Browsing by Subject "Ionization of gases"
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Item A fast preionization source for diffuse discharges containing attachers(Texas Tech University, 1983-12) Cooper, James RandallDiffuse discharge opening switches and most excimer lasers must operate with gas mixtures containing attachers. In self sustained discharges, preionization is required for arc free initiation of these discharges. The preionizer must have a short rise and falltime and must have an extremely accurate timing system because of the attachers in the discharge gas. Also, this device must have sufficient power to produce large volumetrically uniform electron densities in gases at pressures in the one atmosphere range. This paper describes the design and construction of such a preionizer and gives an overview of various preionization techniques previously employed. The device presented here consists of eight coaxial cables for energy storage, which are switched through a master spark gap to eight cables terminated by individual multi-spark arrays. The preionizer and the main discharge are triggered by a single laser (with a beam splitter and with a variable optical delay on one of the beams). Experiments showing the influence of the delay, preionization pulse length, jitter, and durability of the spark sources on the main discharge are described.Item Phase space theory, variational transition-state theory, and classical trajectory studies of gas-phase chemical reactions(Texas Tech University, 1989-05) Song, KihyungThis dissertation is a collection of works on theories of gas-phase chemical reactions. Three main topics are included: phase space theory, microcanonical variational transitionstate theory, and the classical trajectory method. Phase space theory was applied to the reaction (H2O)OH- (CO2.H2O) HCO3-. The available experimental data on this reaction was successfully reproduced by taking into account the dissociation of the HCO3- ion using a dissociation energy of 1.8 eV, which is in good agreement with the reported value. The decomposition of the bromobenzene cation was studied using a variational method developed by Chesnavich. This study showed that the existence of multiple transitionstates strongly depends upon the transitional mode potential. A microcanonical variational method was developed and applied to two systems, HO2 and HeH2+. The HO2 study revealed that a bottleneck in the angular part of the potential can produce multiple transition-states. Also, multiple transition-states are more Ukely to exist for systems with lower well-depth. The HeH2+ study supports this trend. More detailed calculations conserving angular momentum gave similar results. A life-time estimate for the system trapped between the two transition-states was performed with a pseudo-complex assumption. For the HeH2+ system, this lifetime is equal to -200 fs, which is within the limit of experimental detection. The origin of the dynamic threshold for collision-induced dissociation was studied using the boundary trajectory method. This study showed no correlation between the curvature of the minimum energy path potential and the dynamic threshold. The results suggest that the dynamic and energetic thresholds are equal only when an exchange reaction channel is presentItem Photodetachment as a discharge control mechanism in gases containing oxygen(Texas Tech University, 1985-05) Thurmond, Leo ErasmusInterest in high voltage switches for pulsed power applications has increased significantly in the last several years. Inductive energy storage has space and weight advantages over capacitive energy storage, but requires the use of a high power opening switch. Opening switch technology has only recently started to be developed, and several concepts for opening switches are being studied. One of these concepts is the diffuse discharge switch, which shows several advantages over other types of opening switches. One major advantage of the diffuse discharge switch is that it may be controlled externally by an electron beam or by optical means. There are several processes possible for optical control of a diffuse discharge, one of which is photodetachment. In this paper, three experiments are presented which study the possibility of using photodetachment as a discharge control mechanism in gases containing 02 are presented. The first experiment shows the effect of photodetachment outside the discharge and the dependence of the effect on laser energy flux density. The second experiment demonstrates the feedback effect of photodetachment on a glow discharge. Operating conditions for the largest effect are presented. The last experiment simulates the conditions in a high power switching device, and the preliminary results of this study are given.