LIGO Document G1300654-v1
- This poster describes the electronics and optical design%u2014and performance in practice%u2014of a low-noise optical shadow-sensor for the detection of Violin- and Pendulum-mode motion of advanced LIGO suspension fibres. Averaged across the set of four sensors, a Violin-mode displacement sensitivity of (69 +/- 13) pm (rms)/ sqrt-Hz, was achieved at 500 Hz, over a measuring span of +/-0.1 mm about the mean position of the suspension fibre under test. This set of sensors was then taken to the LIGO Lab, Gravitational Wave Observatory test facility, at MIT, where it was retrofitted to an advanced LIGO suspension. Violin-Mode and Pendulum-mode signals were recorded there on the four suspension fibres of a fully-suspended 40 kg aluminium-alloy (dummy) test-mass, simulating an advanced LIGO test-mass/mirror. The results of these measurements are discussed.
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