Investigation of Fluorescent Lamps with Altered Mercury Isotopic Distributions

Varying isotopic distribution of mercury in low pressure mercury-rare gas discharge lamps will affect lamp performance due to changes in resonance radiation transport. The authors have studied the effects of mercury 196Hg concentration in coated F40 T12 (2.5 Torr Ar, 40 watt) and F40 T12 (1.5 Torr, 13% Ar, 87% Kr, 34 watt) lamps. Total light poutput measured with a 2.4 meter integrating sphere and associated electrical measurements were used to determine these effects. Additionally, circulating water bath measurements were carried out for F40 T12 lamps to observe the effect of cold spot temperature on lumen per watt lamp efficiency. Maximum lumens per watt improvements were observed for the lamps studied relative to control groups.