Problems with high voltage TEA Air Laser.

[NerdlabsMadScience]

Hey everyone! I have been working on a TEA laser based off Styropyro's design, from his YT video "DIY Laser made from thin air". It uses the design shown in his video, powered by a 15kv single transistor flyback driver. I'm getting a consistently pulsing spark gap and transverse sparks across the lasing gap but i can't get it to produce the UV laser beam after extensive research and hours of careful adjustment. Can anyone help?

[Twospoons]

To be fair, that Styropyro "design" is a mess, and its amazing he gets any UV at all.  I'm not at all surprised you are having trouble with it.
Check this out instead

  Thats a really nice build, that works very well.

[davekni]

It is possible to build a reasonably simple air (nitrogen) laser.  I put one together in an afternoon/evening from parts in my garage.  (It didn't have any nice packaging or such, just tape and clamps to a scrap of plastic sheet as a base.)  The main key is having a very uniform smooth gap for lasing.  Due to my job, I happen to have a variety of ground steel shafts in my junk, from printer paper transport rollers.  Two such shafts formed the gap.  Rounded the ends to avoid field concentration there.  Hardest single step was tweaking shaft positions to be accurately parallel.  Shafts were in open air.  No housing to contain nitrogen or alter gas pressure.

Of course, there are other important parameters, especially low inductance and adjustable spark gap distance.

Good luck!

[alan sailer]

I can second the design from Les's Lab. It's advantage is that the foil output capacitor is only charged briefly so the dielectric sheet last longer.
It's also very powerful for it's size.

The downside is the price of the doorknob caps.

I'd also second David's story about the discharge electrodes. Uniform is important.

Finally when I first powered up my copy of Les's design the sparks in the laser channel were quite non-uniform. I did a an hour or so futzing with the gap trying to get a uniform discharge. At one point I put in a bit of fluorescent paper and it turns out the darn thing was lasing all along.

[Twospoons]

Les has another video where he makes doorknob caps out of wire leaded ones by stripping the epoxy using acetone, adding screw terminals, and re-potting.

[davekni]

I'd saved some parts from my air laser.  Here's a couple images.  First is without without shafts:



Base is 0.4mm aluminum sheet, 300 x 450mm connected to ground.  On top of that is two 50um polyester (mylar) sheets for dielectric, then 90 x 220mm foil sheets on top of that, taped to top polyester sheet.  These form the two capacitors.  There are no commercial capacitors in this build.  100k resistors went to HV supply (wired together at the supply end).  HV supply not shown here.  HV supply returned to ground.  I think there was a larger resistor in series with HV supply so slow charging rate.
Spark gap is also missing.  Went from back foil sheet to base aluminum sheet.  Included some sort of long plastic lever/handle allowing fine gap distance adjustment by raising or lowering end of lever.  (Lever pivot was probably just a piece of tape.)  Gap is adjusted to maximum possible before rod-to-rod sparks start.

Image with shafts added, held in place with magnets to steel sheet under lower aluminum sheet base.  (Steel sheet in the real version was the top of my steel-case desk.  BTW, I expect the pealing paint on my ancient industrial-surplus desk is more of a lead hazard than the leaded solder I use on top of it.):



Shafts are 6mm diameter and 225mm long.  Tweaking shaft gap by carefully tweaking magnet position was the hardest part.  Had no lever or other mechanical reduction to make that adjustment easier.  Did use some random object for a spacer and measurement tool during adjustment, removed during operation.

Bright white paper fluoresces well to detect beam.  Yellow highlighter marker improves fluorescence.  "Neon" colored objects work well too.

Made some improvements another day before removing this laser from my garage electronics desk.  Above foil sheets had creepage-distance issues around edges even with rounded corners.  Changed to foil sheets covered in polyester on both top and bottom, and curved up to hit outside sides of steel shafts rather than bottom of shafts:



Positioning in image is sloppy.  Didn't take time to make it look precise for this crude photo-only partial reconstruction.

Good luck!

[klugesmith]

Thanks for sharing.   Was you spark gap also held in plece with magnets?   Gap adjusted just as casually?

[davekni]

Was you spark gap also held in place with magnets?   Gap adjusted just as casually?

Spark gap was held mostly by gravity.  A scrap block of aluminum sat on top of the back electrode towards the back edge.  I formed a rounded bulge in some thick copper foil using a bearing ball and rubber mallet.  Bulged foil was the other electrode.  Bulged copper foil taped to a plastic stick towards one end of the stick.  That end of stick taped to aluminum block just past foil, tape forming a crude hing.  Adjusted position of the other end of plastic stick to adjust spark gap distance.  That allows fairly fine adjustment while operating.  Spark gap bulged foil extended down to base ground plane, folded 90 degrees, and attached to ground plane with magnet.

Tuning sequence was:
1) Power off.
2) Adjust rod parallelism by very-slightly increasing gap where sparks were last seen or very-slightly decreasing gap at other end.
3) Set spark gap short for low voltage firing by moving lever end.
4) Power on.
5) Slowly widen spark gap until either lasing starts or sparks between rods start.  Tweak spark gap a bit around that point to verify.
6) If no lasing before rod sparks started, loop back to first power-off step.
For further optimization, I'd continue loop repetition a bit longer even after successful lasing, until widening the spark gap slightly too far would create random sparks along the rods rather than concentrated towards one end.  This made for the best (brightest and lowest divergence) lasing.

I'm struggling to recall the successful operating voltage for spark gap.  Think it was about 5kV, but perhaps more like 7-8kV.  Probably the 7-8kV is when I tried larger-diameter shafts with the second iteration.  If I recall correctly, the larger shaft diameter and higher voltage did create a somewhat larger brighter beam, but seemed more tricky to get operating.

[Weston]

For those who have gotten the TEA air lasers working, whats the altitude and average humidity where you live?

When I was in high school I spent endless hours trying to get this working and never managed to get any laser emission. It was a while ago, so I could have done something wrong, but I remember trying a number of different setups and replicating them decently closely.

My parents house is close to the beach with high humidity and no reduction in air pressure due to altitude. I have always wondered if that could have played a role.

[davekni]

For those who have gotten the TEA air lasers working, whats the altitude and average humidity where you live?

I'm at 155' (47 meters) elevation in western Oregon, but not at coast.  This was in my uninsulated garage, I think during winter.  Garage is somewhat warmer (and therefore lower humidity) than outside since attached to house.  Humidity varies over a wide range.  At the moment (December 18th) it is 65% near that ancient steel-case desk.  Average is probably a little lower this time of year, perhaps 50% typical.  I might have been lucky with low humidity on the days I happened to run this.  Perhaps humidity is a factor in my increased difficulty making a larger lasing area with larger diameter rods (8 or 10mm) spaced farther apart.

[Twospoons]

It wouldn't take much to create reasonably oxygen-free supply of nitrogen. Starting with the exhaust from a clean flame (propane or alcohol) you could then bubble the gas through a strong caustic soda solution to strip the CO₂, then an ice bath to condense most of the water. Further drying could be achieved using a column packed with silica gel or molecular sieves. The result is not going to be 99.999% isotopic Nitrogen, but it should be far better than air, given oxygen is the primary poisoner of N₂ lasing.  There will still be a few % Argon, probably a bit of CO and CO₂.

[klugesmith]

Does anyone have the original Amateur Scientist article ,from early 1970s if I recall correctly?  Making air enriched in N2 or depleted of O2 would fit the style. Spark gap was enclosed, with low flow connection to a vacuum source. Blocking air vent with a fingertip would trigger gap by pressure reduction.

One illustration showed radial  propagation of  a curved voltage step wave  in the sheet capacitor. In more recent times I saw that debunked, as requiring unrealistic risetimes in switch and switch circuit.

[Twospoons]

Yes I've seen that diagram too. Since the wave is propagating at ~ half the speed of light (for Er =4, typical of plastic dielectrics) or 6nS per metre you can see that the wavefront would have to be really steep for that diagram to be true. Like under 100pS. That's in silicon avalanche switch territory, not spark-gap territory.

[klugesmith]

Speaking of atmospheric pressure nitrogen lasers, also discussed in Les Wright's thread:
https://highvoltageforum.net/index.php?topic=1181.msg8513#msg8513

Some readers here might be unfamiliar with the Lateral Science chronicles, which follow the remarkable discoveries of Ernest Glitch in mid-19th century.
I just opened that book for the first time in many years, and found more stories than ever. Here's a recent addition:
http://lateralscience.blogspot.com/2012/07/victorian-nitrogen-laser.html

This picture may convey the style of Lateral Science.