The Longitudinal Feedback System in Tristan AR

Longitudinal dipole instability which had been the problem during the running in of the TRISTAN Accumulation Ring (AR) and the first year of operation has been damped by the feedback system. The dipole oscillation is detected by comparing the phase of the RF component (508.6 MHz) in the bunch signal with the phase of the RF reference signal. The detected oscillation is, after being adjusted in amplitude and phase, fed back into the RF phase shifter at the input stage of the klystron. The damping rate with and without feedback has been measured. The feedback system provides a sufficient damping rate in the synchrotron frequency range of 20 to 40 kHz.