Methods for maximizing the detector count rate for the same scattering angle range and resolution are related to choosing the optimum pinhole collimation parameters which include the source and sample aperture sizes and collimation lengths on small-angle neutron scattering diffractometers located at reactor neutron sources. Calculations and experimental measurements are presented that show enhancements in count rate with the same q-resolution can be achieved by combining both longer flight paths with larger source and sample apertures and beam stop sizes. To be able to both accommodate the larger beam sizes at the detector and to maintain the same range in scattering angle, existing and new detector placement strategies are presented that extend the scattering angle range beyond what is capable with a single 2-D detector.

We report the effect of tail-tethering on vesiculation and complete unbinding of bilayered membranes. Amphiphilic molecules of a bolalipid, resembling the tail-tethered molecular structure of archaeal lipids, with two identical zwitterionic phosphatidylcholine headgroups self-assemble into a large flat lamellar membrane, in contrast to the multilamellar vesicles (MLVs) observed in its counterpart, monopolar nontethered zwitterionic lipids. The antivesiculation is confirmed by small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cyro-TEM). With the net charge of zero and higher bending rigidity of the membrane (confirmed by neutron spin echo (NSE) spectroscopy), the current membrane theory would predict that membranes should stack with each other (aka "bind") due to dominant van der Waals attraction, while the outcome of the nonstacking ("unbinding") membrane suggests that the theory needs to include entropic contribution for the nonvesicular structures. This report pioneers an understanding of how the tail-tethering of amphiphiles affects the structure, enabling better control over the final nanoscale morphology.

Methods to determine the optimal neutron wavelength to maximize detector count rates on small angle neutron scattering (SANS) diffractometers at reactor sources is presented. Three experimental methods are used to determine the choice of optimal wavelength and collimation combination that maximizes the detector count rate. The wavelength optimization methods are applied to two different SANS diffractometers at the NCNR, and all methods are found to confirm the optimal wavelength of approximately 9.5 angstrom +/- 0.5 angstrom for optically thin samples. The optimum wavelength is shifted by the wavelength-dependence of the sample transmission to 8.5 angstrom +/- 0.5 angstrom for thicker absorbing samples or 6.5 angstrom +/- 0.5 angstrom if the amount of multiple scattering needs to be minimized to limit scattering curve distortions. The same optimization methods can be applied to SANS diffractometers at other reactor facilities.

Effects of radiation on the aggregation of nanoplatelets of aluminum oxyhydroxide (boehmite) in slurries of M1+ cation nitrates have been observed using tumbler small-and ultra-small-angle neutron scattering. Nitrate solutions of H, Li, Na, K, and Rb at concentrations of 10(-5) , 10(-3) , 10(-1) , 2, and 4 molal were compared to the results for pure H2O. Primary aggregates consisting of small stacks of boehmite platelets that form immediately after the boehmite is placed in water are smaller for irradiated boehmite than the pristine material. The primary aggregates for irradiated boehmite also appear to have a rougher surface than those observed for unirradiated materials. Both results are possibly due to breaking of the surface OH species and neutralization of the surface. At low salt concentrations, the pH of the irradiated boehmite slurries is lower than that of the corresponding pristine material, indicating that irradiated boehmite adsorbs fewer protons or more hydroxide onto its surface than the pristine boehmite. Increasing the salt concentration decreases the pH to near neutral at 7 due to screening of the electric double layer at the solid/liquid interface. Irradiation does not seem to affect the size of secondary aggregates formed from the aggregation of primary aggregates or the overall size of the primary aggregates.

Hypothesis: A well-defined discoidal bicelle composed of three lipids, specifically zwitterionic long-chain 1,2 dipalmitoyl phosphocholine (DPPC) and short-chain 1,2 dihexanoyl phosphocholine (DHPC) doped with anionic 1,2 dipalmitoyl phosphoglycerol (DPPG) provides a generalized template for the synthesis of hydrophobic polymer nano-rings. The lipid molar ratio of DPPC/DHPC/DPPG is 0.71/0.25/0.04. The detailed investigation and discussion were based on styrene but tested on three other vinyl monomers. Experiments: The structure of nano-rings is identified through the detailed analysis of small angle X-ray/ neutron scattering (SAXS and SANS) data and transmission electron micrographs (TEM), supported by the differential scanning calorimetric (DSC) data before and after polymerization. The investigation covers samples with a styrene-to-lipid ratio ranged varied from 1:50 to 1:10.Findings: The styrene monomers are initially located at both the discoidal planar (long-chain lipid rich) and rim (short-chain lipid rich) regions. During polymerization, they migrate to the more fluid rim regionsection. The formation mechanism involves the interplay of hydrophobic interaction, mismatched miscibility of polystyrene between the ordered and disordered phases, and crystallinity of the long lipid acyl chains. This facile synthesis is proven applicable for several hydrophobic monomers. The well-defined nano-rings greatly enhance the interfacial area and have the potential to be the building blocks for functional materials, if monomers are incorporated with desirable functions, for future applications.(c) 2022 Elsevier Inc. All rights reserved.

The Very Small Angle Neutron Scattering (VSANS) diffractometer at the National Institute of Standards and Technology has been commissioned and is in the user program. A large available space of nearly 2 m along the beam in the sample area not only enhances the existing SANS polarization analysis capability, but also makes it possible for implementation of other polarization analysis capabilities which would not be easily available on existing SANS instruments, including grazing-incidence small-angle neutron scattering with polarization analysis and spherical neutron polarimetry. We present two polarized setups, one for high magnetic sample fields and the other for low magnetic sample fields, together with a versatile and flexible operational platform for polarized beam experiments. The design of a magnetostatic cavity device that provides better field homogeneity and thus longer 3He polarization relaxation time is discussed. It consists of an end-compensated magnetic shielded solenoid with non-identical holes to accommodate the divergent scattered beam in a constrained distance. Significant improvement in polarized neutronic performance, 3He polarization relaxation time, and an extended momentum transfer range for polarization analysis are presented. Improved neutron polarizing devices, double V-shaped supermirror polarizer, adiabatic radio-frequency spin flipper, and a 3He spin analyzer have yielded an initial instrumental flipping ratio of 100, allowing for higher sensitivity to detection of weak magnetic features in the sample.

A description and the performance of the very small angle neutron scattering diffractometer at the National Institute of Standards and Technology are presented. The measurement range of the instrument extends over three decades of momentum transfer q from 2 x 10(-4) to 0.7 angstrom(-1). The entire scattering angle range from 8 x 10(-5) to pi/6 rad (30 degrees) can be measured simultaneously using three separate detector carriages on rails holding nine 2D detector arrays. Versatile choices of collimation options and neutron wavelength selection allow the q resolution and beam intensity to be optimized for the needs of the experiment. High q resolution is achieved using multiple converging-beam collimation with circular pinholes combined with refractive lenses and prisms. Relaxed vertical resolution with much higher beam intensity can be achieved with narrow slit collimation and a broad wavelength range chosen by truncating the moderator source distribution below 4 angstrom with a Be crystalline filter and above 8 angstrom with a supermirror deflector. Polarized beam measurements with full polarization analysis are also provided by a high-performance supermirror polarizer and spin flipper, capable of producing flipping ratios of over 100, along with a high-efficiency He-3 polarization analyzer.

Measurements, calculations and design ideas to mitigate background caused by extraneous scattering in small-angle neutron scattering (SANS) instruments are presented. Scattering includes processes such as incoherent scattering, inelastic scattering and Bragg diffraction. Three primary sources of this type of background are investigated: the beam stop located in front of the detector, the inside lining of the detector vessel and the environment surrounding the sample. SANS measurements were made where materials with different albedos were placed in all three locations. Additional measurements of the angle-dependent scattering over the angular range of 0.7 pi-0.95 pi rad were completed on 16 different shielding materials at five wavelengths. The data were extrapolated to cover scattering angles from pi/2 to pi rad in order to estimate the materials' albedos. Modifications to existing SANS instruments and sample environments to mitigate extraneous scattering from surfaces are discussed.

The random substitutional solid solution between the antiferromagnetic (AFM) full-Heusler alloy Ru$_2$MnSn and the ferromagnetic (FM) full-Heusler alloy Ru$_2$FeSn provides a rare opportunity to study FM-AFM phase competition in a near-lattice-matched, cubic system, with full solubility. At intermediate $x$ in Ru$_2$Mn$_{1-x}$Fe$_x$Sn this system displays suppressed magnetic ordering temperatures, spatially coexisting FM and AFM order, and strong coercivity enhancement, despite rigorous chemical homogeneity. Here, we construct the most detailed temperature- and $x$-dependent understanding of the magnetic phase competition and coexistence in this system to date, combining wide-temperature-range neutron diffraction and small-angle neutron scattering with magnetometry and specific heat measurements on thoroughly characterized polycrystals. A complete magnetic phase diagram is generated, showing FM-AFM coexistence between $x \approx 0.30$ and $x \approx 0.70$. Important new insight is gained from the extracted length scales for magnetic phase coexistence (25-100 nm), the relative magnetic volume fractions and ordering temperatures, in addition to remarkable $x$-dependent trends in magnetic and electronic contributions to specific heat. An unusual feature in the magnetic phase diagram (an intermediate FM phase) is also shown to arise from an extrinsic effect related to a minor Ru-rich secondary phase. The established magnetic phase diagram is then discussed with the aid of phenomenological modeling, clarifying the nature of the mesoscale phase coexistence with respect to the understanding of disordered Heisenberg models.

Milk and milk products are an essential part of global nutrition and the world-wide food industry. Studies of milk components using scattering techniques are well documented in the literature. However, those studies focused on the q scattering wavevector region 10(-3) < q < 2 angstrom(-1). This manuscript presents scattering results in the region 3 x 10(-5) < q < 2 x 10(-2) angstrom(-1), a region that allows the simultaneous study of fat globules and proteins found in commercial food-grade milk. The small and ultra-small angle neutron scattering (SANS and USANS) measurements show that a model based on the Schulz distribution function using uniform spheres was a reasonable choice to successfully fit the scattering features below q = 0.007 angstrom(-1). Contrast measurements using D2O on whole milk were carried out to distinguish fat from protein signals. Casein micelles were found to have mean diameters of 96 +/- 10 nm with 33% polydispersity. The average scattering length density of the micelles varied from -0.04 x 10(-6) angstrom(-2) in homogenized, pasteurized commercial milk to 2.8 x 10(-6) angstrom(-2) with 50% dilution by D2O, with a match point of 43 +/- 3%, as seen in previous studies. It was found that the average diameter of fat globules in homogenized whole milk was 0.47 +/- 0.04 mu m with a polydispersity of 45 +/- 5%, and a volume fraction of 0.034 +/- 0.002 when the scattering length density is fixed at 0.20 x 10(-6) angstrom(-2). These USANS measurements provide an important foundation as similar techniques are employed to study cheese varieties and cheese formation.

In small-angle scattering theory and data modeling, it is generally assumed that each scattered ray - photon or neutron - is only scattered once on its path through the sample. This assumption greatly simplifies the interpretation of the data and is valid in many cases. However, it breaks down under conditions of high scattering power, increasing with sample concentration, scattering contrast, sample path length and ray wavelength. For samples with a significant scattering power, disregarding multiple scattering effects can lead to erroneous conclusions on the structure of the investigated sample. In this paper, the impact of multiple scattering effects on different types of scattering pattern are determined, and methods for assessing and addressing them are discussed, including the general implementation of multiple scattering effects in structural model fits. The modification of scattering patterns by multiple scattering is determined for the sphere scattering function and the Gaussian function, as well as for different Sabine-type functions, including the Debye-Andersen-Brumberger (DAB) model and the Lorentzian scattering function. The calculations are performed using the semi-analytical convolution method developed by Schelten & Schmatz [J. Appl. Cryst. (1980 ▸). 13, 385-390], facilitated by analytical expressions for intermediate functions, and checked with Monte Carlo simulations. The results show how a difference in the shape of the scattering function plotted versus momentum transfer q results in different multiple scattering effects at low q, where information on the particle mass and radius of gyration is contained.

In situ measurements of geological materials under compression and with hydrostatic fluid pressure are important in understanding their behavior under field conditions, which in turn provides critical information for application-driven research. In particular, understanding the role of nano- to micro-scale porosity in the subsurface liquid and gas flow is critical for the high-fidelity characterization of the transport and more efficient extraction of the associated energy resources. In other applications, where parts are produced by the consolidation of powders by compression, the resulting porosity and crystallite orientation (texture) may affect its in-use characteristics. Small-angle neutron scattering (SANS) and ultra SANS are ideal probes for characterization of these porous structures over the nano to micro length scales. Here we show the design, realization, and performance of a novel neutron scattering sample environment, a specially designed compression cell, which provides compressive stress and hydrostatic pressures with effective stress up to 60 MPa, using the neutron beam to probe the effects of stress vectors parallel to the neutron beam. We demonstrate that the neutron optics is suitable for the experimental objectives and that the system is highly stable to the stress and pressure conditions of the measurements.

The small angle neutron scattering (SANS) of nearly Q-independent nuclear spin-incoherent scattering from hydrogen present in most soft matter and biology samples may raise an issue in structure determination in certain soft matter applications. This is true at high wave vector transfer Q where coherent scattering is much weaker than the nearly Q-independent spin-incoherent scattering background. Polarization analysis is capable of separating coherent scattering from spin-incoherent scattering, hence potentially removing the nearly Q-independent background. Here we demonstrate SANS polarization analysis in conjunction with the time-of-flight technique for separation of coherent and nuclear spin-incoherent scattering for a sample of silver behenate back-filled with light water. We describe a complete procedure for SANS polarization analysis for separating coherent from incoherent scattering for soft matter samples that show inelastic scattering. Polarization efficiency correction and subsequent separation of the coherent and incoherent scattering have been done with and without a time-of-flight technique for direct comparisons. In addition, we have accounted for the effect of multiple scattering from light water to determine the contribution of nuclear spin-incoherent scattering in both the spin flip channel and non-spin flip channel when performing SANS polarization analysis. We discuss the possible gain in the signal-to-noise ratio for the measured coherent scattering signal using polarization analysis with the time-of-flight technique compared with routine unpolarized SANS measurements.

Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300-700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a 3 He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the 3 He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed.

We examine quantitatively the instrumental factors that affect the theoretical performance and practical application of conventional pinhole collimation and focusing optics for small-angle neutron scattering (SANS) measurements. We calculate the relative performance of pinhole collimation vis-à-vis focusing by grazing incidence elliptical mirrors and compare the results with a recent ray-tracing simulation to show that the performance gains due to focusing found in the simulation arise largely from assuming a much larger sample size. We also compare measurements of the parasitic scattering from pinhole collimation with that from focusing cylindrical quartz mirrors, and a focusing refractive optic, to stress the importance of signal-to-noise as the true measure of performance for SANS instruments.

Recent progress with the thermally driven spin-state crossover in LaCoO3 has made it increasingly apparent that the nominally nonmagnetic low-spin ground state of this material actually hosts defect-based magnetism. This is investigated here via a small-angle neutron scattering (SANS) study of LaCoO3-d crystals. The results provide (i) the surprising finding that the spin-state crossover is clearly reflected in SANS via quasieleastic and inelastic scattering from paramagnetic spin fluctuations and excitations, and (ii) evidence for the formation, likely around oxygen defects, of local entities known as magnetic excitons. The latter generate distinct magnetic scattering below 60 K, providing valuable quantitative information on exciton densities and interactions. Potential relevance to the unexpected ferromagnetism recently discovered in epitaxial LaCoO3 films is discussed.

This is a good time to be working in neutron scattering instrumentation. The advent ofthe European Spallation Source (Peggs, 2013) and its associated instrument design efforthas sparked a flurry of activity across Europe in devising new and ingenious instrumentconcepts and instrumentation components, optimized for a high-brightness long-pulseneutron source. These range from new technology within

This paper provides a comparison of the capabilities of two techniques for extending the range of conventional small-angle neutron scattering (SANS) towards the micrometre length scale, namely the double-crystal diffraction ultra-small-angle neutron scattering (DCD USANS) technique, which uses perfect silicon crystals in Bragg reflection, and spin-echo SANS (SESANS), a method that uses the spin precessions of a polarized neutron beam. Both methods encode the scattering angle to very high precision. Based on round-robin test measurements, the strengths and weaknesses of the two techniques are discussed with respect to the measurement of the particle size of monodisperse scatterers, and potential performance gains for state-of-the-art DCD USANS and SESANS instruments are investigated.

The resolution ellipses for neutron diffraction peaks at small scattering vectors lie along lines that point to a position vertically above the beam center on the small-angle scattering detector. This gravity effect is only noticeable for neutron beams at long wavelengths and with large wavelength spreads.

We present static light scattering results for Laponite suspensions. Analyzing our data using the Zimm technique, we measure a second virial coefficient of 6.0 × 10-23 m3 at an ionic strength of 10-4 M. Both results agree well with recent theories and computations for the thermodynamics of hard disks. Our data support the conclusion that the classical Onsager result underestimates the repulsive contribution in discotic systems. We also present neutron scattering results at very low q which conclusively confirm the existence of large-scale structure in Laponite gels above the isotropic−nematic transition.