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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, intrinsic emittance with thermal effects, the effects of the emission properties, and parametric studies are discussed, and a new concept and model of the bandgap-spread multilevel field emission is given.