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Sample records for neutronic reaction rate

  1. Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Iron

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    DESIG: E 263 09 ^TITLE: Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Iron ^SIGNUSE: Refer to Guide E 844 for guidance on the selection, irradiation, and quality control of neutron dosimeters. Refer to Practice E 261 for a general discussion of the determination of fast-neutron fluence rate with threshold detectors. Pure iron in the form of foil or wire is readily available and easily handled. Fig. 1 shows a plot of cross section as a function of neutron energy for the fast-neutron reaction 54Fe(n,p)54Mn (1). This figure is for illustrative purposes only to indicate the range of response of the 54Fe(n,p)54Mn reaction. Refer to Guide E 1018 for descriptions of recommended tabulated dosimetry cross sections. 54Mn has a half-life of 312.13 days (3) (2) and emits a gamma ray with an energy of 834.845 keV (5). (2) Interfering activities generated by neutron activation arising from thermal or fast neutron interactions are 2.57878 (46)-h 56Mn, 44.95-d (8) 59Fe, and 5.27...

  2. Neutron Scattering in Hydrogenous Moderators, Studied by Time Dependent Reaction Rate Method

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, L.G.; Moeller, E.; Purohit, S.N.

    1966-03-15

    The moderation and absorption of a neutron burst in water, poisoned with the non-1/v absorbers cadmium and gadolinium, has been followed on the time scale by multigroup calculations, using scattering kernels for the proton gas and the Nelkin model. The time dependent reaction rate curves for each absorber display clear differences for the two models, and the separation between the curves does not depend much on the absorber concentration. An experimental method for the measurement of infinite medium reaction rate curves in a limited geometry has been investigated. This method makes the measurement of the time dependent reaction rate generally useful for thermalization studies in a small geometry of a liquid hydrogenous moderator, provided that the experiment is coupled to programs for the calculation of scattering kernels and time dependent neutron spectra. Good agreement has been found between the reaction rate curve, measured with cadmium in water, and a calculated curve, where the Haywood kernel has been used.

  3. Standard Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 The purpose of this test method is to define a general procedure for determining an unknown thermal-neutron fluence rate by neutron activation techniques. It is not practicable to describe completely a technique applicable to the large number of experimental situations that require the measurement of a thermal-neutron fluence rate. Therefore, this method is presented so that the user may adapt to his particular situation the fundamental procedures of the following techniques. 1.1.1 Radiometric counting technique using pure cobalt, pure gold, pure indium, cobalt-aluminum, alloy, gold-aluminum alloy, or indium-aluminum alloy. 1.1.2 Standard comparison technique using pure gold, or gold-aluminum alloy, and 1.1.3 Secondary standard comparison techniques using pure indium, indium-aluminum alloy, pure dysprosium, or dysprosium-aluminum alloy. 1.2 The techniques presented are limited to measurements at room temperatures. However, special problems when making thermal-neutron fluence rate measurements in high-...

  4. Reaction rates for the s-process neutron source 22Ne+{\\alpha}

    CERN Document Server

    Longland, Richard; Karakas, Amanda I

    2012-01-01

    The 22Ne({\\alpha},n)25Mg reaction is an important source of neutrons for the s-process. In massive stars responsible for the weak component of the s-process, 22Ne({\\alpha},n)25Mg is the dominant source of neutrons, both during core helium burning and in shell carbon burning. For the main s-process component produced in Asymptotic Giant Branch (AGB) stars, the 13C({\\alpha},n)16O reaction is the dominant source of neutrons operating during the interpulse period, with the 22Ne+{\\alpha} source affecting mainly the s-process branchings during a thermal pulse. Rate uncertainties in the competing 22Ne({\\alpha},n)25Mg and 22Ne({\\alpha},{\\gamma})26Mg reactions result in large variations of s-process nucleosynthesis. Here, we present up-to-date and statistically rigorous 22Ne+{\\alpha} reaction rates using recent experimental results and Monte Carlo sampling. Our new rates are used in post-processing nucleosynthesis calculations both for massive stars and AGB stars. We demonstrate that the nucleosynthesis uncertainties ...

  5. Helium Ignition on Accreting Neutron Stars with a New Triple-α Reaction Rate

    Science.gov (United States)

    Peng, Fang; Ott, Christian D.

    2010-12-01

    We investigate the effect of a new triple-α reaction rate from Ogata et al. on helium ignition conditions on accreting neutron stars and on the properties of the subsequent type I X-ray burst. We find that the new rate leads to significantly lower ignition column density for accreting neutron stars at low accretion rates. We compare the results of our ignition models for a pure helium accretor to observations of bursts in ultracompact X-ray binaries (UCXBs), which are believed to have nearly pure helium donors. For \\dot{m}> 0.001 \\dot{m}_{{Edd}}, the new triple-α reaction rate from Ogata et al. predicts a maximum helium ignition column of ~3 × 109 g cm-2, corresponding to a burst energy of ~4 × 1040 erg. For \\dot{m}˜ 0.01 \\dot{m}_{{Edd}} at which intermediate long bursts occur, the predicted burst energies are at least a factor of 10 too low to explain the observed energies of such bursts in UCXBs. This finding adds to the doubts cast on the triple-α reaction rate of Ogata et al. by the low-mass stellar evolution results of Dotter & Paxton.

  6. Helium Ignition on Accreting Neutron Stars with a New Triple-alpha Reaction Rate

    CERN Document Server

    Peng, Fang

    2010-01-01

    We investigate the effect of a new triple-alpha reaction rate from Ogata et al. (2009) on helium ignition conditions on accreting neutron stars and on the properties of the subsequent type I X-ray burst. We find that the new rate leads to significantly lower ignition column density for accreting neutron stars at low accretion rates. We compare the results of our ignition models for a pure helium accretor to observations of bursts in ultra-compact X-ray binary (UCXBs), which are believed to have nearly pure helium donors. For mdot > 0.001 mdot_Edd, the new triple-alpha reaction rate from Ogata et al. (2009) predicts a maximum helium ignition column of ~ 3 x 10^9 g cm^{-2}, corresponding to a burst energy of ~ 4 x 10^{40} ergs. For mdot ~ 0.01 mdot_Edd at which intermediate long bursts occur, the predicted burst energies are at least a factor of 10 too low to explain the observed energies of such bursts in UCXBs. This finding adds to the doubts cast on the triple-alpha reaction rate of Ogata et al. (2009) by th...

  7. 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.

  8. Systematic effects on cross-section data derived from reaction rates at a cold neutron beam

    Energy Technology Data Exchange (ETDEWEB)

    Žerovnik, Gašper, E-mail: gasper.zerovnik@ijs.si [Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); European Commission, Joint Research Centre, Retieseweg 111, B-2440 Geel (Belgium); Becker, Björn [European Commission, Joint Research Centre, Retieseweg 111, B-2440 Geel (Belgium); Belgya, Tamás, E-mail: belgya.tamas@energia.mta.hu [Institute for Energy Security and Environmental Safety, Centre for Energy Research, Hungarian Academy of Sciences, 29-33 Konkoly-Thege Miklós Street, H-1121 Budapest (Hungary); Genreith, Christoph, E-mail: christoph.genreith@frm2.tum.de [Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, D-85748 Garching (Germany); Harada, Hideo, E-mail: harada.hideo@jaea.go.jp [Japan Atomic Energy Agency, Tokai-mura, 319-1195 Ibaraki (Japan); Kopecky, Stefan, E-mail: stefan.kopecky@ec.europa.eu [European Commission, Joint Research Centre, Retieseweg 111, B-2440 Geel (Belgium); Radulović, Vladimir, E-mail: vladimir.radulovic@ijs.si [Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); CEA, DEN, DER, Instrumentation, Sensors and Dosimetry Laboratory, Cadarache, F-13108 St-Paul-Lez-Durance (France); Sano, Tadafumi, E-mail: t-sano@rri.kyoto-u.ac.jp [Research Reactor Institute, Kyoto University, Kumatori-cho, 590-0494 Osaka (Japan); Schillebeeckx, Peter, E-mail: peter.schillebeeckx@ec.europa.eu [European Commission, Joint Research Centre, Retieseweg 111, B-2440 Geel (Belgium); and others

    2015-11-01

    The methodology to derive cross-section data from measurements in a cold neutron beam was studied. Mostly, capture cross-sections at thermal energy are derived relative to a standard cross-section, e.g. the cross-section of the {sup 1}H(n,γ), {sup 14}N(n,γ), or {sup 197}Au(n,γ) reaction, and proportionality between the standard and the measured cross-section, evaluated at different energies in the sub-thermal region, is often assumed. Due to this assumption the derived capture cross-section at thermal energy can be biased by more than 10%. Evidently the bias depends on how much the energy dependence of the cross-section deviates from a direct proportionality with the inverse of the neutron speed. The effect is reduced in case the cross-section is not derived at thermal energy but at an energy close to the average energy of the cold neutron beam. Nevertheless, it is demonstrated that the bias can only be avoided in case the energy dependence of the cross-section is known and proper correction factors are applied. In some cases the results are also biased when the attenuation of the neutron beam within the sample is neglected in the analysis. Some of the cross-section data reported in the literature suffer from such bias effects. Hence, the results have to be corrected using the correction factors presented in this paper.

  9. Neutron spectrum adjustment using reaction rate data acquired with a liquid dosimetry system

    Energy Technology Data Exchange (ETDEWEB)

    Smith, D.L. [Argonne National Lab., IL (United States); Ikeda, Y.; Uno, Y.; Maekawa, F. [JAERI, Tokai (Japan)

    1997-08-01

    A dosimetry technique based on neutron activation of circulating water with dissolved salts is discussed. The neutron source was the FNS accelerator at JAERI, Tokai, Japan. Yttrium chloride hexahydrate (YCl{sub 3{center_dot}}6H{sub 2}O) was the salt (264.9 grams dissolved in 16.094 liters of water). Gamma-ray yields were measured with an intrinsic Ge detector. The following reactions were examined: (1) {sup 16}O(n,p){sup 16}N (E{sub thresh} = 10.245 MeV, t{sub 1/2} = 7.13 sec, E{sub {gamma}} = 6.129 MeV); (2) {sup 37}Cl(n,p){sup 37}S (E{sub thresh} = 4.194 MeV, t{sub 1/2} = 5.05 min, E{sub {gamma}} = 3.104 MeV); (3) {sup 89}Y(n,n{prime}){sup 89m}Y (E{sub thresh} = 0.919 MeV, t{sub 1/2} = 16.06 sec, E{sub {gamma}} = 0.909 MeV). This paper describes use of the generalized least-squares (GLS) method to adjust the neutron spectrum.

  10. SENSMG: First-Order Sensitivities of Neutron Reaction Rates, Reaction-Rate Ratios, Leakage, keff, and α Using PARTISN

    Energy Technology Data Exchange (ETDEWEB)

    Favorite, Jeffrey A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-21

    SENSMG is a tool for computing first-order sensitivities of neutron reaction rates, reaction-rate ratios, leakage, keff, and α using the PARTISN multigroup discrete-ordinates code. SENSMG computes sensitivities to all of the transport cross sections and data (total, fission, nu, chi, and all scattering moments), two edit cross sections (absorption and capture), and the density for every isotope and energy group. It also computes sensitivities to the mass density for every material and derivatives with respect to all interface locations. The tool can be used for one-dimensional spherical (r) and two-dimensional cylindrical (r-z) geometries. The tool can be used for fixed-source and eigenvalue problems. The tool implements Generalized Perturbation Theory (GPT) as discussed by Williams and Stacey. Section II of this report describes the theory behind adjoint-based sensitivities, gives the equations that SENSMG solves, and defines the sensitivities that are output. Section III describes the user interface, including the input file and command line options. Section IV describes the output. Section V gives some notes about the coding that may be of interest. Section VI discusses verification, which is ongoing. Section VII lists needs and ideas for future work. Appendix A lists all of the input files whose results are presented in Sec. VI.

  11. Neutron Reactions in Astrophysics

    CERN Document Server

    Reifarth, R; Käppeler, F

    2014-01-01

    The quest for the origin of matter in the Universe had been the subject of philosophical and theological debates over the history of mankind, but quantitative answers could be found only by the scientific achievements of the last century. A first important step on this way was the development of spectral analysis by Kirchhoff and Bunsen in the middle of the 19$^{\\rm th}$ century, which provided first insight in the chemical composition of the sun and the stars. The energy source of the stars and the related processes of nucleosynthesis, however, could be revealed only with the discoveries of nuclear physics. A final breakthrough came eventually with the compilation of elemental and isotopic abundances in the solar system, which are reflecting the various nucleosynthetic processes in detail. This review is focusing on the mass region above iron, where the formation of the elements is dominated by neutron capture, mainly in the slow ($s$) and rapid ($r$) processes. Following a brief historic account and a sketc...

  12. Measurement of the $^{232}$Th (n, $\\gamma$ )/$^{58}$Ni (n, p) reaction rate ratio in the leakage neutron field of CFBR-II fast burst reactor

    CERN Document Server

    Qiang, Wang; Zihui, Ai; Chun, Zheng; Jian, Gong

    2016-01-01

    A ThO$_{2}$ sample with a nickel activation foil attached was irradiated in the leakage neutron field of CFBR-II reactor. The activities of the active products were measured after irradiation to obtain the reaction rates. The normalized reaction rates were also calculated based on the ENDF/B-VII.1, CENDL-3.1, JENDL-4.0, BROND-2.2 databases. The experimental reaction rate ratio is 4.37 with an uncertainty of 3.9\\% which is coincident with the ratios calculated based on the ENDFB-VII. 1, JENDL-4.0, BROND-2.2 databases, but is 11.2\\% larger than that based on CENDL-3.1 database.

  13. 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

  14. Neutron capture reactions at DANCE

    Science.gov (United States)

    Bredeweg, T. A.

    2008-05-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 4π BaF2 array consisting of 160 active detector elements. The primary purpose of the array is to perform neutron capture cross section measurements on small (>~100 μg) and/or radioactive (DANCE we have performed neutron capture cross section measurements on a wide array of medium to heavy mass nuclides. Measurements to date include neutron capture cross sections on 241,243Am, neutron capture and neutron-induced fission cross sections and capture-to-fission ratio (α = σγ/σf) for 235U using a new fission-tagging detector as well as neutron capture cross sections for several astrophysics branch-point nuclei. Results from several of these measurements will be presented along with a discussion of additional physics information that can be extracted from the DANCE data.

  15. Measuring Neutron-Induced Reaction Cross Sections without Neutrons

    Science.gov (United States)

    Bernstein, L. A.; Schiller, A.; Cooper, J. R.; Hoffman, R. D.; McMahan, M. A.; Fallon, P.; Macchiavelli, A. O.; Mitchell, G.; Tavukcu, E.; Guttormsen, M.

    2003-04-01

    Neutron-induced reactions on radioactive nuclei play a significant role in nuclear astrophysics and many other applied nuclear physics topics. However, the majority of these cross sections are impossible to measure due to the high-background of the targets and the low-intensity of neutron beams. We have explored the possibility of using charged-particle transfer reactions to form the same "pre-compound" nucleus as one formed in a neutron-induced reaction in order to measure the relative decay probabilities of the nucleus as a function of energy. Multiplying these decay probabilities by the neutron absorption cross section will then produce the equivalent neutron-induced reaction cross section. In this presentation I will explore the validity of this "surrogate reaction" technique by comparing results from the recent 157Gd(3He,axng)156-xGd experiment using STARS (Silicon Telescope Array for Reaction Studies) at GAMMASPHERE with reaction model calculations for the 155Gd(n,xng)156-xGd. This work was funded by the US Department of Energy under contracts number W-7405-ENG-48 (LLNL), AC03-76SF00098 (LBNL) and the Norwegian Research Council (Oslo).

  16. Weak Interaction Neutron Production Rates in Fully Ionized Plasmas

    CERN Document Server

    Widom, A; Srivastava, Y N

    2013-01-01

    Employing the weak interaction reaction wherein a heavy electron is captured by a proton to produce a neutron and a neutrino, the neutron production rate for neutral hydrogen gases and for fully ionized plasmas is computed. Using the Coulomb atomic bound state wave functions of a neutral hydrogen gas, our production rate results are in agreement with recent estimates by Maiani {\\it et al}. Using Coulomb scattering state wave functions for the fully ionized plasma, we find a substantially enhanced neutron production rate. The scattering wave function should replace the bound state wave function for estimates of the enhanced neutron production rate on water plasma drenched cathodes of chemical cells.

  17. Eikonal reaction theory for two-neutron removal reactions

    CERN Document Server

    Minomo, K; Egashira, K; Ogata, K; Yahiro, M

    2014-01-01

    The eikonal reaction theory (ERT) proposed lately is a method of calculating one-neutron removal reactions at intermediate incident energies in which Coulomb breakup is treated accurately with the continuum discretized coupled-channels method. ERT is extended to two-neutron removal reactions. ERT reproduces measured one- and two-neutron removal cross sections for 6He scattering on 12C and 208Pb targets at 240 MeV/nucleon and also on a 28Si target at 52 MeV/nucleon. For the heavier target in which Coulomb breakup is important, ERT yields much better agreement with the measured cross sections than the Glauber model.

  18. Spin distribution in neutron induced preequilibrium reactions

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D; Kawano, T; Chadwick, M; Devlin, M; Fotiades, N; Nelson, R O; Mitchell, G E; Garrett, P E; Agvaanluvsan, U; Becker, J A; Bernstein, L A; Macri, R; Younes, W

    2005-10-04

    The preequilibrium reaction mechanism makes an important contribution to neutron-induced reactions above E{sub n} {approx} 10 MeV. The preequilibrium process has been studied exclusively via the characteristic high energy neutrons produced at bombarding energies greater than 10 MeV. They are expanding the study of the preequilibrium reaction mechanism through {gamma}-ray spectroscopy. Cross-section measurements were made of prompt {gamma}-ray production as a function of incident neutron energy (E{sub n} = 1 to 250 MeV) on a {sup 48}Ti sample. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the Los Alamos Neutron Science Center facility. The prompt-reaction {gamma} rays were detected with the large-scale Compton-suppressed Germanium Array for Neutron Induced Excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The {gamma}-ray excitation functions were converted to partial {gamma}-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). Residual state population was predicted using the GNASH reaction code, enhanced for preequilibrium. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshback, Kerman, and Koonin (FKK). The multistep direct part of the FKK theory was calculated for a one-step process. The FKK preequilibrium spin distribution was incorporated into the GNASH calculations and the {gamma}-ray production cross sections were calculated and compared with experimental data. The difference in the partial {gamma}-ray cross sections using spin distributions with and without preequilibrium effects is significant.

  19. Development, improvement and calibration of neutronic reaction rate measurements: elaboration of a base of standard techniques; Developpement, amelioration et calibration des mesures de taux de reaction neutroniques: elaboration d`une base de techniques standards

    Energy Technology Data Exchange (ETDEWEB)

    Hudelot, J.P

    1998-06-19

    In order to improve and to validate the neutronic calculation schemes, perfecting integral measurements of neutronic parameters is necessary. This thesis focuses on the conception, the improvement and the development of neutronic reaction rates measurements, and aims at building a base of standard techniques. Two subjects are discussed. The first one deals with direct measurements by fission chambers. A short presentation of the different usual techniques is given. Then, those last ones are applied through the example of doubling time measurements on the EOLE facility during the MISTRAL 1 experimental programme. Two calibration devices of fission chambers are developed: a thermal column located in the central part of the MINERVE facility, and a calibration cell using a pulsed high flux neutron generator and based on the discrimination of the energy of the neutrons with a time-of-flight method. This second device will soon allow to measure the mass of fission chambers with a precision of about 1 %. Finally, the necessity of those calibrations will be shown through spectral indices measurements in core MISTRAL 1 (UO{sub 2}) and MISTRAL 2 (MOX) of the EOLE facility. In each case, the associated calculation schemes, performed using the Monte Carlo MCNP code with the ENDF-BV library, will be validated. Concerning the second one, the goal is to develop a method for measuring the modified conversion ratio of {sup 238}U (defined as the ratio of {sup 238}U capture rate to total fission rate) by gamma-ray spectrometry of fuel rods. Within the framework of the MISTRAL 1 and MISTRAL 2 programmes, the measurement device, the experimental results and the spectrometer calibration are described. Furthermore, the MCNP calculations of neutron self-shielding and gamma self-absorption are validated. It is finally shown that measurement uncertainties are better than 1 %. The extension of this technique to future modified conversion ratio measurements for {sup 242}Pu (on MOX rods) and

  20. Neutrons in the moon. [neutron flux and production rate calculations

    Science.gov (United States)

    Kornblum, J. J.; Fireman, E. L.; Levine, M.; Aronson, A.

    1973-01-01

    Neutron fluxes for energies between 15 MeV and thermal at depths of 0 to 300 g/sq cm in the moon are calculated by the discrete ordinate mathod with the ANISN code. With the energy spectrum of Lingenfelter et al. (1972). A total neutron-production rate for the moon of 26 plus or minus neutrons/sq cm sec is determined from the Ar-37 activity measurements in the Apollo 16 drill string, which are found to have a depth dependence in accordance with a neutron source function that decreases exponentially with an attenuation length of 155 g/sq cm.

  1. Weak Interaction Neutron Production Rates in Fully Ionized Plasmas

    OpenAIRE

    Widom, A.; Swain, J.; Srivastava, Y. N.

    2013-01-01

    Employing the weak interaction reaction wherein a heavy electron is captured by a proton to produce a neutron and a neutrino, the neutron production rate for neutral hydrogen gases and for fully ionized plasmas is computed. Using the Coulomb atomic bound state wave functions of a neutral hydrogen gas, our production rate results are in agreement with recent estimates by Maiani {\\it et al}. Using Coulomb scattering state wave functions for the fully ionized plasma, we find a substantially enha...

  2. Study of 232Th(n, γ) and 232Th(n,f) reaction rates in a graphite moderated spallation neutron field produced by 1.6 GeV deuterons on lead target

    Science.gov (United States)

    Asquith, N. L.; Hashemi-Nezhad, S. R.; Westmeier, W.; Zhuk, I.; Tyutyunnikov, S.; Adam, J.

    2015-02-01

    The Gamma-3 assembly of the Joint Institute for Nuclear Research (JINR), Dubna, Russia is designed to emulate the neutron spectrum of a thermal Accelerator Driven System (ADS). It consists of a lead spallation target surrounded by reactor grade graphite. The target was irradiated with 1.6 GeV deuterons from the Nuclotron accelerator and the neutron capture and fission rate of 232Th in several locations within the assembly were experimentally measured. 232Th is a proposed fuel for envisaged Accelerator Driven Systems and these two reactions are fundamental to the performance and feasibility of 232Th in an ADS. The irradiation of the Gamma-3 assembly was also simulated using MCNPX 2.7 with the INCL4 intra-nuclear cascade and ABLA fission/evaporation models. Good agreement between the experimentally measured and calculated reaction rates was found. This serves as a good validation for the computational models and cross section data used to simulate neutron production and transport of spallation neutrons within a thermal ADS.

  3. Neutron Thermal Cross Sections, Westcott Factors, Resonance Integrals, Maxwellian Averaged Cross Sections and Astrophysical Reaction Rates Calculated from the ENDF/B-VII.1, JEFF-3.1.2, JENDL-4.0, ROSFOND-2010, CENDL-3.1 and EAF-2010 Evaluated Data Libraries

    Science.gov (United States)

    Pritychenko, B.; Mughabghab, S. F.

    2012-12-01

    We present calculations of neutron thermal cross sections, Westcott factors, resonance integrals, Maxwellian-averaged cross sections and astrophysical reaction rates for 843 ENDF materials using data from the major evaluated nuclear libraries and European activation file. Extensive analysis of newly-evaluated neutron reaction cross sections, neutron covariances, and improvements in data processing techniques motivated us to calculate nuclear industry and neutron physics quantities, produce s-process Maxwellian-averaged cross sections and astrophysical reaction rates, systematically calculate uncertainties, and provide additional insights on currently available neutron-induced reaction data. Nuclear reaction calculations are discussed and new results are presented. Due to space limitations, the present paper contains only calculated Maxwellian-averaged cross sections and their uncertainties. The complete data sets for all results are published in the Brookhaven National Laboratory report.

  4. Neutron Thermal Cross Sections, Westcott Factors, Resonance Integrals, Maxwellian Averaged Cross Sections and Astrophysical Reaction Rates Calculated from the ENDF/B-VII.1, JEFF-3.1.2, JENDL-4.0, ROSFOND-2010, CENDL-3.1 and EAF-2010 Evaluated Data Libraries

    Energy Technology Data Exchange (ETDEWEB)

    Pritychenko, B. [National Nuclear Data Center, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Mughabghab, S.F. [National Nuclear Data Center, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)

    2012-12-15

    We present calculations of neutron thermal cross sections, Westcott factors, resonance integrals, Maxwellian-averaged cross sections and astrophysical reaction rates for 843 ENDF materials using data from the major evaluated nuclear libraries and European activation file. Extensive analysis of newly-evaluated neutron reaction cross sections, neutron covariances, and improvements in data processing techniques motivated us to calculate nuclear industry and neutron physics quantities, produce s-process Maxwellian-averaged cross sections and astrophysical reaction rates, systematically calculate uncertainties, and provide additional insights on currently available neutron-induced reaction data. Nuclear reaction calculations are discussed and new results are presented. Due to space limitations, the present paper contains only calculated Maxwellian-averaged cross sections and their uncertainties. The complete data sets for all results are published in the Brookhaven National Laboratory report.

  5. Parity Violation in Neutron Capture Reactions

    CERN Document Server

    Hayes, A C; Zanini, Luca

    2001-01-01

    In the last decade, the scattering of polarized neutrons on compound nucleus resonances proved to be a powerful experimental technique for probing nuclear parity violation. Longitudinal analyzing powers in neutron transmission measurements on p-wave resonances in nuclei such as $^{139}$La and $^{232}$Th were found to be as large as 10%. Here we examine the possibilities of carrying out a parallel program to measure asymmetries in the $(n,\\gamma$) reaction on these same compound nuclear resonances. Symmetry-violating $(n,\\gamma$) studies can also show asymmetries as large as 10%, and have the advantage over transmission experiments of allowing parity-odd asymmetries in several different gamma-decay branches from the same resonance. Thus, studies of parity violation in the $(n,\\gamma)$ reaction using high efficiency germanium detectors at the Los Alamos Lujan facility, for example, could determine the parity-odd nucleon-nucleon matrix elements in complex nuclei with high accuracy. Additionally, simultaneous stu...

  6. ACDOS3: a further improved neutron dose-rate code

    Energy Technology Data Exchange (ETDEWEB)

    Martin, C.S.

    1982-07-01

    ACD0S3 is a computer code designed primarily to calculate the activities and dose rates produced by neutron activation in a variety of simple geometries. Neutron fluxes, in up to 50 groups and with energies up to 20 MeV, must be supplied as part of the input data. The neutron-source strength must also be supplied, or alternately, the code will compute it from neutral-beam operating parameters in the case where the source is a fusion-reactor injector. ACD0S3 differs from the previous version ACD0S2 in that additional geometries have been added, the neutron cross-section library has been updated, an estimate of the energy deposited by neutron reactions has been provided, and a significant increase in efficiency in reading the data libraries has been incorporated.

  7. Effects of Neutron Skin Thickness in Peripheral Nuclear Reactions

    Institute of Scientific and Technical Information of China (English)

    FANG De-Qing; MA Yu-Gang; CAI Xiang-Zhou; TIAN Wen-Dong; WANG Hong-Wei

    2011-01-01

    Effects of neutron skin thickness in peripheral nuclear collisions are investigated using the statistical abrasion ablation (SAA) model. The reaction cross section, neutron (proton) removal cross section, one-neutron (proton) removal cross section as well as their ratios for nuclei with different neutron skin thickness are studied. It is demonstrated that there are good linear correlations between these observables and the neutron skin thickness for neutron-rich nuclei. The ratio between the (one-)neutron and proton removal cross section is found to be the most sensitive observable of neutron skin thickness. Analysis shows that the relative increase of this ratio could be used to determine the neutron skin size in neutron-rich nuclei.%Effects of neutron skin thickness in peripheral nuclear collisions are investigated using the statistical abrasion ablation (SAA ) model.The reaction cross section,neutron (proton) removal cross section,one-neutron (proton) removal cross section as well as their ratios for nuclei with different neutron skin thickness are studied.It is demonstrated that there are good linear correlations between these observables and the neutron skin thickness for neutron-rich nuclei.The ratio between the (one-)neutron and proton removal cross section is found to be the most sensitive observable of neutron skin thickness.Analysis shows that the relative increase of this ratio could be used to determine the neutron skin size in neutron-rich nuclei.Determining the size and shape of a nucleus is one of the most important subjects since the discovery of atomic nuclei.The rms radii of the neutron (rn) and proton (rp) density distributions are among the most prominent observables for this purpose.Studies for stable nuclei have shown that the nuclear radii are proportional to A1/3,with A being the nuclear mass number.Meanwhile,the density distributions of neutrons and protons in stable nuclei are very similar.

  8. 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.

  9. Tabulated Neutron Emission Rates for Plutonium Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Shores, Erik Frederick [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-07-24

    This work tabulates neutron emission rates for 80 plutonium oxide samples as reported in the literature. Plutonium-­238 and plutonium-­239 oxides are included and such emission rates are useful for scaling tallies from Monte Carlo simulations and estimating dose rates for health physics applications.

  10. Transuranics Transmutation Using Neutrons Spectrum from Spallation Reactions

    Directory of Open Access Journals (Sweden)

    Maurício Gilberti

    2015-01-01

    Full Text Available The aim is to analyse the neutron spectrum influence in a hybrid system ADS-fission inducing transuranics (TRUs transmutation. A simple model consisting of an Accelerator-Driven Subcritical (ADS system containing spallation target, moderator or coolant, and spheres of actinides, “fuel,” at different locations in the system was modelled. The simulation was performed using the MCNPX 2.6.0 particles transport code evaluating capture (n,γ and fission (n,f reactions, as well as the burnup of actinides. The goal is to examine the behaviour and influences of the hard neutron spectrum from spallation reactions in the transmutation, without the contribution or interference of multiplier subcritical medium, and compare the results with those obtained from the neutron fission spectrum. The results show that the transmutation efficiency is independent of the spallation target material used, and the neutrons spectrum from spallation does not contribute to increased rates of actinides transmutation even in the vicinity of the target.

  11. Neutron dose equivalent rate in intermediate energy heavy ion target area

    CERN Document Server

    Li Gui Sheng; Li Zong Wei; Su You Wu; Zhang Shu Mi

    2000-01-01

    The fluence rate distributions of neutrons emitted in the reactions of 50 MeV/u sup 1 sup 8 O-ion on thick Be, Cu, Au targets were measured with an activation method of threshold detectors and the neutron dose equivalent rate distributions at 1 m from the targets in intermediate energy heavy ion target area were obtained using the conversion coefficients for neutron fluence rate to ambient dose equivalent rate.

  12. Inclusive deuteron-induced reactions and final neutron states

    CERN Document Server

    Potel, Gregory; Thompson, Ian J

    2015-01-01

    We present in this paper a formalism for deuteron-induced inclusive reactions. We disentangle direct elastic breakup contributions from other processes (which we generically call non-elastic breakup) implying a capture of the neutron both above and below the neutron emission threshold. The reaction is described as a two step process, namely the breakup of the deuteron followed by the propagation of the neutron-target system driven by an optical potential. The final state interaction between the neutron and the target can eventually form an excited compound nucleus. Within this context, the direct neutron transfer to a sharp bound state is a limiting case of the present formalism.

  13. Search for reaction-in-flight neutrons using thulium activation at the National Ignition Facility

    Science.gov (United States)

    Grim, Gary; Rundberg, Robert; Tonchev, Anton; Fowler, Malcolm; Wilhelmy, Jerry; Archuleta, Tom; Bionta, Richard; Boswell, Mitzi; Gostic, Julie; Griego, Jeff; Knittel, Kenn; Klein, Andi; Moody, Ken; Shaughnessy, Dawn; Wilde, Carl; Yeamans, Charles

    2013-10-01

    We report on measurements of reaction-in-flight (RIF) neutrons at the National Ignition Facility. RIF neutrons are produced in cryogenically layered implision by up-scattered deuterium, or tritium ions that undergo subsequent fusion reactions. The rate of RIF neutron production is proportional to the fuel areal density (| | R) and ion-stopping length in the dense fuel assembly. Thus, RIF neutrons provide information on charge particle stopping in a strongly coupled plasma, where perturbative modeling breaks down. To measure RIF neutrons, a set of thulium activation foils was placed 50 cm from layered cryogenic implosions at the NIF. The reaction 169Tm(n,3n)167Tm has a neutron kinetic energy threshold of 14.96 MeV. We will present results from initial experiments performed during the spring of 2013. Prepared by LANL under Contract DE-AC-52-06-NA25396, TSPA, LA-UR-13-22085.

  14. Neutron Transfer Reactions: Surrogates for Neutron Capture for Basic and Applied Nuclear Science

    Science.gov (United States)

    Cizewski, J. A.; Jones, K. L.; Kozub, R. L.; Pain, S. D.; Peters, W. A.; Adekola, A.; Allen, J.; Bardayan, D. W.; Becker, J. A.; Blackmon, J. C.; Chae, K. Y.; Chipps, K. A.; Erikson, L.; Gaddis, A.; Harlin, C.; Hatarik, R.; Howard, J.; Jandel, M.; Johnson, M. S.; Kapler, R.; Krolas, W.; Liang, F.; Livesay, R. J.; Ma, Z.; Matei, C.; Matthews, C.; Moazen, B.; Nesaraja, C. D.; O'Malley, P.; Patterson, N.; Paulauskas, S. V.; Pelham, T.; Pittman, S. T.; Radford, D.; Rogers, J.; Schmitt, K.; Shapira, D.; Shriner, J. F.; Sissom, D. J.; Smith, M. S.; Swan, T.; Thomas, J. S.; Vieira, D. J.; Wilhelmy, J. B.; Wilson, G. L.

    2009-03-01

    Neutron capture reactions on unstable nuclei are important for both basic and applied nuclear science. A program has been developed at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory to study single-neutron transfer (d,p) reactions with rare isotope beams to provide information on neutron-induced reactions on unstable nuclei. Results from (d,p) studies on 130,132Sn, 134Te and 75As are discussed.

  15. Neutron transfer reactions: Surrogates for neutron capture for basic and applied nuclear science

    Energy Technology Data Exchange (ETDEWEB)

    Cizewski, J. A. [Rutgers University; Jones, K. L. [University of Tennessee; Kozub, R. L. [Tennessee Technological University; Pain, Steven D [ORNL; Peters, W. A. [Rutgers University; Adekola, Aderemi S [ORNL; Allen, J. [Rutgers University; Bardayan, Daniel W [ORNL; Becker, J. [Lawrence Livermore National Laboratory (LLNL); Blackmon, Jeff C [ORNL; Chae, K. Y. [University of Tennessee; Chipps, K. [Colorado School of Mines, Golden; Erikson, Luke [Colorado School of Mines, Golden; Gaddis, A. L. [Furman University; Harlin, Christopher W [ORNL; Hatarik, Robert [Rutgers University; Howard, Joshua A [ORNL; Jandel, M. [Los Alamos National Laboratory (LANL); Johnson, Micah [ORNL; Kapler, R. [University of Tennessee; Krolas, W. [University of Warsaw; Liang, J Felix [ORNL; Livesay, Jake [ORNL; Ma, Zhanwen [ORNL; Matei, Catalin [Oak Ridge Associated Universities (ORAU); Matthews, C. [Rutgers University; Moazen, Brian [University of Tennessee; Nesaraja, Caroline D [ORNL; O' Malley, Patrick [Rutgers University; Patterson, N. P. [University of Surrey, UK; Paulauskas, Stanley [University of Tennessee; Pelham, T. [University of Surrey, UK; Pittman, S. T. [University of Tennessee, Knoxville (UTK); Radford, David C [ORNL; Rogers, J. [Tennessee Technological University; Schmitt, Kyle [University of Tennessee; Shapira, Dan [ORNL; ShrinerJr., J. F. [Tennessee Technological University; Sissom, D. J. [Tennessee Technological University; Smith, Michael Scott [ORNL; Swan, T. P. [University of Surrey, UK; Thomas, J. S. [Rutgers University; Vieira, D. J. [Los Alamos National Laboratory (LANL); Wilhelmy, J. B. [Los Alamos National Laboratory (LANL); Wilson, Gemma L [ORNL

    2009-04-01

    Neutron capture reactions on unstable nuclei are important for both basic and applied nuclear science. A program has been developed at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory to study single-neutron transfer (d,p) reactions with rare isotope beams to provide information on neutron-induced reactions on unstable nuclei. Results from (d,p) studies on {sup 130,132}Sn, {sup 134}Te and {sup 75}As are discussed.

  16. Reducing background neutron rates in NERO

    Science.gov (United States)

    Pellegrini, Eric

    2003-10-01

    The experimental study of neutron rich nuclei can provide important data to better model the production and abundances of heavy elements from the r-process. In order to measure low emission rates of neutrons in certain nuclei, efforts have been made to reduce background rates in NERO (1). Simulations were done to calculate effective passive shielding and testing was carried out to evaluate it. Also, an active shielding system was designed to detect cosmic ray muons in an effort to create a veto in the data acquisition. The results of these efforts are presented here. 1. http://www.nscl.msu.edu/tech/devices/nero/

  17. Neutron Transfer Reactions for Deformed Nuclei Using Sturmian Basis

    CERN Document Server

    Gueorguiev, V G; Escher, J E; Dietrich, F S

    2007-01-01

    We study the spin-parity distribution P(J$^{\\pi}$,E) of $^{156}$Gd excited states above the neutron separation energy that are expected to be populated via the neutron pickup reaction $^{157}$Gd($^{3}$He,$^{4}$He)$^{156}$Gd. In general, modeling of the spin-parity distribution is important for the applicability of the surrogate reaction technique as a method of deducing reaction cross sections. We model excited states in $^{156}$Gd as rotational states built on intrinsic states consisting of a hole in the core where the hole represents neutron removal form a deformed single particle state. The reaction cross section to each excited state is calculated using standard reaction code that uses spherical reaction form-factor input. The spectroscopic factor associated with each form-factor is the expansion coefficient of the deformed neutron state in a spherical Sturmian basis consisting of the spherical reaction form-factors.

  18. Measurement of reaction-in-flight neutrons using thulium activation at the National Ignition Facility

    Science.gov (United States)

    Grim, G. P.; Rundberg, R.; Fowler, M. M.; Hayes, A. C.; Jungman, G.; Boswell, M.; Klein, A.; Wilhelmy, J.; Tonchev, A.; Yeamans, C. B.

    2014-09-01

    We report on the first observation of tertiary reaction-in-flight (RIF) neutrons produced in compressed deuterium and tritium filled capsules using the National Ignition Facility at Lawrence Livermore National Laboratory, Livermore, CA. RIF neutrons are produced by third-order, out of equilibrium ("in-flight") fusion reactions, initiated by primary fusion products. The rate of RIF reactions is dependent upon the range of the elastically scattered fuel ions and therefore a diagnostic of Coulomb physics within the plasma. At plasma temperatures of ˜5 keV, the presence of neutrons with kinetic energies greater than 15 MeV is a unique signature for RIF neutron production. The reaction 169Tm(n,3n)167Tm has a threshold of 15.0 MeV, and a unique decay scheme making it a suitable diagnostic for observing RIF neutrons. RIF neutron production is quantified by the ratio of 167Tm/168Tm observed in a 169Tm foil, where the reaction 169Tm(n,2n)168Tm samples the primary neutron fluence. Averaged over 4 implosions1-4 at the NIF, the 167Tm/168Tm ratio is measured to be 1.5 +/- 0.3 x 10-5, leading to an average ratio of RIF to primary neutron ratio of 1.0 +/- 0.2 x 10-4. These ratios are consistent with the predictions for charged particle stopping in a quantum degenerate plasma.

  19. Indirect rp-process Rate Measurements from Single Neutron Removal

    Science.gov (United States)

    Amthor, A. M.; Bazin, D.; Becerril, A.; Cole, A.; Cook, J.; Estrade, A.; Gade, A.; Howard, M.; Lorusso, G.; Matos, M.; Pereira, J.; Portillo, M.; Schatz, H.; Sherrill, B.; Smith, K.; Stolz, A.; Weisshaar, D.; Zegers, R. G. T.; Galaviz, D.; Chen, A.; Fulop, Zs.; Smith, E.; Wiescher, M.

    2007-10-01

    The structure of nuclei along the rp-process path in Type I X-ray bursts has been studied using neutron removal from radioactive beams produced at the National Superconducting Cyclotron Laboratory. Recently, ^37Ca and ^36K have been studied in this way to reduce the uncertainty in ^35Ar(p,γ)^36K and ^36K(p,γ)^37Ca reaction rates, which are important during burst rise. Under burst conditions these rates are dominated by resonant capture contributions from individual resonances because of the low level density just above the proton threshold, precluding the use of statistical methods based on level density to determine the reaction rates. Therefore, precise structure measurements are required to reduce the orders of magnitude rate uncertainty in these key reactions and thereby constrain X-ray burst models. Preliminary results will be presented along with the implications for X-ray burst models.

  20. Trojan Horse Method for neutrons-induced reaction studies

    Science.gov (United States)

    Gulino, M.; Asfin Collaboration

    2017-09-01

    Neutron-induced reactions play an important role in nuclear astrophysics in several scenario, such as primordial Big Bang Nucleosynthesis, Inhomogeneous Big Bang Nucleosynthesis, heavy-element production during the weak component of the s-process, explosive stellar nucleosynthesis. To overcome the experimental problems arising from the production of a neutron beam, the possibility to use the Trojan Horse Method to study neutron-induced reactions has been investigated. The application is of particular interest for reactions involving radioactive nuclei having short lifetime.

  1. Neutron dose equivalent rate for heavy ion bombardment

    Institute of Scientific and Technical Information of China (English)

    LiGui-Sheng; ZhangTian-Mei; 等

    1998-01-01

    The fluence rate distribution of neutrons in the reactionsof 50MeV/u 18O-ion on thick Be,Cu and Au targets have been measured with an activation method of threshold detectors andthe neutron dose equivalent rate distributions at 1m from the tqrgets in intermediate energy heavy ion target area are obtained by using the conversion factors from neutron fluence rate to neutron doseequivalent rate.

  2. Transfer reactions at the neutron dripline with triton target

    CERN Document Server

    Borge, M J G; Fynbo, H O U; Gomez Camacho, J; Johansen, J; Johansson, H T; Jonson, B; Krücken, R; Kurcewicz, J; Martel, I; Moro, A; Mücher, D; Nilsson, T; Nyman, G; Raabe, R; Randisi, G; Riisager, K; Sambi, S; Sanchez-Benitez, AM; Tengblad, O

    2012-01-01

    Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.

  3. Transfer reactions at the neutron dripline with triton target

    CERN Multimedia

    Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.

  4. 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.

  5. Neutron-induced reaction studies using stored ions

    Science.gov (United States)

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

    2015-11-01

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

  6. Continuum quasiparticle random phase approximation for astrophysical direct neutron capture reaction of neutron-rich nuclei

    OpenAIRE

    Matsuo, Masayuki

    2014-01-01

    We formulate a many-body theory to calculate the cross section of direct radiative neutron capture reaction by means of the Hartree-Fock-Bogoliubov mean-field model and the continuum quasiparticle random phase approximation (QRPA). A focus is put on very neutron-rich nuclei and low-energy neutron kinetic energy in the range of O(1 keV) - O(1 MeV), relevant for the rapid neutron-capture process of nucleosynthesis. We begin with the photo-absorption cross section and the E1 strength function, t...

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

    Science.gov (United States)

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

    2011-07-01

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

  8. Reactions with fast radioactive beams of neutron-rich nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Aumann, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany)

    2005-11-01

    The neutron dripline has presently been reached only for the lightest nuclei up to the element oxygen. In this region of light neutron-rich nuclei, scattering experiments are feasible even for dripline nuclei by utilizing high-energy secondary beams produced by fragmentation. In the present article, reactions of high-energy radioactive beams will be exemplified using recent experimental results mainly derived from measurements of breakup reactions performed at the LAND and FRS facilities at GSI and at the S800 spectrometer at the NSCL. Nuclear and electromagnetically induced reactions allow probing different aspects of nuclear structure at the limits of stability related to the neutron-proton asymmetry and the weak binding close to the dripline. Properties of the valence-neutron wave functions are studied in the one-neutron knockout reaction, revealing the changes of shell structure when going from the beta-stability line to more asymmetric loosely bound neutron-rich systems. The vanishing of the N=8 shell gap for neutron-rich systems like {sup 11}Li and {sup 12}Be, or the new closed N=14, 16 shells for the oxygen isotopes are examples. The continuum of weakly bound nuclei and halo states can be studied by inelastic scattering. The dipole response, for instance, is found to change dramatically when going away from the valley of stability. A redistribution of the dipole strength towards lower excitation energies is observed for neutron-rich nuclei, which partly might be due to a new collective excitation mode related to the neutron-proton asymmetry. Halo nuclei in particular show strong dipole transitions to the continuum at the threshold, being directly related to the ground-state properties of the projectile. Finally, an outlook on future experimental prospects is given. (orig.)

  9. Measuring the Cosmic Ray Muon-Induced Fast Neutron Spectrum by (n,p) Isotope Production Reactions in Underground Detectors

    CERN Document Server

    Galbiati, C; Galbiati, Cristiano; Beacom, John. F.

    2005-01-01

    While cosmic ray muons themselves are relatively easy to veto in underground detectors, their interactions with nuclei create more insidious backgrounds via: (i) the decays of long-lived isotopes produced by muon-induced spallation reactions inside the detector, (ii) spallation reactions initiated by fast muon-induced neutrons entering from outside the detector, and (iii) nuclear recoils initiated by fast muon-induced neutrons entering from outside the detector. These backgrounds, which are difficult to veto or shield against, are very important for solar, reactor, dark matter, and other underground experiments, especially as increased sensitivity is pursued. We used fluka to calculate the production rates and spectra of all prominent secondaries produced by cosmic ray muons, in particular focusing on secondary neutrons, due to their importance. Since the neutron spectrum is steeply falling, the total neutron production rate is sensitive just to the relatively soft neutrons, and not to the fast-neutron compon...

  10. The neutron within the deuteron as a surrogate for neutron-induced reactions

    CERN Document Server

    Bertulani, C A; Hussein, M S; Shubhchintak,; Tran, Viet Nhan Hao

    2016-01-01

    We propose the use of neutron poisons in reactions induced by radioactive beams as a test of theoretical models aiming to relate neutron capture in nuclei with neutron surrogate reactions such as (d,p) reactions. We exploit the approximations necessary to obtain a direct relation between the two reactions; surrogate vs. neutron capture. We also show how this is intimately related to the momentum distribution of the neutron within the deuteron. The models we use are based on the theory of inclusive breakup reactions commonly employed in the treatment of incomplete fusion and surrogate method. Such theories were developed in the 80's by Ichimura, Autern and Vincent [Phys. Rev. C 32, 431 (1985)], Udagawa and Tamura [Phys. Rev. C 24, 1348 (1981)] and Hussein and McVoy [Nucl. Phys. A 445, 124 (1985)]. We use these theories to derive an expression for the proton yield in the reaction A(d,p)B. The capture reaction $n + A \\rightarrow B$ is then extracted using reasonable approximations. By recalling an old method pro...

  11. Neutron halo in 14B studied via reaction cross sections

    Directory of Open Access Journals (Sweden)

    Fukuda M.

    2014-03-01

    Full Text Available Reaction cross sections (σR for the neutron-rich nucleus 14B on Be, C, and Al targets have been measured at several energies in the intermediate energy range of 45–120 MeV/nucleon. The present experimental σR show a significant enhancement relative to the systematics of stable nuclei. The nucleon density distribution was deduced through the fitting procedure with the modified Glauber calculation. The necessity of a long tail in the density distribution was found, which is consistent with the valence neutron in 2s1/2 orbital with the small empirical one-neutron separation energy in 14B.

  12. Microscopic description of neutron emission rates in compound nuclei

    CERN Document Server

    Zhu, Yi

    2014-01-01

    The neutron emission rates in thermal excited nuclei are conventionally described by statistical models with a phenomenological level density parameter that depends on excitation energies, deformations and mass regions. In the microscopic view of hot nuclei, the neutron emission rates can be determined by the external neutron gas densities without any free parameters. Therefore the microscopic description of thermal neutron emissions is desirable that can impact several understandings such as survival probabilities of superheavy compound nuclei and neutron emissivity in reactors. To describe the neutron emission rates microscopically, the external thermal neutron gases are self-consistently obtained based on the Finite-Temperature Hartree-Fock-Bogoliubov (FT-HFB) approach. The results are compared with the statistical model to explore the connections between the FT-HFB approach and the statistical model. The Skyrme FT-HFB equation is solved by HFB-AX in deformed coordinate spaces. Based on the FT-HFB approach...

  13. 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.

  14. High yield neutron generators using the DD reaction

    Energy Technology Data Exchange (ETDEWEB)

    Vainionpaa, J. H.; Harris, J. L.; Piestrup, M. A.; Gary, C. K.; Williams, D. L.; Apodaca, M. D.; Cremer, J. T. [Adelphi technology, 2003 E. Bayshore Rd. 94061, Redwood City, CA (United States); Ji, Qing; Ludewigt, B. A. [Lawrence Berkeley National Lab, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Jones, G. [G and J Enterprise, 1258 Quary Ln, Suite F, Pleasanton California 94566 (United States)

    2013-04-19

    A product line of high yield neutron generators has been developed at Adelphi technology inc. The generators use the D-D fusion reaction and are driven by an ion beam supplied by a microwave ion source. Yields of up to 5 Multiplication-Sign 10{sup 9} n/s have been achieved, which are comparable to those obtained using the more efficient D-T reaction. The microwave-driven plasma uses the electron cyclotron resonance (ECR) to produce a high plasma density for high current and high atomic ion species. These generators have an actively pumped vacuum system that allows operation at reduced pressure in the target chamber, increasing the overall system reliability. Since no radioactive tritium is used, the generators can be easily serviced, and components can be easily replaced, providing essentially an unlimited lifetime. Fast neutron source size can be adjusted by selecting the aperture and target geometries according to customer specifications. Pulsed and continuous operation has been demonstrated. Minimum pulse lengths of 50 {mu}s have been achieved. Since the generators are easily serviceable, they offer a long lifetime neutron generator for laboratories and commercial systems requiring continuous operation. Several of the generators have been enclosed in radiation shielding/moderator structures designed for customer specifications. These generators have been proven to be useful for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA) and fast neutron radiography. Thus these generators make excellent fast, epithermal and thermal neutron sources for laboratories and industrial applications that require neutrons with safe operation, small footprint, low cost and small regulatory burden.

  15. High yield neutron generators using the DD reaction

    Science.gov (United States)

    Vainionpaa, J. H.; Harris, J. L.; Piestrup, M. A.; Gary, C. K.; Williams, D. L.; Apodaca, M. D.; Cremer, J. T.; Ji, Qing; Ludewigt, B. A.; Jones, G.

    2013-04-01

    A product line of high yield neutron generators has been developed at Adelphi technology inc. The generators use the D-D fusion reaction and are driven by an ion beam supplied by a microwave ion source. Yields of up to 5 × 109 n/s have been achieved, which are comparable to those obtained using the more efficient D-T reaction. The microwave-driven plasma uses the electron cyclotron resonance (ECR) to produce a high plasma density for high current and high atomic ion species. These generators have an actively pumped vacuum system that allows operation at reduced pressure in the target chamber, increasing the overall system reliability. Since no radioactive tritium is used, the generators can be easily serviced, and components can be easily replaced, providing essentially an unlimited lifetime. Fast neutron source size can be adjusted by selecting the aperture and target geometries according to customer specifications. Pulsed and continuous operation has been demonstrated. Minimum pulse lengths of 50 μs have been achieved. Since the generators are easily serviceable, they offer a long lifetime neutron generator for laboratories and commercial systems requiring continuous operation. Several of the generators have been enclosed in radiation shielding/moderator structures designed for customer specifications. These generators have been proven to be useful for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA) and fast neutron radiography. Thus these generators make excellent fast, epithermal and thermal neutron sources for laboratories and industrial applications that require neutrons with safe operation, small footprint, low cost and small regulatory burden.

  16. Comparison of fast neutron rates for the NEOS experiment

    Science.gov (United States)

    Ko, Y. J.; Jang, C. H.; Siyeon, Kim; Kim, J. Y.; Kim, H. S.; Seo, K. M.; Han, B. Y.; Sun, G. M.; Jeon, E. J.; Lee, Jaison; Lee, M. H.; Oh, Y. M.; Park, K. S.; Joo, K. K.; Kim, B. R.; Kim, H. J.; Lee, J. Y.; Kim, Y. D.; Park, H. K.; Park, H. S.

    2016-12-01

    The fast neutron rates are compared at the site of the NEOS (Neutrino Experiment Oscillation Short baseline) experiment, a short-baseline neutrino experiment located in a tendon gallery of a commercial nuclear power plant using a 0.78-liter liquid scintillator detector. A pulse shape discrimination technique is used to identify neutron signals. The measurements are performed during the nuclear reactor-on and -off periods, and the fast neutron rates are found to be consistent with each other. The fast neutron rate is also measured at an overground site with a negligible overburden and is found to be 100 times higher than that at the site of the NEOS experiment.

  17. Status of experimental data for neutron induced reactions

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Mamoru [Tohoku Univ., Sendai (Japan)

    1998-11-01

    A short review is presented on the status of experimental data for neutron induced reactions above 20 MeV based on the EXFOR data base and journals. Experimental data which were obtained in a systematic manner and/or by plural authors are surveyed and tabulated for the nuclear data evaluation and the benchmark test of the evaluated data. (author). 61 refs.

  18. Determination of the Astrophysical S(E) Factors or Rates for Radiative Capture Reaction with One Nucleon Transfer Reaction%Determination of the Astrophysical S(E) Factors or Rates for Radiative Capture Reaction with One Nucleon Transfer Reaction

    Institute of Scientific and Technical Information of China (English)

    李志宏; 郭冰; 李云居; 苏俊; 李二涛; 白希祥; 王友宝; 曾晟; 王宝祥; 颜胜权; 李志常; 刘建成; 连钢; 金孙均; 刘鑫; 柳卫平

    2012-01-01

    The radiative capture reaction plays an important role in nuclear astrophysics. We have indirectly measured the astrophysical S(E) factors for some proton capture reactions and reaction rates for several neutron capture reactions with one nucleon transfer reactions at HI-13 tandem accelerator in recent years. Some of them are compiled into IAEA EXFOR database and JINA REACLIB project, and used in the network calculations of Big Bang nucleosynthesis and type-I X-ray bursts.

  19. Neutron Transfer reactions induced by 8Li on 9Be

    CERN Document Server

    Guimarães, V; Amro, H; Assunção, M; Barioni, A; Becchetti, F D; Carmargo, O; Garcia, H; Jiang, H; Kolata, J J; Lichtenthäler, R; Lizcano, D; Martines-Quiroz, E; Jiang, Hao

    2007-01-01

    Angular distributions for the elastic scattering of 8Li on 9Be and the neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for 8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between the experimental differential cross section and finite-range DWBA calculations with the code FRESCO. The spectroscopic factors obtained are compared to shell model calculations and to other experimental values from (d,p) reactions. Using the present values for the spectroscopic factor, cross sections for the direct neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the framework of a potential model.

  20. Neutron transfer reactions in the fp-shell region

    Energy Technology Data Exchange (ETDEWEB)

    Mahgoub, Mahmoud

    2008-06-26

    Neutron transfer reactions were used to study the stability of the magic number N=28 near {sup 56}Ni. On one hand the one-neutron pickup (d,p) reaction was used for precision spectroscopy of single-particle levels in {sup 55}Fe. On the other hand we investigated the two-neutron transfer mechanism into {sup 56}Ni using the pickup reaction {sup 58}Ni((vector)p,t){sup 56}Ni. In addition the reliability of inverse kinematics reactions at low energy to study exotic nuclei was tested by the neutron transfer reactions t({sup 40}Ar,p){sup 42}Ar and d({sup 54}Fe,p){sup 55}Fe using tritium and deuterium targets, respectively, and by comparing the results with those of the normal kinematics reactions. The experimental data, differential cross-section and analyzing powers, are compared to DWBA and coupled channel calculations utilizing the code CHUCK3. By performing the single-neutron stripping reaction ((vector)d,p) on {sup 54}Fe the 1f{sub 7/2} shell in the ground state configuration was found to be partly broken. The instability of the 1f{sub 7/2} shell and the magic number N=28 was confirmed once by observing a number of levels with J{sup {pi}} = 7/2{sup -} at low excitation energies, which should not be populated if {sup 54}Fe has a closed 1f{sub 7/2} shell, and also by comparing our high precision experimental data with a large scale shell model calculation using the ANTOINE code [5]. Calculations including a partly broken 1f{sub 7/2} shell show better agreement with the experiment. The instability of the 1f{sub 7/2} shell was confirmed also by performing the two-neutron pick-up reaction ((vector)p,t) on {sup 58}Ni to study {sup 56}Ni, where a considerable improvement in the DWBA calculation was observed after considering 1f{sub 7/2} as a broken shell. To prove the reliability of inverse kinematics transfer reactions at low energies ({proportional_to} 2 AMeV), the aforementioned single-neutron transfer reaction (d,p) was repeated using a beam of {sup 54}Fe ions and a

  1. Turnover Rate Simulation Using GEM Detector on Neutron Radiography

    Institute of Scientific and Technical Information of China (English)

    SHAN; Chao; LI; Xiao-mei; HU; Shou-yang; ZHOU; Jing; JIAN; Si-yu; BAI; Xin-zhan; YE; Li; ZHOU; Shu-hua

    2012-01-01

    <正>With the advantages of high counting rate, high resolution ratio and high compatibility, GEM (Gas Electron Multiplier) detector has becoming the hot topic in the field of gas detector. Using GEM on neutron radiography, we need a suitable neutron converter. By the action on the converter and ingoing neutron, the outgoing particles could be an alpha or proton, which are charged particles. The charged

  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. Interlaboratory reaction rate program. 12th progress report, November 1976-October 1979

    Energy Technology Data Exchange (ETDEWEB)

    Lippincott, E.P.; McElroy, W.N.; Preston, C.C. (comps.)

    1980-09-01

    The Interlaboratory Reaction Rate UILRR) program is establishing the capability to accurately measure neutron-induced reactions and reaction rates for reactor fuels and materials development programs. The goal for the principal fission reactions, /sup 235/U, /sup 238/U and /sup 239/Pu, is an accuracy to within +- 5% at the 95% confidence level. Accurate measurement of other fission and nonfission reactions is also required, but to a lesser accuracy, between +- 5% and 10% at the 95% confidence level. A secondary program objective is improvement in knowledge of the nuclear parameters involved in the standarization of fuels and materials dosimetry measurements of neutron flux, spectra, fluence and burnup.

  4. Updated and revised neutron reaction data for 233U

    Institute of Scientific and Technical Information of China (English)

    YU Bao-Sheng; CHEN Guo-Chang; ZHANG Hua; CAO Wen-Tian; TANG Guo-You; TAO Xi

    2013-01-01

    A complete set of n+233U neutron reaction data from 10-5 eV-20 MeV is updated and revised based on the evaluated experimental data and the feedback information of various benchmark tests.The main revised quantities are nubars,cross sections as well as angular distributions,etc.The benchmark tests indicate that the present evaluated data achieve very promising results.

  5. Measurement of Fast Neutron Rate for NEOS Experiment

    CERN Document Server

    Ko, Y J; Han, B Y; Jang, C H; Jeon, E J; Joo, K K; Kim, B R; Kim, H J; Kim, H S; Kim, Y D; Lee, Jaison; Lee, J Y; Lee, M H; Oh, Y M; Park, H K; Park, H S; Park, K S; Seo, K M; Siyeon, Kim; Sun, G M

    2016-01-01

    The fast neutron rate is measured at the site of NEOS experiment, a short baseline neutrino experiment located in a tendon gallery of a commercial nuclear power plant, using a 0.78-liter liquid scintillator detector. A pulse shape discrimination technique is used to identify neutron signals. The measurements are performed during the nuclear reactor-on and off periods and found to be ~20 per day for both periods. The fast neutron rate is also measured at an overground site with a negligible overburden and is found to be ~100 times higher than that at the NEOS experiment site.

  6. One-neutron knockout reaction from 20C

    Science.gov (United States)

    Hwang, Jongwon; Samurai Collaboration

    2014-09-01

    Recent researches in neutron-rich nuclei have demonstrated that the depth of each single-particle level varies from that in stable nuclei : some of the well-known magic numbers disappear and new shell closures develop. Cross-shell excitation, transition of a nucleon across a shell gap, can be exploit to probe changes in shell structure. The present work aims at exploration of neutron-unbound states of 19C, especially a hole- state populated by cross-shell excitation, via a one-neutron knockout reaction. The experiment was performed at the RIBF facility in RIKEN. A 20C secondary beam produced by BigRIPS with an energy of 280 MeV/nucleon impinged on a carbon target placed before the SAMURAI spectrometer. By taking full advantage of the analyzer system comprised of a large-acceptance super-conducting dipole magnet, associated tracking detectors, and a large volume neutron detector system, an invariant mass spectrum for the system of 18C + n was reconstructed. Three unbound excited states in 19C were identified including the unknown 1 /21+ state at 2.90 MeV in excitation energy. Details of the measurement and analysis along with results will be presented.

  7. Measurements of neutron dose rates with a balloon in Japan.

    Science.gov (United States)

    Nagaoka, K; Hiraide, I; Sato, K; Yamagami, T; Nakamura, T; Yabutani, T

    2007-01-01

    Measurements of cosmic-ray neutron dose rates with a balloon in Sanriku, Japan (geographic location: 39 degrees N, 142 degrees E; corresponding geomagnetic latitude: 30 degrees N) were conducted at an altitude from 0.2 to 25 km on 25-26 August 2004 when solar activity was at an average level. Neutron dose rates given as ambient dose equivalent rates (H(10)) were measured with high-sensitive neutron dose equivalent counters and electronic silicon personal dosimeters (EPDs). The neutron dose rates increased with increasing altitude, but they were saturated around 15-20 km and decreased with increasing altitude beyond 20 km. The neutron ambient dose equivalent rate was 1.5 microSv/h(- 1) at 20 km. Measured values were corrected for the deviation of the energy response of the dose equivalent counter from the fluence-to-ambient dose equivalent conversion coefficient, and the corrected values were very close to the calculated values with EPCARD. On the other hand, neutron measurements by the EPDs gave about 10 times overestimation because of the high sensitivity to cosmic-ray protons.

  8. Reaction Order Ambiguity in Integrated Rate Plots

    Science.gov (United States)

    Lee, Joe

    2008-01-01

    Integrated rate plots are frequently used in reaction kinetics to determine orders of reactions. It is often emphasised, when using this methodology in practice, that it is necessary to monitor the reaction to a substantial fraction of completion for these plots to yield unambiguous orders. The present article gives a theoretical and statistical…

  9. Measurements of neutron-induced reactions in inverse kinematics and applications to nuclear astrophysics

    OpenAIRE

    2015-01-01

    Neutron capture cross sections of unstable isotopes are important for neutron-induced nucleosynthesis as well as for technological applications. A combination of a radioactive beam facility, an ion storage ring and a high flux reactor would allow a direct measurement of neutron induced reactions over a wide energy range on isotopes with half lives down to minutes. The idea is to measure neutron-induced reactions on radioactive ions in inverse kinematics. This means, the radioactive ions will ...

  10. Evaluation of Neutron Induced Reactions for 32 Fission Products

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyeong Il

    2007-02-15

    Neutron cross sections for 32 fission products were evaluated in the neutron-incident energy range from 10{sup -5} eV to 20 MeV. The list of fission products consists of the priority materials for several applications, extended to cover complete isotopic chains for three elements. The full list includes 8 individual isotopes, {sup 95}Mo, {sup 101}Ru, {sup 103}Rh, {sup 105}Pd, {sup 109}Ag, {sup 131}Xe, {sup 133}Cs, {sup 141}Pr, and 24 isotopes in complete isotopic chains for Nd (8), Sm (9) and Dy (7). Our evaluation methodology covers both the low energy region and the fast neutron region.In the low energy region, our evaluations are based on the latest data published in the Atlas of Neutron Resonances. This resource was used to infer both the thermal values and the resolved resonance parameters that were validated against the capture resonance integrals. In the unresolved resonance region we performed the additional evaluation by using the averages of the resolved resonances and adjusting them to the experimental data.In the fast neutron region our evaluations are based on the nuclear reaction model code EMPIRE-2.19 validated against the experimental data. EMPIRE is the modular system of codes consisting of many nuclear reaction models, including the spherical and deformed Optical Model, Hauser-Feshbach theory with the width fluctuation correction and complete gamma-ray emission cascade, DWBA, Multi-step Direct and Multi-step Compound models, and several versions of the phenomenological preequilibrium models. The code is equipped with a power full GUI, allowing an easy access to support libraries such as RIPL and CSISRS, the graphical package, as well the utility codes for formatting and checking. In general, in our calculations we used the Reference Input Parameter Library, RIPL, for the initial set model parameters. These parameters were properly adjusted to reproduce the available experimental data taken from the CSISRS library. Our evaluations cover cross

  11. Reaction rates for reaction-diffusion kinetics on unstructured meshes

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2017-02-01

    The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model.

  12. Resonances and the thermonuclear reaction rate

    CERN Document Server

    Hussein, M S; Sargeant, A J; Pato, M P

    2003-01-01

    We present an approximate analytic expression for thermonuclear reaction rate of charged particles when the cross section contains a single narrow or wide resonance described by a Breit-Wigner shape. The resulting expression is uniformly valid as the effective energy and resonance energy coalesce. We use our expressions to calculate the reaction rate for $^{12}$C(p,$\\gamma$)$^{13}$N.

  13. Reactions on the surface and inside of neutron stars

    Directory of Open Access Journals (Sweden)

    Rehm K. E.

    2016-01-01

    Full Text Available Measurements from orbiting X-ray satellites during the last decades have provided us with a wealth of information about nuclear reactions thought to occur in the extreme, highdensity environment of neutron stars. With radioactive ion beams from first-generation facilities we have begun to study some of these processes in the laboratory. In this contribution I report on experiments performed with radioactive beams from the ATLAS accelerator at Argonne. I will discuss the nuclear physics of X-ray bursts and super-bursts, the production of in-flight radioactive beams, as well as novel detectors which are used in these experiments.

  14. Ni elemental neutron induced reaction cross-section evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Divadeenam, M.

    1979-03-01

    A completely new evaluation of the nickel neutron induced reaction cross sections was undertaken as a part of the ENDF/B-V effort. (n,xy) reactions and capture reaction time from threshold to 20 MeV were considered for /sup 58/ /sup 60/ /sup 61/ /sup 62/ /sup 64/Ni isotopes to construct the corresponding reaction cross section for natural nickel. Both experimental and theoretical calculated results were used in evaluating different partial cross sections. Precompound effects were included in calculating (n,xy) reaction cross sections. Experimentally measured total section data extending from 0.7 MeV to 20 MeV were used to generate smooth cross section. Below 0.7 to MeV elastic and capture cross sections are represented by resonance parameters. Inelastic angular distributions to the discrete isotopic levels and elemental elastic angular distributions are included in the evaluated data file. Gamma production cross sections and energy distribution due to capture and the (n,xy) reactions were evaluated from experimental data. Finally, error files are constructed for all partial cross sections.

  15. Subterranean production of neutrons, $^{39}$Ar and $^{21}$Ne: Rates and uncertainties

    CERN Document Server

    Šrámek, Ondřej; McDonough, William F; Mukhopadhyay, Sujoy; Peterson, R J

    2015-01-01

    Accurate understanding of the subsurface production of radionuclide $^{39}$Ar rate is necessary for argon dating techniques and noble gas geochemistry of the shallow and the deep Earth, and is also of interest to the WIMP dark matter experimental particle physics community. Our new calculations of subsurface production of neutrons, $^{21}$Ne, and $^{39}$Ar take advantage of the best available tools of nuclear physics to obtain reaction cross sections and spectra (TALYS) and to evaluate neutron propagation in rock (MCNP6). We discuss our method and results in relation to previous studies and show the relative importance of various neutron, $^{21}$Ne, and $^{39}$Ar nucleogenic production channels. Uncertainty in nuclear reaction cross sections, which is the major contributor to overall calculation uncertainty, is estimated from variability in existing experimental and library data. Depending on selected rock composition, on the order of $10^7$-$10^{10}$ {\\alpha} particles are produced in one kilogram of rock pe...

  16. Levels of 186Re populated in thermal neutron capture reaction

    Directory of Open Access Journals (Sweden)

    Bērzinš J.

    2015-01-01

    Full Text Available Levels of 186Re have been studied in the thermal neutron capture reaction with an enriched 185Re target. Evaluation of spectrum measured with GAMS5 allowed to obtain energies and intensities of more than 500 γ-lines assigned to 186Re. Most of the obtained transitions have been placed in the model-independent level scheme of the doubly odd 186Re nucleus, taking into account the available data of earlier experiments as well as the results of recent 187Re(p, d186Re reaction measurements. Structure of the 186Re low-lying levels has been analysed in terms of the particle-plus-rotor coupling model.

  17. Screened Thermonuclear Reaction Rates on Magnetar Surfaces

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-Lin; LUO Zhi-Quan; LIU Jing-Jing; LAI Xiang-Jun

    2008-01-01

    Improving Salpeter's method, we discuss the effect of superstrong magnetic fields (such as those of magnetars) on thermonuclear reaction rates. These most interesting reactions, including the hydrogen burning by the CNO cycle and the helium burning by the triple alpha reaction, are investigated as examples on the magnetar surfaces. The obtained result shows that the superstrong magnetic fields can increase the thermonuclear reaction rates by many orders of magnitude. The enhancement may have significant influence for further study research of the magnetars, especially for the x-ray luminosity observation and the evolution of magnetars.

  18. Heavy Ion Reactions with Neutron-Rich Beams - Proceedings of the Riken International Workshop

    Science.gov (United States)

    Yamaji, S.; Ishihara, M.; Takigawa, N.

    1993-11-01

    The Table of Contents for the book is as follows: * Preface * Opening Address * Fusion I * Heavy Ion Fusion at Subbarrier Energies: Progress and Questions * Angular Momentum in Heavy Ion Subbarrier Interaction * Fusion II * High Precision Fusion Excitation Function Measurements: What Can We Learn from Them? * Transfer Reactions for 16O + 144,152Sm near the Coulomb Barrier * Fusion III * Recent Theoretical Developments in the Study of Subbarrier Fusion * Direct Reaction Approach to Heavy Ion Scattering and Fusion at Energies near Coulomb Barrier * Fusion IV * Roles of Multi-Step Transfer in Fusion Process Induced by Heavy Ion Reactions * Special Session * RIKEN Accelerator Research Facility (RARF) * Fission I * Bimodal Nature of Nuclear Fission * Systematics of Isotope Production Rates: Mass Excess Dependence of Fission Products * Semiclassical Methods for the Multi-Dimensional Quantum Decay * Dynamics of Di-Nucleus Systems: Molecular Resonances * Fission II * The Competition Between Fusion-Fission and Deeply Inelastic Reactions in the Medium Mass Systems * Unstable Nuclei I * Coulomb Dissociation and Momentum Distributions for 11Li → 9Li+n+n Breakup Reactions * Unstable Nuclei II * Elastic Scattering and Fragmentation of Halo Nuclei * Secondary Reactions of Neutron-Rich Nuclei at Intermediate Energies * Life Time of Soft Dipole Excitation * Unstable Nuclei III * Shell Structure of Exotic Unstable Nuclei * Properties of Unstable Nuclei Within the Relativistic Many-Body Theory * Fusion with Unstable Nuclei * Barrier Distributions for Heavy Ion Fusion * Heavy Ion Reactions with Neutron-Rich Beams * Heavy Ion Fusion with Neutron-Rich Beams * Superheavy Elements * Study of α Decays Following 40Ar Bombardment on 238U * Production of Superheavy Elements via Fusion: What is Limiting Us? * Panel Session * Comments * List of Participants

  19. Two-neutron transfer reactions investigating shell stability and inverse kinematics capability

    Energy Technology Data Exchange (ETDEWEB)

    Mahgoub, Mahmoud; Bildstein, Vinzenz; Faestermann, Thomas; Gernhaeuser, Roman; Kroell, Thorsten; Kruecken, Reiner; Maier, Ludwig; Wirth, Hans [Physik-Department E12, TU Muenchen, Garching (Germany); Bohlen, Hans-Gerhard; Kokalova, Tzanka; Oertzen, Wolfram von; Wheldon, Carl [HMI, Berlin (Germany); Bucurescu, Dorel [NIPNE, Bucharest (Romania); Dorsch, Tatiana [Physik-Department E12, TU Muenchen, Garching (Germany); HMI, Berlin (Germany); Hertenberger, Ralf [Sektion Physik, LMU Muenchen (Germany)

    2008-07-01

    Neutron transfer reactions were used to study the stability of the magic number N=28. We investigated neutron pairing correlations using the two-neutron pickup reaction {sup 58}Ni((vector)p,t){sup 56}Ni depending on the fact that nuclei with high neutron pairing are good magic nuclei. The capability of inverse kinematics reactions to study exotic nuclei was tested by the neutron transfer reactions t({sup 40}Ar,p){sup 42} Ar using a tritium target and comparing the results and conclusions with the normal kinematics reactions. The results for the reactions on Ni and Ar compared to DWBA calculations will be presented. Future possibilities for the use of inverse kinematics to study exotic nuclei with radioactive beams are discussed.

  20. EURISOL Multi-MW Target Station - MAFF Configuration - Neutron Fluxes, Fission Rates, Dose Rates and Activation

    CERN Document Server

    Luis, R; Goncalves, I. F; Vaz, P; Kadi, Y; Kharoua, C; Rocca, R; Bermudez, J; Tecchio, L; Negoita, F; Ene, D; David, J.C

    The EURISOL (The EURopean Isotope Separation On-Line Radioactive Ion Beam) project aims atproducing high intensity radioactive ion beams produced by neutron-induced fission on fissile targets(235U) surrounding a liquid mercury converter. A proton beam of 1GeV and 4MW impinges on theconverter, generating, by spallation reactions, high neutron fluxes that induce fission in thesurrounding fissile targets.In this work the state-of-the-art Monte Carlo codes MCNPX and FLUKA were used to assess theneutronics performance of the system, which geometry, inspired in the MAFF concept, allows aversatile manipulation of the fission targets. The first objective of the study was to optimize thegeometry and the materials used in the fuel and reflector elements of the system, in order to achievethe highest possible fission rates. Indeed, it is shown that the appropriate combination of fission targetmaterial and surrounding reflector material leads to the aimed value of 1015 fissions/s per fissiontarget. The second part of this...

  1. A high-rate detection system to study parity violation with polarized epithermal neutrons at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Knudson, J.N.; Bowman, J.D. [Los Alamos National Lab., NM (United States); Crawford, B.E. [Duke Univ., Durham, NC (United States)]|[Triangle Universities Nuclear Laboratory, Durham, NC (United States)

    1995-07-01

    We describe an apparatus for studies of parity violation in neutron-nucleus scattering. This experiment requires longitudinally polarized neutrons from the Los Alamos Neutron Scattering Center over the energy-range from 1 to 1000 eV, the ability to reverse the neutron spin without otherwise affecting the apparatus, the ability to detect neutrons at rates up to 500 MHz, and an appropriate data acquisition system. We will discuss the neutron polarizer, fast neutron spin reverser, detector for transmitted neutrons, and high rate data acquisition system.

  2. Standard Test Method for Measuring Neutron Fluence Rate by Radioactivation of Cobalt and Silver

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This test method covers a suitable means of obtaining the thermal neutron fluence rate, or fluence, in well moderated nuclear reactor environments where the use of cadmium, as a thermal neutron shield as described in Method E262, is undesirable because of potential spectrum perturbations or of temperatures above the melting point of cadmium. 1.2 This test method describes a means of measuring a Westcott neutron fluence rate (Note 1) by activation of cobalt- and silver-foil monitors (See Terminology E170). The reaction 59Co(n,γ)60Co results in a well-defined gamma emitter having a half-life of 1925.28 days (1). The reaction 109Ag(n,˙γ) 110mAg results in a nuclide with a complex decay scheme which is well known and having a half-life of 249.76 days (1). Both cobalt and silver are available either in very pure form or alloyed with other metals such as aluminum. A reference source of cobalt in aluminum alloy to serve as a neutron fluence rate monitor wire standard is available from the National Institute ...

  3. Astrophysical reaction rate for $\\alpha(\\alpha n,\\gamma)$

    CERN Document Server

    Sumiyoshi, K; Goko, S; Kajino, T

    2002-01-01

    We study the astrophysical reaction rate for the formation of $^{9}$Be through the three body reaction $\\alpha(\\alpha n,\\gamma)$. This reaction is one of the key reactions which could bridge the mass gap at A = 8 nuclear systems to produce intermediate-to-heavy mass elements in alpha- and neutron-rich environments such as r-process nucleosynthesis in supernova explosions, s-process nucleosynthesis in asymptotic giant branch (AGB) stars, and primordial nucleosynthesis in baryon inhomogeneous cosmological models. To calculate the thermonuclear reaction rate in a wide range of temperatures, we numerically integrate the thermal average of cross sections assuming a two-steps formation through a metastable $^{8}$Be. Off-resonant and on-resonant contributions from the ground state in $^{8}$Be are taken into account. As input cross section, we adopt the latest experimental data by photodisintegration of $^{9}$Be with laser-electron photon beams, which covers all relevant resonances in $^{9}$Be. We provide the reactio...

  4. Neutron reactions in the hohlraum at the LLNL National Ignition Facility

    Science.gov (United States)

    Bradley, P. A.; Grim, G. P.; Hayes, A. C.; Jungman, Gerard; Rundberg, R. S.; Wilhelmy, J. B.; Hale, G. M.; Korzekwa, R. C.

    2012-07-01

    The National Ignition Facility (NIF) is designed to drive deuterium-tritium (DT) inertial confinement fusion targets to ignition using indirect radiation from laser energy captured in a hohlraum. The projected yields at NIF suggest that interactions of neutrons with the hohlraum can directly probe the neutron spectrum. Different physical parameters of the burning capsule can be probed by different neutron reactions. We suggest a variety of neutron reactions on the gold and uranium present in National Ignition Campaign hohlraums that will be useful for both neutron diagnostics and dosimetry at the NIF. The radiochemical daughter products may then be used to infer the neutron spectrum from the capsule. The downscattered neutrons may be studied by the (n,γ) and (n,n') reactions to infer the areal density of the capsule. The 14 MeV neutron fluence may be measured by (n,2n) daughter products for comparison to neutron spectrometer data. The hydrodynamical mix in the capsule can be studied with RIF neutrons, which are probed by (n,3n) reactions.

  5. How is entropy production rate related to chemical reaction rate?

    CERN Document Server

    Banerjee, Kinshuk

    2013-01-01

    The entropy production rate is a key quantity in irreversible thermodynamics. In this work, we concentrate on the realization of entropy production rate in chemical reaction systems in terms of the experimentally measurable reaction rate. Both triangular and linear networks have been studied. They attain either thermodynamic equilibrium or a non-equilibrium steady state, under suitable external constraints. We have shown that the entropy production rate is proportional to the square of the reaction velocity only around equilibrium and not any arbitrary non-equilibrium steady state. This feature can act as a guide in revealing the nature of a steady state, very much like the minimum entropy production principle. A discussion on this point has also been presented.

  6. Reaction rates for mesoscopic reaction-diffusion kinetics.

    Science.gov (United States)

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  7. Reaction rates for mesoscopic reaction-diffusion kinetics

    Science.gov (United States)

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  8. Stellar neutron capture rates and the s process

    Directory of Open Access Journals (Sweden)

    Käppeler F.

    2012-02-01

    Full Text Available Neutron reactions are responsible for the formation of the elements heavier than iron. The corresponding scenarios relate to helium burning in Red Giant stars (s process and to supernova explosions (r and p processes. The s process, which operates in or near the valley of β-stability, has produced about half of the elemental abundances between Fe and Bi. Accurate (n, γ cross sections are the essential input for s process studies, because they determine the abundances produced by that process. Following a brief summary of the neutron capture processes, the focus will be set on the s process in massive stars, where the role of reliable cross section information is particularly important. Eventually, the intriguing aspects of the origin of 60Fe will be addressed. Attempts to determine the stellar cross section of that isotope are pushing experimental possibilities to their limits and present a pertinent challenge for future facilities.

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

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, C.L.; Rehm, K.E.; Gehring, J. [and others

    1995-08-01

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

  10. Probing the pairing interaction through two-neutron transfer reactions

    Directory of Open Access Journals (Sweden)

    Margueron J.

    2012-12-01

    Full Text Available The treatment of the pairing interaction in mean-field-based models is addressed. In particular, the possibility to use pair transfers as A tool to better constrain this interaction is discussed. First, pairing inter-actions with various density dependencies (surface/volume mixing are used in the microscopic Hartree-Fock-Bogoliubov + quasiparticle random-phase approximation model to generate the form factors to be used in reaction calculations. Cross sections for (p,t two-neutron transfer reactions are calculated in the one-step zero-range distorted-wave Born approximation for some Tin isotopes and for incident proton energies from 15 to 35 MeV. Three different surface/volume mixings of A zero-range density-dependent pairing interaction are employed in the microscopic calculations and the sensitivity of the cross sections to the different mixings is analyzed. Differences among the three different theoretical predictions are found espacially for the nucleus 136Sn and they are more important at the incident proton energy of 15 MeV. We thus indicate (p,t two-neutron transfer reactions with very neutron-rich Sn isotopes and at proton energies around 15 MeV as good experimental cases where the surface/volume mixing of the pairing interaction may be probed. In the second part of the manuscript, ground-state to ground-state transitions are investigated. Approximations made to estimate two-nucleon transfer probabilities in ground-state to ground-state transitions and the physical interpretation of these probabilities are discussed. Probabilities are often calculated by approximating both ground states of the initial nucleus A and of the final nucleus A±2 by the same quasiparticle vacuum. We analyze two improvements of this approach. First, the effect of using two different ground states with average numbers of particles A and A±2 is quantified. Second, by using projection techniques, the role of particle number restoration is analyzed. Our analysis

  11. Reaction rates for a generalized reaction-diffusion master equation.

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2016-01-01

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach, in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is of the order of the reaction radius of a reacting pair of molecules.

  12. Reaction rates for a generalized reaction-diffusion master equation

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2016-01-01

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach, in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is of the order of the reaction radius of a reacting pair of molecules.

  13. Neutron fluence rate measurements at an underground laboratory: A Bayesian approach

    Science.gov (United States)

    Reginatto, Marcel; Kasper, Angelika; Schuhmacher, Helmut; Wiegel, Burkhard; Zimbal, Andreas

    2013-08-01

    We describe the analysis of neutron fluence rate measurements that were carried out at the underground laboratory Felsenkeller, near Dresden, Germany, which is at a depth of 47 m. At this depth, neutrons are mainly produced by natural radioactivity via spontaneous fission and (α, n) reactions, and by reactions induced by cosmic-ray muons. The measurements were made with the NEMUS Bonner sphere spectrometer. This system consists of a set of moderating spheres of different diameters and a 3He-filled proportional counter placed at the center of each sphere. Due to time constraints, it was only possible to use three of the spheres and the "bare detector" (i.e., a 3He-filled proportional counter without a moderating sphere). In addition to the measurements carried out at Felsenkeller, we also made low-level measurements with a set of 3He-filled proportional counters in the UDO underground laboratory at the Asse salt mine, near Braunschweig, Germany, which is at a depth of 490 m. The neutron background at UDO is substantially lower than that at Felsenkeller and these data are useful for setting limits on the background of the 3He-filled proportional counters. To estimate the neutron fluence rate at Felsenkeller, we did an analysis which took into account the measurements at UDO, Felsenkeller, and calibration measurements made at our facility in PTB. The analysis was done using Bayesian parameter estimation. Since the data consisted of low-level measurements, careful attention was given to the modeling of the intrinsic background of the detector and to identifying relevant sources of uncertainty. With the approach developed here, it is possible to estimate the neutron fluence rate with a relatively small uncertainty of the order of 10%. The method should be useful for other underground laboratories.

  14. Stellar neutron capture rates – key data for the s process

    Directory of Open Access Journals (Sweden)

    Käppeler F.

    2013-12-01

    Full Text Available Neutron reactions are responsible for the formation of the elements heavier than iron. The corresponding scenarios relate to the He- and C- burning phases of stellar evolution (s process and to supernova explosions (r and p processes. The s process, which is characterized by low neutron densities, operates in or near the valley of β stability and has produced about half of the elemental abundances between Fe and Bi in the solar system and in the Universe. Because the s abundances are essentially determined by the (n, γ cross sections along the reaction path, accurate neutron data constitute the key input for s process studies. Important constraints for the physical conditions at the stellar sites can be inferred by comparison of the abundance patterns from current s-process models with solar system material or presolar grains. The experimental methods for the determination of stellar (n, γ rates are outlined at the example of recent cross section measurements and remaining quests will be discussed with respect to existing laboratory neutron sources and new developments.

  15. Neutron Transfer Reactions on Neutron-Rich N=50 and N=82 Nuclei Near the r-Process Path

    Energy Technology Data Exchange (ETDEWEB)

    Cizewski, J. A. [Rutgers University; Jones, K. L. [University of Tennessee, Knoxville (UTK); Kozub, R. L. [Tennessee Technological University; Pain, S. D. [Rutgers University; Thomas, J. S. [Rutgers University; Arbanas, Goran [ORNL; Adekola, Aderemi S [ORNL; Bardayan, Daniel W [ORNL; Blackmon, Jeff C [ORNL; Chae, K. Y. [University of Tennessee, Knoxville (UTK); Chipps, K. [Colorado School of Mines, Golden; Dean, David Jarvis [ORNL; Erikson, Luke [Colorado School of Mines, Golden; Gaddis, A. L. [Furman University; Harlin, Christopher W [ORNL; Hatarik, Robert [Rutgers University; Howard, Joshua A [ORNL; Johnson, Micah [ORNL; Kapler, R. [University of Tennessee, Knoxville (UTK); Krolas, W. [University of Warsaw; Liang, J Felix [ORNL; Livesay, Jake [ORNL; Ma, Zhanwen [ORNL; Matei, Catalin [Oak Ridge Associated Universities (ORAU); Moazen, Brian [University of Tennessee, Knoxville (UTK); Nesaraja, Caroline D [ORNL; O' Malley, Patrick [Rutgers University; Paulauskas, Stanley V [ORNL; Shapira, Dan [ORNL; ShrinerJr., J. F. [Tennessee Technological University; Sissom, D. J. [Tennessee Technological University; Smith, Michael Scott [ORNL; Swan, T. P. [University of Surrey, UK; Wilson, Gemma L [ORNL

    2009-01-01

    Neutron transfer (d,p) reaction studies on the N = 50 isotones, 82Ge and 84Se, and A{approx}130 nuclei, 130,132Sn and 134Te, have been measured. Direct neutron capture cross sections for 82Ge and 84Se (n,?) have been calculated and are combined with Hauser-Feshbach expectations to estimate total (n,?) cross sections. The A{approx}130 studies used an early implementation of the ORRUBA array of position-sensitive silicon strip detectors for reaction proton measurements. Preliminary excitation energy and angular distribution results from the A{approx}130 measurements are reported.

  16. Neutron Capture Reactions on lu Isotopes at Dance

    Science.gov (United States)

    Roig, O.; Meot, V.; Daugas, J.-M.; Morel, P.; Jandel, M.; Vieira, D. J.; Bond, E. M.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Keksis, A. L.; Rundberg, R. S.; Ullmann, J. L.; Wouters, J. M.

    2013-03-01

    The DANCE1 (Detector for Advanced Neutron Capture Experiments) array at LANSCE spallation neutron source in Los Alamos has been used to obtain the neutron radiative capture cross sections for 175Lu and 176Lu with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the nucleosynthesis s-process.2,3 Three targets were used to perform these measurements. One was natural Lu foil of 31 mg/cm2 and the other two were isotope-enriched targets of 175Lu and 176Lu. Firstly, the cross sections were obtained by normalizing yield to a well-known cross section at the thermal neutron energy. Now, we want to obtain absolute cross sections of radiative capture through a precise neutron flux determination, an accurate target mass measurement and an efficiency determination of the DANCE array.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nabi, Jameel-Un; Iftikhar, Zafar [GIK Institute of Engineering Sciences and Technology, Faculty of Engineering Sciences, Khyber Pakhtunkhwa (Pakistan); Cakmak, Necla [Karabuek University, Department of Physics, Karabuek (Turkey)

    2016-01-15

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

  18. [Ozone therapy for radiation reactions and skin lesions after neutron therapy in patients with malignant tumors].

    Science.gov (United States)

    Velikaya, V V; Gribova, O V; Musabaeva, L I; Startseva, Zh A; Simonov, K A; Aleinik, A N; Lisin, V A

    2015-01-01

    The article discusses the problem of radiation complications from normal tissues in patients after therapy with fast neutrons of 6.3 MeV. The methods of treatment using ozone technologies in patients with radiation reactions and skin lesions on the areas of irradiation after neutron and neutron-photon therapy have been worked out. Ozone therapy showed its harmlessness and increased efficiency of complex treatment of these patients.

  19. Thermonuclear Reaction Rate Parameterization for Nuclear Astrophysics

    Science.gov (United States)

    Sharp, Jacob; Kozub, Raymond L.; Smith, Michael S.; Scott, Jason; Lingerfelt, Eric

    2004-10-01

    The knowledge of thermonuclear reaction rates is vital to simulate novae, supernovae, X-ray bursts, and other astrophysical events. To facilitate dissemination of this knowledge, a set of tools has been created for managing reaction rates, located at www.nucastrodata.org. One tool is a rate parameterizer, which provides a parameterization for nuclear reaction rate vs. temperature values in the most widely used functional form. Currently, the parameterizer uses the Levenberg-Marquardt method (LMM), which requires an initial estimate of the best-fit parameters. The initial estimate is currently provided randomly from a preselected pool. To improve the quality of fits, a new, active method of selecting parameters has been developed. The parameters of each set in the pool are altered for a few iterations to replicate the input data as closely as possible. Then, the set which most nearly matches the input data (based on chi squared) is used in the LMM as the initial estimate for the final fitting procedure. A description of the new, active algorithm and its performance will be presented. Supported by the U. S. Department of Energy.

  20. Two-temperature reaction and relaxation rates

    Science.gov (United States)

    Kolesnichenko, E.; Gorbachev, Yu.

    2016-09-01

    Within the method of solving the kinetic equations for gas mixtures with internal degrees of freedom developed by the authors and based on the approximate summational invariants (ASI) concept, gas-dynamic equations for a multi-temperature model for the spatially inhomogeneous case are derived. For the two-temperature case, the expressions for the non-equilibrium reaction and relaxation rates are obtained. Special attention is drawn to corresponding thermodynamic equations. Different possibilities of introducing the gas-dynamic variables related to the internal degrees of freedom are considered. One is based on the choice of quantum numbers as the ASI, while the other is based on the choice of internal (vibrational) energy as the ASI. Limits to a one-temperature situation are considered in all the cases. For the cutoff harmonic oscillator model, explicit expressions for the reaction and relaxation rates are derived.

  1. Quantum theory of chemical reaction rates

    Energy Technology Data Exchange (ETDEWEB)

    Miller, W.H. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Chemical Sciences Div.

    1994-10-01

    If one wishes to describe a chemical reaction at the most detailed level possible, i.e., its state-to-state differential scattering cross section, then it is necessary to solve the Schroedinger equation to obtain the S-matrix as a function of total energy E and total angular momentum J, in terms of which the cross sections can be calculated as given by equation (1) in the paper. All other physically observable attributes of the reaction can be derived from the cross sections. Often, in fact, one is primarily interested in the least detailed quantity which characterizes the reaction, namely its thermal rate constant, which is obtained by integrating Eq. (1) over all scattering angles, summing over all product quantum states, and Boltzmann-averaging over all initial quantum states of reactants. With the proper weighting factors, all of these averages are conveniently contained in the cumulative reaction probability (CRP), which is defined by equation (2) and in terms of which the thermal rate constant is given by equation (3). Thus, having carried out a full state-to-state scattering calculation to obtain the S-matrix, one can obtain the CRP from Eq. (2), and then rate constant from Eq. (3), but this seems like ``overkill``; i.e., if one only wants the rate constant, it would clearly be desirable to have a theory that allows one to calculate it, or the CRP, more directly than via Eq. (2), yet also correctly, i.e., without inherent approximations. Such a theory is the subject of this paper.

  2. Neutron capture reactions on Lu isotopes at DANCE

    Directory of Open Access Journals (Sweden)

    Wouters J.M.

    2010-03-01

    Full Text Available The DANCE (Detector for Advanced Neutron Capture Experiments array located at the Los Alamos national laboratory has been used to obtain the neutron capture cross sections for the 175Lu and 176Lu isotopes with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the nucleosynthesis s-process in astrophysics and for applications as in reactor physics or in nuclear medicine. Three targets were used to perform these measurements. One was natLu foil and the other two were isotope-enriched targets of 175Lu and 176Lu. The cross sections are obtained for now through a precise neutron flux determination and a normalization at the thermal neutron cross section value. A comparison with the recent experimental data and the evaluated data of ENDF/B-VII.0 will be presented. In addition, resonances parameters and spin assignments for some resonances will be featured.

  3. 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.

  4. Trojan horse method with neutrons induced reactions: The 17O(n,α)14C reaction

    Science.gov (United States)

    Guardo, G. L.; Spitaleri, C.; Lamia, L.; Gulino, M.; Tang, X.; Bucher, B.; Burjan, V.; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Kroha, V.; La Cognata, M.; Ma, C.; Mrazek, J.; Mukhamedzhanov, A.; Notani, M.; O'Brien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Wiescher, M.

    2017-06-01

    The experimental study of the 17O(n,α)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To over-come the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. In more details, the 17O(n,α)14C reaction has been studied using the quasi-free 2H(17O,α14C)1H reaction, induced at an energy of 43.5 MeV. The measurement allows one to investigate the ℓ=3, 75 keV resonance (E*=8.125 MeV, Jπ=5-), absent in the available direct measurements because of centrifugal suppression effects. Moreover, the results show that the contribution of the 166 keV and 236 keV resonances is in energy agreement with the available direct data. A clear contribution of the -7 keV subthreshold level is also present.

  5. Reaction Rate Parameterization for Nuclear Astrophysics Research

    Science.gov (United States)

    Scott, J. P.; Lingerfelt, E. J.; Smith, M. S.; Hix, W. R.; Bardayan, D. W.; Sharp, J. E.; Kozub, R. L.; Meyer, R. A.

    2004-11-01

    Libraries of thermonuclear reaction rates are used in element synthesis models of a wide variety of astrophysical phenomena, such as exploding stars and the inner workings of our sun. These computationally demanding models are more efficient when libraries, which may contain over 60000 rates and vary by 20 orders of magnitude, have a uniform parameterization for all rates. We have developed an on-line tool, hosted at www.nucastrodata.org, to obtain REACLIB parameters (F.-K. Thielemann et al., Adv. Nucl. Astrophysics 525, 1 (1987)) that represent reaction rates as a function of temperature. This helps to rapidly incorporate the latest nuclear physics results in astrophysics models. The tool uses numerous techniques and algorithms in a modular fashion to improve the quality of the fits to the rates. Features, modules, and additional applications of this tool will be discussed. * Managed by UT-Battelle, LLC, for the U.S. D.O.E. under contract DE-AC05-00OR22725 + Supported by U.S. D.O.E. under Grant No. DE-FG02-96ER40955

  6. Bayesian Estimation of Thermonuclear Reaction Rates

    CERN Document Server

    Iliadis, Christian; Coc, Alain; Timmes, Frank; Starrfield, Sumner

    2016-01-01

    The problem of estimating non-resonant astrophysical S-factors and thermonuclear reaction rates, based on measured nuclear cross sections, is of major interest for nuclear energy generation, neutrino physics, and element synthesis. Many different methods have been applied in the past to this problem, all of them based on traditional statistics. Bayesian methods, on the other hand, are now in widespread use in the physical sciences. In astronomy, for example, Bayesian statistics is applied to the observation of extra-solar planets, gravitational waves, and type Ia supernovae. However, nuclear physics, in particular, has been slow to adopt Bayesian methods. We present the first astrophysical S-factors and reaction rates based on Bayesian statistics. We develop a framework that incorporates robust parameter estimation, systematic effects, and non-Gaussian uncertainties in a consistent manner. The method is applied to the d(p,$\\gamma$)$^3$He, $^3$He($^3$He,2p)$^4$He, and $^3$He($\\alpha$,$\\gamma$)$^7$Be reactions,...

  7. Bayesian Estimation of Thermonuclear Reaction Rates

    Science.gov (United States)

    Iliadis, C.; Anderson, K. S.; Coc, A.; Timmes, F. X.; Starrfield, S.

    2016-11-01

    The problem of estimating non-resonant astrophysical S-factors and thermonuclear reaction rates, based on measured nuclear cross sections, is of major interest for nuclear energy generation, neutrino physics, and element synthesis. Many different methods have been applied to this problem in the past, almost all of them based on traditional statistics. Bayesian methods, on the other hand, are now in widespread use in the physical sciences. In astronomy, for example, Bayesian statistics is applied to the observation of extrasolar planets, gravitational waves, and Type Ia supernovae. However, nuclear physics, in particular, has been slow to adopt Bayesian methods. We present astrophysical S-factors and reaction rates based on Bayesian statistics. We develop a framework that incorporates robust parameter estimation, systematic effects, and non-Gaussian uncertainties in a consistent manner. The method is applied to the reactions d(p,γ)3He, 3He(3He,2p)4He, and 3He(α,γ)7Be, important for deuterium burning, solar neutrinos, and Big Bang nucleosynthesis.

  8. Reaction-in-Flight neutrons as a test of stopping power in degenerate plasmas

    Science.gov (United States)

    Hayes, A. C.; Cerjan, C. J.; Jungman, G.; Fowler, M. M.; Gooden, M. E.; Grim, G. P.; Henry, E.; Rundberg, R. S.; Sepke, S. M.; Schneider, D. H. G.; Singleton, R. L.; Tonchev, A. P.; Wilhelmy, J. B.; Yeamans, C. B.

    2016-05-01

    Cryogenically cooled inertial confinement fusion capsule designs are suitable for studies of reaction-in-flight (RIF) neutrons. RIF neutrons occur when energetically up-scattered ions undergo DT reactions with a thermal ion in the plasma, producing neutrons in the energy range 9-30 MeV. The knock-on ions lose energy as they traverse the plasma, which directly affects the spectrum of the produced RIF neutrons. Here we present measurements from the National Ignition Facility (NIF) of RIF neutrons produced in cryogenic capsules, with energies above 15 MeV. We show that the measured RIFs probe stopping under previously unexplored degenerate plasma conditions and constrain stopping models in warm dense plasma conditions.

  9. Thermal neutron radiative capture cross-section of 186W(n, γ)187W reaction

    Science.gov (United States)

    Tan, V. H.; Son, P. N.

    2016-06-01

    The thermal neutron radiative capture cross section for 186W(n, γ)187W reaction was measured by the activation method using the filtered neutron beam at the Dalat research reactor. An optimal composition of Si and Bi, in single crystal form, has been used as neutron filters to create the high-purity filtered neutron beam with Cadmium ratio of Rcd = 420 and peak energy En = 0.025 eV. The induced activities in the irradiated samples were measured by a high resolution HPGe digital gamma-ray spectrometer. The present result of cross section has been determined relatively to the reference value of the standard reaction 197Au(n, γ)198Au. The necessary correction factors for gamma-ray true coincidence summing, and thermal neutron self-shielding effects were taken into account in this experiment by Monte Carlo simulations.

  10. Experiments on iron shield transmission of quasi-monoenergetic neutrons generated by 43- and 68-MeV protons via the {sup 7}Li(p,n) reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nakashima, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Tanaka, Shun-ichi; Nakao, Noriaki [and others

    1996-03-01

    In order to provide benchmark data of neutrons transmitted through iron shields in the intermediate-energy region, spatial distributions of neutron energy spectra and reaction rates behind and inside the iron shields of thickness up to 130 cm were measured for 43- and 68-MeVp-{sup 7}Li neutrons using a quasi-monoenergetic neutron beam source at the 90-MV AVF cyclotron facility of the TLARA facility in JAERI. The measured data by five kinds of detectors: the BC501A detector, the Bonner ball counter, {sup 238}U and {sup 232}Th fission counters, {sup 7}LiF and {sup nat}LiF TLDs and solid state nuclear track detector, are numerically provided in this report in the energy region between 10{sup -4} eV and the energy of peak neutrons generated by the {sup 7}Li(p,n) reaction. (author).

  11. Dependence of X-Ray Burst Models on Nuclear Reaction Rates

    Science.gov (United States)

    Cyburt, R. H.; Amthor, A. M.; Heger, A.; Johnson, E.; Keek, L.; Meisel, Z.; Schatz, H.; Smith, K.

    2016-10-01

    X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars, and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p, γ), (α, γ), and (α, p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the Kepler stellar evolution code. All relevant reaction rates on neutron-deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 changes in reaction rate with the highest impact were then repeated in the 1D multi-zone model. We find a number of uncertain reaction rates that affect predictions of light curves and burst ashes significantly. The results provide insights into the nuclear processes that shape observables from X-ray bursts, and guidance for future nuclear physics work to reduce nuclear uncertainties in X-ray burst models.

  12. A D-D/D-T fusion reaction based neutron generator system for liver tumor BNCT

    Energy Technology Data Exchange (ETDEWEB)

    Koivunoro, H.; Lou, T.P.; Leung, K. N.; Reijonen, J.

    2003-04-02

    Boron-neutron capture therapy (BNCT) is an experimental radiation treatment modality used for highly malignant tumor treatments. Prior to irradiation with low energetic neutrons, a 10B compound is located selectively in the tumor cells. The effect of the treatment is based on the high LET radiation released in the {sup 10}B(n,{alpha}){sup 7}Li reaction with thermal neutrons. BNCT has been used experimentally for brain tumor and melanoma treatments. Lately applications of other severe tumor type treatments have been introduced. Results have shown that liver tumors can also be treated by BNCT. At Lawrence Berkeley National Laboratory, various compact neutron generators based on D-D or D-T fusion reactions are being developed. The earlier theoretical studies of the D-D or D-T fusion reaction based neutron generators have shown that the optimal moderator and reflector configuration for brain tumor BNCT can be created. In this work, the applicability of 2.5 MeV neutrons for liver tumor BNCT application was studied. The optimal neutron energy for external liver treatments is not known. Neutron beams of different energies (1eV < E < 100 keV) were simulated and the dose distribution in the liver was calculated with the MCNP simulation code. In order to obtain the optimal neutron energy spectrum with the D-D neutrons, various moderator designs were performed using MCNP simulations. In this article the neutron spectrum and the optimized beam shaping assembly for liver tumor treatments is presented.

  13. Facility for neutron induced few body reactions at Bochum University

    Energy Technology Data Exchange (ETDEWEB)

    Bannach, B.; Bodek, K.; Boerker, G.; Kamke, D.; Krug, J.; Lekkas, P.; Luebcke, W.; Stephan, M.

    1987-02-15

    A facility is described which is designed for the measurement of neutron induced three-body breakup. It has been used for the breakup of deuterium and of the nucleus /sup 9/Be. Neutrons are produced by a pulsed beam of deuterons from the Bochum 4MV Dynamitron-Tandem accelerator by bombarding a thick tritium-titanium target or a deuterium gas target. The outgoing beam is collimated by a 4..pi.. shielding to a solid angle of about 1 msr. In most cases, a liquid scintillator (NE232 or a mixture of NE232/Ne213) serves as a target for the neutron beam. Scattered neutrons are detected by Ne213-detectors of different sizes. For testing purposes the differential elastic n-d cross section and simultaneously the respnse of NE232 have beem measured at 22.4 and 7.9 MeV.

  14. Structure and reactions of light neutron rich nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Esbensen, H.

    1993-01-01

    Radioactive beam experiments have made it possible to study the structure of nuclei at the neutron drip line. Pair correlations play a crucial role in such nuclei and characteristic features include an extended neutron halo density and a large dipole strength near threshold. The most detailed studies have been performed for [sup 11]Li. I will present a 3-body model that explains the main features of the data obtained for this nucleus.

  15. Structure and reactions of light neutron rich nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Esbensen, H.

    1993-04-01

    Radioactive beam experiments have made it possible to study the structure of nuclei at the neutron drip line. Pair correlations play a crucial role in such nuclei and characteristic features include an extended neutron halo density and a large dipole strength near threshold. The most detailed studies have been performed for {sup 11}Li. I will present a 3-body model that explains the main features of the data obtained for this nucleus.

  16. CHLORINATION OF AMINO ACIDS: REACTION PATHWAYS AND REACTION RATES.

    Science.gov (United States)

    How, Zuo Tong; Linge, Kathryn; Busetti, Francesco; Joll, Cynthia A

    2017-03-15

    Chlorination of amino acids can result in the formation of organic monochloramines or organic dichloramines, depending on the chlorine to amino acid ratio (Cl:AA). After formation, organic chloramines degrade into aldehydes, nitriles and N-chloraldimines. In this paper, the formation of organic chloramines from chlorination of lysine, tyrosine and valine were investigated. Chlorination of tyrosine and lysine demonstrated that the presence of a reactive secondary group can increase the Cl:AA ratio required for the formation of N,N-dichloramines, and potentially alter the reaction pathways between chlorine and amino acids, resulting in the formation of unexpected by-products. In a detailed investigation, we report rate constants for all reactions in the chlorination of valine, for the first time, using experimental results and modelling. At Cl:AA = 2.8, the chlorine was found to first react quickly with valine (5.4x104 M-1 s-1) to form N-monochlorovaline, with a slower subsequent reaction with N-monochlorovaline to form N,N-dichlorovaline (4.9x102 M-1 s-1), although some N-monochlorovaline degraded into isobutyraldehyde (1.0x10-4 s-1). The N,N-dichlorovaline then competitively degraded into isobutyronitrile (1.3x10-4 s-1) and N-chloroisobutyraldimine (1.2x10-4 s-1). In conventional drinking water disinfection, N-chloroisobutyraldimine can potentially be formed in concentrations higher than its odour threshold concentration, resulting in aesthetic challenges and an unknown health risk.

  17. A coupled deterministic/stochastic method for computing neutron capture therapy dose rates

    Science.gov (United States)

    Hubbard, Thomas Richard

    Neutron capture therapy (NCT) is an experimental method of treating brain tumors and other cancers by: (1) injecting or infusing the patient with a tumor-seeking, neutron target-labeled drug; and (2) irradiating the patient in an intense epithermal neutron fluence. The nuclear reaction between the neutrons and the target nuclei (e.g. sp{10}B(n,alpha)sp7Lirbrack releases energy in the form of high-LET (i.e. energy deposited within the range of a cell diameter) reaction particles which selectively kill the tumor cell. The efficacy of NCT is partly dependent on the delivery of maximum thermal neutron fluence to the tumor and the minimization of radiation dose to healthy tissue. Since the filtered neutron source (e.g. research reactor) usually provides a broad energy spectrum of highly-penetrating neutron and gamma-photon radiation, detailed transport calculations are necessary in order to plan treatments that use optimal treatment facility configurations and patient positioning. Current computational methods for NCT use either discrete ordinates calculation or, more often, Monte Carlo simulation to predict neutron fluences in the vicinity of the tumor. These methods do not, however, accurately calculate the transport of radiation throughout the entire facility or the deposition of dose in all the various parts of the body due to shortcomings of using either method alone. A computational method, specifically designed for NCT problems, has been adapted from the MASH methodology and couples a forward discrete ordinates (Ssb{n}) calculation with an adjoint Monte Carlo run to predict the dose at any point within the patient. The transport from the source through the filter/collimator is performed with a forward DORT run, and this is then coupled to adjoint MORSE results at a selected coupling parallelepiped which surrounds human phantom. Another routine was written to allow the user to generate the MORSE models at various angles and positions within the treatment room. The

  18. Theoretical Standard Model Rates of Proton to Neutron Conversions Near Metallic Hydride Surfaces

    CERN Document Server

    Widom, A

    2006-01-01

    The process of radiation induced electron capture by protons or deuterons producing new ultra low momentum neutrons and neutrinos may be theoretically described within the standard field theoretical model of electroweak interactions. For protons or deuterons in the neighborhoods of surfaces of condensed matter metallic hydride cathodes, such conversions are determined in part by the collective plasma modes of the participating charged particles, e.g. electrons and protons. The radiation energy required for such low energy nuclear reactions may be supplied by the applied voltage required to push a strong charged current across a metallic hydride surface employed as a cathode within a chemical cell. The electroweak rates of the resulting ultra low momentum neutron production are computed from these considerations.

  19. First observations of Pontecorvo reactions with a recoiling neutron

    Energy Technology Data Exchange (ETDEWEB)

    Amsler, C. [California Univ., Berkeley, CA (United States); Armstrong, D.S. [California Univ., Berkeley, CA (United States); Augustin, I. [California Univ., Berkeley, CA (United States); Baker, C.A. [California Univ., Berkeley, CA (United States); Barnett, B.M. [California Univ., Berkeley, CA (United States); Batty, C.J. [California Univ., Berkeley, CA (United States); Beuchert, K. [California Univ., Berkeley, CA (United States); Birien, P. [California Univ., Berkeley, CA (United States); Bluem, P. [California Univ., Berkeley, CA (United States); Bossingham, R. [California Univ., Berkeley, CA (United States); Braune, K. [California Univ., Berkeley, CA (United States); Brose, J. [California Univ., Berkeley, CA (United States); Bugg, D.V. [California Univ., Berkeley, CA (United States); Burchell, M. [California Univ., Berkeley, CA (United States); Case, T. [California Univ., Berkeley, CA (United States); Cooper, A. [California Univ., Berkeley, CA (United States); Cramer, O. [California Univ., Berkeley, CA (United States); Crowe, K.M. [California Univ., Berkeley, CA (United States); Degener, T. [California Univ., Berkeley, CA (United States); Dietz, H.P. [California Univ., Berkeley, CA (United States); Dombrowski, S. v.; Doser, M.; Duennweber, W.; Engelhardt, D.; Englert, M.; Faessler, M.A.; Felix, C.; Hackmann, R.; Haddock, R.P.; Heinsius, F.H.; Herz, M.; Hessey, N.P.; Hidas, P.; Illinger, P.; Jamnik, D.; Kalinowsky, H.; Kaemmle, B.; Kiel, T.; Kisiel, J.; Klempt, E.; Kobel, M.; Koch, H.; Kolo, C.; Koenigsmann, K.; Kuhn, J.; Kunze, M.; Lakata, M.; Landua, R.; Luedemann, J.; Matthaey, H.; Merkel, M.; Merlo, J.P.; Meyer, C.A.; Montanet, L.; Noble, A.; Ould-Saada, F.; Peters, K.; Pinder, C.N.; Pinter, G.; Ravndal, S.; Schaefer, E.; Schmidt, P.; Spanier, S.; Stoeck, H.; Strassburger, C.; Strohbusch, U.; Suffert, M.; Thoma, U.; Urner, D.; Voelcker, C.; Walter, F.; Walther, D.; Wiedner, U.; Winter, N.; Zoll, J.; Zou, B.S.; Zupancic, C.; Crystal Barrel ...

    1995-04-01

    We report the first observations of Pontecorvo reactions of the type pd {yields} Xn. We fully reconstruct the outgoing meson and, for antiprotons stopped in liquid deuterium, we measure: BR ( anti pd {yields} {pi}{sup 0}n) = (7.03 {+-} 0.72) x 10{sup -6}, BR ( anti pd {yields} {eta}n) = (3.19 {+-} 0.48) x 10{sup -6}, BR ( anti pd {yields} {omega}n) = (22.8 {+-} 4.1) x 10{sup -6}, BR ( anti pd {yields} {eta}`n) {<=} 14 x 10{sup -6} (at 95% confidence level). Assuming charge independence, our result for anti pd {yields} {pi}{sup 0}n is compatible with measurements of the only other observed Pontecorvo reaction anti pd {yields} {pi}{sup -}p. The experimental ratios between the above branching ratios are in fair agreement with both the statistical model and dynamical two-step models (assuming N N annihilation into two mesons, with subsequent absorption of one meson on the remaining nucleon). This agreement suggests that there may be appreciable rates for Pontecorvo reactions producing final state mesons with masses above 1 GeV. (orig.)

  20. Neutron-induced reactions on AlF{sub 3} studied using the optical model

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Chun-Wang, E-mail: machunwang@126.com [Institute of Particle and Nuclear Physics, Henan Normal University, Xinxiang 453007 (China); Lv, Cui-Juan [Institute of Particle and Nuclear Physics, Henan Normal University, Xinxiang 453007 (China); Zhang, Guo-Qiang; Wang, Hong-Wei [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Zuo, Jia-Xu [Department of Nuclear and Radiation Safety Research, Nuclear and Radiation Safety Center (MEP), Beijing 100082 (China)

    2015-08-01

    Neutron-induced reactions on {sup 27}Al and {sup 19}F nuclei are investigated using the optical model implemented in the TALYS 1.4 toolkit. Incident neutron energies in a wide range from 0.1 keV to 30 MeV are calculated. The cross sections for the main channels (n, np), (n, p), (n, α), (n, 2n), and (n, γ) and the total reaction cross section (n, tot) of the reactions are obtained. When the default parameters in TALYS 1.4 are adopted, the calculated results agree with the measured results. Based on the calculated results for the n + {sup 27}Al and n + {sup 19}F reactions, the results of the n + {sup 27}Al{sup 19}F reactions are predicted. These results are useful both for the design of thorium-based molten salt reactors and for neutron activation analysis techniques.

  1. National Array of Neutron Detectors (NAND): A versatile tool for nuclear reaction studies

    Energy Technology Data Exchange (ETDEWEB)

    Golda, K.S., E-mail: goldaks@gmail.com [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Jhingan, A.; Sugathan, P. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Singh, Hardev [Department of Physics, Kurukshetra University, Kurukshetra 136119 (India); Singh, R.P. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Behera, B.R. [Department of Physics, Panjab University, Chandigarh 160014 (India); Mandal, S. [Department of Physics and Astrophysics, Delhi University, New Delhi 110007 (India); Kothari, A.; Gupta, Arti; Zacharias, J.; Archunan, M.; Barua, P.; Venkataramanan, S.; Bhowmik, R.K. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Govil, I.M. [Department of Physics, Panjab University, Chandigarh 160014 (India); Datta, S.K.; Chatterjee, M.B. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2014-11-01

    The first phase of the National Array of Neutron Detectors (NAND) consisting of 26 neutron detectors has been commissioned at the Inter University Accelerator Centre (IUAC), New Delhi. The motivation behind setting up of such a detector system is the need for more accurate and efficient study of reaction mechanisms in the projectile energy range of 5–8 MeV/n using heavy ion beams from a 15 UD Pelletron and an upgraded LINAC booster facility at IUAC. The above detector array can be used for inclusive as well as exclusive measurements of reaction products of which at least one product is a neutron. While inclusive measurements can be made using only the neutron detectors along with the time of flight technique and a pulsed beam, exclusive measurements can be performed by detecting neutrons in coincidence with charged particles and/or fission fragments detected with ancillary detectors. The array can also be used for neutron tagged gamma-ray spectroscopy in (HI, xn) reactions by detecting gamma-rays in coincidence with the neutrons in a compact geometrical configuration. The various features and the performance of the different aspects of the array are described in the present paper. -- Highlights: •We report the design, fabrication and installation of a 26 element modular neutron detection system (NAND). •The array has been designed for the fusion–fission studies at near and above the barrier energies. •The relevant characteristics of the array are studied exhaustively and reported. •The efficiency of the detectors are measured and compared with the monte carlo simulations. •The second phase of the array will be augmented with 80 more neutron detectors which will enable the system to measure the neutron multiplicity distribution.

  2. Heat Source Neutron Emission Rate Reduction Studies - Water Induced HF Liberation

    Science.gov (United States)

    Matonic, John; Brown, John; Foltyn, Liz; Garcia, Lawrence; Hart, Ron; Herman, David; Huling, Jeff; Pansoy-Hjelvik, M. E. Lisa; Sandoval, Fritz; Spengler, Diane

    2004-02-01

    Plutonium-238 oxide (238PuO2) is used in the fabrication of general purpose heat sources (GPHS) or light-weight radioisotope heater units (LWRHUs). The heat sources supply the thermal energy used in radioisotope thermoelectric generators to power spacecraft for deep space missions and to heat critical components in the cold environs of space. Los Alamos National Laboratory has manufactured heat sources for approximately two decades. The aqueous purification of 238PuO2 is required, due to rigorous total Pu-content, actinide and non-actinide metal impurity, and neutron emission rate specifications. The 238PuO2 aqueous purification process is a new capability at Los Alamos National Laboratory as previously, aqueous purified 238PuO2 occurred at other DOE complexes. The Pu-content and actinide and non-actinide metal impurity specifications are met well within specification in the Los Alamos process, though reduction in neutron emission rates have been challenging. High neutron emission rates are typically attributed to fluoride content in the oxide. The alpha decay from 238Pu results in α,n reactions with light elements such as 17O, 18O, and 19F resulting in high neutron emission rates in the purified 238PuO2. Simple 16O-exchange takes care of the high NER due to 17O, and 18O. A new method to reduce the NER due to 19F in the purified 238PuO2 is presented in this paper. The method involves addition of water to purified 238PuO2, followed by heating to remove the water and liberating fluoride as HF.

  3. Measurements of neutron-induced reactions in inverse kinematics and applications to nuclear astrophysics

    Directory of Open Access Journals (Sweden)

    Reifarth René

    2015-01-01

    Full Text Available Neutron capture cross sections of unstable isotopes are important for neutron-induced nucleosynthesis as well as for technological applications. A combination of a radioactive beam facility, an ion storage ring and a high flux reactor would allow a direct measurement of neutron induced reactions over a wide energy range on isotopes with half lives down to minutes. The idea is to measure neutron-induced reactions on radioactive ions in inverse kinematics. This means, the radioactive ions will pass through a neutron target. In order to efficiently use the rare nuclides as well as to enhance the luminosity, the exotic nuclides can be stored in an ion storage ring. The neutron target can be the core of a research reactor, where one of the central fuel elements is replaced by the evacuated beam pipe of the storage ring. Using particle detectors and Schottky spectroscopy, most of the important neutron-induced reactions, such as (n,γ, (n,p, (n,α, (n,2n, or (n,f, could be investigated.

  4. Measurements of neutron-induced reactions in inverse kinematics and applications to nuclear astrophysics

    CERN Document Server

    Reifarth, René; Endres, Anne; Göbel, Kathrin; Heftrich, Tanja; Glorius, Jan; Koloczek, Alexander; Sonnabend, Kerstin; Travaglio, Claudia; Weigand, Mario

    2015-01-01

    Neutron capture cross sections of unstable isotopes are important for neutron-induced nucleosynthesis as well as for technological applications. A combination of a radioactive beam facility, an ion storage ring and a high flux reactor would allow a direct measurement of neutron induced reactions over a wide energy range on isotopes with half lives down to minutes. The idea is to measure neutron-induced reactions on radioactive ions in inverse kinematics. This means, the radioactive ions will pass through a neutron target. In order to efficiently use the rare nuclides as well as to enhance the luminosity, the exotic nuclides can be stored in an ion storage ring. The neutron target can be the core of a research reactor, where one of the central fuel elements is replaced by the evacuated beam pipe of the storage ring. Using particle detectors and Schottky spectroscopy, most of the important neutron-induced reactions, such as (n,$\\gamma$), (n,p), (n,$\\alpha$), (n,2n), or (n,f), could be investigated.

  5. Measurements of neutron-induced reactions in inverse kinematics and applications to nuclear astrophysics

    Science.gov (United States)

    Reifarth, René; Litvinov, Yuri A.; Endres, Anne; Göbel, Kathrin; Heftrich, Tanja; Glorius, Jan; Koloczek, Alexander; Sonnabend, Kerstin; Travaglio, Claudia; Weigand, Mario

    2015-05-01

    Neutron capture cross sections of unstable isotopes are important for neutron-induced nucleosynthesis as well as for technological applications. A combination of a radioactive beam facility, an ion storage ring and a high flux reactor would allow a direct measurement of neutron induced reactions over a wide energy range on isotopes with half lives down to minutes. The idea is to measure neutron-induced reactions on radioactive ions in inverse kinematics. This means, the radioactive ions will pass through a neutron target. In order to efficiently use the rare nuclides as well as to enhance the luminosity, the exotic nuclides can be stored in an ion storage ring. The neutron target can be the core of a research reactor, where one of the central fuel elements is replaced by the evacuated beam pipe of the storage ring. Using particle detectors and Schottky spectroscopy, most of the important neutron-induced reactions, such as (n,γ), (n,p), (n,α), (n,2n), or (n,f), could be investigated.

  6. Neutron-induced transmutation reactions in 237Np, 238Pu, and 239Pu at the massive natural uranium spallation target

    Science.gov (United States)

    Zavorka, L.; Adam, J.; Baldin, A. A.; Caloun, P.; Chilap, V. V.; Furman, W. I.; Kadykov, M. G.; Khushvaktov, J.; Pronskikh, V. S.; Solnyshkin, A. A.; Sotnikov, V.; Stegailov, V. I.; Suchopar, M.; Tsoupko-Sitnikov, V. M.; Tyutyunnikov, S. I.; Voronko, V.; Vrzalova, J.

    2015-04-01

    Transmutation reactions in the 237Np, 238Pu, and 239Pu samples were investigated in the neutron field generated inside a massive (m = 512 kg) natural uranium spallation target. The uranium target assembly QUINTA was irradiated with the deuteron beams of kinetic energy 2, 4, and 8 GeV provided by the Nuclotron accelerator at the Joint Institute for Nuclear Research (JINR) in Dubna. The neutron-induced transmutation of the actinide samples was measured off-line by implementing methods of gamma-ray spectrometry with HPGe detectors. Results of measurement are expressed in the form of both the individual reaction rates and average fission transmutation rates. For the purpose of validation of radiation transport programs, the experimental results were compared with simulations of neutron production and distribution performed by the MCNPX 2.7 and MARS15 codes employing the INCL4-ABLA physics models and LAQGSM event generator, respectively. In general, a good agreement between the experimental and calculated reaction rates was found in the whole interval of provided beam energies.

  7. Neutron-capture rates for explosive nucleosynthesis: the case of 68Ni(n, γ)69Ni

    Science.gov (United States)

    Spyrou, A.; Larsen, A. C.; Liddick, S. N.; Naqvi, F.; Crider, B. P.; Dombos, A. C.; Guttormsen, M.; Bleuel, D. L.; Couture, A.; Crespo Campo, L.; Lewis, R.; Mosby, S.; Mumpower, M. R.; Perdikakis, G.; Prokop, C. J.; Quinn, S. J.; Renstrøm, T.; Siem, S.; Surman, R.

    2017-04-01

    Neutron-capture reactions play an important role in heavy element nucleosynthesis, since they are the driving force for the two processes that create the vast majority of the heavy elements. When a neutron capture occurs on a short-lived nucleus, it is extremely challenging to study the reaction directly and therefore the use of indirect techniques is essential. The present work reports on such an indirect measurement that provides strong constraints on the 68Ni(n, γ)69Ni reaction rate. This is done by populating the compound nucleus 69Ni via the β decay of 69Co and measuring the γ-ray deexcitation of excited states in 69Ni. The β-Oslo method was used to extract the γ-ray strength function and the nuclear level density. In addition the half-life of 69Co was extracted and found to be in agreement with previous literature values. Before the present results, the 68Ni(n, γ)69Ni reaction was unconstrained and the purely theoretical reaction rate was highly uncertain. The new uncertainty on the reaction rate based on the present experiment (variation between upper and lower limit) is approximately a factor of 3. The commonly used reaction libraries JINA-REACLIB and BRUSLIB are in relatively good agreement with the experimental rate. The impact of the new rate on weak r-process calculations is discussed.

  8. 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

  9. Possibility of 5He emission in neutron induced reactions

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Jingshang

    2004-01-01

    The unstable nucleus 5He emission has never been included in the widely used statistical model codes as the evaluation tool and interpretation experimental data.The calculated threshold energies of 5He emission from light nuclei to heavy nuclei indicate that in most cases the compound nucleus induced by incident neutron would emit 5He rather than 3He. Since 5He is unstable and can be separated into n+α spontaneously,so neutron is produced in 5He emission process. The formulation of the double-differential cross section of the neutron from the two-body breakup process of emitted 5He is established. Because of the strong recoil effect, the energy balance is strictly taken into account to meet the needs in nuclear engineering. Further improvement of the statistical model calculation codes on this respect is proposed. It is expected that the correlative measurement will be available to account the outgoing neutron and alpha particle simultaneously and to test and verify the existence of 5He emission.

  10. Importance of ~5He Emission in Neutron Induced Reactions

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The statistical model codes as the evaluation tool widely used in the world have long been performedto set up neutron data library below 20 MeV However, an important particle emission of ~5He has neverbeen included in the widely used codes. Based on the calculated threshold energies of ~3He and ~5He emissions for various nuclei, one can find

  11. Dependence of X-Ray Burst Models on Nuclear Reaction Rates

    CERN Document Server

    Cyburt, R H; Heger, A; Johnson, E; Keek, L; Meisel, Z; Schatz, H; Smith, K

    2016-01-01

    X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p,$\\gamma$), ($\\alpha$,$\\gamma$), and ($\\alpha$,p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the {\\Kepler} stellar evolution code. All relevant reaction rates on neutron deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 highest impact reaction rate changes were then repeated in the 1D multi-zone model. We find a number of uncertain reac...

  12. Density effect of the neutron halo nucleus induced reactions in intermediate energy heavy ion collisions

    Institute of Scientific and Technical Information of China (English)

    CAO Xi-Guang; CHEN Jin-Gen; MA Yu-Gang; FANG De-Qing; TIAN Wen-Dong; YAN Ting-Zhi; CAI Xiang-Zhou

    2009-01-01

    Using an isospin-dependent quantum molecular dynamics (IQMD) model, we study the 15C induced reactions from 30-120 MeV/nucleon systematically. Here the valence neutron of 15C is assigned at both 1d5/2 and 2s1/2 states respectively in order to study the density effect of reaction mechanism. It is. believed that the existent neutron halo structure at the 2s1/2 state of 15C will affect the light particle emission evidently.In our calculation, the different density distributions of 15C at two states are calculated by relativistic mean field (RMF) model and introduced in the initiation of IQMD model, respectively. It is found that some observables such as emission fragmentation multiplicity, emission neutron/proton ratio and emission neutrons'kinetic energy spectrum are sensitive to the initial density distribution.

  13. Neutron skin effect of some Mo isotopes in pre-equilibrium reactions

    Indian Academy of Sciences (India)

    M H Bölükdemir; E Tel; S Okuducu; N N Akti

    2011-03-01

    The neutron skin effect has been investigated for even isotopes of molybdenum at 25.6 MeV 94−100Mo(, ) reaction using the geometry-dependent hybrid model of pre-equilibrium nuclear reactions. Here the initial neutron/proton exciton numbers were calculated from the neutron/proton densities obtained from an effective nucleon–nucleon interaction of the Skyrme type. Initial exciton numbers from different radii of even Mo isotopes were used to obtain the corresponding neutron emission spectra. In this investigation the calculated results are compared with the experimental data as also with each other. The results using central densities in the geometry-dependent hybrid model are in better agreement with the experimental data.

  14. Reaction weakening and emplacement of crystalline thrusts: Diffusion control on reaction rate and strain rate

    Science.gov (United States)

    O'Hara, Kieran

    2007-08-01

    In the southern Appalachians, the Blue Ridge-Piedmont crystalline thrust sheet was emplaced onto low-grade Late Precambrian and Paleozoic sedimentary rocks in the footwall along a basal detachment consisting of phyllosilicate-rich mylonites (phyllonites). The phyllonites developed first by mechanical breakdown of feldspar followed by chemical breakdown to white mica in the presence of a pore fluid. Diffusion of solute in the pore fluid is the rate limiting step in controlling reaction rate and also the strain rate. Assuming solute diffusion follows the Stokes-Einstein equation, the shear strain rate is given by ⅆγ/ⅆt=2ωkT/5ηrx for shear stress ≥20 MPa, where n is a constant, ω is a geometric factor, k is Boltzmann's constant, T is absolute temperature, η is water viscosity, r is the atomic radius of the diffusing species, and x is the diffusion distance. A bulk diffusion coefficient in the range of ˜10 -10 to 10 -12 m 2/s over distances of 10-100 m results in strain rates of 10 -14 to 10 -13 s -1 in the temperature range 200-400 °C. It is concluded that greenschist grade crystalline thrust sheets develop on pre-existing basement faults that become weak during reaction softening and localize into high strain phyllonite zones in which pore fluid diffusion controls reaction rate and strain rate.

  15. Production of neutron-rich isotopes in {sup 82}Se+{sup 238}U grazing reaction

    Energy Technology Data Exchange (ETDEWEB)

    Marginean, N.; Corradi, L. [INFN, Laboratori Nazionali di Legnaro Padova (Italy); Berghini, S. [National Institute for Physics and Nuclear Engineering, Bucharest (Romania)] (and others)

    2005-07-01

    The reactions at the grazing angle between heavy ions at energies close to the Coulomb barrier are presently considered as a valuable tool for the production of nuclei far from stability, particularly in the neutron-rich area. Recent high mass-resolution experiments demonstrated that one could observe the transfer of up to six proton stripping (-6p) and six neutron pick-up (+6n) channels with cross sections down to {approx}50-100 {mu}b.

  16. An empirical fit to estimated neutron emission cross sections from proton induced reactions

    Indian Academy of Sciences (India)

    Moumita Maiti; Maitreyee Nandy; S N Roy; P K Sarkar

    2003-01-01

    Neutron emission cross section for various elements from 9Be to 209Bi have been calculated using the hybrid model code ALICE-91 for proton induced reactions in the energy range 25 MeV to 105 MeV. An empirical expression relating neutron emission cross section to target mass number and incident proton energy has been obtained. The simple expression reduces the computation time significantly. The trend in the variation of neutron emission cross sections with respect to the target mass number and incident proton energy has been discussed within the framework of the model used.

  17. Effects of a New Triple-alpha Reaction on X-ray Bursts of a Helium Accreting Neutron Star

    CERN Document Server

    Matsuo, Y; Noda, T; Saruwatari, M; Ono, M; Hashimoto, M; Fujimoto, M

    2011-01-01

    The effects of a new triple-$\\alpha$ reaction rate (OKK rate) on the helium flash of a helium accreting neutron star in a binary system have been investigated. Since the ignition points determine the properties of a thermonuclear flash of type I X-ray bursts, we examine the cases of different accretion rates, $dM/dt (\\dot{M})$, of helium from $3\\times10^{-10} M_{\\odot} \\rm yr^{-1}$ to $3\\times10^{-8} M_{\\odot} \\rm yr^{-1}$, which could cover the observed accretion rates. We find that for the cases of low accretion rates, nuclear burnings are ignited at the helium layers of rather low densities. As a consequence, helium deflagration would be triggered for all cases of lower accretion rate than $\\dot{M}\\simeq 3\\times10^{-8} M_{\\odot} \\rm yr^{-1}$. We find that OKK rate could be barely consistent with the available observations of the X-ray bursts on the helium accreting neutron star. However this coincidence is found to depend on the properties of crustal heating and the neutron star model.We suggest that OKK r...

  18. Measurement method of activation cross-sections of reactions producing short-lived nuclei with 14 MeV neutrons

    CERN Document Server

    Kawade, K; Kasugai, Y; Shibata, M; Iida, T; Takahashi, A; Fukahori, T

    2003-01-01

    We describe a method for obtaining reliable activation cross-sections in the neutron energy range between 13.4 and 14.9 MeV for the reactions producing short-lived nuclei with half-lives between 0.5 and 30 min. We noted neutron irradiation fields and measured induced activities, including (1) the contribution of scattered low-energy neutrons, (2) the fluctuation of the neutron fluence rate during the irradiation, (3) the true coincidence sum effect, (4) the random coincidence sum effect, (5) the deviation in the measuring position due to finite sample thickness, (6) the self-absorption of the gamma-ray in the sample material and (7) the interference reactions producing the same radionuclides or the ones emitting the gamma-ray with the same energy of interest. The cross-sections can be obtained within a total error of 3.6%, when good counting statistics are achieved, including an error of 3.0% for the standard cross-section of sup 2 sup 7 Al (n, alpha) sup 2 sup 4 Na. We propose here simple methods for measuri...

  19. Effective interaction: From nuclear reactions to neutron stars

    Indian Academy of Sciences (India)

    D N Basu

    2014-05-01

    An equation of state (EoS) for symmetric nuclear matter is constructed using the density-dependent M3Y effective interaction and extended for isospin asymmetric nuclear matter. Theoretically obtained values of symmetric nuclear matter incompressibility, isobaric incompressibility, symmetry energy and its slope agree well with experimentally extracted values. Folded microscopic potentials using this effective interaction, whose density dependence is determined from nuclear matter calculations, provide excellent descriptions for proton, alpha and cluster radioactivities, elastic and inelastic scattering. The nuclear deformation parameters extracted from inelastic scattering of protons agree well with other available results. The high density behaviour of symmetric and asymmetric nuclear matter satisfies the constraints from the observed flow data of heavy-ion collisions. The neutron star properties studied using -equilibrated neutron star matter obtained from this effective interaction reconcile with the recent observations of the massive compact stars.

  20. Study of neutron-rich nuclei using deep-inelastic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, I.Y.; Asztalos, S.; Deleplanque, M.; Cederwall, B.; Diamond, R.M.; Fallon, P.; Macchiavelli, A.O.; Phair, L.; Stephens, F.S.; Wozniak, G.J. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Frauendorf, S.G. [Research Center Rossendorf, Dresden (Germany); Becker, J.A.; Henry, E.A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Hua, P.F.; Sarantites, D.G. [Washington University, St. Louis, Missouri 63130 (United States); Saladin, J.X. [University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Yu, C.H. [University of Rochester, Rochester, New York 14627 (United States)

    1997-08-01

    We have used the {sup 48}Ca+{sup 176}Yb reaction to study the population of high-spin states in neutron-rich nuclei by deep-inelastic reactions. Using Gammasphere, we observed gamma transitions from nuclei several neutrons richer than the target. Yrast states with spin up to 20 were populated in this reaction. High-spin states in {sup 175,177,178}Yb were observed. In this region of reduced pairing, a reference based on experimental data was used to derive experimental Routhians. Systematics of experimental Routhians in neutron-rich Yb nuclei compare well with cranked shell-model calculations. {copyright} {ital 1997} {ital The American Physical Society}

  1. Thermal and epithermal neutron fluence rate gradient measurements by PADC detectors in LINAC radiotherapy treatments-field

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, M. T., E-mail: mariate9590@gmail.com; Barros, H.; Pino, F.; Sajo-Bohus, L. [Universidad Simón Bolívar, Nuclear Physics Laboratory, Sartenejas, Caracas (Venezuela, Bolivarian Republic of); Dávila, J. [Física Médica C. A. and Universidad Central de Venezuela, Caracas (Venezuela, Bolivarian Republic of)

    2015-07-23

    LINAC VARIAN 2100 is where energetic electrons produce Bremsstrahlung radiation, with energies above the nucleon binding energy (E≈5.5MeV). This radiation induce (γ,n) and (e,e’n) reactions mainly in the natural tungsten target material (its total photoneutron cross section is about 4000 mb in a energy range from 9-17 MeV). These reactions may occur also in other components of the system (e.g. multi leaf collimator). During radiation treatment the human body may receive an additional dose inside and outside the treated volume produced by the mentioned nuclear reactions. We measured the neutron density at the treatment table using nuclear track detectors (PADC-NTD). These covered by a boron-converter are employed, including a cadmium filter, to determine the ratio between two groups of neutron energy, i.e. thermal and epithermal. The PADC-NTD detectors were exposed to the radiation field at the iso-center during regular operation of the accelerator. Neutron are determined indirectly by the converting reaction {sup 10}B(n,α){sup 7}Li the emerging charged particle leave their kinetic energy in the PADC forming a latent nuclear track, enlarged by chemical etching (6N, NaOH, 70°C). Track density provides information on the neutron density through calibration coefficient (∼1.6 10{sup 4} neutrons /track) obtained by a californium source. We report the estimation of the thermal and epithermal neutron field and its gradient for photoneutrons produced in radiotherapy treatments with 18 MV linear accelerators. It was obsered that photoneutron production have higher rate at the iso-center.

  2. 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.

  3. Moderator design studies for a new neutron reference source based on the D–T fusion reaction

    Energy Technology Data Exchange (ETDEWEB)

    Mozhayev, Andrey V.; Piper, Roman K.; Rathbone, Bruce A.; McDonald, Joseph C.

    2016-06-01

    The radioactive isotope Californium-252 (252Cf) is relied upon internationally as a neutron calibration source for ionizing radiation dosimetry because of its high specific activity. The source may be placed within a heavy-water (D2O) moderating sphere to produce a softened spectrum representative of neutron fields common to commercial nuclear power plant environments, among others. Due to termination of the U.S. Department of Energy loan/lease program in 2012, the expense of obtaining 252Cf sources has undergone a significant increase, rendering high output sources largely unattainable. On the other hand, the use of neutron generators in research and industry applications has increased dramatically in recent years. Neutron generators based on deuterium-tritium (D-T) fusion reaction provide high neutron fluence rates and, therefore, could possibly be used as a replacement for 252Cf. To be viable, the 14.6 MeV D-T output spectrum must be significantly moderated to approximate common workplace environments. This paper presents the results of an effort to select appropriate moderating materials and design a configuration to reshape the primary neutron field toward a spectrum approaching that from a nuclear power plant workplace. A series of Monte-Carlo (MCNP) simulations of single layer high- and low-Z materials are used to identify initial candidate moderators. Candidates are refined through a similar series of simulations involving combinations of 2 to 5 different materials. The simulated energy distribution using these candidate moderators are rated in comparison to a target spectrum. Other properties, such as fluence preservation and/or enhancement, prompt gamma production and other characteristics are also considered.

  4. One-and Two-Neutron Transfer Reactions in 11Be+208Pb and Mechanism of Lowering Fusion Barrier

    Institute of Scientific and Technical Information of China (English)

    WANG Ning; LI Zhu-Xia; WU Xi-Zhen; WANG Nan; SUN Xiu-Quan

    2000-01-01

    We study one-and two-neutron transfer reactions in 11Be+208Pb by using the quantum molecular dynamics model. We find that lowering about 1-2 MeV of the potential barrier of 208Pb for fusion is gained when two neutrons separated from 11Be enter into 208Pb. Whereas no significant change of potential barrier is found when only the halo neutron separated from 11Be enters into 208Pb. The dynamical interplay between suppression and enhancement effects on the fusion probability in reaction 11Be+208Pb stemming from the easy separation of halo neutron and the long extending of neutron distribution is discussed.

  5. Cross section measurement for (n,n{alpha}) reactions by 14 MeV neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Kasugai, Y.; Ikeda, Y.; Uno, Y. [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Yamamoto, H.; Kawade, K.

    1997-03-01

    Nine (n,n{alpha}) cross sections for (n,n{alpha}) reactions induced by 13.5-14.9 MeV neutrons were measured for {sup 51}V, {sup 65}Cu, {sup 71}Ga, {sup 76}Ge, {sup 87}Rb, {sup 91}Zr, {sup 93}Nb, {sup 96}Zr and {sup 109}Ag isotopes by using Fusion Neutronics Source (FNS) at JAERI. The reactions for 91Zr and 96Zr were measured for the first time. The evaluated data of JENDL-3 and ENDF/B-VI were compared with the present data. Some of the evaluated values are much different from our data by a factor more than ten. (author)

  6. Single-charge-exchange reactions and the neutron density at the surface of the nucleus

    Science.gov (United States)

    Loc, Bui Minh; Auerbach, Naftali; Khoa, Dao T.

    2017-07-01

    In this paper, we study the charge-exchange reaction to the isobaric analog state using two types of transition densities. One transition density is equal to the difference of the total neutron density minus the total proton density and the other one is the density of the excess neutrons only. We show that for projectiles that do not probe the interior of the nucleus but mostly the surface of this nucleus, distinct differences in the cross section arise when two types of transition densities are employed. We demonstrate this by considering the (3He,t ) reaction.

  7. Observation of double pygmy resonances in $^{195,196}$Pt and enhanced astrophysical reaction rates

    CERN Document Server

    Giacoppo, F; Eriksen, T K; Görgen, A; Guttormsen, M; Hagen, T W; Larsen, A C; Kheswa, B V; Klintefjord, M; Koehler, P E; Nyhus, H T; Renstr\\om, T; Sahin, E; Siem, S; Tornyi, T G

    2014-01-01

    Our measurements of $^{195,196}$Pt $\\gamma$-strength functions show a double-humped enhancement in the $E_{\\gamma}= 4-8$ MeV region. For the first time, the detailed shape of these resonances is revealed for excitation energies in the quasicontinuum. We demonstrate that the corresponding neutron-capture cross sections and astrophysical reaction rates are increased by up to a factor of 2 when these newly observed pygmy resonances are included. These results lend credence to theoretical predictions of enhanced reaction rates due to such pygmy resonances and hence are important for a better understanding of r-process nucleosynthesis.

  8. Improved resonance reaction rate calculation for lattice physics subsystem

    Energy Technology Data Exchange (ETDEWEB)

    Finch, D.R.

    1974-02-08

    The resonance capture calculations of the HAMMER System and HAMBUR System are derived from a consistent statement of the integral slowing down equation and definitions of the resonance integral. The assumptions made in these treatments are explicitly stated, and and an attempt is made to estimate the possible error in the resonance integral arising from these assumptions. This analysis is made to pin-point those parts of the calculation that can be improved and updated. Based on the analysis of existing calculations a method of calculation is derived which avoids most of the problems encountered in HAMMER and HAMBUR. The chief improvements that result are as follows: Careful attention is paid to calculation of the resonance flux as most errors in existing calculations result from consistently overpredicting fluxes in all regions of a lattice cell. The calculation can be modified to produce as crude or detailed a resonance calculation, at the expense of computer time, as required by the user. Resonances that overlap group boundaries contribute the correct contribution to each group's reaction rates. Overlap between resonances of different isotopes is correctly accounted for. Up-to-date resonance formalisms are used including the Adler-Adler multi-level formulations. Provision is made to easily add new formalisms when required. Streaming effects from neutron leaking into a cell may optionally be included in the calculation of resonance reaction rates. A complete description of the physics contained in this new computational module is provided along with additional information on the numerical techniques employed in the module.

  9. Determination of neutron-induced fission cross-sections of unstable nuclei via surrogate reaction method

    Indian Academy of Sciences (India)

    B K Nayak

    2014-11-01

    Heavy ion reaction studies around Coulomb barrier energies have been generally used to investigate the effect of the structure of projectile/target on reaction dynamics. Other than providing an understanding of basic physics of the reaction dynamics, some of these reactions have been used as tools to serve as surrogates of neutron-induced compound nuclear fission cross-sections involving unstable targets. In this paper, we report some of the recent results on the determination of neutron-induced fission cross-sections of unstable actinides present in Th–U and U–Pu fuel cycles by surrogate reaction method by employing transfer-induced fission studies with 6,7Li beams.

  10. 一维贫铀/聚乙烯交替系统中D-T中子诱发的232Th(n,γ)反应率的测定与分析%Determination of 232Th(n, γ) reaction rate induced by D-T neutrons in one-dimensional alternate depleted uranium/p olyethylene shells

    Institute of Scientific and Technical Information of China (English)

    羊奕伟; 刘荣; 蒋励; 鹿心鑫; 王玫; 严小松

    2014-01-01

    A series of neutron integral fundamental researches of thorium nuclear data in set-ups containing thorium samples is carried out. One-dimensional alternate depleted uranium/polyethylene shells containing thorium samples are constructed by referring to the conceptual design of fusion-fission hybrid reactor, where a D-T neutron source driven by accelerator is used to simulate the fusion core of the reactor. 232Th (n,γ) reaction rates in samples located at different positions in the shells are measured in 5% uncertainty by using activated thorium sample decay γ-ray off-line measurement technique. The results show that the moderation of polyethylene to 14.1 MeV neutron will efficiently increase the capture rate of thorium, and the depleted uranium is also conducible to this increase obviously. The comparison between our measured data and the results available from mainstream nuclear data bank shows that the calculation results from ENDF/B-VI.6 and JENDL-3.3 are around 6% higher than the experimental results, while the newer ENDF/B-VII.0 will achieve better results, around 4% higher than the experimental results. We recommend the ENDF/B-VII.0 to be used in one-dimensional alternate depleted uranium/polyethylene shells related conceptual design when calculating the 232Th (n,γ) reaction rate.%开展了钍样品装置内钍核参数的积分中子学基础研究.参考混合堆概念设计搭建了内部放置了钍样品的一维贫铀/聚乙烯交替系统装置,采用加速器D-T中子源模拟聚变堆芯,利用前期开发的离线伽马测量方法测定了不同位置、不同中子谱情况下的232Th (n,γ)反应率,不确定度约为5%.结果显示,聚乙烯对14.1 MeV中子的慢化作用可有效提升钍俘获率,且贫铀对钍俘获率也有显著提升作用.实验结果与主流核数据库计算结果的对比显示, ENDF/B-VI.6和JENDL-3.3数据库的计算值比实验值平均约大6%,而较新的ENDF/B-VII.0数据库的计

  11. First Measurement of Reaction-in-Flight Neutrons at the National Ignition Facility

    Science.gov (United States)

    Tonchev, Anton; Cerjan, C.; Fortner, D.; Henry, E.; Shaughnessy, D.; Schnieder, D.; Stoeffl, W.; Stoyer, M.; Yeamans, C.; Boswell, M.; Bredeweg, T.; Grim, G.; Jungman, G.; Fowler, M.; Hayes, A.; Obst, A.; Rundberg, R.; Schulz, A.; Wilhelmy, J.; Wilde, C.; Bhike, M.; Fallin, B.; Gooden, M.; Howell, C.; Toenow, W.; LLNL/LANL/TUNL Collaboration

    2014-09-01

    The first measurement of reaction-in-flight (RIF) neutrons, also known as tertiary neutrons, has been performed at the National Ignition Facility (NIF) using an activation technique. Thulium foils positioned at 50 cm from the burning deuterium-tritium (DT) capsule have been exposed to the characteristic DT neutron spectrum. The high-energy part of these neutrons with energies above 15.0 MeV can produce 167Tm via the 169Tm(n,3n) reaction. The 208-keV γ-ray, emitted from the decay of 167Tm with a half-life of 9.2 days, has been measured using two clover detectors. The first preliminary result implies that the ratio of RIF neutrons (En>15.0 MeV) versus the total neutrons is 1x10-4 +/- 3x10-5. The important implication of these measurements on our knowledge of the charged-particle stopping power in strongly coupled quantum-degenerate plasma will be presented.

  12. Neutron and gamma ray total dose rate determination using anisn

    Science.gov (United States)

    Amin, E.; Ashoub, N.; Elkady, A.

    1994-07-01

    The National Center for Nuclear Safety and Radiation Control is in the process of acquiring a computer software library based mainly on internationally widely used computer codes. These codes are to be used as basic tools in safety analysis and radiation control and risk assessment. A complementary part of this activity is to validate the computer codes and set standard procedures with the limits of confidence for the different areas of applications of the one or the other code or set of codes. The present work has been then initiated in order to develop a standard shielding calculating procedure to be applied for the different applications of interest to the center, namely: shielding of nuclear installations, such as the ET-RR-1 reactor, the gamma unit, nuclear accelerator, radiotherapy units; shielding of nuclear sources (mainly neutron and gamma sources); shielding of transportation containers. In developing such a standard method, the sources of error to the final results (i.e. the dose rate and dose rate distribution) have to been identified and the error to be quantified. Through applying the developed procedure to benchmark PWR shielding problems, and to documented results for fission sources in water and concrete, the levels of confidence of the procedure in different application areas have been set.

  13. Neutron and gamma ray total dose rate determination using ANISN

    Energy Technology Data Exchange (ETDEWEB)

    Amin, E.; Elkady, A. [Atomic Energy Authority, Cairo (Egypt). National Center for Nuclear Safety and Radiation Control; Ashoub, N. [Nuclear Research Center, Cairo (Egypt)

    1994-07-01

    The National Center for Nuclear Safety and Radiation Control is in the process of acquiring a computer software library based mainly on internationally widely used computer codes. These codes are to be used as basic tools in safety analysis and radiation control and risk assessment. A complementary part of this activity is to validate the computer codes and set standard procedures with the limits of confidence for the different areas of applications of the one or the other code or set of codes. The present work has been then initiated in order to develop a standard shielding calculating procedure to be applied for the different applications of interest to the center, namely: shielding of nuclear installations, such as the ET-RR-1 reactor, the gamma unit, nuclear accelerator, radiotherapy units; shielding of nuclear sources (mainly neutron and gamma sources); shielding of transportation containers. In developing such a standard method, the sources of error to the final results (i.e. the dose rate and dose rate distribution) have to be identified and the error to be quantified. Through applying the developed procedure to benchmark PWR shielding problems, and to documented results for fission sources in water and concrete, the levels of confidence of the procedure in different application areas have been set. (author).

  14. Study on target spallation reaction cross sections induced by high energy neutrons and heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Takashi [Tohoku Univ., Sendai (Japan). Cyclotron and Radioisotope Center

    1996-03-01

    The target spallation reaction cross sections of neutrons and heavy ions which have not been observed are determined in this paper. The object of this work is to make clear the differences between the spallation reaction cross section of neutron and that of proton by comparing the obtained value of neutron with the known value of proton. To this end, the quasi monochromatic neutron field of 20{approx}50 MeV was developed in 4 cyclotrons, INS, CYRIC, TIARA and RIKEN. The nuclear spallation reaction cross sections of C, Al and Bi were measured in the above field and the distribution of nuclear spallation reaction products in Cu determined by C ion beam of HIMAC. {sup 12}C(n,2n){sup 11}C reaction cross section shows the maximum value of about 20 mb at near 40{approx}50 MeV and then the value gradually decreased to 10 mb. The cross sections of {sup 209}Bi(n,Xn) are shown. The distribution of {sup 61}Cu is lower at the entrance and higher in the depth. (S.Y.)

  15. Reaction-in-Flight Neutrons as a Signature for Shell Mixing in NIF capsules

    CERN Document Server

    Hayes, A C; Grim, G P; Jungman, Gerard; Wilhelmy, J B

    2009-01-01

    We present analytic calculations and results from computational simulations showing that reaction-in-flight (RIF) neutrons act as a robust indicator for mixing of the ablator shell material into the fuel in DT capsules designed for the National Ignition Facility. The sensitivity of RIF neutrons to hydrodynamical mixing arises through the dependence of RIF production on charged-particle stopping lengths in the mixture of DT fuel and ablator material. Since the stopping power in the plasma is a sensitive function of the electron temperature and density, it is also sensitive to mix. RIF production scales approximately inversely with the degree of mixing taking place, and the ratio of RIF to downscattered neutrons provides a measure of the mix fraction and/or the mixing length. For sufficiently high-yield capsules, where spatially resolved RIF images may be possible, neutron imaging could be used to map RIF images into detailed mix images.

  16. Theoretical predictions on production of neutron-deficient nuclei with Z ≥ 93 in multinucleon transfer reactions

    Science.gov (United States)

    Zhu, Long; Su, Jun; Zhang, Feng-Shou

    2017-08-01

    Within the framework of dinuclear system model, the transfer reactions 58Ni + 233U, 58Ni + 238U, and 64Ni + 238U are investigated. The influences of projectile and target neutron numbers on cross sections of producing neutron-deficient actinide nuclei in transfer reactions are studied. It is found that the system 58Ni + 233U with smaller neutron excess is favorable to produce neutron-deficient nuclei. We predict the production cross sections of neutron-deficient nuclei with Z = 93- 98 in transfer reactions 58Ni + 233U and 40Ca + 245Cm with different incident energies. We find the transfer reactions 58Ni + 233U and 40Ca + 245Cm are feasible for producing neutron-deficient actinide nuclei in future experiments.

  17. Reactivity and reaction rate studies on the fourth loading of ZENITH

    Energy Technology Data Exchange (ETDEWEB)

    Cameron, I.R.; Freemantle, R.G.; Reed, D.L.; Wilson, D.J. [General Reactor Physics Division, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)] (and others)

    1963-08-15

    The determination of the excess reactivity, control rod worths, prompt neutron lifetime, flux fine structure, and reaction rates of various nuclides for the fourth loading of the heated zero energy reactor ZENITH is described. The core contains 7.76 kg of U235, giving a carbon/U235 atom ratio of 7578, and forms the most dilute of the range studied. Comparisons of the experimental results with calculations using multigroup diffusion codes are presented. (author)

  18. 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.

  19. Subterranean production of neutrons, 39Ar and 21Ne: Rates and uncertainties

    Science.gov (United States)

    Šrámek, Ondřej; Stevens, Lauren; McDonough, William F.; Mukhopadhyay, Sujoy; Peterson, R. J.

    2017-01-01

    Accurate understanding of the subsurface production rate of the radionuclide 39Ar is necessary for argon dating techniques and noble gas geochemistry of the shallow and the deep Earth, and is also of interest to the WIMP dark matter experimental particle physics community. Our new calculations of subsurface production of neutrons, 21Ne , and 39Ar take advantage of the state-of-the-art reliable tools of nuclear physics to obtain reaction cross sections and spectra (TALYS) and to evaluate neutron propagation in rock (MCNP6). We discuss our method and results in relation to previous studies and show the relative importance of various neutron, 21Ne , and 39Ar nucleogenic production channels. Uncertainty in nuclear reaction cross sections, which is the major contributor to overall calculation uncertainty, is estimated from variability in existing experimental and library data. Depending on selected rock composition, on the order of 107-1010 α particles are produced in one kilogram of rock per year (order of 1-103 kg-1 s-1); the number of produced neutrons is lower by ∼ 6 orders of magnitude, 21Ne production rate drops by an additional factor of 15-20, and another one order of magnitude or more is dropped in production of 39Ar. Our calculation yields a nucleogenic 21Ne /4He production ratio of (4.6 ± 0.6) ×10-8 in Continental Crust and (4.2 ± 0.5) ×10-8 in Oceanic Crust and Depleted Mantle. Calculated 39Ar production rates span a great range from 29 ± 9 atoms kg-rock-1 yr-1 in the K-Th-U-enriched Upper Continental Crust to (2.6 ± 0.8) × 10-4 atoms kg-rock-1 yr-1 in Depleted Upper Mantle. Nucleogenic 39Ar production exceeds the cosmogenic production below ∼700 m depth and thus, affects radiometric ages of groundwater. The 39Ar chronometer, which fills in a gap between 3H and 14C , is particularly important given the need to tap deep reservoirs of ancient drinking water.

  20. Experimental studies of keV energy neutron-induced reactions relevant to astrophysics and nuclear physics

    Energy Technology Data Exchange (ETDEWEB)

    Shima, T.; Kii, T.; Kikuchi, T.; Okazaki, F.; Kobayashi, T.; Baba, T.; Nagai, Y. [Tokyo Inst. of Tech. (Japan). Faculty of Science; Igashira, M.

    1997-03-01

    Nuclear reactions induced by keV energy neutrons provide a plenty of informations for studies of both astrophysics and nuclear physics. In this paper we will show our experimental studies of neutron- induced reactions of light nuclei in the keV energy region by means of a pulsed keV neutron beam and high-sensitivity detectors. Also we will discuss astrophysical and nuclear-physical consequences by using the obtained results. (author)

  1. EURISOL-DS Multi-MWatt Hg Target: Neutron flux and fission rate calculations for the MAFF configuration

    CERN Document Server

    Romanets, Y; Vaz, P; Herrera-Martinez, A; Kadi, Y; Kharoua, C; Lettry, J; Lindroos, M

    The EURISOL (The EURopean Isotope Separation On-Line Radioactive Ion Beam) project aims at producing high intensity radioactive ion beams produced by neutron induced fission on a fissile target (235U) surrounding a liquid mercury converter. A proton beam of 1 GeV and 4 MW impinges on the Hg converter generating by spallation reactions high neutron fluxes. In this work the state-of-the-art Monte Carlo codes MCNPX and FLUKA were used to assess the neutronics performance of the system which geometry, inspired from the MAFF concept, allows a versatile manipulation of the fission targets. The objective of the study was to optimize the geometry of the system and the materials used in the fuel and reflector elements of the system, in order to achieve the highest possible fission rate.

  2. Spin yields of neutron-rich nuclei from deep inelastic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Asztalos, S.J.; Lee, I.Y.; Vetter, K.; Cederwall, B.; Clark, R.M.; Deleplanque, M.A.; Diamond, R.M.; Fallon, P.; Jing, K.; Phair, L.; Macchiavelli, A.O.; Rasmussen, J.O.; Stephens, F.S.; Wozniak, G.J. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Becker, J.A.; Bernstein, L.A.; McNabb, D.P. [Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Hua, P.F.; Sarantites, D.G. [Washington University, St. Louis, Missouri 63130 (United States); Saladin, J.X. [University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States); Yu, C. [University of Rochester, Rochester, New York 14627 (United States); Cizewski, J.A. [Rutgers University, New Brunswick, New Jersey 08903 (United States); Donangelo, R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janiero (Brazil)

    1999-10-01

    The potential for using deep inelastic reactions to populate high-spin states in neutron-rich nuclei is studied in a series of experiments using GAMMASPHERE for {gamma}-ray detection and a silicon strip detector for measuring the angles of projectilelike and targetlike fragments. In three experiments 61 new transitions up to a maximum spin of 22{h_bar} in 12 neutron-rich rare-earth nuclei were found. We observe that {gamma}-ray yields as a function of spin are flatter for all neutron transfer products than for inelastic excitation of either the projectile or target nucleus. Calculations are presented which indicate that this difference cannot be accounted for by quasielastic processes, but more likely are the result of larger energy loss processes, such as deep inelastic reactions. {copyright} {ital 1999} {ital The American Physical Society}

  3. Neutron-induced cross sections of actinides via the surrogate-reaction method

    Directory of Open Access Journals (Sweden)

    Ducasse Q.

    2013-12-01

    Full Text Available The surrogate-reaction method is an indirect way of determining cross sections for reactions that proceed through a compound nucleus. This technique may enable neutron-induced cross sections to be extracted for short-lived nuclei that otherwise cannot be measured. However, the validity of the surrogate method has to be investigated. In particular, the absence of a compound nucleus formation and the Jπ dependence of the decay probabilities may question the method. In this work we study the reactions 238U(d,p239U, 238U(3He,t238Np, 238U(3He,4He237U as surrogates for neutron-induced reactions on 238U, 237Np and 236U, respectively, for which good quality data exist. The experimental set-up enabled the measurement of fission and gamma-decay probabilities. The first results are hereby presented.

  4. Soft error rate simulation and initial design considerations of neutron intercepting silicon chip (NISC)

    Science.gov (United States)

    Celik, Cihangir

    -scale technologies. Prevention of SEEs has been studied and applied in the semiconductor industry by including radiation protection precautions in the system architecture or by using corrective algorithms in the system operation. Decreasing 10B content (20%of natural boron) in the natural boron of Borophosphosilicate glass (BPSG) layers that are conventionally used in the fabrication of semiconductor devices was one of the major radiation protection approaches for the system architecture. Neutron interaction in the BPSG layer was the origin of the SEEs because of the 10B (n,alpha) 7Li reaction products. Both of the particles produced have the capability of ionization in the silicon substrate region, whose thickness is comparable to the ranges of these particles. Using the soft error phenomenon in exactly the opposite manner of the semiconductor industry can provide a new neutron detection system based on the SERs in the semiconductor memories. By investigating the soft error mechanisms in the available semiconductor memories and enhancing the soft error occurrences in these devices, one can convert all memory using intelligent systems into portable, power efficient, directiondependent neutron detectors. The Neutron Intercepting Silicon Chip (NISC) project aims to achieve this goal by introducing 10B-enriched BPSG layers to the semiconductor memory architectures. This research addresses the development of a simulation tool, the NISC Soft Error Analysis Tool (NISCSAT), for soft error modeling and analysis in the semiconductor memories to provide basic design considerations for the NISC. NISCSAT performs particle transport and calculates the soft error probabilities, or SER, depending on energy depositions of the particles in a given memory node model of the NISC. Soft error measurements were performed with commercially available, off-the-shelf semiconductor memories and microprocessors to observe soft error variations with the neutron flux and memory supply voltage. Measurement

  5. TIME SCALES OF FUSION-FISSION REACTIONS CALCULATED FROM PRESCISSION NEUTRON MULTIPLICITIES

    NARCIS (Netherlands)

    SIWEKWILCZYNSKA, K; WILCZYNSKI, J; SIEMSSEN, RH; WILSCHUT, HW

    1995-01-01

    The time scale of fusion-fission reactions was found to be in the range from tau(f) = 5 . 10(-20) to 5 . 10(-19) s. This result was obtained from the analysis of the prescission neutron multiplicities with a new method combining the time-dependent statistical cascade calculations with the nuclear

  6. Characterisation of neutron and gamma-ray emission from thick target Be(p,n) reaction for boron neutron capture therapy

    Energy Technology Data Exchange (ETDEWEB)

    Guzek, J.; Mateva, T.; Tapper, U.A.S. [De Beers Diamond Res. Lab., Southdale (South Africa); McMurray, W.R. [National Accelerator Centre, Van de Graaff Group, P.O. Box 72, Faure 7131 (South Africa); Franklyn, C.B. [Atomic Energy Corporation of South Africa, P.O. Box 582, Pretoria (South Africa)

    1998-04-01

    Low energy accelerator-based neutron sources have promising potential for use in a clinical treatment of cancer with boron neutron capture therapy (BNCT) and boron neutron capture synovectomy (BNCS). Such sources often utilise a thick target Be(p,n) reaction using incident proton energies from several hundred keV to 1-2 MeV above the reaction threshold of 2.06 MeV. The resulting neutron and gamma-ray beams require considerable moderation and filtration in order to obtain thermal and epithermal neutron fluxes for therapy. The detailed knowledge of neutron and gamma-ray spectra, yield and angular distribution are necessary in order to design effective moderators and filters to be used for the treatment. Thick and thin beryllium target neutron and gamma spectra have been investigated in detail using the time-of-flight (TOF) technique, for incident proton energies from above threshold to 4 MeV. The results show characteristics of neutron and gamma-ray production of importance for the application of this neutron source for BNCT and BNCS. (orig.) 6 refs.

  7. Effect of positive Q-value neutron transfers on sub-barrier fusion reactions

    Science.gov (United States)

    Wen, Pei-Wei; Feng, Zhao-Qing; Zhang, Fan; Li, Cheng; Lin, Cheng-Jian; Zhang, Feng-Shou

    2017-06-01

    The role of positive Q-value neutron transfers in sub-barrier fusion reactions has been studied with a modified quantum coupled channels model with all order couplings (CCFULL model). Neutron rearrangement related only to the dynamical matching condition with no free parameters is implemented in the model, which provides a way to understand especially the Q-value dependence of sub-barrier fusion reactions. The fusion cross sections of the collision systems 40Ca+94, 96Zr have been calculated and analyzed. The general trend of experimental data can be reproduced well with additional channels for neutron rearrangement. We find that enhancement of sub-barrier fusion cross sections is closely related to the Q-value of the transferred neutrons, in particular for channels with sequential even number transferred neutrons. Supported by National Natural Science Foundation of China (11635003, 11025524, 11161130520, 11175218, U1332207) National Basic Research Program of China (2010CB832903) European Commission’s 7th Framework Programme (Fp7-PEOPLE-2010-IRSES) Agreement Project (269131)

  8. High frame-rate neutron radiography of dynamic events

    Energy Technology Data Exchange (ETDEWEB)

    Bossi, R.H.; Robinson, A.H.; Barton, J.P.

    1981-11-20

    A system has been developed to perform neutron radiographic analysis of dynamic events having a duration of several milliseconds. The system has been operated in the range of 2000 to 10,000 frames/second. Synchronization has provided high-speed-motion neutron radiographs for evaluation of the firing cycle of 7.62 mm munition rounds within a steel rifle barrel. The system has also been used to demonstrate the ability to produce neutron radiographic movies of two-phase flow. The equipment uses the Oregon State University TRIGA reactor capable of pulsing to 3000 MW peak power, a neutron beam collimator, a scintillator neutron conversion screen coupled to an image intensifier, and a 16 mm high speed movie camera. The peak neutron flux incident at the object position is approximately 4 x 10/sup 11/ n/cm/sup 2/s with a pulse, full width at half maximum, of 9 ms. Special studies have been performed on the scintillator conversion screens and on the effects of statistical limitations on the image quality. Modulation transfer function analysis has been used to assist in the evaluation of the system performance.

  9. Neutron Halo Structure at the Limit of Stability Probed by Breakup Reactions

    Science.gov (United States)

    Nakamura, Takashi

    2013-08-01

    Atomic nuclei along the neutron drip line are investigated experimentally by breakup reactions of the rare isotope beams. Such exotic nuclei often show the neutron halo structure, which is the main focus of this paper. Characteristic features of the Coulomb and nuclear breakup at intermediate to high incident energies are described. Then, recent experimental results on halo nuclei, mainly on 31Ne, obtained at the new-generation RI-beam facility, RIBF (RI Beam factory) at RIKEN, are presented. Perspectives for the breakup experiments using the new facility SAMURAI at RIBF ara also discussed.

  10. Analysis of orbital occupancy of valence neutron in 15C through Coulomb breakup reactions

    Science.gov (United States)

    Singh, P.

    2015-03-01

    The Coulomb breakup reactions 208Pb(15C, 14C + n)208Pb and 181Ta(15C, 14C + n)181Ta have been studied at 68 and 85 A MeV beam energies, respectively, within the framework of the eikonal approximation to investigate the orbital occupancy of valence neutron in the 15C nucleus. The outcomes of the present work favor 0+ ⊗ 2 s 1/2 as the core-neutron coupling for the ground-state structure with 0.91 as a spectroscopic factor.

  11. Analysis of orbital occupancy of valence neutron in {sup 15}C through Coulomb breakup reactions

    Energy Technology Data Exchange (ETDEWEB)

    Singh, P., E-mail: panghal005@gmail.com, E-mail: pardeep.phy@dcrustm.org [Deenbandhu Chhotu Ram University of Science and Technology, Department of Physics (India)

    2015-03-15

    The Coulomb breakup reactions {sup 208}Pb({sup 15}C, {sup 14}C + n){sup 208}Pb and {sup 181}Ta({sup 15}C, {sup 14}C + n){sup 181}Ta have been studied at 68 and 85 A MeV beam energies, respectively, within the framework of the eikonal approximation to investigate the orbital occupancy of valence neutron in the {sup 15}C nucleus. The outcomes of the present work favor 0{sup +} ⊗ 2s{sub 1/2} as the core-neutron coupling for the ground-state structure with 0.91 as a spectroscopic factor.

  12. Near threshold ⁷Li(p,n) ⁷Be reaction as neutron source for BNCT.

    Science.gov (United States)

    Minsky, D M; Kreiner, A J

    2015-12-01

    (7)Li(p,n)(7)Be is an endothermic reaction and working near its threshold (1.88 MeV) has the advantage of neutron spectra with maximum energies of about 100 keV, considerably lower than at higher beam energies, or than using other neutron-producing reactions or as for the uranium fission spectrum, relevant for BNCT based on nuclear reactors. With this primary energy it is much easier to obtain the energies needed for treating deep seated tumors by BNCT (about 10 keV). This work studies bombarding energies up to 2.05 MeV, different beam incidence angles and the effect of the undesirable gamma production via the (7)Li(p,γp') (7)Li reaction.

  13. Description of the proton and neutron radiative capture reactions in the Gamow shell model

    CERN Document Server

    Fossez, K; Płoszajczak, M; Jaganathen, Y

    2015-01-01

    We formulate the Gamow shell model (GSM) in coupled-channel (CC) representation for the description of proton/neutron radiative capture reactions and present the first application of this new formalism for the calculation of cross-sections in mirror reactions 7Be(p,gamma)8B and 7Li(n,gamma)8Li. The GSM-CC formalism is applied to a translationally-invariant Hamiltonian with an effective finite-range two-body interaction. Reactions channels are built by GSM wave functions for the ground state 3/2- and the first excited state 1/2- of 7Be/7Li and the proton/neutron wave function expanded in different partial waves.

  14. Probing the nuclear symmetry energy with heavy-ion reactions induced by neutron-rich nuclei

    Institute of Scientific and Technical Information of China (English)

    CHEN Lie-wen; KO Che-Ming; LI Bao-an; YONG Gao-chan

    2007-01-01

    Heavy-ion reactions induced by neutron-rich nuclei provide a unique means to investigate the equation of state of isospin-asymmetric nuclear matter,especially the density dependence of the nuclear symmetry energy.In particular,recent analyses of the isospin diffusion data in heavyion reactions have already put a stringent constraint on thenuclear symmetry energy around the nuclear matter saturation density.We review this exciting result and discuss its implications on nuclear effective interactions and the neutron skin thickness of heavy nuclei.In addition,we also review the theoretical progress on probing the high density behaviors of the nuclear symmetry energy in heavy-ion reactions induced by high energy radioactive beams.

  15. Neutron-induced capture cross sections of short-lived actinides with the surrogate reaction method

    Directory of Open Access Journals (Sweden)

    Gunsing F.

    2010-03-01

    Full Text Available Determination of neutron-capture cross sections of short-lived nuclei is opening the way to understand and clarify the properties of many nuclei of interest for nuclear structure physics, nuclear astrophysics and particularly for transmutation of nuclear wastes. The surrogate approach is well-recognized as a potentially very useful method to extract neutron cross sections for low-energy compound-nuclear reactions and to overcome the difficulties related to the target radioactivity. In this work we will assess where we stand on these neutron-capture cross section measurements and how we can achieve the short-lived Minor Actinides nuclei involved in the nuclear fuel cycle. The CENBG collaboration applied the surrogate method to determine the neutron-capture cross section of 233Pa (T1/2 = 27 d. The 233Pa (n,γ cross section is then deduced from the measured gamma decay probability of 234Pa compound nucleus formed via the surrogate 232Th(3He,p reaction channel. The obtained cross section data, covering the neutron energy range 0.1 to 1 MeV, have been compared with the predictions of the Hauser-Feshbach statistical model. The importance of establishing benchmarks is stressed for the minor actinides region. However, the lack of desired targets led us to propose recently the 174Yb (3He,pγ reaction as a surrogate reaction for the (n,γ predetermined benchmark cross section of 175Lu. An overview of the experimental setup combining gamma ray detectors such as Ge and C6D6 in coincidence with light charged particles ΔE-E Telescopes will be presented and preliminary results will be discussed.

  16. Low-energy neutron-deuteron reactions with N{sup 3}LO chiral forces

    Energy Technology Data Exchange (ETDEWEB)

    Golak, J.; Skibinski, R.; Topolnicki, K.; Witala, H. [Jagiellonian University, M. Smoluchowski Institute of Physics, Krakow (Poland); Epelbaum, E.; Krebs, H. [Ruhr-Universitaet Bochum, Institut fuer Theoretische Physik II, Bochum (Germany); Kamada, H. [Kyushu Institute of Technology, Department of Physics, Faculty of Engineering, Kitakyushu (Japan); Meissner, Ulf G. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Bonn (Germany); JARA - High Performance Computing Forschungszentrum Juelich, Institute for Advanced Simulation, Institut fuer Kernphysik, Juelich Center for Hadron Physics, Juelich (Germany); Bernard, V. [CNRS/Univ. Paris-Sud, Institut de Physique Nucleaire, Orsay (France); Maris, P.; Vary, J. [Iowa State University, Department of Physics and Astronomy, Ames, Iowa (United States); Binder, S.; Calci, A.; Langhammer, J.; Roth, R. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); Hebeler, K. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Extreme Matter Institute EMMI, Darmstadt (Germany); Nogga, A. [Juelich Center for Hadron Physics, Forschungszentrum Juelich, Institut fuer Kernphysik, Institute for Advanced Simulation, Juelich (Germany); Liebig, S.; Minossi, D. [Juelich Center for Hadron Physics, Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany)

    2014-11-15

    We solve three-nucleon Faddeev equations with nucleon-nucleon and three-nucleon forces derived consistently in the framework of chiral perturbation theory at next-to-next-to-next-to-leading order in the chiral expansion. In this first investigation we include only matrix elements of the three-nucleon force for partial waves with the total two-nucleon (three-nucleon) angular momenta up to 3 (5/2). Low-energy neutron-deuteron elastic scattering and deuteron breakup reaction are studied. Emphasis is put on A{sub y} puzzle in elastic scattering and cross sections in symmetric-space-star and neutron-neutron quasi-free-scattering breakup configurations, for which large discrepancies between data and theory have been reported. (orig.)

  17. Low-energy neutron-deuteron reactions with N3LO chiral forces

    CERN Document Server

    Golak, J; Topolnicki, K; Witala, H; Epelbaum, E; Krebs, H; Kamada, H; Meissner, Ulf-G; Bernard, V; Maris, P; Vary, J; Binder, S; Calci, A; Hebeler, K; Langhammer, J; Roth, R; Nogga, A; Liebig, S; Minossi, D

    2014-01-01

    We solve three-nucleon Faddeev equations with nucleon-nucleon and three-nucleon forces derived consistently in the framework of chiral perturbation theory at next-to-next-to-next-to-leading order in the chiral expansion. In this first investigation we include only matrix elements of the three-nucleon force for partial waves with the total two-nucleon (three-nucleon) angular momenta up to 3 (5/2). Low-energy neutron-deuteron elastic scattering and deuteron breakup reaction are studied. Emphasis is put on Ay puzzle in elastic scattering and cross sections in symmetric-space-star and neutron-neutron quasi-free-scattering breakup configurations, for which large discrepancies between data and theory have been reported.

  18. Nitrogen Detection in Bulk Samples Using a D-D Reaction-Based Portable Neutron Generator

    Directory of Open Access Journals (Sweden)

    A. A. Naqvi

    2013-01-01

    Full Text Available Nitrogen concentration was measured via 2.52 MeV nitrogen gamma ray from melamine, caffeine, urea, and disperse orange bulk samples using a newly designed D-D portable neutron generator-based prompt gamma ray setup. Inspite of low flux of thermal neutrons produced by D-D reaction-based portable neutron generator and interference of 2.52 MeV gamma rays from nitrogen in bulk samples with 2.50 MeV gamma ray from bismuth in BGO detector material, an excellent agreement between the experimental and calculated yields of nitrogen gamma rays indicates satisfactory performance of the setup for detection of nitrogen in bulk samples.

  19. Fusion reactions with the one-neutron halo nucleus 15C

    CERN Document Server

    Alcorta, M; Back, B B; Bedoor, S; Bertone, P F; Deibel, C M; DiGiovine, B; Esbensen, H; Greene, J P; Hoffmann, C R; Jiang, C L; Lighthall, J C; Marley, S T; Pardo, R C; Paul, M; Rogers, A M; Ugalde, C; Wuosmaa, A H

    2011-01-01

    The structure of 15C, with an s1/2 neutron weakly bound to a closed-neutron shell nucleus 14C, makes it a prime candidate for a one-neutron halo nucleus. We have for the first time studied the cross section for the fusion-fission reaction 15C + 232Th at energies in the vicinity of the Coulomb barrier and compared it to the yield of the neighboring 14C + 232Th system measured in the same experiment. At sub-barrier energies, an enhancement of the fusion yield by factors of 2-5 was observed for 15C, while the cross sections for 14C match the trends measured for 12,13C.

  20. Statistical Methods for Thermonuclear Reaction Rates and Nucleosynthesis Simulations

    CERN Document Server

    Iliadis, Christian; Coc, Alain; Timmes, F X; Champagne, Art E

    2014-01-01

    Rigorous statistical methods for estimating thermonuclear reaction rates and nucleosynthesis are becoming increasingly established in nuclear astrophysics. The main challenge being faced is that experimental reaction rates are highly complex quantities derived from a multitude of different measured nuclear parameters (e.g., astrophysical S-factors, resonance energies and strengths, particle and gamma-ray partial widths). We discuss the application of the Monte Carlo method to two distinct, but related, questions. First, given a set of measured nuclear parameters, how can one best estimate the resulting thermonuclear reaction rates and associated uncertainties? Second, given a set of appropriate reaction rates, how can one best estimate the abundances from nucleosynthesis (i.e., reaction network) calculations? The techniques described here provide probability density functions that can be used to derive statistically meaningful reaction rates and final abundances for any desired coverage probability. Examples ...

  1. EXFOR BASICS A SHORT GUIDE TO THE NEUTRON REACTION DATA EXCHANGE FORMAT.

    Energy Technology Data Exchange (ETDEWEB)

    MCLANE,V.; NUCLEAR DATA CENTER NETWORK

    2000-05-19

    This manual is intended as a guide to users of nuclear reaction data compiled in the EXFOR format, and is not intended as a complete guide to the EXFOR System. EXFOR is the exchange format designed to allow transmission of nuclear reaction data between the Nuclear Reaction Data Centers. In addition to storing the data and its' bibliographic information, experimental information is also compiled. The status (e.g., the source of the data) and history (e.g., date of last update) of the data set is also included. EXFOR is designed for flexibility in order to meet the diverse needs of the nuclear reaction data centers. It was originally conceived for the exchange of neutron data and was developed through discussions among personnel from centers situated in Saclay, Vienna, Livermore and Brookhaven. It was accepted as the official exchange format of the neutron data centers at Saclay, Vienna, Brookhaven and Obninsk, at a meeting held in November 1969. As a result of two meetings held in 1975 and 1976 and attended by several charged-particle data centers, the format was further developed and adapted to cover all nuclear reaction data. The exchange format should not be confused with a center-to-user format. Although users may obtain data from the centers in the EXFOR format, other center-to-user formats have been developed to meet the needs of the users within each center's own sphere of responsibility. The EXFOR format, as outlined, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in a format: that is machine-readable (for checking and indicating possible errors); that can be read by personnel (for passing judgment on and correcting errors). The data presently included in the EXFOR exchange file include: a complete compilation of experimental neutron-induced reaction data, a selected compilation of charged-particle-induced reaction data, a selected compilation of photon-induced reaction data.

  2. Measurement of reaction cross sections of {sup 129}I induced by DT neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, Daisuke; Murata, Isao; Takahashi, Akito [Osaka Univ., Suita (Japan). Faculty of Engineering

    1997-03-01

    The cross sections were measured for the {sup 129}I(n,2n){sup 128}I and {sup 129}I(n,{gamma}){sup 130}I reactions by DT neutrons, at OKTAVIAN facility of Osaka University, Japan. The foil activation method was used in the measurement. The sample was a sealed source of {sup 129}I, which was covered with a Cd foil. The irradiations were performed for 75 minutes to obtain the cross section of reaction producing {sup 128}I (T{sub 1/2}=24.99m) and 22 hours for the {sup 130}I (T{sub 1/2}=12.36h), respectively. The gamma-rays emitted from the irradiated sample were measured with a high purity Ge detector. The measured cross sections of {sup 129}I(n,2n){sup 128}I and {sup 129}I(n,{gamma}){sup 130}I reactions were 0.92{+-}0.11 barn and 0.013{+-}0.002 barn, respectively. For the {sup 129}I(n,2n){sup 128}I reaction, the evaluation of JENDL-3.2 overestimates cross section about 60% to the experimental result. However, especially for the {sup 129}I(n,{gamma}) reaction, the measured cross section may include the contribution from the neutrons in MeV region as well as epithermal ones. Also, the obtained cross section of the {sup 129}I(n,{gamma}){sup 130}I reaction was evaluated as an effective production cross section of {sup 130}I including {sup 129}I(n,{gamma}){sup 130m}I reaction. In order to remove the contribution from the epithermal and MeV region neutrons. A new method was proposed for the measurement of (n,{gamma}) reaction cross section. (author)

  3. Determining neutron capture cross sections with the Surrogate Reaction Technique: Measuring decay probabilities with STARS

    Energy Technology Data Exchange (ETDEWEB)

    Church, J A; Ahle, L; Bernstein, L A; Cooper, J; Dietrich, F S; Escher, J; Forssen, C; Ai, H; Amro, H; Babilon, M; Beausang, C; Caggiano, J; Heinz, A; Hughes, R; McCutchan, E; Meyer, D; Plettner, C; Ressler, J; Zamfir, V

    2004-07-14

    Neutron-induced reaction cross sections are sometimes difficult to measure due to target or beam limitations. For two-step reactions proceeding through an equilibrated intermediate state, an alternate ''surrogate reaction'' technique can be applicable, and is currently undergoing investigation at LLNL. Measured decay probabilities for the intermediate nucleus formed in a light-ion reaction can be combined with optical-model calculations for the formation of the same intermediate nucleus via the neutron-induced reaction. The result is an estimation for overall (n,{gamma}/n/2n) cross sections. As a benchmark, the reaction {sup 92}Zr({alpha},{alpha}'), surrogate, for n+{sup 91}Zr, was studied at the A.W. Wright Nuclear Structure Laboratory at Yale. Particles were detected in the silicon telescope STARS (Silicon Telescope Array for Reaction Studies) and {gamma}-ray energies measured with germanium clover detectors from the YRAST (Yale Rochester Array for SpecTroscopy) ball. The experiment and preliminary observations will be discussed.

  4. Microscopic dynamics simulations of heavy-ion fusion reactions induced by neutron-rich nuclei

    CERN Document Server

    Wang, Ning; Zhang, Yingxun; Li, Zhuxia

    2014-01-01

    The heavy-ion fusion reactions induced by neutron-rich nuclei are investigated with the improved quantum molecular dynamics (ImQMD) model. With a subtle consideration of the neutron skin thickness of nuclei and the symmetry potential, the stability of nuclei and the fusion excitation functions of heavy-ion fusion reactions $^{16}$O+$^{76}$Ge, $^{16}$O+$^{154}$Sm, $^{40}$Ca+$^{96}$Zr and $^{132}$Sn+$^{40}$Ca are systematically studied. The fusion cross sections of these reactions at energies around the Coulomb barrier can be well reproduced by using the ImQMD model. The corresponding slope parameter of the symmetry energy adopted in the calculations is $L \\approx 78$ MeV and the surface energy coefficient is $g_{\\rm sur}=18\\pm 1.5$ MeVfm$^2$. In addition, it is found that the surface-symmetry term significantly influences the fusion cross sections of neutron-rich fusion systems. For sub-barrier fusion, the dynamical fluctuations in the densities of the reaction partners and the enhanced surface diffuseness at ...

  5. Cluster-transfer reactions with radioactive beams: a spectroscopic tool for neutron-rich nuclei

    CERN Document Server

    AUTHOR|(CDS)2086156; Raabe, Riccardo; Bracco, Angela

    In this thesis work, an exploratory experiment to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier, as a possible mean to perform $\\gamma$ spectroscopy studies of exotic neutron-rich nuclei at medium-high energies and spins. The experiment was performed at ISOLDE (CERN), employing the heavy-ion reaction $^{98}$Rb + $^{7}$Li at 2.85 MeV/A. Cluster-transfer reaction channels were studied through particle-$\\gamma$ coincidence measurements, using the MINIBALL Ge array coupled to the charged particle Si detectors T-REX. Sr, Y and Zr neutron-rich nuclei with A $\\approx$ 100 were populated by either triton- or $\\alpha$ transfer from $^{7}$Li to the beam nuclei and the emitted complementary charged fragment was detected in coincidence with the $\\gamma$ cascade of the residues, after few neutrons evaporation. The measured $\\gamma$ spectra were studied in detail and t...

  6. Invariant mass spectroscopy of 17C via one-neutron knockout reaction from 18C

    Science.gov (United States)

    Kim, Sunji; Samurai Collaboration

    2014-09-01

    The nuclei away from the β-stability line are expected to have exotic nuclear structures. For example, the ground states of neutron-rich carbon isotopes, 15C, 17C, and 19C, have been predicted to be 5/2+ states in the naive shell model. However, they were identified as 1/2+, 3/2+, and 1/2+, respectively, due to the halo structure and/or nuclear deformation. To understand the properties of the valence orbit relative to the inner orbit in those neutron-rich carbon isotopes, the study of the negative parity states is decisive. The present study focuses on the low-lying negative parity states in 17C above the neutron decay threshold. The experiment was performed for the C(18C,17C*) one-neutron knockout reaction channel at 250 MeV/nucleon using the SAMURAI spectrometer at RIKEN-RIBF, during the first physics runs of the apparatus. The nucleon knockout reaction utilizing the secondary beams in inverse kinematics has become recognized as a sensitive tool for spectroscopy of the nuclei far from the β-stability line. In the presentation, details of the measurement and analysis will be reported together with new results on the low-lying negative parity states in 17C.

  7. Propagation of neutron-reaction uncertainties through multi-physics models of novel LWR's

    Directory of Open Access Journals (Sweden)

    Hernandez-Solis Augusto

    2017-01-01

    Full Text Available The novel design of the renewable boiling water reactor (RBWR allows a breeding ratio greater than unity and thus, it aims at providing for a self-sustained fuel cycle. The neutron reactions that compose the different microscopic cross-sections and angular distributions are uncertain, so when they are employed in the determination of the spatial distribution of the neutron flux in a nuclear reactor, a methodology should be employed to account for these associated uncertainties. In this work, the Total Monte Carlo (TMC method is used to propagate the different neutron-reactions (as well as angular distributions covariances that are part of the TENDL-2014 nuclear data (ND library. The main objective is to propagate them through coupled neutronic and thermal-hydraulic models in order to assess the uncertainty of important safety parameters related to multi-physics, such as peak cladding temperature along the axial direction of an RBWR fuel assembly. The objective of this study is to quantify the impact that ND covariances of important nuclides such as U-235, U-238, Pu-239 and the thermal scattering of hydrogen in H2O have in the deterministic safety analysis of novel nuclear reactors designs.

  8. Boron neutron capture therapy design calculation of a 3H(p,n) reaction based BSA for brain cancer setup

    OpenAIRE

    Bassem Elshahat; Akhtar Naqvi; Nabil Maalej

    2015-01-01

    Purpose: Boron neutron capture therapy (BNCT) is a promising technique for the treatment of malignant disease targeting organs of the human body. Monte Carlo simulations were carried out to calculate optimum design parameters of an accelerator based beam shaping assembly (BSA) for BNCT of brain cancer setup.Methods: Epithermal beam of neutrons were obtained through moderation of fast neutrons from 3H(p,n) reaction in a high density polyethylene moderator and a graphite reflector. The dimensio...

  9. Enzymatic spectrophotometric reaction rate determination of aspartame

    Directory of Open Access Journals (Sweden)

    Trifković Kata T.

    2015-01-01

    Full Text Available Aspartame is an artificial sweetener of low caloric value (approximately 200 times sweeter than sucrose. Aspartame is currently permitted for use in food and beverage production in more than 90 countries. The application of aspartame in food products requires development of rapid, inexpensive and accurate method for its determination. The new assay for determination of aspartame was based on set of reactions that are catalyzed by three different enzymes: α-chymotrypsin, alcohol oxidase and horseradish peroxidase. Optimization of the proposed method was carried out for: (i α-chymotrypsin activity; (ii time allowed for α-chymotrypsin action, (iii temperature. Evaluation of the developed method was done by determining aspartame content in “diet” drinks, as well as in artificial sweetener pills. [Projekat Ministarstva nauke Republike Srbije, br. III46010

  10. Charged-Particle Thermonuclear Reaction Rates: II. Tables and Graphs of Reaction Rates and Probability Density Functions

    CERN Document Server

    Iliadis, Christian; Champagne, Art; Coc, Alain; Fitzgerald, Ryan

    2010-01-01

    Numerical values of charged-particle thermonuclear reaction rates for nuclei in the A=14 to 40 region are tabulated. The results are obtained using a method, based on Monte Carlo techniques, that has been described in the preceding paper of this series (Paper I). We present a low rate, median rate and high rate which correspond to the 0.16, 0.50 and 0.84 quantiles, respectively, of the cumulative reaction rate distribution. The meaning of these quantities is in general different from the commonly reported, but statistically meaningless expressions, "lower limit", "nominal value" and "upper limit" of the total reaction rate. In addition, we approximate the Monte Carlo probability density function of the total reaction rate by a lognormal distribution and tabulate the lognormal parameters {\\mu} and {\\sigma} at each temperature. We also provide a quantitative measure (Anderson-Darling test statistic) for the reliability of the lognormal approximation. The user can implement the approximate lognormal reaction rat...

  11. Thermal neutron cross-section and resonance integral of the 152Sm(n,γ)153Sm reaction induced by pulsed neutrons

    Science.gov (United States)

    Van Do, Nguyen; Khue, Pham Duc; Thanh, Kim Tien; Hien, Nguyen Thi; Kim, Guinyun; Kim, Kwangsoo; Shin, Sung-Gyun; Kye, Yong-Uk; Cho, Moo-Hyun

    2017-10-01

    We measured the thermal neutron cross-section (σ0) and resonance integral (I0) of the 152Sm(n,γ)153Sm reaction relative to that of the 197Au(n,γ)198Au reaction. Sm and Au foils with and without a cadmium cover of 0.5 mm were irradiated with moderated pulsed neutrons produced from the electron linac. The induced activities of the reaction products were determined via high energy resolution HPGe detector. The present results: σ0,Sm =212±8 b and I0,Sm =3.02±0.19 kb are consistent with most of the existing reference data.

  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. Attempts to infer the neutron inelastic cross sections using charged particle induced reactions

    CERN Document Server

    Negret, A; Borcea, C; Bucurescu, D; Deleanu, D; Dessagne, Ph; Filipescu, D; Ghita, D; Glodariu, T; Kerveno, M; Marginean, N; Marginean, R; Mihai, C; Olacel, A; Pascu, S; Plompen, A J M; Sava, T; Stroe, L; Suliman, G

    2014-01-01

    Two experiments were performed at the Tandem accelerator of the Horia Hulubei National Institute for Physics and Nuclear Engineering, IFIN-HH with the purpose to investigate the possibility to use alpha-induced reactions for the calculation of neutron inelastic cross sections based on the Bohr hypothesis of the compound nucleus. A first experiment compared the gamma production cross sections excited in the $^{25}$Mg($\\alpha, n\\gamma$ )$^{28}$Si and the $^{28}Si(n, n′\\gamma)^{28}$Si reactions. A second measurement, supported by the ERINDA project, was dedicated to the measurement of $^{70}Zn(\\alpha, n\\gamma )^{73}$Ge cross sections with the purpose of inferring the neutron inelastic cross sections on $^{73}$Ge.

  14. Fusion reaction around the Coulomb barrier with neutron-rich nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Atsushi [Institute of Physical and Chemical Research, Wako, Saitama (Japan)

    1997-07-01

    Two fusion reactions with neutron-rich nuclei are reported in this work. On the first reaction: {sup 9,10,11}Be+{sup 209}Bi, the fusion cross sections around the coulomb barrier were measured by determing {alpha} disintegration from compound nucleus Fr. In the field of 10-100 mb, the same total fusion cross sections were obtained. The phenomenon {sup 11}Be(neutron halo nucleus) alone increased and decreased was not observed. The fusion cross sections of {sup 27,29,31}Al+{sup 197}Au system were determined by using 130 kcps and 30 kcps of beam strength of {sup 29,31}Al, respectively. The value of {sup 27}Al was reproduced by calculation, but that of {sup 29}Al increased around barrier which could not be explained by CCDEF calculation. (S.Y.)

  15. A physics investigation of deadtime losses in neutron counting at low rates with Cf252

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Louise G [Los Alamos National Laboratory; Croft, Stephen [CANBERRA INDUSTRIES, INC.

    2009-01-01

    {sup 252}Cf spontaneous fission sources are used for the characterization of neutron counters and the determination of calibration parameters; including both neutron coincidence counting (NCC) and neutron multiplicity deadtime (DT) parameters. Even at low event rates, temporally-correlated neutron counting using {sup 252}Cf suffers a deadtime effect. Meaning that in contrast to counting a random neutron source (e.g. AmLi to a close approximation), DT losses do not vanish in the low rate limit. This is because neutrons are emitted from spontaneous fission events in time-correlated 'bursts', and are detected over a short period commensurate with their lifetime in the detector (characterized by the system die-away time, {tau}). Thus, even when detected neutron events from different spontaneous fissions are unlikely to overlap in time, neutron events within the detected 'burst' are subject to intrinsic DT losses. Intrinsic DT losses for dilute Pu will be lower since the multiplicity distribution is softer, but real items also experience self-multiplication which can increase the 'size' of the bursts. Traditional NCC DT correction methods do not include the intrinsic (within burst) losses. We have proposed new forms of the traditional NCC Singles and Doubles DT correction factors. In this work, we apply Monte Carlo neutron pulse train analysis to investigate the functional form of the deadtime correction factors for an updating deadtime. Modeling is based on a high efficiency {sup 3}He neutron counter with short die-away time, representing an ideal {sup 3}He based detection system. The physics of dead time losses at low rates is explored and presented. It is observed that new forms are applicable and offer more accurate correction than the traditional forms.

  16. Estimation of the {alpha} particles and neutron distribution generated during a fusion reaction; Evaluation de la distribution des particules {alpha} et des neutrons issus de la reaction de fusion

    Energy Technology Data Exchange (ETDEWEB)

    Dellacherie, S.

    1997-12-01

    The respective distributions (or density probabilities) of {alpha} particles and neutrons have been modeled using a Monte-Carlo method for the thermonuclear fusion reaction D + T {yields} {alpha} + n + 17.6 MeV. (N.T.).

  17. Measurement of reaction cross sections of fission products induced by DT neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, Daisuke; Murata, Isao; Takahashi, Akito [Osaka Univ., Suita (Japan)

    1998-03-01

    With the view of future application of fusion reactor to incineration of fission products, we have measured the {sup 129}I(n,2n){sup 128}I reaction cross section by DT neutrons with the activation method. The measured cross section was compared with the evaluated nuclear data of JENDL-3.2. From the result, it was confirmed that the evaluation overestimated the cross section by about 20-40%. (author)

  18. Spectroscopy of $^{46}$Ar by the (t,p) two-neutron transfer reaction

    CERN Document Server

    Nowak, K.; Hellgartner, S.; Mücher, D.; Bildstein, V.; Diriken, J.; Elseviers, J.; Gaffney, L.P.; Gernhäuser, R.; Iwanicki, J.; Johansen, J.G.; Huyse, M.; Konki, J.; Kröll, T.; Krücken, T.; Lutter, R.; Orlandi, R.; Pakarinen, J.; Raabe, R.; Reiter, P.; Roger, T.; Schrieder, G.; Seidlitz, M.; Sorlin, O.; Van Duppen, P.; Warr, N.; De Witte, H.; Zielinska, M.

    2016-01-01

    States in the $N=28$ nucleus $^{46}$Ar have been studied by a two-neutron transfer reaction at REX-ISOLDE (CERN). A beam of radioactive $^{44}$ at an energy of 2.16~AMeV and a tritium loaded titanium target were used to populate $^{46}$ by the t($^{44}$,p) two-neutron transfer reaction. Protons emitted from the target were identified in the T-REX silicon detector array. The excitation energies of states in $^{46}$ have been reconstructed from the measured angles and energies of recoil protons. Angular distributions for three final states were measured and based on the shape of the differential cross section an excited state at 3695~keV has been identified as $J^\\pi = 0^+$. The angular differential cross section for the population of different states are compared to calculations using a reaction model employing both sequential and direct transfer of two neutrons. Results are compared to shell model calculations using state-of-the-art effective interactions.

  19. Study of the thermal neutron radiative capture sup 31 P( n ,. gamma. ) reaction

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Xiantang; Shi Zongren; Zhang Ming; Li Guohua; Ding Dazhao (Institute of Atomic Energy, P. O. Box 275, Beijing (CN))

    1989-05-01

    The measurement of the {gamma}-ray spectrum of the {sup 31}P({ital n},{gamma}) reaction induced by thermal neutrons from the heavy water reactor is performed by using three crystal pair spectrometer'', Ge(Li) and HPGe detectors. 128 {gamma}-rays are identified, 24 of them are recognized as primary {gamma}-transitions. The excitation energies of 32 levels are deduced. Two possible levels of 5451.44 keV and 5021.10 keV have not been reported previously. The neutron separation energy is determined to be 7936.65(8) keV and partial cross sections are measured. The thermal neutron capture cross section of {sup 31}P is obtained to be 177(5) mb by comparison with Au({ital n}{sub th}, {gamma}) cross section standard. With the formula of the Lane-Lynn direct interaction, the partial capture cross sections of eight strong primary E1-transitions are calculated and compared with their experimental values, leading to the conclusion that the theoretical values are in coincidence with the experimental ones and the E1-transitions mainly come from 1+ capture state. The correlation analyses of the reduced strengths of E1 and M1 transitions with the spectroscopic factors of (d, p) reaction are performed and the reaction mechanisms discussed.

  20. Evaluation of D(d,n)3 He reaction neutron source models for BNCT irradiation system design

    Institute of Scientific and Technical Information of China (English)

    YAO Ze'en; LUO Peng; Tooru KOBAYASHI; Gerard BENGUA

    2007-01-01

    A mathematical method was developed to calculatc the yield.energy spectrum and angular distribution of neutrons from D(d,n)3 He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in energies lower than 1.0MeV.The data of energy spectrum and angular distribution wefe applied to set up the neutron source model for the beam-shaping-assembly(BSA)design of Boron-Neutron-Capture-Therapy(BNCT)using MCNP-4C code.Three cases of D-D neutron source corresponding to incident deuteron energy of 1000.400 and 150 kaV were investigated.The neutron beam characteristics were compared with the model of a 2.45 MeV mono-energetic and isotropic neutron source using an example BSA designed for BNCT irradiation.The results show significant differences in the neutron beam characteristics,particularly the fast neutron component and fast neutron dose in air,between the non-isotropic neutron source model and the 2.5 MeV mono-energetic and isotropic neutron source model.

  1. Resonance analysis of the {sup 12}C,{sup 13}C({alpha},n) reactions and evaluation of neutron yield data of the reaction

    Energy Technology Data Exchange (ETDEWEB)

    Murata, Toru [AITEL Corp., Tokyo (Japan)

    1998-03-01

    The {sup 12}C({alpha},n){sup 15}O reaction and the {sup 13}C({alpha},n){sup 16}O reaction were analyzed with a resonance formula in the incident {alpha}-particle energy range of 1.0 to 16.0 MeV. With the obtained resonance parameters, branching ratios of the emitted neutrons to the several levels of the residual nucleus and their angular distributions were calculated to obtain the energy spectrum of emitted neutrons. Thick target neutron yield of carbon were also calculated and compared with the experimental data. (author)

  2. Observation of new neutron-deficient isotopes with Z≥92 in multinucleon transfer reactions

    Directory of Open Access Journals (Sweden)

    H.M. Devaraja

    2015-09-01

    Full Text Available In deep inelastic multinucleon transfer reactions of 48Ca + 248Cm we observed about 100 residual nuclei with proton numbers between Z=82 and Z=100. Among them, there are five new neutron-deficient isotopes: 216U, 219Np, 223Am, 229Am and 233Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identification was performed via the α decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei.

  3. Analysis of the role of neutron transfer in asymmetric fusion reactions at subbarrier energies

    Energy Technology Data Exchange (ETDEWEB)

    Ogloblin, A. A. [National Research Center Kurchatov Institute (Russian Federation); Zhang, H. Q.; Lin, C. J.; Jia, H. M. [China Institute of Atomic Energy (China); Khlebnikov, S. V. [Khlopin Radium Institute (Russian Federation); Kuzmin, E. A.; Danilov, A. N.; Demyanova, A. S. [National Research Center Kurchatov Institute (Russian Federation); Trzaska, W. H. [University of Jyväskylä, Department of Physics (Finland); Xu, X. X. [China Institute of Atomic Energy (China); Yang, F. [National Research Center Kurchatov Institute (Russian Federation); Sargsyan, V. V., E-mail: sargsyan@theor.jinr.ru; Adamian, G. G.; Antonenko, N. V. [Joint Institute for Nuclear Research (Russian Federation); Scheid, W. [Institüt für Theoretische Physik der Justus-Liebig-Universität (Germany)

    2015-12-15

    The excitation functions were measured for the {sup 28}Si + {sup 208}Pb complete-fusion (capture) reaction at deep subbarrier energies. The results were compared with the cross sections predicted within the quantum diffusion approach. The role of neutron transfer in the case of positive Q values in the {sup 28}Si + {sup 124}Sn, {sup 208}Pb; {sup 30}Si + {sup 124}Sn, {sup 208}Pb; {sup 20}Ne + {sup 208}Pb; {sup 40}Ca + {sup 96}Zr; and {sup 134}Te + {sup 40}Ca complete-fusion (capture) reactions is discussed.

  4. Neutron time-of-flight spectrometer based on HIRFL for studies of spallation reactions related to ADS project

    Institute of Scientific and Technical Information of China (English)

    张苏雅拉吐; 罗飞; 陈志强; 韩瑞; 刘星泉; 林炜平; 刘建立; 石福栋; 任培培; 田国玉

    2015-01-01

    A Neutron Time-of-Flight (NTOF) spectrometer, based at the Heavy Ion Research Facility in Lanzhou (HIRFL) was developed for studies of neutron production of proton induced spallation reactions related to the ADS project. After the presentation of comparisons between calculated spallation neutron production double-differential cross sections and the available experimental data, a detailed description of the NTOF spectrometer is given. Test beam results show that the spectrometer works well and data analysis procedures are established. The comparisons of the test beam neutron spectra with those of GEANT4 simulations are presented.

  5. Neutron-induced cross sections of actinides via the surrogate-reaction method

    Directory of Open Access Journals (Sweden)

    Tveten G. M.

    2013-03-01

    Full Text Available The surrogate-reaction method is an indirect way of determining cross sections for reactions that proceed through a compound nucleus. This technique may enable neutron-induced cross sections to be extracted for short-lived nuclei that otherwise cannot be measured. However, the validity of the surrogate method for extracting capture cross sections has to be investigated. In this work we study the reactions 238U(d,p239U, 238U(3He,t238Np, 238U(3He,4He237U as surrogates for neutroninduced reactions on 238U, 237Np and 236U, respectively, for which good quality data exist. The experimental set-up enabled the measurement of fission and gamma-decay probabilities. First results are presented and discussed.

  6. Hexagonal boron nitride thin film thermal neutron detectors with high energy resolution of the reaction products

    Energy Technology Data Exchange (ETDEWEB)

    Doan, T.C.; Majety, S.; Grenadier, S.; Li, J.; Lin, J.Y.; Jiang, H.X., E-mail: hx.jiang@ttu.edu

    2015-05-21

    Hexagonal boron nitride (h-BN) is highly promising for solid-state thermal neutron detector applications due to its many outstanding physical properties, especially its very large thermal neutron capture cross-section (~3840 barns for {sup 10}B), which is several orders of magnitude larger than those of most other isotopes. The focus of the present work is to carry out studies on h-BN thin film and detector properties to lay the foundation for the development of a direct-conversion solid-state thermal neutron detector with high sensitivity. The measured carrier mobility-lifetime (μτ) product of h-BN thin films grown on sapphire substrates is 2.83×10{sup −7} cm{sup 2}/V for electrons and holes, which is comparable to the value of about 10{sup −7} cm{sup 2}/V for GaN thin films grown on sapphire. Detectors based on h-BN thin films were fabricated and the nuclear reaction product pulse height spectra were measured. Under a bias of 20 V, very narrow individual peaks corresponding to the reaction product energies of α and Li particles as well as the sum peaks have been clearly resolved in the pulse height spectrum for the first time by a B-based direct-conversion semiconductor neutron detector. Our results indicate that h-BN thin film detectors possess unique advantages including small size, low weight, portability, low voltage operation and high energy resolution of specific reaction products.

  7. Reaction-in-Flight Neutrons as a Test of Stopping Power in Degenerate Plasmas

    CERN Document Server

    Hayes, A C; Schulz, A E; Boswell, M; Fowler, M M; Grim, G; Klein, A; Rundberg, R S; Wilhelmy, J B; Wilson, D

    2014-01-01

    We present the first measurements of reaction-in-flight (RIF) neutrons in an inertial confinement fusion system. The experiments were carried out at the National Ignition Facility, using both Low Foot and High Foot drives and cryogenic plastic capsules. In both cases, the high-energy RIF ($E_n>$ 15 MeV) component of the neutron spectrum was found to be about $10^{-4}$ of the total. The majority of the RIF neutrons were produced in the dense cold fuel surrounding the burning hotspot of the capsule and the data are consistent with a compressed cold fuel that is moderately to strongly coupled $(\\Gamma\\sim$0.6) and electron degenerate $(\\theta_\\mathrm{Fermi}/\\theta_e\\sim$4). The production of RIF neutrons is controlled by the stopping power in the plasma. Thus, the current RIF measurements provide a unique test of stopping power models in an experimentally unexplored plasma regime. We find that the measured RIF data strongly constrain stopping models in warm dense plasma conditions and some models are ruled out b...

  8. Inverse kinematics (p, n) reactions studies using the WINDS slow neutron detector and the SAMURAI spectrometer

    Science.gov (United States)

    Yasuda, J.; Sasano, M.; Zegers, R. G. T.; Baba, H.; Chao, W.; Dozono, M.; Fukuda, N.; Inabe, N.; Isobe, T.; Jhang, G.; Kameda, D.; Kubo, T.; Kurata-Nishimura, M.; Milman, E.; Motobayashi, T.; Otsu, H.; Panin, V.; Powell, W.; Sakai, H.; Sako, M.; Sato, H.; Shimizu, Y.; Stuhl, L.; Suzuki, H.; Tangwancharoen, S.; Takeda, H.; Uesaka, T.; Yoneda, K.; Zenihiro, J.; Kobayashi, T.; Sumikama, T.; Tako, T.; Nakamura, T.; Kondo, Y.; Togano, Y.; Shikata, M.; Tsubota, J.; Yako, K.; Shimoura, S.; Ota, S.; Kawase, S.; Kubota, Y.; Takaki, M.; Michimasa, S.; Kisamori, K.; Lee, C. S.; Tokieda, H.; Kobayashi, M.; Koyama, S.; Kobayashi, N.; Wakasa, T.; Sakaguchi, S.; Krasznahorkay, A.; Murakami, T.; Nakatsuka, N.; Kaneko, M.; Matsuda, Y.; Mucher, D.; Reichert, S.; Bazin, D.; Lee, J. W.

    2016-06-01

    We have combined the low-energy neutron detector WINDS (Wide-angle Inverse-kinematics Neutron Detectors for SHARAQ) and the SAMURAI spectrometer at RIKEN Nishina Center RI Beam Factory (RIBF) in order to perform (p, n) reactions in inverse kinematics for unstable nuclei in the mass region around A ∼ 100 . In this setup, WINDS is used for detecting recoil neutrons and the SAMURAI spectrometer is used for tagging decay channel of heavy residue. The first experiment by using the setup was performed to study Gamow-Teller transitions from 132Sn in April 2014. The atomic number Z and mass-to-charge ratio A / Q of the beam residues were determined from the measurements of time of flight, magnetic rigidity and energy loss. The obtained A / Q and Z resolutions were σA/Q = 0.14 % and σZ = 0.22 , respectively. Furthermore, owing to the large momentum acceptance (50 %) of SAMURAI, the beam residues associated with the γ , 1n and 2n decay channel were measured in the same magnetic field setting. The kinematic loci of the measured recoil neutron energy and laboratory angle are clearly seen. It shows that the excitation energy up to about 20 MeV can be reconstructed.

  9. Tackling the s-process stellar neutron density via the 147Pm(n,?) reaction

    CERN Multimedia

    Branching points along the reaction path of the slow nucleosynthesis process are very special isotopes for which there is competition between neutron capture and β-decay. The accurate knowledge of the decay properties and capture cross sections in the vicinity of these branching points are of key importance for determining the stellar conditions, namely the neutron density and temperature during the main s-process component in low-mass AGB stars. However, accurate values of these quantities, in particular capture cross sections at the corresponding stellar temperatures, are difficult to measure; thus data are very scarce and, when existing, very limited. For the particular and important case of the branching at A=147/148, the main branching point is $^{147}$Pm; for which there was a very challenging and successful activation measurement in 2003 at the stellar neutron energy of kT=25 keV using just 28 ng of material. In the main s-process, however, 95% of the neutron exposure takes place during H-burning epis...

  10. Reaction-in-flight neutrons as a signature for shell mixing in National Ignition Facility capsules

    Science.gov (United States)

    Hayes, A. C.; Bradley, P. A.; Grim, G. P.; Jungman, Gerard; Wilhelmy, J. B.

    2010-01-01

    Analytic calculations and results from computational simulations are presented that suggest that reaction-in-flight (RIF) neutrons can be used to diagnose mixing of the ablator shell material into the fuel in deuterium-tritium (DT) capsules designed for the National Ignition Facility (NIF) [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)]. Such mixing processes in NIF capsules are of fundamental physical interest and can have important effects on capsule performance, quenching the total thermonuclear yield. The sensitivity of RIF neutrons to hydrodynamical mixing arises through the dependence of RIF production on charged-particle stopping lengths in the mixture of DT fuel and ablator material. Since the stopping power in the plasma is a sensitive function of the electron temperature and density, it is also sensitive to mix. RIF production scales approximately inversely with the degree of mixing taking place, and the ratio of RIF to down-scattered neutrons provides a measure of the mix fraction and/or the mixing length. For sufficiently high-yield capsules, where spatially resolved RIF images may be possible, neutron imaging could be used to map RIF images into detailed mix images.

  11. Low-level measuring techniques for neutrons: High accuracy neutron source strength determination and fluence rate measurement at an underground laboratory

    Science.gov (United States)

    Zimbal, Andreas; Degering, Detlev; Reginatto, Marcel; Schuhmacher, Helmut; Wiegel, Burkhard; Zuber, Kai

    2013-08-01

    We report on measuring techniques for neutrons that have been developed at the Physikalisch-Technische Bundesanstalt (PTB), the German National Metrology Institute. PTB has characterized radioactive sources used in the BOREXINO and XENON100 experiments. For the BOREXINO experiment, a 228Th gamma radiation source was required which would not emit more than 10 neutrons per second. The determination of the neutron emission rate of this specially designed 228Th source was challenging due to the low neutron emission rate and because the ratio of neutron to gamma radiation was expected to be extremely low, of the order of 10-6. For the XENON100 detector, PTB carried out a high accuracy measurement of the neutron emission rate of an AmBe source. PTB has also done measurements in underground laboratories. A two month measurement campaign with a set of 3He-filled proportional counters was carried out in PTB's former UDO underground laboratory at the Asse salt mine. The aim of the campaign was to determine the intrinsic background of detectors, which is needed for the analysis of data taken in lowintensity neutron fields. At a later time, PTB did a preliminary measurement of the neutron fluence rate at the underground laboratory Felsenkeller operated by VKTA. By taking into account data from UDO, Felsenkeller, and detector calibrations made at the PTB facility, it was possible to estimate the neutron fluence rate at the Felsenkeller underground laboratory.

  12. Monte carlo simulations of Yttrium reaction rates in Quinta uranium target

    Directory of Open Access Journals (Sweden)

    Suchopár M.

    2017-01-01

    Full Text Available The international collaboration Energy and Transmutation of Radioactive Waste (E&T RAW performed intensive studies of several simple accelerator-driven system (ADS setups consisting of lead, uranium and graphite which were irradiated by relativistic proton and deuteron beams in the past years at the Joint Institute for Nuclear Research (JINR in Dubna, Russia. The most recent setup called Quinta, consisting of natural uranium target-blanket and lead shielding, was irradiated by deuteron beams in the energy range between 1 and 8 GeV in three accelerator runs at JINR Nuclotron in 2011 and 2012 with yttrium samples among others inserted inside the setup to measure the neutron flux in various places. Suitable activation detectors serve as one of possible tools for monitoring of proton and deuteron beams and for measurements of neutron field distribution in ADS studies. Yttrium is one of such suitable materials for monitoring of high energy neutrons. Various threshold reactions can be observed in yttrium samples. The yields of isotopes produced in the samples were determined using the activation method. Monte Carlo simulations of the reaction rates leading to production of different isotopes were performed in the MCNPX transport code and compared with the experimental results obtained from the yttrium samples.

  13. Energy diffusion controlled reaction rate in dissipative Hamiltonian systems

    Institute of Scientific and Technical Information of China (English)

    Deng Mao-Lin; Zhu Wei-Qiu

    2007-01-01

    In this paper the energy diffusion controlled reaction rate in dissipative Hamiltonian systems is investigated by using the stochastic averaging method for quasi Hamiltonian systems. The boundary value problem of mean first-passage time (MFPT) of averaged system is formulated and the energy diffusion controlled reaction rate is obtained as the inverse of MFPT. The energy diffusion controlled reaction rate in the classical Kramers bistable potential and in a two-dimensional bistable potential with a heat bath are obtained by using the proposed approach respectively. The obtained results are then compared with those from Monte Carlo simulation of original systems and from the classical Kramers theory. It is shown that the reaction rate obtained by using the proposed approach agrees well with that from Monte Carlo simulation and is more accurate than the classical Kramers rate.

  14. Neutron-induced reaction cross-section measurements using a small multi-detector array and description of a large array

    Indian Academy of Sciences (India)

    J-P Meulders; I Slypen; S Benck; E Raeymackers; J Cabrera; Ch Dufauquez; T Keutgen; V Roberfroid; I Tilquin; Y El Masri; V Corcalciuc; N Nice

    2001-07-01

    The experimental setup of Louvain-la-Neuve (UCL-Belgium) used to perform lightcharged particle production experiment in fast neutron-induced reactions is presented. A short description of the neutron modular detector DEMON is also given. DEMON is a detector array for neutrons emitted in heavy ion induced reactions at low to intermediate energies.

  15. The 9Be(d,n) 10B-reaction as intense neutron source with continuous energy spectrum

    Science.gov (United States)

    Baumann, F. M.; Domogala, G.; Freiesleben, H.; Paul, H. J.; Puhlvers, S.; Sohlbach, H.

    1986-06-01

    Neutron energy spectra produced by deuterons of 3 to 8 MeV in a thick 9Be-target were measured at various scattering angles. Significant angle dependences were observed. Angular distributions of the most energetic neutrons produced in thin 9Be targets can be described quantitatively in DWBA, which is an indication for a direct reaction mechanism. As a consequence all but 0°-neutrons are polarized to a certain extent. Also presented is the neutron energy spectrum of 7Li(d,n) 8Be at 0° produced in a thick 7Li-target. The potential of these intense 0°-neutron beams with continuous energy distributions is demonstrated by a measurement of the neutron absorption cross section of natural carbon.

  16. Nuclear halo effect on nucleon capture reaction rates at stellar energies

    Institute of Scientific and Technical Information of China (English)

    Liu Zu-Hua; Zhou Hong-Yu

    2005-01-01

    The capture cross sections at stellar energies are very difficult to measure directly. Hence, data are usually evaluated by using indirect methods or extrapolations from the experimental data obtained at the lowest possible energies. The asymptotic normalization coefficient (ANC) approach of the transfer reactions provides a reliable way for the determination of the capture cross sections at stellar energies. By virtue of its reliability, we have calculated the capture cross sections of the 10Be(n,γ)11Be reaction by using nuclear ANC method. 11Be is a well-known neutron halo nucleus with two weakly bound states. As a typical example, we have shown that the radiative cross sections for a nucleon captured into a halo state are obviously enhanced. The enormous enhancement of the capture cross section is just due to the large overlap of the incident neutron wave with the extended tail of the halo. The 10Be(n,γ)11Be capture reaction is involved in the inhomogeneous big-bang nucleosynthesis. We have evaluated its reaction rates at stellar energies with the nuclear ANC method.

  17. Reaction Rate Distributions and Ratios in FR0 Assemblies 1, 2 and 3

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, T.L.

    1966-06-15

    The spatial distribution of different reaction rates and reaction ratios in Assemblies 1, 2 and 3 of the fast reactor FR0 was measured by fission chamber scans and foil activation technique. Assemblies 1 and 2 had cores of undiluted fuel (uranium metal enriched to 20 % U{sup 235}) while the core of Assembly 3 was diluted with about 30 vol. % graphite. All the systems had a thick copper reflector, The experimental results were compared with calculated values obtained from DSN and TDC multigroup spectra and group cross-section sets for the reactions. Good agreement between experiment and calculations is generally obtained in the core region but in the reflector the neutron spectrum is calculated too hard.

  18. Measurement of thermal neutron cross section for {sup 241}Am(n,f) reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Katsuhei; Yamamoto, Shuji; Fujita, Yoshiaki [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Miyoshi, Mitsuharu; Kimura, Itsuro; Kanno, Ikuo; Shinohara, Nobuo

    1997-03-01

    Making use of a standard neutron spectrum field with a pure Maxwellian distribution, the thermal neutron cross section for the {sup 241}Am(n,f) reaction has been measured relative to the reference value of 586.2b for the {sup 235U}(n,f) reaction. For the present measurement, electrodeposited layers of {sup 241}Am and {sup 235}U have been employed as back-to-back type double fission chambers. The present result at neutron energy of 0.0253 eV is 3.15 {+-} 0.097b. The ENDF/B-VI data is in good agreement with the present value, while the JENDL-3.2 data is lower by 4.2%. The evaluated data in JEF-2.2 and by Mughabghab are higher by 0.9% and 1.6%, respectively than the present result. The ratios of the earlier experimental data to the present value are distributed between 0.89 and 1.02. (author)

  19. Quantum Mechanics Rate Constant for the N+ND Reaction

    Institute of Scientific and Technical Information of China (English)

    Ai-jie Zhang; Guo-zhong He

    2011-01-01

    We present nonadiabatic quantum dynamical calculations on the two coupled potential energy surfaces (12A' and 22A') [J.Theor.Comput.Chem.8,849 (2009)] for the reaction.Initial state-resolved reaction probabilities and cross sections for the N+ND→N2+D reaction and N'+ND→N+N'D reaction for collision energies of 5 meV to 1.0 eV are determined,respectively.It is found that the N+ND→N2+D reaction is dominated in the N+ND reaction.In addition,we obtained the rate constants for the N+ND→N2+D reaction which demand further experimental investigations.

  20. Measured Thermal and Fast Neutron Fluence Rates for ATF-1 Holders During ATR Cycle 157D

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Larry Don [Idaho National Lab. (INL), Idaho Falls, ID (United States); Miller, David Torbet [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-03-01

    This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 157D which were measured by the Radiation Measurements Laboratory (RML) as requested by the Power Reactor Programs (ATR Experiments) Radiation Measurements Work Order. This report contains measurements of the fluence rates corresponding to the particular elevations relative to the 80-ft. core elevation. The data in this report consist of (1) a table of the ATR power history and distribution, (2) a hard copy listing of all thermal and fast neutron fluence rates, and (3) plots of both the thermal and fast neutron fluence rates. The fluence rates reported are for the average power levels given in the table of power history and distribution.

  1. Identification of neutron irradiation induced strain rate sensitivity change using inverse FEM analysis of Charpy test

    Science.gov (United States)

    Haušild, Petr; Materna, Aleš; Kytka, Miloš

    2015-04-01

    A simple methodology how to obtain additional information about the mechanical behaviour of neutron-irradiated WWER 440 reactor pressure vessel steel was developed. Using inverse identification, the instrumented Charpy test data records were compared with the finite element computations in order to estimate the strain rate sensitivity of 15Ch2MFA steel irradiated with different neutron fluences. The results are interpreted in terms of activation volume change.

  2. Integral cross section measurements of a few threshold reactions induced by Am/Be neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, Md. Shuza; Hossain, Syed Mohammad; Rumman-Uz-Zaman, Md. [Atomic Energy Research Establishment, Dhaka (Bangladesh). Institute of Nuclear Science and Technology (INST); Spahn, Ingo; Qaim, Syed M. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Neurowissenschaften und Medizin (INM), Nuklearchemie (INM-5); Rakib-Uz-Zaman, Md. [Rajshahi Univ. (Bangladesh). Dept. of Applied Chemistry and Chemical Engineering

    2015-07-01

    Integral cross sections of the reactions {sup 46}Ti(n,p){sup 46}Sc, {sup 47}Ti(n,p){sup 47}Sc, {sup 48}Ti(n,p){sup 48}Sc, {sup 60}Ni(n,p){sup 60}Co and {sup 64}Zn(n,p){sup 64}Cu were measured with fast neutrons (E{sub n} > 1.5 MeV) from an Am/Be source. The results were compared with data calculated using the neutron spectral distribution and the excitation function of each reaction given in the data libraries ENDF/B-VII.0, IRDF-2002, JEFF-3.2 and JENDL-4.0. In general, the integral measurement and the integrated value agreed within ±4%, except for the {sup 46}Ti(n,p){sup 46}Sc reaction where JEFF-3.2 shows a deviation of 7% and the {sup 60}Ni(n,p){sup 60}Co reaction where ENDF/B-VII.0 and IRDF-2002 exhibit deviations upto 8%.

  3. Neutron dose rate for {sup 252} Cf AT source in medical applications

    Energy Technology Data Exchange (ETDEWEB)

    Paredes, L.; Balcazar, M. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Azorin, J. [UAM-I, 09340 Mexico D.F. (Mexico); Francois, J.L. [FI-UNAM, 04510 Mexico D.F. (Mexico)

    2006-07-01

    The AAPM TG-43 modified protocol was used for the calculation of the neutron dose rate of {sup 252}Cf sources for two tissue substitute materials, five normal tissues and six tumours. The {sup 252}Cf AT source model was simulated using the Monte Carlo MCNPX code in spherical geometry for the following factors: a) neutron air kerma strength conversion factor, b) dose rate constant, c) radial dose function, d) geometry factor, e) anisotropy function and f) neutron dose rate. The calculated dose rate in water at 1 cm and 90 degrees from the source long axis, using the Watt fission spectrum, was D{sub n}(r{sub 0}, {theta}{sub 0})= 1.9160 cGy/h-{mu}g. When this value is compared with Rivard et al. calculation using MCNP4B code, 1.8730 cGy/h-{mu}g, a difference of 2.30% is obtained. The results for the reference neutron dose rate in other media show how small variations in the elemental composition between the tissues and malignant tumours, produce variations in the neutron dose rate up to 12.25%. (Author)

  4. Deformation effect on reaction cross sections for neutron-rich Ne-isotopes induced reactions

    CERN Document Server

    Minomo, Kosho; Kimura, Masaaki; Ogata, Kazuyuki; Shimizu, Yoshifumi R; Yahiro, Masanobu

    2011-01-01

    Isotope-dependence of measured reaction cross sections in scattering of $^{28-32}$Ne isotopes from $^{12}$C target at 240 MeV/nucleon is analyzed by the double-folding model with the Melbourne $g$-matrix. The density of projectile is calculated by the mean-field model with the deformed Wood-Saxon potential. The deformation is evaluated by the antisymmetrized molecular dynamics. The deformation of projectile enhances calculated reaction cross sections to the measured values.

  5. New exclusive CHIPS-TPT algorithms for simulation of neutron-nuclear reactions

    Science.gov (United States)

    Kosov, M.; Savin, D.

    2015-05-01

    The CHIPS-TPT physics library for simulation of neutron-nuclear reactions on the new exclusive level is being developed in CFAR VNIIA. The exclusive modeling conserves energy, momentum and quantum numbers in each neutron-nuclear interaction. The CHIPS-TPT algorithms are based on the exclusive CHIPS library, which is compatible with Geant4. Special CHIPS-TPT physics lists in the Geant4 format are provided. The calculation time for an exclusive CHIPS-TPT simulation is comparable to the time of the corresponding Geant4- HP simulation. In addition to the reduction of the deposited energy fluctuations, which is a consequence of the energy conservation, the CHIPS-TPT libraries provide a possibility of simulation of the secondary particles correlation, e.g. secondary gammas, and of the Doppler broadening of gamma lines in the spectrum, which can be measured by germanium detectors.

  6. Neutron capture surrogate reaction on 75As in inverse kinematics using (d,pγ

    Directory of Open Access Journals (Sweden)

    Smith M.S.

    2010-03-01

    Full Text Available The 75As(d,pγ reaction in inverse kinematics as a surrogate for neutron capture was performed at Oak Ridge National Laboratory using a deuterated plastic target. The intensity of the 165 keV γ-ray from 76As in coincidence with ejected protons, from exciting 76As above the neutron separation energy populating a compound state, was measured. A tight geometry of four segmented germanium clover γ-ray detectors together with eight ORRUBA-type silicon-strip charged-particle detectors was used to optimize geometric acceptance. The preliminary analysis of the 75As experiment, and the eïňČcacy and future plans of the (d,pγ surrogate campaign in inverse kinematics, are discussed.

  7. Neutron capture surrogate reaction on 75As in inverse kinematics using (d,pγ)

    Science.gov (United States)

    Peters, W. A.; Cizewski, J. A.; Hatarik, R.; O'Malley, P. D.; Jones, K. L.; Schmitt, K.; Moazen, B. H.; Chae, K. Y.; Pittman, S. T.; Kozub, R. L.; Vieira, D.; Jandel, M.; Wilhelmy, J. B.; Matei, C.; Escher, J.; Bardayan, D. W.; Pain, S. D.; Smith, M. S.

    2010-03-01

    The 75As(d,pγ) reaction in inverse kinematics as a surrogate for neutron capture was performed at Oak Ridge National Laboratory using a deuterated plastic target. The intensity of the 165 keV γ-ray from 76As in coincidence with ejected protons, from exciting 76As above the neutron separation energy populating a compound state, was measured. A tight geometry of four segmented germanium clover γ-ray detectors together with eight ORRUBA-type silicon-strip charged-particle detectors was used to optimize geometric acceptance. The preliminary analysis of the 75As experiment, and the efficacy and future plans of the (d,pγ) surrogate campaign in inverse kinematics, are discussed.

  8. Neutron Capture Surrogate Reaction on 75As in Inverse Kinematics Using (d,p(gamma))

    Energy Technology Data Exchange (ETDEWEB)

    Peters, W A; Cizewski, J A; Hatarik, R; O?Malley, P D; Jones, K L; Schmitt, K; Moazen, B H; Chae, K Y; Pittman, S T; Kozub, R L; Vieira, D; Jandel, M; Wilhelmy, J B; Matei, C; Escher, J; Bardayan, D W; Pain, S D; Smith, M S

    2009-11-09

    The {sup 75}As(d,p{gamma}) reaction in inverse kinematics as a surrogate for neutron capture was performed at Oak Ridge National Laboratory using a deuterated plastic target. The intensity of the 165 keV {gamma}-ray from {sup 76}As in coincidence with ejected protons, from exciting {sup 76}As above the neutron separation energy populating a compound state, was measured. A tight geometry of four segmented germanium clover {gamma}-ray detectors together with eight ORRUBA-type silicon-strip charged-particle detectors was used to optimize geometric acceptance. The preliminary analysis of the {sup 75}As experiment, and the efficacy and future plans of the (d,p{gamma}) surrogate campaign in inverse kinematics, are discussed.

  9. Neutron capture surrogate reaction on 75As in inverse kinematics using (d,p )

    Energy Technology Data Exchange (ETDEWEB)

    Peters, W. A. [Rutgers University; Cizewski, J. A. [Rutgers University; Hatarik, Robert [Rutgers University; O' Malley, Patrick [Rutgers University; Jones, K. L. [University of Tennessee; Schmitt, Kyle [University of Tennessee; Moazen, Brian [University of Tennessee; Chae, K. Y. [University of Tennessee; Pittman, S. T. [University of Tennessee, Knoxville (UTK); Kozub, R. L. [Tennessee Technological University; Vieira, D. J. [Los Alamos National Laboratory (LANL); Jandel, M. [Los Alamos National Laboratory (LANL); Wilhelmy, J. B. [Los Alamos National Laboratory (LANL); Matei, Catalin [Oak Ridge Associated Universities (ORAU); Escher, J. [Lawrence Livermore National Laboratory (LLNL); Bardayan, Daniel W [ORNL; Pain, Steven D [ORNL; Smith, Michael Scott [ORNL

    2010-01-01

    The 75As(d,p ) reaction in inverse kinematics as a surrogate for neutron capture was performed at Oak Ridge National Laboratory using a deuterated plastic target. The intensity of the 165 keV -ray from 76As in coincidence with ejected protons, from exciting 76As above the neutron separation energy populating a compound state, was measured. A tight geometry of four segmented germanium clover -ray detectors together with eight ORRUBA-type silicon-strip charged-particle detectors were used to optimize geometric acceptance. The preliminary analysis of the 75As experiment and the ecacy and future plans of the (d,p ) surrogate campaign in inverse kinematics are discussed.

  10. Neutron spectroscopic factors of $^{55}$Ni hole-states from (p,d) transfer reactions

    CERN Document Server

    Sanetullaev, A; Lynch, W G; Lee, Jenny; Bazin, D; Chan, K P; Coupland, D; Henzl, V; Henzlova, D; Kilburn, M; Rogers, A M; Sun, Z Y; Youngs, M; Charity, R J; Sobotka, L G; Famiano, M; Hudan, S; Shapira, D; Peters, W A; Barbieri, C; Hjorth-Jensen, M; Horoi, M; Otsuka, T; Suzuki, T; Utsuno, Y

    2014-01-01

    Spectroscopic information has been extracted on the hole-states of $^{55}$Ni, the least known of the quartet of nuclei ($^{55}$Ni, $^{57}$Ni, $^{55}$Co and $^{57}$Co), one neutron away from $^{56}$Ni, the N=Z=28 double magic nucleus. Using the $^{1}$H($^{56}$Ni,d)$^{55}$Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f$_{7/2}$, p$_{3/2}$ and the s$_{1/2}$ hole-states of $^{55}$Ni. This new data provides a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s$_{1/2}$ hole-state below Fermi energy.

  11. One-neutron stripping reactions of 11Be and 19C on light target

    Indian Academy of Sciences (India)

    Rajesh Kharab; Ravinder Kumar; Pradeep Singh; H C Sharma

    2007-05-01

    We have calculated the one-neutron absorption cross-section and the longitudinal momentum distribution of the core fragment coming out from the breakup of 11Be and 19C on 9Be target at 63 MeV/A and 88 MeV/A beam energies respectively. The reaction mechanism is treated within the framework of the eikonal approximation. The effective range of the nuclear interaction between the core and the valence neutron within the projectile has been determined by comparing the predicted stripping crosssection with the recently measured one. The effective range for 19C has been found to besmaller than that for 11Be. It qualitatively indicates that 19C is slightly more halo than 11Be. The smaller width, predicted as well as measured, of the LMD of 18C than 10Be also strengthens this fact. The experimental data concerning the LMD of core fragments have been well represented.

  12. EXFOR BASICS A SHORT GUIDE TO THE NEUTRON REACTION DATA EXCHANGE FORMAT.

    Energy Technology Data Exchange (ETDEWEB)

    MCLANE,V.; NUCLEAR DATA CENTER NETWORK

    2000-05-19

    This manual is intended as a guide to users of nuclear reaction data compiled in the EXFOR format, and is not intended as a complete guide to the EXFOR System. EXFOR is the exchange format designed to allow transmission of nuclear reaction data between the Nuclear Reaction Data Centers. In addition to storing the data and its' bibliographic information, experimental information is also compiled. The status (e.g., the source of the data) and history (e.g., date of last update) of the data set is also included. EXFOR is designed for flexibility in order to meet the diverse needs of the nuclear reaction data centers. It was originally conceived for the exchange of neutron data and was developed through discussions among personnel from centers situated in Saclay, Vienna, Livermore and Brookhaven. It was accepted as the official exchange format of the neutron data centers at Saclay, Vienna, Brookhaven and Obninsk, at a meeting held in November 1969.3 As a result of two meetings held in 1975 and 1976 and attended by several charged-particle data centers, the format was further developed and adapted to cover all nuclear reaction data. The exchange format should not be confused with a center-to-user format. Although users may obtain data from the centers in the EXFOR format, other center-to-user formats have been developed to meet the needs of the users within each center's own sphere of responsibility. The EXFOR format, as outlined, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in a format: l that is machine-readable (for checking and indicating possible errors); l that can be read by personnel (for passing judgment on and correcting errors). The data presently included in the EXFOR exchange file include: a complete compilation of experimental neutron-induced reaction data, a selected compilation of charged-particle-induced reaction data, a selected compilation of photon-induced reaction data.

  13. High-precision (p,t) reaction measurement to determine Ne-18(alpha,p)Na-21 reaction rates

    NARCIS (Netherlands)

    Matic, A.; van den Berg, A. M.; Harakeh, M. N.; Wörtche, H. J.; Berg, G. P. A.; Couder, M.; Fisker, J. L.; Goerres, J.; LeBlanc, P.; O'Brien, S.; Wiescher, M.; Fujita, K.; Hatanaka, K.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Tamii, A.; Yosoi, M.; Adachi, T.; Fujita, Y.; Shimbara, Y.; Fujita, H.; Wakasa, T.; Hess, P. O.; Brown, B. A.; Schatz, H.

    2009-01-01

    x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the alpha p process that describes a sequence of (alpha,p) reactions triggered by the Ne-18(alpha,p)Na-21 breakout reaction from the hot CNO cycles. We

  14. Extension of CASCADE.04 to estimate neutron fluence and dose rates and its validation

    Indian Academy of Sciences (India)

    H Kumawat; V Kumar; P Srinivasan

    2009-03-01

    Capability to compute neutron dose rate is introduced for the first time in the new version of the CASCADE.04 code. Two different methods, `track length estimator' and `collision estimator' are adapted for the estimation of neutron fluence rate needed to calculate the ambient dose rate. For the validation of the methods, neutron dose rates are experimentally measured at different locations of a 5Ci Am–Be source, shielded in Howitzer-type system and these results are compared with those estimated using (i) modified CASCADE.04.d and (ii) MCNP4A codes and it is found that the agreement is good. The paper presents details of modification and results of the comparative study.

  15. Real-time observations of lithium battery reactions-operando neutron diffraction analysis during practical operation.

    Science.gov (United States)

    Taminato, Sou; Yonemura, Masao; Shiotani, Shinya; Kamiyama, Takashi; Torii, Shuki; Nagao, Miki; Ishikawa, Yoshihisa; Mori, Kazuhiro; Fukunaga, Toshiharu; Onodera, Yohei; Naka, Takahiro; Morishima, Makoto; Ukyo, Yoshio; Adipranoto, Dyah Sulistyanintyas; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji

    2016-06-30

    Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries.

  16. Beta decay rates of neutron-rich nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Marketin, Tomislav, E-mail: marketin@phy.hr [Department of Physics, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Huther, Lutz [Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, 64289 Darmstadt (Germany); Martínez-Pinedo, Gabriel [Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt, 64289 Darmstadt (Germany); GSI Helmholtzzentrum für Schwerioneneforschung, Planckstraße 1, 64291 Darmstadt (Germany)

    2015-10-15

    Heavy element nucleosynthesis models involve various properties of thousands of nuclei in order to simulate the intricate details of the process. By necessity, as most of these nuclei cannot be studied in a controlled environment, these models must rely on the nuclear structure models for input. Of all the properties, the beta-decay half-lives are one of the most important ones due to their direct impact on the resulting abundance distributions. Currently, a single large-scale calculation is available based on a QRPA calculation with a schematic interaction on top of the Finite Range Droplet Model. In this study we present the results of a large-scale calculation based on the relativistic nuclear energy density functional, where both the allowed and the first-forbidden transitions are studied in more than 5000 neutron-rich nuclei.

  17. Beta decay rates of neutron-rich nuclei

    Science.gov (United States)

    Marketin, Tomislav; Huther, Lutz; Petković, Jelena; Paar, Nils; Martínez-Pinedo, Gabriel

    2016-06-01

    Heavy element nucleosynthesis models involve various properties of thousands of nuclei in order to simulate the intricate details of the process. By necessity, as most of these nuclei cannot be studied in a controlled environment, these models must rely on the nuclear structure models for input. Of all the properties, the beta-decay half-lives are one of the most important ones due to their direct impact on the resulting abundance distributions. In this study we present the results of a large-scale calculation based on the relativistic nuclear energy density functional, where both the allowed and the first-forbidden transitions are studied in more than 5000 neutron-rich nuclei. Aside from the astrophysical applications, the results of this calculation can also be employed in the modeling of the electron and antineutrino spectra from nuclear reactors.

  18. Non-resonant triple alpha reaction rate at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, T.; Tamii, A.; Aoi, N.; Fujita, H.; Hashimoto, T.; Miki, K.; Ogata, K. [Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Carter, J.; Donaldson, L.; Sideras-Haddad, E. [Schools of Physics, University of Witwatersrand, Johannesburg 2050 (South Africa); Furuno, T.; Kawabata, T. [Departments of Physics, Kyoto University, Sakyo, Kyoto, 606-8502 (Japan); Kamimura, M. [RIKEN Nishina Center, Wako, Saitama, 351-0198 (Japan); Nemulodi, F.; Neveling, R.; Smit, F. D.; Swarts, C. [iThemba Laboratory for Accelerator Based Sciences Somerset, West, 7129 (South Africa)

    2014-05-02

    Our experimental goal is to study the non-resonant triple alpha reaction rate at low temperture (T < 10{sup 8} K). The {sup 13}C(p,d) reaction at 66 MeV has been used to probe the alpha-unbound continuum state in {sup 12}C just below the 2{sup nd} 0{sup +} state at 7.65 MeV. The transition strength to the continuum state is predicted to be sensitive to the non-resonant triple alpha reaction rate. The experiment has been performed at iThemba LABS. We report the present status of the experiment.

  19. A sensitivity study of s-process: the impact of uncertainties from nuclear reaction rates

    Science.gov (United States)

    Vinyoles, N.; Serenelli, A.

    2016-01-01

    The slow neutron capture process (s-process) is responsible for the production of about half the elements beyond the Fe-peak. The production sites and the conditions under which the different components of s-process occur are relatively well established. A detailed quantitative understanding of s-process nucleosynthesis may yield light in physical processes, e.g. convection and mixing, taking place in the production sites. For this, it is important that the impact of uncertainties in the nuclear physics is well understood. In this work we perform a study of the sensitivity of s-process nucleosynthesis, with particular emphasis in the main component, on the nuclear reaction rates. Our aims are: to quantify the current uncertainties in the production factors of s-process elements originating from nuclear physics and, to identify key nuclear reactions that require more precise experimental determinations. In this work we studied two different production sites in which s-process occurs with very different neutron exposures: 1) a low-mass extremely metal-poor star during the He-core flash (nn reaching up to values of ∼ 1014cm-3); 2) the TP-AGB phase of a M⊙, Z=0.01 model, the typical site of the main s-process component (nn up to 108 — 109cm-3). In the first case, the main variation in the production of s-process elements comes from the neutron poisons and with relative variations around 30%-50%. In the second, the neutron poison are not as important because of the higher metallicity of the star that actually acts as a seed and therefore, the final error of the abundances are much lower around 10%-25%.

  20. On the 14C(alpha,gamma) reaction rate

    CERN Document Server

    Johnson, E D; Mitchell, J; Miller, L; Kemper, K W

    2009-01-01

    The 14C(alpha,gamma) reaction rate at temperatures below 0.3 GK depends on the properties of two near threshold resonances in 18O, the 1- at 6.198 MeV and the 3- at 6.404 MeV. The alpha+14C Asymptotic Normalization Coefficients (ANCs) for these resonances were determined using the alpha-transfer reactions 14C(7Li,t) and 14C(6Li,d) at sub-Coulomb energies. The 14C(alpha,gamma) reaction rate at low temperatures has been evaluated. Implications of the new reaction rate on the evolution of accreting helium white dwarfs and on the nucleosynthesis of low mass stars during the asymptotic giant branch (AGB) phase are discussed.

  1. Calculation of Prompt Fission Neutron from 233U(n, f) Reaction by Multi-Modal Los Alamos Model%Calculation of Prompt Fission Neutron from 233U(n, f) Reaction by Multi-Modal Los Alamos Model

    Institute of Scientific and Technical Information of China (English)

    郑娜; 钟春来; 樊铁栓

    2012-01-01

    An attempt is made to improve the evaluation of the prompt fission neutron emis- sion from 233U(n, f) reaction for incident neutron energies below 6 MeV. The multi-modal fission approach is applied to the improved version of Los Alamos model and the point by point model. The prompt fission neutron spectra and the prompt fission neutron as a function of fragment mass (usually named "sawtooth" data) v(A) are calculated independently for the three most dominant fission modes (standard I, standard II and superlong), and the total spectra and v(A) are syn- thesized. The multi-modal parameters are determined on the basis of experimental data of fission fragment mass distributions. The present calculation results can describe the experimental data very well, and the proposed treatment is thus a useful tool for prompt fission neutron emission prediction.

  2. Neutron-hole states in 45Ar from p(46Ar,d)45Ar reactions

    CERN Document Server

    Lu, F; Tsang, M B; Bazin, D; Coupland, D; Henzl, V; Henzlova, D; Kilburn, M; Lynch, W G; Rogers, A M; Sanetullaev, A; Sun, Z Y; Youngs, M; Charity, R J; Sobotka, L G; Famiano, M; Hudan, S; Horoi, M; Ye, Y L

    2013-01-01

    To improve the effective interactions in the pf shell, it is important to measure the single particle- and hole- states near the N=28 shell gap. In this paper, the neutron spectroscopic factors of hole-states from the unstable neutron-rich 45Ar (Z=18, N=27) nucleus have been studied using 1H(46Ar, 2H)45Ar transfer reaction in inverse kinematics. Comparison of our results with the particle-states of 45Ar produced in 2H(44Ar, H)45Ar reaction shows that the two reactions populate states with different angular momentum. Using the angular distributions, we are able to confirm the spin assignments of four low-lying states of 45Ar. These are the ground state (f7/2), the first-excited (p3/2), the s1/2 and the d3/2 states. While large basis shell model predictions describe spectroscopic properties of the ground and p3/2 states very well, they fail to describe the s1/2 and d3/2 hole-states.

  3. Gamma ray spectroscopy of neutron-rich actinides after multi-nucleon transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, Andreas; Birkenbach, Benedikt; Reiter, Peter; Hess, Herbert; Lewandowski, Lars; Steinbach, Tim [Institut fuer Kernphysik, Universitaet zu Koeln (Germany); Collaboration: LNL 11.22-Collaboration

    2014-07-01

    Excited states in neutron-rich Th and U nuclei were investigated after multi-nucleon transfer reactions employing the AGATA demonstrator and PRISMA setup at LNL (INFN, Italy). A primary {sup 136}Xe beam of 1 GeV hitting a {sup 238}U target was used to produce the nuclei of interest in the actinide region. Beam-like reaction products in the Xe-Ba-region were identified and selected by the PRISMA spectrometer. Kinematic coincidences between the binary reaction products of beam-like and target-like nuclei are detected with an additional MCP detector. Those coincidences allow clean conditions for in-beam γ-ray spectroscopy. Background contributions from excited fission fragments are successfully discriminated. γ-rays from excited states in beam- and target-like particles were measured with the position sensitive AGATA HPGe detectors. Improved energy resolution after Doppler correction is based on the novel γ-ray tracking technique which was successfully exploited to increase the quality of the γ-spectra. γ-ray spectra of the produced beam-like isotopes in the one-proton and two-proton transfer channels will be presented. Corresponding results from the hard-to-reach neutron-rich isotopes beyond {sup 232}Th will focus on their collective properties and cross section limits for their production.

  4. Evaluation of two-stage system for neutron measurement aiming at increase in count rate at Japan Atomic Energy Agency-Fusion Neutronics Source

    Energy Technology Data Exchange (ETDEWEB)

    Shinohara, K., E-mail: shinohara.koji@jaea.go.jp; Ochiai, K.; Sukegawa, A. [Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan); Ishii, K.; Kitajima, S. [Department of Quantum Science and Energy Engineering, Tohoku University, Sendai, Miyagi 980-8579 (Japan); Baba, M. [Cyclotron and Radioisotope Center, Tohoku University, Sendai, Miyagi 980-8578 (Japan); Sasao, M. [Organization for Research Initiatives and Development, Doshisha University, Kyoto 602-8580 (Japan)

    2014-11-15

    In order to increase the count rate capability of a neutron detection system as a whole, we propose a multi-stage neutron detection system. Experiments to test the effectiveness of this concept were carried out on Fusion Neutronics Source. Comparing four configurations of alignment, it was found that the influence of an anterior stage on a posterior stage was negligible for the pulse height distribution. The two-stage system using 25 mm thickness scintillator was about 1.65 times the count rate capability of a single detector system for d-D neutrons and was about 1.8 times the count rate capability for d-T neutrons. The results suggested that the concept of a multi-stage detection system will work in practice.

  5. Levels of 188Re nucleus populated in thermal neutron capture reaction

    Science.gov (United States)

    Běrziņš, J.; Krasta, T.; Simonova, L.; Balodis, M.; Bondarenko, V.; Jentschel, M.; Urban, W.; Tomandl, I.

    2016-03-01

    Levels of 188Re populated in thermal neutron capture reaction with enriched 187Re targets have been studied. Single γ-ray spectrum of 188Re, measured with the high-resolution crystal diffraction spectrometer GAMS5, as well as γγ-coincidence experiments performed with high efficiency Ge detectors, allowed to develop model-independent level scheme of the doubly-odd 188Re nucleus up to ˜ 1.5 MeV excitation energy. Analysis of the established 188Re level scheme in terms of the quasiparticle-plus-rotor model indicates coexistence of axially-deformed and triaxial structures in the energy range above 400 keV.

  6. Discovery of the shape coexisting 0$^{+}$ state in $^{32}$Mg by a two neutron transfer reaction

    CERN Document Server

    Wimmer, K; Krücken, R; Bildstein, V; Gernhäuser, R; Bastin, B; Bree, N; Diriken, J; Van Duppen, P; Huyse, M; Patronis, N; Vermaelen, P; Voulot, D; Van de Walle, J; Wenander, F; Fraile, L M; Chapman, R; Hadinia, B; Orlandi, R; Smith, J F; Lutter, R; Thirolf, P G; Labiche, M; Blazhev, A; Kalkühler, M; Reiter, P; Seidlitz, M; Warr, N; Macchiavelli, A O; Jeppesen, H B; Fiori, E; Georgiev, G; Schrieder, G; Gupta, S Das; Bianco, G Lo; Nardelli, S; Butterworth, J; Johansen, J; Riisager, K

    2010-01-01

    The Island of Inversion nucleus $^{32}$Mg has been studied by a (t,p) two neutron transfer reaction in inverse kinematics at REX-ISOLDE. The shape coexistent excited 0$^{+}$ state in $^{32}$Mg has been identified by the characteristic angular distribution of the protons of the $\\Delta$L = 0 transfer. The excitation energy of 1058 keV is much lower than predicted by any theoretical model. The low $\\gamma$-ray intensity observed for the decay of this 0$^{+}$ state indicates a lifetime of more than 10 ns. Deduced spectroscopic amplitudes are compared with occupation numbers from shell model calculations.

  7. Studies of Nuclei Close to 132Sn Using Single-Neutron Transfer Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Jones, K. L. [University of Tennessee, Knoxville (UTK); Pain, S. D. [Rutgers University; Kozub, R. L. [Tennessee Technological University; Adekola, Aderemi S [ORNL; Bardayan, Daniel W [ORNL; Blackmon, Jeff C [ORNL; Catford, Wilton N [ORNL; Chae, K. Y. [University of Tennessee, Knoxville (UTK); Chipps, K. [Colorado School of Mines, Golden; Cizewski, J. A. [Rutgers University; Erikson, Luke [Colorado School of Mines, Golden; Gaddis, A. L. [Furman University; Greife, U. [Colorado School of Mines, Golden; Grzywacz, R. K. [University of Tennessee, Knoxville (UTK); Harlin, Christopher W [ORNL; Hatarik, Robert [Rutgers University; Howard, Joshua A [ORNL; James, J. [Colorado School of Mines, Golden; Kapler, R. [University of Tennessee, Knoxville (UTK); Krolas, W. [University of Warsaw; Liang, J Felix [ORNL; Ma, Zhanwen [ORNL; Matei, Catalin [Oak Ridge Associated Universities (ORAU); Moazen, Brian [University of Tennessee, Knoxville (UTK); Nesaraja, Caroline D [ORNL; O' Malley, Patrick [Rutgers University; Patterson, N. P. [University of Surrey, UK; Paulauskas, Stanley [University of Tennessee, Knoxville (UTK); Shapira, Dan [ORNL; ShrinerJr., J. F. [Tennessee Technological University; Sikora, M. [Rutgers University; Sissom, D. J. [Tennessee Technological University; Smith, Michael Scott [ORNL; Swan, T. P. [University of Surrey, UK; Thomas, J. S. [Rutgers University; Wilson, Gemma L [ORNL

    2009-01-01

    Neutron transfer reactions were performed in inverse kinematics using radioactive ion beams of 132Sn, 130Sn, and 134Te and deuterated polyethylene targets. Preliminary results are presented. The Q-value spectra for 133Sn, 131Sn and 135Te reveal a number of previously unobserved peaks. The angular distributions are compatible with the expected lf7/2 nature of the ground state of 133Sn, and 2p3/2 for the 3.4 MeV state in 131Sn.

  8. Upper Limits on the Rates of Binary Neutron Star and Neutron Star-Black Hole Mergers from Advanced LIGO’s First Observing Run

    Science.gov (United States)

    Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Bejger, M.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Cheeseboro, B. D.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio., M., Jr.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; De, S.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Devine, R. C.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Fenyvesi, E.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gehrels, N.; Gemme, G.; Geng, P.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jian, L.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; K, Haris; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chi-Woong; Kim, Chunglee; Kim, J.; Kim, K.; Kim, N.; Kim, W.; Kim, Y.-M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kissel, J. S.; Klein, B.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Lewis, J. B.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Lombardi, A. L.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lück, H.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magaña Zertuche, L.; Magee, R. M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, A.; Miller, B. B.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Nedkova, K.; Nelemans, G.; Nelson, T. J. N.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Perri, L. M.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Qiu, S.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O. E. S.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Setyawati, Y.; Shaddock, D. A.; Shaffer, T.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tomlinson, C.; Tonelli, M.; Tornasi, Z.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Worden, J.; Wright, J. L.; Wu, D. S.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yu, H.; Yvert, M.; Zadrożny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

    2016-12-01

    We report here the non-detection of gravitational waves from the merger of binary-neutron star systems and neutron star-black hole systems during the first observing run of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). In particular, we searched for gravitational-wave signals from binary-neutron star systems with component masses \\in [1,3] {M}⊙ and component dimensionless spins detected the merger of binary-neutron star systems with component mass distributions of 1.35 ± 0.13 M ⊙ at a volume-weighted average distance of ˜70 Mpc, and for neutron star-black hole systems with neutron star masses of 1.4 M ⊙ and black hole masses of at least 5 M ⊙, a volume-weighted average distance of at least ˜110 Mpc. From this we constrain with 90% confidence the merger rate to be less than 12,600 Gpc-3 yr-1 for binary-neutron star systems and less than 3600 Gpc-3 yr-1 for neutron star-black hole systems. We discuss the astrophysical implications of these results, which we find to be in conflict with only the most optimistic predictions. However, we find that if no detection of neutron star-binary mergers is made in the next two Advanced LIGO and Advanced Virgo observing runs we would place significant constraints on the merger rates. Finally, assuming a rate of {10}-7+20 Gpc-3 yr-1, short gamma-ray bursts beamed toward the Earth, and assuming that all short gamma-ray bursts have binary-neutron star (neutron star-black hole) progenitors, we can use our 90% confidence rate upper limits to constrain the beaming angle of the gamma-ray burst to be greater than 2\\buildrel{\\circ}\\over{.} {3}-1.1+1.7 (4\\buildrel{\\circ}\\over{.} {3}-1.9+3.1).

  9. Dependence of Reaction Rate Constants on Density in Supercritical Fluids

    Institute of Scientific and Technical Information of China (English)

    WANGTao; SHENZhongyao

    2002-01-01

    A new method,which correlates rate constants of chemical reactions and density or pressure in supercritical fluids,was developed.Based on the transition state theory and thermodynamic principles, the rate constant can be reasonably correlated with the density of the supercritical fluid,and a correlation equation was obtained. Coupled with the equation of state (EOS) of a supercritical solvent,the effect of pressure on reaction rate constant could be represented.Two typical systems were used to test this method.The result indicates that this method is suitable for dilute supercritical fluid solutions.

  10. Experimental study of the $^{66}$Ni$(d,p)^{67}$Ni one-neutron transfer reaction

    CERN Document Server

    Diriken, J.; Andreyev, A.N.; Antalic, S.; Bildstein, V.; Blazhev, A.; Darby, I.G.; De Witte, H.; Eberth, J.; Elseviers, J.; Fedosseev, V.N.; Flavigny, F.; Fransen, Ch.; Georgiev, G.; Gernhauser, R.; Hess, H.; Huyse, M.; Jolie, J.; Kröll, Th.; Krücken, R.; Lutter, R.; Marsh, B.A.; Mertzimekis, T.; Muecher, D.; Orlandi, R.; Pakou, A.; Raabe, R.; Randisi, G.; Reiter, P.; Roger, T.; Seidlitz, M.; Seliverstov, M.; Sotty, C.; Tornqvist, H.; Van De Walle, J.; Van Duppen, P.; Voulot, D.; Warr, N.; Wenander, F.; Wimmer, K.

    2015-01-01

    The quasi-SU(3) sequence of the positive parity $νg_{9/2}, d_{5/2}, s_{1/2}$ orbitals above the N=40 shell gap are assumed to induce strong quadrupole collectivity in the neutron-rich Fe (Z=26) and Cr (Z=24) isotopes below the nickel region. In this paper the position and strength of these single-particle orbitals are characterized in the neighborhood of $^{68}$Ni (Z=28,N=40) through the $^{66}$Ni($d,p$)$^{67}$Ni one-neutron transfer reaction at 2.95 MeV/nucleon in inverse kinematics, performed at the REX-ISOLDE facility in CERN. A combination of the Miniball $\\gamma$-array and T-REX particle-detection setup was used and a delayed coincidence technique was employed to investigate the 13.3-$\\mu$s isomer at 1007 keV in $^{67}$Ni. Excited states up to an excitation energy of 5.8 MeV have been populated. Feeding of the $νg_{9/2}$ (1007 keV) and $νd_{5/2}$ (2207 keV and 3277 keV) positive-parity neutron states and negative parity ($νpf$) states have been observed at low excitation energy. The extracted relativ...

  11. Lead 207, 208 (n, xn gamma) reactions for neutron energies up to 200 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Pavlik, A.; Vonach, H. [Univ. Wien (Austria). Inst. fuer Radiumforschung und Kernphysik; Chadwick, M.B.; Haight, R.C.; Nelson, R.O.; Wender, S.A.; Young, P.G. [Los Alamos National Lab., NM (United States)

    1994-07-01

    High-resolution {gamma}-ray spectra from the interaction of neutrons in the energy range from 3 to 200 MeV with {sup 207,208}Pb were measured with the white neutron source at the WNR facility at Los Alamos National Laboratory. From these data, excitation functions for prominent {gamma} transitions in {sup 200,202,204,206,207,208}Pb were derived from threshold to 200 MeV incident neutron energy. These {gamma}-production cross sections represent formation cross sections for excited states of the residual nuclei. The results are compared with the predictions of nuclear reaction calculations based on the exciton model for precompound emission, the Hauser-Feshbach theory for compound nuclear decay, and coupled channels calculations to account for direct excitation of collective levels. Good agreement was obtained over the entire energy range covered in the experiment with reasonable model parameters. The results demonstrate that multiple preequilibrium emission has to be taken into account above about 40 MeV, and that the level density model of Ignatyuk should be used instead of the Gilbert-Cameron and back-shifted Fermi-gas models if excitation energies exceed about 30 MeV.

  12. Reaction dynamics and nuclear structure of moderately neutron-rich Ne isotopes by heavy ion reactions

    Directory of Open Access Journals (Sweden)

    Bottoni S.

    2014-03-01

    Full Text Available The heavy ion reaction 22Ne+208Pb at 128 MeV of bombarding energy has been studied using the PRISMA-CLARA experimental setup at Legnaro National Laboratories. Elastic, inelastic and one nucleon transfer cross sections have been measured. The experimental results are presented in parallel with the analysis on existing data for the unstable 24Ne nucleus, from the reaction 24Ne+208Pb at 182 MeV (measured at SPIRAL with the VAMOS-EXOGAM setup. The β2C charge deformation parameter for both 22Ne and 24Ne has been determined by a DWBA analysis of the experimental angular dis- tributions, showing a strong reduction for 24Ne.

  13. Astrophysical reaction rate for alpha(alpha n,gamma) sup 9 Be by photodisintegration

    CERN Document Server

    Sumiyoshi, K; Goko, S; Kajino, T

    2002-01-01

    We study the astrophysical reaction rate for the formation of sup 9 Be through the three body reaction alpha(alpha n,gamma). This reaction is one of the key reactions which could bridge the mass gap at A=8 nuclear systems to produce intermediate-to-heavy mass elements in alpha- and neutron-rich environments such as r-process nucleosynthesis in supernova explosions, s-process nucleosynthesis in asymptotic giant branch (AGB) stars, and primordial nucleosynthesis in baryon inhomogeneous cosmological models. To calculate the thermonuclear reaction rate in a wide range of temperatures, we numerically integrate the thermal average of cross sections assuming a two-steps formation through a metastable sup 8 Be, alpha+alpha[rlhar2] sup 8 Be(n,gamma) sup 9 Be. Off-resonant and on-resonant contributions from the ground state in sup 8 Be are taken into account. As input cross section, we adopt the latest experimental data by photodisintegration of sup 9 Be with laser-electron photon beams, which covers all relevant reson...

  14. Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles

    Science.gov (United States)

    Liechty, Derek S.; Lewis, Mark J.

    2010-01-01

    Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

  15. A new monitor for routine thermal and epithermal neutron fluence rate monitoring in k0 INAA.

    Science.gov (United States)

    Koster-Ammerlaan, M J J; Bacchi, M A; Bode, P; De Nadai Fernandes, E A

    2008-12-01

    The Zr-Au set for monitoring the thermal and epithermal neutron fluence rate and the epithermal spectrum parameter alpha is not always practicable for routine application of INAA in well-thermalized facilities. An alternative set consisting of Cr, Au and Mo provides values for the thermal neutron fluence rate, f and alpha that are not significantly different from those found via the Zr-Au method and the Cd-covered Zr-method. The IRMM standard SMELS-II was analyzed using the (Au-Cr-Mo) monitor and a good agreement was obtained.

  16. State Space Path Integrals for Electronically Nonadiabatic Reaction Rates

    CERN Document Server

    Duke, Jessica Ryan

    2016-01-01

    We present a state-space-based path integral method to calculate the rate of electron transfer (ET) in multi-state, multi-electron condensed-phase processes. We employ an exact path integral in discrete electronic states and continuous Cartesian nuclear variables to obtain a transition state theory (TST) estimate to the rate. A dynamic recrossing correction to the TST rate is then obtained from real-time dynamics simulations using mean field ring polymer molecular dynamics. We employ two different reaction coordinates in our simulations and show that, despite the use of mean field dynamics, the use of an accurate dividing surface to compute TST rates allows us to achieve remarkable agreement with Fermi's golden rule rates for nonadiabatic ET in the normal regime of Marcus theory. Further, we show that using a reaction coordinate based on electronic state populations allows us to capture the turnover in rates for ET in the Marcus inverted regime.

  17. Ultra- cold neutron sources: UCN production rate in solid deuterium converter

    Directory of Open Access Journals (Sweden)

    R Gheisari

    2016-06-01

    Full Text Available A new model is presented herein to calculate optimal value for ultra-cold neutron (UCN production rate of a UCN source. The cold neutron (CN converter is the main component of UCN source. In this paper, we study the UCN source which contains the D2O neutron moderator, the sD2 converter, 590 Mev proton beam, and the spallation target (a mixture of Pb, D2O and Zr. In order to determine the quantities, the neutron transport equation, written in MATLAB, has been combined with the MCNPX simulation code. The neutron transport equation in cylindrical coordinate has been solved everywhere in sD2 by using simulated CN flux as boundary value. By loading a cylindrical shell with different materials, surrounding the converter, different values for UCN production rate and density were obtained. The results of the UCN production rate and density and their comparison with previous results show that the present method has a good capability for optimization of UCN source parameters.

  18. Backward-forward reaction asymmetry of neutron elastic scattering on deuterium

    Science.gov (United States)

    Pirovano, E.; Beyer, R.; Junghans, A. R.; Nankov, N.; Nolte, R.; Nyman, M.; Plompen, A. J. M.

    2017-02-01

    A new measurement of the angular distribution of neutron elastic scattering on deuterium was carried out at the neutron time-of-flight facility nELBE. The backward-forward asymmetry of the reaction was investigated via the direct detection of neutrons scattered at the laboratory angle of 15∘ and 165∘ from a polyethylene sample enriched with deuterium. In order to extend the measurement to neutron energies below 1 MeV, 6Li glass scintillators were employed. The data were corrected for the background and the multiple scattering in the target, the events due to scattering on deuterium were separated from those due to carbon, and the ratio of the differential cross section at 15∘ and 165∘ was determined. The results, covering the energy range from 200 keV to 2 MeV, were found to be in agreement with the theoretical predictions calculated by Canton et al. [Eur. Phys. J. A 14, 225 (2002)], 10.1140/epja/i2001-10122-3 and by Golak et al. [Eur. Phys. J. A 50, 177 (2014)], 10.1140/epja/i2014-14177-7. The comparison with the evaluated nuclear data libraries indicated CENDL-3.1, JEFF-3.2, and JENDL-4.0 as the evaluations that best describe the asymmetry of n -d scattering. ENDF/B-VII.1 is compatible with the data for energies below 700 keV, but above the backward to forward ratio is higher than measured. ROSFOND-2010 and BROND-2.2 resulted to have little compatibility with the data.

  19. Reaction rate in an evanescent random walkers system

    CERN Document Server

    Ré, Miguel A

    2015-01-01

    Diffusion mediated reaction models are particularly ubiquitous in the description of physical, chemical or biological processes. The random walk schema is a useful tool for formulating these models. Recently, evanescent random walk models have received attention in order to include finite lifetime processes. For instance, activated chemical reactions, such as laser photolysis, exhibit a different asymptotic limit when compared with immortal walker models. A diffusion limited reaction model based on a one dimensional continuous time random walk on a lattice with evanescent walkers is presented here. The absorption probability density and the reaction rate are analytically calculated in the Laplace domain. A finite absorption rate is considered, a model usually referred to as imperfect trapping. Short and long time behaviors are analyzed.

  20. Effects of Surfactants on the Rate of Chemical Reactions

    Directory of Open Access Journals (Sweden)

    B. Samiey

    2014-01-01

    Full Text Available Surfactants are self-assembled compounds that depend on their structure and electric charge can interact as monomer or micelle with other compounds (substrates. These interactions which may catalyze or inhibit the reaction rates are studied with pseudophase, cooperativity, and stoichiometric (classical models. In this review, we discuss applying these models to study surfactant-substrate interactions and their effects on Diels-Alder, redox, photochemical, decomposition, enzymatic, isomerization, ligand exchange, radical, and nucleophilic reactions.

  1. Measurements of neutron cross section of the {sup 243}Am(n,{gamma}){sup 244}Am reaction

    Energy Technology Data Exchange (ETDEWEB)

    Hatsukawa, Yuichi; Shinohara, Nobuo; Hata, Kentaro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    The effective thermal neutron cross section of {sup 243}Am(n,{gamma}){sup 244}Am reaction was measured by the activation method. Highly-purified {sup 243}Am target was irradiated in an aluminum capsule by using a research reactor JRR-3M. The tentative effective thermal neutron cross sections are 3.92 b, and 84.44 b for the production of {sup 244g}Am and {sup 244m}Am, respectively. (author)

  2. Neutron fluence depth profiles in water phantom on epithermal beam of LVR-15 research reactor.

    Science.gov (United States)

    Viererbl, L; Klupak, V; Lahodova, Z; Marek, M; Burian, J

    2010-01-01

    Horizontal channel with epithermal neutron beam at the LVR-15 research reactor is used mainly for boron neutron capture therapy. Neutron fluence depth profiles in a water phantom characterise beam properties. The neutron fluence (approximated by reaction rates) depth profiles were measured with six different types of activation detectors. The profiles were determined for thermal, epithermal and fast neutrons.

  3. Reaction rates between water and the Karl Fischer reagent.

    Science.gov (United States)

    Cedergren, A

    1974-04-01

    Reaction rates between water and the Karl Fischer reagent have been determined by potentiometric measurement for various compositions of the Karl Fischer reagent. The study has been made with an iodine complex concentration of 0.3-1.2 mM and sulphur dioxide complex at 0.01-0.5M. The concentration of excess of pyridine had no measurable effect on the rate of the main reaction. The reaction was found to be first-order with respect to iodine complex, to sulphur dioxide complex, and to water. The rate constant was (1.2+/-0.2) x 10(3) 1(2). mole(-2). sec(-1). In an ordinary titration it is therefore essential to keep the sulphur dioxide concentration high for the reaction to go to completion within a reasonable time. The extent of side-reactions was found to be independent of the iodine concentration at low concentrations. The side-reactions increased somewhat with increasing sulphur dioxide pyridine concentrations and decreased to about 60% when the temperature was lowered from 24 degrees to 7 degrees.

  4. The neutron-proton charge-exchange amplitudes measured in the dp {yields} ppn reaction

    Energy Technology Data Exchange (ETDEWEB)

    Mchedlishvili, D.; Chiladze, D. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); Forschungszentrum Juelich, Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Juelich (Germany); Barsov, S.; Dzyuba, A. [Petersburg Nuclear Physics Institute, High Energy Physics Department, Gatchina (Russian Federation); Carbonell, J. [Universite Paris-Sud, IN2P3-CNRS, Institut de Physique Nucleaire, Orsay Cedex (France); Dymov, S. [JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Universitaet Erlangen-Nuernberg, Physikalisches Institut II, Erlangen (Germany); Engels, R.; Gebel, R.; Hartmann, M.; Kacharava, A.; Kamerdzhiev, V.; Lehrach, A.; Lorentz, B.; Maier, R.; Ohm, H.; Prasuhn, D.; Rathmann, F.; Serdyuk, V.; Seyfarth, H.; Stein, H.J.; Stockhorst, H.; Stroeher, H. [Forschungszentrum Juelich, Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Juelich (Germany); Glagolev, V. [JINR, Laboratory of High Energies, Dubna (Russian Federation); Grigoryev, K.; Mikirtychyants, M.; Mikirtychyants, S.; Valdau, Yu. [Forschungszentrum Juelich, Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Juelich (Germany); Petersburg Nuclear Physics Institute, High Energy Physics Department, Gatchina (Russian Federation); Goslawski, P.; Khoukaz, A.; Mielke, M.; Papenbrock, M. [Universitaet Muenster, Institut fuer Kernphysik, Muenster (Germany); Keshelashvili, I. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); University of Basel, Department of Physics, Basel (Switzerland); Komarov, V.; Kulikov, A. [JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Kulessa, P. [H. Niewodniczanski Institute of Nuclear Physics PAN, Krakow (Poland); Lomidze, N.; Nioradze, M.; Tabidze, M. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); Macharashvili, G. [Tbilisi State University, High Energy Physics Institute, Tbilisi (Georgia); JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Merzliakov, S. [Forschungszentrum Juelich, Institut fuer Kernphysik and Juelich Centre for Hadron Physics, Juelich (Germany); JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); Steffens, E. [Universitaet Erlangen-Nuernberg, Physikalisches Institut II, Erlangen (Germany); Trusov, S. [Forschungszentrum Rossendorf, Institut fuer Kern- und Hadronenphysik, Dresden (Germany); Uzikov, Yu. [JINR, Laboratory of Nuclear Problems, Dubna (Russian Federation); M. V. Lomonosov Moscow State University, Department of Physics, Moscow (Russian Federation); Wilkin, C. [UCL, Physics and Astronomy Department, London (United Kingdom)

    2013-04-15

    The unpolarised differential cross section and the two deuteron tensor analysing powers A{sub xx} and A{sub yy} of the vector dp {yields} {l_brace}pp{r_brace}{sub s}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27GeV, data were obtained for small momentum transfers to a {l_brace}pp{r_brace}{sub s} system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters C{sub x,x} and C{sub y,y} that were carried out in the vector dvector p {yields} {l_brace}pp{r_brace}{sub s}n reaction at 1.2 and 2.27GeV. The values obtained for the proton analysing power A{sub y}{sup p} also suggest the need for a radical re-evaluation of the neutron-proton elastic scattering amplitudes at the higher energy. It is therefore clear that such measurements can provide a valuable addition to the neutron-proton database in the charge-exchange region. (orig.)

  5. ATLAS MDT chamber behaviour after neutron irradiation and in a high rate background

    Energy Technology Data Exchange (ETDEWEB)

    Branchini, Paolo; Di Luise, Silvestro; Graziani, Enrico [Dipartimento di Fisica, Universita di Rome Tre and INFN Sezione di Roma Tre, Rome (Italy); Mazzotta, Concetta; Meoni, Evelin; Morello, Gianfranco [Dipartimento di Fisica, Universita della Calabria and INFN Gruppo Collegato di Cosenza, Cosenza (Italy); Passeri, Antonio; Petrucci, Fabrizio [Dipartimento di Fisica, Universita di Rome Tre and INFN Sezione di Roma Tre, Rome (Italy); Policicchio, Antonio [Dipartimento di Fisica, Universita della Calabria and INFN Gruppo Collegato di Cosenza, Cosenza (Italy)], E-mail: antonio.policicchio@cern.ch; Salvatore, Daniela; Schioppa, Marco [Dipartimento di Fisica, Universita della Calabria and INFN Gruppo Collegato di Cosenza, Cosenza (Italy)

    2007-10-21

    Many of the physics processes of interest at the Large Hadron Collider (LHC) will involve muon production in the final state. The Monitored Drift Tube (MDT) chambers, the precision tracking elements of the ATLAS muon spectrometer, are the main tools for the muon identification and measurement. They will operate in the harsh LHC background environment, mainly due to low energy photons and neutrons which will dominate the counting rate in most areas of the spectrometer, where an overall maximum counting rate of 500Hz/cm{sup 2} is expected. The upgrade to Super-LHC will involve fluxes ten times higher. To study the behaviour of MDT chambers under massive neutron irradiation at the level of Super-LHC, a test was performed at the 'Tapiro' Neutron Facility of the ENEA 'La Casaccia' Research Center.

  6. RPMDrate: Bimolecular chemical reaction rates from ring polymer molecular dynamics

    KAUST Repository

    Suleimanov, Yu.V.

    2013-03-01

    We present RPMDrate, a computer program for the calculation of gas phase bimolecular reaction rate coefficients using the ring polymer molecular dynamics (RPMD) method. The RPMD rate coefficient is calculated using the Bennett-Chandler method as a product of a static (centroid density quantum transition state theory (QTST) rate) and a dynamic (ring polymer transmission coefficient) factor. The computational procedure is general and can be used to treat bimolecular polyatomic reactions of any complexity in their full dimensionality. The program has been tested for the H+H2, H+CH 4, OH+CH4 and H+C2H6 reactions. © 2012 Elsevier B.V. All rights reserved.

  7. Neutron Capture Reactions on Fe and Ni Isotopes for the Astrophysical s-process

    CERN Document Server

    Lederer, C; Massimi, C; Žugec, P; Barbagallo, M; Colonna, N; Domingo-Pardo, C; Guerrero, C; Gunsing, F; Käppeler, F; Tain, J L; Altstadt, S; Andrzejewski, J; Audouin, L; Bécares, V; Bečvář, F; Belloni, F; Berthoumieux, E; Billowes, J; Boccone, V; Bosnar, D; Brugger, M; Calviani, M; Calviño, F; Cano-Ott, D; Carrapiço, C; Cerutti, F; Chiaveri, E; Chin, M; Cortés, G; Cortés-Giraldo, M A; Diakaki, M; Duran, I; Dressler, R; Dzysiuk, N; Eleftheriadis, C; Ferrari, A; Fraval, K; Ganesan, S; García, A R; Gómez-Hornillos, M B; Gonçalves, I F; González-Romero, E; Griesmayer, E; Gurusamy, P; Jenkins, D G; Jericha, E; Kadi, Y; Karadimos, D; Kivel, N; Koehler, P; Kokkoris, M; Korschinek, G; Krtička, M; Kroll, J; Langer, C; Leeb, H; Leong, L S; Losito, R; Manousos, A; Marganiec, J; Martínez, T; Mastinu, P F; Mastromarco, M; Meaze, M; Mendoza, E; Mengoni, A; Milazzo, P M; Mingrone, F; Mirea, M; Mondelaers, W; Paradela, C; Pavlik, A; Perkowski, J; Pignatari, M; Plompen, A; Praena, J; Quesada, J M; Rauscher, T; Reifarth, R; Riego, A; Roman, F; Rubbia, C; Sarmento, R; Schillebeeckx, P; Schmidt, S; Schumann, D; Tagliente, G; Tarrío, D; Tassan-Got, L; Tsinganis, A; Valenta, S; Vannini, G; Variale, V; Vaz, P; Ventura, A; Versaci, R; Vermeulen, M J; Vlachoudis, V; Vlastou, R; Wallner, A; Ware, T; Weigand, M; Weiß, C; Wright, T J

    2014-01-01

    Neutron capture cross sections in the keV neutron energy region are the key nuclear physics input to study the astrophysical slow neutron capture process. In the past years, a series of neutron capture cross section measurements has been performed at the neutron time-of-flight facility n\\_TOF at CERN focussing on the Fe/Ni mass region. Recent results and future developments in the neutron time-of-flight technique are discussed.

  8. Study of 11Be on 9Be one neutron transfer reactions at TRIUMF ISAC-II

    Science.gov (United States)

    Braid, Ryan; (Pcb)2 Collaboration; Tigress Collaboration

    2016-09-01

    The structure of neutron-rich Beryllium isotopes displays interesting properties arising from the interplay of alpha clustering and valence neutrons, leading in some cases to halo nuclei. In this presentation, preliminary results of the 11Be on 9Be reaction at 55 MeV and 30.14 MeV leading to two interesting exit channels will be shown, the first one enabling the study of 12Be and the second the study of 10Be. This reaction has advantages over the traditional (d,p) or (d,t) methods, since the reactants are equal in mass they both scatter in a detectable angular range. Additionally, TIGRESS allows precise γ-tagging for the excited states. Some challenges in analysis include the 10Be degeneracy, a large n breakup signature, and multiple particle excitation. The data and ongoing analysis will be presented. This work is partially supported by the US Department of Energy through Grant/Contract No. DE-FG03- 93ER40789 (Colorado School of Mines).

  9. Predicted neutron yield and radioactivity for laser-induced (p,n) reactions in LiF

    Energy Technology Data Exchange (ETDEWEB)

    Swift, D C; McNaney, J M

    2009-01-30

    Design calculations are presented for a pulsed neutron source comprising polychromatic protons accelerated from a metal foil by a short-pulse laser, and a LiF converter in which (p,n) reactions occur. Although the proton pulse is directional, neutrons are predicted to be emitted relatively isotropically. The neutron spectrum was predicted to be similar to the proton spectrum, but with more neutrons of low energy in the opposite direction to the incident protons. The angular dependence of spectrum and intensity was predicted. The (p,n) reactions generate unstable nuclei which decay predominantly by positron emission to the original {sup 7}Li and {sup 19}F isotopes. For the initial planned experiments using a converter 1mm thick, we predict that 0.1% of the protons will undergo a (p,n) reaction, producing 10{sup 9} neutrons. Ignoring the unreacted protons, neutrons, and prompt gamma emission as excited nuclear states decay, residual positron radioactivity (and production of pairs of 511 keV annihilation photons) is initially 4.2MBq decaying with a half-life of 17.22 s for 6 mins ({sup 19}Ne decays), then 135Bq decaying with a half-life of 53.22 days ({sup 7}Be decays).

  10. 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.

  11. First-forbidden $\\mathbf{\\beta}$-decay rates, energy rates of $\\beta$-delayed neutrons and probability of $\\beta$-delayed neutron emissions for neutron-rich nickel isotopes

    CERN Document Server

    Nabi, Jameel-Un; Iftikhar, Zafar

    2016-01-01

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

  12. Liquid Film Diffusion on Reaction Rate in Submerged Biofilters

    DEFF Research Database (Denmark)

    Christiansen, Pia; Hollesen, Line; Harremoës, Poul

    1995-01-01

    Experiments were carried out in order to investigate the influence of liquid film diffusion on reaction rate in a submerged biofilter with denitrification and in order to compare with a theoretical study of the mass transfer coefficient. The experiments were carried out with varied flow, identified...... by the empty bed velocity of inflow and recirculation, respectively 1.3, 2.8, 5.6 and 10.9 m/h. The filter material consisted of 3 mm biostyren spheres. The results indicate that the influence of liquid film diffusion on reaction rate can be ignored....

  13. High Repetition-Rate Neutron Generation by Several-mJ, 35 fs pulses interacting with Free-Flowing D2O

    Science.gov (United States)

    Hah, Jungmoo; Petrov, George; Nees, John; He, Zhaohan; Hammig, Mark; Krushelnick, Karl; Thomas, Alexander

    2016-10-01

    Recent advance in ultra-high power laser technology allows a development of laser-based neutron sources. Here we demonstrate heavy-water based neutron source. Using several-mJ energy pulses from a high-repetition rate (½kHz), ultrashort (35 fs) pulsed laser interacting with a 10 μm diameter stream of free-flowing heavy water (D2O), we get a 2.45 MeV neutron flux of 105/s. In the intentionally generated pre-plasma, laser pulse energy is efficiently absorbed, and energetic deuterons are generated. As a convertor, the bulk heavy water stream target and the large volume of low density D2O vapor near the target are collided with accelerated deuterons, generating neutron through d(d,n)3He reactions. As laser pulse energy increased from 6mJ to 12mJ, the neutron flux increased. From the 2D particle-in-cell simulation, comparable neutron fluxes are shown at the similar laser characteristics to the experiment. Also, simulation shows forward and backward moving deuterons, which are main distributing ions impinging upon D2O stream and vapor, respectively. This material is based upon work supported by the Air Force Office of Scien- tific Research under Award Numbers FA9550-12-1-0310 (Young Investigator Program) and FA9550-14-1-0282.

  14. Measurements of activation reaction rates in transverse shielding concrete exposed to the secondary particle field produced by intermediate energy heavy ions on an iron target

    Science.gov (United States)

    Ogawa, T.; Morev, M. N.; Iimoto, T.; Kosako, T.

    2012-01-01

    Reaction rate distributions were measured inside a 60-cm thick concrete pile placed at the lateral position of a thick (stopping length) iron target that was bombarded with heavy ions, 400 MeV/u C and 800 MeV/u Si. Foils of aluminum and gold, as well as gold, tungsten and manganese covered with cadmium were inserted at various locations in the concrete pile to serve as activation detectors. Features of reaction rate distribution, such as the shape of the reaction rate profile, contribution of the neutrons from intra-nuclear cascade and that from evaporation to the activation reactions are determined by the analysis of measured reaction rates. The measured reaction rates were compared with those calculated with radiation transport simulation codes, FLUKA and PHITS, to verify their capability to predict induced activity. The simulated reaction rates agree with the experimental results within a factor of three in general. However, systematic discrepancies between simulated reaction rates and measured reaction rates attributed to the neutron source terms are observed.

  15. Measured thermal and fast neutron fluence rates for ATF-1 holders during ATR cycle 160A

    Energy Technology Data Exchange (ETDEWEB)

    Walker, B. J. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Miller, D. T. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2017-06-06

    This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 160A which were measured by the Radiation Measurements Laboratory (RML).

  16. Astrophysical neutron capture rates in s- and r-process nucleosynthesis

    CERN Document Server

    Beer, H; Oberhummer, Heinz; Rauscher, T; Mutti, P; Corvi, F; Sedyshev, P V; Popov, Yu P; Popov, Yu.P.

    1997-01-01

    Astrophysical neutron capture rates of light and heavy nuclei have been measured and calculated. For the measurements the activation technique was applied at the 3.75 MV Karlsruhe Van de Graaff accelerator, and at the Geel electron linear accelerator (GELINA) the time-of-flight (TOF) method was used. The calculations were performed using direct and compound nuclear capture models.

  17. Reaction Cross Section Calculations in Neutron Induced Reactions and GEANT4 Simulation of Hadronic Interactions for the Reactor Moderator Material BeO

    Directory of Open Access Journals (Sweden)

    Veli ÇAPALI

    2016-05-01

    Full Text Available BeO is one of the most common moderator material for neutron moderation; due to its high density, neutron capture cross section and physical-chemical properties that provides usage at elevated temperatures. As it’s known, for various applications in the field of reactor design and neutron capture, reaction cross–section data are required. The cross–sections of (n,α, (n,2n, (n,t, (n,EL and (n,TOT reactions for 9Be and 16O nuclei have been calculated by using TALYS 1.6 Two Component Exciton model and EMPIRE 3.2 Exciton model in this study. Hadronic interactions of low energetic neutrons and generated isotopes–particles have been investigated for a situation in which BeO was used as a neutron moderator by using GEANT4, which is a powerful simulation software. In addition, energy deposition along BeO material has been obtained. Results from performed calculations were compared with the experimental nuclear reaction data exist in EXFOR.

  18. Massive Star Evolution Nucleosynthesis and Nuclear Reaction Rate Uncertainties

    CERN Document Server

    Heger, A; Rauscher, T; Hoffman, R D; Boyes, M M

    2002-01-01

    We present a nucleosynthesis calculation of a 25 solar mass star of solar composition that includes all relevant isotopes up to polonium. In particular, all stable isotopes and necessary nuclear reaction rates are covered. We follow the stellar evolution from hydrogen burning till iron core collapse and simulate the explosion using a ``piston'' approach. We discuss the influence of two key nuclear reaction rates, C12(a,g) and Ne22(a,n), on stellar evolution and nucleosynthesis. The former significantly influences the resulting core sizes (iron, silicon, oxygen) and the overall presupernova structure of the star. It thus has significant consequences for the supernova explosion itself and the compact remnant formed. The later rate considerably affects the s-process in massive stars and we demonstrate the changes that different currently suggested values for this rate cause.

  19. A compilation of charged-particle induced thermonuclear reaction rates

    CERN Document Server

    Angulo, C; Rayet, M; Descouvemont, P; Baye, D; Leclercq-Willain, C; Coc, A; Barhoumi, S; Aguer, P; Rolfs, C; Kunz, R; Hammer, J W; Mayer, A; Paradelis, T; Kossionides, S; Chronidou, C; Spyrou, K; Degl'Innocenti, S; Fiorentini, G; Ricci, B; Zavatarelli, S; Providência, C; Wolters, H; Soares, J; Grama, C; Rahighi, J; Shotter, A; Rachti, M L

    1999-01-01

    Low-energy cross section data for 86 charged-particle induced reactions involving light (1 <= Z <= 14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10 sup 6 K to 10 sup 1 sup 0 K are calculated. These evaluations assume either that the target nuclei are in their ground state, or that the target states are thermally populated following a Maxwell-Boltzmann distribution, except in some cases involving isomeric states. Adopted values complemented with lower and upper limits of the rates are presented in tabular form. Analytical approximations to the adopted rates, as well as to the inverse/direct rate ratios, are provided.

  20. A compilation of charged-particle induced thermonuclear reaction rates

    Energy Technology Data Exchange (ETDEWEB)

    Angulo, C.; Arnould, M.; Rayet, M.; Descouvemont, P.; Baye, D.; Leclercq-Willain, C.; Coc, A.; Barhoumi, S.; Aguer, P.; Rolfs, C.; Kunz, R.; Hammer, J.W.; Mayer, A.; Paradellis, T.; Kossionides, S.; Chronidou, C.; Spyrou, K.; Degl' Innocenti, S.; Fiorentini, G.; Ricci, B.; Zavatarelli, S.; Providencia, C.; Wolters, H.; Soares, J.; Grama, C.; Rahighi, J.; Shotter, A.; Rachti, M. Lamehi

    1999-08-23

    Low-energy cross section data for 86 charged-particle induced reactions involving light (1 {<=} Z {<=} 14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10{sup 6} K to 10{sup 10} K are calculated. These evaluations assume either that the target nuclei are in their ground state, or that the target states are thermally populated following a Maxwell-Boltzmann distribution, except in some cases involving isomeric states. Adopted values complemented with lower and upper limits of the rates are presented in tabular form. Analytical approximations to the adopted rates, as well as to the inverse/direct rate ratios, are provided.

  1. ACDOS2: an improved neutron-induced dose rate code

    Energy Technology Data Exchange (ETDEWEB)

    Lagache, J.C.

    1981-06-01

    To calculate the expected dose rate from fusion reactors as a function of geometry, composition, and time after shutdown a computer code, ACDOS2, was written, which utilizes up-to-date libraries of cross-sections and radioisotope decay data. ACDOS2 is in ANSI FORTRAN IV, in order to make it readily adaptable elsewhere.

  2. Determining neutron-capture cross sections via the surrogate reaction technique

    CERN Document Server

    Forssén, C; Escher, J; Hoffman, R D; Kelley, K

    2007-01-01

    Indirect methods play an important role in the determination of nuclear reaction cross sections that are hard to measure directly. In this paper we investigate the feasibility of using the so-called surrogate method to extract neutron-capture cross sections for low energy compound-nuclear reactions in spherical and near-spherical nuclei. We present the surrogate method and develop a statistical nuclear-reaction simulation to explore different approaches to utilize surrogate reaction data. We assess the success of each approach by comparing the extracted cross sections with a predetermined benchmark. In particular, we employ regional systematics of nuclear properties in the 34 <= Z <= 46 region to calculate (n,gamma) cross sections for a series of Zr isotopes, and to simulate a surrogate experiment and the extraction of the desired cross section. We identify one particular approach that may provide very useful estimates of the cross section, and we discuss some of the limitations of the method. General r...

  3. Nuclear reaction rates and opacity in massive star evolution calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bahena, D [Astronomical Institute of the Academy of Sciences, BocnI II 1401, 14131 Praha 4 (Czech Republic); Klapp, J [Instituto Nacional de Investigaciones Nucleares, Km. 36.5 Carr. Mexico-Toluca, 52750 Edo. de Mexico (Mexico); Dehnen, H, E-mail: jaime.klapp@inin.gob.m [Universitaet Konstanz, Fachbereich Physik, Fach M568, D-78457 Konstanz (Germany)

    2010-07-01

    Nuclear reaction rates and opacity are important parameters in stellar evolution. The input physics in a stellar evolution code determines the main theoretical characteristics of the stellar structure, evolution and nucleosynthesis of a star. For different input physics, in this work we calculate stellar evolution models of very massive first stars during the hydrogen and helium burning phases. We have considered 100 and 200M{sub s}un galactic and pregalactic stars with metallicity Z = 10{sup -6} and 10{sup 9}, respectively. The results show important differences from old to new formulations for the opacity and nuclear reaction rates, in particular the evolutionary tracks are significantly affected, that indicates the importance of using up to date and reliable input physics. The triple alpha reaction activates sooner for pregalactic than for galactic stars.

  4. Fast neutron spectrum unfolding of a TRIGA Mark II reactor and measurement of spectrum-averaged cross sections. Integral tests of differential cross sections of neutron threshold reactions

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, M.S.; Hossain, S.M.; Khan, R. [Atomic Energy Research Establishment, Dhaka (Bangladesh). Inst. of Nuclear Science and Technology (INST); Sudar, S. [Debrecen Univ. (Hungary). Inst. of Experimental Physics; Zulquarnain, M.A. [Bangladesh Atomic Energy Commission, Dhaka (Bangladesh); Qaim, S.M. [Forschungszentrum Juelich (Germany). Inst. fuer Neurowissenschaften und Medizin (INM-5)

    2013-07-01

    The spectrum of fast neutrons having energies from 0.5 to 20 MeV in the core of the 3MW TRIGA Mark II reactor at Savar, Dhaka, Bangladesh, was unfolded by activating several metal foils to induce threshold nuclear reactions covering the whole spectrum, and then doing necessary iterative calculations utilizing the activation results and the code SULSA. The analysed shape of the spectrum in the TRIGA core was found to be similar to that of the pure {sup 235}U-fission spectrum, except for the energies between 0.5 and 1.5 MeV, where it was slightly higher than the fission spectrum. Spectrum-averaged cross sections were determined by integral measurements. The integral values measured in this work were compared with the recommended values for a pure fission spectrum as well as with the integrated data deduced from measured and evaluated excitation functions of a few reactions given in some data files. The good agreement between integral measurements and integrated data in case of well-investigated reactions shows that the fast neutron field at the TRIGA Mark II reactor can be used for validation of evaluated data of neutron threshold reactions. (orig.)

  5. Prediction of Rate Constants for Catalytic Reactions with Chemical Accuracy.

    Science.gov (United States)

    Catlow, C Richard A

    2016-08-01

    Ex machina: A computational method for predicting rate constants for reactions within microporous zeolite catalysts with chemical accuracy has recently been reported. A key feature of this method is a stepwise QM/MM approach that allows accuracy to be achieved while using realistic models with accessible computer resources.

  6. Helium Burning Reaction Rate Uncertainties and Consequences for Supernovae

    Science.gov (United States)

    Tur, C.; Heger, A.; Austin, S. M.

    2007-10-01

    The triple alpha and ^12C(,)^16O reaction rates determine the carbon to oxygen ratio at the completion of core helium burning in stars, which, in turn, influences the later stellar burning stages. We explored the dependence of massive star evolution and nucleosynthesis yields on the experimental uncertainties in the triple alpha rate (10 to 12%) and the ^12C(,)^16O rate (25 to 35%) using full stellar models followed to core collapse and including supernova explosion. The production factors of medium-weight elements obtained by using the Lodders (2003) solar abundances for the initial star composition, rather than the abundances of Anders & Grevesse (1989), provide a less stringent constraint on the ^12C(,)^16O rate. Variations within the current uncertainties in both reaction rates, however, induce significant changes in the central carbon abundance at core carbon ignition and in the mass of the supernova remnant. An experiment is being carried out by an NSCL/WMU collaboration to improve the accuracy of the triple alpha reaction rate.

  7. Langevin study of neutron emission in the reactions 16O+181Ta and 19F+178Hf

    Institute of Scientific and Technical Information of China (English)

    YE Wei; WU Feng; YANG Hong-Wei

    2008-01-01

    The pre-scission neutrons measured in the reactions 16O+181Ta and 19F+178Hf are studied via a Langevin equation coupled with a statistical decay model.We find that because of the mass asymmetry of different entrance channels,the spin distributions of compound nuclei would be different,consequently,the measured neutrons in these two reactions would also different.This means that the entrance channel will affect the particle emission in the fission process of hot nuclei.

  8. Cross Sections for Neutron-induced Reactions on Actinide Targets Extracted from Surrogate Experiments: A Status Report

    Energy Technology Data Exchange (ETDEWEB)

    Escher, J E; Burke, J T; Dietrich, F S; Lesher, S R; Scielzo, N D; Thompson, I J; Younes, W

    2009-10-01

    The Surrogate nuclear reactions method, an indirect approach for determining cross sections for compound-nuclear reactions involving difficult-to-measure targets, is reviewed. Focusing on cross sections for neutron-induced reactions on actinides, we review the successes of past and present applications of the method and assess its uncertainties and limitations. The approximations used in the analyses of most experiments work reasonably well for (n,f) cross sections for neutron energies above 1-2 MeV, but lead to discrepancies for low-energy (n,f) reactions, as well as for (n,{gamma}) applications. Correcting for some of the effects neglected in the approximate analyses leads to improved (n,f) results. We outline steps that will further improve the accuracy and reliability of the Surrogate method and extend its applicability to reactions that cannot be approached with the present implementation of the method.

  9. Noise slows the rate of Michaelis-Menten reactions.

    Science.gov (United States)

    Van Dyken, J David

    2017-10-07

    Microscopic randomness and the small volumes of living cells combine to generate random fluctuations in molecule concentrations called "noise". Here I investigate the effect of noise on biochemical reactions obeying Michaelis-Menten kinetics, concluding that substrate noise causes these reactions to slow. I derive a general expression for the time evolution of the joint probability density of chemical species in arbitrarily connected networks of non-linear chemical reactions in small volumes. This equation is a generalization of the chemical master equation (CME), a common tool for investigating stochastic chemical kinetics, extended to reaction networks occurring in small volumes, such as living cells. I apply this equation to a generalized Michaelis-Menten reaction in an open system, deriving the following general result: 〈p〉≤p¯ and 〈s〉≥s¯, where s¯ and p¯ denote the deterministic steady-state concentration of reactant and product species, respectively, and 〈s〉 and 〈p〉 denote the steady-state ensemble average over independent realizations of a stochastic reaction. Under biologically realistic conditions, namely when substrate is degraded or diluted by cell division, 〈p〉≤p¯. Consequently, noise slows the rate of in vivo Michaelis-Menten reactions. These predictions are validated by extensive stochastic simulations using Gillespie's exact stochastic simulation algorithm. I specify the conditions under which these effects occur and when they vanish, therefore reconciling discrepancies among previous theoretical investigations of stochastic biochemical reactions. Stochastic slowdown of reaction flux caused by molecular noise in living cells may have functional consequences, which the present theory may be used to quantify. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Control of serpentinisation rate by reaction-induced cracking

    Science.gov (United States)

    Malvoisin, Benjamin; Brantut, Nicolas; Kaczmarek, Mary-Alix

    2017-10-01

    Serpentinisation of mantle rocks requires the generation and maintenance of transport pathways for water. The solid volume increase during serpentinisation can lead to stress build-up and trigger cracking, which ease fluid penetration into the rock. The quantitative effect of this reaction-induced cracking mechanism on reactive surface generation is poorly constrained, thus hampering our ability to predict serpentinisation rate in geological environments. Here we use a combined approach with numerical modelling and observations in natural samples to provide estimates of serpentinisation rate at mid-ocean ridges. We develop a micromechanical model to quantify the propagation of serpentinisation-induced cracks in olivine. The maximum crystallisation pressure deduced from thermodynamic calculations reaches several hundreds of megapascals but does not necessary lead to crack propagation if the olivine grain is subjected to high compressive stresses. The micromechanical model is then coupled to a simple geometrical model to predict reactive surface area formation during grain splitting, and thus bulk reaction rate. Our model reproduces quantitatively experimental kinetic data and the typical mesh texture formed during serpentinisation. We also compare the model results with olivine grain size distribution data obtained on natural serpentinised peridotites from the Marum ophiolite and the Papuan ultramafic belt (Papua New Guinea). The natural serpentinised peridotites show an increase of the number of olivine grains for a decrease of the mean grain size by one order of magnitude as reaction progresses from 5 to 40%. These results are in agreement with our model predictions, suggesting that reaction-induced cracking controls the serpentinisation rate. We use our model to estimate that, at mid-ocean ridges, serpentinisation occurs up to 12 km depth and reaction-induced cracking reduces the characteristic time of serpentinisation by one order of magnitude, down to values

  11. Study of the N=28 shell closure by one neutron transfer reaction: astrophysical application and {beta}-{gamma} spectroscopy of neutron rich nuclei around N=32/34 and N=40; Etude de la fermeture de couche N=28 autour du noyau {sub 18}{sup 46}Ar{sub 28} par reaction de transfert d'un neutron: application a l'astrophysique et Spectroscopie {beta}-{gamma} de noyaux riches en neutrons de N=32/34 et N=40

    Energy Technology Data Exchange (ETDEWEB)

    Gaudefroy, L

    2005-09-15

    The study of the N=28 shell closure has been presented as well as its astrophysical implications. Moreover the structure of neutron rich nuclei around N=32/34 and 40 was studied. The N=28 shell closure has been studied trough the one neutron transfer reaction on {sup 44,46}Ar nuclei. Excitation energies of states in {sup 45,47}Ar nuclei have been obtained, as well as their angular momenta and spectroscopic factors. These results were used to show that N=28 is still a good magic number in the argon isotopic chain. We interpreted the evolution of the spin-orbit partner gaps in terms of the tensor monopolar proton-neutron interaction. Thanks to this latter, we showed it is not necessary to summon up a reduction of the intensity of the spin-orbit force in order to explain this evolution in N=29 isotopes from calcium to argon chains. The neutron capture rates on {sup 44,46}Ar have been determined thanks to the results of the transfer reaction. Their influence on the nucleosynthesis of {sup 46,48}Ca was studied. We proposed stellar conditions to account for the abnormal isotopic ratio observed in the Allende meteorite concerning {sup 46,48}Ca isotopes. The beta decay and gamma spectroscopy of neutron rich nuclei in the scandium to cobalt region has been studied. We showed that beta decay process is dominated by the {nu}f{sub 5/2} {yields} {pi}f{sub 7/2} Gamow-Teller transition. Moreover, we demonstrated that the {nu}g{sub 9/2} hinders this process in the studied nuclei, and influences their structure, by implying the existence of isomers. Our results show that N=34 is not a magic number in the titanium chain and the superior ones. (author)

  12. Abundances in Astrophysical Environments: Reaction Network Simulations with Reaction Rates from Many-nucleon Modeling

    Science.gov (United States)

    Amason, Charlee; Dreyfuss, Alison; Launey, Kristina; Draayer, Jerry

    2017-01-01

    We use the ab initio (first-principle) symmetry-adapted no-core shell model (SA-NCSM) to calculate reaction rates of significance to type I X-ray burst nucleosynthesis. We consider the 18O(p,γ)19F reaction, which may influence the production of fluorine, as well as the 16O(α,γ)20Ne reaction, which is key to understanding the production of heavier elements in the universe. Results are compared to those obtained in the no-core sympletic shell model (NCSpM) with a schematic interaction. We discuss how these reaction rates affect the relevant elemental abundances. We thank the NSF for supporting this work through the REU Site in Physics & Astronomy (NSF grant #1560212) at Louisiana State University. This work was also supported by the U.S. NSF (OCI-0904874, ACI -1516338) and the U.S. DOE (DE-SC0005248).

  13. Characterizing Neutron-Proton Equilibration in Nuclear Reactions with Subzeptosecond Resolution

    Science.gov (United States)

    Jedele, A.; McIntosh, A. B.; Hagel, K.; Huang, M.; Heilborn, L.; Kohley, Z.; May, L. W.; McCleskey, E.; Youngs, M.; Zarrella, A.; Yennello, S. J.

    2017-02-01

    We study neutron-proton equilibration in dynamically deformed atomic nuclei created in nuclear collisions. The two ends of the elongated nucleus are initially dissimilar in composition and equilibrate on a subzeptosecond time scale following first-order kinetics. We use angular momentum to relate the breakup orientation to the time scale of the breakup. The extracted rate constant is 3 zs-1 , which corresponds to a mean equilibration time of 0.3 zs. This technique enables new insight into the nuclear equation of state that governs many nuclear and astrophysical phenomena leading to the origin of the chemical elements.

  14. The temperature-dependence of elementary reaction rates: beyond Arrhenius.

    Science.gov (United States)

    Smith, Ian W M

    2008-04-01

    The rates of chemical reactions and the dependence of their rate constants on temperature are of central importance in chemistry. Advances in the temperature-range and accuracy of kinetic measurements, principally inspired by the need to provide data for models of combustion, atmospheric, and astrophysical chemistry, show up the inadequacy of the venerable Arrhenius equation--at least, over wide ranges of temperature. This critical review will address the question of how to reach an understanding of the factors that control the rates of 'non-Arrhenius' reactions. It makes use of a number of recent kinetic measurements and shows how developments in advanced forms of transition state theory provide satisfactory explanations of complex kinetic behaviour (72 references).

  15. Exclusive CHIPS-TPT algorithms for simulation of neutron-nuclear reactions

    Science.gov (United States)

    Kosov, Mikhail; Savin, Dmitriy

    2016-09-01

    The CHIPS-TPT physics library for simulation of neutron-nuclear reactions on the new exclusive level is being developed in CFAR VNIIA. The exclusive modeling conserves energy, momentum and quantum numbers in each neutron-nuclear interaction. The CHIPS-TPT algorithms are based on the exclusive CHIPS library, which is compatible with Geant4. Special CHIPS-TPT physics lists in the Geant4 format are provided. The calculation time for an exclusive CHIPS-TPT simulation is comparable to the time of the corresponding inclusive Geant4-HP simulation and much faster for mono-isotopic simulations. In addition to the reduction of the deposited energy fluctuations, which is a consequence of the energy conservation, the CHIPS-TPT libraries provide a possibility of simulation of the secondary particles correlation, e.g. secondary gammas or n-γ correlations, and of the Doppler broadening of the γ-lines in the simulated spectra, which can be measured by germanium detectors.

  16. Neutron-induced reactions relevant for Inertial-Cofinement Fusion Experiments

    Science.gov (United States)

    Boswell, Melissa; Merrill, Frank; Rundberg, R.; Grim, Gary; Wilde, Carl; Hayes, Anna; Fowler, Malcom; Wilhelmy, Jerry

    2012-10-01

    Measuring the fluencies of both the low- & high-energy neutrons is a powerful mechanism for studying the implosion process, and the various parameters that drive inertial confinement fusion. We have developed a number of tools to measure the spectral characteristics of the NIF neutron spectrum. Most of these methods rely on exploiting the energy dependence of (n,γ), (n,2n), (n,3n) and (n,p) reactions on a variety of materials either implicitly present in the NIF implosion or through doping the target capsule or holraum. I will be discussing both prompt activation measurements, and debris activation measurements of these materials currently under development at LANL. Focusing specifically on the development of an in-situ detector to measure short-lived activation products, as well as a low-background counting facility we are developing at the Waste Isolation Pilot Plant (WIPP) to study longer-lived activation products. Furthermore, I will also be discussing several cross section measurements that are important for the interpretation of the data collected from these activation products.

  17. Rate Constant Calculation for Thermal Reactions Methods and Applications

    CERN Document Server

    DaCosta, Herbert

    2011-01-01

    Providing an overview of the latest computational approaches to estimate rate constants for thermal reactions, this book addresses the theories behind various first-principle and approximation methods that have emerged in the last twenty years with validation examples. It presents in-depth applications of those theories to a wide range of basic and applied research areas. When doing modeling and simulation of chemical reactions (as in many other cases), one often has to compromise between higher-accuracy/higher-precision approaches (which are usually time-consuming) and approximate/lower-preci

  18. Influence of projectile neutron number on cross section in cold fusion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Dragojevic, Irena; Dragojevic, I.; Gregorich, K.E.; Dullmann, Ch.E.; Folden III, C.M.; Garcia, M.A.; Gates, J.M.; Nelson, S.L.; Sudowe, R.; Nitsche, H.

    2007-09-01

    Elements 107-112 [1,2] have been discovered in reactions between {sup 208}Pb or {sup 209}Bi targets and projectiles ranging from {sup 54}Cr through {sup 70}Zn. In such reactions, the compound nucleus can be formed at excitation energies as low as {approx}12 MeV, thus this type of reaction has been referred to as 'cold fusion'. The study of cold fusion reactions is an indispensable approach to gaining a better understanding of heavy element formation and decay. A theoretical model that successfully predicts not only the magnitudes of cold fusion cross sections, but also the shapes of excitation functions and the cross section ratios between various reaction pairs was recently developed by Swiatecki, Siwek-Wilczynska, and Wilczynski [3,4]. This theoretical model, also referred to as Fusion by Diffusion, has been the guide in all of our cold fusion studies. One particularly interesting aspect of this model is the large predicted difference in cross sections between projectiles differing by two neutrons. The projectile pair where this difference is predicted to be largest is {sup 48}Ti and {sup 50}Ti. To test and extend this model, {sup 208}Pb({sup 48}Ti,n){sup 255}Rf and {sup 208}Pb({sup 50}Ti,n){sup 257}Rf excitation functions were recently measured at the Lawrence Berkeley National Laboratory's (LBNL) 88-Inch Cyclotron utilizing the Berkeley Gas-filled Separator (BGS). The {sup 50}Ti reaction was carried out with thin lead targets ({approx}100 {micro}g/cm{sup 2}), and the {sup 48}Ti reaction with both thin and thick targets ({approx}470 {micro}g/cm{sup 2}). In addition to this reaction pair, reactions with projectile pairs {sup 52}Cr and {sup 54}Cr [5], {sup 56}Fe and {sup 58}Fe [6], and {sup 62}Ni [7] and {sup 64}Ni [8] will be discussed and compared to the Fusion by Diffusion predictions. The model predictions show a very good agreement with the data.

  19. Shell structure in neutron rich nuclei by means of binary reactions

    Energy Technology Data Exchange (ETDEWEB)

    Angelis, G. de [INFN, Laboratori Nazionali di Legnaro (Italy)

    2014-08-14

    Nuclear structure studies far from stability rely mainly on the availability of radioactive nuclear beams but can complementary be addressed by means of high intensity beams of stable ions. In such contest, deep-inelastic and multinucleon transfer reactions are a powerful tool to populate yrast and non yrast states in neutron-rich nuclei. Particularly successful is here the combination of large acceptance spectrometers with highly segmented gamma-detector arrays. Such devices can provide the necessary channel selectivity to identify very rare signals. The AGATA gamma-ray detector array coupled to the PRISMA spectrometer at the Legnaro National Laboratories (LNL) in Italy is one example. Large data sets have been collected at LNL for nuclei close to the N=20, 28, 40, 50 and 82 shell closures.

  20. Neutron spectroscopic factors of 55Ni hole-states from (p,d transfer reactions

    Directory of Open Access Journals (Sweden)

    A. Sanetullaev

    2014-09-01

    Full Text Available Spectroscopic information has been extracted on the hole-states of 55Ni, the least known of the quartet of nuclei (55Ni, 57Ni, 55Co and 57Cu, one nucleon away from 56Ni, the N=Z=28 double magic nucleus. Using the H1(Ni56,dNi55 transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f7/2, p3/2 and the s1/2 hole-states of 55Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s1/2 hole-state below Fermi energy.

  1. Spectroscopy of Neutron-Deficient Nuclei Near the Z=82 Closed Shell via Symmetric Fusion Reactions

    Directory of Open Access Journals (Sweden)

    Kondev F.G.

    2013-12-01

    Full Text Available In-beam and decay-spectroscopy studies of neutron-deficient nuclei near the Z=82 shell closure were carried out using the Fragment Mass Analyzer (FMA and the Gammasphere array, in conjunction with symmetric fusion reactions and the Recoil Decay Tagging (RDT technique. The primary motivation was to study properties of 179Tl and 180Tl, and their daughter, and grand-daughter isotopes. For the first time, in-beam structures associated with 179Tl and 180Tl were observed, as well as γ rays associated with the 180Tl α decay. No long-lived isomer was identified in 180Tl, in contrast with the known systematics for the heavier odd-odd Tl isotopes.

  2. Neutron spectroscopic factors of {sup 55}Ni hole-states from (p,d) transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sanetullaev, A. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Tsang, M.B., E-mail: tsang@nscl.msu.edu [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Lynch, W.G.; Lee, Jenny; Bazin, D. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Chan, K.P. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Physics Department, Hong Kong Chinese University, Shatin, Hong Kong (China); Coupland, D.; Henzl, V.; Henzlova, D.; Kilburn, M.; Rogers, A.M. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Sun, Z.Y. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Institute of Modern Physics, CAS, Lanzhou 730000 (China); Youngs, M. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Charity, R.J.; Sobotka, L.G. [Department of Chemistry, Washington University, St. Louis, MO 63130 (United States); Famiano, M. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States); Hudan, S. [Department of Chemistry, Indiana University, Bloomington, IN 47405 (United States); Shapira, D. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Peters, W.A. [Rutgers University, Piscataway, NJ 08854 (United States); Barbieri, C. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); and others

    2014-09-07

    Spectroscopic information has been extracted on the hole-states of {sup 55}Ni, the least known of the quartet of nuclei ({sup 55}Ni, {sup 57}Ni, {sup 55}Co and {sup 57}Cu), one nucleon away from {sup 56}Ni, the N=Z=28 double magic nucleus. Using the {sup 1}H({sup 56}Ni,d){sup 55}Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f{sub 7/2}, p{sub 3/2} and the s{sub 1/2} hole-states of {sup 55}Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s{sub 1/2} hole-state below Fermi energy.

  3. Neutron spectroscopic factors of 55Ni hole-states from (p,d) transfer reactions

    Science.gov (United States)

    Sanetullaev, A.; Tsang, M. B.; Lynch, W. G.; Lee, Jenny; Bazin, D.; Chan, K. P.; Coupland, D.; Henzl, V.; Henzlova, D.; Kilburn, M.; Rogers, A. M.; Sun, Z. Y.; Youngs, M.; Charity, R. J.; Sobotka, L. G.; Famiano, M.; Hudan, S.; Shapira, D.; Peters, W. A.; Barbieri, C.; Hjorth-Jensen, M.; Horoi, M.; Otsuka, T.; Suzuki, T.; Utsuno, Y.

    2014-09-01

    Spectroscopic information has been extracted on the hole-states of 55Ni, the least known of the quartet of nuclei (55Ni, 57Ni, 55Co and 57Cu), one nucleon away from 56Ni, the N=Z=28 double magic nucleus. Using the H1(Ni56,d)Ni55 transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f7/2, p3/2 and the s1/2 hole-states of 55Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s1/2 hole-state below Fermi energy.

  4. Pre-equilibrium emission in neutron induced reactions on /sup 54,56/Fe

    Energy Technology Data Exchange (ETDEWEB)

    Avrigeanu, M.; Ivascu, M.; Avrigeanu, V.

    1988-02-01

    The experimentally well known (n,p), (n,..cap alpha..) and (n,2n) reaction excitation functions, from threshold to 20 MeV incident energy, and neutron and proton emission spectra at 14.8 MeV from /sup 54,56/Fe targets are calculated in the frame of the geometry-dependent hybrid pre-equilibrium emission model, including angular momentum and parity conservation, and the Hauser-Feshbach statistical model. Use of a consistent statistical model parameter set enables the validation of the pre-equilibrium emission model. Moreover, an enhanced pre-equilibrium emission from higher spin composite system states, associated with higher incoming orbital momenta, has been evidenced. Higher orbital momenta involved also in the emergent channels of the process are suggested by calculations of the residual nuclei level populations.

  5. Simultaneous measurement of neutron-induced capture and fission reactions at CERN

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero, C. [European Organization for Nuclear Research, Geneva (Switzerland); Centro de Investigaciones Energeticas Medioambientales y Technologicas (CIEMAT), Madrid (Spain); Berthoumieux, E. [European Organization for Nuclear Research, Geneva (Switzerland); Commissariat a l' Energie Atomique Saclay - Irfu, Gif-sur-Yvette (France); Cano-Ott, D.; Mendoza, E.; Becares, V.; Fernandez-Ordonez, M.; Gonzalez-Romero, E.; Marganiec, J.; Martinez, T. [Centro de Investigaciones Energeticas Medioambientales y Technologicas, Madrid (Spain); Andriamonje, S.; Brugger, M.; Calviani, M.; Cerutti, F.; Chiaveri, E.; Chin, M.; Ferrari, A.; Kadi, Y.; Lebbos, E.; Losito, R.; Rubbia, C.; Vlachoudis, V. [European Organization for Nuclear Research, Geneva (Switzerland); Andrzejewski, J.; Perkowski, J. [Uniwersytet Lodzki, Lodz (Poland); Audouin, L.; Tassan-Got, L. [Centre National de la Recherche Scientifique/IN2P3 - IPN, Orsay (France); Barbagallo, M.; Colonna, N.; Marrone, S.; Meaze, M.; Tagliente, G.; Variale, V. [Istituto Nazionale di Fisica Nucleare, Bari (Italy); Becvar, F.; Kroll, J.; Krticka, M. [Charles Univ., Prague (Czech Republic); Belloni, F.; Milazzo, P.M. [Istituto Nazionale di Fisica Nucleare, Trieste (Italy); Billowes, J.; Ware, T.; Wright, T. [Univ. of Manchester, Manchester (United Kingdom); Calvino, F.; Cortes, G.; Gomez-Hornillos, M.B. [Univ. Politecnica de Catalunya, Barcelona (Spain); Carrapico, C.; Goncalves, I.F.; Sarmento, R.; Vaz, P. [Instituto Tecnologico e Nuclear, Lisbon (Portugal); Cortes-Giraldo, M.A.; Lozano, M.; Praena, J.; Quesada, J.M. [Univ. de Sevilla, Sevilla (Spain); Diakaki, M.; Karadimos, D.; Vlastou, R. [National Technical Univ. of Athens, Athens (Greece); Dillmann, I. [Technische Univ. Muenchen, Physik Dept. E12 and Excellence Cluster Universe, Munich (Germany); Domingo-Pardo, C.; Plag, R.; Reifarth, R. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany)] [and others

    2012-03-15

    The measurement of the capture cross-section of fissile elements, of utmost importance for the design of innovative nuclear reactors and the management of nuclear waste, faces particular difficulties related to the {gamma} -ray background generated in the competing fission reactions. At the CERN neutron time-of-flight facility n{sub T}OF we have combined the Total Absorption Calorimeter (TAC) capture detector with a set of three {sup 235}U loaded MicroMegas (MGAS) fission detectors for measuring simultaneously two reactions: capture and fission. The results presented here include the determination of the three detection efficiencies involved in the process: {epsilon}{sub TAC}(n,f), {epsilon}{sub TAC}(n,{gamma}) and {epsilon}{sub MGAS}(n,f). In the test measurement we have succeeded in measuring simultaneously with a high total efficiency the {sup 235}U capture and fission cross-sections, disentangling accurately the two types of reactions. The work presented here proves that accurate capture cross-section measurements of fissile isotopes are feasible at n{sub T}OF. (orig.)

  6. Bayesian Evaluation Including Covariance Matrices of Neutron-induced Reaction Cross Sections of {sup 181}Ta

    Energy Technology Data Exchange (ETDEWEB)

    Leeb, H., E-mail: leeb@kph.tuwien.ac.at; Schnabel, G.; Srdinko, Th.; Wildpaner, V.

    2015-01-15

    A new evaluation of neutron-induced reactions on {sup 181}Ta using a consistent procedure based on Bayesian statistics is presented. Starting point of the evaluation is the description of nuclear reactions via nuclear models implemented in TALYS 1.4. A retrieval of experimental data was performed and covariance matrices of the experiments were generated from an extensive study of the corresponding literature. All reaction channels required for a transport file up to 200 MeV have been considered and the covariance matrices of cross section uncertainties for the most important channels are determined. The evaluation has been performed in one step including all available experimental data. A comparison of the evaluated cross sections and spectra with experimental data and available evaluations is performed. In general the evaluated cross section reflect our best knowledge and give a fair description of the observables. However, there are few deviations from expectation which clearly indicate the impact of the prior and the need to account for model defects. Using the results of the evaluation a complete ENDF-file similarly to those of the TENDL library is generated.

  7. Shell model based reaction rates for rp-process nuclei in the mass range A=44-63

    CERN Document Server

    Fisker, J L; Görres, J; Langanke, K; Martínez-Pinedo, G; Wiescher, M C

    2001-01-01

    We have used large-scale shell-model diagonalization calculations to determine the level spectra, proton spectroscopic factors, and electromagnetic transition probabilities for proton rich nuclei in the mass range A=44-63. Based on these results and the available experimental data, we calculated the resonances for proton capture reactions on neutron deficient nuclei in this mass range. We also calculated the direct capture processes on these nuclei in the framework of a Woods-Saxon potential model. Taking into account both resonant and direct contributions, we determined the ground-state proton capture reaction rates for these nuclei under hot hydrogen burning conditions for temperatures between 10 sup 8 and 10 sup 1 sup 0 K. The calculated compound-nucleus level properties and the reaction rates are presented here; the rates are also available in computer-readable format from the authors.

  8. Reference Materials for Reactor Neutron Fluence Rate and Temperature Measurements

    Science.gov (United States)

    Ingelbrecht, C.

    2003-06-01

    Certified reference materials are distributed by the European Commission through the BCR® programme (over 500 CRMs) including a series of activation and fission monitor materials originally proposed by the Euratom Working Group on Reactor Dosimetry. The current range (18 CRMs) includes materials to cover the complete energy spectrum, and suitable for different irradiation times. Fission monitors are 238UO2 or 237NpO2 in the form of microspheres. Activation monitors are high purity metals (Ni, Cu, Al, Fe, Nb, Rh, or Ti), certified for interfering trace impurities, or dilute aluminium-based alloys. Reference materials newly certified are IRMM-530R A1-0.1%Au, replacing the exhausted IRMM-530 material, used as comparator for k0- standardisation, and three new Al-Co alloys (0.01, 0.1 and 1.0%Co). Others in the process of certification are A1-0.1%Ag and A1-2%Sc for thermal and epithermal fluence rate measurements and two uranium-doped glass materials intended for dosimetry by the fission-track technique. Various alloy compositions have been prepared for use as melt-wire temperature monitors with melting points ranging from 198 to 327ºC.

  9. Excitation functions for the production of radionuclides by neutron-induced reactions on C, O, Mg, Al, Si, Fe, Co, Ni, Cu, Ag, Te, Pb, and U up to 180 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Michel, R., E-mail: michel@irs.uni-hannover.de [Institute for Radioecology and Radiological Protection, Leibniz University Hannover (Germany); Hansmann, D. [Institute for Radioecology and Radiological Protection, Leibniz University Hannover (Germany); Neumann, S. [Institute for Radioecology and Radiological Protection, Leibniz University Hannover (Germany); Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany); Glasser, W. [Institute for Radioecology and Radiological Protection, Leibniz University Hannover (Germany); Schuhmacher, H.; Dangendorf, V.; Nolte, R. [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany); Herpers, U. [Dept. for Nuclear Chemistry, University of Cologne (Germany); Smirnov, A.N.; Ryzhov, I.V. [V. G. Khlopin Radium Institute, St. Petersburg (Russian Federation); Prokofiev, A.V. [The Svedberg Laboratory (TSL), Uppsala University (Sweden); Dept. of Physics and Astronomy, Uppsala University (Sweden); Malmborg, P. [The Svedberg Laboratory (TSL), Uppsala University (Sweden); Kollár, D. [Dept. of Nuclear Physics, Comenius University, Bratislava (Slovakia); Meulders, J.-P. [Université Catholique de Louvain (UCL), Louvain-la-Neuve (Belgium)

    2015-01-15

    Irradiation experiments with well-characterized, quasi mono-energetic neutrons of energies between 32.7 MeV and 175.4 MeV were performed at UCL/Louvain-la-Neuve and TSL/Uppsala. The abundances of relatively short-lived residual radionuclides from 13 different target elements were determined by γ-spectrometry. More than 100 excitation functions of neutron-induced reactions were unfolded based on the neutron spectra and the radionuclide abundances with the aid of additional information that was provided by “guess” excitation functions calculated by the TALYS 1.0 code. The results are compared with the sparse existing data from other authors. The new excitation functions were validated by calculation of and comparison with experimental thick-target production rates. Consistency with neutron excitation functions up to 1.6 GeV, which were derived earlier by unfolding the thick-target production rates, was so demonstrated.

  10. Determination of the Neutron-Capture Rate of 17C for the R-process Nucleosynthesis

    CERN Document Server

    Heine, M; Wu, M -R; Adachi, T; Aksyutina, Y; Alcantara, J; Altstadt, S; Alvarez-Pol, H; Ashwood, N; Aumann, T; Avdeichikov, V; Barr, M; Beceiro-Novo, S; Bemmerer, D; Benlliure, J; Bertulani, C A; Boretzky, K; Borge, M J G; Burgunder, G; Caamano, M; Caesar, C; Casarejos, E; Catford, W; Cederkäll, J; Chakraborty, S; Chartier, M; Chulkov, L V; Cortina-Gil, D; Crespo, R; Pramanik, U Datta; Fernandez, P Diaz; Dillmann, I; Elekes, Z; Enders, J; Ershova, O; Estrade, A; Farinon, F; Fraile, L M; Freer, M; Freudenberger, M; Fynbo, H O U; Galaviz, D; Geissel, H; Gernhäuser, R; Göbel, K; Golubev, P; Diaz, D Gonzalez; Hagdahl, J; Heftrich, T; Heil, M; Heinz, A; Henriques, A; Holl, M; Ickert, G; Ignatov, A; Jakobsson, B; Johansson, H T; Jonson, B; Kalantar-Nayestanaki, N; Kanungo, R; Kelic-Heil, A; Knöbel, R; Kröll, T; Krücken, R; Kurcewicz, J; Kurz, N; Labiche, M; Langer, C; Bleis, T Le; Lemmon, R; Lepyoshkina, O; Lindberg, S; Machado, J; Marganiec, J; Martínez-Pinedo, G; Maroussov, V; Mostazo, M; Movsesyan, A; Najafi, A; Neff, T; Nilsson, T; Nociforo, C; Panin, V; Paschalis, S; Perea, A; Petri, M; Pietri, S; Plag, R; Prochazka, A; Rahaman, A; Rastrepina, G; Reifarth, R; Ribeiro, G; Ricciardi, M V; Rigollet, C; Riisager, K; Röder, M; Rossi, D; del Rio, J Sanchez; Savran, D; Scheit, H; Simon, H; Sorlin, O; Stoica, V; Streicher, B; Taylor, J T; Tengblad, O; Terashima, S; Thies, R; Togano, Y; Uberseder, E; Van de Walle, J; Velho, P; Volkov, V; Wagner, A; Wamers, F; Weick, H; Weigand, M; Wheldon, C; Wilson, G; Wimmer, C; Winfield, J S; Woods, P; Yakorev, D; Zhukov, M V; Zilges, A; Zuber, K

    2016-01-01

    With the R$^{3}$B-LAND setup at GSI we have measured exclusive relative-energy spectra of the Coulomb dissociation of $^{18}$C at a projectile energy around 425~AMeV on a lead target, which are needed to determine the radiative neutron-capture cross sections of $^{17}$C into the ground state of $^{18}$C. Those data have been used to constrain theoretical calculations for transitions populating excited states in $^{18}$C. This allowed to derive the astrophysical cross section $\\sigma^{*}_{\\mathrm{n}\\gamma}$ accounting for the thermal population of $^{17}$C target states in astrophysical scenarios. The experimentally verified capture rate is significantly lower than those of previously obtained Hauser-Feshbach estimations at temperatures $T_{9}\\leq{}1$~GK. Network simulations with updated neutron-capture rates and hydrodynamics according to the neutrino-driven wind model as well as the neutron-star merger scenario reveal no pronounced influence of neutron capture of $^{17}$C on the production of second- and thi...

  11. Investigation of the /sup 59/Co(n,. gamma. )/sup 60/Co reaction with unpolarized and polarized neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Kopecky, J. (Stichting Energieonderzoek Centrum Nederland, Petten. Nuclear Structure Group); Delfini, M.G. (Stichting Energieonderzoek Centrum Nederland, Petten. Nuclear Structure Group; Rijksuniversiteit Utrecht (Netherlands). Fysisch Lab.); Chrien, R.E. (Brookhaven National Lab., Upton, NY (USA))

    1984-10-15

    Capture of 24 keV neutrons and polarized as well as unpolarized thermal neutrons in /sup 59/Co has been investigated. Of the 350 ..gamma..-rays observed 335 could be placed in a /sup 60/Co level scheme containing 144 levels. The reaction Q-value amounts to 7491.92(8) keV. The chi/sup 2/ analysis of the circularly polarized ..gamma..-rays results in 31 unambiguous spin assignments for /sup 60/Co levels. The fraction of the J=4/sup -/ channel in the thermal capture was determined to be (80 +- 1)%. An average ..gamma..-ray multiplicity of 2.3 gammas per neutron capture was observed. The resulting level scheme is compared to shell-model predictions. Possible reaction mechanisms are discussed.

  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. Photo neutron dose equivalent rate in 15 MV X-ray beam from a Siemens Primus Linac

    Directory of Open Access Journals (Sweden)

    A Ghasemi

    2015-01-01

    Full Text Available Fast and thermal neutron fluence rates from a 15 MV X-ray beams of a Siemens Primus Linac were measured using bare and moderated BF 3 proportional counter inside the treatment room at different locations. Fluence rate values were converted to dose equivalent rate (DER utilizing conversion factors of American Association of Physicist in Medicine′s (AAPM report number 19. For thermal neutrons, maximum and minimum DERs were 3.46 × 10 -6 (3 m from isocenter in +Y direction, 0 × 0 field size and 8.36 × 10 -8 Sv/min (in maze, 40 × 40 field size, respectively. For fast neutrons, maximum DERs using 9" and 3" moderators were 1.6 × 10 -5 and 1.74 × 10 -5 Sv/min (2 m from isocenter in +Y direction, 0 × 0 field size, respectively. By changing the field size, the variation in thermal neutron DER was more than the fast neutron DER and the changes in fast neutron DER were not significant in the bunker except inside the radiation field. This study showed that at all points and distances, by decreasing field size of the beam, thermal and fast neutron DER increases and the number of thermal neutrons is more than fast neutrons.

  14. Photo neutron dose equivalent rate in 15 MV X-ray beam from a Siemens Primus Linac.

    Science.gov (United States)

    Ghasemi, A; Pourfallah, T Allahverdi; Akbari, M R; Babapour, H; Shahidi, M

    2015-01-01

    Fast and thermal neutron fluence rates from a 15 MV X-ray beams of a Siemens Primus Linac were measured using bare and moderated BF3 proportional counter inside the treatment room at different locations. Fluence rate values were converted to dose equivalent rate (DER) utilizing conversion factors of American Association of Physicist in Medicine's (AAPM) report number 19. For thermal neutrons, maximum and minimum DERs were 3.46 × 10(-6) (3 m from isocenter in +Y direction, 0 × 0 field size) and 8.36 × 10(-8) Sv/min (in maze, 40 × 40 field size), respectively. For fast neutrons, maximum DERs using 9" and 3" moderators were 1.6 × 10(-5) and 1.74 × 10(-5) Sv/min (2 m from isocenter in +Y direction, 0 × 0 field size), respectively. By changing the field size, the variation in thermal neutron DER was more than the fast neutron DER and the changes in fast neutron DER were not significant in the bunker except inside the radiation field. This study showed that at all points and distances, by decreasing field size of the beam, thermal and fast neutron DER increases and the number of thermal neutrons is more than fast neutrons.

  15. Study of the effect of high dose rate on tissue equivalent proportional counter microdosimetric measurements in mixed photon and neutron fields

    Science.gov (United States)

    Aslam; Qashua, N.; Waker, A. J.

    2011-10-01

    This study describes the measurement of lineal energy spectra carried out with a 5.1 cm (2 in.) diameter spherical tissue equivalent proportional counter (TEPC) simulating 2 μm tissue equivalent (TE) site diameter in low energy mixed photon-neutron fields with varying dose rates generated by employing the McMaster University 1.25 MV double stage Tandetron accelerator. The 7Li (p, n) 7Be reaction was employed to generate a variety of mixed fields of photons and low energy neutrons using proton beam energy ranging 1.89-2.56 MeV. The dose rate at a given beam energy was varied by changing the beam current. Dose rates that resulted in dead times as high as 75% were employed to study the effect of dose rate on quality, microdosimetric averages ( y¯F and y¯D), absorbed dose and dose equivalent. We have observed that high dose rates due to both photons and neutrons in a mixed field of radiation result in pile up of pulses and distort the lineal energy spectrum measured under these conditions. The pile up effect and hence the distortion in the lineal energy spectrum becomes prominent with dose rates, which result in dead times larger than 25% for the high linear energy transfer (LET) radiation component. Intense neutron fields, which may amount to 75% dead time, could result in a 50% or even larger increase in the values of the microsdosimetric averages and the neutron quality factor. This study demonstrates moderate dose rates that do not result in dead times of more than 20-25% due to either of the component radiation or due to both components of mixed field radiation generate results that are acceptable for radiation monitoring.

  16. Application of semiclassical methods to reaction rate theory

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, R.

    1993-11-01

    This work is concerned with the development of approximate methods to describe relatively large chemical systems. This effort has been divided into two primary directions: First, we have extended and applied a semiclassical transition state theory (SCTST) originally proposed by Miller to obtain microcanonical and canonical (thermal) rates for chemical reactions described by a nonseparable Hamiltonian, i.e. most reactions. Second, we have developed a method to describe the fluctuations of decay rates of individual energy states from the average RRKM rate in systems where the direct calculation of individual rates would be impossible. Combined with the semiclassical theory this latter effort has provided a direct comparison to the experimental results of Moore and coworkers. In SCTST, the Hamiltonian is expanded about the barrier and the ``good`` action-angle variables are obtained perturbatively; a WKB analysis of the effectively one-dimensional reactive direction then provides the transmission probabilities. The advantages of this local approximate treatment are that it includes tunneling effects and anharmonicity, and it systematically provides a multi-dimensional dividing surface in phase space. The SCTST thermal rate expression has been reformulated providing increased numerical efficiency (as compared to a naive Boltzmann average), an appealing link to conventional transition state theory (involving a ``prereactive`` partition function depending on the action of the reactive mode), and the ability to go beyond the perturbative approximation.

  17. Estimation of the Polymerization Rate of Liquid Propylene Using Adiabatic Reaction Calorimetry and Reaction Dilatometry

    NARCIS (Netherlands)

    Al-haj Ali, Mohammad; Betlem, Ben; Roffel, Brian; Weickert, Günter

    2007-01-01

    The use of pressure-drop and constant-pressure dilatometry for obtaining rate data for liquid propylene polymerization in filled batch reactors was examined. The first method uses reaction temperature and pressure as well as the compressibility of the reactor contents to calculate the polymerization

  18. Cross-section measurement of the 18F(alpha,p)21Ne reaction and possible implication for neutron production in explosive helium burning

    Energy Technology Data Exchange (ETDEWEB)

    Couture, Aaron Joseph [Los Alamos National Laboratory; Lee, Hye Young [Los Alamos National Laboratory; Couder, Manoel [UNIV OF NOTRE DAME; Falahat, Sascha [UNIV OF NOTRE DAME; Gorres, Joachim [UNIV OF NOTRE DAME; Lamm, Larry O [UNIV OF NOTRE DAME; Le Blanc, P J [UNIV OF NOTRE DAME; O' Brien, Shawn P [UNIV OF NOTRE DAME; Palumbo, Annalia [UNIV OF NOTRE DAME; Stech, Edward J [UNIV OF NOTRE DAME; Strandberg, Elizabeth [UNIV OF NOTRE DAME; Tan, Wanpeng [UNIV OF NOTRE DAME; Ugalde, Claudio [ANL; Wiescher, Michael C. F. [UNIV OF NOTRE DAME

    2009-01-01

    At the high temperature and density conditions of hot or explosive helium burning, the {sup 18}F({alpha},p){sup 21}Ne reaction may compete successfully wilh the {sup 18}F({beta}{sup +}{nu}) decay. This suggesls {sup 21}Ne({alpha},n) as an alternative neutron source in Ihe r-process. We have determined the total cross section of the {sup 18}F({alpha},p){sup 21}Ne reaction by studying the time-reverse reaction {sup 21}Ne(p,{alpha}){sup 18}F. Using the activation technique, the total reaction yield was measured in the proton beam energy range of 2.3-4.0 MeV, which corresponds to energies of 0.5-2.1 MeV in the {sup 18}F + {alpha} system. The resulting yield curve was analyzed in terms of the thick target formalism and the R-matrix theory. The reaction rate was deduced experimentally for the first time for the temperature of 0.1 < T{sub 9} < I. The experimemal reaction rate was compared with Hauser-Feshbach predictions. The astrophysical implications of the new rate are discussed.

  19. Prompt gamma ray diagnostics and enhanced hadron-therapy using neutron-free nuclear reactions

    CERN Document Server

    Giuffrida, L; Cirrone, G A P; Picciotto, A; Korn, G

    2016-01-01

    We propose a series of simulations about the potential use of Boron isotopes to trigger neutron-free (aneutronic) nuclear reactions in cancer cells through the interaction with an incoming energetic proton beam, thus resulting in the emission of characteristic prompt gamma radiation (429 keV, 718 keV and 1435 keV). Furthermore assuming that the Boron isotopes are absorbed in cancer cells, the three alpha-particles produced in each p-11B aneutronic nuclear fusion reactions can potentially result in the enhancement of the biological dose absorbed in the tumor region since these multi-MeV alpha-particles are stopped inside the single cancer cell, thus allowing to spare the surrounding tissues. Although a similar approach based on the use of 11B nuclei has been proposed in [1], our work demonstrate, using Monte Carlo simulations, the crucial importance of the use of 10B nuclei (in a solution containing also 11B) for the generation of prompt gamma-rays, which can be applied to medical imaging. In fact, we demonstr...

  20. Prompt gamma ray diagnostics and enhanced hadron-therapy using neutron-free nuclear reactions

    Science.gov (United States)

    Giuffrida, L.; Margarone, D.; Cirrone, G. A. P.; Picciotto, A.; Cuttone, G.; Korn, G.

    2016-10-01

    We propose a series of simulations about the potential use of Boron isotopes to trigger neutron-free (aneutronic) nuclear reactions in cancer cells through the interaction with an incoming energetic proton beam, thus resulting in the emission of characteristic prompt gamma radiation (429 keV, 718 keV and 1435 keV). Furthermore assuming that the Boron isotopes are absorbed in cancer cells, the three alpha-particles produced in each p-11B aneutronic nuclear fusion reactions can potentially result in the enhancement of the biological dose absorbed in the tumor region since these multi-MeV alpha-particles are stopped inside the single cancer cell, thus allowing to spare the surrounding tissues. Although a similar approach based on the use of 11B nuclei has been proposed in [Yoon et al. Applied Physics Letters 105, 223507 (2014)], our work demonstrate, using Monte Carlo simulations, the crucial importance of the use of 10B nuclei (in a solution containing also 11B) for the generation of prompt gamma-rays, which can be applied to medical imaging. In fact, we demonstrate that the use of 10B nuclei can enhance the intensity of the 718 keV gamma-ray peak more than 30 times compared to the solution containing only 11B nuclei. A detailed explanation of the origin of the different prompt gamma-rays, as well as of their application as real-time diagnostics during a potential cancer treatment, is here discussed.

  1. The neutron-proton charge-exchange amplitudes measured in the dp -> ppn reaction

    CERN Document Server

    Mchedlishvili, D; Carbonell, J; Chiladze, D; Dymov, S; Dzyuba, A; Engels, R; Gebel, R; Glagolev, V; Grigoryev, K; Goslawski, P; Hartmann, M; Kacharava, A; Kamerdzhiev, V; Keshelashvili, I; Khoukaz, A; Komarov, V; Kulessa, P; Kulikov, A; Lehrach, A; Lomidze, N; Lorentz, B; Macharashvili, G; Maier, R; Merzliakov, S; Mielke, M; Mikirtychyants, M; Mikirtychyants, S; Nioradze, M; Ohm, H; Papenbrock, M; Prasuhn, D; Rathmann, F; Serdyuk, V; Seyfarth, H; Stein, H J; Steffens, E; Stockhorst, H; Stroeher, H; Tabidze, M; Trusov, S; Uzikov, Yu; Valdau, Yu; Wilkin, C

    2012-01-01

    The unpolarised differential cross section and the two deuteron tensor analysing powers A_{xx} and A_{yy} of the pol{d}p -> (pp)n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were obtained for small momentum transfers to a (pp) system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters C_{x,x} and C_{y,y} that were carried out in the pol{d}pol{p} -> (pp)n reaction at 1.2 and 2.27GeV. The values obtained for the proton analysing power also suggest th...

  2. Direct measurement of stellar neutron capture rates of 14C and comparison with the Coulomb breakup method

    Science.gov (United States)

    Reifarth, Rene; Heil, M.; Plag, R.; Besserer, U.; Couture, A.; Dababneh, S.; Dörr, L.; Forssén, C.; Görres, J.; Haight, R. C.; Mengoni, A.; O'Brien, S.; Patronis, N.; Rundberg, R. S.; Uberseder, E.; Wiescher, M.; Wilhelmy, J. B.

    The neutron capture cross section of 14 C has been shown to be important for several neutron driven nucleosynthesis scenarios. Due to the high neutron abundance it is expected that the 14 C(n,γ) reaction competes strongly with other neutron-induced reactions on 14 C. The 14 C(n,γ) reaction is also important to validate (n,γ) cross sections obtained via the inverse reaction by the Coulomb breakup method. In principle, 14 C belongs to the few cases where this correspondence can be validated in a convincingly clean way. So far, the example of 14 C is obscured, however, by discrepancies between several experiments and theory. In this contribution we report on a re- analysis of the direct measurements of the 14 C(n,γ) reaction presented on the last NIC conference (Vancouver, 2004). The neutron energies used during the experiment ranged from 30 to 800 keV. The earlier presented disagreement between the direct measurements and the Coulomb breakup method has been resolved.

  3. Au, Bi, Co and Nb cross-section measured by quasimonoenergetic neutrons from p + {sup 7}Li reaction in the energy range of 18–36 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Majerle, M., E-mail: majerle@ujf.cas.cz; Bém, P.; Novák, J.; Šimečková, E.; Štefánik, M.

    2016-09-15

    Au, Bi, Co and Nb samples were irradiated several times with quasi-monoenergetic neutrons from p + {sup 7}Li reaction in the energy range of 18–36 MeV. The activities of the samples were measured with the HPGe detector and the reaction rates were calculated. The cross-sections were extracted using the SAND-II method with the reference cross-sections from the EAF-2010 database. The uncertainties of the final results are discussed.

  4. Neutron-capture rates for explosive nucleosynthesis: the case of 68 Ni( n , γ ) 69 Ni

    Energy Technology Data Exchange (ETDEWEB)

    Spyrou, A.; Larsen, A. C.; Liddick, S. N.; Naqvi, F.; Crider, B. P.; Dombos, A. C.; Guttormsen, M.; Bleuel, D. L.; Couture, A.; Campo, L. Crespo; Lewis, R.; Mosby, S.; Mumpower, M. R.; Perdikakis, G.; Prokop, C. J.; Quinn, S. J.; Renstrøm, T.; Siem, S.; Surman, R.

    2017-02-22

    Neutron-capture reactions play an important role in heavy element nucleosynthesis, since they are the driving force for the two processes that create the vast majority of the heavy elements. When a neutron capture occurs on a short-lived nucleus, it is extremely challenging to study the reaction directly and therefore the use of indirect techniques is essential. The present work reports on such an indirect measurement that provides strong constraints on the 68Ni(n, γ)69Ni reaction rate. This is done by populating the compound nucleus 69Ni via the β decay of 69Co and measuring the γ-ray deexcitation of excited states in 69Ni. The β-Oslo method was used to extract the γ-ray strength function and the nuclear level density. In addition the half-life of 69Co was extracted and found to be in agreement with previous literature values. Before the present results, the 68Ni(n, γ)69Ni reaction was unconstrained and the purely theoretical reaction rate was highly uncertain. The new uncertainty on the reaction rate based on the present experiment (variation between upper and lower limit) is approximately a factor of 3. The commonly used reaction libraries JINA-REACLIB and BRUSLIB are in relatively good agreement with the experimental rate. The impact of the new rate on weak r-process calculations is discussed.

  5. Optimized reaction mechanism rate rules for ignition of normal alkanes

    KAUST Repository

    Cai, Liming

    2016-08-11

    The increasing demand for cleaner combustion and reduced greenhouse gas emissions motivates research on the combustion of hydrocarbon fuels and their surrogates. Accurate detailed chemical kinetic models are an important prerequisite for high fidelity reacting flow simulations capable of improving combustor design and operation. The development of such models for many new fuel components and/or surrogate molecules is greatly facilitated by the application of reaction classes and rate rules. Accurate and versatile rate rules are desirable to improve the predictive accuracy of kinetic models. A major contribution in the literature is the recent work by Bugler et al. (2015), which has significantly improved rate rules and thermochemical parameters used in kinetic modeling of alkanes. In the present study, it is demonstrated that rate rules can be used and consistently optimized for a set of normal alkanes including n-heptane, n-octane, n-nonane, n-decane, and n-undecane, thereby improving the predictive accuracy for all the considered fuels. A Bayesian framework is applied in the calibration of the rate rules. The optimized rate rules are subsequently applied to generate a mechanism for n-dodecane, which was not part of the training set for the optimized rate rules. The developed mechanism shows accurate predictions compared with published well-validated mechanisms for a wide range of conditions.

  6. Toward understanding the rates of reactions at mineral surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Casey, W.H. [Univ. of California Davis, CA (United States). Dept. of Land, Air and Water Resources and Dept. of Geology; Ludwig, C. [EAWAG, Swiss Federal Institute for Environmental Science and Technolgy, Dubendorf (Switzerland). Dept. of Resources and Waste management; Holmen, B. [Univ. of California Davis, CA (United States). Dept. of Land, Air and Water Resources

    1998-12-31

    Environmental geo chemists are commonly called upon to make predictions over long scales of time and distance. In many cases, these predictions involve disequilibrium reactions, such as the decomposition of ozone-depleting gases or the migration rates of groundwater contaminants. These groundwater contaminants interact with mineral surfaces in a complicated fashion that is not understood quantitatively. However, in a real sense, mineral dissolution studies are to the aqueous geo chemists what Escherichia coli are to microbiologists: an inexpensive model system to map out important kinetic relations that can then be extended qualitatively to other settings. This chapter explains that is enormously useful to draw analogies between reactions at mineral surfaces and at dissolved metal-ligand complexes. In this approach, the reactivities of bond between a metal and a water molecule or ligand in the inner-coordination-sphere of the dissolved complex are proxies for bonds between a metal and oxygen at the mineral surface, which cannot be studied directly.

  7. Prompt fission neutron investigation in 235U(nth,f) reaction

    Science.gov (United States)

    Zeynalov, Shakir; Sedyshev, Pavel; Shvetsov, Valery; Sidorova, Olga

    2017-09-01

    The prompt neutron emission in thermal neutron induced fission of 235U has been investigated applying digital signal electronics. The goal was to compare the results of this digital data acquisition and digital signal processing analysis to the results of the pioneering work of Apalin et al. Using a twin Frisch grid ionization chamber for the fission fragment detection and a NE213 equivalent neutron detector in total about 106 neutron coincidences have been registered. The fission fragment kinetic energy, mass and angular distribution has been investigated along with prompt neutron time of flight and pulse shape using a six channel synchronous waveform digitizer with sampling frequency of 250 MHz and 12 bit resolution. The signals have been analyzed using digital pulse processing algorithms, developed by authors. The thermal neutron beam was transported from the IBR-2 reactor to the target with bent mirror neutron guide.

  8. Reaction rate constant for radiative association of CF{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Öström, Jonatan, E-mail: jonatan.ostrom@gmail.com; Gustafsson, Magnus, E-mail: magnus.gustafsson@ltu.se [Applied Physics, Division of Materials Science, Department of Engineering Science and Mathematics, Luleå University of Technology, 97187 Luleå (Sweden); Bezrukov, Dmitry S. [Department of Chemistry, M. V. Lomonosov Moscow State University, Moscow, 119991 (Russian Federation); Nyman, Gunnar [Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg (Sweden)

    2016-01-28

    Reaction rate constants and cross sections are computed for the radiative association of carbon cations (C{sup +}) and fluorine atoms (F) in their ground states. We consider reactions through the electronic transition 1{sup 1}Π → X{sup 1}Σ{sup +} and rovibrational transitions on the X{sup 1}Σ{sup +} and a{sup 3}Π potentials. Semiclassical and classical methods are used for the direct contribution and Breit–Wigner theory for the resonance contribution. Quantum mechanical perturbation theory is used for comparison. A modified formulation of the classical method applicable to permanent dipoles of unequally charged reactants is implemented. The total rate constant is fitted to the Arrhenius–Kooij formula in five temperature intervals with a relative difference of <3%. The fit parameters will be added to the online database KIDA. For a temperature of 10–250 K, the rate constant is about 10{sup −21} cm{sup 3} s{sup −1}, rising toward 10{sup −16} cm{sup 3} s{sup −1} for a temperature of 30 000 K.

  9. Reaction Rate Constant for Radiative Association of CF$^+$

    CERN Document Server

    Öström, Jonatan; Nyman, Gunnar; Gustafsson, Magnus

    2015-01-01

    Reaction rate constants and cross sections are computed for the radiative association of carbon cations ($\\text{C}^+$) and fluorine atoms ($\\text{F}$) in their ground states. We consider reactions through the electronic transition $1^1\\Pi \\rightarrow X^1\\Sigma^+$ and rovibrational transitions on the $X^1\\Sigma^+$ and $a^3\\Pi$ potentials. Semiclassical and classical methods are used for the direct contribution and Breit--Wigner theory for the resonance contribution. Quantum mechanical perturbation theory is used for comparison. A modified formulation of the classical method applicable to permanent dipoles of unequally charged reactants is implemented. The total rate constant is fitted to the Arrhenius--Kooij formula in five temperature intervals with a relative difference of $<3\\:\\%$. The fit parameters will be added to the online database KIDA. For a temperature of $10$ to $250\\:\\text{K}$, the rate constant is about $10^{-21}\\:\\text{cm}^3\\text{s}^{-1}$, rising toward $10^{-16}\\:\\text{cm}^3\\text{s}^{-1}$ fo...

  10. Experimental investigation of the 19F( n, α)16N reaction excitation function in the neutron energy range of 4 to 7.35 MeV

    Science.gov (United States)

    Bondarenko, I. P.; Khryachkov, V. A.; Ivanova, T. A.; Kuz'minov, B. D.; Semenova, N. N.; Sergachev, A. I.

    2013-07-01

    The interaction of neutrons with light nuclei study is of interest for understanding nuclear-reaction mechanisms. Fluorine nuclei are worth particular attention because they are abundant in the core of the promising molten-salt reactors and can noticeably affect the chain reaction kinetics. In this work we have experimentally investigated the 19F( n, α)16N reaction cross-section at neutron energies ranging from 4 to 7.35 MeV.

  11. Evaluation of antioxidants using oxidation reaction rate constants

    Institute of Scientific and Technical Information of China (English)

    SHI Yan; ZHAN Xiancheng; MA Lie; LI Linli; LI Chengrong

    2007-01-01

    An evaluation method for the capacity of antioxidants to protect drugs against oxidation is presented.As a new viewpoint,to determine the priority of the competitive oxidations between the antioxidant and the protected drug,and to compare the drug-protection capacity of antioxidants,it is important to determine their oxidation rate constants using chemical kinetics instead of standard oxidation (or reduction) potentials.Sodium sulfite,sodium bisulfite and sodium pyrosulfite were used as models for the determination of oxidation reaction rate constants in aqueous solutions.In the experiments,sufficient air was continually infused into the solution to keep the concentration of dissolved oxygen constant.The residual concentrations of the antioxidants were determined by iodimetry,and the concentration of dissolved oxygen by oxygen electrode.The data were fitted by linear regressions to obtain the reaction rate constants.It was found that the degradation of sodium sulfite,sodium bisulfite or sodium pyrosulfite obeyed pseudo zero-order kinetics in the buffer solutions.Because of the ionization equilibrium,these three antioxidants have the same ion form in solutions at a definite pH value and therefore their apparent rate constants were essentially the same.The average apparent rate constants of the three antioxidants at 25~C are (1.34±0.03)×10-3 at pH 6.8,(1.20±0.02) x 10-3 at pH 4.0 and (6.58±0.02)×10-3 mol.L-1.h-1 at pH 9.2,respectively.

  12. Neutron capture cross section measurements and theoretical calculation for the {sup 186}W(n,γ){sup 187}W reaction

    Energy Technology Data Exchange (ETDEWEB)

    Al-abyad, Mogahed; Mohamed, Gehan Y. [Atomic Energy Authority, Cairo (Egypt). Experimental Nuclear Physics Dept.

    2017-08-01

    Neutron capture cross section (σ{sub 0}) and resonance integral (I{sub 0}) of the reaction {sup 186}W(n,γ){sup 187}W were measured experimentally using the research reactor (ETRR-2) and an Am-Be neutron source, also calculated using TALYS-1.6 code. The present results of σ{sub 0} are (39.08±2.6, 38.75±0.98 and 38.33 barn) and I{sub 0} are (418.5±74, 439.3±36 and 445.5 barn) by using the reactor, neutron source and TALYS-1.6, respectively. The present results are in acceptable agreement with most of the previous experimental and evaluated data as well as the theoretical calculations.

  13. Application of high-frame-rate neutron radiography to fluid measurement

    Energy Technology Data Exchange (ETDEWEB)

    Mishima, Kaichiro; Hibiki, Takashi [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.

    1997-02-01

    To apply Neutron radiography (NR) technique to multiphase flow research, high frame-rate NR was developed by assembling up-to-date technologies for neutron source, scintillator, high-speed video and image intensifier. This imaging system has several advantages such as a long recording time (up to 21 minutes), high-frame-rate (up to 1000 frames/s) imaging and no need for triggering signal. Visualization studies of air-water two-phase flow in a metallic duct and molten metal-water interaction were performed at the recording speeds of 250, 500 and 1000 frames/s. The qualities of those consecutive images were good enough to observe the flow pattern and behavior. It was demonstrated also that some characteristics of two-phase flow could be measured from those images in collaboration with image processing techniques. By utilizing geometrical information extracted from NR images, data on flow regime, rising velocity of bubbles, and wave height and interfacial area in annular flow could be obtained. By utilizing attenuation characteristics of neutrons in materials, measurements of void profile and average void fraction could be performed. For this purpose, a quantification method, i.e. {Sigma}-scaling method, was proposed based upon the consideration on the effect of scattered neutrons. This method was tested against known void profiles and compared with existing measurement methods and a correlation for void fraction. It was confirmed that this new technique has significant advantages both in visualizing and measuring high-speed fluid phenomena. (J.P.N.)

  14. Application of high-frame-rate neutron radiography to fluid measurement

    Energy Technology Data Exchange (ETDEWEB)

    Mishima, Kaichiro; Hibiki, Takashi [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.

    1997-02-01

    To apply Neutron radiography (NR) technique to multiphase flow research, high frame-rate NR was developed by assembling up-to-date technologies for neutron source, scintillator, high-speed video and image intensifier. This imaging system has several advantages such as a long recording time (up to 21 minutes), high-frame-rate (up to 1000 frames/s) imaging and no need for triggering signal. Visualization studies of air-water two-phase flow in a metallic duct and molten metal-water interaction were performed at the recording speeds of 250, 500 and 1000 frames/s. The qualities of those consecutive images were good enough to observe the flow pattern and behavior. It was demonstrated also that some characteristics of two-phase flow could be measured from those images in collaboration with image processing techniques. By utilizing geometrical information extracted from NR images, data on flow regime, rising velocity of bubbles, and wave height and interfacial area in annular flow could be obtained. By utilizing attenuation characteristics of neutrons in materials, measurements of void profile and average void fraction could be performed. For this purpose, a quantification method, i.e. {Sigma}-scaling method, was proposed based upon the consideration on the effect of scattered neutrons. This method was tested against known void profiles and compared with existing measurement methods and a correlation for void fraction. It was confirmed that this new technique has significant advantages both in visualizing and measuring high-speed fluid phenomena. (J.P.N.)

  15. Nuclear structures near and beyond the neutron drip line studied by breakup reactions at SAMURAI at RIBF

    Science.gov (United States)

    Nakamura, Takashi

    2013-10-01

    Some of the first results from kinematically complete measurements of breakup reactions on neutron-rich boron to oxygen isotopes, along and beyond the neutron drip line, are presented and discussed. These experiments were performed at the recently-commissioned large-acceptance multi-purpose spectrometer SAMURAI (Superconducting Analyser for MUlti-particles from Radio-Isotope Beam) at the new-generation RI beam facility, RIBF, at RIKEN. The experiments aimed at probing the two-neutron Borromean halo nuclei, 19B and 22C, and at exploring the heavy oxygen isotopes, 25,26O, which are beyond the neutron drip line. The study of 19B and 22C has been made primarily by the Coulomb breakup, which is sensitive to the halo states and associated two-neutron correlations. 22C has drawn much attention due to the possibility that it has the largest halo known. In addition, 22C may also exhibit features consistent with the new magic number N=16, as was recently suggested by our inclusive measurement of the momentum distribution of 20C following breakup on a C target. 25O and 26O have drawn much attention since these unbound nuclei may have keys to understand why the neutron drip line ends anomalously closer to the stability for oxygen isotopes. 25O and 26O have been produced by the proton removal reactions on 26F,27Ne, and 27F,28Ne, respectively, at 220-250 MeV/nucleon. Preliminary data are shown and discussed. Finally, some perspectives on future projects using the SAMURAI facility are presented.

  16. Measurement of the dmud quartet-to-doublet molecular formation rate ratio (lambdaq : lambdad) and the mu d hyperfine rate (lambdaqd) using the fusion neutrons from mu- stops in D2 gas

    Science.gov (United States)

    Raha, Nandita

    The MuSun experiment will determine the microd capture rate (micro - + d → n + n + nue) from the doublet hyperfine state Lambdad, of the muonic deuterium atom in the 1S ground state to a precision of 1.5%. Modern effective field theories (EFT) predict that an accurate measurement of Lambdad would determine the two-nucleon weak axial current. This will help in understanding all weak nuclear interactions such as the stellar thermonuclear proton-proton fusion reactions, the neutrino reaction nu + d (which explores the solar neutrino oscillation problem). It will also help us understand weak nuclear interactions involving more than two nucleons---double beta decay---as they do involve a two-nucleon weak axial current term. The experiment took place in the piE3 beam-line of Paul Scherrer Institute (PSI) using a muon beam generated from 2.2 mA proton beam---which is the highest intensity beam in the world. The muons first passed through entrance scintillator and multiwire proportional chamber for determining thier entrance timing and position respectively. Then they were stopped in a cryogenic time projection chamber (cryo-TPC) filled with D2 gas. This was surrounded by plastic scintillators and multiwire proportional chambers for detecting the decay electrons and an array of eight liquid scintillators for detecting neutrons. Muons in deuterium get captured to form microd atoms in the quartet and doublet spin states. These atoms undergo nuclear capture from these hyperfine states respectively. There is a hyperfine transition rate from quartet-to-doublet state---lambdaqd along with dmicrod molecular formation which further undergoes a fusion reaction with the muon acting as a catalyst (MCF). The goal of this dissertation is to measure the dmicro d quartet-to-doublet rate ratio (lambdaq : lambdad) and microd hyperfine rate (lambda qd) using the fusion neutrons from micro. stops in D2 gas. The dmicrod molecules undergo MCF reactions from the doublet and the quartet state

  17. Dependence of the neutron monitor count rate and time delay distribution on the rigidity spectrum of primary cosmic rays

    Science.gov (United States)

    Mangeard, P.-S.; Ruffolo, D.; Sáiz, A.; Nuntiyakul, W.; Bieber, J. W.; Clem, J.; Evenson, P.; Pyle, R.; Duldig, M. L.; Humble, J. E.

    2016-12-01

    Neutron monitors are the premier instruments for precisely tracking time variations in the Galactic cosmic ray flux at GeV-range energies above the geomagnetic cutoff at the location of measurement. Recently, a new capability has been developed to record and analyze the neutron time delay distribution (related to neutron multiplicity) to infer variations in the cosmic ray spectrum as well. In particular, from time delay histograms we can determine the leader fraction L, defined as the fraction of neutrons that did not follow a previous neutron detection in the same tube from the same atmospheric secondary particle. Using data taken during 2000-2007 by a shipborne neutron monitor latitude survey, we observe a strong dependence of the count rate and L on the geomagnetic cutoff. We have modeled this dependence using Monte Carlo simulations of cosmic ray interactions in the atmosphere and in the neutron monitor. We present new yield functions for the count rate of a neutron monitor at sea level. The simulation results show a variation of L with geomagnetic cutoff as observed by the latitude survey, confirming that these changes in L can be attributed to changes in the cosmic ray spectrum arriving at Earth's atmosphere. We also observe a variation in L with time at a fixed cutoff, which reflects the evolution of the cosmic ray spectrum with the sunspot cycle, known as solar modulation.

  18. MCNP{trademark} simulations for identifying environmental contaminants using prompt gamma-rays from thermal neutron capture reactions

    Energy Technology Data Exchange (ETDEWEB)

    Frankle, S.C.; Conaway, J.G.

    1996-12-31

    The primary purposes of the Multispectral Neutron Logging Project, (MSN Project, funded by the U.S. Department of Energy), were to assess the effectiveness of existing neutron- induced spectral gamma-ray logging techniques for identifying environmental contaminants along boreholes, to further improve the technology, and to transfer that technology to industry. Using a pulsed neutron source with a high-resolution gamma-ray detector, spectra from thermal neutron capture reactions may be used to identify contaminants in the borehole environment. Direct borehole measurements such as this complement physical sampling and are useful in environmental restoration projects where characterization of contaminated sites is required and long-term monitoring may be needed for many years following cleanup or stabilization. In the MSN Project, a prototype logging instrument was designed which incorporated a pulsed 14-MeV neutron source and HPGe detector. Experimental measurements to determine minimum detection thresholds with the prototype instrument were conducted in the variable-contaminant test model for Cl, Cd, Sm, Gd, and Hg. We benchmarked an enhanced version of the Monte Carlo N-Particle computer code MCNP{trademark} using experimental data for Cl provide by our collaborators and experimental data from the variable-contaminant test model. MCNP was then used to estimate detection thresholds for the other contaminants used in the variable-contaminant model with the goal of validating the use of MCNP to estimate detection thresholds for many other contaminants that were not measured.

  19. Neutron and Gamma Fluxes and dpa Rates for HFIR Vessel Beltline Region (Present and Upgrade Designs)

    Energy Technology Data Exchange (ETDEWEB)

    Blakeman, E.D.

    2001-01-11

    The Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) is currently undergoing an upgrading program, a part of which is to increase the diameters of two of the four radiation beam tubes (HB-2 and HB-4). This change will cause increased neutron and gamma radiation dose rates at and near locations where the tubes penetrate the vessel wall. Consequently, the rate of radiation damage to the reactor vessel wall at those locations will also increase. This report summarizes calculations of the neutron and gamma flux (particles/cm{sup 2}/s) and the dpa rate (displacements/atom/s) in iron at critical locations in the vessel wall. The calculated dpa rate values have been recently incorporated into statistical damage evaluation codes used in the assessment of radiation induced embrittlement. Calculations were performed using models based on the discrete ordinates methodology and utilizing ORNL two-dimensional and three-dimensional discrete ordinates codes. Models for present and proposed beam tube designs are shown and their results are compared. Results show that for HB-2, the dpa rate in the vessel wall where the tube penetrates the vessel will be increased by {approximately}10 by the proposed enlargement. For HB-4, a smaller increase of {approximately}2.6 is calculated.

  20. Capture rate and neutron helicity asymmetry for ordinary muon capture on hydrogen

    CERN Document Server

    Ando, S; Kubodera, K; Ando, Shung-ichi; Myhrer, Fred; Kubodera, Kuniharu

    2001-01-01

    Applying heavy-baryon chiral perturbation theory to ordinary muon capture (OMC) on a proton, we calculate the capture rate and neutron helicity asymmetry up to next-to-next-to-leading order. For the singlet hyperfine state, we obtain the capture rate Gamma_0 = 695 sec^{-1} while, for the triplet hyperfine state, we obtain the capture rate Gamma_1 = 11.9 sec^{-1} and the neutron asymmetry alpha_1 = 0.93. If the existing formalism is used to relate these atomic capture rate to Gamma_{liq}, the OMC rate in liquid hydrogen, then Gamma_{liq} corresponding to our improved values of Gamma_0 and Gamma_1 is found to be significantly larger than the experimental value. We argue that this apparent difficulity may be correlated to the specious anomaly recently reported for mu^- + p to n + nu_mu + gamma, and we suggest a possibility to remove these two "problems" simply and simultaneously by reexamining the molecular physics input that underlies the conventional analysis of Gamma_{liq}.

  1. Numerical modeling of radioactive neutron capture influence of Hf isotopic composition dynamics rate in the RBMK-1500 reactor

    CERN Document Server

    Jurkevicius, A; Auzelyte, V; Remeikis, V

    2000-01-01

    The nuclide composition of the nuclear fuel and isotopic composition of the hafnium in the radial neutron flux detectors of the RBMK-1500 reactor were numerically modelled. The sequence SAS2 from package SCALE 4.3 was used for calculations. The nuclear fuel nuclide concentrations, the concentration of Hf isotopes, the neutron absorption rate on Hf isotopes and summary absorption rate dependences on the fuel assembly burn up are presented. (author)

  2. Measurements of neutron induced capture and fission reactions on $^{233}$ U (EAR1)

    CERN Multimedia

    The $^{233}$U plays the essential role of ssile nucleus in the Th-U fuel cycle, which has been proposed as a safer and cleaner alternative to the U-Pu fuel cycle. Considered the scarce data available to assess the capture cross section, a measurement was proposed and successfully performed at the n_TOF facility at CERN using the 4$\\pi$ Total Absorp- tion Calorimeter (TAC). The measurement was extremely dicult due to the need to accurately distinguish between capture and fission $\\gamma$-rays without any additional discrim-ination tool and the measured capture cross section showed a signicant disagreement in magnitude when compared with the ENDF/B-VII.1 library despite the agreement in shape. We propose a new measurement that is aimed at providing a higher level of dis-crimination between competing nuclear reactions, to extend the neutron energy range and to obtain more precise and accurate data, thus fullling the demands of the "NEA High Priority Nuclear Data Request List". The setup is envisaged as a combin...

  3. In situ observation of the reaction of scandium and carbon by neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Juarez-Arellano, Erick A., E-mail: eajuarez@unpa.edu.m [Institut fuer Geowissenschaften, Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Universidad del Papaloapan, Circuito Central 200, Parque Industrial, Tuxtepec 68301 (Mexico); Winkler, Bjorn [Institut fuer Geowissenschaften, Universitaet Frankfurt, Altenhoeferallee 1, 60438 Frankfurt a.M. (Germany); Vogel, Sven C. [Los Alamos National Laboratory, Lujan Center. Mail Stop H805, Los Alamos, NM 87545 (United States); Senyshyn, Anatoliy [Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universitaet Muenchen, Lichtenbergstr. 1, D-85747 Garching (Germany); Materialwissenschaft, TU Darmstadt, Petersensstr. 23, D-64287 Darmstadt (Germany); Kammler, Daniel R. [Sandia National Laboratories, Albuquerque, NM 87185 (United States); Avalos-Borja, Miguel [CNyN, UNAM, A. Postal 2681, Ensenada, B.C. (Mexico)

    2011-01-05

    Research highlights: {yields} Exist two ScC cubic phases with B1-structure type differing in site occupancy of C. {yields} A new orthorhombic scandium carbide phase is formed at 1473(50) K. {yields} The recrystallization of alpha-Sc occurs between 1000 and 1223 K. - Abstract: The formation of scandium carbides by reaction of the elements has been investigated by in situ neutron diffraction up to 1823 K. On heating, the recrystallization of {alpha}-Sc occurs between 1000 and 1223 K. The formation of Sc{sub 2}C and ScC (NaCl-B1 type structure) phases has been detected at 1323 and 1373 K, respectively. The formation of a new orthorhombic scandium carbide phase was observed at 1473(50) K. Once the scandium carbides are formed they are stable upon heating or cooling. No other phases were detected in the present study, in which the system was always carbon saturated. The thermal expansion coefficients of all phases have been determined, they are constant throughout the temperature interval studied.

  4. Prompt gamma ray diagnostics and enhanced hadron-therapy using neutron-free nuclear reactions

    Directory of Open Access Journals (Sweden)

    L. Giuffrida

    2016-10-01

    Full Text Available We propose a series of simulations about the potential use of Boron isotopes to trigger neutron-free (aneutronic nuclear reactions in cancer cells through the interaction with an incoming energetic proton beam, thus resulting in the emission of characteristic prompt gamma radiation (429 keV, 718 keV and 1435 keV. Furthermore assuming that the Boron isotopes are absorbed in cancer cells, the three alpha-particles produced in each p-11B aneutronic nuclear fusion reactions can potentially result in the enhancement of the biological dose absorbed in the tumor region since these multi-MeV alpha-particles are stopped inside the single cancer cell, thus allowing to spare the surrounding tissues. Although a similar approach based on the use of 11B nuclei has been proposed in [Yoon et al. Applied Physics Letters 105, 223507 (2014], our work demonstrate, using Monte Carlo simulations, the crucial importance of the use of 10B nuclei (in a solution containing also 11B for the generation of prompt gamma-rays, which can be applied to medical imaging. In fact, we demonstrate that the use of 10B nuclei can enhance the intensity of the 718 keV gamma-ray peak more than 30 times compared to the solution containing only 11B nuclei. A detailed explanation of the origin of the different prompt gamma-rays, as well as of their application as real-time diagnostics during a potential cancer treatment, is here discussed.

  5. Neutron Production Rates by Inverse-Beta Decay in Fully Ionized Plasmas

    CERN Document Server

    Maiani, L; Riquer, V

    2014-01-01

    Recently we showed that the nuclear transmutation rates are largely overestimated in the Widom-Larsen theory of the so called `Low Energy Nuclear Reactions'. Here we show that unbound plasma electrons are even less likely to initiate nuclear transmutations.

  6. Reaction rate theory of radiation exposure: Effects of the dose rate on mutation frequencies

    CERN Document Server

    Manabe, Yuichiro; Nakamura, Issei

    2014-01-01

    We develop a kinetic reaction model for the cells having the irradiated DNA molecules due to the ionizing radiation exposure. Our theory simultaneously accounts for the time-dependent reactions of the DNA damage, the DNA mutation, the DNA repair, and the proliferation and apoptosis of cells in a tissue with a minimal set of model parameters. In contrast to the existing theories for the radiation exposition, we do not assume the relationships between the total dose and the induced mutation frequency. We show good agreement between theory and experiment. Importantly, our result shows a new perspective that the key ingredient in the study of the irradiated cells is the rate constants depending on the dose rate. Moreover, we discuss the universal scaling function for mutation frequencies due to the irradiation at low dose rates.

  7. a Study of Stress Relaxation Rate in Un-Irradiated and Neutron-Irradiated Stainless Steel

    Science.gov (United States)

    Ghauri, I. M.; Afzal, Naveed; Zyrek, N. A.

    Stress relaxation rate in un-irradiated and neutron-irradiated 303 stainless steel was investigated at room temperature. The specimens were exposed to 100 mC, Ra-Be neutron source of continuous energy 2-12 MeV for a period ranging from 4 to 16 days. The tensile deformation of the specimens was carried out using a Universal Testing Machine at 300 K. During the deformation, straining was frequently interrupted by arresting the cross head to observe stress relaxation at fixed load. Stress relaxation rate, s, was found to be stress dependent i.e. it increased with increasing stress levels σ0 both in un-irradiated and irradiated specimens, however the rate was lower in irradiated specimens than those of un-irradiated ones. A further decrease in s was observed with increase in exposure time. The experiential decrease in the relaxation rate in irradiated specimens is ascribed to strong interaction of glide dislocations with radiation induced defects. The activation energy for the movement of dislocations was found to be higher in irradiated specimens as compared with the un-irradiated ones.

  8. Stellar electron capture rates on neutron-rich nuclei and their impact on core-collapse

    CERN Document Server

    Raduta, Ad R; Oertel, M

    2016-01-01

    During the late stages of gravitational core-collapse of massive stars, extreme isospin asymmetries are reached within the core. Due to the lack of microscopic calculations of electron capture (EC) rates for all relevant nuclei, in general simple analytic parameterizations are employed. We study here several extensions of these parameterizations, allowing for a temperature, electron density and isospin dependence as well as for odd-even effects. The latter extra degrees of freedom considerably improve the agreement with large scale microscopic rate calculations. We find, in particular, that the isospin dependence leads to a significant reduction of the global EC rates during core collapse with respect to fiducial results, where rates optimized on calculations of stable $fp$-shell nuclei are used. Our results indicate that systematic microscopic calculations and experimental measurements in the $N\\approx 50$ neutron rich region are desirable for realistic simulations of the core-collapse.

  9. Study of the {sup 17}O(n,α){sup 14}C reaction: Extension of the Trojan Horse Method to neutron induced reactions

    Energy Technology Data Exchange (ETDEWEB)

    Guardo, G. L.; Lamia, L.; Spitaleri, C.; Cherubini, S.; Rapisarda, G. G.; Sergi, M. L. [INFN - Laboratori Nazionali del Sud, Catania, Italy and Department of Physics and Astronomy, University of Catania, Catania (Italy); Gulino, M. [INFN - Laboratori Nazionali del Sud, Catania, Italy and University of Enna (Italy); Tang, X. D.; Bucher, B.; Couder, M.; Davies, P.; Boer, R. de; Fang, X.; Lamm, L.; Ma, C.; Notani, M.; OBrien, S.; Roberson, D.; Tan, W.; Wiescher, M. [Department of Physics and Joint Institute for Nuclear Astrophysics, University of Notre Dame, IN (United States); and others

    2014-05-02

    The experimental study of the {sup 17}O(n,α){sup 14}C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To overcome the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. In more details, the {sup 17}O(n,α){sup 14}C reaction has been studied using the quasi-free {sup 2}H({sup 17}O,α{sup 14}C){sup 1}H reaction, induced at an energy of 43.5 MeV. The measurement allows one to investigate the ℓ=3, 75 keV resonance (E*=8.125 MeV, J{sup π}=5{sup −}), absent in the available direct measurements because of centrifugal suppression effects.

  10. Indirect determination of Li via 74Ge(n,γ)75mGe activation reaction induced by neutrons from 7Li(p,n)7Be reaction

    Science.gov (United States)

    Kumar, Sanjiv; Reddy, G. L. N.; Rao, Pritty; Verma, Rakesh; Ramana, J. V.; Vikramkumar, S.; Raju, V. S.

    2012-03-01

    An indirect method to determine Li by 74Ge(n,γ)75mGe activation reaction induced in a high purity Ge (detector) crystal by neutrons from the 7Li(p,n)7Be reaction in a typical particle-induced γ-ray emission (PIGE) spectroscopy experimental set-up is described. Performed with proton beams of energies in excess of 1.88 MeV, the threshold energy (Eth) of the 7Li(p,n)7Be reaction, the determination involves the activity measurement of 75mGe isotope that has a half-life of 47.7 s and decays with the emission of 139 keV γ-rays. Rapidity, selectivity and sensitivity down to ppm levels are the attractive features of the method. It is a suitable alternative to 7Li(p,p'γ)7Li reaction based PIGE technique in the analyses of matrices that contain light elements such as Be, B, F, Na and Al in significant proportions. Interferences can arise from elements, for example V and Ti, that have Eth ⩽ 1.88 MeV for (p,n) reaction. In the case of elements such as Cu, Mo which have with Eth > 1.88 MeV, the incident proton beam energy can be judiciously selected to avoid or minimize an interference. The method, under optimized irradiation conditions, does not entail a risk of neutron stimulated degradation of the performance of the detector. Besides analytical purposes, the measurement of the 75mGe activity can serve as a powerful tool to monitor even low (˜25 n/cm2 s) thermal neutron fluxes.

  11. Excitation function shape and neutron spectrum of the 7Li(p ,n )7Be reaction near threshold

    Science.gov (United States)

    Martín-Hernández, Guido; Mastinu, Pierfrancesco; Maggiore, Mario; Pranovi, Lorenzo; Prete, Gianfranco; Praena, Javier; Capote-Noy, Roberto; Gramegna, Fabiana; Lombardi, Augusto; Maran, Luca; Scian, Carlo; Munaron, Enrico

    2016-09-01

    The forward-emitted low energy tail of the neutron spectrum generated by the 7Li(p ,n )7Be reaction on a thick target at a proton energy of 1893.6 keV was measured by time-of-flight spectroscopy. The measurement was performed at BELINA (Beam Line for Nuclear Astrophysics) of the Laboratori Nazionali di Legnaro. Using the reaction kinematics and the proton on lithium stopping power the shape of the excitation function is calculated from the measured neutron spectrum. Good agreement with two reported measurements was found. Our data, along with the previous measurements, are well reproduced by the Breit-Wigner single-resonance formula for s -wave particles. The differential yield of the reaction is calculated and the widely used neutron spectrum at a proton energy of 1912 keV was reproduced. Possible causes regarding part of the 6.5% discrepancy between the 197Au(n ,γ ) cross section measured at this energy by Ratynski and Kappeler [Phys. Rev. C 37, 595 (1988), 10.1103/PhysRevC.37.595] and the one obtained using the Evaluated Nuclear Data File version B-VII.1 are given.

  12. Choppers to optimise the repetition rate multiplication technique on a direct geometry neutron chopper spectrometer

    DEFF Research Database (Denmark)

    Vickery, Anette; Deen, P. P.

    2014-01-01

    In recent years the use of repetition rate multiplication (RRM) on direct geometry neutron spectrometers has been established and is the common mode of operation on a growing number of instruments. However, the chopper configurations are not ideally optimised for RRM with a resultant 100 fold flu...... in time resolution probed for a single European Spallation Source (ESS) period, which is ideal to probe complex relaxational behaviour. These two chopper configurations have been simulated for the Versatile Optimal Resolution direct geometry spectrometer, VOR, that will be built at ESS....

  13. Investigation of the Statistical Properties of Stable Eu Nuclei using Neutron-Capture Reactions

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-10-04

    Neutron capture for incident neutron energies <1eV up to 100 keV has been measured for {sup 151,153}Eu targets. The highly efficient DANCE (Detector for Advanced Neutron Capture Experiments) array coupled with the intense neutron beam at Los Alamos Neutron Science Center is used for the experiment. Stable Eu isotopes mass separated and electroplated on Be backings were used. Properties of well-resolved, strong resonances in two Eu nuclei are examined. The parameters for most of these resonances are known. Detailed multiplicity information for each resonance is obtained employing the high granularity of the DANCE array. The radiative decay cascades corresponding to each resonance are obtained in the experiment. The measurements are compared to simulation of these cascades which calculated with various models for the radiative strength function. Comparison between the experimental data and simulation provides an opportunity to investigate the average quantities.

  14. Analysis of reaction rates of single molecules on metal surfaces

    Science.gov (United States)

    Ueba, H.

    2017-10-01

    The experimental results of the action spectra i.e., reaction rate R(V) as a function of a bias voltage V are analyzed for rotation of a single CCH (D) molecule on a Cu (100) surface [5] and hopping of a single H(D)2O molecule on Pd(111) surface [6]. In the former system it is identified that rotation occurs if enough energy stored in the C-H (D) in-plane bending (IPB) mode excited by tunneling electron is transferred to the C-H (D) out of plane bending (OPB) mode (reaction coordinate mode) via the anharmonic mode coupling in a single electron process. The calculated R(V) shows an excellent agreement with the experimental results except at the low bias voltages below V ≃ 60 mV where no experimental data is available for the nonlinear current I dependence of R(I). A reproduction of the experimental R(V) at the higher voltage region allows us to determine the vibrational density of states of the C-H IPB mode and its coupling rate to the C-H (D) OPB mode as well as the inelastic tunneling current to excite IPB mode. A change of a conductance upon excitation of the C-H IPB mode enables us to evaluate the electron-vibration coupling strength inducing the rotation motion of CCH molecule. In the latter system investigated at a high temperature of about 40 K, the constant R(V) due to thermal hopping followed by the rapid increase is satisfactory explained by anharmonic inter-mode coupling between the scissor mode excited by tunneling electrons and the frustrated translation mode for H(D)2O molecule on Pd(111).

  15. A study of the single neutron knockout reaction from silicon-26 and sulfur-30

    Science.gov (United States)

    Reynolds, Robert R., Jr.

    The use of single nucleon and two-like nucleon knockout reactions of medium to heavy mass exotic beams on light targets has proven an invaluable tool in exploring nuclear properties away from the valley of beta-stability up to the proton and neutron drip-lines. The nuclear shell model has had a great amount of success in describing structural properties of nucleons populating states from the 1s1p-shells up to the 2p1f-shells, of particular interest is the success of the USD shell model used in the truncated 2s1d-shell space. The USD Hamiltonian was updated in 2005 to include the effects of exotic nuclei. Using relativistic beam velocities greater then 30% of the speed of light allows for the direct exploration of underlying single particle valence state structure. Comparisons between current shell models and experimental results are showing discrepancies between measured and theoretical cross sections. The focus of the present work is on the single neutron knockout reactions 9Be(26Si,25Si+gamma) and 9 Be(30S,29S+gamma). Relativistic beams containing 26Si and 30S were created at the National Superconducting Cyclotron Laboratory's Coupled-Cyclotron Facility using the A1900 fragment separator. The secondary 376 mg/cm2 thick 9Be target was located at the pivot point of the S800, a large-acceptance, high-resolution spectrometer with a specialized detector system that allowed for accurate event-by-event particle identification of the incident and residual particles based on their mass and charge, as well as providing accurate longitudinal momentum distribution measurements of the post-target beam. The secondary target was also surrounded by SeGA, a gamma-ray detector array specifically designed for accurate Doppler reconstruction of observable gamma-rays into the emitting particles rest frame. Measurements were made of the direct inclusive and individual state population cross sections in the residual states, as well as the first measurements of electromagnetic

  16. NEUTRON IMAGING, RADIOGRAPHY AND TOMOGRAPHY.

    Energy Technology Data Exchange (ETDEWEB)

    SMITH,G.C.

    2002-03-01

    Neutrons are an invaluable probe in a wide range of scientific, medical and commercial endeavors. Many of these applications require the recording of an image of the neutron signal, either in one-dimension or in two-dimensions. We summarize the reactions of neutrons with the most important elements that are used for their detection. A description is then given of the major techniques used in neutron imaging, with emphasis on the detection media and position readout principle. Important characteristics such as position resolution, linearity, counting rate capability and sensitivity to gamma-background are discussed. Finally, the application of a subset of these instruments in radiology and tomography is described.

  17. Manual Choice Reaction Times in the Rate-Domain

    Directory of Open Access Journals (Sweden)

    Chris eHarris

    2014-06-01

    Full Text Available Over the last 150 years, human manual reaction times (RTs have been recorded countless times. Yet, our understanding of them remains remarkably poor. RTs are highly variable with positively skewed frequency distributions, often modelled as an inverse Gaussian distribution reflecting a stochastic rise to threshold (diffusion process. However, latency distribution of saccades are very close to the reciprocal Normal, suggesting that ‘rate’ (reciprocal RT may be the more fundamental variable. We explored whether this phenomenon extends to choice manual RTs. We recorded two-alternative choice RTs from 24 subjects, each with 4 blocks of 200 trials with two task difficulties (easy vs. difficult discrimination and two instruction sets (urgent vs. accurate. We found that rate distributions were, indeed, very close to Normal, shifting to lower rates with increasing difficulty and accuracy, and for some blocks subjects they appeared to become left-truncated, but still close to Normal. Using autoregressive techniques, we found temporal sequential dependencies for lags of at least 3. We identified a transient and steady-state component in each block. Because rates were Normal, we were able to estimate autoregressive weights using the Box-Jenkins technique, and convert to a moving average model using z-transforms to show explicit dependence on stimulus input. We also found a spatial sequential dependence for the previous 3 lags depending on whether the laterality of previous trials was repeated or alternated. This was partially dissociated from temporal dependency as it only occurred in the easy tasks. We conclude that 2-alternative choice manual RT distributions are close to reciprocal Normal and not the inverse Gaussian. This is not consistent with stochastic rise to threshold models, and we propose a simple optimality model in which reward is maximized to yield to an optimal rate, and hence an optimal time to respond. We discuss how it might be

  18. Neutron production at 0{degree} from the {sup 40}Ca+H reaction at E{sub lab}=357A and 565A MeV

    Energy Technology Data Exchange (ETDEWEB)

    Tuve, C.; Albergo, S.; Boemi, D.; Caccia, Z.; Costa, S.; Insolia, A.; Potenza, R.; Reito, S.; Romanski, J.; Russo, G.V. [Universita di Catania and INFN - I, 95129 Catania (Italy); Cronqvist, M.; Lindstrom, P.J. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Chen, C.; Guzik, T.G.; Tull, C.E.; Wefel, J.P. [Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Crawford, H.J.; Engelage, J.; Greiner, L. [Space Science Laboratory, University of California, Berkeley, California 94720 (United States); Knott, C.N.; Waddington, C.J. [University of Minnesota, Minneapolis, Minnesota 55455 (United States); Webber, W.R. [University of New Mexico, Las Cruces, New Mexico 88003 (United States); Soutoul, A.; Testard, O. [Service dAstrophysique, CEN, 91191 Saclay (France); Mitchell, J.W. [NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

    1997-08-01

    Neutrons produced in the {sup 40}Ca+H reaction at E{sub lab}=357A and 565A MeV have been detected using a three-module version of the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range around the beam in the forward direction (0{degree}{minus}3.2{degree}). Semi-inclusive neutron production cross sections, at the two energies, are reported together with neutron energy spectra, angular, rapidity, and transverse momentum distributions. Comparison with a Boltzmann-Nordheim-Vlasov approach + phase space coalescence model is discussed. {copyright} {ital 1997} {ital The American Physical Society}

  19. Boron neutron capture therapy design calculation of a 3H(p,n reaction based BSA for brain cancer setup

    Directory of Open Access Journals (Sweden)

    Bassem Elshahat

    2015-09-01

    Full Text Available Purpose: Boron neutron capture therapy (BNCT is a promising technique for the treatment of malignant disease targeting organs of the human body. Monte Carlo simulations were carried out to calculate optimum design parameters of an accelerator based beam shaping assembly (BSA for BNCT of brain cancer setup.Methods: Epithermal beam of neutrons were obtained through moderation of fast neutrons from 3H(p,n reaction in a high density polyethylene moderator and a graphite reflector. The dimensions of the moderator and the reflector were optimized through optimization of epithermal / fast neutron intensity ratio as a function of geometric parameters of the setup. Results: The results of our calculation showed the capability of our setup to treat the tumor within 4 cm of the head surface. The calculated peak therapeutic ratio for the setup was found to be 2.15. Conclusion: With further improvement in the polyethylene moderator design and brain phantom irradiation arrangement, the setup capabilities can be improved to reach further deep-seated tumor.

  20. The Radiative Strength Function Using the Neutron-Capture Reaction on 151,153Eu

    Science.gov (United States)

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

    2006-03-01

    Radiative strength functions in 152,154Eu nuclei for γ-ray energies below 6 MeV have been investigated. Neutron capture for incident neutron energies <1eV up to 100 keV has been measured for 151,153Eu targets. Properties of γ decay of neutron resonances in 152,154Eu nuclei are examined. The results of measurements are compared to outcome of simulation of γ cascades based on various models for the radiative strength function. Comparison between experimental data and simulation suggests existence of the low-energy resonance in these two nuclei.

  1. Development of Real-Time Measurement of Effective Dose for High Dose Rate Neutron Fields

    CERN Document Server

    Braby, L A; Reece, W D

    2003-01-01

    Studies of the effects of low doses of ionizing radiation require sources of radiation which are well characterized in terms of the dose and the quality of the radiation. One of the best measures of the quality of neutron irradiation is the dose mean lineal energy. At very low dose rates this can be determined by measuring individual energy deposition events, and calculating the dose mean of the event size. However, at the dose rates that are normally required for biology experiments, the individual events can not be separated by radiation detectors. However, the total energy deposited in a specified time interval can be measured. This total energy has a random variation which depends on the size of the individual events, so the dose mean lineal energy can be calculated from the variance of repeated measurements of the energy deposited in a fixed time. We have developed a specialized charge integration circuit for the measurement of the charge produced in a small ion chamber in typical neutron irradiation exp...

  2. Application of high-frame-rate neutron radiography to steam explosion research

    Science.gov (United States)

    Saito, Y.; Mishima, K.; Hibiki, T.; Yamamoto, A.; Sugimoto, J.; Moriyama, K.

    1999-11-01

    To understand the behavior of dispersed molten metal particles dropped into water during the premixing process of steam explosion, experiments were performed by using heated stainless-steel particles simulating dispersed molten metal particles. High-frame-rate neutron radiography was successfully employed for visualization and void fraction measurement. Visualization was conducted by dropping heated stainless-steel particle into heavy water filled in a rectangular tank with the particle diameter (6, 9, and 12 mm) and temperature (600°C, 700°C, 800°C, and 1000°C) as parameters. Steam generation due to direct contact of heated particle and heavy water was successfully visualized by the high-frame-rate neutron radiography at the recording speed of 500 frames/s. From void fraction measurement it was revealed that the amount of generated steam was in proportion to the particle size and temperature. It is suggested that the ambient liquid might be superheated by the particle-liquid contact.

  3. Neutron activation analysis of ceramic tiles and its component and radon exhalation rate.

    Science.gov (United States)

    El-Shershaby, A; Sroor, A; Ahmed, F; Abdel-Haleem, A S; Abdel, Z

    2004-01-01

    The concentrations of 20 trace elements in several ceramics tiles and ceramic composites used in Egypt were elementally analyzed by neutron activation analysis(NAA) technique. The samples and standard were irradiated with reactor for 4 h (in the Second Research Egyptian Reactor(Et-RR-2)) with thermal neutron flux 5.9 x 10(13) n/(cm2 x s). The gamma-ray spectra obtained were measured for several times by means of the hyper pure germanium detection system(HPGe). Also a solid state nuclear track detector(SSNTD) CR-39, was used to measure the emanation rate of radon for these samples. The radium concentrations were found to vary from 0.39-3.59 ppm and the emanation rates were found to vary from (0.728-5.688) x 10(-4) kg/(m2 x s). The elemental analysis of the ceramic tiles and ceramic composites have a great importance in assigning the physical properties and in turn the quality of the material.

  4. Neutron Production in Coincidence with Fragments from the {sup 40}Ca + H Reactions at E{sub lab} = 357 and 565 A MeV

    Energy Technology Data Exchange (ETDEWEB)

    Tuve, C.; Albergo, S.; Boemi, D.; Caccia, Z.; Chen, C.-X.; Costa, S.; Crawford, H.J.; Cronqvist, M.; Engelage, J.; Greiner, L.; Guzik, T.G.; Insolia, A.; Knott, C.N.; Lindstrom, P.J.; Mitchell, J.W.; Potenza, R.; Russo, G.V.; Soutoul, A.; Testard, O.; Tricomi, A.; Tull, C.E.; Waddington, C.J.; Webber, W.R.; Wefel, J.P.

    2000-12-31

    In the frame of the Transport Collaboration neutrons in coincidence with charged fragments produced in the {sup 40}Ca + H reaction at E{sub lab} = 357 and 565 AMeV have been measured at the Heavy Ion Spectrometer System (HISS) facility of the Lawrence Berkeley National Laboratory, using the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range about the beam in the forward direction (0? - 3.2?). In this contribution we report absolute neutron production cross sections in coincidence with charged fragments (10 {<=} Z {<=} 20). The neutron multiplicities have been estimated from the comparison between the neutron cross sections, in coincidence with the fragments, and the elemental cross sections. We have found evidence for a pre-equilibrium emission of prompt neutrons in superposition to a 'slower' deexcitation of the equilibrated remnant by emission of nucleons and fragments, as already seen in the inclusive rapidity distributions.

  5. Neutron beam optimization based on a 7Li(p,n)7Be reaction for treatment of deep-seated brain tumors by BNCT

    Science.gov (United States)

    Zahra Ahmadi, Ganjeh; S. Farhad, Masoudi

    2014-10-01

    Neutron beam optimization for accelerator-based Boron Neutron Capture Therapy (BNCT) is investigated using a 7Li(p,n)7Be reaction. Design and optimization have been carried out for the target, cooling system, moderator, filter, reflector, and collimator to achieve a high flux of epithermal neutron and satisfy the IAEA criteria. Also, the performance of the designed beam in tissue is assessed by using a simulated Snyder head phantom. The results show that the optimization of the collimator and reflector is critical to finding the best neutron beam based on the 7Li(p,n)7Be reaction. Our designed beam has 2.49×109n/cm2s epithermal neutron flux and is suitable for BNCT of deep-seated brain tumors.

  6. Standard and Nonstandard Neutrino-Nucleus Reactions Cross Sections and Event Rates to Neutrino Detection Experiments

    Directory of Open Access Journals (Sweden)

    D. K. Papoulias

    2015-01-01

    Full Text Available In this work, we explore ν-nucleus processes from a nuclear theory point of view and obtain results with high confidence level based on accurate nuclear structure cross sections calculations. Besides cross sections, the present study includes simulated signals expected to be recorded by nuclear detectors and differential event rates as well as total number of events predicted to be measured. Our original cross sections calculations are focused on measurable rates for the standard model process, but we also perform calculations for various channels of the nonstandard neutrino-nucleus reactions and come out with promising results within the current upper limits of the corresponding exotic parameters. We concentrate on the possibility of detecting (i supernova neutrinos by using massive detectors like those of the GERDA and SuperCDMS dark matter experiments and (ii laboratory neutrinos produced near the spallation neutron source facilities (at Oak Ridge National Lab by the COHERENT experiment. Our nuclear calculations take advantage of the relevant experimental sensitivity and employ the severe bounds extracted for the exotic parameters entering the Lagrangians of various particle physics models and specifically those resulting from the charged lepton flavour violating μ-→e- experiments (Mu2e and COMET experiments.

  7. Isovector excitations in 100Nb and their decays by neutron emission studied via the Mo100(t,He3+n reaction at 115 MeV/u

    Directory of Open Access Journals (Sweden)

    K. Miki

    2017-06-01

    Full Text Available Spin–isospin excitations in Nb100 were studied via the Mo100(t,He3 charge-exchange reaction at 115 MeV/u with the goal to constrain theoretical models used to describe the isovector spin response of nuclei. The experiment was performed with a secondary beam of tritons, and 3He particles were analyzed in the S800 magnetic spectrometer. Decay by neutron emission from excited states in Nb100 was observed by using plastic and liquid scintillator arrays. Differential cross sections were analyzed and monopole excitations were revealed by using a multipole decomposition analysis. The Gamow–Teller transition strength observed at low excitation energies, which is important for estimating the electron-capture rate in astrophysical scenarios, was strongly fragmented and reduced compared to single-particle and spherical mean-field models. The consideration of deformation in the theoretical estimates was found to be important to better describe the fragmentation and strengths. A strong excitation of the isovector spin giant monopole resonance was observed, and well reproduced by the mean-field models. Its presence makes the extraction of Gamow–Teller strengths at high excitation energies difficult. The branches for statistical and direct decay by neutron emission were identified in the spectra. The upper limit for the branching ratio by direct decay (integrated over all observed excitations was determined to be 20±6%. Even though the statistical uncertainties in the neutron-coincident data were too large to perform detailed studies of the decay by neutron emission from individual states and resonances, the experiment demonstrates the feasibility of the method.

  8. Measurement of activation reaction rate distributions in a lead assembly bombarded with 500-MeV protons

    CERN Document Server

    Takada, H; Sasa, T; Tsujimoto, K; Yasuda, H

    2000-01-01

    Reaction rate distributions of various activation detectors such as the /sup nat/Ni(n, x)/sup 58/Co, /sup 197/Au(n,2n)/sup 196/Au, and /sup 197/Au(n,4n)/sup 194/Au reactions were measured to study the production and the transport of spallation neutrons in a lead assembly bombarded with protons of 500 MeV. The measured data were analyzed with the nucleon-meson transport code NMTC/JAERI combined with the MCNP4A code using the nuclide production cross sections based on the JENDL Dosimetry File and those calculated with the ALICE-F code. It was found that the NMTC/JAERI-MCNP4A calculations agreed well with the experiments for the low-energy-threshold reaction of /sup nat/Ni(n, x)/sup 58/Co. With the increase of threshold energy, however, the calculation underestimated the experiments, especially above 20 MeV. The reason for the disagreement can be attributed to the underestimation of the neutron yield in the tens of mega-electron-volt regions by the NMTC/JAERI code. (32 refs).

  9. Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate

    Energy Technology Data Exchange (ETDEWEB)

    Croft, Stephen [Oak Ridge National Laboratory (ORNL), One Bethel Valley Road, Oak Ridge, TN (United States); Burr, Tom [International Atomic Energy Agency (IAEA), Vienna (Austria); Favalli, Andrea [Los Alamos National Laboratory (LANL), MS E540, Los Alamos, NM 87545 (United States); Nicholson, Andrew [Oak Ridge National Laboratory (ORNL), One Bethel Valley Road, Oak Ridge, TN (United States)

    2016-03-01

    The declared linear density of {sup 238}U and {sup 235}U in fresh low enriched uranium light water reactor fuel assemblies can be verified for nuclear safeguards purposes using a neutron coincidence counter collar in passive and active mode, respectively. The active mode calibration of the Uranium Neutron Collar – Light water reactor fuel (UNCL) instrument is normally performed using a non-linear fitting technique. The fitting technique relates the measured neutron coincidence rate (the predictor) to the linear density of {sup 235}U (the response) in order to estimate model parameters of the nonlinear Padé equation, which traditionally is used to model the calibration data. Alternatively, following a simple data transformation, the fitting can also be performed using standard linear fitting methods. This paper compares performance of the nonlinear technique to the linear technique, using a range of possible error variance magnitudes in the measured neutron coincidence rate. We develop the required formalism and then apply the traditional (nonlinear) and alternative approaches (linear) to the same experimental and corresponding simulated representative datasets. We find that, in this context, because of the magnitude of the errors in the predictor, it is preferable not to transform to a linear model, and it is preferable not to adjust for the errors in the predictor when inferring the model parameters.

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

    Science.gov (United States)

    Sakurai, Y; Kobayashi, T; Kanda, K

    1994-12-01

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

  11. Probing the nuclear equation of state by heavy-ion reactions and neutron star properties

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, P.K.; Cassing, W.; Thoma, M.H. [Inst. fuer Theoretische Physik, Univ. Giessen (Germany)

    1998-06-01

    We discuss the nuclear equation of state (EOS) using a non-linear relativistic transport model. From the baryon flow for Ni + Ni as well as Au + Au systems we find that the strength of the vector potential has to be reduced at high density or at high relative momenta to describe the experimental flow data at 1-2 A GeV. We use the same dynamical model to calculate the nuclear EOS and then employ this EOS to neutron star structure calculations. We consider the core of the neutron star to be composed of neutrons with an admixture of protons, electrons, muons, sigmas and lambdas at zero temperature. We find that the nuclear equation of state is softer at high densities and hence the maximum mass and the radius of the neutron star are in the observable range of M {proportional_to} 1.7 M{sub s}un and R = 8 km, respectively. (orig.)

  12. Theoretical study on production of heavy neutron-rich isotopes around the N=126 shell closure in radioactive beam induced transfer reactions

    Directory of Open Access Journals (Sweden)

    Long Zhu

    2017-04-01

    Full Text Available In order to produce more unknown neutron-rich nuclei around N=126, the transfer reactions 136Xe + 198Pt, 136–144Xe + 208Pb, and 132Sn + 208Pb are investigated within the framework of the dinuclear system (DNS model. The influence of neutron excess of projectile on production cross sections of target-like products is studied through the reactions 136,144Xe + 208Pb. We find that the radioactive projectile 144Xe with much larger neutron excess is favorable to produce neutron-rich nuclei with charge number less than the target rather than produce transtarget nuclei. The incident energy dependence of yield distributions of fragments in the reaction 132Sn + 208Pb are also studied. The production cross sections of neutron-rich nuclei with Z=72–77 are predicted in the reactions 136–144Xe + 208Pb and 132Sn + 208Pb. It is noticed that the production cross sections of unknown neutron-rich nuclei in the reaction 144Xe + 208Pb are at least two orders of magnitude larger than those in the reaction 136Xe + 208Pb. The radioactive beam induced transfer reactions 139,144Xe + 208Pb, considering beam intensities proposed in SPIRAL2 (Production System of Radioactive Ion and Acceleration On-Line project as well, for production of neutron-rich nuclei around the N=126 shell closure are investigated for the first time. It is found that, in comparison to the stable beam 136Xe, the radioactive beam 144Xe shows great advantages for producing neutron-rich nuclei with N=126 and the advantages get more obvious for producing nuclei with less charge number.

  13. Neutron activation analysis of ceramic tiles and its component and radon exhalation rate

    Institute of Scientific and Technical Information of China (English)

    A. El-Shershaby; A. Sroor; F. Ahmed; A.S. Abdel-Haleem; Z. Abdel

    2004-01-01

    The concentrations of 20 trace elements in several ceramics tiles and ceramic composites used in Egypt were elementally analyzed by neutron activation analysis(NAA) technique. The samples and standard were irradiated with reactor for 4 h( in the Second The gamma-ray spectra obtained were measured for several times by means of the hyper pure germanium detection system( HPGe).Also a solid state nuclear track detector(SSNTD) CR-39, was used to measure the emanation rate of radon for these samples. The radium concentrations were found to vary from 0.39-3.59 ppm and the emanation rates were found to vary from (0.728-5.688) x 10-4The elemental analysis of the ceramic tiles and ceramic composites have a great importance in assigning the physical properties and in turn the quality of the material.

  14. Beta-decay rate and beta-delayed neutron emission probability of improved gross theory

    Science.gov (United States)

    Koura, Hiroyuki

    2014-09-01

    A theoretical study has been carried out on beta-decay rate and beta-delayed neutron emission probability. The gross theory of the beta decay is based on an idea of the sum rule of the beta-decay strength function, and has succeeded in describing beta-decay half-lives of nuclei overall nuclear mass region. The gross theory includes not only the allowed transition as the Fermi and the Gamow-Teller, but also the first-forbidden transition. In this work, some improvements are introduced as the nuclear shell correction on nuclear level densities and the nuclear deformation for nuclear strength functions, those effects were not included in the original gross theory. The shell energy and the nuclear deformation for unmeasured nuclei are adopted from the KTUY nuclear mass formula, which is based on the spherical-basis method. Considering the properties of the integrated Fermi function, we can roughly categorized energy region of excited-state of a daughter nucleus into three regions: a highly-excited energy region, which fully affect a delayed neutron probability, a middle energy region, which is estimated to contribute the decay heat, and a region neighboring the ground-state, which determines the beta-decay rate. Some results will be given in the presentation. A theoretical study has been carried out on beta-decay rate and beta-delayed neutron emission probability. The gross theory of the beta decay is based on an idea of the sum rule of the beta-decay strength function, and has succeeded in describing beta-decay half-lives of nuclei overall nuclear mass region. The gross theory includes not only the allowed transition as the Fermi and the Gamow-Teller, but also the first-forbidden transition. In this work, some improvements are introduced as the nuclear shell correction on nuclear level densities and the nuclear deformation for nuclear strength functions, those effects were not included in the original gross theory. The shell energy and the nuclear deformation for

  15. Different dose rate-dependent responses of human melanoma cells and fibroblasts to low dose fast neutrons.

    Science.gov (United States)

    Dionet, Claude; Müller-Barthélémy, Melanie; Marceau, Geoffroy; Denis, Jean-Marc; Averbeck, Dietrich; Gueulette, John; Sapin, Vincent; Pereira, Bruno; Tchirkov, Andrei; Chautard, Emmanuel; Verrelle, Pierre

    2016-09-01

    To analyze the dose rate influence in hyper-radiosensitivity (HRS) of human melanoma cells to very low doses of fast neutrons and to compare to the behaviour of normal human skin fibroblasts. We explored different neutron dose rates as well as possible implication of DNA double-strand breaks (DSB), apoptosis, and energy-provider adenosine-triphosphate (ATP) levels during HRS. HRS in melanoma cells appears only at a very low dose rate (VLDR), while a high dose rate (HDR) induces an initial cell-radioresistance (ICRR). HRS does not seem to be due either to DSB or to apoptosis. Both phenomena (HRS and ICRR) appear to be related to ATP availability for triggering cell repair. Fibroblast survival after neutron irradiation is also dose rate-dependent but without HRS. Melanoma cells or fibroblasts exert their own survival behaviour at very low doses of neutrons, suggesting that in some cases there is a differential between cancer and normal cells radiation responses. Only the survival of fibroblasts at HDR fits the linear no-threshold model. This new insight into human cell responses to very low doses of neutrons, concerns natural radiations, surroundings of accelerators, proton-therapy devices, flights at high altitude. Furthermore, ATP inhibitors could increase HRS during high-linear energy transfer (high-LET) irradiation.

  16. The functional role of protein dynamics in photosynthetic reaction centers investigated by elastic and quasielastic neutron scattering

    Directory of Open Access Journals (Sweden)

    Pieper Jörg

    2015-01-01

    Full Text Available This short review summarizes our current knowledge about the functional relevance of protein dynamics in photosynthetic reaction centers. In the case of Photosystem II membrane fragments, elastic and quasielastic neutron scattering experiments reveal a dynamical transition at about 240 K corresponding to the activation of picosecond molecular motions. Likewise, a “freezing” of molecular dynamics is observed upon dehydration. Intriguingly, these effects correlate with the pronounced temperature- and hydration-dependence of specific electron transfer steps in Photosystem II indicating that molecular dynamics is an indispensable prerequisite for its function. Thus, electron transfer in Photosystem II appears to be a prototypical example for a dynamics-function correlation. Finally, the laser-neutron pump-probe technique is shown to permit in-situ monitoring of molecular dynamics in specific functional states of a protein in real time.

  17. Proteomic analysis of cellular response induced by boron neutron capture reaction in human squamous cell carcinoma SAS cells.

    Science.gov (United States)

    Sato, Akira; Itoh, Tasuku; Imamichi, Shoji; Kikuhara, Sota; Fujimori, Hiroaki; Hirai, Takahisa; Saito, Soichiro; Sakurai, Yoshinori; Tanaka, Hiroki; Nakamura, Hiroyuki; Suzuki, Minoru; Murakami, Yasufumi; Baiseitov, Diaz; Berikkhanova, Kulzhan; Zhumadilov, Zhaxybay; Imahori, Yoshio; Itami, Jun; Ono, Koji; Masunaga, Shinichiro; Masutani, Mitsuko

    2015-12-01

    To understand the mechanism of cell death induced by boron neutron capture reaction (BNCR), we performed proteome analyses of human squamous tumor SAS cells after BNCR. Cells were irradiated with thermal neutron beam at KUR after incubation under boronophenylalanine (BPA)(+) and BPA(-) conditions. BNCR mainly induced typical apoptosis in SAS cells 24h post-irradiation. Proteomic analysis in SAS cells suggested that proteins functioning in endoplasmic reticulum, DNA repair, and RNA processing showed dynamic changes at early phase after BNCR and could be involved in the regulation of cellular response to BNCR. We found that the BNCR induces fragments of endoplasmic reticulum-localized lymphoid-restricted protein (LRMP). The fragmentation of LRMP was also observed in the rat tumor graft model 20 hours after BNCT treatment carried out at the National Nuclear Center of the Republic of Kazakhstan. These data suggest that dynamic changes of LRMP could be involved during cellular response to BNCR.

  18. Measurement of the (gamma,n) reaction rates of the nuclides 190Pt, 192Pt, and 198Pt in the astrophysical gamma-process

    CERN Document Server

    Vogt, K; Babilon, M; Enders, J; Hartmann, T; Hutter, C; Rauscher, T; Volz, S; Zilges, A

    2001-01-01

    The nucleosynthesis of heavy neutron-deficient nuclei in a stellar photon bath at the temperatures relevant for the astrophysical gamma process was investigated. In order to derive (gamma,n) cross sections and reaction rates, the stellar photon bath was simulated by the superposition of several bremsstrahlung spectra with different endpoint energies. As a first test for this method, the (gamma,n) reaction rates of the platinum isotopes 190Pt, 192Pt, and 198Pt were derived. The results are compared to other experimental data and theoretical calculations.

  19. High-frame rate, fast neutron imaging of two-phase flow in a thin rectangular channel

    CERN Document Server

    Zboray, R; Dangendorf, V; Stark, M; Tittelmeier, K; Cortesi, M; Adams, R

    2015-01-01

    We have demonstrated the feasibility of performing high-frame-rate, fast neutron radiography of air-water two-phase flows in a thin channel with rectangular cross section. The experiments have been carried out at the accelerator facility of the Physikalisch-Technische Bundesanstalt. A polychromatic, high-intensity fast neutron beam with average energy of 6 MeV was produced by 11.5 MeV deuterons hitting a thick Be target. Image sequences down to 10 millisecond exposure times were obtained using a fast-neutron imaging detector developed in the context of fast-neutron resonance imaging. Different two-phase flow regimes such as bubbly slug and churn flows have been examined. Two phase flow parameters like the volumetric gas fraction, bubble size and bubble velocities have been measured. The first results are promising, improvements for future experiments are also discussed.

  20. Study of single particle properties of neutron-rich Na isotopes on the "shore of the island of inversion" by means of neutron-transfer reactions

    CERN Multimedia

    Reiter, P; Blazhev, A A; Riisager, K; Bastin, B; Tengborn, E A; Kruecken, R; Voulot, D; Jeppesen, H B; Hadinia, B; Gernhaeuser, R A; Fynbo, H O U; Georgiev, G P; Habs, D; Fraile prieto, L M; Chapman, R; Nilsson, T; Diriken, J V J; Jenkins, D G; Kroell, T; Leske, J; Huyse, M L; Patronis, N

    We aim at the investigation of single particle properties of neutron-rich Na isotopes around the "shore of the island of inversion". As first experiment of this programme, we propose to study excited states in the isotope $^{29}$Na by a one-neutron transfer reaction with a $^{28}$Na beam at 3 MeV/u obtained from REX-ISOLDE impinging on a CD$_{2}$-target. The $\\gamma$-rays will be detected by the MINIBALL array and the particles by the T-REX array of segmented Si detectors. The main physics aims are to extract from the relative spectroscopic factors information on the configurations contributing to the wave functions of the populated states and, secondly, to identify and characterize negative parity states whose excitation energies reflect directly the N= 28 gap in this region. The results will be compared to recent shell model calculations involving new residual interactions. This will shed new light on the evolution of single particle structure and help to understand the underlying physics relevant for the f...

  1. MCNPX simulations of the silicon carbide semiconductor detector response to fast neutrons from D-T nuclear reaction

    Science.gov (United States)

    Sedlačková, Katarína; Šagátová, Andrea; Zat'ko, Bohumír; Nečas, Vladimír; Solar, Michael; Granja, Carlos

    2016-09-01

    Silicon Carbide (SiC) has been long recognized as a suitable semiconductor material for use in nuclear radiation detectors of high-energy charged particles, gamma rays, X-rays and neutrons. The nuclear interactions occurring in the semiconductor are complex and can be quantified using a Monte Carlo-based computer code. In this work, the MCNPX (Monte Carlo N-Particle eXtended) code was employed to support detector design and analysis. MCNPX is widely used to simulate interaction of radiation with matter and supports the transport of 34 particle types including heavy ions in broad energy ranges. The code also supports complex 3D geometries and both nuclear data tables and physics models. In our model, monoenergetic neutrons from D-T nuclear reaction were assumed as a source of fast neutrons. Their energy varied between 16 and 18.2 MeV, according to the accelerating voltage of the deuterons participating in D-T reaction. First, the simulations were used to calculate the optimum thickness of the reactive film composed of High Density PolyEthylene (HDPE), which converts neutral particles to charged particles and thusly enhancing detection efficiency. The dependency of the optimal thickness of the HDPE layer on the energy of the incident neutrons has been shown for the inspected energy range. Further, from the energy deposited by secondary charged particles and recoiled ions, the detector response was modeled and the effect of the conversion layer on detector response was demonstrated. The results from the simulations were compared with experimental data obtained for a detector covered by a 600 and 1300 μm thick conversion layer. Some limitations of the simulations using MCNPX code are also discussed.

  2. EURISOL-DS multi-MW target unit: Neutronics performance and shielding assessment, dose rate and material activation calculations for the MAFF configuration

    CERN Document Server

    Romanets, Y; Kadi, Y; Luis, R; Goncalves, I F; Tecchio, L; Kharoua, C; Vaz, P; Ene, D; David, J C; Rocca, R; Negoita, F

    2010-01-01

    One of the objectives of the EURISOL (EURopean Isotope Separation On-Line Radioactive Ion Beam) Design Study consisted of providing a safe and reliable facility layout and design for the following operational parameters and characteristics: (a) a 4 MW proton beam of 1 GeV energy impinging on a mercury target (the converter); (b) high neutron fluxes (similar to 3 x 10(16) neutrons/s) generated by spallation reactions of the protons impinging in the converter and (c) fission rate on fissile U-235 targets in excess of 10(15) fissions/s. In this work, the state-of-the-art Monte Carlo codes MCNPX (Pelowitz, 2005) and FLUKA (Vlachoudis, 2009; Ferrari et al., 2008) were used to characterize the neutronics performance and to perform the shielding assessment (Herrera-Martinez and Kadi, 2006; Cornell, 2003) of the EURISOLTarget Unit and to provide estimations of dose rate and activation of different components, in view of the radiation safety assessment of the facility. Dosimetry and activation calculations were perfor...

  3. Measurement of 232Th(n,2n)231Th reaction cross-sections at neutron energies of 14.1 MeV and 14.8 MeV using neutron activation method

    Institute of Scientific and Technical Information of China (English)

    兰长林; 解保林; 张凯; 彭猛; 方开洪

    2015-01-01

    In this study, the activation cross-sections were measured for 232Th(n,2n)231Th reactions at neutron ener-gies of 14.1 and 14.8 MeV, which were produced by a neutron generator through a T(d,n) 4He reaction. In-duced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. In the cross-section calculations, corrections were made regarding the effects of gamma-ray attenuation, dead-time, fluctuation of the neutron flux, and low energy neutrons. The mea-sured cross-sections were compared with the literature data, evaluation data (ENDF-B/VII.1, JENDL-4.0 and CENDL-3.1), and the results of the model calculation (TALYS1.6).

  4. Neutron angular distribution in (γ, n) reactions with linearly polarized γ-ray beam generated by laser Compton scattering

    Energy Technology Data Exchange (ETDEWEB)

    Horikawa, K.; Miyamoto, S.; Mochizuki, T.; Amano, S. [University of Hyogo, Hyogo 678-1205 (Japan); Li, D.; Imasaki, K.; Izawa, Y. [Institute for Laser Technology, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Ogata, K. [Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Chiba, S. [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Japan Atomic Energy Agency, Shirakata-Shirane 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); Hayakawa, T., E-mail: hayakawa.takehito@jaea.go.jp [Japan Atomic Energy Agency, Shirakata-Shirane 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan)

    2014-10-07

    In 1957, Agodi predicted that the neutron angular distribution in (γ, n) reactions with a 100% linearly polarized γ-ray beam for dipole excitation should be anisotropic and universally described by the simple function of a+b⋅cos⁡(2ϕ) at the polar angle θ=90°, where ϕ is the azimuthal angle. However, this prediction has not been experimentally confirmed in over half a century. We have verified experimentally this angular distribution in the (γ, n) reaction for {sup 197}Au, {sup 127}I, and natural Cu targets using linearly polarized laser Compton scattering γ-rays. The result suggests that the (γ{sup →}, n) reaction is a novel tool to study nuclear physics in the giant dipole resonance region.

  5. On the mechanism of effective chemical reactions with turbulent mixing of reactants and finite rate of molecular reactions

    Science.gov (United States)

    Vorotilin, V. P.

    2017-01-01

    A generalization of the theory of chemical transformation processes under turbulent mixing of reactants and arbitrary values of the rate of molecular reactions is presented that was previously developed for the variant of an instantaneous reaction [13]. The use of the features of instantaneous reactions when considering the general case, namely, the introduction of the concept of effective reaction for the reactant volumes and writing a closing conservation equation for these volumes, became possible due to the partition of the whole amount of reactants into "active" and "passive" classes; the reactants of the first class are not mixed and react by the mechanism of instantaneous reactions, while the reactants of the second class approach each other only through molecular diffusion, and therefore their contribution to the reaction process can be neglected. The physical mechanism of reaction for the limit regime of an ideal mixing reactor (IMR) is revealed and described. Although formally the reaction rate in this regime depends on the concentration of passive fractions of the reactants, according to the theory presented, the true (hidden) mechanism of the reaction is associated only with the reaction of the active fractions of the reactants with vanishingly small concentration in the volume of the reactor. It is shown that the rate constant of fast chemical reactions can be evaluated when the mixing intensity of reactants is much less than that needed to reach the mixing conditions in an IMR.

  6. The Experimental Study of Nuclear Astrophysics Reaction Rate of 93Zr(n,γ)94Zr

    Science.gov (United States)

    Gan, L.; Li, Z. H.; Su, J.; Yan, S. Q.; Guo, B.; Du, X. C.; Wu, Z. D.; Zeng, S.; Jin, S. J.; Wang, Y. B.; Bai, X. X.; Zhang, W. J.; Sun, H. B.; Li, E. T.

    The slow neutron capture (s-) process plays a very important role in the nucleosynthesis, which produces about half of the elements heavier than iron. 94Zr is mainly from 93Zr(n,γ)94Zr in the s-process, and the direct component of the 93Zr(n,γ)94Zr capture reaction can be derived from the neutron spectroscopic factor of 94Zr. As the existing neutron spectroscopic factors of 94Zr vary from each other up to 60%, a new work should be adopted to measure it exactly. In the present work, the angular distributions of 94Zr(13C,13C)94Zr, 94Zr(12C,12C)94Zr and 94Zr(12C,13C)93Zr were obtained using the highprecision Q3D magnetic spectrograph. In addition, distorted-wave Born approximation (DWBA) calculations of the transfer differential cross sections were performed. The calculated result displays a good agreement with the experiment data, and a value of 2.60±0.20 for the neutron spectroscopic factor of 94Zr was extracted, and the direct capture cross section versus neutron energy of 93Zr(n,γ)94Zr for the ground state of 94Zr was obtained too.

  7. Neutron capture cross section of $^{90}$Zr Bottleneck in the s-process reaction flow

    CERN Document Server

    Tagliente, G; Milazzo, P M; Moreau, C; Aerts, G; Abbondanno, U; Alvarez, H; Alvarez-Velarde, F; Andriamonje, Samuel A; Andrzejewski, J; Assimakopoulos, Panayiotis; Audouin, L; Badurek, G; Baumann, P; Bečvář, F; Berthoumieux, E; Bisterzo, S; Calviño, F; Calviani, M; Cano-Ott, D; Capote, R; Carrapiço, C; Cennini, P; Chepel, V; Chiaveri, Enrico; Colonna, N; Cortés, G; Couture, A; Cox, J; Dahlfors, M; David, S; Dillman, I; Domingo-Pardo, C; Dridi, W; Durán, I; Eleftheriadis, C; Embid-Segura, M; Ferrant, L; Ferrari, A; Ferreira-Marques, R; Furman, W; Gallino, R; Gonçalves, I; Gonzalez-Romero, E; Gramegna, F; Guerrero, C; Gunsing, F; Haas, B; Haight, R; Heil, M; Herrera-Martínez, A; Igashira, M; Jericha, E; Käppeler, F; Kadi, Y; Karadimos, D; Karamanis, D; Kerveno, M; Köhler, P; Kossionides, E; Krtička, M; Lamboudis, C; Leeb, H; Lindote, A; Lopes, I; Lozano, M; Lukic, S; Marganiec, J; Marrone, S; Martínez, T; Massimi, C; Mastinu, P; Mengoni, A; Mosconi, M; Neves, F; Oberhummer, Heinz; O'Brien, S; Pancin, J; Papachristodoulou, C; Papadopoulos, C; Paradela, C; Patronis, N; Pavlik, A; Pavlopoulos, P; Perrot, L; Pigni, M T; Plag, R; Plompen, A; Plukis, A; Poch, A; Praena, J; Pretel, C; Quesada, J; Rauscher, T; Reifarth, R; Rubbia, Carlo; Rudolf, G; Rullhusen, P; Salgado, J; Santos, J; Sarchiapone, L; Savvidis, I; Stéphan, C; Taín, J L; Tassan-Got, L; Tavora, L; Terlizzi, R; Vannini, G; Vaz, P; Ventura, A; Villamarín, D; Vincente, M, C; Vlachoudis, V; Vlastou, R; Voss, F; Walter, S; Wendler, H; Wiescher, M; Wisshak, K

    2008-01-01

    The neutron capture cross sections of the Zr isotopes have important implications in nuclear astrophysics and for reactor design. The small cross section of the neutron magic nucleus 90Zr, which accounts for more than 50% of natural zirconium represents one of the key isotopes for the stellar s-process, because it acts as a bottleneck in the neutron capture chain between the Fe seed and the heavier isotopes. The same element, Zr, also is an important component of the structural materials used in traditional and advanced nuclear reactors. The (n,γ) cross section has been measured at CERN, using the n_TOF spallation neutron source. In total, 45 resonances could be resolved in the neutron energy range below 70 keV, 10 being observed for the first time thanks to the high resolution and low backgrounds at n_TOF. On average, the Γγ widths obtained in resonance analyses with the R-matrix code SAMMY were 15% smaller than reported previously. By these results, the accuracy of the Maxwellian averaged cross section f...

  8. Characterization of the neutron irradiation system for use in the Low-Dose-Rate Irradiation Facility at Sandia National Laboratories.

    Energy Technology Data Exchange (ETDEWEB)

    Franco, Manuel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-08-01

    The objective of this work was to characterize the neutron irradiation system consisting of americium-241 beryllium (241AmBe) neutron sources placed in a polyethylene shielding for use at Sandia National Laboratories (SNL) Low Dose Rate Irradiation Facility (LDRIF). With a total activity of 0.3 TBq (9 Ci), the source consisted of three recycled 241AmBe sources of different activities that had been combined into a single source. The source in its polyethylene shielding will be used in neutron irradiation testing of components. The characterization of the source-shielding system was necessary to evaluate the radiation environment for future experiments. Characterization of the source was also necessary because the documentation for the three component sources and their relative alignment within the Special Form Capsule (SFC) was inadequate. The system consisting of the source and shielding was modeled using Monte Carlo N-Particle transport code (MCNP). The model was validated by benchmarking it against measurements using multiple techniques. To characterize the radiation fields over the full spatial geometry of the irradiation system, it was necessary to use a number of instruments of varying sensitivities. First, the computed photon radiography assisted in determining orientation of the component sources. With the capsule properly oriented inside the shielding, the neutron spectra were measured using a variety of techniques. A N-probe Microspec and a neutron Bubble Dosimeter Spectrometer (BDS) set were used to characterize the neutron spectra/field in several locations. In the third technique, neutron foil activation was used to ascertain the neutron spectra. A high purity germanium (HPGe) detector was used to characterize the photon spectrum. The experimentally measured spectra and the MCNP results compared well. Once the MCNP model was validated to an adequate level of confidence, parametric analyses was performed on the model to optimize for potential

  9. On the ambiguity of the reaction rate constants in multivariate curve resolution for reversible first-order reaction systems.

    Science.gov (United States)

    Schröder, Henning; Sawall, Mathias; Kubis, Christoph; Selent, Detlef; Hess, Dieter; Franke, Robert; Börner, Armin; Neymeyr, Klaus

    2016-07-13

    If for a chemical reaction with a known reaction mechanism the concentration profiles are accessible only for certain species, e.g. only for the main product, then often the reaction rate constants cannot uniquely be determined from the concentration data. This is a well-known fact which includes the so-called slow-fast ambiguity. This work combines the question of unique or non-unique reaction rate constants with factor analytic methods of chemometrics. The idea is to reduce the rotational ambiguity of pure component factorizations by considering only those concentration factors which are possible solutions of the kinetic equations for a properly adapted set of reaction rate constants. The resulting set of reaction rate constants corresponds to those solutions of the rate equations which appear as feasible factors in a pure component factorization. The new analysis of the ambiguity of reaction rate constants extends recent research activities on the Area of Feasible Solutions (AFS). The consistency with a given chemical reaction scheme is shown to be a valuable tool in order to reduce the AFS. The new methods are applied to model and experimental data.

  10. Molecule-based approach for computing chemical-reaction rates in upper atmosphere hypersonic flows.

    Energy Technology Data Exchange (ETDEWEB)

    Gallis, Michail A.; Bond, Ryan Bomar; Torczynski, John Robert

    2009-08-01

    This report summarizes the work completed during FY2009 for the LDRD project 09-1332 'Molecule-Based Approach for Computing Chemical-Reaction Rates in Upper-Atmosphere Hypersonic Flows'. The goal of this project was to apply a recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary nonequilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological non-equilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, the difference between the two models can exceed 10 orders of magnitude. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates. Extensions of the model to reactions typically found in combustion flows and ionizing reactions are also found to be in very good agreement with available measurements, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.

  11. Measurement of activation cross-sections for high-energy neutron-induced reactions of Bi and Pb

    Science.gov (United States)

    Zaman, Muhammad; Kim, Guinyun; Kim, Kwangsoo; Naik, Haladhara; Shahid, Muhammad; Lee, Manwoo

    2015-08-01

    The cross-sections for 209Bi(n, 4n)206Bi, 209Bi(n, 5n)205Bi, natPb(n, xn)204mPb, natPb(n, xn)203Pb, natPb(n, xn)202mPb,natPb(n, xn)201Pb, natPb(n, xn)200Pb, natPb(n, αxn)203Hg and natPb(n, p xn)202Tl reactions were determined at the Korean Institute of Radiological and Medical Sciences (KIRAMS), Korea in the neutron energy range of 15.2 to 37.2 MeV. The above cross-sections were obtained by using the activation and off-line γ-ray spectrometric technique. The quasi-monoenergetic neutron used for the above reactions are based on the 9Be(p, n) reaction. Simulations of the spectral flux from the Be target were done using the MCNPX program. The cross-sections were estimated with the TALYS 1.6 code using the default parameter. The data from the present work and literature were compared with the data from the EAF-2010 and the TENDL-2013 libraries, and calculated values of TALYS 1.6 code. It shows that appropriate level density model, the γ-ray strength function, and the spin cut-off parameter are needed to obtain a good agreement between experimental data and theoretical values from TALYS 1.6 code.

  12. Radioactive beam EXperiments at ISOLDE : Coulomb excitation and neutron transfer reactions of exotic nuclei.

    CERN Multimedia

    Kugler, E; Ratzinger, U; Wenander, F J C

    2002-01-01

    % IS347 \\\\ \\\\We propose to perform a pilot experiment to study very neutron rich (A<32) Na-Mg and (A<52) K-Ca isotopes in the region around the neutron shell closures of N=20 and N=28 after Coulomb excitation and neutron transfer, and to demonstrate highly efficient and cost-effective ways to bunch, charge-state breed and accelerate already existing mass-separated singly-charged radioactive ion beams. \\\\ \\\\To do this we plan to accelerate the ISOLDE beams up to 2~MeV/u by means of a novel acceleration scheme and to install an efficient $\\gamma$-ray array for low-multiplicity events around the target position.

  13. Neutron production rates by inverse-beta decay in fully ionized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Maiani, L.; Polosa, A.D.; Riquer, V. [Sapienza Universita di Roma, Dipartimento di Fisica (Italy); INFN, Rome (Italy)

    2014-04-15

    Recently we showed that the nuclear transmutation rates are largely overestimated in the Widom-Larsen theory of the so-called 'Low Energy Nuclear Reactions'. Here we show that unbound plasma electrons are even less likely to initiate nuclear transmutations. (orig.)

  14. A new monitor for routine thermal and epithermal neutron fluence rate monitoring in k{sub 0} INAA

    Energy Technology Data Exchange (ETDEWEB)

    Koster-Ammerlaan, M.J.J. [Delft University of Technology, Reactor Institute Delft, Mekelweg 15, 2629JB Delft (Netherlands)], E-mail: m.j.j.koster-ammerlaan@tudelft.nl; Bacchi, M.A. [Centro de Energia Nuclear na Agricultura, Universidade de Sao Paulo 13400-970, Piracicaba (Brazil); Bode, P. [Delft University of Technology, Reactor Institute Delft, Mekelweg 15, 2629JB Delft (Netherlands); Nadai Fernandes, E.A. de [Centro de Energia Nuclear na Agricultura, Universidade de Sao Paulo 13400-970, Piracicaba (Brazil)

    2008-12-15

    The Zr-Au set for monitoring the thermal and epithermal neutron fluence rate and the epithermal spectrum parameter {alpha} is not always practicable for routine application of INAA in well-thermalized facilities. An alternative set consisting of Cr, Au and Mo provides values for the thermal neutron fluence rate, f and {alpha} that are not significantly different from those found via the Zr-Au method and the Cd-covered Zr-method. The IRMM standard SMELS-II was analyzed using the (Au-Cr-Mo) monitor and a good agreement was obtained.

  15. The Radiative Strength Function Using the Neutron-Capture Reaction on 151,153Eu

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-10-04

    Radiative strength functions in {sup 152,154}Eu nuclei for {gamma}-ray energies below 6 MeV have been investigated. Neutron capture for incident neutron energies <1eV up to 100 keV has been measured for {sup 151,153}Eu targets. Properties of resonances in these two nuclei are examined. The measurements are compared to simulation of cascades performed with various models for the radiative strength function. Comparison between experimental data and simulation suggests an existence of the low-energy resonance in these two nuclei.

  16. Measurement of reaction cross-sections for 89Y at average neutron energies of 7.24-24.83 MeV

    Science.gov (United States)

    Zaman, Muhammad; Kim, Guinyun; Naik, Haladhara; Kim, Kwangsoo; Shahid, Muhammad

    2015-05-01

    We measured neutron-induced reaction cross-sections for 89Y(n,γ)90mY and 89Y(n,α)86Rb reactions with the average neutron energy region from 7.45 to 24.83 MeV by an activation and off-line γ-ray spectrometric technique using the MC-50 Cyclotron at Korea Institute of Radiological and Medical Sciences. The neutron-induced reaction cross-sections of 89Y as a function of neutron energy were taken from the TENDL-2013 library. The flux-weighted average cross-sections for 89Y(n,γ)90mY and 89Y(n,α)86Rb reactions were calculated from the TENDL-2013 values based on mono-energetic neutron and by using the neutron energy spectrum from MCNPX 2.6.0 code. The present results are compared with the flux-weighted values of TENDL-2013 and are found to be in good agreement

  17. Cross-section measurements for (n, 2n) reactions on stannum isotopes in the neutron energy range of 13.5 to 14.6 MeV

    Institute of Scientific and Technical Information of China (English)

    PU Zhong-Sheng; YAN Dong; MA Jun; DU Xiao-Fang; GUAN Qiu-Yun

    2008-01-01

    Cross-sections for (n, 2n) reactions have been measured on stannum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data are reported for the following reactions:112Sn(n, 2n)111Sn, 118Sn(n, 2n)117Sn and 124Sn(n, 2n)123mSn. The neutron fluences were determined using the monitor reaction 93Nb(n, 2n)92mNb or 27Al(n, α)24Na. The results of present work were compared with data published previously.

  18. Detection of fast neutrons from D-T nuclear reaction using a 4H-SiC radiation detector

    Science.gov (United States)

    Zatko, Bohumir; Sagatova, Andrea; Sedlackova, Katarina; Necas, Vladimir; Dubecky, Frantisek; Solar, Michael; Granja, Carlos

    2016-09-01

    The particle detector based on a high purity epitaxial layer of 4H-SiC exhibits promising properties in detection of various types of ionizing radiation. Due to the wide band gap of 4H-SiC semiconductor material, the detector can reliably operate at room and also elevated temperatures. In this work we focused on detection of fast neutrons generated the by D-T (deuterium-tritium) nuclear reaction. The epitaxial layer with a thickness of 105 μm was used as a detection part. A circular Schottky contact of a Au/Ni double layer was evaporated on both sides of the detector material. The detector structure was characterized by current-voltage and capacitance-voltage measurements, at first. The results show very low current density (SiC detector is caused by the elastic and inelastic scattering on the silicon or carbide component of the detector material. Another possibility that increases the detection efficiency is the use of a conversion layer. In our measurements, we glued a HDPE (high density polyethylene) conversion layer on the detector Schottky contact to transform fast neutrons to protons. Hydrogen atoms contained in the conversion layer have a high probability of interaction with neutrons through elastic scattering. Secondary generated protons flying to the detector can be easily detected. The detection properties of detectors with and without the HDPE conversion layer were compared.

  19. New Astrophysical Reaction Rate for the $^{12}\\textrm{C}(\\alpha,\\gamma)^{16}\\textrm{O}$ Reaction

    CERN Document Server

    An, Z D; Fan, G T; Li, Y J; Chen, Z P; Sun, Y Y

    2016-01-01

    A new astrophysical reaction rate for $^{12}$C($\\alpha,\\gamma$)$^{16}$O has been evaluated on the basis of a global R-matrix fitting to the available experimental data. The reaction rates of $^{12}$C($\\alpha,\\gamma$)$^{16}$O for stellar temperatures between 0.04 $\\leq$ $T_9$ $\\leq$ 10 are provided in a tabular form and by an analytical fitting expression. At $T_9$ = 0.2, the reaction rate is (7.83 $\\pm$ 0.35)$\\times10^{15}$ $\\rm{cm^3 mol^{-1} s^{-1}}$, where stellar helium burning occurs.

  20. Refit to numerically problematic UMIST reaction rate coefficients

    CERN Document Server

    Röllig, M

    2011-01-01

    Aims. Chemical databases such as the UMIST Database for Astrochemistry (UDFA) are indispensable in the numerical modeling of astrochemical networks. Several of the listed reactions in the UDFA have properties that are problematic in numerical computations: Some are parametrized in a way that leads to extremely divergent behavior for low kinetic temperatures. Other reactions possess multiple entries that are each valid in a different temperature regime, but have no smooth transition when switching from one to another. Numerically, this introduces many difficulties.We present corrected parametrizations for these sets of reactions in the UDFA06 database. Methods. From the tabulated parametrization in UDFA, we created artificial data points and used a Levenberg-Marquardt algorithm to find a set of improved fit parameters without divergent behavior for low temperatures. For reactions with multiple entries in the database that each possess a different temperature regime, we present one joint parametrization that is...

  1. 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)

  2. Analysis of the Nuclear Structure of Rhenium-186 Using Neutron-Induced Reactions

    Science.gov (United States)

    2015-03-26

    MeV. In one possible radioisotope power source design, the energetic electrons could produce scintillation light in a crystal that could in turn...scale deflection occurs at E = 4.0 MeV. Because of neutron damage to the semiconductor crystals, some detectors failed to produce usable spectra

  3. Approaching complete low-spin spectroscopy of 210Bi with a cold-neutron capture reaction

    Science.gov (United States)

    Cieplicka-Oryńczak, N.; Fornal, B.; Leoni, S.; Bazzacco, D.; Blanc, A.; Bocchi, G.; Bottoni, S.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Simpson, G.; Soldner, T.; Szpak, B.; Ur, C.; Urban, W.

    2016-05-01

    The low-spin structure of the 210Bi nucleus was investigated in the neutron capture experiment 209Bi(n ,γ )210Bi performed at ILL Grenoble at the PF1B cold-neutron facility. By using the EXILL multidetector array, consisting of 46 high-purity germanium crystals, and γ γ -coincidence technique, 64 primary γ rays were observed (40 new) and a total number of 70 discrete states (33 new) were located below the neutron binding energy in 210Bi. The analysis of the angular correlations of γ rays provided information about transitions multipolarities, which made it possible to confirm most of the previously known spin-parity assignments and helped establish new ones. The obtained experimental results were compared to shell-model calculations involving one-valence-proton, one-valence-neutron excitations outside the 208Pb core. It has been found that while up to the energy of ˜2 MeV each state observed in 210Bi has its calculated counterpart; at higher excitation energies some levels cannot be described by the valence particle couplings. These states may arise from couplings of valence particles to the 3- octupole phonon of the doubly magic 208Pb core and may serve as a testing ground for models which describe single particle-phonon excitations.

  4. Pop-It Beads to Introduce Catalysis of Reaction Rate and Substrate Depletion Effects

    Science.gov (United States)

    Gehret, Austin U.

    2017-01-01

    A kinesthetic classroom activity was designed to help students understand enzyme activity and catalysis of reaction rate. Students served the role of enzymes by manipulating Pop-It Beads as the catalytic event. This activity illuminates the relationship between reaction rate and reaction progress by allowing students to experience first-hand the…

  5. Apparent Rate Constant for Diffusion-Controlled Three molecular (catalytic) reaction

    OpenAIRE

    Burlatsky, S. F.; Moreau, M

    1996-01-01

    We present simple explicit estimates for the apparent reaction rate constant for three molecular reactions, which are important in catalysis. For small concentrations and $d> 1$, the apparent reaction rate constant depends only on the diffusion coefficients and sizes of the particles. For small concentrations and $d\\le 1$, it is also time -- dependent. For large concentrations, it gains the dependence on concentrations.

  6. Statistical Hauser-Feshbach theory with width fluctuation correction including direct reaction channels for neutron induced reaction at low energies

    CERN Document Server

    Kawano, T; Hilaire, S

    2016-01-01

    A model to calculate particle-induced reaction cross sections with statistical Hauser-Feshbach theory including direct reactions is given. The energy average of scattering matrix from the coupled-channels optical model is diagonalized by the transformation proposed by Engelbrecht and Weidenm\\"{u}ller. The ensemble average of $S$-matrix elements in the diagonalized channel space is approximated by a model of Moldauer [Phys.Rev.C {\\bf 12}, 744 (1975)] using newly parametrized channel degree-of-freedom $\

  7. A high-rate sup 1 sup 0 B-loaded liquid scintillation detector for parity-violation studies in neutron resonances

    CERN Document Server

    Yen Yi Fen; Bolton, R D; Crawford, B E; Delheij, P P J; Hart, G W; Haseyama, T; Frankle, C M; Iinuma, M; Knudson, J N; Masaike, A; Masuda, Y; Matsuda, Y; Mitchell, G E; Penttilae, S I; Roberson, N R; Seestrom, S J; Sharapov, E I; Shimizu, H M; Smith, D A; Stephenson, S L; Szymanski, J J; Yoo, S H; Yuan, V W

    2000-01-01

    We have developed a large-area sup 1 sup 0 B-loaded liquid scintillation detector for parity-violation studies in neutron resonances with high instantaneous neutron fluxes from the LANSCE short-pulse spallation source. The detector has an efficiency of 95%, 85% and 71% at neutron energies of 10, 100 and 1000 eV, respectively. The neutron mean capture time in the detector is (416+-5) ns. We describe the detector and the current-mode signal processing system, that can handle neutron rates up to 500 MHz.

  8. Evaluation of the neutron induced reactions on 235U from 2.25 keV up to 30 MeV

    Directory of Open Access Journals (Sweden)

    Trkov Andrej

    2017-01-01

    Full Text Available An evaluation of fast neutron induced reactions on 235U is performed in the 2.25 keV–30 MeV incident energy range with the code EMPIRE–3.2 Malta, combined with selected experimental data. The reaction model includes a dispersive optical model potential (RIPL 2408 that couples seven levels of the ground-state rotational band and a triple-humped fission barrier with absorption in the wells described within the optical model for fission. EGSM nuclear level densities are used in Hauser-Feshbach calculations of the compound-nuclear decay. The starting values for the model parameters are retrieved from the RIPL-3 data-base. Excellent agreement is achieved with available experimental data for neutron emission, neutron capture and fission, which gives confidence that the quantities for which there is no experimental information are also predicted accurately. In the fast neutron region of the evaluated file, the fission cross section is taken from Neutron Standards, and neutron capture includes fluctuations observed in recent experiments. Other channels are taken directly from model calculations. New evaluation is validated against ICSBEP criticality benchmarks with fast neutron spectra with excellent results.

  9. Reaction rate oscillations during catalytic CO oxidation: A brief overview

    Science.gov (United States)

    Tsotsis, T. T.; Sane, R. C.

    1987-04-01

    It is not the intent here to present a comprehensive review of the dynamic behavior of the catalytic oxidation of CO. This reaction is one of the most widely studied in the field of catalysis. A review paper by Engel and Ertl has examined the basic kinetic and mechanistic aspects, and a comprehensive paper by Razon and Schmitz was recently devoted to its dynamic behavior. Those interested in further study of the subject should consult these reviews and a number of general review papers on catalytic reaction dynamics. The goal is to present a brief overview of certain interesting aspects of the dynamic behavior of this reaction and to discuss a few questions and issues, which are still the subject of study and debate.

  10. "Depletion": A Game with Natural Rules for Teaching Reaction Rate Theory.

    Science.gov (United States)

    Olbris, Donald J.; Herzfeld, Judith

    2002-01-01

    Depletion is a game that reinforces central concepts of reaction rate theory through simulation. Presents the game with a set of follow-up questions suitable for either a quiz or discussion. Also describes student reaction to the game. (MM)

  11. Study of shell evolution in the Ni isotopes via one-neutron transfer reaction in $^{70}$Ni

    CERN Multimedia

    This proposal aims at the study of the single particle properties of the neutron-rich nickel isotopes, specifically of the $^{71}$Ni isotope via a $^{70}$Ni(d,p) $^{71}$Ni reaction. The $^{70}$Ni beam will be delivered by HIE-ISOLDE at 5.5 MeV/u onto a 1.0 mg/cm$^{2}$ CD$_{2}$ target. The protons produced in the (d,p) reaction will be detected with the T-REX silicon array either in singles or in coincidence with $\\gamma$- rays recorded by MINIBALL. The experimental results will be compared with large-scale shell-model calculations using effective interactions that involve large valence spaces for protons and neutrons, with excitations beyond the Z =28 and N=50 shell gap. This comparison will permit the study of the single-particle orbital d$_{5/2}$ that together with the quasi-SU3 partner g$_{9/2}$ gives rise to the collectivity in this region and has direct implications on the $^{78}$Ni.

  12. Dose distributions in a human head phantom for neutron capture therapy using moderated neutrons from the 2.5 MeV proton-7Li reaction or from fission of 235U

    Science.gov (United States)

    Tanaka, Kenichi; Kobayashi, Tooru; Sakurai, Yoshinori; Nakagawa, Yoshinobu; Endo, Satoru; Hoshi, Masaharu

    2001-10-01

    The feasibility of neutron capture therapy (NCT) using an accelerator-based neutron source of the 7Li(p,n) reaction produced by 2.5 MeV protons was investigated by comparing the neutron beam tailored by both the Hiroshima University radiological research accelerator (HIRRAC) and the heavy water neutron irradiation facility in the Kyoto University reactor (KUR-HWNIF) from the viewpoint of the contamination dose ratios of the fast neutrons and the gamma rays. These contamination ratios to the boron dose were estimated in a water phantom of 20 cm diameter and 20 cm length to simulate a human head, with experiments by the same techniques for NCT in KUR-HWNIF and/or the simulation calculations by the Monte Carlo N-particle transport code system version 4B (MCNP-4B). It was found that the 7Li(p,n) neutrons produced by 2.5 MeV protons combined with 20, 25 or 30 cm thick D2O moderators of 20 cm diameter could make irradiation fields for NCT with depth-dose characteristics similar to those from the epithermal neutron beam at the KUR-HWNIF.

  13. Dose distributions in a human head phantom for neutron capture therapy using moderated neutrons from the 2.5 MeV proton-{sup 7}Li reaction or from fission of {sup 235}U

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Kenichi [Department of Nuclear Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto (Japan); Kobayashi, Tooru; Sakurai, Yoshinori [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka (Japan); Nakagawa, Yoshinobu [National Kagawa Children' s Hospital, Zentsuji-cho, Zentsuji, Kagawa (Japan); Endo, Satoru [Department of Applied Nuclear Physics, Hiroshima University, Kagamiyama, Higashi-Hiroshima, Hiroshima (Japan); Hoshi, Masaharu [Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi, Minami-ku, Hiroshima (Japan)

    2001-10-01

    The feasibility of neutron capture therapy (NCT) using an accelerator-based neutron source of the {sup 7}Li(p,n) reaction produced by 2.5 MeV protons was investigated by comparing the neutron beam tailored by both the Hiroshima University radiological research accelerator (HIRRAC) and the heavy water neutron irradiation facility in the Kyoto University reactor (KUR-HWNIF) from the viewpoint of the contamination dose ratios of the fast neutrons and the gamma rays. These contamination ratios to the boron dose were estimated in a water phantom of 20 cm diameter and 20 cm length to simulate a human head, with experiments by the same techniques for NCT in KUR-HWNIF and/or the simulation calculations by the Monte Carlo N-particle transport code system version 4B (MCNP-4B). It was found that the {sup 7}Li(p,n) neutrons produced by 2.5 MeV protons combined with 20, 25 or 30 cm thick D{sub 2}O moderators of 20 cm diameter could make irradiation fields for NCT with depth-dose characteristics similar to those from the epithermal neutron beam at the KUR-HWNIF. (author)

  14. Radiosensitivity of pimonidazole-unlabelled intratumour quiescent cell population to γ-rays, accelerated carbon ion beams and boron neutron capture reaction

    Science.gov (United States)

    Masunaga, S; Sakurai, Y; Tanaka, H; Hirayama, R; Matsumoto, Y; Uzawa, A; Suzuki, M; Kondo, N; Narabayashi, M; Maruhashi, A; Ono, K

    2013-01-01

    Objective To detect the radiosensitivity of intratumour quiescent (Q) cells unlabelled with pimonidazole to accelerated carbon ion beams and the boron neutron capture reaction (BNCR). Methods EL4 tumour-bearing C57BL/J mice received 5-bromo-29-deoxyuridine (BrdU) continuously to label all intratumour proliferating (P) cells. After the administration of pimonidazole, tumours were irradiated with c-rays, accelerated carbon ion beams or reactor neutron beams with the prior administration of a 10B-carrier. Responses of intratumour Q and total (P+Q) cell populations were assessed based on frequencies of micronucleation and apoptosis using immunofluorescence staining for BrdU. The response of pimonidazole-unlabelled tumour cells was assessed by means of apoptosis frequency using immunofluorescence staining for pimonidazole. Results Following c-ray irradiation, the pimonidazole-unlabelled tumour cell fraction showed significantly enhanced radiosensitivity compared with the whole tumour cell fraction, more remarkably in the Q than total cell populations. However, a significantly greater decrease in radiosensitivity in the pimonidazole-unlabelled cell fraction, evaluated using a delayed assay or a decrease in radiation dose rate, was more clearly observed among the Q than total cells. These changes in radiosensitivity were suppressed following carbon ion beam and neutron beam-only irradiaton. In the BNCR, the use of a 10B-carrier, especially L-para-boronophenylalanine-10B, enhanced the sensitivity of the pimonidazole-unlabelled cells more clearly in the Q than total cells. Conclusion The radiosensitivity of the pimonidazole-unlabelled cell fraction depends on the quality of radiation delivered and characteristics of the 10B-carrier used in the BNCR. Advances in knowledge The pimonidazole-unlabelled subfraction of Q tumour cells may be a critical target in tumour control. PMID:23255546

  15. Radiosensitivity of pimonidazole-unlabelled intratumour quiescent cell population to γ-rays, accelerated carbon ion beams and boron neutron capture reaction.

    Science.gov (United States)

    Masunaga, S; Sakurai, Y; Tanaka, H; Hirayama, R; Matsumoto, Y; Uzawa, A; Suzuki, M; Kondo, N; Narabayashi, M; Maruhashi, A; Ono, K

    2013-01-01

    To detect the radiosensitivity of intratumour quiescent (Q) cells unlabelled with pimonidazole to accelerated carbon ion beams and the boron neutron capture reaction (BNCR). EL4 tumour-bearing C57BL/J mice received 5-bromo-2'-deoxyuridine (BrdU) continuously to label all intratumour proliferating (P) cells. After the administration of pimonidazole, tumours were irradiated with γ-rays, accelerated carbon ion beams or reactor neutron beams with the prior administration of a (10)B-carrier. Responses of intratumour Q and total (P+Q) cell populations were assessed based on frequencies of micronucleation and apoptosis using immunofluorescence staining for BrdU. The response of pimonidazole-unlabelled tumour cells was assessed by means of apoptosis frequency using immunofluorescence staining for pimonidazole. Following γ-ray irradiation, the pimonidazole-unlabelled tumour cell fraction showed significantly enhanced radiosensitivity compared with the whole tumour cell fraction, more remarkably in the Q than total cell populations. However, a significantly greater decrease in radiosensitivity in the pimonidazole-unlabelled cell fraction, evaluated using a delayed assay or a decrease in radiation dose rate, was more clearly observed among the Q than total cells. These changes in radiosensitivity were suppressed following carbon ion beam and neutron beam-only irradiaton. In the BNCR, the use of a (10)B-carrier, especially L-para-boronophenylalanine-(10)B, enhanced the sensitivity of the pimonidazole-unlabelled cells more clearly in the Q than total cells. The radiosensitivity of the pimonidazole-unlabelled cell fraction depends on the quality of radiation delivered and characteristics of the (10)B-carrier used in the BNCR. The pimonidazole-unlabelled subfraction of Q tumour cells may be a critical target in tumour control.

  16. Measured thermal and fast neutron fluence rates for ATF-1 holders during ATR cycle 158B/159A

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Larry Don [Idaho National Lab. (INL), Idaho Falls, ID (United States); Miller, David Torbet [Idaho National Lab. (INL), Idaho Falls, ID (United States); Walker, Billy Justin [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-11-01

    This report contains the thermal (2200 m/s) and fast (E>1MeV) neutron fluence rate data for the ATF-1 holders located in core for ATR Cycle 158B/159A which were measured by the Radiation Measurements Laboratory (RML).

  17. Quick and Easy Rate Equations for Multistep Reactions

    Science.gov (United States)

    Savage, Phillip E.

    2008-01-01

    Students rarely see closed-form analytical rate equations derived from underlying chemical mechanisms that contain more than a few steps unless restrictive simplifying assumptions (e.g., existence of a rate-determining step) are made. Yet, work published decades ago allows closed-form analytical rate equations to be written quickly and easily for…

  18. Classical reaction probabilities, cross sections and rate constants for the O( 1D) + H2 → OH + H reaction

    Science.gov (United States)

    Alexander, A. J.; Aoiz, F. J.; Bañares, L.; Brouard, M.; Herrero, V. J.; Simons, J. P.

    1997-10-01

    Reaction probabilitiers total reaction cross sections as a function of collision energy, and rate constants have been calculated using the quasi-classical trajectory (QCT) method for the O( 1D) + H 2 reaction on several ab initio potential energy surfaces (PES), including the recent one by Ho, Hollebeck, Rabitz, Harding and Schatz. Detailed QCT results on the Schinke and Lester PES are compared with recent time-dependent wavepacket calculations on the same PES, showing good agreement. The QCT thermal rate constants calculated on the PES of Ho et al. are in better accord with the experimental determinations than those calculated on the Schinke-Lester PES.

  19. Modeled Neutron Induced Nuclear Reaction Cross Sections for Radiochemsitry in the region of Thulium, Lutetium, and Tantalum I. Results of Built in Spherical Symmetry in a Deformed Region

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, R. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-09-06

    We have developed a set of modeled nuclear reaction cross sections for use in radiochemical diagnostics. Systematics for the input parameters required by the Hauser-Feshbach statistical model were developed and used to calculate neutron induced nuclear reaction cross sections for targets ranging from Terbium (Z = 65) to Rhenium (Z = 75). Of particular interest are the cross sections on Tm, Lu, and Ta including reactions on isomeric targets.

  20. Asymmetric Neutrino Reaction in Magnetized Proto-Neutron Stars in Fully Relativistic Approach

    Directory of Open Access Journals (Sweden)

    Yasutake Nobutoshi

    2012-02-01

    Full Text Available We calculate asymmetric neutrino absorption and scattering cross sections on hot and dense magnetized neutron-star matter including hyperons in fully relativistic mean-field theory. The absorption/scattering cross sections are suppressed/enhanced incoherently in the direction of the magnetic field B = Bẑ. The asymmetry is 2–4% at the matter density ρ0 ≤ ρB ≤ 3ρ0 and temperature T ≤ 40MeV for B = 2 × 1017G. Then we solve the Boltzmann equation for the neutrino transport in 1D attenuation approximation, and get the result that the kick velocity becomes about 300 km/s for the proto-neutron star with 168 solar mass at T = 20MeV.

  1. Optimal moderator materials at various proton energies considering photon dose rate after irradiation for an accelerator-driven ⁹Be(p, n) boron neutron capture therapy neutron source.

    Science.gov (United States)

    Hashimoto, Y; Hiraga, F; Kiyanagi, Y

    2015-12-01

    We evaluated the accelerator beam power and the neutron-induced radioactivity of (9)Be(p, n) boron neutron capture therapy (BNCT) neutron sources having a MgF2, CaF2, or AlF3 moderator and driven by protons with energy from 8 MeV to 30 MeV. The optimal moderator materials were found to be MgF2 for proton energies less than 10 MeV because of lower required accelerator beam power and CaF2 for higher proton energies because of lower photon dose rate at the treatment position after neutron irradiation.

  2. Dependence of neutron rate production with accelerator beam profile and energy range in an ADS-TRIGA RC1 reactor

    Energy Technology Data Exchange (ETDEWEB)

    Firoozabadi, M.M.; Karimi, J. [Birjand Univ. (Iran, Islamic Republic of). Dept. of Physics; Zangian, M. [Shahid Beheshti Univ., Tehran (Iran, Islamic Republic of). Nuclear Engineering Dept.

    2016-12-15

    Lead, mercury, tantalum and tungsten were used as target material for calculation of spallation processes in an ADS-TRIGA RC1 reactor. The results show that tungsten has the highest neutron production rate. Therefore it was selected as target material for further calculations. The sensitivity of neutron parameters of the ADS reactor core relative to a change of beam profile and proton energy was determined. The core assembly and parameters of the TRIGA RC1 demonstration facility were used for the calculation model. By changing the proton energy from 115 to 1 400 MeV by using the intra-nuclear cascade model of Bertini (INC-Bertini), the quantity of the relative difference in % for energy gain (G) and spallation neutron yield (Y{sub n/p}), increases to 289.99 % and 5199.15 % respectively. These changes also reduce the amount of relative difference for the proton beam current (I{sub p}) and accelerator power (P{sub acc}), 99.81 % and 81.28 % respectively. In addition, the use of a Gaussian distribution instead of a uniform distribution in the accelerator beam profile increases the quantity of relative difference for energy gain (G), net neutron multiplication (M) and spallation neutron yield (Y{sub n/p}), up to 4.93 %, 4.9 % and 5.55 % respectively.

  3. Rate constants of reactions of {kappa}-carrageenan with hydrated electron and hydroxyl radical

    Energy Technology Data Exchange (ETDEWEB)

    Abad, L.V. [Nuclear Professional School, School of Engineering Laboratory, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188 (Japan); Philippine Nuclear Research Institute, Commonwealth Avenue, Diliman, Quezon City (Philippines)], E-mail: lvabad@pnri.dost.gov.ph; Saiki, S.; Kudo, H.; Muroya, Y.; Katsumura, Y. [Nuclear Professional School, School of Engineering Laboratory, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188 (Japan); Rosa, A.M. de la [Philippine Nuclear Research Institute, Commonwealth Avenue, Diliman, Quezon City (Philippines)

    2007-12-15

    The rate constants for the reactions of {kappa}-carrageenan with hydrated electron and hydroxyl radical was investigated by pulse radiolysis and laser photolysis. The kinetics of the reaction of hydrated electron indicates no seeming reaction with {kappa}-carrageenan. On the other hand, hydroxyl radical reacts very rapidly with {kappa}-carrageenan at a rate constant of approximately 1.2 x 10{sup 9} M{sup -1} s{sup -1}. This rate constant varies with pH.

  4. for the inference of Furan combustion reaction rate

    KAUST Repository

    Long, Quan

    2016-01-06

    We carry out the design of experiments for the identification of the reaction parameters in Furan combustion. The lacks of information on the true value of the control parameters, specifically, the initial temperature and the initial TBHP concentration, are considered in the design procedure by errors-invariables models. We use two types of observables. The first is a scaler observable, i.e., half decay time of the [TBHP]. The second is the time history of the concentration.

  5. 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...

  6. Calculations to support JET neutron yield calibration: Modelling of neutron emission from a compact DT neutron generator

    Science.gov (United States)

    Čufar, Aljaž; Batistoni, Paola; Conroy, Sean; Ghani, Zamir; Lengar, Igor; Milocco, Alberto; Packer, Lee; Pillon, Mario; Popovichev, Sergey; Snoj, Luka

    2017-03-01

    At the Joint European Torus (JET) the ex-vessel fission chambers and in-vessel activation detectors are used as the neutron production rate and neutron yield monitors respectively. In order to ensure that these detectors produce accurate measurements they need to be experimentally calibrated. A new calibration of neutron detectors to 14 MeV neutrons, resulting from deuterium-tritium (DT) plasmas, is planned at JET using a compact accelerator based neutron generator (NG) in which a D/T beam impinges on a solid target containing T/D, producing neutrons by DT fusion reactions. This paper presents the analysis that was performed to model the neutron source characteristics in terms of energy spectrum, angle-energy distribution and the effect of the neutron generator geometry. Different codes capable of simulating the accelerator based DT neutron sources are compared and sensitivities to uncertainties in the generator's internal structure analysed. The analysis was performed to support preparation to the experimental measurements performed to characterize the NG as a calibration source. Further extensive neutronics analyses, performed with this model of the NG, will be needed to support the neutron calibration experiments and take into account various differences between the calibration experiment and experiments using the plasma as a source of neutrons.

  7. Collective plasma corrections to thermonuclear reactions rates in dense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Tsytovich, V.N. [General Physics Institute, Moscow (Russian Federation)

    2002-01-01

    General kinetic equations for nuclear reaction in dense plasmas are obtained. They take into account the first order collective plasma effects. Together with previously known corrections proportional to Z{sub i}Z{sub j}, the product of the charges Z{sub i} and Z{sub j} of two interacting nuclei, it is shown that there exist corrections proportional to the squares Z{sub i}{sup 2} and Z{sub j}{sup 2} of the charges. It is shown that the Salpeter's [1] correction due to the plasma screening of the interaction potential is at least r/d smaller (r is the nuclei size and d is Debye screening length) than previously thought and is zero in the approximation when the terms of the order r/d are neglected. But the correlation effects in the first approximation in the parameter 1/N{sub d} (where N{sub d} is the number of particle in the Debye sphere) give corrections which often coincide with the first order Salpeter's corrections (found by expansion in another small parameter, the ratio of thermal energy to Gamov's energy). The correlation corrections are {proportional_to} Z{sub i}Z{sub j}, have a different physical meaning than the corrections [1], can have a different sign and are present for reactions where the Salpeter's corrections are zero. Previously in astrophysical applications it was widely used the interpolation formulas between weak and strong Salpeter's screening corrections. Since the correlation correction take place the previously known Salpeter's corrections and the strong correlation corrections is difficult to describe analytically, the interpolation formulas between the weak and strong correlations cannot be yet found. A new type of corrections are found here which are proportional to the square of the charges. They are due to collective change in electrostatic self-energy of the plasma system during the nuclear reactions. The latter corrections are found by taking into account the changes of plasma particle fluctuations by

  8. Multi-path variational transition state theory for chemical reaction rates of complex polyatomic species: ethanol + OH reactions.

    Science.gov (United States)

    Zheng, Jingjing; Truhlar, Donald G

    2012-01-01

    Complex molecules often have many structures (conformations) of the reactants and the transition states, and these structures may be connected by coupled-mode torsions and pseudorotations; some but not all structures may have hydrogen bonds in the transition state or reagents. A quantitative theory of the reaction rates of complex molecules must take account of these structures, their coupled-mode nature, their qualitatively different character, and the possibility of merging reaction paths at high temperature. We have recently developed a coupled-mode theory called multi-structural variational transition state theory (MS-VTST) and an extension, called multi-path variational transition state theory (MP-VTST), that includes a treatment of the differences in the multi-dimensional tunneling paths and their contributions to the reaction rate. The MP-VTST method was presented for unimolecular reactions in the original paper and has now been extended to bimolecular reactions. The MS-VTST and MP-VTST formulations of variational transition state theory include multi-faceted configuration-space dividing surfaces to define the variational transition state. They occupy an intermediate position between single-conformation variational transition state theory (VTST), which has been used successfully for small molecules, and ensemble-averaged variational transition state theory (EA-VTST), which has been used successfully for enzyme kinetics. The theories are illustrated and compared here by application to three thermal rate constants for reactions of ethanol with hydroxyl radical--reactions with 4, 6, and 14 saddle points.

  9. Why does neutron transfer play different roles in sub-barrier fusion reactions $^{32}$S+$^{94,96}$Zr and $^{40}$Ca+$^{94,96}$Zr?

    CERN Document Server

    Sargsyan, V V; Antonenko, N V; Scheid, W; Zhang, H Q

    2014-01-01

    The sub-barrier capture (fusion) reactions $^{32}$S+$^{90,94,96}$Zr, $^{36}$S+$^{90,96}$Zr, $^{40}$Ca+$^{90,94,96}$Zr, and $^{48}$Ca+$^{90,96}$Zr with positive and negative $Q$-values for neutron transfer are studied within the quantum diffusion approach and the universal fusion function representation. For these systems, the s-wave capture probabilities are extracted from the experimental excitation functions and are also analyzed. Different effects of the positive $Q_{xn}$-value neutron transfer in the fusion enhancement are revealed in the relatively close reactions $^{32}$S+$^{94,96}$Zr and $^{40}$Ca+$^{94,96}$Zr.

  10. Production of neutron-rich isotopes by cold fragmentation in the reaction {sup 197}Au + Be at 950 A MeV

    Energy Technology Data Exchange (ETDEWEB)

    Benlliure, J.; Pereira, J. [Universidad de Santiago de Compostela (Spain)]|[Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Schmidt, K.H.; Cortina-Gil, D.; Enqvist, T.; Heinz, A.; Junghans, A.R. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany); Farget, F. [Institut de Physique Nucleaire, 91 - Orsay (France); Taieb, J. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany)]|[Institut de Physique Nucleaire, 91 - Orsay (France)

    1999-09-01

    The production cross sections and longitudinal-momentum distributions of very neutron-rich isotopes have been investigated in the fragmentation of a 950 A MeV {sup 179}Au beam in a beryllium target. Seven new isotopes ({sup 193}Re, {sup 194}Re, {sup 191}W, {sup 192}W, {sup 189}Ta, {sup 187}Hf and {sup 188}Hf) and the five-proton-removal channel were observed for the first time. The reaction mechanism leading to the formation of these very neutron-rich isotopes is explained in terms of the cold-fragmentation process. An analytical model describing this reaction mechanism is presented. (orig.)

  11. Neutron Star-Black Hole Coalescence Rate Inferred from Macronova Observations

    Science.gov (United States)

    Li, Xiang; Hu, Yi-Ming; Jin, Zhi-Ping; Fan, Yi-Zhong; Wei, Da-Ming

    2017-08-01

    Neutron star-black hole (NS-BH) coalescences are widely believed to be promising gravitational-wave sources in the era of advanced detectors of LIGO/Virgo, but the rate of this population is highly uncertain due to the lack of direct detection of such binaries. There is growing evidence for the connection between the observed three luminous macronova (also known as kilonova) events and NS-BH mergers. In this work, we propose, for the first time based on such a link, a fiducial lower limit of NS-BH coalescence rate density {{ R }}{nsbh} ≈ {18.8}-8.6+12.5 {{Gpc}}-3 {{yr}}-1 {({θ }{{j}}/0.1{rad})}-2, where {θ }{{j}} is the typical half-opening angle of the GRB ejecta. After marginalizing over distributions of black hole masses and spins, we find a rate density {{ R }}{nsbh}≥slant {10}2 {{Gpc}}-3 {{yr}}-1, depending upon the equation of state (EoS) of NS material and the properties of the NS-BH system. With the O1 non-observation by advanced LIGO, we show a preference for NS-BH systems with a stiffer NS EoS and a larger contribution from low-mass/high-spin BHs. Our estimate predicts the first detection of an NS-BH system can be as early as the late O2 run or the early O3 run. We expect that future multi-messenger observations can much better constrain NS-BH systems’ properties.

  12. Compositional variability across Mercury's surface revealed by MESSENGER measurements of variations in thermal neutron count rates

    Science.gov (United States)

    Peplowski, P. N.; Lawrence, D. J.; Goldsten, J. O.; Nittler, L. R.; Solomon, S. C.

    2013-12-01

    Measurements by MESSENGER's Gamma-Ray and Neutron Spectrometer (GRNS) have revealed variations in the flux of thermal neutrons across Mercury's northern hemisphere. These variations are interpreted to originate from spatial variations in surface elemental composition. In particular, the measurements are sensitive to the near-surface abundances of elements that absorb thermal neutrons, including major rock-forming elements such as Fe and Ti, minor elements such as Mn and Cl, and rare-earth elements such as Gd and Sm. We have constructed a map of thermal neutron variability across the surface and compared it with known variations in elemental composition and with the distribution of geologic units. Development of the map included the derivation of the macroscopic thermal neutron absorption cross section across the surface, a quantity whose value and variability provides useful constraints on the formation and geochemical evolution of Mercury's crust. Finally, by combining the thermal neutron measurements with previously reported elemental measurements from the GRNS and MESSENGER's X-Ray Spectrometer, we have derived constraints on the abundances of neutron-absorbing elements, including previously unreported limits for some minor and rare-earth elements.

  13. Neutron star-black hole coalescence rate inferred from macronova/kilonova observations

    CERN Document Server

    Li, Xiang; Jin, Zhi-Ping; Fan, Yi-Zhong; Wei, Da-Ming

    2016-01-01

    Neutron star$-$black hole (NS$-$BH) coalescences are widely believed to be promising gravitational wave sources in the era of advanced detectors of LIGO/Virgo but such binaries have never been directly detected yet. Evidence for NS$-$BH coalescences have been suggested in short and hybrid GRB observations, which are examined critically. Based on the suggested connection between the observed macronovae/kilonovae events and NS$-$BH coalescences, we get a fiducial lower limit of NS$-$BH coalescence rate density ${\\cal R}_{\\rm nsbh} \\approx 18.8^{+12.5}_{-8.6} ~{\\rm Gpc^{-3}~ yr^{-1}~ (\\theta_j/0.1~{\\rm rad})^{-2}}$, where $\\theta_{\\rm j}$ is the typical half-opening angle of the GRB ejecta. The real value of ${\\cal R}_{\\rm nsbh}$ is likely at least $\\sim {\\rm a~few}$ times larger, depending upon the equation of state of NS material and the properties of the NS$-$BH system, such as the mass and spin distribution of the black hole. If the link between macronovae/kilonovae and NS$-$BH coalescence is valid, one can ...

  14. Exploration of Spin-down Rate of Neutron Star in High Mass X-ray Binaries

    CERN Document Server

    Dai, Hai-Lang; Li, Xiang-Dong

    2016-01-01

    We use the evolutionary population synthesis method to investigate the statistical properties of the wind-fed neutron star (NS) compact ($P_{\\rm orb}<10$ days) high-mass X-ray binaries (HMXBs) in our Galaxy, based on different spin-down models. We find that the spin-down rate in the supersonic propeller phase given \\textbf{by assuming that the surrounding material is treated as forming a quasi-static atmosphere} or \\textbf{by assuming that the characteristic velocity of matter and the typical Alfv$\\acute{e}$n velocity of material in the magnetospheric boundary layer are comparable to the sound speed in the external medium} is too low to produce the observed number of compact HMXBs. We also find that the models suggested \\textbf{by assuming that the infalling material is ejected with the corotation velocity at the magnetospheric radius when the magnetospheric radius is larger than the corotation radius} and \\textbf{by simple integration of the magnetic torque over the magnetosphere} with a larger spin-down ...

  15. The CIELO Collaboration: Progress in International Evaluations of Neutron Reactions on Oxygen, Iron, Uranium and Plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Chadwick, M. B.; Capote, R.; Trkov, A.; Kahler, A. C.; Herman, M. W.; Brown, D. A.; Hale, G. M.; Pigni, M.; Dunn, M.; Leal, L.; Plompen, A.; Schillebeecks, P.; Hambsch, F. -J.; Kawano, T.; Talou, P.; Jandel, M.; Mosby, S.; Lestone, J.; Neudecker, D.; Rising, M.; Paris, M.; Nobre, G. P. A.; Arcilla, R.; Kopecky, S.; Giorginis, G.; Cabellos, O.; Hill, I.; Dupont, E.; Danon, Y.; Jing, Q.; Zhigang, G.; Tingjin, L.; Hanlin, L.; Xichao, R.; Haicheng, W.; Sin, M.; Bauge, E.; Romain, P.; Morillon, B.; Salvatores, M.; Jacqmin, R.; Bouland, O.; De Saint Jean, C.; Pronyaev, V. G.; Ignatyuk, A.; Yokoyama, K.; Ishikawa, M.; Fukahori, T.; Iwamoto, N.; Iwamoto, O.; Kuneada, S.; Lubitz, C. R.; Palmiotti, G.; Kodeli, I.; Kiedrowski, B.; Roubtsov, D.; Thompson, I.; Quaglioni, S.; Kim, H. I.; KLee, Y. O.; Koning, A. J.; Carlson, A.; Fischer, U.

    2016-11-01

    The CIELO collaboration has studied neutron cross sections on nuclides that significantly impact criticality in nuclear technologies - 16O, 56Fe, 235,8U and 239Pu - with the aim of reducing uncertainties and resolving previous discrepancies in our understanding. This multi-laboratory pilot project, coordinated via the OECD/NEA Working Party on Evaluation Cooperation (WPEC) Subgroup 40 with support also from the IAEA, has motivated experimental and theoretical work and led to suites of new evaluated libraries that accurately reflect measured data and also perform well in integral simulations of criticality.

  16. 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...

  17. Improvement of dose distribution in phantom by using epithermal neutron source based on the Be(p,n) reaction using a 30 MeV proton cyclotron accelerator.

    Science.gov (United States)

    Tanaka, H; Sakurai, Y; Suzuki, M; Takata, T; Masunaga, S; Kinashi, Y; Kashino, G; Liu, Y; Mitsumoto, T; Yajima, S; Tsutsui, H; Takada, M; Maruhashi, A; Ono, K

    2009-07-01

    In order to generate epithermal neutrons for boron neutron capture therapy (BNCT), we proposed the method of filtering and moderating fast neutrons, which are emitted from the reaction between a beryllium target and 30 MeV protons accelerated by a cyclotron, using an optimum moderator system composed of iron, lead, aluminum, calcium fluoride, and enriched (6)LiF ceramic filter. At present, the epithermal-neutron source is under construction since June 2008 at Kyoto University Research Reactor Institute. This system consists of a cyclotron to supply a proton beam of about 1 mA at 30 MeV, a beam transport system, a beam scanner system for heat reduction on the beryllium target, a target cooling system, a beam shaping assembly, and an irradiation bed for patients. In this article, an overview of the cyclotron-based neutron source (CBNS) and the properties of the treatment neutron beam optimized by using the MCNPX Monte Carlo code are presented. The distribution of the RBE (relative biological effectiveness) dose in a phantom shows that, assuming a (10)B concentration of 13 ppm for normal tissue, this beam could be employed to treat a patient with an irradiation time less than 30 min and a dose less than 12.5 Gy-eq to normal tissue. The CBNS might be an alternative to the reactor-based neutron sources for BNCT treatments.

  18. (n,2n) and (n,3n) cross sections of neutron-induced reactions on 150Sm for En from threshold to 35 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D; Mitchell, G; Kawano, T; Becker, J; Wu, C; Devlin, M; Fotiades, N; Nelson, R; Kunieda, S

    2009-03-16

    Cross-section measurements were made of prompt discrete {gamma}-ray production as a function of incident neutron energy (E{sub n} = 1 to 35 MeV) on a {sup 150}Sm sample fo 1550 mg/cm{sup 2} of Sm{sub 2}O{sub 3} enriched to 95.6% in {sup 150}Sm. Results are compared with enhanced Hauser-Feshbach model calculations including the pre-equilibrium reactions. Energetic neutrons were delivered by the Los Alamos Neutron Science Center facility. The prompt-reaction {gamma} rays were detected with the Compton-suppressed Germanium Array for Neutron Induced Excitations (GEANIE). Incident neutron energies were determined by the time-of-flight technique. Excitation functions for thirteen individual {gamma}-rays up to E{sub x} = 0.8 MeV in {sup 149}Sm and one {gamma}-ray transition between the first excited and ground state in {sup 148}Sm were measured. Partial {gamma}-ray cross sections were calculated using GNASH, an enhanced Hauser-Feshbach statistical nuclear reaction model code, and compared with the experimental results. The particle transmission coefficients were calculated with new systematic 'global' optical model potential parameters. The coupled-channel optical model based on the soft rotor model was employed to calculate the particle transmission coefficients. The pre-equilibrium part of the spin distribution in {sup 150}Sm was calculated using the quantum mechanical theory of Feshbach, Kerman, and Koonin (FKK) and incorporated into the GNASH reaction model code. the partial cross sections for discrete {gamma}-ray cascade paths leading to the ground state in {sup 149}Sm and {sup 148}Sm have been summed (without double counting) to estimate lower limits for reaction cross sections. These lower limits are combined with Hauser-Feshbach model calculations to deduce the reaction channel cross sections. These reaction channel cross sections agree with previously measured experimental and ENDF/B-VII evaluations.

  19. Evolutionary implications of the new triple-alpha nuclear reaction rate for low mass stars

    CERN Document Server

    Dotter, Aaron

    2009-01-01

    Context: Ogata et al. (2009; hereafter OKK) presented a theoretical determination of the triple-alpha nuclear reaction rate. Their rate differs from the NACRE rate by many orders of magnitude at temperatures relevant for low mass stars. Aims: We explore the evolutionary implications of adopting the OKK triple-alpha reaction rate in low mass stars and compare the results with those obtained using the NACRE rate. Methods: The triple-alpha reaction rates are compared by following the evolution of stellar models at 1 and 1.5 Msol with Z=0.0002 and Z=0.02. Results: Results show that the OKK rate has severe consequences for the late stages of stellar evolution in low mass stars. Most notable is the shortening--or disappearance--of the red giant phase. Conclusions: The OKK triple-alpha reaction rate is incompatible with observations of extended red giant branches and He burning stars in old stellar systems.

  20. Measurement of neutron capture cross-section of the {sup 71}Ga(n, {gamma}){sup 72}Ga reaction at 0.0536 eV energy

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, M.S. [Institute of Nuclear Science and Technology, Atomic Energy Research Establishment, GPO Box No. 3787, Savar, Dhaka 1000 (Bangladesh)], E-mail: shuza88@yahoo.co.in; Chowdhury, M.H. [Institute of Nuclear Science and Technology, Atomic Energy Research Establishment, GPO Box No. 3787, Savar, Dhaka 1000 (Bangladesh); Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh); Hossain, S.M.; Latif, Sk.A.; Hafiz, M.A.; Islam, M.A.; Zakaria, A.K.M.; Yunus, S.M. [Institute of Nuclear Science and Technology, Atomic Energy Research Establishment, GPO Box No. 3787, Savar, Dhaka 1000 (Bangladesh); Azharul Islam, S.M. [Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh)

    2008-08-15

    The neutron capture cross-section for the {sup 71}Ga(n, {gamma}){sup 72}Ga reaction at 0.0536 eV energy was measured using activation technique based on TRIGA Mark-II research reactor. The {sup 197}Au(n, {gamma}){sup 198}Au monitor reaction was used to determine the effective neutron flux. Neutron absorption and {gamma}-ray attenuation in gallium oxide pellet were corrected in determination of cross-section. The cross-section for the above reaction at 0.0536 eV amounts to 2.75 {+-} 0.14 b. As far as we know there are no experimental data available at our investigated energy. So far we are the first, who carried out experiment with 0.0536 eV neutrons for cross-section measurement. The present result is larger than that of JENDL-3.3, but consistent within the uncertainty range. The value of ENDF/B-VII is higher than this work. The result of this work will be useful to observe energy dependence of neutron capture cross-sections.

  1. Cross Section Measurements of Neutron Induced Reactions on GaAs using Monoenergetic Beams from 7.5 to 15 MeV

    Science.gov (United States)

    Raut, R.; Crowell, A. S.; Fallin, B.; Howell, C. R.; Huibregtse, C.; Kelley, J. H.; Kawano, T.; Kwan, E.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Vieira, D. J.; Wilhelmy, J. B.

    2011-09-01

    Cross section measurements for the neutron induced reactions on GaAs have been carried out at ten different neutron energies from 7.5 to 15 MeV, using the activation technique. The monoenergetic neutron beams were produced via the 2H(d,n)3He reaction, known for it's high neutron yield in the chosen energy regime. GaAs samples were activated along with the Au and Al monitor foils, for estimating the incident neutron flux. The induced activiy was measured using high resolution γ-ray spectroscopy. Five reaction channels viz., 69Ga(n, 2n) Ga, 69Ga(n,p)69mZn, 71Ga(n,p)71mZn, 75As(n, 2n)74As and 75As(n,p)75Ge, have been reported for the comprehensive cross section measurements. The results are compared with the existing literature data and the available evaluations. Statistical model calculations, based on the Hauser-Feshbach formalism, have been carried out using the TALYS and EMPIRE codes and are compared with the experimental values.

  2. Mass-capture rate by the neutron star in be/x-ray Binaries

    OpenAIRE

    Okazaki, A. T.; Hayasaki, K.

    2004-01-01

    Estudiamos la interacci on entre el disco de estrellas Be y la estrella de neutrones en binarias Be/rayos X mediante simulaciones en tres dimensiones SPH. Encontramos que el truncamiento resonante del disco de la estrella Be opera bien excepto para sistemas con excentricidad orbital extremadamente alta o grandes angulos de desalineaci on entre el disco Be y el plano orbital. Debido al truncamiento, la tasa de captura de masa por la estrella de neutrones es sensible tanto a la exc...

  3. Theoretical reaction rates of the $^{12}$C($\\alpha$,$\\gamma$)$^{16}$O reaction from the potential model

    CERN Document Server

    Katsuma, M

    2015-01-01

    The radiative capture cross sections of $^{12}$C($\\alpha$,$\\gamma$)$^{16}$O and derived reaction rates are calculated from the direct capture potential model. The resulting $S$-factor at low energies is found to be dominated by $E$2 transition to the $^{16}$O ground state. The $E$1 and $E$2 $S$-factors at $E_{c.m.}=0.3$ MeV are $S_{E1}\\approx3$ keV~b and $S_{E2}=150^{+41}_{-17}$ keV~b, respectively. The sum of the cascade transition through the excited state of $^{16}$O is $S_{\\rm casc}= 18\\pm4.5$ keV~b. The derived reaction rates at low temperatures seem to be concordant with those from the previous evaluation. For astrophysical applications, our reaction rates below $T_9=3$ are provided in an analytic expression.

  4. Reaction Matrix Calculations in Neutron Matter with Alternating-Layer-Spin Structure under π0 Condensation. II ---Numerical Results---

    Science.gov (United States)

    Tamiya, K.; Tamagaki, R.

    1981-10-01

    Results obtained by applying a formulation based on the reaction matrix theory developed in I are given. Calculations by making use of a modified realistic potential, the Reid soft-core potential with the OPEP-part enhanced due to the isobar (Δ)-mixing, show that the transition to the [ALS] phase of quasi-neutrons corresponding to a typical π0 condensation occurs in the region of (2 ˜ 3) times the nuclear density. The most important ingredients responsible for this transition are the growth of the attractive 3P2 + 3F2 contribution mainly from the spin-parallel pairs in the same leyers and the reduction of the repulsive 3P1 contribution mainly from the spin-antiparallel pairs in the nearest layers; these mainfest themselves as the [ALS]-type localization develops. Properties of the matter under the new phase thus obtained such as the shape of the Fermi surface and the effective mass are discussed.

  5. Measurement of cross section of the {sup 98}Mo(n,γ){sup 99}Mo reaction using monochromatic thermal neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, Md. Shuza; Hossain, Syed Mohammod; Zakaria, A.K.M.; Islam, Mohammod Amirul [Atomic Energy Research Establishment, Dhaka (Bangladesh). Inst. of Nuclear Science and Technology; Afroze, Nazmin [Atomic Energy Research Establishment, Dhaka (Bangladesh). Inst. of Nuclear Science and Technology; Jahangirnagar Univ., Dhaka (Bangladesh). Dept. of Physics

    2015-05-01

    The cross sections of the reaction {sup 98}Mo(n,γ){sup 99}Mo at neutron energies of 0.0334 eV and 0.0536 eV were measured for the first time using the activation technique, and the resulting values of 116 ± 7 mb and 91 ± 5 mb, respectively, are in good agreement with the JENDL-4 and ENDF/B-VII data files. Those measured values were extrapolated to the energy 0.0253 eV assuming 1/v dependence in the thermal region and the results were compared with the integrally measured values reported in the literature. The new data are thus useful to check the evaluated excitation function.

  6. DNA double-strand break induction in Ku80-deficient CHO cells following Boron Neutron Capture Reaction

    Directory of Open Access Journals (Sweden)

    Masunaga Shinichiro

    2011-09-01

    Full Text Available Abstract Background Boron neutron capture reaction (BNCR is based on irradiation of tumors after accumulation of boron compound. 10B captures neutrons and produces an alpha (4He particle and a recoiled lithium nucleus (7Li. These particles have the characteristics of high linear energy transfer (LET radiation and have marked biological effects. The purpose of this study is to verify that BNCR will increase cell killing and slow disappearance of repair protein-related foci to a greater extent in DNA repair-deficient cells than in wild-type cells. Methods Chinese hamster ovary (CHO-K1 cells and a DNA double-strand break (DSB repair deficient mutant derivative, xrs-5 (Ku80 deficient CHO mutant cells, were irradiated by thermal neutrons. The quantity of DNA-DSBs following BNCR was evaluated by measuring the phosphorylation of histone protein H2AX (gamma-H2AX and 53BP1 foci using immunofluorescence intensity. Results Two hours after neutron irradiation, the number of gamma-H2AX and 53BP1 foci in the CHO-K1 cells was decreased to 36.5-42.8% of the levels seen 30 min after irradiation. In contrast, two hours after irradiation, foci levels in the xrs-5 cells were 58.4-69.5% of those observed 30 min after irradiation. The number of gamma-H2AX foci in xrs-5 cells at 60-120 min after BNCT correlated with the cell killing effect of BNCR. However, in CHO-K1 cells, the RBE (relative biological effectiveness estimated by the number of foci following BNCR was increased depending on the repair time and was not always correlated with the RBE of cytotoxicity. Conclusion Mutant xrs-5 cells show extreme sensitivity to ionizing radiation, because xrs-5 cells lack functional Ku-protein. Our results suggest that the DNA-DSBs induced by BNCR were not well repaired in the Ku80 deficient cells. The RBE following BNCR of radio-sensitive mutant cells was not increased but was lower than that of radio-resistant cells. These results suggest that gamma-ray resistant cells have

  7. {sup 48}Ti(n,xnpa{gamma}) reaction cross sections using spallation neutrons for E{sub n} = 1 to 20 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D; Mitchell, G E; Garrett, P E; Agvaanluvsan, U; Becker, J A; Bernstein, L A; Cooper, J R; Hoffman, R D; Younes, W; Devlin, N; Fotiades, N; Nelson, R O

    2005-01-06

    {gamma}-ray excitation functions have been measured for the interaction of fast neutrons with {sup 48}Ti (neutron energy from 1 MeV to 250 MeV). The Los Alamos National Laboratory spallation neutron source, at the LANSCE/WNR facility, provided a ''white'' neutron beam which is produced by bombarding a natural W target with a pulsed proton beam. The prompt-reaction {gamma} rays were measured with the large-scale Compton-suppressed Ge spectrometer, GEANIE. Neutron energies were determined by the time-of-flight technique. Excitation functions were converted to partial {gamma}-ray cross sections, taking into account the dead-time correction, the target thickness, the detector efficiency, and neutron flux (monitored with an in-line fission chamber). The data analysis is presented here for neutron energies between 1 to 20 MeV. Partial {gamma}-ray cross sections for transitions in {sup 47,48}Ti, {sup 48}Sc, and {sup 45}Ca have been determined. These results are compared to Hauser-Feshbach predictions calculated using the STAPRE code, which includes compound nuclear and pre-equilibrium emission. The partial cross sections for {gamma} rays, whose discrete {gamma}-ray cascade path leads to the ground state in {sup 48}Ti, {sup 47}Ti, {sup 48}Sc, and {sup 45}Ca have been summed to obtain estimates of the lower limits for reaction cross sections. Partial cross sections for unobserved {gamma}-rays are predicted from the STAPRE code. These lower limits are combined with Hauser-Feshbach calculations to deduce {sup 48}Ti(n,n'){sup 48}Ti, {sup 48}Ti(n,2n){sup 47}Ti, {sup 48}Ti(n,p){sup 48}Sc, and {sup 48}Ti(n,{alpha}){sup 45}Ca reaction channel cross sections.

  8. Critical evaluation and rate constants of chemoselective ligation reactions for stoichiometric conjugations in water.

    Science.gov (United States)

    Saito, Fumito; Noda, Hidetoshi; Bode, Jeffrey W

    2015-04-17

    Chemoselective ligation reactions have contributed immensely to the development of organic synthesis and chemical biology. However, the ligation of stoichiometric amounts of large molecules for applications such as protein-protein conjugates is still challenging. Conjugation reactions need to be fast enough to proceed under dilute conditions and chemoselective in the presence of unprotected functional groups; the starting materials and products must be stable under the reaction conditions. To compare known ligation reactions for their suitability under these conditions, we determined the second-order rate constants of ligation reactions using peptide substrates with unprotected functional groups. The reaction conditions, the chemoselectivity of the reactions, and the stability of the starting materials and products were carefully evaluated. In some cases, the stability could be improved by modifying the substrate structure. These data obtained under the ligation conditions provide a useful guide to choose an appropriate ligation reaction for synthesis of large molecules by covalent ligation reactions of unprotected substrates in water.

  9. Reaction rates between water and some modified rapidly-reacting Karl Fischer reagents.

    Science.gov (United States)

    Cedergren, A

    1978-04-01

    Rate constants were determined for the reaction between water and various modified Karl Fischer reagents containing formamide, dimethylformamide or N-methylformamide. It was shown that the reaction rate can be increased by a factor of 100 by using a reagent containing 40% v/v formamide in pyridine compared to that obtained by use of the conventional methanolic reagent.

  10. Rate of reaction of dimethylmercury with oxygen atoms in the gas phase

    DEFF Research Database (Denmark)

    Egsgaard, Helge

    1986-01-01

    The rate constant for the reaction of atomic oxygen (O(3P)) with dimethylmercury has been measured at room temperature at a pressure of about 1 Torr using a fast flow system with electron paramagnetic resonance and mass spectrometric detection. Some reaction products were identified. The rate...

  11. Determination of the fission-neutron averaged cross sections of some high-energy threshold reactions of interest for reactor dosimetry

    CERN Document Server

    Arribere, M A; Ribeiro-Guevara, S; Korochinsky, S; Blostein, J J

    2003-01-01

    For three high threshold reactions, we have measured the cross sections averaged over a sup 2 sup 3 sup 5 U fission neutron spectrum. The measured reactions, and corresponding averaged cross sections found, are: sup 1 sup 2 sup 7 I(n,2n) sup 1 sup 2 sup 6 I, (1.36+-0.12) mb; sup 9 sup 0 Zr(n,2n) sup 8 sup 9 sup m Zr, (13.86+-0.83) mu b; and sup 5 sup 8 Ni(n,d+np+pn) sup 5 sup 7 Co, (274+-15) mu b; all referred to the well known standard of (111+-3) mb for the sup 5 sup 8 Ni(n,p) sup 5 sup 8 sup m sup + sup g Co averaged cross section. The measured cross sections are of interest in nuclear engineering for the characterization of the fast neutron component in the energy distribution of reactor neutrons. (author)

  12. Neutron capture cross-section measurement for the {sup 186}W(n,{gamma}){sup 187}W reaction at 0.0536 eV energy

    Energy Technology Data Exchange (ETDEWEB)

    Uddin, M.S. [Institute of Nuclear Science and Technology, Atomic Energy Research Establishment, Savar, GPO Box No. 3787, Dhaka-1000 (Bangladesh)], E-mail: shuza88@yahoo.co.in; Chowdhury, M.H. [Department of Physics, Comilla Victoria Government College, Comilla (Bangladesh); Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh); Hossain, S.M.; Latif, Sk.A.; Hafiz, M.A.; Islam, M.A.; Zakaria, A.K.M. [Institute of Nuclear Science and Technology, Atomic Energy Research Establishment, Savar, GPO Box No. 3787, Dhaka-1000 (Bangladesh); Azharul Islam, S.M. [Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh)

    2008-09-15

    The thermal neutron-induced activation cross section for the {sup 186}W(n,{gamma}){sup 187}W reaction was measured at 0.0536 eV neutron energy using TRIGA Mark-II research reactor, Atomic Energy Research Establishment, Savar, Dhaka, Bangladesh. The {sup 197}Au(n,{gamma}){sup 198}Au monitor reaction induced in a high-purity gold foil was used to determine the effective neutron beam intensity. The activities induced in sample and monitor foils were measured nondestructively by a high-resolution HPGe {gamma}-ray detector. The present experimental cross-section value is the first one at 0.0536 eV. The obtained new cross section that amounts to 26.6{+-}1.6 b is 2% higher than the recently reported data in ENDF/B-VII and 5% lower than that of JENDL-3.3.

  13. Controlling the emotional heart: heart rate biofeedback improves cardiac control during emotional reactions.

    Science.gov (United States)

    Peira, Nathalie; Fredrikson, Mats; Pourtois, Gilles

    2014-03-01

    When regulating negative emotional reactions, one goal is to reduce physiological reactions. However, not all regulation strategies succeed in doing that. We tested whether heart rate biofeedback helped participants reduce physiological reactions in response to negative and neutral pictures. When viewing neutral pictures, participants could regulate their heart rate whether the heart rate feedback was real or not. In contrast, when viewing negative pictures, participants could regulate heart rate only when feedback was real. Ratings of task success paralleled heart rate. Participants' general level of anxiety, emotion awareness, or cognitive emotion regulation strategies did not influence the results. Our findings show that accurate online heart rate biofeedback provides an efficient way to down-regulate autonomic physiological reactions when encountering negative stimuli.

  14. BRUSLIB and NETGEN: the Brussels nuclear reaction rate library and nuclear network generator for astrophysics

    CERN Document Server

    Aikawa, M; Goriely, S; Jorissen, A; Takahashi, K

    2005-01-01

    Nuclear reaction rates are quantities of fundamental importance in astrophysics. Substantial efforts have been devoted in the last decades to measure or calculate them. The present paper presents for the first time a detailed description of the Brussels nuclear reaction rate library BRUSLIB and of the nuclear network generator NETGEN so as to make these nuclear data packages easily accessible to astrophysicists for a large variety of applications. BRUSLIB is made of two parts. The first one contains the 1999 NACRE compilation based on experimental data for 86 reactions with (mainly) stable targets up to Si. The second part of BRUSLIB concerns nuclear reaction rate predictions calculated within a statistical Hauser-Feshbach approximation, which limits the reliability of the rates to reactions producing compound nuclei with a high enough level density. These calculations make use of global and coherent microscopic nuclear models for the quantities entering the rate calculations. The use of such models is utterl...

  15. Neutron multiplicity distributions for 30 MeVu sup 14 N reactions with the indicated targets

    Energy Technology Data Exchange (ETDEWEB)

    1992-06-01

    This report contains short papers on the following topics: Heavy ion reactions; nuclear structure and fundamental interactions; nuclear theory; atomic molecular and materials science; and superconducting cyclotron and instrumentation. (LSP)

  16. Two-neutron stripping in ({sup 18}O, {sup 16}O) and (t,p) reactions

    Energy Technology Data Exchange (ETDEWEB)

    Cavallaro, M.; Agodi, A.; Carbone, D.; Cunsolo, A. [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, I-95125 Catania (Italy); Bondì, M.; Cappuzzello, F.; Nicolosi, D.; Tropea, S. [INFN - Laboratori Nazionali del Sud, Via S. Sofia 62, I-95125 Catania, Italy and Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania (Italy); Borello-Lewin, T.; Rodrigues, M. R. D. [Instituto de Física - Universidade de São Paulo, Rua do Matão Travessa R Nr.187 CEP 05508-090 Cidade Universitária, São Paulo (Brazil); De Napoli, M. [INFN - Sezione di Catania, Via S. Sofia 64, I-95125 Catania (Italy); Garcia, V. N. [Instituto de Física, Universidade Federal Fluminense, Avenida Litoranea s/n, Gragoata, 24210-340, Niteroi, RJ (Brazil); Linares, R.; Lubian, J.; Paes, B. [Instituto de Física, Universidade Federal Fluminense, Avenida Litoranea s/n, Gragoata , 24210-340, Niteroi, RJ (Brazil); Foti, A. [Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, I-95125 Catania, Italy and INFN - Sezione di Catania, Via S. Sofia 64, I-95125 Catania (Italy)

    2014-11-11

    The {sup 12}C({sup 18}O,{sup 16}O){sup 14}C reactions has been investigated at 84 MeV incident energy. The charged ejectiles produced in the reaction have been momentum analyzed and identified by the MAGNEX magnetic spectrometer. Q-value spectra have been extracted with an energy resolution of 160 keV (Full Width at Half Maximum) and several known bound and resonant states of {sup 14}C have been identified up to 15 MeV. In particular, excited states with dominant 2p - 4h configuration are the most populated. The absolute values of the cross sections have been extracted showing a striking similarity with those measured for the same transitions by (t,p) reactions. This indicates that the effect of the {sup 16}O core is negligible in the reaction mechanism.

  17. Measurement of the effective thermal cross section of {sup 134}Cs by triple neutron capture reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, Shoji; Harada, Hideo; Katoh, Toshio [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works; Hatsukawa, Yuichi; Shinohara, Nobuo; Hata, Kentaro; Kobayashi, Katsutoshi; Motoishi, Shoji; Tanase, Masakazu

    1998-03-01

    The effective thermal cross section ({sigma}{sub eff}) of the {sup 134}Cs(n,{gamma}){sup 135}Cs reaction was measured by the activation method and the {gamma}-ray spectroscopic method in order to obtain fundamental data for research on the transmutation of nuclear wastes. The effective thermal cross section of the reaction {sup 134}Cs(n,{gamma}){sup 135}Cs was found to be 140.6{+-}8.5 barns. (author)

  18. Thermal neutron induced (n,p) and (n,alpha) reactions on Ar-37

    NARCIS (Netherlands)

    Bieber, R; Wagemans, C; Goeminne, G; Wagemans, J; Denecke, B; Loiselet, M; Gaelens, M; Geltenbort, P; Oberhummer, H

    1999-01-01

    The Ar-37(n(th),alpha)S-34 and Ar-37(n(th),p)Cl-37 reactions were studied at the high flux reactor of the ILL in Grenoble, For the Ar-37(n(th),alpha(0))S-34 and Ar-37(n(th),p)Cl-37 reaction cross sections, values of (1070 +/- 80) b and (37 +/- 4) b, respectively, were obtained. Both values are about

  19. Production of very neutron-deficient isotopes near sup 1 sup 0 sup 0 Sn via reactions involving light-particle and cluster emission

    CERN Document Server

    La Commara, M; D'Onofrio, A; Gadea, A; Glogowski, M; Jarillo-Herrero, P; Belcari, N; Borcea, R; De Angelis, G; Fahlander, C; aGórska, M; Grawe, H; Hellström, M; Kirchner, R; Rejmund, M; Roca, V; Roeckl, E; Romano, M; Rykaczewski, K; Schmidt, K; Terrasi, F

    2000-01-01

    The production of very neutron-deficient isotopes near sup 1 sup 0 sup 0 Sn has been investigated by using on-line mass separation of evaporation residues produced by heavy-ion induced complete-fusion reactions. We measured the cross sections for sup 9 sup 9 Cd, sup 1 sup 0 sup 0 In, sup 1 sup 0 sup 1 Sn and sup 1 sup 0 sup 2 In via sup 5 sup 8 Ni+ sup 5 sup 8 Ni fusion reactions followed by cluster emission, and via sup 5 sup 8 Ni+ sup 5 sup 0 Cr fusion reactions accompanied by evaporation of protons, neutrons or alpha particles. Both types of reactions yield similar cross sections for the production of exotic nuclei near sup 1 sup 0 sup 0 Sn. The data are discussed in comparison with results obtained from statistical-model calculations.

  20. Neutron emission cross sections at low bombarding energies and the novelty in multistep compound reaction model

    Energy Technology Data Exchange (ETDEWEB)

    Marcinkowski, A. (Ohio Univ., Athens, OH (United States) and Soltan Inst. for Nuclear Study, Warsaw (Poland)); Rapaport, J. (Ohio Univ., Athens, OH (United States)); Finlay, R.W. (Ohio Univ., Athens, OH (United States)); Brient, C. (Ohio Univ., Athens, OH (United States)); Herman, M. (ENEA-C.R.E. ' Clementel' , Bologna (Italy)); Chadwick, M.B. (Lawrence Livermore National Lab., Livermore, CA (United States))

    1993-08-30

    Inelastic neutron emission at 6.7 and 20 MeV incident energies has been measured for monoisotopic samples of [sup 165]Ho and [sup 181]Ta. Time-of-flight spectra were taken at several angles between 15 and 145 using a beam-swinger spectrometer. The cross sections are averaged over 1 MeV energy bins. The 20 MeV data, when compared with the quantum-mechanical statistical multistep calculations have revealed a magnitude problem in the existing theories. A gradual or 'multistep' absorption in the entrance channels is proposed as a way out of the difficulty. This modification turns out to be sufficient for an adequate description of the experimental data. (orig.)

  1. Contribution of neutron-capture reactions in energy release in the fuel core of BN-600

    Science.gov (United States)

    Bahdanovich, R. B.; Romanenko, V. I.; Tikhomirov, G. V.

    2017-01-01

    The use of modern computing powers and calculation methods allows to get closer to reality results of modelling, as well as to explore areas inaccessible to the experiment. Until now, the calculation of the energy released from the capture of neutrons in the reactor core has been given little attention. The method for calculation of the effective energy release components in a nuclear reactor allows to specify the values used by engineering programs for capture energy release in fast reactors. The paper presents improved method and the results of calculation of three models of the reactor BN-600. It is shown that the contribution of capture energy release in effective energy release for fresh fuel is equal to 4%, which is more than for VVER reactors. During the calculation we created a simple calculation model of the fast reactor, considering its features.

  2. Development of a phoswich detector for neutron dose rate measurements in the Earth's atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Doensdorf, Esther Miriam

    2014-04-30

    The Earth is constantly exposed to a stream of energetic particles from outer space. Through the interaction of this radiation with the Earth's magnetosphere and atmosphere a complex radiation field is formed which varies with the location inside the Earth's atmosphere. This radiation field consists of charged and uncharged particles leading to the constant exposure of human beings to radiation. As this ionizing radiation can be harmful for humans, it is necessary to perform dose rate measurements in different altitudes in the Earth's atmosphere. Due to their higher biological effectiveness the exposure to neutrons is more harmful than the exposure to γ-rays and charged particles, which is why the determination of neutron dose rates is the focus of this work. In this work the prototype of a Phoswich detector called PING (Phoswich Instrument for Neutrons and Gammas) is developed to determine dose rates caused by neutrons in the Earth's atmosphere and to distinguish these from γ-rays. The instrument is composed of two different scintillators optically coupled to each other and read out by one common photomultiplier tube. The scintillator package consists of an inner plastic scintillator made of the material BC-412 and a surrounding anti-coincidence made of sodium doped caesium iodide (CsI(Na)). In this work the instrument is calibrated, tested and flown and a procedure for a pulse shape analysis for this instrument is developed. With this analysis it is possible to distinguish pulses from the plastic scintillator and pulses from the CsI(Na). The pulses from the plastic scintillator are mainly due to the interaction of neutrons but there is an energy-dependent contribution of γ-rays to these events. Measurements performed on board an airplane show that the dose rates measured with the developed detector are in the same order of magnitude as results of other instruments. During measurements on board stratospheric balloons the altitude dependence

  3. Neutron-activated determination of chlorine, using the /sup 35/Cl(n,p)/sup 35/S reaction as the basis, in thin coatings of silicon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Perezhogin, G.A.

    1988-01-10

    The neutron-activation determination of chlorine in thin coatings of silicon dioxide on silicon has been shown to be possible through the use of the /sup 55/Cl(n, P)/sup 35/S reaction. The detection limit of chlorine is 3 x 10/sup -9/ g (5 x 10/sup 13/ atoms).

  4. Probing the semi-magicity of $^{68}$Ni via the $^{3}$H($^{66}$Ni,$^{68}$Ni)p two-neutron transfer reaction in inverse kinematics

    CERN Multimedia

    Reiter, P; Blazhev, A A; Kruecken, R; Franchoo, S; Mertzimekis, T; Darby, I G; Van de walle, J; Raabe, R; Elseviers, J; Gernhaeuser, R A; Sorlin, O H; Georgiev, G P; Bree, N C F; Habs, D; Chapman, R; Gaudefroy, L; Diriken, J V J; Jenkins, D G; Kroell, T; Axiotis, M; Huyse, M L; Patronis, N

    We propose to perform the two-neutron transfer reaction $^{3}$H($^{66}$Ni, $^{68}$Ni)$p$ using the ISOLDE radioactive ion beam at 2.7 $A$ MeV and the MINIBALL + T-REX setup to characterize the 0$^{+}$ and 2$^{+}$ states in $^{68}$Ni.

  5. Cross-section measurements of neutron-induced reactions on GaAs using monoenergetic beams from 7.5 to 15 MeV

    Science.gov (United States)

    Raut, R.; Crowell, A. S.; Fallin, B.; Howell, C. R.; Huibregtse, C.; Kelley, J. H.; Kawano, T.; Kwan, E.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Vieira, D. J.; Wilhelmy, J. B.

    2011-04-01

    Cross-section measurements for neutron-induced reactions on GaAs have been carried out at twelve different neutron energies from 7.5 to 15 MeV using the activation technique. The monoenergetic neutron beams were produced via the H2(d,n)He3 reaction. GaAs samples were activated along with Au and Al monitor foils to determine the incident neutron flux. The activities induced by the reaction products were measured using high-resolution γ-ray spectroscopy. Cross sections for five reaction channels, viz., Ga69(n,2n)Ga68, Ga69(n,p)Zn69m, Ga71(n,p)Zn71m, As75(n,2n)As74, and As75(n,p)Ge75, are reported. The results are compared with the previous measurements and available data evaluations. Statistical-model calculations, based on the Hauser-Feshbach formalism, have been carried out using the TALYS and the COH3 codes and are compared with the experimental results.

  6. Neutron decay of deep hole states and isobaric analog states in Sn-115 populated by the (He-3,alpha) reaction at 102 MeV

    NARCIS (Netherlands)

    Soderman, PO; Ringbom, A; Blomgren, J; Olsson, N; Nilsson, L; Bordewijk, JA; van't Hof, G; Hofstee, MA; van der Ploeg, H; van der Werf, SY; Krasznahorkay, A; Balanda, A; Chmielewska, D; Laurent, H

    2001-01-01

    Neutron decay of excited hole states and isobaric analog states (IAS) populated by the Sn-116(He-3,alpha) reaction at an energy of 102 MeV has been investigated. The alpha -particles were analysed in a magnetic spectrograph positioned at 1.4 degrees and detected with a multiwire drift chamber. Excit

  7. Structure of the unbound nucleus 13Be: One-neutron knockout reaction data from 14Be analyzed in a holistic approach

    DEFF Research Database (Denmark)

    Aksyutina, Yu; Aumann, T.; Boretzky, K.

    2013-01-01

    At the ALADIN-LAND setup at GSI the unbound nucleus 13Be has been produced in one-neutron knockout reactions from a 304 MeV/nucleon relativistic beam of 14Be ions impinging on a liquid hydrogen target. An analysis of the data including all available information about 13Be, and in particular recen...

  8. Measurement of fission cross-section for the {sup 232}Th(n,f){sup 141}Ba reaction induced by neutrons around 14 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Chang-Lin; Fang, Kai-Hong [Lanzhou University, School of Nuclear Science and Technology, Lanzhou, Gansu Province (China); Lanzhou University, Engineering Research Center for Neutron Application, Ministry of Education, Lanzhou, Gansu Province (China); Liu, Shuang-Tong; Lv, Tao; Wang, Qiang; Zhang, Zheng-Wei [Lanzhou University, School of Nuclear Science and Technology, Lanzhou, Gansu Province (China); Lai, Cai-Feng [Chinese Academy of Engineering Physics, Institute of Nuclear Physics and Chemistry, Mianyang, Sichuan Province (China)

    2016-11-15

    The fission cross-section of the {sup 232}Th(n,f){sup 141}Ba reaction induced by neutrons around 14 MeV was measured precisely with the neutron activation and off-line gamma-ray spectrometric technique. Neutron fluence was monitored on-line using the accompanying α-particles from the {sup 3}H({sup 2}H,n){sup 4}He reaction, whereas the neutron energies were measured by the method of cross-section ratios of {sup 90}Zr(n,2n){sup 89}Zr to {sup 93}Nb(n,2n){sup 92m}Nb reactions. The experimentally determined {sup 232}Th(n,f){sup 141}Ba reaction cross-sections were 12.2 ± 0.4 mb at E{sub n} = 14.1 ± 0.3 MeV, 13.0 ± 0.5 mb at E{sub n} = 14.5 ± 0.3 MeV and 13.3 ± 0.5 mb at E{sub n} = 14.7 ± 0.3 MeV, respectively. (orig.)

  9. Neutron counting with cameras

    Energy Technology Data Exchange (ETDEWEB)

    Van Esch, Patrick; Crisanti, Marta; Mutti, Paolo [Institut Laue Langevin, Grenoble (France)

    2015-07-01

    A research project is presented in which we aim at counting individual neutrons with CCD-like cameras. We explore theoretically a technique that allows us to use imaging detectors as counting detectors at lower counting rates, and transits smoothly to continuous imaging at higher counting rates. As such, the hope is to combine the good background rejection properties of standard neutron counting detectors with the absence of dead time of integrating neutron imaging cameras as well as their very good spatial resolution. Compared to Xray detection, the essence of thermal neutron detection is the nuclear conversion reaction. The released energies involved are of the order of a few MeV, while X-ray detection releases energies of the order of the photon energy, which is in the 10 KeV range. Thanks to advances in camera technology which have resulted in increased quantum efficiency, lower noise, as well as increased frame rate up to 100 fps for CMOS-type cameras, this more than 100-fold higher available detection energy implies that the individual neutron detection light signal can be significantly above the noise level, as such allowing for discrimination and individual counting, which is hard to achieve with X-rays. The time scale of CMOS-type cameras doesn't allow one to consider time-of-flight measurements, but kinetic experiments in the 10 ms range are possible. The theory is next confronted to the first experimental results. (authors)

  10. Relevance of single-particle and collective excitations in zirconium isotopes populated by neutron transfer reactions in the {sup 90}Zr+{sup 208}Pb system

    Energy Technology Data Exchange (ETDEWEB)

    Pajtler, M. Varga, E-mail: maja.varga@fizika.unios.hr [Department of Physics, University of Osijek, Trg Ljudevita Gaja 6, 31000 Osijek (Croatia); Szilner, S.; Malenica, D. Jelavić; Mijatović, T.; Soić, N. [Ruer Bošković Institute, HR-10001, Zagreb (Croatia); Corradi, L.; Angelis, G. de; Fioretto, E.; Montanari, D.; Stefanini, A. M.; Valiente-Dobón, J. J. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro, I-35020 Legnaro (Italy); Gadea, A. [IFIC, CSIC-Universidad de Valencia, E-46071 Valencia (Spain); Haas, F. [Institut Pluridisciplinaire Hubert Curien, CNRS-IN2P3 and Université de Strasbourg, F-67037 Strasbourg (France); Lunardi, S.; Mengoni, D.; Montagnoli, G.; Recchia, F.; Scarlassara, F. [Dipartimento di Fisica, Universitá di Padova, and Istituto Nazionale di Fisica Nucleare, I-35131 Padova (Italy); Märginean, N. [Horia Hulubei National Institute of Physics and Nuclear Engineering, RO-077125 Bucharest-Magurele (Romania); Pollarolo, G. [Dipartimento di Fisica Teorica, Universitá di Torino,and Istituto Nazionale di Fisica Nucleare, I-10125 Torino (Italy); and others

    2015-10-15

    Multineutron transfer reaction {sup 90}Zr+{sup 208}Pb has been studied at the energy close to the Coulomb barrier energy by using the PRISMA + CLARA set-up. In this fragment-γ coincidence measurement, the selective properties of the reaction mechanism in the population of the specific states have been discussed. Based on the observed γ transitions of neutron transfer channels, namely {sup 89–94}Zr isotopes, their level schemes have been constructed and updated.

  11. Accessing reaction rate constants in on-column reaction chromatography: an extended unified equation for reaction educts and products with different response factors.

    Science.gov (United States)

    Trapp, Oliver; Bremer, Sabrina; Weber, Sven K

    2009-11-01

    An extension of the unified equation of chromatography to directly access reaction rate constants k(1) of first-order reaction in on-column chromatography is presented. This extended equation reflects different response factors in the detection of the reaction educt and product which arise from structural changes by elimination or addition, e.g., under pseudo-first-order reaction conditions. The reaction rate constants k(1) and Gibbs activation energies DeltaG(double dagger) of first-order reactions taking place in a chromatographic system can be directly calculated from the chromatographic parameters, i.e., retention times of the educt E and product P (t(R)(A) and t(R)(B)), peak widths at half height (w(A) and w(B)), the relative plateau height (h(p)) of the conversion profile, and the individual response factors f(A) and f(B). The evaluation of on-column reaction gas chromatographic experiments is exemplified by the evaluation of elution profiles obtained by ring-closing metathesis reaction of N,N-diallytrifluoroacetamide in presence of Grubbs second-generation catalyst, dissolved in polydimethylsiloxane (GE SE 30).

  12. Experimental measurements of the O15(alpha,gamma)Ne19 reaction rate vs. observations of type I X-ray bursts

    CERN Document Server

    Fisker, J L; Görres, J; Wiescher, M; Cooper, R L; Fisker, Jacob Lund; Tan, Wanpeng; Goerres, Joachim; Wiescher, Michael; Cooper, Randall L.

    2007-01-01

    Neutron stars in close binary star systems often accrete matter from their companion stars. Thermonuclear ignition of the accreted material in the atmosphere of the neutron star leads to a thermonuclear explosion which is observed as an X-ray burst occurring periodically between hours and days depending on the accretion rate. The ignition conditions are characterized by a sensitive interplay between the continuously accreting fuel supply and depletion by nuclear burning via the hot CNO cycles. Therefore the ignition depends critically on the hot CNO breakout reaction O15(alpha,gamma)Ne19 that regulates the flow between the beta-limited hot CNO cycle and the rapid proton capture process. Until recently, the O15(alpha,gamma)Ne19 reaction rate was not known experimentally and the theoretical estimates carried significant uncertainties. In this paper we report on the astrophysical consequences of the first measurement of this reaction rate on the thermonuclear instability that leads to type I X-ray bursts on accr...

  13. Simulation of biochemical reactions with time-dependent rates by the rejection-based algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Thanh, Vo Hong, E-mail: vo@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Priami, Corrado, E-mail: priami@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Department of Mathematics, University of Trento, Trento (Italy)

    2015-08-07

    We address the problem of simulating biochemical reaction networks with time-dependent rates and propose a new algorithm based on our rejection-based stochastic simulation algorithm (RSSA) [Thanh et al., J. Chem. Phys. 141(13), 134116 (2014)]. The computation for selecting next reaction firings by our time-dependent RSSA (tRSSA) is computationally efficient. Furthermore, the generated trajectory is exact by exploiting the rejection-based mechanism. We benchmark tRSSA on different biological systems with varying forms of reaction rates to demonstrate its applicability and efficiency. We reveal that for nontrivial cases, the selection of reaction firings in existing algorithms introduces approximations because the integration of reaction rates is very computationally demanding and simplifying assumptions are introduced. The selection of the next reaction firing by our approach is easier while preserving the exactness.

  14. New Generation of Exp eriments for the Investigation of Stellar (p,γ) Reaction Rates Using SAMURAI

    Institute of Scientific and Technical Information of China (English)

    V Panin; A Saastamoinen; L Sobotka; L Trache; T Uesaka; K Yoneda; M Kurokawa; J Blackmon; Z Elekes; D Kim; T Motobayashi; H Otsu; B C Rasco

    2016-01-01

    The future experimental campaign with the SAMURAI setup at RIKEN will explore a wide range of neutron-deficient nuclei with a particular focus on the most critical (p,γ) reaction rates relevant to the astrophysical rp-process in type-I X-ray bursts (XRB). Intense radioactive-ion (RI) beams at an energy of a few hundred MeV/nucleon will be deployed to populate proton-unbound states in the nuclei of interest through the Coulomb excitation or nucleon-removal processes. The decay of these states into a proton and a heavy residue will be measured using complete kinematics and the information about time reversal proton-capture process will be obtained. This method will provide the vital experimental data on the resonances, which dominate the stellar (p,γ) reaction rates, as well as on the direct proton-capture process for some other cases. The experimental setup will utilize for the first time the High-Resolution 90◦-mode of the SAMURAI spectrometer in combination with the existing detection systems, including custom-designed Si-strip detectors for simultaneous detection and tracking of heavy ions and protons emitted from the target. The details of the experimental method and the utilized apparatus are discussed in this paper.

  15. Study of neutron-deficient isotopes of Fl in the 239Pu, 240Pu + 48Ca reactions

    Science.gov (United States)

    Voinov, A. A.; Utyonkov, V. K.; Brewer, N. T.; Oganessian, Yu Ts; Rykaczewski, K. P.; Abdullin, F. Sh; Dmitriev, S. N.; Grzywacz, R. K.; Itkis, M. G.; Miernik, K.; Polyakov, A. N.; Roberto, J. B.; Sagaidak, R. N.; Shirokovsky, I. V.; Shumeiko, M. V.; Tsyganov, Yu S.; Subbotin, V. G.; Sukhov, A. M.; Sabelnikov, A. V.; Vostokin, G. K.; Hamilton, J. H.; Stoyer, M. A.; Strauss, S. Y.

    2016-07-01

    The results of the experiments aimed at the synthesis of Fl isotopes in the 239Pu + 48Ca and 240Pu + 48Ca reactions are presented. The experiment was performed using the Dubna gas-filled recoil separator at the U400 cyclotron. In the 239Pu+48Ca experiment one decay of spontaneously fissioning 284Fl was detected at 245-MeV beam energy. In the 240Pu+48Ca experiment three decay chains of 285Fl were detected at 245 MeV and four decays were assigned to 284Fl at the higher 48Ca beam energy of 250 MeV. The α-decay energy of 285Fl was measured for the first time and decay properties of its descendants 281Cn, 277Ds, 273Hs, 269Sg, and 265Rf were determined more precisely. The cross section of the 239Pu(48Ca,3n)284Fl reaction was observed to be about 20 times lower than those predicted by theoretical models and 50 times less than the value measured in the 244Pu+48Ca reaction. The cross sections of the 240Pu(48Ca,4-3n)284,285Fl at both 48Ca energies are similar and exceed that observed in the reaction with lighter isotope 239Pu by a factor of 10. The decay properties of the synthesized nuclei and their production cross sections indicate rapid decrease of stability of superheavy nuclei with departing from the neutron number N=184 predicted to be the next magic number.

  16. A simple expression for the apparent reaction rate of large wood char gasification with steam.

    Science.gov (United States)

    Umeki, Kentaro; Roh, Seon-Ah; Min, Tai-Jin; Namioka, Tomoaki; Yoshikawa, Kunio

    2010-06-01

    A simple expression for the apparent reaction rate of large wood char gasification with steam is proposed. Large char samples were gasified under steam atmosphere using a thermo-balance reactor. The apparent reaction rate was expressed as the product of the intrinsic rate and the effective factor. The effective factor was modified to include the effect of change in char diameter and intrinsic reaction rate during the reaction. Assuming uniform conversion ratio throughout a particle, the simplified reaction scheme was divided into three stages. In the initial stage, the local conversion ratio increases without particle shrinkage. In the middle stage, the particle shrinks following the shrinking core model without change in the local conversion ratio. In the final stage, the local conversion ratio increases without particle shrinkage. The validity of the modified effective value was confirmed by comparison with experimental results.

  17. Rate constants for the reaction of CF3O radicals with hydrocarbons at 298 K

    DEFF Research Database (Denmark)

    Kelly, C.; Treacy, J.; Sidebottom, H.W.;

    1993-01-01

    Rate constant ratios of the reactions of CF3O radicals with a number of hydrocarbons have been determined at 298 +/- 2 K and atmospheric pressure using a relative rate method. Using a previously determined value k(CF30 + C2H6) = 1.2 x 10(-12) cm3 molecule-1 s-1 these rate constant ratios provide......-1. The importance of the reactions of CF3O radicals with hydrocarbons under atmospheric conditions is discussed....

  18. VizieR Online Data Catalog: Brussels nuclear reaction rate library (Aikawa+, 2005)

    Science.gov (United States)

    Aikawa, M.; Arnould, M.; Goriely, S.; Jorissen, A.; Takahashi, K.

    2005-07-01

    The present data is part of the Brussels nuclear reaction rate library (BRUSLIB) for astrophysics applications and concerns nuclear reaction rate predictions calculated within the statistical Hauser-Feshbach approximation and making use of global and coherent microscopic nuclear models for the quantities (nuclear masses, nuclear structure properties, nuclear level densities, gamma-ray strength functions, optical potentials) entering the rate calculations. (4 data files).

  19. 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.

  20. Cross Section of Isomeric States Produced in Photo-Neutron Reactions

    Science.gov (United States)

    Oprea, C.; Oprea, A.; Mihul, A.

    In this work the cross sections of the isomeric states production in (γ,n) reactions and the corresponding isomeric ratios for some isotopes of Cd, Sn, Mo, Sm in the great dipole resonance region with Talys codes using a standard input including Hauser-Feshbach model were evaluated. For the isomeric ratio calculation two methods were proposed, by using the description of incident gamma flux and experimental isomeric ratio. The obtained results are compared with experimental data from nuclear reactions induced by photons obtained by bremsstrahlung.

  1. Evaluation of target photon dose mixed in mono-energetic neutron fields using {sup 7}Li(p,n){sup 7}Be reaction

    Energy Technology Data Exchange (ETDEWEB)

    Tanimura, Y., E-mail: tanimura.yoshihiko@jaea.go.j [Department of Radiation Protection, Nuclear Science and Research Institute, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai-mura, Ibaraki 319-1195 (Japan); Tsutsumi, M.; Saegusa, J.; Shikaze, Y.; Yoshizawa, M. [Department of Radiation Protection, Nuclear Science and Research Institute, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai-mura, Ibaraki 319-1195 (Japan)

    2010-12-15

    Target photons mixed in the 144, 250 and 565 keV mono-energetic neutron calibration fields were measured using a cylindrical NaI(Tl) detector with 7.62 cm both in diameter and in length. The ambient dose equivalent H*(10) of the photons was evaluated by applying the 'G(E) function' to the measured pulse height spectrum. Neutrons induce photons by nuclear reactions in the NaI(Tl) detector and affect the pulse height spectrum. In order to eliminate the influence of these neutron events, the time-of-flight technique was applied with operating the accelerator in the pulse mode. The ratios by the ambient dose equivalent H*(10) of the photons to the 144, 250 and 565 keV neutrons were evaluated to be 3.3%, 4.7% and 0.9%, respectively. Although high energy photons ranging from 6 to 7 MeV are emitted by the {sup 19}F(p,{alpha}{gamma}){sup 16}O reactions, the dose of the target photons is low enough to calibrate neutron dosemeters except for ones with high sensitivity to the photons.

  2. 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.

  3. Measurements of Fission and Radioactive Capture Reaction Rates Inside the Fuel of the Ipen/MB-01

    Science.gov (United States)

    Mura, Luís Felipe L.; Bitelli, Ulysses d'Utra; Fanaro, Leda C. C. B.

    2011-05-01

    This work presents the measures of the nuclear reaction rates along the radial direction of the fuel pellet by irradiation and posterior gamma spectrometry of a thin slice of fuel pellet of UO2 at 4.3% enrichment. From its irradiation, the rate of radioactive capture and fission had been measured as a function of the radius of the pellet disk using a Ortec GMX HPGe detector. Lead collimators had been used for this purpose. Simulating the fuel pellet in the pin fuel of the IPEN/MB-01 reactor, a thin UO2 disk is used, being inserted in the interior of a dismountable fuel rod. This fuel rod is then placed in the central position of the IPEN/MB-01 reactor core and irradiated during 1 h under a neutron flux of 5 ×108 n/cm2 s. In gamma spectrometry, 10 collimators with different diameters have been used; consequently, the nuclear reactions of radioactive capture that occurs in atoms of 238U and the fission that occurs on both 235U and 238U are measured in function of 10 different regions (diameter of collimator) of the UO2 fuel pellet disk. Nuclear fission produces different fission products such as 143Ce with a yield fission of 5.9% which decay is monitored in this work. Corrections in geometric efficiency due to introduction of collimators on HPGe detection system were estimated using photon transport of MCNP-4C code. Some calculated values of nuclear reaction rate of radioactive capture and fission along the radial direction of the fuel pellet obtained by Monte Carlo methodology, using the MCNP-4C code, are presented and compared to the experimental data showing very good agreement.

  4. 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

  5. Population of neutron unbound states via two-proton knockout reactions

    CERN Document Server

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

    2007-01-01

    The two-proton knockout reaction 9Be(26Ne,O2p) was used to explore excited unbound states of 23O and 24O. In 23O a state at an excitation energy of 2.79(13) MeV was observed. There was no conclusive evidence for the population of excited states in 24O.

  6. Determination of the thermal neutron induced O-17(n,alpha) C-14 reaction cross section

    NARCIS (Netherlands)

    Wagemans, J; Wagemans, C; Bieber, R; Geltenbort, P

    1998-01-01

    The. O-17(n(th),alpha)C-14 reaction cross section was determined at the high flux reactor of the ILL in Grenoble relative to the known N-14(n(th),p)C-14 cross section. For the flux calibration measurements, N-14(2) from the air was used. The O-17(n,alpha) measurements were performed with several hig

  7. Biological shielding assessment and dose rate calculation for a neutron inspection portal

    Science.gov (United States)

    Donzella, A.; Bonomi, G.; Giroletti, E.; Zenoni, A.

    2012-04-01

    With reference to the prototype of neutron inspection portal built and successfully tested in the Rijeka seaport (Croatia) within the EURITRACK (EURopean Illicit Trafficking Countermeasures Kit) project, an assessment of the biological shielding in different set-up configurations of a future portal has been calculated with MCNP Monte Carlo code in the frame of the Eritr@C (European Riposte against Illicit TR@ffiCking) project. In the configurations analyzed the compliance with the dose limits for workers and the population stated by the European legislation is provided by appropriate shielding of the neutron sources and by the delimitation of a controlled area.

  8. Characterization of shock-dependent reaction rates in an aluminum/perfluoropolyether pyrolant

    Science.gov (United States)

    Wilson, Dennis; Granier, John; Johnson, Richard; Littrell, Donald

    2017-01-01

    Energetic formulations of perfluoropolyether (PFPE) and aluminum are highly non-ideal. They release energy via a fast self-oxidized combustion wave rather than a true self-sustaining detonation. Unlike high explosives, the reactions are shock dependent and can be overdriven to control energy release rate. Reaction rate experiments show that the velocity can vary from 1.25 to 3 km/s. This paper examines the effect of the initial shock conditions upon the reaction rate of the explosive. The following conditions were varied in a series of reaction rate experiments: the high explosive booster mass and geometry; shock attenuation; confinement; and rate stick diameter and length. Several experiments designed to isolate and quantify these dependencies are described and summarized.

  9. 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.

  10. Why does neutron transfer play different roles in sub-barrier fusion reactions $^{32}$S+$^{94,96}$Zr and $^{40}$Ca+$^{94,96}$Zr?

    OpenAIRE

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

    2014-01-01

    The sub-barrier capture (fusion) reactions $^{32}$S+$^{90,94,96}$Zr, $^{36}$S+$^{90,96}$Zr, $^{40}$Ca+$^{90,94,96}$Zr, and $^{48}$Ca+$^{90,96}$Zr with positive and negative $Q$-values for neutron transfer are studied within the quantum diffusion approach and the universal fusion function representation. For these systems, the s-wave capture probabilities are extracted from the experimental excitation functions and are also analyzed. Different effects of the positive $Q_{xn}$-value neutron tra...

  11. Investigating neutron-proton pairing in s d -shell nuclei via (p ,3He) and (3He,p ) transfer reactions

    Science.gov (United States)

    Ayyad, Y.; Lee, J.; Tamii, A.; Lay, J. A.; Macchiavelli, A. O.; Aoi, N.; Brown, B. A.; Fujita, H.; Fujita, Y.; Ganioglu, E.; Hatanaka, K.; Hashimoto, T.; Ito, T.; Kawabata, T.; Li, Z.; Liu, H.; Matsubara, H.; Miki, K.; Ong, H. J.; Potel, G.; Sugai, I.; Susoy, G.; Vitturi, A.; Watanabe, H. D.; Yokota, N.; Zenihiro, J.

    2017-08-01

    Neutron-proton pairing correlations are investigated in detail via n p transfer reactions in N =Z s d -shell nuclei. In particular, we study the cross-section ratio of the lowest 0+ and 1+ states as an observable to quantify the interplay between T =0 (isoscalar) and T =1 (isovector) pairing strengths. The experimental results are compared to second-order distorted-wave Born approximation calculations with proton-neutron amplitudes obtained in the shell-model formalism using the universal s d -shell interaction B. Our results suggest underestimation of the nonneglible isoscalar pairing strength in the shell-model descriptions at the expense of the isovector channel.

  12. High accuracy measurement of the $^{235}$U(n,f) reaction cross-section in the 10-30 keV neutron energy range

    CERN Multimedia

    The analysis of the neutron flux of n_TOF (in EAR1) revealed an anomaly in the 10-30 keV neutron energy range. While the flux extracted on the basis of the $^{6}$Li(n,t)$^{4}$He and $^{10}$B(n,$\\alpha$)$^{7}$Li reactions mostly agreed with each other and with the results of FLUKA simulations of the neutron beam, the one based on the $^{235}$U(n,f) reaction was found to be systematically lower, independently of the detection system used. A possible explanation is that the $^{235}$U(n,f) crosssection in that energy region, where in principle should be known with an uncertainty of 1%, may be systematically overestimated. Such a finding, which has a negligible influence on thermal reactors, would be important for future fast critical or subcritical reactors. Furthermore, its interest is more general, since the $^{235}$U(n,f) reaction is often used at that energy to determine the neutron flux, or as reference in measurements of fission cross section of other actinides. We propose to perform a high-accuracy, high-r...

  13. Comparing transfusion reaction rates for various plasma types: a systematic review and meta-analysis/regression.

    Science.gov (United States)

    Saadah, Nicholas H; van Hout, Fabienne M A; Schipperus, Martin R; le Cessie, Saskia; Middelburg, Rutger A; Wiersum-Osselton, Johanna C; van der Bom, Johanna G

    2017-09-01

    We estimated rates for common plasma-associated transfusion reactions and compared reported rates for various plasma types. We performed a systematic review and meta-analysis of peer-reviewed articles that reported plasma transfusion reaction rates. Random-effects pooled rates were calculated and compared between plasma types. Meta-regression was used to compare various plasma types with regard to their reported plasma transfusion reaction rates. Forty-eight studies reported transfusion reaction rates for fresh-frozen plasma (FFP; mixed-sex and male-only), amotosalen INTERCEPT FFP, methylene blue-treated FFP, and solvent/detergent-treated pooled plasma. Random-effects pooled average rates for FFP were: allergic reactions, 92/10(5) units transfused (95% confidence interval [CI], 46-184/10(5) units transfused); febrile nonhemolytic transfusion reactions (FNHTRs), 12/10(5) units transfused (95% CI, 7-22/10(5) units transfused); transfusion-associated circulatory overload (TACO), 6/10(5) units transfused (95% CI, 1-30/10(5) units transfused); transfusion-related acute lung injury (TRALI), 1.8/10(5) units transfused (95% CI, 1.2-2.7/10(5) units transfused); and anaphylactic reactions, 0.8/10(5) units transfused (95% CI, 0-45.7/10(5) units transfused). Risk differences between plasma types were not significant for allergic reactions, TACO, or anaphylactic reactions. Methylene blue-treated FFP led to fewer FNHTRs than FFP (risk difference = -15.3 FNHTRs/10(5) units transfused; 95% CI, -24.7 to -7.1 reactions/10(5) units transfused); and male-only FFP led to fewer cases of TRALI than mixed-sex FFP (risk difference = -0.74 TRALI/10(5) units transfused; 95% CI, -2.42 to -0.42 injuries/10(5) units transfused). Meta-regression demonstrates that the rate of FNHTRs is lower for methylene blue-treated compared with FFP, and the rate of TRALI is lower for male-only than for mixed-sex FFP; whereas no significant differences are observed between plasma types for allergic

  14. A microdosimetric study of {sup 10}B(n,{alpha}){sup 7}Li and {sup 157}Gd(n,{gamma}) reactions for neutron capture therapy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.K.C.; Sutton, M.; Evans, T.M. [Georgia Inst. of Tech., Atlanta, GA (United States); Laster, B.H. [Brookhaven National Lab., Upton, NY (United States). Medical Dept.

    1999-01-01

    This paper presents the microdosimetric analysis for the most interesting cell survival experiment recently performed at the Brookhaven National Laboratory (BNL). In this experiment, the cells were first treated with a gadolinium (Gd) labeled tumor-seeking boronated porphyrin (Gd-BOPP) or with BOPP alone, and then irradiated with thermal neutrons. The resulting cell-survival curves indicate that the {sup 157}Gd(n,{gamma}) reactions are very effective in cell killing. The death of a cell treated with Gd-BOPP was attributed to either the {sup 10}B(n,{alpha}){sup 7}Li reactions or the {sup 157}Gd(n,{gamma}) reactions (or both). However, the quantitative relationship between the two types of reaction and the cell-survival fraction was not clear. This paper presents the microdosimetric analysis for the BNL experiment based on the measured experimental parameters, and the results clearly suggest a quantitative relationship between the two types of reaction and the cell survival fraction. The results also suggest new research in gadolinium neutron capture therapy (GdNCT) which may lead to a more practical modality than the boron neutron capture therapy (BNCT) for treating cancers.

  15. Astrophysical Reaction Rates of the 8Li(p,γ)9Beg.s. Direct Capture Reaction

    Institute of Scientific and Technical Information of China (English)

    Su Jun; WANG You-Bao; LI Zhi-Hong; GUO Bing; LIU Wei-Ping; BAI Xi-Xiang; ZENG Sheng; LIAN Gang; YAN Sheng-Quan; WANG Bao-Xiang

    2006-01-01

    Based 0n the angular distribution of the 8Li(d,n)9Beg.s. reaction at Ec.m.=8.0 MeV and distorted wave Born approximation analysis,the single particle spectroscopic factor S1,3/2 for the ground state of 9Be=8Li(×)p is derived to be 0.64±0.21.In addition,we deduce the astrophysical S-factors and rates of the 8Li(p,γ)9Beg.s. direct capture reaction at energies of astrophysical interests.

  16. Astrophysical S-Factors and Reaction Rates of Threshold (p, n)-Reactions on 99-102Ru

    Science.gov (United States)

    Skakun, Ye.; Rauscher, T.

    2010-08-01

    Astrophysical S-factors of (p, n) reactions on 99Ru, 100Ru, 101Ru, and 102Ru were derived from the sum of experimental isomeric and ground states cross sections measured in the incident proton energy range of 5-9 MeV. They were compared with Hauser-Feshbach statistical model predictions of the NON-SMOKER code. Good agreement was found in the majority of cases. Reaction rates were derived up to 8.7 GK stellar temperature by combining experiment and theory.

  17. Combustion of Bimodal Nano/Micro Aluminum Suspension with New Reaction Rate Model

    Directory of Open Access Journals (Sweden)

    M. Bidabadi

    2008-01-01

    Full Text Available In this study a mathematical model for combustion of bimodal particle in lean flow was developed. The difference between structure of flame in this work and previous ones was that, in those flame was divided by five zones and reaction rate was considered to be constant in reaction zones and also zero in post flame zone. In reality it was obvious with respect to shape and size of different particles in dust, reaction didn't end suddenly. In the present research the heat loss term, which was assumed to be linearly proportional to temperature difference, was added to the energy conservation equation and reaction rate was considered proportional to available amount of fuel, leading to exponentially decreasing of reaction rate. The flame speed and temperature distribution were obtained by solving the energy equation in each zone and matching the temperature and heat flux at the interfacial boundaries. Calculated values of flame speed were in good agreement with experimental data.

  18. Reaction rate estimation of controlled-release antifouling paint binders: Rosin-based systems

    DEFF Research Database (Denmark)

    Meseguer Yebra, Diego; Kiil, Søren; Dam-Johansen, Kim

    2005-01-01

    at product optimisation and innovation (e.g. incorporation of natural active agents). This study seeks to attain scientifically founded knowledge of the reaction mechanisms and the rate of reaction with sea water of a Zn-carboxylate of a synthetic rosin compound. The kinetic expression attained can be used...... have shown that mathematical coating models based on a fundamental knowledge of the underlying mechanisms of A/F paints is a promising tool for accelerated product testing at different operational conditions of a sailing ship or a paint rotor. Such models can also be used for generation of ideas aiming...... rather than pointing at a certain diffusion control in the reaction rate experiments. The reverse reaction is found not to affect the hydrolysis rate within the pores, of antifouling paints significantly. It is concluded, from the reaction mechanism proposed, that the observed partial exchange of Zn2...

  19. Development of Theoretical Methods for Predicting Solvent Effects on Reaction Rates in Supercritical Water Oxidation Processes

    Science.gov (United States)

    2007-11-02

    Tucker, manuscript in preparation. “Examination of Nonequilibrium Solvent Effects on an SN2 Reaction in Supercritical Water,” R. Behera, B...DATES COVERED Final: 7/1/99 - 12/31/02 4. TITLE AND SUBTITLE Development of theoretical methods for predicting solvent effects on reactions ...computational methods for predicting how reaction rate constants will vary with thermodynamic condition in supercritical water (SCW). Towards this

  20. The Relation Between Damping and Reaction Rates of Fermions in Hot Gauge Theories

    CERN Document Server

    Ayala, A P; Weber, A; Ayala, Alejandro; Olivo, Juan Carlos D'; Weber, Axel

    1998-01-01

    We examine the relation between the damping rate of a chiral fermion mode propagating in a hot plasma and the rate at which the mode approaches equilibrium. We show that these two quantities, obtained from the imaginary part of the fermion self-energy, are equal provided the reaction rate is defined using the appropriate wave function of the mode in the medium.