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Plasma Science, IEEE Transactions on

Issue 4 • Date Aug. 2003

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Displaying Results 1 - 10 of 10
  • Examining by the Rayleigh-Fourier method the cylindrical waveguide with axially rippled wall

    Page(s): 752 - 764
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1055 KB) |  | HTML iconHTML  

    Axially corrugated cylindrical waveguides with wall radius described by R0(1+εcos2πz/L), where R0 is the average radius of the periodically rippled wall with period L and amplitude ε, have been largely used as slow-wave structures in high-power microwave generators operating in axisymmetric transverse magnetic (TM) modes. On the basis of a wave formulation whereby the TM eigenmodes are represented by a Fourier-Bessel expansion of space harmonics, this paper investigates the electrodynamic properties of such structures by deriving a dispersion equation through which the relationship between eigenfrequencies and corrugation geometry is explored. Accordingly, it is found that for L/R0≥1 a stopband always exists at any value of ε; the condition L/R0=1 gives the widest first stopband with the band narrowing as the ratio L/R0 increases. For L/R0=0.5 the stopband sharply reduces and becomes vanishingly small when ε<0.10. Illustrative example of such properties is given on considering a corrugated structure with L/R0=1,R0=2.2 cm, and ε=0.1, which yields a stopband of 1.5-GHz width with the central frequency at 8.4 GHz; it is shown that in a ten-period corrugated guide, the attenuation coefficient reaches 165 dB/m, which makes such structures useful as an RF filter or a Bragg reflector. It is also discussed that by varying L/R0 and ε we can find a variety of mode patterns that arise from the combination of surface and volume modes; this fact can be used for obtaining a particular electromagnetic field configuration to favor energy extraction from a resonant cavity. View full abstract»

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  • Low-power microwave plasma source based on a microstrip split-ring resonator

    Page(s): 782 - 787
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (527 KB)  

    Microplasma sources can be integrated into portable devices for applications such as bio-microelectromechanical system sterilization, small-scale materials processing, and microchemical analysis systems. Portable operation, however, limits the amount of power and vacuum levels that can be employed in the plasma source. This paper describes the design and initial characterization of a low-power microwave plasma source based on a microstrip split-ring resonator that is capable of operating at pressures from 0.05 torr (6.7 Pa) up to one atmosphere. The plasma source's microstrip resonator operates at 900 MHz and presents a quality factor of Q=335. Argon and air discharges can be self-started with less than 3 W in a relatively wide pressure range. An ion density of 1.3×1011 cm-3 in argon at 400 mtorr (53.3 Pa) can be created using only 0.5 W. Atmospheric discharges can be sustained with 0.5 W in argon. This low power allows for portable air-cooled operation. Continuous operation at atmospheric pressure for 24 h in argon at 1 W shows no measurable damage to the source. View full abstract»

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  • The estimation of static breakdown voltage for gas-filled tubes at low pressures using dynamic method

    Page(s): 776 - 781
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (383 KB) |  | HTML iconHTML  

    The paper presents experimental data of breakdown voltage as a function of voltage increase rate for nitrogen-filled tubes at pressures of 133 and 399 Pa. By fitting this data using polynomial approximation, static breakdown voltages for these tubes were estimated. The influence of voltage increase rate, voltage step, time interval between successive voltage step, and relaxation time on the static breakdown voltage was analyzed. The processes in gas advanced during breakdown were also analyzed, as well as their influence on the breakdown voltage. View full abstract»

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  • Time-dependent one-dimensional modeling of pulsed plasma discharge in a capillary plasma device

    Page(s): 729 - 735
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (529 KB) |  | HTML iconHTML  

    The capillary plasma device is a relatively new technology for producing plasma vapor after ablating the capillary bore wall using high-magnitude pulsed electric power. Time-dependent behavior of the plasma flow in the capillary plasma device is investigated numerically by solving the radially averaged one-dimensional inviscid conservative equations of gas dynamics using LCPFCT gas dynamics code, which utilizes flux corrected transport (FCT) in solving generalized continuity equations. Joule heating and the mass ablation from the bore wall are incorporated in the numerical modeling. The thermodynamic and transport properties of the plasma are evaluated based on the assumption of local thermodynamic equilibrium and weakly nonideal plasma. At the bore exit, the sonic boundary condition is applied due to the thermally choked flow. The computational results yield the details of the plasma discharge behavior in the capillary bore including high-pressure and high-temperature plasma conditions at the bore exit. The plasma composition at the bore exit shows the significant ionization of the polycarbonate atomic species to the first ionization level, but the second ionization is found to be negligible. Computed mass ablation from the bore wall agrees well with the experimentally determined mass loss, but the assumption of blackbody radiation from the bulk plasma yields the overprediction in mass ablation. View full abstract»

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  • Measurement of the current density profile of a pulsed electron beam for surface treatment

    Page(s): 788 - 792
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (447 KB) |  | HTML iconHTML  

    The current-density profile is a critical information when predicting or analyzing material surface treatment with electron beams. In this paper, a knife-edge technique was implemented in order to retrieve such profile for a pulsed-glow-discharge electron gun used for metal surface treatment. It was found that the beam has basically two components, one that is focused, and another that remains unfocused (homogeneous). The focused portion develops after the peak current is reached and remains focused for longer periods than predicted by previous models. The obtained profiles where used to determine the energy density (fluence) delivered to the target in order to understand the different patterns obtained for SAE4140 steel samples. View full abstract»

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  • Modeling of short-gap ESD under consideration of different discharge mechanisms

    Page(s): 736 - 744
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (533 KB) |  | HTML iconHTML  

    Simulation of short gap electrostatic discharge (ESD) in air needs to consider two processes: a surface process and an avalanche process. Two models, a phenomenological approach and a physical approach, considering both discharge processes are proposed for the simulation of short-gap ESD. A new mathematical derivation for the modeling of the surface process is discussed in detail. A new technique to combine surface and avalanche process models is described. Measured and simulated data based on short-gap ESD are provided and compared. Advantages and drawbacks of the proposed models are discussed. Attained results should help to optimize ESD testing. View full abstract»

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  • Stability of the envelope evolution of a cold-fluid corkscrewing elliptic beam in a uniform-focusing magnetic field

    Page(s): 765 - 770
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (465 KB) |  | HTML iconHTML  

    The envelope oscillations of a cold-fluid corkscrewing elliptic beam in a uniform-focusing magnetic field are studied. In particular, by linearizing the generalized beam envelope equations, the eigenmodes of small-amplitude envelope oscillations are calculated for a cold-fluid corkscrewing elliptic beam oscillating about its equilibrium. All of the eigenmodes are shown to be stable. View full abstract»

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  • Pulse shaping for optimal energy deposition with a cold cathode electron gun for surface treatment

    Page(s): 771 - 775
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (430 KB) |  | HTML iconHTML  

    A pulse-forming network is added in the discharge circuit of a cold-cathode electron gun that gives rise to an improved shape of the pulse, making it closer to the ideal square pulse needed for optimal energy deposition in material surface treatments. It is shown that the circuit can be very accurately designed by means of simulations using empirical equations for the nonlinear response of the gun. Due to the particular nonlinear behavior of the current-voltage in these guns, and the strong nonlinear self-focusing of the beam, the adequate shaping of the temporal profile of the discharge becomes relevant to the efficiency of the system. The effect of using a new discharge circuit for a glow-discharge pulsed electron gun for materials processing is analyzed, showing an almost two-fold improvement in the efficiency of the system regarding the fraction of the energy not wasted in long pulse tails. View full abstract»

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  • Conical electric gun: a new hypervelocity macroparticle launcher based on the Munroe effect

    Page(s): 725 - 728
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (429 KB) |  | HTML iconHTML  

    The Munroe effect is a cumulative hydrodynamic flow where a conically shaped solid liner is imploded on to its axis of symmetry and the oblique impact results in formation of a hypervelocity jet. Acceleration of conical liners using chemical explosives has been well known in armament technology and acceleration using laser ablation is being investigated in connection with inertial confinement fusion. In this paper, we discuss the acceleration of a solid liner using an electrically exploded conductor in the fashion of an electric gun. Fabrication methods and experimental investigations using fast framing photography are described. Scaling behavior expected from such flows is derived in a simple, approximate model. Possible applications are described. View full abstract»

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  • Study of the effects of ECH power and pulse length on preionization in the KSTAR Tokamak

    Page(s): 745 - 751
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (562 KB)  

    In this paper, we present the results of a study of the preionization effects for the Korean Superconducting Tokamak Advanced Research (KSTAR) tokamak (R0=1.8 m, a=0.5 m, κ=2, δ=0.8, BT=3.5 T, Ip=2 MA, Tpulse=300 s) that is under construction by the Korea Basic Science Institute (KBSI). The preionization will be given by the Electron Cyclotron Heating (ECH) System with an 84-GHz 500-kW gyrotron tube being made by Communications and Power Industries. The ECH preionization effects are investigated by a 0-dimensional code (TECHP0D) that includes the operational scenarios of KSTAR tokamak. The code is now improved and advanced with carbon, oxygen, and iron impurity effects, and with the self and mutual inductances of seven pairs of superconducting poloidal coils for the KSTAR tokamak. 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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