Hop - With a career background like that it should be a trivial task for you to build a working triode. ...
Working, yes, but high performance... probably not. I grew up puttering around with vacuum tubes before I was a teen-ager, and learned to appreciate the complexities of them before getting involved with semiconductors in the 1960s. In the Air Force I worked on defensive fire-control systems that had state-of-the-art equipment that used both vacuum tubes and semiconductors, but mostly vacuum tubes... tiny ones about the same diameter as a #2 pencil with teflon-insulated wire leads soldered to forced air cooled terminal boards and shock mounted in silicone. Those puppies were designed to survive the EMP from a nearby nuclear weapon going off in the vicinity of a B-52H heavy bomber, itself heavily loaded to capacity with nukes and hell-bent on mass destruction if the USA had to go to war. Those were scary times, what with a President and his brother and a civil rights leader getting assassinated and a crazy Russian pounding his shoe on a table in the UN. But we were prepared to respond in massive kind if the Big One went up. My EWO counterparts used bigger vacuum tubes: slide-out jamming racks filled with dozens of 4CX250B ceramic beam power tetrodes arranged as distributed RF power amplifiers. They would sometimes fire those puppies up and eliminate communications over a huge radius by broadcasting "white" noise. Amazing how much electrical power you can suck out of eight turbo-fan jet engines and still keep flying.
When it comes to power electronics at high frequencies, no one has come up with a replacement for magnetrons, klystrons, TWTs and BWOs for microwave power handling. Sure, you can push GaAs technology and create microwaves with Gunn diodes and whatnot, but for real "reach out and touch someone hard" kind of power you need vacuum tubes. Semiconductors are catching up (finally) but AFAIK it is still cheaper to use vacuum tubes for serious power from DC to microwaves. However for really high power, switch-mode semiconductors have totally replaced thyratron gas-tube switches.
In our shop we used a water-cooled triode as a series voltage regulator for a 12 kV DC power supply delivering several amperes to an electron-beam hearth. This tube failed twice during the sixteen years I worked there, so I sent it to
a guy in California who rebuilds them. Both failures occurred when cooling water failed and the machine did not shut down, not the fault of the tube. My fault after the first failure for not realizing there was no flow-sensor interlock on the return line of the water supply. Fixed that after the second failure.
I had a pair of 4PR1000A beam power tetrodes configured as screen-grid controlled push-pull variable-amplitude power oscillators, running at 40 kHz or so, driving a Cockcroft-Walton voltage multiplier to provide 1.7 MV terminal potential. The guy I replaced was changing these out every few years when he couldn't get the terminal voltage above one megavolt, but I discovered that no one had bothered to check under the chassis and clean out fifteen years accumulation of gunk, like the stuff that would accumulate on the back of the CRT in old televisions. That's when I discovered that
both ceramic wire-wound grid bias resistors had finally burned out. It would sort-of work with just one grid bias resistor because of the transformer cross-coupled feedback, but only with fresh new tubes. Replaced resistors, cleaned gunk off everything and it has worked fine ever since. Vacuum tubes are
tough if you treat 'em right. Well, at least they now have a half-dozen replacements on hand, unless the old tubes were discarded after I left. Someone told me people swarmed the lab and stole all the "goodies" I had stock-piled over the years I was there.
... This could get very interesting if you were to support the idea that DIY vacuum tubes are really doable in the home workshop. ...
It would have to be a well-equipped workshop to do it right, as Claude Paillard's video demonstrated. Nothing complicated or out of the reach of a determined amateur though. I thought it was a nice touch to use an induction heater to heat the plate to incandescence while pumping on the envelope to encourage outgasing. Didn't look like Claude used any sort of getter with his tubes. It is absolutely necessary to use a capacitor discharge welder to assemble things, but those are easy to make too. Not sure if he was using quartz or boro-silicate glass, but a tube annealing furnace is a good idea to stress-relieve the parts. I actually built one of these furnaces a few years ago from off-the-shelf components available from Omega Engineering. I used mine to melt aluminum to test the durability of our thin-film coatings applied to steel core-pins used in die-casting molds for aluminum engine blocks. So, yes, a determined amateur could make triode vacuum tubes as good as, and probably better, than Lee DeForest ever thought possible. That wouldn't be me though. I am too caught up in PIC microprocessors and learning how to do SMD assembly for now. A gave away most of my vacuum tubes to a fellow who restored "antique" radios, but kept a few power tubes "just in case" I feel the need to play around with tubes again.
... If you need a small DP I can post a couple of photos of a very simple pump that I've designed and built to pump on small experiments like tubes. It can be constructed in an afternoon with simple tools if the materials are at hand. The design defies the normal concept of how a DP works and dramatically reduces the complexity and number of parts required.
I would be interested in seeing your simple pump design. This doesn't involve using aluminum beverage cans does it? Please post some photos!
Hop