Development of Torsion-Bar Antenna for Low-Frequency Gravitational-Wave Observation

Abstract

Torsion-Bar Antenna (TOBA) is a ground-based gravitational-wave detector for low frequency. TOBA can detect intermediate-mass black hole binary mergers, gravitational wave stochastic background, and Newtonian noise. TOBA is also useful for earthquake early warning. TOBA consists of two 10-m test masses suspended horizontally and we aim to detect the torsional rotation of pendulums caused by tidal forces. The resonant frequency of torsional motion is ∼ 1 mHz, therefore TOBA has good design sensitivity of 1 × 10 −19 / √ Hz between 0.1 Hz and 10 Hz. We are currently developing the third prototype detector Phase-III TOBA with 35 cm-scale pendulums at cryogenic temperature to demonstrate noise reduction. The target sensitivity is set to 1 × 10 −15 / √ Hz. In this paper, we will present the principle and science of TOBA and the status of the development of Phase-III TOBA.