The CLIO project

Miyoki, S.; Uchiyama, Takashi; Yamamoto, K.; Kuroda, K.; Akutsu, Tomomi; Kamagasako, S; Nakagawa, N.; Tokunari, Masao; Kasahara, K.; Telada, S.; Tomaru, T.; Suzuki, Toshikazu; Sato, Nobuaki; Shintomi, T.; Haruyama, T.; Yamamoto, A.; Tatsumi, Daisuke; Ando, Masaki; Araya, Akito; Takamori, A.; Takemoto, Shuzo; Momose, H; Hayakawa, Hisao; Morii, Wataru; Akamatsu, Junpei

doi:10.1088/0264-9381/23/8/s29

Cited by 27 publications

(22 citation statements)

References 27 publications

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“…1. The site is part of the tunnel housing the KAGRA gravitational wave telescope (Somiya 2012) and is located below the cosmic-ray research facilities Super Kamiokande, KamLAND, CLIO, and XMASS (Fukuda et al 2003;Araki et al 2005;Miyoki et al 2006;Abe et al 2013). The measuring orientation of the strainmeter is N60°E, horizontal, and it is nearly parallel to the Atotsugawa fault, which is approximately 0.5 km from the instrument (Ohzono et al 2011).…”

Section: The 1500-m Laser Strainmetermentioning

confidence: 99%

Design and operation of a 1500-m laser strainmeter installed at an underground site in Kamioka, Japan

Araya

Takamori

Morii

et al. 2017

Earth Planets Space

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A laser strainmeter with a 1500-m baseline was constructed at an underground site in Kamioka, Gifu Prefecture, Japan, and has been operating since August 2016. The laser interferometer measures the change in distance between two retroreflectors housed in two vacuum chambers with a separation of 1500 m. The retroreflectors are fixed to the ground in the tunnel of the KAGRA gravitational wave telescope. A high-frequency-stabilized laser is used as a light source; it achieves an Allan variance of 3 × 10 −13. Since operations began, ground motions with large amplitude and timescale variations have been detected. The recorded tidal waveform almost agrees with the theoretical waveform; however, a slight difference of ~13% in amplitude is found, likely due to a topographic effect. The strain spectrum of the observed data for the 1500-m strainmeter indicates that the lowest background noise attained is less than 10 −12 in the mHz band. Seismic waves up to 6 × 10 −7 in amplitude have been observed without saturation or fringe steps. The strainmeter, with its excellent resolution, dynamic range, and bandwidth performance, provides a new method for observing low-frequency ground motion on seismic, geodetic, and intermediate timescales.

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Section: The 1500-m Laser Strainmetermentioning

confidence: 99%

Design and operation of a 1500-m laser strainmeter installed at an underground site in Kamioka, Japan

Araya

Takamori

Morii

et al. 2017

Earth Planets Space

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“…Fundamental noise sources that limit their sensitivity are seismic noise, thermal noise, and quantum noise. Among various techniques to reduce these noises, lowering the temperature of mirror-suspension system of the cavities is a way to reduce thermal noise, and KAGRA is the only detector that has taken this path so far (a proof-of-concept cryogenic detector CLIO [Cryogenic Laser Interferometer Observatory] is in Japan but is not currently operational [8]). Since it is necessary that test mass material has high thermal conductivity near the operating temperature 20 K, KAGRA chose sapphire while the other detectors use fused silica.…”

Section: Introductionmentioning

confidence: 99%

Sapphire mirror for the KAGRA gravitational wave detector

Hirose

Bajuk²,

Billingsley

et al. 2014

Phys. Rev. D

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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.

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“…In order to take the other noises into account, an intermediate spectrum before the best sensitivity in figure 2 was used as a background (BG) noise without eddy currents. Figure 4 shows a comparison between the measured spectrum before replacing the coil holder and the calculation from equation (3). The noise floor was almost matched with the calculation from 20 Hz to 200 Hz.…”

Section: Theoretical Estimationmentioning

confidence: 56%

Thermal-noise-limited underground interferometer CLIO

Agatsuma

Arai

Fujimoto

et al. 2010

Class. Quantum Grav.

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We report on the current status of CLIO (Cryogenic Laser Interferometer Observatory), which is a prototype interferometer for LCGT (large scale cryogenic gravitational-wave telescope). LCGT is a Japanese next-generation interferometric gravitational-wave detector featuring the use of cryogenic mirrors and a quiet underground site. The main purpose of CLIO is to demonstrate a reduction of the mirror thermal noise by cooling the sapphire mirrors. CLIO is located in an underground site of the Kamioka mine, 1000 m deep from the mountain top, to verify its advantages. After a few years of commissioning work, we have achieved a thermal-noise-limited sensitivity at room temperature. One of the main results of noise hunting was the elimination of thermal noise caused by a conductive coil holder coupled with a pendulum through magnets.

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The CLIO project

Cited by 27 publications

References 27 publications

Design and operation of a 1500-m laser strainmeter installed at an underground site in Kamioka, Japan

Design and operation of a 1500-m laser strainmeter installed at an underground site in Kamioka, Japan

Sapphire mirror for the KAGRA gravitational wave detector

Thermal-noise-limited underground interferometer CLIO

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