A RF Superconducting Electromechanical Transducer for Gravitational Wave Antennae

Mark F. Bocko, University of Rochester
Warren W. Johnson, Louisiana State University
Valerio Iafolla, I.F.S.I.


An electromechanical transducer based on a superconducting radio-frequency bridge circuit has been developed for use on a gravitational radiation detector. The low electrical loss of superconductors has allowed us to achieve electrical quality factors of several thousand in a lumped element circuit which operates at 4 MHz. The RF bridge could be remotely balanced to one part in 50,000 which led to a displacement noise level of 10–15 meter/Hz, The RF bridge should be useful to measure any physical quantity which can be made to change a capacitance. At the present stage of development capacitance changes of 10–20 F could be detected in a one second integration time. One straightforward improvement, namely the use of a low phase noise quartz crystal oscillator as the bridge excitation source, will yield a reduction of the noise to 10–17 m/'Hz. © 1989 IEEE