Hidden network of long Josephson junctions as a source of strong pinning mechanisms in high temperature superconducting films

In the hypothesis that good quality high temperature superconducting (HTS) films can be modeled as an agglomeration of islands coupled via Josephson contacts, we calculate the critical current density J/sub c/ vs. field in a long Josephson junction (LJJ). The coupling energies in the junction are modulated by defects with given distribution and size. The superconductor is then considered as a network of LJJ between superconducting islands. Each LJJ has a different defect distribution. The model accounts for all main trends of the experimental electromagnetic behavior. The most important issue is that a "hidden" network of LJJ with a suitable distribution of optimized defects is the source of high critical current density in "good quality" films. Therefore any needed response of the film in a given range of field can be designed in advance.