A Sampled Master Oscillator for the Pep-ii B Factory*

A sampled phase-locked loop synchronizes the PEP-II B Factory rings to their SLAC Linac injector. The injection of both electrons and positrons into the separate rings and into their proper RF buckets requires phase shifting the linac RF with respect to the PEP rings. One of every three machine cycles provides the PEP ring an undisturbed reference while the other two thirds of the time the reference is unusable due to the injection scheme. The ring RF must be tunable about its nominal frequency for machine physics use. A sampled phase-locked loop handles the task of synchronizing the PEP-II RF to the linac while maintaining good phase noise. The input reference is sampled at 120 Hz and provides a ring RF signal with less than 0.1° of rms phase jitter at 476 MHz.