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Divertor and midplane materials evaluation system in DIII-D

Journal of Nuclear Materials

Wong, C.P.C.; Rudakov, D.L.; Allain, J.P.; Bastasz, Robert J.; Brooks, N.H.; Brooks, J.N.; Doerner, R.P.; Evans, T.E.; Hassanein, A.; Jacob, W.; Krieger, K.; Litnovsky, A.; McLean, A.G.; Philipps, V.; Pigarov, A.Y.; Wampler, W.R.; Watkins, J.G.; West, W.P.; Whaley, Josh A.; Wienhold, P.

The Divertor Materials Evaluation System (DiMES) at General Atomics has successfully advanced the understanding of plasma surface interaction phenomena involving ITER-relevant materials and has been utilized for advanced diagnostic designs in the lower divertor of DIII-D. This paper describes a series of recent successful experiments. These include the study of carbon deposition in gaps and metallic mirrors as a function of temperature, study of dust migration from the divertor, study of methane injection in order to benchmark chemical sputtering diagnostics, and the measurement of charge exchange neutrals with a hydrogen sensor. In concert with the modification of the lower divertor of DIII-D, the DiMES sample vertical location was modified to match the raised divertor floor. The new Mid-plane Material Exposure Sample (MiMES) design will also be presented. MiMES will allow the study and measurement of erosion and redeposition of material at the outboard mid-plane of DIII-D, including effects from convective transport. We will continue to expose relevant materials and advanced diagnostics to different plasma configurations under various operational regimes, including material erosion and redeposition experiments, and gaps and mirror exposures at elevated temperature. © 2007 Elsevier B.V. All rights reserved.

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TYPE Conference YEAR 2007
ScopusOSTI

Recoil energy distribution of hydrogen isotopes adsorbed on tungsten

Proposed for publication in Journal of Nuclear Materials.

Bastasz, Robert J.; Whaley, Josh A.

The energies of adsorbed H and D recoiled from tungsten surfaces during bombardment with 3 keV Ne{sup +} at oblique angles of incidence were measured. The energy spectra show structure that extends above the elastic recoil energy. We find that the high-energy structure results from multiple collisions, namely recoil of a H isotope followed by scattering from an adjacent W atom, and vice versa. This scattering assisted recoil process is especially prevalent for H isotopes adsorbed on W, owing to the large mass difference between the scattering partners. Such processes will tend to enhance H isotope recycling from plasma-facing W surfaces and reduce energy transfer to the W substrate.

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TYPE Journal Article YEAR 2004
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9 Results
9 Results