Proposal of a non-invasive spectrum diagnostic instrumentation for hard X-rays with high repetitions

Abstract

The X-ray free-electron laser (XFEL) is one of the most powerful tools in scientific frontiers due to its ultra-fast pulse duration and high peak brightness. The non-invasive, energy spectrum monitoring of XFEL pulses is an emerging demand to enhance its operation. This work proposes a non-invasive photo-electron spectrometer equipped with four time-of-flight assemblies to monitor the spectrum of high-repetition-rate XFEL. A comprehensive numerical model is established for start-to-end simulations of the instrumentation, through which the performance of the instrumentation is evaluated and optimized. The simulation results suggest that an energy resolution of 0.05 eV can be fully feasible for XFEL pulses around 1 keV. The position and angular response of the TOF assembly are also discussed, which indicates the transverse radius of XFEL pulses is smaller than 1 mm and that the collecting angle of the design is suitable for monitoring.