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Thread: Excimer laser head

  1. #1
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    Thumbs up Excimer laser head

    This head showed up, was presented as a CO2 laser. First looking at it, I thought, Good! a TEA CO2, just what I have always wanted after previously having a smaller one.

    It turned out to be an excimer unit, from Coherent. What I know is the gas has been removed but believe it was a --Fl compound, the engr. said it was unlikely a XeCl unit.. This kind operates at ~3 ATM pressure, 12ns pulse, 500-1000 pps, about 5-10mJ/1, and has a peak power of maybe1000KW. Can't be more specific, even Coherent could not specifically identify this precisely since the rest of the laser product is missing (case, 2KV DC supply, dataplate, controls, etc..). What is pictured is the charge/pulser for firing (thyristor for long life in this one instead of a spark gap) and the cavity including FC and OC. The small steel tube is the gas port, the 'hole' is probably an internal boss holding the septum (engr. didn't know). Cooling is conduction/convection. Inside is a recirculating blower to maintain a high clearing ratio, a filter, and electrostatic cleaner. It is a TE unit with a ceramic pre-ionizer. It was made for very long life. I don't know it s condition but it looks really clean in the cavity. The attached documets may not be for this head, as Coherent could not properly identify it.

    Well and good and I'm not disappointed but I don't really need an excimer laser, was wanting a CO2 really. Still, too cool to scrap and I have to wonder if it could be filled with N2 which is safer than the other gases and with manual controls work well enough for hobby use. Thought it would be interesting to show it. Maybe someone here has worked with these and can offer accurate information about it.
    Attached Thumbnails Attached Thumbnails excimer head.JPG  

    LTJ_Excimer_0607.pdf  

    TUBraggStar_Industrial.pdf  

    Last edited by opcom; 10-19-2011 at 16:36.

  2. #2
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Excimer frames can in some cases work with N2 and in some rare cases CO2 mix.

    http://192.197.62.35/courses/phtn140...ers.html#PartB

    Ask Dr Csele, if anyone has tried it, he did.

    I'd ask the other excimer and TEA co2 companies what they know.

    Steve

  3. #3
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    Hi opcom -

    Quote Originally Posted by opcom View Post
    Maybe someone here has worked with these and can offer accurate information about it.
    Welcome to PL..

    I can't speak for him, 100%, but I am pretty-sure our NY-neighbor, Wayne Shaffer - http://www.photonlexicon.com/forums/...038-laserwayne - has worked with these, at-least other brands of Excimer, not sure about Cohr heads...

    I'd also doubt he'd be interested in a 'trade' / buy (..but again, I'll let him speak for himself, for-sure.. but, I can-say, the guy knows CO2 lasers like the back of his hand, so, if you are looking for one, I think he might be able to 'hook y'up'.. I'd for-sure mention, this is for *hobby* use, and not 'commercial-use', so you guys don't waste time with homework on the top-notch commercial CO2s he uses / sells.. which, of course, come with a top-notch commercial price-tag...

    IIRC, there are at least 1-2 'old-school' CO2s, in the NY shop, just collecting-dust, and, afaik, they still work... He'll have to take it from here, tho...

    Hope this helps...
    cheers..
    j
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  4. #4
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    Thanks Steve!
    I did not find him as a user here. Is that his lab at the url?

    Coherent didn't want to say anything about the head in an e-mail except for warnings about voltages, toxic gasses, toxic dust, and laser beams. I can't blame them there especially since it may have been charged with a mix under pressure and they don't know is playing with the junked item. I had to call the engineer that replied to my e-mail and ask him. Politely I was able to explain that it was best for safety reasons if I knew as much as possible, because if not myself, the next owner or someone down the line might open it without knowledge. It is clear their wise policy is not to abet the public in repairing incomplete products that are missing safety and control instruments, but it was clear that if I'd had the entire product, they would have been more helpful.

    The voltage input is 2KV, but that is the supply voltage to the pulser. Information about the charge applied to the tube itself was not available. I don't know the voltage needed to ionize the stock mix at 3 atm. pressure, so drawing a blank there. Nitrogen and TEA CO2 from my limited experience use 15-30KV across the electrodes. Much depends on the electrical configuration and dimensions of the cavity. It's got some real nice banks of low inductance caps along the underside of the tube. N2 is the obvious first choice being nonreactive and needing no specific coatings on the mirrors, but CO2 is the grail. It all depends on the electronics package and cavity.




    Thanks dsli_jon!
    I'll look him up. I am also looking for a CW CO2 tube about 35-40W, <=1M length but can consider other configurations. Old-school is fine for my use. Ebay is reasonable and convenient with fixed couplers but it's all from China; I'm a little leery of it.
    Last edited by opcom; 10-19-2011 at 19:31.

  5. #5
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    The excimer looks interesting, from what I know, the limiting factor on these is output windows, which get covered in muck from the discharge eroding the electrodes, and the rather less-than-pleasant gas environment. All the ones I have seen before have been in using a flouride gas, so, fairly well worth avoiding as they are rather corrosive and unplasant. I was offered one for free a while ago, but turned it down, I'm pretty sure that was a Coherent and was flourine based and in the short wavelength UV range. Its probably still in the back of a shed in Essex, and complete, if anyone has a burning desire for an excimer ...

    My mate has some coherent CO2 slabs that he was thinking of selling, I'll PM you if he is. I think they all had matching RF power supplies, around the 50 to 100W mark. I didn;t really pay that much attention to be honest, as small CO2 tubes don't interest me, so I could be wrong.

  6. #6
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    The application may call for 35-50W, either an RF type not much bigger than a Synrad 48, or, a Chinese 40W tube would probably work as well. Divergence smallish <=4mrad. Brand name is not important but power and general reliability are. I've come close to buying a Chinese tube and PS, but there are more durable/better quality units out there like the aluminum RF units.

  7. #7
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    Yep, the slabs run forever, if you can find one at a decent price. They do come up on eBay from time to time .. theres one on there now, but the guy wants crazy money for it .. about 2000 USD, but it is new and with rf PSU.

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