Atomistic insight into helium bubble interactions with cascade-induced sonic and supersonic shock waves in tungsten

Abstract

In the field of irradiation damage, helium bubble accumulation and the evolution of cascade-induced shock waves are critical factors governing damage behavior. Their dynamic coupling in complex irradiation environments represents a fundamental mechanism that significantly impacts microstructural stability and macroscopic property degradation. This study employs molecular dynamics simulations to systematically investigate the synergistic interplay between helium bubbles and collision cascades in tungsten. The results show that the helium/vacancy (He/V) ratio has a significant effect on the thermal peak effect and defect evolution: a low He/V ratio (He/V = 0.1, 0.5, 1) helium bubbles suppress the thermal peak and reduce defects, while a high He/V ratio (He/V = 2, 3) enhances the thermal peak and promotes defect formation. Notably, the mechanism of the supersonic wave demonstrates that helium bubbles' impact on defect evolution is orientation-independent. Under various shock waves, helium bubbles exhibit destruction, expansion, or compression; specifically, supersonic waves tend to destroy the bubble structure, whereas sonic waves favor compression. In addition, helium bubbles promote the formation of dislocation loops, showing four typical evolution modes: the complete collapse of low He/V bubbles into vacancy-type full dislocation loops; partial collapse resulting in fragmented loops attached to the residual bubble; sonic wave-induced vacancy detachment followed by re-aggregation into loops; and the emergence of interstitial-type loops surrounding high He/V bubbles. These results advance our understanding of tungsten’s irradiation tolerance and inform the development of advanced plasma-facing materials for fusion energy applications.