A new method of emittance measurement for electron beams from the Micro-emitter

Abstract

Recently a new type of cathode called Micor-emitter has been put in progress. This cathode is a microfabricated field emitter having the characteristics of very low emittance and high brightness. We cannot measure the emittance of the cathode with conventional methods like the pepper-pot method. The reasons are: (1) the angle between the electron orbit and the axis is very small and (2) we cannot focus the electron beam in the vacuum or on the surface of the material since the current density of the cathode is extremely high. For the emittance measurement for such low emittance and high brightness cathode, we need to expand the beam, and measure the beam's cross section without any slits or apertures. We studied and proposed a new emittance measurement method for the Micro-emitter.