Highly Polished, Grazing Incidence Mirrors Developed For Synchrotron Radiation Beam Lines At Stanford Synchrotron Radiation Laboratory

Abstract

New platinum-coated, vertically deflecting, grazing incidence mirrors with low surface roughness have been developed to prefocus bending magnet radiation from the Stanford Positron Electron Asymmetric Ring (SPEAR) storage ring into two Beam Line VIII grating mono-chromators. In our toroidal grating monochromator (TGM) branch there are two 12° deflecting prefocusing mirrors: a cooled chemically vapor deposited (CVD) SiC cylinder for one-to-one sagittal focusing followed by a fused-silica spheroid for tangential focusing with three-to-one demagnification. In our spherical grating branch the first mirror is a 5° vertically deflecting, cooled SiC toroid designed to focus tangentially on the monochromator entrance slits and sagittally on the exit slits. After the exit slits, a 4° deflecting fused silica mirror is used in each beam line to refocus onto the sample. For this application a cylinder of thin cross section is bent to approximate a toroid. The mirrors are now installed at the Stanford Synchrotron Radiation Laboratory, and performance measurements are planned. Qualitatively, the focus of the TGM optics at the entrance slits appears very good. In this paper we present mirror development highlights, including the choice of SiC for primary mirrors, the measured SiC surface roughness results, and the method developed to test the profile of the toroid during construction.