THEORY OF LONGITUDINAL BEAM HALO IN RF LINACS: II. ENVELOPE-PARTICLE RESONANCES

Using the core/test-particle model described in a compan-ion paper in these proceedings1 (“Theory of Longitudinal Halo in rf Linacs: I. Core/Test-Particle Formulation, ” by J. J. Barnard and S. M. Lund), we analyze longitudinal beam halo produced by resonant self-field interactions in intense, ion-beam rf linacs. It is shown that particles moving in the presence of the space-charge forces of an oscillating, mis-matched ellipsoidal beam bunch can be resonantly driven to large longitudinal amplitude. This resonantly produced halo is first analyzed in a limit where it is most simply un-derstood, with particles moving purely longitudinally and with linear rf focusing. Then modifications of the reso-nance induced by nonlinear rf and transverse-longitudinal coupling are explored.