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Plasma Science, IEEE Transactions on

Issue 2 • Date April 2003

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Displaying Results 1 - 19 of 19
  • Fundamental studies of intense heavy-ion beam interaction with solid targets

    Publication Year: 2003 , Page(s): 221 - 226
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1098 KB)  

    Intense (1011 particles/1 μs ∼300 MeV/u) heavy ion beams are generated in the heavy-ion synchrotron (SIS) of the GSI-Darmstadt facility. Large volumes of strongly coupled plasmas are produced by heavy ion beam interaction with solid targets, with plasma densities close to the solid state, pressures of about 100 kbar, and temperatures of up to 1 eV, with relevance for equation of state (EOS) of matter, astrophysics, and low-entropy shock compression of solids. The plasmas created by ion beam interaction with metallic converters and cryogenic crystals were studied by backlighting shadowgraphy and by time-resolved spectroscopy in the visible and vacuum ultraviolet ranges. Low entropy weak shock waves induced by the ion beams in the metal-plexiglass multilayered targets were visualized by time resolved schlieren measurements, revealing induced multiple shockwaves with pressures higher than 15 kbar in a plexiglass window and propagation velocities up to 35% higher than the speed of sound in plexiglass at room temperature. To get an insight into the plasma dynamics, both types of experiments are simulated by the BIG-2 two-dimensional hydrodynamic code. View full abstract»

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  • Axial magnetic field contacts with nonuniform distributed axial magnetic fields

    Publication Year: 2003 , Page(s): 289 - 294
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB) |  | HTML iconHTML  

    It is well known that axial magnetic fields (AMFs) can keep vacuum arc in diffuse mode at high current. According to our recent research and other published papers, it has been found that vacuum arc can be maintained in high-current diffuse mode at much higher current if nonuniform AMF is applied, that the axial magnetic field is higher at contact periphery than at center. The influence of spatial distribution of AMF on vacuum arc is mainly studied in this paper. Furthermore, two types of AMF contacts with new structures to generate nonuniform AMF are presented. View full abstract»

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  • Numerical simulation of cableguns using MACH2

    Publication Year: 2003 , Page(s): 248 - 255
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (519 KB) |  | HTML iconHTML  

    A radiation-driven ablation model was developed for the MHD code MACH2 to provide a numerical simulation for cableguns. Ablation from the insulator surface is driven by radiation from an optically thin gray gas in the computational domain adjacent to the insulator surface. Two parameters required for the model-specific opacity and vapor layer transmissivity-were determined from baseline experiments. Using these parameter values, numerical simulations for five additional cablegun configurations were compared with experimental measurements obtained using a two-beam laser interferometer. Equations of state models for copper-Teflon and polyethylene plasmas were calculated for use in these simulations. Comparisons were made for radial profiles of electron density, plume velocity, and plume width. Based on the results obtained in this study, it appears that MACH2 simulations can be used to provide reasonable estimates of cablegun plume properties that are difficult or impossible to obtain experimentally, such as the spatial flow details inside the cavity or the temporal distribution of mass loss. View full abstract»

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  • Design and development of driving waveforms for AC plasma display panels

    Publication Year: 2003 , Page(s): 272 - 280
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (749 KB) |  | HTML iconHTML  

    This paper presents design and development of driving waveforms to improve efficacy, contrast, and resolution for ac plasma display panels (PDPs). In the paper, the conventional driving waveforms are first reviewed, and the proposed driving waveforms are then discussed. The driving of PDPs in each subframe is divided into three periods: the reset period, scan period, and sustain period. During the reset period, the proposed ramp-like reset waveforms can enhance the contrast and resolution, and can lower the scan voltage while still sustaining a reliable wall-charge control. Additionally, a square sustain waveform stacked with the ramp-like waveform can induce self-erasing discharges which will improve efficacy during the sustain period. Operation of a PDP and comparison among various driving waveforms are also presented. Experimental results measured from a 46-in PDP system have verified the feasibility of the proposed driving waveforms. View full abstract»

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  • Investigation of anode and cathode jets influence on electric arc properties with current up to 500 kA

    Publication Year: 2003 , Page(s): 201 - 206
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (565 KB) |  | HTML iconHTML  

    A number of phenomena connected with the formation of electrode jets in discharges in hydrogen at a current of 105-106 A, a current growth rate of 1010 A/s, an initial pressure 0.1-4.0 MPa, and a discharge gap length of 5-40 mm were studied. After the secondary breakdown, the jets are observed through a discharge semitransparent channel, widening with velocity (4-7) · 102 m/s. Shockwave formation was detected at the interaction of jets with the surrounding gas and the opposite electrode. Plasma vapor pressure of metal near the end of the tungsten cathode 70 μs after initiation of a discharge was 180 MPa. Thus, magnitude of brightness temperature was 59 · 103 K, with an average charge of ions-m~=3.1, and a concentration of metal vapors n=5.3·1019 cm-3. While those at the end of the anode 90 μs after initiation of discharge: m~=2.6, n=7.4·1019 cm-3. Probable reasons of high-voltage drops near the electrodes (the summarized magnitude of which is ∼1 kV) are discussed on the basis of experimental data. For the first time, the shadow method registered symmetric ejection of material from the all-cathode surface the maximum discharge current was observed. View full abstract»

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  • A 35-GHz low-voltage third-harmonic gyrotron with a permanent magnet system

    Publication Year: 2003 , Page(s): 264 - 271
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (675 KB) |  | HTML iconHTML  

    A systematic theoretical and experimental study on a 35-GHz 45-kV third-harmonic gyrotron with a permanent magnet system is presented in this paper. A complex cavity with gradual transition and a diode magnetron injection gun (MIG) are employed in the gyrotron. A self-consistent field nonlinear theoretical investigation and numerical simulation for electron beam interaction with RF fields are given. The diode MIG is simulated numerically utilizing our code in detail. The permanent magnet system provided the maximum axial magnetic field of about 4.5 kG in the cavity region of the gyrotron. The Ka band third-harmonic complex cavity gyrotron with a permanent magnet system has been designed, constructed, and tested. A pulse output power of 147.3 kW was obtained at a beam voltage of 45 kV with beam current of 32.2 A, corresponding to an efficiency of 10.2%. View full abstract»

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  • The influence of unipolar axial magnetic field on the behavior of vacuum arcs

    Publication Year: 2003 , Page(s): 299 - 302
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (522 KB) |  | HTML iconHTML  

    The behavior of vacuum arcs under the influence of unipolar axial magnetic field (AMF) has been investigated. In experimental investigations, the vacuum arc mode is studied at different arc currents by using high-speed charge-coupled device (CCD) video images. In spite of the AMF, first sign of arc constriction appears at relatively small currents of about 15 kA (RMS). Three different arc modes were found. Based on generalized Ohm's law, the current density distribution in the vacuum arc with unipolar axial magnetic field is computed using three-dimensional finite-element method (FEM) software. The calculated current distribution is confirmed by the vacuum arc appearance taken from CCD video film. The distribution of AMF can be optimized by such experiments and theoretical analysis. View full abstract»

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  • A fault analysis and design consideration of pulsed-power supply for high-power laser

    Publication Year: 2003 , Page(s): 216 - 220
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (365 KB) |  | HTML iconHTML  

    According to the requirements of driving flashlamps, the design of a pulsed-power supply (PPS), based on capacitors as energy storage elements, is presented. Special consideration is given to some possible faults such as capacitor internal short-circuit, bus bar breakdown to ground, flashlamp sudden short or break (open circuit), and closing switch restrike in the preionization branch. These faults were analyzed in detail, and both fault current and voltage waveforms are shown through circuit simulation. Based on the analysis and computation undertaken, the pulsed-power system design and protection requirements are proposed. The preliminary experiments undertaken after circuit simulation demonstrated that the design of the PPS met the project requirements. View full abstract»

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  • Modeling of an EMP simulator using a 3-D FDTD code

    Publication Year: 2003 , Page(s): 207 - 215
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (467 KB) |  | HTML iconHTML  

    Performed self-consistent, three-dimensional (3-D), time-domain calculations for a bounded-wave electromagnetic pulse simulator. The simulator consists of a constant-impedance transverse electromagnetic structure driven by a charged capacitor, discharging through a fast closing switch. These simulations yield the detailed 3-D electromagnetic field structure in the vicinity of the simulator. The prepulse seen in these simulations can be explained quantitatively in terms of capacitive coupling across the switch and the known charging waveform across the capacitor. Placement of a test object within the simulator significantly modifies the electric fields within the test volume, in terms of field strength as well as the frequency spectrum. This means that, for a given simulator, larger objects would be subjected to somewhat lower frequencies. The E-field waveform experienced by a small test object is reasonably close to that for free-space illumination, but the mismatch increases with object size. The use of a resistive sheet as a matching termination significantly reduces radiation leakage as compared to two parallel resistive rods. For a given termination, larger test objects marginally reduce leakage. A physical interpretation of these conclusions is also included. This work is a first step toward full-fledged optimization of such simulators using 3-D modeling. View full abstract»

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  • Good news: you can patch active plasma and collisionless sheath

    Publication Year: 2003
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (158 KB) |  | HTML iconHTML  

    It is shown that the proof of physical inconsistency of the discrete plasma-sheath model with a continuous electric field is based on mathematical error in solving the basic sheath equation. View full abstract»

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  • CW H I laser based on a stationary inverted Lyman population formed from incandescently heated hydrogen gas with certain Group I catalysts

    Publication Year: 2003 , Page(s): 236 - 247
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (631 KB) |  | HTML iconHTML  

    Each of the ionization of Rb+ and cesium and an electron transfer between two K+ ions (K+/K+) provide a reaction with a net enthalpy of an integer multiple of the potential energy of atomic hydrogen, 27.2 eV. The corresponding Group I nitrates provide these reactants as volatilized ions directly or as atoms by undergoing decomposition or reduction to the corresponding metal. The presence of each of the reactants identified as providing an enthalpy of reaction of an integer of that of the potential energy of atomic hydrogen (m·27.2 eV) formed a low applied temperature, extremely low-voltage plasma called a resonance transfer (RT)-plasma having strong vacuum ultraviolet (VUV) emission. In contrast, magnesium and aluminum atoms or ions do not ionize at integer multiples of the potential energy of atomic hydrogen. Mg(NO3)2 or Al(NO3)3 did not form a plasma and caused no emission. For further characterization, we recorded the width of the 6563 Å Balmer α line on light emitted from RT-plasmas. Significant line broadening of 18, 12, and 12 eV was observed from an RT-plasma of hydrogen with KNO3, RbNO3, and CsNO3, respectively, compared to 3 eV from a hydrogen microwave plasma. These results could not be explained by Stark or thermal broadening or electric field acceleration of charged species since the measured field of the incandescent heater was extremely weak, 1 V/cm, corresponding to a broadening of much less than 1 eV. Rather the source of the excessive line broadening is consistent with that of the observed VUV emission, an energetic reaction caused by a resonance energy transfer between hydrogen atoms and K+/K+, Rb+, and cesium, which serve as catalysts. KNO3 and RbNO3 formed the most intense plasma. Remarkably, a stationary inverted Lyman population was observed in the case of an RT-plasma formed with potassium and rubidium catalysts. These catalytic reactions may pump a continuous wave HI laser as predicted by laser equations and a collisional radiative model used to determine that the observed overpopulation was above threshold. View full abstract»

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  • New color-enhancing discharge mode using self-erasing discharge in AC plasma display panel

    Publication Year: 2003 , Page(s): 256 - 263
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (507 KB)  

    A new color-enhancing discharge mode using a self-erasing discharge is proposed based on an analysis of the Ne emission mechanism in a Ne-Xe gas mixture. The effects of the new color-enhancing discharge mode produced by a ramped-square sustain waveform on improving the color reproducibility are examined in an alternate current plasma display panel (ac-PDP) filled with a Ne-Xe gas mixture. When the ramped-square sustain pulses are applied at 150 kHz, the color purities of the blue and green visible emissions are both improved, thereby expanding the color gamut area by about 5.4% without reducing the luminance. View full abstract»

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  • Multistage automodulation using decreasing length cavities

    Publication Year: 2003 , Page(s): 297 - 299
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB) |  | HTML iconHTML  

    It is observed that the length of a coaxial cavity strongly affects the induced gap voltage and the level of automodulation. For high-frequency automodulation for a beam with slow rise-time, a series of cavities with decreasing lengths is proposed. View full abstract»

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  • Coherent structures and their stability in ion temperature gradient turbulence

    Publication Year: 2003 , Page(s): 191 - 195
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (486 KB) |  | HTML iconHTML  

    Periodic arrays of large scale coherent vortices and their stability have been investigated, within the framework of ηi turbulence, using two-dimensional fluid simulation in slab geometry. These vortices, in combination with viscosity damping of small scales, contribute to the formation of a steady state in a system with linearly unstable modes. The steady state comprises of a few vortex convective turn over times and seems to be fairly robust. It has been recognized that a vortex chain, consisting of positive and negative vorticities, continues to move stably in the poloidal direction (along periodic direction). On the other hand, an initial isolated monopole vortex is unstable and leads to a long-lived stable dipolar structure after a few vortex turnover periods. A variety of simple collisional interaction processes among these coherent vortices have also been explored numerically. View full abstract»

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  • Author's reply to "Good news: you can patch active plasma and collisionless sheath"

    Publication Year: 2003
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (145 KB)  

    Godyak and Sternberg (2003) reassert their contention that one can obtain a satisfactory physical solution to the active plasma-collisionless sheath by patching together plasma and sheath. They choose to do it at an arbitrary point where the sheath electric field is kTe /eλD. If one tacks their sheath solution to the full plasma solution, then the field is infinity on the plasma side and finite on the sheath side. Alternatively, if one terminates the plasma solution where the plasma field is kTe/eλD, then one has continuity of electric field, but not of its gradient, since on the sheath side it is zero and on the plasma side of order L/λD, where L is the size of the plasma. Furthermore, in achieving continuity of the field, one has introduced discontinuities in the ion speed and in the particle densities. Thus, in no sense is a joining which denies the existence of a transition layer, smooth. J. Ockendon and H. Ockendon, my colleagues in the production of our paper describing the transition layer (Franklin et al., 1970), privately expressed disappointment in not finding a proof of the existence and uniqueness of our solution. Such a formal mathematical proof has been given recently by Slemrod (2002). Smooth joining of active plasma and collisionless sheath within the context of a fluid model or free fall model of the ion motion, does require a transition layer and of length scale intermediate between L and λD. View full abstract»

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  • Removal of nitrogen oxide in spatially isolated chamber by pulsed intense relativistic electron beam

    Publication Year: 2003 , Page(s): 295 - 296
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (206 KB) |  | HTML iconHTML  

    Nitrogen oxide (NOx) in a chamber spatially isolated from beam source has been removed by a pulsed, intense, relativistic electron beam (PIREB). The chamber is filled up with dry-air-balanced NOx, and is irradiated by the PIREB (2 MeV, 2.2 kA, 85 ns) passing through 1.6-m-long atmosphere. The NOx concentration decreases from 88 to 25 ppm by ten shots of PIREB. View full abstract»

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  • Analysis on plasma chemistry and particle growth in corona discharge process for NOx removal using discrete-sectional method

    Publication Year: 2003 , Page(s): 227 - 235
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    The particle formation and growth combined with plasma chemistry in the pulsed corona discharge process (PCDP) to remove NOx were analyzed by the discrete-sectional model. In the PCDP, most of the NO is converted into NO2 and, later, into HNO3 which reacts with NH3 to form the NH4NO3 particle. In the beginning of the reactor, we have the high concentration of small size particles and, later, the particle size distribution in the reactor becomes bimodal with the large size and small size particles and, finally, becomes monodisperse with the large size particles. As the average electron concentration increases, it takes a shorter reactor length to remove the NOx. As the initial NO and H2O concentrations decrease, the NH3 is consumed more slowly to form the ammonium nitrates particles. As the averaged electron concentration and initial H2O concentration increase, the large size particles grow more quickly and the particle size distribution becomes bimodal earlier. As the initial NO and NH3 concentrations increase, the diameter of large size particles becomes larger by the faster coagulation between particles. The predicted NOx conversion and particle size distribution were in close agreements with the published experimental results at the averaged electron concentration of 2×105 cm-3 in this study. View full abstract»

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  • Pulse forming lines for square pulse generators

    Publication Year: 2003 , Page(s): 196 - 200
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (497 KB) |  | HTML iconHTML  

    The designing of square pulse generators using pulse-forming lines (PFLs) made up of identical L and C, was reviewed in this study. Fourteen different types of PFLs were analyzed utilizing PSpice simulation results. These PFLs are described with respect to their distinct features-the number of forming lines (single or double), the circuit relationship of the PFL and load (parallel or series), and the types of energy storage (current source, voltage source or a combination of both). The characteristic impedance, output parameters such as pulsewidth, voltage and current magnitudes, and pulse power were derived for each scheme. The merits and demerits of the output parameters are also included. View full abstract»

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  • Plasma and heat flux characteristics of a supersonic ammonia or nitrogen/hydrogen-mixture direct-current plasma jet impinging on a flat plate

    Publication Year: 2003 , Page(s): 281 - 288
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (445 KB) |  | HTML iconHTML  

    Spectroscopic and electrostatic probe measurements were made to examine plasma characteristics with or without a titanium plate under nitriding for a 10-kW-class direct-current arc plasma jet generator with a supersonic expansion nozzle in a low-pressure environment. Heat fluxes into the plate from the plasma were also evaluated with a Nickel slug and thermocouple arrangement. Ammonia and mixtures of nitrogen and hydrogen were used as a working gas. The NH3 and N2+3H2 plasmas in the nozzle and in the downstream plume without a substrate plate were in thermodynamical nonequilibrium states. As a result, the H-atom electronic excitation temperature and the N2 molecule-rotational excitation temperature intensively decreased downstream in the nozzle although the NH molecule-rotational excitation temperature did not show an axial decrease. Each temperature was kept in a small range in the plume without a substrate plate except for the NH rotational temperature for NH3 working gas. On the other hand, as approaching the titanium plate, the thermodynamical nonequilibrium plasma came to be a temperature-equilibrium one because the plasma flow tended to stagnate in front of the plate. The electron temperature had a small radial variation near the plate. Both the electron number density and the heat flux decreased radially outward, and an increase in H2 mole fraction raised them at a constant radial position. In cases with NH3 and N2+3H2, a radical of NH with a radially wide distribution was considered to contribute to the better nitriding as a chemically active and non heating process. 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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