Speaker
Description
TOrsion-Bar Antenna (TOBA) is a ground-based gravitational wave detector using torsion pendulums. The resonant frequency of torsional motion is ∼ 1 mHz, therefore TOBA has good sensitivity in low frequency. TOBA can detect IMBH binary mergers, Newtonian noise, and even contribute to earthquake early warning systems. A prototype Phase-III TOBA is under development to demonstrate noise reduction and precise measurement. The target sensitivity for Phase-Ⅲ TOBA is $10^{-15}$/√Hz. To achieve this sensitivity, we need to reduce the noise of the optical system, thermal noise, and seismic noise.
Since TOBA targets the low-frequency band around 0.1 Hz and is planned to be cooled to cryogenic temperatures, it incorporates numerous elements applicable to 3G detectors. This presentation focuses on these key technological components.
First, TOBA plans to utilize silicon test masses and optical elements, which exhibit excellent properties at cryogenic temperatures. Previous research has demonstrated a low-noise optical system using a silicon monolithic interferometer for the readout optics. Furthermore, we are developing suspension fibers with low mechanical loss at low temperatures. Our current R&D is concentrated on sapphire fibers, aiming for a Q value of $10^{-8}$ .
In addition, a primary scientific goal of TOBA is the direct detection of Newtonian noise. The completion of Phase-III is expected to realize this objective, enabling the validation of Newtonian noise models—which are currently limited to estimations relying on models—and leading to the demonstration of noise reduction technologies.