Development of a scintillating-fiber-based beam monitor for the Coherent Muon-to-Electron Transition experiment

COMET is a leading experiment to search for coherent conversion of μ-N→ e-N with a high-intensity pulsed muon beamline, produced by the innovative slow extraction techniques. Therefore, it is critical to measure the characteristics of the muon beam. We set up a Muon Beam Monitor (MBM), where scintillating fibers (SciFi) weaved in the cross shape are coupled to silicon photomultipliers (SiPM), to measure the spatial profile and timing structure of the extracted muon beam for COMET. The MBM detector has been tested successfully with a proton beamline in China Spallation Neutron Source (CSNS) and taken data with good performance in the commissioning run called COMET Phase-α. Experience of the MBM development, such as the mechanical structure and electronics readout, and its beam measurement results will be shared.