Current distribution in a 12 strand Nb3Sn CICC and its influence on ramp rate limitation

Abstract

Direct measurements of the current in each strand of a chrome coated Nb3Sn CICC were performed during current and/or external magnetic field ramps. Severe non-uniformity of the strand currents was found immediately before quench. The currents in some of the strands were also observed to change abruptly at various points during external field ramps. The observed peculiarities of the strands' current behaviors are considered in the present paper and a simple ''ad hoc'' model of the ramp rate limitation phenomenon is proposed based on the hypothesis that current non-uniformity is a main cause of RRL. This model is compared with the experimental results.