Dielectric properties of cryogenic gases
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With the goal of improving the dielectric strength of gaseous cryogens, this dissertation discusses the dielectric properties of cryogenic gas mixtures based on electron kinetics, dielectric modeling, and plasma diagnostics. The electron kinetics work involves the numerical analysis of electron ensembles in cryogenic gas mixtures. The results of the analysis qualitatively predict the varying dielectric strength of the cryogenic gas mixtures. The dielectric modeling work provides the quantitative predictions of gas dielectric strength in terms of breakdown voltages. Specifically, the work develops a new dielectric strength model that can accurately estimate the dielectric strength variations caused by the variation of cryogenic gas mixture composition. The plasma diagnostics work involves the design and development of a plasma experiment, which is used for measuring DC plasmas generated from potential cryogenic gas mixtures. By analyzing the measured results, the electron energy distribution function of each gas mixture is derived, which is subsequently used for calculating plasma parameters including plasma density and plasma temperature. Research tasks discussed in this dissertation are dedicated for the dielectric enhancement of gaseous cryogens, which is pivotal for the development of medium- and high-voltage superconducting power applications.