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Sample records for neutron separation energy

  1. Phase/Shape Transitions and the Two Neutron Separation Energies

    SciTech Connect

    Zamfir, N. V.; Anghel, Sabina; Cata-Danil, G.

    2008-11-11

    We investigated the evolution of experimental two-neutron separation energies (S{sub 2n}) along the isotopic chains for the even-even nuclei. In order to enhance the sensitivity of our search, differential variation of the S{sub 2n} has been investigated. The emphasis is on finding nonmonotonic behaviors which can be correlated with phase/shape transition. Correlations of the ground state S{sub 2n} values with the excited states energies R{sub 4/2} ratio are also discussed.

  2. Two-Neutron Separation Energies Of Even-Even Rare-Earth Neutron-Rich Nuclei

    SciTech Connect

    Benhamouda, N.; Oudih, M. R.; Allal, N. H.; Fellah, M.

    2007-04-23

    The variation of the two-neutron separation energy (S2N), as a function of N, is studied using a microscopic model that includes the pairing effects rigorously within the Fixed-Sharp-BCS method. The model has been tested for ''ordinary'' nuclei and has correctly reproduced the experimental data. The study has then been extended to the neutron-rich nuclei and has shown a relatively important variation of S2N when N= 100 which may be attributed to the existence of a new magic number.

  3. Low-Energy Dipole Modes of Excitation Below the Neutron Separation Energy

    SciTech Connect

    Tonchev, A. P.; Howell, C. R.; Tornow, W.; Angell, C.; Boswell, M.; Karwowski, H. J.; Kelley, J. H.; Tsoneva, N.

    2006-03-13

    The nuclear resonance fluorescence experiments have been performed at the High Intensity Gamma Source (HI{gamma}S) on 138Ba nuclei using four 60% efficient HPGe detectors. Excitation energies, spin, parities, and decay branching ratios were measured for the low-energy dipole modes of excitations. Experimental results on the parity measurement below the neutron separation energy shows that all dipole states in this energy region exhibit E1 excitation. These results are consistent with theoretical prediction of the collective isoscalar nature of this low-energy mode of excitation.

  4. Cross section measurement on 139La (γ,γ') below neutron separation energy

    NASA Astrophysics Data System (ADS)

    Makinaga, A.; Rusev, G.; Schwengner, R.; Dönau, F.; Beyer, R.; Bemmerer, D.; Crespo, P.; Erhard, M.; Junghans, A. R.; Klug, J.; Nair, C.; Schilling, K. D.; Wagner, A.

    2010-06-01

    The γ-ray strength function is an important input quantity for the determination of the photoreaction rate and the neutron capture rate for astrophysics as well as for nuclear technologies. Recent studies show that extra γ-ray strength near the neutron separation energy Sn (pygmy resonance) affects the stellar reaction rate strongly. In this work, the photoabsorption cross section for 139La below Sn was measured using bremsstrahlung produced at the electron accelerator ELBE of Eorschungszentrum Dresden-Rossendorf with an electron beam of 11.5 MeV kinetic energy. Experimental result of 139La is presented.

  5. Dipole strength in Y89 up to the neutron-separation energy

    NASA Astrophysics Data System (ADS)

    Benouaret, N.; Schwengner, R.; Rusev, G.; Dönau, F.; Beyer, R.; Erhard, M.; Grosse, E.; Junghans, A. R.; Kosev, K.; Nair, C.; Schilling, K. D.; Wagner, A.; Bendjaballah, N.

    2009-01-01

    Photoexcitation of the N=50 nucleus Y89 has been performed at the bremsstrahlung facility at the superconducting electron accelerator ELBE at electron energies of Eekin=9.5 and 13.2 MeV. About 250 levels up to the neutron-separation energy were identified. Statistical methods were applied to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. The photoabsorption cross section derived in this way up to the neutron-separation energy is combined with the photoabsorption cross section obtained from (γ, n) data and provides information about the extension of the giant dipole resonance toward energies below the neutron-separation energy. An enhancement of E1 strength has been found in the range from about 6 to 11 MeV. The experimental photoabsorption cross sections of Y89 and of the neighboring N=50 isotones Sr88 and Zr90 are compared with predictions of the quasiparticle-random-phase approximation.

  6. Dipole response of Sr88 up to the neutron-separation energy

    NASA Astrophysics Data System (ADS)

    Schwengner, R.; Rusev, G.; Benouaret, N.; Beyer, R.; Erhard, M.; Grosse, E.; Junghans, A. R.; Klug, J.; Kosev, K.; Kostov, L.; Nair, C.; Nankov, N.; Schilling, K. D.; Wagner, A.

    2007-09-01

    The dipole response of the magic N=50 nucleus Sr88 was studied in photon-scattering experiments at the electron linear accelerator ELBE with bremsstrahlung produced at kinetic electron energies of 9.0, 13.2, and 16.0 MeV. We identified 160 levels up to an excitation energy of 12 MeV. By using polarized photons linear polarizations of about 50 γ transitions were measured that enabled parity assignments to the corresponding states. In the energy range of 6 12 MeV we identified only one M1 transition; all other transitions have E1 character. Thus, E1 character was proven for 63% of the total dipole strength of the observed levels in the given energy range. Statistical methods were applied to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. In this way we derived the photoabsorption cross section up to the neutron-separation energy. This cross section matches well the photoabsorption cross section obtained from (γ,n) data and thus provides information about the extension of the dipole-strength distribution toward energies below the neutron-separation energy. An enhancement of E1 strength at 6 11 MeV may be considered as an indication for a pygmy dipole resonance.

  7. Dipole strength in La139 below the neutron-separation energy

    NASA Astrophysics Data System (ADS)

    Makinaga, A.; Schwengner, R.; Rusev, G.; Dönau, F.; Frauendorf, S.; Bemmerer, D.; Beyer, R.; Crespo, P.; Erhard, M.; Junghans, A. R.; Klug, J.; Kosev, K.; Nair, C.; Schilling, K. D.; Wagner, A.

    2010-08-01

    The γ-ray strength function is an important input quantity for the determination of the photoreaction rate and the neutron capture rate for astrophysics as well as for nuclear technologies. To test model predictions, the photoabsorption cross section of La139 up to the neutron-separation energy was measured using bremsstrahlung produced at the electron accelerator ELBE of Forschungszentrum Dresden-Rossendorf with an electron beam of 11.5 MeV kinetic energy. The experimental data were analyzed by applying Monte Carlo simulations of γ-ray cascades to obtain the intensities of the ground-state transitions and their branching ratios. We found a significant enhancement of electric dipole strength in the energy range from 6 to 10 MeV that may be related with a pygmy dipole resonance. The present data are combined with photoneutron cross sections for La139 and compared with results of calculations on the basis of a quasiparticle-random-phase approximation using an instantaneous-shape sampling.

  8. Radiative thermal neutron-capture cross sections for the 180W(n ,γ ) reaction and determination of the neutron-separation energy

    NASA Astrophysics Data System (ADS)

    Hurst, A. M.; Firestone, R. B.; Szentmiklósi, L.; Sleaford, B. W.; Basunia, M. S.; Belgya, T.; Escher, J. E.; Krtička, M.; Révay, Zs.; Summers, N. C.

    2015-09-01

    Prompt thermal neutron-capture partial γ -ray production cross sections were measured for the first time for the 180W(n ,γ ) reaction using a cold guided-neutron beam at the Budapest Research Reactor. Absolute 181Wγ -ray cross sections were internally standardized using well-known comparator γ -ray cross sections belonging to the other tungsten isotopes present in the 11.35% enriched 180W sample. Transitions were assigned to levels in 181W based largely upon information available in the literature. The total radiative thermal neutron-capture cross section σ0 was determined from the sum of direct prompt γ -ray cross sections populating the ground state and a modeled contribution accounting for ground-state feeding from the quasicontinuum. In this work, we find σ0=21.67 (77 ) b. A new measurement of the cross section for the 5 /2- metastable isomer at 365.6 keV, σ5 /2-(181Wm,14.6 μ s ) =19.96 (55 ) b, is also determined. Additionally, primary γ rays, observed for the first time in the 180W(n ,γ ) reaction, provide the most precise determination for the 181W neutron-separation energy, Sn=6669.02 (16 ) keV.

  9. High energy neutron radiography

    SciTech Connect

    Gavron, A.; Morley, K.; Morris, C.; Seestrom, S.; Ullmann, J.; Yates, G.; Zumbro, J.

    1996-06-01

    High-energy spallation neutron sources are now being considered in the US and elsewhere as a replacement for neutron beams produced by reactors. High-energy and high intensity neutron beams, produced by unmoderated spallation sources, open potential new vistas of neutron radiography. The authors discuss the basic advantages and disadvantages of high-energy neutron radiography, and consider some experimental results obtained at the Weapons Neutron Research (WNR) facility at Los Alamos.

  10. Prototype Neutron Energy Spectrometer

    SciTech Connect

    Stephen Mitchell, Sanjoy Mukhopadhyay, Richard Maurer, Ronald Wolff

    2010-06-16

    The project goals are: (1) Use three to five pressurized helium tubes with varying polyethylene moderators to build a neutron energy spectrometer that is most sensitive to the incident neutron energy of interest. Neutron energies that are of particular interest are those from the fission neutrons (typically around 1-2 MeV); (2) Neutron Source Identification - Use the neutron energy 'selectivity' property as a tool to discriminate against other competing processes by which neutrons are generated (viz. Cosmic ray induced neutron production [ship effect], [a, n] reactions); (3) Determine the efficiency as a function of neutron energy (response function) of each of the detectors, and thereby obtain the composite neutron energy spectrum from the detector count rates; and (4) Far-field data characterization and effectively discerning shielded fission source. Summary of the presentation is: (1) A light weight simple form factor compact neutron energy spectrometer ready to be used in maritime missions has been built; (2) Under laboratory conditions, individual Single Neutron Source Identification is possible within 30 minutes. (3) Sources belonging to the same type of origin viz., (a, n), fission, cosmic cluster in the same place in the 2-D plot shown; and (4) Isotopes belonging to the same source origin like Cm-Be, Am-Be (a, n) or Pu-239, U-235 (fission) do have some overlap in the 2-D plot.

  11. Neutron energy measurements in emergency response applications

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Sanjoy; Guss, Paul; Hornish, Michael; Wilde, Scott; Stampahar, Tom; Reed, Michael

    2009-08-01

    We present significant results in recent advances in the measurement of neutron energy. Neutron energy measurements are a small but significant part of radiological emergency response applications. Mission critical information can be obtained by analyzing the neutron energy given off from radioactive materials. In the case of searching for special nuclear materials, neutron energy information from an unknown source can be of importance. At the Remote Sensing Laboratory (RSL) of National Security Technologies, LLC, a series of materials, viz., liquid organic scintillator (LOS), Lithium Gadolinium Borate (LGB) or Li6Gd(BO3)3 in a plastic matrix, a recently developed crystal of Cesium Lithium Yttrium Chloride, Cs2LiYCl6: Ce (called CLYC)[1], and normal plastic scintillator (BC-408) with 3He tubes have been used to study their effectiveness as a portable neutron energy spectrometer. Comparisons illustrating the strengths of the various materials will be provided. Of these materials, LGB offers the ability to tailor its response to the neutron spectrum by varying the isotopic composition of the key constituents (Lithium, Gadolinium [Yttrium], and Boron). All three of the constituent elements possess large neutron capture cross section isotopes for highly exothermic reactions. These compounds of composition Li6Gd(Y)(BO3)3 can be activated by Cerium ions Ce3+. CLYC, on the other hand, has a remarkable gamma response in addition to superb neutron discrimination, comparable to that of Europium-doped Lithium Iodide (6LiI: Eu). Comparing these two materials, CLYC has higher light output (4500 phe/MeV) than that from 6LiI: Eu and shows better energy resolution for both gamma and neutron pulse heights. Using CLYC, gamma energy pulses can be discriminated from the neutron signals by simple pulse height separation. For the cases of both LGB and LOS, careful pulse shape discrimination is needed to separate the gamma energy signals from neutron pulses. Both analog and digital

  12. A separation of protactinium from neutron-irradiated thorium.

    PubMed

    Lyle, S J; Shendrikar, A D

    1966-01-01

    A convenient-method, based on liquid-liquid extraction with N-benzoyl-N-phenylhydroxylamine in chloroform, is given for the separation of protactinium-233 from neutron-irradiated thorium. PMID:18959855

  13. Phase separation in the crust of accreting neutron stars.

    PubMed

    Horowitz, C J; Berry, D K; Brown, E F

    2007-06-01

    Nucleosynthesis, on the surface of accreting neutron stars, produces a range of chemical elements. We perform molecular dynamics simulations of crystallization to see how this complex composition forms new neutron star crust. We find chemical separation, with the liquid ocean phase greatly enriched in low atomic number elements compared to the solid crust. This phase separation should change many crust properties such as the thermal conductivity and shear modulus. PMID:17677319

  14. High energy neutron dosimeter

    DOEpatents

    Rai, K.S.F.

    1994-01-11

    A device for measuring dose equivalents in neutron radiation fields is described. The device includes nested symmetrical hemispheres (forming spheres) of different neutron moderating materials that allow the measurement of dose equivalents from 0.025 eV to past 1 GeV. The layers of moderating material surround a spherical neutron counter. The neutron counter is connected by an electrical cable to an electrical sensing means which interprets the signal from the neutron counter in the center of the moderating spheres. The spherical shape of the device allows for accurate measurement of dose equivalents regardless of its positioning. 2 figures.

  15. High energy neutron dosimeter

    DOEpatents

    Sun, Rai Ko S.F.

    1994-01-01

    A device for measuring dose equivalents in neutron radiation fields. The device includes nested symmetrical hemispheres (forming spheres) of different neutron moderating materials that allow the measurement of dose equivalents from 0.025 eV to past 1 GeV. The layers of moderating material surround a spherical neutron counter. The neutron counter is connected by an electrical cable to an electrical sensing means which interprets the signal from the neutron counter in the center of the moderating spheres. The spherical shape of the device allows for accurate measurement of dose equivalents regardless of its positioning.

  16. High-energy neutron dosimetry

    NASA Astrophysics Data System (ADS)

    Sutton, Michele Rhea

    2001-12-01

    Fluence-to-dose conversion coefficients for the radiation protection quantity effective dose were calculated for neutrons, photons and protons with energies up to 2 GeV using the MCNPX code. The calculations were performed using the Pacific Northwest National Laboratory versions of the MIRD-V male and female anthropomorphic phantoms modified to include the skin and esophagus. The latest high-energy neutron evaluated cross-section libraries and the recommendations given in ICRP Publication 60 and ICRP Publication 74 were utilized to perform the calculations. Sets of fluence-to- effective dose conversion coefficients are given for anterior-posterior, posterior-anterior, left-lateral, right-lateral and rotational irradiation geometries. This is the first set of dose conversion coefficients over this energy range calculated for the L-LAT irradiation geometry. A unique set of high-energy neutron depth-dose benchmark experiments were performed at the Los Alamos Neutron Science Center/Weapons Neutron Research (LANSCE/WNR) complex. The experiments consisted of filtered neutron beams with energies up to 800 MeV impinging on a 30 x 30 x 30 cm3 tissue-equivalent phantom. The absorbed dose was measured in the phantom at various depths with tissue-equivalent ion chambers. The phantom and the experimental set-up were modeled using MCNPX. Comparisons of the experimental and computational depth- dose distributions indicate that the absorbed dose calculated by MCNPX is within 13% for neutrons with energies up to 750 MeV. This experiment will serve as a benchmark experiment for the testing of high-energy radiation transport codes for the international radiation protection community.

  17. Martian Neutron Energy Spectrometer (MANES)

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Roth, D. R.; Kinnison, J. D.; Goldsten, J. O.; Fainchtein, R.; Badhwar, G.

    2000-01-01

    High energy charged particles of extragalactic, galactic, and solar origin collide with spacecraft structures and planetary atmospheres. These primaries create a number of secondary particles inside the structures or on the surfaces of planets to produce a significant radiation environment. This radiation is a threat to long term inhabitants and travelers for interplanetary missions and produces an increased risk of carcinogenesis, central nervous system (CNS) and DNA damage. Charged particles are readily detected; but, neutrons, being electrically neutral, are much more difficult to monitor. These secondary neutrons are reported to contribute 30-60% of the dose equivalent in the Shuttle and MIR station. The Martian atmosphere has an areal density of 37 g/sq cm primarily of carbon dioxide molecules. This shallow atmosphere presents fewer mean free paths to the bombarding cosmic rays and solar particles. The secondary neutrons present at the surface of Mars will have undergone fewer generations of collisions and have higher energies than at sea level on Earth. Albedo neutrons produced by collisions with the Martian surface material will also contribute to the radiation environment. The increased threat of radiation damage to humans on Mars occurs when neutrons of higher mean energy traverse the thin, dry Martian atmosphere and encounter water in the astronaut's body. Water, being hydrogeneous, efficiently moderates the high energy neutrons thereby slowing them as they penetrate deeply into the body. Consequently, greater radiation doses can be deposited in or near critical organs such as the liver or spleen than is the case on Earth. A second significant threat is the possibility of a high energy heavy ion or neutron causing a DNA double strand break in a single strike.

  18. Prompt Fission Neutron Energy Spectra Induced by Fast Neutrons

    NASA Astrophysics Data System (ADS)

    Staples, Parrish Alan

    Prompt fission neutron energy spectra for ^{235}U and ^{239 }Pu have been measured for fission neutron energies greater than the energy of the incident neutrons inducing fission. The measurements were undertaken to investigate the shape dependence of the fission neutron spectra upon both the incident neutron energy and the mass of the nucleus undergoing fission. Measurements were made for both nuclides at the following incident neutron energies; 0.50 MeV, 1.50 MeV, 2.50 MeV and 3.50 MeV. The data are presented either as relative yields or as ratios of a measured spectrum to the ^{235}U spectrum at 0.50 MeV. Incident neutrons were produced by the ^7Li(p,n)^7Be reaction using a pulsed, bunched proton beam from the 5.5 MV Van de Graaff accelerator at the University of Massachusetts Lowell Pinanski Energy Center. The neutrons were detected by a thin liquid scintillator with good time resolution capabilities; time-of-flight techniques were used for neutron energy determination; in addition pulse-shape-discrimination was used to reduce gamma-ray background levels. The measurements are compared to calculations based on the Los Alamos Model of Madland and Nix to test its predictive capabilities. The data are fit by the Watt equation to determine the mean energy of the spectra, and to facilitate comparison of the results to previous measurements. The data are also compared directly to previous measurements.

  19. Materials and neutronic research at the Low Energy Neutron Source

    NASA Astrophysics Data System (ADS)

    Baxter, David V.

    2016-04-01

    In the decade since the Low Energy Neutron Source (LENS) at Indiana University Center for Exploration of Energy and Matter (CEEM) produced its first neutrons, the facility has made important contributions to the international neutron scattering community. LENS employs a 13MeV proton beam at up to 4kW beam power onto one of two Be targets to produce neutrons for research in fields ranging from radiation effects in electronics to studies of the structure of fluids confined in nanoporous materials. The neutron source design at the heart of LENS facilitates relatively rapid hands-on access to most of its components which provides a foundation for a research program in experimental neutronics and affords numerous opportunities for novel educational experiences. We describe in some detail a number of the unique capabilities of this facility.

  20. A Survey of Chemical Separation in Accreting Neutron Stars

    NASA Astrophysics Data System (ADS)

    Mckinven, Ryan; Cumming, Andrew; Medin, Zach; Schatz, Hendrik

    2016-06-01

    The heavy element ashes of rp-process hydrogen and helium burning in accreting neutron stars are compressed to high density where they freeze, forming the outer crust of the star. We calculate the chemical separation on freezing for a number of different nuclear mixtures resulting from a range of burning conditions for the rp-process. We confirm the generic result that light nuclei are preferentially retained in the liquid and heavy nuclei in the solid. This is in agreement with the previous study of a 17-component mixture of rp-process ashes by Horowitz et al., but extends that result to a much larger range of compositions. We also find an alternative phase separation regime for the lightest ash mixtures which does not demonstrate this generic behavior. With a few exceptions, we find that chemical separation reduces the expected {Q}{{imp}} in the outer crust compared to the initial rp-process ash, where {Q}{{imp}} measures the mean-square dispersion in atomic number Z of the nuclei in the mixture. We find that the fractional spread of Z plays a role in setting the amount of chemical separation and is strongly correlated to the divergence between the two/three-component approximations and the full component model. The contrast in Y e between the initial rp-process ashes and the equilibrium liquid composition is similar to that assumed in earlier two-component models of compositionally driven convection, except for very light compositions which produce nearly negligible convective driving. We discuss the implications of these results for observations of accreting neutron stars.

  1. Separable representation of energy-dependent optical potentials

    NASA Astrophysics Data System (ADS)

    Hlophe, L.; Elster, Ch.

    2016-03-01

    Background: One important ingredient for many applications of nuclear physics to astrophysics, nuclear energy, and stockpile stewardship are cross sections for reactions of neutrons with rare isotopes. Since direct measurements are often not feasible, indirect methods, e.g., (d ,p ) reactions, should be used. Those (d ,p ) reactions may be viewed as three-body reactions and described with Faddeev techniques. Purpose: Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. Optical potentials representing the effective interactions in the neutron (proton) nucleus subsystem are usually non-Hermitian as well as energy dependent. Potential matrix elements as well as transition matrix elements calculated with them must fulfill the reciprocity theorem. The purpose of this paper is to introduce a separable, energy-dependent representation of complex, energy-dependent optical potentials that fulfill reciprocity exactly. Methods: Momentum space Lippmann-Schwinger integral equations are solved with standard techniques to obtain the form factors for the separable representation. Results: Starting from a separable, energy-independent representation of global optical potentials based on a generalization of the Ernst-Shakin-Thaler (EST) scheme, a further generalization is needed to take into account the energy dependence. Applications to n +48Ca ,n +208Pb , and p +208Pb are investigated for energies from 0 to 50 MeV with special emphasis on fulfilling reciprocity. Conclusions: We find that the energy-dependent separable representation of complex, energy-dependent phenomenological optical potentials fulfills reciprocity exactly. In addition, taking into account the explicit energy dependence slightly improves the description of the S matrix elements.

  2. One-neutron knockout from light neutron-rich nuclei at relativistic energies

    SciTech Connect

    Rodriguez-Tajes, C.; Alvarez-Pol, H.; Benjamim, E.; Benlliure, J.; Caamano, M.; Casarejos, E.; Cortina-Gil, D.; Gascon, M.; Kurtukian, T.; Perez-Loureiro, D.; Aumann, T.; Chatillon, A.; Geissel, H.; Nociforo, C.; Prochazka, A.; Simon, H.; Suemmerer, K.; Weick, H.; Winkler, M.; Borge, M. J. G.

    2010-08-15

    One-neutron knockout reactions from neutron-rich nuclei, with Z=6-13 and N=8-22, were studied at the Fragment Separator (GSI) at high beam energies, around 700 MeV/nucleon. Structural phenomena such as the formation of one-neutron halos in odd-mass carbon isotopes ({sup 15,17,19}C) will be discussed. In addition, one-neutron knockout measurements from {sup 22}N were carried out for the first time and demonstrate clearly the change from a 0d{sub 5/2} to a 1s{sub 1/2} orbital for the valence neutron, an effect that is expected above N=14 and that was also observed in {sup 23}O and {sup 24}F. The possibility of an anomalous structure of {sup 26}F, due to a significant 1s{sub 1/2} neutron admixture, will also be discussed in the light of the experimental data obtained in this work. Finally, the ground-state configuration of neutron-rich neon isotopes ({sup 24-28}Ne) was studied, providing new information in a region that is relatively close to the island of inversion.

  3. Neutron-fragment and Neutron-neutron Correlations in Low-energy Fission

    NASA Astrophysics Data System (ADS)

    Lestone, J. P.

    2016-01-01

    A computational method has been developed to simulate neutron emission from thermal-neutron induced fission of 235U and from spontaneous fission of 252Cf. Measured pre-emission mass-yield curves, average total kinetic energies and their variances, both as functions of mass split, are used to obtain a representation of the distribution of fragment velocities. Measured average neutron multiplicities as a function of mass split and their dependence on total kinetic energy are used. Simulations can be made to reproduce measured factorial moments of neutron-multiplicity distributions with only minor empirical adjustments to some experimental inputs. The neutron-emission spectra in the rest-frame of the fragments are highly constrained by ENDF/B-VII.1 prompt-fission neutron-spectra evaluations. The n-f correlation measurements of Vorobyev et al. (2010) are consistent with predictions where all neutrons are assumed to be evaporated isotropically from the rest frame of fully accelerated fragments. Measured n-f and n-n correlations of others are a little weaker than the predictions presented here. These weaker correlations could be used to infer a weak scission-neutron source. However, the effect of neutron scattering on the experimental results must be studied in detail before moving away from a null hypothesis that all neutrons are evaporated from the fragments.

  4. PROCESSES FOR SEPARATING AND RECOVERING CONSTITUENTS OF NEUTRON IRRADIATED URANIUM

    DOEpatents

    Connick, R.E.; Gofman, J.W.; Pimentel, G.C.

    1959-11-10

    Processes are described for preparing plutonium, particularly processes of separating plutonium from uranium and fission products in neutron-irradiated uraniumcontaining matter. Specifically, plutonium solutions containing uranium, fission products and other impurities are contacted with reducing agents such as sulfur dioxide, uranous ion, hydroxyl ammonium chloride, hydrogen peroxide, and ferrous ion whereby the plutoninm is reduced to its fluoride-insoluble state. The reduced plutonium is then carried out of solution by precipitating niobic oxide therein. Uranium and certain fission products remain behind in the solution. Certain other fission products precipitate along with the plutonium. Subsequently, the plutonium and fission product precipitates are redissolved, and the solution is oxidized with oxidizing agents such as chlorine, peroxydisulfate ion in the presence of silver ion, permanganate ion, dichromate ion, ceric ion, and a bromate ion, whereby plutonium is oxidized to the fluoride-soluble state. The oxidized solution is once again treated with niobic oxide, thus precipitating the contamirant fission products along with the niobic oxide while the oxidized plutonium remains in solution. Plutonium is then recovered from the decontaminated solution.

  5. 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.

  6. Intermediate energy neutron beams from the MURR

    SciTech Connect

    Brugger, R.M.; Herleth, W.H. )

    1990-01-01

    Several reactors in the United States are potential candidates to deli1ver beams of intermediate energy neutrons for NCT. At this time, moderators, as compared to filters, appear to be the more effective means of tailoring the flux of these reactors. The objective is to sufficiently reduce the flux of fast neutrons while producing enough intermediate energy neutrons for treatments. At the University of Missouri Research Reactor (MURR), the code MCNP has recently been used to calculate doses in a phantom. First, ideal beams of 1, 35, and 1000 eV neutrons were analyzed to determine doses and advantage depths in the phantom. Second, a high quality beam that had been designed to fit in the thermal column of the MURR, was reanalyzed. MCNP calculations of the dose in phantom in this beam confirmed previous calculations and showed that this beam would be a nearly ideal one with neutrons of the desired energy and also a high neutron current. However, installation of this beam will require a significant modification of the thermal column of the MURR. Therefore, a second beam that is less difficult to build and install, but of lower neutron current, has been designed to fit in MURR port F. This beam is designed using inexpensive A1, S, and Pb. The doses calculated in the phantom placed in this beam show that it will be satisfactory for sample tests, animal tests, and possible initial patient trials. Producing this beam will require only modest modifications of the existing tube.

  7. MASS SEPARATION OF HIGH ENERGY PARTICLES

    DOEpatents

    Marshall, L.

    1962-09-25

    An apparatus and method are described for separating charged, high energy particles of equal momentum forming a beam where the particles differ slightly in masses. Magnetic lenses are utilized to focus the beam and maintain that condition while electrostatic fields located between magnetic lenses are utilized to cause transverse separation of the particles into two beams separated by a sufficient amount to permit an aperture to block one beam. (AEC)

  8. Energy storage device with large charge separation

    DOEpatents

    Holme, Timothy P.; Prinz, Friedrich B.; Iancu, Andrei

    2016-04-12

    High density energy storage in semiconductor devices is provided. There are two main aspects of the present approach. The first aspect is to provide high density energy storage in semiconductor devices based on formation of a plasma in the semiconductor. The second aspect is to provide high density energy storage based on charge separation in a p-n junction.

  9. Compact Neutron Sources for Energy and Security

    NASA Astrophysics Data System (ADS)

    Uesaka, Mitsuru; Kobayashi, Hitoshi

    We choose nuclear data and nuclear material inspection for energy application, and nondestructive testing of explosive and hidden nuclear materials for security application. Low energy (~100 keV) electrostatic accelerators of deuterium are commercially available for nondestructive testing. For nuclear data measurement, electrostatic ion accelerators and L-band (1.428GHz) and S-band (2.856GHz) electron linear accelerators (linacs) are used for the neutron source. Compact or mobile X-band (9.3, 11.424GHz) electron linac neutron sources are under development. A compact proton linac neutron source is used for nondestructive testing, especially water in solids. Several efforts for more neutron intensity using proton and deuteron accelerators are also introduced.

  10. Compact Neutron Sources for Energy and Security

    NASA Astrophysics Data System (ADS)

    Uesaka, Mitsuru; Kobayashi, Hitoshi

    We choose nuclear data and nuclear material inspection for energy application, and nondestructive testing of explosive and hidden nuclear materials for security application. Low energy (˜100keV) electrostatic accelerators of deuterium are commercially available for nondestructive testing. For nuclear data measurement, electrostatic ion accelerators and L-band (1.428GHz) and S-band (2.856GHz) electron linear accelerators (linacs) are used for the neutron source. Compact or mobile X-band (9.3, 11.424GHz) electron linac neutron sources are under development. A compact proton linac neutron source is used for nondestructive testing, especially water in solids. Several efforts for more neutron intensity using proton and deuteron accelerators are also introduced.

  11. Advanced Membrane Separation Technologies for Energy Recovery

    SciTech Connect

    2009-05-01

    This factsheet describes a research project whose goal is to develop novel materials for use in membrane separation technologies for the recovery of waste energy and water from industrial process streams.

  12. Energy Correlation of Prompt Fission Neutrons

    NASA Astrophysics Data System (ADS)

    Elter, Zs.; Pázsit, I.

    2016-03-01

    In all cases where neutron fluctuations in a branching process (such as in multiplicity measurements) are treated in an energy dependent description, the energy correlations of the branching itself (energy correlations of the fission neutrons) need to be known. To date, these are not known from experiments. Such correlations can be theoretically and numerically derived by modelling the details of the fission process. It was suggested earlier that the fact that the prompt neutrons are emitted from the moving fission targets, will influence their energy and angular distributions in the lab system, which possibly induces correlations. In this paper the influence of the neutron emission process from the moving targets on the energy correlations is investigated analytically and via numerical simulations. It is shown that the correlations are generated by the random energy and direction distributions of the fission fragments. Analytical formulas are derived for the two-point energy distributions, and quantitative results are obtained by Monte-Carlo simulations. The results lend insight into the character of the two-point distributions, and give quantitative estimates of the energy correlations, which are generally small.

  13. Probing Dark Energy models with neutrons

    NASA Astrophysics Data System (ADS)

    Pignol, Guillaume

    2015-07-01

    There is a deep connection between cosmology — the science of the infinitely large — and particle physics — the science of the infinitely small. This connection is particularly manifest in neutron particle physics. Basic properties of the neutron — its Electric Dipole Moment and its lifetime — are intertwined with baryogenesis and nucleosynthesis in the early Universe. I will cover this topic in the first part, that will also serve as an introduction (or rather a quick recap) of neutron physics and Big Bang cosmology. Then, the rest of the paper will be devoted to a new idea: using neutrons to probe models of Dark Energy. In the second part, I will present the chameleon theory: a light scalar field accounting for the late accelerated expansion of the Universe, which interacts with matter in such a way that it does not mediate a fifth force between macroscopic bodies. However, neutrons can alleviate the chameleon mechanism and reveal the presence of the scalar field with properly designed experiments. In the third part, I will describe a recent experiment performed with a neutron interferometer at the Institut Laue Langevin that sets already interesting constraints on the chameleon theory. Last, the chameleon field can be probed by measuring the quantum states of neutrons bouncing over a mirror. In the fourth part, I will present the status and prospects of the GRANIT experiment at the ILL.

  14. Separation of radiation defects in Ni and Ni-C alloys under electron and neutron irradiation

    NASA Astrophysics Data System (ADS)

    Arbuzov, S. E.; Danilov, V. L.; Goshchitskii, B. N.; Kar'kin, A. E.; Parkhomenko, V. D.

    2016-02-01

    Complex investigations of radiation damage of Ni and Ni- 880 at. ppm C alloy under electron and neutron irradiation in the region of room temperature hardened and deformed state. In pure nickel, with the deformation microstructure, both in electron and in the neutron irradiation is observed separation of radiation-induced defects. When electron irradiation in the alloy Ni-C separation effect is observed, and when neutron irradiation there is no. This is due to the interaction of carbon atoms with radiation defects. The main sinks for radiation-induced defects are the areas with a high concentration of defects in cascades of atomic displacements.

  15. Measurements of Separate Neutron and Gamma-Ray Coincidences with Liquid Scintillators and Digital PSD Technique

    SciTech Connect

    Flaska, Marek; Pozzi, Sara A

    2007-10-01

    A new technique is presented for the measurement of neutron and/or gamma-ray coincidences. Separate neutron neutron, neutron gamma-ray, gamma-ray neutron, and gamma-ray gamma-ray coincidences are acquired with liquid scintillation detectors and a digital pulse shape discrimination (PSD) technique based on standard charge integration method. The measurement technique allows for the collection of fast coincidences in a time window of the order of a few tens of nanoseconds between the coincident particles. The PSD allows for the acquisition of the coincidences in all particle combinations. The measurements are compared to results obtained with the MCNP-PoliMi code, which simulates neutron and gamma-ray coincidences from from a source on an event-by-event basis. This comparison leads to good qualitative agreement.

  16. Ultrahigh energy neutrinos from galactic neutron stars

    NASA Technical Reports Server (NTRS)

    Helfand, D. J.

    1979-01-01

    An attempt is made to estimate the production rate of ultrahigh energy (UHE) neutrinos from galactic neutron stars. The statistics of various stellar populations are reviewed as well as an evolutionary scheme linking several neutron star environments. An observational test for predicting stellar evolution is made using two mass ratio intervals of less than 0.3 and greater than or approximately equal to 0.3, which is supported by kinematical evidence. Attention is given to the problem of the target material that is required by UHE protons accelerated from the pulsar's surface to their rotational kinetic energy, and to the detectability of neutron stars in the UHE neutrinos by employing the deep underwater muon and neutrino detector (DUMAND) array.

  17. Material identification based upon energy-dependent attenuation of neutrons

    DOEpatents

    Marleau, Peter

    2015-10-06

    Various technologies pertaining to identifying a material in a sample and imaging the sample are described herein. The material is identified by computing energy-dependent attenuation of neutrons that is caused by presence of the sample in travel paths of the neutrons. A mono-energetic neutron generator emits the neutron, which is downscattered in energy by a first detector unit. The neutron exits the first detector unit and is detected by a second detector unit subsequent to passing through the sample. Energy-dependent attenuation of neutrons passing through the sample is computed based upon a computed energy of the neutron, wherein such energy can be computed based upon 1) known positions of the neutron generator, the first detector unit, and the second detector unit; or 2) computed time of flight of neutrons between the first detector unit and the second detector unit.

  18. Post-separation detection of nucleic acids and proteins by neutron activation.

    PubMed Central

    Snapka, R M; Kwok, K; Bernard, J A; Harling, O K; Varshavsky, A

    1986-01-01

    We describe approaches to neutron activation analysis and their application to post-separation autoradiographic detection of biological compounds. Specifically, we have extended the use of a "direct-labeling" method to the post-separation detection of DNA after gel electrophoresis and to the detection of nucleotides separated by TLC. In addition, we describe a more generally applicable "indirect-labeling" method in which separated compounds of interest are selectively bound to ligands containing highly neutron-activatable elements, such as manganese (55Mn), europium (151Eu), or dysprosium (164Dy), and then irradiated with thermal neutrons. This method is illustrated with nucleotides separated by TLC and with proteins separated by polyacrylamide gel electrophoresis. In contrast to the direct-labeling approach, the indirect-labeling method can be adapted to detect any class of substances for which a highly neutron-activatable, selectively binding ligand is available. The theoretically achievable sensitivity of the indirect-labeling method is in the attomole (10(-18) mol) range. Images PMID:3466168

  19. Separations Technology for Clean Water and Energy

    SciTech Connect

    Jarvinen, Gordon D

    2012-06-22

    Providing clean water and energy for about nine billion people on the earth by midcentury is a daunting challenge. Major investments in efficiency of energy and water use and deployment of all economical energy sources will be needed. Separations technology has an important role to play in producing both clean energy and water. Some examples are carbon dioxide capture and sequestration from fossil energy power plants and advanced nuclear fuel cycle scemes. Membrane separations systems are under development to improve the economics of carbon capture that would be required at a huge scale. For nuclear fuel cycles, only the PUREX liquid-liquid extraction process has been deployed on a large scale to recover uranium and plutonium from used fuel. Most current R and D on separations technology for used nuclear fuel focuses on ehhancements to a PUREX-type plant to recover the minor actinides (neptunium, americiu, and curium) and more efficiently disposition the fission products. Are there more efficient routes to recycle the actinides on the horizon? Some new approaches and barriers to development will be briefly reviewed.

  20. Cross-helix separation of tropomyosin molecules in acto-tropomyosin as determined by neutron scattering.

    PubMed Central

    Bivin, D B; Stone, D B; Schneider, D K; Mendelson, R A

    1991-01-01

    The cross-helix separation of Tm molecules in acto-tropomyosin has been determined using neutron scattering. Deuterated Dictyostelium discoideum actin was density matched in a 93% D2O buffer so that effectively only the protonated tropomyosin was "visible" to neutrons. Analysis of the solution scattering pattern in the region of the first oscillation yielded a value for the cross-helix separation of 7.9 +/- 0.3 nm. The implications of this value for the mechanism of the regulation of muscle contraction are discussed in light of recent results by others. Images FIGURE 2 PMID:1829644

  1. Neutron energy spectrum adjustment using deposited metal films on Teflon in the miniature neutron source reactor.

    PubMed

    Nassan, L; Abdallah, B; Omar, H; Sarheel, A; Alsomel, N; Ghazi, N

    2016-01-01

    The focus of this article was on the experimental estimation of the neutron energy spectrum in the inner irradiation site of the miniature neutron source reactor (MNSR), using, for the first time, a selected set of deposited metal films on Teflon (DMFTs) neutron detectors. Gold, copper, zinc, titanium, aluminum, nickel, silver, and chromium were selected because of the dependence of their neutron cross-sections on neutron energy. Emphasis was placed on the usability of this new type of neutron detectors in the total neutron energy spectrum adjustment. The measured saturation activities per target nucleus values of the DMFTs, and the calculated neutron spectrum in the inner irradiation site using the MCNP-4C code were used as an input for the STAY'SL computer code during the adjustment procedure. The agreement between the numerically calculated and experimentally adjusted spectra results was discussed. PMID:26562448

  2. Image demodulation using multidimensional energy separation

    NASA Astrophysics Data System (ADS)

    Maragos, Petros; Bovik, Alan C.

    1995-09-01

    Locally narrow-band images can be modeled as two-dimensional (2D) spatial AM-FM signals with several applications in image texture analysis and computer vision. We formulate an image-demodulation problem and present a solution based on the multidimensional energy operator Phi (f)= \\double-vertical-bar \\inverted-Delta-triangle f \\double-vertical-bar 2-f \\inverted-Delta-triangle 2 f . This nonlinear operator is a multidimensional extension of the one-dimensional (1D) energy-tracking operator Psi (f)=( f\\prime)2 -ff\\prime\\prime , which has been found useful for demodulating 1D AM-FM and speech signals. We discuss some interesting properties of the multidimensional operator and develop a multidimensional energy-separation algorithm to estimate the amplitude envelope and instantaneous frequencies of 2D spatially varying AM-FM signals. Experiments are also presented on applying this 2D energy-demodulation algorithm to estimate the instantaneous amplitude contrast and spatial frequencies of image textures bandpass filtered by means of Gabor filters. The attractive features of the multidimensional energy operator and the 2D energy-separation algorithm are their simplicity, efficiency, and ability to track instantaneously varying

  3. Radial Flux Distribution of Low-Energy Neutrons.

    ERIC Educational Resources Information Center

    Higinbotham, J.

    1979-01-01

    Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron flux using indium as a probe. (GA)

  4. Continuous Energy MC Neutron/Photon

    Energy Science and Technology Software Center (ESTSC)

    1991-10-10

    VIM solves the three-dimensional steady-state multiplication eigenvalue or fixed source neutron or photon (VIM3.0) transport problem using continuous energy-dependent nuclear data. It was designed for the analysis of fast critical experiments. In VIM3.0, the photon interactions i.e., pair production, coherent and incoherent scattering, and photoelectric events, and photon heating are tallied by group, region, and isotope.

  5. A SIGNATURE OF CHEMICAL SEPARATION IN THE COOLING LIGHT CURVES OF TRANSIENTLY ACCRETING NEUTRON STARS

    SciTech Connect

    Medin, Zach; Cumming, Andrew E-mail: cumming@physics.mcgill.ca

    2014-03-01

    We show that convection driven by chemical separation can significantly affect the cooling light curves of accreting neutron stars after they go into quiescence. We calculate the thermal relaxation of the neutron star ocean and crust including the thermal and compositional fluxes due to convection. After the inward propagating cooling wave reaches the base of the neutron star ocean, the ocean begins to freeze, driving chemical separation. The resulting convection transports heat inward, giving much faster cooling of the surface layers than found assuming the ocean cools passively. The light curves including convection show a rapid drop in temperature weeks after outburst. Identifying this signature in observed cooling curves would constrain the temperature and composition of the ocean as well as offer a real time probe of the freezing of a classical multicomponent plasma.

  6. A neutron spectrometer for neutron energies between 1 eV and 10 keV

    SciTech Connect

    Wang, C.K.; Blue, T.E.

    1988-01-01

    In boron neutron capture therapy (BNCT), it is the consensus that epithermal neutron beams have advantages over thermal beams in treating deep-seated brain tumors, and large neutron fields have advantages over narrow beams, since whole-brain irradiations are thought to be necessary in many cases. Epithermal neutron sources for BNCT, which include filtered reactor neutron beams and moderated reactor neutron fields, are currently being developed at many institutions around the world. Neutrons with energies between 1 eV and 10 keV are most suitable for treating brain tumors. However, techniques for measuring neutron spectra in a vacuum in this energy range are not well developed. This paper describes a new type of neutron spectrometer that has a set of response functions that peak at equally spaced intervals on a logarithmic energy scale ranging from 1 eV to 10 keV; therefore, neutron spectra (or histograms) in this energy range can be obtained by properly applying spectrum unfolding techniques to the measured data. The spectrometer is applicable for measurements in a vacuum for both narrow neutron beams and wide neutron fields.

  7. FAST NEUTRON SPECTROMETER USING SPACED SEMICONDUCTORS FOR MEASURING TOTAL ENERGY OF NEUTRONS CAPTURED

    DOEpatents

    Love, T.A.; Murray, R.B.

    1964-04-14

    A fast neutron spectrometer was designed, which utilizes a pair of opposed detectors having a layer of /sup 6/LiF between to produce alpha and T pair for each neutron captured to provide signals, which, when combined, constitute a measure of neutron energy. (AEC)

  8. Dependence on neutron energy of neutron-induced peaks in Ge detectors

    NASA Astrophysics Data System (ADS)

    Gete, E.; Measday, David F.; Moftah, B. A.; Saliba, M. A.; Stocki, Trevor J.

    1997-02-01

    We have studied the peak shapes at 596 and 691 KeV resulting from fast neutron interactions inside germanium detectors. We have used neutrons from a 252Cf source, as well as from the 28Si((mu) -, nv), and 209Bi((pi) -, xn) reactions to compare the peaks and to check for any dependence of peak shape on the incoming neutron energy. In our investigation, no dependence of these peak shapes on the neutron energy spectra has been observed. In a comparison of these peak shapes with other studies we found similar results to ours except for monoenergetic neutron irradiations from 1 to 8 MeV.

  9. Separation and Quantification of Chemically Diverse Analytes in Neutron Irradiated Fissile Materials

    SciTech Connect

    Douglas, Matthew; Friese, Judah I.; Greenwood, Lawrence R.; Farmer, Orville T.; Thomas, Linda MP; Maiti, Tapas C.; Finn, Erin C.; Garofoli, Stephanie J.; Gassman, Paul L.; Huff, Morgan M.; Schulte, Shannon M.; Smith, Steven C.; Thomas, Kathie K.; Bachelor, Paula P.

    2009-10-01

    Quantitative measurement of fission and activation products resulting from neutron irradiation of fissile materials is of interest for applications in environmental monitoring, nuclear waste management, and national security. To overcome mass and spectral interferences, and the relative small quantities of some target analytes, an extensive series of chemical separations is necessary. Based on established separations processes involving co-precipitation, solvent extraction, and ion-exchange and extraction chromatography, we have been evaluating and optimizing a proposed sequence of separation steps to allow for the timely quantification of analytes of interest. For simplicity, much of the chemical separation development work has been performed using stable elements as surrogates for the radioactive material. We have recently evaluated the optimized procedures using an irradiated sample to examine the adequacy of separations for measurement of desired analytes by gamma spectrometry. Here we present the results of this evaluation and describe the radiochemical separations utilized.

  10. Delayed-Neutron Energy Spectra for Thermal Fission of URANIUM-235.

    NASA Astrophysics Data System (ADS)

    Tanczyn, Robert Steven

    An experiment to measure delayed-neutron energy spectra resulting from thermal fission of U-235 has been carried out at the University of Lowell. Delayed neutrons, emitted by the radioactive fission fragments having halflives varying from 0.2 to 56 seconds, are important in the operation and control of fission reactors. In separate experiments at the University of Lowell 1-MW Fission Reactor and 5.5-MV Van de Graaff Accelerator, thermal fission was induced in a U-235 lined hemispherical fission chamber. The resulting fission fragments were transferred by a helium-jet system to a low-background counting area where composite delayed-neutron energy spectra were measured as a function of time after fission. Neutron energies were determined by the time-of-flight technique using beta-neutron correlations for timing. Two types of scintillators were used for neutron detection: Li-6 glass sensitive to neutrons in the energy range 10 - 300 keV, and plastic Pilot U sensitive to neutrons in the range 100 keV - 2.0 MeV. Spectra over the neutron energy range 0.1 - 2.0 MeV were measured for eight different time intervals after fission, each time interval containing varying contributions from the Six-Groups of delayed neutrons. Two of the eight time intervals were chosen to contain significant contributions from the shortest lived Groups 5 and 6. This work presents a brief outline of pertinent background material followed by a detailed discussion of the experimental technique and data analysis leading to final energy spectra. Measured composite energy spectra along with average energies are presented. Comparisons to spectra constructed from the Studsvik compilation are also presented.

  11. Experimental Studies of Prompt Fission Neutron Energy Spectra

    NASA Astrophysics Data System (ADS)

    Sardet, A.; Granier, T.; Laurent, B.; Oberstedt, A.

    Prompt fission neutron spectra were measured in the reactions 238U(n,f), 235U(n,f) and 237Np(n,f) at different incident neutron energies. The neutrons were detected using a coaxial doped p-terphenyl scintillation detector in coincidence with fission fragments and their time-of-flight was recorded. The properties of the neutron detector were determined and the results are presented in this work. A preliminary neutron detection efficiency was applied to data from the neutron-induced fission of 238U at En = 5.2 MeV, leading to encouraging results.

  12. Detecting energy dependent neutron capture distributions in a liquid scintillator

    NASA Astrophysics Data System (ADS)

    Balmer, Matthew J. I.; Gamage, Kelum A. A.; Taylor, Graeme C.

    2015-03-01

    A novel technique is being developed to estimate the effective dose of a neutron field based on the distribution of neutron captures in a scintillator. Using Monte Carlo techniques, a number of monoenergetic neutron source energies and locations were modelled and their neutron capture response was recorded. Using back propagation Artificial Neural Networks (ANN) the energy and incident direction of the neutron field was predicted from the distribution of neutron captures within a 6Li-loaded liquid scintillator. Using this proposed technique, the effective dose of 252Cf, 241AmBe and 241AmLi neutron fields was estimated to within 30% for four perpendicular angles in the horizontal plane. Initial theoretical investigations show that this technique holds some promise for real-time estimation of the effective dose of a neutron field.

  13. High-energy neutron spectroscopy with thick silicon detectors

    NASA Technical Reports Server (NTRS)

    Kinnison, James D.; Maurer, Richard H.; Roth, David R.; Haight, Robert C.

    2003-01-01

    The high-energy neutron component of the space radiation environment in thick structures such as the International Space Station contributes to the total radiation dose received by an astronaut. Detector design constraints such as size and mass have limited the energy range of neutron spectrum measurements in orbit to about 12 MeV in Space Shuttle studies. We present a new method for high-energy neutron spectroscopy using small silicon detectors that can extend these measurements to more than 500 MeV. The methodology is based on measurement of the detector response function for high-energy neutrons and inversion of this response function with measured deposition data to deduce neutron energy spectra. We also present the results of an initial shielding study performed with the thick silicon detector system for high-energy neutrons incident on polyethylene.

  14. High-energy neutron spectroscopy with thick silicon detectors.

    PubMed

    Kinnison, James D; Maurer, Richard H; Roth, David R; Haight, Robert C

    2003-02-01

    The high-energy neutron component of the space radiation environment in thick structures such as the International Space Station contributes to the total radiation dose received by an astronaut. Detector design constraints such as size and mass have limited the energy range of neutron spectrum measurements in orbit to about 12 MeV in Space Shuttle studies. We present a new method for high-energy neutron spectroscopy using small silicon detectors that can extend these measurements to more than 500 MeV. The methodology is based on measurement of the detector response function for high-energy neutrons and inversion of this response function with measured deposition data to deduce neutron energy spectra. We also present the results of an initial shielding study performed with the thick silicon detector system for high-energy neutrons incident on polyethylene. PMID:12537520

  15. Spectral correction factors for conventional neutron dosemeters used in high-energy neutron environments.

    PubMed

    Lee, K W; Sheu, R J

    2015-04-01

    High-energy neutrons (>10 MeV) contribute substantially to the dose fraction but result in only a small or negligible response in most conventional moderated-type neutron detectors. Neutron dosemeters used for radiation protection purpose are commonly calibrated with (252)Cf neutron sources and are used in various workplace. A workplace-specific correction factor is suggested. In this study, the effect of the neutron spectrum on the accuracy of dose measurements was investigated. A set of neutron spectra representing various neutron environments was selected to study the dose responses of a series of Bonner spheres, including standard and extended-range spheres. By comparing (252)Cf-calibrated dose responses with reference values based on fluence-to-dose conversion coefficients, this paper presents recommendations for neutron field characterisation and appropriate correction factors for responses of conventional neutron dosemeters used in environments with high-energy neutrons. The correction depends on the estimated percentage of high-energy neutrons in the spectrum or the ratio between the measured responses of two Bonner spheres (the 4P6_8 extended-range sphere versus the 6″ standard sphere). PMID:25280480

  16. Structure of hydrogenous liquids: separation of coherent and incoherent cross sections using polarised neutrons

    NASA Astrophysics Data System (ADS)

    Stunault, A.; Vial, S.; Pusztai, L.; Cuello, G. J.; Temleitner, L.

    2016-04-01

    The determination of the coherent structure factor of hydrogenous liquids is very difficult: while X-rays are barely sensitive to hydrogen, neutrons results still lack accuracy due to the contamination of the scattering intensities by a huge spin-incoherent signal from the 1H atoms. Using polarised neutrons with polarisation analysis, one can experimentally separate the coherent and incoherent contributions to the scattered intensity. We present the upgrade of the D3 polarised hot neutron diffractometer at ILL to study hydrogenated liquids. We show first data obtained from a test sample of water and detail the data reduction leading to an unprecedented accuracy in the extraction of the coherent signal, representative of the structure.

  17. Dipole-strength distributions up to the particle-separation energies and photodissociation of Mo isotopes

    NASA Astrophysics Data System (ADS)

    Schwengner, R.; Benouaret, N.; Beyer, R.; Dönau, F.; Erhard, M.; Frauendorf, S.; Grosse, E.; Junghans, A. R.; Klug, J.; Kosev, K.; Nair, C.; Nankov, N.; Rusev, G.; Schilling, K. D.; Wagner, A.

    2007-05-01

    Dipole-strength distributions in the nuclides 92Mo, 98Mo and 100Mo have been investigated in photon-scattering experiments with bremsstrahlung at the superconducting electron accelerator ELBE of the Forschungszentrum Rossendorf. A simulation of γ cascades was performed in order to estimate the distribution of inelastic transitions to low-lying states and thus to deduce the primary dipole-strength distribution up to the neutron-separation energies. The absorption cross sections obtained connect smoothly to ( γ, n) cross sections and give novel information about the low-energy tail of the Giant Dipole Resonance below the neutron-separation energies. The experimental cross sections are compared with predictions of a Quasiparticle-Random-Phase Approximation (QRPA) in a deformed basis. Photoactivation experiments were performed at various electron energies to study the 92Mo( γ, n), 92Mo( γ, p), 92Mo( γ, α) and 100Mo( γ, n) reactions. The deduced activation yields are compared with theoretical predictions.

  18. Thermal conductivity and phase separation of the crust of accreting neutron stars.

    PubMed

    Horowitz, C J; Caballero, O L; Berry, D K

    2009-02-01

    Recently, crust cooling times have been measured for neutron stars after extended outbursts. These observations are very sensitive to the thermal conductivity kappa of the crust and strongly suggest that kappa is large. We perform molecular dynamics simulations of the structure of the crust of an accreting neutron star using a complex composition that includes many impurities. The composition comes from simulations of rapid proton capture nucleosynthesis followed by electron captures. We find that the thermal conductivity is reduced by impurity scattering. In addition, we find phase separation. Some impurities with low atomic number Z are concentrated in a subregion of the simulation volume. For our composition, the solid crust must separate into regions of different compositions. This could lead to an asymmetric star with a quadrupole deformation. Observations of crust cooling can constrain impurity concentrations. PMID:19391802

  19. Differential neutron energy spectra measured on spacecraft low Earth orbit

    NASA Technical Reports Server (NTRS)

    Benton, E. V.; Frank, A. L.; Dudkin, E. V.; Potapov, Yu. V.; Akopova, A. B.; Melkumyan, L. V.

    1995-01-01

    Two methods for measuring neutrons in the range from thermal energies to dozens of MeV were used. In the first method, alpha-particles emitted from the (sup 6) Li(n.x)T reaction are detected with the help of plastic nuclear track detectors, yielding results on thermal and resonance neutrons. Also, fission foils are used to detect fast neutrons. In the second method, fast neutrons are recorded by nuclear photographic emulsions (NPE). The results of measurements on board various satellites are presented. The neutron flux density does not appear to correlate clearly with orbital parameters. Up to 50% of neutrons are due to albedo neutrons from the atmosphere while the fluxes inside the satellites are 15-20% higher than those on the outside. Estimates show that the neutron contribution to the total equivalent radiation dose reaches 20-30%.

  20. Dependence of Delayed-Neutron Energy Spectra on the Energy of Neutrons which Induce Fission of Uranium -235

    NASA Astrophysics Data System (ADS)

    Sharfuddin, Quazi

    Delayed neutron energy spectra following both fast and thermal neutron induced fission of U-235 are measured by the time-of-flight technique using beta-neutron correlations. Fast neutrons are produced via the (p,n) reaction in Li-7 using the University of Lowell 5.5 MV Van de Graaff Accelerator, whereas thermal neutrons are produced by surrounding the fission chamber and target assembly with paraffin. Fission fragments stopped in the helium atmosphere of the fission chamber are transferred by a helium jet system to a low background counting room where the composite delayed neutron energy spectra are measured as a function of time after fission. The delayed neutron energy spectra following fast fission of U-235 are compared to those resulting from thermal fission of U-235. Two mathematical methods are developed to deduce the equilibrium delayed neutron spectrum from the composite delayed neutron spectra measured as a function of delay time after fission. These methods are then applied to obtain the equilibrium delayed neutron spectrum from thermal fission of U-235. Finally, the six-group delayed neutron spectra resulting from thermal fission of U-235 are deduced from the measured composite delayed neutron spectra as a function of delay time after fission using a matrix inversion method.

  1. Spectrum tailoring of the neutron energy spectrum in the context of delayed neutron detection

    SciTech Connect

    Koehler, William E; Tobin, Steve J; Sandoval, Nathan P; Fensin, Mike L

    2010-01-01

    For the purpose of measuring plutonium mass in spent fuel, a delayed neutron instrument is of particular interest since, if properly designed, the delayed neutron signal from {sup 235}U is significantly stronger than the signature from {sup 239}Pu or {sup 241}Pu. A key factor in properly designing a delayed neutron instrument is to minimize the fission of {sup 238}U. This minimization is achieved by keeping the interrogating neutron spectrum below {approx} 1 MeV. In the context of spent fuel measurements it is desirable to use a 14 MeV (deuterium and tritium) neutron generator for economic reasons. Spectrum tailoring is the term used to describe the inclusion of material between the 14 MeV neutrons and the interrogated object that lower the neutron energy through nuclear reactions and moderation. This report quantifies the utility of different material combination for spectrum tailoring.

  2. Extraction of protactinium-233 and separation from thermal neutron-irradiated thorium-232 using crown ethers

    SciTech Connect

    Jalhoom, Moayyed G.; Mohammed, Dawood A.; Khalaf, Jumah S.

    2008-07-01

    A new method was developed for the extraction and separation of {sup 233}Pa from thermal neutron-irradiated {sup 232}Th. Solutions of Pa{sup 233} were prepared in LiCI-HCl solutions from which appreciable extraction was obtained using dibenzo-18-crown-6 in 1,2-dichloroethane. The effects of cavity size, substitutions on the crown ring, type of the organic solvent, and temperature on extraction are discussed. Very high separation factors were obtained for the pairs {sup 233}Pa/{sup 232}Th (>105), {sup 233}Pa/{sup 233}U (> 1000), and {sup 232}U/{sup 232}Th (>60). (authors)

  3. New Measurements of Fission Neutron Spectra at Intermediate Energies

    NASA Astrophysics Data System (ADS)

    Ethvignot, Thierry; Granier, Thierry; Haight, Robert C.; O'Donnell, John M.; Devlin, Matthew; Nelson, Ronald O.; Drosg, Roswitha

    2002-04-01

    Interest in obtaining a more detailed understanding of prompt neutron emission in fission is now high. Information on neutron-induced fission of actinides for incident-neutron energies from a few MeV to higher energies, except for data at 14 MeV is sparse. Such measurements are now possible, and the data are needed for design studies of accelerator-driven systems. Moreover, these data provide valuable information to improve our understanding of fission at high excitation energy. As a matter of fact, a theoretical effort has been pursued recently to predict the properties of prompt neutron emission in fission. They are characterized by two basic quantities, the average number of prompt neutrons emitted per fission, which is well known up to 20 MeV, and the neutron energy spectrum, which is not nearly so well known. However, it was shown for a few cases that not only the average energy but also the shape of the Fission Neutron Spectra (FNS) depend on the incident neutron energy. It is particularly interesting to investigate the change in shape of the FNS around the first, second and third chance fission where the properties of the fissioning nucleus drastically change. At the WNR white source, the FNS were measured with the FIGARO set-up, with a ^238U fission chamber as the target. Both incoming and emitted neutron energies were determined with their time of flight. Preliminary results of recorded spectra will be presented at the meeting.

  4. Strong flux of low-energy neutrons produced by thunderstorms.

    PubMed

    Gurevich, A V; Antonova, V P; Chubenko, A P; Karashtin, A N; Mitko, G G; Ptitsyn, M O; Ryabov, V A; Shepetov, A L; Shlyugaev, Yu V; Vildanova, L I; Zybin, K P

    2012-03-23

    We report here for the first time about the registration of an extraordinary high flux of low-energy neutrons generated during thunderstorms. The measured neutron count rate enhancements are directly connected with thunderstorm discharges. The low-energy neutron flux value obtained in our work is a challenge for the photonuclear channel of neutron generation in thunderstorm: the estimated value of the needed high-energy γ-ray flux is about 3 orders of magnitude higher than that one observed. PMID:22540588

  5. 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.

  6. Neutron-star matter within the energy-density functional theory and neutron-star structure

    SciTech Connect

    Fantina, A. F.; Chamel, N.; Goriely, S.; Pearson, J. M.

    2015-02-24

    In this lecture, we will present some nucleonic equations of state of neutron-star matter calculated within the nuclear energy-density functional theory using generalized Skyrme functionals developed by the Brussels-Montreal collaboration. These equations of state provide a consistent description of all regions of a neutron star. The global structure of neutron stars predicted by these equations of state will be discussed in connection with recent astrophysical observations.

  7. New Binding Energy for the Two-Neutron Halo of {sup 11}Li

    SciTech Connect

    Bachelet, C.; Audi, G.; Gaulard, C.; Guenaut, C.; Lunney, D.; Saint Simon, M. de; Thibault, C.; Herfurth, F.

    2008-05-09

    The extended radius of a halo nuclide is very sensitive to the minute binding energy of its valence nucleons. The binding energy of {sup 11}Li has been measured with high precision by using the radio-frequency spectrometer MISTRAL at CERN's ISOLDE facility. The new two-neutron separation energy of 378{+-}5 keV is 25% higher than the previously accepted value with an uncertainty 5 times smaller.

  8. High-Energy Neutron Spectra and Flux Measurements Below Ground

    NASA Astrophysics Data System (ADS)

    Roecker, Caleb; Bernstein, Adam; Marleau, Peter; Vetter, Kai

    2016-03-01

    High-energy neutrons are a ubiquitous and often poorly measured background. Below ground, these neutrons could potentially interfere with antineutrino based reactor monitoring experiments as well as other rare-event neutral particle detectors. We have designed and constructed a transportable fast neutron detection system for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The spectrometer uses a multiplicity technique in order to have a higher effective area than traditional transportable high-energy neutron spectrometers. Transportability ensures a common detector-related systematic bias for future measurements. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. A high-energy neutron may interact in the lead producing many secondary neutrons. The detector records the correlated secondary neutron multiplicity. Over many events, the response can be used to infer the incident neutron energy spectrum and flux. As a validation of the detector response, surface measurements have been performed; results confirm agreement with previous experiments. Below ground measurements have been performed at 3 depths (380, 600, and 1450 m.w.e.); results from these measurements will be presented.

  9. Microscopic calculations of nuclear and neutron matter, symmetry energy and neutron stars

    DOE PAGESBeta

    Gandolfi, S.

    2015-02-01

    We present Quantum Monte Carlo calculations of the equation of state of neutron matter. The equation of state is directly related to the symmetry energy and determines the mass and radius of neutron stars, providing then a connection between terrestrial experiments and astronomical observations. As a result, we also show preliminary results of the equation of state of nuclear matter.

  10. Effect of neutron energy and fluence on deuterium retention behaviour in neutron irradiated tungsten

    NASA Astrophysics Data System (ADS)

    Fujita, Hiroe; Yuyama, Kenta; Li, Xiaochun; Hatano, Yuji; Toyama, Takeshi; Ohta, Masayuki; Ochiai, Kentaro; Yoshida, Naoaki; Chikada, Takumi; Oya, Yasuhisa

    2016-02-01

    Deuterium (D) retention behaviours for 14 MeV neutron irradiated tungsten (W) and fission neutron irradiated W were evaluated by thermal desorption spectroscopy (TDS) to elucidate the correlation between D retention and defect formation by different energy distributions of neutrons in W at the initial stage of fusion reactor operation. These results were compared with that for Fe2+ irradiated W with various damage concentrations. Although dense vacancies and voids within the shallow region near the surface were introduced by Fe2+ irradiation, single vacancies with low concentration were distributed throughout the sample for 14 MeV neutron irradiated W. Only the dislocation loops were introduced by fission neutron irradiation at low neutron fluence. The desorption peak of D for fission neutron irradiated W was concentrated at low temperature region less than 550 K, but that for 14 MeV neutron irradiated W was extended toward the higher temperature side due to D trapping by vacancies. It can be said that the neutron energy distribution could have a large impact on irradiation defect formation and the D retention behaviour.

  11. Low-energy parameters of neutron-neutron interaction in the effective-range approximation

    SciTech Connect

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

    2013-06-15

    The effect of the mass difference between the charged and neutral pions on the low-energy parameters of nucleon-nucleon interaction in the {sup 1}S{sub 0} state is studied in the effective-range approximation. On the basis of experimental values of the singlet parameters of neutron-proton scattering and the experimental value of the virtual-state energy for the neutron-neutron systemin the {sup 1}S{sub 0} state, the following values were obtained for the neutron-neutron scattering length and effective range: a{sub nn} = -16.59(117) fm and r{sub nn} = 2.83(11) fm. The calculated values agree well with present-day experimental results.

  12. Neutron diffraction of hydrogenous materials: Measuring incoherent and coherent intensities separately

    NASA Astrophysics Data System (ADS)

    Temleitner, László; Stunault, Anne; Cuello, Gabriel J.; Pusztai, László

    2015-07-01

    Accurate determination of the coherent static structure factor of any disordered material containing substantial amounts of proton nuclei has proven to be rather problematic by neutron diffraction, due to the large incoherent cross section of 1H. This problem has continued to set severe obstacles to the reliable determination of liquid structures of hydrogenous materials up to this day, by introducing large uncertainties whenever a sample with a 1H content larger than about 20% had to be investigated by neutron diffraction. Huge theoretical efforts over the past 40 years which were aimed at estimating the incoherent background of such data did not result in any practical solution to the problem. Here, we present data for the coherent and incoherent contributions to the total static structure of mixtures of light and heavy water. The measurements were done using the polarized neutron diffraction technique, which uniquely allows determination of the two contributions separately. The data covers a wide range of momentum transfer (0.8-21 Å-1) and the entire composition range, i.e., light water contents between 0 and 100% at five different values. We show that the measured incoherent scattering can be approximated by a Gaussian function. The separately measured coherent intensities exhibit signs of small inelastic contributions. Out of several possible approaches, we have chosen to subtract a cubic background using the reverse Monte Carlo algorithm. This algorithm has the advantage of requiring an actual physical model with thousands of realistic water molecules at the correct density describing the corrected data. Finally, coherent static structure factors for five different compositions of liquid H2O and D2O mixtures are presented for which the huge incoherent background could actually be measured and separated, instead of being approximated as it has been done so far. These experimental results provide a strong hope that determining the structure of hydrogenous

  13. First observations of power MOSFET burnout with high energy neutrons

    SciTech Connect

    Oberg, D.L.; Wert, J.L.; Normand, E.; Majewski, P.P.; Wender, S.A.

    1996-12-01

    Single event burnout was seen in power MOSFETs exposed to high energy neutrons. Devices with rated voltage {ge}400 volts exhibited burnout at substantially less than the rated voltage. Tests with high energy protons gave similar results. Burnout was also seen in limited tests with lower energy protons and neutrons. Correlations with heavy-ion data are discussed. Accelerator proton data gave favorable comparisons with burnout rates measured on the APEX spacecraft. Implications for burnout at lower altitudes are also discussed.

  14. Neutron imaging for geothermal energy systems

    SciTech Connect

    Bingham, Philip R; Anovitz, Lawrence {Larry} M; Polsky, Yarom

    2013-01-01

    Geothermal systems extract heat energy from the interior of the earth using a working fluid, typically water. Three components are required for a commercially viable geothermal system: heat, fluid, and permeability. Current commercial electricity production using geothermal energy occurs where the three main components exist naturally. These are called hydrothermal systems. In the US, there is an estimated 30 GW of base load electrical power potential for hydrothermal sites. Next generation geothermal systems, named Enhanced Geothermal Systems (EGS), have an estimated potential of 4500 GW. EGSs lack in-situ fluid, permeability or both. As such, the heat exchange system must be developed or engineered within the rock. The envisioned method for producing permeability in the EGS reservoir is hydraulic fracturing, which is rarely practiced in the geothermal industry, and not well understood for the rocks typically present in geothermal reservoirs. High costs associated with trial and error learning in the field have led to an effort to characterize fluid flow and fracturing mechanisms in the laboratory to better understand how to design and manage EGS reservoirs. Neutron radiography has been investigated for potential use in this characterization. An environmental chamber has been developed that is suitable for reproduction of EGS pressures and temperatures and has been tested for both flow and precipitations studies with success for air/liquid interface imaging and 3D reconstruction of precipitation within the core.

  15. Testing The High-Energy Prompt Neutron Signature At Low Beam Energies

    SciTech Connect

    Thompson, Scott J.; Kinlaw, Mathew T.; Hunt, Alan W.

    2011-06-01

    Prompt fission neutrons continue to be examined as a signature for detecting the presence of fissionable material. This technique exploits the neutron energy limitations inherent with photonuclear emissions from non-fissionable material, allowing prompt fission neutrons to be identified and engaged for detecting nuclear material. Prompt neutron signal measurements were acquired with bremsstrahlung endpoint energies of 6 MeV for 18 targets comprised of both fissionable and non-fissionable material; delayed neutron measurements were also collected as a reference. The {sup 238}U target was also shielded with increasing thicknesses of lead or borated polyethylene to compare the resulting detection rates of the prompt and delayed fission neutron signals.

  16. Neutron irradiation of superconductors and damage energy scaling of different neutron spectra

    NASA Astrophysics Data System (ADS)

    Hahn, P. A.; Weber, H. W.; Guinan, M. W.; Birtcher, R. C.; Brown, B. S.; Greenwood, L. R.

    1985-08-01

    Three different neutron sources were used to irradiate identical sets of NbTi superconductors up to about half the lifetime dose of a superconducting magnet in a fusion reactor. Based on a careful source characterization of the TRIGA Mark-II reactor in Vienna, the spallation neutron source IPNS at Argonne and the 14 MeV neutron source RTNS-II at Livermore, the damage energy cross sections were calculated for four different types of NbTi alloys (42, 46.5, 49 and 54 wt % Ti). The experimental results on the variations of critical current densities j sub c with neutron dose are found to scale within the experimental uncertainties with the appropriate damage energy cross sections. This first explicit proof of damage energy scaling for j sub c-variations in superconductors is considered to be most valuable for the evaluation of radiation damage in superconductors under fusion reactor conditions.

  17. Delayed Neutron Energy Spectra Following Fast Fission of Uranium

    NASA Astrophysics Data System (ADS)

    Villani, Marcel Franklin

    Delayed neutron energy spectra have been measured for six delay-time intervals following the fast fission of ^{238}U nuclei. The delay-time intervals span the range 0.17 to 10.2 seconds following initial fission while the measured spectra span neutron energies from 10 keV to 4 MeV. The experiment was performed utilizing the UMass/Lowell 5.5 MV Van de Graaff accelerator to produce fast neutrons for inducing fission in a ^{238} U lined fission chamber. The fission fragments were flushed via a helium jet stream to a well-shielded counting room where they were deposited onto a moving tape (magnetic audio tape) and transferred to a beta-neutron time-of-flight spectrometer. By adjusting the tape speed, composite delayed neutron time-of-flight spectra were measured for several different delay-time intervals. These measurements involved beta-neutron coincidences with ^6 Li-loaded glass scintillators for neutron energies from 10 keV to 450 keV and Bicron BC 501 liquid scintillators for the neutron energy range 200 keV-4 MeV. The measured composite delayed neutron energy spectra for ^{238}U are compared to the composite spectra for ^ {235}U and ^{239} Pu, and also to composite spectra derived for ^{238}U from the ENDF/B-VI database, which is based on summation calculations of individual precursor data supplemented by theoretical estimates. The composite spectra of ^{235}U and ^{239}Pu were obtained from previous measurements of delayed neutron spectra at this laboratory. The composite spectra are also decomposed into Keepin six-group spectra and compared with those for ^{239}Pu and ^{235}U. In addition, an equilibrium spectrum has been calculated from the measured composite spectra using several different analytical techniques and is also compared with the equilibrium spectrum of ^{238}U measured in an earlier study at this laboratory.

  18. Comparison Between Digital and Analog Pulse Shape Discrimination Techniques For Neutron and Gamma Ray Separation

    SciTech Connect

    R. Aryaeinejad; John K. Hartwell

    2005-11-01

    Recent advancement in digital signal processing (DSP) using fast processors and computer makes it possible to be used in pulse shape discrimination applications. In this study, we have investigated the feasibility of using a DSP to distinguish between the neutrons and gamma rays by the shape of their pulses in a liquid scintillator detector (BC501), and have investigated pulse shape-based techniques to improve the resolution performance of room-temperature cadmium zinc telluride (CZT) detectors. For the neutron/gamma discrimination, the advantage of using a DSP over the analog method is that in analog system two separate charge-sensitive ADC's are required. One ADC is used to integrate the beginning of the pulse risetime while the second ADC is for integrating the tail part. Using a DSP eliminates the need for separate ADCs as one can easily get the integration of two parts of the pulse from the digital waveforms. This work describes the performance of these DSP techniques and compares the results with the analog method.

  19. Comparison Between Digital and Analog Pulse Shape Discrimination Techniques for Neutron and Gamma Ray Separation

    SciTech Connect

    Rahmat Aryaeinejad

    2005-10-01

    Recent advancements in digital signal processing (DSP) using fast processors and a computer allows one to envision using it in pulse shape discrimination. In this study, we have investigated the feasibility of using a DSP to distinguish between neutrons and gamma rays by the shape of their pulses in a liquid scintillator detector (BC501). For neutron/gamma discrimination, the advantage of using a DSP over the analog method is that in an analog system, two separate charge-sensitive ADCs are required. One ADC is used to integrate the beginning of the pulse rise time while the second ADC is for integrating the tail part. In DSP techniques the incoming pulses coming directly from the detector are immediately digitized and can be decomposed into individual pulses waveforms. This eliminates the need for separate ADCs as one can easily get the integration of two parts of the pulse from the digital waveforms. This work describes the performance of these DSP techniques and compares the results with the analog method.

  20. Neutron energy spectrum from 120 GeV protons on a thick copper target

    SciTech Connect

    Shigyo, Nobuhiro; Sanami, Toshiya; Kajimoto, Tsuyoshi; Iwamoto, Yosuke; Hagiwara, Masayuki; Saito, Kiwamu; Ishibashi, Kenji; Nakashima, Hiroshi; Sakamoto, Yukio; Lee, Hee-Seock; Ramberg, Erik; /Fermilab

    2010-08-01

    Neutron energy spectrum from 120 GeV protons on a thick copper target was measured at the Meson Test Beam Facility (MTBF) at Fermi National Accelerator Laboratory. The data allows for evaluation of neutron production process implemented in theoretical simulation codes. It also helps exploring the reasons for some disagreement between calculation results and shielding benchmark data taken at high energy accelerator facilities, since it is evaluated separately from neutron transport. The experiment was carried out using a 120 GeV proton beam of 3E5 protons/spill. Since the spill duration was 4 seconds, protoninduced events were counted pulse by pulse. The intensity was maintained using diffusers and collimators installed in the beam line to MTBF. The protons hit a copper block target the size of which is 5cm x 5cm x 60 cm long. The neutrons produced in the target were measured using NE213 liquid scintillator detectors, placed about 5.5 m away from the target at 30{sup o} and 5 m 90{sup o} with respect to the proton beam axis. The neutron energy was determined by time-of-flight technique using timing difference between the NE213 and a plastic scintillator located just before the target. Neutron detection efficiency of NE213 was determined on basis of experimental data from the high energy neutron beam line at Los Alamos National Laboratory. The neutron spectrum was compared with the results of multiparticle transport codes to validate the implemented theoretical models. The apparatus would be applied to future measurements to obtain a systematic data set for secondary particle production on various target materials.

  1. Neutron energy-dependent initial DNA damage and chromosomal exchange.

    PubMed

    Tanaka, K; Gajendiran, N; Endo, S; Komatsu, K; Hoshi, M; Kamada, N

    1999-12-01

    This study was undertaken to investigate the biological effect of monoenergetic neutrons on human lymphocyte DNA and chromosomes. Monoenergetic neutrons of 2.3, 1.0, 0.79, 0.57, 0.37 and 0.186 MeV were generated, and 252Cf neutrons and 60Co gamma-rays were also used for comparison. Biological effect was evaluated two ways. The RBE values with the comet assay were estimated as 6.3 and 5.4 at 0.37 MeV and 0.57 MeV relative to that of 60Co gamma-rays, and chromosome aberration rates were also observed in these different levels of monoenergetic neutrons. The yield of chromosome aberrations per unit dose was high at lower neutron energies with a gradual decline with 0.186 MeV neutron energy. The RBE was increased to 10.7 at 0.57 MeV from 3.9 at 252Cf neutrons and reached 16.4 as the highest RBE at 0.37 MeV, but the value decreased to 11.2 at 0.186 MeV. The response patterns of initial DNA damage and chromosome exchange were quite similar to that of LET. These results show that the intensity of DNA damage and chromosomal exchange is LET dependent. RBE of low energy neutrons is higher than that of fission neutrons. Low energy neutrons containing Hiroshima atomic bomb radiation may have created a significantly higher incidence of biological effect in atomic bomb survivors. PMID:10804992

  2. Precise determination of neutron binding energy of 64Cu

    NASA Astrophysics Data System (ADS)

    Telezhnikov, S. A.; Granja, C.; Honzatko, J.; Pospisil, S.; Tomandl, I.

    2016-05-01

    The neutron binding energy in 64Cu has been accurately measured in thermal neutron capture. A composite target of natural Cu and NaCl was used on a high flux neutron beam using a large measuring time. The γ-ray spectrum emitted in the ( n, γ) reaction was measured with a HPGe detector in large statistics (up to 106 events per channel). Intrinsic limitations of HPGe detectors, which restrict the accuracy of energy calibration, were determined. The value B n of 64Cu was determined as 7915.867(24) keV.

  3. Neutron energy spectrum characterization on TMR-1 at the Indiana University neutron source

    NASA Astrophysics Data System (ADS)

    Halstead, Matthew R.; Lee, Sangjin; Petrosky, James; Bickley, Abigail; Sokol, Paul

    The energy spectrum of the Neutron Radiation Effects Program (NREP) beam line, Target-Moderator-Reflector-1 (TMR-1), at Indiana University has not been previously characterized. The facility has a unique proton source with variable pulse length (15-600 ms) and energy (13 MeV). Thus, it can produce a unique and tailored neutron beam when incident on a beryllium target. Through a combination of MCNP-X particle simulations, neutron activation experiments, and application of a spectrum unfolding code (SAND-II), the neutron source is characterized. Eight activation foils and wires were irradiated in the target area and the gamma activity measured. This information was used in an unfolding code, SAND-II, to deconvolve the spectrum, using the MCNP simulations as a basis for the spectral fitting.

  4. Neutron emission profiles and energy spectra measurements at JET

    NASA Astrophysics Data System (ADS)

    Giacomelli, L.; Conroy, S.; Belli, F.; Gorini, G.; Horton, L.; Joffrin, E.; Lerche, E.; Murari, A.; Popovichev, S.; Riva, M.; Syme, B.; JET EFDA Contributors

    2014-08-01

    The Joint European Toras (JET, Culham, UK) is the largest tokamak in the world. It is devoted to nuclear fusion experiments of magnetic confined Deuterium (D) or Deuterium-Tritium (DT) plasmas. JET has been upgraded over the years and recently it has also become a test facility of the components designed for ITER, the next step fusion machine under construction in Cadarache (France). JET makes use of many different diagnostics to measure the physical quantities of interest in plasma experiments. Concerning D or DT plasmas neutron production, various types of detectors are implemented to provide information upon the neutron total yield, emission profile and energy spectrum. The neutron emission profile emitted from the JET plasma poloidal section is reconstructed using the neutron camera (KN3). In 2010 KN3 was equipped with a new digital data acquisition system capable of high rate neutron measurements (<0.5 MCps). A similar instrument will be implemented on ITER and it is currently in its design phase. Various types of neutron spectrometers with different view lines are also operational on JET. One of them is a new compact spectrometer (KM12) based on organic liquid scintillating material which was installed in 2010 and implements a similar digital data acquisition system as for KN3. This article illustrates the measurement results of KN3 neutron emission profiles and KM 12 neutron energy spectra from the latest JET D experimental campaign C31.

  5. Neutron emission profiles and energy spectra measurements at JET

    SciTech Connect

    Giacomelli, L.; Conroy, S.; Belli, F.; Riva, M.; Gorini, G.; Horton, L.; Joffrin, E.; Lerche, E.; Murari, A.; Popovichev, S.; Syme, B.; Collaboration: JET EFDA Contributors

    2014-08-21

    The Joint European Toras (JET, Culham, UK) is the largest tokamak in the world. It is devoted to nuclear fusion experiments of magnetic confined Deuterium (D) or Deuterium-Tritium (DT) plasmas. JET has been upgraded over the years and recently it has also become a test facility of the components designed for ITER, the next step fusion machine under construction in Cadarache (France). JET makes use of many different diagnostics to measure the physical quantities of interest in plasma experiments. Concerning D or DT plasmas neutron production, various types of detectors are implemented to provide information upon the neutron total yield, emission profile and energy spectrum. The neutron emission profile emitted from the JET plasma poloidal section is reconstructed using the neutron camera (KN3). In 2010 KN3 was equipped with a new digital data acquisition system capable of high rate neutron measurements (<0.5 MCps). A similar instrument will be implemented on ITER and it is currently in its design phase. Various types of neutron spectrometers with different view lines are also operational on JET. One of them is a new compact spectrometer (KM12) based on organic liquid scintillating material which was installed in 2010 and implements a similar digital data acquisition system as for KN3. This article illustrates the measurement results of KN3 neutron emission profiles and KM 12 neutron energy spectra from the latest JET D experimental campaign C31.

  6. Compact, energy EFFICIENT neutron source: enabling technology for various applications

    SciTech Connect

    Hershcovitch, A.; Roser, T.

    2009-12-01

    A novel neutron source comprising of a deuterium beam (energy of about 100 KeV) injected into a tube filled with tritium gas and/or tritium plasma that generates D-T fusion reactions, whose products are 14.06 MeV neutrons and 3.52 MeV alpha particles, is described. At the opposite end of the tube, the energy of deuterium ions that did not interact is recovered. Beryllium walls of proper thickness can be utilized to absorb 14 MeV neutrons and release 2-3 low energy neutrons. Each ion source and tube forms a module. Larger systems can be formed from multiple units. Unlike currently proposed methods, where accelerator-based neutron sources are very expensive, large, and require large amounts of power for operation, this neutron source is compact, inexpensive, easy to test and to scale up. Among possible applications for this neutron source concept are sub-critical nuclear breeder reactors and transmutation of radioactive waste.

  7. 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.

  8. Laser Intertial Fusion Energy: Neutronic Design Aspects of a Hybrid Fusion-Fission Nuclear Energy System

    SciTech Connect

    Kramer, Kevin James

    2010-04-08

    This study investigates the neutronics design aspects of a hybrid fusion-fission energy system called the Laser Fusion-Fission Hybrid (LFFH). A LFFH combines current Laser Inertial Confinement fusion technology with that of advanced fission reactor technology to produce a system that eliminates many of the negative aspects of pure fusion or pure fission systems. When examining the LFFH energy mission, a significant portion of the United States and world energy production could be supplied by LFFH plants. The LFFH engine described utilizes a central fusion chamber surrounded by multiple layers of multiplying and moderating media. These layers, or blankets, include coolant plenums, a beryllium (Be) multiplier layer, a fertile fission blanket and a graphite-pebble reflector. Each layer is separated by perforated oxide dispersion strengthened (ODS) ferritic steel walls. The central fusion chamber is surrounded by an ODS ferritic steel first wall. The first wall is coated with 250-500 μm of tungsten to mitigate x-ray damage. The first wall is cooled by Li17Pb83 eutectic, chosen for its neutron multiplication and good heat transfer properties. The Li17Pb83 flows in a jacket around the first wall to an extraction plenum. The main coolant injection plenum is immediately behind the Li17Pb83, separated from the Li17Pb83 by a solid ODS wall. This main system coolant is the molten salt flibe (2LiF-BeF2), chosen for beneficial neutronics and heat transfer properties. The use of flibe enables both fusion fuel production (tritium) and neutron moderation and multiplication for the fission blanket. A Be pebble (1 cm diameter) multiplier layer surrounds the coolant injection plenum and the coolant flows radially through perforated walls across the bed. Outside the Be layer, a fission fuel layer comprised of depleted uranium contained in Tristructural-isotropic (TRISO) fuel particles

  9. Development of multichannel low-energy neutron spectrometer.

    PubMed

    Arikawa, Y; Nagai, T; Abe, Y; Kojima, S; Sakata, S; Inoue, H; Utsugi, M; Iwasa, Y; Murata, T; Sarukura, N; Nakai, M; Shiraga, H; Fujioka, S; Azechi, H

    2014-11-01

    A multichannel low-energy neutron spectrometer for down-scattered neutron (DSN) measurements in inertial confinement fusion (ICF) experiments has been developed. Our compact-size 256-channel lithium-glass-scintillator-based spectrometer has been implemented and tested in ICF experiments with the GEKKO XII laser. We have performed time calibration of the 256-channel analog-to-digital convertor system used for DSN measurements via X-ray pulse signals. We have clearly observed the DD-primary fusion neutron signal and have successfully studied the detector's impulse response. Our detector is soon to be implemented in future ICF experiments. PMID:25430304

  10. Development of multichannel low-energy neutron spectrometer

    SciTech Connect

    Arikawa, Y. Nagai, T.; Abe, Y.; Kojima, S.; Sakata, S.; Inoue, H.; Utsugi, M.; Iwasa, Y.; Sarukura, N.; Nakai, M.; Shiraga, H.; Fujioka, S.; Azechi, H.; Murata, T.

    2014-11-15

    A multichannel low-energy neutron spectrometer for down-scattered neutron (DSN) measurements in inertial confinement fusion (ICF) experiments has been developed. Our compact-size 256-channel lithium-glass-scintillator-based spectrometer has been implemented and tested in ICF experiments with the GEKKO XII laser. We have performed time calibration of the 256-channel analog-to-digital convertor system used for DSN measurements via X-ray pulse signals. We have clearly observed the DD-primary fusion neutron signal and have successfully studied the detector's impulse response. Our detector is soon to be implemented in future ICF experiments.

  11. Calculating fusion neutron energy spectra from arbitrary reactant distributions

    NASA Astrophysics Data System (ADS)

    Eriksson, J.; Conroy, S.; Andersson Sundén, E.; Hellesen, C.

    2016-02-01

    The Directional Relativistic Spectrum Simulator (DRESS) code can perform Monte-Carlo calculations of reaction product spectra from arbitrary reactant distributions, using fully relativistic kinematics. The code is set up to calculate energy spectra from neutrons and alpha particles produced in the D(d, n)3He and T(d, n)4He fusion reactions, but any two-body reaction can be simulated by including the corresponding cross section. The code has been thoroughly tested. The kinematics calculations have been benchmarked against the kinematics module of the ROOT Data Analysis Framework. Calculated neutron energy spectra have been validated against tabulated fusion reactivities and against an exact analytical expression for the thermonuclear fusion neutron spectrum, with good agreement. The DRESS code will be used as the core of a detailed synthetic diagnostic framework for neutron measurements at the JET and MAST tokamaks.

  12. Neutron dose and energy spectra measurements at Savannah River Plant

    SciTech Connect

    Brackenbush, L.W.; Soldat, K.L.; Haggard, D.L.; Faust, L.G.; Tomeraasen, P.L.

    1987-08-01

    Because some workers have a high potential for significant neutron exposure, the Savannah River Plant (SRP) contracted with Pacific Northwest Laboratory (PNL) to verify the accuracy of neutron dosimetry at the plant. Energy spectrum and neutron dose measurements were made at the SRP calibrations laboratory and at several other locations. The energy spectra measurements were made using multisphere or Bonner sphere spectrometers,/sup 3/He spectrometers, and NE-213 liquid scintillator spectrometers. Neutron dose equivalent determinations were made using these instruments and others specifically designed to determine dose equivalent, such as the tissue equivalent proportional counter (TEPC). Survey instruments, such as the Eberline PNR-4, and the thermoluminescent dosimeter (TLD)-albedo and track etch dosimeters (TEDs) were also used. The TEPC, subjectively judged to provide the most accurate estimation of true dose equivalent, was used as the reference for comparison with other devices. 29 refs., 43 figs., 13 tabs.

  13. A New Method of Prompt Fission Neutron Energy Spectrum Unfolding

    SciTech Connect

    Zeynalova, O. V.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.

    2010-11-25

    The prompt neutron emission in spontaneous fission of {sup 252}Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. The goal was to find out the reasons of a long time existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of fission fragments (FF). On the one hand the {sup 252}Cf(sf) reaction is one of the main references for nuclear data, on the other hand the understanding of PFN emission mechanism is very important for nuclear fission theory. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 10{sup 7} fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.

  14. A New Method of Prompt Fission Neutron Energy Spectrum Unfolding

    NASA Astrophysics Data System (ADS)

    Zeynalova, O. V.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.

    2010-11-01

    The prompt neutron emission in spontaneous fission of 252Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. The goal was to find out the reasons of a long time existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of fission fragments (FF). On the one hand the 252Cf (sf) reaction is one of the main references for nuclear data, on the other hand the understanding of PFN emission mechanism is very important for nuclear fission theory. Using a twin Frisch-grid ionization chamber for fission fragment (FF) detection and a NE213-equivalent neutron detector in total about 107 fission fragment-neutron coincidences have been registered. Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12 bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. For the first time the dependence of the number of emitted neutrons as a function of total kinetic energy (TKE) of the fragments is in very good agreement with theoretical calculations in the range of TKE from 140-220 MeV.

  15. Scoping studies - photon and low energy neutron interrogation

    SciTech Connect

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

    1997-11-01

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

  16. Biological Effects of High-Energy Neutrons Measured In Vivo Using a Vertebrate Model

    PubMed Central

    Kuhne, Wendy W.; Gersey, Brad B.; Wilkins, Richard; Wu, Honglu; Wender, Stephen A.; George, Varghese; Dynan, William S.

    2009-01-01

    Interaction of solar protons and galactic cosmic radiation with the atmosphere and other materials produces high-energy secondary neutrons from below 1 to 1000 MeV and higher. Although secondary neutrons may provide an appreciable component of the radiation dose equivalent received by space and high-altitude air travelers, the biological effects remain poorly defined, particularly in vivo in intact organisms. Here we describe the acute response of Japanese medaka (Oryzias latipes) embryos to a beam of high-energy spallation neutrons that mimics the energy spectrum of secondary neutrons encountered aboard spacecraft and high-altitude aircraft. To determine RBE, embryos were exposed to 0–0.5 Gy of high-energy neutron radiation or 0–15 Gy of reference γ radiation. The radiation response was measured by imaging apoptotic cells in situ in defined volumes of the embryo, an assay that provides a quantifiable, linear dose response. The slope of the dose response in the developing head, relative to reference γ radiation, indicates an RBE of 24.9 (95% CI 13.6–40.7). A higher RBE of 48.1 (95% CI 30.0–66.4) was obtained based on overall survival. A separate analysis of apoptosis in muscle showed an overall nonlinear response, with the greatest effects at doses of less than 0.3 Gy. Results of this experiment indicate that medaka are a useful model for investigating biological damage associated with high-energy neutron exposure. PMID:19772468

  17. 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).

  18. Systematics of proton and diproton separation energies for light nuclei

    SciTech Connect

    Cole, B.J.

    1997-10-01

    A simple method to estimate proton and two-proton separation energies of proton-rich nuclei is presented that is sufficiently accurate to allow the prediction of suitable candidates for observable diproton decay. The method is based on the systematics of measured particle separation energies. Predictions for proton-rich nuclei with Z=18{minus}24 are compared with the results of previous calculations. {copyright} {ital 1997} {ital The American Physical Society}

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

    PubMed

    Singh, Surendra; Basu, Saibal

    2009-02-01

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

  20. Neutron scattering and phase separation of Gamma-B crystallin vs. pH, ionic strength and protein concentration

    NASA Astrophysics Data System (ADS)

    Thurston, George; Martini, K. Michael; Desmond, Kenneth; Putzig, Elias; Dell, Zachary; Carter, Dawn; Hollenbeck, Dawn; Dexter, Nicholas; Langner, Andreas; Ross, David; Harkin, Anthony; Nelson, Edward; Zackrisson-Oskolkova, Malin; Stradner, Anna; Dorsaz, Nicolas; Foffi, Giuseppe; Schurtenberger, Peter

    2010-03-01

    We study the pH, ionic strength and concentration dependence of liquid-liquid phase separation and neutron scattering of the eye lens protein Gamma-B crystallin. At pH 7, lowering ionic strength raises the cloud points. Neutron scattering indicates anisotropic protein interactions, in agreement with prior information. At lower pH phase separation disappears, and protein repulsions increase at low ionic strength. We seek to evaluate the roles of (i) patterned charge regulation, (ii) biasing of relative protein orientation due to local charge patches, and (iii) screened net protein charge for these phenomena. We apply a grand-canonical partition function model for charge regulation and other interactions, as input to Monte Carlo and neutron scattering computations.

  1. Magnetic Energy Production by Turbulence in Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Zrake, Jonathan; MacFadyen, Andrew I.

    2013-06-01

    The simultaneous detection of electromagnetic and gravitational wave emission from merging neutron star binaries would greatly aid in their discovery and interpretation. By studying turbulent amplification of magnetic fields in local high-resolution simulations of neutron star merger conditions, we demonstrate that magnetar-level (gsim 1016 G) fields are present throughout the merger duration. We find that the small-scale turbulent dynamo converts 60% of the randomized kinetic energy into magnetic fields on a merger timescale. Since turbulent magnetic energy dissipates through reconnection events that accelerate relativistic electrons, turbulence may facilitate the conversion of orbital kinetic energy into radiation. If 10-4 of the ~1053 erg of orbital kinetic available gets processed through reconnection and creates radiation in the 15-150 keV band, then the fluence at 200 Mpc would be 10-7 erg cm-2, potentially rendering most merging neutron stars in the advanced LIGO and Virgo detection volumes detectable by Swift BAT.

  2. Estimation of neutron energy for first resonance from absorption cross section for thermal neutrons

    NASA Technical Reports Server (NTRS)

    Bogart, Donald

    1951-01-01

    Examination of published data for some 52 isotopes indicates that the neutron energy for which the first resonance occurs is related to the magnitude of the thermal absorption cross section. The empirical relation obtained is in qualitative agreement with the results of a simplified version of the resonance theory of the nucleus of Breit-Wigner.

  3. The Low Energy Neutron Source at Indiana University

    NASA Astrophysics Data System (ADS)

    Baxter, David

    2004-03-01

    The National Science Foundation has recently approved funding for construction of LENS (the Low Energy Neutron Source) at Indiana University and construction of this facility has begun. LENS represents a new paradigm for economically introducing neutron scattering into a university or industrial setting. Neutrons are produced in a long-pulse (1ms) mode through (p,n) reactions on a water-cooled Be target and supplied to three instrument beam lines. In this talk we will describe how LENS will use neutrons to fulfill its three-fold mission in education, materials research, and developing novel instrumentation. Of particular interest are the facility's ability to study cryogenic moderators at significantly lower temperatures than is possible at other facilities and the development of instruments that make use of the neutron spin to perform high-precision measurements of momentum transfer without significant collimation of the beam. The potential for these developments to expand significantly the range of problems amenable to exploration with neutron techniques will be discussed.

  4. 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

  5. High Energy Neutron Induced Gamma Production

    SciTech Connect

    Brown, D A; Johnson, M; Navratil, P

    2007-09-28

    N Division has an interest in improving the physics and accuracy of the gamma data it provides to its customers. It was asked to look into major gamma producing reactions for 14 MeV incident neutrons for several low-Z materials and determine whether LLNL's processed data files faithfully represent the current state of experimental and theoretical knowledge for these reactions. To address this, we surveyed the evaluations of the requested materials, made recommendations for the next ENDL release and noted isotopes that will require further experimental study. This process uncovered several major problems in our translation and processing of the ENDF formatted evaluations, most of which have been resolved.

  6. Multi-neutron transfer reactions at sub-barrier energies.

    SciTech Connect

    Rehm, K. E.

    1998-01-20

    The optimum conditions for multi-neutron transfer have been studied in the system {sup 58}Ni + {sup 124}Sn at bombarding energies at and below the Coulomb barrier. The experiments were performed in inverse kinematics with a {sup 124}Sn beam bombarding a {sup 58}Ni target. The particles were identified with respect to mass and Z in the split-pole spectrograph with a hybrid focal plane detector with mass and Z-resolutions of A/{Delta}A = 150 and Z/{Delta}Z = 70. At all energies the transfer of up to 6 neutrons was observed. The yields for these transfer reactions are found to decrease by about a factor of four for each transferred neutron.

  7. Preliminary On-Orbit Neutron Dose Equivalent and Energy Spectrum Results from the ISS-RAD Fast Neutron Detector (FND)

    NASA Technical Reports Server (NTRS)

    Semones, Edward; Leitgab, Martin

    2016-01-01

    The ISS-RAD instrument was activated on ISS on February 1st, 2016. Integrated in ISS-RAD, the Fast Neutron Detector (FND) performs, for the first time on ISS, routine and precise direct neutron measurements between 0.5 and 8 MeV. Preliminary results for neutron dose equivalent and neutron flux energy distributions from online/on-board algorithms and offline ground analyses will be shown, along with comparisons to simulated data and previously measured neutron spectral data. On-orbit data quality and pre-launch analysis validation results will be discussed as well.

  8. Exotic low-energy separation in 1D quantum liquids

    SciTech Connect

    Carmelo, J.M.P.; Neto, A.H.C.; Campbell, D.K.

    1995-05-01

    We define the low-energy separation of the Hubbard chain in a magnetic field and chemical potential in terms of two {open_quotes}c{close_quotes} and {open_quotes}s{close_quotes} bosonic algebras. This generalizes the usual charge-spin separation, which is recovered in the limit of zero magnetization only. The corresponding pseudoparticle bosonization follows directly from the perturbative character of the pseudoparticle operator basis.

  9. Membrane systems for energy efficient separation of light gases

    SciTech Connect

    Devlin, D.J.; Archuleta, T.; Barbero, R.

    1997-04-01

    Ethylene and propylene are two of the largest commodity chemicals in the United States and are major building blocks for the petrochemicals industry. These olefins are separated currently by cryogenic distillation which demands extremely low temperatures and high pressures. Over 75 billion pounds of ethylene and propylene are distilled annually in the US at an estimated energy requirement of 400 trillion BTU`s. Non-domestic olefin producers are rapidly constructing state-of-the-art plants. These energy-efficient plants are competing with an aging United States olefins industry in which 75% of the olefins producers are practicing technology that is over twenty years old. New separation opportunities are therefore needed to continually reduce energy consumption and remain competitive. Amoco has been a leader in incorporating new separation technology into its olefins facilities and has been aggressively pursuing non-cryogenic alternatives to light gas separations. The largest area for energy reduction is the cryogenic isolation of the product hydrocarbons from the reaction by-products, methane and hydrogen. This separation requires temperatures as low as {minus}150{degrees}F and pressures exceeding 450 psig. This CRADA will focus on developing a capillary condensation process to separate olefinic mixtures from light gas byproducts at temperatures that approach ambient conditions and at pressures less than 250 psig; this technology breakthrough will result in substantial energy savings. The key technical hurdle in the development of this novel separation concept is the precise control of the pore structure of membrane materials. These materials must contain specially-shaped channels in the 20-40A range to provide the driving force necessary to remove the condensed hydrocarbon products. In this project, Amoco is the technology end-user and provides the commercialization opportunity and engineering support.

  10. A preliminary area survey of neutron radiation levels associated with the NASA variable energy cyclotron horizontal neutron delivery system

    NASA Technical Reports Server (NTRS)

    Roberts, W. K.; Leonard, R. F.

    1976-01-01

    The 25 MeV deuteron beam from the NASA variable energy cyclotron incident on a thick beryllium target will deliver a tissue neutron dose rate of 2.14 rad micron A-min at a source to skin distance of 125 cm. A neutron survey of the existing hallways with various shielding configurations made during operating of the horizontal neutron delivery system indicates that minimal amounts of additional neutron shielding material are required to provide a low level radiation environment within a self-contained neutron therapy control station. Measurements also indicate that the primary neutron distribution delivered by a planned vertical delivery system will be minimally perturbed by neutrons backscattered from the floor.

  11. Method and apparatus for component separation using microwave energy

    DOEpatents

    Morrow, Marvin S.; Schechter, Donald E.; Calhoun, Jr., Clyde L.

    2001-04-03

    A method for separating and recovering components includes the steps of providing at least a first component bonded to a second component by a microwave absorbent adhesive bonding material at a bonding area to form an assembly, the bonding material disposed between the components. Microwave energy is directly and selectively applied to the assembly so that substantially only the bonding material absorbs the microwave energy until the bonding material is at a debonding state. A separation force is applied while the bonding material is at the debonding state to permit disengaging and recovering the components. In addition, an apparatus for practicing the method includes holders for the components.

  12. Energy and angular dependence of active-type personal dosemeter for high-energy neutron.

    PubMed

    Rito, Hirotaka; Yamauchi, Tomoya; Oda, Keiji

    2011-07-01

    In order to develop an active-type personal dosemeter having suitable sensitivity to high-energy neutrons, the characteristic response of silicon surface barrier detector has been investigated experimentally and theoretically. An agreement of the shape of pulse-height distribution, its change with radiator thickness and the relative sensitivity was confirmed between the calculated and experimental results for 14.8-MeV neutrons. The angular dependence was estimated for other neutron energies, and found that the angular dependence decreased with the incident energy. The reason was also discussed with regard to the radiator thickness relative to maximum range of recoil protons. PMID:21613268

  13. 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

  14. 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.

  15. Preliminary investigations of Monte Carlo Simulations of neutron energy and LET spectra for fast neutron therapy facilities

    SciTech Connect

    Kroc, T.K.; /Fermilab

    2009-10-01

    No fast neutron therapy facility has been built with optimized beam quality based on a thorough understanding of the neutron spectrum and its resulting biological effectiveness. A study has been initiated to provide the information necessary for such an optimization. Monte Carlo studies will be used to simulate neutron energy spectra and LET spectra. These studies will be bench-marked with data taken at existing fast neutron therapy facilities. Results will also be compared with radiobiological studies to further support beam quality ptimization. These simulations, anchored by this data, will then be used to determine what parameters might be optimized to take full advantage of the unique LET properties of fast neutron beams. This paper will present preliminary work in generating energy and LET spectra for the Fermilab fast neutron therapy facility.

  16. Isothermal separation processes update. Energy Conversion and Utilization Technologies Program

    SciTech Connect

    England, C.

    1984-08-01

    The isothermal processes of membrane separation, supercritical extraction and condensed-phase chromatography were examined using availability analysis, a method which addresses the thermodynamic value of energy as well as its amount. The general approach was to derive equations that identified where energy, expressed in terms of thermodynamic work, is consumed in these processes and how they compare with conventional separation methods. These separation methods are characterized by pure work inputs, chiefly in the form of a pressure drop which supplies the required energy. Equations were derived for the energy requirement in terms of the theories of ideal and regular solutions. This approach is believed to accurately predict the work of separation in terms of the heat of solution and the entropy of mixing. It can form the basis of a convenient calculation method for optimizing membrane and solvent properties for particular applications. Close examination of supercritical extraction found a relatively simple thermodynamic relationship among the thermodynamic properties of the solvent, the entropy of mixing, and the heat of solution. This allows a direct estimate of the work requirements. The actual work, however, is largely due to the requirement to cycle pressure at high levels in this method. Still, the energy requirements are very low, making up for usually high capital costs for equipment. 12 references, 9 figures, 2 tables.

  17. Advanced Nanostructured Molecular Sieves for Energy Efficient Industrial Separations

    SciTech Connect

    Kunhao Li, Michael Beaver

    2012-01-18

    Due to the very small relative volatility difference between propane and propylene, current propane/propylene separation by distillation requires very tall distillation towers (150-250 theoretical plates) and large reflux ratios (up to 15), which is considered to be the most energy consuming large-scale separation process. Adsorptive separation processes are widely considered to be more energy-efficient alternatives to distillation. However, slow diffusion kinetics/mass transport rate through the adsorbent bed often limits the performance of such processes, so further improvements are possible if intra-particle mass transfer rates can be improved. Rive Technology, Inc. is developing and commercializing its proprietary mesoporous zeolite technology for catalysis and separation. With well-controlled intracrystalline mesoporosity, diffusion kinetics through such mesoporous zeolite based catalysts is much improved relative to conventional zeolites, leading to significantly better product selectivity. This 'proof-of-principle' project (DE-EE0003470) is intended to demonstrate that Rive mesoporous zeolite technology can be extended and applied in adsorptive propane/propylene separation and lead to significant energy saving compared to the current distillation process. In this project, the mesoporous zeolite Y synthesis technology was successfully extended to X and A zeolites that are more relevant to adsorbent applications. Mesoporosity was introduced to zeolite X and A for the first time while maintaining adequate adsorption capacity. Zeolite adsorbents were tested for liquid phase separation performance using a pulse flow test unit and the test results show that the separation selectivity of the mesoporous zeolite adsorbent is much closer to optimal for a Simulated Moving Bed (SMB) separation process and the enhanced mesoporosity lead to >100% increase of overall mass transport rate for propane and propylene. These improvements will significantly improve the

  18. Si film separation obtained by high energy proton implantation

    SciTech Connect

    Braley, C.; Mazen, F.; Papon, A.-M.; Rieutord, F.; Charvet, A.-M.; Ntsoenzok, E.

    2012-11-06

    High energy protons implantation in the 1-1.5 MeV range can be used to detach free-standing thin silicon films with thickness between 15 and 30 {mu}m. Recently, we showed that Si orientation has a strong effect on the layer separation threshold fluence and efficiency. While complete delamination of (111)Si films is achieved, (100)Si films separation is more challenging due to blistering phenomena or partial separation of the implanted layer. In this work, we study the fracture mechanism in (100) and (111)Si after high energy implantation in order to understand the origin of such a behavior. We notably point out that fracture precursor defects, i.e. the platelets, preferentially form on (111) planes, as a consequence of the low strain level in the damaged region in our implantation conditions. Fracture therefore propagates easily in (111)Si, while it requires higher fluence to overcome unfavorable precursors orientation and propagate in (100)Si.

  19. NESST: A nuclear energy safety and security treaty-Separating nuclear energy from nuclear weapons

    NASA Astrophysics Data System (ADS)

    McNamara, Brendan

    2012-06-01

    Fission and Fusion energy is matched by the need to completely separate civilian energy programmes from the production of nuclear weapons. The Nuclear Proliferation Treaty (NPT, 1968) muddles these issues together. The case is presented here for making a new Nuclear Energy Security Treaty (NESST) which is rigorous, enforceable without violence, and separate from the political quagmire of nuclear weapons.

  20. Practical neutron dosimetry at high energies

    SciTech Connect

    McCaslin, J.B.; Thomas, R.H.

    1980-10-01

    Dosimetry at high energy particle accelerators is discussed with emphasis on physical measurements which define the radiation environment and provide an immutable basis for the derivation of any quantities subsequently required for risk evaluation. Results of inter-laboratory dosimetric comparisons are reviewed and it is concluded that a well-supported systematic program is needed which would make possible detailed evaluations and inter-comparisons of instruments and techniques in well characterized high energy radiation fields. High-energy dosimetry is so coupled with radiation transport that it is clear their study should proceed concurrently.

  1. Neutron-induced fission: properties of prompt neutron and γ rays as a function of incident energy

    NASA Astrophysics Data System (ADS)

    Stetcu, I.; Talou, P.; Kawano, T.

    2016-06-01

    We have applied the Hauser-Feshbach statistical theory, in a Monte-Carlo implementation, to the de-excitation of fission fragments, obtaining a reasonable description of the characteristics of neutrons and gamma rays emitted before beta decays toward stability. Originally implemented for the spontaneous fission of 252Cf and the neutroninduced fission of 235U and 239Pu at thermal neutron energy, in this contribution we discuss the extension of the formalism to incident neutron energies up to 20 MeV. For the emission of pre-fission neutrons, at incident energies beyond second-chance fission, we take into account both the pre-equilibrium and statistical pre-fission components. Phenomenological parameterizations of mass, charge and TKE yields are used to obtain the initial conditions for the fission fragments that subsequently decay via neutron and emissions. We illustrate this approach for 239Pu(n,f).

  2. High-energy neutron dosimetry with superheated drop detectors.

    PubMed

    d'Errico, F; Agosteo, S; Sannikov, A V; Silari, M

    2002-01-01

    A systematic analysis of the response of dichlorodifluoromethane superheated drop detectors was performed in the 46-133 MeV energy range. Experiments with quasi-monoenergetic neutron beams were performed at the Université Catholique de Leuvain-la-Neuve, Belgium and the Svedberg Laboratory, Sweden, while tests in a broad field were performed at CERN. To determine the response of the detectors to the high-energy beams, the spectra of incident neutrons were folded over functions modelled after the cross sections for the production of heavy ions from the detector elements. The cross sections for fluorine and chlorine were produced in this work by means of the Monte Carlo high-energy transport code HADRON based on the cascade exciton model of nuclear interactions. The new response data permit the interpretation of measurements at high-energy accelerators and on high-altitude commercial flights, where a 30-50% under-response had been consistently recorded with respect to neutron dose equivalent. The introduction of a 1 cm lead shell around the detectors effectively compensates most of the response defect. PMID:12382936

  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. 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.

  5. A more energy efficient product for carbon dioxide separation

    SciTech Connect

    Niswander, R.H.; Edwards, D.J.; DuPart, M.S.; Tse, J.P.

    1993-01-01

    Aqueous solutions of alkanolamines such as monoethanolamine (MEA) have been used for years to separate carbon dioxide and hydrogen sulfide from other gases in continuous absorption/desorption processes to meet very low treated gas specifications. However, MEA can undergo side reactions with CO{sub 2} which produce various types of degradation compounds. These by-products reduce performance of the solvent leading to increased energy consumption and corrosion. This can be a serious problem in applications such as the removal of CO{sub 2} in synthesis gas and natural gas treating with down stream cryogenic equipment. Formulated alkanolamine products based on methyldiethanolamine (MDEA) have made significant advances in energy efficiency, but are still susceptible to degradation and decreased performance. A next generation product, GAS/SPEC CS-PLUS, has now been developed and shown to be even more energy efficient. In addition, it improves separation and overall capacity while maintaining long term performance.

  6. Determination of carrier yields for neutron activation analysis using energy dispersive X-ray spectrometry

    USGS Publications Warehouse

    Johnson, R.G.; Wandless, G.A.

    1984-01-01

    A new method is described for determining carrier yield in the radiochemical neutron activation analysis of rare-earth elements in silicate rocks by group separation. The method involves the determination of the rare-earth elements present in the carrier by means of energy-dispersive X-ray fluorescence analysis, eliminating the need to re-irradiate samples in a nuclear reactor after the gamma ray analysis is complete. Results from the analysis of USGS standards AGV-1 and BCR-1 compare favorably with those obtained using the conventional method. ?? 1984 Akade??miai Kiado??.

  7. Determination of energy distribution for photon and neutron microdosimetry

    NASA Astrophysics Data System (ADS)

    Todo, A. S.

    This work was undertaken to provide basic physical data for use in both microdosimetry and dosimetry of high energy photons and also in the neutron radiation field. Described is the formalism to determine the initial electron energy spectra in water irradiated by photons with energies up to 1 GeV. Calculations were performed with a Monte Carlo computer code, PHOEL-3, which is also described. The code treats explicitly the production of electron-positron pairs, Compton scattering, photoelectric absorption, and the emission of Auger electrons following the occurrence of K-shell vacancies in oxygen. The tables give directly the information needed to specify the absolute single-collision kerma in water, which approximates tissue, at each photon energy. Results for continuous photon energy spectra can be obtained by using linear interpolation with the tables. The conditions under which first-collision kerma approximate absorbed dose are discussed. A formula is given for estimating bremsstrahlung energy loss, one of the principal differences between kerma and absorbed dose in practical cases. A study has been carried out, on the use of cylindrical, energy-proportional pulse-height detector for determining microdosimetric quantities, as neutron fractional dose spectra, D (L), in the function of linear energy transfer (LET). In the present study the Hurst detector was used; this device satisfies the requirement of the Bragg-Gray principle. A Monte Carlo Method was developed to obtain the D(L) spectrum from a measured pulse-height spectrum H(h), and the knowledge of the distribution of recoil-particle track lenght, P(T) in the sensitive volume of the detector. These developed programs to find P(T) and D(L) are presented. The distribution of D(L) in LET were obtained using a known distribution of P(T) and the measured H(h) spectrum fromthe Cf-2 52 neutron source. All the results are discussed and the conclusions are presented.

  8. Neutron radigoraphy of fluid flow for geothermal energy research

    SciTech Connect

    Bingham, Philip R.; Polsky, Yarom; Anovitz, L.; Carmichael, Justin R.; Bilheux, Hassina Z; Jacobson, David; Hussey, Dan

    2015-01-01

    Enhanced geothermal systems seek to expand the potential for geothermal energy by engineering heat exchange systems within the earth. A neutron radiography imaging method has been developed for the study of fluid flow through rock under environmental conditions found in enhanced geothermal energy systems. For this method, a pressure vessel suitable for neutron radiography was designed and fabricated, modifications to imaging instrument setups were tested, multiple contrast agents were tested, and algorithms developed for tracking of flow. The method has shown success for tracking of single phase flow through a manufactured crack in a 3.81 cm (1.5 inch) diameter core within a pressure vessel capable of confinement up to 69 MPa (10,000 psi) using a particle tracking approach with bubbles of fluorocarbon-based fluid as the “particles” and imaging with 10 ms exposures.

  9. Neutron Radiography of Fluid Flow for Geothermal Energy Research

    NASA Astrophysics Data System (ADS)

    Bingham, P.; Polsky, Y.; Anovitz, L.; Carmichael, J.; Bilheux, H.; Jacobsen, D.; Hussey, D.

    Enhanced geothermal systems seek to expand the potential for geothermal energy by engineering heat exchange systems within the earth. A neutron radiography imaging method has been developed for the study of fluid flow through rock under environmental conditions found in enhanced geothermal energy systems. For this method, a pressure vessel suitable for neutron radiography was designed and fabricated, modifications to imaging instrument setups were tested, multiple contrast agents were tested, and algorithms developed for tracking of flow. The method has shown success for tracking of single phase flow through a manufactured crack in a 3.81 cm (1.5 inch) diameter core within a pressure vessel capable of confinement up to 69 MPa (10,000 psi) using a particle tracking approach with bubbles of fluorocarbon-based fluid as the "particles" and imaging with 10 ms exposures.

  10. NE-213-scintillator-based neutron detection system for diagnostic measurements of energy spectra for neutrons having energies greater than or equal to 0. 8 MeV created during plasma operations at the Princeton Tokamak Fusion Test Reactor

    SciTech Connect

    Dickens, J.K.; Hill, N.W.; Hou, F.S.; McConnell, J.W.; Spencer, R.R.; Tsang, F.Y.

    1985-08-01

    A system for making diagnostic measurements of the energy spectra of greater than or equal to 0.8-MeV neutrons produced during plasma operations of the Princeton Tokamak Fusion Test Reactor (TFTR) has been fabricated and tested and is presently in operation in the TFTR Test Cell Basement. The system consists of two separate detectors, each made up of cells containing liquid NE-213 scintillator attached permanently to RCA-8850 photomultiplier tubes. Pulses obtained from each photomultiplier system are amplified and electronically analyzed to identify and separate those pulses due to neutron-induced events in the detector from those due to photon-induced events in the detector. Signals from each detector are routed to two separate Analog-to-Digital Converters, and the resulting digitized information, representing: (1) the raw neutron-spectrum data; and (2) the raw photon-spectrum data, are transmited to the CICADA data-acquisition computer system of the TFTR. Software programs have been installed on the CICADA system to analyze the raw data to provide moderate-resolution recreations of the energy spectrum of the neutron and photon fluences incident on the detector during the operation of the TFTR. A complete description of, as well as the operation of, the hardware and software is given in this report.

  11. NE-213-scintillator-based neutron detection system for diagnostic measurements of energy spectra for neutrons having energies greater than or equal to 0.8 MeV created during plasma operations at the Princeton Tokamak Fusion Test Reactor

    NASA Astrophysics Data System (ADS)

    Dickens, J. K.; Hill, N. W.; Hou, F. S.; McConnell, J. W.; Spencer, R. R.; Tsang, F. Y.

    1985-08-01

    A system for making diagnostic measurements of the energy spectra of greater than or equal to 0.8-MeV neutrons produced during plasma operations of the Princeton Tokamak Fusion Test Reactor (TFTR) has been fabricated and tested and is presently in operation in the TFTR Test Cell Basement. The system consists of two separate detectors, each made up of cells containing liquid NE-213 scintillator attached permanently to RCA-8850 photomultiplier tubes. Pulses obtained from each photomultiplier system are amplified and electronically analyzed to identify and separate those pulses due to neutron-induced events in the detector from those due to photon-induced events in the detector. Signals from each detector are routed to two separate Analog-to-Digital Converters, and the resulting digitized information, representing: (1) the raw neutron-spectrum data; and (2) the raw photon-spectrum data, are transmited to the CICADA data-acquisition computer system of the TFTR. Software programs have been installed on the CICADA system to analyze the raw data to provide moderate-resolution recreations of the energy spectrum of the neutron and photon fluences incident on the detector during the operation of the TFTR. A complete description of, as well as the operation of, the hardware and software is given in this report.

  12. MAGNETIC ENERGY PRODUCTION BY TURBULENCE IN BINARY NEUTRON STAR MERGERS

    SciTech Connect

    Zrake, Jonathan; MacFadyen, Andrew I.

    2013-06-01

    The simultaneous detection of electromagnetic and gravitational wave emission from merging neutron star binaries would greatly aid in their discovery and interpretation. By studying turbulent amplification of magnetic fields in local high-resolution simulations of neutron star merger conditions, we demonstrate that magnetar-level ({approx}> 10{sup 16} G) fields are present throughout the merger duration. We find that the small-scale turbulent dynamo converts 60% of the randomized kinetic energy into magnetic fields on a merger timescale. Since turbulent magnetic energy dissipates through reconnection events that accelerate relativistic electrons, turbulence may facilitate the conversion of orbital kinetic energy into radiation. If 10{sup -4} of the {approx}10{sup 53} erg of orbital kinetic available gets processed through reconnection and creates radiation in the 15-150 keV band, then the fluence at 200 Mpc would be 10{sup -7} erg cm{sup -2}, potentially rendering most merging neutron stars in the advanced LIGO and Virgo detection volumes detectable by Swift BAT.

  13. Thermochemical water decomposition. [hydrogen separation for energy applications

    NASA Technical Reports Server (NTRS)

    Funk, J. E.

    1977-01-01

    At present, nearly all of the hydrogen consumed in the world is produced by reacting hydrocarbons with water. As the supply of hydrocarbons diminishes, the problem of producing hydrogen from water alone will become increasingly important. Furthermore, producing hydrogen from water is a means of energy conversion by which thermal energy from a primary source, such as solar or nuclear fusion of fission, can be changed into an easily transportable and ecologically acceptable fuel. The attraction of thermochemical processes is that they offer the potential for converting thermal energy to hydrogen more efficiently than by water electrolysis. A thermochemical hydrogen-production process is one which requires only water as material input and mainly thermal energy, or heat, as an energy input. Attention is given to a definition of process thermal efficiency, the thermodynamics of the overall process, the single-stage process, the two-stage process, multistage processes, the work of separation and a process evaluation.

  14. Separated-orbit bisected energy-recovered linear accelerator

    DOEpatents

    Douglas, David R.

    2015-09-01

    A separated-orbit bisected energy-recovered linear accelerator apparatus and method. The accelerator includes a first linac, a second linac, and a plurality of arcs of differing path lengths, including a plurality of up arcs, a plurality of downgoing arcs, and a full energy arc providing a path independent of the up arcs and downgoing arcs. The up arcs have a path length that is substantially a multiple of the RF wavelength and the full energy arc includes a path length that is substantially an odd half-integer multiple of the RF wavelength. Operation of the accelerator includes accelerating the beam utilizing the linacs and up arcs until the beam is at full energy, at full energy executing a full recirculation to the second linac using a path length that is substantially an odd half-integer of the RF wavelength, and then decelerating the beam using the linacs and downgoing arcs.

  15. Energy Separation in the Vortical Wake Flows of Turbine Vanes

    NASA Astrophysics Data System (ADS)

    Gostelow, J. P.; Hogg, S. I.; Carscallen, W. E.

    1997-11-01

    A new wide-bandwidth stagnation temperature probe is used to provide time-resolved measurements of the energy separation phenomenon in a vortical wake flow. Measurements are made behind the blunt trailing edge of a turbine nozzle vane mounted in a transonic planar cascade. The energy separation effects are found to be particularily strong at high Mach numbers. Phase averaging is applied to map the Eulerian contours of stagnation temperature and pressure and of entropy increase. The measurements explain anomalies observed in previous time-averaged measurements. At an acquisition frequency of 250 kHz the resolution is still inadequate to resolve fine scale wake turbulence but is adequate to validate computational work which, in turn, helps in the interpretation of the measurements.

  16. Probing energy dissipation, γ-ray and neutron multiplicity in the thermal neutron-induced fission of 239Pu

    NASA Astrophysics Data System (ADS)

    Pahlavani, M. R.; Mirfathi, S. M.

    2016-04-01

    The incorporation of the four-dimensional Langevin equations led to an integrative description of fission cross-section, fragment mass distribution and the multiplicity and energy distribution of prompt neutrons and γ-rays in the thermal neutron-induced fission of 239Pu. The dynamical approach presented in this paper thoroughly reproduces several experimental observables of the fission process at low excitation energy.

  17. Neutron productions in the fragmentation of relativistic heavy nuclei and formation of a beam of high-energy neutrons

    NASA Astrophysics Data System (ADS)

    Yurevich, V. I.

    2016-03-01

    The production of quasimonoenergetic high-energy neutrons at zero angle (0°) in the spallation of relativistic heavy nuclei is discussed by considering the example of the interaction of lead nuclei with light target nuclei. It is shown that this process can be used to generate a beam of high-energy neutrons at existing heavy ion accelerators. At the same time, itmay lead to the appearance of a parasitic neutron beam because of the interaction of the heavy-ion beam used with beam line and experimental setup materials.

  18. Neutron energy determination with a high-purity germanium detector

    NASA Technical Reports Server (NTRS)

    Beck, Gene A.

    1992-01-01

    Two areas that are related to planetary gamma-ray spectrometry are investigated. The first task was the investigation of gamma rays produced by high-energy charged particles and their secondaries in planetary surfaces by means of thick target bombardments. The second task was the investigation of the effects of high-energy neutrons on gamma-ray spectral features obtained with high-purity Ge-detectors. For both tasks, as a function of the funding level, the experimental work was predominantly tied to that of other researchers, whenever there was an opportunity to participate in bombardment experiments at large or small accelerators for charged particles.

  19. Neutron/gamma dose separation by the multiple-ion-chamber technique

    SciTech Connect

    Goetsch, S.J.

    1983-01-01

    Many mixed n/..gamma.. dosimetry systems rely on two dosimeters, one composed of a tissue-equivalent material and the other made from a non-hydrogenous material. The paired chamber technique works well in fields of neutron radiation nearly identical in spectral composition to that in which the dosimeters were calibrated. However, this technique is drastically compromised in phantom due to the degradation of the neutron spectrum. The three-dosimeter technique allows for the fall-off in neutron sensitivity of the two non-hydrogenous dosimeters. Precise and physically meaningful results were obtained with this technique with a D-T source in air and in phantom and with simultaneous D-T neutron and /sup 60/Co gamma ray irradiation in air. The MORSE-CG coupled n/..gamma.. three-dimensional Monte Carlo code was employed to calculate neutron and gamma doses in a water phantom. Gamma doses calculated in phantom with this code were generally lower than corresponding ion chamber measurements. This can be explained by the departure of irradiation conditions from ideal narrow-beam geometry. 97 references.

  20. Preliminary studies for a high energy neutron area monitor

    SciTech Connect

    Devine, R.T.; Hsu, H.H.

    1998-12-01

    Track etch detectors were exposed to neutrons produced by a spallation target struck by a beam of 800 MeV protons. The fields were filtered by 0, 10, and 40 centimeters of polyethylene. The track etch dosimeters were exposed on a polyethylene phantom. The dosimeters were exposed bare and behind lead filters of 0.25, 0.50, 0.75, 1.00, 1.25 and 1.50 cm of lead with the face of the dosimeter perpendicular to the beam and bare and behind lead filters of 0.50, 1.0, and 1.5 cm of lead with angle of incidence 45{degree} and 75{degree}. Monte Carlo calculations of these experimental configurations were done using MCNP and LAHET with input from the calculated spectra. These results are compared with the experimental results to understand the basic processes involved in the production of tracks with high energy neutrons and develop a high energy neutron area monitor.

  1. Techniques for the separation of neutron and gamma irradiations in thermoluminescent LiF

    SciTech Connect

    Abhold, M.E.

    1987-01-01

    The light emission spectra from thermoluminescent LiF in the form of TLD-100 is investigated for irradiations from Cs-137 gammas, thermal neutrons, and Am-241 alphas. The light emission spectra for thermal neutron and Cs-137 gamma irradiations is observed to be identical over the spectral range from 300 nm to 660 nm. The spectral observed for Am-241 alpha irradiations exhibit an enhancement in the spectral region from 520 nm to 600 nm with respect to the gamma and thermal neutron irradiations. This enhancement is shown to be due to contaminants on the surface of the TLD most likely introduced by the standard cleansing rinse in Methanol. The design of a carbon dioxide laser heated TLD reader developed to observe the light emission spectrum of LiF is presented. The TLD reader is shown to exhibit excellent reproducibility in the heating rate, which allows for a repeatability in radiation dose measurements of less than two percent.

  2. Neutron capture of 26Mg at thermonuclear energies

    NASA Astrophysics Data System (ADS)

    Mohr, P.; Beer, H.; Oberhummer, H.; Staudt, G.

    1998-08-01

    The neutron capture cross section of 26Mg was measured relative to the known gold cross section at thermonuclear energies using the fast cyclic activation technique. The experiment was performed at the 3.75 MV Van-de-Graaff accelerator, Forschungszentrum Karlsruhe. The experimental capture cross section is the sum of resonant and direct contributions. For the resonance at En,lab=220 keV our new results are in disagreement with the data from Weigmann, Macklin, and Harvey [Phys. Rev. C 14, 1328 (1976)]. An improved Maxwellian averaged capture cross section is derived from the new experimental data taking into account s- and p-wave capture and resonant contributions. The properties of so-called potential resonances which influence the p-wave neutron capture of 26Mg are discussed in detail.

  3. Neutron techniques. [for study of high-energy particles produced in large solar flares

    NASA Technical Reports Server (NTRS)

    Frye, Glenn M., Jr.; Dunphy, Philip P.; Chupp, Edward L.; Evenson, Paul

    1988-01-01

    Three experimental methods are described which hold the most promise for improved energy resolution, time resolution and sensitivity in the detection of solar neutrons on satellites and/or long duration balloon flights: the neutron calorimeter, the solar neutron track chamber, and the solar neutron decay proton detector. The characteristics of the three methods as to energy range, energy resolution, time resolution, detection efficiency, and physical properties are delineated. Earlier techniques to measure the intensity of high-energy cosmic-ray neutrons at the top of the atmosphere and to search for solar neutrons are described. The past three decades of detector development has now reached the point where it is possible to make comprehensive and detailed measurements of solar neutrons on future space missions.

  4. Symmetry energy from nuclear masses and neutron-star observations using generalised Skyrme functionals

    NASA Astrophysics Data System (ADS)

    Chamel, N.; Fantina, A. F.; Pearson, J. M.; Goriely, S.

    2016-01-01

    We study the constraints imposed by nuclear mass measurements and neutron-star observations on the symmetry energy. For this purpose, we use a family of unified equations of state of neutron-star interiors, based on generalised Skyrme functionals that were fitted to essentially all the experimental nuclear mass data while ensuring a realistic neutron-matter equation of state.

  5. Exploring Neutron-Rich Oxygen Isotopes with MoNA

    SciTech Connect

    Frank, N.; Gade, A.; Peters, W. A.; Thoennessen, M.; Baumann, T.; Bazin, D.; Lecouey, J.-L.; Scheit, H.; Schiller, A.; Brown, J.; DeYoung, P. A.; Finck, J. E.; Hinnefeld, J.; Howes, R.; Luther, B.

    2007-11-30

    The Modular Neutron Array (MoNA) was used in conjunction with a large-gap dipole magnet (Sweeper) to measure neutron-unbound states in oxygen isotopes close to the neutron dripline. While no excited states were observed in {sup 24}O, a resonance at 45(2) keV above the neutron separation energy was observed in {sup 23}O.

  6. Neutron beam optimization for boron neutron capture therapy using the D-D and D-T high-energy neutron sources

    SciTech Connect

    Verbeke, J.M.; Vujic, J.L.; Leung, K.N.

    2000-02-01

    A monoenergetic neutron beam simulation study is carried out to determine the most suitable neutron energy for treatment of shallow and deep-seated brain tumors in the context of boron neutron capture therapy. Two figures-of-merit--the absorbed skin dose and the absorbed tumor dose at a given depth in the brain--are used to measure the neutron beam quality. Based on the results of this study, moderators, reflectors, and delimiters are designed and optimized to moderate the high-energy neutrons from the fusion reactions {sup 2}H(d,n){sup 3}He and {sup 3}H(d,n){sup 4}He down to a suitable energy spectrum. Two different computational models (MCNP and BNCT-RTPE) have been used to study the dose distribution in the brain. With the optimal beam-shaping assembly, a 1-A mixed deuteron/triton beam of energy 150 keV accelerated onto a titanium target leads to a treatment time of 1 h. The dose near the center of the brain obtained with this configuration is > 65% higher than the dose from a typical spectrum produced by the Brookhaven Medical Research Reactor and is comparable to the dose obtained by other accelerator-produced neutron beams.

  7. 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.

  8. Improving the neutron-to-photon discrimination capability of detectors used for neutron dosimetry in high energy photon beam radiotherapy.

    PubMed

    Irazola, L; Terrón, J A; Bedogni, R; Pola, A; Lorenzoli, M; Sánchez-Nieto, B; Gómez, F; Sánchez-Doblado, F

    2016-09-01

    The increasing interest of the medical community to radioinduced second malignancies due to photoneutrons in patients undergoing high-energy radiotherapy, has stimulated in recent years the study of peripheral doses, including the development of some dedicated active detectors. Although these devices are designed to respond to neutrons only, their parasitic photon response is usually not identically zero and anisotropic. The impact of these facts on measurement accuracy can be important, especially in points close to the photon field-edge. A simple method to estimate the photon contribution to detector readings is to cover it with a thermal neutron absorber with reduced secondary photon emission, such as a borated rubber. This technique was applied to the TNRD (Thermal Neutron Rate Detector), recently validated for thermal neutron measurements in high-energy photon radiotherapy. The positive results, together with the accessibility of the method, encourage its application to other detectors and different clinical scenarios. PMID:27337649

  9. 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.

  10. Interacting dark energy collapse with matter components separation

    SciTech Connect

    Delliou, M. Le; Barreiro, T. E-mail: tmbarreiro@ulusofona.pt

    2013-02-01

    We use the spherical collapse model of structure formation to investigate the separation in the collapse of uncoupled matter (essentially baryons) and coupled dark matter in an interacting dark energy scenario. Following the usual assumption of a single radius of collapse for all species, we show that we only need to evolve the uncoupled matter sector to obtain the evolution for all matter components. This gives us more information on the collapse with a simplified set of evolution equations compared with the usual approaches. We then apply these results to four quintessence potentials and show how we can discriminate between different quintessence models.

  11. Broad energy range neutron spectroscopy using a liquid scintillator and a proportional counter: Application to a neutron spectrum similar to that from an improvised nuclear device

    NASA Astrophysics Data System (ADS)

    Xu, Yanping; Randers-Pehrson, Gerhard; Marino, Stephen A.; Garty, Guy; Harken, Andrew; Brenner, David J.

    2015-09-01

    A novel neutron irradiation facility at the Radiological Research Accelerator Facility (RARAF) has been developed to mimic the neutron radiation from an Improvised Nuclear Device (IND) at relevant distances (e.g. 1.5 km) from the epicenter. The neutron spectrum of this IND-like neutron irradiator was designed according to estimations of the Hiroshima neutron spectrum at 1.5 km. It is significantly different from a standard reactor fission spectrum, because the spectrum changes as the neutrons are transported through air, and it is dominated by neutron energies from 100 keV up to 9 MeV. To verify such wide energy range neutron spectrum, detailed here is the development of a combined spectroscopy system. Both a liquid scintillator detector and a gas proportional counter were used for the recoil spectra measurements, with the individual response functions estimated from a series of Monte Carlo simulations. These normalized individual response functions were formed into a single response matrix for the unfolding process. Several accelerator-based quasi-monoenergetic neutron source spectra were measured and unfolded to test this spectroscopy system. These reference neutrons were produced from two reactions: T(p,n)3He and D(d,n)3He, generating neutron energies in the range between 0.2 and 8 MeV. The unfolded quasi-monoenergetic neutron spectra indicated that the detection system can provide good neutron spectroscopy results in this energy range. A broad-energy neutron spectrum from the 9Be(d,n) reaction using a 5 MeV deuteron beam, measured at 60 degrees to the incident beam was measured and unfolded with the evaluated response matrix. The unfolded broad neutron spectrum is comparable with published time-of-flight results. Finally, the pair of detectors were used to measure the neutron spectrum generated at the RARAF IND-like neutron facility and a comparison is made to the neutron spectrum of Hiroshima.

  12. neutron activation analysis using thermochromatography. II. thermochromatographic separation of elements in the analysis of geological samples

    SciTech Connect

    Sattarov, G.; Davydov, A.V.; Khamatov, S.; Kist, A.A.

    1986-07-01

    The use of gas thermochromatography (GTC) in the radioactivation analysis of difficulty soluble samples with a strongly activating substrate is discussed. The effect of sample coarseness and ore type on the rate of extraction of gold and accompanying elements was studied. The limits of detection of 22 elements were compared using neutron activation analysis with GTC and INAA. The analytical parameters of the procedure were estimated.

  13. 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.

  14. Development of lower-energy neutron spectroscopy for areal density measurement in implosion experiment at NIF and OMEGA

    NASA Astrophysics Data System (ADS)

    Izumi, Nobuhiko; Lerche, Richard A.; Phillips, Thomas W.; Schmid, Gregory J.; Moran, Michael J.; Sangster, Thomas C.

    2001-12-01

    Areal density ((sigma) R) is a fundamental parameter that characterizes the performance of an ICF implosion. For high areal densities ((sigma) R>0.1 g/cm2), which will be realized in implosion experiments at NIF and LMJ, the target areal density exceeds the stopping range of charged particles and measurements with charged particle spectroscopy will be difficult. In this region, an areal density measurement method using down shifted neutron counting is a promising alternative. The probability of neutron scattering in the imploded plasma is proportional to the areal density of the plasma. The spectrum of neutrons scattered by the specific target nucleus has a characteristic low energy cut off. This enables separate, simultaneous measurements of fuel and pusher (sigma) Rs. To apply this concept in implosion experiments, the detector should have extremely large dynamic range. Sufficient signal output for low energy neutrons is also required. A lithium-glass scintillation-fiber plate (LG-SCIFI) is a promising candidate for this application. In this paper we propose a novel technique based on down shifted neutron measurements with a lithium-glass sctintillation-fiber plate. The details of instrumentation and background estimation with Monte Carlo calculation are reported.

  15. Development of Lower Energy Neutron Spectroscopy for Areal Density Measurement in Implosion Experiment at NIF and Omega

    SciTech Connect

    Isumi, N; Lerche, R A; Phillips, T W; Schmid, G J; Moran, M J; Sangster, T C

    2001-08-02

    Areal density ({rho}R) is a fundamental parameter that characterizes the performance of an ICF implosion. For high areal densities ({rho}R> 0.1 g/cm{sup 2}), which will be realized in implosion experiments at NIF and LMJ, the target areal density exceeds the stopping range of charged particles and measurements with charged particle spectroscopy will be difficult. In this region, an areal density measurement method using down shifted neutron counting is a promising alternative. The probability of neutron scattering in the imploded plasma is proportional to the areal density of the plasma. The spectrum of neutrons scattered by the specific target nucleus has a characteristic low energy cut off. This enables separate, simultaneous measurements of fuel and pusher {rho}Rs. To apply this concept in implosion experiments, the detector should have extremely large dynamic range. Sufficient signal output for low energy neutrons is also required. A lithium-glass scintillation-fiber plate (LG-SCIFI) is a promising candidate for this application. In this paper we propose a novel technique based on downshifted neutron measurements with a lithium-glass scintillation-fiber plate. The details of instrumentation and background estimation with Monte Carlo calculation are reported.

  16. Differential neutron energy spectra measured on spacecraft in low Earth orbit

    NASA Technical Reports Server (NTRS)

    Dudkin, V. E.; Akopova, A. B.; Melkumyan, L. V.; Benton, E. V.; Frank, A. L.

    1990-01-01

    Two methods for measuring neutrons in the range from thermal energies to dozens of MeV were used. In the first method, alpha-particles emitted from the 6Li(n,alpha)T reaction are detected with the help of plastic nuclear track detectors, yielding results on thermal and resonance neutrons. Also, fission foils are used to detect fast neutrons. In the second method, fast neutrons are recorded by nuclear photographic emulsions (NPE). The results of measurements on board various satellites are presented. The neutron flux density does not appear to correlate clearly with orbital parameters. Up to 50% of neutrons are due to albedo neutrons from the atmosphere while the fluxes inside the satellites are 15-20% higher than those on the outside. Estimates show that the neutron contribution to the total equivalent radiation dose reaches 20-30%.

  17. ARSENATE CARRIER PRECIPITATION METHOD OF SEPARATING PLUTONIUM FROM NEUTRON IRRADIATED URANIUM AND RADIOACTIVE FISSION PRODUCTS

    DOEpatents

    Thompson, S.G.; Miller, D.R.; James, R.A.

    1961-06-20

    A process is described for precipitating Pu from an aqueous solution as the arsenate, either per se or on a bismuth arsenate carrier, whereby a separation from uranium and fission products, if present in solution, is accomplished.

  18. High-energy in-beam neutron measurements of metal-based shielding for accelerator-driven spallation neutron sources

    NASA Astrophysics Data System (ADS)

    DiJulio, D. D.; Cooper-Jensen, C. P.; Björgvinsdóttir, H.; Kokai, Z.; Bentley, P. M.

    2016-05-01

    Metal-based shielding plays an important role in the attenuation of harmful and unwanted radiation at an accelerator-driven spallation neutron source. At the European Spallation Source, currently under construction in Lund, Sweden, metal-based materials are planned to be used extensively as neutron guide substrates in addition to other shielding structures around neutron guides. The usage of metal-based materials in the vicinity of neutron guides however requires careful consideration in order to minimize potential background effects in a neutron instrument at the facility. Therefore, we have carried out a combined study involving high-energy neutron measurements and Monte Carlo simulations of metal-based shielding, both to validate the simulation methodology and also to investigate the benefits and drawbacks of different metal-based solutions. The measurements were carried out at The Svedberg Laboratory in Uppsala, Sweden, using a 174.1 MeV neutron beam and various thicknesses of aluminum-, iron-, and copper-based shielding blocks. The results were compared to geant4 simulations and revealed excellent agreement. Our combined study highlights the particular situations where one type of metal-based solution may be preferred over another.

  19. Neutronics issues and inertial fusion energy: a summary of findings

    SciTech Connect

    Latkowski, J. F., LLNL

    1998-05-29

    We have analyzed and compared five major inertial fusion energy (IFE) and two representative magnetic fusion energy (MFE) power plant designs for their environment, safety, and health (ES&H) characteristics. Our work has focussed upon the neutronics of each of the designs and the resulting radiological hazard indices. The calculation of a consistent set of hazard indices allows comparisons to be made between the designs. Such comparisons enable identification of trends in fusion ES&H characteristics and may be used to increase the likelihood of fusion achieving its full potential with respect to ES&H characteristics. The present work summarizes our findings and conclusions. This work emphasizes the need for more research in low-activation materials and for the experimental measurement of radionuclide release fractions under accident conditions.

  20. Interaction of High-Energy Proton Beam with a Thin Target and Multiplicities of Neutron

    SciTech Connect

    Demirkol, I.; Tatar, M.; Safak, M. S.; Arasoglu, A.; Tel, E.

    2007-04-23

    An important ingredient in the performance of accelerator driven systems for energy production, waste transmutation and other applications are the number of spallation neutrons produced per incident proton. The neutron multiplicities, angular and energy distributions are usually calculated using simulation codes. We have presented multiplicities of the neutrons emitted in the interaction of a high-energy proton (1500 MeV) with a thin target Pb, Bi. In this study we have used the code ISABEL to calculate multiplicities of the neutron emitted. The results obtained have been compared with the available data.

  1. Single event upset and charge collection measurements using high energy protons and neutrons

    SciTech Connect

    Normand, E.; Oberg, D.L.; Wert, J.L.; Ness, J.D.; Majewski, P.P. ); Wender, S.; Gavron, A. )

    1994-12-01

    RAMs, microcontrollers and surface barrier detectors were exposed to beams of high energy protons and neutrons to measure the induced number of upsets as well as energy deposition. The WNR facility at Los Alamos provided a neutron spectrum similar to that of the atmospheric neutrons. Its effect on devices was compared to that of protons with energies of 200, 400, 500, and 800 MeV. Measurements indicate that SEU cross sections for 400 MeV protons are similar to those induced by the atmospheric neutron spectrum.

  2. Neutron fluence and energy reproducibility of a 2-dollar TRIGA reactor Pulse

    SciTech Connect

    Payne, Rosara F.; Drader, Jessica A.; Friese, Judah I.; Greenwood, Lawrence R.; Hines, Corey C.; Metz, Lori A.; Kephart, Jeremy D.; King, Matthew D.; Pierson, Bruce D.; Smith, Jeremy D.; Wall, Donald E.

    2009-10-01

    Washington State University’s 1 MW TRIGA reactor has a long history of utilization for neutron activation analysis (NAA). TRIGA reactors have the ability to pulse, reach supercritical (k>1) for short bursts of time. At this high power and fast time the energy spectrum and neutron fluence are largely uncharacterized. The pulse neutron energy spectrum and fluence were determined by the activation of Cu, Au, Co, Fe, and Ti. These analyses were completed with and without Cd shielding to determine reproducibility between pulses. The applications and implications of the neutron energy and fluence reproducibility to the use of pulsed NAA will be discussed.

  3. Neutron spectra and dose equivalents calculated in tissue for high-energy radiation therapy

    SciTech Connect

    Kry, Stephen F.; Howell, Rebecca M.; Salehpour, Mohammad; Followill, David S.

    2009-04-15

    Neutrons are by-products of high-energy radiation therapy and a source of dose to normal tissues. Thus, the presence of neutrons increases a patient's risk of radiation-induced secondary cancer. Although neutrons have been thoroughly studied in air, little research has been focused on neutrons at depths in the patient where radiosensitive structures may exist, resulting in wide variations in neutron dose equivalents between studies. In this study, we characterized properties of neutrons produced during high-energy radiation therapy as a function of their depth in tissue and for different field sizes and different source-to-surface distances (SSD). We used a previously developed Monte Carlo model of an accelerator operated at 18 MV to calculate the neutron fluences, energy spectra, quality factors, and dose equivalents in air and in tissue at depths ranging from 0.1 to 25 cm. In conjunction with the sharply decreasing dose equivalent with increased depth in tissue, the authors found that the neutron energy spectrum changed drastically as a function of depth in tissue. The neutron fluence decreased gradually as the depth increased, while the average neutron energy decreased sharply with increasing depth until a depth of approximately 7.5 cm in tissue, after which it remained nearly constant. There was minimal variation in the quality factor as a function of depth. At a given depth in tissue, the neutron dose equivalent increased slightly with increasing field size and decreasing SSD; however, the percentage depth-dose equivalent curve remained constant outside the primary photon field. Because the neutron dose equivalent, fluence, and energy spectrum changed substantially with depth in tissue, we concluded that when the neutron dose equivalent is being determined at a depth within a patient, the spectrum and quality factor used should be appropriate for depth rather than for in-air conditions. Alternately, an appropriate percent depth-dose equivalent curve should be

  4. Connecting neutron star observations to three-body forces in neutron matter and to the nuclear symmetry energy.

    PubMed

    Steiner, A W; Gandolfi, S

    2012-02-24

    Using a phenomenological form of the equation of state of neutron matter near the saturation density which has been previously demonstrated to be a good characterization of quantum Monte Carlo simulations, we show that currently available neutron star mass and radius measurements provide a significant constraint on the equation of state of neutron matter. At higher densities we model the equation of state by using polytropes and a quark matter model. We show that observations offer an important constraint on the strength of the three-body force in neutron matter, and thus some theoretical models of the three-body force may be ruled out by currently available astrophysical data. In addition, we obtain an estimate of the symmetry energy of nuclear matter and its slope that can be directly compared to the experiment and other theoretical calculations. PMID:22463511

  5. Solar neutrons and the energy spectrum of flare-accelerated particles

    NASA Astrophysics Data System (ADS)

    Kocharov, G. E.; Mandzhavidze, N. Z.

    1987-10-01

    The Monte Carlo method is used to calculate the generation and escape of neutrons in the framework of the magnetic-arc model. It is shown that the generation of neutrons lasts for 20-30 minutes; the characteristic time of the intensity decline increases with magnetic field gradient and the radius of the coronal part of the arc. The angular distribution of escaping neutrons is anisotropic, with the maximum flux occurring at the limb. The neutron energy spectra are different in different directions. Particular attention is given to the solar-longitude dependence of neutron fluxes in a flare with gamma-ray emission.

  6. Preparative scale separation of thulium from erbium for neutron capture cross section measurements - Part: Preparative scale

    DOE PAGESBeta

    Birnbaum, Eva R.; Bene, Balazs J.; Taylor, Wayne Allen; Sudowe, Ralf

    2016-06-04

    Here, this paper discusses the development of a separation method for isolation of 171Tm from a half-gram irradiated erbium target in support of stockpile stewardship and astrophysics research. The developed procedure is based on cation exchange separation using alpha-hydroxyisobutyric acid (α-HIBA) as chelating agent. It is able to achieve either a decontamination factor of 1.4(4) × 105 with 68.9(3) % recovery or 95.4(3) % recovery with a decontamination factor of 5.82(7) × 103 for a mock 500-mg target containing 17.9 mg thulium in a single pass-through at room temperature.

  7. Separating the Universe into real and fake energy densities

    NASA Astrophysics Data System (ADS)

    Hu, Wayne; Chiang, Chi-Ting; Li, Yin; LoVerde, Marilena

    2016-07-01

    The separate universe technique provides a means of establishing consistency relations between short-wavelength observables and the long-wavelength matter density fluctuations within which they evolve by absorbing the latter into the cosmological background. We extend it to cases where nongravitational forces introduce a Jeans scale in other species like dynamical dark energy or massive neutrinos. The technique matches the synchronous gauge matter density fluctuations to the local expansion using the acceleration equation and accounts for the temporal nonlocality and scale dependence of the long-wavelength response of small scale matter observables, e.g., the nonlinear power spectrum, halo abundance and the implied halo bias, and N -point correlation functions. Above the Jeans scale, the local Friedmann equation relates the expansion to real energy densities and a curvature that is constant in comoving coordinates. Below the Jeans scale, the curvature evolves and acts like a fake density component. In all cases, the matter evolution on small scales is correctly modeled as we illustrate using scalar field dark energy with adiabatic or isocurvature initial conditions across the Jeans scale set by its finite sound speed.

  8. Russian measurements of neutron energy spectra on the Mir orbital station.

    PubMed

    Lyagushin, V I; Dudkin, V E; Potapov, Y V; Sevastianov, V D

    2001-06-01

    Results of the experiments on neutron energy spectra measurements within broad energy range from 5 x 10(-7) to 2 x 10(2) MeV aboard the Mir orbital station and equivalent neutron dose estimation are presented. Four measurement techniques were used during the experiments. The shape of spectra and their absolute values are in good agreement. According to those experiments, an equivalent neutron dose depends upon effective shielding thickness and spacecraft mass. The neutron dose mentioned is comparable with that of ionizing radiation. Neutron flux levels measured aboard the Mir station have shown that a neutron spectrometer involving broad energy range will be used within the radiation monitoring systems in manned space flights. PMID:11855413

  9. Functional Arrays for Light Energy Capture and Charge Separation.

    PubMed

    Flamigni, Lucia

    2016-06-01

    This article draws, with a simplified but rigorous approach, the typical procedure for the design and optimization of functional multicomponent structures for light to chemical energy conversion for two series of multipartite structures based on prototypical chromophores: polypyridyl metal complexes and porphyrinoids. Starting from a photophysical study performed by steady-state and time-resolved spectroscopic methods, the full deactivation dynamics of the light-absorbing chromophore(s) are disclosed. The preferred deactivation step (electron transfer in this case) is then optimized. This can be done by simply operating on the solvent, but also by changing structure/components that can alter electronic and nuclear factors, via continuous feedback with the research groups in charge of the synthesis. With a presentation suitable for a wide audience, it is here discussed how the effective design of functional multicomponent structures for charge separation can be achieved. PMID:27027981

  10. Characterisation of an accelerator-based neutron source for BNCT versus beam energy

    NASA Astrophysics Data System (ADS)

    Agosteo, S.; Curzio, G.; d'Errico, F.; Nath, R.; Tinti, R.

    2002-01-01

    Neutron capture in 10B produces energetic alpha particles that have a high linear energy transfer in tissue. This results in higher cell killing and a higher relative biological effectiveness compared to photons. Using suitably designed boron compounds which preferentially localize in cancerous cells instead of healthy tissues, boron neutron capture therapy (BNCT) has the potential of providing a higher tumor cure rate within minimal toxicity to normal tissues. This clinical approach requires a thermal neutron source, generally a nuclear reactor, with a fluence rate sufficient to deliver tumorcidal doses within a reasonable treatment time (minutes). Thermal neutrons do not penetrate deeply in tissue, therefore BNCT is limited to lesions which are either superficial or otherwise accessible. In this work, we investigate the feasibility of an accelerator-based thermal neutron source for the BNCT of skin melanomas. The source was designed via MCNP Monte Carlo simulations of the thermalization of a fast neutron beam, generated by 7 MeV deuterons impinging on a thick target of beryllium. The neutron field was characterized at several deuteron energies (3.0-6.5 MeV) in an experimental structure installed at the Van De Graaff accelerator of the Laboratori Nazionali di Legnaro, in Italy. Thermal and epithermal neutron fluences were measured with activation techniques and fast neutron spectra were determined with superheated drop detectors (SDD). These neutron spectrometry and dosimetry studies indicated that the fast neutron dose is unacceptably high in the current design. Modifications to the current design to overcome this problem are presented.

  11. SEPARATION OF URANIUM, PLUTONIUM AND FISSION PRODUCTS FROM NEUTRON- BOMBARDED URANIUM

    DOEpatents

    Martin, A.E.; Johnson, I.; Burris, L. Jr.; Winsch, I.O.; Feder, H.M.

    1962-11-13

    A process is given for removing plutonium and/or fission products from uranium fuel. The fuel is dissolved in molten zinc--magnesium (10 to 18% Mg) alloy, more magnesium is added to obtain eutectic composition whereby uranium precipitates, and the uranium are separated from the Plutoniumand fission-product- containing eutectic. (AEC)

  12. SOLVENT EXTRACTION PROCESS FOR SEPARATING URANIUM AND PLUTONIUM FROM AQUEOUS ACIDIC SOLUTIONS OF NEUTRON IRRADIATED URANIUM

    DOEpatents

    Bruce, F.R.

    1962-07-24

    A solvent extraction process was developed for separating actinide elements including plutonium and uranium from fission products. By this method the ion content of the acidic aqueous solution is adjusted so that it contains more equivalents of total metal ions than equivalents of nitrate ions. Under these conditions the extractability of fission products is greatly decreased. (AEC)

  13. Characterization of the high-energy neutron beam of the PRISMA beamline using a diamond detector

    NASA Astrophysics Data System (ADS)

    Cazzaniga, C.; Frost, C. D.; Minniti, T.; Schooneveld, E.; Perelli Cippo, E.; Tardocchi, M.; Rebai, M.; Gorini, G.

    2016-07-01

    The high-energy neutron component (En > 10 MeV) of the neutron spectrum of PRISMA, a beam-line at the ISIS spallation source, has been characterized for the first time. Neutron measurements using a Single-crystal Diamond Detector at a short-pulse source are obtained by a combination of pulse height and time of flight analysis. An XY scan provides a 2D map of the high-energy neutron beam which has a diameter of about 40 mm. The high neutron flux, that has been found to be (3.8 ± 0.7) · 105 cm‑2s‑1 for En > 10 MeV in the centre, opens up for a possible application of the beam-line as a high-energy neutron irradiation position. Results are of interest for the development of the ChipIR beam-line, which will feature an atmospheric-like neutron spectrum for chip irradiation experiment. Furthermore, these results demonstrate that diamond detectors can be used at spallation sources to investigate the transport of high-energy neutrons down instruments which is of interest in general to designers as high-energy neutrons are a source of background in thermal beamlines.

  14. Personnel neutron dosimetry at Department of Energy facilities

    SciTech Connect

    Brackenbush, L.W.; Endres, G.W.R.; Selby, J.M.; Vallario, E.J.

    1980-08-01

    This study assesses the state of personnel neutron dosimetry at DOE facilities. A survey of the personnel dosimetry systems in use at major DOE facilities was conducted, a literature search was made to determine recent advances in neutron dosimetry, and several dosimetry experts were interviewed. It was concluded that personnel neutron dosimeters do not meet current needs and that serious problems exist now and will increase in the future if neutron quality factors are increased and/or dose limits are lowered.

  15. Simultaneous measurement of volume and grain boundary diffusivity separately in Fe thin film with stable nanostructure using polarized neutron reflectivity

    NASA Astrophysics Data System (ADS)

    Chakravarty, Sujay; Shukla, Neeraj; Devishvili, Anton; Vorobiev, Alexei; Amarendra, G.

    2016-08-01

    Polarized neutron reflectivity (PNR) measurements have been used for simultaneous measurement of volume and grain boundary diffusivity separately in stable nanocrystalline Fe thin film at very low homologous temperature (0.2 T m < T < 0.3 T m). PNR measurements were done on Si (substrate)/Fe (150 nm)/[57Fe (3 nm)/natFe (9 nm)]x10 thin film system with periodic 57Fe isotope modulation. PNR from as deposited film shows strong Bragg peaks due to neutron scattering length contrast between 57Fe and natFe layers. Atomic Diffusivity was measured from decrease in the intensity of the Bragg peak due to interdiffusion of 57Fe and natFe layers after annealing the film at three different temperatures 418 K, 483 K and 548 K, respectively for different time intervals starting from 30 min to several hours. The change in the nanostructure of the film after annealing is characterized using grazing incidence x-ray diffraction. No appreciable grain growth within error bar is observed in the film after annealing indicating that the diffusion measurements were done in stable nanostructure. It is observed that the grain boundary diffusivity is two orders of magnitude higher than the volume diffusivity. However, the mechanism of atomic diffusion is similar in both grain and grain boundary.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  17. Neutron emission as a function of fragment energy in the spontaneous fission of /sup 260/Md

    SciTech Connect

    Wild, J.F.; van Aarle, J.; Westmeiser, W.; Lougheed, R.W.; Hulet, E.K.; Moody, K.J.; Dougan, R.J.; Brandt, R.; Patzelt, P.

    1989-04-19

    We have made the first measurement of the number of neutrons emitted in the spontaneous fission of a nuclide in which very high fragment energies dominate the fission process. In bombardments of /sup 254/Es, we produced 28-d /sup 260/Md, which was neutron-counted in a 1-m-diam spherical tank containing a Gd-doped scintillator solution. The average number of neutrons emitted per fission is only 2.58 +- 0.11, substantially less than for other actinides. A direct correlation of neutron multiplicity with fragment excitation energy is clearly demonstrated. 3 refs., 5 figs.

  18. Binding Energies of Hyperonic Matter and Applications to Neutron Stars

    SciTech Connect

    Uechi, Hiroshi; Uechi, Schun T.

    2011-10-21

    The conserving nonlinear, nonchiral {sigma}-{omega}-{rho} hadronic mean-field approximation is applied to saturation properties of nuclear and hyperonic matter, properties of hadron and hadron-quark neutron stars. Nonlinear interactions are renormalized self-consistently as effective coupling constants, effective masses, and sources of equations of motion by maintaining thermodynamic consistency to the mean-field approximation. The effective masses and coupling constants become density-dependent, and they simultaneously determine binding energies and saturation properties of nuclear matter and hyperonic matter. The conserving nonlinear {sigma}-{omega}-{rho} mean-field approximation with vacuum fluctuation corrections and strange quark matter defined by the MIT-bag model were employed to examine properties of hadron-(strange) quark stars. We found that hadron-quark stars become more stable at high densities compared to pure hadronic and strange quark stars.

  19. Analysis of incident-energy dependence of delayed neutron yields in actinides

    SciTech Connect

    Nasir, Mohamad Nasrun bin Mohd Metorima, Kouhei Ohsawa, Takaaki Hashimoto, Kengo

    2015-04-29

    The changes of delayed neutron yields (ν{sub d}) of Actinides have been analyzed for incident energy up to 20MeV using realized data of precursor after prompt neutron emission, from semi-empirical model, and delayed neutron emission probability data (P{sub n}) to carry out a summation method. The evaluated nuclear data of the delayed neutron yields of actinide nuclides are still uncertain at the present and the cause of the energy dependence has not been fully understood. In this study, the fission yields of precursor were calculated considering the change of the fission fragment mass yield based on the superposition of fives Gaussian distribution; and the change of the prompt neutrons number associated with the incident energy dependence. Thus, the incident energy dependent behavior of delayed neutron was analyzed.The total number of delayed neutron is expressed as ν{sub d}=∑Y{sub i} • P{sub ni} in the summation method, where Y{sub i} is the mass yields of precursor i and P{sub ni} is the delayed neutron emission probability of precursor i. The value of Y{sub i} is derived from calculation of post neutron emission mass distribution using 5 Gaussian equations with the consideration of large distribution of the fission fragments. The prompt neutron emission ν{sub p} increases at higher incident-energy but there are two different models; one model says that the fission fragment mass dependence that prompt neutron emission increases uniformly regardless of the fission fragments mass; and the other says that the major increases occur at heavy fission fragments area. In this study, the changes of delayed neutron yields by the two models have been investigated.

  20. Time series analysis and Monte Carlo methods for eigenvalue separation in neutron multiplication problems

    SciTech Connect

    Nease, Brian R. Ueki, Taro

    2009-12-10

    A time series approach has been applied to the nuclear fission source distribution generated by Monte Carlo (MC) particle transport in order to calculate the non-fundamental mode eigenvalues of the system. The novel aspect is the combination of the general technical principle of projection pursuit for multivariate data with the neutron multiplication eigenvalue problem in the nuclear engineering discipline. Proof is thoroughly provided that the stationary MC process is linear to first order approximation and that it transforms into one-dimensional autoregressive processes of order one (AR(1)) via the automated choice of projection vectors. The autocorrelation coefficient of the resulting AR(1) process corresponds to the ratio of the desired mode eigenvalue to the fundamental mode eigenvalue. All modern MC codes for nuclear criticality calculate the fundamental mode eigenvalue, so the desired mode eigenvalue can be easily determined. This time series approach was tested for a variety of problems including multi-dimensional ones. Numerical results show that the time series approach has strong potential for three dimensional whole reactor core. The eigenvalue ratio can be updated in an on-the-fly manner without storing the nuclear fission source distributions at all previous iteration cycles for the mean subtraction. Lastly, the effects of degenerate eigenvalues are investigated and solutions are provided.

  1. Separation of beam and electrons in the spallation neutron source H{sup -} ion source

    SciTech Connect

    Whealton, J.H.; Raridon, R.J.; Leung, K.N.

    1997-12-01

    The Spallation Neutron Source (SNS) requires an ion source producing an H{sup {minus}} beam with a peak current of 35mA at a 6.2 percent duty factor. For the design of this ion source, extracted electrons must be transported and dumped without adversely affecting the H{sup {minus}} beam optics. Two issues are considered: (1) electron containment transport and controlled removal; and (2) first-order H{sup {minus}} beam steering. For electron containment, various magnetic, geometric and electrode biasing configurations are analyzed. A kinetic description for the negative ions and electrons is employed with self-consistent fields obtained from a steady-state solution to Poisson`s equation. Guiding center electron trajectories are used when the gyroradius is sufficiently small. The magnetic fields used to control the transport of the electrons and the asymmetric sheath produced by the gyrating electrons steer the ion beam. Scenarios for correcting this steering by split acceleration and focusing electrodes will be considered in some detail.

  2. Intermediate energy neutrons at WNR. Spin-isospin and energy dependence of the NN interaction and the nuclear response

    SciTech Connect

    Taddeucci, T.N.

    1995-02-01

    This report summarizes results of nuclear physics studies using intermediate energy (50-800 MeV) neutron probes carried out over the past five years using the Neutron Time-of-Flight (NTOF) Facility and Optically-Pumped Ion Source (OPPIS) at LAMPF and the `white` neutron source at the Weapons Neutron Research (WNR) facility. LAMPF did significant work in polarization transfer, while WNR took advantage of the wide neutron energy spectrum available to study energy dependent effects. The major focus of experiments with intermediate energy neutron probes for the next five years will be to explore fundamental details of the spin-isospin and energy dependence of the NN interaction and the nuclear response. To achieve this goal, the WNR white neutron source will be used for nucleon-nucleon and nucleon-nucleus interaction studies over a broad continuous range of incident neutron energy. Measurement of polarization observables using polarized targets or polarized beam should be possible, and will add an important extra dimension to these studies.

  3. Dosimetry and fast neutron energies characterization of photoneutrons produced in some medical linear accelerators

    NASA Astrophysics Data System (ADS)

    Khaled, N. E.; Attalla, E. M.; Ammar, H.; Khalil, W.

    2011-12-01

    This work focusses on the estimation of induced photoneutrons energy, fluence, and strength using nuclear track detector (NTD) (CR-39). Photoneutron energy was estimated for three different linear accelerators, LINACs as an example for the commonly used accelerators. For high-energy linear accelerators, neutrons are produced as a consequence of photonuclear reactions in the target nuclei, accelerator head, field-flattening filters and beam collimators, and other irradiated objects. NTD (CR-39) is used to evaluate energy and fluence of the fast neutron. Track length is used to estimate fast photoneutrons energy for linear accelerators (Elekta 10 MV, Elekta 15 MV, and Varian 15 MV). Results show that the estimated neutron energies for the three chosen examples of LINACs reveals neutron energies in the range of 1-2 MeV for 10 and 15 MV X-ray beams. The fluence of neutrons at the isocenter (Φtotal) is found to be (4×106 n cm2 Gy-1) for Elekta machine 10 MV. The neutron source strengths Q are calculated. It was found to be 0.2×1012 n Gy-1 X-ray at the isocenter. This work represents simple, low cost, and accurate methods of measuring fast neutrons dose and energies.

  4. Measurement of fragment mass distributions in neutron-induced fission reactions at intermediate energies

    NASA Astrophysics Data System (ADS)

    Simutkin, V. D.; Ryzhov, I. V.; Tutin, G. A.; Vaishnene, L. A.; Blomgren, J.; Pomp, S.; Österlund, M.; Andersson, P.; Bevilacqua, R.; Meulders, J. P.; Prieels, R.

    2009-10-01

    Fragment mass distributions from neutron-induced fission of 232Th and 238U have been measured at quasi-monoenergetic neutron beam of the Louvain-la-Neuve cyclotron facility CYCLONE. The measurements have been carried out making use of a multi-section Frisch-gridded ionization chamber. The measurement technique as well as the data processing is described. Preliminary data on primary fragment mass yields are given for an incident neutron energy of 32.8 MeV.

  5. First Attempts on Energy-selective Neutron Imaging at IBR-2

    NASA Astrophysics Data System (ADS)

    Lukin, E. V.; Kozlenko, D. P.; Kichanov, S. E.; Rutkauskas, A. V.; Bokuchava, G. D.; Savenko, B. N.

    A new neutron imaging facility has been started at the IBR-2 high flux pulsed reactor. It isattractive not only for traditional neutron imaging applications but in particular also for thedevelopment of modern energy-selective techniques using a time-of-flight methods.A short overview of the first obtained results of theenergy-selected experiments by means of time-of-flight methods realised on neutron radiography and tomography station on high-flux pulsed reactor IBR-2 are presented.

  6. Neutrons in proton pencil beam scanning: parameterization of energy, quality factors and RBE.

    PubMed

    Schneider, Uwe; Hälg, Roger A; Baiocco, Giorgio; Lomax, Tony

    2016-08-21

    The biological effectiveness of neutrons produced during proton therapy in inducing cancer is unknown, but potentially large. In particular, since neutron biological effectiveness is energy dependent, it is necessary to estimate, besides the dose, also the energy spectra, in order to obtain quantities which could be a measure of the biological effectiveness and test current models and new approaches against epidemiological studies on cancer induction after proton therapy. For patients treated with proton pencil beam scanning, this work aims to predict the spatially localized neutron energies, the effective quality factor, the weighting factor according to ICRP, and two RBE values, the first obtained from the saturation corrected dose mean lineal energy and the second from DSB cluster induction. A proton pencil beam was Monte Carlo simulated using GEANT. Based on the simulated neutron spectra for three different proton beam energies a parameterization of energy, quality factors and RBE was calculated. The pencil beam algorithm used for treatment planning at PSI has been extended using the developed parameterizations in order to calculate the spatially localized neutron energy, quality factors and RBE for each treated patient. The parameterization represents the simple quantification of neutron energy in two energy bins and the quality factors and RBE with a satisfying precision up to 85 cm away from the proton pencil beam when compared to the results based on 3D Monte Carlo simulations. The root mean square error of the energy estimate between Monte Carlo simulation based results and the parameterization is 3.9%. For the quality factors and RBE estimates it is smaller than 0.9%. The model was successfully integrated into the PSI treatment planning system. It was found that the parameterizations for neutron energy, quality factors and RBE were independent of proton energy in the investigated energy range of interest for proton therapy. The pencil beam algorithm has

  7. Neutrons in proton pencil beam scanning: parameterization of energy, quality factors and RBE

    NASA Astrophysics Data System (ADS)

    Schneider, Uwe; Hälg, Roger A.; Baiocco, Giorgio; Lomax, Tony

    2016-08-01

    The biological effectiveness of neutrons produced during proton therapy in inducing cancer is unknown, but potentially large. In particular, since neutron biological effectiveness is energy dependent, it is necessary to estimate, besides the dose, also the energy spectra, in order to obtain quantities which could be a measure of the biological effectiveness and test current models and new approaches against epidemiological studies on cancer induction after proton therapy. For patients treated with proton pencil beam scanning, this work aims to predict the spatially localized neutron energies, the effective quality factor, the weighting factor according to ICRP, and two RBE values, the first obtained from the saturation corrected dose mean lineal energy and the second from DSB cluster induction. A proton pencil beam was Monte Carlo simulated using GEANT. Based on the simulated neutron spectra for three different proton beam energies a parameterization of energy, quality factors and RBE was calculated. The pencil beam algorithm used for treatment planning at PSI has been extended using the developed parameterizations in order to calculate the spatially localized neutron energy, quality factors and RBE for each treated patient. The parameterization represents the simple quantification of neutron energy in two energy bins and the quality factors and RBE with a satisfying precision up to 85 cm away from the proton pencil beam when compared to the results based on 3D Monte Carlo simulations. The root mean square error of the energy estimate between Monte Carlo simulation based results and the parameterization is 3.9%. For the quality factors and RBE estimates it is smaller than 0.9%. The model was successfully integrated into the PSI treatment planning system. It was found that the parameterizations for neutron energy, quality factors and RBE were independent of proton energy in the investigated energy range of interest for proton therapy. The pencil beam algorithm has

  8. 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.

  9. Computational Transport Modeling of High-Energy Neutrons Found in the Space Environment

    NASA Technical Reports Server (NTRS)

    Cox, Brad; Theriot, Corey A.; Rohde, Larry H.; Wu, Honglu

    2012-01-01

    The high charge and high energy (HZE) particle radiation environment in space interacts with spacecraft materials and the human body to create a population of neutrons encompassing a broad kinetic energy spectrum. As an HZE ion penetrates matter, there is an increasing chance of fragmentation as penetration depth increases. When an ion fragments, secondary neutrons are released with velocities up to that of the primary ion, giving some neutrons very long penetration ranges. These secondary neutrons have a high relative biological effectiveness, are difficult to effectively shield, and can cause more biological damage than the primary ions in some scenarios. Ground-based irradiation experiments that simulate the space radiation environment must account for this spectrum of neutrons. Using the Particle and Heavy Ion Transport Code System (PHITS), it is possible to simulate a neutron environment that is characteristic of that found in spaceflight. Considering neutron dosimetry, the focus lies on the broad spectrum of recoil protons that are produced in biological targets. In a biological target, dose at a certain penetration depth is primarily dependent upon recoil proton tracks. The PHITS code can be used to simulate a broad-energy neutron spectrum traversing biological targets, and it account for the recoil particle population. This project focuses on modeling a neutron beamline irradiation scenario for determining dose at increasing depth in water targets. Energy-deposition events and particle fluence can be simulated by establishing cross-sectional scoring routines at different depths in a target. This type of model is useful for correlating theoretical data with actual beamline radiobiology experiments. Other work exposed human fibroblast cells to a high-energy neutron source to study micronuclei induction in cells at increasing depth behind water shielding. Those findings provide supporting data describing dose vs. depth across a water-equivalent medium. This

  10. 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.

  11. Measurement of neutron energy spectra and neutron dose rates from 7Li(p,n)7Be reaction induced on thin LiF target

    NASA Astrophysics Data System (ADS)

    Atanackovic, Jovica; Matysiak, Witold; Dubeau, Jacques; Witharana, Sampath; Waker, Anthony

    2015-02-01

    The measurements of neutron energy spectra and neutron dose rates were performed using the KN Van de Graaff accelerator, located at the McMaster University Accelerator Laboratory (MAL). Protons were accelerated on the thin lithium fluoride (LiF) target and produced mono-energetic neutrons which were measured using three different spectrometers: Bonner Sphere Spectrometer (BSS), Nested Neutron Spectrometer (NNS), and Rotational Proton Recoil Spectrometer (ROSPEC). The purpose of this work is (1) measurement and quantification of low energy accelerator neutron fields in terms of neutron fluence and dose, (2) comparison of results obtained by three different instruments, (3) comparison of measurements with Monte Carlo simulations based on theoretical neutron yields from 7Li(p,n)7Be nuclear reaction, and (4) comparison of results obtained using different neutron spectral unfolding methods. The nominal thickness of the LiF target used in the experiment was 50 μg /cm2, which corresponds to the linear thickness of 0.19 μm and results in approximately 6 keV energy loss for the proton energies used in the experiment (2.2, 2.3, 2.4 and 2.5 MeV). For each of the proton energies, neutron fluence per incident proton charge was measured and several dosimetric quantities of interest in radiation protection were derived. In addition, theoretical neutron yield calculations together with the results of Monte Carlo (MCNP) modeling of the neutron spectra are reported. Consistent neutron fluence spectra were obtained with three detectors and good agreement was observed between theoretically calculated and measured neutron fluences and derived dosimetric quantities for investigated proton energies at 2.3, 2.4 and 2.5 MeV. In the case of 2.2 MeV, some plausibly explainable discrepancies were observed.

  12. Low energy neutron background in deep underground laboratories

    NASA Astrophysics Data System (ADS)

    Best, Andreas; Görres, Joachim; Junker, Matthias; Kratz, Karl-Ludwig; Laubenstein, Matthias; Long, Alexander; Nisi, Stefano; Smith, Karl; Wiescher, Michael

    2016-03-01

    The natural neutron background influences the maximum achievable sensitivity in most deep underground nuclear, astroparticle and double-beta decay physics experiments. Reliable neutron flux numbers are an important ingredient in the design of the shielding of new large-scale experiments as well as in the analysis of experimental data. Using a portable setup of 3He counters we measured the thermal neutron flux at the Kimballton Underground Research Facility, the Soudan Underground Laboratory, on the 4100 ft and the 4850 ft levels of the Sanford Underground Research Facility, at the Waste Isolation Pilot Plant and at the Gran Sasso National Laboratory. Absolute neutron fluxes at these laboratories are presented.

  13. First-forbidden β-decay rates, energy rates of β-delayed neutrons and probability of β-delayed neutron emissions for neutron-rich nickel isotopes

    NASA Astrophysics Data System (ADS)

    Nabi, Jameel-Un; Çakmak, Necla; Iftikhar, Zafar

    2016-01-01

    First-forbidden (FF) transitions can play an important role in decreasing the calculated half-lives specially in environments where allowed Gamow-Teller (GT) transitions are unfavored. Of special mention is the case of neutron-rich nuclei where, due to phase-space amplification, FF transitions are much favored. We calculate the allowed GT transitions in various pn-QRPA models for even-even neutron-rich isotopes of nickel. Here we also study the effect of deformation on the calculated GT strengths. The FF transitions for even-even neutron-rich isotopes of nickel are calculated assuming the nuclei to be spherical. Later we take into account deformation of nuclei and calculate GT + unique FF transitions, stellar β-decay rates, energy rate of β-delayed neutrons and probability of β-delayed neutron emissions. The calculated half-lives are in excellent agreement with measured ones and might contribute in speeding-up of the r-matter flow.

  14. Density dependence of the symmetry energy from neutron skin thickness in finite nuclei

    SciTech Connect

    Vinas, X.; Centelles, M.; Roca-Maza, X.; Warda, M.

    2012-10-20

    The density dependence of the symmetry energy, characterized by the parameter L, is studied using information provided by the neutron skin thickness in finite nuclei. An estimate of L is obtained from experimental data of antiprotonic atoms. We also discuss the ability of parity violating electron scatering to obtain information about the neutron skin thickness in {sup 208}Pb.

  15. High energy neutron and gamma-radiation generated during the solar flares

    NASA Technical Reports Server (NTRS)

    Kocharov, G. E.; Mandzhavidze, N. Z.

    1985-01-01

    The problem of high energy neutrons and gamma rays generation in the solar conditions is considered. It is shown that due to a peculiarity of generation and propagation of neutrons corresponding solar flares should be localized at high helio-longitudes.

  16. ICF ignition capsule neutron, gamma ray, and high energy x-ray images

    NASA Astrophysics Data System (ADS)

    Bradley, P. A.; Wilson, D. C.; Swenson, F. J.; Morgan, G. L.

    2003-03-01

    Post-processed total neutron, RIF neutron, gamma-ray, and x-ray images from 2D LASNEX calculations of burning ignition capsules are presented. The capsules have yields ranging from tens of kilojoules (failures) to over 16 MJ (ignition), and their implosion symmetry ranges from prolate (flattest at the hohlraum equator) to oblate (flattest towards the laser entrance hole). The simulated total neutron images emphasize regions of high DT density and temperature; the reaction-in-flight neutrons emphasize regions of high DT density; the gamma rays emphasize regions of high shell density; and the high energy x rays (>10 keV) emphasize regions of high temperature.

  17. Progress in development of neutron energy spectrometer for deuterium plasma operation in KSTAR

    SciTech Connect

    Tomita, H. Yamashita, F.; Nakayama, Y.; Morishima, K.; Yamamoto, Y.; Sakai, Y.; Hayashi, S.; Kawarabayashi, J.; Iguchi, T.; Cheon, M. S.; Isobe, M.; Ogawa, K.

    2014-11-15

    Two types of DD neutron energy spectrometer (NES) are under development for deuterium plasma operation in KSTAR to understand behavior of beam ions in the plasma. One is based on the state-of-the-art nuclear emulsion technique. The other is based on a coincidence detection of a recoiled proton and a scattered neutron caused by an elastic scattering of an incident DD neutron, which is called an associated particle coincidence counting-NES. The prototype NES systems were installed at J-port in KSTAR in 2012. During the 2012 and 2013 experimental campaigns, multiple shots-integrated neutron spectra were preliminarily obtained by the nuclear emulsion-based NES system.

  18. Experimental Validation of Hybrid Distillation-Vapor Permeation Process for Energy Efficient Ethanol-Water Separation

    EPA Science Inventory

    The energy demand of distillation-based systems for ethanol recovery and dehydration can be significant, particularly for dilute solutions. An alternative separation process integrating vapor stripping with a vapor compression step and a vapor permeation membrane separation step...

  19. Experimental Validation of Hybrid Distillation-Vapor Permeation Process for Energy Efficient Ethanol-Water Separation

    EPA Science Inventory

    The energy demand of distillation-based systems for ethanol recovery and dehydration can be significant, particularly for dilute solutions. An alternative separation process integrating vapor stripping with a vapor compression step and a vapor permeation membrane separation step,...

  20. 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.

  1. Role of neutron transfer and deformation effect in capture process at sub-barrier energies

    NASA Astrophysics Data System (ADS)

    Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.; Zhang, H. Q.

    2012-12-01

    The roles of nuclear deformation and neutron transfer in sub-barrier capture process are studied within the quantum diffusion approach. The change of the deformations of colliding nuclei with neutron exchange can crucially influence the sub-barrier fusion. The sub-barrier capture reactions following the neutron pair transfer are used for the indirect study of neutron-neutron correlation in the surface region of nucleus. The strong surface enhancement of the neutron pairing in nuclei 48Ca, 64Ni, and 116,124,132Sn is demonstrated. Comparing the capture cross sections calculated without the breakup effect and experimental complete fusion cross sections, the breakup was analyzed in reactions with weakly bound projectiles 6,7,9Li and 9Be. A trend of a systematic behavior for the complete fusion suppression as a function of the target charge and bombarding energy is not achieved.

  2. 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.

  3. Neutron fluences and energy spectra in the Cosmos-2044 biosatellite orbit

    NASA Technical Reports Server (NTRS)

    Dudkin, V. E.; Akopova, A. B.; Melkumyan, L. V.; Benton, E. V.; Frank, A. L.

    1992-01-01

    Joint Soviet-American measurements of the neutron component of space radiation (SR) were carried out during the flight of the Soviet biosatellite Cosmos-2044. Neutron flux densities and differential energy spectra were measured inside and on the external surface of the spacecraft. Three energy intervals were employed: thermal (En < or = 0.2 eV), resonance (0.2 eV < En < 1.0 MeV) and fast (En > or = 1.0 MeV) neutrons. The first two groups were measured with U.S. 6LiF detectors, while fast neutrons were recorded both by U.S. fission foils and Soviet nuclear emulsions. Estimations were made of the contributions to absorbed and equivalent doses from each neutron energy interval and a correlation was presented between fast neutron fluxes, measured outside the satellite, and the phase of solar activity (SA). Average dose equivalent rates of 0.018 and 0.14 mrem d-1 were measured for thermal and resonance neutrons, respectively, outside the spacecraft. The corresponding values for fast neutrons were 3.3 (U.S.) and 1.8 (U.S.S.R.) mrem d-1. Inside the spacecraft, a value of 3.5 mrem d-1 was found.

  4. Neutron influences and energy spectra in the Cosmos-2044 biosatellite orbit

    NASA Technical Reports Server (NTRS)

    Dudkin, V. E.; Potapov, Yu. V.; Akopova, A. B.; Melkumyan, L. V.; Rshtuni, Sh. B.; Benton, E, V.; Frank, A. L.

    1995-01-01

    Joint Soviet-American measurements of the neutron component of space radiation (SR) were carried out during the flight of the Soviet biosatellite Cosmos-2044. Neutron flux densities and differential energy spectra were measured inside and on the external surface of the spacecraft. Three energy intervals were employed: thermal (E(sub n) less than or equal to 0.2 eV), resonance (0.2 eV less than E(sub n) less than 1.0 MeV) and fast (E(sub n) greater than or equal to 1.0 MeV) neutrons. The first two groups were measured with U.S. (6)LiF detectors, while fast neutrons were recorded both by U.S. fission foils and Soviet nuclear emulsions. Estimations were made of the contributions to absorbed and equivalent doses from each neutron energy interval and a correlation was presented between fast neutron fluxes, measured outside the satellite, and the phase of solar activity (SA). Average dose equivalent rates of 0.018 and 0.14 mrem d(exp -1) were measured for thermal and resonance neutrons, respectively, outside the spacecraft. The corresponding values for fast neutrons were 3.3 (U.S.) and 1.8 (U.S.S.R.) mrem d(exp -1). Inside the spacecraft, a value of 3.5 mrem d(exp -1) was found.

  5. Observation of the one- to six-neutron transfer reactions at sub-barrier energies

    SciTech Connect

    Jiang, C.L.; Rehm, K.E.; Gehring, J.

    1995-08-01

    It was suggested many years ago that when two heavy nuclei are in contact during a grazing collision, the transfer of several correlated neutron-pairs could occur. Despite considerable experimental effort, however, so far only cross sections for up to four-neutron transfers have been uniquely identified. The main difficulties in the study of multi-neutron transfer reactions are the small cross sections encountered at incident energies close to the barrier, and various experimental uncertainties which can complicate the analysis of these reactions. We have for the first time found evidence for multi-neutron transfer reactions covering the full sequence from one- to six-neutron transfer reactions at sub-barrier energies in the system {sup 58}Ni + {sup 100}Mo.

  6. Research and development separation technology: The DOE Industrial Energy Conservation Program

    SciTech Connect

    Not Available

    1987-07-01

    This brochure summarizes the Office of Industrial Programs' RandD efforts in the advancement of separation technology. The purpose of this brochure is to provide interested parties with information on federal industrial energy conservation activities in separation technology. The brochure is comprised of the following sections: Separation Technology, summarizes the current state of separation technology and its uses. Potential Energy Savings, discusses the potential for industrial energy conservation through the implementation of advanced separation processes. Office of Industrial Programs' RandD Efforts in Separation Technology Development, describes the separation RandD projects conducted by IP. RandD Data Base, lists contractor, principal investigator, and location of each separation-related RandD effort sponsored by IP.

  7. Neutron dose per fluence and weighting factors for use at high energy accelerators

    SciTech Connect

    Cossairt, J.Donald; Vaziri, Kamran; /Fermilab

    2008-07-01

    In June 2007, the United States Department of Energy incorporated revised values of neutron weighting factors into its occupational radiation protection Regulation 10 CFR Part 835 as part of updating its radiation dosimetry system. This has led to a reassessment of neutron radiation fields at high energy proton accelerators such as those at the Fermi National Accelerator Laboratory (Fermilab). Values of dose per fluence factors appropriate for accelerator radiation fields calculated elsewhere are collated and radiation weighting factors compared. The results of this revision to the dosimetric system are applied to americium-beryllium neutron energy spectra commonly used for instrument calibrations. A set of typical accelerator neutron energy spectra previously measured at Fermilab are reassessed in light of the new dosimetry system. The implications of this revision are found to be of moderate significance.

  8. Ring energy and current considerations for spallation neutron source

    SciTech Connect

    Blumberg, L.N.

    1994-04-01

    The most desirable energy E{sub o} of protons from the synchrotron and thus beam current {bar I} to produced a given beam power P{sub B} involves a balanced consideration of neutron production capability, accelerator beam stability, user requirements, and cost considerations. The present solution consists of two 3.6-GeV rings with a 600-MeV Linac injector, a compromise between conflicting factors of cost and technical concern. The authors believe that the design is a conservative one. They could increase the beam energy and/or the repetition rate and thereby decrease the requirement for the number of protons N{sub o} in the ring which in the present design is an extrapolation of about a factor of 7 from existing ring intensities. However, the specified ring acceptance appears quite adequate to contain the required 1.45 10{sup 14} protons/ring and the resulting loss in the target window and target are reasonable. The beam power and current are indeed modest in terms of window and target integrity compared to the 200 MW, 200mA 1-GeV design for the APT. The two-ring approach also offers several practical advantages -- the project is stageable in the sense that only one ring may be required initially to achieve P{sub B} = 2.5 MW power on the target with subsequent expansion to 5 MW with addition of the second ring. Two rings also provide additional reliability in the sense that the user program need not be interrupted by failure of one ring.

  9. Novel modified zeolites for energy-efficient hydrocarbon separations.

    SciTech Connect

    Arruebo, Manuel; Dong, Junhang; Anderson, Thomas (Burns and McDonnell, Kansas City, MO); Gu, Xuehong; Gray, Gary (Goodyear Chemical Company, Akron, OH); Bennett, Ron (Goodyear Chemical Company, Akron, OH); Nenoff, Tina Maria; Kartin, Mutlu; Johnson, Kaylynn (Goodyear Chemical Company, Akron, OH); Falconer, John; Noble, Richard

    2006-11-01

    We present synthesis, characterization and testing results of our applied research project, which focuses on the effects of surface and skeletal modification of zeolites for significant enhancements in current hydrocarbon (HC) separations. Zeolites are commonly used by the chemical and petroleum industries as catalysts and ion-exchangers. They have high potential for separations owing to their unique pore structures and adsorption properties and their thermal, mechanical and chemical properties. Because of zeolites separation properties, low cost, and robustness in industrial process, they are natural choice for use as industrial adsorbents. This is a multidisciplinary effort to research, design, develop, engineer, and test new and improved materials for the separation of branched vs. linear organic molecules found in commercially important HC streams via adsorption based separations. The focus of this project was the surface and framework modification of the commercially available zeolites, while tuning the adsorption properties and the selectivities of the bulk and membrane separations. In particular, we are interested with our partners at Goodyear Chemical, on how to apply the modified zeolites to feedstock isoprene purification. For the characterization and the property measurements of the new and improved materials powder X-ray diffraction (PXRD), Residual Gas Analyzer-Mass Spectroscopy (RGA-MS), Electron Microscopy (SEM/EDAX), temperature programmed desorption (TPD) and surface area techniques were utilized. In-situ carbonization of MFI zeolite membranes allowed for the maximum separation of isoprene from n-pentane, with a 4.1% enrichment of the binary stream with n-pentane. In four component streams, a modified MFI membrane had high selectivities for n-pentane and 1-3-pentadiene over isoprene but virtually no separation for the 2-methyl-2-butene/isoprene pair.

  10. Measurement of high energy neutrons via Lu(n,xn) reactions

    SciTech Connect

    Henry, E.A.; Becker, J.A.; Archer, D.E.; Younes, W.; Stoyer, M.A.; Slaughter, D.

    1997-07-01

    High energy neutrons can be assayed by the use of the nuclear diagnostic material lutetium. We are measuring the (n,xn) cross sections for natural lutetium in order to develop it as a detector material. We are applying lutetium to diagnose the high energy neutrons produced in test target/blanket systems appropriate for the Accelerator Production of Tritium Project. 3 refs., 5 figs., 1 tab.

  11. Results on the neutron energy distribution measurements at the RECH-1 Chilean nuclear reactor

    NASA Astrophysics Data System (ADS)

    Aguilera, P.; Molina, F.; Romero-Barrientos, J.

    2016-07-01

    Neutron activations experiments has been perform at the RECH-1 Chilean Nuclear Reactor to measure its neutron flux energy distribution. Samples of pure elements was activated to obtain the saturation activities for each reaction. Using - ray spectroscopy we identify and measure the activity of the reaction product nuclei, obtaining the saturation activities of 20 reactions. GEANT4 and MCNP was used to compute the self shielding factor to correct the cross section for each element. With the Expectation-Maximization algorithm (EM) we were able to unfold the neutron flux energy distribution at dry tube position, near the RECH-1 core. In this work, we present the unfolding results using the EM algorithm.

  12. New opportunities for quasielastic and inelastic neutron scattering at steady-state sources using mechanical selection of the incident and final neutron energy

    DOE PAGESBeta

    Mamantov, Eugene

    2015-06-12

    We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of themore » scattering angle component out of the equatorial plane.« less

  13. New opportunities for quasielastic and inelastic neutron scattering at steady-state sources using mechanical selection of the incident and final neutron energy

    SciTech Connect

    Mamantov, Eugene

    2015-06-12

    We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of the scattering angle component out of the equatorial plane.

  14. Towards an optimum design of a P-MOS radiation detector for use in high-energy medical photon beams and neutron facilities: analysis of activation materials.

    PubMed

    Price, Robert A

    2005-01-01

    The behaviour of packaged and unpackaged ESAPMOS4 RadFET radiation detectors (NMRC Cork, Ireland) was investigated when used in the mixed photon and neutron environment of a medical linear accelerator operating above the nucleon separation energy and in a 14 MeV neutron field provided by a D-T generator. Within the uncertainty of the experimental set-up (4% at 95% confidence level) the unpackaged device was found to have essentially zero activation dose-burden whereas the packaged device exhibits a considerable degree of post irradiation absorbed dose due to deactivation radiation. PMID:16381751

  15. A Drabkin energy filter for experiments at a spallation neutron source.

    SciTech Connect

    Parizzi, A. A.; Felcher, G. P.; Klose, F.

    2000-11-21

    We present a new approach for dynamic monochromatization of neutrons suitable for time-of-flight experiments at spallation neutron sources. The method requires polarized neutrons and is based on the Drabkin energy filter. In its initial application, this magnetic resonator device, consisting of a polarizer/analyzer system and a wavelength-dependent spin flipper, was proposed for extracting a narrow bandwidth from a broad bandwidth polarized neutron beam. At a spallation neutron source, wavelength is determined by time-of-flight (TOF) from the source to the detector. However, at each instant a spread of wavelengths is recorded due to the non-zero emission time of the source/moderator system. Particularly, high-intensity moderators for cold neutrons produce long ''tails'' in the intensity/time distribution for all wavelengths, degrading the resolution of the experiments. The Drabkin energy filter can be used to cut the neutron tails for all wavelengths, by drifting the resonance condition in synchronization with the TOF. Calculations show that the method is viable, and that substantial resolution gains are obtained by application to a TOF neutron reflectometer.

  16. 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.

  17. Neutron coincidence detectors employing heterogeneous materials

    DOEpatents

    Czirr, J. Bartley; Jensen, Gary L.

    1993-07-27

    A neutron detector relies upon optical separation of different scintillators to measure the total energy and/or number of neutrons from a neutron source. In pulse mode embodiments of the invention, neutrons are detected in a first detector which surrounds the neutron source and in a second detector surrounding the first detector. An electronic circuit insures that only events are measured which correspond to neutrons first detected in the first detector followed by subsequent detection in the second detector. In spectrometer embodiments of the invention, neutrons are thermalized in the second detector which is formed by a scintillator-moderator and neutron energy is measured from the summed signals from the first and second detectors.

  18. Laser inertial fusion-based energy: Neutronic design aspects of a hybrid fusion-fission nuclear energy system

    NASA Astrophysics Data System (ADS)

    Kramer, Kevin James

    This study investigates the neutronics design aspects of a hybrid fusion-fission energy system called the Laser Fusion-Fission Hybrid (LFFH). A LFFH combines current Laser Inertial Confinement fusion technology with that of advanced fission reactor technology to produce a system that eliminates many of the negative aspects of pure fusion or pure fission systems. When examining the LFFH energy mission, a significant portion of the United States and world energy production could be supplied by LFFH plants. The LFFH engine described utilizes a central fusion chamber surrounded by multiple layers of multiplying and moderating media. These layers, or blankets, include coolant plenums, a beryllium (Be) multiplier layer, a fertile fission blanket and a graphite-pebble reflector. Each layer is separated by perforated oxide dispersion strengthened (ODS) ferritic steel walls. The central fusion chamber is surrounded by an ODS ferritic steel first wall. The first wall is coated with 250-500 mum of tungsten to mitigate x-ray damage. The first wall is cooled by Li17Pb83 eutectic, chosen for its neutron multiplication and good heat transfer properties. The Li17Pb 83 flows in a jacket around the first wall to an extraction plenum. The main coolant injection plenum is immediately behind the Li17Pb83, separated from the Li17Pb83 by a solid ODS wall. This main system coolant is the molten salt flibe (2LiF-BeF2), chosen for beneficial neutronics and heat transfer properties. The use of flibe enables both fusion fuel production (tritium) and neutron moderation and multiplication for the fission blanket. A Be pebble (1 cm diameter) multiplier layer surrounds the coolant injection plenum and the coolant flows radially through perforated walls across the bed. Outside the Be layer, a fission fuel layer comprised of depleted uranium contained in Tristructural-isotropic (TRISO) fuel particles having a packing fraction of 20% in 2 cm diameter fuel pebbles. The fission blanket is cooled by

  19. Calculation of neutron and gamma ray energy spectra for fusion reactor shield design: comparison with experiment

    SciTech Connect

    Santoro, R.T.; Alsmiller, R.G. Jr.; Barnes, J.M.; Chapman, G.T.

    1980-08-01

    Integral experiments that measure the transport of approx. 14 MeV D-T neutrons through laminated slabs of proposed fusion reactor shield materials have been carried out. Measured and calculated neutron and gamma ray energy spectra are compared as a function of the thickness and composition of stainless steel type 304, borated polyethylene, and Hevimet (a tungsten alloy), and as a function of detector position behind these materials. The measured data were obtained using a NE-213 liquid scintillator using pulse-shape discrimination methods to resolve neutron and gamma ray pulse height data and spectral unfolding methods to convert these data to energy spectra. The calculated data were obtained using two-dimensional discrete ordinates radiation transport methods in a complex calculational network that takes into account the energy-angle dependence of the D-T neutrons and the nonphysical anomalies of the S/sub n/ method.

  20. Measurements and Calculations of Neutron Scattering Angular Distributions over a Wide Mass and Energy Range

    NASA Astrophysics Data System (ADS)

    Hansen, L. F.

    Neutron elastic and inelastic differential cross sections for targets between (9)Be and (239)Pu at energies, E 14 MeV have been measured using the Livermore and Ohio University neutron time-of-flight facilities. We review here the data and the analyses based on two local microscopic optical potentials: that of Jeukenne, Lejeune and Mahaux, and that of Brieva and Rook. The results are also compared with calculations using global potentials. Coupled channel formalism has been used in the analysis of targets with strong deformations, such as Be, C, Ta, and actinides. The value of the microscopic optical potentials as a tool to predict elastic and inelastic neutron cross sections over a wide mass and energy range is discussed. The need for neutron measurements up to higher energies and their analysis in conjunction with (p,p) and charge exchange (p,n) data is addressed.

  1. Measurements and calculations of neutron scattering angular distributions over a wide mass and energy range

    SciTech Connect

    Hansen, L.F.

    1985-05-01

    Neutron elastic and inelastic differential cross sections for targets between /sup 9/Be and /sup 239/Pu at energies, E > 14 MeV have been measured using the Livermore and Ohio University neutron time-of-flight facilities. We review here the data and the analyses based on two local microscopic optical potentials: that of Jeukenne, Lejeune and Mahaux, and that of Brieva and Rook. The results are also compared with calculations using global potentials. Coupled channel formalism has been used in the analysis of targets with strong deformations, such as Be, C, Ta, and actinides. The value of the microscopic optical potentials as a tool to predict elastic and inelastic neutron cross sections over a wide mass and energy range is discussed. The need for neutron measurements up to higher energies and their analysis in conjunction with (p,p) and charge exchange (p,n) data is addressed. 17 refs.

  2. Proceedings of the International Energy Agency workshop on separation technologies

    SciTech Connect

    Fassbender, L.L.; Ashton, W.B.; Kinzey, B.R.; McDonald, S.C.

    1989-07-01

    An international separations workshop was held to review current international research and development (R and D) activities in separation technologies and to identify important R and D needs. Participants represented government, academia, and industry from Austria, Canada, the Netherlands, Sweden, the United Kingdom, the United States, and West Germany. Workshop activities included an identification of broad areas of R and D that are needed to advance the state of the art in separations science and technology, and some of the more focused, key research efforts needed. Participants, working in groups, developed more detailed R and D recommendations and identified example projects that address knowledge gaps in three major technology areas: (1)membranes, (2) drying, evaporation, distillation, dewatering, and freeze crystallization, and (3) solvent/supercritical fluid extraction. Also, as background for the technical discussions, members of each country represented at the workshop made formal presentations.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  4. Energy-Deposition and Damage Calculations in Core-Vessel Inserts at the Spallation Neutron Source

    SciTech Connect

    Murphy, B.D.

    2002-06-25

    Heat-deposition and damage calculations are described for core-vessel inserts in the target area of the Spallation Neutron Source. Two separate designs for these inserts (or neutron beam tubes) were studied; a single-unit insert and a multi-unit insert. The single unit contains a neutron guide; the multi unit does not. Both units are constructed of stainless steel. For the single unit, separate studies were carried out with the guide composed of stainless steel, glass, and aluminum. Results are also reported for an aluminum window on the front of the insert, a layer of nickel on the guide, a cadmium shield surrounding the guide, and a stainless steel plug in the beam-tube opening. The locations of both inserts were the most forward positions to be occupied by each design respectively thus ensuring that the calculations are conservative.

  5. Accelerator measurement of NaI response to medium energy neutrons and application to a satellite-borne spectrometer

    NASA Technical Reports Server (NTRS)

    Dunphy, P. P.; Chupp, E. L.; Popecki, M.; Forrest, D. J.; Lopiano, D.; Shima, T.; Spinka, H.; Glass, G.; Burleson, G.; Beddo, M.

    1992-01-01

    We report on the response of a prototype detector to medium energy neutrons. The neutrons were produced by n-p scattering of a neutron beam on a hydrogen target. The measurements provide unique data on the efficiency and response of large NaI scintillators to neutrons in the energy range 36-709 MeV. We apply the results to the high-energy mode of the Gamma-Ray Spectrometer (GRS) on the Solar Maximum Mission satellite by estimating its efficiency for neutron detection. This estimate is compared to earlier Monte Carlo calculations of the GRS efficiency.

  6. Excitation of Energy Levels of Fissionable Nucleus Shape Isomers in the Doorway State in Reactions with Neutrons and Deuterons

    SciTech Connect

    Serov, V.I.; Andreev, M.F.; Zavgorodny, V.A.

    2005-05-24

    Measurements were conducted for the fission neutron yields with fission fragments in the (d,pf) reactions at some excitation energies, where threshold neutrons were discovered. These data on the neutron yields in 233U(d,pfn) and 239Pu(d,pfn) reactions have been compared with the dependence of the average of fission neutrons vp(En) in the 233U(n,f) reaction as well as fission probability in the 239Pu(d,pf) reaction on excitation energy, which provides a better understanding of the nuclear fission process in a (d,pf) reaction and the vp(En) dependence on neutron energy.

  7. Symmetry energy and surface properties of neutron-rich exotic nuclei

    SciTech Connect

    Gaidarov, M. K.; Antonov, A. N.; Sarriguren, P.; Moya de Guerra, E.

    2014-07-23

    The symmetry energy, the neutron pressure and the asymmetric compressibility of spherical Ni, Sn, and Pb and deformed Kr and Sm neutron-rich even-even nuclei are calculated within the coherent density fluctuation model using the symmetry energy as a function of density within the Brueckner energy-density functional. The correlation between the thickness of the neutron skin and the characteristics related with the density dependence of the nuclear symmetry energy is investigated for isotopic chains of these nuclei in the framework of the deformed self-consistent mean-field Skyrme HF+BCS method. The mass dependence of the nuclear symmetry energy and the neutron skin thickness are also studied together with the role of the neutron-proton asymmetry. The studied correlations reveal a smoother behavior in the case of spherical nuclei than for deformed ones. We also notice that the neutron skin thickness obtained for {sup 208}Pb with SLy4 force is found to be in a good agreement with the recent data. In addition to the interest that this study may have by itself, we give some numerical arguments in proof of the existence of peculiarities of the studied quantities in Ni and Sn isotopic chains that are not present in the Pb chain.

  8. A novel fast-neutron detector concept for energy-selective imaging and imaging spectroscopy.

    PubMed

    Cortesi, M; Dangendorf, V; Zboray, R; Prasser, H-M

    2014-07-01

    We present and discuss the operational principle of a new fast-neutron detector concept suitable for either energy-selective imaging or for imaging spectroscopy. The detector is comprised of a series of energy-selective stacks of converter foils immersed in a noble-gas based mixture, coupled to a position-sensitive charge readout. Each foil in the various stacks is made of two layers of different thicknesses, fastened together: a hydrogen-rich (plastic) layer for neutron-to-proton conversion, and a hydrogen-free coating to selectively stop/absorb the recoil protons below a certain energy cut-off. The neutron-induced recoil protons, that escape the converter foils, release ionization electrons in the gas gaps between consecutive foils. The electrons are then drifted towards and localized by a position-sensitive charge amplification and readout stage. Comparison of the images detected by stacks with different energy cut-offs allows energy-selective imaging. Neutron energy spectrometry is realized by analyzing the responses of a sufficient large number of stacks of different energy response and unfolding techniques. In this paper, we present the results of computer simulation studies and discuss the expected performance of the new detector concept. Potential applications in various fields are also briefly discussed, in particularly, the application of energy-selective fast-neutron imaging for nuclear safeguards application, with the aim of determining the plutonium content in Mixed Oxide (MOX) fuels. PMID:25085132

  9. A novel fast-neutron detector concept for energy-selective imaging and imaging spectroscopy

    SciTech Connect

    Cortesi, M.; Prasser, H.-M.; Dangendorf, V.; Zboray, R.

    2014-07-15

    We present and discuss the operational principle of a new fast-neutron detector concept suitable for either energy-selective imaging or for imaging spectroscopy. The detector is comprised of a series of energy-selective stacks of converter foils immersed in a noble-gas based mixture, coupled to a position-sensitive charge readout. Each foil in the various stacks is made of two layers of different thicknesses, fastened together: a hydrogen-rich (plastic) layer for neutron-to-proton conversion, and a hydrogen-free coating to selectively stop/absorb the recoil protons below a certain energy cut-off. The neutron-induced recoil protons, that escape the converter foils, release ionization electrons in the gas gaps between consecutive foils. The electrons are then drifted towards and localized by a position-sensitive charge amplification and readout stage. Comparison of the images detected by stacks with different energy cut-offs allows energy-selective imaging. Neutron energy spectrometry is realized by analyzing the responses of a sufficient large number of stacks of different energy response and unfolding techniques. In this paper, we present the results of computer simulation studies and discuss the expected performance of the new detector concept. Potential applications in various fields are also briefly discussed, in particularly, the application of energy-selective fast-neutron imaging for nuclear safeguards application, with the aim of determining the plutonium content in Mixed Oxide (MOX) fuels.

  10. Development of high-energy neutron imaging for use in NDE applications

    SciTech Connect

    Dietrich, F; Hall, J; Logan, C; Schmid, G

    1999-06-01

    We are currently developing a high-energy (10 - 15 MeV) neutron imaging system for use in NDE applications. Our goal is to develop an imaging system capable of detecting cubic-mm-scale voids or other structural defects in heavily-shielded low-Z materials within thick sealed objects. The system will be relatively compact (suitable for use in a small laboratory) and capable of acquiring tomographic image data sets. The design of a prototype imaging detector and multi-axis staging system will be discussed and selected results from recent imaging experiments will be presented. The development of an intense, accelerator-driven neutron source suitable for use with the imaging system will also be discussed. Keywords: neutron imaging, neutron radiography, computed tomography, non-destructive inspection, neutron sources

  11. Neutron range spectrometer

    DOEpatents

    Manglos, S.H.

    1988-03-10

    A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are colliminated along a collimation axis and a position sensitive neutron counter is disposed in the path of the collimated neutron beam. The counter determines positions along the collimation axis of interactions between the neutrons in the neutron beam and a neutron-absorbing material in the counter. From the interaction positions, a computer analyzes the data and determines the neutron energy spectrum of the neutron beam. The counter is preferably shielded and a suitable neutron-absorbing material is He-3. 1 fig.

  12. 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.

  13. Transport analysis of measured neutron energy spectra in a graphite stack with a collimated deuterium-tritium neutron beam

    SciTech Connect

    Tsechanski, A.; Ofek, R.; Goldfeld, A.; Shani, G.

    1989-02-01

    The Ben-Gurion University measurements of neutron energy spectra in a graphite stack, resulting from the scattering of 14.7-MeV neutrons streaming through a 6-cm-diam collimator in a 121-cm-thick paraffin wall, have been used as a benchmark for the compatability and accuracy of discrete ordinates, P/sub n/, and transport calculations and as a tool for fusion reactor neutronics. The transport analysis has been carried out with the DOT 4.2 discrete ordinates code and with cross sections processed with the NJOY code. Most of the parameters affecting the accuracy of the flux and L system scattering cross sections in the P/sub n/ approximation, the quadrature set employed, and the energy multigroup structure. First, a spectrum calculated with DOT 4.2, with a detector located on the axis of the system, was compared with a spectrum calculated with the MCNP Monte Carlo code, which was a preliminary verification of the DOT 4.2 results. Both calculated spectra were in good agreement. Next, the DOT 4.2 calculations were compared with the measured spectra. The comparison showed that the discrepancies between the measurements and the calculations increase as the distance between the detector and the system axis increases. This trend indicates that when the flux is determined mainly by multiple scatterings, a more divided multigroup structure should be employed.

  14. Micronuclei Induction in Human Fibroblasts Exposed In Vitro to Los Alamos High-Energy Neutrons

    NASA Technical Reports Server (NTRS)

    Gersey, Brad; Sodolak, John; Hada, Megumi; Saganti, Prem; Wilkins, Richard; Cucinotta, Francis; Wu, Honglu

    2006-01-01

    High-energy secondary neutrons, produced by the interaction of galactic cosmic rays with the atmosphere, spacecraft structure and planetary surfaces, contribute to a significant fraction to the dose equivalent in crew members and passengers during commercial aviation travel, and astronauts in space missions. The Los Alamos Nuclear Science Center (LANSCE) neutron facility#s ICE House 30L beamline is known to generate neutrons that simulate the secondary neutron spectra of earth#s atmosphere. The neutron spectrum is also similar to that measured onboard spacecraft like the MIR and International Space Station (ISS). To evaluate the biological damage, we exposed human fibroblasts in vitro to the LANSCE neutron beams without degrader at an entrance dose rate of 25 mGy/hr and analyzed the micronuclei (MN) induction. The cells were also placed behind a 9.9 cm water column to study effect of shielding in the protection of neutron induced damages. It was found that the dose response in the MN frequency was linear for the samples with and without shielding and the slope of the MN yield behind the shielding was reduced by a factor of 3.5. Compared to the MN induction in human fibroblasts exposed to a gamma source at a low dose rate, the RBE was found to be 16.7 and 10.0 for the neutrons without and with 9.9 cm water shielding, respectively.

  15. Micronuclei induction in human fibroblasts exposed in vitro to Los Alamos high-energy neutrons

    NASA Astrophysics Data System (ADS)

    Gersey, Brad; Sodolak, John; Hada, Megumi; Saganti, Prem; Wilkins, Richard; Cucinotta, Francis; Wu, Honglu

    High-energy secondary neutrons, produced by the interaction of galactic cosmic rays with the atmosphere, spacecraft structure and planetary surfaces, contribute to a significant fraction to the dose equivalent in crew members and passengers during commercial aviation travel, and astronauts in space missions. The Los Alamos Nuclear Science Center (LANSCE) neutron facility's ICE House 30L beamline is known to generate neutrons that simulate the secondary neutron spectra of earth's atmosphere. The neutron spectrum is also similar to that measured onboard spacecraft like the MIR and International Space Station (ISS). To evaluate the biological damage, we exposed human fibroblasts in vitro to the LANSCE neutron beams without degrader at an entrance dose rate of 25 mGy/h and analyzed the micronuclei (MN) induction. The cells were also placed behind a 9.9 cm water column to study the effect of shielding in the protection of neutron induced damages. It was found that the dose response in the MN frequency was linear for the samples with and without shielding and the slope of the MN yield behind the shielding was reduced by a factor of 3.5. Compared to the MN induction in human fibroblasts exposed to a γ source at a similar low dose rate, the RBE was found to be 16.7 and 10.0 for the neutrons without and with the 9.9 cm water shielding, respectively.

  16. Reaction mechanism interplay in determining the biological effectiveness of neutrons as a function of energy.

    PubMed

    Baiocco, G; Alloni, D; Babini, G; Mariotti, L; Ottolenghi, A

    2015-09-01

    Neutron relative biological effectiveness (RBE) is found to be energy dependent, being maximal for energies ∼1 MeV. This is reflected in the choice of radiation weighting factors wR for radiation protection purposes. In order to trace back the physical origin of this behaviour, a detailed study of energy deposition processes with their full dependences is necessary. In this work, the Monte Carlo transport code PHITS was used to characterise main secondary products responsible for energy deposition in a 'human-sized' soft tissue spherical phantom, irradiated by monoenergetic neutrons with energies around the maximal RBE/wR. Thereafter, results on the microdosimetric characterisation of secondary protons were used as an input to track structure calculations performed with PARTRAC, thus evaluating the corresponding DNA damage induction. Within the proposed simplified approach, evidence is suggested for a relevant role of secondary protons in inducing the maximal biological effectiveness for 1 MeV neutrons. PMID:25848097

  17. Neutron Energy Spectra and Yields from the 7Li(p,n) Reaction for Nuclear Astrophysics

    NASA Astrophysics Data System (ADS)

    Tessler, M.; Friedman, M.; Schmidt, S.; Shor, A.; Berkovits, D.; Cohen, D.; Feinberg, G.; Fiebiger, S.; Krása, A.; Paul, M.; Plag, R.; Plompen, A.; Reifarth, R.

    2016-01-01

    Neutrons produced by the 7Li(p, n)7Be reaction close to threshold are widely used to measure the cross section of s-process nucleosynthesis reactions. While experiments have been performed so far with Van de Graaff accelerators, the use of RF accelerators with higher intensities is planned to enable investigations on radioactive isotopes. In parallel, high-power Li targets for the production of high-intensity neutrons at stellar energies are developed at Goethe University (Frankfurt, Germany) and SARAF (Soreq NRC, Israel). However, such setups pose severe challenges for the measurement of the proton beam intensity or the neutron fluence. In order to develop appropriate methods, we studied in detail the neutron energy distribution and intensity produced by the thick-target 7Li(p,n)7Be reaction and compared them to state-of- the-art simulation codes. Measurements were performed with the bunched and chopped proton beam at the Van de Graaff facility of the Institute for Reference Materials and Measurements (IRMM) using the time-of-flight (TOF) technique with thin (1/8") and thick (1") detectors. The importance of detailed simulations of the detector structure and geometry for the conversion of TOF to a neutron energy is stressed. The measured neutron spectra are consistent with those previously reported and agree well with Monte Carlo simulations that include experimentally determined 7Li(p,n) cross sections, two-body kinematics and proton energy loss in the Li-target.

  18. Alternative separation of exchange and correlation energies in multi-configuration range-separated density-functional theory

    NASA Astrophysics Data System (ADS)

    Stoyanova, Alexandrina; Teale, Andrew M.; Toulouse, Julien; Helgaker, Trygve; Fromager, Emmanuel

    2013-10-01

    The alternative separation of exchange and correlation energies proposed by Toulouse et al. [Theor. Chem. Acc. 114, 305 (2005)] is explored in the context of multi-configuration range-separated density-functional theory. The new decomposition of the short-range exchange-correlation energy relies on the auxiliary long-range interacting wavefunction rather than the Kohn-Sham (KS) determinant. The advantage, relative to the traditional KS decomposition, is that the wavefunction part of the energy is now computed with the regular (fully interacting) Hamiltonian. One potential drawback is that, because of double counting, the wavefunction used to compute the energy cannot be obtained by minimizing the energy expression with respect to the wavefunction parameters. The problem is overcome by using short-range optimized effective potentials (OEPs). The resulting combination of OEP techniques with wavefunction theory has been investigated in this work, at the Hartree-Fock (HF) and multi-configuration self-consistent-field (MCSCF) levels. In the HF case, an analytical expression for the energy gradient has been derived and implemented. Calculations have been performed within the short-range local density approximation on H2, N2, Li2, and H2O. Significant improvements in binding energies are obtained with the new decomposition of the short-range energy. The importance of optimizing the short-range OEP at the MCSCF level when static correlation becomes significant has also been demonstrated for H2, using a finite-difference gradient. The implementation of the analytical gradient for MCSCF wavefunctions is currently in progress.

  19. Alternative separation of exchange and correlation energies in multi-configuration range-separated density-functional theory.

    PubMed

    Stoyanova, Alexandrina; Teale, Andrew M; Toulouse, Julien; Helgaker, Trygve; Fromager, Emmanuel

    2013-10-01

    The alternative separation of exchange and correlation energies proposed by Toulouse et al. [Theor. Chem. Acc. 114, 305 (2005)] is explored in the context of multi-configuration range-separated density-functional theory. The new decomposition of the short-range exchange-correlation energy relies on the auxiliary long-range interacting wavefunction rather than the Kohn-Sham (KS) determinant. The advantage, relative to the traditional KS decomposition, is that the wavefunction part of the energy is now computed with the regular (fully interacting) Hamiltonian. One potential drawback is that, because of double counting, the wavefunction used to compute the energy cannot be obtained by minimizing the energy expression with respect to the wavefunction parameters. The problem is overcome by using short-range optimized effective potentials (OEPs). The resulting combination of OEP techniques with wavefunction theory has been investigated in this work, at the Hartree-Fock (HF) and multi-configuration self-consistent-field (MCSCF) levels. In the HF case, an analytical expression for the energy gradient has been derived and implemented. Calculations have been performed within the short-range local density approximation on H2, N2, Li2, and H2O. Significant improvements in binding energies are obtained with the new decomposition of the short-range energy. The importance of optimizing the short-range OEP at the MCSCF level when static correlation becomes significant has also been demonstrated for H2, using a finite-difference gradient. The implementation of the analytical gradient for MCSCF wavefunctions is currently in progress. PMID:24116558

  20. Non-destructive component separation using infrared radiant energy

    DOEpatents

    Simandl, Ronald F.; Russell, Steven W.; Holt, Jerrid S.; Brown, John D.

    2011-03-01

    A method for separating a first component and a second component from one another at an adhesive bond interface between the first component and second component. Typically the method involves irradiating the first component with infrared radiation from a source that radiates substantially only short wavelengths until the adhesive bond is destabilized, and then separating the first component and the second component from one another. In some embodiments an assembly of components to be debonded is placed inside an enclosure and the assembly is illuminated from an IR source that is external to the enclosure. In some embodiments an assembly of components to be debonded is simultaneously irradiated by a multi-planar array of IR sources. Often the IR radiation is unidirectional. In some embodiments the IR radiation is narrow-band short wavelength infrared radiation.

  1. 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.

  2. Neutron capture cross section of {sup 15}N at stellar energies

    SciTech Connect

    Meissner, J.; Schatz, H.; Herndl, H.; Wiescher, M.; Beer, H.; Kaeppeler, F.

    1996-02-01

    The neutron capture rate on {sup 15}N may be of considerable importance for {ital s}-process nucleosynthesis in red giants as well as for the nucleosynthesis in inhomogeneous big bang scenarios. We measured the reaction cross section of {sup 15}N({ital n},{gamma}){sup 16}N at the Forschungszentrum Karlsruhe with a fast cyclic neutron activation technique at laboratory neutron energies of 25, 152, and 370 keV. Direct capture and shell model calculations were performed to interpret the results. The presented reaction rate is 30{endash}50{percent} smaller than the previously used theoretical rates. {copyright} {ital 1996 The American Physical Society.}

  3. Measurement of changes in water thickness in plant materials using very low-energy neutron radiography

    NASA Astrophysics Data System (ADS)

    Matsushima, U.; Kawabata, Y.; Hino, M.; Geltenbort, P.; Nicolaï, B. M.

    2005-04-01

    Low-energy neutron radiographic images of Hedera leaves were obtained using the very cold neutron (VCN) beam at Institut Laue-Langevin, France. A change in hydrogen concentration measured in a short period by means of neutron radiography indicates a change in water concentration in the plant. A regression model was evaluated to estimate changes in water thickness of the leaves and, the resolution of this method was smaller than 5 μm. The method was effective to measure small changes in water thickness of thin plant leaves.

  4. Demonstrating a directional detector based on neon for characterizing high energy neutrons

    NASA Astrophysics Data System (ADS)

    Hexley, Allie

    2016-03-01

    MITPC is a gas-based time projection chamber used for detecting fast, MeV-scale neutrons. The standard version of the detector relies on a mixture of 600 torr gas composed of 87.5% helium-4 and 12.5% tetrafluoromethane for precisely measuring the energy and direction of neutron-induced nuclear recoils. I describe studies performed with a prototype detector investigating the use of neon, as a replacement for helium-4, in the gas mixture. My discussion focuses on the advantages of neon as the fast neutron target for high energy neutron events (100 MeV) and a demonstration that the mixture will be effective for this event class. I show that the achievable gain and transverse diffusion of drifting electrons in the neon mixture are acceptable and that the detector uptime lost due to voltage breakdowns in the amplification plane is negligible, compared to 20% with the helium-4 mixture.

  5. Demonstrating a directional detector based on neon for characterizing high energy neutrons

    NASA Astrophysics Data System (ADS)

    Hexley, A.; Moulai, M. H.; Spitz, J.; Conrad, J. M.

    2015-11-01

    MITPC is a gas-based time projection chamber used for detecting fast, MeV-scale neutrons. The standard version of the detector relies on a mixture of 600 torr gas composed of 87.5% 4He and 12.5% CF4 for precisely measuring the energy and direction of neutron-induced nuclear recoils. We describe studies performed with a prototype detector investigating the use of Ne, as a replacement for 4He, in the gas mixture. Our discussion focuses on the advantages of Ne as the fast neutron target for high energy neutron events (lesssim100 MeV) and a demonstration that the mixture will be effective for this event class. We find that the achievable gain and transverse diffusion of drifting electrons in the Ne mixture are acceptable and that the detector uptime lost due to voltage breakdowns in the amplification plane is negligible, compared to ~ 20% with the 4He mixture.

  6. Plumbing Neutron Stars to New Depths with the Binding Energy of the Exotic Nuclide Zn82

    NASA Astrophysics Data System (ADS)

    Wolf, R. N.; Beck, D.; Blaum, K.; Böhm, Ch.; Borgmann, Ch.; Breitenfeldt, M.; Chamel, N.; Goriely, S.; Herfurth, F.; Kowalska, M.; Kreim, S.; Lunney, D.; Manea, V.; Minaya Ramirez, E.; Naimi, S.; Neidherr, D.; Rosenbusch, M.; Schweikhard, L.; Stanja, J.; Wienholtz, F.; Zuber, K.

    2013-01-01

    Modeling the composition of neutron-star crusts depends strongly on binding energies of neutron-rich nuclides near the N=50 and N=82 shell closures. Using a recent development of time-of-flight mass spectrometry for on-line purification of radioactive ion beams to access more exotic species, we have determined for the first time the mass of Zn82 with the ISOLTRAP setup at the ISOLDE-CERN facility. With a robust neutron-star model based on nuclear energy-density-functional theory, we solve the general relativistic Tolman-Oppenheimer-Volkoff equations and calculate the neutron-star crust composition based on the new experimental mass. The composition profile is not only altered but now constrained by experimental data deeper into the crust than before.

  7. Use of borated polyethylene to improve low energy response of a prompt gamma based neutron dosimeter

    NASA Astrophysics Data System (ADS)

    Priyada, P.; Ashwini, U.; Sarkar, P. K.

    2016-05-01

    The feasibility of using a combined sample of borated polyethylene and normal polyethylene to estimate neutron ambient dose equivalent from measured prompt gamma emissions is investigated theoretically to demonstrate improvements in low energy neutron dose response compared to only polyethylene. Monte Carlo simulations have been carried out using the FLUKA code to calculate the response of boron, hydrogen and carbon prompt gamma emissions to mono energetic neutrons. The weighted least square method is employed to arrive at the best linear combination of these responses that approximates the ICRP fluence to dose conversion coefficients well in the energy range of 10-8 MeV to 14 MeV. The configuration of the combined system is optimized through FLUKA simulations. The proposed method is validated theoretically with five different workplace neutron spectra with satisfactory outcome.

  8. Benchmarking of activation reaction distribution in an intermediate energy neutron field.

    PubMed

    Ogawa, Tatsuhiko; Morev, Mikhail N; Hirota, Masahiro; Abe, Takuya; Koike, Yuya; Iwai, Satoshi; Iimoto, Takeshi; Kosako, Toshiso

    2011-07-01

    Neutron-induced reaction rate depth profiles inside concrete shield irradiated by intermediate energy neutron were calculated using a Monte-Carlo code and compared with an experiment. An irradiation field of intermediate neutron produced in the forward direction from a thick (stopping length) target bombarded by 400 MeV nucleon(-1) carbon ions was arranged at the heavy ion medical accelerator in Chiba. Ordinary concrete shield of 90 cm thickness was installed 50 cm downstream the iron target. Activation detectors of aluminum, gold and gold covered with cadmium were inserted at various depths. Irradiated samples were extracted after exposure and gamma-ray spectrometry was performed for each sample. Comparison of experimental and calculated shows good agreement for both low- and high-energy neutron-induced reaction except for (27)Al(n,X)(24)Na reaction at the surface. PMID:21515619

  9. Energy-selective neutron imaging for morphological and phase analysis of iron-nickel meteorites.

    PubMed

    Peetermans, S; Grazzi, F; Salvemini, F; Lehmann, E H; Caporali, S; Pratesi, G

    2013-09-21

    We propose energy-selective neutron imaging as a new and non-destructive method to investigate rare metallic meteorites. It is based on attenuation of a neutron beam of limited spectral distribution in a sample depending on the elemental composition and crystalline structure. Radiography and tomography allow obtaining the presence, morphology and orientation information in the bulk of mineral inclusions, oxide crust and crystalline structure. Its usage in classification and meteor formation studies would be of great value. PMID:23869384

  10. Neutron emission effects on fragment mass and kinetic energy distribution from fission of 239{sup Pu} induced by thermal neutrons

    SciTech Connect

    Montoya, M.; Rojas, J.; Lobato, I.

    2010-08-04

    The average of fragment kinetic energy (E-bar sign*) and the multiplicity of prompt neutrons ({nu}(bar sign)) as a function of fragment mass (m*), as well as the fragment mass yield (Y(m*)) from thermal neutron-induced fission of {sup 239}Pu have been measured by Tsuchiya et al.. In that work the mass and kinetic energy are calculated from the measured kinetic energy of one fragment and the difference of time of flight of the two complementary fragments. However they do not present their results about the standard deviation {sigma}{sub E}*(m*). In this work we have made a numerical simulation of that experiment which reproduces its results, assuming an initial distribution of the primary fragment kinetic energy (E(A)) with a constant value of the standard deviation as function of fragment mass ({sigma}{sub E}(A)). As a result of the simulation we obtain the dependence {sigma}{sub E}*(m*) which presents an enhancement between m* = 92 and m* = 110, and a peak at m* = 121.