title: Cryogenic optical testing of an 800 mm lightweight C/SiC composite mirror mounted on a C/SiC optical bench.
abstract: We tested the optical performance at cryogenic temperatures of an 800 mm diameter lightweight mirror, consisting of carbon-fiber reinforced silicon carbide and with a mass of 11.2 kg. The ceramic composite of the mirror was HB-Cesic, developed by ECM, Germany, and Mitsubishi Electric Corporation, Japan. The test was carried out while the mirror was mounted, via Invar stress relief supports, on a lightweight optical bench also made of HB-Cesic. During the test, both the mirror and the optical bench were cooled to 18 K in a liquid-helium chamber. The test consisted of measuring the mirror's change of surface figure with an interferometer installed outside the cryo-chamber. The cryogenic deformation of the mirror was 110 nm RMS with no significant residual deformation after cooling, which is very promising for the applicability of the HB-Cesic composite to large lightweight cryogenic space optics.
authors.affiliation: Graduate School of Science, Nagoya University, Aichi 464-8602, Japan. kaneda@u.phys.nagoya-u.ac.jp
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Kaneda
authors.forename: Masataka
authors.initials: M
authors.lastname: Naitoh
authors.forename: Tadashi
authors.initials: T
authors.lastname: Imai
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Tange
authors.forename: Keigo
authors.initials: K
authors.lastname: Enya
authors.forename: Haruyoshi
authors.initials: H
authors.lastname: Katayama
authors.forename: Kenta
authors.initials: K
authors.lastname: Maruyama
authors.forename: Takao
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Onaka
authors.forename: Masahiro
authors.initials: M
authors.lastname: Suganuma
authors.forename: Ryoko
authors.initials: R
authors.lastname: Kano
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kiriyama
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Mori
authors.forename: Ai
authors.initials: A
authors.lastname: Takahashi