Mercury-free high-intensity discharge with high luminous efficacy and good colour rendering index

A mercury-free high-pressure discharge in a quartz vessel is investigated which achieves a high luminous efficacy of more than 90 lm W−1 and a good colour rendering index of more than 70. It is shown that the favourable properties are achieved by a combination of Xe and AlI3 as mercury is substituted with an admixture of TlI and TmI3. The molecular radiation of the mono-iodide TmI, which is present in large areas of the constricted temperature distribution of the plasma, dominates the spectral radiant flux.