Bulletin of the American Physical Society
62nd Annual Gaseous Electronics Conference
Volume 54, Number 12
Tuesday–Friday, October 20–23, 2009; Saratoga Springs, New York
Session JT2: High Pressure Cold Plasmas and Arcs |
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Chair: Patrick Pedrow, Washington State University Room: Saratoga Hilton Ballroom 2 |
Tuesday, October 20, 2009 4:00PM - 4:15PM |
JT2.00001: Nanosecond Repetitively Pulsed Discharges in Air at Atmospheric Pressure -- Experiment and Theory of Regime Transitions David Pai, Deanna Lacoste, Christophe Laux In atmospheric pressure air preheated from 300 to 1000 K, the Nanosecond Repetitively Pulsed (NRP) method has been used to generate corona, glow, and spark discharges. Experiments have been performed to determine the parameter space (applied voltage, pulse repetition frequency, ambient gas temperature, and inter-electrode gap distance) of each discharge regime. Notably, there is a minimum gap distance for the existence of the glow regime that increases with decreasing gas temperature. A theory is developed to describe the Corona-to-Glow (C-G) and Glow-to-Spark (G-S) transitions for NRP discharges. The C-G transition is shown to depend on the Avalanche-to-Streamer Transition (AST) as well as the electric field strength in the positive column. The G-S transition is due to the thermal ionization instability. The minimum gap distance for the existence of the glow regime can be understood by considering that the applied voltage of the AST must be lower than that of the thermal ionization instability. This is a previously unknown criterion for generating glow discharges, as it does not correspond to the Paschen minimum or to the Meek-Raether criterion. [Preview Abstract] |
Tuesday, October 20, 2009 4:15PM - 4:30PM |
JT2.00002: Electron-Beam Generated Air Plasma Measurements: Effect of Reduced Electric Field Robert Vidmar, Anusha Uppaluri, Kenneth Stalder Measurements of electron density and momentum-transfer collision rate are discussed for plasma generated by an electron beam in air from 1 mT to 636 T as a function of the reduced electric field. A 100 keV electron source operating at a few mA is used to ionize air. A 10 GHz in-phase and quadrature microwave detector measures the electron number density and momentum-transfer collision rate. Optical emissions at 391.4 nm from N$_{2}^{+}$ provide an estimate of volumetric ionization profile along the microwave propagation path. Grids in the air-plasma test cell provide a means of imposing a reduced electric field, while the electron beam ionizes air. Results are discussed in the context of electron density as a function of reduced electric field and pressure. [Preview Abstract] |
Tuesday, October 20, 2009 4:30PM - 4:45PM |
JT2.00003: Surrogate Models of Electrical Conductivity in Air Nicholas Bisek, Mark Kushner, Iain Boyd, Jonathan Poggie Accurately determining the electrical conductivity of a gas is essential when estimating its electromagnetic effects. These effects are important in ionized flows, a condition typically observed in hypersonics because the high kinetic energy partially ionizes the gas as it passes through a strong shock or in regions were plasma-based control devices increase and/or utilize existing ionized flows-fields. Several existing semi-analytic electrical conductivity models are investigated and found to be deficient for the range of conditions present in a representative hypersonic flow that could benefit from these plasma-based technologies. This work utilizes surrogate modeling techniques to develop a general model (response surface), of solutions to Boltzmann's equation, an exact method which uses an extensive list of real collision cross-section data to determine the electrical conductivity of weakly ionized air. The optimal surrogate model, along with existing semi-analytic models, are coupled to a 3D flow solver in order to simulate hypersonic flow around a representative geometry that is utilizing a plasma-based flow control device. This effort helps quantify the importance of using a highly accurate electrical conductivity model (the surrogate model) and provides a framework for modeling solutions to Boltzmann's equation for a flow-field with arbitrary species. [Preview Abstract] |
Tuesday, October 20, 2009 4:45PM - 5:00PM |
JT2.00004: Role of Matching Network Design in Excitation of Atmospheric Plasmas Cameron Moore, Scott Heres, Carl Almgren, George Collins Recent refinements in the design and operation of atmospheric pressure plamsas are presented, specifically that there are advantages possible specific to match network design and selection of components. We show that a more thorough examination of an entire atmospheric plasma system which accounts for systemic compatibility leads to improvements. We present a simple example which considers electrode specifics (sizes, spacings) during selection of match network topology and match network component types and values. [Preview Abstract] |
Tuesday, October 20, 2009 5:00PM - 5:15PM |
JT2.00005: Numerical simulation of anode activity under action of high-current vacuum arc Lijun Wang, Shenli Jia, Dingge Yang, Ke Liu, Liuhou Wang, Zongqian Shi Anode activity is critical for success or failure of vacuum interrupters when arc current attains to a certain limiting value. Based on anode activity model, anode thermal process under action of high-current arc column is simulated. Simulation results show that for sinusoid current, anode surface temperature firstly increases rapidly, then decreases slower. With the increase of heat flux density to anode, anode surface temperature will be increased. The maximal value of anode surface temperature appears near 7ms moment. Simulation results also are compared with experimental results. [Preview Abstract] |
Tuesday, October 20, 2009 5:15PM - 5:30PM |
JT2.00006: Investigation on the voltage characteristic of vacuum arc under different axial magnetic field distributions Zongqian Shi, Xiaochuan Song, Shenli Jia, Xintao Huo, Lijun Wang Axial magnetic field (AMF) is widely used in vacuum interrupters as an effective arc control technique. In this paper, the voltage characteristic of vacuum arc under different AMF distributions is investigated. Experiments with arc current of 10kA (RMS) and gap distance of 6-26mm were conducted with five pairs of specially designed electrodes generating conventional bell-shaped AMF profile and different saddle-shaped AMF distributions. Arc column and cathode spot images were photographed by a high speed digital camera with exposure time of 2 microseconds. The average amplitude and high-frequency oscillation of arc voltage was analyzed based on the light intensity at different positions of arc column, and the dynamic and distribution of cathode spots. Experimental results indicate that saddle-shaped AMF can control vacuum arc much more efficiently than bell-shaped AMF, particularly, at large gap distance. [Preview Abstract] |
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