부산대학교 도서관

The effects of the largest crack–size and size–difference among cracks on the critical current and n–value of the copper–stabilized coated superconducting tape, in which multiple cracks are formed in the superconducting layer, were investigated. As the tools, the model of current shunting at cracks, Monte Carlo simulation method, monitoring method of the crack size and the size–difference among cracks, and calculation method of the upper and lower bounds of the critical current and n–value at the largest crack–size were employed. The main results are summarized as follows. (1) The increase in the largest crack–size with the increase in the crack size distribution width works to reduce both the critical current and the n–value. On the other hand, the increase in the size–difference among the cracks works to raise the critical current value and to reduce the n–value. (2) When the crack size distribution width increases, the effect of reducing the critical current due to the increase of the largest crack–size and the effect of raising the critical current due to the increase of the size–difference among the cracks take place, and the critical current is determined by the sum of these effects. Since the effect of the former is larger than that of the latter, the critical current value decreases with increase in the crack size distribution width. (3) With increase in the crack size distribution width, the effect of reducing the n–value due to the increase in the largest crack–size and the effect of reducing the n–value due to the increase in the size–difference among the cracks take place, and the n–value is determined by the sum total of these effects. Since both of these two effects work to reduce the n–value, as the crack size distribution width increases, the n–value decreases relatively sharply with respect to the critical current.