Testing of an MPXL 30W R

The light engine shown here is an experimental model that was made specifically for fiber lighting systems. The MPXL 30W R is built around a standard integral-ballasted D5s automotive Xe-MH headlamp module to which an elliptical dichroic reflector was added. The light emitted from the arc tube is focused 4.2 cm in front of the mirror flange. The system is optimized for visible light emission as the burner’s jacket is of the UV-block kind (i.e., doped with cerium oxide), while the dichroic mirror is transparent to infrared radiation.

The quartz burner is of a standard 25 W mercury-free type filled with sodium and scandium iodides, balanced for a neutral-white light emission at 4200 K. This lamp has an interesting ignition aid which consists of a low-pressure argon atmosphere in the outer bulb. This gas fill becomes ionized when high-voltage pulses are applied to the electrodes, resulting in an argon discharge which acts both as a source of UV radiation and as a field-enhancing antenna. The formation of this capacitively coupled plasma is facilitated by a thin metal coating applied to one of the burner's pinches, which is a source of secondary electrons.

Although the burner outputs about 1800 lm, which is about as much as a standard 75 W low-voltage halogen lamp with a similar service life, the higher luminance of the electrical arc enables a higher optical efficiency of the lamp-mirror system. As a results this MPXL 30W R can replace 100+ W halogen reflector lamps in general lighting systems. The difference in power consumption is much more limited in special lighting applications as the overdriven halogen lamps used in this case are more efficient. The key advantage of the xenon-MH lamp system is then its much longer service life. Despite its advantages over incandescent lamps, this type of light engine was never developed into a commercial product due to advent of highly efficient semiconductor lamps which revolutionized the lighting industry.