Electron Gun Redux

16 04 2012

The hot cathode electron gun has been a real pain in the ass.

Based on comments we may have one or more of these problems:

1) The hot cathode has been fouled by operation in normal atmosphere. I tried to avoid this, but who knows.

2) When I removed the CRTs glass casing, I may have removed a high voltage anode.

3) The phosphor screen may not be grounded well enough, causing deflection of the electron beam by charge accumulation.

4) The vacuum pressure is too high, scattering the electrons.

5) Something else.

My plan is to set aside the CRT based  electron gun, and try to build a simplified electron gun from scratch.

Previously I purchased a fresh hot cathode designed for electron beam welding.

The gun will consist of a hot cathode floating at -100V and a copper tube segment at +2000V for acceleration. A grounded phosphor screen will reveal any beam that forms.

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One response

19 04 2012
Remy Dyer

Looks like an excellent plan to me :)

I love that you’re posting every gotcha you run into – there’s not enough of this in “mainstream” literature.

If you start to really appreciate Murphy’s Law, then I think this means you’re on the right track.

Take care of all the little things, and the big things will fall into place. (Or so they say).

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