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 2.0×1021 He/m2 and 1.0×1022 D2/m2 is 6.2×1020 D2/m2, 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.