LIGO Document E1600082-v1
- Based on a proof-of-principle measurement, two protected gold-coated elliptical mirrors (45 deg AOI) with a hole at center are needed to measure the scatter at small angle in the TIS measurement at RTS bench in the OTF lab. One of this mirrors will be inserted into the optical path before the integrating sphere in the TIS measurement, while the specular beam will pass through the central hole, the scatter at small angle from 1 deg (defined by the aperture at the integrating sphere) to about 0.5 deg defined by the hole diameter on this mirror and its position will be reflected and focused by a lens into a photo-detector. In addition to total loss, more information about the scattering points will be obtained by the signals from the integrating sphere and the photo-detector.
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