Talk:Xenon arc lamp

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Contents

[edit] Edit conflicts

I accidentally removed Atlant's clarification edit explicitly labeling the anode / cathode in the photo. I tried to put it back in but it looks like we were both editing the page at the same time!

Thanks for letting me know. As you could see by my edit summary, I was wondering what happened. ;-)
Atlant 18:48, 6 March 2006 (UTC)

[edit] Stubs for further Development (moved out of article)

Stub: Supply Design

Stub: Series Injection Igniter

Stub: Typical Circuit

[edit] About the Intro

Shouldn't the section titled "Introduction" either be moved to the Introduction or be renamed? Patiwat 11:24, 2 November 2006 (UTC)

I retitled that section -- how's it look now?
Atlant 13:42, 2 November 2006 (UTC)

[edit] Sentence is garbled

The first phrase of the following sentence needs editing:"An O-ring seals of the tube, so that the naked electrodes do not get into contact with the water." I do not know what the author intends here; so, I will not attemps an edit.


It's been fixed...I was gonna do it but someone beat me to it.

[edit] Under-counter lighting

I recently purchased some xenon under-counter lighting. Reading the article here, it appears this is not what I purchased. Or maybe it is? Can someone explain? Maury 02:05, 1 December 2007 (UTC)

While I'm here... There's a sentence in the History section that I find really confusing... The white, continuous light generated with this arc is of daylight quality but plagued by a rather low efficiency in terms of lumens of visible light output per watt of input power Ok, what is this referring to? The sentence immediately before this is talking about carbon arcs. but this is an article about xenon arcs, so "this arc" could refer to either. Can someone fix? Maury 02:11, 1 December 2007 (UTC)


Perhaps you got some halogen lights? Not really similar, but those are often under the counter lights. KeepOnTruckin Complain to me | my work here 03:34, 2 December 2007 (UTC)
Maybe, but I doubt it. They look like little florescent lamps about 1/2 inch long, and the packaging stated they were a florescent-type system. Maury 14:00, 2 December 2007 (UTC)
Your under-counter lights are xenon-filled tubes, but they are not arc discharge lamps. They are outside the scope of this article. jhawkinson 18:00, 2 December 2007 (UTC)
Soooo, in what article are they within scope? Maury (talk) 23:07, 7 December 2007 (UTC)

It sounds like you have some really interesting counter lights there Maury!

It is unlikely the lamps are xenon arc-lamps or even contain xenon gas. Xenon has the rather annoying property of only efficiently producing light at extremely high current densities. That's why xenon arc lamps have to be run at such high current levels, and why the discharge space is so small. 15,000 watts drive power into a volume the size of a marble!

Many manufacturers have started using "xenon" to describe any lamp which emits a blue-white or "icy white" spectrum. The lamps in your counter light fixtures are most likely made of fused quartz, with a tungsten filament, and pressurized with halogen gas. They may have a coating on the lamp envelopes to filter the light and give it a blue tint. Search for "Quartz Halogen" or "Tungsten Halogen"

It is also possible, but less likely due to cost, that your lights use Compact Fluorescent technology. They would take the form of small "tubes" as you describe, but each fixture would need to include a miniature power supply for the lamp.

If you're feeling keen, disassemble one of the fixtures, take some photos, post them to the commons, and link them to the talk page. We can take a look at them and identify what you have.

HyperLight

[edit] Pressure

The article notes several times that the xenon is under pressure (a lot of pressure). How much pressure is typical?

Also, I don't see an explanation for exactly why high pressure is required for this application or at least practically beneficial, except that it is for "maximum efficiency". Does that mean to get the most visible light vs UV/IR? Or the most light vs heat? Or…? How relevant are spectral emission line-broadening effects? Would be good to state more specifically and in lay terms what the utility of it is here. DMacks (talk) 00:14, 31 January 2008 (UTC)

Re: Charge pressure in a XENON lamp

HyperLight Research replies:

To contact ME: hyperlight.research###remove...thisss.sPaMMerZZZ.#%$??@@##...gmail.com ...I'm an Electrical Engineer and I would be happy to help you. For free. Forever. Even if you're for-profit (just so you don't KILL yourselves) ... :)

...

The reason xenon lamps are charged at dangerously high pressures is to maximize their efficiency.

The higher the pressure, the more xenon atoms per mm2 there are between the ANODE and the CATHODE. The greater the density of xenon atoms, the greater the probability that an electron launched from the CATHODE will strike one, or ideally MORE than one. xenon atoms and release more of its energy before being received by (and dumping its remaining energy to) the ANODE.

That means a smaller, cheaper, lamp can generate MORE LIGHT per volume as long as the user can keep it COOL.

Energy dumped to the ANODE is very, VERY bad. Almost all (like 99.5%) of the electron impact energy on the ANODE is converted to heat.

Thus it is WASTED.

But even worse, it has to be DISPOSED OF; or the anode (or a portion of it) will become WHITE-HOT, vaporize, and deposit itself as a reflective (mirror-like) metal film all over the inside of the lamp envelope; destroying the lamp.

The solutions to this are either by making the anode HUGE and radiating the waste electrons' energy it as infrared energy (radiant heat), or in the case of large (> 10KW) lamps like used in the IMAX projection system; dumping the waste energy to a cold-water coolant loop.

There is a certain "sweet spot" that balances discharge medium pressure (and hence envelope thickness), ignition voltage, operating voltage/current, and emission spectrum, that maximizes electrical-to-optical conversion efficiency.

I'd have to check my datasheets to be sure, but for a 3KW pure-xenon lamp with thoriated electrodes, this pressure is typically around 525psi COLD and 1,200psi HOT.

ALWAYS RESPECT A XENON ARC LAMP. IT IS LIKE A HAND GRENADE COLD ....AND A STAR-IN-A-BOTTLE HOT!!!!!!!!

WE TEST THEM FROM BEHIND 10MM OF POLYCARBONATE SHEET (BULLET PROOF GLASS!!!)

References: http://dafnwebpd.sylvania.com/idmweb/doccontent.dll?LibraryName=ecomcspd^dafnctpd&SystemType=2&LogonId=241c7e274368aaf35f0aeb47d1c60dc9&DocId=003673675&Page=1

For the curious, the SYLVANIA/OSRAM website has a 90+ page document on xenon lamp characteristics.

Perhaps we should add a copy of it to the Wiki commons, if only for the public good/safety!!

Have a look: http://www.sylvania.com/cgi-bin/MsmGo.exe?grab_id=90&EXTRA_ARG=FILTERNAME%3D%2540URL%00%26FILTERVALUE%3Dwww%252Esylvania%252Ecom&host_id=42&page_id=6816256&query=xenon+arc+lamp&hiword=LAMPING+arc+xenon+lamp+LAMPO+LAMPA+LAMPED+LAMPS+


Another user asks: ""I don't think most film students would agree that xenon lamps "advantageously" replaced the older carbon arc lamps for theatrical projection. Quite the contrary, xenon projectors usually are considerably less bright than the old arc lamps, resulting in a conspicuously inferior image on the screen. This is especially true of classic Technicolor films. As time passes, of course, there are fewer and fewer people who remember the quality of carbon arc projection. —Preceding unsigned comment added by 12.214.62.215 (talk) 00:41, 18 February 2008 (UTC) ""...

HyperLight Research replies:

It depends on how you define "advantageously".... ;)

In terms of overall "brightness" versus input power, a XENON arc lamp ABSOLUTELY ANNIHILATES an open-air carbon lamp. By like 3:1 !!! Usually MORE... although there is no guarantee that whatever facility you visited for comparison replaced their carbon-arc sources with xenon-arc lamps of at least 1/3 power.

Perhaps what you are responding to is that a carbon-arc lamp has a better CRI (color rendering index) compared to a xenon lamp, because it has somewhat better emission in the red band.

For more info see: http://en.wikipedia.org/wiki/Color_rendering_index

For reference.. -BARE a carbon-arc lamp appears "daylight white" while a xenon-arc lamp is best described as "icy white" and has a noticeable BLUE cast. However, this can (and almost universally IS) corrected by a dichroic filter (typically called a "hot mirror") between the light source and the projection medium.

For more info see: http://en.wikipedia.org/wiki/Hot_mirror

Xenon arc lamps have universally replaced carbon-arc light sources in theatre projection for numerous reasons:

The most significant is reliability and maintenance requirements. In carbon-arc projectors, the carbon rods are quickly consumed during use. Typical longevity for a set of 12-inch (30 centimeter) carbon rods is about 90 minutes, although some systems can reach up to 3 hours.

In comparison, a xenon arc-lamp has a typical life of approximately 2,000 hours and often up to 5,000 hours. This is the equivalent of up to 3,400 sets of carbon rods that would have to be manually changed, cleaned, and re-lit.

Secondly is emission density.

An IMAX movie projector (which by design essentially requires the "best" light source humans currently have) uses a 20KW or LARGER XENON arc lamp instead of a carbon arc lamp. This is because a XENON lamp produces a *much* shorter arc length (but with equivalent brightness) than a carbon-arc lamp, due to the extremely high pressure (and hence arc density) of the discharge medium.

Because the light source is smaller, it better approximates a true "point source" (infinitely small / infinitely bright) and can better resolve detailed images on the large screen with higher resolution.

This is ESPECIALLY significant on a very large (10+ meter tall) screen as is used in the IMAX projection system.

To learn more about the physics behind this, check out the Wikipedia articles on

optical POINT SOURCES: http://en.wikipedia.org/wiki/Point_source#Light

and APERTURE: http://en.wikipedia.org/wiki/Aperture

This is *my* 20-minute donation to the global knowledge pool. Contact me if you need more info!!!

Cheers!!!

^C^