Axial segregation in metal-halide lamps under varying gravity conditions during parabolic flights

A.J. Flikweert, M. van Kemenade, T. Nimalasuriya, M. Haverlag, G.M.W. Kroesen, W.W. Stoffels

Onderzoeksoutput: Bijdrage aan tijdschriftTijdschriftartikelAcademicpeer review

25 Citaten (Scopus)

Samenvatting

Metal¿halide lamps have high efficiencies. These lamps often contain rare-earth additives (in our case dysprosium iodide) which radiate very efficiently in the visible spectrum. Colour separation is a problem in these lamps; this is caused by axial segregation of these additives as a result of diffusion and convection. To vary the effect of convection, parabolic flights were performed with micro-gravity (0g) and hyper-gravity (∼1.8g) phases. During these flights, the atomic dysprosium density was measured by means of laser absorption spectroscopy. In addition, the lamp voltage, which is strongly influenced by the total amount of Dy in the lamp, was measured. The Dy density and axial segregation are dependent on the gravity. Thedynamic lamp behaviour during the parabolas was investigated: the dysprosium density and lamp voltage followed the gravity variations. When entering the micro-gravity phase, the axial diffusion time constant is the slowest time constant; it is proportional to the mercury pressure in the lamp.
Originele taal-2Engels
Pagina's (van-tot)1599-1605
TijdschriftJournal of Physics D: Applied Physics
Volume39
Nummer van het tijdschrift8
DOI's
StatusGepubliceerd - 2006

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