Modeling and Analysis of Aberrations in Electron Beam Melting (EBM) Systems
[Examensarbete på avancerad nivå]
We present a modeling framework which can be used to study aberrations in an Electron Beam Melting (EBM) system. This is achieved by using COMSOL Multiphysics R software to model the magnetic fields and relativistic charged particle trajectories of a model EBM system. This involves defining a model for the magnetic lenses that handle the functions of focusing, deflecting and correcting the electron beam. Simulations of the magnetic fields have been made for multipole fields up to 24 poles. Methods have been developed for characterization and quantification of the beam in the model. This is done in terms of deflection angles, focusing power and aberration spectra. A realization of aberration correction using a superposition of a Quadrupole and a Hexapole in a single lens is also presented along with aberration coefficients. We conclude with a discussion of the practical implementation of the beam sensing and control in EBM and future use of the modeling tools built for this thesis.
Nyckelord: Electron Beam Melting, Electron Optics, Aberrations, Finite Element Method, Charged Particle Tracing, Magnetostatics