AUTOMATION OF THE LOCK ACQUISITION OF THE 3 KM ARM VIRGO INTERFEROMETER

The aim of the VIRGO project is the detection of the gravitational waves emitted by astrophysical sources in a frequency range between few Hz and few kHz. The detector consist of a power recycled Michelson interferometer (ITF) with 3 km long Fabry-Perot cavities in its arms. To reduce the seismic disturbances, each optical component is suspended to a multi-pendulum system. In order to bring the detector in its working point (the detector "locking"), a complex procedure is required. The mirrors should be aligned with an accuracy better than 10 -9 rad rms, and the relative distance of the suspended optics should be controlled with an accuracy better than 10 -12 m rms.