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中国物理学会期刊

14 T全身超导MRI磁体的技术挑战 —大规模应用强场超导磁体未来十年的发展目标之一

CSTR: 32037.14.aps.70.20202042

Technology challenges of 14 T whole-body superconducting MRI magnets —A target of high-field superconducting magnet technology for large scale applications in next decade

CSTR: 32037.14.aps.70.20202042
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  • 本文首先综述了大规模应用的超导磁体, 依赖并推动铌三锡Nb3Sn导线技术进步, 向更强磁场发展的趋势. 着重分析了超高场14 T全身MRI磁体的挑战性技术. 选择青铜Nb3Sn导线, 采用Nb3Sn线圈和NbTi线圈相结合的混合结构, 对14 T全身MRI磁体进行了电磁概念设计和热稳定性及失超保护仿真分析, 并简要阐述了14 T全身MRI磁体在应力、接头和匀场方面的关键问题. 根据分析结果认为: 1) Nb3Sn导线是14 T全身MRI磁体需要面临的首要挑战性问题 —作为最佳选择的青铜Nb3Sn导线, 其现有产品的性能指标离14 T全身MRI磁体的要求尚存在有一定的差距; 2) 14 T全身MRI磁体的失超保护涉及线圈的铜超比设计、运行电流同线圈电感的协调配置、被动保护的分段策略和主动保护的失超触发控制以及主动屏蔽结构磁体在失超过程中的逸散磁场限制等多个十分复杂的环节, 是最具挑战性的综合性技术.

     

    This paper presents a brief review of the development trend of superconducting magnets in large scale applications towards high magnetic fields, depending on and pushing the Nb3Sn wire technics' continuous improvement. The focus is on analysis of the technology challenges of 14 T whole-body superconducting magnets. Using the Bonze Nb3Sn wires and on the base of a combination design of Nb3Sn and NbTi coils, an electromagnetic conception design of a 14 T whole-body MRI magnet is presented, and the thermal stability and quench protection are analyzed by simulations. The critical issues on stress, joints as well as shimming of 14 T whole-body superconducting magnets are also discussed. According to the results, this paper believes: 1) Nb3Sn wires are of the first important issue for 14 T whole-body superconducting magnets—the Bonze Nb3Sn wire is of the best choice but the performance specifications of the current products need to be improved further to match the requirements; 2) quench protection of 14 T whole-body superconducting magnets is one of the most complicated technics that covers design of the copper to superconductor (Cu/SC) ratio, coordination of the operating current and coil inductances, subdivisions of passive protection circuits and quench triggering control of active protection, as well as the stray field limitation during the transient process.

     

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