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R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Directions of the US-EU Collaboration on Mixed Materials for ITER R. P. Doerner,

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Presentation on theme: "R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Directions of the US-EU Collaboration on Mixed Materials for ITER R. P. Doerner,"— Presentation transcript:

1 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Directions of the US-EU Collaboration on Mixed Materials for ITER R. P. Doerner, M. J. Baldwin, E. Hollmann, D. Nishijima, G. R. Tynan, K. Umstadter and J. Yu Center for Energy Research, University of California – San Diego, USA

2 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Future Directions of PISCES Program* Retention in, and release from, mixed-material codeposits Mixed-species plasma-surface interactions Transient heating of elemental and mixed-material surfaces during plasma exposure using laser pulses Ablation plume physics – Material transport along B (vapor shielding) – Material transport across B (laser blow off, macroscopic particles) Angular and energy distributions of sputtered W particles Addition of transient particle source to the PISCES facility (longer term direction, still conceptual) PISCES * Taken from 2008 US-EU PWI Task Force talk

3 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 US-EU collaboration is contributing to several ITPA DIV/SOL High Priority ITER R&D tasks Changes in retention due to mixed plasma species Tritium release increase during 240°C - 350°C bake Impact of material mixing on retention PISCES

4 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Different materials, heating profiles and implantation doses are being studied Six types of material – Be on W Be on CFC Be 12 W Be 2 C C on Be W on Be Four implantation doses - 3 E 16 D atoms (at room temp.) 3 E 17 D atoms 3 E 18 D atoms 3 E 19 D atoms 350C PISCES

5 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Retention and release from mixed material samples with Be-containing overlayers 200 nm Be layers deposited on substrates at MEdC, Romania Alloys formed and verified at IPP, Garching Samples implanted at room temperature with 200 eV D ions at IPP, Garching to a fluence of 4-5 E22 D/m 2 (~3 E18 D atoms) TDS performed on samples at PISCES, UCSD Assumes all D is released from samples by TDS at 800C (to be confirmed by post-TDS NRA at IPP, Garching) Be on W Be on CFCBe 2 CBe 12 W Total D released 1.3E17 7.4E165.2E16 PISCES

6 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Annealing to 350C is ineffective for release from C layers W layers retain very little implanted D 350 C PISCES

7 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 W Temperature & PMI are coupled NAGDIS-II: He plasma D. Nishijima et al. JNM (2004) Surface morphology Shallow depth Micro-scale PISCES-A: D 2 -He plasma M. Miyamoto et al. NF (2009) K, 1000 s, 2.0x10 24 He + /m 2, 55 eV He + Little morphology Occasional blisters PISCES-B: pure He plasma M.J. Baldwin et al, NF 48 (2008) K, 4290 s, 2x10 26 He + /m 2, 25 eV He + NAGDIS-II: pure He plasma N. Ohno et al., in IAEA-TM, Vienna, K, s, 3.5x10 27 He + /m 2, 11 eV He nm (VPS W on C) (TEM) ~ K> 2000 K ~ 900 – 1900 K Surface morphology Evolving surface Nano-scale fuzz

8 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 A small amount of He (5-20%) in deuterium plasma results in suppression of blisters on W [from M. Miyamoto et al., NF 49(2009)065035] Plasma exposure conditions : fluence 5e25 m -2, 300ºC, E ion ~ 55 eV, 20% He. PISCES

9 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Mixed D/He plasma exposure creates nano-bubbles in the near surface of W and reduces D retention TEM image of nano voidsTDS of mass 4, He and D 2 [from M. Miyamoto et al., NF 49(2009)065035] PISCES

10 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Mixed D/He reduces D migration in W at low temperature dateD Fluence D/m 2 D retained D/m 2 12/ (+He) / / / / With He Addition of He to the D plasma reduced D retention by about a factor of 35. With He, D retention is mainly at the surface, whereas without He, D retention peaks ~ 1 micron beneath the surface. NRA measurements by W. Wampler - SNLA 1e21 D/m 2 ~ 3 mg/m 2 PISCES

11 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Above 900 K, W fuzz occurs. Fuzz is approx. 95% space SEM used to profile fuzz layer thickness over sample surface. Geometric vol. of fuzz layer est. (7.8 x m 3 ±10%). Fuzz layer removed. Mass change (D m =0.87 mg ±1%). Comp. w/ pure W, ( = x10 3 kgm -3 ), fuzz layer is 94 % porous. PISCES

12 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Fuzz growth consumes W bulk s, 1120 K 60 eV He + PISCES-B pure He plasma ~50 ITER shots 9000 s, 1120 K 60 eV He + PISCES-B pure He plasma ~20 ITER shots 2000 s, 1120 K 60 eV He + PISCES-B pure He plasma ~4 ITER shots RN RN RN Confirmation of fuzz growth out of the surface, first suggested by Prof. Yoshida. This growth mechanism may present a concern for W divertor operation where surface fuzz may, or may not, withstand the harsh plasma bombardment environment. PISCES

13 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Effect of He plasma on various grades of W PISCES Japanese ultra-fine-grain W

14 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Re-crystalized W responds very differently. Re-crystalization may lead to greater space in grain boundaries, due to defect migration to grain boundaries, (i.e. grain growth). Such space permits deep fuzz growth at grain boundaries and may affect adhesion of W grains. PISCES

15 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Evidence of surface grain ejection ? 30 o ~20 m Surface X-section beam X-section Surface SR W He T ~1120 K t = 2.2 x 10 4 s He + ~5 x m -2 s -1 E He + ~ 50 eV PISCES

16 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Small pits ~1 m, are found on UFG-W nano-fuzz. Grain ejection? UFG-W (1.5 wt% TiC) He, T ~1120 K, t = 3.6 x 10 3 s, He + ~2.5 x m -2 s -1, E He + ~40 eV 30 o beam Surface Small impressions in the surface that have also developed nano-fuzz Typically, nano-fuzz is uniform in appearance PISCES

17 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Angular distribution measurements of sputtered W atoms (flat surface done, fuzz underway) RF plasma source is used to investigate sputtering details Hiden EQP analyzer can differentiate mass and energy of incoming ions and neutrals Variation in target angle allows measurement of angular distribution of sputtered species (always normal incident plasma ions) Sputtering of W atoms from flat and fuzzy surfaces (made in P-A) are being compared E. Oyarzabal et al., J. App. Phys. 100(2006) PISCES

18 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 Erosion rate of W fuzz Measurements are underway to determine erosion yield and angular distribution of eroded W fuzz Integrated W atom surface loss rate from a nanostructured surface (in P-B) Sputtered Ar on W angular distribution from a smooth surface in rf etcher W fuzz Smooth W PISCES

19 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 PISCES collaborates in several areas within the EU fusion program MD simulations of Be chemical sputtering predicted ion energy dependence ERO modeling of mixed material effects JET ILW marker tiles being produced (with GA) W S/XB measurements Effects of nitrogen impurity seeding, performance test show PISCES can run N 2 plasma (future direction) MD simulations of D on Be predicted subsequent erosion measurements PISCES Exp. from D. Nishijima et al, PPCF 50(2008) Sim. from C. Bjorkas, submit. to New J. Physics (2009).

20 R. Doerner, 8 th EU PWI Task Force Meeting, Warsaw, Poland, Nov. 4-6, 2009 UCSD, MIT and UC Berkeley recently received funding for a 5 yr. Plasma Science Center Center will focus on a multi-scale (experiment and modeling) approach to PMI Effort to focus on fundamental, rather than machine specific, PMI issues Collaborative possibilities abound Several postdoctoral positions available PMI Center


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