Magnetic Flux Density and Radial Distribution of Currents in HTSC Samples of Specific Shape Determined by Genetic Algorithm

Flux distribution in a Bi$\text{}_{2}$Sr$\text{}_{2}$CaCu$\text{}_{2}$O$\text{}_{8}$ superconductor sample, shaped as a thin disk with a hole in the center, and covered with a thin layer of magnetic garnet, was observed by means of magneto-optical Faraday effect. Applying external magnetic field perpendicularly to the sample plane with zero field cooling history, we were able to observe the flux trapped in superconductor, visible as concentric rings. Both directions of the trapped field were observed near the sample surface. Using the genetic algorithm we were able to determine the radial distribution of concentric currents in the sample under study.