Optimization of undulators for a SX‐700 Instrument: Finite element coupled to ray tracing

The flux and total power of the insertion devices to be installed in the XUV beam line at DORIS III have been optimized under the constraint of preserving the source size limited resolution of the monochromator. This was achieved by interactive redesign of undulators, mirror geometry, and mirror coatings. Coupled finite‐element analysis and ray tracing were employed, taking into account the absolute power irradiated by each insertion device and its spatial, angular, and spectral distribution. The angular and spectral dependence of coating reflectivities and realistic thermal boundary conditions as imposed by the manufacturer of the water‐cooled substrates were also considered. A specific example, showing the advantage of coating the first mirror with SiO2 instead of Au for the low‐energy range of the monochromator is discussed in detail.