High-power compact CMH lamp

It is a little known fact that compact G12-capped metal halide lamps are available beyond 150 W. The lamp shown here is a 1st-gen Philips CDM-T 250W, introduced in 2005 and characterized with the compactness of the common 30-150 W CDM-T. The overall lamp is 19 mm longer than the CDM-T 150W and the outer quartz jacket is 2.7 mm wider to accommodate the larger ceramic burner, which is filled with a dysprosium-based salt mix balanced for the emission of warm-white light at 3200 K. With an initial output of 23 klm, similar to that of a 1-kW tungsten-halogen lamp, this is the brightest metal halide source in its category. Interestingly, this is also the first commercial CMH lamp produced by Philips to feature a shaped ceramic arc tube, which was sourced in from Konoshima (Japan) due to the fact that the Dutch did not have suitable burner manufacturing equipment at the time. Another key difference with smaller CDM-Ts lies in the use of a nitrogen atmosphere in the outer bulb to ensure a good thermal dissipation of the arc tube. Because that vessel's end seals have cermet joints that are impervious to hydrogen, there is no need for a getter in the outer bulb, hence the absence of that ubiquitous metallic pellet-holding tab that is seen in almost all compact metal halide lamps. Philips eventually upgraded its CDM-T 250W in 2013 with its own isothermal ceramic burner, filled with an improved cerium-based salt chemistry. This lamp is still available to this day, although it is only made by Philips.