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| Cross section
of a Nb3Sn multifilamentary wire and filaments strand
within the wire |
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| 3-D microtomography
of Nb3Sn multifilamentary wire: 3-D reconstruction,
3-D reconstruction after thresholding and axial cross-section
Inspection of the structural integrity in order to detect the
manufacturing defects and anomalies (e.g. possible inter-filament
contacts) inside the complex structure |
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| Segmentation techniques allow
the partitioning into several constituent components, for detailed
inspection - extraction of the central filaments and of the Nb
sleeve. |
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| Noise reduction in radiographic
images by a wavelet-based multiscale products thresholding scheme |
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| Filament
evolution inside the cross-sections, revealed after filtering
and segmentation. |
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- for each filament a “trace contour”
filter is applied and the centroid Pi of the contour
is determined.
- for the whole set of cross-sections corresponding
to a tomogram, the centroids are fitted by a circle arc
- the center of the circle O’ is
determined and the angle g is calculated
- consequently, the number of cross-sections
Ncs, corresponding to a full rotation (g = 360°), can be evaluated
- the twist-pitch parameter is calculated
by multiplying Ncs with the cross-section width
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| Previous method
for twist-pitch factor evaluation: etching the copper in a nitric
acid solution, thus evidencing the twisted structure
Main drawbacks:
- destructive
- poor visualization of the Nb3Sn
filaments
distortion of the internal structure
digital
radiography
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3D tomographic reconstruction
of a sample after etching |
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