Constant force actuator for gravitational wave detectorʹs seismic attenuation systems (SAS)

We have designed, tested and implemented a UHV-compatible, low-noise, non-contacting force actuator for DC positioning and inertial damping of the rigid body resonances of the Seismic Attenuation System (SAS) designed for the TAMA Gravitational Wave Interferometer. The actuator fully satisfies the stringent zero-force-gradient requirements that are necessary to prevent re-injecting seismic noise into the SAS chain. The actuatorʹs closed magnetic field design makes for particularly low power requirements, and low susceptibility to external perturbations. The actuator retains enough strength to absorb seismic perturbations even during small earthquakes.