Spectrometer for hard X-ray free-electron laser based on diffraction focusing

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 ∆E/E ≈ 2 × 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.

Computer simulations of X-ray spherical wave dynamical diffraction in one and two crystals in the Laue case

“…Computer simulations of X-ray spherical wave dynamical diffraction in one and two single crystals in the Laue case were performed with the aim of exploring the divergent beam diffraction focusing effect in an X-ray energy spectrometer as proposed in the work of Kohn et al (2013). The spectrometer may be used for XFEL single-pulse monitoring.…”

“…Such a rocking curve allows one to investigate the CRL aperture quality. As has been shown by Kohn et al (2013), the diffraction focusing effect may be used to measure the X-ray energy spectrum if the crystal is located at the front of the detector.…”

“…X-ray spherical wave dynamical diffraction in one crystal for any source-to-detector distance was investigated both theoretically and experimentally in a series of works (Aristov et al, 1978(Aristov et al, , 1980(Aristov et al, , 1982Kohn, 1979;Kohn et al, 2000Kohn et al, , 2013Koz'mik & Mihailiuk, 1978;Shulakov & Smirnova, 2001). Recently, a new type of energy spectrometer for X-ray freeelectron lasers (XFELs) was proposed using diffraction focusing (Kohn et al, 2013).…”

An algorithm for calculating diffraction profiles of 2θ scans for multiple diffraction from crystals and thin films

“…The dynamical theory of X-ray diffraction has been devised not only for planewave X-rays but also for spherical-wave X-rays (Kato, 1960;Kohn et al, 2000). A spherical wave of X-ray diffraction can account for X-ray imaging (Kohn et al, 2013). Here, the incident beam waves are assumed to be plane-wave X-rays.…”

Energy flow of Bloch waves in X-ray dynamical diffraction in the Laue case for perfect crystals

“…In the present article, these methods are applied to investigate the X-ray energy flow in crystals. Energy flow considerations are also important in X-ray spectroscopy (Kohn et al, 2013;Guigay & Ferrero, 2016), and the present analytical method is generally applicable, irrespective of the magnitude of the parameters.…”