Field emission cathodes are very useful in very small electron devices.
They can't be called vaccum tubes because they can operate at atmospheric
pressures.
The spacing between elements is small compared to the mean distance between air
molecules.
Tiny structures.
Some have experimented with making sort of integrated circuits using these
but much too complicated
to build compared to semiconductors.
Some have experimented with using carbon nanotubes on cathodes but not very
useful results since I last
looked which was a couple of years ago.
73
Bill wa4lav
________________________________________
From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
jeff millar [jeff@wa1hco.net]
Sent: Sunday, August 14, 2011 1:52 PM
To: amps@contesting.com
Subject: Re: [Amps] Any new tube research? (WAS) Re: New NXP BLF578XR 1200W
LDMOS FET is "indestructible"
Hollow State devices (tubes) have a number of potential advantages over Solid
State Devices.
- Orders of magnitude greater electron mobility (they fly through vacuum
better than through solids)
- Mechanical construction around the perimeter rather than through the body
of the active area
- minimal need for packaging when used in space
Areas of advanced technology include...
Spindt cathodes
- http://en.wikipedia.org/wiki/Field_emitter_array
- Make a sharp point on the atomic scale and electronics emit without
heating
Plasma TV's
- Highly integrated Hollow State device
Relativistic Electron Tubes
- http://en.wikipedia.org/wiki/Gyrotron
- http://en.wikipedia.org/wiki/Free_electron_laser
- basically a free electron Maser
Lastly
- http://www.4p8.com/eric.brasseur/intvac.html
jeff, wa1hco
On 08/13/2011 02:58 PM, Jim Barber wrote:
> I made a side-thread for this since it isn't directly related:
>
> This discussion of "super semis" makes me wonder if anyone is still
> engaged in vacuum tube research these days. Could any of the basic tube
> wear points be improved on with modern technology? Could filaments be
> made to emit twice as long without degradation?
>
> I just looked at the CPI Eimac site and I can't see where they're
> motivated or have the resources to innovate at the basic level. They
> list "Amateur Service" as a product category, which can't bode well for
> volume sales... Assuming MOSFET technology passes tubes by at high power
> levels, will they just go quietly into the night?
>
> I hope not - there's no second chances with current solid state devices.
> Generally speaking, they do not degrade gracefully... ;-)
>
> 73,
> Jim, N7CXI
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