ABSTRACT
New temperature coefficients of quartz elastic coefficients particularly relevant at liquid-helium temperature have been reported recently. Based on this result, frequency-temperature compensated cuts are predicted by calculation and then demonstrated by experiment. Such compensated cuts can definitely fix the issue of remaining temperature sensitivity of crystalline-quartz acoustic cavities unbeatable for their extremely low mechanical loss, as low as $10^{-9}$ , when operated at liquid-He temperature.
ABSTRACT
A new method of probing mechanical losses and comparing the corresponding deposition processes of metallic and dielectric coatings in 1-100 MHz frequency range and cryogenic temperatures is presented. The method is based on the use of high-quality quartz acoustic cavities whose internal losses are orders of magnitude lower than any available coating nowadays. The approach is demonstrated for chromium, chromium/gold, and multilayer tantala/silica coatings. The Ta2O5/SiO2 coating has been found to exhibit a loss angle lower than 1.6 × 10-5 near 30 MHz at 4 K. The results are compared to the previous measurements.