Vision Inspection Methods for Uniformity Enhancement in Long-Length 2G HTS Wire Production

With much effort devoted by many research groups, the performance of 2nd generation (2G) superconducting wires, also called coated conductors (CC), was drastically improved, leading to many meaningful and impressive demonstrations of electric power devices. Now that the performances such as critical current, in-field characteristics, and mechanical strengths became sufficient to the application, the attention has moved to how we can produce long 2G wires with high uniformity. Many in-line inspection tools are tested and introduced to address these challenges. In this paper, we describe two methods that we adopted for in-line monitoring and feedback control of layer deposition. One is for texture control of ion beam assisted deposition (IBAD) of an MgO layer through reflection high-energy electron diffraction (RHEED) pattern monitoring and analysis. The other is for composition control of a superconducting layer through surface color observation and control of metal source evaporation rates. By applying the above two methods, we achieved in-plane texture of about 4.8 ° in the MgO layer, as measured by FWHM of phi-scan of (220) peak, and the critical current of 750 A/12 mm width in the GdBCO layer along the length of more than 650 m, with excellent uniformity.