Articles de revues : « Arcs Plasma »

1

Stepanov, A. V. « Plasma processes in coronal magnetic arcs ». Journal of Optical Technology 72, n^o 8 (1 août 2005) : 585. http://dx.doi.org/10.1364/jot.72.000585.

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Tanaka, Y., K. Tomita, Y. Inada, A. Kumada, K. Hidaka, T. Fujino, K. Suzuki et T. Shinkai. « Non-equilibrium Studies in Switching Arc Plasmas in Japan ». PLASMA PHYSICS AND TECHNOLOGY 4, n^o 3 (2017) : 225–33. http://dx.doi.org/10.14311/ppt.2017.3.225.

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This paper briefly introduce research work examples of non-equilibrium studies in switching arcs. In understanding arc behavior, one often assumes local thermodynamic equilibrium (LTE) condition in the arc plasma. However, actual arc plasmas are not completely and not always in LTE state because of strong temperature change temporally and spatially, and high electric field application etc. Recently, we have a collaboration work in numerical simulations and experimental approaches for decaying arcs without LTE assumption. First, our numerical model is presented for decaying arcs without chemical equilibrium assumption. Secondly, two experimental methods are introduced for measuring electron density in decaying arcs without LTE assumption: Laser Thomson Scattering method and the Schack-Hartmann method. Finally, comparison results is shown between the LTE simulation, the chemically non-equilibrium simulation, and the above experimental measurements.

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Kullen, A., S. Buchert, T. Karlsson, T. Johansson, S. Lileo, A. Eriksson, H. Nilsson, A. Marchaudon et A. N. Fazakerley. « Plasma transport along discrete auroral arcs and its contribution to the ionospheric plasma convection ». Annales Geophysicae 26, n^o 11 (21 octobre 2008) : 3279–93. http://dx.doi.org/10.5194/angeo-26-3279-2008.

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Abstract. The role of intense high-altitude electric field (E-field) peaks for large-scale plasma convection is investigated with the help of Cluster E-field, B-field and density data. The study covers 32 E-field events between 4 and 7 RE geocentric distance, with E-field magnitudes in the range 500–1000 mV/m when mapped to ionospheric altitude. We focus on E-field structures above the ionosphere that are typically coupled to discrete auroral arcs and their return current region. Connected to such E-field peaks are rapid plasma flows directed along the discrete arcs in opposite directions on each side of the arc. Nearly all the E-field events occur during active times. A strong dependence on different substorm phases is found: a majority of intense E-field events appearing during substorm expansion or maximum phase are located on the nightside oval, while most recovery events occur on the dusk-to-dayside part of the oval. For most expansion and maximum phase cases, the average background plasma flow is in the sunward direction. For a majority of recovery events, the flow is in the anti-sunward direction. The net plasma flux connected to a strong E-field peak is in two thirds of the cases in the same direction as the background plasma flow. However, in only one third of the cases the strong flux caused by an E-field peak makes an important contribution to the plasma transport within the boundary plasma sheet. For a majority of events, the area covered by rapid plasma flows above discrete arcs is too small to have an effect on the global convection. This questions the role of discrete auroral arcs as major driver of plasma convection.

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Petrovic, Zoran. « The contribution of Nikola Tesla to plasma physics and current status of plasmas that he studied ». Serbian Journal of Electrical Engineering 3, n^o 2 (2006) : 203–16. http://dx.doi.org/10.2298/sjee0603203p.

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One of the main Interests in science of Nikola Tesla were gas discharges plasmas, their application in lighting and in production of ozone as well as their role in conduction of electricity through the atmosphere. In particular Tesla is well known as the first person to produce rf plasmas. Such plasmas in the present day constitute the main technology required to produce integrated circuits (IC) and have been essential in the revolution that resulted from IC technologies. In addition Tesla participated in studies of arcs especially arcs used as a source of light, corona discharges required to induce plasma chemical reactions and produce ozone and was involved in various aspects of gas breakdown and gaseous dielectrics. His ideas, level of his understanding and current status of these fields are discussed in this review.

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Siemroth, P., B. Juttner, K. Jakubka et N. V. Sakharov. « Measurement of Plasma-Induced Arcs in Tokamaks ». IEEE Transactions on Plasma Science 13, n^o 5 (1985) : 300–303. http://dx.doi.org/10.1109/tps.1985.4316425.

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Hirshfield, J. L., L. A. Levin et O. Danziger. « Vacuum arcs for plasma centrifuge isotope enrichment ». IEEE Transactions on Plasma Science 17, n^o 5 (1989) : 695–700. http://dx.doi.org/10.1109/27.41184.

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Thio, Y., et L. Frost. « Non-ideal plasma behavior of railgun arcs ». IEEE Transactions on Magnetics 22, n^o 6 (novembre 1986) : 1757–62. http://dx.doi.org/10.1109/tmag.1986.1064721.

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8

Wang, Weizhen, Min Jia, Wei Cui et Zhibo Zhang. « Process of Multiple Channel Gliding Arc Assisted Combustion Near Lean Blow-out Limit ». E3S Web of Conferences 233 (2021) : 01027. http://dx.doi.org/10.1051/e3sconf/202123301027.

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Multichannel gliding arcs actuators were designed to enhance the non-premixed combustion of the kerosene (RP-3) and air mixture in a swirl combustor near lean blow-out limit. The instantaneous voltage and current of the multichannel gliding arcs and the 1kHz high-speed CH* chemiluminescence imaging of the combustion process were simultaneously measured to show the characteristics of the process assisted by the plasma. When reaching near lean blow-out limit in a flow rate of 225 SLPM, at the combustor inlet, the emission intensity and projected flame assisted by the multichannel gliding arcs remain the same with decreased fuel flow rates from 3 to 1 ml/min, which assisted by the single gliding arc decreases nevertheless. The flame structure under the influence of plasma actuators with various channel numbers evolves differently owing to the differences in plasma distributions.

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9

Kozlovsky, A. E., et W. B. Lyatsky. « Instability of the magnetosphere-ionosphere convection and formation of auroral arcs ». Annales Geophysicae 12, n^o 7 (30 juin 1994) : 636–41. http://dx.doi.org/10.1007/s00585-994-0636-9.

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Abstract. In this paper we study an instability of the plasma moving towards the Earth near the inner plasma sheet boundary. We include both the interchange instability of the plasma sheet and the magnetosphere-ionosphere interaction instability caused by an effect of field-aligned currents (connected with electron precipitation) on ionospheric conductivity. The instability leads to the separation of steady-state magnetospheric convection into parallel layers. This instability may be responsible for the appearance of quiet auroral arcs inside region 2 of field-aligned currents flowing out of the ionosphere. This instability allows us to explain also the existence of crossing auroral arcs.

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Stryczewska, Henryka Danuta, Grzegorz Komarzyniec et Oleksandr Boiko. « Effect of Plasma Gas Type on the Operation Characteristics of a Three-Phase Plasma Reactor with Gliding Arc Discharge ». Energies 17, n^o 11 (2 juin 2024) : 2696. http://dx.doi.org/10.3390/en17112696.

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Three-phase gliding arc discharge reactors are devices in which it is difficult to maintain stable plasma parameters, be it electrically, physically, or chemically. The main cause of plasma instability is the source, which is freely burning arcs in a three-phase system. In addition, these arcs burn at low currents and are intensively cooled, further increasing their instability. These instabilities translate into the electrical characteristics of the plasma reactor. The analysis for the four gases nitrogen, argon, helium, and air shows that the type of plasma-generating gas and its physical parameters have a strong influence on the operational characteristics of the plasma reactor. Current–voltage, power and frequency characteristics of the plasma reactor were plotted experimentally. Characteristics obtained in this way make it possible to determine the areas of effective operation of the plasma reactor, and to estimate the quality of the generated plasma. Based on the characteristics obtained, a method of controlling the plasma parameters can be developed.

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11

Juttner, B. « On the plasma density of metal vapour arcs ». Journal of Physics D : Applied Physics 18, n^o 11 (14 novembre 1985) : 2221–31. http://dx.doi.org/10.1088/0022-3727/18/11/011.

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12

Park, Won-Taek, et Duk-In Choi. « Numerical Analysis of MPD Arcs for Plasma Acceleration ». IEEE Transactions on Plasma Science 15, n^o 5 (1987) : 618–24. http://dx.doi.org/10.1109/tps.1987.4316763.

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Bourouis, M., M. A. Huerta et F. Rodriguez-Trelles. « Interchange instability in finite conductivity accelerated plasma arcs ». IEEE Transactions on Magnetics 29, n^o 1 (janvier 1993) : 1113–18. http://dx.doi.org/10.1109/20.195737.

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Hantzsche, E. « Theory of the expanding plasma of vacuum arcs ». Journal of Physics D : Applied Physics 24, n^o 8 (14 août 1991) : 1339–53. http://dx.doi.org/10.1088/0022-3727/24/8/017.

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15

Gao, Xiang, et Junyuan Gao. « Electrochemical Mechanism for Fullerene Formation in Plasma Arcs ». Journal of Physical Chemistry 98, n^o 22 (juin 1994) : 5618–21. http://dx.doi.org/10.1021/j100073a007.

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Ertl, K., et B. Jüttner. « Relevance of plasma-induced arcs for divertor tokamaks ». Nuclear Fusion 25, n^o 10 (1 octobre 1985) : 1413–19. http://dx.doi.org/10.1088/0029-5515/25/10/003.

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Fischer, E., T. Kopiczynski, Z. Rozkwitalski et F. K. Kneub�hl. « MPD arcs as plasma sources for recombination lasers ». Applied Physics B Photophysics and Laser Chemistry 38, n^o 2 (octobre 1985) : 79–89. http://dx.doi.org/10.1007/bf00697446.

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18

Xia, Lingbo, Wenlong Gao, Biao Yang, Qinghua Guo, Hongchao Liu, Jiaguang Han, Weili Zhang et Shuang Zhang. « Stretchable Photonic ‘Fermi Arcs’ in Twisted Magnetized Plasma ». Laser & ; Photonics Reviews 12, n^o 1 (5 décembre 2017) : 1700226. http://dx.doi.org/10.1002/lpor.201700226.

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19

Murmantsev, A., A. Veklich, V. Boretskij, M. Bartlová, L. Dostál, J. Píška, D. Šimek, A. Gajdos et O. Tolochyn. « Thermal Plasma of Electric Arc Discharge Between Composite Cu-Cr Electrsodes : Optical Emission and Electrode Surface Interaction ». PLASMA PHYSICS AND TECHNOLOGY 7, n^o 2 (19 décembre 2020) : 43–51. http://dx.doi.org/10.14311/ppt.2020.2.43.

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This work deals with investigations of thermal plasma of electric arc discharge between sintered composite Cu-Cr electrodes, which can be used in electrical contacts of vacuum circuit breakers. Breaking arcs between composite Cu-Cr as well as single-component copper electrodes were used to study the electrical properties, plasma optical emission and electrodes surface modification behavior. In particular, the temporal evolution of plasma emission spectra of electric breaking arcs in air atmosphere was investigated by Optical Emission Spectroscopy (OES). Scanning Electron Microscopy (SEM) with Energy-dispersive X-ray Spectroscopy (EDXS) were applied to analyze the cross-section of working layer of electrodes surface modified by the heat flux from the discharge.

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Baeva, M., et D. Uhrlandt. « Advanced Nonequilibrium Modelling of DC Tungsten-Inert Gas Arcs ». PLASMA PHYSICS AND TECHNOLOGY 4, n^o 3 (2017) : 203–12. http://dx.doi.org/10.14311/ppt.2017.3.203.

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The paper is concerned with the state-of-the-art nonequilibrium modelling of a DC tungsten-inert gas arc plasma. The advanced description involves the two-way interaction between the plasma and the electrodes. Results in atmospheric pressure argon demonstrating important features of the arc plasma are presented and discussed. First results in the presence of metal vapour released from the molten anode are presented. Outlook for further developments in nonequilibrium arc modelling are discussed.

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Fear, R. C., S. E. Milan, R. Maggiolo, A. N. Fazakerley, I. Dandouras et S. B. Mende. « Direct observation of closed magnetic flux trapped in the high-latitude magnetosphere ». Science 346, n^o 6216 (18 décembre 2014) : 1506–10. http://dx.doi.org/10.1126/science.1257377.

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The structure of Earth’s magnetosphere is poorly understood when the interplanetary magnetic field is northward. Under this condition, uncharacteristically energetic plasma is observed in the magnetotail lobes, which is not expected in the textbook model of the magnetosphere. Using satellite observations, we show that these lobe plasma signatures occur on high-latitude magnetic field lines that have been closed by the fundamental plasma process of magnetic reconnection. Previously, it has been suggested that closed flux can become trapped in the lobe and that this plasma-trapping process could explain another poorly understood phenomenon: the presence of auroras at extremely high latitudes, called transpolar arcs. Observations of the aurora at the same time as the lobe plasma signatures reveal the presence of a transpolar arc. The excellent correspondence between the transpolar arc and the trapped closed flux at high altitudes provides very strong evidence of the trapping mechanism as the cause of transpolar arcs.

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Ignesti, A., T. Shimwell, G. Brunetti, M. Gitti, H. Intema, R. J. van Weeren, M. J. Hardcastle et al. « The great Kite in the sky : A LOFAR observation of the radio source in Abell 2626 ». Astronomy & ; Astrophysics 643 (novembre 2020) : A172. http://dx.doi.org/10.1051/0004-6361/202039056.

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Context. The radio source at the center of the galaxy cluster Abell 2626, also known as the Kite, stands out for its unique morphology composed of four symmetric arcs. Previous studies have probed the properties of this source at different frequencies and its interplay with the surrounding thermal plasma, but the puzzle of its origin is still unsolved. Aims. We use a new LOw-Frequency ARray (LOFAR) observation from the LOFAR Two-meter Sky Survey at 144 MHz to investigate the origin of the Kite. Methods. We present a detailed analysis of the new radio data, which we combined with archival radio and X-ray observations. We produced a new, resolved spectral index map of the source with a resolution of 7″ and we studied the spatial correlation of radio and X-ray emission to investigate the interplay between thermal and nonthermal plasma. Results. The new LOFAR data changed our view of the Kite because we discovered two steep-spectrum (α < −1.5) plumes of emission connected to the arcs. The spectral analysis shows, for the first time, a spatial trend of the spectrum along the arcs with evidence of curved synchrotron spectra and a spatial correlation with the X-ray surface brightness. On the basis of our results, we propose that the Kite was originally an X-shaped radio galaxy whose fossil radio plasma, after the end of the activity of the central active galactic nucleus, has been compressed as a consequence of motions of the thermal plasma encompassing the galaxy. The interplay between the compression and advection of the fossil plasma, with the restarting of the nuclear activity of the central galaxy, could have enhanced the radio emission of the fossil plasma producing the arcs of the Kite. We also present the first, low-frequency observation of a jellyfish galaxy in the same field, in which we detect extended, low-frequency emission without a counterpart at higher frequencies.

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Savrukhin, P. V., E. A. Shestakov, A. I. Ermolaeva et R. Yu Solomatin. « Plasma arcs formation in the plasma periphery during disruptions in the T-10 tokamak plasma ». Journal of Physics : Conference Series 907 (octobre 2017) : 012006. http://dx.doi.org/10.1088/1742-6596/907/1/012006.

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Winterberg, F. « Supersonic Vortex Gerdien Arc with Magnetic Thermal Insulation ». Zeitschrift für Naturforschung A 43, n^o 2 (1 février 1988) : 169–76. http://dx.doi.org/10.1515/zna-1988-0213.

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Temperatures up to ~ 5 x 104 oK have been obtained with water vortex Gerdien arcs, and temperatures of ~ 105oK have been reached in hydrogen plasma arcs with magnetic thermal insulation through an externally applied strong magnetic field.It is suggested that a further increase in arc temperatures up to 106oK can conceivably be attained by a combination of both techniques, using a Gerdien arc with a supersonic hydrogen gas vortex.

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ZHAO, Yanjun, Guohua NI, Wei LIU, Hongmei SUN, Siyuan SUI, Dongdong LI, Huan ZHENG, Zhongyang MA et Chi ZHANG. « Dynamic characteristics of multi-arc thermal plasma in four types of electrode configurations ». Plasma Science and Technology 24, n^o 5 (13 avril 2022) : 055407. http://dx.doi.org/10.1088/2058-6272/ac4ee7.

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Abstract The enhanced volume of thermal plasma is produced by a multi-arc thermal plasma generator with three pairs of discharge electrodes driven by three directed current power suppliers. Combined with a high-speed camera and an oscilloscope, which acquire optical and electric signals synchronously, the dynamic behavior of different kinds of multi-arc discharge adjusted by the electrode arrangement is investigated. Also, the spatial distributions and instability of the arc discharge are analyzed in four electrode configurations using the gray value statistical method. It is found that the cathodic arcs mainly show a contracting state, while the anodic arcs have a trend of transition from shrinkage to a diffusion-like state with the increase of the discharge current. As a result of the adjustment of the electrode configuration, a high temperature region formed in the center of the discharge region in configurations of adjacent electrodes with opposite flow distribution and opposite electrodes with swirl flow distribution due to severe fluctuation of arcs. The discharge voltage rises with increased discharge current in this novel multi-arc plasma generator. It is also found that anode ablation mainly occurs on the conical surface at the copper electrode tip, while cathode erosion mainly occurs on the surface of the inserted tungsten and the nearby copper.

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Jacobs, M., W. Gekelman, P. Pribyl, Y. Qian et S. Abarzhi. « Experiments on plasma arcs at a water–air interface ». Physics of Plasmas 28, n^o 5 (mai 2021) : 052114. http://dx.doi.org/10.1063/5.0040880.

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Abdo, Youssef, Vandad Rohani et Laurent Fulcheri. « A Simple Theory for Cathode Jets in Plasma Arcs ». Journal of Physics : Conference Series 1243 (mai 2019) : 012016. http://dx.doi.org/10.1088/1742-6596/1243/1/012016.

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Han-Ming Wu et G. F. Carey. « Nonlinear convective effects on moving boundary AC plasma arcs ». IEEE Transactions on Plasma Science 20, n^o 6 (1992) : 1041–46. http://dx.doi.org/10.1109/27.199570.

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Djakov, B. E., et V. Hermoch. « Plasma jet formation at the electrodes of pulsed arcs ». Vacuum 69, n^o 1-3 (décembre 2002) : 129–32. http://dx.doi.org/10.1016/s0042-207x(02)00320-2.

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Terrones, M., W. K. Hsu, S. Ramos, R. Castillo et H. Terrenes. « The Role of Boron Nitride in Graphite Plasma Arcs ». Fullerene Science and Technology 6, n^o 5 (septembre 1998) : 787–800. http://dx.doi.org/10.1080/10641229809350240.

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Shmelev, D. L., S. A. Chaikovsky et I. V. Uimanov. « On hybrid type of cathode attachment in high current vacuum arcs ». Journal of Physics : Conference Series 2064, n^o 1 (1 novembre 2021) : 012030. http://dx.doi.org/10.1088/1742-6596/2064/1/012030.

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Abstract This paper discusses the issues of a possible change of the type of cathode attachment of high-current vacuum arcs (HCVA) with an average cathode current density of more than 105 A/cm2. This type of HCVA is used as pumping plasma gun in experiments with plasma puff z-pinches. These experiments showed that the measured linear mass of the HCVA plasma jet is much higher (by a factor of 10 or more) than the expected mass, which can be obtained from the assumption that cathode attachment occurs only through a multitude of cathode spots emitting supersonic plasma jets. It is shown that in HCVA of the type under consideration, at some time instant there are two types of cathode attachments - cathode spots and thermionic erosion attachment (TEA). It can be said that HCVA of this type have a hybrid cathodic attachment. Unlike cathode spots, TEA produces a subsonic plasma flow, which contributes to an increase in the linear mass of the HCVA plasma jet.

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Surov, A. V., S. D. Popov, E. O. Serba, A. V. Pavlov, Gh V. Nakonechny, V. A. Spodobin, A. V. Nikonov, D. I. Subbotin et A. M. Borovskoy. « High voltage AC plasma torches with long electric arcs for plasma-chemical applications ». Journal of Physics : Conference Series 825 (12 avril 2017) : 012016. http://dx.doi.org/10.1088/1742-6596/825/1/012016.

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Walker, Kris, Daniel J. Reardon, Eric Thrane et Rory Smith. « Orbital Dynamics and Extreme Scattering Event Properties from Long-term Scintillation Observations of PSR J1603−7202 ». Astrophysical Journal 933, n^o 1 (28 juin 2022) : 16. http://dx.doi.org/10.3847/1538-4357/ac69c6.

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Abstract We model long-term variations in the scintillation of binary pulsar PSR J1603−7202, observed by the 64 m Parkes radio telescope (Murriyang) between 2004 and 2016. We find that the time variation in the scintillation arc curvature is well-modeled by scattering from an anisotropic thin screen of plasma between the Earth and the pulsar. Using our scintillation model, we measure the inclination angle and longitude of ascending node of the orbit, yielding a significant improvement over the constraints from pulsar timing. From our measurement of the inclination angle, we place a lower bound on the mass of J1603−7202's companion of ≳0.5 M ⊙ assuming a pulsar mass of ≳1.2 M ⊙. We find that the scintillation arcs are most pronounced when the electron column density along the line of sight is increased, and that arcs are present during a known extreme scattering event. We measure the distance to the interstellar plasma and its velocity, and we discuss some structures seen in individual scintillation arcs within the context of our model.

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Echim, M. M., M. Roth et J. De Keyser. « Sheared magnetospheric plasma flows and discrete auroral arcs : a quasi-static coupling model ». Annales Geophysicae 25, n^o 1 (1 février 2007) : 317–30. http://dx.doi.org/10.5194/angeo-25-317-2007.

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Abstract. We consider sheared flows in magnetospheric boundary layers of tangential discontinuity type, forming a structure that is embedded in a large-scale convergent perpendicular electric field. We construct a kinetic model that couples the magnetospheric structure with the topside ionosphere. The contribution of magnetospheric electrons and ionospheric electrons and ions is taken into account into the current-voltage relationship derived for an electric potential monotonically decreasing with the altitude. The solution of the current continuity equation gives the distribution of the ionospheric potential consistent with the given magnetospheric electric potential. The model shows that a sheared magnetospheric flow generates current sheets corresponding to upward field-aligned currents, field-aligned potential drops and narrow bands of precipitating energy, as in discrete auroral arcs. Higher velocity magnetospheric sheared flows have the tendency to produce brighter and slightly broader arcs. An increase in arc luminosity is also associated with enhancements of magnetospheric plasma density, in which case the structures are narrower. Finally, the model predicts that an increase of the electron temperature of the magnetospheric flowing plasma corresponds to slightly wider arcs but does not modify their luminosity.

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Williams, P. J. S., C. F. del Pozo, I. Hiscock et R. Fallows. « Velocity of auroral arcs drifting equatorward from the polar cap ». Annales Geophysicae 16, n^o 10 (31 octobre 1998) : 1322–31. http://dx.doi.org/10.1007/s00585-998-1322-0.

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Abstract. The drift velocity of an auroral arc is compared with the component of F-region plasma velocity in the same direction for ten cases where the arc is seen to move steadily equatorward for several minutes without any major change in appearance or orientation. In most cases the two velocities are close, but on two occasions the drift velocity of the arc is much higher than the plasma velocity. From the cases studied it appears that during the growth and recovery phase of the substorm cycle the arc moves with a velocity close to the convection velocity, but during the expansion phase this is not the case.Key words. Magnetospheric physics (auroral phenomena; electric fields; plasma convection)

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Stinebring, Daniel R. « Scintillation Arcs Shed Light on Scattering from Planar Plasma Sheets ». Proceedings of the International Astronomical Union 13, S337 (septembre 2017) : 287–90. http://dx.doi.org/10.1017/s1743921318000479.

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AbstractScintillation arcs provide an unprecedented degree of detail into the scattering of radio waves from pulsars. We review evidence that has emerged over the last fifteen years that: a) the scattering of many nearby pulsars is dominated by one or several relatively thin “screens” of material, b) the resulting image on the sky is highly linear, with axial ratios at least as high as 10:1, and c) this arrangement is persistent for at least one source (B1133+16) for at least 25 years. We expand on the idea of Pen and Levin (2014) and previous authors that such scattering may be caused by linear sheets of plasma seen nearly edge-on. Further analysis of such scintillation arcs, including new work on multi-frequency, multi-epoch observations, should help elucidate the astrophysical nature of these ubiquitous scattering entities, which are currently not convincingly linked with any known structures.

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Graves, David B., et Richard A. Gottscho. « Computer Applications in Plasma Materials Processing ». MRS Bulletin 16, n^o 2 (février 1991) : 16–22. http://dx.doi.org/10.1557/s0883769400057602.

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In manufacturing microelectronic and optoelectronic devices, thin solid films of various sorts are routinely deposited and etched using low pressure, weakly ionized plasmas. The term “plasma” in this context implies an ionized gas with nearly equal numbers of positive and negative charges. This definition is not very restrictive, so. there are an enormous number of phenomena that are termed plasmas. For example, very hot, magnetized, fully ionized plasmas exist in stellar environments and thermonuclear fusion experiments. High temperature electric arcs are a form of plasma as well. In contrast, the plasmas used in electronic materials processing are near room temperature and the gas is usually weakly ionized. Indeed, due to the sensitivity of electronic devices to high temperatures, their low operating temperature is one of the major advantages of plasma processes.Plasma processing is attractive because of two important physiochemical effects: energetic free electrons in the plasma (heated by applied electric fields) dissociate the neutral gas in the plasma to create chemically reactive species; and free positive ions are accelerated by the plasma electric fields to surfaces bounding the plasma. Reactive species created in the plasma diffuse to surfaces and adsorb; wafers to be processed are typically placed on one of these surfaces.The combination of neutral species adsorption and positive ion bombardment results in surface chemical reaction. If the products of the surface reaction are volatile, they leave the surface and etching results. If the products are involatile, a surface film grows.

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WRIGHT, D., P. DELMONT et M. TORRILHON. « Modeling of electric arcs : A study of the non-convective case with strong coupling ». Journal of Plasma Physics 79, n^o 5 (21 mars 2013) : 699–713. http://dx.doi.org/10.1017/s0022377813000317.

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AbstractIn this paper, we investigate a mathematical model for electric arcs. The model is based on the equations of magnetohydrodynamics, where the flow and heat transfer in a plasma is coupled to electrodynamics. Our approach neglects convection and yields a reaction–diffusion model that includes only the core phenomena of electric arcs: Ohmic heating and nonlinear electric conductivity. The equations exhibit interesting mathematical properties like non-unique steady states and instabilities that can be linked to electric arc properties. Additionally, a 3D axisymmetric simulation of the creation and extinction of an electric arc is presented based on a strongly coupled numerical algorithm for the non-convective model. The approach is especially suited for high-current arcs where strong coupling becomes necessary.

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Yang, Chih-Hsiang, Shui-Yang Lien, Chia-Ho Chu, Chung-Yuan Kung, Tieh-Fei Cheng et Pai-Tsun Chen. « Effectively Improved SiO2-TiO2Composite Films Applied in Commercial Multicrystalline Silicon Solar Cells ». International Journal of Photoenergy 2013 (2013) : 1–8. http://dx.doi.org/10.1155/2013/823254.

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Composite silicon dioxide-titanium dioxide (SiO2-TiO2) films are deposited on a large area of 15.6 × 15.6 cm2textured multicrystalline silicon solar cells to increase the incident light trapped within the device. For further improvement of the antireflective coatings (ARCs) quality, dimethylformamide (DMF) solution is added to the original SiO2-TiO2solutions. DMF solution solves the cracking problem, thus effectively decreasing reflectance as well as surface recombination. The ARCs prepared by sol-gel process and plasma-enhanced chemical vapor deposition (PECVD) on multicrystalline silicon substrate are compared. The average efficiency of the devices with improved sol-gel ARCs is 16.3%, only 0.5% lower than that of devices with PECVD ARCs (16.8%). However, from equipment depreciation point of view (the expiration date of equipment is generally considered as 5 years), the running cost (USD/watt) of sol-gel technique is 80% lower than that of PECVD method for the first five years and 66% lower than that of PECVD method from the start of the sixth year. This result proves that sol-gel-deposited ARCs process has potential applications in manufacturing low-cost, large-area solar cells.

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Kozlovsky, A. E., V. V. Safargaleev, J. R. T. Jussila et A. V. Koustov. « Pre-noon high-latitude auroral arcs as a manifestation of the interchange instability ». Annales Geophysicae 21, n^o 12 (31 décembre 2003) : 2303–14. http://dx.doi.org/10.5194/angeo-21-2303-2003.

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Abstract. On 7 December 2000, TV ASC camera in Barentsburg (Svalbard) observed pre-noon (at 09:00–10:00 MLT) rayed auroral arcs, which occurred at the pole-ward edge of the auroral oval after an IMF transition from By -dominated (By = + 8.8, Bz = + 4.3) to strongly northward dominated (By = + 2.7, Bz = + 8.6). The arcs appeared from the area of enhanced luminosity seen in the western (nightside) horizon, and developed to the east, progressing at a velocity of about 1.5 km/s. Simultaneously, the arcs were drifting poleward at a velocity of 300–500 m/s, whose value was equal to the F-region ionospheric plasma drift velocity observed by the Incoherent Scatter Radar (ESR). The arc appearance and motion corresponded well to the poleward expansion of the auroral oval following the IMF shift, which was observed by the UVI on board the Polar satellite. The observed auroras were associated with closed LLBL indicated by the particle precipitation data from DMSP satellites showing also several-keV electrons of PS origin. The observations allow us to suggest that the arcs arise due to the interchange instability that starts to develop at the boundary between the magnetospheric plasma and the magnetosheath flux tubes entering the closed magnetosphere due to the reconnection beyond the cusp after the IMF changes. The interchange instability can be suggested as a possible mechanism for the formation of the LLBL. Key words. Magnetospheric physics (auroral phenomena; magnetopause, cusp and boundary layers; magnetospheric configuration and dynamics)

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Park, Mira, Heemoon Yoon, Byeong Ho Kang, Hayoung Lee, Jisoon An, Taehyun Lee, Hee-Tae Cheong et Sang-Hee Lee. « Deep Learning-Based Precision Analysis for Acrosome Reaction by Modification of Plasma Membrane in Boar Sperm ». Animals 13, n^o 16 (14 août 2023) : 2622. http://dx.doi.org/10.3390/ani13162622.

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The analysis of AR is widely used to detect loss of acrosome in sperm, but the subjective decisions of experts affect the accuracy of the examination. Therefore, we develop an ARCS for objectivity and consistency of analysis using convolutional neural networks (CNNs) trained with various magnification images. Our models were trained on 215 microscopic images at 400× and 438 images at 1000× magnification using the ResNet 50 and Inception–ResNet v2 architectures. These models distinctly recognized micro-changes in the PM of AR sperms. Moreover, the Inception–ResNet v2-based ARCS achieved a mean average precision of over 97%. Our system’s calculation of the AR ratio on the test dataset produced results similar to the work of the three experts and could do so more quickly. Our model streamlines sperm detection and AR status determination using a CNN-based approach, replacing laborious tasks and expert assessments. The ARCS offers consistent AR sperm detection, reduced human error, and decreased working time. In conclusion, our study suggests the feasibility and benefits of using a sperm diagnosis artificial intelligence assistance system in routine practice scenarios.

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Gu, Xiao Yan, Huan Li et Lin Jie Li. « Effect of Laser Power on Stability of Laser-Twin-Wire Hybrid Welding Process ». Applied Mechanics and Materials 341-342 (juillet 2013) : 315–19. http://dx.doi.org/10.4028/www.scientific.net/amm.341-342.315.

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Based on the chaos theory and related algorithm, largest Lyapunov analysis of current of laser-twin-wire pulse MIG welding process are performed from the point of view of nonlinear time sequence. Largest Lyapunov exponent (LLE) of characteristic current under different laser power were calculated, meanwhile synchronous high-speed photography was adopted to observe arc shape and droplet transfer. The results indicate that arc shape and the force state of droplets changes as a result of interactions between laser plasma and arc plasma. Addition of low power laser intensifies the interplay of two arcs, which decreases the stability of welding process. When laser power reaches to a certain extent, a stable cathod spot and a conductive channel are obtained for arcs. Stable welding process and small welding spatter are acquired.

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Cumnock, J. A., L. G. Blomberg, A. Kullen et T. Karlsson. « Small-scale characteristics of extremely high latitude aurora ». Annales Geophysicae 27, n^o 9 (1 septembre 2009) : 3335–47. http://dx.doi.org/10.5194/angeo-27-3335-2009.

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Abstract. We examine 14 cases of an interesting type of extremely high latitude aurora as identified in the precipitating particles measured by the DMSP F13 satellite. In particular we investigate structures within large-scale arcs for which the particle signatures are made up of a group of multiple distinct thin arcs. These cases are chosen without regard to IMF orientation and are part of a group of 87 events where DMSP F13 SSJ/4 measures emissions which occur near the noon-midnight meridian and are spatially separated from both the dawnside and duskside auroral ovals by wide regions with precipitating particles typical of the polar cap. For 73 of these events the high-latitude aurora consists of a continuous region of precipitating particles. We focus on the remaining 14 of these events where the particle signatures show multiple distinct thin arcs. These events occur during northward or weakly southward IMF conditions and follow a change in IMF By. Correlations are seen between the field-aligned currents and plasma flows associated with the arcs, implying local closure of the FACs. Strong correlations are seen only in the sunlit hemisphere. The convection associated with the multiple thin arcs is localized and has little influence on the large-scale convection. This also implies that the sunward flow along the arcs is unrelated to the overall ionospheric convection.

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Kaminska, A., et Michel A. Dudeck. « Electric fluctuations of DC and AC arcs in plasma torches ». High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes) 1, n^o 2 (1997) : 205–18. http://dx.doi.org/10.1615/hightempmatproc.v1.i2.50.

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Qingdong, Pang, et John C. McClure. « Emission Spectrum and Resistivity of Low Power Plasma Weld Arcs ». Spectroscopy Letters 24, n^o 4 (avril 1991) : 487–97. http://dx.doi.org/10.1080/00387019108018132.

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Mahrle, A., S. Rose, M. Schnick, E. Beyer et U. Füssel. « Stabilisation of plasma welding arcs by low power laser beams ». Science and Technology of Welding and Joining 18, n^o 4 (mai 2013) : 323–28. http://dx.doi.org/10.1179/1362171813y.0000000109.

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Wu, Xiangyang, Renyong Tian, Zhiyi Zhang, Yanan Li et Cheng Jin. « Study on the Arcs Interaction in Plasma-GMAW Hybrid Welding ». Journal of Physics : Conference Series 1622 (septembre 2020) : 012030. http://dx.doi.org/10.1088/1742-6596/1622/1/012030.

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Almeida, Nelson A., Mikhail S. Benilov, Larissa G. Benilova, Werner Hartmann et Norbert Wenzel. « Near-Cathode Plasma Layer on CuCr Contacts of Vacuum Arcs ». IEEE Transactions on Plasma Science 41, n^o 8 (août 2013) : 1938–49. http://dx.doi.org/10.1109/tps.2013.2260832.

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Simmons, D. A. R., et K. Henriksen. « Discrete polar cap aurora observed from Spitsbergen ». Polar Record 28, n^o 166 (juillet 1992) : 191–204. http://dx.doi.org/10.1017/s0032247400020659.

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ABSTRACTDiscrete auroral arcs frequently bridge the polar cap connecting the morning and evening sectors of the auroral oval along the line of the transpolar (electron) current. Very high-latitude stations that lie wholly within the oval during the earth's diurnal rotation pass under this bridge twice a day, giving morning and evening maxima. Stations at slightly lower latitudes on Spitsbergen lie within the oval in the evening but under, or even south of, the oval in the morning. From such stations the evening, but not the morning, maximum is readily observed. This study is primarily concerned with the orientation of discrete polar cap arcs in the evening skies over Spitsbergen. It shows that the geomagnetic alignment of these arcs is latitude-dependent between geomagnetic colatitudes 6 to 20°N. At the highest latitudes within this range, the arcs are in transpolar alignment, whereas at the lowest latitudes within the polar cap, they are oval-aligned. At intermediate latitudes, the arcs are observed in transitional phases between transpolar and ovalalignment. The solar alignment of discrete polar cap arcs is a function of corrected geomagnetic local time. In the early afternoon, solar alignment is poor but this gradually improves throughout the late afternoon until there is excellent alignment at the time of the evening maximum. Recent satellite studies of plasma convection in the polar ionosphere have helped to explain some of the visual characteristics of discrete polar cap aurora observed from Spitsbergen, particularly the irregular alignment of arcs in the region of the Harang discontinuity.

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Koustov, A. V., K. Hosokawa, N. Nishitani, K. Shiokawa et H. Liu. « Signatures of moving polar cap arcs in the F-region PolarDARN echoes ». Annales Geophysicae 30, n^o 3 (1 mars 2012) : 441–55. http://dx.doi.org/10.5194/angeo-30-441-2012.

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Abstract. Joint observations of the all-sky camera at Resolute Bay (Nunavut, Canada) and the Polar Dual Auroral Radar Network (PolarDARN) HF radars at Rankin Inlet and Inuvik (Canada) are considered to establish radar signatures of poleward moving polar cap arcs "detaching" from the auroral oval. Common features of the events considered are enhanced power or echo occurrence in the wake of the arcs and enhanced spectral width of these echoes. When the arcs were oriented along some of the radar beams, velocity reversals at the arc location were observed with the directions of the arc-associated flows corresponding to a converging electric field. For the event of 9 December 2007, two arcs were poleward progressing almost along the central beams of the Inuvik radar at the speed close to the E × B drift of the bulk of the F-region plasma as inferred from HF Doppler velocities and from independent measurements by the Resolute Bay ionosonde. In global-scale convection maps inferred from all Super Dual Auroral Radar Network (SuperDARN) radar measurements, the polar cap arcs were often seen close to the reversal line of additional mesoscale convection cells located poleward of the normal cells related to the auroral oval.

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