Compact 3-T superconducting magnet for nucleosynthesis reaction experiments

A compact 3-T superconducting magnet with an active-target time projection chamber and a gamma-ray detector array was constructed for stellar nucleosynthesis studies. This magnet was newly developed based on the previous 1.5-T Helmholtz magnet (Kim and Ahn, 2021) to achieve higher magnetic field and larger space for the detector system. Conduction-cooled Helmholtz coils with an inner diameter of 40 cm generate a central magnetic field of up to 3.0 T at a current of 90.5 A. The operational goal is 2.5 T in nucleosynthesis experiments. The magnet has a large opening between two coils to accommodate the active-target time projection chamber and the gamma-ray detector array. The magnet operates at ramping rates of 0.008–0.02 A/s without quenching and generates highly uniform magnetic field strength within 1% of the central value over a volume of 10 × 10 × 10 cm³, covering a size of active-target time projection chamber. Herein, we report the results of the first excitation test and the field mapping.