Optimization of the cooling system in a double multilayer monochromator

This paper presents the results of heat transfer and deformation analyses of the first of two monochromator crystals installed in a DMM (double multilayer monochromator) for SAXS (small angle X-ray scattering) beamline at the Pohang Light Source (PLS). The DMM was developed to allow precise rotational and linear motion of the crystal. The two crystals have independent driving systems and can be rotated simultaneously, but the first crystal absorbs most of the heat power, so we used the ANSYS program to calculate the temperature distribution and the deformation in the first crystal and in the crystal holder. When the contact geometry between the crystal and the crystal holder is changed, the surface slope error coming from thermal deformation varies. With these analyses of deformation and slope error, an optimized cooling system was designed for the first crystal holder.