Suppressing parametric instabilities in LIGO using low-noise acoustic mode dampers
Name
PhysRevD.100.122003.pdf
Description
Published version
Size
1.3 MB
Format
Adobe PDF
Checksum (MD5)
2a976fd24b3db5dcd57d71bfceec8017
Author(s)
Biscans, Sebastien
Gras, S
Blair, CD
Driggers, J
Evans, M
Fritschel, P
Hardwick, T
Mansell, G
Date Issued
2019
Journal
Physical Review D
Publisher
American Physical Society (APS)
Version
Final published version
Abstract
© 2019 American Physical Society. Interferometric gravitational-wave detectors like LIGO need to be able to measure changes in their arm lengths of order 10-18 m or smaller. This requires very high laser power in order to raise the signal above shot noise. One significant limitation to increased laser power is an optomechanical interaction between the laser field and the detector's test masses that can form an unstable feedback loop. Such parametric instabilities have long been studied as a limiting effect at high power, and were first observed to occur in LIGO in 2014. Since then, passive and active means have been used to avoid these instabilities, though at power levels well below the final design value. Here we report on the successful implementation of tuned, passive dampers to tame parametric instabilities in LIGO. These dampers are applied directly to all interferometer test masses to reduce the quality factors of their internal vibrational modes, while adding a negligible amount of noise to the gravitational-wave output. In accordance with our model, the measured mode quality factors have been reduced by at least a factor of 10 with no visible increase in the interferometer's thermal noise level. We project that these dampers should remove most of the parametric instabilities in LIGO when operating at full power, while limiting the concomitant increase in thermal noise to approximately 1%.
MIT Department
LIGO (Observatory : Massachusetts Institute of Technology)
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
10.1103/PHYSREVD.100.122003
https://doi.org/10.1103/PHYSREVD.100.122003
