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Suppressing parametric instabilities in LIGO using low-noise acoustic mode dampers by Biscans, S.; Gras, S.; Blair, C. D.; Driggers, J.; Evans, M.; Fritschel, P.; Hardwick, T.; Mansell, G. is a scholarly article available to read on EtoBox.

What is Suppressing parametric instabilities in LIGO using low-noise acoustic mode dampers about?

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 opto-mechanical 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 ten with no visible increase in the interferometer's thermal noise level. We

Author

Biscans, S.; Gras, S.; Blair, C. D.; Driggers, J.; Evans, M.; Fritschel, P.; Hardwick, T.; Mansell, G.

Published

2019

Language

EN