3D X-ray Micro-Tomography for Modeling of Nb3Sn
Multifilamentary Superconducting Wires


Cross section of a Nb3Sn multifilamentary wire and filaments strand within the wire

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

Segmentation techniques allow the partitioning into several constituent components, for detailed inspection - extraction of the central filaments and of the Nb sleeve.
Noise reduction in radiographic images by a wavelet-based multiscale products thresholding scheme

Filament evolution inside the cross-sections, revealed after filtering and segmentation.
  • 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

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

3D tomographic reconstruction of a sample after etching