Significant surface-mediated reduction of radiation damage in tungsten revealed by advanced ion channeling analysis

TL;DR

This study combines advanced ion channeling analysis and molecular dynamics simulations to reveal a surface-mediated mechanism that significantly reduces radiation damage in tungsten at elevated temperatures, offering new insights for fusion reactor materials.

Contribution

It introduces a novel combined experimental and simulation approach to identify surface effects and dislocation dynamics responsible for damage reduction in tungsten.

Findings

Surface effect reduces dislocation density near tungsten surface at high temperatures.

Dislocation loops drift towards the surface, decreasing defect density.

A dislocation-free zone and transition region are clearly resolved.

Abstract

Tungsten is a leading candidate material for plasma-facing components in future fusion reactors. Extensive studies have been performed to better understand its behavior under irradiation. Recent experiments of Rutherford backscattering spectrometry in channeling mode indicated a marked reduction in radiation damage in single-crystal tungsten samples irradiated by self-ions when the irradiation temperature was increased from room temperature to 800 K. However, the underlying mechanism for this damage reduction remains unclear. In this work, by combining Rutherford backscattering spectrometry in channeling mode and molecular dynamics simulations, we identify a pronounced surface effect at elevated temperatures, characterized by a significant reduction of dislocation density near the surface. We demonstrate how our unique analysis method can clearly resolve a dislocation-free zone and a transition region with suppressed defect density before reaching the bulk value. The strong surface effect at elevated temperatures is explained by considering the coherent drift motion of dislocation loops towards the surface, highlighting alternative perspectives on mitigating radiation damage by increasing dislocation mobility.