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longitudinal excitation nitrogen laser

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tobias

Fri Oct 21 2011, 01:00AM

Registered Member #1956 Joined: Wed Feb 04 2009, 01:22PM
Location: Jersey City
Posts: 172

cedric

I read your problem about running a 3P motor off 1P grid. How much money do you have to invest? A 1P to 3P inverter would do it...

cedric

Fri Oct 21 2011, 01:33AM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
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Posts: 143

tobias wrote ...

cedric

I read your problem about running a 3P motor off 1P grid. How much money do you have to invest? A 1P to 3P inverter would do it...

it's one option ,I am trying to replace the engine once it for all , so I don't get trouble anymore...

cedric

Fri Oct 21 2011, 01:49AM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
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Posts: 143

I get it to laze, with the fridge pump !!!

1319161770 2941 FT66720 Nitrogene Lasing

hboy007

Fri Oct 21 2011, 08:46AM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
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Posts: 374

That's really sweet, cedric! Congratulations on building one, if not *the* smallest LE N2 laser out there. Have you thought of adding a reservoir so that the fridge pump doesn't need to run all the time?

cedric

Fri Oct 21 2011, 12:40PM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143

hboy007 wrote ...

That's really sweet, cedric! Congratulations on building one, if not *the* smallest LE N2 laser out there. Have you thought of adding a reservoir so that the fridge pump doesn't need to run all the time?

I am not there yet,the lazing is very hieratic ,the beam is not so bright and the beam profile is not very nice ,but all together ,now that I know how to do it ,I am planing to build one bigger (10 cm tube with internal diameter of 6 mm),same capacitor ,and steadier construction, of course I will need better vacuum . I also think this type of setup is perfect for pulse multigas laser (given enough power and a resonator it's possible to laze about anything

The information you provide where very useful for the accomplishment of this project.

now for the details:
the tube size is 7 cm, inside diameter 2.5 mm, the capacitor are rated at 850 pf each (40 kv)the gap of the spark gap is about 1.2 cm with 6 mm round bolt.
the resonator is made of a piece of code bar scanner mirror and a non-identified round piece of glass, the adjustment is made by having a piece of rubber in between the glass and the front panel tighten by 3 bolt , I use a small laser led for the alignment, the interference pattern is a very good tips, once it there you know it work...

hboy007

Fri Oct 21 2011, 02:56PM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
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Posts: 374

erratic lasing can sometimes be fixed by increasing the breakdown voltage of the spark gap which increases the pulse energy.
I would try a larger tube diameter if I had spherical dielectric mirrors. For a planar resonator setup, my personal choice is a narrow inner diameter because of the higher current density.

I always wanted to build a pressurized spark gap with a trigger electrode, perhaps you can get one to work ( given a suitable power source, of course).

cedric

Fri Oct 21 2011, 06:49PM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143

hboy007 wrote ...

erratic lasing can sometimes be fixed by increasing the breakdown voltage of the spark gap which increases the pulse energy.
I would try a larger tube diameter if I had spherical dielectric mirrors. For a planar resonator setup, my personal choice is a narrow inner diameter because of the higher current density.

I always wanted to build a pressurized spark gap with a trigger electrode, perhaps you can get one to work ( given a suitable power source, of course).

for the gap size I am on the edge since I get arc-over once a wile,in my next set up the center electrode will be rounded to increase the breakdown voltage.
what do you mean by spherical dielectric mirrors? I have one from a ssy yag laser witch could be perfect as an out put coupler (I think it is non-planar)
Pressurize triggered spark gap is not out of reach ,from what I know hydrogen is the best for high spm, and high gas purity is important...

one question is how much can we expect from commercial epoxy in term of leak and outgasing ?

hboy007

Fri Oct 21 2011, 08:46PM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374

for concenctric resonators using curved mirrors, I've found this page:

I've seen standard epoxy being used as a "quick fix" sealant for UHV recipients. Time at the beamline is expensive and minor damages from the transport of the experimental setup cannot always be fixed in time.
However, the mixing ratio of the compounds is critical. I also like heating the epoxy a bit because its viscosity improves, it cures faster and the cured resin is stronger. I assume that a more intense curing process also uses up the compounds more thoroughly.

Just get your hair dryer ready next time you're using epoxy glue and heat to 50-60Â°C, allow the epoxy to get sucked into the gaps, then let it rest for a day.

radhoo

Fri Oct 21 2011, 10:41PM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701

hboy007 , thank you for providing your experiment's details on your webpage, a good time to also learn a little german.

I am looking forward to replicate your experiment, and laser design. Would it be possible to replace the spark gap with a hydrogen thyratron? I successfully used such a thyratron in some of my recent experiments, see:

Cedric, I have a few questions regarding your test as well.

cedric wrote ...

I get it to laze, with the fridge pump !!!

Can you elaborate on this part, and maybe provide more pictures, videos, details? How good is a fridge compressor for this purpose? I have one at hand, and it would be my first option in trying this kind of laser. Also can poor vacuum be compensated by higher voltages?

cedric wrote ...

I am not there yet,the lazing is very hieratic ,the beam is not so bright and the beam profile is not very nice ,but all together ,now that I know how to do it ,I am planing to build one bigger (10 cm tube with internal diameter of 6 mm),same capacitor ,and steadier construction, of course I will need better vacuum . I also think this type of setup is perfect for pulse multigas laser (given enough power and a resonator it's possible to laze about anything

Can you try adding a little NaHCO3 inside the tube, the plasma should heat it up and release CO2. I am curious if it changes anything having CO2 inside (2NaHCO3 â†’ Na2CO3 + H2O + CO2 â†’ Na2O + 2CO2 + H2O )
Or adding a little mercury for a mercury vapor atmosphere inside the tube. Just a few ideas, to see if it would still laze.

hboy007

Fri Oct 21 2011, 11:34PM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374

radhoo, I personally have never tried thyratrons myself. Most types that come as tubes with glass envelope are usually rated <10kV and the ones that can handle >30kV (e.g. the Perkin-Elmer 8614/HY-5) are seriously expensive and hard to find, not to speak of stupid import / export restrictions that cripple the opportunity to buy world-wide.
I assume the peak current is in the region of 500A-2kA. Measurements will be needed to get a suitable description.

Can poor vacuum be compensated by higher voltages? Of course, but at a certain price: even longutidinally pumped marx lasers have been proven to work at atmospheric pressure, but the trigger voltage of the tube may well be around 50-100kV for the 100mbar region. In case this voltage cannot be provided, pre-ionisation or pre-triggering with a meshed electrode around the length of the tube may be needed.

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