A Complete Discharging Solution for LIGO

Surface charge on LIGO interferometer optics creates a changing electric field that exerts an oscillating pull on the optics, creating a fake signal. Replacing viton earthquake stops with fused silica reduced charging from $\left( {6\pm 1} \right)\times 10^{-12}$C/cm$^{2}$ to $\left( {-4\pm 1} \right)\times 10^{-14}$ C/cm$^{2}$ per contact. We also investigated three ways to discharge an optic in vacuum. UV light removes negative charge via the photoelectric effect with a time constant of $\left( {9\pm 3} \right)\times 10^{-6}$s$^{-1}$, and neutralizes positive charge by liberating electrons from a reaction mass at a rate of $\left( {-9.89\pm .2} \right)\times 10^{-4}$C/s. Both polarities are discharged faster at lower wavelengths. The energy to reduce negative surface charge by 1/$e$ is $(3\pm 1)\times 10^{-2}$ J/cm$^{2}$, which could damage the reflective optical coatings over time. A Kimball Physics electron gun eliminates positive charge within seconds, but we believe that a modified Bayard-Alpert gauge could be a complete, less expensive, and more robust discharging solution.