High current electron beam acceleration in dielectric-filled RF cavities

Abstract

Summary form only given. The acceleration of charged particles in radio frequency (RF) cavities is a widely used mode in high energy accelerators. Advantages include very high accelerating gradients and very stable phase control. A traditional limitation for such acceleration has been their use for intense, high current beam generation. This constraint arises from the inability to store a large amount of electromagnetic energy in the cavity and from loading effects of the beam on the cavity. We have studied a simple modification to transcend these limitations. Following Humphries and Huang (1983), we have conducted analytic and numerical investigations of RF accelerator cavities in which a high dielectric constant material, such as water, replaces most of the cavity volume. This raises the stored energy in a cavity of given dimensions by a factor /spl epsi///spl epsi//sub 0/. For a water fill, /spl epsi///spl epsi//sub 0//spl sim/80, depending on the frequency. The introduction of high dielectric constant material into the cavity reduces the resonant frequencies by a factor of (/spl epsi///spl epsi//sub 0/)/sup 1/2/. This reduced operating frequency means that existing high efficiency power supplies, at lower frequencies, can be used for an accelerator.