GAS EVOLUTION AND GETTERING IN HIGH-PRESSURE DISCHARGE LAMPS

The use of getters within the jacket of metal halide lamps is necessary to prevent the deleterious influence of gaseous impurities on their performance. A number of experimental metal halide lamps (400 W) were produced using the St 101 getter alloy (84% Zr-16% Al). Analysis of the jacket atmosphere and the getter gives information about the impurity load and the gas release dynamics. About 35 Pa I of hydrogen and 7 Pa I of CO and lower quantities of CO2 and CH4 are evolved. The release seems to be complete within about 1000 h of operation. Practical results confirm that the St 101 alloy, because of its gettering properties and its ability to withstand the contaminating ambient during lamp production, is particularly suited for use in the outer jacket of discharge lamps. © 1979 Pergamon Press Ltd.