In the case of high temperature superconductors, fast neutron irradiation induced defects act as pinning centers for quantized magnetic fields called fluxoids. Pinning these fluxiods is a critical issue, because the fluxoid motion introduces resistance, thus defeating the purpose of the superconductor to conduct current without loss. Therefore, increased fluxoid pinning leads to greater critical currents, making many of the exciting applications possible. A significant effort in this research area is involved in understanding the fundament process of fluxoid pinning and in finding methods to optimize this pinning, thus producing material that can support the highest possible currents. At present, critical currents in high temperature superconductors limit many of the possible applications of these exciting materials.
Residual stresses can exist in materials even when no external loads are applied to the material.
In fact, most fabrication processes leave residual stresses in the material. Most residual stresses in materials are not well understood, and can be either detrimental or beneficial to the life of a component. Our research aims to improve materials by characterizing residual stresses and their influence on material performance. Neutron reflectometry is a very powerful tool for investigating the near surface structure of many materials. The samples must have a smooth, flat surface, the individual layers must be smooth and have uniform thickness throughout, and preferably several cm2 in area.