A high-Q sapphire loaded superconducting cavity resonator

Describes the microwave properties of a sapphire loaded superconducting cavity resonator. The authors report measurements of energy confinement, evanescent field scale lengths and radiation losses. They report high quality factors, in excess of 109 at cryogenic temperatures, for a resonator based on a sapphire element mounted inside a superconducting cavity. From the measured properties we show that resonators of this type have potentially valuable applications as ultra-high-stability oscillators, high-Q filters and as low phase noise frequency sources.