The interaction between stray electrostatic fields and a charged free-falling test mass

TL;DR

This paper experimentally analyzes force noise from stray electrostatic fields on a charged test mass within a conducting enclosure, crucial for gravitational experiments like LISA, and proposes improved measurement and nulling techniques.

Contribution

It introduces an improved electrostatic model and measurement methods to accurately quantify and null stray electrostatic fields affecting charged test masses.

Findings

Set an upper limit of 2 fm/s²/Hz on acceleration noise above 0.1 mHz.

Demonstrated measurement techniques for stray electrostatic fields and forces.

Provided insights for reducing electrostatic noise in gravitational wave detectors.

Abstract

We present an experimental analysis of force noise caused by stray electrostatic fields acting on a charged test mass inside a conducting enclosure, a key problem for precise gravitational experiments. Measurement of the average field that couples to test mass charge, and its fluctuations, is performed with two independent torsion pendulum techniques, including direct measurement of the forces caused by a change in electrostatic charge. We analyze the problem with an improved electrostatic model that, coupled with the experimental data, also indicates how to correctly measure and null the stray field that interacts with test mass charge. Our measurements allow a conservative upper limit on acceleration noise, of 2 fm/s$^2$\rthz\ for frequencies above 0.1 mHz, for the interaction between stray fields and charge in the LISA gravitational wave mission.