Pulse Starting the 100-W Metal Halide Lamp

Cohen, Sheppard; Zaslavsky, G.; Lester, James N.

doi:10.1080/00994480.1989.10748754

Cited by 4 publications

(6 citation statements)

References 2 publications

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“…Optimizing the breakdown and avalanche processes of both cold and warm lamps continues to be a priority in the lamp community. Lowering the breakdown voltage in cold lamps not only reduces the cost of the driving 3 Author to whom any correspondence should be addressed. electronics but also reduces electrode erosion by sputtering, thereby extending the lamp lifetime.…”

Section: Introductionmentioning

confidence: 99%

Avalanche processes in an idealized lamp: I. Measurements of formative breakdown time

Moss

Eden

Kushner

2004

J. Phys. D: Appl. Phys.

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Electrical breakdown of cold (room temperature) metal-halide arc lamps typically occurs through the fill of a rare gas (at a pressure of tens of Torrs) and the vapour produced by the metal donor. Restarting a warm lamp is often made difficult by the high pressure of the metal and metal-halide vapours. To reliably start cold lamps with a minimum voltage and a minimum sputtering of the electrodes, and to restart warm lamps that have a high pressure of the metal and metal-halide vapours, auxiliary sources of ionization are often used. As a point of departure for the study of these processes, measurements of formative breakdown times were made in a cylindrical discharge tube resembling a compact polycrystalline alumina envelope metal-halide lamp. Breakdown times were measured for Ar/Xe gas mixtures at total pressures of 10-90 Torr and biases up to 2 kV applied to a 1.6 cm gap. The data provide a knowledge base for a companion computational investigation. We found that breakdown times generally decreased with small admixtures of Xe in Ar (5-15%) and increased with larger admixtures. We attribute these trends to the changing shape of the tail of the electron energy distribution.

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Section: Introductionmentioning

confidence: 99%

Avalanche processes in an idealized lamp: I. Measurements of formative breakdown time

Moss

Eden

Kushner

2004

J. Phys. D: Appl. Phys.

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“…The source function in equation 2includes the gain and loss terms due to gas phase reactions (neutral chemistry, ion-molecule reactions and electron impact processes) and contributions associated with wall chemistry, including electron emission from surfaces. The brackets and subscript m in equation (3) denote that ρ is only computed on surfaces and in bulk materials. The flux terms φ were formulated using the method of Scharfetter and Gummel [15].…”

Section: Description Of the Modelmentioning

confidence: 99%

“…Although metal halide lamps typically operate in the steady state as multi-atmosphere thermal arcs, during their starting phase the lamps are moderate pressure glow discharges [1][2][3][4][5][6][7][8]. Typical starting conditions for commercial metal halide lamps are a fill of a rare gas such as argon at tens to a few hundred Torr and the vapour pressure of the metal halide dose and/or mercury.…”

Section: Introductionmentioning

confidence: 99%

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Breakdown processes in metal halide lamps

Lay

Moss

Rauf

et al. 2002

Plasma Sources Sci. Technol.

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Metal halide lamps typically have cold fills of tens to a few hundred Torr of a rare gas and the vapour from the dosing of a metal halide solid and mercury. Breakdown and starting of the lamp occurs following application of multi-kV pulses across electrodes separated by a few centimetres. Restarting of warm lamps is often problematic as the available voltage is insufficient to break down the higher pressure (>many atm) of metal halide vapour. In this paper, fundamental processes during breakdown in cold and warm, idealized metal halide lamps in mixtures of Ar and Hg are investigated using a two-dimensional fluid model for plasma transport. We find that the capacitances of the walls of the discharge tube and adjacent ground planes are important in determining the breakdown voltage and avalanche characteristics. The prompt capacitance represented by, for example, external trigger wires provides a larger E/N to sustain ionization early in the avalanche. This effect is lost as the walls charge and shield the plasma from the ground planes. More rapid breakdown occurs in slightly warm lamps having small vapour pressures of Hg due to the resulting Penning mixture. Warmer lamps, having larger mole fractions of Hg, have less efficient breakdown as the increase in momentum transfer of the electrons is not offset by the additional ionization sources of the Penning mixture.

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“…The vaporized metal (-halide) produces the multiatmosphere plasma which is the source of quasi-continuum radiation. Although the steady state voltage of the thermal arc is only tens of volts, many kilovolts are required to breakdown the cold lamp [2]. As excessively high breakdown voltages increase electrode sputtering, thereby reducing lifetimes, there is motivation for developing strategies for lamp starting which minimize the duration of large applied voltages.…”

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confidence: 99%