Based on a He reaction rate model in W, we have analyzed the effect of fusion-relevant He+ flux on the evolution and surface bursting of He nano-bubbles in W. The concentrations of solute He atoms, trapped He atoms, and He nano-bubbles, and the radius of He nano-bubbles have been obtained as a function of depth, He+ dose, and He+ flux. He retentions in W are also calculated as the function of He+ dose and flux. Our modeling shows that the He+ flux varying from 5.0 × 1018 to 5.0 × 1024 m−2·s−1 significantly affects the concentration of solute He atoms diffusing in W and trapped He atoms, the evolution of He nano-bubbles, and He retention in W. Both the concentration and radius of He nano-bubbles in W show the dependence on He+ flux, and their surface bursting leads to an increase () in the W surface area, thus the growth of W nano-fuzz. When He+ flux increases 5.0 × 1018 to 5.0 × 1024m−2·s−1, the bursting rate of He nano-bubbles is greatly reduced, accompanied by an increase in . However, is less dependent on the fusion-relevant He+ flux varying from 9.0 × 1020 to 1.6 × 1022m−2·s−1, which is consistent with the measured W nano-fuzz growth by He/D2 plasmas.
He cluster dynamics in fusion related plasma facing materials