First locking of the Virgo central area interferometer with suspension hierarchical control

Acernese, Fausto; Amico, P.; Arnaud, N.; Babusci, D.; Barillé, R.; Barone, Fabrizio; Barsotti, L.; Barsuglia, M.; Beauville, F.; Bizouard, M. A.; Boccara, C.; Bondu, F.; Bosi, L.; Bradaschia, C.; Bracci, L.; Braccini, S.; Brillet, A.; Brisson, V.; Brocco, L.; Buskulic, D.; Calamai, G.; Calloni, E.; Campagna, E.; Cavalier, F.; Cella, G.; Chassande Mottin, E.; Cleva, F.; Cokelaer, T.; Conforto, G.; Corda, C.; Coulon, J. P.; Cuoco, E.; Dattilo, V.; Davier, M.; de Rosa, R.; di Fiore, L.; di Virgilio, A.; Dujardin, B.; Eleuteri, A.; Enard, D.; Ferrante, I.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Fournier, J. D.; Frasca, S.; Frasconi, F.; Gammaitoni, L.; Gennai, A.; Giazotto, A.; Giordano, G.; Guidi, G.; Heitmann, H.; Hello, P.; Heusse, P.; Holloway, L.; Kreckelberg, S.; La Penna, P.; Loriette, V.; Loupias, M.; Losurdo, G.; Mackowski, J. M.; Majorana, E.; Man, C. N.; Marion, F.; Martelli, F.; Masserot, A.; Massonnet, L.; Mazzoni, M.; Milano, L.; Moreau, J.; Moreau, F.; Morgado, N.; Mornet, F.; Mours, B.; Pacheco, J.; Pai, A.; Palomba, C.; Paoletti, F.; Passaquieti, R.; Passuello, D.; Perniola, B.; Pinard, L.; Poggiani, R.; Punturo, M.; Puppo, P.; Qipiani, K.; Ramonet, J.; Rapagnani, P.; Reita, V.; Remillieux, A.; Ricci, F.; Ricciardi, I.; Russo, G.; Solimeno, S.; Stanga, R.; Toncelli, A.; Tonelli, M.; Tournefier, E.; Travasso, F.; Trinquet, H.; Varvella, M.; Verkindt, D.; Vetrano, F.; Veziant, O.; Viceré, A.; Vinet, J. Y.; Vocca, H.; Yvert, M.

doi:10.1016/j.astropartphys.2003.10.003

Operation of the central portion of Virgo as a simple 6 m Michelson interferometer has given the first demonstration of the possibility to control an interferometer suspended from Virgo full scale multistage seismic attenuators using information derived from the interferometer locking signal. A special role in the control is played by the first stage of these suspensions, an inverted pendulum: besides its seismic preisolation action, this stage has positioning dynamics of several mm, and it allows to exert a very low frequency control at the upper level of the suspension using the interferometer fringe signal. The application of this feedback to the top-stage of the suspension allows corrections of drifts, such as tidal ones, at a stage of the suspension where a large dynamic range in displacements is available, without introducing noise at the level of the mirror, resulting in a significant reduction of the lock keeping force applied directly on the mirror at the lowest stage of the attenuator.