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Tokitani, M.

Publications and source records attributed to Tokitani, M..

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Material mixing during fuzz formation in W and Mo

Helium-induced fuzz formation in tungsten (W) and molybdenum (Mo) is investigated for a range of sample exposure temperatures from 838 K–1075 K (He fluence = 3.4 × 10 25 m -2 and ion energy <39 eV). Thin films of Mo deposited on W substrates show mixing of the film and substrate materials in the fuzz after He plasma exposure, including at 838 K (i.e. below the typical temperature range at which fuzz forms in pure W). Finally, the amount of material mixing increases with exposure temperature due to the increase in bubble size, and leads to significant accumulation of the substrate material at the fuzz surface at the highest temperature investigated, further supporting fuzz growth from the fiber tip outwards by material transport up the fibers.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Effect of a Cr-rich surface layer on D retention in various RAFM steels

In this work, deuterium (D) retention is compared between various reduced-activation ferritic/martensitic steels, including CLF-1, Eurofer, F82H, and Rusfer, exposed to pure D plasma (ion flux ~1.5–2 × 10 21 m -2 s -1 , fluence, &straightphi; D , ~1 × 10 25 m -2 , sample temperature ~373 K, and incident ion energy ~100 eV). It is found that there is a large difference (up to ~30x) in the D retention between CLF-1 and F82H even with the same plasma exposure condition and similar nominal composition. The &straightphi; D dependence of the D retention exhibits a peculiar, counterintuitive feature: the D retention decreases with an increase in &straightphi; D from 2 × 10 23 m -2 to 1 × 10 25 m -2 . Surface analyses reveal that a Cr-rich surface layer is formed during outgassing at 773 K for 1 h before plasma exposure, and that there exists a clear correlation between the D retention and the Cr content in the surface layer.

36 MATERIALS SCIENCE↗