Nb/sub 3/Al superconductors
Nb/sub 3/Al superconductors
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DOI：
10.1109/tasc.2002.1018590
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发表时间：
2002-08
影响因子：
1.8
通讯作者：
T. Takeuchi
中科院分区：
文献类型：
--
作者：
T. Takeuchi
介绍了Nb/sub 3/Al超导体的最新进展。采用直接扩散法由热轧Nb/Al复合材料制成的13 T下46 kA的大电流导体，即将作为聚变磁体的插入线圈导体进行测试。1 GHz NMR磁体为Nb/sub 3/Al加工提供了一种全新的方法，可以显著改善高场J/sub c/特性。RHQT工艺通过bcc过饱和固溶体产生具有细晶粒结构的化学计量Nb/sub 3/Al，因此在整个磁场范围内具有大的J/sub c/。将加热温度控制在扩展的bcc固溶体的狭窄区域内，确保了淬火态线材的室温延展性和沿长段沿着转变的Nb/sub 3/Al的均匀J/sub c/特性。采用绕线反应法制备了Cu包覆RHQT Nb/sub 3/Al导体的螺线管线圈，在21.2T的偏置场下，在2.1K时产生1.3T的附加磁场，并在无偏置场的情况下以持续电流模式工作。RHQT工艺的变体（TRUQ、DRHQ、加铜RHQO）在不牺牲应变容限的情况下显著改善了高场J/sub c/。
Recent progress of Nb/sub 3/Al superconductors is described. A large-current conductor of 46 kA at 13 T, produced from a jelly-roll (JR) Nb/Al composite by a direct diffusion-process, is about to be tested as an insert-coil conductor for fusion magnets. The 1 GHz NMR magnet has given a motivation to do an entirely new approach to Nb/sub 3/Al processing that allows a dramatic improvement in high-field J/sub c/ characteristic. The RHQT process produces a stoichiometric Nb/sub 3/Al with fine-grain structures via a bcc supersaturated solid solution and, hence, large J/sub c/ over the whole range of magnetic fields. Controlling a heating temperature within a narrow region of extended bcc solid solution ensures the room-temperature ductility of as-quenched wires and homogeneous J/sub c/ characteristics of transformed Nb/sub 3/Al along the long piece-length. A solenoid coil fabricated by a wind-and-react method, with Cu clad RHQT Nb/sub 3/Al conductors, could generate an additional 1.3 T at 2.1 K in a bias field of 21.2 T, and was operated in a persistent-current mode without a bias field. The variants of RHQT process (TRUQ, DRHQ, Cu-added RHQO) improved significantly the high-field J/sub c/ without sacrificing the strain tolerance.