Browsing by Author "Tzeng, Yonhua"
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Item An investigation of non-equilibrium electron kinetics in nitrogen(Texas Tech University, 1983-12) Tzeng, YonhuaThe kinetic behavior of electrons immersed in a background gas or gas mixture under the action of an externally applied electric field with or without the influence of the space charge induced electric fields have been investigated. Novel Monte Carlo techniques have been developed and applied to study the evolution of the electrons self-consistently , that is, including the effects of the electric field generated by the space charge and the effects of boundaries. Statistical fluctuations of the macroscopic variables describing the evolution of the electron assembly have been studied. This is important when the total number of electrons is less than about 100. Ensemble averaged descriptions, kinetic in nature, have been used to study the development of an avalanche and the formation and propagation of a streamer. The results from this research program have provided key fundamental knowledge necessary for the explanation of the approach to equilibrium of an assembly of electrons, the effects of scattering processes on the electron velocity distribution, prebreakdown phenomena and manipulating the dielectric properties of gas mixtures used in insulating and switching applications.Item The effect of space charge induced by an electon beam on spark gap operation(Texas Tech University, 1981-08) Tzeng, YonhuaAn investigation into the effect of electron beam induced space charge on the insulating property of a gas in a spark gap is presented. The characteristics of the gas transition from insulator to conductor show strong dependence on the amount and location of the space charge introduced. Investigations of the delay time and the characteristics of the conducting channel have been made. The delay time from the injection of the electron beam to the collapse of the gap voltage ranges from 10^-9 to 10^-3 second. From open shutter photography, we observe that the character of the conducting channel is quite varied. Dark, diffuse, filamentary, or diffuse followed by filamentary (single or multi) channels have been observed, depending on the space charge conditions. The fundamental processes leading to the collapse of insulating property of the gas for various experimental conditions are discussed.