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Plasma Science, IEEE Transactions on

Issue 4 • Date April 2012

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Displaying Results 1 - 25 of 47
  • Table of contents

    Page(s): C1 - 958
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  • IEEE Transactions on Plasma Science publication information

    Page(s): C2
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  • Global Model of \hbox {Cl}_{2}\hbox {/Ar} High-Density Plasma Discharge and 2-D Monte-Carlo Etching Model of InP

    Page(s): 959 - 971
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    A multiscale approach has been developed in order to simulate the etch process of InP in an inductive coupled plasma (ICP) Cl2/Ar plasma discharge. The model consists of three modules: a global kinetic model of the Cl2/Ar plasma discharge, a sheath model, and a 2-D Monte-Carlo etching model. The densities and the fluxes of all neutral and charged species considered in the reaction scheme as well as the electron temperature are calculated from the global model. The angular and energy distribution functions of ions are computed from the sheath model. The output parameters of both the global kinetic model and the sheath model in terms of particle fluxes, ion angular distribution function and ion energy distribution function are used as input parameters in the 2-D etching model. The latter allows tracking in time the evolution of the etched surface. The ultimate goal of the multiscale approach is to predict the etch rate, the etched surface chemical composition, and the etch profile as a function of the operating conditions (power, pressure, gas flow rates, etc). In this paper, the results from the global model are first compared to the measurements carried out in the ICP etching tool, showing a satisfactory agreement. The etching model is then used to simulate the etching of narrow trench and small-diameter hole in InP. The mechanisms involved in the development of undercut below the mask and in the bowing effect are analyzed. The comparison between simulated and experimental etch profiles evidences the important role of Cl adsorption probability on the development of the undercut, and the significant impact of the redeposition of the etched species on the etch rate variation and on the narrowing in the bottom of the etched hole/trench. View full abstract»

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  • Electrical Conductivity Measurements via a Low-Voltage Conductivity Channel

    Page(s): 972 - 979
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    The electrical conductivity in combustion gases with four different compositions (2% potassium with 0%, 10%, 15%, and 20% aluminum by mass added to a hydrocarbon fuel burned in gaseous oxygen) was determined experimentally using conductivity channels with two geometrical configurations, one with a constant bore and one with a tapered bore. Electrical conductivity for these conditions was calculated using the MACH2 numerical code, augmented with a transport property code. The fluid- mechanical conditions in the flow streams were also calculated using the axisymmetric and 1-D (NASA CEA) nozzle flow codes, both of which used the same transport property code to calculate the electrical conductivity. In the laboratory conductivity channel experiments, relatively low applied voltages were chosen to avoid unnecessary electrical heating of the test gas which might possibly have distorted the results. Results indicate that the measured conductivity increased linearly from approximately 10 mhos/m to 20 mhos/m as the aluminum was increased from 0% to 25% by mass. The results presented here differ markedly from those reported in shock tube experiments. The numerical simulation of the constant bore channel underpredicted the experiment within 15% and underpredicted the tapered-bore channel within 30%. The sources of uncertainties are addressed and provide some measure of confidence in the quality of the results. This is the first reported measurement of electrical conductivity values in the combustion products of a quasi-steady flow as a function of composition, together with the validation of these values with a 2-D computation. View full abstract»

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  • The Reactive Thermal Conductivity of Thermal Equilibrium and Nonequilibrium Plasmas: Application to Nitrogen

    Page(s): 980 - 989
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    The accuracy of numerical simulation on plasma behavior depends strongly on the reliability of thermophysical property data. Large number of studies for thermal plasma properties in the local thermodynamic equilibrium (LTE) exist; however, the database for thermal nonequilibrium plasmas is still far from completeness. This paper derives a general expression of total reactive thermal conductivity (TRTC) with great applicability to monatomic, diatomic, and polyatomic gases in terms of a two-temperature model. The derived formula is applied to nitrogen plasmas under thermal equilibrium and nonequilibrium conditions, considering its wide use in plasma systems and switching devices. Typical calculated results of TRTC with two different Saha equations and Guldberg-Waage equations in the temperature range of 300 K-40 000 K under different degrees of nonequilibrium are given and compared with those computed according to Brokaw and Butler's derivation for the special case of LTE plasmas, which shows excellent agreement. The influence of different expressions for Saha equations and Guldberg-Waage equations, together with different pressures of 0.1, 1, 3, 5, and 10 atm, on the TRTC evaluated by this newly developed expression is presented as well. These provide reliable reference data for use in the simulation of plasmas. View full abstract»

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  • Nuclear Radiation-Induced Atmospheric Air Breakdown in a Spark Gap

    Page(s): 990 - 994
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    We have investigated the effect of pre-ionization by a radioactive -ray source on the atmospheric air breakdown conditions in a high-voltage spark gap. A standoff millimeter-wave (mmW) system was used to monitor the breakdown properties. A decrease in breakdown threshold was observed with an increase of radiation dose. We attribute this to a space charge-controlled electron diffusion process in a cloud of radiation-induced ion species of both polarities. The space charge-dependent diffusion coefficient was determined from the measurement data. In addition, we found that the breakdown process shows random spikes with Poisson-like statistical feature. These findings portend the feasibility of remote detection of nuclear radiation using high-power mmWs. View full abstract»

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  • Waves in Warm Constant-Density Cylindrical Electron Beams

    Page(s): 995 - 1009
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    A dispersion equation is derived for waves in a warm constant-density cylindrical electron beam where electrons exhibit 3-D orbits in a uniform magnetic field and where the rigid-rotor beam model has transverse temperatures confined to the beam interior to provide a cold sharp beam edge suitable for matching RF fields. The equation solutions for surface waves in a warm beam emitted from a magnetically shielded gun can be obtained immediately from solutions for surface waves in a cold beam. Validation of such warm-beam solutions was made using TWT hot-test data and particle-in-cell-code simulations. Standard transcendental-equation solutions are found for surface waves in warm small-vorticity beams and space-charge waves in warm large-vorticity beams. Reduced plasma frequencies are increased for surface waves and decreased for space-charge waves by increasing the transverse-temperature thermal parameter. Beam temperatures were included in a Pierce-theory determinantal equation in the small-transverse-wavenumber limit. View full abstract»

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  • Numerical Investigation on Interference and Absorption of Electromagnetic Waves in the Plasma-Covered Cavity Using FDTD Method

    Page(s): 1010 - 1018
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    We present real-time status of the electromagnetic (EM) scattering by the plasma-covered metal cavity, using the 2-D finite-difference time-domain method. The interference and absorption of EM waves of such progresses were analyzed. The variations in their return loss as a function of incident angle, frequency of EM wave, electron density of plasma, and plasma collision frequency were also presented. The results show that when the EM wave hits the cavity at the front aspect angle, the signals propagate along the central axis of the cavity, and the returning waves converge to source for all incident frequencies. On the contrary, when the EM wave hits the cavity at the oblique aspect angle, the combining of reflected waves among the inner walls of the cavity will result in constructive or destructive interference, consequently the returning wave not converging to source any more. The values of peak return loss are extremely different between plasma-covered metal plate and plasma-covered metal cavity. The former is less than 4 dB, while the latter reach to as large as 25 dB. The appropriate parameter regimes of plasma can be chosen for more efficiency design. View full abstract»

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  • An Integrated Antenna-Source System of Very High Ultra Wide-Band Gain for Radiating High-Power Wide-Band Pulses

    Page(s): 1019 - 1026
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    Integrated antenna-source (IAS) systems depends on techniques that reduce the complexity of traditional separated antenna-source systems. The IAS has a number of advantages such as compactness, simplicity, and efficiency. However, the ultra wide-band (UWB) gain of IAS is low since the integrated system employs omni-directional antennas. Here, we propose a new IAS system. We increase the size of capacitance and implement a smooth transition structure in the new system. As a result, the proposed IAS shows a UWB gain of 0.68. It is more than double compared to that of conventional IAS systems. The radiated electric field measured at 4 m from the system has a peak value of 80.8 kV/m and a center frequency of 350 MHz. The radiated power density decreases by half when the radiation angle is changed from 0° to 60°. View full abstract»

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  • V-Shape Folded Rectangular Groove Waveguide for Millimeter-Wave Traveling-Wave Tube

    Page(s): 1027 - 1031
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    A novel slow-wave structure called V-shape folded rectangular groove waveguide is proposed to develop high-power, wide-bandwidth, and high-efficiency millimeter-wave traveling-wave tube. This structure evolves from a conventional rectangular groove waveguide bending the groove with V-shape along its longitudinal direction, which can operate with the sheet electron beam. In this paper, the electromagnetic characteristics and the beam-wave interaction of this structure operating in the V-band are obtained. From our calculations, this circuit structure possesses low transmission loss and can produce an output power of over 900 W ranging from 56 to 65 GHz when the cathode voltage and beam current are set to 12.8 kV and 500 mA, respectively. The corresponding gain and electron efficiency can reach over 36.5 dB and 14%, respectively. View full abstract»

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  • Electromagnetic Analysis of a Disk-Loaded Coaxial Waveguiding Structure for MILO

    Page(s): 1032 - 1041
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    An all-metal disk-loaded coaxial waveguiding structure, for its application in a magnetically insulated line oscillator (MILO), as a slow-wave interaction structure, excited in the TM mode, has been field analyzed. In the analytical model, modal matching technique has been used considering all the space harmonics generated due to the structure axial periodicity in the free-space region inside the structure and stationary modal harmonics caused by the reflections from the disk walls in the disk-occupied region of the structure. The dispersion relation of the structure is obtained considering the continuity of the fields at the interface between these two regions. A system of homogeneous equations is formed in the Fourier components of the field constants. The condition for the nontrivial solution of the equations gives the dispersion relation of the structure in the form of a determinantal equation. The analysis is further extended for the interaction impedance, which has direct relevance with the temporal RF signal growth in the device. The derived dispersion characteristic has been validated as special cases for the known results and has been also validated with those results published in the literature. Furthermore, the structure has been simulated using commercial code “CST Microwave Studio” for the dispersion as well as the interaction impedance characteristics. The simulated values have been found to be in agreement with the theoretically derived results. The dispersion characteristics and the axial interaction impedance of the structure have been plotted for a wide range of structure parameters. Furthermore, the desired operation of the MILO device, the method of structure parameter selection, and the effect of parameter variation have been also discussed. This study would help the design engineers in understanding the physics and in selecting the coaxial disk-loaded structure parameters for their successful use in MILO devices having reasonab- e RF growth rate in synchronism with the electron beam. View full abstract»

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  • The Monte Carlo Simulation of a 1-MW Neutral Beam Injector on RFX-Mod

    Page(s): 1042 - 1052
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    The megawatt-level TPE-RX neutral beam injector is planned to be installed on the RFX-mod reversed field pinch (RFP) experiment. To properly integrate the TPE-RX injector on RFX-mod, a 3-D Monte Carlo simulation of the injector has been carried out. The code simulates the charged and neutral particle trajectories from the acceleration grids of the beam source to the RFP plasma. The simulation includes the neutralization stage, the interaction between the accelerated particles and the magnetic field produced by RFX and the residual ion dump (RID), and the interactions between the accelerated beam and the background gas. The simulation has allowed to estimate the neutralizer and RID efficiency and specifications, the geometry of the beam duct between the injector and RFX-mod, and the necessary degree of magnetic screening. View full abstract»

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  • The Applicability of Dual Stage Ion Optics to Ion Engines for High Power Missions

    Page(s): 1053 - 1063
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    In this paper, the applicability of dual stage ion optics and in particular of the so-called dual stage ion engine to high power, high specific impulse missions will be evaluated. First, the performance limits of conventional two gridded ion engines (GIE) will be discussed and the advantages provided by dual stage ion engines reported. The limits of applicability of a dual stage ion engine will be analyzed analytically and the results confirmed numerically. The lifetime and performance of a three gridded dual stage ion engine (DS3G) will be numerically investigated and compared to those of a conventional GIE assessing for the first time in the open literature under what condition dual stage ion optics provide performance improvements over conventional GIEs and what is its impact on the thruster lifetime. Dual stage ion engines have been found to be capable of providing higher thrust density and longer lifetime with respect to conventional gridded ion engines. View full abstract»

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  • Design and Analysis of a High-Power Electron Beam Source (>\hbox {50} \hbox {KW/cm}^{2}) Confined in a Highly Uniform Magnetic Field Region

    Page(s): 1064 - 1069
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    A directly heated line source emitter with beam power (>; 50 KW/cm2) is developed. The emitter assembly design parameters and beam characteristics are analyzed using a highly uniform magnetically confined region. Circular cross-sectional tungsten cathodes of diameters 0.9 mm and 1.5 mm were used, and their results are compared. The developed emitter configuration ensures low angular divergence, millisecond evaporation time for large samples, operational reproducibility, and beam stability. The emitter source has been tested by experimentally developing extremely homogeneous magnetic field in large cylindrical region of more than one-half of the coil's diameter. View full abstract»

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  • Study of Output Performance of Partially Dielectric Loaded A6 Relativistic Magnetron

    Page(s): 1070 - 1074
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    A three dimensional particle-in-cell code MAGIC-3D is used to examine the output performance of a partially dielectric loaded A6 relativistic magnetron. The side resonators of the resonant structure are loaded symmetrically at angle of 120 with low-loss dielectric material. The simulation of dielectric loaded A6 relativistic magnetron is performed for -mode of operation. The formation of six electron spokes in the oscillation region confirms -mode oscillation of a six vane relativistic magnetron. The results indicate single -mode operation with improved radiated output power of 620 MW with relatively low start-up time in comparison to unfilled resonant structure. A power increase of 40% is found in case of partially filled dielectric resonator in comparison to unfilled dielectric resonators. View full abstract»

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  • Characterization of the Neutron Production in the Modified MA Plasma Focus

    Page(s): 1075 - 1081
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    The PF-1000 plasma-focus (PF) facility equipped with Mather-type coaxial electrodes was modified by the addition of a cathode disk in front of the anode front plate, at a distance of 3 cm and by covering the hole in the anode center. In comparison with the earlier electrode setup, important differences as regards neutron, X-ray, and interferometric diagnostics were observed for this special electrode configuration. The total current during the pinch phase increased on average by about 25%, the total neutron yield decreased to about 20-30%, and the velocity of transformation of the structures in the column (together with constriction) was evidently depressed. The average energy of the electrons and deuterons produced was decreased. The lower energy value of fast deuterons and their lower cross section of fusion DD reactions were probably the reason for the observed decrease in the total neutron yields. View full abstract»

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  • A Plasma Focus Electronic Neutron Generator

    Page(s): 1082 - 1088
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    An electronic neutron generator based on the dense plasma focus emits fast neutron pulses (~20 ns at the source) that allow for the time-of-flight detection of target materials at a standoff of ~3 m. Pulse-power-driven neutron generators have been considered unreliable due to the short lifetime of components such as gas switches and electrodes. The reliable operation of a plasma focus has been demonstrated for up to 25 000 shots at 1 Hz over several experiments with <; 25% variation in the mean neutron yield. The repetition rate is limited to 1 Hz for thermal management reasons. The peak current was 61 kA, with the neutron yield varying from 2.6 × 105 neutrons/pulse to 4.4 × 105 neutrons/pulse (a standard deviation of ~50%) within a given run. The neutron yield distribution variation more strongly correlates with the minimum in the time derivative of the current rather than the peak current in the narrow operating current window of 61 ± 2 kA. Each experiment used a fixed deuterium fuel gas charge. Insulator coating was shown not to be a problem after a total of 250 000 shots. The primary lifetime-limiting factor was a deep hole that was bored into the SS304 anode, eroding it at a rate of ≈6 μg/shot. With a refractory cooled anode, the source could realize an increase in electrode lifetime and a reduction in insulator coating, leading to a long lifetime (~106 pulse) and a fast pulse electronic neutron generator that operates at up to 100 Hz at 108-n/s D-D output. View full abstract»

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  • Effect of Electrode Configuration on the Wastewater Treatment by Underwater Electrical Streamer Discharge

    Page(s): 1089 - 1093
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    The effect of electrode configuration on wastewater treatment by underwater electrical streamer discharge is investigated by comparing a coaxial rod-to-cylinder electrode configuration with a point-to-cylinder one. By using a brilliant-blue FCF solution as monitor pollutants, the dissipated energy per pulse, the degradation rate constant, and the energy consumption in both electrode configurations are compared under different solution conductivities or pH values. The coaxial rod-to-cylinder electrode configuration can dissipate as about three times of energy into the solution as the point-to-cylinder one does during one discharge pulse in our experiment. In both electrode configurations, the degradation of the brilliant-blue FCF solution follows a pseudo first-order rate profile. The degradation rate constant is not significantly influenced by the solution conductivity, but it decreases with increasing the solution pH value. Comparing with the point-to-cylinder configuration, the degradation rate constant in the rod-to-cylinder one was improved by a factor of about 4.3, 3.6, and 2.9 at solution , 7.8, and 10, respectively. The energy consumption increases with increasing the solution conductivity or the solution pH value in both electrode configurations, but it is significantly lower in the rod-to-cylinder one when the solution . Fixing the solution conductivity at 150 , the energy consumption in the rod-to-cylinder system decreases by about 30% and 20% at solution and 7.8, respectively. View full abstract»

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  • Current Control in the Magnetron Systems for Nanofabrication: A Comparison

    Page(s): 1094 - 1097
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    A cylindrical magnetron system and a hybrid inductively coupled plasma-assisted magnetron deposition system were examined experimentally in light of their discharge characteristics with a view to stress the enhanced controllability of the hybrid system. The comparative study has shown that the hybrid magnetron the inductively coupled plasma system is a flexible, powerful, and convenient tool that has certain advantages as compared with the cylindrical dc magnetrons. In particular, the hybrid system features more linear current-voltage characteristics and the possibility of a bias-independent control of the discharge current. View full abstract»

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  • Plasma inactivation of candida albicans by an atmospheric cold plasma brush composed of hollow fibers

    Page(s): 1098 - 1102
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    It remains a challenge to generate the uniform and large-area cold plasma at atmospheric pressure. In this paper, we report a method to generate a reliable and homogeneous brush-shaped plasma plume running at atmospheric pressure. The plasma brush (110 mm in length and 10 mm in width) is mainly composed of well-aligned and hollow optical fibers. Current-voltage measurements indicate that the brush-shaped plasma plume consists of glowlike pulsed discharge with their pulsewidths of several microseconds. The generation of the He/O2 glowlike discharge is further proved by the uniform distribution of O atoms along the transverse location of the plasma brush. This brush-shaped plasma plume is used for the application in the plasma inactivation of Candida albicans cells. About 97% of Candida albicans cells with a population of 105 spores are killed when exposed to the O2/He (volume ratio: 5/95) brush-shaped plasma plume for 150 s. Analysis indicates that plasma-activated species, such as O radicals, may play a crucial role in killing the resistant Candida albicans cells. View full abstract»

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  • Effects of the Operating Conditions on the Electrical Characteristics of Pulse Discharges in Atmospheric-Pressure Pure Helium

    Page(s): 1103 - 1109
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    In this paper, the effects of operating conditions on the electrical characteristics in a dielectric barrier discharge excited by voltage pulses are systematically investigated by means of a 1-D fluid model. The operating conditions refer to barrier fashion, secondary electron emission coefficient , gap width , dielectric constant , and dielectric thickness . Under different operating conditions, the important characteristic quantities of describing the pulse discharges, i.e., discharge current density , breakdown voltage , averaged electron density , averaged dissipated power density , and axial distributions of both electron density and electron temperature , are calculated and analyzed in detail. The present work gives the following significant results. There are almost no effects of the operating condition on the characteristic quantities except for the amplitude of in the first discharge if the accuracy of the model is taken into account. The peak value of nearby the momentary cathode (MC) becomes larger, and large can be obtained by small by increasing of the MC. For small , the breakdown of the gap occurs earlier, and for large , both the small peak value of and the wide area of quasi-neutral plasma bulk can be obtained. All of the parameters except for in the second discharge decrease, the peak value of nearby the MC gets smaller, and the in the cathode sheath presents lower, when decreasing or increasing . View full abstract»

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  • Electrophoretic Deposition of Carbon Nanotubes Auxiliary Layer for Power Saving in AC Plasma Display Panels

    Page(s): 1110 - 1116
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    The carbon nanotube (CNT) auxiliary layers are suggested to reduce the high driving voltage in ac plasma display panel (AC-PDP). The CNT layer, which was integrated on dielectric layer overlapping the PDP bus electrode, was formed by electrophoretic deposition without sheltering further plasma emission light. The effective CNT pretreatment, uniform and thickness distribution of CNTs in the layer result in the excellent field-emission properties of low turn-on field (1.7 V/μm), which was proved to effectively reduce the discharge voltage of display cell with A-type (CNT layer is at the middle of indium-tin-oxide electrode) in a series of discharge testing. The lowest sustain volt- age for turning on the cells was reduced by 30-40 V. The FE-PDP theoretical model was proposed for explaining the testing results. View full abstract»

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  • Applications of Air Plasma for Wound Bleeding Control and Healing

    Page(s): 1117 - 1123
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    The design and the electric and emission characteristics of a handheld air plasma spray are presented. The plasma is generated by 60-Hz periodic discharges between two concentrically cylindrical electrodes. A ring magnet is used to rotate arc discharges, which sprays outward by an airflow. The rotation of arc discharges keeps the generated plasma in nonequilibrium state and at relatively low temperature . The plasma effluent still contains high-energy electrons which dissociate molecular oxygen into atomic oxygen. The emission spectroscopy of the plasma plume reveals that the plasma effluent, which carries abundant atomic oxygen, extends from the cap of the plasma spray about 25 mm. Using pigs as the animal model, in vivo tests of stopping wound bleeding and postoperative observation of wound healing by this air plasma spray were performed. The results show that the bleeding from a cut to an ear artery is stopped swiftly; this air plasma spray also shortens wound healing time to about half (from 14 days to 8 days) after stopping the bleeding of a cross-cut wound in the ham area. View full abstract»

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  • Gliding Arc Plasma-Stimulated Conversion of Pyrogas into Synthesis Gas

    Page(s): 1124 - 1130
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    This paper discusses plasma-assisted conversion of pyrolysis gas (pyrogas) fuel to synthesis gas (syngas, combination of hydrogen and carbon monoxide). Pyrogas is a product of biomass, municipal wastes, or coal-gasification process that usually contains hydrogen, carbon monoxide, carbon dioxide, water, unreacted light and heavy hydrocarbons, and tar. These hydrocarbons diminish the fuel value of pyrogas, thereby necessitating the need for the conversion of the hydrocarbons. Various conditions and reforming reactions were considered for the conversion of pyrogas into syngas. Nonequilibrium plasma reforming is an effective homogenous process which makes use of catalysts unnecessary for fuel reforming. The effectiveness of gliding arc plasma as a nonequilibrium plasma discharge is demonstrated in the fuel reforming reaction processes with the aid of a specially designed low current device also known as gliding arc plasma reformer. Experimental results obtained focus on yield, molar concentration, carbon balance, and enthalpy at different conditions. View full abstract»

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  • Three-Dimensional Simulations of Cylindrical Target Implosion Imaging Using Laser-Driven Proton Source

    Page(s): 1131 - 1133
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    Many experiments, based on the road map of the European High Power laser Energy Research facility project, were performed to study fast electron transport in compressed matter in the context of fast ignition approach to inertial confinement fusion. The generation of high intensity beams from laser-matter interaction extends the possibility to use protons as a diagnostic to image imploding targets in these experiments. The analysis of experimentally obtained proton images requires a careful analysis and accurate numerical simulations using both hydrodynamic and Monte Carlo (MC) codes. An experiment has been performed in 2008 at Rutherford Appleton Laboratory to study fast electron propagation in cylindrical imploding targets illuminated by four laser pulses. In this paper, we present new simulation results in 3-D geometry. Three-dimensional density map is generated by running the 3-D version of the MULTI code. Proton radiography images are then simulated using the MC code MCNPX. 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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