Virgo: a laser interferometer to detect gravitational waves

Abstract

This paper presents a complete description of Virgo, the French-Italian gravitational wave detector. The detector, built at Cascina, near Pisa (Italy), is a very large Michelson interferometer, with 3 km-long arms.In this paper, following a presentation of the physics requirements,leading to the specifications for the construction of the detector, adetailed description of all its different elements is given. Theseinclude civil engineering infrastructures, a huge ultra-high vacuum(UHV) chamber (about 6000 cubic metres), all of the opticalcomponents, including high quality mirrors and their seismic isolatingsuspensions, all of the electronics required to control theinterferometer and for signal detection. The expected performances ofthese different elements are given, leading to an overall sensitivitycurve as a function of the incoming gravitational wave frequency.This description represents the detector as built and used in thefirst data-taking runs. Improvements in different parts have been andcontinue to be performed, leading to better sensitivities. These willbe detailed in a forthcoming paper.