INVESTIGATION FOR THE PROJECTIVE PROPERTIES OF THE SYMMETRIC THE TAPERD CYLINDRICAL DOUBLE POLE PIECE MAGNETIC LENS

The Finite Element Method (FEM) has been used for investigation of design a symmetrical lenses with double tapered cylindrical polepieces. The axial magnetic flux density distribution has been calculated for a bore size of the polepiece at different values of air gap and for different bore diameters . The data of the axial magnetic flux density distribution have been used in computing the projector focal properties. The importance of this work lies in the possibility of designing symmetrical electron lenses with double tapered cylindrical pole pieces used as an projector lens with lowest distortions in transmission electron microscope (TEM)and scanning transmission electron microscope(STEM). In the present work a set of programs wnten by Munro(1975) and Maria(1977) have been used to suggest a new design of magnetic projector lens .Also, the result of the this work are in agood agreement compared with other investigations