Effects of helium bombardment on the deuterium behavior in tungsten

The effects of pre-irradiation with helium ions of fusion relevant energy on trapping of injected deuterium in W was studied by thermal desorption spectrometry technique using high-resolution quadrupole mass spectrometer. Pre-irradiation with He ions caused remarkable effects on the trapping of injected deuterium. Most of the injected deuterium is desorbed between 400 and 600 K for the case without helium pre-irradiation, while additional desorption occurs between 600 and 800 K for the helium pre-irradiation case. Total amount of the trapped deuterium for irradiations of 2.0 x 10(21) He/m(2) and 1.0 x 10(22) D-2/m(2) is 6.2 x 10(20) D-2/m(2), which is more than three times higher than that in the case of no helium pre-irradiation. The present result indicates that irradiation effects of He bombardment must be taken into account to understand and evaluate the behavior of hydrogen isotopes in fusion environment. (C) 2002 Elsevier Science B.V. All rights reserved.