Ling Jiayin, Voccio John, Kim Youngjae, Hahn Seungyong, Bascuñán Juan, Park Dongkeun K, Iwasa Yukikazu
Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 USA.
Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 USA. He is now with Samsung Electronics, Suwon, Korea 135-239.
IEEE Trans Appl Supercond. 2013 Jun;23(3). doi: 10.1109/tasc.2012.2234183. Epub 2012 Dec 20.
This paper presents recent results from our continued development of a 0.5 T whole-body MRI magnet at the Francis Bitter Magnet Laboratory. HyperTech Research Corp. (Columbus, OH) manufactures the MgB conductor for this project. During the past year, we have found that our technique, originally developed successfully to splice unreacted MgB wires, works much better, i.e., of higher reliability, with unreacted MgB wires. This has led us to wind the entire coil components in our persistent-mode MRI magnet with unreacted monofilament MgB wire, having a MgB core of 0.4 mm in diameter, an overall diameter of 0.8 mm bare, 1 mm S-glass insulated. To verify that these coils would not suffer from flux jumping, as they would if wound with monofilament NbTi wire, magnetization studies were performed on monofilament wires of MgB and NbTi (as a reference) at 4.2 K. For the monofilament MgB wire, the results were affirmative. To further ensure the absence of flux jumping that may quench these current-carrying coils, two test coils were wound with unreacted monofilament MgB wire. One MgB coil was operated in driven mode, while the other MgB coil, equipped with a persistent current switch and terminated with a superconducting joint, was operated in persistent mode. The operating temperature range was 4.2-15 K for these MgB coils. The driven mode coil was operated in self-field. The persistent mode coil achieved a persistent current of 100 A, corresponding to a self-field of 1 T in the winding, for 1 hour with no measurable decay. Both test coils were operated quench free.
本文介绍了我们在弗朗西斯·比特磁体实验室持续开发0.5T全身MRI磁体的最新成果。HyperTech Research Corp.（俄亥俄州哥伦布市）为该项目制造MgB导体。在过去的一年里，我们发现我们最初成功开发的用于拼接未反应MgB线的技术，在处理未反应MgB线时效果更好，即可靠性更高。这使我们用未反应的单丝MgB线缠绕了我们的持续模式MRI磁体中的整个线圈组件，该MgB线的MgB芯直径为0.4mm，裸线总直径为0.8mm，S玻璃绝缘后直径为1mm。为了验证这些线圈不会像用单丝NbTi线缠绕时那样出现磁通跳跃，在4.2K下对MgB和NbTi的单丝线（作为参考）进行了磁化研究。对于单丝MgB线，结果是肯定的。为了进一步确保不会出现可能使这些载流线圈失超的磁通跳跃，用未反应的单丝MgB线缠绕了两个测试线圈。一个MgB线圈以驱动模式运行，而另一个配备了持续电流开关并以超导接头端接的MgB线圈以持续模式运行。这些MgB线圈的工作温度范围是4.2 - 15K。驱动模式线圈在自场中运行。持续模式线圈实现了100A的持续电流，对应于绕组中的1T自场，持续1小时且没有可测量的衰减。两个测试线圈均无失超运行。
