Development and characterization of ITD multifilamentary Nb$_{3}$Sn superconductors for 10-15 T field magnets

Inside the European project LHC (the Large Hadron Collider which is currently under construction at CERN), the LASA lab of INFN-Milan has recently carried out a feasibility study and a design of a Nb$_{3}$Sn low-$\beta$ quadrupole as a possible future candidate for the inner triplet in the Interaction Region of LHC. A preliminary research on material has been developed, centered on ITD (Internal Tin Diffusion) Nb$_{3}$Sn wires characterization. Measurements on transport properties have shown values of critical current densities as high as 1480 A/mm$^{2}$ at 12T, 4.2K, corresponding to 1860 A/mm$^{2}$ at 12T, 2.2K. Ic degradation due to cabling has also shown values contained below 15% while the degradation in condition of transversal pressure up to 200 MPa has been found to be in the range of 7% (only 1% irreversible). One of the most important features of Nb$_{3}$Sn is its volume increase during superconducting phase formation; for this reason volume variations have been determined experimentally. However the actual limit of these conductors is the very high value of effective filament size, as drawn out by magnetization measurements. A possible way of limiting the filament size is proposed. A scaling law for our conductors is also proposed, with $J_{c}$ as a function of magnetic field, temperature and strain. Eventually the excellent $J_{c}$ results recently obtained on a new wire are presented ($J_{c}$ near 2000 A/mm$^{2}$ at 12T and 4.2K).