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-01-02-03/IPP/PS, WP10-PWI-01-02-02/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

Outline Introduction Experimental procedure Results Summary and Outlook

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

Outline Introduction Experimental procedure Results Summary and Outlook

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

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

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

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 150 -200 C W: Primary desorption at 150 - 300 C CFC: Broad desorption feature above 400 C Fluence ~ 1024 D/m2

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 D/m2 @ RT Be Be: Primary desorption peak at 150-200 ºC

D release during the temperature hold at 350 ºC Be 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.

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 D/m2 @ RT Be Be2C Be: Primary desorption peak at 150-200ºC Be2C: Additional desorption stage in the high temperature range (> 400 ºC)

D retained fraction in Be-related compounds Be2C Be12W Be Be: ≈ 90 % of initially retained D is released at 350 ºC Compounds: 60-70 % of initially retained D is released at 350 ºC

D release from WC layer WC WC Bulk-W Bulk-W Fluence ~ 1023 D/m2 @ RT WC Bulk-W D release from WC shows primary desorption stage at 400 - 750 K

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 D/m2 @ 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.

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 D/m2 @ RT Be Be2C D release behaviour totally changes in the case of C-rich mixed layer sample

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)

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

Annex

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

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

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

Fluence dependence of D retention Fluence dependence of D retention in Be-related compounds 200 eV D implantation @ 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

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

D release from Be-W simultaneously deposited layer W~10 at.% W~60 at.% Bulk-W Fluence ~ 1023 D/m2 @ 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.

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.

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