Direct observation of size scaling and elastic interaction between nano-scale defects in collision cascades

TL;DR

This study uses in-situ TEM to observe nano-scale defects in tungsten caused by high-energy ion irradiation at cryogenic temperatures, revealing a power-law size distribution and elastic interactions among defects.

Contribution

First direct observation of primary collision cascade damage in tungsten at cryogenic temperatures, confirming theoretical predictions of defect size distribution and elastic interactions.

Findings

Defects follow a power-law size distribution with an upper size limit.

Defects exhibit significant spatial correlations due to elastic interactions.

Observations align with prior theoretical models of cascade damage.

Abstract

Using in-situ transmission electron microscopy, we have directly observed nano-scale defects formed in ultra-high purity tungsten by low-dose high energy self-ion irradiation at 30K. At cryogenic temperature lattice defects have reduced mobility, so these microscope observations offer a window on the initial, primary damage caused by individual collision cascade events. Electron microscope images provide direct evidence for a power-law size distribution of nano-scale defects formed in high-energy cascades, with an upper size limit independent of the incident ion energy, as predicted by Sand et al. [Eur. Phys. Lett., 103:46003, (2013)]. Furthermore, the analysis of pair distribution functions of defects observed in the micrographs shows significant intra-cascade spatial correlations consistent with strong elastic interaction between the defects.