MG12 - Talk detail
 

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Abstract

A prototype of a cryogenic last suspension system.

We have assembled and tested a full scale last stage suspension for the test masses of a cryogenic gravitational wave antenna. The fake mirror is a 20 kg silicon disk having the same dimensions as in the Virgo detector. The payload overall mass of 300 kg has been cooled in a large cryostat equipped with pulse tube cryocoolers. The thermal and mechanical results obtained in the first cooling run were compared to thermo-mechanical simulation. We present the preliminary results of these analyses.

A thermal noise model for a branched system of mechanical harmonic oscillators: some issues for the test masses suspensions.

The prediction of the thermal noise spectrum which limits the sensitivity curve in the gravitational wave interferometers is important for a proper design of the detectors. We have used the normal mode representation to calculate the thermal noise of a branched system of oscillators. The model fits well the mechanical behavior of the last stage suspension system like in the Virgo interferometer and agrees consistently with the predictions coming by the fluctuation-dissipation theorem. Moreover, the developed formalism can be useful to infer informations on the mechanical quantities of the uncoupled elements of the last stage suspension and consequently give some issues for their optimization.

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