Emission spectroscopy for characterizing metal-halide lamps

Abstract

The metal-halide (MH) lamp shows an unwanted axial non-uniform distribution of the metal additives when burning in vertical position, which is caused by the interplay between convection and diffusion. Various MH lamps are investigated by means of emission spectroscopy under varying gravity conditions (1–10g) in a centrifuge. The method yields spectra, axial inhomogeneity parameters and axially integrated intensities. The method is easier than methods used before on the same type of lamp. Measurements on lamps with DyI3 as salt filling are used as a calibration of the setup. After comparison with the earlier measurements, we conclude that the new emission spectroscopy is valid for characterization of MH lamps. Next, we apply the method on commercial lamps (Philips MASTER CosmoWhite). For these lamps, in addition NaI densities at the wall and axial temperature profiles are obtained by using self-reversed lines of Na and Hg, respectively.