Studies on hot atom chemical behavior of energetic ions in solids (9). Effects of helium ion implantation on chemical behavior of deuterium implanted into silicon carbide

In blanket systems for future D-T fusion reactors, energetic helium and tritium are produced by nuclear reaction in tritium breeding materials and implanted into blanket structural materials. Silicon carbide (SiC) is a candidate for blanket structural materials due to its low activation. Therefore, it is important to understand chemical states and retention behaviors of tritium in SiC from a view point of fusion safety. It was previously reported that the deuterium implanted into SiC was trapped with forming Si-D and C-D bonds. In this study, helium ions were pre-implanted and then deuterium ions were implanted into SiC. Thereafter the retention of deuterium in SiC was evaluated by means of XPS and TDS and compared to that obtained for SiC implanted only with deuterium ions. These results indicate that the helium ions pre-implantation would introduced carbon vacancies and could decreased retention of deuterium with forming Si-D bond. (author)