Diagnostic Technique for Impurities in Low Pressure Neon Lamps

The performance of low pressure gas discharge light sources are significantly influenced by small quantities of materials that can be introduced through lamp processing. In this paper the common materials that represent impurities are described and experimental data is provided that detects the threshold of the impurity by tracking emission from the neon discharge. This technique has resolved the presence of hydrogen in the glass tube and the release of hydrocarbons from the getter used with cold cathode electrodes. At temperatures above approximately 200°C, the getter compound starts to release previously trapped materials. For most operational modes of Neon, the glass tube does not exceed 200°C. However, for some Neon Amber turn signal applications the glass temperatures can reach above 250°C. These elevated temperatures can occur particularly for front turn applications that require greater light output than rear applications.