Vibration isolation systems for the beam splitter and signal recycling mirrors of the KAGRA gravitational wave detector

Abstract KAGRA is an underground interferometric gravitational wave detector which currently being commissioned. This relies on high-performance vibration-isolation systems to suspend its key optical components. These suspensions come in four different configurations, of the type-B used for beam splitter and signal recycling mirrors. The suspension comprises payload, three geometric anti-spring filters vertical isolation one inverted pendulum horizontal isolation. payload optic, marionette their recoil masses, hold local displacement sensors coil magnet actuators damping resonant modes oscillation itself. version has a modified lower section accommodate wider component. also equipped with lever, monitor control position suspended optics from ground. All have now been installed vacuum chambers. We describe mechanical, electrical design, measured performance compared requirements.