In the telescopic interferometer KAGRA (Large-scale Cryogenic Gravitational wave Telescope), the mirror made of sapphire (α-alumina) is required. The focal length of mirror is 7 km and it must be finished by polishing after grinding. In order to polish the mirror precisely, polishing characteristics of the Sapphire must be researched. In this study, the polishing characteristics are examined and the dependence of the crystal orientation on the polishing rates is researched. In the experiment, Sapphire wafer is polished by using rotational small tool and SiO_2 abrasive.
