The variable finesse locking technique

Virgo is a power recycled Michelson interferometer, with 3 km long Fabry-Perot cavities in the arms. The locking of the interferometer has been obtained with an original lock acquisition technique. The main idea is to lock the instrument away from its working point. Lock is obtained by misaligning the power recycling mirror and detuning the Michelson from the dark fringe. In this way, a good fraction of light escapes through the antisymmetric port and the power build-up inside the recycling cavity is extremely low. The benefit is that all the degrees of freedom are controlled when they are almost decoupled, and the linewidth of the recycling cavity is large. The interferometer is then adiabatically brought on to the dark fringe. This technique is referred to as variable finesse, since the recycling cavity is considered as a variable finesse Fabry-Perot. This technique has been widely tested and allows us to reach the dark fringe in few minutes, in an essentially deterministic way

Length Sensing and Control in the Virgo Gravitational Wave Interferometer

The gravitational wave detector Virgo is presently being commissioned. A significant part of last year was spent in setting up the cavity length control system. This work was carried out with steps of increasing complexity: locking a simple Fabry-Perot cavity, then a Michelson interferometer with Fabry-Perot cavities in both arms, and finally recycling the light beam into the interferometer. The applied strategy and the main results obtained are describe

The Virgo interferometric gravitational antenna

Submitted to: Class. Quantum Grav.The interferometric gravitational wave detectors represent the ultimate evolution of the classical Michelson interferometer. In order to measure the signal produced by the passage of a gravitational wave, they aim to reach unprecedent sensitivities in measuring the relative displacements of the mirrors. One of them , the 3-km-long Virgo gravitational wave antenna, which will be particularly sensitive in the low frequency range (10-100 Hz), is presently in its commissioning phase. In this paper the various techniques developed in order to reach its target extreme performance are outlined

The status of VIRGO

In this paper the main characteristics of the interferometric gravitational waves detector Virgo are presented as well as its present status and perspectives

A simple line detection algorithm applied to Virgo data

International audienceWe 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

A first study of environmental noise coupling to the Virgo interferometer

International audienceDuring the commissioning of the Virgo interferometer, a search for environmental noise contributions to the dark fringe signal was undertaken. Dedicated tests have been performed to identify major sources of disturbances and to understand the coupling mechanism with the interferometer. The major effect is due to seismic/acoustic noise coupling to the laser beam before the input mode cleaner, then propagating as beam power noise to the ITF dark fringe output signal. In this paper we illustrate the tests performed and preliminary results of our investigation

A first test of a sine-Hough method for the detection of pulsars in binary systems using the E4 Virgo engineering run data

Most of the known pulsars with frequencies lying in the best sensitivity range of the Virgo/LIGO/TAMA interferometers belong to binary systems. Accordingly their frequencies are Doppler shifted in an unknown way. We investigate a new method to search for and extract the parameters of such pulsars. A first preliminary test of this method, performed on the Virgo data recorded during the E4 engineering run, is presented

LIGO and VIRGO: large interferometers searching for gravitational waves

International audienceThe largest interferometric detectors for gravitational waves, LIGO and Virgo, have reached (or are close to) the design sensitivity and have started taking science data. The operation of such detectors is reviewed and the expected sources and detection rates are discussed. LIGO and Virgo might make the first detection, but more advanced detectors will be needed to truly open the field of gravitational wave astronomy: the current ideas and plans for the upgrades of the existing interferometers are presented

Status of coalescing binaries search activities in Virgo

The interferometric gravitational wave detector Virgo is undergoing an advanced phase of its commissioning, during which short runs are routinely performed, in which data are analyzed online and offline, searching for signals from coalescing binary systems. In this report we present the progress of the coalescing binaries search activities in Virgo, and we describe details of the detection pipeline including hardware injections, vetoes, and parameter estimation, using recent data taking

Interferometric detectors of gravitational waves on Earth: the next generations

International audienceThe interferometric detectors of gravitational waves of first generation are now taking data. A first detection might be possible with these instruments, but more sensitive detectors will be needed to start the gravitational wave astronomy. The interferometers of second generation will improve the sensitivity by a factor ten, allowing to explore a universe volume 1000 times larger. The technology is almost ready and the construction will start at the beginning of next decade. The community of the physicists involved in the field has also started to make plans for third generation detectors, for which a long term technology development will be required. The plans for the upgrades of the existing detectors and the scenario for the evolution of the field will be reviewed in this paper