SIMULATION STUDIES OF SPACE-CHARGE-DOMINATED BEAMS IN SPALLATION NEUTRON SOURCES *

Uncontrolled beam losses due to space-charge-induced halo generation are a concern in the accumulator rings of spallation neutron sources, such as SNS and ESS. Such rings are characterized by high beam intensities and low uncontrolled beam loss requirements. It is therefore important to investigate the dynamics of space charge in high intensity rings. We have done this extensively by using a particle tracking approach with a self-consistent particle-in-cell code. We have found that the inclusion of space charge forces is essential in simulating not only the dynamics of halo generation, but also the formation of the observed beam profile shapes under typical conditions. Our results extend the understanding of fundamental space charge physics, which has been developed for linear accelerators, to rings.