Speaker
Description
Conductors and magnets for fusion applications based on High Temperature Superconducting (HTS) materials are currently being designed and tested. Quench propagation in such conductors is an open issue due to the small normal zone propagation velocity when compared to Low Temperature Superconductors. This, in turn, makes the quench detection and the protection of HTS magnets more challenging. Numerical modelling may help in developing alternative quench detection strategy as well as improving the conductor design itself.
Currently, the numerical models used to model quench propagation are based on those developed for LTS conductors, i.e., they are based on a 1-dimensioinal approximation of the conductor along its axis. This strategy proved to be reliable and accurate for LTS conductors. However, most HTS conductor designed so far are characterized by bulky solid parts, thus making the approximation of uniform current and temperature on their cross-section -which is at the basis of the 1D approximation- less accurate.
For this reason, in this work, a fully 3D model able to follow the entire evolution of the quench propagation is presented. The model solves the heat diffusion equation in the solids, from which their temperature is computed; the Navier-Stokes equations, from which the pressure, velocity and temperature of the coolant is retrieved; the electric potential equation, from which the current is derived.
The case study presented in this work focuses on an HTS conductor designed and manufactured by ENEA which was recently tested in SULTAN. The conductor is based on the slotted-core concept, i.e., a core made of aluminum featuring 6 slots where non-soldered tapes are stacked. The cable is then jacketed to provide coolant containment and mechanical support. The conductor was quenched in different conditions in terms of coolant mass flow rate, background magnetic field and transport current.
The 3D model free parameters, such as the thermal contact resistance between the conductor sub-components, are first calibrated and then its results are validated in terms of voltage and temperature, which are both measured in several location along and across the conductor. Such detailed model is then used to interpret some of the collected experimental data.
