member of the helmholtz association reactor-relevant plasma-material interaction studies in linear...

Mem

ber

of

the H

elm

holt

z A

ssoci

ati

on

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


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)


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


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


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


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


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


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


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


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


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


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]


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


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


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


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)


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


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


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]


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


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

member of the helmholtz association reactor-relevant plasma-material interaction studies in linear...

Documents

plasmawall interaction

reactorrelevant pmistudies

linear plasma device

plasma confinement novosibirsk

highlights of pmi

facets of pwi studies

reactor impurities c

special features future