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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 2
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)
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 3
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 4
ASDEX Upgrade in December 2003
70% W covered first wall
still divertor and wall sources of C impurities
frequent boronisation
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 5
Deuterium and Carbon deposition in tile gaps Karl Krieger
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 6
Tritium growth rates in gaps AUG measurement and ITER extrapolationKarl Krieger
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 7
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 8
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 9
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.
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 10
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 11
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 12
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 13
• 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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 14
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 15
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 16
(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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 17
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
Report IPP Garching EU Task Force PWI Meeting, Cadarache Oct 17-19 2005 18
• 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