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KAGRA

The KAGRA interferometer: a detector for the direct observation of Gravitational Waves.

The KAGRA interferometer (Kamioka Gravitational Wave Detector), also known as The Large-scale Cryogenic Gravitational Wave Telescope, is a Japanese gravitational wave detector located in the Kamioka mine in the Gifu prefecture.

The construction of KAGRA stems from an international collaboration of several research institutes such as the Institute for Cosmic Ray Research, the University of Tokyo, NAOJ and the High Energy Accelerator Research Organization.

To develop and test the technologies used in KAGRA, two prototype detectors were previously built.

The first, TAMA 300, is located in Mitaka, Tokyo, and operated from 1998 to 2008, demonstrating the feasibility of KAGRA.

The second, CLIO, was built underground near the KAGRA site and began operating in 2006. The latter was used to test the cryogenic technologies subsequently used in KAGRA.

KAGRA is a Michelson interferometer in which the two three-kilometre-long arms are located more than 200 m underground.
KAGRA is in fact the first gravitational wave detector to be built underground, and it is also the first to operate at low temperatures (equal to about 20 degrees Kelvin).
The construction of the site was long and elaborate, as it was first necessary to prepare the tunnels that were to house the interferometer. The excavation phase began in May 2012 and was completed on 31 March 2014.

KAGRA was completed on 4 October 2019; however, further technical adjustments were required before it could begin observations.

Galli e Morelli contributed to the construction of KAGRA from the very phase of testing the technologies used in it, producing all the components of the attenuation towers and mirror suspensions of the TAMA prototype.

Subsequently, Galli e Morelli, thanks also to the experience gained in the previous LIGO, VIRGO and TAMA experiments, was commissioned by the ICRR (Institute for Cosmic Ray Research) to design, build and supply turnkey the complex seismic attenuation system and the mirror suspensions to be used in KAGRA.

The design phase was a demanding challenge, as it required the study of new technical solutions to be applied to the seismic isolation system in order to meet the ambitious requirements demanded for the Ultra High Vacuum.

The supply included, in addition to the design and manufacture of the mechanical parts, also the chemical cleaning, the heat and surface treatments, and the assembly and calibration of the assemblies in a clean room.