Spectrometer for Hard X-Ray Free Electron Laser Based on Diffraction Focusing

TL;DR

This paper introduces a diffraction focusing spectrometer (DFS) for hard X-ray free electron lasers, achieving high energy resolution and enabling detailed spectral analysis of single XFEL pulses across a broad energy range.

Contribution

The paper presents a novel diffraction focusing spectrometer based on dynamical scattering in a crystal, offering superior resolution and ease of operation compared to existing methods.

Findings

Achieves energy resolution of ΔE/E ≈ 2×10^{-6}

Operates effectively in 5 keV to 20 keV range

Allows detailed spectral structure analysis of XFEL pulses

Abstract

X-ray free electron lasers (XFELs) generate sequences of ultra-short, spatially coherent pulses of x-ray radiation. We propose the diffraction focusing spectrometer (DFS), which is able to measure the whole energy spectrum of the radiation of a single XFEL pulse with an energy resolution of $\Delta E/E\approx 2\times 10^{-6}$. This is much better than for most modern x-ray spectrometers. Such resolution allows one to resolve the fine spectral structure of the XFEL pulse. The effect of diffraction focusing occurs in a single crystal plate due to dynamical scattering, and is similar to focusing in a Pendry lens made from the metamaterial with a negative refraction index. Such a spectrometer is easier to operate than those based on bent crystals. We show that the DFS can be used in a wide energy range from 5 keV to 20 keV.