My new TEA nitrogen laser #1

Note: at any picture you can click and magnify to 1024 x 768 pix

After few days of preparation materials and hardworking, finally my new TEA nitrogen laser is finished.
It work with air, only with distance between electrodes of 0.9 mm, but with many white sparks.
Later was make more distance of about 2 mm, laser not work with air, but with pure N2 work just fine.
(And with less white sparks, though it are always present)

Firstly few diagrams:
(sorry for bad handy drawings)

Triggering unit of about 30 kV pulse lead to Marx bank generator.
Initial voltage is about 15.5 kV, and at output it is about 30 kV. Two capacitors of 1 nF each was charged in parallel, and when triggering pulse make spark at SG1, then this two capacitors are connected in series producing double initial voltage with very fast rise time.

From Marx bank generator, through coaxial cable, sharp pulse lead to dumper capacitor of 500 pF. Blue dot represent place when occur corona preionization just before main plasma discharge. When transferred voltage (or energy) from Marx generator charge dumper capacitor, then self triggered spark gap SG2 begin charge peaker capacitor until voltage reach breakdown voltage between laser electrodes.
This is simplified diagram of TEA laser setup. Initially, dumper capacitor was 500 pF, but later was added another capacitor of same capacitance to increasing stored energy. But I was not observe any differences. This is maybe because Marx generator can't charge both capacitors to same voltage as only one. This mean, that I need add more capacitance at Marx generator to achieving more power.

How looks whole setup:

Whole setup.

Detail of dumper capacitor and SG2.

Laser electrode holders.

0.9 mm distance produce more sparks.

Marx generator below laser head.

Marx generator pulled off.

Plastic cover over laser channel with input for pure nitrogen
How looks this laser channel with plastic cover (now, distance between electrodes is 2 mm)

At next two pictures you can see differences between output power when laser work with air
and with pure Nitrogen. Because distance between laser electrodes was only 0.9 mm, there
is one anomaly caused with white sparks which are stronger at one end (right side) and which
diffuse laser output at this end (less output power):

This is picture with operating laser in air. Left spot is much brighter than right spot.

With pure Nitrogen both spot at papers are brighter, but right side is again weaker.

For comparison between air and pure Nitrogen, I was capture two photos of left spot:

Laser operate with air. Spot is bright, but see next pictures...
With pure Nitrogen (99.9965% of purity) spot is much brighter.

After this bad output at one end, I was make decision to make more distance between
electrodes to minimize white sparking and put plastic cover above laser channel for N2 input.
Now, laser make less white spark, but not yet ideally:

This is one output end without white sparks. But plastic cover is not enough long to cover this output, so there is still present some spark as it shown at next pictures.
Mostly, white spark is occurred at ends of electrodes, but sometimes it are present at middle of electrodes, but this time laser beam is not diffused like in case of 0.9 mm space between electrodes.

Now, both outputs have equally bright laser beam. I was not capture pictures with
paper at both end, but at one end is fluorescent plastic instead paper:

This is both equally output. At middle of electrodes still are present white sparks, but this not make trouble with diffusing any of outputs.
Front end with fluorescent plastic. Seems to me that this plastic have Rhodamine 6G inside, because look same as dissolved R6G in alcohol. I was not yet try lase dye.
Another end show strange shape of spot. I don't know why. Maybe this is because there are still present some sparks. Or electrodes are not good aligned.

To magnify laser spot, I was put photocopier paper at wall 3 meter far from laser head.
Just in time when was planned make more pictures, I was stay in dark - no electricity in
power line (some error in town's power system). Fortunately before this, I was take last
two pictures:

This is spot at 3 meter distance. You can see strange vertical lines which is usually because this laser have low coherence.
To confirm how "big" is laser spot, I was use long exposure ant at least ten shots. Paper is wide 21 cm horizontally, so spot is about 10-15 cm wide. Around spot is also strange lighting, which mean that white sparks still sometimes diffuse output of laser beam.

Next time I hope put rear mirror, and at least double output in one direction. I first need find
this little piece of first surface mirror, make holder, adjustment screws etc. Also, with this mirror
I hope get less divergence and smaller and brighter (I mean, more power) spot at wall.