Experimental study on acoustic resonance phenomena in ageing high-intensity discharge lamps

It is widely thought that ageing a metal halide (MH) lamp will result in changes in the acoustic resonance eigenfrequencies but to date no experimental data on this topic has been reported in the literature. A study on the influence of the operating time on the stability of low-wattage MH lamps is now presented. It is shown that the age of a lamp does not affect the fundamental acoustic eigenfrequency values. The upper limit of the frequency of the highest acoustic resonance band at which the arc will become unstable is not affected by the age of the lamp. However, the lamp age does influence the extent of instability inside the lamp with the lamp voltage significantly increasing.