3D X-ray micro-tomography for modeling of NB3SN multifilamentary superconducting wires

Practical superconducting cables used in large scale applications (e.g. magnets for fusion reactor) consist in superconducting filaments embedded in a normal-conducting matrix. The common technique to reduce the eddy-current losses is to twist the wire and the filaments during the manufacture. This also reduces the time-independent proximity effect between the filaments and its associated loss. Currently, the only method for measuring the twist-pitch consists in evidencing the twisted structure by etching techniques. This method is destructive and does not permit the visualization of the filaments. It is proved in this paper that X-ray micro-tomography permit the non-destructive reconstruction of the 3D image of the ITER-type multifilamentary wire enabling the determination of the number of inter-filament contacts on unite lengths well as the twist-pitch parameter. This can be used to develop a more complex model of the multifilamentary superconducting wire in order to explain the role of the internal wire structure on the superconducting transport properties.