Critical current variation and current transfer length in multifilamentary Bi-2223/Ag tapes

In this work we compare V-I curves and critical currents of a Bi-2223/Ag tape with 55 filaments in an Ag matrix measured at 77 K with test sections of various lengths. The distance between the potential taps on the sample was reduced from 800 mm over 100 mm to 10 mm and 1 mm. Furthermore it is shown how the shape of E-I curves varies with the length of the measured section. We also observed that many of the measured V-I curves have one or more linear sections. They are supposed to be caused by current transfer voltages in the vicinity of filament defects. We also studied the current transfer length in order to see how far from a defect voltages due to the current redistribution between a filament and the matrix can be observed. These results show that the critical currents of multifilamentary tapes could be increased strongly by improving their homogeneity.