Critical current problems in HTc superconductors with nanoscale pinning centers

Abstract

In the paper is investigated the interaction of the nanoscale pinning centers with vortices in layered HTc superconductors, which interaction determines the critical current. Capturing of the vortices in parallel magnetic field in the buffer layer of nanometer thickness is analyzed. In perpendicular magnetic field the pinning of the pancake vortices on the nanodimensional pinning centers is considered. The potential barrier height, current-voltage characteristics, critical current and pinning forces of the HTc superconductors are determined. Important result of the considerations is the statement that for too small dimensions of the pinning centers the critical current vanishes, what has essential meaning from the point of view of the superconducting tapes technological process. In the total energy balance the elastic energy of the vortices lattice has been taken into account, while for calculations of the pinning forces the statistical occupation of the pinning centers by vortices considered. In the paper the author's works devoted to the construction of the model of the fault current limiter will be reviewed too.