page_title: Xenon arc lamp
section_title: Lamp construction
hierarchical_section_title: Xenon arc lamp / Lamp construction
caption_attribution_description: Čeština: Xenonová výbojka 3 kW OSRAM v otevřeném ochranném transportním pouzdru. Zdroj: Carl Roett / HyperLight Research Deutsch: Eine 3KW Xenonlampe. Sie ist etwa 12 inch (~30,5cm) kang und wird in mittelgroßen Theaterprojektoren verwendet. Das Xenongas innerhalb der Lampe befindet sich im Betrieb sowie im ausgeschalteten zustand unter extrem hohen Druck. Die Plastikhülle rundherum fungiert als Schutz der Glashülle der Lampe sowie als Transportbox. English: An 3 KW Xenon Short-Arc Lamp used in medium size movie theatre projectors. It is approximately 12 inches long. The xenon gas inside this lamp is at extremely high pressure, even when the lamp is not operating. The plastic shield surrounding the lamp is designed to contain pieces of the lamp envelope if the lamp is dropped and explodes during shipping.
context_page_description: A xenon arc lamp is a highly specialized type of gas discharge lamp, an electric light that produces light by passing electricity through ionized xenon gas at high pressure. It produces a bright white light that closely mimics natural sunlight, with applications in movie projectors in theaters, in searchlights, and for specialized uses in industry and research to simulate sunlight, often for product testing.
  Xenon headlamps in automobiles are actually metal-halide lamps, where a xenon arc is only used during start-up to correct the color temperature.
context_section_description: All modern xenon short-arc lamps use a fused quartz envelope with thoriated tungsten electrodes.  Fused quartz is the only economically feasible material currently available that can withstand the high pressure (25 atmospheres for an IMAX bulb) and high temperature present in an operating lamp, while still being optically clear.  The thorium dopant in the electrodes greatly enhances their electron emission characteristics.  Because tungsten and quartz have different coefficients of thermal expansion, the tungsten electrodes are welded to strips of pure molybdenum metal or Invar alloy, which are then melted into the quartz to form the envelope seal.
  Because of the very high power levels involved, large lamps are water-cooled. In those used in IMAX projectors, the electrode bodies are made from solid Invar and tipped with thoriated tungsten. An O-ring seals the tube, so that the naked electrodes do not contact the water. In low power applications the electrodes are too cold for efficient electron emission and are not cooled. In high power applications an additional water cooling circuit for each electrode is necessary. To reduce cost, the water circuits are often not separated and the water needs to be deionized to make it electrically non-conductive, which lets the quartz or some laser media dissolve into the water.
  To achieve maximum efficiency, the xenon gas inside short-arc lamps is maintained at an extremely high pressure — up to 30 atmospheres (440 psi / 3040 kPa) — which poses safety concerns.  If a lamp is dropped or ruptures while in service, pieces of the lamp envelope can be thrown at high speed.  To mitigate this, large xenon short-arc lamps are normally shipped in protective shields, which will contain the envelope fragments should breakage occur.  Normally, the shield is removed once the lamp is installed in the lamp housing.  When the lamp reaches the end of its useful life, the protective shield is put back on the lamp, and the spent lamp is then removed from the equipment and discarded. As lamps age, the risk of failure increases, so bulbs being replaced are at the greatest risk of explosion. Lamp manufacturers recommend the use of eye protection when handling xenon short-arc lamps. Some lamps, especially those used in IMAX projectors, require the use of full-body protective clothing.
caption: Perspective view of 3 kW lamp showing plastic safety shield used during shipping.
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