TOF Clock System for BES III

In this paper, a system for providing a precisely timed clock to the time-of-flight (TOF) electronics at Beijing Spectrometer (BES III) is presented. System functions include radio-frequency reference signal transmission and low-jitter clock regeneration and distribution. A new clock synchronizing and monitoring mechanism is developed with off-the-shelf devices to synchronize the clock signal to the beam bunches. The measured short-term jitter performance of the system is 11 ps worst case, and robust synchronization to the beam bunches has also been demonstrated. The system has been installed and is operating reliably.