Resumen de Material laws and numerical methods in applied superconductivity
Harold Steven Ruiz Rondan
One century has elapsed since the discovery of superconductivity by Heike Kamerlingh Onnes, opening a new world of significant applications in technologies ranging from electric power devices such as motors and generators, large magnet systems such as those needed in storage rings for particle accelerators, and electricity transmission in power lines. As it is well-known, the technological usage of any superconducting material is based upon its ability to carry and maintain a current with no applied voltage whatsoever, i.e., with an almost negligible loss of energy even in those cases when the superconductor is subjected to strong enough applied magnetic fields. Although electrical currents can flow with a negligible loss of energy maintaining the superconductor in an appropriate temperature environment, superconductivity can be destroyed by the effect of a sufficiently intense magnetic field or the flow of a current density exceeding a critical value. Indeed, most of the technological applications of the superconductors are directly linked to their magnetic properties, and in particular in the way that they expell the magnetic fields. This fact leads to the classification of superconductors in two different kinds. On the one hand, Type-I superconductors are mainly characterized by a unique curve for the maximal applied magnetic field which a superconductor is able to expell before the sudden transition to the normal state occurs. On the other hand, Type-II superconductors are characterized by a new phase or “mixedstate” where the transition from the superconducting state to the normal state allows the existence of bundles of magnetic flux penetrating the sample (vortices), before reaching the sudden transition to the normal state. This remarkable property allows to preserve the superconducting state with the advantage of sustaining much higher magnetic fields, and therefore carrying much higher current densities. However, this ability is directly related to the pinning efficiency of a given material as the motion of vortices produces a high dissipation
