Parametric Transducer for Gravitational Radiation Detector

A low-noise parametric vibration transducer using a pair of superconducting microwave cavities has been developed for use with cryogenic gravitational radiation antennas. Pumped by a 9.7-GHz SCSO, the cavities convert mechanical vibration into microwave sidebands which, after demodulation, reproduce the low-frequency signal. For the performance test of the transducer system, the cavities were mounted on a 15-kHz prototype disk antenna at 4.2 K. A transducer noise temperature of 23 mK was obtained at the antenna frequency, and hence a quantum noise number of 3.4×10 4 .