Fast Electron Gun Design Methodology Based on Fitting the Beam-Edge Potential Profiles

Abstract

To shorten the design cycle of the 2-D axisymmetric electron gun, a new design methodology is reported in this article. Unlike the method of iterating the electron gun structure through particle simulations, for the primary beam optics design in the anode-cathode gap, this method mainly needs pure electrostatic simulations to achieve the target beam-edge potential profiles. Based on such an approach, the required electron gun structure, including the cathode, control electrode, and anode, can be quickly obtained. The subsequent particle simulations for handling higher order effects typically require minor geometry adjustments relative to the anode-cathode gap to complete the whole design. Following the proposed procedure, the results show that the target beam parameter with good trajectory laminarity would be obtained. The simulations on electron guns with three different configurations also reveal that any control electrode could achieve the same goal if it satisfies the target beam-edge potential profiles. Finally, the factors affecting the electron laminarity are discussed using one of the electron gun configurations. After that, a set of clear and complete primary beam optics design processes for the electron gun is summarized.