Speaker
Description
We present a passive ultraviolet (UV) charge management system for the test masses (TMs) of ground-based laser interferometric gravitational wave detectors. The system uses photoelectron emission from low work-function gold coatings illuminated by 275–285 nm UV light to neutralize unwanted electric charges on the TMs, maintaining them at zero potential. Two implementation schemes are described: (1) distributed discharge of the TMs illuminated by UV LEDs mounted at the eight surrounding earthquake stops, and (2) a conductively linked design enabling centralized discharge on the TM barrel, with potential extension to annular coatings around the high-reflectivity and anti-reflective surfaces. Experimental results show photoelectric currents ≥10 pA for 1.0 mW of incident UV, enabling discharge rates ≥10 V/s for a 1 pF capacitor. With 0.2 mW UV power, charge neutralization of the TM conductive areas to ≤1 pC can be achieved in less than 5 to 75 minutes. The TM maximal potential and capacitance to ground include a combined safety margin of about 10. This technique offers a vacuum-compatible alternative to ion sprayers, significantly reducing operational downtime, though not addressing the discharge of the TM dielectric surfaces. For the configuration with annular coatings, we propose a balanced electrostatic actuator using four parallel-plate capacitors with reduced drive voltages requirements.