Recent Workshops - Tungsten PMI / PFC Work

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1 Recent Workshops - Tungsten PMI / PFC Work D. Buchenauer, R. Kolasinski, and R. Causey 2009 Japan - US Workshop (3 workshops) US-Japan Workshop on Interaction between plasma and high Z material towards steady state operation 10th International Workshop on Hydrogen Isotopes in Fusion Reactor Materials Other meetings: 12th Int. Conference on Plasma Surface Interactions (May 2010) 13th ITPA SOL/divertor meeting (December 2009) Upcoming meetings: 13th Int. Workshop on Plasma Facing Materials and Components for Fusion Applications (Spring 2011)

2 2009 Japan-US Workshop (SNL-CA) Three day workshop (July 21-23, 2009) Heat Removal and Plasma Materials Interactions for Fusion Fusion High Power Density Components and Systems IEA Workshop on Solid Surface Plasma Facing Components Organized by R. Kolasinski and Y. Ueda (Osaka Univ.) US-Japan Bilateral Agreement for Fusion Energy Biennial meeting (alternates with FNST workshop [October 2010]) Critical issues, components and corresponding FNST R&Ds for the next fusion machines (See Clement Wong for details) Next workshop will be in Japan (2011) Participants: 13 US, 6 Japan, 1 Canada 22 Talks ( 34% on W 20% on C/Be 46% other

3 2009 Japan-US: Overview Talks Overview talks highlighted tungsten work on-going in US and Japan Support of ITER in VLT base program [Nygren] Highlighted tungsten nano-morphology (fuzz) studies, erosion / redeposition modeling, tritium retention measurements, and safety issues PMI/PFC in Japan [Ueda] ITER design activities for outer vertical target (prototypes tested) Water cooled DEMO design with W armor being studied (joining to F82H) Tungsten tiles and sample exposure in LHD QUEST ST (hot tungsten walls with open, then closed divertor) TITAN program [Sze] Tungsten studies using PISCES, TPE, and TRIIX Neutron irradiated samples from HFIR Irradiation performance of joining techniques for tungsten to RAFM & ODS steels, and vanadium alloys

4 2009 Japan-US: Additional Topics Molecular dynamics of mixed material formation (Univ. of Tokushima) [Ohya] Chemical sputtering in mixed materials (C/W) (Osaka Univ.) [Ueda] Carbon deposition on He pre-exposed tungsten (Osaka Univ.) [Ueda] Ion beam studies of D retention in W extended to lower energies / higher fluences (Univ. of Toronto) [Haasz] D/T retention in W and Mo using TPE [Shimada] He induced nano structure and mixed material interactions in PISCES [Doerner] Temperature dependence of W blistering in TPE [Kolasinski] Effect of displacement damage on D retention in W [Wampler] Non destructive examination system for ITER prototypes (JAEA) [Seki] Thermal performance of gas-cooled divertors [Yoda] Development and plasma testing of UFG TiC (Tohoku Univ.) [Kurishita] W erosion and redeposition on DiMES [Buchenauer] Low energy ion scattering measurements to examine H adsorption on W [Kolasinski] Work with bulk tungsten

5 High Z Workshop (MIT) Two day workshop (November 9-10, 2009) Newly organized by M. Sakamoto (Kyushu Univ.) and B. Lipshultz US-Japan Bilateral Agreement for Fusion Energy 10 US, 6 Japan All 14 talks focused on W (Mo) Summary available in the January 20, 2010 USBPO Newsletter.

6 High Z Workshop: Tokamaks+LHD Dynamic particle balance studies from C-Mod & DIII-D show near zero wall pumping during steady-state (cryopumped discharges) [Lipshultz, Whyte] Contrasts with static measurements showing large retention in C-Mod TRIAM-1M (Kyushu Univ.) [Sakamoto] 8T steady state field with high Z walls (Mo PFC and SS walls) Studying recycling, codeposition, and impurities with long pulse operation Up to 0.1 H/Mo collected on surface probe (temperature dependent) QUEST (Kyushu Univ.) [Sakamoto] Goal to study steady state operation at high beta (ST). Will also study CT fueling. Starting with VPS-W CS guard limiter, water cooled inner midplane limiter, and APS-W divertor plates. Goal to eventually have hot (< 500 ºC) walls. Micro/nano scale damage and H retention in W exposed to LHD [Tokitani] Use Material Probe System to expose W to H / He plasma (30 s, ~ 1 MW/m 2 ) Observed nanoscale bubbles and cracking / crazing VPS-W coated graphite tiles installed for the 2008 campaign Little macroscopic damage or affect on plasmas, but evidence of nanoscale He bubbles

7 High Z Workshop: Experiments Ion beam induced displacement damage simulates neutron generated traps for H,D,T in W [Wampler using 12 MeV Si] / [Ueda using 300 kev H (Osaka)] Temperature dependence and IBA profiles demonstrate diffusion front, but low retention Occupation of surface sites on W(100) studied using LEIS [Kolasinski] Saturated coverage populates bridge site (DFT calculations needed for comparison) TPE [Shimada] + NAGDIS-II (Nagoya) [Ohno] Imaging plate can detect tritium retained mm s into W / Mo, but quantification difficult (10 3 more sensitive than IBA) He plasma induced nano structured tungsten: PISCES [Doerner] Nano bubbles formed below He sputtering threshold give way to W fuzz (> 900 K) Suppression of blisters with small amount of He in D plasmas (nano bubbles form), and large reduction in deuterium retention Formation of nano bubbles requires large He flux (more effective in reducing D retention if concurrent with D flux). Flux dependence of growth similar to that of W fuzz. W fuzz grows out of the surface (all types), but can also form at large grain boundaries He plasma induced nano structured tungsten: NAGDIS-II (Nagoya) [Ohno] Measured reflectivity changes correlated to W fuzz formation (E He > 20 ev) Laser pulse induces arcing (potential for dust formation)

8 High Z Workshop: Cont.+Modeling Exposure of W fuzz to TEXTOR He plasma [Ueda] Removal of fuzz in erosion zone; enhanced C deposition by fuzz in the no erosion zone APSEDAS used to study W surface modification by low energy He (Kyushu) [Sakamoto] RF plasma (helicon) with optical view of temperature controlled W surface Observed mm scale surface roughening at 1400 K (6.5x10 25 He/m 2 ), but W fuzz not evident. Lower temperatures exposures appeared smooth, and showed an increase in reflectivity with fluence. Modeling the optical response as a layer of complex refractive index (density variation due to bubbles). As depth of layer increases or bubbles increase in size, the reflectivity from the surface can change (and increase or decrease). Analysis indicates that the layer is > 70 nm. Modeling of hydrogen influence on vacancy formation in W crystals (NIFS) [Kato] Surface-energy corrections for DFT calculations of vacancies V 2 formation energy is almost zero or negative, but can be stabilized in the presence of H and at lower temperatures (V 2 H) [but need to overcome vacancy migration barrier] Modeling of bubble evolution in near surface of W (Tokyo Univ. of Science) [Takahashi] Kinetic Monte Carlo Method applied to bubble evolution demonstrates bubble growth and coalescence (compared to experiment); also explored grain boundary effects

9 Hydrogen Workshop (SNL-CA) Two day workshop (May 31 - June 1, 2010) Organized by D. Buchenauer, R. Kolasinski, and R. Causey PSI satellite meeting Encourages work-in-progress and discussion ITER and DEMO research needs discussion Summary available on the VLT website Next workshop will be chaired by W. Jacob (IPP) in spring attendees from 9 countries (US, UK, Canada, France, Germany, Italy, Latvia, Russia, & PRC) One session devoted to tungsten (5 talks) 29 talks ( 36% on W 43% on C/Be 21% other

10 H-Workshop - Tungsten Session Temperature dependence of deuterium retention at displacement damage [Wampler] Refinement of previous work to include model of precipitation in bubbles Deuterium retention in tungsten at high level of displacement damage (Kurchatov) [Khripunov] 3-4 MeV He implantation to simulate high level of displacement damage ( < 80 dpa) Deuterium retention up to 10 at. % in high damage region Deuterium retention in rolled and recrystallized tungsten (IPP) [Jacob] Microstructure effects on D retention (ECR plasma; 38 ev/d) Large near surface reduction in retention for 2000 K recrystallization temperature TDS spectrum also changed (3 different trap energies) Deuterium retention in tungsten damaged by high heat load (IPP) [Ogorodnikova] JUDITH used to simulate ELM damaged W (15 GW/m 2 for 1 ms, 100 times) Increased D retention 6X for stress relieved and recrystallized W (10 25 D/m 2 ) Undamaged stress relieved W had higher retention compared with recrystallized W/Cu-PFM for EAST and related PWI studies (ASIPP, Hefei) [Luo] Development of VPS-W on Cu heat sink (7 MW/m 2 )

11 H-Workshop - Additional Talks D retention in Be-related mixed material (IPP) [Roth] WBe 12 retention under ITER bake out (350 ºC) would retain 30% Structure and Retention of Carbon Deposition Layer on Tungsten (Osaka Univ.) [Ueda] TEXTOR results + Chemical erosion On hydrogen behavior at practical surface (Kyushu Univ.) [Tanabe] Image plate measurements of T retention in W from TPE Characterization of Adsorbed Hydrogen on Tungsten and Beryllium Surfaces [Kolasinski] Technique for identifying occupied site for H on W surfaces being extended to Be Tritium behavior near surface region and bulk of metals exposed to tritium plasma (Kyushu Univ.) [Otsuka] Examination of long term tritium behavior on surfaces and in the bulk of W Thermo-Oxidation of Carbon Films with Tungsten Impurities (Univ. of Toronto) [Davis] Found example of dispersed tungsten impurity NOT blocking oxidation Work with bulk tungsten

12 H-Workshop - Additional Talks Deuterium Ion Driven Permeation Dependence on Tungsten Microstructure (Osaka Univ.) [Lee] Examined effect of varying grain sizes (stress relieved and recrystallized) Diffusivity similar, however no dependence of permeation on temperature Gas-Driven Deuterium Permeation Studies of Fusion-Related Materials [Karnesky] Permeation of deuterium through Mo and W agree with literature (W data aligns with Frauenfelder) Work with bulk tungsten