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Thread: Coherent Innova90-MRA

  1. #11
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    Six nines after the decimal point or better

    99.999999%

    Hydrogen, Oxygen, Nitrogen in the parts per million are too high.

    If you use "dirty" gas it will lase, it will then have a very short life.

    The difference is how the storage tank itself is lined and processed prior to filling.


    In early 2010, 250 Litres of the Krypton was 750$ USD without the Hazmat shipping. It is now at least four times that amount and you are no longer allowed to transport it yourself from the factory, as I did.

    The 270 L/S VACION pump, turbopump, and roughing pump need some special treatment, and the oil in the pumps is Fomblin... Fomblin is in excess of a Euro per Milliliter.

    Once the tube is on station, it is tied to a Sorption pump while the "pump and run" and fill adjust steps are ran, once baked,cleaned, and activated on the high station. The Sorption pump will not pump neon and helium, and a few other things, and needs liquid nitrogen to pump.
    To boost pure red, Neon is an additive. To clean the tube, there is a patent on a mix of Helium, Krypton, and Argon that was found to be an effective scouring agent.

    The key to all this is one tool that cold welds the copper, to maintain the purity in the reservoir, even the best of bellows valves will not last more then six months in this service. In 2010 that tool was 1250$, it is now in excess of 3700$, and that is the manual version, not the hydraulic pumped version. The tungsten carbide dies for the hand version of the tool are good for 100 seals or so before replacement, as pure copper is especially tough on tooling.

    Right now, what is keeping your tube alive is a 1/4 wavelength layer of Hafnium Oxide on the back side of the Brewster Windows. This is the only thing that stands up to Ion Bombardment and sheds dust in a big tube. Air cooled tubes may not need this special blessing.

    If the tube is open to air, to regenerate it requires the vacuum within 15 cm of the cathode fill stem to be 7 x 10-8 Torr or less in order to activate the cathode for long life.

    I had a wealthy sponsor who needed his Lexel and ALC tubes for his business to keep running post factory closure, , else I would have never been able to do this. So we built several stations, I have a crude one at home. What I call crude, for most users would have been world class 15 years ago.

    There is one custom piece of ceramic to metal on the station that I do not picture in photos. In the past I have literally had people threaten my health, trying to obtain the vacuum station. Thank God for Diodes.

    Yes, Dr. Bridges invented the Ion Laser at Hughes with just a regular roughing pump and a diffusion pump with an LN2 trap. . Getting the lifetime to be long enough commercial use required obtaining a very clean vacuum. The diff puimp had to go away.

    The One other caveat is you cannot fully pull the tube below 200 mT (probably a higher pressure on smaller tubes) of gas fill, or your laser power supply passbank will die in a big flash from the tube becoming a close cousin of a thyratron. Ion lasers run right on the edge of where the tube becomes a positive column discharge, but not over the edge. So you will always have a negative delta on the tube resistance curve.

    -


    The 270 L/S VACION pump, turbopump, and roughing pump need some special treatment, and the oil in the pumps is Fomblin... Fomblin is in excess of a Euro per Milliliter.

    The key to all this is one tool that cold welds the copper, to maintain the purity in the reservoir, even the best of bellows valves will not last more then six months in this service. In 2010 that tool was 1250$, it is now in excess of 3700$, and that is the manual version, not the hydraulic pumped version. The tungsten carbide dies for the hand version of the tool are good for 100 seals or so before replacement, as pure copper is especially tough on tooling.

    Right now, what is keeping your tube alive is a 1/4 wavelength layer of Hafnium Oxide on the back side of the Brewster Windows. This is the only thing that stands up to Ion Bombardment and sheds dust.

    If the tube is open to air, to regenerate it requires the vacuum within 15 cm of the cathode fill stem to be 7 x 10-8 Torr or less in order to activate the cathode for long life.

    I had a wealthy sponsor who needed his Lexel and ALC tubes for his business to keep running post factory closure, , else I would have never been able to do this. So we built several stations, I have a crude one at home.

    There is one custom piece of ceramic to metal on the station that I do not picture in photos. In the past I have literally had people threaten my health, trying to obtain the vacuum station. Thank God for Diodes.

    The One other caveat is you cannot fully pull the tube below 200 mT of gas fill, or your laser power supply passbank will die in a big flash from the tube becoming a close cousin of a thyratron. Ion lasers run right on the edge of where the tube becomes a positive column discharge, but not over the edge. So you will always have a negative delta on the tube resistance curve. There are ways around this by adding water cooled resistors when processing, but you never, never, want to be too low,

    The amount of gas in the tube is miniscule. Where gas gets used up is in purging the station and pumps, and filling the regulators. A beginner's mistake is not having something in the fill system, to build a bit of back pressure for the regulators on the output side where it leads into the vacuum. In other words a flow limiter. That limiter needs purged, too. Beginners learn the hard way when they use a standard regulator for filling the tube, and it dumps most of the gas in the tank into the system.

    If you needed a new tube, I would just find an MRA or I90, process it, fill it, run it on station, and send the crated tube over. Once you get over the initial panic of knowing you are changing what used to be a 7,000 to 13,000$ part, they are easy to change, if you take your time and plan ahead. That saying is only for the ceramic ones. The big glass-BeO tubes are worthy of a constant firm panic when changing.


    Some of my colleagues are saying he just typed what? In reality there is quit a bit more to doing it right. Things like protecting the feather edge of the copper (or Nickle) evac tube seal and what you braze your extended fill stem on with.


    A hobbyist, could, get a pulsed home made tube going with just a roughing pump, if you did not care about your Cathode. Lifetime will be in hours, unless you continuously flush the tube while running.

    Steve
    Last edited by mixedgas; 06-10-2024 at 13:43.
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    This makes the effort a bit clear.

    That means, you pinch the copper tube in the front near of the cathode or at another position?

    If you find time, it would be nice if you can send me the MRA Manual

  3. #13
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    Quote Originally Posted by nightlife View Post
    This makes the effort a bit clear.

    That means, you pinch the copper tube in the front near of the cathode or at another position?

    If you find time, it would be nice if you can send me the MRA Manual

    At the cathode = full rebuild only. Through the reservoir is the other method, but painfully slow and requires careful means to manipulate the valves so as to not burn them out. Coherent has a very mean preventative trick waiting for you if you try to take the end bell off to weld in a new cathode and braze it back on.

    Did I mention a glovebox filled with Argon the size of the tube?

    It takes 5-10 flushes of the glovebox to get even close to 95% pure. Welding grade gas is used here after being dried. . When you can run a tungsten lightbulb in the glove box with the glass broken, your glovebox is clean.

    I'm in North East Ohio, USA.

    Steve
    Last edited by mixedgas; 06-10-2024 at 23:03.
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  4. #14
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    you put the whole tube in a box filled with argon to prevent to get air in the tube while connecting?

  5. #15
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    Quote Originally Posted by mixedgas View Post
    Six nines after the decimal point or better

    99.999999%

    Hydrogen, Oxygen, Nitrogen in the parts per million are too high.


    Steve
    At the moment there is only Argon 7.0 (99,99999%) and Krypton (99,9999%) available in austria.

  6. #16
    mixedgas's Avatar
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    That sounds good enough, You have a wonderful laser now, I'd keep it intact. Let me see if I can find an MRA core that lights/lases.

    I pulled the manual from storage, I need to scan it.

    Steve
    Last edited by mixedgas; 06-11-2024 at 11:00.
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  7. #17
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    Quote Originally Posted by mixedgas View Post
    That sounds good enough, You have a wonderful laser now, I'd keep it intact. Let me see if I can find an MRA core that lights/lases.

    I pulled the manual from storage, I need to scan it.

    Steve

    Really nice ,thanks

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