Multiphysics Modelling of the LHC Individually Powered Quadrupole Superconducting Circuits

In the LHC there are 131 different types of circuits connecting main bending magnets, magnets for beam focusing, dipole field correctors, or higher-order correctors. A total of 78 Individually Powered Quadrupole (IPQ) circuits are present in the LHC matching sections, operating either in 1.9 K superfluid helium or in boiling helium at 4.5 K. The superconducting circuits are composed of different elements, at different temperatures, in different materials, connected to each other in a multi-scale and multi-physics domain. The reason to generate and validate these models is driven by the necessity to realize an efficient and reliable multi-physics library of all the LHC superconducting circuits to simulate transients during normal operation of the machine, failure cases, and unexpected events. To simulate this complex scenario, the STEAM (Simulation of Transient Effects in Accelerator Magnets) framework was developed in the Machine Protection and Electrical Integrity Group (MPE) at CERN. The goal of STEAM is subdivided these complex phenomena into sub-problem and solve them with validated tools. For this reason, it contains in-house developed programs used to model transients in superconducting circuits. Once the electrical circuit and the finite element models are generated (thanks to the software packages for the semi-automatic generation) the hierarchical co-simulation framework, provide a common interface to run cooperative simulations of the validated models. These cooperative simulations allow the exchanging of information between several models, ensuring the consistency of the results due to the co-simulation algorithm. During this thesis the main programs used are: PSpice (a commercial tool used to generate the electrical circuit model), STEAM-LEDET (a STEAM in-house tool, used to generate the electro-thermal magnet model), and STEAM-COSIM (used to combine both models, PSpiceand STEAM-LEDET, in a cooperative simulation).