The permanent main magnet is mainly the developing direction through analyzing the advantages and disadvantages between three sort of main magnets : superconductor , routine and permanence . aiming at the different types of the permanent main magnet with edge effects , which ca n ' t reach the demand of nmr imaging , numerical method of magnetic field computation and the theory of shape optimization is applied 因此，本文应用磁场数值分析和形状优化的理论和方法，探索了大空间内均匀磁场的技术，目标是在核磁共振成像主磁体己设计好的基础上，对极靴的形状进行优化设计，尽量扩大样品区磁场均匀的范围。
