Application of positron beam Doppler broadening technique to ion beam irradiation in nickel

The formation processes of vacancy-type defects induced by ion irradiation in nickel were investigated with a variable-energy positron beam Doppler broadening technique in order to find the appropriate experimental condition for in situ positron beam experiments. Nickel ion irradiation at 300–343 K induces an S parameter increase, but the dependence of the S parameter on positron energy is very similar to that of cold-rolled nickel, which suggests positron trapping by small vacancy-type defects such as SFTs. The best experimental condition for investigation of cavity nucleation process by in situ positron beam Doppler experiments is suggested to be around 0.1–0.4 dpa at 773 K.