In 2005, the Committee on Opportunities in High Magnetic Fields issued a challenge to develop a 30 T high-resolution NMR magnet. In response, the National High Magnetic Field Laboratory (NHMFL) is investigating all three commercially available high-temperature superconductors including REBCO, Bi-2212 and most recently, a reinforced Bi-2223 conductor supplied by Sumitomo Electric, designated Type HT-NX. Recent investigations of Type HT-NX conductor at the NHMFL and by others suggest that operation at hoop stress above 400 MPa, and total strain above 0.7% may be feasible. We have fabricated a test coil from a single 240 m length of HT-NX. The coil was successfully operated to 19.5 T in a 14 T background field, with a total applied strain of 0.8% and coil current density of 243 A/mm2. The coil was cycled 20 times from half the design current to full current without observed degradation.

中文翻译：

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用于高场 NMR 磁体的 Bi-2223 插入线圈的制造和测试

2005年，高磁场机会委员会发出了开发30T高分辨率核磁共振磁体的挑战。为此，国家强磁场实验室 (NHMFL) 正在研究所有三种商用高温超导体，包括 REBCO、Bi-2212 以及最近由住友电工提供的强化 Bi-2223 导体，指定为 HT-NX 型。NHMFL 和其他机构最近对 HT-NX 型导体的研究表明，在环向应力高于 400 MPa 且总应变高于 0.7% 的情况下运行可能是可行的。我们用单个 240 m 长的 HT-NX 制造了一个测试线圈。该线圈在 14 T 背景场中成功运行至 19.5 T，总施加应变为 0.8%，线圈电流密度为 243 A/mm2。线圈从设计电流的一半到全电流循环 20 次，没有观察到性能下降。