Ultra small angle neutron scattering from superconducting filament structures

With a perfect crystal camera, ultra small-angle scattering measurements we re performed to investigate the internal diffusion process of tin inside a superconducting multi-filament wire caused by a temperature treatment. Comm ercially available Nb3Sn superconducting multi-filament wires were treated at 700 degrees C with varying ageing times up to 144 h. A theoretical model taking into account the geometrical form, the size distribution, the inter ference term and the multiple scattering has been developed to understand a nd to describe the small angle diffraction pattern. Additionally, the diffu sion of H and D into the filament wires was used to vary the scattering len gth density inside the wires. The results show a direct relationship betwee n the different technological treatments and the characteristic small-angle scattering parameters, like Guinier radius and small-angle scattering prob ability.