Commissioning Tests for the Detector Solenoid of COMET Experiment

COMET experiment is planned to be conducted at the Hadron facility of J-PARC. This experiment searches for the neutrino-less transition of a muon to an electron in a nuclear field known as “μ–e conversion,” which is one of the Charged Lepton Flavor Violation processes. A detector solenoid (DS), which is located at the downstream end of a muon beam line for COMET, is the world's largest cryogen-free superconducting magnet, which is directly cooled by cryocoolers. The DS was fabricated, and the commissioning tests were performed in 2024. The DS has successfully been cooled down to 4.2K and excited to the rated current without training quenches. In addition, the preliminary magnetic field measurement using a 3-axis Hall probe is carried out, and these results have proven the integrity of the magnet.