In this feasibility study, we use finite element method simulations to compare superconductors (SC) coils and permanent magnets (PM) assemblies as main field source for a small-scale magnetic resonance imaging scanner. The motivation behind this investigation is that for certain tissues, e.g., knee ligament, diagnosis can be performed with equipment operating with relatively weak magnetic fields. It is then interesting to assess whether the relaxed field requirement enables alternative technologies, which present some advantages over the well-established helium-cooled low-temperature superconductors. As prototypical magnetic systems, we consider the Helmholtz coil and the Halbach cylinder for the SC and PM cases, respectively. Each possibility is simulated over a wide range of combinations of the fundamental design parameters. We estimate field strength, field homogeneity, and total cost over the service life of the device. From these figures of merit, we evaluate the optimal combinations of design parameters. Finally, we compare the SC and PM systems and we establish the range of field requirement values for which one alternative is more suitable than the other one. The result of the present investigation provides the starting point for more detailed studies where more specific design considerations are taken into account.

中文翻译：

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用于小型磁共振成像设备的超导体和永磁体的比较

在这项可行性研究中，我们使用有限元方法模拟来比较超导体 (SC) 线圈和永磁体 (PM) 组件作为小型磁共振成像扫描仪的主要场源。这项调查背后的动机是，对于某些组织，例如膝关节韧带，可以使用在相对弱磁场下运行的设备进行诊断。然后，有趣的是评估放宽的场要求是否能够实现替代技术，这些技术与成熟的氦冷却低温超导体相比具有一些优势。作为典型的磁系统，我们分别考虑了 SC 和 PM 情况下的亥姆霍兹线圈和 Halbach 圆柱体。每种可能性都在基本设计参数的广泛组合上进行模拟。我们估计设备使用寿命内的场强、场均匀性和总成本。根据这些品质因数，我们评估设计参数的最佳组合。最后，我们比较了 SC 和 PM 系统，并确定了一种替代方案比另一种更适合的现场要求值范围。本调查的结果为更详细的研究提供了起点，其中考虑了更具体的设计考虑。