Bi₂Sr₂CaCu₂O_8+x (Bi-2212) multifilamentary wire is the only high-temperature superconductor manufactured in the form of an isotropic round wire, and so offers a number of advantages for the designers of high field magnets. However, for high-field (>25 T), high-stability magnet applications, ultra-low resistance superconducting joints (R < 10⁻¹² Ω) will be needed to take advantage of the excellent properties of the Bi-2212 wire. This study focuses on the fabrication of compact melt processed joints in small coils of Bi-2212/Ag multifilamentary round wires and the testing of their superconducting performance by inductive resistance measurements. Microstructural analysis is carried out to correlate the microstructure to the superconducting performance of the joints. Our optimized technique led to a reliable process for the preparation of small coils with melt processed joints that occupy very small volumes but can still carry the highest persistent currents reported so far for Bi-2212.

中文翻译：

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超导 Bi-2212 线圈持久接头的开发

Bi ₂ Sr ₂ CaCu ₂ O _8+X (Bi-2212) 复丝线是唯一以各向同性圆线形式制造的高温超导体，因此为高场磁体的设计者提供了许多优势。然而，对于高场（>25 T）、高稳定性磁体应用，超低电阻超导接头（右< 10 ^-12 Ω）需要利用 Bi-2212 线的优异性能。本研究重点关注 Bi-2212/Ag 多丝圆线小线圈中紧凑熔融加工接头的制造，并通过感应电阻测量测试其超导性能。进行微观结构分析，将微观结构与接头的超导性能联系起来。我们的优化技术带来了一种可靠的工艺，用于制备具有熔融加工接头的小型线圈，该线圈占用的体积非常小，但仍然可以承载迄今为止 Bi-2212 报道的最高持续电流。