vacuum tube simulator? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: September 03, 2018, 04:49:32 pm
content: Are there any programs that can be used to simulate the effects going on inside of vacuum tubes? Even proprietary stuff known to exist?I mean from a 3d design standpoint.From what I gather plasma is difficult/unheard of, but how about a harder vacuum ?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 03, 2018, 09:15:55 pm
content: A rubber sheet and some sticks.http://www.dos4ever.com/E1T/E1T.html

author: coppercone2
author_rank: Super Contributor
timestamp: September 03, 2018, 09:19:47 pm
content: How is vacuum tube prototyping done? I would have never thought of the rubber sheets though, kind of like gravity simulation I guessCan you get away with a gasket or do you need a container that has to be glass hermetic?I was imagining some kind of setup where you have a bunch of feedthruoghs and a nice vacuum hose connector and vacuum capable valve in a ceramic or glass base and have a bell jar that seals over it some how...\I assume the largest problem would be hygiene?

author: james_s
author_rank: Super Contributor
timestamp: September 04, 2018, 12:48:49 am
content: I don't know how prototyping of the tubes themselves was typically done, although I know in some stages actual prototype tubes were sealed in envelopes. It would certainly be possible to put a bare tube structure inside a vacuum chamber however I'm not sure that would save any time over just making several prototypes and sealing them in envelopes. The construction of the electrodes is going to be the time consuming part, fusing an envelope over the base can be done in just a few minutes.

author: coppercone2
author_rank: Super Contributor
timestamp: September 04, 2018, 12:56:17 am
content: I thought maybe you can do some things like simulate mechanical damage and such to see how it works slightly deformed or experiment with adding little helmholtz coil things and such.. or maybe experimenting with spacings between parts and stuff quickly?If its oversized you can standardize it and test multiple tubes together.I guess I would have to see someone go through the development process.I kinda thought about it and I thought it might be annoying to try to store all the different sizes of glass tubes you might need, cut the tubes, deal with glass dust, glass fusion.I feel the same way about welding, like sometimes people will weld stuff to their welding table to act as a clamp instead of using clamps, then you can just grind the tiny weld spot off.. but for some reason this seriously irks me and I don't follow this practice. Maybe if I had like a 5 inch thick steel welding table, but it still freaking bugs me.I don't know that much about tubes I guess, about how engineered each one is, or if there is any reason to be able to quickly switch out some kind of sub component or something.If all the geometries are super tight and agree well with the calculations? then I guess what you are saying makes sense. I imagined them to be loose for some reason.I also want to do experiments with laser heating tubes, no matter what the consensus on how retarded it is is. I figured I might be fucking around with mirrors inside of the vacuum chamber or something.

author: David Hess
author_rank: Super Contributor
timestamp: September 04, 2018, 01:02:48 am
content: I have seen the math involved for standard structures so I am not sure what would need to be simulated there.I doubt a reusable mechanical assembly will work well due to outgassing and trying to maintain or even achieve sufficient vacuum. It does not take much residual gas to significantly affect performance.

author: coppercone2
author_rank: Super Contributor
timestamp: September 04, 2018, 01:05:47 am
content: Quote from: David Hess on September 04, 2018, 01:02:48 amDo you think that solder would outgas alot? I know an o-ring is kinda shady, and its hard to make crushable copper gaskets for a bell jar, but the idea I had is to make a bell jar with a invar ring that is revealed on the bottom, then coat this ring with special solder, and make the bottom surface have a similar ring that is also heated, so you can place the belldown jar and melt the solder (using the low melting point s-bond stuff). I thought if you keep it hot but not molten during the vacuum for a while it would offgas everything, then you let it cool.It's gotta be a bit better then rubber I think so long you don't flux it and use some diethyl ether, butane or something even more volitle to clean it before use (I think it will destroy the oxides with scrubbing). Methanol sounds like a good candiate to a somewhat reactive solvent and its easy to obtain in extreme purity.I figure that metal will be generally difficult to keep clean.. I don't know the prosity and such or if the methods commonly used in vacuum systems like particle accelerators which seem to be made of metal. When I saw that stuff it looked like machined stainless but I don't really know.If the solder is no go can you use the crushable copper gaskets? But I think they are mad expensive.Do you need a turbomolecular pump for this work?As for the holders and stuff inside I thought you can just make it out of ceramic and heat it till hot red with a clean torch before use, then quickly cap it.. it should take at least a bit to cool off and absorb any crap from the air even if its pourus on the surface.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 04, 2018, 01:15:34 am
content: There is a YT channel, glasslinger where they show making their own tubes in detail.

author: coppercone2
author_rank: Super Contributor
timestamp: September 04, 2018, 01:21:32 am
content: does anyone else just find this completely unappealing it it regularly involves breaking glass?I am just like imagining I get sidetracked while doing it, and there will be this broken glass stem fucking decorating the area. It makes me feel like a criminal. It's about as appealing as doing experiments on my home septic system. (barf smiley)Spasmenagaliaphobia ?

author: David Hess
author_rank: Super Contributor
timestamp: September 04, 2018, 01:26:51 am
content: During the vacuum tube manufacturing process the entire tube is heated while vacuum is applied to accelerate outgassing and even with that, a getter is used.A hermetic seal and big vacuum orifice strikes me as the right way to try it but I am no expert. Would a turbomolecular pump reach the desired vacuum level?Wikipedia says 10−5to 10−8Pascals for vacuum tubes and I know higher vacuums are requires for higher voltages; CRTs require a much better vacuum than a typical vacuum tube. Turbomolecular pumps can get up to 10−8Pascals so it seems feasible. Your typical vacuum pump for refrigeration service is not going to cut it.

author: coppercone2
author_rank: Super Contributor
timestamp: September 04, 2018, 01:28:35 am
content: Quote from: David Hess on September 04, 2018, 01:26:51 amI am pretty sure it would diffuse oil. There is no way I would think to put a refrigerator pump near it. I think the second stage would be one of those oldschool pumps that has the big flywheel on it and goes dumdumdumdumdum (or maybe clapclapclapclap (quiet clapping) and the first stage would be a turbomolecular pump, and you would do the measurements with cheap ion gauges.As for the getter I imagined putting up meshes of reactive material to heat and pass current through (like nets on a tennis field).\I don't think a bell jar would appreciate being heated hard repeatedly.Does contamination slowly break these things or do they just not function properly at all as soon as there is a bit of it?I wonder if swagelok makes a good enough valve that would work for a while or if you need to some where introduce a stem which you need to fuse. I feel better breaking some kind of replaceable 2 inch long tiny bit of glass.. but it would need to be inserted between some kind of metal fittings or something that unscrews. I don't want some kind of protrusion thats regularly broken coming out of my main vacuum chamber. I am worried the pumps would produce harmful EMI for measurements... and be a power hog...What does contamination actually do to a tube?Also my intention would be to fuse optical grade windows into the base some how, and maybe germanium optics, so infrared and high power laser energy can be beamed into a mirror network

author: joeqsmith
author_rank: Super Contributor
timestamp: September 04, 2018, 01:39:49 am
content: They made a small X-ray tube and show it in operation. Fairly high voltage. This one shows them sealing up the tube. A fair bit is involved. There is a video where he talks about the pumps he uses.

author: coppercone2
author_rank: Super Contributor
timestamp: September 04, 2018, 01:48:25 am
content: I wonder how much of this stuff is for longevity though. I just got like 6 videos to watch through.

author: David Hess
author_rank: Super Contributor
timestamp: September 04, 2018, 02:05:30 am
content: Quote from: coppercone2 on September 04, 2018, 01:28:35 amThis free and excellent bookhas at least one chapter on the subject.QuoteAlso, no matter how tempted you are with the prospect of unlimited power, do not consume any energy field bigger than your head.

author: coppercone2
author_rank: Super Contributor
timestamp: September 04, 2018, 02:11:22 am
content: I am not trying to violate laws of entropy. However I am convinced if this apparatus is built some monkey is going to stick a 'rodin coil' in it and confuse youtube for the next decadeAnd yes it seems incredibly rupe goldberg and complicated but at least its interesting

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 04, 2018, 03:22:17 am
content: It is my impression that most existing tube types were done with a fair amount of trial and error, guided by some rough calculation and 2D pencil and paper field mapping using relaxation methods and a lot of experience with prior designs. The mindset of using simulation methods to design everything just didn't exist in the vacuum tube era. Didn't permeate everything until the eighties or nineties.

author: james_s
author_rank: Super Contributor
timestamp: September 04, 2018, 05:51:38 am
content: Quote from: coppercone2 on September 04, 2018, 01:21:32 amIf you ever did any kind of glassblowing you'd find that breaking glass is a frequent occurrence. It doesn't really matter, glass is easily recyclable. When you do wordworking you end up with a lot of sawdust, if you work with metal you get chips and scraps. That's just the way it is.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 04, 2018, 05:29:16 pm
content: Possible ideas, CST Particle Studio referenced herehttps://arxiv.org/ftp/arxiv/papers/1509/1509.06363.pdfVarious codes here:https://ptsg.egr.msu.edu/(free code -- ready to go, have at it!)TECs may be relevant:https://aip.scitation.org/doi/abs/10.1063/1.4865828?journalCode=phpOther methods? See also related papers:https://www.sciencedirect.com/science/article/pii/S0168900204011179Not hard to find literature. Since you're talking an enterprise-level experiment (creating new vacuum tubes, presumably as an improvement upon existing ones), it's going to be many dollars and hours worth of research, at times frustrating but also rewarding. You will certainly be able to budget a few articles and subscriptions into that research, as well as the classes necessary to understand and work on these topics.As for actually fabricating any, I wonder. It's hard to imagine any improvements upon the classics, even with modern manufacturing methods and materials.I wonder how things could be 3D printed. Maybe laser fusion with wire/fiber material feed? Metal, glass and some ceramics could be done this way. You wouldn't be able to use diverse materials; you'd be limited to, say, iron, copper, nickel and such for cathode and plate materials, with molybdenum and tungsten having to be added in whole wire form, brazed in place. So that would be at least three feeders plus a laser (or e-beam), each of them having multiple axes of movement to coordinate the fabrication of complex structures.I don't know that you'd be able to deposit emissive material in this way though. Classic oxide cathode material is sintered from oxides and carbonates in a pressed powder form, and as far as I know, that porosity is a key part of its operation.Photolithography is a more likely option. Hybrid ceramic substrates (usually alumina) could be metallized, etched, back-etched and so on, creating MEMS structures for cathodes (they'd be directly heated) and grids, with spacings much tighter than any of the classics were able to achieve -- presumably in this way you could make a planar triode with center frequency beyond 20GHz, or a distributed amplifier* with nearly comparable total bandwidth.*It wouldn't be a travelling wave tube, in the conventional sense. It could be a microstrip transmission line, formed from cathodes and plates distributed either side of a grid (ground/shield). These were made from time to time (in the 60s to 80s), using planar triodes and lumped equivalent transmission lines, but a micromachined tube could be a much finer grained model, with much smaller lumps, or true continuous transmission lines, giving very wide bandwidth.You still have the problem of heaters, or field emission noise and reliability if you go that route. There's also the matter of space charge and the virtual cathode, which I don't know what sets its dimensional scale (possibly temperature?), but for conventional oxide cathodes it was always a few tens of thou, so that grid-cathode spacing this close ran into space charge effects which result in higher distortion.You'll still not improve upon the PHEMT, which does all of these things, on a much smaller scale still, without any cost of heater power. And vanishingly small noise. A high voltage PHEMT would be interesting, but GaN is already pushing into power electronics, so I don't see any possible way you'd bring back the tube, at any combination of voltage, current and frequency.Tim

author: coppercone2
author_rank: Super Contributor
timestamp: September 04, 2018, 06:49:45 pm
content: I really wanna try laser heating man, im hot for itI doubt im gonna improve anything or even make something work well but its cool. I see this as a10 year goal maybe.* To at least get the gear together and learn to use and fabricate some of this stuff.Right now at least I have alot of fine pliers and cuttersI am also imagining things like silicon dies hanging inside of vacuum tubes for some kind of hybrid circuits. I am sure something entertaining could be found.*Actually I think its never gonna happen because with the way my fucking test equipment is treating me I am pretty sure when I accumulate enough to do this experiment I will reach some kind of critical mass where I am always fixing some broke ass shithaha maybe if I win the fucking lottery. fucking silicon.how do you guys avoid the urge to assault equipment with a axe? I already tuned a few phones and a laptop into shreds due to annoying transient problems.. consumer is not even worth fucking with when it breaks I think, I just get the sense that I am trying to glue a fucking turd back together.When I don't see protection diodes and common sense shit in circuits I get total rage now. Manufactures 'savings' cost me so much fucking time and energy.

author: Cyberdragon
author_rank: Super Contributor
timestamp: September 04, 2018, 11:06:58 pm
content: Don't go thinking tube stuff will be any better. Once you get the murphy curse, it's permanent.With the murphy curse, tube stuff suffers from odd mechanichal failures in the controls and whatnot that are super annoying. Like a sticky or loose planetary friction drive (ball bearing used wrong), press fit shafts into weird material (breaks loose), heat expansion issues, crunchy ceramic bits, frozen set screws (especially in deep holes), broken button mechanisms, etc.

author: james_s
author_rank: Super Contributor
timestamp: September 05, 2018, 01:41:58 am
content: Even if you had a perfect ideal vacuum pump you'd still have to heat the tube structure to drive the moisture out of the materials, otherwise it will outgas like crazy. You *might* be able to get away with it if you left the pump running continuously.This is the best source of vacuum system information I'm aware of:http://www.repairfaq.org/sam/lasercva.htm

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 05, 2018, 01:52:09 am
content: Quote from: CatalinaWOW on September 04, 2018, 03:22:17 amI don't agree, check my link.

author: coppercone2
author_rank: Super Contributor
timestamp: September 05, 2018, 01:52:26 am
content: how hot do you need to get the surface of glass to outgas good enough?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 05, 2018, 02:48:10 am
content: Quote from: Alex Eisenhut on September 05, 2018, 01:52:09 amI could agree that we are both right. The mindset that everyone starts with Spice or Simulink or some other behavioral similation is new, but I agree that simulations have been used for a long time.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 05, 2018, 02:53:48 am
content: Quote from: CatalinaWOW on September 05, 2018, 02:48:10 amI'll agree that I'm right.

author: james_s
author_rank: Super Contributor
timestamp: September 05, 2018, 02:56:29 am
content: Quote from: coppercone2 on September 05, 2018, 01:52:26 amIn the case of neon tubing, it needs to be heated up to approximately 300C during the final stage of processing. I remember reading about CRT rebuilding but I don't recall the temperature. In that case the oven had to follow a specific ramp up and cool down profile to prevent cracking.

author: rrinker
author_rank: Super Contributor
timestamp: September 05, 2018, 06:11:11 pm
content: Quote from: Alex Eisenhut on September 03, 2018, 09:15:55 pmWell, that was a great time sink - bu I enjoy history so it was a great read. Fascinating stuff.

author: coppercone2
author_rank: Super Contributor
timestamp: September 05, 2018, 06:46:40 pm
content: Quote from: james_s on September 05, 2018, 02:56:29 amThat's pretty hot. 400c will decompose almost all organic things

author: Gyro
author_rank: Super Contributor
timestamp: September 05, 2018, 07:19:07 pm
content: Quote from: james_s on September 05, 2018, 02:56:29 amMaybe this is what you were thinking of. Still a great video...https://www.eevblog.com/forum/chat/the-craft-of-picture-tube-rebuilding/

author: james_s
author_rank: Super Contributor
timestamp: September 06, 2018, 04:26:12 am
content: It wasn't actually that video but it was the same business. The equipment now resides at the Early Television Foundation museum in Ohio and last I checked they were getting it set up. I wish it was somewhere near me, I'd love to volunteer to learn the craft. CRT rebuilding is an art that is in danger of dying.