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Mem
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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
8th International Conference on
Open Magnetic Systems for Plasma ConfinementNovosibirsk, Russia, 6 July 2010
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 InteractionPMI: Plasma-Material InteractionLPD: Linear Plasma Device
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
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)
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
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" LPD ITER divertor
Electron temperature
1 – 20 eV ~1 – 10 eV
El. density 1018 –1019 m-3 ~1020 m-3
Particle flux ~1023 m-2s-1 1024 – 1025 m-2s-1
Particle fluenceup to 1027 m-2 per
exposure1026 – 1027 m-2
per pulse (400 s)
Incident ion energy
~10 – 100 eV (negative bias)
~10 eV
Wall (sample) temperature
300 – 2000 K 500 – 1000 K
Impurities anyC, Be, W, He, Ar
(N2)
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
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 EUROne 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
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
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
Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 10
Typical arc plasma source
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)
LaB6 emitter diameter
~10 cm
LaB6 emitter heating power
~10 kW
LaB6 emitter temperature
1900 K
LaB6 emitter el. current density
20 A/cm2
Arc current up to ~1000 A
Arc voltage up to 200 V
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
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)
Targetchamber
Swing-linearmanipulator
1 m
Sampleinterlock
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
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
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)0 500 1000 1500 2000
0.1
1
0.18 % Be0.41 % Be
0.13 % Be
1.10 % Be
0.03 % Be
Ch
. er
osi
on
yie
ld [
a.u
.]
Ych exp(-t/), where 1/ fBe2 exp(- Ea/Ts)
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
Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 16
400 600 800 1000 12000.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
D2 d
es
orp
tio
n f
lux
[x
10
19 D
/m2 s
]
Temperature [K]
PISCES-A: Fuel retention in CFC NB41
M=4 (D2) desorption spectra(Ts = 470 K, Ei = 120 eV)
=50e25 D/m2
10e25
3e25
1e25
470
K
Ret
enti
on
[D
/m2 ]
Ion fluence [D/m2]
NB41 PISCES-A [1] N11 PISCES-A [2] NB31 TEXTOR [3] DMS780 TEXTOR [3] EK98 TEXTOR [3]
1024 1025 1026 1027
1021
1022
0.35
Total D retention for exposures at Ts = 470 K, Ei = 120 eV
No saturation up to =51026 D/m2
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
Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 17
400 600 800 1000 12000.0
0.1
0.2
0.3
0.4
0.5 D D+Be D+Be+He
D2 d
es
orp
tio
n f
lux
[x
10
19 D
/m2 s
]
Temperature [K]
PISCES-B: Influence of Be+He on retention
Mass 4 (D2) desorption spectra for ATJ fine-grain graphiteexposed to pure D, D+Be, D+Be+He (Ts=720K, Ei=35 eV, fHe=16%)
Be injection prevents further uptake of D retentionHe appears to change the retention mechanism and to reduce retention
Total Deuterium Retention
Pure D, =0.5e26 D/m2:
1.6e21 D/m2
D+Be, =0.5e26 D/m2 before Be, =2e26 D/m2 total:
1.8e21 D/m2
D+Be+He, =0.4e26 D/m2 before Be, =1.7e26 D/m2 total:
0.5e21 D/m2
0.5 K/s
[A. Kreter et al., Phys. Scr. T138 (2009) 014012]
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
0
0.1
0.2
0.3
0.4
0
1
2
4 6 8 10 12 14
T e [
eV]
n e [
101
9 m
-3]
P[mTorr]
Reduction of ne and Te in detachment
Reduction of heat flux in detachment
[N. Ohno et al., Nucl. Fusion 41 (2001) 1055]
ITER will operate in semi-detached regime
Arkadi Kreter "Reactor-relevant PMI Studies in Linear Plasma Devices" 8th Open Systems, Novosibirsk, 6 July 2010 19
ITER domainITER domain
Pilot-PSI: High plasma flux studies
Plasma parameter cover ITER divertor domainForerunner 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 ~1025 H+/m2s Power fluxes > 30 MW/m2
FOMFOM
Chemical erosion of carbon at high fluxes
[J. Westerhout et al., Phys. Scr. T138 (2009) 014017]
Source
Plasma jet
TargetB
Coils
To pumps
CH spectromete
r
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
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
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)
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
1018
1020
1022
1024
1026
10-1
100
101
102
103
ITER:firstwall
VISION-I
ITER divertorITERstrike points
Eion [eV]
ion [m-2s-1]
Covering ITER operational space
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
FOMFOM1 m
• Particle flux ~1024 H+/m2s• Power fluxes ~10 MW/m2
• El. density ~1020 m-3
• El. temperature 1 – 5 eV
Schematic view
True ITER divertor simulator
magnet
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 eVMagnetic field: 0.2T Pulse duration: steady stateFlux density target: ~ 1020-1021 ions/m2.s
Deuterium and Tritium plasmaNeutron Irradiated samples Beryllium samples
[I. Uytdenhouwen, et al., AIP Conf. Proc. 996 (2008) 159]
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 2010JULE-PSI (hot device) first operation is planned for 2014
Schematic viewPlasma source Target chamber Surface analysis Linear manipulator
PMI studies with• Neutron irradiated materials• All wall materials incl. Beryllium• Low quantities of Tritium
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