X-ray thermal diffuse scattering as a texture-robust temperature diagnostic for dynamically compressed solids

TL;DR

This paper develops a texture-aware model of x-ray thermal diffuse scattering (TDS) for cubic polycrystals and demonstrates its robustness as a temperature diagnostic in dynamically compressed solids, regardless of sample texture or deformation.

Contribution

The paper introduces a novel TDS model accounting for texture effects and validates its accuracy against experimental data, showing improved temperature diagnostics in compressed solids.

Findings

Texture-aware TDS model outperforms conventional powder models.

TDS signal remains stable despite sample orientation and texture evolution.

TDS fluctuations are minimal compared to Bragg-peak fluctuations.

Abstract

We present a model of x-ray thermal diffuse scattering (TDS) from a cubic polycrystal with an arbitrary crystallographic texture, based on the classic approach of Warren. We compare the predictions of our model with femtosecond x-ray diffraction patterns obtained from ambient and dynamically compressed rolled copper foils obtained at the High Energy Density (HED) instrument of the European X-Ray Free-Electron Laser (EuXFEL), and find that the texture-aware TDS model yields more accurate results than does the conventional powder model owed to Warren. Nevertheless, we further show that: with sufficient angular detector coverage, the TDS signal is largely unchanged by sample orientation and in all cases strongly resembles the signal from a perfectly random powder; shot-to-shot fluctuations in the TDS signal resulting from grain-sampling statistics are at the percent level, in stark contrast to the fluctuations in the Bragg-peak intensities (which are over an order of magnitude greater); and TDS is largely unchanged even following texture evolution caused by compression-induced plastic deformation. We conclude that TDS is robust against texture variation, making it a flexible temperature diagnostic applicable just as well to off-the-shelf commercial foils as to ideal powders.