co-deposition of deuterium and impurities in plasma-wall interaction simulators marek rubel a, per...
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Co-deposition of deuterium and impurities in plasma-wall interaction simulators
Marek Rubela, Per Peterssona, Arkadi Kreterb
aAlfvén Laboratory, KTH, Association EURATOM–VR, Stockholm, Sweden
bIEK-4, Forschungszentrum Jülich, Association EURATOM, Jülich, Germany
O U T L I N E •Exposures of carbon-based materials: PISCES-A and PSI-2.
•Surface composition of targets: deuterium and impurity species
•Summary and concluding remarks
Content is a bit archaicbut NOT obsolate
- as long asPWI simulators are
in operation.
PISCES-A (1988)
Experiments
The Aim:
To determine erosion of carbon-based materials:CF222, CF222 + 1m SiC, C+SiC 30% – Schunk GmbH;
CL5890PT – Le Carbonne Lorraine
Exposures:D = 1.15 – 2.81 x 1025 (2 samples 8.8 and 31.8 x 1025)
Target T: 623 – 1200 K
Sample size: disk 25 mm
E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737.B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140.
Ion Beam Analysis
E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737.B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140.
Methods:Rutherford Backscattering Spectroscopy (RBS)
Nuclear Reaction Analysis: 3He(d,p)4He and p(11B,)8Be
Thin layer: 50 nm
Thick layer: 3000 nm
Channel Number
Pro
ton
Yie
ld
(co
un
ts)
Deuterium content and distribution
PISCES-A, 1988
Ion Beam Analysis: Impurities
E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737.B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140.
Ba
cks
cat
teri
ng
Yie
ld
(co
un
ts 1
0-2)
Channel Number
PISCES-A, 1988
Yie
ld
(co
un
ts 1
0-2)
Channel Number
B
Impurities from plasma generator:
B and La from LaB6 (cathode)Cu (anode)
Erosion from the chamber wall:
Steel components Fe, Ni, Cr
Deuterium and impurities on samples after single exposures
D and impurity content on samples after single exposures.
Exposure Target T (K) D (1015 cm-2) Imp (1015 cm-2)
Single CL5890PT 673 57 30 - 50
CF 222 1023 29 - 39 36 - 81
CFC + SiC film 1200 9 - 15 88 - 340
C + SiC30 1200 4 - 7 53 - 87
C + SiC30 1200 4 - 10 105 - 410
Double C + SiC30 623 - 823 116 - 158 230 - 300
C + SiC30 1023 15 64 - 120
C + SiC30 873 - 1073 135 – 218 300 – 550
8 exposures CL5890PT 623 – 1200 70 - 3500 44 - 10000
More impurities than deuterium.
E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737.B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140.PISCES-A, 1988
Messages
Highly inhomogeneous distribution of species.
Amount of impurities is greater than the deuterium content.
Exposure Target T (K) D (1015 cm-2) Imp (1015 cm-2)
Single CL5890PT 673 57 30 - 50
CF 222 1023 29 - 39 36 - 81
CFC + SiC film 1200 9 - 15 88 - 340
C + SiC30 1200 4 - 7 53 - 87
C + SiC30 1200 4 - 10 105 - 410
Double C + SiC30 623 - 823 116 - 158 230 - 300
C + SiC30 1023 15 64 - 120
C + SiC30 873 - 1073 135 – 218 300 – 550
8 exposures CL5890PT 623 – 1200 70 - 3500 44 - 10000
E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737.B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140.
Deuterium and impurity content on samples: All results.
Ion Beam Analysis: Impurities
E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737.B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140.PISCES-A, 1988
Ba
cks
cat
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Yie
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un
ts)
Channel Number
Spectra recorded in several points on the graphite sample exposed 8 times to plasma.
Distance between points: 5 mm
PISCES-A (2008) Experiment
The Aim:To determine deuterium retention in graphites and CFCs.(NB-41 = CFC, Snecma; ITER reference carbon material; ATJ = graphite)
Exposure:D = 1- 50 x 1025 m-2
Target T: 370 - 820 K
Sample size: disks 25 mm
Number of samples: 3
A. Kreter et al., Phys. Scr. T138 (2009)
PISCES-A (2008): Example of results
D: 152±5 La 3,4
D: 173±5 La 3,5
D: 155±7 La 3,9
D: 126±5 La 4,8
Sample NB41 (B)
Surface concentration of deuterium and lanthanum (1015 cm-2)
NB41 Sample (C) D: 25 x 1015 cm-2
La: 90 x 1015 cm-2
PSI-2 (Berlin, 1998)
PSI-2 (Berlin, 1998) Experiment
The Aim:To determine deuterium retention in NS-31.(NS-31 = CFC with SiC, Snecma)
Exposure:
D = 1.26 x 1025 (5 h, 7x1021 m-2s-1)
Target T: 420 K
Sample size: disk 20 mm
Ion Beam Analysis of NS-31
Channel Number500 750
1.500
0
Ba
cks
cat
teri
ng
Yie
ld (
Co
un
ts)
0
1.500
Impurities
800
104
0
Ba
cks
cat
teri
ng
Yie
ld (
Co
un
ts)
104
00 800 400
Channel Number
C
Si
Enhanced Proton Scattering: 1500 keV H+, 1 or 3 mm beam
PSI-2 (Berlin, 1998): NS-31
Channel Number500 750
1.500
0
Ba
cks
cat
teri
ng
Yie
ld (
Co
un
ts)
0
1.500
C O
TaLa
Mo
Cu
SiO
C
Si Cu
Mo
Ta La
Messages
Significant amount of co-deposited impurity species originating from the plasma generator.
Not uniform distribution of impurity species on the surfaces in areas located 5-7 mm apart.
Significant difference in the Si content on the surface – very inhomogeneous NS-31 material.
Enhanced Proton Scattering: 1500 keV H+, 1 or 3 mm beam
Summary of Results PSI-2
D: 104 – 152 x 1015 cm-2
B: 46 – 290 x 1015 cm-2
Cu and Ni: 93 – 189 x 1015 cm-2
Mo: 5.0 – 9.0 x 1015 cm-2
La and Ta: 4.2 – 9.9 x 1015 cm-2
Boron and copper (and nickel) are major impurities.
The amount of impurity species exceeds the content of deuterium in the studied surface.
Summary and Concluding Remarks
Plasma generation in PMI simulators is accompanied by erosion of materials from the plasma source and the experimental chamber.
Main impurities are Cu, La, B, Mo, Ni, Ta.These species are co-deposited on the exposed target. Impurity co-deposition is independent on the target Tsurface.
The amount of impurity species usually exceeds the content of deuterium on the studied surface.
Deposition pattern is not homogeneous indicating strong differences in the uniformity of the plasma column.
Summary and Concluding Remarks
It is unreasonable to expect that impurity production can be avoided but the process must be monitored and taken into account when concluding on:
• material erosion (sputter yield changes!);
• fuel retention (surface state plays here crucial role)
• effects of surface modification.
Multiple exposures of targets should probably be avoided unless these are dedicated experiments.
Questions?
Comments?