The development of time-resolved x-ray measurements of shock-compressed solid-state matter.

The use of x-rays to interrogate condensed matter under shock compression has a long history. Light sources, including high-power lasers, have been used since the mid 1980’s to create sub-nanosecond flashes of quasi monochromatic x-rays that can be diffracted from materials synchronously compressed by laser ablation, and more recently both synchrotron and x-ray free-electron-lasers (FELs) have advanced the field considerably. These techniques have led to significant advances in our understanding of plasticity and deformation at the lattice level, as well as the mechanisms underpinning several polymorphic phase transformations. Compression with the largest lasers has allowed diffraction patterns to be obtained at extremely high pressures (> 2TPa) - albeit with low quality diffraction provided by a laser plasma source. In contrast, whilst the optical lasers provide lower shock pressures, at FELs the quality of the diffraction patterns obtained is spectacular, and with the pulse lengths of FELs well below 100-fsec, single-shot data can be obtained on a timescale faster than the period of the most energetic phonons in the system. As well as the structural information that can be obtained from standard diffraction, more recently novel techniques of inelastic scattering have been developed, allowing single-shot measurements of the temperature of the sample to be interrogated. Furthermore, additional sophisticated measurements such as RIXS (Resonant Inelastic X-Ray Scattering) are starting to be developed, that will eneable measurements of the electronic structure of materials under shock conditions to be ascertained alongside structural information.