CURRENT DISTRIBUTION IN A 12-STRAND NB3SN-CICC AND ITS INFLUENCE ON RAMP RATE LIMITATION

Direct measurements of the current in each strand of a chrome coated N b3Sn CICC were performed during current and/or external magnetic field ramps. Severe non-uniformity of the strand currents was found immedia tely before quench. The currents in some of the strands were also obse rved to change abruptly at various points during external field ramps. The observed peculiarities of the strands' current behaviors are cons idered in the present paper and a simple ''ad hoc'' model of the ramp rate limitation phenomenon is proposed based on the hypothesis that cu rrent non-uniformity is a main cause of RRL. This model is compared wi th the experimental results.