Simulation of secondary electron emission in an electron gun

To decrease the size of electron beam in an electron gun, sometimes an aperture with a small hole is used to cut off the electrons with large divergence angle. However, a few secondary electrons may be emitted when the primary electrons bombard on this aperture. This article simulates the secondary electron emission in an electron gun. In the simulation, the aperture is suggested to be a perfect metal electrode first. Therefore, there is no secondary electron emission when the primary electrons bombard on it. Then, it is assumed that some secondary electrons and back scatters can emit from the aperture. This paper also changes the diameter of the hole in aperture. From the comparison of the spot on the screen, the influence of the secondary electrons on the spot profile can be estimated.