  In modeling the properties of superconducting multi-filamentary strands, the
filament twist pitch and the inter-filament transverse resistivity play a
crucial role in the definition of the current transfer length. This affects the
AC losses of NbTi strands, or the transport properties of Nb3Sn wires subject
to a bending strain. Although the effect of filament twist pitch on the
critical current of the strand has been studied, the value of the
inter-filament resistance in Nb3Sn strands is still undefined. We have
performed a direct measurement of the inter-filament transverse resistance
within the cross-section of a Nb3Sn multi-filamentary strand from room
temperature to 4.2K. Results have been compared to the inter-filament
resistance of a sample on which the outer copper stabilization layer was
removed by chemical etching, obtaining interesting indications on the
preferential current paths within the wire cross section.
