Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 1 of 13
Formation of mixed W/C and Mo/C layers in TEXTOR
A. Litnovsky,
V. Philipps, P. Wienhold, S. Richter, K. Krieger,
G. Sergienko, A. Kirscher, A. Kreter, S. Droste, D. Borodin
and TEXTOR Team
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 2 of 13
Mixed layers in TEXTOR
“Naturally” formed during the PWI experiments
Can be observed after exposure of high-Z limiters
in the SOL plasmas using Limiter Lock systems
Example: twin limiters, castellated limiters
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 3 of 13
Exposure of twin W/C limiter in the SOL plasmas of TEXTOR*
W content in the deposit is
the largest neat tangency
point
W found deposited locally on
the carbon part of the limiter
*M. Rubel, V. Philipps, A. Huber and T. Tanabe, Phys. Scr. T81 (1999) 61
Deuterium retention only in
carbon deposition area
W deposited in gaps of C
rough surface despite of C
net erosion area
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 4 of 13
Exposures of castellated limiters: general parameters
Experiment Experiment 1 (Mo castellated limiter II)
Experiment 2(W castellated limiter III)
No. of discharges 39 16
Duration of exposure 219 s. 112 s.
Local Te, eV. ~25 eV ~ 20 eV
Local Ne, cm-3 2.5*1012 6*1012
Averaged fluence 2.0×1020 D/cm2 2.2×1020 D/cm2
Bulk temperature of the limiter 220-260oC 200-250oC
Temperature excursions Local heating of plasma closest edge up to 1600oC
Local heating of plasma closest edge up to 1500oC
Diagnostics used: He beam, fast probe, pyrometers, thermocouples,
video observation system, spectroscopy (D, Mo, W)
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 5 of 13
0 2000 4000 6000 8000 100000,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
Ato
m d
istr
ibu
tio
n 1
017 a
t./c
m2
Distance, micron
A B
EPMAEPMA
0 100 200 300 400 500 600100
101
102
103
104
105
Thickness, nm
MoCDB
MoCDB
SIMS/DEKTAKSIMS/DEKTAKIntensity, a.u.
~ 75 nm
Investigations of deposited layers: Experiment 1
Plasma flow
AB
A: Plasma facing side of the gap
SIMS (calibrated
with Dektak)
EPMAscan
~ 1.7 mm
~ 1.5 mm
Measured spot (~ 30 nm)
Measured spot (~ 30 nm)
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 6 of 13
Investigations of deposited layers:Experiment 1: EPMA signals modeling
0 10 20 30 40 50 60 700
50
100
150
200
250D
ep
os
it t
hic
kn
es
s,
nm
Molybdenum share in the deposit at. %
calculated for Carbon
~ SIMS value
At least ~50 at % Mo in the deposit are needed to suit with SIMS results for this location
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 7 of 13
0 2 4 6 8 10 12 145.0x1016
1.0x1017
1.5x1017
2.0x1017
2.5x1017
3.0x1017
3.5x1017
Distance along the gap, mm
C, at/cm2
Investigations of deposited layers: Experiment 2
Plasma flow
AB
A: Plasma facing side of the gap
SIMS (calibrated
with Dektak)
EPMAscan
~ 1 mmEPMA value
(without W mixing)~ 25 nm
EPMA value (without W mixing)
~ 25 nm
NRA value~ 42 nm
NRA value~ 42 nm
SIMS/DEKTAK value
~ 50 nm
SIMS/DEKTAK value
~ 50 nm
EPMA modeled value (41 at. % W
in the deposit)
EPMA modeled value (41 at. % W
in the deposit)
EPMA, NRA, SIMS/DEKTAK
W castellated limiter
NRAscan
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 8 of 13
Investigations of deposited layers: Experiment 2
W castellated limiter: W mixing quantification
43,7%
69,6%
2,3%
36%
2,5%
41,6%
3,0%
27,3%
3,5% Observations:
Strong W intermixing on the plasma-closest edges of gaps
(>40 at. % of W);
W-share decreases with the depth of the gap
Looks like more W in plasma-shadowed gaps;
More analyses to follow.
open gap shadowed gapPlasma-
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 9 of 13
Comparison of the experiments 1 and 2What are these mixed deposits?
Mo/C W/CNMo/NC (gap edge)~ 50 at % Mo NW/NC (gap edge) ~ 40-70 at % W
D/C < 0.1 D/C <<0.1
Less than 0.1% of impinging D
flux trapped in gaps
Less than 0.1% of impinging D
flux trapped in gaps
The properties of W/C and Mo/C mixed deposits are very similar
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 10 of 13
Comparison of the experiments 1 and 2Similarity of W/C and Mo/C layers: why so?
Same geometry of studied samples
No much difference between Mo and W for EPMA simulation: CKα absorption is similar
Exposure in similar plasma conditions
Y, cm2/mg
Mo W C
19.2 17 6
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 11 of 13
Comparison of the experiments 1 and 2Similarity of W/C and Mo/C layers: why so? Part II
General feature: metal intermixing decreases with the gap depth
Cn+, D+
C0 , D0
Mo
MoC0, D0
65 at.% Mo* 50 at.% Mo
Very low D content: are W/C layers actually an issue for ITER?
*A. Litnovsky et al, Proc. of 32nd EPS, ECA Vol. 29C, P-
1.015 (2005);A. Litnovsky et al.,J. Nucl. Mater. in
press
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 12 of 13
Summary
Mixed W/C and Mo/C deposits observed during investigations of twin
W/C limiters and in the experiments with castellated limiters in TEXTOR
Large share of metal (up to 70 at. %) in the intermixed layers
W/C and Mo/C layers formed in gaps of castellated limiters are similar
Metal share in the deposit decreases with distance
from the metal source
Generally low D-retention in studied mixed layers
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Slide 13 of 13
Thank you
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Additional slide
NRA spot size
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Additional slide
W mixing: detailed results
10000 11000 12000 13000 14000 15000
0
10
20
30
40
50
60
70
80
10000 11000 12000 13000 14000 15000
0
10
20
30
40
50
60
70
80 W mixing in the deposit, at. %
plasma open gap er1b
Distance along the gap, micron
plasma shadowed gap er2b
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Additional slide
SIMS measurement locations
Forschungszentrum Jülich
in der Helmholtz-Gemeinschaft
Institut für Energieforschung - Plasmaphysik
EURATOM Assoziation – FZJ
TEC A. Litnovsky et al., Meeting of the EU TF PWI
SEWG on mixed materials, JET, Culham, July 9, 2007
Additional slide
Encapsulated deposits*
0 100 200 300 4001x102
1x103
1x104
1x105
Thickness, nm
Intensity, a.u.
SubstrateDepositW-layer D
C
W13C
SIMS spectra show an a:C-D deposit with a
thickness of ~120 nm, covered with a ~ 100 nm thick
layer of pure tungsten
*A. Litnovsky et al., Phys. Scr. T128 (2007) 45;
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