  In this paper, we propose an optimized field/circuit coupling approach for
the simulation of magnetothermal transients in superconducting magnets. The
approach improves the convergence of the iterative coupling scheme between a
magnetothermal partial differential model and an electrical lumped-element
circuit. Such a multi-physics, multi-rate and multi-scale problem requires a
consistent formulation and a dedicated framework to tackle the challenging
transient effects occurring at both circuit and magnet level during normal
operation and in case of faults. We derive an equivalent magnet model at the
circuit side for the linear and the non-linear settings and discuss the
convergence of the overall scheme in the framework of optimized Schwarz
methods. The efficiency of the developed approach is illustrated by a numerical
example of an accelerator dipole magnet with accompanying protection system.
