Examination and Analysis of Critical Current Uniformity of Long HTS Tapes by the MCorder

The magnetic circuit (MC) method has been developed to measure the critical current (I_c) of long high temperature superconductor (HTS) tapes continuously since 2010. So far, with the apparatus based on the MC method, namely MCorder, industrial HTS tapes produced by main manufactures worldwide have been measured using the MC method, including Bi2223/Ag multifilament tapes and coated conductors with/without magnetic substrates. The high speed (360 m/h), high accuracy measurement (resolution 1 A) and its adaption to all kinds of HTS tapes make large quantity measurement and statistical evaluation of HTS tape possible. In this paper, criteria for I_c assessment of long HTS tapes is discussed, based on which analysis of samples from different manufacturers worldwide is provided. The measurement result of a Bi2223/Ag tape by MC method is compared with section-by-section four-probe method, and the two methods show good agreement. Fourier analysis is given for analyzing I_c periodicity of a tape with periodical artificial defects.