Microstructure dependence of deuterium retention and blistering in the near-surface region of tungsten exposed to high flux deuterium plasmas of 38 eV at 315 K

Four kinds of tungsten samples were exposed to 76 eV D2+ ions (38 eV D-1) at a flux of 1022 D m-2s-1. For plasma exposure at 315 K, blistering occurred more significantly on the unrecrystallized and single crystal W samples than the partially and fully recrystallized W samples. The un-recrystallized W sample showed the largest retention ratio at the same fluence. For samples exposed to higher fluences (up to 1027 D m-2), the phenomena of bursting release of deuterium and blister bursting were clearly observed. Preliminary positron annihilation measurements indicated that the vacancy concentration in the near-surface region of tungsten increased after the deuterium plasma exposure. The results of electron back-scattering diffraction showed a strong dependence of blistering upon grain orientation, suggesting the possibility of alleviating blistering by selective texturing of tungsten for future fusion reactors