Optimization of Bunch Arrival Time Measurement Algorithm for Cavity Probe

High signal-to-noise ratio and high sensitivity are the biggest characteristics of cavity probes. In TM010 mode of the cavity, the output signal near the paraxial axis has nothing to do with the transverse position of the bunch. The signal amplitude is proportional to the bunch charge, and the signal phase is determined by the bunch arrival time. Therefore, it is very suitable for highresolution bunch arrival time measurement. The SHINE has very high requirements for the measurement accuracy of the bunch arrival time. It is expected that the resolution can be better than 25 fs under the charge of 100 pC by a cavitybased bunch arrival time monitor. For a highQ resonant cavity signal, the signaltonoise ratio of singlepoint sampling will decrease as the signal attenuates. Therefore, there must be an optimal signal processing window to obtain the best system resolution. Numerical simulation and beam experiments were used to find the relationship between the system parameters and the measurement uncertainty. Finally, it is found that there is an optimal data processing window, and this parameter is only related to the signal decay time. Under this window, the measurement uncertainty of the bunch arrival time can obtain the best value.