LIGO Document P070010-x0

Test mass ring dampers with minimum thermal noise

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P - Publications
Advanced laser interferometers gravitational wave detectors may need to substantially reduce the Q-factor of test mass normal modes to eliminate parametric instability. In this Letter we investigate various ring damper configurations for two different laser beam geometries. We show that there is a well-defined location near the mid point of a test mass where the thermal noise degradation from the ring damper is minimised. A Q-factor reduction by a factor of 5 can be obtained for at least 30% of the investigated normal modes at the cost of a 1% increase in thermal noise as seen by a 5 cm diameter incident laser beam. Ring dampers can be up to about 10 mm wide while maintaining minimum thermal noise effect contribution. Of the remaining modes, 30% are very weakly damped.
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Rev P070010-00-Z:
- Full document number: LIGO-P070010-00-Z
- Author(s): David Blair; Slawomir Gras; Li Ju
- Document date: 2007-04-23
- Document received date: 2007-04-25
- Document entry date: 2007-04-25
- Citation reference: Physics Letters A

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