1. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 1 Outline: 1.Introduction 2.Experimental procedure 3.Result 4.Summary Kazuyoshi Sugiyama First results from the RETMIX task Max-Planck-Institut für Plasmaphysik

2. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 2 Present material choice in ITER Be (First wall) Low-Z, Oxygen-getter, No chemical sputtering W (Divertor-throat) High melting point, Less erosion CFC (Divertor-target) Low-Z, No melting in transient heat load Plasma-wall interaction (erosion, migration and deposition) material mixture Fuel retention in mixed materials Task: EFDA-TWS IPP-RETMIX (Characterization of fuel Retention in ITER relevant Mixed materials) Introduction

3. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 3 1. Hydrogen retention in binary layer-substrate systems Combinations of layer-substrate are: *Substrates: CFC (NB31), Graphite (EK98), W (JET-ILW project grade (Plansee)) Be (99.4 at.% purity bulk Be (Goodfellow Co.Ltd.)) Thin (~ 200 nm) layer deposition by PVD process C, W layers by magnetron sputter deposition (IPP Garching) Be layer by Thermionic Vacuum Arc (TVA) deposition (MEdC Bucharest) Deposition temperature: R.T. and 450 °C Deposited Layer Substrate R.T. / 450 °C Sample preparation (1/2)

4. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 4 Sample preparation (2/2) 2. Hydrogen retention in mixed layer Tungsten Carbide / Beryllide W / C annealed at 1370 K -> Tungsten Carbide on Graphite W / Be annealed at 1000K -> Be 12 W on Be Deposited Layer Substrate Mixed layer W/Be after annealing

5. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 5 200eV D + Deposited/Mixed Layer Substrate D + irradiation at IPP High Current Ion Source (flux: ~ 3.0 x 10 19 [/m 2 s]) 600 eV D 3 + -> 200 eV / D (irradiated at R.T.) D + irradiation and evaluation of D retention D implantation & evaluation of D retention Total amount of D retention is determined by Nuclear Reaction Analysis. Using 3 He + -> D ( 3 He, p) 4 He resonant nuclear reaction D ( 3 He, p) 4 He, θ = 135° Proton peak from D ( 3 He, p) 4 He reaction

6. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 6 Layer stability Likely caused by thermal expansion mismatch. (W: ~ 4 x10 -6 K -1, Be: 11.5~16.5 x10 -6 K -1 (20~500 ºC)) Potential issue: hazardous dust formation! Layers were generally stable. W layer deposited on Be at higher temperature (~ 450 C) blew up. Sample evaluation

7. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 7 NO significant dependency on deposition temperature and substrate material. 200eV D + -> Pyro. Graphite (Alimov, Roth) Result obtained by NRA using 800keV 3 He + Low mobility of D in C Most of D in C layer D retention in C layer became saturated at ~ 7 ×10 20 D/m 2 Saturation level is higher than that in pyrolytic graphite by a factor of 2.5 (probably due to poor graphitization of the C layer). D+D+ Substrate C D retention in C-coated samples

8. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 8 D+D+ Substrate Be D retention in Be-coated samples Be on CFC no saturation within D + fluence range (< 10 24 D/m 2 ) Increased surface due to roughness and… D retention in Be layer on graphite / W became saturated at ~ 7 x 10 20 D/m 2 Similar level with C layer Low mobility of D in Be (?) Most of D in Be layer

9. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 9 No saturation in this fluence range D+D+ Substrate W D retention in W-coated samples Result obtained by NRA using 800keV 3 He + 200 eV D + -> PCW (Ogorodnikova, Mayer) Deposited at R.T. Deposited at 450C Higher fluence region: Less D retention than PCW D accumulation in the bulk might be limited because the mobility of D in the substrate (C or Be) is lower than that in W. Lower fluence range: More D retention than PCW High temperature deposition led to decreasing of D retention As deposited W layer might have more trapping sites.

10. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 10 No saturation in this fluence range D retention in CFC substrate samples ~Φ 0.5 200eV D + -> NB31 Be on CFC W on CFC

11. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 11 Pure CFC surfaceBe-coated CFC surface Roughness more than 200 nm Many pores even after coating -> D might be able to penetrate to CFC bulk Surface morphology – CFC sample

12. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 12 Be / W coverage reduces D retention compared to the pure CFC No saturation in this fluence range Reflection of D at the surface (W) Low D concentration at near surface layer (coated layer) (W) Suppression of the chemical sputtering at the surface (W, Be) Increased surface due to roughness D could penetrate into the CFC bulk ~Φ 0.5 200eV D + -> NB31 D retention in CFC substrate samples ~Φ 0.5 200eV D + -> NB31 Be on CFC W on CFC

13. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 13 D+D+ BeBe 12 W No saturation in this fluence range (< ~10 24 D/m 2 ) D retention increases proportional to ~ Φ 0.2. D retention in Be 12 W D maximum concentration at near surface layer reaches saturation above 5 x10 21 D/m 2 fluence range. D distribution expands to deeper region Higher D mobility in Be 12 W than that in pure Be ?

14. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 14 200 eV D + -> PCW (Ogorodnikova, Mayer) 200 eV D + -> Pyro. graphite (Alimov, Roth) D+D+ Substrate WC / W 2 C D retention in Tungsten Carbide No saturation in this fluence range (< ~10 24 D/m 2 ) Trend of D retention in WC/W 2 C layer is closer to that in W compared to the graphite. D maximum concentration at near surface layer reaches saturation above 4 x10 22 D/m 2 fluence range. D distribution expands to deeper region with increasing the incident fluence.

15. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 15 D retention in binary layer-substrate samples C, Be film show similar trend: D in W film in high fluence range showed less retention than PCW. Summary D retention in mixed layer samples No saturation was observed in < 10 24 D/m 2 fluence range. D trapping sites in mixed layer were still unclear. Influence of bulk diffusion in mixed material would be important to understand the impact of T accumulation in mixed layer. - D retention properties in Be 12 W and WC/W 2 C layers were investigated. No significant dependency on deposition temperature and substrate material Low mobility of D in C, Be film D is retained in C, Be film The amount of D retention in PVD film is larger than that in well-crystallized surface by a factor of 2 ~ 3. D accumulation in the bulk was limited by difference of D diffusion properties between W and Be, C. Thermal expansion mismatch between Be and W is potential issue from the viewpoint of dust formation. D in CFC substrate samples did not reach saturation in the < 10 24 D/m 2 fluence range. Amount of D retention decreased by Be, W coating.

16. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 16 Annex

17. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 17 Sample evaluation The quality of Be film Oxygen concentration is high only at the top surface (~30 at.%) and interface (~ 10 at. %). O concentration in the layer is ~ 1.0 at. %. Here shows an example of RBS result obtained from a Be on graphite sample. Be on Graphite CBe

18. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 18 WC WC Pure W layer WC W2CW2C W/C C C W/C layer on C Sample evaluation C in W layer

19. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 19 D retention in W-coated samples Blistering on W-coated Be sample 4.6 x 10 22 D/m 2 3.6 x 10 23 D/m 2 High stress in W layer / bad adhesion between W and Be Dust formation

20. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 20 D( 3 He, )p - peak shows long tail -> D can penetrate into the CFC bulk ! D retention in CFC substrate samples D incident fluence: 4.8 x 10 22 D/m 2 Be on Graphite Beam: 690 keV 3 He + Surface Long tail Depth D incident fluence: 4.8 x 10 22 D/m 2 Be on CFC Beam: 690 keV 3 He + 10 0 10 1 10 2 10 -1 10 -2 Be on CFC: 4.8 x 10 22 D/m 2 Be on Graphite: 4.8 x 10 22 D/m 2

21. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 21 Surface of W film (as deposited)Surface of Be 12 W layer (stochiometry confirmed by RBS) 1070K annealing ->Be 12 W grain (size: ~ 5 m) grew up. Be 12 W layer fabrication

22. Kazuyoshi Sugiyama, SEWG meeting, Culham, 9 -10 July 2007 22 Surface of Be 12 W layer Surface modification – many craters on the Be 12 W grain D retention in Be 12 W layer Surface of Be 12 W layer (after 4x10 23 D/m 2 )