The influence of the additional coil and ferromagnetic rings on high-temperature superconducting engine magnets

Abstract

A plasma engine with high-temperature superconducting (HTS) tapes offers advantages such as high efficiency, high thrust, and high specific impulse. However, due to the magnetic field-dependent characteristics of HTS tapes, the magnetic field at the coil ends tends to decrease rapidly. To mitigate this issue, a small additional coil can be wound at the coil end to enhance the magnetic field, or ferromagnetic rings can be employed to modify the local magnetic flux lines direction within the superconductor, thereby reducing the impact of radial magnetic fields on the critical current of the HTS tapes. In this study, to analyze the effects of the additional coil and ferromagnetic rings, a two-dimensional axisymmetric numerical model is established, and the T-A formulation is utilized to investigate the axial centerline magnetic field distribution of the HTS engine magnet. The simulation results indicate that varying the coil current primarily affects the peak value of the magnetic field without altering its configuration. The addition of an additional coil at the coil end effectively mitigates the rapid decline in the magnetic field at the coil end. The results also indicate that adding ferromagnetic rings can reduce the influence of the radial magnetic field on the critical current, thus enhancing the magnetic field at the coil ends. Furthermore, the results of the radial magnetic field distribution at the end of Coil-4 indicate that ferromagnetic rings can significantly reduce the magnitude of the radial magnetic field at the coil surface.