Research on Eddy Currents in Dry Cool Superconducting MRI Systems Based on Multi-Physics Field Coupling Analysis

This study investigates eddy currents in the dry cool superconducting MRI system by adopting a strong coupling multi-physics analysis method that integrates electromagnetic and mechanical fields. The 3D model is simplified based on the spatial distribution characteristics of the Lorentz force. A set of strong coupling matrix equations is derived by combining mechanical principles with Maxwell’s equations. The weak coupling scheme is implemented by applying displacement boundary conditions and validated through kinetic energy analysis. Through vector analysis, the origin of eddy power is explored, leading to the conclusion that the primary contribution to eddy power stems from the coupling between primary and secondary eddy currents. Furthermore, by analyzing the vector directions of primary and secondary eddy currents at specific mesh elements, the sign (positive or negative) of eddy power at different frequencies is characterized. The results show that the superposition of primary and secondary eddy currents produces positive power when they have a common directional component; conversely, the suppressive effect of secondary eddy currents results in negative power. This research deepens the understanding of the generation mechanism and influence of secondary eddy currents, providing guidance for subsequent dry cool superconducting MRI magnet optimization design.