Cooling of particle beams: Intrabeam scattering, envelope instability and shear

We investigate the dynamics of strongly coupled beams upon cooling, using molecular dynamics (MD) computer simulations. In the quest for crystalline beams in storage rings one has to overcome shear forces in the bending magnets as well as emittance growth due to envelope instabilities and intrabeam scattering (IBS). We show that for zero-current phase-advances σ0<90° even one-dimensional longitudinal cooling is effective, as the beam is stable and the transversal degrees of freedom are cooled indirectly through IBS. The case σ0>90° requires very high three-dimensional cooling rates in order to overcome envelope instabilities. The influence of the bending angle on the cooling process is investigated with two independent simulation codes, whose results agree very well.