Xenon short-arc lamp: Difference between revisions
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Most lamphouses have a mechanical adjustment to shift the position of the cathode end, while the anode end is supported by a post or yoke with an adjustable height. The height of the anode can usually be set during the initial installation, with only the cathode end being adjusted at every lamp change. If you center the cathode end, it will be apparent if the anode position is incorrect because the lamp will not be straight. | Most lamphouses have a mechanical adjustment to shift the position of the cathode end, while the anode end is supported by a post or yoke with an adjustable height. The height of the anode can usually be set during the initial installation, with only the cathode end being adjusted at every lamp change. If you center the cathode end, it will be apparent if the anode position is incorrect because the lamp will not be straight. | ||
[[File:anode-shadow.jpg|right|thumb|450px|Shadow of the anode assembly seen on screen during lamp alignment, once the lens has been removed. ''Photo credit: Katherine Greenleaf'']] | |||
During alignment you will see the following on screen: The shadow of the anode assembly at the end of the lamp is the dark circle, immediately ringed by visible plasma (the electron arc). Surrounding it is the circle of light collected by the [[reflector]], and reflected upon the screen. This area comprises most of what we see, and should appear bright white and essentially even in luminance upon completion of the alignment. | During alignment you will see the following on screen: The shadow of the anode assembly at the end of the lamp is the dark circle, immediately ringed by visible plasma (the electron arc). Surrounding it is the circle of light collected by the [[reflector]], and reflected upon the screen. This area comprises most of what we see, and should appear bright white and essentially even in luminance upon completion of the alignment. | ||
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==Aging== | ==Aging== | ||
[[File:Xenon lamp-blackening envelope.jpg|right|thumb|400px|An aging lamp with burnt off tungsten blackening the envelope.]] | |||
Xenon lamps have a fixed arc gap, but over time the tungsten of the cathode gets burnt off by the plasma, increasing the distance between the electrodes and reducing the light emitted at a given power draw. Burnt off tungsten can also deposit on the envelope, creating black spots and accelerating the effects of aging. | Xenon lamps have a fixed arc gap, but over time the tungsten of the cathode gets burnt off by the plasma, increasing the distance between the electrodes and reducing the light emitted at a given power draw. Burnt off tungsten can also deposit on the envelope, creating black spots and accelerating the effects of aging. | ||
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==Lamp Safety== | ==Lamp Safety== | ||
[[File:Safety gear.jpg|right|thumb|200px|Example of safety gear worn during a lamp change]] | [[File:Safety gear.jpg|right|thumb|200px|Example of safety gear worn during a lamp change]] | ||
An exploding lamp will expel shrapnel in all directions, so a face shield and full-body protective clothing must be worn when handling xenon lamps. Some lamp manufacturers sell safety gear, | The Xenon gas in cold Xenon lamps measures approximately 300 times atmospheric pressure. The Xenon gas in hot Xenon lamps measures approximately 1400 times atmospheric pressure, both of these are extremely dangerous! An exploding lamp will expel shrapnel in all directions, so a face shield and full-body protective clothing '''must'' be worn when handling xenon lamps. Some lamp manufacturers sell safety gear, you can also use protective clothing designed for welding. | ||
Each theater should stock safety gear in multiple sizes. This is especially important for gloves, because ill-fitting gloves will limit dexterity and make handling the lamps more dangerous. | Each theater should stock safety gear in multiple sizes. This is especially important for gloves, because ill-fitting gloves will limit dexterity and make handling the lamps more dangerous. | ||
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Never open the lamphouse or handle the lamp when it’s hot. A hot lamp is under much greater pressure than a cool lamp. Let the lamp cool for at least 10min before handling it. | Never open the lamphouse or handle the lamp when it’s hot. A hot lamp is under much greater pressure than a cool lamp. Let the lamp cool for at least 10min before handling it. | ||
Before performing a lamp change, prepare your workspace. Place the empty shield or other protective enclosure on a clean, clutter free surface with adequate room to work. It should be open and ready to receive the used lamp. Make sure you have a clear path to the lamphouse with no obstacles or tripping hazards. | |||
===Safety Gear Manufacturers=== | ===Safety Gear Manufacturers=== | ||
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*In practice, their packaging is secure enough that it can be very difficult to destroy the lamp in this fashion. | *In practice, their packaging is secure enough that it can be very difficult to destroy the lamp in this fashion. | ||
==Resources== | |||
*[http://zeiss-campus.magnet.fsu.edu/articles/lightsources/xenonarc.html Fundamentals of Xenon Arc Lamps] | |||
==See Also== | ==See Also== | ||