Abstract
Tile specimens from the DIII-D tokamak have been studied to determine their erosion characteristics when exposed to D + ions and O 2 gas. Here, we report results for tile surfaces from the outer midplane. Surface analyses (EDX, XPS, SIMS) indicate that the surface layer is composed primarily of boron, with an overlayer of a B/C mixture. Total hydrocarbon ( ΣC iD j) erosion yields were initially found to be ∼0.01–0.02 C/D +, with limited variations due to D + energy (50 or 200 eV) or specimen temperature (300–700 K). Erosion yields were seen to decrease with fluence by a factor of 1.5–2 over the range ∼4×10 21–3×10 22 D +/m 2. Above ∼ 3×10 22 D +/ m 2 the yields level off. The initial erosion yields are found to be consistent with those for boron-doped graphite. O 2 gas exposure at 523 or 623 K initially removed ∼25% of the trapped D; however, the remaining D could not be removed by baking in O 2 at temperatures up to 623 K.
Published Version
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