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Plasma Science, IEEE Transactions on

Issue 1  Part 2 • Date Feb 2003

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Displaying Results 1 - 14 of 14
  • Initiation of microwave-induced electrical breakdown of high-pressure gases

    Publication Year: 2003 , Page(s): 146 - 156
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (738 KB) |  | HTML iconHTML  

    Measurements of microwave-induced electrical breakdown at 2.45 GHz in Ar, Kr, and Xe have been made in a tunable microwave cavity. The influence of UV illumination on gas breakdown at pressures up to 300 torr, and data on fiber initiator-induced breakdown above atmospheric pressure are presented. A marked decrease in the statistical spread in breakdown was observed with UV illumination, but the maximum pressures at which breakdown occurred with available microwave power, with and without UV illumination, were the same. To initiate breakdown in gases above 1 atm, a conducting fiber was used to enhance the applied macroscopic electric field at the fiber tip. Using 8-μm diameter SiC fibers coated with 0.2-μm-thick Pt, breakdown was obtained with pulses as short as 0.25 ms in the pressure range 1-3 atm for Ar, Kr, and Xe. The required microwave electric field at 2280 torr with one fiber was less than that at 200 torr without a fiber. The increase of the breakdown field with pressure was much slower than linear. The effect of fiber length, diameter, orientation, and conductivity, and of the number of fibers, on the required breakdown electric field, and fiber initiation in Cl2 mixture gases, were also investigated. View full abstract»

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  • Maximum power generation in a piezoelectric pulse generator

    Publication Year: 2003 , Page(s): 123 - 128
    Cited by:  Papers (15)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB) |  | HTML iconHTML  

    This investigation presents and discusses maximization techniques for a high-power piezoelectric pulse generator. Maximizing the piezoelectric generator's output power is done by maximizing the product of generated voltage and output current. The maximization methods are derived from the mechanical and electrical models of the generator and provide design guidelines as to the geometric dimensions of the piezoelectric material and circuital conditions that will produce maximum power in the device. The theoretical results show the peak stack voltage to increase with an increasing thickness to area ratio of the piezoelectric material and with increasing applied force. However, in contrast to the peak output voltage, the peak output current increases with the decreasing of thickness to area ratio of the material. In addition to the physical dimension, the peak stack current increases as the value of the antenna inductor decreases. The output power of the piezoelectric generator, which is the product of output voltage and current, linearly increases with the thickness to area ratio. This result is due to the fact that the output voltage is larger comparing to the output current. Experimental results are also given to verify the theoretical results and represent the performance of several types of piezoelectric materials with different thickness to area ratios. The experimental results show good agreement with theoretical predictions. The results also show the peak power output of the experimental generator ranging from 7 to 28 kW with a corresponding power density from 9 to 173 kW/cm3. View full abstract»

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  • Abatement of nitrogen oxides in a catalytic reactor enhanced by nonthermal plasma discharge

    Publication Year: 2003 , Page(s): 157 - 165
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (462 KB)  

    Removal of nitrogen oxides using a nonthermal plasma process (dielectric barrier discharge) combined with catalyst was investigated. In this system, selective catalytic reduction of nitrogen oxides is affected by the operating condition of the plasma process and, thus, the characteristics of the plasma process were separately examined before combining the two processes. The oxidation of NO to NO2 in the plasma reactor easily took place at room temperature. As the temperature increased, however, the rate of the oxidation greatly decreased, which implies that an additive to increase the reaction rate is necessary. In the presence of ethylene as an additive, the oxidation of NO to NO2 largely enhanced at a temperature range of 100°C-200°C. Comparison of AC with pulse voltage in terms of the energy efficiency for NO oxidation was made, and almost no difference between the two voltage types was observed. The removal of NOx on the catalyst (V2O5/TiO2) was found to largely increase by the plasma discharge. The byproduct formaldehyde formed from ethylene in the plasma reactor could be completely removed in the catalytic reactor while significant amount of carbon monoxide and ammonia slip were observed. The plasma-catalyst system used in this study was able to remove more than 80% of NOx (energy yield: 42 eV/NOx-molecule) at a temperature range of 100°C-200°C that is much lower than typical temperature window of selective catalytic reduction (250°C-450°C). View full abstract»

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  • Performance of closed cycle disk MHD generator with inlet fluctuation of seed fraction

    Publication Year: 2003 , Page(s): 129 - 136
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB) |  | HTML iconHTML  

    The influence of inlet seed fraction fluctuations on the performance of closed-cycle MHD disk power generators is investigated using time-dependent two-dimensional numerical simulation. Here, the nonuniformity scale of the seed fraction, as induced by inlet fluctuations, is assumed to be comparable to the length of the channel or smaller. It is confirmed that inlet fluctuation of the seed fraction can cause instability in nonequilibrium plasma and deteriorate the performance of the generator. As the amplitude of the inlet fluctuation increases, the amplitude of the enthalpy extraction ratio fluctuation becomes enlarged and the mean value is decreased. Furthermore, the amplitude of the enthalpy extraction ratio fluctuation grows larger when the frequency of the inlet fluctuation approaches 8-10 kHz. Although inlet fluctuations induce oscillations in both plasma and flow-field parameters, they display different characteristics at higher frequencies. That is, fluctuation of the former is kept approximately constant with increasing frequency whereas the latter is weakened. This behavior can be attributed to the inertia of the flow field. For pulse-like random inlet fluctuations with high dominant frequency, the fluid field does not have adequate time to respond to variations in seed fraction. The resulting dominant frequency in the flow field is 4-6 kHz. The dominant frequency for the output power is in the same range as the flow field, and these frequencies can be related to the residence time of the working fluid in the channel. View full abstract»

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  • Improvement of luminance efficiency in xenon dielectric barrier discharge flat lamp

    Publication Year: 2003 , Page(s): 176 - 178
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB) |  | HTML iconHTML  

    In this work, to improve the luminance efficiency of the lamp, xenon dielectric barrier discharge flat lamps (DFLs) with new electrode structures were fabricated and electric-optical characteristics were analyzed in respect with various discharge conditions. The luminance efficiency increased as the increasing of the capacitance and the reducing of the dielectric loss, and as the improvement in the transmittance of the generated visible light at the discharge space. The luminance efficiency of the DFL with Al2O3 dielectric layer of 60-μm thickness, matrix shape electrodes and discharge space of 1-mm gap-width was obtained as 26.3 lm/W and the luminance was 4 873 cd/m2. View full abstract»

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  • Nonlinear instability of dust ion-acoustic waves in a plasma with strongly correlated dust grains

    Publication Year: 2003 , Page(s): 119 - 122
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (382 KB) |  | HTML iconHTML  

    The nonlinear propagation of large amplitude dust ion-acoustic waves in a strongly coupled dusty plasma is considered. By employing a two-fluid model, we derive an equation for the dust ion-acoustic (DIA) waves in the presence of ion density fluctuations of dust acoustic waves. The relevant equation for the latter in the presence of the DIA ponderomotive force is obtained by means of the generalized viscoelastic hydrodynamics equations for strongly correlated dust grains, along with a Boltzmann electron distribution and a modified (by the DIA ponderomotive force) Boltzmann ion distribution. The newly derived coupled mode equations are Fourier analyzed to obtain a nonlinear dispersion relation that is useful for investigating the decay and modulational instabilities of coherent DIA waves. The implications to laboratory plasmas are pointed out. View full abstract»

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  • Composition of CxHyOzNt plasmas out of thermal equilibrium using quite different modified forms of Saha and Guldberg-Waage equations

    Publication Year: 2003 , Page(s): 82 - 93
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (983 KB) |  | HTML iconHTML  

    The aim of this work is to discuss the use of quite different modified forms of Saha and Guldberg-Waage equations to determine the composition of CxHyOzNt plasmas in a nonequilibrium thermal state. x, y, z, and t are the initial proportions of carbonic, hydrogen, oxygen, and nitrogen atoms. The computation is made under condition of pressure and electron temperature in the range, respectively, 0.1-1 MPa and 5-30 103 K. We show the influence of each form of Saha and Guldberg-Waage equations on the evolution of major species density, such as hydrogen components (H, H2), carbon monoxide (CO), and electrons. These species have a significant influence on the plasma's performances such as thermal and electrical conductivity through the equilibrium composition. We also give the influence of internal partition function calculation on species concentration within the plasma and discuss the choice of internal temperatures. View full abstract»

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  • Experimental studies on performance of a nonequilibrium disk MHD generator with radio-frequency preionization

    Publication Year: 2003 , Page(s): 166 - 173
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB) |  | HTML iconHTML  

    The possibility of the improvement in performance of a nonequilibrium disk magnetohydrodynamics (MHD) generator by externally applying a radio frequency (RF) electromagnetic field (RF preionization) was examined experimentally. The MHD power generation experiments were carried out using a shock-tube driven disk MHD generator with the RF induction coils for the two inlet stagnation temperatures of 2275(±75) K and 2650(±50) K. As a result, under the conditions of both high and low stagnation temperatures, the output power was increased by the RF preionization. The increase was markedly observed for the low inlet stagnation temperature, where the plasma could not be produced only by the Joule heating attributed to a self-excited electromotive force. For the high inlet stagnation temperature, the plasma state in the MHD channel was improved by the RF preionization, leading to the increase in the output power. For the low inlet stagnation temperature, the marked increase in the output power by the preionization was not only because applying the RF electromagnetic field triggered the plasma production by the Joule heating attributed to a self-excited electromotive force but also because the plasma with the high electrical conductivity was produced in the more upstream region of MHD channel by the Joule heating attributed to the RF electromagnetic field. View full abstract»

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  • The design of a tapered dimple-type mode converter/launcher for high-power gyrotrons

    Publication Year: 2003 , Page(s): 142 - 145
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (370 KB) |  | HTML iconHTML  

    This paper presents the design method for a gyrotron-dimple-type mode converter that is axially up-tapered to prevent inside oscillation. In this up-tapered converter, the propagation constant of the traveling TE modes varies axially since the mean radius grows in the axial direction, requiring a new formulation of the mode coupling in the converter. In this paper, the axial variation of the helix pitch that describes the TE mode propagation is discussed first. Then, the coupling coefficients between TE modes are analytically derived, with which a trial design of a linearly tapered converter is made for a 170-GHz gyrotron. View full abstract»

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  • Alternating-current glow and pseudoglow discharges in atmospheric pressure

    Publication Year: 2003 , Page(s): 174 - 176
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (258 KB) |  | HTML iconHTML  

    Stabilization and control of alternating-current glow and pseudoglow discharges have been studied in atmospheric pressure static air and methane flow gas by a pin-to-pin configuration. The electrode configuration and input power control the amplitude and duration of the discharge current and current pulses. Glow and pseudoglow discharges have been applied to the methane conversion. View full abstract»

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  • Rotation of Coulomb crystals in a magnetized inductively coupled complex plasma

    Publication Year: 2003 , Page(s): 112 - 118
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (847 KB)  

    Under suitable conditions, micron-sized dust particles introduced into inductively coupled argon plasma form a stable microscopic crystal lattice, known as a Coulomb (or plasma) crystal. In the experiment described, an external axial magnetic field was applied to various configurations of Coulomb crystal, including small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The crystals were observed to rotate collectively under the influence of the magnetic field. This paper describes the experimental procedures and the preliminary results of this investigation. View full abstract»

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  • Dynamics of high-voltage pulsed cylindrical sheath

    Publication Year: 2003 , Page(s): 94 - 103
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (634 KB) |  | HTML iconHTML  

    A semi-analytic model of collisionless sheath in plasma immersion ion implantation (PI3) for a step bias with finite rise time in cylindrical geometry has been developed. The model takes into account the formation of the presheath, predicts the sheath overshooting and its further recovery to the steady-state Child value. To verify the model, a sheath dynamics has been investigated experimentally on a 30-kV PI3 setup using the positively biased Langmuir probe technique. The measurements have been carried out in argon and helium plasmas of inductively coupled and hot cathode plasma sources. The model predictions agreed well with the experimental results. View full abstract»

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  • Unipolar arc behavior in high-frequency fields

    Publication Year: 2003 , Page(s): 137 - 141
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (561 KB) |  | HTML iconHTML  

    In the present paper, we describe experimental investigations of unipolar arcs generated in a vacuum arc plasma. An effect of additional injection of the high-frequency power is studied. A coaxial floating arc probe of special design is used for the arc characteristic measurements, and the arc tracks on the polished probe electrodes are studied. The breakdown rate of the probe in the high-frequency plasma discharge is found to have an abrupt cutoff with a frequency approaching the critical value of about 107 Hz. Independent measurement of electrode erosion confirms this effect. The eroded mass reaches the value of 10-12 kg·s-1 for zero frequency and falls to the value of 10-13 kg·s-1 for frequency approaching 107 Hz. View full abstract»

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  • Modeling plasma immersion ion implantation under trapezoidal voltage pulses

    Publication Year: 2003 , Page(s): 104 - 111
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (498 KB) |  | HTML iconHTML  

    In plasma immersion ion implantation (PIII), ions are extracted from the plasma and implanted in a target subjected to high negative voltage pulses. PIII models assume that the uncovering of enough ions at the moving sheath edge establishes a space-charge-limited ion flow that supplies the ion implant current at the target. The present paper reexamines this assumption in one-dimensional planar geometry by relating the implant current at the target to the Child law current through a delay time function that properly accounts for the transit time of the ion through the sheath. Comparison of the total current calculated both at the target and at the leading edge of the sheath demonstrates that the model provides accurate results as long as the ion time scale is shorter than the characteristic times of the applied voltage waveform. 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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