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MODEL VALIDATION ON EAST AND DIII-D EXPERIMENTS TOWARDS UNDERSTANDING OF HIGH-Z MATERIAL EROSION AND MIGRATION IN A MIXED MATERIALS ENVIRONMENT

Ding, R.D.; Xie, H.X.; Ding, F.D.; Wampler, William R.; Wang, L.W.; Chen, J.L.C.; Komm, M.K.; Dejarnac, R.D.; Rudakov, D.L.R.; Bykov, I.B.; Abrams, T.x.; Chan, V.S.C.; Guo, H.Y.G.; Snyder, P.B.S.; Elder, J.D.x.; Stangeby, P.C.S.; Wang, H.Q.W.; Watkins, Jonathan G.; Unterberg, E.A.x.; Brezinsek, S.B.; Kirschner, A.K.

Abstract not provided.

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TYPE Conference Poster YEAR 2019
OSTI

Measurements of tungsten migration in the DIII-D divertor

Physica Scripta

Wampler, William R.; Watkins, Jonathan G.; Rudakov, Dmitry R.; McLean, Adam M.; Unterberg, Ezekial U.; Stangeby, Peter S.

An experimental study of migration of tungsten in the DIII-D divertor is described, in which the outer strike point of L-mode plasmas was positioned on a toroidal ring of tungsten-coated metal inserts. Net deposition of tungsten on the divertor just outside the strike point was measured on graphite samples exposed to various plasma durations using the divertor materials evaluation system. Tungsten coverage, measured by Rutherford backscattering spectroscopy (RBS), was found to be low and nearly independent of both radius and exposure time closer to the strike point, whereas farther from the strike point the W coverage was much larger and increased with exposure time. Depth profiles from RBS show this was due to accumulation of thicker mixed-material deposits farther from the strike point where the plasma temperature is lower. These results are consistent with a low near-surface steady-state coverage on graphite undergoing net erosion, and continuing accumulation in regions of net deposition. This experiment provides data needed to validate, and further improve computational simulations of erosion and deposition of material on plasma-facing components and transport of impurities in magnetic fusion devices. Such simulations are underway and will be reported later.

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TYPE Journal Article YEAR 2017
OSTIDOI

OEDGE modeling of the DIII-D double null 13CH4 puffing experiment

Wampler, William R.; Watkins, Jonathan G.

Unbalanced double null ELMy H-mode configurations in DIII-D are used to simulate the situation in ITER high triangularity, burning plasma magnetic equilibria, where the second X-point lies close to the top of the vacuum vessel, creating a secondary divertor region at the upper blanket modules. The measured plasma conditions in the outer secondary divertor closely duplicated those projected for ITER. {sup 13}CH{sub 4} was injected into the secondary outer divertor to simulate sputtering there. The majority of the {sup 13}C found was in the secondary outer divertor. This material migration pattern is radically different than that observed for main wall {sup 13}CH{sub 4} injections into single null configurations where the deposition is primarily at the inner divertor. The implications for tritium codeposition resulting from sputtering at the secondary divertor in ITER are significant since release of tritium from Be co-deposits at the main wall bake temperature for ITER, 240 C, is incomplete. The principal features of the measured {sup 13}C deposition pattern have been replicated by the OEDGE interpretive code.

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TYPE Conference YEAR 2010
OSTI

DIVIMP modeling of the toroidally-symmetrical injection of 13 CH4 into the upper SOL of DIII-D

Wampler, William R.; Watkins, Jonathan G.

As part of a study of carbon-tritium co-deposition, we carried out an experiment on DIII-D involving a toroidally symmetric injection of {sup 13}CH{sub 4} at the top of a LSN discharge. A Monte Carlo code, DIVIMP-HC, which includes molecular breakup of hydrocarbons, was used to model the region near the puff. The interpretive analysis indicates a parallel flow in the SOL of M {parallel} {approx} 0.4 directed toward the inner divertor. The CH{sub 4} is ionized in the periphery of the SOL and so the particle confinement time, T{sub C}, is not high, only {approx} 5 ms, and about 4X lower than if the CH{sub 4} were ionized at the separatrix. For such a wall injection location, however, approximately 60-75% of the CH{sub 4} gets ionized to C{sup +}, C{sup 2+}, etc., and is efficiently transported along the SOL to the inner divertor, trapping hydrogen by co-deposition there.

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TYPE Conference YEAR 2004
OSTI
25 Results
25 Results