Distribution of transport currents in type-II superconductors investigated by neutron small angle scattering

Neutron diffraction experiments have been performed on Nb--13 percent Ta specimens in order to obtain information about the distribution of transport currents in type-II superconductors. In specimens with homogeneous flux pinning, it was demonstrated that a transport current was carried in the bulk while in a specimen where surface pinning dominated the transport current was essentially carried on the surface. All experimental results could be explained by specific predictions of the critical state model