The Design Method of an Electron Beam Expansion Device Based on Double Solenoid Lenses

A design method for double solenoid electron beam focusing lenses is presented, based on the beam optics theory. Starting from the exit state of the accelerated electron beam, the method adopts two solenoid magnetic lenses to achieve the goal of increasing the beam's transverse cross-sectional size and reducing its divergence angle. Compared to traditional beam-focusing lenses with quadrupole magnets, the device owns a simpler structure, smaller volume, and clear principles, and holds potential for applications in electron beam irradiation, electron beam processing, electron beam testing, etc. This paper theoretically investigates the transmission laws of relativistic electrons (1 meV) in the different magnetic lenses and subsequently models numerically for verification. More specifically, initial energy dispersion (up to ± 2%), manufacturing errors and assembly errors (± 0.1 mm/1mrad) affect beam transmission are discussed. This paper provides guidance for the engineering design and assembly of the device for further usage.