New Image Dissector Tube Designs With Capability for High Resolution and Large Deflection Angles

Abstract

In this paper the imaging properties of the two types of image dissector tubes available on the market are studied. It is found that the vidissector type shows astigmatism even at small deflection angles. The ring-dissector, which in order to be highly resolving must be operated at very high accelerating voltages, shows no image distortion with deflection. New image dissector tube designs are proposed, which both preserve the deflection properties of the ring-dissector tube and give high resolution at much lower accelerating voltages. The new tube designs also make the construction of very compact tubes possible as high deflection angles can be used without loss of resolution. The paper is a theoretical study. The electron images of different tube designs have been calculated numerically and are illustrated by spot diagrams.