A 1.3-GHz/54-mm LTS/HTS NMR magnet, assembled with a three-coil (Coils 1-3) 800-MHz HTS insert in a 500-MHz LTS NMR magnet, is under construction. The innermost HTS insert Coil 1 has a stack of 26 no-insulation (NI) double pancake (DP) coils wound of 6-mm-wide and 75-μm-thick REBCO tapes. In order to keep the hoop strains on REBCO tape <;0.6% at an operating current Iop of 250 A and in a field of 30.5 T, we overbanded each pancake in Coil 1 with a 6-mm-wide, 76-μm-thick 304 stainless steel strip: 7-mm-thick radial build for the central 18 pancakes, while 6-mm-thick for the outer 2 × 17 pancakes. In this paper, Coil 1 was successfully tested at 77 K and 4.2 K. In the 77-K test, the measured critical current was 35.7 A, determined by an E-field criterion of 0.1 μV/cm. The center field magnet constant decreased from 34.2 to 29.3 mT/A, when Iop increased from 5 to 40 A. The field distribution at different Iop along the z-axis was measured. The residual field distributions discharged from 10 and 20 A were recorded. In the 4.2-K test, Coil 1 successfully generated a central field of 8.78 T at 255 A. The magnet constant is 34.4 mT/A, which is same as our designed value. The field homogeneity at the coil center within a ±15-mm region is around 1700 ppm. This large error field must be reduced before field shimming is applied.

中文翻译：

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针对 1.3 GHz LTS/HTS NMR 磁体对具有超带径向结构的 8.66-T REBCO 插入线圈进行测试


正在建造一个 1.3 GHz/54 mm LTS/HTS NMR 磁体，该磁体与三线圈（线圈 1-3）800 MHz HTS 插入件组装在 500 MHz LTS NMR 磁体中。最里面的 HTS 插入线圈 1 具有 26 个由 6 毫米宽、75 微米厚的 REBCO 胶带缠绕而成的非绝缘 (NI) 双薄饼 (DP) 线圈的堆栈。为了在 250 A 的工作电流 Iop 和 30.5 T 的磁场中保持 REBCO 胶带上的环向应变 <;0.6%，我们在线圈 1 中的每个煎饼上都覆盖了 6 毫米宽、76 微米厚的薄膜。 304不锈钢带：中心18个煎饼的径向结构为7毫米厚，外部2×17个煎饼的径向结构为6毫米厚。本文中，线圈1在77K和4.2K下进行了成功测试。在77K测试中，根据0.1μV/cm的电场标准确定，测得的临界电流为35.7A。当Iop从5A增加到40A时，中心磁场常数从34.2mT/A减小到29.3mT/A。测量了不同Iop下沿z轴的场分布。记录从 10 A 和 20 A 放电的残余场分布。在4.2-K测试中，线圈1在255 A下成功产生了8.78 T的中心磁场。磁体常数为34.4 mT/A，与我们的设计值相同。线圈中心 ±15 毫米区域内的场均匀度约为 1700 ppm。在应用场匀场之前必须减小这个大的误差场。