Bunch-by-bunch phase study of the transient state during injection

A high-resolution bunch-by-bunch longitudinal phase measurement system has been developed at the Shanghai Synchrotron Radiation Facility. The system has a high-speed digital signal analyzer to capture the signals from a beam-position-monitor. Then the bunch phases can be collected by using a zero-crossing detection method and a longitudinal delta-over-sum lookup table method consecutively. The phase of the refilled charge is calculated by separating it from the stored bunch. In order to fully explore the evolution of the refilled charge damping oscillation, the transient state during injection was further studied. The arrival time of the refilled charge, the energy mismatch between the injector and the storage ring, and the synchrotron damping time can be obtained in the injection transient process. This system is capable of measuring the bunch-by-bunch phases online, which provides an additional way to monitor the machine status or to optimize the injector. © 2019