Improvement of the Luminous Efficacy in Sc-Na Halide Lamps and Development of Direct Retrofit type Sc-Na Halide Lamps for Operation with Mercury Lamp Ballasts

Abstract

In this paper we will first discuss improvement of the luminous efficacy in Sc-Na halide lamps without special modification of the arc tube configuration and secondly, development of direct retrofit Sc-Na halide lamps for operation with high pressure mercury lamp choke ballasts. To attain a higher lamp efficacy, we studied the influence of the arc tube length-diameter ratio on additive segregation and lamp efficacy, and then determined the optimum additive composition for a set aspect ratio of the arc tube. To operate Sc-Na halide lamps on mercury lamp ballasts, we studied the use of a neon-argon mixture as a starting gas together with a special starting mechanism to prevent ballast overheating and facilitate starting.