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ST388 - Construction and Persistent-mode Operation of a 0.5-T/240-mm Cold Bore MgB2 MRI Magnet at 10-15 K

Construction and Persistent-mode Operation of a 0.5-T/240-mm Cold Bore MgB2 MRI Magnet at 10-15 K
 
Jiayin Ling, John P. Voccio, Seungyong Hahn, Youngjae Kim, Kazuhiro Kajikawa, Jungbin Song, Juan Bascuñán, and Yukikazu Iwasa
 
Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA, 02139, US
 
Abstract—This paper presents construction and persistent-mode operation results of a 0.5-T/240-mm cold-bore MgB2 MRI magnet, wound with monofilament MgB2 wire, at the MIT Francis Bitter Magnet Laboratory. The magnet, of respective inner and outer diameters of 276 and 290 mm and a total height of 460 mm, has computed pre-shim field homogeneity of 200 ppm over a 12-cm Diameter Spherical Volume (DSV). The magnet results presented include: 1) construction details; 2) electromagnetic and cryogenic performances; and 3) protection technique deployed. To limit the continuous length of Hyper Tech supplied MgB2 monofilament wire to <300 m, the magnet was divided into 8 series-connected coils, each equipped with its own persistent current switch (PCS) and superconducting joints. Before assembled into the magnet, each coil was tested in the temperature range 10-15 K, cooled by the affluent helium vapor emanating from a pool of liquid helium below. Each coil, in self-field, carried a minimum of >100-A superconducting current at 15 K and a peak field of 0.5 T. The magnet, designed for liquid-helium-free operation, was immersed in solid nitrogen, an excellent thermal mass enhancer in the operating temperature range 10 - 15 K. In the magnet energizing mode, with adjacent coils solder-connected, the 8 coils were charged simultaneously with all 8 PCSs “opened.” In persistent-mode operation, all PCSs were “closed.”
 
IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), October 2014.
ASC slide presentation 1LOr2A-03 and preprint of manuscript submitted to IEEE Trans. Appl. Supercond. for possible publication.  3rd Prize in Best Student Paper Contest, Large Scale Appl.