Qualification Measurements of the Mid-Field and Low-Field CICC for the Series-Connected Hybrid Magnet With Effects of Electromagnetic Load Cycling and Longitudinal Strain

The cable-in-conduit conductors (CICC) designed for the National High Magnetic Field Laboratory (NHMFL) and Helmholtz Zentrum Berlin (HZB) Series-Connected Hybrid magnets have been qualified. The superconducting coils for the hybrid magnets consist of three CICC configurations graded for different designed fields. Representative samples with the same Nb₃Sn type, cable pattern, and CICC configuration were fabricated and the current sharing temperature (T_CS) and critical current were measured with the intention to quantify the level of degradation from cyclic, transverse electromagnetic loads. In addition the intrinsic strain for the CICC was determined by measuring the T_CS and I_C as a function of applied longitudinal strain. Two conductor grades, for the middle and low fields regions of the coil (MF and LF), are tested at the NHMFL in a split magnet that is equipped with a system that can apply up to 250 kN force in a direction longitudinal to the samples. The samples are hydraulically connected to a cryogenic system which delivers temperature controlled supercritical helium. The reduction in T_CS from electromagnetic load cycling is shown to be insignificant and measurements as a function of strain shown that the MF and LF CICC have intrinsic strains of approximately 0.65% and 0.70% respectively.