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Plasma Science, IEEE Transactions on

Issue 11  Part 3 • Date Nov. 2012

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  • Table of Contents

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

    Page(s): C2
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  • The Rod Degenerate Plasma-Rippled-Wall Waveguide and Its Excitation by Relativistic Electron Beam Injection

    Page(s): 3029 - 3036
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB) |  | HTML iconHTML  

    The dispersion relation of electromagnetic waves in a rippled-wall waveguide with a degenerate plasma column protected by an annular dielectric layer is theoretically investigated. By injecting a thin annular relativistic electron beam (TAREB) in the region between dielectric and metallic cylinders in the aforementioned configuration as an energy source, the excitation of terahertz (THz) electromagnetic waves is investigated. Also, the dependence of dispersion relation and time growth rate on the radius of the dielectric, the corrugation amplitude, and period is studied. Furthermore, it is found that the presence of the degenerate plasma rod in the rippled-wall waveguide leads to obtain high-frequency modes in the THz frequency region. Finally, the electric-field profiles in this waveguide are plotted. View full abstract»

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  • An Efficient, Electrically Small, Three-Dimensional Magnetic EZ Antenna for HPM Applications

    Page(s): 3037 - 3045
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1401 KB) |  | HTML iconHTML  

    Metamaterial (MTM)-inspired antennas leverage techniques that have been developed over the past decade for designing artificial materials whose electromagnetic properties can be tailored to specific applications. One of the key features of the MTM-inspired antennas is their ability to motivate electrically small antenna designs through planar and volumetric loadings of space with resonant parasitic capacitive and inductive structures. In a previous work, we developed the magnetic EZ antenna as a resonant antenna that operates below ka = 0.5. In this paper, we adapt the magnetic EZ antenna concept for use with high-power mesoband quarter-wave oscillator microwave sources that can operate with hundreds of megawatts of peak power and charge voltages in excess of 100 kV in the ultrahigh frequency (500-650 MHz) and demonstrate their performance with charge voltages up to 10 kV. The principal challenges that were overcome in this effort include field management to prevent undesired breakdown and capacitive isolation to decouple the EZ antenna from the source during the charge phase. Antenna design, modeling, and experimental verification are presented here, demonstrating an operating EZ antenna/source system at 510 MHz with antenna ka = 0.436 . The results demonstrate that the EZ antenna is a viable antenna to consider when traditional high-power microwave antennas are too large to be integrated into a given platform. View full abstract»

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  • All Cavity-Magnetron Axial Extraction Technique

    Page(s): 3046 - 3051
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    A compact axial π-mode extraction scheme, which is based on a patent by Greenwood, is demonstrated in conjunction with the UM/L-3 relativistic magnetron using the particle-in-cell code ICEPIC. Cases utilizing Greenwood's extraction technique were compared with power extraction using traditional radial waveguides. Average extracted power values in all simulated axial cases were found to be within +/-6.5% of the radial cases. Cases utilizing 85 ° and 90° sector waveguides were found to have efficiencies up to ten percentage points higher than the radial case. The best performing case was found to use a set of three axially oriented 90 ° sector waveguides, shorted on the upstream side, with the short located 15 cm from the center of the magnetron apertures. View full abstract»

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  • Design of Single-Disk RF Window for High-Power Gyrotron

    Page(s): 3052 - 3055
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1206 KB) |  | HTML iconHTML  

    In this paper, the electrical design of the water-edge-cooled single-disk chemical-vapor-deposited-diamond window for the 120-GHz 1-MW gyrotron has been carried out using the CST Microwave Studio. The return loss (S11) and transmission loss (S21) of the 120-GHz gyrotron window have been obtained as -37.3 dB and -0.04 dB, respectively. The thermal analysis of the RF window for the 1-MW gyrotron has also been carried out using ANSYS software and discussed in this paper. The thermal analysis of the window, during extreme case of operation, has been carried out. The temperature range on the disk surface has been found to be 50°C-150°C. View full abstract»

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  • Numerical Analysis of a Ka-Band Third-Harmonic Magnetron-Type Slotted Peniotron

    Page(s): 3056 - 3061
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB) |  | HTML iconHTML  

    In this paper, we have numerically investigated the operating characteristics of a ka-band magnetron-type slotted peniotron. The third-harmonic four-vane peniotron operates in a circularly polarized 2π mode. The MAGIC3D simulation shows that, with proper acceleration voltage, beam current, and axis-encircling electron beam, the peniotron is predicted to generate a pure 2π-mode electromagnetic wave with output power of 45 kW at 29.7 GHz and conversion efficiency of up to 66.7%. Critical characteristics such as the start oscillation time, output power, and conversion efficiency have been also well examined; and it is shown that a careful control of the beam current and the acceleration voltage is important for the device performance. View full abstract»

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  • Reduction of the Multipactor Threshold Due to Electron Cyclotron Resonance

    Page(s): 3062 - 3069
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (671 KB) |  | HTML iconHTML  

    Single-surface multipactor on metal surfaces is studied in the case when the microwave electric field is superimposed on a dc electric and a permanent magnetic field. Based on a simple analysis of the electron motion, it is predicted that considerable reduction in the multipactor threshold is possible when the electron cyclotron frequency is equal to the microwave field frequency and the permanent magnetic field has the proper orientation with respect to the metal surface. The prediction is confirmed by numerical simulations, and some experimental indications of the reduced multipactor threshold are also presented. View full abstract»

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  • Frequency and Polarization Transformer (10 GHz to 1000 GHz): Interaction of a Whistler Wave With a Collapsing Plasma in a Cavity

    Page(s): 3070 - 3078
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (984 KB) |  | HTML iconHTML  

    This paper investigates the interaction of an electromagnetic wave with a time-varying (collapsing) magnetoplasma medium. Finite-difference time-domain techniques are used to evaluate the effects of collapsing a magnetized plasma in a perfect electric conductor cavity. The evaluation is performed in one dimension to simplify the analysis and highlight the effects on propagation due to the time-varying plasma parameters. The interaction of an electromagnetic wave with a time-varying medium is governed by the property of conservation of the wavenumber. This property can be utilized to construct a frequency transformer. It is shown that switching off the ionization source and creating a decaying magnetoplasma medium in a cavity will upshift the source frequency of 10-1000 GHz for the appropriate choice of initial magnetoplasma parameters. The electric field of the output wave is comparable with that of the source wave. Moreover, the switching angle can alter the polarization of the output wave. View full abstract»

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  • Simulation of Coherence Phenomenon

    Page(s): 3079 - 3086
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    This study gives more details on the coherence (and “chirping”) phenomenon occurring in high-power microwave generation by corona and spark channel discharges in air. Simulation is compared with the experimental evidence. View full abstract»

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  • 300-kA Fast Linear Transformer Driver Stage

    Page(s): 3087 - 3092
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (852 KB) |  | HTML iconHTML  

    A modular linear transformer driver (LTD) is a novel fast-discharge high-pulsed power source for primarily stored energy. In LTDs, a large number of stages (or cavities) can be connected in series or in parallel conveniently to directly generate high power pulses of 50-200 ns with the required voltage or current. This paper introduces an LTD stage developed by us recently. This LTD stage consists of 14 bricks in parallel. Each brick contains two 40-nF capacitors and a compact multigap gas spark switch in series. The switch is a modification of our original version, and the diameter and the height of which have been reduced to 98 and 127 mm, respectively. The circuit model of this stage is established in PSPICE, and its output parameters are obtained through simulation. Driving a rough-matched resistive load of 0.27 Ω, its output current peak is 300 kA with an overall rise time of about 110 ns at a charged voltage of the capacitors of about ±90 kV, agreeing well with its simulation result. View full abstract»

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  • Electrodynamic Simulation of High-Voltage Peaking Switch

    Page(s): 3093 - 3099
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (853 KB) |  | HTML iconHTML  

    This paper discusses the modeling of a peaking switch to study the reduction in rise time for the subnanosecond duration pulses. The effect of the various shapes of input pulse, inductance, and interelectrode distance on the output voltage and wave shape is discussed in this paper. The modeling has been carried out using the electromagnetic and microwave modeling software of Computer Simulation Technology. View full abstract»

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  • Drift-Step-Recovery Diode Characterization by a Bipolar Pulsed Power Circuit

    Page(s): 3100 - 3104
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    A stack of drift- step-recovery diodes (DSRDs) can produce high-voltage pulses with a rise rate of the order of 1 kV/ns. Their building blocks, i.e., the DSRD dies, are designed and manufactured at Soreq Nuclear Research Center based on silicon epitaxial layers. A characterization circuit for DSRDs is presented. The circuit features a power MOSFET, which serves to pump the DSRD in the forward direction and then to pulse it in the reverse direction, and a bias voltage source to balance the forward pumping current with respect to the reverse discharge. Placing the DSRD in series between the MOSFET and the load results in temporal and polarity separation of the MOSFET and DSRD pulses at the load, thus allowing viewing of the net DSRD signal. High-voltage probes are employed to measure the MOSFET and load voltages. Based on this measurement, we formulate the voltage and current extraction of the circuit signals. A 1-ns 190-V epi-Si DSRD die was characterized by this circuit. We show that the DSRD pulses when its reverse discharge is equal to the forward charge, as expected. The DSRD switching loss was measured. An accurate 98% energy balance, which includes the input and output energies with respect to the MOSFET and DSRD switching losses, was obtained. The relationship between the bias voltage, the pumping current, and the main supply voltage is provided. The experimental results are supported by a numerical simulation of the DSRD in the circuit using the Synopsys technological computer-aided design incorporated with a SPICE solver. View full abstract»

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  • Initiation Mechanism of a Negative Nanosecond Pulsed Discharge in Supercritical Carbon Dioxide

    Page(s): 3105 - 3115
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1573 KB) |  | HTML iconHTML  

    This paper deals with the initiation mechanism of a negative nanosecond pulsed discharge in supercritical (SC) carbon dioxide that was examined in detail using Schlieren and photomultiplier techniques. A negative pulsed voltage with a rise time of about 90 ns and half-width of 410 ns was applied to the point electrode. The experimental results show that: 1) The negative primary streamer was of a form quite different than that of a positive one: a bushlike negative streamer and a filamentlike positive streamer; 2) a drastic change in the density dependence of streamer initiation voltage appeared around the subcritical phase in the characteristics for streamer initiation voltage versus medium density; and 3) a shock wave of speed 1-1.5 Mach began growth following a delay of around 50 ns from the streamer initiation. It was predicted from the analysis of the experimental results that the drastic change in the streamer initiation voltage versus medium density characteristics may be due to a transition between the two types of generation mechanisms of the initial electron: electron detachment from negative ions in the gas phase and field electron emission from the point electrode in the SC and liquid phases. The shock wave was presumed to be caused by thermal relaxation of the vibrational energy in carbon dioxide molecules in a decay process of the primary streamer. View full abstract»

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  • Compact Relativistic Magnetron With Gaussian Radiation Pattern

    Page(s): 3116 - 3120
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (911 KB) |  | HTML iconHTML  

    A compact A6 relativistic magnetron is proposed which operates in the π-mode and whose radiation is extracted axially as a TE11 mode through a cylindrical waveguide with the same cross section as that of the anode block. This radiated mode is similar to a Gaussian microwave beam. The advantages of this magnetron include the minimal volume of the applied magnetic field and, as a consequence, the proximity of the electron dump to the anode block for the electrons leaking from the interaction space that minimizes both the diameter and the axial length of the magnetron. By using MAGIC particle-in-cell (PIC) simulations, we demonstrate the possibility of generating a Gaussian radiation pattern with power of about 0.5 GW when the applied voltage is 350 kV. This compact magnetron is easier to implement than the magnetron with diffraction output (MDO), although with reduced efficiency. View full abstract»

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  • Matching Conditions of the RKA Input Cavity Based on the Cavity Absorbing Property Under Intense Beam Loading

    Page(s): 3121 - 3126
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB) |  | HTML iconHTML  

    Based on the equivalent circuit model, expressions for the power absorbed by an externally coupled input cavity of the relativistic klystron amplifier in both cold and hot cavities are derived. The matching conditions are clearly concluded from the expressions for the two cases. Under the guide of the matching conditions, the expressions are applied in the determination of the beam-loaded resonant frequency and the beam-loaded quality factor of the cavity loaded by the intense relativistic electron beam in a particle-in-cell simulation-aided approach presented in this paper. View full abstract»

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  • Announcement: Special Issue for Selected Papers from EAPPC/BEAMS 2012 IEEE Transactions on Plasma Science (October 2013)

    Page(s): 3127
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  • Open access

    Page(s): 3128
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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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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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