Stability Analysis of 14-T-Level High-Performance Nb3Sn Cable-in-Conduit Conductor for a Toroidal Field Coil

Abstract

In view of the fact that the fusion power of fusion reactor is proportional to the fourth power of the toroidal magnetic field, the design of toroidal field (TF) magnetic system is particularly important for achieving higher operating parameters. In order to meet the confinement requirements of high plasma parameters, the high field region of the TF magnetic system can be wound by high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn cable-in-conduit conductor (CICC), with a maximum magnetic field reaching 14.32 T. Since the stable operation of the TF magnetic system relies heavily on the stability of the superconductor, a stability analysis of high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn CICC conductor has been performed. The results indicate that the current sharing temperature of the conductor is 6.9 K under extreme working conditions ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> = 14.32 T), which meets the design requirements; the minimum quench energy (MQE) is 116 mJ/cc under short perturbation, but under long perturbation it is only 20.3 mJ/cc. Therefore, several options may be available to increase the MQE of the conductor, such as reducing the strain, operating current and thermal resistance, or increasing the helium mass flow rate. In addition, the quench behavior of the CICC conductor is also evaluated. Studies have shown that increasing the area of copper and decreasing the thermal resistance and quench detection threshold voltage can lower the hot spot temperature. These analyses provide references for the design of 14-T-level high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn CICC conductor and its quench protection system.