Development of a New S-Shaped Superconducting Hexapole Magnet for ECR Ion Source

With the increasing demand for high-energy particles in accelerators, there is a need to develop compact, small-volume, and high-energy electron cyclotron resonance ion sources (ECRISs). As a key component in heavy ion accelerators and therapy facilities, ECRISs are capable of producing highly charged ions. A novel S-shaped hexapole magnet structure was proposed in 2016, which simplifies the distribution of Lorentz interaction forces in ECRIS superconducting magnets and facilitates achieving the required axial field. However, the fabrication of S-shaped hexapole poses significant challenges. Based on this design, we developed a superconducting S-shaped hexapole prototype for a 14.5 GHz microwave frequency using NbTi. A former with slotted ends was designed to enable the S-shaped winding. A small prototype of S-shaped hexapole used only one cable to realize winding, achieving a continuous uninterrupted winding both from the inside to the outside and from the outside to the inside. During 4.2 K cold testing, the coil attained a self‑field of 1.5 T at a current of 480 A. Under an 8 T background field, it carried 232 A with only a single quench, reaching 98.22% of its load line.