Non-destructive testing of multi-filamentary coated conductors by combination of a high-speed scanning laser observation system and a SQUID gradiometer array system

Abstract

We developed a non-destructive evaluation (NDE) technique combining the high-speed scanning laser observation system and the SQUID gradiometer array system for multi-filamentary coated conductors (CCs). The high-speed scanning laser observation system can detect anomalies in height of the surface and reflectivity, and marks the information of defects on the backside of the substrate. GdBCO CCs striated into five lines were evaluated by using the NDE technique, and three kinds of delamination defects and the electrical shorts between the filaments were evaluated. The SQUID system and the laser system have different strong points and weak points for evaluation of striated CCs. All three types of delamination defects could not be identified unless both the SQUID and the laser systems were used. The combination of these evaluation systems is useful to develop reliable CCs and especially for AC power applications.