Wireless Cryogenic Quartz Thermometer with High Resolution from 400 K to 4.2 K

Abstract

We have measured the temperature dependence of the resonant frequency of a quartz crystal resonator and found it to show really good properties as a cryogenic thermometer with high resolution without magnetic field dependence (up to 8 tesla at 4.2 K) covering the wide range from 400 K to 4.2 K. The quartz crystal resonator sliced either in the “LC” cut or in the “YS” cut from high quality synthetic single crystal quartz was tested and calibrated by using a platinum resistor, thermocouple (Au-0.07atom% Fe/ Chromel) and a germanium resistor under thickness shear mode of operation through either extended cable connection or radio echo telemetric transmission from the resonators. A wireless echo sensor system was constructed and applied to a wireless thermometer for an oxide high temperature superconductor. Temperature reproducibility of the quartz thermosensor is excellent within 0.4 ppm maximum (0.2 ppm typical; 0.002 K) when thermally shocked between room temperature and liquid nitrogen temperature. The resolution reduces from about 1kHz/K at 300 K to about 4Hz/K at 4.2 K but about 8OHz/K at 4.2 K after improvement.