Two forms of attachment of an atmospheric-pressure direct-current arc in argon to a thermionic cathode

Mitrofanov, N. K.; Shkol'nik, S.M.

doi:10.1134/s1063784207060060

Cited by 35 publications

(63 citation statements)

References 16 publications

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“…Note that the comparison of sheath modeling approaches was also performed in a wide range of current densities, 2·10 6 A/m 2 -2·10 7 A/m 2 (typical for atmospheric pressure argon arc, see, for example, Refs. 37,53). In all the considered cases a good agreement was observed.…”

Section: Iv1 Benchmarking Of 1d Code and Sheath Modelssupporting

confidence: 65%

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

et al. 2018

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Atmospheric pressure arcs have recently found application in the production of nanoparticles. Distinguishing features of such arcs are small length and hot ablating anode characterized by intensive electron emission and radiation from its surface. We performed one-dimensional modeling of argon arc, which shows that near-electrode effects of thermal and ionization non-equilibrium play important role in operation of a short arc, because the non-equilibrium regions are up to several millimeters long and are comparable with the arc length. The near-anode region is typically longer than the near-cathode region and its length depends more strongly on the current density. The model was extensively verified and validated against previous simulation results and experimental data. Volt-Ampere characteristic (VAC) of the near-anode region depends on the anode cooling mechanism. The anode voltage is negative. In case of strong anode cooling (water-cooled anode) when anode is cold, temperature and plasma density gradients increase with current density resulting in decrease of the anode voltage (absolute value increases). Falling VAC of the near-anode region suggests the arc constriction near the anode. Without anode cooling, the anode temperature increases significantly with current density, leading to drastic increase in the thermionic emission current from the anode. Correspondingly, the anode voltage increases to suppress the emission -and the opposite trend in the VAC is observed. The results of simulations were found to be independent of sheath model used: collisional (fluid) or collisionless model gave the same plasma profiles for both near-anode and near-cathode regions.Parametric studies of short atmospheric pressure argon arc with tungsten electrodes were performed for various current densities and inter-electrode gap sizes. Non-equilibrium effects in the near-electrode regions were studied. Anodes with and without water cooling were considered. Effect of electron emission on current-voltage characteristic of the near-anode layer was investigated. Analytical formulas for scaling of non-equilibrium regions widths and Volt-Ampere's characteristics of these regions and the whole arc are given in the accompanying paper 44 .The organization of the paper is as follows. In Section II governing equations and boundary conditions for plasma and electrodes are presented. Section III describes numerical procedure of solving the governing equations. Results of simulations including validation of the model and parametric studies of the arc are presented and discussed in Section IV. Conclusions of this work are summarized in Section V.

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Section: Iv1 Benchmarking Of 1d Code and Sheath Modelssupporting

confidence: 65%

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

et al. 2018

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“…12 on an example of a 1 cm-long free-burning atmospheric-pressure argon arc under experimental conditions. 15 The arc voltage predicted by a sheath-accounted model was found to exhibit a variation with the arc current similar to the one revealed by the experiment; it exceeds the experimental values by no more than approximately 2 V in the current range of 20-175 A. About two thirds or more of the arc voltage is contributed by the near-cathode layer.…”

Section: Discussionmentioning

confidence: 55%

“…Results obtained in this work on the rod cathode 3 (which was the one employed in the experiments 15 On the other hand, in cases where the Joule heating is dominating and the cathode is made of thoriated tungsten or other material with a low work function, the space-charge sheath voltage may be quite low.…”

Section: Discussionmentioning

confidence: 93%

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

Benilov

Cunha

2013

Journal of Applied Physics

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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.

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“…Over the past few decades, a large number of studies have been devoted to such arc plasmas in both experiment [3][4][5][6][7][8][9][10][11] and modeling. [12][13][14][15][16] Using optical emission methods, arc properties, including the cathode surface temperature, 3-8 the plasma temperature, [5][6][7][8][9] and so on, have been determined and the effects of different arc conditions, e.g., the operation parameters 3,8,9 and the cathode shapes and materials, [4][5][6] have been extensively investigated. On the other hand, the recent remarkable progress in arc theory enables the electrodes, the sheath regions, and the arc plasma to be included in arc models.…”

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confidence: 99%

Time resolved characterization of a free-burning argon arc after ignition by optical emission spectroscopy

Gao

2011

Journal of Applied Physics

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Implementation of moiré-schlieren deflectometry on a small scale fast capillary plasma discharge J. Appl. Phys. 111, 103301 (2012) Simultaneous translational temperature measurements of different atomic species in plasma flows using scanning Fabry-Perot interferometry Rev. Sci. Instrum. 83, 053111 (2012) Quantitative measurement of hard x-ray spectra for high intensity laser produced plasma Rev. Sci. Instrum. 83, 053502 (2012) X-ray conversion efficiency in vacuum hohlraum experiments at the National Ignition Facility Phys. Plasmas 19, 053301 (2012) Synergetic effects of double laser pulses for the formation of mild plasma in water: Toward non-gated underwater laser-induced breakdown spectroscopy

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Two forms of attachment of an atmospheric-pressure direct-current arc in argon to a thermionic cathode

Cited by 35 publications

References 16 publications

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

Investigation of the short argon arc with hot anode. I. Numerical simulations of non-equilibrium effects in the near-electrode regions

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

Time resolved characterization of a free-burning argon arc after ignition by optical emission spectroscopy

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