Speaker
Description
Quench protection is difficult in HTS magnets due to slow quench propagation – the coils are often overheating before the associated resistive voltage can be detected. Coil winding technologies without electrical insulation between coil turns are being developed to cope with this problem. In these coils, the operation current can by-pass the quenched cable segment to neighboring turn and slower down the hotspot temperature development. In applications requiring ramping of magnet current and good field quality, such as accelerator magnets, turns insulated with metal strips have emerged as an option. The quench behavior and protectability of large metal insulated coils still remains to be analyzed. The existing quench models consider mostly solenoids, where one can profit from axisymmetric modeling assumptions. In this contribution, we explore 3D simulation of metal insulated racetrack geometries with FEM. This allows flexible generation of coil geometries and the ability to simulate local quenches. The challenge is the need for dense meshing and convergence issues due to thin layers which can have very different material properties. We use Quanscient Allsolve software to simulate small racetrack coils with H-phi formulation and run the simulations in cloud. We compare solutions and model performances when meshing both the HTS tape and metal layer, as well as when replacing the metal insulation with thin shell approximation. We report the quench propagation behavior in small racetrack coils, considering the impact of different metal insulation characteristics, and discuss about scaling the models to larger coils.
