Features of Crack Size Distribution- and Voltage Probe Spacing-Dependences of Critical Current and n-Value in Cracked Superconducting Tape, Depicted by Simulation

Features of the dependence of critical current and n-value on the width of crack size distribution and voltage probe spacing in cracked superconducting tape were investigated by simulation and analysis of the simulation results. From the simulation results, the following features were confirmed. The variation of critical current and n-value with position along the longitudinal direction of the superconducting tape increases with increasing width of crack size distribution for any voltage probe spacing, and it decreases with increasing voltage probe spacing for any width of crack size distribution. The n-value varies more sensitively to the width of crack size distribution and voltage probe spacing than critical current. Then, from the analysis of the simulation results, it was confirmed that the largest crack among all cracks plays a major role in determination of critical current, and the phenomenon "critical current decreases with increasing width of crack size distribution and voltage probe spacing" is attributed to the increase in size of the largest crack. Also, it was shown that the upper and lower bounds of critical current and n-value of the region, which is in between the voltage probes and consists of local sections/local regions, can be calculated by using the voltage-current curve of the local section/local region with the largest crack. The application of this calculation method to the simulation results revealed that, in any voltage probe spacing, critical current value shifts from the lower to upper bound, and, in contrast, n-value shifts from the upper to lower bound with increasing width of crack size distribution. Also it was revealed that the difference between the upper and lower bounds becomes smaller and both bounds' values become closer to the actual critical current and n-values, when the voltage-current curve of longer local region is used in calculation.