Measuring the Virgo area tilt noise with a laser gyroscope
  We report on the measurements of tilt noise performed at the Virgo site with a ring laser gyroscope. The apparatus is a He-Ne laser operating in a square cavity mounted on a vertical plane perpendicular to the north-south arm of the inteferometer. We discuss the possibility of using the ring laser signal to improve the performances of the control system of the Virgo seismic suspensions. The comparison between the ring laser signal and the control signals for the longitudinal translations of the inverted pendulum (IP) shows remarkable coherence in the frequency range 20-200 mHz. 
Jacopo Belfi, Nicol\`o Beverini, Filippo Bosi, Giorgio Carelli, Angela   Di Virgilio, Enrico Maccioni and Fabio Stefani
physics.ins-det