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Plasma Science, IEEE Transactions on

Issue 6  Part 2 • Date June 2009

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Displaying Results 1 - 18 of 18
  • Table of contents

    Page(s): C1
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  • IEEE Transactions on Plasma Science publication information

    Page(s): C2
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  • Enhanced Superradiant Smith–Purcell Radiation in a Three-Mirror Quasi-Optical Cavity

    Page(s): 1057 - 1061
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (858 KB) |  | HTML iconHTML  

    Smith-Purcell (SP) radiation has been widely used for the generation of radiation from microwave to optical frequencies, and it has recently become an attractive candidate for a Terahertz (THz) radiation source. Superradiant SP radiation has sharp angular and spectral distributions due to the bunching of the electron beams, and a three-mirror quasi-optical cavity (TMQOC) which has selectivity at both angles and frequency has been designed to enhance this process. The radiation power over 700 W/m at the 99.4 GHz are obtained through using a 45-keV 4-A/m beam skip over a metal grating with period, width, and depth are 1.6, 1.0, and 0.8 mm, respectively. This results show that the TMQOC can greatly enhance the superradiant SP radiation, and one may utilize this effect to design a compact, tunable, and powerful THz radiation source working at room temperature. View full abstract»

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  • A New Reflector Designed for Efficiency Enhancement of CRBWO

    Page(s): 1062 - 1068
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    A new reflector consisting of the inner and outer conductors is introduced into the coaxial relativistic backward wave oscillator for the first time through optimizing the distribution of the electric field and distance between the reflector and the slow wave structure. The improved reflector can excite the superposition of the axial electric fields to benefit the electron premodulation. The improved reflector is investigated by the particle-in-cell numerical simulation. A result of 43% power efficiency, 1.0-GW power, and 7.3-GHz operation frequency is obtained under the diode voltage 530 kV and current 4.4 kA. View full abstract»

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  • Plasma Cathode for a Short-Pulse Dielectric Wall Accelerator

    Page(s): 1069 - 1077
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (478 KB) |  | HTML iconHTML  

    The Beam Research Program at Lawrence Livermore National Laboratory is continuing development of the dielectric wall accelerator (DWA), a type of accelerator which uses stacked pulse-forming lines (PFLs) to apply an accelerating field directly to the beam through a nonconducting vacuum boundary. Here, we report operation of a DWA as an electron diode using a surface flashover plasma cathode. Peak perveances in excess of 6 times 10-6A/V3/2 were measured, with current extraction and pulse train format depending on flashover source timing and PFL switching speed. View full abstract»

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  • Influence of Electrode Characteristics on DC Point-to-Plane Breakdown in High-Pressure Gaseous and Supercritical Carbon Dioxide

    Page(s): 1078 - 1083
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    Discharges in supercritical conditions is a new field in plasma science. The supercritical phase has distinctive properties that may allow for unique plasma processing applications. In this paper, we study plasma generation in a point-to-plane geometry in the micrometer scale. The effects of needle characteristics, including tip diameter and plane electrode surface roughness, on discharge initiation are studied. The influence of pressure, temperature, and fluid density on breakdown voltage and reduced breakdown electric field are also investigated. View full abstract»

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  • A Compact Design for High Voltage Direct Current Circuit Breaker

    Page(s): 1084 - 1091
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (937 KB) |  | HTML iconHTML  

    The absence of current-zero points in the direct current (DC) waveform of high voltage DC (HVDC) circuit breakers makes the interruption process more severe than the case of conventional AC networks with sinusoidal currents. In this way, in the current HVDC networks, a parallel precharged capacitor is inserted to inject the reverse current into the interruption chamber of the vacuum circuit breaker and create the artificial current-zero points. In this paper, a novel method for reverse current injection has been proposed. In this method, two separate helical flux compression generators (HFCGs) have been applied to generate the reverse current and an intense axial magnetic field (AMF), respectively. Numerical simulation of high-current vacuum arc (VA) in the presence of very strong AMF has been presented. For this purpose, the magnetohydrodynamic equations describing the behavior of the VA are coupled to a simple circuit analysis and the previously developed multiphysics model of HFCG. The results indicate that the explosively driven current injection set can make current-zero points properly in a typical HVDC network and lead to successful interruption of fault current. This method needs much less volume and cost in comparison to the parallel precharged capacitor sets. View full abstract»

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  • An Interpretation of Langmuir Probe Floating Voltage Signals in a Cutting Arc

    Page(s): 1092 - 1098
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    An experimental study of the electrostatic probe floating voltage signals in a cutting arc and its physical interpretation in terms of the arc plasma structure is reported. Sweeping electrostatic probes have been used to register the local floating potential and ion current at 3.5 mm from the nozzle exit in a 30-A arc generated by a high energy density cutting torch with a nozzle bore radius of 0.5 mm and an oxygen mass flow rate of 0.71 g ldr s-1. It is found that the floating potential signal presented a central hump with duration almost similar to that corresponding to the ion current signal but having also lateral wings with much larger duration. Capacitive coupling between the probe and the conducting body of the nozzle and arc as a source for the floating potential signal was discarded. It is assumed that the hump in these probe voltage signals results from the presence of an electrostatic field directed in the radial direction outward the arc axis that is caused by thermoelectric effects. The probe floating voltage signal is inverted using the generalized Ohm's law together with the Saha equation, thus obtaining the radial profiles of the temperature, particle densities, radial electric field, and potential of the plasma at the studied section of the arc. The resulting temperature and density profiles derived from our interpretation are in good agreement with the data published elsewhere in this kind of high-pressure arcs. There is not a straightforward connection between the measured hump amplitude in the floating signal (ap4 V) and the derived increase in the plasma potential between the arc edge and the arc center ( ap10 V), due to the global zero current balance condition established by the finite size of the probe. It is shown, however, that the probe takes a floating potential value close to that corresponding to the plasma temperature at the probe center. View full abstract»

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  • Investigation of the Scattering Efficiency in Doppler Reflectometry by Two-Dimensional Full-Wave Simulations

    Page(s): 1099 - 1103
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB) |  | HTML iconHTML  

    Two-dimensional full-wave simulations of Doppler reflectometry in slab and curved geometries have been carried out with the finite-difference time-domain code IPF-FD3D. The goal is to find the instrument response function of the reflectometer that allows the recovery of the poloidal plasma-density-fluctuation-wavenumber spectrum by Doppler reflectometry at different angles of incidence. Apart from nonlinearities caused by high fluctuation levels, the scattering process is found to be strongly dependent on the angle of incidence on the cutoff layer, the beam parameters, and the plasma-density gradient length. In addition, the code was applied to the actual geometry of an ASDEX-Upgrade plasma. View full abstract»

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  • CAD of RF Windows Using Multiobjective Particle Swarm Optimization

    Page(s): 1104 - 1109
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (705 KB) |  | HTML iconHTML  

    In this paper, computer-aided design (CAD) of two types of RF windows, namely, double-disk RF window and pillbox-type RF window, is presented for use in high-power microwave/millimeter-wave sources. The design of double-disk RF window was carried out for 42-GHz band (TE0,3 mode) and 170-GHz band (Gaussian mode), while the design of pillbox-type RF window was carried out for 2.856-GHz band. The requirement for the design of RF window is to minimize the reflections with exact matching at desired resonant frequency. In the present approach, a scattering-matrix code was invoked with recently developed particle swarm optimization (PSO) method in order to optimize the geometrical parameters of the window. Multiobjective optimizations using PSO have been used to achieve optimized tradeoff between matching of desired resonant frequency and minimizing the power reflections in the desired band of operation. View full abstract»

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  • Peculiar Properties of Rodlike Particles Levitating in the Sheath of an RF Plasma

    Page(s): 1110 - 1115
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (359 KB) |  | HTML iconHTML  

    The motion and the equilibrium position of cylindrical particles in a radio-frequency plasma have been interpreted by dipole and quadrupole interaction in two experimental situations. Particles levitating in steady state are aligned either horizontal or vertical in accordance with the theory. However, particles have been observed tilted w.r.t. the vertical when acquiring a horizontal velocity from sailing in the ion stream. Particles in defect of charge fall on the lower electrode, mainly vertically, and build complex ldquowoodyrdquo structures. View full abstract»

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  • Special issue for Selected Paper from the 23rd Symposiium on Fusion Engineering (SOFE 2009)

    Page(s): 1116
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  • Special issue on z-pinch plasmas

    Page(s): 1117
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  • Special issue for invited papers from the 36th International Conference on Plasma Science 2009

    Page(s): 1118
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  • Special issue on the physics of dusty plasmas

    Page(s): 1119
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  • Why we joined ... [advertisement]

    Page(s): 1120
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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

    Page(s): C4
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Aims & Scope

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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Meet Our Editors

Editor-in-Chief
Steven J. Gitomer, Ph.D.
Senior Scientist, US Civilian Research & Development Foundation
Guest Scientist, Los Alamos National Laboratory
1428 Miracerros Loop South
Santa Fe, NM  87505  87505  USA
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