How to make Inexpensive Nitrogen Laser Capacitors!

Episode 16
#laser
#electronics
#optics
Check out my other videos: / leslaboratory​
Please don't forget to like,subscribe and comment for more great content!
If you found this content useful, and would like to support this Channel, please consider supporting this work on Patreon: / leslaboratory
Or donate directly: paypal.me/leslaboratory
Alternatively, please share this content on your social media platforms, it really helps me out!
In response to questions for viewers, I substitute the expensive Doorknob Capacitor in one of my Nitrogen Lasers with inexpensive wire ended capacitors. Will it work? Watch the video to find out!

[@acompletelynormalhuman6392]

I feel like somebody could definitely use the sound of this laser in a old Sci-Fi show and it would fit perfect

[@HuygensOptics]

What you could also do is put two of these in series. The voltage over the "spark gap" at the leads would be half of the value now, preventing this sparking. Of course the resulting capacitance would als be half of the current value, but since they are so cheap that would not really matter. You could actually take a version with a lower voltage rating.

[@LesLaboratory]

Could do, but then inductance will stack up as well. It would be easier to pot it in epoxy or paraffin wax.

[@jimwhitmore9037]

If you look at the wire lead capacitor, there is a "bump" where the wire runs across the barium titanate dielectric under the epoxy insulation. You should be able to trim the wire leads flush with the capacitor body. Seal the wire cut ends with epoxy or urethane glue, or corona dope, insulating varnish, whatever you have. The carefully sand away the epoxy covering the wire bump on the ends, just to the point you see copper. Do not remove enough epoxy that the wire becomes unstable. Then slide the modified capacitor into the place where the door knob capacitor is mounted. You may need some conductive shims, washers, whatever, to adjust the overall thickness. It may even be possible to epoxy a machine screw, a machine nut, or a short threaded bushing, to each side of the modified wire lead capacitor (in the center) to create your own home made, "doorknob" capacitor.

[@LesLaboratory]

Yep, for sure. It is an option I experimented with, and it is quite possible to dig though the epoxy as you say. The interesting thing about stripping the original epoxy (and a goal for a future experiment) is that is should be possible to stack the pucks and sink them in epoxy for a very high voltage, low inductance capacitor.

[@goamarty]

I thought about soldering a piece of metal strip e.g. copper foil or sheet with a hole for a screw to the exposed wire. this has much lower inductance than wire. Then insert the screw in the hole, bend back and epoxy

[@Zenodilodon]

That is a substantial ceramic capacitor you have acquired. I am sure it would make for a very extreme game of hot potato.

[@LesLaboratory]

LOL for sure! You would get a fair crack off of it! :-D

[@christopherleubner6633]

That was a joke to haze newbies in the the lab. Charge a doorknob cap up and toss it to someone. 😅😅😅

[@dmitrylavrov5267]

A comment on the wound polypropylene capacitor... In my experience taking those apart, they are made cleverly: one platter sticks outside the insulator on one end, and other platter sticks outside the insulator on the other end, so the current does not spiral around the capacitor but instead travels along the capacitor.

[@LesLaboratory]

Yes I have pulled a few apart myself, and they do interesting things to try and reduce internal inductance, but you must also take the length of the foils into consideration as well.

[@lomolariful]

I appreciate your sense of entertainment! :-)

[@IvanStepaniuk]

Great content! I was going to subscribe, but it turns out I am already subscribed!

[@LesLaboratory]

Awesome! Thanks for your support :-)

[@saturn1returns]

More videos, Les !

[@LesLaboratory]

They are coming...

[@en2oh]

have you tried trimming the leads and exposing the plate connections directly? Once potted, with a suitable potting compound, you might have a reasonable facsimile of a door knob capacitor. Great video, Les!

[@christopherleubner6633]

Ive done similar for making marx generators that are very quick. To solder to the metalized part you can use a very low melting point solder like indium/tin or tin bismeuth. Get it nice and hot and add a bit of silver to it, stirring with a silver spoon is fine. Then let it cool in convenient sizes. The marx generator was used to power pulsed x-ray tubes. 🤓

[@gamerpaddy]

maybe rubb off the coating on those leaded caps and make your own doorknobs by soldering copper/brass nuts on there

[@LesLaboratory]

Yep, could do that for sure. The epoxy coating is pretty tough though. I have tried to de-pot a few of these with not much success. No solvent seems to touch them. Heat works but cracks the dielectric.

[@knst-wrk4701]

​@@LesLaboratory Try a mixture of acetone and formic acid and let the capacitor sit in it for a day or so. This will turn the coating mushy, and it can then be peeled off. Usually you'll find a silver plated ceramic wafer underneath, ready to be soldered. I used the above solvent formulation quite a bit for quality control in HV assemblies...

[@LesLaboratory]

@@knst-wrk4701 Thanks for the tip, I will give that a go!

[@maksimkonoshenok3980]

​@@LesLaboratory You are handling the blue capacitors incorrectly. Do not strip anything in them. You must remove the spark gap from this structure. And from two capacitors to make two cascade Marx generator. Where the spark gap will be between the capacitors. And you need to come up with a design where the legs of the capacitor will be no more than 5 mm long. Because the laser power will depend on this length. You also need to fill the capacitors with wax or epoxy resin so that there was no spark. Then with the same supply voltage the power will be higher than with one barrel-type capacitor. (From Russia with love :))

[@LesLaboratory]

@@maksimkonoshenok3980 Thanks, already done!, See this video for an update: kzbin.info/www/bejne/hHarmqlqodtpbrc

[@McTroyd]

Would it be enough to put a layer or two of heat shrink over those leads, all the way up to the ceramic package? Or is the voltage high enough here to defeat that?

[@byronwatkins2565]

Clip the leads very short, scrape off the paint in the center of the electrode, and solder the leads directly to the plates.

[@ame7165]

really late to this party, but I've seen axial versions of those capacitors. they aren't as common, but they have high voltage ones and they're still dirt cheap. that's if you can find them in stock somewhere

[@LesLaboratory]

Yeah these things always seem to show up sporadically! It would be interesting to get hold of some large raw barium titanate pucks to have a play with...

[@dancoulson6579]

I wonder if you could use glass tubing of some sort to make a more permenant laser electrode system? Maybe something like a test tube. fill the glass tube with nitrogen at the correct pressure, and then metl the other end shut, with the electrodes coming through. This way you wouldn't have to keep blowing gas over it. You could even add a small amount of oxygen absorbing material, to remove any oxygen left over in the tube.

[@hullinstruments]

You can actually remove the coatings pretty easily. Which would allow the leads to be positioned as protruding from each side. similar to a door knob cap. Then you can even cast it in your own little epoxy body… with screw thread leads, and isolation exactly like an expensive commercially available door knob capacitor. There are many different coatings…, but most of them have a brittle epoxy, so once you make a small starting place with a crack or chip… It’s really easy to get it all off. You could also try putting them in the freezer overnight or in liquid nitrogen and then smacking them on the edge of a wooden table while holding the leads in your hand. The coating should just completely shatter. It’s really easy to chip the coating off of them. You can either use a small hammer, or even squeeze them between vise jaws or pliers. Do it in a way around the edges so that it doesn’t damage the capacitor inside it only chips away the coating. Once you get a few chips in the coating you can take high pressure compressed air and blow into the crack or chip… And it will separate the epoxy from the capacitor. 99% alcohol helps as well, along with compressed air to work its way along the inside and separate the coating. Found this out the hard way by dropping a few of them on the concrete floor and they chipped. Even if the legs becomes damaged you can easily reattach it once the epoxy is removed.

[@poptartmcjelly7054]

Just checked aliexpress and looks like 1000pF 3kV doorknob caps go for around 3 bucks. Not sure how well they'd work considering their price.

[@LesLaboratory]

At that price, it is worth a punt!

[@dalenassar9152]

GREAT STUFF...THUMBS UP AND SUBSCRIBED!!!! Can you tell me what preasure level is in thr N2 channel?? I have an old N2 laser that is almost as big as a small car! ...had it running a few years back.

[@LesLaboratory]

It's atmospheric pressure, no vacuum. The N2 is fed in at a slow rate, enough to stop air diffusing in and remove any N2 that is either warm or not yet fallen back to the ground state. In principle you could put it in a airtight box, flush it with N2 and circulate with a fan.

[@_flying__fish_1112]

Is there any way to get a manual of your lasers? friendly greetings :)

[@tolkienfan1972]

Sixty quid to save a finger? Sounds like a bargain!

[@LesLaboratory]

Indeed! Best not to cheap out on some things!

[@cambridgemart2075]

Would the purge gas from an oxygen generator (concentrator) be pure enough for the N2 laser? They're easy to get hold of and would provide unlimited nitrogen.

[@LesLaboratory]

Probably! Anything more than 0.5% O2 will start to poison the Laser, but from what I read, membrane separators can produce N2 with greater than 99.9% purity, so it should be fine. I have been on the lookout for a membrane separator for some time. That said, the higher power Nitrogen Lasers will Lase plain air and produce enough output to run a Dye Laser.

[@xenon5066]

Have you thought of taking the skin off the capacitor? Maybe try it with a bench grinder until you exposed the wire. Or you cast the wire ended cap into an epoxy puck with the standoffs cast in?

[@LesLaboratory]

Yes, but the epoxy is very tough. Knst-wrk suggested formic acid and acetone, so I will give that a try...

[@hullinstruments]

You can actually remove the coatings pretty easily. Which would allow the leads to be positioned as protruding from each side. similar to a door knob cap. Then you can even cast it in your own little epoxy body… with screw thread leads, and isolation exactly like an expensive commercially available door knob capacitor. There are many different coatings…, but most of them have a brittle epoxy, so once you make a small starting place with a crack or chip… It’s really easy to get it all off. You could also try putting them in the freezer overnight or in liquid nitrogen and then smacking them on the edge of a wooden table while holding the leads in your hand. The coating should just completely shatter. It’s really easy to chip the coating off of them. You can either use a small hammer, or even squeeze them between vise jaws or pliers. Do it in a way around the edges so that it doesn’t damage the capacitor inside it only chips away the coating. Once you get a few chips in the coating you can take high pressure compressed air and blow into the crack or chip… And it will separate the epoxy from the capacitor. 99% alcohol helps as well, along with compressed air to work its way along the inside and separate the coating. Found this out the hard way by dropping a few of them on the concrete floor and they chipped. Even if the legs becomes damaged you can easily reattach it once the epoxy is removed.

[@andrespinardi]

maybe with a mixture of co2, nitrogen and helium you will have a better result

[@johnnycash4034]

Can you show the frequency calculations as to delta the firing rate? Does the channel length effect the firing rate?

[@LesLaboratory]

The firing rate is determined by the overall Capacitance of the system and the Charging Current. The more current you can supply, the faster it will run. There is of course an upper limit, where the dielectric will be stressed to failure point. Additionally Warm Nitrogen gas does not Laser very well. There was no calculation done for the firing rate, I simply measured it.

[@andymouse]

I had a couple of thoughts on the cap's coating but they are already below !...cheers.

[@LesLaboratory]

There is a follow up video as well, where I pot them in epoxy ;-)

[@hullinstruments]

What would happen if you made a similar laser but instead of aluminum…. I used polished copper or bronze? I have hundreds of pounds of buss-bars, ranging in size. Some are only 12mm wide and a few mm thick. But the biggest ones I have are HALF A METER wide and 18mm thick!!!! And every size in between! Most are plated in an extremely thick silver coating. It’s about 95% silver. Some of the bigger busbar segments weigh over 100 pounds individually.

[@LesLaboratory]

I don't see why not. So long as they have good straight edges on them, it should be fine. Thing to bear in mind is that TEA lasers don;t scale very well. The longest one I have has a 1 foot long channel and at that, it is approaching the limit. With lower gas pressure you could probably built a 3ft channel.

[@icebluscorpion]

You have to modify the blue ones otherwise you will not do a good job. The legs have to be cut short as possible also solder the crimped ends after crimping

[@Alexander_Sannikov]

Old CRT TV's have caps similar to these doorknob ones, would they work?

[@LesLaboratory]

Yep, they should do.

[@MongrelShark]

Have you ever tried setting up the spark gap so the UV produced shines on the lasing gap? In theory it might prime the gap a bit and make lasing better. I made a TEA laser many yars back (video on my channel) it kept blowing out the dielectric. Any tips on stopping this from happening? Can you run this on Co2 and get red laser? Sorry for so many questions. Things I haver been pondering for years and just found your excelent channel.

[@LesLaboratory]

I have not tried exposing the channel to UV, but the top electrode of the peaking capacitor is positioned in the cavity, so that it produces ions in the cavity before the laser fires. CO2 might work to product an IR laser at 10 microns. It is something I might investigate.

[@MongrelShark]

@@LesLaboratory very interesting about the ions from the capacitor. I'll have to build another laser one day. Was one of the most fun projects I've done.

[@christopherleubner6633]

At the extreme peak currents almost any gas will lase in a system like this, but some will need a mirror set. For IR a gold HR mirror and a znse window is plenty, for visible use a silver or broad band dielectric mirror for the HR and a bit of microscope slide as the OC. UV is a bit trickier, but an aluminum FS mirror is fine. If using halogens the mirror needs to be a second surface mirror. A silica window is ok for the OC. The gases i tried are CO2 nitrogen and helium for 10.6um far IR, Oxygen and helium for red 6xx nm, pure neon for orange and green, xenon helium for multiple blue green output; but if iR optics are used it lases at some rather strong IR wavelength too, argon helium for mostly the 488nm ion line, and xenon chlorine and helium for a near UV output quite a bit stronger than N2. 🤓😁❤

[@myoniwy]

@Les' Lab I have an idea. What happens if we combine the TEA laser with a Marx generator? Simple two metal bars like in TEA but connected to the two towers Marx generator. One High energy pulse?

[@LesLaboratory]

There are Marx configurations for N2 lasers, but normally just two stages. I don't think there would be much to gain by dumping hundreds of kV in to one, but who knows, maybe interesting things would happen!

[@LarsBerntzon]

Im curious, how can one capacitor discharging into another create high voltage, is there no inductance at all there?

[@LesLaboratory]

The capacitor is already charged to high voltage (about 12 - 17kV or so) Discharging a comparatively large capacitance into a smaller one produces a very fast risetime (subnanosecond) which is required to pump a Laser like this. There is inductance all over the place (foils, leads, chassis etc) and these cause the circuit to 'ring' or oscillate when it fires. This can result in approximately twice the charging voltage appearing across the channel when it fires.

[@InssiAjaton]

I think your screws are steel ones. My reasoning has for years been (without any actual verification) that brass screws would be better in fast rise. All that might be true at medium speeds and iron and Eddy current effects already negated at really high frequencies (and fast rise currents). Maybe I should try some measurements instead of keep speculating? Come to think of it, my 100 kHz LCR meter probably is not up to the task, but the 13 MHz phase meter might. In worst case, I could build something around my 110 MHz amplitude and phase meter, for which I finally got a genuine HP sampling probe. Or maybe you could still extend your tests and reporting?

[@omsingharjit]

12:21 why this laser pack inside acrylic with Vacuum pipe if it's Atmospheric Pressure Tea laser ?

[@LesLaboratory]

To exclude air. Oxygen poisons Laser action.

[@omsingharjit]

@@LesLaboratory so it's pure nitrogen ?

[@LesLaboratory]

@@omsingharjit yes, pure Nitrogen is flowed through the tube.

[@georgegreen3672]

why not use another doorknob to replace the unstable foil capacitor?

[@LesLaboratory]

The peaking cap in this design is not unstable and will last for thousands of shots. If it ain't broke, don't fix it! By the time it fails, the channel is due for a clean anyway, so it's no big deal. The problem with using doorknobs for peaking, is that the inductance of the peaking stage is very critical. Doorknobs are likely to have too large an inductance.

[@georgegreen3672]

@@LesLaboratory I tried these capacitors in longitudinal excitation laser and I found they are very easy to happen breakdown. The seller told me these capacitors are unsuitable for HV impulse circuit. And will it happen in your TEA laser?

[@LesLaboratory]

@@georgegreen3672 It has survived so far! I am only driving it at 17.5kv (half its voltage rating). In a longitudinal setup, I suspect the voltage would be higher?

[@georgegreen3672]

@@LesLaboratory I think the voltage of LE mode is as same as that of TE mode, the difference is nitrogen pressure.