Talk:Flashtube

message: An anonymous editor changed the minimum operating voltage from 100 volts up to 250 volts, and someone else reverted them right back.
I agree with the anonymous editor: I've always found flash lamps operating from something like 250 volts and up (using a voltage doubler from mains voltage in the U.S. and a straight rectifier for 230 vac systems). Even battery systems (as in camera flash units) tend to be 300-voltish.
Has anyone seen any real-world units that operate on 100 volts?
Atlant 12:52, 12 February 2006 (UTC)
replies: text: You are probably right. I revert unexplained anon edits TOO easily sometimes.--Deglr6328 22:16, 12 February 2006 (UTC)
thread_title:  Minimum operating voltage 

message: Requesting information on the subject matter of Xenon flash lamp for Color spectrophotometer, as employed by GretagMacbeth, DATACOLOR etc.Information requested as under :
1. Technial specifications of Voltage, Wattage, Amperage etc.
2. Source from where to buy.
3. Any information relevent.
:How about searching THE INTERNET.--Deglr6328 16:18, 2 May 2006 (UTC)
thread_title:  Xenon flash lamp in Color Spectropphotometers 

message: Discharge lamp redirects here.  Wouldn't it be better if it redirected to Gas-discharge lamp? Bryson430 13:29, 2 August 2007 (UTC)
replies: text: Worse, I've realised that there's a Discharge Lamp and a Discharge lamp article.  I'll try and sort it out. Bryson430 13:31, 2 August 2007 (UTC)
thread_title: Discharge Lamp?

message: I've constructed many flashtubes, and power supplies for them. The section on operation seems to be a bit confusing. The first sentence sounds like it's describing a "Simmer Voltage" type triggering technique, (where the gas is ionized via a constant spark streamer before cuurent is transmitted to the electrodes). The statement "thousands of amperes" is a bit modest; good for small lamps; but more commonly, peak amps can be in the tens-of-thousands to the millions range. The next few sentences seem to be a bit confused themselves, but now apparently describing "external triggering". The last two sentences seem to belong in the "Construction" section. I propose this rewrite as an alternative:
--
The electrodes of the lamp are usually charged with a relaively high voltage, (generally betwwen 250 to 5000 volts), but the gas exhibits extremely high resistance and the lamp will not conduct electricity until the gas is ionized. Once ionized, or triggered, a spark will form between the electrodes, allowing the capacitor voltage to conduct. The sudden surge of amps quickly heats the gas to a plasma state, where electrical resistance becomes very low. There are several methods of triggering.
  
"External Triggering" is the most common method of operation, especially for photographic use. The electrodes are charged to a voltage high enough to respond to triggering, but no higher than the lamp's self-flash threshold. An extremely high voltage pulse, the trigger pulse, is applied directly to, or very near, the glass envelope, usually supplied by a step-up transformer. The short, high voltage pulse creates a capacitor effect, generating an equal but opposite voltage inside the tube. This causes ions to stack up on one or both of the electrodes, forming spark streamers, which propagate at a speed of 1 centimeter in 60 nanoseconds. (A trigger pulse must be have a long enough duration to allow one streamer to reach the opposite electrode, or erratic triggering will result.) The triggering can be enhanced by putting a metal band or reflector onto the glass, or by wrapping a thin wire around the lamp from electrode tip to electode tip. When the spark streamers connect, the full amp load from the capacitor conducts through the lamp, heating the xenon to a high enough temperature for the emmision light. When this current pulse travels through the tube, it ionizes the atoms, causing them to jump to higher energy levels. Within the arc plasma three types of particles exist; electrons, positively ionized atoms, and neutral atoms. The ionized atoms number less than 1%, and accounts for all the emitted light. As they recombine with their lost electrons they immediately drop back to a lower energy state, releasing photons in the process.
"Series Triggering" is more common in high powered, water cooled flash lamps, such as those found in lasers. It is almost identical to external triggering, except series triggering applies the high trigger voltage to the cooling water itself, and often the housing of the unit, so care must be taken when handling these type of systems.
"Simmer Voltage Triggering" is the least common method. In this technique, the capacitor voltage is not initially applied to the electodes, but instead, a high voltage spark streamer is maintained between the electrodes. The high current from the capacitor is delivered to the electrodes using a thyristor or a spark-gap. This type of triggering is used mainly in very fast rise time systems, typically those that discharge in the microsecond regime, such as used in high speed stop-motion photography. If this type of system is not used, the spark streamers will still be in contact with the glass when the full amp load passes through the tube, causing wall ablation. Some microsecond flashlamps are triggered by simply "over-volting", which is by applying a voltage to the electrodes which is much higher than the lamp's self-flash threshold, using a spark gap.
-- 
I have a photo here that shows why external triggering is a bad idea at very high speeds, but not sure how to upload it here. http://en.wikipedia.org/wiki/Image:Xenon_high_speed_flash_and_external_triggering.jpg#Summary
I think this rewrite gives a better view of different methods of operation. The best book I've ever found on the subject is the Perkin-Elmer catalog, (no, really. It is packed with useful information from the people who invented them, backed up with 12 impecible references of its own), which you can read at http://optoelectronics.perkinelmer.com/content/RelatedLinks/CAT_flash.pdf. Another very good source of information, especially for some simplified math equations, (proper operation will never be achieved without proper math), see Don's Xenon Flash and Strobe webpage at http://members.misty.com/don/xeguide.html#eg . Or read the bible of the industry, "Electronic Flash and Strobe" by Harold Edgerton.Zaereth (talk) 01:10, 17 October 2008 (UTC)
thread_title:  Operation Section is a bit confusing 

message: The last line in this section is incorrect. Although the low voltage number of 250 is correct, laser lamps often operate at voltages as high as 5000, but rarely higher than 6000, (beyond this voltage gasses begin to ionize without any trigger, ie: self-flash). Some lamps infact do operate well beyond their self-flash threshold, but those systems are rare. The next problem I see in the last line is the phrase "depending on [] the specific gas mixture. Gasses in flashtubes are never mixed for one simple reason. Electricity will pick the path of least resistance. Arc plasma contains less than 1% of ionized particles, which produce 100% of the light. So the electricity will tend to ionize only the atoms that have the lowest electrical resistance. So, if you have a xenon/neon mix, what you really have is a neon flashtube.Zaereth (talk) 00:52, 31 October 2008 (UTC)
thread_title:  Construction section 

message: Since there has been no objections to my proposed changes, I have gone ahead and implemented them. If there is any comment, please make it here. Thanks.Zaereth (talk) 00:59, 22 November 2008 (UTC)
thread_title:  Changes have been implemented 

message: It might be helpful to add a full paragraph in the article on the circuit you're describing there. The circuit is often called a "Variable Pulse Width Control" circuit, as is described in the Perkin Elmer catalog which I referenced. There are many ways to put one together, and can even be designed to produce square-wave pulses. Perhaps if we start out with the name, then a small paragraph to describe the circuit that would fit better with the style of the rest of the article. What do you think?Zaereth (talk) 23:22, 4 December 2008 (UTC)
replies: text: I think that sounds like a great idea. Would it be legally permissible under Fair Use to illustrate the concept with one of the schematics from the document that I used as a reference in the article, or a schematic based on one of those (possibly simplified, for clarity?)? Ilikefood (talk) 23:54, 4 December 2008 (UTC)
replies: text: I'm rather new to Wikipedia, so I don't know the answer to that question. Personally, I think a paragraph that gives a basic overall view is sufficient, as an encyclopedia should not be an instruction manual. Those who are interested, I think, should have no problem checking out the reference. Zaereth (talk) 00:07, 5 December 2008 (UTC)
replies: text: Okay. Ilikefood (talk) 00:11, 5 December 2008 (UTC)
thread_title:  Vraiable Pulse Width Control triggering 

message: Having completed some further research, I'm adding a couple of new sections, one on other gasses, and the other on safety. If there is any question or comment, please make it here.Zaereth (talk) 19:01, 17 December 2008 (UTC)
thread_title:  Other gasses and safety 

message: A statement was recently added to the Application section about the use of xenon flashtubes in the movie The Andromeda Strain. Since this is not an actual application, I have moved it to a new section labeled popular culture. Zaereth (talk) 18:09, 9 April 2009 (UTC)
thread_title:  Popular culture section 

message: I reverted the following edit as unsourced and incorrect. First designed by engineers Hunter H. Hetfeld and Luke J. Valenter in the late 80's, I'll try to gather some sources on the origins, but flashtube technology got its start in the late 1800s, as open air sparks by photographers like Ernst Mach. I believe Tesla created the first "contained arc" flash apparatus, but it was Harold Edgerton who was the main pioneer in the field, and that was back in the 1930s. Flashtubes have been used in lasers since the 1960s. Zaereth (talk) 23:46, 18 January 2010 (UTC)
thread_title:  Reverted unsourced edit 

message: * http://www.flickr.com/photos/istargazer/217878708/
Unlike the laser beam, the light is gradually dimmed and then changed to another colour...???--124.78.209.251 (talk) 05:10, 26 January 2010 (UTC)
replies: text: I'm not sure what you're asking for. Can you clarify? The light in the above photo is from an incandescent bulb. There is nothing gradual about a flashtube. The light is full spectrum, (all colors), and the flash quickly builds to full power, and then shuts down instantly, as seen in the animation st the bottom of the article. Zaereth (talk) 17:28, 26 January 2010 (UTC)
thread_title:  What is it called for ..... 

message: Controversy: Was it invented in the 1930s or in 1927? --Janke | Talk 17:11, 29 October 2010 (UTC)
replies: text: The first flash apparatus Edgerton made used a mercury arc rectifyer. The flashtube (ie: noble gas discharge lamp) came afterward. It might be worth mentioning that Edgerton employed General Electric to do the glassblowing, but the flashtube as we know it today is something that evolved over the entire decade of the 1930s. Zaereth (talk) 03:00, 1 November 2010 (UTC)
thread_title:  History 

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thread_title:  External links modified (January 2018) 

message: A point and shoot camera doesn't interpret spectral lines (nor does an expensive one).  Sensors pick up a wide range of UV through IR, filtered at varying efficiency by the hot mirror.  Whatever gets through that might selectively make it through the red, green, or blue color filter arrays depending on wavelength.  That's at best.  At worst, the blue filters are letting the least light through, their photo-sites are amplified most heavily, and all we're seeing is the massive CCD bloom from the blasted out exposure of a flash arc.   </br>
The old Foveon sensors used the response of different depths of silicon to different wavelength ranges to detect multiple colors at the same photosite, but even those required heavy de-matrixing in order to get component colors.  Actual spectral cameras exist, but those weren't used for these pictures.  The pages for the pictures in question link to references that don't actually apply (a CCD and a photo-cathode aren't heavily related, nor are the responses of a very specific Fuji sensor to various wavelengths of light when narrow-band filters are stuck in front of it). Certainly 900nm IR isn't being picked up as a 450nm harmonic.  A quick web search indicates that lots of narrow-band blue-pass filters have a peak of much more light passed in the 900nm region though. </br>
In case that wasn't enough, the EXIF of the image indicates the white balance was set to auto, so there's no predictable white reference.  Who knows what the camera would choose as white when there's a blasted out arc in the middle and a flat surface we can only guess by the caption is illuminated by a mixture of the hypothetical greenish blue (which all image editing software indicates it isn't, at least noticeably so.  Depending on the pixel it's either 1/255 greener or 1/255 bluer. A Shortfall Of Gravitas (talk) 11:53, 22 April 2023 (UTC)
thread_title:  Picture captions wrong / misleading