A first study of environmental noise coupling to the Virgo interferometer

During 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.