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FrozenGate by Avery

Homemade CO2 laser

I cannot. I am using a straight borosilicate tube, and then attaching a PVC T joint with similar ID to the tube, then sealing the outside of the tube with JB weld.

Breath for CO2 and N2 for the prototype, and party balloon He. This laser is more than efficient to work with these gas choices.

Though selection of mirrors will be interesting.
 





I'd be wary about PVC being exposed to the high voltage discharge, I can't imagine it would hold up particularly well! Maybe see if you can modify something like this http://www.scientificglass.co.uk/contents/media/l_sgl_bends_with_socket_connection.jpg ?

I was very lucky to pick up 5 znse beam splitters, one mirror, and 3 lenses all for 10.6 microns, and all bar one lens being over an inch in diameter! I also have a mirror salvaged from an old tube to experiment with
 
PVC would be alright as long as it doesn't go the length of the tube. As long as there is a wide enough
gap between the ends there will be enough standoff to prevent arcing. You also have to be careful how you
support it so that nothing will flow through the supports and arc over that way.
 
Good news! The whole laser has been glued down to a length of aluminium channel, pictures below....






I then hooked up the cooling (bucket of distilled water and a fishtank pump), my gast vacuum pump and the PSU kindly donated by spooky, turned it on, and nothing! I came to the conclusion that the rotary vane pump just wasn't pulling enough of a vacuum, as I feared all along, but I hoped that the massive 28kv might make up for it, it didn't. So i was straight on to ebay and found an Edwards 2SC20A two stage vacuum pump locally for 75 quid, so I snapped it up. According to the label it can get to 0.001mm of mercury.



And it works!







Obviously there's no output as the mirrors aren't aligned, but that's what half term is for....

More pictures here CO2 Laser Photos by HDF49 | Photobucket
 
I've been away due to work but I gotta say that is IMPRESSIVE Henry!!

Brilliant piece of work and I can think of a few people who will be watching with interest ;)

If you need tougher electrodes the ones in the standard tubes can be smashed out and are tungsten :)

great stuff all round

cheers

Dave
 
But the question is, can it pop a balloon?

I know there is no output..... Yet.

-Matt
 
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Excellent work! I am impressed!

I love seeing these projects come together so nicely in the end, yet from a pile of scrap in the beginning.

Soon I'll be able to get started on this project again, cannot wait to compare our processes and finished products :)

+1 mate!
 
Thanks for the feedback everyone! I was over the moon when I saw the discharge tube light up for the first time, and after all this work it blood well better pop a balloon. Unfortunately some absolute numpty (me) left the pump plumbed into the laser overnight, and the whole tube filled with oil from the pump overnight! I've drained most of it out and cleaned the optics up, and while I'm away this weekend my Dad said he'd be happy to flush it out a few times with isopropyl alcohol, and I should be able to start aligning the mirrors over half when I'm back on monday, with the aim of an output before I'm back at school.
 
OMG -- does this bring back memories from long ago -
I didn't flood mine, only fogged the insides. I opened mine
to clean the mirror faces, flushed the rest including the tubing
and reassembled. Make sure the brake cleaner doesn't damage
your epoxy - that's potent stuff but a real good cleaner.
Are we having fun yet ???
HMike
 
A day of tinkering in the shed and I haven't mustered any output as far as I can tell. I started off by aligning my HeNe laser down the centre of the bore, then putting on the rear optic with a glass window over the aperture, pulling a vacuum in the tube and then aligning the reflected beam to go straight back down the aperture of the HeNe. I then placed the output coupler on the laser and fiddled with that until I has a secondary dimmer beam coming out of it, and aligned that down the aperture of the HeNe. I rigged up my gas supply ala Jarrod Kinsey Jarrod's Laser World: First CO2 Laser then turned on the PSU with the needle valve wide open, and closed it slowly until I had a discharge in the tube, but unfortunately, even with a ZnSe lens by the aperture I couldn't get a piece of paper to even smolder.

Any ideas why?

My first though is the optics, mainly that the planar HR and unknown reflectivity of the OC are just adding up against me, or the alignment may not be up to scratch. I centred the HeNe down the tube by making sure the laser is central in the aperture and exit end of the laser, however my fear is that the mirror mounts may not be perfectly aligned with the laser tube, so whereas I may have the beam central to both the optics, it could be at an angle to the whole laser tube, if this is the case how do you think I could align the HeNe with the laser properly?

I also fear that the tube may be too short, a 50cm arc and about 70cm between optics may simply be too short for reasonable gain with my amateur construction and gas supply, but I'd have thought some output should be feasible? And are the geometrical properties of my tube too far off? Too short and fat leading to diffraction losses.
 
The color of the plasma in the above pics looks off (far too pink/red - maybe N2 contamination?), might be indicative of incorrect pressure or gas mix. Other than that I'd suspect an alignment issue, but it sounds like your procedure is okay.
 
That image was when there was just air in the tube. What colour should I be going for? My gas mix is 1:2:7 of co2 from baking soda and vinegar, air and helium from a party tank. I have a high relfector optic retrieved from the end of the 80 watt tube spooky gave me, the dielectric coating has degraded badly on half of the optic, but I think it might be worth trying in the laser, it should at least be spherical
 
You'll get a fair amount of water vapor if you don't pass the CO2 from the reactor through a drying agent, and while I don't know the ratios used for commercial CO2 lasers, I don't believe water vapor is a constituent. The CO2 plasmas I've seen in person have always been almost white with a very light hint of pink near the electrodes.
 
As Sig said, too much water might be bad on everything, Next, get rid of the ZnSe optic. If it's lasing, the raw beam will burn -- I've been there. Add the lens when you have a beam. Party tank He sometimes has a sealant stuff in it to keep the balloons up longer like Viagra.......! A little water vapor is not a problem but your reactor could add acid vapors in too. I always used Dry Ice for the CO2.
I put the dry ice in an olive jar with a fitting on the top. CAUTION of pressure -- use a balloon as a safety POP off valve.
HMike
 
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