Development of a Ferroelectric Plasma Source Through Material Degradation Studies and Characterization of Volume and Surface Discharges PDF Download
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Author: Benjamin Charles Masters
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Category :
Languages : en
Pages :
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Author: Benjamin Charles Masters
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
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ISBN:
Category :
Languages : en
Pages : 37
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The development of plasma sources with densities and temperatures in the 1015-1017 cm−3 and 1-10eV ranges which are slowly varying over several hundreds of nanoseconds within several cubic centimeter volumes is of interest for applications such as intense electron beam focusing as part of the x-ray radiography program. In particular, theoretical work [1,2] suggests that replacing neutral gas in electron beam focusing cells with highly conductive, pre-ionized plasma increases the time-averaged e-beam intensity on target, resulting in brighter x-ray sources. This LDRD project was an attempt to generate such a plasma source from fine metal wires. A high voltage (20-60kV), high current (12-45kA) capacitive discharge was sent through a 100 [mu]m diameter aluminum wire forming a plasma. The plasma's expansion was measured in time and space using spectroscopic techniques. Lineshapes and intensities from various plasma species were used to determine electron and ion densities and temperatures. Electron densities from the mid-1015 to mid-1016 cm−3 were generated with corresponding electron temperatures of between 1 and 10eV. These parameters were measured at distances of up to 1.85 cm from the wire surface at times in excess of 1 [mu]s from the initial wire breakdown event. In addition, a hydrocarbon plasma from surface contaminants on the wire was also measured. Control of these contaminants by judicious choice of wire material, size, and/or surface coating allows for the ability to generate plasmas with similar density and temperature to those given above, but with lower atomic masses.
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Category : Aeronautics
Languages : en
Pages : 702
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Author: A. Dunaevsky
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Category : Glow discharges
Languages : en
Pages : 7
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Author: B. Grant Logan
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Category :
Languages : en
Pages :
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Plasmas are employed as a source of unbound electrons for charge neutralizing heavy ion beams to allow them to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length {approx} 0.1-1 m would be suitable. To produce one-meter plasma, large-volume plasma sources based upon ferroelectric ceramics are being developed. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source utilizes the ferroelectric ceramic BaTiO{sub 3} to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) will be covered with ceramic, and high voltage ({approx} 1-5 kV) applied between the drift tube and the front surface of the ceramic by placing a wire grid on the front surface. A prototype ferroelectric source 20 cm long has produced plasma densities of 5 x 10{sup 11} cm{sup -3}. The source was integrated into the previous Neutralized Transport Experiment (NTX), and successfully charge neutralized the K{sup +} ion beam. Presently, the one-meter source is being fabricated. The source is being characterized and will be integrated into NDCX for charge neutralization experiments.
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Languages : en
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The initial density and electron temperature at the surface of a ferroelectric plasma source were deduced from floating probe measurements in an expanding plasma. The method exploits negative charging of the floating probe capacitance by fast flows before the expanding plasma reaches the probe. The temporal profiles of the plasma density can be obtained from the voltage traces of the discharge of the charged probe capacitance by the ion current from the expanding plasma. The temporal profiles of the plasma density, at two different distances from the surface of the ferroelectric plasma source, could be further fitted by using the density profiles for the expanding plasma. This gives the initial values of the plasma density and electron temperature at the surface. The method could be useful for any pulsed discharge, which is accompanied by considerable electromagnetic noise, if the initial plasma parameters might be deduced from measurements in expanding plasma.
Author: A. Dunaevsky
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ISBN:
Category : Ceramics
Languages : en
Pages : 6
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Category : Electrical engineering
Languages : en
Pages : 1948
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Author: Alexandre Likhanskii
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Category :
Languages : en
Pages :
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Plasma engineering is one of the most actively growing research areas in modern science. Over the past decade, plasma engineering became a significant part of aerospace engineering, material processing, medicine, geosciences, etc. One of the main goals of plasma research is to discover new perspectives in a wide range of research areas. It makes plasma engineering a truly interdisciplinary subject. Recently, a significant interest in the aerospace community was caused by the possibility of an active flow control using dielectric barrier discharge (DBD) plasma actuators. A number of groups tried to explain the physics of the experimentally observed phenomena. However, the developed models could hardly explain the DBD phenomena even qualitatively. This thesis presents the first complete, comprehensive, physically-based model, which tracks all essential physics of the DBD plasma actuators and utilizes modern numerical capabilities for efficient simulations. By using the developed model, the physics of the plasma actuators was explained. Based on the understanding of the operation of the conventional DBD, driven by a sinusoidal voltage, a novel configuration was proposed. The sinusoidal driving voltage was substituted by the repetitive nanosecond pulses superimposed on the bias voltage. The advantages of the proposed concept over the conventional one were experimentally validated. The developed model demonstrated flexibility for different plasma engineering areas. The model can be used not only for a description of the DBD plasma actuators, but also for a number of problems involving the gas discharges. By using the developed model, plasma generation by the ferroelectric plasma source, which is used in fusion technology, was explained. In the area of material processing, a significant interest was caused by an apparent possibility of precise high intensity ultra-short laser pulse drilling with negligible melt production. However, the experiments did not validate the theories proposed in literature. In order to explain the experimental data and analyze the possibility of reduction of melt generation, a new model for laser pulse drilling was developed in this thesis. The model comprehensively describes laser-material interaction and explains the significant amount of melt production in the case of ultra-short laser pulses. The results of the simulations are in good agreement with the experimental data.
Author: Nicolas Jeanvoine
Publisher:
ISBN: 9783844004137
Category :
Languages : en
Pages : 150
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