Dynamic response of HTS composite tapes to pulsed currents

Abstract

Dynamic voltage–current characteristics of an HTS Ag/BiSCCO composite tape arestudied both experimentally and theoretically. The tape is subjected to pulsedcurrents with different shapes and magnitudes and voltage traces are measuredusing the four-point method with different locations of potential taps on thesample surface. Clockwise and anticlockwise hysteresis loops are obtained forthe same sample depending on the location of the potential taps. The dynamiccharacteristics deviate substantially from the DC characteristic, especially in the rangeof low voltages where a criterion for the critical current value is usually chosen(1–10 µV cm−1). The critical current determined from dynamic characteristics and its change with thepulse magnitude depend on the location of the potential taps and on the curvebranch chosen for the critical current determination (ascending or descending).The theoretical analysis is based on a model of the magnetic flux diffusion into a compositetape for a superconductor described by the flux creep characteristic. Numerical simulationbased on this model gives results in good agreement with the experimental ones andexplains the observed peculiarities of the dynamic characteristics of HTS composite tapes.The difference between the magnetic diffusion into a tape and a slab is discussed.