<P> Xenon short - arc lamps also are manufactured with a ceramic body and an integral reflector . They are available in many output power ratings with either UV - transmitting or blocking windows . The reflector options are parabolic (for collimated light) or elliptical (for focused light). They are used in a wide variety of applications, such as video projectors, fiber optic illuminators, endoscope and headlamp lighting, dental lighting, and search lights . </P> <P> Xenon short - arc lamps have a negative temperature coefficient like other gas discharge lamps . They are operated at low - voltage, high - current, DC and started with a high voltage pulse of 20 to 50kV . As an example, a 450 W lamp operates normally at 18 V and 25 A once started . They are also inherently unstable, prone to phenomena such as plasma oscillation and thermal runaway . Because of these characteristics, xenon short - arc lamps require a proper power supply that operates without flickering in the flame, which could ultimately damage the electrodes...</P> <P> In 1991 "xenon headlamps" were introduced for vehicles (BMW E32). These are actually metal - halide lamps; the xenon gas is used only to provide some light immediately upon lamp startup, as required for safety in an automotive headlamp application . Full intensity is reached 20 to 30 seconds later once the salts of sodium and scandium are vapourised by the heat of the xenon arc . The lamp envelope is small and the arc spans only a few millimetres . An outer hard glass tube blocks the escape of ultraviolet radiation that would tend to damage plastic headlamp components . The first xenon headlamps contained mercury; newer types do not . </P> <P> These are structurally similar to short - arc lamps except that the distance between the electrodes in glass tube is greatly elongated . When mounted within an elliptical reflector, these lamps are frequently used to simulate sunlight in brief flashes, often for photography . Typical uses include solar cell testing, solar simulation for age testing of materials, rapid thermal processing, and material inspection . </P>

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