Investigating the influence of the operating frequency on the gas phase emitter effect of dysprosium in ceramic metal halide lamps

J Reinelt (1, 2) , M Westermeier (1, 2) , C Ruhrmann (1) , A Bergner (1) , G M J F Luijks (3) , P Awakowicz (1) , J Mentel (1)

1 Electrical Engineering and Plasma Technology
2 RWE Effizienz GmbH
3 Philips Lighting

The dependence of the gas phase emitter effect of Dy on a variation of the operating frequency between some Hz and 2 kHz is investigated in a HID lamp. The buffer gas of the lamp consisting of Ar, Kr and predominantly Hg is seeded with DyI 3, its burner vessel is formed from transparent YAG material. Phase and spatial resolved emission spectroscopy in front of the lamp electrode and pyrometric temperature measurements along the tungsten electrode are performed with a spectroscopic set up. Dy atom and ion densities in front of the electrode are deduced from absolute intensities of optically thin Dy lines and a plasma temperature, derived from the absolute intensity of mercury lines. Phase resolved values of the electrode tip temperature T tip and input power P in are obtained from temperature distributions along the electrode. Distinctly higher Dy ion and atom densities are measured in front of the electrode within the cathodic phase. With increasing operating frequency a reduction of both, atoms and ions, is observed in front of the cathode. In contrast, an increase of the ion density in front of the anode is seen. Moreover, the Dy ion density is drastically reduced by an additional seeding of the lamp with T lI. It is found that an up rating of the Dy ion density is correlated with a decline of T tip and P in. At higher frequencies this effect takes place not only within the cathodic phase but also within the anodic phase. The reduction of the average electrode tip temperature on the order of several hundred Kelvin compared to a YAG lamp with a pure mercury filling is explained by a Dy monolayer on the electrode surface which is sustained by a Dy ion current.

Mots clés: Physical Sciences

J Reinelt, M Westermeier, C Ruhrmann, A Bergner, G M J F Luijks, et al.. Investigating the influence of the operating frequency on the gas phase emitter effect of dysprosium in ceramic metal halide lamps. Journal of Physics D: Applied Physics, 2011, 44 (22), pp.224006. ⟨10.1088/0022-3727/44/22/224006⟩. ⟨hal-00620592⟩