High energy collision cascades in tungsten: dislocation loops structure and clustering scaling laws

TL;DR

This study uses molecular dynamics simulations to analyze high-energy collision cascades in tungsten, revealing defect formation mechanisms and scaling laws relevant for fusion reactor materials.

Contribution

It provides atomic-resolution insights into defect production and clustering in tungsten, aligning simulation results with experimental observations.

Findings

No cascade break-up at high energies

Formation of interstitial and vacancy dislocation loops

Power law distribution of defect cluster sizes

Abstract

Recent experiments on in-situ high-energy self-ion irradiation of tungsten (W) show the occurrence of unusual cascade damage effects resulting from single ion impacts, shedding light on the nature of radiation damage expected in the tungsten components of a fusion reactor. In this paper, we investigate the dynamics of defect production in 150 keV collision cascades in W at atomic resolution, using molecular dynamics simulations and comparing predictions with experimental observations. We show that cascades in W exhibit no subcascade break-up even at high energies, producing a massive, unbroken molten area, which facilitates the formation of large defect clusters. Simulations show evidence of the formation of both 1/2<111> and <100> interstitial-type dislocation loops, as well as the occurrence of cascade collapse resulting in <100> vacancy-type dislocation loops, in excellent agreement with experimental observations. The fractal nature of the cascades gives rise to a scale-less power law type size distribution of defect clusters.