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

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.