Optimization of the Design and Parameters of a Double-Mirror Monochromator for the Fourth-Generation SKIF Synchrotron Light Source

Synchrotron radiation incident on a block of multilayer X-ray mirrors of a two-mirror monochromator heats a silicon substrate, which leads to thermal deformation and an increase in the angular error of the surface shape. The work examines the heating of a block of multilayer X-ray mirrors by a synchrotron beam with a power of up to 200 W with an energy in the range of 8–36 keV at grazing angles of incidence in the range of 0.5°–1.3°. Using SolidWorks software, the silicon-substrate parameters for mirrors with grooves on the end surface are calculated at which the root-mean-square deviation of the angular error of the substrate’s surface shape is about 1 μrad for a grazing angle of 1.3°, and for smaller angles it is less than 1 μrad. Heat is removed from the substrate surface by water using copper radiators. Reducing the beam aperture at the monochromator output makes it possible to obtain rays reflected from the surface of mirrors, which has a standard deviation of the surface shape of an order of 0.5 μrad, while maintaining 88% of the initial beam power at a grazing angle of 1.3°. The use of a piezoelectric actuator to correct the substrate’s surface shape makes it possible to reduce the root-mean-square shape error to 0.1 μrad and 0.05 μrad at grazing angles of 0.9° and 0.5°, respectively.