Modes of current transfer to cathodes of high-pressure arc discharges and their stability

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Publications

The Child–Langmuir law and analytical theory of collisionless to collision-dominated sheaths

Publication . Benilov, M. S.

This paper is concerned with summarizing simple analytical models of space-charge sheaths and tracing their relation to the Child–Langmuir model of an ion sheath. The topics discussed include the Child–Langmuir law and model of a collisionless ion sheath, the Mott–Gurney law and model of a collision-dominated ion sheath, the Bohm model of a collisionless ion–electron sheath, the Su–Lam–Cohen model of a collision-dominated ion–electron sheath, ion sheaths with arbitrary collisionality, high-accuracy boundary conditions for the Child–Langmuir and Mott–Gurney models of an ion sheath and the mathematical sense of Child–Langmuir type models of an ion sheath from the point of view of modern theoretical physics.

2009Journal article

Open access

Bifurcations of current transfer through a collisional sheath with ionization and self-organization on glow cathodes

Publication . Benilov, M. S.

A bifurcation analysis is performed of a dc glow discharge between parallel electrodes and of a dc near cathode space-charge sheath bordering a uniform plasma column. A model of plasma is considered with a single ion species and motion of the charged particles dominated by drift. Bifurcation points are found at which steady-state modes with spots on the cathode branch off from the abnormal mode or from the mode corre sponding to the falling section of the current-density–voltage characteristic. In both discharge configurations, bifurcations in the abnormal mode have been detected; an unexpected result given that loss of stability and pattern appearance in dc gas discharges are usually associated with a negative differential resistance of the discharge. The conclusion is drawn that the two most important mechanisms governing appearance of patterns on glow cathodes, which are electrostatic mechanism and diffusion, produce competing effects: the former favors appearance of modes with multiple spots, while the latter favors appearance of a mode with one spot. This may explain the appearance in experiments of a normal spot or, alternatively, of patterns with multiple spots.

2008Journal article

Open access

Understanding and modelling plasma–electrode interaction in high-pressure arc discharges: a review

Publication . Benilov, M. S.

Considerable advances have been attained during the last decade in the theoretical and experimental investigation of electrode phenomena in high-pressure arc discharges, in particular, in low-current arcs that occur in high-intensity discharge lamps. The aim of this paper is to deliver a concise review of the understanding achieved and modelling methods developed.

2008Journal article

Open access

Comment on ‘Self-organization in cathode boundary layer discharges in xenon’ and ‘Self-organization in cathode boundary layer microdischarges’

Publication . Benilov, M. S.

It is shown that basic mechanisms of glow discharge, which are drift and diffusion of the ions and the electrons, volume ionization and recombination and secondary electron emission, are in principle sufficient to explain patterns on glow cathodes observed in recently published works, so there is no need to introduce special mechanisms to this end.

2007Journal article

Open access

Formation of stationary and transient spots on thermionic cathodes and its prevention

Publication . Almeida, Pedro G. C.; Benilov, M. S.; Cunha, M. D.

Spots on cathodes of high-pressure arc discharges induced by a rapid increase in the arc current are studied numerically and experimentally. Appearance of stationary and transient spots is analysed in the context of the general pattern of steady-state modes of current transfer to thermionic cathodes and their stability. Transient spots are studied in experiments with COST-529 standard lamps. Modelling and experimental results are in reasonable agreement. A method to prevent formation of transient spots on cathodes of high-pressure arc discharges by means of short negative rectangular current pulses is proposed and validated both numerically and experimentally. Experimental indications are found that the main mechanism of blackening of burners of HID lamps that accompanies appearance of transient cathode spots is evaporation of the cathode material and not sputtering.

2008Journal article

Open access