First cryogenic test operation of underground km-scale gravitational-wave observatory KAGRA

Abstract

KAGRA is a second-generation interferometric gravitational-wave detector with 3 km arms constructed at Kamioka, Gifu, Japan. It is now in its final installation phase, which we call bKAGRA (baseline KAGRA), with scientific observations expected to begin in late 2019. One of the advantages of KAGRA is its underground location of at least 200 m below the ground surface, which reduces seismic motion at low frequencies and increases the stability of the detector. Another advantage is that it cools down the sapphire test mass mirrors to cryogenic temperatures to reduce thermal noise. In April-May 2018, we operated a 3 km Michelson interferometer with a cryogenic test mass for 10 d, which was the first time that km-scale interferometer was operated at cryogenic temperatures. In this article, we report the results of this 'bKAGRA Phase 1' operation. We have demonstrated the feasibility of 3 km interferometer alignment and control with cryogenic mirrors.

New sensitivity curves for gravitational-wave signals from cosmological phase transitions

“…In appendix A, we provide a comprehensive review of the strain noise power spectra of several current and future GW experiments. We specifically consider the following ground-based and space-based interferometer experiments: aLIGO, aVirgo, the Kamioka Gravitational-Wave Detector (KAGRA) [95][96][97][98][99], Cosmic Explorer (CE) [100,101], Einstein Telescope (ET) [102][103][104][105], DECIGO, BBO, and LISA. Furthermore, we also consider the following pulsar timing array (PTA) experiments [106]: the North American Nano-Hertz Observatory for Gravitational Waves (NANOGrav) [107][108][109][110], the Parkes Pulsar Timing Array (PPTA) [111,112], the European Pulsar Timing Array (EPTA) [113][114][115], the International Pulsar Timing Array (IPTA) [116][117][118][119], and the Square Kilometre Array (SKA) [120][121][122].…”

Gravitational waves from the quasicircular inspiral of compact binaries in Einstein-aether theory

“…With the expressions for the GW polarization modes in the coordinate space in hand, we are ready to calculate the response function h(t) and its Fourier transformh(f ). In this subsection, we shall focus on L-shape detectors, such as LIGO, Virgo and KAGRA [67]. From [49,58] Here {θ, φ, ψ} are the three angles (polar, azimuthal and polarization angles) that specify the relative orientations of the detector with respect to the source [note that the angle φ here is not the same as the metric perturbation φ used in Eq.…”

The Hunt for Environmental Noise in Virgo during the Third Observing Run

“…The global gravitational-wave detector network currently consists of two Advanced LIGO detectors in Hanford (WA) and Livingston (LA), USA [8]; the Advanced Virgo detector in Italy [9]; the GEO600 detector in Germany [10]; and, the KAGRA [11] underground cryogenic interferometer in Japan. These detectors are power-recycled laser Michelson interferometers with 4 km (LIGO), 3 km (Virgo and KAGRA), and 600 m (GEO) long optical cavities in the arms (folded optical cavities for GEO, Fabry-Perot resonators for LIGO, Virgo, and KAGRA) and squeezed light injected at the output port [12].…”