Design concept of the high-resolution end-station PEAXIS at BESSY II: Wide-Q-range RIXS and XPS measurements on solids, solutions, and interfaces

Abstract

The design of a soft X-ray end-station for the Berlin Electron Synchrotron BESSY II is presented. It will be used for Resonant Inelastic X-ray Scattering (RIXS) and Angle-dependent X-ray Photoelectron Spectroscopy (AdXPS) studies for energy material science. In RIXS-mode the instrument operates with two spherical Variable Line Space (VLS) gratings for energy resolving measurements in two overlapping energy ranges from 200 to 1200eV. The end-station will allow measurements of solid samples, solutions and interfaces in a wide range of experimental conditions with high energy resolution covering a large Q-range realized by a continuous rotation of the RIXS detector arm by 120°.Besides the description of this end-station, a systematic way is shown for the design of a RIXS instrument assessing the grating parameters based on existing theories and for the calculation of optimal instrument settings as a function of photon energy. Different grating inclinations, line densities, groove shapes and RIXS instrument lengths were investigated. Possible parameter combinations were calculated analytically and the resulting instrument performance was determined by ray-tracing simulations using the simulation package RAY. The performance of the RIXS instrument was evaluated by choosing the product of the intensity at the detector and the square of the resolving power as figure of merit to optimize the spectrometer. The robustness of the optimized parameters has been checked in order to define tolerance parameters for the engineering design of the spectrometer.