Virgo is a laser Michelson interferometer with 3-km long Fabry-Perot in the arms, aiming at the detection of gravitational waves emitted by astrophysical sources in the frequency band from 10 Hz to ...few kHz. The core of the detector, the central interferometer, was installed first. It is a recycled Michelson interferometer, with 6-m long arms, obtained by replacing the 3-km long Fabry- Perot cavities with high reflectivity mirrors and using the same components designed for Virgo. In particular all the mirrors of the interferometer are suspended from the seismic isolators that represent the main unique characteristic of the Virgo detector. The interferometer has been controlled by means of a fully digital control system, capable of monitoring and controlling the relative position of the mirrors with an accuracy of 10 exp -12 m. The best displacement sensitivity was 10 exp -13 m/sq rt Hz at 10 Hz and 8 x 10 exp -17 m/sq rt Hz above 1 kHz. This article describes the detector configuration, the tests performed in view of commissioning the full detector and the main results obtained.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The mirrors of interferometric detectors of gravitational waves (GW) are suspended in order to be isolated from external disturbances. A local control system able to keep them correctly aligned and ...to damp the angular modes of the suspension is necessary. In this paper we present the solution adopted for Virgo based on a CCD camera sensor and on digital controls. With this solution the mirrors are kept aligned at the level of less than 1 μrad
rms, enough to lock the interferometer and start the automatic alignment system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We propose a new method for the detection of spectral lines in random noise. It mimics the processing scheme of matching filtering, i.e., a whitening procedure combined with the measurement of the ...correlation between the data and a template. Thanks to the original noise spectrum estimate used in the whitening procedure, the algorithm can easily be tuned to various types of noise. It can thus be applied to the data taken from a wide class of sensors. This versatility and its small computational cost make this method particularly well suited for real-time monitoring in gravitational wave experiments. We show the results of its application to Virgo C4 commissioning data.
Operation of the central portion of Virgo as a simple 6 m Michelson interferometer has given the first demonstration of the possibility to control an interferometer suspended from Virgo full scale ...multistage seismic attenuators using information derived from the interferometer locking signal. A special role in the control is played by the first stage of these suspensions, an inverted pendulum: besides its seismic preisolation action, this stage has positioning dynamics of several mm, and it allows to exert a very low frequency control at the upper level of the suspension using the interferometer fringe signal. The application of this feedback to the top-stage of the suspension allows corrections of drifts, such as tidal ones, at a stage of the suspension where a large dynamic range in displacements is available, without introducing noise at the level of the mirror, resulting in a significant reduction of the lock keeping force applied directly on the mirror at the lowest stage of the attenuator.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We report on an investigation of Virgo Commissioning run 4 data, dedicated to searching signals of the kind supposed to be emitted by inspiral neutron star binary systems. Given the still relatively ...limited sensitivity, the goal was to test some of the elements of the analysis chain, using simulated events, hardware and software injected in the data; the test allowed us to also characterize the detector stability during the run, for the purposes of the inspiral event search.
Virgo status and commissioning results Amico, P; Aoudia, S; Avino, S ...
Classical and Quantum Gravity,
05/2005, Volume:
22, Issue:
10
Journal Article, Conference Proceeding
Peer reviewed
Open access
Virgo is a French–Italian collaboration for the construction and operation of a 3 km long interferometric gravitational wave antenna. The construction of the detector is already completed and the ...commissioning is quite advanced, while the data taking is expected to start in 2005. In this paper, we report on the present status of Virgo and on the results of commissioning activity. In particular, we analyse the first four engineering runs (C1–C4) and discuss the sensitivity obtained in C4.
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