In applications requiring a large magnetic force, permanent magnets with non-parallel magnetization directions can be assembled in a Halbach array to generate a large gradient of magnetic flux density. The saturation magnetization of permanent magnets, however, brings a fundamental limit on the performance of this configuration. In the present work, we investigate experimentally the assembly of cuboid bulk, large grain melt-textured YBa₂Cu₃O 7−x superconductors ( ∼14×14×14 mm³) with orthogonal c-axes so as to form a basic unit of Halbach array. The experiments are carried out at 77 K. The experimental distribution of the magnetic flux density above the array of trapped-field superconductors is compared to a similar array made of permanent magnets. A simple analytical model is developed and is shown to accurately reproduce the main experimental observations. The results suggest that a redistribution occurs in the current flowing in the central sample when the distance between the superconductors is reduced, whereas the neighbouring superconductors are unaffected. It is shown that this current redistribution yields a reduced contribution of the central sample to the magnetic flux density above the centre of the array and a new negative contribution associated with stray fields to the magnetic flux density at this location. This interpretation is confirmed by modelling of the distribution of transport currents in the superconductor using a 3D finite element model.

中文翻译：

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超导线性海尔贝克阵列上方的俘获磁场分布

在需要大磁力的应用中，可以将磁化方向不平行的永磁体组装成海尔贝克阵列，产生大的磁通密度梯度。然而，永磁体的饱和磁化对这种配置的性能带来了根本限制。在目前的工作中，我们通过实验研究了长方体块状、大晶粒熔体织构 YBa ₂ Cu ₃ O的组装 7−X 超导体（ ～14×14×14 mm ³ ) 与正交C-axes 从而形成 Halbach 阵列的基本单元。实验在 77 K 下进行。将捕获场超导体阵列上方的磁通密度实验分布与由永磁体制成的类似阵列进行比较。开发了一个简单的分析模型，并证明它可以准确地再现主要的实验观察结果。结果表明，当超导体之间的距离减小时，中心样品中流动的电流会发生重新分布，而相邻的超导体不受影响。结果表明，这种电流重新分布导致中心样本对阵列中心上方磁通密度的贡献减少，并且与杂散场相关的新负贡献对该位置的磁通密度产生了影响。