Small angle neutron scattering is a technique that is applied across a spectrum of scientific disciplines, with users from chemistry, physics, biology, materials science, engineering and geoscience. LoKI is designed primarily with the needs of the soft matter, biophysics and materials science communities in mind and the trend in all of these fields is towards complexity and heterogeneity.
Complexity manifests itself in the study of multi-component systems studied as a function of multiple environmental conditions (e.g. pressure, temperature, shear, magnetic field) simultaneously. In order to be able to examine the possible parameter space, a combination of faster measurements, measurements on smaller sample volumes, and measurements with good signal-to-noise is required.
Heterogeneity is seen both spatially and temporally. Spatial heterogeneity is manifested as different structure at different length scales, from the nanometre scale to the millimetre scale. This can be driven by applied stimuli such as shear, flow, electrical or magnetic fields, or by intrinsic structural features of the material. Examples of the former are shear banding in surfactant systems and the flow re-orientation of polymers. Examples of the latter are nano-composite materials, multi-component gels, and porosity in rocks. To address this spatial heterogeneity requires a wide Q range to examine the sub-micrometre length scales and small beams to examine the heterogeneity on the millimetre scale. Furthermore, since these heterogeneities are often driven by non-equilibrium conditions, the accessible Q range must be measured simultaneously. Temporal heterogeneity is seen in the form of stimulus-response experiments (e.g. shear relaxation), in the kinetics of formation of materials when the components of the material are mixed (e.g. mixed micelle formation) and in the growth of biomolecule aggregates such as fibrils. In order to examine these systems with sufficient time resolution a high neutron flux is required and a wide simultaneous Q range is needed.
Not only are the systems of interest becoming more complex and heterogeneous, but they are also becoming smaller in volume. Examples of this are the small amounts of protein complexes that can be purified and deuterated, thin film systems such as organic photovoltaics, and bio-mimetic or polymer membranes.
Not So Small Angles
The ability to reach Q values above the typical 0.8 to 1.0 A° −1 opens up significant areas of new science when combined with wide-angle scattering studies and the rapidly advancing fields of materials simulation. The study of, for example, ionic liquids and their ordering in the presence of solutes calls for the combination of SANS, wide-angle scattering and atomistic or coarse-grained molecular dynamics simulations. The analysis techniques used in biological solution scattering, such as ab-initio shape reconstruction, require data out to high Q as do studies of nano-composite materials where the size of the particles or domains may be only a few nanometres.
LoKI is designed to address these needs for by providing a high flux - at least 10 times the current leading reactor based instrument - and a broad simultaneous Q range of at least three orders of magnitude. This is achieved by the choice of instrument length (10m collimation + 10m sample to detector distance instrument with the sample position 20 m from the moderator) and a large solid angle of detector coverage.
Whilst some of the types of experiment mentioned above are done at present, they are often tour-de-force studies pushing the capabilities of today’s instruments. LoKI will provide a world leading combination of high neutron flux and wide simultaneous Q range with the ability to study smaller samples and with these characteristics, LoKI will enable scientists to answer the challenging materials science questions of tomorrow in fields from health and aging, to sustainability and energy security.