Critical currents and AC losses on subsize cables of the NET-EM/LMI 40-kA Nb3Sn cable-in-conduit conductor prototype

Critical currents have been measured on subsize cables, up to the 27-strand level, of the 40-kA NET-EM/LMI Nb₃Sn prototype conductor for the OH solenoid of NET (Next European Torus). Energy losses in basic strands were determined by magnetization cycles. Copper and stainless steel were used as conduit materials to produce CIC (cable-in-conduit) conductors with a 0.35 void fraction, which is lower than that of the full-size conductor. The experimental results have shown that, compared to the single-strand current, practically no degradation is observed in cables with a Cu conduit, while the cables with a stainless steel conduit have a critical current lowered by cool-down strain to 0.57 of the expected current in a 27-strand cable at zero intrinsic strain. The measurements of AC losses have indicated high hysteretic losses (effective diameter of =70 μm). Coupling losses are expected to be negligible