Blister bursting and deuterium bursting release from tungsten exposed to high fluences of high flux and low energy deuterium plasma

Abstract

Deuterium retention and blistering in the near-surface region of tungsten exposed to high fluences (up to 1027 D m−2) of high flux (1022D+ m−2 s−1) and low energy (38 eV) deuterium plasma were examined with scanning electron microscopy, focused ion beam and thermal desorption spectroscopy (TDS). Two kinds of blisters appeared at the recrystallized tungsten exposed to the plasma at 520 K. One is the large blisters with sizes of a few tens of micrometres and varying ratios of height against width (up to 0.6), and the other is the small blisters with sizes of less than a few micrometres and a large ratio of height against diameter (about 0.7). A peculiar phenomenon of blister bursting with a tail, or partially opened or fully opened lid was found on some grains after plasma exposure or TDS experiment. In addition, bursting release of deuterium with sudden peaks was observed in the TDS curve below 700 K at a heating rate of 0.5 K s−1. A new model named ‘step-cascade model’ was proposed to explain the blister bursting. Furthermore, the origin of deuterium retention and blistering as well as future work on high-Z materials were discussed.