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Description
Superconducting magnets in particle accelerators currently use mostly a Nb-Ti alloy, which has a critical temperature (𝑇𝑐) of 9.2 K and a critical field (𝐵𝑐2) of 14.5 T. However, future particle accelerators, such as those beyond the LHC, will require dipole magnets capable of generating fields of 16 T or higher. This necessitates a shift to high-performance superconductors, with the intermetallic compound Nb3Sn being the most commonly chosen material.
High-field Nb3Sn magnets are created by winding Rutherford cables made from wires containing Nb3Sn precursors. During the cabling and winding processes, the wires undergo deformation, increasing the risk of deterioration and loss of transport properties. The heat treatment, which takes place after the winding process, results in the formation of Nb3Sn. A primary challenge is that Nb3Sn is brittle, and stresses from cooling, assembly, and Lorentz forces during magnet energization significantly affect its transport properties. As a result, the operating range of high-performance, high-field magnets is limited by these stresses.
Understanding the behavior of wires under stress, both before and after heat treatment, is critical for investigating the effects of deformation on Nb3Sn wires. To this end, a collaboration between the Genoa section of INFN and CERN is developing a finite element (FE) analysis to simulate wire behavior under deformation. This paper will focus on two key aspects: the effect of cabling-induced deformation on unreacted wires, and the influence of deformation from magnet operation on reacted wires. The paper will present a set of two-dimensional models of the cross-sectional area of an internal tin Nb3Sn wire, some idealized and symmetrical, while others based on SEM images of MQXF quadrupole wires. The differences among these models will be explored, and the simulation results will be compared to the actual wires.
