High Q tunable LC resonator operating at cryogenic temperature

We present a step-motor based cryogenic tuning device for a high Q electrical resonator. The resonator can be tuned in the 145–175 Hz frequency range. Tuning is achieved by moving a superconducting core inside the 3 H superconducting coil of the resonator. The resonator intrinsic quality factor of ${\text{1.8×10}}^6$ is found to be unaffected by the superconducting core and by the drive system. The noise of the resonator has been measured to be thermal. The device has been developed to improve sensitivity and bandwidth performance of cryogenic resonant gravitational wave detectors equipped with resonant capacitance transducers.