The basic idea is you have a source of electrons and a way to get at least some of them going where you want. A simple way to do this is to have a hot charged f

The basic idea is you have a source of electrons and a way to get at least some of them going where you want. A simple way to do this is to have a hot charged filament (source of electrons) and a plate with a hole to attract them. Check out a google image search for "electron gun schematic" to get a better idea.