Thermal expansion and microwave surface reactance of copper from the normal to anomalous skin effect region

Abstract

The microwave surface reactance of copper was measured over the temperature range from 300 to 14 K using the TE011 mode of a cylindrical cavity. The result was that with decreasing temperature the ratio of the reactive-to-resistive component remained at around 1 from 300 to 75 K, and increased to 1.32 at 14 K, in contrast to the theoretical extreme anomalous limit, equal to or higher than ∛. The discrepancy between the measured and theoretical values may be attributed to the quality of the material and the surface finishing. In this experiment an accurate measurement of the resonant frequency is important. Associated with the frequency, we discuss two thermal-expansion measurement techniques: cavity dilatometry and capacitance dilatometry. Further, the usefulness of the present data for studying high-Tc films will be mentioned.