Electromagnetic design and analysis of a bell-shaped superconducting magnet for head fMRI using a novel hybrid optimization method

Abstract In task-state functional magnetic resonance imaging (fMRI) scans, it is often necessary for subjects to perform certain task actions, which is difficult to achieve in traditional whole-body MRI systems. In this study, a bell-shaped head magnetic resonance superconducting magnet was designed using a novel hybrid optimization method that combines linear programming (LP), genetic algorithm (GA), and nonlinear programming (NLP). This magnet design offers the following advantages: (1) The small and compact volume of the magnet structure allows for vertical placement of the system, enabling subjects to be in a sitting position during the scan. (2) The off-center DSV (diameter of spherical volume) region expands the subject's field of view. (3) Only the subject's head is positioned inside the scanning system, freeing the subject's torso to cooperate in performing various tasks. This paper provides a detailed description of the entire design process, conducts a comprehensive analysis of the electromagnetic performance and material mechanical properties of the designed magnet, and designs a passive quench protection system for the subsequent manufacturing of the magnet, with simulations and discussions on the magnet's quenching process under the protection of this system.