• A. Wolski, D.A. Bates, J.M. Byrd
  LBNL, Berkeley, California

Options being considered for the ILC Damping Rings include lattices with circumferences up to 17 km. The circumference, beam current and beam energy place the damping rings in a regime where resistive-wall instability is a concern, particularly as there are very demanding tolerances on the bunch-to-bunch jitter. Generally, it is possible to make good analytical estimates of the coupled-bunch growth rates in a storage ring, but particular features of the damping rings (including the fill pattern, large variations of the lattice functions and beam-pipe cross-section in different parts of the ring, and transverse beam coupling in the long straight sections) make it desirable to study the coupled-bunch instabilities using simulations. Here, we present the results of simulations of the transverse instabilities using a detailed lattice model. A bunch-by-bunch feedback system will be needed to suppress the instabilities, and a model for an appropriate feedback system is included in the simulations.