Space -charge driven resonant beam halo in high-intensity hadron synchrotrons

摘要: With the significant development of high-intensity hadron (proton and heavy ion) accelerator facilities, the
space charge effect has become a major limiting factor for increasing beam intensity because it can drive particle
resonance, forming beam halos and causing beam quality degradation or even beam loss. In studies on space
charge, the particle-core model (PCM) has been widely adopted to describe halo particle formation. In this
paper, we generalize the conventional PCM to include dispersion to investigate the physical mechanism of the
beam halo in high-intensity synchrotrons. In particular, a “1:1 parametric resonance” driven by the combined
effects of space charge and dispersion is identified. A large dispersion is proven to have a damping effect on the
2:1 parametric resonance. The analysis based on the generalized PCM agrees with particle-in-cell simulations.
A beam halo with large mismatch oscillations is also discussed.