CyDet Trigger System for COMET Phase-I

The COMET Phase-I experiment seeks to detect a muon-to-electron conversion whose branching ratio becomes observable only in new physics, targeting a sensitivity 100 times better than the current upper limit on the branching ratio. Utilizing the high-intensity proton beam of J-PARC, the experiment must address challenges such as high detector hit rates and high-radiation environments, which could cause significant dead time in data acquisition. To overcome these challenges, multi-stage online hardware triggering algorithms have already been developed, and trigger boards have been produced. The distance between a Cylindrical Drift Chamber (CDC) with its readout boards and the trigger front-end boards is approximately 5 m to keep the trigger boards away from the high-radiation area. In this paper, the full electronics system was connected with 5 m long cables, and the stability was tested over an 18-hour monitoring period, achieving live times of over 99% in the experiment, assuming 3 min of dead time due to communication errors.