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Sample records for local arc discharge

  1. HOLLOW CARBON ARC DISCHARGE

    DOEpatents

    Luce, J.S.

    1960-10-11

    A device is described for producing an energetic, direct current, hollow, carbon-arc discharge in an evacuated container and within a strong magnetic field. Such discharges are particularly useful not only in dissociation and ionization of high energy molecular ion beams, but also in acting as a shield or barrier against the instreaming of lowenergy neutral particles into a plasma formed within the hollow discharge when it is used as a dissociating mechanism for forming the plasma. There is maintained a predetermined ratio of gas particles to carbon particles released from the arc electrodes during operation of the discharge. The carbon particles absorb some of the gas particles and are pumped along and by the discharge out of the device, with the result that smaller diffusion pumps are required than would otherwise be necessary to dispose of the excess gas.

  2. Reinvestigation of the charge density distribution in arc discharge fusion system

    SciTech Connect

    Sheng, Lin Horng; Yee, Lee Kim; Nan, Phua Yeong; Thung, Yong Yun; Khok, Yong Thian; Rahman, Faidz Abd

    2015-04-24

    A continual arc discharge system has been setup and the light intensity of arc discharge has been profiled. The mathematical model of local energy density distribution in arc discharge fusion has been simulated which is in good qualitative agreement with light intensity profile of arc discharge in the experiments. Eventually, the local energy density distribution of arc discharge system is able to be precisely manipulated to act as heat source in the fabrication of fused fiber devices.

  3. Metal halide arc discharge lamp having short arc length

    NASA Technical Reports Server (NTRS)

    Muzeroll, Martin E. (Inventor)

    1994-01-01

    A metal halide arc discharge lamp includes a sealed light-transmissive outer jacket, a light-transmissive shroud located within the outer jacket and an arc tube assembly located within the shroud. The arc tube assembly includes an arc tube, electrodes mounted within the arc tube and a fill material for supporting an arc discharge. The electrodes have a spacing such that an electric field in a range of about 60 to 95 volts per centimeter is established between the electrodes. The diameter of the arc tube and the spacing of the electrodes are selected to provide an arc having an arc diameter to arc length ratio in a range of about 1.6 to 1.8. The fill material includes mercury, sodium iodide, scandium tri-iodide and a rare gas, and may include lithium iodide. The lamp exhibits a high color rendering index, high lumen output and high color temperature.

  4. Barriers to flashover discharge arcs on Teflon

    NASA Technical Reports Server (NTRS)

    Gossland, M.; Balmain, K. G.

    1982-01-01

    The effect of various barriers (empty gap, copper, Mylar, and nickel mesh) on the probability of simultaneous arc discharging of two physically separated pieces of electron-beam-charged Teflon was studied. For the empty gap barrier, it was found that simultaneous discharges rarely occur when the separation between the samples is greater than approximately 0.4 times the length of their common edge when this length is of the order of 1 cm. Evidence suggests that electromagnetic fields play a larger role than electrons in influencing the occurrence of simultaneous arc discharges.

  5. Stretched arc discharge in produced water.

    PubMed

    Cho, Y I; Wright, K C; Kim, H S; Cho, D J; Rabinovich, A; Fridman, A

    2015-01-01

    The objective of the present study was to investigate the feasibility of stretching an arc discharge in produced water to increase the volume of produced water treated by plasma. Produced water is the wastewater generated by hydraulic fracturing of shale during the production phase in shale-oil or shale-gas exploration. The electric conductivity of produced water is in the range of 50-200 mS/cm, which provides both a challenge and opportunity for the application of plasmas. Stretching of an arc discharge in produced water was accomplished using a ground electrode and two high-voltage electrodes: one positioned close to the ground electrode and the other positioned farther away from the ground. The benefit of stretching the arc is that the contact between the arc and water is significantly increased, resulting in more efficient plasma treatment in both performance and energy cost.

  6. DEVICE AND METHOD FOR PRODUCING A HIGH INTENSITY ARC DISCHARGE

    DOEpatents

    Luce, J.S.

    1960-01-01

    A device is described for producing an energetic d-c carbon arc discharge between widely spaced electrodes with arc currents in excess of 100 amperes in a magnetic field of about 3000 gauss and witnin an evacuated enclo sure at a pressure of about 10/sup -5/ mm Hg. No defining electrodes are used in the device, thus essentially eliminating the problems of shorting which heretofore limited the amount of current that could be produced in an arc discharge. The energetic carbon arc discharge is sustained by the potential across the electrodes and by carbon ions and electrons released from the electrodes during arc operation. A large part of the potential drop of the arc occurs along the arc and many energetic electrons reach the anode because the arc pressure is relatively low, and few collisions occur. The carbon discharge is also an efficient ion pump.

  7. Discharge Characteristics of DC Arc Water Plasma for Environmental Applications

    NASA Astrophysics Data System (ADS)

    Li, Tianming; Sooseok, Choi; Takayuki, Watanabe

    2012-12-01

    A water plasma was generated by DC arc discharge with a hafnium embedded rod-type cathode and a nozzle-type anode. The discharge characteristics were examined by changing the operation parameter of the arc current. The dynamic behavior of the arc discharge led to significant fluctuations in the arc voltage and its frequency. Analyses of the high speed image and the arc voltage waveform showed that the arc discharge was in the restrike mode and its frequency varied within several tens of kilohertz according to the operating conditions. The larger thermal plasma volume was generated by the higher flow from the forming steam with a higher restrike frequency in the higher arc current conditions. In addition, the characteristics of the water plasma jet were investigated by means of optical emission spectroscopy to identify the abundant radicals required in an efficient waste treatment process.

  8. Degradation of Verapamil hydrochloride in water by gliding arc discharge.

    PubMed

    Krishna, Syam; Maslani, Alan; Izdebski, Tomasz; Horakova, Marta; Klementova, Sarka; Spatenka, Petr

    2016-06-01

    This study investigated the influence of gliding arc plasma discharge on the degradation of Verapamil hydrochloride in water. The plasma discharge was characterized by means of optical emission spectroscopy. Spectra of various atomic and molecular species were observed. Aqueous solution of Verapamil hydrochloride was exposed to gliding arc discharge operated in continuous discharge at atmospheric pressure and room temperature. The identification of Verapamil, the degradation mechanisms of Verapamil and its transformation products were performed using liquid chromatography - mass spectrometry (HPLC-MS). Experimental results indicate that the atmospheric pressure gliding arc plasma treatment has noticeable effects on Verapamil with satisfactory degradation efficiency. Plausible mechanisms of the degradation were discussed.

  9. Arcing in LEO - Does the Whole Array Discharge?

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T.; Hillard, G. Barry

    2005-01-01

    The conventional wisdom about solar array arcing in LEO is that only the parts the solar array that are swept over by the arc-generated plasma front are discharged in the initial arc. This limits the amount of energy that can be discharged. Recent work done at the NASA Glenn Research Center has shown that this idea is mistaken. In fact, the capacitance of the entire solar array may be discharged, which for large arrays leads to very large and possibly debilitating arcs, even if no sustained arc occurs. We present the laboratory work that conclusively demonstrates this fact by using a grounded plate that prevents the arc-plasma front from reaching certain array strings. Finally, we discuss the dependence of arc strength and arc pulse width on the capacitance that is discharged, and provide a physical mechanism for discharge of the entire array, even when parts of the array are not accessible to the arc-plasma front. Mitigation techniques are also presented.

  10. Arcing in LEO - Does the Whole Array Discharge?

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T.; Hillard, G. Barry

    2005-01-01

    The conventional wisdom about solar array arcing in LEO is that only the parts the solar array that are swept over by the arc-generated plasma front are discharged in the initial arc. This limits the amount of energy that can be discharged. Recent work done at the NASA Glenn Research Center has shown that this idea is mistaken. In fact, the capacitance of the entire solar array may be discharged, which for large arrays leads to very large and possibly debilitating arcs, even if no sustained arc occurs. We present the laboratory work that conclusively demonstrates this fact by using a grounded plate that prevents the arc-plasma front from reaching certain array strings. Finally, we discuss the dependence of arc strength and arc pulse width on the capacitance that is discharged, and provide a physical mechanism for discharge of the entire array, even when parts of the array are not accessible to the arc-plasma front. Mitigation techniques are also presented.

  11. Arcing in LEO: Does the Whole Array Discharge?

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T.; Hillard, G. Barry

    2005-01-01

    The conventional wisdom about solar array arcing in LEO is that only the parts of the solar array that are swept over by the arc-generated plasma front are discharged in the initial arc. This limits the amount of energy that can be discharged. Recent work done at the NASA Glenn Research Center has shown that this idea is mistaken. In fact, the capacitance of the entire solar array may be discharged, which for large arrays leads to very large and possibly debilitating arcs, even if no sustained arc occurs. We present the laboratory work that conclusively demonstrates this fact by using a grounded plate that prevents the arc-plasma front from reaching certain array strings. Finally, we discuss the dependence of arc strength and arc pulse width on the capacitance that is discharged, and provide a physical mechanism for discharge of the entire array, even when parts of the array are not accessible to the arc-plasma front. Mitigation techniques are also presented.

  12. Electric arc discharge damage to ion thruster grids

    NASA Technical Reports Server (NTRS)

    Beebe, D. D.; Nakanishi, S.; Finke, R. C.

    1974-01-01

    Arcs representative of those occurring between the grids of a mercury ion thruster were simulated. Parameters affecting an arc and the resulting damage were studied. The parameters investigated were arc energy, arc duration, and grid geometry. Arc attenuation techniques were also investigated. Potentially serious damage occurred at all energy levels representative of actual thruster operating conditions. Of the grids tested, the lowest open-area configuration sustained the least damage for given conditions. At a fixed energy level a long duration discharge caused greater damage than a short discharge. Attenuation of arc current using various impedances proved to be effective in reducing arc damage. Faults were also deliberately caused using chips of sputtered materials formed during the operation of an actual thruster. These faults were cleared with no serious grid damage resulting using the principles and methods developed in this study.

  13. Nanocarbons formed under ac arc discharge

    SciTech Connect

    Koprinarov, N.; Marinov, M.; Pchelarov, G.; Konstantinova, M.; Stefanov, R. )

    1995-02-16

    Large quantities of a wide range of carbon net forms have been synthesized and observed by a TEM in a deposit obtained by ac arc discharge in an argon ambient between close proximity electrodes. The forms differ in size and arrangement; these include closed or open end tubes, spiral tube cores, boomerang, single and double cone, arch, spherical with a large hollow core, spherical ordered structures, spherical amorphous, and a variety of polyhedral forms. The step by step growth process is discussed. Initially a two-dimensional carbon net grows spatially. Successive concentric layers grow temporally externally and internally to the initial surface. Due to the weak interaction between the atoms from the different layers, quite often the upper layers do not copy the initial form of the carbon net. The defects that arise define the nature of the deviations from the initial carbon net, the preferred spatial C-C bound angle, and the mechanism of growth characteristic for the structures. 21 refs., 17 figs.

  14. Unstable Behavior of Anodic Arc Discharge for Synthesis of Nanomaterials

    NASA Astrophysics Data System (ADS)

    Gershman, Sophia; Raitses, Yevgeny

    2016-09-01

    Fast imaging and electrical current measurements reveal unstable behavior of the carbon arc discharge for synthesis of nanomaterials. The arc column and the arc attachment region to the anode move in a somewhat sporadic way with a characteristic time in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. A physical mechanism is proposed based on the thermal processes in the arc plasma region interacting with the ablating anode which leads to the shift of the arc to a new anode region. According to the transient heat transfer analysis, the time needed to heat a new anode region is also in a 10-3 sec range. For a 0.6 cm diameter anode used in our experiments, this time yields a frequency of about 200-300 Hz, comparable to the measured frequency of the arc motion. The voltage and current measurements show oscillations with a similar characteristic frequency. The thermal model is indirectly supported by the measured negative differential resistance of the arc discharge during arc oscillations. The observed unstable behavior of the arc may be responsible for the mixing of the flow of nanoparticles during the synthesis of nanoparticles leading to poor selectivity typical for the arc synthesis. The work was supported by US DOE under Contract No. DE-AC02-09CH11466.

  15. Investigating Discharge Ignition Fundamentals of Micro-Cathode Arc Thrusters

    NASA Astrophysics Data System (ADS)

    Teel, George Lewis

    This dissertation is a compilation of studies of the volatile process that vacuum arcs undergo, known as breakdown. Breakdown is a transfer of electrons from one electrode to another. These electrons typically bombard the electrode surfaces causing secondary electron emission and ionization. This expulsion of ions and electrons then proceed to cause arc discharge, is what most people associate as ``the spark.'' This field-emission to breakdown process induces localized heating, which then causes this explosive ionization to occur. Once plasma is formed, high temperatures and pressures are forced on the surrounding surfaces. This initiation process, the effects of this process, and the manipulation of these effects have all been studied and described in this work. A series of initial observations of the before and after effects of discharge have been made through various equipment such as a Scanning Electron Microscope, Energy Dispersive X-Ray, and Confocal Microscope. Methods to develop a resistance measurement scheme provided a means to characterize the thruster's operation over its lifetime. Further characterization of the plasma plume was done through the use of Langmuir probes. Temperature and density distributions were also measured. An entirely new and miniaturized design of the thrusters were developed and initially tested. Last, a new application for these vacuum arc thrusters was studied for use in an underwater environment. The purpose of this work was to further develop a vacuum arc thruster, known as the Micro-Cathode Arc Thruster (muCAT), which has been developed at the George Washington University's Micro Propulsion and Nanotechnology Lab. The muCAT has been developed over the past decade, and in the last 5 years has gone from simple lab circuitry to space flown hardware. Therefore it is imperative to fully understand every aspect of this technology to achieve precisely what missions require. The results of this dissertation have allowed a new

  16. Electron Temperature of the Arc Discharge for Nanomaterial Synthesis

    NASA Astrophysics Data System (ADS)

    Feurer, Matthew; Vekselman, Vladislav; Startton, Brentley; Raitses, Yevgeny; LaboratoryPlasma Nanosynthesis Team

    2016-10-01

    Since the discovery of different allotropes of carbon in the twentieth century many uses have been found for carbon based nanomaterials such as buckyballs, nanotubes (CNTs), and graphene. An atmospheric pressure arc discharge with graphite electrodes is a promising technique for producing large volumes of these carbon nanostructures. Plasma drives the synthesis providing carbon feedstock by anode ablation and sustaining required composition and temperature of nanomaterial species, as such it is important to characterize the plasma used in this process in order to control the quality and attributes of the resulting carbon nanostructures. In work we present detailed in-situ measurements of spatial distribution of arc plasma parameters obtained with optical emission spectroscopy (OES) diagnostics. The plasma temperature has been determined using Boltzmann diagram method with collisional radiative modeling due to plasma deviation from complete local thermodynamic equilibrium (LTE). Results of these measurements demonstrate a strong correlation between arc plasma and synthesis processes. This work was supported by US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  17. Parallel vacuum arc discharge with microhollow array dielectric and anode

    SciTech Connect

    Feng, Jinghua; Zhou, Lin; Fu, Yuecheng; Zhang, Jianhua; Xu, Rongkun; Chen, Faxin; Li, Linbo; Meng, Shijian

    2014-07-15

    An electrode configuration with microhollow array dielectric and anode was developed to obtain parallel vacuum arc discharge. Compared with the conventional electrodes, more than 10 parallel microhollow discharges were ignited for the new configuration, which increased the discharge area significantly and made the cathode eroded more uniformly. The vacuum discharge channel number could be increased effectively by decreasing the distances between holes or increasing the arc current. Experimental results revealed that plasmas ejected from the adjacent hollow and the relatively high arc voltage were two key factors leading to the parallel discharge. The characteristics of plasmas in the microhollow were investigated as well. The spectral line intensity and electron density of plasmas in microhollow increased obviously with the decease of the microhollow diameter.

  18. Numerical simulation of carbon arc discharge for nanoparticle synthesis

    NASA Astrophysics Data System (ADS)

    Kundrapu, M.; Keidar, M.

    2012-07-01

    Arc discharge with catalyst-filled carbon anode in helium background was used for the synthesis of carbon nanoparticles. In this paper, we present the results of numerical simulation of carbon arc discharges with arc current varying from 10 A to 100 A in a background gas pressure of 68 kPa. Anode sublimation rate and current voltage characteristics are compared with experiments. Distribution of temperature and species density, which is important for the estimation of the growth of nanoparticles, is obtained. The probable location of nanoparticle growth region is identified based on the temperature range for the formation of catalyst clusters.

  19. Numerical simulation of carbon arc discharge for nanoparticle synthesis

    SciTech Connect

    Kundrapu, M.; Keidar, M.

    2012-07-15

    Arc discharge with catalyst-filled carbon anode in helium background was used for the synthesis of carbon nanoparticles. In this paper, we present the results of numerical simulation of carbon arc discharges with arc current varying from 10 A to 100 A in a background gas pressure of 68 kPa. Anode sublimation rate and current voltage characteristics are compared with experiments. Distribution of temperature and species density, which is important for the estimation of the growth of nanoparticles, is obtained. The probable location of nanoparticle growth region is identified based on the temperature range for the formation of catalyst clusters.

  20. Solar Array Arcing in LEO How Much Charge is Discharged?

    NASA Technical Reports Server (NTRS)

    Ferguson, D. C.; Vayner, B. V.; Galofaro, J. T.

    2004-01-01

    It is often said that only the solar array or spacecraft surface that can be reached by an arc plume are discharged in a solar array arc in LEO (Low Earth Orbit). We present definitive results from ground test experiments done in the National Plasma Interactions (N-PI) facility at the NASA Glenn Research Center that this idea is mistaken. All structure surfaces in contact with the surrounding plasma and connected to spacecraft ground are discharged, whether the arc plasma can reach them or not. Implications from the strength and damaging effects of areas on LEO spacecraft are discussed, and mitigation techniques are proposed.

  1. REVIEW ARTICLE Fibre optic devices produced by arc discharges

    NASA Astrophysics Data System (ADS)

    Rego, G.

    2010-11-01

    We present an overview of the applications of the electric arc technique related to optical fibre technology. The use of arc discharges ranges from the well-known fibre splicing, going through the fabrication of basic devices such as fibre tapers and microspheres, to tailoring the spectra of UV-induced gratings such as in the apodization of fibre Bragg gratings and also in the fabrication of phase-shifted and sampled fibre Bragg gratings. However, in the past decade a topic more intensively investigated was probably long-period fibre gratings. Therefore, some devices based on arc-induced gratings, namely, phase-shifted and step-changed gratings and bandpass filters are discussed. We also present an electrically insulated thermocouple assembled in situ using arc discharges. This sensor is very useful in the determination of the temperature attained by the fibre during an arc discharge, this property being fundamental for the discussion of the mechanisms of formation and for the understanding of the thermal properties of arc-induced devices.

  2. Fullerenes synthesis by combined resistive heating and arc discharge techniques.

    PubMed

    Kyesmen, Pannan Isa; Onoja, Audu; Amah, Alexander Nwabueze

    2016-01-01

    The two main electrode techniques for fullerenes production; the direct arc technique and the resistive heating of graphite rod were employed in this work. One of the electrodes was resistively heated to high temperature and subjected to arc discharge along its length by the second graphite rod. Fullerenes solid were extracted from carbon soot samples collected from an installed arc discharge system using the solvent extraction method. The fullerenes solid obtained from carbon soot collected for 2 min of arc discharge run when one of the electrodes was resistively heated at different voltages all gave higher yields (maximum of 67 % higher, at 150 A arc current and 200 Torr chamber pressure) compared to when no resistive heating was carried out. Scanning electron microscopy and ultraviolet visible spectroscopy analysis carried out on all fullerenes solid indicated the presence of fullerenes. The enhancement of fullerenes production by combined resistive and direct arc techniques shows prospect for possible use at industrial level for large scale production.

  3. Electrode erosion in arc discharges at atmospheric pressure

    NASA Technical Reports Server (NTRS)

    Hardy, T. L.

    1985-01-01

    An experimental investigation was performed in an effort to measure and increase lifetime of electrodes in an arcjet thruster. The electrode erosion of various anode and cathode materials was measured after tests in an atmospheric pressure nitrogen arc discharge at powers less than 1 kW. A free-burning arc configuration and a constricted arc configuration were used to test the materials. Lanthanum hexaboride and thoriated tungsten had low cathode erosion rates while thoriated tungsten and pure tungsten had the lowest anode erosion rates of the materials tested. Anode cooling, reverse gas flow, and external magnetic fields were all found to reduce electrode mass loss.

  4. Electrode erosion in arc discharges at atmospheric pressure

    NASA Technical Reports Server (NTRS)

    Hardy, T. L.

    1985-01-01

    An experimental investigation was performed in an effort to measure and increase lifetime of electrodes in an arcjet thruster. The electrode erosion of various anode and cathode materials was measured after tests in an atmospheric pressure nitrogen arc discharge at powers less than 1 kW. A free-burning arc configuration and a constricted arc configuration were used to test the materials. Lanthanum hexboride and thoriated tungsten had low cathode erosion rates while thoriated tungsten and pure tungsten had the lowest anode erosion rates of the materials tested. Anode cooling, reverse gas flow, an external magnetic fields were all found to reduce electrode mass loss.

  5. Synthesis of carbon nanotubes by arc discharge in open air.

    PubMed

    Paladugu, Mohan Chand; Maneesh, K; Nair, P Kesavan; Haridoss, Prathap

    2005-05-01

    In this work Carbon nanotubes have been synthesized by arc discharge in open air. A TIG welding ac/dc inverter was used as the power source for arc discharge. During each run of the arc discharge based synthesis, the anode was a low purity (approximately 85% C by weight) graphite rod. The effect of varying the atmosphere on the yield of soot of the carbon nanotube containing carbon soot has been studied. Various soots were produced, purified by oxidation and characterized to confirm formation of carbon nanotubes and their relative quality, using transmission electron microscopy, Raman spectroscopy, and XRD. It was found that the yield of soot formed on the cathode is higher when synthesis is carried out in open air than when carried out in a flowing argon atmosphere. When synthesized in open air, using a 7.2-mm-diameter graphite rod as anode, the yield of soot was around 50% by weight of the graphite consumed. Current and voltage for arcing were at identical starting values in all the experiments. This modified method does not require a controlled atmosphere as in the case of a conventional arc discharge method of synthesis and hence the cost of production may be reduced.

  6. Study of the anodic arc discharge for carbon nanotube production

    NASA Astrophysics Data System (ADS)

    Waldorff, Erik; Keidar, Michael; Wass, Anthony; Friedmann, Peretz

    2003-10-01

    Carbon nanotubes (CNTs) are unique nanostructures with remarkable electronic and mechanical properties. CNTs are currently considered to be a promising candidate as a next generation material having various applications. To-date, a variety of CNT fabrication methods have been developed, among them is an arc discharge method. Arc discharge is a relatively simple method having high rate of CNT production. In this method single-wall and multi-wall nanotubes are produced from an ionized carbon plasma with joule heating from the discharge used to generate the plasma. The University of Michigan carbon nanotube production facility in the Aerospace Engineering Department utilizes the anodic arc discharge. In this type of discharge, the Carbon plasma is supplied mainly by the anode ablation. In addition a buffer gas (Helium) with a pressure range of 100-1000 torr is introduced into the discharge chamber. The experimental anode ablation rate is about 2-4 m3/s and generally increases with the background gas pressure in the considered pressure range.A model of the anodic arc discharge is developed. The main component of this model is the anode ablation kinetics that takes into account the non-free nature of ablation due to the presence of a high-density discharge plasma. Different characteristic sub-regions near the surface, namely, space-charge sheath, Knudsen layer, presheath and a hydrodynamic layer are considered. The ablation rate is determined by the flow velocity at the edge of the Knudsen layer. Coupling solution of the non-equilibrium, Knudsen layer, with hydrodynamic layer and discharge column provides self-consistent solution for the ablation rate and plasma parameter distribution.

  7. Carbon Coating Of Copper By Arc-Discharge Pyrolysis

    NASA Technical Reports Server (NTRS)

    Ebihara, Ben T.; Jopek, Stanley

    1988-01-01

    Adherent, abrasion-resistant coat deposited with existing equipment. Carbon formed and deposited as coating on copper substrate by pyrolysis of hydrocarbon oil in electrical-arc discharges. Technique for producing carbon deposits on copper accomplished with electrical-discharge-machining equipment used for cutting metals. Applications for new coating technique include the following: solar-energy-collecting devices, coating of metals other than copper with carbon, and carburization of metal surfaces.

  8. Numerical modelling of high-pressure arc discharges: matching the LTE arc core with the electrodes

    NASA Astrophysics Data System (ADS)

    Lisnyak, M.; Cunha, M. D.; Bauchire, J.-M.; Benilov, M. S.

    2017-08-01

    A widely used approach to simulation of high-pressure arc discharges is based on the system of magneto-hydrodynamic equations written in the approximation of local thermodynamic equilibrium (LTE). In this work, boundary conditions on the surface of the electrodes are formulated with the use of equations of balance of energy in the non-equilibrium near-electrode layers that separate the LTE bulk plasma and the electrodes. As an example, numerical simulations of a free-burning arc in atmospheric-pressure argon plasma in the current range from 20 to 200 A are reported. Simulation results are in reasonably good agreement with those given by more sophisticated models and with the experiment. Simulations performed for cathodes of slightly different geometries have predicted a strong effect produced by details of the cathode geometry over the distribution of the current density along the cathode surface and therefore over the plasma temperature, an interesting and potentially important result that is worth further numerical investigation and experimental verification.

  9. The layered structure of the carbon arc discharge plasma

    NASA Astrophysics Data System (ADS)

    Vekselman, Vladislav; Stratton, Brentley; Raitses, Yevgeny; LaboratoryPlasma Nanosynthesis Team

    2016-10-01

    The arc discharge with a consumed anode is commonly used for synthesis of nanomaterials such as fullerenes, nanotubes and, more recently, graphene. The role of the arc plasma in nanosynthesis processes, including ablation of the graphite anode, nucleation and growth of nanostructures remains unclear. Our recent fast frame camera measurements revealed arc oscillations associated with the ablation processes at the anode. More sophisticated measurements using optical emission spectroscopy and spectrally resolved fast framing imaging revealed the complex, layered structure of plasma species distribution, which is dynamically changing. The results of this research include time- and space- resolved distributions of plasma species, plasma electron density and temperature. The obtained experimental data suggest a strong correlation between arc plasma parameters and nanosynthesis processes. This work was supported by US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  10. Electron beam charging and ARC discharging of spacecraft insulating materials

    NASA Technical Reports Server (NTRS)

    Balmain, K. G.

    1980-01-01

    The properties of the arc discharges which are caused by the laboratory exposure of dielectric materials to electron beams are examined, the intent being to simulate conditions on synchronous-orbit spacecraft. Extensive experimental studies are reported for planar dielectrics (Teflon, Kapton, Mylar) on the subjects of incident-flux scaling of discharge properties and the effects of high-energy broad-spectrum electron irradiation from a radioisotpe source. In addition a preliminary evaluation is made of the discharge susceptibility of fiber optic waveguides.

  11. Characteristics of electromagnetic interference generated by arc discharges. [in spacecraft

    NASA Technical Reports Server (NTRS)

    Leung, Philip

    1986-01-01

    Electromagnetic interference (EMI) signatures resulting from arc discharges are characterized, and the effects of electrostatic discharges (ESDs) on the design of spacecraft systems are investigated. EMI characterization experiments were performed on Mylar, Teflon, Kapton, fused silica, and fiberglass in a vacuum chamber with acrylic walls; the experimental design and procedures are described. Discharge current pulses and RF spectra generated by the sample materials are examined. The relation between the magnitude of EMI generated during an ESD event and the material, environment, and geometry is studied. The solar-array/plasma interaction is analyzed; particular attention is given to the rate of discharge as a function of plasma density. The physical mechanisms of ESD-generated EMI are discussed. The data reveal that ESD parameters are dependent on the test environment.

  12. Characteristics of electromagnetic interference generated by arc discharges. [in spacecraft

    NASA Technical Reports Server (NTRS)

    Leung, Philip

    1986-01-01

    Electromagnetic interference (EMI) signatures resulting from arc discharges are characterized, and the effects of electrostatic discharges (ESDs) on the design of spacecraft systems are investigated. EMI characterization experiments were performed on Mylar, Teflon, Kapton, fused silica, and fiberglass in a vacuum chamber with acrylic walls; the experimental design and procedures are described. Discharge current pulses and RF spectra generated by the sample materials are examined. The relation between the magnitude of EMI generated during an ESD event and the material, environment, and geometry is studied. The solar-array/plasma interaction is analyzed; particular attention is given to the rate of discharge as a function of plasma density. The physical mechanisms of ESD-generated EMI are discussed. The data reveal that ESD parameters are dependent on the test environment.

  13. Temperature after Arc Discharge Affected by Current Decrement Ratio in Wall Stabilized Arc

    NASA Astrophysics Data System (ADS)

    Sato, Ken; Suzuki, Daichi; Iwao, Toru

    2015-11-01

    Recently, the stable supply of electric power is indispensable in a power generation, and a transmission and distribution system of electric power. The GCB (Gas Circuit Breaker) has been researched for performance improvement of the arc interruption of abnormal fault current without the fail. The GCB has been researched for the high capacity and downsizing for development of practical use. Because the power network is expanded, the capacity of interruption current increased for reliability. The GCB should interrupt the arc of high current and voltage, shorten the time to interrupt, and become the high capability in order to improve the reliability and practicability. It is important to prevent the insulation of re-ignition and thermal re-ignition of arc after the arc interruption. It is mainly considered that the factor of thermal re-ignition is the arc temperature distribution after current zero. The temperature distribution has been elucidated by the current decrement ratio (di/dt). However, the variation of temperature distribution and decrement process of the temperature by the wall radius is also important in order to design the circuit breaker. In this paper, temperature after Arc Discharge Affected by Current Decrement Ratio in Wall Stabilized Arc was elucidated in order to know the effect on the temperature in the wall radius. As a result, when the wall radius decreases, the temperature at 0 A after 200 μs is lower.

  14. Characteristics of the Plasma Environment and Discharge Process in a High-Pressure Pulsed Arc Discharge

    NASA Astrophysics Data System (ADS)

    Tang, Ricky; Hopkins, Matthew; Barnat, Edward

    2016-09-01

    The characteristics and properties of a plasma generated in a pulsed arc discharge are investigated. Arc discharge plasmas are prevalent in the production and treatment of materials. Photodetectors and optical emission spectroscopy (OES) are used to probe the plasmas and characterize their spectral responses. OES allows for species identification and provides information about the state of the plasma, such as the electron temperature. Discharges generated with inert gas such as argon, as well as with nitrogen and air, are studied and compared. In the case of reactive gases, OES also provides information on the possible reactions that took place. Microwave interferometry is used to measure the electron density to provide spatial information on the discharges. In addition, the measurement is synchronized with the discharge pulse to obtain temporal information, for instance, during the pulse initialization phase to investigate the arc discharge process prior to plasma generation, where optical information is absent. Together, this allows for the characterization of the pre-, during, and post-discharge processes.

  15. Method and apparatus for nondestructive testing. [using high frequency arc discharges

    NASA Technical Reports Server (NTRS)

    Hoop, J. M. (Inventor)

    1974-01-01

    High voltage is applied to an arc gap adjacent to a test specimen to develop a succession of high frequency arc discharges. Those high frequency arc discharges generate pulses of ultrasonic energy within the test specimen without requiring the arc discharges to contact that test specimen and without requiring a coupling medium. Those pulses can be used for detection of flaws and measurements of certain properties and stresses within the test specimen.

  16. Laser Thomson scattering in a pulsed atmospheric arc discharge

    NASA Astrophysics Data System (ADS)

    Sommers, Bradley; Adams, Steven

    2015-09-01

    Laser scattering measurements, including Rayleigh, Raman, and Thomson scattering have been performed on an atmospheric pulsed arc discharge. Such laser scattering techniques offer a non-invasive diagnostic to measure gas temperature, electron temperature, and electron density in atmospheric plasma sources, particularly those with feature sizes approaching 1 mm. The pulsed discharge is ignited in a pin to pin electrode geometry using a 6 kV pulse with 10 ns duration. The electrodes are housed in a glass vacuum chamber filled with argon gas. The laser signal is produced by a Nd:Yag laser supply, repetitively pulsed at 10 Hz and frequency quadrupled to operate at 266 nm. The scattered laser signal is imaged onto a triple grating spectrometer, which is used to suppress the Rayleigh scatter signal in order to measure the low amplitude Thomson and Raman signals. Preliminary results include measurements of electron temperature and electron density in the plasma column taken during the evolution of the discharge. The laser system is also used to measure the Rayleigh scattering signal, which provides space and time resolved measurements of gas temperature in the arc discharge.

  17. Quantitative characterization of arc discharge as vacuum interface

    SciTech Connect

    Huang, S.; Zhu, K.; Lu, Y. R.; Wang, S. Z.; Hershcovitch, A.; Yang, L.; Zhang, X. Y.

    2014-12-19

    An arc discharge with channel diameters of 3 mm and 6 mm and lengths between 30mm and 60mm was experimentally investigated for its potential to function as plasma window, i.e., interface vacuum regions of different pressures. In this study, electron temperature of the plasma channel measured spectroscopically varied in the range of 7000K to 15000K, increasing with discharge current while decreasing with gas flow rate. The plasma window had a slightly positive I-V characteristics over the whole range of investigated current 30A–70 A. Measurements of pressure separation capability, which were determined by input current, gas flow rate, discharge channel diameter, and length, were well explained by viscosity effect and “thermal-block” effect. The experimental results of global parameters including temperature, gas flow rate, and voltage had a good agreement with the simulation results calculated by an axis-symmetry Fluent-based magneto-hydrodynamic model.

  18. Atmospheric pressure arc discharge with ablating graphite anode

    SciTech Connect

    Nemchinsky, V. A.; Raitses, Y.

    2015-05-18

    The anodic carbon arc discharge is used to produce carbon nanoparticles. Recent experiments with the carbon arc at atmospheric pressure helium demonstrated the enhanced ablation rate for narrow graphite anodes resulting in high deposition rates of carbonaceous products on the copper cathode (Fetterman et al 2008 Carbon 46 1322–6). The proposed model explains these results with interconnected steady-state models of the cathode and the anode processes. When considering cathode functioning, the model predicts circulation of the particles in the near-cathode region: evaporation of the cathode material, ionization of evaporated atoms and molecules in the near-cathode plasma, return of the resulting ions to the cathode, surface recombination of ions and electrons followed again by cathode evaporation etc. In the case of the low anode ablation rate, the ion acceleration in the cathode sheath provides the major cathode heating mechanism. In the case of an intensive anode ablation, an additional cathode heating is due to latent fusion heat of the atomic species evaporated from the anode and depositing at the cathode. Using the experimental arc voltage as the only input discharge parameter, the model allows us to calculate the anode ablation rate. A comparison of the results of calculations with the available experimental data shows reasonable agreement.

  19. Influence of discharge gap on the discharge stability in a short vacuum arc ion source.

    PubMed

    Chen, L; Zhang, G L; Jin, D Z; Yang, L; Dai, J Y

    2012-02-01

    The influence of the discharge gap between cathode and anode on the discharge stability in a short vacuum arc (SVA) ion source is presented in this paper. Planar cathode and cylindrical hollow anode made of titanium are investigated. There is a great need in present accelerator injection research for SVA source to produce the small deviation of the ion current beam. Current research shows that increasing the short discharge gap can reduce the level of ion current deviation and ion charge deviation from 29% and 31% to 15% and 17%, respectively. A microplasma plume generation mechanism in SVA and scanning electron microscopic results can be used to explain this interesting phenomenon.

  20. Influence of discharge gap on the discharge stability in a short vacuum arc ion source

    SciTech Connect

    Chen, L.; Zhang, G. L.; Jin, D. Z.; Dai, J. Y.; Yang, L.

    2012-02-15

    The influence of the discharge gap between cathode and anode on the discharge stability in a short vacuum arc (SVA) ion source is presented in this paper. Planar cathode and cylindrical hollow anode made of titanium are investigated. There is a great need in present accelerator injection research for SVA source to produce the small deviation of the ion current beam. Current research shows that increasing the short discharge gap can reduce the level of ion current deviation and ion charge deviation from 29% and 31% to 15% and 17%, respectively. A microplasma plume generation mechanism in SVA and scanning electron microscopic results can be used to explain this interesting phenomenon.

  1. A development of arc discharge drawing silica nanowires

    NASA Astrophysics Data System (ADS)

    Kowong, Rattanachai; Putchana, Wuttichai; Ratanavis, Amarin

    2015-07-01

    The Arc Discharge Drawing (ADD) technique offers a promising alternative for fabricating silica nanowires. In the previous study, ADD technique was based on the creation of a high voltage glow discharge between two electrodes. Such a configuration provides the heat zone that occurs perpendicularly to the fiber. With ADD technique, silica wires with diameters as small as 50 nm were achieved. Despite these successes the further development is meant to be continued. In this paper, ADD technique is improved by adding a pair of electrodes. The arc discharge apparatus consisting of four electrodes is proposed. The arranged two pairs of electrodes offer the sandwich-heat source configuration. The computer-controlled stage allows the drawing speeds in the range of 12 mm/s to 25 mm/s. The nanowires can be produced by varying the voltage in the range of 4 kV to 5 kV. The optimum operational voltage is investigated by the scanning electron microscope (SEM) images of the fabricated nanowires. This result strongly suggests further improvements in glass fiber drawing technology to produce nanowires.

  2. Macroparticle generation in DC arc discharge from a WC cathode

    NASA Astrophysics Data System (ADS)

    Zhirkov, Igor; Polcik, Peter; Kolozsvári, Szilard; Rosen, Johanna

    2017-03-01

    We have studied macroparticle generation from a tungsten carbide cathode used in a dc vacuum arc discharge. Despite a relatively high decomposition/melting point (˜3100 K), there is an intensive generation of visible particles with sizes in the range 20-35 μm. Visual observations during the discharge and scanning electron microscopy of the cathode surface and of collected macroparticles indicate a new mechanism for particle formation and acceleration. Based on the W-C phase diagram, there is an intensive sublimation of carbon from the melt resulting from the cathode spot. The sublimation supports the formation of a sphere, which is accelerated upon an explosion initiated by Joule heating at the critical contact area between the sphere and the cathode body. The explosive nature of the particle acceleration is confirmed by surface features resembling the remains of a splash on the droplet surface.

  3. Measurement of anode surface temperature in carbon nanomaterial production by arc discharge method

    SciTech Connect

    Liang, Feng; Tanaka, Manabu; Choi, Sooseok; Watanabe, Takayuki

    2014-12-15

    Highlights: • We measured the temperature of anode surface by two-color pyrometry combined with a high speed camera successfully. • Growth temperature of pyrolytic graphite, MWNTs, and nano-graphite particles were in ranges of 2400–2600 K, 2600–2700 K, and 2700–3500 K, respectively. • High temperature contributes to form thermodynamically unstable material. - Abstract: Nano-graphite particles, multi-wall carbon nanotube (MWNT), and pyrolytic graphite were prepared at different positions of the anode surface in an arc discharge. Graphite electrodes were employed for the arc discharge under helium environment at atmospheric pressure. Nano-sized carbon products were characterized by scanning electron microscopy and transmission electron microscopy. During the arc discharge, two-color pyrometry combined with a high-speed camera was conducted to measure the temperature distribution of the anode surface. The growth temperature of pyrolytic graphite, MWNT, and nano-graphite particles were in the ranges of 2400–2600 K, 2600–2700 K, and 2700–3500 K, respectively. The local temperature of anode surface is a critical parameter to determine the products with different morphologies. The formation mechanism of these carbon nanomaterials is suggested based on the local temperature of anode surface and their thermodynamic stability.

  4. Unstable behavior of anodic arc discharge for synthesis of nanomaterials

    DOE PAGES

    Gershman, Sophia; Raitses, Yevgeny

    2016-07-27

    A short carbon arc operating with a high ablation rate of the graphite anode exhibits a combined motion of the arc and the arc attachment to the anode. A characteristic time scale of this motion is in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. It is also hypothesized that the arc motion could potentially cause mixing of the various nanoparticles synthesized in the arc in the high ablation regime.

  5. Unstable behavior of anodic arc discharge for synthesis of nanomaterials

    SciTech Connect

    Gershman, Sophia; Raitses, Yevgeny

    2016-07-27

    A short carbon arc operating with a high ablation rate of the graphite anode exhibits a combined motion of the arc and the arc attachment to the anode. A characteristic time scale of this motion is in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. It is also hypothesized that the arc motion could potentially cause mixing of the various nanoparticles synthesized in the arc in the high ablation regime.

  6. Unstable behavior of anodic arc discharge for synthesis of nanomaterials

    SciTech Connect

    Gershman, Sophia; Raitses, Yevgeny

    2016-07-27

    A short carbon arc operating with a high ablation rate of the graphite anode exhibits a combined motion of the arc and the arc attachment to the anode. A characteristic time scale of this motion is in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. It is also hypothesized that the arc motion could potentially cause mixing of the various nanoparticles synthesized in the arc in the high ablation regime.

  7. Quantitative characterization of arc discharge as vacuum interface

    SciTech Connect

    Huang, S.; Zhu, K. Lu, Y. R.; Wang, S. Z.; Hershcovitch, A.; Yang, L.; Zhang, X. Y.

    2014-12-15

    An arc discharge with channel diameters of 3 mm and 6 mm and lengths between 30 mm and 60 mm was experimentally investigated for its potential to function as plasma window, i.e., interface vacuum regions of different pressures. Electron temperature of the plasma channel measured spectroscopically varied in the range of 7000 K to 15 000 K, increasing with discharge current while decreasing with gas flow rate. That plasma window had a slightly positive I-V characteristics over the whole range of investigated current 30 A–70 A. Measurements of pressure separation capability, which were determined by input current, gas flow rate, discharge channel diameter, and length, were well explained by viscosity effect and “thermal-block” effect. The experimental results of global parameters including temperature, gas flow rate, and voltage had a good agreement with the simulation results calculated by an axis-symmetry Fluent-based magneto-hydrodynamic model.

  8. Quantitative characterization of arc discharge as vacuum interface

    DOE PAGES

    Huang, S.; Zhu, K.; Lu, Y. R.; ...

    2014-12-19

    An arc discharge with channel diameters of 3 mm and 6 mm and lengths between 30mm and 60mm was experimentally investigated for its potential to function as plasma window, i.e., interface vacuum regions of different pressures. In this study, electron temperature of the plasma channel measured spectroscopically varied in the range of 7000K to 15000K, increasing with discharge current while decreasing with gas flow rate. The plasma window had a slightly positive I-V characteristics over the whole range of investigated current 30A–70 A. Measurements of pressure separation capability, which were determined by input current, gas flow rate, discharge channel diameter,more » and length, were well explained by viscosity effect and “thermal-block” effect. The experimental results of global parameters including temperature, gas flow rate, and voltage had a good agreement with the simulation results calculated by an axis-symmetry Fluent-based magneto-hydrodynamic model.« less

  9. Low pressure arc discharge lamp apparatus with magnetic field generating means

    DOEpatents

    Grossman, Mark W.; George, William A.; Maya, Jakob

    1987-01-01

    A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25.degree. C.

  10. Low pressure arc discharge lamp apparatus with magnetic field generating means

    DOEpatents

    Grossman, M.W.; George, W.A.; Maya, J.

    1987-10-06

    A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25 C. 3 figs.

  11. High Q silica microbubble resonators fabricated by arc discharge

    NASA Astrophysics Data System (ADS)

    Berneschi, S.; Farnesi, D.; Cosi, F.; Nunzi Conti, G.; Pelli, S.; Righini, G. C.; Soria, S.

    2011-09-01

    Microbubble resonators combine the unique properties of whispering gallery mode resonators with the intrinsic capability of integrated microfluidics. Here an improved fabrication method of microbubble resonators is presented, based on the heating of a slightly pressurized capillary by a rotating arc discharge. Rotation of the electrodes, moved out of a fiber splicer, ensures a homogeneous distribution of the heat all over the capillary surface. The demonstrated microbubble resonators have Q factors up to 6×107 at 1550nm. Microbubbles were filled with water and aqueous solutions of ethanol in order to test the refractive index sensing capabilities of such resonators, which also show a good temporal stability. The limit of detection of our microbubble resonator sensor is 10-6RIU.

  12. High Q silica microbubble resonators fabricated by arc discharge.

    PubMed

    Berneschi, S; Farnesi, D; Cosi, F; Conti, G Nunzi; Pelli, S; Righini, G C; Soria, S

    2011-09-01

    Microbubble resonators combine the unique properties of whispering gallery mode resonators with the intrinsic capability of integrated microfluidics. Here an improved fabrication method of microbubble resonators is presented, based on the heating of a slightly pressurized capillary by a rotating arc discharge. Rotation of the electrodes, moved out of a fiber splicer, ensures a homogeneous distribution of the heat all over the capillary surface. The demonstrated microbubble resonators have Q factors up to 6×10(7) at 1550 nm. Microbubbles were filled with water and aqueous solutions of ethanol in order to test the refractive index sensing capabilities of such resonators, which also show a good temporal stability. The limit of detection of our microbubble resonator sensor is 10(-6) RIU.

  13. Discharge ignition in the micro-cathode arc thruster

    NASA Astrophysics Data System (ADS)

    Teel, George; Shashurin, Alexey; Fang, Xiuqi; Keidar, Michael

    2017-01-01

    The breakdown mechanism in the Micro-Cathode Arc Thruster has been studied to better understand the nature of the discharge ignition and to extend the ignition system lifetime. It has been found that optimal material selection of the insulator is an important factor during breakdown. Two opposite processes have been found to cycle during operation. The processes are degradation of the conductive film from the inter-electrode interface and re-deposition of the conductive film due to cathode spot erosion. Initial resistances were found to vary from hundreds of ohms to thousands of ohms based on the initial connectivity of the film to the electrodes. After initial breakdown however, resistances have been found to stabilize in a typical pattern. Materials capable of withstanding high temperatures, high pressures, and smooth surfaces are shown to be beneficial for extending thruster lifetime.

  14. Cathode degradation and erosion in high pressure arc discharges

    NASA Technical Reports Server (NTRS)

    Hardy, T. L.; Nakanishi, S.

    1983-01-01

    The various processes which control cathode erosion and degradation were identified and evaluated. A direct current arc discharge was established between electrodes in a pressure-controlled gas flow environment. The cathode holder was designed for easy testing of various cathode materials. The anode was a water cooled copper collector electrode. The arc was powered by a dc power supply with current and voltage regulated cross-over control. Nitrogen and argon were used as propellants and the materials used were two percent thoriated tungsten, barium oxide impregnated porous tungsten, pure tungsten and lanthanum hexaboride. The configurations used were cylindrical solid rods, wire bundles supported by hollow molybdenum tubes, cylindrical hollow tubes, and hollow cathodes of the type used in ion thrusters. The results of the mass loss tests in nitrogen indicated that pure tungsten eroded at a rate more than 10 times faster than the rates of the impregnated tungsten materials. It was found that oxygen impurities of less than 0.5 percent in the nitrogen increased the mass loss rate by a factor of 4 over high purity nitrogen. At power levels less than 1 kW, cathode size and current level did not significantly affect the mass loss rate. The hollow cathode was found to be operable in argon and in nitrogen only at pressures below 400 and 200 torr, respectively.

  15. Cathode degradation and erosion in high pressure arc discharges

    NASA Technical Reports Server (NTRS)

    Hardy, T. L.; Nakanishi, S.

    1984-01-01

    The various processes which control cathode erosion and degradation were identified and evaluated. A direct current arc discharge was established between electrodes in a pressure-controlled gas flow environment. The cathode holder was designed for easy testing of various cathode materials. The anode was a water cooled copper collector electrode. The arc was powered by a dc power supply with current and voltage regulated cross-over control. Nitrogen and argon were used as propellants and the materials used were two percent thoriated tungsten, barium oxide impregnated porous tungsten, pure tungsten and lanthanum hexaboride. The configurations used were cylindrical solid rods, wire bundles supported by hollow molybdenum tubes, cylindrical hollow tubes, and hollow cathodes of the type used in ion thrusters. The results of the mass loss tests in nitrogen indicated that pure tungsten eroded at a rate more than 10 times faster than the rates of the impregnated tungsten materials. It was found that oxygen impurities of less than 0.5 percent in the nitrogen increased the mass loss rate by a factor of 4 over high purity nitrogen. At power levels less than 1 kW, cathode size and current level did not significantly affect the mass loss rate. The hollow cathode was found to be operable in argon and in nitrogen only at pressures below 400 and 200 torr, respectively.

  16. Cathode degradation and erosion in high pressure arc discharges

    NASA Technical Reports Server (NTRS)

    Hardy, T. L.; Nakanishi, S.

    1984-01-01

    The various processes which control cathode erosion and degradation were identified and evaluated. A direct current arc discharge was established between electrodes in a pressure-controlled gas flow environment. The cathode holder was designed for easy testing of various cathode materials. The anode was a water cooled copper collector electrode. The arc was powered by a dc power supply with current and voltage regulated cross-over control. Nitrogen and argon were used as propellants and the materials used were two percent thoriated tungsten, barium oxide impregnated porous tungsten, pure tungsten and lanthanum hexaboride. The configurations used were cylindrical solid rods, wire bundles supported by hollow molybdenum tubes, cylindrical hollow tubes, and hollow cathodes of the type used in ion thrusters. The results of the mass loss tests in nitrogen indicated that pure tungsten eroded at a rate more than 10 times faster than the rates of the impregnated tungsten materials. It was found that oxygen impurities of less than 0.5 percent in the nitrogen increased the mass loss rate by a factor of 4 over high purity nitrogen. At power levels less than 1 kW, cathode size and current level did not significantly affect the mass loss rate. The hollow cathode was found to be operable in argon and in nitrogen only at pressures below 400 and 200 torr, respectively.

  17. The Effect of Flow Distribution on the Concentration of NO Produced by Pulsed Arc Discharge

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Bao, Bin; Wang, Heli; Liang, Haiyan; He, Junjia; He, Zhenghao; Li, Jin

    2007-12-01

    As a new method to cure acute respiratory distress syndrome (ARDS), high blood pressure and some illnesses related to the lung, NO has recently received more attention. Thermal plasmas produced by arc discharge can create medical NO, but the concentration of NO2 produced by arc discharge must be controlled simultaneously. This paper investigates the characteristics and regulations of NO production at different flow distribution by pulsed arc discharge in dry air with a special pulsed power. The experimental results show that the flow distribution has a considerable effect on the NO concentration, the stabilization of NO. The production of NO2 could be controlled and the ratio of NO2/NO was decreased to about 10% in the arc discharge. Therefore, the arc discharge could produce stable inhaled NO for medical treatment by changing the flow distribution.

  18. Theory of the arc discharge in air blast breakers

    SciTech Connect

    Vogel, H.F.

    1980-08-01

    The complete set of equations obtaining in the arc's length element are given. The arc length is determined when the external circuit equations are closed by an expression for the arc inductance as a function of the radius and length, in addition to our relationships for the radius and voltage gradients.

  19. Computer simulations of processes in solid-state laser radiators and amplifiers with phototube pumping: Electric-discharge pumping sources. Arc discharges

    NASA Astrophysics Data System (ADS)

    Gradov, V. M.; Mak, A. A.; Kromskiy, G. I.; Sklizkov, G. V.; Fedotov, S. I.; Shcherbakov, A. A.

    1986-03-01

    Problems of modeling and computer simulation are analyzed in reference to the design of solid state laser devices with glow tube pumping. Electric pulse and arc discharges are considered specifically. A model was constructed for a cylindrically symmetric column in the diffusion approximation with the correspoinding system of differential equations put in a form for most efficient and accurate simulation of the processes. For most economical use of the computer, the radiation spectrum is optimally subdivided into intervals. It is necessary to validate the assumption of a plasma in the state of local thermodynamic equilibrium by first accounting for and then discounting the various factors which disturb that equilibrium, namely emission of radiation and temperature gradients, as well as diffusion of charged particles toward the walls. In the case of arc discharge, a theory and a model are constructed for determining the electrophysical characteristics and the radiation characteristics of such discharge in inert gases and in vapors of alkali metals.

  20. Thermal blanket metallic film groundstrap and second surface mirror vulnerability to arc discharges

    NASA Technical Reports Server (NTRS)

    Inouye, G. T.; Sanders, N. L.; Komatsu, G. K.; Valles, J. R.; Sellen, J. M., Jr.

    1979-01-01

    Available data on the geosynchronous orbit energetic plasma environment were examined, and a crude model was generated to permit an estimation to be made of the number of arc discharges per year to which a thermal blanket groundstrap would be subjected. Laboratory experiments and a survey of the literature on arc discharge characteristics were performed to define typical and worst case arc discharge current waveforms. In-air tests of different groundstrap configurations to a standardized test pulse were performed and a wide variability of durability values were found. A groundstrap technique, not used thus far, was found to be far superior than the others.

  1. Thermal blanket metallic film groundstrap and second surface mirror vulnerability to arc discharges

    NASA Technical Reports Server (NTRS)

    Inouye, G. T.; Sanders, N. L.; Komatsu, G. K.; Valles, J. R.; Sellen, J. M., Jr.

    1979-01-01

    Available data on the geosynchronous orbit energetic plasma environment were examined, and a crude model was generated to permit an estimation to be made of the number of arc discharges per year to which a thermal blanket groundstrap would be subjected. Laboratory experiments and a survey of the literature on arc discharge characteristics were performed to define typical and worst case arc discharge current waveforms. In-air tests of different groundstrap configurations to a standardized test pulse were performed and a wide variability of durability values were found. A groundstrap technique, not used thus far, was found to be far superior than the others.

  2. Photonic band-gap engineering in UV fiber gratings by the arc discharge technique.

    PubMed

    Cusano, Andrea; Iadicicco, Agostino; Paladino, Domenico; Campopiano, Stefania; Cutolo, Antonello

    2008-09-29

    Localized heat treatments combined with local non-adiabatic tapering is proposed as suitable tool for the engineering of photonic band-gaps in UV-written fiber Bragg gratings (FBGs). In particular, here, we propose the use of the electric arc discharge to achieve localized defects along the FBG structure, however differently from previously reported works, we demonstrate how this post processing tool properly modified can be exploited to achieve the full control of the spectral characteristics of the final device. Also, we show how the suitable choice of the grating features and the correct selection of the defect geometry can be efficiently used to achieve interesting features for both communication and sensing applications.

  3. Scalability of Localized Arc Filament Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2008-01-01

    Temporal flow control of a jet has been widely studied in the past to enhance jet mixing or reduce jet noise. Most of this research, however, has been done using small diameter low Reynolds number jets that often have little resemblance to the much larger jets common in real world applications because the flow actuators available lacked either the power or bandwidth to sufficiently impact these larger higher energy jets. The Localized Arc Filament Plasma Actuators (LAFPA), developed at the Ohio State University (OSU), have demonstrated the ability to impact a small high speed jet in experiments conducted at OSU and the power to perturb a larger high Reynolds number jet in experiments conducted at the NASA Glenn Research Center. However, the response measured in the large-scale experiments was significantly reduced for the same number of actuators compared to the jet response found in the small-scale experiments. A computational study has been initiated to simulate the LAFPA system with additional actuators on a large-scale jet to determine the number of actuators required to achieve the same desired response for a given jet diameter. Central to this computational study is a model for the LAFPA that both accurately represents the physics of the actuator and can be implemented into a computational fluid dynamics solver. One possible model, based on pressure waves created by the rapid localized heating that occurs at the actuator, is investigated using simplified axisymmetric simulations. The results of these simulations will be used to determine the validity of the model before more realistic and time consuming three-dimensional simulations are conducted to ultimately determine the scalability of the LAFPA system.

  4. Monitoring Nanoparticle Synthesis in a Carbon Arc Discharge Environment, In Situ

    NASA Astrophysics Data System (ADS)

    Mitrani, James

    This work presents experimental and theoretical studies of gas-phase synthesis of fullerenes and carbon nanoparticles in the presence of an atmospheric-pressure, arc discharge plasma. Carbon arc discharges have been used for synthesizing carbon nanotubes for over 25 years, and have the potential for economically synthesizing industrial-scale quantities of fullerenes. However, the efficiency and selectivity of fullerene synthesis with carbon arc discharges are quite low. Optimizing carbon arc discharges for fullerene synthesis requires a thorough understanding of the dynamics behind gas-phase nanoparticle synthesis in the presence of an arc discharge plasma. We built a carbon arc discharge setup to study nanoparticle and fullerene synthesis. The laser-induced incandescence (LII) diagnostic was applied for monitoring nanoparticle synthesis, in situ. The LII diagnostic had previously been applied as a combustion diagnostic for in situ measurements of concentrations and sizes of soot particles in flame environments. Prior to the present study, it had never been applied for studying fullerenes, nor had it been applied to study nanoparticles in the presence of an atmospheric-pressure plasma. Therefore, experiments were designed that allowed for the calibration of the LII diagnostic with research-grade, arc-synthesized soot particles and carbon nanotubes. Additionally, the theory and models underpinning the LII diagnostic were adapted to include the presence of an atmospheric-pressure, arc-discharge plasma. Results presented in this work confirm the ability of the LII diagnostic to measure sizes of arc-synthesized nanoparticles in situ, and show the spatial location of high densities of arc-synthesized nanoparticles with respect to the arc discharge plasma. Determining the spatial location of nanoparticle synthesis and growth is crucial for understanding the background conditions (e.g. background gas temperature, electron densities ...) in which nanoparticles nucleate and

  5. Growth of arc in high-pressure, pulsed glow discharge by gas density depletion

    NASA Astrophysics Data System (ADS)

    Imada, Go; Yatsui, Kiyoshi; Masuda, Wataru

    2000-10-01

    Effects of gas density depletion on arc formation of high-pressure, pulsed glow discharge have been investigated by eliminating the other factors which may affect the discharge stability, such as shock waves, residual ions, electrode heating, and discharge products. The gas density depletion has been simulated by utilizing a subsonic gas flow between the curved electrodes combined with a convergent nozzle and a divergent diffuser. A comparison has been made on the discharge in the aerodynamically created gas density depletion with the second discharge in the double-pulse discharge within a stable gas. We have found that the large gas density depletion, Δρ/ρ0˜-3.6% corresponding to a pulse repetition rate (PRR) of ˜50 Hz, tends to cause an arc-like filament or an arc without the shocks, ions, electrode heating, and products. However, the second discharge in the double-pulse discharge becomes an arc in much smaller gas density depletion (Δρ/ρ0˜-1.2% corresponding to PRR ˜3 Hz). Therefore, the collapse of high-pressure, pulsed glow discharge is most likely caused by some factor other than the gas density depletion.

  6. Study on a negative hydrogen ion source with hot cathode arc discharge

    NASA Astrophysics Data System (ADS)

    Lin, S. H.; Fang, X.; Zhang, H. J.; Qian, C.; Ma, B. H.; Wang, H.; Li, X. X.; Zhang, X. Z.; Sun, L. T.; Zhang, Z. M.; Yuan, P.; Zhao, H. W.

    2014-02-01

    A negative hydrogen (H-) ion source with hot cathode arc discharge was designed and fabricated as a primary injector for a 10 MeV PET cyclotron at IMP. 1 mA dc H- beam with ɛ N, RMS = 0.08 π mm mrad was extracted at 25 kV. Halbach hexapole was adopted to confine the plasma. The state of arc discharge, the parameters including filament current, arc current, gas pressure, plasma electrode bias, and the ratio of I_{e^ - } /I_{H^ - } were experimentally studied. The discussion on the result, and opinions to improve the source were given.

  7. Arc discharge regulation of a megawatt hot cathode bucket ion source for the experimental advanced superconducting tokamak neutral beam injector

    SciTech Connect

    Xie Yahong; Hu Chundong; Liu Sheng; Jiang Caichao; Li Jun; Liang Lizhen; Collaboration: NBI Team

    2012-01-15

    Arc discharge of a hot cathode bucket ion source tends to be unstable what attributes to the filament self-heating and energetic electrons backstreaming from the accelerator. A regulation method, which based on the ion density measurement by a Langmuir probe, is employed for stable arc discharge operation and long pulse ion beam generation. Long pulse arc discharge of 100 s is obtained based on this regulation method of arc power. It establishes a foundation for the long pulse arc discharge of a megawatt ion source, which will be utilized a high power neutral beam injection device.

  8. Temporal evolution characteristics of an annular-mode gliding arc discharge in a vortex flow

    SciTech Connect

    Zhao, Tian-Liang; Liu, Jing-Lin; Li, Xiao-Song; Liu, Jin-Bao; Song, Yuan-Hong; Xu, Yong; Zhu, Ai-Min

    2014-05-15

    An annular-mode gliding arc discharge powered by a 50 Hz alternating current (ac) supply was studied in a vortex flow of dry and humid air. Its temporal evolution characteristics were investigated by electrical measurement, temporally resolved imaging, and temporally resolved optical emission spectroscopic measurements. Three discharge stages of arc-ignition, arc-gliding, and arc-extinction were clearly observed in each half-cycle of the discharge. During the arc-gliding stage, the intensity of light emission from the arc root at the cathode was remarkably higher than that at other areas. The spectral intensity of N{sub 2}(C{sup 3}Π{sub u}−B{sup 3}Π{sub g}) during the arc-ignition stage was much higher than that during the arc-gliding stage, which was contrary to the temporal evolutions of spectral intensities for N{sub 2}{sup +}(B{sup 2}Σ{sub u}{sup +}−X{sup 2}Σ{sub g}{sup +}) and OH(A{sup 2}Σ{sup +}−X{sup 2}Π{sub i}). Temporally resolved vibrational and rotational temperatures of N{sub 2} were also presented and decreased with increasing the water vapor content.

  9. Note: Limitations of the optoelectronic control for carbon nanoparticles synthesis via arc-discharge in solution.

    PubMed

    Darias-González, J G; Hernández-Tabares, L; Carrillo-Barroso, E; Ledo-Pereda, L M; Arteche-Díaz, J; Desdín-García, L F

    2014-03-01

    Submerged electric arc discharge in liquids has shown to be a promising method for synthesizing a wide variety of nanomaterials. However, it requires an accurate current stability control to ensure the desired purity and structure of the products. The discharge stability control through light emission has been previously studied, but still requires further investigation to clarify the influence of some parameters. The present work has studied the solution's transmittance variation over time, the correlation between the arc light emission and the arc current, and the feasibility of controlling the arc current by using a specific wavelength of the arc light spectrum. Several limitations of the optoelectronic control were found at low currents (I < 50 A).

  10. Fabrication of graphene from graphite by a thermal assisted vacuum arc discharge system

    NASA Astrophysics Data System (ADS)

    Cheng, Guo-Wei; Chu, Kevin; Chen, Jeng Shiung; Tsai, Jeff T. H.

    2017-04-01

    In this study, graphene was fabricated on copper foils using a high temperature furnace embedded in a vacuum arc discharge method. Combining the advantages of chemical vapor deposition and vacuum arc discharge, single-layer graphene can be fabricated at 600 °C base temperature from the mini furnace embedded with a fast heating via the photon radiation from the vacuum arc to 1100 °C on the substrates' surface. The optimal fabrication condition was determined through a series of experiments on ambient pressure, processing time, arc currents, and the cooling process. Observations by scanning electron microscopy, Raman spectroscopy, and optical microscopy showed that the main products were single-layer graphene, which has a uniform thickness across the entire substrate. The results demonstrated that the combination of a vacuum arc with a thermal method that uses graphite as a carbon source provides a low-cost and straight forward method to synthesize graphene films for graphene-based applications.

  11. Carbon Single-Wall Nanatube Growth in a Volumetrically Confined Arc Discharge System

    SciTech Connect

    Franz, K.J.; Alleman, J.L.; Jones, K.M.; Dillon, A.C.; Heben, M.J.

    2004-01-01

    Carbon nanotubes hold significant promise for a vast number of materials applications due to their unique mechanical, electrical, and gas storage properties. Although carbon single-wall nanotubes (SWNTs) have been synthesized since 1993 by the arc discharge method, and numerous other synthesis methods have since been developed, no method has yet produced 100% pure carbon nanotubes. Instead, a significant amount of impurities—various carbon structures and metal catalysts—are present in the raw soot. While arc discharge was the first method for SWNT synthesis, it also produces more impure raw soot in comparison to the more recently developed laser vaporization, which has produced the purest raw soot to date but is much slower. Geometry and thermal gradient are appreciably different between traditional arc discharge systems and laser vaporization systems. We report that, by incorporating some characteristics inherent to a laser vaporization system into an arc discharge system, improvement in the yield of SWNT raw soot may be achieved. This is accomplished by confining the arc within a 50 mm diameter quartz tube, similar to laser vaporization. We find through transmission electron microscopy and Raman spectroscopy that SWNTs are made in significant numbers in this confined arc discharge system, comparable to laser vaporization synthesized material. Further study is, however, required to prove reproducibility and attain an exact value for the purity of the produced raw soot.

  12. Double-ended metal halide arc discharge lamp with electrically isolated containment shroud

    NASA Technical Reports Server (NTRS)

    Muzeroll, Martin M. (Inventor)

    1994-01-01

    A double-ended arc discharge lamp includes a sealed, light-transmissive outer jacket, a light-transmissive shroud mounted within the outer jacket and directly supported by the outer jacket, and an arc discharge tube mounted within the shroud. The arc tube is typically a metal halide arc discharge tube. In a preferred embodiment, the shroud includes an outwardly flared portion at each end. The outwardly flared portions space the shroud from the outer jacket and support the shroud within the outer jacket. The outwardly flared portions of the shroud can be affixed to the outer jacket by fusing. The outer jacket can be provided with inwardly extending dimples for locating the shroud with respect to the outer jacket. In another embodiment, the outer jacket includes reduced diameter portions near each end which are attached to the shroud.

  13. Stable synthesis of few-layered boron nitride nanotubes by anodic arc discharge

    DOE PAGES

    Yeh, Yao-Wen; Raitses, Yevgeny; Koel, Bruce E.; ...

    2017-06-08

    Boron nitride nanotubes (BNNTs) were successfully synthesized by a dc arc discharge using a boron-rich anode as synthesis feedstock in a nitrogen gas environment at near atmospheric pressure. The synthesis was achieved independent of the cathode material suggesting that under such conditions the arc operates in so-called anodic mode with the anode material being consumed by evaporation due to the arc heating. In order to sustain the arc current by thermionic electron emission, the cathode has to be at sufficiently high temperature, which for a typical arc current density of similar to 100 A/cm2, is above the boron melting pointmore » (2350 K). With both electrodes made from the same boron-rich alloy, we found that the arc operation unstable due to frequent sticking between two molten electrodes and formation of molten droplets. We achieved a stable and reliable arc operation and arc synthesis with the boronrich anode and the cathode made from a refractory metal which has a melting temperature above the melting point of boron. Ex-situ characterization of synthesized BNNTs with electron microscopy and Raman spectroscopy revealed that independent of the cathode material, the tubes are primarily single and double walled. Our results also show evidence of root-growth of BNNTs produced in the arc discharge.« less

  14. Increasing the length of single-wall carbon nanotubes in a magnetically enhanced arc discharge

    NASA Astrophysics Data System (ADS)

    Keidar, Michael; Levchenko, Igor; Arbel, Tamir; Alexander, Myriam; Waas, Anthony M.; Ostrikov, Kostya (Ken)

    2008-01-01

    It is demonstrated that a magnetic field has a profound effect on the length of a single-wall carbon nanotube (SWCNT) synthesized in the arc discharge. The average length of SWCNT increases by a factor of 2 in discharge with magnetic field as compared with the discharge without magnetic field, and the yield of long nanotubes with lengths above 5μm also increases. A model of SWCNT growth on metal catalyst in arc plasma was developed. Monte-Carlo simulations confirm that the increase of the plasma density in the magnetic field leads to an increase in the nanotube growth rate and thus leads to longer nanotubes.

  15. Increasing the length of single-wall carbon nanotubes in a magnetically enhanced arc discharge

    SciTech Connect

    Keidar, Michael; Levchenko, Igor; Ostrikov, Kostya; Arbel, Tamir; Alexander, Myriam; Waas, Anthony M.

    2008-01-28

    It is demonstrated that a magnetic field has a profound effect on the length of a single-wall carbon nanotube (SWCNT) synthesized in the arc discharge. The average length of SWCNT increases by a factor of 2 in discharge with magnetic field as compared with the discharge without magnetic field, and the yield of long nanotubes with lengths above 5 {mu}m also increases. A model of SWCNT growth on metal catalyst in arc plasma was developed. Monte-Carlo simulations confirm that the increase of the plasma density in the magnetic field leads to an increase in the nanotube growth rate and thus leads to longer nanotubes.

  16. Sustained arc temperature: better marker for phase transformation of carbon black to multiwalled carbon nanotubes in arc discharge method

    NASA Astrophysics Data System (ADS)

    Arora, Neha; Sharma, N. N.

    2016-10-01

    The present study investigates the role of temperature in the formation of multiwalled carbon nanotubes from carbon black using arc discharge technique. Carbon black has been used as precursor to synthesize carbon nanotubes in argon atmosphere. The arc current has been varied from 25 to 40 A in order to study the morphological changes in carbon black as it gets converted to multi walled carbon nanotubes (MWCNTs). We observed formation of MWCNTs at an arc current of 25 A; however the recorded temperature data suggested correlation of sustained arc temperature with the nanotube formation rather than the magnitude of current in its absoluteness. Interesting to note is that reported current magnitude in published literature are very high (>40 A) for conversion of carbon black but the present investigation shows that it is possible to convert the carbon black to MWCNTs even at lower current values in case the arc temperature is stabilized and sustained for longer period. Detailed investigations suggested that a sustained stable critical temperature of 1400 °C-1600 °C is essential for the growth of nanotubes and an unstable arc causing temperature fluctuation from critical temperature value yields very low or no MWCNTs.

  17. Comparative characteristics of electron energy spectrum in PIG and arc type discharge plasmas

    NASA Technical Reports Server (NTRS)

    Romanyuk, L. I.; Suavilnyy, N. Y.

    1978-01-01

    The electron distribution functions relative to the velocity component directed along the magnetic field are compared for PIG and arc type discharges. The identity of these functions for the plasma region pierced by the primary electron beam and their difference in the peripheral part of the discharge are shown. It is concluded that the electron distribution function in the PIG type discharge is formed during one transit of the primary electron through the discharge gap. The mechanisms of electron energy spectrum formation in both the axis region and the peripheral region of the discharge are discussed.

  18. Arcing and discharges in high-voltage subsystems of Space Station

    NASA Technical Reports Server (NTRS)

    Singh, N.

    1988-01-01

    Arcing and other types of electrical discharges are likely to occur in high-voltage subsystems of the Space Station. Results from ground and space experiments on the arcing of solar cell arrays are briefly reviewed, showing that the arcing occurs when the conducting interconnects in the arrays are at negative potential above a threshold, which decreases with the increasing plasma density. Furthermore, above the threshold voltages the arcing rate increases with the plasma density. At the expected operating voltages (approximately 200 V) in the solar array for the space station, arcing is expected to occur even in the ambient ionospheric plasma. If the ionization of the contaminants increases the plasma density near the high-voltage systems, the adverse effects of arcing on the solar arrays and the space station are likely to be enhanced, In addition to arcing other discharge processes are likely to occur in high-voltage subsystems. For example, Paschen discharge is likely to occur when the neutral density N sub n greater that 10 to the 12th cu cm, the corresponding neutral pressure P greater than 3 x 10 to the -5 Torr.

  19. Modeling of the ac arc discharge on ice surfaces

    SciTech Connect

    Farzaneh, M.; Zhang, J.; Chen, X.

    1997-01-01

    A model for predicting the flashover voltage of ice-covered insulators energized with ac voltage is presented in this paper. The model takes into account the variation of ice surface conductivity as a function of freezing water conductivity. The effects of the length of the arc on its own characteristics, as well as the ac arc reignition condition, were determined in a laboratory investigation using triangular ice samples. The model is applied to a short string of 5 IEEE standard insulator units. There is an excellent concordance between the 50% flashover voltage calculated from the mathematical model and the experimental results.

  20. Differential Inactivation of Fungal Spores in Water and on Seeds by Ozone and Arc Discharge Plasma.

    PubMed

    Kang, Min Ho; Pengkit, Anchalee; Choi, Kihong; Jeon, Seong Sil; Choi, Hyo Won; Shin, Dong Bum; Choi, Eun Ha; Uhm, Han Sup; Park, Gyungsoon

    2015-01-01

    Seed sterilization is essential for preventing seed borne fungal diseases. Sterilization tools based on physical technologies have recently received much attention. However, available information is very limited in terms of efficiency, safety, and mode of action. In this study, we have examined antifungal activity of ozone and arc discharge plasma, potential tools for seed sterilization. In our results, ozone and arc discharge plasma have shown differential antifungal effects, depending on the environment associated with fungal spores (freely submerged in water or infected seeds). Ozone inactivates Fusarium fujikuroi (fungus causing rice bakanae disease) spores submerged in water more efficiently than arc discharge plasma. However, fungal spores associated with or infecting rice seeds are more effectively deactivated by arc discharge plasma. ROS generated in water by ozone may function as a powerful fungicidal factor. On the other hand, shockwave generated from arc discharge plasma may have greatly contributed to antifungal effects on fungus associated with rice seeds. In support of this notion, addition of ultrasonic wave in ozone generating water has greatly increased the efficiency of seed disinfection.

  1. Differential Inactivation of Fungal Spores in Water and on Seeds by Ozone and Arc Discharge Plasma

    PubMed Central

    Kang, Min Ho; Pengkit, Anchalee; Choi, Kihong; Jeon, Seong Sil; Choi, Hyo Won; Shin, Dong Bum; Choi, Eun Ha; Uhm, Han Sup; Park, Gyungsoon

    2015-01-01

    Seed sterilization is essential for preventing seed borne fungal diseases. Sterilization tools based on physical technologies have recently received much attention. However, available information is very limited in terms of efficiency, safety, and mode of action. In this study, we have examined antifungal activity of ozone and arc discharge plasma, potential tools for seed sterilization. In our results, ozone and arc discharge plasma have shown differential antifungal effects, depending on the environment associated with fungal spores (freely submerged in water or infected seeds). Ozone inactivates Fusarium fujikuroi (fungus causing rice bakanae disease) spores submerged in water more efficiently than arc discharge plasma. However, fungal spores associated with or infecting rice seeds are more effectively deactivated by arc discharge plasma. ROS generated in water by ozone may function as a powerful fungicidal factor. On the other hand, shockwave generated from arc discharge plasma may have greatly contributed to antifungal effects on fungus associated with rice seeds. In support of this notion, addition of ultrasonic wave in ozone generating water has greatly increased the efficiency of seed disinfection. PMID:26406468

  2. Spatiotemporal study of the local thermodynamic equilibrium deviations in high-intensity discharge lamps

    SciTech Connect

    Helali, H.; Bchir, T.; Araoud, Z.; Charrada, K.

    2013-04-15

    The aim of this work is to study the local thermodynamic equilibrium (LTE) deviations in arc discharges plasma generated in high-intensity discharge lamps operating under an ac (50 Hz) power supply. To achieve this goal, we elaborate a two-temperature, two-dimensional, and time-depending model. We have found numerical results almost reproducing the experimental data, which allows us to validate this model. After validation, we have discussed different energy term effects on the LTE deviations.

  3. Detection of nanoparticles in carbon arc discharge with laser-induced incandescence

    DOE PAGES

    Yatom, S.; Bak, J.; Khrabryi, A.; ...

    2017-02-20

    Laser-induced incandescence measurements were conducted in the carbon arc discharge, used for synthesis of carbon nanostructures. The results reveal two spatial regions occupied by dominant populations of carbon particles with different sizes. Close to the axis of the arc, large micron size particles dominate the incandescence signal. In the arc periphery, the dominant population of nanoparticles has diameter of 20 nm. Using a heat transfer model between the gas, arc plasma and the particles, it is shown that such a drastic difference in the particle sizes can be explained by evaporation of the micron-scale particles which move across the arcmore » plasma towards the arc periphery. It is also hypothesized that mass evaporated from the micro particles contributes to the carbon feedstock for the formation of nanostructures. (C) 2017 Elsevier Ltd. All rights reserved.« less

  4. Investigation on oblique shock wave control by arc discharge plasma in supersonic airflow

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Li, Yinghong; Xing, Fei

    2009-10-01

    Wedge oblique shock wave control by arc discharge plasma in supersonic airflow was investigated theoretically, experimentally, and numerically in this paper. Using thermal choking model, the change in oblique shock wave was deduced, which refer that the start point of shock wave shifts upstream, the shock wave angle decreases, and its intensity weakens. Then the theoretical results were validated experimentally in a Mach 2.2 wind tunnel. On the test conditions of arc discharge power of ˜1 kW and arc plasma temperature of ˜3000 K, schlieren photography and gas pressure measurements indicated that the start point of shock wave shifted upstream of ˜4 mm, the shock wave angle decreased 8.6%, and its intensity weakened 8.8%. The deduced theoretical results match the test results qualitatively, so thermal mechanism and thermal choking model are rational to explain the problem of oblique shock wave control by arc discharge plasma. Finally, numerical simulation was developed. Based on thermal mechanism, the arc discharge plasma was simplified as a thermal source term that added to the Navier-Stokes equations. The simulation results of the change in oblique shock wave were consistent with the test results, so the thermal mechanism indeed dominates the oblique shock wave control process.

  5. Investigation on oblique shock wave control by arc discharge plasma in supersonic airflow

    SciTech Connect

    Wang Jian; Li Yinghong; Xing Fei

    2009-10-01

    Wedge oblique shock wave control by arc discharge plasma in supersonic airflow was investigated theoretically, experimentally, and numerically in this paper. Using thermal choking model, the change in oblique shock wave was deduced, which refer that the start point of shock wave shifts upstream, the shock wave angle decreases, and its intensity weakens. Then the theoretical results were validated experimentally in a Mach 2.2 wind tunnel. On the test conditions of arc discharge power of approx1 kW and arc plasma temperature of approx3000 K, schlieren photography and gas pressure measurements indicated that the start point of shock wave shifted upstream of approx4 mm, the shock wave angle decreased 8.6%, and its intensity weakened 8.8%. The deduced theoretical results match the test results qualitatively, so thermal mechanism and thermal choking model are rational to explain the problem of oblique shock wave control by arc discharge plasma. Finally, numerical simulation was developed. Based on thermal mechanism, the arc discharge plasma was simplified as a thermal source term that added to the Navier-Stokes equations. The simulation results of the change in oblique shock wave were consistent with the test results, so the thermal mechanism indeed dominates the oblique shock wave control process.

  6. Temperature and Nitric Oxide Generation in a Pulsed Arc Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Namihira, T.; Sakai, S.; Matsuda, M.; D., Wang; Kiyan, T.; Akiyama, H.; Okamoto, K.; Toda, K.

    2007-12-01

    Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease. To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.

  7. Note: Iodine dissociation with a pulsed arc discharge

    NASA Astrophysics Data System (ADS)

    Saghafifar, H.; Goodarzi, M. S.

    2017-08-01

    A new method is presented to dissociate iodine molecules in gas discharge. A high repetition rate spark gap is designed and used to trigger the circuit. Absorption spectroscopy is applied to measure the dissociation fraction of iodine molecules. It is found that more than 35% of iodine molecules are dissociated. The effect of switching frequency on the dissociation coefficient is investigated by changing the frequency of the rotating spark gap. Pulsed and equivalent direct current circuits are compared, and it is found that in the constant current glow discharge the dissociation fraction is near to the zero and negligible.

  8. Hollow cathodes in high pressure arc discharges. [for arcjet thrusters

    NASA Technical Reports Server (NTRS)

    Hardy, T. L.; Curran, F. M.

    1985-01-01

    An orified hallow cathode was tested at high pressure to improve lifetime and efficiency in arcjet thrusters. It is indicated that the arc would not operate with emission from the insert above 200 torr in nitrogen regardless of insert material, orifice diameter, or gas flow direction. Emission occurred from the insert in argon and xenon although it could not be ascertained whether diffuse or spot emission existed within the cathode. Over the extended range of configurations and operating parameters explored the desired diffuse emission mode could not be obtained at high enough pressures for orified hollow cathodes to operate in the range which is considered for arcjet applications.

  9. Effect of oxygen impurities on atmospheric-pressure surface streamer discharge in argon for large gap arc breakdown

    NASA Astrophysics Data System (ADS)

    Sharma, Ashish; Levko, Dmitry; Raja, Laxminarayan L.

    2016-10-01

    We report the results of a computational study that investigates the effect of impurities (molecular oxygen) on the development of argon surface streamers at atmospheric-pressure conditions. A continuous surface streamer has been proposed as a low-voltage mechanism to generate a conductive bridge for arc breakdown of a large interelectrode gap at high pressures. The streamer discharge model is based on the self-consistent, multispecies, continuum description of the plasma. Below a threshold voltage, no streamer discharge is observed and charge is localized only in the vicinity of the anode in the form of a localized corona. Above this voltage threshold in pure argon, a continuous conductive streamer successfully bridges the gap between two electrodes indicating high probability of transition to the arc. For small oxygen impurities (less than 5%), the threshold voltage is found to decrease by a few hundred volts compared to the threshold voltage in pure argon while the streamer induction time increases. No noticeable changes in the streamer conductivity is obtained for low impurities of oxygen in the above range. An increase of the oxygen density above the 5% impurity level causes a significant decrease in the continuous streamer conductivity and leads to a decrease in the probability of transition to arc.

  10. Pure iron nanoparticles prepared by electric arc discharge method in ethylene glycol

    NASA Astrophysics Data System (ADS)

    Hosseynizadeh Khezri, S.; Yazdani, A.; Khordad, R.

    2012-09-01

    Pure iron nanoparticles (NPs) are fabricated using a simple and low-cost electric arc-discharge method in ethylene glycol (EG). The effect of different arc discharge currents (10, 20 and 30 A) on the size and optical absorption of the NPs is studied. Dynamic light scattering (DLS) and UV-visible spectroscopy data indicate that at the arc current of 10 A, the size of the particles is about 103 nm, and it can raise the arc current leading to larger NPs. UV-visible spectroscopy data show that the solvent gets more and more transparent with time, an effect which, sonication, proves that is related to agglomeration of the NPs. The evidence of pure Fe NPs is investigated by means of X-ray diffraction (XRD) measurement the average size of which is about 14 nm using Scherrer's relation. Magnetization measurements of the samples are carried out by alternating gradient force magnetometer (AGFM). These results have shown that the arc discharge method is an effective method for preparing magnetic fluids in one step and EG is the effective medium for caring Fe NPs against oxidation. Therefore, the method can pave the way for the synthesis of other NPs such as Fe, Fe-Co, Fe-Pt and iron oxide.

  11. Peculiarities of the structure formation of nanoscale coatings from the vacuum arc discharge plasma

    NASA Astrophysics Data System (ADS)

    Kostrin, D. K.; Pikus, M. I.; Smirnov, E. A.; Lisenkov, A. A.

    2017-01-01

    In this paper features of the structure formation of nanoscale coatings (TiN)–(AlN)– (Ti–Al–N) in the vacuum arc discharge plasma are considered. The composition and structure of the formed nanoscale coatings are studied. The main factors influencing the quality of the formed coatings are shown.

  12. Investigation of the role of Yttrium in the production of SWNT by arc discharge

    NASA Astrophysics Data System (ADS)

    Gavillet, J.; Loiseau, A.; Stephan, O.; Tahir, S.; Bernier, P.

    2000-11-01

    We present a TEM study of single wall nanotubes (SWNTs) produced with the electric arc discharge technique using a Ni/Y catalyst (of various relative proportions). The study shows that SWNT ropes grow from metallic nanoparticles which are found to have definite Ni-Y compositions. This link has been confirmed for the different Ni/Y anode compositions investigated.

  13. Size-controlled synthesis and gas sensing application of tungsten oxide nanostructures produced by arc discharge.

    PubMed

    Fang, F; Kennedy, J; Futter, J; Hopf, T; Markwitz, A; Manikandan, E; Henshaw, G

    2011-08-19

    Several different synthetic methods have been developed to fabricate tungsten oxide (WO(3)) nanostructures, but most of them require exotic reagents or are unsuitable for mass production. In this paper, we present a systematic investigation demonstrating that arc discharge is a fast and inexpensive synthesis method which can be used to produce high quality tungsten oxide nanostructures for NO(2) gas sensing measurements. The as-synthesized WO(3) nanostructures are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), finger-print Raman spectroscopy and proton induced x-ray emission (PIXE). The analysis shows that spheroidal-shaped monoclinic WO(3) crystal nanostructures were produced with an average diameter of 30 nm (range 10-100 nm) at an arc discharge current of 110 A and 300 Torr oxygen partial pressure. It is found that the morphology is controlled by the arc discharge parameters of current and oxygen partial pressure, e.g. a high arc discharge current combined with a low oxygen partial pressure results in small WO(3) nanostructures with improved conductivity. Sensors produced from the WO(3) nanostructures show a strong response to NO(2) gas at 325 °C. The ability to tune the morphology of the WO(3) nanostructures makes this method ideal for the fabrication of gas sensing materials.

  14. Growth of small diameter multi-walled carbon nanotubes by arc discharge process

    NASA Astrophysics Data System (ADS)

    T. Chaudhary, K.; J., Ali; P. Yupapin, P.

    2014-03-01

    Multi-walled carbon nanotubes (MWCNTs) are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 torr, 300 torr, and 500 torr. Arc plasma parameters such as temperature and density are estimated to investigate the influences of the ambient pressure and the contributions of the ambient pressure to the growth and the structure of the nanotubes. The plasma temperature and density are observed to increase with the increase in the methane ambient pressure. The samples of MWCNT synthesized at different ambient pressures are analyzed using transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. An increase in the growth of MWCNT and a decrease in the inner tube diameter are observed with the increase in the methane ambient pressure.

  15. Study on a negative hydrogen ion source with hot cathode arc discharge

    SciTech Connect

    Lin, S. H. Fang, X.; Zhang, H. J.; Qian, C.; Ma, B. H.; Wang, H.; Li, X. X.; Zhang, X. Z.; Sun, L. T.; Zhang, Z. M.; Yuan, P.; Zhao, H. W.

    2014-02-15

    A negative hydrogen (H{sup −}) ion source with hot cathode arc discharge was designed and fabricated as a primary injector for a 10 MeV PET cyclotron at IMP. 1 mA dc H{sup −} beam with ε {sub N,} {sub RMS} = 0.08 π mm mrad was extracted at 25 kV. Halbach hexapole was adopted to confine the plasma. The state of arc discharge, the parameters including filament current, arc current, gas pressure, plasma electrode bias, and the ratio of I{sub e{sup −}}/I{sub H{sup −}} were experimentally studied. The discussion on the result, and opinions to improve the source were given.

  16. Preparation of Arc Black and Carbon Nano Balloon by Arc Discharge and Their Application to a Fuel Cell

    NASA Astrophysics Data System (ADS)

    Ikeda, Takashi; Kaida, Shota; Satou, Tosiyuki; Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto; Oke, Shinichiro; Ue, Hitoshi; Okawa, Takashi; Aoyagi, Nobuhiro; Shimizu, Kazuki

    2011-01-01

    Arc black (AcB) was prepared in N2 gas using the twin-torch arc discharge apparatus, and a hollow capsule with graphite layers named a carbon nano balloon (CNB) was obtained by heat treatment of the AcB in Ar gas at 2400 °C. Transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, and compressive resistivity measurement confirmed that the CNB was well graphitized. In the direct methanol fuel cell (DMFC) application of these carbon nanomaterials, catalyst metal nanoparticles were supported on the AcB, and a membrane-electrode assembly (MEA) was formed from the catalyst-supported AcB and the CNB by hotpressing them on an electrolyte film. The MEA containing the CNB resulted in a higher DMFC performance than that without the CNB, indicating that the CNB with lower compressive resistivity than the AcB works as a material for the improvement of electric conductivity in an MEA.

  17. Spatiotemporally resolved characteristics of a gliding arc discharge in a turbulent air flow at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas; Aldén, Marcus; Larsson, Anders; Kusano, Yukihiro; Li, Zhongshan

    2017-01-01

    A gliding arc discharge was generated in a turbulent air flow at atmospheric pressure driven by a 35 kHz alternating current (AC) electric power. The spatiotemporally resolved characteristics of the gliding arc discharge, including glow-type discharges, spark-type discharges, short-cutting events and transitions among the different types of discharges, were investigated using simultaneously optical and electrical diagnostics. The glow-type discharge shows sinusoidal-like voltage and current waveforms with a peak current of hundreds of milliamperes. The frequency of the emission intensity variation of the glow-type discharge is the same as that of the electronic power dissipated in the plasma column. The glow-type discharge can transfer into a spark discharge characterized by a sharp peak current of several amperes and a sudden increase of the brightness in the plasma column. Transitions can also be found to take place from spark-type discharges to glow-type discharges. Short-cutting events were often observed as the intermediate states formed during the spark-glow transition. Three different types of short-cutting events have been observed to generate new current paths between two plasma channel segments, and between two electrodes, as well as between the channel segment and the electrodes, respectively. The short-cut upper part of the plasma column that was found to have no current passing through can be detected several hundreds of microseconds after the short-cutting event. The voltage recovery rate, the period of AC voltage-driving signal, the flow rates and the rated input powers were found to play an important role in affecting the transitions among the different types of discharges.

  18. Influence of Plasma Jet Temperature Profiles in Arc Discharge Methods of Carbon Nanotubes Synthesis

    PubMed Central

    Raniszewski, Grzegorz; Wiak, Slawomir; Pietrzak, Lukasz; Szymanski, Lukasz; Kolacinski, Zbigniew

    2017-01-01

    One of the most common methods of carbon nanotubes (CNTs) synthesis is application of an electric-arc plasma. However, the final product in the form of cathode deposit is composed of carbon nanotubes and a variety of carbon impurities. An assay of carbon nanotubes produced in arc discharge systems available on the market shows that commercial cathode deposits contain about 10% CNTs. Given that the quality of the final product depends on carbon–plasma jet parameters, it is possible to increase the yield of the synthesis by plasma jet control. Most of the carbon nanotubes are multiwall carbon nanotubes (MWCNTs). It was observed that the addition of catalysts significantly changes the plasma composition, effective ionization potential, the arc channel conductance, and in effect temperature of the arc and carbon elements flux. This paper focuses on the influence of metal components on plasma-jet forming containing carbon nanotubes cathode deposit. The plasma jet temperature control system is presented. PMID:28336884

  19. Production of Carbon Clusters by Means of Arc Discharge and Their Application 3.Carbon Nanotubes and Nanocapsules Produced by Arc Discharge and their Applications

    NASA Astrophysics Data System (ADS)

    Saito, Yahachi

    This paper characterizes and describes the growth of carbon nanotubes (multiwall and single-wall) and nanocapsules produced by electric arc discharge. For the preparation of multiwall nanotubes, an electrode of pure carbon is evaporated in helium gas, while single-wall nanotubes are produced with the aid of metal catalysts. When carbon is evaporated together with metals, carbon nanocages filled with fine metal particles (called “nanocapsules”) are produced in addition to single-wall nanotubes. The growth of nanotubes and nanocapsules is discussed. Finally, the application of nanotubes in a field emission electron source (cold cathode) is demonstrated.

  20. The Modification of Carbon with Iron Oxide Synthesized in Electrolysis Using the Arc Discharge Method

    NASA Astrophysics Data System (ADS)

    Endah Saraswati, Teguh; Dewi Indah Prasiwi, Oktaviana; Masykur, Abu; Handayani, Nestri; Anwar, Miftahul

    2017-02-01

    The modification of carbon-based nanomaterials with metals is widely studied due to its unique properties. Here, the modification of carbon nanomaterial with iron oxide has been successfully carried out. This modification was achieved using arc discharge in 50% ethanol liquid media. The anode used in the arc discharge was prepared from a mixture of carbon and iron oxide that was synthesized in electrolysis and was then calcined at 250°C with silicon binder with a mass ratio of 3:1:1, and the cathode used was graphite rod. Both electrodes were set in the nearest gap that could provide an arc during arc-discharging, leading to carbon-based nanoparticle formation. The diffractogram pattern of the X-ray diffraction of the fabricated nanoparticles confirmed the typical peak of carbon, iron oxide and iron. The magnetization value of the result analysis of the vibrating sample magnetometer was 9.9 emu/g. The bandgap energy measurement using diffuse reflectance ultra violet was estimated to be 2.18 eV. Using the transmission electron microscopy, the structure of the nanomaterial produced was observed as carbon-encapsulated iron compound nanoparticles.

  1. Electron beam charging and arc discharging of spacecraft insulating materials

    NASA Technical Reports Server (NTRS)

    Balmain, K. G.

    1983-01-01

    Samples of Mylar and Teflon film were exposed to combinations of monoenergetic electron and lithium ion fluxes in various ratios. The samples' discharge rates and strengths were found to diminish as the ion proportion increased. Various types of capacitors were exposed in air to beta irradiation from a 100 mCie Strontium-90 radioisotope source located at distances ranging from 2 cm to 5 cm from the capacitors. In these preliminary experiments, no evidence of spontaneous electrical breakdown was noted, nor was any change in RF impedance detectable using the available instrumentation. A decrease in DC resistance was noted, apparently due to radiation-induced conductivity. A cylindrical glass vacuum chamber is being assembled. Its inside dimensions are 44 cm diameter by 100 cm length. All necessary associated components and instruments have been acquired, including electron and ion guns, Trek surface potential probe and turbo-molecular pump. A mass-spectrometer detector for leaks and evolved gases will be ordered shortly.

  2. In-process electrical discharge dressing of arc-shaped metal bonded diamond wheels

    NASA Astrophysics Data System (ADS)

    Wang, Kai; Fan, Fei; Tian, Guoyu; Zhang, Feihu; Liu, Zhongde

    2016-10-01

    Due to the high hardness of SiC ceramics, the wear of the arc-shaped metal bonded diamond wheels is very serious during the grinding process of large-aperture aspheric SiC mirrors. The surface accuracy and surface/sub-surface quality of the aspheric mirror will be affected seriously if the grinding wheel is not timely dressed. Therefore, this paper focus on the in-process dressing of the arc-shaped metal bonded diamond wheels. In this paper, the application of the asymmetric arc profile grinding wheel in the grinding of aspheric mirrors is discussed first. Then a rotating cup-shaped electrode in-process electro discharge dressing device for the arc-shaped wheels is developed based on the analysis. The dressing experiments are carried out with the device. The experimental results show that the in-process dressing device can did the dressing for the asymmetric and symmetric arc-shaped wheel. The profile error of the arc can reach to 3μm with the in-process dressing device.

  3. Ion sources with arc-discharge plasma box driven by directly heated LaB(6) electron emitter or cold cathode.

    PubMed

    Ivanov, Alexander A; Davydenko, Vladimir I; Deichuli, Petr P; Shulzhenko, Grigori I; Stupishin, Nikolay V

    2008-02-01

    In the Budker Institute, Novosibirsk, an ion source with arc-discharge plasma box has been developed in the recent years for application in thermonuclear devices for plasma diagnostics. Several modifications of the ion source were provided with extracted current ranging from 1 to 7 A and pulse duration of up to 4 s. Initially, the arc-discharge plasma box with cold cathode was used, with which pulse duration is limited to 2 s by the cathode overheating and sputtering in local arc spots. Recently, a directly heated LaB(6) electron emitter was employed instead, which has extended lifetime compared to the cold cathode. In the paper, characteristics of the beam produced with both arrangements of the plasma box are presented.

  4. Hollow cathode arc discharge as an effective energy source for welding processes in vacuum

    NASA Astrophysics Data System (ADS)

    Nerovnyi, V. M.; Khakhalev, A. D.

    2008-02-01

    This paper presents the results of an investigation of thermal and physical properties of the hollow cathode arc discharge (HCAD) with respect to its application for welding processes in vacuum. The following main parameters of the arc discharge were studied: the external voltage-current (V-I) characteristics; plasma parameters inside the cathode cavity and in the arc external column and the radial heat flux density distribution into the anode. Langmuir electrical probes have been utilized to investigate plasma parameters. Electron energy distribution function was determined from the probe V-I characteristics by the computation of an inverse ill-posed problem. It was shown that, depending on welding parameters, HCAD can exist in two different forms: diffusive or constricted. At currents below 60 A, HCAD has the diffusive form, and with the increase in the current it changes to the constricted form. The discharge constriction phenomenon, we believe, could be explained by the appearance in the external plasma of high velocity electrons with energies from 12 to 22 eV. Parameters of the heat flux into the anode were investigated with spot and split-anode calorimeters. The heat flux density on the anode of the diffusive form of the discharge has a Gaussian distribution. The heat flux of the constricted form is significantly different from the diffusive one and can be approximated by the sum of two combined normal-circular heat sources with different power concentration coefficients. It was also found that the efficiency parameter of the discharge energy transfer to the anode can reach 0.7-0.86 of the discharge voltage, which confirmed that HCAD is a highly effective energy source for welding processes in vacuum. Examples of industrial applications of HCAD for welding, brazing and alloying in vacuum are presented.

  5. Development of cold cathode arc discharge filament based multi-cusp H- ion source

    NASA Astrophysics Data System (ADS)

    Kumar, Rajnish; Ghodke, Dharmraj V.; Senecha, Vinod K.

    2017-08-01

    A cold cathode arc discharge filament based multicusp H- ion source (HNIS) has been developed using an innovative low power igniter system working in a glow discharge regime to achieve a longer lifetime of the filament. This HNIS is cesium-free and its experimental prototype generates a maximum H- ion beam (HNIB) current of 12 mA at 50 keV beam energy in pulse mode with a peak arc power of 27 kW using the triode extraction system. This article presents the results of initial commissioning of the HNIS and steering magnetic field used to separate out the co-extracted electrons from HNIB, verified through experiments and 3-D ion beam simulations.

  6. Optoelectronically automated system for carbon nanotubes synthesis via arc-discharge in solution

    NASA Astrophysics Data System (ADS)

    Bera, Debasis; Brinley, Erik; Kuiry, Suresh C.; McCutchen, Matthew; Seal, Sudipta; Heinrich, Helge; Kabes, Bradley

    2005-03-01

    The method of arc discharge in the solution is unique and inexpensive route for synthesis of the carbon nanotubes (CNTs), carbon onions, and other carbon nanostructures. Such a method can be used for in situ synthesis of CNTs decorated with nanoparticles. Herein, we report a simple and inexpensive optoelectronically automated system for arc discharge in solution synthesis of CNTs. The optoelectronic system maintains a constant gap between the two electrodes allowing a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analog electronic unit, as controller. This computerized feeding system of the anode was used for in situ nanoparticles incorporated CNTs. For example, we have successfully decorated CNTs with ceria, silica, and palladium nanoparticles. Characterizations of nanostructures are performed using high-resolution transmission electron microscopy, scanning transmission electron microscopy, energy dispersive spectroscopy, and scanning electron microscopy.

  7. Multiwalled carbon nanotubes produced by direct current arc discharge in hydrogen gas

    NASA Astrophysics Data System (ADS)

    Jinno, M.; Bandow, S.; Ando, Y.

    2004-11-01

    Multiwalled carbon nanotubes were produced by direct current (DC) arc discharge in the mixture gas of H 2-N 2. Raman scattering spectroscopy was used to characterize the MWNTs. Radial breathing mode vibration signals were observed at 272 and 388 cm -1. Tangential mode vibration signal was observed at ≈1582 cm -1, and other intense signals were also observed at ≈1860 cm -1for the MWNTs produced in the gas with the H 2 contents exceeding 90%. DC arc discharge in pure D 2 was also carried out, by which it was confirmed that the peak position and intensity of the Raman signal at ≈1860 cm -1 were independent of whether the gas was H 2 or D 2. This suggests that the ≈1860 cm -1 band is not associated with hydrogen-based vibrations.

  8. Silicon etch with chromium ions generated by a filtered or non-filtered cathodic arc discharge.

    PubMed

    Scopece, Daniele; Döbeli, Max; Passerone, Daniele; Maeder, Xavier; Neels, Antonia; Widrig, Beno; Dommann, Alex; Müller, Ulrich; Ramm, Jürgen

    2016-01-01

    The pre-treatment of substrate surfaces prior to deposition is important for the adhesion of physical vapour deposition coatings. This work investigates Si surfaces after the bombardment by energetic Cr ions which are created in cathodic arc discharges. The effect of the pre-treatment is analysed by X-ray diffraction, Rutherford backscattering spectroscopy, scanning electron microscopy and in-depth X-ray photoemission spectroscopy and compared for Cr vapour produced from a filtered and non-filtered cathodic arc discharge. Cr coverage as a function of ion energy was also predicted by TRIDYN Monte Carlo calculations. Discrepancies between measured and simulated values in the transition regime between layer growth and surface removal can be explained by the chemical reactions between Cr ions and the Si substrate or between the substrate surface and the residual gases. Simulations help to find optimum and more stable parameters for specific film and substrate combinations faster than trial-and-error procedure.

  9. Note: Arc discharge plasma source with plane segmented LaB{sub 6} cathode

    SciTech Connect

    Akhmetov, T. D. Davydenko, V. I.; Ivanov, A. A.; Kreter, A.; Unterberg, B.; Mishagin, V. V.; Savkin, V. Ya.; Shulzhenko, G. I.

    2016-05-15

    A plane cathode composed of close-packed hexagonal LaB{sub 6} (lanthanum hexaboride) segments is described. The 6 cm diameter circular cathode is heated by radiation from a graphite foil flat spiral. The cathode along with a hollow copper anode is used for the arc discharge plasma production in a newly developed linear plasma device. A separately powered coil located around the anode is used to change the magnetic field strength and geometry in the anode region. Different discharge regimes were realized using this coil.

  10. Spectroscopic studies of plasma in a carbon arc discharge for synthesis of nanomaterials

    NASA Astrophysics Data System (ADS)

    Vekselman, Vladislav; Feurer, Matthew; Yeh, Yao-Wen; Stratton, Brentley; Raitses, Yevgeny; LaboratoryPlasma Nanosynthesis Team

    2016-09-01

    An atmospheric pressure arc discharge with graphite electrodes is commonly used for synthesis of carbon nanomaterials such as buckyballs, nanotubes and graphene. In operation, the graphite anode ablates providing a feedstock material for synthesis these carbon nanostructures. Existing models predict that nucleation and growth of these nanomaterials in an arc discharge are governed by spatial distributions of density and temperature of plasma species. Control of these distributions can potentially enable optimization of nanosynthesis processes, to achieve the best combination of synthesis selectivity at the synthesis yield. In this work, we report first detail measurements of spatial distribution of arc plasma parameters obtained with a set of in-situ diagnostics, including optical emission spectroscopy and fast framing imaging. These parameters were measured in low- and high- anode ablation modes. Results of these measurements demonstrate a strong correlation between arc plasma and synthesis processes. This work was supported by U.S. Department of Energy, Office of Science, Basic Sciences, Materials Sciences and Engineering Division.

  11. Mechanism of Synthesis of Ultra-Long Single Wall Carbon Nanotubes in Arc Discharge Plasma

    SciTech Connect

    Keidar, Michael

    2013-06-23

    In this project fundamental issues related to synthesis of single wall carbon nanotubes (SWNTs), which is relationship between plasma parameters and SWNT characteristics were investigated. Given that among plasma-based techniques arc discharge stands out as very advantageous in several ways (fewer defects, high flexibility, longer lifetime) this techniques warrants attention from the plasma physics and plasma technology standpoint. Both experimental and theoretical investigations of the plasma and SWNTs synthesis were conducted. Experimental efforts focused on plasma diagnostics, measurements of nanostructures parameters, and nanoparticle characterization. Theoretical efforts focused to focus on multi-dimensional modeling of the arc discharge and single wall nanotube synthesis in arc plasmas. It was demonstrated in experiment and theoretically that controlling plasma parameters can affect nanostucture synthesis altering SWNT properties (length and diameter) and leading to synthesis of new structures such as a few-layer graphene. Among clearly identified parameters affecting synthesis are magnetic and electric fields. Knowledge of the plasma parameters and discharge characteristics is crucial for ability to control synthesis process by virtue of both magnetic and electric fields. New graduate course on plasma engineering was introduced into curriculum. 3 undergraduate students were attracted to the project and 3 graduate students (two are female) were involved in the project. Undergraduate student from Historically Black University was attracted and participated in the project during Summer 2010.

  12. Radiographic research of the Bi plasma jet formed by the vacuum arc discharge

    NASA Astrophysics Data System (ADS)

    Artyomov, A. P.; Rousskikh, A. G.; Fedunin, A. V.; Chaikovsky, S. A.; Zhigalin, A. S.; Oreshkin, V. I.

    2017-05-01

    The results of experiments on a soft x-ray radiography (≈ 1-2 keV) of a bismuth plasma formed by the high-current vacuum arc discharge are represented. The plasma gun with the arc current ≈ 60 kA and the current rise time ≈ 7 μs was used to produce the Bi plasma jet. The compact pulsed radiograph XPG-1 (250 kA, 220 ns) with an X-pinch load consisting of four Mo wires with a diameter 25 μm was used as a source of the soft X-ray radiation. The X-ray backlighting images of the researched plasma jet and the Bi step-wedge with a step thickness of ≈ 100 nm were recorded simultaneously in the course of the experiment. A comparison of the plasma jet x-ray image with the current trace has enabled to estimate dependencies of the linear mass on the arc current. The experiments have shown that when the arc current density reaches ≈ 3·105 A/cm2, the evaporation rate of the electrode material reaches ≈ 100 μg/μs, that under the plasma velocity ≈ 0.5 cm/μs, provides a plasma jet linear mass ≈ 200 μg/cm. At a distance of ≈ 1-2 mm from the arc cathode surface, the sharp increase of the jet linear mass (up to ≈ 500 μg/cm) occurred.

  13. Coagulation of carbon nanoparticles in the acoustic field in the vicinity of the arc discharge

    NASA Astrophysics Data System (ADS)

    Shneider, Mikhail

    2016-09-01

    An arc discharge produced in a background inert gase between graphite electrodes is one of the popular methods of nanoparticle synthesis. Nanoparticles and microscopic soot particles are produced in the peripheral region of arc. Intensive soot generation significantly reduces the efficiency of the arc as the technological process for production of fullerenes and other nanoparticles. Experimental studies have shown that exposure of peripheral region of the arc to intense ultrasound leads to a noticeable increase in the efficiency of the nanoparticle synthesis and reduces the soot yield (see, e.g.), because ultrasound causes coagulation of soot particles and decrease of their concentration without affecting the nanoparticles. The paper presents theoretical study of the threshold for the ultrasound intensity required for the coagulation as a function of particle sizes and charge, and background gas parameters. The charge acquired in a thermionic emission, as a result of particles heating by radiation from the arc, is calculated self-consistently. I would like to thank Dr. Yevgeny Raitses, Dr. Igor Kaganovich, and Mr. James Mitrani for their interest in this work and fruitful discussions. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  14. Comparative study of two- and three-dimensional modeling on arc discharge phenomena inside a thermal plasma torch with hollow electrodes

    SciTech Connect

    Kim, Keun Su; Park, Jin Myung; Choi, Sooseok; Kim, Jongin; Hong, Sang Hee

    2008-02-15

    A comparative study between two- and three-dimensional (2D and 3D) modeling is carried out on arc discharge phenomena inside a thermal plasma torch with hollow electrodes, in order to evaluate the effects of arc root configuration characterized by either 2D annular or 3D highly localized attachment on the electrode surface. For this purpose, a more precise 3D transient model has been developed by taking account of 3D arc current distribution and arc root rotation. The 3D simulation results apparently reveal that the 3D arc root attachment brings about the inherent 3D and turbulence nature of plasma fields inside the torch. It is also found that the constricted arc column near the vortex chamber plays an important role in heating and acceleration of injected arc gases by concentrating arc currents on the axis of the hollow electrodes. The inherent 3D nature of arc discharge is well preserved inside the cathode region, while these 3D features slowly diminish behind the vortex chamber where the turbulent flow begins to be developed in the anode region. Based on the present simulation results, it is noted that the mixing effects of the strong turbulent flow on the heat and mass transfer are mainly responsible for the gradual relaxation of the 3D structures of plasma fields into the 2D axisymmetric ones that eventually appear in the anode region near the torch exit. From a detailed comparison of the 3D results with the 2D ones, the arc root configuration seems to have a significant effect on the heat transfer to the electrode surfaces interacting with the turbulent plasma flow. That is, in the 2D simulation based on an axisymmetric stationary model, the turbulence phenomena are fairly underestimated and the amount of heat transferred to the cold anode wall is calculated to be smaller than that obtained in the 3D simulation. For the validation of the numerical simulations, calculated plasma temperatures and axial velocities are compared with experimentally measured ones

  15. Plasma-chemical reactor based on a low-pressure pulsed arc discharge for synthesis of nanopowders

    NASA Astrophysics Data System (ADS)

    Karpov, I. V.; Ushakov, A. V.; Lepeshev, A. A.; Fedorov, L. Yu.

    2017-01-01

    A reactor for producing nanopowders in the plasma of a low-pressure arc discharge has been developed. As a plasma source, a pulsed cold-cathode arc evaporator has been applied. The design and operating principle of the reactor have been described. Experimental data on how the movement of a gaseous mixture in the reactor influences the properties of nanopowders have been presented.

  16. Experimental analysis on the effects of DC arc discharges at various flow regimes

    NASA Astrophysics Data System (ADS)

    Bianchi, G.; Saracoglu, B. H.; Paniagua, G.; Regert, T.

    2015-03-01

    This paper addresses the control of the boundary layer on a compression ramp by means of DC electrical arc discharges. The development and realization of the control system are first described and then assessed in the wind tunnel. The objective of the research was to control the supersonic flow using the minimum amount of energy. The array of electrodes was located at the base of a ramp, where a low momentum flow develops. The electrical discharge was generated by a custom designed electronic facility based on high-voltage ignition coils. The slanted tungsten electrodes were insulated by mounting them in a ceramic support. The discharge evolution was studied through high-speed flow visualizations, while electrical measurements at the high-voltage section of the circuitry allowed to estimate the energy release. The development of a high-speed short exposure Schlieren imaging technique, based on a very short duration laser pulse illumination and a double shot CCD camera, allowed to observe the macroscopic effects associated with the arc establishment between the electrodes (glow, sound wave and heat release). Due to the long residence time, the thermal perturbation spread along the streamwise direction. Cross correlation of Schlieren images with short time separation revealed that in supersonic conditions, the discharges led to an overall acceleration of the flow field underneath the oblique shock wave.

  17. Synthesis and characteristics of Ag/Pt bimetallic nanocomposites by arc-discharge solution plasma processing.

    PubMed

    Pootawang, Panuphong; Saito, Nagahiro; Takai, Osamu; Lee, Sang-Yul

    2012-10-05

    Arc discharge in solution, generated by applying a high voltage of unipolar pulsed dc to electrodes of Ag and Pt, was used as a method to form Ag/Pt bimetallic nanocomposites via electrode erosion by the effects of the electric arc at the cathode (Ag rod) and the sputtering at the anode (Pt rod). Ag/Pt bimetallic nanocomposites were formed as colloidal particles dispersed in solution via the reduction of hydrogen radicals generated during discharge without the addition of chemical precursor or reducing agent. At a discharge time of 30 s, the fine bimetallic nanoparticles with a mean particle size of approximately 5 nm were observed by transmission electron microscopy (TEM). With increasing discharge time, the bimetallic nanoparticle size tended to increase by forming an agglomeration. The presence of the relatively small amount of Pt dispersed in the Ag matrix could be observed by the analytical mapping mode of energy-dispersive x-ray spectroscopy and high-resolution TEM. This demonstrated that the synthesized particle was in the form of a nanocomposite. No contamination of other chemical substances was detected by x-ray photoelectron spectroscopy. Hence, solution plasma could be a clean and simple process to effectively synthesize Ag/Pt bimetallic nanocomposites and it is expected to be widely applicable in the preparation of several types of nanoparticle.

  18. Experimental analysis on the effects of DC arc discharges at various flow regimes

    SciTech Connect

    Bianchi, G.; Saracoglu, B. H. Regert, T.; Paniagua, G.

    2015-03-15

    This paper addresses the control of the boundary layer on a compression ramp by means of DC electrical arc discharges. The development and realization of the control system are first described and then assessed in the wind tunnel. The objective of the research was to control the supersonic flow using the minimum amount of energy. The array of electrodes was located at the base of a ramp, where a low momentum flow develops. The electrical discharge was generated by a custom designed electronic facility based on high-voltage ignition coils. The slanted tungsten electrodes were insulated by mounting them in a ceramic support. The discharge evolution was studied through high-speed flow visualizations, while electrical measurements at the high-voltage section of the circuitry allowed to estimate the energy release. The development of a high-speed short exposure Schlieren imaging technique, based on a very short duration laser pulse illumination and a double shot CCD camera, allowed to observe the macroscopic effects associated with the arc establishment between the electrodes (glow, sound wave and heat release). Due to the long residence time, the thermal perturbation spread along the streamwise direction. Cross correlation of Schlieren images with short time separation revealed that in supersonic conditions, the discharges led to an overall acceleration of the flow field underneath the oblique shock wave.

  19. High-rate chemical vapor deposition of diamond films by dc arc discharge in hydrogen-methane mixture gas

    NASA Astrophysics Data System (ADS)

    Jiang, Xiang-Liu; Zhang, Fang-Qing; Li, Jiang-Qi; Yang, Bin; Chen, Guang-Hua

    1990-12-01

    Polycrystalline diamond films with high growth-rate have been synthesized by dc arc discharge plasma CVD in a mixture gas of CH4 (1) and 112 (99). The diamond films are deposited on water-cooled silicon and molybdenum substrates at gaseous pressure of about 200 Torr. The typical arc discharge is performed at 200V and 4A while the hydrogen flow rate is about 3000 3500 sccm. The crystallinity of diamond films prepared are characterized by Xray differaction (XRD) Raman scattering spectroscopy and scanning electron microscopy (SEM). It is verified by XRD and Raman measurements that the synthesized diamond films are identified as natural cubic diamond structure and contain substantially no graphite or amorphous carbon. SEM photographs show that the crystal grain size reachs 60 80 im with good crystal habit and the average growth rate of diamond films deposited during 4 hours is about 40 - 60 pm/h. As shown by SEM photographs the diamond grain size obviously depends on the local nucleation density. 1.

  20. Subnanosecond Thomson scattering on a vacuum arc discharge in tin vapor.

    PubMed

    Kieft, E R; van der Mullen, J J A M; Banine, V

    2005-08-01

    In a previous series of Thomson scattering (TS) experiments on an extreme ultraviolet producing vacuum arc discharge in tin vapor, background radiation emitted by the plasma was found to make measurements impossible for all parts of the discharge except the prepinch phase. To reduce the level of recorded background radiation, we have built a setup for time and space resolved subnanosecond TS. Results obtained with this new setup are presented for experiments on previously inaccessible parts of the discharge--the ignition phase, pinch phase, and decay phase. For the first two, measurements have been performed at different heights in the plasma. Electron densities for the pinch phase have been derived. For the decay phase, the electron densities confirm previous Stark broadening data. From the overall results, a more complete picture of the plasma evolution can be formed.

  1. An investigation of arc discharging on negatively biased dielectric conductor samples in a plasma

    NASA Technical Reports Server (NTRS)

    Miller, W. L.

    1985-01-01

    Proposals are now being developed for the construction of high-power photovoltaic systems for operation in low Earth orbit, where the plasma number density is about 1,000 to 1,000,000 per cubic cm. Existing data indicate that interactions between the plasma and high-voltage surfaces of an orbiting power system will occur. In ground tests, where the applied voltage is increased negatively from ground, the array current collection shows an approximately linear rise until it terminates in arcing at greater than several hundred volts negative. This arcing may reduce the power generation efficiency and could possibly affect the low-level logic circuits of the spacecraft. Therefore it is important that the arcing phenomenon be well understood. This study is a survey of the behavior of different dielectric-conductor samples, including a solar cell module, that were biased negatively in a low-density plasma environment with the intent of defining arc discharge conditions and characteristics. Procedures and results are discussed.

  2. In situ analysis of formation of carbon nanostructures in arc discharge by optical spectrometry

    NASA Astrophysics Data System (ADS)

    Li, Jian; Hwangbo, George; Shashurin, Alexey; Keidar, Michael

    2011-10-01

    Arc discharge supported by the erosion of anode materials is one of the most practical and efficient methods to synthesize various high-quality carbon nanostructures due to its relatively high growth temperature. By introducing a non- uniform magnetic field with the component normal to arc current, graphene flakes and single-walled carbon nanotubes can be synthesized in one step. In contrast to the growth processes without magnetic field, the magnetically-enhanced arc is confined by the Lorentz force, which generates the plasma jet and makes effective delivery of carbon particles and heat flux. However, there are still unresolved questions concerning the location of the region of nanoparticle synthesis and growth steps of carbon nanostructures. In this work we carried out in situ analysis of the optical spectrum which can provide a unique investigation of the different transformation processes of the carbon and metal catalyst vapors generated from the vaporization of the anode in arc. The experiments were taken for various electrode gaps and different conditions of external magnetic field. Moreover, SEM, TEM, EDX and Raman spectroscopy were employed to characterize the properties of carbon nanotubes and graphene.

  3. In situ analysis of formation of carbon nanostructures in arc discharge by optical spectrometry

    NASA Astrophysics Data System (ADS)

    Li, Jian; Hwangbo, George; Shashurin, Alexey; Keidar, Michael

    2011-10-01

    Arc discharge supported by the erosion of anode materials is one of the most practical and efficient methods to synthesize various high-quality carbon nanostructures due to its relatively high growth temperature. By introducing a non-uniform magnetic field with the component normal to arc current, graphene flakes and single-walled carbon nanotubes can be synthesized in one step. In contrast to the growth processes without magnetic field, the magnetically-enhanced arc is confined by the Lorentz force, which generates the plasma jet and makes effective delivery of carbon particles and heat flux. However, there are still unresolved questions concerning the location of the region of nanoparticle synthesis and growth steps of carbon nanostructures. In this work we carried out in situ analysis of the optical spectrum which can provide a unique investigation of the different transformation processes of the carbon and metal catalyst vapors generated from the vaporization of the anode in arc. The experiments were taken for various electrode gaps and different conditions of external magnetic field. Moreover, SEM, TEM, EDX and Raman spectroscopy were employed to characterize the properties of carbon nanotubes and graphene.

  4. Radiometric characterization of ultra-bright xenon short-arc discharge lamps for novel applications

    NASA Astrophysics Data System (ADS)

    Nakar, Doron; Malul, Asher; Feuermann, Daniel; Gordon, Jeffrey M.

    2007-09-01

    The latest generations of ultra-bright Xenon short-arc discharge lamps have prodigious emissions outside the visible spectrum, primarily in the near infrared. Their brightness distributions are spatially and angularly inhomogeneous due to both the pronounced non-uniformities of the plasma arc and the substantial infrared radiation from the hot electrodes. These characteristics are fortuitously favorable for applications in photonic surgery, biomedical diagnostics, high-temperature chemical reactors and furnaces: cases where the full lamp spectrum is utilizable, and the key is reconstituting the spectral power density of the optimal regions of the lamp's plasma at a remote target. The associated optical systems must be tailored to lamp radiometric properties that are not extensively available and invariably are restricted to visible light due to their widespread use in projection systems. We present experimental measurements for the spectral, spatial and angular distributions of 150 W lamps of this genre, and relate to their ramifications for broadband high-flux applications.

  5. One-step preparation of transparent superhydrophobic coatings using atmospheric arc discharge

    NASA Astrophysics Data System (ADS)

    Li, Jian; Huang, Zhengyong; Wang, Feipeng; Yan, Xinzhu; Wei, Yuan

    2015-08-01

    In this letter, we report a fast, simple, and single step approach to the preparation of transparent super-hydrophobic coatings on a copper conductor via atmosphere pressure arc discharges. The preparation procedures, hydrophobic characteristics, anti-pollution capability, and transparency of the super-hydrophobic coating are presented. A dual micro- and nano-scale hierarchical structure is observed on the super-hydrophobic coating with a water contact angle greater than 150°. The coating is, thus, capable of removing a significant amount of contaminants with a small quantity of water droplets. Attenuated total reflection Fourier transform infrared spectroscopy indicates that hydrophobic methyl groups exist on the surface of the coating. The surface roughness measurement results prove that the super-hydrophobic surface obeys the Cassie-Baxter model and its light scattering is very weak. Results demonstrate the conceptual feasibility of production of optically transparent super-hydrophobic coating by arc spraying of polymers under the atmospheric pressure.

  6. The Effect of High-Pressure Arc Discharge Plasma on the Degradation of Chlorpyrifos

    NASA Astrophysics Data System (ADS)

    Yin, Meiqiang; Ma, Tengcai; Zhang, Jialiang; Huang, Mingjing; Ma, Buzhou

    2006-11-01

    A study is conducted to determine the effect of a kind of high-pressure arc discharge plasma on the degradation rate and kinetic equations of chlorpyrifos in different solvents with the treated times and concentrations as variables. The degradation rate was sorted in different solvents as water, methanol, acetone and then acetoacetate. The tendencies of the degradation rates with treated time in water and methanol were optimally fitted with first-order kinetics equations while those in acetone and acetoacetate were fitted with zeroth-order kinetics equations. The difference was attributed to the stronger polarity of water and methanol. The weak correlation of the degradation rates with time was mainly because the high-temperature of the arc discharge tube and the chemically-active species generated by the discharge. The degradation half-life was extended with increase of chlorpyrifos concentration. A degradation half-life less than 3 min was achieved for chlorpyrifos in water and methanol when the initial concentration was less than 300 μg/ml.

  7. Surface modification by nonthermal plasma induced by using magnetic-field-assisted gliding arc discharge

    NASA Astrophysics Data System (ADS)

    Feng, Zongbao; Saeki, Noboru; Kuroki, Tomoyuki; Tahara, Mitsuru; Okubo, Masaaki

    2012-07-01

    The authors report on the introduction of a magnetic field to gliding arc discharge (GD) in order to enhance surface modification by nonthermal plasma at atmospheric-pressure. The GD is induced between two wire electrodes by using a pulse high-voltage power supply with peak-to-peak voltage of 5 kV. When a magnetic field of 0.25 T is applied, the GD enlarged and a 19-cm-long stretch of plasma is excited. The surface treatment of polyethylene terephthalate and polytetrafluoroethylene films is performed. The adhesion improved by up to ˜30 times due to the enhanced chemical activity in the films.

  8. Synthesis of multiwalled carbon nanotube from different grades of carbon black using arc discharge method

    NASA Astrophysics Data System (ADS)

    Arora, Neha; Sharma, N. N.

    2016-04-01

    This paper describes the synthesis of nanotube from different grades (Tread * A(non-ASTM), N134,N121,N660 and N330)of carbon black using DC arc discharge method at 40A current for 60sec. Carbon black samples of different grades were procured from industry (Aditya Birla Science and Technology Limited, India). Scanning Electron Micrographs (SEM) of the deposited carbon nanostructures suggests that MWCNTs are formed at 40A and for a minimal exposure time of 60sec.The result formed indicates the N330 grade of carbon black gets converted to MWCNTs (Multiwall Carbon nanotube) as compared to other grades.

  9. Sensing and identification of carbon monoxide using carbon films fabricated by methane arc discharge decomposition technique

    PubMed Central

    2014-01-01

    Carbonaceous materials have recently received attention in electronic applications and measurement systems. In this work, we demonstrate the electrical behavior of carbon films fabricated by methane arc discharge decomposition technique. The current-voltage (I-V) characteristics of carbon films are investigated in the presence and absence of gas. The experiment reveals that the current passing through the carbon films increases when the concentration of CO2 gas is increased from 200 to 800 ppm. This phenomenon which is a result of conductance changes can be employed in sensing applications such as gas sensors. PMID:25177219

  10. Performance of carbon arc-discharge nanotubes to hydrogen energy storage.

    PubMed

    Farhat, S; Weinberger, B; Lamari, F D; Izouyar, T; Noe, L; Monthioux, M

    2007-10-01

    Adsorption properties of gram-scale samples of different kind of arc discharge nanotubes were studied, namely: (A) raw collaret collected on the cathode, (B) raw soots collected on the lateral reactor wall, (C) thermally treated soot, and (D) thermally then chemically treated soot. The morphology, structure, and composition of these materials were characterized by SEM, TEM, TGA, and BET. In addition, hydrogen adsorption isotherms were recorded experimentally for A, B, and D samples over the pressure range of 0 to 55 bar at ambient temperature. Our experiments indicated a maximum-yet weak-hydrogen storage at room temperature of approximately 0.13 H2 wt% for the purified product (D).

  11. Synthesis of multiwalled carbon nanotube from different grades of carbon black using arc discharge method

    SciTech Connect

    Arora, Neha; Sharma, N. N.

    2016-04-13

    This paper describes the synthesis of nanotube from different grades (Tread * A(non-ASTM), N134,N121,N660 and N330)of carbon black using DC arc discharge method at 40A current for 60sec. Carbon black samples of different grades were procured from industry (Aditya Birla Science and Technology Limited, India). Scanning Electron Micrographs (SEM) of the deposited carbon nanostructures suggests that MWCNTs are formed at 40A and for a minimal exposure time of 60sec.The result formed indicates the N330 grade of carbon black gets converted to MWCNTs (Multiwall Carbon nanotube) as compared to other grades.

  12. Low-frequency flute instabilities of a hollow cathode arc discharge - Theory and experiment.

    NASA Technical Reports Server (NTRS)

    Ilic, D. B.; Rognlien, T. D.; Self, S. A.; Crawford, F. W.

    1973-01-01

    The characteristics of two low-frequency electrostatic flute instabilities of a low-pressure hollow cathode arc discharge are reported. Mode I has azimuthal mode number m = 1, and occurs when the radial electric field is negative (directed inward), while mode II has m = - 1 and occurs when the field is positive. The radial electric field is controlled by varying the potential of a secondary anode cylinder located close to the outer discharge radius. A linear perturbation analysis, based on the two-fluid equations, is given for a low-beta, collisionless, cylindrical plasma column, immersed in a uniform axial magnetic field, having a Gaussian density profile and an arbitrary radial electric field profile. Reasonable correlation between theory and experiment is demonstrated for both modes.

  13. Discharge coefficient correlations for circular-arc venturi flowmeters at critical /sonic/ flow

    NASA Technical Reports Server (NTRS)

    Arnberg, B. T.; Britton, C. L.; Seidl, W. F.

    1973-01-01

    Experimental data are analyzed to support theoretical predictions for discharge coefficients in circular-arc venturi flow meters operating in the critical sonic flow regime at throat Reynolds numbers above 150 thousand. The data tend to verify the predicted 0.25% decrease in the discharge coefficient during transition from a laminar to turbulent boundary layer. Four different test gases and three flow measurement facilities were used in the experiments with 17 venturis with throat sizes from 0.15 to 1.37 in. and Beta ratios ranging from 0.014 to 0.25. Recommendations are given as to how the effectiveness of future studies in the field could be improved.

  14. Investigation of hydrocarbon oil transformation by gliding arc discharge: comparison of batch and recirculated configurations

    NASA Astrophysics Data System (ADS)

    Whitehead, J. Christopher; Prantsidou, Maria

    2016-04-01

    The degradation of liquid dodecane was studied in a gliding arc discharge (GAD) of humid argon or nitrogen. A batch or recirculating configuration was used. The products in the gaseous and liquid phase were analysed by infrared and chromatography and optical emission spectroscopy was used to identify the excited species in the discharge. The best degradation performance comes from the use of humid N2 but a GAD of humid argon produces fewer gas-phase products but more liquid-phase end-products. A wide range of products such as heavier saturated or unsaturated hydrocarbons both aliphatic and aromatic, and oxidation products mainly alcohols, but also aldehydes, ketones and esters are produced in the liquid-phase. The recirculating treatment mode is more effective than the batch mode increasing the reactivity and changing the product selectivities. Overall, the study shows promising results for the organic liquid waste treatment, especially in the recirculating mode.

  15. Discharge coefficient correlations for circular-arc venturi flowmeters at critical /sonic/ flow

    NASA Technical Reports Server (NTRS)

    Arnberg, B. T.; Britton, C. L.; Seidl, W. F.

    1973-01-01

    Experimental data are analyzed to support theoretical predictions for discharge coefficients in circular-arc venturi flow meters operating in the critical sonic flow regime at throat Reynolds numbers above 150 thousand. The data tend to verify the predicted 0.25% decrease in the discharge coefficient during transition from a laminar to turbulent boundary layer. Four different test gases and three flow measurement facilities were used in the experiments with 17 venturis with throat sizes from 0.15 to 1.37 in. and Beta ratios ranging from 0.014 to 0.25. Recommendations are given as to how the effectiveness of future studies in the field could be improved.

  16. Characterization of Ni ferrites powders prepared by plasma arc discharge process

    NASA Astrophysics Data System (ADS)

    Safari, A.; Gheisari, Kh.; Farbod, M.

    2017-01-01

    The aim of this work was to synthesize a single-phase spinel structure from a mixture of zinc, iron and nickel powders by plasma arc discharge method. A mixture of zinc, iron and nickel powders with the appropriate molar ratio was prepared and formed into a cylindrical shape. The synthesis process was performed in air, oxygen and argon atmospheres with the applied arc current of 400 A and pressure of 1 atm. After establishing an arc between the electrodes, the produced powders were collected and their structure and magnetic properties were examined by XRD and VSM, respectively. ZnO as an impurity was appeared in the as-produced powders owing to the high reactivity of zinc atoms, preventing the formation of Ni-Zn ferrite. A pure spinel structure with the highest saturation magnetization (43.8 emu/g) was observed as zinc powders removed completely from the initial mixture. Morphological evaluations using field emission scanning electron microscopy showed that the mean size of fabricated nanoparticles was in the range 100-200 nm and was dependent on the production conditions.

  17. Physical characteristics of gliding arc discharge plasma generated in a laval nozzle

    SciTech Connect

    Lu, S. Y.; Sun, X. M.; Li, X. D.; Yan, J. H.; Du, C. M.

    2012-07-15

    The dynamic behavior of gliding arc discharge generated in a Laval nozzle has been investigated by electrical diagnostics and a high-speed camera. The results show that the voltage waveform keeps the initial shape as the gas flow rate is small, while it becomes less stable with increasing flow rate. During the first half of a cycle, the voltage rises and after that it decreases. In nitrogen and oxygen, the break down voltage for the arc is between 3.3 and 5.5 kV, while it is between 3.3-7.5 kV in air. The waveform of current I remains almost stable; and for nitrogen and oxygen, the maximum value of current I is between 0.28 and 0.46 A. With increasing flow rate, the power consumption in air first increases and then decreases; it remains in the range of 110-217 W, and gradually increases in nitrogen and oxygen. The power consumption in oxygen is lower than that in nitrogen; the input of the energy density decreases with increasing flow rate for all the three gases. The development of the arc is tracked and recorded by a high-speed camera. The cycle is stable at 10 ms for flow rates up to 1 m{sup 3} h{sup -1}. At a higher flow rate, the cycle becomes unstable.

  18. Shielding conditions of local cavity for underwater arc spot welding

    SciTech Connect

    Ogawa, Y.; Koga, H.

    1996-12-01

    Arc spot welding to join lapped plates is an effective maintenance operation for emergent recovering technique of defects under water. The welding operation is easy and effective except for an excessive amount of weld metal for deep penetration. A special nozzle for CO{sub 2} arc spot welding was designed to maintain this defect. A large amount of swirl shielding gas flow is adopted to discharge the excessive weld metal and to reduce digging action of weld pool. An additional high speed air jet is supplied to reinforce these effects. Almost flat weld bead is obtained by using of this nozzle. The effect of swirl shielding flow and additional air jet on the pressure is studied. When an excessive axial gas flow is used, a pressure at the weld pool becomes high enough to press down the weld surface below original surface level of base plate, and some molten metal is splashed out. Then, it is difficult to get a sound weld geometry. A swirl gas flow is tried to reduce the static pressure on the weld pool. The pressure on the weld pool by the swirl flow becomes much lower compared to the case by axial flow. When the swirl flow is used, a flat bead can be obtained. But some molten metal which is blown out by the swirl gas is resolidified at the edge of the nozzle. The additional high speed air jet is required to blow out the splashed metal from the nozzle completely. It has a suction effect itself. The pressure on the weld pool is also decreased. But the interaction between the swirl flow and the additional jet shows a complicated manner. This paper discusses the interaction between main shielding gas flow and the additional air jet to guarantee the good shielding condition for underwater use.

  19. Synthesis of graphene sheets with high electrical conductivity and good thermal stability by hydrogen arc discharge exfoliation.

    PubMed

    Wu, Zhong-Shuai; Ren, Wencai; Gao, Libo; Zhao, Jinping; Chen, Zongping; Liu, Bilu; Tang, Daiming; Yu, Bing; Jiang, Chuanbin; Cheng, Hui-Ming

    2009-02-24

    We developed a hydrogen arc discharge exfoliation method for the synthesis of graphene sheets (GSs) with excellent electrical conductivity and good thermal stability from graphite oxide (GO), in combination with solution-phase dispersion and centrifugation techniques. It was found that efficient exfoliation and considerable deoxygenation of GO, and defect elimination and healing of exfoliated graphite can be simultaneously achieved during the hydrogen arc discharge exfoliation process. The GSs obtained by hydrogen arc discharge exfoliation exhibit a high electrical conductivity of approximately 2 x 10(3) S/cm and high thermal stability with oxidization resistance temperature of 601 degrees C, which are much better than those prepared by argon arc discharge exfoliation (approximately 2 x 10(2) S/cm, 525 degrees C) and by conventional thermal exfoliation (approximately 80 S/cm, 507 degrees C) with the same starting GO. These results demonstrate that this hydrogen arc discharge exfoliation method is a good approach for the preparation of GSs with a good quality.

  20. Preparation of Metallic Aluminum Compound Particles by Submerged Arc Discharge Method in Aqueous Media

    NASA Astrophysics Data System (ADS)

    Liao, Chih-Yu; Tseng, Kuo-Hsiung; Lin, Hong-Shiou

    2013-02-01

    Fine metal particles are produced by chemical methods, which add surfactants to control particle size and concentration. This study used the submerged arc discharge method (SADM) to prepare metal fluid containing nanoparticles and submicron particles in pure dielectric fluid (deionized water or alcohol). The process is fast and simple, and it does not require the addition of chemical agents. The SADM uses electrical discharge machining (EDM) equipment, and the key parameters of the production process include discharge voltage, current, and pulse discharge on-off duration. This study added a capacitive component between the electrodes and the electrode Z-axis regulation in the control parameters to render the aluminum fluid process smooth, which is the main difference of this article from the literature. The experimental results showed that SADM can produce aluminum particles from nanometer to submicron grade, and it can obtain different compounds from different dielectric fluids. The dielectric fluids used in this study were deionized water and ethanol, and aluminum hydroxide Al(OH)3 particles with suspending power and precipitated aluminum particles were obtained, respectively. The preparations of metal colloid and particles by the SADM process have the characteristics of low cost, high efficiency, high speed, and mass production. Thus, the process has high research value and developmental opportunities.

  1. Copper induced hollow carbon nanospheres by arc discharge method: controlled synthesis and formation mechanism

    NASA Astrophysics Data System (ADS)

    Hu, Rui; Alexandru Ciolan, Mihai; Wang, Xiangke; Nagatsu, Masaaki

    2016-08-01

    Hollow carbon nanospheres with controlled morphologies were synthesized via the copper-carbon direct current arc discharge method by alternating the concentrations of methane in the reactant gas mixture. A self-healing process to keep the structural integrity of encapsulated graphitic shells was evolved gradually by adding methane gas from 0% to 20%. The outer part of the coated layers expanded and hollow nanospheres grew to be large fluffy ones with high methane concentrations from 30% to 50%. A self-repairing function by the reattachment of broken graphitic layers initiated from near-electrode space to distance was also distinctly exhibited. By comparing several comparable metals (e.g. copper, silver, gold, zinc, iron and nickel)-carbon arc discharge products, a catalytic carbon-encapsulation mechanism combined with a core-escaping process has been proposed. Specifically, on the basis of the experimental results, copper could be applied as a unique model for both the catalysis of graphitic encapsulation and as an adequate template for the formation of hollow nanostructures.

  2. Decolorization of Acid Orange 7 solution by gas-liquid gliding arc discharge plasma.

    PubMed

    Du, ChangMing; Shi, TaiHong; Sun, YuWei; Zhuang, XiaoFeng

    2008-06-15

    The decolorization of 180 microM aqueous solutions of Acid Orange 7 (AO7) by means of a non-thermal plasma technique (i.e., the gas-liquid gliding arc discharge, which is generated between at least two metal electrodes with AC high voltage) was investigated in this paper. The effects of the plasma treatment time and the type of feeding gas, including air, oxygen, nitrogen and argon of the dye removal were determined. It is found that the voltage cycles of the gas-liquid gliding arc discharge are characterized by a moderate increase in the tension which is represented by a peak followed by an abrupt decrease and a current peak in the half period (10 ms); the concentration of AO7 solution decreases exponentially to reach 58.9, 77.4, 89.1, 95.1 and 99% in 25, 50, 75, 100 and 125 min, respectively, and the ln(Ct/C0) varies linearly with the treatment time t, indicating that decolorization reaction follow first pseudo-order kinetics with a constant rate of 0.03327 min(-1) when air was used as feeding gas; the decolorization rate during the plasma treatment is the greatest for oxygen as the feeding gas, in turn followed by air and argon, and was the least when using nitrogen. The variations of pH and conductivity and the formations of hydrogen peroxide and ozone are measured.

  3. Preparation of Amine-Functionalized TiO2/Carbon Photocatalyst by Arc Discharge in Liquid

    NASA Astrophysics Data System (ADS)

    Arikawati, Erlina; Pranoto; Endah Saraswati, Teguh

    2017-02-01

    Amine-functionalized titanium dioxide/carbon (TiO2/C) was prepared via the arc discharge method using graphite electrodes and a liquid medium consisting of 50% ethanol with the addition of urea. The arc discharge was conducted using a voltage of 20 to 40 V. X-ray diffraction (XRD) of prepared TiO2/C showed a pattern of definitive peaks at 25.32°, 26.61°, and 36.14°, which are the main characteristic peaks of TiO2, C graphite, and titanium carbide, respectively. The successful surface modification of TiO2/C synthesized in liquid ethanol/urea resulted in better dispersion of nanoparticles in water than TiO2/C synthesized in ethanol only. This surface characteristic was also confirmed via Fourier transform infrared (FTIR) spectra of TiO2/C synthesized in liquid ethanol/urea, which revealed C=O, C–N, C–O, and N–H stretching vibrations at 1600–1700, 1400–1100, 1200–1300, and 3300–3400 cm‑1, respectively. Scanning electron microscopy (SEM) analysis showed that the nanocomposite had a spherical morphology. Transmission electron microscopy (TEM) analysis found that the structure of the nanocomposite was carbon coated with TiO2.

  4. Development of high efficiency Versatile Arc Discharge Ion Source at CERN ISOLDE.

    PubMed

    Penescu, L; Catherall, R; Lettry, J; Stora, T

    2010-02-01

    We report here recent developments of Forced Electron Beam Induced Arc Discharge (FEBIAD) ion sources at the ISOLDE radioactive ion beam facility, hosted at the European Organization for Nuclear Research (CERN). As a result of the propositions to improve the ionization efficiency, two FEBIAD prototypes have been produced and successfully tested in 2008. Off-line studies showed that the 1+ ionization efficiencies for noble gases are 5-20 times larger than with the standard ISOLDE FEBIAD ion sources and reach 60% for radon, which allowed the identification at ISOLDE of (229)Rn, an isotope that had never previously been observed in the laboratory. A factor of 3 increase is also expected for the ionization efficiency of the other elements. The experimental and theoretical methodology is presented. The theoretical model, which gives precise insights on the processes affecting the ionization, is used to design optimal sources (grouped under the name of VADIS--Versatile Arc Discharge Ion Source) for the different chemical classes of the produced isotopes, as already demonstrated for the noble gases.

  5. Silicon etch with chromium ions generated by a filtered or non-filtered cathodic arc discharge

    PubMed Central

    Scopece, Daniele; Döbeli, Max; Passerone, Daniele; Maeder, Xavier; Neels, Antonia; Widrig, Beno; Dommann, Alex; Müller, Ulrich; Ramm, Jürgen

    2016-01-01

    Abstract The pre-treatment of substrate surfaces prior to deposition is important for the adhesion of physical vapour deposition coatings. This work investigates Si surfaces after the bombardment by energetic Cr ions which are created in cathodic arc discharges. The effect of the pre-treatment is analysed by X-ray diffraction, Rutherford backscattering spectroscopy, scanning electron microscopy and in-depth X-ray photoemission spectroscopy and compared for Cr vapour produced from a filtered and non-filtered cathodic arc discharge. Cr coverage as a function of ion energy was also predicted by TRIDYN Monte Carlo calculations. Discrepancies between measured and simulated values in the transition regime between layer growth and surface removal can be explained by the chemical reactions between Cr ions and the Si substrate or between the substrate surface and the residual gases. Simulations help to find optimum and more stable parameters for specific film and substrate combinations faster than trial-and-error procedure. PMID:27877854

  6. Carbon nanoparticles in the radiation field of the stationary arc discharge

    SciTech Connect

    Shneider, M. N.

    2015-07-15

    The paper considers a simple theoretical model of heating the nanoparticles, depending on their size and the parameters of the radiating arc and the surrounding gas. This problem is of interest to diagnostics and modeling of the dynamics of the nanoparticles formation and their local size distribution. Heating of nanoparticles by the radiation can affect the process of synthesis. The degree of heating of the particle is determined by its geometry, which opens, apparently, additional possibilities for nonintrusive optical diagnostics.

  7. Effect of magnetic field on carbon nanotubes and graphene structure synthesized at low pressure via arc discharge process

    NASA Astrophysics Data System (ADS)

    Roslan, M. S.; Chaudary, K. T.; Haider, Z.; Zin, A. F. M.; Ali, J.

    2017-03-01

    Carbon nanomaterials have attracted vast attention due to the rising demand for various nanotechnology applications. The possibility of preparing multi-walled carbon nanotube (MWCNT) and graphene on large scale are demonstrated using direct current arc discharge with transverse magnetic field effect at low ambient pressure. In this work, we study, the effect of external transverse magnetic effect on structural perfection of graphene and multi-walled carbon nanotube. High quality carbon-nanotube were synthesized by arc discharge plasma in Hydrogen ambient at pressure 1 mbar in presence of external transverse magnetic field. The synthesized nanomaterials were characterized by electron microscopy, XRD and Raman Spectroscopy. A significant increase in the quantity and quality of carbon nanotube and graphene in the presence of transverse magnetic field during arc discharge process.

  8. Spectral analysis of the charge and elemental composition of the vacuum arc discharge plasma flux during deposition of carbon coatings

    NASA Astrophysics Data System (ADS)

    Kostrin, D. K.; Trifonov, S. A.; Lisenkov, A. A.

    2017-05-01

    In the present work spectral analysis of the charge and elemental composition of the plasma flux of a vacuum arc discharge on example of clear dispersion of the graphite cathode and also when adding benzene or argon as a working gas is studied. It is shown that the intensity of the main spectral lines of the atomic and molecular carbon in the emission spectrum of the vacuum arc discharge plasma is almost constant for all considered modes of operation, while the intensity of the spectral lines of ionized carbon changes significantly when adding a working gas.

  9. Can We Optimize Arc Discharge and Laser Ablation for Well-Controlled Carbon Nanotube Synthesis?

    NASA Astrophysics Data System (ADS)

    Das, Rasel; Shahnavaz, Zohreh; Ali, Md. Eaqub; Islam, Mohammed Moinul; Abd Hamid, Sharifah Bee

    2016-11-01

    Although many methods have been documented for carbon nanotube (CNT) synthesis, still, we notice many arguments, criticisms, and appeals for its optimization and process control. Industrial grade CNT production is urgent such that invention of novel methods and engineering principles for large-scale synthesis are needed. Here, we comprehensively review arc discharge (AD) and laser ablation (LA) methods with highlighted features for CNT production. We also display the growth mechanisms of CNT with reasonable grassroots knowledge to make the synthesis more efficient. We postulate the latest developments in engineering carbon feedstock, catalysts, and temperature cum other minor reaction parameters to optimize the CNT yield with desired diameter and chirality. The rate limiting steps of AD and LA are highlighted because of their direct role in tuning the growth process. Future roadmap towards the exploration of CNT synthesis methods is also outlined.

  10. In situ synthesis of semiconducting single-walled carbon nanotubes by modified arc discharging method

    NASA Astrophysics Data System (ADS)

    Zhao, Tingkai; Ji, Xianglin; Jin, Wenbo; Yang, Wenbo; Zhao, Xing; Dang, Alei; Li, Hao; Li, Tiehu

    2017-02-01

    Semiconducting single-walled carbon nanotubes (s-SWCNTs) were in situ synthesized by a temperature-controlled arc discharging furnace with DC electric field using Co-Ni alloy powder as catalyst in helium gas. The microstructures of s-SWCNTs were characterized using high-resolution transmission electron microscopy, electron diffraction, and Raman spectrometry apparatus. The experimental results indicated that the best voltage value in DC electric field is 54 V, and the environmental temperature of the reaction chamber is 600 °C. The mean diameter of s-SWCNTs was estimated about 1.3 nm. The chiral vector ( n, m) of s-SWCNTs was calculated to be (10, 10) type according to the electron diffraction patterns.

  11. Measurements of 3D slip velocities and plasma column lengths of a gliding arc discharge

    SciTech Connect

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas; Aldén, Marcus; Li, Zhongshan E-mail: alpers@ma.tum.de; Moseev, Dmitry; Kusano, Yukihiro; Salewski, Mirko; Alpers, Andreas E-mail: alpers@ma.tum.de; Gritzmann, Peter; Schwenk, Martin

    2015-01-26

    A non-thermal gliding arc discharge was generated at atmospheric pressure in an air flow. The dynamics of the plasma column and tracer particles were recorded using two synchronized high-speed cameras. Whereas the data analysis for such systems has previously been performed in 2D (analyzing the single camera image), we provide here a 3D data analysis that includes 3D reconstructions of the plasma column and 3D particle tracking velocimetry based on discrete tomography methods. The 3D analysis, in particular, the determination of the 3D slip velocity between the plasma column and the gas flow, gives more realistic insight into the convection cooling process. Additionally, with the determination of the 3D slip velocity and the 3D length of the plasma column, we give more accurate estimates for the drag force, the electric field strength, the power per unit length, and the radius of the conducting zone of the plasma column.

  12. Electroless nickel plating of arc discharge synthesized carbon nanotubes for metal matrix composites

    NASA Astrophysics Data System (ADS)

    Jagannatham, M.; Sankaran, S.; Prathap, Haridoss

    2015-01-01

    Electroless nickel (EN) plating was performed on arc discharge synthesized multiwalled carbon nanotubes for various deposition times. X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Raman spectroscopy characterization techniques are used to identify the presence of nickel deposition on the carbon nanotubes (CNTs) and the degree of graphitization. The results indicate that impurities are less in the purified CNTs as compared to raw carbon soot. Increasing deposition time up to 60 min increases uniform deposition of nickel throughout the length of the CNTs. However, for deposition time longer than 60 min, nickel particles are seen separated from the surface of the CNTs. Uniformly coated nickel CNTs throughout their length are potential candidates for reinforcements in composite materials. Magnetic properties of the nickel coated CNTs, with deposition time of 30 and 60 min were also evaluated. The magnetic saturation of nickel coated CNTs with deposition time of 30 min is less compared to nickel coated CNTs with deposition time of 60 min.

  13. Account of near-cathode sheath in numerical models of high-pressure arc discharges

    NASA Astrophysics Data System (ADS)

    Benilov, M. S.; Almeida, N. A.; Baeva, M.; Cunha, M. D.; Benilova, L. G.; Uhrlandt, D.

    2016-06-01

    Three approaches to describing the separation of charges in near-cathode regions of high-pressure arc discharges are compared. The first approach employs a single set of equations, including the Poisson equation, in the whole interelectrode gap. The second approach employs a fully non-equilibrium description of the quasi-neutral bulk plasma, complemented with a newly developed description of the space-charge sheaths. The third, and the simplest, approach exploits the fact that significant power is deposited by the arc power supply into the near-cathode plasma layer, which allows one to simulate the plasma-cathode interaction to the first approximation independently of processes in the bulk plasma. It is found that results given by the different models are generally in good agreement, and in some cases the agreement is even surprisingly good. It follows that the predicted integral characteristics of the plasma-cathode interaction are not strongly affected by details of the model provided that the basic physics is right.

  14. Refractory graphite skimmers for supersonic free-jet, supersonic arc-jet, and plasma discharge applications

    NASA Astrophysics Data System (ADS)

    Jordan, D. C.; Barling, R.; Doak, R. B.

    1999-03-01

    The fabrication of molecular beam "skimmers" from electrical discharge machining (EDM) graphite is reported. EDM graphite is highly refractory and is easily machined using conventional cutting and grinding techniques. In its most fine-grained form, EDM graphite can be machined free-standing to a knife-edge lip radius of ˜1 μm, providing excellent skimmer aerodynamics. Being refractory, such EDM skimmers are of particular interest in sampling or collimating high-temperature plasma discharges. Our explicit application is in skimming an electrical discharge supersonic free-jet of molecular nitrogen, forming a molecular beam of A 3Σu+ metastable N2 to be used in the heteroepitaxial growth of III-N wide-band-gap semiconductors. In view of the their economy, ease of manufacture, and excellent aerodynamics, the skimmers may also find use in skimming conventional, nondischarge supersonic free-jets. The performance of the EDM skimmers was tested in a conventional helium supersonic free-jet expansion, measuring the time-of-flight distribution and beam intensity as a function of nozzle pressure and nozzle-skimmer separation. Direct comparison with commercial nickel and copper skimmers showed the EDM graphite skimmers to perform nearly as well as the best commercial metal skimmers. The refractory properties of the skimmers were tested in a high-temperature arc-discharge supersonic free-jet expansion of 10% nitrogen in argon. Exposure to a plasma plume of ˜7500 K for over 6 h produced only relatively minor deterioration of the EDM graphite skimmer.

  15. UV and humidity sensing properties of ZnO nanorods prepared by the arc discharge method.

    PubMed

    Fang, F; Futter, J; Markwitz, A; Kennedy, J

    2009-06-17

    The UV and humidity sensing properties of ZnO nanorods prepared by arc discharge have been studied. Scanning electron microscopy and photoluminescence spectroscopy were carried out to analyze the morphology and optical properties of the as-synthesized ZnO nanorods. Proton induced x-ray emission was used to probe the impurities in the ZnO nanorods. A large quantity of high purity ZnO nanorod structures were obtained with lengths of 0.5-1 microm. The diameters of the as-synthesized ZnO nanorods were found to be between 40 and 400 nm. The nanorods interlace with each other, forming 3D networks which make them suitable for sensing application. The addition of a polymeric film-forming agent (BASF LUVISKOL VA 64) improved the conductivity, as it facilitates the construction of conducting networks. Ultrasonication helped to separate the ZnO nanorods and disperse them evenly through the polymeric agent. Improved photoconductivity was measured for a ZnO nanorod sensor annealed in air at 200 degrees C for 30 min. The ZnO nanorod sensors showed a UV-sensitive photoconduction, where the photocurrent increased by nearly four orders of magnitude from 2.7 x 10(-10) to 1.0 x 10(-6) A at 18 V under 340 nm UV illumination. High humidity sensitivity and good stability were also measured. The resistance of the ZnO nanorod sensor decreased almost linearly with increasing relative humidity (RH). The resistance of the ZnO nanorods changed by approximately five orders of magnitude from 4.35 x 10(11) Omega in dry air (7% RH) to about 4.95 x 10(6) Omega in 95% RH air. It is experimentally demonstrated that ZnO nanorods obtained by the arc discharge method show excellent performance and promise for applications in both UV and humidity sensors.

  16. Complex structure of the carbon arc discharge for synthesis of nanotubes

    NASA Astrophysics Data System (ADS)

    Vekselman, V.; Feurer, M.; Huang, T.; Stratton, B.; Raitses, Y.

    2017-06-01

    Comprehensive non-invasive spectroscopic techniques and electrical measurements of the carbon arc revealed two distinguishable plasma synthesis regions in the radial direction normal to the arc axis. These regions, which are defined as the arc core and the arc periphery, are shown to have very different compositions of carbon species with different densities and temperatures. The colder arc periphery is dominated by carbon diatomic molecules (C2), which are in the minority in the composition of the hot arc core. These differences are due to a highly non-uniform distribution of the arc current, which is mainly conducted through the arc core populated with carbon atoms and ions. Therefore, the ablation of the graphite anode is governed by the arc core, while the formation of carbon molecules occurs in the colder arc periphery. This result is consistent with previous predictions that the plasma environment in the arc periphery is suitable for synthesis of carbon nanotubes.

  17. Localization and local translation of Arc/Arg3.1 mRNA at synapses: some observations and paradoxes.

    PubMed

    Steward, Oswald; Farris, Shannon; Pirbhoy, Patricia S; Darnell, Jennifer; Driesche, Sarah J Van

    2014-01-01

    Arc is a unique immediate early gene whose expression is induced as synapses are being modified during learning. The uniqueness comes from the fact that newly synthesized Arc mRNA is rapidly transported throughout dendrites where it localizes near synapses that were recently activated. Here, we summarize aspects of Arc mRNA translation in dendrites in vivo, focusing especially on features of its expression that are paradoxical or that donot fit in with current models of how Arc protein operates. Findings from in vivo studies that donot quite fit include: (1) Following induction of LTP in vivo, Arc mRNA and protein localize near active synapses, but are also distributed throughout dendrites. In contrast, Arc mRNA localizes selectively near active synapses when stimulation is continued as Arc mRNA is transported into dendrites; (2) Strong induction of Arc expression as a result of a seizure does not lead to a rundown of synaptic efficacy in vivo as would be predicted by the hypothesis that high levels of Arc cause glutamate receptor endocytosis and LTD. (3) Arc protein is synthesized in the perinuclear cytoplasm rapidly after transcriptional activation, indicating that at least a pool of Arc mRNA is not translationally repressed to allow for dendritic delivery; (4) Increases in Arc mRNA in dendrites are not paralleled by increases in levels of exon junction complex (EJC) proteins. These results of studies of mRNA trafficking in neurons in vivo provide a new perspective on the possible roles of Arc in activity-dependent synaptic modifications.

  18. A comparative study of silver nanoparticles synthesized by arc discharge and femtosecond laser ablation in aqueous solution

    NASA Astrophysics Data System (ADS)

    Zhang, Hongqiang; Zou, Guisheng; Liu, Lei; Li, Yong; Tong, Hao; Sun, Zhenguo; Zhou, Y. Norman

    2016-10-01

    Silver nanoparticles have been synthesized by arc discharge and femtosecond laser ablation in polyvinylpyrrolidone (PVP) aqueous solution. Both methods are the simple, cost-effective and environment-friendly way to obtain the purity silver nanoparticles. In this study, the structure, composition, morphology, size and distribution, stability, production rate and sintering properties of silver nanoparticles synthesized by both methods were compared. The spherical or pseudo-spherical silver nanoparticles were synthesized by both methods, and the diameters were below 50 nm. The arc discharge-synthesized particle distribution varied with the breakdown voltage, and laser-synthesized particle size mainly depended on the laser energy. PVP solution could cap and stabilize the silver nanoparticles by Ag-O bond, while arc discharge and laser ablation resulted in some level of PVP degradation during processing. Sliver nanoparticle colloids synthesized by both methods had the high negative values of zeta potential and exhibited the good stability. The maximum production rates of the silver nanoparticles synthesized by arc discharge and femtosecond laser ablation were 6.0 and 3.0 mg/min, respectively. In addition, the sintering properties of silver nanoparticles synthesized by both methods were also discussed.

  19. The application of a non-thermal plasma generated by gas-liquid gliding arc discharge in sterilization

    NASA Astrophysics Data System (ADS)

    Du, Chang Ming; Wang, Jing; Zhang, Lu; Xia Li, Hong; Liu, Hui; Xiong, Ya

    2012-01-01

    Gliding arc discharge has been investigated in recent years as an innovative physicochemical technique for contaminated water treatment at atmospheric pressure and ambient temperature. In this study we tested a gas-liquid gliding arc discharge reactor, the bacterial suspension of which was treated circularly. When the bacterial suspension was passed through the electrodes and circulated at defined flow rates, almost 100% of the bacteria were killed in less than 3.0 min. Experimental results showed that it is possible to achieve an abatement of 7.0 decimal logarithm units within only 30 s. Circulation flow rates and types of feeding gas caused a certain impact on bacteria inactivation, but the influences are not obvious. So, under the promise of sterilization effect, industrial applications can select their appropriate operating conditions. All inactivation curves presented the same three-phase profile showing an apparent sterilization effect. Analysis of the scanning electron microscope images of bacterial cells supports the speculation that the gas-liquid gliding arc discharge plasma is acting under various mechanisms driven essentially by oxidation and the effect of electric field. These results enhance the possibility of applying gas-liquid gliding arc discharge decontamination systems to disinfect bacterial-contaminated water. Furthermore, correlational research indicates the potential applications of this technology in rapid sterilization of medical devices, spacecraft and food.

  20. Experimental study and modeling of the deuterium releasing quantity in a pulsed vacuum arc discharge with a metal deuteride cathode

    NASA Astrophysics Data System (ADS)

    Liu, Fei-Xiang; Long, Ji-Dong; Zheng, Le; Dong, Pan; Li, Chen; Chen, Wei

    2017-04-01

    The pulsed vacuum arc discharge using a metal deuteride cathode is widely applied as a deuterium ion source, where the upper limit of the deuterium ion yield is largely determined by the deuterium releasing quantity (DRQ) from the cathode. This work aims to measure the DRQ at various discharge conditions, and meanwhile develop a simple thermoelectric model to evaluate the deuterium liberation from different sources, such as the crater vicinity during the arc power-on phase and the hot crater in the afterglow. The calculated DRQ are in accordance with the experimental results obtained by measuring the D2 pressure evolution in the early afterglow using a quadrupole mass spectrometer. Furthermore, the model reveals that at low arc current (<10 A), the DRQ orginates dominantly from the crater vicinity, leading to a low conversion efficiency of the released deuterium to ions and a high D:Ti elemental ratio in the released cathode vapor.

  1. Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: circuitry and mechanical design.

    PubMed

    Kia, Kaveh Kazemi; Bonabi, Fahimeh

    2012-12-01

    A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

  2. Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design

    SciTech Connect

    Kia, Kaveh Kazemi; Bonabi, Fahimeh

    2012-12-15

    A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 {mu}s. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

  3. Electric field induced needle-pulsed arc discharge carbon nanotube production apparatus: Circuitry and mechanical design

    NASA Astrophysics Data System (ADS)

    Kia, Kaveh Kazemi; Bonabi, Fahimeh

    2012-12-01

    A simple and low cost apparatus is reported to produce multiwall carbon nanotubes and carbon nano-onions by a low power short pulsed arc discharge reactor. The electric circuitry and the mechanical design details and a micro-filtering assembly are described. The pulsed-plasma is generated and applied between two graphite electrodes. The pulse width is 0.3 μs. A strong dc electric field is established along side the electrodes. The repetitive discharges occur in less than 1 mm distance between a sharp tip graphite rod as anode, and a tubular graphite as cathode. A hydrocarbon vapor, as carbon source, is introduced through the graphite nozzle in the cathode assembly. The pressure of the chamber is controlled by a vacuum pump. A magnetic field, perpendicular to the plasma path, is provided. The results show that the synergetic use of a pulsed-current and a dc power supply enables us to synthesize carbon nanoparticles with short pulsed plasma. The simplicity and inexpensiveness of this plan is noticeable. Pulsed nature of plasma provides some extra degrees of freedom that make the production more controllable. Effects of some design parameters such as electric field, pulse frequency, and cathode shape are discussed. The products are examined using scanning probe microscopy techniques.

  4. Photoelectron emission from metal surfaces induced by VUV-emission of filament driven hydrogen arc discharge plasma

    NASA Astrophysics Data System (ADS)

    Laulainen, J.; Kalvas, T.; Koivisto, H.; Komppula, J.; Tarvainen, O.

    2015-04-01

    Photoelectron emission measurements have been performed using a filament-driven multi-cusp arc discharge volume production H- ion source (LIISA). It has been found that photoelectron currents obtained with Al, Cu, Mo, Ta and stainless steel (SAE 304) are on the same order of magnitude. The photoelectron currents depend linearly on the discharge power. It is shown experimentally that photoelectron emission is significant only in the short wavelength range of hydrogen spectrum due to the energy dependence of the quantum efficiency. It is estimated from the measured data that the maximum photoelectron flux from plasma chamber walls is on the order of 1 A per kW of discharge power.

  5. Characterization of a vacuum-arc discharge in tin vapor using time-resolved plasma imaging and extreme ultraviolet spectrometry.

    PubMed

    Kieft, E R; van der Mullen, J J A M; Kroesen, G M W; Banine, V; Koshelev, K N

    2005-02-01

    Discharge sources in tin vapor have recently been receiving increased attention as candidate extreme ultraviolet (EUV) light sources for application in semiconductor lithography, because of their favorable spectrum near 13.5 nm. In the ASML EUV laboratory, time-resolved pinhole imaging in the EUV and two-dimensional imaging in visible light have been applied for qualitative characterization of the evolution of a vacuum-arc tin vapor discharge. An EUV spectrometer has been used to find the dominant ionization stages of tin as a function of time during the plasma evolution of the discharge.

  6. Synthesis and photocatalytic activity of WO(3) nanoparticles prepared by the arc discharge method in deionized water.

    PubMed

    Ashkarran, A A; Iraji Zad, A; Ahadian, M M; Mahdavi Ardakani, S A

    2008-05-14

    In this paper, we discuss the synthesis and characterization of tungsten trioxide nanoparticles prepared by the arc discharge method in deionized (DI) water. The size and morphology of WO(3) nanoparticles prepared using different arc currents (25, 35 and 45 A) were studied. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) results indicate that at an arc current of 25 A, the size of the particles is about 30 nm, and this increases to 64 nm by increasing the arc current. This size increase caused a decrease of optical band gap from 2.9 to 2.6 eV. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) spectra demonstrate the formation of the WO(3) phase. Photodegradation of Rhodamine B shows that samples prepared at the lowest current have more photocatalytic activity due to having the smallest particle size and highest surface area. The results demonstrate the ability of the arc discharge method for direct formation of WO(3) nanoparticles in DI water medium.

  7. Laser-induced incandescence (LII) diagnostic for in situ monitoring of nanoparticle synthesis in a high-pressure arc discharge

    NASA Astrophysics Data System (ADS)

    Yatom, Shurik; Vekselman, Vladislav; Mitrani, James; Stratton, Brentley; Raitses, Yevgeny; LaboratoryPlasma Nanosynthesis Team

    2016-10-01

    A DC arc discharge is commonly used for synthesis of carbon nanoparticles, including buckyballs, carbon nanotubes, and graphene flakes. In this work we show the first results of nanoparticles monitored during the arc discharge. The graphite electrode is vaporized by high current (60 A) in a buffer Helium gas leading to nanoparticle synthesis in a low temperature plasma. The arc was shown to oscillate, which can possibly influence the nano-synthesis. To visualize the nanoparticles in-situ we employ the LII technique. The nanoparticles with radii >50 nm, emerging from the arc area are heated with a short laser pulse and incandesce. The resulting radiation is captured with an ICCD camera, showing the location of the generated nanoparticles. The images of incandescence are studied together with temporally synchronized fast-framing imaging of C2 emission, to connect the dynamics of arc instabilities, C2 molecules concentration and nanoparticles. The time-resolved incandescence signal is analyzed with combination of ex-situ measurements of the synthesized nanoparticles and LII modeling, to provide the size distribution of produced nanoparticles. This work was supported by US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  8. Dispersion and characterization of arc discharge single-walled carbon nanotubes - towards conducting transparent films

    NASA Astrophysics Data System (ADS)

    Rösner, B.; Guldi, D. M.; Chen, J.; Minett, A. I.; Fink, R. H.

    2014-03-01

    This study addresses a combination of a well-developed and mild dispersion method and high-quality arc discharge single-walled carbon nanotubes (SWCNTs) as starting materials. Thus, we advance in fabrication of transparent, conducting films with extraordinary low material loss during SWCNT processing. The starting material was characterized by means of thermogravimetric analysis, high-resolution transmission electron microscopy and Raman spectroscopy. The quality of the starting material and produced dispersions was evaluated by ultraviolet and visible light absorption spectroscopy and Raman spectroscopy. A transparent conductive film was fabricated by drop-casting, whereas films were obtained with electrical to optical conductivity ratios (σDC/σOp) as high as 2.2, combined with a loss of nanotube material during processing well below 20 wt%. High pressure carbon monoxide conversion (HiPCO) SWCNTs, which are very well described in the literature, were used for comparison.This study addresses a combination of a well-developed and mild dispersion method and high-quality arc discharge single-walled carbon nanotubes (SWCNTs) as starting materials. Thus, we advance in fabrication of transparent, conducting films with extraordinary low material loss during SWCNT processing. The starting material was characterized by means of thermogravimetric analysis, high-resolution transmission electron microscopy and Raman spectroscopy. The quality of the starting material and produced dispersions was evaluated by ultraviolet and visible light absorption spectroscopy and Raman spectroscopy. A transparent conductive film was fabricated by drop-casting, whereas films were obtained with electrical to optical conductivity ratios (σDC/σOp) as high as 2.2, combined with a loss of nanotube material during processing well below 20 wt%. High pressure carbon monoxide conversion (HiPCO) SWCNTs, which are very well described in the literature, were used for comparison. Electronic

  9. The Study of Complex (Ti, Zr, Cs) Nanopowder Influencing the Effective Ionization Potential of Arc Discharge When Mma Welding

    NASA Astrophysics Data System (ADS)

    Sapozhkov, S. B.; Burakova, E. M.

    2016-08-01

    Strength is one of the most important characteristics of a weld joint. Mechanical properties of a weld metal can be improved in a variety of ways. One of the possibilities is to add a nanopowder to the weld metal. Authors of the paper suggest changing the production process of MMA welding electrodes via adding nanopowder Ti, Zr, Cs to electrode components through liquid glass. Theoretical research into the nanopowder influence on the effective ionization potential (Ueff) of welding arc discharge is also necessitated. These measures support arcing stability, improve strength of a weld joint, as the consequence, ensure quality enhancing of a weld joint and the structure on the whole.

  10. Quantitative evaluation of fiber fuse initiation with exposure to arc discharge provided by a fusion splicer

    NASA Astrophysics Data System (ADS)

    Todoroki, Shin-Ichi

    2016-05-01

    The optical communication industry and power-over-fiber applications face a dilemma as a result of the expanding demand of light power delivery and the potential risks of high-power light manipulation including the fiber fuse phenomenon, a continuous destruction of the fiber core pumped by the propagating light and triggered by a heat-induced strong absorption of silica glass. However, we have limited knowledge on its initiation process in the viewpoint of energy flow in the reactive area. Therefore, the conditions required for a fiber fuse initiation in standard single-mode fibers were determined quantitatively, namely the power of a 1480 nm fiber laser and the arc discharge intensity provided by a fusion splicer for one second as an outer heat source. Systematic investigation on the energy flow balance between these energy sources revealed that the initiation process consists of two steps; the generation of a precursor at the heated spot and the transition to a stable fiber fuse. The latter step needs a certain degree of heat accumulation at the core where waveguide deformation is ongoing competitively. This method is useful for comparing the tolerance to fiber fuse initiation among various fibers with a fixed energy amount that was not noticed before.

  11. Covalent functionalization of polyhedral graphitic particles synthesized by arc discharge from graphite.

    PubMed

    Voss, E; Vigolo, B; Medjahdi, G; Hérold, C; Marêché, J-F; Ghanbaja, J; Le Normand, F; Mamane, V

    2017-02-15

    Carbon materials including carbon nanoparticles, such as nanographite, graphene and graphenic materials, and carbon nanotubes are known to be highly hydrophobic. Oxidation treatments are widely used as the best methods to improve their affinity in a liquid medium or a polymer matrix so that they can be dispersed, handled and processed. Here, we have applied eight different oxidation treatments in order to graft oxygen-containing functional groups at the surface of polyhedral graphitic particles synthesized by arc discharge from graphite, also called astralenes. The used functionalization approaches include both standard chemical attack by strong oxidants and radical functionalization of the sp(2) network by direct C[double bond, length as m-dash]C bond opening. Commonly efficient functionalization methods were unsuccessful to functionalize astralenes while radicals generated from arylhydrazine could lead to functionalization of the outer surface of astralenes. The occurrence of functionalization could be shown by TGA coupled with MS and XPS. The reported method represents the first example of functionalization of astralenes. The efficiency of the applied functionalization methods is discussed considering the chemical reactivity of different carbon nanomaterials including graphene and carbon nanotubes.

  12. Scaled Tests and Simulation of Triboelectric Charging and Arc Discharge in an Expanding Dust Plume

    NASA Astrophysics Data System (ADS)

    Sears, J.; Kuhl, A.; Grote, D.; Converse, M.; Kueny, C.; Larson, D.; Poole, B.; Schmidt, A.; Rose, D. V.; Kirkendall, B.

    2015-12-01

    The arc breakdown commonly generated in volcanic eruptions is reproduced in field experiments of rapidly expanding dust clouds driven by explosive charges. The controlled format also conveniently allows us to vary particulate content and velocities and to precisely instrument the event with radiofrequency, optical and spectral sensors. We observe electrical discharges during the turbulent phase of the cloud expansion, which we use as benchmarks to validate a multiphase 3D simulation. The simulation computes electrostatic potentials by considering the hydrodynamics, chemical kinetics and charge transport for a distribution of particle sizes entrained in the expanding gas cloud. A separate hybrid fluid/kinetic plasma code is employed to simulate the avalanche breakdown between charge pockets. Finally the propagation of radiated fields through regions of strongly dispersive partially ionized gas are computed in an electromagnetic finite element solver. Insight from the model validation may help us better understand the connection between plume dynamics and volcanic lightning. Prepared by LLNL under Contract DE-AC52-07NA27344.

  13. High spin-dependent tunneling magnetoresistance in magnetite powders made by arc-discharge

    NASA Astrophysics Data System (ADS)

    Prakash, T.; Williams, G. V. M.; Kennedy, J.; Rubanov, S.

    2016-09-01

    We report the successful synthesis of ferrimagnetic magnetite powders made using an arc-discharge method in a partial oxygen atmosphere. X-ray and electron diffraction measurements show that the powders also contain some antiferromagnetic hematite and a small amount of FeO and Fe that has not oxidized. The Raman data show that there is a small fraction of ferrimagnetic maghemite that cannot be seen in the x-ray diffraction data. There is a wide particle size distribution where there are nanoparticles as small as 7 nm, larger faceted nanoparticles, and particles that are up to 25 μm in diameter. The saturation magnetization at high magnetic fields is ˜74% of that found in the bulk magnetite, where the lower value is due to the presence of some antiferromagnetic hematite. The temperature dependence of the saturation magnetization changes at the Verwey transition temperature, and it has a power low dependence with an exponent of 3/2 at low temperatures and 2.23 at high temperatures above the Verwey transition temperature. Electronic transport measurements were made on a cold-pressed pellet and the electrical resistance had an exponential dependence on temperature that may be due to electrostatic charging during tunneling between small nanoparticles. A large magnetoresistance from spin-dependent tunneling between the magnetite particles was observed that reached -9.5% at 120 K and 8 T.

  14. Long period gratings written in fluorine-doped fibers by electric arc discharge technique

    NASA Astrophysics Data System (ADS)

    Ranjan, Rajeev; Esposito, Flavio; Iadicicco, Agostino; Stǎncǎlie, Andrei; Sporea, Dan; Campopiano, Stefania

    2016-05-01

    In this work, we present long period gratings (LPGs) in two different Fluorine-doped fibers realized by electric arc discharge (EAD) technique. Firstly, we optimized the EAD fabrication procedure for standard Ge-doped fibers where we are able to fabricate relatively short LPGs with deep attenuation bands (up to 32 dB) and trivial power losses. Successively, for the first time to the best of our knowledge, we produced LPGs in F-doped fibers with maximum attenuation band depths in range 25-30 dB and trivial power losses. We also investigated the sensitivity of LPGs fabricated in such F-doped fibers, with surrounding refractive index (SRI) and temperature changes, and compared the results with those of LPGs fabricated in standard fiber. We found that SRI response of LPGs in F-doped fibers is significantly higher than in standard fiber and it strongly depends on the type of F-doped fiber considered, whereas they exhibit a slightly lower sensitivity to temperature compared to LPGs in standard fiber.

  15. Quantitative evaluation of fiber fuse initiation with exposure to arc discharge provided by a fusion splicer.

    PubMed

    Todoroki, Shin-Ichi

    2016-05-03

    The optical communication industry and power-over-fiber applications face a dilemma as a result of the expanding demand of light power delivery and the potential risks of high-power light manipulation including the fiber fuse phenomenon, a continuous destruction of the fiber core pumped by the propagating light and triggered by a heat-induced strong absorption of silica glass. However, we have limited knowledge on its initiation process in the viewpoint of energy flow in the reactive area. Therefore, the conditions required for a fiber fuse initiation in standard single-mode fibers were determined quantitatively, namely the power of a 1480 nm fiber laser and the arc discharge intensity provided by a fusion splicer for one second as an outer heat source. Systematic investigation on the energy flow balance between these energy sources revealed that the initiation process consists of two steps; the generation of a precursor at the heated spot and the transition to a stable fiber fuse. The latter step needs a certain degree of heat accumulation at the core where waveguide deformation is ongoing competitively. This method is useful for comparing the tolerance to fiber fuse initiation among various fibers with a fixed energy amount that was not noticed before.

  16. nanocomposites formed under submerged DC arc discharge: preparation, characterization and photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Avcı, Ahmet; Eskizeybek, Volkan; Gülce, Handan; Haspulat, Bircan; Şahin, Ömer Sinan

    2014-09-01

    A rutile TiO2 (α-TiO2) and hexagonal wurtzite ZnO nanocomposite was directly and synchronously synthesized via arc discharge method submerged in de-ionized water. In correlation with the detailed characterization of the morphology, and crystalline structure of the prepared ZnO-TiO2 nanocomposites, the UV-visible and photoluminescence properties were studied. X-ray diffraction and transmission electron microscopy investigations revealed the co-existence of α-TiO2 and hexagonal wurtzite ZnO phases with the ZnO and α-TiO2 nanoparticles are in nanorod and nanospheres morphologies, respectively. The diameters of the synthesized nanocomposite particles are in the range of 5-70 nm. Interestingly, the as-prepared ZnO-TiO2 nanocomposite shows better photocatalytic activity for photodegradation of the methylene blue dye than both of pure ZnO and TiO2 nanocatalyts. This work would explore feasible routes to synthesize efficient metal or/and metal oxide nanocomposites for degrading organic pollutants, gas sensing or other related applications.

  17. The effect of calcination on multi-walled carbon nanotubes produced by dc-arc discharge.

    PubMed

    Pillai, Sreejarani K; Augustyn, Willem G; Rossouw, Margaretha H; McCrindle, Robert I

    2008-07-01

    Multi-walled carbon nanotubes were synthesized by dc-arc discharge in helium atmosphere and the effect of calcination at different temperatures ranging from 300-600 degrees C was studied in detail. The degree of degradation to the structural integrity of the multi-walled carbon nanotubes during the thermal process was studied by Raman spectroscopy, Scanning electron microscopy and High resolution transmission electron microscopy. The thermal behaviour of the as prepared and calcined samples was investigated by thermogravimetric analysis. Calcination in air at 400 degrees C for 2 hours was found to be an efficient and simple method to eliminate carbonaceous impurities from the nanotube bundles with minimal damage to the tube walls and length. The impurities were oxidized at a faster rate when compared to the nanotubes and gave good yield of about 50%. The nanotubes were observed to be damaged at temperature higher than 450 degrees C. The results show that this method is less destructive when compared liquid phase oxidation with 5 M HNO3.

  18. Electrothermic damage to the nail due to arcing in high-voltage discharge.

    PubMed

    Bielefeld, Lena; Mierdel, Katrin; Pollak, Stefan; Perdekamp, Markus Große

    2013-12-10

    The burn effects in high-voltage electrocutions are manifold ranging from inconspicuous marks to deep charring. Apart from lesions caused by direct contact with a live conductor, the victim's body may suffer flash burns from arcing resulting in extensive scattered or confluent heat damage of the skin. In such cases, the nail plates of fingers and toes may undergo thermal changes which up to now have not been mentioned in the pertinent literature. Macroscopically, the nail shows a yellowish discoloration with tiny and closely arranged verruciform elevations. Histologically, the uppermost layer of the nail plate is interspersed with small vacuoles resembling micro-blisters as seen in the corneal layer of common electric marks. The surface of the nail is coated with a thin film of carbonaceous material. Based on an accidental high-voltage electrocution recently observed by the authors, attention is also drawn to the possible occurrence of contact burns from metal objects heated by the current as this finding is usually described only in victims of lightning strikes and not in the context of high-voltage discharges of technical electricity.

  19. Complex structure of the carbon arc discharge for synthesis of nanotubes

    DOE PAGES

    Vekselman, V.; Feurer, M.; Huang, T.; ...

    2017-06-06

    Comprehensive non-invasive spectroscopic techniques and electrical measurements of the carbon arc revealed two distinguishable plasma synthesis regions in the radial direction normal to the arc axis. These regions, which are defined as the arc core and the arc periphery, are shown to have very different compositions of carbon species with different densities and temperatures. The colder arc periphery is dominated by carbon diatomic molecules (C2), which are in the minority in the composition of the hot arc core. These differences are due to a highly non-uniform distribution of the arc current, which is mainly conducted through the arc core populatedmore » with carbon atoms and ions. Therefore, the ablation of the graphite anode is governed by the arc core, while the formation of carbon molecules occurs in the colder arc periphery. Furthermore, this result is consistent with previous predictions that the plasma environment in the arc periphery is suitable for synthesis of carbon nanotubes.« less

  20. Rating Curve Estimation from Local Levels and Upstream Discharges

    NASA Astrophysics Data System (ADS)

    Franchini, M.; Mascellani, G.

    2003-04-01

    Current technology allows for low cost and easy level measurements while the discharge measurements are still difficult and expensive. Thus, these are rarely performed and usually not in flood conditions because of lack of safety and difficulty in activating the measurement team in due time. As a consequence, long series of levels are frequently available without the corresponding discharge values. However, for the purpose of planning, management of water resources and real time flood forecasting, discharge is needed and it is therefore essential to convert local levels into discharge values by using the appropriate rating curve. Over this last decade, several methods have been proposed to relate local levels at a site of interest to data recorded at a river section located upstream where a rating curve is available. Some of these methods are based on a routing approach which uses the Muskingum model structure in different ways; others are based on the entropy concepts. Lately, fuzzy logic has been applied more and more frequently in the framework of hydraulic and hydrologic problems and this has prompted to the authors to use it for synthesising the rating curves. A comparison between all these strategies is performed, highlighting the difficulties and advantages of each of them, with reference to a long reach of the Po river in Italy, where several hydrometers and the relevant rating curves are available, thus allowing for both a parameterization and validation of the different strategies.

  1. Gyrocenter shift of low-temperature plasmas and the retrograde motion of cathode spots in arc discharges.

    PubMed

    Lee, K C

    2007-08-10

    The gyrocenter shift phenomenon explained the mechanism of radial electric field formation at the high confinement mode transition in fusion devices. This Letter reports that the theory of gyrocenter shift is also applicable to low temperature high collisional plasmas such as arc discharges by the generalization of the theory resulting from a short mean free path compared with the gyroradius. The retrograde motion of cathode spots in the arc discharge is investigated through a model with the expanded formula of gyrocenter shift. It is found that a reversed electric field is formed in front of the cathode spots when they are under a magnetic field, and this reversed electric field generates a rotation of cathode spots opposite to the Amperian direction. The ion drift velocity profiles calculated from the model are in agreement with the experimental results as functions of magnetic flux density and gas pressure.

  2. Synthesis of 3C-SiC nanowires from a graphene/Si configuration obtained by arc discharge method

    NASA Astrophysics Data System (ADS)

    Zhang, Yifan; Sheng, Leimei; Fang, Yanghao; An, Kang; Yu, Liming; Liu, Yi; Zhao, Xinluo

    2017-06-01

    SiC nanowires were fabricated by heat-treating a graphene/Si configuration without using catalyst. This configuration was obtained by depositing few-layer graphene powders on Si (1 1 1) wafer using arc discharge method. The coverage rate of graphene on Si substrate can be controlled by arc discharge duration. The micro morphology observation and spectra characterization indicate that few-layer graphene powders provide carbon source in both nucleation step and growing step through vapor-solid process. The present results show that few-layer graphene can be used to mass-produce 3C-SiC nanowires with diameters from 10 to 50 nm, which is useful for applications of nanodevices and composite materials.

  3. A RF time domain approach for electric arcs detection and localization systems

    NASA Astrophysics Data System (ADS)

    Deacu, Daniela; Tamas, Razvan; Petrescu, Teodor; Paun, Mirel; Anchidin, Liliana; Algiu, Madalina

    2016-12-01

    In this paper we propose a new method for detection and localization of electric arcs by using two ultra-wide band (UWB) antennas together with data processing in the time-domain. The source of electric arcs is localized by computing an average on the inter-correlation functions of the signals received on two channels. By calculating the path length difference to the antennas, the direction of the electric arcs is then found. The novelty of the method consists in the spatial averaging in order to reduce the incertitude caused by the finite sampling rate.

  4. Influence of the temperature of electrode material on its disintegration under the action of an arc discharge in hydrogen

    NASA Technical Reports Server (NTRS)

    Bolotov, A. V.; Yukhimchuk, S. A.

    1985-01-01

    An analysis is made of the electrophysical processes occurring at the end surface of rod electrodes during constant and alternating arc discharge in hydrogen. Experiments are reported on the effect of surface temperature of tungsten electrodes on their erosion. The influence of activating additions of thorium oxide, the structure of the tungsten, and the gas surrounding the electrode on the specific thermal loading and the erosion of the electrodes is discussed.

  5. Supersonic Inlet Flow Control Using Localized Arc Filament Plasma Actuators

    DTIC Science & Technology

    2011-05-10

    one of the diagnostics tool used to observe the flow. Olive oil particles are used to seed the flow for these measurements. The streaking of oil...eliminate image contamination due to ambient light and the arc filaments. The flow is seeded with olive oil particles by a TSI six-jet atomizer in the

  6. Combustion Enhancement Via Stabilized Piecewise Nonequilibrium Gliding Arc Plasma Discharge (Postprint)

    DTIC Science & Technology

    2006-01-01

    19b. TELEPHONE NUMBER (Include Area Code) N/A Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39-18 AIAA JOURNAL Vol. 44, No. 1...surface area Fa = ampere force per unit arc length Fd = drag force I = current i, j = indices representing the two nozzles streams L = distance between...continually loses heat to the surroundings because of the increased arc surface area . The voltage is also continually Fig. 1 Gliding arc plasma system: path

  7. Nonthermal Biological Treatments Using Discharge Plasma Produced by Pulsed Power 5. Inactivation of Cryptosporidium Oocysts by UV Emission Generated from Pulsed Arc Discharge in Water

    NASA Astrophysics Data System (ADS)

    Kunitomo, Shinta

    Cryptosporidium contaminates most surface waters around the world. It is difficult to remove through conventional treatment processes, and is extremely resistant to the method of chemical disinfection typically used to inactivate these microorganisms. We have developed a new technology for inactivating Cryptosporidium oocysts by using a pulsed arc discharge in water, which creates shock waves, UV emissions, and radicals. The pulsed arc is generated between two cylindrical stainless steel rod electrodes, 6 mm in diameter, and 2 mm apart. We applied this method to the inactivation of oocysts in backwash water from a sand-filter unit of a drinking water plant. The results indicate that the major factor influencing inactivation is UV emissions, and that more than 99% of the oocysts in the high turbidity backwash water (80 NTU) are inactivated with an energy of 0.24 kWh/m3.

  8. Particle image velocimetry analysis of the flow around circular cylinder induced by arc discharge rotating in magnetic field

    NASA Astrophysics Data System (ADS)

    Munhoz, D. S.; Bityurin, V. A.; Klimov, A. I.; Moralev, I. A.

    2016-11-01

    An experimental study of the flow around a circular cylinder model with magnetohydrodynamic (MHD) actuator was carried out in subsonic wind tunnels (M < 0.2). Combined (high frequency and pulsed-periodic) electrical discharge was used in this MHD actuator. This intense pulsed-periodic discharge had the following characteristics: voltage amplitude up to 15 kV, current amplitude up to 16 A and frequency up to 1 kHz. Permanent magnets with an induction of B = 0.1 T on the model surface were placed inside the cylindrical model. Annular electrodes were situated on the surface of the cylindrical model. The Lorentz force causes the rotation of the electric arc on the model surface. In turn, the movement of the arc discharge induces the rotation of the gas near the surface of the model. In this experiment were carried out the measurement of the flow velocity profile near the surface of the model on the following operational modes: with plasma and without plasma. A parametric study of the aerodynamic performance of the model was fulfilled with respect to the discharge parameters and the flow velocity. To measure the velocity profile was used particle image velocimetry method.

  9. Photoelectron emission from metal surfaces induced by VUV-emission of filament driven hydrogen arc discharge plasma

    SciTech Connect

    Laulainen, J.; Kalvas, T.; Koivisto, H.; Komppula, J.; Tarvainen, O.

    2015-04-08

    Photoelectron emission measurements have been performed using a filament-driven multi-cusp arc discharge volume production H{sup −} ion source (LIISA). It has been found that photoelectron currents obtained with Al, Cu, Mo, Ta and stainless steel (SAE 304) are on the same order of magnitude. The photoelectron currents depend linearly on the discharge power. It is shown experimentally that photoelectron emission is significant only in the short wavelength range of hydrogen spectrum due to the energy dependence of the quantum efficiency. It is estimated from the measured data that the maximum photoelectron flux from plasma chamber walls is on the order of 1 A per kW of discharge power.

  10. Electric arc localization based on antenna arrays and MUSIC direction of arrival estimation

    NASA Astrophysics Data System (ADS)

    Paun, Mirel; Digulescu, Angela; Tamas, Razvan; Ioana, Cornel

    2015-02-01

    This paper presents an application of antenna arrays and MUSIC algorithm for estimating the location of an electric arc source. The proposed technique can be used to localize arc faults in photovoltaic arrays and their associated transformation stations. The technique was implemented and tested in the laboratory. For this purpose, an experimental setup consisting of 4 antennas, a digital storage oscilloscope with computer connectivity and a PC (Personal Computer) for data processing was built. The results proved that the proposed method is able to estimate the direction of the electric arc source with reasonable accuracy.

  11. Stability of very-high pressure arc discharges against perturbations of the electron temperature

    SciTech Connect

    Benilov, M. S.; Hechtfischer, U.

    2012-04-01

    We study the stability of the energy balance of the electron gas in very high-pressure plasmas against longitudinal perturbations, using a local dispersion analysis. After deriving a dispersion equation, we apply the model to a very high-pressure (100 bar) xenon plasma and find instability for electron temperatures, T{sub e}, in a window between 2400 K and 5500-7000 K x 10{sup 3} K, depending on the current density (10{sup 6}-10{sup 8} A/m{sup 2}). The instability can be traced back to the Joule heating of the electron gas being a growing function of T{sub e}, which is due to a rising dependence of the electron-atom collision frequency on T{sub e}. We then analyze the T{sub e} range occurring in very high-pressure xenon lamps and conclude that only the near-anode region exhibits T{sub e} sufficiently low for this instability to occur. Indeed, previous experiments have revealed that such lamps develop, under certain conditions, voltage oscillations accompanied by electromagnetic interference, and this instability has been pinned down to the plasma-anode interaction. A relation between the mechanisms of the considered instability and multiple anodic attachments of high-pressure arcs is discussed.

  12. Morphological study of graphite-encapsulated iron composite nanoparticles fabricated by a one-step arc discharge method

    NASA Astrophysics Data System (ADS)

    Hu, Rui; Furukawa, Taiki; Wang, Xiangke; Nagatsu, Masaaki

    2017-09-01

    Arc discharge is one of the most efficient approaches to fabricate graphite-encapsulated magnetic nanoparticles. However, given the ultra-fast synthetic procedure, the understanding of tailoring shell morphology and quality over magnetic core has been a long standing challenge. To better comprehend the mechanism of the encapsulating shell growth in plasma, a series of synthetic parameters were investigated systematically in this study. Specifically, (1) the surface morphology of the outmost shell evolved with high integrity by adding CH4 concentration from 0% to 50% to He background gas; (2) a smooth surface with higher graphitization degree was achieved by changing collecting zone closer to the arc center; (3) carbon nano loops on the outmost shell expanded volumetrically to be continuous amorphous cover as the working gas pressure decreases from 100 to 25 Torr. The surface properties (i.e., zeta potential and acid-base character) were also evaluated and explained through XPS technique.

  13. Characterization of an AC glow-type gliding arc discharge in atmospheric air with a current-voltage lumped model

    NASA Astrophysics Data System (ADS)

    Kong, Chengdong; Gao, Jinlong; Zhu, Jiajian; Ehn, Andreas; Aldén, Marcus; Li, Zhongshan

    2017-09-01

    Quantitative characterization of a high-power glow-mode gliding arc (GM-GA) discharge operated in open air is performed using a current-voltage lumped model that is built from the perspective of energy balance and electron conservation. The GM-GA discharge is powered by a 35 kHz alternating current power supply. Instantaneous images of the discharge volume are recorded using a high-speed camera at a frame rate of 50 kHz, synchronized with the simultaneously recorded current and voltage waveforms. Detailed analyzation indicates that the electrical input power is dissipated mainly through the transport of vibrationally excited nitrogen and other active radicals (such as O). The plasma is quite non-thermal with the ratio of vibrational and translational temperatures (Tv/Tg) larger than 2 due to the intense energy dissipation. The electron number density reaches 3 × 1019 m-3 and is always above the steady value owing to the short cutting events, which can recover the electron density to a relatively large value and limits the maximum length of the gliding arc. The slow decaying rate of electrons is probably attributed to the decomposed state of a hot gaseous mixture and the related associative ionization.

  14. CO2 conversion in a gliding arc plasma: 1D cylindrical discharge model

    NASA Astrophysics Data System (ADS)

    Wang, Weizong; Berthelot, Antonin; Kolev, Stanimir; Tu, Xin; Bogaerts, Annemie

    2016-12-01

    CO2 conversion by a gliding arc plasma is gaining increasing interest, but the underlying mechanisms for an energy-efficient process are still far from understood. Indeed, the chemical complexity of the non-equilibrium plasma poses a challenge for plasma modeling due to the huge computational load. In this paper, a one-dimensional (1D) gliding arc model is developed in a cylindrical frame, with a detailed non-equilibrium CO2 plasma chemistry set, including the CO2 vibrational kinetics up to the dissociation limit. The model solves a set of time-dependent continuity equations based on the chemical reactions, as well as the electron energy balance equation, and it assumes quasi-neutrality in the plasma. The loss of plasma species and heat due to convection by the transverse gas flow is accounted for by using a characteristic frequency of convective cooling, which depends on the gliding arc radius, the relative velocity of the gas flow with respect to the arc and on the arc elongation rate. The calculated values for plasma density and plasma temperature within this work are comparable with experimental data on gliding arc plasma reactors in the literature. Our calculation results indicate that excitation to the vibrational levels promotes efficient dissociation in the gliding arc, and this is consistent with experimental investigations of the gliding arc based CO2 conversion in the literature. Additionally, the dissociation of CO2 through collisions with O atoms has the largest contribution to CO2 splitting under the conditions studied. In addition to the above results, we also demonstrate that lumping the CO2 vibrational states can bring a significant reduction of the computational load. The latter opens up the way for 2D or 3D models with an accurate description of the CO2 vibrational kinetics.

  15. XPS and XRD study of FeCl3-graphite intercalation compounds prepared by arc discharge in aqueous solution.

    PubMed

    Yan, Zhang; Zhuxia, Zhang; Tianbao, Li; Xuguang, Liu; Bingshe, Xu

    2008-10-01

    A novel one-step synthesis method of FeCl3-graphite intercalation compounds (FeCl3-GICs) by an arc discharge in aqueous solution was reported for the first time. It presented a simply and controllable way to synthesize FeCl3-GICs. The structure of the stage 7 GICs was examined and characterized by X-ray diffraction. X-ray photoelectron spectroscopic study of stage 7 of FeCl3-GICs was also carried out. The change in the binding energy suggests the nature of charge transfer and lowering of Fermi level as has been reported previously for other acceptor intercalation compounds.

  16. Gas pressure and electron density at the level of the active zone of hollow cathode arc discharges

    NASA Technical Reports Server (NTRS)

    Minoo, M. H.

    1984-01-01

    A model for the longitudinal variations of the partial pressures of electrons, ions, and neutral particles is proposed as a result of an experimental study of pressure variations at the level of the active zone as a function of the various discharge parameters of a hollow cathode arc. The cathode region where the temperature passes through its maximum is called active zone. The proposed model embodies the very important variations which the partial electron and neutral particles pressures undergo at the level of the active zone.

  17. Characteristics of Pulsed Arc Electrohydraulic Discharge for Eccentric Electrode Cylindrical Reactor using Phosphate-Buffered Saline Water

    NASA Astrophysics Data System (ADS)

    Yamatake, Atsushi; Angeloni, Danielle M.; Dickson, Sarah E.; Emelko, Monica B.; Yasuoka, Koichi; Chang, Jen-Shih

    2006-10-01

    Pulsed arc electrohydroulic discharge (PAED) has been proposed as a water treatment technology for the removal of chemical and microbial contaminants. In this work, we examined the fundamental characteristics of a PAED system with an eccentric electrode cylindrical reactor. Phosphate-buffered saline (PBS) water was used in lieu of tap water, because the conductivity of PBS is much higher than that of tap water. The results show that the voltage and current waveforms generated in PBS and tap water are very different due to the higher conductivity of PBS. Strong pressure waves and UV emission were also observed in PBS.

  18. Ongoing characterization of the forced electron beam induced arc discharge ion source for the selective production of exotic species facility

    SciTech Connect

    Manzolaro, M. Andrighetto, A.; Monetti, A.; Scarpa, D.; Rossignoli, M.; Vasquez, J.; Corradetti, S.; Calderolla, M.; Prete, G.; Meneghetti, G.

    2014-02-15

    An intense research and development activity to finalize the design of the target ion source system for the selective production of exotic species (SPES) facility (operating according to the isotope separation on line technique) is at present ongoing at Legnaro National Laboratories. In particular, the characterization of ion sources in terms of ionization efficiency and transversal emittance is currently in progress, and a preliminary set of data is already available. In this work, the off-line ionization efficiency and emittance measurements for the SPES forced electron beam induced arc discharge ion source in the case of a stable Ar beam are presented in detail.

  19. Capacitive coupled RF discharge: modelling at the local and not local statement of the problem

    NASA Astrophysics Data System (ADS)

    Askhatov, R. M.; Chebakova, V. Yu; Zheltukhin, V. S.

    2016-11-01

    The models provided in the research paper describe a capacitive coupled radiofrequency discharge in argon between two parallel plate electrodes, one of which is grounded, and the other is connected to the high-frequency capacitive generator. Herein we review various approaches to simulate a high-frequency capacitive discharge depending on modelled pressure rates. The model of a high-frequency capacitive discharge under low pressure is simulated in non-local approximation, and under high pressure is simulated in local approximation and is sensitive to dimers and molecular ions. We provide calculation data with respect to different pressures and make comparative analysis of data provided by other authors in particular, analysis of data obtained with real experiment.

  20. Comparative process analysis of fullerene production by the arc and the radio-frequency discharge methods.

    PubMed

    Marković, Z; Todorović-Marković, B; Mohai, I; Farkas, Z; Kovats, E; Szepvolgyi, J; Otasević, D; Scheier, P; Feil, S; Romcević, N

    2007-01-01

    In this work, comparative analysis of processes in carbon arc and radio frequency (RF) plasma during fullerene synthesis has been presented. The kinetic model of fullerene formation developed earlier has been verified in both types of plasma reactors. The fullerene yield depended on carbon concentration, velocity of plasma flame and rotational temperature of C2 radicals predominantly. When mean rotational temperature of C2 radicals was 3000 K, the fullerene yield was the highest regardless of the type of used reactor. The zone of fullerene formation is larger significantly in RF plasma reactor compared to arc reactor.

  1. TiO2-assisted degradation of a perfluorinated surfactant in aqueous solutions treated by gliding arc discharge.

    PubMed

    Marouf-Khelifa, Kheira; Abdelmalek, Fatiha; Khelifa, Amine; Addou, Ahmed

    2008-02-01

    The plasma-chemical degradation of Forafac 1110, a perfluorinated non-ionic surfactant, in aqueous solutions was investigated using TiO2 catalysts. The considered plasma was the gliding arc in humid air, which results from an electric discharge at atmospheric pressure and quasi-ambient temperature. Two titanium dioxide powders were used and their synergistic effects on the Forafac degradation were compared. The results were discussed through the evolution of the pH, the conductivity, the fluoride ions concentration released in solutions, the surfactant concentration remaining after treatment and the chemical oxygen demand (COD) measurement. The combination of the plasma-chemical treatment with heterogeneous catalysis through the use of TiO2 accelerated the Forafac degradation, since only 60 min was sufficient to remove 96% instead of 360 min needed in the absence of TiO2. The use of anatase and rutile under the trade-name of Rhodia TiO2 and Merck TiO2, respectively, led to different results, because Rhodia TiO2 has proven to be more efficient. It would seem that the crystalline phase as well as the crystallite size, explain the efficiency of anatase. The advantage of the plasma-catalysis is due to the fact that there is a significant production of the OH* radicals not only generated by the gliding arc discharge but also by TiO2.

  2. Electrode material dependence of two-dimensional electron and vapour density distribution over vacuum arc discharge

    NASA Astrophysics Data System (ADS)

    Inada, Y.; Matsuoka, S.; Kumada, A.; Ikeda, H.; Hidaka, K.

    2017-03-01

    Electrode material dependence of intense-mode vacuum arc behaviour was systematically investigated by using the Shack-Hartmann method capable of simultaneously visualising two-dimensional electron and metal vapour density distributions from single-shot recordings. The electrode materials studied included Cu, CuCr (Cu75Cr25 wt. %), WC, and AgWC (Ag40WC60 wt. %). A comparison between the Cu and CuCr electrodes showed that the metal vapour densities for the CuCr decreased in an even shorter time scale than for the Cu. In the case of the WC electrodes, the widths of the electron density distributions became narrower as the arc current decreased although the electron densities hardly decreased in the decaying process of the arc current. The density measurements conducted at the late stage of the vacuum arcs demonstrated that the metal vapour densities around the anode were maintained at the highest value for the AgWC among the electrode materials in this study.

  3. A local pseudo arc-length method for hyperbolic conservation laws

    NASA Astrophysics Data System (ADS)

    Wang, Xing; Ma, Tian-Bao; Ren, Hui-Lan; Ning, Jian-Guo

    2014-12-01

    A local pseudo arc-length method (LPALM) for solving hyperbolic conservation laws is presented in this paper. The key idea of this method comes from the original arc-length method, through which the critical points are bypassed by transforming the computational space. The method is based on local changes of physical variables to choose the discontinuous stencil and introduce the pseudo arc-length parameter, and then transform the governing equations from physical space to arc-length space. In order to solve these equations in arc-length coordinate, it is necessary to combine the velocity of mesh points in the moving mesh method, and then convert the physical variable in arclength space back to physical space. Numerical examples have proved the effectiveness and generality of the new approach for linear equation, nonlinear equation and system of equations with discontinuous initial values. Non-oscillation solution can be obtained by adjusting the parameter and the mesh refinement number for problems containing both shock and rarefaction waves.

  4. Nonthermal Biological Treatments Using Discharge Plasma Produced by Pulsed Power 6. Production of NO Using Pulsed Arc Discharges and Its Medical Applications

    NASA Astrophysics Data System (ADS)

    Namihira, Takao; Katsuki, Sunao; Akiyama, Hidenori; Okamoto, Kazufumi

    Nitric monoxide (NO) is increasingly being used in medical applications. Current applications use a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially dangerous, given the possibility of an accidental leak of NO from the cylinder. The presence of NO in air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore on-site generation of NO would be very desirable to treat patients with acute respiratory distress syndrome and other related illnesses. Recently, pure NO was generated using a pulsed arc discharge in dry air with an NO2-NO converter and charcoal. The concentration of NO was easily controlled by controlling pulse repetition rate and gas flow rate. This system is already under investigation in an animal experiment.

  5. Stark broadening experiments on a vacuum arc discharge in tin vapor.

    PubMed

    Kieft, E R; van der Mullen, J J A M; Kroesen, G M W; Banine, V; Koshelev, K N

    2004-12-01

    Pinched discharge plasmas in tin vapor are candidates for application in future semiconductor lithography tools. This paper presents time-resolved measurements of Stark broadened linewidths in a pulsed tin discharge. Stark broadening parameters have been determined for four lines of the Sn III spectrum in the range from 522 to 538 nm, based on a cross-calibration to a Sn II line with a previously known Stark width. The influence of the electron temperature on the Stark widths is discussed. Results for the electron densities in the discharge are presented and compared to Thomson scattering results.

  6. A Comparative Study of the Dispersion of Multi-Wall Carbon Nanotubes Made by Arc-Discharge and Chemical Vapour Deposition.

    PubMed

    Frømyr, Tomas-Roll; Bourgeaux-Goget, Marie; Hansen, Finn Knut

    2015-05-01

    A method has been developed to characterize the dispersion of multi-wall carbon nanotubes in water using a disc centrifuge for the detection of individual carbon nanotubes, residual aggregates, and contaminants. Carbon nanotubes produced by arc-discharge have been measured and compared with carbon nanotubes produced by chemical vapour deposition. Studies performed on both pristine (see text) arc-discharge nanotubes is rather strong and that high ultra-sound intensity is required to achieve complete dispersion of carbon nanotube bundles. The logarithm of the mode of the particle size distribution of the arc-discharge carbon nanotubes was found to be a linear function of the logarithm of the total ultrasonic energy input in the dispersion process.

  7. Comparative study on extinction process of gas-blasted air and CO2 arc discharge using two-dimensional electron density imaging sensor

    NASA Astrophysics Data System (ADS)

    Inada, Yuki; Kumada, Akiko; Ikeda, Hisatoshi; Hidaka, Kunihiko; Nakano, Tomoyuki; Murai, Kosuke; Tanaka, Yasunori; Shinkai, Takeshi

    2017-05-01

    Shack-Hartmann type laser wavefront sensors were applied to gas-blasted arc discharges under current-zero phases, generated in a 50 mm-long interelectrode gap confined by a gas flow nozzle, in order to conduct a systematic comparison of electron density decaying processes for two kinds of arc-quenching gas media: air and \\text{C}{{\\text{O}}2} . The experimental results for the air and \\text{C}{{\\text{O}}2} arc plasmas showed that the electron densities and arc diameters became thinner toward the nozzle-throat inlet due to a stronger convection loss in the arc radial direction. In addition, \\text{C}{{\\text{O}}2} had a shorter electron density decaying time constant than air, which could be caused by convection loss and turbulent flow of \\text{C}{{\\text{O}}2} stronger than air.

  8. Structure and magnetic properties of surface alloyed Fe nanocapsules prepared by arc discharge

    NASA Astrophysics Data System (ADS)

    Si, P. Z.; Choi, C. J.; Brück, E.; Geng, D. Y.; Zhang, Z. D.

    2005-12-01

    C-Fe-Si alloy encapsulating Fe nanocapsules were fabricated by arc evaporating the mixture of Fe and SiC powders. The high temperature of the electric arc results in a surface reaction between SiC and Fe nanoparticles and therefore a uniform encapsulation of the Fe nanoparticles with its alloy. The size of the nanocapsules ranges from 10 to 60 nm while most shells are approximately 7 nm in thickness. Air oxidation to the as-prepared sample does not change the shell/core structure but the saturation magnetization and the coercivity are reduced. The characteristics of the nanocapsules were investigated systematically by using X-ray diffraction, transmission electron microscopy, energy dispersive spectra, X-ray photoelectron spectroscopy, and superconducting quantum interference device magnetometer.

  9. Properties of the particles deposited from a low-temperature plasma arc discharge

    NASA Astrophysics Data System (ADS)

    Smolanov, N. A.

    2017-01-01

    The possible mechanisms for the formation of fractal particles of the plasma arc have been studies. The existence of dust structures of two types strongly and weakly magnetic was found. Paramagnetism of particles is the result of the synthesis of titanium carbonitride with embedded (encapsulated) magnetic substrate elements. The magnetization of particles indicates the presence in the test nanostructure particles. inhomogeneous distribution of electric charges in motion conducting bodies (drops) in a magnetized plasma is the reason for the formation of dust particles.

  10. The morphology of carbon-metal composite synthesized in arc discharge

    NASA Astrophysics Data System (ADS)

    Smovzh, D. V.; Sakhapov, S. Z.; Zaikovskii, A. V.

    2016-10-01

    The phase state of nanoparticles and function of distribution by size of particles, formed at joint electric arc spraying of metal (Ni/Cu/Ti/Pt/Zr) - carbon electrode, is studied. It is shown that the metal and carbide nanoparticles with the size of 2-9 nm are formed in the carbon matrix at spraying. When annealing the metal-carbon composites, the metal-containing nanoparticles oxidize and coagulate, forming the agglomerates of 100 nm or more.

  11. Localized arc filament plasma actuators for noise mitigation and mixing enhancement

    NASA Technical Reports Server (NTRS)

    Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

    2008-01-01

    A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

  12. Localized arc filament plasma actuators for noise mitigation and mixing enhancement

    NASA Technical Reports Server (NTRS)

    Samimy, Mohammad (Inventor); Adamovich, Igor (Inventor)

    2010-01-01

    A device for controlling fluid flow. The device includes an arc generator coupled to electrodes. The electrodes are placed adjacent a fluid flowpath such that upon being energized by the arc generator, an arc filament plasma adjacent the electrodes is formed. In turn, this plasma forms a localized high temperature, high pressure perturbation in the adjacent fluid flowpath. The perturbations can be arranged to produce vortices, such as streamwise vortices, in the flowing fluid to control mixing and noise in such flows. The electrodes can further be arranged within a conduit configured to contain the flowing fluid such that when energized in a particular frequency and sequence, can excite flow instabilities in the flowing fluid. The placement of the electrodes is such that they are unobtrusive relative to the fluid flowpath being controlled.

  13. Multiple solutions in the theory of dc glow discharges and cathodic part of arc discharges. Application of these solutions to the modeling of cathode spots and patterns: a review

    NASA Astrophysics Data System (ADS)

    Benilov, M. S.

    2014-10-01

    A new class of stationary solutions in the theory of glow discharges and plasma-cathode interaction in ambient-gas arc discharges has been found over the past 15 years. These solutions exist simultaneously with the solution given in textbooks, which describes a discharge mode with a uniform or smooth distribution of current over the cathode surface, and describes modes with various configurations of cathode spots: normal spots on glow cathodes, patterns of multiple spots recently observed on cathodes of glow microdischarges and spots on arc cathodes. In particular, these solutions show that cathode spots represent a manifestation of self-organization caused by basic mechanisms of the near-cathode space-charge sheath; another illustration of the richness of the gas discharge science. As far as arc cathodes are concerned, the new solutions have proved relevant for industrial applications. This work is dedicated to reviewing the multiple solutions obtained to date, their systematization, and analysis of their properties and physical meaning. The treatment is performed in the context of general trends of self-organization in bistable nonlinear dissipative systems, which allows one to consider glow discharges or arc-cathode interaction within a single physically transparent framework without going into mathematical details and offers a possibility of systematic computation of the multiple solutions. Relevant computational aspects and experimental data are discussed.

  14. Surface properties of plasma-functionalized graphite-encapsulated gold nanoparticles prepared by a direct current arc discharge method

    NASA Astrophysics Data System (ADS)

    Yang, Enbo; Chou, Han; Tsumura, Shun; Nagatsu, Masaaki

    2016-05-01

    The graphite-encapsulated gold nanoparticles (Au@C NPs) fabricated by a direct current arc discharge method were surface-functionalized by an inductively-coupled radio frequency ammonia plasma with a particle explosion technique for enhancing surface modification efficiency. To investigate the structural and surface properties of Au@C NPs, characterizations using x-ray diffraction, high resolution transmission electron microscopy and x-ray photoelectron spectroscopy have been conducted on the untreated and plasma treated Au@C NPs. Based on the experimental results, we give insight into the possible formation of Au ions in the interface between the graphite layers and gold core particles of the Au@C NPs. Finally, the role of the plasma treatment on the surface functionalization of Au@C NPs with amino groups is discussed.

  15. Multiwalled carbon nanotubes mass-produced by dc arc discharge in He-H2 gas mixture

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Guo, Y.; Inoue, S.; Zhao, X.; Ohkohchi, M.; Ando, Y.

    2006-04-01

    Uniform cathode deposits (longer than 15 mm), containing multiwalled carbon nanotubes (MWNTs) inside, were produced by dc arc discharge evaporation with a computer-controlled feeder of a pure-carbon electrode without a metal catalyst in a He-H2 gas mixture. The purification of MWNTs was carried out to remove amorphous carbon and carbon nanoparticles. High-resolution transmission electron microscopy observations and Raman scattering studies show that the MWNTs possess a high crystallinity and a mean outermost diameter of ˜ ˜10 nm. It has been confirmed that the current density in the electron field emission from a purified MWNT mat can reach 77.92 mA/cm2, indicating that the purified MWNTs are a promising candidate electron source in a super high-luminance light-source tube or a miniature X-ray source.

  16. Effect of metal oxide and oxygen on the growth of single-walled carbon nanotubes by electric arc discharge

    NASA Astrophysics Data System (ADS)

    He, Delong; Liu, Yongning; Zhao, Tingkai; Zhu, Jiewu; Yu, Guang

    2008-03-01

    The effect of oxygen on the growth of single-walled carbon nanotubes was studied with Ni-Co alloy powder as catalyst under helium atmosphere of 500 Torr by electric arc discharge. The oxygen included in nickel or (and) cobalt oxides was added in catalyst. The content of oxygen in atmosphere was controlled by changing vacuum degree inside furnace before inputting buffer gas. The examinations of TEM and Raman scattering showed that oxygen in metal oxide as catalyst promotes the nucleation of SWCNT by taking effect on the metal catalyst particles. However, O2 in atmosphere has the role of oxidizing amorphous particles along with nanotubes. When its molar proportion is higher than 0.22 ppm (Parts per million), the carbon nanotubes produced are oxidized and their purity decreases. The diameter of single-walled carbon nanotube obtained under different condition has a narrow distribution around 1.28 nm.

  17. Luminescence properties of boron and nitrogen doped graphene quantum dots prepared from arc-discharge-generated doped graphene samples

    NASA Astrophysics Data System (ADS)

    Dey, Sunita; Govindaraj, A.; Biswas, Kanishka; Rao, C. N. R.

    2014-03-01

    Substitution of heteroatoms in graphene is known to tailor its band gap. Another approach to alter the band gap of graphene is to create zero-dimensional graphene quantum dots (GQDs). Here we present the synthesis and photoluminescence properties of B-doped graphene quantum dots (B-GQDs) for the first time, having prepared the B-GQDs by chemical scissoring of B-doped graphene generated by arc-discharge in gas phase. We compare the photoluminescence properties of B-GQDs with nitrogen-doped GQDs and pristine GQDs. Besides, excitation wavelength independent PL emission, excellent upconversion of PL emission is observed in GQDs as well as B- and N-doped GQDs.

  18. Modeling of high pressure arc-discharge with a fully-implicit Navier-Stokes stabilized finite element flow solver

    NASA Astrophysics Data System (ADS)

    Sahai, A.; Mansour, N. N.; Lopez, B.; Panesi, M.

    2017-05-01

    This work addresses the modeling of high pressure electric discharge in an arc-heated wind tunnel. The combined numerical solution of Poisson’s equation, radiative transfer equations, and the set of Favre-averaged thermochemical nonequilibrium Navier-Stokes equations allows for the determination of the electric, radiation, and flow fields, accounting for their mutual interaction. Semi-classical statistical thermodynamics is used to determine the plasma thermodynamic properties, while transport properties are obtained from kinetic principles with the Chapman-Enskog method. A multi-temperature formulation is used to account for thermal non-equilibrium. Finally, the turbulence closure of the flow equations is obtained by means of the Spalart-Allmaras model, which requires the solution of an additional scalar transport equation. A Streamline upwind Petrov-Galerkin stabilized finite element formulation is employed to solve the Navier-Stokes equation. The electric field equation is solved using the standard Galerkin formulation. A stable formulation for the radiative transfer equations is obtained using the least-squares finite element method. The developed simulation framework has been applied to investigate turbulent plasma flows in the 20 MW Aerodynamic Heating Facility at NASA Ames Research Center. The current model is able to predict the process of energy addition and re-distribution due to Joule heating and thermal radiation, resulting in a hot central core surrounded by colder flow. The use of an unsteady three-dimensional treatment also allows the asymmetry due to a dynamic electric arc attachment point in the cathode chamber to be captured accurately. The current work paves the way for detailed estimation of operating characteristics for arc-heated wind tunnels which are critical in testing thermal protection systems.

  19. Computing anode heating voltage in high-pressure arc discharges and modelling rod electrodes in dc and ac regimes

    NASA Astrophysics Data System (ADS)

    Almeida, N. A.; Cunha, M. D.; Benilov, M. S.

    2017-09-01

    Numerical modelling of near-anode layers in arc discharges in several gases (Ar, Xe and Hg) is performed in a wide range of current densities, anode surface temperatures, and plasma pressures. It is shown that the density of energy flux to the anode is only weakly affected by the anode surface temperature and varies linearly with the current density. This allows one to interpret the results in terms of anode heating voltage (volt equivalent of the heat flux to the anode). The computed data may be useful in different ways. An example considered in this work concerns the evaluation of thermal regime of anodes in the shape of a thin rod operating in the diffuse mode. Invoking the model of nonlinear surface heating for cathodes, one obtains a simple and free of empirical parameters model of thin rod electrodes applicable to dc and ac high-pressure arcs provided that no anode spots are present. The model is applied to a variety of experiments reported in the literature and a good agreement with the experimental data found.

  20. Calculation of net emission coefficient of electrical discharge machining arc plasmas in mixtures of nitrogen with graphite, copper and tungsten

    NASA Astrophysics Data System (ADS)

    Adineh, V. R.; Coufal, O.; Bartlova, M.

    2015-10-01

    This work reports theoretical calculations of electrical discharge machining (EDM) radiative properties for mixture systems of N2-C, N2-Cu and N2-W arc plasmas, in the temperature range of 3000-10 000 K, and at 1 and 10 bar pressures. Radiative properties are computed for various plasma sizes as well as vapour proportions. Calculations consider line overlapping with spectrum coverage from 30 to 10 000 nm. Doppler, Natural, Van-der-Waals, Resonance and Stark broadening are taken into account as the line broadening mechanisms. Besides, continuum calculations consider bound-free and free-free emissions along with molecular bands radiation for selected molecular systems. Results show that contamination vapours of EDM electrode have strong influence on the amount of EDM plasma radiation to the surrounding environment. However, comparison of impurities from workpiece with electrode one indicates that Fe vapour has stronger impact on modifying the EDM arc plasma radiative properties, compared to the C, Cu and W species studied in this research.

  1. Change of the arc attachment mode and its effect on the lifetime in automotive high intensity discharge lamps

    NASA Astrophysics Data System (ADS)

    Alexejev, Alexander; Flesch, Peter; Mentel, Jürgen; Awakowicz, Peter

    2016-10-01

    In modern cars, the new generation Hg-free high intensity discharge (HID) lamps, the so called xenon lamps, take an important role. The long lifetime of these lamps is achieved by doping the tungsten electrodes with thorium. Thorium forms a dipole layer on the electrode surface, thus reducing the work function of tungsten. However, thoriating the electrodes is also an issue of trade and transport regulation, so a substitute is looked into. This work shows the influence of the arc attachment mode on the lifetime of the lamps. The mode of the arc attachment changes during the run-up phase of automotive HID lamps after a characteristic time period depending, i.e., on the filling of the lamps, which is dominated by scandium. It will be shown that this characteristic time period for the change of the attachment mode determines the long term performance of Hg-free xenon lamps. Measurements attributing the mode change to the scandium density in the filling are presented. The emitter effect of scandium will be suggested to be the reason of the mode change.

  2. Fabrication of TiO2/Carbon Photocatalyst using Submerged DC Arc Discharged in Ethanol/Acetic Acid Medium

    NASA Astrophysics Data System (ADS)

    Saraswati, T. E.; Nandika, A. O.; Andhika, I. F.; Patiha; Purnawan, C.; Wahyuningsih, S.; Rahardjo, S. B.

    2017-05-01

    This study aimed to fabricate a modified photocatalyst of TiO2/C to enhance its performance. The fabrication was achieved using the submerged direct current (DC) arc-discharge method employing two graphite electrodes, one of which was filled with a mixture of carbon powder, TiO2, and binder, in ethanol with acetic acid added in various concentrations. The arc-discharge method was conducted by flowing a current of 10-20 A (~20 V). X-ray diffraction (XRD) patterns showed significant placements of the main peak characteristics of TiO2, C graphite, and titanium carbide. The surface analysis using Fourier transform infrared spectroscopy (FTIR) revealed that fabricated TiO2/C nanoparticles had stretching vibrations of Ti-O, C-H, C═O, C-O, O-H and C═C in the regions of 450-550 cm-1, 2900-2880 cm-1, 1690-1760 cm-1, 1050-1300 cm-1, 3400-3700 cm-1 and ~1600 cm-1, respectively. In addition, the study investigated the photocatalysts of unmodified and modified TiO2/C for photodegradation of methylene blue (MB) dye solution under mercury lamp irradiation. The effectiveness of the degradation was defined by the decrease in 60-minute absorbance under a UV-Vis spectrophotometer. Modified TiO2/C proved to be significantly more efficient in reducing dye concentrations, reaching ~70%. It indicated that the oxygen-containing functional groups have been successfully attached to the surface of the nanoparticles and played a role in enhancing photocatalytic activity.

  3. Localized bedrock aquifer distribution explains discharge from a headwater catchment

    NASA Astrophysics Data System (ADS)

    Kosugi, Ken'ichirou; Fujimoto, Masamitsu; Katsura, Shin'ya; Kato, Hiroyuki; Sando, Yoshiki; Mizuyama, Takahisa

    2011-07-01

    Understanding a discharge hydrograph is one of the leading interests in catchment hydrology. Recent research has provided credible information on the importance of bedrock groundwater on discharge hydrographs from headwater catchments. However, intensive monitoring of bedrock groundwater is rare in mountains with steep topography. Hence, how bedrock groundwater controls discharge from a steep headwater catchment is in dispute. In this study, we conducted long-term hydrological observations using densely located bedrock wells in a headwater catchment underlain by granitic bedrock. The catchment has steep topography affected by diastrophic activities. Results showed a fairly regionalized distribution of bedrock aquifers within a scale of tens of meters, consisting of upper, middle, and lower aquifers, instead of a gradual and continuous decline in water level from ridge to valley bottom. This was presumably attributable to the unique bedrock structure; fault lines developed in the watershed worked to form divides between the bedrock aquifers. Spatial expanse of each aquifer and the interaction among aquifers were key factors to explain gentle and considerable variations in the base flow discharge and triple-peak discharge responses of the observed hydrograph. A simple model was developed to simulate the discharge hydrograph, which computed each of the contributions from the soil mantle groundwater, from the lower aquifer, and from the middle aquifer to the discharge. The modeling results generally succeeded in reproducing the observed hydrograph. Thus, this study demonstrated that understanding regionalized bedrock aquifer distribution is pivotal for explaining discharge hydrograph from headwater catchments that have been affected by diastrophic activities.

  4. Degradation of palm oil refinery wastewaters by non-thermal gliding arc discharge at atmospheric pressure.

    PubMed

    Mountapmbeme-Kouotou, P; Laminsi, S; Acayanka, E; Brisset, J-L

    2013-07-01

    The gliding electric discharge in humid air is a source of activated species forming (e.g. (•)OH, (•)NO and their derivatives H2O2, ONO2H and NO3H) which are present in a non-thermal plasma at atmospheric pressure. These species are able to degrade organic pollutants in palm oil refinery wastewaters (PORW). The increase in acidity (pH decrease), conductivity and total dissolved solids (TDS) and the decrease in the total organic carbon (TOC) of PORW samples exposed to the discharge are reported. More than 50% TOC abatement is obtained for 15 min treatment in batch conditions with a laboratory reactor. The organic pollutants of PORW, i.e. mainly fatty acids are degraded according to a pseudo first-order reaction (k* = 0.06 min(-1)). Post discharge reactions are also observed after having switched off the discharge, which suggests that the pseudo first-order (k ≈ 0.05 min(-1)) degradation reactions should be attributed to the diffusion of soluble reactive species, e.g. H2O2 and ONOOH in the liquid target.

  5. Single-walled nanohorns and other nanocarbons generated by submerged arc discharge between carbon electrodes in liquid argon and other media

    NASA Astrophysics Data System (ADS)

    Vasu, K.; Pramoda, K.; Moses, K.; Govindaraj, A.; Rao, C. N. R.

    2014-03-01

    Arc discharge between two graphite electrodes submerged in different liquid media yields various dimensional nanocarbon structures such as 1D carbon nanotubes and 2D graphene. Single-walled carbon nanohorns (SWNHs) prepared by submerged arc discharge in liquid nitrogen medium are found to have nitrogen impurities. Here, we report the structure and properties of pure and nitrogen-doped SWNHs obtained by submerged arc discharge in a liquid argon medium. The absence of an XPS N 1s signal, which is present in nanohorns obtained in liquid nitrogen, indicate that the nanohorns are free from nitrogen impurities. Raman spectra show a strong defect-induced D band and current-voltage characteristics show a slight nonlinear behavior. N2 adsorption of pure SWNHs shows type-IV isotherms with a surface area of 300 m2 g-1. Adsorption of CO2 and H2 in pure SWNHs has also been measured. Arc discharge in other liquid media such as water, ethanol, dimethylformamide (DMF), n-methyl pyrrolidone (NMP), formamide, benzene, heptane and acetone yields different nanocarbon structures including multi-walled carbon nanotubes (MWNTs), few-layer graphene, carbon onions and carbon nanoparticles.

  6. Model of liquid-metal splashing in the cathode spot of a vacuum arc discharge

    SciTech Connect

    Gashkov, M. A.; Zubarev, N. M. Zubareva, O. V.; Mesyats, G. A.; Uimanov, I. V.

    2016-04-15

    The formation of microjets is studied during the extrusion of a melted metal by the plasma pressure from craters formed on a cathode in a burning vacuum arc. An analytic model of liquid-metal splashing that includes two stages is proposed. At the first stage, the liquid motion has the axial symmetry and a liquid-metal wall surrounding the crater is formed. At the second stage, the axial symmetry is broken due to the development of the Plateau–Rayleigh instability in the upper part of the wall. The wall breakup process is shown to have a threshold. The minimal plasma pressure and the minimal electric current flowing through the crater required for obtaining the liquid-metal splashing regime are found. The basic spatial and temporal characteristics of the jet formation process are found using the analytic model.

  7. Joule heat generation in thermionic cathodes of high-pressure arc discharges

    SciTech Connect

    Benilov, M. S.; Cunha, M. D.

    2013-02-14

    The nonlinear surface heating model of plasma-cathode interaction in high-pressure arcs is extended to take into account the Joule effect inside the cathode body. Calculation results are given for different modes of current transfer to tungsten cathodes of different configurations in argon plasmas of atmospheric or higher pressures. Special attention is paid to analysis of energy balances of the cathode and the near-cathode plasma layer. In all the cases, the variation of potential inside the cathode is much smaller than the near-cathode voltage drop. However, this variation can be comparable to the volt equivalent of the energy flux from the plasma to the cathode and then the Joule effect is essential. Such is the case of the diffuse and mixed modes on rod cathodes at high currents, where the Joule heating causes a dramatic change of thermal and electrical regimes of the cathode. The Joule heating has virtually no effect over characteristics of spots on rod and infinite planar cathodes.

  8. Plasma centrifuge with vacuum arc discharge applied to the separation of stable isotopes

    NASA Astrophysics Data System (ADS)

    Delbosco, Edson

    1989-09-01

    The results of a vacuum-arc plasma centrifuge experiment are described. A plasma centrifuge is an apparatus where a plasma column is produced due to the interaction of an electric current with an externally applied magnetic field, vector J x vector B. Among the applications of a rotating plasma, this work deals particularly with its utilization in an isotope enrichment device. The main characteristics of the plasma produced in this experiment are presented, with special attention to the plasma column rotation and the isotope enrichment. The analysis of the results is performed using a fluid model for a completely ionized rigid body rotating plasma column in steady state equilibrium. The main results are: (1) rotation frequency of the plasma column in the range 2 x (exp 4) to 3 x 10 (exp 5) rad/s; (2) enrichment of 10 to 30 pct for the magnesium isotopes, and 290 to 490 pct for the carbon-13 isotope; (3) rigid body rotation of the plasma column only for radii smaller than the characteristic radius of the plasma column, r(sub e); (4) linear dependence of the rotation frequency upon the magnetic field strength only for r is less than r(sub e); (5) existence of an optimum value of the magnetic field for maximum enrichment; and (6) dependence of the rotation frequency upon the inverse of the atomic mass.

  9. Mass spectrometric investigations of plasma chemical reactions in a radiofrequency discharge with Ar/C2H2 and Ar/C2H2/O2 gas mixtures

    NASA Astrophysics Data System (ADS)

    Herrendorf, Ann-Pierra; Sushkov, Vladimir; Hippler, Rainer

    2017-03-01

    Plasma chemical reactions in complex Ar/C2H2 and Ar/C2H2/O2 radiofrequency plasmas with formation of nano-particles are investigated. Growing nano-particles cause a growth instability, which leads to temporal variations and a cyclic behaviour of plasma properties. Mass spectrometric observations show the consumption of C2H2 and the formation of polyacetylene C2nH2 molecules which increases with acetylene gas flow. The cycle frequency is a decreasing function of acetylene consumption. The addition of oxygen to the discharge reduces the cycle frequency and the formation of nano-particles and leads to the formation of CO and CO2 molecules presumably through the oxidation of C2H radicals which are formed in the discharge.

  10. Removal of hexavalent chromium in carbonic acid solution by oxidizing slag discharged from steelmaking process in electric arc furnace

    NASA Astrophysics Data System (ADS)

    Yokoyama, Seiji; Okazaki, Kohei; Sasano, Junji; Izaki, Masanobu

    2014-02-01

    Hexavalent chromium (Cr(VI)) is well-known to be a strong oxidizer, and is recognized as a carcinogen. Therefore, it is regulated for drinking water, soil, groundwater and sea by the environmental quality standards all over the world. In this study, it was attempted to remove Cr(VI) ion in a carbonic acid solution by the oxidizing slag that was discharged from the normal steelmaking process in an electric arc furnace. After the addition of the slag into the aqueous solution contained Cr(VI) ion, concentrations of Cr(VI) ion and total chromium (Cr(VI) + trivalent chromium (Cr(III)) ions decreased to lower detection limit of them. Therefore, the used slag could reduce Cr(VI) and fix Cr(III) ion on the slag. While Cr(VI) ion existed in the solution, iron did not dissolve from the slag. From the relation between predicted dissolution amount of iron(II) ion and amount of decrease in Cr(VI) ion, the Cr(VI) ion did not react with iron(II) ion dissolved from the slag. Therefore, Cr(VI) ion was removed by the reductive reaction between Cr(VI) ion and the iron(II) oxide (FeO) in the slag. This reaction progressed on the newly appeared surface of iron(II) oxide due to the dissolution of phase composed of calcium etc., which existed around iron(II) oxide grain in the slag.

  11. A twice liquid arc discharge approach for synthesis of visible-light-active nanocrystalline Ag:ZnO photocatalyst

    NASA Astrophysics Data System (ADS)

    Ashkarran, Ali Akbar

    2012-05-01

    Ag:ZnO hybrid nanostructures were successfully prepared by a twice arc discharge method in liquid. The visible light photocatalytic activities were successfully demonstrated for the degradation of Rhodamine B (Rh. B), Methyl orange (MO), and Methylene blue (MB) as standard organic compounds under the irradiation of 90 W halogen light for 2 h. The Ag:ZnO nanostructures were characterized by X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and ultraviolet-visible absorption spectroscopy (UV-Vis). The results revealed that the Ag:ZnO nanostructures extended the light absorption spectrum toward the visible region and significantly enhanced the Rh. B photodegradation under visible light irradiation. 3 mM Ag:ZnO nanostructures exhibited highest photocatalytic efficiency. It has been confirmed that the Ag:ZnO nanostructures could be excited by visible light ( E<3.3 eV). The significant enhancement in the Ag:ZnO nanostructures photocatalytic activity under visible light irradiation can be ascribed to the effect of physisorbed noble metal Ag by acting as electron traps in ZnO band gap. A mechanism for photocatalytic degradation of organic pollutant over Ag:ZnO photocatalyst was proposed based on our observations.

  12. Synthesis of branched, nano channeled, ultrafine and nano carbon tubes from PET wastes using the arc discharge method

    SciTech Connect

    Joseph Berkmans, A.; Jagannatham, M.; Priyanka, S.; Haridoss, Prathap

    2014-11-15

    Highlights: • Polymer wastes are converted into ultrafine and nano carbon tubes and spheres. • Simple process with a minimal processing time. • It is a catalyst free and solvent free approach. • This process forms branched ultrafine carbon tubules with nano channels. - Abstract: Upcycling polymer wastes into useful, and valuable carbon based materials, is a challenging process. We report a novel catalyst-free and solvent-free technique for the formation of nano channeled ultrafine carbon tubes (NCUFCTs) and multiwalled carbon nanotubes (MWCNTs) from polyethylene terephthalate (PET) wastes, using rotating cathode arc discharge technique. The soot obtain from the anode contains ultrafine and nano-sized solid carbon spheres (SCS) with a mean diameter of 221 nm and 100 nm, respectively, formed at the lower temperature region of the anode where the temperature is approximately 1700 °C. The carbon spheres are converted into long “Y” type branched and non-branched NCUFCTs and MWCNTs at higher temperature regions where the temperature is approximately 2600 °C, with mean diameters of 364 nm and 95 nm, respectively. Soot deposited on the cathode is composed of MWCNTs with a mean diameter of 20 nm and other nanoparticles. The tubular structures present in the anode are longer, bent and often coiled with lesser graphitization compared to the nanotubes in the soot on the cathode.

  13. Toxicity outcome in patients treated with modulated arc radiotherapy for localized prostate cancer

    PubMed Central

    Lengua, Rafael E.; Gonzalez, Maria F.; Barahona, Kaory; Ixquiac, Milton E.; Lucero, Juan F.; Montenegro, Erick; Lopez Guerra, Jose L.; Jaén, Javier; Linares, Luis A.

    2013-01-01

    Aim This study evaluates the acute toxicity outcome in patients treated with RapidArc for localized prostate cancer. Background Modern technologies allow the delivery of high doses to the prostate while lowering the dose to the neighbouring organs at risk. Whether this dosimetric advantage translates into clinical benefit is not well known. Materials and methods Between December 2009 and May 2012, 45 patients with primary prostate adenocarcinoma were treated using RapidArc. All patients received 1.8 Gy per fraction, the median dose to the prostate gland, seminal vesicles, pelvic lymph nodes and surgical bed was 80 Gy (range, 77.4–81 Gy), 50.4 Gy, 50.4 Gy and 77.4 Gy (range, 75.6–79.2 Gy), respectively. Results The time between the last session and the last treatment follow up was a median of 10 months (range, 3–24 months). The incidence of grade 3 acute gastrointestinal (GI) and genitourinary (GU) toxicity was 2.2% and 15.5%, respectively. Grade 2 acute GI and GU toxicity occurred in 30% and 27% of patients, respectively. No grade 4 acute GI and GU toxicity were observed. Older patients (>median) or patients with V60 higher than 35% had significantly higher rates of grade ≥2 acute GI toxicity compared with the younger ones. Conclusions RapidArc in the treatment of localized prostate cancer is tolerated well with no Grade >3 GI and GU toxicities. Older patients or patients with higher V60 had significantly higher rates of grade ≥2 acute GI toxicity. Further research is necessary to assess definitive late toxicity and tumour control outcome. PMID:25061516

  14. Toxicity outcome in patients treated with modulated arc radiotherapy for localized prostate cancer.

    PubMed

    Lengua, Rafael E; Gonzalez, Maria F; Barahona, Kaory; Ixquiac, Milton E; Lucero, Juan F; Montenegro, Erick; Lopez Guerra, Jose L; Jaén, Javier; Linares, Luis A

    2014-07-01

    This study evaluates the acute toxicity outcome in patients treated with RapidArc for localized prostate cancer. Modern technologies allow the delivery of high doses to the prostate while lowering the dose to the neighbouring organs at risk. Whether this dosimetric advantage translates into clinical benefit is not well known. Between December 2009 and May 2012, 45 patients with primary prostate adenocarcinoma were treated using RapidArc. All patients received 1.8 Gy per fraction, the median dose to the prostate gland, seminal vesicles, pelvic lymph nodes and surgical bed was 80 Gy (range, 77.4-81 Gy), 50.4 Gy, 50.4 Gy and 77.4 Gy (range, 75.6-79.2 Gy), respectively. The time between the last session and the last treatment follow up was a median of 10 months (range, 3-24 months). The incidence of grade 3 acute gastrointestinal (GI) and genitourinary (GU) toxicity was 2.2% and 15.5%, respectively. Grade 2 acute GI and GU toxicity occurred in 30% and 27% of patients, respectively. No grade 4 acute GI and GU toxicity were observed. Older patients (>median) or patients with V60 higher than 35% had significantly higher rates of grade ≥2 acute GI toxicity compared with the younger ones. RapidArc in the treatment of localized prostate cancer is tolerated well with no Grade >3 GI and GU toxicities. Older patients or patients with higher V60 had significantly higher rates of grade ≥2 acute GI toxicity. Further research is necessary to assess definitive late toxicity and tumour control outcome.

  15. Particle-in-cell and Monte Carlo collision simulations of the cathode sheath in an atmospheric direct-current arc discharge

    NASA Astrophysics Data System (ADS)

    Zhou, Wen; Guo, Heng; Jiang, Wei; Li, He-Ping; Li, Zeng-Yao; Lapenta, Giovanni

    2016-10-01

    A sheath is the transition region from plasma to a solid surface, which also plays a critical role in determining the behaviors of many lab and industrial plasmas. However, the cathode sheath properties in arc discharges are not well understood yet due to its multi-scale and kinetic features. In this letter, we have adopted an implicit particle-in-cell Monte Carlo collision (PIC-MCC) method to study the cathode sheath in an atmospheric arc discharge plasma. The cathode sheath thickness, number densities and averaged energies of electrons and ions, the electric field distribution, as well as the spatially averaged electron energy probability function (EEPF), are predicted self-consistently by using this newly developed kinetic model. It is also shown that the thermionic emission at the hot cathode surface is the dominant electron emission process to sustain the arc discharges, while the effects from secondary and field electron emissions are negligible. The present results verify the previous conjectures and experimental observations.

  16. Electromagnetic and acoustic bimodality for the detection and localization of electrical arc faults

    NASA Astrophysics Data System (ADS)

    Vasile, C.; Ioana, C.; Digulescu, A.; Candel, I.

    2016-12-01

    Electrical arc faults pose an important problem to electrical installations worldwide, be it production facilities or distribution systems. In this context, it is easy to assess the economic repercussions of such a fault, when power supply is cut off downstream of its location, while also realizing that an early detection of the on-site smaller scale faults would be of great benefit. This articles serves as a review of the current state-of-the-art work that has been carried out on the subject of detection and localization of electrical arc faults, by exploiting the bimodality of this phenomenon, which generates simultaneously electromagnetic and acoustic waves, propagating in a free space path. En experimental setup has been defined, to demonstrate principles stated in previous works by the authors, and signal processing methods have been used in order to determine the DTOA (difference-of-time-of-arrival) of the acoustic signals, which allows localization of the transient fault. In the end there is a discussion regarding the results and further works, which aims to validate this approach in more real-life applications.

  17. Co-axial discharges

    DOEpatents

    Luce, J. S.; Smith, L. P.

    1960-11-22

    An apparatus is described for producing coaxial arc discharges in an evacuated enclosure and within a strong, confining magnetic field. The arcs are maintained at a high potential difference. Electrons diffuse to the more positive arc from the negative arc, and positive ions diffuse from the more positive arc to the negative arc. Coaxial arc discharges have the advantuge that ions that return to strike the positive arc discharge will lose no energy since they do not strike a solid wall or electrode. These discharges are useful in confining an ionized plasma between the discharges and have the advantage of preventing impurities from the walls of the enclosure from entering the plasma area because of the arc barrier set up by the cylindrical outer arc. (auth)

  18. CO-AXIAL DISCHARGES

    DOEpatents

    Luce, J.S.; Smith, L.P.

    1960-11-22

    A method and apparatus are given for producing coaxial arc discharges in an evacuated enclosure and within a strong, confining magnetic field. The arcs are maintained at a high potential difference. Electrons will diffuse to the more positive arc from the negative arc, and positive ions will diffuse from the more positive arc to the negative arc. Coaxial arc discharges have the advantage that ions which return to strike the positive arc discharge will lose no energy since they do not strike a solid wall or electrode. Those discharges are useful in confining an ionized plasma between the discharges, and have the advantage of preventing impurities from the walls of the enclosure from entering ihe plasma area because of the arc barrier set up bv the cylindrical outer arc.

  19. Dosimetric analysis of isocentrically shielded volumetric modulated arc therapy for locally recurrent nasopharyngeal cancer

    PubMed Central

    Lu, Jia-Yang; Huang, Bao-Tian; Xing, Lei; Chang, Daniel T.; Peng, Xun; Xie, Liang-Xi; Lin, Zhi-Xiong; Li, Mei

    2016-01-01

    This study aimed to investigate the dosimetric characteristics of an isocentrically shielded RapidArc (IS-RA) technique for treatment of locally recurrent nasopharyngeal cancer (lrNPC). In IS-RA, the isocenter was placed at the center of the pre-irradiated brainstem (BS)/spinal cord (SC) and the jaws were set to shield the BS/SC while ensuring the target coverage during the whole gantry rotation. For fifteen patients, the IS-RA plans were compared with the conventional RapidArc (C-RA) regarding target coverage, organ-at-risk (OAR) sparing and monitor units (MUs). The relationship between the dose reduction of BS/SC and some geometric parameters including the angle extended by the target with respect to the axis of BS/SC (Ang_BSSC), the minimum distance between the target and BS/SC (Dist_Min) and the target volume were evaluated. The IS-RA reduced the BS/SC doses by approximately 1–4 Gy on average over the C-RA, with more MUs. The IS-RA demonstrated similar target coverage and sparing of other OARs except for slightly improved sparing of optic structures. More dose reduction in the isocentric region was observed in the cases with larger Ang_BSSC or smaller Dist_Min. Our results indicated that the IS-RA significantly improves the sparing of BS/SC without compromising dosimetric requirements of other involved structures for lrNPC. PMID:27173670

  20. Formation of Sn-M (M=Fe, Al, Ni) alloy nanoparticles by DC arc-discharge and their electrochemical properties as anodes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Gao, Song; Huang, Hao; Wu, Aimin; Yu, Jieyi; Gao, Jian; Dong, Xinglong; Liu, Chunjing; Cao, Guozhong

    2016-10-01

    A direct current arc-discharge method was applied to prepare the Sn-M (M=Fe, Al, Ni) bi-alloy nanoparticles. Thermodynamic is introduced to analyze the energy circumstances for the formation of the nanoparticles during the physical condensation process. The electrochemical properties of as-prepared Sn-M alloy nanoparticles are systematically investigated as anodes of Li-ion batteries. Among them, Sn-Fe nanoparticles electrode exhibits high Coulomb efficiency (about 71.2%) in the initial charge/discharge (257.9 mA h g-1/366.6 mA h g-1) and optimal cycle stability (a specific reversible capacity of 240 mA h g-1 maintained after 20 cycles) compared with others. Large differences in the electrochemical behaviors indicate that the chemical composition and microstructure of the nanoparticles determine the lithium-ion storage properties and the long-term cyclic stability during the charge/discharge process.

  1. Estimation of combined sewer overflow discharge: a software sensor approach based on local water level measurements.

    PubMed

    Ahm, Malte; Thorndahl, Søren; Nielsen, Jesper E; Rasmussen, Michael R

    2016-12-01

    Combined sewer overflow (CSO) structures are constructed to effectively discharge excess water during heavy rainfall, to protect the urban drainage system from hydraulic overload. Consequently, most CSO structures are not constructed according to basic hydraulic principles for ideal measurement weirs. It can, therefore, be a challenge to quantify the discharges from CSOs. Quantification of CSO discharges are important in relation to the increased environmental awareness of the receiving water bodies. Furthermore, CSO discharge quantification is essential for closing the rainfall-runoff mass-balance in combined sewer catchments. A closed mass-balance is an advantage for calibration of all urban drainage models based on mass-balance principles. This study presents three different software sensor concepts based on local water level sensors, which can be used to estimate CSO discharge volumes from hydraulic complex CSO structures. The three concepts were tested and verified under real practical conditions. All three concepts were accurate when compared to electromagnetic flow measurements.

  2. Carbon Nanotube Emissions from Arc Discharge Production: Classification of Particle Types with Electron Microscopy and Comparison with Direct Reading Techniques.

    PubMed

    Ludvigsson, Linus; Isaxon, Christina; Nilsson, Patrik T; Tinnerberg, Hakan; Messing, Maria E; Rissler, Jenny; Skaug, Vidar; Gudmundsson, Anders; Bohgard, Mats; Hedmer, Maria; Pagels, Joakim

    2016-05-01

    An increased production and use of carbon nanotubes (CNTs) is occurring worldwide. In parallel, a growing concern is emerging on the adverse effects the unintentional inhalation of CNTs can have on humans. There is currently a debate regarding which exposure metrics and measurement strategies are the most relevant to investigate workplace exposures to CNTs. This study investigated workplace CNT emissions using a combination of time-integrated filter sampling for scanning electron microscopy (SEM) and direct reading aerosol instruments (DRIs). Field measurements were performed during small-scale manufacturing of multiwalled carbon nanotubes using the arc discharge technique. Measurements with highly time- and size-resolved DRI techniques were carried out both in the emission and background (far-field) zones. Novel classifications and counting criteria were set up for the SEM method. Three classes of CNT-containing particles were defined: type 1: particles with aspect ratio length:width >3:1 (fibrous particles); type 2: particles without fibre characteristics but with high CNT content; and type 3: particles with visible embedded CNTs. Offline sampling using SEM showed emissions of CNT-containing particles in 5 out of 11 work tasks. The particles were classified into the three classes, of which type 1, fibrous CNT particles contributed 37%. The concentration of all CNT-containing particles and the occurrence of the particle classes varied strongly between work tasks. Based on the emission measurements, it was assessed that more than 85% of the exposure originated from open handling of CNT powder during the Sieving, mechanical work-up, and packaging work task. The DRI measurements provided complementary information, which combined with SEM provided information on: (i) the background adjusted emission concentration from each work task in different particle size ranges, (ii) identification of the key procedures in each work task that lead to emission peaks, (iii

  3. Carbon Nanotube Emissions from Arc Discharge Production: Classification of Particle Types with Electron Microscopy and Comparison with Direct Reading Techniques

    PubMed Central

    Ludvigsson, Linus; Isaxon, Christina; Nilsson, Patrik T.; Tinnerberg, Hakan; Messing, Maria E.; Rissler, Jenny; Skaug, Vidar; Gudmundsson, Anders; Bohgard, Mats; Hedmer, Maria; Pagels, Joakim

    2016-01-01

    Introduction: An increased production and use of carbon nanotubes (CNTs) is occurring worldwide. In parallel, a growing concern is emerging on the adverse effects the unintentional inhalation of CNTs can have on humans. There is currently a debate regarding which exposure metrics and measurement strategies are the most relevant to investigate workplace exposures to CNTs. This study investigated workplace CNT emissions using a combination of time-integrated filter sampling for scanning electron microscopy (SEM) and direct reading aerosol instruments (DRIs). Material and Methods: Field measurements were performed during small-scale manufacturing of multiwalled carbon nanotubes using the arc discharge technique. Measurements with highly time- and size-resolved DRI techniques were carried out both in the emission and background (far-field) zones. Novel classifications and counting criteria were set up for the SEM method. Three classes of CNT-containing particles were defined: type 1: particles with aspect ratio length:width >3:1 (fibrous particles); type 2: particles without fibre characteristics but with high CNT content; and type 3: particles with visible embedded CNTs. Results: Offline sampling using SEM showed emissions of CNT-containing particles in 5 out of 11 work tasks. The particles were classified into the three classes, of which type 1, fibrous CNT particles contributed 37%. The concentration of all CNT-containing particles and the occurrence of the particle classes varied strongly between work tasks. Based on the emission measurements, it was assessed that more than 85% of the exposure originated from open handling of CNT powder during the Sieving, mechanical work-up, and packaging work task. The DRI measurements provided complementary information, which combined with SEM provided information on: (i) the background adjusted emission concentration from each work task in different particle size ranges, (ii) identification of the key procedures in each work

  4. Influence of the Conductivity of the Discharge Liquid on the Microbicidal Effect of Transient Electric Arcs in Aqueous Systems

    PubMed Central

    Edebo, L.; Holme, T.; Selin, I.

    1969-01-01

    The microbicidal effect of electrical discharges on microorganisms suspended in the discharge liquid was reduced when the liquid contained high concentrations of inorganic salts (conductivity k ≥ 5 mmho/cm). A higher discharge voltage and a smaller distance between the submerged electrodes counteracted this reduction. The decrease in the microbicidal effect was accompanied by a change in the electrical current and by a decreased yield of microbicidal photons from the electric discharge. Images PMID:4886862

  5. Investigation of micro-structure and micro-hardness properties of 304L stainless steel treated in a hot cathode arc discharge plasma

    SciTech Connect

    Malik, Hitendra K.; Singh, Omveer; Dahiya, Raj P.

    2015-08-28

    We have established a hot cathode arc discharge plasma system, where different stainless steel samples can be treated by monitoring the plasma parameters and nitriding parameters independently. In the present work, a mixture of 70% N{sub 2} and 30% H{sub 2} gases was fed into the plasma chamber and the treatment time and substrate temperature were optimized for treating 304L Stainless Steel samples. Various physical techniques such as x-ray diffraction, energy dispersive x-ray spectroscopy and micro-vickers hardness tester were employed to determine the structural, surface composition and surface hardness of the treated samples.

  6. Investigation of micro-structure and micro-hardness properties of 304L stainless steel treated in a hot cathode arc discharge plasma

    NASA Astrophysics Data System (ADS)

    Malik, Hitendra K.; Singh, Omveer; Dahiya, Raj P.

    2015-08-01

    We have established a hot cathode arc discharge plasma system, where different stainless steel samples can be treated by monitoring the plasma parameters and nitriding parameters independently. In the present work, a mixture of 70% N2 and 30% H2 gases was fed into the plasma chamber and the treatment time and substrate temperature were optimized for treating 304L Stainless Steel samples. Various physical techniques such as x-ray diffraction, energy dispersive x-ray spectroscopy and micro-vickers hardness tester were employed to determine the structural, surface composition and surface hardness of the treated samples.

  7. Local stress distribution around garnet inclusions during hydration of granulite in the Bergen Arcs, Norway

    NASA Astrophysics Data System (ADS)

    Centrella, Stephen; Vrijmoed, Johannes C.; Putnis, Andrew; Austrheim, Håkon

    2017-04-01

    The importance of heterogeneous stress and pressure distribution within a rock has been established over the last decades (see review in Tajčmanová et al., 2015). During a hydration reaction, depending on whether the system is open to mass transfer, the volume changes of the reaction may be accommodated by removing material into the fluid phase that leaves the system (Centrella et al., 2015; Centrella et al., 2016). The magnitudes and the spatial distribution of stress and pressure that evolve during such processes is largely unknown. We present here a natural example where a granulite is hydrated at amphibolite facies conditions from the Bergen Arcs in Norway. Granulitic garnet is associated with kyanite and quartz on one side, and amphibole-biotite on the other side. The first couple replaces the plagioclase of the granulite matrix whereas the second replaces the garnet. We use electron probe microanalysis (EPMA) and X-ray mapping to investigate the spatial and possible temporal relationships between these two parageneses. Gresens' analysis has been used to determine the mass balance and the local volume changes associated with the two reactions. The reaction to kyanite+quartz induces a loss in volume compared to the original plagioclase whereas the second reaction amphibole+biotite gains volume compared to the original garnet. The specific mass evolution associated with both reactions suggests a local mass balance probably associated with a single hydration event. Using the methodology of Vrijmoed & Podladchikov (2015) we test whether the microstructure may be partly related to the local stress heterogeneity around the garnet inclusion. We evaluate the phase assemblage and distribution at chemical equilibrium under a given input pressure field that can be computed with the Thermolab software. By varying the input pressure field using the Finite Element Method and comparing the resulting equilibrium assemblage to the real data an estimate of the local stress

  8. Non-local Effects in a Stratified Glow Discharge With Dusty Particles

    SciTech Connect

    Sukhinin, G. I.; Fedoseev, A. V.; Ramazanov, T. S.; Amangaliyeva, R. Zh.; Dosbolayev, M. K.; Jumabekov, A. N.

    2008-09-07

    The work is aimed to describe non-local effects in the positive column of a low pressure stratified DC glow discharge in argon with dusty particles in a vertical cylindrical discharge tube. The numerical calculations of plasma parameters in the axis of the discharge tube were performed with the help of hybrid model based on the solution of non-local Boltzmann equation for EEDF. Distributions of optical emission from striations were measured experimentally. It is shown that in a stratified positive column the EEDF is not Maxwellian and even non-monotonous. Also, the effect of displacing of optical emission distribution relative to the electric field is shown both by numerical simulation and experimental measurements.

  9. RapidArc Planning and Delivery in Patients With Locally Advanced Head-and-Neck Cancer Undergoing Chemoradiotherapy

    SciTech Connect

    Doornaert, Patricia; Verbakel, Wilko F.A.R.; Bieker, Michael; Slotman, Ben J.; Senan, Suresh

    2011-02-01

    Purpose: Volumetric modulated arc therapy (RapidArc, Varian Medical Systems) permits the delivery of highly conformal dose distributions. We studied planning and delivery in patients who underwent RapidArc for locally advanced head-and-neck cancer (HNC). Methods and Materials: A total of 35 consecutive patients who completed RapidArc with concurrent chemotherapy for Stages III-IV tumors of the oro- and hypopharynx/larynx in our center were identified. All underwent bilateral neck irradiation and 21 patients had at least N2 disease. A simultaneous integrated boost (SIB) delivered 70 Gy (in 2 Gy/fraction) to the planning target volume (PTV){sub boost} and elective nodal regions (PTV{sub elect}) received 57.75 Gy. A standard planning constraint set was used and constraints for parotid glands were individually adapted. Treatments were delivered using two arcs after all plans were verified in a solid water phantom using GafChromic External Beam Therapy films. Results: RapidArc planning generally took 1.5-2 h, which was faster than with our previous seven-field intensity-modulated radiotherapy sliding window technique. Film dosimetry revealed that 0.6% of films exceeded a combination of dose differences {>=}3% or distance to agreement {>=}2 mm. More than 99% of both PTVs received {>=}95% of the prescription dose. Average plan conformity index was 1.13 and mean dose to ipsilateral and contralateral parotid glands were 31.4 Gy and 26.1 Gy, respectively. The mean beam-on time was <3 min and mean number of monitor units was 426. Conclusions: RapidArc achieved excellent target coverage and normal tissue sparing, with delivery completed in less than 3 min. RA is currently our standard intensity-modulated radiotherapy approach for advanced HNC.

  10. Non-local effects in a stratified glow discharge with dust particles

    NASA Astrophysics Data System (ADS)

    Sukhinin, G. I.; Fedoseev, A. V.; Ramazanov, T. S.; Amangaliyeva, R. Zh; Dosbalayev, M. K.; Jumabekov, A. N.

    2008-12-01

    The work is aimed at describing non-local effects in the positive column of a low-pressure stratified dc glow discharge in argon with dust particles in a vertical cylindrical discharge tube. Numerical calculations of plasma parameters in the axis of the discharge tube were performed with the help of a hybrid model based on the solution of a non-local Boltzmann equation for electron energy distribution function (EEDF). Axial distributions of optical emission from striations with dust particles were measured experimentally. Negatively charged dust particles in a low-pressure stratified gas discharge should levitate at the anode-side branch of an electric field distribution above its maximum. At the same time the experiments showed that the dust particles levitate at the cathode side of a stratum. This paradox is explained by the fact that in a low-pressure striated discharge the optical emission distribution is displaced relative to the electric field distribution that was shown both by numerical simulations and experimental measurements.

  11. The making of local hospital discharge arrangements: specifying the role of professional groups.

    PubMed

    Burau, Viola; Bro, Flemming

    2015-08-04

    Timely discharge is a key component of contemporary hospital governance and raises questions about how to move to more explicit discharge arrangements. Although associated organisational changes closely intersect with professional interests, there are relatively few studies in the literature on hospital discharge that explicitly examine the role of professional groups. Recent contributions to the literature on organisational studies of the professions help to specify how professional groups in hospitals contribute to the introduction and routinisation of discharge arrangements. This study builds on a view of organisational and professional projects as closely intertwined, where professionals take up organising roles and where organisations shape professionalism. The analysis is based on a case study of the introduction and routinisation of explicit discharge arrangements for patients with prostate cancer in two hospitals in Denmark. This represents a typical case that involves changes in professional practice without being first and foremost a professional project. The multiple case design also makes the findings more robust. The analysis draws from 12 focus groups with doctors, nurses and secretaries conducted at two different stages in the process of the making of the local discharge arrangements. From the analysis, two distinct local models of discharge arrangements that connect more or less directly to existing professional practice emerge: an 'add-on' model, which relies on extra resources, special activities and enforced change; and an 'embedded model', which builds on existing ways of working, current resources, and perspectives of professional groups. The two models reveal differences in the roles of professional groups in terms of their stakes and involvement in the process of organisational change: whereas in the 'add on' model the professional groups remain at a distance, in the 'embedded model' they are closely engaged. In terms of understanding the

  12. Separation of Radio-Frequency Sources and Localization of Partial Discharges in Noisy Environments

    PubMed Central

    Robles, Guillermo; Fresno, José Manuel; Martínez-Tarifa, Juan Manuel

    2015-01-01

    The detection of partial discharges (PD) can help in early-warning detection systems to protect critical assets in power systems. The radio-frequency emission of these events can be measured with antennas even when the equipment is in service which reduces dramatically the maintenance costs and favours the implementation of condition-based monitoring systems. The drawback of these type of measurements is the difficulty of having a reference signal to study the events in a classical phase-resolved partial discharge pattern (PRPD). Therefore, in open-air substations and overhead lines where interferences from radio and TV broadcasting and mobile communications are important sources of noise and other pulsed interferences from rectifiers or inverters can be present, it is difficult to identify whether there is partial discharges activity or not. This paper proposes a robust method to separate the events captured with the antennas, identify which of them are partial discharges and localize the piece of equipment that is having problems. The separation is done with power ratio (PR) maps based on the spectral characteristics of the signal and the identification of the type of event is done localizing the source with an array of four antennas. Several classical methods to calculate the time differences of arrival (TDOA) of the emission to the antennas have been tested, and the localization is done using particle swarm optimization (PSO) to minimize a distance function. PMID:25923935

  13. Separation of radio-frequency sources and localization of partial discharges in noisy environments.

    PubMed

    Robles, Guillermo; Fresno, José Manuel; Martínez-Tarifa, Juan Manuel

    2015-04-27

    The detection of partial discharges (PD) can help in early-warning detection systems to protect critical assets in power systems. The radio-frequency emission of these events can be measured with antennas even when the equipment is in service which reduces dramatically the maintenance costs and favours the implementation of condition-based monitoring systems. The drawback of these type of measurements is the difficulty of having a reference signal to study the events in a classical phase-resolved partial discharge pattern (PRPD). Therefore, in open-air substations and overhead lines where interferences from radio and TV broadcasting and mobile communications are important sources of noise and other pulsed interferences from rectifiers or inverters can be present, it is difficult to identify whether there is partial discharges activity or not. This paper proposes a robust method to separate the events captured with the antennas, identify which of them are partial discharges and localize the piece of equipment that is having problems. The separation is done with power ratio (PR) maps based on the spectral characteristics of the signal and the identification of the type of event is done localizing the source with an array of four antennas. Several classical methods to calculate the time differences of arrival (TDOA) of the emission to the antennas have been tested, and the localization is done using particle swarm optimization (PSO) to minimize a distance function.

  14. LES of a Jet Excited by the Localized Arc Filament Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2011-01-01

    The fluid dynamics of a high-speed jet are governed by the instability waves that form in the free-shear boundary layer of the jet. Jet excitation manipulates the growth and saturation of particular instability waves to control the unsteady flow structures that characterize the energy cascade in the jet.The results may include jet noise mitigation or a reduction in the infrared signature of the jet. The Localized Arc Filament Plasma Actuators (LAFPA) have demonstrated the ability to excite a high-speed jets in laboratory experiments. Extending and optimizing this excitation technology, however, is a complex process that will require many tests and trials. Computational simulations can play an important role in understanding and optimizing this actuator technology for real-world applications. Previous research has focused on developing a suitable actuator model and coupling it with the appropriate computational fluid dynamics (CFD) methods using two-dimensional spatial flow approximations. This work is now extended to three-dimensions (3-D) in space. The actuator model is adapted to a series of discrete actuators and a 3-D LES simulation of an excited jet is run. The results are used to study the fluid dynamics near the actuator and in the jet plume.

  15. Localization of focal epileptic discharges using functional connectivity magnetic resonance imaging

    PubMed Central

    Stufflebeam, Steven M.; Liu, Hesheng; Sepulcre, Jorge; Tanaka, Naoaki; Buckner, Randy L.; Madsen, Joseph R.

    2011-01-01

    Object In patients with medically refractory epilepsy the accurate localization of the seizure onset zone is critical for successful surgical treatment. The object of this study was to investigate whether the degree of coupling of spontaneous brain activity as measured with functional connectivity MR imaging (fcMR imaging) can accurately identify and localize epileptic discharges. Methods The authors studied 6 patients who underwent fcMR imaging presurgical mapping and subsequently underwent invasive electroencephalography. Results Focal regions of statistically significant increases in connectivity were identified in 5 patients when compared with an ad hoc normative sample of 300 controls. The foci identified by fcMR imaging overlapped the epileptogenic areas identified by invasive encephalography in all 5 patients. Conclusions These results suggest that fcMR imaging may provide an effective high–spatial resolution and noninvasive method of localizing epileptic discharges in patients with refractory epilepsy. PMID:21351832

  16. Localized brain differences in Arc expression between mice showing low vs. high propensity to ethanol sensitization.

    PubMed

    Nona, Christina N; Lam, Marcus; Nobrega, José N

    2016-03-01

    Behavioral sensitization to ethanol (EtOH) manifests as a progressive and enduring increase in locomotor activity with repeated drug exposure. However, not all mice sensitize to EtOH and the neuronal mechanisms mediating vulnerability and resistance to EtOH sensitization remain unclear. We examined regional brain expression of the immediate early gene activity-regulated cytoskeleton-associated protein (Arc) in order to identify brain areas in which neuroplastic changes may contribute to the development and expression of EtOH sensitization. Male DBA/2J mice received 5 biweekly injections of EtOH (2.2g/kg, i.p.) or saline (SAL). They were categorized as high- (HS) or low-sensitized (LS) on the basis of final locomotor activity scores. In both LS and HS mice sacrificed after the last sensitization injection, Arc expression was decreased throughout the brain in comparison to SAL animals. A similar pattern was seen in mice sacrificed after an EtOH challenge two weeks after the last sensitization injection. However in this cohort, Arc expression was significantly increased in the central amygdala (CeA) in LS mice and in SAL mice receiving EtOH for the first time. No significant increases in Arc expression were seen in brains of sensitized (HS) animals. These results indicate an acute EtOH challenge results in different patterns of Arc expression in brains of LS, HS, and SAL mice. The dramatic increases in Arc expression in the CeA in LS and SAL mice showing little or no behavioral activation suggests that neural activity in this region may serve to inhibit the stimulant effects of EtOH. The observation that HS mice do not show increases in Arc expression with an EtOH challenge suggests the possibility that increased tolerance to the Arc-inducing effects of EtOH may be a factor in behavioral sensitization.

  17. Modelling of local ion nitriding in a glow discharge with hollow cathode

    NASA Astrophysics Data System (ADS)

    Budilov, V.; Ramazanov, K.; Khusainov, Yu

    2017-05-01

    The paper presents the results of computer calculations of glow discharge plasma parameters in a hollow cathode zone and modeling of thermal and diffusion processes at local ion nitriding with a hollow cathode. The proposed model of a glow discharge with a hollow cathode with sufficient accuracy allowed to describe the distribution of plasma parameters in a cathode void. Values of plasma parameters in a cathode void formed by a mesh screen and cathode surface were obtained via the probe method. It was found that the use of hollow cathode effect allows to increase the concentration of ions near the treated surface by 1.5 times. The suggested computer model allows to predict the distribution of the temperature field and depth of a diffusion layer at local ion nitriding with a hollow cathode for various configurations and sizes.

  18. A Novel Partial Discharge Localization Method in Substation Based on a Wireless UHF Sensor Array

    PubMed Central

    Li, Zhen; Luo, Lingen; Zhou, Nan; Sheng, Gehao; Jiang, Xiuchen

    2017-01-01

    Effective Partial Discharge (PD) localization can detect the insulation problems of the power equipment in a substation and improve the reliability of power systems. Typical Ultra-High Frequency (UHF) PD localization methods are mainly based on time difference information, which need a high sampling rate system. This paper proposes a novel PD localization method based on a received signal strength indicator (RSSI) fingerprint to quickly locate the power equipment with potential insulation defects. The proposed method consists of two stages. In the offline stage, the RSSI fingerprint data of the detection area is measured by a wireless UHF sensor array and processed by a clustering algorithm to reduce the PD interference and abnormal RSSI values. In the online stage, when PD happens, the RSSI fingerprint of PD is measured via the input of pattern recognition for PD localization. To achieve an accurate localization, the pattern recognition process is divided into two steps: a preliminary localization is implemented by cluster recognition to reduce the localization region, and the compressed sensing algorithm is used for accurate PD localization. A field test in a substation indicates that the mean localization error of the proposed method is 1.25 m, and 89.6% localization errors are less than 3 m. PMID:28820444

  19. A Novel Partial Discharge Localization Method in Substation Based on a Wireless UHF Sensor Array.

    PubMed

    Li, Zhen; Luo, Lingen; Zhou, Nan; Sheng, Gehao; Jiang, Xiuchen

    2017-08-18

    Effective Partial Discharge (PD) localization can detect the insulation problems of the power equipment in a substation and improve the reliability of power systems. Typical Ultra-High Frequency (UHF) PD localization methods are mainly based on time difference information, which need a high sampling rate system. This paper proposes a novel PD localization method based on a received signal strength indicator (RSSI) fingerprint to quickly locate the power equipment with potential insulation defects. The proposed method consists of two stages. In the offline stage, the RSSI fingerprint data of the detection area is measured by a wireless UHF sensor array and processed by a clustering algorithm to reduce the PD interference and abnormal RSSI values. In the online stage, when PD happens, the RSSI fingerprint of PD is measured via the input of pattern recognition for PD localization. To achieve an accurate localization, the pattern recognition process is divided into two steps: a preliminary localization is implemented by cluster recognition to reduce the localization region, and the compressed sensing algorithm is used for accurate PD localization. A field test in a substation indicates that the mean localization error of the proposed method is 1.25 m, and 89.6% localization errors are less than 3 m.

  20. On the influence of localized electric fields and field-aligned currents associated with polar arcs on the global potential distribution

    SciTech Connect

    Marklund, G.T.; Blomberg, L.G. )

    1991-08-01

    The influence of localized field-aligned current, associated with intense transpolar arcs mostly occurring during periods of northward interplaentary magnetic field (IMF), on the global electrodynamics has been investigated using a numerical simulation model. Idealized field-aligned current distributions representing both the region 1/2 system of the auroral oval and the transpolar arc as well as a corresponding ionospheric conductivity distribution are fed into the model to calculate the potential distributions. The transpolar arc has been represented by a few alternative field-aligned current distributions which are different in the way the downward return currents are distributed in the ionosphere. If the conductivity of the main auroral oval is comparable to that of the polar arc the dusk cell will have two local potential minima and thus a region of weak antisunward convection in between. Depending on the direction of the polar arc current sheets the dawn-dusk electric field will either be reversed (or weakened) or intensified at the location of the transpolar arc. The presence of a reversal depend, however, not only on the relative magnitude between the polar arc current sand those of the region 1/2 system but also on the characteristics of the acceleration region and of the conductivity distribution associated with the polar arc. Comparisons are made between the model results and Viking electric field data for a number of polar arc crossings to reveal the most common electrodynamical signatures of these auroral phenomena.

  1. Influence of the oxygen concentration on the formation of crystalline phases of TiO2 during the low-pressure arc-discharge plasma synthesis

    NASA Astrophysics Data System (ADS)

    Ushakov, A. V.; Karpov, I. V.; Lepeshev, A. A.

    2016-02-01

    The synthesis of titanium dioxide (TiO2) nanoparticles with different percentage of anatase and rutile phases is investigated. The synthesis is performed by controlling the oxygen percentage in the gas mixture in the plasmachemical evaporation-condensation process employing a low-pressure arc discharge. In all our experiments, the pressure in the plasmachemical reactor and the average size of particles remain constant and are 60 Pa and 6 nm, respectively. The crystal structure of synthesized TiO2 is studied using X-ray diffraction; the morphology of the particles is analyzed employing transmission electron microscopy. Using X-ray phase analysis, it is established that the concentration of the TiO2 anatase phase decreases upon a decrease in the oxygen concentration in the gas mixture. It is shown that the TiO2 anatase phase is more efficient for photocatalytic decomposition of methylene blue than the rutile phase.

  2. Correlation of some radiative processes resulting from electronic and vibrational spectra of a CN molecule excited in an electric arc discharge

    NASA Astrophysics Data System (ADS)

    Iova, Iancu; Bazavan, M.; Biloiu, Costel; Ilie, Gheorghe; Bulinski, M.

    1998-07-01

    The molecular vibration temperature of the plasma from an interrupt arc discharge in air at atmospheric pressure and at current intensities in the range of 2 divided by 8 Amperes, using electronic and vibration bands of violet [B2(Sigma) + - X2(Sigma) +] and red [A2(Pi) - X2(Sigma) +] systems of the CN molecule was determined. At the equilibrium temperature of 6400 K, 27 lines of Ti, contained as impurity in coal electrode were found. These spectral lines were found in the 247 divided by 340 nm spectral range, having the upper levels of the excitation energies in the 3.60 divided by 5.69 eV range, in the neighborhood of the energy of dissociation of the CN molecule on the fundamental electronic state. Some considerations about the vibrational states populations are also made.

  3. Instability of a Short Anodic Arc Used for Synthesis of Nanomaterials

    NASA Astrophysics Data System (ADS)

    Gershman, Sophia; Raitses, Yevgeny

    2016-10-01

    The short anodic arc discharge is used for the synthesis of nanomaterials and had been presumed stable. We report the results of electrical and fast imaging measurements that reveal a combined motion of the arc column and the arc attachment region to the anode when the arc is operated with a high ablation rate. The arc exhibits a negative differential resistance before the arc motion occurs. The observed arc motion correlates with the arc voltage and current oscillations. The characteristic time of these instabilities is in a 10-3 sec range. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. The measured negative differential resistance of the arc during the oscillations indirectly supports the thermal model. Our model suggests that the injection of the ablating material into the plasma locally reduces the energy flux to the surface and leads to the arc shifting to the adjacent position. The observed arc motion can potentially cause the mixing of the various nanoparticles synthesized in the arc in the high ablation regime leading to the poor selectivity characteristic of the arc synthesis of nanomaterials. US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  4. Low pressure arc electrode

    NASA Technical Reports Server (NTRS)

    Lenn, P. D.; Richter, R.

    1970-01-01

    Reducing the pressure in the vicinity of the arc attachment point by allowing the gas to flow through a supersonic nozzle minimizes local heating rates, prevents ablation, and increases the efficiency of coaxial gas-flow arcs.

  5. Synthesis of few-walled carbon nanotube-Rh nanoparticles by arc discharge: Effect of selective oxidation

    SciTech Connect

    Zhang Yanfeng

    2012-06-15

    Highly crystalline rhodium (Rh) nanoparticles supported on carbon nanotubes were prepared by selective oxidation method. Carbon nanotubes and FeRh nanoparticles were simultaneously generated in hydrogen arc plasma. The as-grown nanomaterials can be purified by heat treatment in open air and by soaking in HCl. X-ray diffraction and selected area electron diffraction results reveal that as-grown FeRh nanoparticles have a typical chemical CsCl-type structure which can be transformed into a face-centered cubic structure by thermal annealing in the purification process. The purification process is selective toward the removal of the amorphous carbon coating the nanoparticles, and transforms Fe to Fe{sub 2}O{sub 3}. Fe{sub 2}O{sub 3} can be easily dissolved in hydrochloric acid, leaving carbon nanotubes-Rh nanoparticles. Rh nanoparticles with diameters of 2-60 nm are deposited uniformly on the surface of the carbon nanotube bundles. This simple and selective chemistry offers a new process for synthesizing and controlling Fe content in carbon nanotube-FeRh nanoparticles. Highlights: Black-Right-Pointing-Pointer High-crystallinity CNTs and FeRh nanoparticles were simultaneously generated in arc plasma. Black-Right-Pointing-Pointer The diameter distribution of CNTs depends on different gases. Black-Right-Pointing-Pointer Heat treatment in open air and soaking in HCl can convert CNTs-FeRh to CNTs-Rh. Black-Right-Pointing-Pointer The selective oxidation mechanisms of metal nanoparticles and carbon materials differ.

  6. The study of micro-arc discharges during cathodic plasma electrolysis of refractory metals using the spectral line shape of Na I lines

    NASA Astrophysics Data System (ADS)

    Jovović, Jovica; Stojadinović, Stevan; Tadić, Nenad; Vasilić, Rastko; Šišović, Nikola M.

    2016-03-01

    The micro-arc discharges during cathodic plasma electrolysis of refractory metals (Zr, Ti, Ta) are studied by means of optical emission spectroscopy. The fitting procedure based on three mutually shifted profiles is developed to analyze the complex line shape of Na I 568.64 nm and 615.86 nm doublets. Each profile includes effects of instrumental, Doppler, Stark, van der Waals and resonance broadening. The results show the existence of three discharge zones with electron number density values Ne1=7× 1014 \\text{cm}-3 , Ne2=(0.5\\text{--}1)× 1016 \\text{cm}-3 and Ne3= (1.5\\text{--}2.8)× 1016 \\text{cm}-3 while those of sodium ground-state atoms are Ng1=1.4×1017 \\text{cm}-3 , Ng2=3.6×1017 \\text{cm}-3 and Ng3=(1.7\\text{--}3.7)×1018 \\text{cm}-3 .

  7. Localization of deformable tumors from short-arc projections using Bayesian estimation

    SciTech Connect

    Hoegele, W.; Zygmanski, P.; Dobler, B.; Kroiss, M.; Koelbl, O.; Loeschel, R.

    2012-12-15

    Purpose: The authors present a stochastic framework for radiotherapy patient positioning directly utilizing radiographic projections. This framework is developed to be robust against anatomical nonrigid deformations and to cope with challenging imaging scenarios, involving only a few cone beam CT projections from short arcs. Methods: Specifically, a Bayesian estimator (BE) is explicitly derived for the given scanning geometry. This estimator is compared to reference methods such as chamfer matching (CM) and the minimization of the median absolute error adapted as tools of robust image processing and statistics. In order to show the performance of the stochastic short-arc patient positioning method, a CIRS IMRT thorax phantom study is presented with movable markers and the utilization of an Elekta Synergy{sup Registered-Sign} XVI system. Furthermore, a clinical prostate CBCT scan of a Varian{sup Registered-Sign} On-Board Imager{sup Registered-Sign} system is utilized to investigate the robustness of the method for large variations of image quality (anterior-posterior vs lateral views). Results: The results show that the BE shifts reduce the initial setup error of up to 3 cm down to 3 mm at maximum for an imaging arc as short as 10 Degree-Sign while CM achieves residual errors of 7 mm at maximum only for arcs longer than 40 Degree-Sign . Furthermore, the BE can compensate robustly for low image qualities using several low quality projections simultaneously. Conclusions: In conclusion, an estimation method for marker-based patient positioning for short imaging arcs is presented and shown to be robust and accurate for deformable anatomies.

  8. Physics of arcing, and implications to sputter deposition

    SciTech Connect

    Anders, Andre

    2003-12-15

    Arcing is a well-known, unwanted discharge regime observed on the surface of sputtering targets. The discharge voltage breaks down to less than 50 V while the current jumps to elevated levels. Arcing is unwanted because it prevents uniform deposition and creates particulates. The issue of arcing has been dealt with by target surface conditioning and by using modern power supplies that have arc suppression incorporated. With increasing quality requirements in terms of uniformity of coatings, and absence of particulates, especially for electrochromic and other advanced coatings applications, the issue of arcing warrants a closer examination with the goal to find other, physics-based, and hopefully better approaches of arcing prevention. From a physics point of view, the onset of arcing is nothing else than the transition of the discharge to a cathodic arc mode, which is characterized by the ignition of non-stationary arc spots. Arc spots operate by a sequence of microexplosions, enabling explosive electron emission, as opposed to secondary electron emission. Arc spots and their fragments have a size distribution in the micrometer and sub-micrometer range, and a characteristic time distribution that has components shorter than microseconds. Understanding the ignition conditions of arc spots are of central physical interest. Spot ignition is associated with electric field enhancement, which can be of geometric nature (roughness,particles), or chemical nature (e.g. oxide formation) and related local accumulation of surface charge. Therefore, it is clear that these issues are of particular concern when operating with high-density plasmas, such as in high-power pulsed sputtering, and when using reactive sputter gases.

  9. Spatial distribution of submarine groundwater discharge and associated nutrients within a local coastal area.

    PubMed

    Hosono, Takahiro; Ono, Masahiko; Burnett, William C; Tokunaga, Takahiro; Taniguchi, Makoto; Akimichi, Tomoya

    2012-05-15

    To understand the local-scale distribution of submarine groundwater discharge (SGD) and dissolved nutrients, a multiple-detector (222)Rn monitoring survey was undertaken along the Mt. Chokai volcanic coast in northern Japan. The surveys revealed that the highest SGD (calculated to be 6.2 × 10(4) m(3) d(-1), within an area of 2 × 10(4) m(2)) with the greatest nutrient fluxes (sum of NO(3)(-), NO(2)(-), and NH(4)(+) (DIN): 9.2 × 10(2) mol d(-1); PO(4)(3-) (DIP): 56 mol d(-1)) is present at the edge of the youngest volcanic lava flow in the area. Recharged groundwater transports nutrients through porous volcanic flows and discharges as SGD near shore. Our results demonstrate that the spatial distribution of SGD in the study area is closely regulated by the local geology and topography. Furthermore, we show that continuous (222)Rn monitoring with a multidetector system at boat speeds of 1-2 knots provides details at a scale one order of magnitude greater than has been reported previously. In addition, the results of our study suggest that SGD-borne DIP may play an important role in the important local oyster production.

  10. Control of a shock wave-boundary layer interaction using localized arc filament plasma actuators

    NASA Astrophysics Data System (ADS)

    Webb, Nathan Joseph

    Supersonic flight is currently possible, but expensive. Inexpensive supersonic travel will require increased efficiency of high-speed air entrainment, an integral part of air-breathing propulsion systems. Although mixed compression inlet geometry can significantly improve entrainment efficiency, numerous Shock Wave-Boundary Layer Interactions (SWBLIs) are generated in this configuration. The boundary layer must therefore develop through multiple regions of adverse pressure gradient, causing it to thicken, and, in severe cases, separate. The associated increase in unsteadiness can have adverse effects on downstream engine hardware. The most severe consequence of these interactions is the increased aerodynamic blockage generated by the thickened boundary layer. If the increase is sufficient, it can choke the flow, causing inlet unstart, and resulting in a loss of thrust and high transient forces on the engine, airframe, and aircraft occupants. The potentially severe consequences associated with SWBLIs require flow control to ensure proper operation. Traditionally, boundary layer bleed has been used to control the interaction. Although this method is effective, it has inherent efficiency penalties. Localized Arc Filament Plasma Actuators (LAFPAs) are designed to generate perturbations for flow control. Natural flow instabilities act to amplify certain perturbations, allowing the LAFPAs to control the flow with minimal power input. LAFPAs also have the flexibility to maintain control over a variety of operating conditions. This work seeks to examine the effectiveness of LAFPAs as a separation control method for an oblique, impinging SWBLI. The low frequency unsteadiness in the reflected shock was thought to be the natural manifestation of a Kelvin-Helmholtz instability in the shear layer above the separation region. The LAFPAs were therefore placed upstream of the interaction to allow their perturbations to convect to the receptivity region (near the shear layer origin

  11. Capacitive coupled RF discharge: modelling at the local statement of the problem

    NASA Astrophysics Data System (ADS)

    Badriev, I. B.; Chebakova, V. Yu; Zheltukhin, V. S.

    2017-01-01

    In this paper a mathematical model of capacitively coupled RF discharge at atmospheric pressure is constructed, a method of numerical realization of the model is developed, and the numerical calculations are carried out. Comparison of the results of the numerical experiments with the data of other authors, in particular, with the experimental data, is demonstrated as well a model adequacy as effectiveness of the numerical method. A results of calculations of the model problem at pressure of 760 Torr, frequency of generator of 13.76 MHz and interelectrode distance of 20mm, in local approximation are presented.

  12. A topological classification of billiards in locally planar domains bounded by arcs of confocal quadrics

    SciTech Connect

    Fokicheva, V V

    2015-10-31

    A new class of integrable billiard systems, called generalized billiards, is discovered. These are billiards in domains formed by gluing classical billiard domains along pieces of their boundaries. (A classical billiard domain is a part of the plane bounded by arcs of confocal quadrics.) On the basis of the Fomenko-Zieschang theory of invariants of integrable systems, a full topological classification of generalized billiards is obtained, up to Liouville equivalence. Bibliography: 18 titles.

  13. Nonmetallic Arc Electrode Composed of Water and Ceramic

    NASA Astrophysics Data System (ADS)

    Deguchi, Mikio

    2008-09-01

    A novel nonmetallic arc electrode named the water-ceramic electrode, which is a combination of water and a ceramic component, is demonstrated. In the water-ceramic electrode, water and the ceramic component are exposed to the discharge space. The metal electrode is completely covered with water and is not exposed to the arc plasma. Under discharge, the ceramic component locally becomes incandescent, where the arc column terminates. The functions of the water and ceramic component are considered to be analogous to those of molten wax and the wick of a candle, respectively. The most remarkable feature of the water-ceramic electrode is that the ceramic component, which is a natural insulator and a representative heatproof material, becomes easily incandescent and locally melts with only an electric discharge.

  14. Comparison of Three Methods for Localizing Interictal Epileptiform Discharges with Magnetoencephalography

    PubMed Central

    Shiraishi, Hideaki; Ahlfors, Seppo P.; Stufflebeam, Steven M.; Knake, Susanne; Larsson, Pål G.; Hämäläinen, Matti S.; Takano, Kyoko; Okajima, Maki; Hatanaka, Keisaku; Saitoh, Shinji; Dale, Anders M.; Halgren, Eric

    2011-01-01

    Purpose To compare three methods of localizing the source of epileptiform activity recorded with magnetoencephalography (MEG): equivalent current dipole (ECD), minimum current estimate (MCE), and dynamic statistical parametric mapping (dSPM), and to evaluate the solutions by comparison with clinical symptoms and other electrophysiological and neuroradiological findings. Methods Fourteen children of 3 to 15 years old were studied. MEG was collected with a whole-head 204-channel helmet-shaped sensor array. We calculated ECDs and made MCE and dSPM movies to estimate the cortical distribution of interictal epileptic discharges (IED) in these patients. Results The results for 4 patients with localization related epilepsy (LRE) and 1 patient with Landau-Kleffner Syndrome were consistent among all 3 analysis methods. In the rest of the patients MCE and dSPM suggested multifocal or widespread activity; in these patients the ECD results were so scattered that interpretation of the results was not possible. For 9 patients with LRE and generalized epilepsy, the epileptiform discharges were wide-spread or only slow waves, but dSPM suggested a possible propagation path of the IED. Conclusion MCE and dSPM could identify the propagation of epileptiform activity with high temporal resolution. The results of dSPM were more stable because the solutions were less sensitive to background brain activity. PMID:21946369

  15. DISCHARGE IMPROVEMENT THROUGH CONTROL OF NEOCLASSICAL TEARING MODES BY LOCALIZED ECCD IN DIII-D

    SciTech Connect

    PRATER,R; LAHAYE,RJ; LOHR,J; LUCE,TC; PETTY,CC; FERRON,JR; HUMPHREYS,DA; STRAIT,EJ; PERKINS,FW; HARVEY,RW

    2002-10-01

    A271 DISCHARGE IMPROVEMENT THROUGH CONTROL OF NEOCLASSICAL TEARING MODES BY LOCALIZED ECCD IN DIII-D. Neoclassical tearing modes (NTMs) are MHD modes which can limit the performance of high beta discharges in tokamaks, in some cases leading to a major disruption. The destabilizing effect which results in NTM growth is a helical decrease in the bootstrap current caused by a local reduction of the plasma pressure gradient by seed magnetic islands. The NTM is particularly well suited to control since the mode is linearly stable although nonlinearly unstable, so if the island amplitude can be decreased below a threshold size the mode will decay and vanish. One means of shrinking the island is the replacement of the missing bootstrap current by a localized current generated by electron cyclotron current drive (ECCD). This method has been applied to the m=3/n=2 neoclassical tearing mode in DIII-D, in H-mode plasmas with ongoing ELMs and sawteeth, both of which generate seed islands periodically. In the case of the 3/2 mode, full suppression was obtained robustly by applying about 1.5 MW of ECCD very near the rational surface of the mode. When the mode first appears in the plasma the stored energy decreases by 20%, but after the mode is stabilized by the ECCD the beta may be raised above the initial threshold pressure by 20% by additional neutral beam heating, thereby generating an improvement in the limiting beta of nearly a factor 2. An innovative automated search algorithm was implemented to find and retain the optimum location for the ECCD in the presence of the mode.

  16. Interbasin flow revisited: The contribution of local recharge to high-discharge springs, Death Valley, CA

    NASA Astrophysics Data System (ADS)

    Anderson, Katherine; Nelson, Stephen; Mayo, Alan; Tingey, David

    2006-05-01

    Springs in the Furnace Creek area (Texas, Travertine, and Nevares Springs) of Death Valley National Park exhibit high discharge rates and depleted δ18O VSMOW (˜-13‰) and δD VSMOW (˜-102‰) values. Isotopic depletion of this magnitude and large spring fluxes (˜10,000 L/min) suggests that modern local recharge in the arid Furnace Creek drainage cannot be responsible for spring fluxes. An alternate explanation, interbasin flow, is difficult to envisage due to the stratigraphic and structural relationships of bedrock in intervening ranges, although it is the most common conceptual model for Furnace Creek spring flows. High-flux springs at Furnace Creek nonetheless respond modestly to modern climate in terms of discharge rate and isotopic composition. Hydrographs show a climate response and variations in time-series stable isotope data of widely spaced springs track one another. Small, but measurable quantities of tritium (<0.2 TU) were found at Nevares Spring, also suggesting a component of modern recharge. Thus, whatever the main source of water for these springs may be, there appears to be a subtle, but recent climatic influence. Estimates of flow at nearby mountain springs produce discharge rates per square kilometer of catchment that, by analogy, could support from 20 to 300% of the flow at large Death Valley springs under the current climate. Yet, 14C model ages suggest valley-bottom springs at Furnace Creek (5500-14,500 yr) contain a large component of older water, suggesting that much of the water was recharged during a pluvial period (Younger Dryas?) when net infiltration would have been much higher and isotopically depleted. 14C model ages are also of similar age, or younger, than many 'up gradient' waters, rather than being older as would be expected for interbasin flow. Chemical evolution models of solutes are consistent with both local recharge and interbasin transfer from Ash Meadows. However, when considered with isotopic constraints, interbasin

  17. INTENSE ENERGETIC GAS DISCHARGE

    DOEpatents

    Luce, J.S.

    1960-03-01

    A method and apparatus for initiating and sustaining an energetic gas arc discharge are described. A hollow cathode and a hollow anode are provided. By regulating the rate of gas flow into the interior of the cathode, the arc discharge is caused to run from the inner surface of the cathode with the result that adequate space-charge neutralization is provided inside the cathode but not in the main arc volume. Thus, the gas fed to the cathode is substantially completely ionized before it leaves the cathode, with the result that an energetic arc discharge can be maintained at lower operating pressures.

  18. Self-mode-locking in erbium-doped fibre lasers with saturable polymer film absorbers containing single-wall carbon nanotubes synthesised by the arc discharge method

    NASA Astrophysics Data System (ADS)

    Tausenev, Anton V.; Obraztsova, Elena D.; Lobach, A. S.; Chernov, A. I.; Konov, Vitalii I.; Konyashchenko, Aleksandr V.; Kryukov, P. G.; Dianov, Evgenii M.

    2007-03-01

    We studied the ring and linear schemes of erbium-doped fibre lasers in which passive mode locking was achieved with the help of saturable absorbers made of high-optical quality films based on cellulose derivatives with dispersed single-wall carbon nanotubes. The films were prepared by the original method with the use of nanotubes synthesised by the arc discharge method. The films exhibit nonlinear absorption at a wavelength of 1.5 μm. Pulses in the form of optical solitons of duration 1.17 ps at a avelength of 1.56 μm were generated in the ring scheme of the erbium laser. The average output power was 1.1 mW at a pulse repetition rate of 20.5 MHz upon pumping by the 980-nm, 25-mW radiation from a laser diode. The pulse duration in the linear scheme was reduced to 466 fs for the output power up to 4 mW and a pulse repetition rate of 28.5 MHz. The specific feature of these lasers is a low pump threshold in the regime of generation of ultrashort pulses.

  19. LASERS: Ultrashort-pulse erbium-doped fibre laser using a saturable absorber based on single-wall carbon nanotubes synthesised by the arc-discharge method

    NASA Astrophysics Data System (ADS)

    Tausenev, A. V.; Obraztsova, E. D.; Lobach, A. S.; Konov, V. I.; Konyashchenko, A. V.; Kryukov, P. G.; Dianov, E. M.

    2007-09-01

    An erbium-doped fibre laser operating in self-mode-locked regime achieved with the help of a saturable absorber based on single-wall carbon nanotubes synthesised by the arc-discharge method is fabricated and studied. Due to the development of an original method for preparing samples, films of the optical quality containing individual single-wall carbon nanotubes were synthesised. The study of the dependence of resonance absorption at a wavelength of 1.5 μm on the laser radiation intensity transmitted through a film showed that these films have nonlinear transmission and can be used in fibre lasers as saturable absorbers to provide self-mode locking. Stable transform-limited pulses having the shape of optical solitons were generated at a wavelength of 1557.5 nm in the laser with a ring resonator. The pulse duration was 1.13 ps at a pulse repetition rate of 20.5 MHz. The continuous output power achieved 1.1 mW upon pumping by a 25-mW laser diode at 980 nm.

  20. Influence of N2 partial pressure on structural and microhardness properties of TiN/ZrN multilayers deposited by Ar/N2 vacuum arc discharge

    NASA Astrophysics Data System (ADS)

    Naddaf, M.; Abdallah, B.; Ahmad, M.; A-Kharroub, M.

    2016-08-01

    The influence of N2 partial pressure on structural, mechanical and wetting properties of multilayered TiN/ZrN thin films deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures is investigated. X-ray diffraction (XRD) results show that the average texturing coefficient of (1 1 1) orientation and the grain size of both TiN and ZrN individual layers increase with increasing the N2 partial pressure. The Rutherford back scattering (RBS) measurements and analysis reveal that incorporation of the nitrogen in the film increases with increasing the N2 partial pressure and both TiN and ZrN individual layers have a nitrogen over-stoichiometry for N2 partial pressure ⩾50%. The change in the film micro-hardness is correlated to the changes in crystallographic texture, grain size, stoichiometry and the residual stress in the film as a function of the N2 partial pressure. In particular, stoichiometry of ZrN and TiN individual is found to play the vital role in determining the multilayer hardness. The multilayer film deposited at N2 partial pressure of 25% has the best stoichiometric ratio of both TiN and ZrN layers and the highest micro-hardness of about 32 GPa. In addition, water contact angle (WCA) measurements and analysis show a decrease in the work of adhesion on increasing the N2 partial pressure.

  1. Using Arc/Info GIS to help implement the National Pollutant Discharge Elimination System (NPDES) stormwater permit for Los Angeles County

    SciTech Connect

    Levine, D.A.; Pace, P.J.; Woods, J.A.; DePoto, W.

    1997-06-01

    One of Los Angeles County Department of Public Works` many responsibilities is to manage non-point pollution that enters the storm drain network within Los Angeles County. The management of this non-point source pollution is mandated by the NPDES guidelines under the Federal Clean Water Act. These guidelines require the County to monitor the drainage network and the storm water and urban runoff flowing through it. The County covers over 3,117 square miles, with the NPDES Permit covering over 3,100 square miles and over 2500 miles of storm drains. A proposed solution to monitor and manage this vast geographic area is centered upon an Arc/Info GIS. Some of the many concerns which need to be addressed include the administration and evaluation of Best Management Practices (BMP`s), storm drain inspection for illegal connections and illicit discharges, and pollutant load assessment and modeling. The storm drain network and other coverages will be related to external data bases currently used for facility management and planning. This system would be used for query purposes to perform spatial modeling and {open_quotes}what if{close_quotes} scenarios needed to create maps and reports required by the permit and to evaluate various BMP implementation strategies.

  2. Optimization of the electric arc discharge synthesis of single-walled carbon nanotubes on the basis of near-IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Itkis, M. E.; Perea, D. E.; Niyogi, S.; Love, J.; Tang, J.; Yu, A.; Kang, C.; Haddon, R. C.

    2004-03-01

    The metal catalyst plays an important role in the synthesis of single-walled carbon nanotubes (SWNT). It was originally reported that nickel and yttrium provide the optimum yield for bulk production of SWNTs by the electric arc discharge technique, at a catalyst composition of 4.0/ at. percent of Ni and 1.0 atomic percent of Y.[1] More recent work suggested a much lower concentration of Ni and Y for optimum SWNT generation: 0.6 atomic percent of Ni and 0.1 atomic percent of Y.[2] Both results were based on TGA, SEM and Raman analysis of milligrams quantities of SWNT soot. Recently we developed a quantitative technique to reliably assess the carbonaceous purity of bulk (10g scale) quantities of SWNTs, based on near-IR spectroscopy.[3] In this presentation we report the utilization of this technique for the determination of the purity of SWNT soot as a function of the catalyst composition. We present the range of optimum concentrations of Ni and Y for the bulk synthesis of the SWNTs. [1] C.Journet et al., Nature 388 (1997) 756; [2] M.Takizawa et al., Chem. Phys. Lett. 326 (2000) 351; [3] M.E. Itkis et al., Nano Lett. 3 (2003) 309.

  3. ZnO nanoparticles decorated on graphene sheets through liquid arc discharge approach with enhanced photocatalytic performance under visible-light

    NASA Astrophysics Data System (ADS)

    Ashkarran, Ali Akbar; Mohammadi, Bahareh

    2015-07-01

    We present an innovative approach for synthesis of zinc oxide-graphene (ZnO-G) hybrid nanostructures through combination of improved hummer and arc discharge methods in liquid. A detailed study of the considerable visible-light photocatalytic activities of these nanostructures for the degradation of Phenol red (PR) and Methyl orange (MO) as standard organic compounds under the irradiation of 90 W halogen light for 2 h has been performed. The ZnO-G nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer Emmett Teller (BET) and ultra violet-visible absorption spectroscopy (UV-vis). The results revealed that the ZnO-G nanostructures extended the light absorption spectrum toward the visible region and remarkably enhanced the photodegradation of standard dyes under visible-light irradiation. It has been confirmed that the ZnO-G nanostructures could be excited by visible-light (E ∼ 2.6 eV). The major enhancement in the photocatalytic activity of ZnO-G nanostructures under visible-light irradiation can be attributed to the effect of electron transport among ZnO nanoparticles (NPs) and graphene sheets. A mechanism for photocatalytic degradation of organic pollutants over ZnO-G photocatalyst was proposed based on our observations.

  4. Exact solution for the self-induced motion of a vortex filament in the arc-length representation of the local induction approximation.

    PubMed

    Van Gorder, Robert A

    2012-11-01

    We review two formulations of the fully nonlinear local induction equation approximating the self-induced motion of the vortex filament (in the local induction approximation), corresponding to the Cartesian and arc-length coordinate systems. The arc-length representation put forth by Umeki [Theor. Comput. Fluid Dyn. 24, 383 (2010)] results in a type of 1+1 derivative nonlinear Schrödinger (NLS) equation describing the motion of such a vortex filament. We obtain exact stationary solutions to this derivative NLS equation; such exact solutions are a rarity. These solutions are periodic in space and we determine the nonlinear dependence of the period on the amplitude.

  5. Welding arc plasma physics

    NASA Technical Reports Server (NTRS)

    Cain, Bruce L.

    1990-01-01

    The problems of weld quality control and weld process dependability continue to be relevant issues in modern metal welding technology. These become especially important for NASA missions which may require the assembly or repair of larger orbiting platforms using automatic welding techniques. To extend present welding technologies for such applications, NASA/MSFC's Materials and Processes Lab is developing physical models of the arc welding process with the goal of providing both a basis for improved design of weld control systems, and a better understanding of how arc welding variables influence final weld properties. The physics of the plasma arc discharge is reasonably well established in terms of transport processes occurring in the arc column itself, although recourse to sophisticated numerical treatments is normally required to obtain quantitative results. Unfortunately the rigor of these numerical computations often obscures the physics of the underlying model due to its inherent complexity. In contrast, this work has focused on a relatively simple physical model of the arc discharge to describe the gross features observed in welding arcs. Emphasis was placed of deriving analytic expressions for the voltage along the arc axis as a function of known or measurable arc parameters. The model retains the essential physics for a straight polarity, diffusion dominated free burning arc in argon, with major simplifications of collisionless sheaths and simple energy balances at the electrodes.

  6. Antenna Deployment for the Localization of Partial Discharges in Open-Air Substations.

    PubMed

    Robles, Guillermo; Fresno, José Manuel; Sánchez-Fernández, Matilde; Martínez-Tarifa, Juan Manuel

    2016-04-15

    Partial discharges are ionization processes inside or on the surface of dielectrics that can unveil insulation problems in electrical equipment. The charge accumulated is released under certain environmental and voltage conditions attacking the insulation both physically and chemically. The final consequence of a continuous occurrence of these events is the breakdown of the dielectric. The electron avalanche provokes a derivative of the electric field with respect to time, creating an electromagnetic impulse that can be detected with antennas. The localization of the source helps in the identification of the piece of equipment that has to be decommissioned. This can be done by deploying antennas and calculating the time difference of arrival (TDOA) of the electromagnetic pulses. However, small errors in this parameter can lead to great displacements of the calculated position of the source. Usually, four antennas are used to find the source but the array geometry has to be correctly deployed to have minimal errors in the localization. This paper demonstrates, by an analysis based on simulation and also experimentally, that the most common layouts are not always the best options and proposes a simple antenna layout to reduce the systematic error in the TDOA calculation due to the positions of the antennas in the array.

  7. Antenna Deployment for the Localization of Partial Discharges in Open-Air Substations

    PubMed Central

    Robles, Guillermo; Fresno, José Manuel; Sánchez-Fernández, Matilde; Martínez-Tarifa, Juan Manuel

    2016-01-01

    Partial discharges are ionization processes inside or on the surface of dielectrics that can unveil insulation problems in electrical equipment. The charge accumulated is released under certain environmental and voltage conditions attacking the insulation both physically and chemically. The final consequence of a continuous occurrence of these events is the breakdown of the dielectric. The electron avalanche provokes a derivative of the electric field with respect to time, creating an electromagnetic impulse that can be detected with antennas. The localization of the source helps in the identification of the piece of equipment that has to be decommissioned. This can be done by deploying antennas and calculating the time difference of arrival (TDOA) of the electromagnetic pulses. However, small errors in this parameter can lead to great displacements of the calculated position of the source. Usually, four antennas are used to find the source but the array geometry has to be correctly deployed to have minimal errors in the localization. This paper demonstrates, by an analysis based on simulation and also experimentally, that the most common layouts are not always the best options and proposes a simple antenna layout to reduce the systematic error in the TDOA calculation due to the positions of the antennas in the array. PMID:27092501

  8. Structural, mechanical, electrical and wetting properties of ZrNx films deposited by Ar/N2 vacuum arc discharge: Effect of nitrogen partial pressure

    NASA Astrophysics Data System (ADS)

    Abdallah, B.; Naddaf, M.; A-Kharroub, M.

    2013-03-01

    Non-stiochiometric zirconium nitride (ZrNx) thin films have been deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures at different N2 partial pressure ratio. The microstructure, mechanical, electrical and wetting properties of these films are studied by means of X-ray diffraction (XRD), micro-Raman spectroscopy, Rutherford back scattering (RBS) technique, conventional micro-hardness testing, electrical resistivity, atomic force microscopy (AFM) and contact angle (CA) measurements. RBS results and analysis show that the (N/Zr) ratio in the film increases with increasing the N2 partial pressure. A ZrNx film with (Zr/N) ratio in the vicinity of stoichiometric ZrN is obtained at N2 partial pressure of 10%. XRD and Raman results indicate that all deposited films have strained cubic crystal phase of ZrN, regardless of the N2 partial pressure. On increasing the N2 partial pressure, the relative intensity of (1 1 1) orientation with respect to (2 0 0) orientation is seen to decrease. The effect of N2 partial pressure on micro-hardness and the resistivity of the deposited film is revealed and correlated to the alteration of grain size, crystallographic texture, stoichiometry and residual stress developed in the film. In particular, it is found that residual stress and nitrogen incorporation in the film play crucial role in the alteration of micro-hardness and resistivity respectively. In addition, CA and AFM results demonstrate that as N2 partial pressure increases, both the surface hydrophobicity and roughness of the deposited film increase, leading to a significant decrease in the film surface free energy (SFE).

  9. Departures from local thermodynamic equilibrium in cutting arc plasmas derived from electron and gas density measurements using a two-wavelength quantitative Schlieren technique

    SciTech Connect

    Prevosto, L.; Mancinelli, B.; Artana, G.; Kelly, H.

    2011-03-15

    A two-wavelength quantitative Schlieren technique that allows inferring the electron and gas densities of axisymmetric arc plasmas without imposing any assumption regarding statistical equilibrium models is reported. This technique was applied to the study of local thermodynamic equilibrium (LTE) departures within the core of a 30 A high-energy density cutting arc. In order to derive the electron and heavy particle temperatures from the inferred density profiles, a generalized two-temperature Saha equation together with the plasma equation of state and the quasineutrality condition were employed. Factors such as arc fluctuations that influence the accuracy of the measurements and the validity of the assumptions used to derive the plasma species temperature were considered. Significant deviations from chemical equilibrium as well as kinetic equilibrium were found at elevated electron temperatures and gas densities toward the arc core edge. An electron temperature profile nearly constant through the arc core with a value of about 14000-15000 K, well decoupled from the heavy particle temperature of about 1500 K at the arc core edge, was inferred.

  10. A freely localized discharge excited by intense microwave beams in high-pressure gases. Physics and applications

    SciTech Connect

    Vikharev, A.L.; Gorbachev, A.M.

    1995-12-31

    In the paper the recent successes of IAP microwave discharge group in studies of a discharge excited by intense converging microwave beams in high-pressure gases are presented. This discharge as a source of nonequilibrium freely localized plasma is very promising for a lot of applications in industry such as surface treatment, thin film deposition and super-pure plasma chemistry. But its successful application depends on the understanding of the physical processes which define dynamics, complicated discharge structure and plasma parameters. In the experiments the microwaves of wavelength 8-mm, pulse power 400 kW, pulse duration 50--500 microsecond, pulses repetition frequency 0.1--10 Hz are used. The main discharge properties in different gases at pressure 100--760 Torr are investigated. Numerical simulation of the discharge dynamics, taking into account heating and displacement of the gas in the nonisobaric case, permits them to generalize the existing results of experimental studies, and to discover new effects associated with the appearance of the plasma filament. Thus, they have shown that ultraviolet (UV) emission call be stimulated from the plasma filament. The efficient generation of UV radiation in a high-pressure discharge shows that its application in plasma chemical reactors for clearing air of industrial pollution (e.g., freon) is promising.

  11. Medium-term results of Mini-arc for urinary stress incontinence in ambulatory patients under local anesthesia

    PubMed Central

    Levi, Almog; Nasra, Rasha; Shachar, Inbar Ben; Braun, Naama Marcus

    2016-01-01

    Abstract Objective To evaluate the medium-term outcome and patient's satisfaction after Single-incision mini-sling (SIMS) procedure done under local anesthesia in ambulatory set up for patients with stress urinary incontinence (SUI). Materials and Methods This is a retrospective cohort study, including all patients submitted to SIMS procedure for SUI with MiniArc (AMS, U.S.A) without concomitant surgery between January 2011 and March 2013. Patients were followed up during 12 months after surgery and once a year subsequently. Telephone interviews were conducted to evaluate patient satisfaction. Outcome masseurs included: SUI cure rate, urinary urge incontinence (UUI) cure rate in patients with mixed urinary incontinence (MUI), intra and post-operative complications and patient satisfaction. Results Ninety-three patients were included with mean follow-up of 23 months. Fifty percent had MUI with predominant SUI. The cure rates of SUI (objective and subjective) were 89%. UUI was cured in 40% of patients. No major complications occur, neither voiding obstruction or groin pain. Telephone interviews conducted after 26 months on average revealed high satisfaction rate from the procedure (8.8 out of 10) and from the local anesthesia. Visual analog scale (VAS) rating was low during and after the procedure (2.38 and 2.69 respectively). Conclusions The SIMS procedure is safe and highly effective for SUI and it can be performed successfully under local anesthesia in an ambulatory setup. PMID:27813384

  12. Identification of discharge zones and quantification of contaminant mass discharges into a local stream from a landfill in a heterogeneous geologic setting

    NASA Astrophysics Data System (ADS)

    Milosevic, N.; Thomsen, N. I.; Juhler, R. K.; Albrechtsen, H.-J.; Bjerg, P. L.

    2012-06-01

    SummaryContaminants from Risby Landfill (Denmark) are expected to leach through the underlying geologic strata and eventually reach the local Risby Stream. Identification of the groundwater discharge zone was conducted systematically by an array of methods including studies on site geology and hydrogeology, ground- and surface water flows and landfill leachate tracing from April 2009 to December 2010. Chemical profiling by driven wells and gradients in streambed temperatures was an efficient method to identify the contaminant discharge area. A considerable variation of leachate indicators, redox parameters and xenobiotic organic compounds were revealed in this area because of a complex geological setting with clay till (interbedded sand lenses) and deposits of sand and peat. Concentrations of leachate indicators decreased from the landfill to the stream, implying attenuation processes. Xenobiotic organic compounds were mainly phenoxy acid herbicides, while petroleum hydrocarbons and chlorinated solvents were found at very few boreholes. Findings of putative metabolites of phenoxy acid herbicides suggest degradation under the anaerobic conditions, which dominated inside and beneath the landfill. The groundwater discharge was quantified by two methods: direct collection of discharged groundwater by seepage meters and calculations from measurement of streambed temperature gradients. The landfill impacted the stream seasonally during dry periods when concentrations in the stream reached groundwater concentration levels. A comparison between mass balance for selected stream stretches and upscaled measurements of the contaminant discharge from groundwater into the stream indicated that only a small part of the actual contaminant discharge of the stream could be explained by the inflowing contaminant discharge from groundwater. Surface runoff and seepage from ponds along the stream impacted by landfill interflow may be important pathways as well. The placement of Risby

  13. Detailed crustal structure in the area of the southern Apennines-Calabrian Arc border from local earthquake tomography

    NASA Astrophysics Data System (ADS)

    Totaro, C.; Koulakov, I.; Orecchio, B.; Presti, D.

    2014-12-01

    We present a new seismic velocity model for the southern Apennines-Calabrian Arc border region with the aim to better define the crustal structures at the northern edge of the Ionian subduction zone. This sector also includes the Pollino Mts. area, where a seismic sequence of thousands of small to moderate earthquakes has been recorded between spring 2010 and 2013. In this sector a seismic gap was previously hypothesized by paleoseismological evidences associated with the lack of major earthquakes in historical catalogs. To perform the tomographic inversion we selected ca. 3600 earthquakes that have occurred in the last thirty years and recorded by permanent and temporary networks managed by INGV and Calabria University. Using for the first time the Local Tomography Software for passive tomography inversion (LOTOS hereinafter) to crustal analysis in southern Italy, we have computed the distribution of Vp, Vs, and the Vp/Vs ratio. The obtained velocity model, jointly evaluated with results of synthetic modeling, as well as with the hypocenter distribution and geological information, gives us new constraints on the geodynamical and structural knowledge of the study area. The comparison between the shallow tomography sections and surface geology shows good correlation between velocity patterns and the main geological features of the study area. In the upper crust a low-velocity anomaly of P- and S-waves is detectable beneath the Pollino Mts. area and seems to separate the Calabrian and southern Apennines domains, characterized by higher velocities. The distributions of high Vp/Vs ratio, representing strongly fractured rocks with likely high fluid content, clearly correlate with areas of significant seismicity. In the lower crust we detect a clear transition from high to low seismic velocities in correspondence with the Tyrrhenian coast of the study area, which may represent the transition from the thinner Tyrrhenian crust to the thicker one beneath Calabria. In this

  14. A Phase II Trial of Arc-Based Hypofractionated Intensity-Modulated Radiotherapy in Localized Prostate Cancer

    SciTech Connect

    Lock, Michael; Best, Lara; Wong, Eugene; Bauman, Glenn; D'Souza, David; Venkatesan, Varagur; Sexton, Tracy; Ahmad, Belal; Izawa, Jonathan; Rodrigues, George

    2011-08-01

    Purpose: To evaluate acute and late genitourinary (GU) and gastrointestinal (GI) toxicity and biochemical control of hypofractionated, image-guided (fiducial markers or ultrasound guidance), simplified intensity-modulated arc therapy for localized prostate cancer. Methods and Materials: This Phase II prospective clinical trial for T1a-2cNXM0 prostate cancer enrolled 66 patients who received 63.2 Gy in 20 fractions over 4 weeks. Fiducial markers were used for image guidance in 30 patients and daily ultrasound for the remainder. Toxicity was scored according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. Results: Median follow-up was 36 months. Acute Phase Grade 2 and 3 toxicity was 34% and 9% for GU vs. 25% and 10% for GI symptoms. One Grade 4 acute GI toxicity occurred in a patient with unrecognized Crohn's disease. Late Grade 2 and 3 toxicity for GU was 14% and 5%, and GI toxicity was 25% and 3%. One late GI Grade 4 toxicity was observed in a patient with significant comorbidities (anticoagulation, vascular disease). Acute GI toxicity {>=}Grade 2 was shown to be a predictor for late toxicity Grade {>=}2 (p < 0.001). The biochemical disease-free survival at 3 years was 95%. Conclusions: Hypofractionated simplified intensity-modulated arc therapy radiotherapy given as 63.2 Gy in 20 fractions demonstrated promising biochemical control rates; however, higher rates of acute Grade 3 GU and GI toxicity and higher late Grade 2 GU and GI toxicity were noted. Ongoing randomized controlled trials should ultimately clarify issues regarding patient selection and the true rate of severe toxicity that can be directly attributed to hypofractionated radiotherapy.

  15. Outcome and toxicity profiles in the treatment of locally advanced lung cancer with volumetric modulated arc therapy.

    PubMed

    Scorsetti, Marta; Navarria, Piera; De Rose, Fiorenza; Ascolese, AnnaMaria; Clerici, Elena; Franzese, Ciro; Lobefalo, Francesca; Reggiori, Giacomo; Mancosu, Pietro; Tomatis, Stefano; Fogliata, Antonella; Cozzi, Luca

    2014-11-01

    To report about the outcome of radiation treatment of advanced lung cancer patients with volumetric modulated arcs [RapidArc (RA)]. Seventy-five consecutive patients (all stages IIIA and IIIB) were treated with RA. Among them 71 % were men; 25.4 % presented unspecified non-small cell lung cancer, 41.3% adenocarcinoma and 33.3 % squamous cell carcinoma. Of them, 54.7 % received sequential chemotherapy while 45.3% were treated with concomitant regimen. Dose prescription ranged from 54 to 72 Gy. Analysis included survival, local control (LC) and toxicity profiles. Median follow-up was 21.2 months (range 6-75). One- two- and five-year actuarial LC was 91.9 ± 3.2, 79.5 ± 5.7 and 67.4 ± 9.5 %, respectively. Median survival was 19.0 ± 1.1 months. Actuarial survival at 1-2-5 years was 80.0 ± 4.6, 38.5 ± 5.9 and 15.2 ± 4.9 %, respectively. Acute toxicity of G2 was reported in 24, 25.3 and 4.0 % of patients for lung, esophageal and hematological profiles. A total of 2.7 % of patients reported G3 toxicity in the esophagus and 5.3 % of the patients experienced G3-G4 hematological toxicity. Significant differences were observed in all cases between concomitant and sequential chemotherapy regiments. Only 1.3 % (1 patient) showed G2 lung late toxicity. No significant correlation was found between toxicity and organ's irradiation levels. RA proved to be a safe and advantageous treatment modality for advanced lung cancer with results in line with expectations from earlier literature.

  16. Mantle Dynamics of Australia-Banda Arc Collision as Inferred from Shear Wave Splitting Analysis of Teleseismic and Local Slab Events

    NASA Astrophysics Data System (ADS)

    Harris, C. W.; Miller, M. S.; O'Driscoll, L.; Porritt, R. W.; Roosmawati, N.; Widiyantoro, S.

    2015-12-01

    Arc-continent collision is an important factor in continent building, orogensis, and ocean closure, yet the details associated with it are not fully understood. East-Timor and the Nusa Tenggara Timur region of Indonesia provide a unique setting to study a young arc-continent collision (~8 Ma) and incipient orogenesis. The NSF funded Banda Arc project affords a rare opportunity to investigate unconstrained processes such as active continental subduction and slab rupture beneath a regional deployment of broadband seismometers. We use data from 35 broadband sensors to analyze seismic anisotropy through measuring shear wave splitting. These stations span the roughly east-west transition from normal oceanic subduction at the Sunda Arc to collision at the Banda Arc, and cross areas associated with back-arc thrusting, arc volcanism, extinct volcanism and a rapidly exhuming forearc. Thirty of the sensors used in the analysis are temporary stations installed by our research team in 2014 and will remain in the field until 2016 or later. The remaining stations are part of the open-access GFZ GEOFON global seismic network. We present preliminary shear wave splitting results for teleseismic (*KS core phases) and local (direct S phase) arrivals in order to inspect the sub-slab mantle and the supra-slab mantle wedge for anisotropic patterns related to olivine flow fabric. These results can be used to assess regional strain linked to ongoing collision and may elucidate any slab tearing that has resulted from the (partial) subduction of buoyant continental material of Australian affinity. Presently, we observe a trend of primarily trench-parallel sub-slab fast polarization directions and perhaps more complicated anisotropy in the mantle wedge. Relative to the trench, there appears to be more spatial variation in fast axis orientation for direct arrivals than teleseismic phases. We discuss how the interpretation of our initial results provides insight into the mantle dynamics of the

  17. Arc-discharge in solution: A novel synthesis method for carbon nanotubes and in situ decoration of carbon nanotubes with nanoparticles

    NASA Astrophysics Data System (ADS)

    Bera, Debasis

    2005-11-01

    During the last decade, carbon nanotubes (CNTs) have been envisioned for a host of different new applications. One of the objectives of the present research is to develop a simplified synthesis method for the production of large-scale, low-cost carbon nanotubes with functionality. Herein, a unique, simple, inexpensive and one-step synthesis route of CNTs and CNTs decorated with nanoparticles is reported. The method is simple arc-discharge in solution (ADS). For this new method, a full-fledged optoelectronically controlled instrument is reported here to achieve high efficiency and continuous bulk production of CNTs. In this system, a constant gap between the two electrodes is maintained using a photosensor which allows a continuous synthesis of the carbon nanostructures. The system operates in a feedback loop consisting of an electrode-gap detector and an analogue electronic unit, as controller. This computerized feed system was also used in single process step to produce in situ-decorated CNTs with a variety of industrially important nanoparticles. To name a few, we have successfully synthesized CNTs decorated with 3--4 nm ceria, silica and palladium nanoparticles for many industrially relevant applications. This process can be extended to synthesize decorated CNTs with other oxide and metallic nanoparticles. Sixty experimental runs were carried out for parametric analysis varying process parameters including voltage, current and precursors. The amount of yield with time, rate of erosion of the anode, and rate of deposition of carbonaceous materials on the cathode electrode were investigated. Normalized kinetic parameters were evaluated for different amperes from the sets of runs. The production rate of pristine CNT at 75 A is as high as 5.89 +/- 0.28 g.min-1. In this study, major emphasis was given on the characterizations of CNTs with and without nanoparticles using various techniques for surface and bulk analysis of the nanostructures. The nanostructures were

  18. Electrical Resistivity Tomography to characterize localized freshwater discharge in coastal environment

    NASA Astrophysics Data System (ADS)

    Kumm, Max; Scheuermann, Alexander; Hauck, Christian; Welti, Nina

    2014-05-01

    North Stradbroke Island, located in the Pacific Ocean about 40 km east of Brisbane in Queensland, Australia, is formed by massive sand dunes of heights up to 229 m. The Island represents a reservoir for vast amounts of groundwater and plays an important role for the regional water supply. Therefore a detailed understanding of its hydrogeological features is of particular interest. In the intertidal zone on the western shores of the island, two localized freshwater springs with 4 m and 6 m in diameter were found. Hydrochemical investigations could not unequivocally identify the source of the freshwater by comparing its chemical properties to adjacent surface water and groundwater features. This case study presents the application of electrical resistivity tomography (ERT) in order to identify the source of the discharged freshwater and to delineate preferential flow paths in the saturated sand sediments. Several measurements with in-line arrays switching 48 electrodes as well as square arrays with 96 electrodes were conducted. The results of two- and three-dimensional data inversion were refined and verified implementing additional information. In-lab resistivity measurements on undisturbed samples of the sand sediments from the area under investigation as well as data from drill cores were considered for the refinement of the inversion model. The field work was impeded by the tides and allowed only for short periods for set up and measurement. A semi-confined aquifer formed by a layer of cemented sand at 7 m to 8 m depth perforated at the location of the springs could be identified. The interpretation of ERT data without considering additional geological and in lab resistivity data did not unambiguously indicate the real geological structure of the subsurface. High conductivities in the saturated sandy sediments lead to low investigation depths. Porosity-conductivity relationships for the loose sediments as well as for the cemented sand layer had to be modified to

  19. Local and remote climatic impacts due to land use degradation in the Amazon "Arc of Deforestation"

    NASA Astrophysics Data System (ADS)

    Silva, Maria Elisa Siqueira; Pereira, Gabriel; da Rocha, Rosmeri Porfírio

    2016-08-01

    Many numerical studies, among them, global and regional models, have been used to simulate climatic impact due to Amazon deforestation. Most of them did not consider deforestation as usually observed and the induced dynamic changes. The present study explores the physical impacts due to Amazon deforestation by considering local and remote changes in the circulation and thermodynamics. For this, numerical experiments were conducted with RegCM3 using a relatively fine horizontal grid spacing (50 km), more realistic deforested areas (similar to the highway-network-shaped), and an updated land use map. The studied period was 2001-2006 October-March. As in most previous studies focusing on Amazon deforestation, the RegCM3-simulated air temperature increases over degraded areas, ranging from 1.0 to 2.5 °C, and precipitation decreases of around 10 %. This result is mainly related to depletion in evapotranspiration rates provided by lesser soil water extraction by the degraded vegetation. The weakening of upward motion in the mid-upper troposphere is an associated mechanism that explains the precipitation decrease after Amazon deforestation. A new result is the simulated precipitation increase, about 10 %, over the eastern South America and the adjacent South Atlantic Ocean. In these areas, the precipitation increase during October-March is associated with intensification of upper-level high pressure (the Bolivian high) coupled with negative geopotential height anomalies southeastward of the center of the high.

  20. Striking Local Distinctions in Basaltic Melts within Nicaraguan Cross-arc Lineaments

    NASA Astrophysics Data System (ADS)

    Her, X.; Walker, J. A.; Roggensack, K.

    2015-12-01

    The Nejapa-Miraflores (NM) and Granada (G) lineaments which cut across the Central American volcanic front (CAVF) host numerous monogenetic vents which have erupted diverse basaltic magmas (e.g., Walker, 1984). As previously shown by Walker (1984), the basaltic magmas loosely fall into two groups: a high Ti, low K group which are reminiscent of MORB or BABB; and a low Ti, high K group which are more typical of subduction zones worldwide. Major element data obtained from over 200 olivine-hosted melt inclusions found within NM and G tephras from six separate monogenetic vents confirm this unusual compositional dichotomy. Melt inclusions from four of the six monogenetic vents are exclusively high- or low-Ti, while two of the volcanoes have both high- and low-Ti melt inclusions. New volatile and trace element data on over 40 of the NM and G melt inclusions has yielded additional compositional distinctions between the high- and low-Ti groups. Least degassed high-Ti melts tend to have lower water contents than their low-Ti counterparts. The high-Ti Inclusions also have lower concentrations of U, Th, Pb, Ba and Cs and lower La/Yb ratios. In addition, there are subtle HFSE variations between the two types of basalts. The overall geochemical differences between the high- and low-Ti groups suggest that the mantle wedge source of the latter contains a greater slab-derived (hemipelagic) sediment melt component than the former linked to a larger flux of hydrous fluids from deeper in the subducting Cocos plate. What is particularly significant is that the contrasting mafic emanations from these monogenetic volcano lineaments demonstrate that transport of fluids, volatiles and basaltic melts in subduction zones can be quite variable and complex on a very localized scale.

  1. Inductive Evolution and MHD in Local Helicity Injection Discharges on Pegasus

    NASA Astrophysics Data System (ADS)

    Barr, Jayson L.

    Local Helicity Injection (LHI) is a promising non-solenoidal startup technique being investigated on the Pegasus ST. Quantifying the current drive available from LHI is important for projecting to larger devices. A lumped-parameter circuit model for LHI startup has been developed for interpretive analysis of LHI plasmas on Pegasus and a tool for projection. The model recreates I p(t) of outboard LHI discharges with varied shape evolution and LHI drive within +/-15 kA with simplistic assumed plasma resistivity. Outboard LHI plasmas are initialized on the low-field-side and expand to lower aspect ratio (A) and full size. At their initially small, high- A shape the injectors are most effective, but a Taylor relaxation current limit prevents Ip growth. As the plasma expands, the Taylor limit rises, but the injectors become less effective. However, the change in geometry induces large inductive voltages that add significant current drive. Plasma inductance models [38,60] have been re-calibrated to quantify these inductive effects for ultralow-A geometries. The majority ( 80%) of current drive in experiment is provided by the inductive effects from the shape evolution, with peak values as high as 6+ V. The available LHI drive typically falls to less than 0.5 V by the time the plasma reaches full size. Large (b/Bt 1--3 %), n=1 magnetic fluctuations are a signature of LHI plasmas. 3-D, resistive MHD simulations [68,69] predict this activity to be the result of motion and large-scale reconnection events of the injected current, and predict the reconnection to be an underlying method of current drive. Magnetic measurements are consistent with the injected current acting as a current stream line-tied to the injectors and undergoing an elliptical motion in the plasma edge on the low-field-side. This is likely the result of kink and magnetic island coalescence instabilities of the injected current, in partial agreement with simulation. Indirect evidence for the occurrence of

  2. The Hippocampus Sparing Volume Modulated Arc Therapy does not Influence Plan Quality on Locally Advanced Nasopharyngeal Carcinoma Patients.

    PubMed

    Gu, Wendong; Li, Qilin; Xi, Dan; Tian, Ye; Mo, Juncong; Pei, Honglei

    2017-06-13

    Irradiation on hippocampus would lead to neuro-cognitive dysfunction in locally advanced nasopharyneal carcinoma (LA-NPC) patients accepting radiotherapy. Our study here aimed to investigate if undergoing hippocampus sparing (HS) volume modulated arc therapy (VMAT) would influence the plan quality in LA NPC patients. We designed three kinds of radiotherapeutic plans for 11 LA NPC patients: conventional VMAT (C-VMAT), HS-VMAT and HS intensity modulated radiation therapy with dynamic multileaf collimator (HS-dMLC). And the dose distribution on targets and surrounding organs at risk (OAR) were carefully evaluated. We found out that the expected doses on hippocampus were significantly lowered in HS-VMAT (899 ± 378 cGy) and HS-dMLC (896 ± 321 cGy) as compared to C-VMAT (1518 ± 337 cGy, p < 0.05), but meaningless difference was presented on plan quality of targets (p > 0.05). Moreover, lower radiation doses on brain stem were observed in HS-VMAT plan in comparison with C-VMAT plan (p < 0.05). However, there were no statistically meaningful diversities in the doses received by other OARs among all plans. Here we concluded that HS-VMAT presented promising advantages on protecting hipppcampus and brain stem as compared to C-VMAT and HS-dMLC, but enthusiastically had no effects on plan quality in LA-NPC patients.

  3. Temperature measurement of an atmospheric pressure arc discharge plasma jet using the diatomic CN (B {sup 2}{sigma}{sup +}-X {sup 2}{sigma}{sup +}, violet system) molecular spectra

    SciTech Connect

    Moon, Se Youn; Kim, D. B.; Gweon, B.; Choe, W.

    2009-03-01

    The CN (B {sup 2}{sigma}{sup +}-X {sup 2}{sigma}{sup +}) molecular emission spectrum is used to measure both the vibrational and rotational temperatures in atmospheric pressure arc jet discharges. The vibrational and rotational temperature effects on the synthetic diatomic molecular spectra were investigated from the (v{sup '},v{sup ''})=(0,0) band to the (5,5) band. The temperatures obtained from the synthetic spectra compared with the experimental result of a low-frequency arc discharge show a vibrational temperature of (4250-5010) K and a rotational temperature of (3760-3980) K for the input power in the range of (80-280) W. As the (0,0) band is isolated from other vibrational transition bands, determination of the rotational temperature is possible based only on the (0,0) band, which simplifies the temperature measurement. From the result, it was found that the CN molecular spectrum can be used as a thermometer for atmospheric pressure plasmas containing carbon and nitrogen.

  4. Strain Localization Within a Syn-Tectonic Pluton in a Back-Arc Extensional Context: the Naxos granodiorite (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Bessiere, Eloïse; Rabillard, Aurélien; Arbaret, Laurent; Jolivet, Laurent; Augier, Romain; Menant, Armel

    2016-04-01

    Naxos Island is part of the central Cyclades (Aegean Sea, Greece) where a series of migmatite-cored metamorphic domes were exhumed below large-scale detachment systems during a Cenozoic back-arc extension. On Naxos, the Miocene exhumation history of the high-temperature metamorphic dome was notably achieved through two anastomosing and closely spaced top-to-the-north detachments belonging to the Naxos-Paros detachment system. According to previous contributions, the late exhumation stages were accompanied by the emplacement of a syn-kinematic I-type granodiorite that intruded a ductile-then-brittle detachment. Later the detachment migrated at the interface between the pluton and the metamorphic unit under ductile-to-brittle conditions. To clarify how extensional deformation was precisely distributed within the pluton, a multi-scale approach from field observations to laboratory investigations was undertaken. Through macro- to micro-structural observations, we show a continuous deformation history from magmatic to solid-state ductile/brittle conditions under an overall north-directed shearing deformation. The early magmatic or sub-solidus deformation is evidenced in a large part of the granodiorite, notably in its southern part where the original intrusive contact is still preserved. Solid-state deformation is recorded further north when approaching the detachment zone, highlighted by a thicker cataclastic zone and numerous pseudotachylite veins. From these field observations, we defined six strain facies, leading us to propose a qualitative strain map of the Naxos granodiorite. Based on field pictures and X-ray tomography of oriented samples collected along the strain gradient, we quantified the intensity of mineralogical fabrics in 2D and 3D. This step required the treatment of 600 rocks samples and pictures using SPO2003 (Shape Preferred Orientation) and Intercepts2003. Measured shape variations of the strain ellipsoid thus corroborate the large-scale strain

  5. Influence of local calibration on the quality of online wet weather discharge monitoring: feedback from five international case studies.

    PubMed

    Caradot, Nicolas; Sonnenberg, Hauke; Rouault, Pascale; Gruber, Günter; Hofer, Thomas; Torres, Andres; Pesci, Maria; Bertrand-Krajewski, Jean-Luc

    2015-01-01

    This paper reports about experiences gathered from five online monitoring campaigns in the sewer systems of Berlin (Germany), Graz (Austria), Lyon (France) and Bogota (Colombia) using ultraviolet-visible (UV-VIS) spectrometers and turbidimeters. Online probes are useful for the measurement of highly dynamic processes, e.g. combined sewer overflows (CSO), storm events, and river impacts. The influence of local calibration on the quality of online chemical oxygen demand (COD) measurements of wet weather discharges has been assessed. Results underline the need to establish local calibration functions for both UV-VIS spectrometers and turbidimeters. It is suggested that practitioners calibrate locally their probes using at least 15-20 samples. However, these samples should be collected over several events and cover most of the natural variability of the measured concentration. For this reason, the use of automatic peristaltic samplers in parallel to online monitoring is recommended with short representative sampling campaigns during wet weather discharges. Using reliable calibration functions, COD loads of CSO and storm events can be estimated with a relative uncertainty of approximately 20%. If no local calibration is established, concentrations and loads are estimated with a high error rate, questioning the reliability and meaning of the online measurement. Similar results have been obtained for total suspended solids measurements.

  6. Partial discharge localization in power transformers based on the sequential quadratic programming-genetic algorithm adopting acoustic emission techniques

    NASA Astrophysics Data System (ADS)

    Liu, Hua-Long; Liu, Hua-Dong

    2014-10-01

    Partial discharge (PD) in power transformers is one of the prime reasons resulting in insulation degradation and power faults. Hence, it is of great importance to study the techniques of the detection and localization of PD in theory and practice. The detection and localization of PD employing acoustic emission (AE) techniques, as a kind of non-destructive testing, plus due to the advantages of powerful capability of locating and high precision, have been paid more and more attention. The localization algorithm is the key factor to decide the localization accuracy in AE localization of PD. Many kinds of localization algorithms exist for the PD source localization adopting AE techniques including intelligent and non-intelligent algorithms. However, the existed algorithms possess some defects such as the premature convergence phenomenon, poor local optimization ability and unsuitability for the field applications. To overcome the poor local optimization ability and easily caused premature convergence phenomenon of the fundamental genetic algorithm (GA), a new kind of improved GA is proposed, namely the sequence quadratic programming-genetic algorithm (SQP-GA). For the hybrid optimization algorithm, SQP-GA, the sequence quadratic programming (SQP) algorithm which is used as a basic operator is integrated into the fundamental GA, so the local searching ability of the fundamental GA is improved effectively and the premature convergence phenomenon is overcome. Experimental results of the numerical simulations of benchmark functions show that the hybrid optimization algorithm, SQP-GA, is better than the fundamental GA in the convergence speed and optimization precision, and the proposed algorithm in this paper has outstanding optimization effect. At the same time, the presented SQP-GA in the paper is applied to solve the ultrasonic localization problem of PD in transformers, then the ultrasonic localization method of PD in transformers based on the SQP-GA is proposed. And

  7. Filtered cathodic arc source

    DOEpatents

    Falabella, S.; Sanders, D.M.

    1994-01-18

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge is described. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45[degree] to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles. 3 figures.

  8. Filtered cathodic arc source

    DOEpatents

    Falabella, Steven; Sanders, David M.

    1994-01-01

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45.degree. to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles.

  9. Rotating Drive for Electrical-Arc Machining

    NASA Technical Reports Server (NTRS)

    Fransen, C. D.

    1986-01-01

    Rotating drive improves quality of holes made by electrical-arc machining. Mechanism (Uni-tek, rotary head, or equivalent) attached to electrical-arc system. Drive rotates electrode as though it were mechanical drill, while an arc disintegrates metal in workpiece, thereby creating hole. Rotating electrode method often used in electric-discharge machining. NASA innovation is application of technique to electrical-arc machining.

  10. Discharge regime of non-ambipolarity with a self-induced steady-state magnetic field in plasma sources with localized radio-frequency power deposition

    SciTech Connect

    Shivarova, A. Lishev, St.; Todorov, D.; Paunska, Ts.

    2015-10-15

    Involving the idea for the Biermann effect known from space physics as well as recent discussions on non-ambipolarity of the electron and ion fluxes in low-pressure discharges, the study builds the discharge pattern in a source with localized RF power deposition outside the region of high electron density. A vortex dc current flowing in an RF discharge and a steady-state magnetic field induced by this current govern the discharge behavior. Owing to a shift in the positions of the electron-density and plasma-potential maxima, the dc current is driven with the purpose of keeping the conservativity of the dc field in the discharge. The results present the spatial structure of a discharge in a regime of non-ambipolarity of the electron and ion fluxes, including its modifications by the magnetic field.

  11. SU-F-P-30: Clinical Assessment of Auto Beam-Hold Triggered by Fiducial Localization During Prostate RapidArc Delivery

    SciTech Connect

    Atkinson, P; Chen, Q

    2016-06-15

    Purpose: To assess the clinical efficacy of auto beam hold during prostate RapidArc delivery, triggered by fiducial localization on kV imaging with a Varian True Beam. Methods: Prostate patients with four gold fiducials were candidates in this study. Daily setup was accomplished by aligning to fiducials using orthogonal kV imaging. During RapidArc delivery, a kV image was automatically acquired with a momentary beam hold every 60 degrees of gantry rotation. The position of each fiducial was identified by a search algorithm and compared to a predetermined 1.4 cm diameter target area. Treatment continued if all the fiducials were within the target area. If any fiducial was outside the target area the beam hold was not released, and the operators determined if the patient needed re-alignment using the daily setup method. Results: Four patients were initially selected. For three patients, the auto beam hold performed seamlessly. In one instance, the system correctly identified misaligned fiducials, stopped treatment, and the patient was re-positioned. The fourth patient had a prosthetic hip which sometimes blocked the fiducials and caused the fiducial search algorithm to fail. The auto beam hold was disabled for this patient and the therapists manually monitored the fiducial positions during treatment. Average delivery time for a 2-arc fraction was increased by 59 seconds. Phantom studies indicated the dose discrepancy related to multiple beam holds is <0.1%. For a plan with 43 fractions, the additional imaging increased dose by an estimated 68 cGy. Conclusion: Automated intrafraction kV imaging can effectively perform auto beam holds due to patient movement, with the exception of prosthetic hip patients. The additional imaging dose and delivery time are clinically acceptable. It may be a cost-effective alternative to Calypso in RapidArc prostate patient delivery. Further study is warranted to explore its feasibility under various clinical conditions.

  12. Simultaneous integrated boost plan comparison of volumetric-modulated arc therapy and sliding window intensity-modulated radiotherapy for whole pelvis irradiation of locally advanced prostate cancer.

    PubMed

    Riou, Olivier; Regnault de la Mothe, Pauline; Azria, David; Aillères, Norbert; Dubois, Jean-Bernard; Fenoglietto, Pascal

    2013-07-08

    Concurrent radiotherapy to the pelvis plus a prostate boost with long-term androgen deprivation is a standard of care for locally advanced prostate cancer. IMRT has the ability to deliver highly conformal dose to the target while lowering irradiation of critical organs around the prostate. Volumetric-modulated arc therapy is able to reduce treatment time, but its impact on organ sparing is still controversial when compared to static gantry IMRT. We compared the two techniques in simultaneous integrated boost plans. Ten patients with locally advanced prostate cancer were included. The planning target volume (PTV) 1 was defined as the pelvic lymph nodes, the prostate, and the seminal vesicles plus setup margins. The PTV2 consisted of the prostate with setup margins. The prescribed doses to PTV1 and PTV2 were 54 Gy in 37 fractions and 74 Gy in 37 fractions, respectively. We compared simultaneous integrated boost plans by means of either a seven coplanar static split fields IMRT, or a one-arc (RA1) and a two-arc (RA2) RapidArc planning. All three techniques allowed acceptable homogeneity and PTV coverage. Static IMRT enabled a better homogeneity for PTV2 than RapidArc techniques. Sliding window IMRT and VMAT permitted to maintain doses to OAR within acceptable levels with a low risk of side effects for each organ. VMAT plans resulted in a clinically and statistically significant reduction in doses to bladder (mean dose IMRT: 50.1 ± 4.6Gy vs. mean dose RA2: 47.1 ± 3.9 Gy, p = 0.037), rectum (mean dose IMRT: 44± 4.5 vs. mean dose RA2: 41.6 ± 5.5 Gy, p = 0.006), and small bowel (V30 IMRT: 76.47 ± 14.91% vs. V30 RA2: 47.49 ± 16.91%, p = 0.002). Doses to femoral heads were higher with VMAT but within accepted constraints. Our findings suggest that simultaneous integrated boost plans using VMAT and sliding window IMRT allow good OAR sparing while maintaining PTV coverage within acceptable levels.

  13. Arc initiation in cathodic arc plasma sources

    SciTech Connect

    Anders, Andre

    2002-01-01

    A "triggerless" arc initiation method and apparatus is based on simply switching the arc supply voltage to the electrodes (anode and cathode). Neither a mechanical trigger electrode nor a high voltage flashover from a trigger electrode is required. A conducting path between the anode and cathode is provided, which allows a hot spot to form at a location where the path connects to the cathode. While the conductive path is eroded by the cathode spot action, plasma deposition ensures the ongoing repair of the conducting path. Arc initiation is achieved by simply applying the relatively low voltage of the arc power supply, e.g. 500 V-1 kV, with the insulator between the anode and cathode coated with a conducting layer and the current at the layer-cathode interface concentrated at one or a few contact points. The local power density at these contact points is sufficient for plasma production and thus arc initiation. A conductive surface layer, such as graphite or the material being deposited, is formed on the surface of the insulator which separates the cathode from the anode. The mechanism of plasma production (and arc initiation) is based on explosive destruction of the layer-cathode interface caused by joule heating. The current flow between the thin insulator coating and cathode occurs at only a few contact points so the current density is high.

  14. Two-year Follow-up of Volumetric-modulated Arc Therapy for Treating Internal Mammary Nodes in Locally Advanced Breast Cancer.

    PubMed

    Kim, Yi-Jun; Kim, Kyubo; Lee, Rena; Kim, Jiyoung; Jung, Wonguen; Paik, Nam-Sun; Moon, Byung-In; Lim, Woosung; Lee, Jihae

    2016-09-01

    We evaluated dosimetric and clinical results of volumetric-modulated arc therapy (VMAT) treating internal mammary nodes (IMNs) in patients with locally advanced breast cancer. Between July 2012 and December 2013, treatment outcomes of 31 patients with stage III breast cancer treated with postoperative radiotherapy including the IMN field using VMAT were analyzed. The median follow-up was 25.2 months. VMAT showed good homogeneity and improved conformity. The incidence of lung toxicity of grade 2 or more was 3.2%, and cardiac toxicity was not observed. No patient developed local recurrence. VMAT appears safe for the treatment of locally advanced breast cancer including the IMN field. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  15. Evaluation of the trade-offs encountered in planning and treating locally advanced head and neck cancer: intensity-modulated radiation therapy vs dual-arc volumetric-modulated arc therapy

    PubMed Central

    Oliver, M; McConnell, D; Romani, M; McAllister, A; Pearce, A; Andronowski, A; Wang, X; Leszczynski, K

    2012-01-01

    Objective The primary purpose of this study was to assess the practical trade-offs between intensity-modulated radiation therapy (IMRT) and dual-arc volumetric-modulated arc therapy (DA-VMAT) for locally advanced head and neck cancer (HNC). Methods For 15 locally advanced HNC data sets, nine-field step-and-shoot IMRT plans and two full-rotation DA-VMAT treatment plans were created in the Pinnacle3 v. 9.0 (Philips Medical Systems, Fitchburg, WI) treatment planning environment and then delivered on a Clinac iX (Varian Medical Systems, Palo Alto, CA) to a cylindrical detector array. The treatment planning goals were organised into four groups based on their importance: (1) spinal cord, brainstem, optical structures; (2) planning target volumes; (3) parotids, mandible, larynx and brachial plexus; and (4) normal tissues. Results Compared with IMRT, DA-VMAT plans were of equal plan quality (p>0.05 for each group), able to be delivered in a shorter time (3.1 min vs 8.3 min, p<0.0001), delivered fewer monitor units (on average 28% fewer, p<0.0001) and produced similar delivery accuracy (p>0.05 at γ2%/2mm and γ3%/3mm). However, the VMAT plans took more planning time (28.9 min vs 7.7 min per cycle, p<0.0001) and required more data for a three-dimensional dose (20 times more, p<0.0001). Conclusions Nine-field step-and-shoot IMRT and DA-VMAT are both capable of meeting the majority of planning goals for locally advanced HNC. The main trade-offs between the techniques are shorter treatment time for DA-VMAT but longer planning time and the additional resources required for implementation of a new technology. Based on this study, our clinic has incorporated DA-VMAT for locally advanced HNC. Advances in knowledge DA-VMAT is a suitable alternative to IMRT for locally advanced HNC. PMID:22806619

  16. Seismic structure of subducted Philippine Sea plate beneath the southern Ryukyu arc by receiver function and local earthquakes tomography

    NASA Astrophysics Data System (ADS)

    Nakamura, M.

    2012-12-01

    Seismic coupling of the Ryukyu subduction zone is assumed to be weak from the lack of historical interplate large earthquakes. However, recent investigation of repeating slow slip events (Heki & Kataoka, 2008), shallow low frequency earthquakes (Ando et al., 2012), and source of 1771 Yaeyama mega-tsunami (Nakamura, 2009), showed that the interplate coupling is not weak in the south of Ryukyu Trench. The biannually repeating SSEs (Mw=6.5) occur at the depth of 20-40 km on the upper interface of the subducted Philippine Sea plate beneath Yaeyama region, where earthquake swarm occurred on 1991 and 1992. To reveal the relation among the crustal structure, earthquake swarms, and occurrence of slow slip events (SSE), local earthquake tomography and receiver function (RF) analysis was computed in the southwestern Ryukyu arc. A tomographic inversion was used to determine P and S wave structures beneath Iriomote Island in the southwestern Ryukyu region for comparison with the locations of the SSE. The seismic tomography (Thurber & Eberhart-Phillips, 1999) was employed. The P- and S- wave arrival time data picked manually by Japan Meteorological Agency (JMA) are used. The 6750 earthquakes from January 2000 to July 2012 were used. For the calculation of the receiver function, the 212 earthquakes whose magnitudes are over 6.0 and epicentral distances are between 30 and 90 degrees were selected. The teleseicmic waveforms observed at two short-period seismometers of the JMA, and one broadband seismometer of F-net of National Research Institute for Earth Science and Disaster Prevention were used. The water level method (the water level is 0.01) is applied to original waveforms. Assuming that each later phase in a RF is the wave converted from P to S at a depth, I transformed the time domain RF into the depth domain one along each ray path in a reference velocity model. The JMA2001 velocity model is used in this study. The results of tomography show that the low Vp and high Vp

  17. Does localized recharge occur at a discharge area within the ground-water flow system of Yucca Mountain, Nevada?

    SciTech Connect

    Czarnecki, J.B.; Kroitoru, L.; Ronen, D. |; Magaritz, M.

    1992-10-01

    Studies done in 1984, at a central site on Franklin Lake playa (also known as Alkali Flat, a major discharge area of the ground-water flow system that includes Yucca Mountain, Nevada, the potential site of a high-level nuclear-waste repository) yield limited hydraulic-head and hydrochemical data from a 3-piezometer nest which indicated a slightly downward hydraulic gradient ({minus}0.02) and decreasing concentration of dissolved solids with increasing depth. Hydraulic-head measurements in June, 1989 made at the piezometer nest showed a substantially larger downward gradient ({minus}0.10) and a 0. 83{minus}meter higher water level in the shallowest piezometer (3.29 meters deep), indicating the possibility of localized recharge. during the period of September-November, 1989, a multilevel sampler was used to obtain detailed hydrochemical profiles of the uppermost 1. 5 m of the saturated zone.

  18. Upscaling Local Submarine Groundwater Discharge Fluxes to Long Island Sound Using Radionuclides and Thermal Infrared Imagery

    NASA Astrophysics Data System (ADS)

    Tamborski, J.; Bokuniewicz, H.; Cochran, K. K.; Rogers, D.

    2016-02-01

    Aerial thermal infrared (TIR) overflights were performed along a coastline cut into a semi-consolidated coastal aquifer system in order to upscale measurements of submarine groundwater discharge (SGD) derived from radionuclide surveys and cluster-well sampling. Two contrasting sites were chosen along the shoreline of Long Island Sound, CT-NY, USA. Site 1 was a sandy glacial outwash beach down gradient from medium-density residential housing, and site 2 was a sandy barrier beach, characteristic of many coastlines. Satellite TIR imagery resolution was found to be too coarse to resolve the distribution of SGD along Long Island. Upscaling airborne TIR data suggests that satellite imagery would require at least 30m spatial resolution for identifying SGD along Long Island. High resolution airborne TIR data identified distinct shoreline segments on the scale of 0.1km that were likely influenced by a mixture of diffuse fresh and circulated seawater SGD. These findings are further supported by pore water salinity, 224,228Ra and 222Rn, where fresh and brackish pore water at Site 1 were high in dissolved 222Rn (15,000 ± 9,000 dpm 100L-1), low in 224Ra (43 ± 32 dpm 100L-1) and moderately high in 228Ra (126 ± 54 dpm 100L-1). SGD composed of circulated seawater only was found to occur where there was a lack of a TIR signature. In these locations, pore water salinity was consistently saline with moderately high 222Rn (10,600 ± 3,900 dpm 100L-1), 224Ra (580 ± 290 dpm 100L-1) and 228Ra (370 ± 240 dpm 100L-1), reflecting longer pore water residence times. Using this multifaceted approach, fluxes of 224Ra and 228Ra (1.4x109 and 4.5x109 dpm m-1 y-1, respectively, August 2014) were upscaled to the entire length of the Long Island Sound estuary utilizing the shoreline's fractal dimension. Resultant SGD fluxes equal 6.9x1011 ± 2.0x1011 and 3.6x1012 ± 3.1x1012 m3 y-1 for 224Ra and 228Ra, respectively.

  19. Cathodic arcs

    SciTech Connect

    Anders, Andre

    2003-10-29

    Cathodic arc plasma deposition has become the technology of choice for hard, wear and corrosion resistant coatings for a variety of applications. The history, basic physics of cathodic arc operation, the infamous macroparticle problem and common filter solutions, and emerging high-tech applications are briefly reviewed. Cathodic arc plasmas standout due to their high degree of ionization, with important consequences for film nucleation, growth, and efficient utilization of substrate bias. Industrial processes often use cathodic arc plasma in reactive mode. In contrast, the science of arcs has focused on the case of vacuum arcs. Future research directions include closing the knowledge gap for reactive mode, large area coating, linear sources and filters, metal plasma immersion process, with application in high-tech and biomedical fields.

  20. Effects of arcing due to spacecraft charging on spacecraft survival

    NASA Technical Reports Server (NTRS)

    Rosen, A.; Sanders, N. L.; Ellen, J. M., Jr.; Inouye, G. T.

    1978-01-01

    A quantitative assessment of the hazard associated with spacecraft charging and arcing on spacecraft systems is presented. A literature survey on arc discharge thresholds and characteristics was done and gaps in the data and requirements for additional experiments were identified. Calculations of coupling of arc discharges into typical spacecraft systems were made and the susceptibility of typical spacecraft to disruption by arc discharges was investigated. Design guidelines and recommended practices to reduce or eliminate the threat of malfunction and failures due to spacecraft charging/arcing were summarized.

  1. Gyrokinetic simulation of global and local Alfven eigenmodes driven by energetic particles in a DIII-D discharge

    SciTech Connect

    Bass, E. M.; Waltz, R. E.

    2013-01-15

    The unstable spectrum of Alfven eigenmodes (AEs) driven by neutral beam-sourced energetic particles (EPs) in a benchmark DIII-D discharge (142111) is calculated in a fully gyrokinetic model using the GYRO code's massively parallel linear eigenvalue solver. One cycle of the slow (equilibrium scale) frequency sweep of the reverse shear Alfven eigenmode (RSAE) at toroidal mode number n=3 is mapped. The RSAE second harmonic and an unstable beta-induced Alfven eigenmode (BAE) are simultaneously tracked alongside the primary RSAE. An observed twist in the eigenmode pattern, caused mostly by shear in the driving EP profile, is shown through artificially varying the E Multiplication-Sign B rotational velocity shear to depend generally on shear in the local wave phase velocity. Coupling to the BAE and to the toroidal Alfven eigenmode limit the RSAE frequency sweeps at the lower and upper end, respectively. While the present fully gyrokinetic model (including thermal ions and electrons) constitutes the best treatment of compressibility physics available, the BAE frequency is overpredicted by about 20% against experiment here and is found to be sensitive to energetic beam ion pressure. The RSAE frequency is more accurately matched except when it is limited by the BAE. Simulations suggest that the experiment is very close to marginal AE stability at points of RSAE-BAE coupling. A recipe for comparing the radial profile of quasilinear transport flux from local modes to that from global modes paves the way for the development of a stiff (critical gradient) local AE transport model based on local mode stability thresholds.

  2. Growth feature of ionic nitrogen doped CNx bilayer films with Ti and TiN interlayer by pulse cathode arc discharge

    NASA Astrophysics Data System (ADS)

    Zhou, Bing; Liu, Zhubo; Piliptsou, D. G.; Rogachev, A. V.; Yu, Shengwang; Wu, Yanxia; Tang, Bin; Rudenkov, A. S.

    2016-01-01

    Using nano-scaled Ti and TiN as interlayer, ionic nitrogen doped carbon (CNx (N+)) bilayer films were prepared at various pulse frequencies by cathode arc technique. Elemental distribution at the interface, bonding compositions, microstructure, and mechanical properties of CNx (N+) bilayer films were investigated in dependence of interlayer and pulse frequency by Auger electron spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, nanoindentation, and surface profilometer. The results showed that the diffusion extent of C atoms at the interface of CNx (N+) bilayers is higher than for the α-C and CNx (N2) bilayers with the same interlayer. Nitrogen atoms could diffuse throughout the pre-deposited Ti and TiN layers into the Si substrate for all CNx (N+) bilayers. Ti interlayer facilitates the introduction of N atoms into the CNx (N+) films and exhibits a certain catalytic effect on the coordination of N atoms with sp2- and sp3-C binding. More nitrogenated and intense CN bonding configurations (mainly graphite-like N) form in the TiN/CNx (N+) bilayer. Ti/CNx (N+) bilayer prepared at low frequency possesses small size and disordering of Csp2 clusters but TiN interlayer weakens the formation of Csp2 bonding and increases the disordering of Csp2 clusters in the films. The residual stress in the bilayer is lower than for CNx (N+) monolayer. The higher hardness and the lower residual stress are present in the TiN/CNx (N+, 10 Hz) bilayer.

  3. Nonsputtering impulse magnetron discharge

    SciTech Connect

    Khodachenko, G. V.; Mozgrin, D. V.; Fetisov, I. K.; Stepanova, T. V.

    2012-01-15

    Experiments with quasi-steady high-current discharges in crossed E Multiplication-Sign B fields in various gases (Ar, N{sub 2}, H{sub 2}, and SF{sub 6}) and gas mixtures (Ar/SF{sub 6} and Ar/O{sub 2}) at pressures from 10{sup -3} to 5 Torr in discharge systems with different configurations of electric and magnetic fields revealed a specific type of stable low-voltage discharge that does not transform into an arc. This type of discharge came to be known as a high-current diffuse discharge and, later, a nonsputtering impulse magnetron discharge. This paper presents results from experimental studies of the plasma parameters (the electron temperature, the plasma density, and the temperature of ions and atoms of the plasma-forming gas) of a high-current low-pressure diffuse discharge in crossed E Multiplication-Sign B fields.

  4. SU-E-T-809: Volumetric Modulated Arc Radiotherapy Vs. Intensity-Modulated Radiotherapy for Locally Advanced Laryngeal Carcinoma: A Dosimetric Study

    SciTech Connect

    Lu, J-Y; Huang, B-T; Zhang, W-Z; Yan, L-J

    2015-06-15

    Purpose: To compare volumetric modulated arc radiotherapy (VMAT) technique with fixed-gantry intensity-modulated radiotherapy (IMRT) technique for locally advanced laryngeal carcinoma. Methods: CT datasets of eleven patients were included. Dual-arc VMAT and 7-field IMRT plans, which were created based on the Eclipse treatment planning system, were compared in terms of dose-volume parameters, conformity index (CI) and homogeneity index (HI) of planning target volume (PTV), as well as organ-at-risk (OAR) sparing, planning time, monitor units (MUs) and delivery time. Results: Compared with the IMRT plans, the VMAT plans provided lower D2% and better CI/HI for the high-risk PTV (PTV1), and provided better CI and comparable HI for the low-risk PTV (PTV2). Concerning the OAR sparing, the VMAT plans demonstrated significantly lower Dmax of the spinal cord (planning OAR volume, PRV) and brainstem (PRV), as well as lower Dmean and V30Gy of the right parotid. No significant differences were observed between the two plans concerning the doses delivered to the thyroid, carotid, oral cavity and left parotid. Moreover, the VMAT planning (147 ± 18 min) consumed 213% more time than the IMRT planning (48 ± 10 min). The MUs of the VMAT plans (556 ± 52) were 64% less than those of the IMRT plans (1684 ± 409), and the average delivery time (2.1 ± 0.1 min) was 66% less than that of the IMRT plans (6.3 ± 0.7 min). Conclusion: Compared with the IMRT technique, the VMAT technique can achieve superior target dose distribution and better sparing of the spinal cord, brainstem and right parotid, with less MUs and less delivery time. It is recommended for the radiotherapy of locally advanced laryngeal carcinoma.

  5. SU-E-T-302: Dosimetric Comparison Between Volumetric Modulated Arc Radiotherapy and Intensity-Modulated Radiotherapy for Locally Recurrent Nasopharyngeal Carcinoma

    SciTech Connect

    Lu, J-Y; Huang, B-T; Zhang, J-Y; Ma, C-C

    2015-06-15

    Purpose: To compare volumetric modulated arc radiotherapy (VMAT) technique with fixed-gantry intensity-modulated radiotherapy (IMRT) technique for locally recurrent nasopharyngeal carcinoma. Methods: CT datasets of eleven nasopharyngeal-carcinoma patients were included. Dual-arc VMAT and seven-field IMRT plans were created for each case, and were then compared in terms of conformity index (CI), homogeneity index (HI) of the planning target volume (PTV), organ-at-risk (OAR) sparing, monitor unit (MU) and delivery time. Results: The D98% (near-minimal dose) of PTV in the VMAT plans was slightly lower than that of the IMRT plans (P < 0.05), while the CI was higher than that of the IMRT plans (P < 0.05). No significant difference was found in the HI between the two plans (P > 0.05). Compared with the IMRT plans, the VMAT plans demonstrated lower Dmean (mean dose) of the bilateral temporal lobes and the whole surrounding normal tissue (P < 0.05), but slightly higher Dmean of brainstem (P < 0.05). In terms of the other OARs, no significant differences were found (P > 0.05). The MUs of the VMAT plans (672 ± 112) was significantly lower than that of the IMRT plans (917 ± 206), by 25 ± 13% (P < 0.05). The average delivery time of the VMAT plans (2.3 ± 0.1 min) was less than that of the IMRT plans (5.1 ± 0.4 min), by 54 ± 3%. Conclusion: For locally recurrent nasopharyngeal carcinoma, the VMAT technique could achieve equivalent or superior dose distribution of the target and better protect the bilateral temporal lobes, compared with the IMRT technique. Moreover, it could reduce the MU and delivery time effectively.

  6. Low-pressure hydrogen discharge maintenance in a large-size plasma source with localized high radio-frequency power deposition

    SciTech Connect

    Todorov, D.; Shivarova, A. Paunska, Ts.; Tarnev, Kh.

    2015-03-15

    The development of the two-dimensional fluid-plasma model of a low-pressure hydrogen discharge, presented in the study, is regarding description of the plasma maintenance in a discharge vessel with the configuration of the SPIDER source. The SPIDER source, planned for the neutral-beam-injection plasma-heating system of ITER, is with localized high RF power deposition to its eight drivers (cylindrical-coil inductive discharges) and a large-area second chamber, common for all the drivers. The continuity equations for the charged particles (electrons and the three types of positive ions) and for the neutral species (atoms and molecules), their momentum equations, the energy balance equations for electrons, atoms and molecules and the Poisson equations are involved in the discharge description. In addition to the local processes in the plasma volume, the surface processes of particle reflection and conversion on the walls as well as for a heat exchange with the walls are included in the model. The analysis of the results stresses on the role of the fluxes (particle and energy fluxes) in the formation of the discharge structure. The conclusion is that the discharge behavior is completely obeyed to non-locality. The latter is displayed by: (i) maximum values of plasma parameters (charged particle densities and temperatures of the neutral species) outside the region of the RF power deposition, (ii) shifted maxima of the electron density and temperature, of the plasma potential and of the electron production, (iii) an electron flux, with a vortex structure, strongly exceeding the total ion flux which gives evidence of a discharge regime of non-ambipolarity and (iv) a spatial distribution of the densities of the neutral species resulting from their fluxes.

  7. Low-pressure hydrogen discharge maintenance in a large-size plasma source with localized high radio-frequency power deposition

    NASA Astrophysics Data System (ADS)

    Todorov, D.; Shivarova, A.; Paunska, Ts.; Tarnev, Kh.

    2015-03-01

    The development of the two-dimensional fluid-plasma model of a low-pressure hydrogen discharge, presented in the study, is regarding description of the plasma maintenance in a discharge vessel with the configuration of the SPIDER source. The SPIDER source, planned for the neutral-beam-injection plasma-heating system of ITER, is with localized high RF power deposition to its eight drivers (cylindrical-coil inductive discharges) and a large-area second chamber, common for all the drivers. The continuity equations for the charged particles (electrons and the three types of positive ions) and for the neutral species (atoms and molecules), their momentum equations, the energy balance equations for electrons, atoms and molecules and the Poisson equations are involved in the discharge description. In addition to the local processes in the plasma volume, the surface processes of particle reflection and conversion on the walls as well as for a heat exchange with the walls are included in the model. The analysis of the results stresses on the role of the fluxes (particle and energy fluxes) in the formation of the discharge structure. The conclusion is that the discharge behavior is completely obeyed to non-locality. The latter is displayed by: (i) maximum values of plasma parameters (charged particle densities and temperatures of the neutral species) outside the region of the RF power deposition, (ii) shifted maxima of the electron density and temperature, of the plasma potential and of the electron production, (iii) an electron flux, with a vortex structure, strongly exceeding the total ion flux which gives evidence of a discharge regime of non-ambipolarity and (iv) a spatial distribution of the densities of the neutral species resulting from their fluxes.

  8. High frequency pacing of edge localized modes by injection of lithium granules in DIII-D H-mode discharges

    DOE PAGES

    Bortolon, A.; Maingi, R.; Mansfield, D. K.; ...

    2016-04-08

    A newly installed Lithium Granule Injector (LGI) was used to pace edge localized modes (ELM) in DIII-D. ELM pacing efficiency was studied injecting lithium granules of nominal diameter 0.3–0.9mm, speed of 50–120 m s-1 and average injection rates up to 100 Hz for 0.9mm granules and up to 700 Hz for 0.3mm granules. The efficiency of ELM triggering was found to depend strongly on size of the injected granules, with triggering efficiency close to 100% obtained with 0.9mm diameter granules, lower with smaller sizes, and weakly depending on granule velocity. Robust ELM pacing was demonstrated in ITER-like plasmas for themore » entire shot length, at ELM frequencies 3–5 times larger than the ‘natural’ ELM frequency observed in reference discharges. Within the range of ELM frequencies obtained, the peak ELM heat flux at the outer strike point was reduced with increasing pacing frequency. The peak heat flux reduction at the inner strike point appears to saturate at high pacing frequency. Lithium was found in the plasma core, with a concurrent reduction of metallic impurities and carbon. Altogether, high frequency ELM pacing using the lithium granule injection appears to be compatible with both H-mode energy confinement and attractive H-mode pedestal characteristics, but further assessment is need« less

  9. High frequency pacing of edge localized modes by injection of lithium granules in DIII-D H-mode discharges

    SciTech Connect

    Bortolon, A.; Maingi, R.; Mansfield, D. K.; Nagy, A.; Roquemore, A. L.; Baylor, L. R.; Commaux, N.; Jackson, G. L.; Gilson, E. P.; Lunsford, R.; Parks, P. B.; Chrystal, C.; Grierson, B. A.; Groebner, R.; Haskey, S. R.; Makowski, M. J.; Lasnier, C. J.; Nazikian, R.; Osborne, T.; Shiraki, D.; Van Zeeland, M. A.

    2016-04-08

    A newly installed Lithium Granule Injector (LGI) was used to pace edge localized modes (ELM) in DIII-D. ELM pacing efficiency was studied injecting lithium granules of nominal diameter 0.3–0.9mm, speed of 50–120 m s-1 and average injection rates up to 100 Hz for 0.9mm granules and up to 700 Hz for 0.3mm granules. The efficiency of ELM triggering was found to depend strongly on size of the injected granules, with triggering efficiency close to 100% obtained with 0.9mm diameter granules, lower with smaller sizes, and weakly depending on granule velocity. Robust ELM pacing was demonstrated in ITER-like plasmas for the entire shot length, at ELM frequencies 3–5 times larger than the ‘natural’ ELM frequency observed in reference discharges. Within the range of ELM frequencies obtained, the peak ELM heat flux at the outer strike point was reduced with increasing pacing frequency. The peak heat flux reduction at the inner strike point appears to saturate at high pacing frequency. Lithium was found in the plasma core, with a concurrent reduction of metallic impurities and carbon. Altogether, high frequency ELM pacing using the lithium granule injection appears to be compatible with both H-mode energy confinement and attractive H-mode pedestal characteristics, but further assessment is need

  10. High frequency pacing of edge localized modes by injection of lithium granules in DIII-D H-mode discharges

    NASA Astrophysics Data System (ADS)

    Bortolon, A.; Maingi, R.; Mansfield, D. K.; Nagy, A.; Roquemore, A. L.; Baylor, L. R.; Commaux, N.; Jackson, G. L.; Gilson, E. P.; Lunsford, R.; Parks, P. B.; Chrystal, C.; Grierson, B. A.; Groebner, R.; Haskey, S. R.; Makowski, M. J.; Lasnier, C. J.; Nazikian, R.; Osborne, T.; Shiraki, D.; Van Zeeland, M. A.

    2016-05-01

    A newly installed Lithium Granule Injector (LGI) was used to pace edge localized modes (ELM) in DIII-D. ELM pacing efficiency was studied injecting lithium granules of nominal diameter 0.3-0.9 mm, speed of 50-120 m s-1 and average injection rates up to 100 Hz for 0.9 mm granules and up to 700 Hz for 0.3 mm granules. The efficiency of ELM triggering was found to depend strongly on size of the injected granules, with triggering efficiency close to 100% obtained with 0.9 mm diameter granules, lower with smaller sizes, and weakly depending on granule velocity. Robust ELM pacing was demonstrated in ITER-like plasmas for the entire shot length, at ELM frequencies 3-5 times larger than the ‘natural’ ELM frequency observed in reference discharges. Within the range of ELM frequencies obtained, the peak ELM heat flux at the outer strike point was reduced with increasing pacing frequency. The peak heat flux reduction at the inner strike point appears to saturate at high pacing frequency. Lithium was found in the plasma core, with a concurrent reduction of metallic impurities and carbon. Overall, high frequency ELM pacing using the lithium granule injection appears to be compatible with both H-mode energy confinement and attractive H-mode pedestal characteristics, but further assessment is needed to determine whether the projected heat flux reduction required for ITER can be met.

  11. Spectral cues for sound localization in cats: a model for discharge rate representations in the auditory nerve.

    PubMed

    May, B J; Huang, A Y

    1997-05-01

    Neural representations of pinna-based spectral cues for sound localization were modeled by simulating auditory nerve discharge rates to noise bursts that had been shaped by filtering properties of the cat's head-related transfer functions (HRTFs) at 179 locations in the frontal field. The auditory nerve model transformed spectral differences between HRTFs into simulated neural rate differences. Linear equations for this transformation were developed from actual auditory nerve responses to a limited subset of HRTF-filtered noise bursts [Rice et al., J. Acoust. Soc. Am. 97, 1764-1776 (1995)]. Signal detection methods were used to investigate simulated neural responses to pairwise changes between HRTFs. The quality of neural representation for these changes, in terms of d' values, declined when the reference HRTF was moved from a central location (0 degree AZ, 0 degree EL) to a large positive azimuth in the horizontal plane (75 degrees AZ, 0 degree EL) or a high elevation in the median plane (0 degree AZ, 75 degrees EL). Most simulated responses exhibited large d' values for comparisons of contralateral versus ipsilateral azimuths, or eccentric versus frontal elevations. This rate information resulted from directionally dependent changes in the overall gain of HRTFs. In addition, fibers with best frequency (BF: the frequency of greatest sensitivity for individual fibers) between 5 and 18 kHz showed large d' values for HRTF contrasts in the immediate frontal field because of the effects of spectral notches (i.e., sharp drops in gain over a narrow frequency range). Spectral notches also played a prominent role in simulations that required identification of HRTF location in the absence of a fixed reference stimulus. These modeling results correspond well with previously described patterns in the cat's localization behaviors.

  12. Flight Model Discharge System

    DTIC Science & Technology

    1988-06-01

    Dielectric Sensor ................................... 12 5 ESA S/N 001 ......................................... 24 6 Preliminary Test Sequence...71 28 Optical Transmission Loss of Contamination "Witness" Slide 3 .................................. 72 29 Apparatus used in FMDS Spectroscopic...Monitor ( TPU ). This sensor detects the electromagnetic pulses generated by the onset of arcing. (2) An active discharge device (plasma source). (3) A

  13. Assessing the Role of Volumetric Modulated Arc Therapy (VMAT) Relative to IMRT and Helical Tomotherapy in the Management of Localized, Locally Advanced, and Post-Operative Prostate Cancer

    SciTech Connect

    Davidson, Melanie T.M.; Blake, Samuel J.; Batchelar, Deidre L.; Cheung, Patrick; Mah, Katherine

    2011-08-01

    Purpose: To quantify differences in treatment delivery efficiency and dosimetry between step-and-shoot intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT) for prostate treatment. Methods and Materials: Twenty-five prostate cancer patients were selected retrospectively for this planning study. Treatment plans were generated for: prostate alone (n = 5), prostate + seminal vesicles (n = 5), prostate + seminal vesicles + pelvic lymph nodes (n = 5), prostate bed (n = 5), and prostate bed + pelvic lymph nodes (n = 5). Target coverage, dose homogeneity, integral dose, monitor units (MU), and sparing of organs at risk (OAR) were compared across techniques. Time required to deliver each plan was measured. Results: The dosimetric quality of IMRT, VMAT, and HT plans were comparable for target coverage (planning target volume V95%, clinical target volume V100% all >98.7%) and sparing of organs at risk (OAR) for all treatment groups. Although HT resulted in a slightly higher integral dose and mean doses to the OAR, it yielded a lower maximum dose to all OAR examined. VMAT resulted in reductions in treatment times over IMRT (mean = 75%) and HT (mean = 70%). VMAT required 15-38% fewer monitor units than IMRT over all treatment volumes, with the reduction per fraction ranging from 100-423 MU from the smallest to largest volumes. Conclusions: VMAT improves efficiency of delivery for equivalent dosimetric quality as IMRT and HT across various prostate cancer treatment volumes in the intact and postoperative settings.

  14. Crust-mantle boundaries in the Taiwan - Luzon arc-continent collision system determined from local earthquake tomography and layered Vp models

    NASA Astrophysics Data System (ADS)

    Ustaszewski, K. M.; Wu, Y.; Suppe, J.; Huang, H.; Carena, S.; Chang, C.

    2011-12-01

    We performed 3D mapping of crust-mantle boundaries in the Taiwan-Luzon arc-continent collision zone using a local earthquake tomographic model, providing better insight into the mode of subduction polarity reversal. The mapped crust-mantle discontinuities include three tectonically distinct Mohos. Furthermore, a crust-mantle boundary marks the eastern limit of the Eurasian lower crust against the mantle of the Philippine Sea plate. It dips steeply to the east underneath eastern and southern Taiwan and steepens progressively towards north until it becomes vertical at 23.7°N. From there it continues northward in a slightly overturned orientation, where the limit of the tomographic model at the northern tip of the island prevents further mapping. In order to map several Moho discontinuities, we contoured a surface of constant Vp = 7.5 km s-1 constrained from local earthquake tomography and confined to regions with a minimum of 500 rays per tomography cell. Additional constraints for the Moho were derived from layered (1D) Vp models using P-wave arrivals of local earthquakes recorded at 52 seismic stations, employing a genetic algorithm. The Moho of the Eurasian and the Philippine Sea plates are topologically disconnected across the plate boundary. Beneath southern Taiwan, the Eurasian Moho dips to the E at 50-60°, following the orientation of the plate boundary and continuous with the Benioff zone. Towards north, the Eurasian Moho twists to become subvertical, again together with the plate boundary. At the same time, it steps westward into a more external position underneath the thrust belt, giving way to the north-dipping Philippine Sea plate. The Philippine Sea plate Moho shallows towards the surface along the Longitudinal Valley suture. It forms a synform-like crustal root with an axis parallel to the trend of geological units at surface and it is interpreted as the base of the magmatic Luzon arc. Towards the north, the crustal root deepens from 30 km to about 70

  15. Elements of arc welding

    SciTech Connect

    Not Available

    1993-07-01

    This paper looks at the following arc welding techniques: (1) shielded metal-arc welding; (2) submerged-arc welding; (3) gas metal-arc welding; (4) flux-cored arc welding; (5) electrogas welding; (6) gas tungsten-arc welding; and (7) plasma-arc welding.

  16. Gliding arc triggered microwave plasma arc at atmospheric pressure for coal gasification application

    NASA Astrophysics Data System (ADS)

    Jain, Vishal; Visani, A.; Patil, C.; Patel, B. K.; Sharma, P. K.; John, P. I.; Nema, S. K.

    2014-08-01

    Plasma torch is device that efficiently converts electrical energy in to thermal energy for various high temperature applications. The conventional plasma torch comprises of consumable electrodes namely anode and cathode electrodes. The replacement of these electrodes is a complex process owing to its cooling and process shut down requirements. However, microwave plasma arc is electrode-less plasma arc system that is an alternative method to conventional arc technology for generating plasma arc. In this technique, microwave power is efficiently coupled to generate plasma arc by using the property of polar molecule to absorb microwave power. The absorption of microwave power is in form of losses due to intermolecular friction and high collisions between the molecules. This is an efficient method because all microwave power can be absorbed by plasma arc. The main feature of microwave plasma arc is its large uniform high temperature column which is not possible with conventional arc discharge methods. Such type of plasma discharge is very useful in applications where sufficient residence time for treat materials is required. Microwave arc does not require any consumable electrodes and hence, it can be operated continuously that makes it very useful for hazardous effluent treatment applications. Further, microwave cannot ionize neutral particles at atmospheric pressure and hence, a gliding arc is initiated between two thin electrodes in the cavity by applying very low power high voltage (3kV) AC source. In this report, the method for generating microwave arc of 1kW power using commercial microwave oven is elaborated.

  17. On Possible Arc Inception on Low Voltage Solar Array

    NASA Technical Reports Server (NTRS)

    Vayner, Boris

    2015-01-01

    Recent analysis of spacecraft failures during the period of 1990-2013 demonstrated clearly that electrostatic discharges caused more than 8 of all registered failures and anomalies, and comprised the most costly losses (25) for operating companies and agencies. The electrostatic discharges on spacecraft surfaces are the results of differential charging above some critical (threshold) voltages. The mechanisms of differential charging are well known, and various methods have been developed to prevent a generation of significant electric fields in areas of triple junctions. For example, low bus voltages in Low Earth Orbit plasma environment and slightly conducting layer over coverglass (ITO) in Geosynchronous Orbit surroundings are believed to be quite reliable measures to prevent discharges on respective surfaces. In most cases, the vulnerable elements of spacecraft (solar arrays, diode boards, etc.) go through comprehensive ground tests in vacuum chambers. However, tests articles contain the miniscule fragments of spacecraft components such as 10-30 solar cells of many thousands deployed on spacecraft in orbit. This is one reason why manufacturing defects may not be revealed in ground tests but expose themselves in arcing on array surface in space. The other reason for ineffectiveness of discharge preventive measures is aging of all materials in harsh orbital environments. The expected life time of modern spacecraft varies within the range of five-fifteen years, and thermal cycling, radiation damages, and mechanical stresses can result in surface erosion on conductive layers and microscopic cracks in coverglass sheets and adhesive films. These possible damages may cause significant increases in local electric field strengths and subsequent discharges. The primary discharges may or may not be detrimental to spacecraft operation, but they can produce the necessary conditions for sustained arcs initiation. Multiple measures were developed to prevent sustained

  18. On Possible Arc Inception on Low Voltage Solar Array

    NASA Technical Reports Server (NTRS)

    Vayner, Boris

    2015-01-01

    Recent analysis of spacecraft failures during the period of 1990-2013 demonstrated clearly that electrostatic discharges caused more than 8 percent of all registered failures and anomalies, and comprised the most costly losses (25 percent) for operating companies and agencies. The electrostatic discharges on spacecraft surfaces are the results of differential charging above some critical (threshold) voltages. The mechanisms of differential charging are well known, and various methods have been developed to prevent a generation of significant electric fields in areas of triple junctions. For example, low bus voltages in Low Earth Orbit plasma environment and slightly conducting layer over cover-glass (ITO) in Geosynchronous Orbit surroundings are believed to be quite reliable measures to prevent discharges on respective surfaces. In most cases, the vulnerable elements of spacecraft (solar arrays, diode boards, etc.) go through comprehensive ground tests in vacuum chambers. However, tests articles contain the miniscule fragments of spacecraft components such as 10-30 solar cells of many thousands deployed on spacecraft in orbit. This is one reason why manufacturing defects may not be revealed in ground tests but expose themselves in arcing on array surface in space. The other reason for ineffectiveness of discharge preventive measures is aging of all materials in harsh orbital environments. The expected life time of modern spacecraft varies within the range of five-fifteen years, and thermal cycling, radiation damages, and mechanical stresses can result in surface erosion on conductive layers and microscopic cracks in cover-glass sheets and adhesive films. These possible damages may cause significant increases in local electric field strengths and subsequent discharges. The primary discharges may or may not be detrimental to spacecraft operation, but they can produce the necessary conditions for sustained arcs initiation. Multiple measures were developed to prevent

  19. Stereotactic body radiation therapy planning with duodenal sparing using volumetric-modulated arc therapy vs intensity-modulated radiation therapy in locally advanced pancreatic cancer: A dosimetric analysis

    SciTech Connect

    Kumar, Rachit; Wild, Aaron T.; Ziegler, Mark A.; Hooker, Ted K.; Dah, Samson D.; Tran, Phuoc T.; Kang, Jun; Smith, Koren; Zeng, Jing; Pawlik, Timothy M.; Tryggestad, Erik; Ford, Eric; Herman, Joseph M.

    2013-10-01

    Stereotactic body radiation therapy (SBRT) achieves excellent local control for locally advanced pancreatic cancer (LAPC), but may increase late duodenal toxicity. Volumetric-modulated arc therapy (VMAT) delivers intensity-modulated radiation therapy (IMRT) with a rotating gantry rather than multiple fixed beams. This study dosimetrically evaluates the feasibility of implementing duodenal constraints for SBRT using VMAT vs IMRT. Non–duodenal sparing (NS) and duodenal-sparing (DS) VMAT and IMRT plans delivering 25 Gy in 1 fraction were generated for 15 patients with LAPC. DS plans were constrained to duodenal D{sub max} of<30 Gy at any point. VMAT used 1 360° coplanar arc with 4° spacing between control points, whereas IMRT used 9 coplanar beams with fixed gantry positions at 40° angles. Dosimetric parameters for target volumes and organs at risk were compared for DS planning vs NS planning and VMAT vs IMRT using paired-sample Wilcoxon signed rank tests. Both DS VMAT and DS IMRT achieved significantly reduced duodenal D{sub mean}, D{sub max}, D{sub 1cc}, D{sub 4%}, and V{sub 20} {sub Gy} compared with NS plans (all p≤0.002). DS constraints compromised target coverage for IMRT as demonstrated by reduced V{sub 95%} (p = 0.01) and D{sub mean} (p = 0.02), but not for VMAT. DS constraints resulted in increased dose to right kidney, spinal cord, stomach, and liver for VMAT. Direct comparison of DS VMAT and DS IMRT revealed that VMAT was superior in sparing the left kidney (p<0.001) and the spinal cord (p<0.001), whereas IMRT was superior in sparing the stomach (p = 0.05) and the liver (p = 0.003). DS VMAT required 21% fewer monitor units (p<0.001) and delivered treatment 2.4 minutes faster (p<0.001) than DS IMRT. Implementing DS constraints during SBRT planning for LAPC can significantly reduce duodenal point or volumetric dose parameters for both VMAT and IMRT. The primary consequence of implementing DS constraints for VMAT is increased dose to other organs at

  20. Plural voltage minima in an arc-heated channel flow

    NASA Astrophysics Data System (ADS)

    Sasoh, A.

    2001-04-01

    In flows through a channel with varying cross-sectional area, the impulse and total enthalpy can be increased by superimposing an electrical discharge. The flow field is determined from the inlet flow condition, channel geometry, and discharge specifications. In this study, steady-state, quasi-one-dimensional flows interacting with an arc discharge are computed numerically. Once the arc column configuration is given, the discharge voltage is computed from the solution of flow field variables. For a constant discharge current, there exist plural column configurations which yield a minimum discharge voltage. This result explains the fluid-dynamic mechanisms of the existence of plural voltage modes in an arcjet operation.

  1. Evaluation of the satellite-based Global Flood Detection System for measuring river discharge: influence of local factors

    NASA Astrophysics Data System (ADS)

    Revilla-Romero, B.; Thielen, J.; Salamon, P.; De Groeve, T.; Brakenridge, G. R.

    2014-11-01

    One of the main challenges for global hydrological modelling is the limited availability of observational data for calibration and model verification. This is particularly the case for real-time applications. This problem could potentially be overcome if discharge measurements based on satellite data were sufficiently accurate to substitute for ground-based measurements. The aim of this study is to test the potentials and constraints of the remote sensing signal of the Global Flood Detection System for converting the flood detection signal into river discharge values. The study uses data for 322 river measurement locations in Africa, Asia, Europe, North America and South America. Satellite discharge measurements were calibrated for these sites and a validation analysis with in situ discharge was performed. The locations with very good performance will be used in a future project where satellite discharge measurements are obtained on a daily basis to fill the gaps where real-time ground observations are not available. These include several international river locations in Africa: the Niger, Volta and Zambezi rivers. Analysis of the potential factors affecting the satellite signal was based on a classification decision tree (random forest) and showed that mean discharge, climatic region, land cover and upstream catchment area are the dominant variables which determine good or poor performance of the measurement sites. In general terms, higher skill scores were obtained for locations with one or more of the following characteristics: a river width higher than 1km; a large floodplain area and in flooded forest, a potential flooded area greater than 40%; sparse vegetation, croplands or grasslands and closed to open and open forest; leaf area index > 2; tropical climatic area; and without hydraulic infrastructures. Also, locations where river ice cover is seasonally present obtained higher skill scores. This work provides guidance on the best locations and limitations

  2. Evaluation of the satellite-based Global Flood Detection System for measuring river discharge: influence of local factors

    NASA Astrophysics Data System (ADS)

    Revilla-Romero, B.; Thielen, J.; Salamon, P.; De Groeve, T.; Brakenridge, G. R.

    2014-07-01

    One of the main challenges for global hydrological modelling is the limited availability of observational data for calibration and model verification. This is particularly the case for real time applications. This problem could potentially be overcome if discharge measurements based on satellite data were sufficiently accurate to substitute for ground-based measurements. The aim of this study is to test the potentials and constraints of the remote sensing signal of the Global Flood Detection System for converting the flood detection signal into river discharge values. The study uses data for 322 river measurement locations in Africa, Asia, Europe, North America and South America. Satellite discharge measurements were calibrated for these sites and a validation analysis with in situ discharge was performed. The locations with very good performance will be used in a future project where satellite discharge measurements are obtained on a daily basis to fill the gaps where real time ground observations are not available. These include several international river locations in Africa: Niger, Volta and Zambezi rivers. Analysis of the potential factors affecting the satellite signal was based on a classification decision tree (Random Forest) and showed that mean discharge, climatic region, land cover and upstream catchment area are the dominant variables which determine good or poor performance of the measurement sites. In general terms, higher skill scores were obtained for locations with one or more of the following characteristics: a river width higher than 1 km; a large floodplain area and in flooded forest; with a potential flooded area greater than 40%; sparse vegetation, croplands or grasslands and closed to open and open forest; Leaf Area Index > 2; tropical climatic area; and without hydraulic infrastructures. Also, locations where river ice cover is seasonally present obtained higher skill scores. The work provides guidance on the best locations and limitations

  3. Local and regional slope instability inferred from sea-floor morphology at accretive and erosive convergent margins: case studies of the offshore Hikurangi and Peru fore-arcs

    NASA Astrophysics Data System (ADS)

    Kukowski, N.; Greinert, J.; Hoth, S.; Henrys, S.

    2009-04-01

    The mechanics of a forearc, a wedge-shaped part of the overriding plate between the trench and the volcanic arc, are elegantly and in a straightforward way described in terms of the critical taper concept. Based on the Mohr-Coulomb failure criterion and applying an elasto-plastic rheology, it describes the state (sub-critical, stable, super-critical) of any point of the wedge as a function of its geometry (slope and dip), basal and internal friction as well as basal and internal fluid pressure parameter. Subduction erosion or the subduction of seamounts and other lower plate topographic features such as basement ridges lead to temporarily increasing surface slope and therefore may facilitate mechanical instability. Here we study the causes of local and regional failure at the central Hikurangi wedge offshore New Zealand's North Island and along the Peruvian margin. The geometry of both margins is well known from seismic studies and swath bathymetry coverage and therefore allows to quantify local slope gradients and other curvature attributes. New high-resolution swath bathymetry data show a complex seafloor morphology from the Rock Garden area, offshore Hikurangi Margin, that coincides with the subduction of a seamount presently located beneath the summit of Rock Garden. Another ridge-shaped lower plate feature is initially colliding with Rock Garden, forming a re-entrant at is seaward flank. The slopes of the accretionary ridges are steeper than 10∘ and often more than 20∘ regionally. Slumping mostly occurs on the trench-ward slopes, with individual failures up to several km2. Critical taper analysis shows that much of the seaward slopes probably are outside the stability field and therefore subject to failure. The most prominent feature of seafloor maps is the trench-ward flank of Rock Garden with a height of 1800 to 2000 m and an average slope of more than 10∘. Extensional faults arranged in two sub-circular arcs indicate that Rock Garden may be on the

  4. Unzipping of the volcano arc, Japan

    USGS Publications Warehouse

    Stern, R.J.; Smoot, N.C.; Rubin, M.

    1984-01-01

    A working hypothesis for the recent evolution of the southern Volcano Arc, Japan, is presented which calls upon a northward-progressing sundering of the arc in response to a northward-propagating back-arc basin extensional regime. This model appears to explain several localized and recent changes in the tectonic and magrnatic evolution of the Volcano Arc. Most important among these changes is the unusual composition of Iwo Jima volcanic rocks. This contrasts with normal arc tholeiites typical of the rest of the Izu-Volcano-Mariana and other primitive arcs in having alkaline tendencies, high concentrations of light REE and other incompatible elements, and relatively high silica contents. In spite of such fractionated characteristics, these lavas appear to be very early manifestations of a new volcanic and tectonic cycle in the southern Volcano Arc. These alkaline characteristics and indications of strong regional uplift are consistent with the recent development of an early stage of inter-arc basin rifting in the southern Volcano Arc. New bathymetric data are presented in support of this model which indicate: 1. (1) structural elements of the Mariana Trough extend north to the southern Volcano Arc. 2. (2) both the Mariana Trough and frontal arc shoal rapidly northwards as the Volcano Arc is approached. 3. (3) rugged bathymetry associated with the rifted Mariana Trough is replaced just south of Iwo Jima by the development of a huge dome (50-75 km diameter) centered around Iwo Jima. Such uplifted domes are the immediate precursors of rifts in other environments, and it appears that a similar situation may now exist in the southern Volcano Arc. The present distribution of unrifted Volcano Arc to the north and rifted Mariana Arc to the south is interpreted not as a stable tectonic configuration but as representing a tectonic "snapshot" of an arc in the process of being rifted to form a back-arc basin. ?? 1984.

  5. Implications of arcing due to spacecraft charging on spacecraft EMI margins of immunity

    NASA Technical Reports Server (NTRS)

    Inouye, G. T.

    1981-01-01

    Arcing due to spacecraft charging on spacecraft EMI margins of immunity was determined. The configuration of the P78-2 spacecraft of the SCATHA program was analyzed. A brushfire arc discharge model was developed, and a technique for initiating discharges with a spark plug trigger was for data configuration. A set of best estimate arc discharge parameters was defined. The effects of spacecraft potentials in limiting the discharge current blowout component are included. Arc discharge source models were incorporated into a SEMCAP EMI coupling analysis code for the DSP spacecraft. It is shown that with no mission critical circuits will be affected.

  6. [The polycentric multiple arc complanar technic, or telebrachytherapy. A 4-year experience (an innovative way for the local control of solid neoplasms)].

    PubMed

    Polico, R; Stea, L; Antonello, M; Princivalli, M; Marchetti, C; Busetto, M; Schiavon, S; Pizzi, G

    1995-01-01

    The coplanar polycentric multiple 180 degrees single arc and narrow beams technique (PMA) allows high radiation doses to be delivered to the target, with similar dose distribution to that of brachytherapy. Since 1990, more than 100 patients have been treated: 80 had NSCLC, 12 had epidermoid head and neck (oral cavity and oropharynx) cancers, 8 brain tumors, 4 esophageal cancers and, sporadically, other patients had many other kinds of tumors, e.g., Hodgkin's and non-Hodgkin's lymphomas and sarcomas. X photons of a 12-MV Linac have always been used. NSCLC patients are assessable for local control, toxicity and survival, while the other patients only for local control and/or toxicity. As for 31 stage I-II lung cancer patients, CR has been observed in 82.8% of them and PR in 13.8%; the response was always assessed with chest radiography, CT, FBS, cytology and/or histology. The overall actuarial survival rate is 71% at 40 months, the disease-free survival rate is 75% and the local progression-free survival rate is 94%. As for 49 stage-III patients, CR has been observed in 40% of them and PR in 56%. The overall disease-free survival is 10% at 28 months (median survival: 14.37 +/- 0.6 months). The disease-free survival rate is 23%. The local progression-free survival rate is similar to the overall survival rate, which seems to prove the very high metastatic spread of this disease in advanced stages. Twelve head and neck cancer patients have been treated, 5 of them in stage II and 7 in stage IV. CR has been observed in all the patients in lower stages (100%), in 4/7 patients in stage IV (57%) and in 4/5 patients (80%) in the T4N0 subgroup. The response of brain tumors treated with the PMA technique is difficult to assess because radiographic, CT and MR images are difficult to correlate with patients clinical status. The patients in our series are still alive, with a medium follow-up of 7 months (range: 2-16 months). A longer follow-up is necessary before any other

  7. Physics of arcing, and implications to sputter deposition

    SciTech Connect

    Anders, Andre

    2005-03-15

    Arc and glow discharges are defined based on their cathode processes. Arcs are characterized by collective electron emission, which can be stationary with hot cathodes (thermionic arcs), or non-stationary with cold cathodes (cathodic arcs). A brief review on cathodic arc properties serves as the starting point to better understand arcing phenomena in sputtering. Although arcing occurs in both metal and reactive sputtering, it is more of an issue in the reactive case. Arcing occurs if sufficiently high field strength leads to thermal runaway of an electron emission site. The role of insulating layers and surface potential adjustment through current leakage is highlighted. In the situation of magnetron sputtering with ''racetrack'', the need for a model with two spatial dimensions is shown. In many cases, arcing is initiated by breakdown of dielectric layers and inclusions. It is most efficiently prevented if formation and excessive charge-up of dielectric layers and inclusions can be avoided.

  8. Physical characteristics of welding arc ignition process

    NASA Astrophysics Data System (ADS)

    Shi, Linan; Song, Yonglun; Xiao, Tianjiao; Ran, Guowei

    2012-07-01

    The existing research of welding arc mainly focuses on the stable combustion state and the research on the mechanism of welding arc ignition process is quite lack. The tungsten inert gas(TIG) touch arc ignition process is observed via a high speed camera and the high time resolution spectral diagnosis system. The changing phenomenon of main ionized element provided the electrons in the arc ignition is found. The metallic element is the main contributor to provide the electrons at the beginning of the discharging, and then the excitated shielding gas element replaces the function of the metallic element. The electron density during the period of the arc ignition is calculated by the Stark-broadened lines of Hα. Through the discussion with the repeatability in relaxation phenomenon, the statistical regularity in the arc ignition process is analyzed. The similar rules as above are observed through the comparison with the laser-assisted arc ignition experiments and the metal inert gas(MIG) arc ignition experiments. This research is helpful to further understanding on the generation mechanism of welding arc ignition and also has a certain academic and practical significance on enriching the welding physical theoretical foundation and improving the precise monitoring on automatic arc welding process.

  9. Pancreatitis - discharge

    MedlinePlus

    Chronic pancreatitis - discharge; Pancreatitis - chronic - discharge; Pancreatic insufficiency - discharge; Acute pancreatitis - discharge ... fluids through an intravenous (IV) tube in your vein and nutrition through a feeding tube or IV. ...

  10. Ear discharge

    MedlinePlus

    ... health care provider if: The discharge is white, yellow, clear, or bloody. The discharge is the result of an injury. The discharge has lasted more than 5 days. There is severe pain. The discharge is ...

  11. Changes in discharge dynamics under the constraints of local and global changes in the Chao Lake basin (China)

    NASA Astrophysics Data System (ADS)

    Chu, Y.; Salles, C.; Rodier, C.; Crès, F.-N.; Huang, L.; Tournoud, M.-G.

    2012-04-01

    Located on the Yangtze basin, the Chao Lake is the fifth largest freshwater lake in China and of great importance in terms of water resources and aquaculture. Its catchment (9130 km2) includes the city of Hefei and large extends of agricultural and rural areas. Fast changes are expected in land uses and agricultural practices for the future, due to the touristic appeal of the Chao Lake shore and the growth of the city of Hefei. Climate changes are also expected in this region, with a high impact on rainfall regime. The consequences of these changes on the sustainability of the water inflows into the lake are a major issue for the economical development of the Chao Lake area even though they are little-known. Our study aims to give tools for estimating such consequences, accounting for uncertainties in scenario data and model parameters. The dynamics of rivers flowing into the Chao Lake is not very well-known, except for the Fengle River. The Fengle catchment (1480 km2) is mainly rural. River discharges are recorded at Taoxi station, upstream its outlet into the lake. 20-year records of daily discharges are available. Nine rain gauges, with daily data, daily temperature and evapotranspiration data are also available. The current dynamics of the Fengle River is characterized in terms of flood frequencies on discharge-duration-frequency curves. The ATHYS freely available hydrological tool (www.athys-soft.org) is used to calibrate and validate a distributed model of the Fengle catchment. Four calibration runs are done on four independent 5-year discharge records. Four different sets of model parameters are discussed. The model is then run for validation. The uncertainties in model predictions are evaluated in terms of errors in the simulated discharges during the validation period, with regards to the 5-year period used for calibration. The model is then applied on scenarios of changes in land uses and climate. Uncertainties in scenarios of changes are estimated

  12. ArgR is an essential local transcriptional regulator of the arcABC operon in Streptococcus suis and is crucial for biological fitness in an acidic environment.

    PubMed

    Fulde, Marcus; Willenborg, Joerg; de Greeff, Astrid; Benga, Laurentiu; Smith, Hilde E; Valentin-Weigand, Peter; Goethe, Ralph

    2011-02-01

    Streptococcus suis is one of the most important pathogens in pigs and can also cause severe infections in humans. Despite its clinical relevance, very little is known about the factors that contribute to its virulence. Recently, we identified a new putative virulence factor in S. suis, the arginine deiminase system (ADS), an arginine catabolic enzyme system encoded by the arcABC operon, which enables S. suis to survive in an acidic environment. In this study, we focused on ArgR, an ADS-associated regulator belonging to the ArgR/AhrC arginine repressor family. Using an argR knockout strain we were able to show that ArgR is essential for arcABC operon expression and necessary for the biological fitness of S. suis. By cDNA expression microarray analyses and quantitative real-time RT-PCR we found that the arcABC operon is the only gene cluster regulated by ArgR, which is in contrast to the situation in many other bacteria. Reporter gene analysis with gfp under the control of the arcABC promoter demonstrated that ArgR is able to activate the arcABC promoter. Electrophoretic mobility shift assays with fragments of the arcABC promoter and recombinant ArgR, and chromatin immunoprecipitation with antibodies directed against ArgR, revealed that ArgR interacts with the arcABC promoter in vitro and in vivo by binding to a region from -147 to -72 bp upstream of the transcriptional start point. Overall, our results show that in S. suis, ArgR is an essential, system-specific transcriptional regulator of the ADS that interacts directly with the arcABC promoter in vivo.

  13. Fluid simulation of carbon arc plasma

    NASA Astrophysics Data System (ADS)

    Hara, Kentaro; Raitses, Yevgeny; Kaganovich, Igor

    2016-09-01

    An arc discharge using graphite electrodes is known to produce carbon nanomaterials, e.g. nanotubes and fullerenes. In order to understand where and how such nanomaterials are synthesized, the plasma properties inside the arc discharge must be characterized. The mechanism of the carbon arc plasma is as follows. Carbon particles evaporate from the graphite anode, which is mainly heated by the electrons. Carbon atoms and ions condensate and form a deposit on the cathode, from which the electrons are thermionically emitted. A one-dimensional fluid model is developed to study the characteristics of the carbon arc plasma in atmospheric pressures. Sheath models for the anode and cathode are coupled to the fluid simulation to obtain the material temperature and sheath potential. In the model, thermal nonequilibrium is assumed and atomic carbon, dimer, and trimer are considered. A typical operating condition of a carbon arc plasma is discharge voltage of 20 V, discharge current of 60 A, the electron radius of 6 to 12 mm, and background pressure of 500 Torr. Transition from low to high ablation mode is obtained from the simulations with a smaller electrode radius and with a larger discharge current, which agrees with experimental observations. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  14. Global and local scale flood discharge simulations in the Rhine River basin for flood risk reduction benchmarking in the Flagship Project

    NASA Astrophysics Data System (ADS)

    Gädeke, Anne; Gusyev, Maksym; Magome, Jun; Sugiura, Ai; Cullmann, Johannes; Takeuchi, Kuniyoshi

    2015-04-01

    The global flood risk assessment is prerequisite to set global measurable targets of post-Hyogo Framework for Action (HFA) that mobilize international cooperation and national coordination towards disaster risk reduction (DRR) and requires the establishment of a uniform flood risk assessment methodology on various scales. To address these issues, the International Flood Initiative (IFI) has initiated a Flagship Project, which was launched in year 2013, to support flood risk reduction benchmarking at global, national and local levels. In the Flagship Project road map, it is planned to identify the original risk (1), to identify the reduced risk (2), and to facilitate the risk reduction actions (3). In order to achieve this goal at global, regional and local scales, international research collaboration is absolutely necessary involving domestic and international institutes, academia and research networks such as UNESCO International Centres. The joint collaboration by ICHARM and BfG was the first attempt that produced the first step (1a) results on the flood discharge estimates with inundation maps under way. As a result of this collaboration, we demonstrate the outcomes of the first step of the IFI Flagship Project to identify flood hazard in the Rhine river basin on the global and local scale. In our assessment, we utilized a distributed hydrological Block-wise TOP (BTOP) model on 20-km and 0.5-km scales with local precipitation and temperature input data between 1980 and 2004. We utilized existing 20-km BTOP model, which is applied globally, and constructed the local scale 0.5-km BTOP model for the Rhine River basin. For the BTOP model results, both calibrated 20-km and 0.5-km BTOP models had similar statistical performance and represented observed flood river discharges, epecially for 1993 and 1995 floods. From 20-km and 0.5-km BTOP simulation, the flood discharges of the selected return period were estimated using flood frequency analysis and were comparable to

  15. Fast-imaging and spectroscopic analysis of atmospheric argon streamers for large gap arc breakdown

    NASA Astrophysics Data System (ADS)

    Pachuilo, Michael; Stefani, Francis; Bengtson, Roger; Raja, Laxminarayan

    2014-10-01

    A non-equilibrium plasma source has been developed to assist in the low-voltage arc breakdown of large electrode gaps. The source consists of a dielectric embedded wire helically wound around a confining cylindrical quartz chamber. Annular electrodes cap the ends of the quartz chamber. An argon feed gas is used to provide a uniform environment and exhausts to ambient atmospheric conditions. A negative polarity 50 kV trigger pulse is applied to the embedded trigger wire to initiate the arc breakdown. Application of the trigger pulse produces a localized coronal discharges along the inner surface of the quartz tube. The corona provides seed electrons through which streamers propagate from one of the main discharge electrode along the quartz surface until it reaches the opposite electrode to bridge the gap. Once the gap is bridged a spark over occurs and robust arc discharge is formed in the chamber volume. Fast imaging of the streamer propagation establishes its velocity in the range of ~ 100 km/s. Spectroscopy of the streamer discharge in atmospheric argon has been conducted and electron temperature and number density estimated from a collision radiative model. Argon spectrum is dominated by neutral argon lines in the 650--950 nm range, and singly ionized argon lines are observed in the ultra-violet to near UV (300--400 nm). Research was performed in connection with AFOSR Contract FA9550-11-1-0062.

  16. The use of Global Positioning System units and ArcGIS Online to engage K-12 Students in Research Being Done in their Local Communities

    NASA Astrophysics Data System (ADS)

    Butcher, C. E.; Sparrow, E. B.; Clucas, T.

    2015-12-01

    Incorporating K-12 students in scientific research processes and opportunities in their communities is a great way to bridge the gap between research and education and to start building science research capacity at an early age. One goal of the Experimental Program to Stimulate Competitive Research (EPSCoR) Alaska Adapting to Changing Environments project is to engage the local community in the research as well as to share results with the people. By giving K-12 students Global Positioning System (GPS) units, and allowing them to collect and map their own data, they are being exposed to some of the research methods being used by scientists in the Alaska ACE project. This hands-on, minds-on method has been successfully used in formal education settings such as a Junior High School classroom in Nuiqsut, Alaska as well as in informal education settings such as summer camps in Barrow, Alaska and Kenai, Alaska. The students progress from mapping by hand to collecting location data with their GPS units and cameras, and imputing this information into ArcGIS Online to create map products. The data collected were from sites ranging from important places in the community to sites visited during summer camps, with students reflecting on data and site significance. Collecting data, using technology, and creating map products contribute to science skills and practices students need to conduct research of their own and to understand research being done around them. The goal of this education outreach implementation is to bring students closer to the research, understand the process of science, and have the students continue to collect data and contribute to research in their communities. Support provided for this work from the Alaska EPSCoR NSF Award #OIA-1208927 and the state of Alaska is gratefully acknowledged.

  17. Monitor For Electrical-Discharge Machining

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.

    1993-01-01

    Circuit monitors electrical-discharge-machining (EDM) process to detect and prevent abnormal arcing, which can produce unacceptable "burn" marks on workpiece. When voltage between EDM electrode and workpiece behaves in manner indicative of abnormal arcing, relay made to switch off EDM power, which remains off until operator attends to EDM setup and resets monitor.

  18. Monitor For Electrical-Discharge Machining

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.

    1993-01-01

    Circuit monitors electrical-discharge-machining (EDM) process to detect and prevent abnormal arcing, which can produce unacceptable "burn" marks on workpiece. When voltage between EDM electrode and workpiece behaves in manner indicative of abnormal arcing, relay made to switch off EDM power, which remains off until operator attends to EDM setup and resets monitor.

  19. NASA GRC and MSFC Space-Plasma Arc Testing Procedures

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T,; Hillard, G. Barry; Vaughn, Jason; Schneider, Todd

    2005-01-01

    Tests of arcing and current collection in simulated space plasma conditions have been performed at the NASA Glenn Research Center (GRC) in Cleveland, Ohio, for over 30 years and at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, for almost as long. During this period, proper test conditions for accurate and meaningful space simulation have been worked out, comparisons with actual space performance in spaceflight tests and with real operational satellites have been made, and NASA has achieved our own internal standards for test protocols. It is the purpose of this paper to communicate the test conditions, test procedures, and types of analysis used at NASA GRC and MSFC to the space environmental testing community at large, to help with international space-plasma arcing-testing standardization. To be discussed are: 1.Neutral pressures, neutral gases, and vacuum chamber sizes. 2. Electron and ion densities, plasma uniformity, sample sizes, and Debuy lengths. 3. Biasing samples versus self-generated voltages. Floating samples versus grounded. 4. Power supplies and current limits. Isolation of samples from power supplies during arcs. 5. Arc circuits. Capacitance during biased arc-threshold tests. Capacitance during sustained arcing and damage tests. Arc detection. Prevention sustained discharges during testing. 6. Real array or structure samples versus idealized samples. 7. Validity of LEO tests for GEO samples. 8. Extracting arc threshold information from arc rate versus voltage tests. 9. Snapover and current collection at positive sample bias. Glows at positive bias. Kapon (R) pyrolisis. 10. Trigger arc thresholds. Sustained arc thresholds. Paschen discharge during sustained arcing. 11. Testing for Paschen discharge threshold. Testing for dielectric breakdown thresholds. Testing for tether arcing. 12. Testing in very dense plasmas (ie thruster plumes). 13. Arc mitigation strategies. Charging mitigation strategies. Models. 14. Analysis of test results

  20. [Ultrastructural localization of lysosomal and nuclear beta-glycerophosphatase activity in the urethral discharge cells of gonorrhea].

    PubMed

    Delektorskiĭ, V V; Dmitriev, G A; Bukhvalov, I B

    1976-01-01

    Activity of acid phosphotase in the urethra discharge in patients with various forms of gonorrhea (acute, torpid, and chronic) was studied with the use of electron-microscopy and biochemical methods. A positive reaction of nuclei of the epithelial cells to acid phosphotase in lysosomes and perichromatin granules was demonstrated. In polymorphononuclear leucocytes the positive reaction to acid phosphotase could be also sometimes observed in granules of the cytoplasm. The electronograms presented testify to heterogeneity and high activity of acid phosphotase in lysosomes. Neither electron-microscopy nor biochemical methods could help reveal any differences in the activity of acid phosphotase in various forms of gonorrhea.

  1. Effect of collimator angles on the dosimetric results of volumetric modulated arc therapy planning for patients with a locally-advanced nasopharyngeal carcinoma

    NASA Astrophysics Data System (ADS)

    Kim, Yong Ho; Park, Dahl; Park, Ha Ryung; Kim, Won Taek; Kim, Dong Hyun; Bae, Jin Suk; Jeon, Gye Rok; Ro, Jung Hoon; Ki, Yongkan

    2017-03-01

    In volumetric modulated arc therapy (VMAT) planning, usually the collimator is rotated to minimize interleaf leakage and the tongue-and-groove effect. The objective of this study was to evaluate the effect of collimator angle on the dosimetric results of VMAT plans for patients with a locally-advanced nasopharyngeal carcinoma (LA-NPC). VMAT treatment planning sets were generated using the same planning parameters, but with different collimator angles for 11 LA-NPC patients. Each set was composed of 10 plans with collimator angles at 0, 5, 10, 15, 20, 25, 35, 40, and 45 degrees. Dosimetric parameters, such as target coverage, organs at risk (OAR), and dose conformity, were analyzed at various collimator angles. With increasing collimator angles, the absorbed doses to the optic apparatus were increased by up to 35% comparing to that at a collimator angle of 0°. The best value of the conformity index (CI) was 0.971 ± 0.023 at collimator angles of 20° and 30°. The worst value of CI was 0.917 ± 0.051 at a collimator angle of 0°. The homogeneity index (HI)95 and HI98 had the best values of 0.106 ± 0.040 and 0.079 ± 0.031, respectively, at a collimator angle of 25°. The worst values of HI95 and HI98 were 0.136 ± 0.039 and 0.105 ± 0.032, respectively, at a collimator angle of of 0°. The maximum doses for some OARs (body, ear, parotid gland, mandible, and brainstem) and the HI did not show any statistically significant differences. However, the mean doses had positive correlations ( r = 0.449 0.773, p<0.001) with the irradiated volume. The CI had a weak positive correlation ( r = 0.316, p<0.001) with the irradiated volume. Other comparison parameters were evaluated as functions of the collimator angle. These findings will give useful information for choosing the collimator angle in VMAT plans for patients with a LA-NPC.

  2. Local analysis of confinement and transport in neutral beam heated DIII-D discharges with negative magnetic shear

    SciTech Connect

    Schissel, D.P.; Greenfield, C.M.; DeBoo, J.C.

    1996-10-01

    High triangularity double-null discharges with weak or negative central magnetic shear and with both an L-mode and an H-mode edge have been produced on DIII-D. The L-mode edge cases are characterized by peaked toroidal rotation, ion temperature, and plasma density profiles with reduced ion transport in the negative shear region. The H-mode edge cases have broader profiles consistent with reduced ion transport, to the neoclassical level, over the entire plasma cross section. The L-mode edge cases have a greater reduction in central ion diffusivity with stronger negative shear while the H-mode edge cases do not exhibit this dependence. Plasma fluctuation measurements show that a dramatic reduction in turbulence accompanies the improved ion confinement. Calculations of sheared E x B flow indicate that this mechanism can overcome the {eta}{sub i} mode growth rate in the region of reduced transport.

  3. Optical arc sensor using energy harvesting power source

    SciTech Connect

    Choi, Kyoo Nam Rho, Hee Hyuk

    2016-06-03

    Wireless sensors without external power supply gained considerable attention due to convenience both in installation and operation. Optical arc detecting sensor equipping with self sustaining power supply using energy harvesting method was investigated. Continuous energy harvesting method was attempted using thermoelectric generator to supply standby power in micro ampere scale and operating power in mA scale. Peltier module with heat-sink was used for high efficiency electricity generator. Optical arc detecting sensor with hybrid filter showed insensitivity to fluorescent and incandescent lamps under simulated distribution panel condition. Signal processing using integrating function showed selective arc discharge detection capability to different arc energy levels, with a resolution below 17 J energy difference, unaffected by bursting arc waveform. The sensor showed possibility for application to arc discharge detecting sensor in power distribution panel. Also experiment with proposed continuous energy harvesting method using thermoelectric power showed possibility as a self sustainable power source of remote sensor.

  4. Optical arc sensor using energy harvesting power source

    NASA Astrophysics Data System (ADS)

    Choi, Kyoo Nam; Rho, Hee Hyuk

    2016-06-01

    Wireless sensors without external power supply gained considerable attention due to convenience both in installation and operation. Optical arc detecting sensor equipping with self sustaining power supply using energy harvesting method was investigated. Continuous energy harvesting method was attempted using thermoelectric generator to supply standby power in micro ampere scale and operating power in mA scale. Peltier module with heat-sink was used for high efficiency electricity generator. Optical arc detecting sensor with hybrid filter showed insensitivity to fluorescent and incandescent lamps under simulated distribution panel condition. Signal processing using integrating function showed selective arc discharge detection capability to different arc energy levels, with a resolution below 17J energy difference, unaffected by bursting arc waveform. The sensor showed possibility for application to arc discharge detecting sensor in power distribution panel. Also experiment with proposed continuous energy harvesting method using thermoelectric power showed possibility as a self sustainable power source of remote sensor.

  5. Hysterectomy - laparoscopic - discharge

    MedlinePlus

    Supracervical hysterectomy - discharge; Removal of the uterus - discharge; Laparoscopic hysterectomy - discharge; Total laparoscopic hysterectomy - discharge; TLH - discharge; Laparoscopic supracervical ...

  6. Radical prostatectomy - discharge

    MedlinePlus

    ... prostatectomy - discharge; Laparoscopic radical prostatectomy - discharge; LRP - discharge; Robotic-assisted laparoscopic prostatectomy - discharge ; RALP - discharge; Pelvic lymphadenectomy - ...

  7. Arc plasma generator of atomic driver for steady-state negative ion source.

    PubMed

    Ivanov, A A; Belchenko, Yu I; Davydenko, V I; Ivanov, I A; Kolmogorov, V V; Listopad, A A; Mishagin, V V; Putvinsky, S V; Shulzhenko, G I; Smirnov, A

    2014-02-01

    The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB6 cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

  8. Arc plasma generator of atomic driver for steady-state negative ion source

    SciTech Connect

    Ivanov, A. A.; Belchenko, Yu. I.; Davydenko, V. I.; Ivanov, I. A.; Kolmogorov, V. V.; Listopad, A. A. Mishagin, V. V.; Shulzhenko, G. I.; Putvinsky, S. V.; Smirnov, A.

    2014-02-15

    The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB{sub 6} cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

  9. Improving the Mach number capabilities of arc driven shock tubes

    NASA Technical Reports Server (NTRS)

    Johnson, J. A., III; Santiago, J.; I, L.

    1980-01-01

    New systematic trends in one of the performance parameters of pressure loaded arc driven shock tubes have been determined. For a given configuration, the Mach number increases with the cube root of capacitor energy; however, the initial driver gas pressure is relatively unimportant. A qualitative model based on the assumption of Joule-preheating by the arc discharge is discussed.

  10. Weld arc simulator

    DOEpatents

    Burr, Melvin J.

    1990-01-30

    An arc voltage simulator for an arc welder permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.

  11. Weld arc simulator

    SciTech Connect

    Burr, M.J.

    1989-03-01

    An arc voltage simulator for an arc welder permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.

  12. Weld arc simulator

    SciTech Connect

    Burr, M.J.

    1990-01-30

    This patent describes an arc voltage simulator for an arc welder which permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.

  13. The relationship between the localization of the generalized spike and wave discharge generators and the response to valproate.

    PubMed

    Szaflarski, Jerzy P; Kay, Benjamin; Gotman, Jean; Privitera, Michael D; Holland, Scott K

    2013-03-01

    Up to 30% of patients with idiopathic generalized epilepsy (IGE) have seizures that are refractory to medication despite appropriate therapy that commonly includes valproate (VPA). The aim of this study was to compare patients with VPA-refractory and VPA-responsive IGE in order to determine whether there are group differences in generalized spike and wave discharge (GSWD) generators that may be associated with VPA resistance. Of 89 IGE patients who underwent electroencephalography (EEG) combined with functional magnetic resonance imaging (fMRI; EEG/fMRI), 25 with GSWDs identified in EEG/fMRI data were included. Simultaneous acquisition of 64 channels of EEG data at 10 kHz was performed using an MRI-compatible EEG cap and amplifier at 4T. VPA resistance was defined as lack of seizure control despite therapeutic dose of VPA. The fMRI blood oxygen-level dependent (BOLD) correlates of GSWD in the entire group involved midline thalamus, frontal regions comprising Brodmann areas 6, 24, and 32, and temporal lobes diffusely. When VPA-responsive and VPA-resistant patients were compared, BOLD signal increases were noted in the VPA-resistant patients in medial frontal cortex, along the paracingulate gyrus (Montreal Neurological Institute; MNI x = 2, y = 13.6, z = 45.9), and anterior insula bilaterally (right MNI x = 37.6, y = 7.8, z = 0.6, left MNI x = -35.3, y = 13.6, z = -5.3). Our findings support the hypothesis that VPA-resistant and VPA-responsive patients may have different GSWD generators. Furthermore, we hypothesize that these differences in GSWD generators may be the reason for different responses to VPA. Wiley Periodicals, Inc. © 2013 International League Against Epilepsy.

  14. The relationship between the localization of the generalized spike and wave discharge generators and the response to valproate

    PubMed Central

    Szaflarski, Jerzy P.; Kay, Benjamin; Gotman, Jean; Privitera, Michael D.; Holland, Scott K.

    2014-01-01

    SUMMARY Purpose: Up to 30% of patients with idiopathic generalized epilepsy (IGE) have seizures that are refractory to medication despite appropriate therapy that commonly includes valproate (VPA). The aim of this study was to compare patients with VPA-refractory and VPA-responsive IGE in order to determine whether there are group differences in generalized spike and wave discharge (GSWD) generators that may be associated with VPA resistance. Methods: Of 89 IGE patients who underwent electroencephalography (EEG) combined with functional magnetic resonance imaging (fMRI; EEG/fMRI), 25 with GSWDs identified in EEG/fMRI data were included. Simultaneous acquisition of 64 channels of EEG data at 10 kHz was performed using an MRI-compatible EEG cap and amplifier at 4T. VPA resistance was defined as lack of seizure control despite therapeutic dose of VPA. Key Findings: The fMRI blood oxygen–level dependent (BOLD) correlates of GSWD in the entire group involved midline thalamus, frontal regions comprising Brodmann areas 6, 24, and 32, and temporal lobes diffusely. When VPA-responsive and VPA-resistant patients were compared, BOLD signal increases were noted in the VPA-resistant patients in medial frontal cortex, along the paracingulate gyrus (Montreal Neurological Institute; MNI x = 2, y = 13.6, z = 45.9), and anterior insula bilaterally (right MNI x = 37.6, y = 7.8, z = 0.6, left MNI x = −35.3, y = 13.6, z = −5.3). Significance: Our findings support the hypothesis that VPA-resistant and VPA-responsive patients may have different GSWD generators. Furthermore, we hypothesize that these differences in GSWD generators may be the reason for different responses to VPA. PMID:23294001

  15. Ion source with improved primary arc collimation

    DOEpatents

    Dagenhart, William K.

    1985-01-01

    An improved negative ion source is provided in which a self-biasing, molybdenum collimator is used to define the primary electron stream arc discharge from a filament operated at a negative potential. The collimator is located between the anode and the filament. It is electrically connected to the anode by means of an appropriate size resistor such that the collimator is biased at essentially the filament voltage during operation. Initially, the full arc voltage appears across the filament to collimator until the arc discharge strikes. Then the collimator biases itself to essentially filament potential due to current flow through the resistor thus defining the primary electron stream without intercepting any appreciable arc power. The collimator aperture is slightly smaller than the anode aperture to shield the anode from the arc power, thereby preventing the exposure of the anode to the full arc power which, in the past, has caused overheating and erosion of the anode collimator during extended time pulsed-beam operation of the source. With the self-biasing collimator of this invention, the ion source may be operated from short pulse periods to steady-state without destroying the anode.

  16. Outer divertor of ASDEX Upgrade in low-density L-mode discharges in forward and reversed magnetic field: II. Analysis of local impurity migration

    NASA Astrophysics Data System (ADS)

    Aho-Mantila, L.; Wischmeier, M.; Krieger, K.; Rohde, V.; Hakola, A.; Potzel, S.; Kirschner, A.; Borodin, D.; the ASDEX Upgrade Team

    2012-10-01

    Part I (Aho-Mantila L. et al 2012 Nucl. Fusion 52 103006) presented a detailed analysis of outer divertor plasma conditions in low-density L-mode discharges in ASDEX Upgrade. In this paper, we analyse the local migration of carbon that originates from 13CH4 injected into these plasmas from the vertical outer target. Notable changes are observed in the local carbon deposition patterns when reversing the magnetic field in the experiments. Kinetic impurity-following simulations are performed using the 3D ERO code package with 2D background plasma solutions calculated with the SOLPS5.0 code package. The modelling shows that the measured changes are due to the changes in plasma collisionality, dissociation and ionization rates, and E × B drift of the impurities. These conditions affect the direction and rate of impurity migration inside and out of the divertor, having wider consequences on the global migration of impurities in a divertor tokamak. It is further shown that the migration pathways are largely determined by carbon ions and, hence, relevant for impurities in general. Neutral carbon and hydrocarbons are deposited only in the near vicinity of the injection, where they affect the local re-deposition efficiency. In this limited region, a perturbation of the local plasma conditions by the methane puff appears likely, yielding a significant uncertainty for interpreting the deposition efficiencies. The local deposition is largely influenced by the magnetic presheath electric field, the structure of which is the main uncertainty in the SOLPS5.0-ERO simulations.

  17. Note: Triggering behavior of a vacuum arc plasma source.

    PubMed

    Lan, C H; Long, J D; Zheng, L; Dong, P; Yang, Z; Li, J; Wang, T; He, J L

    2016-08-01

    Axial symmetry of discharge is very important for application of vacuum arc plasma. It is discovered that the triggering method is a significant factor that would influence the symmetry of arc discharge at the final stable stage. Using high-speed multiframe photography, the transition processes from cathode-trigger discharge to cathode-anode discharge were observed. It is shown that the performances of the two triggering methods investigated are quite different. Arc discharge triggered by independent electric source can be stabilized at the center of anode grid, but it is difficult to achieve such good symmetry through resistance triggering. It is also found that the triggering process is highly correlated to the behavior of emitted electrons.

  18. Note: Triggering behavior of a vacuum arc plasma source

    SciTech Connect

    Lan, C. H. Long, J. D.; Zheng, L.; Dong, P.; Yang, Z.; Li, J.; Wang, T.; He, J. L.

    2016-08-15

    Axial symmetry of discharge is very important for application of vacuum arc plasma. It is discovered that the triggering method is a significant factor that would influence the symmetry of arc discharge at the final stable stage. Using high-speed multiframe photography, the transition processes from cathode-trigger discharge to cathode-anode discharge were observed. It is shown that the performances of the two triggering methods investigated are quite different. Arc discharge triggered by independent electric source can be stabilized at the center of anode grid, but it is difficult to achieve such good symmetry through resistance triggering. It is also found that the triggering process is highly correlated to the behavior of emitted electrons.

  19. Arc tracks on nanostructured surfaces after microbreakdowns

    NASA Astrophysics Data System (ADS)

    Sinelnikov, D.; Bulgadaryan, D.; Hwangbo, D.; Kajita, S.; Kolodko, D.; Kurnaev, V.; Ohno, N.

    2016-09-01

    Studying of initial steps of unipolar arc ignition process is important for reduction of probability of arcing between the plasma and the wall in thermonuclear devices. Tungsten nano-fuzz surface formed by helium plasma irradiation at high fluences and temperatures is a perfect material for arc ignition. Snowflake-like craters were detected on the fuzzy surfaces after short micro-breakdowns. Such sort of craters have not been observed before on any other metallic surfaces. These specific traces are formed due to unique properties of the fuzz structure. The nano-fuzz could be easily melted and vaporized by micro-breakdown current, due to its porosity and bad thermal conductivity, and formation of low conducting metallic vapour under the cathode spot causes discharge movement to the nearest place. Thus, even low current arc can easily move and leave traces, which could be easily observed by a secondary electron microscope.

  20. Innovation approaches to controlling the electric regimes of electric arc furnaces

    NASA Astrophysics Data System (ADS)

    Bikeev, R. A.; Serikov, V. A.; Ognev, A. M.; Rechkalov, A. V.; Cherednichenko, V. S.

    2015-12-01

    The processes of current passage in an ac electric arc furnace (EAF) are subjected to industrial experiments and mathematical simulation. It is shown that, when a charge is melted, arcs between charge fragments exist in series with main arc discharges, and these arcs influence the stability of the main arc discharges. The measurement of instantaneous currents and voltages allowed us to perform a real-time calculation of the electrical characteristics of a three-phase circuit and to determine the θ parameter, which characterizes the nonlinearity of the circuit segment between electrodes. Based on these studies, we created an advanced system for controlling the electric regime of EAF.

  1. Gas arc constriction for plasma arc welding

    NASA Technical Reports Server (NTRS)

    McGee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

    1994-01-01

    A welding torch for plasma arc welding apparatus has an inert gas applied circumferentially about the arc column externally of the constricting nozzle so as to apply a constricting force on the arc after it has exited the nozzle orifice and downstream of the auxiliary shielding gas. The constricting inert gas is supplied to a plenum chamber about the body of the torch and exits through a series of circumferentially disposed orifices in an annular wall forming a closure at the forward end of the constricting gas plenum chamber. The constricting force of the circumferential gas flow about the arc concentrates and focuses the arc column into a more narrow and dense column of energy after exiting the nozzle orifice so that the arc better retains its energy density prior to contacting the workpiece.

  2. Acoustic characteristics of electric arc furnaces

    NASA Astrophysics Data System (ADS)

    Cherednichenko, V. S.; Bikeev, R. A.; Cherednichenko, A. V.; Ognev, A. M.

    2016-06-01

    A mathematical model is constructed to describe the appearance and development of the noise characteristics of superpower electric arc furnaces. The noise formation is shown to be related to the pulsation of the axial plasma flows in arc discharges because of the electrodynamic pressure oscillations caused by the interaction of the self-magnetic field with the current passing in an arc. The pressure in the arc axis changes at a frequency of 100 Hz at the maximum operating pressure of 66 kPa for an arc current of 80 kA. The main ac arc sound frequencies are multiples of 100 Hz, which is supported in the practice of operation of electric arc furnaces. The sound intensity in the furnace laboratory reaches 160 dB and is decreased to 115-120 dB in the working furnace area due to shielding by the furnace jacket, the molten metal, and the molten slag. The appropriateness of increasing the hermetic sealing of electric furnaces and creating furnaces operating at low currents and high transformer voltages is corroborated.

  3. Masking, persistence, and transfer in rotating arcs.

    PubMed

    Geremek, Adam; Stürzel, Frank; da Pos, Osvaldo; Spillmann, Lothar

    2002-10-01

    We demonstrate that the apparent length of a thin white arc on a black disk, rotating concentrically at 2.5 rps, varies with angular length and exposure duration. While short arcs (9-18 degrees ) gradually expand, long arcs (36-72 degrees ) first undergo a brief contraction, before they also expand. On average, perceived elongation asymptotes after 15 s equivalent to visual persistencies ranging from 68 to 170 ms. Using bi- and tri-colored arcs, we find that the apparent increase in length derives from the rear end of the rotating stimulus, while the initial shrinkage derives from contraction of the middle. After 15 s of adaptation, perceived length of the arc decays to actual stimulus length within an average of 6 s and, upon re-exposure of the arc, reaches its former value after only 5 s (priming). When the rotating arc is presented first to one eye and then to the other, apparent elongation transfers partially (46%), suggesting a contribution by the binocular cells in the visual cortex. A partial transfer (26%) also occurs from clockwise to counterclockwise rotation. When tested interocularly, the directional transfer is more pronounced (47%) and equals the interocular transfer under equidirectional conditions, suggesting that the directional transfer (cw versus ccw) might derive from non-directional cortical units. Whereas the initial contraction may be attributable to backward masking, the observed elongation likely reflects a cumulative build-up of after-discharge in cortical neurons over time.

  4. Stability of atmospheric pressure glow discharges

    NASA Astrophysics Data System (ADS)

    Chirokov, Alexandre V.

    There has been a considerable interest in non-thermal atmospheric pressure discharges over the past decade due to increased number of industrial applications. Although non-thermal atmospheric pressure discharges have been intensively studied for the past century the clear physical picture of these discharges is far from being complete. Spontaneous transition of non-thermal atmospheric pressure discharges to thermal discharge and discharge filamentation are among least understood plasma phenomena. The discharge stability and reliable control of plasma parameters are highly desirable for numerous applications. This study focuses on stability of atmospheric pressure glow discharges with respect to filamentation and arcing. Atmospheric pressure glow discharge (APG) is the newest and the most promising addition to the family of non-thermal atmospheric pressure discharges. However this discharge is very susceptible to thermal instability which causes arcing, loss of uniformity and significant damage to electrodes. Suppression of thermal instability and effective control of discharge parameters is critical for industrial applications. A model was developed to understand transition to arc in atmospheric pressure glow discharges. APG discharges that operate in pure helium and in helium with addition of oxygen and nitrogen were considered in these studies. Simulation results indicate that arcing is the result of sheath breakdown rather than thermal instability. It was shown that although sheath breakdown is always followed by overheating the transition to arc in atmospheric glow discharges is not a result of thermal instability. In second part of this research interaction between plasma filaments in dielectric barrier discharges has been studied. This interaction is responsible for the formation of microdischarge patterns reminiscent of two-dimensional crystals. Depending on the application, microdischarge patterns may have a significant influence on DBD performance

  5. Comparative study on interactions between laser and arc plasma during laser-GTA welding and laser-GMA welding

    NASA Astrophysics Data System (ADS)

    Chen, Minghua; Xu, Jiannan; Xin, Lijun; Zhao, Zuofu; Wu, Fufa

    2016-10-01

    This paper describes an investigation on differences in interactions between laser and arc plasma during laser-gas tungsten arc (LT) welding and laser-gas metal arc (LM) welding. The characteristics of LT heat source and LM heat source, such as plasma behavior, heat penetration ability and spectral information were comparably studied. Based on the plasma discharge theory, the interactions during plasma discharge were modeled and analyzed. Results show that in both LT and LM welding, coupling discharge between the laser keyhole plasma and arc happens, which strongly enhance the arc. But, the enhancing effect in LT welding is much more sensitive than that in LM welding when parameters are adjusted.

  6. The Use of Photon Beams of a Flattening Filter-free Linear Accelerator for Hypofractionated Volumetric Modulated Arc Therapy in Localized Prostate Cancer

    SciTech Connect

    Zwahlen, Daniel R.; Lang, Stephanie; Hrbacek, Jan; Glanzmann, Christoph; Kloeck, Stephan; Najafi, Yousef; Streller, Tino; Studer, Gabriela; Zaugg, Kathrin; Luetolf, Urs M.

    2012-08-01

    Purpose: To evaluate the potential usage of flattening filter-free (FFF) photon beams in the treatment of prostate cancer. Methods and Materials: Volumetric-modulated arc therapy (VMAT) treatment planning was performed for 7 patients using TrueBeam{sup Registered-Sign} linear accelerator and photon beams with (X6, X10) and without (X6FFF, X10FFF) flattening filter. Prescribed dose was 19 Multiplication-Sign 3 Gy = 57 Gy. One or two 360 Degree-Sign arcs with dose rate of 600 MU/min for flattened beams, and 1,200 MU/min for FFF beams were used. Results: No difference was detected between the four beams in PTV coverage, conformity, and homogeneity. Mean body dose and body volume receiving 50% of the prescribed dose decreased with increasing mean energy (r{sup 2} = 0.8275, p < 0.01). X6FFF delivered 3.6% more dose compared with the X6 (p < 0.01). X10FFF delivered 3.0% (p < 0.01), and the X10 5.8% (p < 0.01) less mean body dose compared with X6. There was a significant increase in the mean dose to the rectum for the X10 compared with X6 (2.6%, p < 0.01). Mean dose to the bladder increased by 1.3% for X6FFF and decreased by 2.3% for X10FFF. Using a single arc and FFF, treatment time was reduced by 35% (2 SD = 10%). Conclusion: FFF beams resulted in dose distributions similar to flattened beams. X10FFF beam provided the best solution, sparing rectum and bladder and minimizing whole-body dose. FFF beams lead to a time efficient treatment delivery, particularly when combined with hypofractionated VMAT.

  7. Vaginal Discharge

    MedlinePlus

    ... also be on the lookout for symptoms of yeast infections, bacterial vaginosis and trichomoniasis, 3 infections that ... cause changes in your vaginal discharge.Signs of yeast infectionsWhite, cottage cheese-like dischargeSwelling and pain around ...

  8. Gyrokinetic simulation of global and local Alfvén eigenmodes driven by energetic particles in a DIII-D discharge

    NASA Astrophysics Data System (ADS)

    Bass, E. M.; Waltz, R. E.

    2013-01-01

    The unstable spectrum of Alfvén eigenmodes (AEs) driven by neutral beam-sourced energetic particles (EPs) in a benchmark DIII-D discharge (142111) is calculated in a fully gyrokinetic model using the GYRO code's massively parallel linear eigenvalue solver. One cycle of the slow (equilibrium scale) frequency sweep of the reverse shear Alfvén eigenmode (RSAE) at toroidal mode number n =3 is mapped. The RSAE second harmonic and an unstable beta-induced Alfvén eigenmode (BAE) are simultaneously tracked alongside the primary RSAE. An observed twist in the eigenmode pattern, caused mostly by shear in the driving EP profile, is shown through artificially varying the E ×B rotational velocity shear to depend generally on shear in the local wave phase velocity. Coupling to the BAE and to the toroidal Alfvén eigenmode limit the RSAE frequency sweeps at the lower and upper end, respectively. While the present fully gyrokinetic model (including thermal ions and electrons) constitutes the best treatment of compressibility physics available, the BAE frequency is overpredicted by about 20% against experiment here and is found to be sensitive to energetic beam ion pressure. The RSAE frequency is more accurately matched except when it is limited by the BAE. Simulations suggest that the experiment is very close to marginal AE stability at points of RSAE-BAE coupling. A recipe for comparing the radial profile of quasilinear transport flux from local modes to that from global modes paves the way for the development of a stiff (critical gradient) local AE transport model based on local mode stability thresholds.

  9. Arc lamp power supply using a voltage multiplier

    NASA Technical Reports Server (NTRS)

    Leighty, Bradley D.

    1988-01-01

    A power supply is provided for an arc discharge lamp which includes a relatively low voltage high current power supply section and a high voltage starter circuit. The low voltage section includes a transformer, rectifier, variable resistor and a bank of capacitors, while the starter circuit comprises several diodes and capacitors connected as a Cockcroft-Walton multiplier. The starting circuit is effectively bypassed when the lamp arc is established and serves to automatically provide a high starting voltage to re-strike the lamp arc if the arc is extinguished by a power interruption.

  10. The use of electrical discharge for ignition and control of combustion of solid propellants

    NASA Technical Reports Server (NTRS)

    Tachibana, Takeshi; Kobayashi, Tsuruo; Matsuda, Takashi; Kimura, Itsuro

    1987-01-01

    As the first step of the study of the combustion control of solid propellants by electrical discharges, the effects of an arc discharge, which flows along the burning surface, on the burning rate and on the increase of enthalpy of the combustion product were investigated. For specially devised composite propellants, which are composed of Al and Teflon powders, it was shown that the combination can be controlled by an arc discharge; the combustion continues when the arc discharge is applied and is interrupted when the arc discharge breaks. In the present investigation, it was also shown that an arc discharge coupled with a high-frequency electrical discharge has potential as an effective ignition method for solid propellants. For the application of this type of combustion control to an ignitor for a solid propellant rocket motor or to a control rocket motor, this method lacks flexibility in the configuration scale and needs relatively high electric power at the present stage.

  11. Evaluation of localization errors for craniospinal axis irradiation delivery using volume modulated arc therapy and proposal of a technique to minimize such errors.

    PubMed

    Myers, Pamela; Stathakis, Sotirios; Mavroidis, Panayiotis; Esquivel, Carlos; Papanikolaou, Niko

    2013-07-01

    To dosimetrically evaluate the effects of improper patient positioning in the junction area of a VMAT cranio-spinal axis irradiation technique consisting of one superior and one inferior arc and propose a solution to minimize these patient setup errors. Five (n=5) cranio-spinal axis irradiation patients were planned with 2 arcs: one superior and one inferior. In order to mimic patient setup errors, the plans were recalculated with the inferior isocenter shifted by: 1, 2, 5, and 10mm superiorly, and 1, 2, 5, and 10mm inferiorly. The plans were then compared with the corresponding original, non-shifted arc plans on the grounds of target metrics such as conformity number and homogeneity index, as well as several normal tissue dose descriptors. "Gradient-optimized" plans were then created for each patient in an effort to reduce dose discrepancies due to setup errors. Percent differences were calculated in order to compare each of the eight shifted plans with the original non-shifted arc plan, which corresponds to the ideal patient setup. The conformity number was on average lower by 0.9%, 2.7%, 5.8%, and 9.1% for the 1, 2, 5, and 10mm inferiorly-shifted plans and 0.4%, 0.8%, 2.8%, and 6.0% for the respective superiorly-shifted plans. The homogeneity indices were, averaged among the five patients and they indicated less homogeneous dose distributions by 0.03%, 0.3%, 1.0%, and 2.8% for the inferior shifts and 0.2%, 1.2%, 6.3%, and 15.3% for the superior shifts. Overall, the mean doses to the organs at risk deviate by less than 2% for the 1, 2, and 5mm shifted plans. The 10mm shifted plans, however, showed average percent differences, over all studied organs, from the original plan of up to 5.6%. Using "gradient-optimized" plans, the average dose differences were reduced by 0.2%, 0.5%, 1.2%, and 2.1% for 1, 2, 5, and 10mm shifts, respectively compared to the originally optimized plans, and the maximum dose differences were reduced by 11.7%, 8.5%, 12.4%, and 13.9% on

  12. CyberArc: a non-coplanar-arc optimization algorithm for CyberKnife

    NASA Astrophysics Data System (ADS)

    Kearney, Vasant; Cheung, Joey P.; McGuinness, Christopher; Solberg, Timothy D.

    2017-07-01

    The goal of this study is to demonstrate the feasibility of a novel non-coplanar-arc optimization algorithm (CyberArc). This method aims to reduce the delivery time of conventional CyberKnife treatments by allowing for continuous beam delivery. CyberArc uses a 4 step optimization strategy, in which nodes, beams, and collimator sizes are determined, source trajectories are calculated, intermediate radiation models are generated, and final monitor units are calculated, for the continuous radiation source model. The dosimetric results as well as the time reduction factors for CyberArc are presented for 7 prostate and 2 brain cases. The dosimetric quality of the CyberArc plans are evaluated using conformity index, heterogeneity index, local confined normalized-mutual-information, and various clinically relevant dosimetric parameters. The results indicate that the CyberArc algorithm dramatically reduces the treatment time of CyberKnife plans while simultaneously preserving the dosimetric quality of the original plans.

  13. Annular arc accelerator shock tube

    NASA Technical Reports Server (NTRS)

    Leibowitz, L. P. (Inventor)

    1976-01-01

    An annular arc accelerator shock tube employs a cold gas driver to flow a stream of gas from an expansion section through a high voltage electrode section to a test section, thus driving a shock wave in front of it. A glow discharge detects the shock wave and actuates a trigger generator which in turn fires spark-gap switches to discharge a bank of capacitors across a centered cathode and an annular anode in tandem electrode sections. The initial shock wave passes through the anode section from the cathode section thereby depositing energy into the flow gas without the necessity of any diaphragm opening in the gas flow from the expansion section through the electrode sections.

  14. Ion source with improved primary arc collimation

    DOEpatents

    Dagenhart, W.K.

    1983-12-16

    An improved negative ion source is provided in which a self-biasing, molybdenum collimator is used to define the primary electron stream arc discharge from a filament operated at a negative potential. The collimator is located between the anode and the filament. It is electrically connected to the anode by means of an appropriate size resistor such that the collimator is biased at essentially the filament voltage during operation. Initially, the full arc voltage appears across the filament to collimator until the arc discharge strikes. Then the collimator biases itself to essentially filament potential due to current flow through the resistor thus defining the primary electron stream without intercepting any appreciable arc power. The collimator aperture is slightly smaller than the anode aperture to shield the anode from the arc power which, in the past, has caused overheating and erosion of the anode collimator during extended time pulsed-beam operation of the source. With the self-biasing collimator of this invention, the ion source may be operated from short pulse periods to steady-state without destroying the anode.

  15. Rotating arc spark plug

    DOEpatents

    Whealton, John H.; Tsai, Chin-Chi

    2003-05-27

    A spark plug device includes a structure for modification of an arc, the modification including arc rotation. The spark plug can be used in a combustion engine to reduce emissions and/or improve fuel economy. A method for operating a spark plug and a combustion engine having the spark plug device includes the step of modifying an arc, the modifying including rotating the arc.

  16. Helium and Carbon Systematics of the Sangihe Arc, Indonesia: Tracing Volatile Sources in an Arc-Arc Collision

    NASA Astrophysics Data System (ADS)

    Jaffe, L. A.; Hilton, D. R.; Fischer, T. P.; Hartono, U.

    2002-12-01

    The Sangihe and Halmahera arcs in northeastern Indonesia are presently colliding, forming the world's only extant example of an arc-arc collision. We report the first helium and carbon isotopic and relative abundance data from the Sangihe Arc volcanoes as a means to trace magma origins in this complicated tectonic region. Gas chemistry and N-isotopes from the same localities are reported in a companion paper (Clor et al, this volume). There is a distinct regional pattern in He and CO2 variations along the north-south strike of the Sangihe Arc. The two northernmost volcanoes (Awu and Karangetang) have 3He/4He <= 6.4RA (where RA = air 3He/4He), CO2/3He >= 30x109, and δ13C >= -2.0‰ . In contrast, the southern volcanoes along the arc (Ruang, Lokon, Mahawu) have 3He/4He >= 7.0RA, CO2/3He < 7x109 and δ13C < -3.0‰ . The southern volcanoes, therefore, sample volatiles more typical of island arc volcanoes. Resolving the CO2 into component structures (mantle-derived, plus slab-derived organic and limestone CO2 - following the approach of Sano and Marty, Chem. Geol., 1995), the northern volcanoes contain higher than average slab-derived limestone contributions. For example, limestone-derived CO2 makes up > 90% of the total CO2 at Karangetang and ~98% at Awu. These values compare with an average limestone contribution of ~65% in the southern Sangihe arc and ~73% in other arcs worldwide. We are investigating possible reasons for the enhanced limestone contributions in the northern Sangihe arc. The sedimentary mélange wedge is thickest in the north (up to 15km) - where the arcs initially collided. The greater availability of sediment may result in a greater input of subducted sediment, thereby providing enhanced dilution of mantle wedge C inputs. Alternatively, subducted sediments may be more carbonate-rich in the northern segment of the arc. This may reflect obduction of shallow, organic-bearing sediments onto the over-riding plate, leaving only pelagic carbonates to

  17. DC arc weld starter

    DOEpatents

    Campiotti, Richard H.; Hopwood, James E.

    1990-01-01

    A system for starting an arc for welding uses three DC power supplies, a high voltage supply for initiating the arc, an intermediate voltage supply for sustaining the arc, and a low voltage welding supply directly connected across the gap after the high voltage supply is disconnected.

  18. Anode power deposition in quasi-steady MPD arcs. [accelerator anode heat flux measurement

    NASA Technical Reports Server (NTRS)

    Saber, A. J.; Jahn, R. G.

    1973-01-01

    The power deposited in the anode of a quasi-steady MPD accelerator has been measured directly by thermocouples attached to the inside surface of a shell anode which provide a local measurement of anode heat flux. The results over a range of arc currents from 5.5 to 44 kiloamperes and argon mass flows from 1 g/sec to 48 g/sec show that the fraction of the total input power deposited in the anode decreases drastically from 50% at an arc power of 200 kW to 10% at 20 MW, and that anode power is not uniformly deposited in the anode. A theoretical model of the anode heat transfer, including effects of anode work function, electron thermal energy, and anode sheath, can be brought into reasonable agreement with the measurements, provided the effective range of the conduction electrons from within the discharge plasma to the anode surface is properly acknowledged.

  19. Anode power deposition in quasi-steady MPD arcs. [accelerator anode heat flux measurement

    NASA Technical Reports Server (NTRS)

    Saber, A. J.; Jahn, R. G.

    1973-01-01

    The power deposited in the anode of a quasi-steady MPD accelerator has been measured directly by thermocouples attached to the inside surface of a shell anode which provide a local measurement of anode heat flux. The results over a range of arc currents from 5.5 to 44 kiloamperes and argon mass flows from 1 g/sec to 48 g/sec show that the fraction of the total input power deposited in the anode decreases drastically from 50% at an arc power of 200 kW to 10% at 20 MW, and that anode power is not uniformly deposited in the anode. A theoretical model of the anode heat transfer, including effects of anode work function, electron thermal energy, and anode sheath, can be brought into reasonable agreement with the measurements, provided the effective range of the conduction electrons from within the discharge plasma to the anode surface is properly acknowledged.

  20. Non-equilibrium modelling of transferred arcs

    NASA Astrophysics Data System (ADS)

    Haidar, J.

    1999-02-01

    A two-temperature, variable-density, arc model has been developed for description of high-current free-burning arcs, including departures from thermodynamic and chemical equilibrium in the plasma. The treatment includes the arc, the anode and the cathode and considers the separate energy balance of the electrons and the heavy particles, together with the continuity equations for these species throughout the plasma. The output includes a two-dimensional distribution for the temperatures and densities both of the electrons and of the heavy particles, plasma velocity, current density and electrical potential throughout the arc. For a 200 A arc in pure argon at 1 atm, we calculate large differences between the temperatures of the electrons and the heavy particles in the plasma region near the cathode tip, together with large departures from local chemical plasma equilibrium. In the main body of the arc at high plasma temperatures, we predict minor differences between the temperatures of the electrons and the heavy particles, which are inconsistent with recent measurements using laser-scattering techniques showing differences of up to several thousand degrees. However, we find that, for the region in front of the cathode tip, the ground-state level of the neutral atoms is overpopulated relative to the corresponding populations under conditions of LTE, in agreement with experimental observations. These departures from LTE are caused by the injection of a large mass flow of cold gas into the arc core due to arc constriction at the tip of the cathode.

  1. Bone marrow transplant - discharge

    MedlinePlus

    Transplant - bone marrow - discharge; Stem cell transplant - discharge; Hematopoietic stem cell transplant - discharge; Reduced intensity; Non-myeloablative transplant - discharge; Mini transplant - discharge; Allogenic bone marrow transplant - ...

  2. Pediatric heart surgery - discharge

    MedlinePlus

    Congenital heart surgery - discharge; Patent ductus arteriosus ligation - discharge; Hypoplastic left heart repair - discharge; Tetralogy of Fallot repair - discharge; Coarctation of the aorta repair - discharge; ...

  3. Apparatus for gas-metal arc deposition

    DOEpatents

    Buhrmaster, Carol L.; Clark, Denis E.; Smartt, Herschel B.

    1991-01-01

    Apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment with the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspenion of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite.

  4. Method for gas-metal arc deposition

    DOEpatents

    Buhrmaster, C.L.; Clark, D.E.; Smartt, H.B.

    1990-11-13

    Method and apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites are disclosed. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment with the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspension of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite. 1 fig.

  5. Method for gas-metal arc deposition

    DOEpatents

    Buhrmaster, Carol L.; Clark, Denis E.; Smartt, Herschel B.

    1990-01-01

    Method and apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment wiht the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspension of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite.

  6. Characteristics of Atmospheric Pressure Rotating Gliding Arc Plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Zhu, Fengsen; Tu, Xin; Bo, Zheng; Cen, Kefa; Li, Xiaodong

    2016-05-01

    In this work, a novel direct current (DC) atmospheric pressure rotating gliding arc (RGA) plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas flow rate on the arc dynamic behaviour and the formation of reactive species in the N2 and air gliding arc plasmas has been investigated by means of electrical signals, high speed photography, and optical emission spectroscopic diagnostics. Compared to conventional gliding arc reactors with knife-shaped electrodes which generally require a high flow rate (e.g., 10-20 L/min) to maintain a long arc length and reasonable plasma discharge zone, in this RGA system, a lower gas flow rate (e.g., 2 L/min) can also generate a larger effective plasma reaction zone with a longer arc length for chemical reactions. Two different motion patterns can be clearly observed in the N2 and air RGA plasmas. The time-resolved arc voltage signals show that three different arc dynamic modes, the arc restrike mode, takeover mode, and combined modes, can be clearly identified in the RGA plasmas. The occurrence of different motion and arc dynamic modes is strongly dependent on the composition of the working gas and gas flow rate. supported by National Natural Science Foundation of China (No. 51576174), the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120101110099) and the Fundamental Research Funds for the Central Universities (No. 2015FZA4011)

  7. Arc Distribution During the Vacuum Arc Remelting of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Woodside, C. Rigel; King, Paul E.; Nordlund, Chris

    2013-02-01

    Currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting (VAR) is not a known or monitored process parameter. Previous studies indicate that the distribution of arcs can be neither diffuse nor axisymmetric about the center of the furnace. Correct accounting for the heat flux, electric current flux, and mass flux into the ingot is critical to achieving realistic solidification models of the VAR process. The National Energy Technology Laboratory has developed an arc position measurement system capable of locating arcs and determining the arc distribution within an industrial VAR furnace. The system is based on noninvasive magnetic field measurements and a VAR specific form of the Biot-Savart law. The system was installed on a coaxial industrial VAR furnace at ATI Albany Operations in Albany, OR. This article reports on the different arc distributions observed during production of Ti-6Al-4V. It is shown that several characteristic arc distribution modes can develop. This behavior is not apparent in the existing signals used to control the furnace, indicating the measurement system is providing new information. It is also shown that the different arc distribution modes observed may impact local solidification times, particularly at the side wall.

  8. Arc distribution during the vacuum arc remelting of Ti-6Al-4V

    SciTech Connect

    Woodside, Charles Rigel; King, Paul E.; Nordlund, Chris

    2013-01-01

    Currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting (VAR) is not a known or monitored process parameter. Previous studies indicate that the distribution of arcs can be neither diffuse nor axisymmetric about the center of the furnace. Correct accounting for the heat flux, electric current flux, and mass flux into the ingot is critical to achieving realistic solidification models of the VAR process. The National Energy Technology Laboratory has developed an arc position measurement system capable of locating arcs and determining the arc distribution within an industrial VAR furnace. The system is based on noninvasive magnetic field measurements and a VAR specific form of the Biot–Savart law. The system was installed on a coaxial industrial VAR furnace at ATI Albany Operations in Albany, OR. This article reports on the different arc distributions observed during production of Ti-6Al-4V. It is shown that several characteristic arc distribution modes can develop. This behavior is not apparent in the existing signals used to control the furnace, indicating the measurement system is providing new information. It is also shown that the different arc distribution modes observed may impact local solidification times, particularly at the side wall.

  9. Linear volcanic segments in the Sunda Arc, Indonesia: Implications for arc lithosphere control upon volcano distribution

    NASA Astrophysics Data System (ADS)

    Macpherson, C. G.; Pacey, A.; McCaffrey, K. J.

    2012-12-01

    The overall curvature of many subduction zones is immediately apparent and the term island arc betrays the common assumption that subduction zone magmatism occurs in curved zones. This assumption can be expressed by approximating island arcs as segments of small circles on the surface of a sphere. Such treatments predict that the location of arc volcanoes is related to their vertical separation from the slab (in fact, the depth to seismicity in the slab) and require that the primary control on the locus of magmatism lies either within the subducted slab or the mantle wedge that separates the subducted and overriding lithospheric plates. The concept of curved arcs ignores longstanding observations that magmatism in many subduction systems occurs as segments of linearly arranged volcanic centres. Further evidence for this distribution comes from the close relationship between magmatism and large scale, arc-parallel fabrics in some arcs. Similarly, exposures of deep arc crust or mantle often reveal elongation of magmatic intrusions sub-parallel to the inferred trend of the arc. The Sunda Arc forms the Indonesian islands from Sumatra to Alor and provides an important test for models of volcano distribution for several reasons. First, Sunda has hosted abundant historic volcanic activity. Second, with the notable exception of Krakatau, every volcano in the arc is subaerial from base to cone and, therefore, can be readily identified where there is a suitable extent of local mapping that can be used to ground-truth satellite imagery. Third, there are significant changes in the stress regime along the length of the arc, allowing the influence of the upper plate to be evaluated by comparison of different arc segments. Finally, much of the Sunda Arc has proved difficult to accommodate in models that try to relate volcano distribution to the depth to the subducted slab. We apply an objective line-fitting protocol; the Hough Transform, to explore the distribution of volcanoes

  10. Rethinking Recycling in Arcs

    NASA Astrophysics Data System (ADS)

    Kelemen, P.; Behn, M. D.; Jagoutz, O.

    2012-12-01

    Hacker et al EPSL 2011 and Behn et al Nature Geosci 2011 investigated pathways for return of buoyant, subducted material to arc crust. These include (1) diapirs rising into the hot mantle wedge, with extensive melts adding a component to arc magmas, (2) flow of material back up a relatively cold "subduction channel", adding solids to the lower crust and small-degree partial melts to the upper crust, (3) flow from the forearc along the base of arc crust, and (4) imbrication of forearc material into arc crust. These processes add felsic, incompatible-element-rich components to arc crust. The flux of incompatible elements such as Th in arc lavas, thought to be mainly recycled from subducted sediments, is > sediment subduction flux. There are large uncertainties: arc crustal growth rates are imprecise; young, primitive arc lavas may not be representative of magmatic flux into arc crust; sediment subduction flux may have varied. Nevertheless, this result is found for all arcs examined, using recently published growth rates. Perhaps arc growth rates that include subduction erosion are systematically overestimated. Instead or in addition, maybe significant Th comes from material other than sediments. Here, we consider the implications of pathways 1-4 for arc growth rates and incompatible element enrichment, in the context of subduction erosion and arc-arc collision. Subducting arc lithologies can become separated, with only felsic components returned to arc crust. Buoyant lithologies are mobile in viscous instabilities at > 700-800°C. Whereas thin layers such as sediments may become mobile all at once, instabilities may periodically strip the hottest parts from the top of thick buoyant layers, replacing them with hot mantle. In arc-arc collision, the top of a subducting plate starts at about 0°C on the seafloor, so heating is slow. In subduction erosion, forearc material in the subducting package can be > 200°C before erosion so buoyant lithologies reach 700-800

  11. Long arc stabilities with various arc gas flow rates

    NASA Astrophysics Data System (ADS)

    Maruyama, K.; Takeda, K.; Sugimoto, M.; Noguchi, Y.

    2014-11-01

    A new arc torch for use in magnetically driven arc device was developed with a commercially available TIG welding arc torch. The torch has a water-cooling system to the torch nozzle and has a nozzle nut to supply a swirling-free plasma gas flow. Its endurance against arc thermal load is examined. Features of its generated arc are investigated.

  12. XVIIth international symposium on discharges and electrical insulation in vacuum. Volume 1 and 2

    SciTech Connect

    1996-12-31

    This is the proceedings of the XVIIth International Symposium on Discharges and Electrical Insulation in Vacuum, held in Berkeley, CA, July 21-26, 1996. Papers were presented in the following areas: vacuum breakdown and prebreakdown phenomena; vacuum arcs; switching in vacuum; surface flashover; vacuum insulation including magnetic insulation, accelerators, and others; high current diodes, intense particle beams, and vacuum arc ion sources; discharges in the space environment; arcing in controlled fusion devices; emission processes and electrode phenomena; cathodic arc deposition; pseudospark discharges; industrial applications. Separate abstracts have been indexed into the database for some articles from this proceedings.

  13. Mixing gasdynamic laser with nonequilibrium arc excitation

    NASA Astrophysics Data System (ADS)

    Antonov, G. G.; Kovshechnikov, V. B.; Rutberg, F. G.

    2016-05-01

    A mixing gasdynamic laser with nonuniform arc excitation is investigated using a model setup. Tentative analysis of the results indicates the appropriateness of using plasmatrons to improve the efficiency of mixing gasdynamic lasers by making carbon dioxide molecules vibrationally more nonuniform. In addition, a plasmatron serves as a preionization source both for a fast-flow gas-discharge laser and for a gasdynamic laser with combined pumping.

  14. Surface breakdown igniter for mercury arc devices

    DOEpatents

    Bayless, John R.

    1977-01-01

    Surface breakdown igniter comprises a semiconductor of medium resistivity which has the arc device cathode as one electrode and has an igniter anode electrode so that when voltage is applied between the electrodes a spark is generated when electrical breakdown occurs over the surface of the semiconductor. The geometry of the igniter anode and cathode electrodes causes the igniter discharge to be forced away from the semiconductor surface.

  15. Cirrhosis - discharge

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000290.htm Cirrhosis - discharge To use the sharing features on this page, please enable JavaScript. You have cirrhosis of the liver. Scar tissue forms and your ...

  16. Gallstones - discharge

    MedlinePlus

    ... full liquid Pancreatitis - discharge Wet-to-dry dressing changes Review Date 12/2/2016 Updated by: Michael M. Phillips, MD, Clinical Professor of Medicine, The George Washington University School of Medicine, Washington, DC. Also reviewed by ...

  17. Osteomyelitis - discharge

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000297.htm Osteomyelitis - discharge To use the sharing features on this page, please enable JavaScript. You have osteomyelitis , a bone infection caused by bacteria or other ...

  18. Septoplasty - discharge

    MedlinePlus

    ... this page: //medlineplus.gov/ency/patientinstructions/000246.htm Septoplasty - discharge To use the sharing features on this page, please enable JavaScript. Septoplasty is surgery to correct any problems in the ...

  19. Two-dimensional, three-fluid modeling of capillary plasma discharges in electrothermal mass accelerators

    NASA Astrophysics Data System (ADS)

    Esmond, M. J.; Winfrey, A. L.

    2016-06-01

    Electrothermal (ET) plasma launchers have a wide array of applications as mass acceleration devices. An ET plasma launcher utilizes an ET plasma discharge to accelerate a projectile. ET plasma discharges are arc-driven capillary discharges that ablate liner materials and form partially ionized plasmas. ET plasma discharges are generated by driving current pulses through a capillary source. Current pulses typically have peak currents on the order of tens of kA with pulse lengths on the order of hundreds of μs. These types of plasma discharges have been explored for their application to military ballistics, electric thrusters, and nuclear fusion power. ET plasma discharges have been studied using 0D, 1D, and semi-2D fluid models. In this work, a three-fluid, fully two-dimensional model of ET plasma discharges is presented. First approximations used in the newly developed model and code are discussed and simulation results are compared with experiment. Simulation results indicate the development of back flow inside ET plasma discharges due to collisional drag forces between individual plasma species. This back flow is observed for simulations of ET plasma discharges receiving current pulses with peak currents of 10, 20, 30, and 40 kA. Simulation results also reveal the development of fluid perturbations near the breech of the plasma source. These perturbations cause variations in the plasma electrical conductivity and ultimately cause changes in the local ablation rate of the source liner. At higher current pulses, these perturbations are more localized in the region of the source closest to the breech. This effect causes a decrease in the ablated mass in this region relative to the region of the source experiencing the highest ablation.

  20. Arc spot welding technique for underwater use

    SciTech Connect

    Koga, H.; Ide, Y.; Ogawa, Y.

    1995-12-31

    An arc spot welding equipment with special local cavity shroud was developed for underwater salvaging activity. Arc spot welding for lapped plates is an effective method to recover defects. This method in surface is so simple to use widely in the field of railways and chemical plants manufacturing. But there is some problems on the reliability of joint strength and bead shapes. A special arc spot nozzle to improve welding quality was developed. A small outlet of air jet at the bottom of the nozzle was created to maintain the swirl flow of shielding gas and certain rejection of excessive molten metal. This nozzle covers the welding part completely, then it also works as a local cavity shroud under water. This paper describes the design and function of the nozzle for CO{sub 2} arc spot welding system. A programmable controller manages the welding sequence of shielding gas flow, air jet flow, and arcing time. This welding gun is operated manually, but the operation is only to press the gun on the weld point. After that welding will proceed automatically, and arcing time is about three seconds. Whole time for welding which includes pre and post gas flow time is less than ten seconds for surface use, it is required some more additional pre drying process of welding point for underwater use to guarantee the high quality welding results. Fundamental analysis of welding conditions and the effects of air jet were considered.

  1. Diffuse vacuum arc with cerium oxide hot cathode

    NASA Astrophysics Data System (ADS)

    Amirov, R. Kh; Vorona, N. A.; Gavrikov, A. V.; Liziakin, G. D.; Polistchook, V. P.; Samoylov, I. S.; Smirnov, V. P.; Usmanov, R. A.; Yartsev, I. M.; Ivanov, A. S.

    2016-11-01

    Diffuse vacuum arc with hot cathode is one of the perspective plasma sources for the development of spent nuclear fuel plasma reprocessing technology. Experimental data is known for such type of discharges on metal cathodes. In this work discharge with cerium dioxide hot cathode was studied. Cerium dioxide properties are similar to uranium dioxide. Its feature as dielectric is that it becomes conductive in oxygen-free atmosphere. Vacuum arc was studied at following parameters: cathode temperatures were between 2.0 and 2.2 kK, discharge currents was between 30 and 65 A and voltages was in range from 15 to 25 V. Power flows from plasma to cathode were estimated in achieved regimes. Analysis of generated plasma component composition was made by radiation spectrum diagnostics. These results were compared with calculations of equilibrium gaseous phase above solid sample of cerium dioxide in close to experimental conditions. Cerium dioxide vacuum evaporation rate and evaporation rate in arc were measured.

  2. Laser-assisted vacuum arc extreme ultraviolet source: a comparison of picosecond and nanosecond laser triggering

    NASA Astrophysics Data System (ADS)

    Beyene, Girum A.; Tobin, Isaac; Juschkin, Larissa; Hayden, Patrick; O'Sullivan, Gerry; Sokell, Emma; Zakharov, Vassily S.; Zakharov, Sergey V.; O'Reilly, Fergal

    2016-06-01

    Extreme ultraviolet (EUV) light generation by hybrid laser-assisted vacuum arc discharge plasmas, utilizing Sn-coated rotating-disc-electrodes, was investigated. The discharge was initiated by localized ablation of the liquid tin coating of the cathode disc by a laser pulse. The laser pulse, at 1064 nm, was generated by Nd:YAG lasers with variable energy from 1 to 100 mJ per pulse. The impact of shortening the laser pulse from 7 ns to 170 ps on the EUV generation has been investigated in detail. The use of ps pulses resulted in an increase in emission of EUV radiation. With a fixed discharge energy of ~4 J, the EUV conversion efficiency tends to plateau at ~2.4  ±  0.25% for the ps laser pulses, while for the ns pulses, it saturates at ~1.7  ±  0.3%. Under similar discharge and laser energy conditions, operating the EUV source with the ps-triggering resulted also in narrower spectral profiles of the emission in comparison to ns-triggering. The results indicate an advantage in using ps-triggering in laser-assisted discharges to produce brighter plasmas required for applications such as metrology.

  3. Emission spectra analysis of arc plasma for synthesis of carbon nanostructures in various magnetic conditions

    SciTech Connect

    Li Jian; Kundrapu, Madhusudhan; Shashurin, Alexey; Keidar, Michael

    2012-07-15

    Arc discharge supported by the erosion of anode materials is one of the most practical and efficient methods to synthesize various high-quality carbon nanostructures. By introducing a non-uniform magnetic field in arc plasmas, high-purity single-walled carbon nanotubes (SWCNT) and large-scale graphene flakes can be obtained in a single step. In this paper, ultraviolet-visible emission spectra of arc in different spots under various magnetic conditions are analyzed to provide an in situ investigation for transformation processes of evaporated species and growth of carbon nanostructures in arc. Based on the arc spectra of carbon diatomic Swan bands, vibrational temperature in arc is determined. The vibrational temperature in arc center was measured around 6950 K, which is in good agreement with our simulation results. Experimental and simulation results suggest that SWCNT are formed in the arc periphery region. Transmission electronic microscope and Raman spectroscope are also employed to characterize the properties of carbon nanostructures.

  4. Double-discharge stabilization of supersonic CO laser mixtures

    NASA Technical Reports Server (NTRS)

    Srinivasan, G.; Smith, J. A.

    1977-01-01

    Experiments have been conducted to study the applicability of a CW double-discharge stabilization scheme under conditions appropriate for high-energy lasers in supersonic flows. Steady arc-free volume discharges have been produced in a Mach 3 supersonic-flow test cavity using an auxiliary discharge to stabilize the main discharge at low-current densities in N2 and He/CO mixtures. A significant result is the lack of observed plasma E/N changes in response to auxiliary-discharge current changes. Also, where glow discharges were obtained, the energy loading achieved was less than the threshold required for laser operation.

  5. Cardiac catheterization - discharge

    MedlinePlus

    Catheterization - cardiac - discharge; Heart catheterization - discharge: Catheterization - cardiac; Heart catheterization; Angina - cardiac catheterization discharge; CAD - cardiac catheterization discharge; Coronary artery disease - cardiac catheterization ...

  6. Atrial fibrillation - discharge

    MedlinePlus

    Auricular fibrillation - discharge; A-fib - discharge; AF - discharge; Afib - discharge ... been in the hospital because you have atrial fibrillation . This condition occurs when your heart beats faster ...

  7. Development of circuit model for arcing on solar panels

    NASA Astrophysics Data System (ADS)

    Mehta, Bhoomi K.; Deshpande, S. P.; Mukherjee, S.; Gupta, S. B.; Ranjan, M.; Rane, R.; Vaghela, N.; Acharya, V.; Sudhakar, M.; Sankaran, M.; Suresh, E. P.

    2010-02-01

    The increased requirements of payload capacity of the satellites have resulted in much higher power requirements of the satellites. In order to minimize the energy loss during power transmission due to cable loss, use of high voltage solar panels becomes necessary. When a satellite encounters space plasma it floats negatively with respect to the surrounding space plasma environment. At high voltage, charging and discharging on solar panels causes the power system breakdown. Once a solar panel surface is charged and potential difference between surface insulator and conductor exceeds certain value, electrostatic discharge (ESD) may occur. This ESD may trigger a secondary arc that can destroy the solar panel circuit. ESD is also called as primary or minor arc and secondary is called major arc. The energy of minor arc is supplied by the charge stored in the coverglass of solar array and is a pulse of typically several 100 ns to several 100 μs duration. The damage caused by minor arc is less compared to major arcs, but it is observed that the minor arc is cause of major arc. Therefore it is important to develop an understanding of minor arc and mitigation techniques. In this paper we present a linear circuit analysis for minor arcs on solar panels. To study arcing event, a ground experimental facility to simulate space plasma environment has been developed at Facilitation Centre for Industrial Plasma Technologies (Institute for Plasma Research) in collaboration with Indian Space Research Organization's ISRO Satellite Technology Centre (ISAC). A linear circuit model has been developed to explain the experimental results by representing the coverglass, solar cell interconnect and wiring by an LCR circuit and the primary arc by an equivalent LR circuit. The aim of the circuit analysis is to predict the arc current which flows through the arc plasma. It is established from the model that the current depends on various parameters like potential difference between insulator

  8. Arcing in space structures in low Earth orbit

    NASA Technical Reports Server (NTRS)

    Upschulte, B. L.; Marinelli, W. J.; Weyl, G.; Carleton, K. L.

    1992-01-01

    This report describes results of an experimental and theoretical program to investigate arcing of structures containing dielectric and conducting materials when they are biased negatively with respect to a plasma. An argon ion source generated Ar(+) ions of directed energy 20 to 40 eV and density approximately 10(exp 7) cm(exp -3) that impinged upon samples containing a dielectric material on top of a negatively biased Kovar plate. Arcing events were studied for bias voltages between -300 and -1000V with respect to the ion beam. The samples were Dow Corning 93-500 adhesive on Kovar, fused silica cover slips bonded on Kovar, and silicon solar cells mounted on Kovar. Measurements of discharge current, Kovar plate voltage, and radiation from the arc versus time were carried out. Microsecond duration exposure images and optical spectra in the 0.24 to 0.40 micron band were also acquired during arcing events. Arcing events were found to be associated with exposed adhesive and means were found to eliminate arcing altogether. The charging of a silica cover plate and the fields around the plate were calculated using a particle-in-cell code. Models were developed to explain the ignition of the arc and the physical processes occurring during the discharge.

  9. NASA GRC and MSFC Space-Plasma Arc Testing Procedures

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T.; Hillard, G. Barry; Vaughn, Jason; Schneider, Todd

    2007-01-01

    Tests of arcing and current collection in simulated space plasma conditions have been performed at the NASA Glenn Research Center (GRC) in Cleveland, Ohio, for over 30 years and at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, for almost as long. During this period, proper test conditions for accurate and meaningful space simulation have been worked out, comparisons with actual space performance in spaceflight tests and with real operational satellites have been made, and NASA has achieved our own internal standards for test protocols. It is the purpose of this paper to communicate the test conditions, test procedures, and types of analysis used at NASA GRC and MSFC to the space environmental testing community at large, to help with international space-plasma arcing-testing standardization. Discussed herein are neutral gas conditions, plasma densities and uniformity, vacuum chamber sizes, sample sizes and Debye lengths, biasing samples versus self-generated voltages, floating samples versus grounded samples, test electrical conditions, arc detection, preventing sustained discharges during testing, real samples versus idealized samples, validity of LEO tests for GEO samples, extracting arc threshold information from arc rate versus voltage tests, snapover, current collection, and glows at positive sample bias, Kapton pyrolysis, thresholds for trigger arcs, sustained arcs, dielectric breakdown and Paschen discharge, tether arcing and testing in very dense plasmas (i.e. thruster plumes), arc mitigation strategies, charging mitigation strategies, models, and analysis of test results. Finally, the necessity of testing will be emphasized, not to the exclusion of modeling, but as part of a complete strategy for determining when and if arcs will occur, and preventing them from occurring in space.

  10. In the Arc

    NASA Image and Video Library

    2010-04-15

    NASA Cassini spacecraft image holds an unseen treasure orbiting within the bright arc of Saturn G ring: the tiny moonlet Aegaeon. Too small to be seen here, it is thought to be the source of the debris forming the bright arc in the lower right.

  11. TIGER Arc Modification Application

    SciTech Connect

    Armstrong, Hillary

    1995-03-06

    The application enables the geometric correction of TIGER arcs to a more accurate spatial data set. This is done in a structured automated environment according to Census Bureau guidelines and New Mexico state GIS standards. Arcs may be deleted, added, combined, split, and moved relative to a coverage or image displayed in the background.

  12. WSTF electrical arc projects

    NASA Astrophysics Data System (ADS)

    Linley, Larry

    1994-09-01

    The objectives of these projects include the following: validate method used to screen wire insulation with arc tracking characteristics; determine damage resistance to arc as a function of source voltage and insulation thickness; investigate propagation characteristics of Kapton at low voltages; and investigate pyrolytic properties of polyimide insulated (Kapton) wire for low voltage (less than 35 VDC) applications. Supporting diagrams and tables are presented.

  13. WSTF electrical arc projects

    NASA Technical Reports Server (NTRS)

    Linley, Larry

    1994-01-01

    The objectives of these projects include the following: validate method used to screen wire insulation with arc tracking characteristics; determine damage resistance to arc as a function of source voltage and insulation thickness; investigate propagation characteristics of Kapton at low voltages; and investigate pyrolytic properties of polyimide insulated (Kapton) wire for low voltage (less than 35 VDC) applications. Supporting diagrams and tables are presented.

  14. Cross-arc Variations in Lava Chemistry in the Tonga Arc-Lau Back Arc System, 19- 23°S

    NASA Astrophysics Data System (ADS)

    Michael, P. J.; Bezos, A.; Langmuir, C. H.; Escrig, S.; Matzen, A. K.; Asimow, P.; Arculus, R.

    2007-12-01

    The Tonga arc system from 19°-23°S consists of the active Tofua arc, the Eastern Lau Spreading Center (ELSC; a back arc spreading center), and numerous seamounts between them. We use the excellent sampling of ELSC and 34 nearby seamounts, along with sparser published analyses of Tofua arc, to examine the spatial relations of chemistry and melting in this subduction system. The spatial constraints can be used to better understand the nature and mechanism of enrichment that is caused by subduction. Geochemistry along the axis of ELSC is related to its distance to the Tofua arc, which decreases continuously from 100 km in the north to 40 km in the south. The subduction influence (e.g., fluid mobile elements) along ELSC increases in several sharp gradients towards the south as ELSC gets closer to the arc. The six different tectonic segments of ELSC display mixing relationships in trace element ratio-ratio diagrams (e.g., Ba/La vs Th/La) in which one end member is a subduction component that is distinctive for each segment (Escrig et al., this meeting). We explore whether the distinctive subduction components of each ELSC segment are reflected by the Tofua arc that is adjacent to that segment, and by the intervening seamounts. Relationships between the arc, back arc and seamounts are different in the north and the south. In the south where the arc-back arc distance is smaller, the Tofua arc volcanic rocks share the distinctive trace element characteristics of their corresponding ELSC segment, and extend the mixing trajectories to higher, more arc-like values. Seamounts that are located between Tofua arc and ELSC also share the distinctive trace element characteristics of the local arc + back-arc, and are intermediate in their trace element ratios. These observations are consistent with the model of Langmuir et al., (2006) in which magmas of back arc spreading centers form from two components: a dry side similar to mid-ocean ridges and a wet (trenchward) side that

  15. METHOD AND APPARATUS FOR PRODUCING INTENSE ENERGETIC GAS DISCHARGES

    DOEpatents

    Bell, P.R.; Luce, J.S.

    1960-01-01

    A device for producing an energetic gas arc discharge employing the use of gas-fed hollow cathode and anode electrodes is reported. The rate of feed of the gas to the electrodes is regulated to cause complete space charge neutralization to occur within the electrodes. The arc discharge is closely fitted within at least one of the electrodes so tint the gas fed to this electrode is substantially completely ionized before it is emitted into the vacuum chamber. It is this electrode design and the axial potential gradient that exists in the arc which permits the arc to be operated in low pressures and at volthges and currents that permit the arc to be energetic. The use of the large number of energetic ions that are accelerated toward the cathode as a propulsion device for a space vehicle is set forth.

  16. Lazy arc consistency

    SciTech Connect

    Schiex, T.; Gaspin, C.; Regin, J.C.; Verfaillie, G.

    1996-12-31

    Arc consistency filtering is widely used in the framework of binary constraint satisfaction problems: with a low complexity, inconsistency may be detected and domains are filtered. In this paper, we show that when detecting inconsistency is the objective, a systematic domain filtering is useless and a lazy approach is more adequate. Whereas usual arc consistency algorithms produce the maximum arc consistent sub-domain, when it exists, we propose a method, called LAC{tau}, which only looks for any arc consistent sub-domain. The algorithm is then extended to provide the additional service of locating one variable with a minimum domain cardinality in the maximum arc consistent sub-domain, without necessarily computing all domain sizes. Finally, we compare traditional AC enforcing and lazy AC enforcing using several benchmark problems, both randomly generated CSP and real life problems.

  17. Evaluation of a self-aspirating local total enthalpy probe in a low-density arc-heated hypersonic wind tunnel

    NASA Technical Reports Server (NTRS)

    Guy, R. W.; Kantsios, A. G.

    1972-01-01

    A shock-swallowing, self-aspirating, local total enthalpy probe has been evaluated in a low density nonequilibrium, hypervelocity airstream. The probe, which incorporated an air gap to separate the internal and external cooling passages, was tested in an electric archeated wind tunnel at an average Mach number of 11.7 and an average Reynolds number per meter of 57,000. The free stream enthalpy probe data are compared with bulk calorimeter measurements of total enthalpy at the beginning of the gas expansion and with local total enthalpy inferred from a theoretical nonequilibrium gas expansion model by using free stream velocity measurements obtained from a mass flow probe. The three techniques are in relative agreement at the lower enthalpies. However, at the higher enthalpies, the enthalpy probe data lie considerably below the other data. This low data may be caused by the chemical and vibrational energy frozen in the flow not being sensed by the probe. Other problems associated with the shock-swallowing total enthalpy probe are discussed, and recommendations for improving the probe performance are presented.

  18. Radiative heat transfer in plasma of pulsed high pressure caesium discharge

    NASA Astrophysics Data System (ADS)

    Lapshin, V. F.

    2016-01-01

    Two-temperature many component gas dynamic model is used for the analysis of features of radiative heat transfer in pulsed high pressure caesium discharge plasma. It is shown that at a sufficiently high pressure the radial optical thickness of arc column is close to unit (τR (λ) ∼ 1) in most part of spectrum. In this case radiative heat transfer has not local character. In these conditions the photons which are emitted in any point of plasma volume are absorbed in other point remote from an emission point on considerable distance. As a result, the most part of the electric energy put in the discharge mainly near its axis is almost instantly redistributed on all volume of discharge column. In such discharge radial profiles of temperature are smooth. In case of low pressure, when discharge plasma is optically transparent for own radiation in the most part of a spectrum (τR(λ) << 1), the emission of radiation without reabsorption takes place. Radiative heat transfer in plasma has local character and profiles of temperature have considerable gradient.

  19. Dynamics of a discrete auroral arc

    NASA Technical Reports Server (NTRS)

    Bruening, K.; Goertz, C. K.

    1986-01-01

    Porcupine Flight 4 data were used to determine the field-aligned currents associated with a southward moving discrete auroral arc in the postmidnight sector. Three different methods were used for determining the field-aligned current which should give identical results if the arcs are quasi-stationary and no parallel electric field exists between the payload and the dynamo region of the ionosphere. As long as the rocket is above the arc, the three methods agree. The integral of precipitating electron flux, the local magnetic field perturbations, and the divergence of the horizontal Pedersen current all indicate an upward current of 5 + or - 3 microamperes/sq m. Immediately north of the arc a strong downward current of about 10-20 microamperes/sq m is detected. The magnitude, however, is not well known because the rocket's velocity relative to the arc cannot be clearly established. Further north of the southward moving arc, the two methods that can be applied (magnetic field perturbations and divergence of the horizontal Pedersen current) yield contradictory results not only about the magnitude of the current but also about the direction of the current. It is suggested that this discrepancy is due to time-dependent electric field.

  20. Dynamics of a discrete auroral arc

    NASA Astrophysics Data System (ADS)

    Bruening, K.; Goertz, C. K.

    1986-06-01

    Porcupine Flight 4 data were used to determine the field-aligned currents associated with a southward moving discrete auroral arc in the postmidnight sector. Three different methods were used for determining the field-aligned current which should give identical results if the arcs are quasi-stationary and no parallel electric field exists between the payload and the dynamo region of the ionosphere. As long as the rocket is above the arc, the three methods agree. The integral of precipitating electron flux, the local magnetic field perturbations, and the divergence of the horizontal Pedersen current all indicate an upward current of 5 + or - 3 microamperes/sq m. Immediately north of the arc a strong downward current of about 10-20 microamperes/sq m is detected. The magnitude, however, is not well known because the rocket's velocity relative to the arc cannot be clearly established. Further north of the southward moving arc, the two methods that can be applied (magnetic field perturbations and divergence of the horizontal Pedersen current) yield contradictory results not only about the magnitude of the current but also about the direction of the current. It is suggested that this discrepancy is due to time-dependent electric field.

  1. Nipple Discharge

    MedlinePlus

    ... If the ultrasound shows a lesion within a milk duct, you may need a biopsy to confirm that it's a papilloma or to exclude a cancer. Nipple discharge is rarely a sign of breast cancer. But it might be a sign of ...

  2. Pulsed electromagnetic gas accelleration. [incorporation of hollow cathode in plasma discharge and suitability determination of MPD discharge as plasmadynamic laser source

    NASA Technical Reports Server (NTRS)

    Jahn, R. G.

    1973-01-01

    Direct measurement with thermocouples of the power deposited in the anode of a multi-megawatt magnetoplasmadynamic discharge has shown the fractional anode power to decrease from 50% at 200 kW to 10% at 20 MW. Using local measurements of current density, electric potential, and electron temperature, the traditional model for heat conduction to the anode is found to be inadequate. Other experiments in which the voltage-current characteristics and exhaust velocities of MPD arcs using Plexiglas and boron nitride chamber insulators and various mass injection configurations show that ablation can affect nominal accelerator operation in several distinct ways. The incorporation of a hollow cathode in a 7 kA plasma discharge has shown that a stable current attachment can be realized in the cavity without the aid of cathode heaters, keeper electrodes, or emissive coatings.

  3. Triad3A Regulates Synaptic Strength by Ubiquitination of Arc

    PubMed Central

    Mabb, Angela M.; Je, H. Shawn; Wall, Mark J.; Robinson, Camenzind G.; Larsen, Rylan S.; Qiang, Yuan; Corrêa, Sonia A.L.; Ehlers, Michael D.

    2014-01-01

    Summary Activity-dependent gene transcription and protein synthesis underlie many forms of learning-related synaptic plasticity. At excitatory glutamatergic synapses, the immediate early gene product Arc/Arg3.1 couples synaptic activity to postsynaptic endocytosis of AMPA-type glutamate receptors. Although the mechanisms for Arc induction have been described, little is known regarding the molecular machinery that terminates Arc function. Here we demonstrate that the RING domain ubiquitin ligase Triad3A/RNF216 ubiquitinates Arc, resulting in its rapid proteasomal degradation. Triad3A associates with Arc, localizes to clathrin-coated pits, and is associated with endocytic sites in dendrites and spines. In the absence of Triad3A, Arc accumulates, leading to the loss of surface AMPA receptors. Furthermore, loss of Triad3A mimics and occludes Arc-dependent forms of synaptic plasticity. Thus, degradation of Arc by clathrin-localized Triad3A regulates the availability of synaptic AMPA receptors and temporally tunes Arc-mediated plasticity at glutamatergic synapses. PMID:24945773

  4. "Ictal" lateralized periodic discharges.

    PubMed

    Sen-Gupta, Indranil; Schuele, Stephan U; Macken, Micheal P; Kwasny, Mary J; Gerard, Elizabeth E

    2014-07-01

    Whether lateralized periodic discharges (LPDs) represent ictal or interictal phenomena, and even the circumstances in which they may represent one or the other, remains highly controversial. Lateralized periodic discharges are, however, widely accepted as being ictal when they are time-locked to clinically apparent symptoms. We sought to investigate the characteristics of "ictal" lateralized periodic discharges (ILPDs) defined by time-locked clinical symptoms in order to explore the utility of using this definition to dichotomize LPDs into "ictal" and "nonictal" categories. Our archive of all continuous EEG (cEEG) reports of adult inpatients undergoing prolonged EEG monitoring for nonelective indications between 2007 and 2011 was searched to identify all reports describing LPDs. Lateralized periodic discharges were considered ILPDs when they were reported as being consistently time-locked to clinical symptoms; LPDs lacking a clear time-locked correlate were considered to be "nonictal" lateralized periodic discharges (NILPDs). Patient charts and available neuroimaging studies were also reviewed. Neurophysiologic localization of LPDs, imaging findings, presence of seizures, discharge outcomes, and other demographic factors were compared between patients with ILPDs and those with NILPDs. p-Values were adjusted for false discovery rate (FDR). One thousand four hundred fifty-two patients underwent cEEG monitoring at our institution between 2007 and 2011. Lateralized periodic discharges were reported in 90 patients, 10 of whom met criteria for ILPDs. Nine of the patients with ILPDs demonstrated motor symptoms, and the remaining patient experienced stereotyped sensory symptoms. Ictal lateralized periodic discharges had significantly increased odds for involving central head regions (odds ratio [OR]=11; 95% confidence interval [CI]=2.16-62.6; p=0.018, FDR adjusted), with a trend towards higher proportion of lesions involving the primary sensorimotor cortex (p=0.09, FDR

  5. Welding arc initiator

    DOEpatents

    Correy, Thomas B.

    1989-01-01

    An improved inert gas shielded tungsten arc welder is disclosed of the type wherein a tungsten electrode is shielded within a flowing inert gas, and, an arc, following ignition, burns between the energized tungsten electrode and a workpiece. The improvement comprises in combination with the tungsten electrode, a starting laser focused upon the tungsten electrode which to ignite the electrode heats a spot on the energized electrode sufficient for formation of a thermionic arc. Interference problems associated with high frequency starters are thus overcome.

  6. Welding arc initiator

    DOEpatents

    Correy, T.B.

    1989-05-09

    An improved inert gas shielded tungsten arc welder is disclosed of the type wherein a tungsten electrode is shielded within a flowing inert gas, and, an arc, following ignition, burns between the energized tungsten electrode and a workpiece. The improvement comprises in combination with the tungsten electrode, a starting laser focused upon the tungsten electrode which to ignite the electrode heats a spot on the energized electrode sufficient for formation of a thermionic arc. Interference problems associated with high frequency starters are thus overcome. 3 figs.

  7. Arc spraying in China

    NASA Astrophysics Data System (ADS)

    Liu, Xianjun

    2001-03-01

    Although are spraying is not a new technique, recent development of arc spraying device systems, spray wires, research on the coating mechanism, and the dynamic behavior of spraying make it a most active thermal spray process. In China, the arc spraying technique is the most efficient way for long life corrosion protection of steel structures. In addition, the arc spraying process is widely used for renovation and surface modification of machine components, mold making for plastic products, high-temperature corrosion resistance for waterwalls of boilers, antisliding coatings, self-lubricating coatings, etc.

  8. Tokamak ARC damage

    SciTech Connect

    Murray, J.G.; Gorker, G.E.

    1985-01-01

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage.

  9. Electric arc saw apparatus

    DOEpatents

    Deichelbohrer, Paul R [Richland, WA

    1986-01-01

    A portable, hand held electric arc saw has a small frame for supporting an electrically conducting rotary blade which serves as an electrode for generating an electric arc to erode a workpiece. Electric current is supplied to the blade by biased brushes and a slip ring which are mounted in the frame. A pair of freely movable endless belts in the form of crawler treads stretched between two pulleys are used to facilitate movement of the electric arc saw. The pulleys are formed of dielectric material to electrically insulate the crawler treads from the frame.

  10. High current electric arcs above the In-Ga-Sn eutectic alloy

    NASA Astrophysics Data System (ADS)

    Klementyeva, I. B.; Pinchuk, M. E.

    2016-11-01

    The results of investigations of high-current dc and ac arc discharges of atmospheric pressure emerging above the free surface of liquid metal (In-Ga-Sn eutectic alloy) are presented in the paper. The mechanism of the arc formation due to pinch-effect is discussed here.

  11. Development of an Ultralight Pulse Gas Metal ARC Welding System for Shipyard Applications

    DTIC Science & Technology

    2007-07-27

    out aboard ship using the shielded metal arc welding ( SMAW ) process (“stick” welding). This manual process is relatively slow, discharges...using the shielded metal arc welding ( SMAW ) process (“stick” welding). This manual process is relatively slow, discharges considerable fume...process. However, in most cases it is only necessary to bring a single cable lead with no power supply to the job area, which makes the SMAW process

  12. Arc Voltage Between Deion Grid Affected by Division of Arc in Magnetic Driven Arc

    NASA Astrophysics Data System (ADS)

    Inuzuka, Yutaro; Yamato, Takashi; Yamamoto, Shinji; Iwao, Toru

    2016-10-01

    Magnetic driven arc has been applied to DC breaker and fault current limiters. However, it has not been researched, especially stagnation and re-strike of the arc. In this paper, the arc voltage between deion grid affected by division of arc in magnetic driven arc and arc behavior are measured by using the oscilloscope and HSVC (High Speed Video Camera). As a result, arc voltage increased because of division of the arc. The arc mean moving speed increases with increasing the external magnetic field. However, when the arc was not stalemate, the arc moving speed does not change so much. The arc re-strike time increases and stalemate time decreases with increasing the external magnetic field. Therefore, the anode spot moving speed increases 8 times because arc re-strike occurs easily with the external magnetic field. Thus, the erosion of electrodes decreases and the arc movement becomes the smooth. When the arc is divided, the arc voltage increased because of the electrode fall voltage. Therefore, the arc voltage increases with increasing the number of deion grid.

  13. EDITORIAL Metal vapour in atmospheric-pressure arcs Metal vapour in atmospheric-pressure arcs

    NASA Astrophysics Data System (ADS)

    Murphy, Anthony B.

    2010-11-01

    Metal vapour has a significant, and in some cases dominant, influence in many applications of atmospheric-pressure plasmas, including arc welding, circuit interruption and mineral processing. While the influence of metal vapour has long been recognized, it is only recently that diagnostic and computational tools have been sufficiently well-developed to allow this influence to be more thoroughly examined and understood. Some unexpected findings have resulted: for example, that the presence of metal vapour in gas-metal arc welding leads to local minima in the temperature and current density in the centre of the arc. It has become clear that the presence of metal vapour, as well as having intrinsic scientific interest, plays an important role in determining the values of critical parameters in industrial applications, such as the weld penetration in arc welding and the extinction time in circuit breakers. In gas-tungsten arc welding, metal vapour concentrations are formed by evaporation of the weld pool, and are relatively low, typically at most a few per cent. Moreover, the convective flow of the plasma near the weld pool tends to direct the metal vapour plume radially outwards. In gas-metal arc welding, in contrast, metal vapour concentrations can reach over 50%. In this case, the metal vapour is produced mainly by evaporation of the wire electrode, and the strong downwards convective flow below the electrode concentrates the metal vapour in the central region of the arc. The very different metal concentrations and distributions in the two welding processes mean that the metal vapour has markedly different influences on the arc. In gas-tungsten arc welding, the current density distribution is broadened near the weld pool by the influence of the metal vapour on the electrical conductivity of the plasma, and the arc voltage is decreased. In contrast, in gas-metal arc welding, the arc centre is cooled by increased radiative emission and the arc voltage is increased. In

  14. Optical diagnostics of a gliding arc.

    PubMed

    Sun, Z W; Zhu, J J; Li, Z S; Aldén, M; Leipold, F; Salewski, M; Kusano, Y

    2013-03-11

    Dynamic processes in a gliding arc plasma generated between two diverging electrodes in ambient air driven by 31.25 kHz AC voltage were investigated using spatially and temporally resolved optical techniques. The life cycles of the gliding arc were tracked in fast movies using a high-speed camera with framing rates of tens to hundreds of kHz, showing details of ignition, motion, pulsation, short-cutting, and extinction of the plasma column. The ignition of a new discharge occurs before the extinction of the previous discharge. The developed, moving plasma column often short-cuts its current path triggered by Townsend breakdown between the two legs of the gliding arc. The emission from the plasma column is shown to pulsate at a frequency of 62.5 kHz, i.e., twice the frequency of the AC power supply. Optical emission spectra of the plasma radiation show the presence of excited N2, NO and OH radicals generated in the plasma and the dependence of their relative intensities on both the distance relative to the electrodes and the phase of the driving AC power. Planar laser-induced fluorescence of the ground-state OH radicals shows high intensity outside the plasma column rather than in the center suggesting that ground-state OH is not formed in the plasma column but in its vicinity.

  15. Physics of Electrical Discharges to Control and to Utilize Them

    NASA Astrophysics Data System (ADS)

    Yumoto, Motoshige

    Three topics related to the field of the technical committee on electrical discharges (TC-ED) are summarized for this special issue. First one deals with the fundamental process of long gap discharge. As the second one, the topics of a vacuum discharge occurred on the solar cell of the spacecraft is introduced. The last one shows the arc motion in the rail-gun.

  16. ARC-1964-A-31910

    NASA Image and Video Library

    1964-01-24

    Dr. Dean R. Chapman a Ames Research Center scientists studing tektits, holding a simulated tektite created in the Ames arc jet facility (left) and authentic Australian tektite over a map of Australia.

  17. Analogue modeling of arc and backarc deformation in the New Hebrides arc and North Fiji Basin

    NASA Astrophysics Data System (ADS)

    Schellart, W. P.; Lister, G. S.; Jessell, M. W.

    2002-04-01

    In most backarc basins, extension is perpendicular to the arc. Thus individual spreading ridges extend approximately parallel to the arc. In the North Fiji Basin, however, several ancient and active spreading ridges strike 70° 90° to the New Hebrides arc. These high- angle spreading ridges relocated southward during the asymmetric opening of the North Fiji Basin. We have simulated the structural development of the North Fiji Basin and the New Hebrides arc with scaled analogue models, and the results have inspired us to come to several tentative conclusions. We interpret the orientation of the high-angle spreading ridges to be related to the asymmetric opening of the backarc basin around a hinge, where they form close to the hinge. Relocation of these spreading ridges is most likely related to subduction of the West Torres Plateau along the New Hebrides Trench. This resulted in localized collision, retarded rollback of the subducting slab along the northwest corner of the trench, and reduced extension and shearing in the northwest corner of the North Fiji Basin. Backarc extension continued in the rest of the North Fiji Basin owing to continued rollback of the southern part of the subducting slab. Here, active extension was separated from the slightly or nonextending northwest corner by a zone striking at high angle to the New Hebrides arc, i.e., the Hazel Holme extensional zone. Moreover, impingement of the d'Entrecasteaux Ridge into the overriding plate led to local deformation and fragmentation of the arc.

  18. Electric arc saw apparatus

    DOEpatents

    Deichelbohrer, P.R.

    1983-08-08

    A portable, hand-held electric arc saw apparatus comprising a small frame for supporting an electrically conducting rotary blade which serves as an electrode for generating an electric arc between the blade and a workpiece of opposite polarity. Electrically conducting means are provided on said frame for transmitting current to said blade. A pair of freely movable endless belts in the form of crawler treads are employed to facilitate movement of the apparatus relative to the workpiece.

  19. Typical Motion and Extinction Characteristics of the Secondary Arcs Associated with Half-Wavelength Transmission Lines

    NASA Astrophysics Data System (ADS)

    Cong, Haoxi; Li, Qingmin; Xing, Jinyuan; Li, Jinsong

    2014-09-01

    Secondary arc discharge is a complicated physical phenomenon and one of the key fundamental issues associated with ultra high voltage (UHV) half-wavelength transmission lines (HWTL). With the establishment of a physical simulation platform for the HWTLs, experiments were carried out regarding the motion and extinction characteristics of secondary arcs. The cathode arc root and the anode arc root were found to show an obvious polarity effect while the arc column was moving in a spiral, due to their different motion mechanisms. The extinction behavior was also recorded and experiments were designed with different compensation conditions. Results show that the arcing time can be greatly reduced if there exists an electrical compensation network. The research provides fundamentals for understanding the physics involved, especially the motion and extinction mechanisms of the secondary arcs.

  20. The dependence of extracted current on discharge gas pressure in neutral beam ion sources on HL-2A tokamak

    SciTech Connect

    Wei, H. L.; Cao, J. Y.; Rao, J.; Lei, G. J.; Jiang, S. F.; Liu, H.; Yu, L. M.; Xie, W. M.; Li, M.; Yang, X. F.; Zou, G. Q.; Lu, D. L.; Duan, X. R.

    2012-02-15

    The discharge gas pressure is a key factor to influence the extracted current of ion source. In this paper, the dependence of extracted current on discharge gas pressure was investigated in detail at different arc discharge currents. The discharge gas pressure with a very broad range (0.1 Pa-2.7 Pa) was scanned for the first time. It is turned out that, with the increasing of discharge gas pressure, the extracted current increases and the arc voltage decreases at different arc currents; however, when the discharge gas pressure exceeds a certain value, the extracted current decreases. For the same discharge gas pressure, the higher the arc current, the higher the arc voltage and the extracted current are. The arc efficiency was also calculated, and its dependence on gas pressure was almost the same with the dependence of extracted current on gas pressure, but at the same discharge gas pressure, the lower the arc current, the higher the arc efficiency is and the lower the extracted current is.

  1. Arcing in Leo and Geo Simulated Environments: Comparative Analysis

    NASA Technical Reports Server (NTRS)

    Vayner, Boris V.; Ferguson, Dale C.; Galofaro, Joel TY.

    2006-01-01

    Comprehensive tests of two solar array samples in simulated Low Earth Orbit (LEO) and Geosynchronous Orbit (GEO) environments have demonstrated that the arc inception voltage was 2-3 times lower in the LEO plasma than in the GEO vacuum. Arc current pulse wave forms are also essentially different in these environments. Moreover, the wide variations of pulse forms do not allow introducing the definition of a "standard arc wave form" even in GEO conditions. Visual inspection of the samples after testing in a GEO environment revealed considerable damage on coverglass surfaces and interconnects. These harmful consequences can be explained by the discharge energy being one order of magnitude higher in vacuum than in background plasma. The tests also revealed a potential danger of powerful electrostatic discharges that could be initiated on the solar array surface of a satellite in GEO during the ignition of an arcjet thruster.

  2. High velocity pulsed wire-arc spray

    NASA Technical Reports Server (NTRS)

    Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor); Kincaid, Russell W. (Inventor)

    1999-01-01

    Wire arc spraying using repetitively pulsed, high temperature gas jets, usually referred to as plasma jets, and generated by capillary discharges, substantially increases the velocity of atomized and entrained molten droplets. The quality of coatings produced is improved by increasing the velocity with which coating particles impact the coated surface. The effectiveness of wire-arc spraying is improved by replacing the usual atomizing air stream with a rapidly pulsed high velocity plasma jet. Pulsed power provides higher coating particle velocities leading to improved coatings. 50 micron aluminum droplets with velocities of 1500 m/s are produced. Pulsed plasma jet spraying provides the means to coat the insides of pipes, tubes, and engine block cylinders with very high velocity droplet impact.

  3. Catalyst and doping methods for arc graphene

    NASA Astrophysics Data System (ADS)

    Cho, Hyunjin; Oh, InSeoup; Kang, JungHo; Park, Sungchan; Ku, Boncheol; Park, Min; Kwak, Soonjong; Khanra, Partha; Lee, Joong Hee; Jong Kim, Myung

    2014-11-01

    Nitrogen-doped graphene synthesis with ˜g scale has been accomplished using the arc discharge method. The defects formed in the synthesis process were reduced by adding various metal catalysts, among which Bi2O3 was found to be the most effective. Adding dopants to the starting materials increased the electrical conductivity of the graphene product, and the doping concentration in graphene was tuned by adjusting the amount of nitrogen dopants. A step-wise technique to fabricate graphene thin films was developed, including dispersion, separation, and filtering processes. The arc graphene can also find its potential application in supercapacitors, taking advantage of its large surface area and improved conductivity by doping.

  4. Measurement of total ion current from vacuum arc plasmasources

    SciTech Connect

    Oks, Efim M.; Savkin, Konstantin P.; Yushkov, Georgiu Yu.; Nikolaev, Alexey G.; Anders, A.; Brown, Ian G.

    2005-07-01

    The total ion current generated by a vacuum arc plasma source was measured. The discharge system investigated allowed ion collection from the arc plasma streaming through a hemispherical mesh anode with geometric transparency of 72 percent. A range of different cathode materials was investigated, and the arc current was varied over the range 50-500 A. We find that the normalized ion current (Iion/Iarc) depends on the cathode material, with values in the range from 5 percent to 19 percent and generally greater for elements of low cohesive energy. The application of a strong axial magnetic field in the cathode and arc region leads to increased normalized ion current, but only by virtue of enhanced ion charge states formed in a strong magnetic field.

  5. The statistical difference between bending arcs and regular polar arcs

    NASA Astrophysics Data System (ADS)

    Kullen, A.; Fear, R. C.; Milan, S. E.; Carter, J. A.; Karlsson, T.

    2015-12-01

    In this work, the Polar UVI data set by Kullen et al. (2002) of 74 polar arcs is reinvestigated, focusing on bending arcs. Bending arcs are typically faint and form (depending on interplanetary magnetic field (IMF) By direction) on the dawnside or duskside oval with the tip of the arc splitting off the dayside oval. The tip subsequently moves into the polar cap in the antisunward direction, while the arc's nightside end remains attached to the oval, eventually becoming hook-shaped. Our investigation shows that bending arcs appear on the opposite oval side from and farther sunward than most regular polar arcs. They form during By-dominated IMF conditions: typically, the IMF clock angle increases from 60 to 90° about 20 min before the arc forms. Antisunward plasma flows from the oval into the polar cap just poleward of bending arcs are seen in Super Dual Auroral Radar Network data, indicating dayside reconnection. For regular polar arcs, recently reported characteristics are confirmed in contrast to bending arcs. This includes plasma flows along the nightside oval that originate close to the initial arc location and a significant delay in the correlation between IMF By and initial arc location. In our data set, the highest correlations are found with IMF By appearing at least 1-2 h before arc formation. In summary, bending arcs are distinctly different from regular arcs and cannot be explained by existing polar arc models. Instead, these results are consistent with the formation mechanism described in Carter et al. (2015), suggesting that bending arcs are caused by dayside reconnection.

  6. Hysterectomy - vaginal - discharge

    MedlinePlus

    Vaginal hysterectomy - discharge; Laparoscopically assisted vaginal hysterectomy - discharge; LAVH - discharge ... were in the hospital, you had a vaginal hysterectomy. Your surgeon made a cut in your vagina. ...

  7. Tubal ligation - discharge

    MedlinePlus

    ... discharge; Tube tying - discharge; Tying the tubes - discharge; Contraception - tubal ... chap 23. Jensen JT, Mishell DR. Family planning: contraception, sterilization, and pregnancy termination. In: Lentz GM, Lobo ...

  8. High intensity discharge device containing oxytrihalides

    DOEpatents

    Lapatovich, Walter P.; Keeffe, William M.; Liebermann, Richard W.; Maya, Jakob

    1987-01-01

    A fill composition for a high intensity discharge device including mercury, niobium oxytrihalide, and a molecular stabilization agent is provided. The molar ratio of niobium oxytrihalide to the molecular stabilization agent in the fill is in the range of from about 5:1 to about 7.5:1. Niobium oxytrihalide is present in the fill in sufficient amount to produce, by dissociation in the discharge, atomic niobium, niobium oxide, NbO, and niobium dioxide, NbO.sub.2, with the molar ratio of niobium-containing vapor species to mercury in the fill being in the range of from about 0.01:1 to about 0.50:1; and mercury pressure of about 1 to about 50 atmospheres at lamp operating temperature. There is also provided a high intensity discharge device comprising a sealed light-transmissive arc tube; the arc tube including the above-described fill; and an energizing means for producing an electric discharge within the arc tube.

  9. High intensity discharge device containing oxytrihalides

    DOEpatents

    Lapatovich, W.P.; Keeffe, W.M.; Liebermann, R.W.; Maya, J.

    1987-06-09

    A fill composition for a high intensity discharge device including mercury, niobium oxytrihalide, and a molecular stabilization agent is provided. The molar ratio of niobium oxytrihalide to the molecular stabilization agent in the fill is in the range of from about 5:1 to about 7.5:1. Niobium oxytrihalide is present in the fill in sufficient amount to produce, by dissociation in the discharge, atomic niobium, niobium oxide, NbO, and niobium dioxide, NbO[sub 2], with the molar ratio of niobium-containing vapor species to mercury in the fill being in the range of from about 0.01:1 to about 0.50:1; and mercury pressure of about 1 to about 50 atmospheres at lamp operating temperature. There is also provided a high intensity discharge device comprising a sealed light-transmissive arc tube; the arc tube including the above-described fill; and an energizing means for producing an electric discharge within the arc tube. 7 figs.

  10. Synthesis method for ultrananocrystalline diamond in powder employing a coaxial arc plasma gun

    NASA Astrophysics Data System (ADS)

    Naragino, Hiroshi; Tominaga, Aki; Hanada, Kenji; Yoshitake, Tsuyoshi

    2015-07-01

    A new method that enables us to synthesize ultrananocrystalline diamond (UNCD) in powder is proposed. Highly energetic carbon species ejected from a graphite cathode of a coaxial arc plasma gun were provided on a quartz plate at a high density by repeated arc discharge in a compact vacuum chamber, and resultant films automatically peeled from the plate were aggregated and powdered. The grain size was easily controlled from 2.4 to 15.0 nm by changing the arc discharge energy. It was experimentally demonstrated that the proposed method is a new and promising method that enables us to synthesize UNCD in powder easily and controllably.

  11. New algorithm for controlling electric arc furnaces using their vibrational and acoustic characteristics

    NASA Astrophysics Data System (ADS)

    Cherednichenko, V. S.; Bikeev, R. A.; Serikov, V. A.; Rechkalov, A. V.; Cherednichenko, A. V.

    2016-12-01

    The processes occurring in arc discharges are analyzed as the sources of acoustic radiation in an electric arc furnace (EAF). Acoustic vibrations are shown to transform into mechanical vibrations in the furnace laboratory. The shielding of the acoustic energy fluxes onto water-cooled wall panels by a charge is experimentally studied. It is shown that the rate of charge melting and the depth of submergence of arc discharges in the slag and metal melt can be monitored by measuring the vibrational characteristics of furnaces and using them in a universal industrial process-control system, which was developed for EAFs.

  12. Discharge analysis and electrical modeling for the development of efficient dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Pal, U. N.; Kumar, M.; Tyagi, M. S.; Meena, B. L.; Khatun, H.; Sharma, A. K.

    2010-02-01

    Dielectric-barrier discharges (DBDs) are characterized by the presence of at least one insulating layer in contact with the discharge between two planar or cylindrical electrodes connected to an AC/pulse power supply. The dielectric layers covering the electrodes act as current limiters and prevent the transition to an arc discharge. DBDs exist usually in filamentary mode, based on the streamer nature of the discharges. The main advantage of this type of electrical discharges is that nonequilibrium and non-thermal plasma conditions can be established at atmospheric pressure. VUV/UV sources based on DBDs are considered as promising alternatives of conventional mercury-based discharge plasmas, producing highly efficient VUV/UV radiation. The experiments have been performed using two coaxial quartz double barrier DBD tubes, which are filled with Xe/Ar at different pressures. A sinusoidal voltage up to 2.4 kV peak with frequencies from 20 to 100 kHz has been applied to the discharge electrodes for the generation of microdischarges. A stable and uniform discharge is produced in the gas gap between the dielectric barrier electrodes. By comparisons of visual images and electrical waveforms, the filamentary discharges for Ar tube while homogeneous discharge for Xe tube at the same conditions have been confirmed. The electrical modeling has been carried out to understand DBD phenomenon in variation of applied voltage waveforms. The simulated discharge characteristics have been validated by the experimental results.

  13. Research on Mitigation Method against Secondary Arcing on Solar Array

    NASA Astrophysics Data System (ADS)

    Wada, Tomohiro; Masui, Hirokazu; Toyoda, Kazuhiro; Cho, Mengu

    The recent trend of satellite manufacturing is to increase its communication capacity, multi-purpose mission payload, electric power and lifetime. A short-circuit due to discharge on the solar array of the satellite hampers its target by causing serious problems, such as, lowering of power generation that ultimately halts the operation of solar array. In this paper, we have investigated possible mitigation methods against short-circuit due to discharge on solar array by applying coating and by changing the shape of Room Temperature Vulcanization: Silicon adhesive (RTV). The electrostatic discharge is mitigated by obtaining the event of secondary arc generated on each condition.

  14. Consolidating NASA's Arc Jets

    NASA Technical Reports Server (NTRS)

    Balboni, John A.; Gokcen, Tahir; Hui, Frank C. L.; Graube, Peter; Morrissey, Patricia; Lewis, Ronald

    2015-01-01

    The paper describes the consolidation of NASA's high powered arc-jet testing at a single location. The existing plasma arc-jet wind tunnels located at the Johnson Space Center were relocated to Ames Research Center while maintaining NASA's technical capability to ground-test thermal protection system materials under simulated atmospheric entry convective heating. The testing conditions at JSC were reproduced and successfully demonstrated at ARC through close collaboration between the two centers. New equipment was installed at Ames to provide test gases of pure nitrogen mixed with pure oxygen, and for future nitrogen-carbon dioxide mixtures. A new control system was custom designed, installed and tested. Tests demonstrated the capability of the 10 MW constricted-segmented arc heater at Ames meets the requirements of the major customer, NASA's Orion program. Solutions from an advanced computational fluid dynamics code were used to aid in characterizing the properties of the plasma stream and the surface environment on the calorimeters in the supersonic flow stream produced by the arc heater.

  15. Control of arc length during gas metal arc welding

    SciTech Connect

    Madigan, R.B.; Quinn, T.P.

    1994-12-31

    An arc-length control system has been developed for gas metal arc welding (GMAW) under spray transfer welding conditions. The ability to monitor and control arc length during arc welding allows consistent weld characteristics to be maintained and therefore improves weld quality. Arc length control has only been implemented for gas tungsten arc welding (GTAW), where an automatic voltage control (AVC) unit adjusts torch-to-work distance. The system developed here compliments the voltage- and current-sensing techniques commonly used for control of GMAW. The system consists of an arc light intensity sensor (photodiode), a Hall-effect current sensor, a personal computer and software implementing a data interpretation and control algorithms. Arc length was measured using both arc light and arc current signals. Welding current was adjusted to maintain constant arc length. A proportional-integral-derivative (PID) controller was used. Gains were automatically selected based on the desired welding conditions. In performance evaluation welds, arc length varied from 2.5 to 6.5 mm while welding up a sloped workpiece (ramp in CTWD) without the control. Arc length was maintained within 1 mm of the desired (5 mm ) with the control.

  16. Miniaturized cathodic arc plasma source

    DOEpatents

    Anders, Andre; MacGill, Robert A.

    2003-04-15

    A cathodic arc plasma source has an anode formed of a plurality of spaced baffles which extend beyond the active cathode surface of the cathode. With the open baffle structure of the anode, most macroparticles pass through the gaps between the baffles and reflect off the baffles out of the plasma stream that enters a filter. Thus the anode not only has an electrical function but serves as a prefilter. The cathode has a small diameter, e.g. a rod of about 1/4 inch (6.25 mm) diameter. Thus the plasma source output is well localized, even with cathode spot movement which is limited in area, so that it effectively couples into a miniaturized filter. With a small area cathode, the material eroded from the cathode needs to be replaced to maintain plasma production. Therefore, the source includes a cathode advancement or feed mechanism coupled to cathode rod. The cathode also requires a cooling mechanism. The movable cathode rod is housed in a cooled metal shield or tube which serves as both a current conductor, thus reducing ohmic heat produced in the cathode, and as the heat sink for heat generated at or near the cathode. Cooling of the cathode housing tube is done by contact with coolant at a place remote from the active cathode surface. The source is operated in pulsed mode at relatively high currents, about 1 kA. The high arc current can also be used to operate the magnetic filter. A cathodic arc plasma deposition system using this source can be used for the deposition of ultrathin amorphous hard carbon (a-C) films for the magnetic storage industry.

  17. Refractive corneal surgery - discharge

    MedlinePlus

    Nearsightedness surgery - discharge; Refractive surgery - discharge; LASIK - discharge; PRK - discharge ... You had refractive corneal surgery to help improve your vision. This surgery uses a laser to reshape your cornea. It corrects mild-to-moderate nearsightedness, ...

  18. Ventriculoperitoneal shunt - discharge

    MedlinePlus

    ... ventriculoperitoneal - discharge; VP shunt - discharge; Shunt revision - discharge; Hydrocephalus shunt placement - discharge ... Your child has hydrocephalus and needed a shunt placed to drain excess fluid and relieve pressure in the brain. This buildup of brain ...

  19. Brain injury - discharge

    MedlinePlus

    Head injury - discharge; Head trauma - discharge; Contusion - discharge; Shaken baby syndrome - discharge ... done to help them recover from the brain injury. The person may have stayed in a special ...

  20. Lung surgery - discharge

    MedlinePlus

    ... Lung biopsy - discharge; Thoracoscopy - discharge; Video-assisted thoracoscopic surgery - discharge; VATS - discharge ... milk) for 2 weeks after video-assisted thoracoscopic surgery and 6 to 8 weeks after open surgery. ...

  1. Arc characteristics of submerged arc welding with stainless steel wire

    NASA Astrophysics Data System (ADS)

    Li, Ke; Wu, Zhi-sheng; Liu, Cui-rong; Chen, Feng-hua

    2014-08-01

    The arc characteristics of submerged arc welding (SAW) with stainless steel wire were studied by using Analysator Hannover (AH). The tests were carried out under the same preset arc voltage combined with different welding currents. By comparing the probability density distribution (PDD) curves of arc voltage and welding current, the changes were analyzed, the metal transfer mode in SAW was deduced, and the characteristics of a stable arc were summarized. The analysis results show that, with an increase of welding parameters, the short-circuiting peak in the PDD curves of arc voltage decreases gradually until it disappears, and the dominant metal transfer mode changes from flux-wall guided transfer to projected transfer and then to streaming transfer. Moreover, when the PDD curves of arc voltage are both unimodal and generally symmetrical, the greater the peak probability and the smaller the peak span, the more stable the arc becomes.

  2. Arc electrode interaction study

    NASA Technical Reports Server (NTRS)

    Zhou, X.; Berns, D.; Heberlein, J.

    1994-01-01

    The project consisted of two parts: (1) the cathode interaction studies which were a continuation of previous work and had the objective of increasing our understanding of the microscopic phenomena controlling cathode erosion in arc jet thrusters, and (2) the studies of the anode attachment in arc jet thrusters. The cathode interaction studies consisted of (1) a continuation of some modeling work in which the previously derived model for the cathode heating was applied to some specific gases and electrode materials, and (2) experimental work in which various diagnostics was applied to the cathode. The specific diagnostics used were observation of the cathode tip during arcing using a Laser Strobe Video system in conjunction with a tele-microscope, a monochromator with an optical multichannel analyzer for the determination of the cathode temperature distribution, and various ex situ materials analysis methods. The emphasis of our effort was shifted to the cathode materials analysis because a parallel project was in place during the second half of 1993 with a visiting scientist pursuing arc electrode materials studies. As a consequence, the diagnostic investigations of the arc in front of the cathode had to be postponed to the first half of 1994, and we are presently preparing these measurements. The results of last year's study showed some unexpected effects influencing the cathode erosion behavior, such as increased erosion away from the cathode tip, and our understanding of these effects should improve our ability to control cathode erosion. The arc jet anode attachment studies concentrated on diagnostics of the instabilities in subsonic anode attachment arc jet thrusters, and were supplemental measurements to work which was performed by one of the authors who spent the summer as an intern at NASA Lewis Research Center. A summary of the results obtained during the internship are included because they formed an integral part of the study. Two tasks for 1994, the

  3. Bright Arcing Loops

    NASA Image and Video Library

    2016-06-27

    Several arcing loops rotated into view and swirled above an active region, which gave us a nice profile view of the action (June 26-27, 2016). The arcing plasma is tracing magnetic field lines extending out from the active region. Some darker matter also jiggled back and forth near the active region as well, pulled about by magnetic forces. At one point a lick of plasma pushed its way out from the region but quickly fell back into the sun. The images were taken in a wavelength of extreme ultraviolet light. Movies are also available at the Photojournal. http://photojournal.jpl.nasa.gov/catalog/PIA20882

  4. High pressure working mode of hollow cathode arc discharges

    NASA Technical Reports Server (NTRS)

    Minoo, H.; Popovici, C.

    1985-01-01

    The behavior of high pressure cathotrons is discussed. Methods of preheating either the gas or the cathode itself are detailed together with various geometries for the hollow cathode. Three special configurations were tested, and the results are analyzed.

  5. Continued development of a detailed model of arc discharge dynamics

    NASA Technical Reports Server (NTRS)

    Beers, B. L.; Pine, V. W.; Ives, S. T.

    1982-01-01

    Using a previously developed set of codes (SEMC, CASCAD, ACORN), a parametric study was performed to quantify the parameters which describe the development of a single electron indicated avalanche into a negative tip streamer. The electron distribution function in Teflon is presented for values of the electric field in the range of four-hundred million volts/meter to four billon volts/meter. A formulation of the scattering parameters is developed which shows that the transport can be represented by three independent variables. The distribution of ionization sites is used to indicate an avalanche. The self consistent evolution of the avalanche is computed over the parameter range of scattering set.

  6. Arc rifting of the Carolina terrane in northwestern South Carolina

    SciTech Connect

    Dennis, A.J. ); Shervais, J.W. )

    1991-03-01

    Recent mapping and whole-rock geochemistry studies demonstrate that mafic metavolcanic rocks found along the boundary between the exotic Carolina terrane and the Inner Piedmont formed in a subduction-related volcanic arc and do not represent the Iapetan suture. Mafic metavolcanic rocks are spatially and genetically related to zoned mafic-ultramafic intrusive complexes. These rocks are similar to those found in other ancient and modern volcanic island arcs where ankaramites and picrites are well known, and they are locally associated with zoned complexes, e.g., Sierra Foothills-Klamath Mountains of the western U.S. Cordillera. The authors propose that prior to accretion to Laurentia in the early to middle Paleozoic, the Carolina arc terrane underwent an episode of intra-arc rifting which allowed primitive arc magmas to ascend and erupt without significant crystal fractionation or lithospheric assimilation. This interpretation may help resolve some stratigraphic problems in the eastern part of the Carolina terrane (Caroline slate belt).

  7. A stable auroral red (SAR) arc with multiple emission features

    NASA Astrophysics Data System (ADS)

    Mendillo, Michael; Finan, Robert; Baumgardner, Jeffrey; Wroten, Joei; Martinis, Carlos; Casillas, Marcus

    2016-10-01

    Stable auroral red (SAR) arcs offer subvisible evidence for storm time linkages between the inner magnetosphere and the midlatitude ionosphere. A SAR arc's defining characteristics are horizon-to-horizon east-west extent, a few degrees of latitude in meridional extent, emission only at the oxygen 6300Å line, and minimal brightness changes during a night—effects readily provided by steady heat conduction from the ring current-plasmapause interaction region. Here we describe a typical SAR arc (brightness 300 rayleighs) with several superimposed patches of emission in two oxygen lines (with a 6300Å/5577Å ratio of 40). We find no evidence for highly localized heating effects but rather evidence from GPS satellites supporting low-energy electron precipitation as the SAR arc modulating mechanism. Seven brightness peaks with average longitude spacing of 4° define a new spatial pattern for SAR arc studies.

  8. [Redesigning the hospital discharge process].

    PubMed

    Martínez-Ramos, M; Flores-Pardo, E; Uris-Sellés, J

    2016-01-01

    The aim of this article is to show that the redesign and planning process of hospital discharge advances the departure time of the patient from a hospital environment. Quasi-experimental study conducted from January 2011 to April 2013, in a local hospital. The cases analysed were from medical and surgical nursing units. The process was redesigned to coordinate all the professionals involved in the process. The hospital discharge improvement process improvement was carried out by forming a working group, the analysis of retrospective data, identifying areas for improvement, and its redesign. The dependent variable was the time of patient administrative discharge. The sample was classified as pre-intervention, inter-intervention, and post-intervention, depending on the time point of the study. The final sample included 14,788 patients after applying the inclusion and exclusion criteria. The mean discharge release time decreased significantly by 50 min between pre-intervention and post-intervention periods. The release time in patients with planned discharge was one hour and 25 min less than in patients with unplanned discharge. Process redesign is a useful strategy to improve the process of hospital discharge. Besides planning the discharge, it is shown that the patient leaving the hospital before 12 midday is a key factor. Copyright © 2015 SECA. Published by Elsevier Espana. All rights reserved.

  9. ARc Welding (Industrial Processing Series).

    DTIC Science & Technology

    ARC WELDING , *BIBLIOGRAPHIES), (*ARC WELDS, BIBLIOGRAPHIES), ALUMINUM ALLOYS, TITANIUM ALLOYS, CHROMIUM ALLOYS, METAL PLATES, SPOT WELDING , STEEL...INERT GAS WELDING , MARAGING STEELS, MICROSTRUCTURE, HEAT RESISTANT ALLOYS, HEAT RESISTANT METALS, WELDABILITY, MECHANICAL PROPERTIES, MOLYBDENUM ALLOYS, NICKEL ALLOYS, RESISTANCE WELDING

  10. Discharge characteristics of dielectric barrier discharge (DBD) based VUV/UV sources

    NASA Astrophysics Data System (ADS)

    Pal, U. N.; Kumar, M.; Khatun, H.; Sharma, A. K.

    2008-05-01

    Dielectric-barrier discharges (DBDs) are characterized by the presence of at least one insulating layer in contact with the discharge between two planar or cylindrical electrodes connected to an AC/pulse power supply. The dielectric layers covering the electrodes act as current limiters and prevent the transition to an arc discharge. DBDs exist usually in filamentary mode, based on the streamer nature of the discharges. The main advantage of this type of electrical discharges is that nonequilibrium and non-thermal plasma conditions can be established at atmospheric pressure. VUV/UV sources based on DBDs are considered as promising alternatives of conventional mercury-based discharge plasmas, producing highly efficient VUV/UV radiation. The experiments have been performed using coaxial and planar geometry of DBD (gas gap: 1-3 mm) made of quartz with N2/Ar/Xe gas at different pressures. A proper ultra high vacuum system and gas filing system has been made for the processing & characterization of DBD tubes. A RF generator (20-100 kHz, 0-2.4 kV peak) is used for discharges in DBD tube. A stable and uniform discharge is produced in the gas gap between the dielectric barrier electrodes. The discharge characteristics have been analyzed by V-I characteristics & Lissajous figure and found that the spatial discharge processes varies strongly according to the applied voltage waveform, pressure of filled gas and geometry of tube.

  11. Physical constraints by different arc extension regimes. Intraoceanic arc-trench system: an approach with numerical modelling

    NASA Astrophysics Data System (ADS)

    Baitsch Ghirardello, Bettina; Gerya, Taras; Burg, Jean-Pierre

    2010-05-01

    Since most of the modern intraoceanic collision zones have an extension, it is important to understand how and where the extensions are created and what the decisive factors are. Why is there no extension in certain subductions zones? Why can basins with a thin crust be observed, while in other places the crust spreads and a new magmatic arc is produced? What is the involvement of slab fluids and melt production in the mantle wedge for the extension process? In order to answer these questions we performed systematic numerical experiments with a 2D coupled petrological-thermo-mechanical numerical model of an intra-oceanic subduction process. Over time, part of our numerical models developed a spontaneous slab retreat associated with following flattening of the slab angle, and therefore an extension of the overriding plate and formation of a new spreading center. Our results indicate that weakening effects from subduction related melts play a major role in defining where the extension is localized: in the for-arc, the back-arc or within an arc. According to the general trend the stronger the weakening is, the more the extension shifts toward the back-arc direction. The intensity of the forearc weakening by slab derived fluids also plays a notable role: if such weakening is insufficient two plates are strongly coupled which results in a compressive subduction without the overriding plate extension. If we compare the different extension types in our models with observations in nature, we observe a good agreement. For example in nature, intra-arc extension may split initially homogeneous arc in two distinct parts such as the active Mariana arc and the inactive West Mariana Ridge and create thin oceanic crust in the middle like the Mariana Trough, similar to our experiments. In this way observations based on seismic images of the Izu-Bonin-Mariana arc crust and mantle structure can be simulated with our model. For example, the first arc with no back-arc rifting (Kyushu

  12. Fabrication of arc-induced long-period gratings in different silica fibers

    NASA Astrophysics Data System (ADS)

    Ranjan, Rajeev; Esposito, Flavio; Campopiano, Stefania; Iadicicco, Agostino

    2017-05-01

    In this work, we report on recent results about the fabrication of Long Period Gratings (LPGs) in different single mode optical fibers, by means of Electric Arc Discharge (EAD) technique. In particular, the results are related to three optical fibers with different doping elements, i.e.: standard telecommunication Ge-doped SMF28, highly photosensitive B/Gecodoped PS1250/1500, and P-doped P-SM-5 fibers. EAD leads to a point-by-point LPG inscription, due to localized tapering of the transversal size of the core and cladding regions along the fiber, and to changes of the silica refractive index due to the stress relaxation induced by local hot spots. Here, we take into consideration both standard and unconventional silica fibers and the aim of the work is to identify an appropriate "recipe" for each fiber, for manufacturing LPGs with strong and narrow attenuation bands (depth higher than 25 dB) and trivial power losses (<0.5 dB). Indeed, a proper combination of arc power and duration, as well as fiber tension, allows for the appropriate core and cladding modulation and thus for the desired LPGs spectral features. The sensitivity characteristics towards surrounding refractive index (SRI) and temperature changes of these LPGs are also investigated, highlighting the effects of different kind of doping.

  13. Discharge characteristics in liquid helium, liquid nitrogen and pure water preparatory to fabrication of carbon nanomaterials

    NASA Astrophysics Data System (ADS)

    Kawasaki, Hiroharu; Shigematsu, Toshinobu; Imasaka, Kiminobu; Ohshima, Tamiko; Yagyu, Yoshihito; Suda, Yoshiaki

    2012-12-01

    Discharge characteristics and emission spectra of the discharges in low-temperature liquid such as liquid helium have been measured to investigate the conditions for fabrication of carbon nanomaterial by arc discharge in low-temperature liquid. Measurements of the discharge characteristics of the resulting plasma and observation of the associated optical emission spectra show that the behaviour of discharge current over time and the associated spectra depend strongly on discharge voltage and both may be related to the temperature of the carbon target. However, discharge voltage and current with time are almost the same regardless of whether the liquid is pure water, liquid nitrogen, liquid helium and superfluid liquid helium

  14. Variable polarity arc welding

    NASA Technical Reports Server (NTRS)

    Bayless, E. O., Jr.

    1991-01-01

    Technological advances generate within themselves dissatisfactions that lead to further advances in a process. A series of advances in welding technology which culminated in the Variable Polarity Plasma Arc (VPPA) Welding Process and an advance instituted to overcome the latest dissatisfactions with the process: automated VPPA welding are described briefly.

  15. Gas tungsten arc welder

    DOEpatents

    Christiansen, D.W.; Brown, W.F.

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  16. Thermal Arc Spray Overview

    NASA Astrophysics Data System (ADS)

    Hafiz Abd Malek, Muhamad; Hayati Saad, Nor; Kiyai Abas, Sunhaji; Mohd Shah, Noriyati

    2013-06-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  17. Arc Length Gone Global

    ERIC Educational Resources Information Center

    Boudreaux, Gregory M.; Wells, M. Scott

    2007-01-01

    Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

  18. Discharge with Hollow Cathode (Selected Chapters),

    DTIC Science & Technology

    1983-04-12

    view of its mechanism made Rose in [77]. Let us dismantle/select the fundamental conclusions of this work which are based on the study of the...too little in order to support discharge by means of : 7-processes, and therefore the mechanism of secondary processes in the arc with hollow cathode...which leads to the output of electrons from the cathode, thermoemission, then the temperature of cathode surface T3 must be T.=p33OK. Unfortunately, the

  19. Thomson scattering diagnostics of decay processes of Ar/SF6 gas-blast arcs confined by a nozzle

    NASA Astrophysics Data System (ADS)

    Tomita, Kentaro; Gojima, Daisuke; Nagai, Kazuhiko; Uchino, Kiichiro; Kamimae, Ryo; Tanaka, Yasunori; Suzuki, Katsumi; Iijima, Takanori; Uchii, Toshiyuki; Shinkai, Takeshi

    2013-09-01

    Because of its instability, it is difficult to measure precisely the electron density (ne) of a long-gap decaying arc discharge in a circuit breaker. However, it is well known that it is an essential parameter for the determination of success or failure of the current interruption in a circuit breaker. In this paper, the spatiotemporal evolutions of the electron density were successfully measured in decaying SF6 gas-blast arc discharges formed with a long gap (50 mm) in a confined nozzle using laser Thomson scattering. Pure Ar gas and an 80%Ar/20%SF6 mixture gas were used as the arc quenching media at atmospheric pressure. After reducing the current to zero, both the measured ne and arc radius in the Ar/SF6 gas arc clearly decayed more rapidly than in the pure Ar gas arc.

  20. Purification of helium for chromatographic analysis by electrical discharge

    SciTech Connect

    Bondarenko, I.V.; Budovich, V.L.; Myagkov, E.A.; Okhotnikov, B.P.

    1986-02-01

    In order to apply gas discharge purification of helium in chromotographic analysis, the authors have carried out the separation process in the present work at a pressure above the atmospheric pressure. They then carry out the purification in an arc discharge, because it is difficult to achieve a stationary glow discharge at atmospheric pressure. Cylinder discharge chambers were used in the experiments, made of stainless steel with Teflon flanges. A decrease in the nitrogen content by a factor of 7-10 has been obtained in the experiments. The proposed method can be used for the purification of helium from cylinders in different variants of chromatographic analysis.