Mechanical design and finite element analyses of surface bending mechanism for X-ray optics

A new surface diffraction beamline is designed at the Shanghai Synchrotron Radiation Facility (SSRF). The purpose is to provide a high-performance instrument for measurements of the surface interfaces of structures constructed using different materials for researchers from different countries. There are many technical difficulties associated with the construction of the beamline. One of them is the achievement of a high-focusing quality so as to reduce stray lights from substrates because of the small grazing incident angles. Two perpendicular focusing mirrors are adopted to focus the beam. In order to obtain an excellent light spot, the two mirrors are bent to obtain the expected curvature radii and surface errors. In this study, a new X-ray optics bending mechanism is designed for the mirrors, and its principle of operation is described. The mechanical state, the bending resolving power, and the suppression methods for surface errors are studied using finite element analyses. The mirror's minimum bending radius and bending resolving power are 1002 m and 24.2 m, respectively, and its suppression ability for surface error is better than 0.78 μrad. These characteristics are better than the predictions, and further improve the performance of the beamline.