Atomistic study on the dynamic response of helium bubbles to high-energy displacement cascades in tungsten

Abstract

In a fusion reactor, plasma-facing materials simultaneously suffer high-flux low-energy helium/hydrogen irradiation and high-energy neutron bombardment. Numerous modeling studies have focused on radiation damage caused by individual particles, but ignored their synergistic effects. In this study, molecular dynamics simulations were performed to investigate the cascade damage near a pre-existing helium bubble in tungsten. The existence of helium bubbles generally inhibits defect generation but enhances interstitial-type dislocation loop formation. Furthermore, the distance between the primary knock-on atom and the bubble plays an important role in defect evolution. This corresponds to the defect distribution characteristics of the cascade damage in the perfect crystal. In addition, the change in morphology of helium bubbles during cascade damage was considered. Cascade-induced ballistic dissolution of helium from bubbles dominates helium ejection, but damage-assisted thermal dissolution is also observed. This work can contribute to understanding complex damage mechanisms in multiple irradiation fields, such as the fusion environment.