Axial segregation in metal-halide lamps under gravity conditions ranging from 1<i>g</i>to 10<i>g</i>

Nimalasuriya, T Tanya; Thubé, GM; Flikweert, AJ Arjan; Haverlag, M Marco; Kroesen, Gmw Gerrit; Stoffels, WW Winfred; Mullen, van der Jjam Joost

doi:10.1088/0022-3727/40/9/026

Cited by 13 publications

(34 citation statements)

References 14 publications

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“…In order to also study the effect of convection, experiments have also been done at hyper-gravity [11] and normal gravity [10], the future plan is to compare numerical results of the model to these experiments.…”

Section: Discussionmentioning

confidence: 99%

Metal-halide lamps in micro-gravity: experiment and model

Nimalasuriya¹,

Beks²,

Flikweert³

et al. 2008

J. Phys. D: Appl. Phys.

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The results from optical emission spectroscopy experiments of metal-halide lamps under the micro-gravity conditions on board the international space station are compared with the results of a numerical LTE model constructed with the platform Plasimo. At micro-gravity there is no convection which allows for easier modelling and for a separate study of the diffusion-induced radial segregation effect, undisturbed by convection. The plasma parameters that were experimentally determined and compared with the model were the Dy atom and ion density, the Hg ion density and the temperature.The model and experiments applied to a reference lamp burning on a plasma mixture of DyI 3 and Hg were found to be in reasonable agreement with each other. The cross-section for electron-Hg collisions was studied, it was found that the Rockwood values give the correct results. Experimental results guided a sensitivity analysis of the model for the Langevin cross-sections. The ratio of the ion densities Hg + /Dy + was found to be extremely sensitive for the cross-section of the elastic interaction σ (Hg, Dy + ) between the Dy ion and the Hg atom. The sensitivity analysis suggests that equating σ (Hg, Dy + ) to a value that is 10% higher than the Langevin cross-section is the best choice. We also found deviations from LTE in the outer regions of the plasma for relative radial positions of r/R > 50%.

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Section: Discussionmentioning

confidence: 99%

Metal-halide lamps in micro-gravity: experiment and model

Nimalasuriya¹,

Beks²,

Flikweert³

et al. 2008

J. Phys. D: Appl. Phys.

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“…Furthermore parabolic flights were carried out (0-2g, for periods of about 20 s) [17]. More recently a centrifuge was built, which can achieve gravity conditions from 1 to 10g [2,18,19]. The additive distribution in the lamp, in our case the two-dimensional column density of ground state dysprosium atoms in a COST lamp [20], is measured by means of imaging laser absorption spectroscopy (ILAS) [2,18].…”

Section: Introductionmentioning

confidence: 99%

Imaging laser absorption spectroscopy of the metal-halide lamp under hyper-gravity conditions ranging from 1 to 10g

Flikweert¹,

Meunier²,

Nimalasuriya³

et al. 2008

J. Phys. D: Appl. Phys.

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The metal-halide (MH) lamp shows an unwanted non-uniform distribution of the metal additive (Dy in our case), caused by convection and diffusion phenomena. MH lamps with various Hg pressures and burner lengths have been investigated by imaging laser absorption spectroscopy under varying gravity conditions in a centrifuge (1-10g). 2D ground state Dy density profiles have been determined. From these images, the density inhomogeneity and corrected axial segregation parameters are obtained. The profiles and parameters are affected by the axial temperature gradient, which is more pronounced for higher Hg pressures and shorter burner lengths.

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“…This is caused by the combined effects of a different radial distribution of particles in the plasma and the axial convection process, both of which have been researched intensively as axial segregation in metal halide lamps. 7,8 Though the two arc tubes were dosed with the same weight of TlI (15%-20%), the weight of other salts are different (NaI 60%-70%, each rare earth iodide 5%-10% for 3000 K arc tube; NaI 20%-30%, each rare earth iodide 15%-20% for 4000 K arc tube).…”

Section: Methodsmentioning

confidence: 99%

Dimming properties of medium and small wattage ceramic metal halide lamps

Liu

et al. 2013

Lighting Research & Technology

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Ceramic metal halide lamps with rated powers of 70 W and 150 W are dimmed by reducing their operating power. Under dimmed conditions, photometric, colorimetric and electric parameters, as well as the temperature distribution of the outer wall of the arc tube have been measured. As the lamp power is reduced, luminous efficacy and colour rendering index decrease while correlated colour temperature rises. For each lamp, at 70% of its rated power, the luminous efficacy is greater than 80 lm/W, colour rendering index is above 74 and correlated colour temperature increases by less than 800 K. Dimming applications of these lamps are validated by these parameters. Furthermore, the complicated variation of lamp parameters as a function of operating power is explained by the variation of metal halide vapour pressure with wall temperature.

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Axial segregation in metal-halide lamps under gravity conditions ranging from 1gto 10g

Cited by 13 publications

References 14 publications

Metal-halide lamps in micro-gravity: experiment and model

Metal-halide lamps in micro-gravity: experiment and model

Imaging laser absorption spectroscopy of the metal-halide lamp under hyper-gravity conditions ranging from 1 to 10g

Dimming properties of medium and small wattage ceramic metal halide lamps

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