Superconductors, including HTc materials are more and more frequently used in modern nuclear physicsuddevices. During the work of nuclear accelerators arises however the radiation of heavy ions or fastudneutrons, which can reach the superconducting windings, creating nano-sized defects. It influencesudproperties of superconductors. In the paper is given theoretical analysis of the influence of nano-defects onudthe critical current of HTc superconductors. New theoretical model of the critical current is proposed basedudon an analysis of the interaction of nano-defects acting as pinning centers with pancake vortices appearingudin HTc superconductors. Nano-defects from one side destroy the structure of superconducting materials,udwhich effect has negative meaning, while from other side anchorage of individual vortices or vortex latticeudon defects will improve critical current. These both opposite phenomena are considered for HTc materialsudand also for A15 type superconductors, in which superconductivity is strongly related to state of ordering ofudtransition metals as Nb, V in linear chains. The potential barrier against pancake vortices movement hasudbeen considered and calculations of an influence of sizes of nano-defects on current-voltage characteristicsudperformed. Expression for an energy barrier allowed also to determine the time stability of the magneticudvortex structure and flowing current, which effect has especial meaning in the superconducting shields.When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35418
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