Hydrogen and deuterium uptake in helium implanted layer of Mo and W

The accumulation of hydrogen isotopes in the helium (He) implanted layer of Mo and W single crystals was studied, focusing on the effects of the high dose irradiation of He ions and on uptake behavior of hydrogen (H) and deuterium (D) in various H 2 and D 2 pressure. A remarkable H uptake occurs in the He saturated layer of the crystals irradiated by 10 kev 4 He ions to a dose about 2 x 10 22 He/m 2 , after the heat treatment up to 850 K. The integrated amount of retained H reaches the same values before the thermal release procedure, though H-uptake rates depend on the gas pressure. The H is preferentially uptaken in the He saturated layer, when D 2 and/or D 2 O gas is introduced in the vacuum chamber. The large difference between the H- and D-uptake rates suggest the oxide formation at the crystal surface where the microstructure is significantly changed due to the He irradiation.