A Stepped-Diameter Dielectric Resonator for Simultaneous Microwave Surface Resistance Measurement of Monolithic Double-Sided HTS Films

With the widespread application of superconducting thin films in microwave fields and the ongoing development of novel superconducting thin film materials, the precise measurement of surface resistance (RS) has become an important challenge. To address issues in traditional dielectric resonator methods, such as the requirement for multiple samples, insufficient sensitivity in nonlinear measurements of single samples, and difficulties in evaluating systematic errors, this paper proposes an improved image resonator measuring device working in the TE01(1+δ) mode at approximately 12 GHz. By designing a stepped-diameter coaxial cylindrical dielectric column structure, the electromagnetic field distribution in the resonant cavity is optimized, substantially enhancing the quality factor of the working mode. This device achieves a sensitivity of 5626 in the quality factor change per 0.01 mΩ variation in RS at a test value of 0.1 mΩ, demonstrating a significant improvement compared to conventional methods. Additionally, a dual-side measuring scheme and an error compensation algorithm are proposed to improve the measuring efficiency for double-sided thin films while effectively quantifying the impact of potential asymmetry between the test and calibration cavities in the image resonator method on measurement accuracy. Experimental results demonstrate that the measurement uncertainty of this device is better than 2%. Combining high sensitivity and efficiency with low systematic errors, this apparatus provides an efficient and reliable solution for microwave surface resistance measurement of single-sided high-temperature superconducting thin films.