Commissioning feedback systems at VEPP-4M electron-positron collider

One of the basic constraints on the efficiency of the VEPP-4M electron-positron collider in high-energy physics experiments is the longitudinal multibunch instability; the reason for this instability is the interbunch interaction via long-lived wake fields excited by the beam in accelerating resonators. The longitudinal feedback system was developed for suppressing this instability. The VEPP-4M beam intensity is limited by the transverse instability of coupled modes (fast head-tail); the broadband digital feedback system was developed to suppress this instability. A description of both feedback systems is presented, their working characteristics are given, and the first results of testing systems with VEPP-4M beams are described.