Theory and modelling of plasma-cathode interaction in high-pressure arc discharges

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Stability and bifurcations of modes of current transfer to cathodes of DC gas discharges

Publication . Faria, Maria José Gomes; Benilov, Mikhail

Stability of di⁄erent steady-state modes of current transfer to cathodes of DC highpressure arcs and of di⁄erent axially symmetric modes of current transfer of DC glow discharges against small perturbations is investigated in the framework of the linear stability theory. The eigenvalue problem for perturbations is solved with the use of software COMSOL Multiphysics. For the arc discharge, it was found that only the di⁄use mode and the rst 3D spot mode can be stable. The transition between the two modes is non-stationary and accompanied by hysteresis. For the glow discharge, variations of the increments of perturbations with discharge current are investigated for the 1D glow discharge and di⁄erent modes of axially symmetric glow discharge. Both real and complex increments have been detected, meaning that perturbations can vary with time both monotonically and with oscillations. In general, results given by the linear stability theory conrm intuitive concepts developed in the literature and conform to the experiment. On the other hand, the theory provides suggestions for further experimental and theoretical work. Bifurcations encountered in numerical modelling of current transfer to cathodes of DC high-pressure arcs and of DC glow discharges are analyzed. All basic types of steady-state bifurcations (fold, transcritical, pitchfork) have been identied and analyzed. The analysis provides explanations to many results obtained in numerical modelling. In particular, it is shown that dramatic changes of patterns of current transfer to cathodes of both glow and arc discharges, described by numerical modelling, occur through perturbed transcritical bifurcations of rst and second order contact. For the case of the arc discharge, e⁄ect over stability of cathode geometry and temperature of cooling was studied. It was found that changes of patterns of the steady-state modes occur due to interplay of self-organization and geometric factors.

2011Doctoral thesis

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