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. JINST 7 P03012In this paper, following a presentation of the physics requirements, leading to the specifications for the construction of the detector, a detailed description of all its different elements is given. These include civil engineering infrastructures, a huge ultra-high vacuum (UHV) chamber (about 6000 cubic metres), all of the optical components, including high quality mirrors and their seismic isolating suspensions, all of the electronics required to control the interferometer and for signal detection. The expected performances of these different elements are given, leading to an overall sensitivity curve as a function of the incoming gravitational wave frequency.This description represents the detector as built and used in the first data-taking runs. Improvements in different parts have been and continue to be performed, leading to better sensitivities. These will be detailed in a forthcoming paper.

Methods and results of a search for gravitational waves associated with gamma-ray bursts using the GEO 600, LIGO, and Virgo detectors

“…GEO 600 implements a number of advanced interferometric techniques such as signal recycling and squeezed light to improve sensitivity at frequencies above a few hundred Hz [63,64]. The LIGO [65] and Virgo [66] observatories are power-recycled interferometers of similar design, with Fabry-Perot cavities in the arms to increase the effective arm length and improve the sensitivity to GWs. There are two LIGO observatories, located in Hanford, WA, USA and Livingston, LA, USA [65].…”

Two-wave interferences space-time duality: Young slits, Fresnel biprism and Billet bilens

“…Interferences of two optical waves are among the key effects used in modern optics with applications spanning from sensors development, detection of gravitational waves [1], navigation systems [2] or phase-encoded ultrafast communications [3] to cite a few. The observation of interferences has been central in the discovery of the wave nature of light [4] and famous experiments such as Thomas Young's double slits paved the debates and advances of XIX th century physics [5,6].…”

Gravitational wave astronomy: the current status

“…Mechanical thermal noise is one of the main limitation to the sensitivity of laser interferometer GW detectors such as LIGO [38], Virgo [111], GEO [40] and KAGRA [51]. This displacement noise is a direct consequence of the fluctuationdissipation theorem according to which any mechanical system affected by some form of energy dissipation will be driven by a stochastic force whose amplitude depends on the system temperature and the dissipation amplitude [112].…”

“…Since the interferometer is sensing the optical properties of the mirror, opto-mechanical effects such as the variation in the index of refraction of the coating or of the substrate due to the temperature fluctuations is also a potential noise source whose amplitude depends on the mirror temperature [118]. Figure 16 shows the Advanced Virgo sensitivity [111] and the impact of the various type of thermal noises.…”