The Bunched, Beam Interaction with the Hybrid Modes in a Multi-Sectional Ion Linac

The analysis of the transient interaction of the bunched beam with the hybrid modes in the DAW structure of a multi-sectional proton linac is presented. The interaction intensity depends on a frequency spectrum and transverse coupling impedances of the hybrid modes. A frequency spectrum and the transverse impedance of the hybrid modes for accelerating structure with various value of ß have been computed and used for numerical simulation of the transient beam behaviour. The frequences and the transverse shunt impedances of some modes are compared with experimental data. The effect of the initial conditions and the tolerances of the accelerating units and focusing lenses on the beam transverse displacement is presented. The paper contains the evaluation of the beam pulse current limit corresponding to a small deterioration of the beam quality.