Deuterium retention in plasma spray tungsten coatings exposed to low-energy, high flux D plasma |
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Authors: | V.Kh. Alimov H. Nakamura O.V. Ogorodnikova K. Isobe |
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Affiliation: | a Hydrogen Isotope Research Center, University of Toyama, Toyama 930-8555, Japan b Tritium Technology Group, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan c Max-Planck-Institut für Plasmaphysik, EURATOM Association, D-85748 Garching, Germany |
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Abstract: | Two types of porous plasma spray tungsten coatings deposited onto stainless steel and graphite substrates were exposed to low-energy (76 eV ), high-flux (1022 D/m2 s) D plasma to ion fluences of (3-4) × 1026 D/m2 at various temperatures. Deuterium retention in the W coatings was examined by thermal desorption spectroscopy and the D(3He,p)4He nuclear reaction, allowing determination of the D concentration at depths up to 7 μm. The relatively high D concentration (above 0.1 at.%) at depths of several micrometers observed after D plasma exposure at 340-560 K can be related to accumulation of D2 molecules in pores, while at temperatures above 600 K deuterium is accumulated mainly in the form of D atoms chemisorbed on the inner pore surfaces. At exposure temperatures above 500 K, the D retention in the plasma spray W coating on graphite substrate increases significantly due to trapping of diffusing D atoms at carbon dangling bonds located at the edge of a graphite crystallite. |
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