Influence of the Geometrical Configuration of the Iron Shroud on the Optical and Magnetic Properties of the Monopole Symmetric Objective Magnetic Lens

This study investigated the effect of varying the geometric configuration of the iron shroud on the magnetic and optical properties of a magnetic lens. The study compared three novel designs of monopole symmetric object magnetic lenses, differing only in the geometry of the iron shroud. The axial magnetic flux density distribution was calculated using Electron Optical Design program. The results indicated that maximum magnetic flux density increases with a decrease in the air gap width, accompanied by a reduction in half-width value. It was found that one of the proposed designs provides an optimal distribution of magnetic flux lines, with no leakage of magnetic field lines outside the pole region. The optical focal properties of lenses were studied using a program based on Finite Element Method to calculate magnetic field distribution, while the optical properties of electromagnetic lenses were analyzed using Optical Properties Program for Electron Magnetic Lenses. The findings revealed that one of the proposed lenses offers the best magnetic and optical properties. A novel and unprecedented magnetic lens design was invented for the first time. The proposed design is distinguished globally by the protrusion of the pole tip into lens structure, Referred to as the Snub Lens.