ULTRA-STABLE PERFORMANCE OF THE SUPERCONDUCTING CAVITY MASER

Recent measurements on the superconducting cavity maser (SCM) oscillator show frequency stability of parts in 10(15) for times from 1 second to 1000 seconds. Phase noise of approximately -80dB/f3 was also measured. We believe this short- and mid-term performance to be better than that of any known microwave oscillator. In particular, stability at a measuring time of 1 second is 10 times better than that of a hydrogen maser, and phase noise at 8 GHz is more than 20 dB below that of the best multiplied quartz crystal oscillators. Substantial technical improvements have been made to eliminate frequency instability due to operational parameters. They are temperature, pump frequency, pump power, pump frequency polarization, temperature gradient, coupling strength and output VSWR. We have either stabilized the parameter or minimized the coefficient which couples the parameter to the operating frequency. A frequency pulling coil has been implemented and tested to enable the SCM to be slaved to a hydrogen maser with a time constant of approximately 50 seconds. This combination would allow the excellent long term performance of the hydrogen maser to be improved by the newly available short term performance of the SCM.