A Compact Isolation Concept for Future Einstein Telescope

This study presents a novel approach for low frequency isolation system. It is in the framework of E-TEST project which is one of the ongoing projects for the future Einstein Telescope (Europe’s next generation gravitational-wave detector). The isolation system combines passive multi-cascaded pendulums, an inverted pendulum and an active inertial platform in one system. The design of this isolator requires specific attention, but it allows reducing the overall height of the isolation system and provides low frequency isolation. The presentation therefore addresses detailed information of the isolation system design and its dynamics. In addition, it demonstrates the control strategy applied for the inertial platform. The simulation results show that the seismic noise could successfully be reduced by about two orders of magnitude at 1 Hz in both horizontal and vertical directions when the control strategy is applied. To ensure this control performance, the inertial platform is designed in such a way that the first flexible mode appears above 300 Hz.