High-resolution parallel particle-in-cell simulations of beam dynamics in the spallation neutron source linac

In this paper, we present results of using high-performance parallel comput ers to simulate beam dynamics in an early design of the Spallation Neutron Source (SNS) linac. These are among the most detailed linac simulations eve r performed. The simulations have been performed using up to 500 million ma croparticles, which is close to the number of particles in the physical sys tem. The simulations are fully three-dimensional, and utilize RF cavity fie ld data from modeling over 400 RF cavities. Furthermore, they use an improv ed model of the beam dynamics within the cavities. Traditionally, small-sca le two-dimensional simulations have been performed on PCs or workstations. While such simulations are sufficient for rapid design and for predicting r oot mean square properties of the beam, large-scale simulations are essenti al for modeling the tails of the beam. The large-scale parallel simulation results presented here represent a three order of magnitude improvement in simulation capability, in terms of problem size and speed of execution, com pared with typical two-dimensional serial simulations. In this paper we wil l show how large-scale simulations can be used to predict the extent of the beam halo and facilitate design decisions related to the choice of beam pi pe aperture. (C) 2001 Elsevier Science B.V. All rights reserved.