Intrabeam scattering and halo formation in high intensity linac beams

A limiting factor for the performance of high intensity linacs proposed for applications like heavy ion inertial fusion, production of tritium, transmutation of waste and spallation source for neutrons and neutrinos is the control of beam losses. These occur, e.g., through the formation of a halo around the core of the beam containing particles which will eventually collide with the walls of the accelerator pipe. The sum of the applied focusing fields and the intense self-fields produced by the beam charge are nonlinear near the surface of the beam causing instabilities leading to halo formation. Here, we investigate with the help of molecular dynamics computer simulations whether hard Coulomb collisions between the beam particles act as an additional cause for a beam halo. However, for the parameters of the high intensity linacs presently in discussion the beam particles remain sufficiently weakly correlated and intra beam scattering plays no major role in halo formation.