Materials, Methods & Technologies, Volume 12, 2018

Abstract: W is the main wall material in the international fusion device and seeding of N containing gas is under consideration for plasma edge cooling and H isotope removal from the wall. In this environment with residual oxygen gas, it is highly anticipated that WNOx layers are formed on W. Thus, knowledge of H-isotope retention in WNOx layers is important for understanding of H-isotope recycling. Using WNOx (x=0.4±0.2) films prepared on C-plane-cut-sapphire (C-Al2O3) substrate, we have investigated H and D retention, and depth profile of H and D, using D(3He, α)H nuclear reaction analysis (NRA), H(15)O-NRA and elastic recoil detection (ERD). In as-deposited films, we find a high density (0.4x1022 cm-3) of H by 15N -NRA. After low energy D-plasma exposure (~1018 cm-2), we also find a large amount of D-retention (~ 1017 cm-2) by 3He -NRA, as well as high density D by ERD, and that high density of H remains in the film. These results cannot be understood by a simple H-D replacement.