Design and development of the advanced LIGO monolithic fused silica suspension
The detection of gravitational waves remains one of the most challenging prospects faced by experimental physicists. One of the most significant limits to the sensitivity of current, and future, long-baseline interferometric gravitational wave detectors is thermal displacement noise of the test masses and their suspensions. Suspension thermal noise will be an important noise source at operating frequencies between approximately 10 and 30 Hz, and it results from a combination of thermoelastic damping, surface loss and bulk loss associated with the suspension fibres, and weld loss from their attachment. Its effects can be reduced by minimizing thermoelastic loss and optimizing pendulum dilution factor via the appropriate choice of geometry of the suspension fibre and attachment geometry. This paper will discuss the design and fabrication of a prototype of the fused silica suspension stage for use in the advanced LIGO (aLIGO) detector network, analysing in detail the design of the fused silica attachment pieces (ears), together with the suspension assembly techniques. We also present a full thermal noise analysis of the prototype suspension, taking into account for the first time the precise shape of the actual fibres used, and weld loss. We shall demonstrate the suitability of this suspension for installation into aLIGO.
© 2012 IOP Publishing Ltd. Received 9 September 2011, in final form 23 November 2011. Published 12 January 2012. The authors would like to thank Colin Craig and Stephen Craig for their invaluable contribution toward the construction of tooling used in fabrication of the prototype suspension. We are grateful for the financial support provided by Science and Technology Facilities Council (STFC), the Scottish Funding Council (SFC), the Royal Society, the Wolfson Foundation, and the University of Glasgow in the UK. We would also like to thank the NSF in the USA (award nos PHY-05 02641 and PHY-07 57896). 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-0107417. We would like to thank our colleagues in the LSC and VIRGO collaborations and within SUPA for their interest in this work. This paper has LIGO document number P1100091.