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Registered Member #977
Joined: Thu Aug 30 2007, 06:57PM
Location: England
Posts: 74
This has been an ongoing project for about 3 or 4 months now, it's part of my A levels and has so far been a huge learning curve, I feel I'm slowly getting there finally, despite the hefty set back of a burnt out transformer flyback transformer yesterday! The laser tube is 40cm between electrodes, 60cm between mirrors and has a bore of 11mm. The HR is plane, and the OC is zinc selenide of unknown splitting ratio. I won 4 beam splitters, 4 lenses and a mirror all for 10.6 microns on ebay for £50, and thankfully CO2 lasers aren't too picky about OC reflectivity so it should still work. The optics were an absolute bargain, the beam splitters are 35mm, as are two of the lenses and the mirror, so a lot of pricey germanium and zinc selenide. I machined the mirror mounts myself, and they have an acrylic mirror holder to take the strain off the optics when adjusting the mirrors, and to maintain adjustment when replacing the optics. The cooling pump will be an aquarium pump, and the gas supply is going to be a mixture of He, N2 and CO2 fed through a needle valve and out via a vacuum pump. I now need to sort out a power supply, rig up the gas supply, align the mirrors and I should hopefully be lasing.
that's the transformer I had going until yesterday
And here are a few pictures of my progress so far, any advice, questions or neon sign transformers are very welcome!
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
CO2 lasers can be quite efficient ... up to 20% You are looking for a 10kV 20 mA NST, which could give 50 Watts to the laser SO you could end up with 10 W of laser beam at an invisible 10 um wavelength I hope that you are able to provide sufficient safety for yourself and anyone and anything within 10's of meters !
Registered Member #977
Joined: Thu Aug 30 2007, 06:57PM
Location: England
Posts: 74
I'm fully aware of the output and its dangers, there's no point making something if I'm only going to hurt myself or others with it. Thankfully the infrared radiation is absorbed by pretty much everything, hence the need fancy optics. So an acrylic full face shield is more than sufficient at blocking out any reflections. Thanks for your concern though.
Registered Member #977
Joined: Thu Aug 30 2007, 06:57PM
Location: England
Posts: 74
Yes but that's with a direct focused beam! I'm not going to be looking down the bore of the laser when it is running, the purpose of the goggles will be to protect against any scattered radiation. And since the laser can cut acrylic this shows that acrylic is opaque to that radiation.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
just avoid metals in the beampath, as it will be more than just scattered radiation, but actual parts of the beam
scattering will occur with semi-reflecting surfaces (dirty metalic surfaces for instance) or semi-adsorbing surfaces (like glass which will scatter during melting/vaporizing), but anything else metallic will partly reflect the beam in a spatially coherent way (especially gold, copper, and any ally of these metals)
I think you can easily find the list of 10.6µm adsorbing metals... don't forget the other transitions, there is at least one which will easily lase at somewhere like 9µm
Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
Sulaiman wrote ...
industrially 25W CO2 lasers are used to cut 1" thick acrylic ... I hope that you know what you're doing !
Not at any realistic speed - you'd need about 4x that, focussed, with gas assist - at 25W you'd easily see/smell the effect of an unfocussed beam way before it made it through. Biggest risk is accidentally setting fire to combustible materials and not noticing. CO2 lasers seem to be particularly good at starting slow smouldering in cardboard. Fax paper is good for low power tests
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Homemade CO2 laser
