Observations of electric arc cathode region

Pokrzywka, B.; Pellerin, Stéphane; Musioł, Karol; Richard, F.; Chapelle, J.

doi:10.1088/0022-3727/29/11/018

Cited by 14 publications

(14 citation statements)

References 13 publications

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“…2 Several experiments were performed with a pure tungsten cathode. If the plasma gas flow is purely axial (no swirl), the appearance is similar to that described in [18,19]: in the central region with a well-defined mosaic structure surrounded with a wide region covered with tiny craters. current 200 A).…”

Section: Appearance Of the Cs Footprint At The Cathodementioning

confidence: 57%

Current density at the refractory cathode of a high-current high-pressure arc (two modes of cathode spot attachment)

Nemchinsky

2003

J. Phys. D: Appl. Phys.

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Section: Appearance Of the Cs Footprint At The Cathodementioning

confidence: 57%

Current density at the refractory cathode of a high-current high-pressure arc (two modes of cathode spot attachment)

Nemchinsky

2003

J. Phys. D: Appl. Phys.

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“…The modes we call diffuse mode and spot mode are well-known and are described alike by other groups [6]. Beyond these two basic modes, there are various cathodic phenomena described differently by different authors (see, e.g., [7][8][9]). Thus, it is not easy to pinpoint whether different papers present the same discharge mode or not.…”

Section: Introductionmentioning

confidence: 88%

Near-cathode region of a free-burning arc: a spectroscopic investigation

Könemann¹,

Kühn²,

Reiche³

et al. 2003

J. Phys. D: Appl. Phys.

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The cathode as an electron emitter possesses different modes of operation to maintain the current forced upon the discharge. We investigated spectroscopically the near-cathode region of a free-burning low-current argon arc operated at atmospheric pressure in order to measure the plasma parameters of that mode of operation that we call the blue-core mode. For better interpretation of the experimental data we applied a simple two-temperature model. As a result, we can describe the arc plasma up to 100 µm near the cathode surface.

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“…It is important to clarify the thorium atom behavior in the cathode and that at the surface for the cathode lifetime evaluation. 24,25) Here the cathode lifetime is evaluated by coupling with plasma thermofluid characteristics as calculated previously. In order to derive the governing equations, the following assumptions are introduced.…”

Section: Boundary Conditionsmentioning

confidence: 99%

Performance Evaluation of Arc-Electrodes Systems for High Temperature Materials Processing by Computational Simulation

2003

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Thermofluid analysis of an arc flow and the evaluation of the cathode lifetime have been conducted by a computational simulation for the performance improvement of arc-electrodes systems. The effects of arc current, electrode gap, inlet gas flow rate and cathode vertex angle on the temperature and velocity fields of an arc flow are clarified by parametric computations to optimize the operating conditions and torch geometry. The temperature field by an arc flow model shows the quantitative agreement with the available experimental data in the local thermodynamic equilibrium (LTE) region. The cathode lifetime is evaluated successfully by coupling with the computated thermofluid field of an arc flow. The effects of different operating conditions on the cathode lifetime are also discussed for longer lifetime of the arc-electrodes systems.KEY WORDS: computational simulation; arc; electrode; interaction; lifetime evaluation.Under these assumptions, the governing equations for arc and electrodes regions are presented as follows: The radiation loss Ra from arc is given by the multipleterms approximation as a function of plasma temperature from the experimental data for argon.2) inside the electrode ... (5) Heat flux between arc and cathode, anode are respectively given by neglecting space charge effects 13,14) in the very thin sheath and both electrodes evaporation for simplicity 15) ........ (6) ... (7) where the emission current density j e is given by the Richardson-Dushman equationion current j i is given as follows: Boundary ConditionsIn the previous almost studies, temperature distribution on the electrode surface and the current density at the cathode spot are given in assumptions. [4][5][6][7][8][9] In the present study, the temperature and electric potential conditions are given only at the cooled surfaces of anode and cathode, represented as lines CЈDЈ, FA, in Fig. 1 without assuming the current density and temperature at the electrodes surface, represented as lines CD, FG, GB 11) and neglecting sheath boundary Vol. 43 (2003) conditions for the reduction in computation time. 15,17) Because calculated arc temperature and cathode surface temperature are relatively insensitive to those detailed properties of the sheath. Table 1 shows the discharge configuration and operating conditions referring to Gas Tungsten Arc (GTA) plasma facility. Numerical Conditions and Procedures19) A cylindrical thoriated tungsten cathode (Wϩ 2wt%Th) and a plate copper anode are investigated for lifetime evaluation in the present study. The roots of both electrodes are cooled fixedly at 300 K. The thermofluid field is solved by Semi-Implicit-Method for Pressure Linked Equation (SIMPLE) 20) method using Tri Diagonal-Matrix Algorithm (TDMA). The electromagnetic field is solved by Gauss-Seidel method. Here, the grid has 75ϫ102 meshes in the axial and radial directions, respectively. The thermodynamic and transport properties of argon 21,22) and tungsten and copper 23) are given as a function of temperature. Figure 2 shows a schematic i...

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Observations of electric arc cathode region

Cited by 14 publications

References 13 publications

Current density at the refractory cathode of a high-current high-pressure arc (two modes of cathode spot attachment)

Current density at the refractory cathode of a high-current high-pressure arc (two modes of cathode spot attachment)

Near-cathode region of a free-burning arc: a spectroscopic investigation

Performance Evaluation of Arc-Electrodes Systems for High Temperature Materials Processing by Computational Simulation

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