The limits of the electron optical parameters of asysmmetric double polepiece magnetic objective lenses

الملخص EN

The asymmetrical magentic electron lens is of great importance for the electron microscopes intended for high resolution.

Such lenses are de¬termined not only by its geometric structure and shape parameters but also by the gap width to bore diameter (S/D) of its polepieces.

A sys¬tematic investigation has been carried out for asymmetric objective lenses having different bore diameters.

The results indicate that the upper bore diameter of polepiece lens has considerable effects on the electron optical properties.

The Comparison between the two sets of the family of asymmetric lenses provides good performance, and suggests that the ratio of the lens gap width to the bore diameters of its polepiec¬es (S/ D>l) is obtained, and the limits of the upper bore diameters to the lower ones which equals (D1/D2= 3) are favourable.