Wavefront‐propagation simulations supporting the design of a time‐delay compensating monochromator beamline at FLASH2

Wavefront‐propagation simulations have been performed to complete the design of a monochromator beamline for FLASH2, the variable‐gap undulator line at the soft X‐ray free‐electron laser in Hamburg (FLASH). Prior to propagation through the beamline optical elements, the parameters of the photon source were generated using the GENESIS code which includes the free‐electron laser experimental data. Threshold tolerances for the misalignment of mirror angles are calculated and, since diffraction effects were included in the simulations, the minimum quality with respect to the slope errors required for the optics is determined. The new monochromator beamline at FLASH, the free‐electron laser of Hamburg, is designed to work in the soft X‐ray range, covering a spectral range from 1 to 20 nm and with a spectral resolution of approximately 2000. Wave‐propagation simulations were performed to provide the design of this beamline further insights with respect to the optical quality required.