Abstract
As an aid in understanding the breakdown mechanism of metal halide lamps, satatic voltage-current characteristics of the subsidiary and main gap discharges have been measured with 400 watt metal halide lamps, with particular attention given to the effect of the subsidiary discharge on the ionization growth in the main gap. These measurements were conducted with two arrangements. In the first, electrons coming from the subsidiary discharge were accelerated in the main gap with the result that the current increases with a constant voltage characteristics in an “impurity free” lamp, whereas in an impurity contaminated lamp a voltage maximum is observed in the current region of 10-4∼10-3A. In the second arrangement ions were accelerated, and the current growth was found to be caused by the secondary electron emission at the electrode of the opposite end and the subsequent ionization in the main gap. Comparison was made with oscilloscopic traces of the current growth on ac operation and a useful correlation between the dc and ac characteristics was obtained.
