Characterization of the room temperature payload prototype for the cryogenic interferometric gravitational wave detector KAGRA.

KAGRA is a cryogenic interferometric gravitational wave detector currently under construction in the Kamioka mine in Japan. Besides the cryogenic test masses, KAGRA will also rely on room temperature optics which will hang at the bottom of vibration isolation chains. The payload of each chain comprises an optic, a system to align it, and an active feedback system to damp the resonant motion of the suspension itself.

Upper limit on gravitational wave backgrounds at 0.2 Hz with a torsion-bar antenna.

We present the first upper limit on gravitational wave (GW) backgrounds at an unexplored frequency of 0.2 Hz using a torsion-bar antenna (TOBA). A TOBA was proposed to search for low-frequency GWs.

Torsion-bar antenna for low-frequency gravitational-wave observations.

We propose a novel type of gravitational-wave antenna, formed by two bar-shaped test masses and laser-interferometric sensors to monitor their differential angular fluctuations. This antenna has a fundamental sensitivity to low-frequency signals below 1 Hz, even with a ground-based configuration. In addition, it is possible to expand the observation band to a lower limit determined by the observation time, by using modulation and up-conversion of gravitational-wave signals by rotation of the antenna.