Development and research of the Nb3Sn superconductor with improved structure of superconductive layer

The creation of a fine uniform grain structure in Nb3Sn superconductive layers is one of the methods to increase its current-carrying ability. In this work superconductors with ring filaments were developed, produced and studied. The ring filaments have been distributed uniformly in the bronze matrix to supply more uniform Sn diffusion from the bronze matrix to the filaments. The microstructure of the superconducting layer has been investigated using by SEM and TEM methods, and the critical current dependence on the diffusion heat treatment procedure has been studied. It is shown that Nb3Sn layer in such type of filaments has more uniform and fine grain structure without column zone than the ordinary shape of filaments. That leads to an increase for the critical current density of the Nb3Sn layer of wire with ring filaments and allows us to reduce the duration of the reaction.