Simulation and characterization of novel seismic attenuation strategies for the Einstein Telescope

This thesis presents a preliminary simulation investigation into advanced seismic isolation technologies and active control strategies for upgrades of second-generation gravitational wave detectors (Advanced Virgo) and third-generation conceptual designs (Einstein Telescope). Because ground motion limits the detector sensitivity at low frequencies, multi-stage mechanical attenuation systems are essential to suppress environmental noise. Using control theory and the impedance matrix framework developed within the Virgo collaboration's OCTOPUS simulation package, this work models complex multi-body dynamical systems modularly. Key contributions include: - Advanced Virgo Upgrade: characterization of the Stable Recycling Cavities suspensions for the Technical Design Report, verifying that the proposed seed configurations meet the low-frequency sensitivity requirements. - Einstein Telescope: evaluation of the Pendulum Inverted Pendulum (PIP) passive filter to optimize the suspension chain compactness. Longitudinal attenuation was validated in standalone models and integrated into a SuperAttenuator-like chain following ET Suspension Division standards. - Data Management: development of the GWLabDB, a web-based database application for INFN Pisa to streamline experimental tracking and prototype testing. - Experimental Commissioning: participation in hoisting, calibration, and implementation of feedback loops for the Beam Splitter Tower suspension at the ETpathfinder facility in Maastricht.