Alternating Gradient Focusing of Cyclotron External Beam

Abstract

The ¾‐Mev external proton beam from the 20‐inch cyclotron appeared to diverge horizontally from one point and vertically from another point. With a series of three alternately converging and diverging electro‐static lens elements of hyperbolic cross section, it was possible either to focus the external beam to a point or to make it parallel.