Design of the high-resolution BUS XUV-beamline for BESSY II

We present the design characteristics of an XUV undulator beamline for BESSY II, based on a spherical-grating monochromator for the energy range from 35–500 eV. The monochromator will use a moveable pre-mirror and a moveable exit slit and has been optimized for highest resolution. For photon energies up to 200 eV a resolving power of 50 000 up to 80 000 should be achievable, and for higher energies a resolving power of 20 000. All properties of the beamline have been extracted from ray-tracing calculations taking slope errors as well as the characteristics of the source into account.