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Published September 29, 2004 | Published
Book Section - Chapter Open

Seismic isolation and suspension systems for Advanced LIGO

Abstract

To meet the overall isolation and alignment requirements for the optics in Advanced LIGO, the planned upgrade to LIGO, the US laser interferometric gravitational wave observatory, we are developing three sub-systems: a hydraulic external pre-isolator for low frequency alignment and control, a two-stage active isolation platform designed to give a factor of ~1000 attenuation at 10 Hz, and a multiple pendulum suspension system that provides passive isolation above a few hertz. The hydraulic stage uses laminar-flow quiet hydraulic actuators with millimeter range, and provides isolation and alignment for the optics payload below 10 Hz, including correction for measured Earth tides and the microseism. This stage supports the in-vacuum two-stage active isolation platform, which reduces vibration using force feedback from inertial sensor signals in six degrees of freedom. The platform provides a quiet, controlled structure to mount the suspension system. This latter system has been developed from the triple pendulum suspension used in GEO 600, the German/UK gravitational wave detector. To meet the more stringent noise levels required in Advanced LIGO, the baseline design for the most sensitive optics calls for a quadruple pendulum, whose final stage consists of a 40 kg sapphire mirror suspended on fused silica ribbons to reduce suspension thermal noise.

Additional Information

© 2004 Society of Photo-optical Instrumentation Engineers (SPIE). The authors gratefully acknowledge financial support from the following agencies and universities: National Science Foundation, Particle Physics and Astronomy Research Council, the Max-Planck Society, the Universities of Glasgow, Birmingham and Strathclyde. The work at Stanford University is supported by NSF grant PHY-0140297. The work at the LIGO Laboratories and Observatories is supported by NSF grant PHY-0107417. The work at Louisiana State University is supported by NSF grants PHY-0071316 and PHY-0304924 and Louisiana Board of Regents contract LEQSF(2000-03)-RD-A-06.

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