Transient Hg, Ba + , Ca + and Y + Optical Emission Lines of a Mercury HID Lamp Exposed to X-Ray: Thermal Analysis of the Tungsten Electrode with Emissive Mixture Based on Barium, Calcium and Yttrium

A study is made on optical emission spectrum modification during X-ray exposure, in the case of a high-pressure mercury discharge lamp operated at several powers. A strong dependence on the lamp operating power for all the spectral lines intensities is observed. Erosion of the emissive mixture based on barium, calcium and yttrium compounds is evidenced by higher values recorded for spectral line intensities in all cases of X-ray exposure compared with those corresponding to non-irradiated lamps. Boltzmann type functions fitted the experimental data of measured optical emission intensities versus time for Ba + , Ca + and Y + lines. However, X-ray influence on plasma electron temperature is not significant. The spectroscopic data are correlated with the results of electrical measurements and of thermal analysis performed for the electrode having the emissive mixture based on barium, calcium and yttrium compounds. A qualitative explanation of the results is also given.