Two‐stage reflective self‐seeding scheme for high‐repetition‐rate X‐ray free‐electron lasers.

X‐ray free‐electron lasers (XFELs) open a new era of X‐ray based research by generating extremely intense X‐ray flashes. To further improve the spectrum brightness, a self‐seeding FEL scheme has been developed and demonstrated experimentally. As the next step, new‐generation FELs with high repetition rates are being designed, built and commissioned around the world. A high repetition rate would significantly speed up the scientific research; however, alongside this improvement comes new challenges surrounding thermal management of the self‐seeding monochromator. In this paper, a new configuration for self‐seeding FELs is proposed, operated under a high repetition rate which can strongly suppress the thermal effects on the monochromator and provides a narrow‐bandwidth FEL pulse. Three‐dimension time‐dependent simulations have been performed to demonstrate this idea. With this proposed configuration, high‐repetition‐rate XFEL facilities are able to generate narrow‐bandwidth X‐ray pulses without obvious thermal concern on the monochromators. [ABSTRACT FROM AUTHOR]