About understanding and modelling nature. Units. Estimates. Graphical models. Mathematical models. Proportionality. Model fitting. Dimensional analysis. Simulation modelling. The computer tool MAPLE. The roles of the engineer and the technology user. 2A1165, Vector Analysis, 3 p E, J. Scheffel. Learning oriented course in vector calculus. The course is useful for further studies of electromagnetic theory, wave propagation, fluid mechanics, plasma physics, gas dynamics and the theory of relativity. 2U1700 Project Course in Electrical Engineering, 5 p E, ME. Course in development of new technological systems. First year students are offered hands-on projects, primarily carried out at the lab. The students are also trained in project management and presentation techniques. Optional courses: 2A1151 Energy and Fusion Research, 4 p, J. Scheffel, P. Brunsell. An introduction to fusion oriented plasma physics is given. The central areas of fusion research are emphasised. The progress of fusion research and its present state are discussed in the perspective of future power generation. 2A1145 Electromagnetic waves in Dispersive Media, 4 p, E. Tennfors. The course introduces students to methods of treating electromagnetic waves, which form a basis for a wide spectrum of applications in physics and electro-physics. The electromagnetic theory is described by Fourier transforms in space and time which is advantageous when treating propagation and emission of waves in dispersive, anisotropic media. 2A1170 Chaos and Self- organization, 4 p, M. Tendler. A course on self-organization as a new way of addressing nature, economy, biology, and many other aspects of man and environment. The phenomena dealt with are typically far from static equilibrium and are strongly influenced by the external environment and organize themselves through chaotic fluctuations. 2C1133 Elektroteknisk modellerig, 5 p, G. Engdahl. The course describes models for electrical systems and components and how these models can be used to solve design problems and provide understanding of electrophysical phenomena. 2A1001 Master Thesis in Physical Electrotechnology, 20 p. This course (Examensarbete) is normally 20 p and is based on a research project which is usually connected to the research activity of the Laboratory.


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Master theses projects completed during 2005 O. Danielson, Feedback control of resistive wall modes in RFPs and Tokamaks, P. Ronquist, Heat fluxes caused by magnetohydrodynamic modes in a fusion plasma P. Oen, A two-colour interferometer for electron density profile and transport studies 6.2. Graduate education An important part of the research training provided by the division is the opportunity for students to work with professional research and engineering staff on forefront problems in an internationally competitive research environment. Graduate level courses The main institutional work (“IT-tjänst”) is usually carried out within teaching. Thus all teaching Ph D students take a 2 credits pedagogical course at KTH Learning Lab. Within the Ph D course area, new courses in Research Methodology and presentation techniques as well as in Computer methods in electrophysics have been developed during later years. Graduate courses 2A5035 Motion of charged particles, collision processes and basis of transport

theory, 3-5 p, T. Hellsten 2A5041 Magnetohydrodynamics, basic, 2-4 p , J. Scheffel 2A5042 Magnetohydrodynamics, advanced, 1-5 p, T. Hellsten 2A5051 Plasma waves, 1-3 p, E. Tennfors 2A5055 Fusion research, 1-4 p, J. Scheffel 2A5071 Plasma diagnostics, 4 p, P. Brunsell 2A5087 Research methodology and presentation techniques, 2-3 p, J. Scheffel 2A5089 Computer methods in electrophysics, 2 p, J. Scheffel/ 2A5093 Transport processes, 2-4 p, M. Tendler Licentiate degree 2005 D. Yadikin, Feedback control of resistive wall modes in the reversed field pinch, February 2005, KTH PhD degree 2005 M. Laxåback, Fast wave heating and current drive in tokamaks, February 2005, KTH


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7. Publications 7.1. Peer-reviewed journal publications EXTRAP T2R 1. N. Vianello, E. Spada, V. Antoni, M. Spolaore, G. Serianni, G. Regnoli, R.

Cavazzana, H. Bergsåker, J. R. Drake, Self-regulation of ExB flow shear via plasma turbulence, Phys. Rev. Lett. 94, 135001 (2005)

2. N. Vianello, V. Antoni, E. Spada, M. Spolaore, G. Serianni, R. Cavazzana, H.

Bergsåker, M. Cecconello, J. R. Drake, Reynolds and Maxwell stress measurements in the reversed field pinch experiment EXTRAP T2R, Nucl. Fusion 45 (2005) 761-766.

3. P. R. Brunsell, D. Yadikin, D. Gregoratto, R. Paccagnella, Y. Q. Liu, T.

Bolzonella, M. Cecconello, J. R. Drake, M. Kuldkepp, G. Manduchi, G. Marchiori, L. Marrelli, P. Martin, S. Menmuir, S. Ortolani, E. Rachlew, G. Spizzo, and P. Zanca, Active control of multiple resistive wall modes, Plasma Phys. and Control. Fusion 47(2005)B25-B36.

4. P. R. Brunsell, D. Yadikin, D. Gregoratto, R. Paccagnella, Y. Q. Liu, M.

Cecconello, J. R. Drake, G. Manduchi, G. Marchiori, Feedback stabilization of resistive wall modes in a reversed-field pinch, Phys. Plasmas 12, 092508 (2005).

5. D. Gregoratto, J. R. Drake, D. Yadikin, Y. Q. Liu, R. Paccagnella, P. R.

Brunsell, T. Bolzonella, G. Marchiori, M. Cecconello, Studies on the response of resistive-wall modes to applied magnetic perturbations in the EXTRAP T2R reversed field pinch, Phys. Plasmas 12, 092510 (2005).

6. J. R. Drake, P. R. Brunsell, D. Yadikin, M. Cecconello, J. A. Malmberg, D.

Gregoratto, R. Paccagnella, T. Bolzonella, G. Manduchi, L. Marrelli, S. Ortolani, G. Spizzo, P. Zanca, A. Bondeson, and Y. Q. Liu, Experimental and theoretical studies of active control of resistive wall mode growth in the EXTRAP T2R reversed-field pinch, Nucl. Fusion 45 (2005) 557-564.

7. G. Marchiori, A. Masiello, P. Brunsell, D. Yadikin, Open loop characterization

of an active control system of MHD modes, Fusion Eng. Des. 74 (2005) 555-560. 8. M. Cavinato, D. Gregoratto, G. Marchiori, R. Paccagnella, P. Brunsell, D.

Yadikin, Comparison of strategies and regulator design for active control of MHD modes, Fusion Eng. Des. 74 (2005) 549-553.

9. G. Regnoli, H. Bergsåker, E. Tennfors, F. Zonca, E. Martines, G. Serianni, M.

Spolaore, N. Vianello, M. Cecconello, V. Antoni, R. Cavanazza, J.A. Malmberg, Observations of toroidicity-induced Alfvén eigenmodes in a reversed field pinch plasma, Phys. Plasmas 12, 042502 (2005).


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10. Y. Corre, E. Rachlew, M. Cecconello, R. M. Gravestijn, A. Hedqvist, et al., Radiated power and impurity concentrations in the EXTRAP-T2R reversed-field pinch, Physica Scripta 71 (2005) 523.

Plasma-wall interactions 11. P. Wienhold, A. Litnovsky, V. Philipps,, B. Schweer, G. Sergienko, P. Oelhafen,

M. Ley, G. De Temmerman, W. Schneider, D. Hildebrandt, M. Laux, M. Rubel, B. Emmoth, Exposure of metal mirrors in the scrape-off layer of TEXTOR, J. Nucl. Mater. 337-339 (2005) 1116.

12. Litnovsky, V. Philipps, P. Wienhold, G. Sergienko, B. Emmoth, M. Rubel, W.

Breuer, E. Wessel, Experimental investigations of castellated monoblock structures in TEXTOR, J. Nucl. Mater. 337-339 (2005) 917.

13. B. Emmoth, S. Khartsev, A. Pisarev, A. Grishin, U. Karlsson, A. Litnovsky, M.

Rubel, P. Wienhold, Fuel removal from bumper limiter tiles by using a pulsed excimer laser, J. Nucl. Mater. 337-339 (2005) 639.

14. J. Likonen, E. Vainonen-Ahlgren, J.P. Coad, R. Zilliacus, T. Renvall, D.E. Hole,

M. Rubel, K. Arstila, G.F. Matthews, M. Stamp, Beryllium accumulation in the inner divertor of JET, J. Nucl. Mater. 337-339 (2005) 60.

15. S.L. Allen, W.R. Wampler, A.G. McLean, D.G. Whyte, W.P. West, P.C.

Stangeby, N.H. Brooks, D.L. Rudakov, V. Philipps, M. Rubel, G.F. Matthews, A. Nagy, R. Ellis, A.S. Bozek, C-13 transport studies in L-mode divertor plasmas on DIII-D, J. Nucl. Mater. 337-339 (2005) 30.

16. A. Kirschner, V. Philipps, M. Rubel, P. Mertens, Overview of erosion

mechanisms, impurity transport and deposition in TEXTOR and related modeling, Fusion Sci. Technol., 47 (2005) 146. Invited paper in “TEXTOR Special Issue

17. M. Rubel, P. Coad and D. Hole, Accelerator-based ion beam analysis of fusion

reactor materials, Vacuum 78 (2005) 255. 18. M. Rubel, J.P. Coad, D. Hole, J. Likonen, E. Vainonen-Ahlgren, Fuel retention in

the Gas Box divertor of JET, Fusion Sci. Technol. 48 (2005) 569. 19. J.P. Coad, M. Rubel, N. Bekris, D.E. Hole, J. Likonen, E. Vainonen-Ahlgren,

Distribution of hydrogen isotopes, carbon and beryllium on in-vessel surfaces in the various JET divertors, Fusion Sci. Technol. 48 (2005) 551.

20. S. Rosanvallon, N. Bekris, J. Braet, P. Coad, G. Counsell, I. Cristescu, C. Grisolia,

F. Le Guern, G. Ionita, J. Likonen, A. Perevezenstev, G. Piazza, C. Poletiko, M. Rubel, J.M. Weulersse, Williams, Tritium related studies within the JET Fusion Technology Work Programme, Fusion Sci. Technol. 48 (2005) 268.

21. R.A. Pitts, J.P. Coad, D.P. Coster, G. Federici, W. Fundamenski, J. Horacek, K.

Krieger, A. Kukushkin, J. Likonen, G.F. Matthews, M. Rubel, J.D. Strachan,


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Material erosion and migration in tokamaks, Plasma Phys. Control. Fusion 47 (2005) B303.

22. J.P. Coad, H-G Esser, J. Likonen, M Mayer, G Neill, V Philipps, M. Rubel, J

Vince, Diagnostic for studying deposition and erosion processes in JET, Fusion Eng. Des. 74 (2005) 745.

Theoretical fusion plasma physics 23. T. Bergkvist, and T. Hellsten, T. Johnson and M. Laxåback, Non-linear study

of fast particle excitation of global Alfvén eigenmodes during ICRH, Nuclear Fusion 45(2005) 485-493

24. T. Hellsten, M. Laxåback, T. Bergkvist, T. Johnson, F. Meo, F. Nguyen, C.C.

Petty, M. Mantsinen, G. Matthews, J.-M. Noterdaeme, T. Tala, D. Van Eester, P. Andrew, P. Beaumont, V. Bobkov, M. Brix, J. Brzozowski, L.-G. Eriksson, C. Giroud, E. Joffrin, V. Kiptily, J. Mailloux, M.-L. Mayoral, I. Monakhov, R. Sartori, A. Staebler, E. Rachlew, E. Tennfors, A. Tuccillo, A. Walden, K.-D. Zastrow and JET-EFDA Contributors, On the parasitic absorption in FWCD experiments in JET ITB plasmas, Nucl. Fusion 45 No 7 (July 2005) 706-720

25. M. Laxåback and T. Hellsten, Modelling of minority ion cyclotron current drive

during the activated phase of ITER, Nuclear Fusion 45(2005) 1510-1523 26. M. Mantsinen, V. Kiptily, M. Laxåback, A. Salmi, Yu. Baranov, R. Barnsley, P.

Beaumont, S. Conroy, P. de Vries, C. Giroud, C. Gowers, T. Hellsten, L.C. Ingesson, T. Johnson, H. Leggate, M.-L. Mayoral, I. Monakhov, J.-M. Noterdaeme, S. Podda, S. Sharapov, A.A. Tucillo, D. Van Eester, and EFDA JET contributors. Fast ion distributions driven by polychromatic ICRF waves on JET. Plasma Physics and Controlled Fusion, 47(2005)9:1439-1457

27. T. Hellsten and M. Laxåback, Influence of coupling to spectra of weakly damped

eigenmodes in the ion cyclotron range of frequencies on parasitic absorption in rectified radio frequency sheaths, Physics of Plasmas 12(2005) 032505

Computational methods for fusion plasma 28. J.-E. Dahlin and J. Scheffel, A novel feedback algorithm for simulating

controlled dynamics and confinement in the advanced reversed-field pinch, Phys. Plasmas 12 (2005) 062502

Chaos and self-organisation 29. R. Panek, L. Krlin, M. Tendler, et al, Anomalous ion diffusion and radial-

electric-field generation in a turbulent edge plasma potential weakly correlated in time and space, Physica Scripta 72 (2005) 327.

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Other 30. D. Stork, Y. Baranov, P. Belo, L. Bertalot, D. Borba, J. H. Brzozowski, et al.,

Overview of transport, fast particle and heating and current drive physics using tritium in JET plasmas, Nucl. Fusion 45 (2005) S181-S194.

31. M. Tendler, Ph. Rutberg, and G. VanOost, Plasma based treatment and energy

production, Plasma Phys. Control. Fusion 47 (2005) A219-A230. 32. B. Lehnert, Screw-shaped light in extended electromagnetics, Physica Scripta, 72

(2005) S181-S194. 7.2. Invited talks at international conferences EXTRAP T2R 1. P. R. Brunsell, D. Yadikin, D. Gregoratto, R. Paccagnella, Y. Q. Liu, T.

Bolzonella, M. Cecconello, J. R. Drake, M. Kuldkepp, G. Manduchi, G. Marchiori, L. Marrelli, P. Martin, S. Menmuir, S. Ortolani, E. Rachlew, G. Spizzo, and P. Zanca, Active control of multiple resistive wall modes, Invited talk at the 32nd EPS conf. on Plasma Physics, Tarragona, 27 June - 1 July 2005.

Plasma-wall interactions 2. M. Rubel, P. Coad, D. Hole, Fuel inventory in shadowed areas of the JET

divertors. 3rd Int. Workshop on Tritium – Material Interactions, Toyama (Tateyama), Hydrogen Isotope Research Centre, Japan, May, 2005.

3. M. Rubel, G. Sergienko, T. Hirai, A. Huber, A. Kreter, V. Philipps, A.

Pospieszczyk, B. Schweer, O. Schmitz, T. Tanabe, Tungsten erosion and melt layer formation in the TEXTOR tokamak, 2005 Japan-US Workshop on Heat Removal and Plasma Materials Interactions for Fusion, Fusion High Power Density Components and System, and IEA Workshop on Solid Surface Plasma Facing Components; Kyoto, Japan, May 2005.

4. M. Rubel, Analysis of Plasma Facing Materials in Controlled Fusion Devices,

5th Int. Workshop and Summer School on Plasma Physics (Kudowa-2005), Kudowa, Poland, June 2005.

5. R.A. Pitts, J.P. Coad, D.P. Coster, G. Federici, W. Fundamenski, J. Horacek, K.

Krieger, Kukushkin, J. Likonen, G.F. Matthews, M. Rubel, J.D. Strachan and JET-EFDA Contributors, Material erosion and migration in tokamaks, 32nd EPS Conf. on Plasma Physics and Controlled Fusion, P2.004, Tarragona, Spain, July 2005.

6. M. Rubel, J. Likonen, P. Coad, E. Vainonen-Alhgren, D.E. Hole, C-13 injection

in the outer divertor of JET, 6th International Tokamak Physics Activity on SOL


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and Divertor Physics (ITPA-6, SOL-D), Tarragona, Spain, July 2005. Invited talk (presented by V. Philipps)

7. Kreter, G. Sergienko, V. Philipps, A. Huber, A. Pospieszczyk, M. Rubel, B.

Schweer, O. Schmitz, High temperature erosion and melting of tungsten in TEXTOR, 6th International Tokamak Physics Activity on SOL and Divertor Physics (ITPA-6, SOL-D), Tarragona, Spain, July 2005.

8. M. Rubel, Reactor Aspects of Fusion: Issues related to materials and

radioactivity, 7th Carolus Magnus Euro Summer School on Plasma and Fusion Energy Physics, Mechelerhof, The Netherlands, September 2005.

Theoretical fusion plasma physics

9. T. Hellsten, T. Bergkvist, T. Johnson and M. Laxåback, Integrated Modelling

of ICRH and AE Dynamics, IEA Burning Plasma Workshop Taragona Spain (2005)

10. T. Bergkvist, T. Hellsten and T. Johnson, Self-consistent Study of Fast Particle

Redistribution by Alfvén Eigenmodes During ICRH, IAEA Technical Meeting on Fast Particles, Takayama, Japan 2005

11. H. Berk, C. Boswell, M. F. Nave, T. Johnson, S. D. Pinches, S. E. Sharapov and

L. Zahakarov, The puzzle n=0 sub-TAE Frequency Mode, US-European Transport Task Force Workshop, 6th April 2005 - 9th April 2005 , Napa, California, USA.

12. V. Parail, T. Johnson, T. Kiviniemi, J. Lonnroth, P. de Vries, D. Howell, Y.

Kamada, S. Konovalov, N. Oyama, G. Saibene, K. Shinohara and EFDA-JET contributors., Effect of Ripple-Induced Ion Thermal Transport on H-mode Performance, 32nd Plasma Physics Conference, Tarragona, Spain

13. V. Parail, T. Johnson, T. Kiviniemi, J. Lonnroth, P. de Vries, T. Hatae, V.

Hynönen, D. Howell, Y. Kamada, S. Konovalov, T. Kurki-Suonio, N. Oyama, G. Saibene, R. Sartori, K. Shinohara and EFDA-JET contributors., Effect of Ripple-Induced Ion Thermal Transport on H-mode Performance, 15th International Stellarator Workshop, Madrid, Spain

14. J.S. Lönnroth, M. Bécoulet, P. Beyer, G. Corrigan, C. Figarella, W. Fundamenski,

O.E. Garcia, X. Garbet, G. Huysmans, G. Janeschitz, T. Johnson, T. Kiviniemi, S. Kuhn, A. Loarte, V. Naulin, G.W. Pacher, H.D. Pacher, V. Parail, R. Pitts, G. Saibene, P. Snyder, J. Spence, D. Tskhakaya, H. Wilson, Integrated ELM modelling, 10th PET (Plasma Edge Theory Workshop), Julich, Germany

15. L.-G. Eriksson, T. Johnson, M.-L. Mayoral, S. Coda, O. Sauter, R.J. Buttery, D.

McDonald, T. Hellsten, M.J. Mantsinen, A. Mueck, J.-M. Noterdaeme, E. Westerhof, P. de Vries and JET-EFDA contributors, On Ion Cyclotron Current Drive for Sawtooth control, 9th IAEA TM on Energetic Particles in Magnetic Confinement Systems, Takayama, Japan


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7.3. International conference contributions EXTRAP T2R

1. D. Yadikin, P. R. Brunsell, J. R. Drake, Intelligent shell feedback control of resistive wall modes in EXTRAP T2R, Proc. 32nd EPS conf. on Plasma Physics, Tarragona, 27 June - 1 July 2005, Europhysics Conf. Abstracts, Vol. 29C P-4.066 (2005). (Poster)

2. M. Cecconello, P. R. Brunsell, D. Yadikin, J. R. Drake, Rotation evolution of

tearing modes during feedback stabilization of resistive wall modes in a reversed field pinch, Proc. 32nd EPS conf. on Plasma Physics, Tarragona, 27 June - 1 July 2005, Europhysics Conf. Abstracts, Vol. 29C P-4.067 (2005). (Poster)

3. S. Menmuir, M. Cecconello, M. Kuldkepp, E. Rachlew, P. R. Brunsell, J. R.

Drake, Ion and mode rotation in the EXTRAP T2R device during discharges with and without the application of feedback control, Proc. 32nd EPS conf. on Plasma Physics, Tarragona, 27 June - 1 July 2005, Europhysics Conf. Abstracts, Vol. 29C P-4.079 (2005). (Poster)

4. M. Kuldkepp, S. Menmuir, E. Rachlew, Y. Corre, P. R. Brunsell, M.

Cecconello, Oxygen impurity profile studies in the EXTRAP T2R reversed field pinch, Proc. 32nd EPS conf. on Plasma Physics, Tarragona, 27 June - 1 July 2005, Europhysics Conf. Abstracts, Vol. 29C P-1.029 (2005). (Poster)


Bolzonella, M. Cecconello, J. R. Drake, M. Kuldkepp, G. Manduchi, G. Marchiori, L. Marrelli, P. Martin, S. Menmuir, S. Ortolani, E. Rachlew, G. Spizzo, P. Zanca, Feedback control on EXTRAP-T2R with coils covering full surface area of torus, 10:th Workshop on Active control of MHD Stability 2005: "Progress in Kink and Tearing Mode Control", Univ. Wisconsin, Madison, October 31 - November 2 2005. (Talk)

6. J. R. Drake, D. Gregoratto, D. Yadikin, P. R. Brunsell, M. Cecconello, Y. Q.

Liu, Response of RWMs to pre-programmed, external perturbations in the EXTRAP T2R RFP, 10:th Workshop on Active control of MHD Stability 2005: "Progress in Kink and Tearing Mode Control", Univ. Wisconsin, Madison, October 31 - November 2 2005. (Talk)


Bolzonella, M. Cecconello, J. R. Drake, M. Kuldkepp, G. Manduchi, G. Marchiori, L. Marrelli, P. Martin, S. Menmuir, S. Ortolani, E. Rachlew, G. Spizzo, and P. Zanca, Active control of multiple resistive wall modes, 11:th IEA/RFP Workshop, Padova, 10-12 May, 2004, Conzorzio RFX, Padova, Italy. (Talk)


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Plasma-wall interactions

8. M. Rubel, J.P. Coad, J. Likonen, Erosion, deposition and material transport, General TF Fusion Technology Meeting, Culham, United Kingdom, February 2005. (Talk)

9. M. Rubel, E. Fortuna, A. Kreter, E. Wessel, V. Philipps, K. Kurzydłowski,

Overview of comprehensive characterisation of erosion zones on plasma facing components, 7th Int. Symposium of Fusion Nuclear Technology (ISFNT-7), Tokio, Japan, May 2005. (Poster)

10. C. Grisolia, S. Rosanvallon, P. Coad, N. Bekris, J. Braet, D. Brennan, B.

Brichard, G. Counsell, C. Day, J. Likonen, G. Piazza, C. Poletiko, M. Rubel, A. Semerok, JET contributions to ITER technology issues, 7th Int. Symposium of Fusion Nuclear Technology (ISFNT-7), Tokio, Japan, May 2005. (Poster)

11. P. Gąsior, J. Badziak, A. Czarnecka, P. Parys, J. Wołowski, M. Rosiński, V.

Philipps, M. Rubel, The ion diagnostic method: a novel measuring technique for characterization of laser-induced deuterium removal from in-vessel tokamak components, 5th Int. Workshop and Summer School on Plasma Physics (Kudowa-2005), Kudowa, Poland, June 2005. (Talk)

12. B. Emmoth, M. Rubel, V. Philipps, Surface structure modification of plasma-

facing materials in controlled fusion devices, 13th Int. Conf. on Thin Films, Stockholm, Sweden, June 2005. (Poster)

13. G. Sergienko, A. Huber, A. Kreter, V. Philipps, A. Pospieszczyk, M. Rubel, B.

Schweer, O. Schmitz, High temperature erosion of tungsten exposed to the TEXTOR edge plasma, 32nd EPS Conf. on Plasma Physics and Controlled Fusion, Tarragona, Spain, July 2005. Europhys. Conf. Abstracts 29C (2005) P-1.018. (Poster)

14. M. Rubel, J.P. Coad, J. Likonen, G.F. Matthews, E. Vainonen-Ahlgren,

Material migration studies at JET using tracer techniques, 32nd EPS Conf. on Plasma Physics and Controlled Fusion, P2.004, Tarragona, Spain, July 2005. Europhys. Conf. Abstracts 29C (2005) P-2.004. (Poster)

15. G. De Temmerman, M. Rubel, J.P. Coad, R.A. Pitts, J.R. Drake and P.

Oelhafen, Mirror Test for ITER: Optical characterization of metal mirrors in divertor tokamaks, 32nd EPS Conf. on Plasma Physics and Controlled Fusion, Tarragona, Spain, July 2005. Europhys. Conf. Abstracts 29C (2005) P-1.076. (Poster)

16. A. Litnovsky, V. Philipps, P. Wienhold, G. Sergienko, A. Kreter, O. Schmitz, U.

Samm, P. Karduck. M. Blöme, B. Emmoth, M. Rubel, Carbon deposition and fuel accumulation in the castellated limiters exposed under erosion-dominated conditions in the SOL of TEXTOR, 32nd EPS Conf. on Plasma Physics and Controlled Fusion, Tarragona, Spain, July 2005. Europhys. Conf. Abstracts 29C (2005) P-1.015. (Poster)


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17. A. Litnovsky, G. De Temmerman, P. Wienhold, V. Philipps, O. Schmitz, U. Samm, G. Sergienko, P. Oelhafen, M. Rubel and B. Emmoth, Direct comparative test of single crystal and polycrystalline diagnostic mirrors exposed in TEXTOR in erosion conditions, 32nd EPS Conf. on Plasma Physics and Controlled Fusion, Tarragona, Spain, July 2005. Europhys. Conf. Abstracts 29C (2005) P-4.099. (Poster)

18. G. Sergienko, A. Huber, A. Kreter, V. Philipps, M. Rubel, B. Schweer, O.

Schmitz and M. Tokar, Tungsten melting under high power load in the TEXTOR edge plasma, 32nd EPS Conf. on Plasma Physics and Controlled Fusion, Tarragona, Spain, July 2005. Europhys. Conf. Abstracts 29C (2005) P-1.019. (Poster)

19. P. Gąsior, J. Wołowski, J. Badziak, A. Czarnecka, P. Parys, V. Philipps, M.

Rosiński, M. Rubel, Laser-induced detritiation, European Congress on Advanced Materials and Processes EUROMAT 2005, Session: EXTREMAT (Materials for Extreme Environments), Prague, Czech Republic, September 2005.”

20. J. Wołowski, J. Badziak, A. Czarnecka, P. Gąsior, P. Parys, V. Philipps, M.

Rosiński, M. Rubel, Application of ion diagnostics to control the laser-induced removal of surface layer of a carbon substrate, Int. Conf. PLASMA-2005 on Research and Applications of Plasmas (combined with: 3rd German-Polish Conf. On Plasma Diagnostics for Fusion and Applications and with 5th French-Polish Seminar on thermal Plasma in Space and Laboratory), Opole, Poland, September 2005. (Talk)

21. M. Rubel, Overview of recent results of the VR-Euratom Association: Fuel

retention, fuel removal and material migration in tokamaks, 4th General Meeting of the EU TF on Plasma Wall Interactions, Cadarache, France, October 2005. (Talk)

22. A. Litnovsky, V. Philipps, A. Kirschner, P. Wienhold, G. Sergienko, O. Schitz,

A. Kreter, P. Karduck, M. Blöme, B. Emmoth. M. Rubel, Transport of carbon, deposition and fuel accumulation in metallic castellated limiters exposed in the SOL of TEXTOR, 12th Int. Conf. on Fusion Reactor Materials, Abstracts, p. 166, 08-86, Santa Barbara, California, USA, December 2005. (Poster)

23. E. Fortuna, M. Rubel, M. Pisarek, W. Zieliński, M. Miśkiewicz, V. Philipps and

K.J. Kurzydłowski, Properties of co-deposits on graphite high heat flux components, 12th Int. Conf. on Fusion Reactor Materials, Abstracts, p. 67, 04-69, Santa Barbara, California, USA, December 2005. (Poster)

24. M. Rubel, J.P. Coad, Overview of co-deposition and fuel inventory in

castellated divertor structures at JET, 12th Int. Conf. on Fusion Reactor Materials, Abstracts, p. 13, 02B-2, Santa Barbara, California, USA, December 2005. (Talk)


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Theoretical fusion plasma physics

25. T. Hellsten, T. Bergkvist, T. Johnson and M. Laxåback, Effects of Finite Orbit Width and RF-Induced Spatial Diffusion on Ion Cyclotron Emission, 16th RF topical conference in Park City Utah, April 2005, 50 (Poster)

26. T. Johnson, T. Hellsten and L.-G. Eriksson, Analysis of a quasilinear model for

ion-cyclotron interactions in tokamaks,16th RF topical conference in Park City Utah, April 2005, 54 (Poster)

27. T. Hellsten, M. Laxåback, T. Johnson, M. Mantsinen, G. Matthews, P.

Beaumont, C. Challis, D. van Eester, E. Rachlew, T. Bergkvist, C. Giround, E. Joffrin, A. Huber, V. Kiptily, F. Nguyen, J.-M. Noterdaeme, J. Mailloux, M.-L. Mayoral, F. Meo, I. Monakhov, F. Sartori, A. Staebler, E. Tennfors, A. Tuccillo, A.Walden, B. Volodymyr and JET-EFDA contributors, Fast Wave Current Drive in JET ITB-Plasma, 16th RF topical conference in Park City Utah, April 2005, 273 (Poster)

28. T. Hellsten, K. Holmström, T. Johnson, T. Bergkvist and M. Laxåback , ICE

in toroidal plasmas, IAEA Technical Meeting on Fast Particles, Takayama, Japan 2005 (Talk)

29. J.S. Lönnroth, V. Parail, T. Johnson, T. Kiviniemi, G. Saibene, P. de Vries, A.

Loarte, T. Hatae, Y. Kamada, S. Konovalov, N. Oyama, K. Shinohara, K. Tobita, H. Urano and JET-EFDA contributors, Effects of ripple-induced thermal ion losses on H-mode plasma performance, US-European Transport Task Force Workshop, 6th April 2005 - 9th April 2005 , Napa, California, USA. (Poster)

30. T. Hellsten, M. Laxåback, T. Bergkvist, T. Johnson, M. Mantsinen, G.

Matthews, F. Meo, F. Nguyen, J.-M. Noterdaeme, C. C. Petty, T. Tala, D. Van Eester, P. Andrew, P. Beaumont, V. Bobkov, M. Brix, J. Brzozowski, L.-G. Eriksson, C. Giroud, E. Joffrin, V. Kiptily, J. Mailloux, M.-L. Mayoral, I. Monakhov, R. Sartori, A. Staebler, E. Rachlew, E. Tennfors, A. Tuccillo, A. Walden, K.-D. Zastrow and JET-EFDA contributors, Fast Wave Current Drive in JET ITB-Plasma, 16th Topical Conference on Radio Frequency Power in Plasmas, 2005, Park City, Utah, USA. (Poster)

31. T. Johnson, T. Hellsten and L.-G. Eriksson, Analysis of a quasilinear model for

ion-cyclotron interactions in tokamaks, 16th Topical Conference on Radio Frequency Power in Plasmas, 2005, Park City, Utah, USA. (Poster)

32. V. Parail, T. Johnson, J. Lonnroth, T. Kiviniemi, P. de Vries, G. Saibene, Y.

Kamada, N. Oyama, K. Shinohara, S. Konovalov, D. Howell, Magnetic Ripple as a Tool for ELMs Mitigation, ITPA meeting: Transport Physics, Confinement Database and Modeling, Pedestal and Edge groups, Kyoto University, Kyoto 606-8501, Japan (Poster)


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33. T. P. Kiviniemi, V. Parail, T. Johnson, J. Lönnroth, T. Kurki-Suonio, V. Hynönen, J.Heikkinen, S. Sipilä and JET EFDA contributors., Ripple-Induced Fast Ion and Thermal Ion Losses, 32nd Plasma Physics Conference, Tarragona, Spain (Poster)

34. C. J. Boswell, H.L. Berk, D. Borba, T. Johnson, M. F. F. Nave, S. D. Pinches,

S. E. Sharapov and JET EFDA contributors., Observation and Explanation of the JET n=0 Chirping Mode, 32nd Plasma Physics Conference, Tarragona, Spain (Poster)

35. T. Hellsten, M. Laxåback, T. Bergkvist, T. Johnson, F. Meo, F. Nguyen, C.

C. Petty, M. Mantsinen, G. Matthews, J.-M. Noterdaeme, T. Tala, D. Van Eester, P. Andrew, P. Beaumont, V. Bobkov, M. Brix, J. Brzozowski, L.-G. Eriksson, C. Giroud, E. Joffrin, V. Kiptily, J. Mailloux, M.-L. Mayoral, I. Monakhov, R. Sartori, A. Staebler, E. Rachlew, E. Tennfors, A. Tuccillo, A. Walden, K.-D. Zastrow and JET-EFDA contributors, On the parasitic absorption in FWCD experiments in JET ITB plasmas, 32nd Plasma Physics Conference, Tarragona, Spain (Poster)

36. H. Berk, C. Boswell, D. N. Borba, M. F. Nave, T. Johnson, S. D. Pinches, and

S. E. Sharapov, Axisymmetric Phase Space Structures Driven by Fast Ions in JET, 47th Annual Meeting of the APS Division of Plasma Physics, Denver, USA (Poster)

37. H. L. Berk, C. Boswell, D. N. Borba, M. F. Nave, T. Johnson, S. D. Pinches,

and S. E. Sharapov and JET EFDA contributors, Axisymmetric Phase Space Structures Driven by Fast Ions in JET, 9th IAEA TM on Energetic Particles in Magnetic Confinement Systems, Takayama, Japan (Poster)

Computational methods for fusion plasmas

38. J.-E. Dahlin and J. Scheffel, Advanced reversed-field pinch scaling laws, 32nd

EPS Conference on Plasma Physics, Tarragona, Spain, 27 June-1 July, P1.118, 2005 (Poster)

39. J.-E. Dahlin and J. Scheffel, Scaling laws of confinement parameters for the

advanced reversed-field pinch, 47th APS Division of Plasma Physics Meeting, Denver, Colorado, 24-28 October, 2005

7.4. Other publications 1. J.S. Lönnroth, V. Parail, T. Johnson, G. Saibene, T. Kiviniemi, A. Loarte, P. de

Vries, T. Hatae, Y. Kamada, S. Konovalov, N. Oyama, K. Shinohara, K. Tobita, H. Urano and JET EFDA contributors, Effects of Ripple-Induced Ion Thermal Transport on H-mode Plasma Performance, JET report EFD-P(04)7


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8. Staff Professor: Drake, James R.

Hellsten, Torbjörn Tendler, Michael

Professor emeritus: Lehnert, Bo Associate professor: Bergsåker, Henrik

Brunsell, Per Rubel, Marek Scheffel, Jan Tennfors, Einar

Researcher, (PhD): Brzozowski, Jerzy Cecconello, Marco Elevant, Thomas Johnson, Thomas

PhD students: Bergqvist, Tommy Dahlin, Jon-Erik Holmström, Kerstin Laxåback, Martin Yadikin, Dmitriy

Research engineer: Ekman, Rolf Hägerström, Gunder Kindberg, Gunder

Engineer: Ferm, Håkan Westerberg, Lars

Technician: Freiberg, Jesper Workshop technician: Haapasaari, Juhani Head administrator: Forsberg, Birgitta Accountant: Johansson, Anita Administrator: Mau, Ingeborg Administration assistant: Söderhäll, Elisabeth


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9. Professional activity Membership, honours, responsibilities, etc Bergsåker, Henrik • Co-investigator for an EXTRAP T2R experimental project founded by VR Brunsell, Per • Principal-investigator for an EXTRAP T2R experimental project funded by VR Brzozowski, Jerzy • Deputy Leader for EFDA-JET Task Force for Diagnostics Cecconello, Marco • Liaison Officer at EFDA-CSU Garching for ITER Physics Integration Drake, James R. • Member of the Royal Swedish Academy of Engineering Sciences. • Director of Graduate Studies for the School of Electrical Engineering. • Chairman of the Academic Position Recruitment Committee for the Schools of

Electrical Engineering, Information and Communication Technology, and Computer Science and Communication.

• Head of the Swedish Fusion Research Unit, Association EURATOM-VR. • Member of the EU Consultative Committee for the Fusion Programme • Member of the European Fusion Development Agreement Steering Committee. • Member of the Scientific and Technical Committee for the Consorzio RFX

(Padova, Italy). • Member of the Executive Committee, International Energy Agency Trilateral

Agreement (EU, Japan, USA) for a Programme of R&D on Reversed-Field Pinches.

• Director of the Alfvén Center for Space and Fusion Plasma Physics. Hellsten, Torbjörn • Monitoring of the EU fusion programme for STAC • Leader for IMP5 project within the ITM task force • Member of CCFW/CD, • Member of STAC Laxåback, Martin • Member of the JET Programme Execution Committee Lehnert, Bo • Member of Royal Swedish Academy of Sciences, Physics Class • Member of Royal Swedish Academy of Engineering Sciences, Division of Basic

Science • Fellow of the Institute of Mathematics and its Applications, London • Fellow of the Alpha Institute of Advanced Study, Budapest


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Rubel, Marek • European Microbeam Analysis Society, member • 5th Int. Summer School and Workshop on Plasma Physics, Kudowa-2005, Poland:

School director, editor of the proceedings: Physica Scripta T123. • 12th Int. Conf. on Fusion Reactor Materials:, Santa Barbara, California, USA,

Programme Committee member • 11th Int. Workshop on Plasma Facing Materials and Components, Greifswald,

Germany, Programme Committee Member • 8th Int. Workshop on Hydrogen in Fusion Reactor Materials, Huangshan, China,

Int. Programme Committee member • The Swedish Research Council, Evaluation Committee for Atomic, Molecular,

Plasma and Fusion Physics, member • EU Task Force on Plasma Wall Interactions, member, contact person for the

Swedish Euratom Association • EFDA JET: Task Forces: Divertor Physics, Fusion Technology, member, contact

person for the Swedish Euratom Association. Scheffel, Jan • Director of undergraduate and graduate studies at the Alfvén Laboratory, KTH • Chairman of undergraduate studies for the M Sc programme in Engineering and of

Education at KTH • Chairman of undergraduate studies for the Open Entrance programme at KTH • Public relations officer for Swedish fusion research, (a task within EFDA;

European Fusion Development Agreement). • Board member of Vetenskapens Hus (House of Science,

www.vetenskapenshus.albanova.se) • Board member of the School of Electrical Engineering Tendler, Michael • Chair, Plasma Physics Section, Swedish Physical Society • Plasma Physics Board of the European Physical Society • Programme Committee of Annual Workshops ”Role of Electric Fields in Plasma

Confinement.” • Coordinator of the Baltic Sea Area Plasma Physics Net run by the United Nations. • Chair, International Board of Advisors, Euratom – CR Association. • Adviser to the Plasma Physics Division of the American Physical Society on the

International Contacts & Grants Policy • Chair, Board, University I Studium, Tallin, Estonia • Member of IVA Einar Tennfors • Swedish Fusion Research Unit contact person for EFDA-JET Task Force S2S2 Advanced

tokamak Operation • Swedish Fusion Research Unit contact person for EFDA-JET Task Force H: Heating,

current drive and plasma rotation • Member of the EFDA-JET Remote Participation Users Group, representing the Swedish

Fusion Research Unit


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• Member of the EFDA Public Information Group • Member of the Executive Committee for the Fusion Expo consortium Academic and expert activity Opponent, examination committee Brunsell, Per • Examination Committee, PhD thesis defence. David Sundkvist, Uppsala

University Drake, James R. • Examination Committee. PhD thesis defence. Ulf Jordan, Chalmers University of

Technology, Dept of Radio and Space Science. • Opponent. Licentiate Seminar. Magnus Olsson. KTH Electrical Engineering. Technical adviser, expert Drake, James R. • Evaluation in connection with promotion to an associate professorship at

Technical University of Munich, Germany • Evaluation in connection with promotion to a full professorship at the University

of Maryland, USA. • Evaluation in connection with employment of a full professor at the University of

Wisconsin, USA • Expert for applications to VR. Journal referee Brunsell, Per, Phys. Plasmas (2), Plasma Science (1) Cecconello, Marek, Physica Scripta, (1 ) Drake, James R., Nucl. Fusion, Phys. Plasmas Hellsten, Torbjörn, Nucl. Fusion (2), Phys. Plasmas (2) Laxåback, Martin, Nucl. Fusion, (1) Rubel, Marek, Physica Scripta (5), Fus. Eng. Des., (2) Scheffel, Jan, Plasma Phys. and Control. Fusion (2), Phys. Plasmas, (1) Tendler, Michael, Nucl. Fusion (1), Plasma Phys. Control. Fusion (2)


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10. Economy The funding sources for 2005 have included KTH funding for undergraduate education (GRU), research and research training (FOFU), and external funding from the Swedish Research Council (VR) and Euratom (EU). The accounts for the Division of Fusion Plasma Physics for the year 2005 are summarized in the table below.

INCOME 2005 KKR KTH Undergraduate education GRU 1 346KTH Faculty research and research training FOFU 12 136VR, EU Grants 9 787Other external funding 531Sum Income 23 800EXPENDITURES 2005 Salary 11 970Rent 4 079Operations, etc 1 830Administration 1 634KTH (HSG) 3 596Equipment 122Sum Expenditures 23 231RESULT 2005 508


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