We have constructed two “annulus” magnets, YP2800 and YB10; each consists of 2800 YBCO thin square “plate annuli” (YP2800) and 10 YBCO thick “bulk annuli” (YB10). Their trapped field characteristics, spatial and temporal, were investigated and compared, experimentally and analytically. Two sets of field-cooling tests were performed at 77 K: (1) maximum trapped field tests, where a 2-T background field was applied to investigate the maximum trapped field capability of the two magnets; and (2) reduced trapped field tests, where spatial homogeneity improvement of the two magnets was investigated after field cooling with a reduced background field. Also, a Z1 copper shim coil was designed, constructed, and operated, alone and with YP2800 and YB10. When it was operated with the annulus magnets at 77 K, a significant attenuation of the shim coil strength was observed due to the screening currents induced within the annulus magnets.

中文翻译：

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用于紧凑型 NMR 磁体的散装和板环堆栈：俘获场特性和主动匀场性能

我们制作了两种“环形”磁铁，YP2800 和 YB10；每个由 2800 个 YBCO 薄方形“板环”（YP2800）和 10 个 YBCO 厚“块环”（YB10）组成。通过实验和分析对它们的捕获场特征（空间和时间）进行了研究和比较。在 77 K 下进行了两组场冷却测试：（1）最大俘获场测试，应用 2-T 背景场来研究两个磁体的最大俘获场能力；(2) 减少俘获场测试，在减少背景场的场冷却后研究两个磁体的空间均匀性改善情况。此外，单独并与 YP2800 和 YB10 一起设计、建造和运行了 Z1 铜匀场线圈。当它在 77 K 下与环形磁体一起运行时，由于环形磁体内感应的屏蔽电流，观察到匀场线圈强度的显着衰减。