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Hardware Technology

The Quest For the Ultimate Vacuum Tube (ieee.org) 109

An anonymous reader writes: IEEE Spectrum reports on progress in the development of vacuum tube technology, which remains surprisingly relevant in 2015. "In the six decades since vacuum tubes lost out to solid-state devices in computers, receivers, and power supplies, vacuum technology has continued to evolve and branch out into new terrain, sustaining a small but skilled corps of engineers and scientists around the world, as well as a multibillion-dollar industry. That's because the traveling-wave tube and other vacuum devices continue to serve one purpose extremely well: as powerful sources of microwave, millimeter-wave, and submillimeter-wave radiation. And now, ongoing research into a new and potentially revolutionary kind of traveling-wave tube—the ultracompact and ultraefficient cold-cathode TWT—looks poised to deliver the first practical device by the end of this decade."
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The Quest For the Ultimate Vacuum Tube

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  • by QuietLagoon ( 813062 ) on Wednesday November 25, 2015 @02:15PM (#51002975)
    EMPs are the death of solid state devices. But, due to their nature, vacuum tubes can weather EMPs fairly easily.
    • by Adriax ( 746043 )

      Is that why government tends to be decades behind when it comes to technology? A lingering cold war mentality of "No point progressing since the bombs are gonna fall any day now. Then where will your fancy silicon highways and databases be?"

      • by TWX ( 665546 ) on Wednesday November 25, 2015 @02:37PM (#51003145)
        No, happy accident. Kind of like how the old government buildings will protect their inhabitants from the radiation due to all of the lead paint.
      • by creimer ( 824291 )
        U.S. military installations are hardened against EMP attacks. U.S. civilian installations are not, mostly because the electrical industry doesn't want to foot the bill and the government never has enough money for infrastructure projects..
      • by Anonymous Coward

        Getting >50% efficiency from a TWTA at microwave frequencies is easy. Getting >25% from a solid state amplifier at the same frequency is hard, particularly as you get above 30 GHz.

        That's "wall plug" efficiency, and for a decent amount of gain.

        Getting 40-60 dB from a TWTA is easy (1 mW in, >100W out). Getting 50 dB of gain from solid state amps, with 8-10 dB/stage is really hard, particularly at the higher powers. If you want 100W at 30GHz, you're probably ganging up a lot of 4W MMICs, so you have

      • "No point progressing since the bombs are gonna fall any day now. Then where will your fancy silicon highways and databases be?"

        Given that the Internet Protocol and much of the rest of the networking technology that still underpins the Internet were developed as part of a cold-war program to create a communication system that could survive a nuclear attack that destroyed most of it, and still reorganize itself to pass messages quickly, efficiently, and automatically among any nodes that still had SOME path

        • still reorganize itself to pass messages quickly, efficiently, and automatically among any nodes that still had SOME path between them

          Yeah, that was the design. The implementation falls a bit short, as any number of backhoes have proven over the years.

      • No, that's not the reason.

        'Government' is decades behind because it takes that long to make sure something does what you need it to do, and train people to run it and fix it. Then if you find something better, the clock starts again. Unfortunately, you will have to take money from the operations budget on your old stuff to buy the new stuff, and therefore you won't be able to do anything in the meantime. Plus, you need to get the money from Congress, which has a 2 year cycle of having to funnel money into p

    • by rubycodez ( 864176 ) on Wednesday November 25, 2015 @02:37PM (#51003143)

      Vaccuum tube radios were damaged by EMP in the 1962 Kazakhstan Soviet tests, as were diesel generators (shorted windings).

      Facts are our friends.

      • Vaccuum tube radios were damaged by EMP

        The radios, yes. But were the vacuum tubes themselves?

        • by Anonymous Coward on Wednesday November 25, 2015 @03:24PM (#51003611)

          Yes. The voltage spike was enough to cause internal arcs in operating tubes, vaporizing electrode material..
          So the solution for tube equipment is the same as it it for BJTs and FETs - Faraday shield and heavy transient suppression on any unshielded conductors penetrating.
          Just less of it required for tubes as they can tolerate instantaneous voltages well in excess of their rated operating voltages and can dissipate a bit of energy without taking permanent damage, though for complex ultraminiature tubes those margins are orders of magnitude lower than for a simple dumb big triode.

          • by Anonymous Coward

            I work with pulsed high power solid state and vacuum tube RF systems in high voltage environments. Arcs, sparks, transients, and voltage spikes regularly destroy our solid state components but not our high power vacuum tube devices. We use commercial tetrodes in a few systems, making between 80 kW and 600 kW, they are super reliable and robust. We have spare tubes for the 600 kW tetrodes but have never had to replace one and were told by the folks who provided the system 15 years ago not to buy spares, w

          • by Prune ( 557140 )

            The voltage spike was enough to cause internal arcs in operating tubes, vaporizing electrode material.

            That they were operating is the first critical factor. Vacuum arcs between metallic elements that are not boosted by thermionic emission and are just driven by field emission require gradients on the order of gigavolts per meter, so even for small receiver tubes you'd need a difference of several million volts between the electrodes. With the cathode heated when the tube is operating, this is reduced by an order of magnitude. However, an EMP from a nuclear explosion that would generate something like this i

      • by Prune ( 557140 )
        If the wiring around the tubes had protection (say ultrafast spark gaps), the tubes would have come out unscathed, because even close-by electrodes in typical receiver tubes with the cathodes fully heated still need many tens of kV to cause a vacuum arc. A nuke-caused EMP can't directly cause that in a stand-alone tube unless you're in the blast radius -- the voltage was induced in the wiring. That means the damage to the tube comes from the wiring, not directly from the EMP, and so your comment is misleadi
    • by Ormy ( 1430821 ) on Wednesday November 25, 2015 @05:32PM (#51004635)
      I'm getting quite fed up of this myth. Solid state electronics are _momentarily_ disrupted by strong EMP, volatile and some non-volatile memory is wiped, so yes in a mission-critical situation they're not always suitable but capacitors and resistors and transistors all work just fine after the EMP has passed (seconds at most). I witnessed an experiment a few years ago where a strong but highly-localised EMP was directed onto a running consumer PC (windows 95 era). The computer predictably shut down, the CRT monitor had resetted to factory settings but otherwise worked just fine. The PC wouldn't boot because the BIOS had beed completely erased along with HDD firmware and the like, but we transplanted the CPU into a fresh machine and it worked just fine. Anything that doesn't rely on firmware or settings or OS stored on solid state (or magnetic) memory will likely function perfectly after (if not during) an EMP. As a simple example, an EMP would wipe all your gameboy/atari 2600 cartridges but the console hardware would still be working. I'm not trying to downplay the continued-yet-widely-unknown usefulness of vacuum tubes, its just this misconception about EMPs really annoys me sometimes.
      • by Prune ( 557140 )
        I see your anecdote and raise you another one: years ago, using an exploding wire disruptive switch in an LCR circuit (the C was 25 kV, 4 uF -- heavy but portable) and a really basic parabolic antenna, I permanently destroyed a portable CD player a few meters away.

        Also, in military experiments, even diesel generators were disabled by EMP from a nuclear explosion when the stator windings shorted between turns. Your comment only applies to solid-state parts which are either 1) disconnected from wiring that
      • by ncc74656 ( 45571 ) *

        As a simple example, an EMP would wipe all your gameboy/atari 2600 cartridges but the console hardware would still be working.

        Would they? I could see flash, EEPROM, or EPROM probably getting wiped by EMP, but weren't mask-programmed ROMs more common back then? Would they also be vulnerable?

    • I am confident that if I fabricated a transistor as large as a vacuum tube that it would be far more robust.
      • You should call NASA, I bet they're waiting for your call. You got any perpetual motion machines as well?
    • Ironically things like computers and tablets can be relatively resistant to EMP at least if isolated. Its stuff connected to the mains, or with long cable runs or aerials that is most vulnerable. Very high levels of EMP eg from nearby nuclear explosions are very difficult to stop, but even then a substantial Faraday cage can do a great deal. I'm half guessing here but with a multi-layer shield even very sensitive electronics should be virtually immune. The trick is making electronics systems that can keep r

    • I remember when they sneered at the MIG-25 Fox Bat because of the absence of solid state devices. Then, I learned about the Compton Effect and had one of those clarifying moments. Since then, the Russians have gone to fly by wire and on board computers (MIG-29, etc.). I wonder how they are dealing with the EMP issue?
    • Wow. I had no idea.

      Now if they can just micro-miniaturize vacuum tube technology, we can have a vacuum tube computer-on-a-chip.

      And the future envisioned in science fiction stories of the 1940s and '50s can become a reality. D. B. Davis can invent his amazing inventions, and Helen O'Loy can be "born".

    • How resistant are ferrite-core memory boards to EMP?

      Never mind. While using duckduckgo to find out if I spelled "ferrite" correctly, I also found the answer in Wikipedia. https://en.wikipedia.org/wiki/... [wikipedia.org]

      Answer: "relatively unaffected by EMP and radiation".

  • by Anonymous Coward

    I usually delete those spam emails

  • by cayenne8 ( 626475 ) on Wednesday November 25, 2015 @02:18PM (#51003001) Homepage Journal
    How does it sound in a guitar amp???

    ;)

    • by confused one ( 671304 ) on Wednesday November 25, 2015 @06:12PM (#51004845)

      Punchy lows. Solid mids. But where it really excels is highs. They're crisp and clear all the way to 200GHz and beyond. Of course you'll have to use our superflex cable with gold plated oxygen free copper conductors to really hear the difference!

      • Punchy lows. Solid mids. But where it really excels is highs. They're crisp and clear all the way to 200GHz and beyond. Of course you'll have to use our superflex cable with gold plated oxygen free copper conductors to really hear the difference!

        This one? http://www.amazon.com/Denon-AK... [amazon.com]

    • I was on an Air Base where the RADAR folks would sometimes play in the band next door in the Club. The PRR in the height finder was about 400 PPS and that would excite the "A" strings in the guitars. It sounded like plunk plunk..............plunk plunk........ as the antenna swept down and then up. That was back in 1976.
  • Could learn a thing or two from studying vacuum tube technology. Unlike most everything casts from silicon, you can actually "see" electron flow, with enough certainty to end the conceptual debate between hole flow and electron flow.
    • by creimer ( 824291 )

      I don't think Jacob's ladders count.

      http://www.repairfaq.org/sam/jacobs.htm [repairfaq.org]

    • What conceptual debate? Hole flow is a real thing

      • Re: (Score:1, Offtopic)

        by kyubre ( 1186117 )
        No its not. Hole flow is the migration across molecules, of a free valence band. Why is it free? Because the electron that was there, moved. Ergo, all electric current is electron flow and every schematic drawn by every semiconductor engineer got the arrow backwards.
        • Yes, the electron moved but there is *no continuous electron flow*, instead holes flow. Holes are real, holes flow, holes can make current

          • You know, I think we need to settle this once and for all ...

            Holes are for cows ... You are all cows. Cows say moo. MOOOO! MOOOO! Moo cows MOOOO! Moo say the cows. YOU, er, hole-flowing current-producing COWS!!

            And, no, I have no idea what you're talking about, I just think the cow thing is one of the funniest internet memes in years. ;-)

            • It's certainly an old meme, was doing it in IRC in the 90s. There was even a text to "moo" encoding script that could be decoded back into text by receiver with script but without that varying lengths and variations on "moooo!" were displayed

          • by kyubre ( 1186117 )

            If there is no continuous electron flow, there is no continuous hole flow. From the first sub-nanosecond a circuit is completed, it is not a "conceptual" hole that moves, but an electron. There is an appearance of hole migration across molecules, but such an analogy could claim that the valley of a tidal wave is what wipes out coastal villages, when in fact, the valley is the artifact of the crest.

            Perhaps you can point to the hole flow in an electron tube>

            • wrong, the electrons move from many directions to fill a hole, but the hole current vector has direction from positive to negative. you have seriously mistaken mental model of the process

              • by kyubre ( 1186117 )

                Reminds me of the negative vs positive logic arguments as DTL and RTL gave way to TTL (along with specialty, high speed ECL, which retained 'negative' logic).

                While it is true that a "charge" migration can be instrumented and measured as being either positive or negative, the only physical thing that moves is an electron. Nothing else, and by the way - there is no "ether" that fills the void either.

                This all reinforces my point that there is at least some benefit from learning how to troubleshooting a pentod

        • by Too Much Noise ( 755847 ) on Wednesday November 25, 2015 @03:20PM (#51003581) Journal

          If only it were as simple as that. He's still right about one thing though, your initial statement about "conceptual debate between hole flow and electron flow" is misguided. It's just the reasoning that's ... inexact.

          Both 'electron flow' and 'hole flow' are pseudo-particle descriptions of many-body transport phenomena. Heck, there are systems where the pseudo-electrons have anisotropic mass, charge/spin separation, and so on - hardly the behaviour of a free electron. Besides, that 'a free valence band' term you used is misleading - a vacancy is as ill-defined spatially as an extra electron in a strongly-interacting many-body system. 'Electron' and 'hole' flows both are the same concept - quasiparticle linearizations of otherwise (mathematically) intractable systems. So there is no 'conceptual debate', yet neither is a 'real boy^H particle'

          • by kyubre ( 1186117 )

            I didn't get hole flow/electron flow thing till I pictured it as a fireman's water bucket brigade operating in one of two modes and as observed from a 3rd party vantage point.

            Imagine a single water well, and two fire brigades extending off in opposite directions. One bucket brigade has a bucket for every person on the line except one. The other has but a single bucket. They are both moving water from the well to their corresponding fires, but to the third party observer, he sees a bucket moving in the "r

        • ... every schematic drawn by every semiconductor engineer got the arrow backwards.

          As I heard it, The arrow is "backward" because Benjamin Franklin, when doing his work unifying "vitreous" and "resinous" electricity as surplus and deficit of a single charge carrier (and identifying the "electrical pressure" later named "voltage"), took a guess at which corresponded to a surplus of a movable charge carrier. He had a 50% chance to assign "positive" to the TYPICAL moving charge carrier in the situations being

          • by kyubre ( 1186117 )

            ALL the charge carriers are ions - atoms or molecular groups with an unequal electron and proton count, and thus a net charge - which may be either positive or negative (and you're usually working wit a mix of both).

            Yes, you can argue that hole propagation is actually electron movement. But holes act like a coherent physical entity in SO many ways that it's easier to treat them as charge carriers in their own right, with their own properties, than to drill down to the electron hops that underlie them

            For me the big tell is that they participate in the Hall Effect just as if they were a positive charge carrier being deflected by a magnetic field.

            Thank you for the well thought out and logically coherent description of the underlying behaviors at play.

            The "hole" flow as typically dumped on the unsuspecting student of semiconductors, really doesn't mesh well when mated to the metal conductors that source and sink the current flow to them. As mentioned previously, my mental model of semiconductors and the like is a fireman's water brigade, were either the majority of the line has buckets or empty hands.

            For the line where there is but one set of emp

            • As mentioned previously, my mental model of semiconductors and the like is a fireman's water brigade, were either the majority of the line has buckets or empty hands.

              It helps if, instead of a line, you think of a LOT them standing in a two-D array (like in the yard of the burning building, or a section of a parade that's stopped to do a little demo). It's really three-D, but we'll want to use up/down for something else in a bit...

              For metallic electron conduction everybody has TWO buckets, one for each hand

  • The local PBS station in Silicon Valley had to shutdown and merge with a distant PBS station in the 1990's because the station couldn't afford the $50,000 replacement cost of the vacuum tube in their transmission tower.
  • by Anonymous Coward

    You are all cows. Cows say moo. MOOOO! MOOOO! Moo cows MOOOO! Moo say the cows. YOU WARMER, MORE NATURAL SOUNDING COWS!!

    • by TWX ( 665546 )
      I can hear the high-fidelity bovine call in my head as I read your post. Amazing.
    • This Cow guy has a strange appeal, one always wonders how he's going to work the topic of TFA into the cow post like I did for this topic:

      I wonder if the cow guy is going to respond to this one, and how?

  • In my experience, when someone feels the need to insist that something is "surprisingly relevant", it's usually unsurprisingly irrelevant.
  • I worked with TWTs in the 70s, airborne systems not space. We could admit to Ku band capabilities, and the real limiting factor we were concerned with was the high voltage required. And vibration.

    Fabulous devices. Lots of power output. Ours were tough. Radar systems relied on them mostly exclusively, replacing magnetrons. Very difficult to adjust though, and a finite life.

    Now, can we get cold cathode tech into 12AX7s and 6L6s?

  • PMT (Score:4, Informative)

    by sugar and acid ( 88555 ) on Wednesday November 25, 2015 @02:57PM (#51003365)

    The other place vacuum tube technology in a big way still exists is Photomultiplier tubes. Photodiode technology has come on significantly, but for very low light level applications PMTs win. They lose out in quantum efficiency to silicon and ingaas photodiodes at almost all wavelengths of light PMT are actually useful at. But the internal amplification of the tubes means dark noise is very low at low light levels. To the point that PMTs can detect single photon events (photon counting) with a collection area of an inch or larger. Avalanche photodiodes (photodiodes with internal amplification) can do photon counting but only on devices less than a mm, which limits their applications.

    Of course PMTs have their weirdnesses. The gain you apply is not able to be known accurately. The devices have weird non-linearities at low gain. They have a polarisation bias. And many more.

    • by GrpA ( 691294 )

      Not just photomultiplier tubes, but Image Intensifier tubes also - or more commonly known as "night vision goggles". These vacuum tubes have progressed so far that even the best solid-state technology doesn't come close to replacing it, and the best technology that exists still uses around 10 to 100 times the power required for the same approximate level of image.

      Yet these tubes can, depending on manufacture, image single photons.

      Even the new solid state tube hybrids ( eg, Electron Bombarded CMOS ) is still

      • Not just photomultiplier tubes, but Image Intensifier tubes also - or more commonly known as "night vision goggles". These vacuum tubes have progressed so far that even the best solid-state technology doesn't come close to replacing it, and the best technology that exists still uses around 10 to 100 times the power required for the same approximate level of image.

        How come all scientific imaging is done with EMCCD and now sometimes SCMOS?

        Honest question: I've never encountered an image intensifier tube in a

  • So you goggle "vacuum tube nanotechnology" and...

    http://www.newelectronics.co.uk/electronics-technology/how-vacuum-tube-technology-is-being-deployed-at-the-nanoscale/45695/

    .
  • Vacuum tubes make excellent high-power switches (talking the size of a 55-gallon barrel, here), and there are ultra-high-speed switches called Krytrons that are technically a type of vacuum tube, too. Also so far as I know vacuum tube final amps for very high-power transmitters.
  • The root problem here is that every time you think you've found the ultimate vacuum tube, you find one more.
    • This is like reading the reviews on the guitar sites... Is the Ruby tube better than the JJ? Is the Electro Harmonix better or is the Tung-Sol? What about the Mullard? How good is the JAN Sylvania? How do those compare to a NOS RCA? What tube sounds best for clean tone? What is best for overdrive?

      Disclosure: I own two tube based guitar amps, one of which is an old kit I just gutted and am in the process of re-designing...

  • "And now, ongoing research [...] looks poised to deliver the first practical device by the end of this decade."

    So up until now the multibillion-dollar industry has been founded entirely on impractical devices? Or if they mean the first practical vacuum tube of that particular type it might be useful if the summary gave some kind of brief explanation about what makes it different from/better than other vacuum tubes.

    (The TFA probably explains it, but the site is blocked for me.)
  • by steveha ( 103154 ) on Wednesday November 25, 2015 @03:59PM (#51003917) Homepage

    About 70 years ago, E. E. "Doc" Smith wrote a series of books that are wonderful space opera: the "Lensman" series. The space battles just keep escalating throughout the series, getting more over-the-top.

    My favorite plot point: they used the principles of a vacuum tube to make a device whose pieces included grids mounted in the asteroid belt, with more in other orbits closer in to the sun. In effect they turned the inner Solar System into one honking big vacuum tube, and created a weapon that could concentrate a significant fraction of the sun's output onto attacking enemy fleets. This was called the "Sunbeam". (Believe it or not, this wasn't the end of the escalation. The battles got even bigger after that.)

    When you say "ultimate" vacuum tube, I think that one is pretty hard to top.

    P.S. 200-word crossover fan fiction: what would have happened if the Battlestar Galactica reboot show had found Earth, and it was the Earth of the Lensman series?

    http://archiveofourown.org/works/495034 [archiveofourown.org]

    When I was a teen and read those books, I just enjoyed them, but now I'm thinking that it would take a lot of trust to allow Kimball Kinnison to run around acting as judge, jury, and executioner. As readers of the books, we know that he was vetted as deeply as anyone could be by the Arisians, so he can be trusted with that kind of power; but it would be hard for the ordinary people in the world of the books to trust him that much.

    • You can download a few of his books from http://gutenberg.org/ [gutenberg.org]
      I'm reading right now 'The Galaxy Primes', it is a bout psionic humans who find lots of planets settled by humans.
      I read the Lensmen as a boy, at least those which where translated into german.
      Unfortunately I found only two lensmen cycle books on gutenberg.org, but it is still worth reading.
      However the 'escalation to bigger and bigger' is a typical thing at that time in SF ...
      Even Honour Harrington suffers from this a bit.

  • As an aside, never forget that microwave emissions are a natural, expected result of plasmas conducting electric currents. The point seems to have been completely lost on cosmologists who seem to believe that a microwave background signal coming at us from all directions can only be explained in metaphysical Big Bang terms. Actually, there would be nothing particularly difficult about explaining the CMB with plasmas, the most common state for observable matter ... It is simply a matter of explaining why
  • Another vacuum tube technology with current applications and substantial advantages over semiconductor approaches to the same problems is the Thermionic Converter [wikipedia.org]. This is a vacuum-tube technology heat engine that turns temperature differences into electric power - by boiling electrons off a hot electrode and collecting them, at a somewhat more negative voltage (like 0.5 to 1 volt), at a cooler electrode.

    Semiconductor approaches such as the Peltier Cell tend to be limited in operating temperature due to th

  • ....as a vacuum tube (mostly TWT) engineer since 1968:

    I don't remember when they started working on cold cathode tubes, must be about the time they started working on fusion reactors. Both are now going to be ready in "another five years". Meanwhile, satellites in orbit run their tubes for 30,000 hours, limited by the amount of barium and unobtanium that boils out of their cathodes at 1000C. Or, the power supply shits the bed.

    Nobody uses little tubes any more, except rock star guitar players (and wannabees

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