Transverse Beam Blow-Up in a Standing Wave Linac Cavity

The theory of the interaction of a beam with transverse modes in a standing wave linear accelerator is summarized and applied to the design parameters for recently proposed proton linacs. Approximate results are derived for the limiting current and these are checked and extended by detailed numerical calculation of the build-up of transverse fields. For the contemplated linacs, the current limit is of the order of 10 amperes, safely above the design values.