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Yandersen

Sun Mar 03 2013, 07:37AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

I was playing with high voltage discharges through air in a last few weeks and I come to this idea which I hope, may work as kinda gas laser:

So the idea here is to use a strong magnetic field created by a long cylindrical axially-wound air-core coil to compress the discharge arc into a thin plasma wire and push it right into the center of a discharge chamber, aligned with a hole through which the majority of light is supposed to go out.
The benefits of adding the coil, as I understand, will be the prevention of contact between plasma and chamber walls (so only electrodes will get hot), increase of ion density in the discharge path (the number of ion collisions will be higher), increase of light emission along the output line.
What do you think?

I am preparing my soul to build that thing easy-way - without mirror glass pipe, chamber not sealed, using just an air in a discharge, ~5mm between electrodes, connecting coil in series with electrodes and power it all from 16J cap (750V) pulsing the HV to ionize air to trigger the discharge.

Daedronus

Sun Mar 03 2013, 05:35PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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Posts: 370

I think argon lasers already use external coils around the discharge channel like you suggest.

Yandersen

Sun Mar 03 2013, 05:52PM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Seriously? So my thing may work?
Any links to tech articles which can help? Any numeric insight possible?

Update: no success; homemade laser didn't worked - just a bright pulse flashlight at most. 600A at peak, 150us pulse.

Yandersen

Mon Mar 04 2013, 10:00AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Is it actually possible to make a pulse laser from scratch? Say, take a glass tube, fill it with CO2 for example, put a mirror at the end and electrodes and discharge couple hundreds of joules of HV through that? Would it work? Or it will simply blow like a grenade?

Daedronus

Mon Mar 04 2013, 11:09AM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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Sorry, I don't know much about argon laser, I just remember some of them use coils or permanent magnets.
For coils I think they just use the main power supply, basically, the coil is in series with the arc discharge.

I really don't see why a diy pulse gas laser it would not work. This has been done before.
But for a CO2 you need more then just CO2. You could try a low pressure longitudinal N2 laser, this was also done before.

Shrad

Mon Mar 04 2013, 01:10PM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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CO2 will be easy to make, but plain air or N2 will need shorter than 20ns discharge time and low, REALLY LOW inductance path

your setup is close to a longitudinal excitation laser, so there might be plenty of documents on the net

you will need vacuum though

Daedronus

Mon Mar 04 2013, 02:18PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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Edit: scratch that
"The upper-state lifetime of nitrogen is inversely related to pressure; it is approximately 40 nsec at pressures of a few Torr, decreasing to perhaps 2 nsec at 1 atmosphere"

From:

And, check this out:

Yandersen

Mon Mar 04 2013, 08:09PM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Oh, thanks, great resources!
Now I'm convinced that homemade laser from scratch is a waste of time. Seems like just a single high energy (xxxJoules) pulse discharge for at least a dozen of microseconds long is not smg acceptable for laser operation even if it is a single pulse. Am I wrong?

Daedronus

Mon Mar 04 2013, 11:04PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

For N2 laser the problem is the relaxation state, it has a long life time, so after the N atoms get excited then relax/emit the laser light, they are in a state where they can't contribute to the lasing and will absorb the laser light.

That is to say N2 lasers are self quenching.

However, this is not the case with Co2 lasers, you can dump as many joules as you want, even in mili seconds.

Not all is lost with N2, you just need the joules to be at very high voltages (so C is small).
But don't expect too much, I have never seen a N2 laser to do a lot of damage.

TEA CO2 laser are completely different beasts, they can do LOTS of damage.

The easy mode high damage laser is of course the nd:yag.

Shrad

Tue Mar 05 2013, 07:49AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
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Posts: 780

N2 lasers can be pretty powerful, you just need to get to a few Torr as you said, and use an unstable resonator like those VLS337 cartridges

if you need power easily, the way to go is the CO2 laser, either TEA or LE

CO2 laser is quite easy as you can find CO2 dirt cheap and circulate through the cavity at atmospheric pressure without spending a kidney per pulse with special gas mixes

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