Influence of the dispersion of physical parameters on the thermal stability of superconducting coils

For an electrical apparatus using superconducting materials, the wire is always composed of type II superconductor filament and a metal matrix. Moreover, when a coil is built, in order to provide good mechanical behaviour, it is embedded in resin. The study of the coil's transition, which must be provoked for some applications or controlled for other ones, is very important but very difficult because of the numerous temperature-dependent parameters. The difficulties are due to the variation of the flux density in the thickness of the coil and to the simultaneous resolution of the coupled thermal and magnetic equations. In fact, the dissipation term in the heat equation, calculated thanks to the current-sharing model, is a function of T, J and B and takes into account the magnetoresistive effect. Our paper deals with the study of the influence of the thermal conductivity and the specific heat on the stability of a thick superconducting coil. Beyond scientific curiosity, this theoretical study and the obtained results could help the user to design a suitable material for a given application.