Optimal Design and Analysis of a 14 T Actively Shielded MRI Superconducting Magnet for Medium-Sized Animals

This article employs a hybrid optimization method combining two linear programming (LP) steps with one genetic algorithm (GA) step, referred to as 2LP-GA, to successfully design a 14 T/600 mm self-shielding superconducting magnet for medium-sized animal imaging. The magnetic field homogeneity within a spherical volume of 10 cm in diameter is 0.65 ppm. The magnet features a structure integrating a long solenoid with compensation coils and utilizes NbTi and Nb3Sn superconducting materials to reduce manufacturing costs. In addition, this article uses a calculation method for the mechanical properties of superconducting composite materials and applies the obtained parameters to finite element analysis, examining mechanical stresses during winding, cooling, and energization processes. The maximum hoop stress in the coil is 154 MPa. Finally, a quench protection system for the magnet is designed, combining quench detection circuits with active heating methods. Under worst-case quench scenarios, the maximum hotspot temperature and maximum voltage of the coil are limited to 113 K and 1688 V. The analysis also considers stress and stray field variations caused by asynchronous current decay during the quench process.