The performance of a Fresnel-type compound refractive lens for focusing cold neutrons was evaluated. The lens consists of 44 pieces of compound Fresnel-type refractive lenses made of MgF₂ single crystals. The intensity profile of the diffracted neutrons measured over the wavelengths of 9-14 Å was compared with the results of numerical simulations. Good neutron transmission of 0.85 for 9 Å neutrons and a focal length of 3.4 m for 16 Å neutrons were achieved.

We report calculations describing the Bonse-Hart ultra-small-angle neutron scattering (USANS) instrument with triple-bounce Si channel-cut crystals, which show that significant gains in Q-resolution and neutron flux can be achieved using multiple high-order Bragg reflections. These reflections become usable only after combining the Bonse-Hart and time-of-flight (t-o-f) techniques, thus this variant of the USANS camera needs a pulsed neutron source. We demonstrate that t-o-f USANS instruments installed, for example, at the SNS water moderator will improve the current state of the art. Through the use of multiple wavelengths, these will provide means to detect multiple scattering effects.

The microstructure of pore space in sedimentary rocks and its evolution during reaction with pore- or fracture-contained fluids is a critically important factor controlling fluid flow properties in geological formations, including the migration and retention of water, gases and hydrocarbons. The size, distribution and connectivity of these confined geometries (pores, fractures, grain boundaries), collectively dictate how fluids of various chemistries migrate into and through these micro- and nano-environments, wet, and ultimately react with the solid surfaces. In order to interpret the time-temperature-pressure-fluid flow history of any geological system, the physical and chemical "fingerprints" of this evolution preserved in the rock must be fully explored over widely different length scales from the nanoscale to the macroscale. We are experimentally investigating these reaction-controlled changes in rock microstructure by conducting in-situ heating experiments on samples of the Garfield oil shale. Oil shale, an organic-rich fine-grained sedimentary rock, contains significant amounts of kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be extracted. Pyrolysis (heating shale in the absence of oxygen) converts the kerogen in the oil shale to shale oil (synthetic crude oil) and oil shale gas and a solid residue. Through SANS, we clearly observe these kerogen and oxidation release at lower temperatures followed by pore structure reordering and finally enlargement at higher temperatures. These results are compared with preliminary results tracking the natural diagenesis of the commercially-important Eagle Ford shale formations across the oil/gas boundary.

In this study small angle neutron scattering was used to characterize the formation of micelles in aqueous solutions of the detergents DMG and SPC as a function of detergent concentration and ionic strength of the solvent. The effects on the micelle structure of the additives glycerol and PEG, alone as well as in combination typical for membrane protein crystallization, were also explored. This study suggests that the micelles are rod-like in form at the concentrations studied. The size of the micelles was observed to increase with increasing ionic strength but decrease with the addition of glycerol or PEG.

We applied a scintillator-based area detector to the neutron time-of-flight method by developing a new electronics system for this detector, which detector consists of a thin plate of ZnS(Ag)+6Li scintillator optically coupled to wavelength shifter. The spatial resolution was about 0.4mm which is consistent with a fiber width of 0.4 mm. The detection efficiency for thermal neutrons was about 6%. A good-resolution radiographic-image as a function of flight time was obtained.

The structures of kinetically distinct electron transfer complexes formed between the photosynthetic reaction center from Rhodobacter sphaeroides R-26, and a water-soluble cytochrome c₂ were characterized using small angle neutron scattering, SANS. Reaction center-cytochrome c₂ complexes, RC-C, exhibiting predominately single exponential electron transfer kinetics were found to be 1:1 molar complexes, consistent with a low resolution, co-crystal, x-ray structure (Adir et al., 1996), provided that the cofactor separation was adjusted to 14 ± 3 Å. Other RC-C configurations are consistent with SANS data, but are distinguishable by cofactor separation. RC-C preparations exhibiting more complex kinetics were found to have a particle volume markedly greater than that of a 1:1 complex. These results suggest that RC aggregation is associated with the variation in kinetics reported in the literature, and provide evidence that the model for the 1:1 complex in co-crystals is relevant to the solution environment.

Oligo(phenylenevinylene)-poly(ethyleneglycol) (OPV-PEG) diblock copolymers in tetrahydrofuran (THF) solution at concentrations of 5 to 25 g/l self-assemble into rod-like structures with a radius of about 80 Å, for an OPV-PEG diblock copolymer comprising 13 PV and 45 EG monomers. These aggregates consist of a liquid crystalline OPV core and a PEG shell. Addition of about 10% water to the solution induces the formation of a phase of packed rods, as revealed by a sudden and dramatic transition of the scattering pattern. Further addition of water leads to swelling and at about 30% ultimately to disruption of the packed-rod phase.