# Up/down electron gun construction?

Gold Member
up/down electron gun construction??

Greetings!
I'm working on a project that Requires a roughly equal number of up and down spin electrons to be injected into a (vacuum or ATP) chamber. Is there a common device that does this? If not, would it be possible to build one and how would it work? I'm familiar with how electrons in certain devices are produced by "boiling" electrons off a hot tungsten wire, but what is the ratio of up to down spin electrons?

Thanks,
Taylaron

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Bobbywhy
Gold Member

Here is a website that explains how spin up and spin down electrons are produced and also, how a spin analyzer is constructed:
http://web.utk.edu/~cnattras/Phys250Fall2012/modules/module%203/spin.htm [Broken]

Here is website describing an experiment where the electrons’ spin is used to store data using “spintronics”:

“In the prototype device, electrons pass into the polymer, and a magnetic field orients them as spin up or spin down. The electrons can then pass into the conventional magnetic layer, but only if the spin of electrons there are oriented in the same way. If they are not, the resistance is too high for the electrons to pass. So the researchers were able to read spin data from their device based on whether the resistance was high or low.”
http://www.sciencedaily.com/releases/2010/08/100809171533.htm

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mfb
Mentor

I'm familiar with how electrons in certain devices are produced by "boiling" electrons off a hot tungsten wire, but what is the ratio of up to down spin electrons?
Do you have any reason to expect a preferred polarization there? Without an external magnetic field, you do not even have a meaningful direction to say "this is up".

Gold Member

Do you have any reason to expect a preferred polarization there? Without an external magnetic field, you do not even have a meaningful direction to say "this is up".
Are you suggesting that there are roughly equal amounts of up/down spin electrons from a source utilizing thermonic emission? If it's safe to assume that the spins of each emitted electron are random, then that would be acceptable to me. In my experiment I don't need to readily distinguish between up and down electrons, only that there exist roughly equal amounts.

Thanks!

Gold Member

Since the spins of the electrons from the electron gun are randomly oriented, 50% of the electrons in the beam are deflected upward and the other 50% are deflected downward. Before the magnet we cannot predict whether an individual electron will be deflected upward or downward. But after an electron has passed through the magnet, we know the z-component of its spin. We have constructed a spin analyzer.
http://web.utk.edu/~cnattras/Phys250Fall2012/modules/module%203/spin.htm [Broken]

Perfect! Thanks Bobbywhy!

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Gold Member

If I wanted to make an electron gun in the ambient atmosphere, could I use the negative terminal of a tesla coil or flyback transformer as the electron source, then use a series of HV plates to accelerate the electrons like a traditional electron uses? Could I even bust off the ends of a CRT electron gun, replace the tungsten element with the output of the tesla coil? Does the electron emission of a tesla coil even compare to that of a CRT monitor’s tungsten element?

Drakkith
Staff Emeritus

If I wanted to make an electron gun in the ambient atmosphere, could I use the negative terminal of a tesla coil or flyback transformer as the electron source, then use a series of HV plates to accelerate the electrons like a traditional electron uses? Could I even bust off the ends of a CRT electron gun, replace the tungsten element with the output of the tesla coil? Does the electron emission of a tesla coil even compare to that of a CRT monitor’s tungsten element?
You realize that electrons cannot go anywhere without running into air molecules right? At best you would have an electric current that ionizes the air.

mfb
Mentor

You can have moving electrons in gas - but it will not look like a gun, you get something similar to a drift chamber.