STEAM: A Hierarchical Cosimulation Framework for Superconducting Accelerator Magnet Circuits

Simulating the transient effects occurring in superconducting accelerator magnet circuits requires including the mutual electro-thermo-dynamic interaction among the circuit elements, such as power converters, magnets, and protection systems. Nevertheless, the numerical analysis is traditionally done separately for each element in the circuit, leading to possible inconsistent results. We present STEAM, a hierarchical cosimulation framework featuring the waveform relaxation method. The framework simulates a complex system as a composition of simpler, independent models that exchange information. The convergence of the coupling algorithm ensures the consistency of the solution. The modularity of the framework allows integrating models developed with both proprietary and in-house tools. The framework implements a user-customizable hierarchical algorithm to schedule how models participate to the cosimulation, for the purpose of using computational resources efficiently. As a case study, a quench scenario is cosimulated for the inner triplet circuit for the high luminosity upgrade of the Large Hadron Collider at CERN.