1983 Volume 67 Issue 2 Pages 87-92
High pressure sodium lamps have been known as convection phenomena of the arc are so small. Recently, the arc tubes with larger diameter and high pressure xenon filling have been used for the HPS lamps with high color rendition or high luminous efficacy. It was found the convection phenomena were not negligible in such HPS arc tubes. This phenomenon was confirmed by measuring the 475.1nm sodium line intensity and knowing the displacement of the arc axis. The results are:
(1) the convection becomes larger with increasing arc tube diameter and filling xenon pressure,
(2) the convection becomes smaller with increassing the power input. And the temperature difference of the upper and lower side of the arc tube wall inthe horizontal operation was estimated 40-50°C and this local heating of the arc tube will be a problem in the life of HPS lamps.