An application of hp-version finite element methods to quench simulation in axisymmetric MRI magnets

Magnetic Resonance Imaging (MRI) scanners employ superconducting magnets to produce a strong uniform magnetic field over the bore of the scanner as part of the imaging process. Superconductors are preferred, as they can generate the required field strengths without electrical resistance, but, to do this, the materials need to be cooled to very low temperatures, typically around 4.2 K. However, due to imperfections in the windings, cracks and small air gaps in the epoxy resin between the wires, heating can occur leading to a process known as magnet quench. During magnet quench, the magnet temperature rises quickly, and the magnet loses its superconductivity. This work presents an accurate numerical model for predicting magnet quench for axisymmetric MRI scanners by solving the coupled system of thermal, electromagnetic and circuit equations by means of a high order/hp-version finite element method where regions of high gradients are resolved with boundary layer elements. A series of numerical results are included to demonstrate the effectiveness of the approach.