BES3 time-of-flight monitoring system

A Time-of-Flight (TOF) monitoring system has been developed for BES3. The light source is a 442–443 nm laser diode, which is stable and provides a pulse width as narrow as 50 ps and a peak power as large as 2.6 W. Two optical-fiber bundles with a total of 512 optical fibers, including spares, are used to distribute the light pulses to the TOF counters. The design, operation, and performance of the system are described.