Microwave cavity made from YBaCuO

The authors report surface impedance measurements made on a cylindrical cavity resonator constructed entirely from the sintered high-temperature superconductor YBa₂Cu₃O₇ . The temperature dependence of the surface impedance has been measured for five different modes in the frequency range 10-18 GHz and over the temperature range 4-300 K. Values for the penetration depth, linear coefficient of expansion, and normal state resistivity are derived from the data. The ultimate aim of this work is to produce very high Q cavities, operating far below their transition temperatures, where the temperature dependences of superconducting parameters become negligible. Such superconducting cavity resonators show promise as secondary frequency standards of the highest stability. The preliminary results with the first cavity are disappointing from this point of view