Abstract
• He diffusion behavior in W and the evolution of He nano-bubbles at T = 750 − 2500 K are investigated based on the He reaction rate model in W. • The effect of temperature on the growth of He nano-bubbles is compared with our experimental observation. • Increasing the irradiation temperature leads to a significant change in both the radius of He nano-bubbles and He retention. Under fusion-relevant He + irradiations, the W surface temperature is one of the most important parameters for controlling the fuzz growth over the W divertor targets, which is associated with the surface bursting of He nano-bubbles. Using He reaction rate model in W, we investigate the effect of temperature on the growth and surface bursting of He nano-bubbles under low-energy (100 eV) and large-flux (∼10 22 /m 2 ⋅s) He + irradiations. Increasing the irradiation temperature from 750 to 2500 K leads to a significant change in both the radius of He nano-bubbles and He retention. At an elevated temperature, He solute atoms prefer to rapidly diffuse into He nano-bubbles, thus affecting their concentration, growth and surface bursting. The decrease in He retention is attributed to an increase in the hop rate of solute He atoms in the W top layer, resulting in the significant He release from the W surface. The radius and density of He nano-bubbles calculated by our model are consistent with our experimental observation.
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