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Thesis open access


The accumulation and fluctuation of surface charge on the highly reflective optics in the Laser Interferometric Gravitational-Wave Observatory (LIGO) has been determined to be a potential source of noise in the detection of gravitational waves. To test this, a capacitive probe was built using a tuning-fork optical chopper with grounded blades to modulate the capacitance. This probe was used to measure the amount of surface charge and the time it takes for that surface charge to decay on a fused-silica optical substrate in a vacuum environment of 10-5 torr. The probe was determined to have a sensitivity of (2.3±.3)•105 e-/cm2. Charges on the order of 8•107 e-/cm2 and a discharge time constant on the order 170 days was measured for the optic.

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