Collective Effects in the CLIC Damping Rings

Possible performance limitations coming fromcollective effects in the CLIC damping rings are the subject of this paper. In particular, the consequences of space charge, due to the very high beam brilliance, and of the resistive wall impedance, due to the locally very small beam pipe, are considered potentially dangerous in spite of the high beam energy. Space charge has been studied in detail with the HEADTAIL code, which was modified in order to take into account a finer lattice structure. This study also includes requirements on the broad band impedance of the damping rings and ion effects in the electron ring (electron cloud in the positron ring is treated in a companion paper). Its goal is to identify all the potential design constraints determined by these phenomena.