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Unified modelling of near-cathode plasma layers in high-pressure arc discharges

Publication . Almeida, N. A.; Benilov, M. S.; Naidis, G. V.

A model of a near-cathode region in high-pressure arc discharges is developed in the framework of the hydrodynamic (diffusion) approximation. Governing equations are solved numerically in 1D without any further simpliﬁcations, in particular, without explicitly dividing the near-cathode region into a space-charge sheath and a quasi-neutral plasma. Results of numerical simulation are reported for a very high-pressure mercury arc and an atmospheric-pressure argon arc. Physical mechanisms dominating different sections of the near-cathode region are identiﬁed. It is shown that the near-cathode space-charge sheath is of primary importance under conditions of practical interest. Physical bases of simpliﬁed models of the near-cathode region in high-pressure arc discharges are analysed. A comparison of results given by the present model with those given by a simpliﬁed model has revealed qualitative agreement; the agreement is not only qualitative but also quantitative in the case of an atmospheric-pressure argon plasma at moderate values of the near-cathode voltage drop. The modelling data are compared with results of spectroscopic measurements of the electron temperature and density in the near-cathode region.

2008Journal article

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