The effect of non-uniform magnetic field on the energy spread of a low energy electron beam

Abstract

Abstract This work aimed to enhance a resolution of the electron diffraction pattern by improving the longitudinal and lateral coherence of electron beam. Using a uniform magnetic field and slits is a cheap and straightforward method. However, such magnet requires a larger space. Smaller solenoids which create a non-uniform magnetic field are more applicable, especially when space was limited. bTherefore, the effect of a non-uniform magnetic field on the energy spread of the electron beam was investigated numerically and experimentally. The simulation results agreed well (within 10%) with the measurements. It has been found that the ferrite core solenoids together with a narrow slit can be used to improve the beam coherence. However, beam shape observed form the real measurement significantly deviates form the simulation result. In addition the non-uniform magnetic field, the beam trajectory was affected by the electric field form electron gun which causes the change of beam shape and spatial distribution.