Longitudinal Critical Current Profiles in Coated Conductors Examined by Transport and Magnetization Measurements

Critical current (I_c) variations along the coated conductor (CC) have a significant impact on the conductor stability and quench behavior. In the direct current (DC) transport case, localized I_c minimum can lead to the formation of a region with a higher electric field. Joule heating in such a region can disable the operational functionality of the device. Then a sufficiently detailed knowledge of the longitudinal profile of the conductor I_c is in the first place necessary in assessing the conductor eligibility for a specific application. In the second place, it serves to design appropriate electro-thermal stabilization, securing an effective operation, and reducing the probability of conductor degradation during the quench. We report on the experimental investigation of longitudinal I_c homogeneity of CC observed by means of transport and magnetization measurements. Basic information is the CC data from the producer on I_c profiles obtained with ∼1-milimeter spatial resolution by Tapestar^TM XL. We compare it with the result obtained by multi-channel DC transport measurement with 3-millimeter spatial resolution between neighboring contacts on a multiprobe device. Then the whole sample is characterized by a complex AC susceptibility experiment. We analyze possible causes of observed discrepancies between respective methods and discuss the relevance of various techniques for the determination of longitudinal I_c profiles in commercial CC.