Recent findings on blistering and deuterium retention in tungsten exposed to high-fluence deuterium plasma

Blistering and deuterium retention in tungsten exposed to high-fluence (up to 1027 D/m2) of high-flux (1022 D+/m2/s) and low-energy (38 eV) deuterium plasma were examined in the temperature range of 315–1000 K with scanning electron microscopy, focused ion beam, thermal desorption spectroscopy and positron annihilation. There were cavities inside small blisters with the maximum ratio of height against diameter of about 0.7, whereas there were voids/holes along the grain boundary beneath most large blisters but no hollow lid formed. Blistering and deuterium retention showed a significant dependence upon fluence and exposure temperature.