High-pressure sodium lamp technology

Since the development of translucent polycrystalline alumina more than twenty years ago there has been a continuous improvement in high-pressure sodium lamp technology. Lamp lives have quadrupled and light output increased by 20%. There are approximately 16 manufacturers of h.p.s. lamps in the world today and more than 15 sizes of the lamps are now available from 45 to 1000 watts. The light source development is traced with emphasis on the material properties where future improvements can be made.