The effect of O2 impurity on surface morphology of polycrystalline W during low-energy and high-flux He+ irradiation

•Low-energy and high-flux He+ ions were produced using a radio frequency (RF) ion source in present irradiation experiments.•The effect of O2 impurity in He plasma on W surface microstructure was studied in the present work.•When R is larger than 5.2 × 10−2, the erosion yield increased obviously, accompanied by the disappearance of nano-fuzz.•The thickness of nano-fuzz layer was reduced with increasing R from 4.0 × 10−6 to 1.8 × 10-2.