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A four‐circle neutron diffractometer with a new multi‐wafer 331 Si monochromator has been installed and commissioned on a thermal beamline at the High Flux Isotope Reactor at Oak Ridge National Laboratory. The instrument is well suited to studies of nuclear and magnetic structures as a function of composition and temperature, resolving symmetry changes (lattice distortions and local structural changes), mapping the evolution of complex magnetic phases, determining hydrogen bonding, analyzing nuclear and spin densities, mapping diffuse scattering, and exploring fiber diffraction. Three incident wavelengths are available, 1.000, 1.536 and 2.540 Å, with intensities of 2.5 × 106, 2.2 × 107 and 8.0 × 106 neutrons cm−2 s−1, respectively. Either high‐resolution or high‐intensity modes are possible by horizontal bending of the monochromator. With increased bending of the monochromator, the incident flux on the sample passes through a maximum, increasing by ×2.0 for 1.000 Å, by ×3.5 for 1.536 Å and by ×3.5 for 2.540 Å, as compared to the flat condition. The flux increases because the lattice strain in the silicon crystals increases. The ω‐scan peak width increases with monochromator curvature and this width versus scattering angle flattens. Given these effects, the monochromator bending can be adjusted to deliver high intensity primarily for crystal structure refinements or high resolution for resolving symmetry changes. In addition to the traditional step‐scanning mode, a more efficient continuous‐scanning mode was developed, and both these are implemented through a LabView‐based control program, i.e. a modified version of the SPICE software package. A 4 K closed‐cycle helium refrigerator is permanently mounted on the χ‐circle of the goniometer to provide temperature control between 4 and 450 K.

Small-angle neutron scattering (SANS) is a powerful tool for characterizing complex disordered materials, including biological materials. The Bio-SANS instrument of the High Flux Isotope Reactor of Oak Ridge National Laboratory (ORNL) is a high-flux low-background SANS instrument that is, uniquely among SANS instruments, dedicated to serving the needs of the structural biology and biomaterials communities as an open-access user facility. Here, the technical specifications and performance of the Bio-SANS are presented. Sample environments developed to address the needs of the user program of the instrument are also presented. Further, the isotopic labeling and sample preparation capabilities available in the Bio-Deuteration Laboratory for users of the Bio-SANS and other neutron scattering instruments at ORNL are described. Finally, a brief survey of research performed using the Bio-SANS is presented, which demonstrates the breadth of the research that the instrument's user community engages in.

A simple, direct approach to the synthesis of mesoporous amorphous carbon microwires and nanowires with high aspect ratios is described. It involves solvent-free infiltration of a precursor mixture into porous alumina templates. Hybrid membranes consisting of mesoporous carbon inside porous alumina membranes are accessible.

A series of upgrades have been undertaken at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, including the installation of a supercritical hydrogen moderator (T ' 20 K), which has boosted the flux of long-wavelength neutrons by over two orders of magnitude. In order to take advantage of the new capabilities, a 40 m-long small-angle neutron scattering (SANS) instrument has been constructed, which utilizes a mechanical velocity selector, pinhole collimation and a high-count-rate (>10 5 Hz) large-area (1 m 2 ) two-dimensional position-sensitive detector. The incident wavelength (), resolution (Á/), incident collimation and sample-to-detector distance are independently variable under computer control. The detector can be moved up to 45 cm off-axis to increase the overall Q range [<0.001 < Q = (4/)sin < 1 Å À1 , where 2 is the angle of scatter]. The design and characteristics of this instrument are described, along with examples of scattering data to illustrate the performance. research papers J. Appl. Cryst. (2012). 45, 990-998 George D. Wignall et al. Updates to GP SANS instrument at ORNL 997

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A new methodology based on a novel combination of a high-resolution specular x-ray reflectivity and small-angle neutron scattering has been developed to evaluate the structural properties of low-dielectric-constant porous silica thin films about one micrometer thick supported on silicon wafer substrates. To complement these results, film composition was determined by high-energy ion scattering techniques. For the example thin film presented here, the overall film density was found to be (0.55Ϯ0.01) g/cm 3 with a pore wall density of (1.16Ϯ0.05) g/cm 3 and a porosity of (53 Ϯ1)%. The characteristic average dimension for the pores was found to be (65Ϯ1) Å. It was determined that (22.1Ϯ0.5)% of the pores had connective paths to the free surface. The mass fraction of water absorption was (3.0Ϯ0.5)% and the coefficient of thermal expansion was (60 Ϯ20)ϫ10 Ϫ6 /°C from room temperature to 175°C. Lastly, model fitting of the specular x-ray reflectivity data indicated the presence of a thin surface layer with an increased electron density compared to the bulk of the film as well as an interfacial layer with a reduced electron density.