Status of Superconducting Solenoid System for COMET Phase-I Experiment at J-PARC

The COMET Phase-I experiment now under construction at the Hadron Hall of J-PARC aims to search for coherent neutrinoless conversion of a muon to an electron. The experiment requires a large superconducting solenoid system that consists of 5-T pion capture solenoid and 5~3 T matching solenoid and 3-T 90° pion decay/muon transport curved solenoid. The capture solenoid encloses a target to generate pions. The neutron irradiation generated by the target causes various influences to the capture solenoid. One of the major issues is the cooling of the coil that can be degraded due to irradiation. The analyses and the design that accommodate the irradiation were performed. This paper summarizes the concept of the COMET Phase-I experiment and also the design of the solenoid system, including the analyses associated with the neutron irradiation. Manufacturing of the solenoid system has already started, and its status is also reported in this paper.