LRJD 400W (COBR Polam)

This is an unusual Polish metal halide lamp from the R&D Laboratory of POLAM. It was received via a Polish lamp collector without too much information. The suffix 'D' of the name LRJD would normally indicate Daylight colour, however the colour of this lamp is not white. It is about 8000K and slightly greenish. The mechanical construction is almost identical to Osram HQI-T lamps of the 1970s, it is clearly copied from that company's products. However while Osram lamps are filled with Dysprosium-Thallium-Caesium and give a good daylight quality light of very high colour rendering, this Polam lamp contains far more thallium (green), and also indium (blue). Due to the strong green-blue light, the colour rendering is very bad, a little under 60, and there is strong separation of colours along the length of the arc. The efficacy is rather low for a metal halide lamp, just 72 lm/W. It is not known what application this lamp was made for - perhaps some medical or photochemical use. It would certainly not make a good lamp for general lighting due to the poor colour and low efficacy.