Neutron Scattering Spectrometer Research Articles

Design and Manufacture an Elastic Neutron Scattering Spectrometer at the Dalat Nuclear Reactor

The objective of this study is to design an elastic neutron scattering system according to the angle with a sample using thermal neutron beam at the Dalat Nuclear Reactor (DNR). The system is used for research and training in the field of material structure analysis by neutron scattering and diffraction techniques. It is designed on the basis of inheriting the neutron measurement spectrometer systems at the DNR and the scattered neutron measurement systems in the world. The measuring system, which was installed at the horizontal channel 4 of the DNR, consists of 5-helium-3 detectors and a fully electronic system to record the scatter counts and a mechanical system with the possibility of rotating at 15&#730-75&#730 angles. The constructed system is tested for evaluation of the accuracy, stability and reliability of the mechanical and electronic systems of moving detectors by angles.

Inelastic Neutron Scattering Spectrometer INDIGO (Indirect Geometry) at the DARIA Compact Neutron Source

The characteristics of an indirect-geometry spectrometer and possibilities of its creation on a compact pulsed neutron source under conditions of its low luminosity are estimated. The configuration of a secondary spectrometer with a position-sensitive detector and a curved crystal analyzer is proposed, which ensures the capture of scattered neutrons at the largest solid angle. The main parameters of the instrument are calculated analytically. Based on the technical requirements for the parameters of the instrument, the numerical simulation is constructed and calculations of the instrument resolution as a function of the energy transfer are performed applying the Monte Carlo method. The analytical resolution function and the resolution function obtained from the simulation show good agreement when considering the contribution from the pulse width. An estimate of the neutron flux on the sample is obtained. The in-principle possibility of implementation of the neutron spectroscopy method under conditions of a compact source is shown.

Neutron inelastic cross section measurements on 54Fe

A 54Fe(n, n'γ) cross section measurement was performed at the Geel Electron LINear Accelerator of EC-JRC, Geel using the Gamma Array for Inelastic Neutron Scattering spectrometer and a 235U fission chamber for flux normalization. The experimental results are presented in comparison with talys 1.9 default and tuned calculations. The tuned calculation, implying modifications of the optical model parameters, improved significantly the description of the experimental values and led to interesting conclusions regarding the interaction of the 54Fe nucleus with neutrons. Since the results of these calculations were already presented extensively in a dedicated paper, the present article focuses on details related to the experimental particularities and data analysis procedure.

Neutron inelastic scattering on 54Fe

A neutron inelastic scattering experiment was performed at the Geel Electron Linear Accelerator neutron source using an enriched 54Fe sample. The $\gamma$ rays produced in the reaction were detected using the Gamma Array for Inelastic Neutron Scattering spectrometer. For each observed transition we determined the $\gamma$ -production cross section for incident energies ranging from the inelastic threshold ( $\approx 1.434$ MeV) up to 18 MeV. Using these primary data we also calculated the cross section of the first excited level and the total inelastic cross section. Our experimental results are compared with previous reported values, evaluated nuclear data libraries and theoretical calculations performed with the TALYS 1.9 code. A careful tuning of the optical model parameters allowed significant improvements in the description of the experimental results leading to interesting conclusions regarding the interaction of the 54Fe nucleus with neutrons.

Design and Construction of the Control System for Batan Small Angle Neutron Scattering Spectrometer (SMARter)

A 36 m Small Angle Neutron Scattering (SANS) Spectrometer (SMARTer) has been installed in Serpong, Indonesia in 1992. As time goes by, the original main computer was out of order and the instrument had not been operated since 2003. In order to activate the SMARTer, in the year 2005, a work on designing and constructing a new control system for SMARTer was carried out. The main component of this control system is a programmable peripheral I/O (IC PPI 8255) and was assembled as a plug-in board at an ISA slot of a personal computer. An IC PPI 8255 was programmed to control the mechanical movements of the instrument’s components: four neutron guide tubes, six pinholes collimator, a detector and a beam stopper. The test either with or without neutron beam has shown that this control system can be implemented for the mechanical movements of SMARTer. Error of moving the detector in the distance range of 1.5 m – 18 m is only 1 mm and the other movements have no error at all (precise).

Calibration and absolute normalization procedure of a new Deep Inelastic Neutron Scattering spectrometer

We describe the calibration process of a new Deep Inelastic Neutron Scattering (DINS) spectrometer, recently implemented at the Bariloche Electron LINAC (Argentina), consisting in the determination of the incident neutron spectrum, dead-time and electronic delay of the data acquisition line, and detector bank efficiency. For this purpose, samples of lead, polyethylene and graphite of different sizes were employed. Their measured spectra were corrected by multiple scattering, attenuation and detector efficiency effects, by means of an ad hoc Monte Carlo code. We show that the corrected spectra are correctly scaled with respect to the scattering power of the tested materials within a 2% of experimental error, thus allowing us to define an experimental constant that links the arbitrary experimental scale (number of recorded counts per monitor counts) with the involved cross-sections. The present work also serves to analyze the existence of possible sources of systematic errors.

Experimental Evidence of Super Densification of Adsorbed Hydrogen by in-situ Small Angle Neutron Scattering (SANS)

ABSTRACTEntrapping hydrogen molecules within the nanopores of solid adsorbents serves as a unique alternative for on-board storing of hydrogen for transportation purposes. The key advantage of the physisorption process for hydrogen storage is the higher density values achieved with the adsorbed gas, compared to that of the compressed phase, translating into higher storage capacities at lower pressures. The necessary condition for effective adsorption is the presence of narrow micropores of < 2 nm in width which provide the most suitable environment of hydrogen adsorption. Despite numerous theoretical calculations or indirect experimental estimations, there has not been a direct experimental measurement of the density of adsorbed hydrogen as a function of pressure and/or pore size. In the present study, we report on the use of in-situ small angle neutron scattering (SANS) to study the phase behavior of hydrogen confined in narrow micropores. We provide for the first time direct experimental measurements of the effect of pore size and pressure on hydrogen adsorbed on a polyfurfuryl alcohol-derived activated carbon (PFAC), at room temperature and pressures up to 207 bar. SANS studies were carried out at the General-Purpose Small-Angle Neutron Scattering spectrometer of the High Flux Isotope Reactor at Oak Ridge National Laboratory. The measurements covered the Q-range from 0.01 to 0.8 Å-1, covering the pores in the range of 9 to 34 Å of the PFAC material. Initial results suggest that the density of adsorbed hydrogen is higher than the density of bulk hydrogen gas and increases with decreasing pore size.

The Challenge of Observation on Livings Things by Employing an Ultra Small-Angle Neutron Scattering Method

To address the question as to how small-angle scattering is effectively applied to the cell, i.e., ahierarchically ordered system comprising multi-components of macro and small molecules, the size ofwhich ranges from 100 μm to several μm, we reconstructed SANS-J (pinhole small-angle neutronscattering spectrometer at research reactor JRR3, Tokai) to focusing & polarized neutron small-anglespectrometer (SANS-J-II), by employing focusing neutron lenses and high resolution photomultiplier.Consequently, an accessible minimum wave number qmin was improved from 3×10-3 A-1 to mediumultra-small angle scattering of 3×10-4 A-1. The focusing USANS method, thus developed, is crucialto fill the gap in wave number q between those covered by a double crystal method and by a conventionalpin-hole method.

Tandem analyzer crystals system doubles counting rate for Bonse–Hart ultra-small-angle neutron-scattering spectrometer

A new tandem analyzer crystals system was introduced on Bonse–Hart ultra-small-angle neutron-scattering spectrometer at research reactor JRR-3, Tokai, Japan. Conventional Bonse–Hart setup consumes a considerable time to measure a scattering profile of whole q range (2×10 −4 nm −1< q<7×10 −2 nm −1, where q denotes magnitude of scattering vector) due to the step scan system, in which the scattered neutrons from the sample and having different q are measured step by step. To overcome this difficulty two analyzer channel-cut silicon perfect crystals were settled in tandem and each of them diffracted the scattering of different q. In consequence, a simultaneous detection at two different q positions was realized and the measurement time was reduced to half.

Magnetic Excitations in CoO

Magnetic excitations in CoO below T N =289 K were investigated on single crystals and a powder specimen by using inelastic neutron-scattering spectrometers installed at a steady state neutron-source and a pulsed neutron source. In single-crystal data, dispersion relations of the two magnetic excitation modes below 70 meV were determined along the symmetric directions. The magnetic excitations around 120 meV were also observed. Energy spectra on a powder specimen suggest the existence of higher order magnetic excitations spreading up to around 200 meV. The magnetic modes were analyzed in connection with the freedom of an unquenched orbital angular-momentum L of a Co 2+ ion. The magnitude of the spin–orbit interaction and that of the exchange interaction obtained from the analyses are comparable, indicating that those interactions must be simultaneously considered without an approximation of the total-angular-momentum. The lowest two dispersion curves are interpreted as mixing and splitting between a disper...

Recent neutron scattering research and development in India

A national facility for neutron beam research is operated at the research reactor Dhruva at Trombay in India. The research activities involve various nanoscale structural, dynamical and magnetic investigations on materials of scientific interest and technological importance. Thermal neutron has certain special properties that enable, e.g., selective viewing of parts of an organic molecule, hydrogen or water in materials, investigations on minerals and ceramics, and microscopic and mesoscopic characterization of bulk samples. The national facility comprises of eight neutron-scattering spectrometers in the reactor hall, and another four spectrometers in the neutron-guide laboratory. In addition, a neutron radiography facility and a detector development laboratory are located at APSARA reactor. All the instruments including the detectors and electronics have been developed within BARC. A new powder diffractometer (PD-3) is being developed by UGC-DAE-CSR. The national facility is utilized in collaboration with various universities and other institutions.

The proton dynamics of ethylene glycol

The results of inelastic neutron scattering experiments on ethylene glycol at T=300 K, T=348 K and T=393 K by using the ‘direct-geometry’ double time-of-flight neutron-scattering spectrometer DIN-2PI (Frank Laboratory of Neutron Physics, JINR, Dubna) are presented. The quasi-elastic and inelastic components of the neutron scattering have been considered. The diffusion characteristics and generalized frequency distributions for protons of ethylene glycol molecules were obtained from the neutron-scattering spectra.

Neutron Scattering in Structural Biology and Biomolecular Materials

The substantial power of both elastic and inelastic neutron-scattering techniques for the investigation of the structure and dynamics of biological systems and related biomolecular-based materials—as with soft matter in the previous article by Lindner and Wignall—arises primarily from the essentially isomorphous nature of the substitution of deuterium for selected hydrogen atoms in these systems, coupled with the exquisite sensitivity of neutron scattering to this isotopic substitution. Since these systems are comprised of large macromolecules and supramolecular assemblies thereof, their essential structures and dynamics extend from the atomic scale up to very large length scales of the Order of 101–104 Å. Hence neutron sources and neutron-scattering spectrometers optimized for longer wavelength (or “cold”) thermal neutrons are necessary in order to most effectively address the structure and dynamics at the longer length scales inherent to these Systems.The large majority of previous neutron-scattering experiments on biological systems have been performed with reactor neutron sources. Some of the more significant of these are briefly summarized in the following sections. They may be categorized in terms of the nature of the intermolecular order, both orientational and positional, within the System of interest and either the elastic neutron-scattering technique employed to investigate their time-averaged structures or the inelastic neutron-scattering technique employed to investigate their dynamics.

Wide-angle neutron scattering study of thermal denaturation of lysozyme

Many studies of folding-unfolding transition of protein have been carried out for the clarification of the fundamental biological problem of protein folding, namely, how a polypeptide chain attains its native conformation. Although one of the approaches to solve protein-folding mechanisms is evidently to follow denaturation processes of protein, there is little direct evidence showing intramolecular structural changes under thermal perturbation. By using a wide-angle neutron-scattering spectrometer, we have monitored the thermal denaturation process of hen egg-white lysozyme at different pH under the unaggregative condition. The present results show that the temperature elevation gradually induces an intramolecular structural fluctuation prior to a main transition of the tertiary structure without accompanying significant heat absorption, and the multiplicity in the thermal transition observed suggests the presence of hierarchic stability depending on the structural hierarchy which would characterize an energetic landscape of folding-unfolding transition of protein.

Optimization study for small angle neutron scattering spectrometer at the ET-RR-1 reactor

The design principle of a Small Angle Neutron Scattering (SANS) spectrometer is based on producing monochromatic neutron bursts using two phased rotors with curved slots. An optimization study of their number and shape to achieve the highly available intensity of monoenergetic neutrons at the required resolution is given. The study was applied to the improvement of the performance of the pulsed monochromatic double rotor system at ET-RR-1 to operate as SANS spectrometer. It is shown that for rotors having 19 slots each with radius of curvature 96.8 cm, the intensity gain factor is 13. The proposed SANS spectrometer could cover the neutron wavelength range from 2 Å up to 6 Å through small angles of scattering from 5 × 10 −3 rad to 0.1 rad, i.e., the scattering wavevector transfer between 0.6 Å −1 and 0.01 Å −1. The maximum neutron intensity on the specimen is 2 × 10 6 n s −1.

The Manuel Lujan Jr. Neutron Scattering Center

In October 1986, the neutron scattering facility at Los Alamos National Laboratory became a national user facility and a formal user program was initiated in 1988. In July 1989, this facility was dedicated as the Manuel Lujan Jr. Neutron Scattering Center (Lujan Center) in honor of the long-term Congress representative from New Mexico. The Lujan Center, part of the Los Alamos Neutron Science Center (LANSCE), is a pulsed spallation neutron source equipped with time-of-flight neutron-scattering spectrometers for condensed-matter research. Neutron scattering is a powerful technique for probing the microscopic structure of condensed matter. The energies and wavelengths of thermal neutrons closely match typical excitation energies and interatomic distances in solids and liquids. Because neutrons have no charge, they penetrate bulk samples of material to give precise information on the positions and motions of individual atoms. The magnetic moment of a neutron interacts with unpaired electrons, making neutrons ideal for probing microscopic magnetic properties. Because neutron-scattering cross sections do not vary monotonically with the atomic number of the scattering nucleus, neutrons and x-rays can provide complementary structural information. This technique is particularly effective for structural problems in polymer and biological studies because hydrogen and deuterium scatter neutrons strongly but with different cross sections.

Small Angle Neutron Scattering at Mcmaster University

ABSTRACTWe describe the Small Angle Neutron Scattering spectrometer at McMaster University. We then discuss three examples of recent studies using this instrument: (1) the membrane-water interface in multilamellar vesicles; (2) magnetic ordering of Ni0.8Co0.2/Cu multilayers; and (3) precipitate sizes in titanium stabilized interstitial-free steels.