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Plasma Science, IEEE Transactions on

Issue 4  Part 2 • Date April 2011

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  • Table of contents

    Page(s): C1 - 1041
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  • IEEE Transactions on Plasma Science publication information

    Page(s): C2
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  • Particle-in-Cell Simulations of Initial Argon Dielectric-Barrier Discharges

    Page(s): 1042 - 1050
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2058 KB) |  | HTML iconHTML  

    We use the commercial particle-in-cell code MAGIC for simulations of dielectric-barrier discharges (DBDs). The simulations are done in pure argon at atmospheric pressure to avoid many of the complications that occur in air. We study DBDs with an embedded surface electrode and also with an exposed surface electrode. The only particle creation-destruction effect that we consider is the ionization of argon by electron impact. The ion drag is based on the process of charge exchange of an ion with its parent gas. The electron drag cross section is based on the binary-encounter-Bethe cross section with a low energy correction. Our simulations last for only about 1 ns due to the large number of electrons produced, which fill our computer memory. We calculate the momentum imparted to the neutral gas during each time step by collisions with the ions and the electrons, and also the total accumulated momentum density imparted to the neutral gas during the entire simulation. This effect has been called the electrohydrodynamic force. The discharge is so fast that the neutral atoms have no time to move and are considered to be at rest. View full abstract»

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  • High-Performance Interpolation of Stellarator Magnetic Fields

    Page(s): 1051 - 1054
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    We present a new algorithm for interpolation of static current-free magnetic fields based on the use of specialized fourth-degree vector polynomial functions (Maxwell elements) which solve the static current-free Maxwell equations. This method provides sufficient accuracy for the demands of stellarator applications and retains a great speed advantage over direct Biot-Savart calculation of the fields. View full abstract»

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  • Ozone Synthesis Under Surface Discharges in Oxygen: Application of a Concentric Actuator

    Page(s): 1055 - 1060
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    The results of studies on the ozone synthesis under discharges generated on the surface of the ceramic actuator built as the concentric-strip electrode system are presented. Experiments were carried out in pure oxygen. The ozonizer, in which the gas flows with variable linear velocity, was used. The ozone concentrations and the process energy efficiencies show the possibility of effective ozone generation in the reactors with nonconventionally organized discharge space. View full abstract»

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  • Enhanced Stability of Second- and Fourth-Harmonic Gyrotrons Driven by a Frequency-Doubled Prebunched Beam

    Page(s): 1061 - 1066
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    There is currently considerable interest in operating gyrotrons at the second and higher cyclotron harmonics in order to access the near-terahertz regime while reducing magnetic field requirements. High-frequency gyrotrons have successfully operated at the second harmonic. However, competition from the fundamental harmonic increasingly limits operation in the higher order modes needed for the near-terahertz regime. Savilov recently proposed a scheme for frequency-doubled phase bunching of gyrating electron beams in a waveguide resonator formed from Bragg reflectors and with the drive frequency equal to the cyclotron frequency. The advantages of phase prebunching at twice the cyclotron frequency include suppression of the fundamental harmonic, enhanced second-harmonic operation, and increased likelihood of fourth-harmonic operation. We have investigated the use of this phase bunching technique to enhance higher harmonic operation in gyrotron oscillators with annular beams. We compute the frequency-doubled bunching produced by a Bragg-type prebunching cavity and use a large-signal, multimode, and multiharmonic gyrotron oscillator code to simulate the effect of this bunching on a highly overmoded output cavity. Regimes of stable operation are predicted for the second- and fourth-harmonic point designs. View full abstract»

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  • Temporal Evolution of Multipactor Electron Discharge on a Dielectric Under Excitation of High-Power Microwave

    Page(s): 1067 - 1074
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    Using particle-in-cell/Monte Carlo simulation, the time-dependent physics of the multipactor electron discharge on a dielectric is studied within a transmission line model. It is discussed how RF magnetic field influences the initiation of multipactor and the multipactor behaviors at the upstream and downstream sides of the dielectric window. The effect of oblique incident high-power microwave (HPM) on the multipactor characteristic is also discussed. It is found that the interaction of electrons with the electromagnetic field can provide their return to the dielectric surface, which makes a multipactor possible even without any external static field. Multipactor discharge at the downstream side of the dielectric window is demonstrated to have a longer delay time, a smaller electron-surface interaction rate, and a much higher electron mean energy in comparison to those obtained at the upstream side. Thereby, the experimental observation that the threshold power is approximately 20% higher for the downstream side than it is for the upstream side is explained. Generally, the multipactor electron discharge is most likely to take place at the region where the RF electric field is parallel to the dielectric surface. The deposited power is greatest at normal incidence of HPM but is dramatically decreased for angles of obliqueness greater than approximately 5°- 10°. The oblique incident angle does not change the Lissajous behavior of the multipactor discharge on a dielectric but may affect the shape of the Lissajous curve greatly. View full abstract»

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  • Single-Channel Hollow Cathodes in 5–20-eV Argon Discharge for Spacecraft Thruster Applications

    Page(s): 1075 - 1081
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    High-power magnetoplasmadynamic (MPD) thrusters are an attractive option for providing primary propulsion on flagship-class spaceflight missions beyond the Low Earth Orbit (LEO), such as piloted Mars and Mars cargo, and more near-term cargo missions supporting a crewed lunar outpost due to their unique ability to process large amounts of power in a relatively small footprint size. This results in significant savings in system mass and volume over competing propulsion options such as ion or Hall-effect thrusters. This paper presents a partial summary of data from recent research at the University of Southern California, in collaboration with NASA's Jet Propulsion Laboratory, investigating several concerns of the mechanisms influencing the performance and lifetime of high-current single-channel hollow cathodes (SCHCs), the central electrode, and the primary life-limiting component in MPD thrusters. The overall objective of such research is to extend the operational lifetime of the cathode to mission-enabling lengths, generally considered to be in the range of 5-10 000 h. Specifically covered are the trends seen in the discharge efficiency and power, the size of the plasma attachment to the cathode (the active zone), the cathode exit plume plasma density and energy, and the plasma property distributions of the internal plasma column of an SCHC. View full abstract»

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  • Design of Magnetically Tunable Magnetron Injection Guns for Gyrotrons at Multiple Frequencies

    Page(s): 1082 - 1085
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    In this paper, the design of a triode-type magnetically tunable magnetron injection gun (MT-MIG) is presented for 1-MW 110-, 120-, and 127.5-GHz-frequency gyrotrons with the various operating modes. Some basic equations relevant to the problem available in the literature have been used to obtain the preliminary design. Computer simulation has been performed by using the commercially available code EGUN. The triode-type MT-MIG with the accelerating voltage of 80 kV, the beam current of 40 A, the average transverse-to-axial velocity ratio of the electron beam of 1.26-1.35, and the maximum transverse velocity spread of less than 5% has been designed. Tuning of the MT-MIG is performed by varying the magnetic field. View full abstract»

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  • Townsend Instabilities in a Modified Discharge System With Coupled Narrow Gaps

    Page(s): 1086 - 1091
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    Townsend-type discharge in a modified gas discharge cell with coupled narrow gaps between a high-resistivity semiconductor plate and two planar electrodes is experimentally studied in the range of gas pressure 28-352 torr for various interelectrode distances (d1 = 50 μm, d2 = 50 - 320 μm). The effect of various diameters on the photodetector area to the discharge (D = 9 - 12 - 15 mm) are considered as well. It is observed that Townsend discharge is unstable at low current densities for certain experimental parameters. The temporal dynamics of the current fluctuations is measured around I = 50 μA. Interactions of plasmas with surfaces and space charge effects in many cases are the main reason for the nonlinear effects in gas discharges with increasing current. View full abstract»

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  • Atmospheric-Pressure Radio-Frequency Discharge for Degradation of Vinyl Chloride With \hbox {Pt}/\hbox {Al}_{2}\hbox {O}_{3} Catalyst

    Page(s): 1092 - 1098
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    This study investigates the application of a radio-frequency-powered plasma with a Pt/γ-Al2O3 catalyst to decompose the chlorinated volatile organic compound of vinyl chloride (VC) in air. The use of an atmospheric-pressure plasma jet is explored as an innovative technology for the treatment of VC. The effects of some major system parameters such as input power (PWI), plasma energy density, initial concentration of VC (C0), and space velocity (SV) of the catalyst on the plateau temperature (TP) of a reactor and conversions of VC (XVC) are studied and elucidated. The results show that the effectiveness of the plasma-assisted catalysis is evident as indicated by the increase of XVC and the rate constant. At a PWI of 250 W without a catalyst, the values of XVC were 14% and 5.4% for C0 = 200 and 450 ppmv, respectively. In the presence of the Pt/γ-Al2O3 catalyst with an SV of 17 400 h-1, the values of XVC for C0 = 200 and 450 ppmv increased to 49% and 39%, respectively. Note that the values of TP were 550 K and 430 K without and with the Pt/γ-Al2O3 catalyst at an SV of 17 400 h-1 and a PWI of 250 W. The proposed kinetic models describe the relationships of C/C0 with the major parameters for the plasma and plasma-assisted catalytic degradation of VC, showing good agreement with the experimental data. The information obtained is useful for the operation, design, and analysis of plasma devices. View full abstract»

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  • Plasma Degradation of Acid Orange 7 With Contact Glow Discharge Electrolysis

    Page(s): 1099 - 1103
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    This paper focused on how different parameters affect plasma degradation of Acid Orange 7 (AO) with contact glow discharge electrolysis (CGDE). These varied parameters were temperature, applied voltage, discharge time, initial pH of solution, initial dye concentration, and electrolyte concentration. It could be concluded from orthogonal design that applied voltage and discharge time had major effect on the degradation of AO. Under the optimized condition, the reproducibility of the experiment and the catalytic effect of ferric and ferrous ions were also studied. The degradation rate of AO in CGDE was stable and over 95% in reduplicative experiment. Ferric and ferrous ions had apparent catalytic effect on the degradation of AO. In particular, they could greatly reduce the degradation time. In addition, the ferrous ions showed the better catalytic effect than the ferric ions. View full abstract»

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  • Study on Attraction of Laser to Arc Plasma in Laser-TIG Hybrid Welding on Magnesium Alloy

    Page(s): 1104 - 1109
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    This paper presents the results of investigation on the attraction of laser to the electric arc plasma in laser-tungsten inert gas (TIG) hybrid welding of magnesium alloy AZ31B plates. By comparably estimating the characteristics of arc plasma, including the shape, the electron temperature, and density of the arc plasmas in hybrid welding and single TIG welding, three interactions between laser and arc plasma in hybrid welding are managed to be distinguished. The influences of laser power, intensity of arc current, and the distance between laser beam axis and tungsten electrode tip (Dla) on the attraction are analyzed. Moreover, a new mechanism for attraction is proposed by a physical model in the viewpoint of electromagnetic interaction between the currents. It is thought that there exists a current in the welding keyhole in hybrid welding, and the electromagnetic force between this current and arc plasma current is the driving force of the attraction. Attraction happens when the driving force overcomes the stiffness of the electric arc. View full abstract»

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  • Active-Current-Controlled Atmospheric-Plasma Generation Using a Plasma-on-a-Chip

    Page(s): 1110 - 1113
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    An active-current-controlled bias scheme is proposed for atmospheric-plasma generation using a plasma-on-a-chip. A current mirror circuit was used for a pulsed atmospheric discharge. The circuit was able to suppress the discharge current overflow during the glow discharge, which has been known to cause an arc transition. It was successfully demonstrated that such an active-current-controlled scheme can improve the stability of the atmospheric plasma and the lifetime of a plasma-on-a-chip. Moreover, the generated atmospheric plasma was diagnosed by using N2 emission spectra. Electron temperatures for varying the bias conditions were also evaluated. View full abstract»

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  • Spectral Property Investigation of Air Plasma Generated by Pulsed \hbox {CO}_{2} Laser

    Page(s): 1114 - 1119
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    In this paper, the laser propulsion plasma has been diagnosed experimentally using the method of optical emission spectroscopy. The spectral evolution of the air plasma generated by pulsed CO2 laser radiation with a parabolic reflector was studied, with a pulse energy of 2 J and a pulsewidth of 70 ns (full-width at half-maximum). In addition, most of the plasma spectral lines in the visible light region were identified, and the spectra of air plasma were dominated by the emission of single ionization of nitrogen and oxygen, with a weak emission of nitrogen and oxygen atom. Based on the local-thermodynamic-equilibrium state, the basic spectral properties of laser-induced plasma evolution, including the evolution of the plasma spectrum, electron temperature, and electron number density, were analyzed. We utilized the Boltzmann plot to evaluate the electron temperature and the Stark broadening and Stark center frequency shift to evaluate the electron number density. Results proclaimed that the maximum values of the electron temperature and electron number density were about 4.5 × 10 K and 1019 cm-3, respectively. View full abstract»

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  • Electron Density Measurement of DC Positive Arc Propagating Over an Ice Surface Based on \hbox {H}_{\alpha } Line

    Page(s): 1120 - 1124
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    Results of spectroscopic investigation of an arc formed over an ice surface are presented. Direct-current positive voltage is applied to a flat ice surface with a 6-cm air gap to initiate electric discharge. Time-resolved spectra are taken during the propagation of arc along the surface. From the emission spectra, the profile of hydrogen-alpha from Blamer series is used to measure the electron density of the arc column. A method based on broadening of the Hα line considering instrumentation broadening is employed. The electron densities obtained by optical emission spectroscopy show an increase from 1 to 2 × 1017 cm-3 corresponding to current increase from 200 to 700 mA. The electron density at the flashover instant is calculated to be about 2.5 × 1017 cm-3. View full abstract»

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  • A Way for High-Voltage \mu\hbox {s} -Range Square Pulse Generation

    Page(s): 1125 - 1130
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    In this paper, a new way for high-voltage μs -range quasi-square pulse generation based on a ns source pulser and a chopping spark gap is introduced. The source pulser delivered high-voltage source pulse with front edge at ns range to the chopping gap, and the chopping gap chopped the long flat back edge of the source pulse, so that a quasi-square pulse was formed on a high-impedance load. The breakdown-delay characteristics of the chopping gap, which was the most important, were studied in detail. Results of the experiments showed that when the pulse voltage peaked by the first peaking gap was a little lower than or approximate to the breakdown voltage of the chopping gap, the chopping gap broke down at the back edge of the peaked pulse so that the breakdown-delay time can increase from 30 ns to several μs. The breakdown-delay time of chopping gap is confined to the flat top of the peaked pulse. By using this mechanism of breakdown delay, a quasi-square pulse with pulse width of 1.95 μs, amplitude of 55 kV, and front edge of 22 ns was produced on a 1.15-kΩ load. Repetitive chopping pulses at 0.2 Hz were provided to demonstrate the feasibility of the chopping gap. By contrast to the conventional chopping, four essential conditions were concluded. Based on these results, a controllable trigatron-type chopping gap system is introduced to ensure chopping stability. It provides an important new way for μs-range high-voltage square pulse generation. View full abstract»

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  • Design and Implementation of a High Power Density Three-Level Parallel Resonant Converter for Capacitor Charging Pulsed-Power Supply

    Page(s): 1131 - 1140
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    This paper describes the design and implementation of a prototype 30-kW (or 30-kJ/s) pulsed-power supply for capacitor charging. The system operates at 200-kHz maximum switching frequency, which is considerably higher than the conventional practice at this power level, leading to smaller passive components. A high power density of 143 W/in3 is achieved with the converter operating at a high ambient temperature of 65°C with 90°C cooling oil, by utilizing various technologies on topology, control, devices, passives, and thermal management. The experimental results demonstrate that the converter meets the performance requirements while achieving a high power density. View full abstract»

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  • Kinetics of Complex Plasmas Having Dust of Different Materials With Corresponding Size Distribution

    Page(s): 1141 - 1149
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    In this paper, the authors have presented a formulation of the kinetics of complex plasmas, having dust of different materials (different work functions) and size distributions, which is based on the number and energy balance of constituents; this is in deference to the present emphasis on considering complex plasma as an open system. The formulation is based on a size independent dust surface potential; this simplifies the problem to a form, similar to that for the case of uniform size dust grains, characterized by the mean (αm) and the root mean square (αrms) radius of the dust particles. Two cases, viz., complex plasma in thermal equilibrium and complex plasma irradiated by monochromatic radiation, have been considered in detail, and corresponding computations have been made for a mixture of two varieties of dust grains having high (φ2 >; hv) and low (hv >; φ1) work functions. The relevance of the first case to flames and rocket exhausts has been pointed out. The fluctuation of charge corresponding to individual dust grains has also been evaluated. A discussion based on numerical results and conclusion have been also given. View full abstract»

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  • Repetitively Pulsed Relativistic Cherenkov Microwave Oscillator Without a Guiding Magnetic Field

    Page(s): 1150 - 1153
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    Repetitively pulsed modes of operation of a Cherenkov microwave oscillator without an external magnetic field for the electron energies of 0.5 and 1.2 MeV were realized in the experiment. In a batch mode with a 1-Hz repetition frequency, the oscillator efficiencies (taking into account the total diode current) were 8% ±2% and 16% ±3 %, respectively (at 0.2 ±0.04-GW and 2.5 ±0.5-GW peak generation power, respectively). For a batch mode with a 10-Hz repetition frequency, the corresponding efficiencies were 7% ±1% and 15% ±3%, respectively (at 0.17 ±0.03-GW and 2.0 ±0.4-GW peak generation power, respectively). Investigations of the lifetime of velvet-covered cathodes and anode grids of oscillators were carried out in repetitively pulsed modes. The lifetime of the anode grid and velvet-covered cathode for the electron energy of 1.2 MeV was about 3000 pulses, and for the electron energy of 0.5 MeV, it can exceed 11 000 pulses. View full abstract»

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  • Temporal Evolution of the Ion Fluxes for Various Elements in HIPIMS Plasma Discharge

    Page(s): 1154 - 1164
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    In our previously published paper, the life span of metal ions in high-power impulse magnetron sputtering (HIPIMS) discharges was measured up to 5 ms from the start of the pulse. To investigate the influence of the ion mass, ionization energy, and sputter yield on the time evolution and life span of singly and doubly charged metal and gas ions in the HIPIMS plasma discharge, the most frequently used materials for thin-film deposition carbon, aluminium, titanium, chromium, copper, and niobium have been used. The ion energy distribution function of each material was measured using energy resolved mass spectrometry in time-resolved mode. The setup of the mass spectrometer was the same for all materials. To investigate the influence of working gas pressure on the time evolution of ion fluxes, measurements have been performed at two pressures, 0.3 Pa and 3 Pa. View full abstract»

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  • One-Dimensional Modeling of Dielectric Barrier Discharge in Xenon

    Page(s): 1165 - 1172
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    A 1-D fluid model coupled with an external circuit is proposed to study the Xe dielectric barrier discharge (DBD) under a 50-kHz ac sinusoidal voltage. The impact of ions and photons on barrier surfaces and the thermal motion of charged particles in the sheath are taken into account in this model. The spatial and temporal distributions of electrons, ions, and excited, resonance, and metastable particles are investigated. The experimental investigations on discharge current densities under different voltage source amplitudes are analyzed and compared with simulation results. The results reveal that, with the increment of voltage source amplitudes, the waveforms of gas gap voltage and discharge current all move forward the applied voltage, showing a gradually decreased phase shift, which is in good agreement with the experimental observations. The evolution of surface charges accumulated on dielectric barriers can be divided into six stages during an ac cycle, and they play a key role in the ignition and extinction of the discharge. It is concluded that, while the charge difference between the surfaces of a two-side dielectric is up to a certain value and the applied voltage is low enough, the gas breakdown will occur. The spatiotemporal variations of particle densities and electric field indicate that the Xe DBD under the conditions considered in this paper is a typical glow discharge. Furthermore, the electron emission brought by impact of photons on dielectric surfaces can accelerate gap breakdown and strengthen the intensity of the discharge, and the sheath phenomenon is more obvious under the consideration of thermal motion of charged particles in boundary conditions. View full abstract»

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  • A Three-Dimensional Particle-in-Cell Simulation of Quasi-Perpendicular Shock on Fujitsu FX1 Cluster

    Page(s): 1173 - 1179
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    The high-specification computational power of Japan Aerospace Exploration Agency's new supercomputer system, called Fujitsu FX1 cluster, enables us to perform really macroscale 3-D situations with full particle plasma simulation [particle-in-cell (PIC) method]. A fully 3-D kinetic approach to collisionless shock problems, which is one of the most important problems in the space plasma science, is possible, and a challenging run is being executed for a pioneering study of the topic. About 0.4 billion grids are allocated for the electromagnetic fields, and about 0.1 trillion particles are loaded into the simulation run. The computational efficiency of the PIC code is about 8% of the peak performance (4.6 Tflops) using 5776 CPU cores (57 Tflops). The simulation parameters were selected to simulate ESA's Cluster-II spacecraft observational result reported by Seki (in 2009). The full mass ratio mi/me = 1840 was taken for this simulation, and almost one ion inertia length square could be allocated for the simulation. In this simulation, a quite complicated wave activity is found in the shock foot region. In this paper, comparing 3-D results with 2-D simulation results, a 3-D nature of shock transition region of quasi-perpendicular shock is reported. View full abstract»

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  • Erosion and Lifetime Evaluation of Molybdenum Electrode Under High Energy Impulse Current

    Page(s): 1180 - 1186
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    One of the factors of the functional life of the electrodes used in pulse current discharge depends on the erosion of electrodes. There are many areas that have not been investigated and many areas that require additional study. Some studies have presented results related to the erosion of electrodes made of Cu, Cu-W, Ti, graphite, stainless steel, etc. There is little information available on the erosion of molybdenum electrodes. The erosion of electrodes is related with the electrode material (conductivity, melting point, and density) and the Coulomb charge transferred per impulse. In this paper, molybdenum (Mo) was selected as the main electrode material, considering these factors in addition to high erosion resistance due to high work function and better formability. The performance of pulse discharge devices is mainly characterized by static breakdown voltage, prebreakdown voltage, recovery time, delay time, jitter, and reliability. The degradation of these performance parameters (PPs) is related to many critical factors affecting electrode erosion, consisting of peak current, electrode material, electrode geometry, electrode surface roughness, and gas type. The degree with which the electrode-erosion factors (EEFs) affect the PPs of the pulse discharge device relatively varies and has complex interrelationships, and the relative importance weight of each EEF in order to maximize the life of the pulse discharging device is calculated using quality function deployment and analytic network process methodology. This paper presents experimental work carried out to investigate the erosion characteristics of a molybdenum electrode. Testing was performed at 10-11-kA current discharge every 35 s at a rate of 300 discharges per day with a total of 10 000 shots. The experimental results for Mo electrodes indicate approximately 60 μg/C for 5000-C transfers. For 10-11-kA current transfer with Mo electrodes, we can take about 8.5 × 105 shots with wear of 0.3 g without appreciable local wear. View full abstract»

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  • Design and Testing of a 10-MJ Electromagnetic Launch Facility

    Page(s): 1187 - 1191
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    For basic research on electromagnetic launch technology, the Beijing Institute of Special Electromechanical Technology has initiated a program focusing on the design and testing of a 10-MJ electromagnetic launcher facility with the cooperation of Nanjing University and the Institute of Electrical Engineering, Chinese Academy of Sciences. The facility will consist of a 10-MJ prime energy, a 6-m-long railgun, and a control system. A 3.2-MJ pulse power unit (PPU) with 32 100-kJ modular PFN units has been completed and tested, and its prime energy can be easily extended to 10 MJ. A 6-m-long railgun has been built, which can be easily cut into a 4-m-long railgun by which many firings have been done with the new PPU. Construction and testing of the whole facility are being continued. 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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