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Description
Gravitational waves (GWs) detectors have been upgraded over time to enhance their sensitivity, pushing the limits imposed by their infrastructure.
Next generation observatories, Einstein Telescope and Cosmic Explorer, are currently under design, aiming for significant improvement in sensitivity that can have significant implications in scientific research. Among them, the possibility of detecting high-redshift compact object mergers, enhancing signal-to-noise ratios for spinning neutron stars and the stochastic background, and enabling early warnings for multimessenger observations 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, through a combination of theoretical modelling, simulation, and practical control strategies.
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 Signal Recycling (SR) tower.
The model is expected to be tested during the April-May commissioning break, where the control system's performance will be assessed.
