Surface morphology and deuterium retention in tungsten exposed to low-energy, high flux pure and helium-seeded deuterium plasmas

Blistering and deuterium retention in re-crystallized tungsten exposed to low-energy, high flux pure and helium-seeded D plasmas to a fluence of 1027?D?m?2 have been examined with scanning electron microscopy, thermal desorption spectroscopy, and the D(3He,p)4He nuclear reaction at 3He energies varied from 0.69 to 4.0?MeV. In the case of exposure to pure D plasma (38?eV?D?1), blisters with various shapes and sizes depending on the exposure temperature are found on the W surface. No blisters appear at temperatures above 700?K. The deuterium retention increases with the exposure temperature, reaching a maximum value of about 1022?D?m?2 at 480?K, and then decreases as the temperature rises further. Seeding of 76?eV He ions into the D plasma significantly reduces the D retention at elevated temperatures and prevents formation of the blisters.