Re: Halogen lamps

[P3D Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

Good link on lamps in general provided by Bob Wier. Thanks. 
While in the process of reading it, John R comments

>Thanks - that explains an article I read last year, describing the work of
>some technicians who maintain a large IMAX projector. The article
>explained that the bulb is large, and filled with xenon under very high
>pressure, so extreme care has to be taken in changing it. The technicians
>were pleased that all the times a bulb had exploded, it had been in its
>armored enclosure, so nobody had been hurt. :-)

Yes and if you've seen the size of those monsters, I mean lamps, you 
would realize why. The ones I saw exhibited at a Imax theatre were
roughly 4 feet long and I think ran in the 10,000W range or somewhere
in that vicinity. Where I work, (holidays at the moment. :-)) we use
a teeny weeny 6 inch Xe 450W lamp and boy is it powerful nonetheless.
It's generates an intense white arc and is very suitable for reimaging
the arc to a tiny spot. It also generates alot of ozone, which has to
be suitably exhausted, since ozone is poisonous.

John R quotes Bob W quote from the article

>...Since the bulb is small and usually fairly strong, the bulb can be filled
>with gas to a higher pressure than usual. This slows down the
>evaporation of the filament. In addition, the small size of the
>bulb sometimes makes it economical to use premium fill gases such
>as krypton or xenon instead of the cheaper argon. 

BTW, I would like to clarify, in the above post, before anyone gets mislead.
The Xenon lamp used in Imax and the one we use is not the same type of lamp
as the quote above. In the quote above, they are referring to a filament 
lamp filled with Xenon. In the Imax theatre, the Xenon lamp they use and
we use is an arc type lamp. This means that their is no filament perse
as in a tungsten lamp. The light generated in a filament lamp is due to
the high temperature of the filament. In an arc lamp it is generated
by the electric arc through a gas. These lamps also need special power
supplies to initiate the conduction of the gas.

Gabriel




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