High heat load vacuum ultraviolet mirror development in Japan

Abstract

Developments of vacuum ultraviolet (VUV) mirrors and optical elements for intense synchrotron radiation in Japan are reported. High heat load tests of chemical-vapor-deposited silicon carbide (CVD SiC) mirrors, 500 x 50 x 40 mm 3 , were successfully made for undulator radiation with heat flux of 0.4 W/mm 2 . As extensions of various CVD SiC mirrors developed at the Photon Factory, the largest CVD SiC mirror with sintered SiC substrate, 1000 x 140 x 25 mm 3 , and the thin CVD SiC mirror, 300 x 50 x 5 mm 3 , were fabricated by the SP-ring 8 project. Heat load tests of a CVD-SiC-based grating and a multilayer mirror exhibit possibilities of making high heat load optical elements in the VUV and soft x-ray (SX) regions. Measurements of optical properties of CVD SiC mirrors produced by different methods showed that the optical constants in the VUV and SX regions were almost equal to one another. A profilometer for measuring surface figures of large-size aspheric mirrors was constructed on the basis of the Twyman-Green interferometer with heterodyne phase detection method.