Radial Focusing in the Linear Accelerator

Abstract

The focusing mechanism described in the previous paper is applied to the linear accelerator. The defocusing forces in the linear accelerator are derived, and the particular example of a 4-million-volt accelerator 10 meters long is discussed. It is shown that the defocusing forces can be compensated by magnetic or electric lenses of the alternating gradient type using easily attainable field gradients. For example, a defocusing field gradient of 1000 volts per centimeter on a 100-kv proton beam can be compensated by a lens 20 cm long with field gradients of the order of 1000 gauss per centimeter.