Thermal deformation of cryogenically cooled silicon crystals under intense X-ray beams: measurement and finite-element predictions of the surface shape

The shape of cryogenically cooled monochromator crystals deformed by the heat load of the X-ray beam is derived from rocking curve measurements at various vertical positions of a narrow-gap slit downstream from the monochromator. Experimentally, it is observed that the crystal shape changes from concave to convex when beam power increases. The observations are accurately modelled by finite-element analysis, showing an excellent quantitative agreement with experiments.

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