In situ positron beam Doppler broadening measurement of ion-irradiated metals - Current status and potential

The positron beam technique has been widely used as a detection tool for vacancy-type defects in solids, especially defects induced by ion irradiation/implantation that are localized near the surface. To extend this technique to other applications, we constructed unique in situ positron beam measurement equipment combined with an ion beam irradiation chamber. This equipment enables us to measure positron beam Doppler broadening during or immediately after irradiation without any sample handling. With this equipment, defect accumulation and evolution in iron and nickel were investigated at room temperature. In addition, the defect accumulation and annealing process was investigated at temperature below stage III to reveal vacancy configurations after cascade, without any thermal migration after the cascade cooling. In this paper, we summarize these results and discuss ideas for future study.