Load-cell based characterization system for a “Violin-Mode” shadow-sensor in advanced LIGO suspensions

Journal Article · Fri Jul 15 04:00:00 EDT 2016 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4954924· OSTI ID:22597905

Lockerbie, N. A.; Tokmakov, K. V. ^[1]

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1. SUPA (Scottish Universities Physics Alliance) Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG (United Kingdom)

The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which 40 kg test-mass/mirrors are each suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation and a rectangular silicon photodiode detector, which, together, were to bracket the fibre under test. The aim was to detect transverse Violin-Mode resonances in the suspension fibres. Part of the testing procedure involved tensioning a silica fibre sample and translating it transversely through the illuminating NIR beam, so as to measure the DC responsivity of the detection system to fibre displacement. However, an equally important part of the procedure, reported here, was to keep the fibre under test stationary within the beam, whilst trying to detect low-level AC Violin-Mode resonances excited on the fibre, in order to confirm the primary function of the sensor. Therefore, a tensioning system, incorporating a load-cell readout, was built into the test fibre’s holder. The fibre then was excited by a signal generator, audio power amplifier, and distant loudspeaker, and clear resonances were detected. A theory for the expected fundamental resonant frequency as a function of fibre tension was developed and is reported here, and this theory was found to match closely with the detected resonant frequencies as they varied with tension. Consequently, the resonances seen were identified as being proper Violin-Mode fundamental resonances of the fibre, and the operation of the Violin-Mode detection system was validated.

• OSTI ID: 22597905
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 7 Vol. 87; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
FIBERS
GRAVITATIONAL WAVES
INTERFEROMETERS
LASERS
MASS
MIRRORS
POWER AMPLIFIERS
READOUT SYSTEMS
RESONANCE
SENSORS
SIGNALS
SILICA
SILICON
SUSPENSIONS
TESTING