Development of highly polished, grazing incidence mirrors for synchrotron radiation beam lines at SSRL

New platinum-coated grazing incidence mirrors with low surface roughness have been developed to focus bending magnet radiation from the SSRL/SLAC SPEAR storage ring on the entrance slits of two Beam Line VIII grating monochromators. The first mirror in the toroidal grating monochromator (TGM) branch is a cooled SiC cylinder capable of absorbing synchrotron radiation power levels of up to 260 watts without excessive distortion. This mirror deflects the beam vertically through a 120 angle and focuses it sagitally on the TGM entrance slit plane. The second TGM optical element is a fused-silica spherical mirror with a large radius of curvature that deflects the beam vertically through an additional 120 and focuses it tangentially with 3/1 demagnification. The first mirror in our spherical grating branch is a 50-vertically deflecting, cooled SiC toroid designed to focus tangentially on the monochromator entrance slits and sagitally on the exit slits. A 40-deflecting fused silica mirror is used after the exit slits in each beam line to refocus on to the sample. For this application a thin cylinder is bent to approximate an ellipsoid. The mirrors are now installed at SSRL and performance measurements are planned. Qualitatively the focus of the TGM optics at the entrance slit plane appears very good. In this paper the authors discuss considerations leading to the choice of SiC for each of the two first mirrors. They present highlights of the development of these mirrors with some emphasis on SiC polishing techniques. In addition, the specialized metrology developed to produce the more difficult figure of the toroid is described. Measured surface roughness and figure results are presented