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Published September 24, 2015 | public
Journal Article Open

Seismic isolation of Advanced LIGO: Review of strategy, instrumentation and performance


The new generation of gravitational waves detectors require unprecedented levels of isolation from seismic noise. This article reviews the seismic isolation strategy and instrumentation developed for the Advanced LIGO observatories. It summarizes over a decade of research on active inertial isolation and shows the performance recently achieved at the Advanced LIGO observatories. The paper emphasizes the scientific and technical challenges of this endeavor and how they have been addressed. An overview of the isolation strategy is given. It combines multiple layers of passive and active inertial isolation to provide suitable rejection of seismic noise at all frequencies. A detailed presentation of the three active platforms that have been developed is given. They are the hydraulic pre-isolator, the single-stage internal isolator and the two-stage internal isolator. The architecture, instrumentation, control scheme and isolation results are presented for each of the three systems. Results show that the seismic isolation sub-system meets Advanced LIGO's stringent requirements and robustly supports the operation of the two detectors.

Additional Information

© 2015 IOP Publishing Ltd. Received 15 May 2015, revised 29 June 2015. Accepted for publication 6 July 2015. Published 24 August 2015. The authors gratefully thank the National Society Foundation for their support. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation, and operates under cooperative agreement PHY-0757058. Advanced LIGO was built under award PHY-0823459. We thank the JILA group for pioneering the work on active isolation systems using low-frequency inertial sensors, and for demonstrating the feasibility of such multi-stage systems. We thank our colleagues from the suspension groups in GEO, VIRGO and LIGO for introducing us to the benefits of using triangular maraging blades to provide vertical isolation. We thank High Precision Devices for the mechanical design's realization of the Rapid Prototype, the technical demonstrator and the single-stage isolator. We thank Alliance Space systems Incorporation for the mechanical design's realization of the two-stage prototype. We thank Nanometrics, Streckeisen, Geotech, Sercel and Microsense for supplying us with great instruments, and for their technical support. The drawings in figures 9(a), 13(a) and 19(a) are to the credit of Caleb Johns. Figures 9(c), 13(b), (c) and 18(c) were previously used in our conference papers published in the proceedings of the ASPE, [67] and [74], and are re-used with permission from the ASPE. Figure 13(d) is to the credit and is a courtesy of Kate Gushwa, Matthew Heinze and the LIGO Suspension group. Figure 14 is re-used content from LIGO and HPD internal documents [55] and [60]. Figure 19(c) was previously published in our conference paper on the dynamics enhancements of the two-stage system [68], and is re-used with permission from the ASME. Figure 20 combines figures previously used in our article on the BSC-ISI two-stage system, published in Precision Engineering [70]. The figures are re-used and combined with permission from Elsevier. Finally yet importantly, this work would not have been possible without the outstanding support of the LIGO laboratory management, computer and data systems, procurement, facility modification and preparation, assembly and installation teams. This paper carries LIGO Document Number P1200040. Public internal LIGO documents are found at: https://dcc.ligo.org/cgi-bin/DocDB/ DocumentDatabase/. Authors' contribution Fabrice Matichard, Brian Lantz, Richard Mittleman, Ken Mason, Jeffrey Kissel, Jessica McIver and Sebastien Biscans wrote this review. The material reviewed in this article is the fruit of the work of the Seismic Isolation Group (SEI). It is important to us to emphasize the immense contributions of all its members: Dan DeBra, from the Stanford group, pioneered the work on quiet hydraulic actuators. Corwin Hardham led the design of the HEPI actuators and the testing of the first HEPI assemblies. His contribution to the project is immense. Wensheng Hua did numerous controls contributions in the sensor correction and data processing domains. Shyang Wen made a great contribution on the HEPI system. Many of the controls features are to the credit of Chris Kucharczyk, Charles Celerier and Hugo Paris from the Stanford group. The geophones flexure and blades-tuned mass dampers are to the credit of Dan Clark, among many other contributions. Brian Lantz has been the head of the Stanford group and the lead scientist of the SEI group. Ben Abbott, assisted by Samuel Abbott, has been leading the electronics activities. Rich Abbott did the electronics development of the HEPI system. Joe Giamie was the lead scientist, and Dave Ottaway was the lead of the MIT test facilities during the early phase of this project. Laurent Ruet and Pradeep Sarin made great contributions to the ISI propotypes. The team made of Sam Barnum, Sebastien Biscans, Stephany Folley, Mike Hillard, Ken Mason, Myron MacInnis, Fabrice Matichard, Richard Mittleman and Andy Stein led the final design and procurement efforts. The teams at the observatories have succeeded in the incredible challenge to build, assemble, test, install and commission 11 HEPI, 5 HAM-ISI and 5 BSC-ISI systems at each of the two LIGO sites. They also built and tested the platforms for the upcoming third detector. For this achievement, invaluable credits go to the LLO team that was made of Jeremy Birch, Ryan DeRosa, Joe Hanson, Adrien Le Roux, Robert Mitchell, Michael Puma, Jimmy Thomas and Michael Vargas, led by Celine Ramet and Brian O'Reilly; and to the LHO team that was made of Eric Allwine, Corey Gray, Greg Grabeel, Vincent Lhuillier, Hugo Paris, Mitchell Robinson and Krishna Venkateswara led by Hugh Radkhins, Jim Warner, Jeffrey Kissel and Mike Landry. The group is working with Jessica McIver and Duncan Macleod on SEI detector characterization. Matthew Evans has provided invaluable advice to the group over the years. Dennis Coyne, Peter Fritschel, David Shoemaker and Carol Wilkinson have been very inspiring and motivating project/system leaders.

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