WorldWideScience

Sample records for vsop neutron spectra

  1. Neutron and photon spectra in LINACs.

    Science.gov (United States)

    Vega-Carrillo, H R; Martínez-Ovalle, S A; Lallena, A M; Mercado, G A; Benites-Rengifo, J L

    2012-12-01

    A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10(-6) and 1 MeV. Neutron and the Bremsstrahlung spectra show the same features regardless of the linac voltage.

  2. VSOP Science Targets

    OpenAIRE

    Hirabayashi, H.; Inoue, M.; 平林, 久; 井上, 允

    1991-01-01

    The VLBI Space Observatory Programme (VSOP) started in 1989,and the observations will start in 1995. VSOP Science targets are reviewed in relation to Japanese VLBI activities. Regions surrounding accreting disks and jets of Active Galactic Nuclei (AGN) will be the most important targets. The physics and distances to water vapor masing regions in and outside the Galaxy can be studied in more detail. VSOP can cover various objects like young supernova and gravitational lensing objects.

  3. Measuring neutron spectra in radiotherapy using the nested neutron spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Maglieri, Robert, E-mail: robert.maglieri@mail.mcgill.ca; Evans, Michael; Seuntjens, Jan; Kildea, John [Medical Physics Unit, McGill University, Montreal, Quebec H4A 3J1 (Canada); Licea, Angel [Canadian Nuclear Safety Commission, Ottawa, Ontario K1P 5S9 (Canada)

    2015-11-15

    Purpose: Out-of-field neutron doses resulting from photonuclear interactions in the head of a linear accelerator pose an iatrogenic risk to patients and an occupational risk to personnel during radiotherapy. To quantify neutron production, in-room measurements have traditionally been carried out using Bonner sphere systems (BSS) with activation foils and TLDs. In this work, a recently developed active detector, the nested neutron spectrometer (NNS), was tested in radiotherapy bunkers. Methods: The NNS is designed for easy handling and is more practical than the traditional BSS. Operated in current-mode, the problem of pulse pileup due to high dose-rates is overcome by measuring current, similar to an ionization chamber. In a bunker housing a Varian Clinac 21EX, the performance of the NNS was evaluated in terms of reproducibility, linearity, and dose-rate effects. Using a custom maximum-likelihood expectation–maximization algorithm, measured neutron spectra at various locations inside the bunker were then compared to Monte Carlo simulations of an identical setup. In terms of dose, neutron ambient dose equivalents were calculated from the measured spectra and compared to bubble detector neutron dose equivalent measurements. Results: The NNS-measured spectra for neutrons at various locations in a treatment room were found to be consistent with expectations for both relative shape and absolute magnitude. Neutron fluence-rate decreased with distance from the source and the shape of the spectrum changed from a dominant fast neutron peak near the Linac head to a dominant thermal neutron peak in the moderating conditions of the maze. Monte Carlo data and NNS-measured spectra agreed within 30% at all locations except in the maze where the deviation was a maximum of 40%. Neutron ambient dose equivalents calculated from the authors’ measured spectra were consistent (one standard deviation) with bubble detector measurements in the treatment room. Conclusions: The NNS may

  4. Masers and VSOP-2

    Science.gov (United States)

    Elitzur, M.

    2009-08-01

    Maser studies where VSOP-2 can make its strongest impact involve proper motion measurements. In this talk I review outstanding issues in topics ranging from star forming regions to active galactic nuclei in which VSOP-2 proper motion measurements offer the promise of seminal contributions.

  5. Dose spectra from energetic particles and neutrons

    Science.gov (United States)

    Schwadron, Nathan; Bancroft, Chris; Bloser, Peter; Legere, Jason; Ryan, James; Smith, Sonya; Spence, Harlan; Mazur, Joe; Zeitlin, Cary

    2013-10-01

    spectra from energetic particles and neutrons (DoSEN) are an early-stage space technology research project that combines two advanced complementary radiation detection concepts with fundamental advantages over traditional dosimetry. DoSEN measures not only the energy but also the charge distribution (including neutrons) of energetic particles that affect human (and robotic) health in a way not presently possible with current dosimeters. For heavy ions and protons, DoSEN provides a direct measurement of the lineal energy transfer (LET) spectra behind shielding material. For LET measurements, DoSEN contains stacks of thin-thick Si detectors similar in design to those used for the Cosmic Ray Telescope for the Effects of Radiation. With LET spectra, we can now directly break down the observed spectrum of radiation into its constituent heavy-ion components and through biologically based quality factors that provide not only doses and dose rates but also dose equivalents, associated rates, and even organ doses. DoSEN also measures neutrons from 10 to 100 MeV, which requires enough sensitive mass to fully absorb recoil particles that the neutrons produce. DoSEN develops the new concept of combining these independent measurements and using the coincidence of LET measurements and neutron detection to significantly reduce backgrounds in each measurement. The background suppression through the use of coincidence allows for significant reductions in size, mass, and power needed to provide measurements of dose, neutron dose, dose equivalents, LET spectra, and organ doses. Thus, we introduce the DoSEN concept: a promising low-mass instrument that detects the full spectrum of energetic particles, heavy ions, and neutrons to determine biological impact of radiation in space.

  6. Interface design of VSOP'94 computer code for safety analysis

    Science.gov (United States)

    Natsir, Khairina; Yazid, Putranto Ilham; Andiwijayakusuma, D.; Wahanani, Nursinta Adi

    2014-09-01

    Today, most software applications, also in the nuclear field, come with a graphical user interface. VSOP'94 (Very Superior Old Program), was designed to simplify the process of performing reactor simulation. VSOP is a integrated code system to simulate the life history of a nuclear reactor that is devoted in education and research. One advantage of VSOP program is its ability to calculate the neutron spectrum estimation, fuel cycle, 2-D diffusion, resonance integral, estimation of reactors fuel costs, and integrated thermal hydraulics. VSOP also can be used to comparative studies and simulation of reactor safety. However, existing VSOP is a conventional program, which was developed using Fortran 65 and have several problems in using it, for example, it is only operated on Dec Alpha mainframe platforms and provide text-based output, difficult to use, especially in data preparation and interpretation of results. We develop a GUI-VSOP, which is an interface program to facilitate the preparation of data, run the VSOP code and read the results in a more user friendly way and useable on the Personal 'Computer (PC). Modifications include the development of interfaces on preprocessing, processing and postprocessing. GUI-based interface for preprocessing aims to provide a convenience way in preparing data. Processing interface is intended to provide convenience in configuring input files and libraries and do compiling VSOP code. Postprocessing interface designed to visualized the VSOP output in table and graphic forms. GUI-VSOP expected to be useful to simplify and speed up the process and analysis of safety aspects.

  7. VLBI Observing System for VSOP

    Science.gov (United States)

    Ulvestad, J. S.; Murphy, D. W.

    1996-01-01

    The very long baseline interferometry (VLBI) Space Observatory Program (VSOP) satellite is scheduled for launch in September 1996. This paper describes the VLBI observing system for VSOP and its differences from ground radio telescope VLBI systems.

  8. Astrometry with VSOP

    Science.gov (United States)

    Rioja, M.; Porcas, R.; Dodson, R.; Asaki, Y.

    2009-08-01

    Phase referencing has proved to be a useful technique for astronomical ground-based VLBI. We successfully carried out Space--VLBI phase referencing observations for the first time, using VSOP at 5 and 1.6 GHz, and we report here the astrometric results. We also made a direct measure of the orbit uncertainties. In addition we present a new calibration method for mm--VLBI astrometry, source/frequency phase referencing, valid under a wider variety of conditions than conventional phase referencing. Its requirements are compatible with the VSOP-2 mission specifications and would expand its capabilities.

  9. Prompt Fission Neutron Spectra of Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Capote, R; Chen, Y J; Hambsch, F J; Kornilov, N V; Lestone, J P; Litaize, O; Morillon, B; Neudecker, D; Oberstedt, S; Ohsawa, T; Smith, D. L.

    2016-01-01

    The energy spectrum of prompt neutrons emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) “Evaluation of Prompt Fission Neutron Spectra of Actinides”was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei. The following technical areas were addressed: (i) experiments and uncertainty quantification (UQ): New data for neutron-induced fission of 233U, 235U, 238U, and 239Pu have been measured, and older data have been compiled and reassessed. There is evidence from the experimental work of this CRP that a very small percentage of neutrons emitted in fission are actually scission neutrons; (ii) modeling: The Los Alamos model (LAM) continues to be the workhorse for PFNS evaluations. Monte Carlo models have been developed that describe the fission phenomena microscopically, but further development is needed to produce PFNS evaluations meeting the uncertainty targets; (iii) evaluation methodologies: PFNS evaluations rely on the use of the least-squares techniques for merging experimental and model data. Considerable insight was achieved on how to deal with the problem of too small uncertainties in PFNS evaluations. The importance of considering that all experimental PFNS data are “shape” data was stressed; (iv) PFNS evaluations: New evaluations, including covariance data, were generated for major actinides including 1) non-model GMA evaluations of the 235U(nth,f), 239Pu(nth,f), and 233U(nth,f) PFNS based exclusively on experimental data (0.02 ≤ E ≤ 10 MeV), which resulted in PFNS average energies E of 2.00±0.01, 2.073±0.010, and 2.030±0.013 MeV, respectively; 2) LAM evaluations of neutron-induced fission spectra on uranium and plutonium targets with improved UQ for incident energies from thermal up to 30 MeV; and 3) Point-by-Point calculations for 232Th, 234U and 237Np targets; and (v) data

  10. Evaluation of secondary and prompt fission neutron spectra

    Energy Technology Data Exchange (ETDEWEB)

    Porodzinskij, Yu.V.; Sukhovitskij, E.Sh. [Radiation Physics and Chemistry Problems Inst., Minsk-Sosny (Belarus)

    1997-03-01

    A simple model allowing to split neutron emission spectra into reaction partials is suggested. Predicted spectra of (n,n`{gamma}), (n,n`f), etc appear to be much harder than usually evaluated. (author)

  11. Evaluation of secondary and prompt fission neutron spectra

    Energy Technology Data Exchange (ETDEWEB)

    Porodzinskij, Yu.V.; Sukhovitskij, E.Sh. [Radiation Physics and Chemistry Problems Inst., Minsk-Sosny (Belarus)

    1997-03-01

    A simple model allowing to split neutron emission spectra into reaction partials is suggested. Predicted spectra of (n,n`{gamma}), (n,n`f), etc appear to be much harder than usually evaluated. (author)

  12. Space VLBI Mission: VSOP

    Science.gov (United States)

    Murata, Yasuhiro; Hirabayashi, Hisashi; Kobayashi, Hideyuki; Shibata, Katsunori M.; Umemoto, Tomofumi; Edwards, P. G.

    2001-03-01

    We succeeded in performing space VLBI observations using the VLBI satellite HALCA (VSOP satellite), launched in February, 1997 aboard the first M-V rocket developed by ISAS. The mission is led by ISAS and NAO, with the collaborations from CRL, NASA, NRAO, and other institutes and observatories in Europe, Australia, Canada, South-Africa, and China, We succeeded to make a lot of observations and to get the new features from the active galaxies, the cosmic jets, and other astronomical objects.

  13. AGN Science with VSOP and Prospects for VSOP-2

    Science.gov (United States)

    Kameno, S.

    2009-08-01

    VSOP is the first space VLBI project, consisting of a space radio telescope HALCA and many ground radio telescopes. The highest resolution was 0.3 mas using a 30,000-km baseline. In the 8-yr mission lifetime since 1997, the project had completed more than 700 observations, primarily targeting active galactic nuclei (AGNs). AGN jets, lobes, cores, and accreting matter were imaged with a high resolution three times better than that of ground VLBI. In this paper I summarize highlights of VSOP results and also discuss prospects to the next space VLBI mission, VSOP-2.

  14. Fission neutron spectra measurements at LANSCE - status and plans

    Energy Technology Data Exchange (ETDEWEB)

    Haight, Robert C [Los Alamos National Laboratory; Noda, Shusaku [Los Alamos National Laboratory; Nelson, Ronald O [Los Alamos National Laboratory; O' Donnell, John M [Los Alamos National Laboratory; Devlin, Matt [Los Alamos National Laboratory; Chatillon, Audrey [CEA-FRANCE; Granier, Thierry [CEA-FRANCE; Taieb, Julien [CEA-FRANCE; Laurent, Benoit [CEA-FRANCE; Belier, Gilbert [CEA-FRANCE; Becker, John A [LLNL; Wu, Ching - Yen [LLNL

    2009-01-01

    A program to measure fission neutron spectra from neutron-induced fission of actinides is underway at the Los Alamos Neutron Science Center (LANSCE) in a collaboration among the CEA laboratory at Bruyeres-le-Chatel, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The spallation source of fast neutrons at LANSCE is used to provide incident neutron energies from less than 1 MeV to 100 MeV or higher. The fission events take place in a gas-ionization fission chamber, and the time of flight from the neutron source to that chamber gives the energy of the incident neutron. Outgoing neutrons are detected by an array of organic liquid scintillator neutron detectors, and their energies are deduced from the time of flight from the fission chamber to the neutron detector. Measurements have been made of the fission neutrons from fission of {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. The range of outgoing energies measured so far is from 1 MeV to approximately 8 MeV. These partial spectra and average fission neutron energies are compared with evaluated data and with models of fission neutron emission. Results to date will be presented and a discussion of uncertainties will be given in this presentation. Future plans are to make significant improvements in the fission chambers, neutron detectors, signal processing, data acquisition and the experimental environment to provide high fidelity data including mea urements of fission neutrons below 1 MeV and improvements in the data above 8 MeV.

  15. Spectrometer equipment for neutron spectra measurements in mixed neutron/photon fields

    CERN Document Server

    Chernov, V A; Trykov, L A

    2002-01-01

    The paper describes spectrometer equipment in the IPPE experimental laboratory for neutron spectra measurement in mixed (n,gamma) fields. The laboratory was founded in 1957 and it occupies a leading position in the field of nuclear facilities radiation spectrometry and benchmark experiments in Russia. Spectrometer equipment includes spectrometers based on the organic stilbene scintillator, hydrogen counter and Bonner balls. Basic fields of spectrometer application are mixed radiation neutron spectra measurement of radionuclide sources, of nuclear reactors and accelerators; study of neutron transfer through the material, including benchmark experiments and measurement of neutron spectra in the rooms of nuclear facilities.

  16. Spacecraft Design of VSOP-2

    OpenAIRE

    Murata, Y.; Hirabayashi, H.; Group, Next Generation Space VLBI Working

    2004-01-01

    As presented by Hirabayashi et al. (2004) these proceedings, the VSOP-2 mission is currently being planned. Various kinds of developments are being made for the misson, and here we introduce the large antenna, fast switching scheme using CMG, low noise receivers, gigabit data transmission, and high data rate sampling on-board. We are also studying the system configuration of the VSOP-2 satellite and the orbit appropriate for the expected launch vehicle, the M-V rocket. VSOP-2 science goals in...

  17. Status of measurements of fission neutron spectra of Minor Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Drapchinsky, L.; Shiryaev, B. [V.G. Khlopin Radium Inst., Saint Petersburg (Russian Federation)

    1997-03-01

    The report considers experimental and theoretical works on studying the energy spectra of prompt neutrons emitted in spontaneous fission and neutron induced fission of Minor Actinides. It is noted that neutron spectra investigations were done for only a small number of such nuclei, most measurements, except those of Cf-252, having been carried out long ago by obsolete methods and imperfectapparatus. The works have no detailed description of experiments, analysis of errors, detailed numerical information about results of experiments. A conclusion is made that the available data do not come up to modern requirements. It is necessary to make new measurements of fission prompt neutron spectra of transuranium nuclides important for the objectives of working out a conception of minor actinides transmutation by means of special reactors. (author)

  18. Calculating fusion neutron energy spectra from arbitrary reactant distributions

    Science.gov (United States)

    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.

  19. Status of measurements of fission neutron spectra of Minor Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Drapchinsky, L.; Shiryaev, B. [V.G. Khlopin Radium Inst., Saint Petersburg (Russian Federation)

    1997-03-01

    The report considers experimental and theoretical works on studying the energy spectra of prompt neutrons emitted in spontaneous fission and neutron induced fission of Minor Actinides. It is noted that neutron spectra investigations were done for only a small number of such nuclei, most measurements, except those of Cf-252, having been carried out long ago by obsolete methods and imperfectapparatus. The works have no detailed description of experiments, analysis of errors, detailed numerical information about results of experiments. A conclusion is made that the available data do not come up to modern requirements. It is necessary to make new measurements of fission prompt neutron spectra of transuranium nuclides important for the objectives of working out a conception of minor actinides transmutation by means of special reactors. (author)

  20. Vsop2/Astro-G Project

    OpenAIRE

    Tsuboi, Masato

    2008-01-01

    We introduce a new space VLBI project, the Second VLBI Space Observatory Program (VSOP2), following the success of the VLBI Space Observatory Program (VSOP1). VSOP2 has 10 times higher angular resolution, up to about 40 micro arcseconds, 10 times higher frequency up to 43 GHz, and 10 times higher sensitivity compared to VSOP1. Then VSOP2 should become a most powerful tool to observe innermost regions of AGN and astronomical masers. ASTRO-G is a spacecraft for VSOP2 project constructing in ISA...

  1. Determination of neutron spectra using the programs GNSR and SPECTRIX

    CERN Document Server

    Weyrauch, M; Matzke, M

    2002-01-01

    We describe the capabilities and the application of two computer programs, which have been developed in order to facilitate common tasks in neutron spectrometry: GNSR (calculation of response matrices) and SPECTRIX (unfolding). Gas-filled Neutron Spectrometer Response calculates response functions and response matrices of various gas-filled neutron detectors. It can be configured to accommodate the appropriate gas-fillings and supports a number of different neutron beam configurations with a possibility to input calculated or measured neutron beam spectra. The program includes graphical capabilities as well as a context-sensitive help system. SPECTRIX implements several unfolding algorithms as well as support algorithms for unfolding and includes graphics capabilities and context-sensitive help. We apply both programs to a specific example: calculation of the response matrix of a sup 3 He detector and unfolding of the neutron spectrum of a thick accelerator target using the calculated response matrix.

  2. The measurement of neutron and neutron induced photon spectra in fusion reactor related assemblies

    CERN Document Server

    Unholzer, S; Klein, H; Seidel, K

    2002-01-01

    The spectral neutron and photon fluence (or flux) measured outside and inside of assemblies related to fusion reactor constructions are basic quantities of fusion neutronics. The comparison of measured spectra with the results of MCNP neutron and photon transport calculations allows a crucial test of evaluated nuclear data as generally used in fusion applications to be carried out. The experiments concern mixed neutron/photon fields with about the same intensity of the two components. An NE-213 scintillation spectrometer, well described by response matrices for both neutrons and photons, is used as proton-recoil and Compton spectrometer. The experiments described here in more detail address the background problematic of two applications, an iron benchmark experiment with an ns-pulsed neutron source and a deep penetration mock-up experiment for the investigation of the ITER in-board shield system. The measured spectral neutron and photon fluences are compared with spectra calculated with the MCNP code on the b...

  3. Reconstruction of neutron spectra through neural networks; Reconstruccion de espectros de neutrones mediante redes neuronales

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E. [Cuerpo Academico de Radiobiologia, Estudios Nucleares, Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)] e-mail: rvega@cantera.reduaz.mx [and others

    2003-07-01

    A neural network has been used to reconstruct the neutron spectra starting from the counting rates of the detectors of the Bonner sphere spectrophotometric system. A group of 56 neutron spectra was selected to calculate the counting rates that would produce in a Bonner sphere system, with these data and the spectra it was trained the neural network. To prove the performance of the net, 12 spectra were used, 6 were taken of the group used for the training, 3 were obtained of mathematical functions and those other 3 correspond to real spectra. When comparing the original spectra of those reconstructed by the net we find that our net has a poor performance when reconstructing monoenergetic spectra, this attributes it to those characteristic of the spectra used for the training of the neural network, however for the other groups of spectra the results of the net are appropriate with the prospective ones. (Author)

  4. Neutron energy spectra of d(49)-Be and p(41)-Be neutron radiotherapy sources.

    Science.gov (United States)

    Graves, R G; Smathers, J B; Almond, P R; Grant, W H; Otte, V A

    1979-01-01

    Zero-degree neutron energy spectra for the p(41)-Be and d(49)-Be reactions were measured by time-of-flight for neutrons with energies above 1.9 and 1.4 MeV, respectively. Spectral changes resulting from the addition of copper, aluminum, and polyethylene filters to unfiltered beams were determined. Integral yields, average energies, filter material attenuation coefficients, and kerma fractions were computed for these spectra. Calculated spectra for neutron beams filtered by various thicknesses of polyethylene compared favorably with experimental results

  5. Interface design of VSOP'94 computer code for safety analysis

    Energy Technology Data Exchange (ETDEWEB)

    Natsir, Khairina, E-mail: yenny@batan.go.id; Andiwijayakusuma, D.; Wahanani, Nursinta Adi [Center for Development of Nuclear Informatics - National Nuclear Energy Agency, PUSPIPTEK, Serpong, Tangerang, Banten (Indonesia); Yazid, Putranto Ilham [Center for Nuclear Technology, Material and Radiometry- National Nuclear Energy Agency, Jl. Tamansari No.71, Bandung 40132 (Indonesia)

    2014-09-30

    Today, most software applications, also in the nuclear field, come with a graphical user interface. VSOP'94 (Very Superior Old Program), was designed to simplify the process of performing reactor simulation. VSOP is a integrated code system to simulate the life history of a nuclear reactor that is devoted in education and research. One advantage of VSOP program is its ability to calculate the neutron spectrum estimation, fuel cycle, 2-D diffusion, resonance integral, estimation of reactors fuel costs, and integrated thermal hydraulics. VSOP also can be used to comparative studies and simulation of reactor safety. However, existing VSOP is a conventional program, which was developed using Fortran 65 and have several problems in using it, for example, it is only operated on Dec Alpha mainframe platforms and provide text-based output, difficult to use, especially in data preparation and interpretation of results. We develop a GUI-VSOP, which is an interface program to facilitate the preparation of data, run the VSOP code and read the results in a more user friendly way and useable on the Personal 'Computer (PC). Modifications include the development of interfaces on preprocessing, processing and postprocessing. GUI-based interface for preprocessing aims to provide a convenience way in preparing data. Processing interface is intended to provide convenience in configuring input files and libraries and do compiling VSOP code. Postprocessing interface designed to visualized the VSOP output in table and graphic forms. GUI-VSOP expected to be useful to simplify and speed up the process and analysis of safety aspects.

  6. Measurements of {sup 237}Np secondary neutron spectra

    Energy Technology Data Exchange (ETDEWEB)

    Kornilov, N.V.

    1997-03-01

    The activities carried out during the first year of the project are summarized. The main problems for Np spectra measurements arise from high intrinsic gamma-ray activity of the sample and admixture of the oxygen and iron nuclei. The inelastically scattered neutrons and the fission neutrons spectra for {sup 237}Np were measured by time-of-flight spectrometer of the IPPE at incident neutron energies {approx_equal}1.5 MeV, and {approx_equal}0.5 MeV. A solid tritium target and a Li-metallic target were used as neutron sources. The neutron scattering on C sample (C(n,n) standard reaction) was measured to normalize the Np data. The experimental data should be simulated by Monte Carlo method to correct the experimental data for oxygen and iron admixture as well as for multiple scattering of the neutrons in the sample. Therefore the response function of the spectrometer, and the neutron energy distribution from the source were investigated in detail. (author)

  7. Measurements of {sup 237}Np secondary neutron spectra

    Energy Technology Data Exchange (ETDEWEB)

    Kornilov, N.V.

    1997-03-01

    The activities carried out during the first year of the project are summarized. The main problems for Np spectra measurements arise from high intrinsic gamma-ray activity of the sample and admixture of the oxygen and iron nuclei. The inelastically scattered neutrons and the fission neutrons spectra for {sup 237}Np were measured by time-of-flight spectrometer of the IPPE at incident neutron energies {approx_equal}1.5 MeV, and {approx_equal}0.5 MeV. A solid tritium target and a Li-metallic target were used as neutron sources. The neutron scattering on C sample (C(n,n) standard reaction) was measured to normalize the Np data. The experimental data should be simulated by Monte Carlo method to correct the experimental data for oxygen and iron admixture as well as for multiple scattering of the neutrons in the sample. Therefore the response function of the spectrometer, and the neutron energy distribution from the source were investigated in detail. (author)

  8. Neutron emission profiles and energy spectra measurements at JET

    Energy Technology Data Exchange (ETDEWEB)

    Giacomelli, L. [JET-EFDA, Culham Science Centre, Abingdon, 0X14 3DB, United Kingdom and Department of Physics, Università degli Studi di Milano-Bicocca, Milano (Italy); Conroy, S. [JET-EFDA, Culham Science Centre, Abingdon, 0X14 3DB, United Kingdom and Department of Physics and Astronomy, Uppsala University, Uppsala (Sweden); Belli, F.; Riva, M. [Associazione EURATOM-ENEA sulla Fusione, Roma (Italy); Gorini, G. [Department of Physics, Università degli Studi di Milano-Bicocca, Milano, Italy and Istituto di Física del Plasma Piero Caldirola, Milan (Italy); Horton, L.; Joffrin, E.; Lerche, E.; Murari, A.; Popovichev, S.; Syme, B. [JET-EFDA, Culham Science Centre, Abingdon, 0X14 3DB (United Kingdom); 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.

  9. Calculation of prompt neutron spectra for curium isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Ohsawa, Takaaki [Kinki Univ., Higashi-Osaka, Osaka (Japan). Atomic Energy Research Inst.

    1997-03-01

    With the aim of checking the existing evaluations contained in JENDL-3.2 and providing new evaluations based on a methodology proposed by the author, a series of calculations of prompt neutron spectra have been undertaken for curium isotopes. Some of the evaluations in JENDL-3.2 was found to be unphysically hard and should be revised. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Characterization of neutron yield and x-ray spectra of a High Flux Neutron Generator (HFNG)

    Science.gov (United States)

    Nnamani, Nnaemeka; HFNG Collaboration

    2015-04-01

    The High Flux Neutron Generator (HFNG) is a DD plasma-based source, with a self-loading target intended for fundamental science and engineering applications, including 40 Ar/39 Ar geochronology, neutron cross section measurements, and radiation hardness testing of electronics. Our first estimate of the neutron yield, based on the population of the 4.486 hour 115 In isomer gave a neutron yield of the order 108 n/sec; optimization is ongoing to achieve the design target of 1011 n/sec. Preliminary x-ray spectra showed prominent energy peaks which are likely due to atomic line-emission from back-streaming electrons accelerated up to 100 keV impinging on various components of the HFNG chamber. Our x-ray and neutron diagnostics will aid us as we continue to evolve the design to suppress back-streaming electrons, necessary to achieve higher plasma beam currents, and thus higher neutron flux. This talk will focus on the characterization of the neutron yield and x-ray spectra during our tests. A collimation system is being installed near one of the chamber ports for improved observation of the x-ray spectra. This work is supported by NSF Grant No. EAR-0960138, U.S. DOE LBNL Contract No. DE-AC02-05CH11231, U.S. DOE LLNL Contract No. DE-AC52-07NA27344, and the UC Office of the President Award 12-LR-238745.

  12. Measurement of neutron flux spectra in a Tungsten Benchmark by neutron foil activation method

    OpenAIRE

    Negoita, Cezar Ciprian

    2004-01-01

    The nuclear design of fusion devices such as ITER (International Thermonuclear Experimental Reactor), which is an experimental fusion reactor based on the "tokamak" concept, rely on the results of neutron physical calculations. These depend on the knowledge of the neutron and photon flux spectra which is particularly important because it permits to anticipate the possible answers of the whole structure to phenomena such as nuclear heating, tritium breeding, atomic displaceme...

  13. Neutron spectra and dosimetric features of isotopic neutron sources: a review

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98060 Zacatecas, Zac. (Mexico); Martinez O, S. A., E-mail: fermineutron@yahoo.com [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Av. Central del Norte 39-115, 150003 Tunja, Boyaca (Colombia)

    2015-10-15

    A convenient way to produce neutrons is the isotopic neutron source, where the production is through (α, n), (γ, n), and spontaneous fission reactions. Isotopic neutron sources are small, easy to handle, and have a relative low cost. On the other hand the neutron yield is small and mostly of them produces neutrons with a wide energy distribution. In this work, a review is carried out about the the main features of {sup 24}NaBe, {sup 24}NaD{sub 2}O, {sup 116}InBe, {sup 140}LaBe, {sup 238}PuLi, {sup 239}PuBe, {sup 241}AmB, {sup 241}AmBe, {sup 241}AmF, {sup 241}AmLi, {sup 242}CmBe, {sup 210}PoBe, {sup 226}RaBe, {sup 252}Cf and {sup 252}Cf/D{sub 2}O isotopic neutron source. Also, using Monte Carlo methods, the neutron spectra in 31 energy groups, the neutron mean energy; the Ambient dose equivalent, the Personal dose equivalent and the Effective dose were calculated for these isotopic neutron sources. (Author)

  14. New analytical planetary theories VSOP2010

    Science.gov (United States)

    Francou, G.; Simon, J.-L.

    2011-10-01

    The planetary theories VSOP are essentially issued from the research works of P. Bretagnon. After the last version, VSOP2000, he began to make some improvements, but, unfortunately, he did not have time to complete his work. We took up again this work introducing various changes and complements and build two versions : VSOP2010A fitted to DE405 (numerical integration of the JPL) and VSOP2010B, not yet finished, fitted to INPOP08A (numerical integration of the IMCCE at Paris observatory). Over the time interval [1890,2000], the estimated precision is 3 to 10 times better than that of VSOP2000. Over the time interval [-4000,8000], the gain in precision is about 5 times better for the telluric planets and 10 to 50 times better for the outer planets in comparison with VSOP2000.

  15. The VSOP-2 Space VLBI Mission

    Science.gov (United States)

    Hirabayashi, Hisashi; Murata, Yasuhiro; Murphy, David W.

    2002-01-01

    Following the success of the VLBI Space Observatory Program (VSOP), a next generation space VLBI mission, VSOP-2, is currently being planned. Higher observing frequencies, cooled receivers, increased bandwidths and larger telescope diameters will result in gains in resolution and interferometer sensitivity by factors of 10 over the VSOP mission. The use of phase-referencing by fast switching between a calibrator source and the target source is now being studied as this technique allows sources 50-150 times weaker to be observed depending on the frequency band. Such a capability would greatly enhance the VSOP-2 mission. Several other enhancements to the VSOP-2 mission are also presently under investigation including the VSOP-2 spacecraft operating at the same time as a US spacecraft to form what has come to be known as the iARISE (international ARISE) mission.

  16. Vsop2/Astro-G Project

    CERN Document Server

    Tsuboi, Masato

    2008-01-01

    We introduce a new space VLBI project, the Second VLBI Space Observatory Program (VSOP2), following the success of the VLBI Space Observatory Program (VSOP1). VSOP2 has 10 times higher angular resolution, up to about 40 micro arcseconds, 10 times higher frequency up to 43 GHz, and 10 times higher sensitivity compared to VSOP1. Then VSOP2 should become a most powerful tool to observe innermost regions of AGN and astronomical masers. ASTRO-G is a spacecraft for VSOP2 project constructing in ISAS/JAXA since July 2007. ASTRO-G will be launched by JAXA H-IIA rocket in fiscal year 2012. ASTRO-G and ground-based facilities are combined as VSOP2. To achieve the good observation performances, we must realize new technologies. They are large precision antenna, fast-position switching capability, new LNAs, and ultra wide-band down link, etc.. VSOP2 is a huge observation system involving ASTRO-G, ground radio telescopes, tracking stations, and correlators, one institute can not prepare a whole system of VSOP2. Then we mu...

  17. General relativistic spectra of accretion disks around rotating neutron stars

    CERN Document Server

    Bhattacharya, S; Thampan, A V

    2000-01-01

    General relativistic spectra from accretion disks around rotating neutron stars in the appropriate space-time geometry for several different equation of state, spin rates and mass of the compact object have been computed. The analysis involves the computation of the relativistically corrected radial temperature profiles and the effect of Doppler and gravitational red-shifts on the spectra. Light bending effects have been omitted for simplicity. The relativistic spectrum is compared with the Newtonian one and it is shown that the difference between the two is primarily due to the different radial temperature profile for the relativistic and Newtonian disk solutions. To facilitate direct comparison with observations, a simple empirical function has been presented which describes the numerically computed relativistic spectra well. This empirical function (which has three parameters including normalization) also describes the Newtonian spectrum adequately. Thus the function can in principle be used to distinguish...

  18. Self-shielding effects in neutron spectra measurements for neutron capture therapy by means of activation foils.

    Science.gov (United States)

    Pytel, Krzysztof; Józefowicz, Krystyna; Pytel, Beatrycze; Koziel, Alina

    2004-01-01

    The design and optimisation of a neutron beam for neutron capture therapy (NCT) is accompanied by the neutron spectra measurements at the target position. The method of activation detectors was applied for the neutron spectra measurements. Epithermal neutron energy region imposes the resonance structure of activation cross sections resulting in strong self-shielding effects. The neutron self-shielding correction factor was calculated using a simple analytical model of a single absorption event. Such a procedure has been applied to individual cross sections from pointwise ENDF/B-VI library and new corrected activation cross sections were introduced to a spectra unfolding algorithm. The method has been verified experimentally both for isotropic and for parallel neutron beams. Two sets of diluted and non-diluted activation foils covered with cadmium were irradiated in the neutron field. The comparison of activation rates of diluted and non-diluted foils has demonstrated the correctness of the applied self-shielding model.

  19. Measurement of neutron spectra in the experimental reactor LR-0

    Energy Technology Data Exchange (ETDEWEB)

    Prenosil, Vaclav; Mravec, Filip; Veskrna, Martin [Faculty of Informatics, Masaryk University, Botanicka 68a, 612 00 Brno, (Czech Republic); Kostal, Michal [Research Centre Rez, Hlavni 130, 250 68 Husinec-Rez, (Czech Republic); Matej, Zdenek [VF, a.s., Svitavska 588, 679 21 Cerna Hora, (Czech Republic); Cvachovec, Frantisek [Faculty of Military Technology, University of Defense, Brno, (Czech Republic)

    2015-07-01

    The measurement of fast neutron fluxes is important in many areas of nuclear technology. It affects the stability of the reactor structural components, performance of fuel, and also the fuel manner. The experiments performed at the LR-0 reactor were in the past focused on the measurement of neutron field far from the core, in reactor pressure vessel simulator or in biological shielding simulator. In the present the measurement in closer regions to core became more important, especially measurements in structural components like reactor baffle. This importance increases with both reactor power increase and also long term operation. Other important task is an increasing need for the measurement close to the fuel. The spectra near the fuel are aimed due to the planned measurements with the FLIBE salt, in FHR / MSR research, where one of the task is the measurement of the neutron spectra in it. In both types of experiments there is strong demand for high working count rate. The high count rate is caused mainly by high gamma background and by high fluxes. The fluxes in core or in its vicinity are relatively high to ensure safe reactor operation. This request is met in the digital spectroscopic apparatus. All experiments were realized in the LR-0 reactor. It is an extremely flexible light water zero-power research reactor, operated by the Research Center Rez (Czech Republic). (authors)

  20. VSOP-2 Astrometric Accuracy with Phase Referencing

    Science.gov (United States)

    Asaki, Y.; Kono, Y.

    2009-08-01

    The VSOP-2 mission is expected to conduct phase referencing observations with the unprecedented spatial resolutions at 8.4, 22, and 43 GHz together with the ASTRO-G satellite. In this report, VSOP-2 astrometry with phase referencing is examined in detail based on a simulation tool, ARIS.

  1. VSOP Monitoring Observations of 1928+738

    Science.gov (United States)

    Murphy, D. W.; Edwards, P. G.

    2009-08-01

    In this paper we review the VSOP monitoring observations of the core-dominated quasar 1928+738. Combining our VSOP observations with other VLBI data we find that the combined dataset can be well fit using a relativistic ballistic precessing jet model in which the precession is caused by the orbital motion in a binary black hole system.

  2. Phase-resolved spectra of burst oscillations in Neutron Stars

    Science.gov (United States)

    Zoghbi, Abderahmen; Miller, Jon M.

    2017-08-01

    Millisecond oscillations have been observed during thermonuclear bursts from many neutron stars (NS) in LMXBs. Their periods are comparable to the rotational period of the NS, and are thought to be produced by temperature anisotropies on the NS surface. Understanding and correcly modeling these oscillation is a powerful tool to constrain the NS interior. Studying these oscillations has thus far focused on modeling the oscillation profile form these pulsations using mostly XTE data. Here, we take a different approach and extract spectra at different phases of the oscillations. This allows us track the observed spectrum as the NS rotates. We are able to measure temperature changes as the star rotates. The temperature profiles from some bursts show asymetries likely due to Doppler effects. Here, we present detailed results from the phase spectra and discuss their implications on measurements of NS masses and radii.

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

    CERN Document Server

    Kroc, T K

    2012-01-01

    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 optimization. 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.

  4. Unfolding the fast neutron spectra of a BC501A liquid scintillation detector using GRAVEL method

    CERN Document Server

    Chen, Yonghao; Lei, Jiarong; An, Li; Zhang, Xiaodong; Shao, Jianxiong; Zheng, Pu; Wang, Xinhua

    2013-01-01

    Accurate knowledge of the neutron energy spectra is useful in basic research and applications. The overall procedure of measuring and unfolding the fast neutron energy spectra with BC501A liquid scintillation detector is described. The recoil proton spectrum of Am-Be neutrons was obtained experimentally. With the NRESP7 code, the response matrix of detector was simulated. Combining the recoil proton spectrum and response matrix, the unfolding of neutron spectra was performed by GRAVEL iterative algorithm. A MatLab program based on the GRAVEL method was developed. The continuous neutron spectrum of Am-Be source and monoenergetic neutron spectrum of D-T source have been unfolded successfully and are in good agreement with their standard reference spectra. The unfolded Am-Be spectrum are more accurate than the spectra unfolded by artificial neural networks in recent years.

  5. Unfolding the fast neutron spectra of a BC501A liquid scintillation detector using GRAVEL method

    Science.gov (United States)

    Chen, YongHao; Chen, XiMeng; Lei, JiaRong; An, Li; Zhang, XiaoDong; Shao, JianXiong; Zheng, Pu; Wang, XinHua

    2014-10-01

    Accurate knowledge of the neutron energy spectra is useful in basic research and applications. The overall procedure of measuring and unfolding the fast neutron energy spectra with BC501A liquid scintillation detector is described. The recoil proton spectrum of 241Am-Be neutrons was obtained experimentally. With the NRESP7 code, the response matrix of detector was simulated. Combining the recoil proton spectrum and response matrix, the unfolding of neutron spectra was performed by GRAVEL iterative algorithm. A MatLab program based on the GRAVEL method was developed. The continuous neutron spectrum of 241Am-Be source and monoenergetic neutron spectrum of D-T source have been unfolded successfully and are in good agreement with their standard reference spectra. The unfolded 241Am-Be spectrum are more accurate than the spectra unfolded by artificial neural networks in recent years.

  6. Extragalactic Water Maser Observations with VSOP-2

    Science.gov (United States)

    Hagiwara, Y.; VSOP-2 Science Working Group

    2009-08-01

    Space-VLBI is known to achieve greatly increased angular resolution compared with ground-based VLBI observations. VSOP-2 will offer 75 μarcsec angular resolution at 22 GHz. With this improved angular resolution, VSOP-2 observations of H_2O megamaser will refine the measurements of proper motions, accelerations, distances to galaxies, and other physical parameters of galactic nuclei. In this presentation, the prospects of VSOP-2 observations of extragalactic H_2O maser with strong emphasis on H_2O megamaser are presented.

  7. Sci—Fri PM: Dosimetry—02: A Nested Neutron Spectrometer to Measure Neutron Spectra in Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Maglieri, R; Seuntjens, J; Kildea, J [Medical Physics Unit, McGill University, Montreal, Qc (Canada); Licea, A [Canadian Nuclear Safety Commission CNSC, Ottawa, Ontario (Canada)

    2014-08-15

    During high-energy radiotherapy treatments, neutrons are produced in the head of the linac through photonuclear interactions. This has been a concern for many years as photoneutrons contribute to the accepted, yet unwanted, out-of-field doses that pose an iatrogenic risk to patients and an occupational risk to personnel. Presently, in-room neutron measurements are difficult and time-consuming and have traditionally been carried out using Bonner spheres with activation foils and TLDs. In this work, a new detector, the Nested Neutron Spectrometer (NNS) is tested for use in radiotherapy bunkers. The NNS is designed for easy handling and is more practical than the traditional Bonner spheres. The NNS, operated in current mode, was used to measure the dose equivalent, average energy and energy spectrum at several positions in a radiotherapy bunker. The average energy and spectra were compared to Monte Carlo simulations while the dose equivalent was compared to bubble detector measurements. The average energies, as measured by the NNS and Monte Carlo simulations, differed by approximately 30% across the bunker. Measurements of the dose equivalent using the NNS and the bubble detectors agreed within 50% in the maze and less than 10% close to the linac head. Apart from some discrepancies at thermal energies, we also found reasonable agreement between NNS-measured and Monte Carlo-simulated spectra at a number of locations within our radiotherapy bunker. Our results demonstrate that the NNS is a suitable detector to be used in high dose-rate radiotherapy environments.

  8. Calculation of delayed-neutron energy spectra in a QRPA-Hauser-Feshbach model

    Energy Technology Data Exchange (ETDEWEB)

    Kawano, Toshihiko [Los Alamos National Laboratory; Moller, Peter [Los Alamos National Laboratory; Wilson, William B [Los Alamos National Laboratory

    2008-01-01

    Theoretical {beta}-delayed-neutron spectra are calculated based on the Quasiparticle Random-Phase Approximation (QRPA) and the Hauser-Feshbach statistical model. Neutron emissions from an excited daughter nucleus after {beta} decay to the granddaughter residual are more accurately calculated than in previous evaluations, including all the microscopic nuclear structure information, such as a Gamow-Teller strength distribution and discrete states in the granddaughter. The calculated delayed-neutron spectra agree reasonably well with those evaluations in the ENDF decay library, which are based on experimental data. The model was adopted to generate the delayed-neutron spectra for all 271 precursors.

  9. Measurements and parameterization of neutron energy spectra from targets bombarded with 120 GeV protons

    Energy Technology Data Exchange (ETDEWEB)

    Kajimoto, T., E-mail: kajimoto@hiroshima-u.ac.jp [Hiroshima University, Kagamiyama, Higashi-hiroshima 739-8527 (Japan); Shigyo, N. [Kyushu University, Motooka, Nishi-ku, Fukuoka 819-0395 (Japan); Sanami, T. [High Energy Accelerator Research Organization, Oho, Tsukuba, Ibaraki 305-0801 (Japan); Iwamoto, Y. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Hagiwara, M. [High Energy Accelerator Research Organization, Oho, Tsukuba, Ibaraki 305-0801 (Japan); Lee, H.S. [Pohang Accelerator Laboratory, POSTECH, Pohang, Kyungbuk 790-784 (Korea, Republic of); Soha, A.; Ramberg, E.; Coleman, R.; Jensen, D.; Leveling, A.; Mokhov, N.V.; Boehnlein, D.; Vaziri, K. [Fermi National Accelerator Laboratory, Batavia, IL 60510-5011 (United States); Sakamoto, Y. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Ishibashi, K. [Kyushu University, Motooka, Nishi-ku, Fukuoka 819-0395 (Japan); Nakashima, H. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

    2014-10-15

    Highlights: •Neutron energy spectra from targets bombarded with 120 GeV protons were measured. •The neutron energy was determined with the time-of-flight technique. •The measured spectra were compared with those calculated by PHITS and FLUKA. •Large differences were found between measured and calculated spectra. •The study shows the need to improve models for neutron production in the high energy region. -- Abstract: The energy spectra of neutrons were measured by a time-of-flight method for 120 GeV protons on thick graphite, aluminum, copper, and tungsten targets with an NE213 scintillator at the Fermilab Test Beam Facility. Neutron energy spectra were obtained between 25 and 3000 MeV at emission angles of 30°, 45°, 120°, and 150°. The spectra were parameterized as neutron emissions from three moving sources and then compared with theoretical spectra calculated by PHITS and FLUKA codes. The yields of the theoretical spectra were substantially underestimated compared with the yields of measured spectra. The integrated neutron yields from 25 to 3000 MeV calculated with PHITS code were 16–36% of the experimental yields and those calculated with FLUKA code were 26–57% of the experimental yields for all targets and emission angles.

  10. Validation of neutron data libraries by backscattered spectra of Pu-Be Neutrons

    CERN Document Server

    El-Agib, I

    1999-01-01

    Elastically backscattered spectra of Pu-Be neutrons have been measured for SiO sub 2 , water, graphite, paraffin oil and Al slabs using a proton recoil spectrometer. The results were compared with the calculated spectra obtained by the three-dimensional Monte-Carlo transport code MCNP-4B and point-wise cross sections from the ENDF/B-V, ENDF/B-VI, JENDL-3.1 and BROND-2 data libraries. The good agreement between the measured and calculated results indicates that this procedure can be used for validation of different data libraries. This simple method renders possible the detection of oxygen, carbon and hydrogen in bulk samples. (author)

  11. Evaluation of Am-Li neutron spectra data for active well type neutron multiplicity measurements of uranium

    Science.gov (United States)

    Goddard, Braden; Croft, Stephen; Lousteau, Angela; Peerani, Paolo

    2016-09-01

    Safeguarding nuclear material is an important and challenging task for the international community. One particular safeguards technique commonly used for uranium assay is active neutron correlation counting. This technique involves irradiating unused uranium with (α, n) neutrons from an Am-Li source and recording the resultant neutron pulse signal which includes induced fission neutrons. Although this non-destructive technique is widely employed in safeguards applications, the neutron energy spectra from an Am-Li sources is not well known. Several measurements over the past few decades have been made to characterize this spectrum; however, little work has been done comparing the measured and theoretical spectra of various Am-Li sources to each other. This paper examines fourteen different Am-Li spectra, focusing on how these spectra affect simulated neutron multiplicity results using the code Monte Carlo N-Particle eXtended (MCNPX). Two measurement and simulation campaigns were completed using Active Well Coincidence Counter (AWCC) detectors and uranium standards of varying enrichment. The results of this work indicate that for standard AWCC measurements, the fourteen Am-Li spectra produce similar doubles and triples count rates. The singles count rates varied by as much as 20% between the different spectra, although they are usually not used in quantitative analysis, being dominated by scattering which is highly dependent on item placement.

  12. Energy spectra and fluence of the neutrons produced in deformed space-time conditions

    Science.gov (United States)

    Cardone, F.; Rosada, A.

    2016-10-01

    In this work, spectra of energy and fluence of neutrons produced in the conditions of deformed space-time (DST), due to the violation of the local Lorentz invariance (LLI) in the nuclear interactions are shown for the first time. DST-neutrons are produced by a mechanical process in which AISI 304 steel bars undergo a sonication using ultrasounds with 20 kHz and 330 W. The energy spectrum of the DST-neutrons has been investigated both at low (less than 0.4 MeV) and at high (up to 4 MeV) energy. We could conclude that the DST-neutrons have different spectra for different energy intervals. It is therefore possible to hypothesize that the DST-neutrons production presents peculiar features not only with respect to the time (asynchrony) and space (asymmetry) but also in the neutron energy spectra.

  13. A high-resolution neutron spectra unfolding method using the Genetic Algorithm technique

    CERN Document Server

    Mukherjee, B

    2002-01-01

    The Bonner sphere spectrometers (BSS) are commonly used to determine the neutron spectra within various nuclear facilities. Sophisticated mathematical tools are used to unfold the neutron energy distribution from the output data of the BSS. This paper highlights a novel high-resolution neutron spectra-unfolding method using the Genetic Algorithm (GA) technique. The GA imitates the biological evolution process prevailing in the nature to solve complex optimisation problems. The GA method was utilised to evaluate the neutron energy distribution, average energy, fluence and equivalent dose rates at important work places of a DIDO class research reactor and a high-energy superconducting heavy ion cyclotron. The spectrometer was calibrated with a sup 2 sup 4 sup 1 Am/Be (alpha,n) neutron standard source. The results of the GA method agreed satisfactorily with the results obtained by using the well-known BUNKI neutron spectra unfolding code.

  14. Black Hole Shadows and VSOP-2

    Science.gov (United States)

    Takahashi, R.

    2009-08-01

    The radio images in the galactic center with micro-arcsecond resolution will be obtained by the radio interferometer VSOP-2. The apparent sizes of the direct images of the black holes in the nearby massive galaxies such as M87 and Sgr A* also have micro-arcsecond scales, and such black holes will be seen as the shadows in the luminous accreting matter around the black holes. At 43 GHz where VSOP-2 has the highest spatial resolution (38 μarcseconds), the observed images of Sgr A* are smeared out by the interstellar scattering. Therefore, the shadow of Sgr A* will not be resolved at this frequency. In the case of M87, the observed values of the black hole mass and the distance are not precisely determined. The possible minimum angular size of the highest spatial resolution of VSOP-2 corresponds to 12.5 GMBH/c^2 which is smaller than the shadow size of the slowly rotating black hole in the accretion flow with the inner edge of the marginally stable orbit. On the other hand, the possible maximum angular size of the highest spatial resolution of VSOP-2 corresponds to 38.1 GMBH/c^2. In this case, for any value of the black hole spin and the observed inclination angle, the size of the black hole shadow is smaller than the highest spatial resolution of VSOP-2. On the other hand, the observed energy spectrum of the accretion flow in M87 is consistent with the radiatively inefficient accretion flow where the electron temperature is higher than the detection temperature of VSOP-2. This means that the photons from the accretion flow around the black hole in M87 can be detected by VSOP-2. Other related issues are also discussed.

  15. Spectra of the spreading layers on the neutron star surface and constraints on the neutron star equation of state

    CERN Document Server

    Suleimanov, V; Suleimanov, Valery; Poutanen, Juri

    2006-01-01

    Spectra of the spreading layers on the neutron star surface are calculated on the basis of the Inogamov-Sunyaev model taking into account general relativity correction to the surface gravity and considering various chemical composition of the accreting matter. Local (at a given latitude) spectra are similar to the X-ray burst spectra and are described by a diluted black body. Total spreading layer spectra are integrated accounting for the light bending, gravitational redshift, and the relativistic Doppler effect and aberration. They depend slightly on the inclination angle of the neutron star and on the luminosity. These spectra also can be fitted by a diluted black body with the color temperature depending mainly on a neutron star compactness. Constraints on the neutron star compactness were obtained by comparing the theoretical spreading layer spectra with the observed boundary layer spectrum described by a black body of color temperature 2.4 +- 0.1 keV. We obtain the neutron star radius R=15+-1.5 km (for a...

  16. Neutron spectra in two beam ports of the TRIGA Mark III reactor

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H. R.; Hernandez D, V. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98060 Zacatecas (Mexico); Aguilar, F.; Paredes, L. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Rivera M, T., E-mail: fermineutron@yahoo.com [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Legaria, Av. Legaria 694, 11500 Mexico D. F. (Mexico)

    2013-10-15

    The neutron spectra have been measured in two beam ports, radial and tangential, of the TRIGA Mark III nuclear reactor from the National Institute of Nuclear Research. Measurements were carried out with the core with mixed fuel (Leu 8.5/20 and Flip Heu 8.5/70). Two reactor powers, 5 and 10 W, were used during neutron spectra measurements using a Bonner sphere spectrometer with a {sup 6}Lil(Eu) scintillator and 2, 3, 5, 8, 10 and 12 inches-diameter high density polyethylene spheres. The neutron spectra were unfolded using the NSDUAZ unfolding code; from each spectrum the total neutron flux, the neutron mean energy and the neutron ambient dose equivalent dose were determined. Measured spectra show fission (E≥ 0.1 MeV), epithermal (from 0.4 eV up to 0.1 MeV) and thermal neutrons (E≤ 0.4 eV). For both reactor powers the spectra in the radial beam port have similar features which are different to the neutron spectrum characteristics in the tangential beam port. (Author)

  17. VSOP-2 Observations of M 87: A Proposal for a VSOP-2 Key Science Program

    Science.gov (United States)

    Asada, K.; Doi, A.; Kino, M.; Nagai, H.; Nakamura, M.; Kameno, S.; VSOP-2 Science Working Group

    2009-08-01

    We report the advantages and potentials of VSOP-2 observations for studying the central engine of M 87. Extremely high angular resolution of VSOP-2 of 38 μ-arcsecond will provide us the unique opportunity to observe M 87 with spatial resolution of 0.0031 pc. This corresponds to around 10 times the Schwarzschild radius so that VSOP-2 can be a powerful tool to reveal the accretion disk and jet launching site, and investigate the formation, acceleration and collimation of the jet in connection with the physics of the accretion disk. A polished plan based on these studies will be proposed as one of the Key Science Programs of VSOP-2 mission in the category of Active Galactic Nuclei. Key Science Programs (KSPs) are research in important science area performed under the responsibility of the VSOP-2 mission. VSOP-2 Science Working Group begins to investigate potential KSPs. KSPs will be peer-reviewed by VSOP-2 International Science Council (VISC-2).

  18. V.S.O.P. (99/05) computer code system

    Energy Technology Data Exchange (ETDEWEB)

    Ruetten, H.J.; Haas, K.A.; Brockmann, H.; Scherer, W.

    2005-11-01

    V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of the reactor and of the fuel element, processing of cross sections, neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to HTRs and to two spatial dimensions. The code can simulate the reactor operation from the initial core towards the equilibrium core. V.S.O.P.(99 / 05) represents the further development of V.S.O.P. (99). Compared to its precursor, the code system has been improved in many details. Major improvements and extensions have been included concerning the neutron spectrum calculation, the 3-d neutron diffusion options, and the thermal hydraulic section with respect to 'multi-pass'-fuelled pebblebed cores. This latest code version was developed and tested under the WINDOWS-XP - operating system. The storage requirement for the executables and the basic libraries associated with the code amounts to about 15 MB. Another 5 MB are required - if desired - for storage of the source code ({approx}65000 Fortran statements). (orig.)

  19. V.S.O.P. (99/05) computer code system

    Energy Technology Data Exchange (ETDEWEB)

    Ruetten, H.J.; Haas, K.A.; Brockmann, H.; Scherer, W.

    2005-11-01

    V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of the reactor and of the fuel element, processing of cross sections, neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to HTRs and to two spatial dimensions. The code can simulate the reactor operation from the initial core towards the equilibrium core. V.S.O.P.(99 / 05) represents the further development of V.S.O.P. (99). Compared to its precursor, the code system has been improved in many details. Major improvements and extensions have been included concerning the neutron spectrum calculation, the 3-d neutron diffusion options, and the thermal hydraulic section with respect to 'multi-pass'-fuelled pebblebed cores. This latest code version was developed and tested under the WINDOWS-XP - operating system. The storage requirement for the executables and the basic libraries associated with the code amounts to about 15 MB. Another 5 MB are required - if desired - for storage of the source code ({approx}65000 Fortran statements). (orig.)

  20. Neutron spectra at two beam ports of a TRIGA Mark III reactor loaded with HEU fuel.

    Science.gov (United States)

    Vega-Carrillo, H R; Hernández-Dávila, V M; Aguilar, F; Paredes, L; Rivera, T

    2014-01-01

    The neutron spectra have been measured in two beam ports, one radial and another tangential, of the TRIGA Mark III nuclear reactor from the National Institute of Nuclear Research in Mexico. Measurements were carried out with the reactor core loaded with high enriched uranium fuel. Two reactor powers, 5 and 10 W, were used during neutron spectra measurements using a Bonner sphere spectrometer with a (6)LiI(Eu) scintillator and 2, 3, 5, 8, 10 and 12 in.-diameter high-density polyethylene spheres. The neutron spectra were unfolded using the NSDUAZ unfolding code. For each spectrum total flux, mean energy and ambient dose equivalent were determined. Measured spectra show fission, epithermal and thermal neutrons, being harder in the radial beam port.

  1. Spectrometer equipment for photon spectra measurements in mixed neutron/photon fields

    CERN Document Server

    Chernov, V A; Trykov, L A

    2002-01-01

    The paper presents the description of spectrometers in the experimental laboratory of the IPPE for measuring, processing and systematizing of gamma-radiation spectra. The complete set includes spectrometers based on stilbene crystal and silicon Si(Li) detector. Spectrometers are used for photon spectra measuring of the mixed neutron/photon radiation radionuclide sources, nuclear reactors and accelerators; for the study of neutron and photon spectra in materials, including benchmark experiments; for the photon spectra measurements in the rooms of nuclear facilities in order to determine the radionuclide contents of the sources and to provide radiation safety.

  2. Calculation of Prompt Fission Neutron Spectra for ~(235)U (n,f)

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The prompt fission neutron spectra for neutron-induced fission of 235U at En<5 MeV are calculated using the nuclear evaporation theory with a semi-empirical model, in which the non-constant temperature and the constant temperature related to the Fermi gas model

  3. Calculation verification of the utilization of LR-0 for reference neutron spectra

    Science.gov (United States)

    Ján, Milčák; Michal, Košťál; Marie, Švadlenková; Michal, Koleška; Vojtěch, Rypar

    2014-11-01

    Well-defined neutron spectrum is crucial for calibration and testing of detectors for spectrometry and dosimetry purposes. As a possible source of neutrons nuclear reactors can be utilized. In reactor core most of the neutrons are originated from fission and neutron spectra is usually some form of moderated spectra of fast neutrons. The reactor LR-0 is an experimental light-water zero-power pool-type reactor originally designed for research of the VVER type reactor cores, spent-fuel storage lattices and benchmark experiments. The main reactor feature that influences the performance of experiments is the flexible arrangement of the core. Special types of the possible core arrangements on the reactor LR-0 can provide different neutron spectra in special experimental channels. These neutron spectra are modified by inserting different materials around the channel and whole core is driven by standard fuel assemblies. Fast, epithermal or thermal spectra can be simulated using graphite, H2O, D2O insertions, air, Cd foils or fuel with different enrichment.

  4. Secondary neutron spectra from modern Varian, Siemens, and Elekta linacs with multileaf collimators.

    Science.gov (United States)

    Howell, Rebecca M; Kry, Stephen F; Burgett, Eric; Hertel, Nolan E; Followill, David S

    2009-09-01

    Neutrons are a by-product of high-energy x-ray radiation therapy (threshold for [gamma,n] reactions in high-Z material -7 MeV). Neutron production varies depending on photon beam energy as well as on the manufacturer of the accelerator. Neutron production from modern linear accelerators (linacs) has not been extensively compared, particularly in terms of the differences in the strategies that various manufacturers have used to implement multileaf collimators (MLCs) into their linac designs. However, such information is necessary to determine neutron dose equivalents for different linacs and to calculate vault shielding requirements. The purpose of the current study, therefore, was to measure the neutron spectra from the most up-to-date linacs from three manufacturers: Varian 21EX operating at 15, 18, and 20 MV, Siemens ONCOR operating at 15 and 18 MV, and Elekta Precise operating at 15 and 18 MV. Neutron production was measured by means of gold foil activation in Bonner spheres. Based on the measurements, the authors determined neutron spectra and calculated the average energy, total neutron fluence, ambient dose equivalent, and neutron source strength. The shapes of the neutron spectra did not change significantly between accelerators or even as a function of treatment energy. However, the neutron fluence, and therefore the ambient dose equivalent, did vary, increasing with increasing treatment energy. For a given nominal treatment energy, these values were always highest for the Varian linac. The current study thus offers medical physicists extensive information about the neutron production of MLC-equipped linacs currently in operation and provides them information vital for accurate comparison and prediction of neutron dose equivalents and calculation of vault shielding requirements.

  5. Irradiation tests of ITER candidate Hall sensors using two types of neutron spectra.

    Science.gov (United States)

    Ďuran, I; Bolshakova, I; Viererbl, L; Sentkerestiová, J; Holyaka, R; Lahodová, Z; Bém, P

    2010-10-01

    We report on irradiation tests of InSb based Hall sensors at two irradiation facilities with two distinct types of neutron spectra. One was a fission reactor neutron spectrum with a significant presence of thermal neutrons, while another one was purely fast neutron field. Total neutron fluence of the order of 10(16) cm(-2) was accumulated in both cases, leading to significant drop of Hall sensor sensitivity in case of fission reactor spectrum, while stable performance was observed at purely fast neutron spectrum. This finding suggests that performance of this particular type of Hall sensors is governed dominantly by transmutation. Additionally, it further stresses the need to test ITER candidate Hall sensors under neutron flux with ITER relevant spectrum.

  6. Characteristics of the KUR Heavy Water Neutron Irradiation Facility as a neutron irradiation field with variable energy spectra

    Science.gov (United States)

    Sakurai, Yoshinori; Kobayashi, Tooru

    2000-10-01

    The Heavy Water Neutron Irradiation Facility (HWNIF) of the Kyoto University Research Reactor (KUR) was updated in March 1996, mainly for the improvement in neutron capture therapy (NCT). A striking feature of the updated facility is that the energy spectrum of the neutron beam can be controlled from almost pure thermal to epi-thermal, within 5 min by remote control under a continuous reactor operation. This feature is advantageous not only to medical science such as NCT, but also to the other research fields such as physics, engineering, biology, etc. The performance of the updated facility as a neutron irradiation field with variable energy spectra, was characterized. Thermal neutron flux, cadmium ratio, gamma-ray dose rate, etc., at the normal irradiation position for various irradiation modes were determined, mainly on the basis of the measurement using gold activation foils and thermo-luminescent dosimeters (TLDs). The emphasis was on the performance of the new neutron energy spectrum shifter and cadmium thermal neutron filter, that control the mixing ratio of thermal and epi-thermal neutrons, through the change in the heavy water thickness of the spectrum shifter and the aperture size of the cadmium filter. The evaluation of neutron energy spectra at the normal irradiation position was also performed for three representative irradiation modes, in which the neutron intensities are largest of all the irradiation modes. In addition, the irradiation characteristics of two irradiation devices, namely the Irradiation Rail Device and the Remote Patient Carrier, which were updated concurrently with the facility update, were evaluated.

  7. Neutron spectra and H*(10) around and 18 MV Linac by Ann's

    Energy Technology Data Exchange (ETDEWEB)

    Banuelos F, A.; Valero L, C.; Borja H, C. G.; Hernandez D, V. M.; Vega C, H. R., E-mail: alanb535@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2011-10-15

    Neutron spectra and ambient dose equivalent H*(10) were calculated for a radiotherapy room in 16 point-like detectors, 15 located inside the vault room and 1 located outside the bunker. The calculation was carried out using Monte Carlo Methods with the MCNP5 code for a generic radiotherapy room model operating with a 18 MV Linac, obtaining 16 neutron spectra with 47 energy bins, the H*(10) values were calculated from the neutron spectra by the use of the fluence-dose conversion factors. An artificial neural network were designed and trained to determine the neutron H*(10) in 15 different locations inside the vault room from the H*(10) dose calculated for the detector located outside the room, using the calculated dose values as training set, using the scaled conjugated gradient training algorithm. The mean squared error set for the network training was 1E(-14), adjusting the data in 99.992 %. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H*(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. The results shows the using this artificial intelligence technic as a useful tool for the neutron spectrometry and dosimetry by the simplification on the neutronic fields characterization inside radiotherapy rooms avoiding the use of traditional spectrometric systems. And once the H*(10) doses have been calculated, to take the appropriated actions to reduce or prevent the patient and working staff exposure to this undesirable neutron radiation. (Author)

  8. The VSOP 2 mission: Imaging capabilities

    OpenAIRE

    Dodson, R.; Hirabayashi, H.; Murata, Y.; Edwards, P. G.; Wiik, K.; Murphy, D; Kameno, S.

    2004-01-01

    Given the scientific goals of VSOP-2, including the possibility of observations of the shadows of black holes, we have investigated the fidelity of the recovered images given a typical uv-coverage. We find that we can achieve a dynamic range of better than 1000:1.

  9. Determination of the fast neutrons spectra by the Elastic scattering method (n, p)

    CERN Document Server

    Elizalde, J

    1973-01-01

    This work consists in determining the fast neutron spectra emitted by a Pu-Be isotopic source. The implemented technique is based in the spectrometry (n, p). This consists in making to fall on a fast neutrons beams (polyenergetic) over a thin film of hydrogenated material, detecting the spectra of emitted protons at a fix angle. The polyethylene film and the used solid state detector are inside of a vacuum chamber. The detector is placed at 30 degree with respect to direction of the incident neutrons beam. The protons spectra is stored in a multichannel. the energy is obtained with the prior calibration of the system. The data processing involves the transformation of the protons spectra observed at the falling on neutrons spectra over the film. The energy of the neutrons is related with that of the protons, according to the collision kinematical equations. The cross section of elastic collision of the neutrons with the hydrogen atoms is obtained from literature. Applying these relations to the observed spect...

  10. Impact of flows on ion temperatures inferred from neutron spectra produced in NIF DT implosions

    Science.gov (United States)

    Gatu Johnson, M.; Frenje, J. A.; Petrasso, R. D.; Knauer, J. P.; Caggiano, J. A.; Callahan, D. A.; Casey, D. T.; Cerjan, C. J.; Doeppner, T.; Eckart, M. J.; Grim, G. P.; Hartouni, E. P.; Hatarik, R.; Hinkel, D. E.; Hurricane, O. A.; Kritcher, A.; Le Pape, S.; Ma, T.; Munro, D. H.; Patel, P.; Ralph, J. E.; Sayre, D. B.; Spears, B. K.; Yeamans, C. B.; Kilkenny, J. D.

    2015-11-01

    Neutron spectrometers on the NIF provide accurate, directional information of the DT and DD neutron spectra from layered DT implosions. Traditionally, ion temperatures (Tion) , essential for assessing conditions in the hotspot of the implosions, are inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn also impacts broadening and may lead to artificially inflated ``Tion'' values. We examine NIF neutron spectra to assess the impact of flows on measured Tion. Measured DT Ti on is consistently higher than measured DD Tion, which suggests that significant energy is lost to radial or turbulent kinetic fuel motion at peak burn. However, explaining the full observed Tion difference with fuel motion, as calculated from a Ballabio and Murphy analysis, leads to a thermal Tion too low to explain observed yields. These results have improved our understanding of hotspot formation and the concept of ``stagnation'' in layered NIF implosions. This work was supported in part by DOE, LLNL and LLE.

  11. The prediction and measurement of microdosimetric spectra relating to neutron cancer therapy

    CERN Document Server

    Taylor, G C

    2003-01-01

    The primary aim of this work has been to characterise the beam of the MRC's high energy neutron cancer therapy cyclotron at the Clatterbridge Hospital, Bebington, the Wirral, by measuring a series of microdosimetric spectra for a variety of irradiation conditions. In order to interpret the variation between these spectra, so that the underlying physics of the neutron beam could be determined, it was necessary to identify the most influential factors in the production of microdosimetric responses. Experimental procedures were tested in a series of measurements using 14 and 15 MeV monoenergetic neutrons from the Birmingham Dynamitron; these were instrumental in establishing the rigorous calibration regime necessary for the Clatterbridge measurement programme. The (analytical) predictive code NESLES was used to investigate the effect on microdosimetric spectra of having a low energy neutron component in the primary beam,, and also to highlight the shortcomings of the tissue-equivalent media used in microdosimetr...

  12. RDANN a new methodology to solve the neutron spectra unfolding problem

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz R, J.M.; Martinez B, M.R.; Vega C, H.R. [UAZ, Av. Ramon Lopez Velarde No. 801, 98000 Zacatecas (Mexico)

    2006-07-01

    The optimization processes known as Taguchi method and DOE methodology are applied to the design, training and testing of Artificial Neural Networks in the neutron spectrometry field, which offer potential benefits in the evaluation of the behavior of the net as well as the ability to examine the interaction of the weights and neurons inside the same one. In this work, the Robust Design of Artificial Neural Networks methodology is used to solve the neutron spectra unfolding problem, designing, training and testing an ANN using a set of 187 neutron spectra compiled by the International Atomic Energy Agency, to obtain the better neutron spectra unfolded from the Bonner spheres spectrometer's count rates. (Author)

  13. Measurements of Neutron Energy Spectra and Neutron Dose Equivalent Rates of Workplaces in TQNPC-Ⅲ

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>Monitoring for neutron doses is one of the important activities for radiation protection. And the information about neutron energy distributions of the measured fields is necessary for the correct

  14. V.S.O.P. (99) for WINDOWS and UNIX : computer code system for reactor physics and fuel cycle simulation

    OpenAIRE

    Rütten, H. J.; Haas, K. A.; Brockmann, H.; Ohlig, U.; Scherer, W.

    2000-01-01

    V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of the reactor and of the fuel element, processing of cross sections, neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to HTRs and to two spatial dimensions. The...

  15. V.S.O.P.(97) Computer Code System for Reactor Physics and Fuel Cycle Simulation : Input Manual and Comments

    OpenAIRE

    Rütten, H. J.; Haas, K. A.; Brockmann, H.; Ohlig, U.; Scherer, W.

    1998-01-01

    V.S.O.P. (97) is a computer code system for the comprehensive numerical simulation ofthe physics of thermal reactors. It implies processing ofcross sections, the setup ofthe reactor and ofthe fuel element, repeated neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to EM and to two spatial dimensi...

  16. Introducing Nuclear Data Evaluations of Prompt Fission Neutron Spectra

    Energy Technology Data Exchange (ETDEWEB)

    Neudecker, Denise [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-06-17

    Nuclear data evaluations provide recommended data sets for nuclear data applications such as reactor physics, stockpile stewardship or nuclear medicine. The evaluated data are often based on information from multiple experimental data sets and nuclear theory using statistical methods. Therefore, they are collaborative efforts of evaluators, theoreticians, experimentalists, benchmark experts, statisticians and application area scientists. In this talk, an introductions is given to the field of nuclear data evaluation at the specific example of a recent evaluation of the outgoing neutron energy spectrum emitted promptly after fission from 239Pu and induced by neutrons from thermal to 30 MeV.

  17. Feasibility study for creating spectrum changeable neutron calibration fields. Objective and test simulations of spectra for conceptual design

    Energy Technology Data Exchange (ETDEWEB)

    Saegusa, Jun; Tanimura, Yoshihiko; Yoshizawa, Michio; Yoshida, Makoto [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    Feasibility studies were made toward the built of the spectrum changeable neutron calibration fields with the Van-de-Graff accelerator in the Facility of Radiation Standards (FRS) in JAERI. The neutron fields are planed to have various energy spectra to calibrate neutron dosemeters under similar conditions to those in actual workplaces. The objectives and concepts of the fields are discussed, followed by the test simulation results of neutron spectra produced by simple arrangements of a target and moderators. (author)

  18. Neutron spectra in two beam ports of a TRIGA Mark III reactor with HEU fuel

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H. R.; Hernandez D, V. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Paredes G, L.; Aguilar, F., E-mail: fermineutron@yahoo.com [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico)

    2012-10-15

    Before to change the HEU for Leu fuel of the ININ's TRIGA Mark III nuclear reactor the neutron spectra were measured in two beam ports using 5 and 10 W. Measurements were carried out in a tangential and a radial beam port using a Bonner sphere spectrometer. It was found that neutron spectra are different in the beam ports, in radial beam port the amplitude of thermal and fast neutrons are approximately the same while, in the tangential beam port thermal neutron peak is dominant. In the radial beam port the fluence-to-ambient dose equivalent factors are 131{+-}11 and 124{+-}10 p Sv-cm{sup 2} for 5 and 10 W respectively while in the tangential beam port the fluence-to-ambient dose equivalent factor is 55{+-}4 p Sv-cm{sup 2} for 10 W. (Author)

  19. Manual for spktbib: A pc-based catalogue of neutron spectra

    Energy Technology Data Exchange (ETDEWEB)

    Naismith, O.F.; Siebert, B.R.L.

    1996-02-01

    The spectral fluence response of practicable neutron dosemeters for routine use generally does not match the energy dependence of radiation protection quantities such as the ambient dose equivalent H(star)(10). As a consequence, significant errors may be encountered when monitoring in a neutron energy spectrum different from that in which the dosemeter has been calibrated. A collaborative CEC-supported project has been undertaken to develop new neutron calibration fields with energy spectra similar to those found in the working environment. As a first step, a database of neutron spectra and instrument and dosimetric response functions has been prepared. A program package has been developed to assist the collection and manipulation of these data. The features of the programs are described and examples for dosimetric applications are given. This report constitutes an instruction manual for the package.

  20. Manual for SPKTBIB: a PC-based catalogue of neutron spectra

    Energy Technology Data Exchange (ETDEWEB)

    Siebert, B.R.L. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Naismith, O.F.

    1996-02-01

    The spectral fluence response of practicable neutron dosemeters for routine use generally does not match the energy dependence of radiation protection quantities such as the ambient dose equivalent H*(10). As a consequence, significant errors may be encountered when monitoring in a neutron energy spectrum different from that in which the dosemeter has been calibrated. A collaborative CEC-supported project has been undertaken to develop new neutron calibration fields with energy spectra similar to those found in the working environment. As a first step, a database of neutron spectra and instrument and dosimetric response functions has been prepared. A program package has been developed to assist the collection and manipulation of these data. The features of the programs are described and examples for dosimetric applications are given. This report constitutes an instruction manual for the package. (Author).

  1. Measurement of the Surface and Underground Neutron Spectra with the UMD/NIST Fast Neutron Spectrometers

    Science.gov (United States)

    Langford, Thomas J.

    The typical fast neutron detector falls into one of two categories, Bonner sphere spectrometers and liquid scintillator proton recoil detectors. These two detector types have traditionally been used to measure fast neutrons at the surface and in low background environments. The cosmogenic neutron spectrum and flux is an important parameter for a number of experimental efforts, including procurement of low background materials and the prediction of electronic device faults. Fast neutrons can also cause problems for underground low-background experiments, through material activation or signals that mimic rare events. Current detector technology is not sufficient to properly characterize these backgrounds. To this end, the University of Maryland and the National Institute of Standards and Technology designed, developed, and deployed two Fast Neutron Spectrometers (FaNS) comprised of plastic scintillator and 3He proportional counters. The detectors are based upon capture-gated spectroscopy, a technique that demands a delayed coincidence between a neutron scatter and the resulting neutron capture after thermalization. This technique provides both particle identification and knowledge that the detected neutron fully thermalized. This improves background rejection capabilities and energy resolution. Presented are the design, development, and deployment of FaNS-1 and FaNS-2. Both detectors were characterized using standard fields at NIST, including calibrated 252Cf neutron sources and two monoenergetic neutron generators. Measurements of the surface fast neutron spectrum and flux have been made with both detectors, which are compared with previous measurements by traditional detectors. Additionally, FaNS-1 was deployed at the Kimballton Underground Research Facility (KURF) in Ripplemead, VA. A measurement of the fast neutron spectrum and flux at KURF is presented as well. FaNS-2 is currently installed in a shallow underground laboratory where it is measuring the muon

  2. Measurement of leakage neutron spectra from silicon carbide cylinders with D–T neutrons and validation of evaluated nuclear data

    Energy Technology Data Exchange (ETDEWEB)

    Luo, F. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Han, R. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Key Laboratory of Nuclear Data, China Institute of Atomic Energy, Beijing 102413 (China); Nie, Y. [Key Laboratory of Nuclear Data, China Institute of Atomic Energy, Beijing 102413 (China); Chen, Z., E-mail: zqchen@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhang, S. [College of Physics Electronic Information, Inner Mongolia University for the Nationalities, Tongliao 028000 (China); Shi, F.; Lin, W.; Ren, P.; Tian, G.; Sun, Q.; Gou, B. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Ruan, X.; Ren, J. [Key Laboratory of Nuclear Data, China Institute of Atomic Energy, Beijing 102413 (China); Ye, M. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China)

    2016-11-15

    Highlights: • Evaluated data for SiC are validated by a high precision benchmark experiment. • Leakage neutron spectra from SiC cylinders are measured at 60° and 120° using time-of-flight method. • The experimental results are compared with the MCNP-4C calculations with ENDF-BVII.1, JENDL-4.0 and CENDL-3.1 libraries. • The SiC evaluated nuclear data from CENDL-3.1 library was checked for the first time and proved to be reliable. - Abstract: Benchmarking of evaluated nuclear data libraries was performed for 14 MeV neutrons on silicon carbide samples. The experiments were carried out by using the benchmark experimental facility at China Institute of Atomic Energy (CIAE). The leakage neutron spectra from SiC (Φ13 cm × 20 cm) at 60° and 120° and SiC (Φ13 cm × 2 cm) at 60° were measured by the TOF method. The measured spectra are well reproduced by MCNP-4C calculations with the CENDL-3.1, ENDF/B-VII.1 and JENDL-4.0 evaluated nuclear data libraries, except 5–8 MeV range for 20 cm thickness. The discrepancies are mostly considered as caused by the improper evaluation of the angular distribution and secondary neutron energy distribution of the elastic scattering and inelastic scattering in evaluated nuclear data libraries.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kry, Stephen F.; Howell, Rebecca M.; Salehpour, Mohammad; Followill, David S. [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States)

    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

  4. Conclusions from the image analysis of the VSOP Survey

    OpenAIRE

    Dodson, R.; Fomalont, E.; Wiik, K.

    2009-01-01

    In February 1997, the Japanese radio astronomy satellite HALCA was launched to provide the space-bourne element for the VLBI Space Observatory Programme (VSOP) mission. A significant fraction of the mission time was to be dedicated to the VSOP Survey of bright compact Active Galactic Nuclei (AGN) at 5 GHz, which was lead by ISAS. The VSOP Survey Sources are an unbiased dataset of 294 targets, of which 82% were successfully observed. These are now undergoing statistical analysis to tease out t...

  5. Neutron spectra measurement and comparison of the HFR and THOR BNCT beams.

    Science.gov (United States)

    Liu, Yuan-Hao; Nievaart, Sander; Tsai, Pi-En; Liu, Hong-Ming; Moss, Ray; Jiang, Shiang-Huei

    2009-07-01

    This paper aims to measure the spectra of HB11 (high flux reactor, HFR) and the Tsing Hua open-pool reactor (THOR) boron neutron capture therapy (BNCT) beams by multiple activation foils. The self-shielding corrections were made with the aid of MCNP calculations. The initial spectra were adjusted by a sophisticated process named coarse-scaling adjustment using SAND-EX, which can adjust a given coarse-group spectrum into a fine-group structure, i.e. 640 groups, with excellent continuity. The epithermal neutron flux of the THOR beam is about three times of HB11. The thermal neutron flux, boron and gold reaction rates along the central axis of a PMMA phantom are calculated for both adjusted spectra for comparison.

  6. 239Pu Prompt Fission Neutron Spectra Impact on a Set of Criticality and Experimental Reactor Benchmarks

    Science.gov (United States)

    Peneliau, Y.; Litaize, O.; Archier, P.; De Saint Jean, C.

    2014-04-01

    A large set of nuclear data are investigated to improve the calculation predictions of the new neutron transport simulation codes. With the next generation of nuclear power plants (GEN IV projects), one expects to reduce the calculated uncertainties which are mainly coming from nuclear data and are still very important, before taking into account integral information in the adjustment process. In France, future nuclear power plant concepts will probably use MOX fuel, either in Sodium Fast Reactors or in Gas Cooled Fast Reactors. Consequently, the knowledge of 239Pu cross sections and other nuclear data is crucial issue in order to reduce these sources of uncertainty. The Prompt Fission Neutron Spectra (PFNS) for 239Pu are part of these relevant data (an IAEA working group is even dedicated to PFNS) and the work presented here deals with this particular topic. The main international data files (i.e. JEFF-3.1.1, ENDF/B-VII.0, JENDL-4.0, BRC-2009) have been considered and compared with two different spectra, coming from the works of Maslov and Kornilov respectively. The spectra are first compared by calculating their mathematical moments in order to characterize them. Then, a reference calculation using the whole JEFF-3.1.1 evaluation file is performed and compared with another calculation performed with a new evaluation file, in which the data block containing the fission spectra (MF=5, MT=18) is replaced by the investigated spectra (one for each evaluation). A set of benchmarks is used to analyze the effects of PFNS, covering criticality cases and mock-up cases in various neutron flux spectra (thermal, intermediate, and fast flux spectra). Data coming from many ICSBEP experiments are used (PU-SOL-THERM, PU-MET-FAST, PU-MET-INTER and PU-MET-MIXED) and French mock-up experiments are also investigated (EOLE for thermal neutron flux spectrum and MASURCA for fast neutron flux spectrum). This study shows that many experiments and neutron parameters are very sensitive to

  7. V.S.O.P.(97) computer code system for reactor physics and fuel cycle simulation. Input manual and comments

    Energy Technology Data Exchange (ETDEWEB)

    Ruetten, H.J.; Haas, K.A.; Brockmann, H.; Ohlig, U.; Scherer, W.

    1998-04-01

    V.S.O.P. (97) is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies processing of cross sections, the setup of the reactor and of the fuel element, repeated neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to HTRs and to two spatial dimensions. V.S.O.P. (97) can simulate the reactor operation from the initial core towards the equilibrium core. V.S.O.P. (97) - on the basis of V.S.O.P. (94) - has been improved with regard to a more detailed treatment of the build-up and the depletion of the heavy metal isotopes. Their chains now include the minor actinides. Resonance cross sections of the lumped resonance absorbers are evaluated burnup-dependent. Beyond this, the code has been reviewed in many details, aiming at an improved precision in the computer simulation of the features of the reactors and of their fuel cycle. The code consists of about 65000 FORTRAN statements. A memory of 32 MB should be available for its use. (orig.)

  8. V.S.O.P. (99) for WINDOWS and UNIX. Computer code system for reactor physics and fuel cycle simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ruetten, H.J.; Haas, K.A.; Brockmann, H.; Ohlig, U.; Scherer, W.

    2000-10-01

    V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of the reactor and of the fuel element, processing of cross sections, neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to HTRs and to two spatial dimensions. The code can simulate the reactor operation from the initial core towards the equilibrium core. V.S.O.P.(99) represents the further development of V.S.O.P. (97). Compared to its precursor, the code system has been improved in many details. Major extensions have been included concerning the thermal hydraulic sections. Beyond that, the many modules of the code-system have been condensed to only 2 executables in the ''99''-release of V.S.O.P., to be comfortably handled on a WINDOWS-PC or a UNIX-computer. The necessary data input as well as the handling and book-keeping of intermediate data sets has been condensed and simplified. A 64 MB memory should be available for the execution of the code. The hard disk requirement for the executables and the basic libraries associated with the code amounts to about 7 MB. (orig.)

  9. Neutron spectra and H(10) of photoneutrons inside the vault room of an 18 MV Linac

    Energy Technology Data Exchange (ETDEWEB)

    Banuelos F, A.; Borja H, C. G.; Guzman G, K. A.; Valero L, C.; Hernandez D, V. M.; Vega C, H. R., E-mail: lanb535@yahoo.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2012-06-15

    Neutron spectra and the ambient dose equivalent were estimated inside the radiotherapy hall with an 18 MV Linac. Estimations were carried out using Monte Carlo methods where a realist hall was modeled including a phantom made of equivalent tissue. The source term for photoneutrons was calculated using the Tosi et al. function that account for evaporation and knock-on neutrons. The spectra were estimated using two different energy distributions. Detectors were located in several sites inside the hall including the maze and outside the hall door, all detectors were located at the plane were the isocenter is located. In the treatment hall, as the distance respect to the isocenter is increased, the amount of neutrons and the H(10) are reduced, neutrons in the high-energy region are shifted to lower region peaking around 0.1 MeV, however the epithermal and thermal neutrons remain constant due to the room-return effect. In the maze the spectra are dominated by epithermal and thermal neutrons that contributes to produce activation and the production of prompt gamma-rays. (Author)

  10. Maser Astrometry with VERA and VSOP-2

    Science.gov (United States)

    Honma, M.; Bushimata, T.; Choi, Y. K.; Hirota, T.; Imai, H.; Iwadate, K.; Jike, T.; Kameno, S.; Kameya, O.; Kamohara, R.; Kawaguchi, N.; Kijima, M.; Kim, M.; Kobayashi, H.; Kuji, S.; Kurayama, T.; Manabe, S.; Matsui, M.; Matsumoto, N.; Miyaji, T.; Nagayama, T.; Nakagawa, A.; Nakamura, K.; Oh, C. S.; Omodaka, T.; Oyama, T.; Sakai, S.; Sato, K.; Sato, M.; Sasao, T.; Shibata, K. M.; Tamura, Y.; Yamashita, K.

    2009-08-01

    We present recent results of maser astrometry obtained with VERA (VLBI Exploration of Radio Astrometry), which is a Japanese VLBI array dedicated to phase-referencing astrometry to explore the 3-D structure of the Milky Way Galaxy. Since 2004 we have been conducting regular monitoring of maser sources with VERA, and we have already detected parallaxes for several sources, ranging from a few 100 pc to 5 kpc. These results include measurements for Galactic star-forming regions such as ORI-KL, S269, NGC 281 as well as those for late type stars such as VY CMa. We also discuss the VERA---VSOP-2 connection in the near future, and propose astrometric observations with VSOP-2.

  11. Analyzing neutron time-of-flight spectra from the National Ignition Facility using moments

    Science.gov (United States)

    Hatarik, R.; Field, J.; Eckart, M.; Grim, G.; Hartouni, E. P.; Moore, A.; Munro, D.; Sayre, D.

    2016-10-01

    The neutron spectrum produced by an indirectly driven implosion at the National Ignition Facility (NIF) provides valuable insight into the performance of the capsule. There are four neutron time-of-flight (nTOF) spectrometers being used at the NIF which can simultaneously measure DD and DT fusion neutrons on NIF shots. The width of theses peaks have been traditionally associated with the temperature of the plasma, recent work shows that it has to be considered a combination of flow and temperature distributions. This leads to a deviation from a pure gaussian shape of a single temperature static plasma and the presence of higher order moments in the neutron spectrum. The current status of the analysis of neutron spectra from the nTOF diagnostics at the NIF will be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  12. Analytic expression for epithermal neutron spectra amplitudes as a function of water content

    Science.gov (United States)

    Drake, Darrell

    1993-01-01

    The epithermal portion of an equilibrium neutron spectrum in a planetary body is a function of the water content of its material. The neutrons are produced at high energies but are moderated by elastic and inelastic scattering until they either are captured by surrounding nuclei or escape. We have derived an expression that explicitly shows the dependance of epithermal neutron spectra on water content. Additionally, we compared its predictions to calculations done by Boltzman transport code for infinite media for silicon, oxygen, and a possible lunar composition, and we have obtained very good agreement.

  13. A database of neutron spectra, instrument response functions, and dosimetric conversion factors for radiation protection applications

    Energy Technology Data Exchange (ETDEWEB)

    Naismith, O.F. [National Physical Lab., Teddington (United Kingdom); Siebert, B.R.L. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

    1997-09-01

    One of the major problems encountered in dose assessment for neutron radiation protection derives from the imperfect dose equivalent response of the devices used for monitoring. To investigate the performance of such devices in realistic neutron fields and to optimise calibration procedures, knowledge of both the prevalent spectral fluences and the energy response of the dosemeters is required. To facilitate this and similar studies, a database has been developed comprising a catalogue of neutron spectra and energy-dependent response functions together with a software package to manipulate the data in the catalogue. The range of data, features of the programs, and examples for radiation protection applications are described. (author).

  14. A fast and flexible reactor physics model for simulating neutron spectra and depletion in fast reactors

    Science.gov (United States)

    Recktenwald, Geoff; Deinert, Mark

    2010-03-01

    Determining the time dependent concentration of isotopes within a nuclear reactor core is central to the analysis of nuclear fuel cycles. We present a fast, flexible tool for determining the time dependent neutron spectrum within fast reactors. The code (VBUDS: visualization, burnup, depletion and spectra) uses a two region, multigroup collision probability model to simulate the energy dependent neutron flux and tracks the buildup and burnout of 24 actinides, as well as fission products. While originally developed for LWR simulations, the model is shown to produce fast reactor spectra that show high degree of fidelity to available fast reactor benchmarks.

  15. Calculation of prompt fission neutron spectra for 235U(n,f)

    Institute of Scientific and Technical Information of China (English)

    CHEN Yong-Jing; JIA Min; TAO Xi; QIAN Jing; LIU Ting-Jin; SHU Neng-Chuan

    2012-01-01

    The prompt fission neutron spectra for the neutron-induced fission of 235U at En < 5 MeV are calculated using nuclear evaporation theory with a semi-empirical model,in which the nonconstant and constant temperatures related to the Fermi gas model are taken into account. The calculated prompt fission neutron spectra reproduce the experimental data well.For the n(thermal)+235U reaction,the average nuclear temperature of the fission fragment,and the probability distribution of the nuclear temperature,are discussed and compared with the Los Alamos model.The energy carried away by γ rays emitted from each fragment is also obtained and the results are in good agreement with the existing experimental data.

  16. Computational and experimental studies of neutron spectra in the IGR reactor

    CERN Document Server

    Gorin, N V; Litvin, V I; Gajdajchuk, V A; Kazmin, Y M; Pakhnits, V A; Skivka, A S; Vasilev, A P; Pavshuk, V A; Rychev, A S

    2000-01-01

    The results of experiments made in order to determine spectral composition of neutrons in the IGR impulse graphite moderated reactor experimental channel at fuel temperature close to the room one are considered. The set of activation and fission detectors with half-life period more than 0.5 days is applied for the neutron spectrum measurements. The algorithm based on the directed divergence method is used for reconstruction of neutron energy spectra in energy range of 0.6 eV - 18 MeV. The results of calculational studies into the influence of impurities in structural materials on portion of thermal neutrons in he spectrum in the channel centre are discussed as well. The conclusion is made that the calculational results agree well with experimental data

  17. Delayed neutron spectra and their uncertainties in fission product summation calculations

    Energy Technology Data Exchange (ETDEWEB)

    Miyazono, T.; Sagisaka, M.; Ohta, H.; Oyamatsu, K.; Tamaki, M. [Nagoya Univ. (Japan)

    1997-03-01

    Uncertainties in delayed neutron summation calculations are evaluated with ENDF/B-VI for 50 fissioning systems. As the first step, uncertainty calculations are performed for the aggregate delayed neutron activity with the same approximate method as proposed previously for the decay heat uncertainty analyses. Typical uncertainty values are about 6-14% for {sup 238}U(F) and about 13-23% for {sup 243}Am(F) at cooling times 0.1-100 (s). These values are typically 2-3 times larger than those in decay heat at the same cooling times. For aggregate delayed neutron spectra, the uncertainties would be larger than those for the delayed neutron activity because much more information about the nuclear structure is still necessary. (author)

  18. Determination of the fast neutrons spectra by the Elastic scattering method (n, p); Determinacion del espectro de neutrones rapidos por el metodo de la dispersion elastica (n, p)

    Energy Technology Data Exchange (ETDEWEB)

    Elizalde D, J

    1973-07-01

    This work consists in determining the fast neutron spectra emitted by a Pu-Be isotopic source. The implemented technique is based in the spectrometry (n, p). This consists in making to fall on a fast neutrons beams (polyenergetic) over a thin film of hydrogenated material, detecting the spectra of emitted protons at a fix angle. The polyethylene film and the used solid state detector are inside of a vacuum chamber. The detector is placed at 30 degree with respect to direction of the incident neutrons beam. The protons spectra is stored in a multichannel. the energy is obtained with the prior calibration of the system. The data processing involves the transformation of the protons spectra observed at the falling on neutrons spectra over the film. The energy of the neutrons is related with that of the protons, according to the collision kinematical equations. The cross section of elastic collision of the neutrons with the hydrogen atoms is obtained from literature. Applying these relations to the observed spectra it is obtained the falling on neutron spectra over the film. (Author)

  19. New analytical planetary theories VSOP2013 and TOP2013

    Science.gov (United States)

    Simon, J.-L.; Francou, G.; Fienga, A.; Manche, H.

    2013-09-01

    Context. The development of precise numerical integrations of the motion of the planets, taking into account the most recent observations, lead us to improve the two families of analytical planetary theories built in the Institut de mécanique céleste et de calcul des éphémérides (IMCCE), the Variations Séculaires des Orbites Planétaires (VSOP) and the Theory of the Outer Planets (TOP) theories. Aims: We have built the solutions VSOP2010 and TOP2010 fitted to the Jet Propulsion Laboratory (JPL) numerical integration DE405 and the solutions VSOP2013 and TOP2013 fitted to the European recent numerical integration INPOP10a. This paper specifically considers VSOP2013 and TOP2013. Methods: We have improved the construction of VSOP by analytically computing the pertubations due to the asteroids and to Pluto. We have increased the precision of the VSOP solutions of Jupiter and Saturn by using TOP solutions. We have also improved the construction of TOP by computing the perturbations due to the telluric planets from VSOP solutions. Moreover, TOP contains a solution of the motion of the Pluto-Charon barycenter. Results: From 1890 to 2000, the precision of VSOP2013 goes from a few 0.01 mas (planets except Mars and Uranus) up to 0.7 mas (Mars and Uranus). Compared to the previous solution (VSOP2000), this represents an improvement of a factor of 2 to 24, depending on the planet. From -4000 to 8000, the precision is of a few 0.1″ for the telluric planets (1.6″ for Mars), i.e. an improvement of about a factor of 5 compared to VSOP2000. The TOP2013 solution is the best for the motion of the major planets from -4000 to 8000. Its precision is of a few 0.1″ for the four planets, i.e. a gain between 1.5 and 15, depending on the planet compared to VSOP2013. The precision of the theory of Pluto remains valid up to the time span from 0 to 4000. The VSOP2013 and TOP2013 data are available on the WEB server of the IMCCE. VSOP2013 and TOP2013 are available by ftp on: ftp://ftp.imcce.fr/pub/ephem/planets/vsop

  20. Unfolding neutron spectra with BS-TLD system using genetic algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Joelan A.L., E-mail: jasantos@cnen.gov.br [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear; Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Silva, Everton R. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Centro de Informatica; Ferreira, Tiago A.E. [Universidade Federal Rural de Pernambuco (UFRPE), Recife, PE (Brazil). Dept. de Estatistica e Informatica; Fonseca, Evaldo S. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Vilela, Eudice C., E-mail: ecvilela@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil)

    2011-07-01

    Due to the variability of neutron spectrum within the same environment, it is essential that the spectral distribution as function of energy to be characterized. To perform this task, the neutron spectrometer has a primary role in determining the neutron flux ({Phi}{sub E}(E)). Precise information allows radiological quantities establishment related to that spectrum but it is necessary, however, a series of steps with a spectrometric system that can cover a large interval of energy and whose answer is isotropic. The most widely used for accomplishing this task is the spectrometric Bonner spheres system. One of the biggest problems related to neutron spectrometry is the process of data analysis, known as unfolding. Most of the work undertaken to implement new techniques of this process, using data obtained with the scintillator {sup 6}LiI(I). However, characteristics related to the dead time make it not be so effective when used in high flow neutron fields. An alternative to this problem is the use of thermoluminescent detectors (TLD), but the codes used do not provide a more specific response matrix to unfolding the information obtained through these materials, which makes the development of a specific response matrix important to adequately characterize the response obtained by them. This paper proposes using a technique of artificial intelligence called genetic algorithm, which uses bio-inspired mathematical models and through the implementation of a specific matrix to unfolding data obtained from a combination of TLDs embedded in a system of Bonner spheres, such as thermal neutron detectors, to characterize the neutron spectrum as a function of energy. The results obtained with this method were in accordance with reference spectra, thus enables of this technique to unfolding neutrons spectra with BS-TLD system. (author)

  1. Importance of Compton scattering for radiation spectra of isolated neutron stars with weak magnetic fields

    CERN Document Server

    Suleimanov, V

    2007-01-01

    Emergent model spectra of neutron star atmospheres are widely used to fit the observed soft X-ray spectra of different types of isolated neutron stars. We investigate the effect of Compton scattering on the emergent spectra of hot (T_eff > 10^6 K) isolated neutron stars with weak magnetic fields. In order to compute model atmospheres in hydrostatic and radiative equilibrium we solve the radiation transfer equation with the Kompaneets operator. We calculate a set of models with effective temperatures in the range 1 - 5 * 10^6 K, with two values of surface gravity (log g = 13.9 and 14.3) and different chemical compositions. Radiation spectra computed with Compton scattering are softer than those computed without Compton scattering at high energies (E > 5 keV) for light elements (H or He) model atmospheres. The Compton effect is more significant in H model atmospheres and models with low surface gravity. The emergent spectra of the hottest (T_eff > 3 * 10^6 K) model atmospheres can be described by diluted blackb...

  2. Investigating different analytical procedures to unfold neutron energy spectra, using HEPRO software to compare existing algorithms

    CERN Document Server

    Moghimzadeh Mohebi, A

    1999-01-01

    A system of programs is described which can be used for unfolding particle spectra from measured pulse height distribution, provided the corresponding response functions are known. There are two reasons for re-opening the question of unfolding: to discuss the properties of several unfolding algorithms and to describe a system of programs developed in the past to unfold neutron spectra. In the first part, least squares algorithms known from literature are described and discussed together with the MIEKE Monte Carlo unfolding code. The second part contains a detailed description of the codes, which are available on a diskette. In the discussion of examples it is shown that the MIEKE Monte Carlo code is well suited for unfolding neutron and photon induced pulse height distributions. For the resulting particle spectra a consistent uncertainty analysis can be performed.

  3. Theoretical description of prompt fission neutron multiplicity and spectra

    CERN Document Server

    Manailescu, Cristian

    2014-01-01

    The present work concerns two successful models used today: Point by Point (PbP) and the Monte Carlo approaches. The description of the PbP model and of the extended Los Alamos model for higher energies that takes into account the secondary chains and ways is given in Chapter II. In this chapter are given also examples of PbP and most probable fragmentation approach calculations for various quantities which characterize prompt emission: multi-parametric matrices, quantities as a function of fragment mass, quantities as a function of the TKE and total average quantities, for different spontaneous and neutron induced fissioning systems. Special care was given to the TXE partition between the fully accelerated fission fragments, two partition methods used in the PbP model being discussed in details. In Chapter III is given the description of the Monte Carlo treatment included in the FIFRELIN code. Only those aspects that differ from the PbP treatment are emphasized. A special attention is given to the latest dev...

  4. Space VLBI Polarimetry of IDV Sources: Lessons from VSOP and Prospects for VSOP-2

    Science.gov (United States)

    Bach, U.; Krichbaum, T. P.; Bernhart, S.; Impellizzeri, C. M. V.; Kraus, A.; Fuhrmann, L.; Witzel, A.; Zensus, J. A.

    2009-08-01

    To locate and image the compact emission regions in quasars, which are closely connected to the phenomenon of IntraDay Variability (IDV), space VLBI observations are of prime importance. Here we report on VSOP observations of a prominent IDV source, the BL Lac objects S5 0716+714. To monitor their short term variability, these sources were observed with VSOP at 5 GHz in several polarisation sensitive experiments, separated in time by one day to six days, in autumn 2000. Contemporaneous flux density measurements with the Effelsberg 100 m radio telescope were used to directly compare the single dish IDV with changes of the VLBI images. A clear IDV behaviour in total intensity and linear polarization was observed in 0716+714. Analysis of the VLBI data shows that the variations are located inside the VLBI core component of 0716+714. In good agreement with the single-dish measurements, the VLBI ground array images and the VSOP images, both show a decrease in the total flux density of ˜20 mJy and a drop of ˜5 mJy in the linear polarization of the VLBI core. No variability was found in the jet. These findings are supported by VLBA observations of five IDV sources, including 0716+714, in December 2000, that show a similar behaviour. From the variability timescales we estimate a source size of a few micro-arcseconds and brightness temperatures exceeding 1015 K. Independent of whether the interpretation of the IDV seen in the VLBI core is source intrinsic or extrinsic a lower limit of TB > 2×1012 K is obtained by model fitting of the VLBI-core. Our results show that future VSOP2 observations should be accompanied by a single dish monitoring not only to discriminate between source-extrinsic (interstellar scintillation) and source-intrinsic effects but to allow also a proper calibration and interpretation of ultra-high resolution VSOP2 images.

  5. Astrometric Determination of VSOP-2 Orbital Parameters

    Science.gov (United States)

    Fomalont, E.; Moellenbrock, G.; Claussen, M.

    2009-08-01

    VSOP-2 phase referencing, needed to image faint sources and to determine accurate positions, will require an orbit accuracy of about 2 cm at 23 GHz. This accuracy, however, may not be obtainable by direct orbital measurements. We propose an observation scheme, similar to that used at the VLBA, to be included during a phase referencing observation of about one orbit in order to determine a more accurate orbit determination. We show the effects of orbit errors, explain the suggested observations and reduction methods, and discuss the potential problems that might impede the use of this technique.

  6. Effects of Magnetic Field Topology on Secondary Neutron Spectra in MagLIF

    Science.gov (United States)

    Appelbe, Brian; Chittenden, Jeremy

    2015-11-01

    Ignition in Magneto-Inertial Fusion schemes requires both inertial and magnetic confinement of the fuel and charged fusion products. Recent theoretical and experimental work has demonstrated the confinement of charged fusion products by magnetic fields in Magnetized Liner Inertial Fusion (MagLIF) experiments. This confinement can be inferred from the ratio of secondary to primary neutron yields and the shape of secondary neutron spectra. In this work we investigate the effects of magnetic field topology on the shape of secondary neutron spectra. The MagLIF design has a cylindrical geometry and includes both axial and azimuthal magnetic fields. The azimuthal field is initially in the liner surrounding the fuel but instability growth may cause it to penetrate into the fuel. Charged fusion products (such as tritons or alpha particles) that are isotropically emitted and then confined by an axial field will flow parallel and anti-parallel to the field with equal intensities. In the case of tritons, this motion results in a secondary neutron spectrum emitted in the axial direction that is symmetric. However, in an azimuthal field such particles exhibit singular orbits and there is a net ion drift along the axis. This ion drift can cause the secondary neutron spectrum to be asymmetric. We examine the effects on the spectrum shape of confinement by a combination of axial and azimuthal fields.

  7. In-phantom spectra and dose distributions from a high-energy neutron therapy beam

    Energy Technology Data Exchange (ETDEWEB)

    Benck, S. E-mail: benck@fynu.ucl.ac.be; D' Errico, F.; Denis, J.-M.; Meulders, J.-P.; Nath, R.; Pitcher, E.J

    2002-01-01

    In radiotherapy with external beams, healthy tissues surrounding the target volumes are inevitably irradiated. In the case of neutron therapy, the estimation of dose to the organs surrounding the target volume is particularly challenging, because of the varying contributions from primary and secondary neutrons and photons of different energies. The neutron doses to tissues surrounding the target volume at the Louvain-la-Neuve (LLN) facility were investigated in this work. At LLN, primary neutrons have a broad spectrum with a mean energy of about 30 MeV. The transport of a 10x10 cm{sup 2} beam through a water phantom was simulated by means of the Monte Carlo code MCNPX. Distributions of energy-differential values of neutron fluence, kerma and kerma equivalent were estimated at different locations in a water phantom. The evolution of neutron dose and dose equivalent inside the phantom was deduced. Measurements of absorbed dose and of dose equivalent were then carried out in a water phantom using an ionization chamber and superheated drop detectors (SDDs). On the beam axis, the calculations agreed well with the ionization chamber data, but disagreed significantly from the SDD data due to the detector's under-response to neutrons above 20 MeV. Off the beam axis, the calculated absorbed doses were significantly lower than the ionization chamber readings, since gamma fields were not accounted for. The calculated data are doses from neutron-induced charge particles, and these agreed with the values measured by the photon-insensitive SDDs. When exposed to the degraded spectra off the beam axis, the SDD offered reliable estimates of the neutron dose equivalent.

  8. Neutron Generation from Laser-Accelerated Ion Beams: Use of Alternative Deuteron-Rich Targets for Improved Neutron Yield and Control of Neutron Spectra

    Science.gov (United States)

    Albright, B. J.; Yin, L.; Favalli, A.

    2016-10-01

    Laser-ion-beam generation in the break-out afterburner (BOA) acceleration regime has been modeled for several deuteron-rich solid-density targets using the VPIC particle-in-cell code. Monte Carlo modeling of the transport of these beams in a beryllium converter in a pitcher-catcher neutron source configuration shows significant increases in neutron yields may be achievable through judicious choices of laser target material. Additionally, species-separation dynamics in some target materials during the BOA ion acceleration phase can be exploited to control the shapes of the neutron spectra. Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. Funding provided by the Los Alamos National Laboratory Directed Research and Development Program.

  9. Analysis of accelerator based neutron spectra for BNCT using proton recoil spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wielopolski, L.; Ludewig, H.; Powell, J.R.; Raparia, D.; Alessi, J.G.; Lowenstein, D.I.

    1999-03-01

    Boron Neutron Capture Therapy (BNCT) is a promising binary treatment modality for high-grade primary brain tumors (glioblastoma multiforme, GM) and other cancers. BNCT employs a boron-10 containing compound that preferentially accumulates in the cancer cells in the brain. Upon neutron capture by {sup 10}B energetic alpha particles and triton released at the absorption site kill the cancer cell. In order to gain penetration depth in the brain Fairchild proposed, for this purpose, the use of energetic epithermal neutrons at about 10 keV. Phase 1/2 clinical trials of BNCT for GM are underway at the Brookhaven Medical Research Reactor (BMRR) and at the MIT Reactor, using these nuclear reactors as the source for epithermal neutrons. In light of the limitations of new reactor installations, e.g. cost, safety and licensing, and limited capability for modulating the reactor based neutron beam energy spectra, alternative neutron sources are being contemplated for wider implementation of this modality in a hospital environment. For example, accelerator based neutron sources offer the possibility of tailoring the neutron beams, in terms of improved depth-dose distributions, to the individual and offer, with relative ease, the capability of modifying the neutron beam energy and port size. In previous work new concepts for compact accelerator/target configuration were published. In this work, using the Van de Graaff accelerator the authors have explored different materials for filtering and reflecting neutron beams produced by irradiating a thick Li target with 1.8 to 2.5 MeV proton beams. However, since the yield and the maximum neutron energy emerging from the Li-7(p,n)Be-7 reaction increase with increase in the proton beam energy, there is a need for optimization of the proton energy versus filter and shielding requirements to obtain the desired epithermal neutron beam. The MCNP-4A computer code was used for the initial design studies that were verified with benchmark

  10. ANALYSIS OF ACCELERATOR BASED NEUTRON SPECTRA FOR BNCT USING PROTON RECOIL SPECTROSCOPY

    Energy Technology Data Exchange (ETDEWEB)

    WIELOPOLSKI,L.; LUDEWIG,H.; POWELL,J.R.; RAPARIA,D.; ALESSI,J.G.; LOWENSTEIN,D.I.

    1998-11-06

    Boron Neutron Capture Therapy (BNCT) is a promising binary treatment modality for high-grade primary brain tumors (glioblastoma multiforme, GM) and other cancers. BNCT employs a boron-10 containing compound that preferentially accumulates in the cancer cells in the brain. Upon neutron capture by {sup 10}B energetic alpha particles and triton released at the absorption site kill the cancer cell. In order to gain penetration depth in the brain Fairchild proposed, for this purpose, the use of energetic epithermal neutrons at about 10 keV. Phase I/II clinical trials of BNCT for GM are underway at the Brookhaven Medical Research Reactor (BMRR) and at the MIT Reactor, using these nuclear reactors as the source for epithermal neutrons. In light of the limitations of new reactor installations, e.g. cost, safety and licensing, and limited capability for modulating the reactor based neutron beam energy spectra alternative neutron sources are being contemplated for wider implementation of this modality in a hospital environment. For example, accelerator based neutron sources offer the possibility of tailoring the neutron beams, in terms of improved depth-dose distributions, to the individual and offer, with relative ease, the capability of modifying the neutron beam energy and port size. In previous work new concepts for compact accelerator/target configuration were published. In this work, using the Van de Graaff accelerator the authors have explored different materials for filtering and reflecting neutron beams produced by irradiating a thick Li target with 1.8 to 2.5 MeV proton beams. However, since the yield and the maximum neutron energy emerging from the Li-7(p,n)Be-7 reaction increase with increase in the proton beam energy, there is a need for optimization of the proton energy versus filter and shielding requirements to obtain the desired epithermal neutron beam. The MCNP-4A computer code was used for the initial design studies that were verified with benchmark

  11. VSOP-2 Antenna and its Structure

    Science.gov (United States)

    Higuchi, K.; Kishimoto, N.; Mizuno, T.; Kawahara, K.; Tachikawa, S.; Murata, Y.; Tsuboi, M.; Ogawa, H.; Kimura, S.; Ujihara, H.; Meguro, A.; Tanaka, H.; Yoshihara, M.; Iikura, S.

    2009-08-01

    To achieve scientific improvements from VSOP (HALCA) to VSOP-2 (ASTRO-G), the satellite design incorporates the engineering characteristics of a large-scale deployable antenna of offset Cassegrain type with observation bands of 8, 22, and 43 GHz. The antenna subsystem requires the surface accuracy of 0.4mm RMS on the main reflector named LDR (Large-scale Deployable Reflector) of about 9m in diameter. An off-axis paraboloid reflector is adopted to achieve this surface accuracy for millimeter-wave observation. The main reflector is composed of seven deployable modular antennas, and each of the modules employs a new idea of radial-rib/hoop-cable reflector construction to stretch metal mesh and to satisfy the required surface accuracy. The deployment mechanism employs most of the LDR technology developed for JAXA's ETS-VIII satellite, which was launched in December 2006, and both of the two antennas on the ETS-VIII deployed successfully on orbit. Some prototype models of one module have been made to investigate the surface accuracy. In addition, the antenna will have a two-axis adjustment mechanism for the main reflector, and a three-axis adjustment mechanism for the sub-reflector in order to optimize the antenna gain after deployment in orbit.

  12. Spectra of photons and neutrons generated in a heterogeneous head of a 15 MV LINAC at differents field sizes

    Energy Technology Data Exchange (ETDEWEB)

    Benites-Rengifo, J. L.; Vega-Carrillo, H. R.; Velazquez-Fernandez, J. B. [Posgrado en CBAP, Universidad Autonoma de Nayarit, Carretera Tepic-Compostela km 9. C.P. 63780. Xalisco, Nayarit (Mexico); Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Apdo. Postal 336, 98000 Zacatecas, Zac. (Mexico); Posgrado en CBAP, Universidad Autonoma de Nayarit, Carretera Tepic-Compostela km 9. C.P. 63780. Xalisco, Nayarit (Mexico)

    2012-10-23

    Spectra of photons and neutrons were calculated, using the Monte Carlo code MCNP-5 using the e/p/n mode. A heterogeneous model was used to define the linac head where the collimators were modeled to produce five different treatment fields at the isocenter. Photon and neutron spectra were estimated in several points along two directions from the isocenter. The total photon fluence beyond 60 cm behaves according to 1/r{sup 2} rule, while total neutron fluence, beyond 80 cm, can be described by diffusion theory using an infinite plane as a neutron source.

  13. A VLBA Upgrade Conforming to VSOP-2 Specifications

    Science.gov (United States)

    Romney, J. D.

    2009-08-01

    The VLBA was a major participant in the original VSOP mission. NRAO hopes to play a similar role in the VSOP-2 mission, if commensurate support can be obtained for VLBA operations in such a collaboration. While the VLBA's original data system is not compatible with the planned VSOP-2 specifications, the current VLBA Sensitivity Upgrade project will produce a new system that is well-matched to VSOP-2. This upgrade involves replacement of the entire data path downstream from the IFs, and includes a digital sub-band processor, a wideband recording system, and a software correlator. The project's goal is to achieve sustained 4-Gbps operation by 2011, with wideband operation available much earlier for the most scientifically compelling observations. These goals appear to be well matched to the VSOP-2 timeline. This paper presents an overview of the new systems under development, and compares the capabilities of each to the requirements for VSOP-2. Further topics include adaptation of the entire system, and the correlator in particular, to Space VLBI operations, and upgrade aspects that should minimize the data-format incompatibilities that were a substantial difficulty in the first VSOP mission.

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

    Energy Technology Data Exchange (ETDEWEB)

    Atanackovic, Jovica, E-mail: atanacjz@gmail.com [Ontario Power Generation, Whitby, ON, Canada L1N 9E3 (Canada); Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Canada K0J 1J0 (Canada); Matysiak, Witold [University of Florida Proton Therapy Institute, Jacksonville, FL 32206 (United States); Dubeau, Jacques; Witharana, Sampath [DETEC, Gatineau, QC, Canada J8T 4J1 (Canada); Waker, Anthony [University of Ontario Institute of Technology, Oshawa, ON, Canada L1H 7K4 (Canada)

    2015-02-21

    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 {sup 7}Li(p,n){sup 7}Be 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 50μg/cm{sup 2}, which corresponds to the linear thickness of 0.19μm 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.

  15. Study of d-t neutron energy spectra at JET using natural diamond detectors

    CERN Document Server

    Krasilnikov, A V; Belle, P V; Jarvis, O N; Sadler, G J

    2002-01-01

    Four natural diamond detectors (NDDs) have been used for deuterium-tritium neutron spectrometry and flux monitoring during the 1997 tritium experiments (DTE1) carried out in the Joint European Torus (JET). Neutron energy spectra have been measured with three NDDs for discharge scenarios that included (a) hot ion H-mode studies using combined neutral-beam (NB) and ion cyclotron resonance frequency (ICRF) heating, (b) optimized shear experiments using combined NB and ICRF heating, (c) alpha-particles heating experiments with NB heating only and (d) ICRF heating studies without NB heating. Within the statistical accuracy of the data, the spectra can be adequately represented by Gaussian distributions, whose fwhm values provide effective ion temperatures that characterize the energy distributions of the ions taking part in fusion reactions.

  16. Conclusions from the Image Analysis of the VSOP Survey

    Science.gov (United States)

    Dodson, R.; Fomalont, E.; Wiik, K.

    2009-08-01

    In February 1997, the Japanese radio astronomy satellite HALCA was launched to provide the space-bourne element for the VLBI Space Observatory Programme (VSOP) mission. A significant fraction of the mission time was to be dedicated to the VSOP Survey of bright compact Active Galactic Nuclei (AGN) at 5 GHz, which was lead by ISAS. The VSOP Survey Sources are an unbiased dataset of 294 targets, of which 82% were successfully observed. These are now undergoing statistical analysis to tease out the characteristics of typical AGN sources. We present here the summary of the imaging and conclusions we have reached.

  17. Theory of multipolar excitations and neutron scattering spectra of CeB{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Shiina, R [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan); Shiba, H [Department of Physics, Kobe University, Kobe 657-8501 (Japan); Thalmeier, P [Max-Planck-Institut fuer Chemische Physik fester Stoffe, 01187 Dresden (Germany); Takahashi, A [Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551 (Japan); Sakai, O [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan)

    2003-07-23

    Multipolar excitations in the antiferroquadrupolar ordering phase of CeB{sub 6} are studied theoretically. We develop the method of boson expansion of multipoles, and apply it to the Ruderman-Kittel-Kasuya-Yosida model, which has been introduced previously for CeB{sub 6}. Then the neutron scattering spectra are calculated within the dipole approximation and compared with experimental results obtained by Bouvet. The origin of the characteristic peak structures and their dependence on the magnetic field are discussed.

  18. The study of neutron spectra in water bath from Pb target irradiated by 250MeV/u protons

    CERN Document Server

    Li, Yanyan; Ju, Yongqin; Ma, Fei; Zhang, Hongbin; Chen, Liang; Ge, Honglin; Luo, Peng; Zhou, Bin; Zhang, Yanbin; Li, Jianyang; Xu, Junkui; Wang, Songlin; Yang, Yongwei; Yang, Lei

    2014-01-01

    The spallation neutrons were produced by the irradiation of Pb with 250 MeV protons. The Pb target was surrounded by water which was used to slow down the emitted neutrons. The moderated neutrons in the water bath were measured by using the resonance detectors of Au, Mn and In with Cd cover. According to the measured activities of the foils, the neutron flux at different resonance energy were deduced and the epithermal neutron spectra were proposed. Corresponding results calculated with the Monte Carlo code MCNPX were compared with the experimental data to check the validity of the code.

  19. Experimental studies of neutron emission spectra in Li(d,xn) reactions for IFMIF

    Energy Technology Data Exchange (ETDEWEB)

    Hagiwara, Masayuki, E-mail: hagi@post.kek.jp [Cyclotron and Radioisotope Center, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Radiation Science Center, High Energy Accelerator Research Organization (KEK), Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan); Itoga, Toshiro, E-mail: itoga@spring8.or.jp [Cyclotron and Radioisotope Center, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Oishi, Takuji, E-mail: oishi.takuji@canon.co.jp [Cyclotron and Radioisotope Center, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Baba, Mamoru [Cyclotron and Radioisotope Center, Tohoku University, Aoba 6-3, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan)

    2011-10-01

    To improve the accuracy of the neutron emission data in the {sup nat}Li(d,xn) reaction, which will be used as the neutron source in the International Fusion Materials Irradiation Facility (IFMIF), we measured the double-differential neutron emission cross-sections (DDXs) of the d-Li reaction at 25 MeV at the cyclotron facility of Tohoku University. The DDXs were measured at ten laboratory angles between 0{sup o} and 110{sup o} by the time-of-flight method, using a beam-swinger system and a well-collimated neutron flight channel. We used a two-gain method to obtain over most of the energy range of secondary neutrons and reveal the shape of the overall emission spectra including the breakup peak of incident deuterons near half the incidence energy, and several peaks in the high-energy tail due to stripping reactions. The experimental results compared favorably with those obtained using the extended Serber model.

  20. Nuclei of galaxies seen by VSOP; VSOP ga toraeru ginga no chushinkaku

    Energy Technology Data Exchange (ETDEWEB)

    Hirabayashi, H. [Institute of the Space and Astronautical Science,Tokyo (Japan)

    1999-11-05

    Outlined herein is the VSOP (VLBI space observatory programme using superlarge radio telescopes, centered by radio astronomic satellite). VLBI (very long baseline interferometry) is a method for observation by antennas installed on a global scale. Space VLBI uses aerospace devices to improve resolution of VLBI. The interference tests were successfully conducted in 1997 between the radio astronomic satellite (Haruka) and ground antennas. The photo-taking tests were also succeeded in the same year, and the scientific observation has been conducted every day since then. The improvement of resolution is aimed at elucidation of activities at the radio galaxy and quasar centers. Haruka and VLBA have jointly observed an ellipsoidal galaxy M87, to clarify that the jets released therefrom draw a helix with a pitch of about a light-year. They also discover X-ray emitted from a rotational disk, several times larger than a black hole, in an active galaxy. VSOP observes that a quasar has a brightness of 10 trillion degrees C. VSOP can observe orientation of a magnetic field, and deformed heavenly body shape accurately. (NEDO)

  1. Space VLBI polarimetry of IDV sources: Lessons from VSOP and prospects for VSOP2

    CERN Document Server

    Bach, U; Bernhart, S; Impellizzeri, C M V; Kraus, A; Fuhrmann, L; Witzel, A; Zensus, J A

    2008-01-01

    To locate and image the compact emission regions in quasars, which are closely connected to the phenomenon of IntraDay Variability (IDV), space VLBI observations are of prime importance. Here we report on VSOP observations of two prominent IDV sources, the BL Lac objects S5 0716+714. To monitor their short term variability, these sources were observed with VSOP at 5 GHz in several polarisation sensitive experiments, separated in time by one day to six days, in autumn 2000. Contemporaneous flux density measurements with the Effelsberg 100m radio telescope were used to directly compare the single dish IDV with changes of the VLBI images. A clear IDV behaviour in total intensity and linear polarization was observed in 0716+714. Analysis of the VLBI data shows that the variations are located inside the VLBI core component of 0716+714. In good agreement with the single-dish measurements, the VLBI ground array images and the VSOP images, both show a decrease in the total flux density of ~20 mJy and a drop of ~5 mJy...

  2. V.S.O.P. (99/05) Computer Code System : computer code system for reactor physics and fuel cycle simulation

    OpenAIRE

    Scherer, W.; Brockmann, H.; Haas, K. A.; Rütten, H. J.

    2005-01-01

    V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of the reactor and of the fuel element, processing of cross sections, neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to HTRs and to two spatial dimensions. The...

  3. Uranium and Plutonium Average Prompt-fission Neutron Energy Spectra (PFNS) from the Analysis of NTS NUEX Data

    Science.gov (United States)

    Lestone, J. P.; Shores, E. F.

    2014-05-01

    In neutron experiments (NUEX) conducted at the Nevada Test Site (NTS) by Los Alamos National Laboratory, the time-of-flight of fission-neutrons emitted from nuclear tests were observed by measuring the current generated by the collection of protons scattered from a thin CH2 foil many meters from the nuclear device into a Faraday cup. The time dependence of the Faraday cup current is a measure of the energy spectrum of the neutrons that leak from the device. With good device models and accurate neutron-transport codes, the leakage spectra can be converted into prompt fast-neutron-induced fission-neutron energy spectra. This has been done for two events containing plutonium, and for an earlier event containing uranium. The prompt-fission neutron spectra have been inferred for 1.5-MeV 239Pu(n,f) and 235U(n,f) reactions for outgoing neutron energies from 1.5 to ∼10.5 MeV, in 1-MeV steps. These spectra are in good agreement with the Los Alamos fission model.

  4. A Complete Set of VSOP Observations of 3C279

    Science.gov (United States)

    Pant, N. D.; Piner, B. G.; Edwards, P. G.; Hirabayashi, H.; Wehrle, A. E.; Unwin, S. C.

    2009-08-01

    We have compiled a complete set of VSOP observations of 3C279, consisting of eight 5 GHz, and six 1.6 GHz, VSOP observations, all of which include the VLBA in the ground array. We are using the data-set to determine brightness temperature limits from model-fits to the visibilities, the transverse structure of the jet over its first 20 milliarcseconds, and parsec-scale spectral index maps.

  5. The optimization of gamma spectra processing in prompt gamma neutron activation analysis (PGNAA)

    Energy Technology Data Exchange (ETDEWEB)

    Pinault, Jean-Louis [IAEA Expert, 96 rue du Port David, 45370 Dry (France)], E-mail: jeanlouis_pinault@hotmail.fr; Solis, Jose [Instituto Peruano de Energia Nuclear, Av. Canada No. 1470, San Borja, Lima 41 (Peru)

    2009-04-15

    The uncertainty of the elemental analysis is one of the major factors governing the utility of on-line Prompt Gamma Neutron Activation Analysis (PGNAA) in the blending and sorting of bulk materials. In this paper, a general method applicable to Gamma spectra processing is presented and applied to PGNAA in mineral industry. Based on the Fourier transform of spectra and their de-correlation in the Fourier space (the improvement of the conditioning of the correlation matrix), processing of overlapping of characteristic peaks minimizes the propagation of random errors, which optimizes the accuracy and decreases the detection limits of elemental analyses. In comparison with classical methods based on the linear combinations of relevant regions of spectra the improvement may be considerable, especially when several elements are interfering. The method is applied to four case stories covering both borehole logging and on-line analysis on conveyor belt of raw materials.

  6. Importance of Compton scattering to radiation spectra of isolated neutron stars

    CERN Document Server

    Suleimanov, V

    2006-01-01

    Model atmospheres of isolated neutron stars with low magnetic field are calculated with Compton scattering taking into account. Models with effective temperatures 1, 3 and 5 MK, with two values of surface gravity log(g)g = 13.9 and 14.3), and different chemical compositions are calculated. Radiation spectra computed with Compton scattering are softer than the computed with Thomson scattering at high energies (E > 5 keV) for hot (T_eff > 1 MK) atmospheres with hydrogen-helium composition. Compton scattering is more significant to hydrogen models with low surface gravity. The emergent spectra of the hottest (T_eff > 3 MK) model atmospheres can be described by diluted blackbody spectra with hardness factors ~ 1.6 - 1.9. Compton scattering is less important for models with solar abundance of heavy elements.

  7. V.S.O.P. (99/09) computer code system for reactor physics and fuel cycle simulation. Version 2009

    Energy Technology Data Exchange (ETDEWEB)

    Ruetten, H.J.; Haas, K.A.; Brockmann, H.; Ohlig, U.; Pohl, C.; Scherer, W.

    2010-07-15

    V.S.O.P. (99/ 09) represents the further development of V.S.O.P. (99/ 05). Compared to its precursor, the code system has been improved again in many details. The main motivation for this new code version was to update the basic nuclear libraries used by the code system. Thus, all cross section libraries involved in the code have now been based on ENDF/B-VII. V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of the reactor and of the fuel element, processing of cross sections, neutron spectrum evaluation, neutron diffusion calculation in two or three dimensions, fuel burnup, fuel shuffling, reactor control, thermal hydraulics and fuel cycle costs. The thermal hydraulics part (steady state and time-dependent) is restricted to gas-cooled reactors and to two spatial dimensions. The code can simulate the reactor operation from the initial core towards the equilibrium core. This latest code version was developed and tested under the WINDOWS-XP - operating system. (orig.)

  8. The effects of magnetic field topology on secondary neutron spectra in Magnetized Liner Inertial Fusion

    Science.gov (United States)

    Appelbe, B.; Pecover, J.; Chittenden, J.

    2017-03-01

    The Magnetized Liner Inertial Fusion (MagLIF) concept involves the compression of a magnetized fuel such that the stagnated fuel contains a magnetic field that can suppress heat flow losses and confine α particles. Magnetic confinement of α particles reduces the fuel ρR required for ignition. Recent work [1,2] has demonstrated that the magnitude of the magnetic field in deuterium fuel can be inferred from the yields and spectra of secondary DT neutrons. In this work we investigate the potential for using the shape of the secondary neutron spectra to diagnose the magnetic field topology in the stagnated fuel. Three different field topologies that could possibly occur in MagLIF experiments are studied: (1) a cylindrical fuel column containing axial and azimuthal magnetic field components, (2) a fuel column which is pinched at the ends to form a magnetic mirror and (3) a fuel column that has a helical tube shape with magnetic field lines following the helical path of the tube's axis. Each topology is motivated by observations from experimental or simulated MagLIF data. For each topology we use a multi-physics model to investigate the shapes of the secondary neutron spectra emitted from a steady-state stagnated fuel column. It is found that the azimuthal and helical topologies are more suitable than the mirror topology for reproducing an asymmetry in the axial spectra that was observed in experiments. Gorgon MHD simulations of the MagLIF implosion in 1D are also carried out. These show that sufficient azimuthal magnetic field can penetrate from the liner into the fuel to qualitatively reproduce the observed spectral asymmetry.

  9. Measured and calculated fast neutron spectra in a depleted uranium and lithium hydride shielded reactor

    Science.gov (United States)

    Lahti, G. P.; Mueller, R. A.

    1973-01-01

    Measurements of MeV neutron were made at the surface of a lithium hydride and depleted uranium shielded reactor. Four shield configurations were considered: these were assembled progressively with cylindrical shells of 5-centimeter-thick depleted uranium, 13-centimeter-thick lithium hydride, 5-centimeter-thick depleted uranium, 13-centimeter-thick lithium hydride, 5-centimeter-thick depleted uranium, and 3-centimeter-thick depleted uranium. Measurements were made with a NE-218 scintillation spectrometer; proton pulse height distributions were differentiated to obtain neutron spectra. Calculations were made using the two-dimensional discrete ordinates code DOT and ENDF/B (version 3) cross sections. Good agreement between measured and calculated spectral shape was observed. Absolute measured and calculated fluxes were within 50 percent of one another; observed discrepancies in absolute flux may be due to cross section errors.

  10. Gamma Emission Spectra from Neutron Resonances in 234,236,238U Measured Using the Dance Detector at Lansce

    Science.gov (United States)

    Ullmann, J. L.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Jandel, M.; Kawano, T.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wouters, J. M.; Wilhelmy, J. B.; Wu, C. Y.; Becker, J. A.; Chyzh, A.; Baramsai, B.; Mitchell, G. E.; Krticka, M.

    2013-03-01

    An accurate knowledge of the radiative strength function and level density is needed to calculate of neutron-capture cross sections. An additional constraint on these quantities is provided by measurements of γ-ray emission spectra following capture. We present γ-emission spectra from several neutron resonances in 234,236,238U, measured using the DANCE detector at LANSCE. The measurements are compared to preliminary calculations of the cascade. It is observed that the generalized Lorentzian form of the E1 strength function cannot reproduce the shape of the emission spectra, but a better description is made by adding low-lying M1 Lorentzian strength.

  11. Signatures of photon-axion conversion in the thermal spectra and polarization of neutron stars

    CERN Document Server

    Perna, Rosalba; Verde, Licia; van Adelsberg, Matthew; Jimenez, Raul

    2012-01-01

    Conversion of photons into axions under the presence of a strong magnetic field can dim the radiation from magnetized astrophysical objects. Here we perform a detailed calculation aimed at quantifying the signatures of photon-axion conversion in the spectra, light curves, and polarization of neutron stars (NSs). We take into account the energy and angle-dependence of the conversion probability and the surface thermal emission from NSs. The latter is computed from magnetized atmosphere models that include the effect of photon polarization mode conversion due to vacuum polarization. The resulting spectral models, inclusive of the general-relativistic effects of gravitational redshift and light deflection, allow us to make realistic predictions for the effects of photon to axion conversion on observed NS spectra, light curves, and polarization signals. We identify unique signatures of the conversion, such as an increase of the effective area of a hot spot as it rotates away from the observer line of sight. For a...

  12. Measurements of neutron energy spectra from 7Li(p,n)7Be reaction with Bonner sphere spectrometer, Nested Neutron Spectrometer and ROSPEC.

    Science.gov (United States)

    Atanackovic, J; Matysiak, W; Witharana, S; Dubeau, J; Waker, A J

    2014-10-01

    Neutron spectrometry measurements were carried out at the McMaster Accelerator Laboratory (MAL), which is equipped with a 3-MV Van de Graaff-type accelerator. Protons were accelerated onto a thick natural lithium target inducing the (7)Li(p,n)(7)Be threshold reaction. Depending on the proton energy, slightly different poly-energetic neutron fields were produced. Neutron spectra were measured at two incident proton energies: 2.15 and 2.24 MeV, which produced poly-energetic neutrons with maximum kinetic energies of 401 and 511 keV, respectively. Measurements were performed at a distance of 1.5 m from the target in the forward direction with three different instruments: Bonner sphere spectrometer, Nested Neutron Spectrometer and ROtational proton recoil SPECtrometer.

  13. Measurements of neutron streaming energy spectra in shielding ducts; Medidas e calculos de espectro de energia de neutrons emergentes de um duto em uma blindagem

    Energy Technology Data Exchange (ETDEWEB)

    Angioletto, Elcio; Abe, Alfredo Y. [Centro Tecnologico da Marinha em Sao Paulo (CTMSP), SP (Brazil). E-mail: angiolet@net.ipen.br; Coelho, Rogerio P. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

    2000-07-01

    This work presents the measurements of neutron streaming, for different energy ranges, in shielding ducts. The shielding is composed of plates of different materials (borate polyethylene and paraffin). The two ducts are conceived as labyrinths in order to (a three-legged duct) minimize the radiation streaming. A 37 GBq Americium-Beryllium neutron source type was used for the experimental measurements. The fast neutron energy spectra were measured using a detection system with a liquid organic scintillator, NE-213 detector, and appropriate electronic equipment. The results are in good agreement with the literature. The measurements of thermal neutrons intensity were performed with a BF{sub 3} counter. The MCNP-4B code was used to simulate the experiment. The simulation was performed with success, obtaining a small discrepancy (9.0%) between the calculated results and the measurements with the BF{sub 3} counter, at the duct third leg. From the results it was possible to observe the thermal neutron streaming through the duct, the effects of neutron flux moderation, the attenuation in the shielding and also the neutron energy spectra modifications emerging from the shielding. (author)

  14. X-ray bursting neutron star atmosphere models: spectra and color corrections

    CERN Document Server

    Suleimanov, V; Werner, K

    2010-01-01

    X-ray bursting neutron stars in low mass X-ray binaries constitute an appropriate source class to constrain masses and radii of neutron stars, but a sufficiently extended set of corresponding model atmospheres is necessary for these investigations. We computed such a set of model atmospheres and emergent spectra in a plane-parallel, hydrostatic, and LTE approximation with Compton scattering taken into account. The models were calculated for six different chemical compositions: pure hydrogen and pure helium atmospheres, and atmospheres with solar mix of hydrogen and helium, and various heavy element abundances Z = 1, 0.3, 0.1, and 0.01 Z_sun. For each chemical composition the models are computed for three values of surface gravity, log g =14.0, 14.3, and 14.6, and for 20 values of the luminosity in units of the Eddington luminosity, L/L_Edd, in the range 0.001--0.98. The emergent spectra of all models are redshifted and fitted by a diluted blackbody in the RXTE/PCA 3--20 keV energy band, and corresponding valu...

  15. Detector-Response Correction of Two-Dimensional γ-Ray Spectra from Neutron Capture

    Directory of Open Access Journals (Sweden)

    Rusev G.

    2015-01-01

    Full Text Available The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. The detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ and 113Cd(n, γ reactions.

  16. Investigation on the pebble bed flow model in VSOP

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hao, E-mail: haochen.heu@163.com; Fu, Li, E-mail: lifu@mail.tsinghua.edu.cn

    2014-05-01

    In pebble bed high temperature gas cooled reactor (HTR), the fuel pebbles will pass the reactor core several times, in order to flatten the power distribution, and to unify the discharging burnup. But the VSOP code approximates the pebble bed flow because of current computer capability. In order to simulate the pebble bed flow in HTR more realistically and to validate the approximation in pebble bed flow model in VSOP, a new code based on Monte Carlo method has been developed to analysis the characteristic of the pebble bed flow, particularly the average burnup distribution in the core, discharging burnup, and the number of pebble passes. Statistics analysis shows that several millions of Monte Carlo simulation can provide reasonable result and the VSOP treatment of the pebble bed flow model is reasonable. The Monte Carlo simulation can provide more information for the pebble flow and reactor operation.

  17. Energy spectra unfolding of fast neutron sources using the group method of data handling and decision tree algorithms

    Science.gov (United States)

    Hosseini, Seyed Abolfazl; Afrakoti, Iman Esmaili Paeen

    2017-04-01

    Accurate unfolding of the energy spectrum of a neutron source gives important information about unknown neutron sources. The obtained information is useful in many areas like nuclear safeguards, nuclear nonproliferation, and homeland security. In the present study, the energy spectrum of a poly-energetic fast neutron source is reconstructed using the developed computational codes based on the Group Method of Data Handling (GMDH) and Decision Tree (DT) algorithms. The neutron pulse height distribution (neutron response function) in the considered NE-213 liquid organic scintillator has been simulated using the developed MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). The developed computational codes based on the GMDH and DT algorithms use some data for training, testing and validation steps. In order to prepare the required data, 4000 randomly generated energy spectra distributed over 52 bins are used. The randomly generated energy spectra and the simulated neutron pulse height distributions by MCNPX-ESUT for each energy spectrum are used as the output and input data. Since there is no need to solve the inverse problem with an ill-conditioned response matrix, the unfolded energy spectrum has the highest accuracy. The 241Am-9Be and 252Cf neutron sources are used in the validation step of the calculation. The unfolded energy spectra for the used fast neutron sources have an excellent agreement with the reference ones. Also, the accuracy of the unfolded energy spectra obtained using the GMDH is slightly better than those obtained from the DT. The results obtained in the present study have good accuracy in comparison with the previously published paper based on the logsig and tansig transfer functions.

  18. Unfolding the measured neutron spectra in the irradiation chamber of the UZrH reactor using iterative method

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In the procedure of neutron fluence measurement in the whole energy range (10-4 eV~18 MeV), in the irradiation chamber of a UZrH reactor, the neutron energy spectra are unfolded using the method of minimizing directed divergence and SAND-Ⅱ, which are used broadly at home and abroad. These methods belong to the iterative methods.In this article, the procedure of the spectra unfolding using the two methods is described in detail. The neutron spectrum distribution unfolded by the two methods agree well with each other. In the end, the major differences of the two iterative methods are compared with each other, and the main factors affecting the accuracy of the spectra unfolding with the iterative method are discussed.

  19. Application of neural networks for unfolding neutron spectra measured by means of Bonner spheres and activation foils

    CERN Document Server

    Braga, C C

    2001-01-01

    A neural network structure has been used for unfolding neutron spectra measured by means of a Bonner Sphere Spectrometer set and a foil activation set using several neutron induced reactions. The present work used the SNNS (Stuttgart Neural Network Simulator) as the interface for designing, training and validation of the Multilayer Perceptron network. The back-propagation algorithm was applied. The Bonner Sphere set chosen has been calibrated at the National Physical Laboratory, United Kingdom, and uses gold activation foils as thermal neutron detectors. The neutron energy covered by the response functions goes from 0.0001 eV to 14 MeV. The foil activation set chosen has been irradiated at the IEA-R1 research reactor and measured at the Nuclear Metrology Laboratory of IPEN-CNEN/SP. Two types of neutron spectra were numerically investigated: monoenergetic and continuous The unfolded spectra were compared to a conventional method using code SAND-II as part of the neutron dosimetry system SAIPS. Good results wer...

  20. Study of neutron spectra in a water bath from a Pb target irradiated by 250 MeV protons

    Science.gov (United States)

    Li, Yan-Yan; Zhang, Xue-Ying; Ju, Yong-Qin; Ma, Fei; Zhang, Hong-Bin; Chen, Liang; Ge, Hong-Lin; Wan, Bo; Luo, Peng; Zhou, Bin; Zhang, Yan-Bin; Li, Jian-Yang; Xu, Jun-Kui; Wang, Song-Lin; Yang, Yong-Wei; Yang, Lei

    2015-04-01

    Spallation neutrons were produced by the irradiation of Pb with 250 MeV protons. The Pb target was surrounded by water which was used to slow down the emitted neutrons. The moderated neutrons in the water bath were measured by using the resonance detectors of Au, Mn and In with a cadmium (Cd) cover. According to the measured activities of the foils, the neutron flux at different resonance energies were deduced and the epithermal neutron spectra were proposed. Corresponding results calculated with the Monte Carlo code MCNPX were compared with the experimental data to check the validity of the code. The comparison showed that the simulation could give a good prediction for the neutron spectra above 50 eV, while the finite thickness of the foils greatly effected the experimental data in low energy. It was also found that the resonance detectors themselves had great impact on the simulated energy spectra. Supported by National Natural Science Foundation and Strategic Priority Research Program of the Chinese Academy of Sciences (11305229, 11105186, 91226107, 91026009, XDA03030300)

  1. A parametric model to describe neutron spectra around high-energy electron accelerators and its application in neutron spectrometry with Bonner Spheres

    Science.gov (United States)

    Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo

    2010-03-01

    Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.

  2. An approximated method of calculation of neutron spectra in reactor cells; Um metodo aproximado de calculo do espectro de neutrons em celulas de reatores

    Energy Technology Data Exchange (ETDEWEB)

    Caldeira, Alexandre D. [Centro Tecnico Aeroespacial (CTA-IEAv), Sao Jose dos Campos, SP (Brazil). Inst. de Estudos Avancados

    2000-07-01

    This work deals with the cell neutron spectra calculated with the transport equation for an infinite medium applied to the homogenized cell. Considering a radioisotope production reactor fuel cell, as a sample case, the maximum deviation found between the approximated and the S{sub N} methods was 13%. (author)

  3. The Deep Interferometric VSOP--Arecibo Survey (DIVAS)

    Science.gov (United States)

    Edwards, P. G.; Hirabayashi, H.; Ulvestad, J. S.; Salter, C.; Ghosh, T.; Gurvits, L. I.; Fomalont, E. B.

    2009-08-01

    The Deep Interferometric VSOP-Arecibo Survey (DIVAS) program used space VLBI observations of a faint sample of flat-spectrum sources made with the HALCA satellite and the Arecibo telescope to provide the highest possible space VLBI sensitivity at 5 GHz. The main aim of the survey is to compare statistical results on the source structures (e.g., brightness temperatures, sizes, visibilities) with results from the VLBI Space Observatory Programme (VSOP) Survey, to determine whether there are systematic differences in the compact structures of sources selected from samples with limiting flux densities differing by over an order of magnitude.

  4. Inelastic neutron scattering spectra of alkali metal (Na, K) bifluorides: The harmonic overtone of v3

    Science.gov (United States)

    Waddington, Thomas C.; Howard, Joseph; Brierley (in part), Keith P.; Tomkinson, John

    1982-01-01

    Inelastic neutron scattering spectra of MFHF (M  Na and K) have been measured up to energy transfers of ca. 4000 cm -1 Both 0 → 1 and 0 → 2 transitions of the bending ( v2), and antisymmetric stretching ( v3) modes were observed. A normal harmonic (i.e. no quartic contribution) model for the dynamics of the bifluoride ion is entirely consistent with our observations. Evidence of phonon dispersion was observed in the band shape of v3, but no structure attributable to the LO mode could be found. The similarity of the band shapes of v3 for both NaFHF and KFHF is interpreted in terms of a very short range coupling mechanism.

  5. Atmospheres and Spectra of Strongly Magnetized Neutron Stars II Effect of Vacuum Polarization

    CERN Document Server

    Ho, W C G; Ho, Wynn C. G.; Lai, Dong

    2003-01-01

    We study the effect of vacuum polarization on the atmosphere structure and radiation spectra of neutron stars with surface magnetic fields B=10^14-10^15 G, as appropriate for magnetars. Vacuum polarization modifies the dielectric property of the medium and gives rise to a resonance feature in the opacity; this feature is narrow and occurs at a photon energy that depends on the plasma density. Vacuum polarization can also induce resonant conversion of photon modes via a mechanism analogous to the MSW mechanism for neutrino oscillation. We construct atmosphere models in radiative equilibrium with an effective temperature of a few \\times 10^6 K by solving the full radiative transport equations for both polarization modes in a fully ionized hydrogen plasma. We discuss the subtleties in treating the vacuum polarization effects in the atmosphere models and present approximate solutions to the radiative transfer problem which bracket the true answer. We show from both analytic considerations and numerical calculatio...

  6. Opacities and Spectra of the r-process Ejecta from Neutron Star Mergers

    CERN Document Server

    Kasen, Daniel; Barnes, Jennifer

    2013-01-01

    Material ejected during (or immediately following) the merger of two neutron stars may assemble into heavy elements by the r-process. The subsequent radioactive decay of the nuclei can power electromagnetic emission similar to, but significantly dimmer than, an ordinary supernova. Identifying such events is an important goal of future transient surveys, offering new perspectives on the origin of r-process nuclei and the astrophysical sources of gravitational waves. Predictions of the transient light curves and spectra, however, have suffered from the uncertain optical properties of heavy ions. Here we consider the opacity of expanding r-process material and argue that it is dominated by line transitions from those ions with the most complex valence electron structure, namely the lanthanides. For a few representative ions, we run atomic structure models to calculate radiative data for tens of millions of lines. We find that the resulting r-process opacities are orders of magnitude larger than that of ordinary ...

  7. ANDI-03: a genetic algorithm tool for the analysis of activation detector data to unfold high-energy neutron spectra.

    Science.gov (United States)

    Mukherjee, Bhaskar

    2004-01-01

    The thresholds of (n,xn) reactions in various activation detectors are commonly used to unfold the neutron spectra covering a broad energy span, i.e. from thermal to several hundreds of MeV. The saturation activities of the daughter nuclides (i.e. reaction products) serve as the input data of specific spectra unfolding codes, such as SAND-II and LOUHI-83. However, most spectra unfolding codes, including the above, require an a priori (guess) spectrum to starting up the unfolding procedure of an unknown spectrum. The accuracy and exactness of the resulting spectrum primarily depends on the subjectively chosen guess spectrum. On the other hand, the Genetic Algorithm (GA)-based spectra unfolding technique ANDI-03 (Activation-detector Neutron DIfferentiation) presented in this report does not require a specific starting parameter. The GA is a robust problem-solving tool, which emulates the Darwinian Theory of Evolution prevailing in the realm of biological world and is ideally suited to optimise complex objective functions globally in a large multidimensional solution space. The activation data of the 27Al(n,alpha)24Na, 116In(n,gamma)116mIn, 12C(n,2n)11C and 209Bi(n,xn)(210-x)Bi reactions recorded at the high-energy neutron field of the ISIS Spallation source (Rutherford Appleton Laboratory, UK) was obtained from literature and by applying the ANDI-03 GA tool, these data were used to unfold the neutron spectra. The total neutron fluence derived from the neutron spectrum unfolded using GA technique (ANDI-03) agreed within +/-6.9% (at shield top level) and +/-27.2% (behind a 60 cm thick concrete shield) with the same unfolded with the SAND-II code.

  8. Neutron spectra from 647- and 800-MeV proton bombardment of hydrogen and deuterium. [Cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Bjork, C.W.

    1975-12-01

    Zero degree neutron spectra for the inclusive reactions p(p,n) and d(p,n) were obtained. Spectra were obtained for bombarding proton kinetic energies of 647 and 800 MeV. The strongly peaked p(p,n) spectra are well explained via the p(p,n)p..pi../sup +/ reaction primarily through the production of the N*/sub 33/(..delta../sup + +/) resonance. However, there is evidence for n-p final state interactions as well. Calculations have shown the roles of the N*/sub 33/ resonance and the n-p final state interactions in these p(p,n) spectra. The d(p,n) spectra exhibit a strong quasi-elastic charge exchange peak influenced by the final state p-p interaction in the reaction d(p,n)2p. The d(p,n) spectra also show a broad bump at lower neutron momenta qualitatively similar to the p(p,n) spectra. The d(p,n) spectra at lower momenta are nearly explained by nucleon-nucleon single pion production via the N*/sub 33/ resonance but it appears that higher order contributions involving nucleon--nucleon and nucleon--pion interactions are required as well. The d(p,n)2p reaction provides an intense, nearly monoenergetic neutron beam for use as a probe, primarily of the n-p interaction, at medium energies. The d(p,n) and p(p,n) measurements provide zero degree neutron momentum distributions which are very useful in furthering the knowledge about pion production near the N*/sub 33/ resonance. These data provide a challenge to the theoreticians to explain pion production in the two and three nucleon initial states. (auth)

  9. Improved Modeling of Prompt Fission Neutron Spectra for Nuclear Data Evaluations

    Science.gov (United States)

    Neudecker, Denise; Talou, Patrick; Kawano, Toshihiko; Kahler, Albert C.; White, Morgan C.

    2015-10-01

    The prompt fission neutron spectra (PFNS) of major actinides such as 239Pu and 235U are quantities of interest for nuclear physics application areas including reactor physics and national security. Nuclear data evaluations provide recommended data for those application areas based on nuclear theory and experiments. Here, we present improvements made to the effective models predicting the PFNS up to incident neutron energies of 30 MeV and their impact on evaluations. These models describe relevant physics processes better than those used for the current US nuclear data library ENDF/B-VII.1. In addition, the use of higher-fidelity models such as Monte Carlo Hauser-Feshbach calculations will be discussed in the context of future PFNS evaluations. (LA-UR-15-24763) This work was carried out under the auspices of the US Department of Energy, National Nuclear Security Administration and Office of Science, and performed by Los Alamos National Security LLC under Contract DE-AC52-06NA25396.

  10. Electromagnetic emission from long-lived binary neutron star merger remnants II: lightcurves and spectra

    CERN Document Server

    Siegel, Daniel M

    2015-01-01

    Recent observations indicate that in a large fraction of binary neutron star (BNS) mergers a long-lived neutron star (NS) may be formed rather than a black hole. Unambiguous electromagnetic (EM) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (SGRBs) and their afterglow radiation are generated. Furthermore, such EM signals would have profound implications for multimessenger astronomy with joint EM and gravitational-wave (GW) observations of BNS mergers, which will soon become reality with the ground-based advanced LIGO/Virgo GW detector network starting its first science run this year. Here we explore such EM signatures based on the model presented in a companion paper, which provides a self-consistent evolution of the post-merger system and its EM emission starting from an early baryonic wind phase and resulting in a final pulsar wind nebula that is confined by the previously ejected material. Lightcurves and spectra are computed for a wide range of post-merger...

  11. Reflection spectra from an accretion disc illuminated by a neutron star X-ray burst

    CERN Document Server

    Ballantyne, D R

    2004-01-01

    Recent time-resolved X-ray spectra of a neutron star undergoing a superburst revealed an Fe K line and edge consistent with reprocessing from the surrounding accretion disc. Here, we present models of X-ray reflection from a constant density slab illuminated by a blackbody, the spectrum emitted by a neutron star burst. The calculations predict a prominent Fe K line and a rich soft X-ray line spectrum which is superimposed on a strong free-free continuum. The lines slowly vanish as the ionization parameter of the slab is increased, but the free-free continuum remains dominant at energiesless than 1 keV. The reflection spectrum has a quasi-blackbody shape only at energies greater than 3 keV. If the incident blackbody is added to the reflection spectrum, the Fe K equivalent width varies between 100 and 300 eV depending on the ionization parameter and the temperature, kT, of the blackbody. The equivalent width is correlated with kT, and therefore we predict a strong Fe K line when an X-ray burst is at its brighte...

  12. Displacement cross sections and PKA spectra: tables and applications. [Neutron damage energy cross sections to 20 MeV, primary knockon atom spectra to 15 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Doran, D G; Graves, N J

    1976-12-01

    Damage energy cross sections to 20 MeV are given for aluminum, vanadium, chromium, iron, nickel, copper, zirconium, niobium, molybdenum, tantalum, tungsten, lead, and 18Cr10Ni stainless steel. They are based on ENDF/B-IV nuclear data and the Lindhard energy partition model. Primary knockon atom (PKA) spectra are given for aluminum, iron, niobium, tantalum, and lead for neutron energies up to 15 MeV at approximately one-quarter lethargy intervals. The contributions of various reactions to both the displacement cross sections (taken to be proportional to the damage energy cross sections) and the PKA spectra are presented graphically. Spectral-averaged values of the displacement cross sections are given for several spectra, including approximate maps for the Experimental Breeder Reactor-II (EBR-II) and several positions in the Fast Test Reactor (FTR). Flux values are included to permit estimation of displacement rates. Graphs show integral PKA spectra for the five metals listed above for neutron spectra corresponding to locations in the EBR-II, the High Flux Isotope Reactor (HFIR), and a conceptual fusion reactor (UWMAK-I). Detailed calculations are given only for cases not previously documented. Uncertainty estimates are included.

  13. Lens Mapping of Dark Matter Substructure with VSOP-2

    Science.gov (United States)

    Ohashi, S.; Chiba, M.; Inoue, K. T.

    2009-08-01

    Hierarchical clustering models of cold dark matter (CDM) predict that about 5% - 10% of a galaxy-sized halo with mass ˜ 1012 solar masses (M⊙ ) resides in substructures (CDM subhalos) with masses ⪉ 108 M⊙. To directly identify such substructures, we propose to observe radio continuum emission from multiply imaged QSOs using VSOP-2 with a high angular resolution.

  14. VSOP Observations of the Blazar S5 2007+77

    Science.gov (United States)

    Gabányi, K. É.; Krichbaum, T. P.; Kraus, A.; Witzel, A.; Zensus, J. A.

    2009-08-01

    The blazar, S5 2007+77 shows intraday variability in cm wavelengths. Seven epochs of VSOP observations were carried out in 1998 and 1999 at 5 GHz to look for the origin of the variability with the highest achievable angular resolution at cm wavelengths. Here the results of four epochs are analysed, which revealed ˜ 10 % variations in polarized flux density.

  15. Temperature-tuned Maxwell-Boltzmann neutron spectra for kT ranging from 30 up to 50 keV for nuclear astrophysics studies.

    Science.gov (United States)

    Martín-Hernández, G; Mastinu, P F; Praena, J; Dzysiuk, N; Capote Noy, R; Pignatari, M

    2012-08-01

    The need of neutron capture cross section measurements for astrophysics motivates present work, where calculations to generate stellar neutron spectra at different temperatures are performed. The accelerator-based (7)Li(p,n)(7)Be reaction is used. Shaping the proton beam energy and the sample covering a specific solid angle, neutron activation for measuring stellar-averaged capture cross section can be done. High-quality Maxwell-Boltzmann neutron spectra are predicted. Assuming a general behavior of the neutron capture cross section a weighted fit of the spectrum to Maxwell-Boltzmann distributions is successfully introduced.

  16. Measurement of inclusive neutron spectra from p-Be up to 24 GeV/c incident momentum

    CERN Document Server

    Engler, J; Gibbard, B; Mönnig, F; Pack, K; Runge, K; Schopper, Herwig Franz

    1973-01-01

    The authors present data on inclusive neutron spectra produced in an internal Be target of the CERN PS, for incident proton momenta between 8 and 24 GeV/c at 0 degrees , and for incident proton momentum of 19 GeV/c at 50 mrad. (30 refs).

  17. SOURCES 4C : a code for calculating ([alpha],n), spontaneous fission, and delayed neutron sources and spectra.

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, W. B. (William B.); Perry, R. T. (Robert T.); Shores, E. F. (Erik F.); Charlton, W. S. (William S.); Parish, Theodore A.; Estes, G. P. (Guy P.); Brown, T. H. (Thomas H.); Arthur, Edward D. (Edward Dana),; Bozoian, Michael; England, T. R.; Madland, D. G.; Stewart, J. E. (James E.)

    2002-01-01

    SOURCES 4C is a computer code that determines neutron production rates and spectra from ({alpha},n) reactions, spontaneous fission, and delayed neutron emission due to radionuclide decay. The code is capable of calculating ({alpha},n) source rates and spectra in four types of problems: homogeneous media (i.e., an intimate mixture of a-emitting source material and low-Z target material), two-region interface problems (i.e., a slab of {alpha}-emitting source material in contact with a slab of low-Z target material), three-region interface problems (i.e., a thin slab of low-Z target material sandwiched between {alpha}-emitting source material and low-Z target material), and ({alpha},n) reactions induced by a monoenergetic beam of {alpha}-particles incident on a slab of target material. Spontaneous fission spectra are calculated with evaluated half-life, spontaneous fission branching, and Watt spectrum parameters for 44 actinides. The ({alpha},n) spectra are calculated using an assumed isotropic angular distribution in the center-of-mass system with a library of 107 nuclide decay {alpha}-particle spectra, 24 sets of measured and/or evaluated ({alpha},n) cross sections and product nuclide level branching fractions, and functional {alpha}-particle stopping cross sections for Z < 106. The delayed neutron spectra are taken from an evaluated library of 105 precursors. The code provides the magnitude and spectra, if desired, of the resultant neutron source in addition to an analysis of the'contributions by each nuclide in the problem. LASTCALL, a graphical user interface, is included in the code package.

  18. ELECTROMAGNETIC EMISSION FROM LONG-LIVED BINARY NEUTRON STAR MERGER REMNANTS. II. LIGHT CURVES AND SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Siegel, Daniel M. [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Mühlenberg 1, D-14476 Potsdam-Golm (Germany); Ciolfi, Riccardo, E-mail: daniel.siegel@aei.mpg.de, E-mail: riccardo.ciolfi@unitn.it [Physics Department, University of Trento, Via Sommarive 14, I-38123 Trento (Italy)

    2016-03-01

    Recent observations indicate that in a large fraction of binary neutron star (BNS) mergers a long-lived neutron star (NS) may be formed rather than a black hole. Unambiguous electromagnetic (EM) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (SGRBs) and their afterglow radiation are generated. Furthermore, such EM signals would have profound implications for multimessenger astronomy with joint EM and gravitational-wave (GW) observations of BNS mergers, which will soon become reality thanks to the ground-based advanced LIGO/Virgo GW detector network. Here we explore such EM signatures based on the model presented in a companion paper, which provides a self-consistent evolution of the post-merger system and its EM emission up to ∼10{sup 7} s. Light curves and spectra are computed for a wide range of post-merger physical properties. We present X-ray afterglow light curves corresponding to the “standard” and the “time-reversal” scenario for SGRBs (prompt emission associated with the merger or with the collapse of the long-lived NS). The light curve morphologies include single and two-plateau features with timescales and luminosities that are in good agreement with Swift observations. Furthermore, we compute the X-ray signal that should precede the SGRB in the time-reversal scenario, the detection of which would represent smoking-gun evidence for this scenario. Finally, we find a bright, highly isotropic EM transient peaking in the X-ray band at ∼10{sup 2}–10{sup 4} s after the BNS merger with luminosities of L{sub X} ∼ 10{sup 46}–10{sup 48} erg s{sup −1}. This signal represents a very promising EM counterpart to the GW emission from BNS mergers.

  19. Electromagnetic Emission from Long-lived Binary Neutron Star Merger Remnants. II. Lightcurves and Spectra

    Science.gov (United States)

    Siegel, Daniel M.; Ciolfi, Riccardo

    2016-03-01

    Recent observations indicate that in a large fraction of binary neutron star (BNS) mergers a long-lived neutron star (NS) may be formed rather than a black hole. Unambiguous electromagnetic (EM) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (SGRBs) and their afterglow radiation are generated. Furthermore, such EM signals would have profound implications for multimessenger astronomy with joint EM and gravitational-wave (GW) observations of BNS mergers, which will soon become reality thanks to the ground-based advanced LIGO/Virgo GW detector network. Here we explore such EM signatures based on the model presented in a companion paper, which provides a self-consistent evolution of the post-merger system and its EM emission up to ˜107 s. Light curves and spectra are computed for a wide range of post-merger physical properties. We present X-ray afterglow light curves corresponding to the “standard” and the “time-reversal” scenario for SGRBs (prompt emission associated with the merger or with the collapse of the long-lived NS). The light curve morphologies include single and two-plateau features with timescales and luminosities that are in good agreement with Swift observations. Furthermore, we compute the X-ray signal that should precede the SGRB in the time-reversal scenario, the detection of which would represent smoking-gun evidence for this scenario. Finally, we find a bright, highly isotropic EM transient peaking in the X-ray band at ˜102-104 s after the BNS merger with luminosities of LX ˜ 1046-1048 erg s-1. This signal represents a very promising EM counterpart to the GW emission from BNS mergers.

  20. Measurement and calculation of fast neutron and gamma spectra in well defined cores in LR-0 reactor.

    Science.gov (United States)

    Košťál, Michal; Matěj, Zdeněk; Cvachovec, František; Rypar, Vojtěch; Losa, Evžen; Rejchrt, Jiří; Mravec, Filip; Veškrna, Martin

    2017-02-01

    A well-defined neutron spectrum is essential for many types of experimental topics and is also important for both calibration and testing of spectrometric and dosimetric detectors. Provided it is well described, such a spectrum can also be employed as a reference neutron field that is suitable for validating selected cross sections. The present paper aims to compare calculations and measurements of such a well-defined spectra in geometrically similar cores of the LR-0 reactor with fuel containing slightly different enrichments (2%, 3.3% and 3.6%). The common feature to all cores is a centrally located dry channel which can be used for the insertion of studied materials. The calculation of neutron and gamma spectra was realized with the MCNP6 code using ENDF/B-VII.0, JEFF-3.1, JENDL-3.3, ROSFOND-2010 and CENDL-3.1 nuclear data libraries. Only minor differences in neutron and gamma spectra were found in the comparison of the presented reactor cores with different fuel enrichments. One exception is the gamma spectrum in the higher energy region (above 8MeV), where more pronounced variations could be observed.

  1. Coarse-scaling adjustment of fine-group neutron spectra for epithermal neutron beams in BNCT using multiple activation detectors

    Science.gov (United States)

    Liu, Yuan-Hao; Nievaart, Sander; Tsai, Pi-En; Liu, Hong-Ming; Moss, Ray; Jiang, Shiang-Huei

    2009-01-01

    In order to provide an improved and reliable neutron source description for treatment planning in boron neutron capture therapy (BNCT), a spectrum adjustment procedure named coarse-scaling adjustment has been developed and applied to the neutron spectrum measurements of both the Tsing Hua Open-pool Reactor (THOR) epithermal neutron beam in Taiwan and the High Flux Reactor (HFR) in The Netherlands, using multiple activation detectors. The coarse-scaling adjustment utilizes a similar idea as the well-known two-foil method, which adjusts the thermal and epithermal neutron fluxes according to the Maxwellian distribution for thermal neutrons and 1/ E distribution over the epithermal neutron energy region. The coarse-scaling adjustment can effectively suppress the number of oscillations appearing in the adjusted spectrum and provide better smoothness. This paper also presents a sophisticated 9-step process utilizing twice the coarse-scaling adjustment which can adjust a given coarse-group spectrum into a fine-group structure, i.e. 640 groups, with satisfactory continuity and excellently matched reaction rates between measurements and calculation. The spectrum adjustment algorithm applied in this study is the same as the well-known SAND-II.

  2. Neutron reference spectra measurements with the Bonner multi-spheres spectrometer; Medidas de espectros de referencia de neutrons com o espectrometro de multiesferas de Bonner

    Energy Technology Data Exchange (ETDEWEB)

    Lemos Junior, Roberto Mendonca de

    2004-07-01

    This paper aims to define a procedure to use the Bonner Multisphere Spectrometer with a {sup 6}LiI(Eu) detector in order to determine of neutron spectra. It was measured {sup 238}PuBe spectra and same of reference ({sup 241}AmBe, {sup 252}Cf e {sup 252}Cf+D{sub 2}O) published in ISO 8529-1 (2001) Norm. The data were processed by a computer program (BUNKI), which presents the results in neutrons energy fluency. Each input parameter of the program was studied in order to establish their influence in the adjustment result. The environment dose equivalent rate obtained placing the detector 1 m from the {sup 241}AmBe source was 122 {+-} 4 {mu}Sv/h with 7% of uncertainty and 95% of confidence level. The procedure established in this work was tested with the {sup 238}PuBe spectrum, obtaining an environment dose equivalent rate of 286 {+-} 9 {mu}Sv/h, 8% lower than the value measured experimentally used as reference. Through this procedure will be possible to measure neutron spectra in different work places where neutrons sources are used. Knowing these spectra, it will be possible to evaluate which area monitors, are more suitable, as well as, to study better the response of individual neutron monitors, as for instance, to obtain a conversion coefficient more appropriate to the albedo dosimeter used in different work places. As the measurements need a long time to be accomplished, the work optimization is fundamental to reduce the exposing time of the Bonner spectrometer operator. For this reason, an important parameter examined in this paper was the possibility of reducing the number of spheres used during the measurement without changing the final result. Considering the radiation protection standards, this parameter has a huge importance when the measurements are performed in work places where the neutron fluency and gamma rate offer risks to the operator's health, as for instance, in nuclear centrals. Studying this parameter, it was possible to conclude that

  3. Impact of flows on ion temperatures inferred from neutron spectra in asymmetrically driven OMEGA DT implosions

    Science.gov (United States)

    Gatu Johnson, M.; Frenje, J. A.; Seguin, F. H.; Petrasso, R. D.; Aappelbe, B.; Chittenden, J.; Walsh, C.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Marshall, F.; Michel, T.; Stoeckl, C.; Sangster, T. C.; Zylstra, A.

    2016-10-01

    Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by engineering features (such as stalks, fill tubes, tents, or capsule imperfections) or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation we report on an OMEGA experiment with intentionally asymmetric drive, designed to test the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The results provide insight into the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

  4. The statistical model calculation of prompt neutron spectra from spontaneous fission of {sup 244}Cm and {sup 246}Cm

    Energy Technology Data Exchange (ETDEWEB)

    Gerasimenko, B.F. [V.G. Khlopin Radium Inst., Saint Peterburg (Russian Federation)

    1997-03-01

    The calculations of integral spectra of prompt neutrons of spontaneous fission of {sup 244}Cm and {sup 246}Cm were carried out. The calculations were done by the Statistical Computer Code Complex SCOFIN applying the Hauser-Feschbach method as applied to the description of the de-excitation of excited fission fragments by means of neutron emission. The emission of dipole gamma-quanta from these fragments was considered as a competing process. The average excitation energy of a fragment was calculated by two-spheroidal model of tangent fragments. The density of levels in an excited fragment was calculated by the Fermi-gas model. The quite satisfactory agreement was reached between theoretical and experimental results obtained in frames of Project measurements. The calculated values of average multiplicities of neutron number were 2,746 for {sup 244}Cm and 2,927 for {sup 246}Cm that was in a good accordance with published experimental figures. (author)

  5. The statistical model calculation of prompt neutron spectra from spontaneous fission of {sup 244}Cm and {sup 246}Cm

    Energy Technology Data Exchange (ETDEWEB)

    Gerasimenko, B.F. [V.G. Khlopin Radium Inst., Saint Peterburg (Russian Federation)

    1997-03-01

    The calculations of integral spectra of prompt neutrons of spontaneous fission of {sup 244}Cm and {sup 246}Cm were carried out. The calculations were done by the Statistical Computer Code Complex SCOFIN applying the Hauser-Feschbach method as applied to the description of the de-excitation of excited fission fragments by means of neutron emission. The emission of dipole gamma-quanta from these fragments was considered as a competing process. The average excitation energy of a fragment was calculated by two-spheroidal model of tangent fragments. The density of levels in an excited fragment was calculated by the Fermi-gas model. The quite satisfactory agreement was reached between theoretical and experimental results obtained in frames of Project measurements. The calculated values of average multiplicities of neutron number were 2,746 for {sup 244}Cm and 2,927 for {sup 246}Cm that was in a good accordance with published experimental figures. (author)

  6. VSOP Monitoring of the Quasar 1928+738

    Science.gov (United States)

    Murphy, D. W.

    1999-01-01

    One limitation of the VSOP (VLBI Space Observatory Program) mission is that several famous superluminal sources such as 3C273 cannot be monitored with good uv-coverage throughout the lifetime of the VSOP Mission at regular intervals that are spaced closely enough to follow the evolution in the fine-scale source-structure. The reason for this is that the HALCA spacecraft cannot#observe sources outside certain restricted ranges of sun angle, defined to be the time variable angle between the source and the sun. However sources that lie within 10 degrees of the ecliptic poles can be observed throughout the year and observations are not restricted to narrow temporal windows. Furthermore, the best ground-based uv-coverages are obtained for circumpolar sources and consequently these will be the sources for which the maximum amount of space VLBI data will be obtained with a given ground array. We have began a VSOP monitoring campaign at 5 GHz on the relatively low redshift (z=0.3) superluminal quasar 1928+738 which is both a circumpolar source and lies 10 degrees away from the ecliptic pole. 1928+738 is in the S5 polar cap sample and has been well studied both on the arsecond-scale and mas-scale. 22 GHz observations have shown that the motion of the VLBI components in 1928+738 is inconsistent with simple linear expansion along a fixed position angle (PA) for all components. Indeed, 1928+738 was one of the first sources for which helical jet motion was proposed and it has been further proposed that a massive binary black hole (MBBH) system is responsible for the sinusoidal jet ridge line observed at 22 GHz over a S year period. our VSOP observations are designed to check this proposal.

  7. Gamma-Ray Emission Spectra as a Constraint on Calculations of 234 , 236 , 238U Neutron-Capture Cross Sections

    Science.gov (United States)

    Ullmann, J. L.; Krticka, M.; Kawano, T.; Bredeweg, T. A.; Baramsai, B.; Couture, A.; Haight, R. C.; Jandel, M.; Mosby, S.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Wu, C. Y.; Chyzh, A.

    2015-10-01

    Calculations of the neutron-capture cross section at low neutron energies (10 eV through 100's of keV) are very sensitive to the nuclear level density and radiative strength function. These quantities are often poorly known, especially for radioactive targets, and actual measurements of the capture cross section are usually required. An additional constraint on the calculation of the capture cross section is provided by measurements of the cascade gamma spectrum following neutron capture. Recent measurements of 234 , 236 , 238U(n, γ) emission spectra made using the DANCE 4 π BaF2 array at the Los Alamos Neutron Science Center will be presented. Calculations of gamma-ray spectra made using the DICEBOX code and of the capture cross section made using the CoH3 code will also be presented. These techniques may be also useful for calculations of more unstable nuclides. This work was performed with the support of the U.S. Department of Energy, National Nuclear Security Administration by Los Alamos National Security, LLC (Contract DE-AC52-06NA25396) and Lawrence Livermore National Security, LLC (Contract DE-AC52-07NA2734).

  8. Measurements of neutron spectra from iron and boron—in—polyethylene bomareded with 14MeV nuetrons

    Institute of Scientific and Technical Information of China (English)

    ZhouYu-Qing; ChenYuan; 等

    1997-01-01

    The leakage spectra of 14MeV neutrons from spheres of iron and boron-inpolyethylene with three differnet mass ratios of boron carbide to polyethylene were measured over the energy range of 20 keV to 16MeV by using proton recoil method.The integral leakages and removal cross sections at different lower cut-off energy were given.

  9. Determination of neutron spectra formed by 40-MeV deuteron bombardment of a lithium target with multi-foil activation technique

    CERN Document Server

    Maekawa, F; Wada, M; Wilson, P P H; Ikeda, Y

    2000-01-01

    Neutron flux spectra at an irradiation field produced by a 40-MeV deuteron bombardment on a thick lithium-target at Forschungszentrum Karlsruhe, Germany, have been determined by the multi-foil activation technique. Twenty-seven dosimetry reactions having a wide energy range of threshold energies up to 38 MeV were employed as detectors for the neutron flux spectra extending to 55 MeV. The spectra were adjusted with the SAND-II code with the experimental reaction rates based on an iterative method. The adjusted spectra validated quantitatively the Monte Carlo deuteron-lithium (d-Li) neutron source model code (M sup C DeLi) which was used to calculate initial guess spectra and also has been used for IFMIF nuclear designs. Accuracy of the adjusted spectra was approx 10% that was suitable for successive integral tests of activation cross section data.

  10. Neutron flux spectra and radiation damage parameters for the Russian Bor-60 and SM-2 reactors

    Energy Technology Data Exchange (ETDEWEB)

    Karasiov, A.V. [D.V. Efremov Scientific Rresearch Institute of Electrophysical Apparatus, St. Petersburg (Russian Federation); Greenwood, L.R. [Pacific Northwest Laboratory, Richland, WA (United States)

    1995-04-01

    The objective is to compare neutron irradiation conditions in Russian reactors and similar US facilities. Neutron fluence and spectral information and calculated radiation damage parameters are presented for the BOR-60 (Fast Experimental Reactor - 60 MW) and SM-2 reactors in Russia. Their neutron exposure characteristics are comparable with those of the Experimental Breeder Reactor (ERB-II), the Fast Flux Test Facility (FFTF), and the High Flux Isotope Reactor (HFIR) in the United States.

  11. Radiation Testing of Consumer High-Speed LSI Chips for the Next Space VLBI Mission, VSOP-2

    CERN Document Server

    Wajima, Kiyoaki; Murata, Yasuhiro; Hirabayashi, Hisashi

    2007-01-01

    We performed two types of radiation testing on high-speed LSI chips to test their suitability for use in wideband observations by the Japanese next space VLBI mission, VSOP-2. In the total ionization dose experiment we monitored autocorrelation spectra which were taken with irradiated LSI chips and the source current at intervals up to 1,000 hours from the ionization dose, but we could not see any change of these features for the chips irradiated with dose rates expected in the VSOP-2 mission. In the single event effect experiment, we monitored the cross correlation phase and power spectra between the data from radiated and non-radiated devices, and the source current during the irradiation of heavy-ions. We observed a few tens of single event upsets as discrete delay jumps for each LSI. We estimated the occurrence rate of single events in space as between once a few days to once a month. No single event latch-up was seen in any of the LSIs. These results show that the tested LSIs have sufficient tolerance to...

  12. Detectability of Circumstellar SiO Maser Emission on VSOP-2 Baselines

    Science.gov (United States)

    Colomer, F.; Bujarrabal, V.; Ruiz, R. S.; Dodson, R.; Alcolea, J.; Desmurs, J.-F.

    2009-08-01

    We have studied compact circumstellar SiO maser emission at 86 GHz with the Global Millimeter VLBI Array (GMVA), which provides the same spatial resolution as the VSOP-2 to ground baselines at 43 GHz. We present preliminary maps of the emission, estimate the flux and size of the maser spots, and discuss their detectability on baselines from VSOP-2 to ground telescopes.

  13. Estimation of Covariances on Prompt Fission Neutron Spectra and Impact of the PFNS Model on the Vessel Fluence

    Directory of Open Access Journals (Sweden)

    Berge Léonie

    2016-01-01

    Full Text Available As the need for precise handling of nuclear data covariances grows ever stronger, no information about covariances of prompt fission neutron spectra (PFNS are available in the evaluated library JEFF-3.2, although present in ENDF/B-VII.1 and JENDL-4.0 libraries for the main fissile isotopes. The aim of this work is to provide an estimation of covariance matrices related to PFNS, in the frame of some commonly used models for the evaluated files, such as the Maxwellian spectrum, the Watt spectrum, or the Madland-Nix spectrum. The evaluation of PFNS through these models involves an adjustment of model parameters to available experimental data, and the calculation of the spectrum variance-covariance matrix arising from experimental uncertainties. We present the results for thermal neutron induced fission of 235U. The systematic experimental uncertainties are propagated via the marginalization technique available in the CONRAD code. They are of great influence on the final covariance matrix, and therefore, on the spectrum uncertainty band width. In addition to this covariance estimation work, we have also investigated the importance on a reactor calculation of the fission spectrum model choice. A study of the vessel fluence depending on the PFNS model is presented. This is done through the propagation of neutrons emitted from a fission source in a simplified PWR using the TRIPOLI-4® code. This last study includes thermal fission spectra from the FIFRELIN Monte-Carlo code dedicated to the simulation of prompt particles emission during fission.

  14. Estimation of Covariances on Prompt Fission Neutron Spectra and Impact of the PFNS Model on the Vessel Fluence

    Science.gov (United States)

    Berge, Léonie; Litaize, Olivier; Serot, Olivier; Archier, Pascal; De Saint Jean, Cyrille; Pénéliau, Yannick; Regnier, David

    2016-02-01

    As the need for precise handling of nuclear data covariances grows ever stronger, no information about covariances of prompt fission neutron spectra (PFNS) are available in the evaluated library JEFF-3.2, although present in ENDF/B-VII.1 and JENDL-4.0 libraries for the main fissile isotopes. The aim of this work is to provide an estimation of covariance matrices related to PFNS, in the frame of some commonly used models for the evaluated files, such as the Maxwellian spectrum, the Watt spectrum, or the Madland-Nix spectrum. The evaluation of PFNS through these models involves an adjustment of model parameters to available experimental data, and the calculation of the spectrum variance-covariance matrix arising from experimental uncertainties. We present the results for thermal neutron induced fission of 235U. The systematic experimental uncertainties are propagated via the marginalization technique available in the CONRAD code. They are of great influence on the final covariance matrix, and therefore, on the spectrum uncertainty band width. In addition to this covariance estimation work, we have also investigated the importance on a reactor calculation of the fission spectrum model choice. A study of the vessel fluence depending on the PFNS model is presented. This is done through the propagation of neutrons emitted from a fission source in a simplified PWR using the TRIPOLI-4® code. This last study includes thermal fission spectra from the FIFRELIN Monte-Carlo code dedicated to the simulation of prompt particles emission during fission.

  15. Monte Carlo simulation of the experimental pulse height spectra produced in diamond detectors by quasi-mono-energetic neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Milocco, A., E-mail: alberto.milocco@ijs.si [Jožef Stefan Institute, Reactor Physics Department, Jamova 39, 1000 Ljubljana (Slovenia); Pillon, M.; Angelone, M. [Associazione EURATOM-ENEA sulla Fusione, ENEA C.R. Frascati, via E. Fermi 45, 00044 Frascati (Rome) (Italy); Plompen, A.; Krása, A. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, B-2440 Geel (Belgium); Trkov, A. [Jožef Stefan Institute, Reactor Physics Department, Jamova 39, 1000 Ljubljana (Slovenia)

    2013-08-21

    This work was carried out in view of the possible use of diamond detectors as high resolution neutron spectrometers for the ITER project. An MCNP5(X) based computational tool has been developed to simulate the fast neutron response of diamond detectors. The source neutrons are generated by a source routine, developed earlier, that includes deuteron beam energy loss, angular straggling, and two-body relativistic kinematics. The diamond detector routine calculates a pulse height spectrum that is built up by elastic and inelastic scattering, (n,a), (n,p), and (n,d) reaction channels. A combination of nuclear data from ENDF/B-VII.0, TENDL-2010, and ENSDF is used. The simulated spectra are compared with measured spectra. It is shown that the simulation tool allows an interpretation of most of the characteristic features in the spectrum. This is an important step towards the use of diamond detectors for spectral analysis and fluence measurements. {sup ©} 2001 Elsevier Science. All rights reserved.

  16. Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

    Energy Technology Data Exchange (ETDEWEB)

    Hatarik, R., E-mail: hatarik1@llnl.gov; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Mcnaney, J. M.; Munro, D. H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Knauer, J. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)

    2015-11-14

    Neutron time-of-flight diagnostics have long been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d + t → n + α (DT) and d + d → n + {sup 3}He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (T{sub ion}) and cold fuel areal density. We report on novel methodologies used to determine neutron yield, apparent T{sub ion}, and DSR. These methods invoke a single temperature, static fluid model to describe the neutron peaks from DD and DT reactions and a spline description of the DT spectrum to determine the DSR. Both measurements are performed using a forward modeling technique that includes corrections for line-of-sight attenuation and impulse response of the detection system. These methods produce typical uncertainties for DT T{sub ion} of 250 eV, 7% for DSR, and 9% for the DT neutron yield. For the DD values, the uncertainties are 290 eV for T{sub ion} and 10% for the neutron yield.

  17. Energy and Angular Spectra of Albedo Protons and Neutrons Emitted from Hydrated Layers of Lunar Regolith

    Science.gov (United States)

    Townsend, L. W.; Zaman, F.; Schwadron, N. A.; Wilson, J. K.; Spence, H. E.; Case, A. W.; Kasper, J. C.; Mazur, J. E.; Looper, M. D.

    2016-11-01

    Energy and angular yields of albedo protons and neutrons emitted from the lunar surface as a function of hydration layer thickness in the lunar regolith using the MCNP computer code developed at Los Alamos National Laboratory are presented.

  18. Characterization of neutron flux spectra in the irradiation sites of a 37 GBq 241Am-Be isotopic source

    Science.gov (United States)

    Yücel, Haluk; Budak, Mustafa Guray; Karadag, Mustafa; Yüksel, Alptuğ Özer

    2014-11-01

    For the applicability of instrumental neutron activation analysis (NAA) technique, an irradiation unit with a 37 GBq 241Am-Be neutron source was installed at Institute of Nuclear Sciences of Ankara University. Design and configuration properties of the irradiation unit are described. It has two different sample irradiation positions, one is called site #1 having a pneumatic sample transfer system and the other is site #2 having a location for manual use. In order to characterize neutron flux spectra in the irradiation sites, the measurement results were obtained for thermal (Фth) and epithermal neutron fluxes (Фepi), thermal to epithermal flux ratio (f) and epithermal spectrum shaping factors (α) by employing cadmium ratios of gold (Au) and molybdenum (Mo) monitors. The activities produced in these foils were measured by using a p-type, 44.8% relative efficiency HPGe well detector. For the measured γ-rays, self-absorption and true coincidence summing effects were taken into account. Additionally, thermal neutron self-shielding and resonance neutron self-shielding effects were taken into account in the measured results. For characterization of site #1, the required parameters were found to be Фth = (2.11 ± 0.05) × 103 n cm-2 s-1, Фepi = (3.32 ± 0.17) × 101 n cm-2 s-1, f = 63.6 ± 1.5, α = 0.045 ± 0.009, respectively. Similarly, those parameters were measured in site #2 as Фth = (1.49 ± 0.04) × 103 n cm-2 s-1, Фepi = (2.93 ± 0.15) × 101 n cm-2 s-1, f = 50.9 ± 1.3 and α = 0.038 ± 0.008. The results for f-values indicate that good thermalization of fast neutrons on the order of 98% was achieved in both sample irradiation sites. This is because an optimum combination of water and paraffin moderator is used in the present configuration. In addition, the shielding requirements are met by using natural boron oxide powder (5.5 cm) and boron loaded paraffin layers against neutrons, and a 15 cm thick lead bricks against gamma-rays from source and its

  19. Neutron energy spectra of sup 2 sup 5 sup 2 Cf, Am-Be source and of the D(d,n) sup 3 He reaction

    CERN Document Server

    Sang Tae Park

    2003-01-01

    The neutron energy spectrum of the following sources were measured using a fast neutron spectrometer with the NE-213 liquid scintillator: sup 2 sup 5 sup 2 Cf, Am-Be and D(d,n) sup 3 He reaction from a 3 MeV Pelletron accelerator in Tokyo Institute of Technology. The measured proton recoil pulse height data of sup 2 sup 5 sup 2 Cf, Am-Be and D(d,n) sup 3 He were unfolded using the mathematical program to obtain the neutron energy spectrum. The sup 2 sup 5 sup 2 Cf and Am-Be neutron energy spectra were measured and the results obtained showed a good agreement with the spectra usually published in the literature. The neutron energy spectrum from D(d,n) sup 3 He was measured and the results obtained also showed a good agreement with the calculation by time of flight (TOF) methods. (author)

  20. High-Redshift Quasars at the Highest Resolution: VSOP Results

    Science.gov (United States)

    Frey, S.; Gurvits, L. I.; Lobanov, A. P.; Schilizzi, R. T.; Paragi, Z.

    2009-08-01

    We studied the radio structure of high-redshift (z>3) quasars with VSOP at 1.6 and 5 GHz. These sources are the most distant objects ever observed with Space VLBI, at rest-frame frequencies up to ˜25 GHz. Here we give an account of the observations and briefly highlight the most interesting cases and results. These observations allowed us, among other things, to estimate the mass of the central black holes powering these quasars, to identify large misalignments between the milli-arcsecond (mas) and sub-mas scale radio structures, and to detect apparent superluminal motion at sub-mas scale.

  1. Neutron capture cross section and capture gamma-ray spectra of 89Y

    Directory of Open Access Journals (Sweden)

    Katabuchi Tatsuya

    2016-01-01

    Full Text Available The neutron capture cross section of 89Y was measured by the time-of-flight method in an energy range from 15 to 100 keV. A pulse-height weighting technique was applied to derive the capture yield. The absolute cross section was determined based on the standard reaciotn 197 Au(n, γ198 Au reaction. The neutron capture γ-ray spectrum was derived by unfolding the pulse-height spectrum with detector response functions.

  2. Ultraviolet spectra of HZ Herculis/Hercules X-1 from HST: Hot gas during total eclipse of the neutron star

    Science.gov (United States)

    Anderson, Scott F.; Wachter, Stefanie; Margon, Bruce; Downes, Ronald A.; Blair, William P.; Halpern, Jules P.

    1994-01-01

    The Faint Object Spectrograph (FOS) aboard Hubble Space Telescope (HST) has been used in the UV to observe the prototypical X-ray pulsar Her X-1 and its companion HZ Her. Optical spectra were also obtained contemporaneously at the Kitt Peak National Observatory (KPNO) 2.1 m. The FOS spectra encompass the 1150-3300 A range near binary orbital phases 0.5 (X-ray maximum) and at 0.0 (mid-X-ray eclipse). The maximum light spectra show strong, narrow C III, N V, O V, Si IV + O IV), N IV), C IV, He II, and N IV emission lines, extending previous IUE results; the O III lambda 3133 Bowen resonance line is also prominent, confirming that the Bowen mechanism is the source of the strong lambda lambda 4640, 4650 emission complex, also seen at maximum light. Most remarkable, however, are the minimum light spectra, where the object is too faint for reasonable observations from IUE. Despite the total eclipse of the X-ray-emitting neutron star, our spectra show strong emission at N V lambda 1240, S IV + O IV) whose emission dominates the UV light at phase 0.0 might be associated with the 'accretion disk corona,' it is more likely the source is somewhat less hot (but extended) gas above and around the disk, or perhaps circumstellar material such as a stellar wind.

  3. In-phantom spectra and dose distributions from a high-energy neutron therapy beam

    CERN Document Server

    Benck, S; Denis, J M; Meulders, J P; Nath, R; Pitcher, E J

    2002-01-01

    In radiotherapy with external beams, healthy tissues surrounding the target volumes are inevitably irradiated. In the case of neutron therapy, the estimation of dose to the organs surrounding the target volume is particularly challenging, because of the varying contributions from primary and secondary neutrons and photons of different energies. The neutron doses to tissues surrounding the target volume at the Louvain-la-Neuve (LLN) facility were investigated in this work. At LLN, primary neutrons have a broad spectrum with a mean energy of about 30 MeV. The transport of a 10x10 cm sup 2 beam through a water phantom was simulated by means of the Monte Carlo code MCNPX. Distributions of energy-differential values of neutron fluence, kerma and kerma equivalent were estimated at different locations in a water phantom. The evolution of neutron dose and dose equivalent inside the phantom was deduced. Measurements of absorbed dose and of dose equivalent were then carried out in a water phantom using an ionization ch...

  4. The imprint of the crustal magnetic field on the thermal spectra and pulse profiles of isolated neutron stars

    CERN Document Server

    Perna, Rosalba; Pons, Jose' A; Rea, Nanda

    2013-01-01

    Isolated neutron stars (NSs) show a bewildering variety of astrophysical manifestations, presumably shaped by the magnetic field strength and topology at birth. Here, using state-of-the art calculations of the coupled magnetic and thermal evolution of NSs, we compute the thermal spectra and pulse profiles expected for a variety of initial magnetic field configurations. In particular, we contrast models with purely poloidal magnetic fields to models dominated by a strong internal toroidal component. We find that, while the former displays double peaked profiles and very low pulsed fractions, in the latter, the anisotropy in the surface temperature produced by the toroidal field often results in a single pulse profile, with pulsed fractions that can exceed the 50-60% level even for perfectly isotropic local emission. We further use our theoretical results to generate simulated "observed" spectra, and show that blackbody (BB) fits result in inferred radii that can be significantly smaller than the actual NS radi...

  5. Microscopic study of low-lying yrast spectra and deformation systematics in neutron-rich 98−106Sr isotopes

    Indian Academy of Sciences (India)

    Anil Chandan; Suram Singh; Arun Bharti; S K Khosa

    2009-10-01

    Variation-after-projection (VAP) calculations in conjunction with Hartree–Bogoliubov (HB) ansatz have been carried out for = 98–106 strontium isotopes. In this framework, the yrast spectra with ≥ 10+, (2) transition probabilities, quadrupole deformation parameter and occupation numbers for various shell model orbits have been obtained. The results of the calculation for yrast spectra give an indication that it is important to include the hexadecapole–hexadecapole component of the two-body interaction for obtaining various nuclear structure quantities in Sr isotopes. Besides this, it is also found that the simultaneous polarization of 3/2 and 5/2 proton subshells is a significant factor in making a sizeable contribution to the deformation in neutron-rich Sr isotopes.

  6. Characterization of neutron flux spectra in the irradiation sites of a 37 GBq {sup 241}Am-Be isotopic source

    Energy Technology Data Exchange (ETDEWEB)

    Yücel, Haluk [Ankara University, Institute of Nuclear Sciences, 06100 Tandogan, Ankara (Turkey); Budak, Mustafa Guray, E-mail: mbudak@gazi.edu.tr [Gazi University, Gazi Education Faculty, 06500 Teknikokullar, Ankara (Turkey); Karadag, Mustafa [Gazi University, Gazi Education Faculty, 06500 Teknikokullar, Ankara (Turkey); Yüksel, Alptuğ Özer [Ankara University, Institute of Nuclear Sciences, 06100 Tandogan, Ankara (Turkey)

    2014-11-01

    Highlights: • An irradiation unit was installed using a 37 GBq {sup 241}Am-Be neutron source. • The source neutrons moderated by using both water and paraffin. • Irradiation unit was shielded by boron oxide and lead against neutrons and gammas. • There are two sites for irradiations, one of them has a pneumatic transfer system. • Cadmium ratio method was used for irradiation site characterization. - Abstract: For the applicability of instrumental neutron activation analysis (NAA) technique, an irradiation unit with a 37 GBq {sup 241}Am-Be neutron source was installed at Institute of Nuclear Sciences of Ankara University. Design and configuration properties of the irradiation unit are described. It has two different sample irradiation positions, one is called site #1 having a pneumatic sample transfer system and the other is site #2 having a location for manual use. In order to characterize neutron flux spectra in the irradiation sites, the measurement results were obtained for thermal (φ{sub th}) and epithermal neutron fluxes (φ{sub epi}), thermal to epithermal flux ratio (f) and epithermal spectrum shaping factors (α) by employing cadmium ratios of gold (Au) and molybdenum (Mo) monitors. The activities produced in these foils were measured by using a p-type, 44.8% relative efficiency HPGe well detector. For the measured γ-rays, self-absorption and true coincidence summing effects were taken into account. Additionally, thermal neutron self-shielding and resonance neutron self-shielding effects were taken into account in the measured results. For characterization of site #1, the required parameters were found to be φ{sub th} = (2.11 ± 0.05) × 10{sup 3} n cm{sup −2} s{sup −1}, φ{sub epi} = (3.32 ± 0.17) × 10{sup 1} n cm{sup −2} s{sup −1}, f = 63.6 ± 1.5, α = 0.045 ± 0.009, respectively. Similarly, those parameters were measured in site #2 as φ{sub th} = (1.49 ± 0.04) × 10{sup 3} n cm{sup −2} s{sup −1}, φ{sub epi} = (2.93 ± 0

  7. Dual-Frequency VSOP Observations of AO 0235+164

    CERN Document Server

    Frey, S; Altschüler, D R; Davis, M M; Perillat, P; Salter, C J; Aller, H D; Aller, M F; Hirabayashi, H

    2000-01-01

    AO 0235+164 is a very compact, flat spectrum radio source identified as a BL Lac object at a redshift of z=0.94. It is one of the most violently variable extragalactic objects at both optical and radio wavelengths. The radio structure of the source revealed by various ground-based VLBI observations is dominated by a nearly unresolved compact component at almost all available frequencies. Dual-frequency space VLBI observations of AO 0235+164 were made with the VSOP mission in January-February 1999. The array of the Japanese HALCA satellite and co-observing ground radio telescopes in Australia, Japan, China and South Africa allowed us to study AO 0235+164 with an unprecedented angular resolution at frequencies of 1.6 and 5 GHz. We report on the sub-milliarcsecond structural properties of the source. The 5-GHz observations led to an estimate of T_B > 5.8 x 10^{13} K for the rest-frame brightness temperature of the core, which is the highest value measured with VSOP to date.

  8. Neutron Spectra, Fluence and Dose Rates from Bare and Moderated Cf-252 Sources

    Energy Technology Data Exchange (ETDEWEB)

    Radev, Radoslav P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-04-01

    A new, stronger 252Cf source (serial number SR-CF-3050-OR) was obtained from Oak Ridge National Laboratory (ORNL) in 2014 to supplement the existing 252Cf sources which had significantly decayed. A new instrument positioning track system was designed and installed by Hopewell Designs, Inc. in 2011. The neutron field from the new, stronger 252Cf source in the modified calibration environment needed to be characterized as well as the modified neutron fields produced by the new source and seven different neutron moderators. Comprehensive information about our 252Cf source, its origin, production, and isotopic content and decay characteristics needed to be compiled as well. This technical report is intended to address these issues.

  9. Neutron Capture Cross Sections and Gamma Emission Spectra from Neutron Capture on 234,236,238U Measured with DANCE

    Science.gov (United States)

    Ullmann, J. L.; Mosby, S.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Jandel, M.; Kawano, T.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wilhelmy, J. B.; Wu, C.-Y.; Becker, J. A.; Chyzh, A.; Baramsai, B.; Mitchell, G. E.; Krticka, M.

    2014-05-01

    A new measurement of the 238U(n, γ) cross section using a thin 48 mg/cm2 target was made using the DANCE detector at LANSCE over the energy range from 10 eV to 500 keV. The results confirm earlier measurements. Measurements of the gamma-ray emission spectra were also made for 238U(n, γ) as well as 234,236U(n, γ). These measurements help to constrain the radiative strength function used in the cross-section calculations.

  10. Quasi-monoenergetic neutron energy spectra for 246 and 389 MeV (7)Li(p,n) reactions at angles from 0 degrees to 300 degrees

    CERN Document Server

    Iwamoto, Y; Nakamura, T; Nakashima, H; Mares, V; Itoga, T; Matsumoto, T; Nakane, Y; Feldbaumer, E; Jaegerhofer, L; Pioch, C; Tamii, A; Satoh, D; Masuda, A; Sato, T; Iwase, H; Yashima, H; Nishiyama, J; Hagiwara, M; Hatanaka, K; Sakamoto, Y

    2011-01-01

    The authors measured the neutron energy spectra of a quasi-monoenergetic (7)Li(p,n) neutron source with 246 and 389 MeV protons set at seven angles (0 degrees, 2.5 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees and 30 degrees), using a time-of-flight (TOF) method employing organic scintillators NE213 at the Research Center for Nuclear Physics (RCNP) of Osaka University. The energy spectra of the source neutrons were precisely deduced down to 2 MeV at 0 degrees and 10 MeV at other angles. The cross-sections of the peak neutron production reaction at 0 degrees were on the 35-40 mb line of other experimental data, and the peak neutron angular distribution agreed well with the Taddeucci formula. Neutron energy spectra below 100 MeV at all angles were comparable, but the shapes of the continuum above 150 MeV changed considerably with the angle. In order to consider the correction required to derive the response in the peak region from the measured total response for high-energy neutron monitors such as DAR...

  11. A model for non-thermalized neutron spectra emitted from para-hydrogen

    DEFF Research Database (Denmark)

    Schönfeldt, Troels; Batkov, K.; Klinkby, Esben Bryndt

    2016-01-01

    to the high radiation environment near the moderator and cooling demands. One of the very popular materials, used at J-PARC and planed for ESS, is the spin singlet state of H2, para-hydrogen. This study assesses the non-Maxwellian neutron spectral structure achieved in para-hydrogen moderators, which is due...... to the complexity of the inelastic scattering cross section below 50 meV. The analytical description of a thermalized spectrum with slowing down components are discussed, then a formula is developed which is a good description of this non-equilibrium para-hydrogen neutron spectrum.These analytical descriptions...

  12. Accuracy of Mass and Radius Determination for Neutron Stars in X-ray Bursters from Simulated LOFT Spectra

    Science.gov (United States)

    Majczyna, A.; Madej, J.; Różańska, A.; Należyty, M.

    2017-06-01

    We present a simulation of an X-ray spectrum of a hot neutron star, as would be seen by the LAD detector on board of LOFT satellite. We also compute a grid of theoretical spectra corresponding to a range of effective temperatures Teff and surface gravities log g with values corresponding to compact stars in Type I X-ray bursters. A neutron star with the mass M=1.64 M⊙ and the radius R=11.95 km (which yields the surface gravity log g=14.30 [cgs] and the surface redshift z=0.30) is used in simulation. Accuracy of mass and radius determination by fitting theoretical spectra to the observed one is found to be M=1.64+0.16-0.02 M⊙ and R=11.95+1.57-0.40 km (2σ). The confidence contours for these two variables are narrow but elongated, and therefore the resulting constraints on the EOS cannot be strong. Note, that in this paper we aim to discuss error contours of NS mass and radius, whereas discussion of EOS is beyond the scope of this work.

  13. A simple method for the analysis of neutron resonance capture spectra

    NARCIS (Netherlands)

    Clarijs, M.C.; Bom, V.R.; Van Eijk, C.W.E.

    2009-01-01

    Neutron resonance capture analysis (NRCA) is a method used to determine the bulk composition of various kinds of objects and materials. It is based on analyzing direct capture resonance peaks. However, the analysis is complicated by scattering followed by capture effects in the object itself. These

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

    Science.gov (United States)

    Barzilov, Alexander; Novikov, Ivan

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

  15. Gravitationally redshifted absorption lines in the X-ray burst spectra of a neutron star

    NARCIS (Netherlands)

    Cottam, J.; Paerels, F.; Mendez, M.

    2002-01-01

    The fundamental properties of neutron stars provide a direct test of the equation of state of cold nuclear matter, a relationship between pressure and density that is determined by the physics of the strong interactions between the particles that constitute the star. The most straightforward method

  16. Gravitationally redshifted absorption lines in the X-ray burst spectra of a neutron star

    NARCIS (Netherlands)

    Cottam, J.; Paerels, F.; Mendez, M.

    2002-01-01

    The fundamental properties of neutron stars provide a direct test of the equation of state of cold nuclear matter, a relationship between pressure and density that is determined by the physics of the strong interactions between the particles that constitute the star. The most straightforward method

  17. Simplified method for deducing high-energy neutron spectra between 1 and 100 MeV using Foil-Activation Method

    Energy Technology Data Exchange (ETDEWEB)

    Kasugai, Y.; Matsuda, N.; Sakamoto, Y.; Nakashima, H. [Japan Atomic Energy Agency, Tokai-mura, Ibaraki-ken 319-1195 (Japan); Yashima, H. [Research Reactor Inst., Kyoto Univ., Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Matsumura, H.; Iwase, H.; Hirayama, H. [High Energy Accelerator Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Mokhov, N.; Leveling, A.; Boehnlein, D.; Vaziri, K.; Lauten, G. [Fermi National Accelerator Laboratory, Batavia, IL 87545 (United States); Oishi, K. [Shimizu Corporation, 4-17, Echujima 3-chome, Koto-ku, Tokyo 135-8530 (Japan); Nakamura, T. [Tohoku Univ., Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan)

    2011-07-01

    The Japanese and American Study of Muon Interaction and Neutron detection (JASMIN) collaboration, has been conducting shielding experiments using the Fermilab anti-proton target station (Pbar) shielding assembly. A multi-foil technique was used to measure the high energy neutron spectra, in the range of 1 to 100 MeV, for the target station shielding configuration. The neutron spectra were de-convoluted using a new fitting method. This method is based on the assumption that a neutron spectrum can be expressed as a simple sum of two exponentials. The validity of the fitting method was confirmed by comparison with the results obtained using SAND-II computer code and theoretical calculations. Finally, it was found that there are simple correlations between reaction rates and the adjustable parameters in the fitting function. (authors)

  18. Determination of neutron spectra within the energy of 1 keV to 1 MeV by means of reactor dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Sergeyeva, Victoria; Destouches, Christophe; Lyoussi, Abdallah [Instrumentation Sensors and Dosimetry Laboratory, CEA Cadarache 13108, (France); Thiollay, Nicolas; Vigneau, Olivier [Chemical and Radiochemical Analyses Laboratory, CEA Cadarache 13108, (France); Korschinek, Gunther [Maier Leibnitz Laboratorium, Technische Universitaet Munchen, Am Coulombwall 6, 85748 Garching, (Germany); Carcreff, Hubert [OSIRIS Irradiation Programme Support Laboratory, CEA Saclay Gif-sur-Yvette 91191, (France)

    2015-07-01

    The standard procedure for neutron reactor dosimetry is based on neutron irradiation of a target and its post-irradiation analysis by Gamma and/or X-ray spectrometry. Nowadays, the neutron spectra can be easily characterized for thermal and fast energies (respectively 0.025 eV and >1 MeV). In this work we propose a new target and an innovating post-irradiation technique of analysis in order to detect the neutron spectra within the energy of 1 keV to 1 MeV. This article will present the calculations performed for the selection of a suitable nuclear reaction and isotope, the results predicted by simulations, the irradiation campaign that is proposed and the post-irradiation technique of analysis. (authors)

  19. The holistic analysis of gamma-ray spectra in instrumental neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Blaauw, M.

    1993-11-15

    The subject is the computerized analysis of the gamma-ray spectra in INAA. This analysis can be separated in three parts: The conversion of the spectra to information on {gamma}-ray energies and their relative intensities (spectrum reduction), the determination of the relation between the intensity of a {gamma}-ray and the amount of the corresponding element present in the sample (standardization) and the attribution of the {gamma}-ray energies to the elements, including the subsequent computation of the amounts of the elements (interpretation). A {gamma}-ray spectrum can be considered to be the linear sum of the {gamma}-ray spectra of the individual radionuclides present in the sample. Knowing the relative activities of the different radionuclides that may be produced by activation of a single element, a {gamma}-ray spectrum in INAA can also be considered to be the linear sum of the spectra of the elements. This principle has hitherto not been used in INAA to analyze the spectra by linear least squares methods, using all {gamma}-ray energies observed in the spectrum. The implementation of this `holistic` approach required that attention be paid to both spectrum reduction, standardization and interpretation. The thesis describes the methods developed for the holistic analysis of {gamma}-ray spectra in INAA, and present results of experimental comparisons between the holistic and other approaches. (orig./HP).

  20. Gravitationally Redshifted Absorption Lines in the Burst Spectra of the Neutron Star in the X-Ray Binary EXO 0748-676

    Science.gov (United States)

    Cottoam, J.; Paerels, F.; Mendez, M.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    The most straightforward manner of determining masses and radii of neutron stars is by measuring the gravitational redshift of spectral lines produced in the neutron star photosphere; such a measurement would provide direct constraints on the mass-to-radius ratio of the neutron star, and therefore on the equation of state for neutron star matter. Using data taken with the Reflection Grating Spectrometer on board the XMM-Newton observatory we identify, for the first time, significant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO 0748-676. The most significant features are consistent with the Fe XXVI and XXV n=2-3 and O VIII n=1-2 transitions, with a redshift of z=0.35, identical within small uncertainties for the different transitions. This constitutes the first direct and unambiguous measurement of the gravitational redshift in a neutron star.

  1. 3C 84 Expanding Radio Lobe Revealed by VSOP Observations

    Science.gov (United States)

    Asada, K.; Kameno, S.; Shen, Z.-Q.; Shinji, H.; Gabuzda, D. C.; Inoue, M.

    2009-08-01

    We report the detection of the expansion and inner proper motions of a young radio lobe associated with the bright radio source 3C 84 in the Seyfert galaxy NGC 1275 using multi-epoch VSOP observation. The observed inner proper motions are consistent with the evolution scenario of classical double radio sources. The apparent expansion velocity is 0.50 ± 0.09 c, and the age of radio lobe is estimated to be 45.7 ± 8.9 years in 2001. The total flux density at 5 GHz increased at the end of the 1950's, with several peaks in the middle of the 1980's, and is in a decay phase now. The decay of total flux density can be naturally explained by an adiabatic cooling due to the expansion of the radio lobe, and previously measured spectral indices suggest that the emission comes from the surface of the radio lobe.

  2. Measurement of 14 MeV neutron-induced prompt gamma-ray spectra from 15 elements found in cargo containers

    Energy Technology Data Exchange (ETDEWEB)

    Perot, B. [Commissariat a l' Energie Atomique, 13108 St Paul-lez-Durance (France)], E-mail: bertrand.perot@cea.fr; Carasco, C.; Bernard, S.; Mariani, A. [Commissariat a l' Energie Atomique, 13108 St Paul-lez-Durance (France); Szabo, J.-L.; Sannie, G. [Commissariat a l' Energie Atomique, 91191 Gif-Sur-Yvette (France); Valkovic, V.; Sudac, D. [Institute Ruder Boskovic, 54 Bijenicka c., 10000 Zagreb (Croatia); Viesti, G.; Lunardon, M.; Botosso, C.; Nebbia, G.; Pesente, S.; Moretto, S. [INFN and Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy); Zenoni, A.; Donzella, A. [INFN and Universita di Brescia, 38 Via Branze, 25123 Brescia (Italy); Moszynski, M.; Gierlik, M. [Soltan Institute for Nuclear Studies, PL 05-400 Otwock-Swierk (Poland); Klamra, W. [Royal Institute of Technology, 10691 Stockholm (Sweden); Le Tourneur, P. [EADS-SODERN, 20 Av. Descartes, 94451 Limeil-Brevannes Cedex (France)] (and others)

    2008-04-15

    Within the EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) project, the gamma-ray spectra produced in a series of materials by 14-MeV tagged-neutron beams have been collected in the inspection portal equipped with large volume NaI(Tl) detectors, in order to build a database of signatures for various elements: C, N, O, Na, Al, Si, Cl, K, Ca, Cr, Fe, Ni, Cu, Zn, Pb. The measured spectra have been compared with prediction from Monte Carlo simulations to verify the consistency of the relevant nuclear data inputs. This library of measured 14-MeV neutron-induced gamma-ray spectra is currently used in a data processing algorithm to unfold the energy spectra of the transported goods into elementary contributions, thus allowing material identification.

  3. Disk-Jet Connection in the Nearby Low Luminosity AGN M 81: A Proposal for VSOP-2 Key Science Program

    Science.gov (United States)

    Nagai, H.; Asada, K.; Doi, A.; Kino, M.; Kameno, S.; VSOP-2 Science Working Group

    2009-08-01

    We propose a monitoring observation to probe the disk-jet connection in the nearby low luminosity AGN M 81 with VSOP-2 and an X-ray telescope. M 81 is the nearest Active Galactic Nuclei and VSOP-2 can resolve the region near the central black hole and jet-launching region. This proposal is one of the Key Science Programs. Key Science Programs (KSPs) for science observations of Active Galactic Nuclei, are made under the responsibility of the VSOP-2 mission and determined by the VSOP-2 Science Working Group, and by the VISC-2.

  4. Characterization of the Caliban and Prospero Critical Assemblies Neutron Spectra for Integral Measurements Experiments

    Science.gov (United States)

    Casoli, P.; Authier, N.; Jacquet, X.; Cartier, J.

    2014-04-01

    Caliban and Prospero are two highly enriched uranium metallic core reactors operated on the CEA Center of Valduc. These critical assemblies are suitable for integral experiments, such as fission yields measurements or perturbation measurements, which have been carried out recently on the Caliban reactor. Different unfolding methods, based on activation foils and fission chambers measurements, are used to characterize the reactor spectra and especially the Caliban spectrum, which is very close to a pure fission spectrum.

  5. Diffusive properties of water in Artemia cysts as determined from quasi-elastic neutron scattering spectra. [Artemia shrimp

    Energy Technology Data Exchange (ETDEWEB)

    Trantham, E.C.; Rorschach, H.E.; Clegg, J.S.; Hazlewood, C.F.; Nicklow, R.M.; Wakabayashi, N.

    1984-05-01

    Results have been obtained on the quasi-elastic spectra of neutrons scattered from pure water, 20% agarose gel (hydration four grams H/sub 2/O per gram of dry solid) and cysts of the brine shrimp Artemia for hydrations between 0.10 and 1.2 grams H/sub 2/O per gram of dry solids. The spectra were interpreted using a two-component model that included contributions from the covalently bonded protons and the hydration water, and a mobile water fraction. The mobile fraction was described by a jump-diffusion correlation function for the translation motion and a simple diffusive orientational correlation function. The results for the line widths ..gamma..(Q/sup 2/) for pure water were in good agreement with previous measurements. The agarose results were consistent with NMR measurements that show a slightly reduced translational diffusion for the mobile water fraction. The Artemia results show that the translational diffusion coefficient of the mobile water fraction was greatly reduced from that of pure water. The line width was determined mainly by the rotational motion, which was also substantially reduced from the pure water value as determined from dielectric relaxation studies. The translational and rotational diffusion parameters were consistent with the NMR measurements of diffusion and relaxation. Values for the hydration fraction and the mean square thermal displacement as determined from the Q-dependence of line areas were also obtained.

  6. Effects of tertiary MLC configuration on secondary neutron spectra from 18 MV x-ray beams for the Varian 21EX linear accelerator.

    Science.gov (United States)

    Howell, Rebecca M; Kry, Stephen F; Burgett, Eric; Followill, David; Hertel, Nolan E

    2009-09-01

    The effect of the jaw configuration and the presence and configuration of the tertiary multileaf collimator (MLC) on the secondary neutron spectra for an 18 MV Varian 21EX linear accelerator (linac) is investigated in detail. The authors report the measured spectra for four collimator (jaw-and-MLC) configurations. These configurations represent the extreme settings of the jaws and MLC and should therefore describe the range of possible fluence and spectra that may be encountered during use of this linac. In addition to measurements, a Monte Carlo model was used to simulate the four collimator configurations and calculate the energy spectra and fluence at the same location as it was measured. The Monte Carlo model was also used to calculate the sources of neutron production in the linac head for each collimator configuration. They found that photoneutron production in the linac treatment head is dominated by the order in which the primary photon beam intercepts the high-Z material. The primary collimator, which has the highest position in the linac head (in a fixed location), is the largest source of secondary neutrons. Thereafter, the collimator configuration plays a role in where the neutrons originate. For instance, if the jaws are closed, they intercept the beam and contribute substantially to the secondary neutron production. Conversely, if the jaws are open, the MLC plays a larger role in neutron production (assuming, of course, that it intercepts the beam). They found that different collimator configurations make up to a factor of 2 difference in the ambient dose equivalent.

  7. Analysis of neutron diffraction spectra acquired in situ during mechanical loading of shape memory NiTiFe at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, V.B.; Manjeri, R.M. [Advanced Materials Processing and Analysis Center (AMPAC), Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Clausen, B.; Brown, D.W. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Vaidyanathan, R. [Advanced Materials Processing and Analysis Center (AMPAC), Department of Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States)], E-mail: raj@mail.ucf.edu

    2008-05-25

    The Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory was used to acquire neutron diffraction spectra in situ during mechanical loading at 216 and 237 K. The experiments were performed with the objective of following the texture, strain and phase fraction evolution in the trigonal R-phase in a Ni{sub 46.8}Ti{sub 50}Fe{sub 3.2} shape memory alloy. A methodology to quantify the textures, strains and phase fractions using the General Structure Analysis System (GSAS) for Rietveld refinement of neutron diffraction spectra, is implemented and described. Emphasis is placed on evaluating the choice of P3 and P3-bar space groups for the R-phase in the refinements and the impact of this choice on the quantitative analyses of spectra.

  8. Neutron Spectrometric Analysis: Characterization of {sup 3}He Detector Response and Chemometric Data Analysis of Pulse-Height Spectra

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Yun; Choi, Yong Suk; Park, Yong Joon; Song, Kyu Seok [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2008-10-15

    Among many nucleonic gauges using a variety of sources such as alpha, beta, gamma, neutron or X-ray radiation, neutron-based techniques have been successfully used in landmine detection, cargo inspection and soil analysis as well as in the industrial process monitoring such as cement, glass, coal industries, etc. In general, there are three categories of neutron-based methods: fast neutron analysis (FNA), thermal neutron analysis (TNA) and neutron moderation. FNA and TNA utilize the slow or fast neutrons for the generation of characteristic prompt gamma-ray to identify the element of interest in many applications. The neutron moderation is attractive for the process monitoring of the moisture content in the bulk samples. In spite of its many advantages, the false-alarm rate of the neutron method is of great interest in the field operations.

  9. Recoil proton, alpha particle, and heavy ion impacts on microdosimetry and RBE of fast neutrons: analysis of kerma spectra calculated by Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Pignol, J.-P. [Toronto-Sunnybrook Regional Cancer Centre, Radiotherapy Dept., Toronto, Ontario (Canada); Slabbert, J. [National Accelerator Centre, Faure (South Africa)

    2001-02-01

    Fast neutrons (FN) have a higher radio-biological effectiveness (RBE) compared with photons, however the mechanism of this increase remains a controversial issue. RBE variations are seen among various FN facilities and at the same facility when different tissue depths or thicknesses of hardening filters are used. These variations lead to uncertainties in dose reporting as well as in the comparisons of clinical results. Besides radiobiology and microdosimetry, another powerful method for the characterization of FN beams is the calculation of total proton and heavy ion kerma spectra. FLUKA and MCNP Monte Carlo code were used to simulate these kerma spectra following a set of microdosimetry measurements performed at the National Accelerator Centre. The calculated spectra confirmed major classical statements: RBE increase is linked to both slow energy protons and alpha particles yielded by (n,{alpha}) reactions on carbon and oxygen nuclei. The slow energy protons are produced by neutrons having an energy between 10 keV and 10 MeV, while the alpha particles are produced by neutrons having an energy between 10 keV and 15 MeV. Looking at the heavy ion kerma from <15 MeV and the proton kerma from neutrons <10 MeV, it is possible to anticipate y* and RBE trends. (author)

  10. Neutron energy and time-of-flight spectra behind the lateral shield of a high energy electron accelerator beam dump 2, Monte Carlo simulations

    CERN Document Server

    Roesler, Stefan; Rokni, Sayed H; Taniguchi, Shingo

    2003-01-01

    Energy spectra of high-energy neutrons and neutron time-of-flight spectra were calculated for the setup of experiment T-454 performed with a NE213 liquid scintillator at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were created by the interaction a 28.7 GeV electron beam in the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shielding. In order to determine the attenuation length of high-energy neutrons additional concrete shielding of various thicknesses was placed outside the existing shielding. The calculations were performed using the FLUKA interaction and transport code. The energy and time-of-flight spectra were recorded for the location of the detector allowing a detailed comparison with the experimental data. A generally good description of the data is achieved adding confidence to the use of FLUKA for the design of shielding for high-energy electron accelerators. (5 refs).

  11. Neutron energy and time-of-flight spectra behind the lateral shield of a high-energy electron accelerator beam dump. Part 2. Monte Carlo simulations

    CERN Document Server

    Roesler, S; Rokni, S H; Taniguchi, S

    2003-01-01

    Energy spectra of high-energy neutrons and neutron time-of-flight spectra were calculated for the setup of experiment T-454 performed with a NE213 liquid scintillator at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were created by the interaction a 28.7 GeV electron beam in the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shielding. In order to determine the attenuation length of high-energy neutrons additional concrete shielding of various thicknesses was placed outside the existing shielding. The calculations were performed using the FLUKA interaction and transport code. The energy and time-of-flight spectra were recorded for the location of the detector allowing a detailed comparison with the experimental data. A generally good description of the data is achieved adding confidence to the use of FLUKA for the design of shielding for high-energy electron accelerators.

  12. Recoil proton, alpha particle, and heavy ion impacts on microdosimetry and RBE of fast neutrons: analysis of kerma spectra calculated by Monte Carlo simulation.

    Science.gov (United States)

    Pignol, J P; Slabbert, J

    2001-02-01

    Fast neutrons (FN) have a higher radio-biological effectiveness (RBE) compared with photons, however the mechanism of this increase remains a controversial issue. RBE variations are seen among various FN facilities and at the same facility when different tissue depths or thicknesses of hardening filters are used. These variations lead to uncertainties in dose reporting as well as in the comparisons of clinical results. Besides radiobiology and microdosimetry, another powerful method for the characterization of FN beams is the calculation of total proton and heavy ion kerma spectra. FLUKA and MCNP Monte Carlo code were used to simulate these kerma spectra following a set of microdosimetry measurements performed at the National Accelerator Centre. The calculated spectra confirmed major classical statements: RBE increase is linked to both slow energy protons and alpha particles yielded by (n,alpha) reactions on carbon and oxygen nuclei. The slow energy protons are produced by neutrons having an energy between 10 keV and 10 MeV, while the alpha particles are produced by neutrons having an energy between 10 keV and 15 MeV. Looking at the heavy ion kerma from neutrons <10 MeV, it is possible to anticipate y* and RBE trends.

  13. Measurement and Calculation of High-Energy Neutron Spectra behind Shielding at the CERF 120 GeV/c Hadron Beam Facility

    CERN Document Server

    Nakao, N; Roesler, S; Brugger, M; Hagiwara, M; Vincke, H; Khater, H; Prinz, A A; Rokni, S H; Kosako, K

    2008-01-01

    Neutron energy spectra were measured behind the lateral shield of the CERF (CERN-EU High Energy Reference Field) facility at CERN with a 120 GeV/c positive hadron beam (a mixture of mainly protons and pions) on a cylindrical copper target (7-cm diameter by 50-cm long). An NE213 organic liquid scintillator (12.7-cm diameter by 12.7-cm long) was located at various longitudinal positions behind shields of 80- and 160-cm thick concrete and 40-cm thick iron. The measurement locations cover an angular range with respect to the beam axis between 13 and 133 degrees. Neutron energy spectra in the energy range between 32 MeV and 380 MeV were obtained by unfolding the measured pulse height spectra with the detector response functions which have been verified in the neutron energy range up to 380 MeV in separate experiments. Since the source term and experimental geometry in this experiment are well characterized and simple, and results are given in the form of energy spectra, these experimental results are very useful a...

  14. Measurement of very forward neutron energy spectra for 7 TeV proton–proton collisions at the Large Hadron Collider

    Directory of Open Access Journals (Sweden)

    O. Adriani

    2015-11-01

    Full Text Available The Large Hadron Collider forward (LHCf experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC s=7 TeV proton–proton collisions with the pseudo-rapidity η ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results, and the DPMJET 3.04 model describes our results well at the lower pseudo-rapidity ranges. However, no model perfectly explains the experimental results over the entire pseudo-rapidity range. The experimental data indicate a more abundant neutron production rate relative to the photon production than any model predictions studied here.

  15. New prompt fission neutron spectra measurements in the 238U(n,f) reaction with a dedicated setup at LANSCE/WNR

    Science.gov (United States)

    Laurent, Benoit; Marini, Paola; Bélier, Gilbert; Bonnet, Thomas; Chatillon, Audrey; Taieb, Julien; Etasse, David; Devlin, Matthew; Haight, Robert

    2017-09-01

    A new prompt fission neutron spectra (PFNS) measurement in the 238U(n,f) reaction was performed at LANSCE/WNR facility. Evaluated data show discrepancies on the low (below 1 MeV) and high (above 5 MeV) energy parts in the PFNS for different major and minor actinides. The goal is to improve these measurements in a wide range of incident energy. The energy of the incoming neutron, inducing the fission, and the prompt neutron energies, are measured by time-of-flight method. A dedicated fission chamber was developed, in order to improve alpha-fission discrimination, timing resolution, actinide mass, and to reduce the amount of neutron scattering. To detect prompt neutrons, the 54 Chi-Nu scintillator cells array were surrounding the fission chamber. High statistics were recorded during this experiment, allowing a precise study of PFNS behavior as a function of incident neutron energy, from 1 MeV to 200 MeV. This experiment also showed that all the new tools developed to improve PFNS measurements are performing. Therefore, measurements of PFNS with others actinides such as 239Pu are planned.

  16. VSOP-2 Observations of Accretion Disks in Active Galactic Nuclei: A Proposal for a Key Science Program

    Science.gov (United States)

    Doi, A.; VSOP-2 Science Working Group

    2009-08-01

    We report the advantages and potentials of VSOP-2 observations for research on accretion disks, and a polished plan based on this studies may be proposed as one of the Key Science Programs of VSOP-2 mission in the category of Active Galactic Nuclei (AGN). A radiative inefficient accretion flow, a possible model of accretion disks on low-luminosity AGNs, predicts electron temperatures of about 10^9 K at radii within several tens of Schwarzschild radius. The region should be optically thick at the observing frequencies of VSOP-2. Hence, the shape of accretion disks could be imaged with the sensitivity and angular resolutions of VSOP-2 for some nearby low-luminosity AGNs. We show a list of target candidates in terms of their apparent Schwarzschild radius and radio properties. A pre-launch ground-based survey would be needed in order to determine the priority order, which will be useful for preparing an effective VSOP-2 observation plan.

  17. Testing Rate Dependent corrections on timing mode EPIC-pn spectra of the accreting Neutron Star GX 13+1

    CERN Document Server

    Pintore, F; di Salvo, T; Guainazzi, M; D'Aì, A; Riggio, A; Burderi, L; Iaria, R; Robba, N R

    2014-01-01

    When the EPIC-pn instrument on board XMM-Newton is operated in Timing mode, high count rates (>100 cts/s) of bright sources may affect the calibration of the energy scale, resulting in a modification of the real spectral shape. The corrections related to this effect are then strongly important in the study of the spectral properties. Tests of these calibrations are more suitable in sources which spectra are characterised by a large number of discrete features. Therefore, in this work, we carried out a spectral analysis of the accreting Neutron Star GX 13+1, which is a dipping source with several narrow absorption lines and a broad emission line in its spectrum. We tested two different correction approaches on an XMM-Newton EPIC-pn observation taken in Timing mode: the standard Rate Dependent CTI (RDCTI or epfast) and the new, Rate Dependent Pulse Height Amplitude (RDPHA) corrections. We found that, in general, the two corrections marginally affect the properties of the overall broadband continuum, while hints...

  18. VSOP-2 : a space VLBI mission to image central engines and jet launching regions

    Science.gov (United States)

    Kameno, Seiji; Tsuboi, Masato; Murata, Yasuhiro; Doi, Akihiro; Asaki, Yoshiharu; Mochizuki, Nanako; Hagiwara, Yoshi-Aki; Kino, Motoki; Nagai, Hiroshi; Asada, Keiichi; Inoue, Makoto; Sudou, Hiroshi; Sawada-Satoh, Satoko

    VSOP-2 is a space VLBI program using the spacecraft ASTRO-G to be launched in 2015 by the Japan Aerospace eXploration Agency. The array consisting of a 9-m antenna in orbit and ground radio telescopes offers angular resolutions of 40, 80, and 210 microarcsec at 43, 22, and 8 GHz, respectively. The resolution allows us to image accretion disks and jet launching regions in nearby active galactic nuclei such as M 87. Dual polarization receivers enable full Stokes images at all frequency to illustrate magnetic fields in jets. Phase referencing is capable for astrometry by 60-sec-cycle switching maneuvers. Higher sensitivity than the VSOP (HALCA) is achieved by cooled receivers at 22 and 43 GHz, 1-Gbps wideband downlink, and longer coherent integration. We will introduce the mission overview, observational specifications, and key sciences of the VSOP-2. We call for community's scientific contributions to the mission.

  19. VSOP Studies of Internal Structure of the Jet in 3C 273

    Science.gov (United States)

    Lobanov, A. P.

    2009-08-01

    Observations with VSOP provided an excellent tool for imaging relativistic flows in great detail. Enhanced resolution and high-dynamic range of VSOP observations enabled resolving internal structure of the parsec-scale jet in 3C 273. This has provided a unique opportunity to determine accurately physical properties of the flow and study the onset and evolution of Kelvin-Helmholtz instability. Several modes of the instability have been identified and traced along the jet, yielding the most detailed picture of the Kelvin-Helmholtz instability developing in a relativistic jet. Exploring and expanding of this area of studies will certainly be further advanced by the next generation space VLBI mission VSOP-2.

  20. Wide-Band Data Transmission System Expected in the Next Generation Space VLBI Mission: VSOP-2

    Science.gov (United States)

    Murata, Yasuhiro; Hirabayashi, Hisashi

    2002-01-01

    Following the success of the VLBI Space Observatory Program (VSOP), a next generation space VLBI mission (VSOP-2) is currently being planned. We expect the data rate of more than 1 Gbps to get more sensitivity. Here we will present: (1) How to sample the data (on board), including the radiation test results which show we can have the 10 Gbps sampler LSI which can use in space; (2) Possibility of the bit rate more than 1 Gbps to downlink the VLBI data. We studied the link budget for the wide band data transmission, and discussed the various ideas which can get more than 1 Gbps; and (3) What kind of VLBI tracking station and recording system will be expected for the VSOP-2 mission? We will present the idea of using normal radio telescopes as a tracking station, and also review the possibility of recording and processing at the tracking stations and correlators.

  1. VSOP monitoring of the compact BL Lac object AO 0235+164

    CERN Document Server

    Frey, S; Gabuzda, D C; Salter, C J; Altschüler, D R; Perillat, P; Aller, M F; Aller, H D; Hirabayashi, H; Davis, M M

    2005-01-01

    In 1999, the highly compact and variable BL Lac object AO 0235+164 was identified as the highest brightness temperature active galactic nucleus observed with the VLBI Space Observatory Programme (VSOP), with T_B > 5.8 x 10^{13} K. The sub-milliarcsecond radio structure of this source has been studied with dual-frequency (1.6 and 5 GHz), polarization-sensitive VSOP observations during 2001 and 2002. Here we present the results of this monitoring campaign. At the time of these observations, the source was weakly polarized and characterized by a radio core that is clearly resolved on space-ground baselines.

  2. VSOP Imaging of the Quasar PKS 1402+044 at z = 3.2

    Science.gov (United States)

    Yang, J.; Gurvits, L. I.; Frey, S.; Lobanov, A. P.; Hong, X.-Y.

    2009-08-01

    We present results of VSOP observations of the high-redshift (z = 3.2) quasar PKS 1402+044 (J1405+0415) at 1.6 and 5 GHz, and VLA observations at 1.4, 5, 16, and 43 GHz. The source has a pronounced core-jet structure traced by VSOP down to sub-mas angular scales. The results offer a set of observational data enabling physical diagnostics of the inner parsecs of a typical radio-loud quasar.

  3. Development of a photonuclear activation file and measurement of delayed neutron spectra; Creation d'une bibliotheque d'activation photonucleaire et mesures de spectres d'emission de neutrons retardes

    Energy Technology Data Exchange (ETDEWEB)

    Giacri-Mauborgne, M.L

    2005-11-15

    This thesis work consists in two parts. The first part is the description of the creation of a photonuclear activation file which will be used to calculated photonuclear activation. To build this file we have used different data sources: evaluations but also calculations done using several cross sections codes (HMS-ALICE, GNASH, ABLA). This file contains photonuclear activation cross sections for more than 600 nuclides and fission fragments distributions for 30 actinides at tree different Bremsstrahlung energies and the delay neutron spectrum associated. These spectra are not in good agreement with experimental data. That is why we decided to launch measurement of delayed neutrons spectra from photofission. The second part of this thesis consists in demonstrating the possibility to do such measurements at the ELSA accelerator facility. To that purpose, we have developed the detection, the acquisition system and the analysis method of such spectra. These were tested for the measurement of the delayed neutron spectrum of uranium-238 after irradiation in a 2 MeV neutron flux. Finally, we have measured the delayed neutron spectrum of uranium-238 after irradiation in a 15 MeV Bremsstrahlung flux. We compare our results with experimental data. The experiment has allowed us to improve the value of {nu}{sub p}-bar with an absolute uncertainty below 7%, we propose {nu}{sub p}-bar = (3.03 {+-} 0.02) n/100 fissions, and to correct the Nikotin's parameters for the six group representation. Particularly, we have improved the data concerning the sixth group by taking into account results from different irradiation times.

  4. Comparative study of Monte Carlo particle transport code PHITS and nuclear data processing code NJOY for recoil cross section spectra under neutron irradiation

    Science.gov (United States)

    Iwamoto, Yosuke; Ogawa, Tatsuhiko

    2017-04-01

    Because primary knock-on atoms (PKAs) create point defects and clusters in materials that are irradiated with neutrons, it is important to validate the calculations of recoil cross section spectra that are used to estimate radiation damage in materials. Here, the recoil cross section spectra of fission- and fusion-relevant materials were calculated using the Event Generator Mode (EGM) of the Particle and Heavy Ion Transport code System (PHITS) and also using the data processing code NJOY2012 with the nuclear data libraries TENDL2015, ENDF/BVII.1, and JEFF3.2. The heating number, which is the integral of the recoil cross section spectra, was also calculated using PHITS-EGM and compared with data extracted from the ACE files of TENDL2015, ENDF/BVII.1, and JENDL4.0. In general, only a small difference was found between the PKA spectra of PHITS + TENDL2015 and NJOY + TENDL2015. From analyzing the recoil cross section spectra extracted from the nuclear data libraries using NJOY2012, we found that the recoil cross section spectra were incorrect for 72Ge, 75As, 89Y, and 109Ag in the ENDF/B-VII.1 library, and for 90Zr and 55Mn in the JEFF3.2 library. From analyzing the heating number, we found that the data extracted from the ACE file of TENDL2015 for all nuclides were problematic in the neutron capture region because of incorrect data regarding the emitted gamma energy. However, PHITS + TENDL2015 can calculate PKA spectra and heating numbers correctly.

  5. Comparative study of Monte Carlo particle transport code PHITS and nuclear data processing code NJOY for recoil cross section spectra under neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Iwamoto, Yosuke, E-mail: iwamoto.yosuke@jaea.go.jp; Ogawa, Tatsuhiko

    2017-04-01

    Because primary knock-on atoms (PKAs) create point defects and clusters in materials that are irradiated with neutrons, it is important to validate the calculations of recoil cross section spectra that are used to estimate radiation damage in materials. Here, the recoil cross section spectra of fission- and fusion-relevant materials were calculated using the Event Generator Mode (EGM) of the Particle and Heavy Ion Transport code System (PHITS) and also using the data processing code NJOY2012 with the nuclear data libraries TENDL2015, ENDF/BVII.1, and JEFF3.2. The heating number, which is the integral of the recoil cross section spectra, was also calculated using PHITS-EGM and compared with data extracted from the ACE files of TENDL2015, ENDF/BVII.1, and JENDL4.0. In general, only a small difference was found between the PKA spectra of PHITS + TENDL2015 and NJOY + TENDL2015. From analyzing the recoil cross section spectra extracted from the nuclear data libraries using NJOY2012, we found that the recoil cross section spectra were incorrect for {sup 72}Ge, {sup 75}As, {sup 89}Y, and {sup 109}Ag in the ENDF/B-VII.1 library, and for {sup 90}Zr and {sup 55}Mn in the JEFF3.2 library. From analyzing the heating number, we found that the data extracted from the ACE file of TENDL2015 for all nuclides were problematic in the neutron capture region because of incorrect data regarding the emitted gamma energy. However, PHITS + TENDL2015 can calculate PKA spectra and heating numbers correctly.

  6. Spectra and neutron dose of an 18 MV Linac using two geometric models of the head; Espectros y dosis por neutrones de un Linac de 18 MV usando dos modelos geometricos del cabezal

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, M. T.; Pino, F.; Barros, H.; Sajo-Bohus, L. [Universidad Simon Bolivar, Laboratorio de Fisica Nuclear, Sartenejas, Baruta 1080-A, Caracas (Venezuela, Bolivarian Republic of); Davila, J. [Fisica Medica C. A., Av. Francisco de Miranda s/n, Los Palos Grandes, 1060 Miranda (Venezuela, Bolivarian Republic of); Salcedo, E. [Centro Medico Docente La Trinidad, Av. de El Haltillo, Caracas (Venezuela, Bolivarian Republic of); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico); Benites R, J. L., E-mail: mariate9590@gmail.com [Centro de Cancerologia de Nayarit, Servicio de Seguridad Radiologica, Calz. de la Cruz 118 Sur, 63000 Tepic, Nayarit (Mexico)

    2015-10-15

    Full text: Using the Monte Carlo method, by MCNP5 code, simulations were performed with different source terms and 2 geometric models of the head to obtain spectra in energy, flow and doses of photo-neutrons at different positions on the stretcher and in the radiotherapy room. The simplest model was a spherical shell of tungsten; the second was the complete model of a heterogeneous head of an accelerator Varian ix. In both models Tosi function was used as a source term. In addition, for the second model Sheikh-Bagheri distribution was used for photons and photo-neutrons were generated. Also in both models the radiotherapy room of Gurve group of the Teaching Medical Center La Trinidad was included, which is equipped with an accelerator Varian Clinic 2100. In this Center passive detectors PADC (Cr-39) were irradiated with neutron converters, with 18 MeV photons radiation. The measured neutron flow was compared with that obtained with Monte Carlo calculations. The Monte Carlo flows are similar to those measured at the isocenter. The simplest model underestimates the neutron flow compared with the calculated flows with the heterogeneous model of the head. (Author)

  7. Measurement of very forward neutron energy spectra for 7 TeV proton--proton collisions at the Large Hadron Collider

    CERN Document Server

    Adriani, O.; Bonechi, L.; Bongi, M.; Castellini, G.; D'Alessandro, R.; Del Prete, M.; Haguenauer, M.; Itow, Y.; Kasahara, K.; Kawade, K.; Makino, Y.; Masuda, K.; Matsubayashi, E.; Menjo, H.; Mitsuka, G.; Muraki, Y.; Okuno, Y.; Papini, P.; Perrot, A-L.; Ricciarini, S.; Sako, T.; Sakurai, N.; Sugiura, Y.; Suzuki, T.; Tamura, T.; Tiberio, A.; Torii, S.; Tricomi, A.; Turner, W.C.; Zhou, Q.D.

    2015-01-01

    The Large Hadron Collider forward (LHCf) experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC $\\sqrt{s}$ = 7 TeV proton--proton collisions with the pseudo-rapidity $\\eta$ ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the difference in the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results and the DPMJET 3.04 model describes our results well at the lower pseudo-...

  8. V.S.O.P. (99/09) Computer Code System for Reactor Physics and Fuel Cycle Simulation; Version 2009

    OpenAIRE

    Rütten, H.-J.; Haas, K. A.; Brockmann, H.; Ohlig, U.; Pohl, C.; Scherer, W.

    2010-01-01

    V.S.O.P.(99/ 09) represents the further development of V.S.O.P.(99/ 05). Compared to its precursor, the code system has been improved again in many details. The main motivation for this new code version was to update the basic nuclear libraries used by the code system. Thus, all cross section libraries involved in the code have now been based on ENDF/B-VII. V.S.O.P. is a computer code system for the comprehensive numerical simulation of the physics of thermal reactors. It implies the setup of...

  9. Reconstruction of neutron spectra using neural networks starting from the Bonner spheres spectrometric system; Reconstruccion de espectros de neutrones usando redes neuronales a partir del sistema espectrometrico de esferas de Bonner

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz R, J.M.; Martinez B, M.R.; Arteaga A, T.; Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E. [Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)

    2005-07-01

    The artificial neural networks (RN) have been used successfully to solve a wide variety of problems. However to determine an appropriate set of values of the structural parameters and of learning of these, it continues being even a difficult task. Contrary to previous works, here a set of neural networks is designed to reconstruct neutron spectra starting from the counting rates coming from the detectors of the Bonner spheres system, using a systematic and experimental strategy for the robust design of multilayer neural networks of the feed forward type of inverse propagation. The robust design is formulated as a design problem of Taguchi parameters. It was selected a set of 53 neutron spectra, compiled by the International Atomic Energy Agency, the counting rates were calculated that would take place in a Bonner spheres system, the set was arranged according to the wave form of those spectra. With these data and applying the Taguchi methodology to determine the best parameters of the network topology, it was trained and it proved the same one with the spectra. (Author)

  10. VSOP's Legacy for our Understanding of Magnetic Fields in Active Galactic Nuclei

    Science.gov (United States)

    Gabuzda, D. C.

    2009-08-01

    Although relatively few polarisation-sensitive observations were carried out with VSOP, they have had a profound effect on our picture of the compact central regions of radio emission in Active Galactic Nuclei (AGN). The extra resolution provided by these images at relatively low frequencies provided new information about the ``core'' polarisation observed in ground-based images, indicating that this polarised emission is, in many cases, associated with newly emerging jet components, rather than the intrinsically optically thick core. A joint analysis of VSOP and VLBA polarisation observations near in time revealed the first observation of the theoretically predicted 90-degree rotation in polarisation angle associated with the transition from the optically thick to the optically thin regime. Perhaps most significantly, and quite unforeseen, VSOP polarisation observations provided the first clear evidence that at least some of the polarisation associated with the jets of AGN is associated with the ``intrinsic'' magnetic fields of the jets themselves, rather than local phenomena, such as shock compression or shear interaction with the surrounding medium. These extremely important VSOP polarisation observations have had a profound influence on subsequent work in this field, leading to a whole new series of VLBI studies focusing on the possibility that many AGN jets may have helical magnetic fields - which could come about naturally via the combined effect of the rotation of the central supermassive black hole and accretion disk and the jet outflow. These studies, in turn, provide crucial new links with theoretical investigations and concepts, making it possible for VLBI observations to seriously address for the first time such fundamental questions as the launching and collimation mechanisms for the jets. Key VSOP polarisation observations and the fundamentally new studies to which they have led are reviewed.

  11. Nuclear level densities in 208Bi and 209Po from the neutron spectra in the ( p, n) reactions on 208Pb and 209Bi nuclei

    Science.gov (United States)

    Zhuravlev, B. V.; Lychagin, A. A.; Titarenko, N. N.; Demenkov, V. G.; Trykova, V. I.

    2010-07-01

    The spectra of neutrons from the ( p, n) reactions on the 208Pb and 209Bi nuclei were measured in the proton-energy range 8-11 MeV. These measurements were performed by using a time-of-flight spectrometer of fast neutrons on the basis of the pulsed tandem accelerator EGP-15 of the Institute of Physics and Power Engineering (Obninsk, Russian Federation). A high resolution and stability of the time-of-flight spectrometermade it possible to identify reliably low-lying discrete levels alongwith the continuum section of the neutron spectra. The measured data were analyzed on the basis of the statistical equilibrium and preequilibrium models of nuclear reactions. The respective calculations were performed by using the precise formalism of Hauser-Feshbach statistical theory together with the generalizedmodel of a superfluid nucleus and the back-shifted Fermi gas model for the nuclear-level density. The nuclear-level densities in 208Bi and 209Po were determined along with their energy dependences and model parameters. Our results are discussed together with available experimental data and recommendations of model systematics.

  12. Design of an artificial neural network, with the topology oriented to the reconstruction of neutron spectra; Diseno de una red neuronal artificial, con la topologia orientada a la reconstruccion del espectro de neutrones

    Energy Technology Data Exchange (ETDEWEB)

    Arteaga A, T.; Ortiz R, J.M.; Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.; Mercado S, G.A. [Unidades Academicas de Estudios Nucleares, Ingenieria Electrica y Matematicas, Universidad de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)]. e-mail: tarcicio70@yahoo.co.uk

    2006-07-01

    People that live in high places respect to the sea level, in latitudes far from the equator or that they travel by plane, they are exposed to atmospheres of high radiation generated by the cosmic rays. Another atmosphere with radiation is the medical equipment, particle accelerators and nuclear reactors. The evaluation of the biological risk for neutron radiation requires an appropriate and sure dosimetry. A commonly used system is the Bonner Sphere Spectrometer (EEB) with the purpose of reconstructing the spectrum that is important because the equivalent dose for neutrons depends strongly on its energy. The count rates obtained in each sphere are treated, in most of the cases, for iterative methods, Monte Carlo or Maximum Entropy. Each one of them has difficulties that it motivates to the development of complementary procedures. Recently it has been used Artificial Neural Networks, ANN) and not yet conclusive results have been obtained. In this work it was designed an ANN to obtain the neutron energy spectrum neutrons starting from the counting rate of count of an EEB. The ANN was trained with 129 reference spectra obtained of the IAEA (1990, 2001), 24 were built as defined energy, including isotopic sources of neutrons of reference and operational, of accelerators, reactors, mathematical functions, and of defined energy with several peaks. The spectrum was transformed from lethargy units to energy and were reaccommodated in 31 energies using the Monte Carlo code 4C. The reaccommodated spectra and the response matrix UTA4 were used to calculate the prospective count rates in the EEB. These rates were used as entrance and its respective spectrum was used as output during the net training. The net design is Retropropagation type with 5 layers of 7, 140, 140, 140 and 31 neurons, transfer function logsig, tansig, logsig, logsig, logsig respectively. Training algorithm, traingdx. After the training, the net was proven with a group of training spectra and others that

  13. Gamma-Ray Emission Spectra as a Constraint on Calculations of 234,236,238U Neutron-Capture Cross Sections

    Energy Technology Data Exchange (ETDEWEB)

    Ullmann, John Leonard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kawano, Toshihiko [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bredeweg, Todd Allen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baramsai, Bayarbadrakh [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Couture, Aaron Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Haight, Robert Cameron [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Jandel, Marian [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mosby, Shea Morgan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); O' Donnell, John M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rundberg, Robert S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vieira, David J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wilhelmy, Jerry B. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Becker, John A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wu, Ching-Yen [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Krticka, Milan [Charles Univ., Prague (Czech Republic)

    2015-05-28

    Neutron capture cross sections in the “continuum” region (>≈1 keV) and gamma-emission spectra are of importance to basic science and many applied fields. Careful measurements have been made on most common stable nuclides, but physicists must rely on calculations (or “surrogate” reactions) for rare or unstable nuclides. Calculations must be benchmarked against measurements (cross sections, gamma-ray spectra, and <Γγ>). Gamma-ray spectrum measurements from resolved resonances were made with 1 - 2 mg/cm2 thick targets; cross sections at >1 keV were measured using thicker targets. The results show that the shape of capture cross section vs neutron energy is not sensitive to the form of the strength function (although the magnitude is); the generalized Lorentzian E1 strength function is not sufficient to describe the shape of observed gamma-ray spectra; MGLO + “Oslo M1” parameters produces quantitative agreement with the measured 238U(n,γ) cross section; additional strength at low energies (~ 3 MeV) -- likely M1-- is required; and careful study of complementary results on low-lying giant resonance strength is needed to consistently describe observations.

  14. VSOP/Hv1 proton channels sustain calcium entry, neutrophil migration, and superoxide production by limiting cell depolarization and acidification

    National Research Council Canada - National Science Library

    El Chemaly, Antoun; Okochi, Yoshifumi; Sasaki, Mari; Arnaudeau, Serge; Okamura, Yasushi; Demaurex, Nicolas

    2010-01-01

    .... Voltage-gated proton channels (voltage-sensing domain only protein [VSOP]/Hv1) are required for high-level superoxide production by phagocytes, but the mechanism of this effect is not established...

  15. Multi-mirror imaging optics for low-loss transport of divergent neutron beams and tailored wavelength spectra

    CERN Document Server

    Zimmer, Oliver

    2016-01-01

    A neutron optical transport system is proposed which comprises nested short elliptical mirrors located halfway between two common focal points M and M'. It images cold neutrons from a diverging beam or a source with finite size at M by single reflections onto a spot of similar size at M'. Direct view onto the neutron source is blocked by a central absorber with little impact on the transported solid angle. Geometric neutron losses due to source size can be kept small using modern supermirrors and distances M-M' of a few tens of metres. Very short flat mirrors can be used in practical implementations. Transport with a minimum of reflections remedies losses due to multiple reflections that are common in long elliptical neutron guides. Moreover, well-defined reflection angles lead to new possibilities for enhancing the spectral quality of primary beams, such as clear-cut discrimination of short neutron wavelengths or beam monochromation using bandpass supermirrors. Multi-mirror imaging systems may thus complemen...

  16. Measurement of the MACS of {sup 181}Ta(n,γ) at kT=30 keV as a test of a method for Maxwellian neutron spectra generation

    Energy Technology Data Exchange (ETDEWEB)

    Praena, J., E-mail: jpraena@us.es [Universidad de Sevilla (Spain); Centro Nacional de Aceleradores, Sevilla (Spain); Mastinu, P.F. [Laboratori Nazionali di Legnaro, INFN, Padova (Italy); Pignatari, M. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Quesada, J.M. [Universidad de Sevilla (Spain); García-López, J. [Universidad de Sevilla (Spain); Centro Nacional de Aceleradores, Sevilla (Spain); Lozano, M. [Universidad de Sevilla (Spain); Dzysiuk, N. [International Nuclear Safety Center of Ukraine, Kyiv (Ukraine); Capote, R. [NAPC–Nuclear Data Section, International Atomic Energy Agency, Vienna (Austria); Martín-Hernández, G. [Centro de Aplicaciones Tecnólogicas y Desarrollo Nuclear, 5ta y 30, Playa, La Habana (Cuba)

    2013-11-01

    Measurement of the Maxwellian-Averaged Cross-Section (MACS) of the {sup 181}Ta(n,γ) reaction at kT=30 keV by the activation technique using an innovative method for the generation of Maxwellian neutron spectra is presented. The method is based on the shaping of the proton beam to produce a desired neutron spectrum using the {sup 7}Li(p,n) reaction as a neutron source. The characterization of neutron spectra has been performed by combining measured proton distributions, an analytical description of the differential neutron yield in angle and energy of the {sup 7}Li(p,n) reaction, and with Monte Carlo simulations of the neutron transport. A measured value equal to 815±73 mbarn is reported for the MACS of the reaction {sup 181}Ta(n,γ) at kT=30 keV. The MACS of the reaction {sup 197}Au(n,γ) provided by KADoNiS has been used as a reference. -- Author-Highlights: • Generation of Maxwellian neutron spectrum for astrophysics and nuclear data validation. • {sup 7}Li(p,n) reaction and proton distributions conformed by aluminum as a shaper foil. • Measurement of the proton distributions and simulation of the neutron transport. • MACS of {sup 181}Ta(n,γ) at kT=30 keV measured by the activation technique. • First accelerator-based neutron source in Spain.

  17. Mathematical treatment of digitalized spectra of the neutron diffractometer for microcomputer; Tratamiento matematico de espectros digitalizados del difractometro de neutrones para microcomputadora

    Energy Technology Data Exchange (ETDEWEB)

    Macias B, L.R

    1991-06-15

    For the study of materials by means of diffraction, it is required in the first place that the sample is a crystalline material so that the diffraction is possible and the digitized spectra of corresponding diffraction can be generated. This spectra, for any type of study consists of a great number of readings (counting or counts per second Cps) that of some way are related to a determined angle to be able to reproduce a diagram that will be evaluated to conclude the study according to it is. Since the evaluation will depend on the angular readings that are carried out in the mentioned spectra, it is required of a good definition of the curves for its angular reading. Well-known the problem of the no enough definition of the spectra to be able to carry out the angular reading, it was proceeds to outline a possible solution which consists on making a mathematical treatment to the spectra with the purpose of being able to define the angular positions of interest and to correct some operation factors that appear in the spectra. (Author)

  18. A correlated study between effective total macroscopic cross sections and effective energies for neutron beams with continuous spectra

    CERN Document Server

    Kobayashi, H

    1999-01-01

    Two practically useful quantities have been introduced to characterize a continuous-energy-spectrum neutron beam and to describe transmission phenomena of the beam in the field of quantitative neutron radiography. These quantities are the effective energy instead of a peak energy or a mean energy of the spectrum and an effective total macroscopic (ETM) cross section instead of a total macroscopic (TM) cross section as defined for a monochromatic energy. Four neutron beams have been used to measure ETM cross sections at effective energies of 29.8, 17.2, 9.8 meV, and at the In resonance energy of 1.46 eV. Results are studied as a function of estimated effective energy, where the effective energy was estimated by a beam quality indicator (BQI) which has been proposed recently. Validity of ETM cross sections as a function of the effective energy is discussed and correlated with recent nuclear data.

  19. Designs and Development of Multimode Horns for ASTRO-G/VSOP-2 Satellite

    Science.gov (United States)

    Ujihara, H.

    2009-08-01

    The antenna optics of VSOP-2 satellite require low cross polarization, and the volume of the receiver box is limited. Thus, instead of conventional corrugated horns, multimode horns were proposed and designed in order to reduce the axial length and weight of the horns but still compatible with a low cross polarization. These multimode horns were designed for three observational bands of VSOP-2 at 8GHz, 22GHz, 43GHz, all with about the same antenna illumination size. However, the ratio of waveguide and wavelength are slightly different. The 22GHz-horn was designed at first, and the other horns were arranged around it. The properties of the horns were improved by controlling the complex amplitude of higher modes and by fitting the beam width to the antenna optics. The BBM models of horns were tested, and their measured beam patterns agree well with numerical simulations.

  20. Monte Carlo simulation of prompt gamma-ray spectra from depleted uranium under D-T neutron irradiation and electron recoil spectra in a liquid scintillator detector

    CERN Document Server

    Qin, Jianguo; Liu, Rong; Zhu, Tonghua; Zhang, Xinwei; Ye, Bangjiao

    2015-01-01

    To overcome the problem of inefficient computing time and unreliable results in MCNP5 calculation, a two-step method is adopted to calculate the energy deposition of prompt gamma-rays in detectors for depleted uranium spherical shells under D-T neutrons irradiation. In the first step, the gamma-ray spectrum for energy below 7 MeV is calculated by MCNP5 code; secondly, the electron recoil spectrum in a BC501A liquid scintillator detector is simulated based on EGSnrc Monte Carlo Code with the gamma-ray spectrum from the first step as input. The comparison of calculated results with experimental ones shows that the simulations agree well with experiment in the energy region 0.4-3 MeV for the prompt gamma-ray spectrum and below 4 MeVee for the electron recoil spectrum. The reliability of the two-step method in this work is validated.

  1. VizieR Online Data Catalog: VSOP 5GHz AGN survey V. (Dodson+, 2008)

    Science.gov (United States)

    Dodson, R.; Fomalont, E. B.; Wiik, K.; Horiuchi, S.; Hirabayashi, H.; Edwards, P. G.; Murata, Y.; Asaki, Y.; Moellenbrock, G. A.; Scott, W. K.; Taylor, A. R.; Gurvits, L. I.; Paragi, Z.; Frey, S.; Shen, Z.-Q.; Lovell, J. E. J.; Tingay, S. J.; Rioja, M. J.; Fodor, S.; Lister, M. L.; Mosoni, L.; Coldwell, G.; Piner, B. G.; Yang, J.

    2009-08-01

    The VSOP mission and the 5GHz AGN Survey are fully discussed in Hirabayashi et al. (1998Sci...281.1825H, 2000PASJ...52..955H), Paper I (Hirabayashi et al., 2000, Cat J/PASJ/52/997), and Fomalont et al. (2000, Cat. J/ApJS/131/95). Observations began in 1997 August, with the final observations being made in 2003 October. Of the VSS sample of 294 sources, all but 29 were observed. (3 data files).

  2. Measurement of the Antenna Mesh: Characteeristics for VSOP-2/ASTRO-G

    Science.gov (United States)

    Ujihara, H.; Bushimata, T.

    2009-08-01

    The surface of the main reflector antenna of the VSOP-2 satellite is made of metal wire that is woven into a tense mesh. Numerical simulations are required to determine the reflectivity characteristics of the mesh which are functions of the reflecting angle, polarization and frequency of the incident radio wave and the tension of the mesh. These characteristics were measured with the tension of 200g/m, 350g/m, 500g/m.

  3. Verification of the Effectiveness of VSOP-2 Phase Referencing with a Newly Developed Simulation Tool, ARIS

    CERN Document Server

    Asaki, Yoshiharu; Kono, Yusuke; Doi, Akihiro; Dodson, Richard; Pradel, Nicolas; Murata, Yasuhiro; Mochizuki, Nanako; Edwards, Philip G; Sasao, Tetsuo; Fomalont, Edward B

    2007-01-01

    The next-generation space VLBI mission, VSOP-2, is expected to provide unprecedented spatial resolutions at 8.4, 22, and 43GHz. In this report, phase referencing with VSOP-2 is examined in detail based on a simulation tool called ARIS. The criterion for successful phase referencing was to keep the phase errors below one radian. Simulations with ARIS reveal that phase referencing achieves good performance at 8.4GHz, even under poor tropospheric conditions. At 22 and 43GHz, it is recommended to conduct phase referencing observations under good or typical tropospheric conditions. The satellite is required to have an attitude-switching capability with a one-minute or shorter cycle, and an orbit determination accuracy higher than about 10cm at apogee; the phase referencing calibrators are required to have a signal-to-noise ratio larger than four for a single scan. The probability to find a suitable phase referencing calibrator was estimated by using VLBI surveys. From the viewpoint of calibrator availability, VSOP...

  4. Characterization of the neutron spectra at the final of the installations labyrinth with medical accelerators; Caracterizacion del espectro de neutrones al final del laberinto de instalaciones con aceleradores medicos

    Energy Technology Data Exchange (ETDEWEB)

    Carelli, J.; Cruzate, J.A.; Gregori, B.; Papadopulos, S.; Discacciatti, A. [Autoridad Reguladora Nuclear, Av. del Libertador 8250, Buenos Aires (Argentina)]. e-mail: jcarelli@cae.arn.gov.ar

    2006-07-01

    A linear electron accelerator for medical use is an equipment dedicated to the production of collimated beams of electrons and/or photons. In an accelerator of a bigger potential or equal to 6 MV, are produced neutrons starting from the reaction (gamma, n) due to the interaction of the photons with the materials that compose the headset and the target. In this work the theoretical and experimental studies carried out to characterize the neutron spectra to the exit of the labyrinth of three bunkers of different geometry with accelerators of 15 MV, with the purpose of evaluating the effective dose of the occupationally exposure personnel are presented. It was carried out the simulation of the neutron transport with the MCNPX code and the ENDF/B - VI library. With the objective of analyzing the variables that affect the spectral distribution the bunkers of two existent facilities in Argentina were modeled. It was considered a isotropic punctual source located in the supposed position of the target. The spectra of {sup 252} Cf and of Watt of 1.8 MeV of half energy were simulated. The election of the sources was based on published works that suppose initial neutron sources with half energy between 1.8 and 2.3 MeV for accelerators of 15 at 25 MV. Its were considered headsets of different dimensions, with and without phantom of water disperser in the patient's position and several field dimensions in the isocenter. The spectral distribution doesn't present significant differences in the different modeling situations. Its were carried out measurements, with the multisphere spectrometric system based on twelve polyethylene spheres and a spherical detector of {sup 3} He, to the exit of each one of the bunkers. It was carried out the convolution of the spectrum using the MXD{sub F}C33 code (of the UMG33 set), considering as initial spectrum that of the fission type (inverse of the energy). The obtained spectra and the environmental equivalent dose rate in each case

  5. Problems of interference and geometry of the detectors in a beam tube for the determination of the neutron spectra; Problemas de interferencia y geometria de los detectores en un tubo de haces para la determinacion del espectro de neutrones

    Energy Technology Data Exchange (ETDEWEB)

    Paredes G, L.C

    1991-11-15

    The detector materials were selected and proved for the thermal, intermediate and quick energy intervals of the neutron spectra, in the radial tube RW-2 to 1 MW of thermal power during 5 min, being obtained good results respect to the activation of the thin sheets. However, since the exhibition speed, of each experimental arrangement after it irradiation that was of the order of 2 R/h, it was considered that may be more convenient the irradiation, separated from each thin sheet, for that which it was selected the SINCA irradiation system, because it simplified the activities related with the individual irradiation of the thin sheets and the count of the same ones. It was found that the selection, the geometric arrangement and measurement of the activities of the used thin sheets, its are the three factors that more affect the input data of the SAND II code that it will be used in our case for the determination of the neutron spectra of the Reactor. (Author)

  6. Unconventional role of voltage-gated proton channels (VSOP/Hv1) in regulation of microglial ROS production.

    Science.gov (United States)

    Kawai, Takafumi; Okochi, Yoshifumi; Ozaki, Tomohiko; Imura, Yoshio; Koizumi, Schuichi; Yamazaki, Maya; Abe, Manabu; Sakimura, Kenji; Yamashita, Toshihide; Okamura, Yasushi

    2017-09-01

    It has been established that voltage-gated proton channels (VSOP/Hv1), encoded by Hvcn1, support reactive oxygen species (ROS) production in phagocytic activities of neutrophils (El Chemaly et al. ) and antibody production in B lymphocytes (Capasso et al. ). VSOP/Hv1 is a potential therapeutic target for brain ischemia, since Hvcn1 deficiency reduces microglial ROS production and protects brain from neuronal damage (Wu et al. ). In the present study, we report that VSOP/Hv1 has paradoxical suppressive role in ROS production in microglia. Extracellular ROS production was lower in neutrophils of Hvcn1(-/-) mice than WT mice as reported. In contrast, it was drastically enhanced in isolated Hvcn1(-/-) microglia as compared with cells from WT mice. Actin dynamics was altered in Hvcn1(-/-) microglia and intracellular distribution of cytosolic NADPH oxidase subunit, p67, was changed. When expression levels of oxidative stress responsive antioxidant genes were compared between WT and Hvcn1(-/-) in cerebral cortex at different ages of animals, they were slightly decreased in Hvcn1(-/-) mice at younger stage (1 day, 5 days, 3 weeks old), but drastically increased at aged stage (6 months old), suggesting that the regulation of microglial ROS production by VSOP/Hv1 is age-dependent. We also performed brain ischemic stroke experiments and found that the neuroprotective effect of VSOP/Hv1deficiency on infarct volume depended on the age of animals. Taken together, regulation of ROS production by VSOP/Hv1 is more complex than previously thought and significance of VSOP/Hv1 in microglial ROS production depends on age. © 2017 International Society for Neurochemistry.

  7. Energetic neutron and gamma-ray spectra under the earth radiation belts according to "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686" orbital complex and "CORONAS-I" satellite data.

    Science.gov (United States)

    Bogomolov, A V; Dmitriev, A V; Myagkova, I N; Ryumin, S P; Smirnova, O N; Sobolevsky, I M

    1998-01-01

    The spectra of neutrons >10 MeV and gamma-rays 1.5-100 MeV under the Earth Radiation Belts, restored from the data, obtained onboard orbital complex "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686", are presented. The spectra shapes are similar to those for albedo neutrons and gamma-rays, but absolute values of their fluxes (0.2 cm-2 s-1 for neutrons, 0.8 cm-2 s-1 for gamma-rays at the equator and 1.2 cm-2 s-1, 1.9 cm-2 s-1, accordingly, at L=1.9) are several times as large. It is possibly explained by the fact that most of the detected particles were produced by the cosmic ray interactions with the orbital complex matter. Neutron and gamma-ray fluxes obtained from "CORONAS-1" data are near those for albedo particles.

  8. The n,{gamma} discrimination in recoil-proton proportional counters. Application to the measurement of fast neutron spectra; Discrimination n,{gamma} dans les compteurs proportionnels a protons de recul. Application a la mesure des spectres de neutrons rapides

    Energy Technology Data Exchange (ETDEWEB)

    Jeandidier, C. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-07-01

    A description is given of a spectrometry chain working in the energy range of a few keV to 1 MeV, and designed for measurement of fast neutron spectra. It consists of detectors, recoil proton proportional counters built especially for this work by R. COMTE (DEG/SER) and which make it possible to cover the energy range and also associated electronic equipment. A brief description is first given of the physical processes involved: (n,p) collisions in the gas, influence of {gamma} radiation; the method of discrimination is then presented. It is based on the difference in the rise-times of the pulses. In the experiments described here the use of a bi-parametric system made it possible to employ the most simple discrimination device, based on the fact that the high frequency gamma pulse components are, at a given energy, weaker than those of the neutron pulses. Results are given of measurements carried out on the Van der Graaff (mono-energetic neutrons for testing the linearity of the chain and the resolving power of the counters), and of those made in a sub-critical system Hug at Cadarache. (author) [French] On decrit une chaine de spectrometrie travaillant dans le domaine d'energie de quelques keV a 1 MeV destinee a la mesure des spectres de neutrons rapides. Elle comprend les detecteurs, compteurs proportionnels a protons de recul, realises specialement pour cette etude par M. R. COMTE (DEG/SER), permettant de couvrir la gamme d'energie et l'electronique associee. Apres un rappel des processus physiques mis en jeu: chocs (n,p) dans les gaz, influence des rayonnements {gamma}, on expose la methode de discrimination utilisee. Celle-ci est basee sur la difference des temps de montee des impulsions. Au cours des experiences rapportees ici, la mise en oeuvre d'un ensemble bi-parametrique a permis d'utiliser le dispositif de discrimination le plus simple, base sur la remarque que les composantes a haute frequence des impulsions {gamma} sont, a

  9. Characterization of high-energy quasi-monoenergetic neutron energy spectra and ambient dose equivalents of 80-389 MeV 7Li(p,n) reactions using a time-of-flight method

    Science.gov (United States)

    Iwamoto, Yosuke; Hagiwara, Masayuki; Satoh, Daiki; Araki, Shouhei; Yashima, Hiroshi; Sato, Tatsuhiko; Masuda, Akihiko; Matsumoto, Tetsuro; Nakao, Noriaki; Shima, Tatsushi; Kin, Tadahiro; Watanabe, Yukinobu; Iwase, Hiroshi; Nakamura, Takashi

    2015-12-01

    We completed a series of measurements on mono-energetic neutron energy spectra of the 7Li(p,n) reaction with 80-389-MeV protons in the 100-m time-of-flight (TOF) tunnel at the Research Center for Nuclear Physics cyclotron facility. For that purpose, we measured neutron energy spectra of the 80-, 100- and 296-MeV proton incident reactions, which had not been investigated in our previous studies. The neutron peak intensity was 0.9-1.1×1010 neutrons/sr/μC in the incident proton energy region of 80-389 MeV, and it was almost independent of the incident proton energy. The contribution of peak intensity of the spectrum to the total intensity integrated with energies above 3 MeV varied between 0.38 and 0.48 in the incident proton energy range of 80-389 MeV. To consider the correction required to derive a response in the peak region from the measured total responses of neutron monitors in the 100-m TOF tunnel, we proposed the subtraction method using energy spectra between 0° and 25°. The normalizing factor k against 25° neutron fluence to equalize it to 0° neutron fluence in the continuum region ranges from 0.74 to 1.02 depending on the incident proton energy and angle measured. Even without the TOF method, the subtraction method with the k factor almost decreases the response in the continuum region of a neutron spectrum against the total response of neutron monitors.

  10. $\\gamma$-ray energy spectra and multiplicities from the neutron-induced fission of $^{235}$U using STEFF

    CERN Multimedia

    An experiment is proposed to use the STEFF spectrometer at n_TOF to study fragment $\\gamma$-correlations following the neutron-induced fission of $^{235}$U. The STEFF array of 12 NaI detectors will allow measurements of the single $\\gamma$-energy, the $\\gamma$ multiplicity, and the summed $\\gamma$energy distributions as a function of the mass and charge split, and deduced excitation energy in the fission event. These data will be used to study the origin of fission-fragment angular momenta, examining angular distribution eects as a function of incident neutron energy. The principal application of this work is in meeting the NEA high-priority request for improved $\\gamma$ray data from $^{235}$U(n; F). To improve the detection rate and expand the range of detection angles, STEFF will be modied to include two new ssion-fragment detectors each at 45 to the beam direction.

  11. Characterization of the CALIBAN Critical Assembly Neutron Spectra using Several Adjustment Methods Based on Activation Foils Measurement

    Science.gov (United States)

    Casoli, Pierre; Grégoire, Gilles; Rousseau, Guillaume; Jacquet, Xavier; Authier, Nicolas

    2016-02-01

    CALIBAN is a metallic critical assembly managed by the Criticality, Neutron Science and Measurement Department located on the French CEA Center of Valduc. The reactor is extensively used for benchmark experiments dedicated to the evaluation of nuclear data, for electronic hardening or to study the effect of the neutrons on various materials. Therefore CALIBAN irradiation characteristics and especially its central cavity neutron spectrum have to be very accurately evaluated. In order to strengthen our knowledge of this spectrum, several adjustment methods based on activation foils measurements are being studied for a few years in the laboratory. Firstly two codes included in the UMG package have been tested and compared: MAXED and GRAVEL. More recently, the CALIBAN cavity spectrum has been studied using CALMAR, a new adjustment tool currently under development at the CEA Center of Cadarache. The article will discuss and compare the results and the quality of spectrum rebuilding obtained with the UMG codes and with the CALMAR software, from a set of activation measurements carried out in the CALIBAN irradiation cavity.

  12. Characterization of the CALIBAN Critical Assembly Neutron Spectra using Several Adjustment Methods Based on Activation Foils Measurement

    Directory of Open Access Journals (Sweden)

    Casoli Pierre

    2016-01-01

    Full Text Available CALIBAN is a metallic critical assembly managed by the Criticality, Neutron Science and Measurement Department located on the French CEA Center of Valduc. The reactor is extensively used for benchmark experiments dedicated to the evaluation of nuclear data, for electronic hardening or to study the effect of the neutrons on various materials. Therefore CALIBAN irradiation characteristics and especially its central cavity neutron spectrum have to be very accurately evaluated. In order to strengthen our knowledge of this spectrum, several adjustment methods based on activation foils measurements are being studied for a few years in the laboratory. Firstly two codes included in the UMG package have been tested and compared: MAXED and GRAVEL. More recently, the CALIBAN cavity spectrum has been studied using CALMAR, a new adjustment tool currently under development at the CEA Center of Cadarache. The article will discuss and compare the results and the quality of spectrum rebuilding obtained with the UMG codes and with the CALMAR software, from a set of activation measurements carried out in the CALIBAN irradiation cavity.

  13. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for 235U (n ,fission) at Thermal and Fast Neutron Energies

    Science.gov (United States)

    Sonzogni, A. A.; McCutchan, E. A.; Johnson, T. D.; Dimitriou, P.

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 235U 235 fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of 86Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.

  14. Cross section and γ-ray spectra for U238(n,γ) measured with the DANCE detector array at the Los Alamos Neutron Science Center

    Science.gov (United States)

    Ullmann, J. L.; Kawano, T.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wilhelmy, J. B.; Becker, J. A.; Chyzh, A.; Wu, C. Y.; Baramsai, B.; Mitchell, G. E.; Krtička, M.

    2014-03-01

    Background: Accurate knowledge of the U238(n,γ) cross section is important for developing theoretical nuclear reaction models and for applications. However, capture cross sections are difficult to calculate accurately and often must be measured. Purpose: We seek to confirm previous measurements and test cross-section calculations with an emphasis on the unresolved resonance region from 1 to 500 keV. Method: Cross sections were measured from 10 eV to 500 keV using the DANCE detector array at the LANSCE spallation neutron source. The measurements used a thin target, 48 mg/cm2 of depleted uranium. Gamma cascade spectra were also measured to provide an additional constraint on calculations. The data are compared to cross-section calculations using the code CoH3 and cascade spectra calculations made using the code dicebox. Results: This new cross-section measurement confirms the previous data. The measured gamma-ray spectra suggest the need for additional low-lying dipole strength in the radiative strength function. New Hauser-Feshbach calculations including this strength accurately predict the capture cross section without renormalization. Conclusions: The present cross-section data confirm previous measurements. Including additional low-lying dipole strength in the radiative strength function may lead to more accurate cross-section calculations in nuclei where has not been measured.

  15. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for ^{235}U(n,fission) at Thermal and Fast Neutron Energies.

    Science.gov (United States)

    Sonzogni, A A; McCutchan, E A; Johnson, T D; Dimitriou, P

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 ^{235}U fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of ^{86}Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.

  16. Theoretical Time Dependent Thermal Neutron Spectra and Reaction Rates in H{sub 2}O and D{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Purohit, S.N.

    1966-04-15

    The early theoretical and experimental time dependent neutron thermalization studies were limited to the study of the transient spectrum in the diffusion period. The recent experimental measurements of the time dependent thermal neutron spectra and reaction rates, for a number of moderators, have generated considerable interest in the study of the time dependent Boltzmann equation. In this paper we present detailed results for the time dependent spectra and the reaction rates for resonance detectors using several scattering models of H{sub 2}O and D{sub 2}O. This study has been undertaken in order to interpret the integral time dependent neutron thermalization experiments in liquid moderators which have been performed at the AB Atomenergi. The proton gas and the deuteron gas models are inadequate to explain the measured reaction rates in H{sub 2}O and D{sub 2}O. The bound models of Nelkin for H{sub 2}O and of Butler for D{sub 2}O give much better agreement with the experimental results than the gas models. Nevertheless, some disagreement between theoretical and experimental results still persists. This study also indicates that the bound model of Butler and the effective mass 3. 6 gas model of Brown and St. John give almost identical reaction rates. It is also surprising to note that the calculated reaction rate for Cd for the Butler model appears to be in better agreement with the experimental results of D{sub 2}O than of the Nelkin model with H{sub 2}O experiments. The present reaction rate studies are sensitive enough so as to distinguish between the gas model and the bound model of a moderator. However, to investigate the details of a scattering law (such as the effect of the hindered rotations in H{sub 2}O and D{sub 2}O and the weights of different dynamical modes) with the help of these studies would require further theoretical as well as experimental investigations. Theoretical results can be further improved by improving the source for thermal neutrons, the

  17. Iron-line and continuum variations in the XMM-Newton and Suzaku spectra of the neutron-star low-mass X-ray binary 4U 1636-53

    NARCIS (Netherlands)

    Lyu, Ming; Méndez, Mariano; Sanna, Andrea; Homan, Jeroen; Belloni, Tomaso; Hiemstra, Beike

    2014-01-01

    We used six simultaneous XMM-Newton and Rossi X-ray Timing Explorer plus five Suzaku observations to study the continuum spectrum and the iron emission line in the neutron-star low-mass X-ray binary 4U 1636-53. We modelled the spectra with two thermal components (representing the accretion disc and

  18. Indication of the Black Hole Powered Jet in M87 by VSOP Observations

    Science.gov (United States)

    Asada, Keiichi; Nakamura, Masanori; Pu, Hung-Yi

    2016-12-01

    In order to study the collimation and acceleration mechanism of relativistic jets, the jet streamline of M87 at milliarcsecond scale is extensively investigated with images from VSOP observations at 1.6 and 5 GHz. Thanks to the higher angular resolution of VSOP, especially in the direction transverse to the jet, we resolved the jet streamline into three ridgelines at the scale of milli arcseconds. While the properties of the outer two ridgelines are in good agreement with those measured in previous observations and can be expressed by one power-law line with a power law index of 1.7, an inner ridgeline is clearly observed for the first time. We compared the measured size with the outermost streamline expected by Blandford & Znajek's parabolic solutions, which are anchored at the event horizon, with different black hole spin parameters. We revealed that the observed inner ridgeline is narrower than the prediction, suggesting the origin of the inner ridgeline to be part of a spine originating from the spinning black hole. The inner ridgeline becomes very dim at large distances from the central engine at 5 GHz. We considered two possible cases for this; Doppler beaming and/or radiative cooling. Either case seems to be reasonable for its explanation, and future multi-frequency observations will discriminate those two possibilities.

  19. The voltage-gated proton channel Hv1/VSOP inhibits neutrophil granule release.

    Science.gov (United States)

    Okochi, Yoshifumi; Aratani, Yasuaki; Adissu, Hibret A; Miyawaki, Nana; Sasaki, Mari; Suzuki, Kazuo; Okamura, Yasushi

    2016-01-01

    Neutrophil granule exocytosis is crucial for host defense and inflammation. Neutrophils contain 4 types of granules, the exocytotic release of which is differentially regulated. This exocytosis is known to be driven by diverse mediators, including calcium and nucleotides, but the precise molecular mechanism remains largely unknown. We show in the present study that voltage-gated proton (Hv) channels are necessary for the proper release of azurophilic granules in neutrophils. On activation of NADPH oxidase by PMA and IgG, neutrophils derived from Hvcn1 gene knockout mouse exhibited greater secretion of MPO and elastase than WT cells. In contrast, release of LTF enriched in specific granules was not enhanced in these cells. The excess release of azurophilic granules in Hv1/VSOP-deficient neutrophils was suppressed by inhibiting NADPH oxidase activity and, in part, by valinomycin, a potassium ionophore. In addition, Hv1/VSOP-deficient mice exhibited more severe lung inflammation after intranasal Candida albicans infection than WT mice. These findings suggest that the Hv channel acts to specifically dampen the release of azurophilic granules through, in part, the suppression of increased positive charges at the plasma membrane accompanied by the activation of NADPH oxidase in neutrophils. © Society for Leukocyte Biology.

  20. HALCA Observation Results and Implications for VSOP-2 Observations of Blazars

    Science.gov (United States)

    Wajima, K.

    2009-08-01

    We have performed Space VLBI observations of six blazars which have been detected gamma-ray emissions by EGRET. All sources have very compact core-dominant structures and three sources have a brightness temperature greater than 1012 K. We could also determine the jet viewing angle for some of sources and the they have smaller viewing angles of typically less than 5°. We also made short-term variability observations of PKS 1622-297 with the ATCA to investigate compactness of the source. The intraday variability feature at both 4.8 and 8.6 GHz was detected for this source and estimated scattering disk sizes from those results were a few hundred μas, and corresponds to a linear scale of about 1017 cm, which is similar to a size obtained from a theoretical model that assumes the external radiation Compton model can account for the gamma-ray emission. Although these results support the inverse Compton model of the gamma-ray emission from blazars, we could not conclusively determine the mechanism because of insufficient angular resolution by the first Space VLBI mission. Thus, VSOP-2 will be a powerful tool for revealing their energetics and gamma-ray emission mechanisms because of its high angular resolution capability. We present HALCA observation results and summarize some scientific idea with VSOP-2 observation of blazars.

  1. Probing the Exhaust System of the Most Powerful Engines with VSOP-2

    Science.gov (United States)

    Meier, D. L.

    2009-08-01

    I review the current magneto-hydrodynamic mechanisms for the production and propagation of relativistic jets from accreting black holes. There has been quite a bit of progress recently in describing the processes that launch, collimate, and ultimately accelerate jets to their final relativistic speeds. VSOP2 should be able to probe much of this collimation and acceleration region. There also has been a lot of progress on how magnetized jets propagate through the initial few parsecs of interstellar medium in radio galaxies and quasars that can be observed directly. Finally, there has been a bit of progress in understanding how the jet engine very near the black hole ultimately relates to the accretion power plant that supplies its energy, although it is still unknown exactly how some types of black hole jets tie directly into the accretion flow. While VSOP2 will not probe this region directly, it may be able to constrain certain theoretical models of these processes. There may be some surprises in store for us, and we should be ready for them when the data begins coming in.

  2. SUPERNOVA NEUTRINO LIGHT CURVES AND SPECTRA FOR VARIOUS PROGENITOR STARS: FROM CORE COLLAPSE TO PROTO-NEUTRON STAR COOLING

    Energy Technology Data Exchange (ETDEWEB)

    Nakazato, Ken' ichiro; Suzuki, Hideyuki [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan); Sumiyoshi, Kohsuke [Numazu Collage of Technology, 3600 Ooka, Numazu, Shizuoka 410-8501 (Japan); Totani, Tomonori [Department of Astronomy, Kyoto University, Kita-shirakawa Oiwake-cho, Sakyo, Kyoto 606-8502 (Japan); Umeda, Hideyuki [Department of Astronomy, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan); Yamada, Shoichi, E-mail: nakazato@rs.tus.ac.jp [Department of Physics, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)

    2013-03-01

    We present a new series of supernova neutrino light curves and spectra calculated by numerical simulations for a variety of progenitor stellar masses (13-50 M {sub Sun }) and metallicities (Z = 0.02 and 0.004), which would be useful for a broad range of supernova neutrino studies, e.g., simulations of future neutrino burst detection by underground detectors or theoretical predictions for the relic supernova neutrino background. To follow the evolution from the onset of collapse to 20 s after the core bounce, we combine the results of neutrino-radiation hydrodynamic simulations for the early phase and quasi-static evolutionary calculations of neutrino diffusion for the late phase, with different values of shock revival time as a parameter that should depend on the still unknown explosion mechanism. We describe the calculation methods and basic results, including the dependence on progenitor models and the shock revival time. The neutrino data are publicly available electronically.

  3. Direct coupling of annexin A5 to VSOP yields small, protein-covered nanoprobes for MR imaging of apoptosis.

    Science.gov (United States)

    Figge, Lena; Appler, Franziska; Chen, Howard H; Sosnovik, David E; Schnorr, Jörg; Seitz, Oliver; Taupitz, Matthias; Hamm, Bernd; Schellenberger, Eyk

    2014-01-01

    Annexin A5 (Anx) has been extensively used for imaging apoptosis by single-photon emission computed tomography, positron emission tomography, optical imaging and MRI. Recently we introduced ultrasmall Anx-VSOP (very small iron oxide particles)--the smallest high-relaxivity probe for MRI of apoptosis. Here we present a simplified method for the direct coupling of Anx to VSOP, which resulted in nanoparticles that are nearly completely covered with human Anx. These superparamagnetic nanoparticles are only 14.4 ± 2.3 nm in diameter and have higher T2* relaxivity. Compared with existing probes, the small size and the Anx shielding provide prerequisites for good biocompatibility and bioavailability in target tissues. In vitro characterization showed specific binding of Anx-VSOP to apoptotic cells, which led to a signal loss in T2*-weighted MR measurements, while control probe M1324-VSOP produced no such change. Exploratory MRI was done in vivo in a cardiac model of ischemia-reperfusion damage illustrating the potential of the probe for future studies. Copyright © 2014 John Wiley & Sons, Ltd.

  4. VSOP/Hv1 proton channels sustain calcium entry, neutrophil migration, and superoxide production by limiting cell depolarization and acidification.

    Science.gov (United States)

    El Chemaly, Antoun; Okochi, Yoshifumi; Sasaki, Mari; Arnaudeau, Serge; Okamura, Yasushi; Demaurex, Nicolas

    2010-01-18

    Neutrophils kill microbes with reactive oxygen species generated by the NADPH oxidase, an enzyme which moves electrons across membranes. Voltage-gated proton channels (voltage-sensing domain only protein [VSOP]/Hv1) are required for high-level superoxide production by phagocytes, but the mechanism of this effect is not established. We show that neutrophils from VSOP/Hv1-/- mice lack proton currents but have normal electron currents, indicating that these cells have a fully functional oxidase that cannot conduct protons. VSOP/Hv1-/- neutrophils had a more acidic cytosol, were more depolarized, and produced less superoxide and hydrogen peroxide than neutrophils from wild-type mice. Hydrogen peroxide production was rescued by providing an artificial conductance with gramicidin. Loss of VSOP/Hv1 also aborted calcium responses to chemoattractants, increased neutrophil spreading, and decreased neutrophil migration. The migration defect was restored by the addition of a calcium ionophore. Our findings indicate that proton channels extrude the acid and compensate the charge generated by the oxidase, thereby sustaining calcium entry signals that control the adhesion and motility of neutrophils. Loss of proton channels thus aborts superoxide production and causes a severe signaling defect in neutrophils.

  5. Neutron-emission measurements at a white neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Haight, Robert C [Los Alamos National Laboratory

    2010-01-01

    Data on the spectrum of neutrons emittcd from neutron-induced reactions are important in basic nuclear physics and in applications. Our program studies neutron emission from inelastic scattering as well as fission neutron spectra. A ''white'' neutron source (continuous in energy) allows measurements over a wide range of neutron energies all in one experiment. We use the tast neutron source at the Los Alamos Neutron Science Center for incident neutron energies from 0.5 MeV to 200 MeV These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. For the fission neutron measurements, parallel-plate ionization or avalanche detectors identify fission in actinide samples and give the required fast timing pulse. For inelastic scattering, gamma-ray detectors provide the timing and energy spectroscopy. A large neutron-detector array detects the emitted neutrons. Time-of-flight techniques are used to measure the energies of both the incident and emitted neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. We have made preliminary measurements of the fission neutron spectra from {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. Neutron emission spectra from inelastic scattering on iron and nickel have also been investigated. The results obtained will be compared with evaluated data.

  6. [Results of measuring neutrons doses and energy spectra inside Russian segment of the International Space Station in experiment "Matryoshka-R" using bubble detectors during the ISS-24-34 missions].

    Science.gov (United States)

    Khulapko, S V; Liagushin, V I; Arkhangel'skiĭ, V V; Shurshakov, V A; Smith, M; Ing, H; Machrafi, R; Nikolaev, I V

    2014-01-01

    The paper presents the results of calculating the equivalent dose from and energy spectrum of neutrons in the right-hand crewquarters in module Zvezda of the ISS Russian segment. Dose measurements were made in the period between July, 2010 and November, 2012 (ISS Missions 24-34) by research equipment including the bubble dosimeter as part of experiment "Matryoshka-R". Neutron energy spectra in the crewquarters are in good agreement with what has been calculated for the ISS USOS and, earlier, for the MIR orbital station. The neutron dose rate has been found to amount to 196 +/- 23 microSv/d on Zvezda panel-443 (crewquarters) and 179 +/- 16 microSv/d on the "Shielding shutter" surface in the crewquarters.

  7. Dual-frequency VSOP Imaging of a High-redshift Radio Quasar PKS 1402+044

    CERN Document Server

    Yang, J; Lobanov, A; Frey, S; Hong, X Y; Yang, Jun; Gurvits, Leonid; Lobanov, Andrei; Frey, Sandor; Hong, Xiao-Yu

    2006-01-01

    Based on the VLBI Space Observatory Programme (VSOP) observations at 1.6 and 5 GHz, we find that the luminous high-redshift (z=3.215) quasar PKS 1402+044 (J1405+0415) has a pronounced 'core--jet' structure. The jet shows a steeper spectral index and lower brightness temperature with the increase of the distance from the core. The variation of brightness temperature is basically consistent with the shock-in-jet model. Assuming that the jet is collimated by the ambient magnetic field, we estimate the mass of the central object as ~10^9 M_sun. The upper limit of the jet proper motion of PKS 1402+044 is 0.03 mas/yr (~3c) in the east-west direction.

  8. Real-time measurement of low-energy-range neutron spectra on board the space shuttle STS-89 (S/MM-8).

    Science.gov (United States)

    Matsumoto, H; Goka, T; Koga, K; Iwai, S; Uehara, T; Sato, O; Takagi, S

    2001-06-01

    We have developed a real-time, Bonner Ball-type (neutron energy range is from thermal to 15 MeV) neutron spectral measurement system (Bonner Ball Neutron Detector (BBND)) for use on board the International Space Station (ISS). From measurements taken inside STS-89 (S/MM-8), we successfully distinguished neutrons from protons and other particles in a mixed radiation field; a task hitherto considered difficult. Although the experimental period was short, only 3.5 days (January 24-27, 1998), we were able to obtain energy spectral data and the Earth's neutron dose-equivalent map for the ISS orbital conditions (altitude 400 km, orbit inclination angle 51.6 degrees). A method for calculating the neutron energy spectrum and compensating for the particle interaction with the sensors is also described in detail.

  9. Neutron spectra calculation and doses in a subcritical nuclear reactor based on thorium; Calculo de espectros de neutrones y dosis en un reactor nuclear subcritico a base de Torio

    Energy Technology Data Exchange (ETDEWEB)

    Medina C, D.; Hernandez A, P. L.; Hernandez D, V. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico); Sajo B, L., E-mail: dmedina_c@hotmail.com [Universidad Simon Bolivar, Laboratorio de Fisica Nuclear, Apdo. Postal 89000, Caracas 1080A (Venezuela, Bolivarian Republic of)

    2015-10-15

    This paper describes a heterogeneous subcritical nuclear reactor with molten salts based on thorium, with graphite moderator and a source of {sup 252}Cf, whose dose levels in the periphery allows its use in teaching and research activities. The design was done by the Monte Carlo method with the code MCNP5 where the geometry, dimensions and fuel was varied in order to obtain the best design. The result is a cubic reactor of 110 cm side with graphite moderator and reflector. In the central part they have 9 ducts that were placed in the direction of axis Y. The central duct contains the source of {sup 252}Cf, of 8 other ducts, are two irradiation ducts and the other six contain a molten salt ({sup 7}LiF - BeF{sub 2} - ThF{sub 4} - UF{sub 4}) as fuel. For design the k{sub eff}, neutron spectra and ambient dose equivalent was calculated. In the first instance the above calculation for a virgin fuel was called case 1, then a percentage of {sup 233}U was used and the percentage of Th was decreased and was called case 2. This with the purpose to compare two different fuels working inside the reactor. In the case 1 a value was obtained for the k{sub eff} of 0.13 and case 2 of 0.28, maintaining the subcriticality in both cases. In the dose levels the higher value is in case 2 in the axis Y with a value of 3.31 e-3 ±1.6% p Sv/Q this value is reported in for one. With this we can calculate the exposure time of personnel working in the reactor. (Author)

  10. Study of spectral response of a neutron filter. Design of a method to adjust spectra; Etude des moyens de conditionnement de la reponse spectrale d'un filtre a neutrons. Mise au point d'une methode d'ajustement rapide de spectre

    Energy Technology Data Exchange (ETDEWEB)

    Colomb-Dolci, F. [Universite Louis Pasteur, 67 - Strasbourg (France)

    1999-02-01

    The first part of this thesis describes an experimental method which intends to determine a neutron spectrum in the epithermal range [1 eV -10 keV]. Based on measurements of reaction rates provided by activation foils, it gives flux level in each energy range corresponding to each probe. This method can be used in any reactor location or in a neutron beam. It can determine scepter on eight energy groups, five groups in the epithermal range. The second part of this thesis presents a study of an epithermal neutron beam design, in the frame of Neutron Capture Therapy. A beam tube was specially built to test filters made up of different materials. Its geometry was designed to favour epithermal neutron crossing and to cut thermal and fast neutrons. A code scheme was validated to simulate the device response with a Monte Carlo code. Measurements were made at ISIS reactor and experimental spectra were compared to calculated ones. This validated code scheme was used to simulate different materials usable as shields in the tube. A study of these shields is presented at the end of this thesis. (author)

  11. 蒙特卡罗方法对钚燃料堆芯 VSOP 模型的验证%Verification of VSOP Model for Plutonium Fuel Core Based on Monte Carlo Method

    Institute of Scientific and Technical Information of China (English)

    位金锋; 李富; 孙玉良; 张竞宇

    2013-01-01

    VSOP program package is widely used in the engineering design of the pebble bed high-temperature gas-cooled reactor with uranium fuel , but the applicability of VSOP code for pure plutonium fuel core is not completely proven . Uranium and plutonium were recycled from the 250 MW High-Temperature Gas-Cooled Reactor-Pebble-bed-Module (HTR-PM ) spent fuel from the U-Pu fuelled core ,and PuO2 and MOX fuel elements were designed based on this recycled plutonium and uranium .These fuel elements were used to build up a new PuO2 or MOX fuelled core with the same geometry of the original reactor .The random arrangement of coated fuel particles in the fuel pebbles and the random distribution of the fuel pebbles in the core were modeled as the repeated structure of regular shape in the Monte Carlo package MCNP .Based on the same reference of HTR reactor core ,the core effective multiplication factors from VSOP model and Monte Carlo model were compared ,and the causes of the differences were analyzed .Preliminary results show that the VSOP simulation result of the uranium fuel core accords well with the MCNP result ,and the VSOP result of the pure plutonium fuel core is about 2% lower than that of MCNP code .Preliminary results demonstrate the applicability of VSOP code for pure plutonium fuel core , and the improve suggestions of the VSOP code were given .%VSOP程序广泛应用于高温气冷堆铀燃料堆芯设计,而对钚燃料堆芯未经充分验证。本文基于250MW球床模块式高温气冷堆示范电站HTR-PM铀钚循环乏燃料中的铀和钚,设计了PuO2和MOX燃料元件,将新设计的燃料元件重新装入与HTR-PM同样结构和尺寸的堆芯,分别形成纯钚燃料堆芯和MOX燃料堆芯。利用蒙特卡罗方法中规则的重复结构模拟包覆燃料颗粒在燃料球内的随机分布及燃料球在堆芯内的随机分布。针对同一参考堆芯,比较了VSOP模型和MCNP模型的有效增殖因数,并分析了产生差异的

  12. The inelastic scattering neutron angular distribution of reaction 7Li(n,n'γ) 7Li ∗ (478 keV) derived from shape analysis of the Doppler broadened γ spectra at 9, 9.5 and 10 MeV

    Science.gov (United States)

    Feizeng, Huang; Shanglian, Bao; Jinquan, Liu; Wentian, Cao; Zhengde, Huang; Lihua, Zhu; Long, Hou

    1995-02-01

    The angular distributions of the inelastic scattered neutrons from the reaction 7Li(n,n'γ) 7Li ∗ (478 keV) were derived from the shape analysis of the Doppler broadened γ spectra at incident neutron energies of 9, 9.5 and 10 MeV. The measured spectra were fitted to the Monte Carlo simulation results to get the Legendre coefficients of the angular distributions of the inelastic neutron scattering in the center-of-mass (CM) system. The derived results are compared with DWBA calculations. The agreements are rather good.

  13. Ge(Li) detector gamma-ray spectrometer system for measurement of the spectra and production cross sections of. gamma. -rays produced by 14 MeV neutron nonelastic interaction with nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Shen Ronglin; Shi Xiamin; Wu Yongshun; Xing Jinjiang; Ding Dazhao

    1982-02-01

    A 42 cm/sup 3/ Ge(Li) detector gamma-ray spectrometer system for measuring the spectra and the production cross sections of ..gamma..-rays produced by fast neutron nonelastic interaction with nuclei is described in this paper. The incident neutrons are produced by T(d,n)/sup 4/He reaction in an high tension set with the incident deuteron energy of 200 keV. The time of flight technique is used to discriminate between the scattered neutrons and gamma-rays resulting from nonelastic interaction. The ..cap alpha..-particles are picked up by a Si(Au) surface barrier detector and the ARC timing discriminaters are used in both Si(Au) and Ge(Li) channels. The overall time resolution (FWHM) of this system is 4.1 ns typically for energy selection threshold at 400keV. The block diagram of spectrometer system is described in detail. The complex complete shielding damage of Ge(Li) detector in this fast neutron field is well discussed.

  14. VSOP and Stellar Sources - The Case of LS I +61°303

    Science.gov (United States)

    Dougherty, S. M.

    2009-08-01

    Space-VLBI observations of stellar sources represent a challenge since there are few sources with sufficiently high brightness temperature for detection on space-ground baselines. X-ray binaries (XRB) are among the few types of stellar radio sources that can be detected. Observations of the unusual X-ray and γ-ray binary system LS I +61°303 obtained with the HALCA satellite and a 20-element ground array are described. The data in this 48-hour experiment represent some of the best quality VLBI observations of LS I +61°303. No fringes were detected on HALCA baselines. 10-minute snapshot images were produced from the global ground array data and reveal an expansion velocity of 800 km s-1. Some of these image data reveal hints of more extended emission but high-SNR closure phase data do not support relativistic outflow in the plane-of-the-sky in LS I +61°303. The largest closure phase rates are consistent with an outflow of ˜1000 km s-1 as deduced from the image data. The closure phases also show no evidence of structure variation on size scales greater than ˜10 mas. A number of issues related to VSOP2 observations of stellar radio sources are raised.

  15. Raman, FTIR, photoacoustic-infrared, and inelastic neutron scattering spectra of ternary metal hydride salts A2MH5, (A = Ca, Sr, Eu; M = Ir, Rh) and their deuterides.

    Science.gov (United States)

    Barsan, Mirela M; Butler, Ian S; Gilson, Denis F R; Moyer, Ralph O; Zhou, Wei; Wu, Hui; Udovic, Terrence J

    2012-03-15

    The vibrational spectra of the ternary metal hydride (deuteride) salts, A(2)MH(5) and A(2)MD(5), where A = calcium, strontium and europium and M = iridium(I) and rhodium(I), have been assigned using Raman, Fourier transform infrared, photoacoustic infrared, and inelastic neutron scattering spectroscopies and density functional theory (DFT) calculations. The wavenumbers of the infrared-active stretching vibrations depend upon the ionization energies of the central metal atom and the cation. The phase transition in calcium pentahydridoiridate(I) was studied as a function of temperature and pressure.

  16. Spectra and absorbed dose by photo-neutrons in a solid water mannequin exposed to a Linac of 15 MV; Espectros y dosis absorbida por fotoneutrones en un maniqui de agua solida expuesta a una Linac de 15 MV

    Energy Technology Data Exchange (ETDEWEB)

    Benites R, J. [Centro Estatal de Cancerologia de Nayarit, Servicio de Seguridad Radiologica, Calz. de la Cruz 118 Sur, 63000 Tepic, Nayarit (Mexico); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico); Velazquez F, J., E-mail: jlbenitesr@prodigy.net.mx [Universidad Autonoma de Nayarit, Posgrado en Ciencias Biologico Agropecuarias, Carretera Tepic-Compostela Km 9, 63780 Jalisco-Nayarit (Mexico)

    2012-10-15

    Using Monte Carlo methods was modeled a solid water mannequin; according to the ICRU 44 (1989), Tissue substitutes in radiation dosimetry and measurements, of the International Commission on Radiation Units and Measurements; Report 44. This material Wt 1 is made of H (8.1%), C (67.2%), N (2.4%), O (19.9%), Cl (0.1%), Ca (2.3%) and its density is of 1.02 gr/cm{sup 3}. The mannequin was put instead of the patient, inside the treatment room and the spectra and absorbed dose were determined by photo-neutrons exposed to a Linac of 15 MV. (Author)

  17. Investigation of Isfahan miniature neutron source reactor (MNSR) for boron neutron capture therapy by MCNP simulation

    OpenAIRE

    S. Z. Kalantari; H Tavakoli; Nami, M.

    2015-01-01

    One of the important neutron sources for Boron Neutron Capture Therapy (BNCT) is a nuclear reactor. It needs a high flux of epithermal neutrons. The optimum conditions of the neutron spectra for BNCT are provided by the International Atomic Energy Agency (IAEA). In this paper, Miniature Neutron Source Reactor (MNSR) as a neutron source for BNCT was investigated. For this purpose, we designed a Beam Shaping Assembly (BSA) for the reactor and the neutron transport from the core of the reactor t...

  18. MANTA. An Integral Reactor Physics Experiment to Infer the Neutron Capture Cross Sections of Actinides and Fission Products in Fast and Epithermal Spectra

    Energy Technology Data Exchange (ETDEWEB)

    Youinou, Gilles Jean-Michel [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-10-01

    Neutron cross-sections characterize the way neutrons interact with matter. They are essential to most nuclear engineering projects and, even though theoretical progress has been made as far as the predictability of neutron cross-section models, measurements are still indispensable to meet tight design requirements for reduced uncertainties. Within the field of fission reactor technology, one can identify the following specializations that rely on the availability of accurate neutron cross-sections: (1) fission reactor design, (2) nuclear fuel cycles, (3) nuclear safety, (4) nuclear safeguards, (5) reactor monitoring and neutron fluence determination and (6) waste disposal and transmutation. In particular, the assessment of advanced fuel cycles requires an extensive knowledge of transuranics cross sections. Plutonium isotopes, but also americium, curium and up to californium isotope data are required with a small uncertainty in order to optimize significant features of the fuel cycle that have an impact on feasibility studies (e.g. neutron doses at fuel fabrication, decay heat in a repository, etc.). Different techniques are available to determine neutron cross sections experimentally, with the common denominator that a source of neutrons is necessary. It can either come from an accelerator that produces neutrons as a result of interactions between charged particles and a target, or it can come from a nuclear reactor. When the measurements are performed with an accelerator, they are referred to as differential since the analysis of the data provides the cross-sections for different discrete energies, i.e. σ(Ei), and for the diffusion cross sections for different discrete angles. Another approach is to irradiate a very pure sample in a test reactor such as the Advanced Test Reactor (ATR) at INL and, after a given time, determine the amount of the different transmutation products. The precise characterization of the nuclide densities before and after

  19. VSOP Observations of the Gamma-Ray Sources J1733-1304, J1625-2527, and J1015+4926

    Science.gov (United States)

    Nakagawa, A.; Murata, Y.; Edwards, Philip. G.; Wajima, K.; Omodaka, T.

    2009-08-01

    We present results from VSOP and VLBA observations of the active galactic nuclei J1733-1304, J1625-2527, and J1015+4926. These sources have been identified as possible counterparts to gamma-ray sources in the third EGRET catalog. In general, the counterparts to extragalactic EGRET sources have very compact structure, with brightness temperatures (Tb) greater than 1011-1012K. We compare the images of the three sources with previously published images and also examine jet motions and spectral indices. The measured Tb of J1733-1304 are an order of magnitude lower than those of previous measurements, suggesting the VSOP observations were made while the source was in a relatively quiescent state. The relatively low Tb of J1625-2527 is also consistent with the highly variable nature of this source. A comparison of the VSOP observation of J1015+4926 with a VLBA image suggests the existence of stationary jet components.

  20. A search for iron emission lines in the Chandra X-ray spectra of neutron star low-mass X-ray binaries

    CERN Document Server

    Cackett, E M; Homan, J; Van der Klis, M; Lewin, W H G; Méndez, M; Raymond, J; Steeghs, D; Wijnands, R

    2008-01-01

    While iron emission lines are well studied in black hole systems, both in X-ray binaries and Active Galactic Nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, recent observations with Suzaku and XMM-Newton have revealed broad asymmetric iron line profiles in 4 neutron star LMXBs, confirming an inner disk origin for these lines in neutron star systems. Here, we present a search for iron lines in 6 neutron star LMXBs. For each object we have simultaneous Chandra and RXTE observations at 2 separate epochs, allowing for both a high resolution spectrum, as well as broadband spectral coverage. Out of the six objects in the survey, we only find significant iron lines in two of the objects, GX 17+2 and GX 349+2. However, we cannot rule out that there are weak, broad lines present in the other sources. The equivalent width of the line in GX 17+2 is consistent between the 2 epochs, while in GX 349+2 the line equivalent width increases by a factor of ~3 betwe...

  1. Measurement of neutron spectra generated by a 62 AMeV carbon-ion beam on a PMMA phantom using extended range Bonner sphere spectrometers

    Science.gov (United States)

    Bedogni, R.; Amgarou, K.; Domingo, C.; Russo, S.; Cirrone, G. A. P.; Pelliccioni, M.; Esposito, A.; Pola, A.; Introini, M. V.; Gentile, A.

    2012-07-01

    Neutrons constitute an important component of the radiation environment in hadron therapy accelerators. Their energy distribution may span from thermal up to hundred of MeV. The characterization of these fields in terms of dosimetric or spectrometric quantities is crucial for either the patient protection or the facility design aspects. To date, the Extended Range Bonner Sphere Spectrometer (ERBSS) is the only instrument able to simultaneously determine all spectral components in such workplaces. With the aim of providing useful data to the scientific community involved in neutron measurements at hadron therapy facilities, a measurement campaign was carried out at the Centro di AdroTerapia e Applicazioni Nucleari Avanzate (CATANA) of INFN-LNS (Laboratori Nazionali del Sud), where a 62 AMeV carbon ion is available. The beam was directed towards a PMMA phantom, simulating the patient, and two neutron measurement points were established at 0° and 90° with respect to the beam-line. The ERBSSs of UAB (Universidad Autónoma de Barcelona-Grup de Física de les Radiacions) and INFN (Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Frascati) were used to measure the resulting neutron fields. The two ERBSSs use different detectors and sphere diameters, and have been independently calibrated. The FRUIT code was used to unfold the results.

  2. Experimental study of the secondary neutron angular spectra emitted from polyethylene slabs with D-T neutron source%D-T中子与平板型聚乙烯材料作用的次级中子角度谱实验研究

    Institute of Scientific and Technical Information of China (English)

    言杰; 刘荣; 蒋励; 鹿心鑫; 朱通华; 林菊芳; 王玫; 温中伟; 汪一夫

    2011-01-01

    基于反冲质子法建立了一种测量D-T中子与平板型宏观样品作用的次级中子角度谱的实验方法.为保证探测器的能量线性并在较低的中子有效测量下阈(0.5MeV)情况下获得好的中子-伽马射线甄别性能,采用高、低能段分别测量的方法.采用事件记录法,同时记录了次级中子和伴随伽马射线的脉冲形状甄别和脉冲幅度二维信息,利用基于ROOT数据分析平台编写的离线数据分析程序,完成了伴随伽马射线的挑选和扣除,以及高、低两能段反冲质子谱的拼接,并成功的将神经网络技术应用于中子能谱的解谱,获得了D-T中子与9和18cm厚平板型聚乙烯材料作用的0.5—15MeV的次级中子角度谱实验结果.实验模型的MC模拟由MCNP5完成,数据库采用ENDF-VI,实验结果和MC计算结果在实验不确定度范围内一致.%An experimental method of measuring the secondary neutron angular spectrum from polyethylene slab assembly with D-T neutron source based on the proton-recoil method is developed.In order to ensure the energy linearity of the detector and obtain a good neutron-gamma discrimination capability in the case of a low effective neutron threshold(0.5MeV),neutron energy spectrum is measured in two parts:one is in a high energy region and the other in a lower energy region.The pulse shape discrimination(PSD) and the pulse height distribution(PH) two-dimensional information of the secondary neutron and the associated gamma rays are recorded event-by-event simultaneously.The selection and the deduction of the gamma ray events and the joining of the two-segment energy spectra are carried out by using the off-line data analysis programs written in the ROOT data analysis framework.Furthermore,an artificial neural network technique is used to accomplish the unfolding of the neutron spectra successfully.The experimental results of the second neutron angular spectra from 9cm and 18cm thick

  3. Photon and photoneutron spectra produced in radiotherapy Linacs

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Martinez O, S. A. [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Av. Central del Norte Km. 1, Via Paipa Tunja, Boyaca (Colombia); Benites R, J. L. [Universidad Autonoma de Nayarit, Postgrado CBAP, Carretera Tepic Compostela Km. 9, Xalisco, Nayarit (Mexico); Lallena, A. M., E-mail: fermineutron@yahoo.com [Universida de Granada, Departamento de Fisica Atomica, Molecular y Nuclear, E-18071 Granada (Spain)

    2011-10-15

    A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10{sup -6} and 1 MeV. Neutron and Bremsstrahlung spectra show the same features regardless of the linac voltage. The amount of photons and neutrons produced by the 15 MV linac is smaller than that found for the 18 MV linac. As expected, Bremsstrahlung spectra ends according to the voltage used to accelerate the electrons. (Author)

  4. Observation of electromagnetically induced transparency in six-level Rb atoms and theoretical simulation of the observed spectra

    Science.gov (United States)

    Bhattacharyya, Dipankar; Ghosh, Arindam; Bandyopadhyay, Amitava; Saha, Satyajit; De, Sankar

    2015-09-01

    We report the observation of electromagnetically induced transparency (EIT) in a six-level Λ-type system in atomic Rb vapor containing both 87Rb and 85Rb. The experimental observation includes five velocity selective optically pumped (VSOP) absorption dips for both 87Rb and 85Rb. The EIT signal appears on the background of one such VSOP absorption dips. The measured EIT linewidth ({Γ }t) shows sub-natural ({Γ }t \\lt Γ ) values for both lower and higher values of pump Rabi-frequencies. The density matrix based theoretical model for the six-level system is developed and solved numerically by taking into account the Doppler broadening. A complete analytical solution (non perturbative) for a three level Λ-type system has been obtained and compared with the experimentally observed sub-natural EIT linewidth. The simulated spectra are in good agreement with the experimental findings.

  5. New generation of monomer-stabilized very small superparamagnetic iron oxide particles (VSOP) as contrast medium for MR angiography: preclinical results in rats and rabbits.

    Science.gov (United States)

    Taupitz, M; Schnorr, J; Abramjuk, C; Wagner, S; Pilgrimm, H; Hünigen, H; Hamm, B

    2000-12-01

    The purpose of this study was to evaluate the signal enhancement characteristics of very small superparamagnetic iron oxide particles (VSOP)-C63, a new monomer-coated, iron oxide-based magnetic resonance (MR) blood pool contrast medium with a very small particle size and optimized physical properties. Equilibrium MR angiography (MRA) of rats (thoracic and abdominal vessels) was performed at 1.5 T with a three-dimensional gradient-recalled echo (3D GRE) technique (TR/TE 6.6/2.3 msec, flip angle 25 degrees ) before and after (every 3-5 minutes up to 50 minutes) i.v. injection of VSOP-C63 [dosages: 15, 30, 45, 60, 75, and 90 micromol Fe/kg; diameter: 8 nm; relaxivities at 0.47 T: R1 = 30 l/(mmol * s); R2 = 39 l/(mmol * s)]. First-pass MRA images (3D-GRE, TR/TE 4.5/1.7 msec, flip angle 25 degrees ) were obtained with 45 micromol Fe/kg VSOP-C63 in comparison with 0.2 mmol Gd/kg of gadolinium diethylene triamine pentaacetic acid (Gd DTPA; before and every 5 seconds p.i.). MRA (3D GRE, TR/TE 4.5/1.7 msec, flip angle 25 degrees) of coronary vessels in rabbits was performed after i.v. injection of 45 micromol Fe/kg of VSOP-C63. In rats maximal S/N ratio in thoracic and abdominal arteries directly after i.v. injection of VSOP-C63 was 25 +/- 1, 43 +/- 2, 49 +/- 4, 57 +/- 3, 64 +/- 3, and 63 +/- 3 for the different dosages. Blood half-life was dose dependent (15 +/- 2, 20 +/- 3, 29 +/- 6, 37 +/- 5, 61 +/- 16, and 86 +/- 21 minutes). At a dose of 30 micromol Fe/kg even small intrarenal arteries were sharply delineated. First-pass MRA showed no significant difference in the S/N ratio between Gd-DTPA (71.5 +/- 11.5) and VSOP-C63 (65.1 +/- 18. 3). The proximal segments of the coronary arteries in rabbits were clearly depicted at a dose of 45 micromol Fe/kg. The monomer-coated, iron oxide-based contrast medium VSOP-C63 exhibits favorable properties as a blood pool agent for both equilibrium and first-pass MRA. J. Magn. Reson. Imaging 2000;12:905-911. Copyright 2000 Wiley-Liss, Inc.

  6. Velocity anisotropy effect in pump-probe spectra of cesium in a micrometric thickness optical cell

    Science.gov (United States)

    Ghosh, P. N.; Mitra, S.; Ray, B.; Krasteva, A.; Slavov, D.; Todorov, P.; Cartaleva, S.

    2015-01-01

    The pump-probe spectra in a cell of micrometric thickness containing cesium vapor are reported. The line shape and nonlinear features observed in the case of fluorescence in the direction parallel to the cell windows and the transmission spectra observed along the propagation direction of the probe beam show considerable differences in the spectral profiles. We observed Electromagnetically Induced Transparency (EIT) and enhanced Velocity Selective Optical Pumping (VSOP) signals. Atoms moving nearly parallel to the windows and perpendicular to the collinear pump and probe beams will see much lower Doppler shift of incident frequencies and hence will lead to considerable narrowing of the Doppler background in the fluorescence spectra. The coherence decay rate is also low for such atoms as they do not meet with the cell walls. A theoretical model based on five level optical Bloch equations is used to simulate the spectra. The Doppler convolution includes all possible orientation of atomic velocities with respect to the laser beam direction. The simulated curves reproduce the observed sharp EIT peaks and enhanced broad VSOP signals for the closed probe transition in the fluorescence and absorption spectra. The observed effect of the light intensity and temperature change on the non-linear features is reproduced by the simulation.

  7. Inelastic neutron scattering studies of phonon spectra, and simulations of pressure-induced amorphization in tungstates A W O4 (A =Ba ,Sr ,Ca , and Pb )

    Science.gov (United States)

    Goel, Prabhatasree; Gupta, M. K.; Mittal, R.; Rols, S.; Achary, S. N.; Tyagi, A. K.; Chaplot, S. L.

    2015-03-01

    Lattice dynamics and high-pressure phase transitions in A W O4 (A =Ba ,Sr ,Ca , and Pb ) have been investigated using inelastic neutron scattering experiments, ab initio density functional theory calculations, and extensive molecular dynamics simulations. The vibrational modes that are internal to W O4 tetrahedra occur at the highest energies consistent with the relative stability of W O4 tetrahedra. The neutron data and the ab initio calculations are found to be in excellent agreement. The neutron and structural data are used to develop and validate an interatomic potential model. The model is used for classical molecular dynamics simulations to study their response to high pressure. We have calculated the enthalpies of the scheelite and fergusonite phases as a function of pressure, which confirms that the scheelite to fergusonite transition is second order in nature. With increase in pressure, there is a gradual change in the A O8 polyhedra, while there is no apparent change in the W O4 tetrahedra. We found that all the four tungstates amorphize at high pressure. This is in good agreement with available experimental observations which show amorphization at around 45 GPa in BaW O4 and 40 GPa in CaW O4 . Further molecular dynamics simulations at high pressure and high temperature indicate that application of pressure at higher temperature hastens the process of amorphization. On amorphization, there is an abrupt increase in the coordination of the W atom while the bisdisphenoids around the A atom are considerably distorted. The pair-correlation functions of the various atom pairs corroborate these observations. Our observations aid in predicting the pressure of amorphization in SrW O4 and PbW O4 .

  8. The inelastic neutron scattering spectra of [alpha]-3-amino-5-nitro-1,2,4-2H-triazole: Experiment and DFT calculations

    Science.gov (United States)

    Ciezak, Jennifer A.; Trevino, S. F.

    2005-02-01

    The inelastic neutron scattering (INS) spectrum of α-3-amino-5-nitro-1,2,4-triazole is presented through 1200 cm -1. A comparison of the INS spectrum with an isolated molecule B3LYP/6-311G** calculation reveals generally good frequency and intensity agreement with two notable differences in intensity. Periodic density functional theory (DFT) calculations are employed to determine whether the intermolecular hydrogen bonding is the origin of these differences between the B3LYP/6-311G** and INS spectrum.

  9. Recent Re-Measurement of Neutron and Gamma-Ray Spectra 1080 Meters from the APRD (Army Pulse Radiation Division) Critical Facility,

    Science.gov (United States)

    1984-01-01

    spectres d𔄀missions neutroniques et de rayons gamma. On a compar6 les risultats de ces mesures A plusieurs calculs rcents effectu~s par d’autres...les neutrons et le- rayons gamma; on observe toutefois d’importantes differences spectrales. A - faible altitude, les spectres neutroniques son i6g...measurements were performed by both groups, using a variety of tissue-equivalent ion-chambers, Geiger-M(.ller counters and sulphur activation (n,p). In 1980

  10. Measurement of Feynman-x spectra of photons and neutrons in the very forward direction in deep-inelastic scattering at HERA

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, V.; Belousov, A.; Fomenko, A.; Gogitidze, N.; Lebedev, A.; Malinovski, E.; Rusakov, S.; Vazdik, Y. [Lebedev Physical Institute, Moscow (Russian Federation); Baghdasaryan, A.; Zohrabyan, H. [Yerevan Physics Institute, Yerevan (Armenia); Begzsuren, K.; Ravdandorj, T.; Tseepeldorj, B. [Institute of Physics and Technology of the Mongolian Academy of Sciences, Ulaanbaatar (Mongolia); Belov, P.; Brinkmann, M.; Britzger, D.; Campbell, A.J.; Dodonov, V.; Eckerlin, G.; Elsen, E.; Fleischer, M.; Gayler, J.; Ghazaryan, S.; Glazov, A.; Gouzevitch, M.; Haidt, D.; Kleinwort, C.; Krueger, K.; Levonian, S.; Lipka, K.; List, B.; List, J.; Lobodzinski, B.; Meyer, A.B.; Meyer, J.; Niebuhr, C.; Olsson, J.E.; Ozerov, D.; Pahl, P.; Petrukhin, A.; Pirumov, H.; Pitzl, D.; Placakyte, R.; Radescu, V.; Schmitt, S.; Sefkow, F.; Shushkevich, S.; South, D.; Steder, M.; Wuensch, E. [DESY, Hamburg (Germany); Boudry, V.; Specka, A. [LLR, Ecole Polytechnique, CNRS/IN2P3, Palaiseau (France); Brandt, G. [Oxford University, Department of Physics, Oxford (United Kingdom); Brisson, V.; Jacquet, M.; Pascaud, C.; Zhang, Z.; Zomer, F. [LAL, Universite Paris-Sud, CNRS/IN2P3, Orsay (France); Buniatyan, A.; Huber, F.; Sauter, M.; Schoening, A. [Universitaet Heidelberg, Physikalisches Institut, Heidelberg (Germany); Bylinkin, A.; Bystritskaya, L.; Fedotov, A.; Rostovtsev, A. [Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Cantun Avila, K.B.; Contreras, J.G. [CINVESTAV, Departamento de Fisica Aplicada, Merida, Yucatan (Mexico); Ceccopieri, F.; Favart, L.; Grebenyuk, A.; Hreus, T.; Janssen, X.; Roosen, R.; Mechelen, P. van [Brussels and Universiteit Antwerpen, Inter-University Institute for High Energies ULB-VUB, Antwerp (Belgium); Cerny, K.; Pokorny, B.; Polifka, R.; Salek, D.; Valkarova, A.; Zacek, J.; Zlebcik, R. [Charles University, Faculty of Mathematics and Physics, Prague (Czech Republic); Chekelian, V.; Grindhammer, G.; Kiesling, C. [Max-Planck-Institut fuer Physik, Munich (Germany); Dainton, J.B.; Gabathuler, E.; Greenshaw, T.; Klein, M.; Kostka, P.; Kretzschmar, J.; Laycock, P.; Maxfield, S.J.; Mehta, A.; Patel, G.D. [University of Liverpool, Department of Physics, Liverpool (United Kingdom); Daum, K.; Meyer, H. [Fachbereich C, Universitaet Wuppertal, Wuppertal (Germany); Diaconu, C.; Hoffmann, D.; Sauvan, E.; Vallee, C. [CPPM, Aix-Marseille Univ, CNRS/IN2P3, Marseille (France); Dobre, M.; Rotaru, M. [National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest (Romania); Dossanov, A. [Universitaet Hamburg, Institut fuer Experimentalphysik, Hamburg (Germany); Max-Planck-Institut fuer Physik, Munich (Germany); Egli, S.; Horisberger, R. [Paul Scherrer Institut, Villigen (Switzerland); Feltesse, J.; Perez, E.; Schoeffel, L. [CEA, DSM/Irfu, CE-Saclay, Gif-sur-Yvette (France); Ferencei, J. [Slovak Academy of Sciences, Institute of Experimental Physics, Kosice (Slovakia); Goerlich, L.; Mikocki, S.; Nowak, G.; Sopicki, P.; Turnau, J. [Institute for Nuclear Physics, Cracow (Poland); Grab, C. [Institut fuer Teilchenphysik, ETH, Zurich (Switzerland); Henderson, R.C.W. [University of Lancaster, Department of Physics, Lancaster (United Kingdom); Herbst, M.; Schultz-Coulon, H.C. [Kirchhoff-Institut fuer Physik, Universitaet Heidelberg, Heidelberg (Germany); Hladky, J.; Reimer, P. [Academy of Sciences of the Czech Republic, Institute of Physics, Prague (Czech Republic); Jung, H. [Brussels and Universiteit Antwerpen, Inter-University Institute for High Energies ULB-VUB, Antwerp (Belgium); DESY, Hamburg (Germany); Kapichine, M.; Lytkin, L.; Morozov, A.; Spaskov, V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Kogler, R.; Nowak, K. [Universitaet Hamburg, Institut fuer Experimentalphysik, Hamburg (Germany); Landon, M.P.J.; Rizvi, E.; Traynor, D. [University of London, School of Physics and Astronomy, Queen Mary, London (GB); Lange, W.; Naumann, T. [DESY, Zeuthen (DE); Martyn, H.U. [I. Physikalisches Institut der RWTH, Aachen (DE); Mueller, K.; Robmann, P.; Straumann, U.; Truoel, P. [Physik-Institut der Universitaet Zuerich, Zurich (CH); Newman, P.R.; Thompson, P.D. [School of Physics and Astronomy, University of Birmingham, Birmingham (GB); Picuric, I.; Raicevic, N. [University of Montenegro, Faculty of Science, Podgorica (ME); Povh, B. [Max-Planck-Institut fuer Kernphysik, Heidelberg (DE); Sankey, D.P.C. [STFC, Rutherford Appleton Laboratory, Didcot, Oxfordshire (GB); Soloviev, Y. [DESY, Hamburg (DE); Lebedev Physical Institute, Moscow (RU); Stella, B. [Dipartimento di Fisica Universita di Roma Tre (IT); INFN Roma 3, Rome (IT); Sykora, T. [Brussels and Universiteit Antwerpen, Inter-University Institute for High Energies ULB-VUB, Antwerp (BE); Charles University, Faculty of Mathematics and Physics, Prague (CZ); Tsakov, I. [Institute for Nuclear Research and Nuclear Energy, Sofia (BG); Wegener, D. [Institut fuer Physik, TU Dortmund, Dortmund (DE); Collaboration: H1 Collaboration

    2014-06-15

    Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic ep scattering at HERA are presented as a function of the Feynman variable x{sub F} and of the centre-of-mass energy of the virtual photon-proton system W. The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 131 pb{sup -1}. The measurement is restricted to photons and neutrons in the pseudorapidity range η > 7.9 and covers the range of negative four momentum transfer squared at the positron vertex 6 < Q{sup 2} < 100 GeV{sup 2}, of inelasticity 0.05 < y < 0.6 and of 70 < W < 245 GeV. To test the Feynman scaling hypothesis the W dependence of the x{sub F} dependent cross sections is investigated. Predictions of deep-inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections. (orig.)

  11. Isoscalar and neutron modes in the E1 spectra of Ni isotopes and the relevance of shell effects and the continuum

    CERN Document Server

    Papakonstantinou, P; Roth, R

    2015-01-01

    We study theoretically the electric dipole transitions of even Ni isotopes at low energies, using the self-consistent quasi-particle random-phase approximation (RPA) with the D1S Gogny interaction and a continuum-RPA model with the SLy4 Skyrme force. We analyze isoscalar states, isovector states, and the dipole polarizability. We define a reference value for the polarizability, to remove a trivial dependence on the mass number. We compare our results with data and other calculations, with a focus on collective states, shell effects, and threshold transitions. Our results support the presence of a strong isoscalar transition, with little or moderate E1 strength, as a universal feature of ordinary nuclei. In moderately neutron-rich Ni isotopes, namely 68Ni and neighboring isotopes, this transition is found bimodal due to couplings with surface neutrons. An adequate treatment of the continuum states appears essential for describing suprathreshold E1 strength, especially beyond 68Ni. Very exotic isotopes (N>50) a...

  12. Measurement of Feynman-x Spectra of Photons and Neutrons in the Very Forward Direction in Deep-Inelastic Scattering at HERA

    CERN Document Server

    Andreev, V.; Begzsuren, K.; Belousov, A.; Belov, P.; Boudry, V.; Brandt, G.; Brinkmann, M.; Brisson, V.; Britzger, D.; Buniatyan, A.; Bylinkin, A.; Bystritskaya, L.; Campbell, A.J.; Cantun Avila, K.B.; Ceccopieri, F.; Cerny, K.; Chekelian, V.; Contreras, J.G.; Dainton, J.B.; Daum, K.; Diaconu, C.; Dobre, M.; Dodonov, V.; Dossanov, A.; Eckerlin, G.; Egli, S.; Elsen, E.; Favart, L.; Fedotov, A.; Feltesse, J.; Ferencei, J.; Fleischer, M.; Fomenko, A.; Gabathuler, E.; Gayler, J.; Ghazaryan, S.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Gouzevitch, M.; Grab, C.; Grebenyuk, A.; Greenshaw, T.; Grindhammer, G.; Haidt, D.; Henderson, R.C.W.; Herbst, M.; Hladky, J.; Hoffmann, D.; Horisberger, R.; Hreus, T.; Huber, F.; Jacquet, M.; Janssen, X.; Jung, H.; Kapichine, M.; Kiesling, C.; Klein, M.; Kleinwort, C.; Kogler, R.; Kostka, P.; Kretzschmar, J.; Kruger, K.; Landon, M.P.J.; Lange, W.; Laycock, P.; Lebedev, A.; Levonian, S.; Lipka, K.; List, B.; List, J.; Lobodzinski, B.; Lytkin, L.; Malinovski, E.; Martyn, H.U.; Maxfield, S.J.; Mehta, A.; Meyer, A.B.; Meyer, H.; Meyer, J.; Mikocki, S.; Morozov, A.; Muller, K.; Naumann, Th.; Newman, P.R.; Niebuhr, C.; Nowak, G.; Nowak, K.; Olsson, J.E.; Ozerov, D.; Pahl, P.; Pascaud, C.; Patel, G.D.; Perez, E.; Petrukhin, A.; Picuric, I.; Pirumov, H.; Pitzl, D.; Placakyte, R.; Pokorny, B.; Polifka, R.; Povh, B.; Radescu, V.; Raicevic, N.; Ravdandorj, T.; Reimer, P.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Rotaru, M.; Rusakov, S.; Salek, D.; Sankey, D.P.C.; Sauter, M.; Sauvan, E.; Schmitt, S.; Schoeffel, L.; Schoning, A.; Schultz-Coulon, H.C.; Sefkow, F.; Shushkevich, S.; Soloviev, Y.; Sopicki, P.; South, D.; Spaskov, V.; Specka, A.; Steder, M.; Stella, B.; Straumann, U.; Sykora, T.; Thompson, P.D.; Traynor, D.; Truol, P.; Tsakov, I.; Tseepeldorj, B.; Turnau, J.; Valkarova, A.; Vallee, C.; Van Mechelen, P.; Vazdik, Y.; Wegener, D.; Wunsch, E.; Zacek, J.; Zhang, Z.; Zlebcik, R.; Zohrabyan, H.; Zomer, F.

    2014-01-01

    Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic $ep$ scattering at HERA are presented as a function of the Feynman variable $x_F$ and of the centre-of-mass energy of the virtual photon-proton system $W$. The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of $131 \\mathrm{pb}^{-1}$. The measurement is restricted to photons and neutrons in the pseudorapidity range $\\eta>7.9$ and covers the range of negative four momentum transfer squared at the positron vertex $6

  13. Measurements of the neutron energy spectra in the core of IPEN/MB-01 reactor; Medida do espectro de energia dos neutrons no nucleo do reator IPEN/MB-01

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Fernando Prat Goncalves

    2006-07-01

    This work presents the neutron spectrum measurements in the Reactor IPEN/MB-01 using very thin activation detectors in the metallic form, in reactor core, in moderator region. An articulated device allows that the foils are inserted in the central position of reactor core, ensuring that all the foils are irradiated in the same position. The activation detectors of different materials such Au{sup 197}, Mg{sup 24}, Ti{sup 4}'8, In{sup 115}, Sc{sup 45} and others, were selected to cover a large range of neutron spectrum. After the irradiation, the activation detectors were submitted to a spectrometry gamma by using a system of counting with high purity Germanium, to obtain the saturation activity per target nuclide. The saturation activity is one of the main data of input of unfolding code SANDBP, that through an iterative adjustment, modify the spectrum that better agree with the dataset of code input, composition mainly for measure reaction rate per target nuclide and a initial input spectrum, calculated for Hammer-Technion code, supplying a solution spectrum. (author)

  14. Sensitivity analysis of the spectra of the core neutronic source in the calculation of radiation damage in internal of PWR reactor vessel. Internal; Analisis de sensibilidad a los espectros de la fuente neutronica del nucleo en el calculo del dano por irradiacion en los internos de la vasija de un reactor PWR

    Energy Technology Data Exchange (ETDEWEB)

    Cadenas Mendicoa, A. M.; Benito Hernandez, M.; Barrerira Pereira, P.

    2012-07-01

    This study is to analyze the sensitivity to the expected differences in the energy spectra characterizing the neutron source that radiates the vessel internals of a commercial PWR reactor, in order to quantify their influence in the quantities that determine the damage in materials metal.

  15. Measurement and calculation of the fast-neutron and photon spectra from the core boundary to the biological shielding in the WWER-1000 reactor model.

    Science.gov (United States)

    Osmera, B; Cvachovec, F; Kyncl, J; Smutný, V

    2005-01-01

    The fast-neutron and photon space-energy distributions have been measured in an axially (1.25 m active height) and azimuthally (60 degree symmetry sector) shortened model of the WWER-1000 reactor assembled in the LR-0 experimental reactor. The space-energy distributions have been calculated with the stochastic code MCNP and the deterministic three-dimensional code TORT. Selected results are presented and discussed in the paper. This work has been done in the frame of the EU 5th FW project REDOS REDOS, Reactor Dosimetry: Accurate determination and benchmarking of radiation field parameters, relevant for reactor pressure vessel monitoring. EURATOM Programme, Call 2000/C 294/04). All geometry and material composition data of the model as well as the available experimental data were carefully checked and revised.

  16. Light charged particle and neutron velocity spectra in coincidence with projectile fragments in the reaction sup 4 sup 0 Ar(44 A MeV)+ sup 2 sup 7 Al

    CERN Document Server

    Lanzanò, G; Geraci, M; Pagano, A; Aiello, S; Cunsolo, A; Fonte, R; Foti, A; Sperduto, M L; Volant, C; Charvet, J L; Dayras, R; Legrain, R

    2001-01-01

    We present a three source analysis of velocity spectra of light charged particles (LCP) and neutrons emitted in the reaction sup 4 sup 0 Ar+ sup 2 sup 7 Al at 44 A MeV. The light particle (LP) velocity spectra are studied as a function of the detection angle (1.5 deg.

  17. Neutron spectrum unfolding using neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E. [Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)]. E-mail: rvega@cantera.reduaz.mx

    2004-07-01

    An artificial neural network has been designed to obtain the neutron spectra from the Bonner spheres spectrometer's count rates. The neural network was trained using a large set of neutron spectra compiled by the International Atomic Energy Agency. These include spectra from iso- topic neutron sources, reference and operational neutron spectra obtained from accelerators and nuclear reactors. The spectra were transformed from lethargy to energy distribution and were re-binned to 31 energy groups using the MCNP 4C code. Re-binned spectra and UTA4 matrix were used to calculate the expected count rates in Bonner spheres spectrometer. These count rates were used as input and correspondent spectrum was used as output during neural network training. The network has 7 input nodes, 56 neurons as hidden layer and 31 neurons in the output layer. After training the network was tested with the Bonner spheres count rates produced by twelve neutron spectra. The network allows unfolding the neutron spectrum from count rates measured with Bonner spheres. Good results are obtained when testing count rates belong to neutron spectra used during training, acceptable results are obtained for count rates obtained from actual neutron fields; however the network fails when count rates belong to monoenergetic neutron sources. (Author)

  18. Sequential measurements of environmental neutron energy spectrum and neutron dose

    Energy Technology Data Exchange (ETDEWEB)

    Nunomiya, Tomoya; Nakamura, Takashi; Suzuki, Hiroyuki; Terunuma, Kazutaka; Hirabayashi, Naoya; Sato, Youichi; Abe, Sigeru; Rasolonjatovo A.H, Danielle [Tohoku Univ., Dept. of Quantum Science and Energy Engineering, Sendai, Miyagi (Japan)

    2003-03-01

    From April 2001, neutron energy spectra and neutron dose were sequentially measured using 5'' -rem counter and {sup 3}He multi-moderator spectrometer (Boner boll) at Kawauchi-campus of Tohoku University. These data were collected about the relation between the dose level and the solar activities. (author)

  19. VSOP-2 Key Science Program Proposal: Deep Exploration of the Dynamics of the Milky Way Based on High Precision Water Maser Astrometry

    Science.gov (United States)

    Imai, H.

    2009-08-01

    Our Japanese astronomical community is proposing the VSOP-2 key science programs (KSPs) for study of the dynamics of the Milky Way Galaxy (MWG) on the basis of high precision astrometry of h2o maser sources. High angular resolution of VSOP-2 is expected to simultaneously perform 10 micro-arcsecond (μas) level astrometry, which enables the determination of annual parallaxes and secular motions of the maser sources. The proposed KSPs cover the whole scale of the MWG in both the northern or southern hemispheres, except for the Galactic center region. In the southern hemisphere, in particular, ASTRO-G's orbit should provide a great opportunity for obtaining good image quality and astrometric accuracy with a relatively small number of ground-based telescopes. h2o maser sources located behind the Galactic center and in the Large and Small Magellanic Clouds are expected to be the main target sources for the proposed KSPs.

  20. Neutronic studies of the coupled moderators for spallation neutron sources

    Institute of Scientific and Technical Information of China (English)

    Yin Wen; Liang Jiu-Qing

    2005-01-01

    We investigate the neutronic performance of coupled moderators to be implemented in spallation neutron sources by Monte-Carlo simulation and give the slow neutron spectra for the cold and thermal moderators. CH4 moderator can provide slow neutrons with highly desirable characteristics and will be used in low-power spallation neutron soureces. The slow neutron intensity extracted from different angles has been calculated. The capability of moderation of liquid H2 is lower than H2O and liquid CH4 due to lower atomic number density of hydrogen but we can compensate for this disadvantage by using a premoderator. The H2O premoderator of 2cm thickness can reduce the heat deposition in the cold moderator by about 33% without spoiling the neutron pulse.

  1. A Compact High-Energy Neutron Spectrometer

    CERN Document Server

    Brooks, F D; Buffler, A; Dangendorf, V; Herbert, M S; Jones, D T L; Nchodu, M R; Nolte, R; Smit, F D

    2007-01-01

    A compact liquid organic neutron spectrometer (CLONS) based on a single NE213 liquid scintillator (5 cm diam. x 5 cm) is described. The spectrometer is designed to measure neutron fluence spectra over the energy range 2-200 MeV and is suitable for use in neutron fields having any type of time structure. Neutron fluence spectra are obtained from measurements of two-parameter distributions (counts versus pulse height and pulse shape) using the Bayesian unfolding code MAXED. Calibration and test measurements made using a pulsed neutron beam with a continuous energy spectrum are described and the application of the spectrometer to radiation dose measurements is discussed.

  2. Pileup correction of microdosimetric spectra

    CERN Document Server

    Langen, K M; Lennox, A J; Kroc, T K; De Luca, P M

    2002-01-01

    Microdosimetric spectra were measured at the Fermilab neutron therapy facility using low pressure proportional counters operated in pulse mode. The neutron beam has a very low duty cycle (<0.1%) and consequently a high instantaneous dose rate which causes distortions of the microdosimetric spectra due to pulse pileup. The determination of undistorted spectra at this facility necessitated (i) the modified operation of the proton accelerator to reduce the instantaneous dose rate and (ii) the establishment of a computational procedure to correct the measured spectra for remaining pileup distortions. In support of the latter effort, two different pileup simulation algorithms using analytical and Monte-Carlo-based approaches were developed. While the analytical algorithm allows a detailed analysis of pileup processes it only treats two-pulse and three-pulse pileup and its validity is hence restricted. A Monte-Carlo-based pileup algorithm was developed that inherently treats all degrees of pileup. This algorithm...

  3. Iron-line and continuum variations in the XMM-Newton and Suzaku spectra of the neutron-star low-mass X-ray binary 4U 1636-53

    CERN Document Server

    Lyu, Ming; Sanna, Andrea; Homan, Jeroen; Belloni, Tomaso; Hiemstra, Beike

    2014-01-01

    We used six simultaneous XMM-Newton and Rossi X-ray Timing Explorer plus five Suzaku observations to study the continuum spectrum and the iron emission line in the neutron-star low-mass X-ray binary 4U 1636-53. We modelled the spectra with two thermal components (representing the accretion disc and boundary layer), a Comptonised component (representing a hot corona), and either a Gaussian or a relativistic line component to model an iron emission line at about 6.5 keV. For the relativistic line component we used either the diskline, laor or kyrline model, the latter for three different values of the spin parameter. The fitting results for the continuum are consistent with the standard truncated disc scenario. We also find that the flux and equivalent width of the iron line first increase and then decrease as the flux of the Comptonised component increases. This could be explained either by changes in the ionisation state of the accretion disc where the line is produced by reflection, or by light bending of th...

  4. Synovectomy by Neutron capture; Sinovectomia por captura de neutrones

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Torres M, C. [Centro Regional de Estudios Nucleares, Universidad Autonoma de Zacatecas, C. Cipres 10, Fracc. La Penuela, 98000 Zacatecas (Mexico)

    1998-12-31

    The Synovectomy by Neutron capture has as purpose the treatment of the rheumatoid arthritis, illness which at present does not have a definitive curing. This therapy requires a neutron source for irradiating the articulation affected. The energy spectra and the intensity of these neutrons are fundamental since these neutrons induce nuclear reactions of capture with Boron-10 inside the articulation and the freely energy of these reactions is transferred at the productive tissue of synovial liquid, annihilating it. In this work it is presented the neutron spectra results obtained with moderator packings of spherical geometry which contains in its center a Pu{sup 239} Be source. The calculations were realized through Monte Carlo method. The moderators assayed were light water, heavy water base and the both combination of them. The spectra obtained, the average energy, the neutron total number by neutron emitted by source, the thermal neutron percentage and the dose equivalent allow us to suggest that the moderator packing more adequate is what has a light water thickness 0.5 cm (radius 2 cm) and 24.5 cm heavy water (radius 26.5 cm). (Author)

  5. Carbon neutron star atmospheres

    CERN Document Server

    Suleimanov, V F; Pavlov, G G; Werner, K

    2013-01-01

    The accuracy of measuring the basic parameters of neutron stars is limited in particular by uncertainties in chemical composition of their atmospheres. For example, atmospheres of thermally - emitting neutron stars in supernova remnants might have exotic chemical compositions, and for one of them, the neutron star in CasA, a pure carbon atmosphere has recently been suggested by Ho & Heinke (2009). To test such a composition for other similar sources, a publicly available detailed grid of carbon model atmosphere spectra is needed. We have computed such a grid using the standard LTE approximation and assuming that the magnetic field does not exceed 10^8 G. The opacities and pressure ionization effects are calculated using the Opacity Project approach. We describe the properties of our models and investigate the impact of the adopted assumptions and approximations on the emergent spectra.

  6. Neutron scattering studies in the actinide region

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-08-01

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

  7. Neutron spectrometry with artificial neural networks

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.; Rodriguez, J.M.; Mercado S, G.A. [Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico); Iniguez de la Torre Bayo, M.P. [Universidad de Valladolid, Valladolid (Spain); Barquero, R. [Hospital Universitario Rio Hortega, Valladolid (Spain); Arteaga A, T. [Envases de Zacatecas, S.A. de C.V., Zacatecas (Mexico)]. e-mail: rvega@cantera.reduaz.mx

    2005-07-01

    An artificial neural network has been designed to obtain the neutron spectra from the Bonner spheres spectrometer's count rates. The neural network was trained using 129 neutron spectra. These include isotopic neutron sources; reference and operational spectra from accelerators and nuclear reactors, spectra from mathematical functions as well as few energy groups and monoenergetic spectra. The spectra were transformed from lethargy to energy distribution and were re-bin ned to 31 energy groups using the MCNP 4C code. Re-binned spectra and UTA4 response matrix were used to calculate the expected count rates in Bonner spheres spectrometer. These count rates were used as input and the respective spectrum was used as output during neural network training. After training the network was tested with the Bonner spheres count rates produced by a set of neutron spectra. This set contains data used during network training as well as data not used. Training and testing was carried out in the Mat lab program. To verify the network unfolding performance the original and unfolded spectra were compared using the {chi}{sup 2}-test and the total fluence ratios. The use of Artificial Neural Networks to unfold neutron spectra in neutron spectrometry is an alternative procedure that overcomes the drawbacks associated in this ill-conditioned problem. (Author)

  8. Evaluating the control rod modelling approach used in the South African PBMR: comparison of VSOP calculations with ASTRA experiments

    Energy Technology Data Exchange (ETDEWEB)

    Reitsma, F. E-mail: reitsma@aec.co.za; Naidoo, D

    2003-06-01

    The problem of modelling a highly absorbing region in a diffusion calculation is well known and many methods have been developed to accommodate the transport effects in diffusion theory. In this work the use of the equivalent cross-sections method for pebble bed type reactors is evaluated by applying it to calculations of control rod (CR) experiments performed at the ASTRA Critical Facility at the Russian Research Centre, Kurchatov Institute in Moscow. The measured reactivity worths of the CRs situated in the side reflector are compared with the calculated values making use of equivalent diffusion parameters in VSOP. Results obtained were favourable for CRs situated within the first ring of reflector blocks, with larger errors obtained for CRs situated further from the core. An additional method that was investigated is the use of equivalent boron concentrations (EBCs) to represent the absorber region. This is shown to be useful if applied correctly and with care especially in the case of differential CR worth. Practical difficulties exist with both approaches, which makes the investigation of an alternative method, which should remove these shortcomings, attractive.

  9. The Promise of Future VSOP-2 Observations for Studies of Helical Magnetic Fields and Their Evolution in Active Galactic Nuclei

    Science.gov (United States)

    Mahmud, M.; Gabuzda, D.

    2009-08-01

    We present here results of an observational search for Faraday Rotation Measure (RM) gradients transverse to the VLBI jet direction in a sample of BL Lac objects that provide evidence for the presence of helical magnetic fields wrapped around the jets. This project has revealed new transverse RM gradients in several sources. In at least three sources, we observe new features, such as reversal of the transverse RM gradient with time or distance from the core. We discuss how these gradients could potentially be used to infer the intrinsic magnetic field configuration of the region surrounding the central black hole (e.g. dipolar, quadropolar; Blandford 2008). The use of 8 GHz VSOP-2 polarization observations in combination with ground VLBI polarization observations at higher frequencies will give us even higher angular resolution to probe in the central regions of the jet, enabling more accurate determination of the RM gradients on smaller scales, and could help identify possible counter-jets in some sources, which could provide a test for the magnetic field configuration of the black hole.

  10. Neutron-scattering study of the vibrational behavior of trehalose aqueous solutions

    CERN Document Server

    Branca, C; Migliardo, F; Romeo, G; Villari, V; Wanderlingh, U; Colognesi, D

    2002-01-01

    Neutron spectra for hydrated trehalose samples have been obtained by using the time-of-flight spectrometer TOSCA at the ISIS Pulse Neutron Facility (Rutherford Appleton Laboratory, Chilton, UK). Neutron spectra have been compared to the absorbance spectra obtained by Fourier-transform infrared spectroscopy. Finally, a comparison with findings obtained by density functional theory has been performed. 3 Refs.

  11. A proposal to order the neutron data set in neutron spectrometry using the RDANN methodology

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz R, J.M.; Martinez B, M.R.; Vega C, H.R. [UAZ, Av. Ramon Lopez Velarde No. 801, 98000 Zacatecas (Mexico)

    2006-07-01

    A new proposal to order a neutron data set in the design process of artificial neural networks in the neutron spectrometry field is presented for first time. The robust design of artificial neural networks methodology was applied to 187 neutron spectra data set compiled by the International Atomic Energy Agency. Four cases of grouping the neutron spectra were considered and around 1000 different neural networks were designed, trained and tested with different net topologies each one. After carrying out the systematic methodology for all the cases, it was determined that the best neural network topology that produced the best reconstructed neutron spectra was case with 187 neutron spectra data set, determining that the best neural network topology is: 7 entrance neurons, 14 neurons in a hidden layer and 31 neurons in the exit layer, with a value of 0.1 in the learning rate and 0.1 in the moment. (Author)

  12. Compilation of Existing Neutron Screen Technology

    Directory of Open Access Journals (Sweden)

    N. Chrysanthopoulou

    2014-01-01

    Full Text Available The presence of fast neutron spectra in new reactors is expected to induce a strong impact on the contained materials, including structural materials, nuclear fuels, neutron reflecting materials, and tritium breeding materials. Therefore, introduction of these reactors into operation will require extensive testing of their components, which must be performed under neutronic conditions representative of those expected to prevail inside the reactor cores when in operation. Due to limited availability of fast reactors, testing of future reactor materials will mostly take place in water cooled material test reactors (MTRs by tailoring the neutron spectrum via neutron screens. The latter rely on the utilization of materials capable of absorbing neutrons at specific energy. A large but fragmented experience is available on that topic. In this work a comprehensive compilation of the existing neutron screen technology is attempted, focusing on neutron screens developed in order to locally enhance the fast over thermal neutron flux ratio in a reactor core.

  13. Solar neutron decay proton observations in cycle 21

    Science.gov (United States)

    Evenson, Paul; Kroeger, Richard; Meyer, Peter; Reames, Donald

    1990-01-01

    Measurement of the flux and energy spectrum of the protons resulting from the decay of solar flare neutrons gives unique information on the spectrum of neutrons from 5 to 200 MeV. Neutrons from three flares have been observed in this manner during solar cycle 21. The use of the decay protons to determine neutron energy spectra is reviewed, and new and definitive energy spectra are presented for the two large flares on June 3, 1982 and April 25, 1984.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1993-09-01

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

  15. Imaging of VSOP labeled stem cells in agarose phantoms with susceptibility weighted and T2* weighted MR Imaging at 3T: determination of the detection limit.

    Directory of Open Access Journals (Sweden)

    Donald Lobsien

    Full Text Available OBJECTIVES: This study aimed to evaluate the detectability of stem cells labeled with very small iron oxide particles (VSOP at 3T with susceptibility weighted (SWI and T2* weighted imaging as a methodological basis for subsequent examinations in a large animal stroke model (sheep. MATERIALS AND METHODS: We examined ovine mesenchymal stem cells labeled with VSOP in agarose layer phantoms. The experiments were performed in 2 different groups, with quantities of 0-100,000 labeled cells per layer. 15 different SWI- and T2*-weighted sequences and 3 RF coils were used. All measurements were carried out on a clinical 3T MRI. Images of Group A were analyzed by four radiologists blinded for the number of cells, and rated for detectability according to a four-step scale. Images of Group B were subject to a ROI-based analysis of signal intensities. Signal deviations of more than the 0.95 confidence interval in cell containing layers as compared to the mean of the signal intensity of non cell bearing layers were considered significant. RESULTS: GROUP A: 500 or more labeled cells were judged as confidently visible when examined with a SWI-sequence with 0.15 mm slice thickness. Group B: 500 or more labeled cells showed a significant signal reduction in SWI sequences with a slice thickness of 0.25 mm. Slice thickness and cell number per layer had a significant influence on the amount of detected signal reduction. CONCLUSION: 500 VSOP labeled stem cells could be detected with SWI imaging at 3 Tesla using an experimental design suitable for large animal models.

  16. Imaging of VSOP labeled stem cells in agarose phantoms with susceptibility weighted and T2* weighted MR Imaging at 3T: determination of the detection limit.

    Science.gov (United States)

    Lobsien, Donald; Dreyer, Antje Y; Stroh, Albrecht; Boltze, Johannes; Hoffmann, Karl-Titus

    2013-01-01

    This study aimed to evaluate the detectability of stem cells labeled with very small iron oxide particles (VSOP) at 3T with susceptibility weighted (SWI) and T2* weighted imaging as a methodological basis for subsequent examinations in a large animal stroke model (sheep). We examined ovine mesenchymal stem cells labeled with VSOP in agarose layer phantoms. The experiments were performed in 2 different groups, with quantities of 0-100,000 labeled cells per layer. 15 different SWI- and T2*-weighted sequences and 3 RF coils were used. All measurements were carried out on a clinical 3T MRI. Images of Group A were analyzed by four radiologists blinded for the number of cells, and rated for detectability according to a four-step scale. Images of Group B were subject to a ROI-based analysis of signal intensities. Signal deviations of more than the 0.95 confidence interval in cell containing layers as compared to the mean of the signal intensity of non cell bearing layers were considered significant. 500 or more labeled cells were judged as confidently visible when examined with a SWI-sequence with 0.15 mm slice thickness. Group B: 500 or more labeled cells showed a significant signal reduction in SWI sequences with a slice thickness of 0.25 mm. Slice thickness and cell number per layer had a significant influence on the amount of detected signal reduction. 500 VSOP labeled stem cells could be detected with SWI imaging at 3 Tesla using an experimental design suitable for large animal models.

  17. Experimental investigation of new neutron moderator materials

    Energy Technology Data Exchange (ETDEWEB)

    Mocko, Michal [Los Alamos National Laboratory; Daemen, Luke L [Los Alamos National Laboratory; Hartl, Monika [Los Alamos National Laboratory; Huegle, Thomas [Los Alamos National Laboratory; Muhrer, Guenter [Los Alamos National Laboratory

    2010-01-01

    In this study we present experimental investigation of thermal neutron energy spectra produced by lead and bismuth hydroxides (Pb(OH){sub 2}, and Bi(OH){sub 3}). The experimental energy spectra are compared with a thermal neutron energy spectrum of water measured in the same geometry. We present an MCNPX geometry model used to help with the experimental data interpretation. We demonstrate a very good reproduction of the experimental thermal neutron energy spectrum produced by the water moderator. We show a sensitivity study with the Pb(OH){sub 2}, and Bi(OH){sub 3} materials on different combinations of thermal neutron scattering kernels.

  18. Prompt neutron fission spectrum mean energies for the fissile nuclides and /sup 252/Cf

    Energy Technology Data Exchange (ETDEWEB)

    Holden, N.E.

    1985-01-01

    The international standard for a neutron spectrum is that produced from the spontaneous fission of /sup 252/Cf, while the thermal neutron induced fission neutron spectra for the four fissile nuclides, /sup 233/U, /sup 235/U, /sup 239/Pu, and /sup 241/Pu are of interest from the standpoint of nuclear reactors. The average neutron energies of these spectra are tabulated. The individual measurements are recorded with the neutron energy range measured, the method of detection as well as the average neutron energy for each author. Also tabulated are the measurements of the ratio of mean energies for pairs of fission neutron spectra. 75 refs., 9 tabs. (LEW)

  19. Gamma-ray burst spectra

    Science.gov (United States)

    Teegarden, B. J.

    1982-01-01

    A review of recent results in gamma-ray burst spectroscopy is given. Particular attention is paid to the recent discovery of emission and absorption features in the burst spectra. These lines represent the strongest evidence to date that gamma-ray bursts originate on or near neutron stars. Line parameters give information on the temperature, magnetic field and possibly the gravitational potential of the neutron star. The behavior of the continuum spectrum is also discussed. A remarkably good fit to nearly all bursts is obtained with a thermal-bremsstrahlung-like continuum. Significant evolution is observed of both the continuum and line features within most events.

  20. Peculiarities of the modern neutron spectrometry

    Indian Academy of Sciences (India)

    Yu P Popov

    2001-08-01

    Neutron spectrometry provides many branches of science and technology with the necessary data. Usually the main part of the data is supplied by powerful neutron time-of-flight spectrometers. Nevertheless there are many other very effective but simpler and cheaper neutron spectroscopy methods on accelerators, suitable for solution of plenty of scientific and applied problems (for example, in astrophysics and radioactive waste transmutation). The methods of slowing-down spectrometry in lead and graphite, generating of neutron spectra, characteristic for nucleosynthesis in the stars, and neutron spectrometry by means of primary -transition shift are discussed in the report.

  1. Neutron Repulsion

    OpenAIRE

    Manuel, Oliver K.

    2011-01-01

    Earth is connected gravitationally, magnetically and electrically to its heat source - a neutron star that is obscured from view by waste products in the photosphere. Neutron repulsion is like the hot filament in an incandescent light bulb. Excited neutrons are emitted from the solar core and decay into hydrogen that glows in the photosphere like a frosted light bulb. Neutron repulsion was recognized in nuclear rest mass data in 2000 as the overlooked source of energy, the keystone of an arch...

  2. Inequality spectra

    Science.gov (United States)

    Eliazar, Iddo

    2017-03-01

    Inequality indices are widely applied in economics and in the social sciences as quantitative measures of the socioeconomic inequality of human societies. The application of inequality indices extends to size-distributions at large, where these indices can be used as general gauges of statistical heterogeneity. Moreover, as inequality indices are plentiful, arrays of such indices facilitate high-detail quantification of statistical heterogeneity. In this paper we elevate from arrays of inequality indices to inequality spectra: continuums of inequality indices that are parameterized by a single control parameter. We present a general methodology of constructing Lorenz-based inequality spectra, apply the general methodology to establish four sets of inequality spectra, investigate the properties of these sets, and show how these sets generalize known inequality gauges such as: the Gini index, the extended Gini index, the Rényi index, and hill curves.

  3. MCNPX Simulations for Neutron Cross Section Measurements

    OpenAIRE

    Tesinsky, Milan

    2010-01-01

    This thesis presents MCNPX simulations of the SCANDAL set-up used at the Theodor Svedberg Laboratory for neutron scattering cross-section measurements. The thesis describes processes and data important for the upcoming off-line data analysis. In the experiment, neutrons scattered off the target are converted to protons which are stopped in scintillator crystals. The results of presented simulations include a description of the proton spectra in dependence of the neutron-to-proton conversion a...

  4. Information from leading neutrons at HERA

    CERN Document Server

    Khoze, V A; Ryskin, M G

    2006-01-01

    In principle, leading neutrons produced in photoproduction and deep-inelastic scattering at HERA have the potential to determine the pion structure function, the neutron absorptive cross section and the form of the pion flux. To explore this potential we compare theoretical predictions for the x_L and p_t spectra of leading neutrons, and the Q^2 dependence of the cross section, with the existing ZEUS data.

  5. Neutron dosimetry in solid water phantom

    Energy Technology Data Exchange (ETDEWEB)

    Benites-Rengifo, Jorge Luis, E-mail: jlbenitesr@prodigy.net.mx [Centro Estatal de Cancerologia de Nayarit, Calzada de la Cruz 118 Sur, Tepic Nayarit, Mexico and Instituto Tecnico Superior de Radiologia, ITEC, Calle Leon 129, Tepic Nayarit (Mexico); Vega-Carrillo, Hector Rene, E-mail: fermineutron@yahoo.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. postal 336, 98000, Zacatecas, Zac. (Mexico)

    2014-11-07

    The neutron spectra, the Kerma and the absorbed dose due to neutrons were estimated along the incoming beam in a solid water phantom. Calculations were carried out with the MCNP5 code, where the bunker, the phantom and the model of the15 MV LINAC head were modeled. As the incoming beam goes into the phantom the neutron spectrum is modified and the dosimetric values are reduced.

  6. Prompt fission neutron spectrum of actinides

    Energy Technology Data Exchange (ETDEWEB)

    Capote, R. [International Atomic Energy Agency, Vienna (Austria); Chen, Y. -J. [China Institute of Atomic Energy, Beijing (China); Hambsch, F. J. [European Commission, Joint Research Centre - IRRM, Geel (Belgium); Jurado, B. [CENBG, CNRS/IN2P3, Gradignan (France); Kornilov, N. [Ohio Univ., Athens, OH (United States); Lestone, J. P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Litaize, O. [CEA, DEN, DER, SPRC, Saint-Paul-Lez-Durance (France); Morillon, B. [CEA, DAM, DIF, Arpajon (France); Neudecker, D. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Oberstedt, S. [European Commission, Joint Research Centre - IRRM, Geel (Belgium); Ohsawa, T. [Kinki Univ., Osaka-fu (Japan); Otuka, N. [International Atomic Energy Agency, Vienna (Austria); Pronyaev, V. G. [Institute of Physics and Power Engineering, Obninsk (Russian Federation); Saxena, A. [Bhabha Atomic Research Centre, Mumbai (India); Schmidt, K. H. [CENBG, CNRS/IN2P3, Gradignan (France); Serot, O. [CEA, DEN, DER, SPRC, Saint-Paul-Lez-Durance (France); Shcherbakov, O. A. [Petersburg Nuclear Physics Institute of NRC " Kurchatov Institute" , Gatchina (Russian Federation); Shu, N. -C. [China Institute of Atomic Energy, Beijing (China); Smith, D. L. [Argonne National Lab. (ANL), Argonne, IL (United States); Talou, P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Trkov, A. [International Atomic Energy Agency, Vienna (Austria); Tudora, A. C. [Univ. of Bucharest, Magurele (Romania); Vogt, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of California, Davis, CA (United States); Vorobyev, A. S. [Petersburg Nuclear Physics Institute of NRC " Kurchatov Institute" , Gatchina (Russian Federation)

    2016-01-06

    Here, the energy spectrum of prompt neutron emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) "Evaluation of Prompt Fission Neutron Spectra of Actinides" was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei.

  7. Probing neutron star physics using accreting neutron stars

    Directory of Open Access Journals (Sweden)

    Patruno A.

    2010-10-01

    Full Text Available We give an obervational overview of the accreting neutron stars systems as probes of neutron star physics. In particular we focus on the results obtained from the periodic timing of accreting millisecond X-ray pulsars in outburst and from the measurement of X-ray spectra of accreting neutron stars during quiescence. In the first part of this overview we show that the X-ray pulses are contaminated by a large amount of noise of uncertain origin, and that all these neutron stars do not show evidence of spin variations during the outburst. We present also some recent developments on the presence of intermittency in three accreting millisecond X-ray pulsars and investigate the reason why only a small number of accreting neutron stars show X-ray pulsations and why none of these pulsars shows sub-millisecond spin periods. In the second part of the overview we introduce the observational technique that allows the study of neutron star cooling in accreting systems as probes of neutron star internal composition and equation of state. We explain the phenomenon of the deep crustal heating and present some recent developments on several quasi persistent X-ray sources where a cooling neutron star has been observed.

  8. CR-39 detector based thermal neutron flux measurements, in the photo neutron project

    Energy Technology Data Exchange (ETDEWEB)

    Mameli, A.; Greco, F.; Fidanzio, A. [U.O. di Fisica Sanitaria Policlinico A. Gemelli, Universita Cattolica S. Cuore, Roma (Italy); Fusco, V. [U.O. di Radioterapia, Centro di Riferimento Oncologico della Basilicata, CROB Rionero Pz (Italy); Cilla, S.; D' Onofrio, G.; Grimaldi, L.; Augelli, B.G. [U.O. di Fisica Sanitaria, Centro di Ricerca e Formazione ad Alta Tecnologia nelle Scienze Biomediche dell' Universita Cattolica S. Cuore, Campobasso (Italy); Giannini, G.; Bevilacqua, R.; Totaro, P. [Dipartimento di Fisica-Universita di Trieste e INFN Sez Trieste, Padriciano, Trieste (Italy); Tommasino, L. [Consultant, Via Cassia 1727, 00123 Roma (Italy); Azario, L. [Istituto di Fisica, Universita Cattolica del S. Cuore, Roma (Italy); Piermattei, A. [Istituto di Fisica, Universita Cattolica del S. Cuore, Roma (Italy)], E-mail: a.piermattei@rm.unicatt.it

    2008-08-15

    PhoNeS (photo neutron source) is a project aimed at the production and moderation of neutrons by exploiting high energy linear accelerators, currently used in radiotherapy. A feasibility study has been carried out with the scope in mind to use the high energy photon beams from these accelerators for the production of neutrons suitable for boron neutron capture therapy (BNCT). Within these investigations, it was necessary to carry out preliminary measurements of the thermal neutron component of neutron spectra, produced by the photo-conversion of X-ray radiotherapy beams supplied by three LinAcs: 15 MV, 18 MV and 23 MV. To this end, a simple passive thermal neutron detector has been used which consists of a CR-39 track detector facing a new type of boron-loaded radiator. Once calibrated, this passive detector has been used for the measurement of both the thermal neutron component and the cadmium ratio of different neutron spectra. In addition, bubble detectors with a response highly sensitive to thermal neutrons have also been used. Both thermal neutron detectors are simple to use, very compact and totally insensitive to low-ionizing radiation such as electrons and X-rays. The resultant thermal neutron flux was above 10{sup 6} n/cm{sup 2}s and the cadmium ratio was no greater than 15 for the first attempt of photo-conversion of X-ray radiotherapy beams.

  9. Neutron dosimetry and radiation damage calculations for HFBR

    Energy Technology Data Exchange (ETDEWEB)

    Greenwood, L.R.; Ratner, R.T. [Pacific Northwest National Lab., TN (United States)

    1998-03-01

    Neutron dosimetry measurements have been conducted for various positions of the High Flux Beam Reactor (HFBR) at Brookhaven National Laboratory (BNL) in order to measure the neutron flux and energy spectra. Neutron dosimetry results and radiation damage calculations are presented for positions V10, V14, and V15.

  10. Correlation Time-of-flight Spectrometry of Ultracold Neutrons

    CERN Document Server

    Novopoltsev, M I

    2010-01-01

    The fearures of the correlation method used in time-of-flight spectrometry of ultracold neutrons are analyzed. The time-of-flight spectrometer for the energy range of ultracold neutrons is described, and results of its testing by measuring spectra of neutrons passing through interference filters are presented.

  11. Neutron Radiography

    Science.gov (United States)

    Heller, A. K.; Brenizer, J. S.

    Neutron radiography and its related two-dimensional (2D) neutron imaging techniques have been established as invaluable nondestructive inspection methods and quantitative measurement tools. They have been used in a wide variety of applications ranging from inspection of aircraft engine turbine blades to study of two-phase fluid flow in operating proton exchange membrane fuel cells. Neutron radiography is similar to X-ray radiography in that the method produces a 2D attenuation map of neutron radiation that has penetrated the object being examined. However, the images produced differ and are often complementary due to the differences between X-ray and neutron interaction mechanisms. The uses and types of 2D neutron imaging have expanded over the past 15 years as a result of advances in imaging technology and improvements in neutron generators/sources and computers. Still, high-intensity sources such as those from reactors and spallation neutron sources, together with conventional film radiography, remain the mainstay of high-resolution, large field-of-view neutron imaging. This chapter presents a summary of the history, methods, and related variations of neutron radiography techniques.

  12. Spectroscopy of Neutrons Produced by (p,n) Reactions on Lithium

    Science.gov (United States)

    Wielopolski, Lucian; Powell, J.; Ludewig, H.; Raparia, D.; Alessi, J.; Han, Guoping

    1997-05-01

    Alternative to nuclear reactors, epithermal neutron source are being developed for Boron Neutron Capture Therapy (BNCT). Ideally, BNCT requires mono-energetic neutrons from about 1eV to 20keV depending on the tumor depth in brain. Accelerator based filtered neutron beams for BNCT produce continuous neutron spectra that need to be optimised. Neutron spectra resulting from bombarding Li target with protons, with various energies, were measured using proton recoil proportional counters. These spectra were analysed using the PSNS and HEPRO codes. The results from both analysis and Monte Carlo simulations are presented and the issues involved with either of the codes are discussed.

  13. Monte-Carlo simulations of elastically backscattered neutrons from hidden explosives using three different neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    ElAgib, I. [College of Science, King Saud University, P.O. Box 2455 (Saudi Arabia)], E-mail: elagib@ksu.edu.sa; Elsheikh, N. [College of Applied and Industrial Science, University of Juba, Khartoum, P.O. Box 321 (Sudan); AlSewaidan, H. [College of Science, King Saud University, P.O. Box 2455 (Saudi Arabia); Habbani, F. [Faculty of Science, Physics Department, University of Khartoum, Khartoum, P.O. Box 321 (Sudan)

    2009-01-15

    Calculations of elastically backscattered (EBS) neutrons from hidden explosives buried in soil were performed using Monte-Carlo N-particle transport code MCNP5. Three different neutron sources were used in the study. The study re-examines the performance of the neutron backscattering methods in providing identification of hidden explosives through their chemical composition. The EBS neutron energy spectra of fast and slow neutrons of the major constituent elements in soil and an explosive material in form of TNT have shown definite structures that can be used for the identification of a buried landmine.

  14. MAGNETIC NEUTRON SCATTERING

    Energy Technology Data Exchange (ETDEWEB)

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

    2004-07-30

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

  15. MAGNETIC NEUTRON SCATTERING

    Energy Technology Data Exchange (ETDEWEB)

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

    2004-07-30

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

  16. Fusion neutronics

    CERN Document Server

    Wu, Yican

    2017-01-01

    This book provides a systematic and comprehensive introduction to fusion neutronics, covering all key topics from the fundamental theories and methodologies, as well as a wide range of fusion system designs and experiments. It is the first-ever book focusing on the subject of fusion neutronics research. Compared with other nuclear devices such as fission reactors and accelerators, fusion systems are normally characterized by their complex geometry and nuclear physics, which entail new challenges for neutronics such as complicated modeling, deep penetration, low simulation efficiency, multi-physics coupling, etc. The book focuses on the neutronics characteristics of fusion systems and introduces a series of theories and methodologies that were developed to address the challenges of fusion neutronics, and which have since been widely applied all over the world. Further, it introduces readers to neutronics design’s unique principles and procedures, experimental methodologies and technologies for fusion systems...

  17. Development of self-powered neutron detectors for neutron flux monitoring in HCLL and HCPB ITER-TBM

    Energy Technology Data Exchange (ETDEWEB)

    Angelone, M., E-mail: maurizio.angelone@enea.it [Associazione ENEA-EURATOM sulla FusioneENEA C.R. Frascati, Via E. Fermi 45, 00044 Frascati (Italy); Klix, A. [Association KIT-EURATOM, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Pillon, M.; Batistoni, P. [Associazione ENEA-EURATOM sulla FusioneENEA C.R. Frascati, Via E. Fermi 45, 00044 Frascati (Italy); Fischer, U. [Association KIT-EURATOM, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Santagata, A. [ENEA C.R. Casaccia, via Anguillarese Km. 1,300, 00100 Roma (Italy)

    2014-10-15

    Highlights: •Self powered neutron detector (SPND) is attractive neutron monitor for TBM in ITER. •In hard neutron spectra (e.g. TBM) there is the need to optimize their response. •Three state-of-the-art SPNDs were tested using fast and 14 MeV neutrons. •The response of SPNDs is much lower than in thermal neutron flux. •FISPACT calculations performed to find out candidate materials in hard spectra. -- Abstract: Self powered neutron detectors (SPND) have a number of interesting properties (e.g. small dimensions, capability to operate in harsh environments, absence of external bias), so they are attractive neutron monitors for TBM in ITER. However, commercially available SPNDs are optimized for operation in a thermal nuclear reactor where the neutron spectrum is much softer than that expected in a TBM. This fact can limit the use of SPND in a TBM since the effective cross sections for the production of beta emitters are much lower in a fast neutron spectrum. This work represents the first attempt to study SPNDs as neutron flux monitors for TBM. Three state-of-the-art SPND available on the market were bought and tested using fast neutrons at TAPIRO fast neutron source of ENEA Casaccia and with 14 MeV neutrons at the Frascati neutron generator (FNG). The results clearly indicate that in fast neutron spectra, the response of SPNDs is much lower than in thermal neutron flux. Activation calculations were performed using the FISPACT code to find out possible material candidates for SPND suitable for operation in TBM neutron spectra.

  18. Test Measurements On A Resonance Filter Spectrometer Using Electronvolt Neutrons

    OpenAIRE

    Newport, Robert J.; Seeger, P. A.; Williams, W. G.

    1985-01-01

    Inelastic neutron scattering measurements carried out on a prototype spectrometer at the WNR pulsed neutron facility are presented. Energy transfers are determined by differencing time-of-flight spectra taken with and without absorbing foils containing sharp nuclear resonances which define the scattered neutron energy. The quality of the spectra are enhanced by i) applying a double difference technique to improve line shape and ii) using fixed incident and scattered beam filters which discrim...

  19. Neutron Albedo

    CERN Document Server

    Ignatovich, V K

    2005-01-01

    A new, algebraic, method is applied to calculation of neutron albedo from substance to check the claim that use of ultradispersive fuel and moderator of an active core can help to gain in size and mass of the reactor. In a model of isotropic distribution of incident and reflected neutrons it is shown that coherent scattering on separate grains in the case of thermal neutrons increases transport cross section negligibly, however it decreases albedo from a wall of finite thickness because of decrease of substance density. A visible increase of albedo takes place only for neutrons with wave length of the order of the size of a single grain.

  20. Comparison of the iron oxide-based blood-pool contrast medium VSOP-C184 with gadopentetate dimeglumine for first-pass magnetic resonance angiography of the aorta and renal arteries in pigs.

    Science.gov (United States)

    Schnorr, Jörg; Wagner, Susanne; Abramjuk, Claudia; Wojner, Ines; Schink, Tania; Kroencke, Thomas J; Schellenberger, Eyk; Hamm, Bernd; Pilgrimm, Herbert; Taupitz, Matthias

    2004-09-01

    VSOP-C184 at a dose of 0.045 mmol Fe/kg has been shown to be an efficient blood pool contrast medium for equilibrium magnetic resonance angiography (MRA) that can be administered as a bolus. The present study was performed to determine whether VSOP-C184 is also suitable for first-pass MRA. Fifteen MRA examinations at 1.5 T were performed in minipigs using a fast 3D fast low-angle shot (FLASH) sequence (repetition time = 4.5 ms, echo time = 1.7 ms, excitation angle = 25 degrees, matrix 256, body phased-array coil). The citrate-stabilized iron oxide preparation VSOP-C184 was investigated (total particle diameter: 7.0 +/- 0.15 nm; core size: 4 nm) and compared with gadopentetate dimeglumine (Gd-DTPA). The following doses were tested: VSOP-C184: 0.015, 0.025, and 0.035 mmol Fe/kg; Gd-DTPA: 0.1 and 0.2 mmol Gd/kg; n = 3 examinations/dose. Data were analyzed quantitatively (signal enhancement (ENH) and vessel edge definition (VED)) and qualitatively. First-pass MRA using the 3 doses of VSOP-C184 yielded the following ENH: aorta: 9.4 +/- 2.6; 12.31 +/- 1.2; 16.53 +/- 1.7; renal arteries: 7.6 +/- 2.2; 9.9 +/- 1.0; 13.2 +/- 0.5. The values for the 2 doses of Gd-DTPA were aorta: 12.9 +/- 1.0; 16.8 +/- 2.2; renal arteries: 11.2 +/- 1.23; 11.3 +/- 1.7. VED for the 3 doses of VSOP-C184 was aorta: 106.3 +/- 31.0; 135.3 +/- 58.8; 141.3 +/- 71.0; renal arteries: 102.2 +/- 24.3; 146.8 +/- 63.0; 126.9 +/- 37.6 and for the 2 doses of Gd-DTPA, aorta: 157.2 +/- 47.8; 164.2 +/- 36.8; renal arteries: 165.9 +/- 30.4; 170.3 +/- 38.2 respectively. The differences between VSOP-C184 and Gd-DTPA are clinically not relevant and statistically not significant (p > or = .05). Qualitative evaluation of image quality, contrast, and delineation of vessels showed the results obtained with VSOP-C184 at doses of 0.025 and 0.035 mmol Fe/kg to be similar to those of Gd-DTPA at 0.1 and 0.2 mmol Gd/kg. VSOP-C184 is suitable for first-pass MRA at doses of 0.025 and 0.035 mmol Fe/kg and thus, in addition to

  1. Spallation neutron experiment at SATURNE

    Energy Technology Data Exchange (ETDEWEB)

    Meigo, Shin-ichiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-11-01

    The double differential cross sections for (p,xn) reactions and the spectra of neutrons produced from the thick target have been measured at SATURNE in SACLAY from 1994 to 1997. The status of the experiment and the preliminary experimental results are presented. (author)

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

    CERN Document Server

    Doa, Changwoo; Stanley, Christopher; Gallmeier, Franz X; Doucet, Mathieu; Smith, Gregory S

    2013-01-01

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

  3. VSOP-2 Orbit Determination

    Science.gov (United States)

    Takeuchi, H.; VSOP-2 Orbit Determination Sub-Working Group

    2009-08-01

    Precise orbit determination (POD) is a key factor to enable phase referencing observations with Astro-G. A POD accuracy of 30 cm is required for efficient X-band phase referencing observations, accuracy of 6 cm for K-band observations, and accuracy of 3 cm for Q-band observations. For the POD, Astro-G will be equipped with a GPS/Galileo receiver and a SLR (Satellite Laser Ranging) retroreflector array. Four POD antennas will be equipped on four sides of the satellite body, to cover all directions. The SLR will be used as a complement to the GPS at middle-to-high altitude. Because the refroreflector array should always face to the Earth direction, it will be set up on the Ka-link antenna gimbal. The most significant perturbing force for the Astro-G is solar radiation pressure (SRP). The reflectivity of each surface component should be preliminary measured in detail to model the SRP. The estimated achievable POD accuracy at apogee is 10 ˜ 30 cm in nominal case. Phase referencing observations in K- or Q-band can be performed if the enough amount of SLR tracking data can be obtained at high altitudes.

  4. Neutron dosimetry; Dosimetria de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Fratin, Luciano

    1993-12-31

    A neutron irradiation facility was designed and built in order to establish a procedure for calibrating neutron monitors and dosemeters. A 185 GBq {sup 241} Am Be source of known is used as a reference source. The irradiation facility using this source in the air provides neutron dose rates between 9 nSv s{sup -1} and 0,5 {sup {mu}}Sv s{sup -1}. A calibrated 50 nSv s{sup -1} thermal neutron field is obtained by using a specially designed paraffin block in conjunction with the {sup 241} Am Be source. A Bonner multisphere spectrometer was calibrated, using a procedure based on three methods proposed by international standards. The unfold {sup 241} Am Be neutron spectrum was determined from the Bonner spheres data and resulted in a good agreement with expected values for fluence rate, dose rate and mean energy. A dosimetric system based on the electrochemical etching of CR-39 was developed for personal dosimetry. The dosemeter badge using a (n,{alpha}) converter, the etching chamber and high frequency power supply were designed and built specially for this project. The electrochemical etching (ECE) parameters used were: a 6N KOH solution, 59 deg C, 20 kV{sub pp} cm{sup -1}, 2,0 kHz, 3 hours of ECE for thermal and intermediate neutrons and 6 hours for fast neutrons. The calibration factors for thermal, intermediate and fast neutrons were determined for this personal dosemeter. The sensitivities determined for the developed dosimetric system were (1,46{+-} 0,09) 10{sup 4} tracks cm{sup -2} mSv{sup -1} for thermal neutrons, (9{+-}3) 10{sup 2} tracks cm{sup -2} mSV{sup -1} for intermediate neutrons and (26{+-}4) tracks cm{sup -2} mSv{sup -1} for fast neutrons. The lower and upper limits of detection were respectively 0,002 mSv and 0,6 mSv for thermal neutrons, 0,04 mSv and 8 mSv for intermediate neutrons and 1 mSv and 12 mSv for fast neutrons. In view of the 1990`s ICRP recommendations, it is possible to conclude that the personal dosemeter described in this work is

  5. Iron-line and continuum variations in the XMM-Newton and Suzaku spectra of the neutron-star low-mass X-ray binary 4U 1636-53

    NARCIS (Netherlands)

    Lyu, Ming; Mendez, Mariano; Belloni, Tomaso; Homan, Jeroen; Sanna, Andrea; Hiemstra, Beike

    2014-01-01

    We used six simultaneous XMM-Newton and Rossi X-ray Timing Explorer plus five Suzaku observations to study the continuum spectrum and the iron emission line in the neutron-star low-mass X-ray binary 4U 1636-53 as a function of the position of the source in the colour-colour diagram. We modelled the

  6. Iron-line and continuum variations in the XMM-Newton and Suzaku spectra of the neutron-star low-mass X-ray binary 4U 1636-53

    NARCIS (Netherlands)

    Lyu, Ming; Mendez, Mariano; Belloni, Tomaso; Homan, Jeroen; Sanna, Andrea; Hiemstra, Beike

    2014-01-01

    We used six simultaneous XMM-Newton and Rossi X-ray Timing Explorer plus five Suzaku observations to study the continuum spectrum and the iron emission line in the neutron-star low-mass X-ray binary 4U 1636-53 as a function of the position of the source in the colour-colour diagram. We modelled the

  7. Neutron reflectometry

    DEFF Research Database (Denmark)

    Klösgen-Buchkremer, Beate Maria

    2014-01-01

    films or films with magnetic properties. The reason is the peculiar property of neutron light since the mass of a neutron is close to the one of a proton, and since it bears a magnetic moment. The optical properties of matter, when interacting with neutrons, are described by a refractive index......Neutron (and X-ray) reflectometry constitute complementary interfacially sensitive techniques that open access to studying the structure within thin films of both soft and hard condensed matter. Film thickness starts oxide surfaces on bulk substrates, proceeding to (pauci-)molecular layers and up...... to hundreds of nanometers. Thickness resolution for flat surfaces is in the range of few Ǻngstrøm, and as a peculiar benefit, the presence and properties of buried interfaces are accessible. Focus here will be on neutron reflectometry, a technique that is unique in applications involving composite organic...

  8. NIST Calibration of a Neutron Spectrometer ROSPEC.

    Science.gov (United States)

    Heimbach, Craig

    2006-01-01

    A neutron spectrometer was acquired for use in the measurement of National Institute of Standards and Technology neutron fields. The spectrometer included options for the measurement of low and high energy neutrons, for a total measurement range from 0.01 eV up to 17 MeV. The spectrometer was evaluated in calibration fields and was used to determine the neutron spectrum of an Americium-Beryllium neutron source. The calibration fields used included bare and moderated (252)Cf, monoenergetic neutron fields of 2.5 MeV and 14 MeV, and a thermal-neutron beam. Using the calibration values determined in this exercise, the spectrometer gives a good approximation of the neutron spectrum, and excellent values for neutron fluence, for all NIST calibration fields. The spectrometer also measured an Americium-Beryllium neutron field in a NIST exposure facility and determined the field quite well. The spectrometer measured scattering effects in neutron spectra which previously could be determined only by calculation or integral measurements.

  9. Neutron spectrometry and dosimetry with ANNs

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H. R.; Hernandez D, V. M. [Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Gallego, E.; Lorente, A. [Departamento de Ingenieria Nuclear, Universidad Politecnica de Madrid, Jose Gutierrez Abascal 2, 28006 Madrid (Spain)], e-mail: fermineutron@yahoo.com

    2009-10-15

    Artificial neural networks technology has been applied to unfold the neutron spectra and to calculate the effective dose, the ambient equivalent dose, and the personal dose equivalent for {sup 252}Cf and {sup 241}AmBe neutron sources. A Bonner sphere spectrometry with a {sup 6}LiI(Eu) scintillator was utilized to measure the count rates of the spheres that were utilized as input in two artificial neural networks, one for spectrometry and another for dosimetry. Spectra and the ambient dose equivalent were also obtained with BUNKIUT code and the UTA4 response matrix. With both procedures spectra and ambient dose equivalent agrees in less than 10%. (author)

  10. Thermalization of monoenergetic neutrons in a concrete room

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Manzanares A, E.; Hernandez D, V.M.; Mercado, G.A. [UAZ, A.P. 336, 98000 Zacatecas (Mexico); Iniguez, M.P.; Martin M, A. [Universidad de Valladolid, (Spain)

    2006-07-01

    The thermalization of neutrons from monoenergetic neutron sources in a concrete room has been studied. During calibration of neutron detectors it is mandatory to make corrections due to neutron scattering produced by the room walls, therefore this factor must be known in advance. The scattered neutrons are thermalized and produce a neutron field that is directly proportional to source strength and inversely proportional to room total wall-surfaces, the proportional coefficient has been calculated for neutrons whose energy goes from 1 eV to 20 MeV. This coefficient was calculated using Monte Carlo methods for 150, 200 and 300 cm-radius spherical cavity, where monoenergetic neutrons were located at the center, along the spherical cavity radius neutron spectra were calculated at several source-to-detector distances inside the cavity. The obtained coefficient is almost three times larger than the factor normally utilized. (Author)

  11. Isobaric-spin relationships between nuclear spectra

    NARCIS (Netherlands)

    French, J.B.

    1961-01-01

    The simple fact that a one-body energy describes the interaction of a nucleon with a closed neutron subshell is used to establish sets of equations connecting the spectra of nuclei which are related by isobaric-spin when described by means of the nuclear shell model. Certain formal questions about i

  12. Neutron measurements in ITER using the Radial Neutron Camera

    Science.gov (United States)

    Marocco, D.; Esposito, B.; Moro, F.

    2012-03-01

    The Radial Neutron Camera (RNC) is one of the key diagnostic systems of the ITER international fusion experiment. It is designed to measure the uncollided 14 MeV and 2.5 MeV neutrons from deuterium-tritium (DT) and deuterium-deuterium (DD) fusion reactions taking place in the ITER plasma through an array of 45 detectors positioned along collimated lines of sight. Scintillators and diamonds coupled to fast digital acquisition electronics are among the detectors presently considered for the RNC. The RNC will provide spatially resolved measurements of several plasma parameters needed for fusion power estimation, plasma control and plasma physics studies. The line-integrated RNC neutron fluxes are used to evaluate the local profile of the neutron emission (neutron emissivity, s-1m-3) and therefore the total neutron yield and the birth profile of the alpha particles. The temperature profile of the bulk ions can be derived from the Doppler broadened widths of the RNC line-integrated spectra, that also provide insight on the supra-thermal ions produced by the injection in the plasma of electromagnetic waves and neutral particles. The RNC emissivity and temperature measurements can be employed to estimate the composition of the ITER fuel, namely the ratio between the tritium and deuterium densities. Data processing techniques involving spatial inversion and spectra unfolding are necessary to deduce the profile quantities from the line-integrated RNC measurements. The expected performances of the RNC as a diagnostic for the neutron emissivity/ion temperature/fuel ratio profile (measurement range, time resolution, accuracy, precision) have been estimated by means of synthetic data simulating actual RNC measurements. The results of the simulations, together with an overall description of the diagnostic and of the measurement techniques, are presented.

  13. Energy spectrum measurement and dose rate estimation of natural neutrons in Tibet region

    Institute of Scientific and Technical Information of China (English)

    吴建华; 徐勇军; 刘森林; 汪传高

    2015-01-01

    In this work, natural neutron spectra at nine sites in Tibet region were measured using a multi-sphere neutron spectrometer. The altitude-dependence of the spectra total fluence rate and ambient dose equivalent rate were analyzed. From the normalized natural neutron spectra at different altitudes, the spectrum fractions for neutrons of greater than 0.1 MeV do not differ obviously, while those of the thermal neutrons differ greatly from each other. The total fluence rate, effective dose rate and the ambient dose equivalent rate varied with the altitude according to an exponential law.

  14. INVESTIGATION ON THERMAL-FLOW CHARACTERISTICS OF HTGR CORE USING THERMIX-KONVEK MODULE AND VSOP'94 CODE

    Directory of Open Access Journals (Sweden)

    Sudarmono Sudarmono

    2015-03-01

    Full Text Available The failure of heat removal system of water-cooled reactor such as PWR in Three Mile Islands and Fukushima Daiichi BWR makes nuclear society starting to consider the use of high temperature gas-cooled reactor (HTGR. Reactor Physics and Technology Division – Center for Nuclear Reactor Safety and Technology  (PTRKN has tasks to perform research and development on the conceptual design of cogeneration gas cooled reactor with medium power level of 200 MWt. HTGR is one of nuclear energy generation system, which has high energy efficiency, and has high and clean inherent safety level. The geometry and structure of the HTGR200 core are designed to produce the output of helium gas coolant temperature as high as 950 °C to be used for hydrogen production and other industrial processes in co-generative way. The output of very high temperature helium gas will cause thermal stress on the fuel pebble that threats the integrity of fission product confinement. Therefore, it is necessary to perform thermal-flow evaluation to determine the temperature distribution in the graphite and fuel pebble in the HTGR core. The evaluation was carried out by Thermix-Konvek module code that has been already integrated into VSOP'94 code. The HTGR core geometry was done using BIRGIT module code for 2-D model (RZ model with 5 channels of pebble flow in active core in the radial direction. The evaluation results showed that the highest and lowest temperatures in the reactor core are 999.3 °C and 886.5 °C, while the highest temperature of TRISO UO2 is 1510.20 °C in the position (z= 335.51 cm; r=0 cm. The analysis done based on reactor condition of 120 kg/s of coolant mass flow rate, 7 MPa of pressure and 200 MWth of power. Compared to the temperature distribution resulted between VSOP’94 code and fuel temperature limitation as high as 1600 oC, there is enough safety margin from melting or disintegrating. Keywords: Thermal-Flow, VSOP’94, Thermix-Konvek, HTGR, temperature

  15. Spectra from nuclear-excited plasmas

    Science.gov (United States)

    De Young, R. J.; Weaver, W. R.

    1980-01-01

    The paper discusses the spectra taken from He-3(n,p)H-3 nuclear-induced plasmas under high thermal neutron flux, lasing conditions. Also, initial spectra are presented for U-235F6 generated plasmas. From an evaluation of these spectra, important atomic and molecular processes that occur in the plasma can be inferred. The spectra presented are the first to be generated by He-3 and U-235F6 nuclear reactions under high neutron flux, lasing conditions. The U-235(n,ff)FF reaction, which liberates 165 MeV of fission-fragment kinetic energy, creates plasmas that are of great interest, since at sufficiently high densities of U-235F6 the gas becomes self-critical; thus, there is no need for an external driving reactor (source of neutrons). The spectra from mixtures of He-3 and Ar, Xe, Kr, Ne, Cl2, F2 and N2 indicate little difference between high-pressure nuclear-induced plasmas and high-pressure electrically pulsed afterglow plasmas for noble-gas systems

  16. Parameters measurement for the thermal neutron beam in the thermal column hole of Xi’an pulse reactor

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The distribution of the neutron spectra in the thermal column hole of Xi’an pulse reactor was measured with the time-of-flight method.Compared with the thermal Maxwellian theory neutron spectra,the thermal neutron spectra measured is a little softer,and the average neutron energy of the experimental spectra is about 0.042±0.01 eV.The thermal neutron fluence rate at the front end of thermal column hole,measured with gold foil activation techniques,is about 1.18×105 cm-2 s-1.The standard uncertainty of the measured thermal neutron fluence is about 3%.The spectra-averaged cross section of 197Au(n,γ) determined by the experimental thermal neutron spectra is(92.8±0.93) ×10-24 cm2.

  17. Neutron spectrum for neutron capture therapy in boron; Espectro de neutrones para terapia por captura de neutrones en boro

    Energy Technology Data Exchange (ETDEWEB)

    Medina C, D.; Soto B, T. G. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Programa de Doctorado en Ciencias Basicas, 98068 Zacatecas, Zac. (Mexico); Baltazar R, A. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Programa de Doctorado en Ingenieria y Tecnologia Aplicada, 98068 Zacatecas, Zac. (Mexico); Vega C, H. R., E-mail: dmedina_c@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

    2016-10-15

    Glioblastoma multiforme is the most common and aggressive of brain tumors and is difficult to treat by surgery, chemotherapy or conventional radiation therapy. One treatment alternative is the Neutron Capture Therapy in Boron, which requires a beam modulated in neutron energy and a drug with {sup 10}B able to be fixed in the tumor. When the patients head is exposed to the neutron beam, they are captured by the {sup 10}B and produce a nucleus of {sup 7}Li and an alpha particle whose energy is deposited in the cancer cells causing it to be destroyed without damaging the normal tissue. One of the problems associated with this therapy is to have an epithermal neutrons flux of the order of 10{sup 9} n/cm{sup 2}-sec, whereby irradiation channels of a nuclear research reactor are used. In this work using Monte Carlo methods, the neutron spectra obtained in the radial irradiation channel of the TRIGA Mark III reactor are calculated when inserting filters whose position and thickness have been modified. From the arrangements studied, we found that the Fe-Cd-Al-Cd polyethylene filter yielded a ratio between thermal and epithermal neutron fluxes of 0.006 that exceeded the recommended value (<0.05), and the dose due to the capture gamma rays is lower than the dose obtained with the other arrangements studied. (Author)

  18. Neutron dose in and out of 18MV photon fields.

    Science.gov (United States)

    Ezzati, A O; Studenski, M T

    2017-04-01

    In radiation therapy, neutron contamination is an undesirable side effect of using high energy photons to treat patients. Neutron contamination requires adjustments to the shielding requirements of the linear accelerator vault and contributes to the risk of secondary malignancies in patients by delivering dose outside of the primary treatment field. Using MCNPX, an established Monte Carlo code, manufacturer blueprints, and the most up to date ICRP neutron dose conversion factors, the neutron spectra, neutron/photon dose ratio, and the neutron capture gamma ray dose were calculated at different depths and off axis distances in a tissue equivalent phantom. Results demonstrated that the neutron spectra and dose are dependent on field size, depth in the phantom, and off-axis distance. Simulations showed that because of the low neutron absorption cross section of the linear accelerator head materials, the contribution to overall patient dose from neutrons can be up to 1000 times the photon dose out of the treatment field and is also dependent on field size and depth. Beyond 45cm off-axis, the dependence of the neutron dose on field size is minimal. Neutron capture gamma ray dose is also field size dependent and is at a maximum at a depth of about 7cm. It is important to remember that when treating with high energy photons, the dose from contamination neutrons must be considered as it is much greater than the photon dose.

  19. Preliminary Analysis of the Multisphere Neutron Spectrometer

    Science.gov (United States)

    Goldhagen, P.; Kniss, T.; Wilson, J. W.; Singleterry, R. C.; Jones, I. W.; VanSteveninck, W.

    2003-01-01

    Crews working on present-day jet aircraft are a large occupationally exposed group with a relatively high average effective dose from galactic cosmic radiation. Crews of future high-speed commercial aircraft flying at higher altitudes would be even more exposed. To help reduce the significant uncertainties in calculations of such exposures, the Atmospheric Ionizing Radiation (AIR) Project, an international collaboration of 15 laboratories, made simultaneous radiation measurements with 14 instruments on five flights of a NASA ER-2 high-altitude aircraft. The primary AIR instrument was a highly sensitive extended-energy multisphere neutron spectrometer with lead and steel shells placed within the moderators of two of its 14 detectors to enhance response at high energies. Detector responses were calculated for neutrons and charged hadrons at energies up to 100 GeV using MCNPX. Neutron spectra were unfolded from the measured count rates using the new MAXED code. We have measured the cosmic-ray neutron spectrum (thermal to greater than 10 GeV), total neutron fluence rate, and neutron effective dose and dose equivalent rates and their dependence on altitude and geomagnetic cutoff. The measured cosmic-ray neutron spectra have almost no thermal neutrons, a large "evaporation" peak near 1 MeV and a second broad peak near 100 MeV which contributes about 69% of the neutron effective dose. At high altitude, geomagnetic latitude has very little effect on the shape of the spectrum, but it is the dominant variable affecting neutron fluence rate, which was 8 times higher at the northernmost measurement location than it was at the southernmost. The shape of the spectrum varied only slightly with altitude from 21 km down to 12 km (56 - 201 grams per square centimeter atmospheric depth), but was significantly different on the ground. In all cases, ambient dose equivalent was greater than effective dose for cosmic-ray neutrons.

  20. Neutron Repulsion

    CERN Document Server

    Manuel, Oliver K

    2011-01-01

    Earth is connected gravitationally, magnetically and electrically to its heat source - a neutron star that is obscured from view by waste products in the photosphere. Neutron repulsion is like the hot filament in an incandescent light bulb. Excited neutrons are emitted from the solar core and decay into hydrogen that glows in the photosphere like a frosted light bulb. Neutron repulsion was recognized in nuclear rest mass data in 2000 as the overlooked source of energy, the keystone of an arch that locked together these puzzling space-age observations: 1.) Excess 136Xe accompanied primordial helium in the stellar debris that formed the solar system (Fig. 1); 2.) The Sun formed on the supernova core (Fig. 2); 3.) Waste products from the core pass through an iron-rich mantle, selectively carrying lighter elements and lighter isotopes of each element into the photosphere (Figs. 3-4); and 4.) Neutron repulsion powers the Sun and sustains life (Figs. 5-7). Together these findings offer a framework for understanding...

  1. Overview of the Neutron experimental facilities at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Mocko, Michal [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-30

    This presentation gives an overview of the neutron experimental facilities at LANSCE. The layout is mentioned in detail, with a map of the south-side experimental facilities, information on Target-4 and the Lujan Center. Then it goes into detail about neutron sources, specifically continuous versus pulsed. Target 4 is then discussed. In conclusion, we have introduced the south-side experimental facilities in operation at LANSCE. 1L target and Target 4 provide complementary neutron energy spectra. Two spallation neutron sources taken together cover more than 11 orders of magnitude in neutron energy.

  2. NECTAR-A fission neutron radiography and tomography facility

    Energy Technology Data Exchange (ETDEWEB)

    Buecherl, T., E-mail: thomas.buecherl@radiochemie.de [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie (RCM), Walther-Meissner-Str. 3, 85748 Garching (Germany); Lierse von Gostomski, Ch. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie (RCM), Walther-Meissner-Str. 3, 85748 Garching (Germany); Breitkreutz, H.; Jungwirth, M.; Wagner, F.M. [Technische Universitaet Muenchen, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) (Germany)

    2011-09-21

    NECTAR (Neutron Computerized Tomography and Radiography) is a versatile facility for radiographic and tomographic investigations as well as for neutron activation experiments using fission neutrons. The radiation sources for this facility are two plates of highly enriched uranium situated in the moderator vessel in FRM II. Thermal neutrons originating from the main fuel element of the reactor generate in these plates fast neutrons. These can escape through a horizontal beam tube without moderation. The beam can be filtered and manipulated in order to reduce the accompanying gamma radiation and to match the specific experimental tasks. A summary of the main parameters required for experimental set-up and (quantitative) data evaluation is presented. The (measured) spectra of the neutron and gamma radiations are shown along with the effect of different filters on their behavior. The neutron and gamma fluxes, dose rates, L/D-ratios, etc. and the main parameters of the actually used detection systems for neutron imaging are given, too.

  3. Neutronic design of the ITER radial neutron camera

    Energy Technology Data Exchange (ETDEWEB)

    Petrizzi, L. [Associazione EURATOM-ENEA sulla Fusione, ENEA Centro Ricerche, C.P. 65, 00044 Frascati, Rome (Italy)], E-mail: petrizzi@frascati.enea.it; Barnsley, R. [EFDA CSU-Garching (Germany); Bertalot, L.; Esposito, B. [Associazione EURATOM-ENEA sulla Fusione, ENEA Centro Ricerche, C.P. 65, 00044 Frascati, Rome (Italy); Haskell, H. [ITER International Team, Garching (Germany); Mainardi, E.; Marocco, D.; Podda, S. [Associazione EURATOM-ENEA sulla Fusione, ENEA Centro Ricerche, C.P. 65, 00044 Frascati, Rome (Italy); Walker, C. [ITER International Team, Garching (Germany); Villari, S. [Associazione EURATOM-ENEA sulla Fusione, ENEA Centro Ricerche, C.P. 65, 00044 Frascati, Rome (Italy)

    2007-10-15

    This paper summarizes the work, performed in the frame of various EFDA contracts during 2004-2005, on the design review and upgrade of the ITER radial neutron camera (RNC). The RNC, which should provide information on the spatial distribution and energy spectrum of the neutron emission, consists of an ex-vessel system (fan-like collimator with 12 x 3 lines of sights) and an in-vessel system with further 9 lines for a full coverage of the plasma. A Monte Carlo code (MCNP) has been used for the neutronic calculations. The basic ITER model has been developed from the CATIA drawings to include the RNC with all details relevant for the neutronic analysis. In the model the collimator diameters have been set to 2 and 4 cm, respectively, for the ex-vessel and in-vessel systems. A detailed space dependent fusion neutron source (DD and DT phases in various plasma scenarios) has been used with a consistent ion temperature radial profile. A special variance reduction treatment has been developed so that neutrons reach the far regions in the high collimated neutron beam and score with a satisfying statistical error. Neutron and photon fluxes and spectra have been calculated. Approximately, one neutron out of 10{sup 11} emitted in all the plasma reaches a single ex-vessel detector. Therefore, for an emission rate of 1.8 x 10{sup 20} n/s (corresponding to 500 MW fusion power) the flux on the detectors is in the range (1-5) x 10{sup 8} n/(cm{sup 2} s) depending on the poloidal orientation. The fraction of scattered neutrons (>1 MeV) is lower than few % of the total. A measurement simulation software tool (MSST) performing asymmetric Abel inversion of simulated measured neutron signals has also been developed for line of sight and design optimization. Combining information from MCNP calculations and MSST, it has been possible to evaluate the performance of the RNC, check whether the present design of the RNC meets the measurement requirements and optimize the RNC design.

  4. Measurements of the neutron brightness from a phase II solid methane moderator at the LENS neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Shin Yunchang, E-mail: yunchang.shin@yale.ed [Department of Physics, Indiana University Bloomington, IN 47408 (United States); Department of Physics, Yale University, New Haven, CT 06511 (United States); Lavelle, C.M.; Mike Snow, W.; Baxter, David V.; Tong Xin; Yan Haiyang [Department of Physics, Indiana University Bloomington, IN 47408 (United States); Leuschner, Mark [ProCure 420 North Walnut Street Bloomington, IN 47404 (United States)

    2010-08-21

    Measurements of the neutron brightness from a solid methane moderator were performed at the Low Energy Neutron Source (LENS) at the Indiana University Cyclotron Facility (IUCF) to characterize the source and to test our new neutron scattering model of phase II solid methane . A time-of-flight method was used to measure the neutron energy spectrum from the moderator in the energy range of 0.1 meV {approx}1eV. Neutrons were counted with a high efficiency {sup 3}He detector. The solid methane in the moderator occupied phase II and the energy spectra were measured at 20 K and 4 K. We tested our newly developed scattering kernels for phase II solid methane by calculating the neutron brightness expected from the methane moderator at the LENS neutron source using MCNP (Monte Carlo N-particle Transport Code). Within the accuracy of our approximate approach, our model correctly predicts the neutron brightness at both temperatures.

  5. Neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Heger, G. [Rheinisch-Westfaelische Technische Hochschule Aachen, Inst. fuer Kristallographie, Aachen (Germany)

    1996-12-31

    X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (author) 15 figs., 1 tab., 10 refs.

  6. Neutron spectroscopy of magnesium dihydride

    Energy Technology Data Exchange (ETDEWEB)

    Kolesnikov, Alexander I [ORNL; Antonov, Vladimir E. [Institute of Solid State Physics, Russian Ac. Sci., Chernogolovka, Moscow, Russi; Efimchenko, V. S. [Institute of Solid State Physics, Russian Ac. Sci., Chernogolovka, Moscow, Russi; Granroth, Garrett E [ORNL; Klyamkin, S. N. [Moscow State University; Levchenko, A. V. [Institute of Problems of Chemical Physics, Russian Ac. Sci, Chernogolovka, Russia; Sakharov, M. K. [Institute of Solid State Physics, Russian Ac. Sci., Chernogolovka, Moscow, Russi; Ren, Yang [Argonne National Laboratory (ANL)

    2011-01-01

    Inelastic neutron scattering spectra of -MgH2 powder have been measured at T = 7 K with an energy resolution better than 1.5% using the time-of-flight direct geometry spectrometer SEQUOIA. Based on these spectra, the density g(E) of phonon states in -MgH2 has been experimentally constructed for the fist time. Comparing the available experimental data on the heat capacity of -MgH2 with those calculated using the obtained g(E) spectrum confirmed the good accuracy of its determination.

  7. Neutronics of pulsed spallation neutron sources

    CERN Document Server

    Watanabe, N

    2003-01-01

    Various topics and issues on the neutronics of pulsed spallation neutron sources, mainly for neutron scattering experiments, are reviewed to give a wide circle of readers a better understanding of these sources in order to achieve a high neutronic performance. Starting from what neutrons are needed, what the spallation reaction is and how to produce slow-neutrons more efficiently, the outline of the target and moderator neutronics are explained. Various efforts with some new concepts or ideas have already been devoted to obtaining the highest possible slow-neutron intensity with desired pulse characteristics. This paper also reviews the recent progress of such efforts, mainly focused on moderator neutronics, since moderators are the final devices of a neutron source, which determine the source performance. Various governing parameters for neutron-pulse characteristics such as material issues, geometrical parameters (shape and dimensions), the target-moderator coupling scheme, the ortho-para-hydrogen ratio, po...

  8. Polarized neutrons for Australian scientific research

    Science.gov (United States)

    Kennedy, Shane J.

    2005-02-01

    Polarized neutron scattering has been a feature at ANSTO's HIFAR research reactor since the first polarization analysis (PA) spectrometer Longpol began operation over 30 years ago. Since that time, we have improved performance of Longpol and added new capabilities in several reincarnations of the instrument. Most of the polarized neutron experiments have been in the fields of magnetism and superconductivity, and most of that research has involved PA. Now as we plan our next generation neutron beam facility, at the Replacement Research Reactor (RRR), we intend to continue the tradition of PA but with a far broader scope in mind. Our new capabilities will combine PA and energy analysis with both cold and thermal neutron source spectra. We will also provide capabilities for research with polarized neutrons in small-angle neutron scattering and in neutron reflectometry. The discussion includes a brief historical account of the technical developments with a summary of past and present applications of polarized neutrons at HIFAR, and an outline of the polarized neutron capabilities that will be included in the first suite of instruments, which will begin operation at the new reactor in 2006.

  9. Concrete enclosure to shield a neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Villagrana M, L. E.; Rivera P, E.; De Leon M, H. A.; Soto B, T. G.; Hernandez D, V. M.; Vega C, H. R., E-mail: emmanuelvillagrana@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico)

    2012-10-15

    In the aim to design a shielding for a {sup 239}PuBe isotopic neutron source several Monte Carlo calculations were carried out using MCNP5 code. First, a point-like source was modeled in vacuum and the neutron spectrum and the ambient dose equivalent were calculated at several distances ranging from 5 up to 150 cm, these calculations were repeated including air, and a 1 x 1 x 1 m{sup 3} enclosure that was shielded with 5, 15, 20, 25, 30, 50 and 80 cm-thick Portland type concrete walls. At all the points located inside the enclosure neutron spectra from 10{sup -8} up 0.5 MeV were the same regardless the distance from the source showing the room-return effect, for energies larger than 0.5 MeV neutron spectra are diminished as the distance increases. Outside the enclosure it was noticed that neutron spectra becomes -softer- as the concrete thickness increases due to reduction of mean neutron energy. With the ambient dose values the attenuation curve in terms of concrete thickness was calculated. (Author)

  10. Neutron absorbed dose in a pacemaker CMOS

    Energy Technology Data Exchange (ETDEWEB)

    Borja H, C. G.; Guzman G, K. A.; Valero L, C.; Banuelos F, A.; Hernandez D, V. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Paredes G, L., E-mail: fermineutron@yahoo.com [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2012-06-15

    The neutron spectrum and the absorbed dose in a Complementary Metal Oxide Semiconductor (CMOS), has been estimated using Monte Carlo methods. Eventually a person with a pacemaker becomes an oncology patient that must be treated in a linear accelerator. Pacemaker has integrated circuits as CMOS that are sensitive to intense and pulsed radiation fields. Above 7 MV therapeutic beam is contaminated with photoneutrons that could damage the CMOS. Here, the neutron spectrum and the absorbed dose in a CMOS cell was calculated, also the spectra were calculated in two point-like detectors in the room. Neutron spectrum in the CMOS cell shows a small peak between 0.1 to 1 MeV and a larger peak in the thermal region, joined by epithermal neutrons, same features were observed in the point-like detectors. The absorbed dose in the CMOS was 1.522 x 10{sup -17} Gy per neutron emitted by the source. (Author)

  11. Measurement of the 238U neutron-capture cross section and gamma-emission spectra from 10 eV to 100 keV using the DANCE detector at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Ullmann, John L [Los Alamos National Laboratory; Couture, A J [Los Alamos National Laboratory; Keksis, A L [Los Alamos National Laboratory; Vieira, D J [Los Alamos National Laboratory; O' Donnell, J M [Los Alamos National Laboratory; Jandel, M [Los Alamos National Laboratory; Haight, R C [Los Alamos National Laboratory; Rundberg, R S [Los Alamos National Laboratory; Kawano, T [Los Alamos National Laboratory; Chyzh, A [NORTH CAROLINA STATE UNIV; Baramsai, B [NORTH CAROLINA STATE UNIV; Wu, C Y [LLNL; Mitchell, G E [NORTH CAROLINA STATE UNIV; Becker, J A [LLNL; Krticka, M [CHARLES UNIV

    2010-01-01

    A careful new measurement of the {sup 238}U(n,{gamma}) cross section from 10 eV to 100 keV has been made using the DANCE detector at LANSCE. DANCE is a 4{pi} calorimetric scintillator array consisting of 160 BaF{sub 2} crystals. Measurements were made on a 48 mg/cm{sup 2} depleted uranium target. The cross sections are in general good agreement with previous measurements. The gamma-ray emission spectra, as a function of gamma multiplicity, were also measured and compared to model calculations.

  12. Neutron tomography

    Science.gov (United States)

    Crump, James C., III; Richards, Wade J.; Shields, Kevin C.

    1995-07-01

    The McClellan Nuclear Radiation Center's (MNRC) staff in conjunction with a Cooperative Research and Development Agreement (CRDA) with the U.C. Santa Barbara facility has developed a system that can be used for aircraft inspection of jet engine blades. The problem was to develop an inspection system that can detect very low concentrations of hydrogen (i.e., greater than 100 ppm) in metal matricies. Specifically in Titanium alloy jet engine blades. Entrapment and precipitation of hydrogen in metals is an undesirable phenomenon which occurs in many alloys of steel and titanium. In general, metals suffer a loss of mechanical properties after long exposures to hydrogen, especially at high temperatures and pressures, thereby becoming embrittled. Neutron radiography has been used as a nondestructive testing technique for many years. Neutrons, because of their unique interactions with materials, are especially useful in the detection of hydrogen. They have an extremely high interaction cross section for low atomic number nuclei (i.e., hydrogen). Thus hydrogen in a metal matrix can be visualized using neutrons. Traditional radiography is sensitive to the total attenuation integrated over the path of radiation through the material. Increased sensitivity and quantitative cross section resolution can be obtained using three-dimensional volumetric imaging techniques such as tomography. The solution used to solve the problem was to develop a neutron tomography system. The neutron source is the McClellan Nuclear Radiation Center's 1 MW TRIGA reactor. This paper describes the hardware used in the system as well as some of the preliminary results.

  13. Measurements of fusion neutron yields by neutron activation technique: Uncertainty due to the uncertainty on activation cross-sections

    Energy Technology Data Exchange (ETDEWEB)

    Stankunas, Gediminas, E-mail: gediminas.stankunas@lei.lt [Lithuanian Energy Institute, Laboratory of Nuclear Installation Safety, Breslaujos str. 3, LT-44403 Kaunas (Lithuania); EUROfusion Consortium, JET, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Batistoni, Paola [ENEA, Via E. Fermi, 45, 00044 Frascati, Rome (Italy); EUROfusion Consortium, JET, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Sjöstrand, Henrik; Conroy, Sean [Department of Physics and Astronomy, Uppsala University, PO Box 516, SE-75120 Uppsala (Sweden); EUROfusion Consortium, JET, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)

    2015-07-11

    The neutron activation technique is routinely used in fusion experiments to measure the neutron yields. This paper investigates the uncertainty on these measurements as due to the uncertainties on dosimetry and activation reactions. For this purpose, activation cross-sections were taken from the International Reactor Dosimetry and Fusion File (IRDFF-v1.05) in 640 groups ENDF-6 format for several reactions of interest for both 2.5 and 14 MeV neutrons. Activation coefficients (reaction rates) have been calculated using the neutron flux spectra at JET vacuum vessel, both for DD and DT plasmas, calculated by MCNP in the required 640-energy group format. The related uncertainties for the JET neutron spectra are evaluated as well using the covariance data available in the library. These uncertainties are in general small, but not negligible when high accuracy is required in the determination of the fusion neutron yields.

  14. 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.

    Science.gov (United States)

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

    2015-09-11

    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)(3)He and D(d,n)(3)He, 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 (9)Be(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.

  15. A review of neutron scattering correction for the calibration of neutron survey meters using the shadow cone method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang In; Kim, Bong Hwan; Kim, Jang Lyul; Lee, Jung Il [Health Physics Team, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-12-15

    The calibration methods of neutron-measuring devices such as the neutron survey meter have advantages and disadvantages. To compare the calibration factors obtained by the shadow cone method and semi-empirical method, 10 neutron survey meters of five different types were used in this study. This experiment was performed at the Korea Atomic Energy Research Institute (KAERI; Daejeon, South Korea), and the calibration neutron fields were constructed using a {sup 252}Californium ({sup 252}Cf) neutron source, which was positioned in the center of the neutron irradiation room. The neutron spectra of the calibration neutron fields were measured by a europium-activated lithium iodide scintillator in combination with KAERI's Bonner sphere system. When the shadow cone method was used, 10 single moderator-based survey meters exhibited a smaller calibration factor by as much as 3.1 - 9.3% than that of the semi-empirical method. This finding indicates that neutron survey meters underestimated the scattered neutrons and attenuated neutrons (i.e., the total scatter corrections). This underestimation of the calibration factor was attributed to the fact that single moderator-based survey meters have an under-ambient dose equivalent response in the thermal or thermal-dominant neutron field. As a result, when the shadow cone method is used for a single moderator-based survey meter, an additional correction and the International Organization for Standardization standard 8529-2 for room-scattered neutrons should be considered.

  16. Modelling of reaction cross sections and prompt neutron emission

    Science.gov (United States)

    Hambsch, F.-J.; Tudora, A.; Oberstedt, S.

    2010-10-01

    Accurate nuclear data concerning reaction cross sections and the emission of prompt fission neutrons (i.e. multiplicity and spectra) as well as other fission fragment data are of great importance for reactor physics design, especially for the new Generation IV nuclear energy systems. During the past years for several actinides (238U(n, f) and 237Np(n, f)) both the reaction cross sections and prompt neutron multiplicities and spectra have been calculated within the frame of the EFNUDAT project.

  17. Improved Fission Neutron Data Base for Active Interrogation of Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Pozzi, Sara; Czirr, J. Bart; Haight, Robert; Kovash, Michael; Tsvetkov, Pavel

    2013-11-06

    This project will develop an innovative neutron detection system for active interrogation measurements. Many active interrogation methods to detect fissionable material are based on the detection of neutrons from fission induced by fast neutrons or high-energy gamma rays. The energy spectrum of the fission neutrons provides data to identify the fissionable isotopes and materials such as shielding between the fissionable material and the detector. The proposed path for the project is as follows. First, the team will develop new neutron detection systems and algorithms by Monte Carlo simulations and bench-top experiments. Next, They will characterize and calibrate detection systems both with monoenergetic and white neutron sources. Finally, high-fidelity measurements of neutron emission from fissions induced by fast neutrons will be performed. Several existing fission chambers containing U-235, Pu-239, U-238, or Th-232 will be used to measure the neutron-induced fission neutron emission spectra. The challenge for making confident measurements is the detection of neutrons in the energy ranges of 0.01 – 1 MeV and above 8 MeV, regions where the basic data on the neutron energy spectrum emitted from fission is least well known. In addition, improvements in the specificity of neutron detectors are required throughout the complete energy range: they must be able to clearly distinguish neutrons from other radiations, in particular gamma rays and cosmic rays. The team believes that all of these challenges can be addressed successfully with emerging technologies under development by this collaboration. In particular, the collaboration will address the area of fission neutron emission spectra for isotopes of interest in the advanced fuel cycle initiative (AFCI).

  18. Neutron spectrum unfolding using computer code SAIPS

    CERN Document Server

    Karim, S

    1999-01-01

    The main objective of this project was to study the neutron energy spectrum at rabbit station-1 in Pakistan Research Reactor (PARR-I). To do so, multiple foils activation method was used to get the saturated activities. The computer code SAIPS was used to unfold the neutron spectra from the measured reaction rates. Of the three built in codes in SAIPS, only SANDI and WINDOWS were used. Contribution of thermal part of the spectra was observed to be higher than the fast one. It was found that the WINDOWS gave smooth spectra while SANDII spectra have violet oscillations in the resonance region. The uncertainties in the WINDOWS results are higher than those of SANDII. The results show reasonable agreement with the published results.

  19. A wide-range direction neutron spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Luszik-Bhadra, M. E-mail: marlies.luszik-bhadra@ptb.de; D' Errico, F.; Hecker, O.; Matzke, M

    2002-01-01

    A new device is presented which has been developed for measuring the energy and direction of distribution of neutron fluence in fields of broad energy spectra (thermal to 100 MeV) and with a high background of photon, electron and muon radiation. The device was tested in reference fields with different energy and direction distributions of neutron fluence. The direction-integrated fluence spectra agree fairly well with reference spectra. In all cases, the ambient and personal dose equivalent values calculated from measured direction-differential spectra are within 35% of the reference values. Independent measurements of the directional dose equivalent were performed with a directional dose equivalent monitor based on superheated drop detectors.

  20. Reactor Neutrino Spectra

    OpenAIRE

    Hayes, A. C.; Vogel, Petr

    2016-01-01

    We present a review of the antineutrino spectra emitted from reactors. Knowledge of these spectra and their associated uncertainties is crucial for neutrino oscillation studies. The spectra used to date have been determined either by converting measured electron spectra to antineutrino spectra or by summing over all of the thousands of transitions that make up the spectra, using modern databases as input. The uncertainties in the subdominant corrections to β-decay plague both methods, and we ...

  1. Neutron reflectometry

    DEFF Research Database (Denmark)

    Klösgen-Buchkremer, Beate Maria

    2014-01-01

    to hundreds of nanometers. Thickness resolution for flat surfaces is in the range of few Ǻngstrøm, and as a peculiar benefit, the presence and properties of buried interfaces are accessible. Focus here will be on neutron reflectometry, a technique that is unique in applications involving composite organic...... of desired information. In the course, an introduction into the method and an overview on selected instruments at large scale facilities will be presented. Examples will be given that illustrate the potential of the method, mostly based on organic films. Results from the investigation of layered films...... and the detection on nanoscopic roughnesses will be shown. The potential of neutron reflectometry is not only of academic origin. It may turn out to be useful in the design and development of new functional materials even though it will never develop into a standard method to be applied in the product control...

  2. Fast Neutron Detector for Fusion Reactor KSTAR Using Stilbene Scintillator

    CERN Document Server

    Lee, Seung Kyu; Kim, Gi-Dong; Kim, Yong-Kyun

    2011-01-01

    Various neutron diagnostic tools are used in fusion reactors to evaluate different aspects of plasma performance, such as fusion power, power density, ion temperature, fast ion energy, and their spatial distributions. The stilbene scintillator has been proposed for use as a neutron diagnostic system to measure the characteristics of neutrons from the Korea Superconducting Tokamak Advanced Research (KSTAR) fusion reactor. Specially designed electronics are necessary to measure fast neutron spectra with high radiation from a gamma-ray background. The signals from neutrons and gamma-rays are discriminated by the digital charge pulse shape discrimination (PSD) method, which uses total to partial charge ratio analysis. The signals are digitized by a flash analog-to-digital convertor (FADC). To evaluate the performance of the fabricated stilbene neutron diagnostic system, the efficiency of 10 mm soft-iron magnetic shielding and the detection efficiency of fast neutrons were tested experimentally using a 252Cf neutr...

  3. Chemical weapons detection by fast neutron activation analysis techniques

    Science.gov (United States)

    Bach, P.; Ma, J. L.; Froment, D.; Jaureguy, J. C.

    1993-06-01

    A neutron diagnostic experimental apparatus has been tested for nondestructive verification of sealed munitions. Designed to potentially satisfy a significant number of van-mobile requirements, this equipment is based on an easy to use industrial sealed tube neutron generator that interrogates the munitions of interest with 14 MeV neutrons. Gamma ray spectra are detected with a high purity germanium detector, especially shielded from neutrons and gamma ray background. A mobile shell holder has been used. Possible configurations allow the detection, in continuous or in pulsed modes, of gamma rays from neutron inelastic scattering, from thermal neutron capture, and from fast or thermal neutron activation. Tests on full scale sealed munitions with chemical simulants show that those with chlorine (old generation materials) are detectable in a few minutes, and those including phosphorus (new generation materials) in nearly the same time.

  4. Benchmark experiment on vanadium assembly with D-T neutrons. Leakage neutron spectrum measurement

    Energy Technology Data Exchange (ETDEWEB)

    Kokooo; Murata, I.; Nakano, D.; Takahashi, A. [Osaka Univ., Suita (Japan); Maekawa, F.; Ikeda, Y.

    1998-03-01

    The fusion neutronics benchmark experiments have been done for vanadium and vanadium alloy by using the slab assembly and time-of-flight (TOF) method. The leakage neutron spectra were measured from 50 keV to 15 MeV and comparison were done with MCNP-4A calculations which was made by using evaluated nuclear data of JENDL-3.2, JENDL-Fusion File and FENDL/E-1.0. (author)

  5. Artificial neural networks in neutron dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Hernandez D, V.M.; Manzanares A, E.; Mercado, G.A.; Perales M, W.A.; Robles R, J.A. [Unidades Academicas de Estudios Nucleares, UAZ, A.P. 336, 98000 Zacatecas (Mexico); Gallego, E.; Lorente, A. [Depto. de Ingenieria Nuclear, Universidad Politecnica de Madrid, (Spain)

    2005-07-01

    An artificial neural network has been designed to obtain the neutron doses using only the Bonner spheres spectrometer's count rates. Ambient, personal and effective neutron doses were included. 187 neutron spectra were utilized to calculate the Bonner count rates and the neutron doses. The spectra were transformed from lethargy to energy distribution and were re-binned to 31 energy groups using the MCNP 4C code. Re-binned spectra, UTA4 response matrix and fluence-to-dose coefficients were used to calculate the count rates in Bonner spheres spectrometer and the doses. Count rates were used as input and the respective doses were used as output during neural network training. Training and testing was carried out in Mat lab environment. The artificial neural network performance was evaluated using the {chi}{sup 2}- test, where the original and calculated doses were compared. The use of Artificial Neural Networks in neutron dosimetry is an alternative procedure that overcomes the drawbacks associated in this ill-conditioned problem. (Author)

  6. How to produce a reactor neutron spectrum using a proton accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Kimberly A.; Wootan, David W.; Gates, Robert O.; Schmitt, Bruce E.; Asner, David M.

    2015-01-01

    A method for reproducing the neutron energy spectrum present in the core of an operating nuclear reactor using an engineered target in an accelerator proton beam is proposed. The protons interact with a target to create neutrons through various (p,n) type reactions. Spectral tailoring of the emitted neutrons can be used to modify the energy of the generated neutron spectrum to represent various reactor spectra. Through the use of moderators and reflectors, the neutron spectrum can be modified to reproduce many different spectra of interest including spectra in small thermal test reactors, large pressurized water reactors, and fast reactors. The particular application of this methodology is the design of an experimental approach for using an accelerator to measure the betas produced during fission to be used to reduce uncertainties in the interpretation of reactor antineutrino measurements. This approach involves using a proton accelerator to produce a neutron field representative of a power reactor, and using this neutron field to irradiate fission foils of the primary isotopes contributing to fission in the reactor, creating unstable, neutron rich fission products that subsequently beta decay and emit electron antineutrinos. A major advantage of an accelerator neutron source over a neutron beam from a thermal reactor is that the fast neutrons can be slowed down or tailored to approximate various power reactor spectra. An accelerator based neutron source that can be tailored to match various reactor neutron spectra provides an advantage for control in studying how changes in the neutron spectra affect parameters such as the resulting fission product beta spectrum.

  7. How to Produce a Reactor Neutron Spectrum Using a Proton Accelerator

    Science.gov (United States)

    Burns, K.; Wootan, D.; Gates, R.; Schmitt, B.; Asner, D. M.

    A method for reproducing the neutron energy spectrum present in the core of an operating nuclear reactor using an engineered target in an accelerator proton beam is proposed. The protons interact with a target to create neutrons through various (p,n) type reactions. Spectral tailoring of the emitted neutrons can be used to modify the energy of the generated neutron spectrum to represent various reactor spectra. Through the use of moderators and reflectors, the neutron spectrum can be modified to reproduce many different spectra of interest including spectra in small thermal test reactors, large pressurized water reactors, and fast reactors. The particular application of this methodology is the design of an experimental approach for using an accelerator to measure the betas produced during fission to be used to reduce uncertainties in the interpretation of reactor antineutrino measurements. This approach involves using a proton accelerator to produce a neutron field representative of a power reactor, and using this neutron field to irradiate fission foils of the primary isotopes contributing to fission in the reactor, creating unstable, neutron rich fission products that subsequently beta decay and emit electron antineutrinos. A major advantage of an accelerator neutron source over a neutron beam from a thermal reactor is that the fast neutrons can be slowed down or tailored to approximate various power reactor spectra. An accelerator based neutron source that can be tailored to match various reactor neutron spectra provides an advantage for control in studying how changes in the neutron spectra affect parameters such as the resulting fission product beta spectrum.

  8. Spallation Neutron Source (SNS)

    Data.gov (United States)

    Federal Laboratory Consortium — The SNS at Oak Ridge National Laboratory is a next-generation spallation neutron source for neutron scattering that is currently the most powerful neutron source in...

  9. Development of a Bonner Sphere Neutron Spectrometer from a Commercial Neutron Dosimeter

    CERN Document Server

    Chu, M C; Kwok, T; Leung, J K C; Lin, Y C; Liu, H; Luk, K B; Ngai, H Y; Pun, C S J; Wong, H L H

    2016-01-01

    Bonner Spheres have been used widely for the measurement of neutron spectra with neutron energies ranged from thermal up to at least 20 MeV. A Bonner Sphere neutron spectrometer (BSS) was developed by extending a Berthold LB 6411 neutron-dose-rate meter. The BSS consists of a $^{3}$He thermal-neutron detector with integrated electronics, a set of eight polyethylene spherical shells and two optional lead shells of various sizes. The response matrix of the BSS was calculated with GEANT4 Monte Carlo simulation. The BSS had a calibration uncertainty of $\\pm 8.6\\%$ and a detector background rate of $(1.57 \\pm 0.04) \\times 10^{-3}$ s$^{-1}$. A spectral unfolding code NSUGA was developed. The NSUGA code utilizes genetic algorithms and has been shown to perform well in the absence of a priori information.

  10. Development of a Bonner Sphere neutron spectrometer from a commercial neutron dosimeter

    Science.gov (United States)

    Chu, M. C.; Fung, K. Y.; Kwok, T.; Leung, J. K. C.; Lin, Y. C.; Liu, H.; Luk, K. B.; Ngai, H. Y.; Pun, C. S. J.; Wong, H. L. H.

    2016-11-01

    Bonner Spheres have been used widely for the measurement of neutron spectra with neutron energies ranged from thermal up to at least 20 MeV . A Bonner Sphere neutron spectrometer (BSS) was developed by extending a Berthold LB 6411 neutron-dose-rate meter. The BSS consists of a 3He thermal-neutron detector with integrated electronics, a set of eight polyethylene spherical shells and two optional lead shells of various sizes. The response matrix of the BSS was calculated with GEANT4 Monte Carlo simulation. The BSS had a calibration uncertainty of ± 8.6% and a detector background rate of (1.57 ± 0.04) × 10-3 s-1. A spectral unfolding code NSUGA was developed. The NSUGA code utilizes genetic algorithms and has been shown to perform well in the absence of a priori information.

  11. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  12. Neutron Therapy Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Neutron Therapy Facility provides a moderate intensity, broad energy spectrum neutron beam that can be used for short term irradiations for radiobiology (cells)...

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

    Science.gov (United States)

    Tamaki, S; Sato, F; Murata, I

    2015-12-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-08-01

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

  15. MONSTER: a TOF Spectrometer for β-delayed Neutron Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Martínez, T., E-mail: trino.martinez@ciemat.es [Centro de Investigaciones Energéticas, MedioAmbientales y Tecnológicas, CIEMAT, Madrid 28040 (Spain); Cano-Ott, D.; Castilla, J.; Garcia, A.R.; Marin, J.; Martinez, G.; Mendoza, E.; Santos, C.; Tera, F.J.; Villamarin, D. [Centro de Investigaciones Energéticas, MedioAmbientales y Tecnológicas, CIEMAT, Madrid 28040 (Spain); Agramunt, J.; Algora, A.; Domingo, C.; Jordan, M.D.; Rubio, B.; Taín, J.L. [Instituto de Física Corpuscular, CSIC-Universidad de Valencia (Spain); Bhattacharya, C.; Banerjee, K.; Bhattacharya, S.; Roy, P. [Variable Energy Cyclotron Centre (VECC), Kolkata (India); and others

    2014-06-15

    β-delayed neutron (DN) data, including emission probabilities, Pn, and energy spectrum, play an important role in our understanding of nuclear structure, nuclear astrophysics and nuclear technologies. A MOdular Neutron time-of-flight SpectromeTER (MONSTER) is being built for the measurement of the neutron energy spectra and branching ratios. The TOF spectrometer will consist of one hundred liquid scintillator cells covering a significant solid angle. The MONSTER design has been optimized by using Monte Carlo (MC) techniques. The response function of the MONSTER cell has been characterized with mono-energetic neutron beams and compared to dedicated MC simulations.

  16. MONSTER: a TOF Spectrometer for β-delayed Neutron Spectroscopy

    Science.gov (United States)

    Martínez, T.; Cano-Ott, D.; Castilla, J.; Garcia, A. R.; Marin, J.; Martinez, G.; Mendoza, E.; Santos, C.; Tera, F. J.; Villamarin, D.; Agramunt, J.; Algora, A.; Domingo, C.; Jordan, M. D.; Rubio, B.; Taín, J. L.; Bhattacharya, C.; Banerjee, K.; Bhattacharya, S.; Roy, P.; Meena, J. K.; Kundu, S.; Mukherjee, G.; Ghosh, T. K.; Rana, T. K.; Pandey, R.; Saxena, A.; Behera, B.; Penttilä, H.; Jokinen, A.; Rinta-Antila, S.; Guerrero, C.; Ovejero, M. C.

    2014-06-01

    β-delayed neutron (DN) data, including emission probabilities, Pn, and energy spectrum, play an important role in our understanding of nuclear structure, nuclear astrophysics and nuclear technologies. A MOdular Neutron time-of-flight SpectromeTER (MONSTER) is being built for the measurement of the neutron energy spectra and branching ratios. The TOF spectrometer will consist of one hundred liquid scintillator cells covering a significant solid angle. The MONSTER design has been optimized by using Monte Carlo (MC) techniques. The response function of the MONSTER cell has been characterized with mono-energetic neutron beams and compared to dedicated MC simulations.

  17. MONSTER: a TOF Spectrometer for beta-delayed Neutron Spetroscopy

    CERN Document Server

    Martinez, T; Castilla, J; Garcia, A R; Marin, J; Martinez, G; Mendoza, E; Santos, C; Tera, F; Jordan, M D; Rubio, B; Tain, J L; Bhattacharya, C; Banerjee, K; Bhattacharya, S; Roy, P; Meena, J K; Kundu, S; Mukherjee, G; Ghosh, T K; Rana, T K; Pandey, R; Saxena, A; Behera, B; Penttila, H; Jokinen, A; Rinta-Antila, S; Guerrero, C; Ovejero, M C; Villamarin, D; Agramunt, J; Algora, A

    2014-01-01

    Beta-delayed neutron (DN) data, including emission probabilities, P-n, and energy spectrum, play an important role in our understanding of nuclear structure, nuclear astrophysics and nuclear technologies. A MOdular Neutron time-of-flight SpectromeTER (MONSTER) is being built for the measurement of the neutron energy spectra and branching ratios. The TOF spectrometer will consist of one hundred liquid scintillator cells covering a significant solid angle. The MONSTER design has been optimized by using Monte Carlo (MC) techniques. The response function of the MONSTER cell has been characterized with mono-energetic neutron beams and compared to dedicated MC simulations.

  18. Computational evaluation oa a neutron field facility

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, Jose Julio de O.; Pazianotto, Mauricio T., E-mail: jjfilos@hotmail.com, E-mail: mpazianotto@gmail.com [Instituto Tecnologico de Aeronautica (ITA/DCTA), Sao Jose dos Campos, SP (Brazil); Federico, Claudio A.; Passaro, Angelo, E-mail: claudiofederico@ieav.cta.br, E-mail: angelo@ieav.cta.br [Instituto de Estudos Avancados (IEAv/DCTA), Sao Jose dos Campos, SP (Brazil)

    2015-07-01

    This paper describes the results of a study based on computer simulation for a realistic 3D model of Ionizing Radiation Laboratory of the Institute for Advanced Studies (IEAv) using the MCNP5 (Monte Carlo N-Particle) code, in order to guide the installing a neutron generator, produced by reaction {sup 3}H(d,n){sup 4}He. The equipment produces neutrons with energy of 14.1 MeV and 2 x 10{sup 8} n/s production rate in 4 πgeometry, which can also be used for neutron dosimetry studies. This work evaluated the spectra and neutron fluence provided on previously selected positions inside the facility, chosen due to the interest to evaluate the assessment of ambient dose equivalent so that they can be made the necessary adjustments to the installation to be consistent with the guidelines of radiation protection and radiation safety, determined by the standards of National Nuclear Energy Commission (CNEN). (author)

  19. Delayed neutrons measurement at the MEGAPIE target

    Energy Technology Data Exchange (ETDEWEB)

    Panebianco, S.; Bokov, P.; Dore, D.; Letourneau, A.; Prevost, A.; Ridikas, D. [CEA Saclay, Dept. d' Astrophysique de Physique des Particules, de Physique Nucleaire et de l' Instrumentation Associee (DSM/DAPNIA/SPhN), 91- Gif sur Yvette (France); Ledoux, X. [CEA Bruyeres-le-Chatel (CEA DIF, DPTA/SPN), 91 (France). Dept. de Physique Theorique et Appliquee

    2008-07-01

    In the framework of the Neutronic and Nuclear Assessment Task Group of the MEGAPIE experiment we measured the delayed neutron (DN) flux at the top of the target. The measurement was proposed mainly for radioprotection purposes since the DN flux at the top of the target has been estimated to be of the same order of magnitude as the prompt neutron flux. Given the strong model-dependence of DN predictions, the measurement of DN contribution to the total neutron activity at the top of the target was thus desired. Moreover, this measurement is complementary to the DN experiments performed at PNPI (Gatchina) on solid lead and bismuth targets. The DN measurement at MEGAPIE was performed during the start-up phase of the target. In this paper we present a detailed description of the experimental setup and some preliminary results on decay spectra. (authors)

  20. Delayed neutrons measurement at the MEGAPIE target

    CERN Document Server

    Panebianco, Stefano; Dore, Diane; Ledoux, Xavier; Letourneau, Alain; Prevost, Aurelien; Ridikas, Danas

    2007-01-01

    In the framework of the Neutronic and Nuclear Assessment Task Group of the MEGAPIE experiment we measured the delayed neutron (DN) flux at the top of the target. The measurement was proposed mainly for radioprotection purposes since the DN flux at the top of the target has been estimated to be of the same order of magnitude as the prompt neutron flux. Given the strong model-dependence of DN predictions, the measurement of DN contribution to the total neutron activity at the top of the target was thus desired. Moreover, this measurement is complementary to the DN experiments performed at PNPI (Gatchina) on solid lead and bismuth targets. The DN measurement at MEGAPIE was performed during the start-up phase of the target. In this paper we present a detailed description of the experimental setup and some preliminary results on decay spectra.

  1. Solar Energetic Particle Spectra Measured with PAMELA

    Science.gov (United States)

    Ryan, James; Bruno, Alessandro; Boezio, Mirko; Bravar, Ulisse; Christian, Eric; Georgia, De Nolfo; Martucci, Matteo; Merge, Matteo; Munini, Riccardo; Sparvoli, Roberta; Stochaj, Steven; Pamela Collaboration

    2017-01-01

    We have measured the event integrated spectra from several SEP events from 2006 to 2014 in the energy range starting at 80 MeV and extending well above the neutron monitor threshold. The PAMELA instrument is in a high inclination, low Earth orbit and has access to SEPs when at high geographic latitudes. This means that the spectra have been assembled from regularly spaced measurements with gaps during the course of the event. Furthermore, the field of view of PAMELA is small and during the high latitude passes it scans a wide range of asymptotic directions as the spacecraft moves. Correcting for data gaps and solid angle effects, we have compiled event-integrated intensity spectra that typically exhibit power law shapes in energy with an exponential roll over. The events analyzed include two, maybe three, GLEs. In those cases the roll over energy lies above the neutron monitor threshold (1 GV) while the others are lower. We see no qualitative difference between the spectra of GLE vs. non-GLE events. National Science Foundation, NASA, Italian Space Agency, Russian Space Agency.

  2. Design of a transportable high efficiency fast neutron spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Roecker, C., E-mail: calebroecker@berkeley.edu [Department of Nuclear Engineering, University of California at Berkeley, CA 94720 (United States); Bernstein, A.; Bowden, N.S. [Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Cabrera-Palmer, B. [Radiation and Nuclear Detection Systems, Sandia National Laboratories, Livermore, CA 94550 (United States); Dazeley, S. [Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Gerling, M.; Marleau, P.; Sweany, M.D. [Radiation and Nuclear Detection Systems, Sandia National Laboratories, Livermore, CA 94550 (United States); Vetter, K. [Department of Nuclear Engineering, University of California at Berkeley, CA 94720 (United States); Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2016-08-01

    A transportable fast neutron detection system has been designed and constructed for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The transportability of the spectrometer reduces the detector-related systematic bias between different neutron spectra and flux measurements, which allows for the comparison of measurements above or below ground. The spectrometer will measure neutron fluxes that are of prohibitively low intensity compared to the site-specific background rates targeted by other transportable fast neutron detection systems. To measure low intensity high-energy neutron fluxes, a conventional capture-gating technique is used for measuring neutron energies above 20 MeV and a novel multiplicity technique is used for measuring neutron energies above 100 MeV. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. To calibrate and characterize the position dependent response of the spectrometer, a Monte Carlo model was developed and used in conjunction with experimental data from gamma ray sources. Multiplicity event identification algorithms were developed and used with a Cf-252 neutron multiplicity source to validate the Monte Carlo model Gd concentration and secondary neutron capture efficiency. The validated Monte Carlo model was used to predict an effective area for the multiplicity and capture gating analyses. For incident neutron energies between 100 MeV and 1000 MeV with an isotropic angular distribution, the multiplicity analysis predicted an effective area of 500 cm{sup 2} rising to 5000 cm{sup 2}. For neutron energies above 20 MeV, the capture-gating analysis predicted an effective area between 1800 cm{sup 2} and 2500 cm{sup 2}. The multiplicity mode was found to be sensitive to the incident neutron angular distribution.

  3. Unconventional neutron sources for oil well logging

    Energy Technology Data Exchange (ETDEWEB)

    Frankle, C.M., E-mail: cfrankle@lanl.gov; Dale, G.E.

    2013-09-21

    Americium–Beryllium (AmBe) radiological neutron sources have been widely used in the petroleum industry for well logging purposes. There is strong desire on the part of various governmental and regulatory bodies to find alternate sources due to the high activity and small size of AmBe sources. Other neutron sources are available, both radiological ({sup 252}Cf) and electronic accelerator driven (D–D and D–T). All of these, however, have substantially different neutron energy spectra from AmBe and thus cause significantly different responses in well logging tools. We report on simulations performed using unconventional sources and techniques to attempt to better replicate the porosity and carbon/oxygen ratio responses a well logging tool would see from AmBe neutrons. The AmBe response of these two types of tools is compared to the response from {sup 252}Cf, D–D, D–T, filtered D–T, and T–T sources. -- Highlights: • AmBe sources are widely used for well logging purposes. • Governmental bodies would prefer to minimize AmBe use. • Other neutron sources are available, both radiological and electronic. • Tritium–tritium spectrum neutrons have similar logging tool response to AmBe. • A tritium–tritium neutron generator may be a viable AmBe replacement.

  4. Neutron resonance transmission spectroscopy with high spatial and energy resolution at the J-PARC pulsed neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Shinohara, T.; Kai, T.; Ooi, M. [Japan Atomic Energy Agency, 2–4 Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kamiyama, T.; Kiyanagi, Y.; Shiota, Y. [Hokkaido University, Kita 13 Nishi 8 Kita-ku, Sapporo-shi, Hokkaido 060-8628 (Japan); McPhate, J.B.; Vallerga, J.V.; Siegmund, O.H.W. [University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Rd., Sturbridge, MA 01566 (United States)

    2014-05-11

    The sharp variation of neutron attenuation at certain energies specific to particular nuclides (the lower range being from ∼1 eV up to ∼1 keV), can be exploited for the remote mapping of element and/or isotope distributions, as well as temperature probing, within relatively thick samples. Intense pulsed neutron beam-lines at spallation sources combined with a high spatial, high-timing resolution neutron counting detector, provide a unique opportunity to measure neutron transmission spectra through the time-of-flight technique. We present the results of experiments where spatially resolved neutron resonances were measured, at energies up to 50 keV. These experiments were performed with the intense flux low background NOBORU neutron beamline at the J-PARC neutron source and the high timing resolution (∼20 ns at epithermal neutron energies) and spatial resolution (∼55 µm) neutron counting detector using microchannel plates coupled to a Timepix electronic readout. Simultaneous element-specific imaging was carried out for several materials, at a spatial resolution of ∼150 µm. The high timing resolution of our detector combined with the low background beamline, also enabled characterization of the neutron pulse itself – specifically its pulse width, which varies with neutron energy. The results of our measurements are in good agreement with the predicted results for the double pulse structure of the J-PARC facility, which provides two 100 ns-wide proton pulses separated by 600 ns, broadened by the neutron energy moderation process. Thermal neutron radiography can be conducted simultaneously with resonance transmission spectroscopy, and can reveal the internal structure of the samples. The transmission spectra measured in our experiments demonstrate the feasibility of mapping elemental distributions using this non-destructive technique, for those elements (and in certain cases, specific isotopes), which have resonance energies below a few keV, and with lower

  5. Spectrum evaluation at the filter-modified neutron irradiation field for neutron capture therapy in Kyoto University Research Reactor

    Science.gov (United States)

    Sakurai, Yoshinori; Kobayashi, Tooru

    2004-10-01

    The Heavy Water Neutron Irradiation Facility of the Kyoto University Research Reactor (KUR-HWNIF) was updated in March 1996, mainly to improve the facility for neutron capture therapy (NCT). In this facility, neutron beams with various energy spectra, from almost pure thermal to epithermal, are available. The evaluation of the neutron energy spectra by multi-activation-foil method was performed as a series of the facility characterization. The spectra at the normal irradiation position were evaluated for the combinations of heavy-water thickness of the spectrum shifter and the open-close condition of the cadmium and boral filters. The initial spectra were made mainly using a two-dimensional transport code, and the final spectra were obtained using an adjusting code. For the verification of the evaluated spectra, simulation calculations using a phantom were performed on the assumption of NCT-clinical-irradiation conditions. It resulted that the calculated data for the depth neutron-flux distributions were in good agreement with the experimental ones.

  6. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  7. Investigation of Isfahan miniature neutron source reactor (MNSR for boron neutron capture therapy by MCNP simulation

    Directory of Open Access Journals (Sweden)

    S.Z Kalantari

    2015-01-01

    Full Text Available One of the important neutron sources for Boron Neutron Capture Therapy (BNCT is a nuclear reactor. It needs a high flux of epithermal neutrons. The optimum conditions of the neutron spectra for BNCT are provided by the International Atomic Energy Agency (IAEA. In this paper, Miniature Neutron Source Reactor (MNSR as a neutron source for BNCT was investigated. For this purpose, we designed a Beam Shaping Assembly (BSA for the reactor and the neutron transport from the core of the reactor to the output windows of BSA was simulated by MCNPX code. To optimize the BSA performance, two sets of parameters should be evaluated, in-air and in-phantom parameters. For evaluating in-phantom parameters, a Snyder head phantom was used and biological dose rate and dose-depth curve were calculated in brain normal and tumor tissues. Our calculations showed that the neutron flux of the MNSR reactor can be used for BNCT, and the designed BSA in optimum conditions had a good therapeutic characteristic for BNCT.

  8. Evaluation of room-scattered neutrons at the JNC Tokai neutron reference field

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Tadayoshi; Tsujimura, Norio [Japan Nuclear Cycle Development Inst., Tokai, Ibaraki (Japan). Tokai Works; Oyanagi, Katsumi [Japan Radiation Engineering Co., Ltd., Hitachi, Ibaraki (Japan)

    2002-09-01

    Neutron reference fields for calibrating neutron-measuring devices in JNC Tokai Works are produced by using radionuclide neutron sources, {sup 241}Am-Be and {sup 252}Cf sources. The reference field for calibration includes scattered neutrons from the material surrounding sources, wall, floor and ceiling of the irradiation room. It is, therefore, necessary to evaluate the scattered neutrons contribution and their energy spectra at reference points. Spectral measurements were performed with a set of Bonner multi-sphere spectrometers and the reference fields were characterized in terms of spectral composition and the fractions of room-scattered neutrons. In addition, two techniques stated in ISO 10647, the shadow-cone method and the polynomial fit method, for correcting the contributions from the room-scattered neutrons to the readings of neutron survey instruments were compared. It was found that the two methods gave an equivalent result within a deviation of 3.3% at a source-to-detector distance from 50cm to 500cm. (author)

  9. Conceptual design of a camera system for neutron imaging in low fusion power tokamaks

    Science.gov (United States)

    Xie, X.; Yuan, X.; Zhang, X.; Nocente, M.; Chen, Z.; Peng, X.; Cui, Z.; Du, T.; Hu, Z.; Li, T.; Fan, T.; Chen, J.; Li, X.; Zhang, G.; Yuan, G.; Yang, J.; Yang, Q.

    2016-02-01

    The basic principles for designing a camera system for neutron imaging in low fusion power tokamaks are illustrated for the case of the HL-2A tokamak device. HL-2A has an approximately circular cross section, with total neutron yields of about 1012 n/s under 1 MW neutral beam injection (NBI) heating. The accuracy in determining the width of the neutron emission profile and the plasma vertical position are chosen as relevant parameters for design optimization. Typical neutron emission profiles and neutron energy spectra are calculated by Monte Carlo method. A reference design is assumed, for which the direct and scattered neutron fluences are assessed and the neutron count profile of the neutron camera is obtained. Three other designs are presented for comparison. The reference design is found to have the best performance for assessing the width of peaked to broadened neutron emission profiles. It also performs well for the assessment of the vertical position.

  10. Neutron Capture Nucleosynthesis

    CERN Document Server

    Kiss, Miklos

    2016-01-01

    Heavy elements (beyond iron) are formed in neutron capture nucleosynthesis processes. We have proposed a simple unified model to investigate the neutron capture nucleosynthesis in arbitrary neutron density environment. We have also investigated what neutron density is required to reproduce the measured abundance of nuclei assuming equilibrium processes. We found both of these that the medium neutron density has a particularly important role at neutron capture nucleosynthesis. About these results most of the nuclei can formed at medium neutron capture density environment e.g. in some kind of AGB stars. Besides these observations our model is capable to use educational purpose.

  11. Performances of 4H-SiC Schottky diodes as neutron detectors

    Science.gov (United States)

    Lo Giudice, Alessandro; Fasolo, Floriana; Durisi, Elisabetta; Manfredotti, Claudio; Vittone, Ettore; Fizzotti, Franco; Zanini, Alba; Rosi, Giancarlo

    2007-12-01

    Large area 4H-SiC Schottky diodes equipped with a 6LiF converter were tested as neutron detectors in the epithermal column realized for Boron Neutron Capture Therapy (BNCT) applications at the fast reactor TAPIRO (ENEA Casaccia Roma). The neutron spectra were assessed using the Monte Carlo code MCNP-4C. The performances of SiC detectors were evaluated with neutron fluences in the range of 10 9-10 13 cm -2 which is typical for BNCT. Spectra of alpha and tritium particles generated by 6Li(n,α) 3H reaction were collected at various neutron fluences and spectra obtained by interposing polyethylene moderators of different thickness. Only weak damaging effects primarily due to the alpha particles were observed; at neutron fluence of 10 13 cm -2 the count rate decreased by <0.3%. The experimental results were compared with the theoretical ones calculated using MCNP-4C and SRIM codes.

  12. Nuclear reactor neutron shielding

    Energy Technology Data Exchange (ETDEWEB)

    Speaker, Daniel P; Neeley, Gary W; Inman, James B

    2017-09-12

    A nuclear reactor includes a reactor pressure vessel and a nuclear reactor core comprising fissile material disposed in a lower portion of the reactor pressure vessel. The lower portion of the reactor pressure vessel is disposed in a reactor cavity. An annular neutron stop is located at an elevation above the uppermost elevation of the nuclear reactor core. The annular neutron stop comprises neutron absorbing material filling an annular gap between the reactor pressure vessel and the wall of the reactor cavity. The annular neutron stop may comprise an outer neutron stop ring attached to the wall of the reactor cavity, and an inner neutron stop ring attached to the reactor pressure vessel. An excore instrument guide tube penetrates through the annular neutron stop, and a neutron plug comprising neutron absorbing material is disposed in the tube at the penetration through the neutron stop.

  13. Study on neutron radiation field of carbon ions therapy

    CERN Document Server

    Xu, Jun-Kui; Li, Wu-Yuan; Yan, Wei-Wei; Chen, Xi-Meng; Mao, Wang; Pang, Cheng-Guo

    2015-01-01

    Carbon ions offer significant advantages for deep-seated local tumors therapy due to their physical and biological properties. Secondary particles, especially neutrons caused by heavy ion reactions should be carefully considered in treatment process and radiation protection. For radiation protection purposes, the FLUKA Code was used in order to evaluate the radiation field at deep tumor therapy room of HIRFL in this paper. The neutron energy spectra, neutron dose and energy deposition of carbon ion and neutron in tissue-like media was studied for bombardment of solid water target by 430MeV/u C ions. It is found that the calculated neutron dose have a good agreement with the experimental date, and the secondary neutron dose may not exceed one in a thousand of the carbon ions dose at Bragg peak area in tissue-like media.

  14. Spatially resolved remote measurement of temperature by neutron resonance absorption

    Energy Technology Data Exchange (ETDEWEB)

    Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Kockelmann, W.; Pooley, D.E. [STFC, Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX (United Kingdom); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Road, Sturbridge, MA 01566 (United States)

    2015-12-11

    Deep penetration of neutrons into most engineering materials enables non-destructive studies of their bulk properties. The existence of sharp resonances in neutron absorption spectra enables isotopically-resolved imaging of elements present in a sample, as demonstrated by previous studies. At the same time the Doppler broadening of resonance peaks provides a method of remote measurement of temperature distributions within the same sample. This technique can be implemented at a pulsed neutron source with a short initial pulse allowing for the measurement of the energy of each registered neutron by the time of flight technique. A neutron counting detector with relatively high timing and spatial resolution is used to demonstrate the possibility to obtain temperature distributions across a 100 µm Ta foil with ~millimeter spatial resolution. Moreover, a neutron transmission measurement over a wide energy range can provide spatially resolved sample information such as temperature, elemental composition and microstructure properties simultaneously.

  15. Neutron Capture Experiments Using the DANCE Array at Los Alamos

    Science.gov (United States)

    Dashdorj, D.; Mitchell, G. E.; Baramsai, B.; Chyzh, A.; Walker, C.; Agvaanluvsan, U.; Becker, J. A.; Parker, W.; Sleaford, B.; Wu, C. Y.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Krtička, M.; Bečvář, F.

    2009-03-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) is designed for neutron capture measurements on very small and/or radioactive targets. The DANCE array of 160 BaF2 scintillation detectors is located at the Lujan Center at the Los Alamos Neutron Science Center (LANSCE). Accurate measurements of neutron capture data are important for many current applications as well as for basic understanding of neutron capture. The gamma rays following neutron capture reactions have been studied by the time-of-flight technique using the DANCE array. The high granularity of the array allows measurements of the gamma-ray multiplicity. The gamma-ray multiplicities and energy spectra for different multiplicities can be measured and analyzed for spin and parity determination of the resolved resonances.

  16. Resonance capture gamma-ray spectrometry at Lead Slowing-down Neutron Spectrometer

    CERN Document Server

    Pourimani, R; Popov, Y P; Przytula, M; Wojtkiewicz, R

    2002-01-01

    A new method of measurement of the gamma-ray spectra from resonance neutron capture that can be realized at Lead Slowing-down Neutron Spectrometers was proposed and tested experimentally. The specific feature of the method is the shielding of germanium detector by a 'thick' investigated sample that absorbs intensive neutron flux with energies corresponding to sample resonances. In these energy regions the detector response on neutron irradiation is considerably reduced while the sample gamma-ray spectra are greatly strengthened. The detector response gamma-ray spectra are presented and analysed, and the spectra from neutron capture in tantalum resonances at energies 4.28 and 10.36 eV are shown. The obtained results demonstrate the usefulness of the proposed method. Five new excited levels in germanium isotopes are proposed.

  17. Measurement of Neutron Field Characteristics at Nuclear-Physics Instalations for Personal Radiation Monitoring

    CERN Document Server

    Alekseev, A G; Britvich, G I; Kosyanenko, E V; Pikalov, V A; Gomonov, I P

    2003-01-01

    n this work the observed data of neutron spectra on Rostov NEP, Kursk NEP and Smolensk NEP and on the reactor IRT MIPHI are submitted. For measurement of neutron spectra two types of spectrometer were used: SHANS (IHEP design ) and SDN-MS01 (FEI design). The comparison of the data measurements per-formed by those spectrometers above one-type cells on the reactor RBMK is submitted. On the basis of the 1-st horizontal experimental channel HEC-1 of the IRT reactor 4 reference fields of neutrons are investigated. It is shown, that spectra of neutrons of reference fields can be used for imitation of neutron spectra for conditions of NEP with VVER and RBMK type reactors.

  18. Polyethylene terephthalate degradation under reactor neutron irradiation

    Science.gov (United States)

    Chikaoui, K.; Izerrouken, M.; Djebara, M.; Abdesselam, M.

    2017-01-01

    This paper is devoted to study the defects generated by reactor neutron in polyethylene terephthalate (PET) films. The explored fast neutron fluence ranges from 2.02×1016 to 2.07×1018 n cm-2. The induced damages were investigated using ultraviolet-visible spectrophotometry (UV-vis), Fourier Transform Infrared spectrometry (FTIR) and X-ray diffraction (XRD). The UV-vis spectra show important changes indicating the degradation of the chemical structure and the creation of new chromophores. FTIR spectra reveal that the intensities of the different absorption bands decrease linearly under fast neutron irradiation. The internal reference band at 1410 cm-1 is used to follow the overall damage during irradiation. The 1342 cm-1 band corresponding to CH2 wagging of trans conformation of crystalline phase show a sharpe linear decrease as the fast neutrons fluence goes up. The creation of the monosubstituted benzene, investigated using the 1610 cm-1 band. It shows a linear increase with fast neutron fluence. It is found from XRD analysis that the diffraction peak (100) intensity is drastically reduced after irradiation at 2.02×1016 n cm-2.

  19. Neutron spectrometry using artificial neural networks for a Bonner sphere spectrometer with a {sup 3}He detector

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz R, J. M. [Universidad Autonoma de Zacatecas, Unidad Academica de Ingenieria Electrica, Apdo. Postal 336, 98000 Zacatecas (Mexico); Martinez B, M. R.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Apdo. Postal 336, 98000 Zacatecas (Mexico); Gallego D, E.; Lorente F, A. [Universidad Politecnica de Madrid, Departamento de Ingenieria Nuclear, ETSI Industriales, C. Jose Gutierrez Abascal 2, 28006 Madrid (Spain); Mendez V, R.; Los Arcos M, J. M.; Guerrero A, J. E., E-mail: morvymm@yahoo.com.m [CIEMAT, Laboratorio de Metrologia de Radiaciones Ionizantes, Avda. Complutense 22, 28040 Madrid (Spain)

    2011-02-15

    Neutron spectra unfolding and dose equivalent calculation are complicated tasks in radiation protection, are highly dependent of the neutron energy, and a precise knowledge on neutron spectrometry is essential for all dosimetry-related studies as well as many nuclear physics experiments. In previous works have been reported neutron spectrometry and dosimetry results, by using the artificial neural networks (Ann) technology as alternative solution, starting from the count rates of a Bonner spheres system with a {sup 6}LiI(Eu) thermal neutrons detector, 7 polyethylene spheres and the UTA4 response matrix with 31 energy bins. In this work, an Ann was designed and optimized by using the RDAnn methodology for the Bonner spheres system used at CIEMAT Spain, which is composed of a {sup 3}He neutron detector, 12 moderator spheres and a response matrix for 72 energy bins. For the Ann design process a neutrons spectra catalogue compiled by the IAEA was used. From this compilation, the neutrons spectra were converted from lethargy to energy spectra. Then, the resulting energy fluence spectra were re-bin ned by using the MCNP code to the corresponding energy bins of the {sup 3}He response matrix before mentioned. With the response matrix and the re-bin ned spectra the counts rate of the Bonner spheres system were calculated and the resulting re-bin ned neutrons spectra and calculated counts rate were used as the Ann training data set. (Author)

  20. Feasibility study of a SiC sandwich neutron spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jian, E-mail: caepwujian@163.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, Sichuan Province (China); Lei, Jiarong, E-mail: jiarong_lei@163.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, Sichuan Province (China); Jiang, Yong; Chen, Yu; Rong, Ru; Zou, Dehui; Fan, Xiaoqiang [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, Sichuan Province (China); Chen, Gang; Li, Li; Bai, Song [Nanjing Electronic Devices Institute, Nanjing 210016 (China)

    2013-04-21

    Semiconductor sandwich neutron spectrometers are suitable for in-pile measurements of fast reactor spectra thanks to their compact and relatively simple design. We have assembled and tested a sandwich neutron spectrometer based on 4H-silicon carbide (4H-SiC) Schottky diodes. The SiC diodes detect neutrons via neutron-induced charged particles (tritons and alpha particles) produced by {sup 6}Li(n,α){sup 3}H reaction. {sup 6}LiF neutron converter layers are deposited on the front surface of Schottky diodes by magnetron sputtering. The responses of SiC diodes to charged particles were investigated with an {sup 241}Am alpha source. A sandwich neutron spectrometer was assembled with two SiC Schottky diodes selected based on the charged-particle-response experimental results. The low-energy neutron response of the sandwich spectrometer was measured in the neutron field of the Chinese Fast Burst Reactor-II (CFBR-II). Spectra of alpha particles and tritons from {sup 6}Li(n,α){sup 3}H reaction were obtained with two well-resolved peaks. The energy resolution of the sum spectrum was 8.8%. The primary experimental results confirmed the 4H-SiC sandwich neutron spectrometer's feasibility. -- Highlights: ► Sandwich neutron spectrometer employing 4H-SiC as a detecting material has been developed for the first time. ► {sup 6}LiF neutron converter has been deposited on the surface of 4H-SiC Schottky diode. ► Preliminary testing results obtained with the 4H-SiC sandwich neutron spectrometer are presented.

  1. Weapons Neutron Research Facility (WNR)

    Data.gov (United States)

    Federal Laboratory Consortium — The Weapons Neutron Research Facility (WNR) provides neutron and proton beams for basic, applied, and defense-related research. Neutron beams with energies ranging...

  2. Neutron spectrometry and determination of neutron ambient dose equivalents in different LINAC radiotherapy rooms

    Energy Technology Data Exchange (ETDEWEB)

    Domingo, C., E-mail: carles.domingo@uab.ca [Grup de Fisica de les Radiacions, Departament de Fisica. Edifici C, Campus UAB, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Garcia-Fuste, M.J.; Morales, E.; Amgarou, K. [Grup de Fisica de les Radiacions, Departament de Fisica. Edifici C, Campus UAB, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Terron, J.A. [Servicio de Radiofisica, Hospital Universitario Virgen Macarena. E- 41009 Sevilla. Spain (Spain); Rosello, J.; Brualla, L. [ERESA, Avda. Tres Cruces s/n. E-46014 Valencia (Spain); Nunez, L. [Servicio de Radiofisica, Hospital. Puerta de Hierro. E-28222 Majadahonda (Spain); Colmenares, R. [Serv. de Oncologia Radioterapica, Hosp. Ramon y Cajal, E-28049 Madrid (Spain); Gomez, F. [Dpto. de Particulas. Univ. de Santiago. E-15782 Santiago de Compostela. Spain (Spain); Hartmann, G.H. [DKFZ E0400 Im Neuenheimer Feld 280. D-69120 Heidelberg (Germany) (Germany); Sanchez-Doblado, F. [Servicio de Radiofisica, Hospital Universitario Virgen Macarena. E- 41009 Sevilla. Spain (Spain); Dpto. de Fisiologia Medica y Biofisica. Universidad de Sevilla. E-41009 Sevilla. Spain (Spain); Fernandez, F. [Grup de Fisica de les Radiacions, Departament de Fisica. Edifici C, Campus UAB, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Consejo de Seguridad Nuclear, Justo Dorado 11 E-28040 Madrid (Spain)

    2010-12-15

    A project has been set up to study the effect on a radiotherapy patient of the neutrons produced around the LINAC accelerator head by photonuclear reactions induced by photons above {approx}8 MeV. These neutrons may reach directly the patient, or they may interact with the surrounding materials until they become thermalised, scattering all over the treatment room and affecting the patient as well, contributing to peripheral dose. Spectrometry was performed with a calibrated and validated set of Bonner spheres at a point located at 50 cm from the isocenter, as well as at the place where a digital device for measuring neutrons, based on the upset of SRAM memories induced by thermal neutrons, is located inside the treatment room. Exposures have taken place in six LINAC accelerators with different energies (from 15 to 23 MV) with the aim of relating the spectrometer measurements with the readings of the digital device under various exposure and room geometry conditions. The final purpose of the project is to be able to relate, under any given treatment condition and room geometry, the readings of this digital device to patient neutron effective dose and peripheral dose in organs of interest. This would allow inferring the probability of developing second malignancies as a consequence of the treatment. Results indicate that unit neutron fluence spectra at 50 cm from the isocenter do not depend on accelerator characteristics, while spectra at the place of the digital device are strongly influenced by the treatment room geometry.

  3. Calculation of Prompt Fission Neutron Spectrum for 233U(n, f) Reaction by Semi-empirical Method

    Institute of Scientific and Technical Information of China (English)

    CHEN; Yong-jing; LIU; Ting-jin; SHU; Neng-chuan

    2013-01-01

    The prompt fission neutron spectra for neutron-induced fission of 233U for low energy neutron(below 6 MeV)are calculated using the nuclear evaporation theory with a semi-empirical method,in which the partition of the total excitation energy between the fission fragments for the nth+233U fission

  4. Measuring the basic parameters of neutron stars using model atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Suleimanov, V.F. [Universitaet Tuebingen, Institut fuer Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Tuebingen (Germany); Kazan Federal University, Kazan (Russian Federation); Poutanen, J. [University of Turku, Tuorla Observatory, Department of Physics and Astronomy, Piikkioe (Finland); KTH Royal Institute of Technology and Stockholm University, Nordita, Stockholm (Sweden); Klochkov, D.; Werner, K. [Universitaet Tuebingen, Institut fuer Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Tuebingen (Germany)

    2016-02-15

    Model spectra of neutron star atmospheres are nowadays widely used to fit the observed thermal X-ray spectra of neutron stars. This fitting is the key element in the method of the neutron star radius determination. Here, we present the basic assumptions used for the neutron star atmosphere modeling as well as the main qualitative features of the stellar atmospheres leading to the deviations of the emergent model spectrum from blackbody. We describe the properties of two of our model atmosphere grids: i) pure carbon atmospheres for relatively cool neutron stars (1-4MK) and ii) hot atmospheres with Compton scattering taken into account. The results obtained by applying these grids to model the X-ray spectra of the central compact object in supernova remnant HESS 1731-347, and two X-ray bursting neutron stars in low-mass X-ray binaries, 4U 1724-307 and 4U 1608-52, are presented. Possible systematic uncertainties associated with the obtained neutron star radii are discussed. (orig.)

  5. Reactor Neutrino Spectra

    CERN Document Server

    Hayes, A C

    2016-01-01

    We present a review of the antineutrino spectra emitted from reactors. Knowledge of these and their associated uncertainties are crucial for neutrino oscillation studies. The spectra used to-date have been determined by either conversion of measured electron spectra to antineutrino spectra or by summing over all of the thousands of transitions that makeup the spectra using modern databases as input. The uncertainties in the subdominant corrections to beta-decay plague both methods, and we provide estimates of these uncertainties. Improving on current knowledge of the antineutrino spectra from reactors will require new experiments. Such experiments would also address the so-called reactor neutrino anomaly and the possible origin of the shoulder observed in the antineutrino spectra measured in recent high-statistics reactor neutrino experiments.

  6. Neutron shielding for a {sup 252} Cf source

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R.; Manzanares A, E.; Hernandez D, V.M. [Unidades Academicas de Estudios Nucleares e Ingenieria Electrica, Universidad Autonoma de Zacatecas, C. Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Eduardo Gallego, Alfredo Lorente [Depto. de Ingenieria Nuclear, ETS Ingenieros Industriales, Universidad Politecnica de Madrid, C. Jose Gutierrez Abascal 2, 28006 Madrid (Spain)]. e-mail: fermineutron@yahoo.com

    2006-07-01

    To determine the neutron shielding features of water-extended polyester a Monte Carlo study was carried out. Materials with low atomic number are predominantly used for neutron shielding because these materials effectively attenuate neutrons, mainly through inelastic collisions and absorption reactions. During the selection of materials to design a neutron shield, prompt gamma production as well as radionuclide production induced by neutron activation must be considered. In this investigation the Monte Carlo method was used to evaluate the performance of a water-extended polyester shield designed for the transportation, storage, and use of a {sup 252}Cf isotopic neutron source. During calculations a detailed model for the {sup 252}Cf and the shield was utilized. To compare the shielding features of water extended polyester, the calculations were also made for the bare {sup 252}Cf in vacuum, air and the shield filled with water. For all cases the calculated neutron spectra was utilized to determine the ambient equivalent neutron dose at four sites around the shielding. In the case of water extended polyester and water shielding the calculations were extended to include the prompt gamma rays produced during neutron interactions, with this information the Kerma in air was calculated at the same locations where the ambient equivalent neutron dose was determined. (Author)

  7. Neutrons characterization of the nuclear reactor Ian-R1 of Colombia; Caracterizacion de los neutrones del reactor nuclear IAN-R1 de Colombia

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez P, L. X.; Martinez O, S. A. [Universidad Pedagogica y Tecnologica de Colombia, Grupo de Fisica Nuclear Aplicada y Simulacion, Carretera Central del Norte Km. 1, Via Paipa, 150003 Tunja, Boyaca (Colombia); Vega C, H. R., E-mail: s.agustin.martinez@uptc.edu.co [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2014-08-15

    By means of Monte Carlo methods, with the code MCNPX, the neutron characteristics of the research nuclear reactor Ian-R1 of Colombia, in power off but with the neutrons source in their start position, have been valued. The neutrons spectra, the total flow and their average power were calculated in the irradiation spaces inside the graphite reflector, as well as in the cells with air. Also the spectra, the total flow and the absorbed dose were calculated in several places distributed along the radial shaft inside the water moderator. The neutrons total flow was also considered to the long of the axial shaft. The characteristics of the neutrons spectra vary depending on their position regarding the source and the material that surrounds to the cell where the calculation was made. (Author)

  8. Investigations on landmine detection by neutron-based techniques.

    Science.gov (United States)

    Csikai, J; Dóczi, R; Király, B

    2004-07-01

    Principles and techniques of some neutron-based methods used to identify the antipersonnel landmines (APMs) are discussed. New results have been achieved in the field of neutron reflection, transmission, scattering and reaction techniques. Some conclusions are as follows: The neutron hand-held detector is suitable for the observation of anomaly caused by a DLM2-like sample in different soils with a scanning speed of 1m(2)/1.5 min; the reflection cross section of thermal neutrons rendered the determination of equivalent thickness of different soil components possible; a simple method was developed for the determination of the thermal neutron flux perturbation factor needed for multi-elemental analysis of bulky samples; unfolded spectra of elastically backscattered neutrons using broad-spectrum sources render the identification of APMs possible; the knowledge of leakage spectra of different source neutrons is indispensable for the determination of the differential and integrated reaction rates and through it the dimension of the interrogated volume; the precise determination of the C/O atom fraction requires the investigations on the angular distribution of the 6.13MeV gamma-ray emitted in the (16)O(n,n'gamma) reaction. These results, in addition to the identification of landmines, render the improvement of the non-intrusive neutron methods possible.

  9. Investigations on landmine detection by neutron-based techniques

    Energy Technology Data Exchange (ETDEWEB)

    Csikai, J. E-mail: csikai@delfin.klte.hu; Doczi, R.; Kiraly, B

    2004-07-01

    Principles and techniques of some neutron-based methods used to identify the antipersonnel landmines (APMs) are discussed. New results have been achieved in the field of neutron reflection, transmission, scattering and reaction techniques. Some conclusions are as follows: The neutron hand-held detector is suitable for the observation of anomaly caused by a DLM2-like sample in different soils with a scanning speed of 1 m{sup 2}/1.5 min; the reflection cross section of thermal neutrons rendered the determination of equivalent thickness of different soil components possible; a simple method was developed for the determination of the thermal neutron flux perturbation factor needed for multi-elemental analysis of bulky samples; unfolded spectra of elastically backscattered neutrons using broad-spectrum sources render the identification of APMs possible; the knowledge of leakage spectra of different source neutrons is indispensable for the determination of the differential and integrated reaction rates and through it the dimension of the interrogated volume; the precise determination of the C/O atom fraction requires the investigations on the angular distribution of the 6.13 MeV gamma-ray emitted in the {sup 16}O(n,n'{gamma}) reaction. These results, in addition to the identification of landmines, render the improvement of the non-intrusive neutron methods possible.

  10. Constraints on neutron-star theories from nearby neutron star observations

    CERN Document Server

    Neuhäuser, Ralph; Tetzlaff, Nina; Hohle, Markus M; Eisenbeiss, Thomas

    2011-01-01

    We try to constrain the nuclear Equation-of-State (EoS) and supernova ejecta models by observations of young neutron stars in our galactic neighbourhood. There are seven thermally emitting isolated neutron stars known from X-ray and optical observations, the so-called Magnificent Seven, which are young (few Myrs), nearby (few hundred pc), and radio-quiet with blackbody-like X-ray spectra, so that - by observing their surface - we can determine their luminosity, distance, and temperature, hence, their radius. We also see the possibility to determine their current neutron star masses and the masses of their progenitor stars by studying their origin. It is even feasible to find the neutron star which was born in the supernova, from which those Fe60 atoms were ejected, which were recently found in the Earth crust.

  11. Superheated drop neutron spectrometer

    CERN Document Server

    Das, M; Roy, B; Roy, S C; Das, Mala

    2000-01-01

    Superheated drops are known to detect neutrons through the nucleation caused by the recoil nuclei produced by the interactions of neutrons with the atoms constituting the superheated liquid molecule. A novel method of finding the neutron energy from the temperature dependence response of SDD has been developed. From the equivalence between the dependence of threshold energy for nucleation on temperature of SDD and the dependence of dE/dx of the recoil ions with the energy of the neutron, a new method of finding the neutron energy spectrum of a polychromatic as well as monochromatic neutron source has been developed.

  12. Neutron streak camera

    Science.gov (United States)

    Wang, Ching L.

    1983-09-13

    Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

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

    Energy Technology Data Exchange (ETDEWEB)

    Do, Changwoo, E-mail: doc1@ornl.gov [Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Heller, William T.; Stanley, Christopher [Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Gallmeier, Franz X. [Instrument and Source Design Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Doucet, Mathieu [Neutron Data Analysis and Visualization Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Smith, Gregory S. [Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2014-02-11

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

  14. Development and characterization of a high sensitivity segmented Fast Neutron Spectrometer (FaNS-2)

    Science.gov (United States)

    Langford, T. J.; Beise, E. J.; Breuer, H.; Heimbach, C. R.; Ji, G.; Nico, J. S.

    2016-01-01

    We present the development of a segmented fast neutron spectrometer (FaNS-2) based upon plastic scintillator and 3He proportional counters. It was designed to measure both the flux and spectrum of fast neutrons in the energy range of few MeV to 1 GeV. FaNS-2 utilizes capture-gated spectroscopy to identify neutron events and reject backgrounds. Neutrons deposit energy in the plastic scintillator before capturing on a 3He nucleus in the proportional counters. Segmentation improves neutron energy reconstruction while the large volume of scintillator increases sensitivity to low neutron fluxes. A main goal of its design is to study comparatively low neutron fluxes, such as cosmogenic neutrons at the Earth's surface, in an underground environment, or from low-activity neutron sources. In this paper, we present details of its design and construction as well as its characterization with a calibrated 252Cf source and monoenergetic neutron fields of 2.5 MeV and 14 MeV. Detected monoenergetic neutron spectra are unfolded using a Singular Value Decomposition method, demonstrating a 5% energy resolution at 14 MeV. Finally, we discuss plans for measuring the surface and underground cosmogenic neutron spectra with FaNS-2.

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

    Science.gov (United States)

    Saltos, Andrea

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

  16. Neutron anatomy

    Energy Technology Data Exchange (ETDEWEB)

    Bacon, G.E. [Univ. of Sheffield (United Kingdom)

    1994-12-31

    The familiar extremes of crystalline material are single-crystals and random powders. In between these two extremes are polycrystalline aggregates, not randomly arranged but possessing some preferred orientation and this is the form taken by constructional materials, be they steel girders or the bones of a human or animal skeleton. The details of the preferred orientation determine the ability of the material to withstand stress in any direction. In the case of bone the crucial factor is the orientation of the c-axes of the mineral content - the crystals of the hexagonal hydroxyapatite - and this can readily be determined by neutron diffraction. In particular it can be measured over the volume of a piece of bone, utilizing distances ranging from 1mm to 10mm. The major practical problem is to avoid the intense incoherent scattering from the hydrogen in the accompanying collagen; this can best be achieved by heat-treatment and it is demonstrated that this does not affect the underlying apatite. These studies of bone give leading anatomical information on the life and activities of humans and animals - including, for example, the life history of the human femur, the locomotion of sheep, the fracture of the legs of racehorses and the life-styles of Neolithic tribes. We conclude that the material is placed economically in the bone to withstand the expected stresses of life and the environment. The experimental results are presented in terms of the magnitude of the 0002 apatite reflection. It so happens that for a random powder the 0002, 1121 reflections, which are neighboring lines in the powder pattern, are approximately equal in intensity. The latter reflection, being of manifold multiplicity, is scarcely affected by preferred orientation so that the numerical value of the 0002/1121 ratio serves quite accurately as a quantitative measure of the degree of orientation of the c-axes in any chosen direction for a sample of bone.

  17. Absolute monitoring of DD and DT neutron fluences using the associated-particle technique

    Science.gov (United States)

    Hertel, N. E.; Wehring, B. W.

    1980-06-01

    An associated-particle system was constructed for use with a Texas Nuclear neutron generator. Associated-particle and neutron energy spectra were measured simultaneously using this system and an NE-213 proton recoil spectrometer, respectively. The associated-particle system proved to be not only an accurate monitor of DT neutron fluence, but also an accurate monitor of DD contamination in the DT spectrum. The DD and DT neutron fluences calculated from the measured associated-particle counting rates showed the best agreement with the measured neutron fluences when the laboratory distributions were assumed to be isotropic.

  18. Resistivity damage rates in fusion-neutron-irradiated metals at 4. 2 K

    Energy Technology Data Exchange (ETDEWEB)

    Guinan, M.W.; Kinney, J.H.

    1981-01-01

    Changes in electrical resistivity at liquid helium temperature have been used to monitor the production of damage in dilute alloys of vanadium, niobium and molybdenum, and pure tungsten, aluminum and copper irradiated with high energy neutrons. The neutrons were produced at the Livermore rotating-target neutron sources (RTNS-I and RTNS-II). Further experiments on V, Nb and Mo were carried out with 30 MeV d-Be neutrons and slightly degraded fission-spectra neutrons. The results for all six materials are compared to those obtained in a pure fission spectrum. The relative damage production rates are in agreement with predictions based on damage energy calculations.

  19. Time-of-flight discrimination between gamma-rays and neutrons by neural networks

    OpenAIRE

    2012-01-01

    In gamma-ray spectroscopy, a number of neutrons are emitted from the nuclei together with the gamma-rays and these neutrons influence gamma-ray spectra. An obvious method of separating between neutrons and gamma-rays is based on the time-of-flight (tof) technique. This work aims obtaining tof distributions of gamma-rays and neutrons by using feed-forward artificial neural network (ANN). It was shown that, ANN can correctly classify gamma-ray and neutron events. Testing of trained networks on ...

  20. Fast neutron spectrometry with organic scintillators applied to magnetic fusion experiments

    CERN Document Server

    Kaschuck, Y A; Trykov, L A; Semenov, V P

    2002-01-01

    Neutron spectrometry with NE213 liquid scintillators is commonly used in thermonuclear fusion experiments to measure the 2.45 and 14.1 MeV neutron flux. We present the unfolded neutron spectrum, which was accumulated during several ohmic deuterium plasma discharges in the Frascati Tokamak Upgrade using a 2''x2'' NE213 scintillator. In this paper, we review the application of organic scintillator neutron spectrometers to tokamaks, focusing in particular on the comparison between NE213 and stilbene scintillators. Various aspects of the calibration technique and neutron spectra unfolding procedure are considered in the context of their application for fusion neutron spectrometry. Testing and calibration measurements have been carried out using D-D and D-T neutron generator facilities with both NE213 and stilbene scintillators. The main result from these measurements is that stilbene scintillator has better neutron energy resolution than NE213. Our stilbene detector could be used for the determination of the ion ...

  1. Prompt gamma and neutron detection in BNCT utilizing a CdTe detector.

    Science.gov (United States)

    Winkler, Alexander; Koivunoro, Hanna; Reijonen, Vappu; Auterinen, Iiro; Savolainen, Sauli

    2015-12-01

    In this work, a novel sensor technology based on CdTe detectors was tested for prompt gamma and neutron detection using boronated targets in (epi)thermal neutron beam at FiR1 research reactor in Espoo, Finland. Dedicated neutron filter structures were omitted to enable simultaneous measurement of both gamma and neutron radiation at low reactor power (2.5 kW). Spectra were collected and analyzed in four different setups in order to study the feasibility of the detector to measure 478 keV prompt gamma photons released from the neutron capture reaction of boron-10. The detector proved to have the required sensitivity to detect and separate the signals from both boron neutron and cadmium neutron capture reactions, which makes it a promising candidate for monitoring the spatial and temporal development of in vivo boron distribution in boron neutron capture therapy.

  2. Neutron spectrum measurement in D+Be reaction

    Directory of Open Access Journals (Sweden)

    F. Abbasi Davani

    2002-06-01

    Full Text Available   In this project the neutron spectra from the reaction of deutron on beryllium muclei is measured. The energies of deuterons were 7, 10, 13 and 15 MeV, and these measurements are performed at 10, 30 and 50 degrees relative to the beam of deutrons. The detector used is 76 by 76 mm right circular cylender of NE-213 liquid scintillator. The zero crossing technique is used for gamma discriminatin. For the elimination of the background radiation, a Polyethylene block, 40 cm in thickness, with inserted cadmium sheets, and a lead block, 5 cm in thickness, were used. In order to obtain the background radiation spectrum, the latter blocks were placed between the target and the detector to eliminate neutron and gamma radiations reaching the detector directly. FORIST code is used to unfold the neutron spectra from the measured pulse hight spectra and O5S and RESPMG codes are used to obtain the detector response matrix.

  3. Imaging with Scattered Neutrons

    OpenAIRE

    Ballhausen, H.; Abele, H.; Gaehler, R.; Trapp, M.; Van Overberghe, A.

    2006-01-01

    We describe a novel experimental technique for neutron imaging with scattered neutrons. These scattered neutrons are of interest for condensed matter physics, because they permit to reveal the local distribution of incoherent and coherent scattering within a sample. In contrast to standard attenuation based imaging, scattered neutron imaging distinguishes between the scattering cross section and the total attenuation cross section including absorption. First successful low-noise millimeter-re...

  4. Intense fusion neutron sources

    Science.gov (United States)

    Kuteev, B. V.; Goncharov, P. R.; Sergeev, V. Yu.; Khripunov, V. I.

    2010-04-01

    The review describes physical principles underlying efficient production of free neutrons, up-to-date possibilities and prospects of creating fission and fusion neutron sources with intensities of 1015-1021 neutrons/s, and schemes of production and application of neutrons in fusion-fission hybrid systems. The physical processes and parameters of high-temperature plasmas are considered at which optimal conditions for producing the largest number of fusion neutrons in systems with magnetic and inertial plasma confinement are achieved. The proposed plasma methods for neutron production are compared with other methods based on fusion reactions in nonplasma media, fission reactions, spallation, and muon catalysis. At present, intense neutron fluxes are mainly used in nanotechnology, biotechnology, material science, and military and fundamental research. In the near future (10-20 years), it will be possible to apply high-power neutron sources in fusion-fission hybrid systems for producing hydrogen, electric power, and technological heat, as well as for manufacturing synthetic nuclear fuel and closing the nuclear fuel cycle. Neutron sources with intensities approaching 1020 neutrons/s may radically change the structure of power industry and considerably influence the fundamental and applied science and innovation technologies. Along with utilizing the energy produced in fusion reactions, the achievement of such high neutron intensities may stimulate wide application of subcritical fast nuclear reactors controlled by neutron sources. Superpower neutron sources will allow one to solve many problems of neutron diagnostics, monitor nano-and biological objects, and carry out radiation testing and modification of volumetric properties of materials at the industrial level. Such sources will considerably (up to 100 times) improve the accuracy of neutron physics experiments and will provide a better understanding of the structure of matter, including that of the neutron itself.

  5. A proton recoil telescope for neutron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Donzella, A., E-mail: antonietta.donzella@ing.unibs.i [Universita di Brescia, 38 Via Branze, I-25123 Brescia (Italy); INFN Sezione di Pavia, 6 Via Bassi, I-27100 Pavia (Italy); Barbui, M. [INFN Laboratori Nazionali di Legnaro, 2 Viale dell' Universita, I-35020 Legnaro, Padova (Italy); Bocci, F. [INFN and Universita di Pavia, 6 Via Bassi, I-27100 Pavia (Italy); Bonomi, G. [Universita di Brescia, 38 Via Branze, I-25123 Brescia (Italy); INFN Sezione di Pavia, 6 Via Bassi, I-27100 Pavia (Italy); Cinausero, M. [INFN Laboratori Nazionali di Legnaro, 2 Viale dell' Universita, I-35020 Legnaro, Padova (Italy); Fabris, D. [INFN and Universita di Padova, 8 Via Marzolo, I-35131 Padova (Italy); Fontana, A. [INFN Sezione di Pavia, 6 Via Bassi, I-27100 Pavia (Italy); Giroletti, E. [INFN and Universita di Pavia, 6 Via Bassi, I-27100 Pavia (Italy); Lunardon, M.; Moretto, S.; Nebbia, G. [INFN and Universita di Padova, 8 Via Marzolo, I-35131 Padova (Italy); Necchi, M.M. [Universita di Brescia, 38 Via Branze, I-25123 Brescia (Italy); Pesente, S. [INFN and Universita di Padova, 8 Via Marzolo, I-35131 Padova (Italy); Prete, G.; Rizzi, V. [INFN Laboratori Nazionali di Legnaro, 2 Viale dell' Universita, I-35020 Legnaro, Padova (Italy); Viesti, G. [INFN and Universita di Padova, 8 Via Marzolo, I-35131 Padova (Italy); Zenoni, A. [Universita di Brescia, 38 Via Branze, I-25123 Brescia (Italy); INFN Sezione di Pavia, 6 Via Bassi, I-27100 Pavia (Italy)

    2010-01-21

    A new proton recoil telescope (PRT) detector is presented: it is composed by an active multilayer of segmented plastic scintillators as neutron to proton converter, by two silicon strip detectors and by a final thick CsI(Tl) scintillator. The PRT can be used to measure neutron spectra in the range 2-160 MeV. The detector characteristics have been studied in detail with the help of Monte Carlo simulations. The overall energy resolution of the system ranges from about 20% at the lowest neutron energy to about 2% at 160 MeV. The global efficiency is about 3x10{sup -5}. Experimental tests have been performed by using the reaction {sup 13}C(d,n) at 40 MeV deuteron energy.

  6. Photon spectrometry in thermal neutron standard field

    CERN Document Server

    Kudo, K; Koshikawa, S; Toyokawa, H; Ohgaki, H; Matzke, M

    2002-01-01

    An NE213 liquid scintillation counter (5.08 cm in diameter and 5.08 cm long) with an LiF filter was used to measure the energy distribution of photons mixed in a thermal neutron field. The response function matrix of photons in an energy range up to 10 MeV was calculated by the EGS4/PRESTA code and properly folded with a resolution function. Pulse height spectra measured with a set of reference gamma-ray sources were compared to the calculated response function and agreed very well for all reference gamma-ray sources. The GRAVEL and MIEKE codes from the HEPRO program were used to unfold measured pulse height spectra. Energy distributions obtained by the unfolding were applied to evaluate the effective dose equivalent of photons mixed in a thermal neutron field.

  7. International Neutron Radiography Newsletter

    DEFF Research Database (Denmark)

    Domanus, Joseph Czeslaw

    1986-01-01

    At the First World Conference on Neutron Radiography i t was decided to continue the "Neutron Radiography Newsletter", published previously by J.P. Barton, as the "International Neutron Radiography Newsletter" (INRNL), with J.C. Doraanus as editor. The British Journal of Non-Destructive Testing...

  8. Advanced neutron absorber materials

    Science.gov (United States)

    Branagan, Daniel J.; Smolik, Galen R.

    2000-01-01

    A neutron absorbing material and method utilizing rare earth elements such as gadolinium, europium and samarium to form metallic glasses and/or noble base nano/microcrystalline materials, the neutron absorbing material having a combination of superior neutron capture cross sections coupled with enhanced resistance to corrosion, oxidation and leaching.

  9. Prototype Neutron Energy Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. Neutron Spectrum Measurements from Irradiations at NCERC

    Energy Technology Data Exchange (ETDEWEB)

    Jackman, Kevin Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mosby, Michelle A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bredeweg, Todd Allen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hutchens, Gregory Joe [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); White, Morgan Curtis [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-04-15

    Several irradiations have been conducted on assemblies (COMET/ZEUS and Flattop) at the National Criticality Experiments Research Center (NCERC) located at the Nevada National Security Site (NNSS). Configurations of the assemblies and irradiated materials changed between experiments. Different metallic foils were analyzed using the radioactivation method by gamma-ray spectrometry to understand/characterize the neutron spectra. Results of MCNP calculations are shown. It was concluded that MCNP simulated spectra agree with experimental measurements, with the caveats that some data are limited by statistics at low-energies and some activation foils have low activities.

  11. Development of cold neutron depth profiling system at HANARO

    Energy Technology Data Exchange (ETDEWEB)

    Park, B.G. [Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon 305-355 (Korea, Republic of); Sun, G.M., E-mail: gmsun@kaeri.re.kr [Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon 305-355 (Korea, Republic of); Choi, H.D. [Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of)

    2014-07-01

    A neutron depth profiling (NDP) system has been designed and developed at HANARO, a 30 MW research reactor at the Korea Atomic Energy Research Institute (KAERI). The KAERI-NDP system utilizes cold neutrons that are transported along the CG1 neutron guide from the cold neutron source and it consists of a neutron beam collimator, a target chamber, a beam stopper, and charged particle detectors along with NIM-standard modules for charged particle pulse-height analysis. A 60 cm in diameter stainless steel target chamber was designed to control the positions of the sample and detector. The energy distribution of the cold neutron beam at the end of the neutron guide was calculated by using the Monte Carlo simulation code McStas, and a neutron flux of 1.8×10{sup 8} n/cm{sup 2} s was determined by using the gold foil activation method at the sample position. The performance of the charged particle detection of the KAERI-NDP system was tested by using Standard Reference Materials. The energy loss spectra of alpha particles and Li ions emitted from {sup 10}B, which was irradiated by cold neutrons, were measured. The measured peak concentration and the areal density of {sup 10}B in the Standard Reference Material are consistent with the reference values within 1% and 3.4%, respectively.

  12. Development of cold neutron depth profiling system at HANARO

    Science.gov (United States)

    Park, B. G.; Sun, G. M.; Choi, H. D.

    2014-07-01

    A neutron depth profiling (NDP) system has been designed and developed at HANARO, a 30 MW research reactor at the Korea Atomic Energy Research Institute (KAERI). The KAERI-NDP system utilizes cold neutrons that are transported along the CG1 neutron guide from the cold neutron source and it consists of a neutron beam collimator, a target chamber, a beam stopper, and charged particle detectors along with NIM-standard modules for charged particle pulse-height analysis. A 60 cm in diameter stainless steel target chamber was designed to control the positions of the sample and detector. The energy distribution of the cold neutron beam at the end of the neutron guide was calculated by using the Monte Carlo simulation code McStas, and a neutron flux of 1.8×108 n/cm2 s was determined by using the gold foil activation method at the sample position. The performance of the charged particle detection of the KAERI-NDP system was tested by using Standard Reference Materials. The energy loss spectra of alpha particles and Li ions emitted from 10B, which was irradiated by cold neutrons, were measured. The measured peak concentration and the areal density of 10B in the Standard Reference Material are consistent with the reference values within 1% and 3.4%, respectively.

  13. Measuring the basic parameters of neutron stars using model atmospheres

    CERN Document Server

    Suleimanov, V F; Klochkov, D; Werner, K

    2015-01-01

    Model spectra of neutron star atmospheres are nowadays widely used to fit the observed thermal X-ray spectra of neutron stars. This fitting is the key element in the method of the neutronstar radius determination. Here, we present the basic assumptions used for the neutron star atmosphere modeling as well as the main qualitative features of the stellar atmospheres leading to the deviations of the emergent model spectrum from blackbody. We describe the properties of two of our model atmosphere grids: (i) pure carbon atmospheres for relatively cool neutron stars (1--4 MK) and (ii) hot atmospheres with Compton scattering taken into account. The results obtained by applying these grids to model the X-ray spectra of the central compact object in supernova remnant HESS 1731-347, and two X-ray bursting neutron stars in low-mass X-ray binaries, 4U 1724-307 and 4U 1608-52, are presented. Possible systematic uncertainties associated with the obtained neutron star radii are discussed.

  14. Radioactivity measurements of ITER materials using the TFTR D-T neutron field

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, A.; Abdou, M.A. [California Univ., Los Angeles, CA (United States). School of Engineering and Applied Science; Barnes, C.W. [Los Alamos National Lab., NM (United States); Kugel, H.W. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Loughlin, M.J. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking

    1994-08-01

    The availability of high D-T fusion neutron yields at TFTR has provided a useful opportunity to directly measure D-T neutron-induced radioactivity in a realistic tokamak fusion reactor environment for materials of vital interest to ITER. These measurements are valuable for characterizing radioactivity in various ITER candidate materials. for validating complex neutron transport calculations, and for meeting fusion reactor licensing requirements. The radioactivity measurements at TFTR involve potential ITER materials including stainless steel 316, vanadium, titanium, chromium, silicon, iron, cobalt, nickel, molybdenum, aluminum, copper, zinc. zirconium, niobium, and tungsten. Small samples of these materials were irradiated close to the plasma and just outside the vacuum vessel wall of TFTR, locations of different neutron energy spectra. Saturation activities for both threshold and capture reactions were measured. Data from dosimetric reactions have been used to obtain preliminary neutron energy spectra. Spectra from the first wall were compared to calculations from ITER and to measurements from accelerator-based tests.

  15. Controllability of depth dose distribution for neutron capture therapy at the Heavy Water Neutron Irradiation Facility of Kyoto University Research Reactor.

    Science.gov (United States)

    Sakurai, Yoshinori; Kobayashi, Tooru

    2002-10-01

    The updating construction of the Heavy Water Neutron Irradiation Facility of the Kyoto University Research Reactor has been performed from November 1995 to March 1996 mainly for the improvement in neutron capture therapy. On the performance, the neutron irradiation modes with the variable energy spectra from almost pure thermal to epi-thermal neutrons became available by the control of the heavy-water thickness in the spectrum shifter and by the open-and-close of the cadmium and boral thermal neutron filters. The depth distributions of thermal, epi-thermal and fast neutron fluxes were measured by activation method using gold and indium, and the depth distributions of gamma-ray absorbed dose rate were measured using thermo-luminescent dosimeter of beryllium oxide for the several irradiation modes. From these measured data, the controllability of the depth dose distribution using the spectrum shifter and the thermal neutron filters was confirmed.

  16. Measurement of neutron-induced activation cross-sections using spallation source at JINR and neutronic validation of the Dubna code

    Indian Academy of Sciences (India)

    Manish Sharma; V Kumar; H Kumawat; J Adam; V S Barashenkov; S Ganesan; S Golovatiouk; S K Gupta; S Kailas; M I Krivopustov; H S Palsania; V Pronskikh; V M Tsoupko-Sitnikov; N Vladimirova; H Westmeier; W Westmeier

    2007-02-01

    A beam of 1 GeV proton coming from Dubna Nuclotron colliding with a lead target surrounded by 6 cm paraffin produces spallation neutrons. A Th-foil was kept on lead target (neutron spallation source) in a direct stream of neutrons for activation and other samples of 197Au, 209Bi, 59Co, 115In and 181Ta were irradiated by moderated beam of neutrons passing through 6 cm paraffin moderator. The gamma spectra of irradiated samples were analyzed using gamma spectrometry and DEIMOS software to measure the neutron cross-section. For this purpose neutron fluence at the positions of samples is also estimated using PREPRO software. The results of cross-sections for reactions 232Th(, ), 232Th(, 2), 197Au(, ), 197Au(, ), 197Au(, ), 59Co(, ), 59Co(, ), 181Ta(, ) and 181Ta(, ) are given in this paper. Neutronics validation of the Dubna Cascade Code is also done using cross-section data by other experiments.

  17. Measurement of internal conversion electrons from Gd neutron capture

    Energy Technology Data Exchange (ETDEWEB)

    Kandlakunta, P. [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210 (United States); Cao, L.R., E-mail: cao.152@osu.edu [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210 (United States); Mulligan, P. [Nuclear Engineering Program, Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210 (United States)

    2013-03-21

    Gadolinium (Gd) is a suitable material for neutron conversion because of its superior neutron absorption cross-section. However, the principal secondary particles that generate electron-hole pairs in a semiconductor detector after Gd neutron capture are low-energy internal conversion (IC) electrons. We measured the IC electron spectrum due to Gd neutron capture by using a thermal neutron beam and a digitizer-based multidetector spectroscopy. We also discussed the effective use of the IC electrons in the context of a twin-detector design and the associated gamma-ray rejection issues. Extensive simulations of the spectra of IC electrons and gamma rays agreed well with the experimental results; both types of results support the feasibility of the proposed n–γ separation method.

  18. Beta-delayed neutron decay of {sup 33}Na

    Energy Technology Data Exchange (ETDEWEB)

    Radivojevic, Z. E-mail: zoran.radivojevic@phys.jyu.fi; Baumann, P.; Caurier, E.; Cederkaell, J.; Courtin, S.; Dessagne, Ph.; Jokinen, A.; Knipper, A.; Scornet, G.L.G. Le; Lyapin, V.; Miehe, Ch.; Nowacki, F.; Nummela, S.; Oinonen, M.; Poirier, E.; Ramdhane, M.; Trzaska, W.H.; Walter, G.; Aeystoe, J

    2002-04-01

    Beta-delayed neutron decay of {sup 33}Na has been studied using the on-line mass separator ISOLDE. The delayed neutron spectra were measured by time-of-flight technique using fast scintillators. Two main neutron groups at 800(60) and 1020(80) keV were assigned to the {sup 33}Na decay, showing evidence for strong feeding of states at about 4 MeV in {sup 33}Mg. By simultaneous {beta}-{gamma}-n counting the delayed neutron emission probabilities P{sub 1n}=47(6)% and P{sub 2n}=13(3)% were determined. The half-life value for {sup 33}Na, T{sub 1/2}=8.0(3) ms, was measured by three different techniques, one employing identifying gamma transitions and two employing beta and neutron counting.

  19. Observational constraints on neutron star masses and radii

    Energy Technology Data Exchange (ETDEWEB)

    Coleman Miller, M. [University of Maryland, Department of Astronomy and Joint Space-Science Institute, College Park, MD (United States); Lamb, Frederick K. [University of Illinois at Urbana-Champaign, Center for Theoretical Astrophysics and Department of Physics, Urbana, IL (United States); University of Illinois at Urbana-Champaign, Department of Astronomy, Urbana, IL (United States)

    2016-03-15

    Precise and reliable measurements of the masses and radii of neutron stars with a variety of masses would provide valuable guidance for improving models of the properties of cold matter with densities above the saturation density of nuclear matter. Several different approaches for measuring the masses and radii of neutron stars have been tried or proposed, including analyzing the X-ray fluxes and spectra of the emission from neutron stars in quiescent low-mass X-ray binary systems and thermonuclear burst sources; fitting the energy-dependent X-ray waveforms of rotation-powered millisecond pulsars, burst oscillations with millisecond periods, and accretion-powered millisecond pulsars; and modeling the gravitational radiation waveforms of coalescing double neutron star and neutron star - black hole binary systems. We describe the strengths and weaknesses of these approaches, most of which currently have substantial systematic errors, and discuss the prospects for decreasing the systematic errors in each method. (orig.)

  20. Neutron spectroscopy at the turn of the century

    CERN Document Server

    Popov, Yu P

    2003-01-01

    Neutron spectrometry is a powerful method of investigating atomic nuclei and condensed matter. Such investigations provide necessary data for a very wide spectrum of scientific and technological applications from the fundamental problems of the structure of matter and nucleosynthesis in the Universe to atomic power technologies and the structure of condensed matter. The most frequently utilized is the time-of-flight (TOF) method for powerful pulsed neutron sources. However, in many cases, one can use more effective, simpler and cheaper methods. For example, for astrophysics and radioactive waste transmutation problems, it is sufficient to know an average resonance cross section or "resonance integrals" for capture and fission reactions for neutron spectra specific to neutron fluxes in stars or in the active zone of a transmutation reactor. In these cases, the slow-down neutron spectroscopy (SDNS) methods in lead and graphite moderators will be useful. Compared to the TOF method, the lead SDNS gives a 10/sup 3...

  1. Observational Constraints on Neutron Star Masses and Radii

    CERN Document Server

    Miller, M Coleman

    2016-01-01

    Precise and reliable measurements of the masses and radii of neutron stars with a variety of masses would provide valuable guidance for improving models of the properties of cold matter with densities above the saturation density of nuclear matter. Several different approaches for measuring the masses and radii of neutron stars have been tried or proposed, including analyzing the X-ray fluxes and spectra of the emission from neutron stars in quiescent low-mass X-ray binary systems and thermonuclear burst sources; fitting the energy-dependent X-ray waveforms of rotation-powered millisecond pulsars, burst oscillations with millisecond periods, and accretion-powered millisecond pulsars; and modeling the gravitational radiation waveforms of coalescing double neutron star and neutron star -- black hole binary systems. We describe the strengths and weaknesses of these approaches, most of which currently have substantial systematic errors, and discuss the prospects for decreasing the systematic errors in each method...

  2. The influence of Neutron Irradiation in CR-39 polymer

    Directory of Open Access Journals (Sweden)

    Sangeeta Prasher

    2015-06-01

    Full Text Available The script allocates the influence of neutron irradiations on the structural and optical properties of CR-39. The structural properties of the polymer have been examined using the FTIR spectrum of the pristine and neutron beam irradiated polymer. The studies reveal the increase the intensity of some bands with neutron irradiation pointing the increase in the unsaturated behavior of the polymer. The optical properties analyzed using the UV-Vis spectra made it evident that CR-39 gets easily influenced at a fluence of 1016 n/cm2. The glassy characteristics of the polymer also found to diminish with increasing neutron irradiation. Significant variations in the property profile of the polymer have been observed at higher neutron fluence.

  3. Neutron-antineutron oscillations beyond the quasi-free limit

    CERN Document Server

    Davis, E David

    2016-01-01

    Prompted by plans to conduct a new neutron oscillation experiment at the European Spallation Source (ESS), we consider issues associated with the magnetic field that must be present, some of which are potentially exacerbated by the significantly larger length $l$ contemplated for the neutron propagation region. To this end, we introduce a stochastic model of the residual magnetic field within the propagation region which draws on features of magnetic profiles measured during the last free neutron oscillation experiment [conducted at the Institut Laue-Langevin (ILL) in the 1990's]. We average over both fluctuations in the magnetic field sampled by neutrons, and representative spectra of neutron speeds. We find that deviations from the quasi-free result for the antineutron probability do not depend quadratically on $l$ (as a naive perturbative estimate would suggest) but increase only linearly with $l$. As regards the large spikes in the magnetic field which can be expected at, for example, joints in the magnet...

  4. Neutron dosimetric measurements in shuttle and MIR.

    Science.gov (United States)

    Reitz, G

    2001-06-01

    Detector packages consisting of thermoluminescence detectors (TLD), nuclear emulsions and plastic track detectors were exposed at identical positions inside MIR space station and on shuttle flights inside Spacelab and Spacehab during different phases of the solar cycle. The objectives of the investigations are to provide data on charge and energy spectra of heavy ions, and the contribution of events with low-energy deposit (protons, electrons, gamma, etc.) to the dose, as well as the contribution of secondaries, such as nuclear disintegration stars and neutrons. For neutron dosimetry 6LiF (TLD600) and 7LiF (TLD700) chips were used both of which have almost the same response to gamma rays but different response to neutrons. Neutrons in space are produced mainly in evaporation and knock-on processes with energies mainly of 1-10 MeV and up to several 100 MeV, respectively. The energy spectrum undergoes continuous changes toward greater depth in the attenuating material until an equilibrium is reached. In equilibrium, the spectrum is a wide continuum extending down to thermal energies to which the 6LiF is sensitive. Based on the difference of absorbed doses in the 6LiF and 7LiF chips, thermal neutron fluxes from 1 to 2.3 cm-2 s-1 are calculated using the assumption that the maximum induced dose in TLD600 for 1 neutron cm-2 is 1.6 x 10(-10) Gy (Horowitz and Freeman, Nucl. Instr. and Meth. 157 (1978) 393). It is assumed that the flux of high-energy neutrons is at least of that quantity. Tissue doses were calculated taking as a mean ambient absorbed dose per neutron 6 x10(-12) Gy cm2 (for a10 MeV neutron). The neutron equivalent doses for the above-mentioned fluxes are 52 micro Gy d-1 and 120 micro Gy d-1. In recent experiments, a personal neutron dosimeter was integrated into the dosimeter packages. First results of this dosimeter which is based on nuclear track detectors with converter foils are reported. For future measurements, a scintillator counter with

  5. Measurement of photoneutron spectrum at Pohang Neutron Facility

    CERN Document Server

    Kim, G N; Lee, Y S; Skoy, V; Cho, M H; Ko, I S; Namkung, W; Lee, D W; Kim, H D; Ko, S K; Park, S H; Kim, D S; Ro, T I; Min, Y G

    2002-01-01

    The Pohang Neutron Facility, an electron linear accelerator (linac) based pulsed neutron facility, was constructed for nuclear data production in Korea. It consists of an electron linac, a water-cooled Ta target with a water moderator, and a time-of-flight path with an 11 m length. The neutron energy spectra are measured for different water levels inside the moderator and compared with calculations by the Monte Carlo N-Particle transport code. The optimum size of the water moderator is determined based on these results.

  6. Investigation of the response characteristics of OSL albedo neutron dosimeters in a 241AmBe reference neutron field

    Science.gov (United States)

    Liamsuwan, T.; Wonglee, S.; Channuie, J.; Esoa, J.; Monthonwattana, S.

    2017-06-01

    The objective of this work was to systematically investigate the response characteristics of optically stimulated luminescence Albedo neutron (OSLN) dosimeters to ensure reliable personal dosimetry service provided by Thailand Institute of Nuclear Technology (TINT). Several batches of InLight® OSLN dosimeters were irradiated in a reference neutron field generated by the in-house 241AmBe neutron irradiator. The OSL signals were typically measured 24 hours after irradiation using the InLight® Auto 200 Reader. Based on known values of delivered neutron dose equivalent, the reading correction factor to be used by the reader was evaluated. Subsequently, batch homogeneity, dose linearity, lower limit of detection and fading of the OSLN dosimeters were examined. Batch homogeneity was evaluated to be 0.12 ± 0.05. The neutron dose response exhibited a linear relationship (R2=0.9974) within the detectable neutron dose equivalent range under test (0.4-3 mSv). For this neutron field, the lower limit of detection was between 0.2 and 0.4 mSv. Over different post-irradiation storage times of up to 180 days, the readings fluctuated within ±5%. Personal dosimetry based on the investigated OSLN dosimeter is considered to be reliable under similar neutron exposure conditions, i.e. similar neutron energy spectra and dose equivalent values.

  7. Conceptual study of a compact accelerator-driven neutron source for radioisotope production, boron neutron capture therapy and fast neutron therapy

    CERN Document Server

    Angelone, M; Rollet, S

    2002-01-01

    The feasibility of a compact accelerator-driven device for the generation of neutron spectra suitable for isotope production by neutron capture, boron neutron capture therapy and fast neutron therapy, is analyzed by Monte Carlo simulations. The device is essentially an extension of the activator proposed by Rubbia left bracket CERN/LHC/97-04(EET) right bracket , in which fast neutrons are diffused and moderated within a properly sized lead block. It is shown that by suitable design of the lead block, as well as of additional elements of moderating and shielding materials, one can generate and exploit neutron fluxes with the spectral features required for the above applications. The linear dimensions of the diffusing-moderating device can be limited to about 1 m. A full-scale device for all the above applications would require a fast neutron source of about 10**1**4 s**-**1, which could be produced by a 1 mA, 30 MeV proton beam impinging on a Be target. The concept could be tested at the Frascati Neutron Gener...

  8. Pulse-shape analysis for gamma background rejection in thermal neutron radiation using CVD diamond detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kavrigin, P., E-mail: pavel.kavrigin@cividec.at [Vienna University of Technology (Austria); Finocchiaro, P., E-mail: finocchiaro@lns.infn.it [INFN Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Griesmayer, E., E-mail: erich.griesmayer@cividec.at [Vienna University of Technology (Austria); Jericha, E., E-mail: jericha@ati.ac.at [Vienna University of Technology (Austria); Pappalardo, A., E-mail: apappalardo@lns.infn.it [INFN Laboratori Nazionali del Sud, via S.Sofia 62, 95123 Catania (Italy); Weiss, C., E-mail: Christina.Weiss@cern.ch [Vienna University of Technology (Austria); European Organisation for Nuclear Research (CERN), Geneva (Switzerland)

    2015-09-21

    A novel technique for the rejection of gamma background from charged-particle spectra was demonstrated using a CVD diamond detector with a {sup 6}Li neutron converter installed at a thermal neutron beamline of the TRIGA research reactor at the Atominstitut (Vienna University of Technology). Spectra of the alpha particles and tritons of {sup 6}Li(n,T){sup 4}He thermal neutron capture reaction were separated from the gamma background by a new algorithm based on pulse-shape analysis. The thermal neutron capture in {sup 6}Li is already used for neutron flux monitoring, but the ability to remove gamma background allows using a CVD diamond detector for thermal neutron counting. The pulse-shape analysis can equally be applied to all cases where the charged products of an interaction are absorbed in the diamond and to other background particles that fully traverse the detector.

  9. Monte Carlo study of neutronics properties of the modular storage geometry

    Energy Technology Data Exchange (ETDEWEB)

    Bell, Z.W.

    1995-09-01

    The modular storage vault (MSV) geometry was investigated for its effects on the spectrum of neutrons from the spontaneous and induced fission of plutonium. Zinc alloy and aluminum alloy plates that will house neutron detectors and weight sensors were included. It was found that because of the large number of captures by plutonium and the steel and concrete MSV structure, only 12% of the neutron spectrum in the vicinity of the detector position was thermalized and over half of the neutrons incident on the detector position have energy in excess of 100 keV. Based on this, it is recommended that both fast and slow neutron detectors be included in the instrumentation package if plutonium is to be stored an MSV structure. No differences in the neutron spectra were found with different zinc alloys. In addition, insufficient differences in the spectra were found when aluminum was substituted for zinc to warrant any recommendation for one material over the other.

  10. Action spectra again?

    Science.gov (United States)

    Coohill, T P

    1991-11-01

    Action spectroscopy has a long history and is of central importance to photobiological studies. Action spectra were among the first assays to point to chlorophyll as the molecule most responsible for plant growth and to DNA as the genetic material. It is useful to construct action spectra early in the investigation of new areas of photobiological research in an attempt to determine the wavelength limits of the radiation region causing the studied response. But due to the severe absorption of ultraviolet (UV) radiation by biological samples, UV action spectra were first limited to small cells (bacteria and fungi). Advances in techniques (e.g. single cell culture) and analysis allowed accurate action spectra to be reported even for mammalian cells. But precise analytical action spectra are often difficult to obtain when large, pigmented, or groups of cells are investigated. Here some action spectra are limited in interpretation and merely supply a wavelength vs effect curve. When polychromatic sources are employed, the interpretation of action spectra is even more complex and formidable. But such polychromatic action spectra can be more directly related to ambient responses. Since precise action spectra usually require the completion of a relatively large number of careful experiments using somewhat sophisticated equipment over a range of at least six wavelengths, they are often not pursued. But they remain central to the elucidation of the effect being studied. The worldwide community has agreed that stratospheric ozone is depleting, with the possibility of a consequent rise in the amount of UV-B (290-320 nm) reaching the earth's surface. It is therefore essential that new action spectra be completed for UV-B effects on a large variety of responses of human, animal, and aquatic plant systems. Combining these action spectra with the known amounts of UV-B reaching the biosphere can give rise to solar UV effectiveness spectra that, in turn, can give rise to estimates

  11. Acoustic response of superheated droplet detectors to neutrons

    Science.gov (United States)

    Gao, Size; Zhang, Guiying; Ni, Bangfa; Zhao, Changjun; Zhang, Huanqiao; Guan, Yongjing; Chen, Zhe; Xiao, Caijin; Liu, Chao; Liu, Cunxiong

    2012-03-01

    The search for dark matter (DM) is a hot field nowadays, a number of innovative techniques have emerged. The superheated droplet technique is relatively mature; however, it is recently revitalized in a number of frontier fields including the search for DM. In this work, the acoustic response of Superheated Droplet Detectors (SDDs) to neutrons was studied by using a 252Cf neutron source, SDDs developed by the China Institute of Atomic Energy, a sound sensor, a sound card and a PC. Sound signals were filtered. The characteristics of FFT spectra, power spectra and time constants were used to determine the authenticity of the bubbles analyzed.

  12. Modelling of reaction cross sections and prompt neutron emission

    Directory of Open Access Journals (Sweden)

    Oberstedt S.

    2010-10-01

    Full Text Available Accurate nuclear data concerning reaction cross sections and the emission of prompt fission neutrons (i.e. multiplicity and spectra as well as other fission fragment data are of great importance for reactor physics design, especially for the new Generation IV nuclear energy systems. During the past years for several actinides (238U(n, f and 237Np(n, f both the reaction cross sections and prompt neutron multiplicities and spectra have been calculated within the frame of the EFNUDAT project.

  13. Neutron scattering. Experiment manuals

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  14. Grazing Incidence Neutron Optics

    Science.gov (United States)

    Gubarev, Mikhail V. (Inventor); Ramsey, Brian D. (Inventor); Engelhaupt, Darell E. (Inventor)

    2013-01-01

    Neutron optics based on the two-reflection geometries are capable of controlling beams of long wavelength neutrons with low angular divergence. The preferred mirror fabrication technique is a replication process with electroform nickel replication process being preferable. In the preliminary demonstration test an electroform nickel optics gave the neutron current density gain at the focal spot of the mirror at least 8 for neutron wavelengths in the range from 6 to 20.ANG.. The replication techniques can be also be used to fabricate neutron beam controlling guides.

  15. Neutron scatter camera

    Science.gov (United States)

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

    2010-06-22

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

  16. Improved fission neutron energy discrimination with 4He detectors through pulse filtering

    Science.gov (United States)

    Zhu, Ting; Liang, Yinong; Rolison, Lucas; Barker, Cathleen; Lewis, Jason; Gokhale, Sasmit; Chandra, Rico; Kiff, Scott; Chung, Heejun; Ray, Heather; Baciak, James E.; Enqvist, Andreas; Jordan, Kelly A.

    2017-03-01

    This paper presents experimental and computational techniques implemented for 4He gas scintillation detectors for induced fission neutron detection. Fission neutrons are produced when natural uranium samples are actively interrogated by 2.45 MeV deuterium-deuterium fusion reaction neutrons. Fission neutrons of energies greater than 2.45 MeV can be distinguished by their different scintillation pulse height spectra since 4He detectors retain incident fast neutron energy information. To enable the preferential detection of fast neutrons up to 10 MeV and suppress low-energy event counts, the detector photomultiplier gain is lowered and trigger threshold is increased. Pile-up and other unreliable events due to the interrogating neutron flux and background radiation are filtered out prior to the evaluation of pulse height spectra. With these problem-specific calibrations and data processing, the 4He detector's accuracy at discriminating fission neutrons up to 10 MeV is improved and verified with 252Cf spontaneous fission neutrons. Given the 4He detector's ability to differentiate fast neutron sources, this proof-of-concept active-interrogation measurement demonstrates the potential of special nuclear materials detection using a 4He fast neutron detection system.

  17. Neutron field features in a calibration hall

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R. [Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas (Mexico)]. E-mail: rvega@cantera.reduaz.mx; Gallego, E.; Lorente, A. [Nuclear Engineering Department, Universidad Politecnica de Madrid C/Jose Gutierrez Abascal, 2, E-28006- Madrid (Spain)

    2004-07-01

    A new source facility ({sup 241} Am-Be) has been installed in a large size bunker-type room. To characterize the neutron fields in the facility, detailed calculations have been made with MCNP-4C, showing the different components of the neutron radiation reaching the reference points (direct, in scattered, backscattered). The contribution from neutrons scattered in the walls to the total ambient dose equivalent remains reasonably low (< 10%) in the reference points. Additionally, spectra measurements have been performed with a Bonner spheres spectrometer with a {sup 6}LiI(Eu) scintillator (0.4 cm 0 x 0.4 cm), UTA4 response matrix and BUNKIUT unfolding code. The calculated and experimentally obtained spectra are compared, with small differences found in the epithermal and thermal region, attributable to the concrete composition used in the calculations. The H*(10) rate has been determined from the spectra, and then compared to the reading of an active dosemeter (LB 6411), with differences found lower than 8%. (Author)

  18. Neutron spectrum measurement in D + Be reaction

    CERN Document Server

    Abbasi-Davani, F; Aslani, G R; Etaati, G R; Koohi-Fayegh, R

    2002-01-01

    In this project the neutron spectra from the reaction of deuteron on beryllium nuclei is measured. The energies of deuterons were 7, 10, 13 and 15 MeV, and these measurements are performed at 10,30 and 50 degrees relative to the beam of deuterons. The detector used is 76 by 76 mm right circular cylinder of N E-213 liquid scintillator. The zero crossing technique is used for gamma discrimination. For the elimination of the background radiation, a Polyethylene block, 40 cm in thickness, with inserted cadmium sheets, and a lead block, 5 cm in thickness, were used. In order to obtain the background radiation spectrum, the latter blocks were placed between the target and the detector to eliminate neutron and gamma radiations reaching the detector directly. sup F ORIST sup c ode is used to unfold the neutron spectra from the measured pulse high t spectra and sup O 5S sup a nd sup R ESPMG sup c odes are used to obtain the detector response matrix.

  19. Spectroscopy of neutron rich nuclei using cold neutron induced fission of actinide targets at the ILL: the EXILL campaign

    Directory of Open Access Journals (Sweden)

    de France G.

    2014-03-01

    Full Text Available A combination of germanium detectors has been installed at the PF1B neutron guide of the ILL to perform the prompt spectroscopy of neutron-rich nuclei produced in the neutron-capture induced-fission of 235U and 241Pu. In addition LaBr3 detectors from the FATIMA collaboration have been installed in complement with the EXOGAM clovers to measure lifetimes of low-lying excited states. The measured characteristics and online spectra indicate very good performances of the overall setup.

  20. Response of detector modules of the neutron hodoscope SENECA to neutrons with energies 7-70 MeV

    Science.gov (United States)

    v. Edel, G.; Selke, O.; Pöch, C.; Smend, F.; Schumacher, M.; Nolte, R.; Schrewe, U.; Brede, H. J.; Schuhmacher, H.; Henneck, R.

    1993-07-01

    SENECA is a hodoscope for recoil neutrons from photoreactions on nuclei and nucleons in the photon energy range 50-900 MeV. It consists of 32 hexagonal scintillation detector modules in a honeycomb array. Differential detection efficiency spectra of a single module as well as the cross-talk between neighbouring modules were measured at neutron energies between 7 and 70 MeV. Neutron detection efficiencies were determined in the same energy range with an average experimental uncertainty of 7.6%. The experimental results agree with predictions from Monte Carlo codes within the limits of the experimental error.

  1. Advances in neutron tomography

    Indian Academy of Sciences (India)

    W Treimer

    2008-11-01

    In the last decade neutron radiography (NR) and tomography (NCT) have experienced a number of improvements, due to the well-known properties of neutrons interacting with matter, i.e. the low attenuation by many materials, the strong attenuation by hydrogenous constituent in samples, the wavelength-dependent attenuation in the neighbourhood of Bragg edges and due to better 2D neutron detectors. So NR and NCT were improved by sophisticated techniques that are based on the attenuation of neutrons or on phase changes of the associated neutron waves if they pass through structured materials. Up to now the interaction of the neutron spin with magnetic fields in samples has not been applied to imaging techniques despite the fact that it was proposed many years ago. About ten years ago neutron depolarization as imaging signal for neutron radiography or tomography was demonstrated and in principle it works. Now one can present much improved test experiments using polarized neutrons for radiographic imaging. For this purpose the CONRAD instrument of the HMI was equipped with polarizing and analysing benders very similar to conventional scattering experiments using polarized neutrons. Magnetic fields in different coils and in samples (superconductors) at low temperatures could be visualized. In this lecture a summary about standard signals (attenuation) and the more `sophisticated' imaging signals as refraction, small angle scattering and polarized neutrons will be given.

  2. Neutronic Reactor Shield

    Science.gov (United States)

    Fermi, Enrico; Zinn, Walter H.

    The argument of the present Patent is a radiation shield suitable for protection of personnel from both gamma rays and neutrons. Such a shield from dangerous radiations is achieved to the best by the combined action of a neutron slowing material (a moderator) and a neutron absorbing material. Hydrogen is particularly effective for this shield since it is a good absorber of slow neutrons and a good moderator of fast neutrons. The neutrons slowed down by hydrogen may, then, be absorbed by other materials such as boron, cadmium, gadolinium, samarium or steel. Steel is particularly convenient for the purpose, given its effectiveness in absorbing also the gamma rays from the reactor (both primary gamma rays and secondary ones produced by the moderation of neutrons). In particular, in the present Patent a shield is described, made of alternate layers of steel and Masonite (an hydrolized ligno-cellulose material). The object of the present Patent is not discussed in any other published paper.

  3. Neutron beam test of barium fluoride crystal for dark matter direct detection

    Science.gov (United States)

    Guo, C.; Ma, X. H.; Wang, Z. M.; Bao, J.; Dai, C. J.; Guan, M. Y.; Liu, J. C.; Li, Z. H.; Ren, J.; Ruan, X. C.; Yang, C. G.; Yu, Z. Y.; Zhong, W. L.

    2016-10-01

    In order to test the capabilities of Barium Fluoride (BaF2) crystal for dark matter direct detection, nuclear recoils are studied with mono-energetic neutron beam. The energy spectra of nuclear recoils, quenching factors for elastic scattering neutrons and discrimination capability between neutron inelastic scattering events and γ events are obtained for various recoil energies of the F content in BaF2.

  4. Further observations of protons resulting from the decay of neutrons ejected by solar flares

    Science.gov (United States)

    Evenson, P. A.; Kroeger, R.; Meyer, P.

    1985-01-01

    The solar flare of 1984 April 24 produced a large gamma ray fluence with energy 2MeV. The time profile of the interplanetary flux from this flare indicates the presence of decaying solar neutrons. This makes a total of three neutron flares so far observed by this method. The three flares are used to place constraints on the fluence and spectra of neutrons emitted by the Sun.

  5. Neutron Beam Tests of Barium Fluoride Crystal for Dark Matter Direct Detection

    CERN Document Server

    Guo, Cong; Wang, Zhimin; Bao, Jie; Dai, Changjiang; Guan, Mengyun; Liu, Jinchang; Li, Zuhao; Ren, Jie; Ruan, Xichao; Yang, Changgen; Yu, Zeyuan; Zhong, Weili

    2016-01-01

    In order to test the capabilities of Barium Fluoride (BaF2) Crystal for dark matter direct detection, nuclear recoils are studied with mono-energetic neutron beam. The energy spectra of nuclear recoils, quenching factors for elastic scattering neutrons and discrimination capability between neutron inelastic scattering events and {\\gamma} events are obtained for various recoil energies of the F content in BaF2.

  6. Interfacing MCNPX and McStas for simulation of neutron transport

    OpenAIRE

    Klinkby, Esben Bryndt; Lauritzen, Bent; Nonbøl, Erik; Willendrup, Peter Kjær; Filges, Uwe; Wohlmuther, Michael; Gallmeier, Franz X.

    2013-01-01

    Simulations of target-moderator-reflector system at spallation sources are conventionally carried out using Monte Carlo codes such as MCNPX[1] or FLUKA[2, 3] whereas simulations of neutron transport from the moderator and the instrument response are performed by neutron ray tracing codes such as McStas[4, 5, 6, 7]. The coupling between the two simulation suites typically consists of providing analytical fits of MCNPX neutron spectra to McStas. This method is generally successful but has limit...

  7. Developing an interface between MCNP and McStas for simulation of neutron moderators

    OpenAIRE

    Klinkby, Esben Bryndt; Lauritzen, Bent; Nonbøl, Erik; Willendrup, Peter Kjær

    2012-01-01

    Simulations of target-moderator-reflector system at spallation sources are conventionally carried out using MCNP/X whereas simulations of neutron transport and instrument performance are carried out by neutron ray tracing codes such as McStas. The coupling between the two simulations suites typically consists of providing analytical fits from MCNP/X neutron spectra to McStas. This method is generally successful, but as will be discussed in the this paper, there are limitations and a more dire...

  8. Research of Methodocal Questions of Use of Albedo Personal Neutron Dosi-meter

    CERN Document Server

    Alekseev, A G

    2003-01-01

    In the paper the methods of reception of the correct use of neutron albedo dosimeters are considered. The methods of use such dosimeters in fields with different spectra of neutrons are presented. For testing the experi-mental research of sensitivity DVGN-01and DVN-A-01 dosimeters in reference neutron fields was formed on based of 1-st horizontal research channel of IRT MIPHI reactor.

  9. An Exploration of Neutron Detection in Semiconducting Boron Carbide

    Science.gov (United States)

    Hong, Nina

    . Because neutron detection measurements indicate that charge capture in boron carbide is affected by the nanocrystalline/amorphous nature of the semiconductor, the effects of incomplete charge collection efficiencies on the neutron detection efficiencies and pulse height spectra in heterostructured p-n diode neutron detectors have been modeled using a Monte Carlo GEANT4 simulation. The dissertation ends with suggestions for devices with improved neutron detection efficiencies.

  10. A real time scintillating fiber Time of Flight spectrometer for LINAC photoproduced neutrons

    NARCIS (Netherlands)

    Maspero, M; Berra, Alessandro; Conti, Valentina; Giannini, G.; Ostinelli, A.; Prest, M.; Vallazza, E.

    2015-01-01

    The use of high-energy (> 8MeV) LINear ACcelerators (LINACs) for medical cancer treatments causes the photoproduction of secondary neutrons, whose unwanted dose to the patient has to be calculated. The characterization of the neutron spectra is necessary to allow the dosimetric evaluation of the neu

  11. Experimental investigation of space--energy distributions of slow neutrons in water near plane absorber

    Energy Technology Data Exchange (ETDEWEB)

    Hussein, A.; El-Konsol, S.; Novikov, A.; Zakharkin, I.; Hamouda, I.

    1973-12-31

    A mechanical neutron time-of-flight spectrometer was used to measure neutron space-energy distributions near a cadmium plate, of 1 mm thickness, immersed in a water-filled tank. The ET-RR-1 reactor served as a neutron source. Measurements of thermal and resonance neutron distributions, using activation technique, were performed in the tank with and without the cadmium plate. Measurements were made of the neutron spectra emerging normally from the plate ( mu = +1). The spectra were measured at the distances 0, 0.25, 0.5, 1.5, 3.0, and 5.0 cm from the plate surface. An exit tube was used to extract the neutron beam from the region of measurement. The required corrections were introduced to the measured spectra. The measurements are discussed and analyzed in the framework of the neutron temperature approximation. An appreciable softening effect is observed for the measured neutron spectra of mu = +1. The temperature for the spectrum at a distance of 0.25 cm from the plate was 41 deg lower than that of the asymptotic spectrum, and the softening effect relaxed and vanished at a distance of 5 cm. (18 figures) (auth)

  12. Inelastic neutron scattering applied to the investigation of collective excitations in topologically disordered matter

    Directory of Open Access Journals (Sweden)

    J.-B.Suck

    2008-03-01

    Full Text Available Inelastic neutron scattering techniques are introduced here as one of the most important experimental techniques in the investigation of collective excitations in fluids (liquids and compressed gases and amorphous solids. The correlation functions involved, the spectra of which are determined in inelastic neutron scattering experiments, the dispersion relations of the collective excitations and how they are obtained from the measured spectra and finally two of the most often used instrumental techniques are briefly discussed.

  13. Detection efficiency evaluation for a large area neutron sensitive microchannel plate detector

    CERN Document Server

    Wang, Yiming; Liu, Ren

    2016-01-01

    In this paper, the detection efficiency of a large area neutron sensitive microchannel plate detector has been evaluated. A 6LiF/ZnS detector was employed as the benchmark detector, the TOF spectra of these two detectors were simultaneously measured and the energy spectra were then deduced to calculate the detection efficiency curve of the nMCP detector. Tests show the detection efficiency@25.3 meV thermal neutron is 34% for this nMCP detector.

  14. Influence of thermal and resonance neutron on fast neutron flux measurement by Pu-239 fission chamber

    CERN Document Server

    zeng, Lina; Song, Lingli; Zheng, Chun

    2014-01-01

    The Pu-239 fission chambers are widely used to measure fission spectrum neutron flux due to a flat response to fast neutrons. However, in the mean time the resonance and thermal neutrons can cause a significant influence on the measurement if they are moderated, which could be eliminated by using B and Cd covers. At a column enriched uranium fast neutron critical assembly, the fission reaction rates of Pu-239 are measured as 1.791*10-16,2.350*10-16 and 1.385*10-15 per second for 15mm thick B cover, 0.5mm thick Cd cover, and no cover respectively. While the fission reaction rate of Pu-239 is rapidly increased to 2.569*10-14 for a 20mm thick polythene covering fission chamber. The average Pu-239 fission cross-section of thermal and resonance neutrons is calculated to be 500b and 24.95b with the assumption of 1/v and 1/E spectra respectively, then thermal, resonance and fast neutron flux are achieved to be 2.30*106,2.24*106 and 1.04*108cm-2s-1.

  15. Active neutron and gamma-ray imaging of highly enriched uranium for treaty verification.

    Science.gov (United States)

    Hamel, Michael C; Polack, J Kyle; Ruch, Marc L; Marcath, Matthew J; Clarke, Shaun D; Pozzi, Sara A

    2017-08-11

    The detection and characterization of highly enriched uranium (HEU) presents a large challenge in the non-proliferation field. HEU has a low neutron emission rate and most gamma rays are low energy and easily shielded. To address this challenge, an instrument known as the dual-particle imager (DPI) was used with a portable deuterium-tritium (DT) neutron generator to detect neutrons and gamma rays from induced fission in HEU. We evaluated system response using a 13.7-kg HEU sphere in several configurations with no moderation, high-density polyethylene (HDPE) moderation, and tungsten moderation. A hollow tungsten sphere was interrogated to evaluate the response to a possible hoax item. First, localization capabilities were demonstrated by reconstructing neutron and gamma-ray images. Once localized, additional properties such as fast neutron energy spectra and time-dependent neutron count rates were attributed to the items. For the interrogated configurations containing HEU, the reconstructed neutron spectra resembled Watt spectra, which gave confidence that the interrogated items were undergoing induced fission. The time-dependent neutron count rate was also compared for each configuration and shown to be dependent on the neutron multiplication of the item. This result showed that the DPI is a viable tool for localizing and confirming fissile mass and multiplication.

  16. Raman Spectra of Glasses

    Science.gov (United States)

    1986-11-30

    17), Raman spectra, plus a , . theoretical treatment of the data, f complex fluorozirconate 14 I anions in ZBLAN glasses and melts (16), and...based ZBLAN glasses ) 17. ICORS (International Conference on Raman Spectroscopy) Proceedings, London, England. Conferencf 5-9 Sep 88. (Molten silica...RESEARCH FINAL REPORT DTIC CONTRACT N00014-81-K-0501 &JELECTE 1 MAY 81 -- 30 NOV 86 EJJAN041989 V "RAMAN SPECTRA OF GLASSES " 0 During the five years of the

  17. Measurements of double-differential neutron emission cross sections of Nb and Bi for 11.5 MeV neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Ibaraki, Masanobu; Matsuyama, Shigeo; Soda, Daisuke; Baba, Mamoru; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering

    1997-03-01

    Double-differential neutron emission cross sections (DDXs) of Nb and Bi have been measured for 11.5MeV neutrons using the {sup 15N}(d,n){sup 16}O quasi-monoenergetic neutron source at Tohoku University 4.5MV Dynamitron facility. For En`>6MeV, DDXs were measured by the conventional TOF method (single-TOF:S-TOF). For En`<6MeV, where the S-TOF spectra were distorted by the background neutrons, we adopted a double-TOF method (D-TOF). By applying D-TOF method, we obtained DDXs down to 1MeV. (author)

  18. Measurements of double-differential neutron emission cross sections of {sup 6}Li and {sup 7}Li for 18 MeV neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Ibaraki, Masanobu; Baba, Mamoru; Matsuyama, Shigeo; Sanami, Toshiya; Win, T.; Miura, Takako; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering

    1997-03-01

    Double-differential neutron emission cross sections of {sup 6}Li and {sup 7}Li were measured for 18 MeV neutrons at Tohoku University 4.5 MV Dynamitron facility. Neutron emission spectra were obtained down to 1 MeV at 13 angles with energy resolution good enough to separate discrete levels. A care was taken to eliminate the sample-dependent background due to parasitic neutrons. Experimental results were in fair agreement with the JENDL-3.2 data and a simple model considering a three-body breakup process and discrete level excitations. (author)

  19. Characterization of the neutron field of the {sup 241}AmBe in a calibration room; Caracterizacion del campo de neutrones del {sup 241} AmBe en una sala para calibracion

    Energy Technology Data Exchange (ETDEWEB)

    Vega C, H.R. [UAZ, A.P. 336, 98000 Zacatecas (Mexico); Gallego, E.; Lorente, A. [Universidad Politecnica de Madrid, C. Jose Gutierrez Abascal 2, 28006 Madrid (Spain)] e-mail: rvega@cantera.reduaz.mx

    2003-07-01

    The field of neutrons produced by an isotopic source of neutrons of {sup 241} Am Be had been characterized. The characterization was carried out modeling those relevant details of the calibration room and simulating the neutron transport at different distances of the source. The calculated spectra were used to determine the equivalent environmental dose rate. A series of experiments were carried out with the Bonner sphere spectrometric system to measure the spectra in the same points where the calculations were carried out and with these spectra the rates of environmental dose were calculated. By means of a one sphere dosemeter type Berthold the rates of environmental dose were measured. To the one to compare the calculated spectra and measured its were found small differences in the group of the thermal neutrons due to the elementary composition used during the simulation. When comparing the derived rates starting from the calculated spectra with those measured it was found a maxim difference smaller to 13%. (Author)

  20. Status of spallation neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Oyama, Yukio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-03-01

    Existing and planned facilities using proton accelerator driven spallation neutron source are reviewed. These include new project of neutron science proposed from Japan Atomic Energy Research Institute. The present status of facility requirement and accelerator technology leads us to new era of neutron science such as neutron scattering research and nuclear transmutation study using very intense neutron source. (author)