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Plasma Science, IEEE Transactions on

Issue 2  Part 2 • Date April 2008

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Displaying Results 1 - 24 of 24
  • Table of contents

    Page(s): C1 - 457
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    Freely Available from IEEE
  • IEEE Transactions on Plasma Science publication information

    Page(s): C2
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  • A Study of Multiscale Density Fluctuation Measurements

    Page(s): 458 - 461
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    Intriguing parallels between density fluctuation power versus wavenumber on small (in millimeter) and large (in megaparsec) scales are presented. The comparative study is carried out between fusion plasma measurements and cosmological data. Based on predictions from classical fluid turbulence theory, we argue that our observations are consistent with 2-D turbulence. The similar dependencies of density fluctuations on these disparate scales might indicate that primordial turbulence has been expanded to cosmological proportions. View full abstract»

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  • Solitons in Inhomogeneous Magnetized Negative Ion Containing Plasma With Two Temperature Nonisothermal Electrons

    Page(s): 462 - 468
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (277 KB) |  | HTML iconHTML  

    Considering an inhomogeneous plasma having cold positive and negative ions, together with two temperature nonisothermal electrons in the presence of an external magnetic field, the relevant Korteweg-de Vries (KdV) equation is obtained by adopting a reductive perturbation technique. An investigation on the existence and propagation of the modes in such a plasma model reveals that two types of the modes (fast and slow modes) are possible. The KdV equation is solved for its solitary wave solution for both the modes, and the amplitude and width of the resulting fast and slow solitons are examined under the effects of the concentration and temperature of the electron species at lower temperature, negative ion density together with the strength of the magnetic field, and its obliqueness thetas (the angle between the directions of the magnetic field and the wave propagation). It is observed that the properties of the solitons are significantly modified by the presence of the colder electron species and the nonisothermality of the plasma. Unlike the usual case of negative ion containing plasmas, the rarefactive solitons do not occur in the present plasma model. View full abstract»

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  • A New Concept for the Collection of an Electron Beam Configured by an Externally Applied Axial Magnetic Field

    Page(s): 469 - 480
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    A new concept for the collection of an electron beam, which is configured by an externally applied axial magnetic field, is presented. The two major advantages of this new idea are the significant increase of the collector efficiency and the reduction of the power absorption on the collector wall. To demonstrate the concept, an indicative collector design has been prepared for the hollow electron beam of the European 170-GHz 2-MW coaxial gyrotron for the international thermonuclear experimental reactor. The simulation shows that the efficiency of this advanced collector is more than 90%. View full abstract»

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  • Design and Test of a 6.7-GHz Coaxial Bragg Reflector

    Page(s): 481 - 487
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    A coaxial line periodically loaded by circular disks on the inner conductor is designed and constructed to act as a Bragg reflector in the 4.0-10.0-GHz frequency range. This is achieved by placing ten disks (0.35 cm thick and 6.22 cm in diameter) equally spaced by the periodic distance of 1.8 cm on a coaxial waveguide with inner and outer diameters of 6.90 and 4.22 cm, respectively. Analytical discussion and 2- and 3-D computer simulations demonstrate a bandgap of 5.6 GHz centered at the 6.7-GHz design frequency in close agreement with experiments on a periodic structure made from stainless steel. View full abstract»

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  • Simulations of the Multipactor Effect in Hollow Waveguides With Wedge-Shaped Cross Section

    Page(s): 488 - 493
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    Multipactor discharges in waveguides with wedge- shaped cross section are studied both analytically and by means of numerical simulations. It is shown that similar to the case of a rectangular waveguide, a trapped electron trajectory is possible in a wedge-shaped waveguide; however, this trajectory is unstable with respect to small deviations of launch time and initial position of the electrons. Numerical simulations have been carried out taking into account a spread of the electron initial velocity and the action of the radio frequency magnetic field on the electron motion. The simulation results show that growth of the multipactor avalanche is possible in the wedge-shaped waveguide; however, the multipactor threshold in terms of the transmitted power is higher than for the rectangular waveguide with the same propagation constant and cross-section area. View full abstract»

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  • Plasma Dynamics in Opening Switches

    Page(s): 494 - 497
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    The energy balance of a plasma opening switch in the conduction stage is calculated, in which the dominant process is magnetic field penetration into the plasma volume due to the magnetic piston effect. This mechanism is typical for a microsecond plasma opening switch of the mega-ampere range. It is also shown that the process of magnetic field penetration into the switch plasma is determined by the field diffusion near the magnetic piston, followed by the convective transport of magnetic field in the plasma. This transport is due to the field being frozen-in into the plasma flow behind the shock wavefront, which is formed in the plasma accelerated by the magnetic field pressure. The shock wave propagation leads to the formation of directed plasma flow with falling density, velocity, and pressure in the region between the magnetic piston and the shock wavefront. The following analysis of gas dynamics and related electromagnetic problems reveals the most important processes determining plasma and magnetic field dynamics. View full abstract»

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  • Research on the Inactivation Effect of Low-Temperature Plasma on Candida Albicans

    Page(s): 498 - 503
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    A dielectric barrier discharge was used to generate low-temperature plasma to treat Candida albicans. When the gap spacing was 3 mm, the killing log value (KLV) of the plasma on Candida albicans within 20 s of exposure was more than five, and for 4 and 5 mm gap spacing, the KLV within 25 s was more than five. With the extension of exposure time, the decrease in velocity of the number of living Candida albicans was fastest for the gap spacing of 3 mm, and then for 4 and 5 mm spacing. With 60 s of electric field treatment, as the applied voltage increases, the survival number of Candida albicans has no significant difference from that of the control sample. As for the inactivation mechanism of plasma on Candida albicans on the molecular microbiology side, transmission electron microscopic examination and the results of protein, nucleic acid and K+ detection in the extracellular environment showed that the plasma destroyed the outer structure of Candida albicans. Cytoplasm was also released, which caused Candida albicans to be dead. On the plasma physics side, the role of the electric field during Candida albicans inactivation by plasma is considered negligible. Therefore, charged particles and reactive species in plasma might play a dominant role in the process of destroying the outer structure of Candida albicans. View full abstract»

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  • Nanosecond-Pulsed Uniform Dielectric-Barrier Discharge

    Page(s): 504 - 508
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    The authors report a new nanosecond-pulsed dielectric-barrier discharge (DBD) for sterilization and other medical applications. In the literature, several discharges have been reported, with pulse durations on the order of hundreds of nanoseconds. In this paper, a novel pulsed DBD has been developed, with only few tens of nanosecond pulsewidths working uniformly over large range of electrode gap distance in air under atmospheric pressure. View full abstract»

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  • Influence of Nonthermal Plasma Reactor Type on  \hbox {CF}_{4} and \hbox {SF}_{6} Abatements

    Page(s): 509 - 515
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    Dielectric barrier discharge (DBD) and packed-bed reactor (PBR) are two of the commonly used nonthermal-plasma (NTP) reactors. In this paper, these two reactors are applied to remove two perfluorocompounds (PFCs), i.e., CF4 and SF6, which are extensively used in semiconductor- and liquid-crystal-display-manufacturing industries. Experimental results indicated that PBR constructed by packing dielectric pellets (chemical compositions: CuO 64%, ZnO 24%, Al2O3 10%, and MgO 2% by weight) inside the DBD reactor achieved a higher CF4 removal efficiency and a lower SF6 removal efficiency than that of the DBD reactor. In other words, different behavior between CF4 and SF6 removal efficiencies achieved with two different types of NTP reactors was found in this paper. To elucidate this interesting finding, the influences of the discharge power, the reactor temperature, the catalytic effect, the nature of pollutants, and the plasma characteristics of DBD and PBR were investigated. It is found that the last two factors are mainly responsible for the interesting finding. At the same discharge gap, it is well known that PBR possesses higher mean electron energy than nonpacked plasma reactor (like DBD). Nevertheless, the dissociative attachment reaction of SF6 : SF6 + e rarr SF5 - + F plays an important role for SF6 removal at low-electron-energy region. Therefore, a nonpacked plasma reactor is more suitable for SF6 removal; on the contrary, a PBR with higher mean electron energy is favorable for CF4 abatement. The finding provides useful information on selecting an appropriate NTP reactor for removing a specific PFC. View full abstract»

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  • Methanol Synthesis Over Cu and Cu-Oxide-Containing  \hbox {ZnO}/\hbox {Al}_{2}\hbox {O}_{3} Using Dielectric Barrier Discharge

    Page(s): 516 - 518
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    Initially developed for more than 20 years ago, the copper over zinc and aluminum oxide (ZnO/Al2O3) catalyst system is used for low-pressure methanol synthesis. Recently, the Cu/ZnO/Al2O3 (CZA) was shown to be active in a dielectric-barrier discharge (low-temperature plasma). In this paper, the investigation on the copper as the active site of the catalyst was discussed on the basis of experimental results and its characterization analysis. The catalyst was attempted to aid the reaction performance of partial oxidation of methane in order to produce methanol. All CZA-based catalysts were successful in increasing methanol selectivity, and the Cu oxide performed better than a metallic-copper catalyst. View full abstract»

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  • Dynamic Characterization of a UV Fluorescent Lamp

    Page(s): 519 - 523
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    Dynamic modeling of an ultraviolet (UV) fluorescent lamp has been addressed in this paper. Based on a recently developed lamp model, a semiempirical modeling technique has been applied for dynamic modeling of a UV fluorescent lamp. In the modeling stage, simple electrical measurements have been used. In the proposed mathematical model, model parameters have been determined from electrical voltage and current measurements of the lamp under AC operation at operating frequency. In order to calculate the model constants, the lamp data from lamp manufacturers have not been required. Once the model constants have been determined at 50-Hz main fundamental operating frequency, with the same set of parameters, the model can predict the lamp terminal characteristics accurately under different operating conditions. Different operating frequencies, such as low-, medium-, and high-frequency operations, have been considered, and good simulation results have been achieved when the lamp power has been reduced to different operating levels. The simulation results are confirmed by laboratory experiments. View full abstract»

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  • Movement Simulation of Three-Phase Short-Circuit Arcs on Distribution Lines Based on the Coupling of Magnetic Field and Motion

    Page(s): 524 - 529
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    Three-phase short-circuit arcs often cause the breakage of covered conductors on distribution lines, and their movement processes have become an important problem in power-distribution systems. This paper presents the studies on the movement simulation of the three-phase short-circuit arcs. Based on the latest electric arc model and the coupling of magnetic field and motion, this paper develops the procedure to simulate the movement processes of the arcs. Simulation results show that the arcs have different movement directions and behaviors, which are in agreement with the experimental phenomena. This paper is very helpful to design an effective device that prevents the arcs from causing the breakage of the conductor and the damage of the insulator. View full abstract»

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  • Hypersonic MHD Interaction on a Conical Test Body With a Hall Electrical Connection

    Page(s): 530 - 541
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    The MHD interaction around a conical test body in a hypersonic argon flow was experimentally investigated. The aim of the experiment was to produce a database to be used for the validation of numerical codes for the analysis and simulation of the magnetofluid dynamics in hypersonic flows. In these experiments, the flow was obtained in the High-Enthalpy Arc-heated hypersonic wind Tunnel of Alta, Pisa, Italy. Speeds at Mach 6 were reached. In this experiment, the flow and plasma characteristics have been determined. The MHD interaction was obtained in the shock layer of a conical test body placed at the exit of the hypersonic nozzle. The realized electrical configuration allowed the enhancement of the effect of the MHD interaction on the plasma parameters. This was done by utilizing the Hall field to generate the MHD interaction and by short-circuiting the Faraday current inside the plasma of the shock layer. The magnetic-flux density was produced by an array of three magnets located in the test body. Test runs were performed at three different stagnation pressures. Fluid-dynamic, electrical, and optical observations have been done. The experiment showed a large effect of the MHD interaction on the values of the measured quantities. In order to have a test body that is entirely contained in the region where a uniform hypersonic flow has been measured, a test body of smaller size has been constructed and tested. The results obtained in this case confirm the results of the tests with the larger body. View full abstract»

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  • The Quasi-Perpendicular Bow Shock as a Temporal Trapping Barrier and Accelerator of Magnetospheric Particles

    Page(s): 542 - 553
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    The bow shock has been studied so far, mostly as a boundary that influences the particles that are incident from the upstream region (of solar origin). In this paper, we provide, for the first time, observational evidence from the energetic-particle-experiment and the charged-particle-measurement-experiment instruments onboard the IMP-8 spacecraft, showing that ions leaking from the magnetosphere, during storms or substorms, are affected by the quasi-perpendicular (Q-P) bow shock and can be temporally trapped just downstream from the shock in a magnetic configuration opposite to the magnetic mirror. The observations from three representative event periods examined in this paper suggest that magnetospheric energetic ( keV) ions show general flows along the field lines in the direction from the magnetosheath toward the interplanetary space, in both sides of the shock (up- and downstream), and characteristic cross-field anisotropic distributions just downstream from the shock, consistent with a ldquotrapped population.rdquo In a series of successive bow-shock crossings within several hours, the IMP-8 spacecraft observed intensity gradients toward the magnetosheath, which strongly suggest a spatial modulation of magnetospheric ion fluxes at the Q-P bow shock. Highest peaks of ion intensities and a very hard spectrum in the energy range between 100 and 400 keV were observed just at the shock front, which suggest acceleration of magnetospheric particles during their temporal trapping at the bow shock. The observations near the Earth's bow shock examined in this paper are well explained in terms of the shock drift acceleration (SDA) theory for magnetospheric particles reaching the bow shock. The phenomenon discussed here, an apparent temporal trapping-and acceleration-of escaped magnetospheric ions at the Earth's bow shock, appears to be an important mechanism that influences the particle distributions near the Earth's bow shock and may have important applications to ot- her shocks in our solar system (planetary, heliospheric, interplanetary, and corotating shock waves) and the interstellar medium (supernova shocks). View full abstract»

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  • Employing dust particle chains as a wakefield diagnostic

    Page(s): 554 - 558
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    Dust particles often form vertical chains due to the influence of the wakefield produced by streaming ions in the plasma sheath produced within an experimental dusty plasma. These particle chains are proving to be a unique diagnostic tool for investigating the physics behind the basic properties of the ion wakefield in the plasma sheath. In this paper, an experimental method is presented for investigating the wakefield employing a new oscillation technique designed to perturb a two-particle vertical chain. Damped attenuated oscillations are generated via an external dc bias on the lower electrode. A fast Fourier transform is used to produce a spectrum of the oscillation data collected, and a center of mass oscillation is identified. View full abstract»

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  • Special issue on Advance in Plasma Processing for Semiconductor Manufacturing

    Page(s): 559
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  • Special issue on Plasma Science High-Power X-Ray Flash Radiography Sources

    Page(s): 560
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  • Special issue on High Power Particle Beams (BEAMS2008)

    Page(s): 561
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  • Leading the field since 1884 [advertisement]

    Page(s): 562
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  • IEEE copyright form

    Page(s): 563 - 564
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  • IEEE Transactions on Plasma Science Information for authors

    Page(s): C3
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  • Affiliate Plan of the IEEE Nuclear and Plasma Sciences Society [advertisement]

    Page(s): C4
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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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