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Plasma Science, IEEE Transactions on

Issue 6 • Date Dec 1991

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Displaying Results 1 - 25 of 28
  • LTE and near-LTE lighting plasmas

    Publication Year: 1991 , Page(s): 1003 - 1012
    Cited by:  Papers (6)  |  Patents (6)
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    High-pressure mercury lamps, metal halide arc lamps, high-pressure sodium lamps, xenon short-arc lamps, xenon flashlamps, and microwave-excited metal halide lamps are extremely important commercial applications of LTE and near-LTE plasma physics. The author outlines in very brief form the basic plasma science in such light sources. The factors controlling the power balance and the luminous efficacy of such sources are discussed. Current research in modeling these complex plasma devices is described. This has reached the stage that successful CAD models are available for new-product design in mercury and high-pressure sodium lamps, but not yet for metal halide lamps. The behavior of electrodes is discussed as an important practical determinant of lamp life. Directions of future research and development are briefly discussed View full abstract»

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  • Approximate sheath solutions for a planar plasma anode

    Publication Year: 1991 , Page(s): 1235 - 1243
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    Solutions to the anode sheath problem are studied for the case where the electron temperature and plasma temperature are constant and equal. The planar geometry description of steady, low-temperature collisional plasmas permits certain simplifications to the species continuity equations whereby a single, highly nonlinear equation is obtained for the entire region disturbed by the electrode. This equation is given in terms of the electric field and a variable representing the currents. The formulation includes charged-particle production with a net current flow. Solutions are generated with a nontrivial analytic expression for the electric field. Results are described for nitrogen at moderately high densities, which at sufficiently flow currents are realistic for electron-impact ionization and two-body recombination. This case is completely described by two nondimensional groupings, which are sufficient to define the sheath and ambipolar regions. The constants A and a are evaluated using information for nitrogen at 6000 K, corresponding to degrees of ionization above 10-6. Other practical discharge gases are also represented in the example View full abstract»

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  • Plasma reflectors for electronic beam steering in radar systems

    Publication Year: 1991 , Page(s): 1228 - 1234
    Cited by:  Papers (22)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    The author describes investigations into methods of generating a planar plasma for use as a reflector for radar waves. The use of the plasma reflector could allow electronic beam steering at frequencies above what is generally viable for phased arrays. Three aspects of the planar plasma production are investigated: localization of the plasma, main plasma production, and long-term viability of the system. Possible applications include ship-based antennas at X-band, airborne antennas at 94 GHz, and space-based antennas at 60 GHz. The author discusses system considerations for the three potential radar configurations. Results and potential small-scale experiments to test various aspects of the concept are discussed View full abstract»

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  • The response of a microwave multipolar bucket plasma to a high voltage pulse

    Publication Year: 1991 , Page(s): 1272 - 1278
    Cited by:  Papers (6)  |  Patents (5)
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    A collisional model that describes the response of a microwave multipolar bucket plasma to a high voltage pulse is developed for plasma source ion implantation (PSII). The primary purpose is to develop a theoretical model of PSII plasma physics to be used in conjunction with a model of ion-target interaction to optimize PSII processing. Measurements of the sheath position and target current in a 100 mtorr helium plasma are found to be consistent with the model. Sheath thicknesses predicted by the collisional model are significantly less than those predicted by similar noncollisional models View full abstract»

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  • Thermal plasma processing

    Publication Year: 1991 , Page(s): 1078 - 1089
    Cited by:  Papers (15)  |  Patents (3)
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    A review is given of the fundamental aspects involved in material processing using thermal plasma technology. The description of plasma generating devices covers DC plasma torches, DC transferred arcs, RF inductively coupled plasma torches and hybrid combinations of them. Emphasis is given to the identification of the basic energy coupling mechanism in each case and the principal characteristics of the flow and temperature fields in the plasma. Materials processing techniques using thermal plasmas are grouped in two broad categories depending on the role played by the plasma in the process. Only typical examples are given of each type of process. These are grouped under two broad subsections dealing respectively with applications in which the plasma is used as a source of heat in high temperatures, and those in which the plasma is used as a source of chemically active species. The author also deals with plasma diagnostics and mathematical modeling and the role which they can play in the long term development of the technology View full abstract»

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  • Plasma displays

    Publication Year: 1991 , Page(s): 1032 - 1047
    Cited by:  Papers (47)
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    The author describes many of the various approaches which have been used in designing display devices. The emphasis is on device configuration and performance rather than on the physics of the glow discharge. There are three aspects of the physics the author mentions as being unusual to many plasma physicists: the use of priming in display-scanning mechanisms, the use of the Townsend discharge in a positive column for high output and efficacy, and the use of a double-layer sheath as a scannable source of electrons. The adroit use of priming can reduce the number of drive circuits required-an advantage unique in the display art to plasma devices. The gas discharge can be used as a source of electrons which can then excite cathodoluminescent phosphors in a variety of colors. It can also be used as a selection means for liquid-crystal displays. A wide variety of device configurations, using both unidirectional and bidirectional pulse excitations, is described View full abstract»

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  • Gas-phase pulsed power switches

    Publication Year: 1991 , Page(s): 1123 - 1131
    Cited by:  Papers (5)  |  Patents (1)
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    A review of plasma science that is related to gas-phase pulsed power switching is presented. Switch plasmas include uniform glow-type plasmas and constricted arc-type plasmas, and the science involves understanding transport processes in hydrogen, helium, metal vapor, and other plasmas, and electrode processes including limitations related to cathode emission and sheaths. Gas-phase pulsed power switches include spark gaps, vacuum, metal vapor, and low-pressure glow-type switches. The review concludes that the understanding of microscopic processes and plasma electrode interactions is somewhat limited, and that to facilitate the development of efficient, reliable pulsed power devices, there is considerable need for a deeper understanding View full abstract»

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  • Temperature-limited electron bombardment heating method

    Publication Year: 1991 , Page(s): 1279 - 1289
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (916 KB)  

    A temperature-limited electron bombardment heating method capable of heating LaB6 cathodes to 1800°C has been developed. This method heats LaB6 cathodes in a Pierce-type electron gun which is pulsed to 115 kV; 1.9-cm-diameter LaB6 cathodes have been heated to 1800°C, with 370 W/cm2 of heating power. This method has been successfully used in a pulsed power environment where the bombardment filament and LaB6 cathode were simultaneously pulsed to high voltages to produce electron beams. The heating system has produced cathode temperatures in excess of 1750 °C, while the electron gun has been pulsed up to voltages of 115 kV. A dynamic model of the bombardment heating system is developed. This model shows that the temperature-limited bombardment heating system is open-loop unstable. A digital control method is presented which stabilizes the heating system View full abstract»

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  • Improving the signal to noise of FIR polarimetry on constrained-access plasma experiments

    Publication Year: 1991 , Page(s): 1248 - 1253
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    Experimental results are presented that demonstrate the pronounced effects produced on the polarization state of an FIR (far infrared) laser beam when a portion of the beam intersects a metallic tubulation at a glancing angle. The effects produced by this interaction are sufficient to totally obscure the desired measurement of Faraday rotation. A model is developed which qualitatively predicts the observations. A method of suppressing this effect, which is viable for the heterodyne method of measuring Faraday rotation, is presented. It is further shown that reflections off the mechanically vibrating tubulations are the source of a variable effective birefringence, which is perceived as an anomalous Faraday rotation. Minimizing these reflections by threading the inside of the tubulations overcame this problem and allowed measurements to be obtained View full abstract»

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  • Application of weakly ionized plasmas for materials sampling and analysis

    Publication Year: 1991 , Page(s): 1090 - 1113
    Cited by:  Patents (3)
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    The use of weakly ionized plasmas as spectroscopic sources for materials sampling and analysis is reviewed. Plasma sources currently used for this purpose include direct-current and alternating-current plasmas, inductively coupled plasmas, microwave-induced plasmas, surface-wave plasmas, capacitively coupled plasmas, capacitive microwave plasmas, glow discharges, flowing afterglows, theta pinch discharges, exploding films and wires, and laser-produced plasmas. The authors give a summary of relevant characteristics of some of the plasma sources. Included are the source, common method of application, approximate detection limit for that method, applicability for solid sampling, susceptibility to matrix effects, approximate cost, and the most common usage for the method View full abstract»

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  • Nonequilibrium lighting plasmas

    Publication Year: 1991 , Page(s): 991 - 1002
    Cited by:  Papers (4)
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    The science of a variety of devices employing nonequilibrium lightning plasmas is reviewed. The devices include the fluorescent lamp, the low-pressure sodium lamp, the neon sign, ultraviolet lamps, glow indicators, and a variety of devices used by spectroscopists, such as the hollow cathode light source. The plasma conditions in representative commercial devices are described. Recent research on the electron gas, the role of heavy particles, spatial and temporal inhomogeneities, and new electrodeless excitation schemes is reviewed. Areas of future activity are expected to be in new applications of high-frequency electronics to commercial devices, new laser-based cidiagnostics of plasma conditions, and more sophisticated models requiring more reliable and extensive rate coefficient data View full abstract»

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  • Space electric propulsion plasmas

    Publication Year: 1991 , Page(s): 1167 - 1179
    Cited by:  Papers (5)
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    Electric thrusters offer the promise of a substantial improvement in performance over that of conventional chemical rockets currently used in space propulsion applications. There are three basically different ways in which electrical power and propellant inputs might be combined to produce thrust: (1) propellant can be heated electrically and then expanded through a nozzle; (2) electromagnetic body forces can be applied to accelerate a plasma to the desired exhaust velocity; or (3) electrostatic body forces can be applied to accelerate charged particles. Electric thrusters are classified in accordance with the mechanism by which they induce thrust as electrothermal, electromagnetic, and electrostatic. The characteristics of plasmas in electric thrusters along these lines are considered View full abstract»

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  • New structure for a slow-wave Rogowski coil

    Publication Year: 1991 , Page(s): 1290 - 1291
    Cited by:  Papers (3)
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    The author proposes the construction of a slow-wave Rogowski coil wound by using a novel type of three-layered wire that is formed by placing a flexible dielectric strip between two conducting strips. This structure results in a distributed capacitance along the wire. The construction of a slow-wave Rogowski coil can then be easily achieved by directly winding this kind of wire on a toroid with either rectangular or circular cross sections. The construction is then as simple as that for a conventional self-integrating Rogowski coil. Design and experimental results are presented View full abstract»

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  • The electron current to a Langmuir probe in a flowing high-pressure plasma

    Publication Year: 1991 , Page(s): 1254 - 1258
    Cited by:  Papers (5)
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    The electron current to a Langmuir probe in a moving high-pressure plasma has been measured and analyzed. The plasma is an atmospheric-pressure propane flame, and the probe's speed relative to the plasma was varied from 10 ms-1 to 30 ms-1. The current is linearly dependent on the speed and appears to be comprised of two components-one driven by diffusion and the other by convection. A model is devised which can be used to measure the electron density. By comparing the density computed from this model to that measured from the ion current, it has been possible to measure the electron mobility in the flame gases. The value obtained by the authors is in good agreement with theoretical calculations found in the literature View full abstract»

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  • Physics and applications of charged particle beam sources

    Publication Year: 1991 , Page(s): 1143 - 1151
    Cited by:  Papers (2)  |  Patents (1)
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    The authors review the physics and a few applications of charged particle beam sources, most of which originate from, propagate through, or use as a target, a partially ionized plasma. The authors present the plasma phenomena and plasma conditions which are general to most of the charged particle sources, but also other approaches and the current status of the research. The authors describe the applications of charged particle beam sources using partially ionized plasmas in accelerators and ion implantation. The applications covered are those of accelerator sources and ion implantation View full abstract»

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  • Compact pulsed power generator using an inductive energy storage system with two-staged opening switches

    Publication Year: 1991 , Page(s): 1220 - 1227
    Cited by:  Papers (17)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    The pulsed power generator, named ASO-I, is extremely compact and light in comparison with a conventional pulsed power generator, which consists of a Marx bank and a water pulse forming line. The ASO-I has a two-staged opening switch, consisting of fuses in water and a plasma erosion opening switch, and can be operated hundreds of times a day at an output power of 230 kV and 35 kA. The parallel fuses are effective for power multiplication, and small differences in length of the parallel fuses do not influence the output power. The risetime of current through the short-circuit load decreases with the increase of the gap length of the spark gap, which is placed between the fuses and the load. The plasma erosion opening switch can be operated as a second opening switch, and the risetime of the current through the short-circuit load decreases from 250 to 10 ns. The maximum resistance of the plasma erosion opening switch is 3.5 Ω with an open-circuit load View full abstract»

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  • Electric power switches

    Publication Year: 1991 , Page(s): 1132 - 1142
    Cited by:  Papers (1)
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    A review is given of the physics and engineering behavior of arcs in vacuum and axial gas blast under the conditions found in high-voltage circuit breakers. The topics included are: the zero energy switch; current limiting switches; arc control; the gas-blast circuit breakers; the low-current gas-blast arc; arcing with ablation; interruption dynamics; arc modeling; vacuum as a switching element; the vacuum arc; the constricted arc; and the properties of SF6 View full abstract»

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  • Nonequilibrium volume plasma chemical processing

    Publication Year: 1991 , Page(s): 1063 - 1077
    Cited by:  Papers (83)  |  Patents (14)
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    A review is presented of plasma chemical processes occurring in the volume part of electrical nonequilibrium discharges. The role of energetic electrons as initiators of chemical reactions in a cold background gas is discussed. Different discharge types of (glow, corona, silent, RF, and microwave discharges) are investigated with respect to their suitability for plasma processing. Emphasis is placed on the requirements of initiating and maintaining the discharge and, at the same time, optimizing plasma parameters for the desired chemical process. Using large-scale industrial ozone production as an example, the detailed process of discharge optimization is described. Other applications of volume plasma processing include other plasma chemical syntheses as well as decomposition processes such as flue gas treatment and hazardous waste disposal. The author only deals with plasmas which are not in equilibrium View full abstract»

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  • Plasma isotope separation methods

    Publication Year: 1991 , Page(s): 1114 - 1122
    Cited by:  Papers (2)  |  Patents (2)
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    Six major types of isotope separation methods which involve plasma phenomena are discussed. These methods are: plasma centrifuge, AVLIS (atomic vapor laser isotope separation), ion wave, ICR (ion cyclotron resonance), calutron, and gas discharge. The plasma phenomena in these major categories are described. An attempt is made to include enough references so that a more detailed study or evaluation of a particular method could readily be pursued. A brief discussion of isotope separation using mass balance concepts is also included View full abstract»

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  • Plasma physics issues in gas discharge laser development

    Publication Year: 1991 , Page(s): 1013 - 1031
    Cited by:  Papers (2)
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    An account is given of the interplay between partially ionized plasma physics and the development of gas discharge lasers. Gas discharge excitation has provided a wide array of laser devices extending from the soft X-ray region to the far infrared. The scaling of gas discharge lasers in power and energy also covers many orders of magnitude. The particular features of three regimes are discussed: short wavelength lasers (deep UV to soft X-ray), visible and near UV lasers, and infrared molecule gas lasers. The current status (fall, 1990) of these areas is reviewed and an assessment is made of future research topics that are perceived to be important View full abstract»

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  • A multiple-cathode arc-discharge plasma source

    Publication Year: 1991 , Page(s): 1244 - 1247
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    A plasma source for obtaining a 1-cm length of high-fractional ionized plasmas with electron densities in the range of 1015-1017 cm-3 is described. The source consists of a capacitive discharge between a metal anode and an array of small metal cathodes embedded in epoxy, each with a current-limiting resistor. The effect is to have an array of sources which merge into each other, producing the plasma as a whole. The design and performance of the plasma source are presented. The entire system consists of the main electrode and shielding structures, the preionization circuit, and the main discharge circuit. Each of these components is described and the operating parameters and results are given View full abstract»

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  • Laser-produced plasmas in medicine

    Publication Year: 1991 , Page(s): 1209 - 1219
    Cited by:  Papers (9)  |  Patents (1)
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    The authors examine those areas of laser medicine in which plasmas (ionized gases) are produced. In fact, the presence of a plasma is essential for the various applications to succeed. The authors consider examples of the plasmas produced in ophthalmology (e.g., lens membrane destruction following cataract surgery), in urology and gastroenterology (e.g., kidney and gall stone ablation and fragmentation), and in cardiology and vascular surgery (e.g., laser ablation and removal of fibro-fatty and calcified arterial plaque). Experimental data are presented, along with some results from computer simulations of the phenomena. Comments on future directions in these areas are included View full abstract»

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  • Plasmas in MHD power generation

    Publication Year: 1991 , Page(s): 1180 - 1190
    Cited by:  Papers (5)
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    The plasma found in a magnetohydrodynamic (MHD) generator is discussed. An MHD generator is an expansion engine. It delivers electric rather than mechanical power and there are virtually no upper limits to the temperature it can tolerate, the rapidity of its response, or the power a single unit can be designed to deliver. The behavior of the plasma is uncomplicated compared to that encountered in some other devices, and yet complex, because of the precision with which one needs to know it. The topics included are: generator configurations; electron density; electron mobility; mixture rules; the Hall effect; uniformity; two-temperature plasma; ionization growth at a channel inlet; ionization instability; high enthalpy extraction experiments; segmenting; electrode voltage drop; arcs and electrodes; electrical effects of slag; current control; and waves View full abstract»

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  • Thermionic energy conversion plasmas

    Publication Year: 1991 , Page(s): 1191 - 1208
    Cited by:  Papers (3)  |  Patents (5)
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    The author provides a perspective of the nature and scientific characterization of the unique plasmas occurring in the various modes of thermionic converter operation associated with different application requirements. The basic plasma types associated with various modes of converter operation are described, with emphasis on identification and semi-quantitative characterization of the dominant physical processes and utility of each plasma type. Their characteristic advantages are identified with particular applications. The author is concerned primarily with the physics of the various types of plasma employed to conform to the constraints of particular options and applications View full abstract»

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  • Surface processing with partially ionized plasmas

    Publication Year: 1991 , Page(s): 1048 - 1062
    Cited by:  Papers (1)
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    Partially ionized plasmas are used extensively to process surfaces in many areas of technology. Surface processing in this discussion includes deposition of thin films, etching of the surface itself, and modification of the existing surface by oxidation, nitriding, or texturing. Unique materials can be synthesized in reactive gas glow discharges. The development and optimization of plasma processes is impeded by both a lack of understanding of the mechanistic details and by the formidable parameter space associated with plasma equipment. The complexity of the reactive gas plasma environment coupled with the large parameter space causes difficulty in process development and optimization, but offers opportunities for discovery and invention. The ability of partially ionized plasmas to generate uniform fluxes over wide areas of energetic ions and/or reactive neutral atoms or radicals can be expected to ensure continued widespread applications for the plasma processing of surfaces View full abstract»

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IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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Editor-in-Chief
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