254 nm Radiant Efficiency and Spectral Lines of High Output T6 Low Pressure Mercury Discharge Lamps with Neon–Argon Buffer Gases

Abstract

The radiant efficiency of low pressure mercury (LPM) discharge lamps with outer diameter of 19 mm (T6) was measured for various parameters: cold spot temperature, discharge current, and buffer gas pressure. The buffer gas was neon (75%) and argon (25%) with total pressure 133–1333 Pa. The lamps were operated with cold spot temperatures 20–80°C and discharge current 0.8–2.0 A. The electric field, input power, 254 nm radiant power and efficiency, spectra of Hg lines 254–579 nm and rare gas lines 738–850 nm in positive column were measured. It was shown that under discharge condition of cold spot temperature 45°C and current 1.6 A, the 254 nm UV radiant efficiency had a maximum of above 40% for buffer gas pressure 133–267 Pa. The optimal mercury vapor pressure was approximate 1.2 Pa, corresponding to the cold spot temperature around 45°C. The sum of radiant energy percentage of other mercury lines and rare gas lines was less than 10%, which proved that high output LPM lamps can be good choice of UV radiation source.