Analysis and stabilization of AC line synchronized timing system for superKEKB

A timing system provides high-precision signals to allow the controls over a variety of hardware and software components in the accelerator complex. This is guaranteed by the radio frequency (RF) synchronization and trigger signal transmission for subsystems such as klystrons, pulsed magnets, and beam monitors. This trigger signal is usually generated at the same phase of an AC power line to follow the source of the fluctuation of an electrical grid and reduce unwanted variation of the beam quality. A long bucket selection cycle that is necessary for the SuperKEKB damping ring (DR) and main ring (MR) increases the complexity of the timing system. Uncertainty in the timing system and the trigger signal delivery failure caused by a drastic AC power line drift are observed. The cause and effect of timing system failures are analyzed. The solutions to improve the reliability of the timing system by upgrading the software are presented.