Talk:Xenon arc lamp

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)

Answers article
The answers.com article appears to be a word for word copy paste job of this article even down to the wikilinks, pics, and all. I'm not sure if this falls under plagiarism or fair use. I've read here and here that there are issues with answers.com using wikipedia articles but this seems too far to be within the realm of fair use. What needs to be done about this if anything? IRMacGuyver (talk) 07:08, 22 March 2009 (UTC)

Stubs for further Development (moved out of article)
Stub: Supply Design

Stub: Series Injection Igniter

Stub: Typical Circuit

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)

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.

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 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

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^

I note the point above about bulletproof windows. I wonder if we should change the description "protective clothing" back to the original "armor". This danger is not something to minimize. I recall a conversation with the optical engineer who built the projection system for the situation displays used in Cheyenne Mountain, which used 1kW (or larger) xenon lamps. He said that the person changing those bulbs had to wear a "bomb suit". I also recall the Osram handling instructions specifying wearing "artery protection".

On another topic, I think it would be interesting if someone could add a typical emission spectrum. The large near IR emission lines are sometimes useful.

--AJim (talk) 04:57, 11 January 2009 (UTC)

Major problems
This article has some major problems. One is probably the lack of references. The notion that anode heating from "electrons colliding into it" is wrong. The anodes are good conductors, and heat like any other conductor, from the resistance it contains. As long as the anode has sufficient surface area to cope with the number of electrons, and can dissipate heat well enough to prevent cracking of the seal, anode construction is really of little importance. Cathodes, on the other hand, heat from thermionic emission, and vaporize (sputter) from ions impacting the surface. They are usually sharp-tipped to aid in the emission of electrons, to control heat, and to keep the arc centered in the lamp.

Fill pressures of 25 atmospheres seems unlikely. I would definitely like to see a source for that. Krypton arc lamps are typically cold fill pressured to 4 atmospheres, (~ 60 PSI), which in itself is very high for a glass tube to contain.

There is not much mentioned about construction in the construction section. Arc lamp construction is almost identical to flashtube construction, and there are a variety of different methods besides just anode design and ribbon seals.

In the light generation section there is also a lot of talk about the anode, (much of it wrong), and the shape of the plasma, and the dangers of fill pressure, but not much about bound/bound-free/bound transitions and plasma dynamics that actually produce the light. Also, the light production in the near-IR is typically much higher than 10%.

I think this article should include all types of arc lamps, and not just xenon. Like flashtubes, or the neon sign article, the construction and operation for various types of gases is almost identical. The only real difference is in the impedence characterisitics and output spectrum, so it would only be redundent to create separate articles for all the different gases. I might be worth merging this article into the arc lamp article, or leaving that as a so-called "parent article" (like a DAB page, only a little more informative), with main-article links this article, (which I would remane DC arc lamp), and a carbon arc lamp article.

I am planning to begin sorting out all of the information in these, and the gas-discharge lamp article, in a couple of months. If anyone has any input, I am hoping to centralize the discussion over at Talk:Arc lamp. Thanks. Zaereth (talk) 01:14, 26 October 2011 (UTC)


 * OK, after checking several sources, it appears that pressures as high as 50 atmospheres is not uncommon for very small lamps. This has the effect of squeezing a very large arc into a very small space. This is only possible with very small (point source) lamps. This is possible for very small lamps due to the small internal volume, which doesn't allow for much energy stored in the form of pressure. While it does present a hazard of getting glass in one's eyes if it explodes, the low potential energy, (~ 2 joules for a 4 cubic centimeter volume at 50 atmospheres), does not usually pose a significant risk of glass penetrating skin. Safety glasses and gloves dueing handling are usually sufficient. Higher volumes need to use lower cold fill pressures so that the amount of energy stored does not exceed the structural integrity of the glass.


 * Anode design really is of fairly little significance compared to cathode design. The anode is usually made of pure tungsten. When good machinability is required, thoriated or lanthanated tungsten is used. Thoriated tungsten does not improve emissivity, however, but this is not a concern for the anode. The cathose is usually mader of porous tungsten, in which the pores are filled with a compound of barium calcium aluminate, which does increase emmisivity. This gives a lower work function which improves lifetime dramatically.


 * Tungsten doesn't bond to quartz, which is why molybdenum ribbons are often used. For rod seals, the rod of the electrode is wetted with a molten glass, (often borosilicate or BK7), which will bond to both the tungsten and the quartz. Rod seals can generally withstand much higher currents and very high temperatures. Both quartz and tungsten have low coefficients of thermal expansion, so cracking of the seal is only a real problem is the electrodes heat much more than the glass. The glass is usually shrunken around the electrodes of long-arc lamps to allow heat to be transmitted directly from the electrode, through the glass, into the cooling water. The cooling water, 9especially in laser long-arc lamps), often flows across the entire length of the lamp, including both electrodes, so deionized water must be used to prevent short circuiting.


 * The output spectrum in the visual range is nearly a pure continuum, with few spectral lines. 60% of the total output energy is concentrated in the near-IR, between 700 and 900 nanometers. 30% of the total output is in the near-IR, between 900 and 1400 nanometers. The near-IR is dominated with very strong spectral lines. Only 10% of the total output is concentrated in wavelengths shorter than 700 nanometers, (divided between both the visual and UV portions of the spectrum combined).


 * I will do even more research in the coming weeks while I compile a list of sources. Zaereth (talk) 23:56, 26 October 2011 (UTC)

HID Automotive Headlights
I was looking around for a reference to support the 30 bar claim for the pressure of the xenon filling. Although I did find a reference that made the same claim, it was not overly reliable as it had some details incorrect.

However, I did find something interesting that turned out (eventually) to have relevance. I discovered that the use of anything other than ordinary or halogen filament headlights, not exceeding 60 watts in power is not legal for road use in the United Kingdom (according to the letter of English, Scottish and Northern Ireland law). But because HID headlamp assemblies were approved by the EU and given an 'E' designation they became legal for use in the UK, but only on cars assembled in Europe (in practice, it appears a blind eye was turned for non EU manufactured cars). It is illegal to fit HID bulbs to non HID headlight assemblies as the approval applies to the assembly not the bulb. Since the UK has left the EU, HID headlight assemblies are now strictly illegal again as EU approvals no longer apply. However the preponderance of HID headlights suggests that there is probably not a lot anyone can do about it.

The important bit is that the EU approval for HID headlamps requires that "[HID headlight assemblies] shall achieve 90 percent of the (sic) final luminance within 300 milliseconds of power being applied" (curiously: it does not specify whether this is lumens or total light output). So not 20 to 30 seconds as the article currently states (the lamps themselves are likely to be fairly common world wide). I suspect that the 20 to 30 second has come from the first such headlight bulbs which were slow to produce any appreciable light output (making them fairly useless for vehicle headlight use because high brightness is required when (say) flashing one's headlight to alert another motorist of your presence - required by many jurisdictions). The point here is that a high pressure xenon filling (like tens of bar) is required to give the required light output within 300 milliseconds (which is pretty well how long it takes the arc to properly establish). It also means that the light output during normal operation is partially due to the xenon filling and partially due to the metal-halide once it evaporates (because the xenon does not magically disappear) making it a true hybrid lamp. (It does make you wonder why they didn't just stick with a straight xenon lamp but this may be because it was a development from early lamps with less xenon in the filling).

Current HID headlamps emit a bright almost pure white light when the arc is first struck but becomes (not always) noticeably slightly more greenish-blue as the metal-halide components evaporate taking just two or three seconds to do so. However, they are nowhere near the green/blue colour of a normal metal-halide lamp so the xenon is clearly contributing to the light output to a greater or lesser extent). 86.164.61.30 (talk) 17:19, 15 September 2021 (UTC)


 * I find it highly unlikely that such high pressures are used. At a cold-fill of 30 bar, you're talking in the area of about 450 PSI absolute, which tends to be a lot for any glass to handle, and the pressure increases massively during operation as the gas heats and expands. Typical xenon long-arc lamps run more often around the range of 500 torr, or about .67 bar, which is less than atmospheric pressure. Short-arc lamps can sometimes (rarely) get as high as 3000 torr, or around 4 bar (about 3 times atmospheric). As pressure increases, so does lamp efficiency, but starting becomes more and more of a problem, because as the triggering impedance increases exponentially so does the triggering voltage required. At such high pressures, because the voltage drop between the electrodes is so high (often much higher than the run voltage) a boost voltage is often needed to transition from a spark to a glow.


 * Metals are often preferred over xenon due to its high cost and lower resistance, which leads to lowered efficiency. Heavier atoms are more resistant and thus are more efficient than lighter ones. When it comes to mixing gases or vapors, the effect of the lighter gas on the output spectrum is extremely negligible, but the effect on efficiency is massive. A lighter gas only serves to reduce the efficiency of the heavier one. The only reason a fill gas is even needed in the first place is to start the lamp, and get it hot enough to vaporize the metal. Once that happens, nearly all the light is produced by the metal.


 * When it comes to gas discharge lamps, current density plays the most major role in determining the output spectrum and color; by far, far more than fill pressure or gas type. Current that is too low produces spectral-line radiation, while too high produces blackbody radiation resembling a blue-giant star. There is a sweet spot in the middle where the output is mostly greybody radiation, and this is where the arc appears the most white.


 * All in all, I think the automotive lamps are way out of place in this article, which is about a totally different kind of lamp. Just because it uses xenon as a starting point doesn't make it a xenon lamp in the technical sense, anymore than a fluorescent tube is an argon lamp. Zaereth (talk) 19:03, 15 September 2021 (UTC)


 * As I said: I haven't found a reference to support the claim so it may be incorrect. Your point about it being out of place is quite valid. It's totally unreferenced anyway, so that solves the problem. 86.164.61.30 (talk) 13:59, 16 September 2021 (UTC)
 * Xenon at low pressure produces very little light as you can see from high pressure sodium lamps when they are starting. To get a strong light from the xenon during starting of automotive metal halide lamp, you need significant amount of xenon pressure (Several atmospheres usually), as the xenon discharge is very inefficient. This is how automotive metal halide lamps can also operates without mercury. זור987 (talk) 18:41, 16 September 2021 (UTC)


 * Not necessarily. It would be more correct to say that xenon at low energies produces very little light. Pressure has an effect on efficiency, as well as arc length. The higher the pressure or the longer the arc length; the more efficient the discharge will be, but this is true for all gases. More accurately, the greater the number of ion transition for each electron; the higher the efficiency, which is both a function of pressure, diameter, and length. (Mostly diameter and length, as in all impedance equations pressure plays only a minor role. It's a matter of how many ions you can squeeze between the electrodes.) But the same problems occur for starting. Both longer arc length and higher pressures make starting the lamp more difficult, and in this aspect pressure plays the larger role. I could probably see it increasing to such high pressures after starting, because when a metal vaporizes it generally expands by a factor of 50,000 to 100,000 times in volume, but for a cold fill it doesn't seem too plausible. Of course, I may be wrong, seeing as how they are such small lamps, but what we really need are reliable sources that say it. I have plenty of sources on xenon lamps and arc lighting in general, but not much on automotive lamps. Most of that info is still proprietary and not yet really available to the general public. Either way, it's irrelevant to this article.


 * I might also add, that as gases go, xenon is the second heaviest, and heavier than most metals, so it has very high resistivity. Since resistance can be defined as the impedance required to change energy into work, xenon is the most efficient of all the gases except radon, and radon is not used for obvious reasons. A typical xenon long-arc lamp at 500 torr can have efficiencies ranging from 50 to 70%, which is the highest of any lamp. The problem with xenon is that it is extremely rare; there are more gold atoms floating in the ocean than xenon in the atmosphere. Xenon is also exceptionally difficult to separate from krypton, so xenon pure enough for lighting is generally between $25,000 to $50,000 for a 10 liter bottle. Also, despite its high conversion efficiency, it produces a hell of a lot of NIR and UV, so the efficacy is only about 50 lm/w, or about half that of a fluorescent lamp (about 1/4 of a low-pressure sodium). Zaereth (talk) 19:14, 16 September 2021 (UTC)


 * By the way, there is an easy way to find out, if you want to do a little OR, but it doesn't help Wikipedia because it is OR. Anyway, simply put the lamp in a container full of water (or any liquid, oil is probably better). Hold it under a test tube filled with oil, then break the end off the lamp and measure how much gas comes out. From there it's a simple matter of math. (For lamps under vacuum you'd do the reverse, measuring how much space is left after the liquid floods in.) Not too precise, but will give a general idea. Still not good for the purposes of Wikipedia either. Zaereth (talk) 21:10, 16 September 2021 (UTC)