A 4.7 T compact superconducting magnet system for active shielding animal magnetic resonance imaging scanner was designed in this work. The resulting magnet consists of nine coaxial coils symmetrical about the z-axis. The innermost main coils and outermost shielding coils were made up of six inner coils with the positive current direction and three outer coils with the negative current direction, respectively. These nine superconducting coils contribute their efforts together to produce a 4.7 T main background magnetic field, and the peak-to-peak field homogeneity was 2 ppm over a 20 cm region of interest (ROI). The diameter of room temperature bore was 400 mm, which is large enough for most animals imaging, and five Gauss fringe field is restricted within an elliptical region with the size of 1.5 m in radial and 2.2 m in axial direction, much smaller than the regular requirement 2.5 m and 4.0 m, respectively. A hybrid numerical methodology that combined linear programming and nonlinear optimization algorithm for actively shielding homogeneous superconducting magnet was proposed here. From the simulation results, we can see that the homogeneity over ROI and limitation to the five Gauss fringe field can be well controlled, and so does the maximum electromagnetic stress.

中文翻译：

---

高度均匀的超导动物 MRI 扫描仪的紧凑设计方法

本工作设计了一种用于主动屏蔽动物磁共振成像扫描仪的 4.7 T 紧凑型超导磁体系统。由此产生的磁体由关于 z 轴对称的九个同轴线圈组成。最里面的主线圈和最外面的屏蔽线圈分别由六个正电流方向的内线圈和三个负电流方向的外线圈组成。这九个超导线圈共同努力产生 4.7 T 主背景磁场，峰峰值场均匀性在 20 cm 感兴趣区域 (ROI) 上为 2 ppm。室温孔直径为400 mm，对于大多数动物成像足够大，五个高斯条纹场被限制在径向1.5 m，轴向2.2 m的椭圆区域内，分别比常规要求 2.5 m 和 4.0 m 小得多。本文提出了一种将线性规划和非线性优化算法相结合的混合数值方法，用于主动屏蔽均质超导磁体。从仿真结果可以看出，可以很好地控制ROI的均匀性和对五个高斯边缘场的限制，最大电磁应力也是如此。