Focusing of Electrons in Two Dimensions by an Inhomogeneous Magnetic Field

Abstract

FOR the focusing of -rays two essentially different methods have hitherto been used, namely, the semicircular and the lens methods. It will be remembered that the former of these methods has a focusing action only in one plane, which means a greatly reduced intensity in comparison to the lens method. The latter procedure does not utilize the central part of the beam in the focusing, since the resolving power is proportional to the diameter of the central shutter. The lens method cannot, without the use of a special twisted shutter system, separate positive and negative electrons.