Bunched beam cleaning system of SPring-8 booster synchrotron

In order to fill an aimed radio frequency (RF) bucket with an electron beam in the storage ring at SPring-8, the bunched beam cleaning system which we call RF knockout (RF-KO) system is installed in the booster synchrotron. The time width of the beam from the linac operated with 2856 MHz RF is 1 nsec for single-bunch beam operation. The beam is distributed not only in a single RF bucket of the booster synchrotron operated with 508.58 MHz RF but also in other RF buckets. The energy of injected beam is increased from 1 GeV to 8 GeV. The RF-KO system is operated at minimum beam energy of 1 GeV because the required knockout power is reduced. The bunched beam in the satellite RF buckets are coherently shaken by the electromagnetic field produced by four RF-KO electrodes in the vacuum chamber. As the amplitude of betatron oscillation increase, the beam soon begins to collide with a beam duct and is lost. The single-bunch beam injected into the targeted RF bucket is effectively kept alive on the zero-crossing point of RF-KO waveform with a precise timing system. The beam intensity of satellite RF buckets in the storage ring was measured with a photon counting method and determined to be 10^-9 less than that of the main RF bucket.