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Description
Second-generation gravitational wave detectors have progressively improved their sensitivity, approaching the limits of their infrastructure. Next-generation observatories, such as the Einstein Telescope and Cosmic Explorer, aim to further enhance sensitivity, enabling detection of high-redshift compact object mergers and early multimessenger alerts by lowering the minimum detectable frequency.
Seismic noise remains a major challenge for detecting GWs below 10 Hz, as ground vibrations propagate to the mirrors. To optimally operate the detector, it is also very important to minimize the mirrors’ Root-Main-Square (RMS) residual motion. In Virgo, the solution developed to mitigate seismic noise led to the Super-Attenuator (SA), which provides passive seismic isolation for frequencies above 4Hz. However, seismic noise is amplified in the range of 0.1÷3 Hz, increasing the RMS motion with respect to the ground.
This work aims to develop a control system to damp the SA resonances and reduce the mirror’s RMS residual motion. A Python simulation of the SA’s temporal evolution has been implemented by employing state-variable models and ARMA techniques. Full-state feedback has been designed, employing pole placement techniques to manipulate system dynamics and achieve the desired performance in the vertical degree of freedom of the SA towers.