Preparation of 6+1 Core IMD-MgB₂ Wires and Their Properties

Two 100 m MgB2 wires with different conductor structures (Cu core and CuNb core) were designed and fabricated by the internal Mg diffusion process (IMD), and the mechanical and transport superconductivity of the wires were tested. The distribution uniformity of MgB2 superconducting layer along the longitudinal direction of the two wires was analyzed by different methods. It is found that the distribution of superconducting layer tends to be more uniform as the diameter of the wire decreases, and the MgB2 FF fluctuation range of the wire with F0.8 mm is the smallest, and the extreme difference of the base super ratio is 0.02. The study of the uniformity of MgB2 layer distribution shows that the Mg and B densities in the wire are well distributed. The results of the superconductivity tests show that the critical current I-c of the Cu replacement core wire is 19 A (4.2 K, 4 T) higher than the critical current Ic of the CuNb replacement core wire, while the J(c) performance is basically the same. The Mg/B/Nb/Monel matrix composite enable researchers to manufacture high performance MgB2 wires with 100-m class.