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Plasma Science, IEEE Transactions on

Issue 6 • Date Dec. 1988

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Displaying Results 1 - 11 of 11
  • Control of gigawatt REB pulse duration using gas injection

    Publication Year: 1988 , Page(s): 601 - 605
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    A technique for controlling the voltage and current pulse duration of a gigawatt relativistic electron beam (REB) was investigated. The pulse duration of a beam of 250 keV and 10 kA was controlled from 60 ns to 10 ns by injecting gases (air,, argon, and hydrogen) into the diode gap at a pressure ranging from 10/sup -5/ torr to 10/sup -1/. The observed dependence of the pulse duration on the nature and pressure of the gas is explained in terms of volume ionization of the gas by beam electrons. It is concluded that the pulse duration is governed by the time at which the plasma density created by the beam reaches a critical value of the order of beam electron number density.<> View full abstract»

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  • Study of a circuit-breaker arc with self-generated flow. I. Energy transfer in the high-current phase

    Publication Year: 1988 , Page(s): 606 - 614
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (707 KB)  

    This study deals with the first phase of operation, corresponding to the energy transfer between arc and gas and to the pressure rise. The experimental study is devoted to measurements of current, arc voltage, and pressure variations in N/sub 2/ and SF/sub 6/. For currents of the order of 10 kA the mean measured electric field was about 32 V/cm in SF/sub 6/ and 36 V/cm in N/sub 2/. Through a bibliographical study and a modeling approach of the interruption arc, an analysis of the role of the different mechanisms of energy transfer between the arc and SF/sub 6/ was conducted. With a 10 kA pulse, about 80% of the transfer is found to be due to convection and the rest to radiation from the arc. This transfer results in an overpressure of nearly 1 bar in SF/sub 6/ and 2 bar in N/sub 2/. It appears that the operation of this type of circuit breaker is limited to high currents: for currents below 7 kA the overpressure is lower than 0.5 bar, which does not provide efficient blowing at current zero.<> View full abstract»

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  • Study of a circuit-breaker arc with self-generated flow. II. The flow phase

    Publication Year: 1988 , Page(s): 615 - 622
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    For pt.I see ibid., vol.16, no.6, p.606-14 (1988). The experimental results presented concern the variations of the mean electric field and gas mass flow during this phase. The most important part consists of a modeling of the evolution of the interruption arc during the decrease of the current from 1000 A to 0. In this modeling, based on the conservation equations of mass and energy, the boundary conditions are determined by an approximate separate modeling of the arc whereas turbulence is treated through Prandtl's approximation. This theoretical study has been developed in the case of SF/sub 6/ and nitrogen. The computed values of the electric field and temperature show that the arc has a quasi-stationary behaviour as long as the current intensity is greater than a few tens of amperes, for a decay rate of 1.35 A/ mu s. The energy losses are governed by radiation at high current and by turbulence conduction at low current. The most important results concern the conductance, whose evolution time constant, immediately prior to current zero, is 3.5 mu s in SF/sub 6/ and 15 mu s in nitrogen. The difference is essentially due to variations with temperature of thermal conductivity and specific heat in two gases.<> View full abstract»

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  • Pulsed microwave plasma etching of polymers in oxygen and nitrogen for microelectronic applications

    Publication Year: 1988 , Page(s): 631 - 637
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    Gaseous plasma generated by a half-wave rectified power supply are characterized and applied to the etching of photoresist and polymide in oxygen, dry air, or air. Activation energies of 8.6 kcal/mole and 10.9 kcal/mole are calculated for oxygen plasma etching of photoresist and polyimide, respectively. An average power of 625 W at 2.45 GHz is supplied by a magnetron through a rectangular waveguide to a 51-mm diameter quartz tube generating pulsed plasmas in oxygen and nitrogen at pressures between 0.1 torr and 10 torr with a repetitive rate of 60 Hz. The plasmas are studied by a double Langmuir probe and an optical emission spectrometer. Polymers placed in the downstream of the plasma are etched at high rates, especially when external heating is applied to raise the sample temperature. The characteristics of the plasmas and the application to the fast etching of polymers are discussed.<> View full abstract»

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  • Coupling and loading measurements for a dielectric-filled ICRF waveguide coupler

    Publication Year: 1988 , Page(s): 645 - 651
    Cited by:  Papers (2)
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    Experiments were carried out to verify models of the reflection coefficients and the phase transitions for matched or loaded dielectric-filled waveguide couplers in the ion cyclotron range of frequencies (ICRF). A model for the plasma load simulation in the waveguide is developed and examined permanently using the time-domain features of an HP.8510 network analyzer. The loss properties of deionized water, which was used for laboratory waveguide dielectric tests, are also discussed. Close agreement between the coupling models and measurements is noted. For a matched coupler, the optimal power-coupling efficiency obtained is 95% and for a simulated-plasma loaded coupler this value is in the range of 80%, depending upon the plasma load. If it is assumed that the effects of the high neutron flux present in a reactor environment on the dielectric strength of water are negligible (or eliminated), and that the dielectric breakdown strength of water is approximately 3 kV/cm at nearly 80% coupling efficiency, the power handling capability of the water-filled coupler is estimated to be in the range of 3-6 MW.<> View full abstract»

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  • Modeling of the electrostatic corona discharge reactor

    Publication Year: 1988 , Page(s): 652 - 660
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (795 KB)  

    A model is presented for the electrostatic corona discharge reactor (ECDR) in a pin-plate configuration. The main objective is to describe the fundamental chemistry and physics governing the discharge behavior and to predict the ECDR performance under various operating conditions. The electric field strength is estimated assuming a space-charge-free field. A two-term spherical harmonic expansion is used to solve the Boltzmann equation for the electron energy distribution function (EEDF) and calculate the electron-molecule reaction rates using collision cross-section data. Species continuity equations are solved for the dry and wet air systems to predict ozone and NO/sub x/ at various feed flow rates (1630, 4890, 14, 670 cm/s) and an applied voltage of 10 kV. Among the various results reported, it is noted that the calculations indicate the Maxwell EEDF cannot be used because it overpredicts the electron-molecule rate coefficients by several orders of magnitude.<> View full abstract»

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  • An enhancement of ion energy spectra resolution and sensitivity in a multigridded energy analyzer with a retarding grid potential: the variable energy analyzer (VEA)

    Publication Year: 1988 , Page(s): 661 - 666
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    An energy analyzer was developed that allows enhanced resolution of ion energy spectra and sensitivity. The energy analyzer is based on the principles of electrostatic multigrid ion or electron energy analyzers. Studies indicate that geometrical parameters such as grid separation, the grid transparency, and the spatial charge all influence the characteristic curve of the analyzer (typically a plot of collector current versus the retarding potential on the discriminator grid of the analyzer). Through the adjustment of these parameters, the resolution and the sensitivity of the analyzer is improved by a factor of two. It was found that there was an optimum separation distance between the two grids where the analyzer provides optimal resolution.<> View full abstract»

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  • Design of the Reversatron II RFP

    Publication Year: 1988 , Page(s): 667 - 672
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (418 KB)  

    A description is given of the design and initial operation of a small (outer radius/inner radius=50 cm/8 cm) reversed field pinch air core, a thin removable shell, and relatively low field errors. Equilibrium control is simplified by having no vertical field generated by the ohmic heating coils so that the equilibrium is determined solely by the variable index preprogrammed vertical field coil current. The toroidal field and vertical field coils are inductively decoupled from the ohmic heating circuit in order to simplify the programming of these fields. Discharges having a 22 kA plasma current and duration of 500 mu sec are obtained.<> View full abstract»

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  • Analytical solution for capacitive RF sheath

    Publication Year: 1988 , Page(s): 638 - 644
    Cited by:  Papers (52)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    A self-consistent solution for the dynamics of a high voltage, capacitive radio frequency (RF) sheath driven by a sinusoidal current source is obtained under the assumptions of time-independent, collisionless ion motion and inertialess electrons. Expressions are obtained for the time-average ion and electron densities, electric field and potential within the sheath. The nonlinear oscillation motion of the electron sheath boundary and the nonlinear oscillating sheath voltage are also obtained. The effective sheath capacitance and conductance are also determined. It was found that: (1) the ion-sheath thickness S m is √50/27 larger than a Child's law sheath for the DC voltage and ion current density; (2) the sheath capacitance per unit area for the fundamental voltage harmonic is 2.452 ε0 /Sm, where ε0 is the free space permittivity; (3) the ratio of the DC to peak value of the oscillating voltage is 54/125; (4) the second and third voltage harmonics are, respectively, 12.3 and 4.2% of the fundamental; and (5) the conductance per unit area for stochastic heating by the oscillating sheath is 2.98 (λD/Sm)2/3 (e 2n0/mue), where n 0 is the ion density, λD is the Debye length at the plasma-sheath edge, and ue is the mean electron speed View full abstract»

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  • Direct energy conversion of plasma energy

    Publication Year: 1988 , Page(s): 623 - 630
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    An application of ambipolar potential in a magnetized plasma is proposed for direct energy conversion. Analyses of a model device for 20-MW-per-unit-length (without considering end loss) and 14-MW-per-unit-length (with the end loss) are shown. The plasma density profile, the potential distribution in the device, and the voltage-current characteristics are obtained on the basis of the Poisson continuity equation system. As an example, a theoretical energy loss by neutral particles, which should not affect the total efficiency much. Experiments with a small thermal ionization-type device were performed wherein the relations of output voltage versus current and power versus impedance were acquired. the experimental results are compared with the theoretical and a qualitative agreement is obtained View full abstract»

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  • Integrated superconducting microtron

    Publication Year: 1988 , Page(s): 673 - 674
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    With the assumption that high temperature superconductivity will become practical and commercially available, the author discusses the practicality of and advantages to be gained by constructing an integrated superconducting microtron in an evacuated nitrogen or otherwise cooled vessel. Several proposals for electron feed systems are discussed 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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