1. Member of the Helmholtz Association Reactor-relevant Plasma-Material Interaction Studies in Linear Plasma Devices Arkadi Kreter Institute for Energy Research - Plasma Physics, Forschungszentrum Juelich, Association EURATOM-FZJ, Trilateral Euregio Cluster, Germany 8 th International Conference on Open Magnetic Systems for Plasma Confinement Novosibirsk, Russia, 6 July 2010

2. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 2 Outline Introduction: plasma-wall interaction in ITER and beyond Reactor-relevant PMI-studies: Linear Plasma Device vs tokamak PMI-studies in LPDs: how does it work? Highlights of PMI-studies in LPDs: it's all about special features Future of PMI-studies in LPDs: bigger, denser, hotter Frequent abbreviations: PWI: Plasma-Wall Interaction PMI: Plasma-Material Interaction LPD: Linear Plasma Device

3. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 3 Introduction: plasma-wall interaction in ITER and beyond Reactor-relevant PMI-studies: Linear Plasma Device vs tokamak PMI-studies in LPDs: how does it work? Highlights of PMI-studies in LPDs: it's all about special features Future of PMI-studies in LPDs: bigger, denser, hotter

4. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 4 Plasma-wall interaction and reactor availability ITER Plasma-wall conditions in tokamak reactor  High steady-state particle and heat fluxes  Transient events (ELMs, disruptions)  Neutron irradiation (~1 dpa in ITER, >100 dpa in reactor)  Impurities (C, Be, W, He, Ar,...) Plasma-wall interaction processes  Erosion and migration of wall materials  Re-deposition including co-deposition of tritium  Dust production  Embrittlement, swelling and transmutation due to neutrons Consequences for reactor availability  Limited wall lifetime  Safety aspects: tritium retention and dust production Many facets of PWI studies: from very plasma-specific (e.g. impurity transport in a tokamak) to very material-specific (e.g. development of new materials) and component- specific (e.g. plasma-facing component testing in high-heat flux facilities) This talk is on Plasma-Material Interaction (PMI) studies in Linear Plasma Devices (LPDs)

5. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 5 Introduction: plasma-wall interaction in ITER and beyond Reactor-relevant PMI-studies: Linear Plasma Device vs tokamak PMI-studies in LPDs: how does it work? Highlights of PMI-studies in LPDs: it's all about special features Future of PMI-studies in LPDs: bigger, denser, hotter

6. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 6 LPD plasma parameters are relevant to ITER Parameter"typical" LPDITER divertor Electron temperature 1 – 20 eV~1 – 10 eV El. density10 18 –10 19 m -3 ~10 20 m -3 Particle flux~10 23 m -2 s -1 10 24 – 10 25 m -2 s -1 Particle fluence up to 10 27 m -2 per exposure 10 26 – 10 27 m -2 per pulse (400 s) Incident ion energy ~10 – 100 eV (negative bias) ~10 eV Wall (sample) temperature 300 – 2000 K500 – 1000 K Impuritiesany C, Be, W, He, Ar (N 2 ) Transients (ELMs, disruptions) can be simulated by laser or by positive target biasing  Fluence per experiment is ~10x – 100x higher than in present tokamaks  Exposure parameters can be pre-selected with high accuracy to simulate particular ITER conditions

7. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 7 PMI research: LPDs vs. Tokamaks JET Costs of experimental investigations Construction costs Annual exploitation costs Tokamaks ~ 100 – 1000 m EUR ~ 10 – 100 m EUR LPDs~ 1 – 10 m EUR~ 0.1 – 1 m EUR One experimental session (12 pulses) costs ~300 k£ Flexibility of research in LPDs  Good control and reproducibility of exposure parameters  Parameter variations in multi-dimensional parameter space  Easier accessibility (exchange and analysis of material samples)  Higher reliability  Better capabilities of in-situ analyses  PMI studies in LPDs are flexible and cost-effective  Complimentary to tokamak research

8. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 8 Introduction: plasma-wall interaction in ITER and beyond Reactor-relevant PMI-studies: Linear Plasma Device vs tokamak PMI-studies in LPDs: how does it work? Highlights of PMI-studies in LPDs: it's all about special features Future of PMI-studies in LPDs: bigger, denser, hotter

9. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 9 Schematic view of linear plasma device PISCES-B (UCSD, USA) in air-tight enclosure  B field ~0.1 T  Plasma  ~10 cm  Target  1 – 5 cm  Target biasing defines incident ion energy  Neutral pressures in source and target regions are independent Typical features

10. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 10 Typical arc plasma source Parameters Alternative concepts for new LPDs should gain ~10 in plasma density / flux: Cascaded arc (Magnum-psi, FOM, Holland) RF helicon (PMTS, ORNL, USA) Both compatible with high B field (~1 T) LaB 6 emitter diameter ~10 cm LaB 6 emitter heating power ~10 kW LaB 6 emitter temperature 1900 K LaB 6 emitter el. current density 20 A/cm 2 Arc currentup to ~1000 A Arc voltageup to 200 V

11. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 11 Sample surface analysis is integral part of PMI research Analysis methods In-situ and ex-situ analysis Laser-based methods: LIA, LID, LIBS  Talk by B. Schweer Thermal desorption spectrometry (TDS) Ion beam analyses: NRA, RBS, PIXE,.. Electron beam-based techniques: SEM, EDX, WDX, AES,.. Many other abbreviations…  Expensive and time-consuming, but necessary Surface gets deactivated and impurity contaminated when exposed to the air  Immediate analysis preferable (but challenging and expensive) In-situ: real-time surface control during exposure In-vacuo: analysis after experiment but without exposure to the air Ex-situ (post-mortem): analysis after exposure to the air Chemical composition, chemical state and morphology under plasma bombardment

12. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 12 In-situ and in-vacuo analyses In-situ ion beam analysis at DIONISOS (MIT, USA) In-vacuo surface analysis station at PISCES-B (UCSD, USA) Surface analysis (AES, XPS, SIMS) Target chamber Swing-linear manipulator 1 m Sample interlock

13. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 13 Introduction: plasma-wall interaction in ITER and beyond Reactor-relevant PMI-studies: Linear Plasma Device vs tokamak PMI-studies in LPDs: how does it work? Highlights of PMI-studies in LPDs: it's all about special features Future of PMI-studies in LPDs: bigger, denser, hotter

14. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 14 Specific issues of PMI research General abilities of typical LPDs Unique features of particular LPDs and resulting specific missions (only existing experiments considered)  High particle fluence  Well-controlled exposure conditions (i.e. sample temperature, plasma species, energy) Research in LPDs is mainly aimed at effects distinctive for high fluence or specific exposure conditions, e.g. Flux dependence of carbon chemical erosion High-Z material blistering W fuzz formation by He irradiation … PISCES-B (UCSD, USA): capability of working with all ITER materials incl. beryllium Mixed-material R&D for ITER NAGDIS-II (Nagoya U, Japan): high density plasma Detachment studies TPE (INL, USA): tritium and moderate level of radioactivity Tritium permeation Performance of n-irradiated materials DIONISOS (MIT, USA): in-situ surface analysis + target irradiation by MeV ions Dynamics of PMI processes Effects of target irradiation in plasma environment PILOT-PSI (FOM, Holland): high flux plasma PMI studies for ITER-like high-flux divertor conditions

15. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 15 PISCES-B: Mitigation of chemical erosion of carbon by beryllium Beryllium seeding in PISCES-B Mitigation of chemical erosion of carbon by beryllium injection Time (s) 0500100015002000 0.1 1 0.18 % Be0.41 % Be 0.13 % Be 1.10 % Be 0.03 % Be Ch. erosion yield [a.u.] Y ch  exp(-t/  ), where 1/   f Be 2  exp(- E a /T s )  Attributed to formation of beryllium carbide  Potentially favourable for ITER [M.J. Baldwin and R.P. Doerner, Nucl. Fusion 46 (2006) 444] [D. Nishijima et al., J. Nucl. Mater. 363-365 (2007) 1261] Carbon suffers from chemical erosion by methane formation with hydrogen

16. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 16 PISCES-A: Fuel retention in CFC NB41 M=4 (D 2 ) desorption spectra (T s = 470 K, E i = 120 eV)  =50e25 D/m 2 10e25 3e25 1e25 470 K Retention [D/m 2 ] Ion fluence [D/m 2 ] NB41 PISCES-A [1] N11 PISCES-A [2] NB31 TEXTOR [3] DMS780 TEXTOR [3] EK98 TEXTOR [3] 10 24 10 25 10 26 10 27 10 21 10 22  0.35 Total D retention for exposures at T s = 470 K, E i = 120 eV No saturation up to  =5  10 26 D/m 2 ATJ PISCES-A [1] [1] A. Kreter et al., Phys. Scr. T138 (2009) 014012 [2] J. Roth et al., J. Nucl. Mater. 363–365 (2007) 822 [3] A. Kreter et al., J. Phys.: Conf. Series 100 (2008) 062024 Similar behaviour for different CFCs and fine-grain graphites 0.5 K/s CFC NB41 is EU candidate material for ITER divertor target

17. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 17 PISCES-B: Influence of Be+He on retention Mass 4 (D 2 ) desorption spectra for ATJ fine-grain graphite exposed to pure D, D+Be, D+Be+He (T s =720K, E i =35 eV, f He =16%) Be injection prevents further uptake of D retention He appears to change the retention mechanism and to reduce retention Total Deuterium Retention Pure D,  =0.5e26 D/m 2 : 1.6e21 D/m 2 D+Be,  =0.5e26 D/m 2 before Be,  =2e26 D/m 2 total: 1.8e21 D/m 2 D+Be+He,  =0.4e26 D/m 2 before Be,  =1.7e26 D/m 2 total: 0.5e21 D/m 2 0.5 K/s [A. Kreter et al., Phys. Scr. T138 (2009) 014012]

18. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 18 NAGDIS-II: Physics of plasma detachment Plasma in front of target at low and high pressure Reduction of n e and T e in detachment Reduction of heat flux in detachment [N. Ohno et al., Nucl. Fusion 41 (2001) 1055] ITER will operate in semi-detached regime

19. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 19 ITER domain Pilot-PSI: High plasma flux studies Plasma parameter cover ITER divertor domain Forerunner experiment of Magnum-PSI  Up to 1.6 T in pulsed operation (0.4 s)  0.2 T in steady-state  Particle flux up to ~10 25 H + /m 2 s  Power fluxes > 30 MW/m 2 FOM Chemical erosion of carbon at high fluxes [J. Westerhout et al., Phys. Scr. T138 (2009) 014017]

20. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 20 PMI studies in mirror machines ELM simulation in GOL-3 (BINP) and plasma guns E-divertor project on Gamma 10 (Tsukuba U) Open end as divertor simulator  Large diameter high heat plasma flow  Talks by T. Imai, Y. Nakashima  Talk by A.A. Shoshin

21. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 21 Introduction: plasma-wall interaction in ITER and beyond Reactor-relevant PMI-studies: Linear Plasma Device vs tokamak PMI-studies in LPDs: how does it work? Highlights of PMI-studies in LPDs: it's all about special features Future of PMI-studies in LPDs: bigger, denser, hotter

22. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 22 LPDs in future: bigger, denser, hotter Scientific gap: too low plasma densities and fluxes Solutions: High B field for better confinement Novel plasma source Plasma heating Devices:  Magnum-PSI (FOM, Holland)  Paloma (CIEMAT, Spain)  PMTS (Oak Ridge NL, USA) Recognising and filling the gaps in PMI towards ITER and reactor Scientific gap: PMI of neutron damaged materials Solutions: Device in a glove box (moderate level of radioactivity) Device in a hot cell (high level of radioactivity) Hot cells are (Pb-)shielded nuclear radiation containment chambers Devices:  VISION I (SCK-CEN, Mol, Belgium)  JULE-PSI (FZ Jülich, Germany)

23. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 23 Plans for portfolio of complimentary LPDs in TEC Trilateral Euregio Cluster (TEC): FOM, Holland  Magnum-PSI ERM/ KMS with SCK-CEN, Belgium  VISION I FZJ, Germany  JULE-PSI JULE-PSI MAGNUM-PSI 10 18 10 20 10 22 10 24 10 26 10 10 0 1 2 3 ITER: first wall VISION-I ITER divertor ITER strike points E ion [eV]  ion [m -2 s -1 ] Covering ITER operational space

24. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 24 Magnum-PSI: True divertor simulator Design specifications Waiting for delivery of SC magnets to start operation 3 T steady-state, superconducting Plasma heating (Ohmic and helicon wave)  10 cm plasma column Inclined target FOM 1 m Particle flux ~10 24 H + /m 2 s Power fluxes ~10 MW/m 2 El. density ~10 20 m -3 El. temperature 1 – 5 eV Schematic view  True ITER divertor simulator magnet

25. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 25 Plasmatron VISION I: Versatile Instrument for the Study of Ion Interaction Volume: 18 litres Target diameter: ~ 24 cm Ion energies: 20 - 500 eV Magnetic field: 0.2T Pulse duration: steady state Flux density target: ~ 10 20 -10 21 ions/m 2.s Deuterium and Tritium plasma Neutron Irradiated samples Beryllium samples [I. Uytdenhouwen, et al., AIP Conf. Proc. 996 (2008) 159]

26. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 26 JULE-PSI: Jülich Linear Experiment for PSI studies in a Hot Cell Based on PSI-2 / PISCES type device Installation in a Hot Cell for handling of radioactive and toxic materials Existing PSI-2 as forerunner experiment, not in hot cell  Transferred from Humbold U, Berlin to FZJ in 2009  Start of operation in autumn 2010 JULE-PSI (hot device) first operation is planned for 2014 Schematic view Plasma source Target chamber Surface analysisLinear manipulator PMI studies with Neutron irradiated materials All wall materials incl. Beryllium Low quantities of Tritium

27. Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 27 Summary  LPDs provide unique capabilities for reactor-relevant PMI research: flexible and cost-effective.  The value of research increases if aimed at specific open issues of ITER and reactor  New generation of LPDs is aimed to close the scientific gaps on the road to reactors  Mirror machines and other existing devices can contribute to reactor- relevant PMI at moderate costs of re-arrangement  LPD-specific technology-oriented research is needed: development of plasma sources, target manipulators, solutions for vacuum systems, in-situ surface analysis methods