The superconducting-cavity stabilized oscillator and an experiment to direct time variation of the fundamental constants

A precision microwave oscillator system was developed which has a superconducting cavity as its frequency determining element. The frequency stability of the device, called the superconducting-cavity stabilized oscillator (SCSO), was studied using both spectrum analysis and period measurement techniques. For times shorter than one-thousand seconds the frequency fluctuations, as measured by the Allan variance, are smaller than for any other high stability frequency source; the noise floor of the fractional frequency fluctuations is 10 to the minus 16th power at the present time. The long term performance of an ensemble of SCSO systems has been measured relative to the frequency of a cesium-beam frequency standard.