Thermal effects of undulator radiation on Si optics for a plane grating monochromator

Insertion devices on the third-generation 1.5 GeV electron storage ring MAX II will subject the grazing incidence mirrors and gratings of new soft x-ray beamlines to high thermal loads. These thermal loads will cause distortion in the optical surfaces which can be reduced to acceptable levels by the proper choice of substrate material and cooling. A finite element analysis of the temperature variation and thermal distortions is carried out for Si plane mirrors and gratings under thermal load from the 66 mm period undulator planned for MAX II. The energy dependence of the reflectivity for Au-coated mirrors is taken into account. The minimum cooling requirements are determined for each of these optical components in the beamline. The effect of the final induced figure errors on the performance of a plane grating monochromator are discussed.