Bunch-by-Bunch Feedback for PEP II*

The proposed PEP II B factory at SLAC requires a feedback to damp out longitudinal synchrotron oscillations. A time domain, downsampled, bunch-by-bunch feedback system in which each bunch is treated as an oscillator being driven by disturbances from other bunches is presented as we review the evolution of the system design. Results from a synchrotron oscillation damping experiment conducted at the SLAC/SSRIJSPEAR riqg are also presented in this paper. HNTR~DU~TI~N _ Figure 1 is a conceptual diagram of such a The feedback system design incorporates a system. The phase of each bunch is detected and a correction kick for each bunch is phase detector to provide a measure of the bunch phase, digital signal processing to computed and applied by a kicker. The compute an error correction signal and a kicker downsampler allows each digital signal system to correct the energy of the bunches. A processor (DSP) to handle more bunches and, downsampling scheme has been implemented to reduce the size of the hardware. consequently, reduces the size of the system. The hold buffer holds the last kick value computed for each bunch. Other driving terms and disturbances Down (DW Sampler Hold Buffer * Digital Filter *