HIGH Q TUNABLE LC RESONATOR OPERATING AT CRYOGENIC TEMPERATURE

We present a step-motor based cryogenic tuning device for a high Q ele ctrical resonator. The resonator can be tuned in the 145-175 Hz freque ncy range. Tuning is achieved by moving a superconducting core inside the 3 H superconducting coil of the resonator. The resonator intrinsic quality factor of 1.8X10(6) is found to be unaffected by the supercon ducting core and by the drive system. The noise of the resonator has b een measured to be thermal. The device has been developed to improve s ensitivity and bandwidth performance of cryogenic resonant gravitation al wave detectors equipped with resonant capacitance transducers. (C) 1998 American Institute of Physics. [S0034-6748(98)01910-8].