| 摘要 |
A system collects a source of electrons allowing for internal space charge build-up and hence internal self-electric field build-up that results in self-emission at a predetermined location (needle) in the system using components of: a conducting medium at one end of the structure denoted as the needle having a work function of less than Y eV (typical absolute values 3 to 4 eV) acting like a cathode and allowing for field emission; a conducting rod between the needle and cup to transport collected electrons with work function greater than X eV; an annular dielectric insulator, plug, with rod passing through acts as an electrical and mechanical barrier for mounting and as a barrier for pressure differentials; a source of electrons to provide electrons into the cup portion of the assembly acting like an anode; a beam drift tube to house and enable electron transport to the cup-rod assembly, the surface of the cup and rod have a work function greater than X eV; the plug with rod passing through seals and terminates the beam drift tube at one end; the cup-rod-needle assembly may be isolated electrically; the beam drift tube supporting a vacuum of less than 5 Torr; and wherein X−Y≧2.5. |
