DIELECTRIC PROPERTY MEASUREMENT SYSTEM AT CRYOGENIC TEMPERATURES AND MICROWAVE-FREQUENCIES

A system based on the resonant cavity method has been developed to measure the permittivity and loss tangent at 12-18 GHz over the temperature range 80 K-300 K. Changes of permittivity as low as 0.01% in the range 1-30, 3 X 10(-6) for loss tangent values below 10(-2), can be measured without requiring temperature stability. The thermal expansion coefficient and resistivity factor of copper have been measured between 80 K and 300 K. The permittivity of sapphire and loss tangent of alumina of 99.9% purity in the same temperature range are presented.