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Carbon Dioxide Laser This is a CO2 gas laser operating. The hot glowing dot at the top of the image is where the invisible IR laser beam is melting into a vermiculite block. The molten material is incandescent. The pale blue/lilac gas discharge can be seen in the resonant cavity, the full length of the glass tube. I have the whole laser tube inside a Perspex outer tube for visibility and safety. The running voltage between the cathode and anode is 15kV with closer to 30kV for ignition. The glass tube assembly is quite complex as there is a water-cooling jacket that surrounds the discharge tube. Water is circulated around the jacket, including electrodes and both end IR mirrors. Around this is the gas reservoir jacket with an internal spiral return tube just visible in the lower part of the image. I think this is a 40W laser, but I have it running on a homemade power supply so might be less in this test. Keywords: Miscellaneous

Carbon Dioxide Laser

This is a CO2 gas laser operating. The hot glowing dot at the top of the image is where the invisible IR laser beam is melting into a vermiculite block. The molten material is incandescent. The pale blue/lilac gas discharge can be seen in the resonant cavity, the full length of the glass tube. I have the whole laser tube inside a Perspex outer tube for visibility and safety. The running voltage between the cathode and anode is 15kV with closer to 30kV for ignition. The glass tube assembly is quite complex as there is a water-cooling jacket that surrounds the discharge tube. Water is circulated around the jacket, including electrodes and both end IR mirrors. Around this is the gas reservoir jacket with an internal spiral return tube just visible in the lower part of the image. I think this is a 40W laser, but I have it running on a homemade power supply so might be less in this test.

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File information
Filename:laser_co2.jpg
Album name:Tuopeek / Misc
Keywords:Miscellaneous
Filesize:764 KiB
Date added:27 Jan 2026
Dimensions:1486 x 2500 pixels
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DateTime Original:2026:01:27 22:06:35
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Focal length:27 mm
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URL:https://trad-lighting.net/gallery/displayimage.php?pid=1101
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Comment 1 to 9 of 9
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Max   [Tue 27 Jan 2026 at 22:16]
That's super neat! Any rough idea about the power level there? Is there anything metallic in the tube that may resemble a sort of catalyst?
Ria   [Wed 28 Jan 2026 at 00:55]
Fascinating as always, I never know what to expect next from you two Very Happy
Tuopeek   [Wed 28 Jan 2026 at 19:09]
@Ria Smile Always rooting about in junk to find scientific wonders.

@Max Unfortunately, I haven't got anything to measure the beam power at the moment. I can't see any catalyst in the tube. The only metal parts are the cathode and anodes and their construction looks quite basic.
Max   [Thu 29 Jan 2026 at 15:22]
I meant the electrical power. The optical output power can be inferred from the typical 8-12 % efficiency of such laser tubes. OK for the lack of catalyst, the reserve gas volume must be sufficient and the rate of CO2 dissociation low enough to guarantee a long enough useful life then.
Tuopeek   [Thu 29 Jan 2026 at 19:06]
Ah sorry, yes, the consumption is about 220W for this setup and I can vary this too. My set-up here is a ZVS oscillator (~25kHz) stepping up from 18V to around 340V to drive a commercial CO2 laser transformer with built in rectifiers. I measured the supply at 13A 17V when running giving 221W. I can’t imagine the efficiency as being good from my lash-up. I actually have a proper mains PSU for the laser but have never connected it up to compare with this tube. This may well equate to less than 20W laser power with my set up.

The tubes aren't very expensive and are sold with an expected life in hours in a few 1000 hrs which must cover the CO2 gas volume. There may be storage lifetime to with helium loss too. The electrodes don't look like they are made for longevity either.
Max   [Fri 30 Jan 2026 at 06:37]
20W of beam power is already quite a lot! I just checked e-bay, and CO2 laser tubes are surprisingly cheap indeed... may consider getting one to complement my little laser tube collection (several HeNe and one big Ar+, but no CO2 yet).
Tuopeek   [Fri 30 Jan 2026 at 14:07]
Oh, very nice, you have an argon ion laser. I haven't found one of these yet and they're all but extinct now. I worked on one many year ago made by 'Coherent'. It was bit of a beast at over 1m long, running on 3-phase power and water cooled. It was tuneable and could produce a few colours, green being the brightest. First laser I saw that could burn at the time. It had an interesting fault which I think was mainly due to age. If left unused for an extended time it would be very reluctant to start. I could get it going with an external ignitor with a larger pulse voltage and run it for a few hours. It would be ok then and run and start fine until the next long unused period.
Max   [Fri 30 Jan 2026 at 23:19]
I have fond memories of working with an argon ion laser, a Spectra Physics... quite the beast. Ours was tuned at 488 nm for Rayleigh scattering diagnostics of dusty plasmas (a student project during Engineering school). Its beam was powerful enough to cut easily through thick plastic tape. The one I have is just the tube, not the laser head and its heavy invar resonator frame. It's a 20 kW (electric) beast from Coherent, a marvelous piece of glassware, the old tube design type with the single-piece beryllium oxide plasma capillary, before the metal-ceramic tube design became the norm in the late 1990s. Interestingly, the tube is connected to an argon reservoir via a metal capillary and a solenoid valve. The argon pressure was not stable in those tubes apparently. Another very interesting detail is that there is a gas return line from the cathode to the anode. The ionic pumping of argon is so strong that pressure must be equalized at the plasma tube extremities!
Tuopeek   [Sat 31 Jan 2026 at 19:22]
Sound very similar, the moment you mentioned a gas reservoir it rang a bell. I found an old picture I had of the system and see it was a 'Coherent Innova90'.

Comment 1 to 9 of 9
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