Rutherford MgB2 cable with 20 μm twisted filaments inside the Nb/CuNi/CuZn sheath

Abstract

A fine-filamentary CuZn sheathed MgB ₂ wires produced by Hyper Tech Inc were used for 12 strand Rutherford cable of thickness 0.70–0.76 mm. Critical currents of short cable samples were measured at 4.2 K and external fields 4.0–8.0 T and also at temperatures 15–25 K and magnetic fields 1.0– 5.5 T. The threshold of engineering current density $J_e=10^4$ Acm ⁻² for the cable size of 0.72 mm $\times$ 2.55 mm was obtained at field of 4.5 T and temperature 4.2 K and at 2.3 T for 20 K, respectively. Magnetization measurements of the cable with transposed strands and twisted $20\mu m$ filaments have shown reduced AC losses, but, the coupling currents loss contribution was still visible. AC losses measured for the same size Rutherford cable made of single-core wires demonstrate the effect of well decoupled filaments. Consequently, the cabling of thin single-core MgB ₂ wires shows a promising way for low loss conductors suitable for AC applications.