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Plasma Science, IEEE Transactions on

Issue 5 • Date Oct. 2007

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Displaying Results 1 - 25 of 32
  • Table of contents

    Publication Year: 2007 , Page(s): C1 - 1429
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  • IEEE Transactions on Plasma Science publication information

    Publication Year: 2007 , Page(s): C2
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  • Conductivity Measurements of Femtosecond Laser–Plasma Filaments

    Publication Year: 2007 , Page(s): 1430 - 1436
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (191 KB) |  | HTML iconHTML  

    Experiments are performed to characterize the electrical properties of plasma filaments that are generated by self- guided femtosecond laser pulses propagating in air. A single plasma filament passes through a high-voltage sphere pulsed at -100 kV to a grounded electrode, which serves as a current monitor. The experiments utilize moderate electric fields to probe the filament conductivity, thereby avoiding the strong perturbations caused by electric discharges. The measured filament current decreases as ~1/R2 as the separation R between the electrodes is increased up to 1.5 m. The pulselength of the filament current signal is 2 ns (full-width at half-maximum), but the time resolution is limited by the bandwidth of the oscilloscope. The typical plasma density in the conducting filament is 9 times 1015 cm-3, which is inferred from the conductivity measurements and the size of the optical filaments. Comparisons are made with mobility values derived from electron swarm data, where the mobility depends upon the applied electric field. The conductivity of the filament is measured as the laser pulselength is varied from 50 fs to 1.5 ps. We find that relatively long laser pulses (1 ps) produce filaments with the largest conductivity. A model is used to predict the longitudinal position where the plasma filament forms and is in reasonably good agreement with measurements. View full abstract»

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  • Dielectric Electrode Surface Effects on Atmospheric Pressure Glow Discharges in Helium

    Publication Year: 2007 , Page(s): 1437 - 1447
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (645 KB) |  | HTML iconHTML  

    Comparative experimental and theoretical studies are carried with 0.5-mm gaps using metallic and dielectric electrodes to examine the influence of dielectric surfaces upon the behavior of atmospheric pressure glow discharges in helium at frequencies of up to 22 kHz. The charge transfers associated with the discrete discharge current pulses exhibit a direct proportionality to the difference between the breakdown Vb and residual Vr voltages. The introduction of dielectric surfaced electrodes markedly increases the magnitude of Vr, which leads to substantially lower discharge currents. The calculated ionic and electronic charge carrier components comprising the discharge current pulses were found to be approximately equal when both electrodes were either metallic or dielectric. With one electrode metallic and the counter electrode dielectric, the electronic charge carrier component magnitude exceeded that of the ionic one by a factor of 2 in the positive half cycle. View full abstract»

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  • Spatially Resolved Temperature Measurements of Atmospheric-Pressure Normal Glow Microplasmas in Air

    Publication Year: 2007 , Page(s): 1448 - 1455
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (889 KB) |  | HTML iconHTML  

    The rotational and vibrational temperatures of DC normal glow air discharges were measured by comparing modeled optical emission spectra of the N2 second positive system with spectroscopic measurements from the discharges. By using an imaging spectrometer and optical assembly, the temperature measurements were spatially resolved to about 6 mum. Results are presented for a 3.8-mA discharge at an electrode spacing of 400 mum. Rotational temperatures are highest in the near-cathode region around 1500 K and decrease toward the anode to about 1100 K. Throughout the discharge, higher rotational temperatures correspond with lower vibrational temperatures. The maximum vibrational temperature measured is around 5000 K. Emission from the N2 + first negative system was also measured and is only intense in the negative glow (NG) region. The temperature near the anode is sensitive to the anode material. Gold, stainless steel, and tungsten electrodes were studied. Oxidizing anode materials can create a bright and hot anode spot several hundred kelvin warmer than for nonreacting anode materials. In addition, comparisons between spatially resolved and previously studied emission-averaged temperatures indicate that the emission-averaged temperatures correspond to those of the NG regions. View full abstract»

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  • Theoretical Study of a Plasma-Filled Relativistic Cerenkov Generator With Coaxial Slow-Wave Structure

    Publication Year: 2007 , Page(s): 1456 - 1466
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (991 KB) |  | HTML iconHTML  

    The linear and nonlinear theory of a plasma-filled relativistic Cherenkov generator with coaxial slow-wave structure (SWS) is developed. Linear analysis includes the space-charge limiting current, dispersion relations, dispersion curves, and coupling impedance. In nonlinear theory, the electron beam space-charge effect, nonsynchronous interaction, and complex reflection coefficients of the electromagnetic wave at the boundaries of the SWS are taken into account. With the assumption of quasi steady state, the self-consistent equations are numerically calculated using the fourth-order Runge-Kutta method. The effects of the relative phase between inner and outer corrugations, phase and amplitude of the complex reflection coefficient at the boundaries of the SWS, and plasma density on device efficiency are discussed. Efficiencies of up to 37% without plasma and about 50% with plasma density of np = 3-7 times 1011 cm-3 are obtained. View full abstract»

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  • Gigawatt Emission From a 2.4-GHz Compact Magnetically Insulated Line Oscillator (MILO)

    Publication Year: 2007 , Page(s): 1467 - 1475
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1283 KB) |  | HTML iconHTML  

    High-power-microwave (HPM) emission has been observed in S-band with a compact magnetically insulated line oscillator (MILO). The device is driven by a low-impedance Marx generator which was designed and built at Commissariat a l'Energie Atomique, Centre d'Etudes Scientifiques et Techniques d'Aquitaine for HPM experiments. Measurements with fast and sensitive I-dot probes, installed inside the slow-wave structure (SWS), have given the evidence of the MILO oscillation. The main frequency at 2.40 GHz is confirmed by measuring the emitted radiation by using both an in-vacuum antenna and a horn placed in the far-field region. The frequency response of the MILO SWS is compared to a 3-D simulation performed with MAGIC, an electromagnetic particle-in-cell code. In the first configuration, a microwave output power of 1 GW has been obtained, which is in good agreement with the simulations. Then, an optimization of the cathode geometry has led to an increase of the pulse duration and to a better stability of the emission frequency. Finally, based on the fair agreement between the experimental results and the corresponding simulations, a novel design is presented, which should give a higher emitted power at 2.34 GHz. View full abstract»

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  • Development of a High-Current Helicon Ion Source With High Monatomic Fraction for the Application of Neutron Generators

    Publication Year: 2007 , Page(s): 1476 - 1479
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB) |  | HTML iconHTML  

    A high-current helicon ion source has been developed for neutron generator application. High-density plasmas with high electron temperatures are generated by launching helicon waves with a half-helical antenna in various magnetic field configurations. Helicon plasmas with high power efficiency are favorable in building ion sources with high current density and high monatomic ion beam fraction that are required for compact neutron generators. A maximum hydrogen beam current of 50 mA is extracted at 34 kV from the helicon plasma source with 1.9-kW RF power at 13.56 MHz. High current densities of 212 mA/cm2 and high atomic fractions of up to 94% are achieved with this source. These measured beam parameters are mostly consistent with plasma parameters, except for unusually high monatomic beam fraction, which may be due to the existence of energetic electrons in helicon plasmas. View full abstract»

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  • Characterization of a Ferroelectric Atmospheric Pressure Plasma Source

    Publication Year: 2007 , Page(s): 1480 - 1485
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (487 KB) |  | HTML iconHTML  

    A ferroelectric atmospheric pressure plasma source has been characterized. An RF electric field, with a frequency between 190 and 250 kHz, is employed to create plasma on the surface of a ferroelectric disk at atmospheric pressure. Average power consumption was measured, and images of plasma formation during an RF cycle have been collected. Excited neutrals from the ferroelectric and electrode, along with component species of the background gas, have been identified in optical emission spectra. Additionally, the electron temperature has been found to be ~2.3 eV from atomic Boltzmann plots of neutral Ag I lines. Breakdown voltage and heavy-particle temperature are also presented. Additionally, the experiments indicate that piezoelectric resonance effects reduced the required applied voltage to induce breakdown. View full abstract»

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  • Improved Ponderomotive Guiding Center Algorithm

    Publication Year: 2007 , Page(s): 1486 - 1488
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (78 KB) |  | HTML iconHTML  

    The original implementation of the ponderomotive guiding center algorithm is not suitable for modeling the propagation of short laser pulses over long distances. An improved algorithm is given, which improves the accuracy of the calculation, allowing much longer propagation distances to be modeled. View full abstract»

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  • Two-Dimensional Fluid Model of Pulse Sheath in Plasma Immersion Ion Implantation With Dielectric Substrates

    Publication Year: 2007 , Page(s): 1489 - 1495
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    A 2D fluid model is developed to describe the charging effects during plasma immersion ion implantation with dielectric substrates. The spatiotemporal evolution of the surface potential, the accumulated charge dose, and the ion impact angle at the surface of dielectric substrates are calculated with the model. The numerical results demonstrate that the charging effects lead to reduction of the surface potential with time, and the surface potential is nonuniform along the dielectric surface. The lowest value of surface potential is near but not at the edge of the dielectric target. Therefore, the charge accumulation on the dielectric surface is also a function of surface position. The dose nonuniformity is more severe near the edge of the dielectric target. To lengthen the width of the metal electrode that is located below the dielectric target, one can improve the nonuniformity of the accumulated charge dose on the dielectric surface. View full abstract»

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  • Experimental Research on Inactivation of Bacteria by Using Dielectric Barrier Discharge

    Publication Year: 2007 , Page(s): 1496 - 1500
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB) |  | HTML iconHTML  

    S. aureus and E. coli were treated by using dielectric barrier discharge (DBD). It was found that a logarithm reduction factor of 5 for both S. aureus and E. coli could be obtained in less than 120 s of treatment. The results of scanning electron microscopy showed that the low-temperature plasma that was induced by DBD destroyed the outer membrane of the bacteria. It was shown that E. coli was more susceptible to the inactivation effect by the DBD than S. aureus because E. coli has a thinner cell surface structure. This paper compares the bacteria inactivation effect of DBD with that of ozone generator and ultraviolet lamp, and results show that the charged particles and active free radicals penetrating through the outer membrane of the bacteria might play a major role during the treatment process. View full abstract»

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  • Rapid Inactivation of Airborne Bacteria Using Atmospheric Pressure Dielectric Barrier Grating Discharge

    Publication Year: 2007 , Page(s): 1501 - 1510
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (647 KB) |  | HTML iconHTML  

    Dielectric barrier discharge plasma has been known to inactivate many different microorganisms on surfaces when treatment times are on the order of seconds or minutes in duration. In this paper, a unique plasma air cleaning facility was created which combines a dielectric barrier grating discharge (DBGD) with a filterless laboratory-scale ventilation system and is used to treat concentrated bacterial bioaerosol in a moving air stream at air flow rates of 25 L/s. Results indicate that plasma treatment times on the order of milliseconds corresponding to one pass through the DBGD device can achieve 1.5-log reduction in culturable E. coli immediately after contact with plasma and 5-log reduction totally following in the minutes after the plasma treatment. A numerical characterization study was performed to help predict and understand the mechanism of bacteria inactivation in the DBD plasma from a variety of plasma factors. View full abstract»

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  • Recovery of Boundary Image Sticking Using Aging Discharge in AC Plasma Display Panel

    Publication Year: 2007 , Page(s): 1511 - 1517
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1068 KB) |  | HTML iconHTML  

    A full-white aging discharge process is proposed to recover permanent boundary image sticking in an AC plasma display panel. A simultaneous 100-h aging discharge in both boundary image sticking and nonimage sticking cells induced sputtering and redeposition of the MgO surfaces in both cell types, resulting in similar MgO surface morphologies. The luminance characteristics, including the infrared emission and chromaticity coordinates, of the boundary image sticking cells were also compared to those of the nonimage sticking cells. As a result, the full-white aging discharge was found to contribute to the recovery of permanent boundary image sticking cells. View full abstract»

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  • Impedance Spectroscopy Study of Composite Thin Films of Hydrated Polyethylene Glycol

    Publication Year: 2007 , Page(s): 1518 - 1526
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (705 KB) |  | HTML iconHTML  

    A polyethylene glycol (PEG) polymer was synthesized using a dip-coating procedure on 316L stainless-steel (SS) substrate precoated with a primer that consisted of radio-frequency inductively coupled plasma-polymerized di (ethylene glycol) vinyl ether (EO2V). The primer and PEG composite film was studied with profilometer, optical microscope, scanning electron microscope (SEM), and a tape test to evaluate thickness, coverage, morphology, and adhesion, respectively. Response of the PEG composite film to an applied ac voltage was studied as a function of hydration state using impedance spectroscopy (IS). A resistor/capacitor network was used to interpret the impedance spectra. Electrical capacitance of the PEG film decreased with an exponentially decaying term as dehydration progressed. PEG-film capacitance decay was consistent with a model describing water molecules diffusing through the PEG film. View full abstract»

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  • Electrical Equivalent Circuit for AC Plasma Display Panels

    Publication Year: 2007 , Page(s): 1527 - 1532
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (263 KB) |  | HTML iconHTML  

    This paper proposes an equivalent circuit for AC plasma display panels (PDPs). The circuit is composed of nine capacitors, six diodes, and a circuit model for the plasma. The capacitors represent the dielectric and discharge gap capacitances of a PDP. The circuit model for plasma consists of three two-electrode discharge models, three diode bridges to rectify the discharge currents, and two current-controlled current sources to separate the ion and electron currents. The six diodes provide proper current paths for the ions and electrons so that the attraction of electrical charges to the electrodes is represented correctly. The validity of the proposed circuit was checked with experiments on a test PDP. The results of circuit simulation using the proposed equivalent circuit agreed well with experiment in every period of a PDP test waveform, but the previous circuit failed to predict the behavior of sustain charges. View full abstract»

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  • Modeling and Experimental Study on Nitric Oxide Treatment Using Dielectric Barrier Discharge

    Publication Year: 2007 , Page(s): 1533 - 1540
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB) |  | HTML iconHTML  

    In this paper, nonthermal plasma technology was used to remove nitric oxide (NO) from a mixture of air and water vapor. A chemical model was developed to obtain NO removal mechanism and to observe the behavior of the species in the plasma discharge. The influence of water vapor addition on NO removal efficiency was also investigated. Results obtained from the model indicate that the NO removal is mainly achieved by chemical reactions with Oldr, Nldr, and OHldr radicals. Experimental results of the NO removal process in a dielectric barrier discharge are also presented. Several experimental parameters such as power, frequency, initial concentration of NO, and specific input energy were tested, and a NOx removal efficiency of approximately 98% was achieved. View full abstract»

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  • Study of Transmembrane Potentials of Inner and Outer Membranes Induced by Pulsed-Electric-Field Model and Simulation

    Publication Year: 2007 , Page(s): 1541 - 1549
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (349 KB) |  | HTML iconHTML  

    A more proper and realistic multilayer dielectric model of spherical biological cell, in which nuclear was taken into consideration, was proposed based on the classic dielectric model in this paper. The general analytical method was also deduced and analyzed in detail in calculating the time courses of transmembrane potentials of both inner and outer membranes induced by constant and time-varying electric field. The time course of transmembrane potential of the outer membrane for multilayer dielectric model was compared to that of the classical model. It is shown that the latter is larger than the former, particularly for a cell with larger nuclear. The time courses of transmembrane potentials of both inner and outer membranes induced by pulsed electric fields (PEFs) with different durations were also studied based on the multilayer dielectric model. Long PEF targets outer membrane mainly, and there is little influence to cell nucleus, mitochondrion, and other organelles; thus, it causes electroporation to the outer membrane. As the pulse duration decreases, the electroporation effect changes gradually from the outer membrane to intracellular organelle membrane. Ultrashort PEF (tens of nanoseconds) induces larger voltage across the inner membrane and acts mostly on intracellular substructures. However, submicrosecond PEF (several hundreds of nanoseconds) can induce significant voltages across both the inner and outer membranes, therefore, causing damage to both the inner and outer membranes. This property of submicrosecond PEF has much practical value for tumor treatment. View full abstract»

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  • Optical and Electrical Diagnostics of a High-Frequency Glow–Arc Discharge and Its Application to the Synthesis of Carbon Nanofibers

    Publication Year: 2007 , Page(s): 1550 - 1558
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (863 KB) |  | HTML iconHTML  

    In this paper, a detailed diagnostic of an AC glow-to-arc discharge transition is presented. The behavior of the temporal evolution of voltage and current discharges is studied under an atmosphere of helium-methane. In order to determine the rotational temperature, an optical emission-spectroscopy analysis from glow-to-arc regime discharge is carried out, where the OH and bands, respectively, which are situated at 306.357 nm (A2Σ+, ν=0→X2Π, ν'=0) and 516.52 nm (d3Πg, ν'=0→a3Πu, ν"=0), are used. Several metallic atomic lines were used to calculate the electron temperature. The principal discharge parameters, such as temperature and electron density in the arc regime, are determined. As an application of this glow-arc discharge, the synthesis of carbon nanofibers is reported. View full abstract»

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  • Mechanism of Blood Coagulation by Nonthermal Atmospheric Pressure Dielectric Barrier Discharge Plasma

    Publication Year: 2007 , Page(s): 1559 - 1566
    Cited by:  Papers (48)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (811 KB) |  | HTML iconHTML  

    Mechanisms of blood coagulation by direct contact of nonthermal atmospheric pressure dielectric barrier discharge (DBD) plasma are investigated. This paper shows that no significant changes occur in the pH or Ca2+ concentration of blood during discharge treatment. Thermal effects and electric field effects are also shown to be negligible. Investigating the hypothesis that the discharge treatment acts directly on blood protein factors involved in coagulation, we demonstrate aggregation of fibrinogen, an important coagulation factor, with no effect on albumin. We conclude that direct DBD treatment triggers selective natural mechanisms of blood coagulation. View full abstract»

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  • Wall Voltage and Priming Effect Due to Auxiliary Electrode in AC PDP With Auxiliary Electrode

    Publication Year: 2007 , Page(s): 1567 - 1573
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (903 KB) |  | HTML iconHTML  

    Variation of wall voltage and priming effect due to an auxiliary electrode are investigated with the aim of attaining a better understanding of the discharge phenomenon in an ac plasma display panel with an auxiliary electrode. A periodic positive pulse, which is applied to the auxiliary electrode during afterglow, reduced wall charges accumulated on the auxiliary and sustain electrodes so that discharge current decreased with an increase of auxiliary-pulse voltage. In addition, the auxiliary pulse influenced on the priming particles so that the optical output was not changed as much as the reduced current and sustain voltage was lowered. Based on these results, modified auxiliary-pulse waveforms, i.e., dual auxiliary pulses, were applied to the auxiliary electrode to utilize more priming particles to improve luminous efficacy. The proposed auxiliary waveforms improved IR efficiency by 10%-15% as compared to that obtained with a single auxiliary pulse. View full abstract»

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  • Microplasma Trapping of Particles

    Publication Year: 2007 , Page(s): 1574 - 1579
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (650 KB) |  | HTML iconHTML  

    The localized potential gradients created by a microplasma are capable of trapping and concentrating micro- and nanoparticles. In this paper, argon microplasma is generated within a 350-mum discharge gap formed within a microstrip transmission line. Melamine formaldehyde particles (1 mum) are released approximately 2 cm away from the microplasma. The microparticles are then negatively charged by stray electrons, electrostatically drawn toward the potential well of the microplasma, and trapped within the microplasma. The particles are observed to form Coulomb crystals. Time-of-flight experiments show that the particles are trapped in the microplasma by balancing the electrostatic force of the potential well against the molecular drag force. Pulsed plasma data show that the particles retain a net negative charge after the plasma has been extinguished, allowing detection and sorting by electrostatic methods. View full abstract»

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  • Pulsed Dielectric-Surface Flashover in an SF6 Environment

    Publication Year: 2007 , Page(s): 1580 - 1587
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (666 KB) |  | HTML iconHTML  

    A recently upgraded laser-triggered gas switch at Sandia National Laboratories has developed a failure mode that results in the breakdown spark tracking to the inside of the containment envelope. These breakdowns along the surface, or surface flashovers, degrade the performance of the overall switch, causing the switch to prefire in the successive shot. In the following, experimental results of pulsed surface flashover across different dielectric materials in SF6, primarily at atmospheric pressure, as well as flashover and volume breakdown in at pressures from 1.3 to 365.4 kPa are presented. In addition to fast voltage and current monitoring of the breakdown event, an increased emphasis was put on imaging the event as well as gathering optical emission spectra (~200-700 nm) from it. As much as possible, the small-scale experiments were designed to reproduce, at least partly, the conditions as they are found in the large 5-MV switch. An effort was made to determine what changes could be made to reduce the occurrence of surface flashovers, in addition to some broadly applicable conclusions on surface flashovers in an SF6 environment. View full abstract»

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  • Influence of Anode-Region Boundary-Layer Separation on Disk MHD-Generator Performance

    Publication Year: 2007 , Page(s): 1588 - 1597
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (971 KB) |  | HTML iconHTML  

    A time-dependent 2-D large-eddy simulation has been carried out in order to clarify the influence of the wall profile on nonequilibrium plasma-flow behavior and disk magnetohydrodynamic (MHD)-generator performance. The numerical investigation is not limited to the divergent generator channel only, but it also includes the inlet duct. The numerical simulations examined both a straight-disk wall profile and a contoured disk wall profile for a set of possible working conditions. These results show that boundary-layer separation, which is observed to occur near the anode region of the disk MHD generator when using a straight wall profile, is successfully eliminated by the introduction of a contoured wall profile. The suppression of boundary-layer separation improves plasma properties in the generator and leads to dramatic increases in Hall parameter and electrical efficiency. Furthermore, generator performance, as defined in terms of enthalpy extraction ratio and isentropic efficiency, is significantly improved. Although the wall-profile modification might be perceived as seemingly trivial, the influence on system performance can be truly profound. Therefore, the results obtained here should find important practical utility in the performance optimization of a commercially viable disk MHD-generator system. View full abstract»

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  • Special issue on Invited and Plenary Talks of PPPS 2007

    Publication Year: 2007 , Page(s): 1598
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    Freely Available from IEEE

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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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