Diffusion and transformation kinetics of small Helium clusters in bulk Tungsten

TL;DR

This paper investigates the behavior of small helium clusters in tungsten under fusion conditions, focusing on their thermodynamics, kinetics, and role in bubble formation, to better understand material degradation in fusion reactors.

Contribution

It provides a comprehensive computational analysis of helium cluster dynamics in tungsten, elucidating early-stage bubble nucleation relevant to fusion energy materials.

Findings

Helium clusters exhibit specific diffusivity and growth behaviors in tungsten.

Small helium clusters can mutate into nano-bubbles under certain conditions.

The study offers key parameters for modeling helium-induced damage in fusion materials.

Abstract

The production of energy through nuclear fusion poses serious challenges related to the stability and performance of materials in extreme conditions. In particular, the constant bombardment of the walls of the reactor with high doses of He ions is known to lead to deleterous changes in their microstructures. These changes follow from the aggregation of He into bubbles that can grow and blister, potentially leading to the contamination of the plasma, or to the degradation of their mechanical properties. We computationally study the behavior of small clusters of He atoms in W in conditions relevant to fusion energy production. Using a wide range of techniques, we investigate the thermodynamics of the clusters and their kinetics in terms of diffusivity, growth, and breakup, as well as mutation into nano-bubbles. Our study provides the essential ingredients to model the early stages of He exposure leading up to the nucleation of He bubbles.