MAGNETIC-FLUX DENSITY AND RADIAL-DISTRIBUTION OF CURRENTS IN HTSC SAMPLES OF SPECIFIC SHAPE DETERMINED BY GENETIC ALGORITHM

Flux distribution in a Bi2Sr2CaCu2O8 superconductor sample, shaped as a thin disk with a hole in the center, and covered with a thin layer o f magnetic garnet, was observed by means of magneto-optical Faraday ef fect. Applying external magnetic field perpendicularly to the sample p lane with zero field cooling history, we were able to observe the flux trapped in superconductor, visible as concentric rings. Both directio ns of the trapped field were observed near the sample surface. Using t he genetic algorithm we were able to determine the radial distribution of concentric currents in the sample under study.