2019 Volume 58 Issue 1 Pages 116-120
In fabrication and in operation，the copper–stabilized RE (Y, Sm, Dy, Gd, …. ) Ba2Cu3O7–δ superconducting tapes are subjected to thermal, mechanical and electromagnetic stresses/strains. When the superconducting layer is cracked by such stresses, the critical current of the tape is reduced. It has been reported that, in the case where a specifically large crack is formed in addition to many small cracks in the superconducting layer, the critical current value is low when the voltage probe distance in four probe sensing for measurement of voltage–current curve is small, but it becomes higher when the voltage probe distance is larger. In the present work, a simulation study was conducted to describe the variation of critical current value with voltage probe distance under the co–existence of a specifically large crack and many small cracks, by using a model specimen of copper–stabilized superconducting tape, a current shunting model at cracks, and a Monte Carlo method. With the present approach, the experimentally observed increase in critical current value with increasing voltage probe distance was reproduced well. Also, it was shown that the variation of critical current value with position along the longitudinal direction of specimen becomes smaller with increasing voltage probe distance under heterogeneous cracking of the superconducting layer. This result was also in good agreement with the experimentally known feature that the critical current–information is diluted when the voltage probe distance is large.
