LAUSR

Abstract By using scanning electron microscopy and atomic force microscopy, we observe the microscopic surface evolution of W crystals exposed to low-energy (50 eV) He+ irradiations at the temperature of 1050 K. We find that the He+ irradiation leads to the growth and emergence of nanoscale undulations over W (110), and the surface regions with less undulations are dominating the microscopic evolution of W crystals. Analysis shows that the thermodynamic instability of W crystals irradiated is attributed to the He nanobubble driven W surface growth, which has been confirmed by our experimental measurements and He reaction rate model in W. Our study will play a crucial role in understanding the growth process of undulating surface microstructures under fusion-relevant He+ irradiations.