A method for measuring the surface impedance of superconductors in the temperature range 0.4–120 K

A method and a setup for making precision measurements of the temperature dependences of components of surface impedance Z(T) = R(T) + iX(T) of small superconductor crystals in the temperature range 0.4–120 K have been developed. The setup combines a high-quality-factor resonance system for measuring the microwave response of a sample at a frequency of 28 GHz and a refrigerating unit with the use of evaporation of 3He vapors. Measurements of Z(T) of optimally doped YBa2Cu3O6.93 single crystals in the superconducting and normal states were performed to illustrate the operation of the setup.