Xenon lights are true High Intensity Discharge or HID lamps. Although other bright light emitters like halogen and fluorescent bulbs are sometimes referred to as high discharge, technically speaking this is not true. The Xenon lamps are called high intensity because the intensity of the light that is emitted is of such high intensity. In fact the Xenon lamp is the closest to sunlight when it comes to color rendering and brightness.
The Xenon lamp is basically a fused quartz cylinder from which all air has been pumped out and replaced with the Xenon gas. Xenon is used because it ionizes quickly which means that you start to get visible light almost immediately after hitting the switch, unlike other metallic salts powered lamps. Because they are the closest to natural sunlight they are very often found in movie sets where this kind of light is required.
The reason why fused quartz is used is because the Xenon gas inside the lamp is kept under a lot of pressure, often in the neighborhood of 23 atmospheres. As of now this is the only commercially viable material that can tolerate such high pressures while still remaining transparent.
Enough about the technology then lets move on to a little bit of history. Xenon lights were first invented in the 1940s in Germany and have been put to one use or the other since then. The earliest use for this lamp was in search lights because Xenon lamps gave the ability to focus light more than conventional lamps. This meant that a narrow beam of light could be generated much more easily. Since then the most common use for these lamps has been in the movie industry and even now this is the place where large capacity Xenon lamps are used. The lamp is dangerous on two counts, one is because they generate a lot of heat in the near vicinity and this heat is sufficient to give heat burns to people who go too close. The other is that because the Xenon inside the lamp is kept under such high pressure, if the lamp breaks there is a danger of physical injury from flying bits of glass.
Although the movie industry is the most common and biggest user of Xenon lamps, lately vehicles have started coming out with Xenon headlights because the light is much brighter when compared with even halogen bulbs. The lamps in cars are however not pure Xenon lamps in the sense that the gas inside the bulb is not pure Xenon. They are actually metal halide lamps that contain Xenon. The reason for this is that Xenon is the only material that gives you instant light; using normal metal halide lamps will mean that it takes a couple of minutes to power up to optimum temperature. The Xenon in the lamps allow light right from the beginning, and also heats up the bulb sufficiently for the metal halide to take effect.
These kinds of lamps are not available generally speaking, and as of now only luxury car makers provide Xenon headlamps in their cars. Because of the heat generated by the bulbs, they are also not compatible with normal headlamp configurations and they need to come as a unit. They also emit very high quantities of UV light which requires masking so as not to damage delicate headlight components. They are, however, very useful and give off much better light than halogen lamps. Studies have showed that using Xenon lights in the headlights reduced the driver’s reaction times by up to 40%. The only negative thing about them is that because they are such high intensity it tends to cause glare to the drivers of oncoming vehicles. This problem is negated to a large extent in Europe by the compulsory use of automatic headlight levelers, although this is not made mandatory in the US. This is probably the one main reason why Xenon lights have not made it big there, because most road users feel that any safety aspect of having brighter lights is negated by you blinding the oncoming driver. This is however more due to the irresponsible installation of Xenon lights without automatic levelers than because of any inherent fault with the lamp.