Design of synchrotron septum magnet for heavy ion medical machine

Septum magnet is one of the most important devices for beam injection and extraction in circular particle accelerators. Because of the high-field requirements with thin septa and low stray field, the structure of septum magnet is very complicated. In this paper, the design of septum magnet is shown in detail. Based on the finite element software OPERA, the magnetic field homogeneity and stray field distribution are analyzed. The magnets fabrication is finished after structure optimal design. The measurement results show that the magnetic field homogeneity in good field region is better than the designed value. The stray field could reduce to 2 mT after shielding with high permeability magnetic material, which satisfies the physical requirements.