|Xenon short-arc lamp.
Lamps like this are what replaced carbon arc lights in many applications where no other technology would do. Both types of lamp produce light with a small, extremely intense electric arc. Unlike most other kinds of lamps, the light all comes from one very small spot, and there's a huge amount of it. This makes these bulbs suitable for use in search lights and movie projectors where the light needs to be focused into a strong beam: By putting a small source of light at the focal point of a parabolic reflector, you get a beam.
The main advantage of a xenon short arc lamp is that the spark is completely contained in the bulb, which is filled with a fairly high pressure of xenon gas (high enough that larger versions can be quite dangerous and are always handled with a protective case to guard against flying glass). Carbon arc lights operate in the open air, creating smoke and slowly consuming the electrode: They are not completely gone yet, but are pretty much relegated to the point of historical curiosity at this point.
Source: eBay seller cieinternational
Contributor: Theodore Gray
Acquired: 8 December, 2007
Text Updated: 8 December, 2007