Emission Of Electrons Other Then Thermionic?

Are there other ways of making a cathode emit electrons then heating it up?
These could lead to alternative kinds of vacuum tubes.
P.S. Emissions of any kind of negative or positive particles would work. What about the emission of protons or other things?

hmmm ... a proton tube .
i don't think i would want to be in the same room with it .

this topic was touched on in another thread ... way in the past and the recent past .
tim mentioned that the (basically speaking) that the emission density and actual "work" (emmision) that could be had with radioactive materials would be very low .

photoelectric effect and the secondary emmisions such as in photomultiplier tubes?

Also http://en.wikipedia.org/wiki/Vacuum_arc

This post has been edited by ChipUser on April 01, 2011 03:02 pm

Cold cathode tubes exist - e.g. CCFLs don't have heated cathodes.

Also,

http://en.wikipedia.org/wiki/Field_electron_emission

There was also work done on tube tech using carbon nanotubes as cathodes. Any sharp point will bleed electrons if there's enough voltage on it. CNTs are so tiny that the required voltages can be quite low, & can be used in a layer consisting of an enomous number points.
I don't know what ever became of this concept.

As I understand it, electrons get emitted from something when they have enough energy to break loose. The only two ways I am aware of to give them such energy is (1) to heat them up and (2) to put them at high potential. Maybe there are other ways though.

-Adam O.

The presence of microphonics when wires are moved or boards are tapped may indicate that hammering also must be able to dislodge sufficient electons

I hear they fall out when you shake hard enough too

Interesting statement; I wonder just how much centripetal force is necessary to liberate electrons. Probably way more than that required to liberate ions from the substrate, i.e., the electrons are thousands of times lighter than the atoms they cling to, and are held with about the same energy (2-10eV work potential for most materials, vs. 5-20eV binding energy in the crystal lattice). In other words, the solid will rip apart in shreds before you get anything charged. More likely, the friction (triboelectricity) of the rotor in contact with stray gas molecules (since this would obviously have to be done in a vacuum!) would liberate more charge.

Tim

Ok, but what if you spin a beta emitting substance?

Here are some microwave/RF based sources for accelerators:
http://cdsweb.cern.ch/record/1334988?ln=en
http://cdsweb.cern.ch/record/1078804?ln=en
http://users.jyu.fi/~tvkalvas/publications...ib06_kalvas.pdf
http://www.lbl.gov/tt/publications/2744pub1.pdf