Investigations on $N$ Values of Long Bi2223/Ag Tapes

High temperature superconducting tapes with big $n$ values are preferred in high temperature superconducting apparatuses to secure a speeded superconducting-normal transition, a shorten quench detection and protection response time because small $n$ values are associated with unstable resistive behaviors. This paper reports our measurement results of $n$ values distributions along long Bi2223/Ag tapes at 77 K. The results show that the variation of $n$ values is more distinct than that of critical currents along a long Bi2223/Ag tape. And the variation of local $n$ values has more effect on the overall $n$ value and the overall critical current of a long Bi2223/Ag tape than that of local critical currents. As a result, the overall $n$ value is an easy-to-get and reliable parameter to evaluate the critical current homogeneity along a long Bi2223/Ag tape.