Filament Structure Analysis of Multifilament MgB2 Wires by Using X-ray CT

We have investigated the filament structure of 18-filament MgB
₂
wires by using an X-ray computed tomography (CT). For the structural analysis of MgB
₂
filaments and Nb barriers, we adopted two image processing, the adoptive binarization method and the closing technique, to the series of cross-sectional CT images. After the image processing, we successfully eliminated the effect of several artifacts, such as metal artifacts and beam hardening, and extrapolated the area of MgB
₂
filaments and Nb barriers. From the images, we made a three-dimensional model of MgB
₂
filaments and confirmed whether the breakout of the filaments and sausaging phenomena exist or not. Although the broken filaments were not observed, the Nb barrier's break was confirmed in all six inner filaments of the MgB
₂
wire after heat treatment. Moreover, from the statistical distribution analysis, sausaging is more significant in the inner filament than in the outer filament. These results indicate that the X-ray CT observation and advanced image processing is effective in understanding the filament structure in non-destructive ways.