Ling Jiayin, Voccio John P, Hahn Seungyong, Qu Timing, Bascuñán Juan, Iwasa Yukikazu
Francis Bitter Magnet Lab, Plasma Science and Fusion Center, Massachusetts Institute Technology, 170 Albany St, Cambridge, MA 02139, USA.
GE Healthcare, 3001 W Radio Dr, Florence, SC 29501, USA.
Supercond Sci Technol. 2017 Feb;30(2). doi: 10.1088/1361-6668/30/2/024011. Epub 2016 Dec 29.
This paper presents construction details and test results of a persistent-mode 0.5-T MgB magnet developed at the Francis Bitter Magnet Lab, MIT. The magnet, of 276-mm inner diameter and 290-mm outer diameter, consisted of a stack of 8 solenoidal coils with a total height of 460 mm. Each coil was wound with monofilament MgB wire, equipped with a persistent-current switch and terminated with a superconducting joint, forming an individual superconducting loop. Resistive solder joints connected the 8 coils in series. The magnet, after being integrated into a testing system, immersed in solid nitrogen, was operated in a temperature range of 10-13 K. A two-stage cryocooler was deployed to cool a radiation shield and the cold mass that included mainly ~60 kg of solid nitrogen and the magnet. The solid nitrogen was capable of providing a uniform and stable cryogenic environment to the magnet. The magnet sustained a 0.47-T magnetic field at its center persistently in a range of 10-13 K. The current in each coil was inversely calculated from the measured field profile to determine the performance of each coil in persistent-mode operation. Persistent-current switches were successfully operated in solid nitrogen for ramping the magnet. They were also designed to absorb magnetic energy in a protection mechanism; its effectiveness was evaluated in an induced quench.
本文介绍了麻省理工学院弗朗西斯·比特磁体实验室研制的持续模式0.5T MgB磁体的结构细节和测试结果。该磁体内径276mm，外径290mm，由8个螺线管线圈堆叠而成，总高度460mm。每个线圈用单丝MgB线绕制，配备一个持续电流开关，并以超导接头端接，形成一个独立的超导回路。电阻焊接头将8个线圈串联连接。该磁体集成到测试系统中并浸入固态氮后，在10 - 13K的温度范围内运行。部署了一台两级低温制冷机来冷却一个辐射屏蔽层和主要包含约60kg固态氮及磁体的冷质量体。固态氮能够为磁体提供均匀且稳定的低温环境。该磁体在10 - 13K范围内在其中心持续维持0.47T的磁场。根据测量的场分布反向计算每个线圈中的电流，以确定每个线圈在持续模式运行下的性能。持续电流开关在固态氮中成功运行以对磁体进行励磁。它们还被设计用于在保护机制中吸收磁能；其有效性在感应失超中进行了评估。
