Tear down of the DIY High Performance TEA Nitrogen Laser, how to build it and advice!
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- เผยแพร่เมื่อ 30 ก.ย. 2024
- Episode 6
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#optics
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As some of you guys have asked specific questions about the High Performance Nitrogen Laser build, this followup video shows a tear-down of the Nitrogen Laser head, along with specifications for components and general advice if you want to build your own!
Also someone asked if the whole system could be run on plain air, and this is demonstrated
During 17:25 to 17:40 ...If you LISTEN and LOOK, is an interesting 15 second lesson in kenetic gas theory itself!
Thank you wery wery much! All my questions answered in this so short video!
Fantastic! Thanks!
Can we make tea laser's beam continuous by changing the pressure ? If not why ?
Unfortunately no. Once a Nitrogen molecule has emitted a photon, before it returns to the ground state, it falls to a meta-stable level. This has a lifetime of 40uS, so the laser pulse self terminates. With cold nitrogen flowing at high speed, the literature suggests you can get repetition rates in the kHz range though.
@@LesLaboratory how what is the maximum achievable pulse rate of Pulse tea Laser or Maximum Frequency ?
And what low and high pressure of Nitrogen do to the T laser when placed in tube
Made something principal similar but much simpler; a A4 sheet of PC, since it has good HV resistance, and put aluminium foil on almost the entire bottom side with some distance to all the side due to the HV.
On top of the PC equal size of aluminium foil but split in half and separated like 2 mm from each other. At these ends I placed 2 pieces 3 mm polished stainless steel bars in close proximity to each other but not touching. Ground was the bottom foil and on one of the 2 top foils one had a simple spark gap, the other foil was connected to 12kV and a coil between the two top foils.
When energized I got around 3 - 4 pulses per second If I remember right and if I shone it on a normal white A4 paper the room lit up a little from the extremely bright dark blue dot that you could hardly look at. I made that when I was around 16 years old, many, many years ago. Fun times.
Thanks for taking the time to do a more detailed video about how you built the laser. I've wanted to try building a TEA laser for a while, but everything I could find was old enough that most of the sites are broken.
I noticed that the dumper cap is roughly twice the size of the peaking cap. Do you think it would work if I made a dumper of similar construction to the peaker but with either double the area or an extra plate and the same area? Unfortunately I don't have any doorknob caps in my parts stash.
Thanks again for the great content!
Thanks for your Interest. Yes, information is a bit thin on the ground, even with archive.org searches. There are however excellent academic papers on the subject. A lot of Labs were investigating these in the 70's and the experiments are pretty well documented, with plenty of measurements and characterisation.
Yep, the dumper is Twice the size of the Peaker and sure there is no reason why this can't be home made. That said, expect to change the Dielectric more often, and of course the laser will end up more than twice the size.
You might be better of starting with the LC inversion Circuit or "Blumlein" design, in this case the rule of thumb for capacitors is: They should be equal capacitance, and should each have a capacity of no more than 60pF per centimetre of channel length.
I see a lot of designs with massive caps and in the end performance is actually quite low! Contrary to advice on some websites/videos, you can get away with relatively thick Dielectrics as well. Mine is 190 Micron, yes it lowers performance, but you get the tradeoff of longer running times, plus we are using a pressurised gap which pulls back any performance losses anyway.
@@LesLaboratory Thanks for the advice, I think between your videos and response I'm going to give it a shot.
Your laser's deign and construction really seem to be reproducible, most of the ones I've seen online were either too fiddly (the "scrap pile" design) or just monstrous and defeat the simple construction.
I did try to look up the papers referenced on Sam's Laser FAQ, but of course they're all behind paywalls; seems pretty silly to paywall papers from the 70s-80s.
@@drrrrockzo Thanks! Yes it should be reproducible. Still finicky so set up initially but after that it's all good. Yes, paywalls stink for this kind of stuff, but you can still pull useful stuff from Google Scholar.
i believe you said the hv is like 12kv,..is this so low because of the dandy preionizer ??..also, how close timing is preionize to main-bang so to say ??..thank you and great video
Yes, exactly. If the preionizer is not running, the laser won't fire at all at low repetition rates. Timing is not too critical. Within a few microseconds is good enough, as the ions stay in the channel for a short time after the pulse.
@@LesLaboratory thank you !!
..thank you : )
...hearing that the timing is not as critical as expected has charged me up, so to speak
..would you expect Neon to work as i do in a TEA configuration ??
First doubt, apart from the values found on bibliography, I'd like to know what span of voltages are you using. I see you use your self-built variable 30kV ps, but I'm not sure having seen/listened the voltage you use (I understood you fix a V Value far from SG firing value at 1 atm pressure and then you apply pressure to SG till it starts to fire). Also, how much current can supply your ps? Enough for, say, 50-70 pps lasing? Thank you very much 😊
i have 1nF ceramic caps. you know, the tiny blue ones? they are rated for 20kV so 4 of them 2p2s should be 2k pF like your cap bank, and they should be able to take 40kV. can they work or is their something i am missing about these (unfindable) doorknob caps?
edit ill be using the design with 2 homemade caps anyway since it s easier. using messing electrodes (shoulldnt change anything). How large should my caps be on that kind of design? plus, is there a way to get more power into the laser? it seams like there is quite the limit for these kinds of lasers. i cant just double the amps to excite twice as manny nitrogen atoms, bc they get excited by the discharge of the caps anyway... so i gues does increasing voltage help at all? and what about higher pressure in the lasing channel? shouldnt more excited nitrogen atoms mean more photons and more power?
After watching the video, I wanted to assemble this design. The idea of using a spark gap with air removal is especially interesting.
tea and co2 ?
Thanks for the inspired explanation.
This is excellent .... there's plenty of really interesting projects on TH-cam but presented really poorly.... there's also plenty of well presented videos but with rather boring projects.... it's rather rare to get the best of both..... well done!!!
Awesome! Thank you so much!
Very nicely described and fantastic breakdown of all the parts. A long time ago, I tried to build the Scientific American Nitrogen laser in high school with some small success.
Could you describe the ends of the plexiglass channel? How do you align the end mirror?
There seems to be a small hole on each end of the plexiglass channel (lined up with laser channel) and it looks like the nitrogen just eventually purges the air from the channel.
Thanks!
Yes, the ends of the channel are open to atmosphere, and the nitrogen just displaces the air. There ends of the cavity are just plexiglas blocks with holes drilled in them.
Aligning the mirror is easy, since the N2 Laser will emit light without it. Just simply line up the spots and you are all set!
hey
can this be built in complact and small size ?
Can you also give its output power
And what is the wave length that i can get
also can the same gas be used again and again?
Yes, it can be miniaturized! See this vide here (there is a demo of one of these with a channel length of just 6cm).
Output power is estimated at this stage, but since it will drive a dye laser, power is at least 100kW/square centimeter. Probably 200-300kW peak. The average power is measured in milliwatts.
Wavelength is 337.1nm (Ultraviolet)
You could recirculate the gas if you wanted, but that would add complexity.
Great to see the teardown...cheers.
I love your work!!! Will this same setup work with CO2 gas as a CO2 TEA laser?
It might, with the right optics and gas mix. I ordered optics a few weeks back, since this is on my to-do list!
Hi Les!Few thoughts about sparkgap, and please tell me if I'm correct in this:
I understand that the discharge on an pressurized sparkgap is faster than an atmosferic pressure sparkgap.That's because the electrodes are closer and inductance, as a result, is lower?
The voltage in a pressurized SG can be rised higher than at 1 atm?
In the case of a pressurized SG the quenching effect is stronger ?
I was thinking of an atmosferic presure SG magnetic field quenched.Do you yhink that when magnetic field quenches the spark, the spark will be comparable in speed with the pressurized one?
I'm thinking on replacing the sealing, the pump, and all that is related with mantaining pressure with , let's say a sort of ""solid state" spark gap at atmosferic presure, frequency and speed by magnetic field adjustable.
Many thanks!
Yes, as the electrodes are closer, the arc is shorter, and inductance is smaller compared to a wide gap.
As you increase pressure the stand off voltage increases as well, and yes there is better switching speed, quenching, and less jitter with a pressurised gap.
Hmm, Magnetic quenching is not something I have tried, except in Tesla coils, but they are a different animal. I think you might well end up with something overly complicated. If you are using pressurized gas to run the Laser, by not use some to pressurise the gap?
Could you replace the pressurized spark gap with a little xenon flashlamp or a neon bulb?
Unfortunately the breakdown voltage of these is much too low. On top a that the inductance would be too high. Pressurised gaps are the switch of choice for this application. They are inexpensive and robust. I will be doing a video on spark gaps for pulsed power applications at some point.
High great video & channel, I used to work in a high voltage test bay for large switch gear. We had to pay attention to sharp edges (as do you) & oil from finger prints (wipe down with acetone). Would finger prints cause insulation brake down?
Thanks! Cool! I would love to see a HV test bay. Yes, fingerprints contain oils, salts, water and can introduce dirt. This could cause flashover or excessive corona on insulated parts.
Hello. Could you please tell me what size bolts and dome nuts you use in the spark gap?
Thanks
They were M8 brass. I'm sure there are better materials butt they are easy to work with.
Do you have a parts list you can share ? Something that can give the proper dimension of parts like the type of needle valve, inner diameter of the silicone tubing etc.
I am on vacation at the moment, but when I get back, time permitting I should probably write this up, though honestly there is enough info in the video that several viewers have successfully replicated the design.
Les, does the film material have to be an "acetate" or will something like mylar work just as well? Is this cellulose acetate, vinyl, etc? Just having a bit of trouble tracking down the correct thing since stencil sheets appear to be made from a variety of materials and thicknesses. Also for the Al foil, regular or heavy duty? Thanks for any help!!
Acetate or Mylar will do just fine. Other plastics may work. I just use regular aluminium kitchen foil, but is needs to be flat (no pattern stamped into it)
I guess it mostly has to be insulating. I got it to work with those sheets students put on their books
Man, I can't avoid revisit your fantastic videos once again and again. I'm Almost to the point to finally start my own prototype, for which I've been collecting parts for the last years 😅. And I fell in love with your designs, the mini one is simply lovely. I assume you worked long time on optimizing them, as yourself talk about in some video... So why reinvent the wheel!? Even more when the invented one is so perfect in simplicity and performance? So, I thank you so much for having so wonderful 'skirt-ups' videos on lasers... And I hope you don't mind I post some easy questions... Anyway, thanks again! 😊
Really great content. I've been planning to build a pair of lasers to try to do things with optical beat frequency excitation. It occurs to me that the layout of the capacitors might make it difficult to fire two lasers at precisely the same time that are physically spaced some inches apart and oriented in line, at opposition to one another. I might try to build them both onto one single board, and have one of them adjustable to align with the other.
One question, if you might know the answer. Do you have an approximation of the time duration of the beam discharge? I suppose that would be the same as the duration of the spark, right? I'm aiming for something around the nanosecond scale, but I don't know if that's achievable.
Is there a problem if one of the electrodes is higher than the other because of the aluminum foil and the dielectric, or do I have to align the electrodes perfectly,at the same level? How did you do it with your laser? The electrodes will sit on the board without a support, possibly press with a weight for better contact .
Very nice LASER 👍
(and Video of course)
I dont found acetate at 190 microns.It works with copiator transparent sheet?
I heard someone to wear safety glasses.No i think.
Yes, always wear safety glasses. For Nitrogen Lasers, regular poly-carbonate safety glasses are opaque at 337.1nm.
Great video! I was thinking of replacing the pressurized air in the spark gap with some kind of isolation oil to reduce the spark width. Do you think that would be possible? It would eliminate the need of fiddling with compressed air.
I suspect that it would explode with oil. The spark would vaporize the oil, and that vapor would have to go somewhere. Once the oil breaks down, you would also have carbon particles in there as well. Compressed N2 or dry air is a tried, tested, and robust solution.
@@LesLaboratory Ohh, I didnt think about that! Good thing I asked.. Thanks so much! You rock.
Hey, great video ! Is there a possibility to convert the N2 laser into a simple TEA CO2 laser (beside from the mirror and OC) or will that require a different setup ?
In principle, I would say it should be possible, but I have not tried it! I know low pressure TE CO2 Lasers certainly exist. From what I gather it possible to extract megawatts of peak power, even from short channels.
@@LesLaboratory Are you willing to try it out ? I'm going to try it when my laser is complete, so i will report back my findings :)
@@radled5514 I have experimented with oil submerged spark gaps. Not in a sealed container though. I think if you have a small air vent and change the oil regularly it might work ok. Depends if you want experimental things or tried and tested I guess.
At about timestamp 14:20 you mentioned that the plastic dielectric is about 190 microns (0.19mm) thick. I looked at some tables of dielectric strength and could not find any plastic this thin that could hold off 20kV. polyethelene was about 24kV/mm. At 190 microns (I am assuming that 1 mucron is 1/1000mm, is this correct?) that's about only 4.5kV...
For Mylar, the dielectric strength is quoted at 11kV/mil for DC and 7kV/mil at AC. Note this figure is mil, not millimetres. 1mil = 1/1000 inch or 0.0254mm.
www.espemfg.com/mylar-electrical-insulation/#:~:text=Dielectric%20strength.,strength%20of%207.0%20kV%2Fmil.
In the CT design, the HV only appears across the Mylar for nanoseconds, and so you can exceed 11kV/mil by a very wide margin.
@@LesLaboratory THANKS, Have you seen this on how dielectrich hold off more thaan expected.....
th-cam.com/video/MPD7skZ8OSo/w-d-xo.html
I guwss I would feel safer NOT exceeding....I was sure you said 'micron'...which is even smaller.
Great work! This channel is a brilliant resource. I have also built a similar laser recently and am getting pretty reasonable performance. That is, much better than previous lasers I've built of the classic design. I have one question regarding the pressurized spark gap: I found a paper that gives the discharge time as proportional to the square root of the pressure. I'm guessing the main advantage here is the hold off voltage. At least in my laser, the voltage range is pretty limited due to the small size, and I'm not currently running any gas lines. My question is, were you able to see a difference in laser power at the same voltage, but different pressures? DOI: 10.30684/etj.2013.82183
Thanks!
Primarily, a high pressure gap results in a higher hold-off voltage and better stability, but also results in a much narrower gap, reducing the inductance in its conducting state, therefore increasing the switching speed in the system.
For really effective high speed switching, the gap should be overvolted to fire, for example by using a triggered spark-gap.
@@LesLaboratory Great, thanks a lot for the response. The lower inductance is indeed a compelling argument. I started with the triggered spark gap that you described, but I wasn't able to achieve very reliable triggering. I am using a ref-note trigger generator that produced a consistent 20kV impulse, but it was very unreliable in use with my particular laser. Since I am controlling my high voltage supply with a microcontroller, I found another triggering method that is working well for me. I run the high voltage supply at some fractional amount of my desired trigger voltage. Then I run an open-loop interrupt routine that ramps the voltage for a set number of cycles until the spark gap fires. This usually takes about 4 milliseconds until I get a trigger. This works almost like clockwork, but occasionally generates double pulses. In terms of power output, I can't obviously see the difference, despite the additional inductance. I did see that having the spark gap mounted between the peaking capacitor and high voltage was much more consistently lasing than the ground referenced triggered configuration. Now it lases pretty much no matter what, save for when the channel is very misaligned. The next step I want to implement is having some feedback to stop the ramp sequence when a trigger is generated. I am torn between adding a photodiode, or using pretty much any one of my microcontroller peripherals detecting the massive EMI pulse 😅
Hey sir quick question. What if I change the material in the hex bar and base plate to steel? I know steel and aluminum can become corrosive to each other when in contact(so oopsies for the aluminum sheet), but if there are any benefits to using steel I'd like to know.
I suppose you could, stainless would be the material of choice, but it is hard to work, hence my using aluminum. Still, there is nothing wrong with experimenting!
@@LesLaboratory Same me different account. The hardest thing to source at this moment are the mirror mounts, I can probably just machine some, but I'm trying to avoid having to put in that kind of work. Are there any known websites I could visit?
Could a spark plug be used for the spark gap?
Possibly, but the inductance is high. It can be used to trigger one, have a look on my channel for a triggered spark gap.
@@LesLaboratory Ah yeah, forgot their long lead leading to a higher inductance.
Will check, am in the middle of binge watching all your videos :D
Gorgeous laser there
Thanks! :-)
the thickness of the plastic is 190 microns as stated on the video? that is roughly .0075 is this correct? That's extremely thin I was thinking by looking at the video it appeared to be .114 mm?
Yes, 190 microns. This is quite thick in the scheme of things.
This was really well done! Did you explore stacked spark gaps with triggers? I understand from one paper that this can dramatically shorten the time to discharge. Rocketman340 has several videos on a coaxial TEA nitrogen laser that uses water as the dielectric of one of the capacitors. Not many details but looks like a great starting point for an instructable. Thanks for sharing this… Doug
Thanks! Yeah, I saw the videos, and have read some academic papers, interesting stuff. If I get time, I might have a crack at something like that if the gains are high enough.
Anyone able to explain what the purpose of the compressed air is? Does it just increase the density of the air, and there-by decrease the resistance? Making it easier for the spark gap to fire?
I must be wrong, because if that's the goal, you would just make the spark gap smaller... So there must be something else that I don't understand as yet :)
Increasing the pressure increases the breakdown voltage of the gap. At atmospheric pressure the breakdown voltage is a few kV. At a couple of Bar, it is> 17kV.
The rationale for pressurising the gap is switching speed, which also increases with pressure. As the electrodes in a pressurised gap are close together, the inductance of the gap is lower.
With N2 Lasers, for good performance, you need a fast, low inductance gap, and pressurised gaps are the way to go.
Do you think it works with the spark gap longer at atmosferic pressure?t want to construct a simpler spark gap because i am a person with dizabilityes and is very complicated to me to construct your spark gap To know,the person in that picture is my mom.I have 32 years and i want to construct my tea laser(your design) with my mom and my brother help.
It will work with a longer open air gap, but not very well, and it will be loud. It is worth the effort to spend the time making a good gap. It might be work asking folk within your local area (machine shop or whatever) for a hand.
Does the spark gap need to be pressurized can't you just make the spark gap longer
You can make it longer, but by doing so you increase its inductance, which slows down the discharge and drops the output quite considerably. It is really worth the effort to build a pressurised gap. The design shown can be built for under $20 with a performance comparable to commercial units.
120k 3w laser resistor is good?
So long as it is physically large enough to stand off the voltage.
Has anyone ever used a car Sparkplug (Iridium styled) for the spark gap in a design like this? Would it conceivably work? Would it be better to use Tungsten electrodes in place of the Brass electrodes in place or does the functionality would essentially be same without any improvement to the stability or throughput of energies?
People have used common spark plugs as trigger electrodes in gaps like this, but not as the main electrodes.
The self inductance of spark plus is too high for this application and many have an inbuilt resistor in the porcelain stem for EMI suppression.
Only 0.5 Joules or so are commutated by the gap, so there is not a pressing need for tungsten electrodes, brass will do just fine. Tungsten would not wear as much as brass and I had considered it , but it is difficult to work with, especially with hand tools!
Wear isn't really too much of an issue anyway. Even after many thousands of shots, wear is negligible, and all that is required is a quick clean with some steel wool.
hi george..i made 2 trigatrons for a copper chloride laser that used the spark plug as the trigger electrode, a section of alumina tube ( the form for a power resistor ), but the energy discharge was thru 1/2" copper plumbing end caps- of coarse pressurized- worked super
If change Nitrogen to Argon, can this TEA laser work?
Do you mean in the channel, or in the spark gap?
@@LesLaboratory both channel and spark gap
@@georgegreen3672 No. Argon Ion lasers require low voltage but high current, and as far as I know, are only longitudinally excited. Please see here as a starting point: www.repairfaq.org/sam/lasercar.htm
In the gap only, Argon may improve switching time.
Can Argon laser work the same way as Nitrogen laser?
No. Argon Ion lasers require low voltage but high current, and as far as I know, are only longitudinally excited. Please see here as a starting point: www.repairfaq.org/sam/lasercar.htm
@@LesLaboratory Great website.
@@LesLaboratory I am so happy that under your guidance, I can make a very practical laser which means so much to my work.
Have you tried a mixture of different gases? Nitrogen + Helium or Argon or CO2
Not yet. Helium is a well tried and tested buffer gas, though it would require redesign of the channel. I may try Argon in the spark gap as there is evidence in academic papers that it can improve switching speed.
@@LesLaboratory do neon,..i always wanted to try a 5401a TEA- never seen anyone as of yet- got me a ltr flask and a few ideas for a sealed unit..im sure it will work, and where your safety glasses
..or read about it anywhere iether- ive looked -crazy
- i did TE green before- WOW !
@@rickmally5777 I would if I had Neon. Maybe I will look into it at some point. Also, yes, I have safety glasses!
what size gap are you using in the transverse discharge area? I know the spark gap is between 1-1.5mm, will this affect the discharge gap efficiency? Thanks!!! Great build BTW my first laser was built about 40 years ago...didn't use a capacitor discharge because of the gas i was using but got it to lase non the less. This project has inspired me to revisit my laser designs and improve them etc...
The gap in the discharge area is just over 2mm for a supply voltage of 17kV , however in my latest version (video coming soon), it is closer to 4mm with a 23kV supply voltage. The main spark gap is small as it is pressurised, but the channel runs at atmospheric pressure. Pressurised spark gaps significantly improve switching times.
Awesome, what gas laser did you build?
@@LesLaboratory I built several I'll list them... C02, Copper Vapor(technically a vapor not a gas) Nitrogen, Dye flash pumped ,Soft Xray laser (not gas but plasma), Argon, and of course several diode pumped Solid state types. Currently working on a 40Watt Solid state etc.
@@georgeyork8975 Awesome! Those all sound really cool! I have decent vacuum gear, but never got around to doing Ar and CO2. For a while I was making home made x-ray tubes. My first N2 laser was a low pressure laser that worked very well, but it was also very large. Metal vapor lasers interest me. I would like to build a Helium-Selenium Laser one day.
@@LesLaboratory home made xray tubes? I dabbled in that as well hahaha!! I ended up buying manufactured ones but my idea was to make a handheld xray device for on the spot diagnosis and data sent back to the hospital in real time like injuries etc...
@@georgeyork8975 Yep. I built a low energy tube (1-10kV)with a beryllium window, and high energy flash x-ray tubes running at 100-300kV pulsed. Your project sounds very cool and probably expensive!
Tin foil = aluminum foil?
Yes
Yep!
could you use a spark plug for the gap?
In a later video, I use spark plug as a trigger, butbfor the actual gap, you need thick rounded electrodes to minimise inducance, and manage heat.