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Freezing fluctuations

Reducing thermal fluctuation in cryogenic laser interferometric gravitational wave detector CLIO

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Institute for Cosmic Ray Research
2012/02/29

Thermal fluctuation, as evidenced by Brownian motion, is a well-known phenomenon and a fundamental limitation on the accuracy of certain ultraprecise measurements such as interferometric gravitational wave (GW) detectors and laser frequency stabilization using a rigid Fabry-Perot reference cavity. One promising approach for reducing such fluctuations is to use a low-mechanical-loss material at very low temperature.

A CLIO cryostat with a 100m arm tunnel. © Telada

The research group, led by members at Institute for Cosmic Ray Research of the University of Tokyo, experimentally demonstrate for the first time a reduction in a mirror’s thermal fluctuation in a GW detector (CLIO; Cryogenic Laser Interferometer Observatory) with suspended sapphire mirrors at 17K and 18K. The majority of previous efforts to reduce thermal fluctuations in such mirrors have focused on the use of low-loss materials at room temperature. Thus, this achievement provides a new method for overcoming the limitations imposed by thermal fluctuations at room temperature. This cryogenic mirror technology will be used in advanced GW detectors such as KAGRA (formerly the Large-Scale Cryogenic Gravitational Wave Telescope, LCGT), the construction of which began in 2010 in Japan, and the Einstein Telescope in Europe.

Paper

Takashi Uchiyama, Shinji Miyoki, Souichi Telada, Kazuhiro Yamamoto, Masatake Ohashi,Kazuhiro Agatsuma, Koji Arai, Masa-Katsu Fujimoto, Tomiyoshi Haruyama, Seiji Kawamura,Osamu Miyakawa, Naoko Ohishi, Takanori Saito, Takakazu Shintomi, Toshikazu Suzuki,Ryutaro Takahashi, Daisuke Tatsumi,
“Reduction of thermal fluctuations in a cryogenic laser interferometric gravitational wave detector”,
Accepted for publication in Physical Review Letters,
arXiv:1202.3558 (Submitted on 16 Feb 2012)
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