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cathodoluminescence (STRCL) spectroscopy is implemented to assess the local carrier dynamics in a 70-nm-thick, very low threading dislocation (TD) density, pseudomorphic m-plane In 0:05 Ga 0:95 N epilayer grown on a freestanding GaN substrate by metalorganic vapor phase epitaxy. Although TDs or stacking faults are absent, sub-micrometer-wide zonary patterns parallel to the c-axis and 2-m-long-axis figureof-8 patterns parallel to the a-axis are clearly visualized in the monochromatic cathodoluminescence intensity images. Because the STRCL measurement reveals very little spatial variation of low-temperature radiative lifetime, the considerable peak energy variation is interpreted to originate from nonidentical In-incorporation efficiency for the growing surfaces exhibiting various miscut angles. The figure-of-8 patterns are ascribed to originate from the anisotropic, severe m-plane tilt mosaic along the a-axis of the GaN substrate, and the zonary patterns may originate from the m-plane tilt mosaic along the c-axis. #

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The design and manufacture of Nb3Sn conductors for ITER toroidal field (TF) coils have many technical challenges. Although it was demonstrated in the ITER model coil project that the conductors have a sufficiently high performance and the engineering design is valid, unexpected issues arose. Through both theoretical and experimental efforts improved conductors were developed. The Japan Atomic Energy Agency started to procure improved conductors for TF coils as part of the ITER project. Because the required tonnage of Nb3Sn strands is quite large compared with past experience and the required superconducting performance is higher than that of the model coils, quality control techniques are very important for the successful manufacture of the strands. Approximately 60 ton of Nb3Sn strands have been successfully completed under a severe quality control regimen and all strands meet ITER specifications. This paper summarizes the technical developments leading to the first successful mass production of ITER TF conductors.