EFFECT OF NONUNIFORM CURRENT DISTRIBUTION ON THE STABILITY IN NB-TI CABLE-IN-CONDUIT SUPERCONDUCTING CONDUCTOR

30kA-NbTi Demo Poloidal Coil (DPC-U) exhibited instability such as the conductor quenches at 40% of the rated current which is still much sm aller than the expected conductor critical current, It was found that this instability was caused by the non-uniform current distribution in the DPC-U conductor whose strands were insulated from each other, To investigate the instability of the DPC-U conductor, a stability experi ment of a subsize conductor consisting of 27 strands was performed and the effect of the current imbalance on the stability was investigated , The current imbalance was forcibly established in the conductor usin g two current sources in this experiment, The experimental results ind icate that the stability margin decreases as the current imbalance bec omes larger and that the stability margin of the conductor is governed by the stability of the strand with the highest current in the conduc tor. Also, it is confirmed from the experimental results that the inst ability of DPC-U has to be attributed to the current imbalance in the conductor.