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

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."

Comments

Vacuum tubes handle EMP's better

[QuietLagoon]

EMPs are the death of solid state devices. But, due to their nature, vacuum tubes can weather EMPs fairly easily.

Re:Vacuum tubes handle EMP's better

[rubycodez]

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

Facts are our friends.

Re:Vacuum tubes handle EMP's better

[TWX]

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.

Re:Vacuum tubes handle EMP's better

[gstoddart]

And, they won't burn due to all of the asbestos. It really is a win-win situation. ;-)

Re:Vacuum tubes handle EMP's better

[Anonymous Coward]

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.

Re:Vacuum tubes handle EMP's better

[Ormy]

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.

Re:Vacuum tubes handle EMP's better

[St.Creed]

I would *snort* at this, but my gasmask is in the way.

Yeah, but he REAL test!!!

[cayenne8]

How does it sound in a guitar amp???

;)

Re:Yeah, but he REAL test!!!

[confused one]

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!

Re:My beanburger tastes like real meat, which I ha

[TWX]

In my experience, when someone feels the need to insist that something is "surprisingly relevant", it's usually unsurprisingly irrelevant.

What a surprisingly relevant insight...

PMT

[sugar and acid]

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.

Re:Many a young engineer....

[Too Much Noise]

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'