Numerical simulation of quench protection for a 1.5 T persistent mode MgB ₂ conduction-cooled MRI magnet

This is the authors' abstract. We don't add key points for this paper.

The active quench protection of a 1.5 T MgB 2 conduction-cooled MRI magnet operating in persistent current mode is considered. An active quench protection system relies on the detection of the resistive voltage developed in the magnet, which is used to trigger the external energizing of quench heaters located on the surfaces of all ten coil bundles. A numerical integration of the heat equation is used to determine the development of the temperature profile and the maximum temperature in the coil at the origin, or ‘hot spot’, of the quench. Both n -value of the superconductor and magnetoresistance of the wire are included in the simulations. An MgB 2 wire manufactured by Hyper Tech Research, Inc. was used as the basis to model the wire for the simulations. With the proposed active quench protection system, the maximum temperature was limited to 200 K or less, which is considered low enough to prevent damage to the magnet. By substituting Glidcop for the Monel in the wire sheath or by increasing the thermal conductivity of the insulation, the margin for safe operation was further increased, the maximum temperature decreasing by more than 40 K. The strain on the MgB 2 filaments is calculated using ANSYS, verifying that the stress and strain limits in the MgB 2 superconductor and epoxy insulation are not exceeded.