title: 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. A 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 ΔE/E 2 × 10(-6), is proposed. 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 a metamaterial with a negative refraction index. Such a spectrometer is easier to operate than those based on bent crystals. It is shown that the DFS can be used in a wide energy range from 5 keV to 20 keV.
authors: National Research Center `Kurchatov Institute', Kurchatov Square 1, Moscow, Russia.
authors: V G
authors: VG
authors: Kohn
authors: O Y
authors: OY
authors: Gorobtsov
authors: I A
authors: IA
authors: Vartanyants
keywords: compound refractive lenses; diffraction focusing spectrometer; hard X-ray free-electron laser