Title:  Investigation on Dielectric Properties of Gases for Cryogenic and Ambient Temperature Power Applications

Committee: 

Dr. Graber, PamidiAdvisor    

Dr. Saeedifard, Chair

Dr. Harley

Abstract:

The objective of the proposed research is to provide a theoretical foundation to understand and improve the dielectric properties as well as to accurately model the breakdown strength of gases that are used under cryogenic and ambient temperatures for high temperature superconducting (HTS) and conventional power applications. Swarm parameters, which is a collective term for various parameters that explain the transport and kinetic process of electrons in gases, are obtained based on the collision cross section data of the gas species using both theoretical (Boltzmann analysis) and experimental (Langmuir probe plasma diagnostics) means. Both theoretical and experimental approaches are performed for individual gas species as well as for various ratios of binary and ternary mixtures of the individual gases. Swarm parameters not only enable qualitative analysis on breakdown strengths of various gas mixtures, but also serve as the foundation of developing a quantitative model for accurate breakdown voltage estimations. In the proposed study, swarm parameters of the gas mixtures derived from the Boltzmann analysis are validated with those from the Langmuir probe plasma experiment. Moreover, a versatile model, which provides an enhanced accuracy in the estimation of breakdown voltages of gas mixtures, is developed and the performance is verified by comparing its estimated values to the experimental breakdown measurements of various gas mixtures.