Modeling and electrostatic focusing for a field emission electron source

This paper presents theory and analysis of single-tip field emission and electron beam propagation in the electrostatic focusing fields. It is shown that two gate apertures with a focusing anode allow transport of narrow electron beams over long distances without need for a confining magnetic field. Physical mechanisms of the beam formation, transport, field emission energy distributions, the effects of the emission properties, and parametric studies are discussed, emission current formula is derived, and new concept and model of the bandgap-spread multilevel field emission is given.