# Highly efficient angularly resolving x-ray spectrometer optimized for absorption measurements with collimated sources

## TL;DR

This paper presents a highly efficient, angularly resolving x-ray spectrometer optimized for absorption measurements with collimated sources, achieving high energy resolution and low background noise for laser-produced betatron radiation.

## Contribution

The paper introduces a novel spectrometer design that combines high energy and angular resolution with single photon analysis for betatron x-ray sources.

## Key findings

- Achieved < 5 eV energy resolution at 9 keV
- Demonstrated angular resolution enabling simultaneous reference and spectrum recording
- Validated performance through absorption measurements on Cu foil

## Abstract

Highly collimated betatron radiation from a laser wakefield accelerator is a promising tool for spectroscopic measurements. Therefore there is a requirement to create spectrometers suited to the unique properties of such a source. We demonstrate a spectrometer which achieves an energy resolution of < 5 eV at 9 keV and is angularly resolving the x-ray emission allowing the reference and spectrum to be recorded at the same time. The single photon analysis is used to significantly reduce the background noise. Theoretical performance of various configurations of the spectrometer is calculated by a ray-tracing algorithm. The properties and performance of the spectrometer including the angular and spectral resolution are demonstrated experimentally on absorption above the K-edge of a Cu foil backlit by laser-produced betatron radiation x-ray beam.