China’s participation in the international RRT for Ic measurement of superconducting cables organized by IEC/TC90

Abstract

Currently, IEC/TC90 is working on standardizing the method for measuring critical current ( I c ) in superconducting cables. At the end of 2020, an international round robin test (RRT) was organized, in which five Chinese institutions participated, and four accomplished the test. The electric-field versus current ( E - I ) curves obtained by each institution are highly repeatable. Those obtained by different institutions are nearly identical after appropriate curve averaging, indicating high reproducibility, except the last participant's inner core curves. The discrepancy was later determined to be the result of sample cable damage. After excluding highly deviated data, it is determined that the maximum relative standard uncertainty in I c is 0.7%, and the maximum relative standard uncertainty in n -value is 12.8%. The I c values are comparable to Japan's domestic RRT results, but the n -values are significantly different. The test results support the DC four-terminal method as a recommended test method, with a target relative uncertainty of less than 2% for the I c value.