R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 US-EU Collaboration on Mixed Materials for ITER: Past, Present and Future R. P. Doerner, M. J. Baldwin, G. De Temmerman*, E. Hollmann, D. Nishijima, G. R. Tynan, K. Umstadter and J. Yu Center for Energy Research, University of California – San Diego, USA Many European co-authors (see later slide) * MAST

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 History of US-EU Collaboration US withdraws from the ITER Project in In , USDOE asks UCSD to develop plans for the Beryllium decontamination of the PISCES-B facility. Late in 2001, K. Lackner and R. Conn approached the USDOE with a proposal to postpone the decontamination. (US was then considering to rejoin ITER.) [Federici involvement] The US-EU Collaboration on PISCES-B was approved by EFDA and USDOE in FY02, for a three year duration. –EU Coordinator – A. Loarte –US Coordinator – R. Doerner The successful collaboration was renewed in FY05 for a second three year period. Recently, the collaboration was extended for another three year period (FY08-10). We are currently starting the second year of this period. The EU Coordinator is now R. Zagorski. PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 The US-EU Collaboration fine print No funding is directly transferred between the EU and US The EU agrees to supply manpower to assist in the experimental program on PISCES-B (mutually agreed upon scientist usually comes for a one year visit) Several short-term visitors (~ month) can be proposed to investigate high priority tasks –EU visitors include: M. Balden, D. Borodin, C. Brosset, G. De Temmerman, A. Kirschner, A. Kreter, A. Pospieszczyk, R. Pugno, J. Roth, K. Schmid, F. Tabares, A. Widdowson The EU supplies equipment to facilitate the experimental task of the long-term visiting scientist IPP Garching provides material analysis for samples PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 The US-EU Collaboration fine print The USDOE delayed Be decontamination of PISCES-B until the collaboration ends US provides logistical support for visiting EU scientists PISCES-B experimental time can be allocated for EU proposed experiments and model validation measurements UCSD supports Be training and medical monitoring of long-term EU visitors UCSD coordinates P-B program with EU counterparts at EFDA and in the PWI Task Force [everything is done by mutual agreement (EFDA representative, PWI TF Leader, SEWG MM leader, ITER contact, PISCES leader*)] * Remaining permanent member of this counsel retains veto authority PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 The PISCES-B divertor plasma simulator is used to simulate ITER mixed materials PSI. PISCES-B is contained within an isolated safety enclosure to prevent the release of Be dust. PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 PISCES-B has been modified to allow exposure of samples to Be seeded plasma P-B experiments simulate Be erosion from ITER wall, subsequent sol transport and interaction with W baffles or C dump plates, as well as investigation of codeposited materials using witness plates PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 A small beryllium impurity concentration in the plasma drastically suppresses carbon erosion with a characteristic decay time, Be/C Chemical erosion Modeling using ERO and WBC Univ.) continues to try to understand the dominant effects and timescales PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 No influence of Ar on Be/C mitigation process Comparison of CD band decay during Be seeding on C target: with and without added Ar High ion energy case Y(D on Be) ~3e-2, Y(Ar on Be) ~2e-2 Low ion energy case Y(D on Be) ~1e-2, Y(Ar on Be) ~5e-5 This result may improve possibility of ITER achieving Q=10 with CFC divertor material. PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , Stable Be-W alloys Be 12 W W sample Be deposited layer Be x W alloy growth has been measured in PISCES, temperature and availability of Be are crucial factors, growth rate is likely not a big issue for ITER. Retention still needs to be investigated. Thin Be 2 W surface layers always exist, Be 12 W interlayers grow when sufficient surface Be exists PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 From Beryllium experiments: D/C = E –0.43 ( D / C ) 0 exp (2268/T c ) T c > 473K Systematic codeposition studies have provided a means to compare different codeposit retention properties D/Be = (5.82 x )E n ( D / Be ) exp ( /T c ) D/W = (5.13 x )* E n * ( D / W ) * exp ( /T c ) D/C = E –0.43 ( D / C ) 0 exp (2268/473) T c < 473K From Carbon literature: From Tungsten experiments: Be scaling removes (to a large extent) the scatter in the predicted D/Be level in Be codeposits PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 Codeposition scaling can provide insight into expected trends in ITER C retains less T at higher particle energy locations (first wall) C retains more T at lower particle energy regions (dome/divertor) Be retains less T at low particle energy (dome/divertor) Be retains more T at higher particle energy regions (first wall) Where will codeposits preferentially form? PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 Normalized deuterium release behavior of Be codeposits can be used to determine cost-benefit relationship of increasing ITER bake-out temperature PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 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

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 PISCES-B calibrated spectroscopic systems allow composition measurements of mixed-species plasma Typically, emission from neutrals are used to quantitatively determine sputtering yield, chemical erosion, evaporation rate, etc. Mixed-ion species plasma effects are as important as mixed-material effects, and almost equally as unexplored –Absolute Be impurity ion concentration in plasma –Absolute He ion composition of plasma –Absolute Ar ion radiator concentration in plasma –C ion content during CD 4 (or C 2 D 2 ) still ongoing (but difficult) –W under consideration (photon emission coefficients?) Not all plasma operating scenarios are consistent with absolute spectroscopic measurements PISCES-B systems allow for sculpting plasma composition PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 PISCES Mixing He with D-plasma suppresses blisters on W surface and reduces D-retention in W. Pure D 2 plasma (SRWM-3b) D-fluence ~ 5e25 m -2, D ~ 1.0e22 m -2 s -1, T s ~ 573 K, E i ~ 60 eV D 2 -He mixture plasma (SRWM-4b) D-fluence ~ 5e25 m -2, D ~ 0.9e22 m -2 s -1, T s ~ 573 K, E i ~ 50 eV, n He+ /n e ~ 20 % He ions cluster and produce nano-bubbles in the implantation zone (MD predicted) that somehow reduce D diffusion into the bulk W

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 PISCES-B: pure He plasma T s = 1200 K, t = 4290 s, Fluence = 2x10 26 He + /m 2, E i = 25 eV Nano-scale morphology develops on high temperature W surfaces in pure He plasma. Transmission electron microscope (TEM) in Kyushu Univ. Scanning electron microscope (SEM) NAGDIS-II: pure He plasma T s = 1250 K, t = 36,000 s, Fluence = 3.5x10 27 He + /m 2, E i = 11 eV N. Ohno et al., in IAEA-TM, Vienna, 2006 PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 In D 2 He plasmas, nano-morphology persists, but growth rate depends on He + flux. The presence of D 2 does not appear to affect nano-morphology structure. But growth rate can be affected. After a little more than 1 h of He plasma exposure in D 2 0.1He, layer thickness is only ~0.5 m. Layer thickness, ~2.0 m in D 2 0.2He is comparable to pure He. D+He = 4–6×10 22 m –2 s –1 PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 Nano-morphology growth rate depends on He + flux below 7 × m -2 s -1. Two regions of interest: - Layer growth rate increases exponentially for He + fluxes up to ~7×10 21 m -2 s Layer growth rate is optimal for He + fluxes above this. D 2 does not likely affect nano- structured layer growth rate. - Lowest He + flux data point (pure He) fits trend. Nano-structure growth may require surface saturation or mechanism that traps He. ITER (Outer strike plate) A. Kukushkin, ITER Report, [ITER_D_27TKC6] 2008 PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , A thick Be or C layer inhibits nano- morphology. At ~ 15 eV, PMI conditions favor net Be or C deposition. He induced nano-scopic morphology is inhibited. A ~Be 12 W alloy layer is observed on W in a D 2 0.1He plasma w/ Be injection. A C rich layer forms on W in a D 2 0.1He plasma w/ CD 4 injection. At ~15 eV, the stopping range for both D + and He + is under 1 nm in Be or C. D+He = 3×10 22 m –2 s –1 PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 Q-Switched Nd:YAG Laser 1064nm <850 mJ ~5 nsec pulse <1 mrad Two laser systems exist at PISCES to investigate simultaneous laser and plasma irradiation Presently being used on PISCES-A Developing safety systems Debugging delivery optics Diagnostic development Can double as diagnostic beam Long-pulse Laser System msec pulse E pulse = J Up to 50 MJ/m 2 -sec 1/2 Fiber Delivery Available Being installed into PISCES-A Safety systems designed and being incorporated into PISCES-B enclosure Operational in PISCES-B by Jan. 09 PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 Effects of D Loading on W Surface Damage F = 5 x /m 2 F = 5 x /m 2 F = 2 x /m 2 Fluence to surface before laser pulse varied Absorbed Energy Impact ~45 MJ/m 2 s 1/2 (R W ( =1064nm) ~ 70%) V bias = -125V =2x10 22 /m 2 -sec T e =11eV n e =2x10 24 /m 3 T s ~ 50°C SAMPLE PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 Something completely different, angular distributions of sputtered C atoms and clusters (Mo done, W 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 C atoms and clusters are investigated with different noble gas plasma E. Oyarzabal et al., J. App. Phys. 100(2006) PISCES

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 Angular distribution of sputtered atoms, dimers and trimers become more cosine with lower mass ions E. Oyarzabal et al., J. App. Phys. 104(2008)043305

R. Doerner, EU PWI Task Force Meeting, Frascati, Italy, Oct , 2008 Conclusion US-EU collaboration on mixed materials for ITER has been very successful (at least 26 publications) In 2007, PISCES entered the US-Japan TITAN collaboration which should promote US-EU-Japan PMI interactions PISCES participates in bilateral exchanges with ASIPP (China) ITER has expressed interest in also working directly with the PISCES Program PISCES