Numerical and Experimental Analysis of Thermomagnetic Instability in Nb3Sn Wires

Nb ₃ Sn is now recognized as the practical material for the high-field applications from 10 to 16 T, for particle accelerators, fusion and other related fields. However, the obtaining of high Jc in Nb ₃ Sn presently contradicts one of the most important stability criteria: to keep a small filament size, which makes the stability issue particularly prominent. Large filament sizes frequently cause flux jumps in the conductor, making quench detection and protection more challenging for Nb3Sn magnets. In this work, we try to numerically simulate the flux jumps more accurately down to a filamentary scale. Based on the theory of superconducting dynamics, we have established a theoretical model to describe the magnetothermal instability of Nb3Sn wires by considering the superconductor flux dynamics, heat diffusion and temperature response. The preliminary analysis of the test results for LPF3 which is a 16-T hybrid common coil dipole magnet fabricated by Institute of High Energy Physics is conducted to study the causes of its quenching and the impact of flux jumps on the magnet.