Coaxial N2 laser? / General Chatting / Forums

Forums

4hv.org :: Forums :: General Chatting

« Previous topic | Next topic »

Coaxial N2 laser?

Move Thread

LAN_403

Conundrum

Sat Jan 16 2010, 01:55PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

B. Oliveira dos Santos, C. E. Fellows, J. B. de Oliveira e Souza, and C. A. Massone
â€œA 3% Efficiency Nitrogen Laserâ€
Applied Physics B (Photophysics and Laser Chemistry) 41 (1986), pp. 241-244

This is a strange and wonderful article that illustrates an entirely different approach.
Using a coaxial capacitor of only 800 pf, driven by one of three â€œdumperâ€ caps (1.5, 10, or
20 nf), they achieved up to 3 MW output power at efficiencies ranging as high as 3%.
Peculiarly, their pulsewidth decreased as the amount of stored energy increased, which may
suggest that they are pumping a substantial fraction of the nitrogen molecules in their
laser. Well worth reading and thinking over very carefully.

this is intriguing.
by "coaxial capacitor" i assume that they are using an outer copper/etc tube with an inner
wire electrode.

would make sense that this would work,but the tube would have to be *exactly* the right
diameter and perfectly planar to work at all (so likely the B&Q tube wouldn't work)
the best way to achieve this would be to securely clamp and fix the outer tube in place in
multiple locations to a wooden block, and use glass feedthroughs at each end to hold the
wire.

By adjusting the wire diameter (easily done) the cavity gap could be adjusted and once set up it should be stable for quite a long time.

Interestingly such a setup could be used with pc board as the ground plane *only* for
mechanical stability with the tube(s) soldered to a groove in the board.

comments?

-A

Sat Jan 16 2010, 05:58PM

Registered Member #2372 Joined:
Location:
Posts: 62

So did you actually read the paper or do you not have access? because the discharge is still just between two electrodes that are parallel, but this is fed by a coaxial capacitor that is pulse charged from another LC circuit. This is actually a pretty typical way of making a very fast LC circuit where a marx or something pulse charges an intermediate storage capacitor that is frequently a coaxial design with water as the dielectric. The intermediate storage capacitor is then discharged into the load. A coaxial capacitor can be made with whatever dimensions you want in order to minimize the inductance so it can be made as fast as needed. If you want the paper I can email it to you.

brtaman

Sat Jan 16 2010, 06:47PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

dugg wrote ...

So did you actually read the paper or do you not have access? because the discharge is still just between two electrodes that are parallel, but this is fed by a coaxial capacitor that is pulse charged from another LC circuit. This is actually a pretty typical way of making a very fast LC circuit where a marx or something pulse charges an intermediate storage capacitor that is frequently a coaxial design with water as the dielectric. The intermediate storage capacitor is then discharged into the load. A coaxial capacitor can be made with whatever dimensions you want in order to minimize the inductance so it can be made as fast as needed. If you want the paper I can email it to you.

If you have access I would greatly appreciate, if you could mail me the paper.

Best Regards,
brtaman

klugesmith

Sun Jan 17 2010, 08:50AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

B. Oliveira dos Santos, C. E. Fellows, J. B. de Oliveira e Souza, and C. A. Massone
â€œA 3% Efficiency Nitrogen Laserâ€
Applied Physics B (Photophysics and Laser Chemistry) 41 (1986), pp. 241-244

This is a strange and wonderful article that illustrates an entirely different approach.
Using a coaxial capacitor of only 800 pf, driven by one of three â€œdumperâ€ caps (1.5, 10, or
20 nf), they achieved up to 3 MW output power at efficiencies ranging as high as 3%.
Peculiarly, their pulsewidth decreased as the amount of stored energy increased, which may
suggest that they are pumping a substantial fraction of the nitrogen molecules in their
laser. Well worth reading and thinking over very carefully.
...
comments?

N2 laserists and PFN geeks might appreciate the free online article where that paragraph apparently came from:

Retaining that credit is not only the right thing to do, it's on-topic for this 4hv thread. Though its author Jon Joss could be less peevish (as could I).

If you have access I would greatly appreciate, if you could mail me the paper.

We all have access to the cited Applied Physics B article:

You would have to read the terms & conditions, to see if it's legal to pay for 1 copy and then email it to your friends. The analogous traffic in popular music and movies is a subject of vigorous debate.

Proud Mary

Sun Jan 17 2010, 10:03AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Coaxial lasers generally work as pulse forming lines to keep inductance as low as possible and to double the voltage available for the discharge when a hydrogen thyratron/pseudospark/spark gap switch is closed.

Jitter is least when the electrodes are made from material with a low work function such as aluminium.

brtaman

Sun Jan 17 2010, 02:57PM

Registered Member #2161 Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247

Klugesmith wrote ...

If you have access I would greatly appreciate, if you could mail me the paper.

We all have access to the cited Applied Physics B article:

I have a few scientific contributions in the field of management and economics and I could care less, if the entire world has an unpaid copy of one of my articles...if it benefits the science of business I am all for it as long as any article stemming from my work cites the source.

If I was planning on using their research for commercial purposes I would be more than willing to pay, but for a quick home-brew experiment the asking price seems a bit stiff to me.

klugesmith

Sun Jan 17 2010, 03:59PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

brtaman wrote ...
if the entire world has an unpaid copy of one of my articles... I am all for it as long as any article stemming from my work cites the source.

I feel that way too, about my own feeble contributions to the world of published wisdom.

If I was planning on using their research for commercial purposes I would be more than willing to pay, but for a quick home-brew experiment the asking price seems a bit stiff to me.

Agreed. My main point was that if a hobbyist really wants to read a cited journal article, he/she no longer needs to visit an academic library -- the paper can be had immediately via the Internet. Compliance with IP copyright rules is a matter of personal choice -- judgement of rightness, wrongness, and enforcement. I've paid as much as $20 to read papers relevant to significant hobby projects. But when Google showed me a copy illegally posted on a college student's website, I did not snitch -- I grabbed a copy right away.

Conundrum

Mon Jan 18 2010, 12:49AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

it occurs to me that excessive copyright and misuse of patents stifles creativity and innovation.
case in point, the blatant misuse of the patent system on the human genome when the companies involved are doing so purely to stop anyone else doing research on "their" IP.

just my $0.02 worth.

wouldn't the world have been a better place if the patent system required *use* of an idea to validate the patent by a sensible deadline or it became public domain. "First to market" not "First to patent" and all that.

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob