抄録
During high pressure sodium lamp (HPS lamp) operation, are voltage increase. The cause of this phenomenon was investigated by the following methods. At first, the relation between the increase of the lamp voltage and the temperature of the coldest spot, at which excess amalgam condensed, was obtained using a liquid indium bath. It was found that the main cause of the lamp voltage increase was sodium loss and the quantity of the lost sodium in a lamp, which initially contained 7.5 mg sodium and of which lamp voltage increased from about 90 V to about 160 V during the life, was about 5 to 6 mg. Then, the quantity of lost sodium and the attacked position of an almina arc tube were investigated with neutronactivation analysis. It has become clear that lost sodium attacked the low temperature part of the alumina during operation.
