Recent progress in metal halide discharge-lamp research

The use of volatile halides to introduce additive metals into a high-pressure arc discharge provides a light source of superior colour quality and high luminous efficacy; however, complex physical and chemical phenomena arise from additives having important consequences upon the operating characteristics. Although understanding of the underlying processes is presently incomplete, a critical appraisal of recent studies of radiative, compositional, vaporisation, transport and electrical properties reveal significant progress in identifying dominant mechanisms. Moreover, while the formulation of predictive models remains in a rather primitive stage, further progress now appears possible, providing the foundation for a more rational design approach to these lamps from which improved performance may be expected.