AI 中文总结
该研究提出可在极小力下开合的Halbach球形磁体，推导力平衡开合条件并经实验验证，可大幅降低开合力，适用于磁共振等领域的大体积均匀永磁系统。
AI 中文摘要
磁体设计中一个长期存在的目标是用永磁体完全包围一个具有高度均匀磁场的区域，同时保持对该区域的实际可及性。本工作对Halbach构型的机械可及球形磁体进行了理论和实验研究，该磁体可在最小力或零力下开合。我们重点关注由离散磁性单元组成的偶极Halbach球，推导了沿特定切割平面实现无张力开合的条件。这些条件定义了一组连续的几何结构，其中磁拉力相互抵消，仅保留剪切分量，从而实现机械上的轻松开合。我们使用Halbach球的二十面体近似对理论预测进行了实验验证，测量了开合力和磁场特性。结果表明，在保持出色的场均匀性的同时，开合力可降低几个数量级。尽管针对偶极情况进行了详细讨论，但该理论框架具有通用性，适用于更高阶多极Halbach系统。最后，将这些概念扩展到圆柱状Halbach构型，突出了其在磁共振领域用于大体积、高度均匀且机械可及的永磁体系统的潜力。
英文摘要
A long-standing goal in magnet design is to completely surround a volume of highly homogeneous magnetic field with permanent magnets while maintaining practical access to that volume. In this work, we present a theoretical and experimental investigation of mechanically accessible spherical magnets in Halbach configuration that can be opened with minimal or vanishing force. Focusing on dipolar Halbach spheres composed of discrete magnetic subunits, we derive conditions for force-free opening along specific cutting planes. These conditions define a continuous set of geometries for which tensile magnetic forces cancel, leaving only shear components, enabling mechanically effortless opening. The theoretical predictions are validated experimentally using icosahedral approximations of the Halbach sphere, for which both opening forces and magnetic field properties are measured. The results demonstrate that excellent field homogeneity can be preserved while reducing opening forces by orders of magnitude. Although discussed in detail for the dipolar case, the theoretical framework is general and applicable to higher-order multipole Halbach systems. Finally, the concepts are extended to spherocylindrical Halbach configurations, highlighting their potential for large-volume, highly homogeneous, and mechanically accessible permanent-magnet systems for magnetic resonance
Comments12 pages, 10 figures, prepared for a special issue on low field magnetic resonance in J. Magn. Reson
