TUNE TRACKING RFKO BUNCH PURIFICATION WITH BUNCH-BY- BUNCH FEEDBACK AT SPRING-8

The bunch purification of a singlet bunches for the SPring-8 storage ring is performed at the booster synchrotron, by clearing out electrons in neighbouring RF buckets by RF kick (RFKO). The injection period to the storage ring at top-up operation is tens seconds and is not fixed; however the booster is currently running at 1 Hz to stabilize the booster machine parameters. To save energy and the operation cost, we intend the on-demand operation of the booster at injection, however the large tune drift was observed in the on-demand operation and this drift drives the tune to off-resonance of the RFKO frequency. To overcome this tune drift, we are developing a tune tracking RFKO bunch cleaning system with transverse bunch-by-bunch feedback. In this system, the betatron oscillation of the main bunch is excited by positive feedback and the signal from the feedback excites the RFKO system, thus the frequency of the RFKO system is locked to the tune.