Investigation of luminous efficacy in scandium-sodium iodide arc lamps

Abstract

Sc-Na metal halide lamps are occupying an important place as energy saving light sources because of the high luminous efficacy and the good color rendition. In order to realize higher luminous efficacy, authors have investigated the effect of lamp design factors on radiation properties and luminous efficacy under the condition of higher NaScl₄ mole fraction. Based on the results of the precise measurements, the effects of the lamp design factors related to the cold sport temperature on the radiation properties have been well understood. The novel approach as well as the optimization of the lamp design factors at lower cold temperature have realized a high luminous efficacy of 121 lm/W in 400 W scandium-sodium lodide lamps.