Influence of internal magnetic field distribution on critical currents in a single and assembled Bi-2223 tapes

We have investigated the influence of self-field on the critical current density distribution in a Bi-2223 tape and its effect on the current capacity of an assembled conductor. Critical current of a tape is usually measured by four-probe transport method under self-field. On the other hand, the critical current of an assembled conductor cannot be simply summed because the tape experiences different condition of magnetic field due to the interaction among the tapes. To quantify the situation, it is necessary to clarify first how the critical current of a tape is determined at the self-field and then to consider the interaction among the tapes. In this study, it was found that the distribution of critical current density was largely influenced by local magnetic field inside the tape. The results were quantitatively described by a model considering the position dependence and magnetic field dependence of local critical current density. Using such a quantitative model, we numerically investigated the current capacities of assembled conductors with different arrangements of the tapes.