Impact of low energy helium irradiation on plasma facing metals

Effects of helium ion irradiation for tungsten and other metals have been studied extensively as functions of ion energy, temperature and fluence, for a wide range of burning plasma conditions, using not only ion accelerators, but also large-sized plasma confinement devices such as TRIAM-1M and LHD. In this paper, recent results on blistering, erosion and many other irradiation effects such as internal damage evolution, change of mechanical properties and heat load resistance, and synergetic effects with neutron irradiation, are comprehensively reviewed for better understanding of the performance of tungsten under helium plasma bombardment. It is emphasised that helium irradiation is a serious issue for tungsten as a plasma facing material under burning plasma condition.