Microstructure in pure copper irradiated by simultaneous multi-ion beam of hydrogen, helium and self ions

Pure copper was irradiated at 300–500°C by 5 MeV Cu ions (single beam) and Cu ions plus gas atoms (H and He) (dual beam irradiation) simultaneously. The high energy ion irradiation was carried out with the accelerator TIARA at the Takasaki-establishment of JAERI. The ions stop within a few microns from surface level and damage was formed up to this depth. The damage structure was observed as a function of the depth utilizing a focused ion beam (FIB) device. Below 300°C irradiation with a single beam produced a high density of stacking fault tetrahedra (SFT) but void formation was not observed. Large voids were observed with single beam irradiation at 500°C. In specimen irradiated with a dual beam of helium and Ni ions, the number density of voids was increased significantly. In copper irradiated with hydrogen and Ni ions, the number density of voids was not so large. Experimental results show that helium atoms promote void formation. Hydrogen atoms have less effect on void formation than helium atoms in pure copper.