Article - Return of the Vacuum Tube

[soundguruman]

That's what a Nuvistor is, a tube on a wafer, a link "between" solid state and valves...

[J M Fahey]

Not to nitpick, just to add some extra data, the atom size I found implied "normal" gaseous nitrogen at 25ºC and atmospheric pressure, and it was also implied the gas (can't use the word "solid", of course) filled that space.
By definition, a gas fill the container it's in.
The "atom diameter" word was used as small talk vocabulary; they actually said it meant the "atom influence area" diameter, the region of space where an electron would be deflected or otherwise have to deal with said atom, but I do not want to get pedantic with this, just want to introduce some actual size comparisons to have some idea whether it's a practical idea or just a faraway dream.
Anyway, considering nucleus to nucleus distance

In an ideal gas at STP, the molecules have a mean spacing of about 3.3nm.

on which I can't disagree, if you found that number, the electron still has 150/3.3=45 atoms in its path.
Although the possibility of hitting an actual nucleus is *very* small, (I fully agree with that, most of solid matter *is* free space), that doesn't need to happen; forces within and around "atom parts" are the strongest in the Universe.
That's why "solid" matter is "solid"
When I push the door with my finger , it does not get through it, although both my finger and the wood are 99.99% "empty space", because forces between atoms make them maintain their relative position and thus be "rigid".
Same happens with that poor electron trying to move through a gas, so best is to take said gas out.
Lowering "air" (gas) pressure dramatically (as in vacuum tube "vacuum") lowers dramatically the chance that an electron hits a gas atom on its path.
How dramatically:
Normal Atmospheric pressure: 101 kPa (101000 Pascals)
By the way, the article says "no vacuum needed" so I must assume the "nanotubes" are immersed in normal atmosphere.
There is not one word to the contrary.
Vacuum tube pressure: (from Wiki "Vacuum Tubes):

Historically, vacuum levels in production vacuum tubes typically ranged from 10 µPa down to 10 nPa.

or: 0.00001 Pascals to 0.00000001 Pascals.
So inside a vacuum tube an electron can find 0.0000000001 the amount of atoms it can find in free air. (worst case; best case is even 1000 times better).
Talk about "dramatically" less!!!!

Back to something basic that wories me: *nowhere* I found Dr Meyappan saying anything even remotely similar to what the article says he said.

Oh well, I'll stop worrying about this and go back to work, my lunchtime is over.

[R.G.]

There is no air ; in space..... :|
-g

Not bad Gary. 4-28 to 5-29.

[Tom Phillips]

That's what a Nuvistor is, a tube on a wafer, a link "between" solid state and valves...

Although RCA used the word "wafer" in the description of the base, a Nuvistor was really a miniaturized vacuum tube. It was only a link between valves and solid state in that it could be used to build smaller electronic assemblies than conventional tubes of the time. The attached cutaway drawing shows that there was no solid state technology utilized to manufacture Nuvistor tubes.

[km6xz]

It was too bad the Nuvistor was abandoned so early, they had some good properties. Unfortunately for instrumentation and high gain amplifiers their microphonics were terrible despite the RCA marketing point at the time listed lack of microphonics as being a major selling point. They were used in a number of test instruments of the 60s, like the Fairchild lab quality oscilloscopes where most that are still running probably have the original Nuvistors in them.
Earlier there were planar grid tubes, called Lighthouse tubes, that where made in layers that could have been adopted to etching processes. They were the first UHF tubes in the 30s, usually run in grounded grid configuration. The famous 416B low noise hf tube by Western Electric was a later adaptation. They were an acorn shaped and sized metal tube that were forced air cooled and used in grounded grid preamps for microwave relay stations were getting .5db noise figures in the late 50s and 60s. I got a "borrowed" one from a neighbor who worked as a tech for the point to point service for AT&T who gave one to me. I used it for moon-bounce 2 way contacts with the radio telescope that Cornell University was running at Arecibo PR with their meteor crater 1,000 spherical dish. I was 16 at the time and designed and build all my own gear to overcome the 138db path loss at 432Mhz. Without that 416B, the incredibly low return signals would have been impossible to "hear"(used a pen chart recorder to average noise to detect the slow pulse coding of Morse Code at 2 wpm). Solid state did not get close until GasFets were introduced in the 70s. I got an early HP produced GASFet transistor(cost me $86 in 1974 for a metal TO-18a transistor) and quickly built a .5db 150Mhz noise figure preamp that put an end to my needs for exotic tube preamps.
There was a lot if interesting work on tubes in the late 50s, pushing special form of the lowly vacuum tube to higher and higher frequencies, precision and lower noise. Unfortunately there has been no development on vacuum tubes in 60 years except in very high power applications where materials research has greatly increase reliability and power in the 20,000 watt range and higher, per device.
A pair of Eimac 8974 tubes would make a super reliable 4-5 million watt pa or guitar amp if you can find a supply for their single tube 22,000volts at 125 amp max plate current for that overloaded heavy metal sound. Of course, for really high power there were on-site constructed "tubes" that were for 50s and 60s shortwave broadcast or long wave navigation that ran in excess of 4 million watts for a single "tube" that were actually rooms with hatch door that allowed getting inside to replace elements, for example grids that needed to handle 40,000 watts of dissipation and 25 volt, 1000 amp heaters.
Just think of how good tubes could be now if materials research has been applied to small glass and metal ceramic tubes for consumer use during the last 60 years. Now we leave it up to old broken down factories with no automation to produce makeshift highly unreliable and low precision tubes using 1920s technology that varies 20-50% from piece to piece. Some golden ears pay incredible amounts of money thinking they are getting state of the art, precision devices when they are actually only getting the product of 90% hype, 5% value and 5% performance. If these current companies were operating in the 1950s or early 60s, they would go broke in a week when bulk buyers refused their shipments for not meeting spec or high incoming failure rates.

[Steve Conner]

Just think of how good tubes could be now if materials research has been applied to small glass and metal ceramic tubes for consumer use during the last 60 years.

Yeah, just imagine, they could be far smaller, come in cheap plastic packages, last forever and need no heater current! The tube manufacturers did keep on doing materials research, and the result of that was that they all stopped making tubes and got into the newfangled "crystal triodes".

Which everybody now uses except musicians.

[Tom Phillips]

…A pair of Eimac 8974 tubes would make a super reliable 4-5 million watt pa or guitar amp if you can find a supply for their single tube 22,000volts at 125 amp max plate current for that overloaded heavy metal sound...

That must be how Disaster Area achieved their signature sound level. With that cleared up I still wonder what they used for speakers.

[km6xz]

An array of 100,000 watt industrial 3 axis shaker tables?

[überfuzz]

Km6xz - ever heard about the lightbulb consperacy. Max 1000 h lifespann!

[km6xz]

No but I have seen the Adolphe Chailet made light bulb in Livermore California that has been operating continuously for 111 years except for one week when the fire house it was installed in was being renovated. Edison won the marketing success however with bulbs that lasts dozens of hours instead.

[mooreamps]

Not bad Gary. 4-28 to 5-29.

Tracking dates, are we ???? Just when I was beginning to wonder if anyone was still watching..... :|

-g

[Chuck H]

Don't wash your hair in the shower... You may need to close your eyes!

[Chuck H]

No but I have seen the Adolphe Chailet made light bulb in Livermore California that has been operating continuously for 111 years except for one week when the fire house it was installed in was being renovated. Edison won the marketing success however with bulbs that lasts dozens of hours instead.

It's worth noting, for a proper comparison of relative suitability, that all parameters need to be considered in a relevant way. I've also seen that light bulb. It's dim! I wonder how long it would last if you you pushed it hard enough to create the same lumens as a modern bulb?!? ... Relative.

[Tom Phillips]

I was recently using some old photography floodlight bulbs. They were R30 size 300 Watt GE floodlight bulbs left over from the 60's. The last two I had burned out before I finished the session. As I tossed out the last one I noticed that printed right on the bulb it said that the rated life was 6 hours. Another trade off... high performance / short life. Like a drag racing engine.

[Chuck H]

I was recently using some old photography floodlight bulbs. They were R30 size 300 Watt GE floodlight bulbs left over from the 60's. The last two I had burned out before I finished the session. As I tossed out the last one I noticed that printed right on the bulb it said that the rated life was 6 hours. Another trade off... high performance / short life. Like a drag racing engine.

Exactly. "I" could probably make a bulb that would last 1000 years! It wouldn't put out much useful light though. It's still pretty cool that a bulb someone probably bought frpm a hardware store has been in use for over a century.