Abstract
Abstract
China Spallation Neutron Source (CSNS) is a complex system
engineering composed of particle accelerators, a target station, and
neutron spectrometers with various equipment types and
distribution. The collaborative operation of the equipment requires
accurate clock synchronization and trigger distribution. Currently,
to meet the requirements of different system devices, clock
synchronization and trigger distribution in CSNS are implemented
based on different methods, resulting in complex clock and trigger
networks, demanding upgrades, and a lack of unified timestamps. This
paper proposes a clock synchronization and trigger distribution
scheme based on the field-programmable gate array (FPGA) and
single-mode dual-core fiber link. The decoupling of clock phase
synchronization and time base synchronization improves the frequency
of phase compensation. Benefiting from the phase interpolator (PI)
in the FPGA transceivers, high-precision phase compensation and
phase deterministic control are realized, achieving picoseconds
synchronization precision and stability in the four-level
network. Based on the custom lightweight link layer protocol, by
optimizing the routing method of data frames and adopting priority
control, the transmission of multiple data is realized, and the
hardware delay of the critical data, such as interlock, is
guaranteed to be less than 1.5 μs in the four-level system. The
scheme provides a general precise clock synchronization and
distributed trigger method for CSNS devices, simplifies the system
complexity, and is conducive to the system upgrade in the second
stage.