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Thread: LGI-40 russian xenon ion laser

  1. #1

    Default LGI-40 russian xenon ion laser

    Yesterday I've picked up this extremely rare and interesting unit from the delivering company. I know nothing about this laser except that it is a xenon one and works in pulsed mode. The laser head contains a very sophisticated quartz tube with gas fill system, a pile of capacitors and a thick TGI1-1000\25 (1000A, 25 kV) thyratron that is identical to one I have in my CVL system. The laser tube is water cooled. The power unit contains a huge HV transformer, some really big choking coils, HV rectifier and filter and a triggering circuit for the thyratron. This thing is bloody heavy! I had to hire a truck to get it home. The laser head weighs about 50 kg, the power unit is 150-170 kg. The year of manufacture of the laser is 1976. I've posted several photos here, more are in my album at VK.com https://vk.com/album31425290_249134359

    4tFxSk_knho.jpgD3Tkas22_Zw.jpg1RPfJ9ptx6Q.jpgvZySc0QD1mI.jpgUbQ_s41AwkY.jpgcDEh9rLk_Bg.jpgced_SgRtA5A.jpgX0UGqaTl-pM.jpgZoM5XkODRRs.jpgwp_-GPlJaFk.jpgUaj7P8S3FRA.jpgPH3DReFpAfI.jpgvMSqpjh12Hw.jpgzpl21xFTPDU.jpg

  2. #2
    mixedgas's Avatar
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    Having had past experience with similar beasts, although not Russian ones, you need a very low Xenon pressure some place between 20 and 150 Micron. Contrast that to the 250- 350 Millitorr of a small frame Argon Ion laser. I see a fill solenoid there, so I hope it has not leaked up to high Xenon pressure in the tube. They also consume gas rapidly, driving it into the bore walls, and far more rapidly then an Argon ion laser.
    ~
    There are two design regimes for these beasts, at least the US made ones. Large pulse low rep rate, ie 10-20 Hz and lower fill pressures, and very high rep rate, low duty cycle, aka Britt Medical Systems, that actually emits 100-200 mW Average Power when air cooled tube and 2 watts tube when liquid cooled for up to 30 seconds before needing a cool down cycle. The only way to figure out which regime without a manual or data sheet for the laser is to analyze the pulse forming network and the measure the sync oscillator's rate
    ~
    The high rep rate tubes with lower pulse energies operate in a plasma regime where CW ion lasers can't run, and the very short pulses do not heat the gas very much.
    ~
    You might want to ask JSC Plasma if that is one of theirs... Beautiful unit, I hope you can get it lasing.

    Steve
    Last edited by mixedgas; 11-14-2017 at 14:38.
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  3. #3

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    Thanks for such a detailed answer. I have checked the tube for ionization and it glows red with violet near the one of the electrodes. It looks like it leaked a few torr of air. As for the power unit -- I've detached the thyratron trigger and studied it separately. It gives pulses with the repetition rate from 50 to 130 Hz. Actually I am not sure that this tube will lase without refurbishement at a glassblower's workshop. Still looking for a manual for this laser.

  4. #4

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    Wonderful laser and classy plasma tube! I encourage everyone here who has been following my threads about old lasers to visit Laserbuilder's VK page for more of the same. Many of the Soviet lasers I have came from him. Also, his excellent work with both copper vapor and ruby lasers are on LPF under the same name.

  5. #5

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    Thanks, Eidetic!


    You might want to ask JSC Plasma if that is one of theirs...
    Yes, it is the laser of their manufacture. I've already emailed them, but the answer was like "We had stopped manufacturing these lasers very long ago and there is a very little chance of finding the manuals."

  6. #6

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    Update: the power unit appears to be functional, I only need to defeat an interlock that doesn't allow me to switch on the HVDC section in a regular way, with a button on the front panel.
    Last edited by Laserbuilder; 11-15-2017 at 11:44.

  7. #7
    mixedgas's Avatar
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    Quote Originally Posted by Laserbuilder View Post
    Update: the power unit appears to be functional, I only need to defeat an interlock that doesn't allow me to switch on the HVDC section in a regular way, with a button on the front panel.
    ~

    From past experience I would not hit tube electrodes with an a high energy discharge in air if I wanted to recover the tube for Xenon or Argon. Bad things happen with oxidation and heat transfer from the nitrogen. Nitrogen plasmas get very hot compared to inert gasses.
    ~
    Low pressure Xenon has a light silver/grey color with tinges of blue in weak discharges such as tesla coils, and the plasma forms into glowing threads in many cases. Air is always violet or purple with orange at the electrodes and forms uniform plasmas.

    Steve
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  8. #8

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    Which wavelengthes can I expect from this tube when refilled with Argon? Will it lase on regular blue-green lines or will there be other ones with pulsed energizing? Looking at the pulse forming network I can say that it supplies long pulses with a moderate (a few kV) voltage at low rep rate. Not sharp HV pulses like in a nitrogen or Cu laser.

  9. #9
    mixedgas's Avatar
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    488, 514, 476, 457 , a few others, at about 1/3rd the strength of what it would do in Xenon. No visible lines that do not otherwise exist in a CW Argon laser. However there will be, depending on optics and the windows, some possible, powerful UV lines that do not exist in a normal CW laser. No matter what you do, if the mirrors are even close to aligned, you will get 488 as its nearly super-radiant when ran pulsed.
    ~
    Xenon is not stable in CW ion service, but its three main green and blue lines are amazingly high gain when pulsed. What you have is probably a pump for a pulsed dye laser or for a resistor trimmer in making integrated circuit chips or hybrid modules. That was the main use in the United States for the few Xenon lasers that were produced.
    ~
    The trick is determining if the fill stem for pumping the gas is made of borosilicate glass or Quartz. Being an American technician, I have no idea what the old GOST standard materials are for Borosilicate Glass, Glass to Metal Seals, or for Quartz to metal seals. I imagine they are analogs of 7740 Pyrex, 7052 or 7070 Sealing glass, 3320 intermediate glass (yellow-green in color) for graded expansion seals, and Kovar alloy for the Borosilicate, and Molybdenum for sealing to quartz.
    The odds of it being made from leaded glass such as Corning 80 and Dument or Housekeeper seals are nil.
    ~
    Well, after a quick Google, it looks like the available sealing materials are the same alloys and the glass is very similar in expansion to their Western versions, except Kovar is spelled with a Cyrillic equivalent to the "C" sound.
    http://www.relay-start.ru/en/product...ail.php?ID=402
    !~
    The reason why I mention that is two glass tubes have to match each other in expansion rate within 7 parts per million to fusion seal without cracking. So a glass to metal seal will usually have 3 or more different types of glass in it and a very special low expansion alloy. This influences what glass a glassblower would use for a laser tube. For example, many sealed mirror hene lasers are made of 7052 glass, with Kovar ends.
    ~
    If this little laser will lase, imagine what that properly designed tube with a huge pulse engine will do..

    http://pulslaser.de see the ionen laser..

    ~
    Steve
    Last edited by mixedgas; Yesterday at 07:48.
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  10. #10

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    Ok, than it makes sense refilling it with Argon. Xenon is bloody expensive and hard to get... the tube glows like this now, when powered from a neon sign transformer.

    kh8LL9btONc.jpg

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