Some experimental results on quartz-crystal resonators at temperature below 4.2 K

Properties of quartz-crystal resonators at temperature below 4.2 K have been measured for two different types of crystals: 5-MHz resonators of the BVA2 design (electrodeless design) and the conventional 5th overtone, AT-cut design. The Q for both types is increased by about one order of magnitude at 4.2 K. No significant increase in Q below 4.2 K was obtained in either type of resonators. The temperature coefficient near 2 K is greatly reduced compared with the value at 4.2 K for one sample of each type. The BVA
2
sample shows the temperature coefficient of 3 × 10
⁻¹⁰
/K at 2 K. The frequency variation versus dissipated power in crystals is very steep above 10
⁻⁷
W below 4.2 K.