Specific heat of Nb3Sn wires

Multifilamentary superconducting Nb 3 Sn wires are widely used for industrial applications. Wires processed by the Bronze Route technique are characterized by a large number of filaments Nb 1− x Sn x , with 0.18≤ x ≤0.25, corresponding to a distribution of T c between<10 and 18 K. This distribution is a critical property of the wires and is important for the optimization of the conductors. However, it is not accessible to conventional techniques, due to percolation and/or magnetic shielding effects. In order to determine the T c distribution in the sample, we have carried out specific heat measurements of various Nb 3 Sn multifilamentary wires (including the bronze matrix) in zero field and at 14 T. A deconvolution of the calorimetric data at the superconducting transition by means of a thermodynamical model was used for obtaining the distribution of T c in the whole wire volume. The measurements were extended to Nb 3 Sn wires containing Ti additions, and the results were compared. The present calorimetric method is of primary importance for the complete characterization of Nb 3 Sn wires.