Measurements of Superattenuator seismic isolation by Virgo interferometer

Each mirror of the interferometric gravitational wave antenna Virgo is attached to a Superattenuator, a chain of mechanical filters designed to suppress seismic vibrations, starting from a few Hz. The filter chain attenuation has been measured by exciting its suspension point with sinuisodal forces and using the interferometer as sensor. The attenuation, measured at different frequencies, is compliant with the requirements of the next generation antenna Advanced Virgo. In the third generation detector Einstein Telescope, the attenuation is sufficient above 3 Hz, independently of the underground site choice.