Investigation of the influence of the heat treatment and forming regimes on the critical current and pinning force of NbTi superconductors

Abstract

The results obtained in the optimization of NbTi superconductors are set forth. The intermediate annealing temperature is discussed and the influence of final forming on the critical current density and the reduced pinning force is studied. For the types of conductors investigated (1, 19, 55-core conductors), thej c-maximum occurs at different degrees of final forming; it drops as the filament diameter decreases. As to the reduced pinning force, an increase in the number of cores or a reduction of the filament diameters results in a displacement of the maximum and, for optimized conductors, an extension of the maximum towards higher fields is obtained. A final heat treatment makes thej c-values drop.