Perspective on Kilometer-Scale MgB2 Superconducting Wires With 127 Filaments

초록

Since 2015, we have successfully developed magnesium diboride (MgB2) wire at the 3 km-scale and achieved a high critical current density (J(c)) of 3.5 x 10(5) A/mm(2) at 4.2 K and 3 T for various applications. To ensure mechanical strength and performance stability, it is necessary to design MgB2 wire with a large number of internal filaments. In this study, we conducted a comparative analysis of the number/size of filaments and electrical properties of 19 (18 + 1Cu)-, 37 (30 + 7Cu)-, 61 (54 + 7Cu)-, 91 (72 + 19Cu and 78 + 13Cu)-, and 127 (114 + 13Cu)-filament MgB2 wires. Increasing the number of filaments had a minor effect on the fill factor and did not significantly enhance the J(c). However, it was observed that the deformation of the internal filaments became more inhomogeneous. The mean filament size of the 19-filament architecture was approximately 80 mu m, while that of the 127-filament architecture showed a significant reduction, effectively reaching less than 33 mu m. The microstructure and characterization of the produced wires are discussed in detail.

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