The design of the data acquisition system for SPD experiment
The Spin Physics Detector (SPD) experiment at the NICA collider in JINR aims to investigate the spin structure of nucleons and spin-related phenomena. The combination of the number of background processes, the event rate and conditions for event selection makes the use of a classical trigger system impractical, requiring a triggerless data acquisition (DAQ) system. The DAQ system is designed to ensure precise time synchronization, efficient data collection, and high-throughput processing. Its architecture combines commercially available FPGA-based modules and high-speed optical interfaces with custom-developed components based on widely accessible technologies. This approach provides scalability from 180,000 at the initial stage of the experiment to more than 600,000 detector channels in the final configuration and supports data rates up to 20 GB/s or more. The modular system design ensures adaptability for future upgrades while maintaining high efficiency and reliability. Such an approach makes the DAQ system suitable for other high-rate nuclear physics experiments.