Design and progress report for compact cryocooled sapphire oscillator "VCSO"

We report on the development of a compact cryocooled sapphire oscillator "VCSO", designed for operational frequency and timing systems or metrology applications requiring a higher-performance replacement for ultra-stable quartz oscillators. The VCSO matches a new stirling cryocooler requiring only 160 Watts input power with an improved version of the thermo-mechanically compensated silver/sapphire resonator previously developed for the 40K CSO. We describe details of the sapphire resonator electrical and mechanical design, report on analysis of a crossover circuit that, together with an inexpensive 100 MHz quartz clean-up oscillator, reduces bright-line vibration-induced phase noise spikes by 40 dB or more, and report on cryogenic and vibration tests on a candidate cryocooler