Analysis of cathode-spot behavior in high-pressure discharge lamps.

Waymouth, John F.

doi:10.2150/jlve.6.2_5

Cited by 27 publications

(31 citation statements)

References 9 publications

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“…After the problem (1), (2) has been solved for a given U and a distribution of the temperature over the bottom surface of the cathode has been found, one can determine a distribution of density j of the electric current coming to the cathode surface from the plasma, corresponding to this U. (It is implied that a dependence of j on the local temperature of the cathode surface and on the voltage drop in the near-cathode layer is known.…”

Section: The Modelmentioning

confidence: 99%

“…The aim of this section is to discuss general properties of solutions to the problem (1), (2). The problem may have a 1D solution r = r (z) of the form…”

Section: Generalmentioning

confidence: 99%

“…The essence of the problem is as follows: current transfer to thermionic cathodes may occur in a spot mode, when nearly all the current is localised in a region occupying only a small fraction of the cathode surface (the spot), and in a diffuse mode~ when the current is distributed over the front surface of the cathode in a more or less uniform way. High-pressure discharge lamps, welding and fusion devices represent examples of applications for which the question of multiple modes of current transfer to thermionic cathodes is of high importance (e.g., [2,3,4]). …”

Section: Introductionmentioning

confidence: 99%

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Non-linear surface heating and modes of current transfer to thermionic cathodes

Benilov

1998

Czech J Phys

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Section: The Modelmentioning

confidence: 99%

“…The aim of this section is to discuss general properties of solutions to the problem (1), (2). The problem may have a 1D solution r = r (z) of the form…”

Section: Generalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Non-linear surface heating and modes of current transfer to thermionic cathodes

Benilov

1998

Czech J Phys

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“…The electrode tip temperature in metal halide lamps is believed to be 2000-2300 K (30). The pressures of C12 and C1 at 2250 K are almost invariant with respect to changing molar ratio in the SnC12 + NaC1 mixtures.…”

Section: The Snci2 + Naci Systemmentioning

confidence: 99%

The Chemical Composition of Plasmas Generated in High Pressure Discharge Lamps Containing Tin and Sodium Halides

Mucklejohn¹,

Jones²,

Mottram³

et al. 1987

J. Electrochem. Soc.

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In order to model high pressure discharge lamps which contain metal halides, the chemical composition in the plasma region is required. We have developed a procedure for calculating the composition of a plasma in local thermodynamic equilibrium, between 1500 and 6000 K, including the effect of radial diffusion. Mixtures of tin halides and sodium halides, when added to high pressure mercury discharges, produce highly efficient white light sources. We have determined the saturated vapor phase composition of some tin halide/sodium halide mixtures using the results from Knudsen effusion/ mass spectrometric, vapor pressure, and transpiration studies. We report herein a detailed study of the SnC12 + NaC1 (50:50) system and a preliminary investigation of the SnC12 + NaI (50:50) system together with the plasma compositions for the corresponding lamps. These results show that radial diffusion has a highly significant effect on the plasma composition.Our understanding of high pressure sodium lamps has been deepened through the development of a computer model (1). The model is based on solving the energy balance equation to give the radial temperature distribution of an arc. We assume that the electrical energy dissipated in an elemental volume equals the sum of the net heat and radiation losses. The variation of the chemical composition of the plasma with temperature stands at the heart of the model, and is used in the calculations of thermal and electrical conductivities and of radiation losses.A knowledge of the temperature profile enables us to predict the electrical and spectral characteristics of the arc. We have used our model to investigate the variation of efficacy for a high pressure sodium lamp with arc tube bore and current (2), and with arc tube temperature and electrical power dissipation (3). The model has thus contributed directly to the development and improvement of high pressure sodium lamps.Metal halide lamps are able to combine good color appearance and good color rendition with compact size, giving rise to highly efficient white light sources. A large variety of metal halide lamps are available on the market, these are generally confined to powers above 150W. Such lamps are employed in many applications: industrial and commercial interior lighting; exterior floodlighting; theater and stage lighting; set lighting; image projection systems; photoprinting; water sterilization; plant growth; street lighting. The present trend is towards lower power lamps, say below 150W, for use in display lighting. The development of successful low wattage metal halide lamps has proved to be a considerable challenge to the lamp manufacturing industry. To date, only a few low power metal halide lamps are available.The addition of tin halide/sodium halide mixtures to high pressure mercury discharges has been shown to produce lamps which combine high efficacy with good color rendition (4). The inclusion of metal halide systems in high pressure lamps gives rise to both atomic and molecular radiation, the latter being broad-ba...

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“…Mathematical models have been created for the positive plasma column [1]- [3], for the electrode temperature distribution [4]- [6], for the cathode fall zone [7], [8], or for the behavior of the temperature in contraction regions of high-pressure mercury arc [9]. Although the high pressure Hg plasma arc discharges are close to thermodynamic equilibrium, their study is not complete and is far from satisfactory.…”

Section: Introductionmentioning

confidence: 99%

Modeling Nonlinear Coupling between Plasma, Electrodes and Walls for High-Pressure Hg Arc Discharge Lamps

Cristea

Iova

Cristescu

et al. 2000

Contrib. Plasma Phys.

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This paper presents a model able to give a global description of the functioning of high‐pressure Hg arc discharge lamps, with operation in the diffuse cathode mode. For computational simplicity reasons the lamp is fed on d.c. voltage. The nonlinear interactions between different zones (positive column, electrodes and walls of the discharge tube) is considered through Neumann‐Dirichlet mixed boundary conditions at interfaces. We take into account the nonlinearity of physical characteristics of the electrode material and of the silica envelope. Waymouth's measurements are used for the ratio between electron and ion currents. The temperature profile index as function of the z‐coordinate is determined in the vicinity of the cathode.

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Analysis of cathode-spot behavior in high-pressure discharge lamps.

Cited by 27 publications

References 9 publications

Non-linear surface heating and modes of current transfer to thermionic cathodes

Non-linear surface heating and modes of current transfer to thermionic cathodes

The Chemical Composition of Plasmas Generated in High Pressure Discharge Lamps Containing Tin and Sodium Halides

Modeling Nonlinear Coupling between Plasma, Electrodes and Walls for High-Pressure Hg Arc Discharge Lamps

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