Helium bubble evolution under cascade in bcc iron relevant to fusion conditions investigated by a novel coupling MD-OKMC method

The direct interaction between cascade and helium bubbles during the thermal spike phase plays an important role in the helium bubbles evolution in metals, which was not fully considered by the present long-time simulation methods. To address this issue, in this work we developed a coupling MD-OKMC method to investigate the helium bubble evolution under irradiation cascade in bcc iron. The short-time collision cascade was simulated by the molecular dynamics (MD), and the long-time helium bubble evolution was modeled by the object kinetic Monte Carlo (OKMC). The MD and OKMC simulations were alternated to imitate the gradual increase of both irradiation dose and helium concentration under experiment conditions. The impact of temperature on the helium bubble evolution under irradiation cascade in bcc iron was investigated and the results were compared with the data from neutron irradiation experiment. It's found that the results of the coupling MD-OKMC were consistent with the experiment results, and were better in agreement with the experiment than the traditional OKMC.