Discharging fused silica test masses with ultraviolet light

A Kelvin probe and tunable light source were used to study fused silica discharging by UV illumination. The discharge rate scales linearly with charge magnitude and illumination intensity. Optimal discharging occurs at 215 nm, likely due to absorption by E′E′ centers. 90% discharge corresponds to ∼0.1 Jcm−2 incident energy.