LIGO Document P1600325-v4

Observation of a Large Population of Optical Scatterers in the Advanced LIGO Mirrors

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LIGO-P1600325-v4
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P - Publications
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Abstract:
Similar in appearance to images of star clusters, photographs of the LIGO Gravitational Wave detector mirrors illuminated by the standing beam were analyzed with Daophot, an astronomical software tool designed to identify stars within images and ascertain information about the structure of the light point source. Daophot extracted hundreds of thousands of weaker, point-like scatterers, uniformly distributed across the mirror surface, ignoring the smear of actual dirt on the mirror. Through our analysis, we found that the amplitude distribution of the observed scatterers implies that these scatterers are distributed through the depth of the coating while the sheer number of the observed scatterers implies a fundamental, thermodynamic origin. Theoretical material science consideration indicates that these scatterers are a likely source of the mirror dissipation and thermal noise, perhaps pointing the way towards a mitigation strategy, improved sensitivity of Gravitational Wave observatories, and increased Gravitational Wave detection radius into the Universe.
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Notes and Changes:
Revised version of paper submitted to the Journal of Optical Society of America, February 2017

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