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The new mechanism of superconducting current transport in NbTi technical superconductors with composite inner structure, consisting of nanosize plane impurities, is researched. These normal alpha-Ti layers are in the form of superconducror-normal metal-superconductor (S-N-S) structure, and result in the increase of critical current density in magnetic fields up to 5T [1]. In Type II superconductors, the magnitude of a critical current depends on pinning force, which restricts the mobility of magnetic vortices, originating under the operation of a magnetic field and a current. In our analysis, there are no magnetic vortices in the location of alpha-Ti S-N-S packages at particular orientation of a magnetic field. In such structure, the superconducting critical current density is not determined by carry of magnetic vortices, and, so-called, critical depairing current [2]. This mechanism of limitation of a critical current, as it is known, is implemented in thin films, and depends on the value of a superconducting gap. In our case, the critical current appears much bigger, than in the case of mechanism with a critical state with magnetic vortices. The research of influence of characteristic parameters of an alloy (concentration of components and structure of the dropped out phase), orientations of a current and a magnetic field, on the current characteristics is completed.
[1.] Chernyi O.V. et al., Advances in Cryogenic Engineering, v.48 (2002)
[2.] Dew-Hughes D., Low Temperature Physics, v.27, ¹9/10, 967 (2001) |