Tsinghua University, Beijing, People's Republic of China
IHEP Beijing, Beijing, People's Republic of China
The Large High Altitude Air Shower Observatory (LHAASO) [1] 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 sub-nanosecond time synchronization, 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) [2] 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.
[1] Cao Zhen, "A future project at tibet: the large high altitude air shower observatory (LHAASO)", Chinese Phys. C 34 249,2010
[2] P. Moreira, et al, "White Rabbit: Sub-Nanosecond Timing Distribution over Ethernet", ISPCS 2009
