Femtosecond Diffraction and Dynamic High Pressure Science

TL;DR

This paper reviews recent advances in femtosecond x-ray diffraction techniques for studying materials under extreme high-pressure conditions, highlighting new experimental capabilities and insights into material behavior at ultra-high strain rates.

Contribution

It provides a comprehensive overview of the evolution of dynamic compression methods, especially the role of x-ray Free-Electron-Lasers, and discusses recent experimental insights into material deformation and phase transitions.

Findings

FELs enable single-shot diffraction at sub-100 femtoseconds.

Differences observed between static and dynamic compression phases.

Insights into deformation and phase diagrams at ultra-high strain rates.

Abstract

Solid state material at high pressure is prevalent throughout the Universe, and an understanding of the structure of matter under such extreme conditions, gleaned from x-ray diffraction, has been pursued for the best part of a century. The highest pressures that can be reached to date (2 TPa) in combination with x-ray diffraction diagnosis have been achieved by dynamic compression via laser ablation . The past decade has witnessed remarkable advances in x-ray technologies, with novel x-ray Free-Electron-Lasers (FELs) affording the capacity to produce high quality single-shot diffraction data on time scales below 100 fsec. We provide a brief history of the field of dynamic compression, spanning from when the x-ray sources were almost always laser-plasma based, to the current state-of-the art diffraction capabilities provided by FELs. We give an overview of the physics of dynamic compression, diagnostic techniques, and the importance of understanding how the rate of compression influences the final temperatures reached. We provide illustrative examples of experiments performed on FEL facilities that are starting to give insight into how materials deform at ultra-high strain rates, their phase diagrams, and the types of states that can be reached. We emphasize that there often appear to be differences in the crystalline phases observed between use of static and dynamic compression techniques. We give our perspective on both the current state of this rapidly evolving field, and some glimpses of how we see it developing in the near-to-medium term.