High Q value Quartz Tuning Fork in Vacuum as a Potential Thermometer in Millikelvin Temperature Range

The results of a newly developed pulse-demodulation (P-D) technique introduced to determine the resonant characteristics of a high Q value quartz tuning forks in vacuum and millikelvin temperature range are presented. Applying P-D technique to a standard 32 kHz quartz tuning fork with extremely low excitation energy of the order of a few femtojoules, we were able to measure the resonance frequency of the fork’s decay signal with resolution better than 10 \(\upmu \)Hz. Using this highly sensitive measurement technique, we found a continuous and reproducible temperature dependence of the tuning fork’s resonance frequency in the millikelvin temperature range. The observed dependence suggests a potential application for the quartz tuning forks to be used as thermometers in the millikelvin temperature range. We also discuss the physical origin of the observed phenomenon.