Deuterium retention in W and W-Re alloy irradiated with high energy Fe and W ions: Effects of irradiation temperature

Neutron irradiation to W induces defects acting as traps against hydrogen isotopes and transmutation elements such as Re and Os. To investigate synergetic effects on radiation-induced defects and Re, deuterium (D) retention in W and W-5% Re samples were examined after irradiation with 6.4 MeV Fe ions at 523-1273 K followed by exposure to D2 gas at 673 K. The value of D retention in W-5% Re was lower than that in W by orders of magnitude after the irradiation at high temperatures (≥1073 K), while no significant effects of Re addition was observed after irradiation at 523 K. Irradiation with 20 MeV W ions at room temperature followed by exposure to D plasma at 443-743 K also resulted in small difference in D retention between W and W-5% Re samples. The results of positron lifetime measurements showed that the reduced D retention by Re observed after high temperature irradiation was due to suppression of formation of vacancy-type defects (monovacancies and vacancy clusters) by Re.