Neutron optical device to measure mesoscopic space and time correlations and eliminate quasi-elastic scattering from SANS

A recent report by the Basic Energy Sciences Advisory Committee entitled “Challenges at the Frontiers of Matter and Energy” pointed to the need to better understand hierarchical and heterogeneous materials, often at the mesoscopic scale. Such structures can be studied by x-ray and neutron scattering techniques, but they do not generally yield narrow signals in momentum or energy space. The natural way to probe the structure and dynamics of such systems is in terms of the space and time dependence of density correlations within the material. While this need is partially met by Neutron Spin Echo (NSE), and by Spin Echo Small Angle Neutron Scattering (SESANS), no technique is currently able to simultaneously probe both the space and time dependence of the density-density correlation function of materials, over a wide range of length and time scales. General statement of how this problem is being addressed: We have recently developed and built a compact apparatus, which allows static spatial correlation to be measured over length scales, ranging between a few nanometers and several microns. Scattering samples can be placed in any environment, including high magnetic fields, allowing a wide range of materials and thermodynamic parameters to be studied. In its present form, the apparatus, called the double Wollaston prism, is not able to measure the time dependence of density fluctuations. We believe that a relatively simple modification to the device, which consists of adding a suitable RF flipper in front of the Wollaston prisms, will allow this goal to be met. We seek to prove this principle, and develop a design for a device, which can address scientific questions at the forefront of modern material science. Commercial Applications and Other Benefits: By combining the ability to probe both the spatial and time dependence of density fluctuations simultaneously, within a wide range of hierarchical and disordered meso-scale materials, the proposed instrument will open new fields of material science studies. Possibilities include visualizing precipitate coarsening in metal alloys, cavity growth in fatigued metals and ceramics, as well as many aggregation and self-assembly phenomena. Applications are in petrochemicals (colloidal and aggregate dynamics), biotechnology and medicine (membranes, macromolecules), and industry (metallurgy, ceramics, polymers, electrolytes in fuel cells, magnetic sensors and memory). Given the lower cost and size of this system, along with the continuing development of more powerful neutron generators, the proposed instrument will be suitable for neutron studies at weak neutrons sources, which are installed at smaller laboratories, such as at universities.