The Global Control of the Virgo experiment

In order to detect gravitational waves, the kilometric interferometer Virgo needs an active control of the positions of the suspended optical components, keeping the detector at its working point. The constraints are about 10-10m RMS for the longitudinal control (“Locking”) and 10-9rad RMS for the angular degrees of freedom (“Alignment”). A dedicated hardware and software named Global Control is in charge of the Locking and the Alignment loops for the Virgo experiment. This system has been designed to match the synchronization constraint and provide a flexible tool in order to easily integrate the various algorithms needed for the control of Virgo. This paper presents the technical requirements to be fulfilled by the Global Control. Then, the dedicated hardware is described and the overall architecture of the Global Control is shown.