Long-wavelength UV-LEDs and charge management in the detection of gravitational waves in space

TL;DR

This study explores the use of long-wavelength UV-LEDs for charge management in space-based gravitational wave detectors, demonstrating that 275 nm LEDs optimize charge control and support continuous discharge strategies.

Contribution

It introduces a more realistic inertial sensor model and evaluates the effectiveness of longer-wavelength UV-LEDs for charge management in space, advancing previous simpler models.

Findings

275 nm UV-LEDs achieve optimal charge control

Longer wavelengths can effectively replace standard 255 nm LEDs

Continuous discharge strategies are feasible with 275 nm LEDs

Abstract

For the charge management system in gravitational wave detection missions, a continuous discharge strategy is considered by continuously illuminating a test mass (TM) with weak light in such a way to strike a balance between the charging and discharging rates and at the same time avoids the requirement for frequent activation of charge measurements. Built on experiments by one of us based on a simple parallel plate model for inertial sensor, in the present work a more sophisticated inertial sensor model that mimics the surface properties and work function of a cubical TM of an inertial sensor in space (like that of the LISA Pathfinder) is employed to study bipolar charge management system that utilizes UV-LEDs with peak wavelengths of 269 nm, 275 nm, 280 nm, and 295 nm that are longer than the standard 255 nm commonly employed for direct TM illumination. Experimental results indicate that the 275 nm UV-LED achieves optimal performance, maintaining the TM potential closer to zero and at the same time accommodates both rapid discharge and continuous discharge strategies. The present work provides useful input in the future study of system design and optimization for the charge management system.