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We have studied the effects of gamma radiation on flexible superconducting microstrip transmission line structures, to explore their suitability for use in harsh environments where they may be subjected to radiation. In this work, we used two conductor variants: one with only Nb and another with a conductor stack of Al/Nb/Al. Spin-on polyimide HD-4110 was used as the dielectric substrate and both the variants were encapsulated with a layer of HD-4110 to increase the robustness of the structure by protecting the superconducting trace from potential mechanical damage. The resonators were irradiated at room temperature in a vacuum sealed chamber at a pressure of 1E-6 Torr using cobalt-60 as a source of gamma radiation. Samples were exposed to doses up to 60.8 Mrad (608 kGy). Quality factors of the resonators were extracted in the frequency range from 2 to 20 GHz, at various cryogenic temperatures between 1.2 K and 4.2 K, using a closed-cycle cryostat. We observed a small increase in microwave loss for higher temperature ranges, which points to a small change in the superconducting properties of the conductors. The results of this work show that low mass, flexible superconducting cables may be suitable alternatives to bulky coaxial cables for signal transmission at cryogenic temperatures in extreme (radiation) environments. [ABSTRACT FROM AUTHOR]

Real-time monitoring of SF6 status is of exceptional importance to ensure stable operation of the power system, to promptly diagnose whether an insulation failure has occurred and to assess the severity. Considering the excellent physicochemical properties and insulation defects of hexagonal boron nitride, the strategy of surface modification, namely, hydrogenation, fluorination, and combinations of the two ways, is proposed to improve its chemical activity, and the gas-sensing potential of the most effective one is investigated using density functional theory. The typical adsorption models of SF6 decomposition component gases on the surface of F-BN-H are constructed, and the most stable adsorption structures with their density of states, molecular orbitals, and sensing responses are analyzed. The results show that F-BN-H has good sensitivity to decomposition components of SF6. To be specific, SO2 and SOF2 have good adsorption properties, prominent charge transfer, and distinct change in electronic properties. The response of gas adsorption can be detected timely by the change in conductivity, and, additionally, the adsorbent has fast desorption capacity at room temperature. These results indicate that the F-BN-H-based gas sensor is a qualified potential candidate with dependable application and recoverability for detecting SF6 decomposition in high-voltage insulated equipment. [ABSTRACT FROM AUTHOR]

We present the design, fabrication procedure, and measurement results of Nb superconducting microstrip transmission line resonators fabricated using thin-film polyimide HD-4110, including both nonembedded and embedded versions. These resonators were used to characterize the microwave dielectric loss tangent of 20  $\mu$m thick polyimide HD-4110 at deep cryogenic temperatures. We observed high-quality factors (Q) up to 21 040 at 1.2 K in the frequency range of 2–21 GHz for nonembedded resonators, indicating that the dielectric loss tangent can be less than 5 $\times$10−5. Embedded resonators with an additional 20 $\mu$m thick encapsulation layer also exhibited Q values as high as $\sim 19$ 200. Dielectric and conductor (quasiparticle) loss have been compared between the two types of resonators. This study provides information applicable to the design of future high-density, flexible, multilayer superconducting cables, which are of great interest for potential applications in cryogenic electronics systems, including quantum computers. [ABSTRACT FROM PUBLISHER]