Permeation of hydrogen through vanadium under helium ion irradiation

Hydrogen permeation through vanadium was examined under helium ion irradiat ion. The upstream surface of a vanadium membrane was exposed to hydrogen ga s at 673 K and 640 Pa, and the downstream surface was irradiated with 5 keV helium ions. No significant variation in the permeation rate was observed in the initial stage of irradiation. The permeation rate, however, started to decrease at a helium ion dose of 10(21) m(-2) with further irradiation. In this region, the permeation rate dropped immediately by intermission of irradiation and shot up by resumption. These results were successfully expl ained with a model that helium bubbles act as trapping sites of hydrogen an d detrapping is enhanced under irradiation. (C) 2000 Elsevier Science B.V. All rights reserved.