Measurement of the absolute penetration depth and surface resistance of superconductors using the variable spacing parallel plate resonator

We have developed a modified Parallel Plate Transmission Line Resonator with a smoothly variable thickness of the dielectric spacer filled by liquid nitrogen. A cryogenic linear stage is made to vary the spacer from 200 /spl mu/m down to contact with 0.1 /spl mu/m resolution. Estimates of the absolute penetration depth and the surface resistance are based on the analysis of the spacer thickness dependencies of the resonator frequency and Q-factor. The measurements are performed at fixed temperature (77 K), so the result does not depend on an a priori model for the temperature dependence of the penetration depth. The ability of this technique to be employed as a standard for characterization of HTS films for microwave applications is pointed out.