ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
A technique using cavity perturbation of a cooled sapphire disk resonator has been developed to measure the surface impedance Zs=Rs+iXs of high-temperature superconducting thin films. The resonator is excited in the TE011 mode at 14.4 GHz and induces a-b plane screening currents in the sample. The resonator and its enclosure are maintained at 4.2 K while the sample is heated independently on a movable sapphire rod. The thermal isolation of the sample and resonator leaves the measurement virtually free of systematic error and permits the use of a superconducting niobium shield. The combination of low dielectric loss sapphire and a superconducting enclosure results in typical unloaded quality factors (Q) of several million. The ability to move the sample makes the sensitivity variable, allowing surface resistance values from 5 μΩ to several Ω to be measured. Background loss can also be accurately determined at the time of experiment by withdrawing the sample from the influence of the resonator. In addition, sensitive measurements of the penetration depth can be made by spring-loading the film onto quartz spheres glued to the resonator surface; this technique is shown to be free of systematic error up to a temperature of 60 K. © 1997 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1148106
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