Reflection zone plate concept for resonant inelastic x-ray scattering spectrometry.

We simulate a proof-of-principle design of a wavelength dispersive, parallel spectrometer for use in resonant inelastic x-ray scattering (RIXS). The instrument relies on a multiple-channel reflection zone plate (RZP) array, enabling the recording of fluorescence spectra from an acceptance angle of 18  arc min×19  arc min with a mainly source-size-limited resolving power of (0.2-2.6)×10⁴ over an energy range of 21 eV at the L-edge of Fe around 715 eV. An optimal two-dimensional signal readout preserves the spectral resolution to a large extent for widely open exit apertures of ≳50  mm². The geometrical parameters are matched to the PEAXIS end station at the BESSY II synchrotron facility, and relaxed RZP line densities of <9×10²  mm^-1 assure the technical feasibility. An error budget estimation with respect to fabrication and alignment tolerances provides the link to real, RZP-based RIXS experiments in the future.