SUB-NANOSECOND TIMING SYSTEM DESIGN AND DEVELOPMENT FOR LHAASO PROJECT*
G. Gong, Shaomin Chen, Q. Du, Jianming Li, Yinong Liu · 2011
The Large High Altitude Air Shower Observatory (LHAASO) project is designed to trace galactic cosmic ray sources by approximately 10,000 different types of ground air shower detectors. Reconstruction of cosmic ray arrival directions requires a precision of synchronization down to sub-nanosecond, a novel design of the LHAASO timing system by means of packet-based frequency distribution and time synchronization over Ethernet is proposed. The White Rabbit Protocol (WR) is applied as the infrastructure of the timing system, which implements a distributed adaptive phase tracking technology based on Synchronous Ethernet to lock all local clocks, and a real time delay calibration method based on the Precision Time Protocol to keep all local time synchronized within a nanosecond. We also demonstrate the development and test status on prototype WR switches and nodes.