# Single-shot multi-keV X-ray absorption spectroscopy using an ultrashort laser wakefield accelerator source

## TL;DR

This paper demonstrates single-shot multi-keV X-ray absorption spectroscopy using a laser wakefield accelerator, enabling high-resolution measurements of matter heated to eV temperatures and advancing ultrafast energetic process studies.

## Contribution

It introduces a novel single-shot X-ray source from a laser wakefield accelerator capable of high-resolution absorption spectroscopy in the multi-keV range.

## Key findings

- Achieved 1.2 million photons/eV in the 5 keV region.
- Performed high-resolution XANES at the titanium K-edge in a single shot.
- Enabled simultaneous measurement of electron and ion distributions.

## Abstract

Single-shot absorption measurements have been performed using the multi-keV X-rays generated by a laser wakefield accelerator. A 200 TW laser was used to drive a laser wakefield accelerator in a mode which produced broadband electron beams with a maximum energy above 1 GeV and a broad divergence of $\approx15$ miliradians FWHM. Betatron oscillations of these electrons generated $1.2\pm0.2\times10^6$ photons/eV in the 5 keV region, with a signal-to-noise ratio of approximately 300:1. This was sufficient to allow high-resolution XANES measurements at the K-edge of a titanium sample in a single shot. We demonstrate that this source is capable of single-shot, simultaneous measurements of both the electron and ion distributions in matter heated to eV temperatures by comparison with DFT simulations. The unique combination of a high-flux, large bandwidth, few femtosecond duration X-ray pulse synchronised to a high-power laser will enable key advances in the study of ultra-fast energetic processes such as electron-ion equilibration.