Design and numerical analysis of a solid attenuator for high-repetition-rate X-ray free-electron laser endstation

Solid attenuators are crucial instruments used at X-ray free electron laser experimental endstations for rapidly attenuating light intensity. With high-repetition-rate free electron lasers, the absorption plates accumulate heat as the repetition frequency increases, which will limit the use of solid attenuators. We designed a solid attenuator suitable for the FEL-I experimental endstation of Shanghai high-repetition-rate X-ray free-electron laser and extreme (SHINE) light facility, including the physics design, mechanical design, and thermal analysis under the high repetition rate. Through a combination of absorption plates, the precise light intensity across the 3 to 15 keV range was attenuated by 10 grades, and the mechanical design of the solid attenuation was developed with the corresponding cooling solutions. The solid attenuator design is proven to fulfill the high repetition rate of up to 10 kHz through the numerical results at different repetition frequencies and meet the operational requirements planned for SHINE.