1. Sapphire mirror for the KAGRA gravitational wave detector
- Author
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Hiroaki Yamamoto, Norikatsu Mio, Takaaki Kajita, Liyuan Zhang, G. Billingsley, Dan Bajuk, Bob Kestner, Masatake Ohashi, Eiichi Hirose, and Bill Reichman
- Subjects
Physics ,Nuclear and High Energy Physics ,Gravitational-wave observatory ,Birefringence ,Physics::Instrumentation and Detectors ,Gravitational wave ,business.industry ,Detector ,Physics::Optics ,Optics ,Sapphire ,Optoelectronics ,Interferometric gravitational wave detector ,KAGRA ,business ,Refractive index - Abstract
KAGRA, the Japanese interferometric gravitational wave detector currently under construction, will employ sapphire test masses for its cryogenic operation. Sapphire has an advantage in its higher thermal conductivity near the operating temperature 20 K compared to fused silica used in other gravitational wave detectors, but there are some uncertain properties for the application such as hardness, optical absorption, and birefringence. We introduce an optical design of the test masses and our recent R&D results to address the above properties. Test polish of sapphire substrate has especially proven that specifications on the surface are sufficiently met. Recent measurements of absorption and inhomogeneity of the refractive index of the sapphire substrate indicate that the other properties are also acceptable to use sapphire crystal as test masses.
- Published
- 2014