Update on quadruple suspension design for Advanced LIGO

• Published in: Classical and quantum gravity 2012-12, Vol.29 (23), p.235004-25
• Main Authors: Aston, S M, Barton, M A, Bell, A S, Beveridge, N, Bland, B, Brummitt, A J, Cagnoli, G, Cantley, C A, Carbone, L, Cumming, A V, Cunningham, L, Cutler, R M, Greenhalgh, R J S, Hammond, G D, Haughian, K, Hayler, T M, Heptonstall, A, Heefner, J, Hoyland, D, Hough, J, Jones, R, Kissel, J S, Kumar, R, Lockerbie, N A, Lodhia, D, Martin, I W, Murray, P G, O'Dell, J, Plissi, M V, Reid, S, Romie, J, Robertson, N A, Rowan, S, Shapiro, B, Speake, C C, Strain, K A, Tokmakov, K V, Torrie, C, van Veggel, A A, Vecchio, A, Wilmut, I
• Format: Article
• Language: English
• Subjects: Design engineering; Exact sciences and technology; General relativity and gravitation; Gravitational waves; gravitational waves detector suspensions; Interferometry; Noise levels; Pendulums; Physics; Quantum gravity; Silicon dioxide; Thermal noise
• ISSN: 0264-9381; 1361-6382
• DOI: 10.1088/0264-9381/29/23/235004

We describe the design of the suspension systems for the major optics for Advanced LIGO, the upgrade to LIGO-the Laser Interferometric Gravitational-Wave Observatory. The design is based on that used in GEO600-the German/UK interferometric gravitational wave detector, with further development to meet the more stringent noise requirements for Advanced LIGO. The test mass suspensions consist of a four-stage or quadruple pendulum for enhanced seismic isolation. To minimize suspension thermal noise, the final stage consists of a silica mirror, 40 kg in mass, suspended from another silica mass by four silica fibres welded to silica ears attached to the sides of the masses using hydroxide-catalysis bonding. The design is chosen to achieve a displacement noise level for each of the seismic and thermal noise contributions of 10−19 m/√Hz at 10 Hz, for each test mass. We discuss features of the design which has been developed as a result of experience with prototypes and associated investigations.