IRIXS Spectrograph: an ultra high‐resolution spectrometer for tender RIXS

The IRIXS Spectrograph represents a new design of an ultra‐high‐resolution resonant inelastic X‐ray scattering (RIXS) spectrometer that operates at the Ru L3‐edge (2840 eV). First proposed in the field of hard X‐rays by Shvyd'ko [(2015), Phys. Rev. A, 91, 053817], the X‐ray spectrograph uses a combination of laterally graded multilayer mirrors and collimating/dispersing Ge(111) crystals optics in a novel spectral imaging approach to overcome the energy resolution limitation of a traditional Rowland‐type spectrometer [Gretarsson et al. (2020), J. Synchrotron Rad.27, 538–544]. In combination with a dispersionless nested four‐bounce high‐resolution monochromator design that utilizes Si(111) and Al2O3(110) crystals, an overall energy resolution better than 35 meV full width at half‐maximum has been achieved at the Ru L3‐edge, in excellent agreement with ray‐tracing simulations. A resonant inelastic X‐ray scattering (RIXS) spectrograph based upon Montel optics capable of energy resolutions better than 35 meV at the Ru L3‐edge (2840 eV) has been constructed at beamline P01 of the PETRA III synchrotron.