Chaotic behaviour and halo formation from 2D space-charge dominated beams

Abstract “plus il y a d'oscillateurs et plus il y a de couplage entre eux, plus on peut s'attendre a voir du chaos” (“the more there are oscillators the more they couple between themselves and the more one can anticipate chaos to be observed”) David Ruelle [1] In a previous paper [J.-M. Lagniel, Nucl. Instr. and Meth. A 345 (1994) 46], it has been shown that space-charge dominated beams can induce chaotic behaviour of the particle trajectories. This phenomenon, which leads to halo formation has now been studied with a more realistic model than the simple one used in the previous paper. A 2D beam core with uniform density and finite emittance travels through a focusing channel made up of quadrupoles and thin lenses simulating RF gap defocusing effects. Simulation results with and without synchrobetatron coupling are discussed.