Ultra-low phase noise superconducting-cavity stabilised microwave oscillator with application to gravitational radiation detection

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Abstract
A superconducting-cavity stabilised oscillator has been constructed which combines active and passive stabilisation of a 9.6 GHz klystron to obtain a phase noise power spectral density between -170 dB Hz-1 and -180 dB Hz-1 at 5 kHz from the carrier, which represents about 40 dB improvement over the state-of-the-art. The device has been developed for use as a low noise pump for a superconducting parametric upconverter transducer on a gravitational radiation antenna. An RF modulated reflex klystron is actively locked to a TE011 niobium cavity operated at 2K with a loaded Q approximately 108. Power is extracted from the cavity which acts as a high Q filter.