Qu Timing, Michael Philip C, Bascuñán Juan, Lécrevisse Thibault, Guan Mingzhi, Hahn Seungyong, Iwasa Yukikazu
Francis Bitter Magnet Laboratory, Plasma Science and Fusion Center, M.I.T., Cambridge MA, U.S.A. Department of Mechanical Engineering, and State Key Laboratory of Tribology, Tsinghua University, China. He participated in this work while a visiting scientist at MIT, March 2015-February 2016.
Francis Bitter Magnet Laboratory, Plasma Science and Fusion Center, M.I.T., Cambridge MA, U.S.A.
IEEE Trans Appl Supercond. 2017 Jun;27(4). doi: 10.1109/TASC.2016.2633626. Epub 2016 Dec 1.
A 1.3-GHz/54-mm LTS/HTS NMR magnet, assembled with a 3-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-m thick REBCO tapes. In order to keep the hoop strains on REBCO tape < 0.6% at an operating current of 250 A and in a field of 30.5 T, we overbanded each pancake in Coil 1 with a 6-mm wide, 76-m 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 77K and 4.2 K. In the 77-K test, the measured critical current was 35.7 A, determined by an -field criterion of 0.1 V/cm. The center field magnet constant decreased from 34.2 mT/A to 29.3 mT/A, when increased from 5 A to 40 A. The field distribution at different along the -axis was measured. The residual field distributions discharged from 10 A 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.
一台1.3GHz/54毫米的低温超导/高温超导核磁共振磁体正在建造中，它是将一个三线圈（线圈1 - 3）800兆赫兹高温超导插入件安装在一个500兆赫兹低温超导核磁共振磁体中组装而成。最里面的高温超导插入件线圈1由26个无绝缘（NI）双饼（DP）线圈堆叠而成，这些线圈由6毫米宽、75微米厚的稀土钡铜氧（REBCO）带材缠绕而成。为了在250安的工作电流和30.5特斯拉的磁场中使REBCO带上的环向应变小于0.6%，我们用6毫米宽、76微米厚的304不锈钢带对线圈1中的每个饼进行了过带处理：中间18个饼的径向叠层厚度为7毫米，而外侧2×17个饼的厚度为6毫米。在本文中，线圈1在77K和4.2K下成功进行了测试。在77K测试中，根据0.1伏/厘米的电场准则确定，测得的临界电流为35.7安。当电流从5安增加到40安时，中心场磁常数从34.2毫特斯拉/安降至29.3毫特斯拉/安。测量了沿z轴不同电流下的场分布。记录了从10安和20安放电后的剩余场分布。在4.2K测试中，线圈1在255安时成功产生了8.78特斯拉的中心场。磁常数为34.4毫特斯拉/安，与我们的设计值相同。在15毫米区域内线圈中心的场均匀性约为1ppm。在进行场匀场之前，必须减小这个大的误差场。
