The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

Ruhrmann, C; Hoebing, T.; Bergner, Andreas; Groeger, Stephan; Denissen, Cjm Kees; Suijker, Jlg Jos; Awakowicz, Peter; Mentel, J.

doi:10.1063/1.4927734

Cited by 3 publications

(11 citation statements)

References 31 publications

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“…differences between the electrode tip temperatures within the two half periods fade away. This is not only the case for an arc current of 800 mA, switched-dc, according to figure 26, but also for an arc current of 500 mA, switched-dc, as is shown in figure 9(a) of [29]. The courses of T tip ( f ), measured within the La and NLa1 lamps, are not very different from the courses of T tip ( f ) in figures 21 and 23, but in the NLa2-lamp, the courses of T tip ( f ) within the anodic and cathodic half period deviate distinctly from the previous ones.…”

Section: 32mentioning

confidence: 65%

“…The results have shown that the initial assumption may only be correct in the case of high pressure sodium lamps. Instead, it was found that the emitter effect is based on the cataphoretic transport of metal ions [21][22][23][24][25][26][27][28][29]. Other pyrometric cathode temperature measurements in metal halide lamps with a cylindrical quartz burner confirm the finding [30].…”

Section: Introductionmentioning

confidence: 87%

“…An essential part of measurements is performed on a special CMH lamp [20][21][22][23][24][25][26][27][28][29]. Its burner is formed by an ovoid shaped vessel made of yttrium alumina garnet (Y 3 Al 5 O 12 ) shortened YAG, which is a transparent ceramic, and therefore suitable for optical investigations.…”

Section: The Yag Lampmentioning

confidence: 99%

“…The vacuum-sealed bulb is evacuated by a double stage pumping process. It is given in detail in [29,33]. The investigated burner is fixed inside a lower fixture, while a spring inside an upper fixture permits a flexible burner adjustment inside the outer bulb.…”

Section: The Yag Lampmentioning

confidence: 99%

“…In a series of publications the cataphoretic emitter effect of Dy [20][21][22][23][25][26][27], Ce [24], Cs [24], Tm [27,28], La [29] and Sc [12] is investigated. All of these elements were originally applied to improve the efficacy and colour rendering of HID lamps; only later was it discovered that they were also able to reduce the electrode temperature.…”

Section: The Cataphoretic Emitter Effect Induced By Different Metalsmentioning

confidence: 99%

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The cataphoretic emitter effect exhibited in high intensity discharge lamp electrodes

Mentel¹

2018

J. Phys. D: Appl. Phys.

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A mono-layer of atoms, electropositive with respect to the substrate atoms, forms a dipole layer, reducing its work function. Such a layer is generated by diffusion of emitter material from the interior of the substrate, by vapour deposition or by deposition of emitter material onto arc electrodes by cataphoresis. This cataphoretic emitter effect is investigated within metal halide lamps with transparent YAG ceramic burners, and within model lamps. Within the YAG lamps, arcs are operated with switched-dc current between rod shaped tungsten electrodes in high pressure Hg vapour seeded with metal iodides. Within the model lamps, dc arcs are operated between rod-shaped tungsten electrodes—one doped—in atmospheric pressure Ar. Electrode temperatures are determined by -pyrometry, combined with simulation of the electrode heat balance. Plasma temperatures, atom and ion densities of emitter material are determined by emission and absorption spectroscopy. Phase resolved measurements in YAG lamps seeded with CeI3, CsI, DyI3, TmI3 and LaI3 show, within the cathodic half period, a reduction of the electrode temperature and an enhanced metal ion density in front of the electrode, and an opposite behavior after phase reversal. With increasing operating frequency, the state of the cathode overlaps onto the anodic phase—except for Cs, being low in adsorption energy. Generally, the phase averaged electrode tip temperature is reduced by seeding a lamp with emitter material; its height depends on admixtures. Measurements at tungsten electrodes doped with ThO2, La2O3 and Ce2O3 within the model lamp show that evaporated emitter material is redeposited by an emitter ion current onto the electrode surface. It reduces the work function of tungsten cathodes above the evaporation temperature of the emitter material, too; and also of cold anodes, indicating a field reversal in front of them. The formation of an emitter spot at low cathode temperature and high emitter material density is traced back to a locally reduced work function generated by a locally enhanced emitter ion current density.

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Section: 32mentioning

confidence: 65%

Section: Introductionmentioning

confidence: 87%

Section: The Yag Lampmentioning

confidence: 99%

Section: The Yag Lampmentioning

confidence: 99%

Section: The Cataphoretic Emitter Effect Induced By Different Metalsmentioning

confidence: 99%

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The cataphoretic emitter effect exhibited in high intensity discharge lamp electrodes

Mentel¹

2018

J. Phys. D: Appl. Phys.

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Change of the arc attachment mode and its effect on the lifetime in automotive high intensity discharge lamps

Alexejev

Flesch

Mentel

et al. 2016

Journal of Applied Physics

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In modern cars, the new generation Hg-free high intensity discharge (HID) lamps, the so called xenon lamps, take an important role. The long lifetime of these lamps is achieved by doping the tungsten electrodes with thorium. Thorium forms a dipole layer on the electrode surface, thus reducing the work function of tungsten. However, thoriating the electrodes is also an issue of trade and transport regulation, so a substitute is looked into. This work shows the influence of the arc attachment mode on the lifetime of the lamps. The mode of the arc attachment changes during the run-up phase of automotive HID lamps after a characteristic time period depending, i.e., on the filling of the lamps, which is dominated by scandium. It will be shown that this characteristic time period for the change of the attachment mode determines the long term performance of Hg-free xenon lamps. Measurements attributing the mode change to the scandium density in the filling are presented. The emitter effect of scandium will be suggested to be the reason of the mode change.

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The anodic emitter effect and its inversion demonstrated by temperature measurements at doped and undoped tungsten electrodes

Hoebing¹,

Bergner²,

Hermanns³

et al. 2016

J. Phys. D: Appl. Phys.

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The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

Cited by 3 publications

References 31 publications

The cataphoretic emitter effect exhibited in high intensity discharge lamp electrodes

The cataphoretic emitter effect exhibited in high intensity discharge lamp electrodes

Change of the arc attachment mode and its effect on the lifetime in automotive high intensity discharge lamps

The anodic emitter effect and its inversion demonstrated by temperature measurements at doped and undoped tungsten electrodes

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