DESIGN AND APPLICATIONS OF A VERY LOW LOSSES SUPERCONDUCTING LC RESONATOR AT 4.2-K

A superconducting electrical LC resonator has been developed with a niobium wire having a quality factor Q larger than 7 x 10(5) at 7 kHz and 4.2 K. This device is very easy to construct but very high Q values are obtained only if great care is taken to minimize the losses. To measure such Q values accurately at relatively low frequencies, an original experimental set-up has been adopted based on the use of a spectrum analyser. Applications to noise currents and contactless resistivity measurements are discussed.