A Computational Optimization of Magnetic System Consists of Deflector and Lens

        A computation investigation on the design of magnetic deflection and focusing system using the synthesis approach of optimization method has been done. By solving the paraxial ray equation using the Range-KuttaNystrom method the trajectories of the electron beam and the optical properties of the magnetic deflection and focusing system under infinite and zero magnification conditions has been computed.The synthesis approach of optimization method is used in the present work to finding the optimum design of magnetic deflection and focusing system which give rise to the minimum spherical, chromatic, spiral distortion, and radial distortion aberration. The toroidal deflection coil is used as the source of magnetic field, and then the field distribution is determined by using an exponential function.
The moving objective lens concept is included in the computation of system field.The system aberration has been minimized by changing the geometrical shape of the toroidal coil, where the length and angle of the coil varied. By using the optimum axial field distribution, the pole pieces shape which gives rise to these field distributions is found by using the reconstruction method.Computation shows that the smaller aberration coefficients occur when ). The relationship between the four coefficients and length and angle of the coil is the length of the coil (H= 23mm) and angle of the coil (Ø=61o inverse proportional in the cases of zero and infinite magnification conditions, therefore, provides us with the possibility of operating the system with high efficiently in different operation conditions of the system.