Stability measurements with non-uniform current distribution in NbTi cable-in-conduit conductor for SST-1

The stability of a NbTi/Cu-based cable-in-conduit conductor (CICC) was measured with uniform and non-uniform current distributions (NUCD) in the conductor. The sample was prepared using the NbTi/Cu CICC for Steady State Tokamak (SST-1) superconducting magnets. The CICC consists of 135 uncoated strands with 3 × 3 × 3 × 5 twisting pattern. The experiments were performed with stagnant supercritical and liquid helium at different operating pressures in bias magnetic field of ∼6.1 T. It was experimentally found that the conductor stability reduces when NUCD is established among the strands of the conductor. However, the conductor showed good stability around 11 kA current even with NUCD in the conductor. It was also found that the conductor was more stable in liquid helium as compared with supercritical helium.