Background: Irradiation damage in materials has been of major interest for the nuclear materials community due to the needs to well understand and predict the behaviors of fusion reactor materials. Molybdenum (Mo) has been regarded as the potential candidates for the plasma-facing materials (PFMs) in Tokmak fusion reactors. Purpose: The understanding of the irradiation damage behavior of Mo is the major issue for development of key fusion reactors materials. Methods: Polycrystalline molybdenum materials have been irradiated with low-energy (100eV) and high-flux (~1021 ions?m−2?s−1) He+ at the irradiation temperature of 600 oC. The effects of ion dose and annealing temperature on the surface damage of molybdenum are investigated. The morphology

microscopic evolution and distribution of defects of these samples before and after irradiation are compared using scanning electron microscopy (SEM) and non-destructive conductive atomic force microscopy (CAFM). Results: Analysis indicates that He+ irradiation can induce the increase of molybdenum sample grain size. The distribution of irradiation defect is depended on the grain orientation. The specific orientation of molybdenum material has a good performance in irradiation resistance. Conclusion: This work is of guiding significance to the exploration of the suppression of material irradiation damage.Cited