The effect of displacement damage on deuterium retention in tungsten exposed to D neutrals and D2 gas

Samples of polycrystalline ITER-grade W and recrystallized W were irradiated at room temperature with 20MeV W ions to displacement damage up to 0.5dpa. The damaged W samples were then exposed to (i) D neutrals at 403–573K and (ii) D2 gas at 673–1073K and pressures of 1.2 and 100kPa. Trapping of deuterium in the damage zone was examined by the D(3He, p)4He nuclear reaction with 3He energies between 0.69 and 4.0MeV allowing determination of the D concentration up to a depth of 6μm. It has been found that generation of the W-ion-induced displacement damage leads to accumulation of deuterium in the damage zone up to concentration depending on the exposure temperature and, at temperatures ⩾673K, on the D2 gas pressure. Thermal desorption spectra allowed a conclusion that deuterium is mainly accumulated in the form of D atoms bound to inner walls of vacancy clusters.