Ellipsometry noise spectrum, suspension transfer function measurement and closed-loop control of the suspension system in the Q & A experiment

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dc.creatorChen, Sheng-Jui
dc.creatorMei, Hsien-Hao
dc.creatorNi, Wei-Tou
dc.date2005-08-24
dc.date2005-12-01
dc.date.accessioned2026-07-07T06:43:25Z
dc.date.available2026-07-07T06:43:25Z
dc.descriptionThe Q & A experiment, aiming at the detection of vacuum birefringence predicted by quantum electrodynamics, consists mainly of a suspended 3.5 m Fabry-Perot cavity, a rotating permanent dipole magnet and an ellipsometer. The 2.3 T magnet can rotate up to 10 rev/s, introducing an ellipticity signal at twice the rotation frequency. The X-pendulum gives a good isolation ratio for seismic noise above its main resonant frequency 0.3 Hz. At present, the ellipsometry noise decreases with frequency, from 1*10^{-5} rad Hz^{-1/2} at 5 Hz, 2*10^{-6} rad Hz^{-1/2} at 20 Hz to 5*10^{-7} rad Hz^{-1/2} at 40 Hz. The shape of the noise spectrum indicates possible improvement can be made by further reducing the movement between the cavity mirrors. From the preliminary result of yaw motion alignment control, it can be seen that some peaks due to yaw motion of the cavity mirror was suppressed. In this paper, we first give a schematic view of the Q & A experiment, and then present the measurement of transfer function of the compound X-pendulum-double pendulum suspension. A closed-loop control was carried out to verify the validity of the measured transfer functions. The ellipsometry noise spectra with and without yaw alignment control and the newest improvement is presented.
dc.description7 pages, 5 figures, presented in 6th Edoardo Amaldi Conference on Gravitational Waves, June 2005, Okinawa Japan and submitted to Journal of Physics: Conference Series. Some modifications are made according to the referee's comments: mainly to explain the relation between the displacement of cavity mirror and the ellipticity noise spectrum
dc.identifierhttps://arxiv.org/abs/physics/0508176
dc.identifierhttp://arxiv.org/abs/physics/0508176
dc.identifier2006 Journal of Physics: Conference Series 32 244-250
dc.identifierdoi:10.1088/1742-6596/32/1/036
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/102408
dc.subjectInstrumentation and Detectors
dc.titleEllipsometry noise spectrum, suspension transfer function measurement and closed-loop control of the suspension system in the Q & A experiment
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