Equation for cathodic glow sheath

Holló, S.; Nyíri, Balázs

doi:10.1007/bf03177497

Cited by 7 publications

(5 citation statements)

References 19 publications

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“…This current region is known as the normal discharge and the current density as the normal current density [1,3,10]. This region has been investigated theoretically [19,20], but not for the conditions of figure 1.…”

Section: Survey Of Glow Discharge Characteristicsmentioning

confidence: 99%

“…The curves show results obtained with various assumed γ i values. The lines, γ i values and references are: --, 0.01-0.02, [19,47,63]; • • 0.07, [16,20,56,64,140]; -•, 0.1, [47,63]; -• •, 0.2, [63]; and ----, 0.3, [47]. The × (γ i = 0.3) and + (γ i = 0.046) show the results of [84] and [92].…”

Section: Steady-state One-dimensional Modelsmentioning

confidence: 99%

“…Local-field models have been used by many authors [19,47,63,[88][89][90][91][92][93][94] to predict the behaviour of abnormal glow discharges in Ar. In these models, the electron induced ionization rate is described by a spatial (Townsend) ionization coefficient α ei [1,3] that is determined by the local electric field to gas density ratio E/n.…”

Section: Local-field Modelsmentioning

confidence: 99%

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Abnormal glow discharges in Ar: experiments and models

Phelps

2001

Plasma Sources Sci. Technol.

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We review measured and calculated voltages and cathode-fall thicknesses against current and electrode separation for parallel-plane Ar glow discharges in the above-normal, or abnormal, current range. We consider dc and pulsed discharges, but not radio-frequency discharges. Reasons for the very high degree of variability among experiments and models are reviewed and suggestions are made for improving the reliability of both. Variations of a factor of two in experimental cathode-fall voltages at a fixed normalized current density are attributed to differences in the cathode emission properties, varying electrode separation, and effects of discharge tube walls. We explore a wide range of normalized current densities, models of the ionization coefficient against E/n, and the effective electron yields per positive ion reaching the cathode using simple scaling laws. Ionization source terms for local-field and non-local-field models are compared and used as the basis for a simplified non-local model. We discuss the present author's recommendation that, because of current large uncertainties in the electron yield per ion for practical cathodes, the yield used in cathode-fall models should be treated as an unknown. Recent models successfully predict the behaviour of transient abnormal discharges on the microsecond time scale.

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Section: Survey Of Glow Discharge Characteristicsmentioning

confidence: 99%

Section: Steady-state One-dimensional Modelsmentioning

confidence: 99%

Section: Local-field Modelsmentioning

confidence: 99%

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Abnormal glow discharges in Ar: experiments and models

Phelps

2001

Plasma Sources Sci. Technol.

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“…Oscillations in glow discharges have been known for several decades [1], the interest in this phenomenon is indicated by a number of recent experimental and theoretical investigations [2][3][4][5][6][7][8][9][10][11][12][13][14]. The low-current oscillations usually occur in the transition region between the Townsend and the normal glow regimes, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…The transition from Townsend discharge to normal glow discharge is often accompanied by radial constriction of the discharge [14]. Recent theoretical studies [7,8] found these radial effects to be important in the generation of the oscillations. The limits of self-sustained oscillations and the characteristics of damped oscillations (frequency and damping constant) have been studied in detail by the application of external voltage pulses [9] and photoelectron initiated avalanches [10].…”

Section: Introductionmentioning

confidence: 99%

Modelling of low-current self-generated oscillations in a hollow cathode discharge

Z Donkó

1999

J. Phys. D: Appl. Phys.

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Low-current self-generated oscillations in a rectangular hollow cathode discharge in helium gas were investigated experimentally and by means of a two-dimensional self-consistent hybrid model. The model combines Monte Carlo simulation of the motion of fast electrons and a fluid description of slow electrons and positive ions. The low-frequency (20 kHz) oscillations were found to arise as an effect of the interaction of the gas discharge and the external electric circuit - consisting of a stable voltage source, a series resistor and a capacitor formed by the discharge electrodes. Good agreement was found between the experimentally observed and calculated oscillation frequency and current wave forms. Beside these characteristics the modelling also made it possible to calculate the time dependence of numerous other discharge characteristics (e.g. electron multiplication, ion density, potential distribution) and provided detailed insight into the mechanism of oscillations. The advantage of the present model is that considerable deformation of the electric field (due to space charge accumulation) can be taken into account.

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Two-dimensional, hybrid model of low-pressure glow discharges

Fiala¹,

Pitchford²,

Boeuf³

1994

Phys. Rev. E

208

135

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A self-consistent, two-dimensional hybrid Quid-particle model is presented and used to describe the electrical behavior of dc low-pressure discharges in the current range 10 -10 A in argon for products of the gas pressure and the gap spacing (pd) from 1 to 3.3 cm torr. The two-dimensional distributions of the potential, charged particle densities and ionization source term at steady state are shown to illustrate the discharge behavior during the transition from the normal to the abnormal regimes. For the larger values of pd, a positive column region as well as the cathode regions are clearly apparent. The model used here consists of Poisson's equation for the electric field coupled to the continuity equations for the electrons and ions with the important feature that the ionization source term appearing in the continuity equations is nonlocal and determined from a Monte Carlo simulation. This description yields a unified physical picture of discharge behavior in the cathode fall, negative glow, and positive column regions over a wide range of discharge currents. PACS number(s): 52.65.+z, 52.80.Hc I. INTRODUC:TlONThe goal in the work presented here has been to study low-pressure discharge behavior using a two-dimensional (2D) numerical model which is capable of yielding a selfconsistent unified description of a low-pressure glow discharge including the cathode fall, the negative glow, and the positive column. Although most of the qualitative features of the results discussed below are known from experiments and previous models, this work serves to quantify the two-dimensional aspects of steady-state glow discharges and it is intended to provide points for comparison with simpler 1D or analytical models. This work goes a step beyond previously published models in that the kinetic description of the ionization source term used here is needed to predict the field reversals on the discharge axis which occur in certain cases.A comprehensive review of previous modeling of gas discharges (dc and rf) has been recently published by Lister [1], and the book by Raizer [2] gives an excellent and detailed discussion of the physics of glow discharges. We therefore limit our discussion in this section to a summary of the context of the results presented here and refer the reader to these recent publications for a complete discussion of the physics of low-pressure discharges[2] and state-of-the-art modeling [1].Visually, self-sustained, low-pressure. glow discharges consist of several luminous regions which differ in intensity and color and which are clearly separated from each other by regions in which essentially no light is emitted.The diverse regions of emitted radiation of different intensity exist as a result of a distribution of the potential between the electrodes. That is, a large drop in the potential (typically some hundreds of volts) occurs immediately adjacent to the cathode surface in a distance on the order of several ionization mean free paths or less. This cathode fall is followed by a region of near zero and, i...

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Equation for cathodic glow sheath

Cited by 7 publications

References 19 publications

Abnormal glow discharges in Ar: experiments and models

Abnormal glow discharges in Ar: experiments and models

Modelling of low-current self-generated oscillations in a hollow cathode discharge

Two-dimensional, hybrid model of low-pressure glow discharges

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