A Pseudo Plane-wave Gravitational Calibrator for Gravitational Wave Observatories

TL;DR

This paper introduces a novel gravitational calibrator using four quadrupole rotors arranged in a rectangle to produce a pseudo plane-wave gravitational acceleration with minimal positional dependence, enhancing calibration precision.

Contribution

The paper presents a new geometry for gravitational calibration that reduces dependence on test mass position and improves accuracy and safety over existing methods.

Findings

Achieves 0.15% acceleration amplitude uncertainty

Produces ~100 fm/s^2 sinusoidal gravitational acceleration

Minimal dependence on test mass position within 1 cm

Abstract

The precisions of existing gravitational calibrators for gravitational wave observatories are limited by their dependence on the relative position between the calibrators and the observatory's test masses. Here we present a novel geometry consisting of four quadrupole rotors placed at the vertices of a rectangle centered on the test mass. The phases and rotation directions are selected to produce a pseudo plane-wave sinusoidal gravitational acceleration with amplitude of ~ 100 fm/s^2. We show that this acceleration only has minimal dependence on the test mass position relative to the rotor array and can yield 0.15% acceleration amplitude uncertainty while tolerating a 1-cm test mass position uncertainty. The acceleration can be directed precisely along the optical axis of the interferometer arm and applies no torque on the test mass. In addition, the small size of the rotors has significant engineering and safety benefits.