A Low-Frequency Torsion Pendulum with Interferometric Readout

TL;DR

This paper presents a highly sensitive low-frequency torsion pendulum with interferometric readout, capable of detecting minute angular displacements for applications in seismic, gravity, and gravitational wave research.

Contribution

It introduces a novel torsion pendulum system with interferometric measurement achieving unprecedented low noise levels at millihertz frequencies.

Findings

Achieved noise levels of ~200 prad/√Hz between 0.2-30 Hz

Achieved noise levels of ~10 prad/√Hz above 100 Hz

Demonstrated potential applications in gravitational and seismic measurements

Abstract

We describe a torsion pendulum with a large mass-quadrupole moment and a resonant frequency of 2.8 mHz, whose angle is measured using a modified Michelson interferometer. The system achieved noise levels of $\sim200\ \text{prad}/\sqrt{\text{Hz}}$ between 0.2-30 Hz and $\sim10\ \text{prad}/\sqrt{\text{Hz}}$ above 100 Hz. Such a system can be applied to a broad range of fields from the study of rotational seismic motion and elastogravity signals to gravitational wave observation and tests of gravity.