Hydrogen isotope exchange in tungsten irradiated sequentially with low-energy deuterium and protium ions

Hydrogen isotope exchange in tungsten was investigated at various temperatures both after sequential exposure to low-energy deuterium (D) and protium (H) plasmas and after sequential irradiation with low-energy D and H ions. The methods used were thermal desorption spectroscopy, and the D(3He,p)4He nuclear reaction at 3He energies varied from 0.69 to 4.0 MeV, allowing the determination of the D concentration at depths of up to 6 μm. It was found that a major portion of the deuterium initially accumulated in the D-implanted W is released on subsequent exposure to H plasma or irradiation with H ions. Depth profiling of D without and with subsequent H implantation shows strong replacement close to the surface near room temperatures, but extending to all analyzable depths at elevated temperatures.