Reflection, re-emission and permeation of deuterium implanted in Ti6Al4V alloy

Abstract

A Ti6Al4V alloy has been selected as the vacuum vessel structural material in the tokamak physics experiment (TPX) [1] and in the steady state tokamak JT-60 Super Upgrade (JT-60 SU) [2]. To determine the amount of hydrogen retained in titanium alloy during glow discharge cleaning and plasma operation the knowledge of the parameters such as a recombination coefficient K and a particles reflection coefficient R N is necessary. Presence of the non-metallic impurities on the surface strongly affects both the above mentioned parameters. In the present work, the permeation behavior of deuterium has been investigated for deuterium implanted into Ti6Al4V membrane with an incident ion energy 150–1500 eV/D. R N has been determined by means of the thermal desorption technique. The surface chemical composition was controlled in-situ by means of AES and SIMS analyses. Experimentally obtained values of R N are larger than computer simulation results for both the clean Ti6Al4V surface and the surface layer with the concentration of the chemical elements same as that experimentally observed. The calculated values of R N are not significantly different from one another. The amount of retained hydrogen was estimated for TPX condition taking into account the contribution of the reflected particles to the flux balance.