Implementations of Streaming DAQ on Actual Detector Systems

Detector systems in modern nuclear and particle physics experiments must handle numerous channels and high data throughput. Furthermore, the requirements for trigger systems have become increasingly complex, necessitating effective decision-making processes. Streaming readouts and software-based triggering on distributed computers present a natural solution to these challenges, owing to recent technological advances. Therefore, we developed a widely usable streaming data acquisition (DAQ) system based on FairMQ and the Redis key-value database. To address this challenge, we have developed a streaming DAQ system that handles continuous data flow and complex triggering in the software. The DAQ system is relatively simple and can be deployed and operated by a small team. It operates through the cooperation of multiple elementary functional processes, with connections automatically established based on port names, service names, and connection information stored in a database. We applied this DAQ system to actual detector systems, including the Research Center for Nuclear Physics (RCNP) Grand Raiden spectrometer and the Japan Proton Accelerator Research Complex (J-PARC) E50 detector system beam test, utilizing streaming readout and online software triggering. The two detector systems, consisting of plastic scintillation counters and drift chambers, were read out by a field-programmable gate array (FPGA)-based streaming readout time-to-digital converter (TDC) and distributed synchronized clock, where the charge information was obtained from the time-over-threshold (TOT). The streaming DAQ system performed effectively, including the software trigger, on 24-core server computers. The software component of the DAQ system was also applied to a triggered DAQ system for a cylindrical drift chamber (CDC) for the J-PARC COMET experiment, where it demonstrated sufficient performance. We further demonstrated the streaming-capable DAQ system and its practical application, with a focus primarily on the software aspect.