Ion beam analysis of helium and its irradiation effect on hydrogen trapping in W single crystals

Retention of He implanted into W single crystals and the He irradiation effects on H behavior were studied by ion beam analysis techniques. During implantation of ⁴He⁺ with 2-10 keV at 295 K, an accumulation of H started in the He implanted layer when the retained He concentration saturated. For the crystal irradiated by 10 keV He⁺ at 820 K, a remarkable increase of H was found in the He saturated layer, after stopping the implantation and cooling down the crystal below 400 K. Though blisters and exfoliation were observed for the surface irradiated at 820 K, less lattice disorder was found in the implanted layer and the thermal release of H occurred at lower temperature, in comparison with the crystal implanted at 295 K.