Continuous timing measurement using a data-streaming DAQ system

Abstract We have investigated a prototype triggerless data acquisition (DAQ) system for charmed-baryon spectroscopy at J-PARC. A special time-to-digital converter (TDC) dedicated to continuous timing measurement without any external trigger was developed. high dynamic range of the order 1010 realized by introducing heartbeat method, which periodically generates delimiter datum. DAQ software receiving and filtering stream from TDCs also developed based on message-queue application programming interface (API), FairMQ. tested with detectors using electrons positrons converted bremsstrahlung photon beam rate condition up 1.9 MHz/1-mm detector segment. The received 5.4 Gbps six merged them complete set. After sorting certain portion data, searched set corresponding fragments in response penetration positron or electron time separation between hits axis removed unnecessary hits. Around 25 GB RAM CPU threads were required online computing power under test conditions. No silent drop observed.