Simulation study of ion effect in the ILC electron damping ring

Ion effect has been recognized as one of the very high priorities of the R&D for the damping rings of the International Linear Collider (ILC) due to multi-bunch operation of extremely low emittance and very high intensity beam. In this paper, we study the ion density near the beam analytically considering the mini-train fill pattern case. The result shows that the gap between the bunch trains can reduce the ion density significantly. Meanwhile, a simulation code is employed to study the fast ion instability in the ILC electron damping ring. Various fill patterns and gas pressures in the ring are investigated. Feedback system is also applied in the simulation.