Systematic feedback control design for scattered light noise mitigation in Virgo's MultiSAS

Gravitational Wave (GW) detectors are used to gather knowledge on violent cosmic events like the merger of pairs of black holes. These waves are measured using large-scale interferometers, which detect the undulations in spacetime resulting from GWs. Scattered light noise resulting from the horizontal RMS velocity of auxiliary optics limits the attainable sensitivity of GW detectors. A systematic approach for the design of a feedback controller in the suspension systems of these auxiliary optics is presented in this paper. Experimental validation shows a substantial reduction in the RMS velocity compared to the feedback strategy currently employed in these suspension systems.