带有多角形铁轭自屏蔽的MRI超导磁体的优化设计

以八角形铁轭为例，提出了具有多边形铁轭自屏蔽ＭＲＩ超导磁体的优化设计方法，方法基于磁场的球谐波分解，通过优化磁体主线圈的几何参数，消除磁中１２次以下带状谐波磁场分量，对于田形球谐波磁场采用校正线圈或铁磁元件进行校正，多形铁轭磁化磁场的计算采且三维非线性积分方程法，然后根据空间磁场的分布用最小二乘法进行球谐波分解，计算中考虑了铁轭磁化的对称性和周期性变化的规律使方程的阶数大大降低，减少了计算时间，可

DESIGN OPTIMIZATION OF SUPERCONDUCTING MRI MAGNET WITH POLYGONAL IRON YOKE

A design method has been developed to optimize a highly homogeneous superconducting coil configuration with polygonal iron yoke of Magnetic Resonance Imaging (MRI) ,taking octagonal iron yoke as example.The magnetic fields produced by current carrying coils and magnetized iron yoke are decomposed into spherical harmonics respectively. The positions and configurations of the coils are determined by the conditions of the desired center field level and the resultant even zonal harmonics to be zeroes up to 10th order. the tesseral harmonics are eliminated by correction coils or iron elements.The 3D nonlinear integral equation method has been used to calculate the magnetic field induced by polygonal iron yoke,which then is decomposed into spherical harmonics by the least square method.The symmetry and periodicity of the magnetization in the iron yoke are taken into consideration in order to save the computer resources and enhance the calculation precision.