Diffusion rates in a 4-dimensional mapping model of accelerator dynamics (Q1339246)

The problem of diffusion of orbits through chaotic layers of higher dimensional Hamiltonian systems, especially in the slow (Arnold's) diffusion regime is important in view of significant effects it produces after very long times. In the paper, the Chirikov et al. technique is applied to calculate diffusion rates for a 4-dimensional mapping model of accelerator dynamics; physically it refers to hadron beams passing through a focusing element and to the instabilities which might significantly decrease the beam lifetime. For a particular beam geometry, the paper studies the effect of modulational diffusion on the orbits of our map, caused by adding a periodic modulation to the harmonic (betatron) frequencies, these modulations were found to significantly affect the overall stability properties of the motion.