The Effect of Coils Area's Ratio and their Separated Distance on the Optical Performance of the Condenser-Objective Magnetic Lens

The work handles the design of an asymmetric double polepiece magnetic lens for the condenser-objective mode having optimum properties through the change of coils area's ratio and their separated distance, which leads to a highest flux density peak of the magnetic field with a lowest spherical aberration coefficient, at the relativistic corrected voltage (Vr=200 kV) and excitation of (NI=10.5 kA-t). The calculation has been made for the magnetic flux lines trajectories and optical properties to limit the defects in the lens and consequently improve the optical performance of the condenser-objective magnetic lens