An active feedback system to control synchrotron oscillations in the SLC damping rings

Initially, the SLC (Stanford Linear Collider) damping rings accomplished Robinson instability damping by operating the RF accelerating cavities slightly detuned. In order to run the cavities tuned and achieve damping for Robinson instability and synchrotron oscillations at injection, an active feedback system has been developed. The theoretical basis for the feedback system and the development of the hardware are described. Extensive measurements of the loop response including stored beam were performed. Overall performance of the system is also reported. The measured data did not match what the authors´ model had predicted. The measurements did show the expected zero at DC, the first-order cavity pole at 45 KHz, and the second-order beam resonance at the synchrotron frequency. Another pole, and an exponentially increasing phase lag appeared near the synchrotron frequency