MULTISTAGE ACTIVE VIBRATION ISOLATION SYSTEM

The major obstacle to the detection of low-frequency gravitational wav es with an earth-based interferometer is seismic noise. The current de sign of the initial Laser Interferometer Gravitational-Wave Observator y (LIGO) receiver, now under construction, projects that ground noise will limit the operating band to frequencies above 40 Hz. In this arti cle, we describe recent progress on the JILA active vibration isolatio n system. This device is being constructed to demonstrate the technolo gy needed for useful reduction of low-frequency seismic noise in a gra vitational wave interferometer. It consists of three spring-mounted st ages, each of which provides both active and passive isolation. To dat e, all of the control loops on the first two of the three stages have been closed. Together they can reduce large vibrations by at least 70 dB in both vertical and horizontal directions at 1.5 Hz and above. (C) 1998 American Institute of Physics. [S0034-6748(98)04506-7]