We demonstrate an experimental method for the improvement of the magnetic field homogeneity in Halbach magnets by taking magnet material imperfection into account. This method relies on the determination of the magnetization magnitude only for individual magnet blocks based on nuclear magnetic resonance field measurements in a simplified system, which, in our case, consists of four blocks. Then, a set of configurations with highest homogeneities can be found from simplified field map simulations of all possible configurations or by applying sophisticated optimum search algorithms if the number of blocks is large. Finally, the residual effect of angular magnetization deviations can be reduced by the experimental selection of the best configuration from the set found on the simulation step. This selection strategy is based on the conclusions made from statistical analysis of simulated field maps. By applying the described method to our eight-element magnet, we experimentally achieved tenfold field homogeneity improvement. Thus, in the best configuration, we obtained an average value of the magnetic field of 598.0 mT and a half-width of 226.9 ppm for a sample with a diameter of 4 mm and a height of 10 mm. These parameters along with the compact magnet size (40 × 40 × 102 mm3) and weight (0.6 kg) provide reasonable magnet quality compared with analogous systems having more complex magnet arrangements and significantly higher costs.

中文翻译：

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在低成本 Halbach 磁铁的设计和优化中考虑材料缺陷

我们展示了一种通过考虑磁体材料缺陷来改善 Halbach 磁体磁场均匀性的实验方法。该方法仅依赖于基于简化系统中核磁共振场测量的单个磁体块的磁化强度的确定，在我们的例子中，该系统由四个块组成。然后，可以从所有可能配置的简化场图模拟中找到一组具有最高同质性的配置，或者如果块的数量很大，则可以通过应用复杂的优化搜索算法来找到。最后，可以通过从模拟步骤中找到的集合中实验选择最佳配置来减少角磁化偏差的残余影响。该选择策略基于对模拟现场地图的统计分析得出的结论。通过将所描述的方法应用于我们的八元素磁体，我们通过实验实现了十倍的场均匀性改进。因此，在最佳配置中，对于直径为 4 毫米、高度为 10 毫米的样品，我们获得了 598.0 mT 的磁场平均值和 226.9 ppm 的半峰宽。与具有更复杂磁体排列和显着更高成本的类似系统相比，这些参数以及紧凑的磁体尺寸 (40 × 40 × 102 mm3) 和重量 (0.6 kg) 提供了合理的磁体质量。对于直径为 4 mm、高度为 10 mm 的样品，我们获得了 598.0 mT 的磁场平均值和 226.9 ppm 的半峰宽。与具有更复杂磁体排列和显着更高成本的类似系统相比，这些参数以及紧凑的磁体尺寸 (40 × 40 × 102 mm3) 和重量 (0.6 kg) 提供了合理的磁体质量。对于直径为 4 mm、高度为 10 mm 的样品，我们获得了 598.0 mT 的磁场平均值和 226.9 ppm 的半峰宽。与具有更复杂磁体排列和显着更高成本的类似系统相比，这些参数以及紧凑的磁体尺寸 (40 × 40 × 102 mm3) 和重量 (0.6 kg) 提供了合理的磁体质量。