Ion instability in the ILC damping ring

We investigate the ion instability in the ILC electron damping ring with high beam intensity and low-emittance. It is shown that the ion instability can cause beam oscillations that grow exponentially and give a significant limitation in the damping ring. We have performed a weak-strong simulation to show characteristic phenomena of the instability in the damping ring. In particular, we investigated the effects of the various different bunch filling patterns, vacuum pressures and a feedback system on the fast-ion instability. It is also shown that the fast-ion instability can be cured by a bunch-bunch feedback per about 50 turns.