# Charge Management for Gravitational Wave Observatories using UV LEDs

## TL;DR

This study demonstrates charge management on gravitational wave detector components using UV LEDs, achieving controlled charging and discharging with high precision to reduce noise.

## Contribution

It introduces a UV LED-based method for charge control on test masses, improving noise mitigation techniques for gravitational wave observatories.

## Key findings

- Achieved charge and discharge rates of ~10^5 e/s.
- Measured spectral charge noise at 3×10^5 e/√Hz.
- Demonstrated effective charge control using UV LEDs.

## Abstract

Accumulation of electrical charge on the end mirrors of gravitational wave observatories, such as the space-based LISA mission and ground-based LIGO detectors, can become a source of noise limiting the sensitivity of such detectors through electronic couplings to nearby surfaces. Torsion balances provide an ideal means for testing gravitational wave technologies due to their high sensitivity to small forces. Our torsion pendulum apparatus consists of a movable Au-coated Cu plate brought near a Au-coated Si plate pendulum suspended from a non-conducting quartz fiber. A UV LED located near the pendulum photoejects electrons from the surface, and a UV LED driven electron gun directs photoelectrons towards the pendulum surface. We have demonstrated both charging and discharging of the pendulum with equivalent charging rates of $\sim$$10^5 e/\mathrm{s}$, as well as spectral measurements of the pendulum charge resulting in a white noise level equivalent to $3\times10^5 e/\sqrt{Hz}$.