Performance simulation of a diamond channel cut monochromator operating under high-heat load at the European X-Ray Free-Electron Laser Facility

The European X-Ray Free Electron Laser (EuXFEL) is a unique facility that provides femtosecond x-ray pulses of high pulse energy at MHz repetition rate. However, the high peak power results in a high dynamical heat load in the optical components, like monochromators, which reduces the intensity of the transmitted pulses significantly as compared to the full capacity of the EuXFEL source. To address these challenges at the high photon energy instruments of EuXFEL, we propose a diamond channel cut monochromator as an alternative to the standard Si monochromators. Diamond has a lower absorption cross-section at high photon energies and a higher thermal conductivity compared to Si, making diamond a promising candidate for x-ray optics applications under high heat load conditions. Here, we present a finite element model (FEM) of the temperature increase in diamond and the resulting thermal expansion to estimate the changes in the diffraction profile and the expected monochromator transmission depending on the number of pulses.