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    Home-Built Pulsed Argon and/or Krypton (Ar/Kr) Ion Laser

    Sub-Table of Contents



  • Back to Home-Built Pulsed Argon and/or Krypton (Ar/Kr) Ion Laser Sub-Table of Contents.

    Basic Home-Built Ar/Kr Ion Laser Information

    Introduction to Home-Built Ar/Kr Ion Laser

    Although very similar in basic design to the home-built HeNe laser, in some ways, the Ar/Kr ion may be easier to construct and operate since pure argon, krypton, or a mixture may be used for the lasing medium and the quality of the vacuum system may be slightly less critical (though the better the vacuum, the longer the tube will operate between regassing - but this is a simple process). The power supply is a bit more complex but not by much given the existence of modern solid state high voltage rectifiers.

    Output wavelengths can be 488.1 nm (blue) and 514.5 nm (green) using argon and 647 nm (red) using krypton. Other colors may be possible.

    There are some brief comments by Syl Newmann, the author of the original SciAm article on the pulsed argon ion laser in the section: Experiences of People Who Have Built Lasers From Scratch.

    Home-Built Ar/Kr Ion Laser Safety

    There are two areas of safety considerations for the home-built Ar/Kr ion laser (and other similar lasers, for that matter): Provide proper warning signs for both the laser radiation and high voltage. Keep pets and small children out of the area and make sure everyone present is instructed as to the dangers. The use of proper laser safety goggles for the specific wavelength(s) of your laser are highly recommended.

    See the section: Argon/Krypton Ion Laser Safety for more info. However, the pulsed home-built ion laser uses a different sort of power supply than CW commercial types (unless you are attempting something similar to one of these) so some of the details may not apply,)

    For more information, see the chapter: Laser Safety and the more specific information in the section: Ar/Kr Ion Laser Safety. Sample safety labels which can be edited for this laser can be found in the section: Laser Safety Labels and Signs.

    Ar/Kr Ion Laser Construction References and Links

    If anyone reading this has built (or even attempted) an argon, krypton, or other similar ion laser from scratch, please send me mail via the Sci.Electronics.Repair FAQ Email Links Page!

    Home-Built Ar/Kr Ion Laser Description

    Like the HeNe laser the Ar/Kr ion laser is one of the simpler gas lasers in existence, it is probably in the middle of the range of difficulty of home-built lasers discussed in this document and "Light and its Uses", perhaps a tad on the easier side.

    Refer to Typical Home-Built Argon Ion Laser Assembly for a simplified diagram of the overall glasswork and power supply electronics.

    Guidelines to Assure a Successful Home-Built Ar/Kr Ion Laser

    These set of guidelines should be followed during construction of your first home-built pulsed ion laser. The factors below will greatly influence the ultimate output power, beam quality, and whether it produces any coherent light at all! Once you have a working laser, feel free to make modifications - one at a time. Thanks to George Werner (glwerner@sprynet.com) for his comments.

  • Obtain good quality fused quartz optical flats for the Brewster windows. They should be at least 1 mm thick to minimize distortion from the vacuum. These don't have to be expensive - plenty of low cost surplus optics is available. Any candidate Brewster window should pass the following tests:

    1. When viewed edgewise, it must NOT have a greenish (or other color) tint.

    2. When you hold it at arm's length and view something across the room through it, there should be no detectable magnification or minification.

    3. When viewed against a black background in a concentrated light beam (such as sunlight passing through an f/4 concentrating lens) it should show very little scattering of light (from incomplete cleaning or incomplete polishing).

    No other aspect of the laser tube assembly itself is as important as the quality of the Brewster windows to the ultimate outcome of this project! While, certain types of distortion won't prevent lasing (some may even make it more exciting with complex mode structures), this is a complicating factor your first laser can do without.

  • The ball-and-socket construction described in the in the SciAm article is probably not essential but provides an adjustment range so the laser tube assembly is less critical. If you don't use this approach, cut the ends of the laser tube to accept the Brewster windows only >after all glass working (including annealing) has been performed as these steps may affect the angles enough to increase losses. Take care that the angle is close to the correct value for your window material (35.8 degrees from the beam axis for fused quartz) with their perpendiculars as close to parallel as possible. (An error of up to 1/2 degree is acceptable in both cases. Use the /===\ arrangement, not /===/ (which will shift the optical axis). Make sure the inside surfaces of the windows are immaculately clean before installation! They can't really be cleaned properly once attached to the tube.

  • Mount the electrodes in side-arms well away from and with no line-of-sight to the Brewster windows. This will minimize the deposit of a metallic film on the Brewster windows due to sputtering (particularly at the negative electrode).

  • Don't skip the essential cleaning step before final assembly of the Brewster windows to the laser tube. This will greatly reduce the amount of bake-out required once you are under vacuum. It will still be necessary to pass a high current through the tube in both directions for some time as well as running a low temperature torch over areas that aren't heated enough by the discharge. However, the amount of outgassing and required time will be greatly reduced.

    CAUTION: Apparently, it is possible for an electron beam to be produced from the positive electrode during the high current bake-out step which can quickly melt a hole through the tube wall opposite the side-arm if left running for more than a few seconds. The visual effect will first be a spot of bright yellow sodium light from the point of impact. Use lower current and/or make that area of the tube (the outside of the turn) much thicker.

  • Obtain proper laser resonator mirrors. Sorry, you can't make these in your basement. Don't even bother to try silvered or aluminized mirrors (e.g., from barcode scanners), at least not until you have the laser working with real mirrors.

  • Mount everything on a stable base and make sure your mirror mounts have adequate precision! No amount of fiddling will compensate for mirrors that change position on their own. Yes, it may be possible to assemble a working laser mounted on wobbly stands but this isn't recommended!

  • Unless you want to be faithful to the era when the first ion laser was built (and there were no other lasers handy), I'd recommend using a HeNe or collimated diode laser to perform the mirror alignment. Mount the alignment laser to the baseplate so that it will be there whenever you need it. Do the initial alignment once everything is assembled but before actually evacuating the system and filling it with the argon gas. Then, you'll be ready to lase, or at least very close. The card method of alignment can also be used but may be a bit tougher with the recommended narrower bore.

  • Use spectroscopic grade argon and/or krypton gas. The purity of the gas fill is extremely critical to ion laser performance.

  • Make sure you read, understand, and follow ALL the safety guidelines found in the section: Home-Built Ar/Kr Ion Laser Safety.



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    Other Examples of Home-Built Ar/Kr Ion Lasers

    Mark Dinsmore's Ar/Kr Ion Laser

    Well, a brief summary anyhow:

    (From: Mark Dinsmore (dinsmore@ma.ultranet.com).)

    I have built the SciAm pulsed argon ion laser and it worked quite well for me. I think that the key for me was having a good diffusion pump vacuum system. Argon lasers like a pretty low vacuum, and it is easy for a small leak to contaminate them. The pulsed version does have lots of gain, as the bore current is quite high during the pulse. I used a set of 1 meter confocal (if memory serves me!) large frame ion laser optics, with about a 5% transmission output coupler. I used the same optics on the Helium-Selenium (HeSe) laser I built, which was MUCH fussier about setup. Gave a nice ~100 mw multimode output with 12 wavelengths from green to violet! I wish I had had some broadband ion laser optics - you can theoretically get more than 24 wavelengths at once covering red to violet!. There's a HeSe laser on the front cover of "Light and its Uses".

    (From: Sam.)

    So, I wonder why there isn't an article on HeSe lasers in the SciAm collection... See the section: Mark's Helium-Selenium (HeSe) Laser for more info on this laser.

    Anthony Paolini's Ar/Kr Ion Laser

    This is the only recent example I know of for a pulsed ion laser based on the Sci-Am design.

    (From: Anthony Paolini (apaolini@cros.net).)

    Introduction:

    Birth Announcement: It's an Argon! :)

    After considerable time and effort, the Scientific American argon laser has finally sprang to life. It will currently generate ultra intense and highly coherent pulses of blue/green light. The repetition rate is about 2 pulses second likely due to the 8 uF capacitor. I will attempt to increase frequency by reducing capacitance to 1 or 2 uF. Another modification in the works is a gas reservoir to stabilize pressure. The vacuum/gas system turned out to be most critical and demanding. Other critical factors are mirror and window alignment. Here are some details.

    Description:

    The SciAm argon laser is a truly remarkable device and a worthwhile project for any laser hobbyist. It is, in fact, capable of generating the 1 to 2 watts of optical power as the article claims. However, the power is divided among 10 emitted beams. A beam is emitted from each mirror and in both directions from each window face.

    In constructing this project, I did extensive experimentation in the use of various components and configurations. These include vacuum, mirrors, transformer, and igniter coils. The purpose of the notes that follow is to give the prospective argon laser builder the benefits of those experiments. This is what I did that worked!

    Vacuum:

    After experimenting with countless hardware store valves I came to the conclusion that it is not possible to economize on vacuum equipment. My valves are High-Vac type from Kontes. These valves have glass bodies with Teflon seats and o-ring seals. Connections to the pump and laser are through Pyrex to copper graded seals, also available from Kontes. From the graded seals, I used brass range connectors, cutting off the flared ends and silver soldering. The connection to the tube itself is via a #7 Ace Thread and nylon bushing (do not use Teflon bushings as they have a tendency to back themselves out). For any connections that are not soldered, use JB Weld epoxy. It is extremely heat resistant and absolutely vacuum tight.

    Mirrors:

    I experimented with numerous mirror sets and configurations (very costly). The set that worked best were the CVI Laser Corporation AR1-0537-0-2.00CC and AR1-0537-0-488-514. One mirror is flat and the other has a 2-meter radius of curvature. I had an AR coating added to one mirror, which does significantly improve output. Along the lines of optics is window alignment. This step is vital, albeit simple. With the bore sighted HeNe and mirrors aligned as well as the HeNe will allow, create the "window triangle". This should be done at atmospheric pressure as under vacuum, the ball & socket joints will not move. The windows should be positioned vertically rather than horizontally as per the article. Each window will then reflect the HeNe into the room. At some point, the beams will criss-cross (about a meter from the tube). Rotate the windows until the beam spots coincide. Then, by polarizing the HeNe, the tilt of the windows can be adjusted for minimum reflection.

    CAUTION: Do not attempt the pinhole card and spoiler alignment procedure used with the SciAm HeNe laser, as the device has such tremendous ain that the spoiler will not prevent it from lasing.

    Power Supply:

    Currently, I am using a 7500 VAC, 60 mA current limited neon sign transformer. It is configured with the case as ground and dual half-wave rectifiers as per SciAm. A lower voltage transformer would suffice as the device, when properly adjusted, will actually lase with the variac set to an input of about 25 VAC. Optimum performance occurs at an input of about 70 to 80 VAC.

    For triggering, I had originally used the Micro-Mite from Information Unlimited (IU). This is inadequate. The device will lase, but only at about 2 Hz. Although I have not tried a true Oudin coil, the TV flyback transformer with the two-transistor push-pull works very well.

    General Operation:

    After evacuating the tube, baking out, electrode heating (I used the induction heater, IND40, from IU), and flushing with argon several times, very very slowly admit argon with the Variac input set to 70 VAC. Widely spaced flashes will be observed with the frequency increasing as the pressure comes up. Laser action will begin when the pulses reach about 2 to 3 Hz. This is when mirror alignment should be done (watch the window faces for bright blue-green spots to appear). Optimum power is reached at the point just after the flickering stops, but before a true continuous discharge occurs. It is a fine line between ideal pressure and over pressure that immediately extinguishes laser action.

    Comments:

    This device has such incredible gain that it seems a waste to spread its output among 10 different beams. I feel a worthwhile experiment would be an internal cavity mirror configuration similar to the popular CO2 laser design. If there are any questions, comments, or experiment suggestions feel free to contact me via Email.

    Ron Ward's Ion Laser Experiences and Comments

    Between 1976 and 1981 I built 11 ion lasers. The first one was from Scientific American magazine. The last one was RF excited from a SSB/CW ham radio transmitter and 3 kW linear amplifier. I adapted this laser from one published in Applied Physics Letters. RF excitation solved the problem of needing 208 to 220 VAC 3 phase AC in a residence. This last laser was made of quartz and was water cooled. It produced about 700 mW of multi-line power with argon.

    I tried the refrigerator vacuum pump scheme and it was a complete failure. I finally bought a used two stage vacuum pump that was intended for servicing air conditioners. I had to completely disassemble it and give it a real good cleaning to eliminate problems associated with organic contamination. The best thing about this vacuum pump was the electronic vacuum gage and the price.

    It took me a year to assemble the new vacuum system. I carefully examined two vacuum systems in a Chemistry lab at U. C. Davis and set up a metal grid system to mount the vacuum system on just like they did. My leak-valve consisted of two all glass stopcocks separated by about 3 inches. The first one was connected to the gas manifold and the second one connected to the laser tube. Using a file I scratched a small line about 45 degrees from the stopcock hole to one side of the stopcock valve parallel with the rotating valve. To "charge" a laser I would pump down the tube and bombard it to remove any impurities. I also use a propane torch to heat the laser tube and vacuum system during the pump-down process. I would then close the stopcock to the vacuum system and open the stopcock on the manifold side of my leak-valve. This would fill the space between the two stopcocks of the leak-valve with gas. I would then close the stopcock on the manifold side and slowly open the leak-valve stopcock that was scratched and connected to the laser tube to allow a controlled amount of gas to enter the laser tube. I had three cold traps consisting of wide mouth thermoses with a glass coil immersed in liquid nitrogen. I got the liquid nitrogen for the cold traps from a welding gas supply company. I doubt that anyone would sell me liquid nitrogen like that today! The three cold traps were used as follows one was between the mercury (!! --- Sam) diffusion pump and the mechanical pump to prevent oil vapor from contaminating the whole system and to keep mercury vapor out of the mechanical pump. The second one was between the laser tube and the diffusion pump and third one was between the laser tube and McLeod gauge. The mechanical pump exhaust was through a hose to the outside of my house.

    I had many failures trying to blow glass. Finally, I discovered and purchased a copy of C. L. Strong's "Creative Glass Blowing". (Also see "Neon Signs" by Fink, 1909. It has a lot of information about vacuum systems, glass blowing, and getting a neon tube to work. The technology of 1909 is easy to adapt for home construction.) I practiced by using soda-lime glass and a propane torch. By pure luck I found a scientific glass blower at the University of California at Davis. This guy KNEW how to make stuff!!! Ever see a lathe for blowing glass? One of the first things he taught me was to get the proper goggles so I could see what I was doing. He had a U.S. Army surplus flashlight, one of the ones that are made of green plastic with the business end bent at 90 degrees. These flashlights come with clear, frosted white, and red filters. He installed a plastic polarized filter in the flashlight. The second filter (analyzer) was placed in a lens holder made from #10 copper wire. Attached to the rim of the filter holder was a small bar that was adjustable so that the distance between the two Polaroid filters could be spaced so that the glass he was currently working on would fit between the two polarized filters. The analyzer was adjusted so that the minimum amount of light would be transmitted through both filters. With a polarized light source like this you can see the lines of stress while you are working the glass or trying to anneal it! This tool proved to be the most valuable "Secret" to successful glass blowing I know of. Anyone can make one. I recommend using a car taillight and power supply for a brighter light source. I hope that you will tell others about it! Anyway with his encouragement I made a real nice mercury diffusion pump and a McLeod gage.

    I bought my research grade krypton and argon form Lindy gas in 1 liter glass flasks.

    My mirrors were from a Spectra-Physics 164 argon ion laser. The reason that I started with an argon ion laser was that I had these mirrors and the complexity of the argon ion laser in Scientific American seemed about the same as the HeNe laser projects. I used a heavy duty ignition coil pulsed by a relay in place of the Oudin coil. All of the lasers that I built using the ball joints had short operational life's, I think due to contamination. I also used TorrSeal to attach the microscope coveslip mirrors. One of the most difficult tasks was trying to accurately cut the ends of the laser tube at Brewsters angle.



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    Additional Information on Home-Built Ar/Kr Ion Lasers

    Estimate of Home-Built Ar/Kr Ion Laser Output Power

    Given our knowledge of the construction of a modern Ar/Kr ion laser tube and the type of power supply used, we may be able to guestimate an upper bound on the average output power of this apparatus.

    A modern Ar/Kr ion tube with a 50 cm discharge length would likely be rated at over a WATT - perhaps much greater - when run from a high current power supply. Obviously, since this one is pulsed at a very low duty cycle, the power will be reduced considerably.

    Based on these considerations, I would be surprised if the original design produced more than .1 mW. This based on a comparison to a typical modern Ar/Kr ion tube with a 50 cm bore outputting 1 W at 25 A (and the peak power of the SciAm design may be in this ball park). However, with a somewhat more sophisticated power supply and a water jacket for cooling (beware the high voltage!), it should be possible to boost the average power considerably. See the section: Constructing a High Power Ar/Kr Ion Laser at Home?.

    Constructing a High Power Ar/Kr Ion Laser at Home?

    I believe it should be possible to boost the power output of the argon ion laser in "Light and its Uses" somewhat by using a high temperature rated glass for the bore and adding a water jacket, but obtaining power levels similar to commercial ion lasers is probably unrealistic. For starters, a heated filament would be needed for the cathode to enable it to survive for more than a few seconds at AMPS of continouous current. This might be achievable from a salvaged microwave oven magnetron - maybe. :-)

    However, the more fundamental problem is cooling.

    Here is a set of questions from someone with somewhat grandiose ideas:

    "I am a laser hobbyist, and I *really* want to build something which produces a non-red beam. I already have a slew of diodes and HeNe's, but they are all red. I recently found the Scientific American book "Light and its Uses", and it has plans for an argon ion laser. The problem with these plans is that the tube is not sealed and it is a pulsed device with low average power. I want CW, with a sealed tube and a reasonable output. I have developed an idea for a CW argon laser with a ceramic tube and tungsten electrodes. I just have a few questions about the details.

    I think you are probably biting off more than you can chew for even the low pulsed argon ion laser unless you have already built, say, the HeNe laser from "Light and its Uses". Argon ion laser tubes are not cheap - and for a reason. They have to deal with at least 500 to 1,000 W of heat dissipation in the bore. And this is for the 'smallest' air-cooled ion tubes putting out perhaps 10 to 400 mW. Achieving adequete cooling is extremely NON-TRIVIAL!!!. If you look at photos of commercial argon ion laser tubes (see the chapter: Argon/Krypton Ion Lasers), they are MOSTLY COOLING FINS! The internal parts are made of exotic materials like BeO (beryllium oxide - powder is a serious bio-hazard) and tungsten! For more comments on these issues, see the section: Ion Laser Bore Temperature, Materials, and BeO Warning.

    You probably won't end up with a sealed tube either - as it will have a very short life.

    Then, you need to have a vacuum system, tubing, gauges, the appropriate gases, a 5 A or more 100 V current regulated power supply and igniter, etc.

    Light bulb filaments are not designed for emission - they are not coated. You would have to obtain a proper coated tungsten filament. And, of course, a 300 W bulb uses only about 2.5 A so even if you were able to do this and sent current from both ends, you are on the hairy edge. A microwave oven magnetron tube filament might work although these are rated more in the 1 A maximum range - more likely, several in parallel.

    I must say that I encourage you to pursue your interests and passions, but perhaps start with something somewhat less ambitious!

    However, if all you want is a different colored laser, green laser pointers are coming down in price as are other Diode Pumped Solid State (DPSS) lasers. See the section: Diode Pumped Solid State Lasers. And, yellow, orange, and green HeNe lasers (yes, HeNe lasers come in colors other than red!) are also available. See the section: HeNe Tubes of a Different Color.

    Credibility of the Argon Ion Laser from "Light and its Uses"

    A modern Ar/Kr ion laser tube with a bore length similar to the one described in the construction article (see the section: Home-Built Ar/Kr Ion Laser Description, will typically have a narrower bore. For the same 50 cm bore length, the 2 mm inside diameter (ID) of the Scientific American design may be twice that of a typical commercial laser. The current threshold for lasing will be higher and this is likely to result in multi-transverse mode (non-TEM00) operation as well. This isn't necessarily a bad thing in itself but would preclude the use of this laser for interferometry or (gasp!) holography.

    If you decide to attempt the argon ion laser, I would probably recommend using a slightly smaller bore - perhaps 1.2 to 1.5 mm which would be closer to that of a commercial ion tube with the same bore length. Then, the current thresholds should be similar and the narrower bore has a better chance of forcing TEM00 mode as well, though I don't know for sure if this would be guaranteed.

    There have also been comments that this design won't work at all due to the use of a .65 mm ID bore. Aside from difficulties in the fabrication of a laser tube with such a narrow bore (keeping it straight enough, mirror alignment, etc.), there could also be problems with resonator gain resulting in weak or total lack of oscillation. However, I have no idea where the value of .65 mm came from. The article in "Light and its Uses" (from the Amateur Scientist column in Scientific American of February, 1969) clearly specifies the bore ID of 2 mm in more than one place. So, unless a change was made without comment when the book was published (I haven't checked the original magazine), there doesn't appear to be any basis in reality for this concern. :)



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    Alternatives to Constructing an Ar/Kr Ion Laser from Scratch

    Rebuilding an Ar/Kr Ion Tube

    Although not as common as dead HeNe laser tubes, small air-cooled Ar/Kr Ion tubes in non-working condition are available for next to nothing from people who repair these systems. Both internal and external mirror types are common (e.g., NEC-3030 and ALC-60X/Omni-532). Where the tube failed due to low pressure (no lasing) or high pressure (won't start), it may be possible to regas it without too much trouble - at least for experiments. Don't expect to be able to seal off the tube once you are done playing - it is unlikely you will have the needed equipment or skills for it to last more than a few hours, if that. However, such as approach if you get the right sort of tube (not one that failed due to excessive current and sputtering or cathode sag) may be much easier as a means of getting into gas lasers than building one from the ground up.

    For more information, see the section: Sam's Three Part Process for Getting Your Feet Wet in Gas Lasers. That procedure was written with HeNe lasers in mind but can easily be converted for Ar/Kr ion tubes. However, depending on what type you acquire, some portions may not apply (e.g., if yours already has Brewster windows for external mirror operation).

    And, your next question is probably: "Can I convert a HeNe laser into an ion laser?". The short answer is: forget it! The long answer is: forget it! Nearly everything would need to be changed - mirrors, cathode, power supply. About the only thing you'd be left with is the capillary and that would melt down in about 10 milliseconds unless you were running low duty cycle pulsed mode and that probably is much more trouble than it is worth. I've heard of people torturing HeNe tubes by passing AMPs of current through them. The result isn't something to be discussed in public. :)

    The Half-Way Approach for a Home-Built Ar/Kr Ion Laser

    OK, so you really want to play with an external mirror ion laser but don't have access to the resources, a suitable work area, or more likely, the determination to deal with the glassworking, vacuum, gas-fill, and other requirements of a totally home-built Ar/Kr ion tube.

    Argon ion plasma tubes with Brewster windows for use with an external resonator are widely available both new and surplus. With one of these in-hand, and a matching conventional power supply, you can still experience the joy and frustration of constructing and aligning an external mirror laser head. It then is *just* a matter of fabricating the laser platform and mirror mounts, and obtaining a pair of suitable mirrors. There would be NO excuse for failure!

    If you insist on buying new, check out the large well known ion laser manufacturers. The type of ion tube you are interested is probably a small air-cooled model like an ALC-60X. Perhaps, if you can convince them it is for an educational project, they might let you have one that doesn't quite meet their specs for free or at cost. Otherwise, expect to spend several $K! Used and surplus tubes are sometimes offered for sale on the USENET newsgroups alt.lasers and sci.optics, and from the various companies listed in the chapter Laser and Parts Sources. It should be possible to buy one for less than $100 in this manner - but its condition and remaining life may be big unknowns.

    However, you them must obtain or build a power supply for your tube. While you can use the same sort of approach as with the totally home-built design - a neon sign transformer based power supply - this would certainly not make the best use of such a tube though it might be something worth doing initially. (Note: These use a hot cathode and a suitable filament supply would also be needed.) And, there is the issues of cooling - very non-trivial for these small air-cooled tubes. Lose cooling for a minute and the tube will likely be damaged if running at even its idle current of a few amps. The advantage of the SciAm style power supply is that with its low duty cycle, cooling is not an issue. Of course, there won't be much output power either especially given the short bores of these air-cooled tubes!

    Perhaps, after successfully constructing a laser head in this manner, you will have the confidence to proceed with a totally home-built design.

    The opposite situation is also a possibility: Build your own plasma tube but mount it in a used resonator. Depending on your resources, this might be an easier task (though I find that hard to imagine!). External cavity laser heads with dead tubes seem to turn up much more frequently than the other way around (for obvious reasons)! However, in the case of small air-cooled Ar ion heads, both tubes and complete laer heads are readily available at reasonable cost - it is the power supplies that are less common and more expensive.



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    Sam's Laser FAQ, Copyright © 1994-2009, Samuel M. Goldwasser, All Rights Reserved.
    I may be contacted via the
    Sci.Electronics.Repair FAQ Email Links Page.