Commissioning of the FASER Trigger and Data Acquisition Prior to Proton-proton Collision Data-taking at the LHC

FASER is a newly installed experiment at the LHC designed to search for long lived particles produced in high energy proton collisions and decaying several 100 meters downstream. As the experiment aims to measure a rare hypothetical process, it is crucial that the experiment’s trigger and data acquisition (TDAQ) system runs reliably and with minimal deadtime, quick to catch errors and raise alerts. The expected trigger rate is 0.5-1 kHz, dominated by energetic experimental background muons entering the front of the detector. The readout and hardware control is performed on both custom and commercial hardware, while data processing and event building are done in software. The FASER DAQ is envisioned to be a self-monitoring continuously running system during data-taking commencing next year, aiming to be live for the full LHC Run 3 luminosity. The full detector was installed in the tunnel in March 2021, and the readout system has since then been stress-tested by collecting on the order of 100 million noise and cosmic events. The TDAQ system architecture is presented, covering the design philosophy to execution. This is followed by the measured performance of the system during commissioning in the context of full system runs over multiple days and high rate tests designed to push the system’s limits.