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Sample records for neutron reflectometry study

  1. Isotope-Identifying neutron reflectometry

    SciTech Connect

    Nikitenko, Yu. V. Petrenko, A. V.; Gundorin, N. A.; Gledenov, Yu. M.; Aksenov, V. L.

    2015-07-15

    The possibilities of an isotope-indentifying study of layered structures in different regimes of a neutron wave field are considered. The detection of specularly reflected neutrons and secondary radiation (caused by neutron capture) in the form of charged particles, γ quanta, and nuclear fission fragments, as well as neutrons spin-flipped in a noncollinear magnetic field and on nuclei of elements with spin, makes it possible to implement isotope-indentifying neutron reflectometry.

  2. Fibronectin adsorption studied using neutron reflectometry and complementary techniques

    NASA Astrophysics Data System (ADS)

    Al-Jawad, M.; Fragneto, G.; Liu, J.; Chang, S. R.; Clarkson, B.

    2009-10-01

    In implantology it is known that fibronectin affects cell-substrate adhesion, consequently, the structure and composition of the initially adsorbed fibronectin layer to a large extent determines the biological response to a biomaterial implanted into the body. In this study we have used neutron reflectometry and quartz-crystal microbalance with dissipation to investigate the amount of fibronectin adsorbed, the layer density, thickness and structure of films adsorbed to polished silicon oxide surfaces. We have cultured MG63 osteoblast-like cells on surfaces coated and uncoated with fibronectin and monitored the cellular response to these surfaces. The results show that at fibronectin concentrations in the range 0.01 to 0.1mg/ml a single highly hydrated layer of fibronectin approximately 40-50Å in thickness adsorbs to a polished silicon oxide surface and is likely to correspond to one diffuse monolayer of fibronectin arranged side-on. Cells cultured on this fibronectin layer have dramatically different morphology and growth to those grown on bare surfaces. Using a model silicon oxide surface has enabled us to study the substrate/protein interface, together with the impact of a fibronectin layer on the cellular response using consistent experimental conditions across a unique set of experimental techniques.

  3. Mouse fibroblast cell adhesion studied by neutron reflectometry.

    PubMed

    Smith, Hillary L; Hickey, Joseph; Jablin, Michael S; Trujillo, Antoinette; Freyer, James P; Majewski, Jaroslaw

    2010-03-01

    Neutron reflectometry (NR) was used to examine live mouse fibroblast cells adherent on a quartz substrate in a deuterated phosphate-buffered saline environment at room temperature. These measurements represent the first, to our knowledge, successful visualization and quantization of the interface between live cells and a substrate with subnanometer resolution using NR. NR data, attributable to the adhesion of live cells, were observed and compared with data from pure growth medium. Independently of surface cell density, the average distance between the center of the cell membrane region and the quartz substrate was determined to be approximately 180 A. The membrane region ( approximately 80 A thick) contains the membranes of cells that are inhomogeneously distributed or undulating, likely conforming to the nonplanar geometry of the supporting adherence proteins. A second region of cell membranes at a greater distance from the substrate was not detectable by NR due to the resolution limits of the technique employed. Attachment of the live cell samples was confirmed by interaction with both distilled water and trypsin. Distinct changes in the NR data after exposure indicate the removal of cells from the substrate.

  4. Temperature-controlled neutron reflectometry sample cell suitable for study of photoactive thin films

    SciTech Connect

    Yager, Kevin G.; Tanchak, Oleh M.; Barrett, Christopher J.; Watson, Mike J.; Fritzsche, Helmut

    2006-04-15

    We describe a novel cell design intended for the study of photoactive materials using neutron reflectometry. The cell can maintain sample temperature and control of ambient atmospheric environment. Critically, the cell is built with an optical port, enabling light irradiation or light probing of the sample, simultaneous with neutron reflectivity measurements. The ability to measure neutron reflectivity with simultaneous temperature ramping and/or light illumination presents unique opportunities for measuring photoactive materials. To validate the cell design, we present preliminary results measuring the photoexpansion of thin films of azobenzene polymer.

  5. Neutron Reflectometry Studies Define Prion Protein N-terminal Peptide Membrane Binding

    PubMed Central

    Le Brun, Anton P.; Haigh, Cathryn L.; Drew, Simon C.; James, Michael; Boland, Martin P.; Collins, Steven J.

    2014-01-01

    The prion protein (PrP), widely recognized to misfold into the causative agent of the transmissible spongiform encephalopathies, has previously been shown to bind to lipid membranes with binding influenced by both membrane composition and pH. Aside from the misfolding events associated with prion pathogenesis, PrP can undergo various posttranslational modifications, including internal cleavage events. Alpha- and beta-cleavage of PrP produces two N-terminal fragments, N1 and N2, respectively, which interact specifically with negatively charged phospholipids at low pH. Our previous work probing N1 and N2 interactions with supported bilayers raised the possibility that the peptides could insert deeply with minimal disruption. In the current study we aimed to refine the binding parameters of these peptides with lipid bilayers. To this end, we used neutron reflectometry to define the structural details of this interaction in combination with quartz crystal microbalance interrogation. Neutron reflectometry confirmed that peptides equivalent to N1 and N2 insert into the interstitial space between the phospholipid headgroups but do not penetrate into the acyl tail region. In accord with our previous studies, interaction was stronger for the N1 fragment than for the N2, with more peptide bound per lipid. Neutron reflectometry analysis also detected lengthening of the lipid acyl tails, with a concurrent decrease in lipid area. This was most evident for the N1 peptide and suggests an induction of increased lipid order in the absence of phase transition. These observations stand in clear contrast to the findings of analogous studies of Ab and α-synuclein and thereby support the possibility of a functional role for such N-terminal fragment-membrane interactions. PMID:25418300

  6. Deuteration in Biological Neutron Reflectometry.

    PubMed

    Heinrich, Frank

    2016-01-01

    Neutron reflectometry (NR) is uniquely positioned in structural biology, because of its ability to characterize biomolecular interfacial architectures like lipid membranes and membrane-associated proteins nondestructively and in their native environment. Mimicking biological processes, samples can be manipulated and their structural response can be measured. Specific deuteration is an integral part of biological NR as it is essential for resolving, for example, individual components of membrane-bound protein-protein complexes. Data analysis techniques have been developed in the past decade that extract the maximum structural detail from reflectivity data obtained from samples with complex deuteration schemes while avoiding overinterpretation. This is achieved by employing robust methods for the determination of modeling uncertainties. Integrative modeling approaches for NR are emerging as an essential part of the technique. PMID:26791980

  7. An X-ray and neutron reflectometry study of ‘PEG-like’ plasma polymer films

    PubMed Central

    Menzies, Donna J.; Nelson, Andrew; Shen, Hsin-Hui; McLean, Keith M.; Forsythe, John S.; Gengenbach, Thomas; Fong, Celesta; Muir, Benjamin W.

    2012-01-01

    Plasma-enhanced chemical vapour-deposited films of di(ethylene glycol) dimethyl ether were analysed by a combination of X-ray photoelectron spectroscopy, atomic force microscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), X-ray and neutron reflectometry (NR). The combination of these techniques enabled a systematic study of the impact of plasma deposition conditions upon resulting film chemistry (empirical formula), mass densities, structure and water solvation, which has been correlated with the films' efficacy against protein fouling. All films were shown to contain substantially less hydrogen than the original monomer and absorb a vast amount of water, which correlated with their mass density profiles. A proportion of the plasma polymer hydrogen atoms were shown to be exchangeable, while QCM-D measurements were inaccurate in detecting associated water in lower power films that contained loosely bound material. The higher protein resistance of the films deposited at a low load power was attributed to its greater chemical and structural similarity to that of poly(ethylene glycol) graft surfaces. These studies demonstrate the utility of using X-ray and NR analysis techniques in furthering the understanding of the chemistry of these films and their interaction with water and proteins. PMID:21957120

  8. Adsorption of cationic polyacrylamide at the cellulose-liquid interface: a neutron reflectometry study.

    PubMed

    Su, Jielong; Garvey, Christopher J; Holt, Stephen; Tabor, Rico F; Winther-Jensen, Bjorn; Batchelor, Warren; Garnier, Gil

    2015-06-15

    The layer thickness and density of high molecular weight cationic polyacrylamide (CPAM) adsorbed at the cellulose-water interface was quantified by neutron reflectometry. The thickness of a full monolayer of CPAM of constant molecular weight (13 MD) but different charge densities, adsorbed with or without NaCl (10(-3) M), was studied. Thin cellulose films (40±7 Å) of roughness <10 Å were produced by spin coating a cellulose acetate-acetone solution and regenerating by alkaline hydrolysis. Film smoothness was greatly improved by controlling the concentration of cellulose acetate (0.13 wt%) and the hydrolysis time in sodium methoxide. The adsorption thickness of CPAM (40% charge 13 MD) at the solid-D2O interface was 43±4 Å on cellulose and 13±2 Å on silicon, an order of magnitude smaller than the CPAM radius of gyration. At constant molecular weight, the thickness of the CPAM layer adsorbed on cellulose increases with polymer charge density (10±1 Å at 5%). Addition of 10(-3) M NaCl decreased the thickness of CPAM layer already adsorbed on cellulose. However, the adsorption layer on cellulose of a CPAM solution equilibrated in 10(-3) M NaCl is much thicker (89±11 Å for 40% CPAM). For high molecular weight CPAMs adsorbed from solution under constant conditions, the adsorption layer can be varied by 1 order of magnitude via control of the variables affecting electrostatic intra- and inter-polymer chain interactions.

  9. Polarized neutron reflectometry study of thin Fe films prepared on V (100)

    NASA Astrophysics Data System (ADS)

    Liu, Y. T.; Fritzsche, H.; Hauschild, J.; Maletta, H.

    2004-07-01

    The magnetic properties of ultrathin Fe (100) films were investigated by polarized neutron reflectometry (PNR). Fe films with different thicknesses from 1 to 3nm were prepared by Molecular Beam Epitaxy (MBE) on a V buffer layer, which was deposited on a MgO (100) single crystal. In order to avoid oxidation the Fe films were covered with V capping layers. During the preparation process the growth of the films was monitored by low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Combining the information obtained from PNR with X-ray reflectometry (XRR), the thicknesses of the Fe and V layers were determined precisely. From PNR measurements the absolute value of the magnetization of the films could be determined by fitting the spin-up and spin-down neutron reflectivities separately. The magnetic moments of the Fe films show a perfect linear dependence on the film thickness tFe. The fitting line intersects the abscissa at tFe=(0.1+/-0.01)nm. This means that the magnetic properties of the two V/Fe interfaces show up as a constant reduction of the magnetic moment equal to an Fe bulk layer of thickness tFe=(0.1+/-0.01)nm. Also to be corresponded to.

  10. X-ray and neutron reflectometry study of glow-discharge plasma polymer films.

    PubMed

    Nelson, Andrew; Muir, Benjamin W; Oldham, James; Fong, Celesta; McLean, Keith M; Hartley, Patrick G; Oiseth, Sofia K; James, Michael

    2006-01-01

    Radio-frequency glow-discharge plasma polymer thin films of allylamine (AA) and hexamethyldisiloxane (HMDSO) were prepared on silicon wafers and analyzed by a combination of X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray reflectometry (XRR), and neutron reflectometry (NR). AFM and XRR measurements revealed uniform, smooth, defect-free films of 20-30 nm thickness. XPS measurements gave compositional data on all elements in the films with the exception of hydrogen. In combination with XRR and NR, the film composition and mass densities (1.46 and 1.09 g cm(-)(3) for AA and HMDSO, respectively) were estimated. Further NR measurements were conducted with the AA and HMDSO films in contact with water at neutral pH. Three different H(2)O/D(2)O mixtures were used to vary the contrast between the aqueous phase and the polymer. The amount of water penetrating the film, as well as the number of labile protons present, was determined. The AA film in contact with water was found to swell by approximately 5%, contain approximately 3% water, and have approximately 24% labile protons. The HDMSO polymer was found to have approximately 6% labile protons, no thickness increase when in contact with water, and essentially no solvent penetration into the film. The difference in the degree of proton exchange within the films was attributed to the substantially different surface and bulk chemistries of the two films. PMID:16378459

  11. Deuterium Labeling Strategies for Creating Contrast in Structure-Function Studies of Model Bacterial Outer Membranes Using Neutron Reflectometry.

    PubMed

    Le Brun, Anton P; Clifton, Luke A; Holt, Stephen A; Holden, Peter J; Lakey, Jeremy H

    2016-01-01

    Studying the outer membrane of Gram-negative bacteria is challenging due to the complex nature of its structure. Therefore, simplified models are required to undertake structure-function studies of processes that occur at the outer membrane/fluid interface. Model membranes can be created by immobilizing bilayers to solid supports such as gold or silicon surfaces, or as monolayers on a liquid support where the surface pressure and fluidity of the lipids can be controlled. Both model systems are amenable to having their structure probed by neutron reflectometry, a technique that provides a one-dimensional depth profile through a membrane detailing its thickness and composition. One of the strengths of neutron scattering is the ability to use contrast matching, allowing molecules containing hydrogen and those enriched with deuterium to be highlighted or matched out against the bulk isotopic composition of the solvent. Lipopolysaccharides, a major component of the outer membrane, can be isolated for incorporation into model membranes. Here, we describe the deuteration of lipopolysaccharides from rough strains of Escherichia coli for incorporation into model outer membranes, and how the use of deuterated materials enhances structural analysis of model membranes by neutron reflectometry.

  12. Deuterium Labeling Strategies for Creating Contrast in Structure-Function Studies of Model Bacterial Outer Membranes Using Neutron Reflectometry.

    PubMed

    Le Brun, Anton P; Clifton, Luke A; Holt, Stephen A; Holden, Peter J; Lakey, Jeremy H

    2016-01-01

    Studying the outer membrane of Gram-negative bacteria is challenging due to the complex nature of its structure. Therefore, simplified models are required to undertake structure-function studies of processes that occur at the outer membrane/fluid interface. Model membranes can be created by immobilizing bilayers to solid supports such as gold or silicon surfaces, or as monolayers on a liquid support where the surface pressure and fluidity of the lipids can be controlled. Both model systems are amenable to having their structure probed by neutron reflectometry, a technique that provides a one-dimensional depth profile through a membrane detailing its thickness and composition. One of the strengths of neutron scattering is the ability to use contrast matching, allowing molecules containing hydrogen and those enriched with deuterium to be highlighted or matched out against the bulk isotopic composition of the solvent. Lipopolysaccharides, a major component of the outer membrane, can be isolated for incorporation into model membranes. Here, we describe the deuteration of lipopolysaccharides from rough strains of Escherichia coli for incorporation into model outer membranes, and how the use of deuterated materials enhances structural analysis of model membranes by neutron reflectometry. PMID:26791981

  13. Early stages of oxidative stress-induced membrane permeabilization: a neutron reflectometry study.

    PubMed

    Smith, Hillary L; Howland, Michael C; Szmodis, Alan W; Li, Qijuan; Daemen, Luke L; Parikh, Atul N; Majewski, Jaroslaw

    2009-03-18

    Neutron reflectometry was used to probe in situ the structure of supported lipid bilayers at the solid-liquid interface during the early stages of UV-induced oxidative degradation. Single-component supported lipid bilayers composed of gel phase, dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and fluid phase, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), phospholipids were exposed to low-dose oxidative stress generated by UV light and their structures were examined by neutron reflectometry. An interrupted illumination mode, involving exposures in 15 min increments with 2 h intervals between subsequent exposures, and a continuous mode involving a single 60 (or 90) min exposure period were employed. In both cases, pronounced differences in the structure of the lipid bilayer after exposure were observed. Interrupted exposure led to a substantial decrease in membrane coverage but preserved its total thickness at reduced scattering length densities. These results indicate that the initial phase during UV-induced membrane degradation involves the formation of hydrophilic channels within the membrane. This is consistent with the loss of some lipid molecules we observe and attendant reorganization of residual lipids forming hemimicellar edges of the hydrophilic channels. In contrast, continuous illumination produced a graded interface of continuously varied scattering length density (and hence hydrocarbon density) extending 100-150 A into the liquid phase. Exposure of a DPPC bilayer to UV light in the presence of a reservoir of unfused vesicles showed low net membrane disintegration during oxidative stress, presumably because of surface back-filling from the bulk reservoir. Chemical evidence for membrane degradation was obtained by mass spectrometry and Fourier transform infrared spectroscopy. Further evidence for the formation of hydrophilic channels was furnished by fluorescence microscopy and imaging ellipsometry data.

  14. Early Stages of Oxidative Stress-Induced Membrane Permeabilization: A Neutron Reflectometry Study

    PubMed Central

    Smith, Hillary L.; Howland, Michael C.; Szmodis, Alan W.; Li, Qijuan; Daemen, Luke L.; Parikh, Atul N.; Majewski, Jaroslaw

    2009-01-01

    Neutron reflectometry was used to probe in situ the structure of supported lipid bilayers at the solid–liquid interface during the early stages of UV-induced oxidative degradation. Single-component supported lipid bilayers composed of gel phase, dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and fluid phase, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), phospholipids were exposed to low-dose oxidative stress generated by UV light and their structures were examined by neutron reflectometry. An interrupted illumination mode, involving exposures in 15 min increments with 2 h intervals between subsequent exposures, and a continuous mode involving a single 60 (or 90) min exposure period were employed. In both cases, pronounced differences in the structure of the lipid bilayer after exposure were observed. Interrupted exposure led to a substantial decrease in membrane coverage but preserved its total thickness at reduced scattering length densities. These results indicate that the initial phase during UV-induced membrane degradation involves the formation of hydrophilic channels within the membrane. This is consistent with the loss of some lipid molecules we observe and attendant reorganization of residual lipids forming hemimicellar edges of the hydrophilic channels. In contrast, continuous illumination produced a graded interface of continuously varied scattering length density (and hence hydrocarbon density) extending 100–150 Å into the liquid phase. Exposure of a DPPC bilayer to UV light in the presence of a reservoir of unfused vesicles showed low net membrane disintegration during oxidative stress, presumably because of surface back-filling from the bulk reservoir. Chemical evidence for membrane degradation was obtained by mass spectrometry and Fourier transform infrared spectroscopy. Further evidence for the formation of hydrophilic channels was furnished by fluorescence microscopy and imaging ellipsometry data. PMID:19275260

  15. Steric Effects in Ionic Pairing and Polyelectrolyte Interdiffusion within Multilayered Films: A Neutron Reflectometry Study

    SciTech Connect

    Xu, Li; Ankner, John Francis; Sukhishvili, Prof. Svetlana A.

    2011-01-01

    Using a series of polycations synthesized by atom transfer radical polymerization (ATRP), we investigate the effects of the polymer charge density and hydrophobicity on salt-induced interdiffusion of polymer layers within polyelectrolyte multilayer (PEM) films. Polycations with two distinct hydrophobicities and various quaternization degrees (QPDMA and QPDEA) were derived from parent polymers of matched molecular weights poly(2-(dimethylamino)ethyl methacrylate) (PDMA) and poly(2-(diethylamino)ethyl methacrylate) (PDEA) by quaternization with either methyl or ethyl sulfate. Multilayers of these polycations with polystyrene sulfonate (PSS) were assembled in low-salt conditions, and annealed in NaCl solutions to induce layer intermixing. As revealed by neutron reflectometry (NR), polycations with lower charge density resulted in a faster decay of film structure with distance from the substrate. Interestingly, when comparing polymer mobility in QPDEA/PSS and QPDMA/PSS films, layer intermixing was faster in the case of more hydrophobic QPDEA as compared to QPDMA, because of the weaker ionic pairing (due to the presence of a bulky ethyl spacer) between QPDEA and PSS.

  16. Polarized neutron reflectometry in high magnetic fields

    SciTech Connect

    Fritzsche, H.

    2005-11-15

    A simple method is described to maintain the polarization of a neutron beam on its way through the large magnetic stray fields produced by a vertical field of a cryomagnet with a split-coil geometry. The two key issues are the proper shielding of the neutron spin flippers and an additional radial field component in order to guide the neutron spin through the region of the null point (i.e., point of reversal for the vertical field component). Calculations of the neutron's spin rotation as well as polarized neutron reflectometry experiments on an ErFe{sub 2}/DyFe{sub 2} multilayer show the perfect performance of the used setup. The recently commissioned cryomagnet M5 with a maximum vertical field of up to 7.2 T in asymmetric mode for polarized neutrons and 9 T in symmetric mode for unpolarized neutrons was used on the C5 spectrometer in reflectometry mode, at the NRU reactor in Chalk River, Canada.

  17. Neutron reflectometry and spectroscopic ellipsometry studies of cross-linked poly(dimethylsiloxane) after irradiation at 172 nm.

    PubMed

    Graubner, Vera-Maria; Clemens, Daniel; Gutberlet, Thomas; Kötz, Rüdiger; Lippert, Thomas; Nuyken, Oskar; Schnyder, Bernhard; Wokaun, Alexander

    2005-09-13

    Poly(dimethylsiloxane) (PDMS) was irradiated under ambient conditions in air with a Xe2-excimer lamp. The formation of atomic oxygen and ozone during irradiation in air by V-UV photons results in the transformation of PDMS to silicon oxide. The irradiated surfaces were studied by spectroscopic ellipsometry and neutron reflectometry. The measurements revealed the formation of a rough, i.e., between 11 and 20 nm, oxidized surface layer and a decrease of the total layer thickness. The thickness of the oxidized layer decreased for a given PDMS thickness when the polymer was irradiated for longer times and/or higher intensities. The composition of the oxidized layer after irradiation was not uniform through the layer and consisted of a mixture of original polymer and silicon bonded to three or four oxygen atoms (SiOx). The refractive index n determined by ellipsometry reaches a value similar to values reported for SiO2.

  18. Enhanced Magnetism in Field-Cooled [Ni80Fe20/Mn]3 Multilayers Studied Using Polarized Neutron Reflectometry

    NASA Astrophysics Data System (ADS)

    Uilhoorn, W.; Callori, S. J.; Cortie, D. L.; Su, H.-C.; Khaydukov, Y.; Lin, K.-W.; Klose, F.

    2016-04-01

    Here, the interfacial magnetic coupling in an exchange biased [Ni80Fe20/Mn]3 multilayer system has been studied using polarized neutron reflectometry. Previous results on this system indicate the importance of the coupling between the Fe-Mn and Ni-Mn orbitals at the layer interfaces. Magnetic depth profiles of the multilayer were measured at low temperatures under field-cooled and zero-field-cooled conditions. While no definitive interfacial state was found, a magnetic moment enhancement of roughly 20-30% in the applied field direction was observed throughout the bulk of the NiFe layers in the field-cooled state as compared to the zero-field-cooled measurements. The origin of this enhancement also likely stems from Fe-Mn and Ni-Mn orbital coupling, but due to the interfacial roughnesses of the sample, the areas where this coupling plays an important role is no longer confined to the interface.

  19. Neutron-reflectometry study of alcohol adsorption on various DLC coatings

    NASA Astrophysics Data System (ADS)

    Kalin, M.; Simič, R.; Hirayama, T.; Geue, T.; Korelis, P.

    2014-01-01

    Diamond-like carbon (DLC) coatings are notable for their excellent tribological properties. Our understanding of the lubrication of DLC coatings has improved drastically over the past decade. However, only a few details are known about the properties of the adsorbed layers on DLC, which crucially affect their tribological properties under lubricated conditions. In this work we used neutron reflectometry to determine the thickness and the density of adsorbed layers of alcohol molecules on several different types of DLC coatings, i.e., non-hydrogenated (a-C) and hydrogenated, of which both non-doped (a-C:H) and doped (a-C:H:F and a-C:H:Si) coatings were used. The results showed that a 0.9-nm-thick and relatively dense (≈45%) layer of alcohol adsorbed on the a-C coating. In contrast, no adsorption layer was found on the a-C:H, confirming the important role of hydrogen, which predominantly acts as a dangling-bond passivation source and affects the reactivity and tribochemistry of DLC coatings. The incorporation of F into a DLC coating also did not cause an increase in the adsorption ability with respect to alcohol molecules. On the contrary, the incorporation of Si increased the reactivity of the DLC coating so that a 1.3-nm-thick alcohol layer with a 35% bulk density was detected on the surface. We also discuss the very good agreement of the current results with the surface energy of selected coatings found in these experiments.

  20. Chemical Depth Profiling from Neutron Reflectometry

    SciTech Connect

    Tuncay Aktosun

    2006-03-21

    The material profile of a thin film can be analyzed by placing the film on a substrate and by sending a neutron beam onto it at various angles of incidence. Technically, the scattering length density of the film needs to be determined as a function of depth. A reflectometer is used to measure the amount of reflection (reflectivity) as a function of the angle of incidence. Mathematically, this is equivalent to sending the neutron beam onto the film at every energy but at a fixed angle of incidence. The film profile needs to be recovered from the measured reflectivity data. Unfortunately, the unique recovery is impossible, and many distinct unrelated profiles may correspond to the same reflectivity data. In our DOE/EPSCoR sponsored research, we have developed an analytical method to uniquely recover the profile of a thin film from the measured reflectivity data. We have shown that by taking reflectivity measurements with two different substrates, one can uniquely determine the film profile. Previously, it was known that one could uniquely recover the profile by taking reflectivity measurements with three different substrates, and our findings indicate that the same goal can be accomplished by using fewer measurements. At Mississippi State University we started an informal weekly seminar (called ''the reflectometry meeting'') at to attract various undergraduate and graduate students into the field. There were about 3 undergraduate students, 6 graduate students, and 2 faculty members attending these seminars. The PI has collaborated with Dr. Norm Berk at National Institute of Standards and Technology (NIST) on various aspects of neutron reflectometry, from which various interesting problems of theoretical and practical importance have arisen. One of these problems is closely related to the important mathematical problem known as analytic extrapolation. Under appropriate conditions (known to hold in neutron reflectometry), the reflection data taken in a finite interval

  1. Polarized Neutron Reflectometry of Nickel Corrosion Inhibitors.

    PubMed

    Wood, Mary H; Welbourn, Rebecca J L; Zarbakhsh, Ali; Gutfreund, Philipp; Clarke, Stuart M

    2015-06-30

    Polarized neutron reflectometry has been used to investigate the detailed adsorption behavior and corrosion inhibition mechanism of two surfactants on a nickel surface under acidic conditions. Both the corrosion of the nickel surface and the structure of the adsorbed surfactant layer could be monitored in situ by the use of different solvent contrasts. Layer thicknesses and roughnesses were evaluated over a range of pH values, showing distinctly the superior corrosion inhibition of one negatively charged surfactant (sodium dodecyl sulfate) compared to a positively charged example (dodecyl trimethylammonium bromide) due to its stronger binding interaction with the surface. It was found that adequate corrosion inhibition occurs at significantly less than full surface coverage.

  2. Neutron reflectometry study on an interface of octane and D 2O at low surfactant (C 10E 4) concentration

    NASA Astrophysics Data System (ADS)

    Jeng, U.; Esibov, L.; Crow, M. L.; Steyerl, A.

    1996-02-01

    We study the surface and interface roughness of a two-liquid film system using neutron reflectometry. The middle phase and bottom phase are extracted from a three-phase microemulsion containing 2 wt% non-ionic surfactant C 10E 4, 81 wt% D 2O and 17 wt% octane (C 8H 18). The system is formed by spreading a few drops of the middle phase of the microemulsion on the bottom phase of the microemulsion. The middle phase does not wet the bottom phase, but demixes to form a top octane-water mixture layer with a thickness of ∼ 580 Å. The mean surface roughness of the system is found to be 7 Å but the data are insensitive to interface roughness. An extended capillary wave model for a two-liquid-film system is derived to account for the coupling between the surface and interface. The dispersion relation yields two fundamental modes. In a calculation of mean-square roughness (< ζ2> 1/2) a high- k-cutoff is needed to account for non-linear terms in the Navier-Stokes equation. A low- k cutoff is also needed to avoid a “slip phenomenon” at the interface, which characterizes one of the modes. It turns out that for the parameters of our experiment the narrowing of k region is so significant that the mode causing the slip is strongly suppressed. As a consequence, the calculated interface roughness is much smaller than that derived from ordinary capillary wave theory.

  3. Neutron Reflectometry and QCM-D Study of the Interaction of Cellulases with Films of Amorphous Cellulose

    SciTech Connect

    Cheng, Gang; Liu, Zelin; Murton, Jaclyn K.; Jablin, Michael S.; Dubey, Manish; Majewski, Jaroslaw; Halbert, Candice E.; Browning, James F.; Ankner, John; Akgun, Bulent; Wang, Chao; Esker, Alan R.; Sale, Kenneth L.; Simmons, Blake A.; Kent, Michael S.

    2011-06-13

    Improving the efficiency of enzymatic hydrolysis of cellulose is one of the key technological hurdles to reduce the cost of producing ethanol and other transportation fuels from lignocellulosic material. A better understanding of how soluble enzymes interact with insoluble cellulose will aid in the design of more efficient enzyme systems. We report a study involving neutron reflectometry (NR) and quartz crystal microbalance with dissipation monitoring (QCM-D) of the interaction of a fungal enzyme extract (T. viride) and an endoglucanse from A. niger with amorphous cellulose films. The use of amorphous cellulose is motivated by that the fact that several biomass pretreatments currently under investigation disrupt the native crystalline structure of cellulose and increase the amorphous content. NR reveals the profile of water through the film at nanometer resolution and is highly sensitive to interfacial roughness, whereas QCM-D provides changes in mass and film stiffness. NR can be performed using either H₂O- or D₂O-based aqueous reservoirs. NR measurement of swelling of a cellulose film in D₂O and in H₂O revealed that D/H exchange on the cellulose chains must be taken into account when a D₂O-based reservoir is used. The results also show that cellulose films swell slightly more in D₂O than in H₂O. Regarding enzymatic digestion, at 20 °C in H₂O buffer the T. viride cocktail rapidly digested the entire film, initially roughening the surface, followed by penetration and activity throughout the bulk of the film. In contrast, over the same time period, the endoglucanase was active mainly at the surface of the film and did not increase the surface roughness.

  4. The study of perpendicular magnetic anisotropy in the magnetic sensors with linear sensitivity using polarized neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Zhu, T.

    2016-04-01

    The CoFeB sandwiched by Ta and MgO layers enables a perpendicular magnetic anisotropy (PMA) and provides a pathway for such application. In this paper, we reported the origin of PMA in CoFeB using the anomalous Hall effect (AHE) and polarized neutron reflectometry (PNR). From PNR experiments, we obtained the details of the magnetic and structural depth profiles inside the film. It is found that the PMA properties of CoFeB layers deposited above and under MgO layer are different and PNR measurements confirmed that a large PMA in the CoFeB above MgO layer is related to its low magnetization. Based on this PMA mechanism, we obtain a high sensitivity of AHE in the perpendicular CoFeB, which opens a new avenue to detect ultralow magnetic field.

  5. Understanding dynamic changes in live cell adhesion with neutron reflectometry

    SciTech Connect

    Junghans, Ann; Waltman, Mary Jo; Smith, Hillary L.; Pocivavsek, Luka; Zebda, Noureddine; Birukov, Konstantin; Viapiano, Mariano; Majewski, Jaroslaw

    2014-12-10

    In this study, neutron reflectometry (NR) was used to examine various live cells' adhesion to quartz substrates under different environmental conditions, including flow stress. To the best of our knowledge, these measurements represent the first successful visualization and quantization of the interface between live cells and a substrate with sub-nanometer resolution. In our first experiments, we examined live mouse fibroblast cells as opposed to past experiments using supported lipids, proteins, or peptide layers with no associated cells. We continued the NR studies of cell adhesion by investigating endothelial monolayers and glioblastoma cells under dynamic flow conditions. We demonstrated that neutron reflectometry is a powerful tool to study the strength of cellular layer adhesion in living tissues, which is a key factor in understanding the physiology of cell interactions and conditions leading to abnormal or disease circumstances. Continuative measurements, such as investigating changes in tumor cell — surface contact of various glioblastomas, could impact advancements in tumor treatments. In principle, this can help us to identify changes that correlate with tumor invasiveness. Pursuit of these studies can have significant medical impact on the understanding of complex biological problems and their effective treatment, e.g. for the development of targeted anti-invasive therapies.

  6. Neutron Reflectometry Studies of the Adsorbed Structure of the Amelogenin, LRAP

    SciTech Connect

    Tarasevich, Barbara J.; Perez-Salas, Ursula; Masica, David L.; Philo, John; Krueger, Susan; Majkrzak, Charles F.; Gray, Jeffrey J.; Shaw, Wendy J.

    2013-03-21

    Amelogenins make up over 90 percent of the protein present during enamel formation and have been demonstrated to be critical in proper enamel development, but the mechanism governing this control is not well understood. Leucine-rich amelogenin peptide (LRAP) is a 59-residue splice variant of amelogenin and contains the charged regions from the full protein thought to control crystal regulation. In this work, we utilized neutron reflectivity (NR) to investigate the structure and orientation of LRAP adsorbed from solutions onto molecularly smooth COOH-terminated self-assembled monolayers (SAMs) surfaces. Sedimentation velocity experiments revealed that LRAP is primarily a monomer in saturated calcium phosphate (SCP) solutions (0.15 M NaCl) at pH 7.4. LRAP adsorbed as ~33 Å thick layers at ~70% coverage as determined by NR. Rosetta simulations of the dimensions of LRAP in solution (37 Å diameter) indicate that the NR determined z dimension is consistent with an LRAP monomer. Sedimentation velocity experiments and Rosetta simulation show that the LRAP monomer has an extended, asymmetric shape in solution. The NR data suggests that the protein is not completely extended on the surface, having some degree of structure away from the surface. A protein orientation with the C-terminal and inner N-terminal region (~8-24)) located near the surface is consistent with the higher scattering length density (SLD) and higher protein hydration found near the surface by NR. This work presents new information on the tertiary and quaternary structure of LRAP in solution and adsorbed onto surfaces. It also presents further evidence that the monomeric species may be an important functional form of amelogenin proteins.

  7. Neutron Reflectometry and QCM-D Study of the Interaction of Cellulase Enzymes with Films of Amorphous Cellulose

    SciTech Connect

    Halbert, Candice E; Ankner, John Francis; Kent, Michael S; Jaclyn, Murton K; Browning, Jim; Cheng, Gang; Liu, Zelin; Majewski, Jaroslaw; Supratim, Datta; Michael, Jablin; Bulent, Akgun; Alan, Esker; Simmons, Blake

    2011-01-01

    Improving the efficiency of enzymatic hydrolysis of cellulose is one of the key technological hurdles to reduce the cost of producing ethanol and other transportation fuels from lignocellulosic material. A better understanding of how soluble enzymes interact with insoluble cellulose will aid in the design of more efficient enzyme systems. We report a study involving neutron reflectometry (NR) and quartz crystal microbalance with dissipation (QCM-D) of the interaction of a commercial fungal enzyme extract (T. viride), two purified endoglucanses from thermophilic bacteria (Cel9A from A. acidocaldarius and Cel5A from T. maritima), and a mesophilic fungal endoglucanase (Cel45A from H. insolens) with amorphous cellulose films. The use of amorphous cellulose is motivated by the promise of ionic liquid pretreatment as a second generation technology that disrupts the native crystalline structure of cellulose. NR reveals the profile of water through the film at nm resolution, while QCM-D provides changes in mass and film stiffness. At 20 oC and 0.3 mg/ml, the T. viride cocktail rapidly digested the entire film, beginning from the surface followed by activity throughout the bulk of the film. For similar conditions, Cel9A and Cel5A were active for only a short period of time and only at the surface of the film, with Cel9A releasing 40 from the ~ 700 film and Cel5A resulting in only a slight roughening/swelling effect at the surface. Subsequent elevation of the temperature to the Topt in each case resulted in a very limited increase in activity, corresponding to the loss of an additional 60 from the film for Cel9A and 20 from the film for Cel5A, and very weak penetration into and digestion within the bulk of the film, before the activity again ceased. The results for Cel9A and Cel5A contrast sharply with results for Cel45A where very rapid and extensive penetration and digestion within the bulk of the film was observed at 20 C. We speculate that the large differences are due

  8. Understanding dynamic changes in live cell adhesion with neutron reflectometry

    DOE PAGES

    Junghans, Ann; Waltman, Mary Jo; Smith, Hillary L.; Pocivavsek, Luka; Zebda, Noureddine; Birukov, Konstantin; Viapiano, Mariano; Majewski, Jaroslaw

    2014-12-10

    In this study, neutron reflectometry (NR) was used to examine various live cells' adhesion to quartz substrates under different environmental conditions, including flow stress. To the best of our knowledge, these measurements represent the first successful visualization and quantization of the interface between live cells and a substrate with sub-nanometer resolution. In our first experiments, we examined live mouse fibroblast cells as opposed to past experiments using supported lipids, proteins, or peptide layers with no associated cells. We continued the NR studies of cell adhesion by investigating endothelial monolayers and glioblastoma cells under dynamic flow conditions. We demonstrated that neutronmore » reflectometry is a powerful tool to study the strength of cellular layer adhesion in living tissues, which is a key factor in understanding the physiology of cell interactions and conditions leading to abnormal or disease circumstances. Continuative measurements, such as investigating changes in tumor cell — surface contact of various glioblastomas, could impact advancements in tumor treatments. In principle, this can help us to identify changes that correlate with tumor invasiveness. Pursuit of these studies can have significant medical impact on the understanding of complex biological problems and their effective treatment, e.g. for the development of targeted anti-invasive therapies.« less

  9. Surface physics with cold and thermal neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Steyerl, A.

    1991-11-01

    Three aspects of the research project were stressed during the present first year: (1) Setup of the reflectometer facility at the research reactor of the Rhode Island Nuclear Science Center. The installation provides a narrow 'pencil beam' analyzed by time of flight using a chopper system. Following beam characterization and a test measurement of the total cross section of copper single crystal first reflectivity measurements are currently performed using a supermirror. (2) Design study for the ultracold neutron imaging system, with involvement of the relevant industry. Bids are available for several components indicating that it will be very difficult to build the entire system unless further funds become available. (3) Analysis of features of neutron reflection from surfaces with special emphasis on the effect of surface roughness both on the specular beam and the diffusely reflected and refracted intensity. Previous theoretical studies were supplemented by further numerical calculations of diffuse scattering distributions using different models. Application of ultracold and cold neutron reflectometry to the study of liquid-vapor phase transition were discussed. The theoretical work also includes the development of tentative ideas for novel fundamental physics experiments.

  10. Neutron Reflectometry at Elevated Pressures and Temperatures - Novel P-T Cell and Preliminary Experiments

    NASA Astrophysics Data System (ADS)

    Hickmott, D.; Lerner, A. H.; Wang, P.; Majewski, J.; Taylor, M.

    2011-12-01

    Processes at mineral-fluid interfaces control a wide-range of phenomena of crucial importance in energy and environmental applications, including fluid flow, mineral precipitation and dissolution, and corrosion and scaling. In geological systems, geothermal energy production, CO2 sequestration, oil and gas production, and nuclear reactors and waste repositories, these critical mineral-fluid interactions occur at high pressures (P) and temperatures (T). Unfortunately the details of these phenomena are poorly understood because of the technical difficulties with conducting in-situ investigations of mineral/fluid interfaces at relevant geological conditions. Neutron reflectometry offers the possibility of studying fluid/solid processes in-situ at elevated Ps and Ts. In neutron reflectometry an unpolarized neutron beam (wavelength 1.5 to 16 Å) is directed at a solid/fluid (or other) interface at a glancing angle and a range of momentum transfer vectors (Q) are measured elucidating changes in material layering and fluid density within a few dozen Å of the solid/liquid interface. Neutron reflectometry is an ideal technique for investigating such processes at elevated P/T because neutrons are strongly penetrating and able to pass through robust, high P/T aluminum cells with minimal neutron attenuation. Additionally, neutrons are highly sensitive to deuterium due to its large neutron scattering cross section, allowing heavy water to be detected. Thus, neutron scattering has advantages over x-ray techniques, which cannot detect water and which cannot penetrate large-volume P cells. A new LANL neutron cell allows neutron reflectometry studies at conditions up to 200°C and 200 MPa, corresponding to a crustal depth of 6 km. The 5 in. diameter cell is constructed of anodized AA7075 aluminum with a 2 in. diameter sample chamber. The neutron cell and P system can accommodate fluid environments varying in pH and mineral and CO2 saturations. Neutron reflectometry studies will

  11. Understanding dynamic changes in live cell adhesion with neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Junghans, Ann

    Understanding the structure and functionality of biological systems on a nanometer-resolution and short temporal scales is important for solving complex biological problems, developing innovative treatment, and advancing the design of highly functionalized biomimetic materials. For example, adhesion of cells to an underlying substrate plays a crucial role in physiology and disease development, and has been investigated with great interest for several decades. In the talk, we would like to highlight recent advances in utilizing neutron scattering to study bio-related structures in dynamic conditions (e . g . under the shear flow) including in-situ investigations of the interfacial properties of living cells. The strength of neutron reflectometry is its non-pertubative nature, the ability to probe buried interfaces with nanometer resolution and its sensitivity to light elements like hydrogen and carbon. That allows us to study details of cell - substrate interfaces that are not accessible with any other standard techniques. We studied the adhesion of human brain tumor cells (U251) to quartz substrates and their responses to the external mechanical forces. Such cells are isolated within the central nervous system which makes them difficult to reach with conventional therapies and therefore making them highly invasive. Our results reveal changes in the thickness and composition of the adhesion layer (a layer between the cell lipid membrane and the quartz substrate), largely composed of hyaluronic acid and associated proteoglycans, when the cells were subjected to shear stress. Further studies will allow us to determine more conditions triggering changes in the composition of the bio-material in the adhesion layer. This, in turn, can help to identify changes that correlate with tumor invasiveness, which can have significant medical impact for the development of targeted anti-invasive therapies.

  12. Surface physics with cold and thermal neutron reflectometry. Progress report, April 1, 1991--September 30, 1993

    SciTech Connect

    Steyerl, A.

    1993-09-01

    Within the past two and one half years of the project ``Surface Physics With Cold and Thermal Neutron Reflectometry`` a new thermal neutron reflectometer was constructed at the Rhode Island Nuclear Science Center (RINSC). It was used to study various liquid and solid surfaces. Furthermore, neutron reflection experiments were be un at different laboratories in collaboration with Dr. G.P. Fetcher (at Argonne National Laboratory), Dr. T. Russell (IBM Almaden) and Drs. S.K. Satija and A. Karim (at the National Institute for Standards and Technology). The available resources allowed partial construction of an imaging system for ultracold neutrons. It is expected to provide an extremely high resolution in momentum and energy transfer in surface studies using neutron reflectometry. Much of the work reported here was motivated by the possibility of later implementation at the planned Advanced Neutron Source at Oak Ridge. In a separate project the first concrete plans for an intense source of ultracold neutrons for the Advanced Neutron Source were developed.

  13. Morphological origin for the stratification of P3HT:PCBM blend film studied by neutron reflectometry

    SciTech Connect

    Keum, Jong Kahk; Browning, James F.; Halbert, Candice E.; Xiao, Kai; Shao, Ming; Hong, Kunlun

    2013-11-25

    Understanding the origin for the film stratification of electron donor/acceptor blend is crucial for high efficiency organic photovoltaic cell. In this study, P3HT:PCBM blend is deposited onto hydrophilic and hydrophobic substrate to examine the film stratifications. The neutron reflectivity results show that, on the different surfaces, PCBM diffuses toward the two interfacial regions in an identical fashion during thermal annealing. This evidences that the film stratification is not affected by the substrates. Instead, since P3HT remains more amorphous in the interfacial regions and PCBM is miscible with amorphous P3HT, PCBM preferentially diffuses to the interfacial regions, resulting in the stratification.

  14. Neutron reflectometry on highly absorbing films and its application to 10B4C-based neutron detectors

    PubMed Central

    Piscitelli, F.; Khaplanov, A.; Devishvili, A.; Schmidt, S.; Höglund, C.; Birch, J.; Dennison, A. J. C.; Gutfreund, P.; Hall-Wilton, R.; Van Esch, P.

    2016-01-01

    Neutron reflectometry is a powerful tool used for studies of surfaces and interfaces. The absorption in the typical studied materials is neglected and this technique is limited only to the reflectivity measurement. For strongly absorbing nuclei, the absorption can be directly measured by using the neutron-induced fluorescence technique which exploits the prompt particle emission of absorbing isotopes. This technique is emerging from soft matter and biology where highly absorbing nuclei, in very small quantities, are used as a label for buried layers. Nowadays, the importance of absorbing layers is rapidly increasing, partially because of their application in neutron detection; a field that has become more active also due to the 3He-shortage. We extend the neutron-induced fluorescence technique to the study of layers of highly absorbing materials, in particular 10B4C. The theory of neutron reflectometry is a commonly studied topic; however, when a strong absorption is present the subtle relationship between the reflection and the absorption of neutrons is not widely known. The theory for a general stack of absorbing layers has been developed and compared to measurements. We also report on the requirements that a 10B4C layer must fulfil in order to be employed as a converter in neutron detection. PMID:26997902

  15. The Search for Nanobubbles by Using Specular and Off-Specular Neutron Reflectometry.

    PubMed

    Gutfreund, Philipp; Maccarini, Marco; Dennison, Andrew J C; Wolff, Max

    2016-09-01

    We apply specular and off-specular neutron reflection at the hydrophobic silicon/water interface to check for evidence of nanoscopic air bubbles whose presence is claimed after an ad hoc procedure of solvent exchange. Nanobubbles and/or a depletion layer at the hydrophobic/water interface have long been discussed and generated a plethora of controversial scientific results. By combining neutron reflectometry (NR), off-specular reflectometry (OSS), and grazing incidence small angle neutron scattering (GISANS), we studied the interface between hydrophobized silicon and heavy water before and after saturation with nitrogen gas. Our specular reflectometry results can be interpreted by assuming a submolecular sized depletion layer and the off-specular measurements show no change with nitrogen super saturated water. This picture is consistent with the assumption that, following the solvent exchange, no additional nanobubbles are introduced at significant concentrations (if present at all). Furthermore, we discuss the results in terms of the maximum surface coverage of nanobubbles that could be present on the hydrophobic surface compatibly with the sensitivity limit of these techniques. PMID:27516185

  16. Influence of the Human and Rat Islet Amyloid Polypeptides on Structure of Phospholipid Bilayers: Neutron Reflectometry and Fluorescence Microscopy Studies.

    PubMed

    Junghans, Ann; Watkins, Erik B; Majewski, Jaroslaw; Miranker, Andrew; Stroe, Izabela

    2016-05-01

    Neutron reflectivity (NR) and fluorescent microscopy (FM) were used to study the interactions of human (hIAPP) and rat (rIAPP) islet amyloid polypeptides with several formulations of supported model lipid bilayers at the solid-liquid interface. Aggregation and deposition of islet amyloid polypeptide is correlated with the pathology of many diseases, including Alzheimer's, Parkinson, and type II diabetes (T2DM). A central component of T2DM pathology is the deposition of fibrils in the endocrine pancreas, which is toxic to the insulin secreting β-cells. The molecular mechanism by which the cell death occurs is not yet understood, but existing evidence points toward interactions of IAPP oligomers with cellular membranes in a manner leading to loss of their integrity. Our NR and FM results showed that the human sequence variant, hIAPP, had little or no effect on bilayers composed of saturated-acyl chains like zwitterionic DPPC, anionic DPPG, and mixed 80:20 mol % DPPC:DPPG bilayers. In marked contrast, the bilayer structure and stability of anionic unsaturated DOPG were sensitive to protein interaction, and the bilayer was partly solubilized by hIAPP under the conditions used here. The rIAPP, which is considered less toxic, had no perturbing effects on any of the above membrane formulations. Understanding the conditions that result in membrane disruption by hIAPP can be crucial in developing counter strategies to fight T2DM and also physicochemically similar neurodegenerative diseases such as Alzheimer's. PMID:27065348

  17. One directional polarized neutron reflectometry with optimized reference layer method

    SciTech Connect

    Masoudi, S. Farhad; Jahromi, Saeed S.

    2012-09-01

    In the past decade, several neutron reflectometry methods for determining the modulus and phase of the complex reflection coefficient of an unknown multilayer thin film have been worked out among which the method of variation of surroundings and reference layers are of highest interest. These methods were later modified for measurement of the polarization of the reflected beam instead of the measurement of the intensities. In their new architecture, these methods not only suffered from the necessity of change of experimental setup but also another difficulty was added to their experimental implementations. This deficiency was related to the limitations of the technology of the neutron reflectometers that could only measure the polarization of the reflected neutrons in the same direction as the polarization of the incident beam. As the instruments are limited, the theory has to be optimized so that the experiment could be performed. In a recent work, we developed the method of variation of surroundings for one directional polarization analysis. In this new work, the method of reference layer with polarization analysis has been optimized to determine the phase and modulus of the unknown film with measurement of the polarization of the reflected neutrons in the same direction as the polarization of the incident beam.

  18. Neutron reflectometry: Filling Δq with neutrons

    NASA Astrophysics Data System (ADS)

    Pleshanov, N. K.

    2016-06-01

    Luminosity of the reflectometer is defined as the neutron flux incident onto the sample surface for measurements made with a given momentum transfer resolution Δq. The filling of Δq with neutrons near a certain q depends not only on the source luminance and the source-sample tract transmittance, but also on the neutron beam tailoring. The correct choice of the working wavelength and measurements with optimum neutron beam parameters increase luminosity in several times. New optimization criteria for neutron reflectometers are suggested. Standard schemes of the reflectivity measurement with monochromatic and white beams are re-examined. Optimization of reflectivity measurements generally requires numerical calculations. Analytically, its potential is demonstrated by considering thermalized neutron beams. Such innovations as velocity selector on the basis of aperiodic multilayers, small angle Soller collimator with traps for neutrons reflected from the channel walls and fan beam time-of-flight technique are proposed to further increase the luminosity of reflectometers.

  19. Theoretical foundation of X-ray and neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Zhou, Xiao-Lin; Chen, Sow-Hsin

    1995-06-01

    This review attempts to give a systematic exposition of the theoretical foundation underlying surface depth profiling at the molecular level using X-ray and neutron specular reflectometry. It covers the fundamentals of X-ray and neutron interactions with matter, the direct theory of specular reflection from stratified media, the inverse theory of specular reflection for obtaining the surface depth profile from measured specular reflection data, and demonstration of how the theories can be used in practice. The part on X-ray and neutron interactions with matter begins with the basic quantum mechanical and classical electromagnetic descriptions of scattering, discusses the important concepts of scattering and absorption cross sections, the scattering length density and the refractive index of matter, and derives the one-dimensional Helmholtz wave equation which fully describes the specular reflection of slow neutrons and X-rays from a macroscopic stratified medium. The direct theory begins with the development of the solution of the Helmholtz wave equation in the form of a discrete formulation, namely, Parratt's recurrence relation, and proceeds to several continuous formulations, such as the Born and distorted wave Born (DWBA) approximations, the small-curvature approximation (SCA), the modified WKB approximation (MWKB) and the weighted-superposition approximation (WSA), and ends with a discussion about the effect of surface roughness. The inverse theory presents methods for the reconstruction of the depth profile of the surface scattering length density from a set of specular reflection data. This includes the feasibility of data inversion, some simple examples of analytic data inversion, a matrix-iteration method (MIM), and a groove-tracking method (GTM). For demonstration of the use of the theories, we give an example of neutron reflectivity data analyses, from which the surface-layering phenomenon in bicontinuous microemulsions is revealed.

  20. Self-diffusion and defect annihilation in nanocrystalline Fe films probed by neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Chakravarty, Sujoy; Schmidt, Harald; Tietze, Ursula; Lott, Dieter; Lalla, N. P.; Gupta, Ajay

    2009-07-01

    Self-diffusion in ion-beam-sputtered nanocrystalline Fe is studied between 310 and 510°C , using neutron reflectometry on [Fnate(7nm)/F57e(3nm)]15 isotope multilayers. Neutron reflectometry has the advantage over other methods of diffusivity determination, that diffusion lengths on the order of 1 nm and below can be determined. This enables diffusion experiments in a nanostructure which is not significantly modified by grain growth during annealing. The determined diffusivities are time depended and decrease by more than two orders of magnitude during isothermal annealing. In early stages, diffusion is controlled by frozen-in nonequilibrium point defects (interstitials or vacancies) present after deposition. The decrease in the diffusivities can be attributed to the annihilation of these point defects. For very long annealing times the diffusivities above 400°C are in good agreement with volume diffusivities measured in single crystals given in literature. However, at a temperature of 400°C and below the diffusivities are still higher than extrapolated literature data also after more than 8 days of annealing, indicating that defect annihilation is still going on.

  1. Using Neutron Reflectometry to Discern the Structure of Fibrinogen Adsorption at the Stainless Steel/Aqueous Interface.

    PubMed

    Wood, Mary H; Browning, Kathryn L; Barker, Robert D; Clarke, Stuart M

    2016-06-23

    Neutron reflectometry has been successfully used to study adsorption on a stainless steel surface by means of depositing a thin steel film on silicon. The film was characterized using XPS (X-ray photoelectron spectroscopy), TOF-SIMS (time-of-flight secondary ion mass spectrometry), and GIXRD (grazing incidence X-ray diffraction), demonstrating the retention both of the austenitic phase and of the required composition for 316L stainless steel. The adsorption of fibrinogen from a physiologically-relevant solution onto the steel surface was studied using neutron reflectometry and QCM (quartz crystal microbalance) and compared to that on a deposited chromium oxide surface. It was found that the protein forms an irreversibly bound layer at low concentrations, with maximum protein concentration a distance of around 20 Å from the surface. Evidence for a further diffuse reversibly-bound layer forming at higher concentrations was also observed. Both the structure of the layer revealed by the neutron reflectometry data and the high water retention predicted by the QCM data suggest that there is a significant extent of protein unfolding upon adsorption. A lower extent of adsorption was seen on the chromium surfaces, although the adsorbed layer structures were similar, suggesting comparable adsorption mechanisms. PMID:27244444

  2. Comparative structure analysis of magnetic fluids at interface with silicon by neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Avdeev, M. V.; Petrenko, V. I.; Gapon, I. V.; Bulavin, L. A.; Vorobiev, A. A.; Soltwedel, O.; Balasoiu, M.; Vekas, L.; Zavisova, V.; Kopcansky, P.

    2015-10-01

    The adsorption of surfactant coated magnetic nanoparticles from highly stable magnetic fluids on crystalline functionalized silicon is studied by neutron reflectometry. Two types of magnetic fluids based on nanomagnetite dispersed and stabilized in non-polar organic solvent (deuterated benzene) and strongly polar solvent (heavy water) are considered. In both cases the interface shows the formation of just one well-defined adsorption layer of nanoparticles, which is insensitive to the effect of the external magnetic field. Still, the particle concentration in the benzene-based fluid is higher in the vicinity to the silicon surface as compared to the bulk distribution. Despite the presence of an aggregate fraction in the water-based system the width of the adsorption layer is consistent with the size of separated particles, thus showing the preferable adsorption of non-aggregated particles.

  3. Analysis of biosurfaces by neutron reflectometry: From simple to complex interfaces

    DOE PAGES

    Junghans, Ann; Watkins, Erik B.; Barker, Robert D.; Singh, Saurabh; Waltman, Mary Jo; Smith, Hillary L.; Pocivavsek, Luka; Majewski, Jaroslaw

    2015-03-16

    Because of its high sensitivity for light elements and the scattering contrast manipulation via isotopic substitutions, neutron reflectometry (NR) is an excellent tool for studying the structure of soft-condensed material. These materials include model biophysical systems as well as in situ living tissue at the solid–liquid interface. The penetrability of neutrons makes NR suitable for probing thin films with thicknesses of 5–5000 Å at various buried, for example, solid–liquid, interfaces [J. Daillant and A. Gibaud, Lect. Notes Phys. 770, 133 (2009); G. Fragneto-Cusani, J. Phys.: Condens. Matter 13, 4973 (2001); J. Penfold, Curr. Opin. Colloid Interface Sci. 7, 139 (2002)].more » Over the past two decades, NR has evolved to become a key tool in the characterization of biological and biomimetic thin films. Highlighted In the current report are some of the authors' recent accomplishments in utilizing NR to study highly complex systems, including in-situ experiments. Such studies will result in a much better understanding of complex biological problems, have significant medical impact by suggesting innovative treatment, and advance the development of highly functionalized biomimetic materials.« less

  4. Analysis of biosurfaces by neutron reflectometry: From simple to complex interfaces

    SciTech Connect

    Junghans, Ann; Watkins, Erik B.; Barker, Robert D.; Singh, Saurabh; Waltman, Mary Jo; Smith, Hillary L.; Pocivavsek, Luka; Majewski, Jaroslaw

    2015-03-16

    Because of its high sensitivity for light elements and the scattering contrast manipulation via isotopic substitutions, neutron reflectometry (NR) is an excellent tool for studying the structure of soft-condensed material. These materials include model biophysical systems as well as in situ living tissue at the solid–liquid interface. The penetrability of neutrons makes NR suitable for probing thin films with thicknesses of 5–5000 Å at various buried, for example, solid–liquid, interfaces [J. Daillant and A. Gibaud, Lect. Notes Phys. 770, 133 (2009); G. Fragneto-Cusani, J. Phys.: Condens. Matter 13, 4973 (2001); J. Penfold, Curr. Opin. Colloid Interface Sci. 7, 139 (2002)]. Over the past two decades, NR has evolved to become a key tool in the characterization of biological and biomimetic thin films. Highlighted In the current report are some of the authors' recent accomplishments in utilizing NR to study highly complex systems, including in-situ experiments. Such studies will result in a much better understanding of complex biological problems, have significant medical impact by suggesting innovative treatment, and advance the development of highly functionalized biomimetic materials.

  5. Thermal stability of photovoltaic a-Si:H determined by neutron reflectometry

    SciTech Connect

    Qviller, A. J. Haug, H.; You, C. C.; Hasle, I. M.; Marstein, E. S.; Frommen, C.; Hauback, B. C.; Dennison, A. J. C.; Vorobiev, A.; Østreng, E.; Fjellvåg, H.; Hjörvarsson, B.

    2014-12-08

    Neutron and X-ray reflectometry were used to determine the layer structure and hydrogen content of thin films of amorphous silicon (a-Si:H) deposited onto crystalline silicon (Si) wafers for surface passivation in solar cells. The combination of these two reflectometry techniques is well suited for non-destructive probing of the structure of a-Si:H due to being able to probe buried interfaces and having sub-nanometer resolution. Neutron reflectometry is also unique in its ability to allow determination of density gradients of light elements such as hydrogen (H). The neutron scattering contrast between Si and H is strong, making it possible to determine the H concentration in the deposited a-Si:H. In order to correlate the surface passivation properties supplied by the a-Si:H thin films, as quantified by obtainable effective minority carrier lifetime, photoconductance measurements were also performed. It is shown that the minority carrier lifetime falls sharply when H has been desorbed from a-Si:H by annealing.

  6. Water uptake and swelling hysteresis in a nafion thin film measured with neutron reflectometry.

    PubMed

    Kalisvaart, W Peter; Fritzsche, Helmut; Mérida, Walter

    2015-05-19

    Water uptake and swelling in a thin (∼15 nm) Nafion film on SiO2 native oxide on a Si wafer is studied as a function of relative humidity (8-97%) at room temperature and as a function of temperature (25-60 °C) at 97% relative humidity by neutron reflectometry. This is the first report on the behavior of thin Nafion films at elevated temperatures and high humidity. Large hysteresis is observed during the temperature cycle. The observed swelling strain in the film at 60 °C is 48% as compared to the as-deposited state, which is far above any previously observed trend at room temperature. A small decrease in the average SLD suggests that part of the additional swelling is due to thermal expansion, but the estimated D2O/SO3 ratio also increases by 70%. Half of the "excess" absorption and 73% of the additional swelling are retained during cooling back to room temperature. The results provide new insights into the dynamics of Nafion on nanometer scales under fuel cell operating conditions. PMID:25901752

  7. Exploring Strain Induced Magnetization Effects in Metamagnetic Artificial Multiferroics using Polarized Neutron Reflectometry

    NASA Astrophysics Data System (ADS)

    Bennett, Steven; Herklotz, Andreas; Wong, Anthony; Ward, Thomas; Lauter, Valeria

    There is currently a strong drive to realize a controllable magnetic ordering transition for use in next generation spintronic based memory and computation devices. One proposed method to gain such control is the use of a changing strain in a thin film metamagnetic artificial multiferroic system. While basic concepts using electric field actuated piezoelectric strain have been recently demonstrated1, there is very little understanding of the details of strains effect on such magnetic phase transitions. Using the depth sensitive method of polarized neutron reflectometry we have been able to probe the fine details of strains contribution to the metamagnetic transition in thin films of metamagnetic FeRh2. Here we explore the effects of changing lattice strain as a function of depth using both a barium titanate substrate's structural phase transitions3 and He ion implantation. These studies have discovered a remarkably large coupling between the systems strain state and the switching behavior across the magnetostructural metamagnetic transition. 1 Cherifi, R. O. et al. Nat. Mater. 31, 345-351 (2014), 2 Bennett, S. P. et al. Sci. Rep. 5, 9142 (2015), 3 Bennett, S. P. et al. submitted (2015)

  8. Application of polarized neutron reflectometry and x-ray resonant magnetic reflectometry for determining the inhomogeneous magnetic structure in Fe/Gd multilayers.

    SciTech Connect

    Kravtsov, E. A.; Haskel, D.; te Velthuis, S. G. E.; Jiang, J. S.; Kirby, B. J.

    2010-01-01

    The evolution of the magnetic structure of multilayer [Fe (35 {angstrom})/Gd (50 {angstrom}){sub 5}] with variation in temperature and an applied magnetic field was determined using a complementary approach combining polarized neutron and X-ray resonant magnetic reflectometry. Self-consistent simultaneous analysis of X-ray and neutron spectra allowed us to determine the elemental and depth profiles in the multilayer structure with unprecedented accuracy, including the identification of an inhomogeneous intralayer magnetic structure with near-atomic resolution.

  9. Focusing neutron reflectometry: Implementation and experience on the TOF-reflectometer Amor

    NASA Astrophysics Data System (ADS)

    Stahn, J.; Glavic, A.

    2016-06-01

    Neutron reflectometry is a powerful tool to investigate chemical and magnetic depth profiles near surfaces. The advantages of neutrons compared to x-rays are their sensitivity to isotopes, the high penetration capabilities and the high sensitivity to magnetic induction. The biggest disadvantage however is the low flux available, which leads to much longer counting times on much larger samples. In order to boost the performance of neutron reflectometers, a focusing guide system was developed and realised over recent years. Here we report on the application and performance of a down-scaled demonstrator of such a Selene guide, installed as an add-on on the time-of-flight (TOF) reflectometer Amor at the PSI. Due to the limited size of the guide, the flux is concentrated to a footprint of at most 2 mm width. It is thus possible to avoid illumination of contacts even on small samples. Despite the fact that typical samples measured on Amor with a size of 10 × 10mm2 are markedly under illuminated, the presented set-up leads to a reduction in counting time of 80%. The use of the demonstrator thus allows for in-situ or in-operando investigations with a time resolution of a few minutes for a qz range from 0.005Å-1 to 0.08Å-1. Besides a short recapitulation of the concept of focusing reflectometry, a detailed description of the data reduction and its quality is given, followed by an application example.

  10. Characterization of Chemical Speciation in Ultra Thin Uranium Oxide Films by Neutron Reflectometry

    SciTech Connect

    Wang, Peng

    2012-06-20

    Motivation for this project is due to more than 17 kg of HEU and 400 g of Pu have been interdicted through an international effort to control nuclear smuggling. Nuclear forensics - Detection and analysis of nuclear materials recovered from either the capture of unused materials or from the radioactive debris following a nuclear explosion or activities, which can contribute significantly for national security. Develop new nuclear forensic methods can be applied to: (a) Environmental swipes, (b) Small particulates, and (c) Thin films. Conclusions of the project are: (1) A unique approach: Neutron Reflectometry + Surface Enhanced Raman Spectroscopy; and (2) Detection of chemical speciation with {angstrom}-level resolution.

  11. Motofit - integrating neutron reflectometry acquisition, reduction and analysis into one, easy to use, package

    NASA Astrophysics Data System (ADS)

    Nelson, Andrew

    2010-11-01

    The efficient use of complex neutron scattering instruments is often hindered by the complex nature of their operating software. This complexity exists at each experimental step: data acquisition, reduction and analysis, with each step being as important as the previous. For example, whilst command line interfaces are powerful at automated acquisition they often reduce accessibility by novice users and sometimes reduce the efficiency for advanced users. One solution to this is the development of a graphical user interface which allows the user to operate the instrument by a simple and intuitive "push button" approach. This approach was taken by the Motofit software package for analysis of multiple contrast reflectometry data. Here we describe the extension of this package to cover the data acquisition and reduction steps for the Platypus time-of-flight neutron reflectometer. Consequently, the complete operation of an instrument is integrated into a single, easy to use, program, leading to efficient instrument usage.

  12. Plasma diagnostic reflectometry

    SciTech Connect

    Cohen, B.I.; Afeyan, B.B.; Garrison, J.C.; Kaiser, T.B.; Luhmann, N.C. Jr.; Domier, C.W.; Chou, A.E.; Baang, S.

    1996-02-26

    Theoretical and experimental studies of plasma diagnostic reflectometry have been undertaken as a collaborative research project between the Lawrence Livermore National Laboratory (LLNL) and the University of California Department of Applied Science Plasma Diagnostics Group under the auspices of the Laboratory Directed Research and Development Program at LLNL. Theoretical analyses have explored the basic principles of reflectometry to understand its limitations, to address specific gaps in the understanding of reflectometry measurements in laboratory experiments, and to explore extensions of reflectometry such as ultra-short-pulse reflectometry. The theory has supported basic laboratory reflectometry experiments where reflectometry measurements can be corroborated by independent diagnostic measurements.

  13. High-pressure cell for neutron reflectometry of supercritical and subcritical fluids at solid interfaces

    NASA Astrophysics Data System (ADS)

    Carmichael, Justin R.; Rother, Gernot; Browning, James F.; Ankner, John F.; Banuelos, Jose L.; Anovitz, Lawrence M.; Wesolowski, David J.; Cole, David R.

    2012-04-01

    A new high-pressure cell design for use in neutron reflectometry (NR) for pressures up to 50 MPa and a temperature range of 300-473 K is described. The cell design guides the neutron beam through the working crystal without passing through additional windows or the bulk fluid, which provides for a high neutron transmission, low scattering background, and low beam distortion. The o-ring seal is suitable for a wide range of subcritical and supercritical fluids and ensures high chemical and pressure stability. Wafers with a diameter of 5.08 cm (2 in.) and 5 mm or 10 mm thickness can be used with the cells, depending on the required pressure and momentum transfer range. The fluid volume in the sample cell is very small at about 0.1 ml, which minimizes scattering background and stored energy. The cell design and pressure setup for measurements with supercritical fluids are described. NR data are shown for silicon/silicon oxide and quartz wafers measured against air and subsequently within the high-pressure cell to demonstrate the neutron characteristics of the high-pressure cell. Neutron reflectivity data for supercritical CO2 in contact with quartz and Si/SiO2 wafers are also shown.

  14. Structure of electrolyte decomposition products on high voltage spinel cathode materials determined by in situ neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Browning, Jim; Veith, Gabriel; Baggetto, Loic; Dudney, Nancy; Tenhaeff, Wyatt

    2012-02-01

    Interfacial reactions on electrical energy storage (EES) materials mediate their stability, durability, and cycleablity. Understanding these reactions in situ is difficult since they occur at the liquid-solid interface of an optically absorbing material that hinders the use of techniques such as infra-red spectroscopy. Furthermore, since the interfaces involve liquids classic vacuum-based analytical methods can only probe reaction products, which are stable under vacuum. Here, we present the results of an in situ neutron reflectometry study detailing the formation of a thick solid-electrolyte interphase (SEI) on a high voltage spinel cathode material. The cathode/electrolyte system used in this study is a LiMn1.5Ni0.5O4 thin film subjected to a 1.2 molar LiPF6 in 1:1 ethylene carbonate - dimethyl carbonate electrolyte solution.

  15. Monitoring Soil Moisture in Saline Soils using Neutron Probe, Time Domain Reflectometry, and Heat Dissipation Sensor Measurements

    NASA Astrophysics Data System (ADS)

    Reedy, R. C.

    2004-12-01

    Knowledge of spatial and temporal variability of soil moisture content (SMC) is important for understanding of land-atmosphere interactions, groundwater recharge, and water balance. Different measurement methods have contrasting strengths and weaknesses. Traditional neutron probe measurements cannot be automated and are time-intensive. However, there are widespread problems with using automated time domain reflectometry (TDR) for monitoring SMC due to high soil salinity/electrical conductivity. The objective of this study was to show how these limitations can be overcome by using multiple methods. Neutron probe access tubes, TDR probes (coated and uncoated), and heat dissipation sensors (HDS) were installed at an engineered field laboratory in a semiarid setting. The texture of the soils was sandy clay loam, including 0.3 m of uncompacted topsoil with low salinity and non-swelling clays underlain by 1.0 to 1.7 m of compacted subsoil with high salinity and swelling clays. A neutron probe was used to manually measure SMC profiles at 20 locations at approximately monthly intervals over a 3.5 yr period. During a 4 to 5 yr overlapping period, daily automated measurements were made at 8 locations of apparent dielectric constant (Ka) and bulk electrical conductivity (EC) profiles using TDR (128 probes) and matric potential profiles using HDS (54 sensors). TDR measurements in the high salinity soils were effectively calibrated in situ using neutron probe measurements. Modeled estimates of spatial average water content were generally within 0.01 m3/m3. A similar approach was used to combine neutron probe, TDR, and HDS measurements to generate in situ soil water retention functions. These functions were then used to estimate SMC from matric potential measurements. These approaches allowed SMC to be monitored in high salinity swelling soils and provided much higher resolution time series than were obtained from the limited neutron probe measurements.

  16. Separation and correlation of structural and magnetic roughness in a Ni thin film by polarized off-specular neutron reflectometry.

    PubMed

    Singh, Surendra; Basu, Saibal

    2009-02-01

    Diffuse (off-specular) neutron and x-ray reflectometry has been used extensively for the determination of interface morphology in solids and liquids. For neutrons, a novel possibility is off-specular reflectometry with polarized neutrons to determine the morphology of a magnetic interface. There have been few such attempts due to the lower brilliance of neutron sources, though magnetic interaction of neutrons with atomic magnetic moments is much easier to comprehend and easily tractable theoretically. We have obtained a simple and physically meaningful expression, under the Born approximation, for analyzing polarized diffuse (off-specular) neutron reflectivity (PDNR) data. For the first time PDNR data from a Ni film have been analyzed and separate chemical and magnetic morphologies have been quantified. Also specular polarized neutron reflectivity measurements have been carried out to measure the magnetic moment density profile of the Ni film. The fit to PDNR data results in a longer correlation length for in-plane magnetic roughness than for chemical (structural) roughness. The magnetic interface is smoother than the chemical interface. PMID:21817297

  17. Time-of-Flight Polarized Neutron Reflectometry on PLATYPUS: Status and Future Developments

    NASA Astrophysics Data System (ADS)

    Saerbeck, T.; Cortie, D. L.; Brück, S.; Bertinshaw, J.; Holt, S. A.; Nelson, A.; James, M.; Lee, W. T.; Klose, F.

    Time-of-flight (ToF) polarized neutron reflectometry enables the detailed investigation of depth-resolved magnetic structures in thin film and multilayer magnetic systems. The general advantage of the time-of-flight mode of operation over monochromatic instruments is a decoupling of spectral shape and polarization of the neutron beam with variable resolution. Thus, a wide Q-range can be investigated using a single angle of incidence, with resolution and flux well-adjusted to the experimental requirement. Our paper reviews the current status of the polarization equipment of the ToF reflectometer PLATYPUS and presents first results obtained on stratified Ni80Fe20/α-Fe2O3 films, revealing the distribution of magnetic moments in an exchange bias system. An outlook on the future development of the PLATYPUS polarization system towards the implementation of a polarized 3He cell is presented and discussed with respect to the efficiency and high Q-coverage up to 1 Å-1 and 0.15 Å-1 in the vertical and lateral momentum transfer, respectively.

  18. Exchange bias in a nanocrystalline hematite/permalloy thin film investigated with polarized neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Cortie, D. L.; Lin, K.-W.; Shueh, C.; Hsu, H.-F.; Wang, X. L.; James, M.; Fritzsche, H.; Brück, S.; Klose, F.

    2012-08-01

    We investigated a hematite α-Fe2O3/permalloy Ni80Fe20 bilayer film where the antiferromagnetic layer consisted of small hematite grains in the 2 to 16 nm range. A pronounced exchange bias effect occurred below the blocking temperature of 40 K. The magnitude of exchange bias was enhanced relative to reports for identical compounds in large grain, epitaxial films. However, the blocking temperature was dramatically reduced. As the Néel temperature of bulk α-Fe2O3 is known to be very high (860 K), we attribute the low-temperature onset of exchange bias to the well-known finite-size effect which suppresses the Morin transition for nanostructured hematite. Polarized neutron reflectometry was used to place an upper limit on the concentration and length scale of a layer of uncompensated moments at the antiferromagnetic interface. The data were found to be consistent with an induced magnetic region at the antiferromagnetic interface of 0.5-1.0 μB per Fe atom within a depth of 1-2 nm. The field dependence of the neutron spin-flip signal and spin asymmetry was analyzed in the biased state, and the first and second magnetic reversal were found to occur by asymmetric mechanisms. For the fully trained permalloy loop, reversal occurred symmetrically at both coercive fields by an in-plane spin rotation of ferromagnetic domains.

  19. Depth of α-Synuclein in a Bilayer Determined by Fluorescence, Neutron Reflectometry, and Computation

    PubMed Central

    Pfefferkorn, Candace M.; Heinrich, Frank; Sodt, Alexander J.; Maltsev, Alexander S.; Pastor, Richard W.; Lee, Jennifer C.

    2012-01-01

    α-Synuclein (α-syn) membrane interactions are implicated in the pathogenesis of Parkinson's disease. Fluorescence and neutron reflectometry (NR) measurements reveal that α-syn penetrates ∼9–14 Å into the outer leaflet of the bilayer, with a substantial portion of the membrane-bound polypeptide extending into the aqueous solvent. For the first time, to our knowledge, we used NR to obtain direct quantitative evidence of α-syn-induced membrane thinning. To examine the effect of specific residues on membrane penetration depths, we used a series of W4-containing N-terminal peptides. We identified that the first 15 residues (P15) nearly recapitulate the features of the full-length protein (i.e., partition constants, molecular mobility, and insertion of the W4 side chain into the bilayer), and found that as few as the first four N-terminal residues are sufficient for vesicle binding. Although at least one imperfect amphipathic repeat sequence (KAKEGV) is required for α-helical formation, secondary structural formation has little effect on membrane affinity. To develop an N-terminal α-syn model for bilayer interactions, we performed molecular-dynamics simulations of the P15 peptide submerged in a bilayer. The simulation results are highly consistent with experimental data indicating a broad low-energy region (8.5–14.5 Å) for W4 insertion. PMID:22325285

  20. Depth of α-synuclein in a bilayer determined by fluorescence, neutron reflectometry, and computation.

    PubMed

    Pfefferkorn, Candace M; Heinrich, Frank; Sodt, Alexander J; Maltsev, Alexander S; Pastor, Richard W; Lee, Jennifer C

    2012-02-01

    α-Synuclein (α-syn) membrane interactions are implicated in the pathogenesis of Parkinson's disease. Fluorescence and neutron reflectometry (NR) measurements reveal that α-syn penetrates ∼9-14 Å into the outer leaflet of the bilayer, with a substantial portion of the membrane-bound polypeptide extending into the aqueous solvent. For the first time, to our knowledge, we used NR to obtain direct quantitative evidence of α-syn-induced membrane thinning. To examine the effect of specific residues on membrane penetration depths, we used a series of W4-containing N-terminal peptides. We identified that the first 15 residues (P15) nearly recapitulate the features of the full-length protein (i.e., partition constants, molecular mobility, and insertion of the W4 side chain into the bilayer), and found that as few as the first four N-terminal residues are sufficient for vesicle binding. Although at least one imperfect amphipathic repeat sequence (KAKEGV) is required for α-helical formation, secondary structural formation has little effect on membrane affinity. To develop an N-terminal α-syn model for bilayer interactions, we performed molecular-dynamics simulations of the P15 peptide submerged in a bilayer. The simulation results are highly consistent with experimental data indicating a broad low-energy region (8.5-14.5 Å) for W4 insertion.

  1. Imaging spin structures of exchange-coupled materials with neutron reflectometry

    NASA Astrophysics Data System (ADS)

    O'Donovan, K. V.; Borchers, J. A.; Majkrzak, C. F.; Fullerton, E. E.; Hellwig, O.

    2001-03-01

    We used polarized neutron reflectometry to examine the spin structure of an Fe_55Pt_45(200 ÅNi_80Fe_20(500 Åexchange-coupled magnetic film in fields up to 630 mT (near saturation) at room temperature. By measuring both the two spin-flip and the two non-spin-flip cross-sections, we can determine the spin structure as a function of depth throughout the entire sample. Magnetometry of the film indicates spring-magnet behavior.(Physical Review B 62), 11 694 (2000) Our measurements in a field of 16 mT (which ostensibly is in the reversible regime) indicate a twist, which begins in the magnetically soft permalloy, extends throughout a significant fraction of the magnetically hard FePt, contrary to theoretical expectations. At larger fields the permalloy is aligned with the external field and the Bloch wall is localized within the FePt. In remanence we see no twist. Instead, the spins are aligned in one direction, canted with respect to the saturation magnetization, but with disorder at the interface. We will discuss fine details of the spin structure near 16 mT and the evolution of the spin structure from 5 mT through 630 mT and in remanence.

  2. In situ Neutron Reflectometry Measurements of Hydrogen Absorption in Thin Metal Films

    NASA Astrophysics Data System (ADS)

    Munter, A. E.; Heuser, B. J.; Guillermo, N. R.

    1996-03-01

    The absorption of hydrogen and deuterium from the gas phase in thin films of Pd has been measured with neutron reflectometry. 500ÅPd films were magnetron sputtered on polished silicon substrates. At room temperature, H and D were observed to absorb into the Pd film at gas pressures of 60 torr and 1 atm respectively. Genetic algorithm fits to the data indicate an expansion of the metal lattice in the direction normal to the surface plane upon uptake. This may be the result of the hydride phase transformation, but the results are inconclusive. Both H and D appear to be preferentially excluded from the film-substrate interface, with a peak in the concentration profile occuring between the air/film interface and the midpoint of the film. Peak concentrations of 0.6 H/Pd and 0.8 D/Pd were determined from the fits. The effect of H absorption appears to be at least partially reversible upon annealing. The discussion will include expansion of the thin films after absorption, depth profiles of the H and D concentrations, and reversibility. Results for H and D absorption in Nb will be presented as well.

  3. Percolating bulk-heterostructures from neutron reflectometry and small angle scattering data

    NASA Astrophysics Data System (ADS)

    Olds, Daniel; Duxbury, Phillip

    2013-03-01

    We present a novel algorithm for efficiently calculating the simulated small angle scattering data of any discretized morphological model of arbitrary scale and resolution, referred to as the distribution function method (DFM). Unlike standard SAS fitting methods, the DFM algorithm allows for the calculation of form factors and structure factors from complex nanoscale morphologies commonly encountered in many modern polymeric and nanoparticle based systems, which have no exact analytical corollary. The computational efficiency of the DFM algorithm suggests it's use in morphological model refinement. We will present a number of simple examples to demonstrate the accuracy and limits of the algorithm, followed by an example of incorporation of the DFM algorithm into reverse Monte Carlo structural refinement of bulk-heterojunction two-phase morphologies, such as those commonly found in organic photovoltaic devices. We will show that morphological features introduced via direct incorporation of experimental neutron reflectometry and SANS data to the models has a direct effect on the results of device simulations. The authors thank CORE-CM at Michigan State University for it's funding of this research.

  4. Interactions of Endoglucanases with Amorphous Cellulose Films Resolved by Neutron Reflectometry and Quartz Crystal Microbalance with Dissipation Monitoring

    SciTech Connect

    Cheng, Gang; Liu, Zelin; Kent, Michael S; Majewski, Jaroslaw; Michael, Jablin; Jaclyn, Murton K; Halbert, Candice E; Datta, Supratim; Chao, Wang; Brown, Page

    2012-01-01

    A study of the interaction of four endoglucanases with amorphous cellulose films by neutron reflectometry (NR) and quartz crystal microbalance with dissipation monitoring (QCM-D) is reported. The endoglucanases include a mesophilic fungal endoglucanase (Cel45A from H. insolens), a processive endoglucanase from a marine bacterium (Cel5H from S. degradans), and two from thermophilic bacteria (Cel9A from A. acidocaldarius and Cel5A from T. maritima). The use of amorphous cellulose is motivated by the promise of ionic liquid pretreatment as a second generation technology that disrupts the native crystalline structure of cellulose. The endoglucanases displayed highly diverse behavior. Cel45A and Cel5H, which possess carbohydrate-binding modules (CBMs), penetrated and digested within the bulk of the films to a far greater extent than Cel9A and Cel5A, which lack CBMs. While both Cel45A and Cel5H were active within the bulk of the films, striking differences were observed. With Cel45A, substantial film expansion and interfacial broadening were observed, whereas for Cel5H the film thickness decreased with little interfacial broadening. These results are consistent with Cel45A digesting within the interior of cellulose chains as a classic endoglucanase, and Cel5H digesting predominantly at chain ends consistent with its designation as a processive endoglucanase.

  5. 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer spin valve component investigated by polarized neutron reflectometry

    SciTech Connect

    Callori, S. J. Bertinshaw, J.; Cortie, D. L.; Cai, J. W. Zhu, T.; Le Brun, A. P.; Klose, F.

    2014-07-21

    We have observed 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer system using polarized neutron reflectometry. Magnetometry results show magnetic switching for both the biased and free NiFe layers, the latter of which reverses at low applied fields. As these measurements are only capable of providing information about the total magnetization within a sample, polarized neutron reflectometry was used to investigate the reversal behavior of the NiFe layers individually. Both the non-spin-flip and spin-flip neutron reflectometry signals were tracked around the free NiFe layer hysteresis loop and were used to detail the evolution of the magnetization during reversal. At low magnetic fields near the free NiFe coercive field, a large spin-flip signal was observed, indicating magnetization aligned perpendicular to both the applied field and pinned layer.

  6. Magnetic properties of the SiO2(Co)/GaAs interface: Polarized neutron reflectometry and SQUID magnetometry

    NASA Astrophysics Data System (ADS)

    Ukleev, V. A.; Grigoryeva, N. A.; Dyadkina, E. A.; Vorobiev, A. A.; Lott, D.; Lutsev, L. V.; Stognij, A. I.; Novitskiy, N. N.; Mistonov, A. A.; Menzel, D.; Grigoriev, S. V.

    2012-10-01

    The effect of giant injection magnetoresistance (GIMR) was recently observed in a granular SiO2/(54-75 at. % Co) film on a semiconductor GaAs substrate in a temperature range near T=300 K. The magnetoresistance coefficient reaches a value of 105% in a magnetic field of 1.9 T and at a voltage of 90 V. A structural model of the film was proposed based on the results of the grazing-incidence small-angle scattering (GISAXS) and x-ray reflectivity, which showed a specific interface layer 70-75 Å thick separating bulk SiO2(Co) granular film from the semiconductor substrate. This layer is formed by a monolayer of flattened Co particles which are laterally spaced apart much further than the particles in the bulk film. In the present work, using polarized neutron reflectometry (PNR), we study both the structural and magnetic properties of SiO2(Co) film separately in the bulk and in the interface layer, which is possible due to the depth resolution of the method. Temperature-dependent PNR and magnetization measurements performed by Superconducting Quantum Interference Device (SQUID) revealed the occurrence of two types of magnetic nanoparticles with different blocking temperatures and magnetization. The magnetization hysteresis curve demonstrated specific two-loop structure in fields 0.5-2 T. Thus our self-consistent results of PNR, GISAXS, and SQUID measurements emphasize the role of the interface features in the SiO2(Co)/GaAs heterostructures and show a direction for further development of the GIMR theory.

  7. Operando Measurement of Solid Electrolyte Interphase Formation at Working Electrode of Li-Ion Battery by Time-Slicing Neutron Reflectometry.

    PubMed

    Kawaura, Hiroyuki; Harada, Masashi; Kondo, Yasuhito; Kondo, Hiroki; Suganuma, Yoshitake; Takahashi, Naoko; Sugiyama, Jun; Seno, Yoshiki; Yamada, Norifumi L

    2016-04-20

    We report the first operando measurement of solid electrolyte interphase (SEI) formation at an electrode using in situ neutron reflectometry. The results revealed the growth of the SEI and intercalation of ions during the charge reaction. Furthermore, we propose a way of evaluating the charge used for the SEI formation.

  8. Operando Measurement of Solid Electrolyte Interphase Formation at Working Electrode of Li-Ion Battery by Time-Slicing Neutron Reflectometry.

    PubMed

    Kawaura, Hiroyuki; Harada, Masashi; Kondo, Yasuhito; Kondo, Hiroki; Suganuma, Yoshitake; Takahashi, Naoko; Sugiyama, Jun; Seno, Yoshiki; Yamada, Norifumi L

    2016-04-20

    We report the first operando measurement of solid electrolyte interphase (SEI) formation at an electrode using in situ neutron reflectometry. The results revealed the growth of the SEI and intercalation of ions during the charge reaction. Furthermore, we propose a way of evaluating the charge used for the SEI formation. PMID:27031783

  9. Structural features of membrane-bound glucocerebrosidase and α-synuclein probed by neutron reflectometry and fluorescence spectroscopy.

    PubMed

    Yap, Thai Leong; Jiang, Zhiping; Heinrich, Frank; Gruschus, James M; Pfefferkorn, Candace M; Barros, Marilia; Curtis, Joseph E; Sidransky, Ellen; Lee, Jennifer C

    2015-01-01

    Mutations in glucocerebrosidase (GCase), the enzyme deficient in Gaucher disease, are a common genetic risk factor for the development of Parkinson disease and related disorders, implicating the role of this lysosomal hydrolase in the disease etiology. A specific physical interaction exists between the Parkinson disease-related protein α-synuclein (α-syn) and GCase both in solution and on the lipid membrane, resulting in efficient enzyme inhibition. Here, neutron reflectometry was employed as a first direct structural characterization of GCase and α-syn·GCase complex on a sparsely-tethered lipid bilayer, revealing the orientation of the membrane-bound GCase. GCase binds to and partially inserts into the bilayer with its active site most likely lying just above the membrane-water interface. The interaction was further characterized by intrinsic Trp fluorescence, circular dichroism, and surface plasmon resonance spectroscopy. Both Trp fluorescence and neutron reflectometry results suggest a rearrangement of loops surrounding the catalytic site, where they extend into the hydrocarbon chain region of the outer leaflet. Taking advantage of contrasting neutron scattering length densities, the use of deuterated α-syn versus protiated GCase showed a large change in the membrane-bound structure of α-syn in the complex. We propose a model of α-syn·GCase on the membrane, providing structural insights into inhibition of GCase by α-syn. The interaction displaces GCase away from the membrane, possibly impeding substrate access and perturbing the active site. GCase greatly alters membrane-bound α-syn, moving helical residues away from the bilayer, which could impact the degradation of α-syn in the lysosome where these two proteins interact.

  10. Structural Features of Membrane-bound Glucocerebrosidase and α-Synuclein Probed by Neutron Reflectometry and Fluorescence Spectroscopy*

    PubMed Central

    Yap, Thai Leong; Jiang, Zhiping; Heinrich, Frank; Gruschus, James M.; Pfefferkorn, Candace M.; Barros, Marilia; Curtis, Joseph E.; Sidransky, Ellen; Lee, Jennifer C.

    2015-01-01

    Mutations in glucocerebrosidase (GCase), the enzyme deficient in Gaucher disease, are a common genetic risk factor for the development of Parkinson disease and related disorders, implicating the role of this lysosomal hydrolase in the disease etiology. A specific physical interaction exists between the Parkinson disease-related protein α-synuclein (α-syn) and GCase both in solution and on the lipid membrane, resulting in efficient enzyme inhibition. Here, neutron reflectometry was employed as a first direct structural characterization of GCase and α-syn·GCase complex on a sparsely-tethered lipid bilayer, revealing the orientation of the membrane-bound GCase. GCase binds to and partially inserts into the bilayer with its active site most likely lying just above the membrane-water interface. The interaction was further characterized by intrinsic Trp fluorescence, circular dichroism, and surface plasmon resonance spectroscopy. Both Trp fluorescence and neutron reflectometry results suggest a rearrangement of loops surrounding the catalytic site, where they extend into the hydrocarbon chain region of the outer leaflet. Taking advantage of contrasting neutron scattering length densities, the use of deuterated α-syn versus protiated GCase showed a large change in the membrane-bound structure of α-syn in the complex. We propose a model of α-syn·GCase on the membrane, providing structural insights into inhibition of GCase by α-syn. The interaction displaces GCase away from the membrane, possibly impeding substrate access and perturbing the active site. GCase greatly alters membrane-bound α-syn, moving helical residues away from the bilayer, which could impact the degradation of α-syn in the lysosome where these two proteins interact. PMID:25429104

  11. Correlating Interfacial Structure and Magnetism in Thin-Film Oxide Heterostructures Using Transmission Electron Microscopy and Polarized Neutron Reflectometry

    NASA Astrophysics Data System (ADS)

    Spurgeon, Steven Richard

    Oxide thin-films have attracted considerable attention for a new generation of spintronics devices, where both electron charge and spin are used to transport information. However, a poor understanding of the local features that mediate magnetization and coupling in these materials has greatly limited their deployment into new information and communication technologies. This thesis describes direct, local measurements of structure-property relationships in ferrous thin-films and La1--xSrxMnO3 (LSMO) / Pb(ZrxTi1--x)O3 (PZT) thin-film heterostructures using spatially-resolved characterization techniques. In the first part of this thesis we explore the properties of ferrous spintronic thin-films. These films serve as a model system to establish a suite of interfacial characterization techniques for subsequent studies. We then study the static behavior of LSMO / PZT devices with polarization set by the underlying substrate. Using transmission electron microscopy and geometric phase analysis we reveal the presence of significant local strain gradients in these films for the first time. Electron energy loss spectroscopy mapping of the LSMO / PZT interface reveals Mn valence changes induced by charge-transfer screening. Bulk magnetometry and polarized neutron reflectometry indicate that these chemical and strain changes are associated with a graded magnetization across the LSMO layer. Density functional theory calculations are presented, which show that strain and charge-transfer screening act locally to suppress magnetization in the LSMO by changing the Mn orbital polarization. In the second half of this thesis, we explore asymmetric screening effects on magnetization LSMO / PZT composites. We find that the local ferroelectric polarization can vary widely and that this may be responsible for reduced charge-transfer effects, as well as magnetic phase gradients at interfaces. From this information and electron energy loss spectroscopy, we construct a map of the magnetic

  12. A combined reflectometry and quartz crystal microbalance with dissipation setup for surface interaction studies

    SciTech Connect

    Wang Guoliang; Ohlsson, Gabriel; Rodahl, Michael; Edvardsson, Malin; Svedhem, Sofia; Kasemo, Bengt; Hoeoek, Fredrik

    2008-07-15

    We have developed an instrument for surface interaction studies, which combines a newly invented four detector optical reflectometry setup with quartz crystal microbalance with dissipation (QCM-D) monitoring. The design is such that data from both techniques can be obtained simultaneously on the same sensor surface, with the same signal-to-noise ratio and time resolution, as for the individual techniques. In addition, synchronized information about structural transformations, molecular mass, and the hydration of thin films on solid surfaces can be obtained on the same specimen, as validated by monitoring the formation of supported lipid bilayers on a silica-coated QCM sensor surface. We emphasize that the optical (molecular) mass can be separated from the acoustic mass including hydrodynamically coupled solvent, which means, in turn, that the amount of solvent sensed by the QCM-D technique can be dynamically resolved during adsorption processes. In addition, the advantage/necessity to use four, compared to two, detector reflectometry is emphasized.

  13. BioRef II—Neutron reflectometry with relaxed resolution for fast, kinetic measurements at HZB

    NASA Astrophysics Data System (ADS)

    Trapp, M.; Steitz, R.; Kreuzer, M.; Strobl, M.; Rose, M.; Dahint, R.

    2016-10-01

    We present an upgrade to the time-of-flight neutron reflectometer BioRef at the research reactor BER II of the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB). Through the integration of an additional chopper into the existing setup, the available wavelength resolution is significantly extended. Now two distinct operation modes can be used: a high resolution mode with Δλ/λ ranging from 1% to 5%, which allows for the investigation of thick films up to 4000 Å, and a high flux mode with Δλ/λ = 7%-11%. In the high flux mode, reflectivity curves from 0.007 Å-1 to 0.2 Å-1 with three angular settings can be recorded in 7 min. For a single angular setting and its respective window in Q-space, a time resolution of even less than 4 min is reached. The different configurations are documented by respective measurements (a) on a Ni-Ti multilayer and (b) the swelling kinetics of a solid-supported phospholipid coating upon incubation in a polyelectrolyte solution.

  14. Birefringence in anisotropic optical fibres studied by polarised light Brillouin reflectometry

    SciTech Connect

    Smirnov, A S; Burdin, V V; Konstantinov, Yu A; Petukhov, A S; Drozdov, I R; Kuz'minykh, Ya S; Besprozvannykh, V G

    2015-01-31

    Modal birefringence (the difference between the effective refractive indices of orthogonal polarisation modes) is one of the key parameters of anisotropic single-mode fibres, characterising their ability to preserve a linearly polarised state of input light. This parameter is commonly measured using short pieces of fibre, but such procedures are destructive and allow the birefringence to be determined only at the ends of long fibres. In this study, polarised light Brillouin reflectometry is used to assess birefringence uniformity throughout the length of an anisotropic fibre. (optical fibres)

  15. Microwave reflectometry for ICRF coupling studies on TFTR

    NASA Astrophysics Data System (ADS)

    Wilgen, J. B.; Hanson, G. R.; Bigelow, T. S.; Batchelor, D. B.; Collazo, I.; Hoffman, D. J.; Murakami, M.; Rasmussen, D. A.; Stallings, D. C.; Raftopoulos, S.; Wilson, J. R.

    1994-10-01

    A dual-frequency differential-phase reflectometer has been developed for use in ICRF power coupling studies on TFTR. This system has been optimized for measurements of the electron density profile in the edge-gradient region, where density fluctuations are large. Initial proof-of-principle measurements demonstrate that this is an effective way to measure the electron density profile in the plasma-edge region. A new reflectometer launcher is presently being installed on the center axis of the bay-K ICRF antenna on TFTR, along with the associated waveguide transmission line. This will allow direct measurement of the edge-density profile within the high-power-density environment of the ICRF antenna where density profile modification might be expected.

  16. Dielectric studies of alkyl acrylates with primary alcohols using time domain reflectometry

    NASA Astrophysics Data System (ADS)

    Dharmalingam, K.; Ramachandran, K.; Sivagurunathan, P.; Prabhakar Undre, B.; Khirade, P. W.; Mehrotra, S. C.

    Binary polar-polar liquid mixtures of alkyl acrylates (methyl acrylate, ethyl acrylate and butyl acrylate) with primary alcohols (propan-1-ol, butan-1-ol and hexan-1-ol) were subjected to dielectric studies at 303 K for different concentrations using time domain reflectometry (TDR) over the frequency range from 10 MHz to 10 GHz. Static permittivity (ɛ0) dielectric constant at high frequency (ɛ∞) and relaxation time (τ) were found through dielectric measurements for different concentrations of each system. The Bruggeman dielectric factor, Kirkwood correlation factor and the excess inverse relaxation time were determined and discussed to yield information on the molecular interactions of the systems. Deviations from the linearity of various models suggest molecular association through hydrogen bonding between the -OH group of alcohols and C=O group of esters. The results also show a dependence of dielectric parameters on the alkyl chain length of both the alcohols and esters.

  17. Numerical Study of Microwave Reflectometry in Plasmas with 2D Turbulent Fluctuations

    SciTech Connect

    E. Mazzucato

    1998-02-01

    This paper describes a numerical study of the role played by 2D turbulent fluctuations in microwave reflectometry -- a radar technique for density measurements using the reflection of electromagnetic waves from a plasma cutoff. The results indicate that, if the amplitude of fluctuations is below a threshold which is set by the spectrum of poloidal wavenumbers, the measured backward field appears to originate from a virtual location behind the reflecting layer, and to arise from the phase modulation of the probing wave, with an amplitude given by 1D geometric optics. These results suggest a possible scheme for turbulence measurements in tokamaks, where the backward field is collected with a wide aperture antenna, and the virtual reflecting layer is imaged onto the plane of an array of detectors. Such a scheme should be capable of providing additional information on the nature of the short-scale turbulence observed in tokamaks, which still remains one of the unresolved issues in fusion research.

  18. Neutron reflectometry of quaternary gemini surfactants as a function of alkyl chain length: anomalies arising from ion association and premicellar aggregation.

    PubMed

    Li, Pei Xun; Dong, Chu Chuan; Thomas, Robert K; Penfold, J; Wang, Yilin

    2011-03-15

    We have measured the structure and properties of a series of dicationic quaternary ammonium compounds α,ω-bis(N-alkyl dimethyl ammonium)hexane halides (Cn-C6-Cn) for values of the alkyl chain length n of 8, 9, 10, 11, 12, and 16, and a series of α,ω-bis(N-alkyl dimethyl ammonium)diethylether halides (Cn-C2OC2-Cn) for values of n of 8, 12, and 16, as well as C8-C12-C8 and C12-C10-C12 at the air/water interface. Although the critical micelle concentration (CMC) in the two series decreases in the normal way, that is, logarithmically, with increasing chain length, the limiting surface tension at the CMC and the limiting area per molecule both increase with chain length, in the opposite direction from comparable single chain surfactants. The structures of the surface layers, which were determined by neutron reflectometry, indicate that the anomalous behavior of the surface tension and area are probably caused by poor packing of the gemini side chains between adjacent molecules. Comparison of the directly determined surface coverage using neutron reflectometry and the apparent coverage determined by application of the Gibbs equation to surface tension data gives an experimental measurement of the prefactor in the Gibbs equation, which should be 3 for these geminis. It was found to vary from about 3 for the two C16 geminis down to about 1.5 for the two C8 geminis. We have devised a simple quantitative model that explains this variation and earlier observations that the Gibbs prefactor for C12-Cn-C12 (n varying from 3 to 12) is around 2. The model is consistent with the conductivity, NMR, and fluorescence measurements of other authors. This model shows that both dimerization and ion association are required to explain the surface tension behavior of cationic gemini bromide surfactants and that, in many cases, the prefactor itself varies with concentration.

  19. Time-of-flight four-beam neutron reflectometer REFLEX at the high-flux pulsed reactor IBR-2: some polarized neutron reflectometry applications

    NASA Astrophysics Data System (ADS)

    Aksenov, V. L.; Korneev, Daniel A.; Chernenko, L. P.

    1992-11-01

    This paper discusses the new neutron reflectometer being built on the high flux pulsed reactor IBR-2 in Dubna. A new method is suggested for measuring and interpretation of data in the study of inhomogeneous (noncollinear) magnetization depth profile in thin films. It is important to take into account the surface roughness in the interpretation of the data from the measurements of the magnetic field penetration depth in superconductors.

  20. The 3D study of X-mode reflectometry for density profile measurements on the JET tokamak

    NASA Astrophysics Data System (ADS)

    Hacquin, S.; Fonseca, A.; Meneses, L.; Murari, A.; Walsh, M.; JET EFDA contributors, the

    2007-10-01

    An X-mode swept-frequency reflectometry diagnostic has recently been upgraded for density profile measurement on the JET tokamak. To overcome the extensive computing time required for full-wave simulation, a ray-tracing code has been developed for studying the 3D geometry effects on the JET reflectometry measurement of the density profile. Although such a ray-tracing code is not adequate to examine the role of plasma turbulence, comparisons with full-wave computations have shown that it is still a useful tool for simulation of the density profile measurements in the case of smooth spatial variations of the plasma parameters. The effects of the plasma geometry and the radiation pattern of the reflectometer emitting and receiving antennas on the spatial resolution of these measurements are investigated in this paper. In particular, the results point out the weak role played by the multi-dimensional effects on the reflectometry measurements performed in the equatorial mid-plane of large tokamaks such as JET.

  1. Evaluating the solid electrolyte interphase formed on silicon electrodes: A comparison of ex situ X-ray photoelectron spectroscopy and in situ neutron reflectometry

    DOE PAGES

    Doucet, Mathieu; Browning, Jim; Baldwin, J. K.; Winiarz, Jeffrey; Kaiser, Helmut; Taub, H.; Veith, Gabriel M.

    2016-04-15

    This work details the in situ characterization of the interface between a silicon electrode and an electrolyte using a linear fluorinated solvent molecule, 0.1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in deuterated dimethyl perfluoroglutarate (d6-PF5M2) (1.87 x 10-2 mS/cm-1). The solid electrolyte interphase (SEI) composition and thickness determined via in situ neutron reflectometry (NR) and ex situ X-ray photoelectron spectroscopy (XPS) were compared. The data show that SEI expansion and contraction (breathing) during electrochemical cycling was observed via both techniques; however, ex situ XPS suggests that the SEI thickness increases during Si lithiation and decreases during delithiation, while in situ NR suggestsmore » the opposite. The most likely cause of this discrepancy is the selective removal of SEI components (top 20 nm of the SEI) during the electrode rinse process, required to remove electrolyte residue prior to ex situ analysis, demonstrating the necessity of performing SEI characterizations in situ.« less

  2. Evaluating the solid electrolyte interphase formed on silicon electrodes: a comparison of ex situ X-ray photoelectron spectroscopy and in situ neutron reflectometry.

    PubMed

    Fears, T M; Doucet, M; Browning, J F; Baldwin, J K S; Winiarz, J G; Kaiser, H; Taub, H; Sacci, R L; Veith, G M

    2016-05-18

    This work details the in situ characterization of the interface between a silicon electrode and an electrolyte using a linear fluorinated solvent molecule, 0.1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in deuterated dimethyl perfluoroglutarate (d6-PF5M2) (1.87 × 10(-2) mS cm(-1)). The solid electrolyte interphase (SEI) composition and thickness determined via in situ neutron reflectometry (NR) and ex situ X-ray photoelectron spectroscopy (XPS) were compared. The data show that SEI expansion and contraction (breathing) during electrochemical cycling were observed via both techniques; however, ex situ XPS suggests that the SEI thickness increases during Si lithiation and decreases during delithiation, while in situ NR suggests the opposite. The most likely cause of this discrepancy is the selective removal of SEI components (top 20 nm of the SEI) during the electrode rinse process, which is required to remove the electrolyte residue prior to ex situ analysis, demonstrating the necessity of performing SEI characterization in situ. PMID:27149427

  3. Evaluating the solid electrolyte interphase formed on silicon electrodes: a comparison of ex situ X-ray photoelectron spectroscopy and in situ neutron reflectometry.

    PubMed

    Fears, T M; Doucet, M; Browning, J F; Baldwin, J K S; Winiarz, J G; Kaiser, H; Taub, H; Sacci, R L; Veith, G M

    2016-05-18

    This work details the in situ characterization of the interface between a silicon electrode and an electrolyte using a linear fluorinated solvent molecule, 0.1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in deuterated dimethyl perfluoroglutarate (d6-PF5M2) (1.87 × 10(-2) mS cm(-1)). The solid electrolyte interphase (SEI) composition and thickness determined via in situ neutron reflectometry (NR) and ex situ X-ray photoelectron spectroscopy (XPS) were compared. The data show that SEI expansion and contraction (breathing) during electrochemical cycling were observed via both techniques; however, ex situ XPS suggests that the SEI thickness increases during Si lithiation and decreases during delithiation, while in situ NR suggests the opposite. The most likely cause of this discrepancy is the selective removal of SEI components (top 20 nm of the SEI) during the electrode rinse process, which is required to remove the electrolyte residue prior to ex situ analysis, demonstrating the necessity of performing SEI characterization in situ.

  4. Long-range antiferromagnetic order in epitaxial Mn2GaC thin films from neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Ingason, A. S.; Pálsson, G. K.; Dahlqvist, M.; Rosen, J.

    2016-07-01

    The nature of the magnetic structure in magnetic so-called MAX phases is a topic of some controversy. Here we present unpolarized neutron-diffraction data between 3.4 and 290.0 K and momentum transfer between Q =0.0 and1.1 Å-1, as well as complementary x-ray-diffraction data on epitaxial thin films of the MAX phase material Mn2GaC . This inherently layered material exhibits neutron-diffraction peaks consistent with long-ranged antiferromagnetic order with a periodicity of two structural unit cells. The magnetic structure is present throughout the measured temperature range. The results are in agreement with first-principles calculations of antiferromagnetic structures for this material where the Mn-C-Mn atomic trilayers are found to be ferromagnetically coupled internally but spin flipped or rotated across the Ga layers. The present findings have significant bearing on the discussion regarding the nature of the magnetic structure in magnetic MAX phases.

  5. Neutron reflectometry of anionic surfactants on sapphire: A strong maximum in the adsorption near the critical micelle concentration.

    PubMed

    Li, Ning Ning; Thomas, Robert K; Rennie, Adrian R

    2016-06-01

    The adsorption of the anionic surfactants, lithium, sodium and cesium dodecylsulfates, and sodium decylsulfonate, on the positively charged C-plane (0001) of sapphire (alumina) has been measured using neutron reflection. For each of the four surfactants there is a strong maximum in the adsorption at about the critical micelle concentration. The maximum becomes more marked from lithium to cesium. The measurements were reproduced over a range of different physical conditions and could not be accounted for in terms of impurities. The maximum is explained quantitatively by using the combination of a mass action model to calculate the mean activity of the surfactant, and a cooperative model of the adsorption (Frumkin), in which saturation of the layer is not attained until well above the critical micelle concentration. PMID:26990955

  6. Microwave reflectometry for the study of density fluctuations in tokamak plasmas

    SciTech Connect

    Mazzucato, E.; Nazikian, R.

    1990-12-01

    The effect of small scale density fluctuations on the propagation of electromagnetic waves in an inhomogeneous magnetized plasma in the presence of a cutoff is investigated. It is shown that, provided the fluctuation scale length is greater than the free space wavelength of an incident plane wave, the scattered field is strongly enhanced from fluctuations near the turning point. Numerical results for wave propagation in a tokamak plasma demonstrate the feasibility of reflectometry for the localized measurement of density fluctuations in the range k {sub {perpendicular}} {rho}{sub i} {much lt} 1. 19 refs., 6 figs,

  7. Microwave Reflectometry for Magnetically Confined Plasmas

    SciTech Connect

    Mazzucato, E.

    1998-02-01

    This paper is about microwave reflectometry -- a radar technique for plasma density measurements using the reflection of electromagnetic waves by a plasma cutoff. Both the theoretical foundations of reflectometry and its practical application to the study of magnetically confined plasmas are reviewed in this paper. In particular, the role of short-scale density fluctuations is discussed at length, both as a unique diagnostic tool for turbulence studies in thermonuclear plasmas and for the deleterious effects that fluctuations may have on the measurement of the average plasma density with microwave reflectometry.

  8. Formation of He-Rich Layers Observed by Neutron Reflectometry in the He-Ion-Irradiated Cr/W Multilayers: Effects of Cr/W Interfaces on the He-Trapping Behavior.

    PubMed

    Chen, Feida; Tang, Xiaobin; Huang, Hai; Li, Xinxi; Wang, Yan; Huang, Chaoqiang; Liu, Jian; Li, Huan; Chen, Da

    2016-09-21

    Cr/W multilayer nanocomposites were presented in the paper as potential candidate materials for the plasma facing components in fusion reactors. We used neutron reflectometry to measure the depth profile of helium in the multienergy He ions irradiated [Cr/W (50 nm)]3 multilayers. Results showed that He-rich layers with low neutron scattering potential energy form at the Cr/W interfaces, which is in great agreement with previous modeling results of other multilayers. This phenomenon provided a strong evidence for the He trapping effects of Cr/W interfaces and implied the possibility of using the Cr/W multilayer nanocomposites as great He-tolerant plasma facing materials. PMID:27589251

  9. Formation of He-Rich Layers Observed by Neutron Reflectometry in the He-Ion-Irradiated Cr/W Multilayers: Effects of Cr/W Interfaces on the He-Trapping Behavior.

    PubMed

    Chen, Feida; Tang, Xiaobin; Huang, Hai; Li, Xinxi; Wang, Yan; Huang, Chaoqiang; Liu, Jian; Li, Huan; Chen, Da

    2016-09-21

    Cr/W multilayer nanocomposites were presented in the paper as potential candidate materials for the plasma facing components in fusion reactors. We used neutron reflectometry to measure the depth profile of helium in the multienergy He ions irradiated [Cr/W (50 nm)]3 multilayers. Results showed that He-rich layers with low neutron scattering potential energy form at the Cr/W interfaces, which is in great agreement with previous modeling results of other multilayers. This phenomenon provided a strong evidence for the He trapping effects of Cr/W interfaces and implied the possibility of using the Cr/W multilayer nanocomposites as great He-tolerant plasma facing materials.

  10. Study of local properties of fibre Bragg gratings by the method of optical space-domain reflectometry

    SciTech Connect

    Korolev, I G; Vasil'ev, Sergei A; Medvedkov, O I; Dianov, Evgenii M

    2003-08-31

    The method of optical space-domain reflectometry for measuring local spatial characteristics of fibre Bragg gratings (FBGs) is described in detail. It is demonstrated experimentally that, by using IR and UV radiation sources, this method provides good sensitivity ({approx}10{sup -4}) of measuring the modulation amplitude of the induced refractive index in the core of an optical fibre and a high spatial resolution ({approx}100 {mu}m and better). The factors affecting the accuracy of measurements as well as technical and methodological limitations of the method are considered. A comparative analysis of modern methods for studying the spatial properties of FBGs is performed and applications of these methods are considered. (special issue devoted to the memory of academician a m prokhorov)

  11. Microwave dielectric study of an oligomeric electrolyte gelator by time domain reflectometry.

    PubMed

    Kundu, Shyamal Kumar; Yagihara, Shin; Yoshida, Masaru; Shibayama, Mitsuhiro

    2009-07-30

    The dynamics of water molecules in aqueous solutions of an oligomeric electrolyte gelator, poly[pyridinium-1,4-diyliminocarbonyl-1,4-phenylene-methylene chloride] (1-Cl) was characterized by microwave dielectric measurements using the time domain reflectometry method. The dielectric dispersion and absorption curves related to the orientational motion of water molecules were described by the Cole-Cole equation. Discontinuities were observed in the concentration dependence of the dielectric relaxation strength, Deltaepsilonh, as well as in the Cole-Cole parameter, betah. These discontinuities were observed between the samples with concentrations of 6 and 7 g/L 1-Cl/water, which correspond to a change in the transparency. Such a discontinuity corresponds to the observation of the critical concentration of gelation. The interaction between water and 1-Cl molecules was discussed from the tauh-betah diagram. As 1-Cl carries an amide group, it could be expected that 1-Cl may interact hydrophilically with water, but the present result suggests that 1-Cl interact hydrophobically with water.

  12. ATW neutronics design studies.

    SciTech Connect

    Wade, D. C.; Yang, W. S.; Khalil, H.

    2000-11-10

    The Accelerator Transmutation of Waste (ATW) concept has been proposed as a transuranics (TRU) (and long-lived fission product) incinerator for processing the 87,000 metric tonnes of Light Water Reactor used fuel which will have been generated by the time the currently deployed fleet of commercial reactors in the US reach the end of their licensed lifetime. The ATW is proposed to separate the uranium from the transuranics and fission products in the LWR used fuel, to fission the transuranics, to send the LWR and ATW generated fission products to the geologic repository and to send the uranium to either a low level waste disposal site or to save it for future use. The heat liberated in fissioning the transuranics would be converted to electricity and sold to partially offset the cost of ATW construction and operations. Options for incineration of long-lived fission products are under evaluation. A six-year science-based program of ATW trade and system studies was initiated in the US FY 2000 to achieve two main purposes: (1) ''to evaluate ATW within the framework of nonproliferation, waste management, and economic considerations,'' and (2) ''to evaluate the efficacy of the numerous technical options for ATW system configuration.'' This paper summarizes the results from neutronics and thermal/hydraulics trade studies which were completed at Argonne National Laboratory during the first year of the program. Core designs were developed for Pb-Bi cooled and Na cooled 840 MW{sub th} fast spectrum transmuter designs employing recycle. Additionally, neutronics analyses were performed at Argonne for a He cooled 600 MW{sub th} hybrid thermal and fast core design proposed by General Atomics Co. which runs critical for 3/4 and subcritical for 1/4 of its four year once-thin burn cycle. The mass flows and the ultimate loss of transuranic isotopes to the waste stream per unit of heat generated during transmutation have been calculated on a consistent basis and are compared. (Long

  13. Neutron personnel dosimetry intecomparison studies

    SciTech Connect

    Sims, C.S.

    1991-01-01

    The Dosimetry Applications Research (DOSAR) Group at the Oak Ridge National Laboratory (ORNL) has conducted sixteen Neutron Personnel Dosimetry Intercomparison Studies (PDIS) since 1974. During these studies dosimeters are mailed to DOSAR, exposed to low-level (typically in the 0.3 -- 5.0 mSv range) neutron dose equivalents in a variety of mixed neutron-gamma radiation fields, and then returned to the participants for evaluation. The Health Physics Research Reactor (HPRR) was used as the primary radiation source in PDIS 1--12 and radioisotopic neutron sources at DOSAR's Radiation Calibration Laboratory (RADCAL) were mainly used, along with sources and accelerators at cooperating institutions, in PDIS 13--16. Conclusions based on 13,560 measurements made by 146 different participating organizations (102 - US) are presented.

  14. Neutron facility for radiobiological studies

    NASA Astrophysics Data System (ADS)

    Policroniades, Rafael; Varela, A.; Guzman, J.; Graaf, U.

    1997-02-01

    A neutron facility suitable for radiobiological applications is described. The small chamber can house, either, solid targets or a gas target. Using this facility, absorbed doses ranging up to 7.2 Gy were delivered to Drosophila melanogaster larvae in order to study induced somatic mutation and mitiotic recombination. Some preliminary results concerning these effects, related to a mean neutron energy of 2.15 MeV provided by a d + Be source, are presented.

  15. Full-wave Feasibility Study of Magnetic Diagnostic based on O-X Mode Conversion and Oblique Reflectometry Imaging

    NASA Astrophysics Data System (ADS)

    Volpe, F. A.; Choi, M.; Patel, Y.; Meneghini, O.

    2013-10-01

    We present initial two-dimensional full-wave modeling of an innovative diagnostic of the magnetic field vector as a function of the minor radius in the pedestal region. An angularly broad millimeter-wave beam of ordinary (O) polarization is obliquely injected in the magnetized plasma; part of it converts in the extraordinary (X) mode at the O-mode cutoff, the rest is reflected. The reflected beam pattern, measured with an array of receivers, contains information on the angular-dependent mode conversion, which contains information on the magnetic pitch angle at the cutoff. Measurements at various frequencies provide radially resolved measurements of pitch angle. The new technique proposed does not require the plasma to be an overdense emitter of Electron Bernstein Waves and is applicable whenever reflectometry is applicable. Simulations performed with the finite-element COMSOL Multiphysics code in ``DIII-D-like'' plasma slabs confirmed the presence of a minimum in reflectivity of an externally injected O-mode beam. The dependence of such reflectivity ``hole'' upon magnetic field is under study. Future inclusion of toroidal ripple, density and magnetic fluctuation effects, as well as possible extensions to a fully three-dimensional diagnostic of the magnetic field will be discussed. Current address: Imsol-X.

  16. Dielectric relaxation studies of binary mixture of β-picoline and methanol using time domain reflectometry at different temperatures

    NASA Astrophysics Data System (ADS)

    Trivedi, C. M.; Rana, V. A.; Hudge, P. G.; Kumbharkhane, A. C.

    2016-08-01

    Complex permittivity spectra of binary mixtures of varying concentrations of β-picoline and Methanol (MeOH) have been obtained using time domain reflectometry (TDR) technique over frequency range 10 MHz to 25 GHz at 283.15, 288.15, 293.15 and 298.15 K temperatures. The dielectric relaxation parameters namely static permittivity (ɛ0), high frequency limit permittivity (ɛ∞1) and the relaxation time (τ) were determined by fitting complex permittivity data to the single Debye/Cole-Davidson model. Complex nonlinear least square (CNLS) fitting procedure was carried out using LEVMW software. The excess permittivity (ɛ0E) and the excess inverse relaxation time (1/τ)E which contain information regarding molecular structure and interaction between polar-polar liquids were also determined. From the experimental data, parameters such as effective Kirkwood correlation factor (geff), Bruggeman factor (fB) and some thermo dynamical parameters have been calculated. Excess parameters were fitted to the Redlich-Kister polynomial equation. The values of static permittivity and relaxation time increase nonlinearly with increase in the mol-fraction of MeOH at all temperatures. The values of excess static permittivity (ɛ0E) and the excess inverse relaxation time (1/τ)E are negative for the studied β-picoline — MeOH system at all temperatures.

  17. 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.

  18. Neutron tube design study for boron neutron capture therapy application

    SciTech Connect

    Verbeke, J.M.; Lee, Y.; Leung, K.N.; Vujic, J.; Williams, M.D.; Wu, L.K.; Zahir, N.

    1999-05-06

    Radio-frequency (RF) driven ion sources are being developed in Lawrence Berkeley National Laboratory (LBNL) for sealed-accelerator-tube neutron generator application. By using a 5-cm-diameter RF-driven multicusp source H{sup +} yields over 95% have been achieved. These experimental findings will enable one to develop compact neutron generators based on the D-D or D-T fusion reactions. In this new neutron generator, the ion source, the accelerator and the target are all housed in a sealed metal container without external pumping. Recent moderator design simulation studies have shown that 14 MeV neutrons could be moderated to therapeutically useful energy ranges for boron neutron capture therapy (BNCT). The dose near the center of the brain with optimized moderators is about 65% higher than the dose obtained from a typical neutron spectrum produced by the Brookhaven Medical Research Reactor (BMRR), and is comparable to the dose obtained by other accelerator-based neutron sources. With a 120 keV and 1 A deuteron beam, a treatment time of {approx}35 minutes is estimated for BNCT.

  19. Neutron scattering studies in the actinide region

    SciTech Connect

    Beghian, L.E.; Kegel, G.H.R.

    1991-08-01

    During the report period we have investigated the following areas: Neutron elastic and inelastic scattering measurements on {sup 14}N, {sup 181}Ta, {sup 232}Th, {sup 238}U and {sup 239}Pu; Prompt fission spectra for {sup 232}Th, {sup 235}U, {sup 238}U and {sup 239}Pu; Theoretical studies of neutron scattering; Neutron filters; New detector systems; and Upgrading of neutron target assembly, data acquisition system, and accelerator/beam-line apparatus.

  20. Benchmark field study of deep neutron penetration

    SciTech Connect

    Morgan, J.F.; Sale, K. ); Gold, R.; Roberts, J.H.; Preston, C.C. )

    1991-06-10

    A unique benchmark neutron field has been established at the Lawrence Livermore National Laboratory (LLNL) to study deep penetration neutron transport. At LLNL, a tandem accelerator is used to generate a monoenergetic neutron source that permits investigation of deep neutron penetration under conditions that are virtually ideal to model, namely the transport of mono-energetic neutrons through a single material in a simple geometry. General features of the Lawrence Tandem (LATAN) benchmark field are described with emphasis on neutron source characteristics and room return background. The single material chosen for the first benchmark, LATAN-1, is a steel representative of Light Water Reactor (LWR) Pressure Vessels (PV). Also included is a brief description of the Little Boy replica, a critical reactor assembly designed to mimic the radiation doses from the atomic bomb dropped on Hiroshima, and its us in neutron spectrometry. 18 refs.

  1. Fast sweeping reflectometry upgrade on Tore Supra

    SciTech Connect

    Clairet, F.; Bottereau, C.; Molina, D.; Ducobu, L.; Leroux, F.; Barbuti, A.; Heuraux, S.

    2010-10-15

    In order to study the temporal dynamics of turbulence, the sweep time of our reflectometry has been shortened from 20 to 2 {mu}s with 1 {mu}s dead time. Detailed technical aspects of the upgrade are given, namely, about the stability of the ramp generation, the detection setup, and the fast acquisition module. A review of studies (velocity measurement of the turbulence, modifications of the wavenumber spectrum, radial mapping of correlation time, etc.) offered by such improvements is presented.

  2. Model approach to solving the inverse problem of X-ray reflectometry and its application to the study of the internal structure of hafnium oxide films

    SciTech Connect

    Volkov, Yu. O. Kozhevnikov, I. V.; Roshchin, B. S.; Filatova, E. O.; Asadchikov, V. E.

    2013-01-15

    The key features of the inverse problem of X-ray reflectometry (i.e., the reconstruction of the depth profile of the dielectric constant using an experimental angular dependence of reflectivity) are discussed and essential factors leading to the ambiguity of its solution are analyzed. A simple approach to studying the internal structure of HfO{sub 2} films, which is based on the application of a physically reasonable model, is considered. The principles for constructing a film model and the criteria for choosing a minimal number of fitting parameters are discussed. It is shown that the ambiguity of the solution to the inverse problem is retained even for the simplest single-film models. Approaches allowing one to pick out the most realistic solution from several variants are discussed.

  3. Nuclear and neutron matter studies

    SciTech Connect

    Wiringa, R.B.; Akmal, A.; Pandharipande, V.R.

    1995-08-01

    We are studying nuclear and neutron matter with the new Argonne v{sub 18} NN and Urbana 3N potentials. We use variational wave functions and a diagrammatic cluster expansion with Fermi hypernetted and single-operator chain (FHNC/SOC) integral equations to evaluate the energy expectation value. Initial results show some interesting differences with our previous calculations with the older Argonne v{sub 14} potential. In particular, there are a number of diagrams involving L{center_dot}S and L{sup 2} terms which were small with the older model and were rather crudely estimated or even neglected. It appears that these terms are more important with the new potential and will have to be evaluated more accurately. Work on this subject is in progress. A simple line of attack is to just add additional diagrams at the three-body cluster level. A longer term approach may be to adapt some of the methods for evaluating nucleon clusters used in the few-body and closed shell nuclei described above.

  4. Microwave imaging reflectometry in LHD

    NASA Astrophysics Data System (ADS)

    Yamaguchi, S.; Nagayama, Y.; Pavlichenko, R.; Inagaki, S.; Kogi, Y.; Mase, A.

    2006-10-01

    A multichannel reflectometry with an imaging optical system is under development for the measurement of the electron density fluctuations in the Large Helical Device (LHD). The right-hand cutoff layer is utilized as a reflection surface. The angle of an ellipsoidal mirror installed inside the vacuum chamber is remotely adjustable with the ultrasonic motor in order to optimize the illumination angle for the wider range of the plasma parameters. An oscillation due to density fluctuation was observed using the microwave imaging reflectometry for the first time in LHD plasma experiment.

  5. Microwave imaging reflectometry in LHD

    SciTech Connect

    Yamaguchi, S.; Nagayama, Y.; Pavlichenko, R.; Inagaki, S.; Kogi, Y.; Mase, A.

    2006-10-15

    A multichannel reflectometry with an imaging optical system is under development for the measurement of the electron density fluctuations in the Large Helical Device (LHD). The right-hand cutoff layer is utilized as a reflection surface. The angle of an ellipsoidal mirror installed inside the vacuum chamber is remotely adjustable with the ultrasonic motor in order to optimize the illumination angle for the wider range of the plasma parameters. An oscillation due to density fluctuation was observed using the microwave imaging reflectometry for the first time in LHD plasma experiment.

  6. 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

  7. Neutron Scattering Studies of Fluorite Compounds.

    NASA Astrophysics Data System (ADS)

    Hackett, Michael Andrew

    Available from UMI in association with The British Library. Requires signed TDF. The properties of some important compounds with the fluorite structure have been investigated using neutron scattering techniques. All of the compounds in this study have important technological applications, as well as being of intrinsic scientific interest. Inelastic neutron scattering and high temperature technology have been used to measure phonon energies in thorium dioxide at temperatures above 3000K. These phonon energies have been used to determine the elastic constants as a function of temperature. Thorium dioxide provides an interesting comparison with uranium dioxide which has been studied in order to try and establish the cause of the anomalously large enthalpy of this compound. Quasielastic neutron scattering has been used to demonstrate that the dynamic ionic-disorder which occurs in ThO_2 behaves in a similar way to that observed in UO _2 at high temperature. Whilst at only 12K, splittings have been measured in the crystal field excitations of UO_2 which have a significant effect on the theoretical analysis of its thermodynamic properties. This experiment was performed using neutrons scattered with a high energy transfer. Elastic and quasielastic diffuse scattering have both been used to investigate the vacancy-stabilised cubic structure of yttria doped zirconia. Computer modelling of the measured neutron scattering intensities has played a vital role in this part of the study. By the combination of neutron scattering measurements and computational techniques a three part model has been developed for the defect structure in yttria-stabilised zirconia which can explain the ionic conductivity in this compound. Ionic disorder has been observed in the anti-fluorite compounds lithium oxide and magnesium silicide at high temperature, using diffuse quasielastic neutron scattering. The full phonon energy dispersion relation and the elastic constants at high temperature have also

  8. Neutron Scattering Studies of Vortex Matter in Type-II Superconductors

    SciTech Connect

    Xinsheng Ling

    2012-02-02

    The proposed program is an experimental study of the fundamental properties of Abrikosov vortex matter in type-II superconductors. Most superconducting materials used in applications such as MRI are type II and their transport properties are determined by the interplay between random pinning, interaction and thermal fluctuation effects in the vortex state. Given the technological importance of these materials, a fundamental understanding of the vortex matter is necessary. The vortex lines in type-II superconductors also form a useful model system for fundamental studies of a number of important issues in condensed matter physics, such as the presence of a symmetry-breaking phase transition in the presence of random pinning. Recent advances in neutron scattering facilities such as the major upgrade of the NIST cold source and the Spallation Neutron Source are providing unprecedented opportunities in addressing some of the longstanding issues in vortex physics. The core component of the proposed program is to use small angle neutron scattering and Bitter decoration experiments to provide the most stringent test of the Bragg glass theory by measuring the structure factor in both the real and reciprocal spaces. The proposed experiments include a neutron reflectometry experiment to measure the precise Q-dependence of the structure factor of the vortex lattice in the Bragg glass state. A second set of SANS experiments will be on a shear-strained Nb single crystal for testing a recently proposed theory of the stability of Bragg glass. The objective is to artificially create a set of parallel grain boundaries into a Nb single crystal and use SANS to measure the vortex matter diffraction pattern as a function of the changing angle between the applied magnetic field to the grain boundaries. The intrinsic merits of the proposed work are a new fundamental understanding of type-II superconductors on which superconducting technology is based, and a firm understanding of phases

  9. β-delayed neutron emission studies

    NASA Astrophysics Data System (ADS)

    Gómez-Hornillos, M. B.; Rissanen, J.; Taín, J. L.; Algora, A.; Kratz, K. L.; Lhersonneau, G.; Pfeiffer, B.; Agramunt, J.; Cano-Ott, D.; Gorlychev, V.; Caballero-Folch, R.; Martínez, T.; Achouri, L.; Calvino, F.; Cortés, G.; Eronen, T.; García, A.; Parlog, M.; Podolyak, Z.; Pretel, C.; Valencia, E.

    2014-01-01

    The study of β-delayed neutron emission plays a major role in different fields such as nuclear technology, nuclear astrophysics and nuclear structure. However the quality of the existing experimental data nowadays is not sufficient for the various technical and scientific applications and new high precision measurements are necessary to improve the data bases. One key aspect to the success of these high precission measurements is the use of a very pure ion beam that ensures that only the ion of interest is produced. The combination of the IGISOL mass separator with the JYFLTRAP Penning trap is an excellent tool for this type of measurement because of the ability to deliver isobarically and even isomerically clean beams. Another key feature of the installation is the non-chemical selectivity of the IGISOL ion source which allows measurements in the important region of refractory elements. This paper summarises the β-delayed neutron emission studies that have been carried out at the IGISOL facility with two different neutron detectors based on 3He counters in a polyethylene moderator: the Mainz neutron detector and the BEta deLayEd Neutron detector.

  10. Nuclear-spectroscopy problems studied with neutrons

    SciTech Connect

    Raman, S.

    1982-01-01

    Nuclear spectroscopy with neutrons continues to have a major impact on the progress of nuclear science. Neutrons, being uncharged, are particularly useful for the study of low energy reactions. Recent advances in time-of-flight spectroscopy, as well as in the gamma ray spectroscopy following neutron capture, have permitted precision studies of unbound and bound nuclear levels and related phenomena. By going to new energy domains, by using polarized beams and targets, through the invention of new kinds of detectors, and through the general improvement in beam quantity and quality, new features of nuclear structure and reactions have been obtained that are not ony interesting per se but are also grist for old and new theory mills. The above technical advances have opened up new opportunities for further discoveries.

  11. A fundamental study on hyper-thermal neutrons for neutron capture therapy.

    PubMed

    Sakurai, Y; Kobayashi, T; Kanda, K

    1994-12-01

    The utilization of hyper-thermal neutrons, which have an energy spectrum with a Maxwellian distribution at a higher temperature than room temperature (300 K), was studied in order to improve the thermal neutron flux distribution at depth in a living body for neutron capture therapy. Simulation calculations were carried out using a Monte Carlo code 'MCNP-V3' in order to investigate the characteristics of hyper-thermal neutrons, i.e. (i) depth dependence of the neutron energy spectrum, and (ii) depth distribution of the reaction rate in a water phantom for materials with 1/v neutron absorption. It is confirmed that hyper-thermal neutron irradiation can improve the thermal neutron flux distribution in the deeper areas in a living body compared with thermal neutron irradiation. When hyper-thermal neutrons with a 3000 K Maxwellian distribution are incident on a body, the reaction rates of 1/v materials such as 14N, 10B etc are about twice that observed for incident thermal neutrons at 300 K, at a depth of 5 cm. The limit of the treatable depth for tumours having 30 ppm 10B is expected to be about 1.5 cm greater by utilizing hyper-thermal neutrons at 3000 K compared with the incidence of thermal neutrons at 300 K.

  12. Estimation of the daily water consumption by maize under Atlantic climatic conditions (A Coruña, NW Spain) using Frequency Domain Reflectometry - a case study

    NASA Astrophysics Data System (ADS)

    Mestas-Valero, R. M.; Mirás-Avalos, J. M.; Vidal-Vázquez, E.

    2012-03-01

    Climatic variables and soil present a high spatio-temporal variability. Evapotranspiration estimations based on climatic variables may be inadequate for assessing soil water content in the root-influenced zone and/or soil water consumption by plants. Other methods may provide better estimates of this water consumption. The aim of this study was to quantify the soil moisture dynamics in the root-influenced zone and to assess the daily water consumption by the crop using Frequency Domain Reflectometry (FDR). The studied site is located in A Coruña (Spain). The study was carried out from June to October in 2008 and 2009, in a maize (Zea mays, L.) field on a silt-clay textured soil. Evapotranspiration was estimated by the Penman-Monteith equation using meteorological data from a station located on the experimental site. Soil water content in the root-influenced zone (0-60 cm depth) was hourly monitored each 20 cm (0-20 cm, 20-40 cm, and 40-60 cm) using FDR. Evaluations were performed on days with slight or no rainfall. During the study period, the magnitude of the diurnal soil water loss was more evident in the first layer (0-20 cm depth) and less important in the subsequent soil layers. The greatest consumption occurred between 14 and 19 h, up to 53.64% of the total. Overall, daily water consumption increased significantly with soil water content (p-value < 0.001). In general, water losses from the 0-20 cm soil layer were greater than in subsoil horizons due to maize water-uptake and evaporation. In contrast, water content in the deepest part of the soil profile was close to saturation, even on the driest days of the studied period. Evapotranspiration overestimate maize water requirements as its values were greater than those measured with the probe. In conclusion, FDR allows a more accurate estimation of the soil water balance. Therefore, monitoring soil water content would be useful in the assessment of saturation risks or water stress (drought), thus aiding in the

  13. A preliminary neutron crystallographic study of thaumatin

    SciTech Connect

    Teixeira, Susana C. M.; Blakeley, Matthew P.; Leal, Ricardo M. F.; Mitchell, Edward P.; Forsyth, V. Trevor

    2008-05-01

    Preliminary neutron crystallographic data from the sweet protein thaumatin have been recorded using the LADI-III diffractometer at the Institut Laue Langevin (ILL). The results illustrate the feasibility of a full neutron structural analysis aimed at further understanding the molecular basis of the perception of sweet taste. Such an analysis will exploit the use of perdeuterated thaumatin. A preliminary neutron crystallographic study of the sweet protein thaumatin is presented. Large hydrogenated crystals were prepared in deuterated crystallization buffer using the gel-acupuncture method. Data were collected to a resolution of 2 Å on the LADI-III diffractometer at the Institut Laue Langevin (ILL). The results demonstrate the feasibility of a full neutron crystallographic analysis of this structure aimed at providing relevant information on the location of H atoms, the distribution of charge on the protein surface and localized water in the structure. This information will be of interest for understanding the specificity of thaumatin–receptor interactions and will contribute to further understanding of the molecular mechanisms underlying the perception of taste.

  14. Ames collaborative study of cosmic ray neutrons

    NASA Technical Reports Server (NTRS)

    Hewitt, J. E.; Hughes, L.; Mccaslin, J. B.; Stephens, L. D.; Rindi, A.; Smith, A. R.; Thomas, R. H.; Griffith, R. V.; Welles, C. G.; Baum, J. W.

    1976-01-01

    The results of a collaborative study to define both the neutron flux and the spectrum more precisely and to develop a dosimetry package that can be flown quickly to altitude for solar flare events are described. Instrumentation and analysis techniques were used which were developed to measure accelerator-produced radiation. The instruments were flown in the Ames Research Center high altitude aircraft. Neutron instrumentation consisted of Bonner spheres with both active and passive detector elements, threshold detectors of both prompt-counter and activation-element types, a liquid scintillation spectrometer based on pulse-shape discrimination, and a moderated BF3 counter neutron monitor. In addition, charged particles were measured with a Reuter-Stokes ionization chamber system and dose equivalent with another instrument. Preliminary results from the first series of flights at 12.5 km (41,000 ft) are presented, including estimates of total neutron flux intensity and spectral shape and of the variation of intensity with altitude and geomagnetic latitude.

  15. Study of neutron focusing at the Texas Cold Neutron Source. Final report

    SciTech Connect

    Wehring, B.W.; Uenlue, K.

    1996-12-19

    The goals of this three-year study were: (1) design a neutron focusing system for use with the Texas Cold Neutron Source (TCNS) to produce an intense beam of cold neutrons appropriate for prompt gamma activation analysis (PGAA); (2) orchestrate the construction of the focusing system, integrate it into the TCNS neutron guide complex, and measure its performance; and (3) design, setup, and test a cold-neutron PGAA system which utilizes the guided focused cold neutron beam. During the first year of the DOE grant, a new procedure was developed and used to design a focusing converging guide consisting of truncated rectangular cone sections. Detailed calculations were performed using a 3-D Monte Carlo code which the authors wrote to trace neutrons through the curved guide of the TCNS into the proposed converging guide. Using realistic reflectivities for Ni-Ti supermirrors, the authors obtained gains of 3 to 5 for 4 different converging guide geometries. During the second year of the DOE grant, the subject of this final report, Ovonic Synthetic Materials Company was contracted to build a converging neutron guide focusing system to the specifications. Considerable time and effort were spent working with Ovonics on selecting the materials for the converging neutron guide system. The major portion of the research on the design of a cold-neutron PGAA system was also completed during the second year. At the beginning of the third year of the grant, a converging neutron guide focusing system had been ordered, and a cold-neutron PGAA system had been designed. Since DOE did not fund the third year, there was no money to purchase the required equipment for the cold-neutron PGAA system and no money to perform tests of either the converging neutron guide or the cold-neutron PGAA system. The research already accomplished would have little value without testing the systems which had been designed. Thus the project was continued at a pace that could be sustained with internal funding.

  16. Potential of space-borne GNSS reflectometry to constrain simulations of the ocean circulation. A case study for the South African current system

    NASA Astrophysics Data System (ADS)

    Saynisch, Jan; Semmling, Maximilian; Wickert, Jens; Thomas, Maik

    2015-11-01

    The Agulhas current system transports warm and salty water masses from the Indian Ocean into the Southern Ocean and into the Atlantic. The transports impact past, present, and future climate on local and global scales. The size and variability, however, of the respective transports are still much debated. In this study, an idealized model based twin experiment is used to study whether sea surface height (SSH) anomalies estimated from reflected signals of the Global Navigation Satellite System reflectometry (GNSS-R) can be used to determine the internal water mass properties and transports of the Agulhas region. A space-borne GNSS-R detector on the International Space Station (ISS) is assumed and simulated. The detector is able to observe daily SSH fields with a spatial resolution of 1-5∘. Depending on reflection geometry, the precision of a single SSH observation is estimated to reach 3 cm (20 cm) when the carrier phase (code delay) information of the reflected GNSS signal is used. The average precision over the Agulhas region is 7 cm (42 cm). The proposed GNSS-R measurements surpass the radar-based satellite altimetry missions in temporal and spatial resolution but are less precise. Using the estimated GNSS-R characteristics, measurements of SSH are generated by sampling a regional nested general circulation model of the South African oceans. The artificial observations are subsequently assimilated with a 4DVAR adjoint data assimilation method into the same ocean model but with a different initial state and forcing. The assimilated and the original, i.e., the sampled model state, are compared to systematically identify improvements and degradations in the model variables that arise due to the assimilation of GNSS-R based SSH observations. We show that SSH and the independent, i.e., not assimilated model variables velocity, temperature, and salinity improve by the assimilation of GNSS-R based SSH observations. After the assimilation of 90 days of SSH observations

  17. DNA hydration studied by neutron fiber diffraction

    SciTech Connect

    Fuller, W.; Forsyth, V.T.; Mahendrasingam, A.; Langan, P.; Pigram, W.J.

    1994-12-31

    The development of neutron high angle fiber diffraction to investigate the location of water around the deoxyribonucleic acid (DNA) double-helix is described. The power of the technique is illustrated by its application to the D and A conformations of DNA using the single crystal diffractometer, D19, at the Institute Laue-Langevin, Grenoble and the time of flight diffractometer, SXD, at the Rutherford Appleton ISIS Spallation Neutron Source. These studies show the existence of bound water closely associated with the DNA. The patterns of hydration in these two DNA conformations are quite distinct and are compared to those observed in X-ray single crystal studies of two-stranded oligodeoxynucleotides. Information on the location of water around the DNA double-helix from the neutron fiber diffraction studies is combined with that on the location of alkali metal cations from complementary X-ray high angle fiber diffraction studies at the Daresbury Laboratory SRS using synchrotron radiation. These analyses emphasize the importance of viewing DNA, water and ions as a single system with specific interactions between the three components and provide a basis for understanding the effect of changes in the concentration of water and ions in inducing conformations] transitions in the DNA double-helix.

  18. Study of ``neutron bursts'' with Mexico City neutron monitor

    NASA Astrophysics Data System (ADS)

    Stenkin, Yu. V.; Valdés-Galicia, J. F.; Hurtado, A.; Musalem, O.

    2001-11-01

    A search was made for abnormal high multiplicity neutron events, with the combined array of a 6NM64 neutron supermonitor and eight plastic scintillators installed in México City. Some evidences were presented in the last years for such events [Akad. Nauk, Ser. Fiz. 61 (3) (1997) 486; Nucl. Phys. B (Proc. Suppl.) 75A (1999) 333], but their existence was not established beyond any doubt, nor the conditions under which they occur. Our results show the existence of very high multiplicity events in coincidence with high counting rates of the plastic scintillators during several milliseconds. A detailed consideration of the experiment and data on the multiplicities as well as the temporal distributions of the pulses are presented. We propose that the explanation of the peculiar pulse time distributions in the detectors in such events may be found in neutron physics known processes rather than in delayed extensive air showers (EAS) component phenomena as claimed in [Nucl. Phys. B (Proc. Suppl.) 75A (1999) 333]. On the other hand, the origin of these EAS with very high multiplicity of neutrons is a question that remains unanswered.

  19. Neutron scattering study of dilute supercritical solutions

    NASA Astrophysics Data System (ADS)

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

    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.

  20. 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.

  1. Time domain reflectometry in time variant plasmas

    NASA Technical Reports Server (NTRS)

    Scherner, Michael J.

    1992-01-01

    The effects of time-dependent electron density fluctuations on a synthesized time domain reflectometry response of a one-dimensional cold plasma sheath are considered. Numerical solutions of the Helmholtz wave equation, which describes the electric field of a normally incident plane wave in a specified static electron density profile, are used. A study of the effects of Doppler shifts resulting from moving density fluctuations in the electron density profile of the sheath is included. Varying electron density levels corrupt time domain and distance measurements. Reducing or modulating the electron density levels of a given electron density profile affects the time domain response of a plasma and results in motion of the turning point, and the effective motion has a significant effect on measuring electron density locations.

  2. Neutron transport study of a beam port based dynamic neutron radiography facility

    NASA Astrophysics Data System (ADS)

    Khaial, Anas M.

    Neutron radiography has the ability to differentiate between gas and liquid in two-phase flow due both to the density difference and the high neutron scattering probability of hydrogen. Previous studies have used dynamic neutron radiography -- in both real-time and high-speed -- for air-water, steam-water and gas-liquid metal two-phase flow measurements. Radiography with thermal neutrons is straightforward and efficient as thermal neutrons are easier to detect with relatively higher efficiency and can be easily extracted from nuclear reactor beam ports. The quality of images obtained using neutron radiography and the imaging speed depend on the neutron beam intensity at the imaging plane. A high quality neutron beam, with thermal neutron intensity greater than 3.0x 10 6 n/cm2-s and a collimation ratio greater than 100 at the imaging plane, is required for effective dynamic neutron radiography up to 2000 frames per second. The primary objectives of this work are: (1) to optimize a neutron radiography facility for dynamic neutron radiography applications and (2) to investigate a new technique for three-dimensional neutron radiography using information obtained from neutron scattering. In this work, neutron transport analysis and experimental validation of a dynamic neutron radiography facility is studied with consideration of real-time and high-speed neutron radiography requirements. A beam port based dynamic neutron radiography facility, for a target thermal neutron flux of 1.0x107 n/cm2-s, has been analyzed, constructed and experimentally verified at the McMaster Nuclear Reactor. The neutron source strength at the beam tube entrance is evaluated experimentally by measuring the thermal and fast neutron fluxes using copper activation flux-mapping technique. The development of different facility components, such as beam tube liner, gamma ray filter, beam shutter and biological shield, is achieved analytically using neutron attenuation and divergence theories. Monte

  3. Studying the neutron-unbound ^18B

    NASA Astrophysics Data System (ADS)

    Spyrou, A.; Baumann, T.; Bazin, D.; Christian, G.; Mosby, S.; Strogman, M.; Thoennessen, M.; Brown, J.; Deyoung, P. A.; Deline, A.; Finck, J. E.; Russel, A.; Frank, N.; Breitbach, E.; Howes, R.; Peters, W. A.; Schiller, A.

    2009-10-01

    The decay of the neutron-unbound ground state of ^18B was studied for the first time through a single-proton knockout reaction from a 62 MeV/u ^19C beam. The decay energy spectrum was reconstructed from coincidence measurements between the emitted neutron and ^17B fragment using the MoNA/Sweeper setup. An s-wave line shape was used to describe the experimental spectrum resulting in an upper limit for the scattering length of -50 fm which corresponds to a decay energy < 10 keV. Observing an s-wave decay of ^18B provides an experimental verification that the ground state of ^19C includes a large s component. In addition, our results show that the s-d mixing proposed for ^19C is also present in ^18B, therefore no clear signs of an inversion between the s1/2 and d5/2 orbitals can be suggested.

  4. Neutron scattering study of frustrated magnets

    NASA Astrophysics Data System (ADS)

    Qiu, Yiming

    Geometrical frustration in magnets consisting of networks of triangles or tetrahedra of spins can lead to unusual cooperative paramagnetic phases extending to temperatures well below the Curie-Weiss temperature. In many cases, strong fluctuations prevent magnetic order in the absence of an external magnetic field. In this thesis, I study geometrically frustrated antiferromagnets La4Cu3MoO12 and UNi4B and spin ice pyrochlore Dy2Ti2O7 using neutron scattering technique. In La4Cu3MoO12, triangles of magnetic Cu2+ ions form a slightly distorted orthorhombic structure. Despite the large Curie-Weiss temperature (thetaCW = -558 K), antiferromagnetic Neel order develops only at T N = 2.6 K. At low temperatures, the copper spin-1/2 behave as strongly coupled spin-trimers. Inelastic neutron scattering shows excitations from the ground state at 7.5(3) meV and 132.5(5) meV. An additional peak in the neutron scattering spectrum, which appears at 125.0(5) meV on heating is ascribed to a transition between excited states. The wave-vector and temperature-dependence of the inelastic magnetic scattering cross section is consistent with inta-trimer transitions. Magnetic neutron diffraction reveals long range antiferromagnetic order below TN = 2.6 K, which doubles the unit cell along the a direction. The ordered magnetic structure is described as inter-trimer order where spin correlations within trimers are controlled by the strong intra-trimer interactions. UNi4B is a frustrated intermetallic heavy fermion metal exhibiting both geometrical frustration and strong electron correlation. Magnetic U ions occupy the hexagonal basal plane. Neutron scattering reveals that unusual Neel order develops below TN = 20 K with two incommensurate wave vectors and a mixture of commensurate and incommensurate magnetic structure. The commensurate structure can be described as three sublattices of next-nearest neighbors with moments 120° apart and perpendicular to c-axis. Dy2Ti2O7, in which magnetic Dy

  5. MAGNETIC NEUTRON SCATTERING

    SciTech Connect

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

    2004-07-30

    , ranging from large-scale structures and dynamics of polymers and biological systems, to electronic properties of today's technological materials. Neutron scattering developed into a vast field, encompassing many different experimental techniques aimed at exploring different aspects of matter's atomic structure and dynamics. Modern magnetic neutron scattering includes several specialized techniques designed for specific studies and/or particular classes of materials. Among these are magnetic reflectometry aimed at investigating surfaces, interfaces, and multilayers, small-angle scattering for the large-scale structures, such as a vortex lattice in a superconductor, and neutron spin-echo spectroscopy for glasses and polymers. Each of these techniques and many others offer exciting opportunities for examining magnetism and warrant extensive reviews, but the aim of this chapter is not to survey how different neutron-scattering methods are used to examine magnetic properties of different materials. Here, we concentrate on reviewing the basics of the magnetic neutron scattering, and on the recent developments in applying one of the oldest methods, the triple axis spectroscopy, that still is among the most extensively used ones. The developments discussed here are new and have not been coherently reviewed. Chapter 2 of this book reviews magnetic small-angle scattering, and modern techniques of neutron magnetic reflectometry are discussed in Chapter 3.

  6. Small-Angle Neutron Scattering Studies on the Multilamellae Formed by Mixing Lamella-Forming Cationic Diblock Copolymers with Lipids and Their Interaction with DNA.

    PubMed

    Yang, Po-Wei; Lin, Tsang-Lang; Liu, I-Ting; Hu, Yuan; Jeng, U-Ser; Gilbert, Elliot Paul

    2016-02-23

    We demonstrate that the lamella-forming polystyrene-block-poly(N-methyl-4-vinylpyridinium iodine) (PS-b-P4VPQ), with similar sizes of the PS and P4VPQ blocks, can be dispersed in the aqueous solutions by forming lipid/PS-b-P4VPQ multilamellae. Using small-angle neutron scattering (SANS) and 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (d62-DPPC) in D2O, a broad correlation peak is found in the scattering profile that signifies the formation of the loosely ordered d62-DPPC/PS-b-P4VPQ multilamellae. The thicknesses of the hydrophobic and hydrophilic layers of the d62-DPPC/PS-b-P4VPQ multilamellae are close to the PS layer and the condensed brush layer thicknesses as determined from previous neutron reflectometry studies on the PS-b-P4VPQ monolayer at the air-water interface. Such well-dispersed d62-DPPC/PS-b-P4VPQ multilamellae are capable of forming multilamellae with DNA in aqueous solution. It is found that the encapsulation of DNA in the hydrophilic layer of the d62-DPPC/PS-b-P4VPQ multilamellae slightly increases the thickness of the hydrophilic layer. Adding CaCl2 can enhance the DNA adsorption in the hydrophilic brush layer, and it is similar to that observed in the neutron reflectometry study of the DNA adsorption by the PS-b-P4VPQ monolayer. PMID:26818185

  7. Effects of asymmetry and target location on microwave imaging reflectometry

    SciTech Connect

    Ignatenko, M.; Mase, A.; Bruskin, L.G.; Kogi, Y.; Hojo, H.

    2004-10-01

    In this article we perform a numerical study of microwave imaging reflectometry (MIR) and compare it with conventional reflectometry system. As an approximation to the reflections by real plasma fluctuations, a corrugated wheel is used. As far as general performance is concerned, our simulations confirm the results by Munsat et al. [Plasma Phys. Controlled Fusion 45, 469 (2003)] that the MIR system reproduces shape of corrugation far from the wheel while conventional systems fail to do so. We addressed the effects of asymmetry and defocusing of the wheel-reflectometer system as well as spectral sensitivity of the imaging reflectometer. For a particular geometry we estimated the deterioration of the MIR performance due to misalignments and existence of broadband fluctuation000.

  8. Polarized neutron reflectivity study of perpendicular magnetic anisotropy in MgO/CoFeB/W thin films

    NASA Astrophysics Data System (ADS)

    Ambaye, Haile; Zhan, Xiao; Li, Shufa; Lauter, Valeria; Zhu, Tao

    In this work we study the origin of PMA in MgO/CoFeB/W trilayer systems using polarized neutron reflectivity. Recently, the spin Hall effect in the heavy metals, such as Pt and Ta, has been of significant interest for highly efficient magnetization switching of the ultrathin ferromagnets sandwiched by such a heavy metal and an oxide, which can be used for spintronic based memory and logic devices. Most work has focused on heavy-metal/ferromagnet/oxide trilayer (HM/FM/MO) structures with perpendicular magnetic anisotropy (PMA), where the oxide layer plays the role of breaking inversion symmetry .No PMA was found in W/CoFeB/MgO films. An insertion of Hf layer in between the W and CoFeB layers, however, has been found to create a strong PMA. Roughness and formation of interface alloys by interdiffusion influences the extent of PMA. We intend to identify these influences using the depth sensitive technique of PNR. In our previous study, we have successfully performed polarized neutron reflectometry (PNR) measurements on the Ta/CoFeB/MgO/CoFeB/Ta thin film with MgO thickness of 1 nm. The PNR measurements were carried out using the BL-4A Magnetic Reflectometer at SNS. This work has been supported by National Basic Research Program of China (2012CB933102). Research at SNS was supported by the Office of BES, DOE.

  9. Study of a nTHGEM-based thermal neutron detector

    NASA Astrophysics Data System (ADS)

    Li, Ke; Zhou, Jian-Rong; Wang, Xiao-Dong; Xiong, Tao; Zhang, Ying; Xie, Yu-Guang; Zhou, Liang; Xu, Hong; Yang, Gui-An; Wang, Yan-Feng; Wang, Yan; Wu, Jin-Jie; Sun, Zhi-Jia; Hu, Bi-Tao

    2016-07-01

    With new generation neutron sources, traditional neutron detectors cannot satisfy the demands of the applications, especially under high flux. Furthermore, facing the global crisis in 3He gas supply, research on new types of neutron detector as an alternative to 3He is a research hotspot in the field of particle detection. GEM (Gaseous Electron Multiplier) neutron detectors have high counting rate, good spatial and time resolution, and could be one future direction of the development of neutron detectors. In this paper, the physical process of neutron detection is simulated with Geant4 code, studying the relations between thermal conversion efficiency, boron thickness and number of boron layers. Due to the special characteristics of neutron detection, we have developed a novel type of special ceramic nTHGEM (neutron THick GEM) for neutron detection. The performance of the nTHGEM working in different Ar/CO2 mixtures is presented, including measurements of the gain and the count rate plateau using a copper target X-ray source. A detector with a single nTHGEM has been tested for 2-D imaging using a 252Cf neutron source. The key parameters of the performance of the nTHGEM detector have been obtained, providing necessary experimental data as a reference for further research on this detector. Supported by National Natural Science Foundation of China (11127508, 11175199, 11205253, 11405191), Key Laboratory of Neutron Physics, CAEP (2013DB06, 2013BB04) and CAS (YZ201512)

  10. A Dosimetry Study of Deuterium-Deuterium Neutron Generator-based In Vivo Neutron Activation Analysis.

    PubMed

    Sowers, Daniel; Liu, Yingzi; Mostafaei, Farshad; Blake, Scott; Nie, Linda H

    2015-12-01

    A neutron irradiation cavity for in vivo neutron activation analysis (IVNAA) to detect manganese, aluminum, and other potentially toxic elements in human hand bone has been designed and its dosimetric specifications measured. The neutron source is a customized deuterium-deuterium neutron generator that produces neutrons at 2.45 MeV by the fusion reaction 2H(d, n)3He at a calculated flux of 7 × 10(8) ± 30% s(-1). A moderator/reflector/shielding [5 cm high density polyethylene (HDPE), 5.3 cm graphite and 5.7 cm borated (HDPE)] assembly has been designed and built to maximize the thermal neutron flux inside the hand irradiation cavity and to reduce the extremity dose and effective dose to the human subject. Lead sheets are used to attenuate bremsstrahlung x rays and activation gammas. A Monte Carlo simulation (MCNP6) was used to model the system and calculate extremity dose. The extremity dose was measured with neutron and photon sensitive film badges and Fuji electronic pocket dosimeters (EPD). The neutron ambient dose outside the shielding was measured by Fuji NSN3, and the photon dose was measured by a Bicron MicroREM scintillator. Neutron extremity dose was calculated to be 32.3 mSv using MCNP6 simulations given a 10-min IVNAA measurement of manganese. Measurements by EPD and film badge indicate hand dose to be 31.7 ± 0.8 mSv for neutrons and 4.2 ± 0.2 mSv for photons for 10 min; whole body effective dose was calculated conservatively to be 0.052 mSv. Experimental values closely match values obtained from MCNP6 simulations. These are acceptable doses to apply the technology for a manganese toxicity study in a human population. PMID:26509624

  11. A dosimetry study of deuterium-deuterium neutron generator-based in vivo neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Sowers, Daniel A.

    A neutron irradiation cavity for in vivo Neutron Activation Analysis (IVNAA) to detect manganese, aluminum, and other potentially toxic elements in human hand bone has been designed and its dosimetric specifications measured. The neutron source is a customized deuterium-deuterium neutron generator which produces neutrons at 2.45 MeV by the fusion reaction 2H(d, n)3He at a calculated flux of 7 x 108 +/-30% s-1. A moderator/reflector/shielding (5 cm high density polyethylene (HDPE), 5.3 cm graphite & 5.7 cm borated HDPE) assembly has been designed and built to maximize the thermal neutron flux inside the hand irradiation cavity and to reduce the extremity dose and effective dose to the human subject. Lead sheets are used to attenuate bremsstrahlung x rays and activation gammas. A Monte Carlo simulation (MCNP6) was used to model the system and calculate extremity dose. The extremity dose was measured with neutron and photon sensitive film badges and Fuji electronic pocket dosimeter (EPD). The neutron ambient dose outside the shielding was measured by Fuji NSN3, and photon dose by a Bicron MicroREM scintillator. Neutron extremity dose was calculated to be 32.3 mSv using MCNP6 simulations given a 10 min IVNAA measurement of manganese. Measurements by EPD and film badge indicate hand dose to be 31.7 +/- 0.8 mSv for neutron and 4.2 +/- 0.2 mSv for photon for 10 mins; whole body effective dose was calculated conservatively to be 0.052 mSv. Experimental values closely match values obtained from MCNP6 simulations. These are acceptable doses to apply the technology for a manganese toxicity study in a human population.

  12. A Dosimetry Study of Deuterium-Deuterium Neutron Generator-based In Vivo Neutron Activation Analysis.

    PubMed

    Sowers, Daniel; Liu, Yingzi; Mostafaei, Farshad; Blake, Scott; Nie, Linda H

    2015-12-01

    A neutron irradiation cavity for in vivo neutron activation analysis (IVNAA) to detect manganese, aluminum, and other potentially toxic elements in human hand bone has been designed and its dosimetric specifications measured. The neutron source is a customized deuterium-deuterium neutron generator that produces neutrons at 2.45 MeV by the fusion reaction 2H(d, n)3He at a calculated flux of 7 × 10(8) ± 30% s(-1). A moderator/reflector/shielding [5 cm high density polyethylene (HDPE), 5.3 cm graphite and 5.7 cm borated (HDPE)] assembly has been designed and built to maximize the thermal neutron flux inside the hand irradiation cavity and to reduce the extremity dose and effective dose to the human subject. Lead sheets are used to attenuate bremsstrahlung x rays and activation gammas. A Monte Carlo simulation (MCNP6) was used to model the system and calculate extremity dose. The extremity dose was measured with neutron and photon sensitive film badges and Fuji electronic pocket dosimeters (EPD). The neutron ambient dose outside the shielding was measured by Fuji NSN3, and the photon dose was measured by a Bicron MicroREM scintillator. Neutron extremity dose was calculated to be 32.3 mSv using MCNP6 simulations given a 10-min IVNAA measurement of manganese. Measurements by EPD and film badge indicate hand dose to be 31.7 ± 0.8 mSv for neutrons and 4.2 ± 0.2 mSv for photons for 10 min; whole body effective dose was calculated conservatively to be 0.052 mSv. Experimental values closely match values obtained from MCNP6 simulations. These are acceptable doses to apply the technology for a manganese toxicity study in a human population.

  13. Use of ultracold neutrons for condensed-matter studies

    SciTech Connect

    Michaudon, A.

    1997-05-01

    Ultracold neutrons have such low velocities that they are reflected by most materials at all incident angles and can be stored in material bottles for long periods of time during which their intrinsic properties can be studied in great detail. These features have been mainly used for fundamental-physics studies including the detection of a possible neutron electric dipole moment and the precise determination of neutron-decay properties. Ultracold neutrons can also play a role in condensed-matter studies with the help of high-resolution spectrometers that use gravity as a strongly dispersive medium for low-velocity neutrons. Such studies have so far been limited by the low intensity of existing ultracold-neutron sources but could be reconsidered with more intense sources, which are now envisaged. This report provides a broad survey of the properties of ultracold neutrons (including their reflectivity by different types of samples), of ultracold-neutron spectrometers that are compared with other high-resolution instruments, of results obtained in the field of condensed matter with these instruments, and of neutron microscopes. All these subjects are illustrated by numerous examples.

  14. Study of neutron focusing at the Texas Cold Neutron Source. Final report

    SciTech Connect

    Wehring, B.W.; Uenlue, K.

    1995-03-06

    Funds were received for the first year of a three year DOE Nuclear Engineering Research Grant, ``Study of Neutron Focusing at the Texas Cold Neutron Source`` (FGO2-92ER75711). The purpose of this three year study was to develop a neutron focusing system to be used with the Texas Cold Neutron Source (TCNS) to produce an intense beam of neutrons. A prompt gamma activation analysis (PGAA) facility was also to be designed, setup, and tested under the three year project. During the first year of the DOE grant, a new procedure was developed and used to design a focusing converging guide consisting of truncated rectangular cone sections. Detailed calculations were performed using a 3-D Monte Carlo code which we wrote to trace neutrons through the curved guide of the TCNS into the proposed converging guide. Using realistic reflectivities for Ni-Ti supermirrors, we obtained gains of 3 to 5 for the neutron flux averaged over an area of 1 {times} 1 cm.

  15. TEM study of neutron-irradiated iron

    SciTech Connect

    Horton, L.L.; Bentley, J.; Farrell, K.

    1981-01-01

    Results of a transmission electron microscopy study of the defect structure in iron neutron-irradiated to low fluences (less than or equal to 1 dpa) at temperatures of 455 to 1013/sup 0/K are presented. The dislocation microstructures coarsen with increasing irradiation temperature from decorated dislocations, through clusters of dislocation loops, to near-edge, interstitial dislocation loops with b = a<100>, and network segments. Significant cavity formation occurred only at 548 to 723/sup 0/K, with homogeneous distributions found only at 623 and 673/sup 0/K. The maximum swelling of 0.07% occurred at 673/sup 0/K. Large cavities had a truncated octahedral shape with (111) facets and (100) truncations. Damage halos were observed around boron-containing precipitates. The effects of interstitial impurities on microstructural development and the differences in the observed microstructures compared to those in refractory bcc metals are discussed. 8 figures, 6 tables.

  16. Study of a gold-foil-based multisphere neutron spectrometer.

    PubMed

    Wang, Z; Hutchinson, J D; Hertel, N E; Burgett, E; Howell, R M

    2008-01-01

    Multisphere neutron spectrometers with active thermal neutron detectors cannot be used in high-intensity radiation fields due to pulse pile-up and dead-time effects. Thus, a multisphere spectrometer using a passive detection system, specifically gold foils, has been investigated in this work. The responses of a gold-foil-based Bonner sphere neutron spectrometer were studied for two different gold-foil holder designs; an aluminium-polyethylene holder and a polyethylene holder. The responses of the two designs were calculated for four incident neutron beam directions, namely, parallel, perpendicular and at +/-45 degrees relative to the flat surface of the foil. It was found that the use of polyethylene holder resulted in a more isotropic response to neutrons for the four incident directions considered. The computed responses were verified by measuring the neutron spectrum of a 252Cf source with known strength.

  17. X-ray and neutron surface scattering for studying lipid/polymer assemblies at the air-liquid and solid-liquid interfaces.

    PubMed

    Majewski, J; Kuhl, T L; Wong, J Y; Smith, G S

    2000-09-01

    Simple mono- and bilayers, built of amphiphilic molecules and prepared at air-liquid or solid-liquid interfaces, can be used as models to study such effects as water penetration, hydrocarbon chain packing, and structural changes due to head group modification. In the paper, we will discuss neutron and X-ray reflectometry and grazing incidence X-ray diffraction techniques used to explore structures of such ultra-thin organic films in different environments. We will illustrate the use of these methods to characterize the morphologies of the following systems: (i) polyethylene glycol-modified distearoylphosphatidylethanolamine monolayers at air-liquid and solid-liquid interfaces; and (ii) assemblies of branched polyethyleneimine polymer and dimyristoylphophatidylcholine lipid at solid-liquid interfaces.

  18. 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.

  19. Neutron Tube Design Study for Boron Neutron Capture TherapyApplication

    SciTech Connect

    Verbeke, J.M.; Lee, Y.; Leung, K.N.; Vujic, J.; Williams, M.D.; Wu, L.K.; Zahir, N.

    1998-01-04

    Radio-frequency (RF) driven ion sources are being developed in Lawrence Berkeley National Laboratory (LBNL) for sealed-accelerator-tube neutron generator application. By using a 5-cm-diameter RF-driven multicusp source H{sup +} yields over 95% have been achieved. These experimental findings will enable one to develop compact neutron generators based on the D-D or D-T fusion reactions. In this new neutron generator, the ion source, the accelerator and the target are all housed in a sealed metal container without external pumping. Recent moderator design simulation studies have shown that 14 MeV neutrons could be moderated to therapeutically useful energy ranges for boron neutron capture therapy (BNCT). The dose near the center of the brain with optimized moderators is about 65% higher than the dose obtained from a typical neutron spectrum produced by the Brookhaven Medical Research Reactor (BMRR), and is comparable to the dose obtained by other accelerator-based neutron sources. With a 120 keV and 1 A deuteron beam, a treatment time of {approx}35 minutes is estimated for BNCT.

  20. Neutron Studies of Geometrically Frustrated Magnets

    NASA Astrophysics Data System (ADS)

    Gardner, Jason

    2004-03-01

    Antiferromagnetically coupled spins residing on a network of corner sharing triangles (Kagome) or tetrahedra (pyrochlore) have attracted much attention in recent years [1-4] and often display phenomena known broadly as geometrical frustration. Because of their low propensity to order, even for classical spins, antiferromagnetic materials based on a pyrochlore lattice appear to be excellent systems for studying exotic ground states. It has also been shown that ferromagnetically coupled spins can be frustrated on such a lattice, if there is considerable local Ising anisotropy. Detailed neutron scattering measurements (elastic and inelastic scattering) taken on the antiferromagnets, Tb_2Ti_2O7 and Gd_2Ti_2O_7, and the ferromagnet, Ho_2Ti_2O_7, will be presented. The neutron data will be backed up with bulk property results. Evidence of short-range magnetic correlations, frozen moments and long-range magnetic ordering in different parts of applied field and temperature space will be discussed. Tb_2Ti_2O7 is a cooperative paramagnet with an effective paramagnetic moment of 9.7 μ_B, has be shown to magnetically order in modest fields and temperatures, however in zero field the system does not order above 15 mK. Ho_2Ti_2O7 is known as a "dipolar spin ice" [3-4] compound and this will be discussed in some detail. If time permits I will present new results on the magnetic ordering of Gd_2Ti_2O7 in zero field. [1] Magnetic Systems with Competing Interactions, edited by H.T. Diep (World Scientific, Singapore, 1994) and Can. J. Phys. 79, (2001). [2] J. S. Gardner et al., Phys. Rev. Lett., 82, 1012, (1999). [3] S. T. Bramwell and M. P. Gingras, Science, 294, 1495, (2001). [4] A. P. Ramirez et al., Nature, 399, 333 (1999).

  1. Study of neutron rich carbon isotopes

    NASA Astrophysics Data System (ADS)

    Fallon, Paul

    2012-03-01

    Electric quadrupole (E2) matrix elements are important quantities in nuclear structure. In particular they are sensitive to nuclear deformation, the decoupling of proton and neutron degrees of freedom, and are often affected by small components of the nuclear wave function. Neutron-rich carbon isotopes have attracted a great deal of attention recently, both experimentally and theoretically, with regards to the question of spatially extended (halo-like) and decoupled valence neutrons. For example, 19C and the drip-line nucleus 22C are proposed to have ground-state neutron halo structures. Electric quadrupole transition rates in 16C 18C and 20C are among the lowest found throughout the nuclear chart and this fact has been cited by some as evidence for a reduced coupling between the valence neutrons and the core nucleons. In this talk I will present the results from our experiments to measure the transition rates in 16,18,20C and discuss the evidence for a ``decoupling'' of valence neutrons from the core that goes beyond the usual shell model approach. Data will be compared to shell model and no-core (ab-initio) shell model calculations with NN and NN+NNN interactions.

  2. Study of levitating nanoparticles using ultracold neutrons

    NASA Astrophysics Data System (ADS)

    Nesvizhevsky, V. V.; Voronin, A. Yu; Lambrecht, A.; Reynaud, S.

    2012-09-01

    Physical adsorption of atoms, molecules and clusters on the surface is well known. It is linked to many other phenomena in physics, chemistry and biology and has numerous practical applications. Due to limitations of the analytical tools usually used, studies of adsorption are limited to the particle sizes of up to ˜102-103 atoms. Following a general formalism developed in this field, we apply it to even larger objects and discover qualitatively new phenomena. A large particle is bound to the surface in a deep and broad potential well formed by van der Waals/Casimir-Polder forces appearing due to the particle and surface electric polarization. The well depth is significantly larger than the characteristic energy \\frac{3}{2}k_{\\rm{B}} T of a particle's thermal motion; thus such a nanoparticle is settled in long-living states. Nanoparticles in high-excited states form a two-dimensional gas of objects bound to the surface but quasi-freely traveling along the surface under certain conditions. A particularly interesting feature of this model consists in the prediction of small-energy-transfer inelastic scattering of ultracold neutrons (UCN) on solid/liquid surfaces covered by such levitating nanoparticles/nano-droplets. The change in UCN energy is due to the Doppler shift induced by UCN collisions with nanoparticles/nano-droplets; the energy change is almost as small as the UCN initial energy. We compared theoretical estimations of our model to all existing data on inelastic scattering of UCN with small energy transfers and found that they agree quite well. As our theoretical formalism provides robust predictions of some data and the experimental data are rather detailed and precise, we conclude that the recently discovered intriguing phenomenon of small heating of UCN in traps is due to their collisions with such levitating nanoparticles. Moreover, this new phenomenon might be relevant to the striking contradiction between the results of the neutron lifetime

  3. Studies of D-Li neutron source: An overview

    NASA Astrophysics Data System (ADS)

    Gomes, I.; Smith, D. L.

    1994-06-01

    The construction of a neutron source facility able to reproduce the radiation environment predicted for a fusion reactor can be considered a very important milestone for the fusion program. Such a neutron source should allow materials testing over a wide range of neutron flux and neutron fluence. To date, none of the existing facilities reproduce the neutron flux with the energy spectrum of a fusion reactor. As a result, the major part of the required material database is obtained by extrapolations which may not be as reliable as needed to predict the real performance of those materials under fusion reactor conditions. As an example, the effect of the gas production, transmutation, atomic displacement, and other nuclear responses on the ductility and swelling and perhaps other properties as well must be analyzed in samples which have undergone reactor conditions environment. This study is focused on the neutronics analysis of a D-Li neutron source. Neutron induced nuclear responses and neutron transport are calculated with the aim at defining the expected performance of a D-Li neutron source. The first section describes the differences in the magnitude of the neutron flux when material is present or not inside the test cell. The second section deals with nuclear responses such as DPA, helium production, and nuclear heating. In the third section, calculations of the available volume above a threshold DPA value are presented. Section four presents results for the gamma-ray flux distribution. A brief discussion about tritium generation in the lithium jet is given in section flive, and the conclusions are summarized in section six.

  4. Neutron diffraction studies of viral fusion peptides

    NASA Astrophysics Data System (ADS)

    Bradshaw, Jeremy P.; J. M. Darkes, Malcolm; Katsaras, John; Epand, Richard M.

    2000-03-01

    Membrane fusion plays a vital role in a large and diverse number of essential biological processes. Despite this fact, the precise molecular events that occur during fusion are still not known. We are currently engaged on a study of membrane fusion as mediated by viral fusion peptides. These peptides are the N-terminal regions of certain viral envelope proteins that mediate the process of fusion between the viral envelope and the membranes of the host cell during the infection process. As part of this study, we have carried out neutron diffraction measurements at the ILL, BeNSC and Chalk River, on a range of viral fusion peptides. The peptides, from simian immunodeficiency virus (SIV), influenza A and feline leukaemia virus (FeLV), were incorporated into stacked phospholipid bilayers. Some of the peptides had been specifically deuterated at key amino acids. Lamellar diffraction data were collected and analysed to yield information on the peptide conformation, location and orientation relative to the bilayer.

  5. MCNPX Simulation Study of STRAW Neutron Detectors

    SciTech Connect

    Sanjoy Mukhopadhyay, Richard Maurer, Stephen Mitchell

    2010-01-08

    A novel prototype fission meter is being designed at National Security Technologies, LLC, using a thin uniform coating (only 1 micron thick) of {sup 10}B as a neutron converter inside a large array of thin (4 mm diameter) copper tubes. The copper tubes are only 2 mils thick, and each holds the stretched anode wire under tension and high voltage. The tubes are filled with proportional counter gas (a mixture of 90%/10% of Ar/CO{sub 2}). The tubes operate in proportional counter mode and attract mobile charged particles ({alpha}'s) created in the nuclear interaction {sup 10}B(n, {sup 4}He){sup 7}Li. However, a single tube has about 1/7th the sensitivity of a {sup 3}He tube. Modeling is required to determine if enough such tubes could be placed in a neutron detection assembly of the current size to give comparable sensitivity to {sup 3}He. Detectors lined with {sup 10}B lie between {sup 3}He and {sup 10}BF{sub 3} proportional counters and fission chambers in terms of neutron detection efficiency and gamma ray insensitivity. The mean free path of thermal neutrons in {sup 10}B is about 18 {micro}m. It takes about 60 {micro}m of {sup 10}B layer to completely stop thermal neutrons, but the energetic {alpha}-particles generated in the reaction have a range of only 3.3 {micro}m in {sup 10}B environment - hence the thin layer of boron coating on the copper tube. The prototype design is shown in Figure 1. It consists of two panels of three staggered rows of 500-mm-long, 4-mm-diameter straws, with 20 in each row, embedded in 30-mm-thick high density polyethylene (HDPE). The project demonstrates a new application of thin neutron and gamma converter technique (1 micron thin {sup 10}B coated copper tube). It exploits fast timing from multiple straw detectors to count multiplicity of both gamma and neutrons from fissioning materials. The objective is to find a near-term replacement of {sup 3}He gas in neutron detection and measurement (with a very large neutron detection area). All

  6. Study of EAS neutron component temporal structure

    NASA Astrophysics Data System (ADS)

    Gromushkin, D. M.; Petrukhin, A. A.; Stenkin, Yu. V.; Yashin, I. I.

    2011-04-01

    The neutron component of Extensive Air Showers (EAS) carries information about the primary cosmic ray flux as well as about parameters of hadronic interactions at ultra-high energies. We present here the data obtained with the "Neutron" array which is a prototype of a novel type EAS array PRISMA (Stenkin, 2009). The prototype consists of 5 large area scintillator detectors (0.75 m2 each) placed in the corners and in the center of 5 m side square. The scintillator consisting of an alloy of ZnS(Ag) and 6LiF is shaped as a thin layer of grains covered with thin transparent plastic film.

  7. Study of neutron focusing at the Texas Cold Neutron Source: Progress report

    SciTech Connect

    Wehring, B.W.; Uenlue, K.

    1993-01-28

    The purpose of this three year study is to develop a neutron focusing system to be used with the Texas Cold Neutron Source (TCNS) to produce an intense beam of neutrons. A prompt gamma activation analysis (PGAA) facility will also be designed, setup, and tested under this DOE grant. During the first year of the DOE grant, a new procedure was developed and used to design a focusing converging guide consisting of truncated rectangular cone sections. Detailed calculations were performed using a 3-D Monte Carlo code which the authors wrote to trace neutrons through the existing curved guide of the TCNS into the proposed converging guide. Using realistic reflectivities for Ni-Ti supermirrors, they obtained gains of 4 to 5 for the neutron flux averaged over an area of 1 x 1 cm. Two graduate students were supported by the first year of the DOE grant. Both have passed the Nuclear Engineering qualifying examination and have been admitted to candidacy for the doctoral degree at The University of Texas at Austin. Their programs of study and dissertation projects have been approved by the appropriate committees.

  8. Correlation Reflectometry for Turbulence and Magnetic Field Measurements in Fusion Plasmas

    SciTech Connect

    G.J. Kramer; R. Nazikian; and E. Valeo

    2002-07-09

    For the interpretation of correlation reflectometry data a fast two-dimensional full wave code has been developed in which realistic plasma geometries are used. Results of this code are compared with experiments and turbulence correlation lengths and fluctuation levels are extracted with statistical optics methods. It is shown that in general the measured reflectometer correlation length is not equal to the turbulence correlation length. The code is also used to study the possibility of O-X correlation reflectometry in FIRE for the determination of the local magnetic field strength. It was found that this is only possible at very low fluctuation levels.

  9. High-pressure neutron diffraction studies at LANSCE

    NASA Astrophysics Data System (ADS)

    Zhao, Yusheng; Zhang, Jianzhong; Xu, Hongwu; Lokshin, Konstantin A.; He, Duanwei; Qian, Jiang; Pantea, Cristian; Daemen, Luke L.; Vogel, Sven C.; Ding, Yang; Xu, Jian

    2010-06-01

    The development of neutron diffraction under extreme pressure ( P) and temperature ( T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials science, and earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at the Los Alamos Neutron Science Center (LANSCE) to conduct in situ high- P- T neutron diffraction experiments. We have developed a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high P. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. More recently, we have developed high- P low- T gas/liquid cells in conjunction with neutron diffraction. These techniques enable in situ and real-time examination of gas uptake/release processes and allow accurate, time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equations of state, structural phase transitions, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation/decomposition kinetics of methane, CO2 and hydrogen hydrate clathrates, and hydrogen/CO2 adsorption of inclusion compounds such as metal-organic frameworks (MOFs). The aim of our research is to accurately map out phase relations and determine structural parameters (lattice constants, atomic positions, atomic thermal parameters, bond lengths, bond angles, etc.) in the P- T- X space. We are developing further high- P- T technology with a new 2000-ton press, TAPLUS-2000, and a ZIA (Deformation-DIA type) cubic anvil package to routinely achieve pressures up to 20 GPa and temperatures up to 2000 K. The design of a dedicated high- P neutron beamline, LAPTRON, is also underway for simultaneous high- P- T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based

  10. Sensitivity studies for the weak r process: neutron capture rates

    SciTech Connect

    Surman, R.; Mumpower, M.; Sinclair, R.; Jones, K. L.; Hix, W. R.; McLaughlin, G. C.

    2014-04-15

    Rapid neutron capture nucleosynthesis involves thousands of nuclear species far from stability, whose nuclear properties need to be understood in order to accurately predict nucleosynthetic outcomes. Recently sensitivity studies have provided a deeper understanding of how the r process proceeds and have identified pieces of nuclear data of interest for further experimental or theoretical study. A key result of these studies has been to point out the importance of individual neutron capture rates in setting the final r-process abundance pattern for a ‘main’ (A ∼ 130 peak and above) r process. Here we examine neutron capture in the context of a ‘weak’ r process that forms primarily the A ∼ 80 r-process abundance peak. We identify the astrophysical conditions required to produce this peak region through weak r-processing and point out the neutron capture rates that most strongly influence the final abundance pattern.

  11. SEOP polarized 3He Neutron Spin Filters for the JCNS user program

    NASA Astrophysics Data System (ADS)

    Babcock, Earl; Salhi, Zahir; Theisselmann, Tobias; Starostin, Denis; Schmeissner, Johann; Feoktystov, Artem; Mattauch, Stefan; Pistel, Patrick; Radulescu, Aurel; Ioffe, Alexander

    2016-04-01

    Over the past several years the JCNS has been developing in-house applications for neutron polarization analysis (PA). These methods include PA for separation of incoherent from coherent scattering in soft matter studies (SANS), and online polarization for analysis for neutron reflectometry, SANS, GISANS and eventually spectroscopy. This paper will present an overview of the user activities at the JCNS at the MLZ and gives an overview of the polarization 3He methods and devices used. Additionally we will summarise current projects which will further support the user activities using polarised 3He spin filters.

  12. Neutron interstitial brachytherapy for malignant gliomas: a pilot study

    SciTech Connect

    Patchell, R.A.; Maruyama, Y.; Tibbs, P.A.; Beach, J.L.; Kryscio, R.J.; Young, A.B.

    1988-01-01

    Fifty-six patients with malignant glioma were treated with implantation of the neutron-emitting element californium-252 (/sup 252/Cf) within 2 weeks after surgical debulking of the tumor. Implantation was performed using computerized tomography-guided placement of afterloading catheters, and the /sup 252/Cf sources were removed after approximately 300 neutron rads were delivered. Patients then received 6000 to 7000 conventional photon rads by external beam. The total photon-equivalent dose to the tumor ranged from 8100 to 9100 rads. The median survival time was 10 months, with 18-and 24-month survival rates of 28% and 19%, respectively. The results of reoperation or autopsy showed that patients had recurrence of the tumor but that radiation necrosis was restricted to the area of the original tumor. Serious complications occurred in five patients (9%) and consisted of wound infections in three, cerebral edema in one, and radiation necrosis beyond the original tumor margin in one. Previous studies using external-beam neutron radiation have shown that neutrons are capable of totally eradicating malignant gliomas; however, in most cases, unacceptable widespread radiation necrosis has resulted. Neutron implants are a logical way to increase the dose to the tumor and decrease the dose to normal brain. Interstitial neutron radiation can be given safely with /sup 252/Cf, and the survival results achieved by radiation alone using relatively low doses of interstitial neutron radiation from /sup 252/Cf implants plus conventional photon radiation were equal to the results attained with any currently available conventional therapy.

  13. Upgrades to the Polarized Neutron Reflectometer Asterix at LANSCE

    SciTech Connect

    Pynn, Roger

    2015-03-16

    We have upgraded the polarized neutron reflectometer, Asterix, at the Lujan Neutron Scattering Center at Los Alamos for the benefit of the research communities that study magnetic and complex-fluid films, both of which play important roles in support of the DOE’s energy mission. The upgrades to the instrument include: • A secondary spectrometer that was integrated with a Huber sample goniometer purchased with other funds just prior to the start of our project. The secondary spectrometer provides a flexible length for the scattered flight path, includes a mechanism to select among 3 alternative polarization analyzers as well as a support for new neutron detectors. Also included is an optic rail for reproducible positioning of components for Spin Echo Scattering Angle Measurement (SESAME). The entire secondary spectrometer is now non-magnetic, as required for neutron Larmor labeling. • A broad-band neutron polarizer for the incident neutron beam based on the V geometry. • A wide-angle neutron polarization analyzer • A 2d position-sensitive neutron detector • Electromagnetic coils (Wollaston prisms) for SESAME plus the associated power supplies, cooling, safety systems and integration into the data acquisition system. The upgrades allowed a nearly effortless transition between configurations required to serve the polarized neutron reflectometry community, users of the 11 T cryomagnet and users of SESAME.

  14. Slow Neutron Velocity Spectrometer Transmission Studies Of Pu

    DOE R&D Accomplishments Database

    Havens, W. W. Jr.; Melkonian, E.; Rainwater, L. J.; Levin, M.

    1951-05-28

    The slow neutron transmission of several samples of Pu has been investigated with the Columbia Neutron Velocity Spectrometer. Data are presented in two groups, those covering the energy region from 0 to 6 ev, and those covering the region above 6 ev. Below 6 ev the resolution was relatively good, and a detailed study of the cross section variation was made. Work above 6 ev consisted of merely locating levels and obtaining a rough idea of their strengths.

  15. Quasielastic Neutron Scattering Study on Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Masui, T.; Kishimoto, H.; Kikuchi, T.; Ohira-Kawamura, S.; Inamura, Y.; Koga, T.; Nakajima, K.

    2014-04-01

    By using a quasielastic neutron scattering technique (disk-chopper-type spectrometer AMATERAS at J-PARC), we have investigated the microscopic dynamics of polybutadiene (PB) in which silica particles were embedded. The experimental results gave us both a damped vibration mode of PB and jumped diffusion motion of the segments. It was found that these dynamical features remain unaffected by the presence of the silica particle, while the residence time of the jumped diffusion motion becomes longer at the high filler loading.

  16. Neutron-rich B isotopes studied with antisymmetrized molecular dynamics

    SciTech Connect

    Kanada-En`yo, Y.; Horiuchi, H.

    1995-08-01

    Structure of odd-even B isotopes up to the neutron dripline is studied systematically with the antisymmetrized molecular dynamics (AMD). The AMD method has already proved to be a powerful theoretical approach for the systematic study of nuclear structure in extensive region including exotic neutron-rich nuclei as well as ordinary nuclei. It is owing to its flexible nature free from any model assumptions such as the existence of clusters. The energies and other observed data of B isotopes are reproduced well. Especially very good reproduction of electromagnetic properties is obtained. The systematic behavior of the electromagnetic properties is explained in relation to the drastic change between clustering structure and shell-model-like structure. This explanation gives us an important indication that clustering structure in neutron-rich B nuclei is strongly suggested by the experimental data. It is shown that the structure change with increase of the neutron number is largely governed by the shell effect of neutron orbits. Exotic structure with new type of clustering is suggested to evolve in neutron-rich nuclei near the dripline.

  17. Prospect for application of compact accelerator-based neutron source to neutron engineering diffraction

    NASA Astrophysics Data System (ADS)

    Ikeda, Yoshimasa; Taketani, Atsushi; Takamura, Masato; Sunaga, Hideyuki; Kumagai, Masayoshi; Oba, Yojiro; Otake, Yoshie; Suzuki, Hiroshi

    2016-10-01

    A compact accelerator-based neutron source has been lately discussed on engineering applications such as transmission imaging and small angle scattering as well as reflectometry. However, nobody considers using it for neutron diffraction experiment because of its low neutron flux. In this study, therefore, the neutron diffraction experiments are carried out using Riken Accelerator-driven Compact Neutron Source (RANS), to clarify the capability of the compact neutron source for neutron engineering diffraction. The diffraction pattern from a ferritic steel was successfully measured by suitable arrangement of the optical system to reduce the background noise, and it was confirmed that the recognizable diffraction pattern can be measured by a large sampling volume with 10 mm in cubic for an acceptable measurement time, i.e. 10 min. The minimum resolution of the 110 reflection for RANS is approximately 2.5% at 8 μs of the proton pulse width, which is insufficient to perform the strain measurement by neutron diffraction. The moderation time width at the wavelength corresponding to the 110 reflection is estimated to be approximately 30 μs, which is the most dominant factor to determine the resolution. Therefore, refinements of the moderator system to decrease the moderation time by decreasing a thickness of the moderator or by applying the decoupler system or application of the angular dispersive neutron diffraction technique are important to improve the resolution of the diffraction experiment using the compact neutron source. In contrast, the texture evolution due to plastic deformation was successfully observed by measuring a change in the diffraction peak intensity by RANS. Furthermore, the volume fraction of the austenitic phase in the dual phase mock specimen was also successfully evaluated by fitting the diffraction pattern using a Rietveld code. Consequently, RANS has been proved to be capable for neutron engineering diffraction aiming for the easy access

  18. Structure of Protein Layers in Polyelectrolyte Matrices Studied by Neutron Reflectivity

    SciTech Connect

    Kozlovskaya, Veronika; Ankner, John Francis; O'Neill, Hugh Michael; Zhang, Qiu; Kharlampieva, Eugenia

    2011-01-01

    Polyelectrolyte multilayer films obtained by localized incorporation of Green Fluorescent Protein (GFP) within electrostatically assembled matrices of poly(styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH) via spin-assisted layer-by-layer growth were discovered to be highly structured, with closely packed monomolecular layers of the protein within the bio-hybrid films. The structure of the films was evaluated in both vertical and lateral directions with neutron reflectometry, using deuterated GFP as a marker for neutron scattering contrast. Importantly, the GFP preserves its structural stability upon assembly as confirmed by circular dichroism (CD) and in situ attenuated total reflection Fourier Transform Infrared spectroscopy (ATR-FTIR). Atomic force microscopy was complimented with X-ray reflectometry to characterize the external roughness of the biohybrid films. Remarkably, films assembled with a single GFP layer confined at various distances from the substrate exhibit a strong localization of the GFP layer without intermixing into the LbL matrix. However, partial intermixing of the GFP layers with polymeric material is evidenced in multiple-GFP layer films with alternating protein-rich and protein-deficient regions. We hypothesize that the polymer-protein exchange observed in the multiple-GFP layer films suggests the existence of a critical protein concentration which can be accommodated by the multilayer matrix. Our results yield new insights into the mechanism of GFP interaction with a polyelectrolyte matrix and open opportunities for fabrication of bio-hybrid films with well-organized structure and controllable function, a crucial requirement for advanced sensing applications.

  19. Neutron-induced reaction studies using stored ions

    NASA Astrophysics Data System (ADS)

    Glorius, Jan; Litvinov, Yuri A.; Reifarth, René

    2015-11-01

    Storage rings provide unique possibilities for investigations of nuclear reactions. Radioactive ions can be stored if the ring is connected to an appropriate facility and reaction studies are feasible at low beam intensities because of the recycling of beam particles. Using gas jet or droplet targets, charged particle-induced reactions on short-lived isotopes can be studied in inverse kinematics. In such a system a high-flux reactor could serve as a neutron target extending the experimental spectrum to neutron-induced reactions. Those could be studied over a wide energy range covering the research fields of nuclear astrophysics and reactor safety, transmutation of nuclear waste and fusion.

  20. Differential reflectometry versus tactile sense detection of subgingival calculus in dentistry

    NASA Astrophysics Data System (ADS)

    Shakibaie, Fardad; Walsh, Laurence J.

    2012-10-01

    Detecting dental calculus is clinically challenging in dentistry. This study used typodonts with extracted premolar and molar teeth and simulated gingival tissue to compare the performance of differential reflectometry and periodontal probing. A total of 30 extracted teeth were set in an anatomical configuration in stone to create three typodonts. Clear polyvinyl siloxane impression material was placed to replicate the periodontal soft tissues. Pocket depths ranged from 10 to 15 mm. The three models were placed in a phantom head, and an experienced dentist assessed the presence of subgingival calculus first using the DetecTar (differential reflectometry) and then a periodontal probe. Scores from these two different methods were compared to the gold standard (direct examination of the root surface using 20× magnification) to determine the accuracy and reproducibility. Differential reflectometry was more accurate than tactile assessment (79% versus 60%), and its reproducibility was also higher (Cohen kappa 0.54 versus 0.39). Both methods performed better on single rooted premolar teeth than on multirooted teeth. These laboratory results indicate that differential reflectometry allows more accurate and reproducible detection of subgingival calculus than conventional probing, and supports its use for supplementing traditional periodontal examination methods in dental practice.

  1. Neutron powder diffraction study of perdeuterodimethyl sulfone.

    PubMed

    Ibberson, R M

    2007-05-01

    The crystal structure of perdeuterodimethyl sulfone, (CD(3))(2)SO(2) or C(2)D(6)O(2)S, has been refined at 4.5 K against high-resolution neutron powder diffraction data. The structure determined previously by Sands [Z. Kristallogr. (1963), 119, 245-251] at ambient temperature is shown to remain down to liquid helium temperature, and at 4.5 K the S-C and S-O bond distances are 1.441 (2) and 1.760 (2) A, respectively. The molecules are distorted tetrahedra with C(2v) point symmetry (crystallographic symmetry m2m for S and m for C, O and one D atom) and are linked through a network of weak hydrogen bonds in the C-centred orthorhombic structure.

  2. Neutron diffraction studies of natural glasses

    SciTech Connect

    Wright, A.C.; Erwin Desa, J.A.; Weeks, R.A.; Sinclair, R.N.; Bailey, D.K.

    1983-08-01

    A neutron diffraction investigation has been carried out of the structures of several naturally occurring glasses, viz. Libyan Desert glass, a Fulgurite, Wabar glass, Lechatelierite from Canon Diablo, a Tektite, Obsidian (3 samples), and Macusani glass. Libyan Desert sand has also been examined, together with crystalline ..cap alpha..-quartz and ..cap alpha..-cristobalite. A comparison of data for the natural glasses and synthetic vitreous silica (Spectrosil B) in both reciprocal and real space allows a categorisation into Silicas, which closely resemble synthetic vitreous silica, and Silicates, for which the resemblance to silica is consistently less striking. The data support the view that Libyan Desert glass and sand have a common origin, while the Tektite has a structure similar to that of volcanic glasses.

  3. Radiation Damage Study in Natural Zircon Using Neutrons Irradiation

    SciTech Connect

    Lwin, Maung Tin Moe; Amin, Yusoff Mohd.; Kassim, Hasan Abu; Mohamed, Abdul Aziz; Karim, Julia Abdul

    2011-03-30

    Changes of atomic displacements in crystalline structure of natural zircon (ZrSiO{sub 4}) can be studied by using neutron irradiation on the surface of zircon and compared the data from XRD measurements before and after irradiation. The results of neutron irradiation on natural zircon using Pneumatic Transfer System (PTS) at PUSPATI TRIGA Research Reactor in the Malaysian Nuclear Agency are discussed in this work. The reactor produces maximum thermal power output of 1 MWatt and the neutron flux of up to 1x10{sup 13} ncm{sup -2}s{sup -1}. From serial decay processes of uranium and thorium radionuclides in zircon crystalline structure, the emission of alpha particles can produce damage in terms of atomic displacements in zircon. Hence, zircon has been extensively studied as a possible candidate for immobilization of fission products and actinides.

  4. Study of nuclear recoils in liquid argon with monoenergetic neutrons

    NASA Astrophysics Data System (ADS)

    Regenfus, C.; Allkofer, Y.; Amsler, C.; Creus, W.; Ferella, A.; Rochet, J.; Walter, M.

    2012-07-01

    In the framework of developments for liquid argon dark matter detectors we assembled a laboratory setup to scatter neutrons on a small liquid argon target. The neutrons are produced mono-energetically (Ekin = 2.45 MeV) by nuclear fusion in a deuterium plasma and are collimated onto a 3" liquid argon cell operating in single-phase mode (zero electric field). Organic liquid scintillators are used to tag scattered neutrons and to provide a time-of-flight measurement. The setup is designed to study light pulse shapes and scintillation yields from nuclear and electronic recoils as well as from alpha particles at working points relevant for dark matter searches. Liquid argon offers the possibility to scrutinise scintillation yields in noble liquids with respect to the population strength of the two fundamental excimer states. Here we present experimental methods and first results from recent data towards such studies.

  5. Dental optical coherence domain reflectometry explorer

    DOEpatents

    Everett, Matthew J.; Colston, Jr., Billy W.; Sathyam, Ujwal S.; Da Silva, Luiz B.

    2001-01-01

    A hand-held, fiber optic based dental device with optical coherence domain reflectometry (OCDR) sensing capabilities provides a profile of optical scattering as a function of depth in the tissue at the point where the tip of the dental explorer touches the tissue. This system provides information on the internal structure of the dental tissue, which is then used to detect caries and periodontal disease. A series of profiles of optical scattering or tissue microstructure are generated by moving the explorer across the tooth or other tissue. The profiles are combined to form a cross-sectional, or optical coherence tomography (OCT), image.

  6. Fusion materials high energy-neutron studies. A status report

    SciTech Connect

    Doran, D.G.; Guinan, M.W.

    1980-01-01

    The objectives of this paper are (1) to provide background information on the US Magnetic Fusion Reactor Materials Program, (2) to provide a framework for evaluating nuclear data needs associated with high energy neutron irradiations, and (3) to show the current status of relevant high energy neutron studies. Since the last symposium, the greatest strides in cross section development have been taken in those areas providing FMIT design data, e.g., source description, shielding, and activation. In addition, many dosimetry cross sections have been tentatively extrapolated to 40 MeV and integral testing begun. Extensive total helium measurements have been made in a variety of neutron spectra. Additional calculations are needed to assist in determining energy dependent cross sections.

  7. A Fluka study of underground cosmogenic neutron production

    NASA Astrophysics Data System (ADS)

    Empl, A.; Hungerford, E. V.; Jasim, R.; Mosteiro, P.

    2014-08-01

    Neutrons produced by cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically such neutrons can dominate the background, as they are particularly difficult to shield and detect. Since actual data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. Thus validation of any simulation code is necessary to assure reliable results. This work compares in detail predictions of the FLUKA simulation code to existing data, and uses this code to report a simulation of cosmogenic backgrounds for typical detectors embedded in a water tank with liquid scintillator shielding.

  8. Study of PIN diode energy traps created by neutrons

    NASA Astrophysics Data System (ADS)

    Sopko, V.; Sopko, B.; Chren, D.; Dammer, J.

    2013-03-01

    Characterization of radiation defects is still ongoing and finds greater application in the increasing radiation doses on semiconductor detectors in experiments. Studying the changes of silicon PIN diode for high doses of radiation is the fundamental motivation for our measurements. In this article we describe the behavior of the PIN diode and development of the disorder caused by neutrons from a 252Cf and doses up to 8 Gy. The calibration curve for PIN diode shows the effect of disorders as the changes of the voltampere characteristics depending on the dose of neutron irradiation. The measured values for defects are in good agreement with created energy traps.

  9. Ultra Small-Angle Neutron Scattering Study of Porous Glass

    SciTech Connect

    Desai, Reshma R.; Desa, J. A. Erwin; Sen, D.; Mazumder, S.

    2011-07-15

    Compacts of silica micro-spheres prepared for different times at sintering temperatures of 640 deg. C and 740 deg. C have been studied by Ultra Small-Angle Neutron Scattering (USANS) and Scanning Electron Microscopy (SEM). Stress versus strain measurements display several breakage points related to a range of nearest neighbour coordination around each microsphere.

  10. Isolated neutron stars and studies of their interiors

    NASA Astrophysics Data System (ADS)

    Popov, S. B.

    2012-12-01

    In these lectures presented at Baikal summer school on physics of elementary particles and astrophysics 2011, I present a wide view of neutron star astrophysics with special attention paid to young isolated compact objects and studies of the properties of their interiors using astronomical methods.

  11. Nab: precise experimental study of unpolarized neutron beta decay

    NASA Astrophysics Data System (ADS)

    Pocanic, Dinko; Nab Collaboration

    2014-09-01

    Nab, a program of experimental study of unpolarized neutron decays at the Spallation Neutron Source, Oak Ridge, TN, aims to determine a, the electron-neutrino correlation with precision of δa / a =10-3 , and b, the Fierz interference term, with uncertainty δb ~= 3 ×10-3 . Neutron beta decay's simple theoretical description in the Standard Model (SM) is overconstrained by the set of available observables, providing opportunities to search for evidence of SM extensions. Planned Nab results will lead to a new precise determination of the ratio λ =GA /GV , and to significant reductions in the allowed limits for both right- and left-handed scalar and tensor currents. Alternatively, the experiment may detect a discrepancy from SM predictions consistent with certain realizations of supersymmetry. An optimized, asymmetric spectrometer has been designed to achieve the narrow proton momentum response function required to meet the physics goals of the experiment. The apparatus is to be used in a follow-up measurement (ABba) of asymmetry observables A and B in polarized neutron decay. Nab is funded, now in the construction stage, with planned beam readiness in 2016. We discuss the experiment's motivation, expected reach, design and method. Nab, a program of experimental study of unpolarized neutron decays at the Spallation Neutron Source, Oak Ridge, TN, aims to determine a, the electron-neutrino correlation with precision of δa / a =10-3 , and b, the Fierz interference term, with uncertainty δb ~= 3 ×10-3 . Neutron beta decay's simple theoretical description in the Standard Model (SM) is overconstrained by the set of available observables, providing opportunities to search for evidence of SM extensions. Planned Nab results will lead to a new precise determination of the ratio λ =GA /GV , and to significant reductions in the allowed limits for both right- and left-handed scalar and tensor currents. Alternatively, the experiment may detect a discrepancy from SM

  12. RESPECT: Neutron resonance spin-echo spectrometer for extreme studies

    NASA Astrophysics Data System (ADS)

    Georgii, R.; Kindervater, J.; Pfleiderer, C.; Böni, P.

    2016-11-01

    We propose the design of a REsonance SPin-echo spECtrometer for exTreme studies, RESPECT, that is ideally suited for the exploration of non-dispersive processes such as diffusion, crystallization, slow dynamics, tunneling processes, crystal electric field excitations, and spin fluctuations. It is a variant of the conventional neutron spin-echo technique (NSE) by (i) replacing the long precession coils by pairs of longitudinal neutron spin-echo coils combined with RF-spin flippers and (ii) by stabilizing the neutron polarization with small longitudinal guide fields that can in addition be used as field subtraction coils thus allowing to adjust the field integrals over a range of 8 orders of magnitude. Therefore, the dynamic range of RESPECT can in principle be varied over 8 orders of magnitude in time, if neutrons with the required energy are made available. Similarly as for existing NSE-spectrometers, spin echo times of up to approximately 1 μs can be reached if the divergence and the correction elements are properly adjusted. Thanks to the optional use of neutron guides and the fact that the currents for the correction coils are much smaller than in standard NSE, intensity gains of at least one order of magnitude are expected, making the concept of RESPECT also competitive for operation at medium flux neutron sources. RESPECT can also be operated in a MIEZE configuration allowing the investigation of relaxation processes in depolarizing environments as they occur when magnetic fields are applied at the sample position, i.e. for the investigation of the dynamics of flux lines in superconductors, magnetic fluctuations in ferromagnetic materials, and samples containing hydrogen.

  13. Detecting response of microelectromechanical resonators by microwave reflectometry

    NASA Astrophysics Data System (ADS)

    Legrand, B.; Ducatteau, D.; Théron, D.; Walter, B.; Tanbakuchi, H.

    2013-07-01

    Microwave reflectometry is proposed as an effective technique to detect the vibration of capacitively transduced microelectromechanical resonators. The transducer capacitor is probed by an incident wave, which is reflected being modulated by the time variations of the resonator displacement. Calculations demonstrate that the sensitivity of the technique is maximum for a given microwave frequency depending on the transducer total capacitance. Experimental data show that capacitance variations as low as 3 zF/√Hz are measurable at 4 GHz for the studied devices. Such a performance corresponds to a sub-picometer resolution in vibration amplitude of the microelectromechanical resonator. The measurement technique is particularly appropriate for resonant sensors when high signal-to-noise ratio and fully electrical detection are required. It can be used for device resonance frequency up to several hundreds of MHz.

  14. Neutron multiplicities in spontaneous fission and nuclear structure studies

    SciTech Connect

    Hamilton, J.H.; Kormicki, J.; Lu, Q.

    1993-12-31

    New insights into the fission process can be gained by better quantitative knowledge of how the energy released in fission is distributed between the kinetic energy of the two fragments, the excitation energy of the two fragments and the number of neutrons emitted. Studies of prompt gamma-rays emitted in spontaneous fission (SF) with large arrays of Compton suppressed Ge detector arrays are providing new quantitative answers to longstanding questions concerning fission as well as new insights into the structure of neutron-rich nuclei. For the first time the triple gamma coincidence technique was employed in spontaneous fission studies. Studies of SF of {sup 252}Cf and {sup 242}Pu have been carried out. These {gamma}-{gamma}-{gamma} data provide powerful ways to identify uniquely gamma rays from a particular nucleus in the very complex gamma-ray spectra given off by the over 100 different nuclei produced. The emphasis of this paper is on the first quantitative measurements of the multiplicities of the neutrons emitted in SF and the energy levels populated in the fragments. Indeed, in the break up into Mo-Ba pairs, we have identified for the first time fragments associated with from zero up to ten neutrons emitted and observed the excited energy states populated in these nuclei. The zero neutron emission pairs like {sup 104}Mo- {sup 148}Ba, {sup 106}Mo- {sup 146}Ba and {sup 104}Zr- {sup 148}Ce observed in this work are particularly interesting because they represent a type of cold fission or a new mode of cluster radioactivity as proposed by Greiner, Sandulescu and co-workers. These data provide new insights into the processes of cluster radioactivity and cold fission.

  15. 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.

  16. Recent Advances in Neutron Physics

    ERIC Educational Resources Information Center

    Feshbach, Herman; Sheldon, Eric

    1977-01-01

    Discusses new studies in neutron physics within the last decade, such as ultracold neutrons, neutron bottles, resonance behavior, subthreshold fission, doubly radiative capture, and neutron stars. (MLH)

  17. Phase shift reflectometry for wafer inspection

    NASA Astrophysics Data System (ADS)

    Peng, Kuang; Cao, Yiping; Li, Hongru; Sun, Jianfei; Bourgade, Thomas; Asundi, Anand Krishna

    2015-07-01

    In 3D measurement, specular surfaces can be reconstructed by phase shift reflectometry and the system configuration is simple. In this paper, a wafer is measured for industrial inspection to make sure the quality of the wafer by calibrating, phase unwrapping, slope calculation and integration. The profile result of the whole wafer can be reconstructed and it is a curve. As the height of the structures on the wafer is the target we are interested in, by fitting and subtracting the curve surface, the structures on the wafer can be observed on the flat surface. To confirm the quality farther, a part of the wafer is captured and zoomed in to be detected so that the difference between two structures can be observed better.

  18. Birefringence insensitive optical coherence domain reflectometry system

    DOEpatents

    Everett, Matthew J.; Davis, Joseph G.

    2002-01-01

    A birefringence insensitive fiber optic optical coherence domain reflectometry (OCDR) system is provided containing non-polarization maintaining (non-PM) fiber in the sample arm and the reference arm without suffering from signal degradation caused by birefringence. The use of non-PM fiber significantly reduces the cost of the OCDR system and provides a disposable or multiplexed section of the sample arm. The dispersion in the reference arm and sample arm of the OCDR system are matched to achieve high resolution imaging. This system is useful in medical applications or for non-medical in situ probes. The disposable section of non-PM fiber in the sample arm can be conveniently replaced when contaminated by a sample or a patient.

  19. Vascular interventions with optical coherence reflectometry

    NASA Astrophysics Data System (ADS)

    Neet, John M.

    2003-07-01

    There have been many innovations and technological advancements in balloon angioplasty since its introduction in the late 1970's, but percutaneous intervention on a totally occluded artery is still a challenge to the vascular interventionalist. Catheter-based intervention that avoids an invasive surgical procedure is a clear and desired advantage for the patient. A total occlusion challenges the interventionalist because the path of the artery can not be seen in the occluded vessel since the flow of the radiopaque contrast media is blocked. Optical coherence reflectometry techniques have been shown to be able to differentiate between artery wall and occlusive materials allowing the lumen of the blocked artery to be seen inside the occlusion. Light emitting diodes are a critical component of these systems making them technologically possible and economically feasible.

  20. A feasibility design study on a neutron spectrometer for BNCT with liquid moderator.

    PubMed

    Tamaki, S; Sato, F; Murata, I

    2015-12-01

    Neutrons generated by accelerators have various energy spectra. However, only limited methods are available to measure the whole neutron energy spectrum, especially when including the epithermal region that is normally used in BNCT. In the present study, we carried out the design study on a new neutron spectrometer that can measure such a neutron spectrum more accurately, precisely and with higher energy resolution, using an unfolding technique and a liquid moderator.

  1. Study of pipe thickness loss using a neutron radiography method

    SciTech Connect

    Mohamed, Abdul Aziz; Wahab, Aliff Amiru Bin; Yazid, Hafizal B.; Ahmad, Megat Harun Al Rashid B. Megat; Jamro, Rafhayudi B.; Azman, Azraf B.; Zin, Muhamad Rawi Md; Idris, Faridah Mohamad

    2014-02-12

    The purpose of this preliminary work is to study for thickness changes in objects using neutron radiography. In doing the project, the technique for the radiography was studied. The experiment was done at NUR-2 facility at TRIGA research reactor in Malaysian Nuclear Agency, Malaysia. Test samples of varying materials were used in this project. The samples were radiographed using direct technique. Radiographic images were recorded using Nitrocellulose film. The films obtained were digitized to processed and analyzed. Digital processing is done on the images using software Isee!. The images were processed to produce better image for analysis. The thickness changes in the image were measured to be compared with real thickness of the objects. From the data collected, percentages difference between measured and real thickness are below than 2%. This is considerably very low variation from original values. Therefore, verifying the neutron radiography technique used in this project.

  2. Study of pipe thickness loss using a neutron radiography method

    NASA Astrophysics Data System (ADS)

    Mohamed, Abdul Aziz; Wahab, Aliff Amiru Bin; Yazid, Hafizal B.; Ahmad, Megat Harun Al Rashid B. Megat; Jamro, Rafhayudi B.; Azman, Azraf B.; Zin, Muhamad Rawi Md; Idris, Faridah Mohamad

    2014-02-01

    The purpose of this preliminary work is to study for thickness changes in objects using neutron radiography. In doing the project, the technique for the radiography was studied. The experiment was done at NUR-2 facility at TRIGA research reactor in Malaysian Nuclear Agency, Malaysia. Test samples of varying materials were used in this project. The samples were radiographed using direct technique. Radiographic images were recorded using Nitrocellulose film. The films obtained were digitized to processed and analyzed. Digital processing is done on the images using software Isee!. The images were processed to produce better image for analysis. The thickness changes in the image were measured to be compared with real thickness of the objects. From the data collected, percentages difference between measured and real thickness are below than 2%. This is considerably very low variation from original values. Therefore, verifying the neutron radiography technique used in this project.

  3. The neutron moderated detector and groundbased cosmic ray modulation studies

    NASA Technical Reports Server (NTRS)

    Stoker, P. H.; Raubenheimer, B. C.

    1985-01-01

    Reports appear on modulation studies with the neutron monitor without lead. Some of these studies cast doubt on the reliability of this detector. The stability of the neutron moderated detector (NMD) at Sanae, Antarctic is discussed. The barometric coeficient of the 4NMD for epoch 1976 appears not to differ statistically from the 0.73%/mb of the 3NM64. The monthly averaged hourly counting rate of our 4NMD and 3NM64 correlates very well (correlation coefficient: 98%) over the years from 1974-1984, with the 4NMD showing a 8% larger long term modulation effect than the 3NM64, indicating a difference in sensitivities of the two detectors. From this difference in sensitivities spectra of ground level solar proton events and modulation functions of Forbush decreases are deduced.

  4. The structure of fillers, polymers and their interfaces in polymer composites using neutron scattering methods

    SciTech Connect

    Hjelm, R.P.

    1998-12-01

    The neutron scattering methods, small-angle neutron scattering and neutron reflectometry, provide information on the structure of polymer composite materials that is not available from other structural probes. The unique capabilities of these methods derive from three factors. First, the length scales probed correspond to polymer conformation, molecular and domain scales and to the characteristic sizes of many fillers. Second, neutrons are able to penetrate relatively thick samples, allowing bulk samples to be measured, and enabling buried interfaces to be studied. This characteristic also allows for the construction of special sample containment needed for studying materials under stress, extremes in pressure and temperature, etc. Third, neutrons readily distinguish between different light elements, and between different isotopes of the same element. The ability to distinguish between hydrogen and deuterium is particularly important in this regard. New ways of exploiting the capabilities of neutrons are opening up with the development of improved sources and instruments in the US and elsewhere. In this talk the author will discuss the basic concepts that give rise to the unique capabilities of neutron scattering, giving several examples of the uses of neutron scattering techniques in the study of polymer composites. The examples will include the morphology of fillers, polymer binders and matrices, interfaces and defect structures.

  5. Optimization study for an epithermal neutron beam for boron neutron capture therapy at the University of Virginia Research Reactor

    SciTech Connect

    Burns, T.D. Jr.

    1995-05-01

    The non-surgical brain cancer treatment modality, Boron Neutron Capture Therapy (BNCT), requires the use of an epithermal neutron beam. This purpose of this thesis was to design an epithermal neutron beam at the University of Virginia Research Reactor (UVAR) suitable for BNCT applications. A suitable epithermal neutron beam for BNCT must have minimal fast neutron and gamma radiation contamination, and yet retain an appreciable intensity. The low power of the UVAR core makes reaching a balance between beam quality and intensity a very challenging design endeavor. The MCNP monte carlo neutron transport code was used to develop an equivalent core radiation source, and to perform the subsequent neutron transport calculations necessary for beam model analysis and development. The code accuracy was validated by benchmarking output against experimental criticality measurements. An epithermal beam was designed for the UVAR, with performance characteristics comparable to beams at facilities with cores of higher power. The epithermal neutron intensity of this beam is 2.2 {times} 10{sup 8} n/cm{sup 2} {center_dot} s. The fast neutron and gamma radiation KERMA factors are 10 {times} 10{sup {minus}11}cGy{center_dot}cm{sup 2}/n{sub epi} and 20 {times} 10{sup {minus}11} cGy{center_dot}cm{sup 2}/n{sub epi}, respectively, and the current-to-flux ratio is 0.85. This thesis has shown that the UVAR has the capability to provide BNCT treatments, however the performance characteristics of the final beam of this study were limited by the low core power.

  6. Neutron irradiated uranium silicides studied by neutron diffraction and Rietveld analysis

    SciTech Connect

    Birtcher, R.C.; Mueller, M.H.; Richardson, J.W. Jr.

    1990-11-01

    The irradiation behavior of high-density uranium silicides has been a matter of interest to the nuclear industry for use in high power or low enrichment applications. Transmission electron microscopy studies have found that heavy ion bombardment renders U{sub 3}Si and U{sub 3}Si{sub 2} amorphous at temperatures below about 250 C and that U{sub 3}Si becomes mechanically unstable suffering rapid growth by plastic flow. In this present work, crystallographic changes preceding amorphization by fission fragment damage have been studied by high-resolution neutron diffraction as a function of damage produced by uranium fission at room temperature. Initially, both silicides had tetragonal crystal structures. Crystallographic and amorphous phases were studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier-filtering analysis of the non-crystalline scattering component. 13 refs., 5 figs.

  7. Explosives detection studies using Fast-Neutron Transmission Spectroscopy

    SciTech Connect

    Fink, C.L.; Micklich, B.J.; Sagalovsky, L.; Smith, D.L.; Yule, T.J.

    1996-12-31

    Fast-Neutron Transmission Spectroscopy (FNTS) is being investigated for detection of explosives in luggage or air cargo. We present here the principle results of a two-year study of a few-view tomographic FNTS system using the Monte Carlo radiation transport code MCNP to simulate neutron transmission through simple luggage phantoms and Receiver Operator Characteristic (ROC) curves to determine system performance. Elemental distributions along projections through the interrogated object are obtained by analyzing MCNP generated neutron transmission data. Transmission data for few (3-5) angles and relatively coarse resolution ({approximately}2 cm) are used to create a tomographic reconstruction of elemental distributions within the object. The elemental unfolding and tomographic reconstruction algorithms and the concept of transmission-derived cross sections for use in elemental analysis have been validated by application to experimental data. Elemental distributions are combined in an explosives detection algorithm to provide an indication of the presence or absence of explosives. The algorithm in current use, termed the ``equivalent explosive`` algorithm, determines the quantity of explosive that can be formed using the measured amount of the constituent elements in each pixel. Reconstruction and explosives detection algorithms have been applied to a series of randomly packed suitcases to generated ROC that describe system performance in terms of the probability of detection and of false alarms. System studies have been performed to study the operational characteristics and limitations of a FNTS system, and to determine the system`s sensitivity to several important parameters such as neutron source reaction and incident particle energy, flight path length, and the position of the interrogated object.

  8. Neutron scattering study of unconventional superconductors

    SciTech Connect

    Lee, Seunghun

    2014-06-30

    My group’s primary activity at the University of Virginia supported by DOE is to study novel electronic, magnetic, and structural phenomena that emerge out of strong interactions between electrons. Some of these phenomena are unconventional superconductivity, exotic states in frustrated magnets, quantum spin liquid states, and magneto-electricity. The outcome of our research funded by the grant advanced microscopic understanding of the emergence of the collective states in the systems.

  9. Scissors Mode of 162 Dy Studied from Resonance Neutron Capture

    DOE PAGES

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O’Donnell, J. M.; Rundberg, R. S.; et al

    2015-05-28

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions,more » (n,γ) experiments on Gd isotopes, and (γ,γ’) reactions.« less

  10. Scissors Mode of 162Dy Studied from Resonance Neutron Capture

    NASA Astrophysics Data System (ADS)

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Wilhelmy, J. B.

    2015-05-01

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions, (n,γ) experiments on Gd isotopes, and (γ,γ') reactions.

  11. 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.

  12. Feasibility of terahertz reflectometry for discrimination of human early gastric cancers

    PubMed Central

    Ji, Young Bin; Park, Chan Hyuk; Kim, Hyunki; Kim, Sang-Hoon; Lee, Gyu Min; Noh, Sam Kyu; Jeon, Tae-In; Son, Joo-Hiuk; Huh, Yong-Min; Haam, Seungjoo; Oh, Seung Jae; Lee, Sang Kil; Suh, Jin-Suck

    2015-01-01

    We have investigated the feasibility of THz time-domain reflectometry for the discrimination of human early gastric cancer (EGC) from the normal gastric region. Eight fresh EGC tissues, which were resected by endoscopic submucosal dissection, were studied. Of them, six lesions were well discriminated on THz images and the regions well correlated with tumor regions on pathologically mapped images. Four THz parameters could be suggested for quantitative discrimination of EGCs. PMID:25909023

  13. The study of neutron burst shape of a neutron tube driven by dispenser cathode

    NASA Astrophysics Data System (ADS)

    Grishnyaev, Evgeny; Polosatkin, Sergey

    2016-08-01

    A slim-shaped portable DD-neutron generator is developed at Budker institute of Nuclear Physics. The generator is a combination of Cockcroft-Walton voltage multiplier and a sealed gas-filled neutron tube driven by dispenser cathode. Neutron burst shape in pulsed mode of neutron tube operation is measured with stroboscopic time spectrometry, implemented on scintillation detector, and modeled with Comsol Script 1.3 and Comsol Multiphysics 3.5. Modeling appears to be in good agreement with experimental results. Measured pulse rise and fall times are 110 ns and 100 ns respectively.

  14. Systematic study on the performance of elliptic focusing neutron guides

    NASA Astrophysics Data System (ADS)

    Martin Rodriguez, D.; DiJulio, D. D.; Bentley, P. M.

    2016-02-01

    In neutron scattering experiments there is an increasing trend towards the study of smaller volume samples, which make the use of focusing optics more important. Focusing guide geometries based on conic-sections, such as those with parabolic and elliptic shapes, have been extensively used in both recently built neutron instruments and upgrades of existing hardware. A large fraction of proposed instruments at the European Spallation Source feature the requirement of good performance when measuring on small samples. The optimised design of a focusing system comes after time consuming Monte-Carlo (MC) simulations. Therefore, in order to help reduce the time needed to design such focusing systems, it is necessary to study systematically the performance of focusing guides. In the present work, we perform a theoretical analysis of the focusing properties of neutron beams, and validate them using a combination of Monte-Carlo simulations and Particle Swarm Optimisations (PSOs), where there is a close correspondence between the maximum divergence of the beam and the shape of the guide. The analytical results show that two limits can be considered, which bound a range of conic section shapes that provide optimum performance. Finally, we analyse a more realistic guide example and we give an assessment of the importance of the contribution from multiple reflections in different systems.

  15. Advanced Two-Dimensional Thermal Neutron Detectors for Scattering Studies

    SciTech Connect

    Fried, J.; Harder, J.; Mahler, G.J.; Makowiecki, D.S.; Mead, J.A.; Radeka, V.; Schaknowski, N.A.; Smith, G.C.; Yu, B.

    2002-11-18

    Advances in neutron scattering studies will be given a large boost with the advent of new spallation and reactor sources at present under consideration or construction. An important element for future experiments is a commensurate improvement in neutron detection techniques. At Brookhaven, a development program is under way for greatly increasing the angular coverage, rate capability and resolution of detectors for scattering studies. For example, a curved detector with angular coverage of 120{sup o} by 15{sup o} has recently been developed for protein crystallography at a spallation source. Based on neutron detection using {sup 3}He, the detector has the following major, new attributes: eight identical proportional wire segments operating in parallel, a single gas volume with seamless readout at segment boundaries, parallax errors eliminated in the horizontal plane by the detector's appropriate radius of curvature, high-throughput front-end electronics, position decoding based on high performance digital signal processing. The detector has a global rate capability greater than 1 million per second, position resolution less than 1.5 mm FWHM, timing resolution about 1 {micro}s, efficiency of 50% and 90% at 1{angstrom} and 4 {angstrom} respectively, and an active area 1.5 m x 20 cm.

  16. Neutron scattering studies in the actinide region. Progress report, August 1, 1988--July 31, 1991

    SciTech Connect

    Beghian, L.E.; Kegel, G.H.R.

    1991-08-01

    During the report period we have investigated the following areas: Neutron elastic and inelastic scattering measurements on {sup 14}N, {sup 181}Ta, {sup 232}Th, {sup 238}U and {sup 239}Pu; Prompt fission spectra for {sup 232}Th, {sup 235}U, {sup 238}U and {sup 239}Pu; Theoretical studies of neutron scattering; Neutron filters; New detector systems; and Upgrading of neutron target assembly, data acquisition system, and accelerator/beam-line apparatus.

  17. Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging

    NASA Astrophysics Data System (ADS)

    Meneghini, Orso; Volpe, Francesco A.

    2016-11-01

    An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contains information on the magnetic field vector B at the cutoff layer. Probing the plasma with different wave frequencies provides the radial profile of B. Full-wave finite-element simulations are presented here in 2D slab geometry. Modeling confirms the existence of a minimum in reflectivity that depends on the magnetic field at the cutoff, as expected from mode conversion physics, giving confidence in the feasibility of the diagnostic. The proposed reflectometric approach is expected to yield superior signal-to-noise ratio and to access wider ranges of density and magnetic field, compared with related radiometric techniques that require the plasma to emit electron Bernstein waves. Due to computational limitations, frequencies of 10-20 GHz were considered in this initial study. Frequencies above the edge electron-cyclotron frequency (f > 28 GHz here) would be preferable for the experiment, because the upper hybrid resonance and right cutoff would lie in the plasma, and would help separate the O-mode of interest from spurious X-waves.

  18. Pulse reflectometry as an acoustical inverse problem: Regularization of the bore reconstruction

    NASA Astrophysics Data System (ADS)

    Forbes, Barbara J.; Sharp, David B.; Kemp, Jonathan A.

    2002-11-01

    The theoretical basis of acoustic pulse reflectometry, a noninvasive method for the reconstruction of an acoustical duct from the reflections measured in response to an input pulse, is reviewed in terms of the inversion of the central Fredholm equation. It is known that this is an ill-posed problem in the context of finite-bandwidth experimental signals. Recent work by the authors has proposed the truncated singular value decomposition (TSVD) in the regularization of the transient input impulse response, a non-measurable quantity from which the spatial bore reconstruction is derived. In the present paper we further emphasize the relevance of the singular system framework to reflectometry applications, examining for the first time the transient bases of the system. In particular, by varying the truncation point for increasing condition numbers of the system matrix, it is found that the effects of out-of-bandwidth singular functions on the bore reconstruction can be systematically studied.

  19. Preparation of radioactive rare earth targets for neutron capture study

    SciTech Connect

    Miller, G. G.; Rogers, P. S. Z.; Palmer, P. D.; Dry, D. E.; Rundberg, R. S.; Fowler, Malcolm M.; Wilhelmy, J. B.

    2002-01-01

    The understanding of thc details of nucleosynthesis in stars remains a great challenge. Though the basic mechanisms governing the processes have been known since the pioneering work of Burbidge, Burbidge, Fowler and Hoyle (l), we are now evolving into a condition where we can ask more specific questions. Of particular interest are the dynamics of the s ('slow') process. In this process the general condition is one in which sequential neutron captures occur at time scales long compared with the beta decay half lives of the capturing nuclides. The nucleosynthesis period for C or Ne burning stellar shells is believed to be in the year to few year time frame (2). This means that radionuclides with similar half lives to this burning period serve as 'branch point' nuclides. That is, there will be a competition between a capture to the next heavier isotope and a beta decay to the element of nexl higher atomic number. By understanding the abundances of these competing reactions we can learn about the dynamics of the nucleosynthesis process in the stellar medium. Crucial to this understanding is that we have a knowledge of the underlying neutron reaction cross sections on these unstable nuclides in the relevant stellar energy regions (neutrons of 0.1-100 KeV). Tm (1.9 years) and ls'Sm (90 ycws) have decay properties that permit their handling in an open fume hood. These Iwo were therefore selected to be the first radionuclides for neutron capture study in what will be an ongoing effort.

  20. GNSS-Reflectometry based water level monitoring

    NASA Astrophysics Data System (ADS)

    Beckheinrich, Jamila; Schön, Steffen; Beyerle, Georg; Apel, Heiko; Semmling, Maximilian; Wickert, Jens

    2013-04-01

    Due to climate changing conditions severe changes in the Mekong delta in Vietnam have been recorded in the last years. The goal of the German Vietnamese WISDOM (Water-related Information system for the Sustainable Development Of the Mekong Delta) project is to build an information system to support and assist the decision makers, planners and authorities for an optimized water and land management. One of WISDOM's tasks is the flood monitoring of the Mekong delta. Earth reflected L-band signals from the Global Navigation Satellite System show a high reflectivity on water and ice surfaces or on wet soil so that GNSS-Reflectometry (GNSS-R) could contribute to monitor the water level in the main streams of the Mekong delta complementary to already existing monitoring networks. In principle, two different GNSS-R methods exist: the code- and the phase-based one. As the latter being more accurate, a new generation of GORS (GNSS Occultation, Reflectometry and Scatterometry) JAVAD DELTA GNSS receiver has been developed with the aim to extract precise phase observations. In a two week lasting measurement campaign, the receiver has been tested and several reflection events at the 150-200 m wide Can Tho river in Vietnam have been recorded. To analyze the geometrical impact on the quantity and quality of the reflection traces two different antennas height were tested. To track separately the direct and the reflected signal, two antennas were used. To derive an average height of the water level, for a 15 min observation interval, a phase model has been developed. Combined with the coherent observations, the minimum slope has been calculated based on the Least- Squares method. As cycle slips and outliers will impair the results, a preprocessing of the data has been performed. A cycle slip detection strategy that allows for automatic detection, identification and correction is proposed. To identify outliers, the data snooping method developed by Baarda 1968 is used. In this

  1. Reconstruction of edge density profiles on Large Helical Device using ultrashort-pulse reflectometry.

    PubMed

    Yokota, Yuya; Mase, Atsushi; Kogi, Yuichiro; Tokuzawa, Tokihiko; Kawahata, Kazuo; Nagayama, Yoshio; Hojo, Hitoshi

    2008-10-01

    Reflectometry has been expected to be one of the key diagnostics to measure density profiles. We have applied an ultrashort-pulse reflectometry (USPR) system to Large Helical Device in the National Institute for Fusion Science. Wide frequency band system is required to obtain wide density profile since an incident wave is reflected at the density layer corresponding to its cutoff frequency. The reflectometry utilizes an impulse with less than 30 ps pulse width as a source. Since the bandwidth of an impulse has an inverse relation to the pulse width, we can cover the frequency range of micro- to millimeter waves (18-40 GHz) with a single source. The density profiles can be reconstructed by collecting time-of-flight (TOF) signals for each frequency component of an impulse reflected from the corresponding cutoff layer. We utilize the signal record analysis (SRA) method to reconstruct the density profiles from the TOF signal. The effectiveness of the SRA method for the profile reconstruction is confirmed by a simulation study of the USPR using a finite-difference time domain method.

  2. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source.

    PubMed

    Mauro, N A; Vogt, A J; Derendorf, K S; Johnson, M L; Rustan, G E; Quirinale, D G; Kreyssig, A; Lokshin, K A; Neuefeind, J C; An, Ke; Wang, Xun-Li; Goldman, A I; Egami, T; Kelton, K F

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elastic and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (∼100 mg).

  3. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

    SciTech Connect

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Goldman, A. I.; Egami, T.; Kelton, K. F.

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. But, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elastic and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample ( 100 mg).

  4. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source.

    PubMed

    Mauro, N A; Vogt, A J; Derendorf, K S; Johnson, M L; Rustan, G E; Quirinale, D G; Kreyssig, A; Lokshin, K A; Neuefeind, J C; An, Ke; Wang, Xun-Li; Goldman, A I; Egami, T; Kelton, K F

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elastic and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (∼100 mg). PMID:26827330

  5. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

    NASA Astrophysics Data System (ADS)

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Goldman, A. I.; Egami, T.; Kelton, K. F.

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elastic and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (˜100 mg).

  6. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

    DOE PAGES

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; et al

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. But, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elasticmore » and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample ( 100 mg).« less

  7. Simulation study of accelerator based quasi-mono-energetic epithermal neutron beams for BNCT.

    PubMed

    Adib, M; Habib, N; Bashter, I I; El-Mesiry, M S; Mansy, M S

    2016-01-01

    Filtered neutron techniques were applied to produce quasi-mono-energetic neutron beams in the energy range of 1.5-7.5 keV at the accelerator port using the generated neutron spectrum from a Li (p, n) Be reaction. A simulation study was performed to characterize the filter components and transmitted beam lines. The feature of the filtered beams is detailed in terms of optimal thickness of the primary and additive components. A computer code named "QMNB-AS" was developed to carry out the required calculations. The filtered neutron beams had high purity and intensity with low contamination from the accompanying thermal, fast neutrons and γ-rays.

  8. Catheter guided by optical coherence domain reflectometry

    DOEpatents

    Everett, Matthew; Colston, Billy W.; Da Silva, Luiz B.; Matthews, Dennis

    2002-01-01

    A guidance and viewing system based on multiplexed optical coherence domain reflectometry is incorporated into a catheter, endoscope, or other medical device to measure the location, thickness, and structure of the arterial walls or other intra-cavity regions at discrete points on the medical device during minimally invasive medical procedures. The information will be used both to guide the device through the body and to evaluate the tissue through which the device is being passed. Multiple optical fibers are situated along the circumference of the device. Light from the distal end of each fiber is directed onto the interior cavity walls via small diameter optics (such as gradient index lenses and mirrored corner cubes). Both forward viewing and side viewing fibers can be included. The light reflected or scattered from the cavity walls is then collected by the fibers and multiplexed at the proximal end to the sample arm of an optical low coherence reflectometer. The system may also be implemented in a nonmedical inspection device.

  9. STUDY OF A 10-MW CONTINUOUS SPALLATION NEUTRON SOURCE.

    SciTech Connect

    RUGGIERO,A.G.LUDEWIG,H.SHAPIRO,S.

    2003-05-12

    This paper reports on the feasibility study of a proton Super-Conducting Linac as the driver for an Accelerator-based Continuous Neutron Source (ACNS) [1] to be located at Brookhaven National Laboratory (BNL). The Linac is to be operated in the Continuous Wave (CW) mode to produce an average 10 MW of beam power. The Linac beam energy is taken to be 1.25 GeV. The required average proton beam intensity in exit is then 8 mA.

  10. 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.

  11. Precision Neutron Decay Studies with the Nab and UCNB Experiments

    NASA Astrophysics Data System (ADS)

    Sprow, Aaron; Nab Collaboration; UCNB Collaboration

    2016-03-01

    Precision neutron decay correlation experiments are a sensitive means to study the standard model and probe for beyond the standard model physics. Nab and UCNB are two such experiments that will measure the neutrino-electron correlation term, a, and the neutrino asymmetry, B, respectively. Thick, highly-segmented silicon detectors will be used to directly measure the proton and electron from each decay event in coincidence, leading to the extraction of these angular correlations. Preliminary work to understand the systematic uncertainties associated with these experiments, as well as the early analysis of data taken from the 2015-2016 beam time at Los Alamos National Laboratory will be presented.

  12. Infrared absorption study of neutron-transmutation-doped germanium

    NASA Technical Reports Server (NTRS)

    Park, I. S.; Haller, E. E.

    1988-01-01

    Using high-resolution far-infrared Fourier transform absorption spectroscopy and Hall effect measurements, the evolution of the shallow acceptor and donor impurity levels in germanium during and after the neutron transmutation doping process was studied. The results show unambiguously that the gallium acceptor level concentration equals the concentration of transmutated Ge-70 atoms during the whole process indicating that neither recoil during transmutation nor gallium-defect complex formation play significant roles. The arsenic donor levels appear at full concentration only after annealing for 1 h at 450 C. It is shown that this is due to donor-radiation-defect complex formation. Again, recoil does not play a significant role.

  13. Decay studies of the highly neutron-deficient indium isotopes

    SciTech Connect

    Wouters, J.M.

    1982-02-01

    An extension of the experimentally known nuclidic mass surface to nuclei far from the region of beta-stability is of fundamental interest in providing a better determination of the input parameters for the various nuclear mass formulae, allowing a more accurate prediction of the ultimate limits of nuclear stability. In addition, a study of the shape of the mass surface in the vicinity of the doubly-closed nuclide /sup 100/Sn provides initial information on the behavior of the shell closure to be expected when Z = N = 50. Experiments measuring the decay energies of /sup 103/ /sup 105/In by ..beta..-endpoint measurements are described with special attention focused on the development of a plastic scintillator ..beta..-telescope coupled to the on-line mass separator RAMA (Recoil Atom Mass Analyzer). An attempt to measure the ..beta..-endpoint energy of /sup 102/In is also briefly described. The experimentally determined decay energies and derived masses for /sup 103/ /sup 105/In are compared with the predictions of different mass models to identify which models are more successful in this region. Furthermore, the inclusion in these comparisons of the available data on the neutron-rich indium nuclei permits a systematic study of their ground state mass behavior as a function of the neutron number between the shell closures at N = 50 and N = 82. These analyses indicate that the binding energy of /sup 103/In is 1 MeV larger than predicted by the majority of the mass models. An examination of the Q/sub EC/ surface and the single- and two-neutron separation energies in the vicinity of /sup 103/ /sup 105/In is also performed to investigate further the deviation and other possible systematic variations in the mass surface in a model-independent way.

  14. A survey of reflectometry techniques with applications to TFTR

    SciTech Connect

    Collazo, I.; Stacey, W.M.; Wilgen, J.; Hanson, G.; Bigelow, T.; Thomas, C.E.; Bretz, N.

    1993-12-01

    This report presents a review of reflectometry with particular attention to eXtraordinary mode (X-mode) reflectometry using the novel technique of dual frequency differential phase. The advantage of using an X-mode wave is that it can probe the edge of the plasma with much higher resolution and using a much smaller frequency range than with the Ordinary mode (O-Mode). The general problem with previous full phase reflectometry techniques is that of keeping track of the phase (on the order of 1000 fringes) as the frequency is swept over the band. The dual frequency phase difference technique has the advantage that since it is keeping track of the phase difference of two frequencies with a constant frequency separation, the fringe counting is on the order of only 3 to 5 fringes. This fringe count, combined with the high resolution of the X-mode wave and the small plasma access requirements of reflectometry, make X-mode reflectometry a very attractive diagnostic for today`s experiments and future fusion devices.

  15. Neutron scattering studies on URu2Si2

    NASA Astrophysics Data System (ADS)

    Bourdarot, Frederic; Raymond, Stephane; Regnault, Louis-Pierre

    2014-11-01

    This paper aims to review some of the neutron scattering studies performed on URu2Si2 in Grenoble. This compound has been studied for a quarter of century because of a so-called hidden-order ground state visible by most of the bulk experiments but almost invisible by microscopic probes like neutrons, muons NMR or X-ray. We stress on some aspects that were not addressed previously. Firstly, the comparison of the cell parameters in the 1-2-2 systems seems to point that the magnetic properties of URu2Si2 are leading by an U4+ electronic state. Secondly, a compilation of the different studies of the tiny antiferromagnetic moment indicates that the tiny antiferromagnetic moment has a constant value which may indicate that it is not necessarily extrinsic. We also present the last development on the magnetic form factor measurement in which the magnetic density rotates when entering in the hidden-order state. To end, the thermal dependence of the two most intense magnetic excitations at Q0 = (1,0,0) and Q1 = (0.6,0,0) seems to indicate two different origins or processes for these excitations.

  16. 5 MW pulsed spallation neutron source, Preconceptual design study

    SciTech Connect

    Not Available

    1994-06-01

    This report describes a self-consistent base line design for a 5 MW Pulsed Spallation Neutron Source (PSNS). It is intended to establish feasibility of design and as a basis for further expanded and detailed studies. It may also serve as a basis for establishing project cost (30% accuracy) in order to intercompare competing designs for a PSNS not only on the basis of technical feasibility and technical merit but also on the basis of projected total cost. The accelerator design considered here is based on the objective of a pulsed neutron source obtained by means of a pulsed proton beam with average beam power of 5 MW, in {approx} 1 {mu}sec pulses, operating at a repetition rate of 60 Hz. Two target stations are incorporated in the basic facility: one for operation at 10 Hz for long-wavelength instruments, and one operating at 50 Hz for instruments utilizing thermal neutrons. The design approach for the proton accelerator is to use a low energy linear accelerator (at 0.6 GeV), operating at 60 Hz, in tandem with two fast cycling booster synchrotrons (at 3.6 GeV), operating at 30 Hz. It is assumed here that considerations of cost and overall system reliability may favor the present design approach over the alternative approach pursued elsewhere, whereby use is made of a high energy linear accelerator in conjunction with a dc accumulation ring. With the knowledge that this alternative design is under active development, it was deliberately decided to favor here the low energy linac-fast cycling booster approach. Clearly, the present design, as developed here, must be carried to the full conceptual design stage in order to facilitate a meaningful technology and cost comparison with alternative designs.

  17. Study of SMM flares in gamma-rays and neutrons

    NASA Technical Reports Server (NTRS)

    Dunphy, Philip P.; Chupp, Edward L.

    1992-01-01

    This report summarizes the results of the research supported by NASA grant NAGW-2755 and lists the papers and publications produced through the grant. The objective of the work was to study solar flares that produced observable signals from high-energy (greater than 10 MeV) gamma-rays and neutrons in the Solar Maximum Mission (SMM) Gamma-Ray Spectrometer (GRS). In 3 of 4 flares that had been studied previously, most of the neutrons and neutral pions appear to have been produced after the 'main' impulsive phase as determined from hard x-rays and gamma-rays. We, therefore, proposed to analyze the timing of the high-energy radiation, and its implications for the acceleration, trapping, and transport of flare particles. It was equally important to characterize the spectral shapes of the interacting energetic electrons and protons - another key factor in constraining possible particle acceleration mechanisms. In section 2.0, we discuss the goals of the research. In section 3.0, we summarize the results of the research. In section 4.0, we list the papers and publications produced under the grant. Preprints or reprints of the publications are attached as appendices.

  18. 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.

  19. Enzymes for carbon sequestration: neutron crystallographic studies of carbonic anhydrase

    SciTech Connect

    Fisher, S. Z. Kovalevsky, A. Y.; Domsic, J.; Mustyakimov, M.; Silverman, D. N.; McKenna, R.; Langan, P.

    2010-11-01

    The first neutron crystal structure of carbonic anhydrase is presented. The structure reveals interesting and unexpected features of the active site that affect catalysis. Carbonic anhydrase (CA) is a ubiquitous metalloenzyme that catalyzes the reversible hydration of CO{sub 2} to form HCO{sub 3}{sup −} and H{sup +} using a Zn–hydroxide mechanism. The first part of catalysis involves CO{sub 2} hydration, while the second part deals with removing the excess proton that is formed during the first step. Proton transfer (PT) is thought to occur through a well ordered hydrogen-bonded network of waters that stretches from the metal center of CA to an internal proton shuttle, His64. These waters are oriented and ordered through a series of hydrogen-bonding interactions to hydrophilic residues that line the active site of CA. Neutron studies were conducted on wild-type human CA isoform II (HCA II) in order to better understand the nature and the orientation of the Zn-bound solvent (ZS), the charged state and conformation of His64, the hydrogen-bonding patterns and orientations of the water molecules that mediate PT and the ionization of hydrophilic residues in the active site that interact with the water network. Several interesting and unexpected features in the active site were observed which have implications for how PT proceeds in CA.

  20. Neutron diffraction study of U-10 wt% Mo alloy

    NASA Astrophysics Data System (ADS)

    Seong, Baek-Seok; Lee, Chang-Hee; Lee, Jeong-Soo; Shim, Hae-Seop; Lee, Jin-Ho; Kim, Ki Hwan; Kim, Chang Kyu; Em, Vyacheslav

    2000-01-01

    The structural properties of a U-10 wt% Mo powder sample prepared by the centrifugal atomization method were investigated by the Rietveld total profile analysis method. The high resolution neutron powder diffractometer at the HANARO research reactor in Taejon, Korea, was used for a series of neutron diffraction pattern measurements for the study. The sample was synthesized by the centrifugal atomization method and was found to consist of two γ-U solid solution phases having identical bcc structures, but slightly different lattice dimensions, and accordingly different Mo content. When the sample was annealed for 10 h at 600°C, the two solid solution phases with different Mo contents merged into a uniform single phased γ-U solid solution. The diffraction pattern of the annealed sample showed two additional weak reflections, which could be indexed as a super lattice structure U 3Mo derived from the bcc cell by a /1 1 0/-1 1 0/0 0 1/ type lattice transformation. The disorder-order phase transition leading to the formation of ordered metastable phase U 3Mo should be of the first-order.

  1. 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.

  2. Neutron diffraction study of aluminous hydroxide δ-AlOOD

    NASA Astrophysics Data System (ADS)

    Vanpeteghem, C. B.; Sano, A.; Komatsu, K.; Ohtani, E.; Suzuki, A.

    2007-11-01

    We have determined the position of deuterium atoms in δ-AlOOD by neutron powder diffraction at ambient pressure. As previously reported by theoretical and experimental studies, the deuterium atoms are located in the tunnel formed by the chains of AlO6 octahedra. The data are best fit with the P21 nm structure, producing bond lengths of D O1 of 1.552(2) Å, O2 D of 1.020(2) Å and O1 O2 of 2.571(2). This study confirms that the hydrogen bond is asymmetric at ambient conditions in agreement with recent single-crystal synchrotron study for δ-AlOOH.

  3. Study of Neutron-Unbound States with MoNA

    NASA Astrophysics Data System (ADS)

    Kuchera, A. N.; Spyrou, A.; Smith, J. K.; Baumann, T.; Christian, G.; De Young, P. A.; Finck, J. E.; Frank, N.; Jones, M. D.; Kohley, Z.; Mosby, S.; Peters, W. A.; Thoennessen, M.

    2015-06-01

    The Modular Neutron Array (MoNA) in conjunction with the large-gap Sweeper magnet at the NSCL is an effective setup to explore neutron-unbound states and has been operating for ten years. Neutron-unbound nuclei beyond the drip-line as well as neutron unbound excited states of bound nuclei have been populated primarily using proton removal reactions. A recent example, the search for 3n emission of the decay of 15Be to1 12Be, is discussed.

  4. 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.

  5. Design study of a medical proton linac for neutron therapy

    SciTech Connect

    Machida, S.; Raparia, D.

    1988-08-26

    This paper describes a design study which establishes the physical parameters of the low energy beam transport, radiofrequency quadrupole, and linac, using computer programs available at Fermilab. Beam dynamics studies verify that the desired beam parameters can be achieved. The machine described here meets the aforementioned requirements and can be built using existing technology. Also discussed are other technically feasible options which could be attractive to clinicians, though they would complicate the design of the machine and increase construction costs. One of these options would allow the machine to deliver 2.3 MeV protons to produce epithermal neutrons for treating brain tumors. A second option would provide 15 MeV protons for isotope production. 21 refs., 33 figs.

  6. Using Neutrons to Study Fluid-Rock Interactions in Shales

    NASA Astrophysics Data System (ADS)

    DiStefano, V. H.; McFarlane, J.; Anovitz, L. M.; Gordon, A.; Hale, R. E.; Hunt, R. D.; Lewis, S. A., Sr.; Littrell, K. C.; Stack, A. G.; Chipera, S.; Perfect, E.; Bilheux, H.; Kolbus, L. M.; Bingham, P. R.

    2015-12-01

    Recovery of hydrocarbons by hydraulic fracturing depends on complex fluid-rock interactions that we are beginning to understand using neutron imaging and scattering techniques. Organic matter is often thought to comprise the majority of porosity in a shale. In this study, correlations between the type of organic matter embedded in a shale and porosity were investigated experimentally. Selected shale cores from the Eagle Ford and Marcellus formations were subjected to pyrolysis-gas chromatography, Differential Thermal Analysis/Thermogravimetric analysis, and organic solvent extraction with the resulting affluent analyzed by gas chromatography-mass spectrometry. The pore size distribution of the microporosity (~1 nm to 2 µm) in the Eagle Ford shales was measured before and after solvent extraction using small angle neutron scattering. Organics representing mass fractions of between 0.1 to 1 wt.% were removed from the shales and porosity generally increased across the examined microporosity range, particularly at larger pore sizes, approximately 50 nm to 2 μm. This range reflects extraction of accessible organic material, including remaining gas molecules, bitumen, and kerogen derivatives, indicating where the larger amount of organic matter in shale is stored. An increase in porosity at smaller pore sizes, ~1-3 nm, was also present and could be indicative of extraction of organic material stored in the inter-particle spaces of clays. Additionally, a decrease in porosity after extraction for a sample was attributed to swelling of pores with solvent uptake. This occurred in a shale with high clay content and low thermal maturity. The extracted hydrocarbons were primarily paraffinic, although some breakdown of larger aromatic compounds was observed in toluene extractions. The amount of hydrocarbon extracted and an overall increase in porosity appeared to be primarily correlated with the clay percentage in the shale. This study complements fluid transport neutron

  7. Neutron production from flattening filter free high energy medical linac: A Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Najem, M. A.; Abolaban, F. A.; Podolyák, Z.; Spyrou, N. M.

    2015-11-01

    One of the problems arising from using a conventional linac at high energy (>8 MV) is the production of neutrons. One way to reduce neutron production is to remove the flattening filter (FF). The main purpose of this work was to study the effect of FF removal on neutron fluence and neutron dose equivalent inside the treatment room at different photon beam energies. Several simulations based on Monte Carlo techniques were carried out in order to calculate the neutron fluence at different locations in the treatment room from different linac energies with and without a FF. In addition, a step-and-shoot intensity modulated radiotherapy (SnS IMRT) for prostate cancer was modelled using the 15 MV photon beam with and without a FF on a water phantom to calculate the neutron dose received in a full treatment. The results obtained show a significant drop-off in neutrons fluence and dose equivalent when the FF was removed. For example, the neutron fluence was decreased by 54%, 76% and 75% for 10, 15 and 18 MV, respectively. This can decrease the neutron dose to the patient as well as reduce the shielding cost of the treatment room. The neutron dose equivalent of the SnS IMRT for prostate cancer was reduced significantly by 71.3% when the FF was removed. It can be concluded that the flattening filter removal from the head of the linac could reduce the risk of causing secondary cancers and the shielding cost of radiotherapy treatment rooms.

  8. Neutron field produced by 25 MeV deuteron on thick beryllium for radiobiological study; energy spectrum.

    PubMed

    Takada, Masashi; Mihara, Erika; Sasaki, Michiya; Nakamura, Takashi; Honma, Toshihiko; Kono, Koji; Fujitaka, Kazunobu

    2004-01-01

    Biological data is necessary for estimation of protection from neutrons, but there is a lack of data on biological effects of neutrons for radiation protection. Radiological study on fast neutrons has been done at the National Institute of Radiological Sciences. An intense neutron source has been produced by 25 MeV deuterons on a thick beryllium target. The neutron energy spectrum, which is essential for neutron energy deposition calculation, was measured from thermal to maximum energy range by using an organic liquid scintillator and multi-sphere moderated 3He proportional counters. The spectrum of the gamma rays accompanying the neutron beam was measured simultaneously with the neutron spectrum using the organic liquid scintillator. The transmission by the shield of the spurious neutrons originating from the target was measured to be less than 1% by using the organic liquid scintillator placed behind the collimator. The measured neutron energy spectrum is useful in dose calculations for radiobiology studies.

  9. Scissors mode of Gd nuclei studied from resonance neutron capture

    NASA Astrophysics Data System (ADS)

    Kroll, J.; Baramsai, B.; Becker, J. A.; Bečvár, F.; Bredeweg, T. A.; Couture, A.; Chyzh, A.; Dashdorj, D.; Haight, R. C.; Heil, M.; Jandel, M.; Käppeler, F.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Parker, W.; Reifarth, R.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Vieira, D. J.; Walker, C. L.; Wilhelmy, J. B.; Wouters, J. M.; Wu, C. Y.

    2012-10-01

    Spectra of γ rays following the neutron capture at isolated resonances of stable Gd nuclei weremeasured. The objectives were to get new information on photon strength of 153,155-159Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength ΣB(M1)↑, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum ΣB(M1)↑ increases with A and for 157,159Gd it is significantly higher compared to 156,158Gd.

  10. Scissors mode of Gd nuclei studied from resonance neutron capture

    SciTech Connect

    Kroll, J.; Baramsai, B.; Becker, J. A.; and others

    2012-10-20

    Spectra of {gamma} rays following the neutron capture at isolated resonances of stable Gd nuclei were measured. The objectives were to get new information on photon strength of {sup 153,155-159}Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength {Sigma}B(M1){up_arrow}, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum {Sigma}B(M1){up_arrow} increases with A and for {sup 157,159}Gd it is significantly higher compared to {sup 156,158}Gd.

  11. An inelastic neutron scattering study of dietary phenolic acids.

    PubMed

    Marques, M Paula M; Batista de Carvalho, Luís A E; Valero, Rosendo; Machado, Nelson F L; Parker, Stewart F

    2014-04-28

    The conformational preferences and hydrogen-bonding motifs of several potential chemopreventive hydroxycinnamic derivatives were determined by inelastic neutron scattering spectroscopy. The aim is to understand their recognized beneficial activity and establish reliable structure-activity relationships for these types of dietary phytochemicals. A series of phenolic acids with different hydroxyl/methoxyl ring substitution patterns were studied: trans-cinnamic, p-coumaric, m-coumaric, trans-caffeic and ferulic acids. Their INS spectra were completely assigned by theoretical calculations performed at the Density Functional Theory level, for the isolated molecule, dimeric centrosymmetric species and the solid (using plane-wave expansion approaches). Access to the low energy vibrational region of the spectra enabled the identification of particular modes associated with intermolecular hydrogen-bonding interactions, which are the determinants of the main conformational preferences and antioxidant capacity of these systems.

  12. Study of the muon-induced neutron background with the LVD detector

    SciTech Connect

    Menghetti, H.; Selvi, M.

    2005-09-08

    High energy neutrons, generated as a product of cosmic muon interaction in the rock or in the detector passive material, represent the most dangerous background for a large list of topics like reactor neutrino studies, the search for SN relic neutrinos, solar antineutrinos, etc.Up to now there are few measurements of the muon-produced neutron flux at large depth underground. Moreover it is difficult to reproduce the measured data with Monte Carlo simulation because of the large uncertainties in the neutron production and propagation models.We present here the results of such a measurement with the LVD detector, which is well suited for the detection of neutrons produced by cosmic-ray muons, reporting the neutron flux at various distances from the muon track, for different neutron energies (E > 20 MeV) and as a function of the muon track length in scintillator.

  13. Final report on Seed Money Project 3210-0346: Feasibility study for californium cold neutron source

    SciTech Connect

    Alsmiller, R.G.; Henderson, D.L.; Montgomery, B.H.

    1988-10-01

    A study has been completed of the feasibility and cost of building a cold neutron source that is not dependent on a reactor or accelerator. The neutron source is provided by up to ten /sup 252/Cf capsules, each containing 50 mg of the isotope produced in the High-Flux Isotope Reactor. The neutrons are moderated by heavy water and liquid deuterium to attain, in practice, a peak cold neutron flux of 1.4 /times/ 10/sup 13/ neutrons/(m/sup 2//center dot/s). The new facility would be located in the TURF Californium Facility. The estimated cost of the Californium Cold Neutron Source Facility is $6.5 million. 6 figs., 1 tab.

  14. Physics of frustrated systems: A neutron scattering study

    NASA Astrophysics Data System (ADS)

    Gasparovic, Goran

    Frustration refers to the inability of a system to simultaneously satisfy all interactions. The principal ingredients of frustration are (i) competition between interactions within the system, and (ii) conflicting constraints established by symmetry, or higher energy interactions. The behavior of frustrated systems is generally difficult to predict, and often results in novel cooperative states and phenomena. Frustration is common in disordered systems, in this dissertation, however, we focus on frustrated systems without quenched disorder. Effects of frustration tend to be pronounced when coupled with weak connectivity. Weak connectivity refers to a topology in which the order in one part of the system does not constrain the order in other parts. We have used neutron scattering to study structurally and magnetically frustrated systems, both strongly and weakly connected. In ZrW2O8 and Sc2(WO4) 3, anomalously large Negative Thermal Expansion (NTE) has been observed over a wide temperature range. Analysis indicates that the NTE effect in these materials is driven by folding of rigid units consisting of strongly bonded oxygen-metal polyhedra. Weak connectivity is manifested by structural under-constraint, which enables soft optical phonons. Using neutron scattering, we observed an unusually high density-of-states at low energies, and mapped the dispersion relations of the most intense phonon modes. While in conventional materials soft phonon modes typically signal an imminent structural phase transition, in NTE materials the transition is frustrated by the incompatibility between the crystal symmetry and the symmetry of the soft phonon modes. This results in the unusual NTE effect. RbFe(MoO4)2 is a frustrated, quasi-classical ( S = 5/2), quasi-two-dimensional Heisenberg antiferromagnet on a triangular lattice, with easy-plane anisotropy. In RbFe(MoO4)2, frustrated units (triangles) share edges, and are strongly connected. Although a long range magnetic order is

  15. Neutron-induced charged-particle emission studies below 100 MeV at WNR

    SciTech Connect

    Haight, R.C.; Lee, T.M.; Sterbenz, S.M.

    1994-07-01

    Charged-particles produced by neutron bombardment of selected targets with Z=5 through 53 have been studied for neutron energies from 1 MeV to about 100 MeV using the spallation neutron source at WNR/LAMPF. Particle detection with energy measurement and particle identification is accomplished by two-element {Delta}E-E counters, three-element {Delta}E{sub l}-{Delta}E{sub 2}-E counters or with pulse-shape discrimination using scintillators directly in the neutron beam. The experimental techniques for these measurements are described and comparisons made among the different approaches. This presentation introduces five papers contributed to this conference.

  16. Acoustic Reflectometry versus Tympanometry in Pediatric Middle Ear Screenings.

    ERIC Educational Resources Information Center

    Holmes, Alice E.; And Others

    1989-01-01

    Use of acoustic reflectometry was compared with tympanometry in middle ear screenings for 357 children, aged 5 months to 19 years. Results were analyzed according to sex, age, and sensorineural hearing status. Intratest reliability was highly significant and positive predictive accuracy and specificity rates were excellent, but sensitivity rates…

  17. Directly coupled vs conventional time domain reflectometry in soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Time domain reflectometry (TDR), a technique for estimation of soil water, measures the travel time of an electromagnetic pulse on electrodes embedded in the soil, but has limited application in commercial agriculture due to costs, labor, and sensing depth. Conventional TDR systems have employed ana...

  18. Measurement of the neutron energy spectrum on the Godiva IV fast burst assembly for application to neutron dosimetry studies

    SciTech Connect

    Casson, W.H.; Hsu, H.H.; Paternoster, R.R.; Butterfield, K.B.

    1996-06-01

    In June, 1995, Los Alamos National Laboratory hosted the 23rd U.S. Department of Energy sponsored Nuclear Accident Dosimetry Study at the Los Alamos Critical Experiments Facility. The participants tested their facilities accident dosimeters under a variety of neutrons fields produced by the Solution High Energy Burst Assembly (SHEBA) and the Godiva IV fast burst assembly. To provide useful information for the evaluation of the results, the neutron energy Spectrum was determined and the delivered absorbed dose to tissue. The measurement of the neutron energy spectrum on Godiva provides a unique problem in that the burst, which is nearly Gaussian in time, has a full width at half maximum of around 50 microseconds. The neutron spectrum was first determined at low-power while running at delayed critical using a standard set of Bonner spheres. At the same time, the response of a set of TLD dosimeters were measured. After that, measurements were conducted during a burst with another set of TLDs and with sulfur pellets.

  19. Study of the ratio of non-neutron to neutron dose components of cosmic radiation at typical commercial flight altitudes.

    PubMed

    Romero, A M; Saez-Vergara, J C; Rodriguez, R; Domínguez-Mompell, R

    2004-01-01

    CIEMAT, in close co-operation with Iberia Airlines, carried out an extensive programme of in-flight measurements, covering both hemispheres, during the years 2001 and 2002. Although the instrumentation onboard included different active devices, the results presented here were obtained from a polyethylene/tungsten-moderated rem meter (SWENDI2; Eberline) and an ionisation chamber (RSS-131; Reuter-Stokes) used for measuring the ambient dose equivalent due to the neutron and the non-neutron components of cosmic radiation, respectively. This paper presents a study of each of the dose components mentioned as a function of the vertical cut-off rigidity and the flight altitude. The ratio between the two components is also presented to determine the variations in cosmic radiation composition as a function of the aforementioned parameters. The experimental results have also been compared with those predicted by the code EPCARD3.2 for the non-neutron and the neutron components of the ambient dose equivalent.

  20. Methods for lipid nanostructure investigation at neutron and synchrotron sources

    NASA Astrophysics Data System (ADS)

    Kiselev, M. A.

    2011-03-01

    A lipid membrane is a main component of biological membranes. Contemporary bionanotechnologies use phospholipids and ceramides as basic components of drugs and cosmetic preparations. Phospholipids-based nanoparticles are used as drug carriers. Effective development of bionanotechnologies in Russia calls for creation of physical methods to diagnose the particle nanostructure which would be promising for application in pharmacology. Radiation with wavelengths of 1-10 Å is an adequate instrument for detecting the nanostructure of lipid bi- and monolayers. The review deals with methods that apply neutron scattering and synchrotron radiation for studying nanostructures of lipid membranes, phospholipid nanoparticles, and phospholipid monolayers on a water surface by techniques of diffraction, small-angle scattering, and reflectometry. The importance of the mutually complementary application of neutron and synchrotron radiation for solving urgent problems of membrane biophysics, microbiology, dermapharmacology, and bionanotechnologies is demonstrated by particular examples of studies of phospholipid membranes and ceramide-based membranes. The efficiency of development and application of new methods for solving urgent problems of biophysics is shown. The review is written on the basis of results obtained over the period of 1999-2010 at the Joint Institute for Nuclear Research (JINR) Laboratory of Neutron Physics in collaboration with the Pharmaceutical Departments of universities of France (Paris-Sud, Chatenay Malabry) and Germany (Martin Luther University, Halle). The experiments were performed at various European and Russian neutron and synchrotron sources.

  1. Quantum states of neutrons in the gravitational and centrifugal potentials in a new GRANIT spectrometer

    ScienceCinema

    None

    2016-07-12

    We will discuss the scientific program to be studied in a new gravitational spectrometer GRANIT in a broad context of quantum states (quantum behaviour) of ultracold neutrons (UCN) in gravitational [1] and centrifugal [2] potentials, as well as applications of these phenomena/spectrometer to various domains of physics, ranging from studies of fundamental short-range interactions and symmetries to neutron quantum optics and reflectometry using UCN. All these topics, as well as related instrumental and methodical developments have been discussed during dedicated GRANIT-2010 Workshop [3]. The GRANIT spectrometer has been recently installed at the Institut Laue-Langevin, Grenoble, France [4] and could become operational in near future. 1. V.V. Nesvizhevsky et al (2002), Nature 415, 297. 2. V.V. Nesvizhevsky et al (2010), Nature Physics 6, 114. 3. GRANIT-2010, Les Houches, 14-19 february 2010. 4. M. Kreuz et al (2009), NIM 611, 326.

  2. Target studies for accelerator-based boron neutron capture therapy

    SciTech Connect

    Powell, J.R.; Ludewig, H.; Todosow, M.; Reich, M.

    1996-03-01

    Two new concepts, NIFTI and DISCOS, are described. These concepts enable the efficient production of epithermal neutrons for BNCT (Boron Neutron Capture Therapy) medical treatment, utilizing a low current, low energy proton beam impacting on a lithium target. The NIFTI concept uses an iron layer that strongly impedes the transmission of neutrons with energies above 24 KeV. Lower energy neutrons readily pass through this iron ``filter``, which has a deep ``window`` in its scattering cross section at 24 KeV. The DISCOS concept uses a rapidly rotating, high g disc to create a series of thin ({approximately} 1 micron thickness) liquid lithium targets in the form of continuous films through which the proton beam passes. The average energy lost by a proton as it passes through a single target is small, approximately 10 KeV. Between the targets, the proton beam is reaccelerated by an applied DC electric field. The DISCOS approach enables the accelerator -- target facility to operate with a beam energy only slightly above the threshold value for neutron production -- resulting in an output beam of low-energy epithermal neutrons -- while achieving a high yield of neutrons per milliamp of proton beam current.

  3. Neutron-induced reactions in the hohlraum to study reaction in flight neutrons

    NASA Astrophysics Data System (ADS)

    Boswell, M. S.; Elliott, S. R.; Guiseppe, V.; Kidd, M.; Rundberg, B.; Tybo, J.

    2013-04-01

    We are currently developing the physics necessary to measure the Reaction In Flight (RIF) neutron flux from a NIF capsule. A measurement of the RIF neutron flux from a NIF capsule could be used to deduce the stopping power in the cold fuel of the NIF capsule. A foil irradiated at the Omega laser at LLE was counted at the LANL low-background counting facility at WIPP. The estimated production rate of 195Au was just below our experimental sensitivity. We have made several improvements to our counting facility in recent months. These improvements are designed to increase our sensitivity, and include installing two new low-background detectors, and taking steps to reduce noise in the signals.

  4. Study of {beta}-Decay in the Proton-Neutron Interacting Boson-Fermion Model

    SciTech Connect

    Zuffi, L.; Brant, S.; Yoshida, N.

    2006-04-26

    We study {beta}-decay in odd-A nuclei together with the energy levels and other properties in the proton-neutron interacting-boson-fermion model. We also report on the preliminary results in the odd-odd nuclei in the proton-neutron interacting boson-fermion-fermion model.

  5. Neutron Scattering Techniques in the Study of Phase Transitions.

    NASA Astrophysics Data System (ADS)

    Rogge, Ronald Benjamin

    The properties of thermal neutrons make them particularly adept for studies of condensed matter materials and the study of phase transitions in condensed matter systems. A variety of neutron scattering techniques have been employed to study the phase transitions in Cu_3Au and CsCoBr_3, which are representatives of the two principle types of phase transitions. The binary alloy Cu_3Au undergoes a first order phase transition from its low temperature ordered phase in which the atoms preferentially occupy the sites of a simple cubic lattice, to its high temperature disordered phase at 667 +/- 3K. Although a well studied system, the results reported in this thesis shall demonstrate that there is still much that can be learned from Cu_3Au. Within the context of the Landau theory of phase transitions, there exists, in addition to the order-disorder temperature, T_{c}, upper and lower spinodal temperatures, T_{su} and T_{sl}. These mark the first temperatures upon approaching the phase transition from above and below respectively, at which metastable droplets of the second phase can fluctuate out of the first phase. Until recently, there has however been little physical evidence supporting the existence of the spinodal temperatures. Elastic and inelastic neutron scattering measurements have been performed over an extended temperature range with an emphasis on temperatures near T_{c}. The lattice constant data, order-parameter data and phonon data provided by these measurements all indicate that there are two temperature regimes just below T_{c} with a crossover between these regimes in the range of T_{c}-35K to T _{c}-25K. This crossover temperature is interpreted as the lower spinodal temperature of Cu _3Au. CsCoBr_3 is believed to pass through at least two and possibly three magnetic phase transitions. The highest temperature transition is a second -order phase transition at approximately T_ {rm N1} = 28.3 +/- 0.1K. in the high temperature paramagnetic phase, the

  6. DETECTORS AND EXPERIMENTAL METHODS: Study on spatial resolution of micromegas as a neutron detector under condition of high neutron flux and γ ray background

    NASA Astrophysics Data System (ADS)

    Wang, Wen-Xin; Zhang, Yi; Wang, Ji-Jin; Hu, Bi-Tao

    2009-02-01

    In this paper Micromegas has been designed to detect neutrons. The simulation of the spatial resolution of Micromegas as neutron detector is carried out by GEANT4 toolkit. The neutron track reconstruction method based on the time coincidence technology is employed in the present work. The influence of the flux of incident 14 MeV neutron and high gamma background on the spatial resolution is carefully studied. Our results show that the spatial resolution of the detector is sensitive to the neutron flux, but insensitive to the intensity of γ background if the neutron track reconstruction method proposed by our group is used. The γ insensitivity makes it possible for us to use the Micromegas detector under condition which has high γ-rays background.

  7. Measurement of shear-wave velocity by ultrasound critical-angle reflectometry (UCR)

    NASA Technical Reports Server (NTRS)

    Mehta, S.; Antich, P.; Blomqvist, C. G. (Principal Investigator)

    1997-01-01

    There exists a growing body of research that relates the measurement of pressure-wave velocity in bone to different physiological conditions and treatment modalities. The shear-wave velocity has been less studied, although it is necessary for a more complete understanding of the mechanical properties of bone. Ultrasound critical-angle reflectometry (UCR) is a noninvasive and nondestructive technique previously used to measure pressure-wave velocities both in vitro and in vivo. This note describes its application to the measurement of shear-wave velocity in bone, whether directly accessible or covered by soft tissue.

  8. Full-wave simulations on ultrashort-pulse reflectometry for helical plasmas

    SciTech Connect

    Hojo, H.; Fukuchi, A.; Itakura, A.; Mase, A.

    2004-10-01

    The full-wave simulations on ultrashort-pulse reflectometry for helical plasmas are studied based on the FDTD method in two dimensions. The propagation of an ultrashort-pulse electromagnetic wave is computed in helical plasmas modeled for the Large Helical Device magnetic field configuration. The density-profile reconstruction is performed by the Abel inversion method with the time delay data for the reflected waves from plasma, and it is shown that the reconstructed density profile coincides well with the original profile.

  9. Progress on the Europium Neutron-Capture Study using DANCE

    SciTech Connect

    Agvaanluvsan, U; Becker, J A; Macri, R A; Parker, W; Wilk, P; Wu, C Y; Bredeweg, T A; Esch, E; Haight, R C; O'Donnell, J M; Reifarth, R; Rundberg, R S; Schwantes, J M; Ullmann, J L; Vieira, D J; Wilhelmy, J B; Wouters, J M; Mitchell, G E; Sheets, S A; Becvar, F; Krticka, M

    2006-09-05

    The accurate measurement of neutron-capture cross sections of the Eu isotopes is important for many reasons including nuclear astrophysics and nuclear diagnostics. Neutron capture excitation functions of {sup 151,153}Eu targets were measured recently using a 4{pi} {gamma}-ray calorimeter array DANCE located at the Los Alamos Neutron Science Center for E{sub n} = 0.1-100 keV. The progress on the data analysis efforts is given in the present paper. The {gamma}-ray multiplicity distributions for the Eu targets and Be backing are significantly different. The {gamma}-ray multiplicity distribution is found to be the same for different neutron energies for both {sup 151}Eu and {sup 153}Eu. The statistical simulation to model the {gamma}-ray decay cascade is summarized.

  10. Progress on the europium neutron capture study using DANCE

    NASA Astrophysics Data System (ADS)

    Agvaanluvsan, U.; Becker, J. A.; Macri, R. A.; Parker, W.; Wilk, P.; Wu, C. Y.; Bredeweg, T. A.; Esch, E.; Haight, R. C.; O'Donnell, J. M.; Reifarth, R.; Rundberg, R. S.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Mitchell, G. E.; Sheets, S.; Bečvář, F.; Krtička, M.

    2007-08-01

    The accurate measurement of neutron capture cross sections of the Eu isotopes is important for many reasons including nuclear astrophysics and nuclear diagnostics. Neutron capture excitation functions of 151,153Eu targets were measured recently using a 4π γ-ray calorimeter array DANCE located at the Los Alamos Neutron Science Center for En = 0.1-100 keV. The progress on the data analysis efforts is given in the present paper. The γ-ray multiplicity distributions for the Eu targets and Be backing are significantly different. The γ-ray multiplicity distribution is found to be the same for different neutron energies for both 151Eu and 153Eu. The statistical simulation to model the γ-ray decay cascade is summarized.

  11. Neutron activation studies and the effect of exercise on osteoporosis

    SciTech Connect

    Harrison, J.E.

    1984-01-01

    A technique is described to measure calcium content by in vivo neutron activation analysis of the trunk and upper thighs. In postmenopausal women, estrogen and calcium or fluoride reversed osteoporosis.

  12. Using FLUKA to Study Concrete Square Shield Performance in Attenuation of Neutron Radiation Produced by APF Plasma Focus Neutron Source

    NASA Astrophysics Data System (ADS)

    Nemati, M. J.; Habibi, M.; Amrollahi, R.

    2013-04-01

    In 2010, representatives from the Nuclear Engineering and physics Department of Amirkabir University of Technology (AUT) requested development of a project with the objective of determining the performance of a concrete shield for their Plasma Focus as neutron source. The project team in Laboratory of Nuclear Engineering and physics department of Amirkabir University of Technology choose some shape of shield to study on their performance with Monte Carlo code. In the present work, the capability of Monte Carlo code FLUKA will be explored to model the APF Plasma Focus, and investigating the neutron fluence on the square concrete shield in each region of problem. The physical models embedded in FLUKA are mentioned, as well as examples of benchmarking against future experimental data. As a result of this study suitable thickness of concrete for shielding APF will be considered.

  13. Use of complementary neutron techniques in studying the effect of a solid/liquid interface on bulk solution structures

    SciTech Connect

    Butler, P.D.; Hamilton, W.A.; Magid, L.J.

    1996-12-31

    By appropriate combination of neutron scattering techniques, it is possible to obtain structural information at various distances from a solid/liquid interface and thus probe in some detail how the surface structures evolve into bulk structures. We have used neutron reflectometry (NR) with a newly developed shear cell, near surface small angle neutron scattering (NSSANS) again in combination with the new shear cell, and regular small angle neutron scattering (SANS) with a standard Couette shear cell to probe the structures formed in our aqueous surfactant systems and how they react to a flow field, particularly in the near surface region of a solid/liquid interface. We present data for a 20mM aqueous solutions of 70% cetyltrimethylammonium 3,5-dichlorobenzoate (abbreviated CTA3,5ClBz) and 30% CTAB. This system forms a very viscoelastic solution containing long threadlike micelles. NR only probes to a depth of about 0.5 {mu}m from the surface in these systems and clearly indicates that adsorbed onto the surface is, surfactant layer which is insensitive to shear. The depth probed by the NSSANS is on the order of 20-30 {mu}m and is determined by the transmission of the sample, the angle of incidence, and the wavelength. In this region, the rods align under shear into a remarkably well ordered hexagonal crystal. The SANS from the Couette cell averages over the entire sample, so that the signal is dominated by scattering from the bulk. While the near surface hexagonal structure is clearly visible, these data are not consistent with the crystal structure persisting throughout the bulk, leading to the postulate that the bulk structure is a two dimensional (2D) liquid where the rods align with the flow, but do not order in the other two dimensions.

  14. Land-surface studies with a directional neutron detector.

    SciTech Connect

    Desilets, Darin; Brennan, James S.; Mascarenhas, Nicholas; Marleau, Peter

    2009-09-01

    Direct measurements of cosmic-ray neutron intensity were recorded with a neutron scatter camera developed at SNL. The instrument used in this work is a prototype originally designed for nuclear non-proliferation work, but in this project it was used to characterize the response of ambient neutrons in the 0.5-10 MeV range to water located on or above the land surface. Ambient neutron intensity near the land surface responds strongly to the presence of water, suggesting the possibility of an indirect method for monitoring soil water content, snow water equivalent depth, or canopy intercepted water. For environmental measurements the major advantage of measuring neutrons with the scatter camera is the limited (60{sup o}) field of view that can be obtained, which allows observations to be conducted at a previously unattainable spatial scales. This work is intended to provide new measurements of directional fluxes which can be used in the design of new instruments for passively and noninvasively observing land-surface water. Through measurements and neutron transport modeling we have demonstrated that such a technique is feasible.

  15. Luminosity class of neutron reflectometers

    NASA Astrophysics Data System (ADS)

    Pleshanov, N. K.

    2016-10-01

    The formulas that relate neutron fluxes at reflectometers with differing q-resolutions are derived. The reference luminosity is defined as a maximum flux for measurements with a standard resolution. The methods of assessing the reference luminosity of neutron reflectometers are presented for monochromatic and white beams, which are collimated with either double diaphragm or small angle Soller systems. The values of the reference luminosity for unified parameters define luminosity class of reflectometers. The luminosity class characterizes (each operation mode of) the instrument by one number and can be used to classify operating reflectometers and optimize designed reflectometers. As an example the luminosity class of the neutron reflectometer NR-4M (reactor WWR-M, Gatchina) is found for four operation modes: 2.1 (monochromatic non-polarized beam), 1.9 (monochromatic polarized beam), 1.5 (white non-polarized beam), 1.1 (white polarized beam); it is shown that optimization of measurements may increase the flux at the sample up to two orders of magnitude with monochromatic beams and up to one order of magnitude with white beams. A fan beam reflectometry scheme with monochromatic neutrons is suggested, and the expected increase in luminosity is evaluated. A tuned-phase chopper with a variable TOF resolution is recommended for reflectometry with white beams.

  16. Dynamics of camphor sulphonic acid: a quasielastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Bée, M.; Djurado, D.; Combet, J.; Gonzalez, M. A.

    2002-03-01

    Molecular motions in mono-hydrated racemic camphor sulphonic acid (±)-10-C 10H 16O 4S --H 3O + which is abbreviated as (CSA-H 2O) were investigated using incoherent neutron scattering techniques. Analysis of the intensity of the purely elastic scattering over a wide temperature range (4-340 K) carried out with a high-resolution backscattering spectrometer revealed the onset of molecular motions at ca. 100 K which could be observed on the 10 -10 s time-scale up to T=180 K. These motions were identified as 120° jumps of the methyl groups. Quasielastic measurements using both the backscattering and the time-of-flight techniques enabled to study this movement from 150 to 340 K. The corresponding characteristic time was found to follow an Arrhenius law with an activation energy ΔH=12.0±0.2 kJ mol -1. All the methyl groups appear as dynamically equivalent. That result is at contrast with earlier studies on conducting polymers where CSA was introduced as a counter-ion and for which the intermolecular effects were found to strongly influence the dynamics. Inspection of the low frequency part of the vibrational spectrum evidences deformations of the C-C-S angle and rotational oscillations of the hydration molecules.

  17. GNSS-Reflectometry: Forest canopies polarization scattering properties and modeling

    NASA Astrophysics Data System (ADS)

    Wu, Xuerui; Jin, Shuanggen

    2014-09-01

    Nowadays, GNSS-Reflectometry (GNSS-R) can be a new promising remote sensing tool in the ocean, snow/ice and land surfaces, e.g., vegetation biomass monitoring. Although GNSS-R provides a potentially special L-band multi-angular and multi-polarization measurement, the theoretical vegetation scattering properties and mechanisms for GNSS-R are not understood clearly. In this paper, the GNSS-R vegetation polarization scattering properties are studied and modeled at different incidence angles (specular direction). The bistatic scattering model Bi-mimics is employed, which is the first-order radiative transfer equation. As a kind of forest stand, the Aspen’s crown layer is composed of entire leaves, and its parameters in Mimics handbook are used as model input. The specular circular polarizations (co-polarization RR and cross-polarization LR) are simulated. For cross-polarization, the received polarization is assumed as a linear (horizontal and vertical) polarizations and ±45° linear polarizations. Therefore, the HR VR, +45R and -45R polarizations are simulated here. Contributions from different scattering components at RR, LR and VR polarization are also presented. For co-polarization, it is large in the whole specular angles (10-80°). The scattering trends of the other cross polarization (HR, LR, +45R and -45R) are a little similar when compared to the RR and RV. Therefore, the RHCP and V polarizations are more favorable to collect the reflected signals. The trunk heights and crown depths do not affect the scattering trends of RR, RV and RL, while the trunk height has some effect on the scattering amplitude of different polarizations. The azimuth angle has more effects on RR, RL and RV scattering, especially in lower than 50°. The observation angles and polarization combinations are extremely important for GNSS-R remote sensing.

  18. Neutron diffraction and quasielastic neutron scattering studies of films of intermediate-length alkanes adsorbed on a graphite surface

    NASA Astrophysics Data System (ADS)

    Diama, Armand

    Over the past several years, we have conducted a variety of elastic neutron diffraction and quasielastic neutron scattering experiments to study the structure and the dynamics of films of two intermediate-length alkane molecules (C nH2n+2), adsorbed on a graphite basal-plane surface. The two molecules are the normal alkane n-tetracosane [n-CH 3(CH2)22CH3] and the branched alkane squalane (C30H62 or 2, 6, 10, 15, 19, 23-hexamethyltetracosane) whose carbon backbone is the same length as teteracosane. The temperature dependence of the monolayer structure of tetracosane and squalane was investigated using elastic neutron diffraction and evidence of two phase transitions was observed. Both the low-coverage tetracosane (C 24H50) and squalane (C30H62) monolayers have crystalline-to-"smectic" and "smectic"-to-isotropic fluid phase transitions upon heating. The diffusive motion in the tetracosane and squalane monolayers has been investigated by quasielastic neutron scattering. Two different quasielastic neutron scattering spectrometers at the Center for Neutron Research, National Institute of Standards and Technology (NIST) have been used. The spectrometers differ in both their dynamic range and energy resolution allowing molecular motions to be investigated on time scales in the range 10-13--10 -9 s. On these time scales, we observe evidence of translational, rotational, and intermolecular diffusive motions in the tetracosane and squalane monolayers. We conclude that the molecular diffusive motion in the two monolayers is qualitatively similar. Thus, despite the three methyl sidegroups at each end of the squalane molecule, its monolayer structure, phase transitions, and dynamics are qualitatively similar to that of a monolayer of the unbranched tetracosane molecules. With the higher resolution spectrometer at NIST, we have also investigated the molecular diffusive motion in multilayer tetracosane films. The analysis of our measurements indicates slower diffusive motion in

  19. 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).

  20. 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.

  1. Study of muon-induced neutron production using accelerator muon beam at CERN

    SciTech Connect

    Nakajima, Y.; Lin, C. J.; Ochoa-Ricoux, J. P.; Draeger, E.; White, C. G.; Luk, K. B.; Steiner, H.

    2015-08-17

    Cosmogenic muon-induced neutrons are one of the most problematic backgrounds for various underground experiments for rare event searches. In order to accurately understand such backgrounds, experimental data with high-statistics and well-controlled systematics is essential. We performed a test experiment to measure muon-induced neutron production yield and energy spectrum using a high-energy accelerator muon beam at CERN. We successfully observed neutrons from 160 GeV/c muon interaction on lead, and measured kinetic energy distributions for various production angles. Works towards evaluation of absolute neutron production yield is underway. This work also demonstrates that the setup is feasible for a future large-scale experiment for more comprehensive study of muon-induced neutron production.

  2. Study of absolute fast neutron dosimetry using CR-39 track detectors

    NASA Astrophysics Data System (ADS)

    El-Sersy, A. R.

    2010-06-01

    In this work, CR-39 track detectors have extensively been used in the determination of fast neutron fluence-to-dose factor. The registration efficiency, ɛ, of CR-39 detectors for fast neutrons was calculated using different theoretical approaches according to each mode of neutron interaction with the constituent atoms (H, C and O) of the detector material. The induced proton-recoiled showed the most common interaction among the others. The dependence of ɛ on both neutron energy and etching time was also studied. In addition, the neutron dose was calculated as a function of neutron energy in the range from 0.5 to 14 MeV using the values of (d E/d X) for each recoil particle in CR-39 detector. Results showed that the values of ɛ were obviously affected by both neutron energy and etching time where the contribution in ɛ from proton recoil was the most. The contribution from carbon and oxygen recoils in dose calculation was pronounced due to their higher corresponding values of d E/d X in comparison to those from proton recoils. The present calculated fluence-to-dose factor was in agreement with that either from ICRP no. 74 or from TRS no. 285 of IAEA, which reflected the importance of using CR-39 in absolute fast neutron dosimetry.

  3. Beta Decay Study of Neutron-rich Magnesium

    NASA Astrophysics Data System (ADS)

    Ash, John; Rajabali, Mustafa; Griffin Collaboration

    2015-10-01

    Within the ``island of inversion'' around the N = 20 shell gap, isotopes of magnesium, and aluminum deviate from the expected closed-shell structure. Particles promoted across the N = 20 shell gap result in a lower energy deformed ground state configuration rather than the expected spherical configuration. An experiment was conducted at TRIUMF laboratory in the summer of 2015 to study the decay of ``island of inversion'' isotopes 33 , 34 , 35Mg and the structure of the respective daughter nuclei. The isotopes of interest were produced by a proton beam from TRIUMF's 500 MeV cyclotron impacting on a UCx target. The magnesium decays populated states along the decay chain in Al, Si, P, and S isotopes. The new GRIFFIN spectrometer in the ISAC-I facility was used to detect the gamma rays. Two sets of scintillators, one for detecting the beta particles (SCEPTAR) and the other for detecting beta-delayed neutrons (DESCANT), were also used in conjunction with GRIFFIN. The GRIFFIN data were energy calibrated and partially analyzed for this project. New algorithms were developed for the analysis. Preliminary results for new transitions detected in 34Mg as well as the half lives obtained will be presented in their current form. This research was supported by the Tennessee Tech research office.

  4. Neutron powder diffraction study of sulfated zirconia catalysts

    SciTech Connect

    Li, X.; Lager, G.A.; Loong, C.K.

    1997-07-01

    In situ neutron powder diffraction method was used to investigate the crystal structures, phase abundance and thermal stability of sulfated zirconia catalysts prepared by impregnation of hydrous zirconium oxide gels with 0.5 M H{sub 2}SO{sub 4} solutions. The sample studied was precipitated at pH = 10 and dried for 5 h at 493 K, and then calcined at 853 K for 3 h. Diffraction data were collected in the temperature range 295-1273 K in an Ar atmosphere and analyzed using the Rietveld method. Only the metastable tetragonal phase was observed below 673 K. Above this temperature, the sample consisted of a mixture of tetragonal (T) and monoclinic (M) phases in the proportions (T:M wt%) 85:15 (1073 K) and 61:39 (1273 K). Surface modification by sulfation was found to retard the onset of the tetragonal-to-monoclinic transformation relative to pure zirconia. The decrease in peak-broadening at the higher temperatures reflects both an increase in crystallite size and a decrease in microstrain.

  5. Neutron diffraction studies for realtime leaching of catalytic Ni.

    PubMed

    Iles, Gail N; Devred, François; Henry, Paul F; Reinhart, Guillaume; Hansen, Thomas C

    2014-07-21

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni2Al3 and NiAl3 continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials. PMID:25053313

  6. Neutron diffraction studies for realtime leaching of catalytic Ni

    SciTech Connect

    Iles, Gail N. Reinhart, Guillaume; Devred, François; Henry, Paul F. Hansen, Thomas C.

    2014-07-21

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni{sub 2}Al{sub 3} and NiAl{sub 3} continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials.

  7. Fast Neutron Radioactivity and Damage Studies on Materials

    SciTech Connect

    Anderson, S.; Spencer, J.; Wolf, Z.; Gallagher, G.; Pellett, D.; Boussoufi, M.; Volk, J.; /Fermilab

    2007-07-23

    Many materials and electronics need to be tested for the radiation environment expected at linear colliders (LC) to improve reliability and longevity since both accelerator and detectors will be subjected to large fluences of hadrons, leptons and gammas. Examples include NdFeB magnets, considered for the damping rings, injection and extraction lines and final focus, electronic and electro-optic devices to be utilized in detector readout, accelerator controls and the CCDs required for the vertex detector, as well as high and low temperature superconducting materials (LTSMs) because some magnets will be superconducting. Our first measurements of fast neutron, stepped doses at the UC Davis McClellan Nuclear Reactor Center (UCD MNRC) were presented for NdFeB materials at EPAC04 where the damage appeared proportional to the distances between the effective operating point and Hc. We have extended those doses, included other manufacturer's samples and measured induced radioactivities. We have also added L and HTSMs as well as a variety of relevant semiconductor and electro-optic materials including PBG fiber that we studied previously only with gamma rays.

  8. Neutron diffraction studies for realtime leaching of catalytic Ni

    NASA Astrophysics Data System (ADS)

    Iles, Gail N.; Devred, François; Henry, Paul F.; Reinhart, Guillaume; Hansen, Thomas C.

    2014-07-01

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni2Al3 and NiAl3 continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials.

  9. Dose evaluation of boron neutron capture synovectomy using the THOR epithermal neutron beam: a feasibility study

    NASA Astrophysics Data System (ADS)

    Wu, Jay; Chang, Shu-Jun; Chuang, Keh-Shih; Hsueh, Yen-Wan; Yeh, Kuan-Chuan; Wang, Jeng-Ning; Tsai, Wen-Pin

    2007-03-01

    Rheumatoid arthritis is one of the most common epidemic diseases in the world. For some patients, the treatment with steroids or nonsteroidal anti-inflammatory drugs is not effective, thus necessitating physical removal of the inflamed synovium. Alternative approaches other than surgery will provide appropriate disease control and improve the patient's quality of life. In this research, we evaluated the feasibility of conducting boron neutron capture synovectomy (BNCS) with the Tsing Hua open-pool reactor (THOR) as a neutron source. Monte Carlo simulations were performed with arthritic joint models and uncertainties were within 5%. The collimator, reflector and boron concentration were optimized to reduce the treatment time and normal tissue doses. For the knee joint, polyethylene with 40%-enriched Li2CO3 was used as the collimator material, and a rear reflector of 15 cm thick graphite and side reflector of 10 cm thick graphite were chosen. The optimized treatment time was 5.4 min for the parallel-opposed irradiation. For the finger joint, polymethyl methacrylate was used as the reflector material. The treatment time can be reduced to 3.1 min, while skin and bone doses can be effectively reduced by approximately 9% compared with treatment using the graphite reflector. We conclude that using THOR as a treatment modality for BNCS could be a feasible alternative in clinical practice.

  10. Phase shift reflectometry for sub-surface defect detection

    NASA Astrophysics Data System (ADS)

    Asundi, Anand; Lei, Huang; Eden, Teoh Kang Min; Sreemathy, Parthasarathy; May, Watt Sook

    2012-11-01

    Phase Shift Reflectometry has recently been seen as a novel alternative to interferometry since it can provide warpage measurement over large areas with no need for large optical components. To confirm its capability and to explore the use of this method for sub-surface defect detection, a Chinese magic mirror is used. This bronze mirror which dates back to the Chinese Han Dynasty appears at first sight to be an ordinary convex mirror. However, unlike a normal mirror, when illuminated by a beam of light, an image is formed onto a screen. It has been hypothesized that there are indentations inside the mirror which alter the path of reflected light rays and hence the reflected image. This paper explores various methods to measure these indentations. Of the methods test Phase Shift Reflectometry (PSR) was found suitable to be the most suitable both in terms of the sensitivity and the field of view.

  11. New signal processing technique for density profile reconstruction using reflectometry

    SciTech Connect

    Clairet, F.; Bottereau, C.; Ricaud, B.; Briolle, F.; Heuraux, S.

    2011-08-15

    Reflectometry profile measurement requires an accurate determination of the plasma reflected signal. Along with a good resolution and a high signal to noise ratio of the phase measurement, adequate data analysis is required. A new data processing based on time-frequency tomographic representation is used. It provides a clearer separation between multiple components and improves isolation of the relevant signals. In this paper, this data processing technique is applied to two sets of signals coming from two different reflectometer devices used on the Tore Supra tokamak. For the standard density profile reflectometry, it improves the initialization process and its reliability, providing a more accurate profile determination in the far scrape-off layer with density measurements as low as 10{sup 16} m{sup -1}. For a second reflectometer, which provides measurements in front of a lower hybrid launcher, this method improves the separation of the relevant plasma signal from multi-reflection processes due to the proximity of the plasma.

  12. Remote Strain Sensing of CFRP Using Microwave Frequency Domain Reflectometry

    NASA Technical Reports Server (NTRS)

    Wilson, William C.; Moore, Jason P.; Juarez, Peter D.

    2016-01-01

    NASA's Advanced Composites Project is investigating technologies that increase automated remote inspection of aircraft composite structures. Therefore, microwave Frequency Domain Reflectometry (FDR) is being investigated as a method of enabling rapid remote measurement of strain occurring at the first ply of a composite fiber reinforced polymer (CFRP) structure using Radio Frequency (RF) Electro-Magnetic (EM) radiation. While microwave reflectometry has been used to detect disbonds in CFRP structures, its use in detecting strain has been limited. This work will present data demonstrating the measurement of the reactance changes due to loading conditions that are indicative of strain in a CFRP structure. In addition, the basic EM signature will be presented along with an analysis of temperature and humidity effects.

  13. Scoping studies - photon and low energy neutron interrogation

    SciTech Connect

    Becker, G.; Harker, Y.; Jones, J.; Harmon, F.

    1997-11-01

    High energy photon interrogation of waste containers, with the aim of producing photo nuclear reactions, in specific materials, holds the potential of good penetration and rapid analysis. Compact high energy ({le} 10 MeV) photon sources in the form of electron linacs producing bremstrahlung radiation are readily available. Work with the Varitron variable energy accelerator at ISU will be described. Advantages and limitations of the technique will be discussed. Using positive ion induced neutron producing reactions, it is possible to generate neutrons in a specific energy range. By this means, variable penetration and specific reactions can be excited in the assayed material. Examples using the {sup 3}H(p,n) and {sup 7}Li(p,n) reactions as neutron sources will be discussed. 4 refs., 7 figs.

  14. A Study of Neutron Leakage in Finite Objects

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

    A computationally efficient 3DHZETRN code capable of simulating High charge (Z) and Energy (HZE) and light ions (including neutrons) under space-like boundary conditions with enhanced neutron and light ion propagation was recently developed for simple shielded objects. Monte Carlo (MC) benchmarks were used to verify the 3DHZETRN methodology in slab and spherical geometry, and it was shown that 3DHZETRN agrees with MC codes to the degree that various MC codes agree among themselves. One limitation in the verification process is that all of the codes (3DHZETRN and three MC codes) utilize different nuclear models/databases. In the present report, the new algorithm, with well-defined convergence criteria, is used to quantify the neutron leakage from simple geometries to provide means of verifying 3D effects and to provide guidance for further code development.

  15. Review of Livermore-Led Neutron Capture Studies Using DANCE

    SciTech Connect

    Parker, W; Sheets, S; Agvaanluvsan, U; Becker, J; Becvar, F; Bredeweg, T; Clement, R; Couture, A; Esch, E; Haight, R; Jandel, M; Krticka, M; Mitchell, G; Macri, R; O'Donnell, J; Reifarth, R; Rundberg, R; Schwantes, J; Ullmann, J; Vieira, D; Wouters, J; Wilk, P

    2007-05-11

    We have made neutron capture cross-section measurements using the white neutron source at the Los Alamos Science Center, the DANCE detector array (Detector for Advanced Neutron Capture Experiments) and targets important for basic science and stockpile stewardship. In this paper, we review results from (n,{gamma}) reactions on {sup 94,95}Mo, {sup 152,154,157,160,nat}Gd, {sup 151,153}Eu and {sup 242m}Am for neutron energies from < 1eV up to {approx} 20 keV. We measured details of the {gamma}-ray cascade following neutron capture, for comparison with results of statistical model simulations. We determined the neutron energy dependent (n,{gamma}) cross section and gained information about statistical decay properties, including the nuclear level density and the photon strength function. Because of the high granularity of the detector array, it is possible to look at gamma cascades with a specified number of transitions (a specific multiplicity). We simulated {gamma}-ray cascades using a combination of the DICEBOX/GEANT computer codes. In the case of the deformed nuclei, we found evidence of a scissors-mode resonance. For the Eu, we also determined the (n,{gamma}) cross sections. For the {sup 94,95}Mo, we focused on the spin and parity assignments of the resonances and the determination of the photon strength functions for the compound nuclei {sup 95,96}Mo. Future plans include measurements on actinide targets; our immediate interest is in {sup 242m}Am.

  16. Application of an ultraminiature thermal neutron monitor for irradiation field study of accelerator-based neutron capture therapy

    PubMed Central

    Ishikawa, Masayori; Tanaka, Kenichi; Endo, Satrou; Hoshi, Masaharu

    2015-01-01

    Phantom experiments to evaluate thermal neutron flux distribution were performed using the Scintillator with Optical Fiber (SOF) detector, which was developed as a thermal neutron monitor during boron neutron capture therapy (BNCT) irradiation. Compared with the gold wire activation method and Monte Carlo N-particle (MCNP) calculations, it was confirmed that the SOF detector is capable of measuring thermal neutron flux as low as 105 n/cm2/s with sufficient accuracy. The SOF detector will be useful for phantom experiments with BNCT neutron fields from low-current accelerator-based neutron sources. PMID:25589504

  17. Application of an ultraminiature thermal neutron monitor for irradiation field study of accelerator-based neutron capture therapy.

    PubMed

    Ishikawa, Masayori; Tanaka, Kenichi; Endo, Satrou; Hoshi, Masaharu

    2015-03-01

    Phantom experiments to evaluate thermal neutron flux distribution were performed using the Scintillator with Optical Fiber (SOF) detector, which was developed as a thermal neutron monitor during boron neutron capture therapy (BNCT) irradiation. Compared with the gold wire activation method and Monte Carlo N-particle (MCNP) calculations, it was confirmed that the SOF detector is capable of measuring thermal neutron flux as low as 10(5) n/cm(2)/s with sufficient accuracy. The SOF detector will be useful for phantom experiments with BNCT neutron fields from low-current accelerator-based neutron sources.

  18. Interfacial assembly of proteins and peptides: recent examples studied by neutron reflection

    PubMed Central

    Zhao, XiuBo; Pan, Fang; Lu, Jian R.

    2009-01-01

    Through reviewing a number of recent neutron reflection studies of interfacial adsorption of peptides and proteins, this paper aims to demonstrate the significance of this technique in studying interfacial biomolecular processes by illustrating the typical structural details that can be derived. The review will start with the introduction of relevant theoretical background, followed by an outline of representative biomolecular systems that have recently been studied to indicate the technical strengths of neutron reflection. PMID:19656822

  19. Simplified optical correlation-domain reflectometry without reference path.

    PubMed

    Shizuka, Makoto; Hayashi, Neisei; Mizuno, Yosuke; Nakamura, Kentaro

    2016-05-20

    We develop a simplified configuration for optical correlation-domain reflectometry (OCDR) without an explicit reference path. Instead, the Fresnel-reflected light generated at the distal open end of the sensing fiber is exploited as a reference light. After the fundamental demonstration, the optimal incident power is found to be approximately 8 dBm. We also show that the loss near the distal end should not be applied, unlike in the case of Brillouin-based OCDR. PMID:27411116

  20. Sustaining knowledge in the neutron generator community and benchmarking study.

    SciTech Connect

    Barrentine, Tameka C.; Kennedy, Bryan C.; Saba, Anthony W.; Turgeon, Jennifer L.; Schneider, Julia Teresa; Stubblefield, William Anthony; Baldonado, Esther

    2008-03-01

    In 2004, the Responsive Neutron Generator Product Deployment department embarked upon a partnership with the Systems Engineering and Analysis knowledge management (KM) team to develop knowledge management systems for the neutron generator (NG) community. This partnership continues today. The most recent challenge was to improve the current KM system (KMS) development approach by identifying a process that will allow staff members to capture knowledge as they learn it. This 'as-you-go' approach will lead to a sustainable KM process for the NG community. This paper presents a historical overview of NG KMSs, as well as research conducted to move toward sustainable KM.

  1. Monitoring crystal dissolution at nanometer resolution using laser reflectometry

    NASA Astrophysics Data System (ADS)

    Eggington, P. J.; Taylor, A. G.

    2000-01-01

    Laser reflectometry has been used for the first time as an in situ real-time monitor of the dissolution of the (0 0 1) face of KClO 3 crystals into aqueous solution. During the dissolution process the reflected light was subject to constructive and destructive interference caused by the movement of crystal boundaries. This produced Fabry-Perot oscillations similar to the widely exploited phenomenon used in the laser reflectometry-based metrology of semiconductor surfaces. The method is adapted and theoretical fits to the observed data are presented. The quality of the data allows dissolution rates of 100 nm s -1 to be measured accurately. Data gained by this method was used to verify the concentration dependence of the dissolution rate and confirm it as a diffusion-controlled mechanism. The hydrodynamic radius of the diffusing ions was found to be 0.224 nm, in agreement with literature values. The potential of laser reflectometry for use as an effective probe sensitive to changes in crystal surface morphology during dissolution has also been demonstrated.

  2. Analysis of bacterial growth by UV/Vis spectroscopy and laser reflectometry

    NASA Astrophysics Data System (ADS)

    Peña-Gomar, Mary Carmen; Viramontes-Gamboa, Gonzalo; Peña-Gomar, Grethel; Ortiz Gutiérrez, Mauricio; Hernández Ramírez, Mariano

    2012-10-01

    This work presents a preliminary study on an experimental analysis of the lactobacillus bacterial growth in liquid medium with and without the presence of silver nanoparticles. The study aims to quantify the bactericidal effect of nanoparticles. Quantification of bacterial growth at different times was analyzed by spectroscopy UV/visible and laser reflectometry near the critical angle. From these two techniques the best results were obtained by spectroscopy, showing that as the concentration of silver nanoparticles increases, it inhibits the growth of bacteria, it only grows 63% of the population. Regarding Laser Reflectometry, the variation of reflectance near the critical angle is measured in real time. The observed results at short times are reasonable, since they indicate a gradual growth of the bacteria and the stabilization stage of the population. But at long time, the observed results show abrupt changes caused by temperature effects. The bacteria were isolated from samples taken from commercial yougurth, and cultured in MRS broth at pH 6.5, and controlled with citric acid and constant temperature of 32 °C. Separately, silver nanoparticles were synthesized at 3 °C from aqueous solutions of 1.0 mM silver nitrate and chemically reduced with sodium borohydride to 2.0 mM, with magnetic stirring.

  3. 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.

  4. Dynamics of a hydrogenated silica xerogel: A neutron scattering study

    SciTech Connect

    Fontana, A.; Orsingher, L.; Rossi, F.

    2006-11-01

    Neutron scattering measurements of a hydrogenated vitreous silica (or xerogel) sample reveal an unexpectedly high mean-square displacement of the silanol hydrogen atoms at 150 and 300 K. At 150 K, the spectrum mimics the boson peak of vitreous silica. The finding suggests a large local displacement of the boson peak modes at the breaking points of the continuous random network.

  5. Nab: a precise study of unpolarized neutron beta decay

    NASA Astrophysics Data System (ADS)

    Pocanic, Dinko; Nab Collaboration

    2015-10-01

    Nab is a program of measurements of unpolarized neutron decays at the Spallation Neutron Source, Oak Ridge, TN. Nab aims to determine a, the e- ν correlation with precision of δa / a =10-3 , and b, the Fierz interference term, with uncertainty δb ~= 3 ×10-3 . The set of available observables overconstrains neutron beta decay in the Standard Model (SM), opening the door to searches for evidence of possible SM extensions. Projected Nab results will lead to a new precise determination of the ratio λ =GA /GV , and to significant reductions in the allowed limits for both right- and left-handed scalar and tensor currents. Alternatively, Nab may detect a discrepancy from SM predictions consistent with certain realizations of supersymmetry. A long asymmetric spectrometer, optimized to achieve the required narrow proton momentum response function, is currently under construction. The apparatus is to be used in follow-up measurements (ABba experiment) of asymmetry observables A and B in polarized neutron decay. Nab is planned for beam readiness in 2016. We discuss the experiment's motivation, expected reach, design and method, and update its status. Work supported by NSF Grants PHY-1126683, 1205833, 1307328, 1506320, and others.

  6. Low-level gamma and neutron monitoring based on use of proportional counter filled with 3He in polythene moderator: study of the responses to gamma and neutrons.

    PubMed

    Pszona, S; Bantsar, A; Tulik, P; Wincel, K; Zaręba, B

    2014-10-01

    It has been shown that a proportional counter filled with (3)He placed centrally inside a polythene sphere opens a new possibility for measuring gamma photons and neutrons in the separate pulse-height windows. The responses to gamma and neutrons (in terms of ambient dose equivalent) of the detector assembly consisting of 203-mm polythene sphere with centrally positioned 40-mm diameter (3)He proportional counter have been studied. The response to secondary gammas from capture process in hydrogen has also been studied. The rather preliminary studies indicate that the proposed measuring system has very promising features as an ambient dose equivalent device for mixed gamma-neutron fields.

  7. 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.

  8. a Neutron Scattering Study of Liquid HELIUM-4.

    NASA Astrophysics Data System (ADS)

    Andersen, Ken Holst

    Available from UMI in association with The British Library. The results of high-resolution, high-accuracy, high-precision neutron inelastic measurements on liquid ^4He are presented. In the collective excitation region, the temperature -dependence of the sharp one-phonon peak is studied and seen to exhibit a qualitative change at T_ {lambda}. The Woods-Svensson hypothesis that the scattering separates naturally into parts proportional to the macroscopic normal and superfluid densities is tested and is found to be too simplistic to describe the detailed temperature dependence. A novel theoretical approach by Glyde and Griffin is evaluated. Their formulation establishes the microscopic connection between the Bose condensate and the phonon excitations in superfluid ^4He. The present parameterisation of their model describes the qualitative temperature dependence well. At high momentum transfer we obtain estimates of the momentum distribution above and below T _lambda, by extracting the Q-dependence of the fourth central moment of the scattering. The obtained n(p) at T > T_lambda is in very good agreement with theoretical calculations. Our low-temperature momentum distribution is more sharply peaked than at high temperature, but reflects the lack of higher -order terms in the short-time expansion used for extraction of the fourth moment. Estimates of the mean kinetic energy per atom are obtained and are slightly higher than previous experimental estimates, but in agreement with theoretical calculations. From this, we evaluate the magnitude of the condensate fraction, and find n_0(T=0) = 10.3 +/- 1.0%.

  9. An apparatus for studying spallation neutrons in the Aberdeen Tunnel laboratory

    NASA Astrophysics Data System (ADS)

    Blyth, S. C.; Chan, Y. L.; Chen, X. C.; Chu, M. C.; Hahn, R. L.; Ho, T. H.; Hsiung, Y. B.; Hu, B. Z.; Kwan, K. K.; Kwok, M. W.; Kwok, T.; Lau, Y. P.; Lee, K. P.; Leung, J. K. C.; Leung, K. Y.; Lin, G. L.; Lin, Y. C.; Luk, K. B.; Luk, W. H.; Ngai, H. Y.; Ngan, S. Y.; Pun, C. S. J.; Shih, K.; Tam, Y. H.; Tsang, R. H. M.; Wang, C. H.; Wong, C. M.; Wong, H. L.; Wong, H. H. C.; Wong, K. K.; Yeh, M.

    2013-09-01

    In this paper, we describe the design, construction and performance of an apparatus installed in the Aberdeen Tunnel laboratory in Hong Kong for studying spallation neutrons induced by cosmic-ray muons under a vertical rock overburden of 611 m water equivalent (m.w.e.). The apparatus comprises six horizontal layers of plastic-scintillator hodoscopes for determining the direction and position of the incident cosmic-ray muons. Sandwiched between the hodoscope planes is a neutron detector filled with 650 kg of liquid scintillator doped with about 0.06% of Gadolinium by weight for improving the efficiency of detecting the spallation neutrons. Performance of the apparatus is also presented.

  10. Optical absorption and luminescence studies of fast neutron-irradiated complex oxides for jewellery applications

    NASA Astrophysics Data System (ADS)

    Mironova-Ulmane, N.; Skvortsova, V.; Popov, A. I.

    2016-07-01

    We studied the optical absorption and luminescence of agate (SiO2), topaz (Al2[SiO4](F,OH)2), beryl (Be3Al2Si6O18), and prehnite (Ca2Al(AlSi3O10)(OH)2) doped with different concentrations of transition metal ions and exposed to fast neutron irradiation. The exchange interaction between the impurity ions and the defects arising under neutron irradiation causes additional absorption as well as bands' broadening in the crystals. These experimental results allow us to suggest the method for obtaining new radiation-defect induced jewellery colors of minerals due to neutron irradiation.

  11. The optimization study of Bonner sphere in the epi-thermal neutron irradiation field for BNCT.

    PubMed

    Ueda, H; Tanaka, H; Maruhashi, A; Ono, K; Sakurai, Y

    2011-12-01

    The optimization study on the Bonner sphere in the epi-thermal neutron irradiation field for BNCT was done for the moderator material, moderator size, and activation foils as a neutron detector in the sphere. The saturated activity for the activation foil was obtained from the calculated response, and the effective energy range for each Bonner sphere was determined from the saturated activity. We can see that boric acid solution moderator is suitable for the spectrum measurement of a epi-thermal neutron irradiation field.

  12. An accelerator-based neutron microbeam system for studies of radiation effects

    PubMed Central

    Xu, Yanping; Randers-Pehrson, Gerhard; Marino, Stephen A.; Bigelow, Alan W.; Akselrod, Mark S.; Sykora, Jeff G.; Brenner, David J.

    2011-01-01

    A novel neutron microbeam is being developed at the Radiological Research Accelerator Facility (RARAF) of Columbia University. The RARAF microbeam facility has been used for studies of radiation bystander effects in mammalian cells for many years. Now a prototype neutron microbeam is being developed that can be used for bystander effect studies. The neutron microbeam design here is based on the existing charged particle microbeam technology at the RARAF. The principle of the neutron microbeam is to use the proton beam with a micrometre-sized diameter impinging on a very thin lithium fluoride target system. From the kinematics of the 7Li(p,n)7Be reaction near the threshold of 1.881 MeV, the neutron beam is confined within a narrow, forward solid angle. Calculations show that the neutron spot using a target with a 17-µm thick gold backing foil will be <20 µm in diameter for cells attached to a 3.8-µm thick propylene-bottomed cell dish in contact with the target backing. The neutron flux will roughly be 2000 per second based on the current beam setup at the RARAF singleton accelerator. The dose rate will be about 200 mGy min−1. The principle of this neutron microbeam system has been preliminarily tested at the RARAF using a collimated proton beam. The imaging of the neutron beam was performed using novel fluorescent nuclear track detector technology based on Mg-doped luminescent aluminum oxide single crystals and confocal laser scanning fluorescent microscopy. PMID:21131327

  13. High energy neutron treatment for pelvic cancers: study stopped because of increased mortality.

    PubMed Central

    Errington, R D; Ashby, D; Gore, S M; Abrams, K R; Myint, S; Bonnett, D E; Blake, S W; Saxton, T E

    1991-01-01

    OBJECTIVE--To compare high energy fast neutron treatment with conventional megavoltage x ray treatment in the management of locally advanced pelvic carcinomas (of the cervix, bladder, prostate, and rectum). DESIGN--Randomised study from February 1986; randomisation to neutron treatment or photon treatment was unstratified and in the ratio of 3 to 1 until January 1988, when randomisation was in the ratio 1 to 1 and stratified by site of tumour. SETTING--Mersey regional radiotherapy centre at Clatterbridge Hospital, Wirral. PATIENTS--151 patients with locally advanced, non-metastatic pelvic cancer (27 cervical, 69 of the bladder, seven prostatic, and 48 of the rectum). INTERVENTION--Randomisation to neutron treatment was stopped in February 1990. MAIN OUTCOME MEASURES--Patient survival and causes of death in relation to the development of metastatic disease and treatment related morbidity. RESULTS--In the first phase of the trial 42 patients were randomised to neutron treatment and 14 to photon treatment, and in the second phase 48 to neutron treatment and 47 to photon treatment. The relative risk of mortality for photons compared with neutrons was 0.66 (95% confidence interval 0.40 to 1.10) after adjustment for site of tumour and other important prognostic factors. Short term and long term complications were similar in both groups. CONCLUSIONS--The trial was stopped because of the increased mortality in patients with cancer of the cervix, bladder, or rectum treated with neutrons. PMID:1903663

  14. High Time Resolution Studies of X-Ray Bursts: Neutron Star Structure

    NASA Astrophysics Data System (ADS)

    Zhang, William

    1998-04-01

    Galactic low mass X-ray binaries distinguish themselves from the X-Ray pulsars by two characteristics: (1) they emit X-ray bursts due to unstable nuclear burning of accreted matter on the neutron star surface, and (2) they do not appear to emit coherent pulsations, even though they are believed to harbor fast-spinning neutron stars. One of the ``holy grails'' of X-ray astronomy in the 1980's was to measure the spin rates of these neutron stars so as to establish these neutron stars as progenitors of milli-second radio pulsars. Since the launch of the Rossi X-Ray Timing Explorer in 1995, highly coherent flux oscillations, with a Q-value of several hundred, have been observed during the X-ray bursts of several low mass X-ray binaries. All aspects of these oscillations, i.e., coherence, frequency stability from one burst to another for a given binary, their absence and presence at different phases of the bursts, strongly indicate that these oscillations are due to rotation of the neutron star. A very promising interpretation is that they are due to a combination of the neutron star rotation and surface temperature variations during the unstable nuclear burning. Therefore it is quite appropriate to call these neutron stars nuclear powered pulsars. These oscillations offer a unique opportunity to probe the neutron star structure. In this talk I will review the observational status of these oscillations and show how we could use them to study the intrinsic properties of the neutron star (mass, radius, and magnetic field).

  15. Suitability of Chinese oil well loggers for an epidemiologic study of the carcinogenic effects of neutrons.

    PubMed

    Inskip, P D; Wang, Z Y; Fen, Y S

    1991-11-01

    Neutron exposures to 191 well loggers at four oil fields in China were measured over a 3-mo period using CR-39 polycarbonate dosimeters. Doses (96% less than 0.02 mGy) were slightly lower than literature values for well loggers in North America, possibly because of differences in drilling activity. Because doses are so low, an epidemiologic study of cancer among Chinese well loggers is unlikely to be informative about the carcinogenicity of neutrons relative to sparsely ionizing radiation.

  16. Passive neutron design study for 200-L waste drums

    SciTech Connect

    Menlove, H.O.; Beddingfield, D.B.; Pickrell, M.M.

    1997-09-01

    We have developed a passive neutron counter for the measurement of plutonium in 200-L drums of scrap and waste. The counter incorporates high efficiency for the multiplicity counting in addition to the traditional coincidence counting. The {sup 252}Cf add-a-source feature is used to provide an accurate assay over a wide range of waste matrix materials. The room background neutron rate is reduced by using 30 cm of external polyethylene shielding and the cosmic-ray background is reduced by statistical filtering techniques. Monte Carlo Code calculations were used to determine the optimum detector design, including the gas pressure, size, number, and placement of the {sup 3}He tubes in the moderator. Various moderators, including polyethylene, plastics, teflon, and graphite, were evaluated to obtain the maximum efficiency and minimum detectable mass of plutonium.

  17. 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.

  18. Feasibility study of extremity dosemeter based on polyallyldiglycolcarbonate (CR-39) for neutron exposure.

    PubMed

    Chau, Q; Bruguier, P

    2007-01-01

    In nuclear facilities, some activities such as reprocessing, recycling and production of bare fuel rods expose the workers to mixed neutron-photon fields. For several workplaces, particularly in glove boxes, some workers expose their hands to mixed fields. The mastery of the photon extremity dosimetry is relatively good, whereas the neutron dosimetry still raises difficulties. In this context, the Institute for Radiological Protection and Nuclear Safety (IRSN) has proposed a study on a passive neutron extremity dosemeter based on chemically etched CR-39 (PADC: polyallyldiglycolcarbonate), named PN-3, already used in routine practice for whole body dosimetry. This dosemeter is a chip of plastic sensitive to recoil protons. The chemical etching process amplifies the size of the impact. The reading system for tracks counting is composed of a microscope, a video camera and an image analyser. This system is combined with the dose evaluation algorithm. The performance of the dosemeter PN-3 has been largely studied and proved by several laboratories in terms of passive individual neutron dosemeter which is used in routine production by different companies. This study focuses on the sensitivity of the extremity dosemeter, as well as its performance in the function of the level of the neutron energy. The dosemeter was exposed to monoenergetic neutron fields in laboratory conditions and to mixed fields in glove boxes at workplaces.

  19. The GNSS Reflectometry Response to the Ocean Surface

    NASA Astrophysics Data System (ADS)

    Chang, Paul; Jelenak, Zorana; Soisuvarn, Seubson; Said, Faozi

    2016-04-01

    Global Navigation Satellite System - Reflectometry (GNSS-R) exploits signals of opportunity from the Global Navigation Satellite System (GNSS). GNSS transmitters continuously transmit navigation signals at L-band toward the earth's surface. The scattered power reflected off the earth's surface can be sensed by specially designed GNSS-R receivers. The reflected signal can then be used to glean information about the surface of the earth, such as ocean surface roughness, snow depth, sea ice extent, and soil moisture. The use of GNSS-R for ocean wind retrievals was first demonstrated from aircraft. On July 8 2014, the TechDemoSat-1 satellite (TDS-1) was launched by Surrey Satellite Technology, Ltd as a technology risk reduction mission into sun-synchronous orbit. This paper investigates the GNSS-R measurements collected by the Space GNSS Receiver-Remote Sensing Instrument (SGR-ReSI) on board the TDS-1 satellite. The sensitivity of the SGR-ReSI measurements to the ocean surface winds and waves are characterized. The effects of sea surface temperature, wind direction, and rain are also investigated. The SGR-ReSI measurements exhibited sensitivity through the entire range of wind speeds sampled in this dataset, up to 35 m/s. A significant dependence on the larger waves was observed for winds < 6 m/s. Additionally, an interesting dependence on SST was observed where the slope of the SGR-ReSI measurements is positive for winds < 5 m/s and reverses for winds > 5 m/s. There appeared to be very little wind direction signal, and investigation of the rain impacts found no apparent sensitivity in the data. These results are shown through the analysis of global statistics and examination of a few case studies. This released SGR-ReSI dataset provided the first opportunity to comprehensively investigate the sensitivity of satellite-based GNSS-R measurements to various ocean surface parameters. The upcoming NASA's Cyclone Global Navigation Satellite System (CYGNSS) satellite

  20. Study of magnetism at surfaces by scattering of neutrons at grazing incidence

    SciTech Connect

    Felcher, G.P.

    1984-07-01

    Neutrons can provide information on magnetic phenomena at surfaces. The simplest experiment involves the measurement of the reflectivity of a well-collimated beam from the surface, as a function either of the neutron wavelength or of the angle of incidence theta/sub i/. Using polarized neutrons, the spin-dependent reflectivity of a magnetically-active material can determine the depth profile of the magnetic induction B. A prototype instrument at the Intense Pulsed Neutron Source at Argonne has already demonstrated the feasibility of this technique in determining the penetration depth of an external magnetic field in superconductors. Further experiments are being planned to study the magnetic disturbances close to the surface of ferromagnets; a first experiment on films of iron oxides showed a remarkable change of the magnetic depth profile with increasing oxidation.

  1. Advanced Neutron Source Cross Section Libraries (ANSL-V): ENDF/B-V based multigroup cross-section libraries for advanced neutron source (ANS) reactor studies

    SciTech Connect

    Ford, W.E. III; Arwood, J.W.; Greene, N.M.; Moses, D.L.; Petrie, L.M.; Primm, R.T. III; Slater, C.O.; Westfall, R.M.; Wright, R.Q.

    1990-09-01

    Pseudo-problem-independent, multigroup cross-section libraries were generated to support Advanced Neutron Source (ANS) Reactor design studies. The ANS is a proposed reactor which would be fueled with highly enriched uranium and cooled with heavy water. The libraries, designated ANSL-V (Advanced Neutron Source Cross Section Libraries based on ENDF/B-V), are data bases in AMPX master format for subsequent generation of problem-dependent cross-sections for use with codes such as KENO, ANISN, XSDRNPM, VENTURE, DOT, DORT, TORT, and MORSE. Included in ANSL-V are 99-group and 39-group neutron, 39-neutron-group 44-gamma-ray-group secondary gamma-ray production (SGRP), 44-group gamma-ray interaction (GRI), and coupled, 39-neutron group 44-gamma-ray group (CNG) cross-section libraries. The neutron and SGRP libraries were generated primarily from ENDF/B-V data; the GRI library was generated from DLC-99/HUGO data, which is recognized as the ENDF/B-V photon interaction data. Modules from the AMPX and NJOY systems were used to process the multigroup data. Validity of selected data from the fine- and broad-group neutron libraries was satisfactorily tested in performance parameter calculations.

  2. Thermal-hydraulic studies of the Advanced Neutron Source cold source

    SciTech Connect

    Williams, P.T.; Lucas, A.T.

    1995-08-01

    The Advanced Neutron Source (ANS), in its conceptual design phase at Oak Ridge National Laboratory, was to be a user-oriented neutron research facility producing the most intense steady-state flux of thermal and cold neutrons in the world. Among its many scientific applications, the production of cold neutrons was a significant research mission for the ANS. The cold neutrons come from two independent cold sources positioned near the reactor core. Contained by an aluminum alloy vessel, each cold source is a 410-mm-diam sphere of liquid deuterium that functions both as a neutron moderator and a cryogenic coolant. With nuclear heating of the containment vessel and internal baffling, steady-state operation requires close control of the liquid deuterium flow near the vessel`s inner surface. Preliminary thermal-hydraulic analyses supporting the cold source design were performed with heat conduction simulations of the vessel walls and multidimensional computational fluid dynamics simulations of the liquid deuterium flow and heat transfer. This report presents the starting phase of a challenging program and describes the cold source conceptual design, the thermal-hydraulic feasibility studies of the containment vessel, and the future computational and experimental studies that were planned to verify the final design.

  3. Surface-Enhanced Infrared Spectroscopy and Neutron Reflectivity Studies of Ubiquinone in Hybrid Bilayer Membranes under Potential Control.

    PubMed

    Quirk, Amanda; Lardner, Michael J; Tun, Zin; Burgess, Ian J

    2016-03-01

    Surface-enhanced infrared adsorption spectroscopy (SEIRAS) and neutron reflectometry (NR) were employed to characterize ubiquinone (UQ) containing hybrid bilayer membranes. The biomimetic membrane was prepared by fusing phospholipid vesicles on a hydrophobic octadecanethiol monolayer self-assembled on a thin gold film. Using SEIRAS, the assembly of the membrane is monitored in situ. The presence of ubiquinone is verified by the characteristic carbonyl peaks from the quinone ester. A well-ordered distal lipid leaflet results from fusion of vesicles with and without the addition of ubiquinone. With applied potential, the hybrid bilayer membrane in the absence of UQ behaves in the same way as previously reported solid supported phospholipid membranes. When ubiquinone is incorporated in the membrane, electric field induced changes in the distal leaflet are suppressed. Changes in the infrared vibrations of the ubiquinone due to applied potential indicate the head groups are located in both polar and nonpolar environments. The spectroscopic data reveal that the isoprenoid unit of the ubiquinone is likely lying in the midplane of the lipid bilayer while the head has some freedom to move within the hydrophobic core. The SEIRAS experiments show redox behavior of UQ incorporated in a model lipid membrane that are otherwise inaccessible with traditional electrochemistry techniques. PMID:26867110

  4. SU-E-T-304: Study of Secondary Neutrons From Uniform Scanning Proton Beams

    SciTech Connect

    Islam, M; Zheng, Y; Benton, E

    2014-06-01

    Purpose: Secondary neutrons are unwanted byproducts from proton therapy and exposure from secondary radiation during treatment could increase risk of developing a secondary cancer later in a patient's lifetime. The purpose of this study is to investigate secondary neutrons from uniform scanning proton beams under various beam conditions using both measurements and Monte Carlo simulations. Methods: CR-39 Plastic Track Nuclear Detectors (PNTD) were used for the measurement. CR-39 PNTD has tissue like sensitivity to the secondary neutrons but insensitive to the therapeutic protons. In this study, we devised two experimental conditions: a) hollow-phantom; phantom is bored with a hollow cylinder along the direction of the beam so that the primary proton passes through the phantom without interacting with the phantom material, b) cylindrical-phantom; a solid cylinder of diameter close to the beam diameter is placed along the beam path. CR-39 PNTDs were placed laterally inside a 60X20X35 cm3 phantom (hollow-phantom) and in air (cylindrical-phantom) at various angles with respect to the primary beam axis. We studied for three different proton energies (78 MeV, 162 MeV and 226 MeV), using a 4 cm modulation width and 5cm diameter brass aperture for the entire experiment and simulation. A comparison of the experiment was performed using the Monte Carlo code FLUKA. Results: The measured secondary neutron dose equivalent per therapeutic primary proton dose (H/D) ranges from 2.1 ± 0.2 to 25.42 ± 2.3 mSv/Gy for the hollow phantom study, and 2.7 ± 0.3 to 46.4 ± 3.4 mSv/Gy for the cylindrical phantom study. Monte Carlo simulations predicated neutron dose equivalent from measurements within a factor of 5. Conclusion: The study suggests that the production of external neutrons is significantly higher than the production of internal neutrons.

  5. Numerical study of neutron beam divergence in a beam-fusion scenario employing laser driven ions

    NASA Astrophysics Data System (ADS)

    Alejo, A.; Green, A.; Ahmed, H.; Robinson, A. P. L.; Cerchez, M.; Clarke, R.; Doria, D.; Dorkings, S.; Fernandez, J.; McKenna, P.; Mirfayzi, S. R.; Naughton, K.; Neely, D.; Norreys, P.; Peth, C.; Powell, H.; Ruiz, J. A.; Swain, J.; Willi, O.; Borghesi, M.; Kar, S.

    2016-09-01

    The most established route to create a laser-based neutron source is by employing laser accelerated, low atomic-number ions in fusion reactions. In addition to the high reaction cross-sections at moderate energies of the projectile ions, the anisotropy in neutron emission is another important feature of beam-fusion reactions. Using a simple numerical model based on neutron generation in a pitcher-catcher scenario, anisotropy in neutron emission was studied for the deuterium-deuterium fusion reaction. Simulation results are consistent with the narrow-divergence (∼ 70 ° full width at half maximum) neutron beam recently served in an experiment employing multi-MeV deuteron beams of narrow divergence (up to 30° FWHM, depending on the ion energy) accelerated by a sub-petawatt laser pulse from thin deuterated plastic foils via the Target Normal Sheath Acceleration mechanism. By varying the input ion beam parameters, simulations show that a further improvement in the neutron beam directionality (i.e. reduction in the beam divergence) can be obtained by increasing the projectile ion beam temperature and cut-off energy, as expected from interactions employing higher power lasers at upcoming facilities.

  6. Event-by-event study of prompt neutrons from 239Pu(n,f)

    SciTech Connect

    Vogt, R; Randrup, J; Pruet, J; Younes, W

    2009-07-23

    Employing a recently developed Monte-Carlo model, we study the fission of {sup 240}Pu induced by neutrons with energies from thermal to just below the threshold for second chance fission. Current measurements of the mean number of prompt neutrons emitted in fission, together with less accurate measurements of the neutron energy spectra, place remarkably fine constraints on predictions of microscopic calculations. In particular, the total excitation energy of the nascent fragments must be specified to within 1MeV to avoid disagreement with measurements of the mean neutron multiplicity. The combination of the Monte-Carlo fission model with a statistical likelihood analysis also presents a powerful tool for the evaluation of fission neutron data. Of particular importance is the fission spectrum, which plays a key role in determining reactor criticality. We show that our approach can be used to develop an estimate of the fission spectrum with uncertainties several times smaller than current experimental uncertainties for outgoing neutron energies of less than 2 MeV.

  7. Event-by-Event Study of Prompt Neutrons from 239Pu

    SciTech Connect

    Vogt, R; Randrup, J; Pruet, J; Younes, W

    2010-01-15

    Employing a recently developed Monte Carlo model, we study the fission of {sup 240}Pu induced by neutrons with energies from thermal to just below the threshold for second chance fission. Current measurements of the mean number of prompt neutrons emitted in fission, together with less accurate measurements of the neutron energy spectra, place remarkably fine constraints on predictions of microscopic calculations. In particular, the total excitation energy of the nascent fragments must be specified to within 1 MeV to avoid disagreement with measurements of the mean neutron multiplicity. The combination of the Monte Carlo fission model with a statistical likelihood analysis also presents a powerful tool for the evaluation of fission neutron data. Of particular importance is the fission spectrum, which plays a key role in determining reactor criticality. We show that our approach can be used to develop an estimate of the fission spectrum with uncertainties several times smaller than current experimental uncertainties for outgoing neutron energies of less than 2 MeV.

  8. Crystal structure of human tooth enamel studied by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ouladdiaf, Bachir; Rodriguez-Carvajal, Juan; Goutaudier, Christelle; Ouladdiaf, Selma; Grosgogeat, Brigitte; Pradelle, Nelly; Colon, Pierre

    2015-02-01

    Crystal structure of human tooth enamel was investigated using high-resolution neutron powder diffraction. Excellent agreement between observed and refined patterns is obtained, using the hexagonal hydroxyapatite model for the tooth enamel, where a large hydroxyl deficiency ˜70% is found in the 4e site. Rietveld refinements method combined with the difference Fourier maps have revealed, however, that the hydroxyl ions are not only disordered along the c-axis but also within the basal plane. Additional H ions located at the 6h site and forming HPO42- anions were found.

  9. Neutron and x-ray scattering studies of premartensitic phenomena

    SciTech Connect

    Shapiro, S.M.

    1987-01-01

    This paper discusses neutron and x-ray investigations of some metallic alloys which are known to exhibit martensitic transformations. It is shown that precursor effects are usually present in the diffuse scattering and in the phonon dispersion curves, but the transition cannot be described in terms of the soft mode picture used in the Landau and Devonshire theory to describe structural phase transitions. In addition, it is noted that it is inappropriate to look at these microstructures as incommensurate systems, but more correctly as a coherent coexistence of two phases.

  10. 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.

  11. Neutron reflectivity studies of composite nanoparticle - copolymer thin films

    NASA Astrophysics Data System (ADS)

    Lauter-Pasyuk, V.; Lauter, H. J.; Ausserre, D.; Gallot, Y.; Cabuil, V.; Hamdoun, B.; Kornilov, E. I.

    1998-06-01

    Neutron reflection was used for the investigation of a new class of copolymers - composite materials, consisting of symmetric polystyrene-polybuthylmethacrylate (PS-PBMA) diblock copolymer with incorporated nanoparticles γ-Fe 2O 3 of a few nanometers in diameter. The presence of the nanoparticles induces an elastic distortion of the copolymer matrix. From the experiments we obtained information about the lamellar order of the polymer matrix, the distribution of the nanoparticles in the film and the distortion of the interfaces caused by the nanoparticles.

  12. A neutron diffraction study of RMn2O5 multiferroics

    NASA Astrophysics Data System (ADS)

    Radaelli, P. G.; Chapon, L. C.

    2008-10-01

    The magnetic properties of RMn2O5 multiferroics as obtained by unpolarized and polarized neutron diffraction experiments are reviewed. We discuss the qualitative features of the magnetic phase diagram in both zero magnetic field and in field and analyze the commensurate magnetic structure and its coupling to an applied electric field. The origin of ferroelectricity is discussed based on calculations of the ferroelectric polarization predicted by different microscopic coupling mechanisms (exchange-striction and cycloidal spin-orbit models). A minimal model containing a small set of parameters is also presented in order to understand the propagation of the magnetic structure along the c-direction.

  13. New frequency translation technique for FM-CW reflectometry.

    PubMed

    Meneses, Luis; Cupido, Luis; Manso, M E

    2010-10-01

    In broadband microwave reflectometry, coherent detection is widely used to obtain the phase information and to improve the systems sensitivity, both in diagnostics measuring the electronic density profile and plasma fluctuations. Coherent detection uses a translated version of the probing signal to guarantee a stable intermediate frequency. Here, a novel technique to generate the frequency translation by double frequency conversion is presented and its advantages over the commonly used single frequency conversion techniques employing image rejection mixers are discussed. The results obtained with the new frequency translator modules developed for the three JET FM-CW reflectometers, operating successfully at JET since mid-2009, are presented. PMID:21061479

  14. Microwave Imaging Reflectometry for the Visualization of Turbulence in Tokamaks

    SciTech Connect

    E. Mazzucato

    1999-12-16

    Understanding the mechanism of anomalous transport in magnetically confined plasmas requires the use of sophisticated diagnostic tools for the measurement of short-scale turbulent fluctuations. This paper describes the conceptual design of an experimental technique for the global visualization of density fluctuations in tokamaks. The proposed method is based on microwave reflectometry and consists in using a large diameter probing beam, collecting the reflected waves with a large aperture antenna, and forming an image of the reflecting plasma layer onto a 2D array of microwave receivers. Based on results from a series of numerical simulations, the theoretical feasibility conditions of the proposed method are discussed.

  15. Development of microwave imaging reflectometry in large helical device.

    PubMed

    Yamaguchi, S; Nagayama, Y; Kuwahara, D; Yoshinaga, T; Shi, Z B; Kogi, Y; Mase, A

    2008-10-01

    Three key devices of the microwave imaging reflectometry (MIR) are under development in large helical device (LHD). The 2-D mixer array is developed by stacking the one-dimensional array of the planar Yagi-Uda antenna. The new type of the bandpass filter bank is modified to match the requirement of the MIR. The low-cost quadrature demodulator is also developed for the phase detection system. By using the low-price commercial wireless devices, the development cost becomes much lower than the expensive waveguide system. These devices enable the development of 2-D/3-D microwave imaging system for the plasma diagnostics and industrial applications.

  16. Continuous liquid level measurements with time-domain reflectometry

    NASA Technical Reports Server (NTRS)

    Cruz, J. E.; Rogers, E. H.; Heister, A. E.

    1973-01-01

    Description of the basic principles of radar measurements of cryogenic liquid levels in storage vessels by time-domain reflectometry. The probe consists of a right circular coaxial transmission line positioned vertically in the storage vessel and having holes drilled in the outer conductor to permit penetration of the liquid into the annular gap. RF pulses transmitted through the probe are reflected at liquid/gas interface and returned for sampling at the input. The measured delay of the return pulse is displayed as the level of liquid in the vessel.

  17. Nondestructive evaluation of composites by optical time domain reflectometry

    NASA Technical Reports Server (NTRS)

    Claus, R. O.; Bennette, D. D.; Jackson, B. S.

    1985-01-01

    Results in the measurement of slowly varying mechanical loading functions on composites using optical time domain reflectometry (OTDR) in imbedded optical fiber during both simulated manufacture and use are reviewed. First, the basic theoretical and experimental principles of the OTDR system are described. Next, the mechanical system of the composite and the imbedded fiber is analyzed. Results of measurement obtained for various loading functions applied to material specimens are then described and system limitations on spatial resolution, strain amplitude sensitivity, and frequency response are explained in terms of the range and resolution limits of the OTDR system.

  18. Profile measurements of thin liquid films using reflectometry

    NASA Astrophysics Data System (ADS)

    Hanchak, M. S.; Vangsness, M. D.; Byrd, L. W.; Ervin, J. S.; Jones, J. G.

    2013-11-01

    Microscope-based reflectometry was used to measure the thickness profile of thin films of n-octane on silicon wafer substrates. Coupled with micro-positioning motorized stages and custom software, two-dimensional profiles of the film thickness from the adsorbed film (˜10 nm) to the intrinsic meniscus (˜1000 nm) were automatically and repeatedly measured. The reflectometer aperture was modified to provide better spatial resolution in areas of high curvature, the transition region, where evaporative flux is at a maximum. This technique will provide data for the validation of both existing and future models of thin film evaporation.

  19. Studies of the neutron radiation environment inside the International Space Station obtained by the Bonner Ball Neutron Detector

    NASA Astrophysics Data System (ADS)

    Koshiishi, H.; Chishiki, A.; Matsumoto, H.; Takagi, S.; Goka, T.

    The Bonner Ball Neutron Detector (BBND) experiment was conducted on the US Laboratory Module of the International Space Station (ISS) as part of the science program of NASA's Human Research Facility (HRF) in order to evaluate the neutron radiation environment inside the ISS. The BBND consists of six He-3 proportional counters, which are covered with polyethylene moderators of various thickness, and gadolinium eliminators to make each counter have different energy response function to incident neutrons. Thus, the BBND measures the neutron energy spectrum from thermal neutron up to 15 MeV. The experiment was performed over 8 months from Mar. 23 2001 through Nov. 15 2001 during solar maximum. The neutron energy spectrum in 22 bins and the dose equivalent evaluated using the ICRP-74 coefficients with 1-minute temporal resolution are obtained by the BBND. The real-time data acquisition of the BBND enables us to discuss the neutron radiation environment at different location on the ISS orbit, such as in the South Atlantic Anomaly (SAA) and in high-latitude regions. Comparisons are also made between solar maximum and solar minimum using earlier data obtained by the pre-cursor experiment during 3.5 days on STS-89 (SpaceShuttle-Mir-Mission No.8) in 1998. Additionally, a few solar flares associated with large proton events occurred during the measurement period, which enhanced the radiation damage caused by the neutron radiation environment. The influence of solar events on the neutron radiation environment is also discussed.

  20. HEIMDAL: A thermal neutron powder diffractometer with high and flexible resolution combined with SANS and neutron imaging - Designed for materials science studies at the European Spallation Source

    NASA Astrophysics Data System (ADS)

    Holm, Sonja L.; Lefmann, Kim; Henry, Paul F.; Bertelsen, Mads; Schefer, Jürg; Christensen, Mogens

    2016-08-01

    HEIMDAL will be a multi length scale neutron scattering instrument for the study of structures covering almost nine orders of magnitude from 0.01 nm to 50 mm. The instrument is accepted for construction at the European Spallation Source (ESS) and features a variable resolution thermal neutron powder diffractometer (TNPD), combined with small angle neutron scattering (SANS) and neutron imaging (NI). The instrument uses a novel combination of a cold and a thermal guide to fulfill the diverse requirements for diffraction and SANS. With an instrument length of 170 m, HEIMDAL will take advantage of the high neutron flux of the long pulse at ESS, whilst maintaining a high q-resolution due to the long flight path. The q-range coverage is up to 20 Å-1 allowing low-resolution PDF analysis. With the addition of SANS, HEIMDAL will be able to cover a uniquely broad length scale within a single instrumental set-up. HEIMDAL will be able to accommodate modern materials research in a broad variety of fields, and the task of the instrument will be to study advanced functional materials in action, as in situ and in operandi at multiple length scales (0.01-100 nm) quasi simultaneously. The instrument combines state-of-the-art neutron scattering techniques (TNPD, SANS, and NI) with the goal of studying real materials, in real time, under real conditions. This article describes the instrument design ideas, calculations and results of simulations and virtual experiments.

  1. A comprehensive spectrometry study of a stray neutron radiation field in scanning proton therapy.

    PubMed

    Mares, Vladimir; Romero-Expósito, Maite; Farah, Jad; Trinkl, Sebastian; Domingo, Carles; Dommert, Martin; Stolarczyk, Liliana; Van Ryckeghem, Laurent; Wielunski, Marek; Olko, Pawel; Harrison, Roger M

    2016-06-01

    The purpose of this study is to characterize the stray neutron radiation field in scanning proton therapy considering a pediatric anthropomorphic phantom and a clinically-relevant beam condition. Using two extended-range Bonner sphere spectrometry systems (ERBSS), Working Group 9 of the European Radiation Dosimetry Group measured neutron spectra at ten different positions around a pediatric anthropomorphic phantom irradiated for a brain tumor with a scanning proton beam. This study compares the different systems and unfolding codes as well as neutron spectra measured in similar conditions around a water tank phantom. The ten spectra measured with two ERBSS systems show a generally similar thermal component regardless of the position around the phantom while high energy neutrons (above 20 MeV) were only registered at positions near the beam axis (at 0°, 329° and 355°). Neutron spectra, fluence and ambient dose equivalent, H (*)(10), values of both systems were in good agreement (<15%) while the unfolding code proved to have a limited effect. The highest H (*)(10) value of 2.7 μSv Gy(-1) was measured at 329° to the beam axis and 1.63 m from the isocenter where high-energy neutrons (E  ⩾  20 MeV) contribute with about 53%. The neutron mapping within the gantry room showed that H (*)(10) values significantly decreased with distance and angular position with respect to the beam axis dropping to 0.52 μSv Gy(-1) at 90° and 3.35 m. Spectra at angles of 45° and 135° with respect to the beam axis measured here with an anthropomorphic phantom showed a similar peak structure at the thermal, fast and high energy range as in the previous water-tank experiments. Meanwhile, at 90°, small differences at the high-energy range were observed. Using ERBSS systems, neutron spectra mapping was performed to characterize the exposure of scanning proton therapy patients. The ten measured spectra provide precise information about the exposure of healthy organs to

  2. A comprehensive spectrometry study of a stray neutron radiation field in scanning proton therapy

    NASA Astrophysics Data System (ADS)

    Mares, Vladimir; Romero-Expósito, Maite; Farah, Jad; Trinkl, Sebastian; Domingo, Carles; Dommert, Martin; Stolarczyk, Liliana; Van Ryckeghem, Laurent; Wielunski, Marek; Olko, Pawel; Harrison, Roger M.

    2016-06-01

    The purpose of this study is to characterize the stray neutron radiation field in scanning proton therapy considering a pediatric anthropomorphic phantom and a clinically-relevant beam condition. Using two extended-range Bonner sphere spectrometry systems (ERBSS), Working Group 9 of the European Radiation Dosimetry Group measured neutron spectra at ten different positions around a pediatric anthropomorphic phantom irradiated for a brain tumor with a scanning proton beam. This study compares the different systems and unfolding codes as well as neutron spectra measured in similar conditions around a water tank phantom. The ten spectra measured with two ERBSS systems show a generally similar thermal component regardless of the position around the phantom while high energy neutrons (above 20 MeV) were only registered at positions near the beam axis (at 0°, 329° and 355°). Neutron spectra, fluence and ambient dose equivalent, H *(10), values of both systems were in good agreement (<15%) while the unfolding code proved to have a limited effect. The highest H *(10) value of 2.7 μSv Gy-1 was measured at 329° to the beam axis and 1.63 m from the isocenter where high-energy neutrons (E  ⩾  20 MeV) contribute with about 53%. The neutron mapping within the gantry room showed that H *(10) values significantly decreased with distance and angular position with respect to the beam axis dropping to 0.52 μSv Gy-1 at 90° and 3.35 m. Spectra at angles of 45° and 135° with respect to the beam axis measured here with an anthropomorphic phantom showed a similar peak structure at the thermal, fast and high energy range as in the previous water-tank experiments. Meanwhile, at 90°, small differences at the high-energy range were observed. Using ERBSS systems, neutron spectra mapping was performed to characterize the exposure of scanning proton therapy patients. The ten measured spectra provide precise information about the exposure of healthy organs to thermal

  3. A comprehensive spectrometry study of a stray neutron radiation field in scanning proton therapy

    NASA Astrophysics Data System (ADS)

    Mares, Vladimir; Romero-Expósito, Maite; Farah, Jad; Trinkl, Sebastian; Domingo, Carles; Dommert, Martin; Stolarczyk, Liliana; Van Ryckeghem, Laurent; Wielunski, Marek; Olko, Pawel; Harrison, Roger M.

    2016-06-01

    The purpose of this study is to characterize the stray neutron radiation field in scanning proton therapy considering a pediatric anthropomorphic phantom and a clinically-relevant beam condition. Using two extended-range Bonner sphere spectrometry systems (ERBSS), Working Group 9 of the European Radiation Dosimetry Group measured neutron spectra at ten different positions around a pediatric anthropomorphic phantom irradiated for a brain tumor with a scanning proton beam. This study compares the different systems and unfolding codes as well as neutron spectra measured in similar conditions around a water tank phantom. The ten spectra measured with two ERBSS systems show a generally similar thermal component regardless of the position around the phantom while high energy neutrons (above 20 MeV) were only registered at positions near the beam axis (at 0°, 329° and 355°). Neutron spectra, fluence and ambient dose equivalent, H *(10), values of both systems were in good agreement (<15%) while the unfolding code proved to have a limited effect. The highest H *(10) value of 2.7 μSv Gy‑1 was measured at 329° to the beam axis and 1.63 m from the isocenter where high-energy neutrons (E  ⩾  20 MeV) contribute with about 53%. The neutron mapping within the gantry room showed that H *(10) values significantly decreased with distance and angular position with respect to the beam axis dropping to 0.52 μSv Gy‑1 at 90° and 3.35 m. Spectra at angles of 45° and 135° with respect to the beam axis measured here with an anthropomorphic phantom showed a similar peak structure at the thermal, fast and high energy range as in the previous water-tank experiments. Meanwhile, at 90°, small differences at the high-energy range were observed. Using ERBSS systems, neutron spectra mapping was performed to characterize the exposure of scanning proton therapy patients. The ten measured spectra provide precise information about the exposure of healthy organs to thermal

  4. Cosmic ray heliospheric transport study with neutron monitor data

    NASA Astrophysics Data System (ADS)

    Ahluwalia, H. S.; Ygbuhay, R. C.; Modzelewska, R.; Dorman, L. I.; Alania, M. V.

    2015-10-01

    Determining transport coefficients for galactic cosmic ray (GCR) propagation in the turbulent interplanetary magnetic field (IMF) poses a fundamental challenge in modeling cosmic ray modulation processes. GCR scattering in the solar wind involves wave-particle interaction, the waves being Alfven waves which propagate along the ambient field (B). Empirical values at 1 AU are determined for the components of the diffusion tensor for GCR propagation in the heliosphere using neutron monitor (NM) data. At high rigidities, particle density gradients and mean free paths at 1 AU in B can only be computed from the solar diurnal anisotropy (SDA) represented by a vector A (components Ar, Aϕ, and Aθ) in a heliospherical polar coordinate system. Long-term changes in SDA components of NMs (with long track record and the median rigidity of response Rm ~ 20 GV) are used to compute yearly values of the transport coefficients for 1963-2013. We confirm the previously reported result that the product of the parallel (to B) mean free path (λ||) and radial density gradient (Gr) computed from NM data exhibits a weak Schwabe cycle (11y) but strong Hale magnetic cycle (22y) dependence. Its value is most depressed in solar activity minima for positive (p) polarity intervals (solar magnetic field in the Northern Hemisphere points outward from the Sun) when GCRs drift from the polar regions toward the helioequatorial plane and out along the heliospheric current sheet (HCS), setting up a symmetric gradient Gθs pointing away from HCS. Gr drives all SDA components and λ|| Gr contributes to the diffusive component (Ad) of the ecliptic plane anisotropy (A). GCR transport is commonly discussed in terms of an isotropic hard sphere scattering (also known as billiard-ball scattering) in the solar wind plasma. We use it with a flat HCS model and the Ahluwalia-Dorman master equations to compute the coefficients α (=λ⊥/λ∥) and ωτ (a measure of turbulence in the solar wind) and transport

  5. Cable Damage Detection System and Algorithms Using Time Domain Reflectometry

    SciTech Connect

    Clark, G A; Robbins, C L; Wade, K A; Souza, P R

    2009-03-24

    This report describes the hardware system and the set of algorithms we have developed for detecting damage in cables for the Advanced Development and Process Technologies (ADAPT) Program. This program is part of the W80 Life Extension Program (LEP). The system could be generalized for application to other systems in the future. Critical cables can undergo various types of damage (e.g. short circuits, open circuits, punctures, compression) that manifest as changes in the dielectric/impedance properties of the cables. For our specific problem, only one end of the cable is accessible, and no exemplars of actual damage are available. This work addresses the detection of dielectric/impedance anomalies in transient time domain reflectometry (TDR) measurements on the cables. The approach is to interrogate the cable using time domain reflectometry (TDR) techniques, in which a known pulse is inserted into the cable, and reflections from the cable are measured. The key operating principle is that any important cable damage will manifest itself as an electrical impedance discontinuity that can be measured in the TDR response signal. Machine learning classification algorithms are effectively eliminated from consideration, because only a small number of cables is available for testing; so a sufficient sample size is not attainable. Nonetheless, a key requirement is to achieve very high probability of detection and very low probability of false alarm. The approach is to compare TDR signals from possibly damaged cables to signals or an empirical model derived from reference cables that are known to be undamaged. This requires that the TDR signals are reasonably repeatable from test to test on the same cable, and from cable to cable. Empirical studies show that the repeatability issue is the 'long pole in the tent' for damage detection, because it is has been difficult to achieve reasonable repeatability. This one factor dominated the project. The two-step model-based approach is

  6. A molecular beam epitaxy facility for in situ neutron scattering

    SciTech Connect

    Dura, J. A.; LaRock, J.

    2009-07-15

    A molecular beam epitaxy (MBE) facility has been built to enable in situ neutron scattering measurements during growth of epitaxial layers. While retaining the full capabilities of a research MBE chamber, this facility has been optimized for polarized neutron reflectometry measurements. Optimization includes a compact lightweight portable design, a neutron window, controllable magnetic field, deposition across a large 76 mm diameter sample with exceptional flux uniformity, and sample temperatures continuously controllable from 38 to 1375 K. A load lock chamber allows for sample insertion, storage of up to 4 samples, and docking with other facilities. The design and performance of this chamber are described here.

  7. Real-time locating and speed measurement of fibre fuse using optical frequency-domain reflectometry

    PubMed Central

    Jiang, Shoulin; Ma, Lin; Fan, Xinyu; Wang, Bin; He, Zuyuan

    2016-01-01

    We propose and experimentally demonstrate real-time locating and speed measurement of fibre fuse by analysing the Doppler shift of reflected light using optical frequency-domain reflectometry (OFDR). Our method can detect the start of a fibre fuse within 200 ms which is equivalent to a propagation distance of about 10 cm in standard single-mode fibre. We successfully measured instantaneous speed of propagating fibre fuses and observed their subtle fluctuation owing to the laser power instability. The resolution achieved for speed measurement in our demonstration is 1 × 10−3 m/s. We studied the fibre fuse propagation speed dependence on the launched power in different fibres. Our method is promising for both real time fibre fuse monitoring and future studies on its propagation and termination. PMID:27146550

  8. Real-time locating and speed measurement of fibre fuse using optical frequency-domain reflectometry.

    PubMed

    Jiang, Shoulin; Ma, Lin; Fan, Xinyu; Wang, Bin; He, Zuyuan

    2016-05-05

    We propose and experimentally demonstrate real-time locating and speed measurement of fibre fuse by analysing the Doppler shift of reflected light using optical frequency-domain reflectometry (OFDR). Our method can detect the start of a fibre fuse within 200 ms which is equivalent to a propagation distance of about 10 cm in standard single-mode fibre. We successfully measured instantaneous speed of propagating fibre fuses and observed their subtle fluctuation owing to the laser power instability. The resolution achieved for speed measurement in our demonstration is 1 × 10(-3) m/s. We studied the fibre fuse propagation speed dependence on the launched power in different fibres. Our method is promising for both real time fibre fuse monitoring and future studies on its propagation and termination.

  9. Real-time locating and speed measurement of fibre fuse using optical frequency-domain reflectometry.

    PubMed

    Jiang, Shoulin; Ma, Lin; Fan, Xinyu; Wang, Bin; He, Zuyuan

    2016-01-01

    We propose and experimentally demonstrate real-time locating and speed measurement of fibre fuse by analysing the Doppler shift of reflected light using optical frequency-domain reflectometry (OFDR). Our method can detect the start of a fibre fuse within 200 ms which is equivalent to a propagation distance of about 10 cm in standard single-mode fibre. We successfully measured instantaneous speed of propagating fibre fuses and observed their subtle fluctuation owing to the laser power instability. The resolution achieved for speed measurement in our demonstration is 1 × 10(-3) m/s. We studied the fibre fuse propagation speed dependence on the launched power in different fibres. Our method is promising for both real time fibre fuse monitoring and future studies on its propagation and termination. PMID:27146550

  10. Real-time locating and speed measurement of fibre fuse using optical frequency-domain reflectometry

    NASA Astrophysics Data System (ADS)

    Jiang, Shoulin; Ma, Lin; Fan, Xinyu; Wang, Bin; He, Zuyuan

    2016-05-01

    We propose and experimentally demonstrate real-time locating and speed measurement of fibre fuse by analysing the Doppler shift of reflected light using optical frequency-domain reflectometry (OFDR). Our method can detect the start of a fibre fuse within 200 ms which is equivalent to a propagation distance of about 10 cm in standard single-mode fibre. We successfully measured instantaneous speed of propagating fibre fuses and observed their subtle fluctuation owing to the laser power instability. The resolution achieved for speed measurement in our demonstration is 1 × 10‑3 m/s. We studied the fibre fuse propagation speed dependence on the launched power in different fibres. Our method is promising for both real time fibre fuse monitoring and future studies on its propagation and termination.

  11. Studies of neutron-rich nuclei far from stability at TRISTAN

    SciTech Connect

    Gill, R.L.

    1984-01-01

    The ISOL facility, TRISTAN, is a user facility located at Brookhaven National Laboratory's High Flux Beam Reactor. Short-lived, neutron-rich nuclei, far from stability, are produced by thermal neutron fission of /sup 235/U. An extensive array of experimental end stations are available for nuclear structure studies. These studies are augmented by a variety of long-lived ion sources suitable for use at a reactor facility. Some recent results at TRISTAN are presented as examples of using an ISOL facility to study series of nuclei, whereby an effective means of conducting nuclear structure investigations is available.

  12. Doppler shift estimation for GNSS reflectometry using a land topography adapted reflection model

    NASA Astrophysics Data System (ADS)

    Semmling, Maximilian; Peraza, Luis; Falck, Carsten; Gerland, Sebastian; Wickert, Jens

    2016-04-01

    A GNSS setup with a receiver capable for reflectometry is operated by GFZ at Kongsfjorden (Spitsbergen), 78°54'14''N, 11°52'37''E, 512 m above ellipsoid (WGS-84). This permanent station at the Zeppelin mountain outpost, operated by the Norwegian Polar Institute (NPI), accumulates data since Summer 2013 observing reflections over the fjord and the adjacent land surface. Especially the presence of sea ice over the fjord and snow cover over land are of interest for reflectometry to investigate altimetry and remote sensing applications. The setup contains a GORS (GNSS Occultation Reflectometry Scatterometry) two-frontend receiver, which is based on commercial JAVAD hardware. The receiver is connected to one up-looking and one horizon-looking patch antenna with right-handed and left-handed circular polarization, respectively. Both antennas are installed on the same mount approximately 475 m above the fjord mean sea level. Reflections are observed at low transmitter elevation angles (between 10 and 2°). For these geometries the relative Doppler shift (sea surface reflected relative to direct signal) is almost constant 0.5 to 0.6 Hz and can be calculated with an established reflection model. Rather easily, sea surface reflections are identified in the data and the corresponding reflection points are located. About 55 daily recurring reflection events over the fjord are observed. They form a fan-shaped swath with 3 to 13 km distance around the receiver, corresponding to elevations of 10° to 2°. Also signatures of potential land reflections are found in the data. About 13 daily recurring events extend mainly over land. The potential land signatures have a rather variable Doppler shift between 0.2 to 1Hz. The significant topography of the mountainous surrounding, which varies between sea level and 900 m altitude, prevents the use of established reflection models. A topography adapted reflection model, which considers sloped surface facets, is developed. It incorporates

  13. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-15

    An X-mode polarized V band (50 GHz–75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz–19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from −1 km/s to −3 km/s.

  14. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-01

    An X-mode polarized V band (50 GHz-75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz-19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from -1 km/s to -3 km/s.

  15. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak.

    PubMed

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-01

    An X-mode polarized V band (50 GHz-75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz-19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from -1 km/s to -3 km/s.

  16. Neutron diffraction studies of amphipathic helices in phospholipid bilayers

    SciTech Connect

    Bradshaw, J.P.; Gilchrist, P.J.; Duff, K.C.; Saxena, A.M.

    1994-12-31

    The structural feature which is thought to facilitate the interaction of many peptides with phospholipid bilayers is the ability to fold into an amphipathic helix. In most cases the exact location and orientation of this helix with respect to the membrane is not known, and may vary with factors such as pH and phospholipid content of the bilayer. The growing interest in this area is stimulated by indications that similar interactions can contribute to the binding of certain hormones to their cell-surface receptors. We have been using the techniques of neutron diffraction from stacked phospholipid bilayers in an attempt to investigate this phenomenon with a number of membrane-active peptides. Here we report some of our findings with three of these: the bee venom melittin; the hormone calcitonin; and a synthetic peptide representing the ion channel fragment of influenza A M2 protein.

  17. Powder neutron diffraction studies of a carbonate fluorapatite

    SciTech Connect

    Leventouri, Th.; Chakoumakos, B. C.; Moghaddam, H. Y.; Perdikatsis, V.

    2000-02-01

    Atomic positional disorder of a single-phase natural carbonate fluorapatite (francolite) is revealed from analysis of the atomic displacement parameters (ADPs) refined from neutron powder diffraction data as a function of temperature and carbonate content. The ADPs of the francolite show a strong disturbance at the P, O3, and F sites. When it is heat treated to partially or completely remove the carbonate, the ADPs as well as the other structural parameters resemble those of a fluorapatite (Harding pegmatite) that was measured under the same conditions. The various structural changes are consistent with a substitution mechanism whereby the planar carbonate group replaces a phosphate group and lies on the mirror plane of the apatite structure. (c) 2000 Materials Research Society.

  18. 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.

  19. 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.

  20. 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.

  1. Fast Neutron Damage Studies on NdFeB Materials

    SciTech Connect

    Anderson, S.; Spencer, J.; Wolf, Z.; Baldwin, A.; Pellett, D.; Boussoufi, M.; /UC, Davis

    2005-05-17

    Many materials and electronics need to be tested for the radiation environment expected at linear colliders (LC) since both accelerator and detectors will be subjected to large fluences of hadrons, leptons and {gamma}'s over the life of the facility [1]. While the linacs will be superconducting, there are still many uses for NdFeB in the damping rings, injection and extraction lines and final focus. Our understanding of the situation for rare earth, permanent magnet materials was presented at PAC03 [2]. Our first measurements of fast neutron, stepped doses at the UC Davis McClellan Nuclear Reactor Center (UCD MNRC) were presented at EPAC04 [3]. We have extended the doses, included other manufacturer's samples, and measured induced radioactivities which are discussed in detail.

  2. Error-disturbance uncertainty relations studied in neutron optics

    NASA Astrophysics Data System (ADS)

    Sponar, Stephan; Sulyok, Georg; Demirel, Bulent; Hasegawa, Yuji

    2016-09-01

    Heisenberg's uncertainty principle is probably the most famous statement of quantum physics and its essential aspects are well described by a formulations in terms of standard deviations. However, a naive Heisenberg-type error-disturbance relation is not valid. An alternative universally valid relation was derived by Ozawa in 2003. Though universally valid Ozawa's relation is not optimal. Recently, Branciard has derived a tight error-disturbance uncertainty relation (EDUR), describing the optimal trade-off between error and disturbance. Here, we report a neutron-optical experiment that records the error of a spin-component measurement, as well as the disturbance caused on another spin-component to test EDURs. We demonstrate that Heisenberg's original EDUR is violated, and the Ozawa's and Branciard's EDURs are valid in a wide range of experimental parameters, applying a new measurement procedure referred to as two-state method.

  3. Study of a Li doped CsI scintillator crystal as a neutron detector

    NASA Astrophysics Data System (ADS)

    Madi Filho, T.; Pereira, M. C. C.; Berretta, J. R.; Cárdenas, J. P. N.

    2015-07-01

    The radiation monitoring system is an important requirement in the premises of a nuclear reactor. A variety of types of radiation (neutrons. gamma. beta and fission products) exist in a reactor. associated to the broad energy spectrum of these radiations. implying the need of detectors to be used in the reactor system and security. as well as radiation monitoring. As the neutron sources are associated to gamma radiation. it is necessary that the neutron detecting system may be capable to discriminate the gamma interference. In our work environment. there are two Nuclear Research Reactors and a neutron irradiator with two AmBe sources (592GBq of Am. each). These conditions warrant the development of new types of detectors. Due to the absence of charge in the neutron. it is necessary to use a converter material that generates radiations capable to produce signals in the detector. Materials with high cross section. like Li or B. are used for this purpose. The CsIcrystal doped with 6Li has been studied. The concentration of the lithium doping element (Li) studied was 10-3M. The detector test was done using an AmBe source (37GBq) and gamma sources. The crystal was coupled to a photomultiplier.

  4. Study of the beam-induced neutron flux and required shielding for DIANA

    NASA Astrophysics Data System (ADS)

    Best, Andreas; Couder, Manoel; Famiano, Michael; Lemut, Alberto; Wiescher, Michael

    2013-11-01

    Low energy accelerators in underground locations have emerged as a powerful tool for the measurement of critical nuclear reactions for the study of energy production and element synthesis in astrophysics. While cosmic ray induced background is substantially reduced, beam induced background on target impurities and depositions on target and collimator materials remain a matter of serious concern. The Dual Ion Accelerator for Nuclear Astrophysics (DIANA) is proposed to operate as a low-level background facility in an underground location. One of the main goals of DIANA is the study of neutron sources in stellar helium burning. For these experiments DIANA is a neutron radiation source which may affect other nearby low background level experiments. We therefore investigated the required laboratory layout to attenuate the neutron flux generated in a worst-case scenario to a level below the natural background in the underground environment. Detailed Monte Carlo calculations of the neutron propagation in the laboratory show that a neutron flux many orders of magnitude above expected values gets attenuated below the natural background rate using a 1 m thick water-shielded door as well as an emergency access/egress maze.

  5. High-Pressure Neutron Diffraction Studies for Materials Sciences and Energy Sciences

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Los Alamos High Pressure Materials Research Team

    2013-05-01

    The development of neutron diffraction under extreme pressure (P) and temperature (T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials sciences, as well as earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at LANSCE to conduct in situ high P-T neutron diffraction experiments. We have worked out a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high-P and low-T. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. Recently, we have developed high-P low-T gas/fluid cells in conjunction with neutron diffraction and inelastic neutron scattering instruments. These techniques enable in-situ and real-time examination of gas uptake/release processes and allow high-resolution time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equation of state, structural phase transition, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation of methane and hydrogen clathrates, and hydrogen adsorption of the inclusion compounds such as the recently discovered metal-organic frameworks (MOFs). The aim of our research is to accurately map phase diagram, lattice parameters, thermal parameters, bond lengths, bond angles, neighboring atomic environments, and phase stability in P-T-X space. We are currently developing further high P-T technology with a new "true" triaxial loading press, TAP_6x, to compress cubic sample package to achieve pressures up to 20 GPa and temperatures up to 2000 K in routine experiments. The implementation of TAP_6x300 with high-pressure neutron beamlines is underway for simultaneous high P-T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based on high

  6. Time-Domain Reflectometry for Tamper Indication in Unattended Monitoring Systems for Safeguards

    SciTech Connect

    Tedeschi, Jonathan R.; Smith, Leon E.; Moore, David E.; Sheen, David M.; Conrad, Ryan C.

    2014-12-01

    The International Atomic Energy Agency (IAEA) continues to expand its use of unattended, remotely monitored measurement systems. An increasing number of systems and an expanding family of instruments create challenges in terms of deployment efficiency and the implementation of data authentication measures. Pacific Northwest National Laboratory (PNNL) leads a collaboration that is exploring various tamper-indicating (TI) measures that could help to address some of the long-standing detector and data-transmission authentication challenges with IAEA’s unattended systems. PNNL is investigating the viability of active time-domain reflectometry (TDR) along two parallel but interconnected paths: (1) swept-frequency TDR as the highly flexible, laboratory gold standard to which field-deployable options can be compared, and (2) a low-cost commercially available spread-spectrum TDR technology as one option for field implementation. This report describes PNNL’s progress and preliminary findings from the first year of the study, and describes the path forward.

  7. Two-dimensional full-wave code for reflectometry simulations in TJ-II

    SciTech Connect

    Blanco, E.; Heuraux, S.; Estrada, T.; Sanchez, J.; Cupido, L.

    2004-10-01

    A two-dimensional full-wave code in the extraordinary mode has been developed to simulate reflectometry in TJ-II. The code allows us to study the measurement capabilities of the future correlation reflectometer that is being installed in TJ-II. The code uses the finite-difference-time-domain technique to solve Maxwell's equations in the presence of density fluctuations. Boundary conditions are implemented by a perfectly matched layer to simulate free propagation. To assure the stability of the code, the current equations are solved by a fourth-order Runge-Kutta method. Density fluctuation parameters such as fluctuation level, wave numbers, and correlation lengths are extrapolated from those measured at the plasma edge using Langmuir probes. In addition, realistic plasma shape, density profile, magnetic configuration, and experimental setup of TJ-II are included to determine the plasma regimes in which accurate information may be obtained.

  8. Analysis of water film thickness on contact lens by reflectometry technique

    NASA Astrophysics Data System (ADS)

    Wang, Michael R.; Lu, Hui; Wang, Jianhua; Shen, Meixiao

    2011-03-01

    We report the use of optical reflectometry technique for evaluation of water film on contact lens. The water film can be measured through the spectral dependent reflectance evaluation, which is carried out by illuminating the contact lens with a white light and collecting the returning light with an optical fiber coupled to a spectrometer. Water film thinning process has been observed on different soft contact lenses and minimum measurable thickness is about 0.85 μm. The measurement is fast and accurate. The water film measurement can be valuable for contact lens design to improve its hydrophilic properties. The technique can be extended for the study of tear film dynamics in an eye.

  9. 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.

  10. Studies on the response of 3He and 4He proportional counters to monoenergetic fast neutrons

    NASA Astrophysics Data System (ADS)

    Manolopoulou, M.; Fragopoulou, M.; Stoulos, S.; Koukorava, C.; Spyrou, A.; Perdikakis, G.; Hashemi-Nezhad, S. R.; Zamani, M.

    2006-06-01

    Two helium filled proportional counters ( 3He and 4He) were studied to establish the optimum operating conditions when these counters are used for fast neutron measurements, as well as to examine the linearity of the pulse height with neutron energy. The detectors were irradiated with mono-energetic neutrons in the energy range of 230 keV-22 MeV, produced via 7Li(n,p) 7Be, 2H(d,n) 3He and 3H(d,n) 4He reactions in a Tandem Van de Graff accelerator. The gamma ray contribution to the obtained pulse height distribution and the resolution of the counters as a function of shaping time constant and applied high voltage were studied.

  11. Appraisal of a cementitious material for waste disposal: Neutron imaging studies of pore structure and sorptivity

    SciTech Connect

    McGlinn, Peter J.; Beer, Frikkie C. de; Aldridge, Laurence P.; Radebe, Mabuti J.; Nshimirimana, Robert; Brew, Daniel R.M.; Payne, Timothy E.; Olufson, Kylie P.

    2010-08-15

    Cementitious materials are conventionally used in conditioning intermediate and low level radioactive waste. In this study a candidate cement-based wasteform has been investigated using neutron imaging to characterise the wasteform for disposal in a repository for radioactive materials. Imaging showed both the pore size distribution and the extent of the cracking that had occurred in the samples. The rate of the water penetration measured both by conventional sorptivity measurements and neutron imaging was greater than in pastes made from Ordinary Portland Cement. The ability of the cracks to distribute the water through the sample in a very short time was also evident. The study highlights the significant potential of neutron imaging in the investigation of cementitious materials. The technique has the advantage of visualising and measuring, non-destructively, material distribution within macroscopic samples and is particularly useful in defining movement of water through the cementitious materials.

  12. Polarisation reflectometry of anisotropic optical fibres

    SciTech Connect

    Konstantinov, Yurii A; Kryukov, Igor' I; Pervadchuk, Vladimir P; Toroshin, Andrei Yu

    2009-11-30

    Anisotropic, polarisation-maintaining fibres have been studied using a reflectometer and integrated optic polariser. Linearly polarised pulses were launched into the fibre under test at different angles between their plane of polarisation and the main optical axis of the fibre. A special procedure for the correlation analysis of these reflectograms is developed to enhance the reliability of the information about the longitudinal optical uniformity of anisotropic fibres. (optical fibres and fibreoptic sensors)

  13. Neutron induced damage in reactor pressure vessel steel: An X-ray absorption fine structure study

    NASA Astrophysics Data System (ADS)

    Kuri, G.; Cammelli, S.; Degueldre, C.; Bertsch, J.; Gavillet, D.

    2009-03-01

    The radiation damage produced in reactor pressure vessel (RPV) steels during neutron irradiation is a long-standing problem of considerable practical interest. In this study, an extended X-ray absorption fine structure (EXAFS) spectroscopy has been applied at Cu, Ni and Mn K-edges to systematically investigate neutron induced radiation damage to the metal-site bcc structure of RPV steels, irradiated with neutrons in the fluence range from 0.85 to 5.0 × 1019 cm-2. An overall similarity of Cu, Ni and Mn atomic environment in the iron matrix is observed. The radial distribution functions (RDFs), derived from EXAFS data have been found to evolve continuously as a function of neutron fluence describing the atomic-scale structural modifications in RPVs by neutron irradiations. From the pristine data, long range order beyond the first- and second-shell is apparent in the RDF spectra. In the irradiated specimens, all near-neighbour peaks are greatly reduced in magnitude, typical of damaged material. Prolonged annealing leads annihilation of point defects to give rise to an increase in the coordination numbers of near-neighbour atomic shells approaching values close to that of non-irradiated material, but does not suppress the formation of nano-sized Cu and/or Ni-rich-precipitates. Total amount of radiation damage under a given irradiation condition has been determined. The average structural parameters estimated from the EXAFS data are presented and discussed.

  14. 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.

  15. A study on artificial rare earth (RE2O3) based neutron absorber.

    PubMed

    Kim, Kyung-O; Kim, Jong Kyung

    2015-11-01

    A new concept of a neutron absorption material (i.e., an artificial rare earth compound) was introduced for criticality control in a spent fuel storage system. In particular, spent nuclear fuels were considered as a potential source of rare earth elements because the nuclear fission of uranium produces a full range of nuclides. It was also found that an artificial rare earth compound (RE2O3) as a High-Level Waste (HLW) was naturally extracted from pyroprocessing technology developed for recovering uranium and transuranic elements (TRU) from spent fuels. In this study, various characteristics (e.g., activity, neutron absorption cross-section) were analyzed for validating the application possibility of this waste compound as a neutron absorption material. As a result, the artificial rare earth compound had a higher neutron absorption probability in the entire energy range, and it can be used for maintaining sub-criticality for more than 40 years on the basis of the neutron absorption capability of Boral™. Therefore, this approach is expected to vastly improve the efficiency of radioactive waste management by simultaneously keeping HLW and spent nuclear fuel in a restricted space.

  16. A study on artificial rare earth (RE2O3) based neutron absorber.

    PubMed

    Kim, Kyung-O; Kim, Jong Kyung

    2015-11-01

    A new concept of a neutron absorption material (i.e., an artificial rare earth compound) was introduced for criticality control in a spent fuel storage system. In particular, spent nuclear fuels were considered as a potential source of rare earth elements because the nuclear fission of uranium produces a full range of nuclides. It was also found that an artificial rare earth compound (RE2O3) as a High-Level Waste (HLW) was naturally extracted from pyroprocessing technology developed for recovering uranium and transuranic elements (TRU) from spent fuels. In this study, various characteristics (e.g., activity, neutron absorption cross-section) were analyzed for validating the application possibility of this waste compound as a neutron absorption material. As a result, the artificial rare earth compound had a higher neutron absorption probability in the entire energy range, and it can be used for maintaining sub-criticality for more than 40 years on the basis of the neutron absorption capability of Boral™. Therefore, this approach is expected to vastly improve the efficiency of radioactive waste management by simultaneously keeping HLW and spent nuclear fuel in a restricted space. PMID:26241833

  17. Application of Neutron Reflectivity for Studies of Biomolecular Structures and Functions at Interfaces

    SciTech Connect

    Johs, Alexander; Liang, Liyuan; Gu, Baohua; Ankner, John Francis; Wang, Wei

    2009-01-01

    Structures and functions of cell membranes are of central importance in understanding processes such as cell signaling, chemotaxis, redox transformation, biofilm formation, and mineralization occurring at interfaces. This chapter provides an overview of the application of neutron reflectivity (NR) as a unique tool for probing biomolecular structures and mechanisms as a first step toward understanding protein protein, protein lipid, and protein mineral interactions at the membrane substrate interfaces. Emphasis is given to the review of existing literature on the assembly of biomimetic membrane systems, such as supported membranes for NR studies, and demonstration of model calculations showing the potential of NR to elucidate molecular fundamentals of microbial cell mineral interactions and structure functional relationships of electron transport pathways. The increased neutron flux afforded by current and upcoming neutron sources holds promise for elucidating detailed processes such as phase separation, formation of microdomains, and membrane interactions with proteins and peptides in biological systems.

  18. Neutron Compton scattering as a molecular characterization technique: A study on NaHF{sub 2}

    SciTech Connect

    Colognesi, D.; Pietropaolo, A.; Senesi, R.; Ramirez-Cuesta, A. J.

    2007-11-01

    Inelastic neutron scattering experiments were performed at intermediate and high momentum transfers, up to 85-90 A ring {sup -1}, to study the proton momentum distribution in polycrystalline sodium hydrogen fluoride (NaHF{sub 2}) at low temperature (below 5 K). The H mean kinetic energy was extracted and compared to the results from hydrogen-projected density of phonon states derived from intermediate momentum transfer inelastic neutron scattering and lattice dynamics simulations. A reasonable agreement between the two figures was found. In addition, relevant aspects of high momentum transfer neutron scattering from NaHF{sub 2} were explored in detail, ranging from an alternative evaluation of final state effects to the role played by the instrumental resolution and to the possibility to reconstruct the potential felt by a proton from its momentum distribution.

  19. A neutronic feasibility study for LEU conversion of the Budapest research reactor.

    SciTech Connect

    Pond, R. B.

    1998-10-16

    A neutronic feasibility study for conversion of the Budapest Research Reactor (BRR) from HEU to LEU fuel was performed at Argonne National Laboratory in cooperation with the KFKI Atomic Energy Research Institute in Hungary. Comparisons were made of the reactor performance with the current HEU (36%) fuel and with a proposed LEU (19.75%) fuel. Cycle lengths, thermal neutron fluxes, and rod worths were calculated in equilibrium-type cores for each type of fuel. Relative to the HEU fuel, the LEU fuel has up to a 50% longer fuel cycle length, but a 7-10% smaller thermal neutron flux in the experiment locations. The rod worths are smaller with the LEU fuel, but are still large enough to easily satisfy the BRR shutdown margin criteria. Irradiation testing of four VVR-M2 LEU fuel assemblies that are nearly the same as the proposed BRR LEU fuel assemblies is currently in progress at the Petersburg Nuclear Physics Institute.

  20. X-ray studies of neutron stars and their magnetic fields

    PubMed Central

    MAKISHIMA, Kazuo

    2016-01-01

    Utilizing results obtained over the past quarter century mainly with Japanese X-ray astronomy satellites, a review is given to some aspects of neutron stars (NSs), with a particular emphasis on the magnetic fields (MFs) of mass-accreting NSs and magnetars. Measurements of electron cyclotron resonance features in binary X-ray pulsars, using the Ginga and Suzaku observatories, clarified that their surface MFs are concentrated in a narrow range of (1–7) × 108 T. Extensive studies of magnetars with Suzaku reinforced their nature as neutron stars with truly strong MFs, and revealed several important clues to their formation, evolution, and physical states. Taking all these results into account, a discussion is made on the origin and evolution of these strong MFs. One possible scenario is that the MF of NSs is a manifestation of some fundamental physics, e.g., neutron spin alignment or chirality violation, and the MF makes transitions from strong to weak states. PMID:27169348

  1. Inelastic neutron scttering study o fcrystal field levels in PrOs4As12

    SciTech Connect

    Chi, Songxue; Dai, Pengcheng; Barnes, Ted {F E }; Kang, H. J.; Lynn, J. W.; Ye, Feng; Maple, M. B.

    2008-01-01

    We use neutron scattering to study the Pr$^{3+}$ crystalline electric field (CEF) excitations in the filled skutterudite PrOs$_4$As$_{12}$. By comparing the observed levels and their strengths under neutron excitation with the theoretical spectrum and neutron excitation intensities, we identify the Pr$^{3+}$ CEF levels, and show that the ground state is a magnetic $\\Gamma_4^{(2)}$ triplet, and the excited states $\\Gamma_1$, $\\Gamma_4^{(1)}$ and $\\Gamma_{23}$ are at 0.4, 13 and 23~meV, respectively. A comparison of the observed CEF levels in PrOs$_4$As$_{12}$ with the heavy fermion superconductor PrOs$_4$Sb$_{12}$ reveals the microscopic origin of the differences in the ground states of these two filled skutterudites.

  2. Capability and limitation study of the DDT passive-active neutron waste assay instrument

    SciTech Connect

    Nicholas, N.J.; Coop, K.L.; Estep, R.J.

    1992-05-01

    The differential-dieaway-technique passive-active neutron assay system is widely used by transuranic waste generators to certify their drummed waste for eventual shipment to the Waste Isolation Pilot Plant (WIPP). Stricter criteria being established for waste emplacement at the WIPP site has led to a renewed interest in improvements to and a better understanding of current nondestructive assay (NDA) techniques. Our study includes the effects of source position, extreme matrices, high neutron backgrounds, and source self-shielding to explore the system`s capabilities and limitations and to establish a basis for comparison with other NDA systems. 11 refs.

  3. Capability and limitation study of the DDT passive-active neutron waste assay instrument

    SciTech Connect

    Nicholas, N.J.; Coop, K.L.; Estep, R.J.

    1992-05-01

    The differential-dieaway-technique passive-active neutron assay system is widely used by transuranic waste generators to certify their drummed waste for eventual shipment to the Waste Isolation Pilot Plant (WIPP). Stricter criteria being established for waste emplacement at the WIPP site has led to a renewed interest in improvements to and a better understanding of current nondestructive assay (NDA) techniques. Our study includes the effects of source position, extreme matrices, high neutron backgrounds, and source self-shielding to explore the system's capabilities and limitations and to establish a basis for comparison with other NDA systems. 11 refs.

  4. Trap-assisted studies of odd, neutron-rich isotopes from Tc to Pd

    NASA Astrophysics Data System (ADS)

    Kurpeta, J.; Jokinen, A.; Penttilä, H.; Płochocki, A.; Rissanen, J.; Urban, W.; Äystö, J.

    2014-01-01

    We review the present and future of trap-assisted structure studies of odd, neutron-rich Tc, Ru, Rh and Pd isotopes at the limits of present experimental techniques. These nuclei of refractory elements are produced in light-particle induced fission and filtered by their mass number with the IGISOL mass separator. Further mass separation with the JYFLTRAP Penning trap system provides a clean, monoisotopic beam perfectly suited for precise nuclear spectroscopy. Connecting the IGISOL and the JYFLTRAP facilities to the recently installed MCC30/15 cyclotron opens new prospects for post-trap spectroscopy of very exotic, neutron-rich nuclei.

  5. Study of asymmetric fission yield behavior from neutron-deficient Hg isotope

    SciTech Connect

    Perkasa, Y. S.; Waris, A. Kurniadi, R. Su'ud, Z.

    2014-09-30

    A study of asymmetric fission yield behavior from a neutron-deficient Hg isotope has been conducted. The fission yield calculation of the neutron-deficient Hg isotope using Brownian Metropolis shape had showed unusual result at decreasing energy. In this paper, this interesting feature will be validated by using nine degree of scission shapes parameterization from Brosa model that had been implemented in TALYS nuclear reaction code. This validation is intended to show agreement between both model and the experiment result. The expected result from these models considered to be different due to dynamical properties that implemented in both models.

  6. Feasibility study on pinhole camera system for online dosimetry in boron neutron capture therapy.

    PubMed

    Katabuchi, Tatsuya; Hales, Brian; Hayashizaki, Noriyosu; Igashira, Masayuki; Khan, Zareen; Kobayashi, Tooru; Matsuhashi, Taihei; Miyazaki, Koichi; Ogawa, Koichi; Terada, Kazushi

    2014-06-01

    The feasibility of a pinhole camera system for online dosimetry in boron neutron capture therapy (BNCT) was studied. A prototype system was designed and built. Prompt γ-rays from the (10)B(n,α)(7)Li reaction from a phantom irradiated with neutrons were detected with the prototype system. An image was reconstructed from the experimental data. The reconstructed image showed a good separation of the two borated regions in the phantom. The counting rates and signal-to-noise ratio when using the system in actual BNCT applications are also discussed.

  7. Suitability of Chinese oil well loggers for an epidemiologic study of the carcinogenic effects of neutrons.

    PubMed

    Inskip, P D; Wang, Z Y; Fen, Y S

    1991-11-01

    Neutron exposures to 191 well loggers at four oil fields in China were measured over a 3-mo period using CR-39 polycarbonate dosimeters. Doses (96% less than 0.02 mGy) were slightly lower than literature values for well loggers in North America, possibly because of differences in drilling activity. Because doses are so low, an epidemiologic study of cancer among Chinese well loggers is unlikely to be informative about the carcinogenicity of neutrons relative to sparsely ionizing radiation. PMID:1752747

  8. Neutron Studies of Tb2Mo2O7

    SciTech Connect

    Gardner, Jason; Ehlers, Georg; Diallo, Souleymane Omar

    2012-01-01

    We have used the new high energy resolution spectrometer (BaSiS), at the Spallation Neutron Source in Oak Ridge, to conclusively prove the existence of a low energy mode at 0.34(1) meV in the spin glass Tb{sub 2}Mo{sub 2}O{sub 7}. This mode is reminiscent of the excitation observed in the ordered phases of both Tb{sub 2}Ti{sub 2}O{sub 7} and Tb{sub 2}Sn{sub 2}O{sub 7}. The dynamical nature of the transition seen in the magnetization at {approx} 25 K suggests that this frustrated magnet shows a dynamic crossover between a high-temperature phase of poorly correlated, quickly relaxing spins to a low-temperature regime with much slower, short ranged spin correlations extending no further than to the next nearest neighbor. Existing theories explain the spin glass transition in terms of a phase transition and order parameters, and assume the existence of a distinct spin glass phase. There is no evidence for such a phase in Tb{sub 2}Mo{sub 2}O{sub 7}.

  9. Density functional and neutron diffraction studies of lithium polymer electrolytes.

    SciTech Connect

    Baboul, A. G.

    1998-06-26

    The structure of PEO doped with lithium perchlorate has been determined using neutron diffraction on protonated and deuterated samples. The experiments were done in the liquid state. Preliminary analysis indicates the Li-O distance is about 2.0 {angstrom}. The geometries of a series of gas phase lithium salts [LiCF{sub 3}SO{sub 3}, Li(CF{sub 3}SO{sub 2}){sub 2}N, Li(CF{sub 3}SO{sub 2}){sub 2}CH, LiClO{sub 4}, LiPF{sub 6}, LiAsF{sub 6}] used in polymer electrolytes have been optimized at B3LYP/6-31G(d) density functional level of theory. All local minima have been identified. For the triflate, imide, methanide, and perchlorate anions, the lithium cation is coordinated to two oxygens and have binding energies of ca 141 kcal/mol at the B3LYP/6-311+G(3df,2p)/B3LYP/6-31G* level of theory. For the hexafluoroarsenate and hexafluorophosphate the lithium cation is coordinated to three oxygens and have binding energies of ca. 136 kcal/mol.

  10. The neutronics studies of fusion fission hybrid power reactor

    SciTech Connect

    Zheng Youqi; Wu Hongchun; Zu Tiejun; Yang Chao; Cao Liangzhi

    2012-06-19

    In this paper, a series of neutronics analysis of hybrid power reactor is proposed. The ideas of loading different fuels in a modular-type fission blanket is analyzed, fitting different level of fusion developments, i.e., the current experimental power output, the level can be obtained in the coming future and the high-power fusion reactor like ITER. The energy multiplication of fission blankets and tritium breeding ratio are evaluated as the criterion of design. The analysis is implemented based on the D-type simplified model, aiming to find a feasible 1000MWe hybrid power reactor for 5 years' lifetime. Three patterns are analyzed: 1) for the low fusion power, the reprocessed fuel is chosen. The fuel with high plutonium content is loaded to achieve large energy multiplication. 2) For the middle fusion power, the spent fuel from PWRs can be used to realize about 30 times energy multiplication. 3) For the high fusion power, the natural uranium can be directly used and about 10 times energy multiplication can be achieved.

  11. Combined X-ray and neutron fibre diffraction studies of biological and synthetic polymers.

    SciTech Connect

    Parrot, I. M.; Urban, Volker S; Gardner, K. H.; Forsyth, V. T.

    2005-04-01

    The fibrous state is a natural one for polymer molecules which tend to assume regular helical conformations rather than the globular structures characteristic of many proteins. Fibre diffraction therefore has broad application to the study of a wide range of biological and synthetic polymers. The purpose of this paper is to illustrate the general scope of the method and in particular to demonstrate the impact of a combined approach involving both X-ray and neutron diffraction methods. While the flux of modern X-ray synchrotron radiation sources allows high quality datasets to be recorded with good resolution within a very short space of time, neutron studies can provide unique information through the ability to locate hydrogen or deuterium atoms that are often difficult or impossible to locate using X-ray methods. Furthermore, neutron fibre diffraction methods can, through the ability to selectively label specific parts of a structure, be used to highlight novel aspects of polymer structure that can not be studied using X-rays. Two examples are given. The first describes X-ray and neutron diffraction studies of conformational transitions in DNA. The second describes structural studies of the synthetic high-performance polymer poly(p-phenylene terephthalamide) (PPTA), known commercially as Kevlar{reg_sign} or Twaron{reg_sign}.

  12. A study on the utilization of tritide titanium targets for monoenergetic neutron production

    NASA Astrophysics Data System (ADS)

    Karamanis, D.

    2002-10-01

    Proton beam interaction with a tritide titanium target in an electrostatic accelerator was studied by measuring the produced neutron rate as a function of bombarding time. The results are analyzed in the frame of target temperature increase, extension of existing low energy interaction model and SRIM simulation. Special emphasis is put on the evaluation of the release of radiotoxic tritium from the solid target.

  13. 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.

  14. A study of neutron radiation quality with a tissue-equivalent proportional counter for a low-energy accelerator-based in vivo neutron activation facility.

    PubMed

    Aslam; Waker, A J

    2011-02-01

    The accelerator-based in vivo neutron activation facility at McMaster University has been used successfully for the measurement of several minor and trace elements in human hand bones due to their importance to health. Most of these in vivo measurements have been conducted at a proton beam energy (E(p)) of 2.00 MeV to optimise the activation of the selected element of interest with an effective dose of the same order as that received in chest X rays. However, measurement of other elements at the same facility requires beam energies other than 2.00 MeV. The range of energy of neutrons produced at these proton beam energies comes under the region where tissue-equivalent proportional counters (TEPCs) are known to experience difficulty in assessing the quality factor and dose equivalent. In this study, the response of TEPCs was investigated to determine the quality factor of neutron fields generated via the (7)Li(p, n)(7)Be reaction as a function of E(p) in the range 1.884-2.56 MeV at the position of hand irradiation in the facility. An interesting trend has been observed in the quality factor based on ICRP 60, Q(ICRP60), such that the maximum value was observed at E(p)=1.884 MeV (E(n)=33±16 keV) and then continued to decline with increasing E(p) until achieving a minimum value at E(p)=2.0 MeV despite a continuous increase in the mean neutron energy with E(p). This observation is contrary to what has been observed with direct fast neutrons where the quality factor was found to increase continuously with an increase in E(p) (i.e. increasing E(n)). The series of measurements conducted with thermal and fast neutron fields demonstrate that the (14)N(n, p)(14)C produced 580 keV protons in the detector play an important role in the response of the counter under 2.0 MeV proton energy (E(n) ≤ 250 keV). In contrast to the lower response of TEPCs to low-energy neutrons, the quality factor is overestimated in the range 1-2 depending on beam energy <2.0 MeV. This study provides

  15. Distributed dynamic strain measurement using optical frequency-domain reflectometry.

    PubMed

    Zhou, Da-Peng; Chen, Liang; Bao, Xiaoyi

    2016-08-20

    Distributed dynamic strain measurement based on optical frequency-domain reflectometry is proposed. The technique makes use of the wide scanning range of a tunable laser source in a short sweeping time, and subdivides the overall spectrum into narrower frequency windows. The advantage of subdividing the laser spectral range is to improve the measurement uncertainty induced by the laser wavelength difference between repeated scans. The noise-limited dynamic strain resolution is investigated experimentally, indicating that a minimum detectable strain is less than 200 nε for a spatial resolution of 20 cm. By measuring the subdivided spectral shifts in the time sequence along the sensing fiber, the dynamic strain can be properly quantified over a 30 m measurement range for a highest sampling rate of up to 50 Hz. PMID:27556996

  16. Monitoring oil-water mixture separation by time domain reflectometry

    NASA Astrophysics Data System (ADS)

    Bruvik, E. M.; Hjertaker, B. T.; Folgerø, K.; Meyer, S. K.

    2012-12-01

    Effective separation of water and oil is an essential part of petroleum production. Time domain reflectometry (TDR) can be used to profile the separation of hydrocarbon oil-water mixtures. In such two-component systems, metal electrodes will become oil-coated due to their affinity to oil. This coating layer will impact water content measurements. By combining the TDR signals from two probes in a novel configuration, the thickness of the oil layer on the electrodes can be estimated and its effect on the TDR measurements corrected for. The probes consist of two rods of different diameter and spacing to a common ground/guard electrode. The measurement principle is demonstrated using a light fuel oil and a thicker organic oil. The results indicate that oil and water levels can be monitored during separation if the metal electrode oil-coating effect is accounted for.

  17. Development of 3D microwave imaging reflectometry in LHD (invited).

    PubMed

    Nagayama, Y; Kuwahara, D; Yoshinaga, T; Hamada, Y; Kogi, Y; Mase, A; Tsuchiya, H; Tsuji-Iio, S; Yamaguchi, S

    2012-10-01

    Three-dimensional (3D) microwave imaging reflectometry has been developed in the large helical device to visualize fluctuating reflection surface which is caused by the density fluctuations. The plasma is illuminated by the probe wave with four frequencies, which correspond to four radial positions. The imaging optics makes the image of cut-off surface onto the 2D (7 × 7 channels) horn antenna mixer arrays. Multi-channel receivers have been also developed using micro-strip-line technology to handle many channels at reasonable cost. This system is first applied to observe the edge harmonic oscillation (EHO), which is an MHD mode with many harmonics that appears in the edge plasma. A narrow structure along field lines is observed during EHO.

  18. Terahertz reflectometry imaging for low and high grade gliomas

    PubMed Central

    Ji, Young Bin; Oh, Seung Jae; Kang, Seok-Gu; Heo, Jung; Kim, Sang-Hoon; Choi, Yuna; Song, Seungri; Son, Hye Young; Kim, Se Hoon; Lee, Ji Hyun; Haam, Seung Joo; Huh, Yong Min; Chang, Jong Hee; Joo, Chulmin; Suh, Jin-Suck

    2016-01-01

    Gross total resection (GTR) of glioma is critical for improving the survival rate of glioma patients. One of the greatest challenges for achieving GTR is the difficulty in discriminating low grade tumor or peritumor regions that have an intact blood brain barrier (BBB) from normal brain tissues and delineating glioma margins during surgery. Here we present a highly sensitive, label-free terahertz reflectometry imaging (TRI) that overcomes current key limitations for intraoperative detection of World Health Organization (WHO) grade II (low grade), and grade III and IV (high grade) gliomas. We demonstrate that TRI provides tumor discrimination and delineation of tumor margins in brain tissues with high sensitivity on the basis of Hematoxylin and eosin (H&E) stained image. TRI may help neurosurgeons to remove gliomas completely by providing visualization of tumor margins in WHO grade II, III, and IV gliomas without contrast agents, and hence, improve patient outcomes. PMID:27782153

  19. Towards High Accuracy Reflectometry for Extreme-Ultraviolet Lithography.

    PubMed

    Tarrio, Charles; Grantham, Steven; Squires, Matthew B; Vest, Robert E; Lucatorto, Thomas B

    2003-01-01

    Currently the most demanding application of extreme ultraviolet optics is connected with the development of extreme ultraviolet lithography. Not only does each of the Mo/Si multilayer extreme-ultraviolet stepper mirrors require the highest attainable reflectivity at 13 nm (nearly 70 %), but the central wavelength of the reflectivity of these mirrors must be measured with a wavelength repeatability of 0.001 nm and the peak reflectivity of the reflective masks with a repeatability of 0.12 %. We report on two upgrades of our NIST/DARPA Reflectometry Facility that have given us the ability to achieve 0.1 % repeatability and 0.3 % absolute uncertainty in our reflectivity measurements. A third upgrade, a monochromator with thermal and mechanical stability for improved wavelength repeatability, is currently in the design phase.

  20. Multiplex detection of disease marker proteins with arrayed imaging reflectometry

    NASA Astrophysics Data System (ADS)

    Yadav, Amrita; Sriram, Rashmi; Miller, Benjamin L.

    2010-02-01

    Arrayed Imaging Reflectometry, or "AIR", is a new label-free optical technique for detecting proteins. AIR relies on binding-induced changes in the response of an antireflective coating on the surface of a silicon chip. Thus far, we have demonstrated the use of AIR for the detection of pathogenic E. coli, and for multiplex detection of a broad range of proteins in human serum. Creation of the near-perfect antireflective coating on the surface of silicon requires careful control over preparation of the chip surface prior to probe molecule immobilization. We present methods for highly reproducible, solution-phase silanization and glutaraldehyde functionalization of silicon chips carrying a layer of thermal oxide. Following functionalization with antibodies and passivation of remaining reactive groups, these surfaces provide exceptional performance in the AIR assay.

  1. Adaptive array technique for differential-phase reflectometry in QUEST

    SciTech Connect

    Idei, H. Hanada, K.; Zushi, H.; Nagata, K.; Mishra, K.; Itado, T.; Akimoto, R.; Yamamoto, M. K.

    2014-11-15

    A Phased Array Antenna (PAA) was considered as launching and receiving antennae in reflectometry to attain good directivity in its applied microwave range. A well-focused beam was obtained in a launching antenna application, and differential-phase evolution was properly measured by using a metal reflector plate in the proof-of-principle experiment at low power test facilities. Differential-phase evolution was also evaluated by using the PAA in the Q-shu University Experiment with Steady State Spherical Tokamak (QUEST). A beam-forming technique was applied in receiving phased-array antenna measurements. In the QUEST device that should be considered as a large oversized cavity, standing wave effect was significantly observed with perturbed phase evolution. A new approach using derivative of measured field on propagating wavenumber was proposed to eliminate the standing wave effect.

  2. Novel catheter enabling simultaneous radiofrequency ablation and optical coherence reflectometry

    PubMed Central

    Herranz, D.; Lloret, Juan; Jiménez-Valero, Santiago; Rubio-Guivernau, J. L.; Margallo-Balbás, Eduardo

    2015-01-01

    A novel radiofrequency ablation catheter has been developed with integrated custom designed optics, enabling real-time monitoring of radiofrequency ablation procedures through polarization-sensitive optical coherence reflectometry. The optics allow for proper tissue illumination through a view-port machined in the catheter tip, thus providing lesion depth control over the RF ablation treatment. The system was verified in an in-vitro model of swine myocardium. Optical performance and thermal stability was confirmed after more than 25 procedures, without any damage to the optical assembly induced by thermal stress or material degradation. The use of this catheter in RF ablation treatments may make possible to assess lesion depth during therapy, thus translating into a reduction of potential complications on the procedure. PMID:26417499

  3. Event-by-event study of neutron observables in spontaneous and thermal fission

    SciTech Connect

    Vogt, R; Randrup, J

    2011-09-14

    The event-by-event fission model FREYA is extended to spontaneous fission of actinides and a variety of neutron observables are studied for spontaneous fission and fission induced by thermal neutrons with a view towards possible applications for SNM detection. We have shown that event-by-event models of fission, such as FREYA, provide a powerful tool for studying fission neutron correlations. Our results demonstrate that these correlations are significant and exhibit a dependence on the fissioning nucleus. Since our method is phenomenological in nature, good input data are especially important. Some of the measurements employed in FREYA are rather old and statistics limited. It would be useful to repeat some of these studies with modern detector techniques. In addition, most experiments made to date have not made simultaneous measurements of the fission products and the prompt observables, such as neutron and photons. Such data, while obviously more challenging to obtain, would be valuable for achieving a more complete understanding of the fission process.

  4. Evidence for Gamow-Teller Decay of ^{78}Ni Core from Beta-Delayed Neutron Emission Studies.

    PubMed

    Madurga, M; Paulauskas, S V; Grzywacz, R; Miller, D; Bardayan, D W; Batchelder, J C; Brewer, N T; Cizewski, J A; Fijałkowska, A; Gross, C J; Howard, M E; Ilyushkin, S V; Manning, B; Matoš, M; Mendez, A J; Miernik, K; Padgett, S W; Peters, W A; Rasco, B C; Ratkiewicz, A; Rykaczewski, K P; Stracener, D W; Wang, E H; Wolińska-Cichocka, M; Zganjar, E F

    2016-08-26

    The β-delayed neutron emission of ^{83,84}Ga isotopes was studied using the neutron time-of-flight technique. The measured neutron energy spectra showed emission from states at excitation energies high above the neutron separation energy and previously not observed in the β decay of midmass nuclei. The large decay strength deduced from the observed intense neutron emission is a signature of Gamow-Teller transformation. This observation was interpreted as evidence for allowed β decay to ^{78}Ni core-excited states in ^{83,84}Ge favored by shell effects. We developed shell model calculations in the proton fpg_{9/2} and neutron extended fpg_{9/2}+d_{5/2} valence space using realistic interactions that were used to understand measured β-decay lifetimes. We conclude that enhanced, concentrated β-decay strength for neutron-unbound states may be common for very neutron-rich nuclei. This leads to intense β-delayed high-energy neutron and strong multineutron emission probabilities that in turn affect astrophysical nucleosynthesis models. PMID:27610848

  5. Evidence for Gamow-Teller Decay of 78Ni Core from Beta-Delayed Neutron Emission Studies

    NASA Astrophysics Data System (ADS)

    Madurga, M.; Paulauskas, S. V.; Grzywacz, R.; Miller, D.; Bardayan, D. W.; Batchelder, J. C.; Brewer, N. T.; Cizewski, J. A.; Fijałkowska, A.; Gross, C. J.; Howard, M. E.; Ilyushkin, S. V.; Manning, B.; Matoš, M.; Mendez, A. J.; Miernik, K.; Padgett, S. W.; Peters, W. A.; Rasco, B. C.; Ratkiewicz, A.; Rykaczewski, K. P.; Stracener, D. W.; Wang, E. H.; Wolińska-Cichocka, M.; Zganjar, E. F.

    2016-08-01

    The β -delayed neutron emission of Ga,8483 isotopes was studied using the neutron time-of-flight technique. The measured neutron energy spectra showed emission from states at excitation energies high above the neutron separation energy and previously not observed in the β decay of midmass nuclei. The large decay strength deduced from the observed intense neutron emission is a signature of Gamow-Teller transformation. This observation was interpreted as evidence for allowed β decay to 78Ni core-excited states in Ge,8483 favored by shell effects. We developed shell model calculations in the proton f p g9 /2 and neutron extended f p g9 /2+d5 /2 valence space using realistic interactions that were used to understand measured β -decay lifetimes. We conclude that enhanced, concentrated β -decay strength for neutron-unbound states may be common for very neutron-rich nuclei. This leads to intense β -delayed high-energy neutron and strong multineutron emission probabilities that in turn affect astrophysical nucleosynthesis models.

  6. Neutron spin echo study of the dynamics of undercooled selenium

    NASA Astrophysics Data System (ADS)

    Simon, Ch.; Faivre, G.; Zorn, R.; Batallan, F.; Legrand, J. F.

    1992-03-01

    We present neutron spin echo measurements on the structural relaxation of undercooled liquid selenium above glass transition. We find a two-stage relaxation process essentially similar to that generally observed in liquids, except for the fact that the slow-stage characteristic time tau_1 varies with the temperature T more slowly than η(T)/T, where η(T) is the macroscopic viscosity. We interpret this apparent discrepancy with respect to the usually found scaling law as the manifestation of the equilibrium-polymer nature of liquid selenium. On the other hand, the data suggest that the Kohlrausch exponent of the slow stage is temperature dependent. Concerning the rapid stage of the relaxation, we show that a possible alternative to the mode-coupling interpretation is to attribute it to the existence of local inhomogeneities of the density close to the glass transition. Nous présentons des résultats de mesures au spectromètre à écho de spin sur la relaxation structurale du sélenium en surfusion près de la transition vitreuse. Nous trouvons une relaxation en deux étapes, essentiellement conforme à celle trouvée antérieurement dans d'autres liquides, à ceci près que le temps caractéristique tau_1 du stade lent varie avec la température T plus lentement que η(T)/T, où η(T) est la viscosité macroscopique. Nous interprétons cet écart apparent à la loi d'échelle généralement observée comme la manifestation du fait que le sélénium liquide est un polymère d'équilibre. L'analyse des données suggège d'autre part que l'exposant de Kohlrausch du stade lent dépend de la température. Quant au stade rapide de la relaxation, nous montrons qu'il peut être interprété, sans recourir à la théorie du couplage de modes, par l'existance d'hétérogénéités locales de la densité au voisinage de la transition vitreuse.

  7. Studies of Long Period Variability in Neutron Star HMXB Systems

    NASA Technical Reports Server (NTRS)

    Heindl, William A.

    1998-01-01

    The purpose of this effort was to investigate the long term, quasi-periodic variability of the X-ray emission from the accreting X-ray pulsars LMC X-4 and SMC X-1. These high mass X-ray binary (HMXB) sources are known to vary in a nearly periodic fashion with cycle lengths of about 30 and 60 days respectively. The prevailing model for such behavior is that it is due to the precession of a tilted accretion disk around the neutron star which is the source of the X-ray emission. As the disk precesses, it periodically obscures the emitting region, resulting in reduced flux as observed at the Earth. The obscuration is not strictly periodic, as the disk precession period changes as the total mass and size of the disk change through variable accretion processes. This model is well established for the long-period variability in the X-ray pulsar Her X-1. With this work, my collaborators and I sought to test whether this model works for LMC X-4 and SMC X-1. Observations with the pointed instruments on the Rossi X-ray Timing Explorer (RXTE) were carried out in order to observe changes in the X-ray spectrum and total flux which were correlated with the long period cycles in these objects. One of the main predictions of the precessing disk model is that the periods of low emission are caused not by changes in the central source, but by increased absorption of that flux as seen at the Earth. Such behavior would be observed in the X-ray spectrum as a relative lack of low energy X-rays (which are more easily absorbed) as compared to high energy X-rays. This is what was observed for SMC X-1, landing strong support to the precessing disk model for this system. For LMC X-1, however, the absorption was consistent with zero at the time of minimum flux. The entire spectrum appeared to be equally reduced. This is not supporting evidence for the model. However, it also does not rule out a precessing disk. If at the time of minimum flux, the intervening disk is so thick that no flux, even

  8. Phase separation and ordering process in Al-Li alloys studied by small-angle neutron scattering and neutron diffraction

    SciTech Connect

    Furusaka, M.; Fujikawa, S.I.; Tranquada, J.M.

    1993-07-01

    To study phase separation kinetics of Al-9.5at.%Li polycrystalline alloys in which precipitates have ordered Al{sub 3}Li ({delta}{prime}) structure, profile analysis of small-angle neutron scattering and superlattice reflections (100) and (110) were done. A small-angle scattering instrument and a triple-axis spectrometer in elastic mode were used in the measurements. Strong texture was observed in the reflections. Therefore, measurements were done using the crystal orientation where the intensity of the reflection was at the maximum. Profiles of small-angle scattering and superlattice reflections were almost identical at higher momentum transfer side. At lower momentum transfer side, small-angle scattering showed interference effects, but superlattice reflection did not show any sign of interference. Integrated intensities of superlattice reflections were obtained and compared with small-angle scattering intensity. The order parameter was not saturated in the {delta}{prime} precipitates at the early stage of the phase separation process.

  9. 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.

  10. 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; 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 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

  11. EPR study of new defects in neutron irradiated KS-4V and KU1 fused silica

    NASA Astrophysics Data System (ADS)

    Lagomacini, J. C.; Bravo, D.; Martín, P.; Ibarra, A.; Martín, A.; López, F. J.

    2010-11-01

    Electron paramagnetic resonance (EPR) studies have been carried out on high purity fused silica KS-4V (low OH content) and KU1 (high OH content), irradiated with fast neutrons (E > 0.1 MeV) at a high fluence of 1022 n/m2. The spectrum of irradiated samples shows various well-known types of paramagnetic defects, POR, NBOHC and E'. Their thermal stability has also been studied by heating the samples in air up to 775 °C. A detailed analysis of the spectra shows that the POR spectrum of neutron-irradiated KS-4V and KU1 has two contributions from centres POR(I) and POR(II), which show very different thermal annealing behaviour. POR(I) is identified with the POR centre previously reported, whereas POR(II) is associated to the effects of fast neutrons. Moreover, a new broad line centred at g = 2.02 is reported that we suggest could be associated to oxygen-hole centres in the neighbourhood of the high amount of tracks generated by ion displacement due to fast neutrons.

  12. High-resolution neutron crystallographic studies of the hydration of the coenzyme cob(II)alamin

    SciTech Connect

    Jogl, Gerwald; Wang, Xiaoping; Mason, Sax A.; Kovalevsky, Andrey; Mustyakimov, Marat; Fisher, Zöe; Hoffman, Christina; Kratky, Christoph; Langan, Paul

    2011-06-01

    High-resolution crystallographic studies of the hydration of the coenzyme cob(II)alamin have provided hydrogen-bond parameters of unprecedented accuracy for a biomacromolecule. The hydration of the coenzyme cob(II)alamin has been studied using high-resolution monochromatic neutron crystallographic data collected at room temperature to a resolution of 0.92 Å on the original D19 diffractometer with a prototype 4° × 64° detector at the high-flux reactor neutron source run by the Institute Laue–Langevin. The resulting structure provides hydrogen-bonding parameters for the hydration of biomacromolecules to unprecedented accuracy. These experimental parameters will be used to define more accurate force fields for biomacromolecular structure refinement. The presence of a hydrophobic bowl motif surrounded by flexible side chains with terminal functional groups may be significant for the efficient scavenging of ligands. The feasibility of extending the resolution of this structure to ultrahigh resolution was investigated by collecting time-of-flight neutron crystallographic data during commissioning of the TOPAZ diffractometer with a prototype array of 14 modular 2° × 21° detectors at the Spallation Neutron Source run by Oak Ridge National Laboratory.

  13. Sustaining knowledge in the neutron generator community and benchmarking study. Phase II.

    SciTech Connect

    Huff, Tameka B.; Stubblefield, William Anthony; Cole, Benjamin Holland, II; Baldonado, Esther

    2010-08-01

    This report documents the second phase of work under the Sustainable Knowledge Management (SKM) project for the Neutron Generator organization at Sandia National Laboratories. Previous work under this project is documented in SAND2008-1777, Sustaining Knowledge in the Neutron Generator Community and Benchmarking Study. Knowledge management (KM) systems are necessary to preserve critical knowledge within organizations. A successful KM program should focus on people and the process for sharing, capturing, and applying knowledge. The Neutron Generator organization is developing KM systems to ensure knowledge is not lost. A benchmarking study involving site visits to outside industry plus additional resource research was conducted during this phase of the SKM project. The findings presented in this report are recommendations for making an SKM program successful. The recommendations are activities that promote sharing, capturing, and applying knowledge. The benchmarking effort, including the site visits to Toyota and Halliburton, provided valuable information on how the SEA KM team could incorporate a KM solution for not just the neutron generators (NG) community but the entire laboratory. The laboratory needs a KM program that allows members of the workforce to access, share, analyze, manage, and apply knowledge. KM activities, such as communities of practice (COP) and sharing best practices, provide a solution towards creating an enabling environment for KM. As more and more people leave organizations through retirement and job transfer, the need to preserve knowledge is essential. Creating an environment for the effective use of knowledge is vital to achieving the laboratory's mission.

  14. Study on generating of thermal neutron scattering cross sections for LiH

    SciTech Connect

    Wang, L.; Jiang, X.; Zhao, Z.; Chen, L.

    2013-07-01

    LiH is designated as a promising moderator and shielding material because of its low density, high melting point and large fraction of H atoms. However, lack of the thermal neutron cross sections of LiH makes numerical calculation deviate from experimental data to some extent. As a result, it is necessary to study LiH thermal kernel effect. The phonon property of LiH has been investigated by first-principles calculations using the plane-wave pseudo potential method with CASTEP code. The scattering law and the thermal neutron scattering cross sections for Li and H have been generated using this distribution. The results have been compared with zirconium hydride data. The GASKET and NJOY/LEAPR codes have been used in the calculation of scattering law, whose results have been compared with the reference; the discrepancy mainly comes from phonon spectrums and its expansion. LEAPR had the capability to compute scattering through larger energy and momentum transfers than GASKET did. By studying LiH phonon spectrum and constructing the model of LiH thermal kernel and scattering matrix, the ACE format LiH thermal neutron cross sections for MCNP software could be made and used for reactor Neutronics calculation. (authors)

  15. Feasibility study of the neutron dose for real-time image-guided proton therapy: A Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Kim, Jin Sung; Shin, Jung Suk; Kim, Daehyun; Shin, Eunhyuk; Chung, Kwangzoo; Cho, Sungkoo; Ahn, Sung Hwan; Ju, Sanggyu; Chung, Yoonsun; Jung, Sang Hoon; Han, Youngyih

    2015-07-01

    Two full rotating gantries with different nozzles (multipurpose nozzle with MLC, scanning dedicated nozzle) for a conventional cyclotron system are installed and being commissioned for various proton treatment options at Samsung Medical Center in Korea. The purpose of this study is to use Monte Carlo simulation to investigate the neutron dose equivalent per therapeutic dose, H/D, for X-ray imaging equipment under various treatment conditions. At first, we investigated the H/D for various modifications of the beamline devices (scattering, scanning, multi-leaf collimator, aperture, compensator) at the isocenter and at 20, 40 and 60 cm distances from the isocenter, and we compared our results with those of other research groups. Next, we investigated the neutron dose at the X-ray equipment used for real-time imaging under various treatment conditions. Our investigation showed doses of 0.07 ~ 0.19 mSv/Gy at the X-ray imaging equipment, depending on the treatment option and interestingly, the 50% neutron dose reduction was observed due to multileaf collimator during proton scanning treatment with the multipurpose nozzle. In future studies, we plan to measure the neutron dose experimentally and to validate the simulation data for X-ray imaging equipment for use as an additional neutron dose reduction method.

  16. Subaru/HDS study of CH stars: elemental abundances for stellar neutron-capture process studies

    NASA Astrophysics Data System (ADS)

    Goswami, Aruna; Aoki, Wako; Karinkuzhi, Drisya

    2016-01-01

    A comprehensive abundance analysis providing rare insight into the chemical history of lead stars is still lacking. We present results from high-resolution (R ˜ 50 000) spectral analyses of three CH stars, HD 26, HD 198269 and HD 224959, and, a carbon star with a dusty envelope, HD 100764. Previous studies on these objects are limited by both resolution and wavelength regions and the results differ significantly from each other. We have undertaken to reanalyse the chemical composition of these objects based on high-resolution Subaru spectra covering the wavelength regions 4020-6775 Å. Considering local thermodynamic equilibrium and using model atmospheres, we have derived the stellar parameters, the effective temperatures Teff, surface gravities log g, and metallicities [Fe/H] for these objects. The derived parameters for HD 26, HD 100764, HD 198269 and HD 224959 are (5000, 1.6, -1.13), (4750, 2.0 -0.86), (4500, 1.5, -2.06) and (5050, 2.1, -2.44), respectively. The stars are found to exhibit large enhancements of heavy elements relative to iron in conformity to previous studies. Large enhancement of Pb with respect to iron is also confirmed. Updates on the elemental abundances for several s-process elements (Y, Zr, La, Ce, Nd, Sm and Pb) along with the first-time estimates of abundances for a number of other heavy elements (Sr, Ba, Pr, Eu, Er and W) are reported. Our analysis suggests that neutron-capture elements in HD 26 primarily originate in the s-process while the major contributions to the abundances of neutron-capture elements in the more metal-poor objects HD 224959 and HD 198269 are from the r-process, possibly from materials that are pre-enriched with products of the r-process.

  17. X-ray and neutron scattering studies of complex confined fluids.

    SciTech Connect

    Sinha, S. K.

    1999-08-04

    We review recent X-ray and neutron scattering studies of the structure and dynamics of confined complex fluids. This includes the study of polymer conformations and binary fluid phase transitions in porous media using Small Angle Neutron scattering, and the use of synchrotrons radiation to study ordering and fluctuation phenomena at solid/liquid and liquid/air interfaces. Ordering of liquids near a solid surface or in confinement will be discussed, and the study, via specular and off-specular X-ray reflectivity, of capillary wave fluctuations on liquid polymer films. Finally, we shall discuss the use of high-brilliance beams from X-ray synchrotrons to study via photon correlation spectroscopy the slow dynamics of soft condensed matter systems.

  18. Neutron reflectivity studies of single lipid bilayers supported on planar substrates

    SciTech Connect

    Krueger, S.; Orts, W.J.; Berk, N.F.; Majkrzak, C.F.; Koenig, B.W.

    1994-12-31

    Neutron reflectivity was used to probe the structure of single phosphatidylcholine (PC) lipid bilayers adsorbed onto a planar silicon surface in an aqueous environment. Fluctuations in the neutron scattering length density profiles perpendicular to the silicon/water interface were determined for different lipids as a function of the hydrocarbon chain length. The lipids were studied in both the gel and liquid crystalline phases by monitoring changes in the specularly-reflected neutron intensity as a function of temperature. Contrast variation of the neutron scattering length density was applied to both the lipid and the solvent. Scattering length density profiles were determined using both model-independent and model-dependent fitting methods. During the reflectivity measurements, a novel experimental set-up was implemented to decrease the incoherent background scattering due to the solvent. Thus, the reflectivity was measured to Q {approx} 0.3{Angstrom}{sup -1}, covering up to seven orders of magnitude in reflected intensity, for PC bilayers in D{sub 2}O and silicon-matched (38% D{sub 2}O/62% H{sub 2}O) water. The kinetics of lipid adsorption at the silicon/water interface were also explored by observing changes in the reflectivity at low Q values under silicon-matched water conditions.

  19. High-resolution neutron crystallographic studies of the hydration of the coenzyme cob(II)alamin.

    PubMed

    Jogl, Gerwald; Wang, Xiaoping; Mason, Sax A; Kovalevsky, Andrey; Mustyakimov, Marat; Fisher, Zöe; Hoffman, Christina; Kratky, Christoph; Langan, Paul

    2011-06-01

    The hydration of the coenzyme cob(II)alamin has been studied using high-resolution monochromatic neutron crystallographic data collected at room temperature to a resolution of 0.92 Å on the original D19 diffractometer with a prototype 4° × 64° detector at the high-flux reactor neutron source run by the Institute Laue-Langevin. The resulting structure provides hydrogen-bonding parameters for the hydration of biomacromolecules to unprecedented accuracy. These experimental parameters will be used to define more accurate force fields for biomacromolecular structure refinement. The presence of a hydrophobic bowl motif surrounded by flexible side chains with terminal functional groups may be significant for the efficient scavenging of ligands. The feasibility of extending the resolution of this structure to ultrahigh resolution was investigated by collecting time-of-flight neutron crystallographic data during commissioning of the TOPAZ diffractometer with a prototype array of 14 modular 2° × 21° detectors at the Spallation Neutron Source run by Oak Ridge National Laboratory.

  20. High resolution neutron crystallographic studies of the hydration of coenzyme cob(II)alamin

    SciTech Connect

    Jogl, Gerwald; Wang, Xiaoping; Mason, Sax; Kovalevsky, Andrey; Mustyakimov, Marat; Fisher, Zoe; Hoffmann, Christina; Kratky, Christoph; Langan, Paul

    2011-01-01

    The hydration of coenzyme cob(II)alamin has been studied using high resolution monochromatic neutron crystallographic data collected at room temperature to a resolution of surrounded by flexible side chains with terminal functional groups may be significant for 0.92 on the original diffractometer D19 with a prototype 4o x 64o detector at the high-flux reactor neutron source run by the Institute Laue Langevin. The resulting structure provides H bonding parameters for the hydration of biomacromolecules to unprecedented accuracy. These experimental parameters will be used to define more accurate force-fields for biomacromolecular structure refinement. The presence of a hydrophobic bowl motif efficient scavenging of ligands. The feasibility of extending the resolution of this structure to ultra high resolution was investigated by collecting time-of-flight neutron crystallographic data on diffractometer TOPAZ with a prototype array of 14 modular 21o x 21o detectors at the Spallation Neutron Source run by Oak Ridge National Laboratory.

  1. Inverse kinematics (p, n) reactions studies using the WINDS slow neutron detector and the SAMURAI spectrometer

    NASA Astrophysics Data System (ADS)

    Yasuda, J.; Sasano, M.; Zegers, R. G. T.; Baba, H.; Chao, W.; Dozono, M.; Fukuda, N.; Inabe, N.; Isobe, T.; Jhang, G.; Kameda, D.; Kubo, T.; Kurata-Nishimura, M.; Milman, E.; Motobayashi, T.; Otsu, H.; Panin, V.; Powell, W.; Sakai, H.; Sako, M.; Sato, H.; Shimizu, Y.; Stuhl, L.; Suzuki, H.; Tangwancharoen, S.; Takeda, H.; Uesaka, T.; Yoneda, K.; Zenihiro, J.; Kobayashi, T.; Sumikama, T.; Tako, T.; Nakamura, T.; Kondo, Y.; Togano, Y.; Shikata, M.; Tsubota, J.; Yako, K.; Shimoura, S.; Ota, S.; Kawase, S.; Kubota, Y.; Takaki, M.; Michimasa, S.; Kisamori, K.; Lee, C. S.; Tokieda, H.; Kobayashi, M.; Koyama, S.; Kobayashi, N.; Wakasa, T.; Sakaguchi, S.; Krasznahorkay, A.; Murakami, T.; Nakatsuka, N.; Kaneko, M.; Matsuda, Y.; Mucher, D.; Reichert, S.; Bazin, D.; Lee, J. W.

    2016-06-01

    We have combined the low-energy neutron detector WINDS (Wide-angle Inverse-kinematics Neutron Detectors for SHARAQ) and the SAMURAI spectrometer at RIKEN Nishina Center RI Beam Factory (RIBF) in order to perform (p, n) reactions in inverse kinematics for unstable nuclei in the mass region around A ∼ 100 . In this setup, WINDS is used for detecting recoil neutrons and the SAMURAI spectrometer is used for tagging decay channel of heavy residue. The first experiment by using the setup was performed to study Gamow-Teller transitions from 132Sn in April 2014. The atomic number Z and mass-to-charge ratio A / Q of the beam residues were determined from the measurements of time of flight, magnetic rigidity and energy loss. The obtained A / Q and Z resolutions were σA/Q = 0.14 % and σZ = 0.22 , respectively. Furthermore, owing to the large momentum acceptance (50 %) of SAMURAI, the beam residues associated with the γ , 1n and 2n decay channel were measured in the same magnetic field setting. The kinematic loci of the measured recoil neutron energy and laboratory angle are clearly seen. It shows that the excitation energy up to about 20 MeV can be reconstructed.

  2. Study on the impact of pair production interaction on D-T controllable neutron density logging.

    PubMed

    Yu, Huawei; Zhang, Li; Hou, Boran

    2016-05-01

    This paper considers the effect of pair production on the precision of D-T controllable neutron source density logging. Firstly, the principle of the traditional density logging and pulsed neutron density logging are analyzed and then gamma ray cross sections as a function of energy for various minerals are compared. In addition, the advantageous areas of Compton scattering and pair production interactions on high-energy gamma ray pulse height spectrum and the errors of a controllable source density measurement are studied using a Monte Carlo simulation method. The results indicate that density logging mainly utilizes the Compton scattering of gamma rays, while the attenuation of neutron induced gamma rays and the precision of neutron gamma density measurements are affected by pair production interactions, particularly in the gamma rays with energy higher than 2MeV. By selecting 0.2-2MeV energy range and performing proper lithology correction, the effect of pair production can be eliminated effectively and the density measurement error can be rendered close to the precision of chemical source density logging. PMID:26945102

  3. RTOG phase I study on fast neutron teletherapy for squamous cell carcinoma of the esophagus

    SciTech Connect

    Laramore, G.E.; Davis, R.B.; Olson, M.H.; Cohen, L.; Raghaven, V.; Griffin, T.W.; Rogers, C.C.; Al-Abdulla, A.S.M.; Gahbauer, R.A.; Davis, L.W.

    1983-04-01

    From August, 1977, though January, 1981, the Radiation Therapy Oncology Goup sponsored a Pase I study (RTOG 77-09) on the use of fast neutrons for treating inoperable squamous cell carcinomas of the esophagus. A total of 39 evaluable patients were treated with curative intent using either fast neutrons alone or in combination with low LET irradiation as part of a mixed beam fractionation scheme. Actuarial survival curves are presented for both the ''neutrons alone'' and the ''mixed beam'' treatment goups. There was no significant survival difference between these goups of patients. The projected survival at two years is less than 10%, which is comparable weth megavoltage photon results for an unselected series of patients. The size of the primary lesion and the initial Karnofsky performance status were found to be the most important prognostic indications for prolonged survival. Sixteen of 39 patients were felt to have achieved local clearance of their tumor at some time during their follow-up with the median time until a local recurrence being 17 months. Treatment related complications and patterns of metastatic spread are discussed. In general, it appeared that the response of large tumors to neutron irradiation resulted in necrosis and fistula formation. In many cases this was accompanied by persistent/ recurrent tumor within the high dose radiation volume.

  4. Study on the impact of pair production interaction on D-T controllable neutron density logging.

    PubMed

    Yu, Huawei; Zhang, Li; Hou, Boran

    2016-05-01

    This paper considers the effect of pair production on the precision of D-T controllable neutron source density logging. Firstly, the principle of the traditional density logging and pulsed neutron density logging are analyzed and then gamma ray cross sections as a function of energy for various minerals are compared. In addition, the advantageous areas of Compton scattering and pair production interactions on high-energy gamma ray pulse height spectrum and the errors of a controllable source density measurement are studied using a Monte Carlo simulation method. The results indicate that density logging mainly utilizes the Compton scattering of gamma rays, while the attenuation of neutron induced gamma rays and the precision of neutron gamma density measurements are affected by pair production interactions, particularly in the gamma rays with energy higher than 2MeV. By selecting 0.2-2MeV energy range and performing proper lithology correction, the effect of pair production can be eliminated effectively and the density measurement error can be rendered close to the precision of chemical source density logging.

  5. Neutron irradiation study of Nd-Fe-B permanent magnets made from melt-spun ribbons

    SciTech Connect

    Brown, R.D.; Cost, J.R.; Meisner, G.P.; Brewer, E.G.

    1988-01-01

    Radiation-induced changes in the magnetization of sintered Nd-Fe-B permanent magnets are known to vary widely among specimens produced by different manufacturers. Samples of Nd-Fe-B MAGNEQUENCH magnets, which are made from melt-spun ribbons, have now been studied and show a much reduced sensitivity to neutron irradiation than do sintered Nd-Fe-B magnets. All melt-spun ribbon-based MAGNEQUENCH magnets, i.e., epoxy-bonded, hot-pressed, and die-upset magnets, show essentially the same slow decrease in magnetic remanence with neutron dose. Measurements of the open-circuit remanence B/sub r//B/sub ro/ at various times during the irradiation show a decay of only 1.5% of the preirradiated value for the MAGNEQUENCH magnets after 1 hour of irradiation, or a dose of 1.4 /times/ 10/sup 16/ neutrons/cm/sup 2/, compared to a 4.6% drop in remanence for the best sintered Nd-Fe-B magnet (Sumitomo 3OH) with the same irradiation dose. Moreover, after 5.3 hours of irradiation, the remanence drops by only 3% for the MAGNEQUENCH magnets. Magnets made from melt-spun ribbons are thus the least sensitive to neutron irradiation so far measured for Nd-Fe-B permanent magnets, but are somewhat more sensitive than samarium-cobalt magnets. 12 refs., 1 fig.

  6. Fast-neutron spectroscopy studies using induced-proton tracks in PADC track detectors

    NASA Astrophysics Data System (ADS)

    El-Sersy, A. R.; Eman, S. A.

    2010-06-01

    In this work, a simple and adequate method for fast-neutron spectroscopy is proposed. This method was performed by free-in-air fast-neutron irradiation of CR-39 Nuclear Track Detectors (NTD) using an Am-Be source. Detectors were then chemically etched to remove few layers up to a thickness of 6.25 μm. By using an automatic image analyzer system for studying the registration of the induced-proton tracks in the NTD, the obtained data were analyzed via two tracks shapes. In the first one, the elliptical tracks were eliminated from the calculation and only the circular ones were considered in developing the response function. In the second method all registered tracks were considered and the corresponding response function was obtained. The rate of energy loss of the protons as a function of V[(d E/d X) - V] was calculated using the Monte Carlo simulation. The induced-proton energy was extracted from the corresponding d E/d X in NTD using a computer program based on the Bethe-Bloch function. The energy of the incident particles was up to few hundred MeV/nucleon. The energy of the interacting neutrons was then estimated by means of the extracted induced-proton energies and the scattering angle. It was found that the present resulting energy distribution of the fast-neutron spectrum from the Am-Be source was similar to that given in the literature where an average neutron energy of 4.6MeV was obtained.

  7. Inelastic Neutron Scattering Studies of the Dynamics of Glass-Forming Materials in Confinement

    NASA Astrophysics Data System (ADS)

    Zorn, Reiner

    2015-03-01

    The study of the dynamics of glass-forming liquids in nanoscopic confinement may contribute to the understanding of the glass transition. Especially, the question of a cooperativity length scale may be addressed. In this presentation, results obtained by inelastic neutron scattering are presented. The first experiments were done to study the α relaxation of glass-forming liquids and polymers in nanoporous silica. Neutron scattering is a suitable method to study such composite materials because the scattering of the liquid component can be emphasized by proper choice of isotopes. By combining time-of-flight spectroscopy and backscattering spectroscopy it is possible to cover the large dynamical range spanned by the dynamics of glass-forming materials. The experiments demonstrated a broadening of the spectrum of relaxation times with faster as well as slower components compared to the bulk. In later experiments `soft' confinement in a microemulsion was used to reduce surface effects. In this system a definite acceleration of the dynamics was observed. In all cases the glass-specific fast vibrational dynamics (boson peak) was also studied, revealing a characteristic confinement dependence which allows conclusions on its nature. Finally, studies were carried out on polymers by neutron spin echo spectroscopy with the aim of observing the confinement effect on polymer specific dynamics (Rouse motion). These studies showed that a comparatively simple model is able to explain the deviation from bulk behavior.

  8. Experimental study of neutron noise with criticality safety applications in mind

    SciTech Connect

    Barnett, C.S.

    1985-11-01

    A study has been conducted on the statistics of detected neutrons that leaked from four subcritical reflected, enriched-uranium assemblies, to explore the feasibility of developing a criticality warning system based on neutron noise analysis. Studies were conducted on three possible discriminators, i.e., three signatures that might be used to discriminate among assemblies of various multiplications. The noise analysis techniques studied performed well enough in deeply subcritical situations to deserve testing in an applications environment. They have a good chance of detecting changes in reactivity that are potentially dangerous. One can expect sharpest results when doing comparisons, i.e., when comparing two records, one taken in the past under circumstances known to be normal and one taken now to search for change.

  9. The performance of reflectometers at continuous wave and pulsed-neutron sources

    SciTech Connect

    Fritzsimmons, M.R.; Pynn, R.

    1995-12-01

    To quantify gains from time-of-flight (TOF) methods, identical reflectometers viewing a continuous wave (CW) neutron source and a variety of pulsed-neutron sources were simulated using a Monte Carlo technique. Reflectivity profiles obtained for a simple thin-film, reflecting,sample were nearly identical in all simulations, and models fitted to the simulated data yielded parameters (film thickness, surface roughness, and scattering length density) that were equally accurate and precise in all cases. The simulations confirm the power of the TOF method and demonstrate that the performance of pulsed sources for reflectometry does not scale simply as the inverse duty factor of the source. In the case of long-pulse sources, the simulations suggest that pulse tails have little effect on results obtained from specular reflectometry and that maximum brightness of the neutron source should be the primary design criterion.

  10. The NIST NBSR and Cold Neutron Research Facility

    SciTech Connect

    Rush, J.J.

    1994-12-31

    The 20 MW Neutron Beam Split-Core Reactor (NBSR) has nine radial thermal beam tubes, and a large, highly accessible (35cm) cold source serving an extensive network of eight guide tubes. In operation or under construction are twenty-five neutron beam instruments (20 for neutron scattering) and about a dozen other facilities for neutron trace analysis, dosimetry and irradiation. The 6 x 15cm cold neutron guides are coated with {sup 58}Ni, and the last three being installed this fall are coated top and bottom with supermirrors for further increases in intensity. The new semi-spherical liquid hydrogen source will be described, along with the eight scattering instruments (reflectometry, SANS and high-resolution spectroscopy) which have, or will have, an extensive use in biological research. These instruments will likely provide the best overall capability in the U.S. for the next decade for a number of applications in biomolecular structure and dynamics.

  11. Optimization of the FM-CW reflectometry W-band antenna for core density profile measurements on ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Hacquin, S.; Wagner, D.; Manso, M.; Borreicho, J.; Farinha, L.

    2003-03-01

    A numerical study of the focused hog-horn antenna used for the W-band channel of the ASDEX Upgrade frequency modulated continuous wave reflectometry system is performed here. A mode matching code is used to accuretely model wave propagation in waveguide and antenna structures. Then the field distribution (amplitude and phase) in the horn aperture given by this code is used as an input for other codes computing wave propagation in the plasma. Evaluating the received energy in the antenna, we first analyze plasma effects as the nonalignment between the antenna and the plasma equatorial plane. We show in the case of an unfocused antenna that ray-tracing results are in qualitative agreement with full wave calculations. Simulations also confirm that hog-horn antennas allow improving the measurement performances in comparison with unfocused antennas. The role of location of the focusing point of a hog-horn antenna (depending on the antenna design) is then studied. It appears that the focusing point position should be optimized to maximize the energy received in the antenna. Finally, we show that a new design for the W-band antenna on the ASDEX Upgrade broadband reflectometry system could improve the performances of this diagnostic.

  12. Macular Pigment Optical Density in Chinese Primary Open Angle Glaucoma Using the One-Wavelength Reflectometry Method

    PubMed Central

    Ji, Yuying; Zuo, Chengguo; Lin, Mingkai; Zhang, Xiongze; Li, Miaoling; Mi, Lan; Liu, Bing; Wen, Feng

    2016-01-01

    Purpose. To investigate macular pigment optical density (MPOD) and its relationship with retinal thickness in primary open angle glaucoma (POAG) patients using the one-wavelength reflectometry method. Methods. A total of 30 eyes from 30 POAG patients (18 males and 12 females, mean age 47.27 ± 16.93) and 52 eyes from 52 controls (27 males and 25 females, mean age 49.54 ± 19.15) were included in this prospective, observational, case-control study. MPOD was measured in a 7-degree area using one-wavelength reflectometry method. Two parameters, max and mean optical density (OD), were used for analyses. Spectral-domain-optical coherence tomography was used to measure retinal thickness, including central retinal thickness (CRT), the macular ganglion cell complex (GCC), and the circumpapillary retinal nerve fiber layer (RNFL). Results. Both maxOD and meanOD were significantly reduced in POAG patients compared with normal subjects (P < 0.001). GCC, CRT, and RNFL thicknesses were also significantly reduced in POAG patients (P < 0.001). GCC thickness had a positive relationship with MPOD. Conclusions. MPOD within the 7-degree area was significantly lower in Chinese POAG patients than in control subjects, and GCC thickness was significantly and positively associated with MPOD. Whether the observed lower MPOD in POAG contributes to the disease process or is secondary to pathological changes caused by the disease (such as loss of ganglion cells) warrants further and longitudinal study. PMID:27144013

  13. Macular Pigment Optical Density in Chinese Primary Open Angle Glaucoma Using the One-Wavelength Reflectometry Method.

    PubMed

    Ji, Yuying; Zuo, Chengguo; Lin, Mingkai; Zhang, Xiongze; Li, Miaoling; Mi, Lan; Liu, Bing; Wen, Feng

    2016-01-01

    Purpose. To investigate macular pigment optical density (MPOD) and its relationship with retinal thickness in primary open angle glaucoma (POAG) patients using the one-wavelength reflectometry method. Methods. A total of 30 eyes from 30 POAG patients (18 males and 12 females, mean age 47.27 ± 16.93) and 52 eyes from 52 controls (27 males and 25 females, mean age 49.54 ± 19.15) were included in this prospective, observational, case-control study. MPOD was measured in a 7-degree area using one-wavelength reflectometry method. Two parameters, max and mean optical density (OD), were used for analyses. Spectral-domain-optical coherence tomography was used to measure retinal thickness, including central retinal thickness (CRT), the macular ganglion cell complex (GCC), and the circumpapillary retinal nerve fiber layer (RNFL). Results. Both maxOD and meanOD were significantly reduced in POAG patients compared with normal subjects (P < 0.001). GCC, CRT, and RNFL thicknesses were also significantly reduced in POAG patients (P < 0.001). GCC thickness had a positive relationship with MPOD. Conclusions. MPOD within the 7-degree area was significantly lower in Chinese POAG patients than in control subjects, and GCC thickness was significantly and positively associated with MPOD. Whether the observed lower MPOD in POAG contributes to the disease process or is secondary to pathological changes caused by the disease (such as loss of ganglion cells) warrants further and longitudinal study. PMID:27144013

  14. Diurnally Varying Hydrogen Volatiles or Regolith Temperature? Mare and Highlands Studies of the Moon's Diurnally Modulating Epithermal Neutron Flux Using LRO's LEND, Diviner, and LOLA Instruments

    NASA Astrophysics Data System (ADS)

    McClanahan, T. P.; LEND Team; Parsons, A. M.; Williams, J. P.; Mazarico, E.

    2015-10-01

    In this study we seek to discriminate the source of variation that is diurnally modulating the Moon's neutron emission flux. We characterize the neutron emission flux from the topography in the northern mare and highlands regions.

  15. Body composition to climate change studies - the many facets of neutron induced prompt gamma-ray analysis

    SciTech Connect

    Mitra,S.

    2008-11-17

    In-vivo body composition analysis of humans and animals and in-situ analysis of soil using fast neutron inelastic scattering and thermal neutron capture induced prompt-gamma rays have been described. By measuring carbon (C), nitrogen (N) and oxygen (O), protein, fat and water are determined. C determination in soil has become important for understanding below ground carbon sequestration process in the light of climate change studies. Various neutron sources ranging from radio isotopic to compact 14 MeV neutron generators employing the associated particle neutron time-of-flight technique or micro-second pulsing were implemented. Gamma spectroscopy using recently developed digital multi-channel analyzers has also been described.

  16. Studies on osteoporosis. V. Comparison of methods of evaluation of osteoporosis and study of chromosome changes induced by neutron activation

    SciTech Connect

    Robin, J.C.; Sirianni, S.R.; Pragay, D.A.; Ambrus, J.L.

    1981-01-01

    In vivo activation analysis was compared with ashing and atomic absorption spectrophotometry for the determination of total skeletal calcium content in mice. The results were close to identical. The possible mutagenic-carcinogenic effect of repeated exposure to whole body neutron irradiation was studied by chromosome analysis. Under the conditions of these experiments, no significant chromosome changes were seen.

  17. Curvature effect in grazing X-ray reflectometry

    NASA Astrophysics Data System (ADS)

    Bridou, F.

    1994-09-01

    Grazing X-ray reflectometry is currently used for the characterization of thin layer stacks. The parameters to be determined are thickness, roughness, and optical index. They can be worked out by fitting the recorded reflectivity curve, with a theoretical one calculated with the appropriate parameters. In such a calculation, the sample is supposed to be flat. It can be shown experimentally that the curvature of the sample modifies the expected reflectivity. An example of a saddle shaped sample, with opposite main curvature in two perpendicular directions shows typical differences on recorded curves for these two perpendicular directions. In order to make a quantitative study of the effect of the sample curvature, five pairs of spherical silica substrates have been made and coated with similar TiN layers. A theoretical study has also been made. It is shown that, for a given set-up, the sample curvature changes the aperture of the reflected beam with respect to that of the incident beam. At grazing incidence, the aperture change is significant in the incidence plane, while it can be neglected in the plane perpendicular to the incidence plane. As a consequence of the aperture change, the recorded intensity can be increased or decreased, depending on the position of the source image with respect to the position and width of the stop aperture in the image space. A calculation has been made, taking into account the geometrical characteristics of the equipment. The results have been compared with the reflectivity curves measured for the TiN layers deposited on the curved silica substrates. It can be seen that the anomalies in the reflectivity curves, induced by the substrate curvature in the plateau region are well accounted for by the model. La réflectométrie en X rasants est utilisée couramment pour la caractérisation d'empilements de couches minces. Les paramètres á déterminer sont : épaisseurs, rugosités et indices. On peut y accéder en ajustant la courbe

  18. Understanding the Internal Structure of Layered Organic Compounds deposited on mineral surface using Neutron Reflectivity

    NASA Astrophysics Data System (ADS)

    Ambaye, Haile; Jagadamma, Sindhu; Petridis, Loukas; Mayes, Melanie; Lauter, Valeria

    2013-03-01

    Organic carbon (OC) stabilization in soils plays a significant role in the global C cycle, therefore the understanding of the structure and function of the OC-soil mineral interface is of high importance. To study the internal structure, films with different combination of simple OC compounds, natural organic matter (NOM), Bi-layers of SA (Stearic Acid) on Glucose and NOM/Hydrophilic-NOM/Hydrophobic-NOM were deposited onto sapphire using spin coating. The phobic and phylic fractions of the NOM are operationally separated by exchange resins. We obtained detailed structural depth profile of the films using the depth-sensitive technique of the neutron reflectometry. The neutron reflectivity data were collected at the MAGICS Reflectometer at Spallation Neutron Source at the ORNL. Self-assembled ordering of SA in a repeating bi-layer structure was observed when it was deposited on NOM, phylic-NOM and Glucose. However, when SA was added to phobic-NOM no ordering of SA was detected. The formation of distinct, immiscible layers is due to insolubility of SA with NOM/Hydrophilic-NOM and Glucose. Our results reveal that the OC-mineral interface form complex layering and that the sequence of the layering depends on the compounds. The work was supported by ORNL (LDRD), BES and DOE.

  19. Studies of neutron and proton nuclear activation in low-Earth orbit

    NASA Technical Reports Server (NTRS)

    Laird, C. E.

    1982-01-01

    The expected induced radioactivity of experimental material in low Earth orbit was studied for characteristics of activating particles such as cosmic rays, high energy Earth albedo neutrons, trapped protons, and secondary protons and neutrons. The activation cross sections for the production of long lived radioisotopes and other existing nuclear data appropriate to the study of these reactions were compiled. Computer codes which are required to calculate the expected activation of orbited materials were developed. The decreased computer code used to predict the activation of trapped protons of materials placed in the expected orbits of LDEF and Spacelab II. Techniques for unfolding the fluxes of activating particles from the measured activation of orbited materials are examined.

  20. Effects of Pressure on Stability of Biomolecules in Solutions Studied by Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Bellissent-Funel, Marie-Claire-; Appavou, Marie-Sousai; Gibrat, Gabriel

    Studies of the pressure dependence on protein structure and dynamics contribute not only to the basic knowledge of biological molecules but have also a considerable relevance in full technology, like in food sterilization and pharmacy. Conformational changes induced by pressure as well as the effects on the protein stability have been mostly studied by optical techniques (optical absorption, fluorescence, phosphorescence), and by NMR. Most optical techniques used so far give information related to the local nature of the used probe (fluorescent or phosphorescent tryptophan). Small angle neutron scattering and quasi-elastic neutron scattering provide essential complementary information to the optical data, giving quantitative data on change of conformation of soluble globular proteins such as bovine pancreatic trypsin inhibitor (BPTI) and on the mobility of protons belonging to the protein surface residues.

  1. Study of the defects in oxygen implanted silicon subjected to neutron irradiation and high pressure annealing

    NASA Astrophysics Data System (ADS)

    Jung, W.; Kaniewska, M.; Misiuk, A.; Londos, C. A.

    2004-07-01

    This paper reports on capacitance measurements on Czochralski-grown and float-zone silicon subjected to oxygen implantation, subsequent neutron irradiation and finally high pressure thermal anneals. The purpose of this work was the study of the effect of irradiation on the formation of thermal donors in silicon. The observed changes in the C-V characteristic curves and profiles are discussed. We found that oxygen-ion implantation followed by neutron irradiation results in shallow and deep level acceptor-like defects formation. Prolonged heat treatment leads to thermal donor generation as usual in Cz-Si annealed at 450°C. The most striking result of the study is finding that high pressure thermal anneals result in extra donor formation. The effects mentioned above may lead to changes in the type of conductivity depending on oxygen content in the material, hydrostatic pressure and an extent of damage caused by the irradiation.

  2. Hydrogen species motion in piezoelectrics: A quasi-elastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Alvine, K. J.; Tyagi, M.; Brown, C. M.; Udovic, T. J.; Jenkins, T.; Pitman, S. G.

    2012-03-01

    Hydrogen is known to damage or degrade piezoelectric materials, at low pressure for ferroelectric random access memory applications, and at high pressure for hydrogen-powered vehicle applications. The piezoelectric degradation is in part governed by the motion of hydrogen species within the piezoelectric materials. We present here quasi-elastic neutron scattering (QENS) measurements of the local hydrogen species motion within lead zirconate titanate (PZT) and barium titanate (BTO) on samples charged by exposure to high-pressure gaseous hydrogen (≈17 MPa). Neutron vibrational spectroscopy (NVS) studies of the hydrogen-enhanced vibrational modes are presented as well. Results are discussed in the context of theoretically predicted interstitial hydrogen lattice sites and compared to comparable bulk diffusion studies of hydrogen diffusion in lead zirconate titanate.

  3. Modeling and Simulation Optimization and Feasibility Studies for the Neutron Detection without Helium-3 Project

    SciTech Connect

    Ely, James H.; Siciliano, Edward R.; Swinhoe, Martyn T.; Lintereur, Azaree T.

    2013-01-01

    This report details the results of the modeling and simulation work accomplished for the ‘Neutron Detection without Helium-3’ project during the 2011 and 2012 fiscal years. The primary focus of the project is to investigate commercially available technologies that might be used in safeguards applications in the relatively near term. Other technologies that are being developed may be more applicable in the future, but are outside the scope of this study.

  4. Structure of Light Neutron-rich Nuclei Studied with Transfer Reactions

    SciTech Connect

    Wuosmaa, A. H.

    2015-01-01

    Transfer reactions have been used for many years to understand the shell structure of nuclei. Recent studies with rare-isotope beams extend this work and make it possible to probe the evolution of shell structure far beyond the valley of stability, requiring measurements in inverse kinematics. We present a novel technical approach to measurements in inverse kinematics, and apply this method to different transfer reactions, each of which probes different properties of light, neutron-rich nuclei.

  5. Neutron scattering studies of non-Fermi liquid behavior in Ce compounds

    NASA Astrophysics Data System (ADS)

    Park, J.-G.; Adroja, D. T.; McEwen, K. A.; Murani, A. P.; So, J.-Y.; Beirne, E.; Echizen, Y.; Takabatake, T.

    2002-03-01

    We have studied the inelastic neutron scattering from two Ce heavy fermion compounds, Ce(Ni0.935Cu0.065)Sn and Ce(Rh0.8Pd0.2)Sb, that are located at the magnetic-non-magnetic boundary. We find that the magnetic scattering follows a power law scaling behavior, and that the dynamical susceptibility, as deduced from the magnetic scattering, shows E/T scaling behavior with significantly different exponents for the two systems.

  6. Structure and dynamics of cadmium telluride studied by x-ray and inelastic neutron scattering

    SciTech Connect

    Niedziela, Jennifer L; Stone, Matthew B

    2014-01-01

    We present a combined study of density functional theory, x-ray diffraction, and inelastic neutron scattering examining the temperature dependent structure and lattice dynamics of commercially available cadmium telluride. A subtle change in the structure is evinced near 80~K, which manifests also in the measured phonon density of states. There is no change to the long-range ordered structure. The implications of the change in relation to structural defects are discussed.

  7. Structure and dynamics of cadmium telluride studied by x-ray and inelastic neutron scattering

    SciTech Connect

    Niedziela, J. L.; Stone, M. B.

    2014-09-08

    We present a combined study of density functional theory, x-ray diffraction, and inelastic neutron scattering examining the temperature dependent structure and lattice dynamics of commercially available cadmium telluride. A subtle change in the structure is evinced near 80 K, which manifests also in the measured phonon density of states. There is no change to the long-range ordered structure. The implications of the change in relation to structural defects are discussed.

  8. Anomalous vibrational modes in acetanilide as studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Barthes, Mariette; Eckert, Juegen; Johnson, Susanna W.; Moret, Jacques; Swanson, Basil I.; Unkefer, Clifford J.

    1992-10-01

    A study of the anomalous modes in acetanilide and five deuterated derivatives by incoherent inelastic neutron scattering is reported. These data show that the dynamics of the amide and methyl groups influence each other. In addition, the anomalous temperature behaviour of the NH out-of-plane bending mode is confirmed. These observations suggest that the self-trapping mechanism in ACN may be more complex than hitherto assumed.

  9. Study of astrophysical ({alpha}, n) reactions using light-neutron rich radioactive nuclear beams

    SciTech Connect

    Ishiyama, Hironobu; Watanabe, Yutaka; Imai, Nobuaki; Hirayama, Yoshikazu; Miyatake, Hiroari; Tanaka, Masa-Hiko; Yoshikawa, Nobuharu; Jeong, Sunchan; Fuchi, Yoshihide; Katayama, Ichiro; Nomura, Toru; Ishikawa, Tomoko; Das, Suranjan K.; Mizoi, Yutaka; Fukuda, Tomokazu; Hashimoto, Takashi; Nishio, Katsuhisa; Mitsuoka, Shinichi; Ikezoe, Hiroshi; Matsuda, Makoto

    2006-07-12

    A systematic study of astrophysical reaction rates of ({alpha}, n) reactions on light neutron-rich nuclei using low-energy radioactive nuclear beams is in progress at the tandem facility of Japan Atomic Energy Agency. Exclusive measurements of 8Li({alpha}, n)11B and 12B({alpha}, n)15N reaction cross sections have been performed successfully. Their excitation functions together with the experimental method are presented.

  10. Microdosimetric study for secondary neutrons in phantom produced by a 290 MeV/nucleon carbon beam.

    PubMed

    Endo, Satoru; Tanaka, Kenichi; Takada, Masashi; Onizuka, Yoshihiko; Miyahara, Nobuyuki; Sato, Tatsuhiko; Ishikawa, Masayori; Maeda, Naoko; Hayabuchi, Naofumi; Shizuma, Kiyoshi; Hoshi, Masaharu

    2007-09-01

    Absorbed doses from main charged-particle beams and charged-particle fragments have been measured with high accuracy for particle therapy, but there are few reports for doses from neutron components produced as fragments. This study describes the measurements on neutron doses produced by carbon beams; microdosimetric distributions of secondary neutrons produced by 290 MeV/nucleon carbon beams have been measured by using a tissue equivalent proportional counter at the Heavy Ion Medical Accelerator in Chiba, Japan at the National Institute of Radiological Sciences. The microdosimetric distributions of the secondary neutron were measured on the distal and lateral faces of a body-simulated acrylic phantom (300 mm height x 300 mm width x 253 mm thickness). To confirm the dose measurements, the neutron energy spectra produced by incident carbon beams in the acrylic phantom were simulated by the particle and heavy ion transport code system. The absorbed doses obtained by multiplying the simulated neutron energy spectra with the kerma factor calculated by MCNPX agree with the corresponding experimental data fairly well. Downstream of the Bragg peak, the ratio of the neutron dose to the carbon dose at the Bragg peak was found to be a maximum of 1.4 x 10(-4) and the ratio of neutron dose was a maximum of 3.0 x 10(-7) at a lateral face of the acrylic phantom. The ratios of neutrons to charged particle fragments were 11% to 89% in the absorbed doses at the lateral and the distal faces of the acrylic phantom. We can conclude that the treatment dose will not induce serious secondary neutron effects at distances greater than 90 mm from the Bragg peak in carbon particle therapy.

  11. Microdosimetric study for secondary neutrons in phantom produced by a 290 MeV/nucleon carbon beam

    SciTech Connect

    Endo, Satoru; Tanaka, Kenichi; Takada, Masashi; Onizuka, Yoshihiko; Miyahara, Nobuyuki; Sato, Tatsuhiko; Ishikawa, Masayori; Maeda, Naoko; Hayabuchi, Naofumi; Shizuma, Kiyoshi; Hoshi, Masaharu

    2007-09-15

    Absorbed doses from main charged-particle beams and charged-particle fragments have been measured with high accuracy for particle therapy, but there are few reports for doses from neutron components produced as fragments. This study describes the measurements on neutron doses produced by carbon beams; microdosimetric distributions of secondary neutrons produced by 290 MeV/nucleon carbon beams have been measured by using a tissue equivalent proportional counter at the Heavy Ion Medical Accelerator in Chiba, Japan at the National Institute of Radiological Sciences. The microdosimetric distributions of the secondary neutron were measured on the distal and lateral faces of a body-simulated acrylic phantom (300 mm heightx300 mm widthx253 mm thickness). To confirm the dose measurements, the neutron energy spectra produced by incident carbon beams in the acrylic phantom were simulated by the particle and heavy ion transport code system. The absorbed doses obtained by multiplying the simulated neutron energy spectra with the kerma factor calculated by MCNPX agree with the corresponding experimental data fairly well. Downstream of the Bragg peak, the ratio of the neutron dose to the carbon dose at the Bragg peak was found to be a maximum of 1.4x10{sup -4} and the ratio of neutron dose was a maximum of 3.0x10{sup -7} at a lateral face of the acrylic phantom. The ratios of neutrons to charged particle fragments were 11% to 89% in the absorbed doses at the lateral and the distal faces of the acrylic phantom. We can conclude that the treatment dose will not induce serious secondary neutron effects at distances greater than 90 mm from the Bragg peak in carbon particle therapy.

  12. Studying Phobos subsurface structure elementary composition by neutron and gamma-rays spectrometers "NS HEND" from "Phobos-Grunt" mission.

    NASA Astrophysics Data System (ADS)

    Kozyrev, S. Alexander; Litvak, Maxim; Malakhov, Alexey; Mokrousov, Maxim; Mitrofanov, Igor; Sanin, Anton; Schulz, Rita; Shvetsov, Valery; Rogozhin, Alexander; Timoshenko, Genagy; Tretyakov, Vladislav; Vostrukhin, Andrey

    The Neutron Spectrometer HEND (NS HEND) has been proposed for studying elemental com-position of Phobos (the Mars's moon) regolith by "Phobos-Grunt" mission. NS HEND have been selected by the Federal Space Agency of Russia for the Lander of the "Phobos-Grunt" mission scheduled for launch in 2011. The shallow subsurface of Phobos might be studied by observations of induced nuclear gamma-ray lines and neutron emission. Secondary gamma-rays and neutrons are produced by energetic Galactic Cosmic Rays within 1-2 meter layer of subsur-face. The knowledge of the spectral density of neutrons in addition to measurements of nuclear gamma lines allows to deconvolve concentrations of soil-constituting elements. That is why nuclear instruments include both the segment for detection of gamma ray lines and segment of neutron spectrometer for the measurement of the neutron leakage spectra. Moreover, mea-surements of neutrons at 2.2 MeV line will also allow to study the content of hydrogen within subsurface layer about 1 meter deep. This instrument, will be able to provide observational data for composition of Phobos regolith and content of natural radioactive elements K, U and Th, and also for content of hydrogen or water ice in the Phobos subsurface. At present, the flight units of NS HEND instrument is manufactured, tested and current go through physical calibration.

  13. Lithiation of Crystalline Silicon As Analyzed by Operando Neutron Reflectivity.

    PubMed

    Seidlhofer, Beatrix-Kamelia; Jerliu, Bujar; Trapp, Marcus; Hüger, Erwin; Risse, Sebastian; Cubitt, Robert; Schmidt, Harald; Steitz, Roland; Ballauff, Matthias

    2016-08-23

    We present an operando neutron reflectometry study on the electrochemical incorporation of lithium into crystalline silicon for battery applications. Neutron reflectivity is measured from the ⟨100⟩ surface of a silicon single crystal which is used as a negative electrode in an electrochemical cell. The strong scattering contrast between Si and Li due to the negative scattering length of Li leads to a precise depth profile of Li within the Si anode as a function of time. The operando cell can be used to study the uptake and the release of Li over several cycles. Lithiation starts with the formation of a lithium enrichment zone during the first charge step. The uptake of Li can be divided into a highly lithiated zone at the surface (skin region) (x ∼ 2.5 in LixSi) and a much less lithiated zone deep into the crystal (growth region) (x ∼ 0.1 in LixSi). The total depth of penetration was less than 100 nm in all experiments. The thickness of the highly lithiated zone is the same for the first and second cycle, whereas the thickness of the less lithiated zone is larger for the second lithiation. A surface layer of lithium (x ∼ 1.1) remains in the silicon electrode after delithiation. Moreover, a solid electrolyte interface is formed and dissolved during the entire cycling. The operando analysis presented here demonstrates that neutron reflectivity allows the tracking of the kinetics of lithiation and delithiation of silicon with high spatial and temporal resolution.

  14. Lithiation of Crystalline Silicon As Analyzed by Operando Neutron Reflectivity.

    PubMed

    Seidlhofer, Beatrix-Kamelia; Jerliu, Bujar; Trapp, Marcus; Hüger, Erwin; Risse, Sebastian; Cubitt, Robert; Schmidt, Harald; Steitz, Roland; Ballauff, Matthias

    2016-08-23

    We present an operando neutron reflectometry study on the electrochemical incorporation of lithium into crystalline silicon for battery applications. Neutron reflectivity is measured from the ⟨100⟩ surface of a silicon single crystal which is used as a negative electrode in an electrochemical cell. The strong scattering contrast between Si and Li due to the negative scattering length of Li leads to a precise depth profile of Li within the Si anode as a function of time. The operando cell can be used to study the uptake and the release of Li over several cycles. Lithiation starts with the formation of a lithium enrichment zone during the first charge step. The uptake of Li can be divided into a highly lithiated zone at the surface (skin region) (x ∼ 2.5 in LixSi) and a much less lithiated zone deep into the crystal (growth region) (x ∼ 0.1 in LixSi). The total depth of penetration was less than 100 nm in all experiments. The thickness of the highly lithiated zone is the same for the first and second cycle, whereas the thickness of the less lithiated zone is larger for the second lithiation. A surface layer of lithium (x ∼ 1.1) remains in the silicon electrode after delithiation. Moreover, a solid electrolyte interface is formed and dissolved during the entire cycling. The operando analysis presented here demonstrates that neutron reflectivity allows the tracking of the kinetics of lithiation and delithiation of silicon with high spatial and temporal resolution. PMID:27447734

  15. Neutron study of B 12 coenzyme at 15 K

    NASA Astrophysics Data System (ADS)

    Bouquiere, J. P.

    1992-06-01

    This high resolution and low temperature study, at 15 K, of the vitamin B 12 coenzyme ( C72H100N18O17PCo) was undertaken to confirm and clarify the water networks identified at 279 K by Savage [1]. Details of the data collection and refinement of the low temperature structure are described, a comparison of the coenzyme molecule structures at 15 and 279 K is made, and that of solvent structures outlined.

  16. A study on fast digital discrimination of neutron and gamma-ray for improvement neutron emission profile measurement

    SciTech Connect

    Uchida, Y. Takada, E.; Fujisaki, A.; Isobe, M.; Ogawa, K.; Shinohara, K.; Tomita, H.; Kawarabayashi, J.; Iguchi, T.

    2014-11-15

    Neutron and γ-ray (n-γ) discrimination with a digital signal processing system has been used to measure the neutron emission profile in magnetic confinement fusion devices. However, a sampling rate must be set low to extend the measurement time because the memory storage is limited. Time jitter decreases a discrimination quality due to a low sampling rate. As described in this paper, a new charge comparison method was developed. Furthermore, automatic n-γ discrimination method was examined using a probabilistic approach. Analysis results were investigated using the figure of merit. Results show that the discrimination quality was improved. Automatic discrimination was applied using the EM algorithm and k-means algorithm.

  17. A study on fast digital discrimination of neutron and gamma-ray for improvement neutron emission profile measurementa)

    PubMed Central

    Uchida, Y.; Takada, E.; Fujisaki, A.; Isobe, M.; Shinohara, K.; Tomita, H.; Kawarabayashi, J.; Iguchi, T.

    2014-01-01

    Neutron and γ-ray (n-γ) discrimination with a digital signal processing system has been used to measure the neutron emission profile in magnetic confinement fusion devices. However, a sampling rate must be set low to extend the measurement time because the memory storage is limited. Time jitter decreases a discrimination quality due to a low sampling rate. As described in this paper, a new charge comparison method was developed. Furthermore, automatic n-γ discrimination method was examined using a probabilistic approach. Analysis results were investigated using the figure of merit. Results show that the discrimination quality was improved. Automatic discrimination was applied using the EM algorithm and k-means algorithm. PMID:25430297

  18. Scissors Mode of 162 Dy Studied from Resonance Neutron Capture

    SciTech Connect

    Baramsai, B.; Bečvář, F.; Bredeweg, T. A.; Haight, R. C.; Jandel, M.; Kroll, J.; Krtička, M.; Mitchell, G. E.; O’Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Wilhelmy, J. B.

    2015-05-28

    Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from 3He-induced reactions, (n,γ) experiments on Gd isotopes, and (γ,γ’) reactions.

  19. Molecular motion of ferrocene in a faujasite-type zeolite: A quasielastic neutron scattering study

    SciTech Connect

    Kemner, E.; Schepper, I.M. de; Schmets, A.J.M.; Grimm, H.; Overweg, A.R.; Santen, R.A. van

    2000-02-24

    The authors study the molecular motion of ferrocene Fe(C{sub 5}H{sub 5}){sub 2} locked up in the supercages of KY zeolite at temperatures 22 K {le} T {le} 238 K by means of quasielastic neutron scattering. The geometry of the motion is determined to be a 5-fold internal jump reorientation of the cyclopentadienyl C{sub 5}H{sub 5} rings around the symmetry axis of the ferrocene molecule. The mean residence time was obtained for these jumps as well as the activation energy for the process. A comparison was made of NMR results on ferrocene in faujasite-type zeolites and quasielastic neutron scattering results on pure ferrocene.

  20. Neutron diffraction study of a nitrogen martensitic steel 0Kh16N4AB under load

    NASA Astrophysics Data System (ADS)

    Sumin, V. V.; Papushkin, I. V.; Bannykh, O. A.; Blinov, V. M.; Lukáš, P.

    2008-01-01

    An austenitic-martensitic nitrogen steel 0Kh16N4AB has been studied under load using high-resolution neutron diffraction analysis on an FSD neutron diffractometer at an IBR-2 reactor (Dubna) and on a diffractometer with a focusing monochromator on a reactor of the Nuclear Physics Institute (Czech Republic). Young's moduli calculated from different reflections of the martensite and austenite phases have been obtained. It has been found that the yield strength σ0.2 corresponding to the slip plane (111) of the austenite phase is anomalously low and that with increasing degree of uniaxial tension the width of lines (111)γ strongly grows. In the steel under consideration the plane (111) of the austenite phase appears to be an easy-slip plane that ensures the enhanced properties of the steel, i.e., the combination of a high ultimate strength (1600 MPa) with a high plasticity (δ = 16%).

  1. The Minor Actinide Transmutation-Incineration Potential Studies in High Intensity Neutron Fluxes

    SciTech Connect

    Letourneau, A.; Chabod, S.; Foucher, Y.; Marie, F.; Ridikas, D.; Veyssiere, Ch.; Blandin, Ch.

    2005-05-24

    In the framework of nuclear waste transmutation studies, the Mini-INCA project has been initiated at CEA/DSM with objectives to determine optimal conditions for transmutation and incineration of Minor Actinides (MA) in high intensity neutron fluxes. Our experimental tools based on alpha- and gamma-spectroscopy of irradiated samples and the development of fission micro-chambers could gather both microscopic information on nuclear reactions (total and partial cross sections for neutron capture and/or fission reactions) and macroscopic information on transmutation and incineration potentials. Cross sections of selected actinides (241Am, 242Am, 242Pu, 237Np, 238Np) have already been measured at ILL, showing some discrepancies when compared to evaluated data libraries but in overall good agreement with recent experimental data.

  2. Neutron-diffraction study of the magnetic structure of PrCoAl 4

    NASA Astrophysics Data System (ADS)

    Schobinger-Papamantellos, P.; Wilkinson, C.; Tung, L. D.; Buschow, K. H. J.; McIntyre, G. J.

    2004-12-01

    The magnetic structure of PrCoAl4 has been studied by neutron diffraction from a single crystal. The Pr moments order at a temperature near to 20 K with a sine-wave longitudinal amplitude-modulated structure. The length of the wave vector q = (0 0qz) is almost temperature independent with qz = 0.4087 (5) , and only the first harmonic was observed down to 2 K. The amplitude of the wave, 2.05(3) μB/Pr atom at 2 K, is reduced compared to the Pr3+ free-ion moment value g JμB = 3.2μB , due to strong crystal-field effects. One difference between the present and previously reported neutron powder-diffraction results concerns the wave vector length. The reason for this may lie in the different magnetic microstructure (stacking faults) of the material depending on the thermochemical history of each sample.

  3. Inelastic neutron scattering study of water in hydrated LTA-type zeolites.

    PubMed

    Corsaro, Carmelo; Crupi, Vincenza; Majolino, Domenico; Parker, Stewart F; Venuti, Valentina; Wanderlingh, Ulderico

    2006-01-26

    The vibrational dynamics of water molecules encapsulated in synthetic Na-A and Mg-exchanged A zeolites were studied versus temperature by inelastic neutron scattering (INS) measurements (30-1200 cm(-1)) as a function of the induced ion-exchange percentage by using the indirect geometry tof spectrometer TOSCA at the ISIS pulse neutron facility (RAL, UK). The experimental INS spectra were compared with those of ice Ih to characterize the structural changes induced by confinement on the H2O hydrogen-bonded network. We observed, after increasing the Mg2+ content, a tendency of water molecules to restore the bulklike arrangements together with more hindered dynamics. These results are confirmed by the analysis of the evaluated one-phonon amplitude-weighted proton vibrational density of states aimed, in particular, to follow the evolution of the water molecules librational mode region.

  4. In-Situ Studies of Intercritically Austempered Ductile Iron Using Neutron Diffraction

    SciTech Connect

    Druschitz, Alan; Aristizabal, Ricardo; Druschitz, Edward; Hubbard, Camden R; Watkins, Thomas R; Walker, Larry R; Ostrander, M

    2012-01-01

    Intercritically austempered ductile irons hold promise for applications requiring fatigue durability, excellent castability, low production energy requirements, reduced greenhouse gas emissions and excellent machinability. In the present study, four different ductile iron alloys, containing manganese and nickel as the primary austenite-stabilizing elements, were heat treated to obtain different quantities of austenite in the final microstructure. This paper reports the microstructures and phases present in these alloys. Further, lattice strains and diffraction elastic constants in various crystallographic directions and the transformation characteristics of the austenite as a function of applied stress were determined using in-situ loading with neutron diffraction at the second generation Neutron Residual Stress Facility (NRSF2) at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL).

  5. Antikaons in neutron star studied with recent versions of relativistic mean-field models

    NASA Astrophysics Data System (ADS)

    Gupta, Neha; Arumugam, P.

    2013-03-01

    We study the impact of additional couplings in the relativistic mean field (RMF) models, in conjunction with antikaon condensation, on various neutron star properties. We analyze different properties such as in-medium antikaon and nucleon effective masses, antikaon energies, chemical potentials and the mass-radius relations of neutron star (NS). We calculate the NS properties with the RMF (NL3), E-RMF (G1, G2) and FSU2.1 models, which are quite successful in explaining several finite nuclear properties. Our results show that the onset of kaon condensation in NS strongly depends on the parameters of the Lagrangian, especially the additional couplings which play a significant role at higher densities where antikaons dominate the behavior of equation of state.

  6. Magnetization studies of YBa 2Cu 3O 7-x irradiated by fast neutrons

    NASA Astrophysics Data System (ADS)

    Wisniewski, A.; Baran, M.; Przysłupski, P.; Szymczak, H.; Pajaczkowska, A.; Pytel, B.; Pytel, K.

    1988-02-01

    Studies of the effect of fast neutron damage on the magnetic hysteresis of YBa 2Cu 3O 7-x ceramic samples subjected to fluence of neutrons of 2∗10 16 n/cm 2 up to 6∗10 17 n/cm 2 have been performed. irradiation up to dose of 1∗10 17 did not cause any change in the critical temperature. However it causes a strong increase of the magnetic hysteresis which is presumably connected with the creation of defects. The critical current density at 77 K in H = 10 k0e for the sample irradiated with the dose 1∗10 17 n/cm 2 was estimated to be 520 A/cm 2 as compared to 29 A/cm 2 for the reference non-irradiated sample, non-irradiated sample.

  7. Neutron diffraction and reflectivity studies of the Cr Neel transition in Fe/Cr(001) superlatices

    SciTech Connect

    Fullerton, E.E.; Adenwalla, S.; Felcher, G.P.

    1995-12-31

    The effects on the interlayer coupling of the Cr Neel transition is studied in Fe/Cr(001) superlattices. The Neel transition is suppressed for Cr layer thickness < 42 {angstrom}. For > 42{angstrom} of Cr, the Neel temperature TN initially increases rapidly and then asymptotically approaches its bulk value with a three-dimensional transition-temperature shift exponent value of {lambda}=1.4{+-}0.3. Neutron diffraction confirms both the Cr antiferromagnetic order and the existence of the incommensurate, transverse spin density wave whose nesting wavevector is the same as that of bulk Cr. The ordering of the Cr dramatically alters the coupling of the Fe layers. The biquadratic Fe interlayer coupling observed for T>T{sub N} vanishes below T{sub N} as confirmed by polarized neutron reflectivity. The behavior can be understood in terms of finite-size and spin frustration effects at rough Fe-Cr interfaces.

  8. Beta-decay study of neutron rich isotopes of Bromine and Krypton

    SciTech Connect

    Miernik, Krzysztof A; Gross, Carl J; Grzywacz, Robert Kazimierz; Madurga, M; Mendez, II, Anthony J; Miller, D.; Padgett, S; Paulauskas, Stanley V; Rykaczewski, Krzysztof Piotr; Stracener, Daniel W; Wolinska-Cichocka, Marzena; Zganjar, E. F.; Batchelder, J. C.; Brewer, N.T.; Cartegni, L.; Fijalkowska, Aleksandra G; Hamilton, J. H.; Hwang, J. K.; Ilyushkin, S.; Jost, Carola U; Karny, M.; Korgul, A.; Krolas, W.; Liu, S.H.; Ramayya, A. V.; Surman, Rebecca; Winger, J. A.; Wolinska-Cichocka, M

    2013-01-01

    Short lived neutron rich nuclei including 93 Br, 93 Kr and 94 Kr were produced in proton induced fission of 238 U at the HRIBF in Oak Ridge. Their beta decay was studied by means of a high resolution on line mass separator and beta gamma spectroscopy methods. The half life of 93Br T1/2 = 152(8) ms and delayed branching ratio of Pn = 53-8+11 may be compared to the previously reported values of T1/2 = 102(10) ms and Pn = 68(7)%. At the same time the half life of 94Kr T1/2 = 227(14) ms and B delayed branching ratio of Pn = 1.9+0.6 0.2 % of 93Kr are in very good agreement with literature values. The decay properties of 93Br include four new gamma transitions following beta delayed neutron emission.

  9. A study of oil lubrication in a rotating engine using stroboscopic neutron imaging

    NASA Astrophysics Data System (ADS)

    Schillinger, Burkhard; Brunner, Johannes; Calzada, Elbio

    2006-11-01

    Even at modern high-flux neutron sources, the required exposure time for one neutron radiography image with high counting statistics is in the order of 1 s. Continuous time-resolved imaging of objects in motion is thus very limited in time resolution and signal dynamics. However, repetitive motions can be recorded with a stroboscopic technique: A triggerable accumulating detector is triggered for many identical time windows of the cyclic motion until sufficient fluence is accumulated for one image. The image is read out, the delay for the time window is shifted and the recording repeated until a complete movie of the cyclic motion can be put together. We report about a study of oil flux in a running, electrically driven BMW engine out of current production.

  10. Examining small molecule: HIV RNA interactions using arrayed imaging reflectometry

    NASA Astrophysics Data System (ADS)

    Chaimayo, Wanaruk; Miller, Benjamin L.

    2014-03-01

    Human Immunodeficiency Virus (HIV) has been the subject of intense research for more than three decades as it causes an uncurable disease: Acquired Immunodeficiency Syndrome, AIDS. In the pursuit of a medical treatment, RNAtargeted small molecules are emerging as promising targets. In order to understand the binding kinetics of small molecules and HIV RNA, association (ka) and dissociation (kd) kinetic constants must be obtained, ideally for a large number of sequences to assess selectivity. We have developed Aqueous Array Imaged Reflectometry (Aq-AIR) to address this challenge. Using a simple light interference phenomenon, Aq-AIR provides real-time high-throughput multiplex capabilities to detect binding of targets to surface-immobilized probes in a label-free microarray format. The second generation of Aq-AIR consisting of high-sensitivity CCD camera and 12-μL flow cell was fabricated. The system performance was assessed by real-time detection of MBNL1-(CUG)10 and neomycin B - HIV RNA bindings. The results establish this second-generation Aq-AIR to be able to examine small molecules binding to RNA sequences specific to HIV.

  11. The interpretation of reflectometry measurements of plasma fluctuations

    SciTech Connect

    Bretz, N.

    1991-10-01

    Wave reflections from density fluctuations with magnitudes and frequencies typical of drift waves have been investigated. Both drift waves and the reflected phase and amplitude depend on the density gradient scale length, and this common feature implies that both the angular deviation of a normally propagating wave and the phase change on reflection are of order unity. Thus the surface will always appear rough'' and amplitude variations will always be large. For smaller amplitude waves numerical solutions of the one dimensional full wave equation for the propagation near cutoff frequencies has been used to show how to interpret reflectometry measurements. For density perturbations with wavelengths near the density scale length, the external fluctuating phase can be simply interpreted in terms of a fluctuating density near the cutoff layer. However, the amplitude of the phase response falls substantially as the fluctuation wavelength, {Lambda}, approaches the free space wavelength of the reflected wave, {lambda}{sub o}, and the location of the maximum response moves out in front of the cutoff layer following the wave matching condition k{sub {Lambda}} = 2k {approx} 2{eta}(x)k{sub 0}. Similarly, correlation measurements of density fluctuations from probe waves of different wavelengths are shown to be limited to about four times the average reflected wavelength. 12 refs., 9 figs.

  12. Reflectometry as a fluctuation diagnostic: A one-dimensional simulation

    SciTech Connect

    Chou, A.E.; Luhmann, N.C. Jr.; Peebles, W.A.; Rhodes, T.L. )

    1992-10-01

    Reflectometry is currently employed to characterize turbulence in fusion plasmas worldwide and is expected to be a major diagnostic on the next generation of machines (e.g., ITER). Until recently, little was known about the response of a reflectometer to fluctuations (degree of localization of the signal, sensitivity to fluctuation wave number, dependence on density scale length, etc.). To elucidate these properties, we have been modeling reflectometer behavior with a code based on solution of a one-dimensional full wave equation. The code models an infinite plane plasma with density gradient in the {ital x} direction and solves the full wave equation to find the electric field of the reflectometer's electromagnetic wave. It can simulate stationary and moving density perturbations with arbitrary waveforms and wave numbers in plasmas with arbitrary density profiles. We present results of test cases comparing computational results to known analytic solutions for linear and 1{minus}{alpha}{sup 2}/{ital x}{sup 2} plasma density profiles, which show very good agreement.

  13. Neutron Scattering Studies of Nanomagnetism and Artificially Structured Materials

    SciTech Connect

    Fitzsimmons, M.R.; Bader, S.D.; Borchers, J.A.; Felcher, G.P.; Furdyna, J.K.; Hoffmann, A.; Kortright, J.B.; Schuller, Ivan K.; Schulthess, T.C.; Sinha, S.K.; Toney, M.F.; Weller, D.; Wolf, S.

    2003-02-01

    Nanostructured magnetic materials are intensively studied due to their unusual properties and promise for possible applications. The key issues in these materials relate to the connection between their physical properties (transport, magnetism, mechanical, etc.) and their chemical-physical structure. In principle, a detailed knowledge of the chemical and physical structure allows calculation of their physical properties. Theoretical and computational methods are rapidly evolving so that magnetic properties of nanostructured materials might soon be predicted. Success in this endeavor requires detailed quantitative understanding of the magnetic structure and properties.

  14. Polarized Neutron Studies on Antiferromagnetic Single Crystals: Technical Report No. 4

    DOE R&D Accomplishments Database

    Nathans, R.; Riste, T.; Shirane, G.; Shull, C.G.

    1958-11-26

    The theory of neutron scattering by magnetic crystals as given by Halpern and Johnson predicts changes in the polarization state of the neutron beam upon scattering which depend upon the relative orientation of the neutron polarization vector and the crystal magnetic axis. This was investigated experimentally with a polarized beam spectrometer using single crystals of Cr{sub 2}O{sub 3} and alpha - Fe{sub 2}O{sub 3} in which reside unique antiferromagnetic axes. Studies were made on several different reflections in both crystals for a number of different temperatures both below and above the Neel point. Results support the theoretical predictions and indicate directions for the moments in these crystals consistent with previous work. A more detailed study of the polarization changes in the (111) reflection in alpha - Fe{sub 2}O{sub 3} at room temperature on application of a magnetic field was carried out, The results indicate that the principal source of the parasitic ferromagnetism in hematite is essentially independent of the orientation of the antiferromagnetic domains within the crystal.

  15. Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

    DOE PAGES

    Wang, H.; Kirkham, M. J.; Watkins, T. R.; Payzant, E. A.; Salvador, J. R.; Thompson, A. J.; Sharp, J.; Brown, D.; Miller, D.

    2016-02-17

    N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubicmore » symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. Ultimately, this knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.« less

  16. Annealing studies of silicon microstrip detectors irradiated at high neutron fluences

    NASA Astrophysics Data System (ADS)

    Miñano, M.; Balbuena, J. P.; García, C.; González, S.; Lacasta, C.; Lacuesta, V.; Lozano, M.; Martí i Garcia, S.; Pellegrini, G.; Ullán, M.

    2008-06-01

    Silicon p-type detectors are being investigated for the development of radiation-tolerant detectors for the luminosity upgrade of the CERN large hadron collider (Super-LHC (sLHC)). Microstrip detectors have been fabricated by CNM-IMB with an n-side read-out on p-type high-resistivity float zone substrates. They have been irradiated with neutrons at the TRIGA Mark II nuclear reactor in Ljubljana. The irradiation fluxes match with the expected doses for the inner tracker at the sLHC (up to 10 16 equivalent 1 MeV neutrons cm -2). The macroscopic properties of the irradiated prototypes after irradiation were characterized at the IFIC-Valencia laboratory. The charge collection studies were carried out by means of a radioactive source setup as well as by an infrared laser illumination. The annealing behavior was studied in detail on a microstrip detector irradiated with a flux of 10 15 equivalent 1 MeV neutrons cm -2. Collected charge measurements were made after accelerated annealing times at 80 °C up to an equivalent annealing time of several years at room temperature. This note reports on the recorded results from the annealing of the irradiated p-type microstrip sensor.

  17. Decay studies of neutron deficient rare earth isotopes with OASIS

    SciTech Connect

    Gilat, J.; Nitschke, J.M.; Wilmarth, P.A.; Vierinen, K.; Firestone, R.B.

    1987-09-01

    We report results on the decay of /sup 124/Pr, /sup 124,125/Ce, /sup 124,125/La, /sup 134-136/Eu, /sup 134-136/Sm, /sup 134-136/Pm, /sup 144/Ho, /sup 141,142,144/Dy, /sup 140,141,142,144/Tb, /sup 140-142/Gd, and /sup 140-142/Eu, produced by /sup 92/Mo(H.I.,xpyn) reactions at the Berkeley SuperHILAC, and studied with the OASIS on-line mass separator facility. Half-lives, delayed proton branching ratios, ..gamma..-ray energies and intensities, partial decay schemes and several J/sup ..pi../ assignments are presented. Level systematics of the even mass Nd and Sm isotopes and of the nu h/sub 11/2/ - nu s/sub 1/2/ isomers for N = 77 are discussed.

  18. Dynamics of biopolymers on nanomaterials studied by quasielastic neutron scattering and MD simulations

    NASA Astrophysics Data System (ADS)

    Dhindsa, Gurpreet K.

    Neutron scattering has been proved to be a powerful tool to study the dynamics of biological systems under various conditions. This thesis intends to utilize neutron scattering techniques, combining with MD simulations, to develop fundamental understanding of several biologically interesting systems. Our systems include a drug delivery system containing Nanodiamonds with nucleic acid (RNA), and two specific model proteins, beta-Casein and Inorganic Pyrophosphatase (IPPase). RNA and nanodiamond (ND) both are suitable for drug-delivery applications in nano-biotechnology. The architecturally flexible RNA with catalytic functionality forms nanocomposites that can treat life-threatening diseases. The non-toxic ND has excellent mechanical and optical properties and functionalizable high surface area, and thus actively considered for biomedical applications. In this thesis, we utilized two tools, quasielastic neutron scattering (QENS) and Molecular Dynamics Simulations to probe the effect of ND on RNA dynamics. Our work provides fundamental understanding of how hydrated RNA motions are affected in the RNA-ND nanocomposites. From the experimental and Molecular Dynamics Simulation (MD), we found that hydrated RNA motion is faster on ND surface than a freestanding one. MD Simulation results showed that the failure of Stokes Einstein relation results the presence of dynamic heterogeneities in the biomacromolecules. Radial pair distribution function from MD Simulation confirmed that the hydrophilic nature of ND attracts more water than RNA results the de-confinement of RNA on ND. Therefore, RNA exhibits faster motion in the presence of ND than freestanding RNA. In the second project, we studied the dynamics of a natively disordered protein beta-Casein which lacks secondary structures. In this study, the temperature and hydration effects on the dynamics of beta-Casein are explored by Quasielastic Neutron Scattering (QENS). We investigated the mean square displacement (MSD) of

  19. Study of the triton-burnup process in different JET scenarios using neutron monitor based on CVD diamond

    NASA Astrophysics Data System (ADS)

    Nemtsev, G.; Amosov, V.; Meshchaninov, S.; Popovichev, S.; Rodionov, R.

    2016-11-01

    We present the results of analysis of triton burn-up process using the data from diamond detector. Neutron monitor based on CVD diamond was installed in JET torus hall close to the plasma center. We measure the part of 14 MeV neutrons in scenarios where plasma current varies in a range of 1-3 MA. In this experiment diamond neutron monitor was also able to detect strong gamma bursts produced by runaway electrons arising during the disruptions. We can conclude that CVD diamond detector will contribute to the study of fast particles confinement and help predict the disruption events in future tokamaks.

  20. Neutron-emission measurements at a white neutron source

    SciTech Connect

    Haight, Robert C

    2010-01-01

    Data on the spectrum of neutrons emittcd from neutron-induced reactions are important in basic nuclear physics and in applications. Our program studies neutron emission from inelastic scattering as well as fission neutron spectra. A ''white'' neutron source (continuous in energy) allows measurements over a wide range of neutron energies all in one experiment. We use the tast neutron source at the Los Alamos Neutron Science Center for incident neutron energies from 0.5 MeV to 200 MeV These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. For the fission neutron measurements, parallel-plate ionization or avalanche detectors identify fission in actinide samples and give the required fast timing pulse. For inelastic scattering, gamma-ray detectors provide the timing and energy spectroscopy. A large neutron-detector array detects the emitted neutrons. Time-of-flight techniques are used to measure the energies of both the incident and emitted neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. We have made preliminary measurements of the fission neutron spectra from {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. Neutron emission spectra from inelastic scattering on iron and nickel have also been investigated. The results obtained will be compared with evaluated data.

  1. Dibaryons in neutron stars

    NASA Technical Reports Server (NTRS)

    Olinto, Angela V.; Haensel, Pawel; Frieman, Joshua A.

    1991-01-01

    The effects are studied of H-dibaryons on the structure of neutron stars. It was found that H particles could be present in neutron stars for a wide range of dibaryon masses. The appearance of dibaryons softens the equations of state, lowers the maximum neutron star mass, and affects the transport properties of dense matter. The parameter space is constrained for dibaryons by requiring that a 1.44 solar mass neutron star be gravitationally stable.

  2. Manufacturing techniques studies of ceramics by neutron and γ-ray radiography

    SciTech Connect

    Latini, R. M.; Bellido, A. V. B.; Souza, M. I. S.; Almeida, G. L.

    2014-11-11

    In this study, the aim was to evaluate capabilities and constraints of radiographic imagery using thermal neutrons and gamma-rays as tools to identify the type of technique employed in ceramics manufacturing especially that used in prehistoric Brazilian pottery from Acre state. For this purpose, radiographic images of test objects made with clay of this region using both techniques - palette and rollers - have been acquired with a system comprised of a source of gamma-rays or thermal neutrons and a corresponding X-ray or neutron-sensitive Imaging Plate as detector. For the neutrongraphy samples were exposed to a thermal neutron flux of order of 10{sup 5}n.cm{sup −2}.s{sup −1} for 3 minutes at main port of Argonauta research reactor of the Instituto de Engenharia Nuclear - IEN/CNEN. The radiographic images using γ-rays from {sup 165}Dy (95 keV) and {sup 198}Au (412 keV) both produced at this reactor, have been acquired under an exposure time of a couple of hours. After acquisition, images have undergone a treatment to improve their quality through enhancement of their contrast, a procedure involving corrections of the beam divergence, sample shape and averaging of the attenuation map profile. Preliminary results show that difference between manufacturing techniques is better identified by radiography using low energy γ-rays from {sup 165}Dy rather than neutrongraphy or γ-rays from {sup 198}Au. Nevertheless, disregarding the kind of employed radiation, it should be stressed that feasibility to apply the technique is tightly tied to homogeneity of the clay itself and tempers due to their different attenuation.

  3. Manufacturing techniques studies of ceramics by neutron and γ-ray radiography

    NASA Astrophysics Data System (ADS)

    Latini, R. M.; Souza, M. I. S.; Almeida, G. L.; Bellido, A. V. B.

    2014-11-01

    In this study, the aim was to evaluate capabilities and constraints of radiographic imagery using thermal neutrons and gamma-rays as tools to identify the type of technique employed in ceramics manufacturing especially that used in prehistoric Brazilian pottery from Acre state. For this purpose, radiographic images of test objects made with clay of this region using both techniques - palette and rollers - have been acquired with a system comprised of a source of gamma-rays or thermal neutrons and a corresponding X-ray or neutron-sensitive Imaging Plate as detector. For the neutrongraphy samples were exposed to a thermal neutron flux of order of 105n.cm-2.s-1 for 3 minutes at main port of Argonauta research reactor of the Instituto de Engenharia Nuclear - IEN/CNEN. The radiographic images using γ-rays from 165Dy (95 keV) and 198Au (412 keV) both produced at this reactor, have been acquired under an exposure time of a couple of hours. After acquisition, images have undergone a treatment to improve their quality through enhancement of their contrast, a procedure involving corrections of the beam divergence, sample shape and averaging of the attenuation map profile. Preliminary results show that difference between manufacturing techniques is better identified by radiography using low energy γ-rays from 165Dy rather than neutrongraphy or γ-rays from 198Au . Nevertheless, disregarding the kind of employed radiation, it should be stressed that feasibility to apply the technique is tightly tied to homogeneity of the clay itself and tempers due to their different attenuation.

  4. Laterally patterned spin-valve superlattice: Magnetometry and polarized neutron scattering study

    SciTech Connect

    Brüssing, F.; Devishvili, A.; Zabel, H.; Toperverg, B. P.; Badini Confalonieri, G. A.; Theis-Bröhl, K.

    2015-04-07

    The magnetization reversal of magnetic multilayers with spin-valve like characteristics, patterned into an array of parallel stripes, was structurally and magnetically analyzed, in detail, via x-ray scattering, magnetometry, and polarized neutron reflectivity. Each stripe contains a multiple repetition of the layer sequence [Fe/Cr/Co/Cr]. X-ray and neutron scattering maps of the patterned multilayer show rich details resulting from the superposition of Bragg peaks representing the lateral in-plane periodicity and the out-of-plane multilayer period. Detailed analysis of specular and off-specular polarized neutron intensity was used to ascertain the antiparallel alignment of the Co and Fe magnetization within the kink region of their combined hysteresis loop between the coercive fields of Fe and Co layers. This includes also an examination of domain formation and inter- as well as intra-stripe correlation effects upon magnetization reversal. Our combined study shows that the shape induced anisotropy via patterning is capable of overriding the four-fold crystal anisotropy but is unable to eliminate the ripple domain state of the Co layers, already present in the continuous multilayer.

  5. Study of Neutron-Capture Element Abundances in Metal-Poor Stars

    NASA Astrophysics Data System (ADS)

    Li, Hongjie; Shen, Xiaojing; Liang, Shuai; Cui, Wenyuan; Zhang, Bo

    2013-02-01

    This work describes a study of elemental abundances for 30 metal-poor stars whose chemical abundances provide excellent information for setting constraints on models of neutron-capture processes. Based on the abundances of main r- and weak r-process stars, the abundance patterns of main r-process and weak r-process are obtained. The two r-process component coefficients are defined to determine the relative contributions from individual neutron-capture process to abundances of metal-poor stars. Based on the component coefficients, we find that metal-poor stars BD+42621 and HD 4306 are also weak r-process stars, which means that the abundance pattern produced by weak r-process is stable. All metal-poor star abundances contain the contributions of both main r-process and weak r-process. The elements produced by weak r-process have increased along with Fe over the polluted history. Most of the metal-poor star abundances do not follow the pattern observed in the solar system, but there is a small fraction that do. For the low-[Sr/Fe] star BD-185550 ([Sr/Fe] lsim -1), neutron-capture element abundances can be explained by the mixture of two r-process components. Since lighter elements in this star cannot be fitted by the two components, the abundance pattern of P-component is estimated from those abundances.

  6. A study of Gd-based parallel plate avalanche counter for thermal neutrons by MC simulation

    NASA Astrophysics Data System (ADS)

    Rhee, J. T.; Kim, H. G.; Ahmad, Farzana; Jeon, Y. J.; Jamil, M.

    2013-12-01

    In this work, we demonstrate the feasibility and characteristics of a single-gap parallel plate avalanche counter (PPAC) as a low energy neutron detector, based on Gd-converter coating. Upon falling on the Gd-converter surface, the incident low energy neutrons produce internal conversion electrons which are evaluated and detected. For estimating the performance of the Gd-based PPAC, a simulation study has been performed using GEANT4 Monte Carlo (MC) code. The detector response as a function of incident neutron energies in the range of 25-100 meV has been evaluated with two different physics lists. Using the QGSP_BIC_HP physics list and assuming 5 μm converter thickness, 11.8%, 18.48%, and 30.28% detection efficiencies have been achieved for the forward-, the backward-, and the total response of the converter-based PPAC. On the other hand, considering the same converter thickness and detector configuration, with the QGSP_BERT_HP physics list efficiencies of 12.19%, 18.62%, and 30.81%, respectively, were obtained. These simulation results are briefly discussed.

  7. Liquid 1-propanol studied by neutron scattering, near-infrared, and dielectric spectroscopy.

    PubMed

    Sillrén, P; Matic, A; Karlsson, M; Koza, M; Maccarini, M; Fouquet, P; Götz, M; Bauer, Th; Gulich, R; Lunkenheimer, P; Loidl, A; Mattsson, J; Gainaru, C; Vynokur, E; Schildmann, S; Bauer, S; Böhmer, R

    2014-03-28

    Liquid monohydroxy alcohols exhibit unusual dynamics related to their hydrogen bonding induced structures. The connection between structure and dynamics is studied for liquid 1-propanol using quasi-elastic neutron scattering, combining time-of-flight and neutron spin-echo techniques, with a focus on the dynamics at length scales corresponding to the main peak and the pre-peak of the structure factor. At the main peak, the structural relaxation times are probed. These correspond well to mechanical relaxation times calculated from literature data. At the pre-peak, corresponding to length scales related to H-bonded structures, the relaxation times are almost an order of magnitude longer. According to previous work [C. Gainaru, R. Meier, S. Schildmann, C. Lederle, W. Hiller, E. Rössler, and R. Böhmer, Phys. Rev. Lett. 105, 258303 (2010)] this time scale difference is connected to the average size of H-bonded clusters. The relation between the relaxation times from neutron scattering and those determined from dielectric spectroscopy is discussed on the basis of broad-band permittivity data of 1-propanol. Moreover, in 1-propanol the dielectric relaxation strength as well as the near-infrared absorbance reveal anomalous behavior below ambient temperature. A corresponding feature could not be found in the polyalcohols propylene glycol and glycerol.

  8. Optimising the neutron environment of Radiation Portal Monitors: A computational study

    NASA Astrophysics Data System (ADS)

    Gilbert, Mark R.; Ghani, Zamir; McMillan, John E.; Packer, Lee W.

    2015-09-01

    Efficient and reliable detection of radiological or nuclear threats is a crucial part of national and international efforts to prevent terrorist activities. Radiation Portal Monitors (RPMs), which are deployed worldwide, are intended to interdict smuggled fissile material by detecting emissions of neutrons and gamma rays. However, considering the range and variety of threat sources, vehicular and shielding scenarios, and that only a small signature is present, it is important that the design of the RPMs allows these signatures to be accurately differentiated from the environmental background. Using Monte-Carlo neutron-transport simulations of a model 3He detector system we have conducted a parameter study to identify the optimum combination of detector shielding, moderation, and collimation that maximises the sensitivity of neutron-sensitive RPMs. These structures, which could be simply and cost-effectively added to existing RPMs, can improve the detector response by more than a factor of two relative to an unmodified, bare design. Furthermore, optimisation of the air gap surrounding the helium tubes also improves detector efficiency.

  9. Laterally patterned spin-valve superlattice: Magnetometry and polarized neutron scattering study

    NASA Astrophysics Data System (ADS)

    Brüssing, F.; Toperverg, B. P.; Devishvili, A.; Badini Confalonieri, G. A.; Theis-Bröhl, K.; Zabel, H.

    2015-04-01

    The magnetization reversal of magnetic multilayers with spin-valve like characteristics, patterned into an array of parallel stripes, was structurally and magnetically analyzed, in detail, via x-ray scattering, magnetometry, and polarized neutron reflectivity. Each stripe contains a multiple repetition of the layer sequence [Fe/Cr/Co/Cr]. X-ray and neutron scattering maps of the patterned multilayer show rich details resulting from the superposition of Bragg peaks representing the lateral in-plane periodicity and the out-of-plane multilayer period. Detailed analysis of specular and off-specular polarized neutron intensity was used to ascertain the antiparallel alignment of the Co and Fe magnetization within the kink region of their combined hysteresis loop between the coercive fields of Fe and Co layers. This includes also an examination of domain formation and inter- as well as intra-stripe correlation effects upon magnetization reversal. Our combined study shows that the shape induced anisotropy via patterning is capable of overriding the four-fold crystal anisotropy but is unable to eliminate the ripple domain state of the Co layers, already present in the continuous multilayer.

  10. X-ray studies of neutron stars and their magnetic fields.

    PubMed

    Makishima, Kazuo

    2016-01-01

    Utilizing results obtained over the past quarter century mainly with Japanese X-ray astronomy satellites, a review is given to some aspects of neutron stars (NSs), with a particular emphasis on the magnetic fields (MFs) of mass-accreting NSs and magnetars. Measurements of electron cyclotron resonance features in binary X-ray pulsars, using the Ginga and Suzaku observatories, clarified that their surface MFs are concentrated in a narrow range of (1-7) × 10(8) T. Extensive studies of magnetars with Suzaku reinforced their nature as neutron stars with truly strong MFs, and revealed several important clues to their formation, evolution, and physical states. Taking all these results into account, a discussion is made on the origin and evolution of these strong MFs. One possible scenario is that the MF of NSs is a manifestation of some fundamental physics, e.g., neutron spin alignment or chirality violation, and the MF makes transitions from strong to weak states. PMID:27169348

  11. Neutron Scattering Studies of Pre-Transitional Effects in Solid-Solid Phase Transformations

    SciTech Connect

    Shapiro, S. M.

    1999-06-30

    Neutron scattering studies have played a fundamental role in understanding solid-solid phase transformations, particularly in studying the lattice dynamical behavior associated with precursor effects. A review of the studies performed on solids exhibiting Martensitic transformations is given below. The mode softening and associated elastic diffuse scattering, previously observed in NiAl alloys, will be discussed as well as more recent work on Ni{sub 2}MnGa, a system exhibiting magnetic order as well as a Martensitic transformation. Also, new results on the precursor effects in ordered and disordered FePt alloys will be presented.

  12. Effective crop evapotranspiration measurement using time-domain reflectometry technique in a sub-humid region

    NASA Astrophysics Data System (ADS)

    Srivastava, R. K.; Panda, R. K.; Halder, Debjani

    2016-06-01

    The primary objective of this study was to evaluate the performance of the time-domain reflectometry (TDR) technique for daily evapotranspiration estimation of peanut and maize crop in a sub-humid region. Four independent methods were used to estimate crop evapotranspiration (ETc), namely, soil water balance budgeting approach, energy balance approach—(Bowen ratio), empirical methods approach, and Pan evaporation method. The soil water balance budgeting approach utilized the soil moisture measurement by gravimetric and TDR method. The empirical evapotranspiration methods such as combination approach (FAO-56 Penman-Monteith and Penman), temperature-based approach (Hargreaves-Samani), and radiation-based approach (Priestley-Taylor, Turc, Abetw) were used to estimate the reference evapotranspiration (ET0). The daily ETc determined by the FAO-56 Penman-Monteith, Priestley-Taylor, Turc, Pan evaporation, and Bowen ratio were found to be at par with the ET values derived from the soil water balance budget; while the methods Abetw, Penman, and Hargreaves-Samani were not found to be ideal for the determination of ETc. The study illustrates the in situ applicability of the TDR method in order to make it possible for a user to choose the best way for the optimum water consumption for a given crop in a sub-humid region. The study suggests that the FAO-56 Penman-Monteith, Turc, and Priestley-Taylor can be used for the determination of crop ETc using TDR in comparison to soil water balance budget.

  13. Soil water content determination with cosmic-ray neutron sensor: Correcting aboveground hydrogen effects with thermal/fast neutron ratio

    NASA Astrophysics Data System (ADS)

    Tian, Zhengchao; Li, Zizhong; Liu, Gang; Li, Baoguo; Ren, Tusheng

    2016-09-01

    The cosmic-ray neutron sensor (CRNS), which estimates field scale soil water content, bridges the gap between point measurement and remote sensing. The accuracy of CRNS measurements, however, is affected by additional hydrogen pools (e.g., vegetation, snow, and rainfall interception). The objectives of this study are to: (i) evaluate the accuracy of CRNS estimates in a farmland system using depth and horizontal weighted point measurements, (ii) introduce a novel method for estimating the amounts of hydrogen from biomass and snow cover in CRNS data, and (iii) propose a simple approach for correcting the influences of aboveground hydrogen pool (expressed as aboveground water equivalent, AWE) on CRNS measurements. A field experiment was conducted in northeast China to compare soil water content results from CRNS to in-situ data with time domain reflectometry (TDR) and neutron probe (NP) in the 0-40 cm soil layers. The biomass water equivalent (BWE) and snow water equivalent (SWE) were observed to have separate linear relationships with the thermal/fast neutron ratio, and the dynamics of BWE and SWE were estimated correctly in the crop seasons and snow-covered seasons, respectively. A simple approach, which considered the AWE, AWE at calibration, and the effective measurement depth of CRNS, was introduced to correct the errors caused by BWE and SWE. After correction, the correlation coefficients between soil water contents determined by CRNS and TDR were 0.79 and 0.77 during the 2014 and 2015 crop seasons, respectively, and CRNS measurements had RMSEs of 0.028, 0.030, and 0.039 m3 m-3 in the 2014 and 2015 crop seasons and the snow-covered seasons, respectively. The experimental results also indicated that the accuracies of CRNS estimated BWE and SWE were affected by the distributions of aboveground hydrogen pools, which were related to the height of the CRNS device above ground surface.

  14. Time-frequency analysis for microwave reflectometry data processing in the HL-2A tokamak.

    PubMed

    Zhong, W L; Shi, Z B; Zou, X L; Ding, X T; Huang, X L; Dong, Y B; Liu, Z T; Xiao, W W; Ji, X Q; Cui, Z Y; Liu, Yi; Yan, L W; Yang, Q W; Duan, X R

    2011-10-01

    The Choi-Williams distribution (CWD) technique is introduced as a time-frequency tool for processing data measured from the new developed homodyne and the fixed frequency reflectometry in the HL-2A tokamak. The comparison between spectrogram and CWD for the simulated signal is presented. It indicates that the CWD can greatly improve the representation of the time-frequency content of the multi-components signal. Its effectiveness is demonstrated through two applications in HL-2A, which are the extraction of beat frequencies from the frequency modulated-continuous wave reflectometry (FM-CW) and the characterizing of the fluctuations. The density profile inversed from the group delay of the FM-CW and the density fluctuations deduced from the fixed-frequency reflectometry would be more reliable and accurate by using the CWD technique.

  15. Time-frequency analysis for microwave reflectometry data processing in the HL-2A tokamak

    NASA Astrophysics Data System (ADS)

    Zhong, W. L.; Shi, Z. B.; Zou, X. L.; Ding, X. T.; Huang, X. L.; Dong, Y. B.; Liu, Z. T.; Xiao, W. W.; Ji, X. Q.; Cui, Z. Y.; Liu, Yi; Yan, L. W.; Yang, Q. W.; Duan, X. R.

    2011-10-01

    The Choi-Williams distribution (CWD) technique is introduced as a time-frequency tool for processing data measured from the new developed homodyne and the fixed frequency reflectometry in the HL-2A tokamak. The comparison between spectrogram and CWD for the simulated signal is presented. It indicates that the CWD can greatly improve the representation of the time-frequency content of the multi-components signal. Its effectiveness is demonstrated through two applications in HL-2A, which are the extraction of beat frequencies from the frequency modulated-continuous wave reflectometry (FM-CW) and the characterizing of the fluctuations. The density profile inversed from the group delay of the FM-CW and the density fluctuations deduced from the fixed-frequency reflectometry would be more reliable and accurate by using the CWD technique.

  16. Active Time-Domain Reflectometry for Unattended Safeguards Systems FY15 Report

    SciTech Connect

    Tedeschi, Jonathan R.; Smith, Leon E.; Moore, David E.; Sheen, David M.; Conrad, Ryan C.; Gavric, Gordan

    2015-09-01

    The International Atomic Energy Agency (IAEA) continues to expand its use of unattended measurement systems. An increasing number of systems and an expanding family of instruments create challenges in terms of deployment efficiency and the implementation of data authentication measures. In collaboration with the IAEA, tamper-indicating measures to address data-transmission authentication challenges with unattended safeguards systems are under investigation. Pacific Northwest National Laboratory (PNNL) is studying the viability of active time-domain reflectometry (TDR) along two parallel but interconnected paths: (1) swept-frequency TDR as the highly flexible, laboratory gold standard to which field-deployable options can be compared, and (2) a low-cost commercially available spread-spectrum TDR technology as one option for field implementation. This report describes PNNL’s FY15 progress in the viability study including: an overview of the TDR methods under investigation; description of the testing configurations and mock tampering scenarios; results from a preliminary sensitivity comparison of the two TDR methods; demonstration of a quantitative metric for estimating field performance that acknowledges the need for high detection probability while minimizing false alarms. FY15 progress reported here sets the stage for a rigorous comparison of the candidate TDR methods, over a range of deployment scenarios and perturbing effects typical of IAEA unattended monitoring systems.

  17. Trapping of Implanted He at Cu/Nb Interfaces Measured by Neutron Reflectometry

    SciTech Connect

    Wang, Peng; Zhernenkov, Mikhail; Kashinath, Abishek; Demkowicz, Michael; Baldwin, Jon K.; Majewski, Jaroslaw

    2012-06-20

    In single crystalline metals, He is insoluble and precipitates into bubbles. In contrast, Cu-Nb multilayers show no evidence of bubble formation below a critical concentration. The conclusions of this paper are: (1) He is trapped at Cu/Nb , Cu/Mo interfaces; (2) He is trapped interstitially; (3) The interface swells {approx} 10 times; and (4) The layered structure retains despite the swell of interfaces.

  18. A plastic scintillator-based 2D thermal neutron mapping system for use in BNCT studies.

    PubMed

    Ghal-Eh, N; Green, S

    2016-06-01

    In this study, a scintillator-based measurement instrument is proposed which is capable of measuring a two-dimensional map of thermal neutrons within a phantom based on the detection of 2.22MeV gamma rays generated via nth+H→D+γ reaction. The proposed instrument locates around a small rectangular water phantom (14cm×15cm×20cm) used in Birmingham BNCT facility. The whole system has been simulated using MCNPX 2.6. The results confirm that the thermal flux peaks somewhere between 2cm and 4cm distance from the system entrance which is in agreement with previous studies. PMID:26986813

  19. High-frequency collective excitations in molten and glassy Te studied by inelastic neutron scattering

    SciTech Connect

    Ruiz-Martin, M. D.; Jimenez-Ruiz, M.; Bermejo, F. J.

    2006-03-01

    The spectra of collective excitations of liquid and glassy tellurium have been studied by means of inelastic neutron scattering. Here we report on the dynamics of liquid Te as measured at two different temperatures, just above melting (T{sub m}=723 K) and at {approx}1000 K as well as the glass that is studied at room temperature. Estimates for the velocity of propagating excitations for both temperatures have been obtained from the experimental data, and a contrasting behavior is found with respect to anomalies shown by the adiabatic sound velocity measured by ultrasound methods. The origin of such differences is finally discussed.

  20. Projected Shell Model Study of Yrast States of Neutron-Deficient Odd-Mass Pr Nuclei

    SciTech Connect

    Ibanes, A.; Ortiz, Mark E; Velazquez, V.; Galindo-Uribarri, Alfredo {nmn}; Hess, P. O.; Sun, Y.

    2011-01-01

    A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A = 130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the 125,127,129,131,133Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J (2), kinetic moment of inertia J (1), the crossing of rotational bands, and backbending effects.

  1. Projected shell model study of yrast states of neutron-deficient odd-mass Pr nuclei

    SciTech Connect

    Ibanez-Sandoval, A.; Ortiz, M. E.; Velazquez, V.; Galindo-Uribarri, A.; Hess, P. O.; Sun, Y.

    2011-03-15

    A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A=130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the {sup 125,127,129,131,133}Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J{sup (2)}, kinetic moment of inertia J{sup (1)}, the crossing of rotational bands, and backbending effects.

  2. Observation of Wetland Dynamics with Global Navigation Satellite Signals Reflectometry

    NASA Astrophysics Data System (ADS)

    Zuffada, C.; Shah, R.; Nghiem, S. V.; Cardellach, E.; Chew, C. C.

    2015-12-01

    Wetland dynamics is crucial to changes in both atmospheric methane and terrestrial water storage. The Intergovernmental Panel on Climate Change's Fifth Assessment Report (IPCC AR5) highlights the role of wetlands as a key driver of methane (CH4) emission, which is more than one order of magnitude stronger than carbon dioxide as a greenhouse gas in the centennial time scale. Among the multitude of methane emission sources (hydrates, livestock, rice cultivation, freshwaters, landfills and waste, fossil fuels, biomass burning, termites, geological sources, and soil oxidation), wetlands constitute the largest contributor with the widest uncertainty range of 177-284 Tg(CH4) yr-1 according to the IPCC estimate. Wetlands are highly susceptible to climate change that might lead to wetland collapse. Such wetland destruction would decrease the terrestrial water storage capacity and thus contribute to sea level rise, consequently exacerbating coastal flooding problems. For both methane change and water storage change, wetland dynamics is a crucial factor with the largest uncertainty. Nevertheless, a complete and consistent map of global wetlands still needs to be obtained as the Ramsar Convention calls for a wetlands inventory and impact assessment. We develop a new method for observations of wetland change using Global Navigation Satellite Signals Reflectometry (GNSS-R) signatures for global wetland mapping in synergy with the existing capability, not only as a static inventory but also as a temporal dataset, to advance the capability for monitoring the dynamics of wetland extent relevant to addressing the science issues of CH4 emission change and terrestrial water storage change. We will demonstrate the capability of the new GNSS-R method over a rice field in the Ebro Delta wetland in Spain.

  3. Mare and Highlands Studies of Correlated Observations of the Moon's Diurnally Modulating Epithermal Neutron Flux using LRO's LEND, Diviner and LOLA instruments.

    NASA Astrophysics Data System (ADS)

    McClanahan, T. P.

    2015-12-01

    Several independent observational studies have identified a modulating diurnal signal in the Moon's neutron leakage flux. Those studies show that the diurnally varying neutron flux signal is of global extent, that the phase of the flux modulations are similar, that the flux minima occur at dawn and that the maxima occur at dusk. Two plausible hypotheses suggest differing explanations for the flux modulation. 1) Diurnally variant surface hydration or 2) Regolith temperature variation, which may modulate the neutron leakage flux with temperature. Studies of the high-latitudes found that for the north and south polar regions >75°, the amplitude of the neutron flux modulation was significantly greater for poleward-facing slopes (PFS) as compared to equator-facing slopes (EFS). If regolith temperature alone is driving the neutron flux modulation, then EFS should exhibit the greater diurnal amplitude, opposite the observation. More recently, studies of the neutron leakage flux in the mid-latitudes indicated that the greater amplitude of the neutron flux modulation on EFS was greater than PFS and is consistent with an interpretation that regolith temperature is modulating the neutron flux towards the northern Mare. However, between +/-(65° to 72°) latitude the ratio of the EFS to PFS neutron flux amplitudes inverts, with the PFS maintaining the greater amplitude as compared to the EFS. In this study the lunar mid to upper latitudes +/-(45° to 90°) will be studied in an effort to discriminate the source of the neutron flux modluation. Neutron, temperature and topography observations by the Lunar Reconnaissance Orbiter's (LRO) Lunar Exploration Neutron Detector (LEND), Diviner Radiometer, and Lunar Orbiter Laser Altimiter (LOLA) will be used to investigate the properties of the neutron leakage flux. Correlated studies of these three datasets in Mare and highlands regions will be used to determine the neutron flux characteristics of their respective EFS and PFS.

  4. Recent advances on optical reflectometry for access network diagnostics and distributed sensing

    NASA Astrophysics Data System (ADS)

    He, Zuyuan; Fan, Xinyu; Liu, Qingwen; Du, Jiangbing

    2015-07-01

    In this invited talk, we will present the advances in research and development activities of optical reflectometry in our laboratory. The performance of phase-sensitive coherent OTDR, which is developed for distributed vibration measurement, is reported with the results of field tests. The performance of time-gated digital OFDR, which is developed for optical access network diagnostics, is also reported. We will also discuss how to increase the frequency sweep span of the linearly-swept optical source, a very important part for improving the performance of optical reflectometry.

  5. Sequence and spread spectrum time domain reflectometry for transmission line analysis

    NASA Astrophysics Data System (ADS)

    Reis, Jacklyn; Castro, Agostinho L. S.; Costa, João C. W. A.; Riu, Jaume R. I.; Ericson, Klas

    2007-09-01

    This paper describes Sequence Time Domain Reflectometry (STDR) and Spread Spectrum Time Domain Reflectometry (SSTDR), which utilizes concepts from direct sequence spread spectrum communications, as a technique for detecting impedance mismatches in telephone lines (twisted pair). The aim of this paper is to present methodologies for characterizing a subscriber loop, which is used for Digital Subscriber Line (DSL) technology, based on STDR and SSTDR tests. Those tests enable the TDR functionality to be incorporated into a DSL transceiver integrated circuit eliminating the need for costly test equipment. In addition to the cost savings, the characteristics of the STDR and SSTDR offer improved spectral compatibility, interference immunity and fault resolvability.

  6. Polarization sensitive optical low-coherence reflectometry for blood glucose monitoring in human subjects

    NASA Astrophysics Data System (ADS)

    Solanki, Jitendra; Choudhary, Om Prakash; Sen, P.; Andrews, J. T.

    2013-07-01

    A device based on polarization sensitive optical low-coherence reflectometry is developed to monitor blood glucose levels in human subjects. The device was initially tested with tissue phantom. The measurements with human subjects for various glucose concentration levels are found to be linearly dependent on the ellipticity obtainable from the home-made phase-sensitive optical low-coherence reflectometry device. The linearity obtained between glucose concentration and ellipticity are explained with theoretical calculations using Mie theory. A comparison of results with standard clinical methods establishes the utility of the present device for non-invasive glucose monitoring.

  7. Performance study of polycrystalline CVD diamond detectors for fast neutron monitoring

    SciTech Connect

    Singh, Arvind Kumar, Amit Topkar, Anita

    2014-04-24

    Diamond detectors using polycrystalline CVD diamond substrates of thickness 300μm and 100μm were fabricated for fast neutron monitoring application.. The characterization of detectors was carried out using various tests such as leakage current, capacitance and alpha particle response. The performance of detectors was evaluated for fast neutrons at different neutron yields. The results presented in this work demonstrate that the diamond detectors will be suitable for monitoring fast neutrons.

  8. A Double Transducer for High Precision Ultrasonic Time-Domain Reflectometry Measurements

    PubMed Central

    Stade, Sam; Hakkarainen, Tuomas; Kallioinen, Mari; Mänttäri, Mika; Tuuva, Tuure

    2015-01-01

    Membrane fouling, where unwanted particles accumulate on the membrane surface and reduce its permeability, causes problems in membrane filtration processes. With ultrasonic time-domain reflectometry (UTDR) it is possible to measure the extent of membrane fouling and hence take actions to minimize it. However, the usability of UTDR is very limited to constant filtration conditions if the sonic velocity, which has a great impact on UTDR measurement accuracy, is unknown. With a reference transducer the actual sonic velocity can be measured. This requires another transducer to be installed in the module, where there may be only limited space or the module dimensions may not be suitable for the reference transducer. A double transducer described in this study eliminates the need for a separate reference transducer because in the double transducer the reference measurement is included in the design of the transducer holder. Two sensors in the same holder require less space. Other advantage is that the double transducer can be placed near the measurement target and hence the local sonic velocity can be determined. PMID:26131667

  9. Application of spatial time domain reflectometry measurements in heterogeneous, rocky substrates

    NASA Astrophysics Data System (ADS)

    Gonzales, C.; Scheuermann, A.; Arnold, S.; Baumgartl, T.

    2016-10-01

    Measurement of soil moisture across depths using sensors is currently limited to point measurements or remote sensing technologies. Point measurements have limitations on spatial resolution, while the latter, although covering large areas may not represent real-time hydrologic processes, especially near the surface. The objective of the study was to determine the efficacy of elongated soil moisture probes—spatial time domain reflectometry (STDR)—and to describe transient soil moisture dynamics of unconsolidated mine waste rock materials. The probes were calibrated under controlled conditions in the glasshouse. Transient soil moisture content was measured using the gravimetric method and STDR. Volumetric soil moisture content derived from weighing was compared with values generated from a numerical model simulating the drying process. A calibration function was generated and applied to STDR field data sets. The use of elongated probes effectively assists in the real-time determination of the spatial distribution of soil moisture. It also allows hydrologic processes to be uncovered in the unsaturated zone, especially for water balance calculations that are commonly based on point measurements. The elongated soil moisture probes can potentially describe transient substrate processes and delineate heterogeneity in terms of the pore size distribution in a seasonally wet but otherwise arid environment.

  10. Transient absorption spectroscopy on spiropyran monolayers using nanosecond pump-probe Brewster angle reflectometry.

    PubMed

    Siebenhofer, Bernhard; Gorelik, Sergey; Lear, Martin J; Song, Hong Yan; Nowak, Christoph; Hobley, Jonathan

    2013-05-01

    Self-assembled monolayers of 11-(3',3'-dimethyl-6,8-dinitrospiro[chromene-2,2'-indoline]-1'-yl) undecanoic acid (amphiphilic spiropyran) at the air-water interface are studied using Brewster angle reflectometry. Transient kinetics of the spiropyran to merocyanine conversion are recorded in a UV-pump, VIS-probe configuration. By varying the probe wavelength using an optical parametric oscillator, we are able to reconstruct absorption spectra of intermediate states with a time-resolution of 10 nanoseconds, limited by the temporal convolution of the two laser pulses. After UV irradiation, spiropyran converts to merocyanine in two stages. The first occurs within a timescale of several tens of nanoseconds and is heavily convoluted with the system response time, whereas the second stage occurs over a few hundred nanoseconds. During the rise time there is a small red shift in the transient absorption spectrum of ~20 nm. We assign the red shift and the slower kinetics to the isomerization of a merocyanine isomer cis about the central methine bond to those that are trans about the same bond. PMID:23396378

  11. Ultra-violet and visible absorption characterization of explosives by differential reflectometry

    NASA Astrophysics Data System (ADS)

    Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E.

    2013-03-01

    This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R2 > 0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and π-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials.

  12. Time-domain reflectometry probing systems for the monitoring of hydrological processes in the unsaturated zone

    NASA Astrophysics Data System (ADS)

    Kallioras, A.; Khan, A.; Piepenbrink, M.; Pfletschinger, H.; Koniger, F.; Dietrich, P.; Schuth, C.

    2016-08-01

    Precise measurements of the downward movement of precipitation through the unsaturated zone, as well as return flow of moisture to the atmosphere via evaporation, have always been challenging in regard to in-situ monitoring techniques. This study investigates the profile of volumetric water-content fluctuations within the unsaturated zone through a combination of field techniques, including in-situ measurements of the volumetric porewater content at different depths using specially designed time-domain reflectometry (TDR) probes. The probes are installed through direct-push vibro-coring methods, at significant depths within the unsaturated zone, providing continuous readings of the soil-moisture content throughout the unsaturated column. The measured waveform is analyzed by using the inverse modeling approach resulting in an apparent relative dielectric permittivity profile of the surrounding medium along the TDR probe length. The approach sufficiently analyzes the mechanisms of water fluxes through significant depths within the unsaturated zone, which in turn can be used to quantify groundwater recharge at areas where the unsaturated zone hydrology plays a key role in the recharge of the underlying aquifers (such as arid and hydrologically sensitive areas). The approach was applied at an experimental field site in the Upper Rhine Valley, Germany.

  13. Skin Cancer Detection by Spectroscopic Oblique-Incidence Reflectometry: Classification and Physiological Origins

    NASA Astrophysics Data System (ADS)

    Garcia-Uribe, Alejandro; Kehtarnavaz, Nasser; Marquez, Guillermo; Prieto, Victor; Duvic, Madeleine; Wang, Lihong V.

    2004-05-01

    Data obtained from 102 skin lesions in vivo by spectroscopic oblique-incidence reflectometry were analyzed. The participating physicians initially divided the skin lesions into two visually distinguishable groups based on the lesions' melanocytic conditions. Group 1 consisted of the following two cancerous and benign subgroups: (1) basal cell carcinomas and squamous cell carcinomas and (2) benign actinic keratoses, seborrheic keratoses, and warts. Group 2 consisted of (1) dysplastic nevi and (2) benign common nevi. For each group, a bootstrap-based Bayes classifier was designed to separate the benign from the dysplastic or cancerous tissues. A genetic algorithm was then used to obtain the most effective combination of spatiospectral features for each classifier. The classifiers, tested with prospective blind studies, reached statistical accuracies of 100% and 95% for groups 1 and 2, respectively. Properties that related to cell-nuclear size, to the concentration of oxyhemoglobin, and to the concentration of deoxyhemoglobin as well as the derived concentration of total hemoglobin and oxygen saturation were defined to explain the origins of the classification outcomes.

  14. Ultra-violet and visible absorption characterization of explosives by differential reflectometry.

    PubMed

    Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E

    2013-03-15

    This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R(2)>0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and π-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials.

  15. Gamma radiation influence on silica optical fibers measured by optical backscatter reflectometry and Brillouin sensing technique

    NASA Astrophysics Data System (ADS)

    Wosniok, A.; Sporea, D.; Neguţ, D.; Krebber, K.

    2016-05-01

    We have studied the influence of gamma rays on physical properties of different commercially available silica optical fibers stepwise irradiated up to a total dose of 100 kGy. The detection of radiation-induced changes in silica glass offers the possibility of using selected optical fibers as distributed radiation sensors. The measurements performed by us were based on optical backscatter reflectometry and Brillouin distributed sensing. The measurement methods enable an analysis of radiation-induced modification of the group refractive index and density of the optical fibers. The most distinct physical effect observed by us concerns the increase of the optical attenuation with rising total radiation doses. Quantitative measurement results indicate a crucial impact of fiber dopants on radiation-induced physical and sensory characteristics of silica optical fibers affected by differences in fiber fabrication techniques. Based on the obtained results, the suitability of distributed Brillouin sensing for dosimetry applications seems to be improved by modifying the refractive index profile of the fiber core.

  16. Study of a new central compact object: The neutron star in the supernova remnant G15.9+0.2

    NASA Astrophysics Data System (ADS)

    Klochkov, D.; Suleimanov, V.; Sasaki, M.; Santangelo, A.

    2016-08-01

    We present our study of the central point source CXOU J181852.0-150213 in the young Galactic supernova remnant (SNR) G15.9+0.2 based on the recent ~90 ks Chandra observations. The point source was discovered in 2005 in shorter Chandra observations and was hypothesized to be a neutron star associated with the SNR. Our X-ray spectral analysis strongly supports the hypothesis of a thermally emitting neutron star associated with G15.9+0.2. We conclude that the object belongs to the class of young cooling low-magnetized neutron stars referred to as central compact objects (CCOs). We modeled the spectrum of the neutron star with a blackbody spectral function and with our hydrogen and carbon neutron star atmosphere models, assuming that the radiation is uniformly emitted by the entire stellar surface. Under this assumption, only the carbon atmosphere models yield a distance that is compatible with a source located in the Galaxy. In this respect, CXOU J181852.0-150213 is similar to two other well-studied CCOs, the neutron stars in Cas A and in HESS J1731-347, for which carbon atmosphere models were used to reconcile their emission with the known or estimated distances.

  17. Using neutron scattering to explore new magnetoelectric phenomena in both thin films and skyrmion lattices

    NASA Astrophysics Data System (ADS)

    White, Jonathan

    2014-03-01

    Neutron scattering continues to be an invaluable tool for exploring the microscopic magnetic properties of magnetoelectric (ME) and multiferroic materials. Here I will present studies where neutron scattering techniques less commonly used for studying MEs have provided pivotal insight into new ME coupling phenomena. Firstly, we have used polarized neutron reflectometry (PNR) in a study of multiferroic and strained orthorhombic (o-) LuMnO3 thin films. Unlike bulk o-LuMnO3 which is a commensurate antiferromagnet, the films display drastically different properties and are simultaneously incommensurately antiferromagnetic and ferromagnetic at low temperature. The pivotal PNR experiments allowed us to measure the spatial distribution of the ferromagnetic magnetization in the films, and show that the ferromagnetism is most pronounced close to the film-substrate interface which is highly strained due to the lattice mismatch. We could further show the ferromagnetism and antiferromagnetism in the film to be directly coupled, and so demonstrate the promising functional properties of these films. Secondly, we have used small-angle neutron scattering (SANS) to study the topologically protected magnetic spin vortices, or skyrmions, in the chiral-lattice ME insulator Cu2OSeO3. Until 2012, skyrmions had been observed only in (semi)conducting B20 compounds where it is known that they can be manipulated by conduction electrons. From our SANS experiments on Cu2OSeO3, we show that applied electric fields can control the skyrmion lattice orientation in insulators, and in an essentially lossless manner that is dependent on both the size and sign of the electric field. These results provide the first evidence for a the electric field control of topologically protected magnetism in bulk magnetoelectrics.

  18. Neutron diffraction study of hydrogen-bond symmetrization in δ-AlOOD

    NASA Astrophysics Data System (ADS)

    Sano-Furukawa, A.; Hattori, T.; Kuribayashi, T.

    2013-12-01

    δ-AlOOH, a high-pressure polymorph of diaspore, is an important hydrous mineral in the deep earth that has the ability to transport hydrogen into the lower mantle. Theoretical studies have pointed out that hydrogen would locate at the center between two oxygen atoms at high pressure, which is so called hydrogen-bond symmetrization [1]. It was also suggested that the symmetrization would trigger the increase of bulk modulus, which is one of the important parameters of minerals at high pressure. The transition of δ-AlOOH(D) at high pressure has been suggested by X-ray and neutron diffraction [2, 3]. X-ray diffraction study found that the axes a and b where the hydrogen bond is oriented become less compressible above 12 GPa in δ-AlOOD. Neutron diffraction study on δ-AlOOD up to 9.2 GPa showed the increase of O-D bond distance, that is considered as a precousor phenomena of the symmetrization. However, the pressure was insufficient to observe the symmetrization. To investigate the symmetrization of hydrogen bond directly, we conducted neutron diffraction experiments to 16.7 GPa at PLANET, MLF in J-PARC. Powder sample of δ-AlOOD was loaded in Paris-Edinburgh press with double-toroid sintered diamond anvils with methanol-ethanol mixture of pressure medium. In the experiments, the disappearance of 120 refrection was observed at 12.1 GPa, indicating the transition from P21nm to Pnnm, which can be attributed to the disorder of hydrogen bond or the symmtrization. Results of Rietveld refienment will be shown in the presentation. [1] Tsuchiya et al., Geophys. Res. Lett., 29, 1909, 2002. [2] Sano-Furukawa et al., Am. Mineral., 93, 1558-1567, 2008. [3] Sano-Furukawa et al., Am. Mineral., 94, 1255-1261, 2009.

  19. Neutron diffraction, specific heat and magnetization studies on Nd2CuTiO6

    NASA Astrophysics Data System (ADS)

    Rayaprol, S.; Kaushik, S. D.; Kumar, Naresh; Singh, K.; Guillou, F.; Simon, C.

    2016-05-01

    Structural and physical properties of a double-perovskite compound, Nd2CuTiO6 have been studied using neutron diffraction, magnetization and specific heat measurements. The compound crystallizes in an orthorhombic structure in space group Pnma. The interesting observation we make here is that, though no long range magnetic order is observed between 2 and 300K, the low temperature specific heat and magnetic susceptibility behavior exhibits non-Fermi liquid like behavior in this insulating compound. The magnetization and specific heat data are presented and discussed in light of these observations.

  20. Inelastic neutron scattering study of light-induced dynamics of a photosynthetic membrane system

    SciTech Connect

    Furrer, A.; Stoeckli, A.

    2010-01-15

    Inelastic neutron scattering was employed to study photoeffects on the molecular dynamics of membranes of the photosynthetic bacterium Rhodopseudomonas viridis. The main photoactive parts of this biomolecular system are the chlorophyll molecules whose dynamics were found to be affected under illumination by visible light in a twofold manner. First, vibrational modes are excited at energies of 12(2) and 88(21) cm{sup -1}. Second, a partial 'freezing' of rotational modes is observed at energies of 1.2(3) and 2.9(5) cm{sup -1}. These results are attributed to a possible coupling between molecular motions and particular mechanisms in the photosynthetic process.