RLOD#43 (2020.07.24) 1975 Radium HRI 2000W D1

Radium and Osram of West Germany began developing high-wattage daylight metal halide lamps for general lighting applications in 1967 using a newly formulated triple rare earth fill chemistry suitable for high arc power loads. The 2 kW model featured here was introduced in 1970 and was optimized to the listed specifications the following year. In order to obtain properly high performances the electrode gap length was shortened to 105 mm so as to raise the arc power load to 170 W/cm, which is about 40 % higher than in the earlier neutral-white version of the lamp, introduced in 1964. This not only reduces the heat conduction losses of the arc, resulting in an 85 lm/W efficacy, this also raised the mean source luminance to 920 cd/cm², 74 % higher than in the neutral-white lamp, thereby enabling a much more effective optical control of the emitted light. Combined to that, the lamp's Tl-Dy-Ho-Tm/Cs fill chemistry delivers a light color of near daylight quality, which made this type of light source highly popular in professional sports lighting, especially where color TV broadcasting was involved. As a matter of fact, the primary motivation for the release of these large daylight metal halide lamps was the 1972 summer Olympic Games in Munich.