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Sample records for mev neutron scattering

  1. Elastic Neutron Scattering at 96 MeV

    SciTech Connect

    Hildebrand, A.; Blomgren, J.; Atac, A.; Bergenwall, B.; Johansson, C.; Klug, J.; Mermod, P.; Nilsson, L.; Pomp, S.; Esterlund, M.; Dangtip, S.; Tippawan, U.; Phansuke, P.; Jonsson, O.; Renberg, P.-U.; Prokofiev, A.; Nadel-Turonski, P.; Elmgren, K.; Olsson, N.; Blideanu, V.

    2005-05-24

    A facility for detection of scattered neutrons in the energy interval 50-130 MeV, SCANDAL (SCAttered Nucleon Detection AssembLy), has recently been installed at the 20 - 180-MeV neutron beam line of The Svedberg Laboratory, Uppsala. Elastic neutron scattering from 12C, 16O, 56Fe, 89Y, and 208Pb has been studied at 96 MeV in the 10-70 deg. interval. The results from 12C and 208Pb have recently been published,6 while the data from 16O, 56Fe, and 89Y are under analysis. The achieved energy resolution, 3.7 MeV, is about an order of magnitude better than for any previous experiment above 65 MeV incident energy. The present experiment represents the highest neutron energy where the ground state has been resolved from the first excited state in neutron scattering. A novel method for normalization of the absolute scale of the cross section has been used. The estimated normalization uncertainty, 3%, is unprecedented for a neutron-induced differential cross section measurement on a nuclear target. The results are compared with modern optical model predictions, based on phenomenology or microscopic theory. Applications for these measurements are nuclear-waste incineration, single-event upsets in electronics, and fast-neutron therapy.

  2. Neutron-neutron quasifree scattering in nd breakup at 10 MeV

    NASA Astrophysics Data System (ADS)

    Malone, R. C.; Crowe, B.; Crowell, A. S.; Cumberbatch, L. C.; Esterline, J. H.; Fallin, B. A.; Friesen, F. Q. L.; Han, Z.; Howell, C. R.; Markoff, D.; Ticehurst, D.; Tornow, W.; Witała, H.

    2016-03-01

    The neutron-deuteron (nd) breakup reaction provides a rich environment for testing theoretical models of the neutron-neutron (nn) interaction. Current theoretical predictions based on rigorous ab-initio calculations agree well with most experimental data for this system, but there remain a few notable discrepancies. The cross section for nn quasifree (QFS) scattering is one such anomaly. Two recent experiments reported cross sections for this particular nd breakup configuration that exceed theoretical calculations by almost 20% at incident neutron energies of 26 and 25 MeV [1, 2]. The theoretical values can be brought into agreement with these results by increasing the strength of the 1S0 nn potential matrix element by roughly 10%. However, this modification of the nn effective range parameter and/or the 1S0 scattering length causes substantial charge-symmetry breaking in the nucleon-nucleon force and suggests the possibility of a weakly bound di-neutron state [3]. We are conducting new measurements of the cross section for nn QFS in nd breakup. The measurements are performed at incident neutron beam energies below 20 MeV. The neutron beam is produced via the 2H(d, n)3He reaction. The target is a deuterated plastic cylinder. Our measurements utilize time-of-flight techniques with a pulsed neutron beam and detection of the two emitted neutrons in coincidence. A description of our initial measurements at 10 MeV for a single scattering angle will be presented along with preliminary results. Also, plans for measurements at other energies with broad angular coverage will be discussed.

  3. Elastic neutron scattering at 96 MeV from {sup 12}C and {sup 208}Pb

    SciTech Connect

    Klug, J.; Blomgren, J.; Atac, A.; Bergenwall, B.; Hildebrand, A.; Johansson, C.; Mermod, P.; Pomp, S.; Tippawan, U.; Nilsson, L.; Elmgren, K.; Olsson, N.; Jonsson, O.; Prokofiev, A.V.; Renberg, P.-U.; Nadel-Turonski, P.; Dangtip, S.; Phansuke, P.; Oesterlund, M.; Le Brun, C.

    2003-12-01

    A facility for detection of scattered neutrons in the energy interval 50-130 MeV, SCANDAL, has recently been installed at the 20-180 MeV neutron beam line of the The Svedberg Laboratory, Uppsala. Elastic neutron scattering from {sup 12}C and {sup 208}Pb has been studied at 96 MeV in the 10 deg. -70 deg. interval. The achieved energy resolution, 3.7 MeV, is about an order of magnitude better than for any previous experiment above 65 MeV incident energy. The present experiment represents the highest neutron energy where the ground state has been resolved from the first excited state in neutron scattering. A novel method for normalization of the absolute scale of the cross section has been used. The estimated normalization uncertainty, 3%, is unprecedented for a neutron-induced differential cross section measurement on a nuclear target. The results are compared with modern optical model predictions based on phenomenology or microscopic nuclear theory.

  4. Scattering of 14.1 Mev Neutrons in Aluminum, Copper and Molybdenum.

    NASA Astrophysics Data System (ADS)

    Wagiran, Husin Bin

    Available from UMI in association with The British Library. The time of flight spectrometer based on the associated particle time of flight technique has been constructed in the present work to measure the elastic and non-elastic differential cross-sections of 14.1 MeV neutrons scattered from D-T fusion reactor blanket materials, Al, Cu and Mo. The 14.1 MeV neutrons were produced from T(d,n)He^4 reaction by accelerating the deuteron beam up to 140 keV using S.A.M.E.S. type J electrostatic accelerator. The time origin of the neutron was determined by detecting the associated alpha-particles using Ne102A thin plastic scintillator which provide 100% detection efficiency. A plastic scintillator NE102A mounted on a fast focused photomultiplier tube Philip 56 AVP was used in the neutron channel which provide 2.2 +/- 0.2 ns time resolution at FWHM. The angular distributions of 14.1 MeV neutrons scattered from the thin Al, Cu and Mo samples were measured in the angular range between 0^circ to 90^circ. The data are presented for elastic scattering and non-elastic neutrons scattering in the energy ranges (5-14) MeV in 3 MeV intervals. The differential inelastic cross-sections in Al to the sum of 0.84 and 1.04 MeV states are also presented. The differential elastic scattering cross-sections are compared to the results from ENDF-BIV and other published data. Legendre polynomial fits were produced and the integrated elastic cross-sections obtained from the fits were compared with the data of ENDF -BIV and others. The results of the differential elastic scattering cross-sections are compared to the prediction of earlier global optical models using optical model programme SCAT-2. The differential cross-sections of 14.1 MeV neutrons scattered from thick sample of Al and Cu were measured at various thicknesses over the angular range between 0 ^circ to 90^ circ. No similar measurements have been found to compare with the present work. The variation of measured cross-sections with

  5. Coupled-channel analysis of neutron scattering from /sup 12/C between 9 and 15 MeV

    SciTech Connect

    Hansen, L.F.; Meigooni, A.S.

    1986-07-01

    A deformed and energy dependent phenomenological optical model potential and coupled-channel formalism for deformed nuclei have been used in the analysis of elastic and inelastic (Q = 4.439 MeV) scattering, and analyzing power for neutrons scattered from /sup 12/C in the energy range of 9 to 15 MeV. 6 refs., 1 fig., 1 tab.

  6. Neutron transition densities for 48Ca from proton scattering at 200 and 318 MeV

    NASA Astrophysics Data System (ADS)

    Feldman, A. E.; Kelly, J. J.; Flanders, B. S.; Khandaker, M. A.; Seifert, H.; Boberg, P.; Hyman, S. D.; Karen, P. H.; Norum, B. E.; Welch, P.; Chen, Q.; Bacher, A. D.; Berg, G. P.; Stephenson, E. J.; Nanda, S.; Saha, A.; Scott, A.

    1994-04-01

    Differential cross sections and analyzing powers for scattering of 200 and 318 MeV protons have been measured for states of 48Ca up to 7 MeV of excitation. The data cover c.m. momentum transfers from approximately 0.4 to 3.0 fm-1. Neutron transition densities were extracted for the 2+1,3-1,3-2,4+2, and 5-1 states using density-dependent empirical effective interactions previously calibrated upon elastic and inelastic scattering data for 16O and 40Ca. The corresponding proton transition densities were obtained from electron scattering data and held fixed during the analysis. Fits performed to the data for either energy provide excellent predictions for the other. Neutron densities fitted to data for either energy independently agree very well with each other and with the densities fitted to both data sets simultaneously. These densities are also consistent with earlier data for 500 MeV protons. The energy-independence of the extracted transition densities demonstrates that residual errors in the reaction model are compatible with the error bands estimated by the fitting procedure. Several additional tests of the model dependence of the results were performed also. The proton and neutron transition densities are compared with calculations based upon the extended random phase approximation, which includes 2p2h correlations. These calculations are most successful for densities dominated by 1p1h configurations, whereas densities requiring substantial 2p2h contributions tend to be underestimated.

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

    SciTech Connect

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

    1980-02-01

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

  8. Neutron scattering differential cross sections for 23Na from 1.5 to 4.5 MeV

    NASA Astrophysics Data System (ADS)

    Vanhoy, J. R.; Hicks, S. F.; Chakraborty, A.; Champine, B. R.; Combs, B. M.; Crider, B. P.; Kersting, L. J.; Kumar, A.; Lueck, C. J.; Liu, S. H.; McDonough, P. J.; McEllistrem, M. T.; Peters, E. E.; Prados-Estévez, F. M.; Sidwell, L. C.; Sigillito, A. J.; Watts, D. W.; Yates, S. W.

    2015-07-01

    Measurements of neutron elastic and inelastic scattering cross sections from 23Na have been performed for sixteen incident neutron energies between 1.5 and 4.5 MeV. These measurements were complemented by γ-ray excitation functions using the (n ,n‧ γ) reaction to include excited levels not resolved in the neutron detection measurements. The time-of-flight (TOF) technique was employed for background reduction in both neutron and γ-ray measurements and for energy determination in neutron detection measurements. Previous reaction model evaluations relied primarily on neutron total cross sections and four (n, n0) and (n, n1) angular distributions in the 5 to 9 MeV range. The inclusion of more inelastic channels and measurements at lower incident neutron energies provide additional information on direct couplings between elastic and inelastic scattering as a function of angular momentum transfer. Reaction model calculations examining collective direct-coupling and compound absorption components were performed.

  9. The Angular Distribution of Neutrons Scattered from Deuterium below 2 MeV

    NASA Astrophysics Data System (ADS)

    Nankov, N.; Plompen, A. J. M.; Kopecky, S.; Kozier, K. S.; Roubtsov, D.; Rao, R.; Beyer, R.; Grosse, E.; Hannaske, R.; Junghans, A. R.; Massarczyk, R.; Schwengner, R.; Yakorev, D.; Wagner, A.; Stanoiu, M.; Canton, L.; Nolte, R.; Röttger, S.; Beyer, J.; Svenne, J.

    2014-05-01

    Neutron elastic scattering measurements were carried out at the nELBE neutron time-of-flight facility at a 6 m flight path. Energies below 2 MeV were studied using a setup consisting of eight 6Li-glass detectors placed at nominal angles of 15∘ and 165∘ with respect to the incident neutron beam. A deuterated polyethylene sample with 99.999% enrichment in deuterium was used. These angles were chosen since an earlier study showed that the ratio of the differential cross section at these angles is the most sensitive to differences in evaluated files and model calculations. Accurate 165∘/15∘ angle ratios were obtained. Above 1 MeV these are somewhat larger than given by ENDF/B-VII. Simultaneously the early day experiments using a proportional counter to infer angular distributions from deuterium recoil pulse height distributions are being studied through a new experiment with such a device at the Physikalisch-Technische Bundesanstalt (PTB). At 500 keV this experiment favors ENDF/B-VII over JENDL-4.0, while at lower energies agreement with the data is similar.

  10. Ambiguities in the elastic scattering of 8 MeV neutrons from adjacent nuclei

    NASA Astrophysics Data System (ADS)

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

    1990-12-01

    Ratios of the cross sections for the elastic scattering of 8 MeV neutrons from adjacent nuclei are measured over the angular range ~ 20°-160° for the target pairs 51V/Cr, 59Co/ 58Ni, Cu/Zn, 89Y/ 93Nb, 89Y/Zr, 93Nb/Zr, In/Cd and 209Bi/Pb. The observed ratios vary from unity by as much as a factor of ~2 at some angles for the lighter target pairs. The ratios are generally consistent with a model based upon a real Woods-Saxon potential whose geometry is essentially constant between pairs, and whose strength has an ( N- Z)/ A (symmetry) component with a magnitude of ~ 16 MeV. For pairs with A > 100, a constant-geometry derivative Woods-Saxon imaginary potential, with a symmetry strength of ~15 MeV, explains the ratios. However, for the lighter nuclei, the difffuseness of the imaginary potential varies rapidly near the N = 28 and N = 50 shell closures, and for the 59Co- 58Ni and Cu-Zn pairs, the imaginary symmetry-potential strength is about twice the 15 MeV global value. A method for approximating the spin-spin potential is given, and it is shown that this interaction makes a negligible contribution to the calculated ratios. However, channel coupling can lead to large reorientation effects which can substantially change the calculated ratios. Differences in the spin-orbit interaction between neighboring pairs can significantly affect the calculated ratios.

  11. Angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by 12C nuclei

    NASA Astrophysics Data System (ADS)

    Bystritsky, V. M.; Grozdanov, D. N.; Zontikov, A. O.; Kopach, Yu. N.; Rogov, Yu. N.; Ruskov, I. N.; Sadovsky, A. B.; Skoy, V. R.; Barmakov, Yu. N.; Bogolyubov, E. P.; Ryzhkov, V. I.; Yurkov, D. I.

    2016-07-01

    The work is devoted to measuring the angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by 12C nuclei. A portable ING-27 neutron generator (designed and fabricated at VNIIA, Moscow) with a built-in 64-pixel silicon α-detector was used as a source of tagged neutrons. The γ-rays of characteristic nuclear radiation from 12C were detected with a spectrometric system that consisted of 22 γ-detectors based on NaI(Tl) crystals arranged around the carbon target. The measured angular distribution of 4.43-MeV γ-rays is analyzed and compared with the results of other published experimental works.

  12. Test of charge symmetry in neutron-proton elastic scattering at 477 MeV

    SciTech Connect

    Abegg, R.; Bandyopadhyay, D.; Birchall, J.; Cairns, E.W.; Coombes, H.; Davis, C.A.; Davison, N.E.; Delheij, P.P.J.; Green, P.W.; Greeniaus, L.G.; Gubler, H.P.; Healy, D.C.; Lapointe, C.; Lee, W.P.; McDonald, W.J.; Miller, C.A.; Moss, G.A.; Plattner, G.R.; Poffenberger, P.R.; Ramsay, W.D.; Roy, G.; Soukup, J.; Svenne, J.P.; Tkachuk, R.; van Oers, W.T.H.; Wait, G.D.; Zhang, Y.P.

    1986-06-16

    An experiment resulting in the first measurement of the isospin-mixing, charge-symmetry violating component of the n-italic-p-italic interaction has been performed. The experiment determined the difference in the angles of the zero crossing of the neutron and proton analyzing powers A-italic/sub n-italic/ and A-italic/sub p-italic/ at 477 MeV. In terms of the laboratory scattering angle of the neutron, the measured difference t-italich-italice-italict-italica-italic/sub 0//sub n-italic/(A/sub n/)= -t-italich-italice-italict-italica-italic/sub 0//sub n-italic/(A/sub p/) = +0.13X(de +- 0.06 X(de( +- 0.03X(de) where the second error is a worst case estimate of systematic error. The resulting difference in the analyzing powers at the zero-crossing angle A-italic/sub n-italic/-A/sub p/ = +0.0037 +- 0.0017( +- 0 .0008).

  13. Measurement of the Wolfenstein parameters for proton-proton and proton-neutron scattering at 500 MeV

    SciTech Connect

    Marshall, J.A.

    1984-07-01

    Using liquid hydrogen and liquid deuterium targets respectively, forward angle (ten degrees to sixty degrees in the center of Mass) free proton-proton and quasielastic proton-proton and proton-neutron triple scattering data at 500 MeV have been obtained using the high resolution spectrometer at the Los Alamos Meson Physics Facility. The data are in reasonable agreement with recent predictions from phase shift analyses, indicating that the proton-nucleon scattering amplitudes are fairly well determined at 500 MeV. 32 references.

  14. Investigation of Three-Body Force Effects in Neutron-Deuteron Scattering at 95 MeV

    SciTech Connect

    Mermod, P.; Blomgren, J.; Bergenwall, B.; Hildebrand, A.; Johansson, C.; Klug, J.; Oesterlund, M.; Pomp, S.; Nilsson, L.; Olsson, N.; Tippawan, U.; Jonsson, O.; Prokofiev, A.; Renberg, P.-U.; Nadel-Turonski, P.; Maeda, Y.; Sakai, H.; Tamii, A.

    2005-05-24

    We have measured the neutron-deuteron (nd) elastic-scattering differential cross section at 95 MeV incident neutron energy, using both the Medley and the SCANDAL setups at TSL in Uppsala. The full angular distribution was covered by detecting recoil deuterons from thin CD2 targets, and the result was normalized to the neutron-proton (np) cross section. Recent theories predict that three-nucleon (3N) force effects, if present, would affect the cross section in the minimum region by about 30%. The results are compared with theoretical calculations and are well described if 3N forces are included.

  15. Ambiguities in the elastic scattering of 8 MeV neutrons from adjacent nuclei

    SciTech Connect

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

    1989-10-01

    Ratios of the cross sections for elastic scattering of 8 MeV neutrons from adjacent nuclei are measured over the angular range {approx}20{degree} {minus} 160{degree} for the target pairs {sup 51}V/Cr, {sup 59}Co/{sup 58}Ni, Cu/Zn, {sup 89}Y/{sup 93}Nb, {sup 89}Y/Zr, {sup 93}Nb/Zr, In/Cd and {sup 209}Bi/Pb. The observed ratios vary from unity by as much as a factor of {approx}2 at some angles for the lighter target pairs. Approximately half the measured ratios are reasonably explained by a simple spherical optical model, including size and isospin contributions. In all cases, the geometry of the real optical--model potential is essentially the same for neighboring nuclei, and the real--potential strengths are consistent with the Lane model. In contrast, it is found that the imaginary potential may be quite different for adjacent nuclei, and the nature of this difference is examined. It is shown that the spin--spin interaction has a negligible effect on the calculation of the elastic--scattering ratios, but that channel coupling, leading to a large reorientation of the target ground state, can be a consideration, particularly in the {sup 59}Co/{sup 58}Ni case. In the A {approx} 50--60 region the calculated ratios are sensitive to spin--orbit effects, but the exact nature of this interaction must await more definitive polarization measurements. The measured and calculated results suggest that the concept of a conventional global'' or even regional'' optical potential provides no more than a qualitative representation of the physical reality for a number of cases. 48 refs., 14 figs., 3 tabs.

  16. Re-evaluation of neutron-{sup 4}He elastic scattering data near 20 MeV

    SciTech Connect

    Drosg, M.; Avalos Ortiz, R.; Hoop, B.

    2011-06-15

    Measured differential elastic-scattering cross sections of 17.72-, 20.97-, and 23.72-MeV neutrons from liquid helium-4 were re-evaluated and were corrected for sample-size and multiple-scattering effects by means of a Monte Carlo technique implemented in a more recent code (mcnpx). Results indicate that earlier corrections via the code maggie-2 overestimated the size of multiple-scattering effects by an order of magnitude. The corrected differential cross sections and Legendre coefficients obtained by least-squares fits are given.

  17. Evidence of three-body force effects in neutron-deuteron scattering at 95 MeV

    SciTech Connect

    Mermod, P.; Blomgren, J.; Hildebrand, A.; Johansson, C.; Klug, J.; Oesterlund, M.; Pomp, S.; Tippawan, U.; Bergenwall, B.; Nilsson, L.; Olsson, N.; Jonsson, O.; Prokofiev, A.; Renberg, P.-U.; Nadel-Turonski, P.; Maeda, Y.; Sakai, H.; Tamii, A.

    2005-12-15

    Recently, we have reported a measurement of the neutron-deuteron elastic scattering differential cross section at 95 MeV. In the present work, the previous results are confirmed with an independent measurement performed with another setup. The new data cover the full angular distribution by combining neutron detection and deuteron detection, and have an unprecedented precision in the region of the cross-section minimum, where three-nucleon forces are expected to be significant. The effect already identified in the previous measurement is clearly seen in the present data, which agree well with theoretical descriptions including three-nucleon forces.

  18. The gamma rays associated with the inelastic scattering of 14 MeV neutrons in large samples of iron

    NASA Astrophysics Data System (ADS)

    Al-Shalabi, B.; Cox, A. J.

    1983-02-01

    Iron is likely to be a common construction material in the first generation of fusion reactors and a knowledge of the effect of multiple scattering processes in large samples of this material is important for reactor design. In the present work, the angular distributions of gamma rays produced after the inelastic scattering of 14 MeV neutrons in increasing thicknesses of iron samples have been measured. The measurements were performed using an associated particle time of flight system to gate the gamma-ray signals and reduce the background to an acceptable level. The 14 MeV neutrons were produced by the T(d, n) 4He reaction with the deuterons being accelerated in a 150 KV SAMES type J accelerator at Aston and in the 3 MeV dynamitron at the Joint Radiation Centre, Birmingham. The incident neutron flux was monitored by counting the alpha particles associated with the neutrons passing through the sample. The gamma rays were detected by a NaI(Tl) scintillator mounted on a 56 AVP photo-multiplier tube. The samples of iron varied in thickness from 2 to 10.5 cm. In each case, the differential cross sections for gamma ray production at angles varying between 20° and 90° to the incident neutron beam were measured. The results were fitted to an even order Legendre polynomial. The increase in effective cross section σ due to multiple scattering effects as the sample thickness increased was found to obey the law σ = σ0 exp αx in the region considered for each sample where x is the sample thickness in mean free paths and α has an average value of 0.17 ± 1 (mean free paths) -1. The results have been analysed on a semi-empirical model based on the assumption of continuous slowing down.

  19. The prediction of Neutron Elastic Scattering from Tritium for E(n) = 6-14 MeV

    SciTech Connect

    Anderson, J D; Dietrich, F S; Luu, T; McNabb, D P; Navratil, P; Quaglioni, S

    2010-06-14

    In a recent report Navratil et al. evaluated the angle-integrated cross section and the angular distribution for 14-MeV n+T elastic scattering by inferring these cross sections from accurately measured p+3He angular distributions. This evaluation used a combination of two theoretical treatments, based on the no-core shell model and resonating-group method (NCSM/RGM) and on the R-matrix formalism, to connect the two charge-symmetric reactions n+T and p+{sup 3}He. In this report we extend this treatment to cover the neutron incident energy range 6-14 MeV. To do this, we evaluate angle-dependent correction factors for the NCSM/RGM calculations so that they agree with the p+{sup 3}He data near 6 MeV, and using the results found earlier near 14 MeV we interpolate these correction factors to obtain correction factors throughout the 6-14 MeV energy range. The agreement between the corrected NCSM/RGM and R-Matrix values for the integral elastic cross sections is excellent ({+-}1%), and these are in very good agreement with total cross section experiments. This result can be attributed to the nearly constant correction factors at forward angles, and to the evidently satisfactory physics content of the two calculations. The difference in angular shape, obtained by comparing values of the scattering probability distribution P({mu}) vs. {mu}(the cosine of the c.m. scattering angle), is about {+-}4% and appears to be related to differences in the two theoretical calculations. Averaging the calculations yields P({mu}) values with errors of {+-}2 1/2 % or less. These averaged values, along with the corresponding quantities for the differential cross sections, will form the basis of a new evaluation of n+T elastic scattering. Computer files of the results discussed in this report will be supplied upon request.

  20. Forward-angle neutron-proton scattering at 96 MeV

    SciTech Connect

    Johansson, C.; Blomgren, J.; Atac, A.; Bergenwall, B.; Hildebrand, A.; Klug, J.; Mermod, P.; Pomp, S.; Oesterlund, M.; Dangtip, S.; Tippawan, U.; Elmgren, K.; Jonsson, O.; Prokofiev, A.V.; Renberg, P.-U.; Nadel-Turonski, P.; Nilsson, L.; Olsson, N.

    2005-02-01

    The differential np scattering cross section has been measured at 96 MeV in the angular range {theta}{sub c.m.}=20 deg. -76 deg. Together with an earlier data set at the same energy, covering the angles {theta}{sub c.m.}=74 deg. -180 deg., a new data set has been formed in the angular range {theta}{sub c.m.}=20 deg. - 180 deg. This extended data set has been normalized to the experimental total np cross section, resulting in a renormalization of the earlier data of 0.7%, which is well within the reported normalization uncertainty for that experiment. A novel normalization technique has been investigated. The results on forward np scattering are in reasonable agreement with theory models and partial wave analyses and have been compared with data from the literature.

  1. Measurements of the differential cross sections for elastic and inelastic scattering of 14-MeV neutrons in natural chromium, iron, nickel, and niobium

    SciTech Connect

    Christodoulou, E.G. . Dept. of Radiology); Tsirliganis, N.C. . Dept. of Electrical Engineering and Electronics); Knoll, G.F. . Dept. of Nuclear Engineering and Radiological Sciences)

    1999-07-01

    The time-of-flight technique was used with the ring scattering geometry in a laboratory with low neutron-scattering background to measure the angular distributions of the cross sections for elastic and inelastic scattering of 14-MeV neutrons in natural chromium, iron, nickel, and niobium. Specifically for inelastic scattering, the measurements included the 1.43- and 4.56-MeV levels of [sup 52]Cr; the 0.85-, (2.94 to 3.12)-, and (4.46 to 4.51)-MeV level groups of [sup 56]Fe; the 1.33-MeV level of [sup 60]Ni combined with the 1.45-MeV level of [sup 58]Ni; and the 4.48-MeV level of [sup 58]Ni. Pulses of neutrons with time width of 0.9 to 1.1 ns were produced via the D-T reaction in a 150-keV linear accelerator, with average intensities of 9 [times] 10[sup 8] n/s. The scattering angles ranged from [approximately]16 to [approximately]160 deg, with a typical step of [approximately]10 deg. The overall uncertainty for the elastic scattering cross section was in the range of 7 to 10% for all materials, except around the minima of the angular distribution for niobium. The uncertainties for the inelastic scattering cross sections were estimated to be between 8 and 24%. The measured angular distributions were compared with the evaluations in the ENDF/B-VI, JENDL-3, CENDL-2, BROND-2, and JEF-2 nuclear data libraries. For elastic scattering, there are no significant discrepancies in general, neither among the evaluations nor between the present data and the evaluations. For the inelastic scattering there are substantial discrepancies both in shape and magnitude among the evaluations (when available) as well as between the present data and the evaluations.

  2. Secondary neutron spectrum from 250-MeV passively scattered proton therapy: Measurement with an extended-range Bonner sphere system

    SciTech Connect

    Howell, Rebecca M.; Burgett, E. A.

    2014-09-15

    Purpose: Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire

  3. Neutron scattering and models: Titanium

    SciTech Connect

    Smith, A.B.

    1997-07-01

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

  4. Proton-Proton Scattering at 105 Mev and 75 Mev

    DOE R&D Accomplishments Database

    Birge, R. W.; Kruse, U. E.; Ramsey, N. F.

    1951-01-31

    The scattering of protons by protons provides an important method for studying the nature of nuclear forces. Recent proton-proton scattering experiments at energies as high as thirty Mev{sup 1} have failed to show any appreciable contribution to the cross section from higher angular momentum states, but it is necessary to bring in tensor forces to explain the magnitude of the observed cross section.

  5. Neutron scattering and absorption properties

    SciTech Connect

    Holden, N.E.

    1993-12-01

    The Table in this report presents an evaluated set of values for the experimental quantities, which characterize the properties for scattering and absorption of neutrons. The neutron cross section is given for room temperature neutrons, 20.43{degree}C, corresponds to a thermal neutron energy of 0.0253 electron volts (eV) or a neutron velocity of 2200 meters/second. The neutron resonance integral is defined over the energy range from 0.5 eV to 0.1 {times} 10{sup 6} eV, or 0.1 MeV. A list of the major references used is given below. The literature cutoff data is October 1993. Uncertainties are given in parentheses. Parentheses with two or more numbers indicate values to the excited states(s) and to the ground state of the product nucleus.

  6. MAGNETIC NEUTRON SCATTERING

    SciTech Connect

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

    2004-07-30

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

  7. Neutron scattering in Australia

    SciTech Connect

    Knott, R.B.

    1994-12-31

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

  8. Thermal neutron scattering in graphite

    NASA Astrophysics Data System (ADS)

    Al-Qasir, Iyad Ibrahim

    Generation IV Very High Temperature Reactor (VHTR) concepts, are graphite moderated and gas cooled thermal spectrum reactors. The characteristics of the low energy (E < 1 eV) neutron spectrum in these reactors will be dictated by the process of neutron slowing-down and thermalization in the graphite moderator. The ability to accurately predict this process in these reactors can have significant neutronic and safety implications. In reactor design calculations, thermal neutron scattering cross section libraries are needed for the prediction of the thermal neutron environment in the core. Currently used libraries (ENDF/B-VII) are a product of the 1960s and remain based on many physical approximations. In addition, these libraries show noticeable discrepancies with experimental data. In this work, investigation of thermal neutron scattering in graphite as a function of temperature was performed. The fundamental input for the calculation of thermal neutron scattering cross sections, i.e., the phonon frequency distribution and/or the dispersion relations, was generated using a modern approach that is based on quantum mechanical electronic structure (ab initio) simulations combined with a lattice dynamics direct method supercell approach. The calculations were performed using the VASP and PHONON codes. The VASP calculations used the local density approximation, and the projector augmented-wave pseudopotential. A supercell of 144 atoms was used; and the integration over the Brillouin zone was confined to a 3x3x4 k-mesh generated by the Monkhorst-Pack scheme. A plane-wave basis set with an energy cutoff of 500 eV was applied. The corresponding dispersion relations, heat capacity, and phonon frequency distribution show excellent agreement with experimental data. Despite the use of the above techniques to produce more accurate input data, the examination of the results indicated persistence of the inconsistencies between calculations and measurements at neutron energies

  9. Small Angle Neutron Scattering

    SciTech Connect

    Urban, Volker S

    2012-01-01

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

  10. Calculates Thermal Neutron Scattering Kernel.

    Energy Science and Technology Software Center (ESTSC)

    1989-11-10

    Version 00 THRUSH computes the thermal neutron scattering kernel by the phonon expansion method for both coherent and incoherent scattering processes. The calculation of the coherent part is suitable only for calculating the scattering kernel for heavy water.

  11. Little Boy neutron spectrum below 3 MeV

    SciTech Connect

    Evans, A.E.; Bennett, E.F.; Yule, T.J.

    1984-01-01

    The leakage neutron spectrum from the Little Boy replica has been measured from 12 keV to 3 MeV using a high-resolution /sup 3/He ionization chamber, and from 1 keV to 3 MeV using proton-recoil proportional counters. The /sup 3/He-spectrometer measurements were made at distances of 0.75 and 2.0 m from the active center and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly. Proton-recoil measurments were made at 90/sup 0/ to the assembly axis at distances of 0.75 and 2.0 m, with a shielded measurement made at 2.0 m to estimate background due to scattering. The /sup 3/He spectrometer was calibrated at Los Alamos using monoenergetic /sup 7/Li(p,n)/sup 7/Be neutrons to generate a family of response functions. The proton-recoil counters were calibrated at Argonne by studying the capture of thermal neutrons by nitrogen in the counters, by observation of the 24-keV neutron resonance in iron, and by relating to the known hydrogen content of the counters. The neutron spectrum from Little Boy was found to be highly structured, with peaks corresponding to minima in the iron total neutron cross section. In particular, influence of the 24-keV iron window was evident in both sets of spectra. The measurements provide information for dosimetry calculations and also a valuable intercomparison of neutron spectrometry using the two different detector types. Spectra measured with both detectors are in essential agreement. 8 references, 7 figures, 2 tables.

  12. Neutron-induced 2.2 MeV background in gamma ray telescopes

    NASA Technical Reports Server (NTRS)

    Zanrosso, E. M.; Long, J. L.; Zych, A. D.; White, R. S.

    1985-01-01

    Neutron-induced gamma ray production is an important source of background in Compton scatter gamma ray telescopes where organic scintillator material is used. Most important is deuteron formation when atmospheric albedo and locally produced neutrons are thermalized and subsequently absorbed in the hydrogenous material. The resulting 2.2 MeV gamma ray line radiation essentially represents a continuous isotropic source within the scintillator itself. Interestingly, using a scintillator material with a high hydrogen-to-carbon ratio to minimize the scintillator material with a high hydrogen-to-carbon ratio to minimize the neutron-induced 4.4 MeV carbon line favors the np reaction. The full problem of neutron-induced background in Compton scatter telescopes has been previously discussed. Results are presented of observations with the University of California balloon-borne Compton scatter telescope where the 2.2 MeV induced line emission is prominently seen.

  13. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

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

  14. Neutron Scattering Stiudies

    SciTech Connect

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

    2007-04-18

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

  15. Neutron scattering from elemental uranium and thorium

    SciTech Connect

    Smith, A.B. |; Chiba, S.

    1995-01-01

    Differential neutron-scattering cross sections of elemental uranium and thorium are measured from {approx} 4.5 to 10.0 MeV in steps of {approx} 0.5 MeV. Forty or more differential values are obtained at each incident energy, distributed between {approx} 17{degree} and 160{degree}. Scattered-neutron resolutions are carefully defined to encompass contributions from the first four members of the ground-state rotational band (0{sup 2} g.s., 2{sup +}, 4{sup +} and 6{sup +} states). The experimental results are interpreted in the context of coupled-channels rotational models, and comparisons made with the respective ENDF/B-VI evaluated files. These comparisons suggest some modifications of the ENDF/B-VI {sup 238}U and {sup 232}Th evaluations.

  16. Direct Measurement of Neutron-Neutron Scattering

    SciTech Connect

    Sharapov, E.I.; Furman, W.I.; Lychagin, W.I.; Muzichka, G.V.; Nekhaev, G.V.; Safronov, Yu.V.; Shvetsov, V.N.; Strelkov, A.V.; Bowman, C.D.; Crawford, B.E.; Stephenson, S.L.; Howell, C.R.; Tornow, W.; Levakov, B.G.; Litvin, V.I.; Lyzhin, A.E.; Magda, E.P.; Mitchell, G.E.

    2003-08-26

    In order to resolve long-standing discrepancies in indirect measurements of the neutron-neutron scattering length ann and contribute to solving the problem of the charge symmetry of the nuclear force, the collaboration DIANNA (Direct Investigation of ann Association) plans to measure the neutron-neutron scattering cross section {sigma}nn. The key issue of our approach is the use of the through-channel in the Russia reactor YAGUAR with a peak neutron flux of 10{sup 18} /cm2/s. The proposed experimental setup is described. Results of calculations are presented to connect {sigma}nn with the nn-collision detector count rate and the neutron flux density in the reactor channel. Measurements of the thermal neutron fields inside polyethylene converters show excellent prospects for the realization of the direct nn-experiment.

  17. Comparison of experimental and computational neutron spectroscopy at a 14 MeV neutron generator facility

    NASA Astrophysics Data System (ADS)

    Waller, Edward; Cousins, Tom; Desrosiers, Marc; Jones, Trevor; Buhr, Rob; Rambousky, Ronald

    2009-05-01

    At any neutron production facility, the energy spectrum at any meaningful distance from the target will be modified. For the case of a facility used to provide reference irradiations of electronics and other devices at various target-to-device distances it is important to have knowledge of these spectral modifications. In addition, it is desirable to have the ability to generate near real-time measurement capability. Advances in neutron metrology have made it possible to determine neutron energy spectra in real time to high levels of accuracy. This paper outlines a series of experimental measurements and theoretical calculations designed to quantify the scattering effects for a 14 MeV neutron generator facility, and makes appropriate recommendations for near real-time measurements of these fields.

  18. Production of 14 MeV neutrons by heavy ions

    DOEpatents

    Brugger, Robert M.; Miller, Lowell G.; Young, Robert C.

    1977-01-01

    This invention relates to a neutron generator and a method for the production of 14 MeV neutrons. Heavy ions are accelerated to impinge upon a target mixture of deuterium and tritium to produce recoil atoms of deuterium and tritium. These recoil atoms have a sufficient energy such that they interact with other atoms of tritium or deuterium in the target mixture to produce approximately 14 MeV neutrons.

  19. COMPTEL neutron response at 17 MeV

    NASA Technical Reports Server (NTRS)

    Oneill, Terrence J.; Ait-Ouamer, Farid; Morris, Joann; Tumer, O. Tumay; White, R. Stephen; Zych, Allen D.

    1992-01-01

    The Compton imaging telescope (COMPTEL) instrument of the Gamma Ray Observatory was exposed to 17 MeV d,t neutrons prior to launch. These data were analyzed and compared with Monte Carlo calculations using the MCNP(LANL) code. Energy and angular resolutions are compared and absolute efficiencies are calculated at 0 and 30 degrees incident angle. The COMPTEL neutron responses at 17 MeV and higher energies are needed to understand solar flare neutron data.

  20. Calculations of neutron spectra after neutron neutron scattering

    NASA Astrophysics Data System (ADS)

    Crawford, B. E.; Stephenson, S. L.; Howell, C. R.; Mitchell, G. E.; Tornow, W.; Furman, W. I.; Lychagin, E. V.; Muzichka, A. Yu; Nekhaev, G. V.; Strelkov, A. V.; Sharapov, E. I.; Shvetsov, V. N.

    2004-09-01

    A direct neutron-neutron scattering length, ann, measurement with the goal of 3% accuracy (0.5 fm) is under preparation at the aperiodic pulsed reactor YAGUAR. A direct measurement of ann will not only help resolve conflicting results of ann by indirect means, but also in comparison to the proton-proton scattering length, app, shed light on the charge-symmetry of the nuclear force. We discuss in detail the analysis of the nn-scattering data in terms of a simple analytical expression. We also discuss calibration measurements using the time-of-flight spectra of neutrons scattered on He and Ar gases and the neutron activation technique. In particular, we calculate the neutron velocity and time-of-flight spectra after scattering neutrons on neutrons and after scattering neutrons on He and Ar atoms for the proposed experimental geometry, using a realistic neutron flux spectrum—Maxwellian plus epithermal tail. The shape of the neutron spectrum after scattering is appreciably different from the initial spectrum, due to collisions between thermal-thermal and thermal-epithermal neutrons. At the same time, the integral over the Maxwellian part of the realistic scattering spectrum differs by only about 6 per cent from that of a pure Maxwellian nn-scattering spectrum.

  1. A search for solar neutrons from 10-100 MeV

    NASA Technical Reports Server (NTRS)

    Monn, S.; Simnett, G. M.; White, R. S.

    1974-01-01

    A search for solar neutrons is reported from a balloon flight launched from Palestine, Texas on Sept. 26, 1971. The sun was observed from 8:30 to 19:30 CST. The neutrons were detected with a telescope consisting of two 0.5 sq m scintillation detectors spaced 1 meter apart using a double-scattering/time-of-flight technique. Upper limits for solar neutrons in the energy intervals 10 to 30, 30 to 50, and 50 to 100 MeV are .00011, .00026 and .00059 neutron/sq cm-sec, respectively. These are combined into an overall upper limit of .00051 neutron/sq cm-sec.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  3. Earth albedo neutrons from 10 to 100 MeV.

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Simnett, G. M.; White, R. S.

    1972-01-01

    We report the measurement of the energy and angular distributions of earth albedo neutrons from 10 to 100 MeV at 40 deg N geomagnetic latitude from a balloon at 120,000 ft, below 4.65 g/sq cm. The albedo-neutron omnidirectional energy distribution is flat to 50 MeV, then decreases with energy. The absolute neutron energy distribution is of the correct strength and shape for the albedo neutrons to be the source of the protons trapped in earth's inner radiation belt.

  4. A Monte Carlo comparison of PGNAA system performance using 252Cf neutrons, 2.8-MeV neutrons and 14-MeV neutrons

    NASA Astrophysics Data System (ADS)

    Naqvi, A. A.

    2003-10-01

    Monte Carlo simulations were carried out to compare performance of a 252Cf neutron and a 14-MeV neutron-based prompt γ-ray neutron activation analysis (PGNAA) system with that of the 2.8-MeV neutron-based PGNAA system at King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia. Since the energy of neutron beam used in the KFUPM PGNAA system is very close to that produced by a DD neutron generator, performance comparison between a DD and a DT neutron generator-based PGNAA system is highly desired. For the sake of comparison, the calculations were carried out for the PGNAA system with geometry similar to the KFUPM PGNAA system. These calculations were required to determine improvement in performance of the KFUPM PGNAA system if its 2.8-MeV neutron source is replaced by a 252Cf neutron source or a 14-MeV neutron source. Results of the calculations revealed that the geometry of the 252Cf neutron and the 2.8-MeV neutron-based PGNAA system are not significantly different but the geometry of the 14-MeV neutron-based system is significantly different from that of the 2.8-MeV neutron-based PGNAA system. Accordingly, the prompt γ-ray yields from the 252Cf neutron and the 2.8-MeV neutron-based PGNAA system is comparable but prompt γ-ray yields from 14-MeV neutron-based PGNAA system are about three times smaller than that from the 2.8-MeV neutron-based PGNAA system. This study has shown that performance of the 252Cf neutron-based PGNAA system is comparable with that of the 2.8-MeV neutron-based PGNAA system but the performance of the 14-MeV neutron-based PGNAA system is poorer than that of the 2.8-MeV neutron-based PGNAA system.

  5. Neutron scatter camera

    DOEpatents

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

    2010-06-22

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

  6. Contraband detection via neutron elastic scattering

    SciTech Connect

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

    1993-04-01

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

  7. A diamond 14 MeV neutron energy spectrometer with high energy resolution.

    PubMed

    Shimaoka, Takehiro; Kaneko, Junichi H; Ochiai, Kentaro; Tsubota, Masakatsu; Shimmyo, Hiroaki; Chayahara, Akiyoshi; Umezawa, Hitoshi; Watanabe, Hideyuki; Shikata, Shin-ichi; Isobe, Mitsutaka; Osakabe, Masaki

    2016-02-01

    A self-standing single-crystal chemical vapor deposited diamond was obtained using lift-off method. It was fabricated into a radiation detector and response function measurements for 14 MeV neutrons were taken at the fusion neutronics source. 1.5% of high energy resolution was obtained by using the (12)C(n, α)(9)Be reaction at an angle of 100° with the deuteron beam line. The intrinsic energy resolution, excluding energy spreading caused by neutron scattering, slowing in the target and circuit noises was 0.79%, which was also the best resolution of the diamond detector ever reported. PMID:26931845

  8. A diamond 14 MeV neutron energy spectrometer with high energy resolution

    NASA Astrophysics Data System (ADS)

    Shimaoka, Takehiro; Kaneko, Junichi H.; Ochiai, Kentaro; Tsubota, Masakatsu; Shimmyo, Hiroaki; Chayahara, Akiyoshi; Umezawa, Hitoshi; Watanabe, Hideyuki; Shikata, Shin-ichi; Isobe, Mitsutaka; Osakabe, Masaki

    2016-02-01

    A self-standing single-crystal chemical vapor deposited diamond was obtained using lift-off method. It was fabricated into a radiation detector and response function measurements for 14 MeV neutrons were taken at the fusion neutronics source. 1.5% of high energy resolution was obtained by using the 12C(n, α)9Be reaction at an angle of 100° with the deuteron beam line. The intrinsic energy resolution, excluding energy spreading caused by neutron scattering, slowing in the target and circuit noises was 0.79%, which was also the best resolution of the diamond detector ever reported.

  9. Response of LaBr3(Ce) scintillators to 2.5 MeV fusion neutrons

    NASA Astrophysics Data System (ADS)

    Cazzaniga, C.; Nocente, M.; Tardocchi, M.; Croci, G.; Giacomelli, L.; Angelone, M.; Pillon, M.; Villari, S.; Weller, A.; Petrizzi, L.; Gorini, G.; ASDEX Upgrade Team; JET-EFDA Contributors

    2013-12-01

    Measurements of the response of LaBr3(Ce) to 2.5 MeV neutrons have been carried out at the Frascati Neutron Generator and at tokamak facilities with deuterium plasmas. The observed spectrum has been interpreted by means of a Monte Carlo model. It is found that the main contributor to the measured response is neutron inelastic scattering on 79Br, 81Br, and 139La. An extrapolation of the count rate response to 14 MeV neutrons from deuterium-tritium plasmas is also presented. The results are of relevance for the design of γ-ray diagnostics of fusion burning plasmas.

  10. Response of LaBr{sub 3}(Ce) scintillators to 2.5 MeV fusion neutrons

    SciTech Connect

    Cazzaniga, C.; Nocente, M.; Gorini, G.; Tardocchi, M.; Croci, G.; Giacomelli, L.; Angelone, M.; Pillon, M.; Villari, S.; Weller, A.; Petrizzi, L.; Collaboration: ASDEX Upgrade Team; JET-EFDA Contributors

    2013-12-15

    Measurements of the response of LaBr{sub 3}(Ce) to 2.5 MeV neutrons have been carried out at the Frascati Neutron Generator and at tokamak facilities with deuterium plasmas. The observed spectrum has been interpreted by means of a Monte Carlo model. It is found that the main contributor to the measured response is neutron inelastic scattering on {sup 79}Br, {sup 81}Br, and {sup 139}La. An extrapolation of the count rate response to 14 MeV neutrons from deuterium-tritium plasmas is also presented. The results are of relevance for the design of γ-ray diagnostics of fusion burning plasmas.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  12. Fast-neutron scattering from vibrational palladium nuclei

    SciTech Connect

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

    1993-10-01

    Neutron total cross sections of elemental palladium are measured from {approx}0.6--4.5 MeV. These results, combined with others previously reported from this laboratory, provide a detailed knowledge of the neutron total cross sections of palladium from {approx}0.1--20 MeV. Differential neutron elastic-scattering cross sections are measured from {approx}1.5--10 MeV in sufficient energy and angle detail to well define the energy-average behavior. Concurrently, neutron inelastic-scattering cross sections are measured from {approx}1.5--8 MeV. Inelastically-scattered neutron groups are observed corresponding to excitations of: 306 {+-} 14, 411 {+-} 47, {approx}494, 791 {+-} 20, 924 {+-} 20, 1,156 {+-} 24, 1,358 {+-} 35, 1,554 {+-} 47 and 1,706 {+-} 59 keV, with additional tentative groups at 1,938 and 2,059 keV. Particular attention is given to the inelastic excitation of the 2{sup +} yrast states of the even isotopes. This broad data base is examined in the context of optical-statistical and coupled-channels models. The resulting model parameters are consistent with systematic trends in this vibrational mass region previously noted at this laboratory, and provide a suitable vehicle for many applications.

  13. Response of LaBr3(Ce) scintillators to 14 MeV fusion neutrons

    NASA Astrophysics Data System (ADS)

    Cazzaniga, C.; Nocente, M.; Tardocchi, M.; Rebai, M.; Pillon, M.; Camera, F.; Giaz, A.; Pellegri, L.; Gorini, G.

    2015-04-01

    The response of a 3″×3″ LaBr3(Ce) scintillator to 14 MeV neutron irradiation has been measured at the Frascati Neutron Generator and simulated by means of a dedicated MCNP model. Several reactions are found to contribute to the measured response, with a key role played by neutron inelastic scattering and (n,2n) reactions on 79Br, 81Br and 139La isotopes. An overall 43% efficiency to 14 MeV neutron detection above an experimental threshold of 0.35 MeV is calculated and confirmed by measurements. Post irradiation activation of the crystal has been also observed and is explained in terms of nuclear decays from the short lived 78Br and 80Br isotopes produced in (n,2n) reactions. The results presented in this paper are of relevance for the design of γ-ray detectors in burning plasma fusion experiments of the next generation, such as ITER, where capability to perform measurements in an intense 14 MeV neutron flux is required.

  14. Analysis of a measured neutron background below 6 MeV for fast-neutron imaging systems

    NASA Astrophysics Data System (ADS)

    Ide, K.; Becchetti, M. F.; Flaska, M.; Poitrasson-Riviere, A.; Hamel, M. C.; Polack, J. K.; Lawrence, C. C.; Clarke, S. D.; Pozzi, S. A.

    2012-12-01

    Detailed and accurate information on the neutron background is relevant for many applications that involve radiation detection, both for non-coincidence and coincidence countings. In particular, for the purpose of developing advanced neutron-detection techniques for nuclear non-proliferation and nuclear safeguards, the energy-dependent, ground-level, neutron-background information is needed. There are only a few previous studies available about the neutron background below 10 MeV, which is a typical neutron energy range of interest for nuclear non-proliferation and nuclear-safeguards applications. Thus, there is a potential for further investigation in this energy range. In this paper, neutron-background measurement results using organic-liquid scintillation detectors are described and discussed, with a direct application in optimization simulations of a fast-neutron imager based on liquid scintillators. The measurement was performed in summer 2011 in Ann Arbor, Michigan, USA, and the measurement setup consisted of several EJ-309 liquid scintillators and a fast waveform digitizer. The average neutron flux below 6 MeV was measured to be approximately 4e-4 counts/cm2/s. In addition, the relationship between the neutron-background count rate and various environmental quantities, such as humidity, at Earth's ground level was investigated and the results did not reveal any straightforward dependences. The measured pulse height distribution (PHD) was unfolded to determine the energy spectrum of the background neutrons. The unfolded neutron-background spectrum was implemented to a previously-created MCNPX-PoliMi model of the neutron-scatter camera and simple-backprojection images of the background neutrons were acquired. Furthermore, a simulated PHD was obtained with the MCNPX-PoliMi code using the "Cosmic-Ray Shower Library" (CRY) source sub-routine which returns various types of radiation, including neutrons and photons at a surface, and accounts for solar cycle

  15. LOW VOLTAGE 14 Mev NEUTRON SOURCE

    DOEpatents

    Little, R.N. Jr.; Graves, E.R.

    1959-09-29

    An apparatus yielding high-energy neutrons at the rate of 10/sup 8/ or more per second by the D,T or D,D reactions is described. The deuterium gas filling is ionized by electrons emitted from a filament, and the resulting ions are focused into a beam and accelerated against a fixed target. The apparatus is built in accordance with the relationship V/sub s/ = A--B log pd, where V/sub s/ is the sparking voltage, p the gas pressure, and d the gap length between the high voltage electrodes. Typical parameters to obtain the high neutron yields are 55 to 80 kv, 0.5 to 7.0 ma beam current, 5 to 12 microns D/sub 2/, and a gap length of 1 centimeter.

  16. Polarization transfer in n-p scattering at 50 MeV

    NASA Astrophysics Data System (ADS)

    Woolverton, H. L.; Nath, S.; Hiebert, J. C.; Northcliffe, L. C.; Woodward, And W.

    1985-05-01

    The polarization transfer parameter Dt(180°) for n-p scattering has been measured at 50 MeV for the first time. Polarized neutrons produced in the 2H(darrow,narrow) 3He reaction were scattered from the hydrogen in a polyethylene target and the polarization of the recoil protons emitted at 0° was measured in a carbon polarimeter. The result of this measurement tests the prediction of Dt from a phase shift analysis of the N-N data and that of a theoretical proposal concerning n-p charge exchange.

  17. Neutron scattering on deformed nuclei

    NASA Astrophysics Data System (ADS)

    Hansen, L. F.; Haight, R. C.; Pohl, B. A.; Wong, C.; Lagrange, Ch.

    1985-01-01

    Measurements of neutron elastic and inelastic differential cross sections around 14 MeV for 9Be, C, 181Ta, 232Th, 238U, and 239Pu have been analyzed using a coupled channel (CC) formalism for deformed nuclei and phenomenological global optical model potentials (OMP). For the actinide targets these results are compared with the predictions of a semi-microscopic calculation using Jeukenne, Lejeune, and Mahaux (JLM) microscopic OMP and a deformed ground state nuclear density. The overall agreement between calculations and the measurements is reasonably good even for the very light nuclei, where the quality of the fits is better than those obtained with spherical OMP.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  19. An 8-element neutron double-scatter directional detector

    NASA Astrophysics Data System (ADS)

    Vanier, Peter E.; Forman, Leon

    2005-09-01

    We have constructed a fast-neutron double-scatter spectrometer that efficiently measures the neutron spectrum and direction of a spontaneous fission source. The device consists of two planes of organic scintillators, each having an area of 125 cm2, efficiently coupled to photomultipliers. The four scintillators in the front plane are 2 cm thick, giving almost 25% probability of detecting an incident fission-spectrum neutron at 2 MeV by proton recoil and subsequent ionization. The back plane contains four 5-cm-thick scintillators which give a 40% probability of detecting a scattered fast neutron. A recordable double-scatter event occurs when a neutron is detected in both a front plane detector and a back plane detector within an interval of 500 nanoseconds. Each double-scatter event is analyzed to determine the energy deposited in the front plane, the time of flight between detectors, and the energy deposited in the back plane. The scattering angle of each incident neutron is calculated from the ratio of the energy deposited in the first detector to the kinetic energy of the scattered neutron.

  20. Pohang Neutron Facility Based on 100 Mev Electron Linac

    NASA Astrophysics Data System (ADS)

    Kim, G. N.; Ahmed, H.; Machrafi, R.; Son, D.; Lee, Y. S.; Skoy, V.; Kang, H. S.; Cho, M. H.; Ko, I. S.; Namkung, W.

    2003-06-01

    Pohang Neutron Facility (PNF) is a pulsed neutron facility based on the 100-MeV electron linear accelerator. It was constructed for nuclear data production in Korea, and it consists of an electron linear accelerator, a water-cooled Ta target with a water moderator and a time-of-flight path with an 11 m length. The 100-MeV electron linac uses a thermionic RF-gun, an alpha magnet, four quadrupole magnets, two SLAC-type accelerating sections, a quadrupole triplet, and a beam-analyzing magnet. It has been equipped with a new four-position sample changer controlled remotely by a CAMAC data acquisition system, which allows the simultaneous accumulation of the neutron time-of-flight spectra from 4 different samples. The neutron total cross sections of natural In and Cu have been measured in the neutron energy range from 0.1 eV to 100 eV by the neutron time-of-flight method.

  1. Neutron densities in 120Sn observed by polarized proton scattering

    NASA Astrophysics Data System (ADS)

    Sakaguchi, H.; Takeda, H.; Taki, T.; Yosoi, M.; Itoh, M.; Kawabata, T.; Ishikawa, T.; Uchida, M.; Tsukahara, N.; Noro, T.; Yoshimura, M.; Fujimura, H.; Yoshida, H.; Obayashi, E.; Tamii, A.; Akimune, H.

    2001-06-01

    Cross sections, analyzing powers and spin rotation parameters of proton elastic scattering from 58Ni and 120Sn have been measured at intermediate energies. By elastic scattering off N~=Z nuclei like 58Ni at intermediate energies we can study medium modification of the nucleon-nucleon (NN) interaction inside the nucleus, because proton distributions in target nuclei are constrained by charge distributions measured by electron scattering and neutron distributions can be assumed to be the same as proton's. In order to explain our experimental data of 58Ni at large scattering angles, it was found to be necessary to use experimental densities deduced from charge densities measured by electron scattering and to modify the coupling constants and the masses of exchanged σ and ω mesons in the RIA, assuming linear dependencies of meson properties to nuclear densities. Parameters of the medium effect have been searched to reproduce the data. For N≠Z nuclei, neutron density distribution can be extracted from the elastic scattering, assuming the same medium modifications fixed by the 58Ni data and using proton distributions obtained from charge distributions. We have searched neutron density distributions obtained from charge distributions. We have searched neutron density distribution so as to reproduce 120Sn data at the proton incident energy of 300 MeV. Deduced neutron distribution has an increase at the nuclear center, which is consistent with the 3s1/2 orbit wave function as expected in 120Sn. At energies other than 300 MeV, experimental data of 120Sn have been also well reproduced by the neutron distribution obtained at 300 MeV. .

  2. Measured neutron carbon kerma factors from 14. 1 MeV to 18 MeV

    SciTech Connect

    Deluca, P.M. Jr.; Barschall, H.H.; Haight, R.C.; McDonald, J.C.

    1984-01-01

    For A-150 tissue-equivalent plastic, the total neutron kerma is dominated by the hydrogen kerma. Tissue kerma is inferred with reasonable accuracy by normalization to the kerma factor ratio between tissue and A-150 plastic. Because of the close match in the hydrogen abundance in these materials, the principal uncertainty is due to the kerma factors of carbon and oxygen. We have measured carbon kerma factor values of 0.183 +- 0.015 10/sup -8/ cGy cm/sup 2/ and 0.210 +- 0.16 10/sup -8/ cGy cm/sup 2/ at 14.1-MeV and 15-MeV neutron energy, respectively. A preliminary value of 0.297 +- 0.03 10/sup -8/ cGy cm/sup 2/ has been determined at 17.9 MeV. A recent microscopic cross section measurement of the (n,n'3..cap alpha..) reaction in carbon at 14.1-MeV energy gives a kerma factor of 0.184 +- 0.019 10/sup 8/ cGy cm/sup 2/ in agreement with the present result. 9 refs., 4 figs., 2 tabs.

  3. Industrial applications using 14 MeV neutrons at KFUPM

    NASA Astrophysics Data System (ADS)

    Aksoy, A.; Khiari, F. Z.; Al-Haddad, M. N.

    1999-06-01

    The objective of this study is to develop a database for the technical capability of the KFUPM 14 MeV Neutron Activation Analysis (NAA) Facility for applications to various local industries in the Kingdom. Since the 14 MeV NAA is a well-established non-destructive, rapid and sensitive technique for elemental bulk analysis, the applications of the technique are spread over wide areas such as oil, petrochemicals, metal and mining, medicine, agriculture and environment. The applications are mostly done for determination of light elements such as oxygen, nitrogen, fluorine, silicon and phosphorus, which are relatively difficult to determine by other methods. The results of the analysis are mainly used for quality and process control. The progress made in developing the KFUPM 14 MeV NAA Facility for industrial applications will be summarized. Preliminary results of the analysis of the data collected using the facility will be presented and discussed.

  4. The 14 MeV Frascati neutron generator

    NASA Astrophysics Data System (ADS)

    Martone, M.; Angelone, M.; Pillon, M.

    1994-09-01

    The 14-MeV Frascati neutron generator (FNG) uses the T(d, n)α fusion reaction to produce 5.0 × 10 11 n/s. In FNG a beam of deuterons is accelerated up to 300 keV by means of a linear electrostatic tube and directed onto a tritiated-titanium target containing 37 × 10 10 Bq of tritium. This paper describes the FNG facility and its auxiliary apparatus as well as the neutron source calibration performed using the associated α-particle method.

  5. Reaction cross sections on carbon for neutron energies from 11. 5 to 19 MeV

    SciTech Connect

    Antolkovic, B. ); Dietze, G.; Klein, H. )

    1991-01-01

    This paper reports on neutron-induced reaction cross sections for carbon measured in the 11.5- to 19-MeV energy range. The response of an NE-213 scintillation detector is measured in steps of at least 0.5 MeV for monoenergetic neutrons, applying suitable time-of-flight techniques, and compared with Monte Carlo simulations. The total cross sections of all reactions with charged particles (except carbon recoil protons) in the exit channel are determined with respect to the n-p scattering cross section. In addition, the {sup 12}C(n,n{prime}3{alpha}) reaction is investigated for neutron energies of 11.9, 12.9, 14.0, 14.8, 17.0, and 19.0 MeV using the nuclear emulsion technique. As it is kinematically complete, this measurement yields the total and partial cross sections for the various channels of the {sup 12}C(n,n{prime}3{alpha}) reaction. The experimental data show deviations of up to {plus minus}25% from those recommended in ENDF/B-V, while a recent evaluation by Axton is partially confirmed. Reasonable agreement is found with most of the recent scattering experiments; thus, this data set represents a valuable constraint for further evaluations. The analysis performed, however, has shown that additional data from some partial reaction cross sections are needed.

  6. Scintillating-fiber imaging detector for 14-MeV neutrons

    SciTech Connect

    Ress, D.; Lerche, R.A.; Ellis, R.J.; Heaton, G.W.; Nelson, M.B.; Mant, G.; Lehr, D.E.

    1994-07-25

    The authors have created a detector to image the neutrons emitted by imploded inertial-confinement fusion targets. The 14-MeV neutrons, which are produced by deuterium-tritium fusion events in the target, pass through an aperture to create an image on the detector. The neutron radiation is converted to blue light (430 nm) with a 20-cm-square array of plastic scintillating fibers. Each fiber is 10-cm long with a 1-mm-square cross section; approximately 35-thousand fibers make up the array. The resulting blue-light image is reduced and amplified by a sequence of fiber-optic tapers and image intensifiers, then acquired by a CCD camera. The fiber-optic readout system was tested optically for overall throughput the resolution. The authors plan to characterize the scintillator array reusing an ion-beam neutron source as well as DT-fusion neutrons emitted by inertial confinement targets. Characterization experiments will measure the light-production efficiency, spatial resolution, and neutron scattering within the detector. Several neutron images of laser-fusion targets have been obtained with the detector. Several neutron images of laser-fusion targets have been obtained with the detector. They describe the detector and their characterization methods, present characterization results, and give examples of the neutron images.

  7. Understanding inelastically scattered neutrons from water on a time-of-flight small-angle neutron scattering (SANS) instrument

    NASA Astrophysics Data System (ADS)

    Do, Changwoo; Heller, William T.; Stanley, Christopher; Gallmeier, Franz X.; Doucet, Mathieu; Smith, Gregory S.

    2014-02-01

    It is generally assumed by most of the small-angle neutron scattering (SANS) user community that a neutron's energy is unchanged during SANS measurements. Here, the scattering from water, specifically light water, was measured on the EQ-SANS instrument, a time-of-flight (TOF) SANS instrument located at the Spallation Neutron Source of Oak Ridge National Laboratory. A significant inelastic process was observed in the TOF spectra of neutrons scattered from water. Analysis of the TOF spectra from the sample showed that the scattered neutrons have energies consistent with room-temperature thermal energies (~20 meV) regardless of the incident neutron's energy. With the aid of Monte Carlo particle transport simulations, we conclude that the thermalization process within the sample results in faster neutrons that arrive at the detector earlier than expected based on the incident neutron energies. This thermalization process impacts the measured SANS intensities in a manner that will ultimately be sample- and temperature-dependent, necessitating careful processing of the raw data into the SANS cross-section.

  8. Neutron Scattering Simulations at the University of Kentucky Accelerator Laboratory

    NASA Astrophysics Data System (ADS)

    Nguyen, Thienan; Jackson, Daniel; Hicks, S. F.; Rice, Ben; Vanhoy, J. R.

    2015-10-01

    The Monte-Carlo N-Particle Transport code (MCNP) has many applications ranging from radiography to reactor design. It has particle interaction capabilities, making it useful for simulating neutron collisions on surfaces of varying compositions. The neutron flux within the accelerator complex at the University of Kentucky was simulated using MCNP. With it, the complex's capabilities to contain and thermalize 7 MeV neutrons produced via 2H(d,n)3He source reaction to an acceptable level inside the neutron hall and adjoining rooms were analyzed. This will aid in confirming the safety of researchers who are working in the adjacent control room. Additionally, the neutron transport simulation was used to analyze the impact of the collimator copper shielding on various detectors located around the neutron scattering hall. The purpose of this was to attempt to explain any background neutrons that are observed at these detectors. The simulation shows that the complex performs very well with regards to neutron containment and thermalization. Also, the tracking information for the paths taken by the neutrons show that most of the neutrons' lives are spent inside the neutron hall. Finally, the neutron counts were analyzed at the positions of the neutron monitor detectors located at 90 and 45 degrees relative to the incident beam direction. This project was supported in part by the DOE NEUP Grant NU-12-KY-UK-0201-05 and the Donald A. Cowan Physics Institute at the University of Dallas.

  9. Neutron Inelastic Scattering Mechanism and Measurement of Neutron Asymmetry Using Time of Flight Technique

    NASA Astrophysics Data System (ADS)

    Al Azzawe, A. J. M.

    2007-02-01

    Inelastic scattering is an essential reaction for other nuclear reactions to detect the optical model and compound nucleus formation within the range of (0.4- 5.0) MeV neutron incident energy by using time of flight technique. The time of flight system (TOFS) installed on the horizontal channel reactor RRA has been used to measure the asymmetry of scattered fast neutrons, when data acquisition and system control were recorded event by event by HP — computer via CAMAC system. Eight NE 213 neutron counters were used in order to detect neutron inelastic scattering in the forward direction (4 neutron counters at 0° angle) and in the backward direction (4 neutron counters at 180° angle) to measure the asymmetry of fast neutron. Each neutron counter was 50cm in length and 8cm in diameter, viewed by two (58 — DVP) photomultiplier tubes. The contribution of direct interaction to the compound nucleus formation was deduced from the asymmetry in the neutron detection at the same direction of these eight neutron counters. A time resolution of 8.2 ns between the eight neutron counters and one of the two Ge(Li) detectors has been obtained.

  10. Parity Violation in Proton-Proton Scattering at 47 Mev.

    NASA Astrophysics Data System (ADS)

    Tanner, Danelle Mary

    A measurement of parity-violation in proton-proton scattering at 47 MeV has been completed by observing the longitudinal analyzing power. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). where (sigma)('+)((sigma)('-)) is the scattering cross section for positive (negative) helicity. Polarized protons from an atomic beam ion source were accelerated by the 224-cm Texas A&M University cyclotron to an energy of 50 MeV, producing a vertically polarized beam. A superconducting solenoid magnet precessed the beam polarization into the horizontal plane after which a 47.6(DEGREES) bending magnet precessed the polarization into the longtitudinal direction (p(,z) = 0.69 (+OR-) 0.02). RF transitions reversed the polarization direction every 21 msec. Protons scattered from the high pressure ((DBLTURN)37 atm), 42-cm long H(,2) gas target were detected by four plastic scintillators located in the target chamber. Photomultiplier tubes amplified the light from the scintillators, providing a signal proportional to the scattered beam intensity. A lock-in amplifier (LIA) synchronized to the spin-flip frequency compared the scattered intensity to the total beam intensity, measured with a Faraday cup. The output of the LIA was integrated for one second and then read by an ADC. Polarimeters were used to monitor both beam intensity and polarization profiles. A series of tests were performed to determine the role of spurious asymmetries due to changes in beam position and angle, and due to beam intensity modulations correlated with the spin reversal. The result after correction for beam intensity modulation was A(,z) = -(4.6 (+OR-) 2.6) x 10('-7). A more conservative result, taking into account all of the possible spurious asymmetries was A(,z) = -(4.6 (+OR-) 4.2) x 10('-7).

  11. Neutron induced fission of U isotopes up to 100 MeV

    SciTech Connect

    Lestone, J.P.; Gavron, A.

    1993-10-01

    We have developed a statistical model description of the neutron induced fission of U isotopes using densities of intrinsic states and spin cut off parameters obtained directly from appropriate Nilsson model single particle levels. The first chance fission cross sections are well reproduced when the rotational contributions to the nuclear level densities are taken into account. In order to fit the U(n,f) cross sections above the threshold of second chance fission, we need to: (1) assume that the triaxial level density enhancement is washed out at an excitation energy of {approximately}7 MeV above the triaxial barriers with a width of {approximately}1 MeV, implying a {gamma} deformation for the first barriers of 10{degree} < {gamma} < 20{degree}; and (2) include pre-equilibrium particle emission in the calculations. Above an incoming neutron kinetic energy of {approximately}17 MeV our statistical model U(n,f) cross sections increasingly overestimate the experimental data when so called ``good`` optical model potentials are used to calculate the compound nucleus formation cross sections. This is not surprising since at these high energies little data exists on the scattering of neutrons to help guide the choice of optical model parameters. A satisfactory reproduction of all the available U(n,f) cross sections above 17 MeV is obtained by a simple scaling of our calculated compound nucleus formation cross sections. This scaling factor falls from 1.0 at 17 MeV to 0.82 at 100 MeV.

  12. Neutron scattering cross section measurements for thulium-169 via the time-of-flight technique

    NASA Astrophysics Data System (ADS)

    Alimeti, Afrim

    This research provides the first direct neutron scattering cross section measurements for 169Tm via the time-of-flight technique. The neutron elastic and inelastic scattering cross-section angular distributions for 169Tm were measured at 590-keV and 1000-keV incident neutron energies. Differential cross-section excitation functions were also measured in 0.1-MeV steps at 125° (scattering angle) from 495-keV to 1000-keV incident neutron energy. The measured neutron scattering cross sections for the elastic group at 0.5-MeV to 1.0-MeV incident neutron energy range are in reasonable agreement with the JENDL-4.0 evaluation, which is based on nuclear reaction model calculations, and with the earlier measurements made by Ko et al. via the (n, n' gamma) technique for states above 100 keV via the (n, n' gamma) reaction at incident energies in the 0.2-MeV to 1.0-MeV range. The 5.5-MeV Van de Graaff accelerator at Lowell was operated in the pulsed and bunched beam mode producing subnanosecond pulses at a 5-MHz repetition frequency to generate neutrons via the 7Li(p,n) 7Be reaction using a thin metallic elemental lithium target.

  13. np Elastic-scattering experiments with polarized neutron beams

    SciTech Connect

    Chalmers, J.S.; Ditzler, W.R.; Hill, D.; Hoftiezer, J.; Johnson, K.; Shima, T.; Shimizu, H.; Spinka, H.; Stanek, R.; Underwood, D.

    1985-01-01

    Measurements of the spin transfer parameters, K/sub NN/ and K/sub LL/, at 500, 650, and 800 MeV are presented for the reaction p-vector d ..-->.. n-vector pp at 0/sup 0/. The data are useful input to the NN data base and indicate that the quasi-free charge exchange (CEX) reaction is a useful mechanism for producing neutrons with at least 40% polarization at energies as low as 500 MeV. Measurements of np elastic scattering observables C/sub LL/ and C/sub SL/ covering 35/sup 0/ to 172/sup 0/ are performed using a polarized neutron beam at 500, 650, and 800 MeV. Preliminary results are presented. 3 refs., 6 figs.

  14. 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.

  15. Upper limits to the quiet-time solar neutron flux from 10 to 100 MeV

    NASA Technical Reports Server (NTRS)

    Moon, S.; Simnett, G. M.; White, R. S.

    1975-01-01

    The UCR large area solid-angle double scatter neutron telescope was flown to search for solar neutrons on 3 balloon flights on September 26, 1971, May 14, 1972 and September 19, 1972. The first two flights were launched from Palestine, Texas and the third from Cape Girardeau, Missouri. The float altitude on each flight was at about 5 g/sq cm residual atmosphere. Neutrons from 10 to 100 MeV were measured. No solar flares occurred during the flights. Upper limits to the quiet time solar neutron fluxes at the 95% confidence level are .00028, .00046, .00096 and .00090 neutrons/sq cm-sec in the energy intervals of 10-30, 30-50, 50-100 and 10-100 MeV, respectively.

  16. Measurement of secondary neutron emission double-differential cross sections for 9Be induced by 21.65 ± 0.07 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Lan, Changlin; Ruan, Xichao; Chen, Guochang; Nie, Yangbo; Huang, Hanxiong; Bao, Jie; Zhou, Zuying; Tang, Hongqing; Kong, Xiangzhong; Peng, Meng

    2016-05-01

    The neutron emission double-differential cross sections (DDX) of 9Be was measured at an incident neutron energy of 21.65 MeV, using the multi-detector fast neutron time-of-flight (TOF) spectrometer on HI-13 Tandem Accelerator at the China Institute of Atomic Energy (CIAE). The data were deduced by comparing the measured TOF spectra with the calculated ones using a realistic Monte-Carlo simulation. The DDX were normalized to n-p scattering cross sections which are a neutron scattering standard. The results of the elastic scattering angular distributions (DX) and the secondary neutron emission DDX at 25 different angles from 15 deg to 145 deg were presented. Meanwhile, a theoretical model based on the unified Hauser-Feshbach and exciton model for light nuclei was used to describe the double-differential cross sections of n+9Be, and the theoretical calculation results were compared with the measured cross sections.

  17. Neutron Radii from Low Energy Pion Scattering.

    NASA Astrophysics Data System (ADS)

    Gyles, William

    Recent electron scattering measurements and muonic atom studies have allowed precise determinations of the charge distributions of nuclei. Measurements of the neutron distributions, however, have not progressed to this degree of sophistication, largely because of the uncertainties in the hadron-nucleus interaction. Charge distribution measurements provide good tests of nuclear structure calculations, but measurements of neutron distributions will provide independent constraints on these calculations and the potentials used. In this experiment, (pi)('-) differential cross section ratios were measured on pairs of isotopes (('36)S,('32)S), (('34)S,('32)S) with 50 MeV pions and (('26)Mg,('24)Mg) with 45 MeV pions. Absolute differential cross sections were also measured for ('32)S and ('24)Mg. Magnetic spectro -meters were used to collect the data. The cross section ratios were compared to optical model calcula-tions in which the parameters of a Fermi function representing the neutron distribution of the larger isotope of each pair were varied. The rms radius difference between the two isotopes producing the best fit was found to be independent of the details of the optical potential used, as long as the potential produced a fit to the absolute cross sections. The neutron distribution of the larger isotope was also rep-resented as a Fermi function modified by a sum of spherical Bessel functions, the coefficients of which were allowed to vary. The results for the rms radius differences were consistent with the Fermi function fits, except for ('34)S-('32)S, where the results differed by a full standard deviation. The rms radius differences found for the sulfur isotopes agreed with the results of shell-model calculations by Hodgson (Str82,Hod83). The extracted rms radius difference of the magnesium isotopes was one standard deviation less than the shell-model prediction. The results for the Fermi function fits, Fourier Bessell fits and the single particle potential (SPP

  18. Neutron Emission Spectra from Inelastic Scattering on 58,60Ni with a White Neutron Source at FIGARO

    SciTech Connect

    Rochman, D.; Haight, R.C.; O'Donnell, J. M.; Devlin, M.; Ethvignot, T.; Granier, T.; Grimes, S.M.; Talou, P.

    2005-05-24

    Neutron emission spectra from inelastic neutron scattering on natural nickel at the FIGARO facility have been measured by a double time-of-flight technique. The incident neutrons are produced from the spallation source of the Weapons Neutron Research facility, and their energies are determined by time of flight. The emitted neutrons and gamma rays are detected by 16 liquid scintillators and one high-resolution germanium or one barium-fluoride detector, respectively. The results for incident neutron energies from 2 to 10 MeV are compared with predictions of nuclear model calculations performed with the code EMPIRE-II. Finally, the level density parameters 'a' and ''{delta}'' are extracted.

  19. Neutron-proton spin-correlation parameter A sub z z at 68 MeV

    SciTech Connect

    Hammans, M.; Brogli-Gysin, C.; Burzynski, S.; Campbell, J.; Haffter, P.; Henneck, R.; Lorenzon, W.; Pickar, M.A.; Sick, I. ); Konter, J.A.; Mango, S.; van den Brandt, B. )

    1991-05-06

    We report a first measurement of the spin-correlation parameter {ital A}{sub {ital z}{ital z}} in neutron-proton scattering at 67.5 MeV. The results, obtained in the angular range 105{degree}{le}{theta}{sub c.m.}{le}170{degree} with typical accuracies of 0.008, are highly sensitive to the {sup 3}{ital S}{sub 1}-{sup 3}{ital D}{sub 1} mixing parameter {epsilon}{sub 1}. A phase-shift analysis based on the current world data yields a value of {epsilon}{sub 1} significantly higher than predicted by modern potential models.

  20. Little Boy neutron spectrum below 1 MeV

    SciTech Connect

    Evans, A.E.

    1984-01-01

    A high-resolution /sup 3/He ionization chamber of the type development by Cuttler and Shalev was used to study the neutron spectrum from the Little Boy mockup. Measurements were made at distances of 0.75 and 2.0 m and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly, which was operated at power levels from 8.6 to 450 mW. Detector efficiency as a function of energy as well as parameters for correction of pulse-height distributions for proton-recoil and wall effects were determined from a set of response functions for monoenergetic neutrons measured at the Los Alamos 3.75-MeV Van de Graaff Accelerator Facility. Pulse-shape discrimination was used to separate /sup 3/He-recoil pulses from the pulse-height distribution. The spectrum was found to be highly structured, with peaks corresponding to minima in the total neutron cross section of iron. In particular, 15% of the neutrons above the epithermal peak in energy were found to be in the 24-keV iron window. Lesser peaks out to 700 keV are also attributable to filtering action of the weapon's heavy iron casing. Data taken using experimental proton-recoil proportional counters are compared with the high-resolution spectra.

  1. American Conference on Neutron Scattering 2014

    SciTech Connect

    Dillen, J. Ardie

    2014-12-31

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

  2. Neutron scattering in polymer physics

    NASA Astrophysics Data System (ADS)

    Richter, D.

    2000-03-01

    By example this short review presents recent scientific advances which were achieved by the application of neutron scattering to polymer systems, thereby, keeping in mind also practical applications. We first focus on experiments on the structure and morphology of polymer systems covering conformational studies, investigations on polymer-microemulsions systems and the observation of aggregation states in living polymerization. Thereafter, we present recent results in the field of polymer dynamics. We begin with local motions which are behind the classical relaxation processes in polymer melts. Then we relate to universal dynamics, we address the Rouse model and its limits, present new results on the dynamic miscibility in blends and display the latest investigations on entanglement dynamics. Finally, we report first observations of ripplon excitations of phase boundaries in diblock copolymer melts.

  3. Energy spectrum and flux of 3- to 20-Mev neutrons and 1- to 10-Mev gamma rays in the atmosphere

    NASA Technical Reports Server (NTRS)

    Klumpar, D. M.; Lockwood, J. A.; Saint Onge, R. N.; Friling, L. A.

    1973-01-01

    An experiment is described which was designed to measure the neutron and gamma ray energy spectrums and fluxes in the energy intervals 3 to 20 MeV and 1 to 10 MeV, respectively. In addition, from the 3 to 20-MeV proton recoil spectrums it is possible to infer the shape of the neutron energy spectrum from 20 to 50 MeV. The detecting system utilized a separate charged particle rejection scheme and a two-parameter display system for the output from the pulse shape discrimination which separated gamma rays from neutrons (n). Two long-duration flights were made with this detector in 1970 at Palestine, Tex. (P sub c = 4.6 Gv) and at Ft. Churchill, Canada (P sub c = 0.3 Gv).

  4. Spin observables in neutron-proton elastic scattering

    SciTech Connect

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

    1995-07-15

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

  5. Fast-neutron scattering cross sections of elemental zirconium

    SciTech Connect

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

    1982-12-01

    Differential neturon-elastic-scattering cross sections of elemental zirconium are measured from 1.5 to 4.0 MeV at intervals of less than or equal to 200 keV. Inelastic-neutron-scattering cross sections corresponding to the excitation of levels at observed energies of: 914 +- 25, 1476 +- 37, 1787 +- 23, 2101 +- 26, 2221 +- 17, 2363 +- 14, 2791 +- 15 and 3101 +- 25 keV are determined. The experimental results are interpreted in terms of the optical-statistical model and are compared with corresponding quantities given in ENDF/B-V.

  6. Neutron spin echo scattering angle measurement (SESAME)

    SciTech Connect

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

    2005-05-15

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

  7. Fast-neutron scattering cross sections of elemental silver

    SciTech Connect

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

    1982-05-01

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

  8. High resolution inelastic gamma-ray measurements with a white neutron source from 1 to 200 MeV

    SciTech Connect

    Nelson, R.O.; Laymon, C.M.; Wender, S.A.

    1990-01-01

    Measurements of prompt gamma rays following neutron-induced reactions have recently been made at the spallation neutron source at the WNR target area of LAMPF using germanium detectors. These experiments provide extensive excitation function data for inelastic neutron scattering as well as for other reactions such as (n,{alpha}), (n,n{alpha}), (n,p), (n,np), (n,nnp) and (n,xn) for 1 {le} {times} {le} 11. The continuous energy coverage available from 1 MeV to over 200 MeV is ideal for excitation function measurements and greatly extends the energy range for such data. The results of these measurements will provide a database for interpretation of gamma-ray spectra from the planned Mars Observer mission, aid in radiation transport calculations, allow verification of nuclear reaction models, and improve the evaluated neutron reaction data base.

  9. Material classification by fast neutron scattering

    NASA Astrophysics Data System (ADS)

    Buffler, A.; Brooks, F. D.; Allie, M. S.; Bharuth-Ram, K.; Nchodu, M. R.

    2001-02-01

    The scattering of a beam of fast monoenergetic neutrons is used to determine elemental compositions of bulk samples (0.2-0.8 kg) of materials composed from one or more of the elements H, C, N, O, Al, S, Fe and Pb. Scattered neutrons are detected by liquid scintillators placed at forward and at backward angles. Different elements are identified by their characteristic scattering signatures derived either from a combination of time-of-flight and pulse height measurements, or from pulse height measurements alone. Scattering signatures measured for multi-element samples are analysed to determine atom fractions for H, C, N, O and other elements in the sample. Atom fractions determined from scattering signatures are insensitive to neutron interactions in material surrounding the scattering sample, provided the amount of material is not excessive. The atom fraction data are used to classify scattering material into categories including "explosives", "illicit drugs" and "other materials" for the purpose of contraband detection.

  10. Neutron Elastic and Inelastic Scattering Cross Sections on ^NatFe and ^23Na

    NASA Astrophysics Data System (ADS)

    Kersting, Luke; Lueck, Collin J.; Hicks, S. F.; Crider, B. P.; McEllistrem, M. T.; Peters, E. E.; Vanhoy, J. R.

    2010-10-01

    Neutron elastic and inelastic scattering angular distributions from ^NatFe and ^23Na at incident neutron energies of 3.57 and 3.81 MeV have been measured at the University of Kentucky 7 MV Van de Graaff laboratory using neutron time-of-flight techniques. The neutron beam was produced using the ^3H(p,n)He^3reaction. The scattered neutrons were detected at angles between 20 and 150 in 10 intervals with a hexafluorbenzene detector located approximately 3 m from the scattering samples. Neutron scattering differential cross sections were deduced. These cross sections and their uncertainties are important for understanding neutron-induced reactions in fission reactors and are important for fission reactor criticality calculations.

  11. Cross Sections and Analyzing Powers of Nitrogen -15(PROTON, NEUTRON)OXYGEN-15 at 200 Mev and 494 Mev.

    NASA Astrophysics Data System (ADS)

    Ciskowski, Douglas Edward

    Differential cross sections and analyzing powers have been measured for the ^{15} N(p,n)^{15}O(g.s.) reaction at bombarding energies of 200 MeV and 494 MeV. The 494 MeV data were obtained at the LAMPF Neutron Time-Of -Flight Facility on an 82 m flight path with a resolution of about 2.7 MeV. The 200 MeV data were obtained at IUCF on a 76 m flight path with a resolution of about 1.1 MeV. At both energies, the measured analyzing power is small, the magnitude is less than.2 for momentum transfers of less than 1 fm^{-1}. In contrast, both Relativistic and standard DWIA calculations predict a maximum of A = -.7 near q = 0.7 fm ^{-1}.

  12. Neutrons scattering studies in the actinide region

    SciTech Connect

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

    1992-09-01

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

  13. Neutrons scattering studies in the actinide region

    NASA Astrophysics Data System (ADS)

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

    1992-09-01

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

  14. Design of a backscatter 14-MeV neutron time-of-flight spectrometer for experiments at ITER

    SciTech Connect

    Dzysiuk, N.; Hellesen, C.; Conroy, S.; Ericsson, G.; Hjalmarsson, A.; Skiba, M.

    2014-08-21

    Neutron energy spectrometry diagnostics play an important role in present-day experiments related to fusion energy research. Measurements and thorough analysis of the neutron emission from the fusion plasma give information on a number of basic fusion performance quantities, on the condition of the neutron source and plasma behavior. Here we discuss the backscatter Time-of-Flight (bTOF) spectrometer concept as a possible instrument for performing high resolution measurements of 14 MeV neutrons. The instrument is based on two sets of scintillators, a first scatterer exposed to a collimated neutron beam and a second detector set placed in the backward direction. The scintillators of the first set are enriched in deuterium to achieve neutron backscattering. The energy resolution and efficiency of a bTOF instrument have been determined for various geometrical configurations. A preliminary design of optimal geometry for the two scintillator sets has been obtained by Monte Carlo simulations based on the MCNPX code.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

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

    SciTech Connect

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

    2013-01-01

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

  17. Scattering corrections in neutron radiography using point scattered functions

    NASA Astrophysics Data System (ADS)

    Kardjilov, N.; de Beer, F.; Hassanein, R.; Lehmann, E.; Vontobel, P.

    2005-04-01

    Scattered neutrons cause distortions and blurring in neutron radiography pictures taken at small distances between the investigated object and the detector. This defines one of the most significant problems in quantitative neutron radiography. The quantification of strong scattering materials such as hydrogenous materials—water, oil, plastic, etc.—with a high precision is very difficult due to the scattering effect in the radiography images. The scattering contribution in liquid test samples (H 2O, D 2O and a special type oil ISOPAR L) at different distances between the samples and the detector, the so-called Point Scattered Function (PScF), was calculated with the help of MCNP-4C Monte Carlo code. Corrections of real experimental data were performed using the calculated PScF. Some of the results as well as the correction algorithm will be presented.

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

    SciTech Connect

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

    1991-07-01

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

  19. 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

  20. Scattering of slow neutrons by bound nuclei

    NASA Astrophysics Data System (ADS)

    Nowak, Ernst

    1982-09-01

    The T-operator for scattering of slow neutrons by a system of bound nuclei is calculated up to quadratic terms in the scattering length. Binding effects as well as effects of multiple scattering have to be included in order to avoid inconsistencies. For the discussion of binding effects one can adopt methods developed by Dietze and Nowak [1] for treating scattering by an elastically bound nucleus. In particular the case of coherent elastic scattering is discussed: we show how the corrections can be expressed in terms of correlation functions and that binding effects are most important for scattering by light nuclei.

  1. Elastic Compton Scattering from the Deuteron Near 100 MeV

    NASA Astrophysics Data System (ADS)

    Kovash, Michael; Shoniyozov, Khayrullo; Compton@MAX-lab Collaboration

    2015-10-01

    Differential cross sections for elastic Compton scattering from targets of carbon and deuterium have been measured from 86 to 113 MeV using a tagged bremsstrahlung beam at the MAX 1 electron storage ring in Lund, Sweden. Photon spectra were collected in 2009 and 2010 at scattering angles of 60, 120 and 150 degrees using three very large, high efficiency NaI spectrometers, each with a FWHM resolution of approximately 2 MeV. The deuterium target consisted of a cryogenic liquid cell of 17 cm length. Improvements made to the running conditions of previous MAX-lab data sets include the use of multi-hit time digitizers, and reduced instantaneous counting rates in both the tagging and the NaI detectors. GEANT4 simulations have been used to determine the photon detector response and efficiency, as well as the photon losses in the targets. The overall accuracy of this procedure is verified by comparing the current carbon results with previous data. The new deuterium cross sections will be presented and compared with the earlier results from this collaboration. The combined data set will be compared with recent Chiral Effective Field Theory calculations to determine the values of the neutron polarizabilities, αn and βn.

  2. Hierarchical optimization for neutron scattering problems

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  3. Measurement of the H(n,n)H Elastic Scattering Angular Distribution at En = 15 MeV

    SciTech Connect

    Bateman, F.B.; Carlson, A.D.; Al-Quraishi, S.I.; Brient, C.E.; Carter, D.E.; Grimes, S.M.; Massey, T.N.; Wheeler, R.T.; Boukharouba, N.; Haight, R.C.

    2005-05-24

    We have undertaken an experiment to measure the relative differential cross section for neutron scattering from hydrogen at a neutron energy of 15 MeV, for center-of-mass scattering angles from 60 degrees to 180 degrees. A total of eleven E-{delta}E telescopes were used to detect the scattered protons at laboratory angles of 0, {+-}12, {+-}24, {+-}36, {+-}48, and {+-}60 degrees. This experiment is intended to extend the earlier work performed by this group at 10.04 MeV. To avoid possible dead-time problems and amplifier summing noise a unique approach to data acquisition was taken The data acquisition is based on eleven individual data-acquisition boards, one for each detector telescope, installed in separate personal computers, each running independently. In this way, no multiplexing of the detector signals is required, and the noise associated with the summing of the signals is eliminated. Also an additional acquisition board and personal computer are used for a neutron detector, with gamma-ray discrimination, as a neutron monitor. A detailed description of the data-acquisition system will be given, and results from preliminary experiments will be presented.

  4. Measurement of the Absolute Elastic and Inelastic Differential Neutron Cross Sections for 23Na Between 2 and 4 MeV

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Chakraborty, A.; Crider, B. P.; McEllistrem, M. T.; Peters, E. E.; Prados-Estévez, F. M.; Yates, S. W.; Hicks, S. F.; Kersting, L. J.; Luke, C. J.; McDonough, P. J.; Sigillito, A. J.; Vanhoy, J. R.

    2013-03-01

    Elastic and inelastic neutron scattering angular distributions have been measured from 23Na for incident neutron energies between 2 and 4 MeV at the University of Kentucky using neutron time-of-flight techniques. The cross sections obtained are important for applications in nuclear reactor development and other areas, and they are an energy region in which existing data are very sparse. Absolute cross sections were obtained by normalizing Na angular distributions to the well-known np cross sections.

  5. Precision Measurement of 56Fe(n,n γ) Cross Sections Using 14.1 MeV Neutrons

    NASA Astrophysics Data System (ADS)

    Wang, Haoyu; Koltick, David

    2016-03-01

    Integral production cross sections for 846.8 keV and 1238.3 keV prompt gamma rays from 14.1 MeV neutrons interactions on 56Fe are reported. The experimental technique takes advantage of the 1.5 nanosecond coincidence timing resolution between the neutron production time and the gamma ray detection time to reject noise, together with the large 30% solid angle gamma ray coverage. The scattering angle coverage with respect to the neutron beam direction extends from 60 degrees to 120 degrees. The neutron flux is measured using the detected associated alpha-particle from the D-T fusion reaction produced using an associated particle neutron generator. Present cross section measurements using other techniques with limited timing resolution and solid angle coverage are in agreement at neutron energies lower than 6 MeV. At higher neutron energies reported results can disagree by more than 20%. The more accurate technique used in these measurements can distinguish between the differences in the present reported results at higher neutron energies. The author would like to thank TechSource, Inc. and Advanced Physics Technologies, LLC. for their support in this work.

  6. Spectral measurements of neutrons produced by 52 MeV protons with activation detectors

    NASA Astrophysics Data System (ADS)

    Shin, Kazuo; Saito, Takatsugu; Fujii, Masahiko; Nakamura, Takashi

    The accuracy of the neutron spectral measurement of energy up to ˜40 MeV with activation detectors was examined using high energy neutrons from thick targets bombarded by 52 MeV protons. The measured activation rates were unfolded with the modified SAND-II code and compared with the neutron spectra measured by the NE-213 scintillator. Quite good agreement in absolute values was obtained between the spectra recorded by these two different detectors. The activation detector was shown to be useful for neutron spectroscopy at energies higher than ˜ 10 MeV.

  7. (65)Cu isomeric cross sections for (n,α) reaction using approximately 14MeV neutrons.

    PubMed

    Durusoy, Ayşe; Reyhancan, Iskender Atilla; Akçalı, Özgür

    2015-05-01

    In this paper, activation cross-section measurements for the (65)Cu(n,α)(62m)Co (T1/2=13.86min.) reaction at six different neutron energies ranging from 13.6 and 14.9MeV are presented. The fast neutrons were produced via (3)H(d, n)(4)He reactions from an SAMES T-400 neutron generator. An activation technique was used to measure induced gamma activities. A high-resolution gamma-ray spectrometer with a high-purity germanium (HpGe) detector was used to acquire the data. The measured cross section data were corrected for gamma-ray attenuations, pulse pile-up effects, dead time, variations in neutron flux, and contributions from scattered low-energy neutrons. The measured cross sections were compared with statistical model calculations (TALYS 1.6 code), the experimental data available in the literature and the data obtained from TENDL. PMID:25728005

  8. Neutron induced pion production on C, Al, Cu, and W at neutron energies of 200--600 MeV

    SciTech Connect

    Brooks, M.L.

    1991-10-01

    Inclusive double differential neutron induced {pi}{sup +} and {pi}{sup {minus}} production cross sections were measured for four separate targets: C, Al, Cu and W. The neutron energy range was 200--600 MeV and the pion angular range was 25{degrees}--125{degrees}. The charge, scattering angle and energy of the pions were measured using a magnetic spectrometer. The measurements are compared with intranuclear cascade (INC) calculations and a previous experiment that measured the sum of the {pi}{sup +} and {pi}{sup {minus}} cross sections. Our data agree with the measured data, but the INC calculations give only moderate agreement with the double differential cross sections as well as with angular distributions and total cross sections as a function of neutron energy. The ratio of {pi}{sup {minus}}:{pi}{sup +} was found to increase rapidly with decreasing neutron energy and the pion production was found to increase approximately as A{sup 2/3} for the different targets. 31 refs., 55 figs., 6 tabs.

  9. 14-MeV Neutron Generator Used as a Thermal Neutron Source

    SciTech Connect

    Dioszegi,I.

    2008-08-10

    One of the most important applications of the general purpose Monte Carlo N-Particle (MCNPS and MCNPX) codes is neutron shielding design. We employed this method to simulate the shield of a 14-MeV neutron generator used as a thermal neutron source providing an external thermal neutron beam for testing large area neutron detectors developed for diffraction studies in biology and also useful for national security applications. Nuclear reactors have been the main sources of neutrons used for scientific applications. In the past decade, however, a large number of reactors have been shut down, and the importance of other, smaller devices capable of providing neutrons for research has increased. At Brookhaven National Laboratory a moderated Am-Be neutron source with shielding is used for neutron detector testing. This source is relatively weak, but provides a constant flux of neutrons, even when not in use. The use of a 14 MeV energized neutron generator, with an order of magnitude higher neutron flux has been considered to replace the Am-Be source, but the higher fast neutron yield requires a more careful design of moderator and shielding. In the present paper we describe a proposed shielding configuration based on Monte Carlo calculations, and provide calculated neutron flux and dose distributions. We simulated the neutron flux distribution of our existing Am-Be source surrounded by a paraffin thermalizer cylinder (radius of 17.8 cm), 0.8 mm cadmium, and borated polyethylene as biological shield. The thermal neutrons are available through a large opening through the polyethylene and cadmium. The geometrical model for the MCNPS and MCNPX2 simulations is shown in Fig. 1. We simulated the Am-Be source neutron energy distribution as a point source having an energy distribution of four discrete lines at 3.0 (37%), 5.0 (35%), 8.0 (20%) and 11.0 (8%) MeV energies. The estimated source strength based on the original specifications is 6.6 {center_dot} 10{sup 6} neutrons

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

    DOE PAGESBeta

    Grammer, K. B.; Alarcon, R.; Barrón-Palos, L.; Blyth, D.; Bowman, J. D.; Calarco, J.; Crawford, C.; Craycraft, K.; Evans, D.; Fomin, N.; et al

    2015-05-08

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

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

    SciTech Connect

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

    2015-05-08

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  13. Measurement of np elastic scattering spin-spin correlation parameters at 484, 634, and 788 MeV

    SciTech Connect

    Garnett, R.W.

    1989-03-01

    The spin-spin correlation parameters C/sub LL/ and C/sub SL/ were measured for np elastic scattering at the incident neutron kinetic energy of 634 MeV. Good agreement was obtained with previously measured data. Additionally, the first measurement of the correlation parameter C/sub SS/ was made at the three energies, 484, 634, and 788 MeV. It was found that the new values, in general, do not agree well with phase shift predictions. A study was carried out to determine which of the isospin-0 partial waves will be affected by this new data. It was found that the /sup 1/P/sub 1/ partial wave will be affected significantly at all three measurement energies. At 634 and 788 MeV, the /sup 3/S/sub 1/ phase shifts will also change. 29 refs., 21 figs., 16 tabs.

  14. BUILDING A NETWORK FOR NEUTRON SCATTERING EDUCATION

    SciTech Connect

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

    2008-10-01

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

  15. Neutron Background Characterization for a Coherent Neutrino-Nucleus Scattering experiment at SNS

    NASA Astrophysics Data System (ADS)

    Gerling, Mark

    2014-03-01

    Coherent Neutrino Nucleus Scattering (CNNS) is a theoretical well-grounded, but as-yet unverified process. The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) may provide an optimal platform for detection of CNNS, possibly with existing detector technology. A proto-collaboration of groups from several institutions has come together to investigate this option and propose an experiment for the first-time observation of CNNS. Currently, the largest risk to such an experiment comes from an unknown background of beam-induced high-energy neutrons that penetrate the existing SNS concrete shielding. We have deployed a neutron scatter camera at the SNS during beam operation and performed preliminary measurements of the neutron backgrounds at a promising experimental location. In order to measure neutrons as high as 100 MeV, we needed to make modifications to the neutron scatter camera and expand its capabilities beyond its standard operating range of 1-14MeV. We have identified sources of high-energy neutrons and continue to investigate other possible locations that may allow a successful CNNS experiment to go forward. The imaging capabilities of the neutron scatter camera will allow more optimal shielding designs that take into account neutron flux anisotropies at the selected experiment locations.

  16. Study of 180 Mev Proton Inelastic Scattering from SILICON-28 and SILICON-30.

    NASA Astrophysics Data System (ADS)

    Chen, Quan

    This thesis reports the measurement of cross section and analyzing power angular distribution of elastic and inelastic scattering of 180 MeV proton for ^ {28}Si and ^{30} Si. Measurements were carried out using the proton beam available at the Indiana University Cyclotron Facility. The scattered protons were detected using the QDDM magnetic spectrometer. The DWIA framework, in which most inelastic proton scattering observables are analyzed, has three ingredients, (1) NN-effective interaction, (2) transition density, and (3) distorted waves. The procedure used here to obtain effective NN-interaction empirically is that first suggested by J. J. Kelly. It models effective NN-interaction guided by the nuclear matter theory(G-matrix) and employs the local density approximation(LDA). By using the transitions, for which transition densities are known, it fits the inelastic observable to determine the parameters used to model the momentum transfer(q) and density(k_{F }) dependence of the effective interaction (here reference to as empirical interaction). The distorted waves are calculated in a self-consistent manner from the model empirical interaction. The salient results are: (1) It is observed that, although the data base was increased by combining the ^{16}O observable with those of ^{28}Si, it still was not large enough to determine all the parameters without ambiguity in terms of which the effective NN-interaction was modeled. (2) The model prediction of cross section and analyzing power in terms of DWIA, using both the Paris -g and empirical interaction, with the observed are compared. It is clear that the results and the technique used to obtain effective NN-interaction shows that there is substantial potential to gain both qualitative and quantitative insight into how the interaction between two nucleons is modified within the nuclear medium. In particular, at low-q effective interaction is reduced and at high-q repulsion is enhanced compared to free interaction

  17. Nuclear sizes of /sup 40,42,44,48/Ca from elastic scattering of 104 MeV alpha particles. I. Experimental results and optical potentials

    SciTech Connect

    Gils, H.J.; Friedman, E.; Rebel, H.; Buschmann, J.; Zagromski, S.; Klewe-Nebenius, H.; Neumann, B.; Pesl, R.; Bechtold, G.

    1980-04-01

    Differential cross sections for elastic scattering of 104 MeV ..cap alpha.. particles from /sup 40,42,44,48/Ca have been measured with high angular accuracy over a wide angular range. Optical model analysis based on a Fourier-Bessel description of the real potential reveals isotopic differences which, in particular for /sup 48/Ca, indicate a small neutron skin.

  18. Neutron scattering analysis with microscopic optical model potentials

    SciTech Connect

    Hansen, L.F.

    1991-09-03

    A review of microscopic optical model potentials used in the analysis of neutron scattering and analyzing power data below 100 MeV (5 {le}E{sub n}{le}100 MeV) is presented. The quality of the fits to the data over a wide massd ({sup 6}Li-{sup 239}Pu) and energy range is discussed. It is shown that reasonably good agreement with the data is obtained with only three parameters, {lambda}{sub V}, {lambda}{sub W}, and {lambda}{sub SO}, which show a smooth mass and energy dependence. These parameters are normalizing constants to the real (V), and imaginary (W) central potentials and the real spin-orbit (V{sub SO}) potential. 14 refs., 7 figs.

  19. Neutron Scattering Applied to Materials Problems

    SciTech Connect

    Morris, James R; Wang, Xun-Li; Fultz, B.

    2006-01-01

    Neutron scattering techniques for studying materials have been applied for more than 50 years, in part led by Clifford G. Shull and Bertram N. Brockhouse, who shared the 1994 Nobel Prize in physics. The award was given for their developments in studying both the structure and dynamics of materials. The application of neutron scattering to materials has received significantly greater attention in the last few years, due to the construction of the Spallation Neutron Source (SNS) at the Oak Ridge National laboratory. The SNS will provide unprecedented access to a wide variety of instruments designed for materials research. The idea for this series of articles originated during the 2005 TMS Annual Meeting. Two symposia were devoted to neutron scattering: Neutron Scattering in Materials Research; and Neutron Diffraction Characterization of Mechanical Behavior. the goal of these articles is to introduce techniques for studying materials using neutrons, particularly to answer what are considered traditional materials problems. The first article discusses structure and phase analysis. Neutrons may be used for diffraction, similar to x-rays. However, in certain circumstances, they bring particular advantages. For example, x-rays have difficulty 'seeing' light elements, particularly when heavier elements are present, whereas neutrons may scatter effectively from elements such as hydrogen and its isotopes. The scattering strength of neutrons is sensitive to the isotopic composition. This can be used to examine the influence of a particular element. Neutrons also interact magnetically, allowing their use for studying magnetic order in materials. Because neutrons are highly penetrating, in-situ investigations under special sample environments (e.g., temperature, magnetic field, high pressure) have become routine. The second article describes applications for studying residual stress and mechanical deformation. neutrons are better able to penetrate engineering components

  20. Inelastic Neutron Scattering from Glass Formers

    NASA Astrophysics Data System (ADS)

    Buchenau, U.

    Neutron spectra below and above the glass transition temperature show a pronounced difference between strong and fragile glass formers in Angell's fragility scheme. The strong anharmonic increase of the inelastic scattering with increasing temperature in fragile substances is absent in the strongest glass former SiO2. That difference is reflected in the temperature dependence of Brillouin sound velocities above the glass transition. Coherent inelastic neutron scattering data indicate a mixture of sound waves and local modes at the low frequency boson peak. A relation between the fragility and the temperature dependence of the transverse hypersound velocity at the glass temperature is derived.

  1. Monte Carlo simulation of neutron scattering instruments

    SciTech Connect

    Seeger, P.A.

    1995-12-31

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

  2. Elastic and inelastic scattering of neutrons from 56Fe

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    The differential cross sections for elastic and inelastic scattered neutrons from 56Fe have been measured at the University of Kentucky Accelerator Laboratory (www.pa.uky.edu/accelerator) for incident neutron energies between 2.0 and 8.0 MeV and for the angular range 30° to 150°. Time-of-flight techniques and pulse-shape discrimination were employed for enhancing the neutron energy spectra and for reducing background. An overview of the experimental procedures and data analysis for the conversion of neutron yields to differential cross sections will be presented. These include the determination of the energy-dependent detection efficiencies, the normalization of the measured differential cross sections, and the attenuation and multiple scattering corrections. Our results will also be compared to evaluated cross section databases and reaction model calculations using the TALYS code. This work is supported by grants from the U.S. Department of Energy-Nuclear Energy Universities Program: NU-12-KY-UK-0201-05, and the Donald A. Cowan Physics Institute at the University of Dallas.

  3. Neutron-photon multigroup cross sections for neutron energies less than or equal to400 MeV. Revision 1

    SciTech Connect

    Alsmiller, R.G. Jr.; Barnes, J.M.; Drischler, J.D.

    1986-01-01

    For a variety of applications, e.g., accelerator shielding design, neutrons in radiotherapy, radiation damage studies, etc., it is necessary to carry out transport calculations involving medium-energy (greater than or equal to20 MeV) neutrons. A previous paper described neutron-photon multigroup cross sections in the ANISN format for neutrons from thermal to 400 MeV. In the present paper the cross-section data presented previously have been revised to make them agree with available experimental data. 7 refs., 1 fig.

  4. Calculated neutron-induced cross sections for /sup 53/Cr from 1 to 20 MeV

    SciTech Connect

    Shibata, K.; Hetrick, D.M.

    1987-05-01

    Neutron-induced cross sections of /sup 53/Cr have been calculated in the energy regions from 1 to 20 MeV. The quantities obtained are the cross sections for the reactions (n,n'..gamma..), (n,2n), (n,np), (n,n..cap alpha..), (n,p..gamma..), (n,pn), (n,..cap alpha gamma..), (n,..cap alpha..n), (n,d), (n,t), (n,/sup 3/He), and (n,..gamma..), as well as the spectra of emitted neutrons, protons, alpha particles, and gamma rays. The precompound process was included above 5 MeV in addition to the compound process. For the inelastic scattering, the contribution of the direct interaction was calculated with DWBA. 36 refs., 23 figs., 11 tabs.

  5. Designing of the 14 MeV neutron moderator for BNCT

    NASA Astrophysics Data System (ADS)

    Cheng, Dao-Wen; Lu, Jing-Bin; Yang, Dong; Liu, Yu-Min; Wang, Hui-Dong; Ma, Ke-Yan

    2012-09-01

    In boron neutron capture therapy (BNCT), the ratio of the fast neutron flux to the neutron flux in the tumor (RFNT) must be less than 3%. If a D-T neutron generator is used in BNCT, the 14 MeV neutron moderator must be optimized to reduce the RFNT. Based on the neutron moderation theory and the simulation results, tungsten, lead and diamond were used to moderate the 14 MeV neutrons. Satisfying RFNT of less than 3%, the maximum neutron flux in the tumor was achieved with a three-layer moderator comprised of a 3 cm thick tungsten layer, a 14 cm thick lead layer and a 21 cm thick diamond layer.

  6. Inelastic neutron scattering from zircon

    SciTech Connect

    Nipko, J.C.; Loong, C.K.

    1997-07-14

    A lattice dynamical investigation of zircon (ZrSiO{sub 4}) has been carried out to obtain a microscopic understanding of its thermodynamic properties, as well as to examine possible soft modes that may contribute to the phase transformation to scheelite type under high pressure. We have measured the neutron weighted phonon density of states of zircon from a polycrystalline sample. The neutron spectra reveal one-phonon excitations extending to 1130 cm{sup -1}, with phonon bands centered at 226, 298, 363, 540, 661, 726, 945, and 1081 cm{sup -1}. A quantitative analysis of the neutron results was carried out using a lattice dynamical rigid-ion model. 4 refs., 3 figs.

  7. Energy-resolved neutron SEU measurements from 22 to 160 MeV

    SciTech Connect

    Johansson, K.; Dyreklev, P.; Granbom, B.; Olsson, N.; Blomgren, J.; Renberg, P.U.

    1998-12-01

    The energy dependence of the neutron- induced single-event upset (NSEU) cross section for Static RAMs have been measured, using quasi-monoenergetic neutrons of five different energies from 22 to 160 MeV. The measured SEU cross sections were corrected for the low-energy neutron tail by an iterative folding procedure. A clear energy dependence has been found. The SEU rate has been compared both with results from testing with a neutron spallation spectrum up to 800 MeV and the measured SEU rate from In-Flight experiments at 10 km.

  8. 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.

  9. Off-specular scattering in neutron reflectometry

    SciTech Connect

    Pynn, R.; Baker, S.M.; Smith, G.; Fitzsimmons, M.

    1995-03-01

    When neutrons are scattered at small angles from planar, laterally homogeneous, stratified media, only specular (mirror like) reflection is observed. Sample inhomogeneities, such as interfacial roughness or voids, give rise to off-specular scattering which has been observed in many experiments with neutrons and x-rays. The easiest way to describe this scattering theoretically is based on the distorted-wave Born approximation (DWBA), which uses the neutron wavefunctions that describe reflection from a smooth surface as the basis functions for perturbation theory. From the DWBA one may obtain a number of qualitative results which are supported by experiment. Examples include the Yoneda fringes observed in reflection experiments with microscopically rough surfaces and the constant-q{sub z} fringes observed for multilayers with correlated, rough interfaces. One must, however, use the DWBA with care. When the correlation range within the reflecting interfaces is large--for example, when a surface is composed of misoriented facets--the approximation breaks down. Some authors have also reported a lack of quantitative agreement between versions of the DWBA calculations and the scattering observed with microscopically rough surfaces. A remarkable feature of neutron (or x-ray) reflectometry is the length scales that are probed within reflecting surfaces. These range from a few hundred Angstroms up to several microns, allowing neutron scattering to probe objects of a size normally visible by optical microscopy! The intent of this paper is to provide a simple description of scattering from rough surfaces that is accessible to a wide audience. Mathematical completeness is sacrificed in favor of intuitive arguments and experimental examples.

  10. First experimental results from 2MeV proton tandem accelerator for neutron productiona)

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, A.; Belchenko, Yu.; Burdakov, A.; Davydenko, V.; Ivanov, A.; Khilchenko, A.; Konstantinov, S.; Krivenko, A.; Kuznetsov, A.; Mekler, K.; Sanin, A.; Shirokov, V.; Sorokin, I.; Sulyaev, Yu.; Tiunov, M.

    2008-02-01

    A 2MeV proton tandem accelerator with vacuum insulation was developed and first experiments are carried out in the Budker Institute of Nuclear Physics (Novosibirsk). The accelerator is designed for neutron production via reaction Li7(p,n)Be7 for the boron neutron-capture therapy of the brain tumors, and for explosive detection based on 9.1724MeV resonance gamma, which are produced via reaction C13(p,γ)N14, absorption in nitrogen.

  11. Simulation experiments for gamma-ray mapping of planetary surfaces: Scattering of high-energy neutrons

    NASA Technical Reports Server (NTRS)

    Brueckner, J.; Englert, P.; Reedy, R. C.; Waenke, H.

    1986-01-01

    The concentration and distribution of certain elements in surface layers of planetary objects specify constraints on models of their origin and evolution. This information can be obtained by means of remote sensing gamma-ray spectroscopy, as planned for a number of future space missions, i.e., Mars, Moon, asteroids, and comets. To investigate the gamma-rays made by interactions of neutrons with matter, thin targets of different composition were placed between a neutron-source and a high-resolution germanium spectrometer. Gamma-rays in the range of 0.1 to 8 MeV were accumulated. In one set of experiments a 14-MeV neutron generator using the T(d,n) reaction as neutron-source was placed in a small room. Scattering in surrounding walls produced a spectrum of neutron energies from 14 MeV down to thermal. This complex neutron-source induced mainly neutron-capture lines and only a few scattering lines. As a result of the set-up, there was a considerable background of discrete lines from surrounding materials. A similar situation exists under planetary exploration conditions: gamma-rays are induced in the planetary surface as well as in the spacecraft. To investigate the contribution of neutrons with higher energies, an experiment for the measurement of prompt gamma radiation was set up at the end of a beam-line of an isochronous cyclotron.

  12. Neutron scattering facility for the calibration of the response to nuclear recoils

    NASA Astrophysics Data System (ADS)

    Jochum, J.; Chambon, B.; Drain, D.; von Feilitzsch, F.; Gascon, J.; Huber, M.; Jagemann, T.; de Jésus, M.; Lachenmaier, T.; Lanfranchi, J.-C.; Martineau, O.; Potzel, W.; Rüdig, A.; Schnagl, J.; Simon, E.; Stark, M.; Stern, M.; Wulandari, H.

    2002-02-01

    A possibility to search for elementary particles as dark matter candidates is to detect elastic scattering with cryogenic detectors. For the interpretation of the data one has to determine the detector response to nuclear recoils, the so-called quenching factors. They can differ for the heat-, for the scintillation- and for the ionization-signal and can be measured by scattering of neutrons. The CRESST- and the EDELWEISS-collaborations have set up a neutron scattering facility for cryogenic detectors at the tandem-accelerator of the Munich `Maier-Leibniz-Labor.' The scattering angle and the time-of-flight of the neutrons are measured by an array of liquid scintillator cells. The pulsed high energy (11 MeV) neutron beam is created by nuclear reaction of a 11B on a H2-gas target. The set-up and the results of first tests are presented. .

  13. Neutron inelastic scattering by amino acids

    SciTech Connect

    Thaper, C.L.; Sinha, S.K.; Dasannacharya, B.A.

    1982-01-01

    Inelastic neutron scattering experiments on normal, N-deuterated glycine, normal and N-deuterated alanine, L-valine, L-tyrosine and, L-phenylalanine at 100 K, are reported. Coupling of the external modes to different hydrogens is discussed.

  14. Treatment experience: locally advanced sarcomas with 15 MeV fast neutrons

    SciTech Connect

    Ornitz, R.; Herskovic, A.; Schell, M.; Fender, F.; Rogers, C.C.

    1980-06-01

    Experience with ten evaluable osseous sarcomas and ten evaluable advanced soft tissue sarcomas treated with neutrons of a mean neutron energy of 15 MeV are described. Neutron irradiation with or without conventional megavoltage radiotherapy is an effective modality in the treatment of these patients. No correlation between response rate and grade or whether fast neutrons alone or combined with megavoltage radiotherapy was noted. Those patients receiving a neutron dose of 2195 neutron plus gamma rads or greater all had a complete response.

  15. Study of the fission spectrum of less than 1 MeV neutrons using a Lithium-glass detector

    NASA Astrophysics Data System (ADS)

    Bastola, Suraj; Rees, Lawrence; Bart, Czirr

    2011-10-01

    The fission spectrum of neutrons with kinetic energies less than 1 MeV is of considerable practical importance for the design of nuclear reactors. However, it is not as precisely known as that for higher energy neutrons. One of the major problems scientists have previously encountered is room return neutrons. These are neutrons that reflect from the walls, ceiling or floor of the lab. Another problem is finding a way to measure accurately the neutron time of flight. This is the time neutrons take to travel from a fission event to the detector. Time of flight is used to measure the neutron energy. To avoid the room return, I am going to perform an experiment about 45 feet above the ground in the BYU Indoor Practice Facility, so that neutrons from the source will not scatter from nearby surfaces and return to the detector. To find the time of flight to a greater accuracy, I have been using a Time to Amplitude Converter (TAC). A TAC has a capacitor that charges linearly as the voltage builds up. With a 12-bit digitizer system, we can measure the time to 0.1 nanoseconds, whereas the same digitizer can only measure time in steps of 4 nanoseconds. So, we will get a more accurate measurement of time of flight with the TAC.

  16. Resonance effects in neutron scattering lengths

    SciTech Connect

    Lynn, J.E.

    1989-06-01

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

  17. 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.

  18. Elastic and inelastic neutron scattering cross sections for fission reactor applications

    SciTech Connect

    Hicks, S. F.; Combs, B.; Downes, L.; Girgis, J.; Kersting, L. J.; Lueck, C. J.; McDonough, P. J.; Schniederjan, J.; Sidwell, L.; Sigillito, A. J.; Chakraborty, A.; Crider, B. P.; Kumar, A.; McEllistrem, M. T.; Peters, E. E.; Prados-Estevz, F. M.; Vanhoy, J. R.; Watts, D.; Yates, S. W.

    2013-04-19

    Nuclear data important for the design and development of the next generation of light-water reactors and future fast reactors include neutron elastic and inelastic scattering cross sections on important structural materials, such as Fe, and on coolant materials, such as Na. These reaction probabilities are needed since neutron reactions impact fuel performance during irradiations and the overall efficiency of reactors. While neutron scattering cross sections from these materials are available for certain incident neutron energies, the fast neutron region, particularly above 2 MeV, has large gaps for which no measurements exist, or the existing uncertainties are large. Measurements have been made at the University of Kentucky Accelerator Laboratory to measure neutron scattering cross sections on both Fe and Na in the region where these gaps occur and to reduce the uncertainties on scattering from the ground state and first excited state of these nuclei. Results from measurements on Fe at incident neutron energies between 2 and 4 MeV will be presented and comparisons will be made to model calculations available from data evaluators.

  19. Elastic and inelastic neutron scattering cross sections for fission reactor applications

    NASA Astrophysics Data System (ADS)

    Hicks, S. F.; Chakraborty, A.; Combs, B.; Crider, B. P.; Downes, L.; Girgis, J.; Kersting, L. J.; Kumar, A.; Lueck, C. J.; McDonough, P. J.; McEllistrem, M. T.; Peters, E. E.; Prados-Estevz, F. M.; Schniederjan, J.; Sidwell, L.; Sigillito, A. J.; Vanhoy, J. R.; Watts, D.; Yates, S. W.

    2013-04-01

    Nuclear data important for the design and development of the next generation of light-water reactors and future fast reactors include neutron elastic and inelastic scattering cross sections on important structural materials, such as Fe, and on coolant materials, such as Na. These reaction probabilities are needed since neutron reactions impact fuel performance during irradiations and the overall efficiency of reactors. While neutron scattering cross sections from these materials are available for certain incident neutron energies, the fast neutron region, particularly above 2 MeV, has large gaps for which no measurements exist, or the existing uncertainties are large. Measurements have been made at the University of Kentucky Accelerator Laboratory to measure neutron scattering cross sections on both Fe and Na in the region where these gaps occur and to reduce the uncertainties on scattering from the ground state and first excited state of these nuclei. Results from measurements on Fe at incident neutron energies between 2 and 4 MeV will be presented and comparisons will be made to model calculations available from data evaluators.

  20. Research and development of a dedicated collimator for 14.2 MeV fast neutrons for imaging using a D-T generator

    NASA Astrophysics Data System (ADS)

    Sabo-Napadensky, I.; Weiss-Babai, R.; Gayer, A.; Vartsky, D.; Bar, D.; Mor, I.; Chacham-Zada, R.; Cohen, M.; Tamim, N.

    2012-06-01

    One of the main problems in neutron imaging is the scattered radiation that accompanies the direct neutrons that reach the imaging detectors and affect the image quality. We have developed a dedicated collimator for 14.2 MeV fast neutrons. The collimator optimizes the amount of scattered radiation to primary neutrons that arrive at the imaging plane. We have used different materials within the collimator in order to lower the scattered radiation that arrives at the scanned object. The image quality and the signal to noise ratios that are measured show that a mixture of BORAX (Na2B4O7ṡ10H2O) and water in the experimental beam collimator give the best results. We have used GEANT4 to simulate the collimator performance, the simulations predict the optimized material looking on the ratios of the scattered to primary neutrons that contribute in the detector. We present our experimental setup, report the results of the experimental and related simulation studies with neutrons beam generated by a 14.2 MeV D-T neutron generator.

  1. Studies of parity and time reversal symmetries in neutron scattering from165Ho

    NASA Astrophysics Data System (ADS)

    Haase, D. G.; Gould, C. R.; Koster, J. E.; Roberson, N. R.; Seagondollar, L. W.; Soderstrum, J. P.; Schneider, M. B.; Zhu, X.

    1988-12-01

    We describe searches for parity and time reversal violations in the scattering of polarized neutrons from polarized and aligned165Ho targets. We have completed a search with 7.1 and 11.0 MeV neutrons for PoddTodd terms in the elastic scattering forward amplitude of the form s. ( I×K), where s is the neutron spin, I is the target spin and k is the neutron momentum vector. The target was a single crystal of holmium, polarized horizontally along its b axis by a 1 Tesla magnetic field. The neutrons were polarized vertically. Differences in the neutron transmission were measured for neutrons with spins parallel (antiparallel) to I×k. The P,T violating analyzing powers were found to be consistent with zero at the few 10-3 level: ρP,T(7.1 MeV)=-0.88 (±2.02) x 10-3, ρP,T(11.0 MeV)=-0.4 (±2.88) x 10-3. We have also attempted to find enhancements with MeV neutrons in P-violation due to the term s k. We are preparing an aligned target cryostat for investigations of PevenTodd terms {bd(Ik)(I×k)s} in neutron scattering. The target will be a single crystal cylinder of165Ho cooled to 100 mK in a bath of liquid helium and rotated by a shaft from a room temperature stepping motor. The cylinder will be oriented vertically and the alignment ( c) axis oriented horizontally. Warming or rotation of the sample allows one to separate effects that mimic the sought-after time reversal violating term.

  2. Neutron Scattering Experiment Automation with Python

    SciTech Connect

    Zolnierczuk, Piotr A; Riedel, Richard A

    2010-01-01

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

  3. Directional neutron detectors for use with 14 MeV neutrons :fiber scintillation methods for directional neutron detection.

    SciTech Connect

    Sunnarborg, Duane A.; Peel, Justin D.; Mascarenhas, Nicholas; Mengesha, Wondwosen

    2005-10-01

    Current Joint Test Assembly (JTA) neutron monitors rely on knock-on proton type detectors that are susceptible to X-rays and low energy gamma rays. We investigated two novel plastic scintillating fiber directional neutron detector prototypes. One prototype used a fiber selected such that the fiber width was less than 2.1mm which is the range of a proton in plastic. The difference in the distribution of recoil proton energy deposited in the fiber was used to determine the incident neutron direction. The second prototype measured both the recoil proton energy and direction. The neutron direction was determined from the kinematics of single neutron-proton scatters. This report describes the development and performance of these detectors.

  4. Measurement and evaluation of neutron spectra above 0.1 MeV in the JMTR

    NASA Astrophysics Data System (ADS)

    Sakurai, Kiyoshi

    1983-08-01

    The evaluation of fast neutron spectra from the Japan Materials Testing Reactor (JMTR) have been performed by using the critical facility of the JMTR and by a combination of the multi-foil activation method and the adjustment codes (SAND II and NEUPAC). In order to measure and evaluate the neutron spectra above 0.1 MeV, resonance detectors such as manganese, gold and copper have been used to determine the neutron flux level in the {1}/{E} region and threshold detectors such as silver, rhodium, indium, uranium, aluminum, magnesium and titanium have been used to determine the neutron flux level above 0.1 MeV. The foils for the measurement of the neutron reaction rate were separately irradiated. The 115In(n,n') 115mIn reaction is used for the monitoring of the average fast neutron flux in the irradiation period, and the slight difference of each irradiation condition was corrected. The guess spectra for the neutron spectrum adjustment were calculated by using the one-dimensional discrete-ordinates code ANISN with the slab model for the JMTR core. Some important points were concluded through the adjustment procedure of the neutron spectrum: the adjusted spectrum from 0.1 to 1 MeV depends on the accuracy of the neutron cross section data for the threshold detectors such as silver and rhodium, and also on the accuracy of these reaction rates. The ratios of neutron flux above 0.183 MeV to neutron flux above 1 MeV were calculated from the guess spectra and the adjusted spectra, and the ratios were in good agreement with each other.

  5. Neutron Emission Spectra from Inelastic Scattering on 58,60Ni with a White Neutron Source at FIGARO.

    SciTech Connect

    Rochman, D.; O'Donnell, J. M.; Devlin, M. J.; Ethvignot, T.; Granier, T.; Grimes, S. M.

    2005-01-01

    Neutron emission spectra from inelastic neutron scattering on natural nickel at the FIGARO facility have been measured by a double time-of-flight technique. The incident neutrons are produced from the spallation source of the Weapons Neutron Research facility, and their energies are determined by time of flight. The emitted neutrons and gamma rays are detected by 16 liquid scintillators and one high-resolution germanium or one barium-fluoride detector, respectively. The results for incident neutron energies from 2 to 10 MeV are compared with predictions of nuclear model calculations performed with the code EMPIRE-II. Finally, the level density parameters 'a' and '{Delta}E' are extracted.

  6. Neutron Scattering Cross Section Measurements for 169Tm via the (n,n') Technique

    SciTech Connect

    Alimeti, Afrim; Kegel, Gunter H.R.; Egan, James J.; DeSimone, David J.; McKittrick, Thomas M.; Ji, Chuncheng; Tremblay, Steven E.; Roldan, Carlos; Chen Xudong; Kim, Don S.

    2005-05-24

    The neutron physics group at the University of Massachusetts Lowell (UML) has been involved in a program of scattering cross-section measurements for highly deformed nuclei such as 159Tb, 169Tm, 232Th, 235U, 238U, and 239Pu. Ko et al. have reported neutron inelastic scattering data from 169Tm for states above 100 keV via the (n,n'{gamma}) reaction at incident energies in the 0.2 MeV to 1.0 MeV range. In the present research, in which the time-of-flight method was employed, direct (n,n') measurements of neutrons scattered from 169Tm in the 0.2 to 1.0 MeV range were taken. It requires that our 5.5-MeV Van de Graaff accelerator be operated in the pulsed and bunched beam mode producing subnanosecond pulses at a 5-MHz repetition frequency. Neutrons are produced by the 7Li(p,n)7Be reaction using a thin metallic elemental lithium target.

  7. Inelastic neutron scattering studies of novel quantum magnets

    NASA Astrophysics Data System (ADS)

    Plumb, Kemp W.

    Inelastic neutron scattering was used to study the magnetic excitation spectrum of three quantum magnets: (i) the double perovskite Ba2FeReO 6; (ii) the two-dimensional square lattice Heisenberg antiferromagnet Sr2CuO2Cl2; and (iii) the quasi-two-dimensional frustrated two-leg ladder BiCu2PO6. We have conducted inelastic neutron scattering measurements on powder samples of the double perovskite compound Ba2FeReO6. The measurements revealed two well defined dispersing spin wave modes. No excitation gap was observable and the spectrum can be explained with a local moment model incorporating the interactions of Fe spins with spin-orbital locked degrees of freedom on the Re site. The results reveal that both significant electronic correlations and spin-orbit coupling on the Re site play a significant role in the spin dynamics of Ba2FeReO6. High resolution neutron scattering measurements of magnetic excitations in the parent cuprate Sr2CuO2Cl2 reveal a significant dispersion and momentum dependent damping of the zone boundary magnons. We directly compare our measurements with previous resonant inelastic x-ray scattering measurements and find a ~25 meV discrepancy between the two techniques for the measured zone boundary energy at (1/2, 0). The deviations are greatest precisely in the region of phase space where the magnon damping is strongest. This comparison shows that the inelastic x-ray spectrum must contain significant contributions from higher energy excitations not previously considered. Our measurements demonstrate that the high energy continuum of magnetic fluctuations is a ubiquitous feature of the magnetic spectrum among insulating monolayer cuprates, and that these excitations couple to both inelastic neutron and light scattering. A comprehensive series of inelastic neutron scattering measurements was used to investigate spin excitations in the frustrated two-leg ladder compound BiCu2PO6. The measurements revealed six branches of steeply dispersing triplon

  8. Measurements of the neutron activation cross sections for Bi and Co at 386 MeV.

    PubMed

    Yashima, H; Sekimoto, S; Ninomiya, K; Kasamatsu, Y; Shima, T; Takahashi, N; Shinohara, A; Matsumura, H; Satoh, D; Iwamoto, Y; Hagiwara, M; Nishiizumi, K; Caffee, M W; Shibata, S

    2014-10-01

    Neutron activation cross sections for Bi and Co at 386 MeV were measured by activation method. A quasi-monoenergetic neutron beam was produced using the (7)Li(p,n) reaction. The energy spectrum of these neutrons has a high-energy peak (386 MeV) and a low-energy tail. Two neutron beams, 0° and 25° from the proton beam axis, were used for sample irradiation, enabling a correction for the contribution of the low-energy neutrons. The neutron-induced activation cross sections were estimated by subtracting the reaction rates of irradiated samples for 25° irradiation from those of 0° irradiation. The measured cross sections were compared with the findings of other studies, evaluated in relation to nuclear data files and the calculated data by Particle and Heavy Ion Transport code System code. PMID:24368868

  9. New techniques in neutron data measurements above 30 MeV

    SciTech Connect

    Lisowski, P.W.; Haight, R.C.

    1991-01-01

    Recent developments in experimental facilities have enabled new techniques for measurements of neutron interactions above 30 MeV. Foremost is the development of both monoenergetic and continuous neutron sources using accelerators in the medium energy region between 100 and 800 MeV. Measurements of the reaction products have been advanced by the continuous improvement in detector systems, electronics and computers. Corresponding developments in particle transport codes and in the theory of nuclear reactions at these energies have allowed more precise design of neutron sources, experimental shielding and detector response. As a result of these improvements, many new measurements are possible and the data base in this energy range is expanding quickly.

  10. AN 8-ELEMENT FAST-NEUTRON DOUBLE-SCATTER DIRECTIONAL DETECTOR.

    SciTech Connect

    VANIER, P.E.; FORMAN, L.

    2005-07-31

    We have constructed a fast-neutron double-scatter spectrometer that efficiently measures the neutron spectrum and direction of a spontaneous fission source. The device consists of two planes of organic scintillators, each having an area of 125 cm{sup 2}, efficiently coupled to photomultipliers. The four scintillators in the front plane are 2 cm thick, giving almost 25% probability of detecting an incident fission-spectrum neutron at 2 MeV by proton recoil and subsequent ionization. The back plane contains four 5-cm-thick scintillators which give a 40% probability of detecting a scattered fast neutron. A recordable double-scatter event occurs when a neutron is detected in both a front plane detector and a back plane detector within an interval of 500 nanoseconds. Each double-scatter event is analyzed to determine the energy deposited in the front plane, the time of flight between detectors, and the energy deposited in the back plane. The scattering angle of each incident neutron is calculated from the ratio of the energy deposited in the first detector to the kinetic energy of the scattered neutron.

  11. Measurement of the Detection Efficiency of the Kloe Calorimeter for Neutrons Between 20 and 174 Mev

    NASA Astrophysics Data System (ADS)

    Gauzzi, P.; Anelli, M.; Battistoni, G.; Bertolucci, S.; Bini, C.; Branchini, P.; Curceanu, C.; de Zorzi, G.; di Domenico, A.; di Micco, B.; Ferrari, A.; Fiore, S.; Gauzzi, P.; Giovannella, S.; Happacher, F.; Iliescu, M.; Martini, M.; Miscetti, S.; Nguyen, F.; Passeri, A.; Prokofiev, A.; Sala, P.; Sciascia, B.; Sirghi, F.

    2008-06-01

    The detection efficiency of a KLOE calorimeter prototype to neutrons of kinetic energy of 21, 46 and 174 MeV has been measured by exposing it to the neutron beam of the The Svedberg Laboratory, Uppsala. The measurement of the neutron detection efficiency of a NE110 scintillator provided a reference calibration. At the lowest trigger threshold, the ratio between the calorimeter and scintillator efficiency ranges from 2.5 to 3.2.

  12. Calibration procedure for a neutron monitor at energies below 20 MeV

    NASA Astrophysics Data System (ADS)

    Öhrn, A.; Blomgren, J.; Park, H.; Khurana, S.; Nolte, R.; Schmidt, D.; Wilhelmsen, K.

    2008-07-01

    A liquid scintillation detector aimed for neutron energy and fluence measurements in the energy region below 20 MeV has been calibrated using monoenergetic and white spectrum neutron fields. Careful measurements of the proton light output function and the response matrix have been performed allowing for the application of unfolding techniques using existing codes. The response matrix is used to characterize monoenergetic neutron fields produced by the T(d,n) reaction at low deuteron energies.

  13. Upper limit to the 1-20 MeV solar neutron flux.

    NASA Technical Reports Server (NTRS)

    Lockwood, J. A.; Ifedili, S. O.; Jenkins, R. W.

    1973-01-01

    The upper limit on the quiet time solar neutron flux from 1 to 20 MeV has been measured to be less than .002 neutrons at the 95% confidence level. This result is deduced from the OGO-6 neutron detector measurements of the 'day-night' effect near the equator at low altitudes for the period from June 7 to Dec. 23, 1969. The OGO-6 detector had very low (less than 4%) counting rate contributions from locally produced neutrons in the detecting system and the spacecraft and from charged-particle interactions in the neutron sensor.

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

    SciTech Connect

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

    2009-10-25

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

  15. Determination of Neutron Spectrum by the Dosimetry Foil Method up to 37 Mev

    NASA Astrophysics Data System (ADS)

    Simakov, S. P.; Bém, P.; Burjan, V.; Fischer, U.; Forrest, R. A.; Götz, M.; Honusek, M.; Kroha, V.; Novàk, J.; Šimečková, E.

    2009-08-01

    The dosimetry activation foil technique was used for the determination of a white neutron spectrum at the U120M cyclotron facility of NPI/Řež. The neutrons were produced by 37 MeV protons slowing down in the thick heavy water target and have an energy distribution extending up to 37 MeV. To cover the whole energy range a set of 10 foils Al, Ti, Fe, Co, Ni, Y, Nb, In, Lu, and Au was used. The γ-rays from the decaying nuclei produced in 26 activation reactions were detected. The cross sections for these reaction were chosen from European Activation File EAF-2007 (up to 55 MeV) after intercomparison with the dosimetry cross section library IRDF-2002 which represents the cross section only up to 20 MeV and other high energy libraries. For the spectrum determination the SAND-II code was used after it had been modified to input dosimetry cross sections above 20 MeV in an arbitrary group structure. The guessed neutron spectrum which is needed to start an adjustment procedure was combined from those measured and calculated by the MCNPX code. The uncertainty of the adjusted neutron spectrum was estimated using the uncertainties of measured specific γ-activities induced in nuclides and dosimetry cross sections. It is less than 10% in the energy range below 25 MeV, the sensitivity domain of the most dosimetry reactions, but increases above this energy.

  16. Neutron scattering studies of heavy Fermions

    NASA Astrophysics Data System (ADS)

    Shapiro, S. M.

    1985-08-01

    Heavy Fermions are f electron materials characterized by a large linear term in the low temperature specific heat and a large magnetic susceptibility at low temperatures. This implies that there is a narrow peak in the f electron density of states at the Fermi energy. Typical examples are CeAl3, UBe13, CeCu2Si2, CeCu6, U2Zn17 and UPt3. Neutron scattering measurements can play an important role in understanding the magnetic interactions in these systems. Measurements of the form reveal details about the nature of the wave functions. Inelastic scattering studies gives information about the energy scale of the spin fluctuations and the narrow f-resonance. Such measurements on the above systems are reviewed with the goal of establishing systematics between the information obtained in neutron studies and that from bulk measurements.

  17. Complex Protein Structures by Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Glusker, Jenny

    2008-03-01

    Neutron scattering by an atom, unlike X-ray scattering, does not depend on the atomic number of that atom. Deuterium atoms scatter neutrons to the same extent as carbon or oxygen atoms and give positive peaks in a nuclear density map, while its isotope, hydrogen, gives a negative peak. Therefore neutron diffraction provides two results that are difficult to obtain from macromolecular X-ray diffraction studies: (1) the locations of hydrogen atoms, including the more mobile ones, and (2) the extent to which a hydrogen atom can be replaced by deuterium. The method shows whether an amino acid side chain (at a given pH value) is ionized or not. For example, one can ascertain whether histidine residues are singly or doubly protonated at the pH of study. Neutron diffraction studies can also be used to determine the absolute configuration of the course of a biochemical reaction by anomalous scattering and enzymatic deuteration of the substrate. Neutron diffraction experiments, however, require large crystals and these are often impossible to obtain for many macromolecules. Examples of reports of the use of neutron diffraction to provide information on enzymatic mechanism will be presented. This includes descriptions of our work on the enzyme D-xylose isomerase for which the orientation of a metal ion-bound water molecule in the active site was found. This water, thought to be involved in the isomerization step, was shown to be water (rather than hydroxyl) at pH 8.0. This analysis also revealed that one lysine has two rather than three attached hydrogen atoms and therefore lacks a positive charge. High-resolution X-ray studies (at 0.94 å) indicate how some side chains might move during catalysis. This combination of neutron and X-ray diffraction can contribute greatly to the elucidation of enzyme mechanisms. I thank Amy Katz, Xinmin Li, H. L. Carrell, Leighton Coates, Leif Hanson, Joel Harp, Paul Langan, and Benno Schoenborn who were involved in many of the described

  18. Medical applications of neutron inelastic scattering

    NASA Astrophysics Data System (ADS)

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

    1999-10-01

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

  19. Phase Shift Analyses of pp Elastic Scattering between 500 and 800 MeV

    NASA Astrophysics Data System (ADS)

    Nagata, J.; Yoshino, H.; Matsuda, M.

    1995-03-01

    The single-energy phase-shift analyses of pp elastic scattering have been made by using double-spin and triple-spin correlation parameters measured at SIN in the incident energy region TL = 447-580 MeV, and at LAMPF at TL = 735 MeV. The scattering amplitudes have been almost uniquely determined at TL = 500, 530, 560, 580 and 735 MeV. The Argand diagrams of 1D2-, 3P2- and 3F3-wave amplitudes show counter clockwise behavior. The obtained I = 1 amplitudes in the present analysis will contribute to the determination of the I = 0 amplitudes of np scattering in the same energy region.

  20. Neutron scattering in the ribosome structure

    NASA Astrophysics Data System (ADS)

    Serdyuk, Igor N.

    1997-02-01

    Thermal neutron scattering has become a powerful instrument for studying the ribosome and its components. The application of neutron scattering allowed to establish some principal features of the ribosome structure: non-homogeneous distribution of the RNA and protein within ribosomal particles, the RNA role as a framework in the arrangement and maintenance of the structure of ribosomal particles, and the globular character of ribosomal proteins. The use of selective deuteration of separate ribosomal proteins in combination with the triangulation method revealed mutual spatial arrangement (the 3D-map) of all the ribosomal proteins within the small particle and in the most part of the large ribosomal particle. An essential impact has been made in the structural studies of ribosomes with the development of novel experimental approaches: triple isotopic substitution and spin contrast variation. These approaches with direct interpretation of spherical harmonics provide new possibilities for constructing models of ribosomal particles, opening principally new perspectives for joint use of X-ray synchrotron diffraction in crystals and small-angle neutron scattering in solution.

  1. Neutron scattering studies of the heavy Fermion superconductors

    NASA Astrophysics Data System (ADS)

    Goldman, A. I.

    Recent neutron scattering measurements of the heavy Fermion superconductors are described. Those materials offer an exciting opportunity for neutron scattering since the f-electrons, which couple directly to magnetic scattering measurements, seem to be the same electrons which form the superconducting state below T sub c. In addition, studies of the magnetic fluctuations in these, and other heavy Fermion systems, by inelastic magnetic neutron scattering can provide information about the nature of the low temperature Fermi liquid character of these novel compounds.

  2. Inelastic neutron scattering in valence fluctuation compounds

    SciTech Connect

    Jon M Lawrence

    2011-02-15

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

  3. Tailoring the Neutron Spectrum from a 14-MeV Neutron Generator to Approximate a Spontaneous-Fission Spectrum

    SciTech Connect

    James Simpson; David Chichester

    2011-06-01

    Many applications of neutrons for non-invasive measurements began with isotopic sources such as AmBe or Cf-252. Political factors have rendered AmBe undesirable in the United States and other countries, and the supply of Cf-252 is limited and significantly increasing in price every few years. Compact and low-power deuterium-tritium (DT) electronic neutron generators can often provide sufficient flux, but the 14-MeV neutron spectrum is much more energetic (harder) than an isotopic neutron source. A series of MCNP simulations were run to examine the extent to which the 14-MeV DT neutron spectrum could be softened through the use of high-Z and low-Z materials. Some potential concepts of operation require a portable neutron generator system, so the additional weight of extra materials is also a trade-off parameter. Using a reference distance of 30 cm from the source, the average neutron energy can be lowered to be less than that of either AmBe or Cf-252, while obtaining an increase in flux at the reference distance compared to a bare neutron generator. This paper discusses the types and amounts of materials used, the resulting neutron spectra, neutron flux levels, and associated photon production.

  4. Tailoring the Neutron Spectrum from a 14-MeV Neutron Generator to Approximate a Spontaneous-Fission Spectrum

    NASA Astrophysics Data System (ADS)

    Simpson, J. D.; Chichester, D. L.

    2011-12-01

    Many applications of neutrons for non-invasive measurements began with isotopic sources such as AmBe or Cf-252. Political factors have rendered AmBe undesirable in the United States and other countries, and the supply of Cf-252 is limited and significantly increasing in price every few years. Compact and low-power deuterium-tritium (DT) electronic neutron generators can often provide sufficient flux, but the 14-MeV neutron spectrum is much more energetic (harder) than an isotopic neutron source. A series of MCNP simulations was run to examine the extent to which the 14-MeV DT neutron spectrum could be softened through the use of high-Z and low-Z materials. Some potential concepts of operation require a portable neutron generator system, so the additional weight of extra materials is also a trade-off parameter. Using a reference distance of 30 cm from the source, the average neutron energy can be lowered to be less than that of either AmBe or Cf-252, while obtaining an increase in flux at the reference distance compared to a bare neutron generator. This paper discusses the types and amounts of materials used, the resulting neutron spectra, neutron flux levels, and associated photon production.

  5. Tailoring the Neutron Spectrum from a 14-MeV Neutron Generator to Approximate a Spontaneous-Fission Spectrum

    SciTech Connect

    Simpson, J. D.; Chichester, D. L.

    2011-12-13

    Many applications of neutrons for non-invasive measurements began with isotopic sources such as AmBe or Cf-252. Political factors have rendered AmBe undesirable in the United States and other countries, and the supply of Cf-252 is limited and significantly increasing in price every few years. Compact and low-power deuterium-tritium (DT) electronic neutron generators can often provide sufficient flux, but the 14-MeV neutron spectrum is much more energetic (harder) than an isotopic neutron source. A series of MCNP simulations was run to examine the extent to which the 14-MeV DT neutron spectrum could be softened through the use of high-Z and low-Z materials. Some potential concepts of operation require a portable neutron generator system, so the additional weight of extra materials is also a trade-off parameter. Using a reference distance of 30 cm from the source, the average neutron energy can be lowered to be less than that of either AmBe or Cf-252, while obtaining an increase in flux at the reference distance compared to a bare neutron generator. This paper discusses the types and amounts of materials used, the resulting neutron spectra, neutron flux levels, and associated photon production.

  6. Slow-Neutron Scattering by Rotators. II

    NASA Technical Reports Server (NTRS)

    Volkin, Howard C.

    1960-01-01

    The methods developed in a previous paper for extending the neutron scattering formalism of Zemach and Glauber to any type of molecular rotator have been employed to derive generalized forms generalized forms of the differential cross sections for rotator scattering. A mass-ratio expansion for the treatment of the high-energy limit is illustrated on the classical cross section and then employed in the treatment of the more general quantum-mechanical expression for the differential cross section. The results apply to an arbitrarily asymmetric rotator. The very low energy approximation is carried out for the symmetric rotator, and the procedure is compared with the explicit summing of the partial cross sections for individual rotational transitions. The inelastic correction to the static approximation for interference scattering is calculated to an accuracy of first order in the mass ratios for the case of the symmetric rotator.

  7. Performances of a method for reconstructing the energy of neutrons detected by a double scattering spectrometer

    SciTech Connect

    Agnello, M.; Botta, E.; Bressani, T.; Calvo, D.; Gianotti, P.; Iazzi, F.; Lamberti, C.; Minetti, B. ); Balocco, E. )

    1992-10-01

    This paper reports on a neutron spectrometer based on the double scattering technique which has been designed and built at the Laboratorio Tecnologico of INFN - Turin (Italy) for Cold Fusion experiments. The operating principle for the reconstruction of the energy can be applied to various fields (neutron emission from sources, fission and fusion) and is described together with the performed tests: a resolution of less than 560 KeV FWHM has been obtained for neutrons of 2.45 MeV, in a typical running configuration.

  8. Measurement and evaluation of selected 14-MeV neutron cross sections for fusion

    SciTech Connect

    Meadows, J.W.; Smith, D.L.; Cox, S.A.

    1985-01-01

    Experimental neutron-activation cross-section data in the vicinity of 14 MeV are evaluated for several reactions of fusion-related interest using a least-squares method. New experimental measurements are performed at 14.7 MeV for all of these considered reactions and for some commonly-used standard reactions as well. Comparison is made between measured and evaluated results.

  9. Neutron scattering from the Kondo Insulator SmB6

    NASA Astrophysics Data System (ADS)

    Broholm, Collin

    A review of neutron scattering work probing the Kondo insulator SmB6 is presented with special emphasis on assessing the topology of the underlying strongly renormalized band structure. A 14 meV excition dominates the spectrum and is evidence of strong electron correlations [1]. Though the data generally supports the proposal that SmB6 is a topological Kondo insulator, specific heat and high-resolution neutron scattering data show a continuum of states well below the bulk transport gap, which enrich the problem and may connect to the recent surprising de Haas van Alpen results. ``Interaction Driven Subgap Spin Exciton in the Kondo Insulator SmB6,'' W. T. Fuhrman, J. Leiner, P. Nikolic, G. E. Granroth, M. B. Stone, M. D. Lumsden, L. DeBeer-Schmitt, P. A. Alekseev, J.-M. Mignot, S. M. Koohpayeh, P. Cottingham, W. Adam Phelan, L. Schoop, T. M. McQueen, and C. Broholm, Phys. Rev. Lett. 114, 036401 (2015). Supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Material Sciences and Engineering, under Grant No. DEFG02-08ER46544 and the Gordon and Betty Moore Foundation.

  10. Elastic and inelastic scattering of 15N ions by 9Be at 84 MeV

    NASA Astrophysics Data System (ADS)

    Rudchik, A. T.; Chercas, K. A.; Kemper, K. W.; Rusek, K.; Rudchik, A. A.; Herashchenko, O. V.; Koshchy, E. I.; Pirnak, Val. M.; Piasecki, E.; Trzcińska, A.; Sakuta, S. B.; Siudak, R.; Strojek, I.; Stolarz, A.; Ilyin, A. P.; Ponkratenko, O. A.; Stepanenko, Yu. M.; Shyrma, Yu. O.; Szczurek, A.; Uleshchenko, V. V.

    2016-03-01

    Angular distributions of the 9Be + 15N elastic and inelastic scattering were measured at Elab(15N) = 84 MeV (Ec.m. = 31.5 MeV) for the 0-6.76 MeV states of 9Be and 0-6.32 MeV states of 15N. The data were analyzed within the optical model and coupled-reaction-channels method. The elastic and inelastic scattering, spin reorientations of 9Be in ground and excited states and 15N in excited states as well as the most important one- and two-step transfer reactions were included in the channels-coupling scheme. The parameters of the 9Be + 15N optical potential of Woods-Saxon form as well as deformation parameters of these nuclei were deduced. The analysis showed that the 9Be + 15N pure potential elastic scattering dominates at the forward angles whereas the ground state spin reorientation of 9Be gives a major contribution to the elastic scattering cross sections at the large angles. Contributions from particle transfers are found to be negligible for the present scattering system.

  11. Gamma-ray-spectroscopy following high-flux 14-MeV neutron activation

    SciTech Connect

    Williams, R.E.

    1981-10-12

    The Rotating Target Neutron Source (RTNS-I), a high-intensity source of 14-MeV neutrons at the Lawrence Livermore National Laboratory (LLNL), has been used for applications in activation analysis, inertial-confinement-fusion diagnostic development, and fission decay-heat studies. The fast-neutron flux from the RTNS-I is at least 50 times the maximum fluxes available from typical neutron generators, making these applications possible. Facilities and procedures necessary for gamma-ray spectroscopy of samples irradiated at the RTNS-I were developed.

  12. Neutron-proton effective mass splitting in neutron-rich matter at normal density from analyzing nucleon-nucleus scattering data within an isospin dependent optical model

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Hua; Guo, Wen-Jun; Li, Bao-An; Chen, Lie-Wen; Fattoyev, Farrukh J.; Newton, William G.

    2015-04-01

    The neutron-proton effective mass splitting in asymmetric nucleonic matter of isospin asymmetry δ and normal density is found to be mn-p* ≡ (mn* - mp*) / m = (0.41 ± 0.15) δ from analyzing globally 1088 sets of reaction and angular differential cross sections of proton elastic scattering on 130 targets with beam energies from 0.783 MeV to 200 MeV, and 1161 sets of data of neutron elastic scattering on 104 targets with beam energies from 0.05 MeV to 200 MeV within an isospin dependent non-relativistic optical potential model. It sets a useful reference for testing model predictions on the momentum dependence of the nucleon isovector potential necessary for understanding novel structures and reactions of rare isotopes.

  13. Differential Cross Sections for Neutron Elastic and Inelastic Scattering on 23Na

    NASA Astrophysics Data System (ADS)

    Vanhoy, J. R.; Hicks, S. F.; Chakraborty, A.; Champine, B. R.; Combs, B.; Crider, B. P.; Kersting, L. J.; Kumar, A.; Lueck, C. J.; McDonough, P. J.; McEllistrem, M. T.; Peters, E. E.; Prados-Estévez, F. M.; Sidwell, L.; Sigillito, A.; Watts, D. W.; Yates, S. W.

    2014-03-01

    Measurements of neutron elastic and inelastic scattering from 23Na have been performed for sixteen incident neutron energies above 1.5 MeV with the 7-MV University of Kentucky Accelerator using the 3H(p,n) reaction as the neutron source. These measurements were complemented by γ-ray excitation functions using the (n,n'γ) reaction. The time-of-flight technique is employed for background reduction in both neutron and γ- ray measurements and for determining the energy of the scattered neutrons. Cross section determinations support fuel cycle and structural materials research and development. Previous reaction model evaluations [1] relied primarily on total cross sections and four (n,n0) and (n,n1) angular distributions in the En = 5 to 9 MeV range. The inclusion of more inelastic channels at lower neutron energies provides additional information on direct couplings between elastic and inelastic scattering as a function of angular momentum transfer. Reaction model calculations examining direct collective and statistical properties were performed.

  14. First experimental results from 2 MeV proton tandem accelerator for neutron production.

    PubMed

    Kudryavtsev, A; Belchenko, Yu; Burdakov, A; Davydenko, V; Ivanov, A; Khilchenko, A; Konstantinov, S; Krivenko, A; Kuznetsov, A; Mekler, K; Sanin, A; Shirokov, V; Sorokin, I; Sulyaev, Yu; Tiunov, M

    2008-02-01

    A 2 MeV proton tandem accelerator with vacuum insulation was developed and first experiments are carried out in the Budker Institute of Nuclear Physics (Novosibirsk). The accelerator is designed for neutron production via reaction (7)Li(p,n)(7)Be for the boron neutron-capture therapy of the brain tumors, and for explosive detection based on 9.1724 MeV resonance gamma, which are produced via reaction (13)C(p,gamma)(14)N, absorption in nitrogen. PMID:18315262

  15. First experimental results from 2 MeV proton tandem accelerator for neutron production

    SciTech Connect

    Kudryavtsev, A.; Belchenko, Yu.; Burdakov, A.; Davydenko, V.; Ivanov, A.; Khilchenko, A.; Konstantinov, S.; Krivenko, A.; Kuznetsov, A.; Mekler, K.; Sanin, A.; Shirokov, V.; Sorokin, I.; Sulyaev, Yu.; Tiunov, M.

    2008-02-15

    A 2 MeV proton tandem accelerator with vacuum insulation was developed and first experiments are carried out in the Budker Institute of Nuclear Physics (Novosibirsk). The accelerator is designed for neutron production via reaction {sup 7}Li(p,n){sup 7}Be for the boron neutron-capture therapy of the brain tumors, and for explosive detection based on 9.1724 MeV resonance gamma, which are produced via reaction {sup 13}C(p,{gamma}){sup 14}N, absorption in nitrogen.

  16. Analysis of elastic {alpha}-nucleus scattering data at 240 MeV

    SciTech Connect

    Alvi, M. A.; Madani, J. H.; Hakmi, A. M.

    2007-06-15

    Working within the framework of the Coulomb modified Glauber model we fit the elastic differential scattering cross section of 240 MeV {alpha} particle on {sup 58}Ni using the effective N-{alpha} amplitude with one adjustable parameter. It is found that once the effective amplitude is calibrated on {sup 58}Ni by varying the adjustable parameter, it very nicely reproduces the available elastic {alpha} scattering data on other nuclei at the same energy.

  17. Scattering of {sup 8}He on {sup 208}Pb at 22 MeV

    SciTech Connect

    Marquinez-Duran, G.; Sanchez-Benitez, A. M.; Martel, I.; Berjillos, R.; Duenas, J. A.; Parkar, V. V.; Acosta, L.; Rusek, K.; Alvarez, M. A. G.; Gomez-Camacho, J.; Borge, M. J. G.; Cruz, C.; Cubero, M.; Pesudo, V.; Tengblad, O.; Chbihi, A.; Fernandez-Garcia, J. P.; Moro, A. M.; Fernandez-Martinez, B.; Labrador, J. A.; and others

    2013-06-10

    The skin nucleus {sup 8}He is investigated by measuring the angular distribution of the elasticly scattered {sup 8}He and the {sup 6,4}He fragments produced in the collision with a {sup 208}Pb target at 22 MeV, just above the Coulomb barrier. The experiment was carried out at SPIRAL/GANIL in 2010. Here we present preliminary results for the elastic scattering.

  18. Probing fine magnetic particles with neutron scattering

    SciTech Connect

    Pynn, R.

    1991-12-31

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

  19. Probing fine magnetic particles with neutron scattering

    SciTech Connect

    Pynn, R.

    1991-01-01

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

  20. Phase sensitive small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Brok, Erik; Majkrzak, Charles F.; Krycka, Kathryn

    It is a well-known problem that information about the scattered wave is lost in scattering experiments because the measured quantity is the modulus squared of the complex wave function. This ''phase problem'' leads to ambiguity in determining the physical properties of the scattering sample. Small angle neutron scattering (SANS) is a useful technique for determining the structure of biomolecules, in particular proteins that cannot be crystallized and studied with x-ray crystallography. However, because the biomolecules are usually suspended in a liquid the observed scattering is an average of all possible orientations, making it difficult to obtain three dimensional structural information. In a proposed method polarized SANS and magnetic nanoparticle references attached to the sample molecules is used to obtain phase sensitive structural information and simultaneously circumvent the problem of orientational averaging (Majkrzak et al. J. Appl. Cryst. 47, 2014) If realized and perfected the technique is very promising for unambiguous determination of the three dimensional structure of biomolecules. We demonstrate the principles of our method and show the first experimental data obtained on a simple test system consisting of core shell magnetic nanoparticles.

  1. Calculations of neutron shielding data for 10-100 MeV proton accelerators.

    PubMed

    Chen, C C; Sheu, R J; Jian, S H

    2005-01-01

    The characteristics of neutron sources and their attenuation in concrete were investigated in detail for protons with energies ranging from 10 to 100 MeV striking on target materials of C, N, Al, Fe, Cu and W. A two-step approach was adopted: thick-target double-differential neutron yields were first calculated from the (p, xn) cross sections recommended in the ICRU Report 63; further, transport simulations of those neutrons in concrete were performed by using the FLUKA Monte Carlo code. The purpose of this study is to provide reasonably accurate parameters for shielding design for 10-100 MeV proton accelerators. Source terms and the corresponding attenuation lengths in concrete for several target materials are given as a function of proton energies and neutron emission angles. PMID:16604637

  2. Neutron Scattering Studies of Fluorite Compounds

    NASA Astrophysics Data System (ADS)

    Goff, Jonathan Peter

    1992-01-01

    Available from UMI in association with The British Library. Requires signed TDF. The nature and mobility of defects in ionic materials with the fluorite structure have been studied using neutron scattering techniques. These systems model the behaviour of the fission fuel UO_2 at elevated temperature. A powder sample of beta -PbF_2 has been investigated using neutron diffraction, which gives the time-averaged occupation of sites in the unit cell. The temperature dependence of the lattice parameter, the concentration of Frenkel defects, and the thermal parameters of both fluorine and lead ions, have been determined at temperatures from ambient to well above the transition to the fast-ion phase. The defect structure of the anion-excess fluorite (Sr,Y)Cl_{2.03} has been studied using the coherent diffuse scattering from single -crystal samples. Excess chlorine ions are found to aggregate into cuboctahedral clusters whose ionic coordinates agree with those calculated from a simple hard sphere model. At elevated temperature the scattering exhibits quasielastic energy broadening, indicating the dynamic nature of the disorder. It is possible to account for the high temperature scattering in terms of 'snapshot' models of the diffusing anions and their associated relaxation fields, and to estimate the anion self diffusion coefficient from coherent scattering alone. Consistent and complementary information on the diffusion of chlorine ions in (Sr,Y)Cl_ {2.03} has been obtained from the quasielastic energy broadening of the single-crystal incoherent scattering measured at elevated temperature. Comparison with previous results from SrCl_2 shows that chlorine diffusion is faster in (Sr,Y)Cl_{2.03 }, and that the diffusional process in the anion-excess fluorite resembles that found when the level of thermally generated disorder is high in the pure compound. The coherent scatterer UO_{2 + delta} (delta = 0.13,0.14) transforms from a mixture of oxides at ambient temperature to a

  3. Neutron scattering instrumentation for biology at spallation neutron sources

    SciTech Connect

    Pynn, R.

    1994-12-31

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

  4. Dynamics of Ammonia Borane Using Neutron Scattering

    SciTech Connect

    Brown, Craig; Jacques, Teresa; Hess, Nancy J.; Daemen, Luke L.; Mamontov, Eugene; Linehan, John C.; Stowe, Ashley C.; Autrey, Thomas

    2006-11-15

    We have used both the backscattering (HFBS) and time-of-flight (DCS) neutron spectrometers to investigate the proton dynamics in ammonia borane, a compound of intense interest as a model for 'chemical hydrogen storage' materials. Results indicate that the deposition of ammonia borane on a mesoporous silicate results in longer proton residence times and lower energy barriers for proton motion compared to bulk ammonia borane. The reduced activation energy for proton motions may partly explain the improved thermolysis and lowering the activation barrier for the loss of the first equivalent of H2. In addition, the phonon density of states for neat ammonia borane compares well with other spectroscopic results, with the intense peak at 22 meV assigned to the librational NH3 and BH3 modes, whereas ammonia borane on MCM-41 displays a broad, featureless spectrum indicating a poorly crystalline material.

  5. Ultra high resolution neutron scattering: Neutron Resonance Spin-Echo and Larmor Diffraction

    NASA Astrophysics Data System (ADS)

    Walters, Andrew; Keller, Thomas; Keimer, Bernhard

    2012-02-01

    The TRISP spectrometer at the FRM II neutron source near Munich, Germany, is a unique world-leading neutron scattering instrument which employs the Neutron Resonance Spin-Echo technique (NRSE). Linewidths of dispersive excitations with energy transfers up to 50 meV can be measured with an energy resolution in the μeV range without the restrictive flux limitations that normally apply to high resolution neutron triple-axis spectrometers. Pioneering studies on the electron-phonon interaction in elemental superconductorsootnotetextP. Aynajian et al., Science 319 1509 (2008) and the lifetimes of magnetic excitations in archetypal magnetic systems will be reviewed.ootnotetextS. Bayrakci et al., Science 312 1928 (2006) The instrument can also be used as a Larmor diffractometer, enabling d-spacings to be measured with a resolution of δdd ˜10-6, i.e. more than one order of magnitude more sensitive than conventional diffraction techniques.ootnotetextC. Pfleiderer et al., Science 316 1871 (2007) Ongoing and future NRSE and Larmor diffraction projects will be outlined, especially in regard to prospective studies which will take full advantage of the new low temperature and high pressure sample environment capabilities now available at TRISP.

  6. Measurement of the free neutron-proton analyzing power and spin transfer parameters in the charge exchange region at 790 MeV

    SciTech Connect

    Ransome, R.D.

    1981-07-01

    The free neutron-proton analyzing power and the spin transfer parameters (K/sub NN/, K/sub SS/, K/sub SL/, and K/sub LL/) were measured at the Los Alamos Meson Physics Facility at 790 MeV between 165/sup 0/ and 180/sup 0/ center of mass. A 40% polarized neutron beam incident on a liquid hydrogen target was used. The recoil protons were momentum analyzed with a magnetic spectrometer to isolate elastic scatters. A large solid angle carbon polarimeter was used to measure the proton polarization. The measurements are the first at this energy and are in basic agreement with pre-existing phase shift solutions. The proton-carbon analyzing power was measured between 500 and 750 MeV. An empirical fit to the proton-carbon analyzing power between 100 and 750 MeV was done.

  7. Absolute neutron fluence measurements between 0.5 and 3MeV and their intercomparisons

    NASA Astrophysics Data System (ADS)

    Wu, M. W.; Guung, T. C.; Pei, C. C.; Yang, T. N.; Hwang, W. S.; Thomas, D. J.

    1999-02-01

    Primary standards of monoenergetic neutron fluences for 0.565, 1.5 and 2.5MeV neutrons produced by the 7Li(p,n)7Be reaction have been developed for the calibration of neutron dosimeters and spectrometers. The fluences for 0.565MeV neutrons were measured using both H2 and CH4 proton recoil proportional counters with the measured spectra fitted to the modified SPEC-4 Monte Carlo simulations for the subtraction of gamma and recoil carbons. The fluences for 1.5 and 2.5MeV neutrons were determined with vacuum-type proton recoil telescopes. Various uncertainties for each detector are analyzed and its overall uncertainty is 3.1% for gas counter and less than 3% for the telescope. These neutron fluence standards have been intercompared with those of the National Physical Laboratory of the United Kingdom by the use of two transfer instruments: a long counter and a 3He detector. The comparison results will be presented and discussed.

  8. Deeply Virtual Compton Scattering off the Neutron

    SciTech Connect

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

    2007-12-14

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

  9. Biophysical applications of neutron Compton scattering

    NASA Astrophysics Data System (ADS)

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

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

  10. Deeply virtual compton scattering off the neutron.

    PubMed

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

    2007-12-14

    The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e,e'gamma)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_{q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced. PMID:18233443

  11. Deeply Virtual Compton Scattering off the neutron

    SciTech Connect

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

    2007-12-01

    The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D$({\\vec e},e'\\gamma)X$ cross section measured at $Q^2$=1.9 GeV$^2$ and $x_B$=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to $E_q$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

  12. Neutron elastic scatter for detection and identification of obscured objects

    NASA Astrophysics Data System (ADS)

    Gomberg, Henry J.; Charatis, George; Wang, David; McEllistrem, Marcus R.

    1993-11-01

    Neutron Elastic Scatter (NES) may be used for non-destructively assaying materials for the presence of narcotics, explosives, or other contraband. The technology relies on the high penetrating power of neutrons to reach through varying thickness of shielding materials, and also on the large probabilities for elastic scattering of neutrons. Elastic scattering probabilities are the largest of all neutron induced events, exceeding any single non-elastic process typically by a factor of ten or more. Indeed, usually the elastic scattering probability is larger than the sum of all inelastic processes.

  13. Phonon dynamics and inelastic neutron scattering of sodium niobate

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  14. Deuteron scattering on {sup 6}Li at an energy of 25 MeV

    SciTech Connect

    Burtebayev, N.; Artemov, S. V.; Duisebayev, B. A.; Kerimkulov, Zh. K.; Kuranov, S. B.; Sakuta, S. B.

    2010-05-15

    At an energy of 25 MeV and in the angular range 7{sup o}-175{sup o} in the laboratory frame, angular distributions were measured for elastic deuteron scattering on {sup 6}Li nuclei and for the respective inelastic-scattering processes accompanied by the transitions to the ground state (1+) of the {sup 6}Li nucleus and to its excited state at E{sub x} = 2.186 MeV (J{sup {pi}} = 3{sup +}). The resulting data were analyzed on the basis of the optical model of the nucleus and the coupled-reaction-channel method with allowance for the mechanism of alpha-particle-cluster exchange. It is shown that only upon including, in the analysis, channel coupling and the exchange mechanism can the experimental cross sections for elastic and inelastic scattering be reproduced over the entire range of angles.

  15. DPA damage analysis for 14-MeV neutrons on PFC materials

    NASA Astrophysics Data System (ADS)

    Kim, Dong-woo; Lee, Bo-young; Ko, Seung-kook; Kim, Hee-soo; Noh, Seung-jung

    2015-06-01

    The dpa (displacement per atom) damage for 14-MeV neutron in a pfc materials was simulated using MCNPX/SPECTER code. The dpa values in the main components of the structural material SS316L, Fe, Cr and Ni, were calculated to analyze the effect of nuclear damage. According to the neutron wall load for ITER design base, a neutron flux of 3.5 × 1013 neutrons/cm2·sec was applied. The simulated dpa values were found to be as 3.0 dpa/fpy for Fe, 2.9 dpa/fpy for Cr and 3.1 dpa/fpy for Ni. For practical experiments, the simulated dpa values due to the irradiation damage of 17-MeV protons were found to be as 0.67 dpa at the peak and 0.05 at the surface for SS316L using by SRIM code at the same fluence. For the 17-MeV proton irradiation, the Bragg peak appears at a 0.64-mm depth. Also, SS316L specimens irradiated by a 17-MeV proton beam with a fluence of 1016 protons/cm2 were analyzed by using transmission electron microscopy.

  16. ORELA measurements to meet fusion energy neutron cross section needs. [2 to 80 MeV

    SciTech Connect

    Larson, D C

    1980-01-01

    Major neutron cross section measurements made at the Oak Ridge Electron Linear Accelerator (ORELA) that are useful to the fusion energy program are reviewed. Cross sections for production of gamma rays with energies 0.3 < E/sub ..gamma../ < 10.5 MeV were measured as a function of neutron energy over the range 0.1 < E/sub n/ < 20.0 MeV for Li, C, N, O, F, Na, Mg, Al, Si, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Nb, Mo, Ag, Sn, Ta, W, Au, Pb, and Th. Neutron emission cross sections have been measured for /sup 7/Li, Al, Ti, Cu, and Nb for 1 < E/sub n/ < 20 MeV. Some results of recent neutron total cross section measurements from 2 to 80 MeV for eleven materials (C, O, Al, Si, Ca, Cr, Fe, Ni, Cu, Au, and Pb) of interest to the FMIT project are presented. Finally, future directions of the ORELA program are outlined. 4 figures, 3 tables.

  17. Development of an encapsulated scintillating fiber detector as a 14-MeV neutron sensor

    NASA Astrophysics Data System (ADS)

    Singkarat, S.; Boonyawan, D.; Hoyes, G. G.; Tippawan, U.; Vilaithong, T.; Garis, N. S.; Kobus, H.

    1997-02-01

    A scintillating fiber detector has been developed and tested for use as a 14-MeV neutron sensor. The detector, designated an "Encapsulated Scintillating Fiber Detector (EFD)", is composed of a parallel array of 0.5 × 0.5 × 15 mm BCF-12 plastic scintillating fibers encapsulated in clear BC-600 optical cement. The 85 fibers from a 12 × 12 mm square array, with a separation gap of 0.8-1 mm, in the center of the 40 mm diameter × 15 mm thick hardened optical cement. It can be directly coupled to an ordinary 2 in. diameter photomultiplier tube and its simple electronics. The response of the detector to gamma-rays from isotopic sources, as well as to 2.6- and 14-MeV monoenergetic neutrons from a neutron generator has been evaluated. The detector shows 3 distinct properties simultaneously, i.e. (1) good gamma-ray pulse height reduction, (2) discrimination against 14-MeV neutrons entering at angles non-parallel to the fiber axis, and (3) production of a full energy peak of 14-MeV recoil protons in the direction of the fiber axes. Investigations by Monte Carlo simulation are also included.

  18. Generation of high-energy (>15 MeV) neutrons using short pulse high intensity lasers

    SciTech Connect

    Petrov, G. M.; Davis, J.; Petrova, Tz. B.; Higginson, D. P.; McNaney, J. M.; McGuffey, C.; Qiao, B.; Beg, F. N.

    2012-09-15

    A roadmap is suggested and demonstrated experimentally for the production of high-energy (>15 MeV) neutrons using short pulse lasers. Investigation with a 3D Monte Carlo model has been employed to quantify the production of energetic neutrons. Numerical simulations have been performed for three nuclear reactions, d(d,n){sup 3}He, {sup 7}Li(d,n){sup 8}Be, and {sup 7}Li(p,n){sup 7}Be, driven by monoenergetic ion beams. Quantitative estimates for the driver ion beam energy and number have been made and the neutron spectra and yield in the ion propagation direction have been evaluated for various incident ion energies. In order to generate neutron fluence above a detection limit of 10{sup 6} neutrons/sr, either {approx}10{sup 10} protons with energy 20-30 MeV or comparable amount of deuterons with energy 5-10 MeV are required. Experimental verification of the concept with deuterons driven by the Titan laser (peak intensity 2 Multiplication-Sign 10{sup 19} W/cm{sup 2}, pulse duration of 9 ps, wavelength 1.05 {mu}m, and energy of 360 J) is provided with the generation of neutrons with energy of up to 18 MeV from {sup 7}Li(d,n){sup 8}Be reactions. Future research will focus on optimized schemes for ion acceleration for production of high-energy neutrons, which will involve efficient target design, laser parameter optimization, and converter material.

  19. Neutron-induced Fission Cross Section of 240242Pu up to En = 3 MeV

    NASA Astrophysics Data System (ADS)

    Salvador-Castiñeira, P.; Bryś, T.; Hambsch, F.-J.; Oberstedt, S.; Pretel, C.; Vidali, M.

    2014-05-01

    The neutron-induced fission cross sections of 240,242Pu have been measured at JRC-IRMM with incident neutron energy from 0.2 MeV up to 3 MeV. A Twin-Frisch Grid Ionization Chamber (TFGIC) has been used in a back-to-back geometry. The measurements have been performed using the secondary standards 237Np and 238U as a reference. The purity of the plutonium samples was 99.89% for 240Pu and 99.97% for 242Pu. The results obtained follow the ENDF/B-VII.1 evaluation for 240Pu, but some discrepancies are visible around E/n = 1 MeV for 242Pu. In addition, the spontaneous fission half-life has been measured for both isotopes.

  20. Neutron Induced Reactions with the 17 Mev Facility at the Athens Tandem Accelerator NCSR 'Demokritos'

    NASA Astrophysics Data System (ADS)

    Vlastou, R.; Kalamara, A.; Serris, M.; Diakaki, M.; Kokkoris, M.; Paneta, V.; Axiotis, M.; Lagoyannis, A.

    In the 5.5 MV tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" monoenergetic neutron beams have been produced in the energy range∼ 15-20 MeV using anew Ti-tritiated target of 373 GBq activity, by means of the 3H(d,n)4He reaction. The corresponding deuteron beam energies obtained from the accelerator, were in the 1.5-4.5MeV range.The maximum flux has been determined to be of the order of 106 n/cm2 s, implementing reference reactions. The 17.1MeV neutron beam has been used for the measurement of 197Au(n,2n) reaction cross section. Theoretical calculations have been performed via the statistical model code EMPIRE and compared to the experimental data of the present work and data from literature.

  1. Measurement of the Absolute Elastic and Inelastic Differential Neutron Cross Sections for 23Na between 2 and 4 MeV

    NASA Astrophysics Data System (ADS)

    Kumar, Ajay; McEllistrem, M. T.; Crider, B. P.; Peters, E. E.; Prados-Estevez, F. M.; Chakraborty, A.; Yates, S. W.; Sigillito, A.; McDonough, P. J.; Kersting, L. J.; Luke, C. J.; Hicks, S. F.; Vanhoy, J. R.

    2011-10-01

    Elastic and inelastic neutron scattering angular distributions for 23Na sample were measured at the University of Kentucky using the time-of-flight (ToF) technique, between 2 and 4 MeV incident neutron energies.Normalization of yields into scattering cross sections was accomplished by comparison of Na yields to the yields obtained from hydrogen in polyethylene samples via the well-known n-p scattering cross sections.The 3H(p,n) differential cross sections are used to determine the energy-dependent efficiency of the main detector. Because the efficiency of this detector appears as a ratio in the comparison of scattered yields from different samples, the absolute values of the 3H(p,n) cross sections are not critical, but their energy dependence is. This work is supported by the U.S. DOE contract no. DE-AC07-051D14517.

  2. NEUTRON CROSS SECTION COVARIANCES FROM THERMAL ENERGY TO 20 MeV.

    SciTech Connect

    ROCHMAN,D.; HERMAN, M.; OBLOZINSKY, P.; MUGHABGHAB, S.F.; PIGNI, M.; KAWANO, T.

    2007-04-27

    We describe new method for energy-energy covariance calculation from the thermal energy up to 20 MeV. It is based on three powerful basic components: (i) Atlas of Neutron Resonances in the resonance region; (ii) the nuclear reaction model code EMPIRE in the unresolved resonance and fast neutron regions, and (iii) the Bayesian code KALMAN for correlations and error propagation. Examples for cross section uncertainties and correlations on {sup 90}Zr and {sup 193}Ir illustrate this approach in the resonance and fast neutron regions.

  3. Enhanced reaction rates in NDP analysis with neutron scattering

    SciTech Connect

    Downing, R. Gregory

    2014-04-15

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

  4. Neutron propagation and 2.2 MeV gamma-ray line production in the solar atmosphere

    NASA Technical Reports Server (NTRS)

    Wang, H. T.; Ramaty, R.

    1974-01-01

    The 2.2 MeV gamma ray line intensity from the sun was calculated using a Monte Carlo method for neutron propagation in the solar atmosphere. Detailed results are provided on the total gamma ray yield per neutron and on the time profile of the 2.2 MeV line from an instantaneous and monoenergetic neutron source. The parameters which have the most significant effects on the line intensity are the energies of the neutrons, the position of the neutron source on the sun, and the abundance of He-3 in the photosphere. For an isotropic neutron source which is not too close to the limb of the sun, the gamma ray yield is between about 0.02 to 0.2 photons per neutron, provided that the neutron energies are in the range 1 to 100 MeV and the ratio He-3/H is less than about .00005.

  5. Measurements of NE-213 response functions to neutrons of energies up to several tens of MeV

    NASA Astrophysics Data System (ADS)

    Shin, Kazuo; Ishii, Yoshiaki; Uwamino, Yoshitomo; Sakai, Hideyuki; Numata, Shigco

    1991-10-01

    Measurements of neutron response functions of a 3 in. × 3 in. NE-213 scintillator were made for neutron energies from 10 MeV to 73 MeV using neutrons from a quasi-monoenergetic neutron source of p- 7Li and a white source from thick Be and Cu targets. Neutrons sampled into small energy bins by TOF signals were utilized in the response measurements. Response functions calculated by the Monte Carlo method were compared with the measured data, thus clearing problems in the calculation model. Based on the measured and calculated data, a new response matrix which covered from 0 to 76 MeV was constructed. The matrix was successfully applied to unfold a pulse-height spectrum of up to several tens of MeV neutrons that were transmitted through a 50 cm concrete shield.

  6. Lithium Blanket Module (LBM) dosimetry measurements at the LOTUS 14-MeV neutron source facility

    SciTech Connect

    Tsang, F.Y.; Leo, W.; Sahraoui, C.; Wuthrich, S.; Shaer, M.

    1986-11-01

    A series of passive dosimetry irradiation experiments were performed inside the Lithium Blanket Module (LBM) with the 14-MeV neutron source at the Ecole Polytechnique Federale de Lausane (EPFL). Sets of passive dosimetry foils were utilized to measure fusion-reactor-blanket neutronic environments. The dosimeter reaction data are analyzed and compared with calculational models. These experimental results demonstrate the ability to simulate low power deuterium-tritium (D-T) plasma shots by measuring the neutron field in a reactor-representative fusion blanket environment. The dosimeter results can determine the entire neutron spectrum along the full length of the LBM test rod. The set of selected dosimetry materials meets the requirements of neutronic characterization in future LBM-TFTR D-T and high power deuterium-deuterium (D-D) plasma experiments.

  7. Crystal fields in YbInNi4 determined with magnetic form factor and inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Severing, A.; Givord, F.; Boucherle, J.-X.; Willers, T.; Rotter, M.; Fisk, Z.; Bianchi, A.; Fernandez-Diaz, M. T.; Stunault, A.; Rainford, B. D.; Taylor, J.; Goremychkin, E.

    2011-04-01

    The magnetic form factor of YbInNi4 has been determined via the flipping ratios R with polarized neutron diffraction, and the scattering function S(Q,ω) was measured in an inelastic neutron scattering experiment. Both experiments were performed with the aim of determining the crystal-field scheme. The magnetic form factor clearly excludes the possibility of a Γ7 doublet as the ground state. The inelastic neutron data exhibit two almost equally strong peaks at 3.2 meV and 4.4 meV which points, in agreement with earlier neutron data, toward a Γ8 quartet ground state. Further possibilities such as a quasiquartet ground state are discussed.

  8. Response of a diamond detector sandwich to 14 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Osipenko, M.; Ripani, M.; Ricco, G.; Caiffi, B.; Pompili, F.; Pillon, M.; Verona-Rinati, G.; Cardarelli, R.

    2016-05-01

    In this paper we present the measurement of the response of 50 μm thin diamond detectors to 14 MeV neutrons. Such neutrons are produced in fusion reactors and are of particular interest for ITER neutron diagnostics. Among semiconductor detectors diamond has properties most appropriate for harsh radiation and temperature conditions of a fusion reactor. However, 300-500 μm thick diamond detectors suffer significant radiation damage already at neutron fluences of the order of 1014 n/cm2. It is expected that a 50 μm thick diamond will withstand a fluence of >1016 n /cm2. We tested two 50 μm thick single crystal CVD diamonds, stacked to form a "sandwich" detector for coincidence measurements. The coincidence between two diamonds allows to suppress background and increase detection efficiency. The detector measured the conversion of 14 MeV neutrons, impinging on one diamond, into α particles which were detected in the second diamond in coincidence with nuclear recoil. For 12C(n , α)9Be reaction the total energy deposited in the detector gives access to the initial neutron energy value. The measured 14 MeV neutron detection sensitivity through this reaction by a detector of an effective area 3×3 mm2 was 5 ×10-7 counts cm2/n. This value is in good agreement with Geant4 simulations. The energy resolution of the detector was found to be 870 keV FWHM, but according to Geant4 simulations only about 160 keV FWHM were intrinsic.

  9. μCF based 14 MeV intense neutron source

    NASA Astrophysics Data System (ADS)

    Anisimov, V. V.; Cavalleri, E.; Karmanov, F. I.; Konobeyev, A. Yu.; Latysheva, L. N.; Ponomarev, L. I.; Pshenichnov, I. A.; Slobodtchouk, V. I.; Vecchi, M.

    1999-06-01

    Results of a design study for an advanced scheme of a μCF based 14 MeV intense neutron source for test material irradiation including the liquid lithium primary target and a low temperature liquid deuterium-tritium (D-T) mixture as a secondary target are presented. According to this scheme negative pions are produced inside a 150-cm-long 0.75-cm-radius lithium target. Pions and muons resulting from the pion decay in flight are collected in the backward direction and stopped in the D-T mixture. The fusion chamber has the shape of a 10-cm-radius sphere surrounded by two 0.03-cm-thickness titanium shells. Assuming 100 fusions per muon in this scheme one can produce 14-MeV neutrons with a source strength up to 1017 n/s. A neutron flux of up to 1014 n/cm2/s can be achieved in a test volume of about 2.5 l and on the surface of about 350 cm2. The results of the thermophysical and thermomechanical analysis show that the technological limits are not exceeded. This source has the advantage of producing the original 14 MeV fusion spectrum without tails, isotropically into a 4π solid angle, contrary to the d-Li stripping neutron source.

  10. Elastic and Inelastic Neutron Scattering with a C7LYC Array

    NASA Astrophysics Data System (ADS)

    Wilson, G. L.; Brown, T.; Chowdhury, P.; Doucet, E.; Lister, C. J.; D'Olympia, N.; Devlin, M.; Mosby, S.

    2015-10-01

    A scintillator array of 16 1'' ×1'' Cs2LiYCl6 (CLYC) detectors has been commissioned for low energy nuclear science. Standard CLYC crystals detect both gamma rays and neutrons rays with excellent pulse shape discrimination, with thermal neutrons detected via the 6Li(n, α)t reaction. Our discovery of spectroscopy-grade response of CLYC for fast neutrons via the 35Cl(n,p) reaction, with a pulse height resolution of under 10 % in the < 8 MeV range, led to our present array of 7Li enriched C7LYC detectors, where the large thermal neutron response is essentially eliminated. While the intrinsic efficiency of C7LYC for fast neutron detection is low, the array can be placed near the target since a long TOF arm is no longer needed for neutron energy measurement, thus recovering efficiency through increased solid angle coverage. The array was recently deployed at Los Alamos to test its capability in measuring differential scattering cross sections as a function of energy for 56Fe and 238U. The incident energy from a white neutron source was measured via TOF, and the scattered neutron energy via the pulse height. Techniques, analysis and first results will be discussed. Supported by the NNSA Stewardship Science Academic Alliance Program under Grant DE-NA00013008.

  11. Lattice Waves, Spin Waves, and Neutron Scattering

    DOE R&D Accomplishments Database

    Brockhouse, Bertram N.

    1962-03-01

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

  12. Neutron Compton scattering from selectively deuterated acetanilide

    NASA Astrophysics Data System (ADS)

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

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

  13. Inelastic Neutron Scattering Study of Mn

    SciTech Connect

    Zhong, Y.; Sarachik, M.P.; Friedman, J.R.; Robinson, R.A.; Kelley, T.M.; Nakotte, H.; Christianson, A.C.; Trouw, F.; Aubin, S.M.J.; Hendrickson, D.N.

    1998-11-09

    The authors report zero-field inelastic neutron scattering experiments on a 14-gram deuterated sample of Mn{sub 12}-Acetate consisting of a large number of identical spin-10 magnetic clusters. Their resolution enables them to see a series of peaks corresponding to transitions between the anisotropy levels within the spin-10 manifold. A fit to the spin Hamiltonian H = {minus}DS{sub z}{sup 2} + {mu}{sub B}B{center_dot}g{center_dot}S-BS{sub z}{sup 4} + C(S{sub +}{sup 4} + S{sub {minus}}{sup 4}) yields an anisotropy constant D = (0.54 {+-} 0.02) K and a fourth-order diagonal anisotropy coefficient B = (1.2 {+-} 0.1) x 10{sup {minus}3}K. Unlike EPR measurements, their experiments do not require a magnetic field and yield parameters that do not require knowledge of the g-value.

  14. rvec p + sup 13 rvec C elastic scattering at 500 MeV

    SciTech Connect

    Tanaka, N.

    1990-01-01

    For the first time, an elastic scattering experiment was performed at LAMPF using polarized protons and a polarized target nucleus ({rvec p} + {sup 13}{rvec C}). The analyzing powers (A{sub ooon}({Theta})) and (A{sub oonn}({Theta})) were measured using an incident beam energy of 500 MeV over the laboratory angular range of 10{degree}--30{degree}. Motivation for the experiment and some preliminary results and conclusions are presented. 12 refs., 7 figs.

  15. Direct experimental reconstruction of the pp elastic scattering matrix at 579 MeV

    SciTech Connect

    Aprile, E.; Eisenegger, C.; Hausammann, R.; Heer, E.; Hess, R.; Lechanoine-Leluc, C.; Leo, W.R.; Morenzoni, S.; Onel, Y.; Rapin, D.; Mango, S.

    1981-04-20

    We have made, for the first time, a direct reconstruction of the pp elastic scattering matrix at 579 MeV from a series of experiments performed with a polarized beam line. Fifteen observables consisting of the polarization, two-spin correlation and transfer parameters, and three-spin parameters were measured at seven angles between 66/sup 0/ and 90/sup 0/ center of mass. The experimental results and reconstructed amplitudes are presented and compared to a phase-shift analysis.

  16. Parity Nonconservation in Proton-water Scattering at 800 MeV

    DOE R&D Accomplishments Database

    Nagle, D. E.; Bowman, J. D.; Carlini, R.; Mischke, R. E.; Frauenfelder, H.; Harper, R. W.; Yuan, V.; McDonald, A. B.; Talaga, R.

    1982-01-01

    A search has been made for parity nonconservation in the scattering of 800 MeV polarized protons from an unpolarized water target. The result is for the longitudinal asymmetry, A{sub L} = +(6.6 +- 3.2) x 10{sup -7}. Control runs with Pb, using a thickness which gave equivalent beam broadening from Coulomb multiple scattering, but a factor of ten less nuclear interactions than the water target, gave A{sub L} = -(0.5 +- 6.0) x 10{sup -7}.

  17. Partial-wave analysis of all nucleon-nucleon scattering data below 350 MeV

    SciTech Connect

    Stoks, V.G.J.; Klomp, R.A.M.; Rentmeester, M.C.M.; de Swart, J.J. )

    1993-08-01

    We present a multienergy partial-wave analysis of all [ital NN] scattering data below [ital T][sub lab]=350 MeV, published in a regular physics journal between 1955 and 1992. After careful examination, our final database consists of 1787 [ital pp] and 2514 [ital np] scattering data. Our fit to these data results in [chi][sup 2]/[ital N][sub df]=1.08, with [ital N][sub df]=3945 the total number of degrees of freedom. All phase shifts and mixing parameters can be determined accurately.

  18. Evaluating the 239Pu Prompt Fission Neutron Spectrum Induced by Thermal to 30 MeV Neutrons

    NASA Astrophysics Data System (ADS)

    Neudecker, D.; Talou, P.; Kawano, T.; Kahler, A. C.; Rising, M. E.; White, M. C.

    2016-03-01

    We present a new evaluation of the 239Pu prompt fission neutron spectrum (PFNS) induced by thermal to 30 MeV neutrons. Compared to the ENDF/B-VII.1 evaluation, this one includes recently published experimental data as well as an improved and extended model description to predict PFNS. For instance, the pre-equilibrium neutron emission component to the PFNS is considered and the incident energy dependence of model parameters is parametrized more realistically. Experimental and model parameter uncertainties and covariances are estimated in detail. Also, evaluated covariances are provided between all PFNS at different incident neutron energies. Selected evaluation results and first benchmark calculations using this evaluation are briefly discussed.

  19. Deuterium microscopy using 17 MeV deuteron-deuteron scattering

    NASA Astrophysics Data System (ADS)

    Reichart, Patrick; Moser, Marcus; Greubel, Christoph; Peeper, Katrin; Dollinger, Günther

    2016-03-01

    Using 17 MeV deuterons as a micrometer focused primary beam, we performed deuterium microscopy by using the deuteron-deuteron (dd) scattering reaction. We describe our new box like detector setup consisting of four double sided silicon strip detectors (DSSSD) with 16 strips on each side, each covering up to 0.5 sr solid angle for coincidence detection. This method becomes a valuable tool for studies of hydrogen incorporation or dynamic processes using deuterium tagging. The background from natural hydrocarbon or water contamination is reduced by the factor 150 ppm of natural abundance of deuterium in hydrogen. Deuterium energies of up to 25 MeV, available at the microprobe SNAKE, are ideal for the analysis of thin freestanding samples so that the scattered particles are transmitted to the detector. The differential cross section for the elastic scattering reaction is about the same as for pp-scattering (~100 mb/sr). The main background due to nuclear reactions is outside the energy window of interest. Deuteron-proton (dp) scattering events give an additional signal for hydrogen atoms, so the H/D-ratio can be monitored in parallel. A deuterium detection limit due to accidental coincidences of 3 at-ppm down to less than 1 at-ppm is demonstrated on deuterated polypropylen sheets as well as thick polycarbonate sheets after various stages of coincidence filtering that is possible with our granular detector.

  20. Time gating for energy selection and scatter rejection: High-energy pulsed neutron imaging at LANSCE

    NASA Astrophysics Data System (ADS)

    Swift, Alicia; Schirato, Richard; McKigney, Edward; Hunter, James; Temple, Brian

    2015-09-01

    The Los Alamos Neutron Science Center (LANSCE) is a linear accelerator in Los Alamos, New Mexico that accelerates a proton beam to 800 MeV, which then produces spallation neutron beams. Flight path FP15R uses a tungsten target to generate neutrons of energy ranging from several hundred keV to ~600 MeV. The beam structure has micropulses of sub-ns width and period of 1.784 ns, and macropulses of 625 μs width and frequency of either 50 Hz or 100 Hz. This corresponds to 347 micropulses per macropulse, or 1.74 x 104 micropulses per second when operating at 50 Hz. Using a very fast, cooled ICCD camera (Princeton Instruments PI-Max 4), gated images of various objects were obtained on FP15R in January 2015. Objects imaged included blocks of lead and borated polyethylene; a tungsten sphere; and a tungsten, polyethylene, and steel cylinder. Images were obtained in 36 min or less, with some in as little as 6 min. This is novel because the gate widths (some as narrow as 10 ns) were selected to reject scatter and other signal not of interest (e.g. the gamma flash that precedes the neutron pulse), which has not been demonstrated at energies above 14 MeV. This proof-of-principle experiment shows that time gating is possible above 14MeV and is useful for selecting neutron energy and reducing scatter, thus forming clearer images. Future work (simulation and experimental) is being undertaken to improve camera shielding and system design and to precisely determine optical properties of the imaging system.

  1. Fast neutron (14.5 MeV) radiography: a comparative study

    SciTech Connect

    Klann, R.T.

    1996-07-01

    Fast neutron (14.5 MeV) radiography is a type of non-destructive analysis tool that offers its own benefits and drawbacks. Because cross-sections vary with energy, a different range of materials can be examined with fast neutrons than can be studied with thermal neutrons, epithermal neutrons, or x-rays. This paper details these differences through a comparative study of fast neutron radiography to the other types of radiography available. The most obvious difference among the different types of radiography is in the penetrability of the sources. Fast neutrons can probe much deeper and can therefore obtain details of the internals of thick objects. Good images have been obtained through as much as 15 cm of steel, 10 cm of water, and 15 cm of borated polyethylene. In addition, some objects were identifiable through as much as 25 cm of water or 30 cm of borated polyethylene. The most notable benefit of fast neutron radiography is in the types of materials that can be tested. Fast neutron radiography can view through materials that simply cannot be viewed by X rays, thermal neutrons, or epithermal neutrons due to the high cross-sections or linear attenuation coefficients involved. Cadmium was totally transparent to the fast neutron source. Fast neutron radiography is not without drawbacks. The most pronounced drawback has been in the quality of radiograph produced. The image resolution is only about 0.8 mm for a 1.25 cm thick object, whereas, other forms of radiography have much better resolution.

  2. Quantum Monte Carlo calculations of neutron-alpha scattering.

    SciTech Connect

    Nollett, K. M.; Pieper, S. C.; Wiringa, R. B.; Carlson, J.; Hale, G. M.; Physics

    2007-07-13

    We describe a new method to treat low-energy scattering problems in few-nucleon systems, and we apply it to the five-body case of neutron-alpha scattering. The method allows precise calculations of low-lying resonances and their widths. We find that a good three-nucleon interaction is crucial to obtain an accurate description of neutron-alpha scattering.

  3. Quantum Monte Carlo Calculations of Neutron-{alpha} Scattering

    SciTech Connect

    Nollett, Kenneth M.; Pieper, Steven C.; Wiringa, R. B.; Carlson, J.; Hale, G. M.

    2007-07-13

    We describe a new method to treat low-energy scattering problems in few-nucleon systems, and we apply it to the five-body case of neutron-alpha scattering. The method allows precise calculations of low-lying resonances and their widths. We find that a good three-nucleon interaction is crucial to obtain an accurate description of neutron-alpha scattering.

  4. Inelastic Neutron Scattering Study of the Specific Features of the Phase Transitions in (NH4)2WO2F4

    SciTech Connect

    Smirnov, Lev S; Kolesnikov, Alexander I; Flerov, I. N.; Laptash, N. M.

    2009-01-01

    Oxyfluoride (NH4)2WO2F4 has been studied by the inelastic neutron scattering method over a wide temperature range 10 300 K at two initial neutron energies of 15 and 60 meV. The role of tetrahedral ammonium groups in the mechanism of sequential phase transitions at T1 = 201 K and T2 = 160 K has been discussed.

  5. Fusion of time-dependent gamma production spectra from thermal neutron capture and fast neutron inelastic scattering to improve material detection

    NASA Astrophysics Data System (ADS)

    Gozani, T.; Elsalim, M.; Strellis, D.; Brown, D.

    2003-06-01

    Neutron-based inspection techniques are unique in their ability to provide material specific signatures, thus offering very high performance and automatic detection of explosives and other contraband. Thermal neutron capture gamma spectroscopy provides excellent sensitivities to hydrogen, nitrogen, chlorine, and other elements, which are characteristic to most explosives, drugs and other contraband that may be smuggled into the country. Fast neutron gamma production (mostly through inelastic scattering) provides good sensitivity to carbon and oxygen. When necessary, these two types of complementary interactions can be combined to yield a more accurate material determination inside small to medium size containers. Standard pulsed 14 MeV electronic neutron generators offer an efficient way to obtain these two types of interactions. Fast (14 MeV) neutrons are produced during the pulse. After the pulse, only the decaying thermal neutron population exists, and thus pure neutron capture gamma-rays are produced. Unfortunately, during the pulse (which is normally much longer than the neutron thermalization time) the fast neutron interactions are highly "contaminated" by the interactions of thermal neutrons within the object and the nearby gamma-ray detectors. This creates high background and spectral interferences in the common medium resolution detectors, such as NaI, BGO, etc. The use of an appropriate shielding, neutron spectrum tailoring, full spectral feature analysis as well as temporal information ("die-away" time) resulted in significant performance enhancements in detection of explosives, drugs and other contraband in difficult geometries.

  6. The Neutron-Neutron ^1S0 Scattering Length via the Reaction π^-d→γ nn

    NASA Astrophysics Data System (ADS)

    Saliba, M. A.; Measday, D. F.; Stocki, T. J.; Christy, M. E.; Doyle, B. C.; Gorringe, T. P.; Jiang, C.; Kovash, M. A.; Liu, K.; Bassalleck, B.; Stasko, J.; Wolfe, D.; Korkmaz, E.; Opper, A.; Sim, K.; Fischer, H.; Ottewell, D.

    1997-10-01

    A measurement of the ^1S0 neutron-neutron scattering length, a quantity crucial to the discussion of charge symmetry breaking in the NN interaction, has been carried out at TRIUMF by studying the shape of the photon energy spectrum from the reaction π^-d→γ nn in the region near the endpoint. A 40.5 MeV pion beam was degraded and stopped in a liquid deuterium target and all three final state particles from the reaction were detected in triple coincidence. The experimental photon energy spectrum was reconstructed from the measured momenta of the two neutrons, and contains 133,000 counts in the top 450 keV region near the endpoint. The experimental resolution was taken into account using Monte Carlo techniques. The data were analyzed using a model of this reaction based on a half off-shell NN T matrix and the elementary γπ operator due to Lee and Nozawa.

  7. Utilization of new 150-MeV neutron and proton evaluations in MCNP

    SciTech Connect

    Little, R.C.; Frankle, S.C.; Hughes, H.G. III; Prael, R.E.

    1997-10-01

    MCNP{trademark} and LAHET{trademark} are two of the codes included in the LARAMIE (Los Alamos Radiation Modeling Interactive Environment) code system. Both MCNP and LAHET are three-dimensional continuous-energy Monte Carlo radiation transport codes. The capabilities of MCNP and LAHET are currently being merged into one code for the Accelerator Production of Tritium (APT) program at Los Alamos National Laboratory. Concurrently, a significant effort is underway to improve the accuracy of the physics in the merged code. In particular, full nuclear-data evaluations (in ENDF6 format) for many materials of importance to APT are being produced for incident neutrons and protons up to an energy of 150-MeV. After processing, cross-section tables based on these new evaluations will be available for use fin the merged code. In order to utilize these new cross-section tables, significant enhancements are required for the merged code. Neutron cross-section tables for MCNP currently specify emission data for neutrons and photons only; the new evaluations also include complete neutron-induced data for protons, deuterons, tritons, and alphas. In addition, no provision in either MCNP or LAHET currently exists for the use of incident charged-particle tables other than for electrons. To accommodate the new neutron-induced data, it was first necessary to expand the format definition of an MCNP neutron cross-section table. The authors have prepared a 150-MeV neutron cross-section library in this expanded format for 15 nuclides. Modifications to MCNP have been implemented so that this expanded neutron library can be utilized.

  8. 14 MeV neutron work at the Lawrence Livermore National Laboratory

    SciTech Connect

    Hansen, L.F.

    1985-07-01

    The 14 MeV neutron work at Lawrence Livermore National Laboratory (LLNL) covers two main areas of interest to this Symposium: (1) measurements and calculations of differential cross sections; and (2) integral measurements of the neutron and gamma emission spectra. In both areas a large number of materials have been studied, spanning a wide mass range (6 < A < 239), of interest to fusion and hybrid reactors. In this presentation a brief description of the experimental techniques and calculational analysis is given for each of the above areas and the measured and calculated cross sections are discussed. 28 refs., 7 figs., 3 tabs.

  9. Lithium Blanket Module dosimetry measurements at the LOTUS 14-MeV neutron source facility

    SciTech Connect

    Tsang, F.Y.; Leo, W.R.; Sahraoui, C.; Wuthrich, S.; Harker, Y.D.

    1986-01-01

    This paper describes the measurements and results of the dosimeter material reaction rates inside the Lithium Blanket Module (LBM) after irradiation by the LOTUS 14-MeV neutron source at the Ecole Polytechnique Federale de Lausanne. The measurement program has been designed to utilize sets of passive dosimeter materials in the form of foils and wires. The dosimetry materials reaction thresholds and interaction response ranges chosen for this series of measurements encompass the entire neutron spectra along the full length of the LBM fuel rods.

  10. Test of 600 and 750 MeV NN matrix on elastic scattering Glauber model calculations

    NASA Astrophysics Data System (ADS)

    Brissaud, I.

    1980-09-01

    The 600 and 750 MeV proton nucleus elastic scattering cross section and polarization calculations have been performed in the framework of the Glauber model to test the pp and pn scattering amplitudes deduced from a phase shift analysis by Bystricky, Lechanoine and Lehar. It is well known that up to now we do not possess a non-phenomenological NN scattering matrix at intermediate energies. However proton-nucleus scattering analyses are used to extract information about short range correlations1), Δ resonance2) or pion condensation presences)... etc. Most scattering calculations made at these energies have been done with phenomenological NN amplitudes having a gaussian q-dependence 10050_2005_Article_BF01438168_TeX2GIFE1.gif A(q) = {kσ }/{4π }(α + i) e^{ - β ^2 q^2 /2} and 10050_2005_Article_BF01438168_TeX2GIFE2.gif C(q) = {kσ }/{4π }iq(α + i) D_e - β ^2 q^2 /2 K and σ being respectively the projectile momentum and the total pN total cross section. The parameters α, β and D are badly known and are adjusted by fitting some specific reactions as p+4He elastic scattering4). Even when these amplitudes provide good fits to the data, our understanding of the dynamics of the scattering remains obscure.

  11. Design Analyses and Shielding of HFIR Cold Neutron Scattering Instruments

    SciTech Connect

    Gallmeier, F.X.; Selby, D.L.; Winn, B.; Stoica, D.; Jones, A.B.; Crow, L.

    2011-07-01

    Research reactor geometries and special characteristics present unique dosimetry analysis and measurement issues. The introduction of a cold neutron moderator and the production of cold neutron beams at the Oak Ridge National Laboratory High Flux Isotope Reactor have created the need for modified methods and devices for analyzing and measuring low energy neutron fields (0.01 to 100 meV). These methods include modifications to an MCNPX version to provide modeling of neutron mirror reflection capability. This code has been used to analyze the HFIR cold neutron beams and to design new instrument equipment that will use the beams. Calculations have been compared with time-of-flight measurements performed at the start of the neutron guides and at the end of one of the guides. The results indicate that we have a good tool for analyzing the transport of these low energy beams through neutron mirror and guide systems for distance up to 60 meters from the reactor. (authors)

  12. Inelastic neutron scatter iron concentrations of the moon from orbital gamma ray data

    NASA Technical Reports Server (NTRS)

    Davis, P. A., Jr.; Bielefeld, M. J.

    1981-01-01

    The considered investigation is concerned with the relation between KREEP and thermal neutron flux depression. The Fe(n, n-prime gamma) concentrations of selected lunar regions were calculated by energy-band analysis of the 0.803-0.872 MeV band. The result of the investigation will be used to evaluate the reliability of the previously determined Fe(n, gamma) values. A 0.803-0.872 MeV band was isolated from the Apollo 15 and 16 orbital gamma ray spectra. Preliminary regression analysis of regional ground truth count rates and Fe concentrations showed this energy interval to be optimum for the 0.8467 MeV inelastic scatter (n, n-prime gamma)Fe peak.

  13. Preequilibrium neutron emission in fusion of WVHo+ SC at 25 MeV per nucleon

    SciTech Connect

    Holub, E.; Hilscher, D.; Ingold, G.; Jahnke, U.; Orf, H.; Rossner, H.; Zank, W.P.; Schroeder, W.U.; Gemmeke, H.; Keller, K.

    1986-01-01

    Neutrons were measured in coincidence with evaporation residues from the reaction WVHo+(300 MeV) SC. The evaporation residue velocity distribution is indicative of an average transfer of 80% of the full linear momentum in this reaction. The energy spectra of the coincident neutrons exhibit evaporative and preequilibrium components associated with integral multiplicities of M/sub EV/ = (9.5 +- 0.5) and M/sub PE/ = (1.7 +- 0.3), respectively. The experimental neutron energy and angular distributions are analyzed in terms of multiple-source parametrizations, assuming two or three emitters. The results are compared to those obtained from other inclusive and exclusive associated-particle data. It is observed that the emission patterns of the preequilibrium neutrons are in accord with the predictions of a Fermi-jet model, for neutron angles forward of 35, while this model fails to reproduce the data at angles in the vicinity of 90 and beyond. Various different nucleon momentum distributions have been employed in the model comparison. The insufficiency of the Fermi-jet model to reproduce the data is attributed to the neglect of two-body collisions in this one-body theory. In contrast, the shape of the angle-integrated preequilibrium-neutron energy spectrum is well reproduced with the Harp-Miller-Berne preequilibrium model, if an initial exciton number of n0 = 15 is adopted. This value, as well as the preequilibrium neutron multiplicity, is at variance with systematics established previously.

  14. Neutron Scattering from Polymers: Five Decades of Developing Possibilities.

    PubMed

    Higgins, J S

    2016-06-01

    The first three decades of my research career closely map the development of neutron scattering techniques for the study of molecular behavior. At the same time, the theoretical understanding of organization and motion of polymer molecules, especially in the bulk state, was developing rapidly and providing many predictions crying out for experimental verification. Neutron scattering is an ideal technique for providing the necessary evidence. This autobiographical essay describes the applications by my research group and other collaborators of increasingly sophisticated neutron scattering techniques to observe and understand molecular behavior in polymeric materials. It has been a stimulating and rewarding journey. PMID:27276548

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

    SciTech Connect

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

    2010-01-01

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

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

    PubMed

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  19. Single event upsets calculated from new ENDF/B-VI proton and neutron data up to 150 MeV

    SciTech Connect

    Chadwick, M.B.; Normand, E.

    1999-06-01

    Single-event upsets (SEU) in microelectronics are calculated from newly-developed silicon nuclear reaction recoil data that extend up to 150 MeV, for incident protons and neutrons. Calculated SEU cross sections are compared with measured data.

  20. A scintillating-fiber 14-MeV neutron detector on TFTR during DT operation

    SciTech Connect

    Wurden, G.A.; Chrien, R.E.; Barnes, C.W.; Sailor, W.C.; Roquemore, A.L.; Lavelle, M.J.; O`Gara, P.M.; Jordan, R.J.

    1994-07-01

    A compact 14-MeV neutron detector using an array of scintillating fibers has been tested on the TFTR tokamak under conditions of a high gamma background. This detector uses a fiber-matrix geometry, a magnetic field-insensitive phototube with an active HV base and pulse-height discrimination to reject low-level pulses from 2.5 MeV neutron and intense gammas. Laboratory calibrations have been performed at EG&G Las Vegas using a pulsed DT neutron generator and a 30 kCi {sup 60}Co source as background, at PPPL using DT neutron sources, and at LANL using an energetic deuterium beam and target at a tandem Van de Graaff accelerator. During the first high power DT shots on TFTR in December 1993, the detector was 15.5 meters from the torus in a large collimator. For a rate of 1 {times} 10{sup 18} n/sec from the tokamak, it operated in an equivalent background of 1 {times} 10{sup 10} gammas/cm{sup 2}/sec ({approximately}4 mA current drain) at a DT count rate of 200 kHz.

  1. Inelastic Neutron Scattering Study of Ce3Sn and Ce3In

    NASA Astrophysics Data System (ADS)

    Wang, C. H.; Lawrence, J. M.; Christianson, A. D.; Goremychkin, E. A.; Bauer, E. D.; de Souza, N. R.; Kolesnikov, A. I.

    2009-03-01

    In Ce3Sn and Ce3In, the linear coefficients of specific heat γ are 260 mJ/mol Ce-K^2 and 700 mJ/mol Ce-K^2, respectively. The Wilson ratio is 7.0 for Ce3Sn and 11.5 for Ce3In. Such large values suggest the presence of ferromagnetic correlations in the ground state. Hence, this system is a potential candidate for studying the magnetic instability at a quantum critical point (QCP). As an initial measurement, we have measured the magnetic inelastic neutron scattering line shape of polycrystalline samples to determine the crystal field (CF) excitations. The low temperature spectrum of both Ce3Sn and Ce3In consist of a quasi- elastic line and two obvious inelastic lines resulting from the two excited crystal field doublets of Ce^3+ in the tetragonal symmetry. The quasi-elastic linewidth,which is related to the Kondo scale, is 3.2meV for Ce3Sn and 1.5meV for Ce3In, consistent with the linear coefficients of specific heat. For Ce3Sn the two CF excitations are at 20meV and 35meV while for Ce3In, the splitting is much larger giving the two excitations at 15meV and 47meV.

  2. Modern Techniques for Inelastic Thermal Neutron Scattering Analysis

    NASA Astrophysics Data System (ADS)

    Hawari, A. I.

    2014-04-01

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

  3. Response function stability of single crystal diamond detectors to 14 MeV neutrons

    SciTech Connect

    Zbořil, Miroslav Zimbal, Andreas

    2014-11-15

    Detectors based on single crystal synthetic diamond show promise as neutron spectrometers for the ITER project. In this work, the stability of the response function of two diamond detectors was tested at the Physikalisch-Technische Bundesanstalt (PTB) accelerator using a 14 MeV neutron field and a method of time-resolved fluence monitoring. In addition, measurements at the PTB ion-microbeam were made to investigate the charge collection properties of the detectors in more detail. The {sup 12}C(n,α){sup 9}Be peak response of one of the detectors was found to be stable within 1% after irradiation with a neutron fluence of 8 × 10{sup 9} cm{sup −2}. The absolute value of the peak response of this detector was determined as 8.65(26) × 10{sup −5} cm{sup 2}.

  4. Response function stability of single crystal diamond detectors to 14 MeV neutrons.

    PubMed

    Zbořil, Miroslav; Zimbal, Andreas

    2014-11-01

    Detectors based on single crystal synthetic diamond show promise as neutron spectrometers for the ITER project. In this work, the stability of the response function of two diamond detectors was tested at the Physikalisch-Technische Bundesanstalt (PTB) accelerator using a 14 MeV neutron field and a method of time-resolved fluence monitoring. In addition, measurements at the PTB ion-microbeam were made to investigate the charge collection properties of the detectors in more detail. The (12)C(n,α)(9)Be peak response of one of the detectors was found to be stable within 1% after irradiation with a neutron fluence of 8 × 10(9) cm(-2). The absolute value of the peak response of this detector was determined as 8.65(26) × 10(-5) cm(2). PMID:25430252

  5. Design status of an intense 14 MeV neutron source for cancer therapy

    NASA Astrophysics Data System (ADS)

    Yao, Ze-En; Su, Tong-Ling; Cheng, Shang-Wen; Jia, Wen-Bao

    2002-09-01

    Design and development of an intense 14 MeV neutron source for cancer therapy is in progress at the Institute of Nuclear Research of Lanzhou University. The neutrons from the T(d,n) 4He reaction are produced by bombarding a rotating titanium tritide target with a 40 mA deuteron beam at 600 keV. The designed neutron yield is 8×10 12 n/s and the maximum dose rate at a 100 cm source-to-skin distance is 25 cGy/min. The HV terminal, accelerating column and HV power supply are enclosed inside a stainless steel pressure vessel containing 6 atm SF 6 gas to provide the electrical insulation.

  6. A novel approach to neutron scattering instrumentation for probing multiscale dynamics in soft and biological matter

    DOE PAGESBeta

    Mamontov, Eugene

    2016-06-29

    We present a concept and ray-tracing simulation results of a mechanical device that will enable inelastic neutron scattering measurements where the data at energy transfers from a few eV to several hundred meV can be collected in a single, gapless spectrum. Besides covering 5 orders of magnitude on the energy (time) scale, the device provides data over 2 orders of magnitude on the scattering momentum (length) scale in a single measurement. Such capabilities are geared primarily toward soft and biological matter, where the broad dynamical features of relaxation origin largely overlap with vibration features, thus necessitating gapless spectral coverage overmore » several orders of magnitude in time and space. Furthermore, neutron scattering experiments with such a device are performed with a fixed neutron final energy, which enables measurements, with neutron energy loss in the sample, at arbitrarily low temperatures over the same broad spectral range. Lastly, this capability is also invaluable in biological and soft matter research, as the variable temperature dependence of different relaxation components allows their separation in the scattering spectra as a function of temperature.« less

  7. A novel approach to neutron scattering instrumentation for probing multiscale dynamics in soft and biological matter

    NASA Astrophysics Data System (ADS)

    Mamontov, Eugene

    2016-09-01

    We present a concept and ray-tracing simulation of a mechanical device that will enable inelastic neutron scattering measurements where the data at energy transfers from a few μeV to several hundred meV can be collected in a single, gapless spectrum. Besides covering 5 orders of magnitude on the energy (time) scale, the device provides data over 2 orders of magnitude on the scattering momentum (length) scale in a single measurement. Such capabilities are geared primarily toward soft and biological matter, where the broad dynamical features of relaxation origin largely overlap with vibration features, thus necessitating gapless spectral coverage over several orders of magnitude in time and space. Furthermore, neutron scattering experiments with such a device are performed with a fixed neutron final energy, which enables measurements, with neutron energy loss in the sample, at arbitrarily low temperatures over the same broad spectral range. This capability is also invaluable in biological and soft matter research, as the variable temperature dependence of different relaxation components allows their separation in the scattering spectra as a function of temperature.

  8. A novel approach to neutron scattering instrumentation for probing multiscale dynamics in soft and biological matter.

    PubMed

    Mamontov, Eugene

    2016-09-01

    We present a concept and ray-tracing simulation of a mechanical device that will enable inelastic neutron scattering measurements where the data at energy transfers from a few μeV to several hundred meV can be collected in a single, gapless spectrum. Besides covering 5 orders of magnitude on the energy (time) scale, the device provides data over 2 orders of magnitude on the scattering momentum (length) scale in a single measurement. Such capabilities are geared primarily toward soft and biological matter, where the broad dynamical features of relaxation origin largely overlap with vibration features, thus necessitating gapless spectral coverage over several orders of magnitude in time and space. Furthermore, neutron scattering experiments with such a device are performed with a fixed neutron final energy, which enables measurements, with neutron energy loss in the sample, at arbitrarily low temperatures over the same broad spectral range. This capability is also invaluable in biological and soft matter research, as the variable temperature dependence of different relaxation components allows their separation in the scattering spectra as a function of temperature. PMID:27355223

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

    SciTech Connect

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

    2009-09-15

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

  10. Polycrystalline neutron scattering for Geant4: NXSG4

    NASA Astrophysics Data System (ADS)

    Kittelmann, T.; Boin, M.

    2015-04-01

    An extension to Geant4 based on the nxs library is presented. It has been implemented in order to include effects of low-energy neutron scattering in polycrystalline materials, and is made available to the scientific community.

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

    SciTech Connect

    DIOSZEGI,I.

    2007-10-28

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

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

    SciTech Connect

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

    1993-09-01

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

  13. Phenomenological optical potential analysis of proton-carbon elastic scattering at 200 MeV

    NASA Technical Reports Server (NTRS)

    Bidasaria, H. B.; Townsend, L. W.

    1982-01-01

    Differential cross sections for 200 MeV protons elastically scattered from C-12 were analyzed utilizing a local, complex, spin-dependent optical potential with a harmonic well radial dependence. Analyses were performed using the WKB and eikonal approximations. For the latter, first-order corrections to he phase shifts were incorporated to account for the spin-orbit contribution. Large disagreement between theory and experiment was observed when the usual Thomas form for the spin-orbit potential was utilized. Substantial improvement was obtained by allowing the parameters in the central and spin-orbit potential terms to vary independently.

  14. Nuclear sizes of /sup 40,42,44,48/Ca from elastic scattering of 104 MeV alpha particles. II. Nuclear density distributions

    SciTech Connect

    Gils, H.J.; Friedman, E.; Majka, Z.; Rebel, H.

    1980-04-01

    The elastic scattering of 104 MeV ..cap alpha.. particles from /sup 40,42,44,48/Ca has been analyzed by a single-folding model with a density-dependent effective interaction. Nuclear density distributions have been extracted using various descriptions including Fourier-Bessel series which distinctly reduces the model dependence of the results and enables realistic estimates of errors. Differences of the density shapes of the Ca isotopes are well determined showing evidence for a neutron skin in /sup 48/Ca. The resulting root mean square radii are compared to the results obtained from other methods. The sensitivity and limitations of various methods are discussed.

  15. Amplitude description of elastic pp scattering at 800 MeV

    NASA Astrophysics Data System (ADS)

    Moravcsik, Michael J.; Arash, Firooz; Goldstein, Gary R.

    1985-04-01

    Recent polarization data on proton-proton elastic scattering at 800 MeV taken at LAMPF are used for an amplitude analysis using the optimal formalism. The direct analysis of data is done in the transversity frame, which is best suited to parity-conserving reactions. From the results, amplitudes are also obtained in the helicity frame and the ``magic'' frame. Agreement with previous amplitudes obtained from an energy-dependent phase-shift analysis is good. The comparison of the helicity amplitudes c and e strengthens previous suggestions for a possible triplet-state dibaryon resonance. The comparison of the amplitudes am and cm in the magic frame indicates a possible domination of the process near 90° scattering angle by one-particle-exchange mechanism involving exchanged particles with natural parity.

  16. LET spectrometry of 14 MeV (D-T) neutrons using CR-39 track detectors

    NASA Astrophysics Data System (ADS)

    Sahoo, G. S.; Tripathy, S. P.; Sunil, C.; Sarkar, P. K.

    2013-04-01

    Linear energy transfer (LET) spectrum in water in the range of 12 keV/μm to 382 keV/μm due to 14 MeV (D-T) neutrons is estimated using the track size parameters in two different types of CR-39 track detectors, viz. Intercast (1.5 mm) and Pershore (0.5 mm). Another set of CR-39s (Intercast) combined with 1 mm polyethylene (PE) radiators is exposed to study the effect of enhanced recoils on the LET spectrum. The detection efficiencies for all these cases and the enhancement ratio due to PE radiator are determined. Using this LET spectrum, the microdosimetric spectra of absorbed doses and dose equivalents are estimated based on the Q-L conversion factors as given in ICRP 60. The shape of the LET spectra are found to be similar in all the cases, however, the dose equivalents obtained with the CR-39+PE radiator is about 20% more than the other detectors without PE. The ratios of dose equivalents obtained from LET spectra (HLET) and the ambient dose equivalent (H*(10)) obtained from fluence-to-dose equivalent conversion factors (ICRP 74) for 14 MeV neutrons are used to estimate the dose response of the detectors. H*(10) is also measured using a neutron rem meter, the response of which is found to be about 23% less than the actual dose.

  17. Inelastic Neutron Scattering on Multiferroics NdFe3(BO3)4

    NASA Astrophysics Data System (ADS)

    Hayashida, Shohei; Soda, Minoru; Itoh, Shinichi; Yokoo, Tetsuya; Ohgushi, Kenya; Kawana, Daichi; Masuda, Takatsugu

    Inelastic neutron scattering experiment is performed on single crystals of multiferroics NdFe3(11BO3)4 to explore the magnetic excitations. Fe-centered dispersive excitation with the band width of 5 meV is observed along the crystallographic c∗ direction and that of 3 meV is along the a∗ direction. The energy gap of 0.57 meV due to an axial-type anisotropy is ob- served at the AF zone center. The energy of Nd-centered flat excitation is 1 meV. Furthermore, anticrossing of the Fe- and Nd-centered excitations is observed, meaning the existence of the f -d coupling, i.e., the interaction between the Nd3+ and Fe3+ moments. Spin-wave analysis on the observed neutron spectrum revealed the underlying magnetic Hamiltonian in NdFe3(11BO3)4. Discussion on the axial-type anisotropy in the ab - plane based on the magnetic model leads to the conclusion that the anisotropy of the Nd3+ ion plays a main role in the determination of the structures of both magnetic moment and electric polarization in NdFe3(BO3)4.

  18. Elastic and Inelastic Scattering of Neutrons using a CLYC array

    NASA Astrophysics Data System (ADS)

    Brown, Tristan; Doucet, E.; Chowdhury, P.; Lister, C. J.; Wilson, G. L.; Devlin, M.; Mosby, S.

    2015-10-01

    CLYC scintillators, which have dual neutron and gamma response, have recently ushered in the possibility of fast neutron spectroscopy without time-of-flight (TOF). A 16-element array of 1'' x 1'' 6Li-depleted CLYC crystals, where pulse-shape-discrimination is achieved via digital pulse processing, has been commissioned at UMass Lowell. In an experiment at LANSCE, high energy neutrons were used to bombard 56Fe and 238U targets, in order to measure elastic and inelastic neutron scattering cross sections as a function of energy and angle with the array. The array is placed very close to the targets for enhanced geometrical solid angles for scattered neutrons compared to standard neutron-TOF measurements. A pulse-height spectrum of scattered neutrons in the detectors is compared to the energy of the incident neutrons, which is measured via the TOF of the pulsed neutrons from the source to the detectors. Recoil corrections are necessary to combine the energy spectra from all the detectors to obtain angle-integrated elastic and inelastic cross-sections. The detection techniques, analysis procedures and results will be presented. Supported by NNSA-SSAA program through DOE Grant DE-NA00013008.

  19. Evidence for a narrow N{sup *}(1685) resonance in quasifree Compton scattering on the neutron

    SciTech Connect

    Kuznetsov, V.; Polyakov, M. V.; Bellini, V.; Giusa, A.; Mammoliti, F.; Randieri, C.; Russo, G.; Sperduto, M. L.; Boiko, T.; Chebotaryov, S.; Dho, H.-S.; Kim, W.; Milman, E.; Ni, A.; Gervino, G.; Ghio, F.; Kim, A.; Perevalova, I. A.; Vall, A. N.; Sutera, C. M.

    2011-02-15

    The study of quasifree Compton scattering on the neutron in the energy range of E{sub {gamma}}=0.75-1.5 GeV is presented. The data reveal a narrow peak at W{approx}1.685 GeV. This result, being considered in conjunction with the recent evidence for a narrow structure at W{approx}1.68 GeV in {eta} photoproduction on the neutron, suggests the existence of a nucleon resonance with unusual properties: a mass M{approx}1.685 GeV, a narrow width {Gamma}{<=}30 MeV, and the much stronger photoexcitation on the neutron than on the proton.

  20. Efficient Energy Conversion of the 14 MeV Neutrons in DT Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Winterberg, F.

    2013-02-01

    In DT fusion 80 % of the energy released goes into 14 MeV neutrons, and only the remaining 20 % into charged particles. Unlike the charged particles, the uncharged neutrons cannot be confined by a magnetic field, and for this reason cannot be used for a direct conversion into electric energy. Instead, the neutrons have to be slowed down in some medium, heating this medium to a temperature of less than 103 K, with the heat removed from this medium to drive a turbo-generator. This conversion of nuclear into electric energy has a Carnot efficiency of about 30 %. For the 80 % of the energy released into neutrons, the efficiency is therefore no more than 24 %. While this low conversion efficiency cannot be overcome in magnetic confinement concepts, it can be overcome in inertial confinement concepts, by surrounding the inertial confinement fusion target with a sufficiently thick layer of liquid hydrogen and a thin outer layer of boron, to create a hot plasma fire ball. The hydrogen layer must be chosen just thick and dense enough to be heated by the neutrons to 100,000 K. The thusly generated, fully ionized, and rapidly expanding fire ball can drive a pulsed magnetohydrodynamic generator at an almost 100 % Carnot efficiency, or possibly be used to generate hydrocarbons.

  1. Protactinium neutron-induced fission up to 200 MeV

    NASA Astrophysics Data System (ADS)

    Maslov, V.

    2010-03-01

    The theoretical evaluation of 230-233Pa(n,F) cross sections is based on direct data, 230-234Pa fission probabilities and ratios of fission probabilities in first-chance and emissive fission domains, surrogate for neutroninduced fission. First chance fission cross sections trends of Pa are based on consistent description of 232Th(n,F), 232Th(n,2n) and 238U(n,F), 238U(n,xn) data, supported by the ratio surrogate data by Burke et al., 2006, for the 237U(n,F) reaction. Ratio surrogate data on fission probabilities of 232Th(6 Li,4 He)234Pa and 232 Th(6 Li,d)236U by Nayak et al., 2008, support the predicted 233Pa(n, F) cross section at En=11.5-16.5 MeV. The predicted trends of 230-232Pa(n, F) cross section up to En=20 MeV, are consistent with fissilities of Pa nuclides, extracted by 232Th(p,F) (Isaev et al., 2008) and 232Th(p,3n) (Morgenstern et al., 2008) data analysis. The excitation energy and nucleon composition dependence of the transition from asymmetric to symmetric scission for fission observables of Pa nuclei is defined by analysis of p-induced fission of 232Th at Ep=1-200 MeV. Predominantly symmetric fission in 232Th(p,F) at En( p)=200 MeV as revealed by experimental branching ratios (Dujvestijn et al., 1999) is reproduced. Steep transition from asymmetric to symmetric fission with increase of nucleon incident energy is due to fission of neutron-deficient Pa (A≤229) nuclei. A structure of the potential energy surface (a drop of f f symmetric and asymmetric fission barriers difierence (EfSYM - EfASYM) from ~3.5 MeV to ~1 MeV) of N-deficient Pa nuclides (A≤226) and available phase space at outer fission saddles, are shown to be responsible for the sharp increase with En( p) of the symmetric fission component contribution for 232Th(p,F) and 230-233 Pa(n, F) reactions. That is a strong evidence of emissive fission nature of moderately excited Pa nuclides, reliably quantified only up to En( p)~20(30) MeV. Predicted fission cross section of 232Pa(n,F) coincides

  2. Small angle neutron scattering from nanometer grain sized materials

    SciTech Connect

    Epperson, J.E.; Siegel, R.W.

    1991-11-01

    Small angie neutron scattering has been utilized, along with a number of complementary characterization methods suitable to the nanometer size scale, to investigate the structures of cluster-assembled nanophase materials. Results of these investigations are described and problems and opportunities in using small angle scattering for elucidating nanostructures are discussed.

  3. Analysis of 6Li Scattering at 240 MeV Using Different Nuclear Potentials

    NASA Astrophysics Data System (ADS)

    Al-Ghamdi, A. H.; Ibraheem, Awad A.

    2016-06-01

    Angular distributions of the elastic and inelastic scattering cross sections of 6Li projectile on different heavy ion target nuclei including the 24Mg, 28Si, 48Ca, 58Ni, 90Zr, and 116Sn at energy of 240 MeV have been analyzed by using two different folded potentials based on the CDM3Y6 and São Paulo potentials for the real part of the optical potential, while the imaginary parts have a phenomenological Woods-Saxon shape. Coupled channel calculations for the low-lying 2+ state at 1.369, 1.779, 3.832, 1.454, 2.186, and 1.29 MeV for 24Mg, 28Si, 48Ca, 58Ni, 90Zr, and 116Sn, respectively, have been carried out, and the best fit values for B(EL) with the above models have been extracted by fitting the inelastic scattering cross section and compared with the values of previous works. The total reaction cross section and real and imaginary volume integrals have also been investigated.

  4. Neutron flux from a 14-MeV neutron generator with tungsten filter for research in NDA methods for nuclear safeguards and security

    SciTech Connect

    Rennhofer, H.; Pedersen, B.; Crochemore, J.-M.

    2009-12-02

    The Joint Research Centre has taken into operation a new experimental device designed for research in the fields of nuclear safeguards and security applications. The research projects currently undertaken include detection of shielded contraband materials, detection of fissile materials, and mass determination of small fissile materials in shielded containers. The device, called the Pulsed Neutron Interrogation Test Assembly (PUNITA), incorporates a pulsed 14-MeV (D-T) neutron generator and a large graphite mantle surrounding the sample cavity. By pulsing the neutron generator with a frequency in the range of 10 to 150 Hz, a sample may be interrogated first by fast neutrons and a few hundred micro-seconds later by a pure thermal neutron flux. The permanent detection systems incorporated in PUNITA include {sup 3}He neutrons detectors, HPGe gamma detectors, and lanthanum bromide scintillation detectors.We have studied the effects of placing a tungsten liner around the neutron generator target. The 14-MeV neutrons induce (n, 2n) and (n, 3n) reactions. In addition the mean neutron energy emitted from generator/tungsten assembly is reduced to about 1 MeV. Both of these effects increase the thermal neutron flux in the sample cavity. The paper describes the observed advantages of the tungsten liner with respect to increase in thermal flux, and better shielding capabilities of the nearby gamma and neutron detectors.

  5. Reference neutron fields of the KIGAM for the neutron energy range between 144 keV and 2.5 MeV

    NASA Astrophysics Data System (ADS)

    Kim, G. D.; Woo, H. J.; Choi, H. W.; Park, J. W.; Trinh, T. A.

    2012-08-01

    The Korea Institute of Geoscience and Mineral Resources (KIGAM) is constructing a reference neutron field facility as a national project. Neutron fields consist of mono-energetic sources of 144 keV, 250 keV, 565 keV, and 2.5 MeV have a fluence range from 102 neutrons/cm2/sec to 103 neutrons/cm2/sec. The systems for the reference neutron fields, such as a duo-plasmatron ion source, a 4-MHz beam bunching system, a neutron chamber, an irradiation room, a neutron time-of-flight (n-TOF) system, a long-counter, and a sample moving system, were designed and fabricated. The neutron energies of the reference neutron fields and their spreads were observed by using the n-TOF system. The neutron fluence was measured by using a long-counter for energies below 1 MeV and a proton-recoil counter for 2.5 MeV. The long-counter efficiency was calibrated by the Japan Atomic Energy Agency (JAEA) which had a traceability of mono-energetic neutron sources to both Japanese and international standards. The efficiency of the proton-recoil counter was obtained by using a calculation with detailed construction information.

  6. Neutron production from beam-modifying devices in a modern double scattering proton therapy beam delivery system

    PubMed Central

    Pérez-Andújar, Angélica; Newhauser, Wayne D; DeLuca, Paul M

    2014-01-01

    In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient. PMID:19147903

  7. Neutron production from beam-modifying devices in a modern double scattering proton therapy beam delivery system.

    PubMed

    Pérez-Andújar, Angélica; Newhauser, Wayne D; Deluca, Paul M

    2009-02-21

    In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient. PMID:19147903

  8. Determination of alumina in sintered aluminium powder by activation with 14-MeV neutrons.

    PubMed

    Español, C E; Marafuschi, A M

    1970-07-01

    Fast neutrons of 14 MeV produced in the IMICAM CISE 150-kV generator by the (d, t) reaction in a tritium-titanium target, were used in the indirect determination of Al(2)O(3). The samples were irradiated for 30 sec and the total (16)N activity was determined, by counting for ten 2-sec periods and graphically integrating. The standards were a known sintered aluminium powder and nylon pieces of identical shape. The method is competitive with the chemical one, because of its quickness, sensitivity and precision. PMID:18960787

  9. The world's first pelletized cold neutron moderator at a neutron scattering facility

    NASA Astrophysics Data System (ADS)

    Ananiev, V.; Belyakov, A.; Bulavin, M.; Kulagin, E.; Kulikov, S.; Mukhin, K.; Petukhova, T.; Sirotin, A.; Shabalin, D.; Shabalin, E.; Shirokov, V.; Verhoglyadov, A.

    2014-02-01

    In July 10, 2012 cold neutrons were generated for the first time with the unique pelletized cold neutron moderator CM-202 at the IBR-2M reactor. This new moderator system uses small spherical beads of a solid mixture of aromatic hydrocarbons (benzene derivatives) as the moderating material. Aromatic hydrocarbons are known as the most radiation-resistant hydrogenous substances and have properties to moderate slow neutrons effectively. Since the new moderator was put into routine operation in September 2013, the IBR-2 research reactor of the Frank Laboratory of Neutron Physics has consolidated its position among the world's leading pulsed neutron sources for investigation of matter with neutron scattering methods.

  10. Low-Energy Neutron Scattering from Heavy Nuclei

    NASA Astrophysics Data System (ADS)

    Horton, Christopher Adams

    Fast neutron inelastic scattering cross sections for the 44.9-keV level in ^{238} U and the 49.4-keV level in ^{232 }Th, and the elastic scattering cross sections of ^{209}Bi and ^{232}Th have been measured using the neutron time-of-flight technique, at an incident neutron energy of 127 keV at six scattering angles from 45 ^circ to 122.5^circ . Neutrons were produced by the ^7 Li(p,n)^7Be reaction. A detector using two photomultiplier tubes in fast coincidence was built for these low-energy measurements. The detector efficiency was determined by comparison with that of a ^{235}U fission chamber. Special attention was paid to determining the efficiency near the ^7Li(p,n)^7Be reaction threshold. The spectrum unfolding included the removal of tails on the peaks which were assumed to be exponential functions. The inelastic peaks were stripped from the elastic peaks by using the shape of the bismuth elastic peak as a standard. Corrections for neutron attenuation were computed analytically. Corrections for multiple scattering were determined using a Monte Carlo method. Results were normalized to the ^{238}U differential elastic scattering cross sections and angular distributions. The angular distributions and integrated cross sections are compared with the ENDF/B-VI evaluation cross sections and with results at similar energies from previous measurements. The use of iron neutron filters for measuring cross sections at low energies is also discussed.

  11. A high temperature high pressure cell for quasielastic neutron scattering

    SciTech Connect

    Yang, F.; Meyer, A.; Kaplonski, J.; Unruh, T.; Mamontov, E.

    2011-08-15

    We present our recent development of a high temperature high pressure cell for neutron scattering. Combining a water cooled Nb1Zr pressure cell body with an internal heating furnace, the sample environment can reach temperatures of up to 1500 K at a pressure of up to 200 MPa at the sample position, with an available sample volume of about 700 mm{sup 3}. The cell material Nb1Zr is specifically chosen due to its reasonable mechanical strength at elevated temperatures and fairly small neutron absorption and incoherent scattering cross sections. With this design, an acceptable signal-to-noise ratio of about 10:1 can be achieved. This opens new possibilities for quasielastic neutron scattering studies on different types of neutron spectrometers under high temperature high pressure conditions, which is particularly interesting for geological research on, e.g., water dynamics in silicate melts.

  12. A high temperature high pressure cell for quasielastic neutron scattering.

    PubMed

    Yang, F; Kaplonski, J; Unruh, T; Mamontov, E; Meyer, A

    2011-08-01

    We present our recent development of a high temperature high pressure cell for neutron scattering. Combining a water cooled Nb1Zr pressure cell body with an internal heating furnace, the sample environment can reach temperatures of up to 1500 K at a pressure of up to 200 MPa at the sample position, with an available sample volume of about 700 mm(3). The cell material Nb1Zr is specifically chosen due to its reasonable mechanical strength at elevated temperatures and fairly small neutron absorption and incoherent scattering cross sections. With this design, an acceptable signal-to-noise ratio of about 10:1 can be achieved. This opens new possibilities for quasielastic neutron scattering studies on different types of neutron spectrometers under high temperature high pressure conditions, which is particularly interesting for geological research on, e.g., water dynamics in silicate melts. PMID:21895254

  13. Small angle scattering signals for (neutron) computerized tomography

    SciTech Connect

    Strobl, M.; Treimer, W.; Hilger, A.

    2004-07-19

    Small angle neutron scattering is a well-established tool for the determination of microscopic structures in various materials. With the ultrasmall angle neutron scattering technique (USANS), structures with sizes of approximately 50 nm to 50 {mu}m can be resolved by a double crystal diffractometer (DCD). USANS signals recorded with a special DCD were used for tomographic purposes investigating the macroscopic structure of a sample with a maximum resolution of 200 {mu}m. Thereby, macroscopic regions within the sample with different ultrasmall angle scattering properties, i.e., with different microscopic structures, could be imaged by the means of tomographic reconstruction from projections (on a macroscopic scale)

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

    PubMed

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

    2011-07-01

    Inelastic neutron scattering measurements typically require two orders of magnitude longer data collection times and larger sample sizes than neutron diffraction studies. Inelastic neutron scattering measurements on pressurised samples are particularly challenging since standard high-pressure apparatus restricts sample volume, attenuates the incident and scattered beams, and contributes background scattering. Here, we present the design of a large volume two-layered piston-cylinder pressure cell with optimised transmission for inelastic neutron scattering experiments. The design and the materials selected for the construction of the cell enable its safe use to a pressure of 1.8 GPa with a sample volume in excess of 400 mm(3). The design of the piston seal eliminates the need for a sample container, thus providing a larger sample volume and reduced absorption. The integrated electrical plug with a manganin pressure gauge offers an accurate measurement of pressure over the whole range of operational temperatures. The performance of the cell is demonstrated by an inelastic neutron scattering study of UGe(2). PMID:21806195

  15. Activation cross sections for reactions induced by 14 MeV neutrons on natural tantalum

    SciTech Connect

    Luo Junhua; Tuo Fei; Kong Xiangzhong

    2009-05-15

    Cross sections for (n,2n), (n,p), (n,n{sup '}{alpha}), (n,t), (n,d{sup '}), and (n,{alpha}) reactions have been measured on tantalum isotopes at the neutron energies of 13.5 to 14.7 MeV using the activation technique. Data are reported for the following reactions: {sup 181}Ta(n,2n){sup 180}Ta{sup g}, {sup 181}Ta(n,p){sup 181}Hf, {sup 181}Ta(n,n{sup '}{alpha}){sup 177}Lu{sup m}, {sup 181}Ta(n,t){sup 179}Hf{sup m2}, {sup 181}Ta(n,d{sup '}){sup 180}Hf{sup m}, and {sup 181}Ta(n,{alpha}){sup 178}Lu{sup m}. The neutron fluences were determined using the monitor reaction {sup 27}Al(n,{alpha}){sup 24}Na. Results were discussed and compared with the previous works.

  16. Light-ion production in the interaction of 96 MeV neutrons with oxygen

    SciTech Connect

    Tippawan, U.; Pomp, S.; Atac, A.; Blomgren, J.; Dangtip, S.; Hildebrand, A.; Johansson, C.; Klug, J.; Mermod, P.; Oesterlund, M.; Bergenwall, B.; Nilsson, L.; Olsson, N.; Prokofiev, A.V.; Nadel-Turonski, P.; Corcalciuc, V.; Koning, A.J.

    2006-03-15

    Double-differential cross sections are reported for light-ion (p, d, t, {sup 3}He, and {alpha}) production in oxygen induced by 96 MeV neutrons. Energy spectra are measured at eight laboratory angles from 20 degree sign to 160 degree sign in steps of 20 degree sign . Procedures for data taking and data reduction are presented. Deduced energy-differential and production cross sections are reported. Experimental cross sections are compared to theoretical reaction model calculations and experimental data at lower neutron energies in the literature. The measured proton data agree reasonably well with the results of the model calculations, whereas the agreement for the other particles is less convincing. The measured production cross sections for protons, deuterons, tritons, and {alpha} particles support the trends suggested by data at lower energies.

  17. A National Spallation Neutron Source for neutron scattering

    SciTech Connect

    Appleton, B.R.

    1996-10-01

    The National Spallation Neutron Source is a collaborative project or perform the conceptual design for a next generation neutron source for the Department of Energy. This paper reviews the need and justification for a new neutron source, the origins and structure of the collaboration formed to address this need, and the community input leading up to the current design approach. A reference design is presented for an accelerator based spallation neutron source that would begin operation at about 1 megawatt of power but designed so that it could be upgraded to significantly higher powers in the future. The technology approach, status, and progress on the conceptual design to date are presented.

  18. Neutron Scattering Study on spin dynamics in superconducting (TlRb)2Fe4Se5

    SciTech Connect

    Chi, Songxue; Ye, Feng; Bao, Wei; Fang, Dr. Minghu; Wang, H.D.; Dong, C.H.; Savici, Andrei T; Granroth, Garrett E; Stone, Matthew B; Fishman, Randy Scott

    2013-01-01

    Spin dynamics in superconducting (Tl,Rb)2Fe4Se5 was investigated using the inelastic neutron scattering technique. Spin wave branches that span an energy range from 6.5 to 209 meV are success- fully described by a Heisenberg model whose dominant interactions include only the in-plane nearest (J1 and J0 1) and next nearest neighbor (J2 and J0 2) exchange terms within and between the tetramer spin blocks, respectively. These exchange constants, experimentally determined in this work, would crucially constrain the diverse theoretical viewpoints on magnetism and superconductivity in the Fe-based materials.

  19. RBE of quasi-monoenergetic 60 MeV neutron radiation for induction of dicentric chromosomes in human lymphocytes.

    PubMed

    Nolte, R; Mühlbradt, K-H; Meulders, J P; Stephan, G; Haney, M; Schmid, E

    2005-12-01

    The production of dicentric chromosomes in human lymphocytes by high-energy neutron radiation was studied using a quasi-monoenergetic 60 MeV neutron beam. The average yield coefficient [see text] of the linear dose-response relationship for dicentric chromosomes was measured to be (0.146+/-0.016) Gy-1. This confirms our earlier observations that above 400 keV, the yield of dicentric chromosomes decreases with increasing neutron energy. Using the linear-quadratic dose-response relationship for dicentric chromosomes established in blood of the same donor for 60Co gamma-rays as a reference radiation, an average maximum low-dose RBE (RBEM) of 14+/-4 for 60 MeV quasi-monoenergetic neutrons with a dose-weighted average energy [see text] of 41.0 MeV is obtained. A correction procedure was applied, to account for the low-energy continuum of the quasi-monoenergetic spectral neutron distribution, and the yield coefficient alpha for 60 MeV neutrons was determined from the measured average yield coefficient [see text]. For alpha, a value of (0.115+/-0.026) Gy-1 was obtained corresponding to an RBEM of 11+/-4. The present experiments extend earlier investigations with monoenergetic neutrons to higher energies. PMID:16283348

  20. Monte Carlo code for neutron scattering instrumentation design and analysis

    SciTech Connect

    Daemen, L.; Fitzsimmons, M.; Hjelm, R.; Olah, G.; Roberts, J.; Seeger, P.; Smith, G.; Thelliez, T.

    1996-09-01

    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) at the Los Alamos National Laboratory (LANL). The development of next generation, accelerator based neutron sources calls for the design of new instruments for neutron scattering studies of materials. It will be necessary, in the near future, to evaluate accurately and rapidly the performance of new and traditional neutron instruments at short- and long-pulse spallation neutron sources, as well as continuous sources. We have developed a code that is a design tool to assist the instrument designer model new or existing instruments, test their performance, and optimize their most important features.

  1. Fast detection of 14 MeV neutrons on the TFTR neutron collimator

    SciTech Connect

    Goeler, S. von; Roquemore, A.L.; Johnson, L.C.; Bitter, M.; Diesso, M.; Fredrickson, E.; Long, D.; Strachan, J.

    1995-12-01

    Current mode operation of the NE451 ZnS Scintillation Detectors of the TFTR Neutron Collimator has enabled us to record the development of radial neutron emission profiles with much faster speed and higher accuracy than in the pulse counting mode. During high-power DT operation, the intrinsic shot noise on the detector traces was so low that the authors could observe sawtooth instabilities and disruptions with good precision and, in addition, were able to identify precursor MHD activity and fishbone instabilities. These results demonstrate that in future tritium burning machines like ITER or TPX, the neutron collimator should be designed not only as a monitor of radial fusion power profiles but also as a wave detector for MHD activity.

  2. Characteristics of high-energy neutrons estimated using the radioactive spallation products of Au at the 500-MeV neutron irradiation facility of KENS.

    PubMed

    Matsumura, Hiroshi; Masumoto, Kazuyoshi; Nakao, Noriaki; Wang, Qingbin; Toyoda, Akihiro; Kawai, Masayoshi; Aze, Takahiro; Fujimura, Masatsugu

    2005-01-01

    We carried out a shielding experiment of high-energy neutrons, generated from a tungsten target bombarded with primary 500-MeV protons at KENS, which penetrated through a concrete shield in the zero-degree direction. We propose a new method to evaluate the spectra of high-energy neutrons ranging from 8 to 500 MeV. Au foils were set in a concrete shield, and the reaction rates for 13 radionuclides produced by the spallation reactions on the Au targets were measured by radiochemical techniques. The experimental results were compared with those obtained by the MARS14 Monte-Carlo code. A good agreement (between them) was found for energies beyond 100 MeV. The profile of the neutron spectrum, ranging from 8 to 500 MeV, does not depend on the thickness of the concrete shield. PMID:16604584

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

    SciTech Connect

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

    2015-02-15

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

  4. Microscopic study of neutron elastic scattering from {sup 12}C, {sup 40}Ca, and {sup 208}Pb at intermediate energies

    SciTech Connect

    Alvi, M. A.; Arafah, M. R.; Madani, J. H.; Ahmad, I.

    2009-02-15

    Recent neutron elastic scattering differential cross section data for {sup 12}C, {sup 40}Ca, and {sup 208}Pb at several energies from 65 to 225 MeV have been analyzed using Glauber multiple scattering model, suitably modified to enlarge angular range of validity. The center of mass and Pauli pair correlations have been considered. The effect of the phase variation of the NN scattering amplitude on the calculated cross sections has been studied. A medium modification of the 'elementary' NN interaction is also considered. The neutron differential cross sections have been calculated using the phenomenological and the recently proposed semiphenomenological neutron and proton target densities so as to check the validity of the semiphenomenological density model. We found that our method of analysis gives a very good description of the experimental data.

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

    SciTech Connect

    Billinge, Simon

    2011-06-17

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

  6. {sup {bold 6}}Li(vector)+{sup {bold 12}}C inelastic scattering at 30 and 50 MeV

    SciTech Connect

    Kerr, P.L.; Kemper, K.W.; Green, P.V.; Mohajeri, K.; Myers, E.G.; Schmidt, B.G.; Hnizdo, V.

    1996-09-01

    A complete set of analyzing powers (AP`s), {ital iT}{sub 11}, {ital T}{sub 20}, {ital T}{sub 21}, and {ital T}{sub 22}, for 50 MeV {sup 12}C({sup 6}Li(vector),{sup 6}Li) elastic scattering and inelastic scattering to the {sup 12}C(2{sup +}, 4.44 MeV), {sup 12}C(0{sup +}, 7.65 MeV), and {sup 12}C(3{sup {minus}}, 9.64 MeV) states over the center-of-mass (c.m.) angular range 10{degree}{endash}115{degree} is reported. In addition, cross sections for the excited states 3{sup +}(2.18 MeV), 2{sup +}(4.31 MeV), and 1{sup +}(5.65 MeV) of {sup 6}Li were measured by using the inverse-kinematics reaction {sup 6}Li({sup 12}C,{sup 12}C) at 100 MeV. A combined analysis of the new 50 MeV data and previous 30 MeV data has been carried out using the coupled-channels (CC) code FRESCO. The CC calculations use an optical potential with double-folded (DF) real central, Woods-Saxon imaginary central, and Thomas real spin-orbit (SO) potentials. Calculations include reorientation terms and coupling to the first three excited states of {sup 6}Li and the first two nonzerospin states of {sup 12}C. The {sup 6}Li coupling strengths were fixed by the measured {sup 6}Li excited-state cross sections. The elastic-scattering cross sections and A.P.`s are described well. The need for an explicit SO potential is apparent in the elastic and inelastic-scattering AP`s {ital iT}{sub 11}, more so at 30 MeV than at 50 MeV. The rank-2 AP`s up to 50{degree} c.m. arise mainly from ground-state reorientation effects. The DF potential normalization constant {ital N} approaches unity for the 50 MeV data. At both energies, the {sup 12}C(2{sup +}) cross sections are underestimated at large angles, and the description of the {sup 12}C(3{sup {minus}}) cross sections is poor in detail. The {sup 12}C(3{sup {minus}}) AP`s and the {sup 12}C(2{sup +}) {ital iT}{sub 11} are not reproduced at either energy. {copyright} {ital 1996 The American Physical Society.}

  7. Personal dose equivalent conversion coefficients for neutron fluence over the energy range of 20 to 250 MeV

    SciTech Connect

    Mclean, Thomas D; Justus, Alan L; Gadd, S Milan; Olsher, Richard H; Devine, Robert T

    2009-01-01

    Monte Carlo simulations were performed to extend existing neutron personal dose equivalent fluence-to-dose conversion coefficients to an energy of 250 MeV. Presently, conversion coefficients, H(p,slab)(10,alpha)/Phi, are given by ICRP-74 and ICRU-57 for a range of angles of radiation incidence (alpha = 0, 15, 30, 45, 60 and 75 degrees ) in the energy range from thermal to 20 MeV. Standard practice has been to base operational dose quantity calculations <20 MeV on the kerma approximation, which assumes that charged particle secondaries are locally deposited, or at least that charged particle equilibrium exists within the tally cell volume. However, with increasing neutron energy the kerma approximation may no longer be valid for some energetic secondaries such as protons. The Los Alamos Monte Carlo radiation transport code MCNPX was used for all absorbed dose calculations. Transport models and collision-based energy deposition tallies were used for neutron energies >20 MeV. Both light and heavy ions (HIs) (carbon, nitrogen and oxygen recoil nuclei) were transported down to a lower energy limit (1 keV for light ions and 5 MeV for HIs). Track energy below the limit was assumed to be locally deposited. For neutron tracks <20 MeV, kerma factors were used to obtain absorbed dose. Results are presented for a discrete set of angles of incidence on an ICRU tissue slab phantom.

  8. Personal dose equivalent conversion coefficients for neutron fluence over the energy range of 20-250 MeV.

    PubMed

    Olsher, R H; McLean, T D; Justus, A L; Devine, R T; Gadd, M S

    2010-03-01

    Monte Carlo simulations were performed to extend existing neutron personal dose equivalent fluence-to-dose conversion coefficients to an energy of 250 MeV. Presently, conversion coefficients, H(p,slab)(10,alpha)/Phi, are given by ICRP-74 and ICRU-57 for a range of angles of radiation incidence (alpha = 0, 15, 30, 45, 60 and 75 degrees ) in the energy range from thermal to 20 MeV. Standard practice has been to base operational dose quantity calculations <20 MeV on the kerma approximation, which assumes that charged particle secondaries are locally deposited, or at least that charged particle equilibrium exists within the tally cell volume. However, with increasing neutron energy the kerma approximation may no longer be valid for some energetic secondaries such as protons. The Los Alamos Monte Carlo radiation transport code MCNPX was used for all absorbed dose calculations. Transport models and collision-based energy deposition tallies were used for neutron energies >20 MeV. Both light and heavy ions (HIs) (carbon, nitrogen and oxygen recoil nuclei) were transported down to a lower energy limit (1 keV for light ions and 5 MeV for HIs). Track energy below the limit was assumed to be locally deposited. For neutron tracks <20 MeV, kerma factors were used to obtain absorbed dose. Results are presented for a discrete set of angles of incidence on an ICRU tissue slab phantom. PMID:19887515

  9. Neutron interrogation of high-enriched uranium by a 4 MeV linac

    NASA Astrophysics Data System (ADS)

    Lakosi, László; Nguyen, Cong Tam

    2008-07-01

    For revealing unauthorized transport (illicit trafficking) of nuclear materials, a non-destructive method reported earlier, utilizing a 4 MeV linear accelerator for photoneutron interrogation, was further developed. The linac served as a pulsed neutron source for assay of highly enriched uranium. Produced in beryllium or heavy water by bremsstrahlung, neutrons subsequently induced fission in the samples. Delayed neutrons were detected by a newly designed neutron collar built up of 14 3He counters embedded in a polyethylene moderator. A PC controlled multiscaler served as a time analyzer, triggering the detector startup by the beam pulse. Significant progress was achieved in enhancing the detector response, hence the sensitivity for revealing illicit material. A lower sensitivity limit of the order of 10 mg 235U was determined in a 20 s measurement time with a reasonable amount of beryllium (170 g) or of heavy water (100 g) and a mean electron current of 10 μA. Sensitivity can be further enhanced by increasing the measurement time.

  10. Material Classification by Analysis of Prompt Photon Spectra Induced by 14-Mev Neutrons

    NASA Astrophysics Data System (ADS)

    Barzilov, Alexander; Novikov, Ivan

    Neutron based technologies are widely used in the field of bulk material analysis. These methods employ characteristic prompt gamma rays induced by a neutron probe for classification of the interrogated object using the elemental parameters extracted from the spectral data. Automatic data analysis and material classification algorithms are required for applications where access to nuclear spectroscopy expertise is limited and/or the autonomous robotic operation is necessary. Data obtained with neutron based systems differ from elemental composition evaluations based on chemical formulae due to statistical nature of nuclear reactions, presence of shielding and cladding, and other environmental conditions. Experimental data that are produced by the spectral decomposition can be expressed graphically as sets of overlapping classes in a multidimensional space of measured elemental intensities. To discriminate between classes of various materials, decision-tree and pattern recognition algorithms were studied. Results of application of these methods to data sets obtained for a pulsed 14-MeV neutron generator based active interrogation system are discussed.

  11. Measurement of the n-p elastic scattering angular distribution at E{sub n}=14.9 MeV

    SciTech Connect

    Boukharouba, N.; Bateman, F. B.; Carlson, A. D.; Brient, C. E.; Grimes, S. M.; Massey, T. N.; Haight, R. C.; Carter, D. E.

    2010-07-15

    The relative differential cross section for the elastic scattering of neutrons by protons was measured at an incident neutron energy E{sub n}=14.9 MeV and for center-of-mass scattering angles ranging from about 60 deg. to 180 deg. Angular distribution values were obtained from the normalization of the integrated data to the n-p total elastic scattering cross section. Comparisons of the normalized data to the predictions of the Arndt et al. phase-shift analysis, those of the Nijmegen group, and with the ENDF/B-VII.0 evaluation are sensitive to the value of the total elastic scattering cross section used to normalize the data. The results of a fit to a first-order Legendre polynomial expansion are in good agreement in the backward scattering hemisphere with the predictions of the Arndt et al. phase-shift analysis, those of the Nijmegen group, and to a lesser extent, with the ENDF/B-VII.0 evaluation. A fit to a second-order expansion is in better agreement with the ENDF/B-VII.0 evaluation than with the other predictions, in particular when the total elastic scattering cross section given by Arndt et al. and the Nijmegen group is used to normalize the data. A Legendre polynomial fit to the existing n-p scattering data in the 14 MeV energy region, excluding the present measurement, showed that a best fit is obtained for a second-order expansion. Furthermore, the Kolmogorov-Smirnov test confirms the general agreement in the backward scattering hemisphere and shows that significant differences between the database and the predictions occur in the angular range between 60 deg. and 120 deg. and below 20 deg. Although there is good overall agreement in the backward scattering hemisphere, more precision small-angle scattering data and a better definition of the total elastic cross section are needed for an accurate determination of the shape and magnitude of the angular distribution.

  12. Calculated shielding characteristics of eight materials for neutrons and secondary photons produced by monoenergetic source neutrons with energies less than 400 MeV

    SciTech Connect

    Nakanishi, Noriyoshi; Shikata, Takashi; Fujita, Shin; Kosako, Toshiso

    1995-10-01

    Shielding characteristics of iron, lead, ordinary concrete, heavy concrete, graphite, marble, water, and paraffin were calculated for monoenergetic source neutrons with energies < 400 MeV. The depth dependence of neutron and secondary photon transmitted dose equivalents at the exit surfaces of shields of varying thickness is exhibited for some monoenergetic source neutrons and for each material. Their shielding characteristics are compared and discussed in terms of the degradation process of neutron energy and the change of neutron spectrum in typical shielding materials. Calculations were carried out by using the one-dimensional discrete ordinates code ANISN-JR and the cross-section library DLC-87/HILO. Systematic knowledge concerning the shielding of neutrons with energies < 400 MeV was successfully obtained.

  13. Experimental verification of a method to create a variable energy neutron beam from a monoenergetic, isotropic source using neutron elastic scatter and time of flight

    NASA Astrophysics Data System (ADS)

    Whetstone, Zachary D.; Flaska, Marek; Kearfott, Kimberlee J.

    2016-08-01

    An experiment was performed to determine the neutron energy of near-monoergetic deuterium-deuterium (D-D) neutrons that elastically scatter in a hydrogenous target. The experiment used two liquid scintillators to perform time of flight (TOF) measurements to determine neutron energy, with the start detector also serving as the scatter target. The stop detector was placed 1.0 m away and at scatter angles of π/6, π/4, and π/3 rad, and 1.5 m at a scatter angle of π/4 rad. When discrete 1 ns increments were implemented, the TOF peaks had estimated errors between -21.2 and 3.6% relative to their expected locations. Full widths at half-maximum (FWHM) ranged between 9.6 and 20.9 ns, or approximately 0.56-0.66 MeV. Monte Carlo simulations were also conducted that approximated the experimental setup and had both D-D and deuterium-tritium (DT) neutrons. The simulated results had errors between -17.2 and 0.0% relative to their expected TOF peaks when 1 ns increments were applied. The largest D-D and D-T FWHMs were 26.7 and 13.7 ns, or approximately 0.85 and 4.98 MeV, respectively. These values, however, can be reduced through manipulation of the dimensions of the system components. The results encourage further study of the neutron elastic scatter TOF system with particular interest in application to active neutron interrogation to search for conventional explosives.

  14. X-ray and Neutron Scattering of Water.

    PubMed

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

    2016-07-13

    This review article focuses on the most recent advances in X-ray and neutron scattering studies of water structure, from ambient temperature to the deeply supercooled and amorphous states, and of water diffusive and collective dynamics, in disparate thermodynamic conditions and environments. In particular, the ability to measure X-ray and neutron diffraction of water with unprecedented high accuracy in an extended range of momentum transfers has allowed the derivation of detailed O-O pair correlation functions. A panorama of the diffusive dynamics of water in a wide range of temperatures (from 400 K down to supercooled water) and pressures (from ambient up to multiple gigapascals) is presented. The recent results obtained by quasi-elastic neutron scattering under high pressure are compared with the existing data from nuclear magnetic resonance, dielectric and infrared measurements, and modeling. A detailed description of the vibrational dynamics of water as measured by inelastic neutron scattering is presented. The dependence of the water vibrational density of states on temperature and pressure, and in the presence of biological molecules, is discussed. Results about the collective dynamics of water and its dispersion curves as measured by coherent inelastic neutron scattering and inelastic X-ray scattering in different thermodynamic conditions are reported. PMID:27195477

  15. The sup 252 Cf(sf) neutron spectrum in the 5- to 20-MeV energy range

    SciTech Connect

    Marten, H.; Richter, D.; Seeliger, D. ); Fromm, W.D. ); Bottger, R.; Klein, H. )

    1990-11-01

    This paper reports on the {sup 252}Cf neutron spectrum measured at high energies with a miniature ionization chamber and two different NE-213 neutron detectors. The gamma-ray background and the main cosmic background caused by muons were suppressed by applying efficient pulse-shape discrimination. On the basis of two-dimensional spectroscopy of the neutron time-of-flight and scintillation pulse height, the sliding bias method is used to minimize experimental uncertainties. The experimental data, corrected for several systematic influences, confirm earlier results that show negative deviations from a reference Maxwellian distribution with a 1.42-MeV spectrum temperature for neutron energies above 6 MeV. Experimental results of this work are compared with various statistical model approaches to the {sup 252}Cf(sf) neutron spectrum.

  16. Large area double scattering telescope for balloon-borne studies of neutrons and gamma rays

    NASA Technical Reports Server (NTRS)

    Zych, A. D.; Herzo, D.; Koga, R.; Millard, W. A.; Moon, S.; Ryan, J.; Wilson, R.; White, R. S.; Dayton, B.

    1975-01-01

    A large area double scattering telescope for balloon-borne research is described. It measures the flux, energy and direction of 2-100 MeV neutrons and 0.5-30 MeV gamma rays. These measurements are made using time-of-flight and pulse height analysis techniques with two large tanks of mineral oil liquid scintillator. Results from Monte Carlo calculations of the efficiency, energy resolution and angular resolution are presented and the electronics implementation for the processing of 80 photomultiplier tubes signals will be discussed. The detector weighs 800 kg with a large part of this weight being the liquid scintillator (320 kg). It will be flown at 3 mbars for flight durations up to 40 hours. The first flight is planned for Spring, 1975.

  17. Neutron scattering study of a quasi-2D spin-1/2 dimer system Piperazinium Hexachlorodicuprate under hydrostatic pressure

    SciTech Connect

    Hong, Tao; Stock, C.; Cabrera, I.; Broholm, C.; Qiu, Y.; Leao, J. B.; Poulton, S. J.; Copley, J.R.D.

    2010-01-01

    We report inelastic neutron scattering study of a quasi-two-dimensional S=1/2 dimer system piperazinium hexachlorodicuprate under hydrostatic pressure. The spin gap {Delta} becomes softened with the increase of the hydrostatic pressure up to P = 9.0 kbar. The observed threefold degenerate triplet excitation at P = 6.0 kbar is consistent with the theoretical prediction and the bandwidth of the dispersion relation is unaffected within the experimental uncertainty. At P = 9.0 kbar the spin gap is reduced to {Delta} = 0.55 meV from {Delta} = 1.0 meV at ambient pressure.

  18. Neutron total cross section measurements in the energy region from 47 keV to 20 MeV

    SciTech Connect

    Poenitz, W.P.; Whalen, J.F.

    1983-05-01

    Neutron total cross sections were measured for 26 elements. Data were obtained in the energy range from 47 keV to 20 MeV for 11 elements in the range of light-mass fission products. Previously reported measurements for eight heavy and actinide isotopes were extended to 20 MeV. Data were also obtained for Cu (47 keV to 1.4 MeV) and for Sc, Zn, Nd, Hf, and Pt (1.8 to 20 MeV). The present work is part of a continuing effort to provide accurate neutron total cross sections for evaluations and for optical-model parameteriztions. The latter are required for the derivation of other nuclear-data information of importance to applied programs. 37 references.

  19. Pion scattering from polarized sup 15 N at T sub. pi. =164 MeV

    SciTech Connect

    Meier, R.; Boschitz, E.T.; Ritt, S.; Tacik, R.; Wessler, M. Institut fuer Experimentelle Kernphysik der Universitaet Karlsruhe, Karlsruhe ); Konter, J.A.; Mango, S.; Renker, D.; van den Brandt, B. ); Meyer, W.; Thiel, W. ); Mach, R. ); Amaudruz, P.; Johnson, R.R.; Smith, G.R.; Weber, P. University of Britich Columbia, Vancouver, BC )

    1990-11-01

    The analyzing power {ital A}{sub {ital y}} was measured for {pi}{sup +}{endash}{sup 15}{rvec N} elastic scattering at {ital T}{sub {pi}}=164 MeV between 40{degree} and 100{degree} using a polarized {sup 15}NH{sub 3} target. Within the statistical accuracy of the data {ital A}{sub {ital y}}({theta}) was found to be zero over the full angular range. These data together with differential cross sections from the literature are compared with theoretical predictions based on a momentum-space coupled-channel formalism. While the cross section is very well reproduced there are large discrepancies in the analyzing power for which large spin effects are predicted close to the cross-section minima. Possible deficiencies in the theoretical model are discussed.

  20. Low-energy theorems for nucleon-nucleon scattering at Mπ=450 MeV

    NASA Astrophysics Data System (ADS)

    Baru, V.; Epelbaum, E.; Filin, A. A.

    2016-07-01

    We apply the low-energy theorems to analyze the recent lattice QCD results for the two-nucleon system at a pion mass of Mπ≃450 MeV obtained by the NPLQCD Collaboration. We find that the binding energies of the deuteron and dineutron are inconsistent with the low-energy behavior of the corresponding phase shifts within the quoted uncertainties and vice versa. Using the binding energies of the deuteron and dineutron as input, we employ the low-energy theorems to predict the phase shifts and extract the scattering length and the effective range in the S31 and S10 channels. Our results for these quantities are consistent with those obtained by the NPLQCD Collaboration from effective field theory analyses but are in conflict with their determination based on the effective-range approximation.

  1. Scattering of 42 MeV alpha particles from copper-65

    NASA Technical Reports Server (NTRS)

    Stewart, W. M.; Seth, K. K.

    1973-01-01

    Beams of 42-MeV alpha particles were elastically and inelastically scattered from Cu-65 in an attempt to excite states which may be described in terms of an excited core model. Angular distributions were measured for 17 excited states. Seven of the excited states had angular distributions similar to a core quadrupole excitation and eight of the excited states had angular distributions similar to a core octupole excitation. The excited state at 2.858 MeV had an angular distribution which suggests that it may have results from the particle coupling to a two-phonon core state. An extended particle-core coupling calculation was performed and the predicted energy levels and reduced transition probabilities compared to the experimental data. The low lying levels are described quite well and the wavefunctions of these states explain the large spectroscopic factors measured in stripping reactions. For Cu-65 the coupling of the particle to the core is no larger weak as in the simpler model, and configuration mixing results.

  2. Fragility of complexity biophysical systems by neutron scattering

    NASA Astrophysics Data System (ADS)

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

    2006-11-01

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

  3. Birefringent neutron prisms for spin echo scattering angle measurement

    NASA Astrophysics Data System (ADS)

    Pynn, Roger; Fitzsimmons, M. R.; Lee, W. T.; Stonaha, P.; Shah, V. R.; Washington, A. L.; Kirby, B. J.; Majkrzak, C. F.; Maranville, B. B.

    2009-09-01

    In the first decade of the 19th century, an English chemist, William Wollaston, invented an arrangement of birefringent prisms that splits a beam of light into two spatially separated beams with orthogonal polarizations. We have constructed similar devices for neutrons using triangular cross-section solenoids and employed them for Spin Echo Scattering Angle Measurement (SESAME). A key difference between birefringent neutron prisms and their optical analogues is that it is hard to embed the former in a medium which has absolutely no birefringence because this implies the removal of all magnetic fields. We have overcome this problem by using the symmetry properties of the Wollaston neutron prisms and of the overall spin echo arrangement. These symmetries cause a cancellation of Larmor phase aberrations and provide robust coding of neutron scattering angles with simple equipment.

  4. A compact neutron scatter camera for field deployment.

    PubMed

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

    2016-08-01

    We describe a very compact (0.9 m high, 0.4 m diameter, 40 kg) battery operable neutron scatter camera designed for field deployment. Unlike most other systems, the configuration of the sixteen liquid-scintillator detection cells are arranged to provide omnidirectional (4π) imaging with sensitivity comparable to a conventional two-plane system. Although designed primarily to operate as a neutron scatter camera for localizing energetic neutron sources, it also functions as a Compton camera for localizing gamma sources. In addition to describing the radionuclide source localization capabilities of this system, we demonstrate how it provides neutron spectra that can distinguish plutonium metal from plutonium oxide sources, in addition to the easier task of distinguishing AmBe from fission sources. PMID:27587113

  5. Cross sections for neutron-producing reactions induced by 14. 1 MeV neutrons incident on /sup 6/Li, /sup 7/Li, /sup 10/B, /sup 11/B, and carbon

    SciTech Connect

    Drosg, M.; Lisowski, P.W.; Drake, D.M.; Hardekopf, R.A.; Muellner, M.

    1988-10-01

    Using the time-of-flight technique, we have measured neutron emission spectra for /sup 6/Li, /sup 7/Li, /sup 10/B, /sup 11/B and carbon at an incident neutron energy of 14.1 MeV and at 10 angles between 30/degree/ and 143/degree/. Double differential cross sections and their integrated values have been extracted and are presented in tables and graphs. The nonelastic portion of the neutron emission spectra is noticeably higher than expected which may be due to uncertainties in the input library (ENDF/B-IV) used in the Monte Carlo correction for multiple scattering. In particular, the library for /sup 11/B appears to be very unrealistic with an integrated elastic cross section which should be higher by 50%. 20 refs., 1 fig., 12 tabs.

  6. Measurement of the detection efficiency of the KLOE calorimeter for neutrons between 22 and 174 MeV

    NASA Astrophysics Data System (ADS)

    Anelli, M.; Battistoni, G.; Bertolucci, S.; Bini, C.; Branchini, P.; Curceanu, C.; de Zorzi, G.; di Domenico, A.; di Micco, B.; Ferrari, A.; Fiore, S.; Gauzzi, P.; Giovannella, S.; Happacher, F.; Iliescu, M.; Martini, M.; Miscetti, S.; Nguyen, F.; Passeri, A.; Prokofiev, A.; Sala, P.; Sciascia, B.; Sirghi, F.; Klone Collaboration

    2009-01-01

    A prototype of the high-sampling lead-scintillating fiber KLOE calorimeter has been exposed to neutron beams of 21, 46 and 174 MeV, provided by the The Svedberg Laboratory, Uppsala, to test its neutron detection efficiency. The measurement of the neutron detection efficiency of an NE110 scintillator provided a reference calibration. The measured efficiency is larger than what expected considering the scintillator thickness of the KLOE prototype only. This result proves the existence of a contribution from the passive material to neutron detection efficiency, in a high-sampling calorimeter configuration.

  7. A more informative approach for characterization of polymer monolithic phases: small angle neutron scattering/ultrasmall angle neutron scattering.

    PubMed

    Ford, Kathleen M; Konzman, Brian G; Rubinson, Judith F

    2011-12-15

    Neutron scattering techniques have been used frequently to characterize geological specimens and to determine the structures of glasses and of polymers as solutions, suspensions, or melts. Little work has been reported on their application in determining polymers' structural properties relevant to separations. Here, we present a comparison of characterization results from nitrogen porosimetry and from combined small angle neutron scattering (SANS) and ultrasmall angle neutron scattering (USANS) experiments. We show that SANS is extremely sensitive to the pore characteristics. Both approaches can provide information about porosity and pore characteristics, but the neutron scattering techniques provide additional information in the form of the surface characteristics of the pores and their length scales. Fits of the scattering data show that cylindrical pores are present with diameters down to 0.6 μm and that, for length scales down to approxmately 20 Å, the material shows self-similar (fractal) slopes of -3.4 to -3.6. Comparison of these characteristics with other examples from the scattering literature indicate that further investigation of their meaning for chromatographic media is required. PMID:22066706

  8. 196Pt(n,xn yp γ) reactions using spallation neutrons from En=1 to 250 MeV

    NASA Astrophysics Data System (ADS)

    Tavukcu, E.; Bernstein, L. A.; Hauschild, K.; Becker, J. A.; Garrett, P. E.; McGrath, C. A.; McNabb, D. P.; Younes, W.; Chadwick, M. B.; Nelson, R. O.; Johns, G. D.; Mitchell, G. E.

    2001-11-01

    Neutron-induced reactions on 196Pt were studied over the neutron energy range from 1 to 250 MeV. A ``white'' neutron beam was provided by the spallation neutron source of the Weapons Neutron Research facility at the Los Alamos Neutron Science Center. The prompt reaction γ rays were measured with the large-scale Compton-suppressed Ge spectrometer GEANIE. The incident neutron energy was determined by the time-of-flight technique. Excitation functions for γ-ray transitions in 184,186,188,190-196Pt and 189,191,193Ir isotopes are compared with enhanced Hauser-Feshbach reaction modeling, as implemented in the reaction code GNASH. Overall, the model predictions agree well with the measured γ-ray yields. Discrepancies appear, however, due to inadequate discrete-level information in the calculations describing the preequilibrium process.

  9. Inspection of the objects on the sea floor by using 14 MeV tagged neutrons

    SciTech Connect

    Valkovic, V.; Sudac, D.; Obhodas, J.; Matika, D.; Kollar, R.; Nad, K.; Orlic, Z.

    2011-07-01

    Variety of objects found on the sea floor needs to be inspected for the presence of materials which represent the threat to the environment and to the safety of humans. We have demonstrated that the sealed tube 14 MeV neutron generator with the detection of associated alpha particles can be used underwater when mounted inside ROV equipped with the hydraulic legs and variety of sensors for the inspection of such objects for the presence of threat materials. Such a system is performing the measurement by using the NaI gamma detector and an API-120 neutron generator which could be rotated in order to maximize the inspected target volume. The neutron beam intensity during the 10-30 min. measurements is usually 1 x 10{sup 7} n/s in 4{pi}. In this report the experimental results for some of commonly found objects containing TNT explosive or its simulant are presented. The measured gamma spectra are dominant by C, O and Fe peaks enabling the determination of the presence of explosives inside the ammunition shell. Parameters influencing the C/O ratio are discussed in some details. (authors)

  10. Neutron scattering in detwinned SrFe2As2 single crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Song, Yu; Li, Yu; Zhang, Rui; Wang, Weiyi; Man, Haoran; Dai, Pengcheng

    Abstract:Large SrFe2As2 single crystals (2cm) were grown with self-flux method. The basic sample characterizations were described by XRD, MPMS and PPMS. Orthorhombic a along horizontal orientation and b along vertical orientation were determined by X-ray Laue diffraction. The crystals were cut into rectangular pieces along the [1, 1, 0] and [1,-1,0] directions by high precision wire saw. The device for sample detwinning was made of 6061 aluminum alloy with low neutron incoherent scattering cross section. Uniaxial pressure can be applied by a spring along orthorhombic [0, 1, 0] direction by tuning the screw in one end. The pressure can be calculated by the known elasticity coefficient (k = 10.5 N/mm) and the compression of the spring (Δx). Our neutron scattering experiments were carried out using the MAPS at the ISIS in England. Low Energy (such as Ei =80meV) with different temperatures ,especially around (TN = Ts = 193 K) is done in the time-of-fight experiment. It is interesting to find out the pressure induced spin excitation anisotropy. After careful analysis,we conclude that resistivity and spin excitation anisotropies are likely intimately connected. The results also compared with similar experiment in parent BaFe2As2 in Murlin at the ISIS. Keywards: neutron scattering, detwin, SrFe2As2, single crystals Figure 1, Large SrFe2As2 single crystals grown with self-flux method.

  11. Fractal properties of lysozyme: a neutron scattering study.

    PubMed

    Lushnikov, S G; Svanidze, A V; Gvasaliya, S N; Torok, G; Rosta, L; Sashin, I L

    2009-03-01

    The spatial structure and dynamics of hen egg white lysozyme have been investigated by small-angle and inelastic neutron scattering. Analysis of the results was carried using the fractal approach, which allowed determination of the fractal and fracton dimensions of lysozyme, i.e., consideration of the protein structure and dynamics by using a unified approach. Small-angle neutron scattering studies of thermal denaturation of lysozyme have revealed changes in the fractal dimension in the vicinity of the thermal denaturation temperature that reflect changes in the spatial organization of protein. PMID:19391977

  12. Collective microdynamics of liquid lithium: An inelastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskiĭ, N. M.; Novikov, A. G.; Savostin, V. V.

    2010-05-01

    A portion of the dispersion curve for collective modes in liquid lithium has been constructed from experimental data on inelastic scattering of slow neutrons obtained on the DIN-2PI neutron spectrometer (IBR-2 reactor, Joint Institute for Nuclear Research, Dubna, Russia). Measurements have been performed at a temperature of 500 K ( T m (Li) = 453.7 K). The coherent scattering component has been separated from the experimental spectra and analyzed. Information on the characteristics of collective excitations in liquid lithium has been derived.

  13. Proton vibrational dynamics in lithium imide investigated through incoherent inelastic and Compton neutron scattering.

    PubMed

    Pietropaolo, A; Colognesi, D; Catti, M; Nale, A-C; Adams, M A; Ramirez-Cuesta, A J; Mayers, J

    2012-11-28

    In the present study we report neutron spectroscopic measurements on polycrystalline lithium imide, namely, incoherent inelastic neutron scattering at 20 K, and neutron Compton scattering from 10 K up to room temperature. From the former technique the H-projected density of phonon states up to 100 meV is derived, while the latter works out the spherically averaged single-particle (i.e., H, Li, and N) momentum distributions and, from this, the mean kinetic energies. Only for H at the lowest investigated temperature, non-gaussian components of its momentum distribution are detected. However, these components do not seem directly connected to the system anharmonicity, being fully compatible with the simple N-H bond anisotropy. Neutron data are also complemented by ab initio lattice dynamics simulations, both harmonic and, at room temperature, carried out in the framework of the so-called "quantum colored noise thermostat" method. The single-particle mean kinetic energies in lithium imide as a function of temperature show a quite peculiar behavior at the moment not reproduced by ab initio lattice dynamics methods, at least as far as H and Li are concerned. As matter of fact, neither their low temperature values nor their temperature trends can be precisely explained in terms of standard phonon calculations. PMID:23206005

  14. High-Accuracy Analysis of Compton Scattering in Chiral EFT: Proton and Neutron Polarisabilities

    NASA Astrophysics Data System (ADS)

    Griesshammer, Harald W.; Phillips, Daniel R.; McGovern, Judith A.

    2013-10-01

    Compton scattering from protons and neutrons provides important insight into the structure of the nucleon. A new extraction of the static electric and magnetic dipole polarisabilities αE 1 and βM 1 of the proton and neutron from all published elastic data below 300 MeV in Chiral Effective Field Theory shows that within the statistics-dominated errors, the proton and neutron polarisabilities are identical, i.e. no iso-spin breaking effects of the pion cloud are seen. Particular attention is paid to the precision and accuracy of each data set, and to an estimate of residual theoretical uncertainties. ChiEFT is ideal for that purpose since it provides a model-independent estimate of higher-order corrections and encodes the correct low-energy dynamics of QCD, including, for few-nucleon systems used to extract neutron polarisabilities, consistent nuclear currents, rescattering effects and wave functions. It therefore automatically respects the low-energy theorems for photon-nucleus scattering. The Δ (1232) as active degree of freedom is essential to realise the full power of the world's Compton data.Its parameters are constrained in the resonance region. A brief outlook is provided on what kind of future experiments can improve the database. Supported in part by UK STFC, DOE, NSF, and the Sino-German CRC 110.

  15. Neutron-induced fission cross section of 233Pa between 1.0 and 3.0 MeV.

    PubMed

    Tovesson, F; Hambsch, F J; Oberstedt, A; Fogelberg, B; Ramström, E; Oberstedt, S

    2002-02-11

    The energy dependent neutron-induced fission cross section of 233Pa has for the first time been measured directly with monoenergetic neutrons. This nuclide is an important intermediary in a thorium based fuel cycle, and its fission cross section is a key parameter in the modeling of future advanced fuel and reactor concepts. A first experiment resulted in four cross section values between 1.0 and 3.0 MeV, establishing a fission threshold in excess of 1 MeV. Significant discrepancies were found with a previous indirect experimental determination and with model estimates. PMID:11863801

  16. Empirical formula on (n,(3)He) reaction cross sections at 14.6MeV neutrons.

    PubMed

    Yiğit, Mustafa

    2015-11-01

    The systematic behavior of the cross sections of (n,(3)He) nuclear reactions has been studied by various researches at neutron energy of 14.6MeV. A new empirical formula based on the Q-value dependence of the cross sections of the investigated reaction has been proposed. The cross sections obtained from the new formula are compared with the other proposed formulae results and the experimental data. It seems that the present formula based on the Q-value dependence provides the good description for cross sections of neutron-induced (n,(3)He) nuclear reactions at 14.6MeV. PMID:26218596

  17. Experimental study of quasi-elastic scattering of ultracold neutrons

    NASA Astrophysics Data System (ADS)

    Steyerl, A.; Yerozolimsky, B. G.; Serebrov, A. P.; Geltenbort, P.; Achiwa, N.; Pokotilovski, Yu. N.; Kwon, O.; Lasakov, M. S.; Krasnoshchokova, I. A.; Vasilyev, A. V.

    2002-08-01

    Ultracold neutrons (UCN) are lost from traps if they are quasi-elastically scattered from the wall with an energy gain sufficient to exceed the Fermi potential for the wall. Possible mechanisms of a quasi-elastic energy transfer are, for instance, scattering from hydrogen diffusing in an impurity surface layer or on surface waves at a liquid wall. Using two different experimental methods at the UCN source of the Institut Laue-Langevin we have investigated both the energy-gain and the energy-loss side of quasi-elastic UCN scattering on Fomblin grease coated walls. For Fomblin oil and similar new types of oil we report up-scattering data as a function of temperature and energy transfer. These low-temperature oils may be used in an improved measurement of the neutron lifetime, which requires extremely low wall reflection losses.

  18. Polarised neutron scattering from dynamic polarised targets in biology

    NASA Astrophysics Data System (ADS)

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

    1991-10-01

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

  19. Realization of adiabatic Aharonov-Bohm scattering with neutrons

    NASA Astrophysics Data System (ADS)

    Sjöqvist, Erik; Almquist, Martin; Mattsson, Ken; Gürkan, Zeynep Nilhan; Hessmo, Björn

    2015-11-01

    The adiabatic Aharonov-Bohm (AB) effect is a manifestation of the Berry phase acquired when some slow variables take a planar spin around a loop. While the effect has been observed in molecular spectroscopy, direct measurement of the topological phase shift in a scattering experiment has been elusive in the past. Here, we demonstrate an adiabatic AB effect by explicit simulation of the dynamics of unpolarized very slow neutrons that scatter on a long straight current-carrying wire.

  20. Event-Based Processing of Neutron Scattering Data

    SciTech Connect

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

    2015-09-16

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

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

    SciTech Connect

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

    2006-06-14

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

  2. Neutron-induced fission cross sections of 242Pu from 0.3 MeV to 3 MeV

    NASA Astrophysics Data System (ADS)

    Salvador-Castiñeira, P.; Bryś, T.; Eykens, R.; Hambsch, F.-J.; Göök, A.; Moens, A.; Oberstedt, S.; Sibbens, G.; Vanleeuw, D.; Vidali, M.; Pretel, C.

    2015-10-01

    The majority of the next generation of nuclear power plants (GEN-IV) will work in the fast-neutron-energy region, as opposed to present day thermal reactors. This leads to new and more accurate nuclear-data needs for some minor actinides and structural materials. Following those upcoming demands, the Organisation for Economic Cooperation and Development Nuclear Energy Agency performed a sensitivity study. Based on the latter, an improvement in accuracy from the present 20% to 5% is required for the 242Pu(n ,f ) cross section. Within the same project both the 240Pu(n ,f ) cross section and the 242Pu(n ,f ) cross section were measured at the Van de Graaff accelerator of the Joint Research Centre at the Institute for Reference Materials and Measurements, where quasimonoenergetic neutrons were produced in an energy range from 0.3 MeV up to 3 MeV. A twin Frisch-grid ionization chamber has been used in a back-to-back configuration as fission-fragment detector. The 242Pu(n ,f ) cross section has been normalized to three different isotopes: 237Np(n ,f ) , 235U(n ,f ) , and 238U(n ,f ) . A comprehensive study of the corrections applied to the data and the uncertainties associated is given. The results obtained are in agreement with previous experimental data at the threshold region up to 0.8 MeV. The resonance-like structure at 0.8 to 1.1 MeV, visible in the evaluations and in most previous experimental values, was not reproduced with the same intensity in this experiment. For neutron energies higher than 1.1 MeV, the results of this experiment are slightly lower than the Evaluated Nuclear Data File/B-VII.1 evaluation but in agreement with the experiment of Tovesson et al. (2009) as well as Staples and Morley (1998). Finally, for energies above 1.5 MeV, the results show consistency with the present evaluations.

  3. Identification and rejection of scattered neutrons in AGATA

    NASA Astrophysics Data System (ADS)

    Şenyiğit, M.; Ataç, A.; Akkoyun, S.; Kaşkaş, A.; Bazzacco, D.; Nyberg, J.; Recchia, F.; Brambilla, S.; Camera, F.; Crespi, F. C. L.; Farnea, E.; Giaz, A.; Gottardo, A.; Kempley, R.; Ljungvall, J.; Mengoni, D.; Michelagnoli, C.; Million, B.; Palacz, M.; Pellegri, L.; Riboldi, S.; Şahin, E.; Söderström, P. A.; Valiente Dobon, J. J.

    2014-01-01

    γ Rays and neutrons, emitted following spontaneous fission of 252Cf, were measured in an AGATA experiment performed at INFN Laboratori Nazionali di Legnaro in Italy. The setup consisted of four AGATA triple cluster detectors (12 36-fold segmented high-purity germanium crystals), placed at a distance of 50 cm from the source, and 16 HELENA BaF2 detectors. The aim of the experiment was to study the interaction of neutrons in the segmented high-purity germanium detectors of AGATA and to investigate the possibility to discriminate neutrons and γ rays with the γ-ray tracking technique. The BaF2 detectors were used for a time-of-flight measurement, which gave an independent discrimination of neutrons and γ rays and which was used to optimise the γ-ray tracking-based neutron rejection methods. It was found that standard γ-ray tracking, without any additional neutron rejection features, eliminates effectively most of the interaction points due to recoiling Ge nuclei after elastic scattering of neutrons. Standard tracking rejects also a significant amount of the events due to inelastic scattering of neutrons in the germanium crystals. Further enhancements of the neutron rejection was obtained by setting conditions on the following quantities, which were evaluated for each event by the tracking algorithm: energy of the first and second interaction point, difference in the calculated incoming direction of the γ ray, and figure-of-merit value. The experimental results of tracking with neutron rejection agree rather well with GEANT4 simulations.

  4. Neutron-scattering studies of magnetic superconductors

    SciTech Connect

    Sinha, S.K.; Crabtree, G.W.; Hinks, D.G.; Mook, H.A.; Pringle, O.A.

    1982-01-01

    Results obtained in the last few years obtained by neutron diffraction on the nature of the magnetic ordering in magnetic superconductors are reviewed. Emphasis is given to studies of the complex intermediate phase in ferromagnetic superconductors where both superconductivity and ferromagnetism appear to coexist.

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

    SciTech Connect

    William Charlton

    2007-07-01

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

  6. Rat mammary cell survival following irradiation with 14. 3-MeV neutrons

    SciTech Connect

    Mahler, P.A.; Gould, M.N.; DeLuca, P.M. Jr.; Pearson, D.W.; Clifton, K.H.

    1982-08-01

    The survival of rat mammary gland cells irradiated in situ with either single or split doses of 14.3-MeV neutrons was determined by an in vivo transplantation assay. The single-dose data are best fit to the multitarget single-hit model by the parameters D/sub o/ = 97 cGy and n = 0.6 while the split-dose data are best fit by the parameters D/sub o/ = 100 cGy and n = 1.2.Analysis of the combined data sets suggests that the two survival curves are not identical. Comparison of these data with previously published results following irradiation with 250-kVp X rays is reported.

  7. Rat mammary-cell survival following irradiation with 14. 3-MeV neutrons

    SciTech Connect

    Mahler, P.A.; Gould, M.N.; DeLuca, P.M. Jr.; Pearson, D.W.; Clifton, K.H.

    1982-01-01

    The survival of rat mammary gland cells irradiated in situ with either single or split doses of 14.3-MeV neutrons was determined by an in vivo transplantation assay. The single-dose data are best fit to the multitarget single-hit model by the parameters D/sub 0/ = 97 cGy and n = 0.6 while the split-dose data are best fit by the parameters D/sub 0/ = 100 cGy and n = 1.2. Analysis of the combined data sets suggests that the two survival curves are not identical. Comparison of these data with previously published results following irradiation with 250-kVp x-rays is reported.

  8. Radiative capture of polarized neutrons by polarized protons at Tn=183 MeV

    NASA Astrophysics Data System (ADS)

    Xu, G.; Pate, S. F.; Bloch, C.; Vigdor, S. E.; Bowyer, S. M.; Bowyer, T. W.; Jacobs, W. W.; Meyer, H. O.; Pierce, E.; Sowinski, J.; Whiddon, C.; Wissink, S. W.; Jolivette, P. L.; Pickar, M. A.

    1995-12-01

    In order to provide a quantitative test of theoretical calculations incorporating meson-exchange currents and intermediate Δ resonances, we measure the normal-component spin correlation coefficient CNN, the differential cross section dσ/dΩ, and the neutron and proton analyzing powers An and Ap, each as a function of angle, for n-->p-->-->dγ at Tn=183 MeV. Our n-->p-->-->dγ results, combined with the previous cross section and photon asymmetry data collected in the past decade, place quite strong constraints on model calculations. Our data are in excellent agreement with theoretical predictions by Jaus and Woolcock that incorporate meson-exchange and isobar current effects and relativistic corrections, signifying great recent progress in our understanding of these effects in the nucleon-nucleon system.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  10. Small angle neutron scattering from high impact polystyrene

    SciTech Connect

    Pringle, O.A.

    1981-01-01

    High impact polystyrene (HIPS) is a toughened plastic composed of a polystyrene matrix containing a few percent rubber in the form of dispersed 0.1 to 10 micron diameter rubber particles. Some commercial formulations of HIPS include the addition of a few percent mineral oil, which improves the toughness of the plastic. Little is known about the mechanism by which the mineral oil helps toughen the plastic. It is hypothesized that the oil is distributed only in the rubber particles, but whether this hypothesis is correct was not known prior to this work. The size of the rubber particles in HIPS and their neutron scattering length density contrast with the polystyrene matrix cause HIPS samples to scatter neutrons at small angles. The variation of this small angle neutron scattering (SANS) signal with mineral oil content has been used to determine the location of the oil in HIPS. The SANS spectrometer at the University of Missouri Research Reactor Facility (MURR) was used to study plastic samples similar in composition to commercial HIPS. The MURR SANS spectrometer is used to study the small angle scattering of a vertical beam of 4.75 A neutrons from solid and liquid samples. The scattered neutrons are detected in a 54 x 60 cm/sup 2/ position sensitive detector designed and built at MURR. A series of plastic samples of varying rubber and oil content and different rubber domain sizes and shapes were examined on the MURR SANS spectrometer. Analysis of the scattering patterns showed that the mineral oil is about eight to ten times more likely to be found in the rubber particles than in the polystyrene matrix. This result confirmed the hypothesis that the mineral oil is distributed primarily in the rubber particles.

  11. Level Lifetimes in 132,134Xe from Inelastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Peters, E. E.; Chakraborty, A.; Crider, B. P.; Kumar, A.; Prados-Estévez, F. M.; Ashley, S. F.; McEllistrem, M. T.; Yates, S. W.

    2013-10-01

    The stable isotopes of xenon span a region which exhibits an evolution from spherical to gamma-soft behavior; thus the structure of these nuclei may provide insight into the nature of this transition. Highly enriched (>99.9%) 132Xe and 134Xe gases were converted to solid 132XeF2 and 134XeF2, which were used as scattering samples for inelastic neutron scattering measurements at the University of Kentucky Accelerator Laboratory. Lifetimes of levels up to 3.5 MeV in excitation energy in 132Xe and 134Xe were determined using the Doppler-shift attenuation method. New transitions and levels have been observed and reduced transition probabilities have also been determined. This new information will be examined in an effort to elucidate the structure of these two transitional nuclei. This material is based upon work supported by the U.S. National Science Foundation under grant no. PHY-0956310.

  12. Characterization of a Thermo Scientific D711 D-T neutron generator located in a low-scatter facility

    SciTech Connect

    Hayes, John W.; Finn, Erin; Greenwood, Larry; Wittman, Rick

    2014-03-01

    A dosimetry experiment used to measure the neutron flux and spectrum of a D-T neutron generator is presented. The D-T generator at Pacific Northwest National Laboratory is installed in the middle of a large room to minimize scatter of neutrons back to the sample. The efficacy of maintaining a pure fast neutron field for the sample is investigated. Twenty-one positions within 13 cm of the neutron source contained foils or wires of Fe, Ni, Al with additional Au, and In monitors at some locations. Spectral adjustment of the neutron flux at each position based on measured reaction rates and theoretical Monte Carlo calculations show that at least 99.1% of the spectrum lies above 110 keV for all measured positions, and neutrons above 14 MeV can account for as much as 91% at locations along the axis of the generator and close to the source. The 14 MeV component drops to 77% in radial positions far from the source. The largest total flux observed was 8.29E+08 n/cm2-s (±1.4%) in the center of the cooling cap, although additional experiments have shown this value could be as high as 1.20E+09 n/cm2-s.

  13. Optimizing Moderator Dimensions for Neutron Scattering at the Spallation Neutron Source

    SciTech Connect

    Zhao, Jinkui; Robertson, Lee; Herwig, Kenneth W; Gallmeier, Franz X; Riemer, Bernie

    2013-01-01

    In this work, we investigate the effect of neutron moderator dimensions on the performance of neutron scattering instruments at the Spallation Neutron Source. In a recent study of the planned second target station at the Spallation Neutron Source (SNS) facility [1,2], we have found that the dimensions of a moderator play a significant role in determining its surface brightness. A smaller moderator may be significantly brighter for a smaller viewing area [4]. One of the immediate implications of this finding is that for modern neutron scattering instrument designs, moderator dimensions and brightness have to be incorporated as an integrated optimization parameter. Here, we establish a strategy of matching neutron scattering instruments with moderators using analytical and Monte Carlo techniques. In order to simplify our treatment, we group the instruments into two broad categories, those with natural collimation and those that use neutron guide systems. We found that the cross-sections of the sample and the neutron guide, respectively, are the deciding factors for choosing the moderator. Beam divergence plays no role as long as it is within the reach of practical constraints. Namely, the required divergence is not too large for the guide or sample to be located close enough to the moderator on an actual spallation source.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  15. A workshop on enhanced national capability for neutron scattering

    SciTech Connect

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

    2009-01-01

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

  16. Immersive Visual Analytics for Transformative Neutron Scattering Science

    SciTech Connect

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

    2016-01-01

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

  17. Time reversal invariance violation in neutron-deuteron scattering

    SciTech Connect

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

    2011-06-15

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

  18. Benchmarking the inelastic neutron scattering soil carbon method

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. 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.

  20. Generalized diffusion equation and analytical expressions to neutron scattering experiments

    NASA Astrophysics Data System (ADS)

    Fa, Kwok Sau

    2014-12-01

    An integro-differential diffusion equation with linear force, based on the continuous time random walk model, is considered. The equation generalizes the ordinary and fractional diffusion equations. Analytical expressions related to neutron scattering experiments are presented and analyzed, which can be used to describe, for instance, biological systems.

  1. Dialkylimidazolium chloroaluminates: Ab initio calculations, Raman and neutron scattering measurements

    SciTech Connect

    Takahasi, S. ); Curtiss, L.A.; Gosztola, D.; Koura, N. ); Loong, C.K.; Saboungi, M.L. . Materials Science Div.)

    1993-04-01

    The Raman and neutron scattering spectra of 46 mol% AlCl[sub 3] -54 mol% 1-ethyl-3-methyl imidazolium chloride (EMIC) and 67 mol% AlCl[sub 3] - 33 mol% EMIC melts are presented. Ab initio molecular orbital calculations have been carried out on structures of chloroaluminate anion and EMI cation and the interaction between anion and cation.

  2. Neutron scattering effects on fusion ion temperature measurements.

    SciTech Connect

    Ziegler, Lee; Starner, Jason R.; Cooper, Gary Wayne; Ruiz, Carlos L.; Franklin, James Kenneth; Casey, Daniel T.

    2006-06-01

    To support the nuclear fusion program at Sandia National Laboratories (SNL), a consistent and verifiable method to determine fusion ion temperatures needs to be developed. Since the fusion temperature directly affects the width in the spread of neutron energies produced, a measurement of the neutron energy width can yield the fusion temperature. Traditionally, the spread in neutron energies is measured by using time-of-flight to convert a spread in neutron energies at the source to a spread in time at detector. One potential obstacle to using this technique at the Z facility at SNL is the need to shield the neutron detectors from the intense bremsstrahlung produced. The shielding consists of eight inches of lead and the concern is that neutrons will scatter in the lead, artificially broaden the neutron pulse width and lead to an erroneous measurement. To address this issue, experiments were performed at the University of Rochester's Laboratory for Laser Energetics, which demonstrated that a reliable ion temperature measurement can be achieved behind eight inches of lead shielding. To further expand upon this finding, Monte Carlo N-Particle eXtended (MCNPX) was used to simulate the experimental geometric conditions and perform the neutron transport. MCNPX was able to confidently estimate results observed at the University of Rochester.

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

    SciTech Connect

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

    2014-11-24

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

  4. Long-Lifetime Low-Scatter Neutron Polarization Target

    SciTech Connect

    Dr. Jonathan M. Richardson

    2004-07-09

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

  5. Thermal-neutron-capture prompt-gamma emission spectra of representative coals. [1. 5 to 11 MeV

    SciTech Connect

    Herzenberg, C L; Olson, I K

    1981-12-01

    Prompt gamma ray emission spectra have been calculated from 1.5 to 11 MeV for a wide range of coal compositions exposed to a thermal neutron flux. These include contributions to the spectra from all of the major and minor elements present in the coals. Characteristics of the spectra are discussed and correlated with the coal compositions.

  6. 207,208Pb(n,xnγ) reactions for neutron energies from 3 to 200 MeV

    NASA Astrophysics Data System (ADS)

    Vonach, H.; Pavlik, A.; Chadwick, M. B.; Haight, R. C.; Nelson, R. O.; Wender, S. A.; Young, P. G.

    1994-10-01

    High-resolution γ-ray spectra from the interaction of neutrons in the energy range from 3 to 200 MeV with 207,208Pb were measured with the white neutron source at the weapons neutron research (WNR) facility at Los Alamos National Laboratory. From these data, excitation functions for prominent γ transitions in 200,202,204,206,207,208Pb were derived from threshold to 200 MeV incident neutron energy. These γ-production cross sections reflect the excitation cross sections for the respective residual nuclei. The results are compared with the predictions of nuclear reaction calculations based on the exciton model for precompound emission, the Hauser-Feshbach theory for compound nucleus decay, and coupled channels calculations to account for direct excitation of collective levels. Good agreement was obtained over the entire energy range covered in the experiment with reasonable model parameters. The results of this work clearly demonstrate that multiple preequilibrium emission has to be taken into account above about 40 MeV, and that the level density model of Ignatyuk, which accounts for the gradual disappearance of shell effects with increasing excitation energy, should be used instead of the Gilbert-Cameron and backshifted Fermi-gas models if excitation energies exceed about 30 MeV. No indication for a reduction of the nuclear moment of inertia below the rigid body value was found.

  7. Code System for NE-213 Unfolding of Neutron Spectra up to 100 MeV with Response Function Error Propagation.

    Energy Science and Technology Software Center (ESTSC)

    1987-09-30

    Version 00 The REFERDOU system can be used to calculate the response function of a NE-213 scintillation detector for energies up to 100 MeV, to interpolate and spread (Gaussian) the response function, and unfold the measured spectrum of neutrons while propagating errors from the response functions to the unfolded spectrum.

  8. Incoherent neutron scattering in acetanilide and three deuterated derivatives

    NASA Astrophysics Data System (ADS)

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

    1991-03-01

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

  9. Nonspecular neutron scattering from highly aligned phospholipid membranes

    NASA Astrophysics Data System (ADS)

    Münster, C.; Salditt, T.; Vogel, M.; Siebrecht, R.; Peisl, J.

    1999-05-01

    We report a neutron scattering study of multilamellar membranes supported on solid substrates. In contrast to previous work, the high degree of orientational alignment allows for a clear distinction between specular and nonspecular reflectivity contributions. In particular, we demonstrate that by using the specific advantages of neutron optics the nonspecular scattering can be mapped over a wide range of reciprocal space. Several orders of magnitude in scattering signal and parallel momentum transfer can easily be recorded in multilamellar stacks of lipid membranes. This opens up the possibility to study fluctuations, and more generally lateral structure parameters of membrane on length scales between a few Å up to several μm. The first results obtained for a system of partially hydrated 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) indicate strong deviations from the predictions of the standard Caillé model.

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

    NASA Astrophysics Data System (ADS)

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

    2003-06-01

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

  11. Study on neutron scattering in light water

    NASA Astrophysics Data System (ADS)

    Scotta, Juan Pablo; Marquez Damian, Ignacio; Noguere, Gilles; Bernard, David

    2016-03-01

    It is presented a method to produce covariance matrices of the light water total cross section from thermal scattering laws of the JEFF-3.1.1 nuclear data library and CAB model. The generalized least square method was used to fit the LEAPR module parameters of the processing tool NJOY with light water experimental transmission measurements at 293.6K with CONRAD code. The marginalization technique was applied to account for systematic uncertainties.

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

    SciTech Connect

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

    2013-12-15

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

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

    PubMed

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

    2013-12-01

    In this work, we investigate the effect of neutron moderator dimensions on the performance of neutron scattering instruments at the Spallation Neutron Source (SNS). In a recent study of the planned second target station at the SNS facility, we have found that the dimensions of a moderator play a significant role in determining its surface brightness. A smaller moderator may be significantly brighter over a smaller viewing area. One of the immediate implications of this finding is that for modern neutron scattering instrument designs, moderator dimensions and brightness have to be incorporated as an integrated optimization parameter. Here, we establish a strategy of matching neutron scattering instruments with moderators using analytical and Monte Carlo techniques. In order to simplify our treatment, we group the instruments into two broad categories: those with natural collimation and those that use neutron guide systems. For instruments using natural collimation, the optimal moderator selection depends on the size of the moderator, the sample, and the moderator brightness. The desired beam divergence only plays a role in determining the distance between sample and moderator. For instruments using neutron optical systems, the smallest moderator available that is larger than the entrance dimension of the closest optical element will perform the best (assuming, as is the case here that smaller moderators are brighter). PMID:24387465

  14. Wide-angle mechanical velocity selection for scattered neutrons in inelastic neutron spectrometers

    NASA Astrophysics Data System (ADS)

    Mamontov, E.

    2014-09-01

    We have analyzed the performance of the proposed mechanical device suitable for wide-angle velocity selection of neutrons scattered at the sample position in inelastic neutron spectrometers. The proposed wide-angle velocity selector (WAVES) is essentially a collimator that rotates about the vertical axis passing through the sample position, whose blades are not radial, but instead shaped to optimize the transmission of neutrons of the targeted velocity. The rotation phase of the selector does not need to be synchronized with the incident beam pulses, as long as the incident neutrons can reach the sample position, which greatly simplifies the selector control and makes it suitable for neutron spectrometers at both pulsed and steady sources. We discuss applications of the proposed selector in various types of the inverted-geometry neutron spectrometers.

  15. γ production and neutron inelastic scattering cross sections for 76Ge

    NASA Astrophysics Data System (ADS)

    Rouki, C.; Domula, A. R.; Drohé, J. C.; Koning, A. J.; Plompen, A. J. M.; Zuber, K.

    2013-11-01

    The 2040.7-keV γ ray from the 69th excited state of 76Ge was investigated in the interest of Ge-based double-β-decay experiments like the Germanium Detector Array (GERDA) experiment. The predicted transition could interfere with valid 0νββ events at 2039.0 keV, creating false signals in large-volume 76Ge enriched detectors. The measurement was performed with the Gamma Array for Inelastic Neutron Scattering (GAINS) at the Geel Electron Linear Accelerator (GELINA) white neutron source, using the (n,n'γ) technique and focusing on the strongest γ rays originating from the level. Upper limits obtained for the production cross section of the 2040.7-keV γ ray showed no possible influence on GERDA data. Additional analysis of the data yielded high-resolution cross sections for the low-lying states of 76Ge and related γ rays, improving the accuracy and extending existing data for five transitions and five levels. The inelastic scattering cross section for 76Ge was determined for incident neutron energies up to 2.23 MeV, significantly increasing the energy range for which experimental data are available. Comparisons with model calculations using the talys code are presented indicating that accounting for the recently established asymmetric rotor structure should lead to an improved description of the data.

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

    SciTech Connect

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

    1998-12-31

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

  17. The GDT-based 14MeV neutron source for fission fuel systems

    NASA Astrophysics Data System (ADS)

    Ivanov, Alexander

    2009-11-01

    The gas dynamic trap (GDT) is an axisymmetric mirror device with a high mirror ratio and with a mirror to mirror length exceeding a mean free path for the ion scattering into loss cone. A version of GDT with multi-component plasma was proposed for generation of high D-T neutron flux in localized zones to serve the needs of fusion material tests [1]. Conceptual studies demonstrated that the D-T neutron flux would reach ˜2MW/m^2 in these zones if the device consumes 60MW. This approach can only be realized if the high beta plasma in the GDT with anisotropic fast ions is stable against MHD and kinetic instabilities. This has been already proven both theoretically and experimentally. Recently, application of the GDT neutron source as a driver for a fission --fusion hybrid and minor actinides burner was considered. This requires certain modifications to be introduced into the initial approach, since then overall efficiency of the driver becomes important. These physical and technical modifications are discussed in the paper. [4pt] [1] I.A.Kotelnikov,V.V.Mirnov, V.P.Nagorny, D.D.Ryutov, In: Plasma Phys. Controll. Fusion Res., 2, IAEA, Vienna, p.309, 1985

  18. FEASIBILITY OF MEASURING IRON IN VIVO USING FAST 14 MEV NEUTRONS.

    SciTech Connect

    WIELOPOLSKI, L.

    2005-05-01

    In this short report, I reassess the feasibility of measuring iron in vivo in the liver and heart of thalassemia patients undergoing chelation therapy. Despite the multiplicity of analytical methods for analyzing iron, only two, magnetic resonance imaging, and magnetic susceptibility, are suitable for in vivo applications, and these are limited to the liver because of the heart's beat. Previously, a nuclear method, gamma-resonance scattering, offered a quantitative measure of iron in these organs; however, it was abandoned because it necessitated a nuclear reactor to produce the radioactive source. I reviewed and reassessed the status of two alternative nuclear methods, based on iron spectroscopy of gamma rays induced by fast neutron inelastic scattering and delayed activation in iron. Both are quantitative methods with high specificity for iron and adequate penetrating power to measure it in organs sited deep within the human body. My experiments demonstrated that both modalities met the stated qualitative objectives to measure iron. However, neutron dosimetry revealed that the intensity of the neutron radiation field was too weak to reliably assess the minimum detection limits, and to allow quantitative extrapolations to measurements in people. A review of the literature, included in this report, showed that these findings agree qualitatively with the published results, although the doses reported were about three orders-of-magnitude higher than those I used. Reviewing the limitations of the present work, steps were outlined for overcoming some of the shortcomings. Due to a dearth of valid quantitative alternatives for determining iron in vivo, I conclude that nuclear methods remain the only viable option. However, from the lessons learned, further systematic work is required before embarking on clinical studies.

  19. Energy measurement of prompt fission neutrons in 239Pu(n,f) for incident neutron energies from 1 to 200 MeV

    SciTech Connect

    Haight, Robert C; Devlin, Matthew J; Nelson, Ronald O; O' Donnell, John M; Chatillon, Audrey; Granier, Thierry; Taieb, Julien; Belier, Gilbert; Laurent, Benoit; Noda, Shusaku

    2010-01-01

    An experimental campaign was started in 2002 in the framework of a collaboration belween CEA-DAM and the Los Alamos National Laboratory to measure the prompt fission neutron spectra (PFNS) for incident neutron energies from 1 to 200 MeV with consistent error uncertainties over the whole energy range. The prompt neutron spectra in {sup 235,238}U(n,f) and {sup 237}Np(n,f) have been already studied successfully. A first attempt to characterize the prompt neutrons emitted during the fission of the {sup 239}Pu was done in 2007. This contribution will focus on the results obtained during the final experiment to measure the PFNS in {sup 239}Pu(n,f) performed in 2008. Prompt fission neutron spectra in the neutron-induced fission of {sup 239}Pu have been measured for incident neutron energies from 1 to 200 MeV at the Los Alamos Neutron Science Center. Mean energies obtained from the spectra are discussed and compared to theoretical model calculation.

  20. 2009 International Conference on Neutron Scattering (ICNS 2009)

    SciTech Connect

    Gopal Rao, PhD; Gillespie, Donna

    2010-08-05

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

  1. Cross sections of the (n ,p ) reaction on the 78Se and 80Se isotopes measured for 13.73 MeV to 14.77 MeV and estimated for 10 MeV to 20 MeV neutron energies

    NASA Astrophysics Data System (ADS)

    Attar, F. M. D.; Dhole, S. D.; Bhoraskar, V. N.

    2014-12-01

    The cross sections of 78Se(n ,p ) 78As and 80Se(n ,p ) 80As reactions were measured at five neutron energies over the range 13.73 MeV to 14.77 MeV using 56Fe and 19F as monitor elements, respectively. The cross sections were also theoretically estimated using EMPIRE-II and TALYS codes over 10 MeV to 20 MeV neutrons and matched with the experimental cross sections by making proper choice of the model parameters. The theoretical and experimental cross sections of 80Se(n ,p ) 80As reaction are smaller as compared to the 78Se(n ,p ) 78As reaction at each neutron energy. This difference is attributed to the competing 80Se(n ,2 n )79Se and 80Se( n ,α )Ge77m reactions, which effectively decrease the cross sections of 80Se(n ,p ) 80As reaction as compared to that of the 78Se(n ,p ) 78As reaction over the neutron energy range used in the present work. The cross sections of 78Se(n ,p ) 78As and 80Se(n ,p ) 80As reactions estimated by the EMPIRE-II code initially increase but later on decrease with neutron energy, respectively, above 16 MeV and 19 MeV, whereas those estimated by the TALYS code continuously increase with neutron energy. The present results indicate that the trends in the variation of cross section with neutron energy depend on the model used in the calculations. The cross sections of the 80Se(n ,p ) 80As reaction at different neutron energies reported in the present work can be added as a new data in the nuclear data library.

  2. Development of a new method for measurement of neutron detector efficiency up to 20 MeV

    SciTech Connect

    Kornilov, N. V.; Grimes, S. M.; Massey, T. N.; Brient, C. E.; Carter, D. E.; O'Donnell, J. E.; Bateman, F. B.; Carlson, A. D.; Haight, R. C.; Boukharouba, N.

    2014-09-03

    A new approach to neutron detector efficiency has been taken. A neutron detector has been calibrated with a 252Cf source at low energy. The calibration can be extended to energies above 8 MeV based on the 252Cf results. The techniques uses the fact that the cross section for a symmetric reaction with nucleus of atomic number A yielding a final nucleus with atomic number (2A-1) and a neutron A + A → (2A – 1) + n. This reaction must be symmetric about 90° in the center-of-mass system. Furthermore, the laboratory energies for the neutrons at the paired energies differ substantially. Thus, an efficiency known at one of the two angles can be used to determine the efficiency to higher energies or, for a negative Q, to lower neutron energies.

  3. Development of a new method for measurement of neutron detector efficiency up to 20 MeV

    DOE PAGESBeta

    Kornilov, N. V.; Grimes, S. M.; Massey, T. N.; Brient, C. E.; Carter, D. E.; O'Donnell, J. E.; Bateman, F. B.; Carlson, A. D.; Haight, R. C.; Boukharouba, N.

    2014-09-03

    A new approach to neutron detector efficiency has been taken. A neutron detector has been calibrated with a 252Cf source at low energy. The calibration can be extended to energies above 8 MeV based on the 252Cf results. The techniques uses the fact that the cross section for a symmetric reaction with nucleus of atomic number A yielding a final nucleus with atomic number (2A-1) and a neutron A + A → (2A – 1) + n. This reaction must be symmetric about 90° in the center-of-mass system. Furthermore, the laboratory energies for the neutrons at the paired energies differmore » substantially. Thus, an efficiency known at one of the two angles can be used to determine the efficiency to higher energies or, for a negative Q, to lower neutron energies.« less

  4. Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

    SciTech Connect

    Andersson, P. Andersson-Sunden, E.; Sjöstrand, H.; Jacobsson-Svärd, S.

    2014-08-01

    In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm{sup −1}, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful

  5. Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

    NASA Astrophysics Data System (ADS)

    Andersson, P.; Andersson-Sunden, E.; Sjöstrand, H.; Jacobsson-Svärd, S.

    2014-08-01

    In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm-1, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication

  6. Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator.

    PubMed

    Andersson, P; Andersson-Sunden, E; Sjöstrand, H; Jacobsson-Svärd, S

    2014-08-01

    In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm(-1), solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful

  7. Neutron Scattering of Aromatic and Aliphatic Liquids

    PubMed Central

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

    2016-01-01

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

  8. Neutron Scattering of Aromatic and Aliphatic Liquids.

    PubMed

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

    2016-07-01

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

  9. Measurements of the Differential Cross Sections for the Elastic n-{sup 3}H and n-{sup 2}H Scattering at 14.1 MeV by Using an Inertial Confinement Fusion Facility

    SciTech Connect

    Frenje, J. A.; Li, C. K.; Seguin, F. H.; Casey, D. T.; Petrasso, R. D.; McNabb, D. P.; Navratil, P.; Quaglioni, S.; Sangster, T. C.; Glebov, V. Yu; Meyerhofer, D. D.

    2011-09-16

    For the first time the differential cross section for the elastic neutron-triton (n-{sup 3}H) and neutron-deuteron (n-{sup 2}H) scattering at 14.1 MeV has been measured by using an inertial confinement fusion facility. In these experiments, which were carried out by simultaneously measuring elastically scattered {sup 3}H and {sup 2}H ions from a deuterium-tritium gas-filled inertial confinement fusion capsule implosion, the differential cross section for the elastic n-{sup 3}H scattering was obtained with significantly higher accuracy than achieved in previous accelerator experiments. The results compare well with calculations that combine the resonating-group method with an ab initio no-core shell model, which demonstrate that recent advances in ab initio theory can provide an accurate description of light-ion reactions.

  10. Quantifying the information measured by neutron scattering instruments

    SciTech Connect

    Johnson, M.W.

    1997-09-01

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

  11. Lattice dynamics in copper indium diselenide by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Derollez, P.; Fouret, R.; Laamyem, A.; Hennion, B.; Gonzalez, J.

    1999-05-01

    The phonon dispersion curves along the [100] and [001] directions of CuInSe2 have been measured by inelastic neutron scattering. The neutron measurements reveal the uncertainty of optical measurements because of the large absorption of this material. The lattice dynamics is analysed with a rigid ion model: Born-von Karman short range interactions associated with long range electrostatic forces. The calculated dispersion curves are in good agreement with the experiment. The atomic displacements associated with each vibrational mode are used to discuss the optical phonons. The obtained results provide a strong experimental basis from which we can validate the ab initio methods.

  12. Inclusive proton spectra and total reaction cross sections for proton-nucleus scattering at 800 MeV

    SciTech Connect

    McGill, J.A.

    1981-08-01

    Current applications of multiple scattering theory to describe the elastic scattering of medium energy protons from nuclei have been shown to be quite successful in reproducing the experimental cross sections. These calculations use the impulse approximation, wherein the scattering from individual nucleons in the nucleus is described by the scattering amplitude for a free nucleon. Such an approximation restricts the inelastic channels to those initiated by nucleon-nucleon scattering. As a first step in determining the nature of p + nucleus scattering at 800 MeV, both total reaction cross sections and (p,p') inclusive cross sections were measured and compared to the free p + p cross sections for hydrogen, deuterium, calcium 40, carbon 12, and lead 208. It is concluded that as much as 85% of all reactions in a nucleus proceed from interactions with a single nucleon in the nucleus, and that the impulse approximation is a good starting point for a microscopic description of p + nucleus interactions at 800 MeV.

  13. Neutron and Raman scattering studies of surface adsorbed molecular vibrations and bulk phonons in ZrO{sub 2} nanoparticles

    SciTech Connect

    Ozawa, Masakuni; Suzuki, Suguru; Loong, C.K.; Nipko, J.C.

    1996-12-31

    Inelastic neutron scattering was used to study the phonon densities of states of zirconia nanoparticles, the O-H stretch vibrations of physisorbed water molecules, and chemisorbed hydroxyl groups on the surface. Raman scattering was also used to measure the zone-center phonon modes. The observed distinct phonon frequencies and band widths at 10-120 meV reflect the different crystalline symmetries and compositional fluctuations in the small grain and interfacial regions of monoclinic ZrO{sub 2}, tetragonal or mixed cubic and tetragonal rare-earth-modified zirconia. The dynamics of water and hydroxyl groups on varying local structures of these zirconias result in the different frequencies of the O-H stretch vibrations at 400-600 meV.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  15. Neutron-induced fission cross section of 240Pu from 0.5 MeV to 3 MeV

    NASA Astrophysics Data System (ADS)

    Salvador-Castiñeira, P.; Bryś, T.; Eykens, R.; Hambsch, F.-J.; Göök, A.; Moens, A.; Oberstedt, S.; Sibbens, G.; Vanleeuw, D.; Vidali, M.; Pretel, C.

    2015-07-01

    240Pu has recently been pointed out by a sensitivity study of the Organization for Economic Cooperation and Development (OECD) Nuclear Energy Agency (NEA) to be one of the isotopes whose fission cross section lacks accuracy to meet the upcoming needs for the future generation of nuclear power plants (GEN-IV). In the High Priority Request List (HPRL) of the OECD, it is suggested that the knowledge of the 240Pu(n ,f ) cross section should be improved to an accuracy within 1-3 %, compared to the present 5%. A measurement of the 240Pu cross section has been performed at the Van de Graaff accelerator of the Joint Research Center (JRC) Institute for Reference Materials and Measurements (IRMM) using quasi-monoenergetic neutrons in the energy range from 0.5 MeV to 3 MeV. A twin Frisch-grid ionization chamber (TFGIC) has been used in a back-to-back configuration as fission fragment detector. The 240Pu(n ,f ) cross section has been normalized to three different isotopes: 237Np(n ,f ) , 235U (n ,f ) , and 238U (n ,f ) . Additionally, the secondary standard reactions were benchmarked through measurements against the primary standard reaction 235U (n ,f ) in the same geometry. A comprehensive study of the corrections applied to the data and the associated uncertainties is given. The results obtained are in agreement with previous experimental data at the threshold region. For neutron energies higher than 1 MeV, the results of this experiment are slightly lower than the ENDF/B-VII.1 evaluation, but in agreement with the experiments of Laptev et al. (2004) as well as Staples and Morley (1998).

  16. 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.

  17. Inelastic neutron scattering studies of 76Ge and 76Se: relevance to elevance to neutrinoless double-β decay

    NASA Astrophysics Data System (ADS)

    Crider, B. P.; Peters, E. E.; Ross, T. J.; McEllistrem, M. T.; Prados-Estévez, F. M.; Allmond, J. M.; Vanhoy, J. R.; Yates, S. W.

    2015-05-01

    Inelastic neutron scattering measurements were performed at the University of Kentucky Accelerator Laboratory on enriched 76Ge and 76Se scattering samples. From measurements at incident neutron energies from 2.0 to 4.0 MeV, many new levels were identified and characterized in each nucleus; level lifetimes, transition probabilities, multipole mixing ratios, and other properties were determined. In addition, γ-ray cross sections for the 76Ge(n,n'γ) reaction were measured at neutron energies up to 5.0 MeV, with the goal of determining the cross sections of γ rays in 2040-keV region, which corresponds to the region of interest in the neutrinoless double β decay of 76Ge. Gamma rays from the three strongest branches from the 3952-keV level were observed, but the previously reported 2041-keV γ ray was not. Population cross sections across the range of incident neutron energies were determined for the 3952-keV level, resulting in a cross section of ~0.1 mb for the 2041-keV branch using the previously determined branching ratios. Beyond this, the data from these experiments indicate that previously unreported γ rays from levels in 76Ge can be found in the 2039-keV region.

  18. Inelastic neutron scattering studies of Ge-76 and Se-76: relevance to neutrinoless double-beta decay

    SciTech Connect

    Crider, Ben; Peters, Erin; Ross, T.J.; McEllistrem, M; Prados-Estevez, F.; Allmond, James M; Vanhoy, J.R.; Yates, S.W.

    2015-01-01

    Inelastic neutron scattering measurements were performed at the University of Kentucky Accelerator Laboratory on enriched Ge-76 and Se-76 scattering samples. From measurements at incident neutron energies from 2.0 to 4.0 MeV, many new levels were identified and characterized in each nucleus; level lifetimes, transition probabilities, multipole mixing ratios, and other properties were determined. In addition, gamma-ray cross sections for the Ge-76(n,n'gamma) reaction were measured at neutron energies up to 5.0 MeV, with the goal of determining the cross sections of gamma rays in 2040-keV region, which corresponds to the region of interest in the neutrinoless double beta decay of Ge-76. Gamma rays from the three strongest branches from the 3952-keV level were observed, but the previously reported 2041-keV gamma ray was not. Population cross sections across the range of incident neutron energies were determined for the 3952-keV level, resulting in a cross section of similar to 0.1 mb for the 2041-keV branch using the previously determined branching ratios. Beyond this, the data from these experiments indicate that previously unreported gamma rays from levels in Ge-76 can be found in the 2039-keV region.

  19. Production of neutrons up to 18 MeV in high-intensity, short-pulse laser matter interactions

    SciTech Connect

    Higginson, D. P.; McNaney, J. M.; Swift, D. C.; Mackinnon, A. J.; Patel, P. K.; Petrov, G. M.; Davis, J.; Frenje, J. A.; Jarrott, L. C.; Tynan, G.; Beg, F. N.; Kodama, R.; Nakamura, H.; Lancaster, K. L.

    2011-10-15

    The generation of high-energy neutrons using laser-accelerated ions is demonstrated experimentally using the Titan laser with 360 J of laser energy in a 9 ps pulse. In this technique, a short-pulse, high-energy laser accelerates deuterons from a CD{sub 2} foil. These are incident on a LiF foil and subsequently create high energy neutrons through the {sup 7}Li(d,xn) nuclear reaction (Q = 15 MeV). Radiochromic film and a Thomson parabola ion-spectrometer were used to diagnose the laser accelerated deuterons and protons. Conversion efficiency into protons was 0.5%, an order of magnitude greater than into deuterons. Maximum neutron energy was shown to be angularly dependent with up to 18 MeV neutrons observed in the forward direction using neutron time-of-flight spectrometry. Absolutely calibrated CR-39 detected spectrally integrated neutron fluence of up to 8 x 10{sup 8} n sr{sup -1} in the forward direction.

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

    SciTech Connect

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

    2014-01-14

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

  1. Solid phases of spatially nanoconfined oxygen: a neutron scattering study.

    PubMed

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

    2014-01-14

    We present a comprehensive neutron scattering study on solid oxygen spatially confined in 12 nm wide alumina nanochannels. Elastic scattering experiments reveal a structural phase sequence known from bulk oxygen. With decreasing temperature cubic γ-, orthorhombic β- and monoclinic α-phases are unambiguously identified in confinement. Weak antiferromagnetic ordering is observed in the confined monoclinic α-phase. Rocking scans reveal that oxygen nanocrystals inside the tubular channels do not form an isotropic powder. Rather, they exhibit preferred orientations depending on thermal history and the very mechanisms, which guide the structural transitions. PMID:24437900

  2. Contrast variation in spin-echo small angle neutron scattering

    SciTech Connect

    Chen, Wei-Ren; Herwig, Kenneth W; Li, Xin; Liu, Emily; Liu, Yun; Pynn, Roger; Robertson, J. L.; Shew, Chwen-Yang; Smith, Gregory Scott; Wu, Bin

    2012-01-01

    The principle of using contrast variation spin-echo small angle neutron scattering (SESANS) technique for colloidal structural investigation is discussed. Based on the calculations of several model systems, we find that the contrast variation SESANS technique is not sensitive in detecting the structural characteristics of colloidal suspensions consisting of particles with uniform scattering length density profiles. However, its capability of resolving the structural heterogeneity, at both intra- and inter-colloidal length scales, is clearly demonstrated. The prospect of using this new technique to investigate the structural information that is difficult to be probed by other ways is also explored.

  3. Quasi-elastic neutron scattering studies of protein dynamics

    SciTech Connect

    Rorschach, H.E.

    1993-05-25

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

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

    NASA Astrophysics Data System (ADS)

    Marcucci, L. E.; Machleidt, R.

    2014-11-01

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

  5. Diffraction limit of the theory of multiple small-angle neutron scattering by a dense system of scatterers

    NASA Astrophysics Data System (ADS)

    Dzheparov, F. S.; Lvov, D. V.

    2016-02-01

    Multiple small-angle neutron scattering by a high-density system of inhomogeneities has been considered. A combined approach to the analysis of multiple small-angle neutron scattering has been proposed on the basis of the synthesis of the Zernike-Prince and Moliére formulas. This approach has been compared to the existing multiple small-angle neutron scattering theory based on the eikonal approximation. This comparison has shown that the results in the diffraction limit coincide, whereas differences exist in the refraction limit because the latter theory includes correlations between successive scattering events. It has been shown analytically that the existence of correlations in the spatial position of scatterers results in an increase in the number of unscattered neutrons. Thus, the narrowing of spectra of multiple small-angle neutron scattering observed experimentally and in numerical simulation has been explained.

  6. Accurate Development of Thermal Neutron Scattering Cross Section Libraries

    SciTech Connect

    Hawari, Ayman; Dunn, Michael

    2014-06-10

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

  7. 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.

  8. Bragg optics computer codes for neutron scattering instrument design

    SciTech Connect

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

    1997-09-01

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

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

    SciTech Connect

    Hayter, J.B.

    1987-01-01

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

  10. 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.

  11. Small-angle neutron scattering from micellar solutions

    NASA Astrophysics Data System (ADS)

    Aswal, V. K.; Goyal, P. S.

    2004-07-01

    Micellar solutions are the suspension of the colloidal aggregates of the sur- factant molecules in aqueous solutions. The structure (shape and size) and the interaction of these aggregates, referred to as micelles, depend on the molecular architecture of the surfactant molecule, presence of additives and the solution conditions such as tempera- ture, concentration etc. This paper gives the usefulness of small-angle neutron scattering to the study of micellar solutions with some of our recent results.

  12. Neutron scattering from amorphous, disordered and nanocrystalline materials

    SciTech Connect

    Price, D.L.

    1994-10-01

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

  13. Activation Cross-Sections for 14.2 MeV Neutrons on Molybdenum

    NASA Astrophysics Data System (ADS)

    Srinivasa Rao, C. V.; Lakshmana Das, N.; Thirumala Rao, B. V.; Rama Rao, J.

    1981-12-01

    Using the activation method, the cross-section for the following reactions on molybdenum were measured employing the mixed powder technique and Ge(Li) gamma-ray spectroscopy: 94Mo(n, 2n)93mMo, 3.5 ± 0.5 mbarn; 92Mo(n, 2n)91mMo, 19 ± 3 mbarn; 92Mo(n, 2n)91m+gMo, 226 ± 11 mbarn; 100Mo(n, p)100m2Nb, 9 ± 1 mbarn; 98Mo(n, p)98Nb, 10 ± 1 mbarn; 97Mo(n, p)97mNb, 5 ± 1 mbarn; 96Mo(n, p)96Nb, 12 ± 2 mbarn; 92Mo(n, α)89mZr, 2.1 ± 0.5 mbarn; and 92Mo(n, α)89m+gZr 24 ± 6 mbarn; the neutron energy was 14.2 ± 0.2 MeV. The experimental cross-sections were compared with the predictions of evaporation model and of different versions of pre-equilibrium model. The master equation approach appears to give satisfactory results.

  14. High-Precision Determination of the Neutron Coherent Scattering Length

    PubMed Central

    Wagh, Apoorva G.; Abbas, Sohrab

    2005-01-01

    The neutron coherent scattering length bc has been determined interferometrically to an uncertainty of about 5 × 10−5 by measuring the nondispersive phase. We propose improving the uncertainty to about 10−6 by optimizing various parameters of the interferometric experiment. Any uncertainty in the bc determination arising from possible variations in the constitution of the ambient air can be eliminated by performing the experiment in vacuum. When such uncertainty is attained, it becomes necessary to account for the neutron beam refraction at the sample-ambient interfaces, to infer the correct bc from the observed phase. The formula for the phase used hitherto is approximate and would significantly overestimate bc. The refractive index for neutrons can thus be determined to a phenomenal uncertainty of about 10−12. PMID:27308128

  15. The MCLIB library: Monte Carlo simulation of neutron scattering instruments

    SciTech Connect

    Seeger, P.A.

    1995-09-01

    Monte Carlo is a method to integrate over a large number of variables. Random numbers are used to select a value for each variable, and the integrand is evaluated. The process is repeated a large number of times and the resulting values are averaged. For a neutron transport problem, first select a neutron from the source distribution, and project it through the instrument using either deterministic or probabilistic algorithms to describe its interaction whenever it hits something, and then (if it hits the detector) tally it in a histogram representing where and when it was detected. This is intended to simulate the process of running an actual experiment (but it is much slower). This report describes the philosophy and structure of MCLIB, a Fortran library of Monte Carlo subroutines which has been developed for design of neutron scattering instruments. A pair of programs (LQDGEOM and MC{_}RUN) which use the library are shown as an example.

  16. Scientific opportunities with advanced facilities for neutron scattering

    SciTech Connect

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

    1984-01-01

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

  17. Event-Based Processing of Neutron Scattering Data

    DOE PAGESBeta

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

    2015-09-16

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

  18. Elastic scattering and breakup of 11Be on protons at 26.9 A MeV

    NASA Astrophysics Data System (ADS)

    Chen, J.; Lou, J. L.; Ye, Y. L.; Li, Z. H.; Ge, Y. C.; Li, Q. T.; Li, J.; Jiang, W.; Sun, Y. L.; Zang, H. L.; Aoi, N.; Ideguchi, E.; Ong, H. J.; Ayyad, Y.; Hatanaka, K.; Tran, D. T.; Yamamoto, T.; Tanaka, M.; Suzuki, T.; Tho, N. T.; Rangel, J.; Moro, A. M.; Pang, D. Y.; Lee, J.; Wu, J.; Liu, H. N.; Wen, C.

    2016-03-01

    The elastic scattering and breakup of the halo nucleus 11Be on protons at an incident energy of 26.9 A MeV have been measured. The 11Be+p elastic scattering cross sections at various energies, including the present one, are systematically analyzed with the Chapel Hill 89 (CH89) and Koning-Delaroche (KD) global optical model potentials (OMPs), and the corresponding normalization factors are obtained. An extended version of the continuum-discretized coupled-channels (XCDCC) formalism, including dynamic core excitation effects, is applied to analyze the elastic scattering and breakup data. It is found that the core excitation plays a moderate role in the elastic scattering and breakup reaction of the halo nucleus 11Be, being consistent with previous results at higher energies.

  19. Compton scattering from C12 using tagged photons in the energy range 65-115 MeV

    NASA Astrophysics Data System (ADS)

    Myers, L. S.; Shoniyozov, K.; Preston, M. F.; Anderson, M. D.; Annand, J. R. M.; Boselli, M.; Briscoe, W. J.; Brudvik, J.; Capone, J. I.; Feldman, G.; Fissum, K. G.; Hansen, K.; Henshaw, S. S.; Isaksson, L.; Jebali, R.; Kovash, M. A.; Lewis, K.; Lundin, M.; MacGregor, I. J. D.; Middleton, D. G.; Mittelberger, D. E.; Murray, M.; Nathan, A. M.; Nutbeam, S.; O'Rielly, G. V.; Schröder, B.; Seitz, B.; Stave, S. C.; Weller, H. R.; Compton@Max-Lab Collaboration

    2014-03-01

    Elastic scattering of photons from C12 has been investigated using quasimonoenergetic tagged photons with energies in the range 65-115 MeV at laboratory angles of 60∘, 120∘, and 150∘ at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the 12C(γ ,γ)12C cross section to the bound-nucleon polarizabilities.

  20. Cluster folding model for /sup 12/C(/sup 6/Li,/sup 6/Li) scattering at 156 Mev

    SciTech Connect

    Majka, Z.; Gils, H.J.; Rebel, H.

    1982-06-01

    A double-folding cluster model generated from d-..cap alpha.. and ..cap alpha..-..cap alpha.. interactions and internal cluster wave functions of the projectile and the target nuclei is proposed to describe the differential cross sections for /sup 6/Li elastic scattering from /sup 12/C at 156 MeV. Results of these calculations are compared with standard double-folding models and the phenomenological optical model predictions.

  1. Elastic and inelastic scattering of polarized [sup 6]Li by [sup 26]Mg at 60 MeV

    SciTech Connect

    Ward, R.P.; Clarke, N.M. School of Physics and Space Research, University of Birmingham, Edgbaston, Birmingham B152TT ); Pearce, K.I.; Pinder, C.N. ); Blyth, C.O.; Choi, H.D.; Dee, P.R.; Roman, S.; Tungate, G. ); Davis, N.J. )

    1994-08-01

    Angular distributions of differential cross section and vector analyzing power have been measured for the elastic and inelastic scattering of polarized [sup 6]Li by [sup 26]Mg at 60 MeV bombarding energy. The data have been compared with the results of coupled-channels calculations using phenomenological potentials and coupling strengths derived from inelastic scattering cross-section data and [ital B]([ital E]2) values. The data are reproduced by calculations including couplings between the ground and excited states of the projectile.

  2. Precision neutron interferometric measurement of the n- 3He coherent neutron scattering length

    NASA Astrophysics Data System (ADS)

    Huffman, P. R.; Jacobson, D. L.; Schoen, K.; Arif, M.; Black, T. C.; Snow, W. M.; Werner, S. A.

    2004-07-01

    A measurement of the n- 3He coherent scattering length using neutron interferometry is reported. The result, bc =(5.8572±0.0072) fm , improves the measured precision of any single measurement of bc by a factor of eight; the previous world average, bc =(5.74±0.04) fm , now becomes bc =(5.853±0.007) fm . Measurements of the n-p , n-d , and n- 3He coherent scattering lengths have now been performed using the same technique, thus allowing one to extract the scattering length ratios: parameters that minimize systematic errors. We obtain values of bn 3He / bnp =(-1.5668±0.0021) and bnd / bnp =(-1.7828±0.0014) . Using the new world average value of bc and recent high-precision spin-dependent scattering length data also determined by neutron optical techniques, we extract new values for the bound singlet and triple scattering lengths of b0 =(9.949±0.027) fm and b1 =(4.488±0.017) fm for the n- 3He system. The free nuclear singlet and triplet scattering lengths are a0 =(7.456±0.020) fm and a1 =(3.363±0.013) fm . The coherent scattering cross section is σc =(4.305±0.007) b and the total scattering cross section is σs =(5.837±0.014) b . Comparisons of a0 and a1 to the only existing high-precision theoretical predictions for the n- 3He system, calculated using a resonating group technique with nucleon-nucleon potentials incorporating three-nucleon forces, have been performed. Neutron scattering length measurements in few-body systems are now sensitive enough to probe small effects not yet adequately treated in present theoretical models.

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

    PubMed Central

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

    2015-01-01

    Measurements and calculations of beam attenuation and background scattering for common materials placed in a neutron beam are presented over the temperature range of 300–700 K. Time-of-flight (TOF) measurements have also been made, to determine the fraction of the background that is either inelastic or quasi-elastic scattering as measured with a 3He detector. Other background sources considered include double Bragg diffraction from windows or samples, scattering from gases, and phonon scattering from solids. Background from the residual air in detector vacuum vessels and scattering from the 3He detector dome are presented. The thickness dependence of the multiple scattering correction for forward scattering from water is calculated. Inelastic phonon background scattering at small angles for crystalline solids is both modeled and compared with measurements. Methods of maximizing the signal-to-noise ratio by material selection, choice of sample thickness and wavelength, removal of inelastic background by TOF or Be filters, and removal of spin-flip scattering with polarized beam analysis are discussed. PMID:26306088

  4. Monte Carlo simulations of neutron spectral fluence, radiation weighting factor and ambient dose equivalent for a passively scattered proton therapy unit

    NASA Astrophysics Data System (ADS)

    Zheng, Yuanshui; Fontenot, Jonas; Taddei, Phil; Mirkovic, Dragan; Newhauser, Wayne

    2008-01-01

    Stray neutron exposures pose a potential risk for the development of secondary cancer in patients receiving proton therapy. However, the behavior of the ambient dose equivalent is not fully understood, including dependences on neutron spectral fluence, radiation weighting factor and proton treatment beam characteristics. The objective of this work, therefore, was to estimate neutron exposures resulting from the use of a passively scattered proton treatment unit. In particular, we studied the characteristics of the neutron spectral fluence, radiation weighting factor and ambient dose equivalent with Monte Carlo simulations. The neutron spectral fluence contained two pronounced peaks, one a low-energy peak with a mode around 1 MeV and one a high-energy peak that ranged from about 10 MeV up to the proton energy. The mean radiation weighting factors varied only slightly, from 8.8 to 10.3, with proton energy and location for a closed-aperture configuration. For unmodulated proton beams stopped in a closed aperture, the ambient dose equivalent from neutrons per therapeutic absorbed dose (H*(10)/D) calculated free-in-air ranged from about 0.3 mSv/Gy for a small scattered field of 100 MeV proton energy to 19 mSv/Gy for a large scattered field of 250 MeV proton energy, revealing strong dependences on proton energy and field size. Comparisons of in-air calculations with in-phantom calculations indicated that the in-air method yielded a conservative estimation of stray neutron radiation exposure for a prostate cancer patient.

  5. Testing helicity-dependent γγ → γγ scattering in the region of MeV

    NASA Astrophysics Data System (ADS)

    Homma, K.; Matsuura, K.; Nakajima, K.

    2016-01-01

    Light-by-light scatterings contain rich information on photon coupling to virtual and real particle states. In the context of quantum electrodynamics (QED), photons can couple to a virtual e^+e^- pair. Photons may also couple to known resonance states in the context of quantum chromodyanmics and electroweak dynamics in higher energy domains and possibly couple to unknown resonance states beyond the standard model. The perturbative QED calculations manifestly predict a maximized cross section at the MeV scale; however, no example of exact real-photon-real-photon scattering has yet been observed. Hence, we propose direct measurement with the maximized cross section at the center-of-mass system energy of 1-2 MeV to establish a firm footing at the MeV scale. Given current state of the art high power lasers, helicity-dependent elastic scattering may be observed at a reasonable rate, if a photon-photon collider exploiting γ -rays generated by the inverse nonlinear Compton process with electrons delivered from laser-plasma accelerators (LPA) are properly designed. We show that such verification is feasible in a table-top scale collider, which may be an unprecedented breakthrough in particle accelerators for basic physics research in contrast to energy frontier colliders.

  6. Validity of the relativistic impulse approximation for elastic proton-nucleus scattering at energies lower than 200 MeV

    SciTech Connect

    Li, Z. P.; Hillhouse, G. C.; Meng, J.

    2008-07-15

    We present the first study to examine the validity of the relativistic impulse approximation (RIA) for describing elastic proton-nucleus scattering at incident laboratory kinetic energies lower than 200 MeV. For simplicity we choose a {sup 208}Pb target, which is a spin-saturated spherical nucleus for which reliable nuclear structure models exist. Microscopic scalar and vector optical potentials are generated by folding invariant scalar and vector scattering nucleon-nucleon (NN) amplitudes, based on our recently developed relativistic meson-exchange model, with Lorentz scalar and vector densities resulting from the accurately calibrated PK1 relativistic mean field model of nuclear structure. It is seen that phenomenological Pauli blocking (PB) effects and density-dependent corrections to {sigma}N and {omega}N meson-nucleon coupling constants modify the RIA microscopic scalar and vector optical potentials so as to provide a consistent and quantitative description of all elastic scattering observables, namely, total reaction cross sections, differential cross sections, analyzing powers and spin rotation functions. In particular, the effect of PB becomes more significant at energies lower than 200 MeV, whereas phenomenological density-dependent corrections to the NN interaction also play an increasingly important role at energies lower than 100 MeV.

  7. Use of a small accelerator as a source of 14-MeV neutrons for shielding studies

    SciTech Connect

    Chapman, G.T.; Morgan, G.L.; McConnell, J.W.

    1980-11-01

    It is important in calculating complex shields such as those proposed for the fusion reactors to ascertain that the neutron cross-section data sets used in the calculations are as accurate as possible and that the calculational methods used to transport the neutrons are as reliable as practical. To assure that both these criteria are met, a project at the Oak Ridge National Laboratory (ORNL) is being conducted in which a small accelerator is used to provide 14-MeV neutrons via the T(d,n)/sup 4/He reaction and an NE-213 detector is used to measure the neutron and gamma-ray pulse-height spectra of the radiations transported through and/or created in very thick laminated shields of stainless steel (type 304) and borated polyethylene.

  8. (International Panel on 14 MeV Intense Neutron Source Based on Accelerators for Fusion Materials Study)

    SciTech Connect

    Thoms, K.R.; Wiffen, F.W.

    1991-02-14

    Both travelers were members of a nine-person US delegation that participated in an international workshop on accelerator-based 14 MeV neutron sources for fusion materials research hosted by the University of Tokyo. Presentations made at the workshop reviewed the technology developed by the FMIT Project, advances in accelerator technology, and proposed concepts for neutron sources. One traveler then participated in the initial meeting of the IEA Working Group on High Energy, High Flux Neutron Sources in which efforts were begun to evaluate and compare proposed neutron sources; the Fourth FFTF/MOTA Experimenters' Workshop which covered planning and coordination of the US-Japan collaboration using the FFTF reactor to irradiate fusion reactor materials; and held discussions with several JAERI personnel on the US-Japan collaboration on fusion reactor materials.

  9. Identification of human in vitro cell lines with greater intrinsic cellular radiosensitivity to 62. 5 MeV (p [yields] Be[sup +]) neutrons than 4 MeV photons

    SciTech Connect

    Warenius, H.M.; Browning, P.G.; Morton, I.E. ); Britten, R.A. ); Peacock, J.H. )

    1994-03-01

    The purpose was to identify human in vitro cell lines with a high relative cellular sensitivity to fast neutrons as compared to photons and to examine their relationship to intrinsic photon radiosensitivity and cellular proliferation kinetics. The clonogenic cell survival following exposure to low LET, 4 MeV photons or, high LET, 62.5 MeV (p [yields] Be[sup +]) fast neutrons and the cell survival following exposure to low LET, 4 MeV photons or, high LET, 62.5 MeV (p [yields] Be[sup +]) fast neutrons and the cell kinetic parameters of 30 human in vitro cell lines, covering a wide range of histologies, were analyzed alone and with previously published data of Fertil and Malaise. The relative survival at 1.6 Gy of neutrons (SF[sub 1.6]) compared to 2 Gy of photons (SF[sub 2]) and the cell kinetic parameters of the 30 cell lines were also compared. The relative lethality of 62.5 MeV fast neutrons was assessed by comparing the ratio [alpha] neutrons/[alpha] photons or SF[sub 1.6] neutrons/SF[sub 2] photons to SF[sub 2] photons. Cellular proliferation kinetics were measured by flow cytometry following BrdU incorporation and the relationship of cellular proliferation to relative neutron lethality was measured by comparing the [alpha] neutron/[alpha] photon ratio to the labelling index (LI), potential doubling (T[sub pot]) and ploidy. The majority of cell survival curves obtained following exposure to 62.5 MeV fast neutrons were curvilinear with beta values of similar order to those obtained with low LET 4 MeV photons. Comparison of alpha values for neutrons and photons revealed a relatively neutron sensitive subset of 9 out of 30 in vitro cell lines. This subset was not, however, distinguishable when 1.6 Gy of neutrons was compared to 2 Gy of photons. There was no correlation between cell survival with neutrons or photons and the cell kinetic parameters T[sub pot] or LI or with DNA ploidy. 30 refs., 4 figs., 1 tab.

  10. Observation of 2.45 MeV neutrons correlated with natural atmospheric lightning discharges by Lead-Free Gulmarg Neutron Monitor

    NASA Astrophysics Data System (ADS)

    Ishtiaq, P. M.; Mufti, S.; Darzi, M. A.; Mir, T. A.; Shah, G. N.

    2016-01-01

    The first experimental evidence of detecting the neutrons correlated with the natural atmospheric lightning discharges (NALD) was obtained with Lead-Free Gulmarg Neutron Monitor (LFGNM) operating at High Altitude Research Laboratory, Gulmarg, Kashmir, India, and was reported in the year 1985. The neutron observations still continue with LFGNM. However, the current configuration of LFGNM is the upgraded version of the system used earlier to record neutron bursts (in the recording period of 320 μs in four successive electronic gates of 80 μs each) supposedly originating from an NALD. In the current system the neutron recording time period/interval has been extended to 1260 μs with 63 successive gates of 20 μs each. The system also simultaneously records the differential times—maximum up to 14—between the consecutive strokes of a multistroke lightning flash. The distance between an NALD channel and LFGNM setup is determined empirically by making use of the time delay (td)/time of flight (TOF) measurement of the first detected neutron subsequent to the sensing of the electrostatic field variation caused by the initiation of an NALD in the ambient atmosphere of the LFGNM setup. Assuming a priori incident energy as 2.45 MeV of the detected neutrons supposedly generated due to the fusion of deuterium ions in the lightning discharge channel leads to quantifying the neutron emission flux if the NALD channel distance with respect to the LFGNM setup is established. In this paper we discuss the experiment and the time profiles of several of a large number of the major neutron burst events recorded with LFGNM in association with NALDs. Moreover, a rare and an extraordinary neutron burst event, in terms of its associated "td/TOF" of first detected neutron after triggering, recorded by this system is specifically discussed. In this event, the recorded TOF of 14 μs of the escaping neutron detected by the system immediately after getting triggered by the NALD that struck a

  11. Nuclear physics in the 10--300 MeV energy range using a pulsed white neutron source

    SciTech Connect

    Bowman, C.D.; Wender, S.A.; Auchampaugh, G.F.

    1985-01-20

    A new pulsed white neutron source is under construction at the Los Alamos WNR facility. The neutrons are produced by LAMPF proton micropulses striking thick targets of various materials. Beam parameters include energy of 800 MeV, pulse rate of approximately 50,000 Hz, 0.4 nsec pulse width, average current as high as 6..mu..a, and a useful neutron energy range from 3 to 300 MeV. The facility will receive beam approximately 80% of the time LAMPF is operational; it increases by a factor of 1000 the experimental capability over the present system at the WNR when beam intensity, angular distribution, and availability are taken into account. In addition to established white source techniques, the facility is also highly competitive with monoenergetic sources for a wide class of experiments such as neutron capture ..gamma.. ray spectroscopy and neutron-induced charged particle reactions. The facility should be operational in about nine months. Arrangements are underway to make the facility readily accessible to visiting experiments.

  12. Nuclear physics in the 10 to 300 MeV energy range using a pulsed white neutron source

    SciTech Connect

    Bowman, C.D.; Wender, S.A.; Auchampaugh, G.F.

    1984-01-01

    A new pulsed white neutron source is under construction at the Los Alamos WNR facility. The neutrons are produced by LAMPF proton micropulses striking thick targets of various materials. Beam parameters include energy of 800 MeV, pulse rate of approximately 50,000 Hz, 0.4 nsec pulse width, average current as high as 6..mu..a, and a useful neutron energy range from 3 to 300 MeV. The facility will receive beam approximately 80% of the time LAMPF is operational; it increased by a factor of 1000 the experimental capability over the present system at the WNR when beam intensity, angular distribution, and availability are taken into account. In addition to established white source techniques, the facility is also highly competitive with monoenergetic sources for a wide class of experiments such as neutron capture ..gamma.. ray spectroscopy and neutron-induced charged particle reactions. The facility should be operational in about nine months. Arrangements are underway to make the facility readily accessible to visiting experimenters.

  13. Nuclear physics in the 10-300 MeV energy range using a pulsed white neutron source

    NASA Astrophysics Data System (ADS)

    Bowman, C. D.; Wender, S. A.; Auchampaugh, G. F.

    1985-01-01

    A new pulsed white neutron source is under construction at the Los Alamos WNR facility. The neutrons are produced by LAMPF proton micropulses striking thick targets of various materials. Beam parameters include energy of 800 MeV, pulse rate of approximately 50,000 Hz, 0.4 nsec pulse width, average current as high as 6μa, and a useful neutron energy range from 3 to 300 MeV. The facility will receive beam approximately 80% of the time LAMPF is operational; it increases by a factor of 1000 the experimental capability over the present system at the WNR when beam intensity, angular distribution, and availability are taken into account. In addition to established white source techniques, the facility is also highly competitive with monoenergetic sources for a wide class of experiments such as neutron capture γ ray spectroscopy and neutron-induced charged particle reactions. The facility should be operational in about nine months. Arrangements are underway to make the facility readily accessible to visiting experiments.

  14. Nuclear physics in the 10 to 300 MeV energy range using a pulsed white neutron source

    NASA Astrophysics Data System (ADS)

    Bowman, C. D.; Wender, S. A.; Auchampaugh, G. F.

    A new pulsed white neutron source is under construction at the Los Alamos WNR facility. The neutrons are produced by LAMPF proton micropulses striking thick targets of various materials. Beam parameters include energy of 800 MeV, pulse rate of approximately 50,000 Hz, 0.4 nsec pulse width, average current as high as 6(MU)a, and a useful neutron energy range from 3 to 300 MeV. The facility will receive beam approximately 80% of the time LAMPF is operational; it increased by a factor of 1000 the experimental capability over the present system at the WNR when beam intensity, angular distribution, and availability are taken into account. In addition to established white source techniques, the facility is also highly competitive with monoenergetic sources for a wide class of experiments such as neutron capture (GAMMA) ray spectroscopy and neutron-induced charged particle reactions. The facility should be operational in about nine months. Arrangements are underway to make the facility readily accessible to visiting experimenters.

  15. Development of a gaseous proton-recoil detector for fission cross section measurements below 1 MeV neutron energy

    NASA Astrophysics Data System (ADS)

    Marini, P.; Mathieu, L.; Aïche, M.; Czajkowski, S.; Jurado, B.; Tsekhanovich, I.

    2016-03-01

    The elastic H(n,p) reaction is sometimes used to measure neutron flux, in order to produce high precision measurements. The use of this technique is not straightforward to use below incident neutron energy of 1 MeV, due to a high background in the detected proton spectrum. Experiments have been carried out at the AIFIRA facility to investigate such background and determine its origin and components. Based on these investigations, a gaseous proton-recoil detector has been designed, with a reduced low energy background.

  16. Measurement of neutron spectra generated from bombardment of 4 to 24 MeV protons on a thick {sup 9}Be target and estimation of neutron yields

    SciTech Connect

    Paul, Sabyasachi; Sahoo, G. S.; Tripathy, S. P. E-mail: tripathy@barc.gov.in; Sunil, C.; Bandyopadhyay, T.; Sharma, S. C.; Ramjilal,; Ninawe, N. G.; Gupta, A. K.

    2014-06-15

    A systematic study on the measurement of neutron spectra emitted from the interaction of protons of various energies with a thick beryllium target has been carried out. The measurements were carried out in the forward direction (at 0° with respect to the direction of protons) using CR-39 detectors. The doses were estimated using the in-house image analyzing program autoTRAK-n, which works on the principle of luminosity variation in and around the track boundaries. A total of six different proton energies starting from 4 MeV to 24 MeV with an energy gap of 4 MeV were chosen for the study of the neutron yields and the estimation of doses. Nearly, 92% of the recoil tracks developed after chemical etching were circular in nature, but the size distributions of the recoil tracks were not found to be linearly dependent on the projectile energy. The neutron yield and dose values were found to be increasing linearly with increasing projectile energies. The response of CR-39 detector was also investigated at different beam currents at two different proton energies. A linear increase of neutron yield with beam current was observed.

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

    SciTech Connect

    Alexei Klimenko

    2004-05-01

    The deuterium nucleus is a system of two nucleons (proton and neutron) bound together. The configuration of the system is described by a quantum-mechanical wave function and the state of the nucleons at a given time is not know a priori. However, by detecting a backward going proton of moderate momentum in coincidence with a reaction taking place on the neutron in deuterium, the initial state of that neutron can be inferred if we assume that the proton was a spectator to the reaction. This method, known as spectator tagging, was used to study the electron scattering from high-momentum neutrons in deuterium. The data were taken with a 5.765 GeV polarized electron beam on a deuterium target in Jefferson Laboratory's Hall B, using the CLAS detector. The accumulated data cover a wide kinematic range, reaching values of the invariant mass of the unobserved final state W* up to 3 GeV. A data sample of approximately 5 - 10{sup 5} events, with protons detected at large scattering angles (as high as 136 degrees) in coincidence with the forward electrons, was selected. The product of the neutron structure function with the initial nucleon momentum distribution F{sub 2n}. S was extracted for different values of W*, backward proton momenta p{sub s} and momentum transfer Q{sup 2}. The data were compared to a calculation based on the spectator approximation and using the free nucleon form factors and structure functions. A strong enhancement in the data, not reproduced by the model, was observed at cos(theta{sub pq}) > -0.3 (where theta{sub pq} is the proton scattering angle relative to the direction of the momentum transfer) and can be associated with the contribution of final state interactions (FSI) that were not incorporated into the model. The bound nucleon structure function F{sub 2n} was studied in the region cos(theta{sub pq}) < -0.3 as a function of W* and scaling variable x*. At high spectator proton momenta the struck neutron is far off its mass shell. At p{sub s

  18. Monte Carlo Code System for Calculation of Multiple Scattering of Neutrons in the Resonance Region.

    Energy Science and Technology Software Center (ESTSC)

    1983-01-25

    Version 00 MCRTOF systematically calculates capture and scattering probabilities for neutrons incident on a material disk, with neutron cross sections calculated from the resonance parameters. Capture, front and rear face scattering, transmission, etc., probabilities are obtained from the average destinations of the incident neutrons.

  19. Energy dependence of the optical model of neutron scattering from niobium

    SciTech Connect

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

    1985-05-01

    Neutron differential-elastic-scattering cross sections of niobium were measured from 1.5 to 10.0 MeV at intervals of less than or equal to200 keV below 4.0 MeV, and of approx. =500 keV from 4.0 to 10.0 MeV. Ten to more than fifty differential-cross-section values were determined at each incident energy, distributed over the angular range approx. =20 to 160/sup 0/. The observed values were interpreted in the context of the spherical optical-statistical model. It was found that the volume integral of the real potential decreased with energy whereas the integral of the imaginary part increased. The energy dependence in both cases was consistent with a linear variation. There is a dispersion relationship between the real and imaginary potentials, and when this was used, in conjunction with the experimental imaginary potential, it was possible to predict the observed energy dependence of the real potential to a good degree of accuracy, thus supporting the consistency of the data and its analysis. The real-potential well depths needed to give the correct binding energies of the 2d/sub 5/2/, 3s/sub 1/2/, 2d/sub 3/2/ and 1g/sub 7/2/ particle states and of the 1g/sub 9/2/ hole state are in reasonable agreement with those given by a linear extrapolation of the scattering potential. However, the well depths needed to give the observed binding of the 2p/sub 3/2/, 1f/sub 5/2/ and 2p/sub 1/2/ hole states are about 10% less than the extrapolated values. 40 refs., 5 figs.

  20. Light output and response function of an NE-213 scintillator to neutrons up to 100 MeV

    NASA Astrophysics Data System (ADS)

    Uwamino, Yoshitomo; Shin, Kazuo; Fujii, Masahiko; Nakamura, Takashi

    1982-12-01

    Light output of the NE-213 organic scintillator to 22.6, 27.6 and 48.7 MeV protons were obtained by the analysis of recoil proton spectra by monoenergetic neutron injection into the scintillator. The neutrons were generated by the proton bombardment on a thin lithium target backed with a thick carbon beam stopper. The measured light outputs were slightly smaller than the extrapolation of other works. Birks' semiempirical formula was fitted to these measured data and our previous experimental data of 11.03, 9.01 and 8.05 MeV protons and the formula failed to fit them completely over this wide energy region. A Monte Carlo code to calculate response functions of an NE-213 scintillator was improved by, 1) using these measured light output data, 2) using new cross sections of ENDF/B-IV, O5S and Guerra's compiled data, and 3) replacing the evaporation model of the C(n, p), C(n, pn) and C(n, 2n) reactions with the two-body reaction model. Results of this revised Monte Carlo calculation generally agreed well with the measured response functions of other works. Response functions of a 7.62-cm-diameter by 7.62-cm-long NE-213 scintillator to neutrons of energies up to 100 MeV were calculated by this Monte Carlo code.

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

    SciTech Connect

    Farrer, R.; Longshore, A.

    1995-06-01

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

  2. Large momentum transfer neutron pickup with the (. pi. /sup +/,p) and (p,d) reactions. [90 and 180 MeV, 800 MeV

    SciTech Connect

    Smith, G.R.

    1980-01-01

    The (p,d) reaction was studied for the first time at 800 MeV on seven targets ranging from /sup 7/Li to /sup 40/Ca. The experimental resolution (approx. 400 keV) attained was sufficient to observe many discrete levels in each of the residual nuclei. A modified version of the one-nucleon model successfully describes the magnitude and angular dependence of almost all of the transitions observed. A specific counter example to the two-nucleon model of the reaction mechanism is suggested. The calculations are also sensitive to the neutron single-particle wave function, in accordance with the expectation that the high-momentum components of this wave function are probed at higher bombarding energies. States that have never been seen before were strongly populated in the high excitation region (up to 25 MeV) of some of the residual nuclei. The relative intensities of the other levels observed suggest that coupled-channels mechanisms play an important role for some of these states. Explicit calculations were performed to confirm this for several examples. The first high-resolution measurements of the (..pi../sup +/,p) reaction were also performed on /sup 6/Li, /sup 7/Li, /sup 12/C, and /sup 13/C at pion bombarding energies on and off the pion-nucleon resonance. Calculations employing a one-nucleon model of the reaction mechanism similar to the model successfully used for the (p,d) reaction are unable to account for transitions in the (..pi../sup +/,p) reaction. It is, however, unclear whether this failure is due to a fundamental inadequacy of the model or improper treatment of details in the calculations. A striking similarity was observed in the spectra of the (..pi../sup +/,p) and 800-MeV (p,d) reactions on the same target; this result implies a similar mechanism for the two reactions. 120 references, 97 figures, 15 tables.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  4. 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.

  5. Measurement of the Coherent Neutron Scattering Length of 3He

    PubMed Central

    Ketter, W.; Heil, W.; Badurek, G.; Baron, M.; Loidl, R.; Rauch, H.

    2005-01-01

    By means of neutron interferometry the s-wave neutron scattering length of the 3He nucleus was re-measured at the Institut Laue-Langevin (ILL). Using a skew symmetrical perfect crystal Si-interferometer and a linear twin chamber cell, false phase shifts due to sample misalignment were reduced to a negligible level. Simulation calculations suggest an asymmetrically alternating measuring sequence in order to compensate for systematic errors caused by thermal phase drifts. There is evidence in the experiment’s data that this procedure is indeed effective. The neutron refractive index in terms of Sears’ exact expression for the scattering amplitude has been analyzed in order to evaluate the measured phase shifts. The result of our measurement, b′c = (6.000 ± 0.009) fm, shows a deviation towards a greater value compared to the presently accepted value of b′c = (5.74 ± 0.07) fm, confirming the observation of the partner experiment at NIST. On the other hand, the results of both precision measurements at NIST and ILL exhibit a serious 12σ (12 standard uncertainties) deviation, the reason for which is not clear yet.

  6. The bound coherent neutron scattering lengths of the oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Fischer, Henry E.; Simonson, J. Mike; Neuefeind, Jörg C.; Lemmel, Hartmut; Rauch, Helmut; Zeidler, Anita; Salmon, Philip S.

    2012-12-01

    The technique of neutron interferometry was used to measure the bound coherent neutron scattering length bcoh of the oxygen isotopes 17O and 18O. From the measured difference in optical path between two water samples, either H217O or H218O versus H2natO, where nat denotes the natural isotopic composition, we obtain bcoh,17O = 5.867(4) fm and bcoh,18O = 6.009(5) fm, based on the accurately known value of bcoh,natO = 5.805(4) fm which is equal to bcoh,16O within the experimental uncertainty. Our results for bcoh,17O and bcoh,18O differ appreciably from the standard tabulated values of 5.6(5) fm and 5.84(7) fm, respectively. In particular, our measured scattering-length contrast of 0.204(3) fm between 18O and natO is nearly a factor of 6 greater than the tabulated value, which renders feasible neutron diffraction experiments using 18O isotope substitution and thereby offers new possibilities for measuring the partial structure factors of oxygen-containing compounds, such as water.

  7. The bound coherent neutron scattering length of the oxygen isotopes

    SciTech Connect

    Fischer, Henry E; Simonson, J Michael {Mike}; Neuefeind, Joerg C; Lemmel, Hartmut; Rauch, Helmut; Zeidler, Anita; Salmon, Phil

    2012-01-01

    The technique of neutron interferometry was used to measure the bound coherent neutron scattering length bcoh of the oxygen isotopes 17O and 18O. From the measured difference in optical path between two water samples, either H2 17O or H2 18O versus H2 natO, where nat denotes the natural isotopic composition, we obtain bcoh , 17O = 5.867(4) fm and bcoh , 18O = 6.009(5) fm, based on the accurately known value of bcoh , natO = 5.805(4) fm which is equal to bcoh , 16O within the experimental uncertainty. Our results for bcoh , 17O and bcoh , 18O differ appreciably from the standard tabulated values of 5.6(5) fm and 5.84(7) fm, respectively. In particular, our measured scattering length contrast of 0.204(3) fm between 18O and natO is nearly a factor of 6 greater than the tabulated value, which renders feasible neutron diffraction experiments using 18O isotope substitution and thereby offers new possibilites for measuring the partial structure factors of oxygen-containing compounds, such as water.

  8. Interplay of the elastic and inelastic channels in the 16O+27Al scattering at Elab = 280 MeV

    NASA Astrophysics Data System (ADS)

    Cappuzzello, F.; Nicolosi, D.; Linares, R.; Oliveira, J. R. B.; Lubian, J.; Agodi, C.; Carbone, D.; Cavallaro, M.; de Faria, P. N.; Foti, A.; Rodrigues, M. R. D.

    2016-06-01

    Recent data indicated a nuclear rainbow-like pattern in the elastic scattering of 16O + 27Al at E_{lab}=100 MeV that arises from couplings of the ground to the low-lying states of the 27Al nucleus. Similar effect was identified in the elastic angular distribution of 16O + 12C at E_{lab}=281 and 330 MeV. These experiments show a crucial role of microscopic details of nuclear structure in the elastic scattering of heavy ions at energies well above the Coulomb barrier. In this work we investigate the 16O + 27Al system at E_{lab}=280 MeV for which a coupled channel calculation predicts a pronounced nuclear rainbow-like structure. Obtained experimental data show evidences of an important coupling of the elastic channel to the inelastic. Coupled channel calculations reproduce the experimental angular distributions when a re-normalization factor on the real part of the optical potential is introduced. A proper theoretical approach still requires a high degree of accuracy for the nuclear structure models and new tools to deal with collective excitations.

  9. Electron Scattering From High-Momentum Neutrons in Deuterium

    SciTech Connect

    A.V. Klimenko; S.E. Kuhn

    2005-10-12

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

  10. Irradiation Effect of 14 MeV Neutron on Interlaminar Shear Strength of Glass Fiber Reinforced Plastics

    SciTech Connect

    Nishimura, A.; Hishinuma, Y.; Seo, K.; Tanaka, T.; Muroga, T.; Nishijima, S.; Katagiri, K.; Takeuchi, T.; Shindo, Y.; Ochiai, K.; Nishitani, T.; Okuno, K.

    2006-03-31

    Design activity of International Thermonuclear Experimental Reactor clarifies intense neutron streaming from ports for neutral beam injectors. Energy spectrum of the streaming is very wide and 14 MeV neutron and gamma ray are the typical radiations. Large amount of glass fiber reinforced plastics will be used in a superconducting magnet system as an electric insulation material and a support structure, for such organic material is easy to manufacture, and light and cheap. In this report, effects of 14 MeV neutron and gamma ray irradiation on interlaminar shear strength and fracture mode are investigated using G-10CR small specimen of which configuration was proposed as a standard for evaluation of the interlaminar shear strength. A short beam test under three point bending was conducted at room temperature and 77 K. Neutron fluence of 3.91 x 1019 n/m2 was irradiated and the specimens did not show clear degradation of the strength. On the other hand, gamma ray irradiation of 1 MGy made the specimen weaker and 10 MGy caused delamination. Most of the specimens showed both of interlaminar cracking and bending fracture, but some specimens were fractured with irregular shear occurred on the planes connecting loading point and supporting points.

  11. Experimental characterization of a prototype secondary spectrometer for vertically scattering multiple energy analysis at cold-neutron triple axis spectrometers

    NASA Astrophysics Data System (ADS)

    Toft-Petersen, Rasmus; Groitl, Felix; Kure, Mathias; Lim, Joshua; Čermák, Petr; Alimov, Svyatoslav; Wilpert, Thomas; Le, Manh Duc; Quintero-Castro, Diana; Niedermayer, Christof; Schneidewind, Astrid; Habicht, Klaus

    2016-09-01

    A thorough experimental characterization of a multiplexing backend with multiple energy analysis on a cold-neutron triple axis spectrometer (cTAS) is presented. The prototype employs two angular segments (2 θ -segments) each containing five vertically scattering analyzers (energy channels), which simultaneously probe an energy transfer range of 2 meV at the corresponding two scattering angles. The feasibility and strength of such a vertically scattering multiple energy analysis setup is clearly demonstrated. It is shown, that the energy resolution near the elastic line is comparable to the energy resolution of a standard cTAS. The dispersion relation of the antiferromagnetic excitations in MnF2 has been mapped out by performing constant energy transfer maps. These results show that the tested setup is virtually spurion free. In addition, focusing effects due to (mis)matching of the instrumental resolution ellipsoid to the excitation branch are clearly evident.

  12. Neutron induced fission of 238U at incident neutron energies from 1.2 to 5.8 MeV

    NASA Astrophysics Data System (ADS)

    Vivès, F.; Hambsch, F.-J.; Oberstedt, S.; Barreau, G.; Bax, H.

    1998-10-01

    The reaction 238U(n,f) has been studied at IRMM at different incident neutron energies ranging from En=1.2 to 5.8 MeV. The existence of vibrational resonances in the region of the threshold of the fission cross-section and the proton pairing effect should induce variations in the fission fragment properties. The fission fragment mass, mean total kinetic energy (TKE¯) and angular distributions have been investigated with a double Frisch-gridded ionization chamber. For each incident neutron energy, more than 105 events have been accumulated. The TKE¯ shows an increasing trend up to En=3.5 MeV with a sudden drop at roughly En=3.8 MeV which might be related to the onset of pair breaking. Above En=3.8 MeV TKE¯ is again continually increasing. The two-dimensional mass-TKE distributions have been compared by means of a fit with theoretical calculations performed recently in the frame of the multi-modal random neck-rupture model. Actually, two solutions are possible with assuming either two or three Gaussians for the asymmetric part of the mass distribution. However, both solutions lead to the same physical interpretation. The solution with three Gaussians is more in line with the theoretical predictions. In any case the super-long symmetric mode has to be included, in order to explain the dip in TKE¯ close to symmetry.

  13. High-pressure neutron scattering of Prussian blue analogue magnets

    NASA Astrophysics Data System (ADS)

    Pajerowski, Daniel

    Pressure sensitive magnetism is known to be useful in sensors, and while applications tend to use metallic alloys, molecule based magnets (MBMs) have been shown to have large inverse magnetostrictive (IMS) response. A promising group of MBMs are the Prussian blue analogues (PBAs), in which magnetic ordering can be tuned by external stimuli such as light, electric field, and pressure. Previously, high pressure neutron scattering of nickel hexacyanochromate hydrate has shown direct evidence for isomerization of the cyanide linkage with applied pressure. Other probes have suggested a similar effect in iron hexacyanochromate hydrate, although there has yet to be direct crystallographic evidence. Neutron diffraction is sensitive to organic elements, even while in the presence of metals, and we have performed experiments above 1 GPa to look for linkage isomerism in iron hexacyanochromate. These results are supported by bulk probes and calculations.

  14. Neutron scatter studies of chromatin structures related to functions

    SciTech Connect

    Bradbury, E.M.

    1992-01-01

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

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

    SciTech Connect

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

    1999-10-14

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

  16. Collective aspects of /sup 91/Zr by (d,d/sup prime/) scattering at 17 MeV

    SciTech Connect

    Horodynski-Matsushigue, L.B.; Borello-Lewin, T.; Dietzsch, O.

    1986-05-01

    The /sup 91/Zr(d,d')/sup 91/Zr( reaction has been investigated at 17 MeV incident energy. Up to 4.8 MeV excitation, 73 levels, some of them new, were identified. Angular distributions associated to approx.40 levels were attributed to pure L = 2, 3, or 5 excitations, concentrated in energy regions where the /sup 90/Zr core exhibits 2/sup +/, 3/sup -/, and 5/sup -/ states. The partial deformation parameters ..beta../sub L//sup prime/ obtained show agreement with those from low energy proton scattering for L = 2, but there is a systematic difference for L = 3 and L = 5, which is discussed. Attention is drawn to the high excitation probability of the first excited state of /sup 91/Zr, as measured by the ..beta../sub 2/approx. =0.18 value obtained, a factor of approx.2 above all other values for nuclei with A = 90 +- 2.

  17. Elastic scattering measurements for the system {sup 7}Be+{sup 28}Si at 17.2 MeV

    SciTech Connect

    Sgouros, O.; Pakou, A.; Aslanoglou, X.; Soukeras, V.; Pierroutsakou, D.; Boiano, A.; Mazzocco, M.; Parascandolo, C.; Signorini, C.; Strano, E.; Torresi, D.; Acosta, L.; Marquinez-Duran, G.; Martel, I.; Boiano, C.; Grebosz, J.; Keeley, N.; Strojek, I.; La Commara, M.; Rusek, K.; and others

    2015-02-24

    Elastic scattering of {sup 7}Be+{sup 28}Si was studied at several near barrier energies for probing the energy dependence of the optical potential. Our analysis at 17.2 MeV will be presented in this article and discussed, in terms of Continuum Coupled Channel Calculations (CDCC). This research is part of a long term plan concerning the energy dependence of the optical potential for weakly bound projectiles, at near barrier energies and for probing the potential threshold anomaly. The experiment took place at the EXOTIC facility - Laboratori Nationali di Legnaro (LNL), and refers to an angular distribution measurement, using the detector array EXPADES (Exotic Particle Detection System). Results at 9 MeV (Rutherford region) were also analyzed and were used for estimating the solid angle. Our analysis for other energies is under process.

  18. Elastic scattering measurements for the system 7Be +28Si at 17.2 MeV

    NASA Astrophysics Data System (ADS)

    Sgouros, O.; Pakou, A.; Pierroutsakou, D.; Mazzocco, M.; Acosta, L.; Aslanoglou, X.; Boiano, A.; Boiano, C.; Grebosz, J.; Keeley, N.; La Commara, M.; Marquinez-Duran, G.; Martel, I.; Parascandolo, C.; Rusek, K.; Sánchez-Benítez, A. M.; Signorini, C.; Soukeras, V.; Stiliaris, E.; Strano, E.; Strojek, I.; Torresi, D.

    2015-02-01

    Elastic scattering of 7Be +28Si was studied at several near barrier energies for probing the energy dependence of the optical potential. Our analysis at 17.2 MeV will be presented in this article and discussed, in terms of Continuum Coupled Channel Calculations (CDCC). This research is part of a long term plan concerning the energy dependence of the optical potential for weakly bound projectiles, at near barrier energies and for probing the potential threshold anomaly. The experiment took place at the EXOTIC facility - Laboratori Nationali di Legnaro (LNL), and refers to an angular distribution measurement, using the detector array EXPADES (Exotic Particle Detection System). Results at 9 MeV (Rutherford region) were also analyzed and were used for estimating the solid angle. Our analysis for other energies is under process.

  19. 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.

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

    SciTech Connect

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

    2011-01-15

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

  1. 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.

  2. 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.

  3. Time Delay in Neutron-Alpha Resonant Scattering

    SciTech Connect

    Hoop, Bernard; Hale, Gerald M.

    2011-10-24

    Time delay analysis of neutron-alpha resonant scattering cross sections supports characterization of the lowest 3/2{sup +} level in {sup 5}He as fundamentally an n-{alpha} resonance on the second Riemann energy sheet of both n-{alpha} and deuteron-{sup 3}H channels, with an associated shadow pole on a different unphysical sheet that, through its associated zero on the physical sheet, contributes to the large {sup 4}He(n,d){sup 3}H cross section.

  4. Proton dynamics in bacterial spores, a neutron scattering investigation

    NASA Astrophysics Data System (ADS)

    Colas de la Noue, Alexandre; Peters, Judith; Gervais, Patrick; Martinez, Nicolas; Perrier-Cornet, Jean-Marie; Natali, Francesca

    2015-01-01

    Results from first neutron scattering experiments on bacterial spores are reported. The elastic intensities and mean square displacements have a non-linear behaviour as function of temperature, which is in agreement with a model presenting more pronounced variations at around 330 K (57 ∘C) and 400 K (127 ∘C). Based on the available literature on thermal properties of bacterial spores, mainly referring to differential scanning calorimetry, they are suggested to be associated to main endothermic transitions induced by coat and/or core bacterial response to heat treatment.

  5. Comparison between electron and neutron Compton scattering studies

    NASA Astrophysics Data System (ADS)

    Moreh, Raymond; Finkelstein, Yacov; Vos, Maarten

    2015-05-01

    We compare two techniques: Electron Compton Scattering (ECS) and neutron Compton scattering (NCS) and show that using certain incident energies, both can measure the atomic kinetic energy of atoms in molecules and solids. The information obtained is related to the Doppler broadening of nuclear levels and is very useful for deducing the widths of excited levels in many nuclei in self absorption measurements. A comparison between the atomic kinetic energies measured by the two methods on the same samples is made. Some results are also compared with calculated atomic kinetic energies obtained using the harmonic approximation where the vibrational frequencies were taken from IR/Raman optical measurements. The advantages of the ECS method are emphasized.

  6. The role of neutron scattering in molecular and cellular biology

    NASA Astrophysics Data System (ADS)

    Worcester, D. L.

    1982-09-01

    Neutron scattering measurements of biological macromolecules and materials have provided answers to numerous questions about molecular assemblies and arrangements. Studies of ribosomes, viruses, membranes, and other biological structures are reviewed, with emphasis on the importance of both deuterium labelling and contrast variation with H2O/D2O exchange. Although many studies of biological molecules have been made using contrast variation alone, it is the deuterium labelling experiments that have provided the most precise information and answers to major biological questions. This is largely the result of the low resolution of scattering data and the consequent rapid increase of information content that specific deuterium labelling provides. Procedures for specific deuterium labelling `in vivo' are described for recent work on myelin membranes together with basic aspects of such labelling useful for future research.

  7. Asymptotic neutron scattering laws for anomalously diffusing quantum particles

    NASA Astrophysics Data System (ADS)

    Kneller, Gerald R.

    2016-07-01

    The paper deals with a model-free approach to the analysis of quasielastic neutron scattering intensities from anomalously diffusing quantum particles. All quantities are inferred from the asymptotic form of their time-dependent mean square displacements which grow ∝tα, with 0 ≤ α < 2. Confined diffusion (α = 0) is here explicitly included. We discuss in particular the intermediate scattering function for long times and the Fourier spectrum of the velocity autocorrelation function for small frequencies. Quantum effects enter in both cases through the general symmetry properties of quantum time correlation functions. It is shown that the fractional diffusion constant can be expressed by a Green-Kubo type relation involving the real part of the velocity autocorrelation function. The theory is exact in the diffusive regime and at moderate momentum transfers.

  8. Asymptotic neutron scattering laws for anomalously diffusing quantum particles.

    PubMed

    Kneller, Gerald R

    2016-07-28

    The paper deals with a model-free approach to the analysis of quasielastic neutron scattering intensities from anomalously diffusing quantum particles. All quantities are inferred from the asymptotic form of their time-dependent mean square displacements which grow ∝t(α), with 0 ≤ α < 2. Confined diffusion (α = 0) is here explicitly included. We discuss in particular the intermediate scattering function for long times and the Fourier spectrum of the velocity autocorrelation function for small frequencies. Quantum effects enter in both cases through the general symmetry properties of quantum time correlation functions. It is shown that the fractional diffusion constant can be expressed by a Green-Kubo type relation involving the real part of the velocity autocorrelation function. The theory is exact in the diffusive regime and at moderate momentum transfers. PMID:27475344

  9. The frustrated fcc antiferromagnet Ba2 YOsO6: Structural characterization, magnetic properties and neutron scattering studies

    DOE PAGESBeta

    Kermarrec, E.; Marjerrison, Casey A.; Thompson, C. M.; Maharaj, Dalini D.; Levin, K.; Kroeker, S.; Granroth, Garrett E.; Flacau, Roxana; Yamani, Zahra; Greedan, John E.; et al

    2015-02-26

    Here we report the crystal structure, magnetization, and neutron scattering measurements on the double perovskite Ba2 YOsO6. The Fmmore » $$\\bar{3}$$m space group is found both at 290 K and 3.5 K with cell constants a0=8.3541(4) Å and 8.3435(4) Å, respectively. Os5+ (5d3) ions occupy a nondistorted, geometrically frustrated face-centered-cubic (fcc) lattice. A Curie-Weiss temperature θ ~₋700 K suggests the presence of a large antiferromagnetic interaction and a high degree of magnetic frustration. A magnetic transition to long-range antiferromagnetic order, consistent with a type-I fcc state below TN~69 K, is revealed by magnetization, Fisher heat capacity, and elastic neutron scattering, with an ordered moment of 1.65(6) μB on Os5+. The ordered moment is much reduced from either the expected spin-only value of ~3 μB or the value appropriate to 4d3 Ru5+ in isostructural Ba2 YRuO6 of 2.2(1) μB, suggesting a role for spin-orbit coupling (SOC). Triple-axis neutron scattering measurements of the order parameter suggest an additional first-order transition at T=67.45 K, and the existence of a second-ordered state. We find time-of-flight inelastic neutron results reveal a large spin gap Δ~17 meV, unexpected for an orbitally quenched, d3 electronic configuration. In conclusion, we discuss this in the context of the ~5 meV spin gap observed in the related Ru5+,4d3 cubic double perovskite Ba2YRuO6, and attribute the ~3 times larger gap to stronger SOC present in this heavier, 5d, osmate system.« less

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    SciTech Connect

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

    1995-12-31

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed Central

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

    2013-01-01

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

  14. Intruder structures observed in {sup 122}Te through inelastic neutron scattering

    SciTech Connect

    Hicks, S.F.; Alexander, G.K.; Aubin, C.A.; Burns, M.C.; Collard, C.J.; Walbran, M.M.; Vanhoy, J.R.; Jensen, E.; Garrett, P.E.; Martin, A.; Warr, N.; Kadi, M.; Yates, S.W.

    2005-03-01

    The excited levels of {sup 122}Te to 3.3- MeV excitation have been studied using {gamma}-ray spectroscopy following inelastic neutron scattering. The decay characteristics of these levels have been determined from {gamma}-ray excitation functions, angular distributions at E{sub n}-1.72,2.80, and 3.35 MeV, Doppler shifts, and {gamma}{gamma} coincidences. Electromagnetic transition rates were deduced for many levels, as were multipole-mixing and branching ratios. Level energies and electromagnetic transition rates were compared to interacting boson model (IBM) calculations, both with and without intruder-state mixing, and to particle-core coupling model calculations. The energies of low-lying levels of {sup 122}Te are well described by the IBM with intruder-state mixing calculations, and observed transition rates support emerging intruder bands built on 0{sup +} levels. The other models considered do not produce enough low-lying positive parity states; however, U(5) energies to the four quadrupole-phonon level agree very well with observations when states with large intruder configurations are ignored. Mixed-symmetry and quadrupole-octupole excitations have been investigated, but mixing with other configurations and fragmentation of strength prohibit a clear identification of these states.

  15. Radiation damage induced in Al2O3 single crystal sequentially irradiated with reactor neutrons and 90 MeV Xe ions

    NASA Astrophysics Data System (ADS)

    Zirour, H.; Izerrouken, M.; Sari, A.

    2016-06-01

    The present investigation reports the effect of 90 MeV Xe ion irradiation on neutron irradiated Al2O3 single crystals. Three irradiation experiments were performed, with neutrons only, 90 MeV Xe ions only and with neutrons followed by 90 MeV Xe ions. Neutron and 90 MeV Xe ion irradiations were performed at NUR research reactor, Algiers, Algeria and at GANIL accelerator, Caen, France respectively. After irradiation, the radiation damage was investigated by Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), optical absorption measurements, and X-ray diffraction (XRD) techniques. Raman technique revealed that the concentration of the defects formed in Al2O3 samples subsequently irradiated with neutrons and 90 MeV Xe ions is lower than that formed in Al2O3 samples which were irradiated only with neutrons. This reveals the occurrence of ionization-induced recovery of the neutron damage. Furthermore, as revealed by XRD analysis, a new peak is appeared at about 2θ = 38.03° after irradiation at high fluence (>3 × 1013 Xe/cm2). It can be assigned to the formation of new lattice plane.

  16. High-precision covariant one-boson-exchange potentials for np scattering below 350 MeV

    SciTech Connect

    Franz Gross; Alfred Stadler

    2007-12-01

    All realistic potential models for the two-nucleon interaction are to some extent based on boson exchange. However, in order to achieve an essentially perfect fit to the scattering data, characterized by a chi2/Ndata~ 1, previous potentials have abandoned a pure one boson-exchange mechanism (OBE). Using a covariant theory, we have found a true OBE potential that fits the 2006 world np data below 350 MeV with a chi2/Ndata = 1.00 for 3612 data. Our potential has fewer adjustable parameters than previous high precision potentials, and also reproduces the experimental triton binding energy without introducing additional irreducible three-nucleon forces.

  17. Detailed study of the T = 0, NN interaction via N-italic-arrow-rightP- scattering at 68 MEV

    SciTech Connect

    Henneck, R.; Campbell, J.; Gysin, C.; Hammans, M.; Lorenzon, W.; Pickar, M.A.; Sick, I.; Konter, J.A.; Mango, S.; Van den Brandt, B.; and others

    1988-11-20

    We report on first results for a measurement of the spin correlation parameter A/sub z//sub z/ in n-italic-arrow-rightp-arrow-right scattering at 68 MeV, which is highly sensitive to the mixing parameter epsilon/sub 1/. A phase shift analysis of these data, together with forthcoming results of our measurements of /sup d//sup sigma//sub d//sub ..cap omega../ and A/sub y/ at the same energy is expected to allow a determination of epsilon/sub 1/ to within /similar to/ +- 0.3/sup 0/.

  18. Resonant inelastic X-ray scattering spectrometer with 25meV resolution at the Cu K -edge

    DOE PAGESBeta

    Ketenoglu, Didem; Harder, Manuel; Klementiev, Konstantin; Upton, Mary; Taherkhani, Mehran; Spiwek, Manfred; Dill, Frank-Uwe; Wille, Hans-Christian; Yavaş, Hasan

    2015-06-27

    An unparalleled resolution is reported with an inelastic X-ray scattering instrument at the CuK-edge. Based on a segmented concave analyzer, featuring single-crystal quartz (SiO2) pixels, the spectrometer delivers a resolution near 25meV (FWHM) at 8981eV. Besides the quartz analyzer, the performance of the spectrometer relies on a four-bounce Si(553) high-resolution monochromator and focusing Kirkpatrick–Baez optics. The measured resolution agrees with the ray-tracing simulation of an ideal spectrometer. The performance of the spectrometer is demonstrated by reproducing the phonon dispersion curve of a beryllium single-crystal.

  19. Small-angle neutron scattering of nanocrystalline terbium with random paramagnetic susceptibility.

    PubMed

    Balaji, G; Ghosh, S; Döbrich, F; Eckerlebe, H; Weissmüller, J

    2008-06-01

    We report magnetic small-angle neutron scattering (SANS) data for the nanocrystalline rare earth metal Terbium in its paramagnetic state. Whereas critical scattering dominates at large momentum transfer, q, the (magnetic-) field response of the scattering at small q arises from the spatial nonuniformity of the paramagnetic susceptibility tensor. The finding of an interrelation between SANS and the susceptibility suggests a way for characterizing the nonuniform magnetic interactions in hard magnets by neutron scattering. PMID:18643454

  20. Evaluation of the Doppler-Broadening of Gamma-Ray Spectra from Neutron Inelastic Scattering on Light Nuclei

    SciTech Connect

    Womble, Phillip C.; Barzilov, Alexander; Novikov, Ivan; Howard, Joseph; Musser, Jason

    2009-03-10

    Neutron-induced gamma-ray reactions are extensively used in the nondestructive analysis of materials and other areas where the information about the chemical composition of a substance is crucial. The common technique to find the intensity of the gamma ray is to fit gamma-ray line shape with an analytical function, for example, a Gaussian. However, the Gaussian fitting may fail if the gamma-ray peak is Doppler-broadened since this leads to the miscalculation of the area of the peak and, therefore, to misidentification of the material. Due to momentum considerations, Doppler-broadening occurs primarily with gamma rays from neutron-induced inelastic scattering reactions with light nuclei. The recoiling nucleus of interest must have excited states whose lifetimes are much smaller than the time of flight in the material. We have examined various light nuclei bombarded by 14 MeV neutrons to predict when the peak shape of a neutron-induced gamma ray emitted from these nuclei will be Doppler-broadened. We have found that nearly all the gamma rays from neutron-induced gamma-ray reactions on light elements (A<20) are Doppler-broadened with only a few exceptions. This means that utilization of resolution curves derived from isotopic sources or thermal neutron capture reactions have little value in the analysis.

  1. TANGRA-Setup for the Investigation of Nuclear Fission Induced by 14.1 MeV Neutrons

    NASA Astrophysics Data System (ADS)

    Ruskov, I. N.; Kopatch, Yu. N.; Bystritsky, V. M.; Skoy, V. R.; Shvetsov, V. N.; Hambsch, F.-J.; Oberstedt, S.; Noy, R. Capote; Sedyshev, P. V.; Grozdanov, D. N.; Ivanov, I. Zh.; Aleksakhin, V. Yu.; Bogolubov, E. P.; Barmakov, Yu. N.; Khabarov, S. V.; Krasnoperov, A. V.; Krylov, A. R.; Obhođaš, J.; Pikelner, L. B.; Rapatskiy, V. L.; Rogachev, A. V.; Rogov, Yu. N.; Ryzhkov, V. I.; Sadovsky, A. B.; Salmin, R. A.; Sapozhnikov, M. G.; Slepnev, V. M.; Sudac, D.; Tarasov, O. G.; Valković, V.; Yurkov, D. I.; Zamyatin, N. I.; Zeynalov, Sh. S.; Zontikov, A. O.; Zubarev, E. V.

    The new experimental setup TANGRA (Tagged Neutrons & Gamma Rays), for the investigation of neutron induced nuclear reactions, e.g. (n,xn'), (n,xn'γ), (n,γ), (n,f), on a number of important isotopes for nuclear science and engineering (235,238U, 237Np, 239Pu, 244,245,248Cm) is under construction and being tested at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in Dubna. The TANGRA setup consists of: a portable neutron generator ING-27, with a 64-pixel Si charge-particle detector incorporated into its vacuum chamber for registering of α-particles formed in the T(d, n)4He reaction, as a source of 14.1 MeV steady-state neutrons radiation with an intensity of ∼5x107n/s; a combined iron (Fe), borated polyethylene (BPE) and lead (Pb) compact shielding-collimator; a reconfigurable multi-detector (neutron plus gamma ray detecting system); a fast computer with 2 (x16 channels) PCI-E 100 MHz ADC cards for data acquisition and hard disk storage; Linux ROOT data acquisition, visualization and analysis software. The signals from the α-particle detector are used to 'tag' the neutrons with the coincident α-particles. Counting the coincidences between the α-particle and the reaction-product detectors in a 20ns time-interval improves the effect/background-ratio by a factor of ∼200 as well as the accuracy in the neutron flux determination, which decreases noticeably the overall experimental data uncertainty.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    SciTech Connect

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

    2015-12-21

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

  5. Monte Carlo and analytical model predictions of leakage neutron exposures from passively scattered proton therapy

    SciTech Connect

    Pérez-Andújar, Angélica; Zhang, Rui; Newhauser, Wayne

    2013-12-15

    Purpose: Stray neutron radiation is of concern after radiation therapy, especially in children, because of the high risk it might carry for secondary cancers. Several previous studies predicted the stray neutron exposure from proton therapy, mostly using Monte Carlo simulations. Promising attempts to develop analytical models have also been reported, but these were limited to only a few proton beam energies. The purpose of this study was to develop an analytical model to predict leakage neutron equivalent dose from passively scattered proton beams in the 100-250-MeV interval.Methods: To develop and validate the analytical model, the authors used values of equivalent dose per therapeutic absorbed dose (H/D) predicted with Monte Carlo simulations. The authors also characterized the behavior of the mean neutron radiation-weighting factor, w{sub R}, as a function of depth in a water phantom and distance from the beam central axis.Results: The simulated and analytical predictions agreed well. On average, the percentage difference between the analytical model and the Monte Carlo simulations was 10% for the energies and positions studied. The authors found that w{sub R} was highest at the shallowest depth and decreased with depth until around 10 cm, where it started to increase slowly with depth. This was consistent among all energies.Conclusion: Simple analytical methods are promising alternatives to complex and slow Monte Carlo simulations to predict H/D values. The authors' results also provide improved understanding of the behavior of w{sub R} which strongly depends on depth, but is nearly independent of lateral distance from the beam central axis.

  6. A 14-MeV Intense Neutron Source Based on Muon-Catalyzed Fusion - I: An Advanced Design

    SciTech Connect

    Anisimov, Viatcheslav V.; Arkhangel'sky, Vladimir A.; Ganchuk, Nikolay S.; Yukhimchuk, Arkady A.; Cavalleri, Emanuela; Karmanov, Fedor I.; Konobeyev, Alexander Yu.; Slobodtchouk, Victor I.; Latysheva, Lioudmila N.; Pshenichnov, Igor A.; Ponomarev, Leonid I.; Vecchi, Marcello

    2001-03-15

    The results of the design study of an advanced scheme for the 14-MeV intense neutron source based on muon-catalyzed fusion ({mu}CF) are presented. A pion production target (liquid lithium) and a synthesizer [liquid deuterium-tritium (D-T) mixture] are considered. Negative pions are produced inside a 17/7 T magnetic field by an intense (2-GeV,12-mA) deuteron beam interacting with the 150-cm-long, 0.75-cm-radius lithium target. Muons from the pion decay are collected in the backward direction and stopped in the D-T mixture of the synthesizer. The synthesizer has the shape of a 10-cm-radius sphere surrounded by two 0.03-cm-thick titanium shells. At 100 {mu}CF events/muon, it can produce up to 10{sup 17}n/s of 14-MeV neutrons. A quasi-isotropic neutron flux up to 10{sup 14} n/cm{sup 2}.s{sup -1} can be achieved in the test volume of {approx}2.5 l with an irradiated surface of {approx}350 cm{sup 2}. The thermophysical and thermomechanical analyses show that the technological limits are not exceeded.

  7. Identification of materials hidden inside a container by using the 14 MeV tagged neutron beam

    NASA Astrophysics Data System (ADS)

    Sudac, Davorin; Pesente, Silvia; Nebbia, Giancarlo; Viesti, Giuseppe; Valkovic, Vladivoj

    2007-08-01

    The results of the experiments aiming to confirm the presence of explosive inside the container by using the 14 MeV tagged neutron beam are presented. Measurements were performed with paper, sugar, flour, fertilizer, tobacco and explosive (Semtex1a) as target material placed in the center of an empty container. Additional measurements were done with paper and explosive placed in the center of the container filled with the iron matrix of 0.2 gcm-3 density and with the paper target shielded by the 5.1 cm thick iron shield. The results of time of flight measurements and gamma ray spectra obtained by 14 MeV tagged neutron beam have showed that investigated materials could be well distinguished in the triangle plot with coordinates being the number of counts in the carbon peak, the number of counts in oxygen peak and the number of counts in transmitted neutron peak. By using such presentation we have been able to separate paper from Semtex1a, both hidden inside the 0.2 gcm-3 iron matrix. We have also been able to confirm the presence of 64.4 kg of paper behind the 5.1 cm thick iron shield corresponding to the range of 300 keV X-rays.

  8. A 14 MeV neutron generator as a source of various charged particles produced in fusion reactions

    NASA Astrophysics Data System (ADS)

    Drozdowicz, Krzysztof; Dankowski, Jan; Gabańska, Barbara; Igielski, Andrzej; Janik, Władysław; Kurowski, Arkadiusz; Woźnicka, Urszula

    2014-05-01

    Measuring the energy of ions from the thermonuclear reaction in future energetic tokamaks (like ITER) is important in order to obtain information on the energetic balance in a plasma toroidal column. Detectors made of synthetic diamond can be used for the spectrometry of ions which accompany burning plasma. A fast neutron (14 MeV) generator, which is a linear accelerator of deuterons, is based on the nuclear reaction T(d,n)α in a tritium target. The energy of alpha particles produced in the D-T reaction in the neutron generator is the same (maximum 3.5 MeV) as the energy of alpha particles present in the hot D-T plasma in tokamaks. Other reactions in the target also occur and the energy spectra of various created ions can be also measured. The experiments have been performed with an ion spectrometry made possible with the use of scCVD diamond detectors at the fast neutron generator (IGN-14) at the Institute of Nuclear Physics in Kraków, Poland.

  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 PAGESBeta

    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. The energy dependence of the cosmic-ray neutron leakage flux in the range 0.01-10 MeV.

    NASA Technical Reports Server (NTRS)

    Jenkins, R. W.; Ifedili, S. O.; Lockwood, J. A.; Razdan, H.

    1971-01-01

    Measurement of the cosmic-ray neutron leakage flux and energy spectrum in the range 1 to 10 MeV by a neutron detector on the Ogo 6 satellite from June 7 to Sept. 30, 1969. The same detector simultaneously measured the total leakage flux, having 75% of its response to the leakage flux in the interval from 1 keV to 1 MeV. For a neutron energy spectrum of the form AE to the minus gamma in the range from 1 to 10 MeV, the upper limit to gamma for polar regions was found to be 1.0 and for the equatorial regions was 1.2. For the polar regions, the lower limit to gamma was found to be 0.8. This energy spectrum at 1 to 10 MeV is slightly flatter than Newkirk (1963) predicted.

  12. A laser-Compton scattering prototype experiment at 100 MeV linac of Shanghai Institute of Applied Physics

    SciTech Connect

    Luo, W.; Fan, G. T.; Fan, G. W.; Li, Y. J.; Xu, Y.; Yang, L. F.; Xu, W.; Pan, Q. Y.; Cai, X. Z.; Chen, J. G.; Chen, Y. Z.; Guo, W.; Liu, W. H.; Lin, G. Q.; Ma, Y. G.; Shen, W. Q.; Xu, B. J.; Xu, J. Q.; Zhang, H. O.; Yan, Z.; and others

    2010-01-15

    As a prototype of the Shanghai Laser Electron Gamma Source in the Shanghai Synchrotron Radiation Facility, an x-ray source based on laser-Compton scattering (LCS) has been installed at the terminal of the 100 MeV linac of the Shanghai Institute of Applied Physics. LCS x-rays are generated by interactions between Q-switched Nd:yttrium aluminum garnet laser pulses [with wavelength of 1064 nm and pulse width of 21 ns (full width at half maximum)] and electron bunches [with energy of 108 MeV and pulse width of 0.95 ns (rms)] at an angle of 42 deg. between laser and electron beam. In order to measure the energy spectrum of LCS x-rays, a Si(Li) detector along the electron beam line axis is positioned at 9.8 m away from a LCS chamber. After background subtraction, the LCS x-ray spectrum with the peak energy of 29.1{+-}4.4|{sub stat}{+-}2.1|{sub syst} keV and the peak width (rms) of 7.8{+-}2.8|{sub stat}{+-}0.4|{sub syst} keV is observed. Normally the 100 MeV linac operates with the electron macropulse charge of 1.0 nC/pulse, and the electron and laser collision repetition rate of 20 Hz. Therefore, the total LCS x-ray flux of (5.2{+-}2.0)x10{sup 2} Hz can be achieved.

  13. A laser-Compton scattering prototype experiment at 100 MeV linac of Shanghai Institute of Applied Physics.

    PubMed

    Luo, W; Xu, W; Pan, Q Y; Cai, X Z; Chen, J G; Chen, Y Z; Fan, G T; Fan, G W; Guo, W; Li, Y J; Liu, W H; Lin, G Q; Ma, Y G; Shen, W Q; Shi, X C; Xu, B J; Xu, J Q; Xu, Y; Zhang, H O; Yan, Z; Yang, L F; Zhao, M H

    2010-01-01

    As a prototype of the Shanghai Laser Electron Gamma Source in the Shanghai Synchrotron Radiation Facility, an x-ray source based on laser-Compton scattering (LCS) has been installed at the terminal of the 100 MeV linac of the Shanghai Institute of Applied Physics. LCS x-rays are generated by interactions between Q-switched Nd:yttrium aluminum garnet laser pulses [with wavelength of 1064 nm and pulse width of 21 ns (full width at half maximum)] and electron bunches [with energy of 108 MeV and pulse width of 0.95 ns (rms)] at an angle of 42 degrees between laser and electron beam. In order to measure the energy spectrum of LCS x-rays, a Si(Li) detector along the electron beam line axis is positioned at 9.8 m away from a LCS chamber. After background subtraction, the LCS x-ray spectrum with the peak energy of 29.1+/-4.4|(stat)+/-2.1|(syst) keV and the peak width (rms) of 7.8+/-2.8|(stat)+/-0.4|(syst) keV is observed. Normally the 100 MeV linac operates with the electron macropulse charge of 1.0 nC/pulse, and the electron and laser collision repetition rate of 20 Hz. Therefore, the total LCS x-ray flux of (5.2+/-2.0) x 10(2) Hz can be achieved. PMID:20113090

  14. Elastic /ital p//sub /up arrow//p/sub /up arrow// scattering between 240 and 470 MeV

    SciTech Connect

    Onel, Y.; Hausammann, R.; Heer, E.; Hess, R.; Lechanoine-Leluc, C.; Leo, W. R.; Rapin, D.; Jaccard, S.; Mango, S.

    1989-07-01

    The polarization parameter /ital P//sub /ital n/000/, the two-spin parameters/ital D//sub /ital n/0/ital n/0/, /ital K//sub /ital n/00/ital n//, /ital D//sub /ital s//prime/0/ital s/0/,/ital D//sub /ital s//prime/0/ital k/0/ and the three-spin parameters /ital M//sub /ital s//prime/0/ital sn//and /ital M//sub /ital s//prime/0/ital kn// have been measured for /ital pp/ elastic scatteringangles between 60/degree/ and 88/degree/ center of mass at 241 and 314 MeV incidentkinetic energies, and between 38/degree/ c.m. and 98/degree/ c.m. at 341, 366, and 398MeV. At 473 MeV, only /ital P//sub /ital n/000/ and /ital D//sub /ital s//prime/0/ital k/0/ weremeasured between 34/degree/ c.m. and 62/degree/ c.m. The experiment was performed at SINusing a polarized proton beam and a polarized butanol target. The polarizationof the scattered proton was analyzed in a carbon polarimeter. The influence ofthese high-precision data on the Saclay-Geneva phase-shift analysis isdiscussed.

  15. Elastic and inelastic scattering of polarized protons from carbon-12 at 400, 600, and 700 MeV

    SciTech Connect

    Jones, K.W.

    1984-04-01

    Good resolution cross section and analyzing power (p vector, p') data for many states in /sup 12/C up to an excitation energy of 21 MeV and spanning a momentum transfer range of 0.3 to 2.1 fm/sup -1/ were obtained using the High Resolution Spectrometer at the Clinton P. Anderson Meson Physics Facility at incident beam energies of 398, 597, and 698 MeV. Optical model potentials were obtained from the elastic scattering data. Inelastic data were analyzed in the Distorted Wave Impulse Approximation using the Love-Franey effective nucleon-nucleon interaction. The energy dependent isoscalar natural parity cross sections were underestimated, while phase difficulties were encountered in fitting analyzing powers. The energy independent isovector natural parity cross sections were reasonably reproduced, but analyzing powers were not, the calculations yielding positive trends whereas the data are of opposite sign. The energy independent isoscalar and isovector unnatural parity cross sections were quite well reproduced up to moderate momentum transfers, and striking successes were observed for some analyzing power data. Systematics of energy dependence together with the results of the DWIA calculations permitted the assignment of spin, parity and isospin quantum numbers to states in the 18-21 MeV excitation region. 64 references.

  16. Dual sightline measurements of MeV range deuterons with neutron and gamma-ray spectroscopy at JET

    NASA Astrophysics Data System (ADS)

    Eriksson, J.; Nocente, M.; Binda, F.; Cazzaniga, C.; Conroy, S.; Ericsson, G.; Giacomelli, L.; Gorini, G.; Hellesen, C.; Hellsten, T.; Hjalmarsson, A.; Jacobsen, A. S.; Johnson, T.; Kiptily, V.; Koskela, T.; Mantsinen, M.; Salewski, M.; Schneider, M.; Sharapov, S.; Skiba, M.; Tardocchi, M.; Weiszflog, M.; Contributors, JET

    2015-11-01

    Observations made in a JET experiment aimed at accelerating deuterons to the MeV range by third harmonic radio-frequency (RF) heating coupled into a deuterium beam are reported. Measurements are based on a set of advanced neutron and gamma-ray spectrometers that, for the first time, observe the plasma simultaneously along vertical and oblique lines of sight. Parameters of the fast ion energy distribution, such as the high energy cut-off of the deuteron distribution function and the RF coupling constant, are determined from data within a uniform analysis framework for neutron and gamma-ray spectroscopy based on a one-dimensional model and by a consistency check among the individual measurement techniques. A systematic difference is seen between the two lines of sight and is interpreted to originate from the sensitivity of the oblique detectors to the pitch-angle structure of the distribution around the resonance, which is not correctly portrayed within the adopted one dimensional model. A framework to calculate neutron and gamma-ray emission from a spatially resolved, two-dimensional deuteron distribution specified by energy/pitch is thus developed and used for a first comparison with predictions from ab initio models of RF heating at multiple harmonics. The results presented in this paper are of relevance for the development of advanced diagnostic techniques for MeV range ions in high performance fusion plasmas, with applications to the experimental validation of RF heating codes and, more generally, to studies of the energy distribution of ions in the MeV range in high performance deuterium and deuterium-tritium plasmas.

  17. Quasielastic neutron scattering measurements of n-butane in its crystalline, plastic, and liquid phases

    NASA Astrophysics Data System (ADS)

    Bradley, K. F.; Chen, S.-H.; Brun, T. O.

    1991-10-01

    We report here measurements of quasielastic neutron scattering from n-butane at temperatures of 90, 115, 125 and 190 K and in a momentum transfer range of 0.8-2.4 Å-1. These measurements confirm that between 115 and 125 K butane forms a plastic crystal in which the centers of mass of the butane molecules form a crystalline structure, but the individual molecules are free to rotate. At these two intermediate temperatures, there exists both an elastic peak, characteristic of a solid structure, and quasielastic components arising from the rotational motions of the butane molecules. At 90 K, the butane scatters neutrons only elastically, while at 190 K, the butane scatters neutrons only quasielastically. In both the plastic and the liquid phases, the presence of at least two quasielastic processes must be assumed in order to explain the measurements. In the plastic crystal, we associate a broad Lorentzian component with intramolecular reorientations about the central carbon-carbon bond and a second, relatively narrow, Lorentzian component with whole molecule rotations. The latter process gives rise to a rotational quasielastic peak having a width of 400 μeV, which is constant to within the instrumental resolution of 70 μeV at both temperatures and at all measured momentum transfers. In a continuous diffusion model, this width corresponds to a rotational diffusion constant of 0.277 rad2/ps, a value which is about 3.5 times larger than one extracted from a molecular dynamics simulation of n-butane in the plastic phase recently published by Refson and Pawley [Mol. Phys. 61, 669 (1987); 61, 693 (1987)]. On the other hand, the first process, which corresponds to the carbon-carbon reorientation peak, is about 16 meV wide, indicating that this reorientation occurs on a time scale of about 0.1 ps. The absence of this broad peak in the solid butane at 90 K indicates that this fast carbon-carbon reorientation is coupled to an aspect of the structure or dynamics of the plastic

  18. Neutron-Induced Fission Cross Sections of Nuclei in the Vicinity of 208Pb at Incident Energies below 60 MeV

    NASA Astrophysics Data System (ADS)

    Ryzhov, Igor V.; Tutin, Gennady A.; Eismont, Vilen P.; Mitryukhin, Andrey G.; Oplavin, Valery S.; Soloviev, Sergey M.; Meulders, Jean-Pierre; El Masri, Youssef; Keutgen, Thomas; Prieels, René; Nolte, Ralf

    2005-05-01

    Neutron-induced fission cross sections of 205Tl, 204, 206, 207, 208Pb, and 209Bi have been measured at incident energies of 32.8, 45.3, and 59.9 MeV. The measurements were performed at the Louvain-la-Neuve neutron beam facility using the 7Li (p, n) reaction as neutron source. Fission fragments were detected with a multi-section Frisch-gridded ionization chamber (MFGIC). Neutron fluence measurements were based on the 238U(n, f) reaction. The neutron fluence monitoring procedure was asserted by crosscheck measurement, in which the 59.9-MeV neutron beam fluence was simultaneously determined with the MFGIC and with a fission chamber monitor calibrated relative to a proton-recoil telescope.

  19. Cross sections and differential spectra for reactions of 2-20 MeV neutrons of /sup 27/Al

    SciTech Connect

    Blann, M.; Komoto, T.T.

    1988-01-01

    This report summarizes product yields, secondary n,p and ..cap alpha.. spectra, and ..gamma..-ray spectra calculated for incident neutrons of 2-20 MeV on /sup 27/Al targets. Results are all from the code ALICE, using the version ALISO which does weighting of results for targets which are a mix of isotopes. Where natural isotopic targets are involved, yields and n,p,..cap alpha.. spectra will be reported weighted over isotopic yields. Gamma-ray spectra, however, will be reported for the most abundant isotope.

  20. Calculations of Neutron- and Proton-Induced Reactions up to 200 MeV for Target 238U

    SciTech Connect

    Yu Hongwei; Zhao Zhixiang; Cai Chonghai

    2005-05-24

    The calculations of neutron- and proton-induced reaction up to 200 MeV for target 238U are performed; the calculated results are generally in good agreement with experimental data, and the physics is rational. The theoretical framework consists of the spherical optical model, intranuclear cascade mechanism for nucleon emission based on empirical formula, preequilibrium emission theory based on exciton model, evaporation model, and Hauser-Feshbach statistical theory with a width fluctuation correction. The fission widths are calculated using the Bohr-Wheeler formula.

  1. [BIOLOGICAL EFFECTIVENESS OF FISSION SPECTRUM NEUTRONS AND PROTONS WITH ENERGIES OF 60-126 MEV DURING ACUTE AND PROLONGED IRRADIATION].

    PubMed

    Shafirkin, A V

    2015-01-01

    Neutrons of the fission spectrum are characterized by relatively high values of linear energy transfer (LET). Data about their effects on biological objects are used to evaluate the risk of delayed effects of accelerated ions within the same LET range that serve as an experimental model of the nuclei component of galactic cosmic rays (GCR). Additionally, risks of delayed consequences to cosmonaut's health and average lifetime from certain GCR fluxes and secondary neutrons can be also prognosticated. The article deals with comparative analysis of the literature on reduction of average lifespan (ALS) of animals exposed to neutron reactor spectrum, 60-126 MeV protons, and X- and γ-rays in a broad range of radiation intensity and duration. It was shown that a minimal lifespan reduction by 5% occurs due to a brief exposure to neutrons with the absorbed dose of 5 cGy, whereas same lifespan reduction due to hard X- and γ-radiation occurs after absorption of a minimal dose of 100 cGy. Therefore, according to the estimated minimal ALS reduction in mice, neutron effectiveness is 20-fold higher. Biological effectiveness of protons as regards ALS reduction is virtually equal to that of standard types of radiation. Exposure to X- and γ-radiation with decreasing daily doses, and increasing number of fractions and duration gives rise to an apparent trend toward a less dramatic ALS reduction in mice; on the contrary, exposure to neutrons of varying duration had no effect on threshold doses for the specified ALS reductions. Factors of relative biological effectiveness of neutrons reached 40. PMID:26934784

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

    SciTech Connect

    Brubaker, Erik

    2015-10-01

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

  3. An experimental setup for measurement of neutron energy spectra in lithium with collimated 14.7 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Ofek, R.; Tsechanski, A.; Profio, A. E.; Shani, G.

    1989-06-01

    Neutron energy spectra in an 88 cm diameter, 88 cm long lithium tank were measured with the Ben Gurion University experimental setup. In this setup, the lithium tank is separated from the DT neutron generator by a 120 cm thick paraffin wall with a 6 cm diameter collimator through it, along the axis of the neutron generator and the lithium tank. This enables unidirectionality and monoenergeticity of the neutrons penetrating the lithium tank. A neutron energy spectrum is obtained by unfolding with the code FORIST of proton-recoil spectra measured by an NE213 liquid scintillator. The important features of the spectrometry system, comprised of the NE213 scintillator and the attached electronic system, are the high pulse shape discrimination capability of the NE213 scintillator, which enables the separation of neutron and gamma events, relatively high energy resolution, and the system linearity. Also the simultaneous measurement of the low gain and high gain proton-recoil spectra prevents a distortion of the unfolded neutron spectrum. The neutron energy spectra are absolutely normalized and internormalized to each other by an absolutely calibrated, second NE213 scintillator, placed close to the neutron generator. The measured neutron energy spectra inside the lithium tank were compared to some preliminary calculations of the spectra, carried out with the discrete-ordinates transport code DOT4.2. Both spectra are in poor agreement. These discrepancies are assigned mainly to the inadequancy of the transport calculations. Finally, the distribution of the tritium production in the lithium tank, with the same experimental configurations, was calculated with the code DOT4.2 as well. The results indicate that the collimated neutron beam configuration is inappropriate for the purpose of tritium breeding ratio measurements.

  4. Measurements of fission product yield in the neutron-induced fission of 238U with average energies of 9.35 MeV and 12.52 MeV

    NASA Astrophysics Data System (ADS)

    Mukerji, Sadhana; Krishnani, Pritam Das; Shivashankar, Byrapura Siddaramaiah; Mulik, Vikas Kaluram; Suryanarayana, Saraswatula Venkat; Naik, Haladhara; Goswami, Ashok

    2014-07-01

    The yields of various fission products in the neutron-induced fission of 238U with the flux-weightedaveraged neutron energies of 9.35 MeV and 12.52 MeV were determined by using an off-line gammaray spectroscopic technique. The neutrons were generated using the 7Li(p, n) reaction at Bhabha Atomic Research Centre-Tata Institute of Fundamental Research Pelletron facility, Mumbai. The gamma- ray activities of the fission products were counted in a highly-shielded HPGe detector over a period of several weeks to identify the decaying fission products. At both the neutron energies, the fission-yield values are reported for twelve fission product. The results obtained from the present work have been compared with the similar data for mono-energetic neutrons of comparable energy from the literature and are found to be in good agreement. The peak-to-valley (P/V) ratios were calculated from the fission-yield data and were found to decreases for neutron energy from 9.35 to 12.52 MeV, which indicates the role of excitation energy. The effect of the nuclear structure on the fission product-yield is discussed.

  5. Measurement of neutron detection efficiency between 22 and 174 MeV using two different kinds of Pb-scintillating fiber sampling calorimeters

    NASA Astrophysics Data System (ADS)

    Anelli, M.; Bertolucci, S.; Bini, C.; Branchini, P.; Corradi, G.; Curceanu, C.; De Zorzi, G.; Di Domenico, A.; Di Micco, B.; Ferrari, A.; Fiore, S.; Gauzzi, P.; Giovannella, S.; Happacher, F.; Iliescu, M.; Lucà, A.; Martini, M.; Miscetti, S.; Nguyen, F.; Passeri, A.; Prokofiev, A.; Sarra, I.; Sciascia, B.; Sirghi, F.; Tagnani, D.

    2010-05-01

    We exposed a prototype of the lead-scintillating fiber KLOE calorimeter to neutron beam of 21, 46 and 174 MeV at The Svedberg Laboratory, Uppsala, to study its neutron detection efficiency. This has been found larger than what expected considering the scintillator thickness of the prototype. We show preliminary measurement carried out with a different prototype with a larger lead/fiber ratio, which proves the relevance of passive material to neutron detection efficiency in this kind of calorimeters.

  6. Decay Properties and State Lifetimes in 128Te from an Inelastic Neutron Scattering (n,ng) Reaction.

    NASA Astrophysics Data System (ADS)

    Boehringer, John

    2002-03-01

    Gamma-ray spectroscopy following inelastic neutron scattering has been used to study the low-lying level structure of the 128Te nucleus. Measurements were made at the University of Kentucky Van de Graaff Laboratory; excited levels to 3.3 MeV excitation were studied. Gamma-ray angular distributions and Doppler shifts were measured at 2.2, 2.8 and 3.3 MeV, and g-ray excitation functions were measured between 2 MeV and 3.4 MeV in 90 keV steps. These data have been used to compile a level and decay scheme, deduce level spins and parities, lifetimes, branching ratios and multipole-mixing ratios. Electromagnetic transition rates determined from these data will be presented. Experimental results will be compared to model calculations from the interacting boson model and the particle-core coupling model. This work was supported in part by a grant from the National Science Foundation.

  7. Development and high temperature testing by 14 MeV neutron irradiation of single crystal diamond detectors

    NASA Astrophysics Data System (ADS)

    Pilotti, R.; Angelone, M.; Pagano, G.; Loreti, S.; Pillon, M.; Sarto, F.; Marinelli, M.; Milani, E.; Prestopino, G.; Verona, C.; Verona-Rinati, G.

    2016-06-01

    In the present paper, the performances of single crystal diamond detectors "ad hoc" designed to operate at high temperature are reported. The detectors were realized using commercial CVD single crystal diamond films, 500 micron thick with metal contacts deposited by sputtering method on each side. The new detector layout is based upon mechanical contacts between the diamond film and the electric ground. The detector was first characterized by measuring the leakage current as function of temperature and applied biasing voltage (I-V characteristics). The results obtained using two different metal contacts, Pt and Ag respectively, while irradiated with 14 MeV neutrons at the Frascati neutron generator (FNG) are reported and compared. It is shown that diamond detectors with Ag metal contacts can be properly operated in spectrometric mode up to 240oC with energy resolution (FWHM) of about 3.5%.

  8. Statistical Model Analysis of (n, α) Cross Sections for 4.0-6.5 MeV Neutrons

    NASA Astrophysics Data System (ADS)

    Khuukhenkhuu, G.; Odsuren, M.; Gledenov, Y. M.; Zhang, G. H.; Sedysheva, M. V.; Munkhsaikhan, J.; Sansarbayar, E.

    2016-02-01

    The statistical model based on the Weisskopf-Ewing theory and constant nuclear temperature approximation is used for systematical analysis of the 4.0-6.5 MeV neutron induced (n, α) reaction cross sections. The α-clusterization effect was considered in the (n, α) cross sections. A certain dependence of the (n, α) cross sections on the relative neutron excess parameter of the target nuclei was observed. The systematic regularity of the (n, α) cross sections behaviour is useful to estimate the same reaction cross sections for unstable isotopes. The results of our analysis can be used for nuclear astrophysical calculations such as helium burning and possible branching in the s-process.

  9. Calibration of neutron-yield diagnostics in attenuating and scattering environments

    SciTech Connect

    Hahn, K. D.; Ruiz, C. L.; Chandler, G. A.; Leeper, R. J.; McWatters, B. R.; Smelser, R. M.; Torres, J. A.; Cooper, G. W.; Nelson, A. J.

    2012-10-15

    We have performed absolute calibrations of a fusion-neutron-yield copper-activation diagnostic in environments that significantly attenuate and scatter neutrons. We have measured attenuation and scattering effects and have compared the measurements to Monte Carlo simulations using the Monte Carlo N-Particle code. We find that measurements and simulations are consistent within 10%.

  10. Inter-pulse high-resolution gamma-ray spectra using a 14 MeV pulsed neutron generator

    USGS Publications Warehouse

    Evans, L.G.; Trombka, J.I.; Jensen, D.H.; Stephenson, W.A.; Hoover, R.A.; Mikesell, J.L.; Tanner, A.B.; Senftle, F.E.

    1984-01-01

    A neutron generator pulsed at 100 s-1 was suspended in an artificial borehole containing a 7.7 metric ton mixture of sand, aragonite, magnetite, sulfur, and salt. Two Ge(HP) gamma-ray detectors were used: one in a borehole sonde, and one at the outside wall of the sample tank opposite the neutron generator target. Gamma-ray spectra were collected by the outside detector during each of 10 discrete time windows during the 10 ms period following the onset of gamma-ray build-up after each neutron burst. The sample was measured first when dry and then when saturated with water. In the dry sample, gamma rays due to inelastic neutron scattering, neutron capture, and decay were counted during the first (150 ??s) time window. Subsequently only capture and decay gamma rays were observed. In the wet sample, only neutron capture and decay gamma rays were observed. Neutron capture gamma rays dominated the spectrum during the period from 150 to 400 ??s after the neutron burst in both samples, but decreased with time much more rapidly in the wet sample. A signal-to-noise-ratio (S/N) analysis indicates that optimum conditions for neutron capture analysis occurred in the 350-800 ??s window. A poor S/N in the first 100-150 ??s is due to a large background continuum during the first time interval. Time gating can be used to enhance gamma-ray spectra, depending on the nuclides in the target material and the reactions needed to produce them, and should improve the sensitivity of in situ well logging. ?? 1984.

  11. Elastic scattering of polarized protons on helium three at 800 MeV

    SciTech Connect

    Azizi, A.

    1985-07-01

    A set of spin dependent parameters and cross sections has been measured for polarized p-/sup 3/He elastic scattering over the range of q .7 to 4.2 fm/sup -1/. The experiment was done at the Los Alamos Meson Physics Facility (LAMPF) using the High Resolution Spectrometer (HRS) with a polarized proton beam at .8 GeV. The focal plane polarimeter of the HRS was used to determine the spin direction of the scattered proton. Since /sup 3/He is one of the simplest nuclei, polarized p-/sup 3/He scattering provides a very sensitive test of multiple scattering theories. The theoretical analysis was done by using two different wave functions for /sup 3/He as input to the multiple scattering theory. The theoretical calculations and experimental data together will give us useful information about nucleon-nucleon amplitudes and also help us to obtain a better understanding of the scattering process. 68 refs., 55 figs., 9 tabs.

  12. A precision measurement of the neutron-neutron scattering length from the reaction pi(-)d going to gamma nn

    NASA Astrophysics Data System (ADS)

    Saliba, Michael Angelo

    1998-11-01

    A measurement of the 1S0 neutron-neutron scattering length ann has been carried out at TRIUMF by studying the shape of the photon energy spectrum from the reaction πsp-d /to /gamma nn in the region near the endpoint. A 40.5 MeV pion beam was degraded and stopped in a liquid deuterium target and all three final state particles from the reaction were detected in triple coincidence. The photon was detected in a large NaI(Tl) crystal, while the neutrons were detected in a 2 m x 2 m position-sensitive array of plastic scintillation counters, located at a distance of 3 m from the target. The experimental photon energy spectrum was reconstructed to a resolution of 40 keV FWHM from the measured momenta of the two neutrons, and contains 123,000 counts in the top 450 keV region near the endpoint after background subtraction. The value of ann is determined from a comparison of this experimental spectrum to simulated spectra that are being developed simultaneously at the University of Kentucky. These spectra are derived from a new model of this reaction that is based on a half off-shell NN T matrix and the elementary γpi operator due to Lee and Nozawa. The experimental geometry and resolution are taken into account using Monte Carlo techniques. A comparison of our final experimental spectrum to a preliminary set of the simulated spectra has yielded the provisional result of ann = -21.8 /pm 0.3 fm (theoretical errors excluded) before correction for electromagnetic effects. This preliminary result is in disagreement with the currently accepted experimental value of ann = -18.5 /pm 0.3 fm, however we stress that the theoretical model is still under development. We anticipate that our final result will make a significant contribution to the discussion of charge symmetry breaking in the strong interaction, particularly with regard to the current uncertainty that surrounds the contribution of the (/rho - /omega) mixing term in standard meson-theoretic potentials.

  13. Neutron spectra produced by 30, 35 and 40 MeV proton beams at KIRAMS MC-50 cyclotron with a thick beryllium target

    NASA Astrophysics Data System (ADS)

    Shin, Jae Won; Bak, Sang-In; Ham, Cheolmin; In, Eun Jin; Kim, Do Yoon; Min, Kyung Joo; Zhou, Yujie; Park, Tae-Sun; Hong, Seung-Woo; Bhoraskar, V. N.

    2015-10-01

    Neutrons over a wide range of energies are produced by bombarding a 1.05 cm thick beryllium target with protons of different energies delivered by the MC-50 Cyclotron of the Korea Institute of Radiological Medical Sciences (KIRAMS). The neutron flux Φ(En) versus neutron energy En, produced by protons of 30, 35, and 40 MeV energies, was obtained by using the GEANT4 code with a data-based hadronic model. For the experimental validation of the simulated neutron spectra, a number of pure aluminum and iron oxide samples were irradiated with the neutrons produced by 30, 35, and 40 MeV protons at 20 μA beam current. The gamma-ray activities of 24Na and 56Mn produced, respectively, through 27Al(n,α)24Na and 56Fe(n,p)56Mn reactions were measured by a HPGe detector. The neutron flux Φ(En) at each neutron energy from the simulation was multiplied with the evaluated cross-sections σ(En) of the respective nuclear reaction, and the summation ∑ Φ(En) σ(En) was calculated over the neutron spectrum for each proton energy of 30, 35, and 40 MeV. The measured gamma-ray activities of 24Na and 56Mn were found in good agreement with the activities estimated by using the summed values of ∑ Φ(En) σ(En) along with other parameters in a neutron activation method.

  14. Measurement of the Two-Halo Neutron Transfer Reaction {sup 1}H({sup 11}Li,{sup 9}Li){sup 3}H at 3A MeV

    SciTech Connect

    Tanihata, I.; Alcorta, M.; Bandyopadhyay, D.; Bieri, R.; Buchmann, L.; Davids, B.; Galinski, N.; Howell, D.; Mills, W.; Mythili, S.; Openshaw, R.; Padilla-Rodal, E.; Ruprecht, G.; Sheffer, G.; Shotter, A. C.; Trinczek, M.; Walden, P.; Savajols, H.; Roger, T.; Caamano, M.

    2008-05-16

    The p({sup 11}Li,{sup 9}Li)t reaction has been studied for the first time at an incident energy of 3A MeV at the new ISAC-2 facility at TRIUMF. An active target detector MAYA, built at GANIL, was used for the measurement. The differential cross sections have been determined for transitions to the {sup 9}Li ground and first excited states in a wide range of scattering angles. Multistep transfer calculations using different {sup 11}Li model wave functions show that wave functions with strong correlations between the halo neutrons are the most successful in reproducing the observation.

  15. Thulium-169 neutron inelastic scattering cross section measurements via the (169)Tm(n,n'gamma) reaction

    NASA Astrophysics Data System (ADS)

    Ko, Young June

    1999-11-01

    A neutron inelastic scattering study for low-lying states of thulium-169 below 1 MeV has been pursued by the detection of gamma rays from the 169Tm(n,n'γ) reaction. The inelastic level cross sections, which are important to obtain nuclear potential parameters and to understand reaction mechanisms, were obtained in this study. Incident neutrons were generated by bombarding a metallic lithium target with protons from the Lowell Van de Graaff accelerator. A germanium detector was used for gamma-ray observation. Excitation functions were measured from 0.2 to 1 MeV in 50 keV intervals at a scattering angle of 125°. Gamma-ray production cross sections were obtained for 37 observed transitions from 16 levels. Gamma-ray angular distributions from 35° to 135°, in 10° steps were measured at a neutron energy of 750 keV. The angular distributions were fitted with Legendre polynomials of even (up to fourth) order. Neutron inelastic level cross sections were inferred from the excitation functions and the angular distributions. Because cross-section data from previous experimental or theoretical work were not available, no direct comparison with previous work was made. A comparison of the magnitude and behavior of the (n,inelastic) cross section for thulium with those of neighboring odd-A nuclei indicated reasonable agreement. A classical model for angular momentum transfer indicates that states with spin >=/(+) may be excited only through the compound nucleus process, but for states with spin <=/(-) compound nucleus and direct interaction processes may both participate in the excitation.

  16. Inelastic neutron scattering study of Ni-substituted Ce0.5Fe4Sb12 skutterudite compounds

    NASA Astrophysics Data System (ADS)

    Girard, L.; Adroja, D. T.; Chapon, L.; Taylor, J. W.; Viennois, R.; Ravot, D.; Paschen, S.

    2012-12-01

    An inelastic neutron scattering study of the filled and partially-filled skutterudite compounds RFe4Sb12 and R0.5Fe2.75Ni1.25Sb12 (where R = Ce and La) was carried out to understand the nature of the spin dynamics. Strong magnetic scattering was observed in Ce0.5Fe2.75Ni1.25Sb12 at ~ 5 meV. The integrated intensity of this peak does not follow the Ce3+ form factor, but exhibits a maximum at a momentum transfer (|Q|) of 2 Å-1. We attribute this feature to a Ce3+ crystal field excitation in the presence of magnetic exchange interactions. This picture is supported by thermodynamic and magnetic properties. Finally, we confirm the presence of a spin gap in CeFe4Sb12 suggested by our previous work.

  17. Neutron yield and induced radioactivity: a study of 235-MeV proton and 3-GeV electron accelerators.

    PubMed

    Hsu, Yung-Cheng; Lai, Bo-Lun; Sheu, Rong-Jiun

    2016-01-01

    This study evaluated the magnitude of potential neutron yield and induced radioactivity of two new accelerators in Taiwan: a 235-MeV proton cyclotron for radiation therapy and a 3-GeV electron synchrotron serving as the injector for the Taiwan Photon Source. From a nuclear interaction point of view, neutron production from targets bombarded with high-energy particles is intrinsically related to the resulting target activation. Two multi-particle interaction and transport codes, FLUKA and MCNPX, were used in this study. To ensure prediction quality, much effort was devoted to the associated benchmark calculations. Comparisons of the accelerators' results for three target materials (copper, stainless steel and tissue) are presented. Although the proton-induced neutron yields were higher than those induced by electrons, the maximal neutron production rates of both accelerators were comparable according to their respective beam outputs during typical operation. Activation products in the targets of the two accelerators were unexpectedly similar because the primary reaction channels for proton- and electron-induced activation are (p,pn) and (γ,n), respectively. The resulting residual activities and remnant dose rates as a function of time were examined and discussed. PMID:25628454

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Prem, Manfred; Krexner, Gerhard; Peterlik, Herwig

    2006-11-01

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

  20. Radiation damage study using small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

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

    2000-03-01

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