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 10(27) Dm(-2) have been examined with scanning electron microscopy, thermal desorption spectroscopy, and the D(He-3, p)He-4 nuclear reaction at He-3 energies varied from 0.69 to 4.0MeV. In the case of exposure to pure D plasma (38 eVD(-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 Dm(-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.