Key mechanistic features of swelling and blistering of helium-ion-irradiated tungsten

TL;DR

This study investigates helium-ion-induced swelling and blistering in tungsten, revealing that blister cavities form at helium peaks and nanobubbles coalesce into cracks, supporting the gas pressure model of blister formation.

Contribution

First direct experimental evidence for the interbubble fracture mechanism in helium-induced blistering of tungsten.

Findings

Blister cavities form at helium peak depths.

Nanobubbles coalesce into nanocracks.

Supports the gas pressure model for blistering.

Abstract

Helium-ion-induced swelling and blistering of single-crystal tungsten is investigated using a Helium Ion Microscope for site-specific dose-controlled irradiation (at 25 keV) with analysis by Helium Ion Microscopy, Atomic Force Microscopy and Transmission Electron Microscopy (cross-sectioning by Focused Ion Beam milling). Our measurements show that the blister cavity forms at the depth of the helium peak and that nanobubbles coalesce to form nanocracks within the envelope of the ion stopping range, causing swelling of the blister shell. These results provide the first direct experimental evidence for the interbubble fracture mechanism proposed in the framework of the gas pressure model for blister formation.