This article needs to be updated.December 2019)(
|Part of||Kamioka Observatory|
|Location(s)||Gifu Prefecture, Japan|
|Organization||University of Tokyo|
|Altitude||414 m (1,358 ft)|
|Telescope style||gravitational-wave observatory|
|Length||3,000 m (9,842 ft 6 in)|
|Related media on Wikimedia Commons|
The Kamioka Gravitational Wave Detector (KAGRA), formerly the Large Scale Cryogenic Gravitational Wave Telescope (LCGT), is a project of the gravitational wave studies group at the Institute for Cosmic Ray Research (ICRR) of the University of Tokyo. It became operational on 25 February 2020, when it began data collection. It is Asia's first gravitational wave observatory, the first in the world built underground, and the first whose detector uses cryogenic mirrors. The design calls for an operational sensitivity equal to, or greater than, LIGO.
The ICRR was established in 1976 for cosmic ray studies. The LCGT project was approved on 22 June 2010. In January 2012, it was given its new name, KAGRA, deriving the "KA" from its location at the Kamioka mine and "GRA" from gravity and gravitational radiation. The project is led by Nobelist Takaaki Kajita who had a major role in getting the project funded and constructed.
Two prototype detectors have been constructed to develop technologies needed for KAGRA. The first, TAMA 300, was located in Mitaka, Tokyo and operated 1998-2008, demonstrating the feasibility of KAGRA. The second, CLIO, has been operating since 2006 underground near the KAGRA site, and is being used to develop cryogenic technologies for KAGRA.
KAGRA has two arms, 3 km (1.9 mi) long, which form a laser interferometric gravitational wave detector. It is built in the Kamioka Observatory near the neutrino physics experiments. The excavation phase of tunnels was started in May 2012 and was completed on 31 March 2014.
KAGRA will detect gravitational waves from binary neutron star mergers at up to 240 Mpc away with a signal to noise ratio of 10. The expected number of detectable events in a year is two or three. To achieve the required sensitivity, the existing state of the art techniques as used by LIGO and VIRGO (low-frequency vibration-isolation system, high-power laser system, Fabry-Pérot cavities, resonant side band extraction method, and so on) will be extended with the use of an underground location, cryogenic mirrors, and a suspension point interferometer.
KAGRA has suffered numerous delays. Early planning had hoped to begin construction in 2005 and observation in 2009 but is now likely to enter operation in April 2020. Excess water in the tunnels caused significant delays in 2014 and 2015.
Initial operation ("iKAGRA") with room-temperature test masses was hoped to begin in December 2015. The first operation of the interferometer happened in March 2016. As of early 2019, the project hoped to complete the KAGRA detector by the end of 2019 to join a gravitational wave observation campaign of LIGO and Virgo. The construction of KAGRA was completed 4 October 2019, with the construction taking nine years. However, further technical adjustments were needed before it could start observations. The "baseline" planned cryogenic operation ("bKAGRA") is planned to follow in 2020.
- TAMA300, an early prototype in Japan.
- CLIO, a current prototype that is developing cryogenic technologies.
- DECIGO, a proposed Japanese space-based interferometer.
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We hope that the beginning of the project will be in 2005 and the observations will start in 2009.
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