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Sample records for neutron total scattering

  1. Total cross sections for neutron scattering

    NASA Astrophysics Data System (ADS)

    Chinn, C. R.; Elster, Ch.; Thaler, R. M.; Weppner, S. P.

    1995-02-01

    Measurements of neutron total cross sections are both extensive and extremely accurate. Although they place a strong constraint on theoretically constructed models, there are relatively few comparisons of predictions with experiment. The total cross sections for neutron scattering from 16O and 40Ca are calculated as a function of energy from 50 to 700 MeV laboratory energy with a microscopic first-order optical potential derived within the framework of the Watson expansion. Although these results are aleady in qualitative agreement with the data, the inclusion of medium corrections to the propagator is essential to correctly predict the energy dependence given by the experiment. In the region between 100 and 200 MeV, where off-shell tρ calculations for both 16O and 40Ca overpredict the experiment, the modification due to the nuclear medium reduces the calculated values. Above 300 MeV these corrections are very small and depending on the employed nuclear mean field tend to compensate for the underprediction of the off-shell tρ results.

  2. Neutron Total Scattering Analysis of Nanoparticles

    NASA Astrophysics Data System (ADS)

    Proffen, Th.

    2012-01-01

    Nanoparticles are entering many aspects of our lives as they often possess properties their bulk counterparts lack. The arsenal of structural characterization techniques for bulk materials is well established. In the case of nanomaterials these tools are just starting to emerge. In this paper the total scattering approach applied to nanomaterials and the promises it holds are discussed.

  3. Neutron total scattering cross sections of elemental antimony

    SciTech Connect

    Smith, A.B.; Guenther, P.T.; Whalen, J.F.

    1982-11-01

    Neutron total cross sections are measured from 0.8 to 4.5 MeV with broad resolutions. Differential-neutron-elastic-scattering cross sections are measured from 1.5 to 4.0 MeV at intervals of 50 to 200 keV and at scattering angles distributed between 20 and 160 degrees. Lumped-level neutron-inelastic-scattering cross sections are measured over the same angular and energy range. The exPerimental results are discussed in terms of an optical-statistical model and are compared with respective values given in ENDF/B-V.

  4. Total cross sections for ultracold neutrons scattered from gases

    DOE PAGES

    Seestrom, Susan Joyce; Adamek, Evan R.; Barlow, Dave; ...

    2017-01-30

    Here, we have followed up on our previous measurements of upscattering of ultracold neutrons (UCNs) from a series of gases by making measurements of total cross sections on the following gases hydrogen, ethane, methane, isobutene, n-butane, ethylene, water vapor, propane, neopentane, isopropyl alcohol, and 3He. The values of these cross sections are important for estimating the loss rate of trapped neutrons due to residual gas and are relevant to neutron lifetime measurements using UCNs. The effects of the UCN velocity and path-length distributions were accounted for in the analysis using a Monte Carlo transport code. Results are compared to ourmore » previous measurements and with the known absorption cross section for 3He scaled to our UCN energy. We find that the total cross sections for the hydrocarbon gases are reasonably described by a function linear in the number of hydrogen atoms in the molecule.« less

  5. Total cross sections for ultracold neutrons scattered from gases

    NASA Astrophysics Data System (ADS)

    Seestrom, S. J.; Adamek, E. R.; Barlow, D.; Blatnik, M.; Broussard, L. J.; Callahan, N. B.; Clayton, S. M.; Cude-Woods, C.; Currie, S.; Dees, E. B.; Fox, W.; Hoffbauer, M.; Hickerson, K. P.; Holley, A. T.; Liu, C.-Y.; Makela, M.; Medina, J.; Morley, D. J.; Morris, C. L.; Pattie, R. W.; Ramsey, J.; Roberts, A.; Salvat, D. J.; Saunders, A.; Sharapov, E. I.; Sjue, S. K. L.; Slaughter, B. A.; Walstrom, P. L.; Wang, Z.; Wexler, J.; Womack, T. L.; Young, A. R.; Vanderwerp, J.; Zeck, B. A.

    2017-01-01

    We have followed up on our previous measurements of upscattering of ultracold neutrons (UCNs) from a series of gases by making measurements of total cross sections on the following gases hydrogen, ethane, methane, isobutene, n -butane, ethylene, water vapor, propane, neopentane, isopropyl alcohol, and 3He . The values of these cross sections are important for estimating the loss rate of trapped neutrons due to residual gas and are relevant to neutron lifetime measurements using UCNs. The effects of the UCN velocity and path-length distributions were accounted for in the analysis using a Monte Carlo transport code. Results are compared to our previous measurements and with the known absorption cross section for 3He scaled to our UCN energy. We find that the total cross sections for the hydrocarbon gases are reasonably described by a function linear in the number of hydrogen atoms in the molecule.

  6. Measured Total Cross Sections of Slow Neutrons Scattered by Solid Deuterium and Implications for Ultracold Neutron Sources

    SciTech Connect

    Atchison, F.; Blau, B.; Brandt, B. van den; Brys, T.; Daum, M.; Fierlinger, P.; Hautle, P.; Henneck, R.; Heule, S.; Kirch, K.; Kohlbrecher, J.; Kuehne, G.; Konter, J.A.; Pichlmaier, A.; Wokaun, A.; Bodek, K.; Kasprzak, M.; Kuzniak, M.; Geltenbort, P.; Zmeskal, J.

    2005-10-28

    The total scattering cross sections for slow neutrons with energies in the range 100 neV to 3 meV for solid ortho-{sup 2}H{sub 2} at 18 and 5 K, frozen from the liquid, have been measured. The 18 K cross sections are found to be in excellent agreement with theoretical expectations and for ultracold neutrons dominated by thermal up scattering. At 5 K the total scattering cross sections are found to be dominated by the crystal defects originating in temperature induced stress but not deteriorated by temperature cycles between 5 and 10 K.

  7. Fast-neutron total and scattering cross sections of sup 58 Ni and nuclear models

    SciTech Connect

    Smith, A.B.; Guenther, P.T.; Whalen, J.F. ); Chiba, S. . Tokai Research Establishment)

    1991-07-01

    The neutron total cross sections of {sup 58}Ni were measured from {approx} 1 to > 10 MeV using white-source techniques. Differential neutron elastic-scattering cross sections were measured from {approx} 4.5 to 10 MeV at {approx} 0.5 MeV intervals with {ge} 75 differential values per distribution. Differential neutron inelastic-scattering cross sections were measured, corresponding to fourteen levels with excitations up to 4.8 MeV. The measured results, combined with relevant values available in the literature, were interpreted in terms of optical-statistical and coupled-channels model using both vibrational and rotational coupling schemes. The physical implications of the experimental results nd their interpretation are discussed in the contexts of optical-statistical, dispersive-optical, and coupled-channels models. 61 refs.

  8. Measured Total Cross Sections of Slow Neutrons Scattered by Gaseous and Liquid 2H2

    NASA Astrophysics Data System (ADS)

    Atchison, F.; van den Brandt, B.; Bryś, T.; Daum, M.; Fierlinger, P.; Hautle, P.; Henneck, R.; Kirch, K.; Kohlbrecher, J.; Kühne, G.; Konter, J. A.; Pichlmaier, A.; Wokaun, A.; Bodek, K.; Kasprzak, M.; Kuźniak, M.; Geltenbort, P.; Giersch, M.; Zmeskal, J.; Hino, M.; Utsuro, M.

    2005-06-01

    The total scattering cross sections for slow neutrons with energies E in the range 300 neV to 3 meV for gaseous and liquid ortho-2H2 have been measured. The cross sections for 2H2 gas are found to be in excellent agreement with both the Hamermesh and Schwinger and the Young and Koppel models. For liquid 2H2, we confirm the existing experimental data in the cold neutron range and the discrepancy with the gas models. We find a clear 1/√(E') dependence at low energies for both states. A simple explanation for the liquid 2H2 cross section is offered.

  9. Fast-neutron total and scattering cross sections of {sup 58}Ni and nuclear models

    SciTech Connect

    Smith, A.B.; Guenther, P.T.; Whalen, J.F.; Lawson, R.D.; Chiba, S.

    1991-12-31

    An extensive experimental and theoretical study of the fast-neutron interaction with {sup 58}Ni was undertaken. The neutron total cross sections of {sup 58}Ni were measured from {approx} 1 to > 10 MeV using white source techniques. Differential neutron elastic-scattering cross sections were measured from {approx} 4.5 to 10 MeV at {approx} 0.5 Mev intervals with {ge} 75 differential values per distribution. Differential neutron inelastic-scattering cross sections were measured, corresponding to fourteen levels with excitations up to {approx} 4.8 Mev. The measured results, combined with lower-energy values previously obtained at this laboratory and with relevant values available in the literature, were interpreted in terms of optical-statistical, dispersive-optical and coupled-channels models using both vibrational and rotational coupling schemes. The physical implications of the experimental results and their interpretation are discussed. The considerations are being extended to collective vibrational nuclei generally, exploring the potential for utilizing electro-magnetic matrix elements, deduced from experiment or predicted by the shell model, to determine the strengths of the neutron interaction. Detailed aspects of this work are given in the Laboratory Report, ANL/NDM-120 (in press). 9 refs., 10 figs.

  10. Fast-neutron total and scattering cross sections of sup 58 Ni and nuclear models

    SciTech Connect

    Smith, A.B.; Guenther, P.T.; Whalen, J.F.; Lawson, R.D.; Chiba, S.

    1991-01-01

    An extensive experimental and theoretical study of the fast-neutron interaction with {sup 58}Ni was undertaken. The neutron total cross sections of {sup 58}Ni were measured from {approx} 1 to > 10 MeV using white source techniques. Differential neutron elastic-scattering cross sections were measured from {approx} 4.5 to 10 MeV at {approx} 0.5 Mev intervals with {ge} 75 differential values per distribution. Differential neutron inelastic-scattering cross sections were measured, corresponding to fourteen levels with excitations up to {approx} 4.8 Mev. The measured results, combined with lower-energy values previously obtained at this laboratory and with relevant values available in the literature, were interpreted in terms of optical-statistical, dispersive-optical and coupled-channels models using both vibrational and rotational coupling schemes. The physical implications of the experimental results and their interpretation are discussed. The considerations are being extended to collective vibrational nuclei generally, exploring the potential for utilizing electro-magnetic matrix elements, deduced from experiment or predicted by the shell model, to determine the strengths of the neutron interaction. Detailed aspects of this work are given in the Laboratory Report, ANL/NDM-120 (in press). 9 refs., 10 figs.

  11. Accelerating Nanoscale Research with Neutron Total Scattering: Linking Structure and Function in Finite Materials

    NASA Astrophysics Data System (ADS)

    Page, Katharine

    2012-10-01

    h -abstract-pard In contrast to bulk materials, nanomaterials and nanoparticles, comprised of a few hundred to tens of thousands of atoms, require every atom's position to be located in order to understand their structure-property relationships. New behavior can arise with a constricted, expanded, or distorted lattice, variation in surface termination structure, ligand capping or stabilization, or with the increasingly diverse set of shapes and architectures appearing in nanoscience literature today: tubes, pyramids, stars, core-shell and matrix-confined particles, multilayer films, etc. Pair distribution function (PDF) analysis, based on spallation neutron or synchrotron x-ray total scattering data, has emerged as a very promising characterization method for nanomaterials in recent years. Total scattering methods provide information about every pair of atoms probed in a diffraction experiment and thus contain an unexploited wealth of information for finite systems. In this contribution we will present our work establishing the influence of particle size and shape on the nature and correlation of local atomic dipoles in finite ferroelectric systems. We also review current data-driven modeling capabilities and outline the need for evolution of robust computational tools to follow other complex nanoscale phenomena with scattering data. pard-/abstract-

  12. The total, elastic and inelastic scattering fast neutron cross sections of natural chromium

    SciTech Connect

    Guenther, P.T.; Smith, J.F.; Whalen, A.B.

    1982-12-01

    The present experimental results comprise a comprehensive intermediate resolution neutron total and scattering cross-section data base for elemental chromium over the energy range from 1.5 to 4.0 MeV. Nonetheless, due to the fluctuating nature of the cross sections involved, the definition of energy-averaged cross sections is uncertain. The consequences of these energy-dependent fluctuations and attendant complications influence the data analysis and interpretation. All finite sample total crosssection measurements result in effective cross sections that have to be corrected to yield the true energyaveraged cross sections. This was accomplished by concurrent multiple sample thickness measurements the results of which were then linearly extrapolated to the zero thickness cross section. It was noted that the resulting sample thickness correction showed marked local fluctuations necessitating an energy by energy treatment. Furthermore, the cross sections, even after averaging over wide energy intervals, retained undulations that complicated comparisons with model calculations. Quantitative comparisons of the present elastic and inelastic scattering results with those obtained at isolated energies by other authors were difficult, if not deceptive, due to persistent fluctuations.

  13. Neutron total and scattering cross sections of /sup 6/Li in the few MeV region

    SciTech Connect

    Smith, A.; Guenther, P.; Whalen, J.

    1980-02-01

    Neutron total cross sections of /sup 6/Li are measured from approx. 0.5 to approx. 4.8 MeV at intervals of approx.< 10 keV. Neutron differential elastic-scattering cross sections are measured from 1.5 to 4.0 MeV at approx.> 10 scattering angles and at incident-neutron intervals of approx.< 100 keV. Neutron differential inelastic-scattering cross sections are measured in the incident-energy range 3.5 to 4.0 MeV. The experimental results are extended to lower energies using measured neutron total cross sections recently reported elsewhere by the authors. The composite experimental data (total cross sections from 0.1 to 4.8 MeV and scattering cross sections from 0.22 to 4.0 MeV) are interpreted in terms of a simple two-level R-matrix model which describes the observed cross sections and implies the reaction cross section in unobserved channels; notably the (n;..cap alpha..)t reaction (Q = 4.783 MeV). The experimental and calculational results are compared with previously reported results as summarized in the ENDF/B-V evaluated nuclear data file.

  14. Neutron total scattering study of the delta and beta phases of Bi2O3.

    PubMed

    Hull, Stephen; Norberg, Stefan T; Tucker, Matthew G; Eriksson, Sten G; Mohn, Chris E; Stølen, Svein

    2009-10-28

    The highly disordered structure of the delta phase of Bi2O3, which possesses the highest known oxide-ion conductivity, has been studied using neutron powder diffraction. A detailed analysis of data collected at 1033(3) K using Rietveld refinement indicates that the time-averaged structure of delta-Bi2O3 can be described using the accepted model of a disordered, anion-deficient fluorite structure in space group Fm3m. However, reverse Monte Carlo modelling of the total (Bragg plus diffuse) scattering demonstrates that the local anion environment around the Bi3+ resembles the distorted square pyramidal arrangement found within the stable alpha and metastable beta phases at ambient temperature, which is characteristic of the cation's 6s2 lone-pair configuration. Similarities between the structures of the highly disordered delta phase and the ambient temperature metastable beta phase are used to support this assignment and assess the validity of previous structural models based on short-range ordering of vacancies within the cubic lattice of delta-Bi2O3.

  15. New insight into the properties of proton conducting oxides from neutron total scattering

    SciTech Connect

    Proffen, Thomas E; Kim, Hyunjeong; Malavasi, Lorenzo; Flor, Giorgio

    2008-01-01

    In recent years there has been a growing interest in searching for new proton conducting materials that could be successfully used in medium temperature solid oxide fuel cells (SOFC). In particular, proton conducting oxides have been the subject of a massive research activity. Among the most promising oxide the acceptor doped cerates appears to be those most appealing in view of practical applications. A relevant aspect of these materials is the investigation of the local distortion of the structure arising from water incorporation. This kind of study is of great help in defining how the structure changes in order to accommodate the proton which is usually thought to enter the structure in form of hydroxyl group where the oxygen vacancy results from the acceptor doping on the Ce site. Atomistic simulation work confirmed that the preferential location of dopant ions is on the Ce site. To the best of our knowledge the only experimental work addressing the role of dopant and water incorporation on the local structure of V-doped cerates is a X-ray absorption spectroscopy (XAS) work carried out by Longo and coworkers at the Y K-edge. The main conclusion of that work was the observation that Y-doping induces a distortion of the parent BaCe0{sub 3} structure resulting in a significantly distorted Y local environment. However, local structure information derived from XAS study does not provide a direct structural information and depends strongly upon the model used to calcualte theoretical {chi}(k) which is not unique. Moreover, the XAS analysis usually provide significant information only up to the second shell. As a consequence, a more reliable and useful technique to investigate the local arrangement in these proton conducting oxides appears to be the Pair Distribution Function (PDF) analysis derived from total neutron scattering measurements. In the present work we investigated the pure BaCeO{sub 3} and the acceptor doped BaCe{sub 0.90}Y{sub 0.10}O{sub 2.85} compounds

  16. Measured Total Cross Sections of Slow Neutrons Scattered by Gaseous and Liquid {sup 2}H{sub 2}

    SciTech Connect

    Atchison, F.; Brandt, B. van den; Brys, T.; Daum, M.; Fierlinger, P.; Hautle, P.; Henneck, R.; Kirch, K.; Kohlbrecher, J.; Kuehne, G.; Konter, J.A.; Pichlmaier, A.; Wokaun, A.; Bodek, K.; Kasprzak, M.; Kuzniak, M.; Geltenbort, P.; Giersch, M.; Zmeskal, J.; Hino, M.

    2005-06-03

    The total scattering cross sections for slow neutrons with energies E in the range 300 neV to 3 meV for gaseous and liquid ortho-{sup 2}H{sub 2} have been measured. The cross sections for {sup 2}H{sub 2} gas are found to be in excellent agreement with both the Hamermesh and Schwinger and the Young and Koppel models. For liquid {sup 2}H{sub 2}, we confirm the existing experimental data in the cold neutron range and the discrepancy with the gas models. We find a clear 1/{radical}(E{sup '}) dependence at low energies for both states. A simple explanation for the liquid {sup 2}H{sub 2} cross section is offered.

  17. MAGNETIC NEUTRON SCATTERING

    SciTech Connect

    ZALIZNYAK,I.A.; LEE,S.H.

    2004-07-30

    Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern science

  18. Neutron scattering in Australia

    SciTech Connect

    Knott, R.B.

    1994-12-31

    Neutron scattering techniques have been part of the Australian scientific research community for the past three decades. The High Flux Australian Reactor (HIFAR) is a multi-use facility of modest performance that provides the only neutron source in the country suitable for neutron scattering. The limitations of HIFAR have been recognized and recently a Government initiated inquiry sought to evaluate the future needs of a neutron source. In essence, the inquiry suggested that a delay of several years would enable a number of key issues to be resolved, and therefore a more appropriate decision made. In the meantime, use of the present source is being optimized, and where necessary research is being undertaken at major overseas neutron facilities either on a formal or informal basis. Australia has, at present, a formal agreement with the Rutherford Appleton Laboratory (UK) for access to the spallation source ISIS. Various aspects of neutron scattering have been implemented on HIFAR, including investigations of the structure of biological relevant molecules. One aspect of these investigations will be presented. Preliminary results from a study of the interaction of the immunosuppressant drug, cyclosporin-A, with reconstituted membranes suggest that the hydrophobic drug interdigitated with lipid chains.

  19. Advances in total scattering analysis

    SciTech Connect

    Proffen, Thomas E; Kim, Hyunjeong

    2008-01-01

    In recent years the analysis of the total scattering pattern has become an invaluable tool to study disordered crystalline and nanocrystalline materials. Traditional crystallographic structure determination is based on Bragg intensities and yields the long range average atomic structure. By including diffuse scattering into the analysis, the local and medium range atomic structure can be unravelled. Here we give an overview of recent experimental advances, using X-rays as well as neutron scattering as well as current trends in modelling of total scattering data.

  20. Small Angle Neutron Scattering

    SciTech Connect

    Urban, Volker S

    2012-01-01

    Small Angle Neutron Scattering (SANS) probes structural details at the nanometer scale in a non-destructive way. This article gives an introduction to scientists who have no prior small-angle scattering knowledge, but who seek a technique that allows elucidating structural information in challenging situations that thwart approaches by other methods. SANS is applicable to a wide variety of materials including metals and alloys, ceramics, concrete, glasses, polymers, composites and biological materials. Isotope and magnetic interactions provide unique methods for labeling and contrast variation to highlight specific structural features of interest. In situ studies of a material s responses to temperature, pressure, shear, magnetic and electric fields, etc., are feasible as a result of the high penetrating power of neutrons. SANS provides statistical information on significant structural features averaged over the probed sample volume, and one can use SANS to quantify with high precision the structural details that are observed, for example, in electron microscopy. Neutron scattering is non-destructive; there is no need to cut specimens into thin sections, and neutrons penetrate deeply, providing information on the bulk material, free from surface effects. The basic principles of a SANS experiment are fairly simple, but the measurement, analysis and interpretation of small angle scattering data involves theoretical concepts that are unique to the technique and that are not widely known. This article includes a concise description of the basics, as well as practical know-how that is essential for a successful SANS experiment.

  1. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

    Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ˜ 1 nm up to ˜ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ˜ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area…) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer

  2. The Structure of Ethylbenzene, Styrene and Phenylacetylene Determined by Total Neutron Scattering.

    PubMed

    Szala-Bilnik, Joanna; Falkowska, Marta; Bowron, Daniel T; Hardacre, Christopher; Youngs, Tristan G A

    2017-07-03

    Organic solvents such as phenylacetylene, styrene and ethylbenzene are widely used in industrial processes, especially in the production of rubber or thermoplastics. Despite their important applications detailed knowledge about their structure is limited. In this paper the structures of these three aromatic solvents were investigated using neutron diffraction. The results show that many of their structural characteristics are similar, although the structure of phenylacetylene is more ordered and has a smaller solvation sphere than either ethylbenzene or styrene. Two regions within the first coordination sphere, in which the surrounding molecules show different preferable orientations with respect to the central molecule, were found for each liquid. Additionally, the localisation of the aliphatic chains reveals that they tend to favour closer interactions with each other than to the aromatic rings of the adjacent molecules. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Neutron Scattering Stiudies

    SciTech Connect

    Kegel, Gunter H.R.; Egan, James J

    2007-04-18

    This project covers four principal areas of research: Elastic and inelastic neutron scattering studies in odd-A terbium, thulium and other highly deformed nuclei near A=160 with special regard to interband transitions and to the investigation of the direct-interaction versus the compound-nucleus excitation process in these nuclei. Examination of new, fast photomultiplier tubes suitable for use in a miniaturized neutron-time-of-flight spectrometer. Measurement of certain inelastic cross sections of 238U. Determination of the multiplicity of prompt fission gamma rays in even-A fissile actinides. Energies and mean lives of fission isomers produced by fast fission of even-Z, even-A actinides. Study of the mean life of 7Be in different host matrices and its possible astro-physical significance.

  4. Total neutron scattering investigation of the structure of a cobalt gallium oxide spinel prepared by solvothermal oxidation of gallium metal

    NASA Astrophysics Data System (ADS)

    Playford, Helen Y.; Hannon, Alex C.; Tucker, Matthew G.; Lees, Martin R.; Walton, Richard I.

    2013-11-01

    A new solvothermal synthesis route to mixed-metal gallium oxides with the spinel structure has been developed for ternary oxides of ideal composition Ga3-xMxO4-y (M=Co, Zn, Ni). The structure of the novel cobalt gallate produced in this manner, Ga1.767(8)Co0.973(8)O3.752(8), has been determined from total neutron scattering to be a partially defective spinel with mixed-valent cobalt (approximately 25% Co3+ and 75% Co2+) and with vacancies on approximately 6% of oxygen sites. Pair distribution function (PDF) analysis reveals significant local deviations from the average cubic structure, which are attributed to the conflicting coordination preferences of the Co2+ (potential Jahn-Teller distortion) and Ga3+ (Ga off-centring). Reverse Monte Carlo (RMC) modelling supports this conclusion since different metal-oxygen bond-distance distributions are found for the two cations in the refined configuration. An investigation of magnetic properties shows evidence of short-range magnetic order and spin-glass-like behaviour, consistent with the structural disorder of the material.

  5. Atomic displacements in the charge ice pyrochlore Bi2Ti2O6O' studied by neutron total scattering

    NASA Astrophysics Data System (ADS)

    Shoemaker, Daniel P.; Seshadri, Ram; Hector, Andrew L.; Llobet, Anna; Proffen, Thomas; Fennie, Craig J.

    2010-04-01

    The oxide pyrochlore Bi2Ti2O6O' is known to be associated with large displacements of Bi and O' atoms from their ideal crystallographic positions. Neutron total scattering, analyzed in both reciprocal and real space, is employed here to understand the nature of these displacements. Rietveld analysis and maximum entropy methods are used to produce an average picture of the structural nonideality. Local structure is modeled via large-box reverse Monte Carlo simulations constrained simultaneously by the Bragg profile and real-space pair distribution function. Direct visualization and statistical analyses of these models show the precise nature of the static Bi and O' displacements. Correlations between neighboring Bi displacements are analyzed using coordinates from the large-box simulations. The framework of continuous symmetry measures has been applied to distributions of O'Bi4 tetrahedra to examine deviations from ideality. Bi displacements from ideal positions appear correlated over local length scales. The results are consistent with the idea that these nonmagnetic lone-pair containing pyrochlore compounds can be regarded as highly structurally frustrated systems.

  6. Superconductivity, antiferromagnetism, and neutron scattering

    NASA Astrophysics Data System (ADS)

    Tranquada, John M.; Xu, Guangyong; Zaliznyak, Igor A.

    2014-01-01

    High-temperature superconductivity in both the copper-oxide and the iron-pnictide/chalcogenide systems occurs in close proximity to antiferromagnetically ordered states. Neutron scattering has been an essential technique for characterizing the spin correlations in the antiferromagnetic phases and for demonstrating how the spin fluctuations persist in the superconductors. While the nature of the spin correlations in the superconductors remains controversial, the neutron scattering measurements of magnetic excitations over broad ranges of energy and momentum transfers provide important constraints on the theoretical options. We present an overview of the neutron scattering work on high-temperature superconductors and discuss some of the outstanding issues.

  7. A New Polyethylene Scattering Law Determined Using Inelastic Neutron Scattering

    SciTech Connect

    Lavelle, Christopher M; Liu, C; Stone, Matthew B

    2013-01-01

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S (Q, E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for T =300 K, and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 300 K which are used to improve the scattering law for HDPE. We describe the experimental methods, review some of the past HDPE scattering laws, and compare computations using these models to the measured S (Q, E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the 1 phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work.

  8. Neutron scatter camera

    DOEpatents

    Mascarenhas, Nicholas; Marleau, Peter; Brennan, James S.; Krenz, Kevin D.

    2010-06-22

    An instrument that will directly image the fast fission neutrons from a special nuclear material source has been described. This instrument can improve the signal to background compared to non imaging neutron detection techniques by a factor given by ratio of the angular resolution window to 4.pi.. In addition to being a neutron imager, this instrument will also be an excellent neutron spectrometer, and will be able to differentiate between different types of neutron sources (e.g. fission, alpha-n, cosmic ray, and D-D or D-T fusion). Moreover, the instrument is able to pinpoint the source location.

  9. Neutron scattering and models: Titanium

    SciTech Connect

    Smith, A.B.

    1997-07-01

    Differential neutron elastic-scattering cross sections of elemental titanium were measured from 4.5 {r_arrow} 10.0 MeV in incident energy increments of {approx} 0.5 MeV. At each energy the measurements were made at forty or more scattering angles distributed between {approx} 17 and 160{degree}. Concurrently, differential neutron inelastic-scattering cross sections were measured for observed excitations of 0.975 {+-} 0.034, 1.497 {+-} 0.033, 2.322 {+-} 0.058, 3.252 {+-} 0.043, 3.700 {+-} 0.093, 4.317 {+-} 0.075 and 4.795 {+-} 0.100 MeV. All of the observed inelastically-scattered neutron groups were composites of contributions from several isotopes and/or levels. The experimental results were used to develop energy-average optical, statistical and coupled-channels models.

  10. Neutron scattering by Dirac multipoles

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Khalyavin, D. D.

    2017-06-01

    Scattering by magnetic charge formed by Dirac multipoles that are magnetic and polar is examined in the context of materials with properties that challenge conventional concepts. An order parameter composed of Dirac quadrupoles has been revealed in the pseudo-gap phase of ceramic, high-T c superconductors on the basis of Kerr effect and magnetic neutron Bragg diffraction measurements. Construction of Dirac quadrupoles that emerge from centrosymmetric sites used by Cu ions in the ceramic superconductor Hg1201 is illustrated, together with selection rules for excitations that will feature in neutron inelastic scattering, and RIXS experiments. We report magnetic scattering amplitudes for diffraction by polar multipoles that have universal value, because they are not specific to ceramic superconductors. To illustrate this attribute, we consider neutron Bragg diffraction from a magnetically ordered iridate (Sr2IrO4) and discuss shortcomings in published interpretations of diffraction data.

  11. Neutron Scattering Studies of Cement

    NASA Astrophysics Data System (ADS)

    Allen, Andrew

    2010-03-01

    Despite more than a century of research, basic questions remain regarding both the internal structure and the role of water in Ordinary Portland cement (OPC) concrete, the world's most widely used manufactured material. Most such questions concern the primary hydration product and strength-building phase of OPC paste, the calcium silicate hydrate (C-S-H) gel. When cement and water are mixed, this phase precipitates as clusters of nanoscale (nearly amorphous) colloidal particles with an associated water-filled inter-particle pore system. Most attempts to characterize the C-S-H gel and the behavior of the associated water involve drying or other processes that, themselves, change the bound water content within and around the gel. Neutron scattering methods do not suffer from this disadvantage. Furthermore, the neutron isotope effect and the neutron's sensitivity to molecular motion have enabled considerable progress to be made in recent years by: (i) determining the C-S-H composition, density and gel structure in small-angle neutron scattering (SANS) H/D contrast variation studies; (ii) elucidating the changing state of water within cement as hydration progresses using quasielastic neutron scattering (QENS); and (iii) measuring the production and consumption of nanoscale calcium hydroxide (CH), a by-product of cement hydration that co-exists with the C-S-H gel, using inelastic neutron scattering (INS). These experiments have provided new insights into the physics and chemistry of cement hydration, and have implications for the design of new concretes with pozzolanic cement additions that are intended to address environmental concerns and sustainability issues.

  12. Thermal neutron scattering evaluation framework

    NASA Astrophysics Data System (ADS)

    Chapman, Chris; Leal, Luiz; Rahnema, Farzad; Danon, Yaron; Arbanas, Goran

    2017-09-01

    A neutron scattering kernel data evaluation framework for computation of model-dependent predictions and their uncertainties is outlined. In this framework, model parameters are fitted to double-differential cross section measurements and their uncertainties. For convenience, the initial implementation of this framework uses the molecular dynamics model implemented in the GROMACS code. It is applied to light water using the TIP4P/2005f interaction model. These trajectories computed by GROMACS are then processed using nMOLDYN to compute the density of states, which is then used to calculate the scattering kernel using the Gaussian approximation. Double differential cross sections computed from the scattering kernel are then fitted to double-differential scattering data measured at the Spallation Neutron Source detector at Oak Ridge National Laboratory. The fitting procedure is designed to yield optimized model-parameters and their uncertainties in the form of a covariance matrix, from which new evaluations of thermal neutron scattering kernel will be generated. The Unified Monte Carlo method will be used to fit the simulation data to the experimental data.

  13. Structural evolution across the insulator-metal transition in oxygen-deficient BaTiO3-δ studied using neutron total scattering and Rietveld analysis

    DOE PAGES

    Jeong, I.-K.; Lee, Seunghun; Jeong, Se-Young; ...

    2011-08-29

    Oxygen-deficient BaTiO3-δ exhibits an insulator-metal transition with increasing δ. We performed neutron total scattering measurements to study structural evolution across an insulator-metal transition in BaTiO3-δ. Despite its significant impact on resistivity, slight oxygen reduction (δ=0.09) caused only a small disturbance on the local doublet splitting of Ti-O bond. This finding implies that local polarization is well preserved under marginal electric conduction. In the highly oxygen-deficient metallic state (δ=0.25), however, doublet splitting of the Ti-O bond became smeared. The smearing of the local Ti-O doublet is complemented with long-range structural analysis and demonstrates that the metallic conduction in the highly oxygen-reducedmore » BaTiO3-δ is due to the appearance of nonferroelectric cubic lattice.« less

  14. Local structural disorder in Zn{sub 0.9}Co{sub 0.1}O nanocrystals studied using neutron total scattering analysis

    SciTech Connect

    Jeong, I.-K.; Lee, Seunghun; Llobet, A.

    2012-10-01

    Neutron total scattering measurements were performed at 300 K and 15 K to study local structural disorder in deuterium plasma treated and as-prepared Zn{sub 0.9}Co{sub 0.1}O nanocrystalline powder. We found that static disorder becomes a determining factor for atomic pair correlations on the length scale larger than r{approx}9A. On the source of the static disorder, we propose a partial occupancy of Zn/Co further away from its crystallographic site along the c-axis. Between the deuterium plasma treated and as-prepared Zn{sub 0.9}Co{sub 0.1}O samples, we observed no local structural difference, which suggests that no additional disorder is induced by the deuterium plasma treatment.

  15. Biological neutron scattering: Now and the future

    SciTech Connect

    Trewhella, J.

    1996-06-01

    Neutrons have an important role to play in structural biology. Neutron crystallography, small-angle neutron scattering and inelastic neutron scattering techniques can all contribute unique information on biomolecular structures. In particular, solution scattering techniques can give critical information on the conformations an dispositions of the components of complex assemblies under a wide variety of relevant conditions. The power of these methods are demonstrated for examples by protein/DNA complexes, and Ca{sup 2+}- binding proteins complexed with their regulatory targets. In addition, we demonstrate the utility of a new structural approach suing neutron resonance scattering. The impact of biological neutron scattering to date has been constrained principally by the available fluxes at neutron sources and the true potential of these approaches will only be realized with the development of new more powerful neutron sources.

  16. Enhanced reaction rates in NDP analysis with neutron scattering

    SciTech Connect

    Downing, R. Gregory

    2014-04-15

    Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.

  17. Enhanced reaction rates in NDP analysis with neutron scattering

    NASA Astrophysics Data System (ADS)

    Downing, R. Gregory

    2014-04-01

    Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.

  18. Enhanced reaction rates in NDP analysis with neutron scattering.

    PubMed

    Downing, R Gregory

    2014-04-01

    Neutron depth profiling (NDP) makes accessible quantitative information on a few isotopic concentration profiles ranging from the surface into the sample a few micrometers. Because the candidate analytes for NDP are few, there is little interference encountered. Furthermore, neutrons have no charge so mixed chemical states in the sample are of no direct concern. There are a few nuclides that exhibit large probabilities for neutron scattering. The effect of neutron scattering on NDP measurements has not previously been evaluated as a basis for either enhancing the reaction rates or as a source of measurement error. Hydrogen is a common element exhibiting large neutron scattering probability found in or around sample volumes being analyzed by NDP. A systematic study was conducted to determine the degree of signal change when neutron scattering occurs during analysis. The relative signal perturbation was evaluated for materials of varied neutron scattering probability, concentration, total mass, and geometry. Signal enhancements up to 50% are observed when the hydrogen density is high and in close proximity to the region of analysis with neutron beams of sub thermal energies. Greater signal enhancements for the same neutron number density are reported for thermal neutron beams. Even adhesive tape used to position the sample produces a measureable signal enhancement. Because of the shallow volume, negligible distortion of the NDP measured profile shape is encountered from neutron scattering.

  19. Medical applications of neutron inelastic scattering

    NASA Astrophysics Data System (ADS)

    Kehayias, Joseph J.; Banuk-Waitekus, Anathea; Valtuena, Silvia; Sheahan, Charles A.

    1999-10-01

    A sealed, D-T, pulsed neutron generator is used for the in vivo measurement of body carbon and oxygen by neutron inelastic scattering. The generator is operated at 10 KHz, at a neutron output of about 2 X 107 n/s/4(pi) . Gamma ray spectra are collected with two B4Ge3O12 crystal detectors. The measurements are used to measure fat and lean content and distribution in the body, with minimal radiation exposure (0.08 mSv). When combined with other measurements (such as total body potassium), this whole body scanning device provides us with the `quality of lean mass', a measurable outcome of treatments designed to improve nutritional status and function. The method is used in studies of human nutrition and for assessing the efficacy of new anti-obesity and anti-cachexia pharmaceuticals.

  20. Neutron scattering from a ferrofluid

    SciTech Connect

    Lin, M.Y. |; Luo, W.; Lynn, J.

    1995-12-31

    Small angle neutron scattering experiments were performed on a eicosane-based ferrofluid. An average size of 88 {angstrom} can be extracted from the data, in agreement with results from electron microscopy. Below the frozen temperature of eicosane, however, the particles are seen to be in larger aggregates with a fractal dimension of 2.15, similar to those formed under reaction-limited cluster aggregation (RLCA) conditions. At high concentrations, particles form larger aggregates even in the liquid state. Applying a magnetic field introduces new structure and changes the density inside the aggregates.

  1. American Conference on Neutron Scattering 2014

    SciTech Connect

    Dillen, J. Ardie

    2014-12-31

    Scientists from the around the world converged in Knoxville, TN to have share ideas, present technical information and contribute to the advancement of neutron scattering. Featuring over 400 oral/poster presentations, ACNS 2014 offered a strong program of plenary, invited and contributed talks and poster sessions covering topics in soft condensed matter, hard condensed matter, biology, chemistry, energy and engineering applications in neutron physics – confirming the great diversity of science that is enabled by neutron scattering.

  2. Neutron scattering: Technological achievements and illustrative results

    SciTech Connect

    Chiba, S. ); Takahashi, A. ); Klein, H. ); Smith, A. )

    1991-01-01

    Contemporary neutron scattering endeavors (energies {le} = 25 MeV), using monoenergetic sources and the time-of-flight technique, are reviewed. Facilities and techniques are described, with attention to the optimization of measurement systems. Discrete scattering results are illustrated in fundamental and applied contexts. Techniques for and results from continuum neutron emission studies are discussed, with the implications on physical models and on neutron applications in energy systems. 45 refs., 14 figs.

  3. A neutron total scattering study of local coordination in KTiOPO4 from room temperature to 900 °C.

    PubMed

    Norberg, Stefan T; Thomas, Pamela A; Tucker, Matthew G

    2011-05-04

    Neutron total (Bragg plus diffuse) scattering data have been analysed by means of bond valence constrained reverse Monte Carlo modelling, using RMCProfile software, in order to simultaneously probe the natures of the short- and long-range structural correlations in potassium titanyl phosphate, KTiOPO(4) (KTP). The diffraction data were collected at room temperature, 300, 500, 700 and 900 °C, and the resulting partial radial distribution functions, g(jk)(r), were thoroughly investigated in order to obtain information about the structural aspects that cause reduced second harmonic generation (SHG) with increasing temperature in KTP. The -TiO(6)-PO(4)- lattice shows very little rigid unit motion up to 900 °C and the PO(4) tetrahedra were likewise unchanged. However, subtle changes regarding oxygen disordering around the TiO(6) octahedra, i.e. the number of short titanyl bonds, and K(+) cation displacement along the c axis are carefully mapped out. The latter has a direct detrimental effect on the SHG response, whilst the anisotropic Ti-O bond distribution seems to be a prerequisite for the SHG effect.

  4. Neutron spin echo scattering angle measurement (SESAME)

    SciTech Connect

    Pynn, R.; Fitzsimmons, M.R.; Fritzsche, H.; Gierlings, M.; Major, J.; Jason, A.

    2005-05-15

    We describe experiments in which the neutron spin echo technique is used to measure neutron scattering angles. We have implemented the technique, dubbed spin echo scattering angle measurement (SESAME), using thin films of Permalloy electrodeposited on silicon wafers as sources of the magnetic fields within which neutron spins precess. With 30-{mu}m-thick films we resolve neutron scattering angles to about 0.02 deg. with neutrons of 4.66 A wavelength. This allows us to probe correlation lengths up to 200 nm in an application to small angle neutron scattering. We also demonstrate that SESAME can be used to separate specular and diffuse neutron reflection from surfaces at grazing incidence. In both of these cases, SESAME can make measurements at higher neutron intensity than is available with conventional methods because the angular resolution achieved is independent of the divergence of the neutron beam. Finally, we discuss the conditions under which SESAME might be used to probe in-plane structure in thin films and show that the method has advantages for incident neutron angles close to the critical angle because multiple scattering is automatically accounted for.

  5. Neutron scattering and models : molybdenum.

    SciTech Connect

    Smith, A.B.

    1999-05-26

    A comprehensive interpretation of the fast-neutron interaction with elemental and isotopic molybdenum at energies of {le} 30 MeV is given. New experimental elemental-scattering information over the incident energy range 4.5 {r_arrow} 10 MeV is presented. Spherical, vibrational and dispersive models are deduced and discussed, including isospin, energy-dependent and mass effects. The vibrational models are consistent with the ''Lane potential''. The importance of dispersion effects is noted. Dichotomies that exist in the literature are removed. The models are vehicles for fundamental physical investigations and for the provision of data for applied purposes. A ''regional'' molybdenum model is proposed. Finally, recommendations for future work are made.

  6. Neutrons scattering studies in the actinide region

    SciTech Connect

    Kegel, G.H.R.; Egan, J.J.

    1992-09-01

    During the report period were investigated the following areas: prompt fission neutron energy spectra measurements; neutron elastic and inelastic scattering from [sup 239]Pu; neutron scattering in [sup 181]Ta and [sup 197]Au; response of a [sup 235]U fission chamber near reaction thresholds; two-parameter data acquisition system; black'' neutron detector; investigation of neutron-induced defects in silicon dioxide; and multiple scattering corrections. Four Ph.D. dissertations and one M.S. thesis were completed during the report period. Publications consisted of three journal articles, four conference papers in proceedings, and eleven abstracts of presentations at scientific meetings. There are currently four Ph.D. and one M.S. candidates working on dissertations directly associated with the project. In addition, three other Ph.D. candidates are working on dissertations involving other aspects of neutron physics in this laboratory.

  7. Measurement of neutron scattering lengths using neutron interferometry

    NASA Astrophysics Data System (ADS)

    Shahi, Chandra B.

    This thesis describes the details on building a new Neutron Interferometry and Optics Facility (NIOFa), the measurement of the incoherent neutron scattering length bi of 3He, and the measurement of the coherent neutron scattering length bc of 4He at National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). A new monochromatic beamline and facility has been installed at the NCNR devoted to neutron interferometry in the research areas of spin control, spin manipulation, quantum mechanics, quantum information science, spintronics, and material science. This facility is possible in part because of advances in decoherence free subspace interferometer designs that have demonstrated consistent contrast in the presence of vibrational noise; a major environmental constraint that has prevented neutron interferometry from being applied at other neutron facilities. This new facility, NIOFa, is located in the guide hall of the NCNR upstream of the existing Neutron Interferometry and Optics Facility (NIOF) and has several advantages over the NIOF including higher incident flux, better neutron polarization, and increased accessibility. The measurement of the incoherent neutron scattering length bi of 3He was done using a (220) single silicon crystal skew symmetric interferometer. This experiment requires both a polarized beam and a polarized target. We report bi = -2.35 +/- 0.014 (stat.) +/- 0.014 (syst.). This experiment is a revision of the previous experiment which was done in 2008, and partially explains the non-zero phase shift seen in 2008 experiment even if target cell was completely unpolarized. The measurement of the coherent neutron scattering length b c of the 4He was done using a (111) single silicon crystal interferometer. The neutron interferometry and optics facility at NIST had been used previously to determine the coherent scattering lengths for n- 1H, n-2H, and n-3He to less than 1% relative uncertainty. We report bc of the 4He

  8. Hierarchical optimization for neutron scattering problems

    SciTech Connect

    Bao, Feng; Archibald, Rick; Bansal, Dipanshu; Delaire, Olivier

    2016-06-15

    We present a scalable optimization method for neutron scattering problems that determines confidence regions of simulation parameters in lattice dynamics models used to fit neutron scattering data for crystalline solids. The method uses physics-based hierarchical dimension reduction in both the computational simulation domain and the parameter space. We demonstrate for silicon that after a few iterations the method converges to parameters values (interatomic force-constants) computed with density functional theory simulations.

  9. Hierarchical optimization for neutron scattering problems

    SciTech Connect

    Bao, Feng; Archibald, Rick; Bansal, Dipanshu; Delaire, Olivier

    2016-03-14

    In this study, we present a scalable optimization method for neutron scattering problems that determines confidence regions of simulation parameters in lattice dynamics models used to fit neutron scattering data for crystalline solids. The method uses physics-based hierarchical dimension reduction in both the computational simulation domain and the parameter space. We demonstrate for silicon that after a few iterations the method converges to parameters values (interatomic force-constants) computed with density functional theory simulations.

  10. Hierarchical optimization for neutron scattering problems

    DOE PAGES

    Bao, Feng; Archibald, Rick; Bansal, Dipanshu; ...

    2016-03-14

    In this study, we present a scalable optimization method for neutron scattering problems that determines confidence regions of simulation parameters in lattice dynamics models used to fit neutron scattering data for crystalline solids. The method uses physics-based hierarchical dimension reduction in both the computational simulation domain and the parameter space. We demonstrate for silicon that after a few iterations the method converges to parameters values (interatomic force-constants) computed with density functional theory simulations.

  11. Neutron inelastic scattering measurements on the stable isotopes of titanium

    NASA Astrophysics Data System (ADS)

    Olacel, A.; Belloni, F.; Borcea, C.; Boromiza, M.; Dessagne, P.; Henning, G.; Kerveno, M.; Negret, A.; Nyman, M.; Pirovano, E.; Plompen, A. J. M.

    2017-07-01

    The results of a neutron inelastic scattering experiment performed at the Geel Electron Linear Accelerator pulsed white neutron source of the European Commission Joint Research Centre are reported. The neutrons with energies up to 18 MeV interacted with a natTi sample and the γ rays resulting from inelastic scattering reactions on the stable isotopes were detected using the Gamma Array for Inelastic Neutron Scattering (GAINS) spectrometer. We were able to measure the γ -production cross sections for 21 transitions in the five stable Ti isotopes. From these, the level cross sections and the total inelastic cross sections were determined. Our experimental results are compared with theoretical calculations performed using the talys 1.8 code, evaluated nuclear data libraries, and also with previously reported results.

  12. BUILDING A NETWORK FOR NEUTRON SCATTERING EDUCATION

    SciTech Connect

    Pynn, Roger; Baker, Shenda Mary; Louca, Despo A; McGreevy, Robert L; Ekkebus, Allen E; Kszos, Lynn A; Anderson, Ian S

    2008-10-01

    In a concerted effort supported by the National Science Foundation, the Department of Commerce, and the Department of Energy, the United States is rebuilding its leadership in neutron scattering capability through a significant investment in U.S. neutron scattering user facilities and related instrumentation. These unique facilities provide opportunities in neutron scattering to a broad community of researchers from academic institutions, federal laboratories, and industry. However, neutron scattering is often considered to be a tool for 'experts only' and in order for the U.S. research community to take full advantage of these new and powerful tools, a comprehensive education and outreach program must be developed. The workshop described below is the first step in developing a national program that takes full advantage of modern education methods and leverages the existing educational capacity at universities and national facilities. During March 27-28, 2008, a workshop entitled 'Building a Network for Neutron Scattering Education' was held in Washington, D.C. The goal of the workshop was to define and design a roadmap for a comprehensive neutron scattering education program in the United States. Successful implementation of the roadmap will maximize the national intellectual capital in neutron sciences and will increase the sophistication of research questions addressed by neutron scattering at the nation's forefront facilities. (See Appendix A for the list of attendees, Appendix B for the workshop agenda, Appendix C for a list of references. Appendix D contains the results of a survey given at the workshop; Appendix E contains summaries of the contributed talks.) The workshop brought together U.S. academicians, representatives from neutron sources, scientists who have developed nontraditional educational programs, educational specialists, and managers from government agencies to create a national structure for providing ongoing neutron scattering education. A

  13. Toward a new polyethylene scattering law determined using inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Lavelle, C. M.; Liu, C.-Y.; Stone, M. B.

    2013-05-01

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S(Q,E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for ambient temperatures (˜300 K), and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 294 K which are used to improve the scattering law for HDPE. We review some of the past HDPE scattering laws, describe the experimental methods, and compare computations using these models to the measured S(Q,E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the one phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work.

  14. Neutron scattering of advanced magnetic materials

    NASA Astrophysics Data System (ADS)

    Yusuf, S. M.; Kumar, Amit

    2017-09-01

    An overview of notable contributions of neutron scattering in the advancement of magnetic materials has been presented. A brief description of static neutron scattering techniques, viz., diffraction, depolarization, small angle scattering, and reflectivity, employed in the studies of advanced magnetic materials, is given. Apart from providing the up-to-date literature, this review highlights the importance of neutron scattering techniques in achieving microscopic as well as mesoscopic understanding of static magnetic properties of the following selective classes of advanced magnetic materials: (i) magnetocaloric materials, (ii) permanent magnets, (iii) multiferroic materials, (iv) spintronic materials, and (v) molecular magnetic materials. In the area of magnetocaloric materials, neutron diffraction studies have greatly improved the understanding of magneto-structural coupling by probing (i) atomic site distribution, (ii) evolution of structural phases and lattice parameters across the TC, and (iii) microscopic details of magnetic ordering in several potential magnetocaloric materials. Such an understanding is vital to enhance the magnetocaloric effect. Structural and magnetic investigations, employing neutron diffraction and allied techniques, have helped to improve the quality of permanent magnets by tailoring (understanding) structural phases, magnetic ordering, crystallinity, microstructure (texture), and anisotropy. The neutron diffraction studies of structural distortions/instabilities and magnetic ordering in multiferroic materials have improved the microscopic understanding of magnetoelectric coupling that allows one to control magnetic order by an electric field and electric order by a magnetic field in multiferroic materials. In the field of molecular magnetic materials, neutron diffraction studies have enhanced the understanding of (i) structural and magnetic ordering, (ii) short-range structural and magnetic correlations, (iii) spin density distribution

  15. Monte Carlo simulation of neutron scattering instruments

    SciTech Connect

    Seeger, P.A.

    1995-12-31

    A library of Monte Carlo subroutines has been developed for the purpose of design of neutron scattering instruments. Using small-angle scattering as an example, the philosophy and structure of the library are described and the programs are used to compare instruments at continuous wave (CW) and long-pulse spallation source (LPSS) neutron facilities. The Monte Carlo results give a count-rate gain of a factor between 2 and 4 using time-of-flight analysis. This is comparable to scaling arguments based on the ratio of wavelength bandwidth to resolution width.

  16. Precision Neutron Scattering Length Measurements with Neutron Interferometry

    NASA Astrophysics Data System (ADS)

    Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Shahi, C. B.; Wietfeldt, F. E.; Black, T. C.

    2011-10-01

    Since its inception, single-crystal neutron interferometry has often been utilized for precise neutron scattering length, b, measurements. Scattering length data of light nuclei is particularly important in the study of few nucleon interactions as b can be predicted by two + three nucleon interaction (NI) models. As such they provide a critical test of the accuracy 2+3 NI models. Nuclear effective field theories also make use of light nuclei b in parameterizing mean-field behavior. The NIST neutron interferometer and optics facility has measured b to less than 0.8% relative uncertainty in polarized 3He and to less than 0.1% relative uncertainty in H, D, and unpolarized 3He. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons are Bragg diffracted in the blades to produce two spatially separate (yet coherent) beam paths much like an optical Mach-Zehnder interferometer. A gas sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths which is proportional to b. This talk will focus on the latest scattering length measurement for n-4He which ran at NIST in Fall/Winter 2010 and is currently being analyzed.

  17. ^3He neutron spin filters for polarized neutron scattering.

    NASA Astrophysics Data System (ADS)

    Chen, Wangchun; Borchers, Julie; Chen, Ying; O'Donovan, Kevin; Erwin, Ross; Lynn, Jeffrey; Majkrzak, Charles; McKenney, Sarah; Gentile, Thomas

    2006-03-01

    Polarized neutron scattering (PNS) is a powerful tool that probes the magnetic structures in a wide variety of magnetic materials. Polarized ^3He gas, produced by optical pumping, can be used to polarize or analyze neutron beams because of the strong spin dependence of the neutron absorption cross section for ^3He. Polarized ^3He neutron spin filters (NSF) have been of great interest in PNS community due to recent significant improvement of their performance. Here I will discuss successful applications using ^3He NSFs in polarized neutron reflectometry (PNR) and triple-axis spectrometry (TAS). In PNR, a ^3He NSF in conjunction with a position-sensitive detector allows for efficient polarization analysis of off-specular scattering over a broad range of reciprocal space. In TAS, a ^3He NSF in combination with a double focusing pyrolytic graphite monochromator provides greater versatility and higher intensity compared to a Heusler polarizer. Finally I will present the results from patterned magnetically-coupled thin films in PNR and our first ``proof-of-principle'' experiment in TAS, both of which were performed using ^3He NSF(s) at the NIST Center for Neutron Research.

  18. Neutron scattering of transuranium materials

    SciTech Connect

    Lander, G.H.

    1986-01-01

    A number of neutron experiments on transuranium materials are reviewed. Purpose of these experiments, which range from studies of crystal fields in the oxides to excitations in PuSb, is to increase our understanding of the 5f electron behavior across the first half of the actinide series. Comparisons are made with the more familiar uranium analogues.

  19. Fast neutron scattering near shell closures: Scandium

    SciTech Connect

    Smith, A.B.; Guenther, P.T.

    1992-08-01

    Neutron differential elastic- and inelastic-scattering cross sections are measured from [approx] 1.5 to 10 MeV with sufficient detail to define the energy-averaged behavior of the scattering processes. Neutrons corresponding to excitations of 465 [plus minus] 23, 737 [plus minus] 20, 1017 [plus minus] 34, 1251 [plus minus] 20, 1432 [plus minus] 23 and 1692 [plus minus] 25 keV are observed. It is shown that the observables, including the absorption cross section, are reasonably described with a conventional optical-statistical model having energy-dependent geometric parameters. These energy dependencies are alleviated when the model is extended to include the contributions of the dispersion relationship. The model parameters are conventional, with no indication of anomalous behavior of the neutron interaction with [sup 45]Sc, five nucleons from the doubly closed shell at [sup 40]Ca.

  20. Fast neutron scattering near shell closures: Scandium

    SciTech Connect

    Smith, A.B.; Guenther, P.T.

    1992-08-01

    Neutron differential elastic- and inelastic-scattering cross sections are measured from {approx} 1.5 to 10 MeV with sufficient detail to define the energy-averaged behavior of the scattering processes. Neutrons corresponding to excitations of 465 {plus_minus} 23, 737 {plus_minus} 20, 1017 {plus_minus} 34, 1251 {plus_minus} 20, 1432 {plus_minus} 23 and 1692 {plus_minus} 25 keV are observed. It is shown that the observables, including the absorption cross section, are reasonably described with a conventional optical-statistical model having energy-dependent geometric parameters. These energy dependencies are alleviated when the model is extended to include the contributions of the dispersion relationship. The model parameters are conventional, with no indication of anomalous behavior of the neutron interaction with {sup 45}Sc, five nucleons from the doubly closed shell at {sup 40}Ca.

  1. Resonance effects in neutron scattering lengths

    SciTech Connect

    Lynn, J.E.

    1989-06-01

    The nature of neutron scattering lengths is described and the nuclear effects giving rise to their variation is discussed. Some examples of the shortcomings of the available nuclear data base, particularly for heavy nuclei, are given. Methods are presented for improving this data base, in particular for obtaining the energy variation of the complex coherent scattering length from long to sub-/angstrom/ wave lengths from the available sources of slow neutron cross section data. Examples of this information are given for several of the rare earth nuclides. Some examples of the effect of resonances in neutron reflection and diffraction are discussed. This report documents a seminar given at Argonne National Laboratory in March 1989. 18 refs., 18 figs.

  2. Neutron scattering studies of glassy Li+ superionics

    NASA Astrophysics Data System (ADS)

    Heitmann, Tom; Zella, Leo; Zaidi, Ali; Rathore, Munesh; Dalvi, Anshuman; Mitra, Saibal

    2013-03-01

    Two distinct neutron scattering techniques were implemented in the study of glassy superionic materials composed of a complex network of their interconnected sub-units: Li2O, NH4H2PO2, and Li2SO4. The use of disordered materials underlies an effort to promote Li+ mobility, while suppressing e- conductivity, which makes them good candidates for use as electrolytes in lithium ion batteries. We present triple-axis spectrometer results of energy resolved vs. energy integrated neutron scattering that indicate the presence of a broad range of dynamic processes in the materials, rather than well-defined excitations. Additionally, we report on neutron diffraction data that demonstrates the formation of crystallites within the material upon annealing up to 450 °C. Such crystallites hinder the performance of the materials as electrolytes, which is evident in thin film devices where heating is unavoidable during fabrication.

  3. Neutron Scattering Experiment Automation with Python

    SciTech Connect

    Zolnierczuk, Piotr A; Riedel, Richard A

    2010-01-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory currently holds the Guinness World Record as the world most powerful pulsed spallation neutron source. Neutrons scattered off atomic nuclei in a sample yield important information about the position, motions, and magnetic properties of atoms in materials. A neutron scattering experiment usually involves sample environment control (temperature, pressure, etc.), mechanical alignment (slits, sample and detector position), magnetic field controllers, neutron velocity selection (choppers) and neutron detectors. The SNS Data Acquisition System (DAS) consists of real-time sub-system (detector read-out with custom electronics, chopper interface), data preprocessing (soft real-time) and a cluster of control and ancillary PCs. The real-time system runs FPGA firmware and programs running on PCs (C++, LabView) typically perform one task such as motor control and communicate via TCP/IP networks. PyDas is a set of Python modules that are used to integrate various components of the SNS DAS system. It enables customized automation of neutron scattering experiments in a rapid and flexible manner. It provides wxPython GUIs for routine experiments as well as IPython command line scripting. Matplotlib and numpy are used for data presentation and simple analysis. We will present an overview of SNS Data Acquisition System and PyDas architectures and implementation along with the examples of use. We will also discuss plans for future development as well as the challenges that have to be met while maintaining PyDas for 20+ different scientific instruments.

  4. Neutron scattering study of dilute supercritical solutions

    SciTech Connect

    Cochran, H.D.; Wignall, G.D.; Shah, V.M.; Londono, J.D.; Bienkowski, P.R.

    1994-10-01

    Dilute solutions in supercritical solvents exhibit interesting microstructures that are related to their dramatic macroscopic behavior. In typical attractive solutions, solutes are believed to be surrounded by clusters of solvent molecules, and solute molecules are believed to congregate in the vicinity of one another. Repulsive solutions, on the other hand, exhibit a local region of reduced solvent density around the solute with solute-solute congregation. Such microstructures influence solubility, partial molar volume, reaction kinetics, and many other properties. We have undertaken to observe these interesting microstructures directly by neutron scattering experiments on dilute noble gas systems including Ar. The three partial structure factors for such systems and the corresponding pair correlation functions can be determined by using the isotope substitution technique. The systems studied are uniquely suited for our objectives because of the large coherent neutron scattering length of the isotope {sup 36}Ar and because of the accurate potential energy functions that are available for use in molecular simulations and theoretical calculations to be compared with the scattering results. We will describe our experiment, the unique apparatus we have built for it, and the neutron scattering results from our initial allocations of beam time. We will also describe planned scattering experiments to follow those with noble gases, including study of long-chain molecules in supercritical solvents. Such studies will involve hydrocarbon mixtures with and without deuteration to provide contrast.

  5. Virtual experiments: Combining realistic neutron scattering instrument and sample simulations

    NASA Astrophysics Data System (ADS)

    Farhi, E.; Hugouvieux, V.; Johnson, M. R.; Kob, W.

    2009-08-01

    A new sample component is presented for the Monte Carlo, ray-tracing program, McStas, which is widely used to simulate neutron scattering instruments. The new component allows the sample to be described by its material dynamic structure factor, which is separated into coherent and incoherent contributions. The effects of absorption and multiple scattering are treated and results from simulations and previous experiments are compared. The sample component can also be used to treat any scattering material which may be close to the sample and therefore contaminates the total, measured signal.

  6. Contraband detection via neutron elastic scattering

    SciTech Connect

    Gomberg, H.J.; Charatis, G.; Brundage, J.

    1993-04-01

    Reliable detection of explosives and narcotics depends on generating signatures of compounds which characterize them. Major explosives and also alkaloid narcotics contain unique concentrations of Carbon (C), Nitrogen (N), and Oxygen (O). The kinematic energy shifts of neutrons scattered through angles larger than 140{degrees} allows separate determinations of C, N, and O; ratios of N/C and O/C together give clear signatures of the presence of plastic explosives or narcotics. The ability to detect these signatures under conditions similar to those that would obtain for airport screening has been demonstrated for neutrons for energies less {le} 3 MeV. Strong N resonances and a deep window for scattering from O enhance the confidence of element quantification. Detection of contraband in large cargo containers presents a much more difficult problem. Use of higher energy neutrons is now being tested for shielding penetration, so narcotic signatures could be identified behind the shielding of cargo containers. Scattered neutron spectra, or {open_quotes}signatures{close_quotes} of different organic compounds will be presented.

  7. A mechanical rotator for neutron scattering measurements

    NASA Astrophysics Data System (ADS)

    Thaler, A.; Northen, E.; Aczel, A. A.; MacDougall, G. J.

    2016-12-01

    We have designed and built a mechanical rotation system for use in single crystal neutron scattering experiments at low temperatures. The main motivation for this device is to facilitate the application of magnetic fields transverse to a primary training axis, using only a vertical cryomagnet. Development was done in the context of a triple-axis neutron spectrometer, but the design is such that it can be generalized to a number of different instruments or measurement techniques. Here, we discuss some of the experimental constraints motivating the design, followed by design specifics, preliminary experimental results, and a discussion of potential uses and future extension possibilities.

  8. Deep inelastic neutron scattering in condensed hydrogen

    NASA Astrophysics Data System (ADS)

    Bafile, Ubaldo; Celli, Milva; Zoppi, Marco

    1996-02-01

    The neutron cross-section of molecular hydrogen that is measured by deep inelastic neutron scattering (DINS) is compared with two distinct models. One is a generalization of the molecular Young and Koppel model (1964) that takes into account the modification to the translational kinetic energy that is induced by quantum effects. The second model assumes a free particle wave function for the final state of the proton (C. Andreani et al., 1995). The comparison between these two models, and with the experimental results, provides information on the crossover between the molecular and atomic regime of hydrogen in DINS.

  9. Neutron scattering from solid 3He

    NASA Astrophysics Data System (ADS)

    Schanen, R.; Sherline, T. E.; Toader, A. M.; Boyko, V.; Mat'as, S.; Meschke, M.; Schöttl, S.; Adams, E. D.; Cowan, B.; Godfrin, H.; Goff, J. P.; Roger, M.; Saunders, J.; Siemensmeyer, K.; Takano, Y.

    2003-05-01

    Multiple spin exchange leads, according to present understanding, to a variety of magnetically ordered states in solid 3He, depending on pressure and applied magnetic field. We report the status of experiments to directly determine these structures by neutron scattering. The large neutron absorption cross section, and associated sample heating, impose severe experimental demands on the design of the sample cell. We report on our proposed solution, including details of the sintered heat exchanger necessary to cool the sample, as well as the PrNi 5 nuclear demagnetization stage. The use of NMR in parallel experiments to characterise growth of the solid sample within the sinter is also discussed.

  10. Total body calcium analysis. [neutron irradiation

    NASA Technical Reports Server (NTRS)

    Lewellen, T. K.; Nelp, W. B.

    1974-01-01

    A technique to quantitate total body calcium in humans is developed. Total body neutron irradiation is utilized to produce argon 37. The radio argon, which diffuses into the blood stream and is excreted through the lungs, is recovered from the exhaled breath and counted inside a proportional detector. Emphasis is placed on: (1) measurement of the rate of excretion of radio argon following total body neutron irradiation; (2) the development of the radio argon collection, purification, and counting systems; and (3) development of a patient irradiation facility using a 14 MeV neutron generator. Results and applications are discussed in detail.

  11. Submoment expansion of neutron-scattering sources

    SciTech Connect

    Williams, M.L.

    2000-02-01

    The submoment method was originally introduced to compute spherical harmonic moments of the neutron elastic-scattering source for discrete ordinates calculations with pointwise nuclear data. This work extends the submoment method to include discrete-level inelastic, as well as elastic, S-wave reactions. New applications of the submoment expansion to compute spherical harmonic moments of the slowing-down density and the elastic removal rate are also presented. Numerical stability and computational considerations are discussed.

  12. Neutron scattering at the OPAL research reactor

    NASA Astrophysics Data System (ADS)

    McIntyre, Garry J.; Holden, Peter J.

    2016-09-01

    The current suite of 14 neutron scattering instruments at the multipurpose OPAL research reactor is described. All instruments have been constructed following best practice, using state-of-the-art components and in close consultation with the regional user base. First results from the most recently commissioned instruments match their design performance parameters. Selected recent scientific highlights illustrate some unique combinations of instrumentation and the regional flavour of topical applications.

  13. Inelastic neutron scattering in valence fluctuation compounds

    SciTech Connect

    Jon M Lawrence

    2011-02-15

    The valence fluctuation compounds are rare earth intermetallics where hybridization of the nearly-localized 4f electrons with the conduction electrons leads to incorporation of the 4f's into the itinerant states. This hybridization slows down the conduction electrons and hence gives them a heavy effective mass, justifying application of the term 'heavy Fermion' (HF) to these materials. During the project period, we grew large single crystals of several such compounds and measured their properties using both standard thermodynamic probes and state-of-the-art inelastic neutron scattering. We obtained three main results. For the intermediate valence compounds CePd{sub 3} and YbAl{sub 3}, we showed that the scattering of neutrons by the fluctuations of the 4f magnetic moment does not have the momentum dependence expected for the itinerant heavy mass state; rather, the scattering is more typical of a localized spin fluctuation. We believe that incoherent scattering localizes the excitation. For the heavy Fermion compound Ce(Ni{sub 0.935}Pd{sub 0.065}){sub 2}Ge{sub 2}, which sits at a T = 0 critical point for transformation into an antiferromagnetic (AF) phase, we showed that the scattering from the AF fluctuations does not exhibit any of the divergences that are expected at a phase transition. We speculate that alloy disorder profoundly suppresses the growth of the fluctuating AF regions, leading to short range clusters rather than regions of infinite size. Finally, we explored the applicability of key concepts used to describe the behavior of rare earth heavy Fermions to uranium based HF compounds where the 5f electrons are itinerant as opposed to localized. We found that scaling laws relating the spin fluctuation energy measured in neutron scattering to the low temperature specific heat and susceptibility are valid for the uranium compounds, once corrections are made for AF fluctuations; however, the degeneracy of the high temperature moment is smaller than expected

  14. Neutron scattering studies of multiferroics

    NASA Astrophysics Data System (ADS)

    Cabrera, Ivelisse M.

    Magnetoelectric multiferroics are systems that exhibit magnetic and ferroelectric order. In strongly coupled multiferroics, competing magnetic interactions can break spatial inversion symmetry and yield ferroelectricity through a magnetic phase transition. In this dissertation, I present original work on the multiferroic properties of Ni3V2O8 and critical phenomena in TbMnO3 and RbFe(MoO4)2. Ni3V2O8 is an insulating magnet where Ni-spins order in a longitudinal amplitude modulated pattern along the a axis in the high-temperature incommensurate (HTI) phase. Upon cooling to the low-temperature incommensurate phase, an additional spine site spin component along b results in a cycloidal structure that breaks spatial inversion symmetry, yielding ferroelectricity. Electric control of multiferroic domains is demonstrated quantitatively and qualitatively using polarized magnetic neutron diffraction. We show that magnetic and ferroelectric domains are strongly coupled in this system and that definite cycloid handedness is achieved by antisymmetric Dzyaloshinskii-Moriya interactions. Ni3 V2O8 displays a memory effect where the system reverts to the previous polarization state upon exiting and re-entering the multiferroic phase through a first order phase transition. Our results suggest that small multiferroic domains in the paraelectric, commensurate phase retain the polarization history and reestablish it upon re-entering the multiferroic phase. TbMnO3 is a frustrated magnet similar to Ni3V 2O8 which undergoes two magnetic phase transitions before becoming multiferroic. A temperature-dependent magnetic diffraction study near TN reveals that this system orders through a continuous phase transition. Further studies in the HTI phase are needed to clarify whether a novel, weak transition exists at around 39 K. Our results support the single irreducible representation model as the system enters the HTI phase. RbFe(MoO4)2 is a nearly 2D antiferromagnet that enters the

  15. Neutron scattering instrumentation for biology at spallation neutron sources

    SciTech Connect

    Pynn, R.

    1994-12-31

    Conventional wisdom holds that since biological entities are large, they must be studied with cold neutrons, a domain in which reactor sources of neutrons are often supposed to be pre-eminent. In fact, the current generation of pulsed spallation neutron sources, such as LANSCE at Los Alamos and ISIS in the United Kingdom, has demonstrated a capability for small angle scattering (SANS) - a typical cold- neutron application - that was not anticipated five years ago. Although no one has yet built a Laue diffractometer at a pulsed spallation source, calculations show that such an instrument would provide an exceptional capability for protein crystallography at one of the existing high-power spoliation sources. Even more exciting is the prospect of installing such spectrometers either at a next-generation, short-pulse spallation source or at a long-pulse spallation source. A recent Los Alamos study has shown that a one-megawatt, short-pulse source, which is an order of magnitude more powerful than LANSCE, could be built with today`s technology. In Europe, a preconceptual design study for a five-megawatt source is under way. Although such short-pulse sources are likely to be the wave of the future, they may not be necessary for some applications - such as Laue diffraction - which can be performed very well at a long-pulse spoliation source. Recently, it has been argued by Mezei that a facility that combines a short-pulse spallation source similar to LANSCE, with a one-megawatt, long-pulse spallation source would provide a cost-effective solution to the global shortage of neutrons for research. The basis for this assertion as well as the performance of some existing neutron spectrometers at short-pulse sources will be examined in this presentation.

  16. Polarized neutron scattering on HYSPEC: the HYbrid SPECtrometer at SNS

    NASA Astrophysics Data System (ADS)

    Zaliznyak, Igor A.; Savici, Andrei T.; Ovidiu Garlea, V.; Winn, Barry; Filges, Uwe; Schneeloch, John; Tranquada, John M.; Gu, Genda; Wang, Aifeng; Petrovic, Cedomir

    2017-06-01

    We describe some of the first polarized neutron scattering measurements performed at HYSPEC [1-4] spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. We discuss details of the instrument setup and the experimental procedures in the mode with full polarization analysis. Examples of polarized neutron diffraction and polarized inelastic neutron data obtained on single crystal samples are presented.

  17. Polarized neutron scattering on HYSPEC: the HYbrid SPECtrometer at SNS

    SciTech Connect

    Zaliznyak, Igor; Savici, Andrei T; Garlea, Vasile O; Winn, Barry L; Schneelock, John; Tranquada, John M.; Gu, G. D.; Wang, Aifeng; Petrovic, C

    2017-01-01

    We describe some of the first polarized neutron scattering measurements performed at HYSPEC spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. We discuss details of the instrument setup and the experimental procedures in the mode with the full polarization analysis. Examples of the polarized neutron diffraction and the polarized inelastic neutron data obtained on single crystal samples are presented.

  18. A thermal neutron scattering law for yttrium hydride

    NASA Astrophysics Data System (ADS)

    Zerkle, Michael; Holmes, Jesse

    2017-09-01

    Yttrium hydride (YH2) is of interest as a high temperature moderator material because of its superior ability to retain hydrogen at elevated temperatures. Thermal neutron scattering laws for hydrogen bound in yttrium hydride (H-YH2) and yttrium bound in yttrium hydride (Y-YH2) prepared using the ab initio approach are presented. Density functional theory, incorporating the generalized gradient approximation (GGA) for the exchange-correlation energy, is used to simulate the face-centered cubic structure of YH2 and calculate the interatomic Hellmann-Feynman forces for a 2 × 2 × 2 supercell containing 96 atoms. Lattice dynamics calculations using PHONON are then used to determine the phonon dispersion relations and density of states. The calculated phonon density of states for H and Y in YH2 are used to prepare H-YH2 and Y-YH2 thermal scattering laws using the LEAPR module of NJOY2012. Analysis of the resulting integral and differential scattering cross sections demonstrates adequate resolution of the S(α,β) function. Comparison of experimental lattice constant, heat capacity, inelastic neutron scattering spectra and total scattering cross section measurements to calculated values are used to validate the thermal scattering laws.

  19. Neutron scattering studies of premartensitic phenomena

    SciTech Connect

    Shapiro, S.M.

    1989-01-01

    Elastic neutron diffraction and inelastic neutron scattering are ideal techniques for studying premartensitic behavior in metallic alloys. By necessity, real, bulk samples are probed replete with their intrinsic defects. Also, because of the properties of the neutron it is straightforward to probe the behavior of the phonon modes away from the zone center which is probed in the normal ultrasonic techniques. A wide variety of alloys exhibiting martensitic transformations have been studied. It will be shown that most systems undergoing diffusionless transformations exhibit premartensitic behavior in that precursor effects are seen at temperatures well above the martensitic transformation temperature, T{sub M}. This behavior manifests itself in an anomalous temperature dependence of the energy of a particular phonon mode as the temperature approaches T{sub M}. The wavevector of this mode is frequently away from the zone center (i.e., q {ne} O). This softening is nearly always accompanied by elastic diffuse scattering at the same wavevector. Particular examples to be discussed are the alkali metals, {omega}-phase materials and Ni-based alloys. 34 refs., 9 figs.

  20. Cryogen free cryostat for neutron scattering experiments

    NASA Astrophysics Data System (ADS)

    Kirichek, O.; Down, R. B. E.; Manuel, P.; Keeping, J.; Bowden, Z. A.

    2014-12-01

    Most very low temperature (below 1K) experiments at advanced neutron facilities are based on dilution and 3He refrigerator inserts used with Orange cryostats, or similar systems. However recent increases in the cost of liquid helium caused by global helium supply problems, has raised significant concern about the affordability of such cryostats. Here we present the design and test results of a cryogen free top-loading cryostat with a standard KelvinoxVT® dilution refrigerator insert which provides sample environment for neutron scattering experiments in the temperature range 35 mK - 300 K. The dilution refrigerator insert operates in a continuous regime. The cooling time of the insert is similar to one operated in the Orange cryostat. The main performance criteria such as base temperature, cooling power, and circulation rate are compatible with the technical specification of a standard dilution refrigerator. In fact the system offers operating parameters very similar to those of an Orange cryostat, but without the complication of cryogens. The first scientific results obtained in ultra-low temperature neutron scattering experiment with this system are also going to be discussed.

  1. Probing fine magnetic particles with neutron scattering

    SciTech Connect

    Pynn, R.

    1991-12-31

    Because thermal neutrons are scattered both by nuclei and by unpaired electrons, they provide an ideal probe for studying the atomic and magnetic structures of fine-grained magnetic materials, including nanocrystalline solids, thin epitaxial layers, and colloidal suspensions of magnetic particles, known as ferrofluids. Diffraction, surface reflection, and small angle neutron scattering (SANS) are the techniques used. With the exception of surface reflection, these methods are described in this article. The combination of SANS with refractive-index matching and neutron polarisation analysis is particularly powerful because it allows the magnetic and atomic structures to be determined independently. This technique has been used to study both dilute and concentrated ferrofluid suspensions of relatively monodisperse cobalt particles, subjected to a series of applied magnetic fields. The size of the cobalt particle core and the surrounding surfactant layer were determined. The measured interparticle structure factor agrees well with a recent theory that allows correlations in binary mixtures of magnetic particles to be calculated in the case of complete magnetic alignment. When one of the species in such a binary mixture is a nonmagnetic, cyclindrical macromolecule, application of a magnetic field leads to some degree of alignment of the nonmagnetic species. This result has been demonstrated with tobacco mosaic virus suspended in a water-based ferrofluid.

  2. Probing fine magnetic particles with neutron scattering

    SciTech Connect

    Pynn, R.

    1991-01-01

    Because thermal neutrons are scattered both by nuclei and by unpaired electrons, they provide an ideal probe for studying the atomic and magnetic structures of fine-grained magnetic materials, including nanocrystalline solids, thin epitaxial layers, and colloidal suspensions of magnetic particles, known as ferrofluids. Diffraction, surface reflection, and small angle neutron scattering (SANS) are the techniques used. With the exception of surface reflection, these methods are described in this article. The combination of SANS with refractive-index matching and neutron polarisation analysis is particularly powerful because it allows the magnetic and atomic structures to be determined independently. This technique has been used to study both dilute and concentrated ferrofluid suspensions of relatively monodisperse cobalt particles, subjected to a series of applied magnetic fields. The size of the cobalt particle core and the surrounding surfactant layer were determined. The measured interparticle structure factor agrees well with a recent theory that allows correlations in binary mixtures of magnetic particles to be calculated in the case of complete magnetic alignment. When one of the species in such a binary mixture is a nonmagnetic, cyclindrical macromolecule, application of a magnetic field leads to some degree of alignment of the nonmagnetic species. This result has been demonstrated with tobacco mosaic virus suspended in a water-based ferrofluid.

  3. Neutron Scattering Structure and Dynamics in Hydrazine

    NASA Astrophysics Data System (ADS)

    Acatrinei, Alice; Hartl, Monika; Daemen, Luke; Forster, Diana; Kickbusch, Rainer; Luger, Peter; Lentz, Dieter

    2007-10-01

    The Lewis Acid Base theory is a fundamental concept in chemistry. One way of describing a chemical bond is to look at the charge distribution within a molecule. By studying the charge densities in electron-deficient compounds such as hydrazine borane, a more detailed view of the bonding situations is achieved. Our interest in hydrazine borane comes from many reasons. First of all it allows examining the experimental charge density of a so called donor acceptor bond on one of the simplest molecules. N2H4BH3 is a potential hydrogen storage material which has not been studied in detail so far. Finally, it contains N-N bonds that are of interest due to their torsional vibrations. We performed neutron powder diffraction on the powder diffractometer NPDF at 15K and 95K and determined the hydrogen positions in N2H4BH3. We synthesized the completely labelled compound N2D4(11BD3)2. We investigated the hydrogen bonding and the N-N torsional dynamics by using incoherent inelastic neutron scattering on the Filter Difference Spectrometer FDS. While IR and RAMAN spectroscopy only show weak signal for torsional and librational modes, these modes are quite strong in neutron vibrational spectroscopy. We present neutron diffraction data and vibrational spectra and their interpretation using molecular modelling calculations.

  4. Structural evolution across the insulator-metal transition in oxygen-deficient BaTiO3-δ studied using neutron total scattering and Rietveld analysis

    SciTech Connect

    Jeong, I.-K.; Lee, Seunghun; Jeong, Se-Young; Won, C. J.; Hur, N.; Llobet, A.

    2011-08-29

    Oxygen-deficient BaTiO3-δ exhibits an insulator-metal transition with increasing δ. We performed neutron total scattering measurements to study structural evolution across an insulator-metal transition in BaTiO3-δ. Despite its significant impact on resistivity, slight oxygen reduction (δ=0.09) caused only a small disturbance on the local doublet splitting of Ti-O bond. This finding implies that local polarization is well preserved under marginal electric conduction. In the highly oxygen-deficient metallic state (δ=0.25), however, doublet splitting of the Ti-O bond became smeared. The smearing of the local Ti-O doublet is complemented with long-range structural analysis and demonstrates that the metallic conduction in the highly oxygen-reduced BaTiO3-δ is due to the appearance of nonferroelectric cubic lattice.

  5. Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

    DOE PAGES

    Grammer, K. B.; Alarcon, R.; Barrón-Palos, L.; ...

    2015-05-08

    Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many-body physics. Unfortunately, the pair correlation function g(r) inferred from neutron scattering measurements of the differential cross section dσ/dΩ from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43 and 16.1 meV on liquid hydrogen at 15.6 K (which is dominated by the parahydrogen component)more » using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1 meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra nonequilibrium component of orthohydrogen. Liquid parahydrogen is also a widely used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. Furthermore, we describe our measurements and compare them with previous work.« less

  6. Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

    SciTech Connect

    Grammer, K. B.; Alarcon, R.; Barrón-Palos, L.; Blyth, D.; Bowman, J. D.; Calarco, J.; Crawford, C.; Craycraft, K.; Evans, D.; Fomin, N.; Fry, J.; Gericke, M.; Gillis, R. C.; Greene, G. L.; Hamblen, J.; Hayes, C.; Kucuker, S.; Mahurin, R.; Maldonado-Velázquez, M.; Martin, E.; McCrea, M.; Mueller, P. E.; Musgrave, M.; Nann, H.; Penttilä, S. I.; Snow, W. M.; Tang, Z.; Wilburn, W. S.

    2015-05-08

    Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many-body physics. Unfortunately, the pair correlation function g(r) inferred from neutron scattering measurements of the differential cross section dσ/dΩ from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43 and 16.1 meV on liquid hydrogen at 15.6 K (which is dominated by the parahydrogen component) using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1 meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra nonequilibrium component of orthohydrogen. Liquid parahydrogen is also a widely used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. Furthermore, we describe our measurements and compare them with previous work.

  7. Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

    NASA Astrophysics Data System (ADS)

    Grammer, K. B.; Alarcon, R.; Barrón-Palos, L.; Blyth, D.; Bowman, J. D.; Calarco, J.; Crawford, C.; Craycraft, K.; Evans, D.; Fomin, N.; Fry, J.; Gericke, M.; Gillis, R. C.; Greene, G. L.; Hamblen, J.; Hayes, C.; Kucuker, S.; Mahurin, R.; Maldonado-Velázquez, M.; Martin, E.; McCrea, M.; Mueller, P. E.; Musgrave, M.; Nann, H.; Penttilä, S. I.; Snow, W. M.; Tang, Z.; Wilburn, W. S.

    2015-05-01

    Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many-body physics. Unfortunately, the pair correlation function g (r ) inferred from neutron scattering measurements of the differential cross section d/σ d Ω from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43 and 16.1 meV on liquid hydrogen at 15.6 K (which is dominated by the parahydrogen component) using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1 meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra nonequilibrium component of orthohydrogen. Liquid parahydrogen is also a widely used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. We describe our measurements and compare them with previous work.

  8. Neutron scattering studies of amorphous Invar alloys

    SciTech Connect

    Fernandez-Baca, J.A.

    1989-01-01

    This paper reviews recent inelastic neutron scattering experiments performed to study the spin dynamics of two amorphous Invar systems: Fe/sub 100-x/B/sub x/ and Fe/sub 90-x/Ni/sub x/Zr/sub 10/. As in crystalline Invar Fe/sub 65/Ni/sub 35/ and Fe/sub 3/Pt, the excitation of conventional long-wavelength spin waves in these amorphous systems cannot account for the relatively rapid change of their magnetization with temperature. These results are discussed in terms of additional low-lying excitations which apparently have a density of states similar to the spin waves.

  9. Deeply Virtual Compton Scattering off the Neutron

    NASA Astrophysics Data System (ADS)

    Mazouz, M.; Camsonne, A.; Camacho, C. Muñoz; Ferdi, C.; Gavalian, G.; Kuchina, E.; Amarian, M.; Aniol, K. A.; Beaumel, M.; Benaoum, H.; Bertin, P.; Brossard, M.; Chen, J.-P.; Chudakov, E.; Craver, B.; Cusanno, F.; de Jager, C. W.; Deur, A.; Feuerbach, R.; Fieschi, J.-M.; Frullani, S.; Garçon, M.; Garibaldi, F.; Gayou, O.; Gilman, R.; Gomez, J.; Gueye, P.; Guichon, P. A. M.; Guillon, B.; Hansen, O.; Hayes, D.; Higinbotham, D.; Holmstrom, T.; Hyde, C. E.; Ibrahim, H.; Igarashi, R.; Jiang, X.; Jo, H. S.; Kaufman, L. J.; Kelleher, A.; Kolarkar, A.; Kumbartzki, G.; Laveissiere, G.; Lerose, J. J.; Lindgren, R.; Liyanage, N.; Lu, H.-J.; Margaziotis, D. J.; Meziani, Z.-E.; McCormick, K.; Michaels, R.; Michel, B.; Moffit, B.; Monaghan, P.; Nanda, S.; Nelyubin, V.; Potokar, M.; Qiang, Y.; Ransome, R. D.; Réal, J.-S.; Reitz, B.; Roblin, Y.; Roche, J.; Sabatié, F.; Saha, A.; Sirca, S.; Slifer, K.; Solvignon, P.; Subedi, R.; Sulkosky, V.; Ulmer, P. E.; Voutier, E.; Wang, K.; Weinstein, L. B.; Wojtsekhowski, B.; Zheng, X.; Zhu, L.

    2007-12-01

    The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e→,e'γ)X cross section measured at Q2=1.9GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to Eq, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

  10. Deeply virtual compton scattering off the neutron.

    PubMed

    Mazouz, M; Camsonne, A; Camacho, C Muñoz; Ferdi, C; Gavalian, G; Kuchina, E; Amarian, M; Aniol, K A; Beaumel, M; Benaoum, H; Bertin, P; Brossard, M; Chen, J-P; Chudakov, E; Craver, B; Cusanno, F; de Jager, C W; Deur, A; Feuerbach, R; Fieschi, J-M; Frullani, S; Garçon, M; Garibaldi, F; Gayou, O; Gilman, R; Gomez, J; Gueye, P; Guichon, P A M; Guillon, B; Hansen, O; Hayes, D; Higinbotham, D; Holmstrom, T; Hyde, C E; Ibrahim, H; Igarashi, R; Jiang, X; Jo, H S; Kaufman, L J; Kelleher, A; Kolarkar, A; Kumbartzki, G; Laveissiere, G; Lerose, J J; Lindgren, R; Liyanage, N; Lu, H-J; Margaziotis, D J; Meziani, Z-E; McCormick, K; Michaels, R; Michel, B; Moffit, B; Monaghan, P; Nanda, S; Nelyubin, V; Potokar, M; Qiang, Y; Ransome, R D; Réal, J-S; Reitz, B; Roblin, Y; Roche, J; Sabatié, F; Saha, A; Sirca, S; Slifer, K; Solvignon, P; Subedi, R; Sulkosky, V; Ulmer, P E; Voutier, E; Wang, K; Weinstein, L B; Wojtsekhowski, B; Zheng, X; Zhu, L

    2007-12-14

    The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e,e'gamma)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_{q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

  11. Biophysical applications of neutron Compton scattering

    NASA Astrophysics Data System (ADS)

    Wanderlingh, U. N.; Albergamo, F.; Hayward, R. L.; Middendorf, H. D.

    Neutron Compton scattering (NCS) can be applied to measuring nuclear momentum distributions and potential parameters in molecules of biophysical interest. We discuss the analysis of NCS spectra from peptide models, focusing on the characterisation of the amide proton dynamics in terms of the width of the H-bond potential well, its Laplacian, and the mean kinetic energy of the proton. The Sears expansion is used to quantify deviations from the high-Q limit (impulse approximation), and line-shape asymmetry parameters are evaluated in terms of Hermite polynomials. Results on NCS from selectively deuterated acetanilide are used to illustrate this approach.

  12. Neutron scattering kernel for solid deuterium

    NASA Astrophysics Data System (ADS)

    Granada, J. R.

    2009-06-01

    A new scattering kernel to describe the interaction of slow neutrons with solid deuterium was developed. The main characteristics of that system are contained in the formalism, including the lattice's density of states, the Young-Koppel quantum treatment of the rotations, and the internal molecular vibrations. The elastic processes involving coherent and incoherent contributions are fully described, as well as the spin-correlation effects. The results from the new model are compared with the best available experimental data, showing very good agreement.

  13. Deeply Virtual Compton Scattering off the Neutron

    SciTech Connect

    Mazouz, M.; Guillon, B.; Real, J.-S.; Voutier, E.

    2007-12-14

    The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e-vector,e{sup '}{gamma})X cross section measured at Q{sup 2}=1.9 GeV{sup 2} and x{sub B}=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E{sub q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

  14. Toward a resolution of the neutron-neutron scattering-length issue

    NASA Astrophysics Data System (ADS)

    Howell, C. R.; Chen, Q.; Carman, T. S.; Hussein, A.; Gibbs, W. R.; Gibson, B. F.; Mertens, G.; Moore, C. F.; Morris, C.; Obst, A.; Pasyuk, E.; Roper, C. D.; Salinas, F.; Slaus, I.; Sterbenz, S.; Tornow, W.; Walter, R. L.; Whiteley, C. R.; Whitton, M.

    1998-12-01

    We report a high-precision determination of the 1S0 neutron-neutron scattering length (ann) using the 2H(π-,nγ)n reaction. The value obtained in the present work is -18.50+/- 0.05 (statistical) +/- 0.44 (systematic) +/- 0.30 (theoretical) fm, which is consistent with the values from previous measurements. Combining our result with previous measurements reduces the total uncertainty in the world average of ann to +/-0.4 fm, matching the accuracy to which the charge-symmetric parameter app is determined.

  15. Multiple small angle neutron scattering: A new two-dimensional ultrasmall angle neutron scattering technique

    SciTech Connect

    Gruenzweig, C.; Hils, T.; Muehlbauer, S.; Ay, M.; Lorenz, K.; Georgii, R.; Gaehler, R.; Boeni, P.

    2007-11-12

    We report on the demonstration experiment of the multiple small angle neutron scattering (MSANS) technique at a 5.6 m long neutron beam line, leading to a q resolution of 3x10{sup -4} A{sup -1}. The MSANS technique is based on two two-dimensional multihole apertures placed at the front end of the collimator and close to the sample, respectively. By choosing the proper MSANS geometry, individual diffraction patterns are superimposed leading to a large gain in intensity. Using MSANS as an option for standard small angle neutron scattering beam lines, the q resolution could be increased to 10{sup -5} A{sup -1} without dramatically sacrificing intensity.

  16. Fast-neutron elastic scattering from elemental vanadium

    SciTech Connect

    Smith, A.B.; Guenther, P.T.; Lawson, R.D.

    1988-03-01

    Differential neutron elastic- and inelastic-scattering cross sections of vanadium were measured from 4.5 to 10 MeV. These results were combined with previous 1.5 to 4.0 MeV data from this laboratory, the 11.1 MeV elastic-scattering results obtained at Ohio University, and the reported neutron total cross sections to energies of approx.20.0 MeV, to form a data base which was interpreted in terms of the spherical optical-statistical model. A fit to the data was achieved by making both the strengths and geometries of the optical-model potential energy dependent. This energy dependence was large below approx.6.0 MeV. Above approx.6.0 MeV the energy dependencies are smaller, and similar to those characteristic of global models. Using the dispersion relationship and the method of moments, the optical-model potential energy deduced from 0.0 to 11.1 MeV neutron-scattering data was extrapolated to higher energies and to the bound-state regime. This extrapolation leads to predicted neutron total cross sections that are within 3% of the experimental values throughout the energy range 0.0 to 20.0 MeV. Furthermore, the values of the volume-integral-per-nucleon of the real potential are in excellent agreement with those needed to reproduce the observed binding energies of particle- and hole-states. The latter gives clear evidence of the Fermi surface anomaly. Using only the 0.0 to 11.1 MeV data, the predicted E < O behavior of the strength and radius of the real shell-model Woods-Saxon potential are somewhat different from those obtained by Mahaux and Sartor in their analysis of nuclei near closed shells. 61 refs., 9 figs., 2 tabs.

  17. Study of Scattered Background Neutron in NIF and Time-of Flight (TOF) to Measure Neutron

    SciTech Connect

    Song, P; Moran, M; Phillips, T; Lerche, R; Koch, J; Eder, D

    2005-08-31

    Some of the planned core diagnostics for National Ignition Facility (NIF) will use neutron time-of-flight (TOF) spectroscopy techniques to gather information for primary neutron yield measurement or neutron imaging. This technique has been widely and routinely used at other laser facilities including Nova and Omega. TOF methods will also be used to observe target fuel areal density <{rho}R> (radial integral of density) via measuring the number of primary 14.1 MeV neutrons that are down-scattered to lower energies by nuclear collisions inside the compressed target core. The substantially larger target chamber size and higher neutron yield for NIF raises issues related to the large number of scattered neutrons produced by high yield deuterium-tritium (D-T) shots at NIF. The effect of primary neutrons scattered by the walls of the massive target chamber and structures both inside and outside the chamber will contribute a significant scattered background signal when trying to determine the number of neutrons down-scattered from the target core. The optimum detector locations outside the target chamber or target bay wall will be proposed. Appropriate collimators at the chamber port and the bay wall (between the neutron source at target chamber center (TCC) and detector) that maximize detection of signal neutrons while minimizing the background from scattered neutrons and neutron induced gamma rays will also be presented.

  18. Lattice Waves, Spin Waves, and Neutron Scattering

    DOE R&D Accomplishments Database

    Brockhouse, Bertram N.

    1962-03-01

    Use of neutron inelastic scattering to study the forces between atoms in solids is treated. One-phonon processes and lattice vibrations are discussed, and experiments that verified the existence of the quantum of lattice vibrations, the phonon, are reviewed. Dispersion curves, phonon frequencies and absorption, and models for dispersion calculations are discussed. Experiments on the crystal dynamics of metals are examined. Dispersion curves are presented and analyzed; theory of lattice dynamics is considered; effects of Fermi surfaces on dispersion curves; electron-phonon interactions, electronic structure influence on lattice vibrations, and phonon lifetimes are explored. The dispersion relation of spin waves in crystals and experiments in which dispersion curves for spin waves in Co-Fe alloy and magnons in magnetite were obtained and the reality of the magnon was demonstrated are discussed. (D.C.W)

  19. Neutron Compton scattering from selectively deuterated acetanilide

    NASA Astrophysics Data System (ADS)

    Wanderlingh, U. N.; Fielding, A. L.; Middendorf, H. D.

    With the aim of developing the application of neutron Compton scattering (NCS) to molecular systems of biophysical interest, we are using the Compton spectrometer EVS at ISIS to characterize the momentum distribution of protons in peptide groups. In this contribution we present NCS measurements of the recoil peak (Compton profile) due to the amide proton in otherwise fully deuterated acetanilide (ACN), a widely studied model system for H-bonding and energy transfer in biomolecules. We obtain values for the average width of the potential well of the amide proton and its mean kinetic energy. Deviations from the Gaussian form of the Compton profile, analyzed on the basis of an expansion due to Sears, provide data relating to the Laplacian of the proton potential.

  20. Neutron scattering from charged polymer lattices

    SciTech Connect

    Hayter, J.B.

    1987-12-02

    Aqueous suspensions of charged polymer latex particles exhibit several forms of ordered structure, the particular form depending on the size, number density and charge of the latex particles, and on the ionic strength of the aqueous medium. At low ionic strength, the inter-particle potential may become sufficiently long-ranged to generate crystalline order, which usually shows bcc symmetry at low density and becomes fcc above about 3% volume fraction of latex in the system. As the ionic strength increases, the crystalline structure melts, and ordered liquid structures develop. This paper reviews some of the recent small-angle neutron scattering experiments on polymer latex suspensions, in the light of new theoretical methods which permit in situ analysis of the particle size and charge. The discussion also encompasses new experimental methods for studying latex structures under dynamic shear conditions.

  1. Confined dynamics in poly(ethylene terephthalate): a coherent and incoherent neutron scattering study

    NASA Astrophysics Data System (ADS)

    Sanz, Alejandro; Nogales, Aurora; Puente-Orench, Inés; García-Gutiérrez, Mari-Cruz; Campo, Javier; Haussler, Wolfgang; Soccio, Michelina; Lotti, Nadia; Munari, Andrea; Ezquerra, Tiberio A.

    2014-11-01

    We show that the combination of dielectric relaxation with neutron spin echo and incoherent neutron backscattering measurements performed in deuterated and protonated poly(ethylene terephthalate) suggests that the intrinsic dynamics of semicrystalline polymers occurs in an homogeneous scenario, similar to that valid to describe the dynamics of totally amorphous polymers. The quasielastic neutron scattering data are satisfactorily described by a theoretical model that considers that the proton mobility follows a random jump-diffusion in a restricted environment.

  2. Neutron beam characterization measurements at the Manuel Lujan Jr. neutron scattering center

    SciTech Connect

    Mocko, Michal; Muhrer, Guenter; Daemen, Luke L; Kelsey, Charles T; Duran, Michael A; Tovesson, Fredrik K

    2010-01-01

    We have measured the neutron beam characteristics of neutron moderators at the Manuel Lujan Jr. Neutron Scattering Center at LANSCE. The absolute thermal neutron flux, energy spectra and time emission spectra were measured for the high resolution and high intensity decoupled water, partially coupled liquid hydrogen and partially coupled water moderators. The results of our experimental study will provide an insight into aging of different target-moderator-reflector-shield components as well as new experimental data for benchmarking of neutron transport codes.

  3. Local structures of polar wurtzites Zn1-xMgxO studied by raman and 67Zn/25Mg NMR spectroscopies and by total neutron scattering

    SciTech Connect

    Proffen, Thomas E; Kim, Yiung- Il; Cadars, Sylvian; Shayib, Ramzy; Feigerle, Charles S; Chmelka, Bradley F; Seshadri, Ram

    2008-01-01

    Research in the area of polar semiconductor heterostructures has been growing rapidly, driven in large part by interest in two-dimensional electron gas (2DEG) systems. 2DEGs are known to form at heterojunction interfaces that bear polarization gradients. They can display extremely high electron mobilities, especially at low temperatures, owing to spatial confinement of carrier motions. Recent reports of 2DEG behaviors in Ga{sub 1-x}Al{sub x}N/GaN and Zn{sub 1-x}Mg{sub x}O/ZnO heterostructures have great significance for the development of quantum Hall devices and novel high-electron-mobility transistors (HEMTs). 2DEG structures are usually designed by interfacing a polar semiconductor with its less or more polar alloys in an epitaxial manner. Since the quality of the 2DEG depends critically on interface perfection, as well as the polarization gradient at the heterojunction, understanding compositional and structural details of the parent and alloy semiconductors is an important component in 2DEG design and fabrication. Zn{sub 1-x}Mg{sub x}O/ZnO is one of the most promising heterostructure types for studies of 2DEGs, due to the large polarization of ZnO, the relatively small lattice mismatch, and the large conduction band offsets in the Zn{sub 1-x}Mg{sub x}O/ZnO heterointerface. Although 2DEG formation in Zn{sub 1-x}Mg{sub x}O/ZnO heterostructures have been researched for some time, a clear understanding of the alloy structure of Zn{sub 1-x}Mg{sub x}O is currently lacking. Here, we conduct a detailed and more precise study of the local structure of Zn{sub 1-x}Mg{sub x}O alloys using Raman and solid-state nuclear magnetic resonance (NMR), in conjunction with neutron diffraction techniques.

  4. Impact of the Cryogen Free Revolution on Neutron Scattering Laboratories

    NASA Astrophysics Data System (ADS)

    Kirichek, Oleg

    A global shortage of helium gas can seriously jeopardise the scientific programmes of neutron scattering laboratories due to the use of cryogenic sample environment in the majority of the neutron scattering experiments. Recently developed cryogen-free technology allows a significant reduction or even a complete elimination of liquid helium consumption. Here we review the impact of the cryogen-free revolution on cryogenic equipment used at large neutron facilities, such as cryostats, dilution refrigerators, superconducting magnets and other cryogenic systems. Particular attention is given to the newly developed superconducting magnets for neutron diffraction and spectroscopy experiments. Use of the cryogen-free approach, as well as cutting-edge superconducting magnet technology and advanced neutron optics allows researcher to achieve extraordinary performance in their experiments, opening up new opportunities in neutron scattering research.

  5. Quasielastic neutron scattering in biology: Theory and applications

    DOE PAGES

    Vural, Derya; Hu, Xiaohu; Lindner, Benjamin; ...

    2016-06-15

    Neutrons scatter quasielastically from stochastic, diffusive processes, such as overdamped vibrations, localized diffusion and transitions between energy minima. In biological systems, such as proteins and membranes, these relaxation processes are of considerable physical interest. We review here recent methodological advances and applications of quasielastic neutron scattering (QENS) in biology, concentrating on the role of molecular dynamics simulation in generating data with which neutron profiles can be unambiguously interpreted. We examine the use of massively-parallel computers in calculating scattering functions, and the application of Markov state modeling. The decomposition of MD-derived neutron dynamic susceptibilities is described, and the use of thismore » in combination with NMR spectroscopy. We discuss dynamics at very long times, including approximations to the infinite time mean-square displacement and nonequilibrium aspects of single-protein dynamics. Lastly, we examine how neutron scattering and MD can be combined to provide information on lipid nanodomains.« less

  6. Quasielastic neutron scattering in biology: Theory and applications

    SciTech Connect

    Vural, Derya; Hu, Xiaohu; Lindner, Benjamin; Jain, Nitin; Miao, Yinglong; Cheng, Xiaolin; Liu, Zhuo; Hong, Liang; Smith, Jeremy C.

    2016-06-15

    Neutrons scatter quasielastically from stochastic, diffusive processes, such as overdamped vibrations, localized diffusion and transitions between energy minima. In biological systems, such as proteins and membranes, these relaxation processes are of considerable physical interest. We review here recent methodological advances and applications of quasielastic neutron scattering (QENS) in biology, concentrating on the role of molecular dynamics simulation in generating data with which neutron profiles can be unambiguously interpreted. We examine the use of massively-parallel computers in calculating scattering functions, and the application of Markov state modeling. The decomposition of MD-derived neutron dynamic susceptibilities is described, and the use of this in combination with NMR spectroscopy. We discuss dynamics at very long times, including approximations to the infinite time mean-square displacement and nonequilibrium aspects of single-protein dynamics. Lastly, we examine how neutron scattering and MD can be combined to provide information on lipid nanodomains.

  7. Neutron scattering investigations of frustated magnets

    NASA Astrophysics Data System (ADS)

    Fennell, Tom

    This thesis describes the experimental investigation of frustrated magnetic systems based on the pyrochlore lattice of corner-sharing tetrahedra. Ho2Ti207 and Dy2Ti207 are examples of spin ices, in which the manifold of disordered magnetic groundstates maps onto that of the proton positions in ice. Using single crystal neutron scattering to measure Bragg and diffuse scattering, the effect of applying magnetic fields along different directions in the crystal was investigated. Different schemes of degeneracy removal were observed for different directions. Long and short range order, and the coexistence of both could be observed by this technique.The field and temperature dependence of magnetic ordering was studied in Ho2Ti207 and Dy2Ti207. Ho2Ti2()7 has been more extensively investigated. The field was applied on [00l], [hh0], [hhh] and [hh2h]. Dy2Ti207 was studied with the field applied on [00l] and [hho] but more detailed information about the evolution of the scattering pattern across a large area of reciprocal space was obtained.With the field applied on [00l] both materials showed complete degeneracy removal. A long range ordered structure was formed. Any magnetic diffuse scattering vanished and was entirely replaced by strong magnetic Bragg scattering. At T =0.05 K both materials show unusual magnetization curves, with a prominent step and hysteresis. This was attributed to the extremely slow dynamics of spin ice materials at this temperature.Both materials were studied in greatest detail with the field applied on [hh0]. The coexistence of long and short range order was observed when the field was raised at T = 0.05 K. The application of a field in this direction separated the spin system into two populations. One could be ordered by the field, and one remained disordered. However, via spin-spin interactions, the field restricted the degeneracy of the disordered spin population. The neutron scattering pattern of Dy2Ti207 shows that the spin system was separated

  8. Point Scattered Function (PScF) for fast neutron radiography

    NASA Astrophysics Data System (ADS)

    Hassan, Mohamed H.

    2009-08-01

    Fast neutron radiography opened up a new range of possibilities to image extremely dense objects. The removal of the scattering effect is one of the most challenging problems in neutron imaging. Neutron scattering in fast neutron radiography did not receive much attention compared with X-ray and thermal neutron radiography. The purpose of this work is to investigate the behavior of the Point Scattered Function (PScF) as applied in fast neutron radiography. The PScF was calculated using MCNP as a spatial distribution of scattered neutrons over the detector surface for one emitting source element. Armament and explosives materials, namely, Rifle steel, brass, aluminum and trinitrotoluene (TNT) were simulated. Effect of various sample thickness and sample-to-detector distance were considered. Simulated sample geometries included a slab with varying thickness, a sphere with varying radii, and a cylinder with varying base radii. Different neutron sources, namely, Cf-252, DT as well as DD neutron sources were considered. Neutron beams with zero degree divergence angle; and beams with varying angles related to the normal to the source plane were simulated. Curve fitting of the obtained PScF, in the form of Gaussian function, were given to be used in future work using image restoration codes. Analytical representation of the height as well as the Full Width at Half Maximum (FWHM) of the obtained Gaussian functions eliminates the need to calculate the PScF for sample parameters that were not investigated in this study.

  9. LANSCE '90: The Manuel Lujan Jr. Neutron Scattering Center

    SciTech Connect

    Pynn, R.

    1990-01-01

    This paper describes progress that has been made at the Manuel Lujan Jr. Neutron Scattering Center (LANSCE) during the past two years. Presently, LANSCE provides a higher peak neutron flux than any other pulsed spallation neutron source. There are seven spectrometers for neutron scattering experiments that are operated for a national user program sponsored by the US Department of Energy. Two more spectrometers are under construction. Plans have been made to raise the number of beam holes available for instrumentation and to improve the efficiency of the target/moderator system. 9 refs., 4 figs.

  10. Early history of neutron scattering at Oak Ridge

    SciTech Connect

    Wilkinson, M.K.

    1985-07-01

    Most of the early development of neutron scattering techniques utilizing reactor neutrons occurred at the Oak Ridge National Laboratory during the years immediately following World War II. C.G. Shull, E.O. Wollan, and their associates systematically established neutron diffraction as a quantitative research tool and then applied this technique to important problems in nuclear physics, chemical crystallography, and magnetism. This article briefly summarizes the very important research at ORNL during this period, which laid the foundation for the establishment of neutron scattering programs throughout the world. 47 refs., 10 figs.

  11. Absolute cross-section normalization of magnetic neutron scattering data.

    PubMed

    Xu, Guangyong; Xu, Zhijun; Tranquada, J M

    2013-08-01

    We discuss various methods to obtain the resolution volume for neutron scattering experiments, in order to perform absolute normalization on inelastic magnetic neutron scattering data. Examples from previous experiments are given. We also try to provide clear definitions of a number of physical quantities which are commonly used to describe neutron magnetic scattering results, including the dynamic spin correlation function and the imaginary part of the dynamic susceptibility. Formulas that can be used for general purposes are provided and the advantages of the different normalization processes are discussed.

  12. Absolute cross-section normalization of magnetic neutron scattering data

    NASA Astrophysics Data System (ADS)

    Xu, Guangyong; Xu, Zhijun; Tranquada, J. M.

    2013-08-01

    We discuss various methods to obtain the resolution volume for neutron scattering experiments, in order to perform absolute normalization on inelastic magnetic neutron scattering data. Examples from previous experiments are given. We also try to provide clear definitions of a number of physical quantities which are commonly used to describe neutron magnetic scattering results, including the dynamic spin correlation function and the imaginary part of the dynamic susceptibility. Formulas that can be used for general purposes are provided and the advantages of the different normalization processes are discussed.

  13. A neutron imaging device for sample alignment in a pulsed neutron scattering instrument

    SciTech Connect

    Grazzi, F.; Scherillo, A.; Zoppi, M.

    2009-09-15

    A neutron-imaging device for alignment purposes has been tested on the INES beamline at ISIS, the pulsed neutron source of Rutherford Appleton Laboratory (U.K.). Its use, in conjunction with a set of movable jaws, turns out extremely useful for scattering application to complex samples where a precise and well-defined determination of the scattering volume is needed.

  14. A neutron imaging device for sample alignment in a pulsed neutron scattering instrument

    NASA Astrophysics Data System (ADS)

    Grazzi, F.; Scherillo, A.; Zoppi, M.

    2009-09-01

    A neutron-imaging device for alignment purposes has been tested on the INES beamline at ISIS, the pulsed neutron source of Rutherford Appleton Laboratory (U.K.). Its use, in conjunction with a set of movable jaws, turns out extremely useful for scattering application to complex samples where a precise and well-defined determination of the scattering volume is needed.

  15. Studies of 54,56Fe Neutron Scattering Cross Sections

    NASA Astrophysics Data System (ADS)

    Hicks, S. F.; Vanhoy, J. R.; French, A. J.; Henderson, S. L.; Howard, T. J.; Pecha, R. L.; Santonil, Z. C.; Crider, B. P.; Liu, S.; McEllistrem, M. T.; Peters, E. E.; Prados-Estévez, F. M.; Ross, T. J.; Yates, S. W.

    2015-05-01

    Elastic and inelastic neutron scattering differential cross sections and γ-ray production cross sections have been measured on 54,56Fe at several incident energies in the fast neutron region between 1.5 and 4.7 MeV. All measurements were completed at the University of Kentucky Accelerator Laboratory (UKAL) using a 7-MV Model CN Van de Graaff accelerator, along with the neutron production and neutron and γ-ray detection systems located there. The facilities at UKAL allow the investigation of both elastic and inelastic scattering with nearly mono-energetic incident neutrons. Time-of-flight techniques were used to detect the scattered neutrons for the differential cross section measurements. The measured cross sections are important for fission reactor applications and also for testing global model calculations such as those found at ENDF, since describing both the elastic and inelastic scattering is important for determining the direct and compound components of the scattering mechanism. The γ-ray production cross sections are used to determine cross sections to unresolved levels in the neutron scattering experiments. Results from our measurements and comparisons to model calculations are presented.

  16. NEUTRON SPECTROSCOPY BY DOUBLE SCATTER AND ASSOCIATED PARTICLE TECHNIQUES.

    SciTech Connect

    DIOSZEGI,I.

    2007-10-28

    Multiple detectors can provide [1,2] both directional and spectroscopic information. Neutron spectra may be obtained by neutron double scatter (DSNS), or the spontaneous fission associated particle (AP) technique. Spontaneous fission results in the creation of fission fragments and the release of gamma rays and neutrons. As these occur at the same instant, they are correlated in time. Thus gamma ray detection can start a timing sequence relative to a neutron detector where the time difference is dominated by neutron time-of-flight. In this paper we describe these techniques and compare experimental results with Monte Carlo calculations.

  17. Modern Techniques for Inelastic Thermal Neutron Scattering Analysis

    NASA Astrophysics Data System (ADS)

    Hawari, A. I.

    2014-04-01

    A predictive approach based on ab initio quantum mechanics and/or classical molecular dynamics simulations has been formulated to calculate the scattering law, S(κ⇀,ω), and the thermal neutron scattering cross sections of materials. In principle, these atomistic methods make it possible to generate the inelastic thermal neutron scattering cross sections of any material and to accurately reflect the physical conditions of the medium (i.e, temperature, pressure, etc.). In addition, the generated cross sections are free from assumptions such as the incoherent approximation of scattering theory and, in the case of solids, crystalline perfection. As a result, new and improved thermal neutron scattering data libraries have been generated for a variety of materials. Among these are materials used for reactor moderators and reflectors such as reactor-grade graphite and beryllium (including the coherent inelastic scattering component), silicon carbide, cold neutron media such as solid methane, and neutron beam filters such as sapphire and bismuth. Consequently, it is anticipated that the above approach will play a major role in providing the nuclear science and engineering community with its needs of thermal neutron scattering data especially when considering new materials where experimental information may be scarce or nonexistent.

  18. Neutron scattering studies in the actinide region. Progress report, August 1, 1992--July 31, 1993

    SciTech Connect

    Kegel, G.H.R.; Egan, J.J.

    1993-09-01

    This report discusses the following topics: Prompt fission neutron energy spectra for {sup 235}U and {sup 239}Pu; Two-parameter measurement of nuclear lifetimes; ``Black`` neutron detector; Data reduction techniques for neutron scattering experiments; Inelastic neutron scattering studies in {sup 197}Au; Elastic and inelastic scattering studies in {sup 239}Pu; and neutron induced defects in silicon dioxide MOS structures.

  19. Model for neutron total cross-section at low energies for nuclear grade graphite

    NASA Astrophysics Data System (ADS)

    Galván Josa, V. M.; Dawidowski, J.; Santisteban, J. R.; Malamud, F.; Oliveira, R. G.

    2015-04-01

    At subthermal neutron energies, polycrystalline graphite shows a large total cross-section due to small angle scattering processes. In this work, a new methodology to determine pore size distributions through the neutron transmission technique at subthermal energies is proposed and its sensitivity is compared with standard techniques. A simple model based on the form factor for spherical particles, normally used in the Small Angle Neutron Scattering technique, is employed to calculate the contribution of small angle effect to the total scattering cross-section, with the width and center of the radii distributions as free parameters in the model. Small Angle X-ray Scattering experiments were performed to compare results as a means to validate the method. The good agreement reached reveals that the neutron transmission technique is a useful tool to explore small angle scattering effects. This fact can be exploited in situations where large samples must be scanned and it is difficult to investigate them with conventional methods. It also opens the possibility to apply this method in energy-resolved neutron imaging. Also, since subthermal neutron transmission experiments are perfectly feasible in small neutron sources, the present findings open new possibilities to the work done in such kind of facilities.

  20. Towards neutron scattering experiments with sub-millisecond time resolution

    DOE PAGES

    Adlmann, F. A.; Gutfreund, Phillip; Ankner, John Francis; ...

    2015-02-01

    Neutron scattering techniques offer several unique opportunities in materials research. However, most neutron scattering experiments suffer from the limited flux available at current facilities. This limitation becomes even more severe if time-resolved or kinetic experiments are performed. A new method has been developed which overcomes these limitations when a reversible process is studied, without any compromise on resolution or beam intensity. We demonstrate that, by recording in absolute time the neutron detector events linked to an excitation, information can be resolved on sub-millisecond timescales. Specifically, the concept of the method is demonstrated by neutron reflectivity measurements in time-of-flight mode atmore » the Liquids Reflectometer located at the Spallation Neutron Source, Oak Ridge National Laboratory, Tennessee, USA, combined with in situ rheometry. Finally, the opportunities and limitations of this new technique are evaluated by investigations of a micellar polymer solution offering excellent scattering contrast combined with high sensitivity to shear.« less

  1. Towards neutron scattering experiments with sub-millisecond time resolution

    SciTech Connect

    Adlmann, F. A.; Gutfreund, Phillip; Ankner, John Francis; Browning, James F.; Parizzi, Andre A.; Vacaliuc, Bogdan; Halbert, Candice E.; Rich, J. P.; Dennison, A. J. C.; Wolff, Max

    2015-02-01

    Neutron scattering techniques offer several unique opportunities in materials research. However, most neutron scattering experiments suffer from the limited flux available at current facilities. This limitation becomes even more severe if time-resolved or kinetic experiments are performed. A new method has been developed which overcomes these limitations when a reversible process is studied, without any compromise on resolution or beam intensity. We demonstrate that, by recording in absolute time the neutron detector events linked to an excitation, information can be resolved on sub-millisecond timescales. Specifically, the concept of the method is demonstrated by neutron reflectivity measurements in time-of-flight mode at the Liquids Reflectometer located at the Spallation Neutron Source, Oak Ridge National Laboratory, Tennessee, USA, combined with in situ rheometry. Finally, the opportunities and limitations of this new technique are evaluated by investigations of a micellar polymer solution offering excellent scattering contrast combined with high sensitivity to shear.

  2. APPARATUS FOR MEASURING TOTAL NEUTRON CROSS SECTIONS

    DOEpatents

    Cranberg, L.

    1959-10-13

    An apparatus is described for measuring high-resolution total neutron cross sections at high counting rate in the range above 50-kev neutron energy. The pulsed-beam time-of-flight technique is used to identify the neutrons of interest which are produced in the target of an electrostatic accelerator. Energy modulation of the accelerator . makes it possible to make observations at 100 energy points simultaneously. 761O An apparatus is described for monitoring the proton resonance of a liquid which is particulariy useful in the continuous purity analysis of heavy water. A hollow shell with parallel sides defines a meander chamber positioned within a uniform magnetic fieid. The liquid passes through an inlet at the outer edge of the chamber and through a spiral channel to the central region of the chamber where an outlet tube extends into the chamber perpendicular to the magnetic field. The radiofrequency energy for the monitor is coupled to a coil positioned coaxially with the outlet tube at its entrance point within the chamber. The improvement lies in the compact mechanical arrangement of the monitor unit whereby the liquid under analysis is subjected to the same magnetic field in the storage and sensing areas, and the entire unit is shielded from external electrostatic influences.

  3. Neutron scattering of iron-based superconductors

    SciTech Connect

    Shamoto, S; Wakimoto, S; Kodama, K.; Ishikado, Motoyuki; Christianson, Andrew D; Lumsden, Mark D; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Arai, Masatoshi; Kakurai, K.; Esaka, Fumitaka; Iyo, Akira; Kito, Hijiri; Eisaki, Hiroshi

    2011-01-01

    Low-energy spin excitations have been studied on polycrystalline LaFeAsO{sub 1-x}F{sub x} samples by inelastic neutron scattering. The Q-integrated dynamical spin susceptibility {chi}{double_prime}({omega}) of the superconducting samples is found to be comparable to that of the magnetically ordered parent sample. On the other hand, {chi}{double_prime}({omega}) almost vanishes at x = 0.158, where the superconducting transition temperature T{sub c} is suppressed to 7 K. In addition, {chi}{double_prime}({omega}) in optimally doped LaFeAsO{sub 0.918}F{sub 0.082} with T{sub c} = 29 K exhibits a spin resonance mode. The peak energy, E{sub res}, when scaled by k{sub B}T{sub c} is similar to the value of about 4.7 reported in other high-T{sub c} iron-based superconductors. This result suggests that there is intimate relationship between the dynamical spin susceptibility and high-T{sub c} superconductivity in iron-based superconductors, and is consistent with a nesting condition between Fermi surfaces at the {Gamma} and M points.

  4. Neutron Scattering from Magnetically Frustrated Ruthenium Pyrochlores

    NASA Astrophysics Data System (ADS)

    Broholm, Collin

    2008-03-01

    Spin-1 ruthenium pyrochlores feature strong exchange interactions and deeply suppressed N'eel ordering. In addition a doping induced metallic phase has been demonstrated. I discuss neutron scattering experiments that explore the strongly frustrated quantum magnetism of Y2Ru2O7 [1] and Pr2-xBixRu2O7 [2]. In Y2Ru2O7 (θCW= --1100 K, TN=77 K) much of the magnetic spectral weight is concentrated in a 20 meV spectral peak above an 11 meV low temperature gap in the excitation spectrum. In Pr2-xBixRu2O7 magnetic order which occurs for T

  5. Multiple magnetic scattering in small-angle neutron scattering of Nd–Fe–B nanocrystalline magnet

    PubMed Central

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P.; Keiderling, Uwe; Ono, Kanta

    2016-01-01

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd–Fe–B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd–Fe–B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd–Fe–B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters. PMID:27321149

  6. Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

    PubMed

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

    2016-06-20

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

  7. Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet

    NASA Astrophysics Data System (ADS)

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P.; Keiderling, Uwe; Ono, Kanta

    2016-06-01

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

  8. Chemical Binding Effects in Neutron Resonance Scattering and Absorption.

    NASA Astrophysics Data System (ADS)

    Shamaoun, Adib Iskandar

    The Doppler broadening of neutron absorption and scattering resonances is an effect of considerable importance in calculating reactor parameters. This broadening is known to depend upon the state of the atom from which the scattering of the neutron occurs. This dependence is called the chemical binding effect. A key assumption in the usual computations of Doppler broadening is to ignore the dependence of the total resonance width on the chemical binding state of the compound nucleus. This is an excellent approximation for the gamma line. We derive an expression for the neutron line width as a function of the energy of the compound nucleus for an ideal gas. The influence of energy on the width with energy is examined at two different temperatures 4K and 1000K. It is found that these effects are very small, of the order of 10^{4-} . The assumption of constancy of the resonance width is thus shown to be a good approximation for the neutron line width. Also we examine the influence of the crystalline binding on the 6.67 eV resonance energy of U-238 line shape in uranium carbide and uranium dioxide. This model treats the crystal as a gas with an effective temperature and an effective mass determined by harmonic crystal phonon spectrum developed by Koppel and Houston. Based on this model, the line shape of U-238 is Gaussian plus a recoilless part. We also compute the broadening using a harmonic crystal model. As the temperature of U-238 target is decreased, disagreement between the two models becomes pronounced. However the results agree in the limiting case of high temperature. As the nucleus becomes more tightly bound, shifts in the resonance peak to lower energies are also observed. A general formula for the differential scattering cross section is developed starting from the transition probability (T-matrix). The formalism is applied to the gas and harmonic crystal models to determine the chemical binding effect. Although the resonance broadening is determined in

  9. Total body nitrogen analysis. [neutron activation analysis

    NASA Technical Reports Server (NTRS)

    Palmer, H. E.

    1975-01-01

    Studies of two potential in vivo neutron activation methods for determining total and partial body nitrogen in animals and humans are described. A method using the CO-11 in the expired air as a measure of nitrogen content was found to be adequate for small animals such as rats, but inadequate for human measurements due to a slow excretion rate. Studies on the method of measuring the induced N-13 in the body show that with further development, this method should be adequate for measuring muscle mass changes occurring in animals or humans during space flight.

  10. Incoherent Neutron Scattering Measurements of Hydrogen-Charged Zircaloy-4

    SciTech Connect

    Garlea, Elena; Choo, Hahn; Garlea, Vasile O; Liaw, Peter K; Hubbard, Camden R

    2007-01-01

    Qualitative and quantitative phase measurements were conducted on Zircaloy-4 round bars using neutron scattering techniques. The mapping through the thickness of the specimens using neutron diffraction showed the presence of the face-centered-cubic delta zirconium hydride ({delta}-ZrH{sub 2}) phase on the surface. To determine the relative amount of hydrogen in the Zircaloy-4 samples, the increase of the incoherent scattering with the hydrogen content was calibrated using standard samples for which the hydrogen content was known.

  11. In-situ soil carbon analysis using inelastic neutron scattering

    USDA-ARS?s Scientific Manuscript database

    In situ soil carbon analysis using inelastic neutron scattering (INS) is based on the emission of 4.43 MeV gamma rays from carbon nuclei excited by fast neutrons. This in-situ method has excellent potential for easily measuring soil carbon since it does not require soil core sampling and processing ...

  12. The interpretation of polycrystalline coherent inelastic neutron scattering from aluminium

    PubMed Central

    Roach, Daniel L.; Ross, D. Keith; Gale, Julian D.; Taylor, Jon W.

    2013-01-01

    A new approach to the interpretation and analysis of coherent inelastic neutron scattering from polycrystals (poly-CINS) is presented. This article describes a simulation of the one-phonon coherent inelastic scattering from a lattice model of an arbitrary crystal system. The one-phonon component is characterized by sharp features, determined, for example, by boundaries of the (Q, ω) regions where one-phonon scattering is allowed. These features may be identified with the same features apparent in the measured total coherent inelastic cross section, the other components of which (multiphonon or multiple scattering) show no sharp features. The parameters of the model can then be relaxed to improve the fit between model and experiment. This method is of particular interest where no single crystals are available. To test the approach, the poly-CINS has been measured for polycrystalline aluminium using the MARI spectrometer (ISIS), because both lattice dynamical models and measured dispersion curves are available for this material. The models used include a simple Lennard-Jones model fitted to the elastic constants of this material plus a number of embedded atom method force fields. The agreement obtained suggests that the method demonstrated should be effective in developing models for other materials where single-crystal dispersion curves are not available. PMID:24282332

  13. Crystal structure and local structure of Mg(2-x)Pr(x)Ni4 (x = 0.6 and 1.0) deuteride using in situ neutron total scattering.

    PubMed

    Sakaki, K; Terashita, N; Kim, H; Proffen, T; Majzoub, E H; Tsunokake, S; Nakamura, Y; Akiba, E

    2013-06-17

    We studied crystal structure and local structure of Mg(2-x)Pr(x)Ni4 (x = 0.6 and 1.0) and their deuterides using in situ neutron total scattering and first-principles calculations. The total scattering data were analyzed using Rietveld refinement and pair distribution function analysis (PDF). The crystal structure of Mg(2-x)Pr(x)Ni4 before deuterium absorption was C15b in space group F43m. No difference between the crystal and local (PDF) structures was observed. The crystal structure of Mg1.0Pr1.0Ni4D(∼4) was found to be orthorhombic in space group Pmn2(1), with three deuterium occupation sites: PrNi3 and two types of bipyramidal Pr2MgNi2 that have a plane of symmetry composed of MgNi2. There is no significant difference between the crystal structure and the local structure of Mg1.0Pr1.0Ni4D(∼4). On the other hand, the average crystal structure of the Mg-rich Mg1.4Pr0.6Ni4D(∼3.6) was C15b with two deuterium occupation sites: PrNi3 and MgPrNi2 suggesting that the deuterium occupation shifts away from the Pr2MgNi2 bipyramid. First-principles relaxed structures also showed the shift of the hydrogen occupation site toward the Pr atom of the bipyramid, when induced by Mg substitution for the opposing Pr, resulting in hydrogen occupation in the MgPrNi2 tetrahedral site. The PDF pattern of Mg1.4Pr0.6Ni4D(∼3.6) cannot be refined below 7.2 Å in atomic distances using the C15b structure which was obtained from Rietveld refinement but can be done using an orthorhombic structure. It suggests that Mg1.4Pr0.6Ni4D(∼3.6) was locally distorted to the orthorhombic.

  14. Neutron scattering for materials science. Materials Research Society proceedings

    SciTech Connect

    Shapiro, S.M. ); Moss, S.C. ); Jorgensen, J.D. )

    1990-01-01

    Neutron Scattering is by now a well-established technique which has been used by condensed matter scientists to probe both the structure and the dynamical interactions in solids and liquids. The use of neutron scattering methods in materials science research has in turn increased dramatically in recent years. The symposium presented in this book was assembled to bring together scientists with a wide range of interest, including high-T{sub c} superconducting materials, phase transformations, neutron depth profiling, structure and dynamics of glasses and liquids, surfaces and interfaces, porous media, intercalation compounds and lower dimensional systems, structure and dynamics of polymers, residual stress analysis, ordering and phase separation in alloys, and magnetism in alloys and multilayers. The symposium included talks covering the latest advances in broad areas of interest such as Rietveld structure refinement, triple axis spectrometry, quasi elastic scattering and diffusion, small angle scattering and surface scattering.

  15. Anomalous neutron Compton scattering cross sections in ammonium hexachlorometallates

    NASA Astrophysics Data System (ADS)

    Krzystyniak, M.; Chatzidimitriou-Dreismann, C. A.; Lerch, M.; Lalowicz, Z. T.; Szymocha, A.

    2007-03-01

    The authors have performed neutron Compton scattering measurements on ammonium hexachloropalladate (NH4)2PdCl6 and ammonium hexachlorotellurate (NH4)2TeCl6. Both substances belong to the family of ammonium metallates. The aim of the experiment was to investigate the possible role of electronic environment of a proton on the anomaly of the neutron scattering intensity. The quantity of interest that was subject to experimental test was the reduction factor of the neutron scattering intensities. In both samples, the reduction factor was found to be smaller than unity, thus indicating the anomalous neutron Compton scattering from protons. Interestingly, the anomaly decreases with decreasing scattering angle and disappears at the lowest scattering angle (longest scattering time). The dependence of the amount of the anomaly on the scattering angle (scattering time) is the same in both substances (within experimental error). Also, the measured widths of proton momentum distributions are equal in both metallates. This is consistent with the fact that the attosecond proton dynamics of ammonium cations is fairly well decoupled from the dynamics of the sublattice of the octahedral anions PdCl62- and TeCl62-, respectively. The hypothesis is put forward that proton-electron decoherence processes are responsible for the considered effect. Decoherence processes may have to do rather with the direct electronic environment of ammonium protons and not with the electronic structure of the metal-chlorine bond.

  16. Spin echo small angle neutron scattering using a continuously pumped {sup 3}He neutron polarisation analyser

    SciTech Connect

    Parnell, S. R.; Li, K.; Yan, H.; Stonaha, P.; Li, F.; Wang, T.; Baxter, D. V.; Snow, W. M.; Washington, A. L.; Walsh, A.; Chen, W. C.; Parnell, A. J.; Fairclough, J. P. A.; Pynn, R.

    2015-02-15

    We present a new instrument for spin echo small angle neutron scattering (SESANS) developed at the Low Energy Neutron Source at Indiana University. A description of the various instrument components is given along with the performance of these components. At the heart of the instrument are a series of resistive coils to encode the neutron trajectory into the neutron polarisation. These are shown to work well over a broad range of neutron wavelengths. Neutron polarisation analysis is accomplished using a continuously operating neutron spin filter polarised by Rb spin-exchange optical pumping of {sup 3}He. We describe the performance of the analyser along with a study of the {sup 3}He polarisation stability and its implications for SESANS measurements. Scattering from silica Stöber particles is investigated and agrees with samples run on similar instruments.

  17. Hierarchical Pore Morphology of Cretaceous Shale: A Small-Angle Neutron Scattering and Ultrasmall-Angle Neutron Scattering Study

    DOE PAGES

    Bahadur, J.; Melnichenko, Y. B.; Mastalerz, Maria; ...

    2014-09-25

    Shale reservoirs are becoming an increasingly important source of oil and natural gas supply and a potential candidate for CO2 sequestration. Understanding the pore morphology in shale may provide clues to making gas extraction more efficient and cost-effective. The porosity of Cretaceous shale samples from Alberta, Canada, collected from different depths with varying mineralogical compositions, has been investigated by small- and ultrasmall-angle neutron scattering. Moreover these samples come from the Second White Specks and Belle Fourche formations, and their organic matter content ranges between 2 and 3%. The scattering length density of the shale specimens has been estimated using themore » chemical composition of the different mineral components. Scattering experiments reveal the presence of fractal and non-fractal pores. It has been shown that the porosity and specific surface area are dominated by the contribution from meso- and micropores. The fraction of closed porosity has been calculated by comparing the porosities estimated by He pycnometry and scattering techniques. There is no correlation between total porosity and mineral components, a strong correlation has been observed between closed porosity and major mineral components in the studied specimens.« less

  18. Hierarchical Pore Morphology of Cretaceous Shale: A Small-Angle Neutron Scattering and Ultrasmall-Angle Neutron Scattering Study

    SciTech Connect

    Bahadur, J.; Melnichenko, Y. B.; Mastalerz, Maria; Furmann, Agnieszka; Clarkson, Chris R.

    2014-09-25

    Shale reservoirs are becoming an increasingly important source of oil and natural gas supply and a potential candidate for CO2 sequestration. Understanding the pore morphology in shale may provide clues to making gas extraction more efficient and cost-effective. The porosity of Cretaceous shale samples from Alberta, Canada, collected from different depths with varying mineralogical compositions, has been investigated by small- and ultrasmall-angle neutron scattering. Moreover these samples come from the Second White Specks and Belle Fourche formations, and their organic matter content ranges between 2 and 3%. The scattering length density of the shale specimens has been estimated using the chemical composition of the different mineral components. Scattering experiments reveal the presence of fractal and non-fractal pores. It has been shown that the porosity and specific surface area are dominated by the contribution from meso- and micropores. The fraction of closed porosity has been calculated by comparing the porosities estimated by He pycnometry and scattering techniques. There is no correlation between total porosity and mineral components, a strong correlation has been observed between closed porosity and major mineral components in the studied specimens.

  19. Data acquisition system for the neutron scattering instruments at the intense pulsed neutron source

    SciTech Connect

    Crawford, R.K.; Daly, R.T.; Haumann, J.R.; Hitterman, R.L.; Morgan, C.B.; Ostrowski, G.E.; Worlton, T.G.

    1981-01-01

    The Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory is a major new user-oriented facility which is now coming on line for basic research in neutron scattering and neutron radiation damage. This paper describes the data-acquisition system which will handle data acquisition and instrument control for the time-of-flight neutron-scattering instruments at IPNS. This discussion covers the scientific and operational requirements for this system, and the system architecture that was chosen to satisfy these requirements. It also provides an overview of the current system implementation including brief descriptions of the hardware and software which have been developed.

  20. Neutron scattering study on U-dichalcogenides

    NASA Astrophysics Data System (ADS)

    Metoki, N.; Kaneko, K.; Ikeda, S.; Sakai, H.; Yamamoto, E.; Haga, Y.; Homma, Y.; Shiokawa, Y.

    2010-03-01

    We will report the results of our recent inelastic neutron scattering study on β-US2. This compound shows a semi-metallic or narrow gap semi-conducting behaviour at room temperature. A clear exponential up-turn of the resistivity in the order of ~106 Ωcm has been observed below 100 K. We found a sharp inelastic peak at the excitation energy of about 7 meV at 8 K. The Q-dependence of the peak intensity is in good agreement with the magnetic form factor of U4+ ion and no clear dispersion relation has been observed. Therefore we concluded that this is a crystalline electric field (CEF) excitation peak. The excitation energy is in good agreement with the CEF level scheme obtained from the susceptibility data. The CEF peak intensity decreases with increasing temperature and becomes much weaker than the calculated temperature factor expected from the CEF level scheme. Furthermore a quasi-elastic response appears, and coexists with a broadened CEF peak at higher temperatures. The quasi-elastic component is not due to phonon, because the temperature dependence of the intensity is inconsistent with calculation. We concluded that this quasi-elastic response is a hybridization effect of U-5f electrons with, most likely, p-electrons of sulfur. It is highly interesting that the energy scale of the CEF peak (~7 meV) is very close to the conduction gap (90K), and the quasi-elastic component appears above the characteristic temperature of about 100 K. Our data strongly suggest that the crossover of 5f character plays an import role for the metal-insulating transition in β-US2.

  1. Large volume high-pressure cell for inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Wang, W.; Sokolov, D. A.; Huxley, A. D.; Kamenev, K. V.

    2011-07-01

    Inelastic neutron scattering measurements typically require two orders of magnitude longer data collection times and larger sample sizes than neutron diffraction studies. Inelastic neutron scattering measurements on pressurised samples are particularly challenging since standard high-pressure apparatus restricts sample volume, attenuates the incident and scattered beams, and contributes background scattering. Here, we present the design of a large volume two-layered piston-cylinder pressure cell with optimised transmission for inelastic neutron scattering experiments. The design and the materials selected for the construction of the cell enable its safe use to a pressure of 1.8 GPa with a sample volume in excess of 400 mm3. The design of the piston seal eliminates the need for a sample container, thus providing a larger sample volume and reduced absorption. The integrated electrical plug with a manganin pressure gauge offers an accurate measurement of pressure over the whole range of operational temperatures. The performance of the cell is demonstrated by an inelastic neutron scattering study of UGe2.

  2. Large volume high-pressure cell for inelastic neutron scattering.

    PubMed

    Wang, W; Sokolov, D A; Huxley, A D; Kamenev, K V

    2011-07-01

    Inelastic neutron scattering measurements typically require two orders of magnitude longer data collection times and larger sample sizes than neutron diffraction studies. Inelastic neutron scattering measurements on pressurised samples are particularly challenging since standard high-pressure apparatus restricts sample volume, attenuates the incident and scattered beams, and contributes background scattering. Here, we present the design of a large volume two-layered piston-cylinder pressure cell with optimised transmission for inelastic neutron scattering experiments. The design and the materials selected for the construction of the cell enable its safe use to a pressure of 1.8 GPa with a sample volume in excess of 400 mm(3). The design of the piston seal eliminates the need for a sample container, thus providing a larger sample volume and reduced absorption. The integrated electrical plug with a manganin pressure gauge offers an accurate measurement of pressure over the whole range of operational temperatures. The performance of the cell is demonstrated by an inelastic neutron scattering study of UGe(2).

  3. Large volume high-pressure cell for inelastic neutron scattering

    SciTech Connect

    Wang, W.; Kamenev, K. V.; Sokolov, D. A.; Huxley, A. D.

    2011-07-15

    Inelastic neutron scattering measurements typically require two orders of magnitude longer data collection times and larger sample sizes than neutron diffraction studies. Inelastic neutron scattering measurements on pressurised samples are particularly challenging since standard high-pressure apparatus restricts sample volume, attenuates the incident and scattered beams, and contributes background scattering. Here, we present the design of a large volume two-layered piston-cylinder pressure cell with optimised transmission for inelastic neutron scattering experiments. The design and the materials selected for the construction of the cell enable its safe use to a pressure of 1.8 GPa with a sample volume in excess of 400 mm{sup 3}. The design of the piston seal eliminates the need for a sample container, thus providing a larger sample volume and reduced absorption. The integrated electrical plug with a manganin pressure gauge offers an accurate measurement of pressure over the whole range of operational temperatures. The performance of the cell is demonstrated by an inelastic neutron scattering study of UGe{sub 2}.

  4. Fast Neutron Inelastic Scattering Cross Sections in THORIUM-232.

    NASA Astrophysics Data System (ADS)

    Ciarcia, Christopher Albert

    Fast neutron inelastic scattering cross sections for levels between 700-1550-keV excitation energy in the actinide nucleus, ('232)Th, have been measured using the (n,n') time-of-flight technique. Two series of measurements were undertaken using neutrons with a typical energy spread of 8-10 keV, generated by the ('7)Li(p,n)('7)Be reaction. These measurments for 125(DEGREES)-differential scattering cross sections were performed over the incident neutron energy regions of (i) 0.950-1.550 MeV, in 50-keV intervals with the time-of-flight spectrometer optimized to detect 0.200 -0.400-MeV scattered neutrons and (ii) 1.200-2.000 MeV, in 100-keV intervals with the time-of-flight spectrometer optimized to detect 0.400-0.800-MeV scattered neutrons. Over these scattered energy regions, an overall energy resolution of less than 15 keV was maintained. The relative neutron fluence was determined for each individual measurement, by positioning the main detector at 0(DEGREES) to view the primary neutron flux. Relative normalization was achieved by measuring the direct neutron flux from the lithium target with a fixed overhead monitor detector in both measurements. Main detector response was determined by comparison with a ('235)U fission chamber of known efficiency. Techniques for unfolding the complicated spectra obtained from these (n,n') studies were developed, employing user interactive computer codes to (i) generate simulated scattered neutron group response functions, (ii) subtract background effects from the measured spectra, (iii) approximate the background subtracted spectra in a weighted least-squares fashion by a superposition of response functions and (iv) make corrections for neutron absorption, finite scatterer size effects and multiple neutron scattering. Support codes consisting of graphics interaction packages, data file manipulation and transfer utility routines were created to assist in the spectral analysis procedure. Excitation function and angular distribution

  5. 2010 American Conference on Neutron Scattering (ACNS 2010)

    SciTech Connect

    Billinge, Simon

    2011-06-17

    The ACNS provides a focal point for the national neutron user community to strengthen ties within this diverse group, while at the same time promoting neutron research among colleagues in related disciplines identified as “would-be” neutron users. The American Conference on Neutron Scattering thus serves a dual role as a national user meeting and a scientific meeting. As a venue for scientific exchange, the ACNS showcases recent results and provides forums for scientific discussion of neutron research in diverse fields such as hard and soft condensed matter, liquids, biology, magnetism, engineering materials, chemical spectroscopy, crystal structure, and elementary excitations, fundamental physics and development of neutron instrumentation through a combination of invited talks, contributed talks and poster sessions. As a “super-user” meeting, the ACNS fulfills the main objectives of users' meetings previously held periodically at individual national neutron facilities, with the advantage of a larger and more diverse audience. To this end, each of the major national neutron facilities (NIST, LANSCE, HFIR and SNS) have an opportunity to exchange information and update users, and potential users, of their facility. This is also an appropriate forum for users to raise issues that relate to the facilities. For many of the national facilities, this super-user meeting should obviate the need for separate user meetings that tax the time, energy and budgets of facility staff and the users alike, at least in years when the ACNS is held. We rely upon strong participation from the national facilities. The NSSA intends that the American Conference on Neutron Scattering (ACNS) will occur approximately every two years, but not in years that coincide with the International or European Conferences on Neutron Scattering. The ACNS is to be held in association with one of the national neutron centers in a rotating sequence, with the host facility providing local organization

  6. A method for using neutron elastic scatter to create a variable energy neutron beam from a nearly monoenergetic neutron source

    NASA Astrophysics Data System (ADS)

    Whetstone, Z. D.; Kearfott, K. J.

    2015-07-01

    This work describes preliminary investigation into the design of a compact, portable, variable energy neutron source. The proposed method uses elastic neutron scatter at specific angles to reduce the energy of deuterium-deuterium or deuterium-tritium (D-T) neutrons. The research focuses on D-T Monte Carlo simulations, both in idealized and more realistic scenarios. Systematic uncertainty of the method is also analyzed. The research showed promise, but highlighted the need for discrimination of multiply-scattered neutrons, either through a pulsed generator or associated particle imaging.

  7. A Neutron Scattering Kernel of Solid Methane in phase II

    NASA Astrophysics Data System (ADS)

    Shin, Yunchang; Snow, William Michael; Liu, Cnen-Yu; Lavelle, Christopher M.; Baxter, David V.

    2008-04-01

    A neutron scattering cross section model of solid methane was studied for the cold neutron moderator of Low Energy Neutron Source (LENS) at IUCF/Indiana University especially in temperature range of 20.4 4K. The analytical scattering kernel was adapted from Ozaki.et al .[1][2] to describe molecular rotation in this temperature range. This model includes a molecular translation and intra-molecular vibration as well as the rotational degree of freedom in effective ways. For more broad applications into monte carlo simulations, neutron scattering libraries for MCNP were produced from the frequency spectrums using NJOY code. We have tested this newly- developed scattering kernels for phase II solid methane by calculating the neutron spectral intensity expected from the methane moderator at the LENS neutron source using MCNP. The predictions are compared to the measured energy spectra. The simulations agree with the measurement data at both temperatures. The simulation results show good agreement with measurement data in different temperatures. [1] Y. Ozaki, Y. Kataoka, and T. Yamamoto, The Journal of Chemical Physics 73, 3442 (1980). [2] Y. Ozaki, Y. Kataoka, K. Otaka, and T. Yamamoto, Can. J. Physics. 59, 275 (1981).

  8. Data reduction for time-of-flight small-angle neutron scattering with virtual neutrons

    NASA Astrophysics Data System (ADS)

    Du, Rong; Tian, Haolai; Zuo, Taisen; Tang, Ming; Yan, Lili; Zhang, Junrong

    2017-09-01

    Small-angle neutron scattering (SANS) is an experimental technique to detect material structures in the nanometer to micrometer range. The solution of the structural model constructed from SANS strongly depends on the accuracy of the reduced data. The time-of-flight (TOF) SANS data are dependent on the wavelength of the pulsed neutron source. Therefore, data reduction must be handled very carefully to transform measured neutron events into neutron scattering intensity. In this study, reduction algorithms for TOF SANS data are developed and optimized using simulated data from a virtual neutron experiment. Each possible effect on the measured data is studied systematically, and suitable corrections are performed to obtain high-quality data. This work will facilitate scientific research and the instrument design at China Spallation Neutron Source.

  9. X-ray and Neutron Scattering of Water.

    PubMed

    Amann-Winkel, Katrin; Bellissent-Funel, Marie-Claire; Bove, Livia E; Loerting, Thomas; Nilsson, Anders; Paciaroni, Alessandro; Schlesinger, Daniel; Skinner, Lawrie

    2016-07-13

    This review article focuses on the most recent advances in X-ray and neutron scattering studies of water structure, from ambient temperature to the deeply supercooled and amorphous states, and of water diffusive and collective dynamics, in disparate thermodynamic conditions and environments. In particular, the ability to measure X-ray and neutron diffraction of water with unprecedented high accuracy in an extended range of momentum transfers has allowed the derivation of detailed O-O pair correlation functions. A panorama of the diffusive dynamics of water in a wide range of temperatures (from 400 K down to supercooled water) and pressures (from ambient up to multiple gigapascals) is presented. The recent results obtained by quasi-elastic neutron scattering under high pressure are compared with the existing data from nuclear magnetic resonance, dielectric and infrared measurements, and modeling. A detailed description of the vibrational dynamics of water as measured by inelastic neutron scattering is presented. The dependence of the water vibrational density of states on temperature and pressure, and in the presence of biological molecules, is discussed. Results about the collective dynamics of water and its dispersion curves as measured by coherent inelastic neutron scattering and inelastic X-ray scattering in different thermodynamic conditions are reported.

  10. Mirror nuclei 3H and 3He binding energies difference and low energy parameters of neutron-neutron scattering

    NASA Astrophysics Data System (ADS)

    Babenko, V. A.; Petrov, N. M.

    2015-07-01

    A relationship between the binding energy difference for the mirror nuclei 3H and 3He and the low energy parameters of neutron-neutron and proton-proton scattering is established. The experimental values for the difference of 3H and 3He binding energies and the low-energy proton-proton scattering parameters are used to obtain the values for the neutron-neutron scattering length a nn = -18.38(55) fm and the effective range r nn = 2.84(4) fm. The calculated neutron-neutron scattering length is in good agreement with one of the two well-known and differing experimental values of this quantity.

  11. Fluence-compensated down-scattered neutron imaging using the neutron imaging system at the National Ignition Facility

    SciTech Connect

    Casey, D. T. Munro, D. H.; Grim, G. P.; Landen, O. L.; Spears, B. K.; Fittinghoff, D. N.; Field, J. E.; Smalyuk, V. A.; Volegov, P. L.; Merrill, F. E.

    2016-11-15

    The Neutron Imaging System at the National Ignition Facility is used to observe the primary ∼14 MeV neutrons from the hotspot and down-scattered neutrons (6-12 MeV) from the assembled shell. Due to the strong spatial dependence of the primary neutron fluence through the dense shell, the down-scattered image is convolved with the primary-neutron fluence much like a backlighter profile. Using a characteristic scattering angle assumption, we estimate the primary neutron fluence and compensate the down-scattered image, which reveals information about asymmetry that is otherwise difficult to extract without invoking complicated models.

  12. A compact neutron scatter camera for field deployment

    DOE PAGES

    Goldsmith, John E. M.; Gerling, Mark D.; Brennan, James S.

    2016-08-23

    Here, we describe a very compact (0.9 m high, 0.4 m diameter, 40 kg) battery operable neutron scatter camera designed for field deployment. Unlike most other systems, the configuration of the sixteen liquid-scintillator detection cells are arranged to provide omnidirectional (4π) imaging with sensitivity comparable to a conventional two-plane system. Although designed primarily to operate as a neutron scatter camera for localizing energetic neutron sources, it also functions as a Compton camera for localizing gamma sources. In addition to describing the radionuclide source localization capabilities of this system, we demonstrate how it provides neutron spectra that can distinguish plutonium metalmore » from plutonium oxide sources, in addition to the easier task of distinguishing AmBe from fission sources.« less

  13. A compact neutron scatter camera for field deployment

    SciTech Connect

    Goldsmith, John E. M.; Gerling, Mark D.; Brennan, James S.

    2016-08-23

    Here, we describe a very compact (0.9 m high, 0.4 m diameter, 40 kg) battery operable neutron scatter camera designed for field deployment. Unlike most other systems, the configuration of the sixteen liquid-scintillator detection cells are arranged to provide omnidirectional (4π) imaging with sensitivity comparable to a conventional two-plane system. Although designed primarily to operate as a neutron scatter camera for localizing energetic neutron sources, it also functions as a Compton camera for localizing gamma sources. In addition to describing the radionuclide source localization capabilities of this system, we demonstrate how it provides neutron spectra that can distinguish plutonium metal from plutonium oxide sources, in addition to the easier task of distinguishing AmBe from fission sources.

  14. A compact neutron scatter camera for field deployment

    SciTech Connect

    Goldsmith, John E. M.; Gerling, Mark D.; Brennan, James S.

    2016-08-23

    Here, we describe a very compact (0.9 m high, 0.4 m diameter, 40 kg) battery operable neutron scatter camera designed for field deployment. Unlike most other systems, the configuration of the sixteen liquid-scintillator detection cells are arranged to provide omnidirectional (4π) imaging with sensitivity comparable to a conventional two-plane system. Although designed primarily to operate as a neutron scatter camera for localizing energetic neutron sources, it also functions as a Compton camera for localizing gamma sources. In addition to describing the radionuclide source localization capabilities of this system, we demonstrate how it provides neutron spectra that can distinguish plutonium metal from plutonium oxide sources, in addition to the easier task of distinguishing AmBe from fission sources.

  15. A compact neutron scatter camera for field deployment

    NASA Astrophysics Data System (ADS)

    Goldsmith, John E. M.; Gerling, Mark D.; Brennan, James S.

    2016-08-01

    We describe a very compact (0.9 m high, 0.4 m diameter, 40 kg) battery operable neutron scatter camera designed for field deployment. Unlike most other systems, the configuration of the sixteen liquid-scintillator detection cells are arranged to provide omnidirectional (4π) imaging with sensitivity comparable to a conventional two-plane system. Although designed primarily to operate as a neutron scatter camera for localizing energetic neutron sources, it also functions as a Compton camera for localizing gamma sources. In addition to describing the radionuclide source localization capabilities of this system, we demonstrate how it provides neutron spectra that can distinguish plutonium metal from plutonium oxide sources, in addition to the easier task of distinguishing AmBe from fission sources.

  16. Fragility of complexity biophysical systems by neutron scattering

    NASA Astrophysics Data System (ADS)

    Magazù, Salvatore; Migliardo, Federica; Bellocco, Ersilia; Laganà, Giuseppina; Mondelli, Claudia

    2006-11-01

    Neutron scattering is an exceptional tool to investigate structural and dynamical properties of systems of biophysical interest, such as proteins, enzymes, lipids and sugars. Moreover, elastic neutron scattering enhances the investigation of atomic motions in hydrated proteins in a wide temperature range and on the picosecond timescale. Homologous disaccharides, such as trehalose, maltose and sucrose, are cryptobiotic substances, since they allow to many organisms to undergo in a “suspended life” state, known as cryptobiosis in extreme environmental conditions. The present paper is aimed to discuss the fragility degree of disaccharides, as evaluated of the temperature dependence of the mean square displacement by elastic neutron scattering, in order to link this feature with their bioprotective functions.

  17. Neutrino scattering from hydrodynamic modes in hot and dense neutron matter

    NASA Astrophysics Data System (ADS)

    Shen, Gang; Reddy, Sanjay

    2014-03-01

    We calculate the scattering rate of low-energy neutrinos in hot and dense neutron matter encountered in neutrons stars and supernovae in the hydrodynamic regime. We find that the Brillouin peak, associated with the sound mode, and the Rayleigh peak, associated with the thermal diffusion mode, dominate the dynamic structure factor. Although the total scattering cross section is constrained by the compressibility sum rule, the differential cross section calculated using the hydrodynamic response function differs from results obtained in approximate treatments often used in astrophysics such as random phase approximations. We identified these differences and discuss their implications for neutrino transport in supernovae.

  18. Characterization of Lithium Borohydride using Neutron Scattering Techniques

    NASA Astrophysics Data System (ADS)

    Hartman, Michael; Rush, Jack; Udovic, Terry

    2006-03-01

    Lithium borohydride, LiBH4, is a complex metal hydride that shows great promise as a hydrogen storage medium with a volumetric hydrogen density of 122 kg H/m^3 and a gravimetric hydrogen density of 18.5 wt. %. While numerous NMR, Raman, and infrared investigations have been reported in the literature, neutron scattering investigations of LiBH4 have been limited due to the large neutron absorption cross-section of naturally occurring lithium and boron. We have recently synthesized an isotopically-enriched lithium borohydride, containing ^7Li and ^11B, which eliminates the large neutron absorption cross-section that arises from the presence of ^6Li and ^10B. The results of powder neutron diffraction, inelastic neutron scattering, and quasi-elastic neutron scattering investigations on the ^7Li^11BH4 material are presented. These measurements provide a fundamental understanding of the behavior of hydrogen within lithium borohydride, and they provide a basis to understand changes concomitant with the introduction of catalytic or destabilizing compounds.

  19. Quasielastic neutron scattering in biology: Theory and applications.

    PubMed

    Vural, Derya; Hu, Xiaohu; Lindner, Benjamin; Jain, Nitin; Miao, Yinglong; Cheng, Xiaolin; Liu, Zhuo; Hong, Liang; Smith, Jeremy C

    2017-01-01

    Neutrons scatter quasielastically from stochastic, diffusive processes, such as overdamped vibrations, localized diffusion and transitions between energy minima. In biological systems, such as proteins and membranes, these relaxation processes are of considerable physical interest. We review here recent methodological advances and applications of quasielastic neutron scattering (QENS) in biology, concentrating on the role of molecular dynamics simulation in generating data with which neutron profiles can be unambiguously interpreted. We examine the use of massively-parallel computers in calculating scattering functions, and the application of Markov state modeling. The decomposition of MD-derived neutron dynamic susceptibilities is described, and the use of this in combination with NMR spectroscopy. We discuss dynamics at very long times, including approximations to the infinite time mean-square displacement and nonequilibrium aspects of single-protein dynamics. Finally, we examine how neutron scattering and MD can be combined to provide information on lipid nanodomains. This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo.

  20. Scattered Neutron Tomography Based on A Neutron Transport Inverse Problem

    SciTech Connect

    William Charlton

    2007-07-01

    Neutron radiography and computed tomography are commonly used techniques to non-destructively examine materials. Tomography refers to the cross-sectional imaging of an object from either transmission or reflection data collected by illuminating the object from many different directions.

  1. Neutron scattering at Australia's replacement research reactor

    NASA Astrophysics Data System (ADS)

    Robinson, R. A.; Kennedy, S. J.

    2002-01-01

    On August 25 1999, the Australian government gave final approval to build a research reactor to replace the existing HIFAR reactor at Lucas Heights. The replacement reactor, which will commence operation in 2005, will be multipurpose in function, with capabilities for both neutron-beam research and radioisotope production. Regarding beams, cold and thermal neutron sources are to be installed and the intent is to use supermirror guides, with coatings with critical angles up to 3 times that of natural Ni, to transport cold and thermal neutron beams into a large modern guide hall. The reactor and all the associated infrastructure, with the exception of the neutron beam instruments, is to be built by INVAP, SE and subcontractors in a turnkey contract. The goal is to have at least eight leading-edge neutron-beam instruments ready in 2005, and they will be developed by ANSTO and other contracted organisations, in consultation with the Australian user community and interested overseas parties. A review of the planned scientific capabilities, a description of the facility and a status report on the activities so far is given.

  2. Inelastic Neutron Scattering of Nitric Acid Hydrates

    NASA Astrophysics Data System (ADS)

    Baloh, P.; Grothe, H.; Martín-Llorente, B.; Parker, S.

    2009-04-01

    The IPCC report 2007 underlines the particular importance of aerosol particles for the water cycle and the radiation balance, and thus for the global climate.[1] The contribution of aerosols and clouds to radiative forcing might be comparable to the most important greenhouse gases like CO2 but is comparatively less understood. Nitric acid hydrates are important constituents of solid cloud particles in the lower polar Stratosphere (Polar Stratospheric Clouds) and the upper Troposphere (Cirrus clouds). The exact phase composition of these particles is still a matter of controversial discussion.[2] Especially, metastable modifications have, as recent measurements show, a particular relevance for the atmosphere, which has been ignored up to now.[3] Spectroscopic data for their detection are urgently needed and can be gathered with laboratory models. Only recently we have recorded the FTIR and Raman spectra of all nitric acid hydrates, stable and metastable.[4,5] These data have been corroborated by X-ray diffraction measurements.[6] However, when interpreting the spectroscopic data it became evident that not all bands could be explained reasonably. Here, DFT calculations were extremely helpful,[7] but still the translational and librational bands were not fully understood. Hence, inelastic neutron scattering was employed in order to investigate this region. The INS measurements were carried out with the instrument TOSCA at the ISIS of the Rutherford Appleton Laboratory, UK. The samples were prepared ex-situ in an amorphous state and were transferred into a helium-bath-cryostat, where the sample has been annealed between 20 K and 220 K. Characteristic changes of translational and librational modes have been observed and have been correlated with phase transitions. [1] Intergovernmental Panel on Climate Change, 4th Assessment Report "Climate Change 2007: The Physical Science Basis, Summary for Policymakers", Geneva, 2007; www.ipcc.ch [2] H. Grothe, H. Tizek and I. K

  3. Event-based processing of neutron scattering data

    NASA Astrophysics Data System (ADS)

    Peterson, Peter F.; Campbell, Stuart I.; Reuter, Michael A.; Taylor, Russell J.; Zikovsky, Janik

    2015-12-01

    Many of the world's time-of-flight spallation neutrons sources are migrating to recording individual neutron events. This provides for new opportunities in data processing, the least of which is to filter the events based on correlating them with logs of sample environment and other ancillary equipment. This paper will describe techniques for processing neutron scattering data acquired in event mode which preserve event information all the way to a final spectrum, including any necessary corrections or normalizations. This results in smaller final uncertainties compared to traditional methods, while significantly reducing processing time and memory requirements in typical experiments. Results with traditional histogramming techniques will be shown for comparison.

  4. Event-Based Processing of Neutron Scattering Data

    SciTech Connect

    Peterson, Peter F.; Campbell, Stuart I.; Reuter, Michael A.; Taylor, Russell J.; Zikovsky, Janik L.

    2015-09-16

    Many of the world's time-of-flight spallation neutrons sources are migrating to the recording of individual neutron events. This provides for new opportunities in data processing, the least of which is to filter the events based on correlating them with logs of sample environment and other ancillary equipment. This paper will describe techniques for processing neutron scattering data acquired in event mode that preserve event information all the way to a final spectrum, including any necessary corrections or normalizations. This results in smaller final errors, while significantly reducing processing time and memory requirements in typical experiments. Results with traditional histogramming techniques will be shown for comparison.

  5. Complete Monte Carlo Simulation of Neutron Scattering Experiments

    NASA Astrophysics Data System (ADS)

    Drosg, M.

    2011-12-01

    In the far past, it was not possible to accurately correct for the finite geometry and the finite sample size of a neutron scattering set-up. The limited calculation power of the ancient computers as well as the lack of powerful Monte Carlo codes and the limitation in the data base available then prevented a complete simulation of the actual experiment. Using e.g. the Monte Carlo neutron transport code MCNPX [1], neutron scattering experiments can be simulated almost completely with a high degree of precision using a modern PC, which has a computing power that is ten thousand times that of a super computer of the early 1970s. Thus, (better) corrections can also be obtained easily for previous published data provided that these experiments are sufficiently well documented. Better knowledge of reference data (e.g. atomic mass, relativistic correction, and monitor cross sections) further contributes to data improvement. Elastic neutron scattering experiments from liquid samples of the helium isotopes performed around 1970 at LANL happen to be very well documented. Considering that the cryogenic targets are expensive and complicated, it is certainly worthwhile to improve these data by correcting them using this comparatively straightforward method. As two thirds of all differential scattering cross section data of 3He(n,n)3He are connected to the LANL data, it became necessary to correct the dependent data measured in Karlsruhe, Germany, as well. A thorough simulation of both the LANL experiments and the Karlsruhe experiment is presented, starting from the neutron production, followed by the interaction in the air, the interaction with the cryostat structure, and finally the scattering medium itself. In addition, scattering from the hydrogen reference sample was simulated. For the LANL data, the multiple scattering corrections are smaller by a factor of five at least, making this work relevant. Even more important are the corrections to the Karlsruhe data due to the

  6. Van der Waals Type Model for Neutron-Proton Elastic Scattering at High Energies

    NASA Astrophysics Data System (ADS)

    Aleem, F.

    1980-12-01

    The most recent measurements of the angular distribution and total cross-section for neutron-proton elastic scattering between 70< pL <400 GeV/c with squared four momentum transfer -t ≤ 3.6 (GeV/c)2 have been explained using Van der Waals type model.

  7. A Method for Neutron Scattering Quantification and Correction Applied to Neutron Imaging

    NASA Astrophysics Data System (ADS)

    Raventos, Marc; Harti, Ralph P.; Lehmann, Eberhard; Grünzweig, Christian

    Either the composition, the thickness or the density of a sample can be derived, given the other two are known, by measuring the attenuation of a given incident radiation intensity through the sample. However, in the case of neutron imaging, the separation of the transmitted intensity from the scattered intensity using scintillator-based detection systems is yet to be solved. Several methods have been proposed for the correction of disturbing neutron scattering, but they are only applicable to specific materials or require some a-priori knowledge of the sample. Here we present a method for white beam neutron imaging which compares transmitted neutron images at different distances from the scintillator to improve the quantification capabilities of neutron imaging.

  8. Development of the methods for simulating the neutron spectrometers and neutron-scattering experiments

    NASA Astrophysics Data System (ADS)

    Manoshin, S. A.; Belushkin, A. V.; Ioffe, A. I.

    2016-07-01

    Reviewed are the results of simulating the neutron scattering instruments with the program package VITESS upgraded by the routines for treating the polarized neutrons, as developed by the authors. The reported investigations have been carried out at the Frank Laboratory for Neutron Physics at JINR in collaboration with the Juelich research center (Germany). The performance of the resonance and gradient adiabatic spin flippers, the Drabkin resonator, the classical and resonance spin-echo spectrometers, the spin-echo diffractometer for the small-angle neutron scattering, and the spin-echo spectrometer with rotating magnetic fields is successfully modeled. The methods for using the 3D map of the magnetic field from the input file, either mapped experimentally or computed using the finite-elements technique, in the VITESS computer code, are considered in detail. The results of neutron-polarimetry experiments are adequately reproduced by our simulations.

  9. Polarised neutron scattering from dynamic polarised targets in biology

    NASA Astrophysics Data System (ADS)

    Knop, W.; Hirai, M.; Olah, G.; Meerwinck, W.; Schink, H.-J.; Stuhrman, H. B.; Wagner, R.; Wenkow-EsSouni, M.; Zhao, J.; Schärpf, O.; Crichton, R. R.; Krumpolc, M.; Nierhaus, K. H.; Niinikoski, T. O.; Rijllart, A.

    1991-10-01

    The contrast giving rise to neutron small-angle scattering can be enhanced considerably by polarisation of the hydrogen nuclei [J. des Coizeaux and G. Jannink, Les Polymères en Solution, Les Editions de Physique, F-91944 Les Ulis, France (1987)]. Using polarised neutrons the scattering from protonated labels in a deuterated matrix will increase by an order of magnitude. This is the basis of nuclear spin contrast variation, a method which is of particular interest for the in situ structure determination of macromolecular components. A new polarised target for neutron scattering has been designed by CERN and tested successfully at FRG-1 of the GKSS research centre. For the purpose of thermal-neutron scattering the frozen solutions of biomolecules are immersed in liquid helium 4, which is thermally coupled to the cooling mixture of helium 3/helium 4 of the dilution refrigerator. The nuclear spins are aligned with respect to the external magnetic field-parallel or antiparallel-by dynamic nuclear polarisation (DNP). The gain in neutron scattering compared to earlier experiments using direct cooling of the sample by helium 3 is a factor of 30. Another factor of 30 arises from the installation of the cold source and the beryllium reflector in FRG-1 [W. Knop et al., J. Appl. Cryst. 22 (1989) 352]. Pure nuclear spin targets are produced from dynamic polarised targets by selective depolarisation. In biological material only the hydrogen isotopes contribute significantly to polarised neutron scattering. Thus, saturation of the proton NMR yields a deuteron target, provided the target material has been enriched by the latter isotope. A proton target is obtained from the dynamic polarised target by saturation of deuteron NMR. This leads to six additional scattering functions reflecting the proton and deuteron spin densities and the correlations between the polarised isotopes. Polarised neutron scattering from nuclear spin targets of apoferritin and various derivatives of the

  10. A neutron detector to monitor the intensity of transmitted neutrons for small-angle neutron scattering instruments

    NASA Astrophysics Data System (ADS)

    De Lurgio, Patrick M.; Klann, Raymond T.; Fink, Charles L.; McGregor, Douglas S.; Thiyagarajan, Pappannan; Naday, Istvan

    2003-06-01

    A semiconductor-based neutron detector was developed at Argonne National Laboratory (ANL) for use as a neutron beam monitor for small-angle neutron scattering instruments. The detector is constructed using a coating of 10B on a gallium-arsenide semiconductor detector and is mounted directly within a cylindrical (2.2 cm dia. and 4.4 cm long) enriched 10B 4C beam stop in the time-of-flight Small Angle Neutron Diffractometer (SAND) instrument at the Intense Pulsed Neutron Source (IPNS) facility at ANL. The neutron beam viewed by the SAND is from a pulsed spallation source moderated by a solid methane moderator that produces useful neutrons in the wavelength range of 0.5-14 Å. The SAND instrument uses all detected neutrons in the above wavelength range sorted by time-of-flight into 68 constant Δ T/ T=0.05 channels. This new detector continuously monitors the transmitted neutron beam through the sample during scattering measurements and takes data concurrently with the other detectors in the instrument. The 10B coating on the GaAs detector allows the detection of the cold neutron spectrum with reasonable efficiency. This paper describes the details of the detector fabrication, the beam stop monitor design, and includes a discussion of results from preliminary tests using the detector during several run cycles at the IPNS.

  11. Parity nonconserving spin rotation in weak neutron-proton scattering

    NASA Astrophysics Data System (ADS)

    Avishai, Y.

    1984-07-01

    Parity nonconservation in weak n-p scattering is studied at threshold wehre neutron spin rotation might occur. We use the DDH weak NN force and a separable form with S, P and D partial waves in the strong NN interaction. The contribution of various spin-isospin components to the weak NN scattering amplitude is evaluated and the spin rotation angle is found to be -2.35 × 10 -9 rad/cm. The sources of possible errors are indicated.

  12. Optics for Advanced Neutron Imaging and Scattering

    SciTech Connect

    Moncton, David E.; Khaykovich, Boris

    2016-03-30

    During the report period, we continued the work as outlined in the original proposal. We have analyzed potential optical designs of Wolter mirrors for the neutron-imaging instrument VENUS, which is under construction at SNS. In parallel, we have conducted the initial polarized imaging experiment at Helmholtz Zentrum, Berlin, one of very few of currently available polarized-imaging facilities worldwide.

  13. A workshop on enhanced national capability for neutron scattering

    SciTech Connect

    Hurd, Alan J; Rhyne, James J; Lewis, Paul S

    2009-01-01

    This two-day workshop will engage the international neutron scattering community to vet and improve the Lujan Center Strategic Plan 2007-2013 (SP07). Sponsored by the LANL SC Program Office and the University of California, the workshop will be hosted by LANSCE Professor Sunny Sinha (UCSD). Endorsement by the Spallation Neutron Source will be requested. The discussion will focus on the role that the Lujan Center will play in the national neutron scattering landscape assuming full utilization of beamlines, a refurbished LANSCE, and a 1.4-MW SNS. Because the Lujan Strategic Plan is intended to set the stage for the Signature Facility era at LANSCE, there will be some discussion of the long-pulse spallation source at Los Alamos. Breakout groups will cover several new instrument concepts, upgrades to present instruments, expanded sample environment capabilities, and a look to the future. The workshop is in keeping with a request by BES to update the Lujan strategic plan in coordination with the SNS and the broader neutron community. Workshop invitees will be drawn from the LANSCE User Group and a broad cross section of the US, European, and Pacific Rim neutron scattering research communities.

  14. Development of new methods for studying nanostructures using neutron scattering

    SciTech Connect

    Pynn, Roger

    2016-03-18

    The goal of this project was to develop improved instrumentation for studying the microscopic structures of materials using neutron scattering. Neutron scattering has a number of advantages for studying material structure but suffers from the well-known disadvantage that neutrons’ ability to resolve structural details is usually limited by the strength of available neutron sources. We aimed to overcome this disadvantage using a new experimental technique, called Spin Echo Scattering Angle Encoding (SESAME) that makes use of the neutron’s magnetism. Our goal was to show that this innovation will allow the country to make better use of the significant investment it has recently made in a new neutron source at Oak Ridge National Laboratory (ORNL) and will lead to increases in scientific knowledge that contribute to the Nation’s technological infrastructure and ability to develop advanced materials and technologies. We were successful in demonstrating the technical effectiveness of the new method and established a baseline of knowledge that has allowed ORNL to start a project to implement the method on one of its neutron beam lines.

  15. Immersive Visual Analytics for Transformative Neutron Scattering Science

    SciTech Connect

    Steed, Chad A; Daniel, Jamison R; Drouhard, Margaret; Hahn, Steven E; Proffen, Thomas E

    2016-01-01

    The ORNL Spallation Neutron Source (SNS) provides the most intense pulsed neutron beams in the world for scientific research and development across a broad range of disciplines. SNS experiments produce large volumes of complex data that are analyzed by scientists with varying degrees of experience using 3D visualization and analysis systems. However, it is notoriously difficult to achieve proficiency with 3D visualizations. Because 3D representations are key to understanding the neutron scattering data, scientists are unable to analyze their data in a timely fashion resulting in inefficient use of the limited and expensive SNS beam time. We believe a more intuitive interface for exploring neutron scattering data can be created by combining immersive virtual reality technology with high performance data analytics and human interaction. In this paper, we present our initial investigations of immersive visualization concepts as well as our vision for an immersive visual analytics framework that could lower the barriers to 3D exploratory data analysis of neutron scattering data at the SNS.

  16. Neutron scattering studies of 54,56Fe with monoenergetic neutrons

    NASA Astrophysics Data System (ADS)

    Hicks, S. F.; Combs, B. M.; Henderson, S. L.; Sidwell, L. C.; Vanhoy, J. R.; Garza, E.; Steves, J.; Chakraborty, A.; Crider, B. P.; Prados-Estevez, F. M.; Kumar, A.; McEllistrem, M. T.; Peters, E. E.; Ross, T. J.; Yates, S. W.

    2013-10-01

    Neutron scattering data for Fe are important for the development of next generation fission reactors, since Fe is an important structural material in all proposed reactor designs, as well as in existing reactors. How neutrons interact with Fe has an important impact on fuel performance during irradiations and the overall efficiency of fission reactors. While differential scattering cross sections have been previously measured at several incident neutron energies in the fast neutron region, questions remain regarding the uncertainties for existing cross sections and for neutron inelastic scattering. Elastic and inelastic differential scattering cross sections have been measured on 54,56Fe at the University of Kentucky Accelerator Laboratory in the fast neutron energy region between 1.7 and 4 MeV. Results from our measurements and comparisons to model calculations will be presented. This material is based on work supported by the Department of Energy under grant NEUP: NU-12-KY-UK-0201-05 and by the Cowan Physics Fund at the Univ. of Dallas.

  17. Optimizing moderator dimensions for neutron scattering at the spallation neutron source.

    PubMed

    Zhao, J K; Robertson, J L; Herwig, Kenneth W; Gallmeier, Franz X; Riemer, Bernard W

    2013-12-01

    In this work, we investigate the effect of neutron moderator dimensions on the performance of neutron scattering instruments at the Spallation Neutron Source (SNS). In a recent study of the planned second target station at the SNS facility, we have found that the dimensions of a moderator play a significant role in determining its surface brightness. A smaller moderator may be significantly brighter over a smaller viewing area. One of the immediate implications of this finding is that for modern neutron scattering instrument designs, moderator dimensions and brightness have to be incorporated as an integrated optimization parameter. Here, we establish a strategy of matching neutron scattering instruments with moderators using analytical and Monte Carlo techniques. In order to simplify our treatment, we group the instruments into two broad categories: those with natural collimation and those that use neutron guide systems. For instruments using natural collimation, the optimal moderator selection depends on the size of the moderator, the sample, and the moderator brightness. The desired beam divergence only plays a role in determining the distance between sample and moderator. For instruments using neutron optical systems, the smallest moderator available that is larger than the entrance dimension of the closest optical element will perform the best (assuming, as is the case here that smaller moderators are brighter).

  18. The Effect of Anisotropic Scatter on Atmospheric Neutron Transport

    DTIC Science & Technology

    2015-03-26

    and Training Command In Partial Fulfillment of the Requirements for the Degree of Master of Science in Nuclear Engineering Nicholas J. McIntee...Anisotropy is present in the angular distributions of neutrons departing from a nuclear scattering event. This anisotropy cannot be defined in a closed...distribution PDF is apparent, with a significant forward bias

  19. Time reversal invariance violation in neutron-deuteron scattering

    SciTech Connect

    Song, Young-Ho; Gudkov, Vladimir; Lazauskas, Rimantas

    2011-06-15

    Time reversal invariance-violating (TRIV) effects in low-energy elastic neutron-deuteron scattering are calculated using meson exchange and EFT-type TRIV potentials in a distorted-wave Born approximation with realistic hadronic strong interaction wave functions, obtained by solving the three-body Faddeev equations in configuration space. The relation between TRIV and parity-violating observables is discussed.

  20. Benchmarking the inelastic neutron scattering soil carbon method

    USDA-ARS?s Scientific Manuscript database

    The herein described inelastic neutron scattering (INS) method of measuring soil carbon was based on a new procedure for extracting the net carbon signal (NCS) from the measured gamma spectra and determination of the average carbon weight percent (AvgCw%) in the upper soil layer (~8 cm). The NCS ext...

  1. Contribution to Neutron Fluence and Neutron Absorbed Dose from Double Scattering Proton Therapy System Components

    PubMed Central

    Pérez-Andújar, A.; Newhauser, W. D.; DeLuca, P. M.

    2010-01-01

    Proton therapy offers low integral dose and good tumor comformality in many deep-seated tumors. However, secondary particles generated during proton therapy, such as neutrons, are a concern, especially for passive scattering systems. In this type of system, the proton beam interacts with several components of the treatment nozzle that lie along the delivery path and can produce secondary neutrons. Neutron production along the beam's central axis in a double scattering passive system was examined using Monte Carlo simulations. Neutron fluence and energy distribution were determined downstream of the nozzle's major components at different radial distances from the central axis. In addition, the neutron absorbed dose per primary proton around the nozzle was investigated. Neutron fluence was highest immediately downstream of the range modulator wheel (RMW) but decreased as distance from the RMW increased. The nozzle's final collimator and snout also contributed to the production of high-energy neutrons. In fact, for the smallest treatment volume simulated, the neutron absorbed dose per proton at isocenter increased by a factor of 20 due to the snout presence when compared with a nozzle without a snout. The presented results can be used to design more effective local shielding components inside the treatment nozzle as well as to better understand the treatment room shielding requirements. PMID:20871789

  2. Neutron Scattering Investigation of Phonon Scattering Rates in Ag1-xSb1+xTe2+x (x = 0, 0.1, and 0.2)

    SciTech Connect

    Abernathy, Douglas L; Budai, John D; Delaire, Olivier A; Ehlers, Georg; Hong, Tao; Karapetrova, Evguenia A.; Ma, Jie; May, Andrew F; McGuire, Michael A; Specht, Eliot D

    2014-01-01

    The phonon dispersions and scattering rates of the thermoelectric material AgSbTe$_{2}$ were measured as a function of temperature with inelastic neutron scattering. The results show that phonon scattering rates are large and weakly dependent on temperature. The lattice thermal conductivity was calculated from the measured phonon lifetimes and group velocities, providing good agreement with bulk transport measurements. The measured phonon scattering rates and their temperature dependence are compared with models of phonon scattering by anharmonicity and point defect. We find that these processes cannot account for the large total phonon scattering rates observed, and their lack of temperature dependence. Neutron and synchrotron diffraction measurements on single crystals revealed an extensive nanostructure from cation ordering, which is likely responsible for the strong phonon scattering.

  3. Raman Scattering with Attentuated - Total-Reflection

    NASA Astrophysics Data System (ADS)

    Reed, Christopher Edward

    Two experiments and supporting calculations were done to see whether using Kretschmann prisms to generate an enhancement by coupling to surface plasmon-polaritons (SPPs) can help in observing Raman scattering by monolayers of molecules. The experiments were done in ultra-high vacuum (UHV). In one, semi-transparent silver films were evaporated onto glass prisms held at 110(DEGREES)K. Attenuated -total-reflectivity (ATR) curves were taken as the prisms warmed to room temperature; the initially very broad and shallow reflectivity dips irreversibly deepened and narrowed, approaching those of films evaporated onto room-temperature substrates. We concluded that delocalized SPPs in cold -evaporated silver films are strongly damped and thus do not contribute to their surface enhanced Raman scattering (SERS) and also that we could not combine SERS with enhancement due to coupling to SPPs. Curve-fitting yielded effective dielectric constants and film thicknesses. In the second experiment we observed Raman scattering by a few monolayers of pyridine adsorbed on smooth silver films deposited at room temperature onto the glass prisms. We used three configurations; light incident from and collected in vacuum, incident through the prism and collected in vacuum, and incident and collected through the prism. The first configuration worked best. Heating of the films limited the incident power we could use. Another limitation was a large background when light was incident and collected through the prism. Possible solutions to these problems are discussed. Using the 2 x 2 matrix method for electromagnetic calculations in multilayers, the reflectivities and electric fields due to incident light were calculated. Combining this with the electromagnetic Green's functions of Mills and Maradudin, which we show work in a more general situation, yields the radiation by an oscillating electric dipole in an arbitrary multilayer. The 2 x 3 matrix giving the polarized radiation in a particular

  4. Neutron Angular Scatter Effects in 3DHZETRN: Quasi-Elastic

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Werneth, Charles M.; Slaba, Tony C.; Badavi, Francis F.; Reddell, Brandon D.; Bahadori, Amir A.

    2017-01-01

    The current 3DHZETRN code has a detailed three dimensional (3D) treatment of neutron transport based on a forward/isotropic assumption and has been compared to Monte Carlo (MC) simulation codes in various geometries. In most cases, it has been found that 3DHZETRN agrees with the MC codes to the extent they agree with each other. However, a recent study of neutron leakage from finite geometries revealed that further improvements to the 3DHZETRN formalism are needed. In the present report, angular scattering corrections to the neutron fluence are provided in an attempt to improve fluence estimates from a uniform sphere. It is found that further developments in the nuclear production models are required to fully evaluate the impact of transport model updates. A model for the quasi-elastic neutron production spectra is therefore developed and implemented into 3DHZETRN.

  5. Neutron scattering and models: Iron. Nuclear data and measurements series

    SciTech Connect

    Smith, A.B.

    1995-08-01

    Differential elastic and inelastic neutron-scattering cross sections of elemental iron are measured from 4.5 to 10 MeV in increments of {approx} 0.5 MeV. At each incident energy the measurements are made at forty or more scattering angles distributed between {approx} 17{degrees} and 160{degrees}, with emphasis on elastic scattering and inelastic scattering due to the excitation of the yrast 2{sup +} state. The measured data is combined with earlier lower-energy results from this laboratory, with recent high-precision {approx} 9.5 {yields} 15 MeV results from the Physilalisch Technische Bundesanstalt and with selected values from the literature to provide a detailed neutron-scattering data base extending from {approx} 1.5 to 26 MeV. This data is interpreted in the context of phenomenological spherical-optical and coupled-channels (vibrational and rotational) models, and physical implications discussed. Deformation, coupling, asymmetry and dispersive effects are explored. It is shown that, particularly in a collective context, a good description of the interaction of neutrons with iron is achieved over the energy range {approx} 0 {yields} 26 MeV, avoiding the dichotomy between high and low-energy interpretations found in previous work.

  6. Long-Lifetime Low-Scatter Neutron Polarization Target

    SciTech Connect

    Dr. Jonathan M. Richardson

    2004-07-09

    Polarized neutrons scattering is an important technology for characterizing magnetic and other materials. Polarized helium three (P-3He) is a novel technology for creating polarized beams and, perhaps more importantly, for the analysis of polarization in highly divergent scattered beams. Analysis of scattered beams requires specialized targets with complex geometries to ensure accurate results. Special materials and handling procedures are required to give the targets a long useful lifetime. In most cases, the targets must be shielded from stray magnetic fields from nearby equipment. SRL has developed and demonstrated hybrid targets made from glass and aluminum. We have also developed and calibrated a low-field NMR system for measuring polarization lifetimes. We have demonstrated that our low-field system is able to measure NMR signals in the presence of conducting (metallic) cell elements. We have also demonstrated a non-magnetic valve that can be used to seal the cells. We feel that these accomplishments in Phase I are sufficient to ensure a successful Phase II program. The commercial market for this technology is solid. There are over nine neutron scattering centers in the US and Canada and over 22 abroad. Currently, the US plans to build a new $1.4B scattering facility called the Spallation Neutron Source (SNS). The technology developed in this project will allow SRL to supply targets to both existing and future facilities. SRL is also involved with the application of P-3He to medical imaging.

  7. Fast-neutron scattering cross sections of elemental silver

    SciTech Connect

    Smith, A.B.; Guenther, P.T.

    1982-05-01

    Differential neutron elastic- and inelastic-scattering cross sections of elemental silver are measured from 1.5 to 4.0 MeV at intervals of less than or equal to 200 keV and at 10 to 20 scattering angles distributed between 20 and 160/sup 0/. Inelastically-scattered neutron groups are observed corresponding to the excitation of levels at; 328 +- 13, 419 +- 50, 748 +- 25, 908 +- 26, 1150 +- 38, 1286 +- 25, 1507 +- 20, 1623 +- 30, 1835 +- 20 and 1944 +- 26 keV. The experimental results are used to derive an optical-statistical model that provides a good description of the observed cross sections. The measured values are compared with corresponding quantities given in ENDF/B-V.

  8. Incoherent neutron scattering in acetanilide and three deuterated derivatives

    NASA Astrophysics Data System (ADS)

    Barthes, Mariette; Almairac, Robert; Sauvajol, Jean-Louis; Moret, Jacques; Currat, Roland; Dianoux, José

    1991-03-01

    Incoherent-neutron-scattering measurements of the vibrational density of states of acetanilide and three deuterated derivatives are presented. These data allow one to identify an intense maximum, assigned to the N-H out-of-plane bending mode. The data display the specific behavior of the methyl torsional modes: large isotopic shift and strong low-temperature intensity; confirm our previous inelastic-neutron-scattering studies, indicating no obvious anomalies in the range of frequency of the acoustic phonons. In addition, the data show the existence of thermally activated quasielastic scattering above 100 K, assigned to the random diffusive motion of the methyl protons. These results are discussed in the light of recent theoretical models proposed to explain the anomalous optical properties of this crystal.

  9. Anisotropic Elastic Resonance Scattering model for the Neutron Transport equation

    SciTech Connect

    Mohamed Ouisloumen; Abderrafi M. Ougouag; Shadi Z. Ghrayeb

    2014-11-24

    The resonance scattering transfer cross-section has been reformulated to account for anisotropic scattering in the center-of-mass of the neutron-nucleus system. The main innovation over previous implementations is the relaxation of the ubiquitous assumption of isotropic scattering in the center-of-mass and the actual effective use of scattering angle distributions from evaluated nuclear data files in the computation of the angular moments of the resonant scattering kernels. The formulas for the high order anisotropic moments in the laboratory system are also derived. A multi-group numerical formulation is derived and implemented into a module incorporated within the NJOY nuclear data processing code. An ultra-fine energy mesh cross section library was generated using these new theoretical models and then was used for fuel assembly calculations with the PARAGON lattice physics code. The results obtained indicate a strong effect of this new model on reactivity, multi-group fluxes and isotopic inventory during depletion.

  10. 2009 International Conference on Neutron Scattering (ICNS 2009)

    SciTech Connect

    Gopal Rao, PhD; Gillespie, Donna

    2010-08-05

    The ICNS provides a focal point for the worldwide neutron user community to strengthen ties within this diverse group, while at the same time promoting neutron research among colleagues in related disciplines identified as would-be neutron users. The International Conference on Neutron Scattering thus serves a dual role as an international user meeting and a scientific meeting. As a venue for scientific exchange, the ICNS showcases recent results and provides forums for scientific discussion of neutron research in diverse fields such as hard and soft condensed matter, liquids, biology, magnetism, engineering materials, chemical spectroscopy, crystal structure, and elementary excitations, fundamental physics and development of neutron instrumentation through a combination of invited talks, contributed talks and poster sessions. Each of the major national neutron facilities (NIST, LANSCE, ANL, HFIR and SNS), along with their international counterparts, has an opportunity to exchange information with each other and to update users, and potential users, of their facility. This is also an appropriate forum for users to raise issues that relate to the facilities.

  11. Inelastic Neutron Scattering on 160Gd

    NASA Astrophysics Data System (ADS)

    Lesher, S. R.; Casarella, C.; Crider, B. P.; Ikeyama, R.; Marsh, I.; Peters, E. E.; Prados-Estévez, F. M.; Smith, M. K.; Tully, Z.; Vanhoy, J. R.; Aprahamian, A.; Yates, S. W.

    2014-03-01

    The nature of low-lying excitations, Kπ=0+ bands in deformed nuclei remain enigmatic in the field, especially in relationship to quadrupole vibrations. One method of characterizing these states beyond excitation energies is through measurements of absolute transition probabilities. In the rare earth region of deformation, there are five stable Gd isotopes, 154Gd, 156Gd, and 158Gd have been studied to obtain B(E2) values, a fourth, 160Gd is the focus of this work. We have examined 160Gd with the (n, n'γ) reaction and neutron energies up to 3.0 MeV to confirm known 0+ states.

  12. Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

    SciTech Connect

    Overbury, Steven {Steve} H; Coates, Leighton; Herwig, Kenneth W; Kidder, Michelle

    2011-10-01

    This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

  13. Neutron scattering for analysis of processes in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Balagurov, A. M.; Bobrikov, I. A.; Samoylova, N. Yu; Drozhzhin, O. A.; Antipov, E. V.

    2014-12-01

    The review is concerned with analysis and generalization of information on application of neutron scattering for elucidation of the structure of materials for rechargeable energy sources (mainly lithium-ion batteries) and on structural rearrangements in these materials occurring in the course of electrochemical processes. Applications of the main methods including neutron diffraction, small-angle neutron scattering, inelastic neutron scattering, neutron reflectometry and neutron introscopy are considered. Information on advanced neutron sources is presented and a number of typical experiments are outlined. The results of some studies of lithium-containing materials for lithium-ion batteries, carried out at IBR-2 pulsed reactor, are discussed. The bibliography includes 50 references.

  14. Pores in Marcellus Shale: A Neutron Scattering and FIB-SEM Study

    SciTech Connect

    Gu, Xin; Cole, David R.; Rother, Gernot; Mildner, David F. R.; Brantley, Susan L.

    2015-01-26

    The production of natural gas has become more and more important in the United States because of the development of hydraulic fracturing techniques, which significantly increase the permeability and fracture network of black shales. The pore structure of shale is a controlling factor for hydrocarbon storage and gas migration. In this work, we investigated the porosity of the Union Springs (Shamokin) Member of the Marcellus Formation from a core drilled in Centre County, PA, USA, using ultrasmall-angle neutron scattering (USANS), small-angle neutron scattering (SANS), focused ion beam scanning electron microscopy (FIB-SEM), and nitrogen gas adsorption. The scattering of neutrons by Marcellus shale depends on the sample orientation: for thin sections cut in the plane of bedding, the scattering pattern is isotropic, while for thin sections cut perpendicular to the bedding, the scattering pattern is anisotropic. The FIB-SEM observations allow attribution of the anisotropic scattering patterns to elongated pores predominantly associated with clay. The apparent porosities calculated from scattering data from the bedding plane sections are lower than those calculated from sections cut perpendicular to the bedding. A preliminary method for estimating the total porosity from the measurements made on the two orientations is presented. This method is in good agreement with nitrogen adsorption for both porosity and specific surface area measurements. Neutron scattering combined with FIB-SEM reveals that the dominant nanosized pores in organic-poor, clay-rich shale samples are water-accessible sheetlike pores within clay aggregates. In contrast, bubble-like organophilic pores in kerogen dominate organic-rich samples. Lastly, developing a better understanding of the distribution of the water-accessible pores will promote more accurate models of water–mineral interactions during hydrofracturing.

  15. Pores in Marcellus Shale: A Neutron Scattering and FIB-SEM Study

    DOE PAGES

    Gu, Xin; Cole, David R.; Rother, Gernot; ...

    2015-01-26

    The production of natural gas has become more and more important in the United States because of the development of hydraulic fracturing techniques, which significantly increase the permeability and fracture network of black shales. The pore structure of shale is a controlling factor for hydrocarbon storage and gas migration. In this work, we investigated the porosity of the Union Springs (Shamokin) Member of the Marcellus Formation from a core drilled in Centre County, PA, USA, using ultrasmall-angle neutron scattering (USANS), small-angle neutron scattering (SANS), focused ion beam scanning electron microscopy (FIB-SEM), and nitrogen gas adsorption. The scattering of neutrons bymore » Marcellus shale depends on the sample orientation: for thin sections cut in the plane of bedding, the scattering pattern is isotropic, while for thin sections cut perpendicular to the bedding, the scattering pattern is anisotropic. The FIB-SEM observations allow attribution of the anisotropic scattering patterns to elongated pores predominantly associated with clay. The apparent porosities calculated from scattering data from the bedding plane sections are lower than those calculated from sections cut perpendicular to the bedding. A preliminary method for estimating the total porosity from the measurements made on the two orientations is presented. This method is in good agreement with nitrogen adsorption for both porosity and specific surface area measurements. Neutron scattering combined with FIB-SEM reveals that the dominant nanosized pores in organic-poor, clay-rich shale samples are water-accessible sheetlike pores within clay aggregates. In contrast, bubble-like organophilic pores in kerogen dominate organic-rich samples. Lastly, developing a better understanding of the distribution of the water-accessible pores will promote more accurate models of water–mineral interactions during hydrofracturing.« less

  16. Concentration of hydrogen in titanium measured by neutron incoherent scattering

    SciTech Connect

    Chen-Mayer, H.H.; Mildner, D.F.R.; Lamaze, G.P.; Lindstrom, R.M.; Paul, R.L.; Kvardakov, V.V.; Richards, W.J.

    1998-12-31

    Mass fractions of hydrogen in titanium matrices have been measured using neutron incoherent scattering (NIS) and compared with results from prompt gamma activation analysis (PGAA). Qualitatively, NIS is a more efficient technique than PGAA which involves neutron absorption, and the former may be suitable for on-line analysis. However, for NIS the scattering contribution comes from both the hydrogen and the matrix, whereas prompt gamma emission has minimal matrix effect. To isolate the signal due to hydrogen scattering, a set of polypropylene films is used to simulate the increasing amount of hydrogen, and the scattered intensity is monitored. From this response, an unknown amount of the hydrogen can be deduced empirically. The authors have further attempted a first principle calculation of the intensity of the scattered signal from the experimental systems, and have obtained good agreement between calculation and the measurements. The study can be used as a reference for future applications of the scattering method to other hydrogen-in-metal systems.

  17. The total neutron cross section of liquid para-hydrogen

    NASA Astrophysics Data System (ADS)

    Celli, M.; Rhodes, N.; Soper, A. K.; Zoppi, M.

    1999-12-01

    We have measured, using the pulsed neutron source ISIS, the total neutron cross section of liquid para-hydrogen in the vicinity of the triple point. The experimental results compare only qualitatively with the results of the Young and Koppel theory. However, a much better agreement is found once modifications are included in the model which effectively take into account the intermolecular interactions.

  18. Quantifying the information measured by neutron scattering instruments

    SciTech Connect

    Johnson, M.W.

    1997-09-01

    The concept of the information content of a scientific measurement is introduced, and a theory is presented which enables the information that may be obtained by a neutron scattering instrument to be calculated. When combined with the time taken to perform the measurement the bandwidth of the instrument is obtained. This bandwidth is effectively a figure of merit which is of use in three respects: in the design of neutron instrumentation, the optimisation of measurements, and in the comparison of one instrument with another.

  19. ASIC for Small Angle Neutron Scattering Experiments at the SNS

    NASA Astrophysics Data System (ADS)

    De Geronimo, Gianluigi; Fried, Jack; Smith, Graham C.; Yu, Bo; Vernon, Emerson; Britton, Charles L.; Bryan, William L.; Clonts, Lloyd G.; Frank, Shane S.

    2007-06-01

    We present an ASIC for a 3He gas detector to be used in small angle neutron scattering experiments at the spallation neutron source in oak ridge. The ASIC is composed of 64 channels with low noise charge amplification, filtering, timing and amplitude measurement circuits, where an innovative current-mode peak-detector and digitizer (PDAD) is adopted. The proposed PDAD provides at the same time peak detection and A/D conversion in real time, at low power, and without requiring a clock signal. The channels share an efficient data sparsification and derandomization scheme, a 30-bit 256 deep FIFO, and low voltage differential signaling.

  20. System Construction of the Stilbene Compact Neutron Scatter Camera

    SciTech Connect

    Goldsmith, John E. M.; Gerling, Mark D.; Brennan, James S.; Throckmorton, Daniel J.; Helm, Jonathan Ivers

    2016-10-01

    This report documents the construction of a stilbene-crystal-based compact neutron scatter camera. This system is essentially identical to the MINER (Mobile Imager of Neutrons for Emergency Responders) system previously built and deployed under DNN R&D funding,1 but with the liquid scintillator in the detection cells replaced by stilbene crystals. The availability of these two systems for side-by-side performance comparisons will enable us to unambiguously identify the performance enhancements provided by the stilbene crystals, which have only recently become commercially available in the large size required (3” diameter, 3” deep).

  1. Neutron scatter studies of chromatin structures related to function

    SciTech Connect

    Not Available

    1990-01-01

    In the Progress Report for last year (7-1-88 to 6-30-89) we proposed to complete the following experiments: (1) Structure of TFIIIA/DNA complex, (2) Effect of histone acetylation on nucleosome structure, and (3) Location of lysine rich histone H5 on the nucleosome. Our major source of neutrons is LANSCE, LANL. However, for the period of this report LANSCE has been down between cycles of operation. Continuing neutron scatter studies have been carried out at the Institute Laue Langevin, Grenoble, France, on the trimmed nucleosome core particles. X-ray scatter studies have been carried out at DESY, Hamburg on the histone octamer and trimmed octamer. X-ray scatter studies have been performed also at LANL on proposed objectives. We have continued with the following of our research program; (i) assembly of fully characterized nucleosomes; (ii) effect of histone acetylation on nucleosomes; (iii) effect of full acetylation of H3 and H4 on nucleosome DNA linking number; (iv) assembly and characterization of defined minichromosomes; (v) neutron and X-ray scatter of the histone octamer and trimmed octamer; (vi) structural studies of human sperm chromatin, histones and protamines. 5 refs.

  2. Theory of neutron scattering by electrons in magnetic materials

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.

    2015-10-01

    A theory of neutron scattering by magnetic materials is reviewed with emphasis on the use of electronic multipoles that have universal appeal, because they are amenable to calculation and appear in theories of many other experimental techniques. The conventional theory of magnetic neutron scattering, which dates back to Schwinger (1937 Phys. Rev. 51 544) and Trammell (1953 Phys. Rev. 92 1387), yields an approximation for the scattering amplitude in terms of magnetic dipoles formed with the spin (S) and orbital angular momentum (L) of valence electrons. The so-called dipole-approximation has been widely adopted by researchers during the past few decades that has seen neutron scattering develop to its present status as the method of choice for investigations of magnetic structure and excitations. Looking beyond the dipole-approximation, however, reveals a wealth of additional information about electronic degrees of freedom conveniently encapsulated in magnetic multipoles. In this language, the dipole-approximation retains electronic axial dipoles, S and L. At the same level of approximation are polar dipoles—called anapoles or toroidal dipoles—allowed in the absence of a centre of inversion symmetry. Anapoles are examples of magneto-electric multipoles, time-odd and parity-odd irreducible tensors, that have come to the fore as signatures of electronic complexity in materials.

  3. Applications of neutron scattering to heterogeneous catalysis

    NASA Astrophysics Data System (ADS)

    Parker, Stewart F.; Lennon, David

    2016-09-01

    Historically, most studies of heterogeneous catalysts that have used neutron vibrational spectroscopy have employed indirect geometry instruments with a low (<40 cm-1) final energy. In this paper we examine the reasons why this has been the case and highlight the advantages and disadvantages of this approach. We then show how some of these may be overcome by the use of direct geometry spectrometers. We illustrate the use of direct geometry spectrometers with examples from reforming of methane to synthesis gas (CO + H2) over Ni/Al2O3 catalysts and an operando study of CO oxidation. We conclude with a proposal for a unique instrument that combines both indirect and direct geometry spectrometers.

  4. Neutron Scattering of Aromatic and Aliphatic Liquids

    PubMed Central

    Falkowska, Marta; Bowron, Daniel T.; Manyar, Haresh G.

    2016-01-01

    Abstract Organic solvents, such as cyclohexane, cyclohexene, methylcyclohexane, benzene and toluene, are widely used as both reagents and solvents in industrial processes. Despite the ubiquity of these liquids, the local structures that govern the chemical properties have not been studied extensively. Herein, we report neutron diffraction measurements on liquid cyclohexane, cyclohexene, methylcyclohexane, benzene and toluene at 298 K to obtain a detailed description of the local structure in these compounds. The radial distribution functions of the centres of the molecules, as well as the partial distribution functions for the double bond for cyclohexene and methyl group for methylcyclohexane and toluene have been calculated. Additionally, probability density functions and angular radial distribution functions were extracted to provide a full description of the local structure within the chosen liquids. Structural motifs are discussed and compared for all liquids, referring specifically to the functional group and aromaticity present in the different liquids. PMID:26990367

  5. Complete Monte Carlo Simulation of Neutron Scattering Experiments

    SciTech Connect

    Drosg, M.

    2011-12-13

    In the far past, it was not possible to accurately correct for the finite geometry and the finite sample size of a neutron scattering set-up. The limited calculation power of the ancient computers as well as the lack of powerful Monte Carlo codes and the limitation in the data base available then prevented a complete simulation of the actual experiment. Using e.g. the Monte Carlo neutron transport code MCNPX [1], neutron scattering experiments can be simulated almost completely with a high degree of precision using a modern PC, which has a computing power that is ten thousand times that of a super computer of the early 1970s. Thus, (better) corrections can also be obtained easily for previous published data provided that these experiments are sufficiently well documented. Better knowledge of reference data (e.g. atomic mass, relativistic correction, and monitor cross sections) further contributes to data improvement. Elastic neutron scattering experiments from liquid samples of the helium isotopes performed around 1970 at LANL happen to be very well documented. Considering that the cryogenic targets are expensive and complicated, it is certainly worthwhile to improve these data by correcting them using this comparatively straightforward method. As two thirds of all differential scattering cross section data of {sup 3}He(n,n){sup 3}He are connected to the LANL data, it became necessary to correct the dependent data measured in Karlsruhe, Germany, as well. A thorough simulation of both the LANL experiments and the Karlsruhe experiment is presented, starting from the neutron production, followed by the interaction in the air, the interaction with the cryostat structure, and finally the scattering medium itself. In addition, scattering from the hydrogen reference sample was simulated. For the LANL data, the multiple scattering corrections are smaller by a factor of five at least, making this work relevant. Even more important are the corrections to the Karlsruhe data

  6. Benchmarking a first-principles thermal neutron scattering law for water ice with a diffusion experiment

    NASA Astrophysics Data System (ADS)

    Holmes, Jesse; Zerkle, Michael; Heinrichs, David

    2017-09-01

    The neutron scattering properties of water ice are of interest to the nuclear criticality safety community for the transport and storage of nuclear materials in cold environments. The common hexagonal phase ice Ih has locally ordered, but globally disordered, H2O molecular orientations. A 96-molecule supercell is modeled using the VASP ab initio density functional theory code and PHONON lattice dynamics code to calculate the phonon vibrational spectra of H and O in ice Ih. These spectra are supplied to the LEAPR module of the NJOY2012 nuclear data processing code to generate thermal neutron scattering laws for H and O in ice Ih in the incoherent approximation. The predicted vibrational spectra are optimized to be representative of the globally averaged ice Ih structure by comparing theoretically calculated and experimentally measured total cross sections and inelastic neutron scattering spectra. The resulting scattering kernel is then supplied to the MC21 Monte Carlo transport code to calculate time eigenvalues for the fundamental mode decay in ice cylinders at various temperatures. Results are compared to experimental flux decay measurements for a pulsed-neutron die-away diffusion benchmark.

  7. Neutron Scattering of Aromatic and Aliphatic Liquids.

    PubMed

    Falkowska, Marta; Bowron, Daniel T; Manyar, Haresh G; Hardacre, Christopher; Youngs, Tristan G A

    2016-07-04

    Organic solvents, such as cyclohexane, cyclohexene, methylcyclohexane, benzene and toluene, are widely used as both reagents and solvents in industrial processes. Despite the ubiquity of these liquids, the local structures that govern the chemical properties have not been studied extensively. Herein, we report neutron diffraction measurements on liquid cyclohexane, cyclohexene, methylcyclohexane, benzene and toluene at 298 K to obtain a detailed description of the local structure in these compounds. The radial distribution functions of the centres of the molecules, as well as the partial distribution functions for the double bond for cyclohexene and methyl group for methylcyclohexane and toluene have been calculated. Additionally, probability density functions and angular radial distribution functions were extracted to provide a full description of the local structure within the chosen liquids. Structural motifs are discussed and compared for all liquids, referring specifically to the functional group and aromaticity present in the different liquids. ©2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  8. Neutron Incoherent Scattering Measurements on Hydrogen-Charged Zircaloy-4

    SciTech Connect

    Garlea, Elena; Garlea, Vasile O; Choo, Hahn; Hubbard, Camden R; Liaw, Peter K

    2006-01-01

    Neutron incoherent scattering measurements were conducted on Zircaloy-4 round bars. The specimens were charged in a tube furnace at 430 C, using a 12.5 vol. % hydrogen in an argon mixture for 30, 60, and 90 minutes at 13.8 kPa pressure. The volume-average neutron diffraction measurements showed the presence of the face-centered-cubic delta zirconium hydride ({delta}.ZrH{sub 2}) phase in the hydrogenated specimens. The assessment of the background in the diffraction profiles due to the incoherent scattering from the hydrogen atoms was carried out by performing inelastic scans around zero energy transfer and at a fixed two-theta value for which there was only flat background and no coherent scattering. To estimate the relative amount of hydrogen in the Zircaloy-4 samples, the increase in incoherent scattering intensities with hydrogen content was calibrated using samples for which the hydrogen content was known. Measurement of the background scattering from locations within the round bar was also performed to map the distribution of hydrogen content.

  9. Spin observables in neutron-proton elastic scattering

    SciTech Connect

    Ahmidouch, A.; Arnold, J.; van den Brandt, B.; Daum, M.; Demierre, P.; Drevenak, R.; Finger, M. |; Finger, M. Jr.; Franz, J.; Goujon, N.; Hautle, P.; Janout, Z. Jr.; Hajdas, W.; Heer, E.; Hess, R.; Koger, R.; Konter, J.A.; Lacker, H.; Lechanoine-LeLuc, C.; Lehar, F.; Mango, S.; Mascarini, C.; Rapin, D.; Roessle, E.; Schmelzbach, P.A.; Schmitt, H.; Sereni, P.; Slunecka, M.

    1995-07-15

    We describe here two experiments presently running at PSI using the NA2 polarized neutron beam. They are devoted to the measurement of 2- and 3-spin observables in {ital np} elastic scattering for kinetic energies from 230 to 590 MeV with a center of mass angular range from 60 to 180 degrees. The goal is to determine the five {ital NN} scattering amplitudes for isospin 0 in a model independent way. Preliminary results for {ital K}{sub {ital OSKO}} and {ital K}{sub {ital OSSO}} spin-transfers are presented.

  10. Solid phases of spatially nanoconfined oxygen: A neutron scattering study

    SciTech Connect

    Kojda, Danny; Wallacher, Dirk; Hofmann, Tommy; Baudoin, Simon; Hansen, Thomas; Huber, Patrick

    2014-01-14

    We present a comprehensive neutron scattering study on solid oxygen spatially confined in 12 nm wide alumina nanochannels. Elastic scattering experiments reveal a structural phase sequence known from bulk oxygen. With decreasing temperature cubic γ-, orthorhombic β- and monoclinic α-phases are unambiguously identified in confinement. Weak antiferromagnetic ordering is observed in the confined monoclinic α-phase. Rocking scans reveal that oxygen nanocrystals inside the tubular channels do not form an isotropic powder. Rather, they exhibit preferred orientations depending on thermal history and the very mechanisms, which guide the structural transitions.

  11. Quasi-elastic neutron scattering studies of protein dynamics

    SciTech Connect

    Rorschach, H.E.

    1993-05-25

    Results that shed new light on the study of protein dynamics were obtained by quasi-elastic neutron scattering. The triple axis instrument H-9 supplied by the cold source was used to perform a detailed study of the quasi-elastic spectrum and the Debye-Waller factor for trypsin in powder form, in solution, and in crystals. A preliminary study of myoglobin crystals was also done. A new way to view the results of quasi-elastic scattering experiments is sketched, and the data on trypsin are presented and analyze according to this new picture.

  12. Neutron and Synchrotron X-Ray Scattering Studies of Superconductors

    SciTech Connect

    Tranquada,J.M.

    2008-09-01

    Superconductors hold the promise for a more stable and efficient electrical grid, but new isotropic, high-temperature superconductors are needed in order to reduce cable manufacturing costs. The effort to understand high-temperature superconductivity, especially in the layered cuprates, provides guidance to the search for new superconductors. Neutron scattering has long provided an important probe of the collective excitations that are involved in the pairing mechanism. For the cuprates, neutron and x-ray diffraction techniques also provide information on competing types of order, such as charge and spin stripes, that appear to be closely connected to the superconductivity. Recently, inelastic x-ray scattering has become competitive for studying phonons and may soon provide valuable information on electronic excitations. Examples of how these techniques contribute to our understanding of superconductivity are presented.

  13. Neutron scattering cross section measurements for Fe56

    DOE PAGES

    Ramirez, A. P. D.; Vanhoy, J. R.; Hicks, S. F.; ...

    2017-06-09

    Elastic and inelastic differential cross sections for neutron scattering from 56Fe have been measured for several incident energies from 1.30 to 7.96 MeV at the University of Kentucky Accelerator Laboratory. Scattered neutrons were detected using a C6D6 liquid scintillation detector using pulse-shape discrimination and time-of-flight techniques. The deduced cross sections have been compared with previously reported data, predictions from evaluation databases ENDF, JENDL, and JEFF, and theoretical calculations performed using different optical model potentials using the TALYS and EMPIRE nuclear reaction codes. The coupled-channel calculations based on the vibrational and soft-rotor models are found to describe the experimental (n,n0) andmore » (n,n1) cross sections well.« less

  14. Accurate Development of Thermal Neutron Scattering Cross Section Libraries

    SciTech Connect

    Hawari, Ayman; Dunn, Michael

    2014-06-10

    The objective of this project is to develop a holistic (fundamental and accurate) approach for generating thermal neutron scattering cross section libraries for a collection of important enutron moderators and reflectors. The primary components of this approach are the physcial accuracy and completeness of the generated data libraries. Consequently, for the first time, thermal neutron scattering cross section data libraries will be generated that are based on accurate theoretical models, that are carefully benchmarked against experimental and computational data, and that contain complete covariance information that can be used in propagating the data uncertainties through the various components of the nuclear design and execution process. To achieve this objective, computational and experimental investigations will be performed on a carefully selected subset of materials that play a key role in all stages of the nuclear fuel cycle.

  15. Light dark matter scattering in outer neutron star crusts

    NASA Astrophysics Data System (ADS)

    Cermeño, Marina; Pérez-García, M. Ángeles; Silk, Joseph

    2016-09-01

    We calculate for the first time the phonon excitation rate in the outer crust of a neutron star due to scattering from light dark matter (LDM) particles gravitationally boosted into the star. We consider dark matter particles in the sub-GeV mass range scattering off a periodic array of nuclei through an effective scalar-vector interaction with nucleons. We find that LDM effects cause a modification of the net number of phonons in the lattice as compared to the standard thermal result. In addition, we estimate the contribution of LDM to the ion-ion thermal conductivity in the outer crust and find that it can be significantly enhanced at large densities. Our results imply that for magnetized neutron stars the LDM-enhanced global conductivity in the outer crust will tend to reduce the anisotropic heat conduction between perpendicular and parallel directions to the magnetic field.

  16. Neutron scattering cross section measurements for 56Fe

    NASA Astrophysics Data System (ADS)

    Ramirez, A. P. D.; Vanhoy, J. R.; Hicks, S. F.; McEllistrem, M. T.; Peters, E. E.; Mukhopadhyay, S.; Harrison, T. D.; Howard, T. J.; Jackson, D. T.; Lenzen, P. D.; Nguyen, T. D.; Pecha, R. L.; Rice, B. G.; Thompson, B. K.; Yates, S. W.

    2017-06-01

    Elastic and inelastic differential cross sections for neutron scattering from 56Fe have been measured for several incident energies from 1.30 to 7.96 MeV at the University of Kentucky Accelerator Laboratory. Scattered neutrons were detected using a C6D6 liquid scintillation detector using pulse-shape discrimination and time-of-flight techniques. The deduced cross sections have been compared with previously reported data, predictions from evaluation databases ENDF, JENDL, and JEFF, and theoretical calculations performed using different optical model potentials using the talys and empire nuclear reaction codes. The coupled-channel calculations based on the vibrational and soft-rotor models are found to describe the experimental (n ,n0 ) and (n ,n1 ) cross sections well.

  17. Scientific opportunities with advanced facilities for neutron scattering

    SciTech Connect

    Lander, G.H.; Emery, V.J.

    1984-01-01

    The present report documents deliberations of a large group of experts in neutron scattering and fundamental physics on the need for new neutron sources of greater intensity and more sophisticated instrumentation than those currently available. An additional aspect of the Workshop was a comparison between steady-state (reactor) and pulsed (spallation) sources. The main conclusions were: (1) the case for a new higher flux neutron source is extremely strong and such a facility will lead to qualitatively new advances in condensed matter science and fundamental physics; (2) to a large extent the future needs of the scientific community could be met with either a 5 x 10/sup 15/ n cm/sup -2/s/sup -1/ steady state source or a 10/sup 17/ n cm/sup -2/s/sup -1/ peak flux spallation source; and (3) the findings of this Workshop are consistent with the recommendations of the Major Materials Facilities Committee.

  18. Neutron scattering study of the ferromagnetic superconductor UGe2

    NASA Astrophysics Data System (ADS)

    Kernavanois, N.; Grenier, B.; Huxley, A.; Ressouche, E.; Sanchez, J. P.; Flouquet, J.

    2001-11-01

    Unpolarized and polarized neutron scattering experiments have been performed at ambient pressure on a single crystal of the itinerant electron superconductor UGe2 in both the ferromagnetic and the paramagnetic phases. Unpolarized neutrons have confirmed the ZrGa2-type orthorhombic crystal structure of UGe2 and a ferromagnetic ordering below TC=53 K with the moments aligned along the a axis. No evidence of any modulated component for the magnetic structure has been found. Polarized neutron data have shown a large and almost spherical magnetization distribution at the U sites and no induced moment at the Ge sites. Refinements of the magnetic structure factors within the dipolar approximation allow the magnitude of the orbital and spin uranium moments to be quantified, and a comparison to the measured static magnetization reveals that there is no diffuse contribution.

  19. Event-Based Processing of Neutron Scattering Data

    DOE PAGES

    Peterson, Peter F.; Campbell, Stuart I.; Reuter, Michael A.; ...

    2015-09-16

    Many of the world's time-of-flight spallation neutrons sources are migrating to the recording of individual neutron events. This provides for new opportunities in data processing, the least of which is to filter the events based on correlating them with logs of sample environment and other ancillary equipment. This paper will describe techniques for processing neutron scattering data acquired in event mode that preserve event information all the way to a final spectrum, including any necessary corrections or normalizations. This results in smaller final errors, while significantly reducing processing time and memory requirements in typical experiments. Results with traditional histogramming techniquesmore » will be shown for comparison.« less

  20. PREFACE: 5th European Conference on Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Mikula, Pavel; Hlinka, Jiří; Prokeš, Karel; Dohnálek, Jan; Šittner, Petr; Javorský, Pavel

    2012-02-01

    This volume contains proceedings of ECNS 2011, held in Prague, Czech Republic, 17-22 July 2011. ECNS 2011 was the fifth Conference in a series of meetings organized in various European cities under patronage of the European Neutron Scattering Association, and was preceded by the European Neutron Scattering Conferences in Interlaken (1996), Budapest (1999), Montpellier (2003) and Lund (2007). The positive atmosphere of the Prague meeting of the neutron community can certainly be attributed to recent progress in the extension of the European neutron experimental base, in particular the completion of the ISIS second target station and considerable progress in the European Spallation Source project in Lund. The success of ECNS 2011 has been manifested by the participation of 698 scientists from 36 countries, who presented 231 talks and 534 posters. This proceedings contains 112 papers from authors who wished to have the written versions of their contributions published. The contributions illustrate the broad scale of scientific problems investigated by neutron scattering methods and give a picture of growing activities in the field. The conference chairmen wish to express their thanks to all colleagues who contributed to the organization and preparation of ECNS 2011, in particular the members of the International Advisory Committee, the International Program Committee and the Local Organizing Committee. We very much appreciate the role of Professor Michael Steiner, the President of ENSA, and all ENSA representatives who contributed valuable conceptual input and advice in the preparatory phase of the conference organization. Special thanks go to the editors and all the referees who helped us to publish the ECNS 2011 Proceedings in such a short time. Vladimír SechovskýPetr Lukáš Conference chairmen The PDF contains photographs from the conference and a full list of participants.

  1. Crystals for neutron scattering studies of quantum magnetism

    SciTech Connect

    Yankova, Tantiana; Hüvonen, Dan; Mühlbauer, Sebastian; Schmidiger, David; Wulf, Erik; Hong, Tao; Garlea, Vasile O; Custelcean, Radu; Ehlers, Georg

    2012-01-01

    We review a strategy for targeted synthesis of large single crystal samples of prototype quantum magnets for inelastic neutron scattering experiments. Four case studies of organic copper halogenide S = 1/2 systems are presented. They are meant to illustrate that exciting experimental results pertaining to the forefront of many-body quantum physics can be obtained on samples grown using very simple techniques, standard laboratory equipment, and almost no experience in advanced crystal growth techniques.

  2. Bragg optics computer codes for neutron scattering instrument design

    SciTech Connect

    Popovici, M.; Yelon, W.B.; Berliner, R.R.; Stoica, A.D.

    1997-09-01

    Computer codes for neutron crystal spectrometer design, optimization and experiment planning are described. Phase space distributions, linewidths and absolute intensities are calculated by matrix methods in an extension of the Cooper-Nathans resolution function formalism. For modeling the Bragg reflection on bent crystals the lamellar approximation is used. Optimization is done by satisfying conditions of focusing in scattering and in real space, and by numerically maximizing figures of merit. Examples for three-axis and two-axis spectrometers are given.

  3. (US-Japan cooperative program on neutron scattering)

    SciTech Connect

    Moon, R.M.

    1990-06-11

    The traveler participated in a meeting on May 22, 1990, at JAERI Headquarters, Tokyo, Japan, to discuss methods of arranging for JAERI participation in the design of the ANS. On May 23, 1990, while at Tokai Research Establishment, Tokai, Japan, he toured the new JRR-3 reactor and attended the Steering Committee Meeting at which plans and budgets for the US-Japan Cooperative Program on Neutron Scattering were discussed and approved.

  4. Neutron scattering from amorphous, disordered and nanocrystalline materials

    SciTech Connect

    Price, D.L.

    1994-10-01

    The author has described the power of neutron diffraction and inelastic scattering techniques for determining the structure and dynamics of disordered systems, using the archetypal glass SiO{sub 2} as a detailed example. Of course the field of amorphous and disordered systems contains a much greater variety of types of materials exhibiting a wide range of possible types of disorder. The author gives a brief review of the varieties of order and disorder exhibited by condensed matter.

  5. Simulation of a complete inelastic neutron scattering experiment

    NASA Astrophysics Data System (ADS)

    Edwards, H.; Lefmann, K.; Lake, B.; Nielsen, K.; Skaarup, P.

    A simulation of an inelastic neutron scattering experiment on the high-temperature superconductor La2-xSrxCuO4 is presented. The complete experiment, including sample, is simulated using an interface between the experiment control program and the simulation software package (McStas) and is compared with the experimental data. Simulating the entire experiment is an attractive alternative to the usual method of convoluting the model cross section with the resolution function, especially if the resolution function is nontrivial.

  6. Quasielastic neutron scattering study of POSS ligand dynamics

    SciTech Connect

    Jalarvo, Niina H; Tyagi, Madhusudan; Crawford, Michael

    2015-01-01

    Polyoligosilsesquioxanes are molecules having cage-like structures composed of silicon and oxygen. These molecules can have a wide variety of functional ligands attached to them. Depending on the nature of the ligand, interesting properties and applications are found. In this work we present results from quasielastic neutron scattering measurements of four different POSS molecules that illustrate the presence of strong coupling between the ligand dynamics and the POSS crystal structures.

  7. SANS (small-angle neutron scattering) from polymers and colloids

    SciTech Connect

    Hayter, J.B.

    1987-01-01

    Small-angle neutron scattering (SANS) has been remarkably successful in providing detailed quantitative structural information on complex everyday materials, such as polymers and colloids, which are often of considerable industrial as well as academic interest. This paper reviews some recent SANS experiments on polymers and colloids, including ferrofluids, and discusses the use of these apparently complex systems as general physical models of the liquid or solid state.

  8. Recent neutron scattering results from Gd-based pyrochlore oxides

    NASA Astrophysics Data System (ADS)

    Gardner, Jason

    2009-03-01

    In my presentation I will present recent results that have determined the spin-spin correlations in the geometrically frustrated magnets Gd2Sn2O7 and Gd2Ti2O7. This will include polarised neutron diffraction, inelastic neutron scattering and neutron spin echo data. One sample of particular interest is Gd2Sn2O7 which is believed to be a good approximation to a Heisenberg antiferromagnet on a pyrochlore lattice with exchange and dipole-dipole interactions. Theoretically such a system is expected to enter long range ordered ground state known as the ``Palmer Chalker'' state [1]. We show conclusively, through neutron scattering data, that the system indeed enters an ordered state with the Palmer-Chalker spin configuration below Tc = 1 K [2-3]. Within this state we have also observed long range collective spin dynamics, spin waves. This work has been performed in collaboration with many research groups including G. Ehlers (SNS), R. Stewart (ISIS). [0pt] [1] S. E. Palmer and J. T. Chalker, Phys. Rev. B 62, 488 (2000). [0pt] [2] J. R. Stewart, G. Ehlers, A. S. Wills, S. T. Bramwell, and J. S. Gardner, J. Phys.: Condens. Matter 16, L321 (2004). [0pt] [3] J R Stewart, J S Gardner, Y. Qiu and G Ehlers, Phys. Rev. B. 78, 132410 (2008)

  9. Neutrino scattering rates in neutron star matter with {delta} isobars

    SciTech Connect

    Chen Yanjun; Guo Hua; Liu Yuxin

    2007-03-15

    We take the {delta}-isobar degrees of freedom into account in neutron star matter and evaluate their contributions to neutrino scattering cross sections and mean free paths. The neutron star matter is described by means of an effective hadronic model in the relativistic mean-field approximation. It is found that {delta} isobars may be present in neutron stars. The electron chemical potential does not decrease and the neutrino abundance does not increase with the increase of the density when neutrinos are trapped in the matter with {delta} isobars. The large vector coupling constant between the {delta}{sup -} and neutrino and the high spin of the {delta} influence significantly the neutrino scattering cross section and lead the contribution of the {delta}{sup -} to the dominance of the scattering rates. In neutrino-trapped case, the presence of {delta}s causes the neutrino mean free path to decrease drastically compared to that in the matter in which baryons are only nucleons.

  10. Elastic and inelastic scattering of neutrons on 238U nucleus

    NASA Astrophysics Data System (ADS)

    Capote, R.; Trkov, A.; Sin, M.; Herman, M. W.; Soukhovitskiĩ, E. Sh.

    2014-04-01

    Advanced modelling of neutron induced reactions on the 238U nucleus is aimed at improving our knowledge of neutron scattering. Capture and fission channels are well constrained by available experimental data and neutron standard evaluation. A focus of this contribution is on elastic and inelastic scattering cross sections. The employed nuclear reaction model includes - a new rotational-vibrational dispersive optical model potential coupling the low-lying collective bands of vibrational character observed in even-even actinides; - the Engelbrecht-Weidenmüller transformation allowing for inclusion of compound-direct interference effects; - and a multi-humped fission barrier with absorption in the secondary well described within the optical model for fission. Impact of the advanced modelling on elastic and inelastic scattering cross sections including angular distributions and emission spectra is assessed both by comparison with selected microscopic experimental data and integral criticality benchmarks including measured reaction rates (e.g. JEMIMA, FLAPTOP and BIG TEN). Benchmark calculations provided feedback to improve the reaction modelling. Improvement of existing libraries will be discussed.

  11. Neutron Scattering Cross Sections for Natural Carbon in the Energy Range 2-133 keV

    SciTech Connect

    Gritzay, O; Gnidak, M; Kolotyi, V; Korol, O; Razbudey, V; Venedyktov, V; Richardson, J H; Sale, K

    2006-06-14

    Natural carbon is well known as reactor structure material and at the same time as one of the most important neutron scattering standards, especially at energies less than 2 MeV, where the neutron total and neutron scattering cross sections are essentially identical. The best neutron total cross section experimental data for natural carbon in the range 1-500 keV have uncertainties of 1-4%. However, the difference between these data and those based on R-matrix analysis and used in the ENDF libraries is evident, especially in the energy range 1-60 keV. Experimental data for total scattering neutron cross sections for this element in the energy range 1-200 keV are scanty. The use of the technique of neutron filtered beams developed at the Kyiv Research Reactor makes it possible to reduce the uncertainty of the experimental data and to measure the neutron scattering cross sections on natural carbon in the energy range 2-149 keV with accuracies of 3-6%. Investigations of the neutron scattering cross section on carbon were carried out using 5 filters with energies 2, 3.5, 24, 54 and 133 keV. The neutron scattering cross sections were measured using a detector system covering nearly 2{pi}. The detector consisting of {sup 3}He counters (58 units), was located just above the carbon samples. The {sup 3}He counters (CHM-37, 7 atm, diameter =18 mm, L=50 cm) are placed in five layers (12 or 11 in each layer). To determine the neutron scattering cross section on carbon the relative method of measurement was used. The isotope {sup 208}Pb was used as the standard. The normalization factor, which is a function of detector efficiency, thickness of the carbon samples, thickness of the {sup 208}Pb sample, geometry, etc., for each sample and for each filter energy has been obtained through Monte Carlo calculations by means of the MCNP4C code. The results of measurements of the neutron scattering cross sections at reactor neutron filtered beams with energies in the range 2-133 keV on

  12. Neutron scattering measurements in {sup 197}Au from 850 keV to 2.0 MeV

    SciTech Connect

    O`Connor, M.; Chen, J.; Egan, J.J.

    1995-10-01

    Differential elastic and inelastic neutron scattering cross-sections for low lying levels in {sup 197}Au have been measured for incident neutron energies of 1.0 MeV, 1.5 MeV and 2.0 MeV. In addition, the total neutron cross sections in {sup 197}Au was measured from 850 keV to 1.5 MeV. For both experiments the UML 5.5 MV Van-de-Graaff accelerator with a Mobley post acceleration compression system, produced subnanosecond proton pulses which generated neutrons via the {sup 7}Li(p,n) {sup 7}Be reaction.

  13. Chiral Three-Nucleon Interactions in Light Nuclei, NeutronScattering, and Neutron Matter

    NASA Astrophysics Data System (ADS)

    Lynn, J. E.; Tews, I.; Carlson, J.; Gandolfi, S.; Gezerlis, A.; Schmidt, K. E.; Schwenk, A.

    2016-02-01

    We present quantum Monte Carlo calculations of light nuclei, neutronscattering, and neutron matter using local two- and three-nucleon (3 N ) interactions derived from chiral effective field theory up to next-to-next-to-leading order (N2LO ). The two undetermined 3 N low-energy couplings are fit to the 4He binding energy and, for the first time, to the spin-orbit splitting in the neutron-α P -wave phase shifts. Furthermore, we investigate different choices of local 3 N -operator structures and find that chiral interactions at N2LO are able to simultaneously reproduce the properties of A =3 ,4 ,5 systems and of neutron matter, in contrast to commonly used phenomenological 3 N interactions.

  14. Chiral Three-Nucleon Interactions in Light Nuclei, NeutronScattering, and Neutron Matter.

    PubMed

    Lynn, J E; Tews, I; Carlson, J; Gandolfi, S; Gezerlis, A; Schmidt, K E; Schwenk, A

    2016-02-12

    We present quantum Monte Carlo calculations of light nuclei, neutronscattering, and neutron matter using local two- and three-nucleon (3N) interactions derived from chiral effective field theory up to next-to-next-to-leading order (N(2)LO). The two undetermined 3N low-energy couplings are fit to the (4)He binding energy and, for the first time, to the spin-orbit splitting in the neutron-α P-wave phase shifts. Furthermore, we investigate different choices of local 3N-operator structures and find that chiral interactions at N(2)LO are able to simultaneously reproduce the properties of A=3,4,5 systems and of neutron matter, in contrast to commonly used phenomenological 3N interactions.

  15. A High Count Rate Neutron Beam Monitor for Neutron Scattering Facilities

    SciTech Connect

    Barnett, Amanda; Crow, Lowell; Diawara, Yacouba; Hayward, J P; Hayward, Jason P; Menhard, Kocsis; Sedov, Vladislav N; Funk, Loren L

    2013-01-01

    Abstract Beam monitors are an important diagnostic tool in neutron science facilities. Present beam monitors use either ionization chambers in integration mode, which are slow and have no timing information, or pulse counters which can easily be saturated by high beam intensities. At high flux neutron scattering facilities, neutron beam monitors with very low intrinsic efficiency (10-5) are presently selected to keep the counting rate within a feasible range, even when a higher efficiency would improve the counting statistics and yield a better measurement of the incident beam. In this work, we report on a high count rate neutron beam monitor. This beam monitor offers good timing with an intrinsic efficiency of 10-3 and a counting rate capability of over 1,000,000 cps without saturation.

  16. Chiral Three-Nucleon Interactions in Light Nuclei, NeutronScattering, and Neutron Matter

    SciTech Connect

    Lynn, J. E.; Tews, I.; Carlson, Joseph Allen; Gandolfi, Stefano; Gezerlis, A.; Schmidt, K. E.; Schwenk, A.

    2016-02-09

    Here we present quantum Monte Carlo calculations of light nuclei, neutron- scattering, and neutron matter using local two- and three-nucleon (3N) interactions derived from chiral e effective fi eld theory up to next-to-next-to-leading order (N2LO). The two undetermined 3N low-energy couplings are fi t to the 4He binding energy and, for the first time, to the spin-orbit splitting in the neutron- P-wave phase shifts. Furthermore, we investigate different choices of local 3N-operator structures and find that chiral interactions at N2LO are able to simultaneously reproduce the properties of A = 3; 4; 5 systems and of neutron matter, in contrast to commonly used phenomenological 3N interactions.

  17. Chiral Three-Nucleon Interactions in Light Nuclei, NeutronScattering, and Neutron Matter

    DOE PAGES

    Lynn, J. E.; Tews, I.; Carlson, Joseph Allen; ...

    2016-02-09

    Here we present quantum Monte Carlo calculations of light nuclei, neutron- scattering, and neutron matter using local two- and three-nucleon (3N) interactions derived from chiral e effective fi eld theory up to next-to-next-to-leading order (N2LO). The two undetermined 3N low-energy couplings are fi t to the 4He binding energy and, for the first time, to the spin-orbit splitting in the neutron- P-wave phase shifts. Furthermore, we investigate different choices of local 3N-operator structures and find that chiral interactions at N2LO are able to simultaneously reproduce the properties of A = 3; 4; 5 systems and of neutron matter, in contrastmore » to commonly used phenomenological 3N interactions.« less

  18. Chamber for mechanical testing in H2 with observation by neutron scattering

    NASA Astrophysics Data System (ADS)

    Connolly, Matthew; Bradley, Peter; Slifka, Andrew; Drexler, Elizabeth

    2017-06-01

    A gas-pressure chamber has been designed, constructed, and tested at a moderate pressure (3.4 MPa, 500 psi) and has the capability of mechanical loading of steel specimens for neutron scattering measurements. The chamber will allow a variety of in situ neutron scattering measurements: in particular, diffraction, quasielastic scattering, inelastic scattering, and imaging. The chamber is compatible with load frames available at the user facilities at the NIST Center for Neutron Research and Oak Ridge National Laboratory Spallation Neutron Source. A demonstration of neutron Bragg edge imaging using the chamber is presented.

  19. Target correlation effects on neutron-nucleus total, absorption, and abrasion cross sections

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Townsend, Lawrence W.; Wilson, John W.

    1991-01-01

    Second order optical model solutions to the elastic scattering amplitude were used to evaluate total, absorption, and abrasion cross sections for neutron nucleus scattering. Improved agreement with experimental data for total and absorption cross sections is found when compared with first order (coherent approximation) solutions, especially below several hundred MeV. At higher energies, the first and second order solutions are similar. There are also large differences in abrasion cross section calculations; these differences indicate a crucial role for cluster knockout in the abrasion step.

  20. Cross correlation calculations and neutron scattering analysis for a portable solid state neutron detection system

    NASA Astrophysics Data System (ADS)

    Saltos, Andrea

    In efforts to perform accurate dosimetry, Oakes et al. [Nucl. Intrum. Mehods. (2013)] introduced a new portable solid state neutron rem meter based on an adaptation of the Bonner sphere and the position sensitive long counter. The system utilizes high thermal efficiency neutron detectors to generate a linear combination of measurement signals that are used to estimate the incident neutron spectra. The inversion problem associated to deduce dose from the counts in individual detector elements is addressed by applying a cross-correlation method which allows estimation of dose with average errors less than 15%. In this work, an evaluation of the performance of this system was extended to take into account new correlation techniques and neutron scattering contribution. To test the effectiveness of correlations, the Distance correlation, Pearson Product-Moment correlation, and their weighted versions were performed between measured spatial detector responses obtained from nine different test spectra, and the spatial response of Library functions generated by MCNPX. Results indicate that there is no advantage of using the Distance Correlation over the Pearson Correlation, and that weighted versions of these correlations do not increase their performance in evaluating dose. Both correlations were proven to work well even at low integrated doses measured for short periods of time. To evaluate the contribution produced by room-return neutrons on the dosimeter response, MCNPX was used to simulate dosimeter responses for five isotropic neutron sources placed inside different sizes of rectangular concrete rooms. Results show that the contribution of scattered neutrons to the response of the dosimeter can be significant, so that for most cases the dose is over predicted with errors as large as 500%. A possible method to correct for the contribution of room-return neutrons is also assessed and can be used as a good initial estimate on how to approach the problem.

  1. Electron Scattering From a High-Momentum Neutron in Deuterium

    SciTech Connect

    Klimenko, Alexei

    2004-05-01

    The deuterium nucleus is a system of two nucleons (proton and neutron) bound together. The configuration of the system is described by a quantum-mechanical wave function and the state of the nucleons at a given time is not know a priori. However, by detecting a backward going proton of moderate momentum in coincidence with a reaction taking place on the neutron in deuterium, the initial state of that neutron can be inferred if we assume that the proton was a spectator to the reaction. This method, known as spectator tagging, was used to study the electron scattering from high-momentum neutrons in deuterium. The data were taken with a 5.765 GeV polarized electron beam on a deuterium target in Jefferson Laboratory's Hall B, using the CLAS detector. The accumulated data cover a wide kinematic range, reaching values of the invariant mass of the unobserved final state W* up to 3 GeV. A data sample of approximately 5 - 105 events, with protons detected at large scattering angles (as high as 136 degrees) in coincidence with the forward electrons, was selected. The product of the neutron structure function with the initial nucleon momentum distribution F2n. S was extracted for different values of W*, backward proton momenta ps and momentum transfer Q2. The data were compared to a calculation based on the spectator approximation and using the free nucleon form factors and structure functions. A strong enhancement in the data, not reproduced by the model, was observed at cos(thetapq) > -0.3 (where theta{sub pq} is the proton scattering angle relative to the direction of the momentum transfer) and can be associated with the contribution of final state interactions (FSI) that were not incorporated into the model. The bound nucleon structure function F2n was studied in the region cos(thetapq) < -0.3 as a function of W* and scaling variable x*. At high spectator proton momenta the struck neutron is far

  2. Measurement of Total Cross Sections at Pohang Neutron Facility

    SciTech Connect

    Kim, Guinyun; Meaze, A.K.M.M.H.; Ahmed, Hossain; Son, Dongchul; Lee, Young Seok; Kang, Hengsik; Cho, Moo-Hyun; Ko, In Soo; Namkung, Won; Ro, Tae-Ik.; Chung, Won-Chung; Kim, Young Ae; Yoo, Kun Joong; Chang, Jong Hwa

    2005-05-24

    The Pohang Neutron Facility, which consists of an electron linear accelerator, a water-cooled Ta target with a water moderator, and a time-of-flight path with an 11 m length has been operated since 2000. We report the status activities on the neutron total cross-section measurements in the neutron energy region from 0.01 eV to 100 eV by the neutron time-of-flight method at Pohang Neutron Facility. A 6Li-ZnS(Ag) scintillator with a diameter of 12.5 cm and a thickness of 1.5 cm has been used as a neutron detector. The background level has been determined by using notch-filters of Co, In, and Cd sheets. In order to reduce the gamma rays from Bremsstrahlung and that from neutron capture, we have employed a neutron-gamma separation system based on their different pulse shape. The present measurements for Ag, Hf, and Ta samples are compared with the previous ones and the evaluated data in ENDF/B-VI. The resonance parameters for Ag and Hf samples have been extracted from the transmission data by using the SAMMY code.

  3. Neutron scattering measurements of low-dimensional quantum systems

    NASA Astrophysics Data System (ADS)

    Haravifard, Sara

    Low dimensional quantum magnets which display a collective singlet ground state and a gap in their magnetic excitation spectrum provide a framework for much exotic phase behavior in new materials, with high temperature superconductivity being the best appreciated example. Neutron scattering techniques can be applied to study a wide variety of problems in condensed matter physics. These techniques are particularly useful as applied to understanding the magnetic properties of quantum magnets that display exotic phases. SrCu2(BO3)2, is a rare example of a two-dimensional quantum magnet for which an exact theoretical solution describing its ground state is known to be a collective singlet. Previous high resolution neutron scattering measurements identified the most prominent features of the spin excitation spectrum in SrCu2(BO3)2, including the presence of one and two triplet excitations and weak dispersion characteristic of subleading terms in the spin Hamiltonian. The resemblance between the spin gap behavior in the Mott insulator SrCu 2(BO3)2 and that associated with high temperature superconductors motivated the consideration of the significance of doping in order to understand the properties of this quantum magnetic system. For this reason, a series of neutron scattering studies on doped SrCu2(BO 3)2 were initiated. These series of investigations began with the performance of neutron scattering measurements on a SrCu(2-x)Mgx(BO 3)2 single crystal in order to introduce magnetic vacancies to the system. These results revealed the presence of new spin excitations within the singlet-triplet gap of this system. Application of a magnetic field induces Zeeman-split states associated with un-paired spins which exist as a consequence of doping with quenched non-magnetic impurities. Additional substantial broadening of both the one and two triplet excitations is observed in the doped system as compared to the pure system. Theoretical calculations are shown to qualitatively

  4. Pore accessibility by methane and carbon dioxide in coal as determined by neutron scattering

    SciTech Connect

    He, Lilin; Melnichenko, Yuri B; Mastalerz, Maria; Sakurovs, Richard; Radlinski, Andrzej Pawell; Blach, Tomasz P

    2012-01-01

    Contrast-matching ultrasmall-angle neutron scattering (USANS) and small-angle neutron scattering (SANS) techniques were used for the first time to determine both the total pore volume and the fraction of the pore volume that is inaccessible to deuterated methane, CD{sub 4}, in four bituminous coals in the range of pore sizes between {approx}10 {angstrom} and {approx}5 {micro}m. Two samples originated from the Illinois Basin in the U.S.A., and the other two samples were commercial Australian bituminous coals from the Bowen Basin. The total and inaccessible porosity were determined in each coal using both Porod invariant and the polydisperse spherical particle (PDSP) model analysis of the scattering data acquired from coals both in vacuum and at the pressure of CD{sub 4}, at which the scattering length density of the pore-saturating fluid is equal to that of the solid coal matrix (zero average contrast pressure). The total porosity of the coals studied ranged from 7 to 13%, and the volume of pores inaccessible to CD{sub 4} varied from {approx}13 to {approx}36% of the total pore volume. The volume fraction of inaccessible pores shows no correlation with the maceral composition; however, it increases with a decreasing total pore volume. In situ measurements of the structure of one coal saturated with CO{sub 2} and CD{sub 4} were conducted as a function of the pressure in the range of 1-400 bar. The neutron scattering intensity from small pores with radii less than 35 {angstrom} in this coal increased sharply immediately after the fluid injection for both gases, which demonstrates strong condensation and densification of the invading subcritical CO{sub 2} and supercritical methane in small pores.

  5. Small-angle neutron scattering study of radiation-induced defects in synthetic quartz

    SciTech Connect

    Lebedev, V. M. Lebedev, V. T.; Orlov, S. P.; Pevzner, B. Z.; Tolstikhin, I. N.

    2006-12-15

    The supraatomic structure of single crystals of synthetic quartz was studied by thermal neutron small-angle scattering in the initial state (dislocation densities 54 and 570 cm{sup -2}) and after irradiation in the WWR-M reactor (Petersburg Nuclear Physics Institute) by fast neutrons with energies E{sub n} > 0.1 MeV at fluences F{sub n} = 0.2 x 10{sup 17} -5 x 10{sup 18} neutrons/cm{sup 2}. It is established that fast neutrons form point, linear, and volume defects in the lattice throughout the entire volume of a sample. Large-volume structures-amorphous-phase nuclei-reach sizes of {approx}100 nm in quartz, while occupying a small total volume of {approx}0.3% even at the maximum fluence 5 x 10{sup 18} neutrons/cm{sup 2}. The main fraction of the damaged volume (up to 5%) corresponds to point (with a radius of gyration of 1-2 nm) and linear defects, giving a comparable contribution ({approx}1-4%). The extended linear structures with a radius of 2 nm, even at a moderate fluence of 7.7 x 10{sup 17} neutrons/cm{sup 2}, have a significant total length per volume unit ({approx}10{sup 11} cm/cm{sup 3}) and can form a connected network with a cell {approx}30 nm in size in the sample. Foreign atoms and molecules can migrate through channels of this network.

  6. Small-angle neutron scattering from samples of expanded carbon

    SciTech Connect

    Bogdanov, S. G. Valiev, E. Z.; Dorofeev, Yu. A.; Pirogov, A. N.; Skryabin, Yu. N.; Makotchenko, V. G.; Nazarov, A. S.; Fedorov, V. E.

    2006-12-15

    The subatomic structure of expanded graphite has been investigated by small-angle neutron scattering. Samples were synthesized during quick thermal decomposition of intercalated compounds based on oxidized graphite. They had a low bulk density (up to 0.1 g/cm{sup 3}) and were characterized by considerable small-angle scattering. It has been established that majority of the volume of expanded graphite samples is occupied by participles with characteristic sizes in two ranges: from 6 to 8 nm and from 20 to 30 nm. Small particles have properties of a surface fractal with the dimension D{sub s} = 2.4-2.6, whereas the larger particles are mainly smooth and have the dimension D{sub s} = 2.0-2.1. The specific surface of the samples studied was determined from the small-angle scattering data.

  7. Survey of background scattering from materials found in small-angle neutron scattering

    PubMed Central

    Barker, J. G.; Mildner, D. F. R.

    2015-01-01

    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 3He 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 3He 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. PMID:26306088

  8. Survey of background scattering from materials found in small-angle neutron scattering.

    PubMed

    Barker, J G; Mildner, D F R

    2015-08-01

    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.

  9. Protein Dynamics Studied by Quasi-elastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Chu, Xiang-Qiang; Mamontov, Eugene; Lagi, Marco; Chen, Sow-Hsin; Gajapathy, Manavalan; Ng, Joseph; Weiss, Kevin; Coates, Leighton; Fratini, Emiliano; Baglioni, Piero

    2012-02-01

    The biological function and activities of proteins are intimately related to their structures and dynamics. Nowadays, neutron scattering is one of the most powerful tools to study the protein dynamics. In this study, we use quasielastic neutron scattering (QENS) at the Spallation Neutron Source, ORNL, to study relaxational dynamics of two structurally different proteins --- hen egg white lysozyme and an inorganic pyrophosphatase from a hyperthermophile, in the time range of 10ps to 1ns. We experimentally prove that the slow dynamics of globular proteins can be described by the mode-coupling theory (MCT) that was originally developed for glass-forming molecular liquids. The MCT predicts the appearance of a logarithmic decay for a glass-forming liquid. Such dynamic behavior is also observed by recent molecular dynamics (MD) simulations on protein molecules. In addition, we compare the temperature dependence of the dynamics of the two proteins with completely different activity profiles. Our results greatly help understanding the relation between protein dynamics and their biological functions.

  10. Electron Scattering From High-Momentum Neutrons in Deuterium

    SciTech Connect

    A.V. Klimenko; S.E. Kuhn

    2005-10-12

    We report results from an experiment measuring the semi-inclusive reaction D(e,e'p{sub s}) where the proton p{sub s} is moving at a large angle relative to the momentum transfer. If we assume that the proton was a spectator to the reaction taking place on the neutron in deuterium, the initial state of that neutron can be inferred. This method, known as spectator tagging, can be used to study electron scattering from high-momentum (off-shell) neutrons in deuterium. The data were taken with a 5.765 GeV electron beam on a deuterium target in Jefferson Laboratory's Hall B, using the CLAS detector. A reduced cross section was extracted for different values of final-state missing mass W*, backward proton momentum {rvec p}{sub s} and momentum transfer Q{sup 2}. The data are compared to a simple PWIA spectator model. A strong enhancement in the data observed at transverse kinematics is not reproduced by the PWIA model. This enhancement can likely be associated with the contribution of final state interactions (FSI) that were not incorporated into the model. A ''bound neutron structure function'' F{sub 2n}{sup eff} was extracted as a function of W* and the scaling variable x* at extreme backward kinematics, where effects of FSI appear to be smaller. For p{sub s} > 400 MeV/c, where the neutron is far off-shell, the model overestimates the value of F{sub 2n}{sup eff} in the region of x* between 0.25 and 0.6. A modification of the bound neutron structure function is one of possible effects that can cause the observed deviation.

  11. Inelastic scattering of neutrons and possible biological applications.

    PubMed

    Egelstaff, P A

    1976-05-01

    The field of neutron inelastic scattering has probably been developed to the stage where it can begin to help the biologist. Because essentially no experimental data have been obtained, it is difficult either to draw conclusions or to make forecasts except on the basis of general hypotheses. It seems likely, however, that the next stage is up to biologists. After reviewing those biological problems in which molecular dynamics might play an important role, they should suggest specimens of interest which can give inelastic peaks with existing spectrometers operating with 5 to 10-A neutrons at angles greater than 5degrees and with resolutions of approximately 50 mueV. These specimens may involve molecules slightly smaller and more mobile than some biologists would like, but a successful outcome might lead to the development of spectrometers capable of working in a more satisfactory range. In this event the return may well prove rewarding to the biologists.

  12. A novel small-angle neutron scattering detector geometry

    PubMed Central

    Kanaki, Kalliopi; Jackson, Andrew; Hall-Wilton, Richard; Piscitelli, Francesco; Kirstein, Oliver; Andersen, Ken H.

    2013-01-01

    A novel 2π detector geometry for small-angle neutron scattering (SANS) applications is presented and its theoretical performance evaluated. Such a novel geometry is ideally suited for a SANS instrument at the European Spallation Source (ESS). Motivated by the low availability and high price of 3He, the new concept utilizes gaseous detectors with 10B as the neutron converter. The shape of the detector is inspired by an optimization process based on the properties of the conversion material. Advantages over the detector geometry traditionally used on SANS instruments are discussed. The angular and time resolutions of the proposed detector concept are shown to satisfy the requirements of the particular SANS instrument. PMID:24046504

  13. Neutron Scattering Studies of Vapor Deposited Amorphous Ice

    NASA Astrophysics Data System (ADS)

    Kolesnikov, A. I.; Li, J.-C.; Dong, S.; Bailey, I. F.; Eccleston, R. S.; Hahn, W.; Parker, S. F.

    1997-09-01

    Inelastic neutron scattering spectra were measured for amorphous ice H2O and D2O produced by low-temperature and low-rate vapor deposition. The data show that the deposition produced the low-density amorphous form of ice, i.e., the high-density amorphous ice observed by x-ray [A. H. Narten, C. G. Venkatesh, and S. A. Rice, J. Chem. Phys. 64, 1106 (1976)] and electron diffraction [P. Jenniskens and D. F. Blake, Science 265, 753 (1994)] under similar conditions was not detected. This result was confirmed by separate neutron diffraction experiments. Vibrational spectra of the deposited amorphous ice were dissimilar to that of ice Ih/Ic, as was believed previously.

  14. Neutron scatter studies of chromatin structures related to functions

    SciTech Connect

    Bradbury, E.M.

    1992-01-01

    Despite of setbacks in the lack of neutrons for the proposed We have made considerable progress in chromatin reconstitution with the VLR histone H1/H5 and in understanding the dynamics of nucleosomes. A ferromagnetic fluid was developed to align biological molecules for structural studies using small-angle-neutron-scattering. We have also identified and characterized an intrinsically bent DNA region flanking the RNA polymerase I binding site of the ribosomal RNA gene in Physarum Polycephalum. Finally projects in progress are in the areas of studying the interatctions of histone H4 amino-terminus peptide 1-23 and acetylated 1-23 peptide with DNA using thermal denaturation; study of GGAAT repeats found in human centromeres using high resolution Nuclear magnetic Resonance and nuclease sentivity assay; and the role of histones and other sperm specific proteins with sperm chromatin.

  15. Fractal Approach in Petrology: Combining Ultra-Small Angle (USANA) and Small Angle Neutron Scattering (SANS)

    SciTech Connect

    LoCelso, F.; Triolo, F.; Triolo, A.; Lin, J.S.; Lucido, G.; Triolo, R.

    1999-10-14

    Ultra small angle neutron scattering instruments have recently covered the gap between the size resolution available with conventional intermediate angle neutron scattering and small angle neutron scattering instruments on one side and optical microscopy on the other side. Rocks showing fractal behavior in over two decades of momentum transfer and seven orders of magnitude of intensity are examined and fractal parameters are extracted from the combined USANS and SANS curves.

  16. From x-ray telescopes to neutron scattering: Using axisymmetric mirrors to focus a neutron beam

    NASA Astrophysics Data System (ADS)

    Khaykovich, B.; Gubarev, M. V.; Bagdasarova, Y.; Ramsey, B. D.; Moncton, D. E.

    2011-03-01

    We demonstrate neutron beam focusing by axisymmetric mirror systems based on a pair of mirrors consisting of a confocal ellipsoid and hyperboloid. Such a system, known as a Wolter mirror configuration, is commonly used in X-ray telescopes. The axisymmetric Wolter geometry allows nesting of several mirror pairs to increase collection efficiency. We implemented a system containing four nested Ni mirror pairs, which was tested by the focusing of a polychromatic neutron beam at the MIT Reactor. In addition, we have carried out extensive ray-tracing simulations of the mirrors and their performance in different situations. The major advantages of the Wolter mirrors are nesting for large angular collection and aberration-free performance. We discuss how these advantages can be utilized to benefit various neutron scattering methods, such as imaging, SANS, and time-of-flight spectroscopy.

  17. Parity violation in low-energy neutron-deuteron scattering

    NASA Astrophysics Data System (ADS)

    Song, Young-Ho; Lazauskas, Rimantas; Gudkov, Vladimir

    2011-01-01

    Parity-violating effects for low-energy elastic neutron deuteron scattering are calculated for Desplanques, Donoghue, and Holstein (DDH) and effective field theory types of weak potentials in a distorted-wave Born approximation, using realistic hadronic strong interaction wave functions, obtained by solving three-body Faddeev equations in configuration space. The resulting relation between physical observables and low-energy constants can be used to fix low-energy constants from experiments. Potential model dependencies of parity-violating effects are discussed.

  18. Parity violation in low-energy neutron-deuteron scattering

    SciTech Connect

    Song, Young-Ho; Gudkov, Vladimir; Lazauskas, Rimantas

    2011-01-15

    Parity-violating effects for low-energy elastic neutron deuteron scattering are calculated for Desplanques, Donoghue, and Holstein (DDH) and effective field theory types of weak potentials in a distorted-wave Born approximation, using realistic hadronic strong interaction wave functions, obtained by solving three-body Faddeev equations in configuration space. The resulting relation between physical observables and low-energy constants can be used to fix low-energy constants from experiments. Potential model dependencies of parity-violating effects are discussed.

  19. Neutron scatter studies of chromatin structure related to functions

    SciTech Connect

    Bradbury, E.M.

    1989-01-01

    Neutron scatter studies have been performed at LANSCE, LANL and at the Institute Laue Langevin, Grenoble, France. In the previous progress report (April 1, 1988--July 1, 1988) the following objectives were listed: shape of the histone octamer; location of the N-terminal domains of histone in the nucleosome core particle (specific aim 1 of original grant proposal); effect of acetylation on nucleosome structure (specific aim 2); location of the globular domain of histone H1 (specific aim 6); and complexes of the transcription factor 3A with its DNA binding site. Progress is briefly discussed.

  20. Thermal Denaturation of DNA Studied with Neutron Scattering

    SciTech Connect

    Wildes, Andrew; Theodorakopoulos, Nikos; Valle-Orero, Jessica; Cuesta-Lopez, Santiago; Peyrard, Michel; Garden, Jean-Luc

    2011-01-28

    The melting transition of DNA, whereby the strands of the double-helix structure completely separate at a certain temperature, has been characterized using neutron scattering. A Bragg peak from B-form fiber DNA has been measured as a function of temperature, and its widths and integrated intensities have been interpreted using the Peyrard-Bishop-Dauxois model with only one free parameter. The experiment is unique, as it gives spatial correlation along the molecule through the melting transition where other techniques cannot.

  1. Muon capture on the deuteron and the neutron-neutron scattering length

    NASA Astrophysics Data System (ADS)

    Marcucci, L. E.; Machleidt, R.

    2014-11-01

    Background: We consider the muon capture reaction μ-+2H→νμ+n +n , which presents a "clean" two-neutron (n n ) system in the final state. We study here its capture rate in the doublet hyperfine initial state (ΓD). The total capture rate for the muon capture μ-+3He→νμ+3H (Γ0) is also analyzed, although, in this case, the n n system is not so clean anymore. Purpose: We investigate whether ΓD (and Γ0) could be sensitive to the n n S -wave scattering length (an n), and we check on the possibility to extract an n from an accurate measurement of ΓD. Method: The muon capture reactions are studied with nuclear potentials and charge-changing weak currents, derived within chiral effective field theory. The next-to-next-to-next-to-leading-order chiral potential with cutoff parameter Λ =500 MeV is used, but the low-energy constant (LEC) determining an n is varied so as to obtain an n=-18.95 ,-16.0 ,-22.0 , and +18.22 fm. The first value is the present empirical one, while the last one is chosen such as to lead to a di-neutron bound system with a binding energy of 139 keV. The LEC's cD and cE, present in the three-nucleon potential and axial-vector current (cD), are constrained to reproduce the A =3 binding energies and the triton Gamow-Teller matrix element. Results: The capture rate ΓD is found to be 399 (3 ) s-1 for an n=-18.95 and -16.0 fm; and 400 (3 ) s-1 for an n=-22.0 fm. However, in the case of an n=+18.22 fm, the result of 275 (3 ) s-1 [ 135 (3 ) s-1 ] is obtained, when the di-neutron system in the final state is unbound (bound). The total capture rate Γ0 for muon capture on 3He is found to be 1494(15), 1491(16), 1488(18), and 1475(16) s-1 for an n=-18.95 ,-16.0 ,-22.0 , and +18.22 fm, respectively. All the theoretical uncertainties are due to the fitting procedure and radiative corrections. Conclusions: Our results seem to exclude the possibility of constraining a negative an n with an uncertainty of less than ˜±3 fm through an accurate

  2. Evaluation of the /sup 238/U neutron total cross section

    SciTech Connect

    Smith, A.; Poenitz, W.P.; Howerton, R.J.

    1982-12-01

    Experimental energy-averaged neutron total cross sections of /sup 238/U were evaluated from 0.044 to 20.0 MeV using regorous numerical methods. The evaluated results are presented together with the associated uncertainties and correlation matrix. They indicate that this energy-averaged neutron total cross section is known to better than 1% over wide energy regions. There are somwewhat larger uncertainties at low energies (e.g., less than or equal to 0.2 MeV), near 8 MeV and above 15 MeV. The present evaluation is compard with values given in ENDF/B-V.

  3. Small-angle neutron scattering study of polymeric micellar structures

    SciTech Connect

    Wu, G.; Chu, B. ); Schneider, D.K. )

    1994-11-17

    Polymeric micellar structures formed by a PEO-PPO-PEO copolymer in o-xylene in the presence of water were investigated by small-angle neutron scattering. In order to reveal the detailed micellar structure, different contrasts among the micellar core, the micellar shell, and the dispersing medium (background) were constructed by selectively changing the protonated/deuterated combination of water and xylene. The micellar structure could be well described by a core-shell structure with the scattering behavior of the micellar shell being very similar to that of a star polymer. The solubilized water existed not only in the micellar core but also in the micellar shell. The volume fraction of a copolymer segments in the micellar shell was rather low, being of the order of 0.2. There seemed to be no sharp interface between the micellar core and the micellar shell. 25 refs., 11 figs., 4 tabs.

  4. Small angle neutron scattering using a triple axis spectrometer

    SciTech Connect

    Ahmend, F.U.; Kamal, I.; Yunus, S.M.

    1994-12-31

    SANS technique has been developed on a triple axis neutron spectrometer at TRIGA Mark II (3 MW) research reactor, AERE, Savar, Dhaka, Bangladesh. Double crystal (with very small mosaic spread {approximately} 1 min.) diffraction known as Bonse and Hart`s method has been employed in this technique. Such a device is a useful tool for small angle scattering in the Q range between 10{sup -5} and 10{sup -1} {Angstrom}{sup -1} and for real time experiments at short time scales. Therefore, large objects and large distance interparticle correlations can be investigated easily by this method. Test measurements using alumina (Al{sub 2}O{sub 3}) sample has been carried out to exploit this method. The radius of gyration has been determined and the data has been fitted to the scattering function of a sphere.

  5. Measured Neutron Spectra and Dose Equivalents From a Mevion Single-Room, Passively Scattered Proton System Used for Craniospinal Irradiation.

    PubMed

    Howell, Rebecca M; Burgett, Eric A; Isaacs, Daniel; Price Hedrick, Samantha G; Reilly, Michael P; Rankine, Leith J; Grantham, Kevin K; Perkins, Stephanie; Klein, Eric E

    2016-05-01

    To measure, in the setting of typical passively scattered proton craniospinal irradiation (CSI) treatment, the secondary neutron spectra, and use these spectra to calculate dose equivalents for both internal and external neutrons delivered via a Mevion single-room compact proton system. Secondary neutron spectra were measured using extended-range Bonner spheres for whole brain, upper spine, and lower spine proton fields. The detector used can discriminate neutrons over the entire range of the energy spectrum encountered in proton therapy. To separately assess internally and externally generated neutrons, each of the fields was delivered with and without a phantom. Average neutron energy, total neutron fluence, and ambient dose equivalent [H* (10)] were calculated for each spectrum. Neutron dose equivalents as a function of depth were estimated by applying published neutron depth-dose data to in-air H* (10) values. For CSI fields, neutron spectra were similar, with a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate continuum between the evaporation and thermal peaks. Neutrons in the evaporation peak made the largest contribution to dose equivalent. Internal neutrons had a very low to negligible contribution to dose equivalent compared with external neutrons, largely attributed to the measurement location being far outside the primary proton beam. Average energies ranged from 8.6 to 14.5 MeV, whereas fluences ranged from 6.91 × 10(6) to 1.04 × 10(7) n/cm(2)/Gy, and H* (10) ranged from 2.27 to 3.92 mSv/Gy. For CSI treatments delivered with a Mevion single-gantry proton therapy system, we found measured neutron dose was consistent with dose equivalents reported for CSI with other proton beamlines. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  6. Characterization of photosynthetic supramolecular assemblies using small angle neutron scattering

    SciTech Connect

    Tiede, D.M.; Marone, P.; Wagner, A.M.; Thiyagarajan, P.

    1995-12-31

    We are using small angle neutron scattering (SANS) to resolve structural features of supramolecular assemblies of photosynthetic proteins in liquid and frozen solutions. SANS resolves the size, shape, and structural homogeneity of macromolecular assemblies in samples identical to those used for spectroscopic assays of photosynthetic function. Likely molecular structures of the supramolecular assemblies can be identified by comparing experimental scattering data with scattering profiles calculated for model supramolecular assemblies built from crystal structures of the individual proteins. SANS studies of the Rhodobacter sphaeroides reaction center, RC, presented here, show that the detergent solubilized RC exists in a variety of monomeric and aggregation states. The distribution between monomer and aggregate was found to depend strongly upon detergent, temperature and nature of additives, such as ethylene glycol used for low temperature spectroscopy and polyethylene glycol used for crystallization. Likely aggregate structures are being identified by fitting the experimental scattering profiles with those calculated for model aggregates built-up using the RC crystal structure. This work establishes the foundation for using SANS to identify intermediates in the RC crystallization pathways, and for determining likely structures of complexes formed between the RC and its physiological reaction partners, cytochrome c, and the LHI antenna complex.

  7. Ultra-small-angle neutron scattering with azimuthal asymmetry.

    PubMed

    Gu, X; Mildner, D F R

    2016-06-01

    Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding to the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. The aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry.

  8. Neutron-19C scattering: Towards including realistic interactions

    NASA Astrophysics Data System (ADS)

    Deltuva, A.

    2017-09-01

    Low-energy neutron-19C scattering is studied in the three-body n + n +18C model using a realistic nn potential and a number of shallow and deep n-18C potentials, the latter supporting deeply-bound Pauli-forbidden states that are projected out. Exact Faddeev-type three-body scattering equations for transition operators including two- and three-body forces are solved in the momentum-space partial-wave framework. Phase shift, inelasticity parameter, and cross sections are calculated. For the elastic n-19C scattering in the JΠ =0+ partial wave the signatures of the Efimov physics, i.e., the pole in the effective-range expansion and the elastic cross section minimum, are confirmed for both shallow and deep models, but with clear quantitative differences between them, indicating the importance of a proper treatment of deeply-bound Pauli-forbidden states. In contrast, the inelasticity parameter is mostly correlated with the asymptotic normalization coefficient of the 19C bound state. Finally, in the regime of very weak 19C binding and near-threshold (bound or virtual) excited 20C state the standard Efimovian behaviour of the n-19C scattering length and cross section was confirmed, resolving the discrepancies between earlier studies by other authors (Mazumdar et al., 2006 [20], Yamashita et al., 2007 [23]).

  9. Ultra-small-angle neutron scattering with azimuthal asymmetry

    PubMed Central

    Gu, X.; Mildner, D. F. R.

    2016-01-01

    Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding to the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. The aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry. PMID:27275140

  10. Ultra-small-angle neutron scattering with azimuthal asymmetry

    SciTech Connect

    Gu, X.; Mildner, D. F. R.

    2016-05-16

    Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding to the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. Furthermore, the aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry.

  11. Ultra-small-angle neutron scattering with azimuthal asymmetry

    DOE PAGES

    Gu, X.; Mildner, D. F. R.

    2016-05-16

    Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding tomore » the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. Furthermore, the aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry.« less

  12. Inference of total DT fusion neutron yield from prompt gamma-ray measurements at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Church, J. A.; Herrmann, H. W.; Stoeffl, W.; Caggiano, J. A.; Cerjan, C.; Sayre, D.

    2014-10-01

    Prompt D-T fusion gamma-rays measured at the National Ignition Facility (NIF) with the Gamma-ray Reaction History detector (GRH) have been used recently to infer the total DT fusion neutron yield of inertial confinement fusion (ICF) implosions. DT fusion produces energetic gamma-rays (16.75 MeV) with a small branching ratio of approximately (4.2 +/- 2.0)e-5 γ/n. While the large error bar precludes use of the branching ratio for an accurate yield determination, the gamma-rays themselves provide the most unperturbed measure of fusion burn and can be used for such a purpose. A cross-calibration for the DT fusion gamma-ray to neutron signal is obtained via low areal density exploding pusher implosions which have mostly unperturbed neutron and gamma-ray signals. The calibration is then used to infer total DT neutron yield from gamma-ray measurements on high areal-density, cryogenically layered implosions in which neutrons are heavily down-scattered (up to 30%). Furthermore, the difference between the gamma-ray inferred total DT yield and the primary neutron yield (unscattered neutrons) can be used to estimate the total down-scatter fraction. Error analysis and comparison of yield values will be presented. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, LLNL-ABS-657694.

  13. Single-Volume Neutron Scatter Camera for High-Efficiency Neutron Imaging and Source Characterization. Year 2 of 3 Summary

    SciTech Connect

    Brubaker, Erik

    2015-10-01

    The neutron scatter camera (NSC), an imaging spectrometer for fission energy neutrons, is an established and proven detector for nuclear security applications such as weak source detection of special nuclear material (SNM), arms control treaty verification, and emergency response. Relative to competing technologies such as coded aperture imaging, time-encoded imaging, neutron time projection chamber, and various thermal neutron imagers, the NSC provides excellent event-by-event directional information for signal/background discrimination, reasonable imaging resolution, and good energy resolution. Its primary drawback is very low detection efficiency due to the requirement for neutron elastic scatters in two detector cells. We will develop a singlevolume double-scatter neutron imager, in which both neutron scatters can occur in the same large active volume. If successful, the efficiency will be dramatically increased over the current NSC cell-based geometry. If the detection efficiency approaches that of e.g. coded aperture imaging, the other inherent advantages of double-scatter imaging would make it the most attractive fast neutron detector for a wide range of security applications.

  14. Rhodopsin Photoactivation Dynamics Revealed by Quasi-Elastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchhithranga M. C. D.; Chawla, Udeep; Mamontov, Eugene; Brown, Michael; Chu, Xiang-Qiang

    2015-03-01

    Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision. During photoactivation, the chromophore retinal dissociates from protein yielding the opsin apoprotein. What are the changes in protein dynamics that occur during the photoactivation process? Here, we studied the microscopic dynamics of dark-state rhodopsin and the ligand-free opsin using quasielastic neutron scattering (QENS). The QENS technique tracks individual hydrogen atom motion because of the much higher neutron scattering cross-section of hydrogen than other atoms. We used protein with CHAPS detergent hydrated with heavy water. The activation of proteins is confirmed at low temperatures up to 300 K by mean-square displacement (MSD) analysis. The QENS experiments at temperatures ranging from 220 K to 300 K clearly indicate an increase in protein dynamic behavior with temperature. The relaxation time for the ligand-bound protein rhodopsin is faster compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which unlike protein, manifests localized motions.

  15. The fluctuating ribosome: thermal molecular dynamics characterized by neutron scattering

    NASA Astrophysics Data System (ADS)

    Zaccai, Giuseppe; Natali, Francesca; Peters, Judith; Řihová, Martina; Zimmerman, Ella; Ollivier, J.; Combet, J.; Maurel, Marie-Christine; Bashan, Anat; Yonath, Ada

    2016-11-01

    Conformational changes associated with ribosome function have been identified by X-ray crystallography and cryo-electron microscopy. These methods, however, inform poorly on timescales. Neutron scattering is well adapted for direct measurements of thermal molecular dynamics, the ‘lubricant’ for the conformational fluctuations required for biological activity. The method was applied to compare water dynamics and conformational fluctuations in the 30 S and 50 S ribosomal subunits from Haloarcula marismortui, under high salt, stable conditions. Similar free and hydration water diffusion parameters are found for both subunits. With respect to the 50 S subunit, the 30 S is characterized by a softer force constant and larger mean square displacements (MSD), which would facilitate conformational adjustments required for messenger and transfer RNA binding. It has been shown previously that systems from mesophiles and extremophiles are adapted to have similar MSD under their respective physiological conditions. This suggests that the results presented are not specific to halophiles in high salt but a general property of ribosome dynamics under corresponding, active conditions. The current study opens new perspectives for neutron scattering characterization of component functional molecular dynamics within the ribosome.

  16. Time-resolved quasielastic neutron scattering studies of native photosystems.

    PubMed

    Pieper, Jörg

    2010-01-01

    The internal molecular dynamics of proteins plays an important role in a number of functional processes in native photosystems. Prominent examples include the photocycle of bacteriorhodopsin and electron transfer in the reaction center of plant photosystem II. In this regard, the recently developed technique of time-resolved quasielastic neutron scattering with laser excitation opens up new perspectives for the study of protein/membrane dynamics in specific functional states of even complex systems. The first direct observation of a functionally modulated protein dynamics has just recently been reported for the model system bacteriorhodopsin (Pieper et al., Phys. Rev. Lett. 100, 2008, 228103.), where a transient softening of the protein was observed on a timescale of approximately 1 ms along with the large-scale structural change in the M-intermediate of bacteriorhodopsin. In contrast, photosystem II membrane fragments with inhibited electron transfer show a suppression of protein dynamics approximately 160 mus after the actinic laser flash (Pieper and Renger, Biochemistry 48, 2009, 6111). This effect may reflect aggregation-like conformational changes capable of dissipation of excess excitation energy to prevent photodamage in the absence of Q(A)-->Q(B) electron transfer. These findings indicate that proteins exhibit a remarkable flexibility to accommodate different functional processes. This contribution will discuss methodical aspects, challenges, and recent applications of laser-excited, time-resolved quasielastic neutron scattering.

  17. Compact turnkey focussing neutron guide system for inelastic scattering investigations

    NASA Astrophysics Data System (ADS)

    Brandl, G.; Georgii, R.; Dunsiger, S. R.; Tsurkan, V.; Loidl, A.; Adams, T.; Pfleiderer, C.; Böni, P.

    2015-12-01

    We demonstrate the performance of a compact neutron guide module which boosts the intensity in inelastic neutron scattering experiments by approximately a factor of 40. The module consists of two housings containing truly curved elliptic focussing guide elements, positioned before and after the sample. The advantage of the module lies in the ease with which it may be reproducibly mounted on a spectrometer within a few hours, on the same timescale as conventional sample environments. It is particularly well suited for samples with a volume of a few mm3, thus enabling the investigation of materials which to date would have been considered prohibitively small or samples exposed to extreme environments, where there are space constraints. We benchmark the excellent performance of the module by measurements of the structural and magnetic excitations in single crystals of model systems. In particular, we report the phonon dispersion in the simple element lead. We also determine the magnon dispersion in the spinel ZnCr2Se4 (V = 12.5 mm3), where strong magnetic diffuse scattering at low temperatures evolves into distinct helical order.

  18. Compact turnkey focussing neutron guide system for inelastic scattering investigations

    SciTech Connect

    Brandl, G.; Georgii, R.; Dunsiger, S. R.; Tsurkan, V.; Loidl, A.; Adams, T.; Pfleiderer, C.; Böni, P.

    2015-12-21

    We demonstrate the performance of a compact neutron guide module which boosts the intensity in inelastic neutron scattering experiments by approximately a factor of 40. The module consists of two housings containing truly curved elliptic focussing guide elements, positioned before and after the sample. The advantage of the module lies in the ease with which it may be reproducibly mounted on a spectrometer within a few hours, on the same timescale as conventional sample environments. It is particularly well suited for samples with a volume of a few mm{sup 3}, thus enabling the investigation of materials which to date would have been considered prohibitively small or samples exposed to extreme environments, where there are space constraints. We benchmark the excellent performance of the module by measurements of the structural and magnetic excitations in single crystals of model systems. In particular, we report the phonon dispersion in the simple element lead. We also determine the magnon dispersion in the spinel ZnCr{sub 2}Se{sub 4} (V = 12.5 mm{sup 3}), where strong magnetic diffuse scattering at low temperatures evolves into distinct helical order.

  19. (Neutron scatter studies of chromatin structure related to function)

    SciTech Connect

    Bradbury, E.M.

    1990-01-01

    This study is concerned with the application of neutron scatter techniques to the different structural states of nucleosomes and chromatin with the long term objective of understanding how the enormous lengths of DNA are folded into chromosomes. Micrococcal nuclease digestion kinetics have defined two subnucleosome particles; the chromatosome with 168 bp DNA, the histone octamer and one H1 and the nucleosome core particle with 146 bp DNA and the histone octamer. As will be discussed, the structure of the 146 bp DNA core particle is known in solution at low resolution from neutron scatter studies and in crystals. Based on this structure, the authors have a working model for the chromatosome and the mode of binding of H1. In order to define the structure of the nucleosome and also the different orders of chromatin structures they need to know the paths of DNA that link nucleosomes and the factors associated with chromosome functions that act on those DNA paths. The major region for this situation is the inherent variabilities in nucleosome DNA sequences, in the histone subtypes and their states of chemical modification and in the precise locations of nucleosomes. Such variabilities obscure the underlying principles that govern the packaging of DNA into the different structural states of nucleosomes and chromatin. The only way to elucidate these principles is to study the structures of nucleosomes and oligonucleosomes that are fully defined. They have largely achieved these objectives.

  20. Neutron scattering studies of disordered carbon anode materials

    NASA Astrophysics Data System (ADS)

    Papanek, P.; Kamitakahara, W. A.; Zhou, P.; Fischer, J. E.

    2001-09-01

    Carbon-based anodes show many promising properties in lithium-ion rechargeable batteries. So-called `disordered carbons' are characterized by a substantial amount of residual hydrogen, and exhibit large Li uptake capacities. We have employed a variety of neutron scattering techniques, coupled with computer simulations, to study the composition, local atomic structure, and vibrational dynamics of such materials. Radial distribution function analysis of neutron diffraction data, and incoherent inelastic scattering show that the structural motif is a planar graphene fragment, with edge carbons terminated by single hydrogen atoms, and random stacking between fragments. The vibrational spectra of the hydrogen-rich carbons are remarkably similar to the spectra of the polycyclic aromatic hydrocarbon coronene in the medium-frequency region. At low frequencies, only a boson peak is observed, characteristic for glassy and disordered materials, and this feature shifts upon doping. The results are consistent with two proposed mechanisms for Li capacity, one analogous to conventional intercalation but with Li on both sides of graphene fragments, the other involving bonding of Li to H-terminated edge carbons.

  1. Salt induced polystyrene latex flocs investigated by neutron scattering.

    PubMed

    Kwaambwa, Habauka M; Hellsing, Maja S; Wasbrough, Matthew J; Bleuel, Markus; Rennie, Adrian R

    2017-11-01

    Studies with a model system consisting of polystyrene latex particles showed that the protein from seeds of Moringa trees adsorbs to the surface and causes flocculation as unusually dense aggregates. In this study, electrolytes sodium chloride (NaCl), ferric chloride (FeCl3) and aluminium sulfate (Al2(SO4)3) have been used to aggregate model polystyrene particles. The study augments previous work using neutron scattering on the flocculation of polystyrene latex with protein from seeds of Moringa trees that had indicated higher floc dimension, df, values as the concentration of particles increased. The measurements were made using ultra small-angle neutron scattering. Generally the fractal dimension, and thus the floc density, increased with particle concentration and salt concentration. Flocculation was apparent at much lower concentrations of FeCl3 and Al2(SO4)3 than of NaCl. The values of df were found not to simply scale with ionic strength for the three electrolytes studied with FeCl3 being the most effective flocculating agent. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. The fluctuating ribosome: thermal molecular dynamics characterized by neutron scattering

    PubMed Central

    Zaccai, Giuseppe; Natali, Francesca; Peters, Judith; Řihová, Martina; Zimmerman, Ella; Ollivier, J.; Combet, J.; Maurel, Marie-Christine; Bashan, Anat; Yonath, Ada

    2016-01-01

    Conformational changes associated with ribosome function have been identified by X-ray crystallography and cryo-electron microscopy. These methods, however, inform poorly on timescales. Neutron scattering is well adapted for direct measurements of thermal molecular dynamics, the ‘lubricant’ for the conformational fluctuations required for biological activity. The method was applied to compare water dynamics and conformational fluctuations in the 30 S and 50 S ribosomal subunits from Haloarcula marismortui, under high salt, stable conditions. Similar free and hydration water diffusion parameters are found for both subunits. With respect to the 50 S subunit, the 30 S is characterized by a softer force constant and larger mean square displacements (MSD), which would facilitate conformational adjustments required for messenger and transfer RNA binding. It has been shown previously that systems from mesophiles and extremophiles are adapted to have similar MSD under their respective physiological conditions. This suggests that the results presented are not specific to halophiles in high salt but a general property of ribosome dynamics under corresponding, active conditions. The current study opens new perspectives for neutron scattering characterization of component functional molecular dynamics within the ribosome. PMID:27849042

  3. Probing the binding and spatial arrangement of molecular hydrogen in porous hosts via neutron Compton scattering.

    PubMed

    Krzystyniak, Maciej; Adams, Mark A; Lovell, Arthur; Skipper, Neal T; Bennington, Stephen M; Mayers, Jerry; Fernandez-Alonso, Felix

    2011-01-01

    The adsorption of molecular hydrogen (H2) in the alkali-graphite intercalate KC24 has been studied using simultaneous neutron diffraction and Compton scattering. Neutron Compton scattering data for the (H2)xKC24 system (x = 0-2.5) were measured at T = 1.5 K as a function of the relative orientation between the neutron beam and the intercalate c-axis. Synchronous with the above proton-recoil measurements, high-resolution diffraction patterns were measured in backscattering geometry. From these diffraction measurements, the intrinsic mosaicity of the Papyex-based intercalate was determined to be approximately 15 degrees half-width-at-half-maximum, in good agreement with previous studies [Finkelstein et al., Physica B, 2000, 291, 213]. Hydrogen uptake by the intercalate leads to a distinct and readily detectable broadening of the isotropic Compton profile compared to bulk H2, indicative of an enhanced interaction of the H2 molecule with the surrounding solid-state environment. Total proton-recoil intensities also scale linearly with the amount of adsorbed hydrogen. Taking as our starting point previous experimental and theoretical results, the isotropic widths of the proton momentum distributions can be explained on the basis of three energy scales, namely, intramolecular H-H vibrations, followed by H-H librations and H2 centre-of-mass translations. From the coverage dependence of these neutron data, we also establish an upper bound of approximately 10 meV for intermolecular hydrogen-hydrogen interactions. Finally, we observe a weak anisotropy of the width of the proton momentum distributions. Comparison of these experimental data with first-principles predictions indicates that subtle quantum mechanical effects associated with particle delocalisation and exchange lie at the heart of the observed behaviour. Overall, these results demonstrate the suitability and largely untapped potential of neutron Compton scattering to explore H2 uptake by solid-state hosts.

  4. Density of states in solid deuterium: Inelastic neutron scattering study

    SciTech Connect

    Frei, A.; Gutsmiedl, E.; Morkel, C.; Mueller, A. R.; Paul, S.; Urban, M.; Schober, H.; Rols, S.; Unruh, T.; Hoelzel, M.

    2009-08-01

    The dynamics of solid deuterium (sD{sub 2}) is studied by means of inelastic scattering (coherent and incoherent) of thermal and cold neutrons at different temperatures and para-ortho ratios. In this paper, the results for the generalized density of states (GDOS) are presented and discussed. The measurements were performed at the thermal neutron time-of-flight (TOF) instrument IN4 at ILL Grenoble and at the cold neutron TOF instrument TOFTOF at FRM II Garching. The GDOS comprises besides the hcp phonon excitations of the sD{sub 2} the rotational transitions J=0{yields}1 and J=1{yields}2. The intensities of these rotational excitations depend strongly on the ortho-D{sub 2} molecule concentration c{sub o} in sD{sub 2}. Above E=10 meV there are still strong excitations, which very likely may originate from higher-energy damped optical phonons and multiphonon contributions. A method for separating the one-phonon and multiphonon contributions to the density of states will be presented and discussed.

  5. Structural analysis of molybdo-zinc-phosphate glasses: Neutron scattering, FTIR, Raman scattering, MAS NMR studies

    NASA Astrophysics Data System (ADS)

    Renuka, C.; Shinde, A. B.; Krishna, P. S. R.; Reddy, C. Narayana

    2016-08-01

    Vitreous samples were prepared in the xMoO3-17ZnO-(83-x) NaPO3 with 35 ≥ x ≥ 55 glass forming system by energy efficient microwave heating method. Structural evolution of the vitreous network was monitored as a function of composition by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), Raman scattering, Magic Angle Spin Nuclear magnetic resonance (MAS NMR) and Neutron scattering. Addition of MoO3 to the ZnO-NaPO3 glass leads to a pronounced increase in glass transition temperature (Tg) suggesting a significant increase in network connectivity and strength. In order to analyze FTIR and Raman scattering, a simple structural model is presented to rationalize the experimental observations. A number of structural units are formed due to network modification, and the resulting glass may be characterized by a network polyhedral with different numbers of unshared corners. 31P MAS NMR confirms a clear distinction between structural species having 3, 2, 1, 0 bridging oxygens (BOs). Further, Neutron scattering studies were used to probe the structure of these glasses. The result suggests that all the investigated glasses have structures based on chains of four coordinated phosphate and six coordinated molybdate units, besides, two different lengths of P-O bonds in tetrahedral phosphate units that are assigned to bonds of the P-atom with terminal and bridging oxygen atoms.

  6. Thermal Neutron Capture and Thermal Neutron Burn-up of K isomeric state of 177mLu: a way to the Neutron Super-Elastic Scattering cross section

    SciTech Connect

    Roig, O.; Belier, G.; Meot, V.; Daugas, J.-M.; Romain, P.

    2006-03-13

    Thermal neutron radiative capture and burn-up measurements of the K isomeric state in 177Lu form part of an original method to indirectly obtain the neutron super-elastic scattering cross section at thermal energy. Neutron super-elastic scattering, also called neutron inelastic acceleration, occurs during the neutron collisions with an excited nuclear level. In this reaction, the nucleus could partly transfer its excitation energy to the scattered neutron.

  7. Nature of radiation defects in synthetic quartz according to the small-angle neutron scattering data

    SciTech Connect

    Lebedev, V. M. Lebedev, V. T.; Orlov, S. P.; Pevzner, B. Z.; Tolstikhin, I. N.

    2007-05-15

    The supraatomic structure of single crystals of synthetic quartz in the initial state with a dislocation density of 570 cm{sup -2} and after irradiation in the VVR-M reactor at the Petersburg Nuclear Physics Institute with fast neutrons having the energy E{sub n} > 1 MeV in the range of fluences F{sub n} = 7.7 x 10{sup 17} -2.1 x 10{sup 20} neutrons/cm{sup 2} has been studied by small-angle scattering of thermal neutrons. It is established that fast neutrons form point, linear, and volume lattice defects throughout the entire sample volume. Large-volume structures (nuclei of the amorphous phase) in quartz, reaching {approx}100 nm in size, occupy a small total volume ({approx}1.5%) even at the maximum fluence 2.1 x 10{sup 20} neutrons/cm{sup 2}. The majority of damage is related to the point defects with the radius of gyration of 1-2 nm and linear defects, which give comparable contributions up to several percent.

  8. A Workshop on Methods for Neutron Scattering Instrument Design. Introduction and Summary

    SciTech Connect

    Hjelm, Rex P.

    1996-12-31

    The future of neutron and x-ray scattering instrument development and international cooperation was the focus of the workshop on ``Methods for Neutron Scattering Instrument Design`` September 23-25 at the E.O. Lawrence Berkeley National Laboratory. These proceedings are a collection of a portion of the invited and contributed presentations.

  9. Measurement of the neutron-neutron scattering length using the π-d capture reaction

    NASA Astrophysics Data System (ADS)

    Chen, Q.; Howell, C. R.; Carman, T. S.; Gibbs, W. R.; Gibson, B. F.; Hussein, A.; Kiser, M. R.; Mertens, G.; Moore, C. F.; Morris, C.; Obst, A.; Pasyuk, E.; Roper, C. D.; Salinas, F.; Setze, H. R.; Slaus, I.; Sterbenz, S.; Tornow, W.; Walter, R. L.; Whiteley, C. R.; Whitton, M.

    2008-05-01

    We have determined a value for the 1S0 neutron-neutron scattering length (ann) from high-precision measurements of time-of-flight spectra of neutrons from the H2(π-,nγ)n capture reaction. The measurements were done at the Los Alamos Meson Physics Facility by the E1286 Collaboration. The high spatial resolution of our γ-ray detector enabled us to make a detailed assessment of the systematic uncertainties in our techniques. The value obtained in the present work is ann=-18.63±0.10 (statistical) ± 0.44 (systematic) ± 0.30 (theoretical) fm. This result is consistent with previous determinations of ann from the π-d capture reaction. We found that the analysis of the data with calculations that use a relativistic phase-space factor gives a more negative value for ann by 0.33 fm over the analysis done using a nonrelativistic phase-space factor. Combining the present result with the previous ones from π-d capture gives ann=-18.63±0.27(expt)±0.30 fm (theory). For the first time the combined statistical and systematic experimental uncertainty in ann is smaller than the theoretical uncertainty and comparable to the uncertainty in the proton-proton 1S0 scattering length (app). This average value of ann when corrected for the magnetic-moment interaction of the two neutrons becomes -18.9 ± 0.4 fm, which is 1.6 ± 0.5 fm different from the recommended value of app, thereby confirming charge symmetry breaking at the 1% confidence level.

  10. Advanced research capabilities for neutron science and technology: Neutron polarizers for neutron scattering

    SciTech Connect

    Penttila, S.I.; Fitzsimmons, M.R.; Delheij, P.J.

    1998-12-01

    The authors describe work on the development of polarized gaseous {sup 3}He cells, which are intended for use as neutron polarizers. Laser diode arrays polarize Rb vapor in a sample cell and the {sup 3}He is polarized via collisions. They describe development and tests of such a system at LANSCE.

  11. PREFACE: 6th Meeting of the Spanish Neutron Scattering Association (SETN2012)

    NASA Astrophysics Data System (ADS)

    2014-11-01

    The bi-annual Meeting of the Spanish Neutron Scattering Association, VI RSETN, took place in the magnificent world heritage ancient city of Segovia, Spain, from 24-27 June 2012, at the historical building ''Palacio de Mansilla''. It was the sixth in a series of successful scientific meetings, beginning in 2002 (San Sebastián), and followed by conferences in Puerto de la Cruz (Canary Islands, 2004), Jaca (Aragón, 2006), Sant Feliú de Guixols (Cataluña, 2008) and Gijón (Asturias, 2010). The conference covered a broad range of topics related to the use of neutron scattering techniques, from soft matter and biosciences to magnetism, condensed matter as well as advanced neutron instrumentation and applications. In addition to those topics, Spanish scientists working at neutron facilities reported recent upgrades of neutron instruments. The VI RSETN was organized by a group of research scientists belonging to different institutions in Madrid: CSIC, Universidad Complutense and Universidad Politécnica de Madrid, in cooperation with the Spanish Society for Neutron Techniques (SETN, 'Sociedad Española de Técnicas Neutrónicas'). The meeting attracted around 90 participants. The total number of oral presentations was 36, including plenary and invited talks, both from domestic and foreign speakers. In addition, the number of posters was around 20. The success of the VI RSETN was due to the efforts of many colleagues involved at all stages of the meeting. We would like to thank the scientific committee, the local organizing committee, the chairs of the conference sessions as well as all the reviewers who agreed generously to help with the process. We would also like to emphasize the excellent scientific quality of all the presentations and posters, and we thank the support received from our sponsors (SETN, ICMM-CSIC, ESS-Bilbao, ILL, Carburos Metálicos), which was really important for the conference success. Finally, we hope that the readers will enjoy the 28

  12. Proceedings of a workshop on methods for neutron scattering instrumentation design

    SciTech Connect

    Hjelm, R.P.

    1997-09-01

    The future of neutron and x-ray scattering instrument development and international cooperation was the focus of the workshop. The international gathering of about 50 participants representing 15 national facilities, universities and corporations featured oral presentations, posters, discussions and demonstrations. Participants looked at a number of issues concerning neutron scattering instruments and the tools used in instrument design. Objectives included: (1) determining the needs of the neutron scattering community in instrument design computer code and information sharing to aid future instrument development, (2) providing for a means of training scientists in neutron scattering and neutron instrument techniques, and (3) facilitating the involvement of other scientists in determining the characteristics of new instruments that meet future scientific objectives, and (4) fostering international cooperation in meeting these needs. The scope of the meeting included: (1) a review of x-ray scattering instrument design tools, (2) a look at the present status of neutron scattering instrument design tools and models of neutron optical elements, and (3) discussions of the present and future needs of the neutron scattering community. Selected papers were abstracted separately for inclusion to the Energy Science and Technology Database.

  13. Small angle neutron scattering studies of vesicle stability

    SciTech Connect

    Mang, J.T.; Hjelm, R.P.

    1997-10-01

    Small angle neutron scattering (SANS) was used to investigate the structure of mixed colloids of egg yolk phosphatidylcholine (EYPC) with the bile salt, cholylglycine (CG), in D{sub 2}O as a function of pressure (P) and temperature (T). At atmospheric pressure, the system forms an isotropic phase of mixed, single bilayer vesicles (SLV`s). Increasing the external hydrostatic pressure brought about significant changes in particle morphology. At T = 25 C, application of a pressure of 3.5 MPa resulted in the collapse of the SLV`s. Further increase of P, up to 51.8 MPa, resulted in a transition from a phase of ordered (stacked), collapsed vesicles to one of stacked, ribbon-like particles. A similar collapse of the vesicles was observed at higher temperature (T = 37 C) with increasing P, but at this temperature, no ribbon phase was found at the highest pressure explored.

  14. Neutron spin rotation in $\\vec{n}$-$d$ scattering

    SciTech Connect

    Schiavilla, Rocco; Viviani, Michele; Girlanda, L.; Kievsky, Alejandro; Marcucci, Laura

    2008-07-01

    The neutron spin rotation induced by parity-violating (PV) components in the nucleon-nucleon potential is studied in $\\vec{n}$-$d$ scattering at zero energy. Results are obtained corresponding to the Argonne $v_{18}$ two-nucleon and Urbana-IX three-nucleon strong-interaction potentials in combination with either the DDH or pionless EFT model for the weak-interaction potential. We find that this observable is dominated by the contribution of the long-range part of the PV potential associated with pion exchange. Thus its measurement could provide a further constraint, complementary to that coming from measurements of the photon asymmetry in $\\vec{n}$-$p$ radiative capture, on the strength of this component of the hadronic weak interaction.

  15. Quasielastic neutron scattering and microscopic dynamics of liquid ethylene glycol

    NASA Astrophysics Data System (ADS)

    Sobolev, O.; Novikov, A.; Pieper, J.

    2007-04-01

    Quasielastic neutron scattering (QENS) by liquid ethylene glycol was analyzed using different model approaches. It was found that approximation of the QENS spectra by a set of Lorentzian functions corresponding to the translational and rotational motions produce physically unrealistic results. At the same time, the Fourier transform of the stretched-exponential function exp(-( t/ τ) β) fits the experimental data well, and results of the fit are in good agreement with those obtained earlier for other systems. The stretching parameter β was found Q independent and shows weak temperature dependence. The mean relaxation time as a function of Q departs strongly from the simple diffusion low and can be approximated by a power law < τw> = τ0Q- γ with the exponent parameter γ = 2.4.

  16. Structural investigation of carbon/carbon composites by neutron scattering

    NASA Astrophysics Data System (ADS)

    Prem, Manfred; Krexner, Gerhard; Peterlik, Herwig

    2006-11-01

    Carbon/carbon (C/C) composite material was investigated by means of small-angle as well as wide-angle elastic neutron scattering. The C/C-composites were built up from bi-directionally woven fabrics from PAN-based carbon fibers. Pre-impregnation with phenolic resin was followed by pressure curing and carbonization at 1000 °C and a final heat treatment at either 1800 or 2400 °C. Measurements of the samples were performed in orientations arranging the carbon fibers, respectively, parallel and perpendicular to the incoming beam. Structural features of the fibers as well as the inherently existing pores are presented and the influence of the heat treatment is discussed. The results are compared to earlier X-ray investigations of carbon fibers and C/C-composites.

  17. Neutron scattering studies on chromatin higher-order structure

    SciTech Connect

    Graziano, V.; Gerchman, S.E.; Schneider, D.K.; Ramakrishnan, V.

    1994-12-31

    We have been engaged in studies of the structure and condensation of chromatin into the 30nm filament using small-angle neutron scattering. We have also used deuterated histone H1 to determine its location in the chromatin 30nm filament. Our studies indicate that chromatin condenses with increasing ionic strength to a limiting structure that has a mass per unit length of 6-7 nucleosomes/11 nm. They also show that the linker histone H1/H5 is located in the interior of the chromatin filament, in a position compatible with its binding to the inner face of the nucleosome. Analysis of the mass per unit length as a function of H5 stoichiometry suggests that 5-7 contiguous nucleosomes need to have H5 bound before a stable higher order structure can exist.

  18. Coherent Neutron Scattering and Collective Dynamics in the Protein, GFP

    PubMed Central

    Nickels, Jonathan D.; Perticaroli, Stefania; O’Neill, Hugh; Zhang, Qiu; Ehlers, Georg; Sokolov, Alexei P.

    2013-01-01

    Collective dynamics are considered to be one of the major properties of soft materials, including biological macromolecules. We present coherent neutron scattering studies of the low-frequency vibrations, the so-called boson peak, in fully deuterated green fluorescent protein (GFP). Our analysis revealed unexpectedly low coherence of the atomic motions in GFP. This result implies a low amount of in-phase collective motion of the secondary structural units contributing to the boson peak vibrations and fast conformational fluctuations on the picosecond timescale. These observations are in contrast to earlier studies of polymers and glass-forming systems, and suggest that random or out-of-phase motions of the β-strands contribute greater than two-thirds of the intensity to the low-frequency vibrational spectra of GFP. PMID:24209864

  19. Observation of boson peaks by inelastic neutron scattering in polyolefins

    SciTech Connect

    Annis, B.K.; Lohse, D.J.; Trouw, F.

    1999-07-01

    Inelastic neutron scattering was used to probe the nature of the boson peak in atactic polypropylene (aPP), head-to-head polypropylene (hhPP), polyisobutylene (PIB) and a 1/1 mass ratio hhPP/PIB blend. Atactic polypropylene is among the most {open_quotes}fragile{close_quotes} of glass formers and was found to have a shoulder rather than the distinctive peak exhibited by the other three polymers. This difference is already apparent at 15 K where relaxations are not expected to occur. The results suggest that the fragility of hhPP is intermediate between aPP and PIB. Within this group of polymers which have similar chemical structures the position of the boson peak appears to correlate with the glass transition temperature and the cohesive energy density. The possibility of a correlation with chain stiffness as expressed by the characteristic ratio is also discussed. {copyright} {ital 1999 American Institute of Physics.}

  20. Radiation damage study using small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Rétfalvi, E.; Török, Gy; Rosta, L.

    2000-03-01

    Nuclear radiation provides important changes in the microstructure of metallic components of nuclear power plant and research reactors, influencing their mechanical properties. The investigation of this problem has primary interest for the safety and life-time of such nuclear installations. For the characterization of this kind of nanostructures small angle neutron scattering technique is a very useful tool. We have carried out experiments on samples of irradiated reactor vessel material and welded components of VVER-440-type reactors on the SANS instrument at the Budapest Research Reactor. In our measurements irradiated as well as non-irradiated samples were compared and magnetic field was applied for viewing the magnetic structure effects of the materials. A clear modification of the structure due to irradiation was obtained. Our data were analyzed by the ITP92 code, the inverse Fourier transform program of O. Glatter [1].

  1. LANSCE (Los Alamos Neutron Scattering Center) target data collection system

    SciTech Connect

    Kernodle, A.K. )

    1988-01-01

    The Los Alamos Neutron Scattering Center (LANSCE) Target Data Collection System is the result of an effort to provide a base of information from which to draw conclusions on the performance and operational condition of the overall LANSCE target system. During the conceptualization of the system several purposes and goals were defined. A survey was made of custom as well as off the shelf hardware and software which was capable of meeting these goals. The first stage of this system was successfully implemented for the LANSCE run cycle 52. From the operational experience gained thus far with the LANSCE Target Data Collection System, it would appear as though this system will indeed meet all of the previously defined requirements that seem to develop after a new system is installed.

  2. Neutron scatter studies of chromatin structures related to functions

    SciTech Connect

    Bradbury, E.M.

    1992-01-01

    We have made considerable progress in chromatin reconstitution with very lysine rich histone H1/H5 and in understanding the dynamics of nucleosomes. A ferromagnetic fluid was developed to align biological molecules for structural studies using small-angle-neutron-scattering. We have also identified and characterized in intrinsically bent DNA region flaking the RNA polymerase I binding site of the ribosomal RNA gene in Physarum Polycephalum. Finally projects in progress are in the areas of studying the interactions of histone H4 amino-terminus peptide 1-23 and acetylated 1-23 peptide with DNA using thermal denaturation; study of GGAAT repeats found in human centromeres using high resolution Nuclear Magnetic Resonance and nuclease sentivity assay; and the role of histones and other sperm specific proteins with sperm chromatin.

  3. Quasielastic neutron scattering study of water confined in carbon nanopores

    SciTech Connect

    Chathoth, S. M.; Mamontov, E.; Kolesnikov, A. I.; Gogotsi, Y.; Wesolowski, D. J.

    2011-07-26

    Microscopic dynamics of water confined in nanometer and sub-nanometer pores of carbide-derived carbon (CDC) were investigated using quasielastic neutron scattering (QENS). The temperature dependence of the average relaxation time, ‹τ›, exhibits super-Arrhenius behavior that could be described by Vogel-Fulcher-Tammann (VFT) law in the range from 250 K to 190 K; below this temperature, ‹τ› follows Arrhenius temperature dependence. The temperature of the dynamic crossover between the two regimes in water confined in the CDC pores is similar to that observed for water in hydrophobic confinement of the larger size, such as 14 Å ordered mesoporous carbon (CMK) and 16 Å double-wall carbon nanotubes. Thus, the dynamical behavior of water remains qualitatively unchanged even in the very small hydrophobic pores.

  4. Quasielastic neutron scattering study of water confined in carbon nanopores

    SciTech Connect

    Mavila Chathoth, Suresh; Mamontov, Eugene; Kolesnikov, Alexander I; Gogotsi, Yury G.; Wesolowski, David J

    2011-01-01

    Microscopic dynamics of water confined in nanometer and sub-nanometer pores of carbide-derived carbon (CDC) were investigated using quasielastic neutron scattering (QENS). The temperature dependence of the average relaxation time, {tau}, exhibits super-Arrhenius behavior that could be described by Vogel-Fulcher-Tammann (VFT) law in the range from 250 K to 190 K; below this temperature, {tau} follows Arrhenius temperature dependence. The temperature of the dynamic crossover between the two regimes in water confined in the CDC pores is similar to that observed for water in hydrophobic confinement of the larger size, such as 14 {angstrom} ordered mesoporous carbon (CMK) and 16 {angstrom} double-wall carbon nanotubes. Thus, the dynamical behavior of water remains qualitatively unchanged even in the very small hydrophobic pores.

  5. Dynamics in viscous orthoterphenyl: Results from coherent neutron scattering

    NASA Astrophysics Data System (ADS)

    Bartsch, E.; Fujara, F.; Legrand, J. F.; Petry, W.; Sillescu, H.; Wuttke, J.

    1995-07-01

    We have measured coherent neutron scattering from deuterated orthoterphenyl on a spin echo and a backscattering spectrometer. In agreement with mode coupling theory, pair correlations decay in two steps and follow the same scaling laws as those found previously for self-correlations. The temperature evolution of the intermediate plateau is compatible with the previously established Tc=290 K. The spatial resolution has not been sufficient to fully resolve oscillations of parameters as functions of Q, which are predicted by mode coupling theory. Within this limitation, we find that the double peak structure of S(Q) is not expressed in the nonergodicity parameter fcQ and that the de Gennes narrowing is missing.

  6. Diffusion of water in bentonite clay: Neutron scattering study

    NASA Astrophysics Data System (ADS)

    Sharma, V. K.; Prabhudesai, S. A.; Dessai, R. Raut; Erwin Desa, J. A.; Mitra, S.; Mukhopadhyay, R.

    2013-02-01

    Diffusion of water confined in natural bentonite clay is studied using the quasi-elastic neutron scattering (QENS) technique. X-ray diffraction shows a well-defined crystalline structure of the clay with an interlayer spacing of 13 Å. The QENS experiment has been carried out on hydrated as well as dehydrated clay at 300 K. Significant quasi-elastic broadening was observed in case of hydrated bentonite clay whereas dehydrated clay did not show any broadening over the instrument resolution. Analysis of QENS data reveals that diffusion of water occurs through jump diffusion characterized by random distribution of jump lengths. Diffusion of water in clay is found to be hindered vis a vis bulk water.

  7. Reveal protein dynamics by combining computer simulation and neutron scattering

    NASA Astrophysics Data System (ADS)

    Hong, Liang; Smith, Jeremy; CenterMolecular Biophysics Team

    2014-03-01

    Protein carries out most functions in living things on the earth through characteristic modulation of its three-dimensional structure over time. Understanding the microscopic nature of the protein internal motion and its connection to the function and structure of the biomolecule is a central topic in biophysics, and of great practical importance for drug design, study of diseases, and the development of renewable energy, etc. Under physiological conditions, protein exhibits a complex dynamics landscape, i.e., a variety of diffusive and conformational motions occur on similar time and length scales. This variety renders difficult the derivation of a simplified description of protein internal motions in terms of a small number of distinct, additive components. This difficulty is overcome by our work using a combined approach of Molecular Dynamics (MD) simulations and the Neutron Scattering experiments. Our approach enables distinct protein motions to be characterized separately, furnishing an in-depth understanding of the connection between protein structure, dynamics and function.

  8. Neutron and synchrotron radiation scattering by nonpolar magnetic fluids

    SciTech Connect

    Aksenov, V. L.; Avdeev, M. V.; Shulenina, A. V.; Zubavichus, Y. V.; Veligzhanin, A. A.; Rosta, L.; Garamus, V. M.; Vekas, L.

    2011-09-15

    The complex approach (which comprises different physical methods, including neutron and synchrotron radiation scattering) is justified in the structural analysis of magnetic fluids (MFs). Investigations of MFs based on nonpolar organic solvents with magnetite nanoparticles (2-20 nm in size) coated by various monocarboxylic acids have been performed. It is shown that the use of saturated linear acids with various alkyl chain (C12-C18) lengths instead of unsaturated oleic acid (alkyl chain C18 with a kink in the middle due to the double bond in the cis-configuration) in the classical stabilization procedure for the given type of magnetic fluids leads to a decrease in the mean size and polydispersity of nanoparticles in the final systems.

  9. The use of neutron scattering in nuclear weapons research

    SciTech Connect

    Juzaitis, R.J.

    1995-10-01

    We had a weapons science breakout session last week. Although it would have been better to hold it closer in time to this workshop, I think that it was very valuable. it may have been less of a {open_quotes}short-sleeve{close_quotes} workshop environment than we would have liked, but as the first time two communities-the weapons community and the neutron scattering community- got together, it was a wonderful opportunity to transfer information during the 24 presentations that were made. This report contains discussions on the fundamental analysis of documentation of the enduring stockpile; LANSCE`s contribution to weapons; spallation is critical to understanding; weapons safety assessments; applied nuclear physics requires cross section information; fission models need refinement; and establishing teams on collaborative projects.

  10. Neutron scatter studies of chromatin structures related to functions

    SciTech Connect

    Bradbury, E.M.

    1991-01-01

    We have completed a study on the structure of trypsin trimmed histone octamers using small angle neutron and X-ray scattering studies and nuclear magnetic resonance. We have also completed studies on the structure of TFIIIA induced DNA bending by a circular permutation gel electrophoresis assay. Individual acetylated species of core histones from butyrate treated HeLa cells were isolated and reconstituted into nucleosomes using a 5S rDNA nucleosome positioning DNA sequence from sea urchin. These nucleosomes were characterized by sulfhydryl group probing, nucleoprotein particle gel electrophoresis and DNase I footprinting. Fully acetylated species of histones H3 and H4 were also reconstituted in closed circular minichromosomes and the effect of DNA topology changes caused by acetylation was studied. Finally, protamines isolated from human sperm were characterized and a full set of core histones were isolated and characterized. 7 refs.

  11. Design studies related to an in vivo neutron activation analysis facility for measuring total body nitrogen.

    PubMed

    Stamatelatos, I E; Chettle, D R; Green, S; Scott, M C

    1992-08-01

    Design studies relating to an in vivo prompt capture neutron activation analysis facility measuring total body nitrogen are presented. The basis of the design is a beryllium-graphite neutron collimator and reflector configuration for (alpha, n) type radionuclide neutron sources (238PuBe or 241AmBe), so as to reflect leaking, or out-scattered, neutrons towards the subject. This improves the ratio of thermal neutron flux to dose and the spatial distribution of thermal flux achieved with these sources, whilst retaining their advantage of long half-lives as compared to 252Cf based systems. The common problem of high count-rate at the detector, and therefore high nitrogen region of interest background due to pile-up, is decreased by using a set of smaller (5.1 cm diameter x 10.2 cm long) NaI(Tl) detectors instead of large ones. The facility described presents a relative error of nitrogen measurement of 3.6% and a nitrogen to background ratio of 2.3 for 0.45 mSv skin dose (assuming ten 5.1 cm x 10.2 cm NaI(Tl) detectors).

  12. Characterization of neutron scatter for the 25-m neutron time of flight detector at the Z Accelerator

    NASA Astrophysics Data System (ADS)

    Norris, Edward; Hahn, Kelly; Chandler, Gordon; Ruiz, Carlos; Styron, Jedediah; Cooper, Gary; Jones, Brent; Torres, Jose; Spencer, Decker; Nelson, Alan

    2016-10-01

    We are investigating neutron scattering effects using Monte Carlo simulations for neutron time of flight (NTOF) detectors fielded at the Z Accelerator at Sandia National Laboratories. For the radial NTOF detector at 25 m, a large scatter distribution is observed during and after primary DD neutron signals produced during inertial-confinement fusion experiments which obfuscates inference of quantities such as ion temperature, yield, and liner areal density. We present comparisons of measurements with simulation results. We also propose improvements to this line-of-sight. Sandia is sponsored by the U.S. DOE's NNSA under contract DE-AC04-94AL85000.

  13. Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering

    DOE PAGES

    Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchithranga M.d.c.; ...

    2015-01-27

    Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision under dim light conditions. During rhodopsin photoactivation, the chromophore retinal undergoes cis-trans isomerization, and subsequently dissociates from the protein yielding the opsin apoprotein [1]. What are the changes in protein dynamics that occur during the rhodopsin photoactivation process? Here, we studied the microscopic dynamics of the dark-state rhodopsin and the ligand-free opsin using quasi-elastic neutron scattering (QENS). The QENS technique tracks the individual hydrogen atom motions in the protein molecules, because the neutron scattering cross-section of hydrogen is much higher than other atoms [2-4]. We used protein (rhodopsin/opsin) samples with CHAPSmore » detergent hydrated with heavy water. The solvent signal is suppressed due to the heavy water, so that only the signals from proteins and detergents are detected. The activation of proteins is confirmed at low temperatures up to 300 K by the mean-square displacement (MSD) analysis. Our QENS experiments conducted at temperatures ranging from 220 K to 300 K clearly indicate that the protein dynamic behavior increases with temperature. The relaxation time for the ligand-bound protein rhodopsin was longer compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which forms a band around the protein molecule in the micelle. Unlike the protein, the CHAPS detergent manifests localized motions that are the same as in the bulk empty micelles. Furthermore QENS provides unique understanding of the key dynamics involved in the activation of the GPCR involved in the visual process.« less

  14. Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering

    SciTech Connect

    Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchithranga M.d.c.; Chawla, Udeep; Mamontov, Eugene; Brown, Michael F.; Chu, Xiang -Qiang

    2015-01-27

    Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision under dim light conditions. During rhodopsin photoactivation, the chromophore retinal undergoes cis-trans isomerization, and subsequently dissociates from the protein yielding the opsin apoprotein [1]. What are the changes in protein dynamics that occur during the rhodopsin photoactivation process? Here, we studied the microscopic dynamics of the dark-state rhodopsin and the ligand-free opsin using quasi-elastic neutron scattering (QENS). The QENS technique tracks the individual hydrogen atom motions in the protein molecules, because the neutron scattering cross-section of hydrogen is much higher than other atoms [2-4]. We used protein (rhodopsin/opsin) samples with CHAPS detergent hydrated with heavy water. The solvent signal is suppressed due to the heavy water, so that only the signals from proteins and detergents are detected. The activation of proteins is confirmed at low temperatures up to 300 K by the mean-square displacement (MSD) analysis. Our QENS experiments conducted at temperatures ranging from 220 K to 300 K clearly indicate that the protein dynamic behavior increases with temperature. The relaxation time for the ligand-bound protein rhodopsin was longer compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which forms a band around the protein molecule in the micelle. Unlike the protein, the CHAPS detergent manifests localized motions that are the same as in the bulk empty micelles. Furthermore QENS provides unique understanding of the key dynamics involved in the activation of the GPCR involved in the visual process.

  15. New Very Small Angle Neutron Scattering (VSANS) Instrument

    NASA Astrophysics Data System (ADS)

    Van Every, E.; Deyhim, A.; Kulesza, J.

    2016-09-01

    The design of a new Very Small Angle Neutron Scattering (VSANS) Instrument for use in National Institute of Standards And Technology (NIST) will be discussed. This instrument is similar to a shorter instrument we designed and delivered to ANSTO in Australia called the Bilby SANS instrument. The NIST VSANS and the ANSTO Bilby SANS instruments have very similar dimensions for length and diameter and have similar requirements for internal detector motion, top access port, walkway supports, and ports; however, the Bilby SANS instrument vacuum requirement was lower (7.5×10-5 Torr) and the entire (60,000 pound) vessel was required to move 1.5 meters on external rails with a repeatability of 100 um, which ADC achieved. The NIST VSANS length is 24 meter, internal diameter 2.3 meter with three internal carriages. The NIST VSANS instrument, which covers the usual SANS range will also allow configuration to cover the range between q ∼⃒ 10-4 A-1 to 10-3 A-1 with a sample beam current of (104 neutrons/s). The key requirements are a second position-sensitive detector system having a 1 mm pixel size and a longer sample-detector flight path of 20 m (i.e., a 40 m instrument).

  16. Direct Observation of Neutron Scattering in MoNA Scintillator Detectors

    NASA Astrophysics Data System (ADS)

    Rogers, W. F.; Mosby, S.; Frank, N.; Kuchera, A. N.; Thoennessen, M.; MoNA Collaboration

    2017-01-01

    Monte Carlo simulations provide an important tool for the interpretation of neutron scattering data in the MoNA and LISA arrays at NSCL. Neutron energy and trajectory are determined by time of flight and position of first light produced in the array. Neutrons elastically scattered from H and inelastically from C typically produce light above detector threshold, while those elastically scattered from C produce light below threshold (``dark scattering'') and are redirected in flight, thus lowering energy and trajectory resolution. In order to test the effectiveness of our Geant4/MENATE_R simulations, we conducted an experiment at the LANSCE facility at Los Alamos National Laboratory to observe scattering of individual neutrons with well defined energy and trajectory in 16 MoNA detector bars arranged in two different stack geometries. Neutrons with energies ranging from 0.5 to 800 MeV emerged from a 3 mm collimator in the 90m shed on the WNR 4FP15L flight path to enter the array at a well defined point. Several features of neutron scattering are compared with simulation predictions, including hit multiplicity, scattering angle, mean distance between scatters, and the effect of dark scatter redirection. Results to date will be presented. Work supported by NSF Grant PHY-1506402.

  17. A United Effort for Crystal Growth, Neutron Scattering, and X-ray Scattering Studies of Novel Correlated Electron Materials

    SciTech Connect

    Lee, Young S.

    2015-02-12

    The research accomplishments during the award involved experimental studies of correlated electron systems and quantum magnetism. The techniques of crystal growth, neutron scattering, x-ray scattering, and thermodynamic & transport measurements were employed, and graduate students and postdoctoral research associates were trained in these techniques.

  18. Neutrons scattering studies in the actinide region. Progress report, August 1, 1991--July 31, 1992

    SciTech Connect

    Kegel, G.H.R.; Egan, J.J.

    1992-09-01

    During the report period were investigated the following areas: prompt fission neutron energy spectra measurements; neutron elastic and inelastic scattering from {sup 239}Pu; neutron scattering in {sup 181}Ta and {sup 197}Au; response of a {sup 235}U fission chamber near reaction thresholds; two-parameter data acquisition system; ``black`` neutron detector; investigation of neutron-induced defects in silicon dioxide; and multiple scattering corrections. Four Ph.D. dissertations and one M.S. thesis were completed during the report period. Publications consisted of three journal articles, four conference papers in proceedings, and eleven abstracts of presentations at scientific meetings. There are currently four Ph.D. and one M.S. candidates working on dissertations directly associated with the project. In addition, three other Ph.D. candidates are working on dissertations involving other aspects of neutron physics in this laboratory.

  19. Assessment of beryllium and molybdenum nuclear data files with the RPI neutron scattering system in the energy region from 0.5 to 20 MeV

    NASA Astrophysics Data System (ADS)

    Daskalakis, Adam; Blain, Ezekiel; Leinweber, Gregory; Rapp, Michael; Barry, Devin; Block, Robert; Danon, Yaron

    2017-09-01

    A series of neutron scattering benchmark measurements were performed on beryllium and molybdenum with the Rensselaer Polytechnic Institute's Neutron Scattering System. The pulsed neutron source was produced by the Rensselaer Polytechnic Institute's Linear Accelerator and a well collimated neutron beam was incident onto the samples located at a distance of 30.07 m. Neutrons that scattered from the sample were measured using the time-of-flight by eight EJ-301 liquid scintillator detectors positioned 0.5 m from the sample of interest. A total of eight experiments were performed with two sample thicknesses each, measured by detectors placed at two sets of angles. All data were processed using pulse shape analysis that separated the neutron and gamma ray events and included a gamma misclassification correction to account for erroneously identified gamma rays. A detailed model of the neutron scattering system simulated each experiment with several current evaluated nuclear data libraries and their predecessors. Results for each evaluation were compared to the experimental data using a figure-of-merit. The neutron scattering system has been used as a means to quantify a library's performance.

  20. IB: a Monte Carlo Simulation Tool for Neutron Scattering Instrument Design under Parallel Virtual Machine

    SciTech Connect

    Zhao, Jinkui

    2011-01-01

    IB is a Monte Carlo simulation tool for aiding neutron scattering instrument designs. It is written in C++ and implemented under Parallel Virtual Machine. The program has a few basic components, or modules, that can be used to build a virtual neutron scattering instrument. More complex components, such as neutron guides and multichannel beam benders, can be constructed using the grouping technique unique to IB. Users can specify a collection of modules as a group. For example, a neutron guide can be constructed by grouping four neutron mirrors together that make up the four sides of the guide. IB s simulation engine ensures that neutrons entering a group will be properly operated upon by all members of the group. For simulations that require higher computer speed, the program can be run in parallel mode under the PVM architecture. Initially, the program was written for designing instruments on pulsed neutron sources, it has since been used to simulate reactor based instruments as well.

  1. Neutron activation analysis of total diet food composites for iodine

    SciTech Connect

    Allegrini, M.; Boyer, K.W.; Tanner, J.T.

    1981-09-01

    The iodine content of Total Diet food composites was measured using neutron activation analysis. The interfering element chlorine was separated using a modified combustion and gas phase procedure. The average recovery was 94.8% (standard deviation 2.9) for the 10 matrices that were tested. In addition, iodine was measured in National Bureau of Standards Standard Reference Materials, which have no certified values for this element. Preliminary findings of iodine content of adult Total Diet market baskets collected during Fiscal Year 1980 in different regions of the United States ranged from 292 to 901 ..mu..g/day for a 2900 kcal intake.

  2. Neutron scattering studies of superconducting MgB2 tapes

    NASA Astrophysics Data System (ADS)

    Bellingeri, E.; Malagoli, A.; Modica, M.; Braccini, V.; Siri, A. S.; Grasso, G.

    2003-02-01

    The capability of manufacturing long superconducting MgB2 wires with already remarkable critical currents makes this material a very promising candidate for future applications. Tapes are prepared by the powder-in-tube technique. After the cold working procedure typically carried out by wire drawing and cold rolling, it has been found that a final sintering step carried out in argon atmosphere is a key process for further improving the superconducting properties of the conductors. To study the effect of the deformation and heat treatment processes, we performed neutron scattering experiment. Due to the high penetration depth of neutron inside matter, it was possible to analyse the MgB2 phase still wrapped in the Ni sheath. Our studies were carried out by a full spectra refinement by the Rietveld method. In the starting superconducting powder a large Mg deficiency was observed. In the tapes we found that the large forces applied during the cold working induced a large MgB2 lattice deformation, and that it is partly relaxed during the final sintering process. An important correlation of the residual stress with the critical temperature and the pinning properties was pointed out. We also observed the appearance of detrimental secondary phases during the sintering process. In particular, the MgB2 phase reacted with the nickel sheath and MgB2Ni2.5 was formed at temperatures higher than 850 °C. These results are of basic importance for a further optimization of the transport properties at moderate fields where applications of MgB2 tapes are already envisageable.

  3. A biophysical study of clathrin utilizing light scattering, neutron scattering and structure based computer modeling

    NASA Astrophysics Data System (ADS)

    Ferguson, Matthew Lee

    A principal component in the protein coats of certain post-golgi and endocytic vesicles is clathrin, which appears as a three-legged heteropolymer (known as a triskelion) that assembles into polyhedral baskets principally made up of pentagonal and hexagonal faces. In vitro, this assembly depends on the pH, with baskets forming more readily at low pH and less readily at high pH. We have developed procedures, based on static and dynamic light scattering, to determine the radius of gyration, Rg, and hydrodynamic radius, RH, of isolated triskelia under conditions where basket assembly occurs. Calculations based on rigid molecular bead models of a triskelion show that the measured values can be accounted for by bending of the legs and a puckering at the vertex. We also show that the values of Rg and R H measured for clathrin triskelia in solution are qualitatively consistent with the conformation of an individual triskelion that is part of a "D6 barrel" basket assembly measured by cryo-EM tomography. We extended this study by performing small angle neutron scattering (SANS) experiments on isolated triskelia in solution under conditions where baskets do not assemble. SANS experiments were consistent with previous static light scattering experiments but showed a shoulder in the scattering function at intermediate q-values just beyond the central diffraction peak (the Guinier regime). Theoretical calculations based on rigid bead models of a triskelion showed well-defined features in this region different from the experiment. A flexible bead-spring model of a triskelion and Brownian dynamics simulations were used to generate a time averaged scattering function. This model adequately described the experimental data for flexibilities close to previous estimates from the analysis of electron micrographs.

  4. Neutron inelastic scattering in natural Cu as a background in neutrinoless double-β decay experiments

    NASA Astrophysics Data System (ADS)

    Boswell, M. S.; Elliott, S. R.; Perepelitsa, D. V.; Devlin, M.; Fotiades, N.; Nelson, R. O.; Kawano, T.; Guiseppe, V. E.

    2013-06-01

    Background: Experiments designed to study rare processes, such as neutrinoless double-β decay (0νββ), are crucial tests for physics beyond the standard model. These experiments rely on reducing the intrinsic radioactive background to unprecedented levels, while adequately shielding the detectors from external sources of radioactivity.Purpose: The purpose of this work is focused on understanding the background rates from neutron interactions in Cu shielding in regions around the Q values of many candidate 0νββ decay isotopes, as well as providing data for benchmarking Monte Carlo simulations of background events.Methods: Using the broad-spectrum neutron beam at Los Alamos Neutron Science Center, we have measured γ rays emitted from inelastic neutron scattering on natCu.Results: We extracted the level cross sections from the γ-production cross section for 46 energy levels in natCu. These level cross sections were compared with the available experimental data, as well as the ENDF/B-VII evaluation for discrete levels.Conclusions: For energy levels above 2 MeV we found significant discrepancies between the suggested level cross sections for both nuclei and our data. We found reasonable agreement between our measurement and the ENDF/B-VII evaluation for the total neutron inelastic cross section in 63Cu. Our measurement of the total neutron inelastic scattering cross section in 65Cu was 30% lower than the ENDF/B-VII evaluations, which we attribute to unobserved transitions in 65Cu. Furthermore, we found that the implementation of the ENDF/B-VII evaluation in simulations did not properly model the decay properties of the nucleus to the degree necessary for estimating backgrounds in rear-event searches. Finally, we examined the potential implications of our measurements on 0νββ measurements and found that many of the commonly studied 0νββ isotopes had Q values below the cutoff for ENDF/B-VII evaluated discrete levels in either Cu nucleus.

  5. Velocity-dependent optical potential for neutron elastic scattering from 1 p -shell nuclei

    NASA Astrophysics Data System (ADS)

    Ghabar, I. N.; Jaghoub, M. I.

    2015-06-01

    Background: The conventional optical model is quite successful in describing the nucleon elastic scattering data from medium and heavy nuclei. However, its success in describing the light 1 p -shell nuclei is somewhat limited. The velocity-dependent optical potential resulted in a significant improvement in describing the elastic angular distributions for light nuclei in the low energy region. Purpose: To extend the formalism of the velocity-dependent potential to higher energies, and to assess its importance in describing neutron elastic scattering data from light 1 p -shell nuclei at high energies. Method: We fit the angular distribution data for neutron elastic scattering from 12C and 16O using (i) the velocity-dependent optical potential and (ii) the conventional optical potential. The results of the two models are then compared. At low energies, we compare our angular distribution fits with the fits of other works that exist in the literature. Furthermore, the total integrated cross sections in addition to the analyzing power are calculated using the velocity-dependent optical potential and compared to the experimental data. Results: The velocity-dependent potential resulted in significant improvements in describing the angular distributions particularly in the large-angle scattering region and for certain energy ranges. This model is important where the experimental data show structural effects from nuclear surface deformations, which are important in light nuclei. Furthermore, the calculated total elastic cross sections and analyzing power are in good agreement with the experimental data. Conclusions: The velocity-dependent potential gives rise to surface-peaked real terms in the optical model. Such terms account, at least partly, for the structural effects seen in the angular distribution data. The energy range over which the surface terms are needed is found to depend on the target nucleus. Other works that have introduced real surface terms in the optical

  6. Geometry Survey of the Time-of-Flight Neutron-Elastic Scattering (Antonella) Experiment

    SciTech Connect

    Oshinowo, Babatunde O.; Izraelevitch, Federico

    2016-10-17

    The Antonella experiment is a measurement of the ionization efficiency of nuclear recoils in silicon at low energies [1]. It is a neutron elastic scattering experiment motivated by the search for dark matter particles. In this experiment, a proton beam hits a lithium target and neutrons are produced. The neutron shower passes through a collimator that produces a neutron beam. The beam illuminates a silicon detector. With a certain probability, a neutron interacts with a silicon nucleus of the detector producing elastic scattering. After the interaction, a fraction of the neutron energy is transferred to the silicon nucleus which acquires kinetic energy and recoils. This kinetic energy is then dissipated in the detector producing ionization and thermal energy. The ionization produced is measured with the silicon detector electronics. On the other hand, the neutron is scattered out of the beam. A neutron-detector array (made of scintillator bars) registers the neutron arrival time and the scattering angle to reconstruct the kinematics of the neutron-nucleus interaction with the time-of-flight technique [2]. In the reconstruction equations, the energy of the nuclear recoil is a function of the scattering angle with respect to the beam direction, the time-of-flight of the neutron and the geometric distances between components of the setup (neutron-production target, silicon detector, scintillator bars). This paper summarizes the survey of the different components of the experiment that made possible the off-line analysis of the collected data. Measurements were made with the API Radian Laser Tracker and I-360 Probe Wireless. The survey was completed at the University of Notre Dame, Indiana, USA in February 2015.

  7. High resolution measurement of neutron inelastic scattering cross-sections for 23Na

    NASA Astrophysics Data System (ADS)

    Rouki, C.; Archier, P.; Borcea, C.; De Saint Jean, C.; Drohé, J. C.; Kopecky, S.; Moens, A.; Nankov, N.; Negret, A.; Noguère, G.; Plompen, A. J. M.; Stanoiu, M.

    2012-04-01

    The neutron inelastic scattering cross-section of 23Na has been measured in response to the relevant request of the OECD-NEA High Priority Request List, which requires a target uncertainty of 4% in the energy range up to 1.35 MeV for the development of sodium-cooled fast reactors. The measurement was performed at the GELINA facility with the Gamma Array for Inelastic Neutron Scattering (GAINS), featuring eight high purity germanium detectors. The setup is installed at a 200 m flight path from the neutron source and provides high resolution measurements using the (n,n'γ)-technique. The sample was an 80 mm diameter metallic sodium disk prepared at IRMM. Transitions up to the seventh excited state were observed and the differential gamma cross-sections at 110° and 150° were measured, showing mostly isotropic gamma emission. From these the gamma production, level and inelastic cross-sections were determined for neutron energies up to 3838.9 keV. The results agree well with the existing data and the evaluated nuclear data libraries in the low energies, and provide new experimental points in the little studied region above 2 MeV. Following a detailed review of the methodology used for the gamma efficiency calibrations and flux normalization of GAINS data, an estimated total uncertainty of 2.2% was achieved for the inelastic cross-section integrals over the energy ranges 0.498-1.35 MeV and 1.35-2.23 MeV, meeting the required targets.

  8. Study of new substrate THGEMs with low neutron scattering and low radioactivity

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Niu, S.; Xie, Y.; Yan, J.; Lü, J.; Hu, T.; Wang, Z.; Cai, X.; Fang, J.; Yu, B.; Sun, X.; Liu, Y.; Liu, W.; Sun, L.

    2015-10-01

    New types of Thick Gaseous Electron Multipliers (THGEMs) made of PCB-type substrates, including Ceramic, Kapton, PTFE, and in addition to FR-4, were developed for applications requiring low neutron absorption, scattering, and low natural radioactivity, such as the THGEM-based neutron detector, and the THGEM-based gaseous multiplier (GPM). Using Geant4 simulation, the result of the total neutron absorption and scattering ratio of bare substrate is Kapton(high) > FR-4 > Ceramic > PTFE (low). The Ceramic and PTFE substrates have lower ratios about 0.707% and 0.635% per layer(0.2 mm thick) respectively. The gamma-induced electron background is the reverse, Ceramic > PTFE > FR-4 > Kapton, from 1.5% to 0.7% at 1.0 MeV, which induces highest electron background in the range of 0~7 MeV. The natural radioactivity background was measured for these types of substrate samples. The Ceramic substrate has lower radioactivity, 232Th = 8.8±0.9 Bq/kg, 238U = 6.3±0.9 Bq/kg, and 40K is too low to be detected. Some THGEM samples were produced by these four types of substrates in the same shape: 0.2-mm thickness, 0.2-mm hole diameter, 0.6-mm pitch, and 70-μm rim. The performances of these new substrate THGEMs are promising. The effective gain is at the 104 level and the gain was stable during more than 100 hours continuous test. The energy resolution @ Ar+IsoB = 97:3 is at the level of 20% to 27%. These new substrate THGEMs are available in 200×200 mm2 size and even larger, some of them are applied to neutron flux monitor detector and gaseous photomultipliers (GPM).

  9. The Manuel Lujan Jr. Neutron Scattering Center (LANSCE) experiment reports 1993 run cycle. Progress report

    SciTech Connect

    Farrer, R.; Longshore, A.

    1995-06-01

    This year the Manuel Lujan Jr. Neutron Scattering Center (LANSCE) ran an informal user program because the US Department of Energy planned to close LANSCE in FY1994. As a result, an advisory committee recommended that LANSCE scientists and their collaborators complete work in progress. At LANSCE, neutrons are produced by spallation when a pulsed, 800-MeV proton beam impinges on a tungsten target. The proton pulses are provided by the Clinton P. Anderson Meson Physics Facility (LAMPF) accelerator and a associated Proton Storage Ring (PSR), which can Iter the intensity, time structure, and repetition rate of the pulses. The LAMPF protons of Line D are shared between the LANSCE target and the Weapons Neutron Research (WNR) facility, which results in LANSCE spectrometers being available to external users for unclassified research about 80% of each annual LAMPF run cycle. Measurements of interest to the Los Alamos National Laboratory (LANL) may also be performed and may occupy up to an additional 20% of the available beam time. These experiments are reviewed by an internal program advisory committee. This year, a total of 127 proposals were submitted. The proposed experiments involved 229 scientists, 57 of whom visited LANSCE to participate in measurements. In addition, 3 (nuclear physics) participating research teams, comprising 44 scientists, carried out experiments at LANSCE. Instrument beam time was again oversubscribed, with 552 total days requested an 473 available for allocation.

  10. New neutron imaging techniques to close the gap to scattering applications

    NASA Astrophysics Data System (ADS)

    Lehmann, Eberhard H.; Peetermans, S.; Trtik, P.; Betz, B.; Grünzweig, C.

    2017-01-01

    Neutron scattering and neutron imaging are activities at the strong neutron sources which have been developed rather independently. However, there are similarities and overlaps in the research topics to which both methods can contribute and thus useful synergies can be found. In particular, the spatial resolution of neutron imaging has improved recently, which - together with the enhancement of the efficiency in data acquisition- can be exploited to narrow the energy band and to implement more sophisticated methods like neutron grating interferometry. This paper provides a report about the current options in neutron imaging and describes how the gap to neutron scattering data can be closed in the future, e.g. by diffractive imaging, the use of polarized neutrons and the dark-field imagining of relevant materials. This overview is focused onto the interaction between neutron imaging and neutron scattering with the aim of synergy. It reflects mainly the authors’ experiences at their PSI facilities without ignoring the activities at the different other labs world-wide.

  11. Initial characterization of mudstone nanoporosity with small angle neutron scattering using caprocks from carbon sequestration sites.

    SciTech Connect

    McCray, John; Navarre-Sitchler, Alexis; Mouzakis, Katherine; Heath, Jason E.; Dewers, Thomas A.; Rother, Gernot

    2010-11-01

    Geological carbon sequestration relies on the principle that CO{sub 2} injected deep into the subsurface is unable to leak to the atmosphere. Structural trapping by a relatively impermeable caprock (often mudstone such as a shale) is the main trapping mechanism that is currently relied on for the first hundreds of years. Many of the pores of the caprock are of micrometer to nanometer scale. However, the distribution, geometry and volume of porosity at these scales are poorly characterized. Differences in pore shape and size can cause variation in capillary properties and fluid transport resulting in fluid pathways with different capillary entry pressures in the same sample. Prediction of pore network properties for distinct geologic environments would result in significant advancement in our ability to model subsurface fluid flow. Specifically, prediction of fluid flow through caprocks of geologic CO{sub 2} sequestration reservoirs is a critical step in evaluating the risk of leakage to overlying aquifers. The micro- and nanoporosity was analyzed in four mudstones using small angle neutron scattering (SANS). These mudstones are caprocks of formations that are currently under study or being used for carbon sequestration projects and include the Marine Tuscaloosa Group, the Lower Tuscaloosa Group, the upper and lower shale members of the Kirtland Formation, and the Pennsylvanian Gothic shale. Total organic carbon varies from <0.3% to 4% by weight. Expandable clay contents range from 10% to {approx}40% in the Gothic shale and Kirtland Formation, respectively. Neutrons effectively scatter from interfaces between materials with differing scattering length density (i.e. minerals and pores). The intensity of scattered neutrons, I(Q), where Q is the scattering vector, gives information about the volume of pores and their arrangement in the sample. The slope of the scattering data when plotted as log I(Q) vs. log Q provides information about the fractality or geometry of

  12. Data Driven Study of Neutron Response Using Quasielastic Neutrino Scattering in the Minerva Experiment

    NASA Astrophysics Data System (ADS)

    Peters, Evan; Minerva Collaboration

    2016-09-01

    Understanding how particles behave in detectors is a critical part of analyzing data from neutrino experiments, but neutral particles are difficult to characterize. The purpose of this project was to calibrate the neutron response in Quasielastic antineutrino scattering (QE) events in the Minerva detector. We applied quasi-elastic assumptions to estimate the outgoing neutron kinematics in QE scattering, and then added modifications to improve the model's predictions for neutron response in data. We compared these kinematic predictions of neutron energy and angle to Monte Carlo simulations of QE scattering and to the behavior of reconstructed energy ``blobs'' that characterize neutral particle behavior in simulated and real Minerva data. Filtering events for neutron energy, angle, and distance from the interaction vertex, we derive calibration functions for both the simulation and real data. Future work will include potential changes to the blobbing algorithms and refinement of the calibration technique using rigorous statistical methods.

  13. Neutron and light scattering studies of light-harvesting photosynthetic antenna complexes

    SciTech Connect

    Tang, Kuo-Hsiang; Blankenship, Robert E.

    2011-06-28

    Small-angle neutron scattering (SANS) and dynamic light scattering (DLS) have been employed in studying the structural information of various biological systems, particularly in systems without high-resolution structural information available. In this report, we briefly present some principles and biological applications of neutron scattering and DLS, compare the differences in information that can be obtained with small-angle X-ray scattering (SAXS), and then report recent studies of SANS and DLS, together with other biophysical approaches, for light-harvesting antenna complexes and reaction centers of purple and green phototrophic bacteria.

  14. Neutron scattering and diffraction instrument for structural study on biology in Japan

    SciTech Connect

    Niimura, Nobuo

    1994-12-31

    Neutron scattering and diffraction instruments in Japan which can be used for structural studies in biology are briefly introduced. Main specifications and general layouts of the instruments are shown.

  15. Measurements of neutron scattering angular distributions with a new scintillator setup

    NASA Astrophysics Data System (ADS)

    Pirovano, Elisa; Beyer, Roland; Junghans, Arnd; Nolte, Ralf; Nyman, Markus; Plompen, Arjan

    2017-09-01

    A new experimental setup for the measurement of neutron scattering cross sections and angular distributions is currently being developed at the neutron time-of-flight facility GELINA, at the JRC-Geel. Up to 32 liquid organic scintillators are employed for the detection of neutrons scattered from a sample of the investigated material. The differential cross section is measured at eight different angles, and the angle-integrated cross section is obtained from the differential data by numerical integration. Two experiments for the study of scattering on iron were carried out, one at GELINA and the other at nELBE (HZDR). The first results for the angular distributions of elastic scattering in the neutron energy range from 2 to 6 MeV are here presented and compared with evaluations from the major nuclear data libraries.

  16. Resonant Neutron Scattering from YBa_2Cu_3O_7

    NASA Astrophysics Data System (ADS)

    Fong, Hung Fai

    1996-03-01

    Recently our ( Collaborators: B. Keimer, D. Reznik, P. Bourges, I. Aksay ) study on the 41 meV magnetic resonance in YBa_2Cu_3O7 ( H. F. Fong, B. Keimer, P. W. Anderson, D. Reznik, F. Doğan, I. A. Aksay, Phy. Rev. Lett. \\underbar 75), 316 (1995) has received considerable attention. Evidence for this mode had already been collected by other groups, but our demonstration that the resonance disappears in the normal state has stimulated a large body of theoretical work. We have extended our study in several respects, using both polarized and unpolarized neutron scattering techniques. First, by calibrating the measured magnetic intensity against calculated structure factors of optical phonons and against antiferromagnetic spin waves in the same crystal after deoxygenation to YBa_2Cu_3O_6.2, we have established the absolute scale of its dynamical susceptibility \\chi''(q,ω) in the superconducting state and a limit on its magnitude in the normal state. Second, we have measured the energy and absolute spectral weight of the resonance accurately as a function of temperature. Our experimental results will be discussed in the light of recent theoretical work. Recent measurements of the high energy spin waves in the antiferromagnetic YBa_2Cu_3O_6.2 will also be reported.

  17. Heparin's solution structure determined by small-angle neutron scattering.

    PubMed

    Rubinson, Kenneth A; Chen, Yin; Cress, Brady F; Zhang, Fuming; Linhardt, Robert J

    2016-12-01

    Heparin is a linear, anionic polysaccharide that is widely used as a clinical anticoagulant. Despite its discovery 100 years ago in 1916, the solution structure of heparin remains unknown. The solution shape of heparin has not previously been examined in water under a range of concentrations, and here is done so in D2 O solution using small-angle neutron scattering (SANS). Solutions of 10 kDa heparin-in the millimolar concentration range-were probed with SANS. Our results show that when sodium concentrations are equivalent to the polyelectrolyte's charge or up to a few hundred millimoles higher, the molecular structure of heparin is compact and the shape could be well modeled by a cylinder with a length three to four times its diameter. In the presence of molar concentrations of sodium, the molecule becomes extended to nearly its full length estimated from reported X-ray measurements on stretched fibers. This stretched form is not found in the presence of molar concentrations of potassium ions. In this high-potassium environment, the heparin molecules have the same shape as when its charges were mostly protonated at pD ≈ 0.5, that is, they are compact and approximately half the length of the extended molecules.

  18. Coherent neutron scattering and collective dynamics on mesoscale

    SciTech Connect

    Novikov, Vladimir; Schweizer, Kenneth S; Sokolov, Alexei P

    2013-01-01

    By combining, and modestly extending, a variety of theoretical concepts for the dynamics of liquids in the supercooled regime, we formulate a simple analytic model for the temperature and wavevector dependent collective density fluctuation relaxation time that is measurable using coherent dynamic neutron scattering. Comparison with experiments on the ionic glass-forming liquid Ca K NO3 in the lightly supercooled regime suggests the model captures the key physics in both the local cage and mesoscopic regimes, including the unusual wavevector dependence of the collective structural relaxation time. The model is consistent with the idea that the decoupling between diffusion and viscosity is reflected in a different temperature dependence of the collective relaxation time at intermediate wavevectors and near the main (cage) peak of the static structure factor. More generally, our analysis provides support for the ideas that decoupling information and growing dynamic length scales can be at least qualitatively deduced by analyzing the collective relaxation time as a function of temperature and wavevector, and that there is a strong link between dynamic heterogeneity phenomena at the single and many particle level. Though very simple, the model can be applied to other systems, such as molecular liquids.

  19. Direct measurement of densification rate using a neutron scattering technique

    NASA Astrophysics Data System (ADS)

    Morris, E. M.; Wingham, D.

    2012-12-01

    A non-destructive method for measuring density, based on neutron-scattering, has been used in the dry snow area of the Greenland Ice Sheet to derive profiles of densification rate over periods ranging from a few days to 5 years. From these observations we have derived a constitutive law for the compaction of dry snow relating strainrate to stress, temperature and the "type" of snow, that is, whether the snow is part of a "winter" wind-compacted layer with rounded grains or a "summer" lower-density hoar layer. We suggest that the processes which allow compaction of the snow also promote sintering, by bringing the snow grains into closer proximity. Higher temperatures increase the initial densification rate for a snow element but also, over time, harden it more rapidly. The net result is a much-reduced apparent activation energy for snow densification, similar to that used by Herron and Langway in their empirical equation derived from ice core density profiles.

  20. Neutron scattering studies of ferromagnetic superconductor UGe2 under pressure

    NASA Astrophysics Data System (ADS)

    Sokolov, D. A.; Huxley, A. D.; Ritz, R.; Pfleiderer, C.; Keller, T.

    2010-03-01

    Observation of an unconventional superconductivity in ferromagnetic UGe2 when ferromagnetism is suppressed by pressure indicates a dramatic modification of its electronic structure near the Quantum Critical Point [1]. We present high resolution measurements of the lattice constants of ferromagnetic superconductor UGe2 under pressure probed by a novel technique, which utilizes Larmor precession of polarized neutrons and surpasses the resolution of conventional scattering methods by an order of magnitude. We have observed sharp anomalies at the Curie temperature, TC and at TX, which marks the crossover regime. Our studies under pressure of 10, and 12 kbar indicate that the sharp anomaly corresponding to TC shifted to lower temperature in agreement with a phase diagram. At the pressure corresponding to an onset of superconductivity, 10kbar, the lattice expansion corresponding to ferromagnetic transition undergoes a first order transition and increases by a factor of 3. The results indicate a complex response of the electronic structure of UGe2 to external pressure and suggest a strong magnetoelastic coupling as one of multiple energy scales that stabilize superconductivity in UGe2. [1] S. S. Saxena, et al., Nature 406, 587 (2000)

  1. Water dynamics in graphite oxide investigated with neutron scattering.

    PubMed

    Buchsteiner, Alexandra; Lerf, Anton; Pieper, Jörg

    2006-11-16

    Graphite oxide is an inorganic multilayer system that preserves the layered structure of graphite but not the conjugated bond structure. In the past few years, detailed studies of the static structure of graphite oxide were carried out. This was mainly done by NMR investigations and led to a new structural model of graphite oxide. The layer distance of graphite oxide increases with increasing humidity level, giving rise to different spacings of the carbon layers in the range from 6 to 12 A. As a consequence, different types of motions of water and functional groups appear. Information about the mobility of the water molecules is not yet complete but is crucial for the understanding of the structure of the carbon layers as well as the intercalation process. In this paper, the hydration- and temperature-dependent dynamic behavior of graphite oxide will be investigated by quasielastic neutron scattering using the time-of-flight spectrometer NEAT at the Hahn-Meitner-Institut Berlin. The character of the embedded water does not change over a wide range of hydration levels. Especially the interlayer water remains tightly bound and does not show any translational motion. In samples with excess water, however, the water is also distributed in noninterlayer voids, leading to the observation of additional motions of bulklike or confined water. The dynamic behavior of hydrated graphite oxide can be described by a consistent model that combines two two-site jump motions for the motions of the water molecules and the motions of OH groups.

  2. Neutron polarizabilities from Compton scattering on the deuteron?

    NASA Astrophysics Data System (ADS)

    Karakowski, Jonathan J.; Miller, Gerald A.

    1999-07-01

    A calculation of deuteron Compton scattering using nonrelativistic perturbation theory is presented, with the primary motivation of investigating the feasibility of determining the neutron polarizabilities from this type of experiment. This calculation is expected to be valid for energies below 100 MeV. Pion-exchange, relativistic, and recoil corrections are also included. The low-energy theorem for gauge invariance is shown to be satisfied. The relative effects of the different terms and their effects on the determinations of the polarizabilities are discussed at energies of 49, 69, and 95 MeV. The cross section is dominated by the seagull, polarizability, and electromagnetic multipole interactions. Relativistic and pion-exchange terms are also important, while recoil corrections and multipoles of L=2 and greater are negligible. The calculation provides a reasonable description of the experimental data points at 49 and 69 MeV. The polarizabilities are difficult to determine at these energies. A more accurate determination of the polarizabilities may be possible at 95 MeV.

  3. Neutron-scattering studies of Yb-bearing silicate glasses

    SciTech Connect

    Ellison, A.J.G.; Loong, C.K.; Wagner, J.

    1993-09-01

    The static and dynamic magnetic response of the Yb{sup 3+} ions in 2Na{sub 2}O{center_dot}Yb{sub 2}O{sub 3}{center_dot}6SiO{sub 2} glass and the isochemical crystalline silicate Na{sub 3}YbSi{sub 3}O{sub 9} has been studied by neutron diffraction, inelastic magnetic-scattering, and magnetic susceptibility measurements. The rare earth sites in the glass have an average coordination number of 5.6 {plus_minus} 0.5 and give a mean rare earth-oxygen bond length of 2.23 {Angstrom}; average Si-O and O-O coordination numbers and bond distances are comparable to those in vitreous SiO{sub 2}. The magnetic excitation spectrum of the Na{sub 3}YbSi{sub 3}O{sub 9} material was analyzed by a crystal-field model using a method of descending symmetry. The magnetic susceptibility and the excitation spectrum of the Yb glasses can be described by a distribution of ligand-field effects on the Yb{sup 3+} ions that are similar to the nominal crystal field in crystalline Na{sub 3}YbSi{sub 3}O{sub 9}.

  4. Phonon dynamics and inelastic neutron scattering of sodium niobate

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Gupta, M. K.; Mittal, R.; Zbiri, M.; Rols, S.; Schober, H.; Chaplot, S. L.

    2014-05-01

    Sodium niobate (NaNbO3) exhibits an extremely complex sequence of structural phase transitions in the perovskite family and therefore provides an excellent model system for understanding the mechanism of structural phase transitions. We report temperature dependence of inelastic neutron scattering measurements of phonon densities of states in sodium niobate. The measurements are carried out in various crystallographic phases of this material at various temperatures from 300 to 1048 K. The phonon spectra exhibit peaks centered on 19, 37, 51, 70, and 105 meV. Interestingly, the peak near 70 meV shifts significantly towards lower energy with increasing temperature, while the other peaks do not exhibit any appreciable shift. The phonon spectra at 783 K show prominent change and become more diffusive as compared to those at 303 K. In order to better analyze these features, we have performed first-principles lattice dynamics calculations based on the density functional theory. The computed phonon density of states is found to be in good agreement with the experimental data. Based on our calculation we are able to assign the characteristic Raman modes in the antiferroelectric phase, which are due to the folding of the T (ω = 95 cm-1) and Δ (ω = 129 cm-1) points of the cubic Brillouin zone, to the A1g symmetry.

  5. Directional Stand-off Detection of Fast Neutrons and Gammas Using Angular Scattering Distributions

    SciTech Connect

    Vanier P. e.; Dioszegi, I.; Salwen, C.; Forman, L.

    2009-10-25

    We have investigated the response of a DoubleScatter Neutron Spectrometer (DSNS) for sources at long distances (gr than 200 meters). We find that an alternative method for analyzing double scatter data avoids some uncertainties introduced by amplitude measurements in plastic scintillators.Time of flight is used to discriminate between gamma and neutron events, and the kinematic distributions of scattering angles are assumed to apply. Non-relativistic neutrons are most likely to scatter at 45°, while gammas with energies greater than 2 MeV are most likely to be forward scattered. The distribution of scattering angles of fission neutrons arriving from a distant point source generates a 45° cone, which can be back-projected to give the source direction. At the same time, the distribution of Compton-scattered gammas has a maximum in the forward direction, and can be made narrower by selecting events that deposit minimal energy in the first scattering event. We have further determined that the shape of spontaneous fission neutron spectra at ranges gr than 110 m is still significantly different from thecosmic ray background.

  6. Scattering for mixtures of hard spheres: comparison of total scattering intensities with model.

    PubMed

    Anderson, B J; Gopalakrishnan, V; Ramakrishnan, S; Zukoski, C F

    2006-03-01

    The angular dependence of the intensity of x-rays scattered from binary and ternary hard sphere mixtures is investigated and compared to the predictions of two scattering models. Mixture ratio and total volume fraction dependent effects are investigated for size ratios equal to 0.51 and 0.22. Comparisons of model predictions with experimental results indicate the significant impact of the role of particle size distributions in interpreting the angular dependence of the scattering at wave vectors probing density fluctuations intermediate between the sizes of the particles in the mixture.

  7. FAST NEUTRON SOURCE DETECTION AT LONG DISTANCES USING DOUBLE SCATTER SPECTROMETRY.

    SciTech Connect

    FORMAN,L.VANIER,P.WELSH,K.

    2003-08-03

    Fast neutrons can be detected with relatively high efficiency, >15%, using two planes of hydrogenous scintillator detectors where a scatter in the first plane creates a start pulse and scatter in the second plane is separated by time-of-flight. Indeed, the neutron spectrum of the source can be determined as the sum of energy deposited by pulse height in the first added to the energy of the second found by time-of-flight to the second detector. Gamma rays can also create a double scatter by Compton interaction in the first with detection in the second, but these events occur in a single time window because the scattered photons all travel at the speed of light. Thus, gamma ray events can be separated from neutrons by the time-of-flight differences. We have studied this detection system with a Cf-252 source using Bicron 501A organic scintillators and report on the ability to efficiently detect fast neutrons with high neutron/gamma detection ratios. We have further studied cosmic-ray neutron background detection response that is the dominant background in long range detection. We have found that most of the neutrons are excluded from the time-of-flight window because they are either too high in energy, >10 keV, or too low, < 10 keV. Moreover, if the detection planes are position-sensitive, the angular direction of the source can be determined by the ratio of the energy of scattered protons in the first detector relative to the position and energy of the scattered neutron detected in the second. This ability to locate the source in theta is useful, but more importantly increases the signal to noise relative to cosmic-ray produced neutrons that are relatively isotropic. This technique may be used in large arrays to detect neutrons at ranges up to 0.5 kilometer.

  8. Thermal neutron scattering law calculations using ab initio molecular dynamics

    NASA Astrophysics Data System (ADS)

    Wormald, Jonathan; Hawari, Ayman I.

    2017-09-01

    In recent years, methods for the calculation of the thermal scattering law (i.e. S(α,β), where α and β are dimensionless momentum and energy transfer variables, respectively) were developed based on ab initio lattice dynamics (AILD) and/or classical molecular dynamics (CMD). While these methods are now mature and efficient, further advancement in the application of such atomistic techniques is possible using ab initio molecular dynamics (AIMD) methods. In this case, temperature effects are inherently included in the calculation, e.g. phonon density of states (DOS), while using ab initio force fields that eliminate the need for parameterized semi-empirical force fields. In this work, AIMD simulations were performed to predict the phonon spectra as a function of temperature for beryllium and graphite, which are representative nuclear reactor moderator and reflector materials. Subsequently, the calculated phonon spectra were utilized to predict S(α,β) using the LEAPR module of the NJOY code. The AIMD models of beryllium and graphite were 5 × 5 × 5 crystal unit cells (250 atoms and 500 atoms respectively). Electronic structure calculations for the prediction of Hellman-Feynman forces were performed using density functional theory with a GGA exchange correlation functional and corresponding core electron pseudopotentials. AIMD simulations of 1000-10,000 time-steps were performed with the canonical ensemble (NVT thermostat) for several temperatures between 300 K and 900 K. The phonon DOS were calculated as the power spectrum of the AIMD predicted velocity autocorrelation functions. The resulting AIMD phonon DOS and corresponding inelastic thermal neutron scattering cross sections at 300 K, where anharmonic effects are expected to be small, were found to be in reasonable agreement with the results generated using traditional AILD. This illustrated the validity of the AIMD approach. However, since the impact of the temperature on the phonon DOS (e.g. broadening of

  9. Total Electron Scattering Cross Sections for Simple Perfluorocarbons

    NASA Astrophysics Data System (ADS)

    Nishimura, Hiroyuki; Nishimura, Fumio; Nakamura, Yoshiharu; Okuda, Keisuke

    2003-05-01

    Total electron scattering cross sections for CF4, C2F6 and C3F8 have been measured in the energy range between 1.25 eV and 3000 eV using a compact linear transmission apparatus. Electrons scattered into a narrow forward angular range that should be counted in the scattered one were estimated utilizing measured quantities. The present results for CF4 agree well with available data at low and high energies, while some discrepancies were seen at intermediate energies. Measured results for C2F6 and C3F8 were shown at high energies for the first time. Upper bound of the elastic cross sections for these molecules were estimated at electron energies higher than 20 eV.

  10. Shape optimization of the total scattering cross section for cylindrical scatterers

    NASA Astrophysics Data System (ADS)

    Jacobsson, Per; Rylander, Thomas

    2009-08-01

    We propose and test a gradient-based shape optimization algorithm for the total scattering cross section of infinitely long cylinders, by means of changing the shape of the cylinder's cross section. On the basis of the optical theorem, we derive sensitivity expressions for both dielectric and metal cylinders given an incident plane wave, where the wave vector is perpendicular to the cylinder axis. Both the transverse electric (TE) case and the transverse magnetic case are considered. The sensitivity expressions are based on the continuum form of Maxwell's equations, and they provide the sensitivity with respect to an arbitrary number of shape parameters in terms of the field solution of the original scattering problem and an adjoint scattering problem. These results are used to construct a gradient-based optimization algorithm that we exploit for the reduction of the total scattering cross section in the TE case for metal cylinders, e.g., struts used in reflector antennas. We present optimized cross sections that are oblong in the direction of the incident wave vector, and some of these designs feature corrugations that are parallel to the cylinder axis. We show designs with asymmetric cross sections that yield a low monostatic scattering cross section for certain directions in combination with a low total scattering cross section, which can be used to reduce the noise temperature contributions from the upper strut in an inverted Y tripod reflector antenna.

  11. Dynamic processes in biological membrane mimics revealed by quasielastic neutron scattering.

    PubMed

    Lautner, Lisa; Pluhackova, Kristyna; Barth, Nicolai K H; Seydel, Tilo; Lohstroh, Wiebke; Böckmann, Rainer A; Unruh, Tobias

    2017-08-01

    Neutron scattering is a powerful tool to study relaxation processes in biological membrane mimics in space and time. Combining different inelastic and quasielastic neutron scattering techniques, a large dynamic range can be covered: from atomic to mesoscopic lengths and from femto- to some hundreds of nanoseconds in time. This allows studies on e.g. the diffusion of lipids, the membrane undulation motions, the dispersion of sound waves in membranes as well as the mutual interactions of membrane constituents such as lipids, proteins, and additives. In particular, neutron scattering provides a quite direct experimental approach to the inter-atomic and inter-molecular potentials on length and time scales which are perfectly accessible by molecular dynamics (MD) simulations. Neutron scattering experiments may thus substantially support the further refinement of biomolecular force fields for MD simulations by supplying structural and dynamical information with high spatial and temporal resolution. In turn, MD simulations support the interpretation of neutron scattering data. The combination of both, neutron scattering experiments and MD simulations, yields an unprecedented insight into the molecular interactions governing the structure and dynamics of biological membranes. This review provides an overview of the molecular dynamics in biological membrane mimics as revealed by neutron scattering. It focuses on the latest findings such as the fundamental molecular mechanism of lateral lipid diffusion as well as the influence of additives and proteins on the short-time dynamics of lipids. Special emphasis is placed on the comparison of recent neutron scattering and MD simulation data with respect to molecular membrane dynamics on the pico- to nanosecond time scale. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. "Hot background" of the mobile inelastic neutron scattering system for soil carbon analysis.

    PubMed

    Kavetskiy, Aleksandr; Yakubova, Galina; Prior, Stephen A; Torbert, H Allen

    2016-01-01

    The problem of gamma spectrum peak identification arises when conducting soil carbon analysis using the inelastic neutron scattering (INS) system. Some spectral peaks could be associated with radioisotopes appearing due to neutron activation of both the measurement system and soil samples. The investigation of "hot background" gamma spectra from the construction materials, whole measurement system, and soil samples over time showed that activation of (28)Al isotope can contribute noticeable additions to the soil neutron stimulated gamma spectra.

  13. Monte-Carlo simulation of soil carbon measurements by inelastic neutron scattering

    USDA-ARS?s Scientific Manuscript database

    Measuring soil carbon is critical for assessing the potential impact of different land management practices on carbon sequestration. The inelastic neutron scattering (INS) of fast neutrons (with energy around 14 MeV) on carbon-12 nuclei produces gamma rays with energy of 4.43 MeV; this gamma flux ca...

  14. 16th National School on Neutron and X-ray Scattering

    ScienceCinema

    Chakoumakos, Bryan; Achilles, Cherie; Cybulskis, Viktor; Gilbert, Ian

    2016-07-12

    Students talk about their experience at the 16th National School on Neutron and X-ray Scattering, or NXS 2014. Jointly conducted by Oak Ridge and Argonne national laboratories, NXS immerses graduate students in national user facilities to learn in a hands-on environment how to use neutrons and X-rays in their research.

  15. 16th National School on Neutron and X-ray Scattering

    SciTech Connect

    Chakoumakos, Bryan; Achilles, Cherie; Cybulskis, Viktor; Gilbert, Ian

    2014-07-02

    Students talk about their experience at the 16th National School on Neutron and X-ray Scattering, or NXS 2014. Jointly conducted by Oak Ridge and Argonne national laboratories, NXS immerses graduate students in national user facilities to learn in a hands-on environment how to use neutrons and X-rays in their research.

  16. Mantid-Data analysis and visualization package for neutron scattering and μ SR experiments

    NASA Astrophysics Data System (ADS)

    Arnold, O.; Bilheux, J. C.; Borreguero, J. M.; Buts, A.; Campbell, S. I.; Chapon, L.; Doucet, M.; Draper, N.; Ferraz Leal, R.; Gigg, M. A.; Lynch, V. E.; Markvardsen, A.; Mikkelson, D. J.; Mikkelson, R. L.; Miller, R.; Palmen, K.; Parker, P.; Passos, G.; Perring, T. G.; Peterson, P. F.; Ren, S.; Reuter, M. A.; Savici, A. T.; Taylor, J. W.; Taylor, R. J.; Tolchenov, R.; Zhou, W.; Zikovsky, J.

    2014-11-01

    The Mantid framework is a software solution developed for the analysis and visualization of neutron scattering and muon spin measurements. The framework is jointly developed by software engineers and scientists at the ISIS Neutron and Muon Facility and the Oak Ridge National Laboratory. The objectives, functionality and novel design aspects of Mantid are described.

  17. The Manuel Lujan, Jr. Neutron Scattering Center LANSCE experiment reports 1989 run cycle

    SciTech Connect

    Hyer, D.K.; DiStravolo, M.A.

    1990-10-01

    This report contains a listing and description of experiments carried on at the LANSCE neutron scattering facility in the following areas: High Density Powder Diffraction; Neutron Powder Diffractometer, (NPD); Single Crystal Diffractometer, (SCD); Low-Q Diffractometer, (LQD); Surface Profile Analysis Reflectometer, (SPEAR); Filter Difference Spectrometer, (FDS); and Constant-Q Spectrometer.

  18. Hot background” of the mobile inelastic neutron scattering system for soil carbon analysis

    USDA-ARS?s Scientific Manuscript database

    The problem of gamma spectrum peaks identification arises when conducting soil carbon (and other elements) analysis using the mobile inelastic neutron scattering (MINS) system. Some gamma spectrum peaks could be associated with radioisotopes appearing due to neutron activation of both the MINS syste...

  19. Total Scattering and Pair Distribution Function Analysis in Modelling Disorder in PZN

    DOE PAGES

    Whitfield, Ross E.; Goossens, Darren J; Welberry, T. R.

    2016-01-01

    The ability of the pair distribution function (PDF) analysis of total scattering (TS) from a powder to determine the local ordering in ferroelectric PZN (PbZn1/3Nb2/3O3) has been explored by comparison with a model established using single-crystal diffuse scattering (SCDS). While X-ray PDF analysis is discussed, the focus is on neutron diffraction results because of the greater extent of the data and the sensitivity of the neutron to oxygen atoms, the behaviour of which is important in PZN. The PDF was shown to be sensitive to many effects not apparent in the average crystal structure, including variations in the B-site—O separationmore » distances and the fact that (110) Pb2+ displacements are most likely. A qualitative comparison between SCDS and the PDF shows that some features apparent in SCDS were not apparent in the PDF. These tended to pertain to short-range correlations in the structure, rather than to interatomic separations. For example, in SCDS the short-range alternation of the B-site cations was quite apparent in diffuse scattering at (½ ½ ½), whereas it was not apparent in the PDF.« less

  20. Total Scattering and Pair Distribution Function Analysis in Modelling Disorder in PZN

    SciTech Connect

    Whitfield, Ross E.; Goossens, Darren J; Welberry, T. R.

    2016-01-01

    The ability of the pair distribution function (PDF) analysis of total scattering (TS) from a powder to determine the local ordering in ferroelectric PZN (PbZn1/3Nb2/3O3) has been explored by comparison with a model established using single-crystal diffuse scattering (SCDS). While X-ray PDF analysis is discussed, the focus is on neutron diffraction results because of the greater extent of the data and the sensitivity of the neutron to oxygen atoms, the behaviour of which is important in PZN. The PDF was shown to be sensitive to many effects not apparent in the average crystal structure, including variations in the B-site—O separation distances and the fact that (110) Pb2+ displacements are most likely. A qualitative comparison between SCDS and the PDF shows that some features apparent in SCDS were not apparent in the PDF. These tended to pertain to short-range correlations in the structure, rather than to interatomic separations. For example, in SCDS the short-range alternation of the B-site cations was quite apparent in diffuse scattering at (½ ½ ½), whereas it was not apparent in the PDF.

  1. The FN method for anisotropic scattering in neutron transport theory: the critical slab problem.

    NASA Astrophysics Data System (ADS)

    Gülecyüz, M. C.; Tezcan, C.

    1996-08-01

    The FN method which has been applied to many physical problems for isotropic and anisotropic scattering in neutron transport theory is extended for problems for extremely anisotropic scattering. This method depends on the Placzek lemma and the use of the infinite medium Green's function. Here the Green's function for extremely anisotropic scattering which was expressed as a combination of the Green's functions for isotropic scattering is used to solve the critical slab problem. It is shown that the criticality condition is in agreement with the one obtained previously by reducing the transport equation for anisotropic scattering to isotropic scattering and solving using the FN method.

  2. The atomic structure of lead-free Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}-(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} by using neutron total scattering analysis

    SciTech Connect

    Jeong, I.-K.; Ahn, J. S.

    2012-12-10

    We conducted neutron total scattering measurements on lead-free Ba(Zr{sub 0.2}Ti{sub 0.8})O{sub 3}-0.5(Ba{sub 0.7}Ca{sub 0.3})TiO{sub 3} (BZT-0.5BCT) ceramic at 300 K and 150 K, and studied both long-range and local structures near the morphotropic phase boundary. Despite the long-range phase transition from tetragonal to rhombohedral structures, we found that local atomic structure of BZT-0.5BCT barely changes between 300 K and 150 K. To incorporate both long-range and local structures in a consistent way, we performed reverse Monte Carlo modeling. In BZT-0.5BCT, we found that the Ca substitution on Ba sites causes little impact on the local displacement of Ti ion but enhances octahedral tilting of ZrO{sub 6}, resulting in nonuniform lattice distortion.

  3. Fission, total and neutron capture cross section measurements at ORELA

    SciTech Connect

    Guber, K.H.; Spencer, R.R.; Leal, L.C.; Larson, D.C.; Dos Santos, G.; Harvey, J.A.; Hill, N.W.

    1998-08-01

    In support of the Nuclear Criticality Predictability Program established in response to the Defense Nuclear Facility Safety Board Recommendation 93-2, time-of-flight (TOF) measurements of the fission cross sections of {sup 233}U in the neutron energy range from 0.36 eV to several hundred keV have been initiated at the Oak Ridge Electron Linear Accelerator (ORELA). Also total and capture cross sections of Al, Cl, and K in the energy range from about 100 eV to several hundred keV have been measured or are under way. The goal is to derive accurate cross section representations for the materials involved in criticality calculations of fuel storage, transportation, etc., configurations. Additional high-resolution measurements of the total cross sections of {sup 233}U below a few keV neutron energy are being planned for 1998, as well as for the other involved material. Evaluated data files in ENDF-6 format will be processed into formats for use in criticality analysis and utilized in benchmark data testing. Finally the data will be submitted for inclusion in ENDF/B.

  4. Characterization of a Thermo Scientific D711 D-T neutron generator located in a low-scatter facility

    SciTech Connect

    Hayes, John W.; Finn, Erin; Greenwood, Larry; Wittman, Rick

    2014-03-01

    A dosimetry experiment used to measure the neutron flux and spectrum of a D-T neutron generator is presented. The D-T generator at Pacific Northwest National Laboratory is installed in the middle of a large room to minimize scatter of neutrons back to the sample. The efficacy of maintaining a pure fast neutron field for the sample is investigated. Twenty-one positions within 13 cm of the neutron source contained foils or wires of Fe, Ni, Al with additional Au, and In monitors at some locations. Spectral adjustment of the neutron flux at each position based on measured reaction rates and theoretical Monte Carlo calculations show that at least 99.1% of the spectrum lies above 110 keV for all measured positions, and neutrons above 14 MeV can account for as much as 91% at locations along the axis of the generator and close to the source. The 14 MeV component drops to 77% in radial positions far from the source. The largest total flux observed was 8.29E+08 n/cm2-s (±1.4%) in the center of the cooling cap, although additional experiments have shown this value could be as high as 1.20E+09 n/cm2-s.

  5. High Field Pulsed Magnets for Neutron Scattering at the Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Granroth, G. E.; Lee, J.; Fogh, E.; Christensen, N. B.; Toft-Petersen, R.; Nojiri, H.

    2015-03-01

    A High Field Pulsed Magnet (HFPM) setup, is in use at the Spallation Nuetron Source(SNS), Oak Ridge National Laboratory. With this device, we recently measured the high field magnetic spin structure of LiNiPO4. The results of this study will be highlighted as an example of possible measurements that can be performed with this device. To further extend the HFPM capabilities at SNS, we have learned to design and wind these coils in house. This contribution will summarize the magnet coil design optimization procedure. Specifically by varying the geometry of the multi-layer coil, we arrive at a design that balances the maximum field strength, neutron scattering angle, and the field homogeneity for a specific set of parameters. We will show that a 6.3kJ capacitor bank, can provide a magnetic field as high as 30T for a maximum scattering angle around 40° with homogeneity of +/- 4 % in a 2mm diameter spherical volume. We will also compare the calculations to measurements from a recently wound test coil. This work was supported in part by the Lab Directors' Research and Development Fund of ORNL.

  6. Investigation of the tripoli porous structure by small-angle neutron scattering

    SciTech Connect

    Avdeev, M. V.; Blagoveshchenskii, N. M.; Garamus, V. M.; Novikov, A. G. Puchkov, A. V.

    2011-12-15

    The characteristics of the tripoli porous structure have been investigated by small-angle neutron scattering (SANS). Tripoli is a finely porous sedimentary rock formed by small spherical opal particles. Its main component is aqueous silica SiO{sub 2} {center_dot} nH{sub 2}O (80-90%). Tripoli is widely used in practice as a working medium for sorption filters and in some other commercial and construction technologies. The shape of the experimental SANS curves indicates the presence of small and large pores in tripoli. The small-pore size was estimated to be {approx}100 Angstrom-Sign . The size of large pores turned out to be beyond the range of neutron wave vector transfers Q that are available for the instrument used; however, their size was indirectly estimated to be {approx}(2000-2500) Angstrom-Sign . The pores of both groups behave as surfacetype fractal scatterers with the fractal dimension D {approx} 2.2-2.6. The densities of pores of these two groups differ by approximately three orders of magnitude ({approx}10{sup 16} and {approx}10{sup 13} cm{sup -3} for small and large pores, respectively); the fraction of large pores amounts to 70-80% of the total pore volume. The found pore characteristics (their densities, sizes, and relative volumes) are in satisfactory agreement (when a comparison is possible) with the absorption data.

  7. Insight into asphaltene nanoaggregate structure inferred by small angle neutron and X-ray scattering.

    PubMed

    Eyssautier, Joëlle; Levitz, Pierre; Espinat, Didier; Jestin, Jacques; Gummel, Jérémie; Grillo, Isabelle; Barré, Loïc

    2011-06-02

    Complementary neutron and X-ray small angle scattering results give prominent information on the asphaltene nanostructure. Precise SANS and SAXS measurements on a large q-scale were performed on the same dilute asphaltene-toluene solution, and absolute intensity scaling was carried out. Direct comparison of neutron and X-ray spectra enables description of a fractal organization made from the aggregation of small entities of 16 kDa, exhibiting an internal fine structure. Neutron contrast variation experiments enhance the description of this nanoaggregate in terms of core-shell disk organization, giving insight into core and shell dimensions and chemical compositions. The nanoaggregates are best described by a disk of total radius 32 Å with 30% polydispersity and a height of 6.7 Å. Composition and density calculations show that the core is a dense and aromatic structure, contrary to the shell, which is highly aliphatic. These results show a good agreement with the general view of the Yen model (Yen, T. F.; et al. Anal. Chem.1961, 33, 1587-1594) and as for the modified Yen model (Mullins, O. C. Energy Fuels2010, 24, 2179-2207), provide characteristic dimensions of the asphaltene nanoaggregate in good solvent.

  8. Total electron scattering cross sections. I - He, Ne, Ar, Xe

    NASA Technical Reports Server (NTRS)

    Nickel, J. C.; Imre, K.; Register, D. F.; Trajmar, S.

    1985-01-01

    The apparatus and experimental procedures used to obtain total electron scattering cross sections are described, and results are presented for He, Ne, Ar and Xe in the 4-300 eV incident energy range, together with statistical errors. The results are generally found to be in good agreement with previous data except at low impact energies. Serious discrepancies remain in Xe below 20 eV impact energy.

  9. Characterisation of amorphous and nanocrystalline molecular materials by total scattering

    SciTech Connect

    Billinge, Simon J.L.; Dykhne, Timur; Juhás, Pavol; Boin, Emil; Taylor, Ryan; Florence, Alastair J.; Shankland, Kenneth

    2010-09-17

    The use of high-energy X-ray total scattering coupled with pair distribution function analysis produces unique structural fingerprints from amorphous and nanostructured phases of the pharmaceuticals carbamazepine and indomethacin. The advantages of such facility-based experiments over laboratory-based ones are discussed and the technique is illustrated with the characterisation of a melt-quenched sample of carbamazepine as a nanocrystalline (4.5 nm domain diameter) version of form III.

  10. Pulsed Neutron Scattering Studies of Strongly Fluctuating solids, Final Report

    SciTech Connect

    Collin Broholm

    2006-06-22

    The conventional description of a solid is based on a static atomic structure with small amplitude so-called harmonic fluctuations about it. This is a final technical report for a project that has explored materials where fluctuations are sufficiently strong to severely challenge this approach and lead to unexpected and potentially useful materials properties. Fluctuations are enhanced when a large number of configurations share the same energy. We used pulsed spallation source neutron scattering to obtain detailed microscopic information about structure and fluctuations in such materials. The results enhance our understanding of strongly fluctuating solids and their potential for technical applications. Because new materials require new experimental techniques, the project has also developed new techniques for probing strongly fluctuating solids. Examples of material that were studied are ZrW2O8 with large amplitude molecular motion that leads to negative thermal expansion, NiGa2S4 where competing interactions lead to an anomalous short range ordered magnet, Pr1- xBixRu2O7 where a partially filled electron shell (Pr) in a weakly disordered environment produces anomalous metallic properties, and TbMnO3 where competing interactions lead to a magneto-electric phase. The experiments on TbMnO3 exemplify the relationship between research funded by this project and future applications. Magneto-electric materials may produce a magnetic field when an electric field is applied or vise versa. Our experiments have clarified the reason why electric and magnetic polarization is coupled in TbMnO3. While this knowledge does not render TbMnO3 useful for applications it will focus the search for a practical room temperature magneto-electric for applications.

  11. Dynamics of water in prussian blue analogues: Neutron scattering study

    SciTech Connect

    Sharma, V. K.; Mitra, S.; Thakur, N.; Yusuf, S. M.; Mukhopadhyay, R.; Juranyi, Fanni

    2014-07-21

    Dynamics of crystal water in Prussian blue (PB), Fe(III){sub 4}[Fe(II)(CN){sub 6}]{sub 3}.14H{sub 2}O and its analogue Prussian green (PG), ferriferricynaide, Fe(III){sub 4}[Fe(III)(CN){sub 6}]{sub 4}.16H{sub 2}O have been investigated using Quasielastic Neutron Scattering (QENS) technique. PB and its analogue compounds are important materials for their various interesting multifunctional properties. It is known that crystal water plays a crucial role towards the multifunctional properties of Prussian blue analogue compounds. Three structurally distinguishable water molecules: (i) coordinated water molecules at empty nitrogen sites, (ii) non-coordinated water molecules in the spherical cavities, and (iii) at interstitial sites exist in PB. Here spherical cavities are created due to the vacant sites of Fe(CN){sub 6} units. However, PG does not have any such vacant N or Fe(CN){sub 6} units, and only one kind of water molecules, exists only at interstitial sites. QENS experiments have been carried out on both the compounds in the temperature range of 260–360 K to elucidate the dynamical behavior of different kinds of water molecules. Dynamics is found to be much more pronounced in case of PB, compared to PG. A detailed data analysis showed that localized translational diffusion model could describe the observed data for both PB and PG systems. The average diffusion coefficient is found to be much larger in the PB than PG. The obtained domain of dynamics is found to be consistent with the geometry of the structure of the two systems. Combining the data of the two systems, a quantitative estimate of the dynamics, corresponding to the water molecules at different locations is made.

  12. Total cross section of electron scattering by fluorocarbon molecules

    NASA Astrophysics Data System (ADS)

    Yamada, T.; Ushiroda, S.; Kondo, Y.

    2008-12-01

    A compact linear electron transmission apparatus was used for the measurement of the total electron scattering cross section at 4-500 eV. Total cross sections of chlorofluorocarbon (CCl2F2), hydrochlorofluorocarbon (CHClF2), perfluoropropane (C3F8), perfluoro-n-pentane (C5F12), perfluoro-n-hexane (C6F14) and perfluoro-n-octane (C8F18) were obtained experimentally and compared with the values obtained from a theoretical calculation and semi-empirical model calculation.

  13. Elastic and inelastic neutron scattering cross sections for fission reactor applications

    NASA Astrophysics Data System (ADS)

    Hicks, S. F.; Chakraborty, A.; Combs, B.; Crider, B. P.; Downes, L.; Girgis, J.; Kersting, L. J.; Kumar, A.; Lueck, C. J.; McDonough, P. J.; McEllistrem, M. T.; Peters, E. E.; Prados-Estevz, F. M.; Schniederjan, J.; Sidwell, L.; Sigillito, A. J.; Vanhoy, J. R.; Watts, D.; Yates, S. W.

    2013-04-01

    Nuclear data important for the design and development of the next generation of light-water reactors and future fast reactors include neutron elastic and inelastic scattering cross sections on important structural materials, such as Fe, and on coolant materials, such as Na. These reaction probabilities are needed since neutron reactions impact fuel performance during irradiations and the overall efficiency of reactors. While neutron scattering cross sections from these materials are available for certain incident neutron energies, the fast neutron region, particularly above 2 MeV, has large gaps for which no measurements exist, or the existing uncertainties are large. Measurements have been made at the University of Kentucky Accelerator Laboratory to measure neutron scattering cross sections on both Fe and Na in the region where these gaps occur and to reduce the uncertainties on scattering from the ground state and first excited state of these nuclei. Results from measurements on Fe at incident neutron energies between 2 and 4 MeV will be presented and comparisons will be made to model calculations available from data evaluators.

  14. Diffraction pattern from thermal neutron incoherent elastic scattering and the holographic reconstruction of the coherent scattering length distribution

    SciTech Connect

    Sur, B.; Anghel, V.N.P.; Rogge, R.B.; Katsaras, J.

    2005-01-01

    The diffraction of spherical waves (S waves) interacting with a periodic scattering length distribution produces characteristic intensity patterns known as Kossel and Kikuchi lines (collectively called K lines). The K-line signal can be inverted to give the three-dimensional structure of the coherent scattering length distribution surrounding the source of S waves - a process known as 'Gabor holography' or, simply, 'holography'. This paper outlines a kinematical formulation for the diffraction pattern of monochromatic plane waves scattering from a mixed incoherent and coherent S-wave scattering length distribution. The formulation demonstrates that the diffraction pattern of plane waves incident on a sample with a uniformly random distribution of incoherent scatterers is the same as that from a sample with a single incoherent scatterer per unit cell. In practice, one can therefore reconstruct the holographic data from samples with numerous incoherent S-wave scatterers per unit cell. Thus atomic resolution thermal neutron holography is possible for materials naturally rich in incoherent thermal neutron scatterers, such as hydrogen (e.g., biological and polymeric materials). Additionally, holographic inversions from single-wavelength data have suffered from the so-called conjugate or twin-image problem. The formulation presented for holographic inversion - different from those used previously [e.g., T. Gog et al., Phys. Rev. Lett. 76, 3132 (1996)] - eliminates the twin-image problem for single-wavelength data.

  15. Results of total cross section measurements for 197Au in the neutron energy region from 4 to 108 keV at GELINA

    NASA Astrophysics Data System (ADS)

    Sirakov, I.; Becker, B.; Capote, R.; Dupont, E.; Kopecky, S.; Massimi, C.; Schillebeeckx, P.

    2013-11-01

    Transmission measurements have been performed to determine the total cross section for neutron-induced reactions with 197Au in the energy region from 4keV to 108keV. The experiments were carried out at a 50m measurement station of the time-of-flight facility GELINA using a 6Li glass scintillator. The average total cross section as a function of neutron energy was derived after correcting the observed average transmission for cross section fluctuations due to resonance structures. The results have been compared with literature data and with the total cross section resulting from a dispersive coupled-channel optical model potential. The neutron strength function for s -wave neutrons and an orbital-independent scattering radius, together with their covariance matrix, have been derived in the neutron energy region between 4keV and 108keV through a parameterization of the total cross section based on a nuclear reaction theory.

  16. Neutron-driven collectivity in light tin isotopes: Proton inelastic scattering from 104Sn

    NASA Astrophysics Data System (ADS)

    Corsi, A.; Boissinot, S.; Obertelli, A.; Doornenbal, P.; Dupuis, M.; Lechaftois, F.; Matsushita, M.; Péru, S.; Takeuchi, S.; Wang, H.; Aoi, N.; Baba, H.; Bednarczyk, P.; Ciemala, M.; Gillibert, A.; Isobe, T.; Jungclaus, A.; Lapoux, V.; Lee, J.; Martini, M.; Matsui, K.; Motobayashi, T.; Nishimura, D.; Ota, S.; Pollacco, E.; Sakurai, H.; Santamaria, C.; Shiga, Y.; Sohler, D.; Steppenbeck, D.; Taniuchi, R.

    2015-04-01

    Inelastic scattering cross sections to individual bound excited states of 104Sn were measured at 150 MeV/u beam energy and analyzed to evaluate the contribution of neutron and proton collectivity. State-of-the-art Quasi-Particle Random Phase Approximation (QRPA) with the D1M Gogny interaction reproduces the experimental proton collectivity and our inelastic scattering cross sections once used as input for a reaction calculation together with the Jeukenne-Lejeune-Mahaux (JLM) potentials. Experimental inelastic scattering cross section decreases by 40(24)% from 112Sn to 104Sn. The present work shows that (i) proton and neutron collectivities are proportional over a large range of tin isotopes (including 104Sn), as is typical for isoscalar excitations, and (ii) the neutron collectivity dominates. It suggests that the plateau in the mass range A = 106- 112 displayed by E2 transition probabilities is driven by neutron collectivity.

  17. Characterization and Modeling of Off-Specular Neutron Scattering for Analysis of Two Dimensional Ordered Structures

    NASA Astrophysics Data System (ADS)

    Metting, Christopher; Maranville, Brian; Kienzle, Paul; Briber, Robert; Dura, Joseph; Majkrzak, Chuck

    2011-03-01

    The University of Maryland along with NIST Center for Neutron Research (NCNR) and the NSF funded DANSE project are currently developing off-specular neutron reflectometry modeling software for fitting scattering data from multilayer samples. The software includes a robust sample representation scheme for easy development of various models. Theory functions are being calculated using a variety of approximations. The suite of approximations allows for the evaluation of each calculation's usefulness in representing the scattering data. In this presentation we describe corrections made to a purely Born approximation that capture dynamical scattering and resolution effects seen in measured data. We then show modeled data taken on the Advanced Neutron Diffractometer/Reflectometer (AND/R) at the NIST Center for Neutron Research (NCNR) from a sample of gold pillars using a substrate modified Born approximation, and compare it to a model which uses a purely Born approximation.

  18. Neutron scattering studies of BiFeO(3) multiferroics: a review for microscopists.

    PubMed

    Sosnowska, I M

    2009-11-01

    Application of the neutron scattering technique in the study of crystal and magnetic properties of multiferroic BiFeO(3) is presented. The crucial role of the neutron scattering technique, complementary to X-ray diffraction method and transmission electron microscopy, is shown. Especially the ultra high-resolution time-of-flight (TOF) neutron diffraction technique used by Sosnowska et al. to detect the magnetic cycloid ordering and its role in studies of physical properties of BiFeO(3) and its alloys are reviewed. The first inelastic neutron scattering patterns of magnetic excitations in BiFeO(3) are also presented. Applications of different microscopy techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), field emission TEM and SEM (FESEM and FETEM), magnetic force microscope (MFM) and polarization force microscopy (PFM) bring insight on the fundamental problem of ferroelectricity and confirm the potential of BiFeO(3) multiferroic material for nanoscale devices.

  19. TRANSP modelling of total and local neutron emission on MAST

    NASA Astrophysics Data System (ADS)

    Klimek, I.; Cecconello, M.; Gorelenkova, M.; Keeling, D.; Meakins, A.; Jones, O.; Akers, R.; Lupelli, I.; Turnyanskiy, M.; Ericsson, G.; the MAST Team

    2015-02-01

    The results of TRANSP simulations of neutron count rate profiles measured by a collimated neutron flux monitor-neutron camera (NC)—for different plasma scenarios on MAST are reported. In addition, the effect of various plasma parameters on neutron emission is studied by means of TRANSP simulation. The fast ion redistribution and losses due to fishbone modes, which belong to a wider category of energetic particle modes, are observed by the NC and modelled in TRANSP.

  20. Neutron scattering studies in the actinide region. Progress report, August 1, 1991--July 31, 1994

    SciTech Connect

    Kegel, G.H.R.; Egan, J.J.

    1994-09-01

    During the period August 1, 1991 to July 31, 1994 the authors report progress on the following: (a) prompt fission neutron energy spectra for {sup 235}U and {sup 239}Pu; (b) two-parameter measurement of nuclear lifetimes; (c) `black` neutron detector; (d) data reduction techniques for neutron scattering experiments; (e) elastic and inelastic neutron scattering studies in {sup 197}Au; (f) elastic and inelastic neutron scattering studies in {sup 239}Pu; (g) neutron induced defects in silicon dioxide MOS structures; (h) response of a {sup 235}U fission chamber near reaction thresholds; (i) efficiency calibration of a liquid scintillation detector using the WNR facility at LAMPF; (j) prompt fission neutron energy spectrum measurements below the incident neutron energy; (k) multi-parameter data acquisition system; (l) accelerator improvements; (m) non-DOE supported research. Eight Ph.D. dissertations and two M.S. theses were completed during the report period. Publications consisted of 6 journal articles, 10 conference proceedings, and 19 abstracts of presentations at scientific meetings. One invited talk was given.

  1. High-temperature high pressure cell for neutron-scattering studies

    NASA Astrophysics Data System (ADS)

    Chen, Qianli; Holdsworth, Stuart; Embs, Jan; Pomjakushin, Vladimir; Frick, Bernhard; Braun, Artur

    2012-12-01

    In this study, a simple high-temperature high pressure cell concept has been developed to enable neutron diffraction and quasi-elastic and inelastic neutron-scattering studies to be conducted on large-volume powder samples of ceramic proton conductors at pressures of up to 1 GPa and at temperatures of up to 770 K. Details of the cell are provided, along with the first experimental neutron diffractograms (at 0.62 GPa and 300 K), quasi-elastic neutron-scattering spectra (at 0.58 GPa and 770 K) and inelastic neutron spectra (at 0.75 GPa and 530 K) determined for samples of BaCe0.8Y0.2O3.

  2. A Clean Measurement of the Neutron Skin of 208Pb Through Parity Violating Electron Scattering

    SciTech Connect

    Riad Suleiman

    2003-07-01

    The difference between the neutron radius Rn of a heavy nucleus and the proton radius Rp is believed to be on the order of several percent. This qualitative feature of nuclei, which is essentially a neutron skin, has proven to be elusive to pin down experimentally in a rigorous fashion. A new Jefferson Lab experiment will measure the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 208Pb. Since the Z-boson couples mainly to neutrons, this asymmetry provides a measure of the size of Rn that can be interpreted with as much confidence as the traditional electron scattering data. The projected experimental precision corresponds to a 1% determination of Rn, which will have a big impact on nuclear theory and its application to neutron rich matter such as neutron stars.

  3. Prospects for using coherent elastic neutrino-nucleus scattering to measure the nuclear neutron form factor

    NASA Astrophysics Data System (ADS)

    Patton, Kelly; McLaughlin, Gail; Scholberg, Kate; Engel, Jon; Schunck, Nicolas

    2017-01-01

    Coherent elastic neutrino-nucleus scattering is a potential probe of nuclear neutron form factors. We show that the neutron root-mean-square (RMS) radius can be measured with tonne-scale detectors of argon, germanium, or xenon. In addition, the fourth moment of the neutron distribution can be studied experimentally using this method. The impacts of both detector size and detector shape uncertainty on such a measurement were considered. The important limiting factor was found to be the detector shape uncertainty. In order to measure the neutron RMS radius to 5%, comparable to current experimental uncertainties, the detector shape uncertainty needs to be known to 1% or better.

  4. Measurement of the Neutron Radius of 208Pb Through Parity-Violation in Electron Scattering

    DOE PAGES

    Abrahamyan, Sergey; Albataineh, Hisham; Aniol, Konrad; ...

    2012-03-15

    We report the first measurement of the parity-violating asymmetry APV in the elastic scattering of polarized electrons from 208Pb. APV is sensitive to the radius of the neutron distribution (Rn). The result APV = 0.656 ± 0.060 (stat) ± 0.013 (syst) corresponds to a difference between the radii of the neutron and proton distributions Rn-Rp = 0.33-0.18+0.16 fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.

  5. Neutron-scattering experiment on solid 3He

    NASA Astrophysics Data System (ADS)

    Mat'aš, S.; Bat'ko, I.; Boyko, V.; Schöttl, S.; Siemensmeyer, K.; Raasch, S.; Radulov, I.; Adams, E. D.; Scherline, T. E.

    The central aim of our work is the characterisation of magnetic and crystallographic properties of solid 3He on a microscopic scale. This can only be achieved using neutron-diffraction techniques. The potential of neutron methods in magnetism and their application to nuclear magnetism is well known. They were very successful in the recent investigation of spontaneous nuclear order in copper and silver. The high neutron absorption cross section makes the application of neutron diffraction in solid 3He very difficult - but a careful feasibility study of diffraction experiments shows that new results of fundamental importance in the field of magnetism may be gained.

  6. Neutron scattering studies of the dynamics of biopolymer-water systems using pulsed-source spectrometers

    SciTech Connect

    Middendorf, H.D.; Miller, A.

    1994-12-31

    Energy-resolving neutron scattering techniques provide spatiotemporal data suitable for testing and refining analytical models or computer simulations of a variety of dynamical processes in biomolecular systems. This paper reviews experimental work on hydrated biopolymers at ISIS, the UK Pulsed Neutron Facility. Following an outline of basic concepts and a summary of the new instrumental capabilities, the progress made is illustrated by results from recent experiments in two areas: quasi- elastic scattering from highly hydrated polysaccharide gels (agarose and hyaluronate), and inelastic scattering from vibrational modes of slightly hydrated collagen fibers.

  7. Investigation of condensed matter by means of elastic thermal-neutron scattering

    SciTech Connect

    Abov, Yu. G.; Dzheparov, F. S.; Elyutin, N. O.; Lvov, D. V. Tyulyusov, A. N.

    2016-07-15

    The application of elastic thermal-neutron scattering in investigations of condensed matter that were performed at the Institute for Theoretical and Experimental Physics is described. An account of diffraction studies with weakly absorbing crystals, including studies of the anomalous-absorption effect and coherent effects in diffuse scattering, is given. Particular attention is given to exposing the method of multiple small-angle neutron scattering (MSANS). It is shown how information about matter inhomogeneities can be obtained by this method on the basis of Molière’s theory. Prospects of the development of this method are outlined, and MSANS theory is formulated for a high concentration of matter inhomogeneities.

  8. Thermal neutron scattering data for 7LiF and BeF2

    NASA Astrophysics Data System (ADS)

    Wang, Jia; Song, Hongzhou; Hu, Zehua; Ye, Tao; Sun, Weili

    2017-09-01

    Based on the coherent elastic, incoherent elastic, coherent inelastic and incoherent inelastic scattering processes, a code named SIRIUS is developed to produce thermal neutron scattering data for crystals in ENDF-6 format. The phonon band structures and projected phonon densities of states of 7LiF and BeF2 crystals were calculated by Hellman-Feynman Theorem combined with a lattice dynamics direct method. Finally the thermal neutron scattering data for 7LiF and BeF2 crystals are given.

  9. Scattering correction algorithm for neutron radiography and tomography tested at facilities with different beam characteristics

    NASA Astrophysics Data System (ADS)

    Hassanein, René; de Beer, Frikkie; Kardjilov, Nikolay; Lehmann, Eberhard

    2006-11-01

    A precise quantitative analysis with the neutron radiography technique of materials with a high-neutron scattering cross section, imaged at small distances from the detector, is impossible if the scattering contribution from the investigated material onto the detector is not eliminated in the right way. Samples with a high-neutron scattering cross section, e.g. hydrogenous materials such as water, cause a significant scattering component in their radiographs. Background scattering, spectral effects and detector characteristics are identified as additional causes for disturbances. A scattering correction algorithm based on Monte Carlo simulations has been developed and implemented to take these effects into account. The corrected radiographs can be used for a subsequent tomographic reconstruction. From the results one can obtain quantitative information, in order to detect e.g. inhomogeneity patterns within materials, or to measure differences of the mass thickness in these materials. Within an IAEA-CRP collaboration the algorithms have been tested for applicability on results obtained at the South African SANRAD facility at Necsa, the Swiss NEUTRA facilities at PSI as well as the German CONRAD facility at HMI, all with different initial neutron spectra. Results of a set of dedicated neutron radiography experiments are being reported.

  10. Probing neutron-skin thickness with total reaction cross sections

    NASA Astrophysics Data System (ADS)

    Horiuchi, W.; Suzuki, Y.; Inakura, T.

    2014-01-01

    We analyze total reaction cross sections, σR, to explore their sensitivity to the neutron-skin thickness of nuclei. We cover 91 nuclei of O, Ne, Mg, Si, S, Ca, and Ni isotopes. The cross sections are calculated in the Glauber theory using the density distributions obtained with the Skyrme-Hartree-Fock method in three-dimensional coordinate space. Defining a reaction radius, aR=√σR/π , to characterize the nuclear size and target (proton or 12C) dependence, we find an empirical formula for expressing aR with the point matter radius and the skin thickness, and assess two practical ways of determining the skin thickness from proton-nucleus σR values measured at different energies or from σR values measured for different targets.

  11. Total X-Ray Scattering of Spider Dragline Silk

    NASA Astrophysics Data System (ADS)

    Benmore, C. J.; Izdebski, T.; Yarger, J. L.

    2012-04-01

    Total x-ray scattering measurements of spider dragline silk fibers from Nephila clavipes, Argiope aurantia, and Latrodectus hesperus all yield similar structure factors, with only small variations between the different species. Wide-angle x-ray scattering from fibers orientated perpendicular to the beam shows a high degree of anisotropy, and differential pair distribution functions obtained by integrating over wedges of the equatorial and meridian planes indicate that, on average, the majority (95%) of the atom-atom correlations do not extend beyond 1 nm. Futhermore, the atom-atom correlations between 1 and 3 nm are not associated with the most intense diffraction peaks at Q=1-2Å-1. Disordered molecular orientations along the fiber axis are consistent with proteins in similar structural arrangements to those in the equatorial plane, which may be associated with the silk’s greater flexibility in this direction.

  12. Photon scattering from /sup 90/Zr below neutron emission threshold

    SciTech Connect

    Alarcon, R.; Laszewski, R.M.; Nathan, A.M.; Hoblit, S.D.

    1987-09-01

    Cross sections for elastic and inelastic scattering of monochromatic photons from /sup 90/Zr have been measured for excitations between 8.1 and 10.5 MeV. The observed inelastic cross sections sigma/sub el//sub el//sub i/ correspond to transitions to the 02 , 21 , 22 , and 23 states. A simple theoretical description using the Brink-Axel hypothesis and estimates of the level density and of the total photon interaction cross section sigma/sub el//sub T/ gives predictions for the individual cross sections that are in very good agreement with data. The E1 strength corresponding to the inferred sigma/sub el//sub T/ amounts to about B(E1up-arrow)--0.5 eS fmS for the energy range under consideration.

  13. Quantification of Organic Porosity and Water Accessibility in Marcellus Shale Using Neutron Scattering

    SciTech Connect

    Gu, Xin; Mildner, David F. R.; Cole, David R.; Rother, Gernot; Slingerland, Rudy; Brantley, Susan L.

    2016-04-28

    Pores within organic matter (OM) are a significant contributor to the total pore system in gas shales. These pores contribute most of the storage capacity in gas shales. Here we present a novel approach to characterize the OM pore structure (including the porosity, specific surface area, pore size distribution, and water accessibility) in Marcellus shale. By using ultrasmall and small-angle neutron scattering, and by exploiting the contrast matching of the shale matrix with suitable mixtures of deuterated and protonated water, both total and water-accessible porosity were measured on centimeter-sized samples from two boreholes from the nanometer to micrometer scale with good statistical coverage. Samples were also measured after combustion at 450 °C. Analysis of scattering data from these procedures allowed quantification of OM porosity and water accessibility. OM hosts 24–47% of the total porosity for both organic-rich and -poor samples. This porosity occupies as much as 29% of the OM volume. In contrast to the current paradigm in the literature that OM porosity is organophilic and therefore not likely to contain water, our results demonstrate that OM pores with widths >20 nm exhibit the characteristics of water accessibility. In conclusion, our approach reveals the complex structure and wetting behavior of the OM porosity at scales that are hard to interrogate using other techniques.

  14. Quantification of Organic Porosity and Water Accessibility in Marcellus Shale Using Neutron Scattering

    DOE PAGES

    Gu, Xin; Mildner, David F. R.; Cole, David R.; ...

    2016-04-28

    Pores within organic matter (OM) are a significant contributor to the total pore system in gas shales. These pores contribute most of the storage capacity in gas shales. Here we present a novel approach to characterize the OM pore structure (including the porosity, specific surface area, pore size distribution, and water accessibility) in Marcellus shale. By using ultrasmall and small-angle neutron scattering, and by exploiting the contrast matching of the shale matrix with suitable mixtures of deuterated and protonated water, both total and water-accessible porosity were measured on centimeter-sized samples from two boreholes from the nanometer to micrometer scale withmore » good statistical coverage. Samples were also measured after combustion at 450 °C. Analysis of scattering data from these procedures allowed quantification of OM porosity and water accessibility. OM hosts 24–47% of the total porosity for both organic-rich and -poor samples. This porosity occupies as much as 29% of the OM volume. In contrast to the current paradigm in the literature that OM porosity is organophilic and therefore not likely to contain water, our results demonstrate that OM pores with widths >20 nm exhibit the characteristics of water accessibility. In conclusion, our approach reveals the complex structure and wetting behavior of the OM porosity at scales that are hard to interrogate using other techniques.« less

  15. Quantification of Organic Porosity and Water Accessibility in Marcellus Shale Using Neutron Scattering

    SciTech Connect

    Gu, Xin; Mildner, David F. R.; Cole, David R.; Rother, Gernot; Slingerland, Rudy; Brantley, Susan L.

    2016-04-28

    Pores within organic matter (OM) are a significant contributor to the total pore system in gas shales. These pores contribute most of the storage capacity in gas shales. Here we present a novel approach to characterize the OM pore structure (including the porosity, specific surface area, pore size distribution, and water accessibility) in Marcellus shale. By using ultrasmall and small-angle neutron scattering, and by exploiting the contrast matching of the shale matrix with suitable mixtures of deuterated and protonated water, both total and water-accessible porosity were measured on centimeter-sized samples from two boreholes from the nanometer to micrometer scale with good statistical coverage. Samples were also measured after combustion at 450 °C. Analysis of scattering data from these procedures allowed quantification of OM porosity and water accessibility. OM hosts 24–47% of the total porosity for both organic-rich and -poor samples. This porosity occupies as much as 29% of the OM volume. In contrast to the current paradigm in the literature that OM porosity is organophilic and therefore not likely to contain water, our results demonstrate that OM pores with widths >20 nm exhibit the characteristics of water accessibility. In conclusion, our approach reveals the complex structure and wetting behavior of the OM porosity at scales that are hard to interrogate using other techniques.

  16. Small angle neutron scattering study of fatigue induced grain boundary cavities

    SciTech Connect

    Page, R.; Roth, M.; Weertman, J.R.

    1982-07-01

    Small angle neutron scattering (SANS) has been used to study grain boundary cavitation in high purity copper fatigued at elevated temperatures. SANS is an extremely sensitive method for observing cavities. Void volume fractions of less than 10/sup -6/ can be detected. Analysis of scattering data yields values for the total void volume per unit volume and the total number of voids in a fatigued sample. The size distribution of the voids also can be calculated. From a series of specimens, each fatigued under identical conditions but for varying lengths of time, it is possible to obtain the void nucleation rate and the rate of growth of the total void volume and of the individual voids. Extrapolation of curves of void volume fraction vs time of fatigue to zero time shows that cavitation begins upon commencement of fatiguing without any measurable incubation time. Void nucleation is continuous throughout fatigue Calculated values of the individual void growth rate agree very well, as regards time dependence, temperature dependence, and even absolute value, with growth rates derived from a theory of fatigueinduced cavitation based on transient effects in vacancy diffusion.

  17. Calculation of the total and total ionization cross sections for positron scattering on atomic hydrogen

    SciTech Connect

    Bray, I. ); Stelbovics, A.T. )

    1994-04-01

    The total and total ionization cross sections for positron scattering on atomic hydrogen are calculated by applying the convergent-close-coupling method to the model where positronium-formation channels are omitted. This model accurately describes the physics of the scattering whenever the positronium formation cross section is negligible, in particular, above 100 eV for this system. The total ionization cross section results in this energy region are in excellent agreement with the recent measurements of Jones [ital et] [ital al]. [J. Phys. B 26, L483 (1993)], and so lie below the earlier measurements of Spicher [Phys. Rev. Lett. 64, 1019 (1990)], and the recent calculations of Acacia [ital et] [ital al]. [Phys. Rev. Lett. (to be published)]. The total cross section is in very good agreement with the recent measurements of Zhou [ital et] [ital al]. (unpublished) down to 30 eV.

  18. Development of Grazing Incidence Optics for Neutron Imaging and Scattering

    NASA Technical Reports Server (NTRS)

    Gubarev, M. V.; Khaykovich, B.; Liu, D.; Ramsey, B. D.; Zavlin, V. E.; Kilaru, K.; Romaine, S.; Rosati, R. E.; Bruni, R.; Moncton, D. E.

    2012-01-01

    Because of their wave nature, thermal and cold neutrons can be reflected from smooth surfaces at grazing incidence angles, be reflected by multilayer coatings or be refracted at boundaries of different materials. The optical properties of materials are characterized by their refractive indices which are slightly less than unity for most elements and their isotopes in the case of cold and thermal neutrons as well as for x-rays. The motivation for the optics use for neutrons as well as for x-rays is to increase the signal rate and, by virtue of the optic's angular resolution, to improve the signal-to-noise level by reducing the background so the efficiency of the existing neutron sources use can be significantly enhanced. Both refractive and reflective optical techniques developed for x-ray applications can be applied to focus neutron beams. Typically neutron sources have lower brilliance compared to conventional x-ray sources so in order to increase the beam throughput the neutron optics has to be capable of capturing large solid angles. Because of this, the replicated optics techniques developed for x-ray astronomy applications would be a perfect match for neutron applications, so the electroformed nickel optics under development at the Marshall Space Flight Center (MSFC) can be applied to focus neutron beams. In this technique, nickel mirror shells are electroformed onto a figured and superpolished nickel-plated aluminum cylindrical mandrel from which they are later released by differential thermal contraction. Cylindrical mirrors with different diameters, but the same focal length, can be nested together to increase the system throughput. The throughput can be increased further with the use of the multilayer coatings deposited on the reflectivr surface of the mirror shells. While the electroformed nickel replication technique needs to be adopted for neutron focusing, the technology to coat the inside of cylindrical mirrors with neutron multilayers has to be

  19. Cavitation on deterministically nanostructured surfaces in contact with an aqueous phase: a small-angle neutron scattering study.

    PubMed

    Melnichenko, Yuri B; Lavrik, N V; Popov, E; Bahadur, J; He, L; Kravchenko, I I; Smith, G; Pipich, V; Szekely, N K

    2014-08-26

    The structure of deterministically nanopatterned surfaces created using a combination of electron beam lithography and reactive ion etching was evaluated using small-angle neutron scattering (SANS). Samples exhibit 2D neutron scattering patterns that confirm the presence of ordered nanoscale cavities consistent with the targeted morphologies as well as with SEM data analysis. Comparison of SANS intensities obtained from samples in air and in contact with an aqueous phase (pure deuterium oxide, D2O, or a contrast matched mixture of D2O + H2O) reveals formation of stable gaseous nanobubbles trapped inside the cavities. The relative volume of nanobubbles depends strongly on the hydrophobicity of the cavity walls. In the case of hydrophobic surfaces, nanobubbles occupy up to 87% of the total cavity volume. The results demonstrate the high degree of sensitivity of SANS measurements for detecting and characterizing nano- and mesoscale bubbles with the volume fraction as low as ∼10(-6).

  20. Elastic Scattering Spectroscopy (ESS): an Instrument-Concept for Dynamics of Complex (Bio-) Systems From Elastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Benedetto, Antonio; Kearley, Gordon J.

    2016-10-01

    A new type of neutron-scattering spectroscopy is presented that is designed specifically to measure dynamics in bio-systems that are difficult to obtain in any other way. The temporal information is largely model-free and is analogous to relaxation processes measured with dielectric spectroscopy, but provides additional spacial and geometric aspects of the underlying dynamics. Numerical simulations of the basic instrument design show the neutron beam can be highly focussed, giving efficiency gains that enable the use of small samples. Although we concentrate on continuous neutron sources, the extension to pulsed neutron sources is proposed, both requiring minimal data-treatment and being broadly analogous with dielectric spectroscopy, they will open the study of dynamics to new areas of biophysics.

  1. Elastic Scattering Spectroscopy (ESS): an Instrument-Concept for Dynamics of Complex (Bio-) Systems From Elastic Neutron Scattering.

    PubMed

    Benedetto, Antonio; Kearley, Gordon J

    2016-10-05

    A new type of neutron-scattering spectroscopy is presented that is designed specifically to measure dynamics in bio-systems that are difficult to obtain in any other way. The temporal information is largely model-free and is analogous to relaxation processes measured with dielectric spectroscopy, but provides additional spacial and geometric aspects of the underlying dynamics. Numerical simulations of the basic instrument design show the neutron beam can be highly focussed, giving efficiency gains that enable the use of small samples. Although we concentrate on continuous neutron sources, the extension to pulsed neutron sources is proposed, both requiring minimal data-treatment and being broadly analogous with dielectric spectroscopy, they will open the study of dynamics to new areas of biophysics.

  2. Elastic Scattering Spectroscopy (ESS): an Instrument-Concept for Dynamics of Complex (Bio-) Systems From Elastic Neutron Scattering

    PubMed Central

    Benedetto, Antonio; Kearley, Gordon J.

    2016-01-01

    A new type of neutron-scattering spectroscopy is presented that is designed specifically to measure dynamics in bio-systems that are difficult to obtain in any other way. The temporal information is largely model-free and is analogous to relaxation processes measured with dielectric spectroscopy, but provides additional spacial and geometric aspects of the underlying dynamics. Numerical simulations of the basic instrument design show the neutron beam can be highly focussed, giving efficiency gains that enable the use of small samples. Although we concentrate on continuous neutron sources, the extension to pulsed neutron sources is proposed, both requiring minimal data-treatment and being broadly analogous with dielectric spectroscopy, they will open the study of dynamics to new areas of biophysics. PMID:27703184

  3. Magnetic scattering in the simultaneous measurement of small-angle neutron scattering and Bragg edge transmission from steel.

    PubMed

    Oba, Yojiro; Morooka, Satoshi; Ohishi, Kazuki; Sato, Nobuhiro; Inoue, Rintaro; Adachi, Nozomu; Suzuki, Jun-Ichi; Tsuchiyama, Toshihiro; Gilbert, Elliot Paul; Sugiyama, Masaaki

    2016-10-01

    Pulsed neutron sources enable the simultaneous measurement of small-angle neutron scattering (SANS) and Bragg edge transmission. This simultaneous measurement is useful for microstructural characterization in steel. Since most steels are ferromagnetic, magnetic scattering contributions should be considered in both SANS and Bragg edge transmission analyses. An expression for the magnetic scattering contribution to Bragg edge transmission analysis has been derived. The analysis using this expression was applied to Cu steel. The ferrite crystallite size estimated from this Bragg edge transmission analysis with the magnetic scattering contribution was larger than that estimated using conventional expressions. This result indicates that magnetic scattering has to be taken into account for quantitative Bragg edge transmission analysis. In the SANS analysis, the ratio of magnetic to nuclear scattering contributions revealed that the precipitates consist of body-centered cubic Cu0.7Fe0.3 and pure Cu, which probably has 9R structure including elastic strain and vacancies. These results show that effective use of the magnetic scattering contribution allows detailed analyses of steel microstructure.

  4. Magnetic scattering in the simultaneous measurement of small-angle neutron scattering and Bragg edge transmission from steel1

    PubMed Central

    Oba, Yojiro; Morooka, Satoshi; Ohishi, Kazuki; Sato, Nobuhiro; Inoue, Rintaro; Adachi, Nozomu; Suzuki, Jun-ichi; Tsuchiyama, Toshihiro; Gilbert, Elliot Paul; Sugiyama, Masaaki

    2016-01-01

    Pulsed neutron sources enable the simultaneous measurement of small-angle neutron scattering (SANS) and Bragg edge transmission. This simultaneous measurement is useful for microstructural characterization in steel. Since most steels are ferromagnetic, magnetic scattering contributions should be considered in both SANS and Bragg edge transmission analyses. An expression for the magnetic scattering contribution to Bragg edge transmission analysis has been derived. The analysis using this expression was applied to Cu steel. The ferrite crystallite size estimated from this Bragg edge transmission analysis with the magnetic scattering contribution was larger than that estimated using conventional expressions. This result indicates that magnetic scattering has to be taken into account for quantitative Bragg edge transmission analysis. In the SANS analysis, the ratio of magnetic to nuclear scattering contributions revealed that the precipitates consist of body-centered cubic Cu0.7Fe0.3 and pure Cu, which probably has 9R structure including elastic strain and vacancies. These results show that effective use of the magnetic scattering contribution allows detailed analyses of steel microstructure. PMID:27738416

  5. Investigating Structure and Dynamics of Proteins in Amorphous Phases Using Neutron Scattering.

    PubMed

    Castellanos, Maria Monica; McAuley, Arnold; Curtis, Joseph E

    2017-01-01

    In order to increase shelf life and minimize aggregation during storage, many biotherapeutic drugs are formulated and stored as either frozen solutions or lyophilized powders. However, characterizing amorphous solids can be challenging with the commonly available set of biophysical measurements used for proteins in liquid solutions. Therefore, some questions remain regarding the structure of the active pharmaceutical ingredient during freezing and drying of the drug product and the molecular role of excipients. Neutron scattering is a powerful technique to study structure and dynamics of a variety of systems in both solid and liquid phases. Moreover, neutron scattering experiments can generally be correlated with theory and molecular simulations to analyze experimental data. In this article, we focus on the use of neutron techniques to address problems of biotechnological interest. We describe the use of small-angle neutron scattering to study the solution structure of biological molecules and the packing arrangement in amorphous phases, that is, frozen glasses and freeze-dried protein powders. In addition, we discuss the use of neutron spectroscopy to measure the dynamics of glassy systems at different time and length scales. Overall, we expect that the present article will guide and prompt the use of neutron scattering to provide unique insights on many of the outstanding questions in biotechnology.

  6. A method for moisture measurement in porous media based on epithermal neutron scattering.

    PubMed

    El Abd, A

    2015-11-01

    A method for moisture measurement in porous media was proposed. A wide beam of epithermal neutrons was obtained from a Pu-Be neutron source immersed in a cylinder made of paraffin wax. (3)He detectors (four or six) arranged in the backward direction of the incident beam were used to record scattered neutrons from investigated samples. Experiments of water absorption into clay and silicate bricks, and a sand column were investigated by neutron scattering. While the samples were absorbing water, scattered neutrons were recorded from fixed positions along the water flow direction. It was observed that, at these positions scattered neutrons increase as the water uptake increases. Obtained results are discussed in terms of the theory of macroscopic flow in porous media. It was shown that, the water absorption processes were Fickian and non Fickian in the sand column and brick samples, respectively. The advantages of applying the proposed method to study fast as well as slow flow processes in porous media are discussed.

  7. STUDY MAGNETIC EXCITATIONS IN DOPED TRANSITION METAL OXIDES USING INELASTIC NEUTRON SCATTERING

    SciTech Connect

    Dai, Pengcheng

    2014-02-18

    Understanding the interplay between magnetism and superconductivity continues to be a “hot” topic in modern condensed matter physics. The discovery of high-temperature superconductivity in iron-based materials in 2008 provided an unique opportunity to compare and contrast these materials with traditional high-Tc copper oxide superconductors. Neutron scattering plays an important role in determining the dynamical spin properties in these materials. This proposal is a continuation of previous DOE supported proposal. This report summarizes the final progress we have made over from May 2005 till Aug. 2013. Overall, we continue to carry out extensive neutron scattering experiments on Fe-based materials, focusing on understanding their magnetic properties. In addition, we have established a materials laboratory at UT that has allowed us to grow these superconductors. Because neutron scattering typically demands a large amount of samples, by growing these materials in our own laboratory, we can now pursuit neutron scattering experiments over the entire electronic phase diagram, focusing on regions of interests. The material synthesis laboratory at UT was established entirely with the support of DOE funding. This not only allowed us to carry out neutron scattering experiments, but also permit us to provide samples to other US/International collaborators for studying these materials.

  8. Neutron Scattering Collimation Wheel Instrument for Imaging Research

    NASA Astrophysics Data System (ADS)

    Van Every, E.; Deyhim, A.

    2016-09-01

    The design of a state-of-the-art selector wheel instrument to support the area of neutron imaging research (neutron radiography/ tomography) is discussed. The selector wheel is installed on the DINGO Radiography instrument at the Bragg Institute HB2 beamline at ANSTO in Sidney Aus. The selector wheel consists of a single axis drum filled with a wax/steel shielding mixture and six square cutouts for neutron optics and a larger solid shielding sector to act as a shutter. This paper focuses on the details of design and shielding of the selector wheel.

  9. Structured water in polyelectrolyte dendrimers: Understanding small angle neutron scattering results through atomistic simulation

    NASA Astrophysics Data System (ADS)

    Wu, Bin; Kerkeni, Boutheïna; Egami, Takeshi; Do, Changwoo; Liu, Yun; Wang, Yongmei; Porcar, Lionel; Hong, Kunlun; Smith, Sean C.; Liu, Emily L.; Smith, Gregory S.; Chen, Wei-Ren

    2012-04-01

    Based on atomistic molecular dynamics (MD) simulations, the small angle neutron scattering (SANS) intensity behavior of a single generation-4 polyelectrolyte polyamidoamine starburst dendrimer is investigated at different levels of molecular protonation. The SANS form factor, P(Q), and Debye autocorrelation function, γ(r), are calculated from the equilibrium MD trajectory based on a mathematical approach proposed in this work. The consistency found in comparison against previously published experimental findings (W.-R. Chen, L. Porcar, Y. Liu, P. D. Butler, and L. J. Magid, Macromolecules 40, 5887 (2007)) leads to a link between the neutron scattering experiment and MD computation, and fresh perspectives. The simulations enable scattering calculations of not only the hydrocarbons but also the contribution from the scattering length density fluctuations caused by structured, confined water within the dendrimer. Based on our computational results, we explore the validity of using radius of gyration RG for microstructure characterization of a polyelectrolyte dendrimer from the scattering perspective.

  10. Elastic and Inelastic Neutron Scattering with a C7LYC Array

    NASA Astrophysics Data System (ADS)

    Wilson, G. L.; Brown, T.; Chowdhury, P.; Doucet, E.; Lister, C. J.; D'Olympia, N.; Devlin, M.; Mosby, S.

    2015-10-01

    A scintillator array of 16 1'' ×1'' Cs2LiYCl6 (CLYC) detectors has been commissioned for low energy nuclear science. Standard CLYC crystals detect both gamma rays and neutrons rays with excellent pulse shape discrimination, with thermal neutrons detected via the 6Li(n, α)t reaction. Our discovery of spectroscopy-grade response of CLYC for fast neutrons via the 35Cl(n,p) reaction, with a pulse height resolution of under 10 % in the < 8 MeV range, led to our present array of 7Li enriched C7LYC detectors, where the large thermal neutron response is essentially eliminated. While the intrinsic efficiency of C7LYC for fast neutron detection is low, the array can be placed near the target since a long TOF arm is no longer needed for neutron energy measurement, thus recovering efficiency through increased solid angle coverage. The array was recently deployed at Los Alamos to test its capability in measuring differential scattering cross sections as a function of energy for 56Fe and 238U. The incident energy from a white neutron source was measured via TOF, and the scattered neutron energy via the pulse height. Techniques, analysis and first results will be discussed. Supported by the NNSA Stewardship Science Academic Alliance Program under Grant DE-NA00013008.

  11. Simulation experiments for gamma-ray mapping of planetary surfaces: Scattering of high-energy neutrons

    NASA Technical Reports Server (NTRS)

    Brueckner, J.; Englert, P.; Reedy, R. C.; Waenke, H.

    1986-01-01

    The concentration and distribution of certain elements in surface layers of planetary objects specify constraints on models of their origin and evolution. This information can be obtained by means of remote sensing gamma-ray spectroscopy, as planned for a number of future space missions, i.e., Mars, Moon, asteroids, and comets. To investigate the gamma-rays made by interactions of neutrons with matter, thin targets of different composition were placed between a neutron-source and a high-resolution germanium spectrometer. Gamma-rays in the range of 0.1 to 8 MeV were accumulated. In one set of experiments a 14-MeV neutron generator using the T(d,n) reaction as neutron-source was placed in a small room. Scattering in surrounding walls produced a spectrum of neutron energies from 14 MeV down to thermal. This complex neutron-source induced mainly neutron-capture lines and only a few scattering lines. As a result of the set-up, there was a considerable background of discrete lines from surrounding materials. A similar situation exists under planetary exploration conditions: gamma-rays are induced in the planetary surface as well as in the spacecraft. To investigate the contribution of neutrons with higher energies, an experiment for the measurement of prompt gamma radiation was set up at the end of a beam-line of an isochronous cyclotron.

  12. N-SAP and G-SAP neutron and gamma ray albedo model scatter shield analysis program

    NASA Technical Reports Server (NTRS)

    Sapovchak, B. J.; Stephenson, L. D.

    1967-01-01

    Computer program calculates neutron or gamma ray first order scattering from a plane or cylindrical surface to a detector point. The SAP Codes, G-SAP and N-SAP, constitute a multiple scatter albedo model shield analysis.

  13. Determination of hydrogen in niobium by cold neutron prompt gamma ray activation analysis and neutron incoherent scattering

    SciTech Connect

    R.L. Paul; H.H. Cheu-Maya; G.R. Myneni

    2002-11-01

    The presence of trace amounts of hydrogen in niobium is believed to have a detrimental effect on the mechanical and superconducting properties. Unfortunately, few techniques are capable of measuring hydrogen at these levels. We have developed two techniques for measuring hydrogen in materials. Cold neutron prompt gamma-ray activation analysis (PGAA) has proven useful for the determination of hydrogen and other elements in a wide variety of materials. Neutron incoherent scattering (NIS), a complementary tool to PGAA, has been used to measure trace hydrogen in titanium. Both techniques were used to study the effects of vacuum heating and chemical polishing on the hydrogen content of superconducting niobium.

  14. The neutron-gamma Feynman variance to mean approach: Gamma detection and total neutron-gamma detection (theory and practice)

    NASA Astrophysics Data System (ADS)

    Chernikova, Dina; Axell, Kåre; Avdic, Senada; Pázsit, Imre; Nordlund, Anders; Allard, Stefan

    2015-05-01

    Two versions of the neutron-gamma variance to mean (Feynman-alpha method or Feynman-Y function) formula for either gamma detection only or total neutron-gamma detection, respectively, are derived and compared in this paper. The new formulas have particular importance for detectors of either gamma photons or detectors sensitive to both neutron and gamma radiation. If applied to a plastic or liquid scintillation detector, the total neutron-gamma detection Feynman-Y expression corresponds to a situation where no discrimination is made between neutrons and gamma particles. The gamma variance to mean formulas are useful when a detector of only gamma radiation is used or when working with a combined neutron-gamma detector at high count rates. The theoretical derivation is based on the Chapman-Kolmogorov equation with the inclusion of general reactions and corresponding intensities for neutrons and gammas, but with the inclusion of prompt reactions only. A one energy group approximation is considered. The comparison of the two different theories is made by using reaction intensities obtained in MCNPX simulations with a simplified geometry for two scintillation detectors and a 252Cf-source. In addition, the variance to mean ratios, neutron, gamma and total neutron-gamma are evaluated experimentally for a weak 252Cf neutron-gamma source, a 137Cs random gamma source and a 22Na correlated gamma source. Due to the focus being on the possibility of using neutron-gamma variance to mean theories for both reactor and safeguards applications, we limited the present study to the general analytical expressions for Feynman-alpha formulas.

  15. Parity violation in neutron deuteron scattering in pionless effective field theory

    NASA Astrophysics Data System (ADS)

    Vanasse, Jared J.

    In this dissertation the parity violating neutron deuteron scattering amplitudes are calculated using pionless effective field theory to leading order. The five low energy parity violating constants present in pionless effective field theory are estimated by matching onto the ``best" values for the parameters of the model by Desplanques, Donoghue, and Holstein (DDH). Using these estimates and the calculated amplitudes, predictions for the spin rotation of a neutron through a deuteron target are given with a value of 1.8 × 10-8 rad cm-1. Also given are the longitudinal analyzing power in neutron deuteron scattering with a polarized neutron yielding 2.2 × 10-8, and a polarized deuteron giving 4.0 × 10-8. These observables are discussed in the broader context of hadronic parity violation and as possible future experiments to determine the values of the five low energy parity violating constant present in pionless effective theory.

  16. Development and prospects of Very Small Angle Neutron Scattering (VSANS) techniques

    NASA Astrophysics Data System (ADS)

    Xuo, Tai-Sen; Cheng, He; Chen, Yuan-Bo; Wang, Fang-Wei

    2016-07-01

    Very Small Angle Neutron Scattering (VSANS) is an upgrade of the traditional Small Angle Neutron Scattering (SANS) technique which can cover three orders of magnitude of length scale from one nanometer to one micrometer. It is a powerful tool for structure calibration in polymer science, biology, material science and condensed matter physics. Since the first VSANS instrument, D11 in Grenoble, was built in 1972, new collimation techniques, focusing optics (multi-beam converging apertures, material or magnetic lenses, and focusing mirrors) and higher resolution detectors combined with the long flight paths and long incident neutron wavelengths have been developed. In this paper, a detailed review is given of the development, principles and application conditions of various VSANS techniques. Then, beam current gain factors are calculated to evaluate those techniques. A VSANS design for the China Spallation Neutron Source (CSNS) is thereby presented. Supported by National Natural Science Foundation of China (21474119, 11305191)

  17. Shielding for neutron scattered dose to the fetus in patients treated with 18 MV x-ray beams.

    PubMed

    Roy, S C; Sandison, G A

    2000-08-01

    Neutrons are associated with therapeutic high energy x-ray beams as a contaminant that contributes significant unwanted dose to the patient. Measurement of both photon and neutron scattered dose at the position of a fetus from chest irradiation by a large field 18 MV x-ray beam was performed using an ionization chamber and superheated drop detector, respectively. Shielding construction to reduce this scattered dose was investigated using both lead sheet and borated polyethylene slabs. A 7.35 cm lead shield reduced the scattered photon dose by 50% and the scattered neutron dose by 40%. Adding 10 cm of 5% borated polyethylene to this lead shield reduced the scattered neutron dose by a factor of 7.5 from the unshielded value. When the 5% borated polyethylene was replaced by the same thickness of 30% borated polyethylene there was no significant change in the reduction of neutron scatter dose. The most efficient shield studied reduced the neutron scatter dose by a factor of 10. The results indicate that most of the scattered neutrons present at the position of the fetus produced by an 18 MV x-ray beam are of low energy and in the thermal to 0.57 MeV range since lead is almost transparent to neutrons with energies lower than 0.57 MeV. This article constitutes the first report of an effective shield to reduce neutron dose at the fetus when treating a pregnant woman with a high energy x-ray beam.

  18. Probing Spin Frustration in High-symmetry Magnetic Nanomolecules by Inelastic Neutron Scattering

    SciTech Connect

    Garlea, Vasile O; Nagler, Stephen E; Zarestky, Jerel L; Stassis, C.; Vaknin, D.; Kogerler, P.; McMorrow, D. F.; Niedermayer, C.; Tennant, D. A.; Lake, B.; Qiu, Y.; Exler, M.; Schnack, J.; Luban, M.

    2006-01-01

    Low temperature inelastic neutron scattering studies have been performed to characterize the low energy magnetic excitation spectrum of the magnetic nanomolecule {l_brace}Mo{sub 72}Fe{sub 30}{r_brace}. This unique highly symmetric cluster features spin frustration and is one of the largest discrete magnetic molecules studied to date by inelastic neutron scattering. The 30 s=5/2 Fe{sup III} ions, embedded in a spherical polyoxomolybdate molecule, occupy the vertices of an icosidodecahedron and are coupled via nearest-neighbor antiferromagnetic interactions. The overall energy scale of the excitation and the gross features of the temperature dependence of the observed neutron scattering are explained by a quantum model of the frustrated spin cluster. However, no satisfactory theoretical explanation is yet available for the observed magnetic field dependence.

  19. Use of a high repetition rate neutron generator for in vivo body composition measurements via neutron inelastic scattering

    SciTech Connect

    Kehayias, J.J.; Ellis, K.J.; Cohn, S.H.; Weinlein, J.H.

    1986-01-01

    A small D-T neutron generator with a high pulse rate is used for the in vivo measurement of body carbon, oxygen and hydrogen. The core of the neutron generator is a 13 cm-long Zetatron tube pulsed at a rate of 10 kHz delivering 10/sup 3/ to 10/sup 4/ neutrons per pulse. A target-current feedback system regulates the source of the accelerator to assure constant neutron output. Carbon is measured by detecting the 4.44 MeV ..gamma..-rays from inelastic scattering. The short half-life of the 4.44 MeV state of carbon requires detection of the ..gamma..-rays during the 10 ..mu..s neutron pulse. Generators with low pulsing rate were found inappropriate for carbon measurements because of their low duty-cycle (high neutron output during the pulse). In vivo measurements were performed with normal volunteers using a scanning bed facility for a dose less than 25 mrem. This technique offers medical as well as general bulk analysis applications. 8 refs., 5 figs.

  20. Neutron scattering and the 30 S ribosomal subunit of E. coli

    SciTech Connect

    Moore, P.B.; Engelman, D.M.; Langer, J.A.; Ramakrishnan, V.R.; Schindler, D.G.; Schoenborn, B.P.; Sillers, I.Y.; Yabuki, S.

    1982-01-01

    This paper reviews the progress made in the study of the internal organization of the 30 S ribosomal subunit of E. coli by neutron scattering since 1975. A map of that particle showing the position of 14 of the subunit's 21 proteins is presented, and the methods currently used for collecting and analyzing such data are discussed. Also discussed is the possibility of extending the interpretation of neutron mapping data beyond the limits practical today. 30 references, 5 figures.

  1. Neutron Scattering and the 30 S Ribosomal Subunit of E. Coli

    DOE R&D Accomplishments Database

    Moore, P. B.; Engelman, D. M.; Langer, J. A.; Ramakrishnan, V. R.; Schindler, D. G.; Schoenborn, B. P.; Sillers, I. Y.; Yabuki, S.

    1982-06-01

    This paper reviews the progress made in the study of the internal organization of the 30 S ribosomal subunit of E. coli by neutron scattering since 1975. A map of that particle showing the position of 14 of the subunit's 21 proteins is presented, and the methods currently used for collecting and analyzing such data are discussed. Also discussed is the possibility of extending the interpretation of neutron mapping data beyond the limits practical today.

  2. Experimental methods in the study of neutron scattering at small angles

    SciTech Connect

    Dragolici, Cristian A.

    2014-11-24

    Small angle scattering (SAS) is the collective name given to the techniques of small angle neutron (SANS) and X-ray (SAXS) scattering. They offer the possibility to analyze particles without disturbing their natural environment. In each of these techniques radiation is elastically scattered by a sample and the resulting scattering pattern is analyzed to provide information about the size, shape and orientation of some component of the sample. Accordingly, a large number of methods and experimental patterns have been developed to ease the investigation of condensed matter by use of these techniques. Some of them are the discussed in this paper.

  3. Studies of parity and time reversal symmetries in neutron scattering from165Ho

    NASA Astrophysics Data System (ADS)

    Haase, D. G.; Gould, C. R.; Koster, J. E.; Roberson, N. R.; Seagondollar, L. W.; Soderstrum, J. P.; Schneider, M. B.; Zhu, X.

    1988-12-01

    We describe searches for parity and time reversal violations in the scattering of polarized neutrons from polarized and aligned165Ho targets. We have completed a search with 7.1 and 11.0 MeV neutrons for PoddTodd terms in the elastic scattering forward amplitude of the form s. ( I×K), where s is the neutron spin, I is the target spin and k is the neutron momentum vector. The target was a single crystal of holmium, polarized horizontally along its b axis by a 1 Tesla magnetic field. The neutrons were polarized vertically. Differences in the neutron transmission were measured for neutrons with spins parallel (antiparallel) to I×k. The P,T violating analyzing powers were found to be consistent with zero at the few 10-3 level: ρP,T(7.1 MeV)=-0.88 (±2.02) x 10-3, ρP,T(11.0 MeV)=-0.4 (±2.88) x 10-3. We have also attempted to find enhancements with MeV neutrons in P-violation due to the term s k. We are preparing an aligned target cryostat for investigations of PevenTodd terms {bd(Ik)(I×k)s} in neutron scattering. The target will be a single crystal cylinder of165Ho cooled to 100 mK in a bath of liquid helium and rotated by a shaft from a room temperature stepping motor. The cylinder will be oriented vertically and the alignment ( c) axis oriented horizontally. Warming or rotation of the sample allows one to separate effects that mimic the sought-after time reversal violating term.

  4. The synthetic scattering function and application to the design of cold moderators for pulsed neutron sources: a fast response methane based array

    SciTech Connect

    Granada, J. R.; Mayer, R. E.; Gillette, V. H.

    1997-09-01

    The Synthetic Scattering Function (SSF) allows a simple description of the incoherent interaction of slow neutrons with hydrogenous materials. The main advantages of this model reside in the analytical expressions that it produces for double-differential cross sections, energy-transfer kernels, and total cross sections, which in turn permit the fast evaluation of neutron scattering and transport properties. In this work we briefly discuss basic features of the SSF, review some previous applications to a number of moderating materials, and present new Monte Carlo results for a fast time-response moderator concept based on methane at low temperatures. (auth)

  5. Inelastic neutron scattering cross-section measurements on 7Li and 63,65Cu

    NASA Astrophysics Data System (ADS)

    Nyman, Markus; Belloni, Francesca; Ichinkhorloo, Dagvadorj; Pirovano, Elisa; Plompen, Arjan; Rouki, Chariklia

    2017-09-01

    The γ-ray production cross section for the 477.6-keV transition in 7Li following inelastic neutron scattering has been measured from the reaction threshold up to 18 MeV. This cross section is interesting as a possible standard for other inelastic scattering measurements. The experiment was conducted at the Geel Electron LINear Accelerator (GELINA) pulsed white neutron source with the Gamma Array for Inelastic Neutron Scattering (GAINS) spectrometer. Previous measurements of this cross section are reviewed and compared with our results. Recently, this cross section has also been calculated using the continuum discretized coupled-channels (CDCC) method. Experiments for studying neutrinoless double-β decay (2β0ν) or other very rare processes require greatly reducing the background radiation level (both intrinsic and external). Copper is a common shielding and structural material, used extensively in experiments such as COBRA, CUORE, EXO, GERDA, and MAJORANA. Understanding the background contribution arising from neutron interactions in Cu is important when searching for very weak experimental signals. Neutron inelastic scattering on natCu was investigated with GAINS. The results are compared with previous experimental data and evaluated nuclear data libraries.

  6. Modeling down-scattered neutron images from cryogenic fuel implosions at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Raman, Kumar; Casey, Dan; Callahan, Debra; Clark, Dan; Fittinghoff, David; Grim, Gary; Hatchett, Steve; Hinkel, Denise; Jones, Ogden; Kritcher, Andrea; Seek, Scott; Suter, Larry; Merrill, Frank; Wilson, Doug

    2016-10-01

    In experiments with cryogenic deuterium-tritium (DT) fuel layers at the National Ignition Facility (NIF), an important technique for visualizing the stagnated fuel assembly is to image the 6-12 MeV neutrons created by scatters of the 14 MeV hotspot neutrons in the surrounding cold fuel. However, such down-scattered neutron images are difficult to interpret without a model of the fuel assembly, because of the nontrivial neutron kinematics involved in forming the images. For example, the dominant scattering modes are at angles other than forward scattering and the 14 MeV neutron fluence is not uniform. Therefore, the intensity patterns in these images usually do not correspond in a simple way to patterns in the fuel distribution, even for simple fuel distributions. We describe our efforts to model synthetic images from ICF design simulations with data from the National Ignition Campaign and after. We discuss the insight this gives, both to understand how well the models are predicting fuel asymmetries and to inform how to optimize the diagnostic for the types of fuel distributions being predicted. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  7. Probing photoinduced spin states in spin-crossover molecules with neutron scattering

    NASA Astrophysics Data System (ADS)

    Ridier, K.; Craig, G. A.; Damay, F.; Fennell, T.; Murrie, M.; Chaboussant, G.

    2017-03-01

    We report a neutron-scattering investigation of the spin-crossover compound [Fe (ptz) 6] (BF4)2 , which undergoes an abrupt thermal spin transition from high spin (HS), S =2 , to low spin (LS), S =0 , around 135 K. The HS magnetic state can be restored at low temperature under blue/green light irradiation. We have developed a specially designed optical setup for neutron scattering to address the magnetic properties of the light-induced HS state. By using neutron diffraction, we demonstrate that significant HS/LS ratios (of up to 60%) can be obtained with this experimental setup on a sample volume considered large (400 mg), while a complete recovery of the LS state is achieved using near-infrared light. Finally, with inelastic neutron scattering (INS) we have observed magnetic transitions arising from the photo-induced metastable HS S =2 state split by crystal-field and spin-orbit coupling. We interpret the INS data assuming a spin-only model with a zero-field splitting of the S =2 ground state. The obtained parameters are D ≈-1.28 ±0.03 meV and |E |≈0.08 ±0.03 meV. The present results show that in situ magnetic inelastic neutron-scattering investigations on a broad range of photomagnetic materials are now possible.

  8. Neutron scattering characterization of pure and rare-earth modified zirconia catalysis.

    SciTech Connect

    Loong, C.-K.; Ozawa, M.; Richardson, J. W., Jr.; Suzuki, S.; Thiyagarajan, P.

    1997-11-18

    The combined application of neutron powder diffraction, small angle neutron scattering and neutron inelastic scattering has led to improved understanding of the crystal phases, defect structure, microstructure and hydroxyl/water dynamics in pure and lanthanide-modified zirconia catalysts. Powder diffraction experiments quantified the degree of stabilization and provided evidence for static, oxygen vacancy-induced atomic displacements in stabilized zirconia. Quantitative assessment of Bragg peak breadths led to measurements of ''grain size'', representing coherency length of long-range ordered atomic arrangements (crystals). Small angle neutron scattering provided a separate measurement of ''grain size'', representing the average size of the primary particles in the aggregates, and the evolution of porosity (micro- versus meso-) and surface roughness caused by RE modification and heat treatment. Finally, the dynamics of hydrogen atoms associated with surface hydroxyls and adsorbed water was investigated by neutron-inelastic scattering, revealing changes in frequency and band breadth of O-H stretch, H-O-H bend, and librational motion of water molecules.

  9. Precision measurement of the n-4He scattering length using neutron interferometry

    NASA Astrophysics Data System (ADS)

    Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Black, T. C.; Shahi, C. B.; Wietfeldt, F. E.

    2010-11-01

    The NIST neutron interferometer and optics facility (NIOF) is currently performing a precision measurement of the n-4He scattering length to less than 0.3% relative uncertainty. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons entering the interferometer are Bragg diffracted in the blades to produce two spatially separate yet coherent beam paths much like an optical Mach-Zehnder interferometer. A sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths. This phase difference is directly related to the sample's scattering length. Neutron scattering lengths are one parameter that can be predicted using advanced theoretical models describing two and three nucleon interactions. In an effort to provide tests and/or benchmarks of these theoretical models, the NIOF has already performed precision measurements of neutron scattering lengths to less than 1% relative uncertainty in several low Z gases: H, D, 3He, and polarized 3He. A preliminary result of this work will be given.

  10. Total scattering analysis of cation coordination and vacancy pair distribution in Yb substituted δ-Bi2O3.

    PubMed

    Leszczynska, M; Liu, X; Wrobel, W; Malys, M; Norberg, S T; Hull, S; Krok, F; Abrahams, I

    2013-11-13

    Reverse Monte Carlo (RMC) modelling of neutron total scattering data, combined with conventional Rietveld analysis of x-ray and neutron data, has been used to describe the cation coordination environments and vacancy pair distribution in the oxide ion conducting electrolyte Bi3YbO6. The thermal variation of the cubic fluorite unit cell volume, monitored by variable temperature x-ray and neutron experiments, reveals significant curvature, which is explained by changes in the oxide ion distribution. There is a significant increase in tetrahedral oxide ion vacancy concentration relative to δ-Bi2O3, due to the creation of Frenkel defects associated with the Yb(3+) cation. The tetrahedral oxide ion vacancy concentration increases from room temperature to 800 °C, but little change is observed in the vacancy pair distribution with temperature. The vacancy pair distributions at both temperatures are consistent with a favouring of [100] vacancy pairs.

  11. FAST NEUTRON SPECTROMETER USING SPACED SEMICONDUCTORS FOR MEASURING TOTAL ENERGY OF NEUTRONS CAPTURED

    DOEpatents

    Love, T.A.; Murray, R.B.

    1964-04-14

    A fast neutron spectrometer was designed, which utilizes a pair of opposed detectors having a layer of /sup 6/LiF between to produce alpha and T pair for each neutron captured to provide signals, which, when combined, constitute a measure of neutron energy. (AEC)

  12. Form fluctuations of polymer loaded spherical microemulsions studied by neutron scattering and dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Kuttich, B.; Falus, P.; Grillo, I.; Stühn, B.

    2014-08-01

    We investigate the structure and shell dynamics of the droplet phase in water/AOT/octane microemulsions with polyethyleneglycol (MW = 1500) molecules loaded in the droplets. Size and polydispersity of the droplets is determined with small angle X-ray scattering and small angle neutron scattering experiments. Shell fluctuations are measured with neutron spin echo spectroscopy and related to the dynamic percolation seen in dielectric spectroscopy. Shell fluctuations are found to be well described by the bending modulus of the shell and the viscosities inside and outside the droplets. Addition of the polymer decreases the modulus for small droplets. For large droplets the opposite is found as percolation temperature shifts to higher values.

  13. Intermolecular associations in an equimolar formamide-water solution based on neutron scattering and DFT calculations.

    PubMed

    Abdelmoulahi, Hafedh; Ghalla, Houcine; Nasr, Salah; Darpentigny, Jacques; Bellissent-Funel, Marie-Claire

    2016-10-07

    In the present work, we have investigated the intermolecular associations of formamide with water in an equimolar formamide-water solution (FA-Water) by means of neutron scattering in combination with density functional theory calculations. The neutron scattering data were analyzed to deduce the structure factor SM(q) and the intermolecular pair correlation function gL(r). By considering different hydrogen bonded FA-Water associations, it has been shown that some of them describe well the local order in the solution. Natural bond orbital and atoms in molecules analyses have been performed to give more insight into the properties of hydrogen bonds involved in the more probable models.

  14. Small Angle Neutron Scattering at the National Institute of Standards and Technology

    PubMed Central

    Hammouda, B.; Krueger, S.; Glinka, C. J.

    1993-01-01

    The small angle neutron scattering technique is a valuable method for the characterization of morphology of various materials. It can probe inhomogeneities in the sample (whether occurring naturally or introduced through isotopic substitution) at a length scale from the atomic size (nanometers) to the macroscopic (micrometers) size. This work provides an overview of the small angle neutron scattering facilities at the National Institute of Standards and Technology and a review of the technique as it has been applied to polymer systems, biological macromolecules, ceramic, and metallic materials. Specific examples have been included. PMID:28053456

  15. Background Neutron Studies for Coherent Elastic Neutrino-Nucleus Scattering Measurements at the SNS

    NASA Astrophysics Data System (ADS)

    Markoff, Diane; Coherent Collaboration

    2015-10-01

    The COHERENT collaboration has proposed to measure coherent, elastic neutrino-nucleus scattering (CE νNS) cross sections on several nuclear targets using neutrinos produced at the Spallation Neutron Source (SNS) located at the Oak Ridge National Laboratory. The largest background of concern arises from beam-induced, fast neutrons that can mimic a nuclear recoil signal event in the detector. Multiple technologies of neutron detection have been employed at prospective experiment sites at the SNS. Analysis of these data have produced a consistent picture of the backgrounds expected for a CE νNS measurement. These background studies show that at suitable locations, the fast neutrons of concern arrive mainly in the prompt 1.3 μs window and the neutrons in the delayed window are primarily of lower energies that are relatively easier to shield.

  16. Theoretical study on neutron distribution of 208Pb by parity-violating electron scattering

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Zhang, Cun; Ren, Zhong-Zhou; Xu, Chang

    2016-03-01

    The precise determination of neutron distribution has important implications for both nuclear structure and nuclear astrophysics. The purpose of this paper is to study the characteristics of neutron distribution of 208Pb by parity-violating electron scattering (PVS). Parity-violating asymmetries of 208Pb with different types of neutron skins are systematically calculated and compared with the experimental data of PREx. The results indicate that the PVS experiments are very sensitive to the nuclear neutron distributions. From further PVS measurements, detailed information on nuclear neutron distributions can be extracted. Supported by the National Natural Science Foundation of China (11505292, 11175085, 11235001, 11447226), by the Shandong Provincial Natural Science Foundation, China (BS2014SF007), by the Fundamental Research Funds for the Central Universities (15CX02072A, 15CX02070A, 15CX05026A, 13CX10022A, 14CX02157A).

  17. Distributed data processing and analysis environment for neutron scattering experiments at CSNS

    NASA Astrophysics Data System (ADS)

    Tian, H. L.; Zhang, J. R.; Yan, L. L.; Tang, M.; Hu, L.; Zhao, D. X.; Qiu, Y. X.; Zhang, H. Y.; Zhuang, J.; Du, R.

    2016-10-01

    China Spallation Neutron Source (CSNS) is the first high-performance pulsed neutron source in China, which will meet the increasing fundamental research and technique applications demands domestically and overseas. A new distributed data processing and analysis environment has been developed, which has generic functionalities for neutron scattering experiments. The environment consists of three parts, an object-oriented data processing framework adopting a data centered architecture, a communication and data caching system based on the C/S paradigm, and data analysis and visualization software providing the 2D/3D experimental data display. This environment will be widely applied in CSNS for live data processing.

  18. International Conference on Surface X-ray and Neutron Scattering (SXNS-11)

    SciTech Connect

    Michael J. Bedzyk

    2011-06-17

    The 11th International Surface X-ray and Neutron Scattering (SXNS) Conference was held on July 13-17, 2010, on the Northwestern University (NU) campus, in Evanston Illinois and hosted by the NU Materials Research Science and Engineering Center. This biennial conference brought together a community of 164 attendees from 16 countries. The field now makes use of a broad range of new experimental capabilities that have been made possible through the development of increasingly brilliant X-ray and neutron sources around the world, including third generation synchrotron sources, neutron reactor and spallation sources, as well as the recent development of X-ray lasers.

  19. New opportunities for quasielastic and inelastic neutron scattering at steady-state sources using mechanical selection of the incident and final neutron energy

    SciTech Connect

    Mamantov, Eugene

    2015-06-12

    We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of the scattering angle component out of the equatorial plane.

  20. New opportunities for quasielastic and inelastic neutron scattering at steady-state sources using mechanical selection of the incident and final neutron energy

    DOE PAGES

    Mamantov, Eugene

    2015-06-12

    We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of themore » scattering angle component out of the equatorial plane.« less

  1. New generation of cryogen free advanced superconducting magnets for neutron scattering experiments

    NASA Astrophysics Data System (ADS)

    Kirichek, O.; Brown, J.; Adroja, D. T.; Manuel, P.; Kouzmenko, G.; Bewley, R. I.; Wotherspoon, R.

    2012-12-01

    Recent advances in superconducting technology and cryocooler refrigeration have resulted in a new generation of advanced superconducting magnets for neutron beam applications. These magnets have outstanding parameters such as high homogeneity and stability at highest magnetic fields possible, a reasonably small stray field, low neutron scattering background and larger exposure to neutron detectors. At the same time the pulse tube refrigeration technology provides a complete re-condensing regime which allows to minimise the requirements for cryogens without introducing additional noise and mechanical vibrations. The magnets can be used with dilution refrigerator insert which expands the temperature range from 20mK to 300K. Here we are going to present design, test results and the operational data of the 14T magnet for neutron diffraction and the 9T wide angle chopper magnet for neutron spectroscopy developed by Oxford Instruments in collaboration with ISIS neutron source. First scientific results obtained from the neutron scattering experiments with these magnets are also going to be discussed.

  2. CdZnTe γ detector for deep inelastic neutron scattering on the VESUVIO spectrometer

    NASA Astrophysics Data System (ADS)

    Andreani, C.; D'Angelo, A.; Gorini, G.; Imberti, S.; Pietropaolo, A.; Rhodes, N. J.; Schooneveld, E. M.; Senesi, R.; Tardocchi, M.

    In this paper it is shown that solid-state cadmium-zinc-telluride (CZT) is a promising photon detector for neutron spectroscopy in a wide energy interval, ranging from thermal ( 25 meV) to epithermal ( 70 eV) neutron energies. In the present study two CZT detectors were tested as part of the inverse-geometry neutron spectrometer VESUVIO operating at the ISIS pulsed neutron source. The response of the CZT detector to photon emission from radiative neutron capture in 238U was determined by biparametric measurements of neutron time of flight and photon energy. The scattering response function F(y) from a Pb sample has been derived using both CZT and conventional 6Li-glass scintillator detectors. The former showed both an improved signal to background ratio and higher efficiency as compared to 6Li glass, allowing us to measure F(y) up to the fourth 238U absorption energy (Er=66.02 eV). Due to the small size of CZT detectors, their use is envisaged in arrays, with high spatial resolution, for neutron-scattering studies at high energy (ω>1 eV) and low wavevector (q <10 Å-1) transfers.

  3. D-D neutron-scatter measurements for a novel explosives-detection technique

    NASA Astrophysics Data System (ADS)

    Lehnert, A. L.; Flaska, M.; Kearfott, K. J.

    2012-11-01

    A series of measurements has been completed that provides a benchmark for Monte Carlo simulations related to an algorithm for explosives detection using active neutron interrogation. The original simulations used in algorithm development, based on land-sea cargo container screening, have been adapted to model active neutron interrogation of smaller targets. These smaller-scale measurements are easily accomplished in a laboratory environment. Benchmarking measurements were completed using a D-D neutron generator, two neutron detectors, as well as a variety of scatter media including the explosives surrogate melamine (C3H6N6). Measurements included 90°, 120°, or 150° neutron scatter geometries and variations in source-detector shielding, target presence, and target identity. Comparisons of measured and simulated neutron fluxes were similar, with correlation coefficients greater than 0.7. The simulated detector responses also matched very closely with the measured photon and neutron pulse height distributions, with correlation coefficients exceeding 0.9. The experiments and simulations also provided insight into potential application of the new method to the problem of explosives detection in small objects such as luggage and small packages.

  4. The structure of alkali silicate gel by total scattering methods

    SciTech Connect

    Benmore, C.J.; Monteiro, Paulo J.M.

    2010-06-15

    The structure of the alkali silicate gel (ASR) collected from the galleries of Furnas Dam in Brazil was determined by a pair distribution function (PDF) analysis of high energy X-ray diffraction data. Since this method is relatively new to concrete structure analysis a detailed introduction on the PDF method is given for glassy SiO{sub 2}. The bulk amorphous structure of the dam material is confirmed as no Bragg peaks are observed in the scattered intensity. The real space results show that the local structure of the amorphous material is similar to kanemite (KHSi{sub 2}O{sub 5}:3H{sub 2}O) however the long range layer structure of the crystal is broken up in the amorphous state, so that ordering only persists of the length scale of a few polyhedra. The silicate layer structure is a much more disordered than predicted by molecular dynamics models. The X-ray results are consistent with the molecular dynamics model of Kirkpatrick et al. (2005) [1] which predicts that most of the water resides in pores within the amorphous network rather than in layers. The total scattering data provide a rigorous basis against which other models may also be tested.

  5. Active helium target: Neutron scalar polarizability extraction via Compton scattering

    SciTech Connect

    Morris, Meg Hornidge, David; Annand, John; Strandberg, Bruno

    2015-12-31

    Precise measurement of the neutron scalar polarizabilities has been a lasting challenge because of the lack of a free-neutron target. Led by the University of Glasgow and the Mount Allison University groups of the A2 collaboration in Mainz, Germany, preparations have begun to test a recent theoretical model with an active helium target with the hope of determining these elusive quantities with small statistical, systematic, and model-dependent errors. Apparatus testing and background-event simulations have been carried out, with the full experiment projected to run in 2015. Once determined, these values can be applied to help understand quantum chromodynamics in the nonperturbative region.

  6. Total internal reflection and dynamic light scattering microscopy of gels

    NASA Astrophysics Data System (ADS)

    Gregor, Brian F.

    Two different techniques which apply optical microscopy in novel ways to the study of biological systems and materials were built and applied to several samples. The first is a system for adapting the well-known technique of dynamic light scattering (DLS) to an optical microscope. This can detect and scatter light from very small volumes, as compared to standard DLS which studies light scattering from volumes 1000x larger. The small scattering volume also allows for the observation of nonergodic dynamics in appropriate samples. Porcine gastric mucin (PGM) forms a gel at low pH which lines the epithelial cell layer and acts as a protective barrier against the acidic stomach environment. The dynamics and microscopic viscosity of PGM at different pH levels is studied using polystyrene microspheres as tracer particles. The microscopic viscosity and microrheological properties of the commercial basement membrane Matrigel are also studied with this instrument. Matrigel is frequently used to culture cells and its properties remain poorly determined. Well-characterized and purely synthetic Matrigel substitutes will need to have the correct rheological and morphological characteristics. The second instrument designed and built is a microscope which uses an interferometry technique to achieve an improvement in resolution 2.5x better in one dimension than the Abbe diffraction limit. The technique is based upon the interference of the evanescent field generated on the surface of a prism by a laser in a total internal reflection geometry. The enhanced resolution is demonstrated with fluorescent samples. Additionally. Raman imaging microscopy is demonstrated using the evanescent field in resonant and non-resonant samples, although attempts at applying the enhanced resolution technique to the Raman images were ultimately unsuccessful. Applications of this instrument include high resolution imaging of cell membranes and macroscopic structures in gels and proteins. Finally, a third

  7. Current Status of the Experiment on Direct Measurement of Neutron-Neutron Scattering Length at the Reactor YAGUAR

    SciTech Connect

    Furman, W. I.; Muzichka, A. Yu.; Lychagin, E. V.; Nekhaev, G. V.; Sharapov, E. I.; Shvetsov, V. N.; Strelkov, A. V.; Crawford, B. E.; Stephenson, S. L.; Howell, C. R.; Tornow, W.; Kandiev, Ya.; Levakov, B. G.; Litvin, V. I.; Lyzhin, A. E.; Tchernukhin, Yu. I.; Mitchell, G. E.

    2009-03-31

    A new experiment was proposed in 2002 to perform the first direct measurement of neutron-neutron scattering on the powerful pulsed reactor YAGUAR located at Snezhinsk, Ural region, Russia. Extensive efforts were made to model the background conditions and to optimize the set-up design. To make the experiment feasible it was necessary to suppress the background from various origins by more than 16 orders of magnitude for thermal neutrons and 14 orders of magnitude for fast neutrons. In 2003 a channel was drilled under the reactor and equipped for time-of-flight measurements. During the next two years at this channel there were carried out a series of test experiments aimed at verifying the accuracy of the background modeling. Good agreement of the measured results with the calculated values enabled us to make the final design of the full scale set-up. During 2005-2006 the experimental system was manufactured. After vacuum tests at JINR the set-up was mounted at the YAGUAR reactor hall. In 2006-2007 calibration measurements with noble gases were performed. The results confirmed the validity of the modeling of the full scale experiment and verified the calibration. The first preliminary experiments for nn-scattering were performed in April 2008. These recent results are discussed.

  8. Fast oxygen diffusion in bismuth oxide probed by quasielastic neutron scattering

    DOE PAGES

    Mamontov, Eugene

    2016-09-24

    In this paper, we present the first, to our knowledge, study of solid state oxygen translational diffusion by quasielastic neutron scattering. Such studies in the past might have been precluded by relatively low diffusivities of oxygen anions in the temperature range amenable to neutron scattering experiments. To explore the potential of the quasielastic scattering technique, which can deduce atomic diffusion jump length of oxygen anions through the momentum transfer dependence of the scattering signal, we have selected the fastest known oxygen conductor, bismuth oxide. Finally, we have found the oxygen anion jump length in excellent agreement with the nearest oxygen-vacancymore » distance in the anion sublattice of the fluorite-related structure of bismuth oxide.« less

  9. Fast oxygen diffusion in bismuth oxide probed by quasielastic neutron scattering

    SciTech Connect

    Mamontov, Eugene

    2016-09-24

    In this paper, we present the first, to our knowledge, study of solid state oxygen translational diffusion by quasielastic neutron scattering. Such studies in the past might have been precluded by relatively low diffusivities of oxygen anions in the temperature range amenable to neutron scattering experiments. To explore the potential of the quasielastic scattering technique, which can deduce atomic diffusion jump length of oxygen anions through the momentum transfer dependence of the scattering signal, we have selected the fastest known oxygen conductor, bismuth oxide. Finally, we have found the oxygen anion jump length in excellent agreement with the nearest oxygen-vacancy distance in the anion sublattice of the fluorite-related structure of bismuth oxide.

  10. Fast oxygen diffusion in bismuth oxide probed by quasielastic neutron scattering

    SciTech Connect

    Mamontov, Eugene

    2016-09-24

    In this paper, we present the first, to our knowledge, study of solid state oxygen translational diffusion by quasielastic neutron scattering. Such studies in the past might have been precluded by relatively low diffusivities of oxygen anions in the temperature range amenable to neutron scattering experiments. To explore the potential of the quasielastic scattering technique, which can deduce atomic diffusion jump length of oxygen anions through the momentum transfer dependence of the scattering signal, we have selected the fastest known oxygen conductor, bismuth oxide. Finally, we have found the oxygen anion jump length in excellent agreement with the nearest oxygen-vacancy distance in the anion sublattice of the fluorite-related structure of bismuth oxide.

  11. Experimental measurements with Monte Carlo corrections and theoretical calculations of neutron inelastic scattering cross section of 115In

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Xiao, Jun; Luo, Xiaobing

    2016-10-01

    The neutron inelastic scattering cross section of 115In has been measured by the activation technique at neutron energies of 2.95, 3.94, and 5.24 MeV with the neutron capture cross sections of 197Au as an internal standard. The effects of multiple scattering and flux attenuation were corrected using the Monte Carlo code GEANT4. Based on the experimental values, the 115In neutron inelastic scattering cross sections data were theoretically calculated between the 1 and 15 MeV with the TALYS software code, the theoretical results of this study are in reasonable agreement with the available experimental results.

  12. Neutron scattered dose equivalent to a fetus from proton radiotherapy of the mother.

    PubMed

    Mesoloras, Geraldine; Sandison, George A; Stewart, Robert D; Farr, Jonathan B; Hsi, Wen C

    2006-07-01

    Scattered neutron dose equivalent to a representative point for a fetus is evaluated in an anthropomorphic phantom of the mother undergoing proton radiotherapy. The effect on scattered neutron dose equivalent to the fetus of changing the incident proton beam energy, aperture size, beam location, and air gap between the beam delivery snout and skin was studied for both a small field snout and a large field snout. Measurements of the fetus scattered neutron dose equivalent were made by placing a neutron bubble detector 10 cm below the umbilicus of an anthropomorphic Rando phantom enhanced by a wax bolus to simulate a second trimester pregnancy. The neutron dose equivalent in milliSieverts (mSv) per proton treatment Gray increased with incident proton energy and decreased with aperture size, distance of the fetus representative point from the field edge, and increasing air gap. Neutron dose equivalent to the fetus varied from 0.025 to 0.450 mSv per proton Gray for the small field snout and from 0.097 to 0.871 mSv per proton Gray for the large field snout. There is likely to be no excess risk to the fetus of severe mental retardation for a typical proton treatment of 80 Gray to the mother since the scattered neutron dose to the fetus of 69.7 mSv is well below the lower confidence limit for the threshold of 300 mGy observed for the occurrence of severe mental retardation in prenatally exposed Japanese atomic bomb survivors. However, based on the linear no threshold hypothesis, and this same typical treatment for the mother, the excess risk to the fetus of radiation induced cancer death in the first 10 years of life is 17.4 per 10,000 children.

  13. Neutron scattered dose equivalent to a fetus from proton radiotherapy of the mother

    SciTech Connect

    Mesoloras, Geraldine; Sandison, George A.; Stewart, Robert D.; Farr, Jonathan B.; Hsi, Wen C.

    2006-07-15

    Scattered neutron dose equivalent to a representative point for a fetus is evaluated in an anthropomorphic phantom of the mother undergoing proton radiotherapy. The effect on scattered neutron dose equivalent to the fetus of changing the incident proton beam energy, aperture size, beam location, and air gap between the beam delivery snout and skin was studied for both a small field snout and a large field snout. Measurements of the fetus scattered neutron dose equivalent were made by placing a neutron bubble detector 10 cm below the umbilicus of an anthropomorphic Rando[reg] phantom enhanced by a wax bolus to simulate a second trimester pregnancy. The neutron dose equivalent in milliSieverts (mSv) per proton treatment Gray increased with incident proton energy and decreased with aperture size, distance of the fetus representative point from the field edge, and increasing air gap. Neutron dose equivalent to the fetus varied from 0.025 to 0.450 mSv per proton Gray for the small field snout and from 0.097 to 0.871 mSv per proton Gray for the large field snout. There is likely to be no excess risk to the fetus of severe mental retardation for a typical proton treatment of 80 Gray to the mother since the scattered neutron dose to the fetus of 69.7 mSv is well below the lower confidence limit for the threshold of 300 mGy observed for the occurrence of severe mental retardation in prenatally exposed Japanese atomic bomb survivors. However, based on the linear no threshold hypothesis, and this same typical treatment for the mother, the excess risk to the fetus of radiation induced cancer death in the first 10 years of life is 17.4 per 10 000 children.

  14. Measurement of the neutron electric form factor GEn in quasielastic scattering

    SciTech Connect

    Donal Day

    2003-07-15

    We have measured the electric form factor of the neutron, GEn, at two momentum transfers (Q2= 0.5 and Q2= 1.0 GeV/c2) through quasielastic scattering in Jefferson Lab's Hall C. Longitudinally polarized electrons scattered from polarized deuterated ammonia and GEn was extracted from the beam-target asymmetry AVed which, in quasielastic kinematics, is particularly sensitive to GEn and insensitive to MEC and FSI.

  15. Coherent Scattering Investigations at the Spallation Neutron Source: a Snowmass White Paper

    SciTech Connect

    Akimov, D.; Bernstein, A.; BarbeauP.,; Barton, P. J.; Bolozdynya, A.; Cabrera-Palmer, B.; Cavanna, F.; Cianciolo, Vince; Collar, J.; Cooper, R. J.; Dean, D. J.; Efremenko, Yuri; Etenko, A.; Fields, N.; Foxe, M.; Figueroa-Feliciano, E.; Fomin, N.; Gallmeier, F.; Garishvili, I.; Gerling, M.; Green, M.; Greene, Geoffrey; Hatzikoutelis, A.; Henning, Reyco; Hix, R.; Hogan, D.; Hornback, D.; Jovanovic, I.; Hossbach, T.; Iverson, Erik B; Klein, S. R.; Khromov, A.; Link, J.; Louis, W.; Lu, W.; Mauger, C.; Marleau, P.; Markoff, D.; Martin, R. D.; Mueller, Paul Edward; Newby, J.; Orrell, John L.; O'Shaughnessy, C.; Penttila, Seppo; Patton, K.; Poon, A. W.; Radford, David C; Reyna, D.; Ray, H.; Scholberg, K.; Sosnovtsev, V.; Tayloe, R.; Vetter, K.; Virtue, C.; Wilkerson, J.; Yoo, J.; Yu, Chang-Hong

    2013-01-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, Tennessee, provides an intense flux of neutrinos in the few tens-of-MeV range, with a sharply-pulsed timing structure that is beneficial for background rejection. In this white paper, we describe how the SNS source can be used for a measurement of coherent elastic neutrino-nucleus scattering (CENNS), and the physics reach of different phases of such an experimental program (CSI: Coherent Scattering Investigations at the SNS).

  16. X-ray and neutron total scattering analysis of Hy·(Bi0.2Ca0.55Sr0.25)(Ag0.25Na0.75)Nb3O10·xH2O perovskite nanosheet booklets with stacking disorder

    SciTech Connect

    Metz, Peter; Koch, Robert; Cladek, Bernadette; Page, Katharine; Neuefeind, Joerg; Misture, Scott

    2016-05-23

    Ion-exchanged Aurivillius materials form perovskite nanosheet booklets wherein well-defined bi-periodic sheets, with ~11.5 Å thickness, exhibit extensive stacking disorder. The perovskite layer contents were defined initially using combined synchrotron X-ray and neutron Rietveld refinement of the parent Aurivillius structure. The structure of the subsequently ion-exchanged material, which is disordered in its stacking sequence, is analyzed using both pair distribution function (PDF) analysis and recursive method simulations of the scattered intensity. Combined X-ray and neutron PDF refinement of supercell stacking models demonstrates sensitivity of the PDF to both perpendicular and transverse stacking vector components. Further, hierarchical ensembles of stacking models weighted by a standard normal distribution are demonstrated to improve PDF fit over 1–25 Å. Recursive method simulations of the X-ray scattering profile demonstrate agreement between the real space stacking analysis and more conventional reciprocal space methods. The local structure of the perovskite sheet is demonstrated to relax only slightly from the Aurivillius structure after ion exchange.

  17. Secondary neutron spectrum from 250-MeV passively scattered proton therapy: Measurement with an extended-range Bonner sphere system

    PubMed Central

    Howell, Rebecca M.; Burgett, E. A.

    2014-01-01

    Purpose: Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire

  18. Secondary neutron spectrum from 250-MeV passively scattered proton therapy: Measurement with an extended-range Bonner sphere system

    SciTech Connect

    Howell, Rebecca M.; Burgett, E. A.

    2014-09-15

    Purpose: Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire

  19. Secondary neutron spectrum from 250-MeV passively scattered proton therapy: measurement with an extended-range Bonner sphere system.

    PubMed

    Howell, Rebecca M; Burgett, E A

    2014-09-01

    Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire energy range being measured, i.e., thermal to

  20. Structural and mechanical properties of cardiolipin lipid bilayers determined using neutron spin echo, small angle neutron and X-ray scattering, and molecular dynamics simulations

    DOE PAGES

    Pan, Jianjun; Cheng, Xiaolin; Sharp, Melissa; ...

    2014-10-29

    We report that the detailed structural and mechanical properties of a tetraoleoyl cardiolipin (TOCL) bilayer were determined using neutron spin echo (NSE) spectroscopy, small angle neutron and X-ray scattering (SANS and SAXS, respectively), and molecular dynamics (MD) simulations. We used MD simulations to develop a scattering density profile (SDP) model, which was then utilized to jointly refine SANS and SAXS data. In addition to commonly reported lipid bilayer structural parameters, component distributions were obtained, including the volume probability, electron density and neutron scattering length density.

  1. Structural and mechanical properties of cardiolipin lipid bilayers determined using neutron spin echo, small angle neutron and X-ray scattering, and molecular dynamics simulations

    SciTech Connect

    Pan, Jianjun; Cheng, Xiaolin; Sharp, Melissa; Ho, Chian-Sing; Khadka, Nawal; Katsaras, John

    2014-10-29

    We report that the detailed structural and mechanical properties of a tetraoleoyl cardiolipin (TOCL) bilayer were determined using neutron spin echo (NSE) spectroscopy, small angle neutron and X-ray scattering (SANS and SAXS, respectively), and molecular dynamics (MD) simulations. We used MD simulations to develop a scattering density profile (SDP) model, which was then utilized to jointly refine SANS and SAXS data. In addition to commonly reported lipid bilayer structural parameters, component distributions were obtained, including the volume probability, electron density and neutron scattering length density.

  2. Low energy neutron deuteron scattering to N3LO

    NASA Astrophysics Data System (ADS)

    Margaryan, Arman; Vanasse, Jared; Springer, Roxanne

    2015-10-01

    We calculate the next-to-next-to-next-to-leading order (N3LO) nd scattering amplitude in the framework of nonrelativistic pionless effective field theory (EFTπ/). This theory is only valid when the typical momentum exchange in the scattering is smaller then the mass of the pion. The power counting parameter for EFTπ/ is the ratio Q/Λπ /, where Q is the typical momentum exchange in the scattering and Λπ / is the EFTπ/ breakdown scale, Λπ / scattering at leading order requires summing an infinite set of diagrams. The first nonzero polarization-dependent observables occur at N2LO. At N3LO new 2-body forces appear, which introduce four new EFTπ/ coefficients. These coefficients are fixed by the 3PJ and 1P1 phase shifts of NN scattering. We find that these terms have an important impact. The results of this calculation at N3LO will be important for understanding spin polarization observables in nd scattering, in particular the longstanding Ay puzzle. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics, under Award Number DE-FG02-05ER41368.

  3. Dynamical theory applications to neutron scattering from periodic nanostructures

    NASA Astrophysics Data System (ADS)

    Ashkar, Rana

    The self-assembly of matter in nano-confinements is a potential cost-effective method for fabricating ultra-dense films of ordered nanomaterials. Non-destructively probing the depth-dependent lateral order in such films challenges conventional microscopy techniques, and the submicron size of a single confinement is impractical for scattering experiments. This problem can be overcome if the confining medium is made up of an array of identical confining cells, such as a diffraction grating, because scattering then appears at Bragg peaks. The caveat is that the periodicity of the sample amplifies dynamical scattering effects that are not accounted for in approximate scattering theories and a complete dynamical theory (DT) calculation becomes unavoidable. Unlike traditional diffraction techniques that measure in reciprocal space and must resolve individual Bragg peaks, the Spin-Echo Scattering Angle Measurement (SESAME) technique overcomes this resolution problem by Fourier transforming the scattering signal and directly measuring real-space density correlations. In addition, the technique allows access to length scales of interest (few-tens-of-nanometers to several-microns). The combination of DT and SESAME has been successfully tested on periodic nanostructures and has been implemented in the study of confined matter. The dynamical theory can also be used as a reference for studying the limits of validity of approximate theories (such as DWBA and POA) on periodic systems.

  4. Neutron scattering in concrete and wood: Part II--Oblique incidence.

    PubMed

    Facure, A; Silva, A X; Rivera, J C; Falcão, R C

    2008-01-01

    The knowledge of neutron reflection coefficients is of practical interest when projecting the shielding of radiotherapy rooms, since it is known that about 75% of the neutrons at the maze entrance of these rooms are scattered neutrons. In a previous paper, the energy spectra of photoneutrons were calculated, when reflected by ordinary, high-density concrete and wood barriers, using the MCNP5 code, considering normal incidence and neutron incident energies varying between 0.1 and 10 MeV. It was found that the mean energy of the reflected neutrons does not depend on the reflection angle and that these mean energies are lower in wood and barytes concrete, compared with ordinary concrete. In the present work, the simulation of neutron reflection coefficients were completed, considering the case when these particles do not collide frontally with the barriers, which constitute the radiotherapy room walls. Some simulations were also made to evaluate how neutron equivalent doses at the position of the room door is affected when the maze walls are lined with neutron absorbing materials, such as wood itself or borated polyethylene. Finally, capture gamma rays dose at the entrance of rooms with different maze lengths were also simulated. The results were discussed in the light of the albedo concepts presented in the literature and some of these results were confronted with others, finding good agreement between them.

  5. An automated analysis workflow for optimization of force-field parameters using neutron scattering data

    DOE PAGES

    Lynch, Vickie E.; Borreguero, Jose M.; Bhowmik, Debsindhu; ...

    2017-03-27

    Large-scale simulations and data analysis are often required to explain neutron scattering experiments to establish a connection between the fundamental physics at the nanoscale and data probed by neutrons. In order to perform simulations at experimental conditions it is critical to use correct force-field (FF) parameters which are unfortunately not available for most complex experimental systems. In this work, we have developed a workflow optimization technique to provide optimized FF parameters by comparing molecular dynamics (MD) to neutron scattering data. Here, we describe the workflow in detail by using an example system consisting of tRNA and hydrophilic nanodiamonds in amore » deuterated water (D2O) environment. Quasi-elastic neutron scattering (QENS) data show a faster motion of the tRNA in the presence of nanodiamond than without the ND. In order to compare the QENS and MD results quantitatively, a proper choice of FF parameters is necessary. We use an efficient workflow to optimize the FF parameters between the hydrophilic nanodiamond and water by comparing to the QENS data. Our results show that we can obtain accurate FF parameters by using this technique. The workflow can be generalized to other types of neutron data for FF optimization, such as vibrational spectroscopy and spin echo.« less

  6. Large-area proportional counter camera for the US National Small-Angle Neutron Scattering Facility

    SciTech Connect

    Abele, R.K.; Allin, G.W.; Clay, W.T.; Fowler, C.E.; Kopp, M.K.

    1980-01-01

    An engineering model of a multiwire position-sensitive proportional-counter (PSPC) was developed, tested, and installed at the US National Small-Angle Neutron Scattering Facility at ORNL. The PSPC is based on the RC-encoding and time-difference decoding method to measure the spatial coordinates of the interaction loci of individual scattered neutrons. The active area of the PSPC is 65 cm x 65 cm, and the active depth is 3.6 cm. The spatial uncertainty in both coordinates is approx. 1.0 cm (fwhm) for thermal neutrons; thus, a matrix of 64 x 64 picture elements is resolved. The count rate capability for randomly detected neutrons is 10/sup 4/ counts per second, with < 3% coincidence loss. The PSPC gas composition is 63% /sup 3/He, 32% Xe, and 5% CO/sub 2/ at an absolute pressure of approx. 3 x 10/sup 5/ Pa (3 atm). The detection efficiency is approx. 90% for the 0.475-nm (4.75-A) neutrons used in the scattering experiments.

  7. Investigation of phonon-like excitation in hydrated protein powders by neutron scattering

    NASA Astrophysics Data System (ADS)

    Chu, Xiang-Qiang (Rosie); Mamontov, Eugene; O'Neill, Hugh; Zhang, Qiu; Kolesnikov, Alexander

    2013-03-01

    Detecting the phonon dispersion relations in proteins is essential for understanding the intra-protein dynamical behavior. Such study has been attempted by X-ray in recent years. However, for such detections, neutrons have significant advantages in resolution and time-efficiency compare to X-rays. Traditionally the collective motions of atoms in protein molecules are hard to detect using neutrons, because of high incoherent scattering background from intrinsic hydrogen atoms in the protein molecules. The recent availability of a fully deuterated green fluorescent protein (GFP) synthesized by the Bio-deuteration Lab at ORNL opens new possibilities to probe collective excitations in proteins using inelastic neutron scattering. Using a direct time-of-flight Fermi chopper neutron spectrometer, we obtained a full map of the meV phonon-like excitations in the fully deuterated protein. The Q range of the observed excitations corresponds to the length scale close to the size of the secondary structures of proteins and reflects the collective intra-protein motions. Our results show that hydration of GFP seems to harden, not soften, the collective motions. This result is counterintuitive but in agreement with the observations by previous neutron scattering experiments. Sample preparation was supported by facilities operated by the Center for Structural Molecular Biology at ORNL which is supported by the U.S. DOE, Office of Science, Office of Biological and Environmental Research Project ERKP291.

  8. An automated analysis workflow for optimization of force-field parameters using neutron scattering data

    NASA Astrophysics Data System (ADS)

    Lynch, Vickie E.; Borreguero, Jose M.; Bhowmik, Debsindhu; Ganesh, Panchapakesan; Sumpter, Bobby G.; Proffen, Thomas E.; Goswami, Monojoy

    2017-07-01

    Large-scale simulations and data analysis are often required to explain neutron scattering experiments to establish a connection between the fundamental physics at the nanoscale and data probed by neutrons. However, to perform simulations at experimental conditions it is critical to use correct force-field (FF) parameters which are unfortunately not available for most complex experimental systems. In this work, we have developed a workflow optimization technique to provide optimized FF parameters by comparing molecular dynamics (MD) to neutron scattering data. We describe the workflow in detail by using an example system consisting of tRNA and hydrophilic nanodiamonds in a deuterated water (D2O) environment. Quasi-elastic neutron scattering (QENS) data show a faster motion of the tRNA in the presence of nanodiamond than without the ND. To compare the QENS and MD results quantitatively, a proper choice of FF parameters is necessary. We use an efficient workflow to optimize the FF parameters between the hydrophilic nanodiamond and water by comparing to the QENS data. Our results show that we can obtain accurate FF parameters by using this technique. The workflow can be generalized to other types of neutron data for FF optimization, such as vibrational spectroscopy and spin echo.

  9. Neutron inelastic-scattering cross sections of /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 239/Pu and /sup 240/Pu. [LMFBR

    SciTech Connect

    Smith, A.B.; Guenther, P.T.

    1982-01-01

    Differential-neutron-emission cross sections of /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 239/Pu and /sup 240/Pu are measured between approx. = 1.0 and 3.5 MeV with the angle and magnitude detail needed to provide angle-integrated emission cross sections to approx. < 3% accuracies. Emitted-neutron resolutions are quantitatively defined and vary from approx. = 0.1 to 0.35 MeV. The experimental results are corrected for fisson-neutron contributions to obtain pseudo-elastic-neutron-scattering cross sections which, together with the neutron total cross sections, define the non-elastic cross sections to within well specified energy resolutions. These results imply inelastic-neutron-scattering cross sections which are compared with comparable quantities derived from ENDF/B-V. Good general agreement is noted for /sup 232/Th, /sup 233/U, /sup 235/U and /sup 238/U inelastic-scattering values, poor agreement is observed for /sup 240/Pu, and a serious discrepancy exists in the case of /sup 239/Pu.

  10. Time reversal invariance violating and parity conserving effects in neutron-deuteron scattering

    SciTech Connect

    Song, Young-Ho; Gudkov, Vladimir; Lazauskas, Rimantas

    2011-08-15

    Time reversal invariance violating and parity conserving effects for low-energy elastic neutron-deuteron scattering are calculated for meson exchange and effective field theory type potentials in a distorted wave-born approximation using realistic hadronic wave functions, obtained by solving three-body Faddeev equations in configuration space.

  11. Neutron Coherent Scattering Length Determination With a Dual Non-Dispersive Sample

    SciTech Connect

    Abbas, Sohrab; Wagh, Apoorva G.; Loidl, R.; Lemmel, H.; Rauch, H.

    2011-07-15

    We report here a preliminary interferometric determination of neutron coherent scattering length b{sub C} for silicon using a dual non-dispersive sample. A large and exactly non-dispersive phase measured by this method can afford an order of magnitude improvement in the precision of b{sub C} determination to within a few parts in 10{sup 6}.

  12. A computer code for predicting gamma production cross sections by neutron inelastic scattering from light nuclei

    NASA Technical Reports Server (NTRS)

    George, M. C.

    1972-01-01

    Gamma-ray production cross section by the inelastic scattering of neutrons from light nuclei are considered. The applicability of optical model potential is discussed. Based on experimental data, a cascade approach is developed to calculate the inelastic gamma production cross sections. In the case of O-16 using computer code LINGAP in conjunction with ABACUS-2; results are compared with reported values.

  13. Applying the neutron scatter camera to treaty verification and warhead monitoring.

    SciTech Connect

    Cooper, Robert Lee; Gerling, Mark; Brennan, James S.; Mascarenhas, Nicholas; Mrowka, Stanley; Marleau, Peter

    2010-12-01

    The neutron scatter camera was originally developed for a range of SNM detection applications. We are now exploring the feasibility of applications in treaty verification and warhead monitoring using experimentation, maximum likelihood estimation method (MLEM), detector optimization, and MCNP-PoliMi simulations.

  14. A novel approach to neutron scattering instrumentation for probing multiscale dynamics in soft and biological matter

    SciTech Connect

    Mamontov, Eugene

    2016-06-29

    We present a concept and ray-tracing simulation results of a mechanical device that will enable inelastic neutron scattering measurements where the data at energy transfers from a few eV to several hundred meV can be collected in a single, gapless spectrum. Besides covering 5 orders of magnitude on the energy (time) scale, the device provides data over 2 orders of magnitude on the scattering momentum (length) scale in a single measurement. Such capabilities are geared primarily toward soft and biological matter, where the broad dynamical features of relaxation origin largely overlap with vibration features, thus necessitating gapless spectral coverage over several orders of magnitude in time and space. Furthermore, neutron scattering experiments with such a device are performed with a fixed neutron final energy, which enables measurements, with neutron energy loss in the sample, at arbitrarily low temperatures over the same broad spectral range. Lastly, this capability is also invaluable in biological and soft matter research, as the variable temperature dependence of different relaxation components allows their separation in the scattering spectra as a function of temperature.

  15. Application of Geant4 simulation for analysis of soil carbon inelastic neutron scattering measurements

    USDA-ARS?s Scientific Manuscript database

    Inelastic neutron scattering (INS) was applied to determine soil carbon content. Due to non-uniform soil carbon depth distribution, the correlation between INS signals with some soil carbon content parameter is not obvious; however, a proportionality between INS signals and average carbon weight per...

  16. Gate-opening effect in ZIF-8: the first experimental proof using inelastic neutron scattering

    DOE PAGES

    Casco, M. E.; Cheng, Y. Q.; Daemen, L. L.; ...

    2016-01-28

    In order to understand the behavior of industrial molecular separations, the gate-opening phenomenon in ZIFs are of paramount importance. We show for the first time using in situ inelastic neutron scattering (INS) the swinging of the -CH3 groups and the imidazolate linkers in the prototypical ZIF-8 and ZIF-8@AC hybrid materials upon exposure to mild N2 pressure.

  17. Gate-opening effect in ZIF-8: the first experimental proof using inelastic neutron scattering.

    PubMed

    Casco, M E; Cheng, Y Q; Daemen, L L; Fairen-Jimenez, D; Ramos-Fernández, E V; Ramirez-Cuesta, A J; Silvestre-Albero, J

    2016-03-04

    The gate-opening phenomenon in ZIFs is of paramount importance to understand their behavior in industrial molecular separations. Here we show for the first time using in situ inelastic neutron scattering (INS) the swinging of the -CH3 groups and the imidazolate linkers in the prototypical ZIF-8 and ZIF-8@AC hybrid materials upon exposure to mild N2 pressure.

  18. New Results on CaH2 Thermal Neutron Scattering Cross Sections

    SciTech Connect

    Serot, O.

    2005-05-24

    Calcium hydride (CaH2) is a compound of interest in the frame of a current research program on the transmutation of long-lived nuclear wastes. Since CaH2 is relatively stable in liquid sodium, it is one possible material that can be used for local moderation of the neutron spectrum in fast neutron reactors such as PHENIX. In order to describe the moderated region from Monte Carlo and/or deterministic calculations, thermal neutron scattering data are needed. In particular, an adequate treatment of the thermal inelastic scattering cross sections for bound hydrogen is requested. The present work aims at the determination of these data. The first step was the measurement of the phonon frequency spectrum, which was carried out on the three axis spectrometer of the Institut Laue Langevin in Grenoble (France). This phonon frequency spectrum has already been published and so only a brief description of this measurement will be given here. Then, from physical grounds, the acoustic mode has been weighted relative to the optical modes in order to treat Hydrogen atoms bound in CaH2. The S({alpha},{beta}) scattering laws have been generated for various temperatures using the NJOY code working in the incoherent approximation and the Gaussian approximation. The deduced incoherent elastic and incoherent inelastic cross sections are shown and discussed. These new thermal neutron scattering data will be proposed in the JEFF3.1 European library.

  19. Informing the improvement of forest products durability using small angle neutron scattering

    Treesearch

    Nayomi Plaza-Rodriguez; Sai Venkatesh Pingali; Shuo Qian; William T. Heller; Joseph E. Jakes

    2016-01-01

    A better understanding of how wood nanostructure swells with moisture is needed to accelerate the development of forest products with enhanced moisture durability. Despite its suitability to study nanostructures, small angle neutron scattering (SANS) remains an underutilized tool in forest products research. Nanoscale moisture-induced structural changes in intact and...

  20. Time-independent one-speed neutron transport equation with anisotropic scattering in absorbing media

    SciTech Connect

    Hangelbroek, R. J.

    1980-06-01

    This report treats the time-independent, one-speed neutron transport equation with anisotropic scattering in absorbing media. For nuclear gain operators existence and uniqueness of solutions to the half-space and finite-slab problems are proved in L/sub 2/-space. The formulas needed for explicit calculations are derived by the use of perturbation theory techniques.

  1. A novel approach to neutron scattering instrumentation for probing multiscale dynamics in soft and biological matter

    SciTech Connect

    Mamontov, Eugene

    2016-06-29

    We present a concept and ray-tracing simulation results of a mechanical device that will enable inelastic neutron scattering measurements where the data at energy transfers from a few eV to several hundred meV can be collected in a single, gapless spectrum. Besides covering 5 orders of magnitude on the energy (time) scale, the device provides data over 2 orders of magnitude on the scattering momentum (length) scale in a single measurement. Such capabilities are geared primarily toward soft and biological matter, where the broad dynamical features of relaxation origin largely overlap with vibration features, thus necessitating gapless spectral coverage over several orders of magnitude in time and space. Furthermore, neutron scattering experiments with such a device are performed with a fixed neutron final energy, which enables measurements, with neutron energy loss in the sample, at arbitrarily low temperatures over the same broad spectral range. Lastly, this capability is also invaluable in biological and soft matter research, as the variable temperature dependence of different relaxation components allows their separation in the scattering spectra as a function of temperature.

  2. A novel approach to neutron scattering instrumentation for probing multiscale dynamics in soft and biological matter

    DOE PAGES

    Mamontov, Eugene

    2016-06-29

    We present a concept and ray-tracing simulation results of a mechanical device that will enable inelastic neutron scattering measurements where the data at energy transfers from a few eV to several hundred meV can be collected in a single, gapless spectrum. Besides covering 5 orders of magnitude on the energy (time) scale, the device provides data over 2 orders of magnitude on the scattering momentum (length) scale in a single measurement. Such capabilities are geared primarily toward soft and biological matter, where the broad dynamical features of relaxation origin largely overlap with vibration features, thus necessitating gapless spectral coverage overmore » several orders of magnitude in time and space. Furthermore, neutron scattering experiments with such a device are performed with a fixed neutron final energy, which enables measurements, with neutron energy loss in the sample, at arbitrarily low temperatures over the same broad spectral range. Lastly, this capability is also invaluable in biological and soft matter research, as the variable temperature dependence of different relaxation components allows their separation in the scattering spectra as a function of temperature.« less

  3. A novel approach to neutron scattering instrumentation for probing multiscale dynamics in soft and biological matter

    NASA Astrophysics Data System (ADS)

    Mamontov, Eugene

    2016-09-01

    We present a concept and ray-tracing simulation of a mechanical device that will enable inelastic neutron scattering measurements where the data at energy transfers from a few μeV to several hundred meV can be collected in a single, gapless spectrum. Besides covering 5 orders of magnitude on the energy (time) scale, the device provides data over 2 orders of magnitude on the scattering momentum (length) scale in a single measurement. Such capabilities are geared primarily toward soft and biological matter, where the broad dynamical features of relaxation origin largely overlap with vibration features, thus necessitating gapless spectral coverage over several orders of magnitude in time and space. Furthermore, neutron scattering experiments with such a device are performed with a fixed neutron final energy, which enables measurements, with neutron energy loss in the sample, at arbitrarily low temperatures over the same broad spectral range. This capability is also invaluable in biological and soft matter research, as the variable temperature dependence of different relaxation components allows their separation in the scattering spectra as a function of temperature.

  4. a Technique to Calibrate Neutron-Proton Elastic Scattering Spin Observables Near 183 Mev

    NASA Astrophysics Data System (ADS)

    Bowyer, Theodore William

    Free neutron-proton scattering is one of the most fundamental reactions we can study in the field of nuclear physics, yet the n-p scattering data base is quite sparse. The data that does exist is often plagued by systematic uncertainties associated with the determination of beam and/or target polarizations. In contrast, there is an abundance of high quality, high statistics p-p elastic scattering data. We report on a technique which we have developed which exploits the high quality of the p-p data to calibrate n-p elastic scattering spin observables by simultaneous measurement of vec n-vec p and p-vec p elastic scattering by bombarding a polarized proton target with a mixed beam of polarized neutrons and protons. This technique has allowed us to calibrate the n-p elastic spin observables at 183 MeV: the beam and target analyzing powers A _{n}(theta_{p}),A _{p}(theta p), and the spin correlation coefficient, C_{NN}( theta_{p}). The mixed secondary beam was produced by bombarding a liquid deuterium target with a 200 MeV beam of polarized protons. The experiment was preformed in the Polarized Neutron Facility at the Indiana University Cyclotron Facility utilizing a left-right symmetric detection system, sensitive to both scattered protons and neutrons, and spanned the laboratory angular range of 24^circ to 62^circ. We identified free scattering events through a number of kinematic correlations. We compare our results to various phase shift calculations and potential models and examine the sensitivity of magnitude of various phase shifts results to the inclusion of our data into the n-p data base.

  5. Testing Monte Carlo Simulations for Neutron Scattering in MoNA

    NASA Astrophysics Data System (ADS)

    Hamann, A.; Garrett, S.; Seagren, T.; Taylor, N. E.; Rogers, W. F.; MoNA Collaboration

    2015-10-01

    Monte Carlo simulations provide an important tool for nuclear physics research, both in preparing for experiments, and in interpreting experimental data. The Modular Neutron Array (MoNA) and the Large area multi-Institutional Scintillator Array (LISA) are used in conjunction with the Sweeper Magnet and charged particle detector chamber at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University to study the properties of exotic, neutron-rich nuclei. We use simulations to model our BC408 scintillator detectors and extract physics results from experimental data. We have developed specific simulations in preparation for an experiment we will conduct at the Los Alamos Neutron Science Center (LANSCE), where we will direct a well-defined neutron beam onto a cluster of 16 MoNA detector bars and observe the scattering patterns of single neutrons. Simulations enable us to study the predicted light output generated by individual neutron scattering channels from Carbon and Hydrogen. The data we will generate in the LANSCE experiment will provide a large experimental database with which to test the reliability of our simulations. This is important since our understanding of nuclei far from stability is becoming increasingly reliant on simulations. this work supported by NSF Grants PHY-1101745 and PHY-1506402.

  6. Microstructural investigations on Russian reactor pressure vessel steels by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Ulbricht, A.; Boehmert, J.; Strunz, P.; Dewhurst, C.; Mathon, M.-H.

    The effect of radiation embrittlement has a high safety significance for Russian VVER reactor pressure vessel steels. Heats of base and weld metals of the as-received state, irradiated state and post-irradiation annealed state were investigated using small-angle neutron scattering (SANS) to obtain insight about the microstructural features caused by fast neutron irradiation. The SANS intensities increase in the momentum transfer range between 0.8 and 3 nm-1 for all the material compositions in the irradiated state. The size distribution function of the irradiation-induced defect clusters has a pronounced maximum at 1 nm in radius. Their content varies between 0.1 and 0.7 vol.% dependent on material composition and increases with the neutron fluence. The comparison of nuclear and magnetic scattering indicates that the defects differ in their composition. Thermal annealing reduces the volume fraction of irradiation defect clusters.

  7. Measurement of the angular distribution of neutron-proton scattering at 10 MeV

    SciTech Connect

    Haight, R.C.; Bateman, F.B.; Grimes, S.M.; Brient, C.E.; Massey, T.N.; Wasson, O.A.; Carlson, A.D.; Zhou, H.

    1995-12-31

    The relative angular distribution of neutrons scattered from protons was measured at an incident neutron energy of 10 MeV at the Ohio University Accelerator Laboratory. An array of 11 detector telescopes at laboratory angles of 0 to 60 degrees was used to detect recoil protons from neutron interactions with a CH{sub 2} (polypropylene) target. Data for 7 of these telescopes were obtained with one set of electronics and are presented here. These data, from 108 to 180 degrees for the center-of-mass scattering angles, have a small slope which agrees better with angular distributions predicted by the Arndt phase shifts than with the ENDF/B-VI angular distribution.

  8. The role of CP violating scatterings in baryogenesis—case study of the neutron portal

    SciTech Connect

    Baldes, Iason; Bell, Nicole F.; Millar, Alexander; Volkas, Raymond R.; Petraki, Kalliopi E-mail: n.bell@unimelb.edu.au E-mail: kpetraki@nikhef.nl

    2014-11-01

    Many baryogenesis scenarios invoke the charge parity (CP) violating out-of-equilibrium decay of a heavy particle in order to explain the baryon asymmetry. Such scenarios will in general also allow CP violating scatterings. We study the effect of these CP violating scatterings on the final asymmetry in a neutron portal scenario. We solve the Boltzmann equations governing the evolution of the baryon number numerically and show that the CP violating scatterings play a dominant role in a significant portion of the parameter space.

  9. Nanoscale Structure in AgSbTe2 Determined by Diffuse Elastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Specht, E. D.; Ma, J.; Delaire, O.; Budai, J. D.; May, A. F.; Karapetrova, E. A.

    2015-06-01

    Diffuse elastic neutron scattering measurements have confirmed that AgSbTe2 has a hierarchical structure, with defects on length scales from nanometers to microns. While scattering from this mesoscale structure is consistent with previously proposed structures in which Ag and Sb order on a NaCl lattice, more diffuse scattering from nanoscale structures suggests a structural rearrangement in which hexagonal layers form a combination of ( ABC), ( ABA), and ( AAB) polytypes. Consequently, the AgCrSe2 structure is the best-fitting model for the local atomic arrangements.

  10. A small angle neutron scattering study of mica based glass-ceramics with applications in dentistry

    NASA Astrophysics Data System (ADS)

    Kilcoyne, S. H.; Bentley, P. M.; Al-Jawad, M.; Bubb, N. L.; Al-Shammary, H. A. O.; Wood, D. J.

    2004-07-01

    We are currently developing machinable and load-bearing mica-based glass-ceramics for use in restorative dental surgery. In this paper we present the results of an ambient temperature small angle neutron scattering (SANS) study of several such ceramics with chemical compositions chosen to optimise machinability and strength. The SANS spectra are all dominated by scattering from the crystalline-amorphous phase interface and exhibit Q-4 dependence (Porod scattering) indicating that, on a 100Å scale, the surface of the crystals is smooth.

  11. Nanoscale structure in AgSbTe2 determined by diffuse elastic neutron scattering

    SciTech Connect

    Specht, Eliot D; Ma, Jie; Delaire, Olivier A; Budai, John D; May, Andrew F; Karapetrova, Evguenia A.

    2015-01-01

    Diffuse elastic neutron scattering measurements confirm that AgSbTe2 has a hierarchical structure, with defects on length scales from nanometers to microns. While scattering from mesoscale structure is consistent with previously-proposed structures in which Ag and Sb order on a NaCl lattice, more diffuse scattering from nanoscale structure suggests a structural rearrangement in which hexagonal layers form a combination of (ABC), (ABA), and (AAB) stacking sequences. The AgCrSe2 structure is the best-fitting model for the local atomic arrangements.

  12. Elastic neutron scattering studies at 96 MeV for transmutation.

    PubMed

    Osterlund, M; Blomgren, J; Hayashi, M; Mermod, P; Nilsson, L; Pomp, S; Ohrn, A; Prokofiev, A V; Tippawan, U

    2007-01-01

    Elastic neutron scattering from (12)C, (14)N, (16)O, (28)Si, (40)Ca, (56)Fe, (89)Y and (208)Pb has been studied at 96 MeV in the10-70 degrees interval, using the SCANDAL (SCAttered Nucleon Detection AssembLy) facility. The results for (12)C and (208)Pb have recently been published, while the data on the other nuclei are under analysis. The achieved energy resolution, 3.7 MeV, is about an order of magnitude better than for any previous experiment above 65 MeV incident energy. A novel method for normalisation of the absolute scale of the cross section has been used. The estimated normalisation uncertainty, 3%, is unprecedented for a neutron-induced differential cross section measurement on a nuclear target. Elastic neutron scattering is of utmost importance for a vast number of applications. Besides its fundamental importance as a laboratory for tests of isospin dependence in the nucleon-nucleon, and nucleon-nucleus, interaction, knowledge of the optical potentials derived from elastic scattering come into play in virtually every application where a detailed understanding of nuclear processes is important. Applications for these measurements are dose effects due to fast neutrons, including fast neutron therapy, as well as nuclear waste incineration and single event upsets in electronics. The results at light nuclei of medical relevance ((12)C, (14)N and (16)O) are presented separately. In the present contribution, results on the heavier nuclei are presented, among which several are of relevance to shielding of fast neutrons.

  13. Quasi-free Compton scattering and the polarizabilities of the neutron

    NASA Astrophysics Data System (ADS)

    Kossert, K.; Camen, M.; Wissmann, F.; Ahrens, J.; Annand, J. R. M.; Arends, H.-J.; Beck, R.; Caselotti, G.; Grabmayr, P.; Jahn, O.; Jennewein, P.; Levchuk, M. I.; L'vov, A. I.; McGeorge, J. C.; Natter, A.; Olmos de León, V.; Petrun'kin, V. A.; Rosner, G.; Schumacher, M.; Seitz, B.; Smend, F.; Thomas, A.; Weihofen, W.; Zapadtka, F.

    Differential cross-sections for quasi-free Compton scattering from the proton and neutron bound in the deuteron have been measured using the Glasgow/Mainz photon tagging spectrometer at the Mainz MAMI accelerator together with the Mainz [48]cm ;SPMOslash; × [64]cm NaI(Tl) photon detector and the Göttingen SENECA recoil detector. The data cover photon energies ranging from [200]MeV to [400]MeV at θLABγ = 136.2°. Liquid deuterium and hydrogen targets allowed direct comparison of free and quasi-free scattering from the proton. The neutron detection efficiency of the SENECA detector was measured via the reaction p(γ,π+n). The ``free'' proton Compton scattering cross-sections extracted from the bound proton data are in reasonable agreement with those for the free proton which gives confidence in the method to extract the differential cross-section for free scattering from quasi-free data. Differential cross-sections on the free neutron have been extracted and the difference of the electromagnetic polarizabilities of the neutron has been determined to be αn - βn = 9.8+/-3.6(stat)+2.1-1.1(syst)+/-2.2(model) in units of [10-4]fm3. In combination with the polarizability sum αn + βn = 15.2+/-0.5 deduced from photoabsorption data, the neutron electric and magnetic polarizabilities, αn = 12.5+/-1.8(stat)+1.1-0.6(syst)+/-1.1(model) and βn = 2.7+/-1.8(stat)+0.6-1.1(syst)+/-1.1(model) are obtained. The backward spin polarizability of the neutron was determined to be γ(n)π = (58.6+/-4.0)×10-4fm4.

  14. Expected total counts for the Self-Interrogation Neutron Resonance Densitometry measurements of spent nuclear fuel

    SciTech Connect

    Rossa, Riccardo; Borella, Alessandro; Van der Meer, Klaas; Labeau, Pierre-Etienne; Pauly, Nicolas

    2015-07-01

    The Self-Interrogation Neutron Resonance Densitometry (SINRD) is a passive neutron technique that aims at a direct quantification of {sup 239}Pu in spent fuel assemblies by measuring the attenuation of the neutron flux in the energy region close to the 0.3 eV resonance of {sup 239}Pu. The {sup 239}Pu mass is estimated by calculating the SINRD signature, that is the ratio between the neutron counts in the fast energy region and around the 0.3 eV resonance region. The SINRD measurement approach in this study consisted in introducing a small neutron detector in the central guide tube of a PWR 17x17 fuel assembly. In order to measure the neutron flux in the energy regions defined in the SINRD signature, different detector types were used. The response of a bare {sup 238}U fission chamber is considered for the determination of the fast neutron flux, while other thermal-epithermal detectors wrapped in neutron absorbers are envisaged to measure the neutron flux around the resonance region. This paper provides an estimation of the total neutron counts that can be achieved with the detector types proposed for the SINRD measurement. In the first section a set of detectors are evaluated in terms of total neutron counts and sensitivity to the {sup 239}Pu content, in order to identify the optimal measurement configuration for each detector type. Then a study is performed to increase the total neutron counts by increasing the detector size. The study shows that the highest total neutron counts are achieved by using either {sup 3}He or {sup 10}B proportional counters because of the high neutron efficiency of these detectors. However, the calculations indicate that the biggest contribution to the measurement uncertainty is due to the measurement of the fast neutron flux. Finally, similar sensitivity to the {sup 239}Pu content is obtained by using the different detector types for the measurement of the neutron flux close to the resonance region. Therefore, the total neutron counts

  15. On calibration of the response of liquid argon detectors to nuclear recoils using inelastic neutron scattering on 40Ar

    NASA Astrophysics Data System (ADS)

    Polosatkin, S.; Grishnyaev, E.; Dolgov, A.

    2014-10-01

    A method for measuring of ionization and scintillation yields in liquid argon from recoils with particular energy—8.2 keV—is proposed. The method utilizes a process of inelastic scattering of monoenergetic neutrons produced by fusion DD neutron generator. Features of kinematics of inelastic scattering result in a sufficient (fifteen times) increase in count rate of useful events relative to a traditional scheme using elastic scattering with the same recoil energy and comparable energy resolution.

  16. New evaluation of thermal neutron scattering libraries for light and heavy water

    NASA Astrophysics Data System (ADS)

    Marquez Damian, Jose Ignacio; Granada, Jose Rolando; Cantargi, Florencia; Roubtsov, Danila

    2017-09-01

    In order to improve the design and safety of thermal nuclear reactors and for verification of criticality safety conditions on systems with significant amount of fissile materials and water, it is necessary to perform high-precision neutron transport calculations and estimate uncertainties of the results. These calculations are based on neutron interaction data distributed in evaluated nuclear data libraries. To improve the evaluations of thermal scattering sub-libraries, we developed a set of thermal neutron scattering cross sections (scattering kernels) for hydrogen bound in light water, and deuterium and oxygen bound in heavy water, in the ENDF-6 format from room temperature up to the critical temperatures of molecular liquids. The new evaluations were generated and processable with NJOY99 and also with NJOY-2012 with minor modifications (updates), and with the new version of NJOY-2016. The new TSL libraries are based on molecular dynamics simulations with GROMACS and recent experimental data, and result in an improvement of the calculation of single neutron scattering quantities. In this work, we discuss the importance of taking into account self-diffusion in liquids to accurately describe the neutron scattering at low neutron energies (quasi-elastic peak problem). To improve modeling of heavy water, it is important to take into account temperature-dependent static structure factors and apply Sköld approximation to the coherent inelastic components of the scattering matrix. The usage of the new set of scattering matrices and cross-sections improves the calculation of thermal critical systems moderated and/or reflected with light/heavy water obtained from the International Criticality Safety Benchmark Evaluation Project (ICSBEP) handbook. For example, the use of the new thermal scattering library for heavy water, combined with the ROSFOND-2010 evaluation of the cross sections for deuterium, results in an improvement of the C/E ratio in 48 out of 65

  17. Early Years of Neutron Scattering and Its Manpower Development in Indonesia

    SciTech Connect

    Marsongkohadi

    2008-03-17

    In this paper I shall give a short history of the development of neutron scattering at the Research Centre for Nuclear Techniques (PPTN), in Bandung, and the early development of a more advanced facilities at the Neutron Scattering Laboratory (NSL BATAN), Centre of Technology for Nuclear Industrial Materials, in Serpong. The first research reactor in Indonesia was the TRIGA MARK II in Bandung, which became operational in 1965, with a power of 250 KW, upgraded to 1 MW in 1971, and to 2 MW in 2000. The neutron scattering activities was started in 1967, with the design and construction of the first powder diffractometer, and put in operation in 1970. It was followed by the second instrument, the filter detector spectrometer built in 1975 in collaboration with the Bhabha Atomic Research Centre (BARC), India. A powder diffractometer for magnetic studies was built in 1980, and finally, a modification of the filter detector spectrometer to measure textures was made in 1986. A brief description of the design and construction of the instruments, and a highlight of some research topics will be presented. Early developments of neutron scattering activities at the 30 MW, RSG-GAS reactor in Serpong in choosing suitable research program, which will be mainly centred around materials testing/characterization, and materials/condensed matter researches has been agreed. Instrument planning and layout which were appropriate to carry out the program had been decided. Manpower development for the neutron scattering laboratory is a severe problem. The efforts to overcome this problem has been solved. International Cooperation through workshops and on the job trainings also support the supply of qualified manpower.

  18. Realizing total reciprocity violation in the phase for photon scattering.

    PubMed

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-02-22

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices.

  19. Realizing total reciprocity violation in the phase for photon scattering

    PubMed Central

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-01-01

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices. PMID:28225031

  20. Realizing total reciprocity violation in the phase for photon scattering

    NASA Astrophysics Data System (ADS)

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-02-01

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices.