Quench Co-Simulation of Canted Cos-Theta Magnets

Abstract

Canted Cos-Theta (CCT) magnets can use conducting formers in which eddy currents are induced during current change. This is relevant during magnet ramping or discharging after a quench, particularly when using energy extraction. CCT magnets provide substantial flexibility in terms of generating the required field shape, including the combined function field in a curved bore. However, this flexibility results in magnet geometry that often requires three-dimensional (3D) quench simulations. We propose a cooperative simulation (cosimulation) developed at CERN as part of the STEAM framework with finite element (FiQuS) and finite difference (LEDET) tools. It allows for a 3D quench simulation of a CCT magnet with great geometrical detail while maintaining reasonable computational cost. FiQuS simulates the transient electromagnetics of the entire magnet and the transient thermal behavior of the formers. The thin 3D insulation layers between the coil windings and formers are collapsed into two-dimensional surfaces, thus considerably reducing the meshing complexity and solution time. LEDET is used for 3D simulation of a quench transient, including heat diffusion in the windings, ohmic loss, and inter-filament coupling loss. Using the finite difference tool for resolving temperatures in coil windings with many turns greatly improves the simulation efficiency. In the co-simulation communication, data exchange, and convergence is controlled and achieved programmatically. A complete numerical approach is proposed, and the CCT magnet simulation results are presented and discussed.