1. D retention and release behaviour of Be/C/W mixed materials
Max-Planck-Institut für Plasmaphysik
D retention and release behaviour of Be/C/W mixed materials
(WP10-PWI /IPP/PS, WP10-PWI /MEdC/PS)
K. Sugiyama, K. Krieger, J. Roth
Max-Planck-Institut für Plasmaphysik, EURATOM Association
A. Anghel, C. Porosnicu, C.P. Lungu
National Institute for Laser, Plasma and Radiation Physics of Romania,
Association EURATOM-MEdC
M.J. Baldwin, R.P. Doerner
Center for Energy Research, University of California at San Diego

2. Outline Introduction Experimental procedure Results
Summary and Outlook

3. Introduction Be W CFC Wall materials in ITER
690 m2 Be: first wall and start-up limiter modules
140 m2 W: divertor dome / baffle region
55 m2 CFC: divertor strike point areas Be W
CFC
Material mixture
Tritium retention in mixed materials
Experimental approach in this task
Preparation of ITER relevant (Be-related) mixed material samples
Investigation of D retention and release behaviour of mixed materials
Wall baking for tritium removal in ITER
240 ºC: Main chamber
350 ºC: Divertor region

4. Outline Introduction Experimental procedure Results
Summary and Outlook

5. Experimental procedure
Sample preparation
Be12W fabrication by annealing of W film on Be substrate sample at 1073K, 10 hours
Be2C fabrication by annealing of C film on Be substrate sample at 773K, 3 hours
WC fabrication by annealing of W film on graphite substrate sample at 1373K, 4 hours
Compounds fabrication by thermal treatment of Be-W / Be-C / W-C system
Be-W / Be-C simultaneously deposited layers
Be-related depositions were prepared by Thermionic Vacuum Arc (TVA) deposition method in MEdC
Upgrade of TVA setup for the simultaneous deposition
Depositions were successfully done with varying Be/W and Be/C ratios

6. Experimental procedure
Sample preparation
Be12W fabrication by annealing of W film on Be substrate sample at 1073K, 10 hours
Be2C fabrication by annealing of C film on Be substrate sample at 773K, 3 hours
WC fabrication by annealing of W film on graphite substrate sample at 1373K, 4 hours
Compounds fabrication by thermal treatment of Be-W / Be-C / W-C system
Be-W / Be-C simultaneously deposited layers
D implantation to prepared layers
200 eV D ions implantation in the High Current Ion Source in IPP-Garching
Flux ~ 1019 D/m2, Fluences up to ~1023 D/m2
Post mortem analysis for the prepared samples
D release behaviour analysis by Thermal Desorption Spectroscopy (TDS)
Quantitative analysis by Nuclear Reaction Analysis using D(3He, p)4He reaction

7. Outline Introduction Experimental procedure Results
Be-related compounds layer
W-C compound (WC) layer
Be-W simultaneously deposited layer
Be-C simultaneously deposited layer
Summary and Outlook

8. Typical desorption from pure materials
Typical D desorption spectra from pure materials Be
Fluence ~ 1023 D/m2
D implantation to each material
200 eV D implantation in the High Current Ion Source in IPP-Garching
Flux ~ 1019 D/m2
Implantation temperature: RT
W (ITER-grade)
Fluence ~ 1023 D/m2
Desorption flux [1014 D2/cm2/s]
CFC (NB31)
Be: Sharp desorption peak at C
W: Primary desorption at C
CFC: Broad desorption feature above 400 C
Fluence ~ 1024 D/m2

9. D desorption from Be-related compounds
D implantation to Be-related compound layers
Be2C: Additional desorption stage in the high temperature range (> 400 ºC)
Be2C
D fluence ~ 1023 RT Be
Be: Primary desorption peak at ºC

10. D release during the temperature hold at 350 ºCBe
Be2C
The desorption flux drops down when the temperature reaches the plateau at 350 ºC.
The desorption flux reaches almost background level during the 20 min. hold.
5-10 % of retained D additionally released during the temperature hold at 350 ºC.

11. D desorption from Be-related compounds
D implantation to Be-related compound layers
Be12W
Be12W: The primary desorption peak becomes less intense and broader
D fluence ~ 1023 RT Be
Be2C
Be: Primary desorption peak at ºC
Be2C: Additional desorption stage in the high temperature range (> 400 ºC)

12. D retained fraction in Be-related compounds
Be2C
Be12W Be
Be: ≈ 90 % of initially retained D is released at 350 ºC
Compounds: % of initially retained D is released at 350 ºC

13. D release from WC layer WC WC Bulk-W Bulk-W
Fluence ~ 1023 RT WC
Bulk-W
D release from WC shows primary desorption stage at K

14. D release from Be-W simultaneously deposited layer
W~10 at.%
W~60 at.%
Bulk-W
W~10 at.%
W~60 at.%
Be12W Be
240ºC
350ºC
Fluence ~ 1023 RT Be
Be12W
Mixing of W in Be slightly changes the D desorption behaviour.
The retention amount decreases by increase of W fraction in Be.

15. D release from Be-C simultaneously deposited layer
C ~ 50 at.%
C ~ 8 at.%
240ºC
Be2C Be
C ~ 8 at.%
350ºC
C ~ 50 at.%
Fluence ~ 1023 RT Be
Be2C
D release behaviour totally changes in the case of C-rich mixed layer sample

16. How will the wall baking work in ITER ?
Best performance will be expected for:
・ removal from clean Be deposit
・ the removal from Be-hydrogen codeposition formed at “cool” areas W C
Be12W
Be2C
The efficiency is marginal for:
・ Be-W codeposited layer and compounds
・ “Be-rich” Be-C mixed deposition
Less efficiency for:
・ “C-rich” (C conc. > 50 at.%) Be-C mixed deposition
・ the hot surface (temperature is > 350ºC during a discharge)

17. Summary and Outlook What we have done are: Messages: Outlook:
Mixed material sample fabrication (collaboration with MEdC)
- TVA setup successfully upgraded for the Be-W / Be-C simultaneous deposition
Investigation of D release from mixed materials for the assessment of T removal operation in ITER (wall baking at 240 ºC / 350 ºC)
Messages:
D release behaviour is affected by material mixing
- Influence of C is more significant.
- T removal efficiency of 350 ºC baking decreases by material mix compared to the case of pure Be or W.
Outlook:
D implantation to mixed material samples at high temperatures
- Temperature dependence of D retention in mixed material samples
Further upgrade of TVA setup for Be-W-C (ternary) simultaneous deposition

18. Annex

19. Compound layer formation
Compound layer preparation
Be-related compounds fabrication by thermal treatment of Be-W / Be-C system
Be2C
Be12W fabrication by annealing of W film on Be substrate sample at 1073K, 10 hours
Be2C fabrication by annealing of C film on Be substrate sample at 773K, 3 hours
Be12W

20. Tungsten carbide layer formation
W on graphite: annealed at ~1300 K, 4 hrs
Ch. Linsmeier et al. (2001)
M. Balden
W on graphite: W layer is completely changed to WC layer

21. Chemical state: Be-W simultaneously deposited layer
Sputter XPS depth profiling
Sample: Be ~ 80%, W ~20 %
Most of Be is metallic and the rest is oxide.
Almost no alloy

22. Fluence dependence of D retention
Fluence dependence of D retention in Be-related compounds
200 eV D RT
Expected fluence to the wall after single ITER discharge (400 s) W
Be-film
Be-bulk
Literature data:
Be-bulk: Anderl et al. (2001)
Graphite: Staudenmaier et al. (1979)
W: Ogorodnikova et al. (2003)
Be2C
Graphite
Be12W

23. D retention in mixed material layers
Be-C simultaneously deposited layer
Be-W simultaneously deposited layer

24. D release from Be-W simultaneously deposited layer
W~10 at.%
W~60 at.%
Bulk-W
Fluence ~ 1023 RT Be
240ºC
350ºC
Be12W
W~60 at.%
Bulk-W
Be12W
W~10 at.% Be
Mixing of W in Be slightly changes the D desorption behaviour.
The retention amount decreases by increase of W fraction in Be.

25. D retention in Be at different implantation temperatures
Implantation temperature [K]
U. Toronto: A.A. Haasz et al. (1997)
SNL/LANL: R.A. Causey et al. (1997)
PISCES-B: R.P. Doerner et al. (1997)
INEEL: R.A. Anderl et al.(1997)
DiMES: W.P. Wampler et al. (1996)
Literature data
Be film
Be12W
This study
Amount of D retention in the Be decrease with the implantation temperature, especially, above 200 ºC.

26. Influence of implantation temperature
D implantation to Be layers at different temperatures
350ºC
300ºC
150ºC RT
240ºC RT
150 ºC
300 ºC
D desorption in the low temperature stage is reasonably reduced by increase of implantation temperature.
Obviously no D desorption at temperature below the implantation temperature