report ipp garching eu task force pwi meeting, cadarache oct 17-19 2005 1 max-planck-institut für...

Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 1

Max-Planck-Institut für Plasmaphysik

compiled by Arne Kallenbach(IPP - EU-PWI contact person)

presented by Joachim Roth


Erosion behaviour and impurity location in tokamaks

Material transport and re-deposition

Fuel recycling, retention and removal

Transient heat loads

Edge modelling, erosion and deposition modelling

Edge and SOL physics

Task force relevant diagnostics

IPP-GarchingBelinGreifswald

Chemical erosion in ASDEX Up and beam experiments.

D/XB calibration.

Determination of main chamber sources.

W experiment in ASDEX Up

C sources and sinks.C material transport by tracer injection.C deposition in remote areas.

W transport in the SOL.

Sticking parameters of hydrocarbons.C erosion and re-deposition in PSI-2 simulator.

Gas balance in ASDEX Up.

Fuel retention in CFC

Mixed layers in lab. experiments.

Removal of carbon films by active species in lab. experiments.

ELM power deposition characteristics

Disruption power deposition.

Disruption mitigation techniques.

W erosion and transport modelling with DIVIMP.

Edge modelling with B2.5

SOL transport and parallel flow measurement

Main chamber wall plasma interaction.

Development of Quartz microbalance technique.

Topics proposed by IPP Garching, Oct 2001

Chemical Erosion: S. BrezinsekGas balance: T. LoarerTransient heat loads: A. LoarteHigh-Z: R. Neu

SOLPS modelling of edge and divertor profiles

(D. Coster, A. Chankin)

Flow measurements for D and C(H.W. Müller, R. Pugno)


1995/1996 W-divertor:

W is feasible in divertor tokamak

main chamber is strong source of C

1999/2000 W-tiles in main chamber:

no impact on plasma performance

2001/2003 W centr. col. (start-up lim.):

start-up possible, strong reduction

of W inventory after x-point formation,

erosion mainly by ions

2003/2005 W divertor, LFS limiter:

confirmation of '96 divertor results,

erosion at LFS limiter dominated

by fast ions (NBI) and accelerated ions (ICRH)

guard/ICRHlimiter

aux.limiter

hor.plate

lower PSL

roofbaffle

2006/2007(planned)

W-coating starting with campaign

2003/2004

2004/2005

2005/2006

Milestones of W programme / Schematic view of W PFCs


ASDEX Upgrade in December 2003

70% W covered first wall

still divertor and wall sources of C impurities

frequent boronisation


Deuterium and Carbon deposition in tile gaps Karl Krieger


Tritium growth rates in gaps AUG measurement and ITER extrapolationKarl Krieger


Temperature dependence of a-C:D layer depositionMatej Mayer

Si sample

Heater

Electricalconnection

0 50 100 150 200

0.01

0.1

1 C D

Rel

ativ

e A

mo

un

t [t

o C

at

RT

]

Temperature [°C]

• Temperature dependence of layer deposition determined with heated long term samples

• Layer deposition depends strongly on sample temperature

• Probably due to re-erosion by atomic hydrogen


Glow Discharge Removal of Hydrocarbon Co-Deposits Ch. Hopf

0 50 1000.01

0.1

1

eros

ion

rate

(nm

/sec

)

% O2

Erosion of soft a-C:H inO

2/He ECR-Plasma

Substrate Bias: -400Vp = 0.5 Pa

Only 10 % O2 concentration needed in GDC to obtain highest achievable rates.

Use of He/O2 mixture plasmas• Stability of glow discharge• Less sputtering compared to pure O2 discharge or heavier noble gas admixtures• Good experience with He GDCs

Oxidation of W in O2 plasma saturates and is reversible in an H2 discharge

0 20 40 600

1

2

3

4

5

6

7

oxyg

en c

over

age

(10

16 c

m-2)

exposure time (min)

W coatings polished W

H2 plasma


Parameters: 10 % He Glow discharge ~ 300 V Ion flux ~ 1014 cm-2 s-1

Average erosion rate of carbon co-deposits on AUG tiles:

1.1 ± 1.0 × 1013 cm-2 s-1

or~ 100 hours for 1 micrometer

before

after

after before

Glow Discharge Removal of Hydrocarbon Co-Deposits V. Rohde

O2/He glow in discharge test chamber O2/He glow discharge in ASDEX Upgrade

49 h total O2/He glow time600 V, 5.4A98% He + 2% O2

• Mass spectroscopy• T exhaust increased by factor of ~30

compared to pure He (R. Neu)• 50 a-C:H marker films for erosion

analysis• Arcs developed on tiles coated with B

oxide layers.


50 a-C:H erosion probes: poloidal scanChristian Hopfsectors 6, 7, 8

C removedNo C removed

Effective erosion on first wall and in large ports

No erosion in shielded places, such as tile gaps, behind first wall, and in deep in the divertor

anode


arc traceslower PSL

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

100

200

300

Th

ickn

ess [n

m]

Sector

a-C:H left of 350 nm SiO

2

n = 1.6 layer

Anodes:

Outer Divertor

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

ICR

H

ICR

H

ICR

H

ICR

H

50 a-C:H erosion probes: toroidal scanChristian Hopf


HS IUD OUD BG6 LIM0

10

20

30

40

50

60

70

80

Ato

mic

Fra

ctio

n (%

)

B

12C D O

13C

before O2 glow

HS IUD OUD0

10

20

30

40

50

60

70

80

90

Ato

mic

Fra

ctio

n (

%)

B

12C D O 13C

after O2 glow

Films after 2004/2005campaign are nohydrocarbon films

Surface modifications on ASDEX Upgrade tilesChristian Hopf


• Removal of carbon co-deposits from wall surfaces in He/O2 GDC plasmas works

20 g C removed (mass spectroscopy)

• Glow discharge cleaningworks on plasma-facing surfacesdoes not work in shielded areas and tile gaps

• There were almost no carbon films in AUG after 2004/2005 campaignmainly oxidised B layers

• Insulating layers lead to arcing and suppress GDC

Conclusion for He/O2 GDC Christian Hopf


Be diffuses fast through Be/W alloy and forms alloy at the interface

• Be12W phase starts forming at the interface

• W on Be transforms completely to Be12W upon annealing at 1070 K

Material mixing: W on BeW Depth Profiles and Reaction KineticsKarl Ertl

0 5000 10000 15000 20000 250001

10

100

W c

on

cen

tra

tion

(%

)

Depth (1015cm-2)

1070 K 30 min 120 min 180 min 600 min

Be12

W


XPS clearly shows new Be-W alloy phaseDifferent from Be2W identified previouslyFrom composition: Be12W

Melting temperature <1750°C

BeO

Be

Be12W

W

Material mixing: W on BeChemical phase identification Ch. Linsmeier


(A. Wiltner, Ch. Linsmeier, JNM 337–339 (2005) 951)

• Surface alloying: monolayer at 300 K, limited to first nm

• Excess Be disappears above 770 K, no bulk diffusion, sublimation

• Phase identification as Be2W

Material mixing: Be on WMixed layer formation Almut Wiltner


Binding energy (eV)

110115

N(E

) (

Arb

uni

ts)

050

010

0015

0020

00

Be 1s

Met

allic

Be

111

.80

eV

Be

oxid

e

3035

020

0040

00

W 4f

Ber

yllid

e 1

11.1

5 eV

W 3

1.0

eV

Beryllidedoubletshifts-0.25 eV

STD

1050 oC

750 oC

570 oC

W 17% Be 83%

W 15% Be 85%

W 23% Be 77%

XPS confirms beryllidesBe2W (A. Wiltner et al. J. Nucl. Mater. (2005)) IBA results in 2.5 1015 Be/cm2 (1 ML) at 1050°C

Be-seeded D plasmabias 75 Vtypical fluences:1x1022 D/cm2

1x1019 Be/cm2

Material mixing: Be on WBe-seeded plasma in PISCES R. Doerner, M. Baldwin


• W-beryllide phases form in the interaction of W with Be, and bear the potential of a major malfunction: at 1070 K W-beryllide phases can form which melt below 1700 K

• For W on Be this phase has clearly been identified as Be12W through ion beam and XPS analysis.

• However,

• under typical ITER conditions (0.1% Be in incident D flux ) only a thin Be2W layer will form, excess Be will sputter/reflect/evaporate and deposit elsewhere

• Studies using higher Be plasma concentrations ( up to 1% ) are underway in PISCES-B

Conclusion for Be/W interaction

report ipp garching eu task force pwi meeting, cadarache oct 17-19 2005 1 max-planck-institut für...

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