An ultra-high quality factor microwave sapphire loaded superconducting cavity transducer

The performance of a prototype ultra-high quality factor (Q>10/sup 8/) Sapphire Loaded Superconducting Cavity Transducer (SLSCT) operating at X-band is described. The measured displacement noise floor of 3.0/spl plusmn/0.6/spl times/10/sup -16/ m//spl radic/(Hz) (/spl sim/2/spl times/10/sup -11/ g//spl radic/(Hz)) at 1 kHz was an order of magnitude better than a similar room temperature transducer, and several orders of magnitude better than current commercially available accelerometers. Improvements in the transducer´s microwave system should enable the noise floor to be lowered by several orders of magnitude. An electromagnetic model of the transducer has also been developed which permits the tuning coefficient, and hence the displacement sensitivity to be accurately predicted.