Analysis of Quench Detection and Protection of a Nb3Sn CCT Technology Demonstrator Dipole for FCC

From 2016, Paul Scherrer Institut (PSI) started an activity related to developing design, construction and testing of the superconducting magnets. My thesis work is part of this activity and mainly concerns the design and construction of an innovative high-field superconducting magnet of the Canted-Cosine-Theta (CCT) type - a possible candidate for the Future Circular Collider (FCC) 16 T dipole magnet design. The unique mechanical structure intercepts the accumulated forces lowering the stress on the windings, constituting intrinsic stress management in the high-field Nb3Sn accelerator magnets. However, this structure also constitutes a barrier for heat to quickly propagate in case of a quench. To succeed in the CCT-type magnet design and construction, quench protection is a challenging task that requires a detailed investigation of the electrothermal behavior of this magnet. In this thesis, the potential detection and protection concepts are studied by the multiphysics simulations on a two-layer short model built at PSI and also in a subscale experiment. The 2D User-Defined Elements (UDEs) developed at Lawrence Berkeley National Laboratory (LBNL) in ANSYS Mechanical APDL, which support multi-dependence material properties and include the effect of inter-filament coupling currents, are adapted and used in the coupled electrothermal, electrodynamic, and electrical-circuits calculations for a two-layer CCT-type magnet with different protection methods, such as Coupling-Loss Induced Quench (CLIQ) and Energy-Extraction (EE) system. A first-of-a-kind CCT-type magnet protection study using UDEs is presented. The generic model method is validated through the test data of CCT4, a model magnet constructed at LBNL, protected by an energy-extraction system. The simulation predictions are the first steps of the conceptual design and feasibility validation of the construction of a fast and efficient quench protection system for CCT-type magnets to be operated in an accelerator. These calculations are to be compared to the experimental data in the near future on the PSI's first 1-m long two-layer CCT-type model magnet, CD1. Furthermore, these studies lay the ground for the four-layer CCT protection concepts for FCC.