Hydrogen recycling constant during ion bombardment

Abstract

The validity of a simple diffusion model based on the assumptions of small ion range compared with diffusion length, negligible hydrogen-defect interaction and second order thermal desorption is analysed in its application to hydrogen re-emission from, and accumulation in, materials during ion implantation. Comparison with experiment have been made for different metals (Mo, Ni, SS) and nonmetals (carbon, pyrographite, uglesitall, BN, TiC, TiO 2, SiO 2, TiB 2). The model calculations disagree with experimental measurements of re-emission during the transient stage of implantation, when re-emission is less than 100%, but give very good agreement with experiments on the accumulation of hydrogen in materials at high ion fluences. The recycling parameter R = D/K may be derived from the high-dose experiments and used for further predictions of hydrogen retention in the first wall.