14 November 2013 Optical contamination control in the Advanced LIGO ultra-high vacuum system
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Abstract
Fused silica optics in the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors are extremely sensitive to optical scattering and absorption losses induced by both particulate and hydrocarbon contamination. At full power, the optical surfaces are illuminated with up to 200 kW/cm2. Additionally, the round-trip test mass cavity loss budget is limited to 70 ppm total from all sources. Even low-level contaminants can result in laser damage to optics during the operation the interferometers, and/or the unacceptable reduction of overall detector sensitivity. These risks are mitigated by a two-pronged approach: quantifying contamination sources and the extent of contamination, then reducing sources and cleaning optics in-situ. As a result of these ongoing efforts, we now have a better understanding of what the contamination levels and sources are, and have made significant improvements to methods of controlling contamination, thus protecting the optics from losses and laser damage in the Advanced LIGO Interferometers.
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Margot H Phelps, Kaitlin E. Gushwa, Calum I. Torrie, "Optical contamination control in the Advanced LIGO ultra-high vacuum system", Proc. SPIE 8885, Laser-Induced Damage in Optical Materials: 2013, 88852E (14 November 2013); doi: 10.1117/12.2047327; https://doi.org/10.1117/12.2047327
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