A Study of the Collective Beam Instabilities in the Damping Ring of the VEPP-5 Injection Complex

— The collective beam instabilities in the damping ring of the VEPP-5 injection complex have been investigated. Wakefields created by the charged-particle beam distort the potential well of the accelerating RF system, which leads to beam lengthening and to distortion of the shape of its longitudinal distribution. The longitudinal beam profile has been measured by a dissector and a streak camera, and the process of potential well distortion of the RF system is theoretically justified. A model of the coupling impedance in the form of an equivalent RLC circuit has been constructed, and its parameters are estimated by comparing the simulation data to experimental results. The obtained model of the coupling impedance has been used to predict the behavior of the damping ring beam after modification of the accelerator vacuum system.