Studies of photonuclear neutron emission during the start-up phase of the Alcator C tokamak

International Nuclear Information System (INIS)

Pappas, D.S.; Furnstahl, R.; Kochanski, G.P.

1981-05-01

Alcator C operations commenced with discharge cleaning and tokamak operation using hydrogen filling gas. Prior to and during these experiments no deuterium gas was allowed into the device. The earliest operation resulted in dosimeter readings of a few Roentgen per shot in the vicinity of the limiter and a localized source of neutron emission of up to 10 9 neutrons/shot. A strong correlation of the neutron emissions with hard x-ray emissions from the limiter and nonthermal features on the synchrotron emissions was observed during these discharges. Gamma energy spectroscopy of the activated limiter after removal from Alcator allowed identification of 16 radioisotopes which were consistent with photonuclear processes (γ,n , γ,p , γ,α reactions) arising in the limiter. After seven months of hydrogen operation conditions were achieved that resulted in substantially less non-thermal activity. Typical neutron emission rates of equal to or less than 10 6 n/sec were observed, i.e., about four orders of magnitude less than the expected D-D thermonuclear neutron emission rates for the same type of discharge if D 2 was used as the filling gas

Space resolved measurements of neutrons and ion emission on plasma focus

International Nuclear Information System (INIS)

Jaeger, U.

1980-05-01

This report describes space-resolved measurements of neutrons and of accelerated charged particles, emitted by a plasmafocus-device. The neutron source has been measured with one and two-dimensional paraffin collimators. The space resolution is 5 mm along the axis and the radius, with a time resolution of 10 ns. In order to make quantitative statements about the neutron yield, neutron-scattering, absorption and nuclear reactions were taken into account. Part of the neutron measurements are carried out together with time and space resolved measurements of the electron density to study possible correlations between nsub(e) and Ysub(n). The following results about the neutron measurement were obtained: The neutron emission reaches its maximum between 40 and 60 ns after the maximum compression. The emission region is limited to a well defined range of 0 50 ns it has been observed a broadening of the emission region in + z-direction. The emission profiles in lower and in higher pressure regimes are almost the same. (orig./HT) [de

X-ray and neutron emission studies in a new Filippov type plasma focus

Energy Technology Data Exchange (ETDEWEB)

Babazadeh, A.R.; Banoushi, A. [Technical University of Amirkabir, Tehran (Iran, Islamic Republic of). Dept. of Physics; Roshan, M.V.; Habibi, H.; Nasiry, A.; Memarzadeh, M.; Lamehi, M.; Kiai, S.M. Sadat [Atomic Energy Organization of Iran (AEOI), Tehran (Iran, Islamic Republic of). Nuclear Fusion Research Center

2002-03-01

We have performed experimental comparative studies of the X-ray and neutron emission generated by the new Filippov-type plasma focus 'Dena', (90 kJ, 25 kV, 288{mu}F) in the pressure range of 0.6-1 torr. Time-integrated and time-resolved detectors, together with an X-ray pin-hole camera, along with a Be filter of 10{mu}m thickness have been used. For a working gas of neon and a at insert anode, the maximum soft and hard X-rays (SXR-HXR) yield obtained was 16 V and 1.5 V/shot over a 4{pi} solid angle, respectively, for a charging voltage range of 16-20 kV. As for the argon gas, the similar results such as 3.5 and 2 V/shot have been found, leading to a total conversion efficiency of X-ray emission of 0.09 % (for neon) and 0.03 % (for argon) of the stored energy. These efficiencies have been improved by the employment of a conic insert anode up to 0.4% and 0.1%. With deuterium puffing gas and a at insert anode, the maximum emission yield has been found to be 2.5 V for SXR and 1 V for HXR/shot which produce an ultimate emission profile width (FWHM) of 70-90 ns for X-rays and neutrons, giving rise to a maximum neutron yield of 1.2 x 10{sup 9}. Nevertheless, the maximum yield has been increased up to 5.5 times with the conic insert anode. In order to increase the neutron yield, we have introduced a krypton admixture to the deuterium filling gas and found that, for a krypton pressure of about 0.1 torr, the neutron yield increases by a factor of 3.5 for the flat insert and 1.5 for the conic insert anodes. (author)

Mechanisms of fission neutron emission

International Nuclear Information System (INIS)

Maerten, H.

1991-01-01

The time evolution in fission is the starting point for discussing not only the main mechanism of fission neutron emission, the evaporation from fully accelerated fragments, but also possible secondary ones connected with dynamical features of nuclear fission. ''Asymptotic'' conditions as relevant for describing the particle release from highly excited, rapidly moving fragments are defined. Corresponding statistical model approaches to fission neutron emission, based on the adequate consideration of the intricate fragment occurrence probability, reproduce most of the experimental data. The remarkable influence of fission modes on neutron observables is analyzed in the framework of a macroscopic-microscopic scission point model consistent with energy conservation. Finally, chances and deficiencies for solving the mechanism puzzle are summarized. (author). 87 refs, 21 figs

Neutron emissivity profile camera diagnostics considering present and future tokamaks

International Nuclear Information System (INIS)

Forsberg, S.

2001-12-01

This thesis describes the neutron profile camera situated at JET. The profile camera is one of the most important neutron emission diagnostic devices operating at JET. It gives useful information of the total neutron yield rate but also about the neutron emissivity distribution. Data analysis was performed in order to compare three different calibration methods. The data was collected from the deuterium campaign, C4, in the beginning of 2001. The thesis also includes a section about the implication of a neutron profile camera for ITER, where the issue regarding interface difficulties is in focus. The ITER JCT (Joint Central Team) proposal of a neutron camera for ITER is studied in some detail

Neutron emissivity profile camera diagnostics considering present and future tokamaks

Energy Technology Data Exchange (ETDEWEB)

Forsberg, S. [EURATOM-VR Association, Uppsala (Sweden)

2001-12-01

This thesis describes the neutron profile camera situated at JET. The profile camera is one of the most important neutron emission diagnostic devices operating at JET. It gives useful information of the total neutron yield rate but also about the neutron emissivity distribution. Data analysis was performed in order to compare three different calibration methods. The data was collected from the deuterium campaign, C4, in the beginning of 2001. The thesis also includes a section about the implication of a neutron profile camera for ITER, where the issue regarding interface difficulties is in focus. The ITER JCT (Joint Central Team) proposal of a neutron camera for ITER is studied in some detail.

Study of Beta-Delayed Neutron Emission by Neutron-Rich Nuclei and Analysis of the Nuclear Reaction Mechanism responsible for the Yields of these Nuclei

International Nuclear Information System (INIS)

Bazin, D.

1987-07-01

Among the nuclear mechanisms used for the production of nuclei far from stability, the projectile fragmentation process has recently proved its efficiency. However, at Fermi energies, one has to take into account some collective and relaxation effects which drastically modify the production cross-sections. The spectroscopic study of very neutron-rich nuclei is very dependent of these production rates. A study of beta-delayed neutron emission which leads to new measurements of half-lives and neutron delayed emission probabilities is achieved with a liquid scintillator detector. The results which are then compared to different theories are of interest for the understanding of natural production of heavy elements (r processus) [fr

Delayed neutron emission near the shell-closures

Directory of Open Access Journals (Sweden)

Borzov Ivan

2016-01-01

Full Text Available The self-consistent Density Functional + Continuum QRPA approach (DF+CQRPA provides a good description of the recent experimental beta-decay half-lives and delayed neutron emission branchings for the nuclei approaching to (and beyond the neutron closed shells N = 28; 50; 82. Predictions of beta-decay properties are more reliable than the ones of standard global approaches traditionally used for the r-process modelling. An impact of the quasi-particle phonon coupling on the delayed multi-neutron emission rates P2n, P3n,… near the closed shells is also discussed.

Theoretical descriptions of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1991-01-01

Brief descriptions are given of the observables in neutron emission in fission together with early theoretical representations of two of these observables, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity ν-bar p . This is followed by summaries, together with examples, of modern approaches to the calculation of these two quantities. Here, emphasis is placed upon the predictability and accuracy of the new approaches. In particular, the dependencies of N(E) and ν-bar p upon the fissioning nucleus and its excitation energy are discussed. Then, recent work in multiple-chance fission and other recent work involving new measurements are presented and discussed. Following this, some properties of fission fragments are mentioned that must be better known and better understood in order to calculate N(E) and ν-bar p with higher accuracy than is currently possible. In conclusion, some measurements are recommended for the purpose of benchmarking simultaneous calculations of neutron emission and gamma emission in fission. (author). 32 refs, 26 figs

Fission-neutrons source with fast neutron-emission timing

Energy Technology Data Exchange (ETDEWEB)

Rusev, G., E-mail: rusev@lanl.gov; Baramsai, B.; Bond, E.M.; Jandel, M.

2016-05-01

A neutron source with fast timing has been built to help with detector-response measurements. The source is based on the neutron emission from the spontaneous fission of {sup 252}Cf. The time is provided by registering the fission fragments in a layer of a thin scintillation film with a signal rise time of 1 ns. The scintillation light output is measured by two silicon photomultipliers with rise time of 0.5 ns. Overall time resolution of the source is 0.3 ns. Design of the source and test measurements using it are described. An example application of the source for determining the neutron/gamma pulse-shape discrimination by a stilbene crystal is given.

Neutron emission spectra and level density of hot rotating 132Sn

International Nuclear Information System (INIS)

Aggarwal, Mamta

2008-01-01

The neutron emission spectrum of the highly excited compound nuclear system 132 Sn is investigated at high spin. The doubly magic nucleus 132 Sn undergoes a shape transition at high angular momentum which affects the nuclear level density and neutron emission probability considerably. The interplay of temperature, shape, deformation and rotational degrees of freedom and their influence on neutron emission is emphasized. We predict an enhancement of nucleonic emission at those spins where the nucleus suffers a transition from a spherical to deformed shape. (author)

Neutron emission in heavy ion induced reactions at 10 MeV/A

International Nuclear Information System (INIS)

Benrachi, F.

1984-01-01

The neutron emission mechanism in reactions induced by heavy ions (in which a high energy component had already been observed) has been investigated. To get informations on the desexcitation mode which is responsible of that component and on the sharing of the excitation energy between the fragments, a very disymmetric system 14 N+ 165 Ho at E inc=10,5 MeV/a.m.u. was studied. The neutrons are preferentially emitted forward in the direction of the quasi-projectile and are in average highly energetic. The calculations of the excitation energies and of the multiplicities showed that the detected events are mainly coming from peripheral processes with a weak angular momentum exchange. The analysis of the energy spectra and of the invariance cross section maps pointed out a strong asymmetry and then proved that at least two neutron sources were involved in that reaction mechanism. Studying these two components in terms of a sequential mechanism i.e. an emission from the totally equilibrated quasi-target and quasi-projectile, the whole neutron emission could not be explained. To interpret the experimental results, non statistical models with a preequilibrium emission at the collision beginning were used [fr

The impact of the tensor interaction on the β-delayed neutron emission of the neutron-rich Ni isotopes

Directory of Open Access Journals (Sweden)

Sushenok E.O.

2018-01-01

Full Text Available The neutron emission of the β-decay of 74;76;78;80Ni are studied within the quasiparticle random phase approximation with the Skyrme interaction. The coupling between one- and two-phonon terms in the wave functions of the low-energy 1+ states of the daughter nuclei is taken into account. It is shown that the strength decrease of the neutronproton tensor interaction leads to the increase of the half-life and the neutron-emission probability.

Neutron emission during acceleration of 252Cf fission fragments

International Nuclear Information System (INIS)

Batenkov, O.I.; Blinov, M.V.; Blinov, A.B.; Smirnov, S.N.

1991-01-01

We investigate neutron emission during acceleration of fission fragments in the process of spontaneous fission of 252 Cf. Experimental angular and energy distributions of neutrons are compared with the results of calculations of neutron evaporation during fragment acceleration. (author). 8 refs, 3 figs

Investigation of neutron emission in a cold fusion experiment in palladium

International Nuclear Information System (INIS)

Szustakowski, M.; Farny, J.; Muniak, M.; Nowak, A.; Parys, P.; Skrzeczanowski, W.; Socha, R.; Teter, J.; Wolski, J.; Wolowski, J.; Woryna, E.

1989-01-01

This paper reports on the experiments dealing with performance of nuclear fusion at room temperature actually which create a great sensation and are carried out in various laboratories. This interest arises from the results achieved by Fleischmann and Pons, and it results from their paper that there exists a possibility of obtaining an ignition owing to nuclear fusion reactions during usual electrochemical process--namely the electrolysis of D O with use of the system of Pd-Pt electrodes. From this reason the measurements of the yield and behavior of neutron emission give the information about processes of interest. At the IPPLM the cold fusion experiments have been conducted from the beginning of April 1989. In the first experiment the reliable evidence of neutron emission was obtained. A number of irregularly repeated neutron pulses of the level of 10 5 per pulse was recorded. The measurements of the neutron emission, in this experiment, were performed with the use of three independent methods employing the 2.5 MeV neutron spectrometer, the scintillation neutron detector as well as the nuclear track detector. neutron emission had been first recorded after 106 hours of the electrolysis process of D 2 O

Energy spectra of neutrons accompanying the emission fission of 238U

International Nuclear Information System (INIS)

Smirenkin, G.N.; Lovchikova, G.N.; Trufanov, A.M.; Svirin, M.I.; Polyakov, A.V.; Vinogradov, V.A.; Dmitriev, V.D.; Boykov, G.S.

1996-01-01

The spectra of fission neutrons emitted from 238U are measured for the first time by the time-of-flight method at incident-neutron energies of 16.0 and 17.7 MeV. Analysis of the neutron spectra shows that experimental results at incident-neutron energies of 14.7, 16.0, and 17.7 MeV (above the threshold of chance fission) differ significantly from those obtained at a neutron energy of 2.9 MeV (below the threshold of chance fission). Owing to the prefission emission of neutrons, the observed spectra of neutrons from emission fission exhibit a characteristic growth of the neutron yield in both hard and soft sections of the spectrum of secondary neutrons. This growth manifests itself as a step in the first case and as a rise in the second case, where it results in a noticeable excess of neutrons over the statistical-model predictions for E<2 MeV. The first feature in the spectra of neutrons from emission fission can be associated with the nonequilibrium decay of an excited fissile nucleus. On the contrary, the origin of the second feature has yet to be clarified. Additional measurements of angular distributions of secondary neutrons may prove helpful in this respect

LORINE: Neutron emission Locator by SOI detectors

Energy Technology Data Exchange (ETDEWEB)

Hamrita, H.; Kondrasovs, V.; Borbotte, J. M.; Normand, S. [CEA, LIST, Laboratoire Capteurs et Architectures Electronique, F-91191 Gif-sur-Yvette Cedex (France); Saurel, N. [CEA, DAM, VALDUC, F-21120 Is sur Tille (France)

2009-07-01

The aim of this work is to develop a fast Neutron Emission Locator based on silicon on Insulator detector (LORINE). This locator can be used in the presence of significant flux of gamma radiation. LORINE was developed to locate areas containing a significant amount of actinide during the dismantling operations of equipment. From the results obtained in laboratory, we have proposed the prototype of neutron emission locator as follows: the developed design consists of 5 SOI (Silicon-on-insulator) detectors (1*1 cm{sup 2}) with their charge preamplifiers and their respective converters. All are installed on 5 faces of a boron polyethylene cube (5*5*5 cm{sup 3}). This cube plays the role of neutron shielding between the several detectors. The design must be so compact for use in glove boxes. An electronic card based on micro-controller has been made to control sensors and to send the necessary information to the computer. Location of fast neutron sources does not yet exist in a so compact design and it can be operated in the presence of very important gamma radiation flux

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.

Maser Emission from Gravitational States on Isolated Neutron Stars

Science.gov (United States)

Tepliakov, Nikita V.; Vovk, Tatiana A.; Rukhlenko, Ivan D.; Rozhdestvensky, Yuri V.

2018-04-01

Despite years of research on neutron stars, the source of their radio emission is still under debate. Here we propose a new coherent mechanism of pulsar radio emission based on transitions between gravitational states of electrons confined above the pulsar atmosphere. Our mechanism assumes that the coherent radiation is generated upon the electric and magnetic dipole transitions of electrons falling onto the polar caps of the pulsar, and predicts that this radiation occurs at radio frequencies—in full agreement with the observed emission spectra. We show that while the linearly polarized electric dipole radiation propagates parallel to the neutron star surface and has a fan-shape angular spectrum, the magnetic dipole emission comes from the magnetic poles of the pulsar in the form of two narrow beams and is elliptically polarized due to the spin–orbit coupling of electrons confined by the magnetic field. By explaining the main observables of the pulsar radio emission, the proposed mechanism indicates that gravitational quantum confinement plays an essential role in the physics of neutron stars.

Studies of neutron emission from relativistic nuclear interactions

CERN Document Server

Guo, S L; Wang, Y L; Guo, H Y; Sá Ben-Hao; Zheng, Y M; Brandt, R; Vater, P; Wan, J S; Ochs, M; Kulakov, B A; Sosnin, A N; Krivopustov, M I; Butsev, V S; Bradnova, V

1999-01-01

Studies were carried out on the yields and spatial distributions of secondary neutrons produced in the relativistic nuclear interactions of 1.5 GeV to 14.4 GeV projectiles p, d and alpha-particles with targets Pb and U/Pb. CR-39 track detectors were used to measure the neutrons. It shows that: (1) Secondary neutrons are produced in the whole length of Pb or U targets having a thickness of 20 cm. The neutron intensities produced by proton bombardments are reduced along the proton beam direction in the targets. The higher the energy of protons, the lower the reduction rate of the neutrons. The reduction rate of neutrons in U target is higher than in Pb target for the same energy of protons. (2) The radial intensities of neutrons decrease as the distance increases from the target central line. (3) The neutron yield in U target by proton bombardments is approx 55% higher than in Pb target. (4) The ratio of neutron yield by 14.4 GeV alpha to 7.3 GeV d bombardment in Pb target is 1.74+-0.20.

Neutron emission study after muon capture by nuclei

International Nuclear Information System (INIS)

Bouyssy, Alain.

1974-01-01

Muon capture by nuclei, used in the beginning for checking the weak interaction, is now a method of investigation of nuclear structure. Study of spectrum, asymmetry and polarization of emitted neutrons after polarized muon capture has been done in three directions: weak coupling constants, final state interaction, nuclear wave functions. The neutron intensity and helicity are very dependent of the neutron - residual nucleus interaction, while the asymmetry is sensitive to the wave functions used for the proton. Moreover if the induced tensor coupling constant is different from zero the asymmetry is increased. Longitudinal polarization experiments, with those for neutron intensity, would be of great interest to give informations on neutron asymmetry [fr

Study of the trace tritium content in deuterium plasmas of the JET tokamak based on neutron emission spectroscopy measurements

Energy Technology Data Exchange (ETDEWEB)

Ringmar, David

2001-02-01

This thesis describes a study of the evolution of the trace tritium content in the JET tokamak. The study is based on measurements of the neutron emission, which were performed with the magnetic proton recoil (MPR) spectrometer. Data analysis procedures used to extract the results are described in some detail. The thesis also describes a simplified theoretical model to calculate the absolute tritium concentration with a comparison to the experimental results. The present study covers the time period 1996-2000 and the evolution of neutron emission spectroscopy (NES) results are compared with information from related diagnostic sources, and used to discuss the important issue of how tritium is retained in the JET tokamak.

Study of the trace tritium content in deuterium plasmas of the JET tokamak based on neutron emission spectroscopy measurements

International Nuclear Information System (INIS)

Ringmar, David

2001-02-01

This thesis describes a study of the evolution of the trace tritium content in the JET tokamak. The study is based on measurements of the neutron emission, which were performed with the magnetic proton recoil (MPR) spectrometer. Data analysis procedures used to extract the results are described in some detail. The thesis also describes a simplified theoretical model to calculate the absolute tritium concentration with a comparison to the experimental results. The present study covers the time period 1996-2000 and the evolution of neutron emission spectroscopy (NES) results are compared with information from related diagnostic sources, and used to discuss the important issue of how tritium is retained in the JET tokamak

T-odd angular correlations in the emission of prompt gamma rays and neutrons in nuclear fission induced by polarized neutrons

International Nuclear Information System (INIS)

Danilyan, G. V.; Klenke, J.; Krakhotin, V. A.; Kopach, Yu. N.; Novitsky, V. V.; Pavlov, V. S.; Shatalov, P. B.

2011-01-01

Study of the T-odd three-vector correlation in the emission of prompt neutrons from 235 U fission by polarized cold neutrons has been continued at the facility MEPHISTO of the FRM II reactor (Technical University of Munich). The sought correlation was not found within experimental error of 2.3 × 10 −5 . The upper limit for the asymmetry coefficient has been set to vertical bar D n vertical bar −5 at 99% confidence level, whereas for ternary fission correlation coefficient D α = (170±20) × 10 −5 . This limit casts doubt on a model that explains the three-vector correlation in ternary fission by the Coriolis mechanism. At the same time, five-vector correlation in the emission of prompt fission neutrons has been measured, which describes the rotation of the fissioning nucleus at the moment it breaks (ROT effect). At the angle 22.5° to the fission axis, the correlation coefficient was found to be (1.57 ± 0.20) × 10 −4 , while at the angle of 67.5° it is zero within the experimental uncertainty. The existence of ROT effect in the emission of prompt fission neutrons can be explained by the anisotropy of neutron emission in the rest frame of the fragment (fission fragments are aligned with respect to the axis of deformation of the fissioning nucleus), similar to the mechanism of ROT effect in the emission of prompt γ-rays.

A study on fast digital discrimination of neutron and gamma-ray for improvement neutron emission profile measurement

International Nuclear Information System (INIS)

Uchida, Y.; Takada, E.; Fujisaki, A.; Isobe, M.; Ogawa, K.; Shinohara, K.; Tomita, H.; Kawarabayashi, J.; Iguchi, T.

2014-01-01

Neutron and γ-ray (n-γ) discrimination with a digital signal processing system has been used to measure the neutron emission profile in magnetic confinement fusion devices. However, a sampling rate must be set low to extend the measurement time because the memory storage is limited. Time jitter decreases a discrimination quality due to a low sampling rate. As described in this paper, a new charge comparison method was developed. Furthermore, automatic n-γ discrimination method was examined using a probabilistic approach. Analysis results were investigated using the figure of merit. Results show that the discrimination quality was improved. Automatic discrimination was applied using the EM algorithm and k-means algorithm

A study on fast digital discrimination of neutron and gamma-ray for improvement neutron emission profile measurement

Energy Technology Data Exchange (ETDEWEB)

Uchida, Y., E-mail: h1312101@mailg.nc-toyama.ac.jp; Takada, E.; Fujisaki, A. [National Institute of Technology, Toyama College, 13 Hongo-machi, Toyama 939-8630 (Japan); Isobe, M. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); The Graduate University for Advanced Studies (SOKENDAI), 322-6 Oroshi-cho, Toki 509-5292 (Japan); Ogawa, K. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Shinohara, K. [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0913 (Japan); Tomita, H.; Kawarabayashi, J.; Iguchi, T. [Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

2014-11-15

Neutron and γ-ray (n-γ) discrimination with a digital signal processing system has been used to measure the neutron emission profile in magnetic confinement fusion devices. However, a sampling rate must be set low to extend the measurement time because the memory storage is limited. Time jitter decreases a discrimination quality due to a low sampling rate. As described in this paper, a new charge comparison method was developed. Furthermore, automatic n-γ discrimination method was examined using a probabilistic approach. Analysis results were investigated using the figure of merit. Results show that the discrimination quality was improved. Automatic discrimination was applied using the EM algorithm and k-means algorithm.

Fast Neutron Emission Tomography of Used Nuclear Fuel Assemblies

Science.gov (United States)

Hausladen, Paul; Iyengar, Anagha; Fabris, Lorenzo; Yang, Jinan; Hu, Jianwei; Blackston, Matthew

2017-09-01

Oak Ridge National Laboratory is developing a new capability to perform passive fast neutron emission tomography of spent nuclear fuel assemblies for the purpose of verifying their integrity for international safeguards applications. Most of the world's plutonium is contained in spent nuclear fuel, so it is desirable to detect the diversion of irradiated fuel rods from an assembly prior to its transfer to ``difficult to access'' storage, such as a dry cask or permanent repository, where re-verification is practically impossible. Nuclear fuel assemblies typically consist of an array of fuel rods that, depending on exposure in the reactor and consequent ingrowth of 244Cm, are spontaneous sources of as many as 109 neutrons s-1. Neutron emission tomography uses collimation to isolate neutron activity along ``lines of response'' through the assembly and, by combining many collimated views through the object, mathematically extracts the neutron emission from each fuel rod. This technique, by combining the use of fast neutrons -which can penetrate the entire fuel assembly -and computed tomography, is capable of detecting vacancies or substitutions of individual fuel rods. This paper will report on the physics design and component testing of the imaging system. This material is based upon work supported by the U.S. Department of Energy, Office of Defense Nuclear Nonproliferation Research and Development within the National Nuclear Security Administration, under Contract Number DE-AC05-00OR22725.

Investigation and analysis of neutron emission characteristics in Denaplasma focus facility

International Nuclear Information System (INIS)

Goodarzi, Sh.; Amrollahi, R.; Babazadeh, A.; Nasiri, A.

2003-01-01

Since the first experiments with plasma focus facilities in 1960' s. These devices are known as intense sources of neutron when the working gas contains deuterium with a proper density. Most of the emitted neutrons are produced by D-D reactions, but the mechanism of these reactions in not still clear completely. In this paper, the results of experimental investigations of neutron emission characteristics in D ena p lasma focus facility (Filipov type, 90 kJ, 25 kV) over a range of discharge voltages and pressures are presented. Out working gases are D 2 and D 2+%1 Kr, two different conic and flat insert anodes were employed. We have simultaneously measured the total emission in our experiments for analyzing the neutron generation mechanism in this device. We have found the upper and lower pressure limits and the optimum pressure for neutron generation, and we have observed the double pluses structure of neutron signal for the first time in this device. Form the experimental results, it seems that both thermonuclear and no thermonuclear mechanisms are always present in neutron generation, but their contribution in the total yield is strongly dependent on experimental conditions (initial pressure, discharge voltage, gas admixture, etc.). It was found that the range of variation of total neutron yield and neutron emission anisotropy factor for experiments with D + %1 Kr is wider than experiments with D 2, and the best neutron emission results belongs to discharges in D 2 + %1 Kr with a conic insert anode. By employing D 2 + %1 Kr with a conic insert anode, and varying pressure between 0.3-2 torr at a discharge voltage of 16 kV, it can be deduced that in low pressures ( n ∝ I α ρ ∝E α / 2 was found about 3.62 for D 2 + %1 Kr and 3 for D 2

Theory of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1989-01-01

Following a summary of the observables in neutron emission in fission, a brief history is given of theoretical representations of the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity /bar /nu///sub p/. This is followed by descriptions, together with examples, of modern approaches to the calculation of these quantities including recent advancements. Emphasis will be placed upon the predictability and accuracy of the modern approaches. In particular, the dependence of N(E) and /bar /nu///sub p/ on the fissioning nucleus and its excitation energy will be discussed, as will the effects of and competition between first-, second- and third-chance fission in circumstances of high excitation energy. Finally, properties of neutron-rich (fission-fragment) nuclei are discussed that must be better known to calculate N(E) and /bar /nu///sub p/ with higher accuracy than is currently possible. 17 refs., 11 figs

Theory of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1998-01-01

A survey of theoretical representations of two of the observables in neutron emission in fission is given, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity bar ν p . Early representations of the two observables are presented and their deficiencies are discussed. This is followed by summaries and some examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the recent models. In particular, the dependencies of N(E) and bar ν p upon the fissioning nucleus and its excitation energy are treated in detail for the Los Alamos model. Recent work in the calculation of the prompt fission neutron spectrum matrix N(E, E n ), where E n is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of the ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches. This paper is an extension of a similar paper presented at the International Centre for Theoretical Physics in 1996

Recent activities for β-decay half-lives and β-delayed neutron emission of very neutron-rich isotopes

Energy Technology Data Exchange (ETDEWEB)

Dillmann, Iris [TRIUMF, Vancouver BC, V6T 2A3, Canada and GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt (Germany); Abriola, Daniel [Laboratorio Tandar, Comisión Nacional de Energía Atómica, B1650KINA, San Martín, Buenos Aires (Argentina); Singh, Balraj [Department of Physics and Astronomy, McMaster University, Hamilton ON, L8S 4M1 (Canada)

2014-05-02

Beta-delayed neutron (βn) emitters play an important, two-fold role in the stellar nucleosynthesis of heavy elements in the 'rapid neutron-capture process' (r process). On one hand they lead to a detour of the material β-decaying back to stability. On the other hand, the released neutrons increase the neutron-to-seed ratio, and are re-captured during the freeze-out phase and thus influence the final solar r-abundance curve. A large fraction of the isotopes inside the r-process reaction path are not yet experimentally accessible and are located in the (experimental) 'Terra Incognita'. With the next generation of fragmentation and ISOL facilities presently being built or already in operation, one of the main motivation of all projects is the investigation of these very neutron-rich isotopes. A short overview of one of the planned programs to measure βn-emitters at the limits of the presently know isotopes, the BRIKEN campaign (Beta delayed neutron emission measurements at RIKEN) will be given. Presently, about 600 β-delayed one-neutron emitters are accessible, but only for a third of them experimental data are available. Reaching more neutron-rich isotopes means also that multiple neutron-emission becomes the dominant decay mechanism. About 460 β-delayed two-, three-or four-neutron emitters are identified up to now but for only 30 of them experimental data about the neutron branching ratios are available, most of them in the light mass region below A=30. The International Atomic and Energy Agency (IAEA) has identified the urgency and picked up this topic recently in a 'Coordinated Research Project' on a 'Reference Database for Beta-Delayed Neutron Emission Data'. This project will review, compile, and evaluate the existing data for neutron-branching ratios and half-lives of β-delayed neutron emitters and help to ensure a reliable database for the future discoveries of new isotopes and help to constrain astrophysical and

Low-background measurements of neutron emission from Ti metal in pressurized deuterium gas

International Nuclear Information System (INIS)

Menlove, H.O.; Paciotti, M.A.; Claytor, T.N.; Tuggle, D.G.

1991-01-01

A wide variety of neutron detector systems have been used at various research facilities to search for anomalous neutron emission from deuterated metals. Some of these detector systems are summarized here together with possible sources of spurious signals from electronic noise. During the past two years, we have performed experiments to measure neutron emission from pressurized D 2 gas mixed with various forms of titanium metal chips and sponge. Details concerning the neutron detectors, experimental procedures, and results have been reported previously. Our recent experiments have focused on increasing the low-level neutron emission and finding a way to trigger the emission. To improve our detection sensitivity, we have increased the shielding in our counting laboratory, changed to low-background 3 He tubes, and set up additional detector systems in deep underground counting stations. This report is an update on this experimental work. 7 refs., 5 figs., 4 tabs

Ohmic ion temperature and thermal diffusivity profiles from the JET neutron emission profile monitor

Energy Technology Data Exchange (ETDEWEB)

Esposito, B. (ENEA, Frascati (Italy). Centro Ricerche Energia); Marcus, F.B.; Conroy, S.; Jarvis, O.N.; Loughlin, M.J.; Sadler, G.; Belle, P. van (Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking); Adams, J.M.; Watkins, N. (AEA Industrial Technology, Harwell (United Kingdom))

1993-10-01

The JET neutron emission profile monitor was used to study ohmically heated deuterium discharges. The radial profile of the neutron emissivity is deduced from the line-integral data. The profiles of ion temperature, T[sub i], and ion thermal diffusivity, [chi][sub i], are derived under steady-state conditions. The ion thermal diffusivity is higher than, and its scaling with plasma current opposite to, that predicted by neoclassical theory. (author).

Ohmic ion temperature and thermal diffusivity profiles from the JET neutron emission profile monitor

International Nuclear Information System (INIS)

Esposito, B.

1993-01-01

The JET neutron emission profile monitor was used to study ohmically heated deuterium discharges. The radial profile of the neutron emissivity is deduced from the line-integral data. The profiles of ion temperature, T i , and ion thermal diffusivity, χ i , are derived under steady-state conditions. The ion thermal diffusivity is higher than, and its scaling with plasma current opposite to, that predicted by neoclassical theory. (author)

Interaction of 14 MeV neutrons with hydrogenated target proton emission calculation

International Nuclear Information System (INIS)

Martin, G.; Perez, N.; Desdin.

1996-01-01

Using neutron emission data of a 14 MeV neutron generator, a paraffin target, and based on the n + H 1 → n '+ p reaction, have been obtained the characteristics of the proton emission in a proton-neutron mixed field. It was used Monte Carlo simulation and it was obtained the proton output as function of the converter width and the energy spectrum of protons corresponding to different converter thickness. Among 0.07 and 0.2 cm there is a maximum zone for the proton emission. The energy spectrum agrees with obtained on previous papers. Figures showing these results are provided

Neutron emission and fragment yield in high-energy fission

International Nuclear Information System (INIS)

Grudzevich, O. T.; Klinov, D. A.

2013-01-01

The KRIS special library of spectra and emission probabilities in the decays of 1500 nuclei excited up to energies between 150 and 250 MeV was developed for correctly taking into account the decay of highly excited nuclei appearing as fission fragments. The emission of neutrons, protons, and photons was taken into account. Neutron emission fromprimary fragments was found to have a substantial effect on the formation of yields of postneutron nuclei. The library was tested by comparing the calculated and measured yields of products originating from the fission of nuclei that was induced by high-energy protons. The method for calculating these yields was tested on the basis of experimental data on the thermal-neutroninduced fission of 235 U nuclei

Effects of Neutron Emission on Fragment Mass and Kinetic Energy Distribution from Thermal Neutron-Induced Fission of 235U

International Nuclear Information System (INIS)

Montoya, M.; Rojas, J.; Saetone, E.

2007-01-01

The mass and kinetic energy distribution of nuclear fragments from thermal neutron-induced fission of 235 U(n th ,f) have been studied using a Monte-Carlo simulation. Besides reproducing the pronounced broadening in the standard deviation of the kinetic energy at the final fragment mass number around m = 109, our simulation also produces a second broadening around m = 125. These results are in good agreement with the experimental data obtained by Belhafaf et al. and other results on yield of mass. We conclude that the obtained results are a consequence of the characteristics of the neutron emission, the sharp variation in the primary fragment kinetic energy and mass yield curves. We show that because neutron emission is hazardous to make any conclusion on primary quantities distribution of fragments from experimental results on final quantities distributions

The fast neutron emission spectrum of 252-Cf

International Nuclear Information System (INIS)

Bensch, F.

1979-07-01

The aim of this work was a new measurement of the neutron emission spectrum of 252-Cf neutron standard sources as the IAEA is offering to users. The main feature was the application of gas-filled proton-recoil spectrometers and no TOF technique. The special interest of this document was in the temperature parameter of the Maxwellian distribution and in its relative deviations. In this connection, special measurements with high energy resolution were carried out in a search for fine structure neutron groups, which have been observed in some TOF measurements, but could not be reproduced during this measurement

Theoretical models of neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1992-01-01

A brief survey of theoretical representations of two of the observables in neutron emission in fission is given, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity bar v p . Early representations of the two observables are presented and their deficiencies are discussed. This is followed by summaries and examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the new models. In particular, the dependencies of N(E) and bar v p upon the fissioning nucleus and its excitation energy are treated. Recent work in the calculation of the prompt fission neutron spectrum matrix N(E,E n ), where E n is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of our ability to calculate these observables with confidence, the direction of future theoretical efforts, and limititations to current and future calculations. Finally, recommendations are presented as to which model should be used currently and which model should be pursued in future efforts

Measurements of double-differential neutron emission cross sections of {sup 6}Li and {sup 7}Li for 18 MeV neutrons

Energy Technology Data Exchange (ETDEWEB)

Ibaraki, Masanobu; Baba, Mamoru; Matsuyama, Shigeo; Sanami, Toshiya; Win, T.; Miura, Takako; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering

1997-03-01

Double-differential neutron emission cross sections of {sup 6}Li and {sup 7}Li were measured for 18 MeV neutrons at Tohoku University 4.5 MV Dynamitron facility. Neutron emission spectra were obtained down to 1 MeV at 13 angles with energy resolution good enough to separate discrete levels. A care was taken to eliminate the sample-dependent background due to parasitic neutrons. Experimental results were in fair agreement with the JENDL-3.2 data and a simple model considering a three-body breakup process and discrete level excitations. (author)

Determination of the emission rate for the 14 MeV neutron generator with the use of radio-yttrium

Directory of Open Access Journals (Sweden)

Laszynska Ewa

2015-06-01

Full Text Available The neutron emission rate is a crucial parameter for most of the radiation sources that emit neutrons. In the case of large fusion devices the determination of this parameter is necessary for a proper assessment of the power release and the prediction for the neutron budget. The 14 MeV neutron generator will be used for calibration of neutron diagnostics at JET and ITER facilities. The stability of the neutron generator working parameters like emission and angular homogeneity affects the accuracy of calibration other neutron diagnostics. The aim of our experiment was to confirm the usefulness of yttrium activation method for monitoring of the neutron generator SODERN Model: GENIE 16. The reaction rate induced by neutrons inside the yttrium sample was indirectly measured by activation of the yttrium sample, and then by means of the γ-spectrometry method. The pre-calibrated HPGe detector was used to determine the yttrium radioactivity. The emissivity of neutron generator calculated on the basis of the measured radioactivity was compared with the value resulting from its electrical settings, and both of these values were found to be consistent. This allowed for a positive verification of the reaction cross section that was used to determine the reaction rate (6.45 × 10−21 reactions per second and the neutron emission rate (1.04 × 108 n·s−1. Our study confirms usefulness of the yttrium activation method for monitoring of the neutron generator.

Neutron stimulated emission computed tomography: Background corrections

International Nuclear Information System (INIS)

Floyd, Carey E.; Sharma, Amy C.; Bender, Janelle E.; Kapadia, Anuj J.; Xia, Jessie Q.; Harrawood, Brian P.; Tourassi, Georgia D.; Lo, Joseph Y.; Kiser, Matthew R.; Crowell, Alexander S.; Pedroni, Ronald S.; Macri, Robert A.; Tajima, Shigeyuki; Howell, Calvin R.

2007-01-01

Neutron stimulated emission computed tomography (NSECT) is an imaging technique that provides an in-vivo tomographic spectroscopic image of the distribution of elements in a body. To achieve this, a neutron beam illuminates the body. Nuclei in the body along the path of the beam are stimulated by inelastic scattering of the neutrons in the beam and emit characteristic gamma photons whose unique energy identifies the element. The emitted gammas are collected in a spectrometer and form a projection intensity for each spectral line at the projection orientation of the neutron beam. Rotating and translating either the body or the beam will allow a tomographic projection set to be acquired. Images are reconstructed to represent the spatial distribution of elements in the body. Critical to this process is the appropriate removal of background gamma events from the spectrum. Here we demonstrate the equivalence of two background correction techniques and discuss the appropriate application of each

Study of proton and 2 protons emission from light neutron deficient nuclei around A=20

International Nuclear Information System (INIS)

Zerguerras, T.

2001-09-01

Proton and two proton emission from light neutron deficient nuclei around A=20 have been studied. A radioactive beam of 18 Ne, 17 F and 20 Mg, produced at the Grand Accelerateur National d'Ions Lourds by fragmentation of a 24 Mg primary beam at 95 MeV/A, bombarded a 9 Be target to form unbound states. Proton(s) and nuclei from the decay were detected respectively in the MUST array and the SPEG spectrometer. From energy and angle measurements, the invariant mass of the decaying nucleus could be reconstructed. Double coincidence events between a proton and 17 F, 16 O, 15 O, 14 O and 18 Ne were registered to obtain excitation energy spectra of 18 Ne, 17 F, 16 F, 15 F et 19 Na. Generally, the masses measures are in agreement with previous experiments. In the case of 18 Ne, excitation energy and angular distributions agree well with the predictions of a break up model calculation. From 17 Ne proton coincidences, a first experimental measurement of the ground state mass excess of 18 Na has been obtained and yields 24,19(0,15)MeV. Two proton emission from 17 Ne and 18 Ne excited states and the 19 Mg ground state was studied through triple coincidences between two proton and 15 O, 16 O and 17 Ne respectively. In the first case, the proton-proton relative angle distribution in the center of mass has been compared with model calculation. Sequential emission from excited states of 17 Ne, above the proton emission threshold, through 16 F is dominant but a 2 He decay channel could not be excluded. No 2 He emission from the 1.288 MeV 17 Ne state, or from the 6.15 MeV 18 Ne state has been observed. Only one coincidence event between 17 Ne and two proton was registered, the value of the one neutron stripping reaction cross section of 20 Mg being much lower than predicted. (author)

Study of thermoluminescence emissions of dosimetric phosphors; the detection of intermediate neutrons

International Nuclear Information System (INIS)

Santos, E.N. dos.

1979-01-01

Thermally stimulated luminescence (TSL) studies have been carried out in cold-pressed CaSO 4 +DY 2 O 3 +KCl (specimen 1) and natural CaF 2 +DY 2 O 3 + KCl (specimen 2) polycrystaline samples. The ratios of the TSL sensivities of specimens 1 and 2 relative to that of 6 LiF:Mg;Ti (TLD-600) are found to be 24 and 3, respectively. The minimum detectable neutron fluence has been determined to be approximately 3.5X10 5 n/cm 2 . The determination of the effective half-life of the TSL emission lead to the identification of the isotope responsible for the self-irradiation of the specimens: 165 66 DY. (F.E.) [pt

Neutron response study using PADC

International Nuclear Information System (INIS)

El-Badry, B.A; Hegazy, T.M; Morsy, A.A.; Zaki, M.F.

2007-01-01

The results of an experimental work aimed at improving the performances of the Cr-39 nuclear track detector for neutron dosimetry applications. So, a set of Cr-39 plastic detectors was exposed to 252 Cf neutron source, which has the emission rate of 0.68 x 10 8 s ( -1), and neutron dose equivalent rate 1m apart from the source is equal to 3.8 mrem/h. The detection of fast neutrons performed with Cr-39 detector foils, subsequent chemical etching and evaluation of the etched tracks by an automatic track counting system was studied. It is found that the track density grows with the increase of neutron dose and etching time. These results. are compared with previous work. It is found that there is a matching and good agreement with their investigations

Study of the RP-10 reactor neutron beam applied to the neutron radiography

International Nuclear Information System (INIS)

Zegarra, Manuel; Lopez, Alcides

2013-01-01

We have studied the RP-10 reactor radial neutron beam No. 3, which is used for neutron radiographies, by comparing radiograph's with and without the inner duct, and neutron flux determination with in flakes along the external duct, being the presence of photons creating signals at comparable levels of neutron effects, which reduce the quality of the analysis, values around 10 6 and 10 4 n/cm 2 s for thermal and epithermal flux were obtained respectively. It is recommended evaluate the design of the internal duct which presents strong photon emission. (authors).

Post-scission fission theory: Neutron emission in fission

International Nuclear Information System (INIS)

Madland, D.G.

1997-01-01

A survey of theoretical representations of two of the observables in neutron emission in fission is given, namely, the prompt fission neutron spectrum N (E) and the average prompt neutron multiplicity bar ν p . Early representations of the two observables are presented and their deficiencies are discussed. This is followed by summaries and examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the recent models. In particular, the dependencies of N (E) and bar ν p upon the fissioning nucleus and its excitation energy are treated. Recent work in the calculation of the prompt fission neutron spectrum matrix N (E, E n ), where E n is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of our ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches

Phillips-Tikhonov regularization with a priori information for neutron emission tomographic reconstruction on Joint European Torus

Energy Technology Data Exchange (ETDEWEB)

Bielecki, J.; Scholz, M.; Drozdowicz, K. [Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Krakow (Poland); Giacomelli, L. [CCFE, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Istituto di Fisica del Plasma “P. Caldirola,” Milano (Italy); Kiptily, V.; Kempenaars, M. [CCFE, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Conroy, S. [CCFE, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Department of Physics and Astronomy, Uppsala University (Sweden); Craciunescu, T. [IAP, National Institute for Laser Plasma and Radiation Physics, Bucharest (Romania); Collaboration: EUROfusion Consortium, JET, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)

2015-09-15

A method of tomographic reconstruction of the neutron emissivity in the poloidal cross section of the Joint European Torus (JET, Culham, UK) tokamak was developed. Due to very limited data set (two projection angles, 19 lines of sight only) provided by the neutron emission profile monitor (KN3 neutron camera), the reconstruction is an ill-posed inverse problem. The aim of this work consists in making a contribution to the development of reliable plasma tomography reconstruction methods that could be routinely used at JET tokamak. The proposed method is based on Phillips-Tikhonov regularization and incorporates a priori knowledge of the shape of normalized neutron emissivity profile. For the purpose of the optimal selection of the regularization parameters, the shape of normalized neutron emissivity profile is approximated by the shape of normalized electron density profile measured by LIDAR or high resolution Thomson scattering JET diagnostics. In contrast with some previously developed methods of ill-posed plasma tomography reconstruction problem, the developed algorithms do not include any post-processing of the obtained solution and the physical constrains on the solution are imposed during the regularization process. The accuracy of the method is at first evaluated by several tests with synthetic data based on various plasma neutron emissivity models (phantoms). Then, the method is applied to the neutron emissivity reconstruction for JET D plasma discharge #85100. It is demonstrated that this method shows good performance and reliability and it can be routinely used for plasma neutron emissivity reconstruction on JET.

Radial profiles of neutron emission from ohmic discharges in JET

International Nuclear Information System (INIS)

Cheetham, A.; Gottardi, N.; Jarvis, O.N.

1989-01-01

Neutron emission profiles from several ohmically heated discharges have been studied using a variety of analytical techniques to extract the ion temperature profiles which are found to agree well, both in shape and magnitude, with the electron temperature profiles as measured by the LIDAR Thomson scattering diagnostic. (author) 7 refs., 3 figs

Fast neutron-gamma discrimination on neutron emission profile measurement on JT-60U

International Nuclear Information System (INIS)

Ishii, K.; Okamoto, A.; Kitajima, S.; Sasao, M.; Shinohara, K.; Ishikawa, M.; Baba, M.; Isobe, M.

2010-01-01

A digital signal processing (DSP) system is applied to stilbene scintillation detectors of the multichannel neutron emission profile monitor in JT-60U. Automatic analysis of the neutron-γ pulse shape discrimination is a key issue to diminish the processing time in the DSP system, and it has been applied using the two-dimensional (2D) map. Linear discriminant function is used to determine the dividing line between neutron events and γ-ray events on a 2D map. In order to verify the validity of the dividing line determination, the pulse shape discrimination quality is evaluated. As a result, the γ-ray contamination in most of the beam heating phase was negligible compared with the statistical error with 10 ms time resolution.

Neutron emission from impacted solid LiD samples

International Nuclear Information System (INIS)

Kaushik, T.C.; Shyam, A.; Kulkarni, L.V.; Srinivasan, M.

1993-01-01

Nylon projectiles with 0.1 g to 0.3 g mass, accelerated to velocities of 0.2-1 km/s using a 60 cm long electromagnetic accelerator (railgun), have been impacted upon solid lithium deuteride (LiD) samples of 3 proportional counters. The output from the BF 3 set-up is monitored in several ways to characterize the possible neutron emission from the target. This includes a simple technique of counting the single channel analyser (SCA) output through a dead-time unit to identify bursts of < 100 μs duration. Counting is started after a delay of ∼ 1 ms to avoid the initial interference from the capacitor bank discharge. The signal is also recorded in a storage oscilloscope from the start of projectile acceleration along with a time marker just before the impact. From a number of shots taken with and without the samples, a significant evidence of neutron emission from the LiD samples appears to emerge. The experiments suggest that approximately 100 neutrons might be generated during every such impact in a duration of < 4 ms. (author). 7 refs., 3 figs

Array detector for neutron pre-emission investigations

International Nuclear Information System (INIS)

Petrascu, M.; Cruceru, I.; Bordeanu, C.

1999-01-01

It was predicted that in a fusion experiment induced by 11 Li halo nuclei on light targets, due to the very large dimension of 11 Li, one may expect that the valence neutrons will not be absorbed together with the 9 Li core, but will be emitted in the early stage of the fusion process. The experiment aiming at checking this expectation was performed at the RIKEN-RIPS facility. It was found from neutron energy spectra measurements, that an important number of fusions, more than 30%, are preceded by the pre-emission of one or two neutrons. In the position spectra measurements a very narrow neutron component has been found. This component is much narrower than that calculated by using the Cluster Shell Model Approximation (COSMA). The recent results of time- position coincidence measurements show that within the narrow component the neutrons are pre-emitted predominantly as neutron pairs. The Program Advisory Committee of RIKEN has approved a new measurement at RIKEN Ring Cyclotron aiming at investigation of neutron-neutron coincidences by using a new neutron array detector. This detector has been recently accomplished within the collaboration existing between IFIN-HH, Romania and RIKEN, Japan. The array system consists of 81 4 x 4 x 12 cm 3 BC400 plastic scintillators each coupled to XP2972 Phototubes. The mounting and the testing of the new neutron array detector will be done at RIKEN. The components of one of the 81 elements of the array detector are shown in a photo. The Monte Carlo calculated neutron detection efficiencies as a function of energy are shown. This detector will be used for the investigation of neutron-neutron coincidences in the case of Si( 11 Li, fusion) reaction. The cross- talk between adjacent and non adjacent detectors will be determined by using a 9 Li beam. As it is known in the case of Si( 9 Li, fusion) the neutrons are of evaporation origin, and since these neutrons are emitted in 4 π the chance for detecting 2 coincident neutrons in the

Study of calculated and measured time dependent delayed neutron yields

International Nuclear Information System (INIS)

Waldo, R.W.

1980-05-01

Time-dependent delayed neutron emission is of interest in reactor design, reactor dynamics, and nuclear physics studies. The delayed neutrons from neutron-induced fission of 232 U, 237 Np, 238 Pu, 241 Am, /sup 242m/Am, 245 Cm, and 249 Cf were studied for the first time. The delayed neutron emission from 232 Th, 233 U, 235 U, 238 U, 239 Pu, 241 Pu, and 242 Pu were measured as well. The data were used to develop an empirical expression for the total delayed neutron yield. The expression gives accurate results for a large variety of nuclides from 232 Th to 252 Cf. The data measuring the decay of delayed neutrons with time were used to derive another empirical expression predicting the delayed neutron emission with time. It was found that nuclides with similar mass-to-charge ratios have similar decay patterns. Thus the relative decay pattern of one nuclide can be established by any measured nuclide with a similar mass-to-charge ratio. A simple fission product yield model was developed and applied to delayed neutron precursors. It accurately predicts observed yield and decay characteristics. In conclusion, it is possible to not only estimate the total delayed neutron yield for a given nuclide but the time-dependent nature of the delayed neutrons as well. Reactors utilizing recycled fuel or burning actinides are likely to have inventories of fissioning nuclides that have not been studied until now. The delayed neutrons from these nuclides can now be incorporated so that their influence on the stability and control of reactors can be delineated. 8 figures, 39 tables

Experimental verification of neutron emission method for measuring of fissile material content in spent fuel

International Nuclear Information System (INIS)

Abou-Zaid, A.A.; Pytel, K.

1999-01-01

A non-destructive method of measurement of fissile nuclides content remained in spent fuel from research reactor is presented. The method, called the neutron emission one, is based on counting of fission neutrons emitted from fissile isotopes: 235 U, 239 Pu, 241 Pu. Fissions are induced mainly by neutrons supplied by the external neutron source. Another effects contribute also to the measured neutron population, e. g. source neutrons from penetrating the fuel without being captured and scattered, neutrons (α,n) reactions and from spontaneous fissions of actinides. Complexity of phenomena occurring within the measurement facility required the detailed numerical simulation and experimental studies prior design of ultimate measurement stand. In the previous paper, the results of Monte Carlo simulation on optimisation of measuring stand for neutron emission method were presented. On the basis of those results, the experimental stand for Maria reactor fuel investigation has been designed and manufactured. The present paper, being the continuation of previous one, contains the description of experimental facility and the results of measurements for the fresh fuel (without burnup) and the fuel mock-up (without fissile materials). Although some discrepancies were found between Monte Carlo and experimental results, the main conclusions concerning the optimal geometry of measuring facility have been confirmed. (author)

Contributions to the theory of fission neutron emission

International Nuclear Information System (INIS)

Seeliger, D.; Maerten, H.; Ruben, A.

1990-03-01

This report gives a compilation of recent work performed at Technical University, Dresden by D. Seeliger, H. Maerten and A. Ruben on the topic of fission neutron emission. In the first paper calculated fission neutron spectra are presented using the temperature distribution model FINESSE for fissioning actinide nuclei. In the second paper, starting from a general energy balance, Terrell's approach is generalized to describe average fragment energies as a function of incident energy; trends of fragment energy data in the Th-Pu region are well reproduced. In the third contribution, prompt fission neutron spectra and fragment characteristics for spontaneous fission of even Pu-isotopes are presented and discussed in comparison with experimental data using a phenomenological scission point model including temperature dependent shell effects. In the fourth paper, neutron multiplicities and energy spectra as well as average fragment energies for incident energies from threshold to 20 MeV (including multiple-chance fission) for U-238 are compared with traditional data representations. (author). Refs, figs and tabs

Elemental analysis using instrumental neutron activation analysis and inductively coupled plasma atomic emission spectrometry: a comparative study

International Nuclear Information System (INIS)

Chung, Yong Sam; Choi, Kwang Soon; Moon, Jong Hwa; Kim, Sun Ha; Lim, Jong Myoung; Kim, Young Jin; Quraishi, Shamshad Begum

2003-05-01

Elemental analyses for certified reference materials were carried out using instrumental neutron activation analysis and inductively coupled plasma-atomic emission spectrometry. Five Certified Reference Materials (CRM) were selected for the study on comparative analysis of environmental samples. The CRM are Soil (NIST SRM 2709), Coal fly ash (NIST SRM 1633a), urban dust (NIST SRM 1649a) and air particulate on filter media (NIST SRM 2783 and human hair (GBW 09101)

Neutrino emissivity in the quark-hadron mixed phase of neutron stars

Energy Technology Data Exchange (ETDEWEB)

Spinella, William M. [Computational Science Research Center San Diego State University, San Diego, CA (United States); San Diego State University, Department of Physics, San Diego, CA (United States); Weber, Fridolin [San Diego State University, Department of Physics, San Diego, CA (United States); University of California San Diego, Center for Astrophysics and Space Sciences, La Jolla, CA (United States); Contrera, Gustavo A. [CONICET, Buenos Aires (Argentina); CONICET - Dept. de Fisica, UNLP, IFLP, La Plata (Argentina); Universidad Nacional de La Plata, Grupo de Gravitacion, Astrofisica y Cosmologia, Facultad de Ciencias Astronomicas y Geofisicas, La Plata (Argentina); Orsaria, Milva G. [CONICET, Buenos Aires (Argentina); Universidad Nacional de La Plata, Grupo de Gravitacion, Astrofisica y Cosmologia, Facultad de Ciencias Astronomicas y Geofisicas, La Plata (Argentina)

2016-03-15

Numerous theoretical studies using various equation of state models have shown that quark matter may exist at the extreme densities in the cores of high-mass neutron stars. It has also been shown that a phase transition from hadronic matter to quark matter would result in an extended mixed phase region that would segregate phases by net charge to minimize the total energy of the phase, leading to the formation of a crystalline lattice. The existence of quark matter in the core of a neutron star may have significant consequences for its thermal evolution, which for thousands of years is facilitated primarily by neutrino emission. In this work we investigate the effect a crystalline quark-hadron mixed phase can have on the neutrino emissivity from the core. To this end we calculate the equation of state using the relativistic mean-field approximation to model hadronic matter and a nonlocal extension of the three-flavor Nambu-Jona-Lasinio model for quark matter. Next we determine the extent of the quark-hadron mixed phase and its crystalline structure using the Glendenning construction, allowing for the formation of spherical blob, rod, and slab rare phase geometries. Finally we calculate the neutrino emissivity due to electron-lattice interactions utilizing the formalism developed for the analogous process in neutron star crusts. We find that the contribution to the neutrino emissivity due to the presence of a crystalline quark-hadron mixed phase is substantial compared to other mechanisms at fairly low temperatures (

SU-G-IeP4-04: DD-Neutron Source Collimation for Neutron Stimulated Emission Computed Tomography: A Monte Carlo Simulation Study

Energy Technology Data Exchange (ETDEWEB)

Fong, G; Kapadia, A [Carl E Ravin Advanced Imaging Laboratories, Durham, North Carolina (United States)

2016-06-15

Purpose: To optimize collimation and shielding for a deuterium-deuterium (DD) neutron generator for an inexpensive and compact clinical neutron imaging system. The envisioned application is cancer diagnosis through Neutron Stimulated Emission Computed Tomography (NSECT). Methods: Collimator designs were tested with an isotropic 2.5 MeV neutron source through GEANT4 simulations. The collimator is a 52×52×52 cm{sup 3} polyethylene block coupled with a 1 cm lead sheet in sequence. Composite opening was modeled into the collimator to permit passage of neutrons. The opening varied in shape (cylindrical vs. tapered), size (1–5 cm source-side and target-side openings) and aperture placements (13–39 cm from source-side). Spatial and energy distribution of neutrons and gammas were tracked from each collimator design. Parameters analyzed were primary beam width (FWHM), divergence, and efficiency (percent transmission) for different configurations of the collimator. Select resultant outputs were then used for simulated NSECT imaging of a virtual breast phantom containing a 2.5 cm diameter tumor to assess the effect of the collimator on spatial resolution, noise, and scan time. Finally, composite shielding enclosure made of polyethylene and lead was designed and evaluated to block 99.99% of neutron and gamma radiation generated in the system. Results: Analysis of primary beam indicated the beam-width is linear to the aperture size. Increasing source-side opening allowed at least 20% more neutron throughput for all designs relative to the cylindrical openings. Maximum throughput for all designs was 364% relative to cylindrical openings. Conclusion: The work indicates potential for collimating and shielding a DD neutron generator for use in a clinical NSECT system. The proposed collimator designs produced a well-defined collimated neutron beam that can be used to image samples of interest with millimeter resolution. Balance in output efficiency, noise reduction, and scan

SU-G-IeP4-04: DD-Neutron Source Collimation for Neutron Stimulated Emission Computed Tomography: A Monte Carlo Simulation Study

International Nuclear Information System (INIS)

Fong, G; Kapadia, A

2016-01-01

Purpose: To optimize collimation and shielding for a deuterium-deuterium (DD) neutron generator for an inexpensive and compact clinical neutron imaging system. The envisioned application is cancer diagnosis through Neutron Stimulated Emission Computed Tomography (NSECT). Methods: Collimator designs were tested with an isotropic 2.5 MeV neutron source through GEANT4 simulations. The collimator is a 52×52×52 cm"3 polyethylene block coupled with a 1 cm lead sheet in sequence. Composite opening was modeled into the collimator to permit passage of neutrons. The opening varied in shape (cylindrical vs. tapered), size (1–5 cm source-side and target-side openings) and aperture placements (13–39 cm from source-side). Spatial and energy distribution of neutrons and gammas were tracked from each collimator design. Parameters analyzed were primary beam width (FWHM), divergence, and efficiency (percent transmission) for different configurations of the collimator. Select resultant outputs were then used for simulated NSECT imaging of a virtual breast phantom containing a 2.5 cm diameter tumor to assess the effect of the collimator on spatial resolution, noise, and scan time. Finally, composite shielding enclosure made of polyethylene and lead was designed and evaluated to block 99.99% of neutron and gamma radiation generated in the system. Results: Analysis of primary beam indicated the beam-width is linear to the aperture size. Increasing source-side opening allowed at least 20% more neutron throughput for all designs relative to the cylindrical openings. Maximum throughput for all designs was 364% relative to cylindrical openings. Conclusion: The work indicates potential for collimating and shielding a DD neutron generator for use in a clinical NSECT system. The proposed collimator designs produced a well-defined collimated neutron beam that can be used to image samples of interest with millimeter resolution. Balance in output efficiency, noise reduction, and scan time

232Th and 238U neutron emission cross section calculations and analysis of experimental data

International Nuclear Information System (INIS)

Tel, E.

2004-01-01

In this study, pre-equilibrium neutron-emission spectra produced by (n,xn) reactions on nuclei 2 32Th and 2 38U have been calculated. Angle-integrated cross sections in neutron induced reactions on targets 2 32Th and 2 38U have been calculated at the bombarding energies up to 18 MeV. We have investigated multiple pre-equilibrium matrix element constant from internal transition for 2 32Th (n,xn) neutron emission spectra. In the calculations, the geometry dependent hybrid model and the cascade exciton model including the effects of pre-equilibrium have been used. In addition, we have described how multiple pre-equilibrium emissions can be included in the Feshbach-Kerman-Koonin (FKK) fully quantum-mechanical theory. By analyzing (n,xn) reaction on 232 T h and 2 38U, with the incident energy from 2 Me V to 18 Me V, the importance of multiple pre-equilibrium emission can be seen cleady. All calculated results have been compared with experimental data. The obtained results have been discussed and compared with the available experimental data and found agreement with each other

Measurements of double-differential neutron emission cross sections of Nb and Bi for 11.5 MeV neutrons

Energy Technology Data Exchange (ETDEWEB)

Ibaraki, Masanobu; Matsuyama, Shigeo; Soda, Daisuke; Baba, Mamoru; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering

1997-03-01

Double-differential neutron emission cross sections (DDXs) of Nb and Bi have been measured for 11.5MeV neutrons using the {sup 15N}(d,n){sup 16}O quasi-monoenergetic neutron source at Tohoku University 4.5MV Dynamitron facility. For En`>6MeV, DDXs were measured by the conventional TOF method (single-TOF:S-TOF). For En`<6MeV, where the S-TOF spectra were distorted by the background neutrons, we adopted a double-TOF method (D-TOF). By applying D-TOF method, we obtained DDXs down to 1MeV. (author)

Compact activation detectors for measuring of neutron emission on plasma focus installations

International Nuclear Information System (INIS)

Krokhin, O.N.; Nikulin, V.Ya.; Peregudova, E.V.; Volobuev, I.V.

2005-01-01

The paper presents the two compact simple systems for the measurement of the absolute neutron yield in the range 10 6 - 10 12 neutrons/pulse and higher and spatial anisotropy of neutron radiation. The systems are destined for the registration of the short duration neutron radiation of the pulsed plasma installations, such as Plasma Focus (PF), z-pinches and others plasma installations. This paper also includes the results of the neutron emission measurements on different PF installations: 'Tulip' (P.N. Lebedev Physical Institute, Moscow Russia), the PF-1000 and PF-150 installations (Institute of Plasma Physics and Laser Microfusion, Warsaw, Poland)

Beamed neutron emission driven by laser accelerated light ions

Science.gov (United States)

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

2016-05-01

Highly anisotropic, beam-like neutron emission with peak flux of the order of 109 n/sr was obtained from light nuclei reactions in a pitcher-catcher scenario, by employing MeV ions driven by a sub-petawatt laser. The spatial profile of the neutron beam, fully captured for the first time by employing a CR39 nuclear track detector, shows a FWHM divergence angle of ˜ 70^\\circ , with a peak flux nearly an order of magnitude higher than the isotropic component elsewhere. The observed beamed flux of neutrons is highly favourable for a wide range of applications, and indeed for further transport and moderation to thermal energies. A systematic study employing various combinations of pitcher-catcher materials indicates the dominant reactions being d(p, n+p)1H and d(d,n)3He. Albeit insufficient cross-section data are available for modelling, the observed anisotropy in the neutrons’ spatial and spectral profiles is most likely related to the directionality and high energy of the projectile ions.

Determination of the emission rate for the 14 MeV neutron generator with the use of radio-yttrium

OpenAIRE

Laszynska Ewa; Jednorog Slawomir; Ziolkowski Adam; Gierlik Michal; Rzadkiewicz Jacek

2015-01-01

The neutron emission rate is a crucial parameter for most of the radiation sources that emit neutrons. In the case of large fusion devices the determination of this parameter is necessary for a proper assessment of the power release and the prediction for the neutron budget. The 14 MeV neutron generator will be used for calibration of neutron diagnostics at JET and ITER facilities. The stability of the neutron generator working parameters like emission and angular homogeneity affects the accu...

Use of prompt gamma emissions from polyethylene to estimate neutron ambient dose equivalent

Energy Technology Data Exchange (ETDEWEB)

Priyada, P.; Sarkar, P.K., E-mail: pradip.sarkar@manipal.edu

2015-06-11

The possibility of using measured prompt gamma emissions from polyethylene to estimate neutron ambient dose equivalent is explored theoretically. Monte Carlo simulations have been carried out using the FLUKA code to calculate the response of a high density polyethylene cylinder to emit prompt gammas from interaction of neutrons with the nuclei of hydrogen and carbon present in polyethylene. The neutron energy dependent responses of hydrogen and carbon nuclei are combined appropriately to match the energy dependent neutron fluence to ambient dose equivalent conversion coefficients. The proposed method is tested initially with simulated spectra and then validated using experimental measurements with an Am–Be neutron source. Experimental measurements and theoretical simulations have established the feasibility of estimating neutron ambient dose equivalent using measured neutron induced prompt gammas emitted from polyethylene with an overestimation of neutron dose at very low energies. - Highlights: • A new method for estimating H{sup ⁎}(10) using prompt gamma emissions from HDPE. • Linear combination of 2.2 MeV and 4.4 MeV gamma intensities approximates DCC (ICRP). • Feasibility of the method was established theoretically and experimentally. • The response of the present technique is very similar to that of the rem meters.

Neutron-Activated Gamma-Emission: Technology Review

Science.gov (United States)

2012-01-01

in Be9 + α  C12 + n and Be9 + α  3He4 + n. Chadwick (5) made use of the naturally occurring α-emitter polonium - 210 , which decays to lead-206 with...emission, the variation of gamma attenuation with distance and the presence of organic clutter (in food , fertilizer, dirt road, etc.) makes it 8...a neutron source by mixing a radioisotope that emits alpha particles, such as radium or polonium , with a low atomic weight isotope, usually in the

Survey on neutron pre-emission at the fusion of 11 Li halo nuclei with light targets

International Nuclear Information System (INIS)

Petrascu, M.

1999-01-01

The neutron halo nuclei characterized by very large matter radii, small separation energy and small internal momentum of the valence neutrons, were discovered by Tanihata and co-workers. Until now, the halo nuclei were investigated mostly by elastic, inelastic scattering and breakup processes. It was recently predicted, that due to the very large dimension of 11 Li, one may expect, that in a fusion experiment on a light target, the valence neutrons will not be absorbed together with the 9 Li core, but will be emitted in the early stage of the reaction process. The first experiment aiming to check this expectation, was performed at the RIKEN-RIPS facility. In the experimental setup, the MUSIC chamber, achieved in the frame of IFIN-HH - RIKEN cooperation, played an important role. The obtained results confirm the prediction, indicating to a novel pre-emission effect (near 40 %, for one or two neutrons). The pre-emission of neutron pairs was investigated by time-position coincidences. It is considered that the pre-emission of neutron pairs is responsible for the experimentally observed strong neutron focusing effect. An experiment aiming to a large number of n-n coincidences, based on a new neutron array detector built in the frame of IFIN-HH - RIKEN cooperation, is in preparation. A model for the pre-emission probabilities calculations has been also worked out. Good agreement with the experimental data has been obtained. (author)

Development of a direct measurement system for the standardization of neutron emission rates

International Nuclear Information System (INIS)

Ogheard, Florestan

2012-01-01

The manganese bath technique is the reference method for neutron source emission rates calibration. It is used to calibrate neutron sources using radionuclides (AmBe, PuBe, "2"5"2Cf,...) in terms of neutron emission rate under 4π sr. As a complement to this technique, the anisotropy of the source is measured using a rotating source holder and a neutron long counter. The neutron source to be measured is immersed in a manganese sulphate solution whereby the emitted neutrons are captured within the bath contents. In a typical configuration (a 1 m diameter sphere and a concentrated solution), approximately half of the neutrons lead to the creation of "5"6Mn via the "5"5Mn(n, γ) capture reaction. The "5"6Mn radionuclide has a half-life of approximately 2.6 hours and the bath reaches saturation when the number of nuclei decaying is equal to the number of nuclei created per unit time. The neutron emission rate from the source can then be deduced from the "5"6Mn activity at saturation, assuming proper modelling of the nuclear reactions occurring in the bath. The manganese bath facility at LNE-LNHB has been recently refurbished in order to comply with appropriate safety and radioprotection regulations. This has lead to the upgrading of both the measurement methodology and the modelling of the bath, and a study on the development of a new detector for the on-line measurement of the manganese activity was started. This new detector uses the β-γ coincidence measurement method. The beta channel consists of two photomultipliers tubes which allow the detection of Cerenkov light, and the gamma channel uses a solid scintillation detector. The advantage of this measurement method is that it allows the determination of the bath activity without any prior calibration, unlike the former method which uses a gamma-ray detector calibrated using a high activity manganese source. The principle of the Cerenkov-gamma coincidence measurement has been validated by a prototype of the

Properties of neutron-rich nuclei studied by fission product nuclear chemistry

International Nuclear Information System (INIS)

Meyer, R.A.; Henry, E.A.; Griffin, H.C.; Lien, O.G. III; Lane, S.M.; Stevenson, P.C.; Yaffe, R.P.; Skarnemark, G.

1979-09-01

A review is given of the properties of neutron-rich nuclei studied by fission product nuclear chemistry and includes the techniques used in elemental isolation and current research on the structure of nuclei near 132 Sn, particle emission, and coexisting structure in both neutron-poor and neutron-rich nuclei. 35 references

Study of beta-delayed neutron with proton-neutron QRPA plus statistical model

International Nuclear Information System (INIS)

Minato, Futoshi; Iwamoto, Osamu

2015-01-01

β-delayed neutron is known to be important for safety operation of nuclear reactor and prediction of elemental abundance after freeze-out of r-process. A lot of researches on it have been performed. However, the experimental data are far from complete since the lifetime of most of the relevant nuclei is so short that one cannot measure in a high efficiency. In order to estimate half-lives and delayed neutron emission probabilities of unexplored nuclei, we developed a new theoretical method which combines a proton-neutron quasi-particle random-phase-approximation and the Hauser-Feshbach statistical model. The present method reproduces experimentally known β-decay half-lives within a factor of 10 and about 40% of within a factor of 2. However it fails to reproduce delayed neutron emission probabilities. We discuss the problems and remedy for them to be made in future. (author)

Investigation of the neutron emission spectra of some deformed nuclei for (n, xn) reactions up to 26 MeV energy

International Nuclear Information System (INIS)

Kaplan, A.; Bueyuekuslu, H.; Tel, E.; Aydin, A.; Boeluekdemir, M.H.

2011-01-01

In this study, neutron-emission spectra produced by (n, xn) reactions up to 26 MeV for some deformed target nuclei as 165 Ho, 181 Ta, 184 W, 232 Th and 238 U have been investigated. Also, the mean free path parameter's effect for 9n, xn) neutron-emission spectra has been examined. In the calculations, pre-equilibrium neutron-emission spectra have been calculated by using new evaluated hybrid model and geometry dependent hybrid model, full exciton model and cascade exciton model. The reaction equilibrium component has been calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental data and found agreement with each other. (author)

Spin-down of neutron stars by neutrino emission

International Nuclear Information System (INIS)

Dvornikov, Maxim; Dib, Claudio

2010-01-01

We study the spin-down of a neutron star during its early stages due to the neutrino emission. The mechanism we consider is the subsequent collisions of the produced neutrinos with the outer shells of the star. We find that this mechanism can indeed slow down the star rotation but only in the first tens of seconds of the core formation, which is when the appropriate conditions of flux and collision rate are met. We find that this mechanism can extract less than 1% of the star angular momentum, a result which is much less than previously estimated by other authors.

Reactivity and neutron emission measurements of highly burnt PWR fuel rod samples

International Nuclear Information System (INIS)

Murphy, M.F.; Jatuff, F.; Grimm, P.; Seiler, R.; Brogli, R.; Meier, G.; Berger, H.-D.; Chawla, R.

2006-01-01

Fuel rods with burnup values beyond 50 GWd/t are characterised by relatively large amounts of fission products and a high abundance of major and minor actinides. Of particular interest is the change in the reactivity of the fuel as a function of burnup and the capability of modern codes to predict this change. In addition, the neutron emission from burnt fuel has important implications for the design of transport and storage facilities. Measurements have been made of the reactivity effects and the neutron emission rates of highly burnt uranium oxide and mixed oxide fuel rod samples coming from a pressurised water reactor (PWR). The reactivity measurements have been made in a PWR lattice in the PROTEUS zero-energy reactor moderated in turn with: water, a water and heavy water mixture and water containing boron. A combined transport flask and sample changer was used to insert the 400 mm long burnt fuel rod segments into the reactor. Both control rod compensation and reactor period methods were used to determine the reactivities of the samples. For the range of burnup values investigated, an interesting exponential relationship has been found between the neutron emission rate and the measured reactivity

Search for neutron emission during the electrolysis of heavy water

International Nuclear Information System (INIS)

Coelho, P.R.P.; Saxena, R.N.; Morato, S.P.; Goldman, I.D.; Pinho, A.G. de; Nascimento, I.C.

1990-03-01

A liquid scintillator detector NE 213 with pulse shape discrimination technique was used to observe neutrons during the electrolysis of heavy water with a palladium cathode. From the measured fore and background couting rates, a neutron emission rate of (8.2 ± 2.9) x 10 -3 n/(sec.g.) Pd was determined implying (2.9 ± 1.0) x 10 -24 fusions / [(dd pair).sec.] as compared to ≅ 10 -23 fusion/ [(dd pair).sec.] reported by Jones et al. using titanium electrode. (author) [pt

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

Energy Technology Data Exchange (ETDEWEB)

Lan, Changlin [School of Nuclear Science & Technology, Lanzhou University, Lanzhou 730000 (China); Ruan, Xichao; Chen, Guochang; Nie, Yangbo; Huang, Hanxiong; Bao, Jie; Zhou, Zuying; Tang, Hongqing [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Kong, Xiangzhong; Peng, Meng [School of Nuclear Science & Technology, Lanzhou University, Lanzhou 730000 (China)

2016-05-15

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

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

Energy Technology Data Exchange (ETDEWEB)

Haight, R.C.; Lee, T.M.; Sterbenz, S.M. [and others

1994-07-01

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

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

International Nuclear Information System (INIS)

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

1994-01-01

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

Study of neutron spectrometers for ITER

Energy Technology Data Exchange (ETDEWEB)

Kaellne, Jan

2005-11-15

A review is presented of the developments in the field of neutron emission spectrometry (NES) which is of relevance for identifying the role of NES diagnostics on ITER and selecting suitable instrumentation. Neutron spectrometers will be part of the ITER neutron diagnostic complement and this study makes a special effort to examine which performance characteristics the spectrometers should possess to provide the best burning plasma diagnostic information together with neutron cameras and neutron yield monitors. The performance of NES diagnostics is coupled to how much interface space can be provided which has lead to an interest to find compact instruments and their NES capabilities. This study assesses all known spectrometer types of potential interest for ITER and makes a ranking of their performance (as demonstrated or projected), which, in turn, are compared with ITER measurement requirements as a reference; the ratio of diagnostic performance to interface cost for different spectrometers is also discussed for different spectrometer types. The overall result of the study is an assessment of which diagnostic functions neutron measurements can provide in burning plasma fusion experiments on ITER and the role that NES can play depending on the category of instrument installed. Of special note is the result that much higher quality diagnostic information can be obtained from neutron measurements with total yield monitors, profile flux cameras and spectrometers when the synergy in the data is considered in the analysis and interpretation.

The cocoon emission - an electromagnetic counterpart to gravitational waves from neutron star mergers

Science.gov (United States)

Gottlieb, Ore; Nakar, Ehud; Piran, Tsvi

2018-01-01

Short gamma-ray bursts are believed to arise from compact binary mergers (either neutron star-neutron star or black hole-neutron star). If so, their jets must penetrate outflows that are ejected during the merger. As a jet crosses the ejecta, it dissipates its energy, producing a hot cocoon that surrounds it. We present here 3D numerical simulations of jet propagation in mergers' outflows, and we calculate the resulting emission. This emission consists of two components: the cooling emission, the leakage of the thermal energy of the hot cocoon, and the cocoon macronova that arises from the radioactive decay of the cocoon's material. This emission gives a brief (∼1 h) blue, wide angle signal. While the parameters of the outflow and jet are uncertain, for the configurations we have considered, the signal is bright (∼-14 to -15 absolute magnitude) and outshines all other predicted ultraviolet-optical signals. The signal is brighter when the jet breakout time is longer, and its peak brightness does not depend strongly on the highly uncertain opacity. A rapid search for such a signal is a promising strategy to detect an electromagnetic merger counterpart. A detected candidate could be then followed by deep infrared searches for the longer but weaker macronova arising from the rest of the ejecta.

Beta-delayed gamma and neutron emission near the double shell closure at 78Ni

International Nuclear Information System (INIS)

Rykaczewski, Krzysztof Piotr; Mazzocchi, C.; Grzywacz, R.; Batchelder, J. C.; Bingham, C.R.; Fong, D.; Hamilton, J.H.; Hwang, J.K.; Karny, M.; Krolas, W.; Liddick, S. N.; Morton, A. C.; Mantica, P. F.; Mueller, W. F.; Steiner, M.; Stolz, A.; Winger, J.A.

2005-01-01

An experiment was performed at the National Superconducting Cyclotron Laboratory at Michigan State University to investigate β decay of very neutron-rich cobalt isotopes. Beta-delayed neutron emission from 71-74 Co has been observed for the first time. Preliminary results are reported

Impact of the layout of the ITER Radial Neutron Camera in-port system on the measurement of the neutron emissivity profile

International Nuclear Information System (INIS)

Marocco, D.; Moro, F.; Esposito, B.; Brolatti, G.; Villari, R.; Salasca, S.; Cantone, B.

2013-01-01

Highlights: ► MCNP ITER model ‘Alite-4′ has been updated with the new Port Plug structure (three vertical drawers). ► Two different layouts for the Radial Neutron Camera (RNC) in-vessel system have been considered. ► The impact of both layouts on the RNC diagnostic performance has been assessed. ► The analysis provides useful information for a proper integration of the RNC in the EPP1. -- Abstract: The Radial Neutron Camera (RNC), located in the ITER Equatorial Port Plug 1 (EPP1), is designed to provide the neutron emissivity profile through the measurement of the neutron flux along several collimated channels. The present design of the RNC is based on collimating structures: an ex-port system viewing the plasma core and an in-port system composed by two detector cassettes viewing the upper and lower plasma edges. A design of the EPP1 in which the diagnostics are installed in three completely independent vertical drawers is under study. In this frame, space optimization and integration issues suggest two possible solutions for the layout of the in-port RNC cassettes: the first one in which both cassettes are located in a side drawer; the second one in which the two cassettes lie in the central drawer, on opposite sides of the ex-port RNC cut-out. This paper describes the work performed to assess the impact of the two different in-port system layouts on the capability of the RNC to measure the neutron emissivity profile by means of MCNP and diagnostic performance calculations. The results of the analysis provide guidelines for the integration of the RNC into the EPP1 showing that the proximity of the in-port cassettes to the ex-port cut-out strongly increases the amount of uncollimated and scattered neutrons at the detector positions, thus reducing the diagnostic measurement capability

Gamma-ray emission spectra from spheres with 14 MeV neutron source

International Nuclear Information System (INIS)

Yamamoto, Junji; Kanaoka, Takeshi; Murata, Isao; Takahashi, Akito; Sumita, Kenji

1989-01-01

Energy spectra of neutron-induced gamma-rays emitted from spherical samples were measured using a 14 MeV neutron source. The samples in use were LiF, Teflon:(CF 2 ) n , Si, Cr, Mn, Co, Cu, Nb, Mo, W and Pb. A diameter of the sphere was either 40 or 60 cm. The gamma-ray energy in the emission spectra covered the range from 500 keV to 10 MeV. Measured spectra were compared with transport calculations using the nuclear data files of JENDL-3T and ENDF/B-IV. The agreements between the measurements and the JENDL-3T calculations were good in the emission spectra for the low energy gamma-rays from inelastic scattering. (author)

Study of neutron-rich $^{51−53}$ Ca isotopes via $\\beta$-decay

CERN Multimedia

The high Q$_\\beta$ values in certain neutron-rich regions of the chart of nuclides opens up the possibility to study states in the daughter nuclei which lie at high excitation energy, above the neutron separation threshold. We propose to perform spectroscopy of the $\\beta$-delayed neutron emission of the $^{51-53}$K isotopes to study the population of single-particle or particle-hole states both below and above the neutron separation threshold. The VANDLE neutron detector will be used in combination with the IDS tape station setup and Ge detectors.

Pulsed neutron intensity from rectangular shaped light water moderator with fast-neutron reflector

International Nuclear Information System (INIS)

Kiyanagi, Yoshiaki; Iwasa, Hirokatsu

1982-01-01

With a view to enhancing the thermal-neutron intensity obtained from a pulsed neutron source, an experimental study has been made to determine the optimum size of a rectangular shaped light water moderator provided with fast neutron reflector of beryllium oxide or graphite, and decoupled thermal-neutronically by means of Cd sheet. The optimum dimensions for the moderator are derived for the neutron emission surface and the thickn ess, for the cases in which the neutron-producing target is placed beneath the moderator (''wing geometry'') or immediately behind the moderator (''slab geometry''). The major conclusions drawn from the experimental results are as follows. The presence of the Cd decoupler inserted between the moderator and reflector prevent the enhancement of thermal-neutron emission time gained by the provision of reflector. With a graphite reflector about 14 cm thick, (a) the optimum area of emission surface would be 25 x 25 cm 2 for wing geometry and still larger for slab geometry, and (b) the optimum moderator thickness would be 5.5 cm for slab geometry and 8.5 cm for wing geometry. It is thus concluded that a higher neutron emission intensity can be obtained with slab than with wing geometry provided that a large emission surface can be adopted for the moderator. (author)

Classification of JET Neutron and Gamma Emissivity Profiles

Science.gov (United States)

Craciunescu, T.; Murari, A.; Kiptily, V.; Vega, J.; Contributors, JET

2016-05-01

In thermonuclear plasmas, emission tomography uses integrated measurements along lines of sight (LOS) to determine the two-dimensional (2-D) spatial distribution of the volume emission intensity. Due to the availability of only a limited number views and to the coarse sampling of the LOS, the tomographic inversion is a limited data set problem. Several techniques have been developed for tomographic reconstruction of the 2-D gamma and neutron emissivity on JET. In specific experimental conditions the availability of LOSs is restricted to a single view. In this case an explicit reconstruction of the emissivity profile is no longer possible. However, machine learning classification methods can be used in order to derive the type of the distribution. In the present approach the classification is developed using the theory of belief functions which provide the support to fuse the results of independent clustering and supervised classification. The method allows to represent the uncertainty of the results provided by different independent techniques, to combine them and to manage possible conflicts.

A device for quantitative plutonium testing in mixed fuel by its neutron emission

International Nuclear Information System (INIS)

Gadzhiev, G.I.; Gorobets, A.K.; Golushko, V.V.; Dunaev, E.S.; Leshchenko, Yu.I.

1987-01-01

A device for quantitative plutonium testing in mixed fuel by its neutron emission is described. The method of ''assigned dead time'' for isolation of neutrons of spontaneous fission is used in the device. The main characteristics of the registrating equipment specifying the regime of measuring and affecting testing errors are presented. The results of spontaneous fission neutrons detection in the range up to 100 g of plutonium linearly depend on 240 Pu. Sensitivity of testing makes up about 28 pul./s per 1 g of 240 Pu

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.

Strong γ-ray emission from neutron unbound states populated in β-decay: Impact on (n,γ) cross-section estimates

International Nuclear Information System (INIS)

Tain, J. L.; Guadilla, V.; Valencia, E.; Algora, A.

2017-01-01

Total absorption gamma-ray spectroscopy is used to measure accurately the intensity of γ emission from neutron-unbound states populated in the β-decay of delayed-neutron emitters. From the comparison of this intensity with the intensity of neutron emission one can deduce information on the (n,γ) cross section for unstable neutron-rich nuclei of interest in r process abundance calculations. A surprisingly large γ branching was observed for a number of isotopes. Here, the results are compared with Hauser-Feshbach calculations and discussed.

Effect of gas filling pressure and operation energy on ion and neutron emission in a medium energy plasma focus device

Science.gov (United States)

Niranjan, Ram; Rout, R. K.; Srivastava, Rohit; Kaushik, T. C.

2018-03-01

The effects of gas filling pressure and operation energy on deuterium ions and neutrons have been studied in a medium energy plasma focus device, MEPF-12. The deuterium gas filling pressure was varied from 1 to 10 mbar at an operation energy of 9.7 kJ. Also, the operation energy was varied from 3.9 to 9.7 kJ at a deuterium gas filling pressure of 4 mbar. Time resolved emission of deuterium ions was measured using a Faraday cup. Simultaneously, time integrated and time resolved emissions of neutrons were measured using a silver activation detector and plastic scintillator detector, respectively. Various characteristics (fluence, peak density, and most probable energy) of deuterium ions were estimated using the Faraday cup signal. The fluence was found to be nearly independent of the gas filling pressure and operation energy, but the peak density and most probable energy of deuterium ions were found to be varying. The neutron yield was observed to be varying with the gas filling pressure and operation energy. The effect of ions on neutrons emission was observed at each operation condition.

Vanadium Beta Emission Detectors for Reactor In-Core Neutron Monitoring

Energy Technology Data Exchange (ETDEWEB)

Andersson, I Oe; Soederlund, B

1969-06-15

In-core flux measurements are becoming increasingly important in both power reactors and test reactors. In particular power distribution measurements in large power reactors have to be performed with a great number of neutron detectors capable of withstanding high integrated flux values. This report presents a summary of the development and application of a new type of nuclear radiation sensor, a beta emission detector, for measurements at high neutron flux levels. The work has been carried out at the Section for Instrumentation and has been the basis for a type of neutron detector employed in the Marviken in-core system as well as for other types. The report describes the design and principle of operation, experiments and tests. Also included are the results and comments from a long-term irradiation of some detectors in the Halden reactor.

Study of proton and 2 protons emission from light neutron deficient nuclei around A=20; Etude de l'emission proton et de deux protons dans les noyaux legers deficients en neutrons de la region A=20

Energy Technology Data Exchange (ETDEWEB)

Zerguerras, T

2001-09-01

Proton and two proton emission from light neutron deficient nuclei around A=20 have been studied. A radioactive beam of {sup 18}Ne, {sup 17}F and {sup 20}Mg, produced at the Grand Accelerateur National d'Ions Lourds by fragmentation of a {sup 24}Mg primary beam at 95 MeV/A, bombarded a {sup 9}Be target to form unbound states. Proton(s) and nuclei from the decay were detected respectively in the MUST array and the SPEG spectrometer. From energy and angle measurements, the invariant mass of the decaying nucleus could be reconstructed. Double coincidence events between a proton and {sup 17}F, {sup 16}O, {sup 15}O, {sup 14}O and {sup 18}Ne were registered to obtain excitation energy spectra of {sup 18}Ne, {sup 17}F, {sup 16}F, {sup 15}F et {sup 19}Na. Generally, the masses measures are in agreement with previous experiments. In the case of {sup 18}Ne, excitation energy and angular distributions agree well with the predictions of a break up model calculation. From {sup 17}Ne proton coincidences, a first experimental measurement of the ground state mass excess of {sup 18}Na has been obtained and yields 24,19(0,15)MeV. Two proton emission from {sup 17}Ne and {sup 18}Ne excited states and the {sup 19}Mg ground state was studied through triple coincidences between two proton and {sup 15}O, {sup 16}O and {sup 17}Ne respectively. In the first case, the proton-proton relative angle distribution in the center of mass has been compared with model calculation. Sequential emission from excited states of {sup 17}Ne, above the proton emission threshold, through {sup 16}F is dominant but a {sup 2}He decay channel could not be excluded. No {sup 2}He emission from the 1.288 MeV {sup 17}Ne state, or from the 6.15 MeV {sup 18}Ne state has been observed. Only one coincidence event between {sup 17}Ne and two proton was registered, the value of the one neutron stripping reaction cross section of {sup 20}Mg being much lower than predicted. (author)

Measurement and analysis of 14 MeV neutron-induced double-differential neutron emission cross sections needed for fission and fusion reactor technology

International Nuclear Information System (INIS)

Wang Dahai.

1990-10-01

The main objectives of this IAEA Co-ordinated Research Programme are to improve the data on 14 MeV neutron-induced double-differential neutron emission cross sections for materials needed for fission and fusion reactor technology. This report summarizes the conclusions and recommendations which were agreed by all participants during the Second Research Co-ordination Meeting

Polarized X-Ray Emission from Magnetized Neutron Stars: Signature of Strong-Field Vacuum Polarization

Science.gov (United States)

Lai, Dong; Ho, Wynn C.

2003-08-01

In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein type resonance across which an x-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to a unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized x rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magnetic field and geometry.

Polarized x-ray emission from magnetized neutron stars: signature of strong-field vacuum polarization.

Science.gov (United States)

Lai, Dong; Ho, Wynn C G

2003-08-15

In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein type resonance across which an x-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to a unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized x rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magnetic field and geometry.

Estimation of delayed neutron emission probability by using the gross theory of nuclear β-decay

International Nuclear Information System (INIS)

Tachibana, Takahiro

1999-01-01

The delayed neutron emission probabilities (P n -values) of fission products are necessary in the study of reactor physics; e.g. in the calculation of total delayed neutron yields and in the summation calculation of decay heat. In this report, the P n -values estimated by the gross theory for some fission products are compared with experiment, and it is found that, on the average, the semi-gross theory somewhat underestimates the experimental P n -values. A modification of the β-decay strength function is briefly discussed to get more reasonable P n -values. (author)

Reactivity and neutron emission measurements of burnt PWR fuel rod samples in LWR-PROTEUS phase II

International Nuclear Information System (INIS)

Murphy, M. F.; Jatuff, F.; Grimm, P.; Seiler, R.; Brogli, R.; Meier, G.; Berger, H. D.; Chawla, R.

2004-01-01

Measurements have been made of the reactivity effects and the neutron emission rates of uranium oxide and mixed oxide burnt fuel samples having a wide range of burnup values and coming from a Pressurised Water Reactor (PWR). The reactivity measurements have been made in a PWR lattice moderated in turn with: water, a water and heavy water mixture, and water containing boron. An interesting relationship has been found between the neutron emission rate and the measured reactivity. (authors)

Source characterization of Purnima Neutron Generator (PNG)

International Nuclear Information System (INIS)

Bishnoi, Saroj; Patel, T.; Paul, Ram K.; Sarkar, P.S.; Adhikari, P.S.; Sinha, Amar

2011-01-01

The use of 14.1 MeV neutron generators for the applications such as elemental analysis, Accelerated Driven System (ADS) study, fast neutron radiography requires the characterization of neutron source i.e neutron yield (emission rate in n/sec), neutron dose, beam spot size and energy spectrum. In this paper, a series of experiments carried out to characterize this neutron source. The neutron source has been quantified with neutron emission rate, neutron dose at various source strength and beam spot size at target position

Calculations of the main free path on neutron emission cross-section for spallation reaction of target and fuel nuclei

International Nuclear Information System (INIS)

Tel, E.; Kisoglu, H. F.; Topaksu, A. K.; Aydin, A.; Kaplan, A.

2007-01-01

There are several new technological application fields of fast neutrons such as accelerator-driven incineration/ transmutation of the long-lived radioactive nuclear wastes (in particular transuranium nuclides) to short-lived or stable isotopes by secondary spallation neutrons produced by high-intensity, intermediate-energy, charged-particle beams, prolonged planetary space missions, shielding for particle accelerators. Especially, accelerator driven subcritical systems (ADS) can be used for fission energy production and /or nuclear waste transmutation as well as in the intermediate-energy accelerator driven neutron sources, ions and neutrons with energies beyond 20 MeV, the upper limit of exiting data files that produced for fusion and fission applications. In these systems, the neutron scattering cross sections and emission differential data are very important for reactor neutronics calculations. The transition rate calculation involves the introduction of the parameter of mean free path determines the mean free path of the nucleon in the nuclear matter. This parameter allows an increase in mean free path, with simulation of effect, which is not considered in the calculations, such as conservation of parity and angular momentum in intra nuclear transitions. In this study, we have investigated the multiple preequilibrium matrix element constant from internal transition for Uranium, Thorium, (n,xn) neutron emission spectra. The neutron-emission spectra produced by (n,xn) reactions on nuclei of some target (for spallation) have been calculated. In the calculations, we have used the geometry dependent hybrid model and the cascade exciton model including the effects of the preequilibrium. The pre-equilibrium direct effects have been examined by using full exciton model. All calculated results have been compared with the experimental data. The obtained results have been discussed and compared with the available experimental data and found agreement with each other

Fast neutron emission in the interaction of 9 MeV/nucleon 12C and 20Ne ions with 181Ta nuclei

International Nuclear Information System (INIS)

Kozulin, Eh.M.; Blinov, M.V.; Kovalenko, S.S.; Mozhaev, A.N.; Borcha, K.; Penionzhkevich, Yu.Eh.

1987-01-01

Energy spectra and angular distributions have been measured for neutrons emitted from the 12 C(105 MeV)+ 181 Ta and 20 Ne(180 MeV)+ 181 Ta reactions. The obtained experimental data suggest a conclusion that both the equilibrium and pre-equilibrium components of the neutron emission are present in each reaction. However, yields and angular distributions of the pre-equilibrium neutrons emitted in these reactions are considerably different. By comparing the present results with other data, it is shown that the pre-equilibrium neutron emission has a more isotropic distribution than that for protons for the same entrance channel of the reaction. Besides, an information has been obtained on a dependence of the preequilibrium neutron and proton yields on the projectile mass. The data are analysed in terms of a statistical model describing the emission of evaporated neutrons, as well as in terms of the ''rotating hot spot'' model and the moving source model, for preequilibrium neutrons

Collective neutrino-pair emission due to Cooper pairing of protons in superconducting neutron stars

International Nuclear Information System (INIS)

Leinson, L.B.

2001-01-01

The neutrino emission due to formation and breaking of Cooper pairs of protons in superconducting cores of neutron stars is considered with taking into account the electromagnetic coupling of protons to ambient electrons. It is shown that collective response of electrons to the proton quantum transition contributes coherently to the complete interaction with a neutrino field and enhances the neutrino-pair production. Our calculation shows that the contribution of the vector weak current to the ννbar emissivity of protons is much larger than that calculated by different authors without taking into account the plasma effects. Partial contribution of the pairing protons to the total neutrino radiation from the neutron star core is very sensitive to the critical temperatures for the proton and neutron pairing. We show domains of these parameters where the neutrino radiation, caused by a singlet-state pairing of protons is dominating

Study of proton and 2 protons emission from light neutron deficient nuclei around A=20; Etude de l'emission proton et de deux protons dans les noyaux legers deficients en neutrons de la region A=20

Energy Technology Data Exchange (ETDEWEB)

Zerguerras, T

2001-09-01

Proton and two proton emission from light neutron deficient nuclei around A=20 have been studied. A radioactive beam of {sup 18}Ne, {sup 17}F and {sup 20}Mg, produced at the Grand Accelerateur National d'Ions Lourds by fragmentation of a {sup 24}Mg primary beam at 95 MeV/A, bombarded a {sup 9}Be target to form unbound states. Proton(s) and nuclei from the decay were detected respectively in the MUST array and the SPEG spectrometer. From energy and angle measurements, the invariant mass of the decaying nucleus could be reconstructed. Double coincidence events between a proton and {sup 17}F, {sup 16}O, {sup 15}O, {sup 14}O and {sup 18}Ne were registered to obtain excitation energy spectra of {sup 18}Ne, {sup 17}F, {sup 16}F, {sup 15}F et {sup 19}Na. Generally, the masses measures are in agreement with previous experiments. In the case of {sup 18}Ne, excitation energy and angular distributions agree well with the predictions of a break up model calculation. From {sup 17}Ne proton coincidences, a first experimental measurement of the ground state mass excess of {sup 18}Na has been obtained and yields 24,19(0,15)MeV. Two proton emission from {sup 17}Ne and {sup 18}Ne excited states and the {sup 19}Mg ground state was studied through triple coincidences between two proton and {sup 15}O, {sup 16}O and {sup 17}Ne respectively. In the first case, the proton-proton relative angle distribution in the center of mass has been compared with model calculation. Sequential emission from excited states of {sup 17}Ne, above the proton emission threshold, through {sup 16}F is dominant but a {sup 2}He decay channel could not be excluded. No {sup 2}He emission from the 1.288 MeV {sup 17}Ne state, or from the 6.15 MeV {sup 18}Ne state has been observed. Only one coincidence event between {sup 17}Ne and two proton was registered, the value of the one neutron stripping reaction cross section of {sup 20}Mg being much lower than predicted. (author)

Research on background neutron of 226Ra γ source

International Nuclear Information System (INIS)

Ji Changsong

1996-01-01

This work studies the background neutron emission of 226 Ra γ source: the mechanism of resulting in background neutron is studied; a thesis that the (α, n) type reaction on Radium carriers Cl or Br is the main source of creating background neutron emission of 226 Ra γ source has been proposed and certificated; a proposal of substitution of Cl carrier by Br in radium source produced in China in order to reduce background neutron emission is put forward. A result to reduce the background neutron from 96.4 neutrons/4πsmgRa to 6.1 neutrons/4πsmgRa is obtained

Emission of fast neutrons in the iteraction of 12C and 20Ne ions at energy 9 MeV/nucleon with 181Ta nuclei

International Nuclear Information System (INIS)

Kozulin, E.M.; Blinov, M.V.; Borcha, K.; Kovalenko, S.S.; Mozhaev, A.N.; Penionzhkevich, Y.E.

1987-01-01

The energy spectra and angular distributions have been measured for neutrons emitted in the reactions 12 C(105 MeV)+ 181 Ta and 20 Ne(180 MeV)+ 181 Ta. The experimental data obtained permitted the conclusion that there are equilibrium and pre-equilibrium components in the emission of neutrons in each of the reactions. The yields and angular distributions of pre-equilibrium neutrons from these reactions are appreciably different. From comparison of results of the present work with the data from other studies, information is obtained on the dependence of the yield of pre-equilibrium neutrons and protons on the incident-ion mass. The analysis is carried out with the use of the statistical model for describing the emission of evaporation neutrons and also use of the ''rotating spot'' and ''moving source'' models for pre-equilibrium neutrons

Monte Carlo calculation of correction factors for radionuclide neutron source emission rate measurement by manganese bath method

International Nuclear Information System (INIS)

Li Chunjuan; Liu Yi'na; Zhang Weihua; Wang Zhiqiang

2014-01-01

The manganese bath method for measuring the neutron emission rate of radionuclide sources requires corrections to be made for emitted neutrons which are not captured by manganese nuclei. The Monte Carlo particle transport code MCNP was used to simulate the manganese bath system of the standards for the measurement of neutron source intensity. The correction factors were calculated and the reliability of the model was demonstrated through the key comparison for the radionuclide neutron source emission rate measurements organized by BIPM. The uncertainties in the calculated values were evaluated by considering the sensitivities to the solution density, the density of the radioactive material, the positioning of the source, the radius of the bath, and the interaction cross-sections. A new method for the evaluation of the uncertainties in Monte Carlo calculation was given. (authors)

Neutron measurement techniques for tokamak plasmas

International Nuclear Information System (INIS)

Jarvis, O.N.

1994-01-01

The present article reviews the neutron measurement techniques that are currently being applied to the study of tokamak plasmas. The range of neutron energies of primary interest is limited to narrow bands around 2.5 and 14 MeV, and the variety of measurements that can be made for plasma diagnostic purposes is also restricted. To characterize the plasma as a neutron source, it is necessary only to measure the total neutron emission, the relative neutron emissivity as a function of position throughout the plasma, and the energy spectra of the emitted neutrons. In principle, such measurements might be expected to be relatively easy. That this is not the case is, in part, attributable to practical problems of accessibility to a harsh environment but is mostly a consequence of the time-scale on which the measurements have to be made and of the wide range of neutron emission intensities that have to be covered: for tokamak studies, the time-scale is of the order of 1 to 100 ms and the neutron intensity ranges from 10 12 to 10 19 s -1 . (author)

First- and second-chance proton emission in the interactions of fast neutrons with 92Mo

International Nuclear Information System (INIS)

Qaim, S.M.; Wolfle, R.; Strohmaier, B.

1989-01-01

Cross sections were measured radiochemically for the 92 Mo(n,p) 92 Nb m and 92 Mo(n,n'p +pn+d) 91 Nb m reactions over the neutron energy range of 9.0--10.6 MeV, and for the latter reaction also between 12.6 and 14.4 MeV. Use was made of high-resolution γ-ray and x-ray spectroscopy. Statistical-model calculations taking into account precompound effects were performed for fast neutron induced reactions on 92 Mo. The calculational results agree well with the experimental data on emitted proton spectra as well as on the excitation functions of various reaction channels. The second-chance proton emission is significant for incident neutron energies above 11 MeV; between 13 and 14 MeV it is comparable to the first-chance proton emission

Statistical and non statistical models for delayed neutron emission: applications to nuclei near A = 90

International Nuclear Information System (INIS)

De Oliveira, Z.M.

1980-01-01

A detailed analysis of the simple statistical model description for delayed neutron emission of 87 Br, 137 I, 85 As and 135 Sb has been performed. In agreement with experimental findings, structure in the #betta#-strength function is required to reproduce the envelope of the neutron spectrum from 87 Br. For 85 As and 135 Sb the model is found incapable of simultaneously reproducing envelopes of delayed neutron spectra and neutron branching ratios to excited states in the final nuclei for any choice of #betta#-strength function. The results indicate that partial widths for neutron emission are not compatible with optical-model transmission coefficients. The simple shell model with pairing is shown to qualitatively describe the main features of the #betta#-strength functions for decay of 87 Br and 91 93 95 97 Rb. It is found that the location of apparent resonances in the experimental data are in rough agreement with the location of centroids of strength calculated with this model. An extension of the shell model picture which includes the Gamow-Teller residual interaction is used to investigate decay properties of 84 86 As, 86 92 Br and 88 102 Rb. For a realistic choice of interaction strength, the half lives of these isotopes are fairly well reproduced and semiquantitative agreement with experimental #betta#-strength functions is found. Delayed neutron emission probabilities are reproduced for precursors nearer stability with systematic deviations being observed for the heavier nuclei. Contrary to the assumption of a structureless Gamow-Teller giant resonance as embodied gross theory of #betta#-decay, we find that structures in the tail of the Gamow-Teller giant resonances are expected which strongly influence the decay properties of nuclides in this region

Anisotropies of the neutron emission of the 'Focus' discharge compared with different theoretical models; Anisotropies de l'emission neutronique de la decharge 'Focus' comparees a divers modeles theoriques

Energy Technology Data Exchange (ETDEWEB)

Patou, Claude; Simonnet, Alain

1969-08-06

When a plasma emits enough neutrons to make an analysis of this neutrons possible, the study of emission characteristics allows the mechanism governing fusion reaction to be specified. The experimental study of neutron flow and energy anisotropies is herein compared with various possible theoretical models. It seems that the 'Boiler' model (thermal plasma in movement) matches the obtained results. Only observed flow values in the discharge axis remain unexplained. Although the study approach does not allow to be sure of plasma thermalization in the strict meaning of the term, it seems that there is a relatively well established anisotropy of the speed distribution function of reacting ions [French] Lorsqu'un plasma emet suffisamment de neutrons pour les soumettre a l'analyse, l'etude des caracteristiques de l'emission permet de preciser le mecanisme responsable des reactions de fusion. L'etude experimentale des anisotropies du flux et de l'energie des neutrons est comparee a divers modeles theoriques possibles. Il semble que le modele du 'Boiler' - plasma thermique en mouvement - s'accorde avec nos resultats. Seules les valeurs des flux observes selon l'axe de la decharge restent sans explication. Bien que ce moyen d'etude ne permette pas d'etre certain de la thermalisation du plasma au sens strict du terme, il semble cependant qu'on se trouve en presence d'une isotropie relativement bien realisee de la fonction de distribution des vitesses des ions qui entrent en reaction. (auteurs)

Neutron pre-emission at the fusion of 11 Li halo nuclei with Si targets

International Nuclear Information System (INIS)

Petrascu, M.; Isbasescu, A.; Petrascu, H.; Bordeanu, C.; David, I.; Lazar, I.; Mihai, I.; Vaman, G.; Tanihata, I.; Kobayashi, T.; Korsheninnikov, A.; Fukuda, S.; Kumagai, H.; Momota, S.; Ozawa, A.; Yoshida, K.; Nikolski, E.; Giurgiu, M.

1997-01-01

In this contribution, the first experiment on fusion of 11 Li halo nuclei with Si targets is reported. A novel effect consisting of a large neutron pre-emission probability in the fusion process was observed. The neutron halo nuclei are characterized by very large matter radii, small separation energy and small internal momentum of the valence neutrons. Until now, the halo nuclei were investigated mostly by elastic, inelastic scattering and breakup processes. It was recently predicted that due to the very large dimension of 11 Li, one may expect, that in a fusion experiment on a light target, the valence neutrons will not be absorbed together with the 9 Li core, but will be emitted in the early stage of the reaction process. The experiment aiming to check this expectation, performed at RIKEN-RIPS facility, is described. In the experimental arrangement, three main parts are present: the first part contains the detectors used for the control, identification and determination of the beam characteristics; the second part consists of a Multiple Sampling Ionisation Chamber (MUSIC), used for identification of the inclusive evaporation residue spectra produced in the detector-target; the third part consists of two wall neutron detectors, each made up of 15 plastic scintillators. This detector was used for the energy and position determination of the neutrons originating from the target. The projectile energy range was 11.2 - 15.2 AMeV, centered at 13 AMeV. The neutrons resulting from the reaction were measured by time-of-light technique. The position on the 'wall' of the detected neutrons could be also determined. The measured neutron spectra from 11 Li and 9 Li are shown. A marked different between the two spectra was found and it is explained by the contribution of a large amount of pre-emission (breakup) processes, in case of 11 Li projectiles. The position spectra point out the evaporation origin of the neutrons in case of 9 Li projectiles while for 11 Li only the

Gamma-burst emission from neutron-star accretion

Science.gov (United States)

Colgate, S. A.; Petschek, A. G.; Sarracino, R.

1983-01-01

A model for emission of the hard photons of gamma bursts is presented. The model assumes accretion at nearly the Eddington limited rate onto a neutron star without a magnetic field. Initially soft photons are heated as they are compressed between the accreting matter and the star. A large electric field due to relatively small charge separation is required to drag electrons into the star with the nuclei against the flux of photons leaking out through the accreting matter. The photon number is not increased substantially by Bremsstrahlung or any other process. It is suggested that instability in an accretion disc might provide the infalling matter required.

Study of neutron rich nuclei by delayed neutron decay using the Tonnerre multidetector; Etude de la decroissance par neutrons retardes de noyaux legers riches en neutrons avec le multidetecteur tonnerre

Energy Technology Data Exchange (ETDEWEB)

Timis, C.N

2001-07-01

A new detection array for beta delayed neutrons was built. It includes up to 32 plastic scintillation counters 180 cm long located at 120 cm from the target. Neutron energy spectra are measured by time-of-flight in the 300 keV-15 MeV range with good energy resolution. The device was tested with several known nuclei. Its performances are discussed in comparison with Monte Carlo simulations. They very high overall detection efficiency on the TONNERRE array made it possible to study one and two neutron emission of {sup 11}Li. A complete decay scheme was obtained. The {sup 33}Mg and {sup 35}Al beta decays were investigated for the first time by neutron and gamma spectroscopy. Complete decay schemes were established and compared to large scale shell-model calculations. (authors)

Comparison of experimental and calculated neutron emission spectra and angular distributions

International Nuclear Information System (INIS)

Gruppelaar, H.; Akkermans, J.M.

1980-06-01

Experimental and calculated neutron emission spectra and angular distributions have been intercompared for 14.6-MeV neutron-induced reactions. The experimental data, measured by Hermsdorf et al., cover 34 elements in a large mass range. To calculate the differential neutron scattering cross sections a unified model of preequilibrium neutron emission was used, in which the generalized master equation of Mantzouranis et al. was solved with a fast exact matrix method, recently introduced by Akkermans. For the scattering kernel a three-term Legendre polynomial representation was adopted, which was either derived from the differential free nucleon-nucleon scattering cross section or fitted to obtain optimal agreement with the set of experimental data of Hermsdorf et al. The results of the last-mentioned calculation are quite acceptable in view of the fact that only two global parameters have been to describe the angular distributions of all experimental data. The report contains tables and graphs of the calculated Legendre coefficients and graphs of energy-averaged angular distributions for all 34 elements. It is further shown that improvements in the energy and angular distributions could be obtained by means of adjustment of the level-density parameters of the individual residual nuclei. Finally a short discussion is devoted to the problems of fitting angular distributions at backward angles by varying the model parameters or the specification of the initial condition. It is indicated that the so-called preequilibrium phase of the nuclear reaction actually consists of two different stages, the first one generating the forward-peaked angular distributions and the second one showing angular distributions symmetric about 90 0

Measurement of differential and double-differential neutron emission cross-sections for {sup 9}Be at 21.94 MeV neutrons

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yaling [Lanzhou University, School of Nuclear Science and Technology, Lanzhou (China); Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China); Ruan, Xichao; Huang, Hanxiong; Ren, Jie; Li, Xia; Nie, Yangbo [China Institute of Atomic Energy, Key Laboratory of Nuclear Data, Beijing (China); Li, Yongming [Chinese Academy of Engineering Physics, Mianyang, Sichuan (China); Zhou, Bin [Chinese Academy of Sciences, Institute of High Energy Physics, Beijing (China); Wei, Zheng; Yao, Zeen [Lanzhou University, School of Nuclear Science and Technology, Lanzhou (China); Engineering Research Center for Neutron Application, Ministry of Education, Lanzhou University, Lanzhou (China); Gao, Xiaofei; Yang, Lei [Chinese Academy of Sciences, Institute of Modern Physics, Lanzhou (China)

2017-12-15

The secondary neutron emission differential and double-differential cross sections (DX and DDXs) of n + {sup 9}Be have been measured at the neutron energy of 21.94 MeV using the multi-detector fast neutron time-of-flight (TOF) spectrometer. The data was derived by comparing the measured TOF spectra with detailed Monte Carlo simulation, and corrected with n-p scattering cross section. Meanwhile, theoretical calculations based on the Hauser-Feshbach and exciton model have been performed to compare with experimental data. Measured differential cross sections were also compared with other measurements. It was found that the experimental results were in agreement with other measurements and theoretical calculations, while discrepancies were also present in the whole energy region and at some angles. (orig.)

Acoustic, electromagnetic, neutron emissions from fracture and earthquakes

CERN Document Server

Lacidogna, Giuseppe; Manuello, Amedeo

2015-01-01

This book presents the relevant consequences of recently discovered and interdisciplinary phenomena, triggered by local mechanical instabilities. In particular, it looks at emissions from nano-scale mechanical instabilities such as fracture, turbulence, buckling and cavitation, focussing on vibrations at the TeraHertz frequency and Piezonuclear reactions. Future applications for this work could include earthquake precursors, climate change, energy production, and cellular biology. A series of fracture experiments on natural rocks demonstrates that the TeraHertz vibrations are able to induce fission reactions on medium weight elements accompanied by neutron emissions. The same phenomenon appears to have occurred in several different situations, particularly in the chemical evolution of the Earth and Solar System, through seismicity (rocky planets) and storms (gaseous planets). As the authors explore, these phenomena can also explain puzzles related to the history of our planet, like the ocean formation or th...

The IRK time-of-flight facility for measurements of double-differential neutron emission cross sections

International Nuclear Information System (INIS)

Pavlik, A.; Priller, A.; Steier, P.; Vonach, H.; Winkler, G.

1994-01-01

In order to improve the present experimental data base of energy- and angle-differential neutron emission cross sections at 14 MeV incident-neutron energy, a new time-of-flight (TOF) facility was installed at the Institut fuer Radiumforschung und Kernphysik (IRK), Vienna. The set-up was particularly designed to more precisely measure the high-energy part of the secondary neutron spectra and consists of three main components: (1) a pulsed neutron generator of Cockcroft-Walton type producing primary neutrons via the T(d,n)-reaction, (2) a tube system which can be evacuated containing the neutron flight path, the sample, collimators and the sample positioning system, and (3) the neutron detectors with the data acquisition equipment. Removing the air along the neutron flight path results in a drastic suppression of background due to air-scattered neutrons in the spectrum of the secondary neutrons. For every secondary neutron detected in the main detector, the time-of-flight, the pulse-shape information and the recoil energy are recorded in list-mode via a CAMAC system connected to a PDP 11/34 on-line computer. Using a Micro VAX, the multiparameter data are sorted and reduced to double-differential cross sections

Research on pinches driven by Speed-2 generator: Hard X-ray and neutron emission in plasma focus configuration

Energy Technology Data Exchange (ETDEWEB)

Soto, L.; Moreno, J.; Silva, P.; Sylvester, G.; Zambra, M.; Pavez, C. [Comision Chilena de Energia Nuclear, Santiago (Chile); Pavez, C. [Universidad de Concepcion (Chile); Raspa, V. [Buenos Aires Univ., PLADEMA, CONICET and INFIP (Argentina); Castillo, F. [Insitituto de Ciencias Nucleares, UNAM (Mexico); Kies, W. [Heinrich-Heine-Univ., Dusseldorf (Germany)

2004-07-01

Speed-2 is a generator based on Marx technology and was designed in the University of Dusseldorf. Speed-2 consists on 40 +/- Marx modules connected in parallel (4.1 {mu}F equivalent Marx generator capacity, 300 kV, 4 MA in short circuit, 187 kJ, 400 ns rise time, dI/dt {approx} 10{sup 13} A/s). Currently Speed-2 is operating at CCHEN (Chilean nuclear energy commission), being the most powerful and energetic device for dense transient plasma in the Southern Hemisphere. Most of the previous works developed in Speed-2 at Dusseldorf were done in a plasma focus configuration for soft X-ray emission and the neutron emission from Speed-2 was not completely studied. The research program at CCHEN considers experiments in different pinch configurations (plasma focus, gas puffed plasma focus, gas embedded Z-pinch, wire arrays) at current of hundred of kilo- to mega-amperes, using the Speed-2 generator. The Chilean operation has begun implementing and developing diagnostics in a conventional plasma focus configuration operating in deuterium in order to characterize the neutron emission and the hard X-ray production. Silver activation counters, plastics CR39 and scintillator-photomultiplier detectors are used to characterize the neutron emission. Images of metallic plates with different thickness are obtained on commercial radiographic film, Agfa Curix ST-G2, in order to characterize an effective energy of the hard X-ray outside of the discharge. (authors)

Production and characterization of 228Th calibration sources with low neutron emission for GERDA

Science.gov (United States)

Baudis, L.; Benato, G.; Carconi, P.; Cattadori, C.; De Felice, P.; Eberhardt, K.; Eichler, R.; Petrucci, A.; Tarka, M.; Walter, M.

2015-12-01

The GERDA experiment at the Laboratori Nazionali del Gran Sasso (LNGS) searches for the neutrinoless double beta decay of 76Ge. In view of the GERDA Phase II data collection, four new 228Th radioactive sources for the calibration of the germanium detectors enriched in 76Ge have been produced with a new technique, leading to a reduced neutron emission rate from (α, n) reactions. The gamma activities of the sources were determined with a total uncertainty of ~4% using an ultra-low background HPGe detector operated underground at LNGS. The neutron emission rate was determined using a low background LiI(Eu) detector and a 3He counter at LNGS. In both cases, the measured neutron activity is ~10-6 n/(sṡBq), with a reduction of about one order of magnitude with respect to commercially available 228Th sources. Additionally, a specific leak test with a sensitivity to leaks down to ~10 mBq was developed to investigate the tightness of the stainless steel capsules housing the sources after their use in cryogenic environment.

Comparison of fission probabilities with emission of long range particles under the action of slow and fast neutrons on various materials; Probabilites comparees de fission avec emission de particules de long parcours pour divers materiaux sous l'action des neutrons lents et rapides

Energy Technology Data Exchange (ETDEWEB)

Netter, F; Faraggi, H; Garin-Bonnet, A; Julien, J; Corge, C [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Turkiewicz, J [Institut de Recherches Nucleaire de Varsovie (Poland)

1958-07-01

The authors describe relative cross-section measurements of fission of the isotopes of uranium and plutonium (more particularly {sup 235}U, {sup 238}U, {sup 239}Pu), with emission of long range particles, under the action of neutrons of various energies: thermal neutrons, pile neutrons, neutrons produced with the Van de Graaff accelerator by reaction of protons on tritium. The measurements are carried out: 1) with the aid of photographic plates, by submitting to the action of the neutrons a layer of fissile material coupled with an Ilford nuclear emulsion of 200 microns; a tin sheet laying between the plate and the layer stops the {alpha} particles and the fission fragments. By an appropriate development the tracks of the long range particles can be distinguished in the emulsion, from the tracks of the recoil protons resulting of fission neutrons, or of the last primary neutrons. For neutrons of energy under 1 MeV, the compared frequency of the tracks of long range particles and of the recoils caused by the fission neutrons gives a measurement of the fission cross-section with emission of long range particles relative to the product of the fission cross-section by the mean number of neutrons emitted by fission. For neutrons of higher energy, one measures only the frequency of the tracks of long range particles, comparatively with the flux of primary neutrons. Some precautions are taken to eliminate the action of thermal neutrons in the measurements with fast neutrons. 2) with the aid of a system of ionization chamber and proportional counter, the rate of coincidence between the impulsions caused by the long range particles and the impulsions provided by one of the fission fragments is measured comparatively with the counting rate of fission fragme (author) [French] Les auteurs decrivent des mesures relatives a la section efficace de fission des isotopes de l'uranium et du plutonium (notamment {sup 235}U, {sup 238}U, {sup 239}Pu) avec emission de particules de long

Study of the loading mode dependence of the twinning in random textured cast magnesium by acoustic emission and neutron diffraction methods

Czech Academy of Sciences Publication Activity Database

Čapek, J.; Máthis, K.; Clausen, B.; Stráská, J.; Beran, Přemysl; Lukáš, Petr

2014-01-01

Roč. 602, APR (2014), s. 25-32 ISSN 0921-5093 R&D Projects: GA ČR(CZ) GAP204/12/1360 Institutional support: RVO:61389005 Keywords : magnesium * acoustic emission * neutron diffraction * deformation twinning Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.567, year: 2014

Experimental detection of iron overload in liver through neutron stimulated emission spectroscopy

International Nuclear Information System (INIS)

Kapadia, A J; Tourassi, G D; Sharma, A C; Crowell, A S; Kiser, M R; Howell, C R

2008-01-01

Iron overload disorders have been the focus of several quantification studies involving non-invasive imaging modalities. Neutron spectroscopic techniques have demonstrated great potential in detecting iron concentrations within biological tissue. We are developing a neutron spectroscopic technique called neutron stimulated emission computed tomography (NSECT), which has the potential to diagnose iron overload in the liver at clinically acceptable patient dose levels through a non-invasive scan. The technique uses inelastic scatter interactions between atomic nuclei in the sample and incoming fast neutrons to non-invasively determine the concentration of elements in the sample. This paper discusses a non-tomographic application of NSECT investigating the feasibility of detecting elevated iron concentrations in the liver. A model of iron overload in the human body was created using bovine liver tissue housed inside a human torso phantom and was scanned with a 5 MeV pulsed beam using single-position spectroscopy. Spectra were reconstructed and analyzed with algorithms designed specifically for NSECT. Results from spectroscopic quantification indicate that NSECT can currently detect liver iron concentrations of 6 mg g -1 or higher and has the potential to detect lower concentrations by optimizing the acquisition geometry to scan a larger volume of tissue. The experiment described in this paper has two important outcomes: (i) it demonstrates that NSECT has the potential to detect clinically relevant concentrations of iron in the human body through a non-invasive scan and (ii) it provides a comparative standard to guide the design of iron overload phantoms for future NSECT liver iron quantification studies

$\\beta$-decay and $\\beta$-delayed Neutron Emission Measurements at GSI-FRS Beyond N=126, for r-process Nucleosynthesis

CERN Document Server

Caballero-Folch, R; Cortès, G; Taín, J L; Agramunt, J; Algora, A; Ameil, F; Ayyad, Y; Benlliure, J; Bowry, M; Calviño, F; Cano-Ott, D; Davinson, T; Dillmann, I; Estrade, A; Evdokimov, A; Faestermann, T; Farinon, F; Galaviz, D; García-Ríos, A; Geissel, H; Gelletly, W; Gernhäuser, R; Gómez-Hornillos, M B; Guerrero, C; Heil, M; Hinke, C; Knöbel, R; Kojouharov, I; Kurcewicz, J; Kurz, N; Litvinov, Y; Maier, L; Marganiec, J; Marta, M; Martínez, T; Montes, F; Mukha, I; Napoli, D R; Nociforo, C; Paradela, C; Pietri, S; Podolyák, Zs; Prochazka, A; Rice, S; Riego, A; Rubio, B; Schaffner, H; Scheidenberger, C; Smith, K; Sokol, E; Steiger, K; Sun, B; Takechi, M; Testov, D; Weick, H; Wilson, E; Winfield, J S; Wood, R; Woods, P J; Yeremin, A

2014-01-01

New measurements of very exotic nuclei in the neutron-rich region beyond N=126 have been performed at the GSI facility with the fragment separator (FRS). The aim of the experiment is to determine half-lives and beta-delayed neutron emission branching ratios of isotopes of Hg, Tl and Pb in this region. This contribution summarizes final counting statistics for identification and for implantation, as well as the present status of the data analysis of the half-lives. In summary, isotopes of Pt, Au, Hg, Ti, Pb, Bi, Po, At, Rn and Fr were clearly identified and several of them (Hg208-211, Tl211-215, Pb214-218) were implanted with enough statistics to determine their half-lives. About half of them are expected to be neutron emitters, in such cases it will become possible to obtain the neutron emission probabilities, P-n.

Summary Report of Consultants' Meeting on Beta-Delayed Neutron Emission Evaluation

International Nuclear Information System (INIS)

Abriola, Daniel; Singh, Balraj; Dillmann, Iris

2011-12-01

A summary is given of a Consultants' Meeting assembled to assess the viability of a new IAEA Co-ordinated Research Project (CRP) on Beta-delayed neutron emission evaluation. The current status of the field was reviewed, cases in which new measurements are needed were identified and the current theoretical models were examined. The best known cases were selected as standards and were assessed and preliminary best values of the emission probabilities were obtained. The need of such a CRP was strongly agreed. Both the technical discussions and the expected outcome of such a project are described, along with detailed recommendations for its implementation. (author)

The Statistics of Emission and Detection of Neutrons and Photons from Fissile Samples for Safeguard Applications

International Nuclear Information System (INIS)

Enqvist, Andreas

2008-03-01

One particular purpose of nuclear safeguards, in addition to accounting for known materials, is the detection, identifying and quantifying unknown material, to prevent accidental and clandestine transports and uses of nuclear materials. This can be achieved in a non-destructive way through the various physical and statistical properties of particle emission and detection from such materials. This thesis addresses some fundamental aspects of nuclear materials and the way they can be detected and quantified by such methods. Factorial moments or multiplicities have long been used within the safeguard area. These are low order moments of the underlying number distributions of emission and detection. One objective of the present work was to determine the full probability distribution and its dependence on the sample mass and the detection process. Derivation and analysis of the full probability distribution and its dependence on the above factors constitutes the first part of the thesis. Another possibility of identifying unknown samples lies in the information in the 'fingerprints' (pulse shape distribution) left by a detected neutron or photon. A study of the statistical properties of the interaction of the incoming radiation (neutrons and photons) with the detectors constitutes the second part of the thesis. The interaction between fast neutrons and organic scintillation detectors is derived, and compared to Monte Carlo simulations. An experimental approach is also addressed in which cross correlation measurements were made using liquid scintillation detectors. First the dependence of the pulse height distribution on the energy and collision number of an incoming neutron was derived analytically and compared to numerical simulations. Then an algorithm was elaborated which can discriminate neutron pulses from photon pulses. The resulting cross correlation graphs are analyzed and discussed whether they can be used in applications to distinguish possible sample

The Statistics of Emission and Detection of Neutrons and Photons from Fissile Samples for Safeguard Applications

Energy Technology Data Exchange (ETDEWEB)

Enqvist, Andreas

2008-03-15

One particular purpose of nuclear safeguards, in addition to accounting for known materials, is the detection, identifying and quantifying unknown material, to prevent accidental and clandestine transports and uses of nuclear materials. This can be achieved in a non-destructive way through the various physical and statistical properties of particle emission and detection from such materials. This thesis addresses some fundamental aspects of nuclear materials and the way they can be detected and quantified by such methods. Factorial moments or multiplicities have long been used within the safeguard area. These are low order moments of the underlying number distributions of emission and detection. One objective of the present work was to determine the full probability distribution and its dependence on the sample mass and the detection process. Derivation and analysis of the full probability distribution and its dependence on the above factors constitutes the first part of the thesis. Another possibility of identifying unknown samples lies in the information in the 'fingerprints' (pulse shape distribution) left by a detected neutron or photon. A study of the statistical properties of the interaction of the incoming radiation (neutrons and photons) with the detectors constitutes the second part of the thesis. The interaction between fast neutrons and organic scintillation detectors is derived, and compared to Monte Carlo simulations. An experimental approach is also addressed in which cross correlation measurements were made using liquid scintillation detectors. First the dependence of the pulse height distribution on the energy and collision number of an incoming neutron was derived analytically and compared to numerical simulations. Then an algorithm was elaborated which can discriminate neutron pulses from photon pulses. The resulting cross correlation graphs are analyzed and discussed whether they can be used in applications to distinguish possible

Study of the delayed neutron emission through the time-of-flight method. Application to 49K, 50K and 51K

International Nuclear Information System (INIS)

Rachidi, J.

1983-04-01

This work is dedicated to the study of the emission of delayed neutrons observed in the decay of 49 K, 50 K and 51 K. Spectroscopic data are non-existent for these 3 isotopes, so we have had to design a specific detection system based on a large-surface scintillation counter. A series of n-γ coincidence measurement has allowed us to determine the energy levels of the non-bound states of 49 Ca, 50 Ca and 51 Ca and to establish the nature of the beta transitions (K → Ca). We have measured the energy of the delayed neutrons through the time-of-flight method. Our results are consistent with the model of the p-n states based on the Bansac-French's works. This model shows that the non-bound states of the calcium isotopes discovered in the experiment are represented by simple configurations of the (sd) -1 (fp) n type. (A.C.)

Bi-Modal Model for Neutron Emissions from PuO2 and MOX Holdup

International Nuclear Information System (INIS)

Menlove, Howard; Lafleur, Adrienne

2015-01-01

The measurement of uranium and plutonium holdup in plants during process activity and for decommissioning is important for nuclear safeguards and material control. The amount of plutonium and uranium holdup in glove-boxes, pipes, ducts, and other containers has been measured for several decades using both neutron and gamma-ray techniques. For the larger containers such as hot cells and glove-boxes that contain processing equipment, the gamma-ray techniques are limited by self-shielding in the sample as well as gamma absorption in the equipment and associated shielding. The neutron emission is more penetrating and has been used extensively to measure the holdup for the large facilities such as the MOX processing and fabrication facilities in Japan and Europe. In some case the totals neutron emission rates are used to determine the holdup mass and in other cases the coincidence rates are used such as at the PFPF MOX fabrication plant in Japan. The neutron emission from plutonium and MOX has 3 primary source terms: 1) Spontaneous fission (SF) from the plutonium isotopes, 2) The (α,n) reactions from the plutonium alpha particle emission reacting with the oxygen and other impurities, and 3) Neutron multiplication (M) in the plutonium and uranium as a result of neutrons created by the first two sources. The spontaneous fission yield per gram is independent of thickness, whereas, the above sources 2) and 3) are very dependent on the thickness of the deposit. As the effective thickness of the deposit becomes thin relative to the alpha particle range, the (α,n) reactions and neutrons from multiplication (M) approach zero. In any glove-box, there will always be two primary modes of holdup accumulation, namely direct powder contact and non-contact by air dispersal. These regimes correspond to surfaces in the glove-box that have come into direct contact with the process MOX powder versus surface areas that have not had direct contact with the powder. The air dispersal of Pu

Testing the Young Neutron Star Scenario with Persistent Radio Emission Associated with FRB 121102

International Nuclear Information System (INIS)

Kashiyama, Kazumi; Murase, Kohta

2017-01-01

Recently a repeating fast radio burst (FRB) 121102 has been confirmed to be an extragalactic event and a persistent radio counterpart has been identified. While other possibilities are not ruled out, the emission properties are broadly consistent with Murase et al. that theoretically proposed quasi-steady radio emission as a counterpart of both FRBs and pulsar-driven supernovae. Here, we constrain the model parameters of such a young neutron star scenario for FRB 121102. If the associated supernova has a conventional ejecta mass of M ej ≳ a few M ⊙ , a neutron star with an age of t age ∼ 10–100 years, an initial spin period of P i ≲ a few ms, and a dipole magnetic field of B dip ≲ a few × 10 13 G can be compatible with the observations. However, in this case, the magnetically powered scenario may be favored as an FRB energy source because of the efficiency problem in the rotation-powered scenario. On the other hand, if the associated supernova is an ultra-stripped one or the neutron star is born by the accretion-induced collapse with M ej ∼ 0.1 M ⊙ , a younger neutron star with t age ∼ 1–10 years can be the persistent radio source and might produce FRBs with the spin-down power. These possibilities can be distinguished by the decline rate of the quasi-steady radio counterpart.

Testing the Young Neutron Star Scenario with Persistent Radio Emission Associated with FRB 121102

Energy Technology Data Exchange (ETDEWEB)

Kashiyama, Kazumi [Department of Physics, The University of Tokyo, Bunkyo, Tokyo 113-0033 (Japan); Murase, Kohta [Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States)

2017-04-10

Recently a repeating fast radio burst (FRB) 121102 has been confirmed to be an extragalactic event and a persistent radio counterpart has been identified. While other possibilities are not ruled out, the emission properties are broadly consistent with Murase et al. that theoretically proposed quasi-steady radio emission as a counterpart of both FRBs and pulsar-driven supernovae. Here, we constrain the model parameters of such a young neutron star scenario for FRB 121102. If the associated supernova has a conventional ejecta mass of M {sub ej} ≳ a few M {sub ⊙}, a neutron star with an age of t {sub age} ∼ 10–100 years, an initial spin period of P{sub i} ≲ a few ms, and a dipole magnetic field of B {sub dip} ≲ a few × 10{sup 13} G can be compatible with the observations. However, in this case, the magnetically powered scenario may be favored as an FRB energy source because of the efficiency problem in the rotation-powered scenario. On the other hand, if the associated supernova is an ultra-stripped one or the neutron star is born by the accretion-induced collapse with M {sub ej} ∼ 0.1 M {sub ⊙}, a younger neutron star with t {sub age} ∼ 1–10 years can be the persistent radio source and might produce FRBs with the spin-down power. These possibilities can be distinguished by the decline rate of the quasi-steady radio counterpart.

Characteristics of Fabricated SiC Neutron Detectors for Neutron Flux Monitoring

Energy Technology Data Exchange (ETDEWEB)

Kim, Han Soo; Ha, Jang Ho; Park, Se Hwan; Lee, Kyu Hong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Cheol Ho [Hanyang University, Seoul (Korea, Republic of)

2011-05-15

An SPND (Self-powered Neutron Detector) is commonly used for neutron detection in NPP (Nuclear Power Plant) by virtue of un-reactivity for gamma-rays. But it has a drawback, which is that it cannot detect neutrons in real time due to beta emissions (about > 48 s) after reactions between neutrons and {sup 103}Rh in an SPND. And Generation IV reactors such as MSR (Molten-salt reactor), SFR (Sodium-cooled fast reactor), and GFR (Gas-cooled fast reactor) are designed to compact size and integration type. For GEN IV reactor, neutron monitor also must be compact-sized to apply such reactor easily and much more reliable. The wide band-gap semiconductors such as SiC, AlN, and diamond make them an attractive alternative in applications in harsh environments by virtue of the lower operating voltage, faster charge-collection times compared with gas-filled detectors, and compact size.1) In this study, two PIN-type SiC semiconductor neutron detectors, which are for fast neutron detection by elastic and inelastic scattering SiC atoms and for thermal neutron detection by charged particle emissions of 6LiF reaction, were designed and fabricated for NPP-related applications. Preliminary tests such as I-V and alpha response were performed and neutron responses at ENF in HANARO research reactor were also addressed. The application feasibility of the fabricated SiC neutron detector as an in-core neutron monitor was discussed

Exploring the manifestation and nature of a dineutron in two-neutron emission using a dynamical dineutron model

Science.gov (United States)

Grigorenko, L. V.; Vaagen, J. S.; Zhukov, M. V.

2018-03-01

Emission of two neutrons or two protons in reactions and decays is often discussed in terms of "dineutron" or "diproton" emission. The discussion often leans intuitively on something described by Migdal-Watson approximation. In this work we propose a way to formalize situations of dineutron emission. It is demonstrated that properly formally defined dineutron emission may reveal properties which are drastically different from those traditionally expected, and properties which are actually observed in three-body decays.

Radioactively powered emission from black hole-neutron star mergers

International Nuclear Information System (INIS)

Tanaka, Masaomi; Wanajo, Shinya; Hotokezaka, Kenta; Kyutoku, Koutarou; Kiuchi, Kenta; Sekiguchi, Yuichiro; Shibata, Masaru

2014-01-01

Detection of the electromagnetic counterparts of gravitational wave (GW) sources is important to unveil the nature of compact binary coalescences. We perform three-dimensional, time-dependent, multi-frequency radiative transfer simulations for radioactively powered emission from the ejecta of black hole (BH)-neutron star (NS) mergers. Depending on the BH to NS mass ratio, spin of the BH, and equations of state of dense matter, BH-NS mergers can eject more material than NS-NS mergers. In such cases, radioactively powered emission from the BH-NS merger ejecta can be more luminous than that from NS-NS mergers. We show that, in spite of the expected larger distances to BH-NS merger events, the observed brightness of BH-NS mergers can be comparable to or even higher than that of NS-NS mergers. We find that, when the tidally disrupted BH-NS merger ejecta are confined to a small solid angle, the emission from BH-NS merger ejecta tends to be bluer than that from NS-NS merger ejecta for a given total luminosity. Thanks to this property, we might be able to distinguish BH-NS merger events from NS-NS merger events by multi-band observations of the radioactively powered emission. In addition to the GW observations, such electromagnetic observations can potentially provide independent information on the progenitors of GW sources and the nature of compact binary coalescences.

Dynamics of 120 and 20 kV plasma focus devices with respect to density and current distribution, neutron and X-ray emission

International Nuclear Information System (INIS)

Decker, G.; Nahrath, B.; Oppenlaender, T.; Pross, G.; Rueckle, B.; Schmidt, H.; Shakhatre, M.; Trunk, M.

1976-01-01

Our experiments have aimed at two goals: 1) better understanding of the dynamics and neutron production of the focus phase and 2) improved scaling of the neutron yield by operating a high voltage focus. 1) For the first goal, experiments with a 30 kJ/ 16 kV plasma focus of the Mather type (NESSI) were performed. The simultaneously applied diagnostics include interferometry, X-ray photography with channel plates, magnetic probes and neutron emission. In the established chronology we can distinguish 5 phases in the development of the plasma focus: a compression phase is followed by a short (8 ns) very dense phase, where the density peaks at a minimum radius (t = 0 in our chronology). The plasma cylinder expands to a relatively long lasting (30 to 70 ns) quiescent phase before instabilities occur. This short unstable phase is followed by a decay phase during which the neutron emission peaks. Important correlations between the plasma parameters and the neutron emission are discussed. 2) Under the assumption that the neutron yield scales with a high power of the current, we concluded that a high voltage focus could result in higher neutron yield as compared with a lower voltage device of the same energy. The proper adjustments of the discharge parameters necessary due to the very short current risetime have been investigated. (orig.) [de

Importance of the (n,gamma) Cm-247 Evaluation on Neutron Emission in Fast Reactor Fuel Cycle Analysis

International Nuclear Information System (INIS)

Benoit Forget; Mehdi Asgari; Rodolfo M. Ferrer

2007-01-01

As part of the GNEP program, it is envisioned to build a fast reactor for the transmutation of minor actinides. The spent nuclear fuel from the current fleet of light water reactors would be recycled, the current baseline is the UREX+1a process, and would act as a feed for the fast reactor. As the fuel is irradiated in a fast reactor a certain quantity of minor actinides would thus build up in the fuel stream creating possible concerns with the neutron emission of these minor actinides for fuel transportation, handling and fabrication. Past neutronic analyses had not tracked minor actinides above Cm-246 in the transmutation chain, because of the small influence on the overall reactor performance and cycle parameters. However, when trying to quantify the neutron emission from the recycled fuel with high minor actinide content, these higher isotopes play an essential role and should be included in the analysis. In this paper, the influence of tracking these minor actinides on the calculated neutron emission is presented. Also presented is the particular influence of choosing a different evaluated cross section data set to represent the minor actinides above Cm-246. The first representation uses the cross-sections provided by MC2-2 for all isotopes, while the second representation uses infinitely diluted ENDF/BVII.0 cross-sections for Cm-247 to Cf-252 and MC2-2 for all other isotopes

Plasma-erosion-enhanced neutron emission in fiber-generated dense Z-pinches

International Nuclear Information System (INIS)

Mosher, D.; Colombant, D.

1990-01-01

Experiments in which dense z-pinches are created from high-current discharges through frozen deuterium fibers have reported neutron yields far in excess of those expected from thermal processes. A simple analysis based on pinch collapse due to the sausage instability has successfully predicted the relative variation of neutron yield with discharge current, but model assumptions precluded prediction of absolute values of the yield. A pinch-collapse model derived from a 2-dimensional, nonlinear treatment of the sausage instability, combined with space-charged-limited (SCL) ion orbital dynamic for the vacuum region above the pinches and between the expanding flares, leads to neutron yields four or more orders-of-magnitude below experimental values. Here, the same pinch-collapse model is used in conjunction with a low-density plasma background above the collapsing pinches. Ions are accelerated across the space-charge sheath separating the background plasma from the flares, which electron emission from the flares is strongly insulated by the z-discharge magnetic field. The sheath gap increases in time, i.e., the background plasma erodes, at a rate determined by its density and the SCL ion current density which, in turn, depends on the z-discharge dynamics and the associated induced electromagnetic fields. A model incorporating the above processes is used to determine the accelerated ion energy spectrum and associated neutron yield as functions of the discharge, instability, and background parameters

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

Energy Technology Data Exchange (ETDEWEB)

Nasir, Mohamad Nasrun bin Mohd, E-mail: monasr211@gmail.com; Metorima, Kouhei, E-mail: kohei.m2420@hotmail.co.jp; Ohsawa, Takaaki, E-mail: ohsawa@mvg.biglobe.ne.jp; Hashimoto, Kengo, E-mail: kengoh@pp.iij4u.or.jp [Graduate School of Science and Engineering, Kindai University, Kowakae, Higashi-Osaka, 577-8502 (Japan)

2015-04-29

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

Diabatic emission of neutrons: A probe for the energy dissipation mechanism in nucleus-nucleus collisions

International Nuclear Information System (INIS)

Noerenberg, W.; Cassing, W.

1984-05-01

The precompound emission of neutrons in central nucleus-nucleus collisions is investigated within the framework of dissipative diabatic dynamics. For 92 Mo + 92 Mo at bombarding energies between 7.5 and 20 MeV/u the differential neutron multiplicities dMsub(n)/dEsub(n) are estimated from the decay of highly excited diabatic single-particle states. The energy spectra have an almost exponential high-energy tail with effective temperatures up to 10 MeV for 20 MeV/u bombarding energy. (orig.)

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

Science.gov (United States)

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

2016-09-01

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

Measurement and analysis of 14 MeV neutron-induced double-differential neutron emission cross sections needed for fission and fusion reactor technology

International Nuclear Information System (INIS)

Wang Dahai; Mehta, M.K.

1988-07-01

The main objectives of this IAEA Co-ordinated Research Programme are to improve the current status of data for 14 MeV neutron-induced double-differential neutron emission cross sections for V, Cr, Fe, Nb, Ta and 238 U. The principal objectives of this first meeting were to report on the status of participants' work, to exchange experience in experimental work and to establish the future work. Considering the unsatisfactory status of the data for 6 Li, 7 Li, 9 Be, Mo, W and Bi and their importance in fusion reactor technology participants agreed to include these isotopes in the programme

Study of the neutron-photon competition during fission fragment de-excitation

International Nuclear Information System (INIS)

Min, Dong Pil.

1976-01-01

A program was developed to study in detail the competition between neutron and photon emissions during the different stages of the nucleus de-excitation. The main conclusions of this work are the following: the neutron-photon competition fairly depends of the initial spin of the primary fragment. It has a strong effect on the mean number of emitted neutrons, on the photon energy, and to a lower degree, on the mean energy per neutron. A relation between the mean initial spin of the heavy fragment for the almost symmetrical fission, the mean initial spin of the heavy fragment for a very asymmetric fission and the corresponding values of the mean number of emitted neutrons is given. The mean initial excitation energy must increase of about 9MeV for the nucleus to emit one more neutron. Two reasons are given to explain the fact that the measured neutron multiplicity variance is higher for the heavy fragment than for the light one: either the existence of a covariance between spin and excitation energy distribution, or a dispersion of the values of the mean number of emitted neutrons due to the mass and charge distribution resulting from experimental incertitudes. The mean energy per neutron calculated with the program is in good agreement with measured values [fr

Modeling of neutron emission spectroscopy in JET discharges with fast tritons from (T)D ion cyclotron heating

International Nuclear Information System (INIS)

Tardocchi, M.; Gorini, G.; Andersson Sunden, E.; Conroy, S.; Ericsson, G.; Gatu Johnson, M.; Giacomelli, L.; Hellesen, C.; Hjalmarsson, A.; Kaellne, J.; Ronchi, E.; Sjoestrand, H.; Weiszflog, M.; Johnson, T.; Lamalle, P. U.

2006-01-01

The measurement of fast ion populations is one of the diagnostic capabilities provided by neutron emission spectroscopy (NES). NES measurements were carried out during JET trace tritium campaign with the magnetic proton recoil neutron spectrometer. A favorable plasma scenario is (T)D where the resulting 14 MeV neutron yield is dominated by suprathermal emission from energetic tritons accelerated by radio frequency at their fundamental cyclotron frequency. Information on the triton distribution function has been derived from NES data with a simple model based on two components referred to as bulk (B) and high energy (HE). The HE component is based on strongly anisotropic tritium distribution that can be used for routine best-fit analysis to provide tail temperature values (T HE ). This article addresses to what extent the T HE values are model dependent by comparing the model above with a two-temperature (bi-) Maxwellian model featuring parallel and perpendicular temperatures. The bi-Maxwellian model is strongly anisotropic and frequently used for radio frequency theory

Determination of the ion thermal diffusivity from neutron emission profiles in decay

International Nuclear Information System (INIS)

Sasao, M.; Adams, J.M.; Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van

1994-01-01

Spatial profiles of the neutron emission from deuterium plasmas are routinely obtained at the Joint European Torus (JET) using the line-integrated signals measured with a multichannel instrument. It is shown that the manner in which these profiles relax following the termination of strong heating with neutral beam injection (NBI) permits the local thermal diffusivity (χ i ) to be obtained with an accuracy of about 20%. (author)

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

Neutron response study

International Nuclear Information System (INIS)

Endres, G.W.R.; Fix, J.J.; Thorson, M.R.; Nichols, L.L.

1981-01-01

Neutron response of the albedo type dosimeter is strongly dependent on the energy of the incident neutrons as well as the moderating material on the backside of the dosimeter. This study characterizes the response of the Hanford dosimeter for a variety of neutron energies for both a water and Rando phantom (a simulated human body consisting of an actual human skeleton with plastic for body muscles and certain organs). The Hanford dosimeter response to neutrons of different energies is typical of albedo type dosimeters. An approximate two orders of magnitude difference in response is observed between neutron energies of 100 keV and 10 MeV. Methods were described to compensate for the difference in dosimeter response between a laboratory neutron spectrum and the different spectra encountered at various facilities in the field. Generally, substantial field support is necessary for accurate neutron dosimetry

$\\beta$-decay study of neutron-rich Tl and Pb isotopes

CERN Multimedia

It is proposed to study the structure of neutron-rich nuclei beyond $^{208}$Pb. The one-proton hole $^{211-215}$Tl and the semi magic $^{213}$Pb will be produced and studied via nuclear and atomic spectroscopy searching for long-lived isomers and investigating the $\\beta$-delayed $\\gamma$- emission to build level schemes. Information on the single particle structure in $^{211-215}$Pb, especially the position of the g$_{9/2}$ and i$_{11/2}$ neutron orbitals, will be extracted along with lifetimes. The $\\beta$-decay will be complemented with the higher spin selectivity that can be obtained by resonant laser ionization to single-out the decay properties of long-living isomers in $^{211,213}$Tl and $^{213}$Pb.

Neutron emission from projectile-like and target-like fragments in the 18O+48Ti reaction at E(18O)=116 MeV

International Nuclear Information System (INIS)

Chambon, B.; Drain, D.; Pastor, C.; Dauchy, A.; Giorni, A.; Morand, C.

1982-07-01

Angular correlations between neutrons and projectile-like fragments detected near the grazing angle were analysed by assuming two incoherent neutrons sources. One source describes slower neutrons evaporated by target-like fragments in equilibrium. The faster, forward-peaked neutrons originate from a second source strongly correlated with the projectile-like fragments with regards to velocity and direction. In some cases neutron emission may even be attributed to known neutron emitter levels in excited ejectiles

Determination of the ion thermal diffusivity from neutron emission profiles in decay

International Nuclear Information System (INIS)

Sasao, M.; Adam, J.M.; Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van

1992-01-01

Spatial profiles of neutron emission are routinely obtained at the Joint European Torus (JET) from line-integrated emissivities measured with a multi-channel instrument. It is shown that the manner in which the emission profiles relax following termination of strong heating with Neutral Beam Injection (NBI) permits the local thermal diffusivity (χ i ) to be obtained with an accuracy of about 20%. The radial profiles of χ i for small minor radius (r/a 2 /s for H-mode plasmas with plasma current I p = 3.1 MA and toroidal field B T = 2.3T. The experimental value of χ i is smallest for Z eff = 2.2 and increases weakly with increasing Z eff . The experimental results disagree by two orders of magnitude with predictions from an ion temperature gradient driven turbulence model. (author) 6 refs., 3 figs

Dynamics of 120 and 20 kV plasma focus devices with respect to density and current distribution, and neutron and X-ray emission

International Nuclear Information System (INIS)

Decker, G.; Nahrath, B.; Oppenlaender, T.; Pross, G.; Rueckle, B.; Schmidt, H.; Shakhatre, M.; Trunk, M.

1977-01-01

The experiments had two goals: (1) Better understanding of the dynamics and neutron production of the focus phase and (2) improved scaling of the neutron yield by operating a high-voltage focus. For the first goal, experiments with a 30-kJ/16-kV plasma focus of the Mather type (NESSI) were performed. The simultaneously applied diagnostics include interferometry, X-ray photography with channel plates, magnetic probes and scintillator/photomultiplier detectors for measuring hard X-ray and neutron emission. In the established chronology one can distinguish five phases in the development of the plasma focus: A compression phase is followed by a short (8 ns) very dense phase, where the density peaks at a minimum radius (t=0, authors' chronology). The plasma cylinder expands to a relatively long-lasting (30 to 70 ns) quiescent phase before instabilities occur. This short unstable phase is followed by a decay phase during which the neutron emission peaks. Important correlations between the plasma parameters and the neutron emission are discussed. Secondly, on the assumption that the neutron yield scales with a high power of the current, it was concluded that a high-voltage focus could result in higher neutron yield as compared with a lower voltage device of the same energy. The proper adjustments of the discharge parameters necessary due to the very short current risetime were investigated. (author)

Strong Neutron Pairing in core+4n Nuclei.

Science.gov (United States)

Revel, A; Marqués, F M; Sorlin, O; Aumann, T; Caesar, C; Holl, M; Panin, V; Vandebrouck, M; Wamers, F; Alvarez-Pol, H; Atar, L; Avdeichikov, V; Beceiro-Novo, S; Bemmerer, D; Benlliure, J; Bertulani, C A; Boillos, J M; Boretzky, K; Borge, M J G; Caamaño, M; Casarejos, E; Catford, W N; Cederkäll, J; Chartier, M; Chulkov, L; Cortina-Gil, D; Cravo, E; Crespo, R; Datta Pramanik, U; Díaz Fernández, P; Dillmann, I; Elekes, Z; Enders, J; Ershova, O; Estradé, A; Farinon, F; Fraile, L M; Freer, M; Galaviz, D; Geissel, H; Gernhäuser, R; Golubev, P; Göbel, K; Hagdahl, J; Heftrich, T; Heil, M; Heine, M; Heinz, A; Henriques, A; Ignatov, A; Johansson, H T; Jonson, B; Kahlbow, J; Kalantar-Nayestanaki, N; Kanungo, R; Kelic-Heil, A; Knyazev, A; Kröll, T; Kurz, N; Labiche, M; Langer, C; Le Bleis, T; Lemmon, R; Lindberg, S; Machado, J; Marganiec, J; Movsesyan, A; Nacher, E; Najafi, M; Nilsson, T; Nociforo, C; Paschalis, S; Perea, A; Petri, M; Pietri, S; Plag, R; Reifarth, R; Ribeiro, G; Rigollet, C; Röder, M; Rossi, D; Savran, D; Scheit, H; Simon, H; Syndikus, I; Taylor, J T; Tengblad, O; Thies, R; Togano, Y; Velho, P; Volkov, V; Wagner, A; Weick, H; Wheldon, C; Wilson, G; Winfield, J S; Woods, P; Yakorev, D; Zhukov, M; Zilges, A; Zuber, K

2018-04-13

The emission of neutron pairs from the neutron-rich N=12 isotones ^{18}C and ^{20}O has been studied by high-energy nucleon knockout from ^{19}N and ^{21}O secondary beams, populating unbound states of the two isotones up to 15 MeV above their two-neutron emission thresholds. The analysis of triple fragment-n-n correlations shows that the decay ^{19}N(-1p)^{18}C^{*}→^{16}C+n+n is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a ^{14}C core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay ^{21}O(-1n)^{20}O^{*}→^{18}O+n+n, attributed to its formation through the knockout of a deeply bound neutron that breaks the ^{16}O core and reduces the number of pairs.

Determination of the ion thermal diffusivity from neutron emission profiles in decay

Energy Technology Data Exchange (ETDEWEB)

Sasao, M. (National Inst. for Fusion Science, Nagoya (Japan)); Adams, J.M. (AEA Industrial Technology, Harwell (United Kingdom)); Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van (Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking)

1994-01-01

Spatial profiles of the neutron emission from deuterium plasmas are routinely obtained at the Joint European Torus (JET) using the line-integrated signals measured with a multichannel instrument. It is shown that the manner in which these profiles relax following the termination of strong heating with neutral beam injection (NBI) permits the local thermal diffusivity ([chi][sub i]) to be obtained with an accuracy of about 20%. (author).

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; JET Contributors

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.

Calculations to support JET neutron yield calibration: Modelling of neutron emission from a compact DT neutron generator

Energy Technology Data Exchange (ETDEWEB)

Čufar, Aljaž, E-mail: aljaz.cufar@ijs.si [Reactor Physics Department, Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Batistoni, Paola [ENEA, Department of Fusion and Nuclear Safety Technology, I-00044 Frascati, Rome (Italy); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Conroy, Sean [Uppsala University, Department of Physics and Astronomy, PO Box 516, SE-75120 Uppsala (Sweden); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Ghani, Zamir [Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Lengar, Igor [Reactor Physics Department, Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Milocco, Alberto; Packer, Lee [Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Pillon, Mario [ENEA, Department of Fusion and Nuclear Safety Technology, I-00044 Frascati, Rome (Italy); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Popovichev, Sergey [Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Snoj, Luka [Reactor Physics Department, Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); EUROfusion Consortium, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)

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.

Estimation of neutron energy distributions from prompt gamma emissions

Science.gov (United States)

Panikkath, Priyada; Udupi, Ashwini; Sarkar, P. K.

2017-11-01

A technique of estimating the incident neutron energy distribution from emitted prompt gamma intensities from a system exposed to neutrons is presented. The emitted prompt gamma intensities or the measured photo peaks in a gamma detector are related to the incident neutron energy distribution through a convolution of the response of the system generating the prompt gammas to mono-energetic neutrons. Presently, the system studied is a cylinder of high density polyethylene (HDPE) placed inside another cylinder of borated HDPE (BHDPE) having an outer Pb-cover and exposed to neutrons. The emitted five prompt gamma peaks from hydrogen, boron, carbon and lead can be utilized to unfold the incident neutron energy distribution as an under-determined deconvolution problem. Such an under-determined set of equations are solved using the genetic algorithm based Monte Carlo de-convolution code GAMCD. Feasibility of the proposed technique is demonstrated theoretically using the Monte Carlo calculated response matrix and intensities of emitted prompt gammas from the Pb-covered BHDPE-HDPE system in the case of several incident neutron spectra spanning different energy ranges.

Measurement of the cross section for electromagnetic dissociation with neutron emission in Pb-Pb collisions at √SNN=2.76 TeV

International Nuclear Information System (INIS)

Abelev, B.; Garishvili, I.; Soltz, R.; Adam, J.; Bielcik, J.; Cepila, J.; Krelina, M.; Krus, M.; Pachr, M.; Petracek, V.; Petran, M.; Pospisil, V.; Smakal, R.; Tlusty, D.; Wagner, V.; Zach, C.; Vajzer, M.; Adamova, D.; Bielcikova, J.; Kushpil, S.; Kushpil, V.; Sumbera, M.; Adare, A.M.; Aronsson, T.; Caballero Orduna, D.; Caines, H.; Harris, J.W.; Hicks, B.; Hille, P.T.; Ma, R.; Oh, S.; Smirnov, N.; Aggarwal, M.M.; Bhati, A.K.; Chawla, I.; Rathee, D.; Sharma, N.; Aglieri Rinella, G.; Augustinus, A.; Baltasar Dos Santos Pedrosa, F.; Betev, L.; Brun, R.; Carena, F.; Carena, W.; Carminati, F.; Cavicchioli, C.; Chapeland, S.; Chibante Barroso, V.; Chochula, P.; Conesa del Valle, Z.; Costa, F.; Del Castillo Sanchez, E.; Di Mauro, A.; Divia, R.; Floris, M.; Fuchs, U.; Gheata, A.; Agocs, A.G.; Barnafoldi, G.G.; Bencedi, G.; Berenyi, D.; Boldizsar, L.; Denes, E.; Hamar, G.; Levai, P.; Agostinelli, A.; Arcelli, S.; Basile, M.; Bellini, F.; Cifarelli, L.; Falchieri, D.; Guerzoni, B.; Scioli, G.; Zichichi, A.; Aguilar Salazar, S.; Alfaro Molina, R.; Almaraz Avina, E.; Belmont-Moreno, E.; Cruz Alaniz, E.; Gonzalez-Trueba, L.H.; Grabski, V.; Martinez Davalos, A.; Menchaca-Rocha, A.; Ahammed, Z.; Basu, S.; Chattopadhyay, S.; Choudhury, S.; De, S.; Dubey, A.K.; Dutta Majumdar, M.R.; Ghosh, P.; Khan, S.A.; Mohanty, B.; Muhuri, S.; Mukherjee, M.; Nayak, T.K.; Baldisseri, A.; Borel, H.; Castillo Castellanos, J.; Charvet, J.L.; Geuna, C.; Pereira Da Costa, H.; Rakotozafindrabe, A.; Yang, H.

2012-01-01

The first measurement of neutron emission in electromagnetic dissociation of 208 Pb nuclei at the LHC is presented. The measurement is performed using the neutron zero degree calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at √S NN = 2.76 TeV with neutron emission are σ singleEMD =187.4 ± 0.2(stat) +13.2 -11.2 (syst) b and σ mutualEMD = 5.7±0.1(stat) ± 0.4(syst) b, respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model. (authors)

Study on neutron irradiation behavior of beryllium as neutron multiplier

Energy Technology Data Exchange (ETDEWEB)

Ishitsuka, Etsuo [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment

1998-03-01

More than 300 tons beryllium is expected to be used as a neutron multiplier in ITER, and study on the neutron irradiation behavior of beryllium as the neutron multiplier with Japan Materials Testing Reactor (JMTR) were performed to get the engineering data for fusion blanket design. This study started as the study on the tritium behavior in beryllium neutron reflector in order to make clear the generation mechanism on tritium of JMTR primary coolant since 1985. These experiences were handed over to beryllium studies for fusion study, and overall studies such as production technology of beryllium pebbles, irradiation behavior evaluation and reprocessing technology have been started since 1990. In this presentation, study on the neutron irradiation behavior of beryllium as the neutron multiplier with JMTR was reviewed from the point of tritium release, thermal properties, mechanical properties and reprocessing technology. (author)

Introducing single-crystal scattering and optical potentials into MCNPX: Predicting neutron emission from a convoluted moderator

Energy Technology Data Exchange (ETDEWEB)

Gallmeier, F.X., E-mail: gallmeierfz@ornl.gov [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Iverson, E.B.; Lu, W. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Baxter, D.V. [Center for the Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408 (United States); Muhrer, G.; Ansell, S. [European Spallation Source, ESS AB, Lund (Sweden)

2016-04-01

Neutron transport simulation codes are indispensable tools for the design and construction of modern neutron scattering facilities and instrumentation. Recently, it has become increasingly clear that some neutron instrumentation has started to exploit physics that is not well-modeled by the existing codes. In particular, the transport of neutrons through single crystals and across interfaces in MCNP(X), Geant4, and other codes ignores scattering from oriented crystals and refractive effects, and yet these are essential phenomena for the performance of monochromators and ultra-cold neutron transport respectively (to mention but two examples). In light of these developments, we have extended the MCNPX code to include a single-crystal neutron scattering model and neutron reflection/refraction physics. We have also generated silicon scattering kernels for single crystals of definable orientation. As a first test of these new tools, we have chosen to model the recently developed convoluted moderator concept, in which a moderating material is interleaved with layers of perfect crystals to provide an exit path for neutrons moderated to energies below the crystal's Bragg cut–off from locations deep within the moderator. Studies of simple cylindrical convoluted moderator systems of 100 mm diameter and composed of polyethylene and single crystal silicon were performed with the upgraded MCNPX code and reproduced the magnitude of effects seen in experiments compared to homogeneous moderator systems. Applying different material properties for refraction and reflection, and by replacing the silicon in the models with voids, we show that the emission enhancements seen in recent experiments are primarily caused by the transparency of the silicon and void layers. Finally we simulated the convoluted moderator experiments described by Iverson et al. and found satisfactory agreement between the measurements and the simulations performed with the tools we have developed.

Measurement and analysis of double-differential neutron emission spectra in (P,N) and (α,N) reactions

International Nuclear Information System (INIS)

Okamoto, K.; Mehta, M.K.

1988-05-01

The second IAEA Research Co-ordination Meeting on Measurement and Analysis of Double-Differential Neutron Emission Spectra in (p,n) and (α,n) Reactions was convened by the IAEA Nuclear Data Section at the IAEA Headquarters in Vienna during 8-10 February, 1988. The main objectives of the Co-ordinated Research Project for which this meeting was held are (i) to extract systematic information about nuclear level densities as a function of excitation energy by analysing the neutron emission spectra from (p,n) and (α,n) reactions on properly selected targets and bombarding energy range, and (ii) to parametrize this information into appropriate phenomenological models to enable reliable extrapolation for general use of level density information in basic and applied nuclear physics related problems. Detailed conclusions and recommendations, together with a summary of the programme during 1988/1989 are attached in the Appendices

Studies of Neutron Stars at Optical/IR Wavelengths

OpenAIRE

Mignani, R. P.; Bagnulo, S.; De Luca, A.; Israel, G. L.; Curto, G. Lo; Motch, C.; Perna, R.; Rea, N.; Turolla, R.; Zane, S.

2006-01-01

In the last years, optical studies of Isolated Neutron Stars (INSs) have expanded from the more classical rotation-powered ones to other categories, like the Anomalous X-ray Pulsars (AXPs) and the Soft Gamma-ray Repeaters (SGRs), which make up the class of the magnetars, the radio-quiet INSs with X-ray thermal emission and, more recently, the enigmatic Compact Central Objects (CCOs) in supernova remnants. Apart from 10 rotation-powered pulsars, so far optical/IR counterparts have been found f...

Detection of special nuclear material from delayed neutron emission induced by a dual-particle monoenergetic source

Energy Technology Data Exchange (ETDEWEB)

Mayer, M. [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Nattress, J.; Jovanovic, I., E-mail: ijov@umich.edu [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2016-06-27

Detection of unique signatures of special nuclear materials is critical for their interdiction in a variety of nuclear security and nonproliferation scenarios. We report on the observation of delayed neutrons from fission of uranium induced in dual-particle active interrogation based on the {sup 11}B(d,n γ){sup 12}C nuclear reaction. Majority of the fissions are attributed to fast fission induced by the incident quasi-monoenergetic neutrons. A Li-doped glass–polymer composite scintillation neutron detector, which displays excellent neutron/γ discrimination at low energies, was used in the measurements, along with a recoil-based liquid scintillation detector. Time-dependent buildup and decay of delayed neutron emission from {sup 238}U were measured between the interrogating beam pulses and after the interrogating beam was turned off, respectively. Characteristic buildup and decay time profiles were compared to the common parametrization into six delayed neutron groups, finding a good agreement between the measurement and nuclear data. This method is promising for detecting fissile and fissionable materials in cargo scanning applications and can be readily integrated with transmission radiography using low-energy nuclear reaction sources.

Bi-Modal Model for Neutron Emissions from PuO{sub 2} and MOX Holdup

Energy Technology Data Exchange (ETDEWEB)

Menlove, Howard; Lafleur, Adrienne [Los Alamos National Laboratory, Safeguard Science and Technology Group, NEN-1, MS E540, Los Alamos, NM, 87545 (United States)

2015-07-01

The measurement of uranium and plutonium holdup in plants during process activity and for decommissioning is important for nuclear safeguards and material control. The amount of plutonium and uranium holdup in glove-boxes, pipes, ducts, and other containers has been measured for several decades using both neutron and gamma-ray techniques. For the larger containers such as hot cells and glove-boxes that contain processing equipment, the gamma-ray techniques are limited by self-shielding in the sample as well as gamma absorption in the equipment and associated shielding. The neutron emission is more penetrating and has been used extensively to measure the holdup for the large facilities such as the MOX processing and fabrication facilities in Japan and Europe. In some case the totals neutron emission rates are used to determine the holdup mass and in other cases the coincidence rates are used such as at the PFPF MOX fabrication plant in Japan. The neutron emission from plutonium and MOX has 3 primary source terms: 1) Spontaneous fission (SF) from the plutonium isotopes, 2) The (α,n) reactions from the plutonium alpha particle emission reacting with the oxygen and other impurities, and 3) Neutron multiplication (M) in the plutonium and uranium as a result of neutrons created by the first two sources. The spontaneous fission yield per gram is independent of thickness, whereas, the above sources 2) and 3) are very dependent on the thickness of the deposit. As the effective thickness of the deposit becomes thin relative to the alpha particle range, the (α,n) reactions and neutrons from multiplication (M) approach zero. In any glove-box, there will always be two primary modes of holdup accumulation, namely direct powder contact and non-contact by air dispersal. These regimes correspond to surfaces in the glove-box that have come into direct contact with the process MOX powder versus surface areas that have not had direct contact with the powder. The air dispersal of Pu

Determination of the ion thermal diffusivity from neutron emission profiles in decay

Energy Technology Data Exchange (ETDEWEB)

Sasao, M. (National Inst. for Fusion Science, Nagoya (Japan)); Adam, J.M. (AEA Industrial Technology, Harwell (United Kingdom)); Conroy, S.; Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van (Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking)

1992-01-01

Spatial profiles of neutron emission are routinely obtained at the Joint European Torus (JET) from line-integrated emissivities measured with a multi-channel instrument. It is shown that the manner in which the emission profiles relax following termination of strong heating with Neutral Beam Injection (NBI) permits the local thermal diffusivity ([chi][sub i]) to be obtained with an accuracy of about 20%. The radial profiles of [chi][sub i] for small minor radius (r/a < 0.6) were found to be flat and to take values between 0.3 and 1.1 m[sup 2]/s for H-mode plasmas with plasma current I[sub p] = 3.1 MA and toroidal field B[sub T] = 2.3T. The experimental value of [chi][sub i] is smallest for Z[sub eff] = 2.2 and increases weakly with increasing Z[sub eff]. The experimental results disagree by two orders of magnitude with predictions from an ion temperature gradient driven turbulence model. (author) 6 refs., 3 figs.

Neutron emission from deuterium plasma focus

International Nuclear Information System (INIS)

Antanasijevic, R.; Banjanac, R.; Dragic, A.; Djordjevic, D.; Joksimovic, D.; Maric, Z.; Udovicic, V.; Vukovic, J.

1998-01-01

The anisotropy of emitted neutrons is investigated on a small 'Mather-type' plasma focus device (PF). This problem is of importance for determining the nature of the fusion reaction mechanisms. Mica detectors together with thick uranium foils were used for both detection and angular distribution measurements of the neutrons. Previously, the annealing of the detectors was done and measured after the irradiation with neutrons from Am-Be source. Also, annealing ability of H-plasma focus has been tested. Geometry of detectors in both experiments was the same. (authors)

Measurement of the Cross Section for Electromagnetic Dissociation with Neutron Emission in Pb-Pb Collisions at √sNN = 2.76 TeV

CERN Document Server

Abelev, Betty; Adamova, Dagmar; Adare, Andrew Marshall; Aggarwal, Madan; Aglieri Rinella, Gianluca; Agocs, Andras Gabor; Agostinelli, Andrea; Aguilar Salazar, Saul; Ahammed, Zubayer; Ahmad, Arshad; Ahmad, Nazeer; Ahn, Sang Un; Akindinov, Alexander; Aleksandrov, Dmitry; Alessandro, Bruno; Alfaro Molina, Jose Ruben; Alici, Andrea; Alkin, Anton; Almaraz Avina, Erick Jonathan; Alme, Johan; Alt, Torsten; Altini, Valerio; Altinpinar, Sedat; Altsybeev, Igor; Andrei, Cristian; Andronic, Anton; Anguelov, Venelin; Anielski, Jonas; Anticic, Tome; Antinori, Federico; Antonioli, Pietro; Aphecetche, Laurent Bernard; Appelshauser, Harald; Arbor, Nicolas; Arcelli, Silvia; Arend, Andreas; Armesto, Nestor; Arnaldi, Roberta; Aronsson, Tomas Robert; Arsene, Ionut Cristian; Arslandok, Mesut; Augustinus, Andre; Averbeck, Ralf Peter; Awes, Terry; Aysto, Juha Heikki; Azmi, Mohd Danish; Bach, Matthias Jakob; Badala, Angela; Baek, Yong Wook; Bailhache, Raphaelle Marie; Bala, Renu; Baldini Ferroli, Rinaldo; Baldisseri, Alberto; Baldit, Alain; Baltasar Dos Santos Pedrosa, Fernando; Ban, Jaroslav; Baral, Rama Chandra; Barbera, Roberto; Barile, Francesco; Barnafoldi, Gergely Gabor; Barnby, Lee Stuart; Barret, Valerie; Bartke, Jerzy Gustaw; Basile, Maurizio; Bastid, Nicole; Basu, Sumit; Bathen, Bastian; Batigne, Guillaume; Batyunya, Boris; Baumann, Christoph Heinrich; Bearden, Ian Gardner; Beck, Hans; Belikov, Iouri; Bellini, Francesca; Bellwied, Rene; Belmont-Moreno, Ernesto; Bencedi, Gyula; Beole, Stefania; Berceanu, Ionela; Bercuci, Alexandru; Berdnikov, Yaroslav; Berenyi, Daniel; Berzano, Dario; Betev, Latchezar; Bhasin, Anju; Bhati, Ashok Kumar; Bhom, Jihyun; Bianchi, Livio; Bianchi, Nicola; Bianchin, Chiara; Bielcik, Jaroslav; Bielcikova, Jana; Bilandzic, Ante; Bjelogrlic, Sandro; Blanco, F; Blanco, Francesco; Blau, Dmitry; Blume, Christoph; Bock, Nicolas; Bogdanov, Alexey; Boggild, Hans; Bogolyubsky, Mikhail; Boldizsar, Laszlo; Bombara, Marek; Book, Julian; Borel, Herve; Borissov, Alexander; Bose, Suvendu Nath; Bossu, Francesco; Botje, Michiel; Bottger, Stefan; Boyer, Bruno Alexandre; Braidot, Ermes; Braun-Munzinger, Peter; Bregant, Marco; Breitner, Timo Gunther; Browning, Tyler Allen; Broz, Michal; Brun, Rene; Bruna, Elena; Bruno, Giuseppe Eugenio; Budnikov, Dmitry; Buesching, Henner; Bufalino, Stefania; Bugaiev, Kyrylo; Busch, Oliver; Buthelezi, Edith Zinhle; Caballero Orduna, Diego; Caffarri, Davide; Cai, Xu; Caines, Helen Louise; Calvo Villar, Ernesto; Camerini, Paolo; Canoa Roman, Veronica; Cara Romeo, Giovanni; Carena, Francesco; Carena, Wisla; Carminati, Federico; Casanova Diaz, Amaya Ofelia; Castillo Castellanos, Javier Ernesto; Casula, Ester Anna Rita; Catanescu, Vasile; Cavicchioli, Costanza; Ceballos Sanchez, Cesar; Cepila, Jan; Cerello, Piergiorgio; Chang, Beomsu; Chapeland, Sylvain; Charvet, Jean-Luc Fernand; Chattopadhyay, Sukalyan; Chattopadhyay, Subhasis; Chawla, Isha; Cherney, Michael Gerard; Cheshkov, Cvetan; Cheynis, Brigitte; Chiavassa, Emilio; Chibante Barroso, Vasco Miguel; Chinellato, David; Chochula, Peter; Chojnacki, Marek; Choudhury, Subikash; Christakoglou, Panagiotis; Christensen, Christian Holm; Christiansen, Peter; Chujo, Tatsuya; Chung, Suh-Urk; Cicalo, Corrado; Cifarelli, Luisa; Cindolo, Federico; Cleymans, Jean Willy Andre; Coccetti, Fabrizio; Colamaria, Fabio; Colella, Domenico; Conesa Balbastre, Gustavo; Conesa del Valle, Zaida; Constantin, Paul; Contin, Giacomo; Contreras, Jesus Guillermo; Cormier, Thomas Michael; Corrales Morales, Yasser; Cortes Maldonado, Ismael; Cortese, Pietro; Cosentino, Mauro Rogerio; Costa, Filippo; Cotallo, Manuel Enrique; Crochet, Philippe; Cruz Alaniz, Emilia; Cuautle, Eleazar; Cunqueiro, Leticia; D'Erasmo, Ginevra; Dainese, Andrea; Dalsgaard, Hans Hjersing; Danu, Andrea; Das, Debasish; Das, Indranil; Das, Kushal; Dash, Ajay Kumar; Dash, Sadhana; De, Sudipan; de Barros, Gabriel; De Caro, Annalisa; de Cataldo, Giacinto; de Cuveland, Jan; De Falco, Alessandro; De Gruttola, Daniele; De Marco, Nora; De Pasquale, Salvatore; de Rooij, Raoul Stefan; Del Castillo Sanchez, Eduardo; Delagrange, Hugues; Deloff, Andrzej; Demanov, Vyacheslav; Denes, Ervin; Deppman, Airton; Di Bari, Domenico; Di Giglio, Carmelo; Di Liberto, Sergio; Di Mauro, Antonio; Di Nezza, Pasquale; Diaz Corchero, Miguel Angel; Dietel, Thomas; Divia, Roberto; Djuvsland, Oeystein; Dobrin, Alexandru Florin; Dobrowolski, Tadeusz Antoni; Dominguez, Isabel; Donigus, Benjamin; Dordic, Olja; Driga, Olga; Dubey, Anand Kumar; Ducroux, Laurent; Dupieux, Pascal; Dutta Majumdar, AK; Dutta Majumdar, Mihir Ranjan; Elia, Domenico; Emschermann, David Philip; Engel, Heiko; Erdal, Hege Austrheim; Espagnon, Bruno; Estienne, Magali Danielle; Esumi, Shinichi; Evans, David; Eyyubova, Gyulnara; Fabris, Daniela; Faivre, Julien; Falchieri, Davide; Fantoni, Alessandra; Fasel, Markus; Fearick, Roger Worsley; Fedunov, Anatoly; Fehlker, Dominik; Feldkamp, Linus; Felea, Daniel; Fenton-Olsen, Bo; Feofilov, Grigory; Fernandez Tellez, Arturo; Ferretti, Alessandro; Ferretti, Roberta; Figiel, Jan; Figueredo, Marcel; Filchagin, Sergey; Finogeev, Dmitry; Fionda, Fiorella; Fiore, Enrichetta Maria; Floris, Michele; Foertsch, Siegfried Valentin; Foka, Panagiota; Fokin, Sergey; Fragiacomo, Enrico; Fragkiadakis, Michail; Frankenfeld, Ulrich Michael; Fuchs, Ulrich; Furget, Christophe; Fusco Girard, Mario; Gaardhoje, Jens Joergen; Gagliardi, Martino; Gago, Alberto; Gallio, Mauro; Gangadharan, Dhevan Raja; Ganoti, Paraskevi; Garabatos, Jose; Garcia-Solis, Edmundo; Garishvili, Irakli; Gerhard, Jochen; Germain, Marie; Geuna, Claudio; Gheata, Andrei George; Gheata, Mihaela; Ghidini, Bruno; Ghosh, Premomoy; Gianotti, Paola; Girard, Martin Robert; Giubellino, Paolo; Gladysz-Dziadus, Ewa; Glassel, Peter; Gomez, Ramon; Gonzalez Ferreiro, Elena; Gonzalez-Trueba, Laura Helena; Gonzalez-Zamora, Pedro; Gorbunov, Sergey; Goswami, Ankita; Gotovac, Sven; Grabski, Varlen; Graczykowski, Lukasz Kamil; Grajcarek, Robert; Grelli, Alessandro; Grigoras, Alina Gabriela; Grigoras, Costin; Grigoriev, Vladislav; Grigoryan, Ara; Grigoryan, Smbat; Grinyov, Boris; Grion, Nevio; Grosse-Oetringhaus, Jan Fiete; Grossiord, Jean-Yves; Grosso, Raffaele; Guber, Fedor; Guernane, Rachid; Guerra Gutierrez, Cesar; Guerzoni, Barbara; Guilbaud, Maxime Rene Joseph; Gulbrandsen, Kristjan Herlache; Gunji, Taku; Gupta, Anik; Gupta, Ramni; Gutbrod, Hans; Haaland, Oystein Senneset; Hadjidakis, Cynthia Marie; Haiduc, Maria; Hamagaki, Hideki; Hamar, Gergoe; Hanratty, Luke David; Hansen, Alexander; Harmanova, Zuzana; Harris, John William; Hartig, Matthias; Hasegan, Dumitru; Hatzifotiadou, Despoina; Hayrapetyan, Arsen; Heckel, Stefan Thomas; Heide, Markus Ansgar; Helstrup, Haavard; Herghelegiu, Andrei Ionut; Herrera Corral, Gerardo Antonio; Herrmann, Norbert; Hess, Benjamin Andreas; Hetland, Kristin Fanebust; Hicks, Bernard; Hille, Per Thomas; Hippolyte, Boris; Horaguchi, Takuma; Hori, Yasuto; Hristov, Peter Zahariev; Hrivnacova, Ivana; Huang, Meidana; Humanic, Thomas; Hwang, Dae Sung; Ichou, Raphaelle; Ilkaev, Radiy; Ilkiv, Iryna; Inaba, Motoi; Incani, Elisa; Innocenti, Gian Michele; Ippolitov, Mikhail; Irfan, Muhammad; Ivan, Cristian George; Ivanov, Andrey; Ivanov, Marian; Ivanov, Vladimir; Ivanytskyi, Oleksii; Jacholkowski, Adam Wlodzimierz; Jacobs, Peter; Jancurova, Lucia; Jangal, Swensy Gwladys; Janik, Malgorzata Anna; Janik, Rudolf; Jayarathna, Sandun; Jena, Satyajit; Jha, Deeptanshu Manu; Jimenez Bustamante, Raul Tonatiuh; Jirden, Lennart; Jones, Peter Graham; Jung, Hyung Taik; Jusko, Anton; Kakoyan, Vanik; Kalcher, Sebastian; Kalinak, Peter; Kalisky, Matus; Kalliokoski, Tuomo Esa Aukusti; Kalweit, Alexander Philipp; Kanaki, Kalliopi; Kang, Ju Hwan; Kaplin, Vladimir; Karasu Uysal, Ayben; Karavichev, Oleg; Karavicheva, Tatiana; Karpechev, Evgeny; Kazantsev, Andrey; Kebschull, Udo Wolfgang; Keidel, Ralf; Khan, Mohisin Mohammed; Khan, Shuaib Ahmad; Khanzadeev, Alexei; Kharlov, Yury; Kileng, Bjarte; Kim, Beomkyu; Kim, Dong Jo; Kim, Do Won; Kim, Jonghyun; Kim, Jin Sook; Kim, Minwoo; Kim, Se Yong; Kim, Seon Hee; Kim, Taesoo; Kirsch, Stefan; Kisel, Ivan; Kiselev, Sergey; Kisiel, Adam Ryszard; Klay, Jennifer Lynn; Klein, Jochen; Klein-Bosing, Christian; Kliemant, Michael; Kluge, Alexander; Knichel, Michael Linus; Knospe, Anders Garritt; Koch, Kathrin; Kohler, Markus; Kolojvari, Anatoly; Kondratiev, Valery; Kondratyeva, Natalia; Konevskih, Artem; Korneev, Andrey; Kour, Ravjeet; Kowalski, Marek; Kox, Serge; Koyithatta Meethaleveedu, Greeshma; Kral, Jiri; Kralik, Ivan; Kramer, Frederick; Kraus, Ingrid Christine; Krawutschke, Tobias; Krelina, Michal; Kretz, Matthias; Krivda, Marian; Krizek, Filip; Krus, Miroslav; Kryshen, Evgeny; Krzewicki, Mikolaj; Kucheriaev, Yury; Kuhn, Christian Claude; Kuijer, Paul; Kurashvili, Podist; Kurepin, A; Kurepin, AB; Kuryakin, Alexey; Kushpil, Svetlana; Kushpil, Vasily; Kweon, Min Jung; Kwon, Youngil; La Pointe, Sarah Louise; La Rocca, Paola; Ladron de Guevara, Pedro; Lakomov, Igor; Langoy, Rune; Lara, Camilo Ernesto; Lardeux, Antoine Xavier; Lazzeroni, Cristina; Le Bornec, Yves; Lea, Ramona; Lechman, Mateusz; Lee, Ki Sang; Lee, Sung Chul; Lefevre, Frederic; Lehnert, Joerg Walter; Leistam, Lars; Lemmon, Roy Crawford; Lenhardt, Matthieu Laurent; Lenti, Vito; Leon Monzon, Ildefonso; Leon Vargas, Hermes; Leoncino, Marco; Levai, Peter; Lien, Jorgen; Lietava, Roman; Lindal, Svein; Lindenstruth, Volker; Lippmann, Christian; Lisa, Michael Annan; Liu, Lijiao; Loenne, Per-Ivar; Loggins, Vera; Loginov, Vitaly; Lohn, Stefan Bernhard; Lohner, Daniel; Loizides, Constantinos; Loo, Kai Krister; Lopez, Xavier Bernard; Lopez Torres, Ernesto; Lovhoiden, Gunnar; Lu, Xianguo; Luettig, Philipp; Lunardon, Marcello; Luo, Jiebin; Luparello, Grazia; Luquin, Lionel; Luzzi, Cinzia; Ma, Rongrong; Maevskaya, Alla; Mager, Magnus; Mahapatra, Durga Prasad; Maire, Antonin; Mal'Kevich, Dmitry; Malaev, Mikhail; Maldonado Cervantes, Ivonne Alicia; Malinina, Ludmila; Malzacher, Peter; Mamonov, Alexander; Manceau, Loic Henri Antoine; Manko, Vladislav; Manso, Franck; Manzari, Vito; Mao, Yaxian; Marchisone, Massimiliano; Mares, Jiri; Margagliotti, Giacomo Vito; Margotti, Anselmo; Marin, Ana Maria; Marin Tobon, Cesar Augusto; Markert, Christina; Martashvili, Irakli; Martinengo, Paolo; Martinez, Mario Ivan; Martinez Davalos, Arnulfo; Martinez Garcia, Gines; Martynov, Yevgen; Mas, Alexis Jean-Michel; Masciocchi, Silvia; Masera, Massimo; Masoni, Alberto; Mastromarco, Mario; Mastroserio, Annalisa; Matthews, Zoe Louise; Matyja, Adam Tomasz; Mayani, Daniel; Mayer, Christoph; Mazer, Joel; Mazzoni, Alessandra Maria; Meddi, Franco; Menchaca-Rocha, Arturo Alejandro; Mercado Perez, Jorge; Meres, Michal; Miake, Yasuo; Milano, Leonardo; Milosevic, Jovan; Mischke, Andre; Mishra, Aditya Nath; Miskowiec, Dariusz; Mitu, Ciprian Mihai; Mlynarz, Jocelyn; Mohanty, Ajit Kumar; Mohanty, Bedangadas; Molnar, Levente; Montano Zetina, Luis Manuel; Monteno, Marco; Montes, Esther; Moon, Taebong; Morando, Maurizio; Moreira De Godoy, Denise Aparecida; Moretto, Sandra; Morsch, Andreas; Muccifora, Valeria; Mudnic, Eugen; Muhuri, Sanjib; Mukherjee, Maitreyee; Muller, Hans; Munhoz, Marcelo; Musa, Luciano; Musso, Alfredo; Nandi, Basanta Kumar; Nania, Rosario; Nappi, Eugenio; Nattrass, Christine; Naumov, Nikolay; Navin, Sparsh; Nayak, Tapan Kumar; Nazarenko, Sergey; Nazarov, Gleb; Nedosekin, Alexander; Nicassio, Maria; Nielsen, Borge Svane; Niida, Takafumi; Nikolaev, Sergey; Nikolic, Vedran; Nikulin, Sergey; Nikulin, Vladimir; Nilsen, Bjorn Steven; Nilsson, Mads Stormo; Noferini, Francesco; Nomokonov, Petr; Nooren, Gerardus; Novitzky, Norbert; Nyanin, Alexandre; Nyatha, Anitha; Nygaard, Casper; Nystrand, Joakim Ingemar; Oeschler, Helmut Oskar; Oh, Saehanseul; Oh, Sun Kun; Oleniacz, Janusz; Oppedisano, Chiara; Ortiz Velasquez, Antonio; Ortona, Giacomo; Oskarsson, Anders Nils Erik; Otwinowski, Jacek Tomasz; Oyama, Ken; Pachmayer, Yvonne Chiara; Pachr, Milos; Padilla, Fatima; Pagano, Paola; Paic, Guy; Painke, Florian; Pajares, Carlos; Pal, S; Pal, Susanta Kumar; Palaha, Arvinder Singh; Palmeri, Armando; Papikyan, Vardanush; Pappalardo, Giuseppe; Park, Woo Jin; Passfeld, Annika; Patalakha, Dmitri Ivanovich; Paticchio, Vincenzo; Pavlinov, Alexei; Pawlak, Tomasz Jan; Peitzmann, Thomas; Pereira Da Costa, Hugo Denis Antonio; Pereira De Oliveira Filho, Elienos; Peresunko, Dmitri; Perez Lara, Carlos Eugenio; Perez Lezama, Edgar; Perini, Diego; Perrino, Davide; Peryt, Wiktor Stanislaw; Pesci, Alessandro; Peskov, Vladimir; Pestov, Yury; Petracek, Vojtech; Petran, Michal; Petris, Mariana; Petrov, Plamen Rumenov; Petrovici, Mihai; Petta, Catia; Piano, Stefano; Piccotti, Anna; Pikna, Miroslav; Pillot, Philippe; Pinazza, Ombretta; Pinsky, Lawrence; Pitz, Nora; Piuz, Francois; Piyarathna, Danthasinghe; Ploskon, Mateusz Andrzej; Pluta, Jan Marian; Pocheptsov, Timur; Pochybova, Sona; Podesta Lerma, Pedro Luis Manuel; Poghosyan, Martin; Polichtchouk, Boris; Pop, Amalia; Porteboeuf-Houssais, Sarah; Pospisil, Vladimir; Potukuchi, Baba; Prasad, Sidharth Kumar; Preghenella, Roberto; Prino, Francesco; Pruneau, Claude Andre; Pshenichnov, Igor; Puchagin, Sergey; Puddu, Giovanna; Pujol Teixido, Jordi; Pulvirenti, Alberto; Punin, Valery; Putis, Marian; Putschke, Jorn Henning; Quercigh, Emanuele; Qvigstad, Henrik; Rachevski, Alexandre; Rademakers, Alphonse; Radomski, Sylwester; Raiha, Tomi Samuli; Rak, Jan; Rakotozafindrabe, Andry Malala; Ramello, Luciano; Ramirez Reyes, Abdiel; Raniwala, Rashmi; Raniwala, Sudhir; Rasanen, Sami Sakari; Rascanu, Bogdan Theodor; Rathee, Deepika; Read, Kenneth Francis; Real, Jean-Sebastien; Redlich, Krzysztof; Reichelt, Patrick; Reicher, Martijn; Renfordt, Rainer Arno Ernst; Reolon, Anna Rita; Reshetin, Andrey; Rettig, Felix Vincenz; Revol, Jean-Pierre; Reygers, Klaus Johannes; Riccati, Lodovico; Ricci, Renato Angelo; Richert, Tuva; Richter, Matthias Rudolph; Riedler, Petra; Riegler, Werner; Riggi, Francesco; Rodrigues Fernandes Rabacal, Bartolomeu; Rodriguez Cahuantzi, Mario; Rodriguez Manso, Alis; Roed, Ketil; Rohr, David; Rohrich, Dieter; Romita, Rosa; Ronchetti, Federico; Rosnet, Philippe; Rossegger, Stefan; Rossi, Andrea; Roukoutakis, Filimon; Roy, Christelle Sophie; Roy, Pradip Kumar; Rubio Montero, Antonio Juan; Rui, Rinaldo; Ryabinkin, Evgeny; Rybicki, Andrzej; Sadovsky, Sergey; Safarik, Karel; Sahoo, Raghunath; Sahu, Pradip Kumar; Saini, Jogender; Sakaguchi, Hiroaki; Sakai, Shingo; Sakata, Dosatsu; Salgado, Carlos Albert; Salzwedel, Jai; Sambyal, Sanjeev Singh; Samsonov, Vladimir; Sanchez Castro, Xitzel; Sandor, Ladislav; Sandoval, Andres; Sano, Masato; Sano, Satoshi; Santo, Rainer; Santoro, Romualdo; Sarkamo, Juho Jaako; Scapparone, Eugenio; Scarlassara, Fernando; Scharenberg, Rolf Paul; Schiaua, Claudiu Cornel; Schicker, Rainer Martin; Schmidt, Christian Joachim; Schmidt, Hans Rudolf; Schreiner, Steffen; Schuchmann, Simone; Schukraft, Jurgen; Schutz, Yves Roland; Schwarz, Kilian Eberhard; Schweda, Kai Oliver; Scioli, Gilda; Scomparin, Enrico; Scott, Patrick Aaron; Scott, Rebecca; Segato, Gianfranco; Selyuzhenkov, Ilya; Senyukov, Serhiy; Seo, Jeewon; Serci, Sergio; Serradilla, Eulogio; Sevcenco, Adrian; Sgura, Irene; Shabetai, Alexandre; Shabratova, Galina; Shahoyan, Ruben; Sharma, Natasha; Sharma, Satish; Shigaki, Kenta; Shimomura, Maya; Shtejer, Katherin; Sibiriak, Yury; Siciliano, Melinda; Sicking, Eva; Siddhanta, Sabyasachi; Siemiarczuk, Teodor; Silvermyr, David Olle Rickard; Silvestre, catherine; Simonetti, Giuseppe; Singaraju, Rama Narayana; Singh, Ranbir; Singha, Subhash; Sinha, Bikash; Sinha, Tinku; Sitar, Branislav; Sitta, Mario; Skaali, Bernhard; Skjerdal, Kyrre; Smakal, Radek; Smirnov, Nikolai; Snellings, Raimond; Sogaard, Carsten; Soltz, Ron Ariel; Son, Hyungsuk; Song, Jihye; Song, Myunggeun; Soos, Csaba; Soramel, Francesca; Sputowska, Iwona; Spyropoulou-Stassinaki, Martha; Srivastava, Brijesh Kumar; Stachel, Johanna; Stan, Ionel; Stefanek, Grzegorz; Stefanini, Giorgio; Steinbeck, Timm Morten; Steinpreis, Matthew; Stenlund, Evert Anders; Steyn, Gideon Francois; Stiller, Johannes Hendrik; Stocco, Diego; Stolpovskiy, Mikhail; Strabykin, Kirill; Strmen, Peter; Suaide, Alexandre Alarcon do Passo; Subieta Vasquez, Martin Alfonso; Sugitate, Toru; Suire, Christophe Pierre; Sukhorukov, Mikhail; Sultanov, Rishat; Sumbera, Michal; Susa, Tatjana; Szanto de Toledo, Alejandro; Szarka, Imrich; Szczepankiewicz, Adam; Szostak, Artur Krzysztof; Tagridis, Christos; Takahashi, Jun; Tapia Takaki, Daniel Jesus; Tauro, Arturo; Tejeda Munoz, Guillermo; Telesca, Adriana; Terrevoli, Cristina; Thader, Jochen Mathias; Thomas, Deepa; Tieulent, Raphael Noel; Timmins, Anthony; Tlusty, David; Toia, Alberica; Torii, Hisayuki; Tosello, Flavio; Trzaska, Wladyslaw Henryk; Tsuji, Tomoya; Tumkin, Alexandr; Turrisi, Rosario; Tveter, Trine Spedstad; Ulery, Jason Glyndwr; Ullaland, Kjetil; Ulrich, Jochen; Uras, Antonio; Urban, Jozef; Urciuoli, Guido Marie; Usai, Gianluca; Vajzer, Michal; Vala, Martin; Valencia Palomo, Lizardo; Vallero, Sara; van der Kolk, Naomi; van Leeuwen, Marco; Vande Vyvre, Pierre; Vannucci, Luigi; Vargas, Aurora Diozcora; Varma, Raghava; Vasileiou, Maria; Vasiliev, Andrey; Vechernin, Vladimir; Veldhoen, Misha; Venaruzzo, Massimo; Vercellin, Ermanno; Vergara, Sergio; Vernet, Renaud; Verweij, Marta; Vickovic, Linda; Viesti, Giuseppe; Vikhlyantsev, Oleg; Vilakazi, Zabulon; Villalobos Baillie, Orlando; Vinogradov, Alexander; Vinogradov, Leonid; Vinogradov, Yury; Virgili, Tiziano; Viyogi, Yogendra; Vodopianov, Alexander; Voloshin, Kirill; Voloshin, Sergey; Volpe, Giacomo; von Haller, Barthelemy; Vranic, Danilo; Øvrebekk, Gaute; Vrlakova, Janka; Vulpescu, Bogdan; Vyushin, Alexey; Wagner, Boris; Wagner, Vladimir; Wan, Renzhuo; Wang, Dong; Wang, Mengliang; Wang, Yifei; Wang, Yaping; Watanabe, Kengo; Wessels, Johannes; Westerhoff, Uwe; Wiechula, Jens; Wikne, Jon; Wilde, Martin Rudolf; Wilk, Alexander; Wilk, Grzegorz Andrzej; Williams, Crispin; Windelband, Bernd Stefan; Xaplanteris Karampatsos, Leonidas; Yaldo, Chris G; Yang, Hongyan; Yang, Shiming; Yasnopolsky, Stanislav; Yi, JunGyu; Yin, Zhongbao; Yoo, In-Kwon; Yoon, Jongik; Yu, Weilin; Yuan, Xianbao; Yushmanov, Igor; Zach, Cenek; Zampolli, Chiara; Zaporozhets, Sergey; Zarochentsev, Andrey; Zavada, Petr; Zaviyalov, Nikolai; Zbroszczyk, Hanna Paulina; Zelnicek, Pierre; Zgura, Sorin Ion; Zhalov, Mikhail; Zhang, Haitao; Zhang, Xiaoming; Zhou, Daicui; Zhou, Fengchu; Zhou, You; Zhu, Jianhui; Zhu, Xiangrong; Zichichi, Antonino; Zimmermann, Alice; Zinovjev, Gennady; Zoccarato, Yannick Denis; Zynovyev, Mykhaylo

2012-01-01

The first measurement of neutron emission in electromagnetic dissociation of 208Pb nuclei at the LHC is presented. The measurement is performed using the neutron Zero Degree Calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at √sNN = 2.76 TeV with neutron emission are σ_single EMD = 187.2±0.2 (stat.) +13.8−12.0 (syst.) b and σ_mutual EMD = 6.2 ± 0.1 (stat.) ±0.4 (syst.) b respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model.

Procedure for measurement of anisotropy factor for neutron sources

International Nuclear Information System (INIS)

Creazolla, Prycylla Gomes

2017-01-01

Radioisotope neutron sources allow the production of reference fields for calibration of neutron detectors for radiation protection and analysis purposes. When the emission rate of these sources is isotropic, no correction is necessary. However, variations in source encapsulation and in the radioactive material concentration produce differences in its neutron emission rate, relative to the source axis, this effect is called anisotropy. In this study, is describe a procedure for measuring the anisotropy factor of neutron sources performed in the Laboratório de Metrologia de Neutrons (LN) using a Precision Long Counter (PLC) detector. A measurement procedure that takes into account the anisotropy factor of neutron sources contributes to solve some issues, particularly with respect to the high uncertainties associated with neutron dosimetry. Thus, a bibliographical review was carried out based on international standards and technical regulations specific to the area of neutron fields, and were later reproduced in practice by means of the procedure for measuring the anisotropy factor in neutron sources of the LN. The anisotropy factor is determined as a function of the angle of 90° in relation to the cylindrical axis of the source. This angle is more important due to its high use in measurements and also of its higher neutron emission rate if compared with other angles. (author)

On the illumination of neutron star accretion discs

Science.gov (United States)

Wilkins, D. R.

2018-03-01

The illumination of the accretion disc in a neutron star X-ray binary by X-rays emitted from (or close to) the neutron star surface is explored through general relativistic ray tracing simulations. The applicability of the canonical suite of relativistically broadened emission line models (developed for black holes) to discs around neutron stars is evaluated. These models were found to describe well emission lines from neutron star accretion discs unless the neutron star radius is larger than the innermost stable orbit of the accretion disc at 6 rg or the disc is viewed at high inclination, above 60° where shadowing of the back side of the disc becomes important. Theoretical emissivity profiles were computed for accretion discs illuminated by hotspots on the neutron star surfaces, bands of emission and emission by the entirety of the hot, spherical star surface and in all cases, the emissivity profile of the accretion disc was found to be well represented by a single power law falling off slightly steeper than r-3. Steepening of the emissivity index was found where the emission is close to the disc plane and the disc can appear truncated when illuminated by a hotspot at high latitude. The emissivity profile of the accretion disc in Serpens X-1 was measured and found to be consistent with a single unbroken power law with index q=3.5_{-0.4}^{+0.3}, suggestive of illumination by the boundary layer between the disc and neutron star surface.

Summary of neutron measurements for the Viking Program

International Nuclear Information System (INIS)

Anderson, M.E.

1975-01-01

The results of neutron measurements for 238 Pu-fueled, 683-W (thermal) capsules fabricated for the Viking Program (Mars Lander) are presented. These results include, for each capsule, the total neutron emission rate and neutron multiplication and, for one capsule, the neutron energy spectrum. A precision long counter was used for the neutron emission rate measurements and a single stilbene crystal for the neutron spectrum measurement. (U.S.)

Performance Study of an aSi Flat Panel Detector for Fast Neutron Imaging of Nuclear Waste

Energy Technology Data Exchange (ETDEWEB)

Schumann, M.; Mauerhofer, E. [Institute of Energy and Climate Research - Nuclear Waste Management and Reactor Safety, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Engels, R.; Kemmerling, G. [Central Institute for Engineering, Electronics and Analytics - Electronic Systems, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Frank, M. [MATHCCES - Department of Mathematics, RWTH Aachen University, 52062 Aachen (Germany); Havenith, A.; Kettler, J.; Klapdor-Kleingrothaus, T. [Institute of Nuclear Engineering and Technology Transfer, RWTH Aachen University, 52062 Aachen (Germany); Schitthelm, O. [Corporate Technology, Siemens AG, 91058 Erlangen (Germany)

2015-07-01

Radioactive waste must be characterized to check its conformance for intermediate storage and final disposal according to national regulations. For the determination of radio-toxic and chemo-toxic contents of radioactive waste packages non-destructive analytical techniques are preferentially used. Fast neutron imaging is a promising technique to assay large and dense items providing, in complementarity to photon imaging, additional information on the presence of structures in radioactive waste packages. Therefore the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA) using 14 MeV neutrons is studied in a cooperation framework of Forschungszentrum Juelich GmbH, RWTH Aachen University and Siemens AG. However due to the low neutron emission of neutron generators in comparison to research reactors the challenging task resides in the development of an imaging detector with a high efficiency, a low sensitivity to gamma radiation and a resolution sufficient for the purpose. The setup is composed of a commercial D-T neutron generator (Genie16GT, Sodern) with a surrounding shielding made of polyethylene, which acts as a collimator and an amorphous silicon flat panel detector (aSi, 40 x 40 cm{sup 2}, XRD-1642, Perkin Elmer). Neutron detection is achieved using a general propose plastic scintillator (EJ-260, Eljen Technology) linked to the detector. The thermal noise of the photodiodes is reduced by employing an entrance window made of aluminium. Optimal gain and integration time for data acquisition are set by measuring the response of the detector to the radiation of a 500 MBq {sup 241}Am-source. Detector performance was studied by recording neutron radiography images of materials with various, but well known, chemical compositions, densities and dimensions (Al, C, Fe, Pb, W, concrete, polyethylene, 5 x 8 x 10 cm{sup 3}). To simulate gamma-ray emitting waste radiographs in presence of a gamma-ray sources ({sup 60}Co, {sup 137}Cs, {sup 241

Design and construction of a fast (neutron) spectrometer for magnetic confinement fusion studies

International Nuclear Information System (INIS)

Lagattu, A.

1980-09-01

Neutron emission in conjunction with the 'Tokamak' devices studied in order to carry out controlled fusion is done at present on a short time scale (a few hundred milliseconds). Obtaining spectrometric information on this emission made it necessary to design sufficiently fast equipment to adapt to this situation. The basis of the equipment selected is conventional: NE213 liquid scintillator in conjunction with a fast photomultiplier. A commercialized fast neutron gamma discriminator (approximately 210 5 S -1 ) was used. The data acquisition and processing system was specially made for this occasion. This assembly, so designed and constructed, was tested on a particle accelerator and on the TFR Tokamak. In the best conditions a spectrum of 60 milliseconds was produced. Hence several spectra can be recorded during an experiment. The rejection of gamma radiations by the discriminator exceeds 99% in such conditions [fr

Prompt neutrons from {sup 236}U fission fragments

Energy Technology Data Exchange (ETDEWEB)

Boldeman, J W; Musgrove, A.R. de L.; Walsch, R L

1971-03-01

Measurements were made of prompt neutron emission in the thermal neutron fission of {sup 235}U. The mean neutron emission per fragment was obtained for particular values of the fragment mass and total kinetic energy. A direct neutron counting method was employed and a comparison made with data from previous experiments of this type. (author)

14 MeV calibration of JET neutron detectors—phase 1: calibration and characterization of the neutron source

Science.gov (United States)

Batistoni, P.; Popovichev, S.; Cufar, A.; Ghani, Z.; Giacomelli, L.; Jednorog, S.; Klix, A.; Lilley, S.; Laszynska, E.; Loreti, S.; Packer, L.; Peacock, A.; Pillon, M.; Price, R.; Rebai, M.; Rigamonti, D.; Roberts, N.; Tardocchi, M.; Thomas, D.; Contributors, JET

2018-02-01

In view of the planned DT operations at JET, a calibration of the JET neutron monitors at 14 MeV neutron energy is needed using a 14 MeV neutron generator deployed inside the vacuum vessel by the JET remote handling system. The target accuracy of this calibration is  ±10% as also required by ITER, where a precise neutron yield measurement is important, e.g. for tritium accountancy. To achieve this accuracy, the 14 MeV neutron generator selected as the calibration source has been fully characterised and calibrated prior to the in-vessel calibration of the JET monitors. This paper describes the measurements performed using different types of neutron detectors, spectrometers, calibrated long counters and activation foils which allowed us to obtain the neutron emission rate and the anisotropy of the neutron generator, i.e. the neutron flux and energy spectrum dependence on emission angle, and to derive the absolute emission rate in 4π sr. The use of high resolution diamond spectrometers made it possible to resolve the complex features of the neutron energy spectra resulting from the mixed D/T beam ions reacting with the D/T nuclei present in the neutron generator target. As the neutron generator is not a stable neutron source, several monitoring detectors were attached to it by means of an ad hoc mechanical structure to continuously monitor the neutron emission rate during the in-vessel calibration. These monitoring detectors, two diamond diodes and activation foils, have been calibrated in terms of neutrons/counts within  ±5% total uncertainty. A neutron source routine has been developed, able to produce the neutron spectra resulting from all possible reactions occurring with the D/T ions in the beam impinging on the Ti D/T target. The neutron energy spectra calculated by combining the source routine with a MCNP model of the neutron generator have been validated by the measurements. These numerical tools will be key in analysing the results from the in

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

Energy Technology Data Exchange (ETDEWEB)

Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L. [Instrument and Source Division, Oak Ridge National Laboratory, P.O. Box 2008, MS6466, Oak Ridge, Tennessee 37831 (United States)

2016-06-15

Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm{sup 2} to 20 × 20 mm{sup 2}. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

The neutronic design and performance of the Indiana University Cyclotron Facility (IUCF) Low Energy Neutron Source (LENS)

Science.gov (United States)

Lavelle, Christopher M.

Neutron scattering research is performed primarily at large-scale facilities. However, history has shown that smaller scale neutron scattering facilities can play a useful role in education and innovation while performing valuable materials research. This dissertation details the design and experimental validation of the LENS TMR as an example for a small scale accelerator driven neutron source. LENS achieves competitive long wavelength neutron intensities by employing a novel long pulse mode of operation, where the neutron production target is irradiated on a time scale comparable to the emission time of neutrons from the system. Monte Carlo methods have been employed to develop a design for optimal production of long wavelength neutrons from the 9Be(p,n) reaction at proton energies ranging from 7 to 13 MeV proton energy. The neutron spectrum was experimentally measured using time of flight, where it is found that the impact of the long pulse mode on energy resolution can be eliminated at sub-eV neutron energies if the emission time distribution of neutron from the system is known. The emission time distribution from the TMR system is measured using a time focussed crystal analyzer. Emission time of the fundamental cold neutron mode is found to be consistent with Monte Carlo results. The measured thermal neutron spectrum from the water reflector is found to be in agreement with Monte Carlo predictions if the scattering kernels employed are well established. It was found that the scattering kernels currently employed for cryogenic methane are inadequate for accurate prediction of the cold neutron intensity from the system. The TMR and neutronic modeling have been well characterized and the source design is flexible, such that it is possible for LENS to serve as an effective test bed for future work in neutronic development. Suggestions for improvements to the design that would allow increased neutron flux into the instruments are provided.

Neutron emission as a probe of fusion-fission and quasi-fission dynamics

International Nuclear Information System (INIS)

Hinde, D.J.

1991-01-01

Pre- and post scission neutron yeilds have been measured as a function of projectile mass, compound nucleus fissility, and fission mass-split and total kinetic energy (TKE) for 27 fusion-fission and quasi-fission reactions induced by beams of 16,18 O, 40 Ar and 64 Ni. A new method of interpretation of experimental pre-scission neutron multiplicities ν-pre and mean kinetic energies ε ν allows the extraction of fission time scales with much less uncertainty than previously, all fusion-fission results being consistent with a dynamical time scale of (35±15) x 10 -21 s for symmetric fission. All reactions show that ν-pre falls quite rapidly with increasing mass-asymmetry; evidence is presented that for fusion-fission reactions this is partly due to a reduction of the dynamical fission time scale with mass-asymmetry. For quasi-fission, the data indicate that the pre-scission multiplicity and mean neutron kinetic energy are very sensitive to the final mass-asymmetry, but that the time scale is virtually independent of mass-asymmetry. It is concluded that for fusion-fission there is no dependence of ν-pre on TKE, whilst for 64 Ni-induced quasi-fission reactions, a strong increase of ν-pre with decreasing TKE is observed, probably largely caused by neutron emission during the acceleration time of the fission fragments in these fast reactions. Interpretation of post-scission multiplicities in terms of fragment excitation energies leads to deduced time scales consistent with those determined from the pre-scission data. 54 refs., 17 tabs., 25 figs

Technical feasibility study for the D-T neutron monitor using activation of the flowing water

International Nuclear Information System (INIS)

Uno, Yoshitomo; Kaneko, Junichi; Nishitani, Takeo; Maekawa, Fujio; Tanaka, Teruya; Ikeda, Yujiro; Takeuchi, Hiroshi

2001-03-01

The experimental study of technical feasibility for the D-T neutron monitor using activation of the flowing water was performed at FNS/JAERI as the ITER/EDA R and D Task T499. The temporal resolution for pulsed neutrons was measured and dependence of the temporal resolution on flowing velocity was studied. The temporal resolution of 50 ms that is better than 100 ms of the requirement for ITER was achieved. We found that the temporal resolution is determined by a turbulent dispersion of the flow. The experiment for validation of the method determining the absolute D-T neutron flux was carried out by using the stainless steel (SS 316)/Water assembly to simulate the neutron field in the blanket region of ITER. The neutron emission rate measured with the water activation has a good agreement with that with the neutron yield monitor with associated α detector, and this technique shows the accuracy of the absolute neutron flux better than 10%. At the application on ITER-FEAT, the neutron activation with fluid flow has a dynamic range of 50 kW - 500 MW operation with a temporal resolution of 78 ms at the flow velocity of 10 m/s. (author)

Neutral currents and neutrino emission of stars

International Nuclear Information System (INIS)

Gershtejn, S.S.; Folomeshkin, V.N.; Khlopov, M.Yu.; Eramzhyan, R.A.

1975-01-01

Possible emission of ν sub(e) ν tilde sub(e) and ν sub(μ) ν tilde sub(μ) pairs in nucleon collisions or nuclear transitions has been studied. Neutrino pair emission in neutron collision turns out to be essential for cooling of neutron stars. Neutrino pair emission in nuclear transitions is effective just before the core implosion of a hot massive star and at the initial stage of implosion (till a full dissociation of nuclei into nucleons)

Experimental study of the interaction of 14-MeV neutrons with 238U

International Nuclear Information System (INIS)

Voignier, J.

1968-01-01

A study has been made of the interaction of fast neutrons with natural uranium from the experimental point of view over a wide energy range. The scattering energy spectra have been obtained by the time-of-flight method developed during previous work. The cross-section σ t , the elastic cross-section σ e , and the inelastic neutron emission cross-section σ ne have been measured at 14 MeV. The average number, η, of neutrons produced by interaction is deduced from this last measurement. The experimental results are analyzed in the second part of the report. The fission spectrum and the evaporation spectrum have been deduced from the energy spectrum of the secondary neutrons. The energy spectrum of the inelastic neutrons is represented by a relationship of the type:N (E) = A E exp (-E/T e ) + B √ E exp (-E/T f )/. The parameter A, B, T e and T f have been evaluated. Finally the values obtained for the various cross sections are compared with previous results. (author) [fr

Neutron stars velocities and magnetic fields

Science.gov (United States)

Paret, Daryel Manreza; Martinez, A. Perez; Ayala, Alejandro.; Piccinelli, G.; Sanchez, A.

2018-01-01

We study a model that explain neutron stars velocities due to the anisotropic emission of neutrinos. Strong magnetic fields present in neutron stars are the source of the anisotropy in the system. To compute the velocity of the neutron star we model its core as composed by strange quark matter and analice the properties of a magnetized quark gas at finite temperature and density. Specifically we have obtained the electron polarization and the specific heat of magnetized fermions as a functions of the temperature, chemical potential and magnetic field which allow us to study the velocity of the neutron star as a function of these parameters.

A proposed experiment for studying the direct neutron-neutron interaction

International Nuclear Information System (INIS)

Hassan Fikry, A.R.; Maayouf, R.M.A.

1979-01-01

An experiment for studying the direct neutron-neutron interaction is suggested. The experiment is based on the combined use of an accelerator, e.g., an electron linear accelerator, together with a mobile pulsed reactor; or using a pulsed beam reactor together with a mobile neutron generator

Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

DEFF Research Database (Denmark)

Muhrer, G.; Schonfeldt, T.; Iverson, E. B.

2016-01-01

The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, ......-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering. (C) 2016 Elsevier B.V. All rights reserved....

Investigation of thick-target neutron emission from Be-9(d,n)B-10 at E/sub d/ = 7 MeV for angles other than zero degrees

International Nuclear Information System (INIS)

Smith, D.L.; Meadows, J.W.; Guenther, P.T.

1985-01-01

Double-differential measurements of neutron emission from a thick beryllium target bombarded with 7-MeV deuterons are made for neutrons above 800 keV, over the angular range of 0 to 155 0 . The angular dependence of the neutron yield is found to be quite anisotropic. The importance of this anisotropy in integral neutron-induced reaction cross-section investigations is illustrated. 7 refs.,

YAP scintillators for resonant detection of epithermal neutrons at pulsed neutron sources

International Nuclear Information System (INIS)

Tardocchi, M.; Gorini, G.; Pietropaolo, A.; Andreani, C.; Senesi, R.; Rhodes, N.; Schooneveld, E. M.

2004-01-01

Recent studies indicate the resonance detector (RD) technique as an interesting approach for neutron spectroscopy in the electron volt energy region. This work summarizes the results of a series of experiments where RD consisting of YAlO 3 (YAP) scintillators were used to detect scattered neutrons with energy in the range 1-200 eV. The response of YAP scintillators to radiative capture γ emission from a 238 U analyzer foil was characterized in a series of experiments performed on the VESUVIO spectrometer at the ISIS pulsed neutron source. In these experiments a biparametric data acquisition allowed the simultaneous measurements of both neutron time-of-flight and γ pulse height (energy) spectra. The analysis of the γ pulse height and neutron time of flight spectra permitted to identify and distinguish the signal and background components. These measurements showed that a significant improvement in the signal-to-background ratio can be achieved by setting a lower level discrimination on the pulse height at about 600 keV equivalent photon energy. Present results strongly indicate YAP scintillators as the ideal candidate for neutron scattering studies with epithermal neutrons at both very low (<5 deg.) and intermediate scattering angles

Online monitoring of fast neutron (DT/DD) at Purnima neutron generator

International Nuclear Information System (INIS)

Bishnoi, S.; Patel, T.; Shukla, M.; Adhikari, P.S.; Sinha, A.

2012-01-01

A neutron generator (NG) at Purnima Labs, BARC has been developed for DT accelerator driven zero power subcritical (ADSS) system. Subcritical core of ADSS will be coupled to the NG for benchmarking experiments. Kinetic parameters of ADSS such as K-source, flux, power etc depends on this external neutron source strength injected to the core. However the neutron emission rate of NG does not remain stable throughout its operation. In view of this a reliable, precise and online monitoring of NG's neutron emission rate is required. An online neutron monitoring system based on associated particle method has been designed, developed and installed at NG. The monitoring unit consists of an ion implanted planar silicon detector, placed inside the drift tube of NG at an angle with respect to D + beam direction. A series of experiments were carried out with increasing neutron yield to optimize the position of detector such that it has sufficient counting statistics and minimum pileup. A complementary calibration procedure for validating these results based on activation technique was also carried out with standard Cu foil. The reaction rate monitored with online monitor and foil activation technique were compared, their variations with the predicted (theoretical) results were within 16%. This paper deals with the development and performance of online neutron monitoring system for DT and DD neutrons

Beta-delayed fission and neutron emission calculations for the actinide cosmochronometers

International Nuclear Information System (INIS)

Meyer, B.S.; Howard, W.M.; Mathews, G.J.; Takahashi, K.; Moeller, P.; Leander, G.A.

1989-01-01

The Gamow-Teller beta-strength distributions for 19 neutron-rich nuclei, including ten of interest for the production of the actinide cosmochronometers, are computed microscopically with a code that treats nuclear deformation explicitly. The strength distributions are then used to calculate the beta-delayed fission, neutron emission, and gamma deexcitation probabilities for these nuclei. Fission is treated both in the complete damping and WKB approximations for penetrabilities through the nuclear potential-energy surface. The resulting fission probabilities differ by factors of 2 to 3 or more from the results of previous calculations using microscopically computed beta-strength distributions around the region of greatest interest for production of the cosmochronometers. The indications are that a consistent treatment of nuclear deformation, fission barriers, and beta-strength functions is important in the calculation of delayed fission probabilities and the production of the actinide cosmochronometers. Since we show that the results are very sensitive to relatively small changes in model assumptions, large chronometric ages for the Galaxy based upon high beta-delayed fission probabilities derived from an inconsistent set of nuclear data calculations must be considered quite uncertain

The Binary Neutron Star Event LIGO/Virgo GW170817 160 Days after Merger: Synchrotron Emission across the Electromagnetic Spectrum

Science.gov (United States)

Margutti, R.; Alexander, K. D.; Xie, X.; Sironi, L.; Metzger, B. D.; Kathirgamaraju, A.; Fong, W.; Blanchard, P. K.; Berger, E.; MacFadyen, A.; Giannios, D.; Guidorzi, C.; Hajela, A.; Chornock, R.; Cowperthwaite, P. S.; Eftekhari, T.; Nicholl, M.; Villar, V. A.; Williams, P. K. G.; Zrake, J.

2018-03-01

We report deep Chandra X-ray Observatory (CXO), Hubble Space Telescope (HST), and Karl J. Jansky Very Large Array (VLA) observations of the binary neutron star event GW170817 at t spectrum extending for eight orders of magnitude in frequency enables the most precise measurement of the index p of the distribution of non-thermal relativistic electrons N(γ )\\propto {γ }-p accelerated by a shock launched by a neutron star (NS)–NS merger to date. We find p = 2.17 ± 0.01, which indicates that radiation from ejecta with Γ ∼ 3–10 dominates the observed emission. While constraining the nature of the emission process, these observations do not constrain the nature of the relativistic ejecta. We employ simulations of explosive outflows launched in NS ejecta clouds to show that the spectral and temporal evolution of the non-thermal emission from GW170817 is consistent with both emission from radially stratified quasi-spherical ejecta traveling at mildly relativistic speeds, and emission from off-axis collimated ejecta characterized by a narrow cone of ultra-relativistic material with slower wings extending to larger angles. In the latter scenario, GW170817 harbored a normal short gamma-ray burst (SGRB) directed away from our line of sight. Observations at t ≤ 200 days are unlikely to settle the debate, as in both scenarios the observed emission is effectively dominated by radiation from mildly relativistic material.

Neutron sawtooth behavior in the PLT, DIII-D, and TFTR tokamaks

International Nuclear Information System (INIS)

Lovberg, J.A.; Heidbrink, W.W.; Strachan, J.D.; Zaveryaev, V.S.

1988-10-01

The effect of the sawtooth instability on the 2.5 MeV neutron emission in the PLT, DIII-D, and TFTR tokamaks is studied. In thermonuclear plasmas, the instability typically results in a 20% reduction in emission. The time evolution of the thermonuclear neutron signal suggests that the sawtooth crash consists of four phases. First, the electron density profile flattens rapidly (in /approximately/30μsec on PLT) but, in some cases, there is little associated change in neutron emission, suggesting that most reacting ions remain confined in the sawtooth region but do not completely mix. After the electron sawtooth, the ions continue to mix, resulting in a /approximately/10% reduction in neutron emission in /approximately/0.5 msec. The emission then decays more slowly during the final two phases. Thermalization of reacting ions on a /approximately/3/tau//sub ii/ time scale accounts for only /approximately/20% of the slow drop. Most of the slow drop seems to be caused by loss of ion energy from the mixing region (an ion heat pulse). 36 refs., 15 figs., 1 tabs

A semi-empirical formula on the pre-neutron-emission fragment mass distribution in nuclear fission

International Nuclear Information System (INIS)

Wang Fucheng; Hu Jimin

1988-03-01

A 5-Gauss semi-empirical formula on the pre-neutron-emission fragment mass distribution is given. The absolute standard deviation and maximum departure between calculated values and experimental data for (n,f) and (n,n'f) fission reactions from 232 Th to 245 Cm are approximately 0.4% and 0.8%, respectively. The error will get bigger if the formula is used at higher excitation energies

Hot nuclei studied with high efficiency neutron detectors

International Nuclear Information System (INIS)

Galin, J.

1990-01-01

We have shown the invaluable benefit that a high efficiency 4π neutron detector can bring to the study of reaction mechanisms following collisions of heavy nuclei at intermediate energy. Analysis requires Monte-Carlo simulations for comparison between experimental data and any emission model. In systematic measurements with projectiles of velocity corresponding to energies between 27 and 77 MeV/u, where both the influence of beam velocity and mass have been investigated separately, it has been shown that the projectile-target mass asymmetry, much more than velocity, has a decisive influence on energy dissipation. The closer the projectile mass to the target mass, the more energy is dissipated per unit mass of the considered projectile plus target system. The latter presents all the characteristics of a thermalized system, evaporating a copious number of light particles: up to about 40 neutrons (after efficiency correction) and 11 light charged particles in the most dissipative collisions between Kr+Au, and 90 neutrons for Pb+U with a yet unknown number of l.c.p. In the Kr experiment, these particles are isotropically emitted in the frame of a fused system, excited with 1.2 GeV. Moreover, l.c.p. exhibit Maxwellian energy distributions as in any standard evaporation process. We are now eager to better characterize the properties of the Pb+Au (U) systems for which about 1/3 of the neutrons are freed in a rather large fraction of all collisions. The thermalized energy should then approach very closely the total binding energy of the two interacting nuclei

Neutron to proton ratios of quasiprojectile and midrapidity emission in the 58Ni+58Ni reaction at 52 MeV/nucleon

International Nuclear Information System (INIS)

Theriault, D.; Vallee, A.; Gingras, L.; Larochelle, Y.; Roy, R.; April, A.; Beaulieu, L.; Grenier, F.; Lemieux, F.; Moisan, J.; St-Pierre, C.; Turbide, S.; Samri, M.; Borderie, B.; Rivet, M. F.; Bougault, R.; Colin, J.; Cussol, D.; Durand, D.; Lecolley, J.F.

2005-01-01

By combining data from a charged particle 58 Ni+ 58 Ni experiment at 52 MeV/nucleon with an 36 Ar+ 58 Ni experiment at 50 MeV/nucleon for which free neutrons have been detected, an increase in the neutron to proton ratio of the whole nuclear material at midrapidity has been experimentally observed in the reaction 58 Ni+ 58 Ni at 52 MeV/nucleon. The neutron-to-proton ratio of the quasi-projectile emission is analyzed for the same reactions and is seen to decrease below the ratio of the initial system. Those observations suggest that an asymmetric exchange of neutrons and protons between the quasiprojectile and the midrapidity region exists

Projected study of neutronic decay of giant resonances and continuum states

International Nuclear Information System (INIS)

Blumenfeld, Y.; Chomaz, P.; Fortier, S.; Frascaria, N.; Gales, S.; Guillot, J.; Langevin, H.; Laurent, H.; Maison, J.M.; Nguyen Van Giai

1988-01-01

A project to study the decay of very excited states in nuclei is presented. A multidetector to measure these modes for excited structures situated beyond the neutron emission threshold is proposed. Coincidence experiments would allow a study of the wave functions of these elementary excitations and of the damping mechanisms in the nuclear domain. The definition of the characteristics of the system; tests to be carried out before selecting a detector; and nonscientific and nontechnical aspects of the project are also presented [fr

Study and building of a detection array for delayed neutrons: TONNERRE

International Nuclear Information System (INIS)

Martin, Thierry

1998-01-01

This work has been undertaken within a French-Romanian collaboration in order to build a high efficiency detector array for delayed neutrons: barrel-shaped TONNERRE. Some neutron-rich nuclei decay through 1, 2 or 3 neutron emission after β - decay. More exotic nuclei will be produced by SPIRAL at GANIL. An array with high efficiency and good resolution is then required. Thirty two BC400 plastic scintillators (160 x 20 x 4 cm 3 ) allow us to get the time of flight neutron spectra. They are bent for uniform flight path and viewed by a photomultiplier tube at both ends. Simulations have allowed to establish scintillator size and to minimize light attenuation. Intrinsic efficiency and crosstalk have been measured with 252 Cf and compared to GEANT. 1 to 5 MeV neutrons are detected with good timing and position properties. Other counters will be built for neutrons from 300 keV to 1 MeV. Planned to run at several particle accelerators (GANIL, CERN, and others), TONNERRE is modular and many geometries are possible. (author)

Influence of nucleon density distribution in nucleon emission probability

International Nuclear Information System (INIS)

Paul, Sabyasachi; Nandy, Maitreyee; Mohanty, A.K.; Sarkar, P.K.; Gambhir, Y.K.

2014-01-01

Different decay modes are observed in heavy ion reactions at low to intermediate energies. It is interesting to study total neutron emission in these reactions which may be contributed by all/many of these decay modes. In an attempt to understand the importance of mean field and the entrance channel angular momentum, we study their influence on the emission probability of nucleons in heavy ion reactions in this work. This study owes its significance to the fact that once population of different states are determined, emission probability governs the double differential neutron yield

Physical methods for studying minerals and solid materials: X-ray, electron and neutron diffraction; scanning and transmission electron microscopy; X-ray, electron and ion spectrometry

International Nuclear Information System (INIS)

Eberhart, J.-P.

1976-01-01

The following topics are discussed: theoretical aspects of radiation-matter interactions; production and measurement of radiations (X rays, electrons, neutrons); applications of radiation interactions to the study of crystalline materials. The following techniques are presented: X-ray and neutron diffraction, electron microscopy, electron diffraction, X-ray fluorescence analysis, electron probe microanalysis, surface analysis by electron emission spectrometry (ESCA and Auger electrons), scanning electron microscopy, secondary ion emission analysis [fr

Neutron-scattering studies of chromatin

International Nuclear Information System (INIS)

Bradbury, E.M.; Baldwin, J.P.; Carpenter, B.G.; Hjelm, R.P.; Hancock, R.; Ibel, K.

1976-01-01

It is clear that a knowledge of the basic molecular structure of chromatin is a prerequisite for any progress toward an understanding of chromosome organization. With a two-component system, protein and nucleic acid, neutrons have a particularly powerful application to studies of the spatial arrangements of these components because of the ability, by contrast matching with H 2 O-D 2 O mixtures, to obtain neutron-scattering data on the individual components. With this approach it has been shown that the neutron diffraction of chromatin is consistent with a ''beads on a string'' model in which the bead consists of a protein core with DNA coiled on the outside. However, because chromatin is a gel and gives limited structural data, confirmation of such a model requires extension of the neutron studies by deuteration of specific chromatin components and the isolation of chromatin subunits. Although these studies are not complete, the neutron results so far obtained support the subunit model described above

Neutron scattering studies in the actinide region

International Nuclear Information System (INIS)

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

1993-09-01

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

Decay Studies of Very Neutron Rich Nuclei near 78Ni

International Nuclear Information System (INIS)

Winger, J. A.; Ilyushkin, S.; Korgul, A.; Gross, Carl J; Rykaczewski, Krzysztof Piotr; Batchelder, J. C.; Goodin, C.; Grzywacz, R.; Hamilton, J. H.; Krolas, W.; Liddick, Sean; Mazzocchi, C.; Nelson, C.; Padgett, Stephen; Piechaczek, A.; Rajabali, M. M.; Shapira, Dan; Zganjar, E. F.

2008-01-01

The properties of beta-gamma and beta-delayed neutron emission from 76-79 Cu and 83-85 Ga were measured at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. Selected results on the decay properties of copper isotopes are briefly presented and discussed

Optimising the neutron environment of Radiation Portal Monitors: A computational study

Energy Technology Data Exchange (ETDEWEB)

Gilbert, Mark R., E-mail: mark.gilbert@ccfe.ac.uk [United Kingdom Atomic Energy Authority, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Ghani, Zamir [United Kingdom Atomic Energy Authority, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); McMillan, John E. [Department of Physics and Astronomy, University of Sheffield, Hicks building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Packer, Lee W. [United Kingdom Atomic Energy Authority, Culham Science Centre, Abingdon OX14 3DB (United Kingdom)

2015-09-21

Efficient and reliable detection of radiological or nuclear threats is a crucial part of national and international efforts to prevent terrorist activities. Radiation Portal Monitors (RPMs), which are deployed worldwide, are intended to interdict smuggled fissile material by detecting emissions of neutrons and gamma rays. However, considering the range and variety of threat sources, vehicular and shielding scenarios, and that only a small signature is present, it is important that the design of the RPMs allows these signatures to be accurately differentiated from the environmental background. Using Monte-Carlo neutron-transport simulations of a model {sup 3}He detector system we have conducted a parameter study to identify the optimum combination of detector shielding, moderation, and collimation that maximises the sensitivity of neutron-sensitive RPMs. These structures, which could be simply and cost-effectively added to existing RPMs, can improve the detector response by more than a factor of two relative to an unmodified, bare design. Furthermore, optimisation of the air gap surrounding the helium tubes also improves detector efficiency.

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

International Nuclear Information System (INIS)

Wehring, B.W.; Uenlue, K.

1995-01-01

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

Overview of neutron and confined escaping alpha diagnostics planned for ITER

Energy Technology Data Exchange (ETDEWEB)

Sasao, M [Department of Quantum Science and Energy Engineering, Tohoku University, Sendai (Japan); Krasilnikov, A V [TRINITI, Troitsk (Russian Federation); Nishitani, T [JAERI, Tokai (Japan); Batistoni, P [ENEA, Frascati, Rome (Italy); Zaveryaev, V [Kurchatov Institute, Moscow (Russian Federation); Kaschuck, Yu A [TRINITI, Troitsk (Russian Federation); Popovichev, S [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon (United Kingdom); Iguchi, T [Nagoya University, Nagoya, (Japan); Jarvis, O N [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon (United Kingdom); Kallne, J [Department of Neutron Research, Uppsala University, Uppsala (Sweden); Fiore, C L [PPL, MIT, Cambridge (United States); Roquemore, L [PPPL, Princeton (United States); Heidbrink, W W [Department of Physics and Astronomy, UC Irvine (United States); Donne, A J H [FOM-Instituut voor Plasmafysica (Netherlands); Costley, A E [ITER IT, Naka Joint Work Site (Japan); Walker, C [ITER IT, Garching Joint Work Site (Germany)

2004-07-01

Fusion product measurements planned for ITER are reviewed from the viewpoint of alpha particle-related physics studies. Recent advances in fusion plasma physics have extended the desirable measurement requirements to the megahertz region for neutron emission rate, better resolution of neutron profiles for the study of internal transport barriers (ITBs), etc. Employing threshold counters and/or scintillation detectors confers megahertz capability on neutron emission rate measurement. The changes in the neutron/alpha particle birth profile due to the formation of ITB and its deviation from uniformity on the magnetic flux surface can be measured by addition of eight viewing chords in an equatorial port plug and seven viewing chords from the divertor to the original radial neutron camera. On the other hand, it is still difficult to measure the distributions of confined and escaping alpha particles. Several proposals to resolve these difficulties are currently under investigation.

Calibration of the JET neutron yield monitors using the delayed neutron counting technique

International Nuclear Information System (INIS)

van Belle, P.; Jarvis, O.N.; Sadler, G.; de Leeuw, S.; D'Hondt, P.; Pillon, M.

1990-01-01

The time-resolved neutron yield is routinely measured on the JET tokamak using a set of fission chambers. At present, the preferred technique is to employ activation reactions to determine the neutron fluence at a well-chosen position and to relate the measured fluence to the total neutron emission by means of neutron transport calculations. The delayed neutron counting method is a particularly convenient method of performing the activation measurement and the fission cross sections are accurately known. This paper outlines the measurement technique as used on JET

Semiconductor Thermal Neutron Detector

Directory of Open Access Journals (Sweden)

Toru Aoki

2014-02-01

Full Text Available The  CdTe  and  GaN  detector  with  a  Gd  converter  have  been developed  and  investigated  as  a  neutron  detector  for neutron  imaging.  The  fabricated  Gd/CdTe  detector  with  the  25  mm  thick  Gd  was  designed  on  the  basis  of  simulation results  of  thermal  neutron  detection  efficiency  and  spatial  resolution.  The  Gd/CdTe  detector  shows  the  detection  of neutron  capture  gamma  ray  emission  in  the  155Gd(n,  g156Gd,  157Gd(n,  g158Gd  and  113Cd(n,  g114Cd  reactions  and characteristic X-ray emissions due to conversion-electrons generated inside the Gd film. The observed efficient thermal neutron detection with the Gd/CdTe detector shows its promise in neutron radiography application. Moreover, a BGaN detector has also investigated to separate neutron signal from gamma-ray clearly. 

Comparing neutron and X-ray images from NIF implosions

Directory of Open Access Journals (Sweden)

Wilson D.C.

2013-11-01

Full Text Available Directly laser driven and X-radiation driven DT filled capsules differ in the relationship between neutron and X-ray images. Shot N110217, a directly driven DT-filled glass micro-balloon provided the first neutron images at the National Ignition Facility. As seen in implosions on the Omega laser, the neutron image can be enclosed inside time integrated X-ray images. HYDRA simulations show the X-ray image is dominated by emission from the hot glass shell while the neutron image arises from the DT fuel it encloses. In the absence of mix or jetting, X-ray images of a cryogenically layered THD fuel capsule should be dominated by emission from the hydrogen rather than the cooler plastic shell that is separated from the hot core by cold DT fuel. This cool, dense DT, invisible in X-ray emission, shows itself by scattering hot core neutrons. Germanium X-ray emission spectra and Ross pair filtered X-ray energy resolved images suggest that germanium doped plastic emits in the torus shaped hot spot, probably reducing the neutron yield.

Accretion dynamics and polarized x-ray emission of magnetized neutron stars

International Nuclear Information System (INIS)

Arons, J.

1991-01-01

The basic ideas of accretion onto magnetized neutron stars are outlined. These are applied to a simple model of the structure of the plasma mound sitting at the magnetic poles of such as star, in which upward diffusion of photons is balanced by their downward advection. This steady flow model of the plasma's dynamical state is used to compute the emission of polarized X-rays from the optically thick, birefringent medium. The linear polarization of the continuum radiation emerging from the quasi-static mound is found to be as much as 40% at some rotation phases, but is insensitive to the geometry of the accretion flow. The role of the accretion shock, whose detailed polarimetric and spectral characteristics have yet to be calculated, is emphasized as the final determinant of the properties of the emerging X-rays. Some results describing the fully time dependent dynamics of the flow are also presented. In particular, steady flow onto a neutron star is shown to exhibit formation of ''photon bubbles,'' regions of greatly reduced plasma density filled with radiation which form and rise on millisecond time scales. The possible role of these complex structures in the flow for the formation of the emergent spectrum is briefly outlined

Accretion dynamics and polarized X-ray emission of magnetized neutron stars

Science.gov (United States)

Arons, Jonathan

1991-01-01

The basic ideas of accretion onto magnetized neutron stars are outlined. These are applied to a simple model of the structure of the plasma mound sitting at the magnetic poles of such a star, in which upward diffusion of photons is balanced by their downward advection. This steady flow model of the plasma's dynamical state is used to compute the emission of polarized X-raysfrom the optically thick, birefringent medium. The linear polarization of the continuum radiation emerging from the quasi-static mound is found to be as much as 40 percent at some rotation phases, but is insensitive to the geometry of the accretion flow. The role of the accretion shock, whose detailed polarimetric and spectral characteristics have yet to be calculated, is emphasized as the final determinant of the properties of the emerging X-rays. Some results describing the fully time dependent dynamics of the flow are also presented. In particular, steady flow onto a neutron star is shown to exhibit formation of 'photon bubbles', regions of greatly reduced plasma density filled with radiation which form and rise on millisecond time scale. The possible role of these complex structures in the flow for the formation of the emergent spectrum is briefly outlined.

Neutron yield of medical electron accelerators

International Nuclear Information System (INIS)

McCall, R.C.

1988-01-01

Shielding calculations for medical electron accelerators above about 10 MeV require some knowledge of the neutron emission from the machine. This knowledge might come from the manufacturer's specifications or from published measurements of the neutron leakage of that particular model and energy of accelerator. In principle, the yield can be calculated if details of the accelerator design are known. These details are often not available because the manufacturer considers them proprietary. A broader knowledge of neutron emission would be useful and it is the purpose of this paper to present such information

Tunnel disintegration and neutron emission probability

International Nuclear Information System (INIS)

Tani, Toyu; Kobayashi, Yukio.

1993-01-01

It is shown that the main features of the so-called cold fusion, that is, poor reproducibility, high t/n ratio and the energy spectrum of neutrons, can be explained by the 'tunnel disintegration' of a deuterium and the subsequent 'dipole disintegration' of a deuteron. Especially, the 2.45-MeV peak found in the energy spectrum, which has been considered to be owing to the d-d nuclear fusion, is explained by this mechanism, and therefore the observation of 2.45-MeV neutrons may not be a direct verification of the d-d nuclear fusion. (author)

Commissioning of the IDS Neutron Detector and $\\beta$-decay fast-timing studies at IDS

CERN Document Server

Piersa, Monika

2016-01-01

The following report describes my scientific activities performed during the Summer Student Programme at ISOLDE. The main part of my project was focused on commissioning the neutron detector dedicated to nuclear decay studies at ISOLDE Decay Station (IDS). I have participated in all the steps needed to make it operational for the IS609 experiment. In the testing phase, we obtained expected detector response and calibrations confirmed its successful commissioning. The detector was mounted in the desired geometry at IDS and used in measurements of the beta-delayed neutron emission of $^8$He. After completing aforementioned part of my project, I became familiar with the fast-timing method. This technique was applied at IDS in the IS610 experiment performed in June 2016 to explore the structure of neutron-rich $^{130-134}$Sn nuclei. Since the main part of my PhD studies will be the analysis of data collected in this experiment, the second part of my project was dedicated to acquiring knowledge about technical de...

Spallation Neutron Emission Spectra in Some Amphoter Target Nuclei by Proton Beam Up to 140 MeV Energy

International Nuclear Information System (INIS)

Yildirim, G.

2008-01-01

In the present study, the (p,xn) reaction neutron-emission spectra for some amphoter target nuclei as 27 A l, 64 Z n, 120 S n, and 208 P b were investigated up to 140 MeV incident proton energy. The pre-equilibrium calculations were calculated by using the hybrid model, the geometry dependent hybrid model, the full exciton model and the cascade exciton model. The reaction equilibrium component was calculated with a traditional compound nucleus model developed by Weisskopf Ewing. Calculation results have been discussed and compared with the available experimental data in literature

Boron analysis for neutron capture therapy using particle-induced gamma-ray emission

International Nuclear Information System (INIS)

Nakai, Kei; Yamamoto, Yohei; Okamoto, Emiko; Yamamoto, Tetsuya; Yoshida, Fumiyo; Matsumura, Akira; Yamada, Naoto; Kitamura, Akane; Koka, Masashi; Satoh, Takahiro

2015-01-01

The neutron source of BNCT is currently changing from reactor to accelerator, but peripheral facilities such as a dose-planning system and blood boron analysis have still not been established. To evaluate the potential application of particle-induced gamma-ray emission (PIGE) for boron measurement in clinical boron neutron capture therapy, boronophenylalanine dissolved within a cell culture medium was measured using PIGE. PIGE detected 18 μgB/mL f-BPA in the culture medium, and all measurements of any given sample were taken within 20 min. Two hours of f-BPA exposure was required to create a boron distribution image. However, even though boron remained in the cells, the boron on the cell membrane could not be distinguished from the boron in the cytoplasm. - Highlights: • PIGE was evaluated for measuring blood boron concentration during clinical BNCT. • PIGE detected 18 μgB/mL f-BPA in culture medium. • All measurements of any given sample were taken within 20 min. • Two hours of f-BPA exposure is required to create boron distribution image by PIGE. • Boron on the cell membrane could not be distinguished from boron in the cytoplasm.

Experimental study of a fast plasma focus discharge operated in the range of tens of joules emitting neutrons

International Nuclear Information System (INIS)

Tarifeno Saldivia, Eriel Esteban

2011-01-01

In this doctoral research, a small plasma focus discharge operated at tens of joules and kilo amperes has been experimentally studied. This device produces a coaxial discharge by an electrode arrange which consists of an inner electrode, a cylindrical insulator, and an outer electrode. The discharge is driven by a capacitive generator and it is operated at pressures of some millibars. Typical electrical parameters of the device are T/4∼150ns, 160 nF, 40 nH, 30-100J, 40-70kA. When Deuterium is used as filling gas, neutrons are produced by fusion reactions. The device, namely PF-50J, is one of the most extreme plasma focus reported in the literature to emit neutrons. The results of this work have demonstrated that the same dynamics found in larger machines (operated from kJ to MJ) is also found in this extremely low energy device which means that after the discharge is initiated, a plasma sheet is formed over the insulator. By the action of the Lorentz force, the plasma sheet moves axially. When the sheet reaches the top end of the inner electrode, it starts to implode radially to finally form a dense plasma column (pinch). Finally, the plasma column is disrupted 5-10ns after column formation. Shock piston velocities of the order of 10 4 -10 5 m/s were estimated from experiments for each discharge dynamical phase. Typical pinch densities of 10 24-25 m -3 were also observed in PF-50J. An interesting feature observed in this work is the formation of axial jet-like structures which appears at late times almost hundred nanoseconds after pinch disruption. These structures are composed by a metallic plasma which results from ablation of the inner electrode. The mechanism responsible for the formation of this kind of structure is still unknown, although evidence suggests that the phenomena is not related to the pinch formation process. One of the principal motivations of this thesis was to study the optimization for neutron emission in the PF-50J device. This plasma focus

A comparative study of neutron activation analysis and proton-induced X-ray emission analysis for the determination of heavy metals in estuarine sediments

Science.gov (United States)

Randle, K.; Al-Jundi, J.; Mamas, C. J. V.; Sokhi, R. S.; Earwaker, L. G.

1993-06-01

Our work on heavy metals in the estuarine environment has involved the use of two multielement techniques: neutron activation analysis (NAA) and proton-induced X-ray emission (PIXE) analysis. As PIXE is essentially a surface analytical technique problems may arise due to sample inhomogeneity and surface roughness. In order to assess the contribution of these effects we have compared the results from PIXE analysis with those from a technique which analyzes a larger bulk sample rather than just the surface. An obvious method was NAA. A series of sediment samples containing particles of variable diameter were compared. Pellets containing a few mg of sediment were prepared from each sample and analyzed by the PIXE technique using both an absolute and a comparitive method. For INAA the rest of the sample was then irradiated with thermal neutrons and element concentrations determined from analyses of the subsequent gamma-ray spectrum. Results from the two methods are discussed.

Ti(r) profiles from the JET neutron profile monitor for ohmic discharges

Energy Technology Data Exchange (ETDEWEB)

Esposito, B. (ENEA, Frascati (Italy). Centro Ricerche Energia); Marcus, F.B.; Conroy, S.; Jarvis, O.N.; Loughlin, M.J.; Sadler, G.; Belle, P. van (Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking); Adams, J.M.; Watkins, N. (AEA Industrial Technology, Harwell (United Kingdom))

1991-01-01

A study has been made of the neutron emissivity, using the JET neutron profile monitor, obtained for ohmically heated deuterium discharges. Both one-dimensional (1-D) best-fit inversion procedures and 2-D tomography have been used to deduce the radial profile of the neutron emission from the line-integral data. The profiles of ion temperature and ion thermal conductivity are then derived. The scaling of the ion thermal conductivity with plasma current is found to be opposite to that of neoclassical theory. (author) 4 refs., 5 figs.

Neutron Sources for Standard-Based Testing

Energy Technology Data Exchange (ETDEWEB)

Radev, Radoslav [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); McLean, Thomas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-11-10

The DHS TC Standards and the consensus ANSI Standards use ²⁵²Cf as the neutron source for performance testing because its energy spectrum is similar to the ²³⁵U and ²³⁹Pu fission sources used in nuclear weapons. An emission rate of 20,000 ± 20% neutrons per second is used for testing of the radiological requirements both in the ANSI standards and the TCS. Determination of the accurate neutron emission rate of the test source is important for maintaining consistency and agreement between testing results obtained at different testing facilities. Several characteristics in the manufacture and the decay of the source need to be understood and accounted for in order to make an accurate measurement of the performance of the neutron detection instrument. Additionally, neutron response characteristics of the particular instrument need to be known and taken into account as well as neutron scattering in the testing environment.

Study on neutron beam probe. Study on the focused neutron beam

Energy Technology Data Exchange (ETDEWEB)

Kotajima, Kyuya; Suzuki, K.; Fujisawa, M.; Takahashi, T.; Sakamoto, I. [Tohoku Univ., Sendai (Japan). Faculty of Engineering; Wakabayashi, T.

1998-03-01

A monoenergetic focused neutron beam has been produced by utilizing the endoenergetic heavy ion reactions on hydrogen. To realize this, the projectile heavy ion energy should be taken slightly above the threshold energy, so that the excess energy converted to the neutron energy should be very small. In order to improve the capability of the focused neutron beam, some hydrogen stored metal targets have also been tested. Separating the secondary heavy ions (associated particles) from the primary ions (accelerated particles) by using a dipole magnet, a rf separator, and a particle identification system, we could directly count the produced neutrons. This will leads us to the possibility of realizing the standard neutron field which had been the empty dream of many neutron-related researchers in the world. (author)

A study on the utilization of hyper-thermal neutrons for neutron capture therapy

International Nuclear Information System (INIS)

Sakurai, Yoshinori; Kobayashi, Tooru; Kanda, Keiji

1993-01-01

The utilization of hyper-thermal neutrons, which have an energy spectrum of a Maxwellian distribution of a higher temperature than the room temperature of 300 K, was studied in order to improve the thermal neutron flux distribution at the deeper part in a living body for neutron capture therapy. Simulation calculations were carried out using MCNP-V3 in order to confirm the characteristics of hyper-thermal neutrons, i.e., (1) depth dependence of neutron energy spectrum, and (2) depth distribution of the reaction rate in a water phantom for materials with 1/v neutron absorption. It is confirmed that the hyper-thermal neutron irradiation can improve the thermal neutron flux distribution in the deeper and wider area in a living body compared with the thermal neutron irradiation. Practically, by the incidence of the hyper-thermal neutrons with a 3000 K Maxwellian distribution, the thermal neutron flux at 5 cm depth can be given about four times larger than by the incidence of the thermal neutrons of 300 K. (author)

The tokamak as a neutron source

International Nuclear Information System (INIS)

Hendel, H.W.; Jassby, D.L.

1989-11-01

This paper describes the tokamak in its role as a neutron source, with emphasis on experimental results for D-D neutron production. The sections summarize tokamak operation, sources of fusion and non-fusion neutrons, principal neutron detection methods and their calibration, neutron energy spectra and fluxes outside the tokamak plasma chamber, history of neutron production in tokamaks, neutron emission and fusion power gain from JET and TFTR (the largest present-day tokamaks), and D-T neutron production from burnup of D-D tritons. This paper also discusses the prospects for future tokamak neutron production and potential applications of tokamak neutron sources. 100 refs., 16 figs., 4 tabs

Characterization of the energy distribution of neutrons generated by 5 MeV protons on a thick beryllium target at different emission angles

Energy Technology Data Exchange (ETDEWEB)

Agosteo, S. [Politecnico di Milano, Dipartimento di Energia, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)] [Istituto Nazionale di Fisica Nucleare, Sezione di Milano, via Celoria 16, 20133 Milano (Italy); Colautti, P., E-mail: paolo.colautti@lnl.infn.it [INFN, Laboratori Nazionali di Legnaro (LNL), Via dell' Universita, 2, I-35020 Legnaro (PD) (Italy); Esposito, J., E-mail: juan.esposito@tin.it [INFN, Laboratori Nazionali di Legnaro (LNL), Via dell' Universita, 2, I-35020 Legnaro (PD) (Italy); Fazzi, A.; Introini, M.V.; Pola, A. [Politecnico di Milano, Dipartimento di Energia, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)] [Istituto Nazionale di Fisica Nucleare, Sezione di Milano, via Celoria 16, 20133 Milano (Italy)

2011-12-15

Neutron energy spectra at different emission angles, between 0 Degree-Sign and 120 Degree-Sign from the Be(p,xn) reaction generated by a beryllium thick-target bombarded with 5 MeV protons, have been measured at the Legnaro Laboratories (LNL) of the Italian National Institute for Nuclear Physics research (INFN). A new and quite compact recoil-proton spectrometer, based on a monolithic silicon telescope, coupled to a polyethylene converter, was efficiently used with respect to the traditional Time-of-Flight (TOF) technique. The measured distributions of recoil-protons were processed through an iterative unfolding algorithm in order to determine the neutron energy spectra at all the angles accounted for. The neutron energy spectrum measured at 0 Degree-Sign resulted to be in good agreement with the only one so far available at the requested energy and measured years ago with TOF technique. Moreover, the results obtained at different emission angles resulted to be consistent with detailed past measurements performed at 4 MeV protons at the same angles by TOF techniques.

Large solid-angle spectrometers for studies of double-differential charged-particle and neutron emission cross sections

International Nuclear Information System (INIS)

Baba, M.; Matsuyama, S.; Sanami, T.; Soda, D.; Matsuyama, I.; Ohkubo, T.; Iwasaki, S.; Hirakawa, N.

1995-01-01

The large solid-angle spectrometer developed for studies of double-differential cross sections of (n, charged particle) and (n, xn') reactions using a gas-filled gridded-ionization chamber and an 80-cm long liquid scintillator is described. The charged particle spectrometer is a twin gas-filled gridded-ionization chamber with solid angle close to 4 π designed to achieve high stopping power and background suppression. The neutron spectrometer is a long NE213 liquid scintillation detector having position sensitivity. It is used as a large single spectrometer or a position sensitive detector covering wide scattering angle. The facility design, performance and examples of application are discussed. The conclusion is made that the facility provides a useful mean for studies in particular for reactions with small cross sections and/or for neutron sources with low intensity. 15 refs., 15 figs

Neutron bursts from long laboratory sparks

Science.gov (United States)

Kochkin, P.; Lehtinen, N. G.; Montanya, J.; Van Deursen, A.; Ostgaard, N.

2016-12-01

Neutron emission in association with thunderstorms and lightning discharges was reported by different investigators from ground-based observation platforms. In both cases such emission is explained by photonuclear reaction, since high-energy gamma-rays in sufficient fluxes are routinely detected from both, lightning and thunderclouds. The required gamma-rays are presumably generated by high-energy electrons in Bremsstrahlung process after their acceleration via cold and/or relativistic runaway mechanisms. This phenomenon attracted moderate scientific attention until fast neutron bursts (up to 10 MeV) from long 1 MV laboratory sparks have been reported. Clearly, with such relatively low applied voltage the electrons are unable to accelerate to the energies required for photo/electro disintegration. Moreover, all known elementary neutron generation processes are not capable to explain this emission right away. We performed an independent laboratory experiment on long sparks with the aim to confirm or disprove the neutron emission from them. The experimental setup was assembled at High-Voltage Laboratory in Barcelona and contained a Marx generator in a cone-cone spark gap configuration. The applied voltage was as low as 800 kV and the gap distance was only 60 cm. Two ns-fast cameras were located near the gap capturing short-exposure images of the pre-breakdown phenomenon at the expected neutron generation time. A plastic scintillation detector sensitive to neutrons was covered in 11 cm of lead and placed near the spark gap. The detector was calibrated and showed good performance in neutron detection. Apart of it, voltage, currents through both electrodes, and three X-ray detectors were also monitored in sophisticated measuring system. We will give an overview of the previous experimental and theoretical work in this topic, and present the results of our new experimental campaign. The conclusions are based on good signal-to-noise ratio measurements and are

A neutron beam polarizer for study of parity violation in neutron-nucleus interactions

International Nuclear Information System (INIS)

Penttilae, S.I.; Bowman, J.D.; Frankle, C.M.; Seestrom, S.J.; Yen, Yi-Fen; Delheij, P.P.J.; Haase, D.G.; Postma, H.

1994-01-01

A dynamically-polarized proton target operating at 5 Tesla and 1 K has been built to, neutron beam for studies of parity violation in compound-nuclear resonances. Nearly 0.9 proton polarization was obtained in an electron-beam irradiated ammonia target. This was used to produce a neutron beam polarization of 0.7 at epithermal energies. The combination of the polarized proton target and the LANSCE spallation neutron source produces the most intense pulsed polarized epithermal neutron beam in the world. The neutron-beam polarizer is described and methods to determine neutron beam polarization are presented

Phase density of neutrons emitted by an atmosphereless planet

International Nuclear Information System (INIS)

Goryachev, B.I.; Isakov, A.I.; Lin'kova, N.V.

1986-01-01

An approach to calculation of small planet neutron emission characteristics is developed. Using artificial satellites and space probes information on the planet surface may be obtained by analyzing neutron emission being the result of cosmic rays effect. Available calculation methods permit to calculate angular distribution and neutron flux F 0 from planet surface as a function of its surface layer chemical composition. Neutron flux measured by a sattelite and F 0 flux may be connected by a function describing neuton phase density near the planet

Cadmium-Zinc-Telluride photon detector for epithermal neutron spectroscopy--pulse height response characterisation

International Nuclear Information System (INIS)

Tardocchi, M.; Pietropaolo, A.; Andreani, C.; Bracco, A.; D'Angelo, A.; Gorini, G.; Imberti, S.; Senesi, R.; Rhodes, N.J.; Schooneveld, E.M.

2004-01-01

The Resonance Detector Spectrometer was recently revised for neutron spectroscopic studies in the eV energy region. In this technique one makes use of a photon detector to record the gamma emission from analyser foils used as neutron-gamma converters. The pulse-height response of a Cadmium-Zinc-Telluride photon detector to neutron capture emission from 238 U and 197 Au analyser foils was characterised in the neutron energy range 1-200 eV. The experiment was performed on the VESUVIO spectrometer at the ISIS neutron-pulsed source. A biparametric data acquisition, specifically developed for these measurements, allowed the simultaneous measurements of both the neutron time of flight and γ pulse-height spectra. Through the analysis of the γ pulse-height spectra the main components of the signal associated with resonant and non-resonant neutron absorption were identified. It was also shown that, in principle, energy discrimination can be used to improve the signal to background ratio of the neutron time-of-flight measurement

Studies on application of radiation and radioisotopes -Studies on application of neutron activation analysis-

Energy Technology Data Exchange (ETDEWEB)

Jung, Yong Sam; Jung, Yung Joo; Jung, Eui Sik; Lee, Sang Mee [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Kim, Nak Bae [Korea Institute of Geology, Mining and Materials, Taejon (Korea, Republic of)

1995-07-01

To apply Neutron activation analysis to routine analysis of environmental samples utilizing the research reactor (TRIGA MK-III), improving effects of analytical sensitivity have been investigated using both of thermal and epithermal neutron irradiating technique. Identification and development of analytical procedure was carried out using three kinds of standard reference materials (urban particulate matter, coal fly ash, soil). In addition, the confidence of this method was established by participation in collaborative research for the training and apply of international credit of analytical procedure. Practical studies on air dust samples have also been carried out regionally and seasonally. For the investigation on emission source of special element, enrichment factor was calculated in urban and rural area. Besides, a suitable process of biological sample (pine needle) analyses has been established by carrying out identification of uncertainty using standard reference material. The concentration of elements in practical samples were also determined regionally and seasonally. 14 figs, 26 tabs, 67 refs. (Author).

Studies on application of radiation and radioisotopes -Studies on application of neutron activation analysis-

International Nuclear Information System (INIS)

Jung, Yong Sam; Jung, Yung Joo; Jung, Eui Sik; Lee, Sang Mee; Kim, Nak Bae

1995-07-01

To apply Neutron activation analysis to routine analysis of environmental samples utilizing the research reactor (TRIGA MK-III), improving effects of analytical sensitivity have been investigated using both of thermal and epithermal neutron irradiating technique. Identification and development of analytical procedure was carried out using three kinds of standard reference materials (urban particulate matter, coal fly ash, soil). In addition, the confidence of this method was established by participation in collaborative research for the training and apply of international credit of analytical procedure. Practical studies on air dust samples have also been carried out regionally and seasonally. For the investigation on emission source of special element, enrichment factor was calculated in urban and rural area. Besides, a suitable process of biological sample (pine needle) analyses has been established by carrying out identification of uncertainty using standard reference material. The concentration of elements in practical samples were also determined regionally and seasonally. 14 figs, 26 tabs, 67 refs. (Author)

Survey of neutron spectra generated by the fission of heavy nuclei induced by fast neutrons

International Nuclear Information System (INIS)

Lovchikova, G.N.; Trufanov, A.M.

1997-01-01

A review of neutron fission spectra measurements is presented. This review and the results of this analysis was performed with the participation of the authors. It is shown that there is a need for additional measurements of the energy and angular distributions of secondary neutrons in order to improve the understanding of the neutron emission mechanism in fission. (author). 21 refs, 6 figs

PANDORA, a large volume low-energy neutron detector with real-time neutron-gamma discrimination

Science.gov (United States)

Stuhl, L.; Sasano, M.; Yako, K.; Yasuda, J.; Baba, H.; Ota, S.; Uesaka, T.

2017-09-01

The PANDORA (Particle Analyzer Neutron Detector Of Real-time Acquisition) system, which was developed for use in inverse kinematics experiments with unstable isotope beams, is a neutron detector based on a plastic scintillator coupled to a digital readout. PANDORA can be used for any reaction study involving the emission of low energy neutrons (100 keV-10 MeV) where background suppression and an increased signal-to-noise ratio are crucial. The digital readout system provides an opportunity for pulse shape discrimination (PSD) of the detected particles as well as intelligent triggering based on PSD. The figure of merit results of PANDORA are compared to the data in literature. Using PANDORA, 91 ± 1% of all detected neutrons can be separated, while 91 ± 1% of the detected gamma rays can be excluded, reducing the gamma ray background by one order of magnitude.

Magnetic particles studied with neutron depolarization and small-angle neutron scattering

International Nuclear Information System (INIS)

Rosman, R.

1991-01-01

Materials containing magnetic single-domain particles, referred to as 'particulate media', have been studied using neutron depolarization (ND) and small-angle neutron scattering (SANS). In a ND experiment the polarization vector of a polarized neutron beam is analyzed after transmission through a magnetic medium. Such an analysis in general yields the correlation length of variations in magnetic induction along the neutron path (denoted 'magnetic correlation length'), mean orientation of these variations and mean magnetic induction. In a SANS experiment, information about nuclear and magnetic inhomogeneities in the medium is derived from the broadening of a generally unpolarized neutron beam due to scattering by these inhomogeneities. Spatial and magnetic microstructure of a variety of particulate media have been studied using ND and/or SANS, by determination of the magnetic or nuclear correlation length in these media in various magnetic states. This thesis deals with the ND theory and its application to particulate media. ND and SANS experiments on a variety of particulate media are discussed. (author). 178 refs., 97 figs., 8 tabs

Unexpected high-energy γ emission from decaying exotic nuclei

Directory of Open Access Journals (Sweden)

A. Gottardo

2017-09-01

Full Text Available The N=52 Ga83 β decay was studied at ALTO. The radioactive 83Ga beam was produced through the ISOL photofission technique and collected on a movable tape for the measurement of γ-ray emission following β decay. While β-delayed neutron emission has been measured to be 56–85% of the decay path, in this experiment an unexpected high-energy 5–9 MeV γ-ray yield of 16(4% was observed, coming from states several MeVs above the neutron separation threshold. This result is compared with cutting-edge QRPA calculations, which show that when neutrons deeply bound in the core of the nucleus decay into protons via a Gamow–Teller transition, they give rise to a dipolar oscillation of nuclear matter in the nucleus. This leads to large electromagnetic transition probabilities which can compete with neutron emission, thus affecting the β-decay path. This process is enhanced by an excess of neutrons on the nuclear surface and may thus be a common feature for very neutron-rich isotopes, challenging the present understanding of decay properties of exotic nuclei.

Neutron field inside a PET Cyclotron vault room

International Nuclear Information System (INIS)

Vega C, H.R.; Mendez, R.; Iniguez, M.P.; Climent, J.M.; Penuelas, I.; Barquero, R.

2006-01-01

The neutron field around a Positron Emission Tomography cyclotron was investigated during 18 F radioisotope production with an 18 MeV proton beam. In this study the Ion Beam Application cyclotron, model Cyclone 18/9, was utilized. Measurements were carried out with a Bonner sphere neutron spectrometer with pairs of thermoluminescent dosemeters (TLD600 and TLD700) as thermal neutron detector. The TLDs readouts were utilized to unfold the neutron spectra at three different positions inside the cyclotron's vault room. With the spectra the Ambient dose equivalent was calculated. Neutron spectra unfolding were performed with the BUNKIUT code and the UTA4 response matrix. Neutron spectra were also determined by Monte Carlo calculations using a detailed model of cyclotron and vault room. (Author)

Demonstration of Neutron Resonance capture applied to a Cultural Heritage study of Antique Benin Bronzes

International Nuclear Information System (INIS)

Blaauw, M.; Postma, H.; Mutti, P.

2001-01-01

In many cases of historical and archaeological studies physical techniques Instrumental Neutron Activation Analysis (INAA) X-Ray Fluorescence (XRF) and Proton Induced X-ray Emission (PIXE) are used to get information about the element composition of objects. INAA is usually carried out using small samples taken from the object . XRF and PIXE only yield surface information, and require cleaning of the surface to suppress the effect of external contamination. Such actions on artefacts are unwanted. Recently neutron capture resonances have been used to identify elements in artefacts using a set of γray detectors and a time-of flight system at the GELINA facility. This allows identification and quantification of elements of precious artefacts in an fully non-destructive way and with very little activation Because of the novelly of the method the principles of neutron resonance capture analysis (NRC A) will be discussed and the results of an applications to a comparative study of two Benin Bronzes presented

Use of ultracold neutrons for condensed-matter studies

Energy Technology Data Exchange (ETDEWEB)

Michaudon, A.

1997-05-01

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

Use of ultracold neutrons for condensed-matter studies

International Nuclear Information System (INIS)

Michaudon, A.

1997-05-01

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

A neutron beam polarizer for study of parity violation in neutron-nucleus interactions

International Nuclear Information System (INIS)

Penttilae, S.I.; Bowman, J.D.; Delheij, P.P.; Frankle, C.M.; Haase, D.G.; Postma, H.; Seestrom, S.J.; Yen, Y.

1995-01-01

A dynamically-polarized proton target operating at 5 Tesla and 1 K has been built to polarize an epithermal neutron beam for studies of parity violation in compound-nuclear resonances. Nearly 0.9 proton polarization was obtained in an electron-beam irradiated ammonia target. This was used to produce a neutron beam polarization of 0.7 at epithermal energies. The combination of the polarized proton target and the LANSCE spallation neutron source produces the most intense pulsed polarized epithermal neutron beam in the world. The neutron-beam polarizer is described and methods to determine neutron beam polarization are presented. copyright 1995 American Institute of Physics

Target system neutronics study for NXGENS

International Nuclear Information System (INIS)

Willis, C.; Muhrer, G.

2007-01-01

The Materials Test Station (MTS) [E. Pitcher, G. Muhrer, H. Trellue, Neutronics Assessment of the LANSCE Materials Test Station as an Irradiation Facility for the JIMO Space Reactor, LA-CP-04-0903.], a spallation target station, planned for construction at the Los Alamos Neutron Science Center (LANSCE), will provide the opportunity to test the prototype of a long-pulse spallation source neutron scattering instrument (NXGENS). In this paper, we present the target-moderator neutronics optimization study that was performed in support of NXGENS

Summary of alpha-neutron sources in GADRAS

International Nuclear Information System (INIS)

Mitchell, Dean James; Thoreson, Gregory G.; Harding, Lee T.

2012-01-01

A common source of neutrons for calibration and testing is alpha-neutron material, named for the alpha-neutron nuclear reaction that occurs within. This material contains a long-lived alpha-emitter and a lighter target element. When the alpha particle from the emitter is absorbed by the target, neutrons and gamma rays are released. Gamma Detector Response and Analysis Software (GADRAS) includes built-in alpha-neutron source definitions for AcC, AmB, AmBe, AmF, AmLi, CmC, and PuC. In addition, GADRAS users may create their own alpha-neutron sources by placing valid alpha-emitters and target elements in materials within their one-dimensional models (1DModel). GADRAS has the ability to use pre-built alpha-neutron sources for plotting or as trace-sources in 1D models. In addition, if any material (existing or user-defined) specified in a 1D model contains both an alpha emitter in conjunction with a target nuclide, or there is an interface between such materials, then the appropriate neutron-emission rate from the alpha-neutron reaction will be computed. The gamma-emissions from these sources are also computed, but are limited to a subset of nine target nuclides. If a user has experimental data to contribute to the alpha-neutron gamma emission database, it may be added directly or submitted to the GADRAS developers for inclusion. The gadras.exe.config file will be replaced when GADRAS updates are installed, so sending the information to the GADRAS developers is the preferred method for updating the database. This is also preferable because it enables other users to benefit from your efforts.

Velocity-space sensitivity of neutron spectrometry measurements

DEFF Research Database (Denmark)

Jacobsen, Asger Schou; Salewski, Mirko; Eriksson, J.

2015-01-01

Neutron emission spectrometry (NES) measures the energies of neutrons produced in fusion reactions. Here we present velocity-space weight functions for NES and neutron yield measurements. Weight functions show the sensitivity as well as the accessible regions in velocity space for a given range...

Used Fuel Cask Identification through Neutron Profile

Energy Technology Data Exchange (ETDEWEB)

Rauch, Eric Benton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-11-20

Currently, most spent fuel is stored near reactors. An interim consolidated fuel storage facility would receive fuel from multiple sites and store it in casks on site for decades. For successful operation of such a facility there is need for a way to restore continuity of knowledge if lost as well as a method that will indicate state of fuel inside the cask. Used nuclear fuel is identifiable by its radiation emission, both gamma and neutron. Neutron emission from fission products, multiplication from remaining fissile material, and the unique distribution of both in each cask produce a unique neutron signature. If two signatures taken at different times do not match, either changes within the fuel content or misidentification of a cask occurred. It was found that identification of cask loadings works well through the profile of emitted neutrons in simulated real casks. Even casks with similar overall neutron emission or average counts around the circumference can be distinguished from each other by analyzing the profile. In conclusion, (1) identification of unaltered casks through neutron signature profile is viable; (2) collecting the profile provides insight to the condition and intactness of the fuel stored inside the cask; and (3) the signature profile is stable over time.

Response functions of superfluid neutron matter

Energy Technology Data Exchange (ETDEWEB)

Keller, Jochen; Sedrakian, Armen [Institut fuer Theoretische Physik, Goethe Universitaet, 60438 Frankfurt/Main (Germany)

2011-07-01

We investigate the response of pair-correlated neutron matter under conditions relevant to neutron stars to external weak probes and compute its neutrino emissivity in vector and axialvector channels. To derive the response functions we sum up an infinite chain of particle-hole ladder diagrams within finite-temperature Green's function theory. The polarization tensor of matter is evaluated in the limit of small momentum transfers. The calculated neutrino emission via the weak neutral current processes of pair-breaking and recombination of Cooper-pairs in neutron stars causes a cooling of their baryonic interior, and represents an important mechanism for the thermal evolution of the star within a certain time domain.

Light particle emission measurements in heavy ion reactions. Final report, June 1, 1981-May 31, 1984

International Nuclear Information System (INIS)

Petitt, G.A.

1984-01-01

Progress in instrumentation development reported includes improvements in the design of position sensitive neutron detectors, design of a thin-walled, spherical, aluminum target chamber, and use of thin silicon detectors to detect and identify evaporation residues from fusion reactions. The problem of the short lifetime of evaporation residue detectors is addressed by using a pair of large area, multi-wire proportional counters followed by a thin sheet of plastic scintillator. Neutron emission associated with fission has been studied, as well as nonequilibrium emission associated with inelastic products and evaporation residue. An experiment was performed to study neutron emission associated with fission and fission-like events in the case of the Er composite system. Other work in progress includes neutron emissions from the C + Gd and Ne + Nd reactions. 9 refs

Design of neutron diagnostic for MTX

International Nuclear Information System (INIS)

Ogawa, Toshihide; Oasa, Kazumi; Hoshino, Katsumichi; Odajima, Kazuo; Maeda, Hikosuke

1990-07-01

A neutron diagnostic system was designed for the Microwave Tokamak Experiment being carried out at the lawrence Livermore National Laboratory. High speed measurements are important to this experiment. Plastic scintillator is used for this fast response detection of neutron. Proportional counters and fission counters are used for the total neutron emission rate measurements. (author)

Study of neutron fields around an intense neutron generator.

Science.gov (United States)

Kicka, L; Machrafi, R; Miller, A

2017-12-01

Neutron fields in the vicinity of the newly built neutron facility, at the University of Ontario Institute of Technology (UOIT), have been investigated in a series of Monte Carlo simulations and measurements. The facility hosts a P-385 neutron generator based on a deuterium-deuterium fusion reaction. The neutron fluence at different locations around the neutron generator facility has been simulated using MCNPX 2.7E Monte Carlo particle transport program. To characterize neutron fields, three neutron sources were modeled with distributions corresponding to different incident deuteron energies of 90kV, 110kV, and 130kV. Measurements have been carried out to determine the dose rate at locations adjacent to the generator using bubble detectors (BDs). The neutron intensity was evaluated and the total dose rates corresponding to different applied acceleration potentials were estimated at various locations. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-03-01

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

Layered magnets: polarized neutron reflection studies

Energy Technology Data Exchange (ETDEWEB)

Zabel, H; Schreyer, A [Ruhr-Univ. Bochum, Lehrstuhl fuer Experimentalphysik/Festkoerperphysik, Bochum (Germany)

1996-11-01

Neutron reflectivity measurements from extended surfaces, thin films and superlattices provide information on the chemical profile parallel to the film normal, including film thicknesses, average composition and interfacial roughness parameters. Reflectivity measurements with polarized neutrons are particularly powerful for analyzing the magnetic density profiles in thin films and superlattices in addition to chemical profiles. The basic theory of polarized neutron reflectivity is provided, followed by some examples and more recent applications concerning polarized neutron reflectivity studies from exchange coupled Fe/Cr superlattices. (author) 5 figs., 13 refs.

Tritium and neutron measurements from deuterated Pd-Si

International Nuclear Information System (INIS)

Claytor, T.N.; Tuggle, D.G.; Menlove, H.O.; Seeger, P.A.; Doty, W.R.; Rohwer, R.K.

1990-01-01

Evidence has been found for tritium and neutron production in palladium and silicon stacks when pulsed with a high electric current. These palladium-silicon stacks consist of alternating layers of pressed palladium and silicon powder. A pulsed high electric current is thought to promote non equilibrium conditions important for tritium and neutron production. More than 2000 hours of neutron counting time has been accumulated in a underground, low background, environment with high efficiency counters (21%). Neutron emission has occurred as infrequent burst or as low level emission lasting for up to 20 hours. In eight of 30 cells, excess tritium greater than 3 sigma has been observed. In each of these measurements, with the powder system, the ratio of tritium detected to total integrated total neutrons inferred has been anomalously high. Recent cells have shown reproducible tritium generation at a level of about 0.5 nCi/hr. Several hydrogen and air control cells have been run with no anomalous excess tritium or neutron emission above background. A significant amount of the total palladium inventory (18%) has been checked for tritium contamination by three independent means. 12 refs., 6 figs., 2 tabs

Theory of neutron star magnetospheres

CERN Document Server

Curtis Michel, F

1990-01-01

An incomparable reference for astrophysicists studying pulsars and other kinds of neutron stars, "Theory of Neutron Star Magnetospheres" sums up two decades of astrophysical research. It provides in one volume the most important findings to date on this topic, essential to astrophysicists faced with a huge and widely scattered literature. F. Curtis Michel, who was among the first theorists to propose a neutron star model for radio pulsars, analyzes competing models of pulsars, radio emission models, winds and jets from pulsars, pulsating X-ray sources, gamma-ray burst sources, and other neutron-star driven phenomena. Although the book places primary emphasis on theoretical essentials, it also provides a considerable introduction to the observational data and its organization. Michel emphasizes the problems and uncertainties that have arisen in the research as well as the considerable progress that has been made to date.

Thermal neutron flux measurements using neutron-electron converters; Mesure de flux de neutrons thermiques avec des convertisseurs neutrons electrons

Energy Technology Data Exchange (ETDEWEB)

Le Meur, R; Lecomte, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-07-01

The operation of neutron-electron converters designed for measuring thermal neutron fluxes is examined. The principle is to produce short lived isotopes emitting beta particles, by activation, and to measure their activity not by extracting them from the reactor, but directly in the reactor using the emitted electrons to deflect the needle of a galvanometer placed outside the flux. After a theoretical study, the results of the measurements are presented; particular attention is paid to a new type of converter characterized by a layer structure. The converters are very useful for obtaining flux distributions with more than 10{sup 7} neutrons cm{sup -2}*sec{sup -1}. They work satisfactorily in pressurized carbon dioxide at 400 Celsius degrees. Some points still have to be cleared up however concerning interfering currents in the detectors and the behaviour of the dielectrics under irradiation. (authors) [French] On examine le fonctionnement de convertisseurs neutrons electrons destines a des mesures de flux de neutrons thermiques. Le principe est de former par activation des isotopes a periodes courtes et a emission beta et de mesurer leur activite non pas en les sortant du reacteur, mais directement en pile, utilisant les electrons emis pour faire devier l'aiguille d'un galvanometre place hors flux. Apres une etude theorique, on indique des resultats de mesures obtenus, en insistant particulierement sur un nouveau type de convertisseur, caracterise par sa structure stratifiee. Les convertisseurs sont tres interessants pour tracer, des cartes de flux a partir de 10{sup 7} neutrons cm{sup -2}*s{sup -1}. Ils sont utilisables pour des flux de 10{sup 14} neutrons cm{sup -2}*s{sup -1}. Ils fonctionnent correctement dans du gaz carbonique sous pression a 400 C. Des points restent cependant a eclaircir concernant les courants parasites dans les detecteurs et le comportement des dielectriques pendant leur irradiation. (auteur)

Neutron capture studies of {sup 206}Pb at a cold neutron beam

Energy Technology Data Exchange (ETDEWEB)

Schillebeeckx, P.; Kopecky, S.; Quetel, C.R.; Tresl, I.; Wynants, R. [Institute for Reference Materials and Measurements, European Commission, Joint Research Centre, Geel (Belgium); Belgya, T.; Szentmiklosi, L. [Institute for Energy Security and Environmental Safety, Centre for Energy Research, Budapest (Hungary); Borella, A. [Institute for Reference Materials and Measurements, European Commission, Joint Research Centre, Geel (Belgium); SCK CEN, Mol (Belgium); Mengoni, A. [Nuclear Data Section, International Atomic Energy Agency (IAEA), Wagramerstrasse 5, PO Box 100, Vienna (Austria); Agenzia Nazionale per le Nuove Tecnologie, l' Energia e lo Sviluppo Economico Sostenibile (ENEA), Bologna (Italy)

2013-11-15

Gamma-ray transitions following neutron capture in {sup 206}Pb have been studied at the cold neutron beam facility of the Budapest Neutron Centre using a metallic sample enriched in {sup 206}Pb and a natural lead nitrate powder pellet. The measurements were performed using a coaxial HPGe detector with Compton suppression. The observed {gamma} -rays have been incorporated into a decay scheme for neutron capture in {sup 206}Pb. Partial capture cross sections for {sup 206}Pb(n, {gamma}) at thermal energy have been derived relative to the cross section for the 1884 keV transition after neutron capture in {sup 14}N. From the average crossing sum a total thermal neutron capture cross section of 29{sup +2}{sub -1} mb was derived for the {sup 206}Pb(n, {gamma}) reaction. The thermal neutron capture cross section for {sup 206}Pb has been compared with contributions due to both direct capture and distant unbound s-wave resonances. From the same measurements a thermal neutron-induced capture cross section of (649 {+-} 14) mb was determined for the {sup 207}Pb(n, {gamma}) reaction. (orig.)

Reevaluation of the average prompt neutron emission multiplicity (nubar) values from fission of uranium and transuranium nuclides

International Nuclear Information System (INIS)

Holden, N.E.; Zucker, M.S.

1984-01-01

In response to a need of the safeguards community, we have begun an evaluation effort to upgrade the recommended values of the prompt neutron emission multiplicity distribution, P/sub nu/ and its average value, nubar. This paper will report on progress achieved thus far. The evaluation of the uranium, plutonium, americium and curium nuclide's nubar values will be presented. The recommended values will be given and discussed. 61 references

Study of associated gamma from niobium under 14. 9 MeV neutron bombardments

Energy Technology Data Exchange (ETDEWEB)

Zhou Hongyu; Yan Yiming; Fan Guoying; Lan Liqiac; Sun Suxu; Wang Qi; Hua Ming; Han Chongzhen; Liu Shuzhenn; Rong Yaning; and others

1989-02-01

The gamma ray spectra from niobium under 14.9 MeV neutron bombardments were measured by means of a pulsed /ital T/(/ital d/, /ital n/)/sup 4/He neutron source, associated particle method, Ge(Li) detector and time-of-flight technique at 7 angles between 30/degree/ and 140/degree/. 79 gamma lines were determined by a high resolution gamma spectrum analysis program, and reaction types and transition levels of 62 lines were roughly assigned. There were 40 ones of 79 lines, which were first found in reactions induced by neutrons. The differential cross sections of every gamma line at 7 angles were determined. It is shown that associated gamma ray emissions from this reaction are basically isotropic.

Beta-delayed neutron decay of $^{33}$Na

CERN Document Server

Radivojevic, Z; Caurier, E; Cederkäll, J; Courtin, S; Dessagne, P; Jokinen, A; Knipper, A; Le Scornet, G; Lyapin, V G; Miehé, C; Nowacki, F; Nummela, S; Oinonen, M; Poirier, E; Ramdhane, M; Trzaska, W H; Walter, G; Äystö, J

2002-01-01

Beta-delayed neutron decay of /sup 33/Na has been studied using the on-line mass separator ISOLDE. The delayed neutron spectra were measured by time-of-flight technique using fast scintillators. Two main neutron groups at 800(60) and 1020(80) keV were assigned to the /sup 33/Na decay, showing evidence for strong feeding of states at about 4 MeV in /sup 33/Mg. By simultaneous beta - gamma -n counting the delayed neutron emission probabilities P/sub 1n/ = 47(6)% and P /sub 2n/ = 13(3)% were determined. The half-life value for /sup 33 /Na, T/sub 1/2/ = 8.0(3) ms, was measured by three different techniques, one employing identifying gamma transitions and two employing beta and neutron counting. (21 refs).

Development of a new neutron multi-detector

International Nuclear Information System (INIS)

Senoville, Matthieu

2013-01-01

Beta-decay is a crucial tool in exploring the structure of exotic nuclei. The decay of neutron-rich nuclei is often followed by the emission of delayed neutrons. This work focuses on the R and -gamma discrimination was investigated using the FASTER digital electronics. First, the well-known charge comparison method was studied and performances superior to those obtained with standard analogue electronics were obtained. Different methods were also explored and compared quantitatively. Except for the method of Gatti and De Martini, charge comparison provides the best discrimination. In order to overcome the limitations of liquid scintillators for low-energy neutrons (En [fr

Anisotropy of neutron sources of Neutron Metrology Laboratory, IRD, Brazil; Anisotropia de fontes de neutrons do Laboratorio de Metrologia de Neutrons

Energy Technology Data Exchange (ETDEWEB)

Silva, A.C.F.; Silva, F.S.; Leite, S.P.; Creazolla, P.G; Patrão, K.C.S.; Fonseca, E.S. da; Fernandes, S.S.; Pereira, W.W., E-mail: Alexander.camargo@oi.com.br, E-mail: s.felippesouza@gmail.com, E-mail: karla@ird.gov.br, E-mail: walsan@ird.gov.br, E-mail: evaldo@ird.gov.br, E-mail: simonesilvafernandes@gmail.com, E-mail: prycyllacreazolla@gmail.com, E-mail: leitesprk@gmail.com [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Laboratorio Nacional de Metrologia; Fundação Técnico Educacional Souza Marques (FTESM), Rio de Janeiro, RJ (Brazil)

2017-11-01

The anisotropy measurements have as main objective to define the emission of the radiation by different angles of an encapsulated neutron source. The measurements were performed using a Long Accuracy Counter (PLC) Detector in the Low Dispersion Room of the LNMRI / IRD with different neutron sources. Each measurement was made using a support for the source, emulated through an arduino system to rotate it. The carrier is marked with a variation of 5 °, ranging from 0 ° to 360 °, for the work in question only half, 0 ° to 180 ° is used for a total of nineteen steps. In this paper three sources of {sup 241}AmBe (α, n) 5.92 GBq (16 Ci) were used, neutron sources having the following dimensions: 105 mm in height and 31 mm in diameter. The PLC was positioned at a distance of 2 meters from the neutron source and has a radius of 15 cm for the detection area. The anisotropy factor of the {sup 241}AmBe source was 17%. The results in this work will focus mainly on the area of radioprotection and studies that will improve the process of routine measurements in laboratories and instrument calibrations. (author)

Study and building of a detection array for delayed neutrons: TONNERRE; Etude et realisation d`un ensemble de detection pour neutrons retardes: TONNERRE

Energy Technology Data Exchange (ETDEWEB)

Martin, Thierry [Lab. de Physique Corpusculaire, Caen Univ., 14 - Caen (France)

1998-11-09

This work has been undertaken within a French-Romanian collaboration in order to build a high efficiency detector array for delayed neutrons: barrel-shaped TONNERRE. Some neutron-rich nuclei decay through 1, 2 or 3 neutron emission after {beta}{sup -} decay. More exotic nuclei will be produced by SPIRAL at GANIL. An array with high efficiency and good resolution is then required. Thirty two BC400 plastic scintillators (160 x 20 x 4 cm{sup 3}) allow us to get the time of flight neutron spectra. They are bent for uniform flight path and viewed by a photomultiplier tube at both ends. Simulations have allowed to establish scintillator size and to minimize light attenuation. Intrinsic efficiency and crosstalk have been measured with {sup 252}Cf and compared to GEANT. 1 to 5 MeV neutrons are detected with good timing and position properties. Other counters will be built for neutrons from 300 keV to 1 MeV. Planned to run at several particle accelerators (GANIL, CERN, and others), TONNERRE is modular and many geometries are possible. (author) 48 refs., 78 figs., 20 tabs.

Procedures for measurement of anisotropy factor of neutron sources

International Nuclear Information System (INIS)

Creazolla, P.G.; Camargo, A.; Astuto, A.; Silva, F.; Pereira, W.W.

2017-01-01

Radioisotope sources of neutrons allow the production of reference fields for calibration of neutron measurement devices for radioprotection and analysis purposes. When the emission rate of these sources is isotropic, no correction is necessary. However, variations in the source capsule material and variations in the concentration of the emitting material may produce differences in its neutron emission rate relative to the source axis, this effect is called anisotropy. A proposed procedure for measuring the anisotropy factor of the sources belonging to the IRD/LNMRI/LN Neutron Metrology Laboratory using a Precision Long Counter (PLC) detector will be presented

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Neutron activation analysis: Modelling studies to improve the neutron flux of Americium-Beryllium source

Energy Technology Data Exchange (ETDEWEB)

Didi, Abdessamad; Dadouch, Ahmed; Tajmouati, Jaouad; Bekkouri, Hassane [Advanced Technology and Integration System, Dept. of Physics, Faculty of Science Dhar Mehraz, University Sidi Mohamed Ben Abdellah, Fez (Morocco); Jai, Otman [Laboratory of Radiation and Nuclear Systems, Dept. of Physics, Faculty of Sciences, Tetouan (Morocco)

2017-06-15

Americium–beryllium (Am-Be; n, γ) is a neutron emitting source used in various research fields such as chemistry, physics, geology, archaeology, medicine, and environmental monitoring, as well as in the forensic sciences. It is a mobile source of neutron activity (20 Ci), yielding a small thermal neutron flux that is water moderated. The aim of this study is to develop a model to increase the neutron thermal flux of a source such as Am-Be. This study achieved multiple advantageous results: primarily, it will help us perform neutron activation analysis. Next, it will give us the opportunity to produce radio-elements with short half-lives. Am-Be single and multisource (5 sources) experiments were performed within an irradiation facility with a paraffin moderator. The resulting models mainly increase the thermal neutron flux compared to the traditional method with water moderator.

Neutron scattering studies in the actinide region

International Nuclear Information System (INIS)

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

1991-08-01

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

MODELS OF KILONOVA/MACRONOVA EMISSION FROM BLACK HOLE–NEUTRON STAR MERGERS

International Nuclear Information System (INIS)

Kawaguchi, Kyohei; Shibata, Masaru; Kyutoku, Koutarou; Tanaka, Masaomi

2016-01-01

Black hole–neutron star (BH–NS) mergers are among the most promising gravitational-wave sources for ground-based detectors, and gravitational waves from BH–NS mergers are expected to be detected in the next few years. The simultaneous detection of electromagnetic counterparts with gravitational waves would provide rich information about merger events. Among the possible electromagnetic counterparts from BH–NS mergers is the so-called kilonova/macronova, emission powered by the decay of radioactive r-process nuclei, which is one of the best targets for follow-up observations. We derive fitting formulas for the mass and the velocity of ejecta from a generic BH–NS merger based on recently performed numerical-relativity simulations. We combine these fitting formulas with a new semi-analytic model for a BH–NS kilonova/macronova lightcurve, which reproduces the results of radiation-transfer simulations. Specifically, the semi-analytic model reproduces the results of each band magnitude obtained by the previous radiation-transfer simulations within ∼1 mag. By using this semi-analytic model we found that, at 400 Mpc, the kilonova/macronova is as bright as 22–24 mag for cases with a small chirp mass and a high black hole spin, and >28 mag for a large chirp mass and a low black hole spin. We also apply our model to GRB 130603B as an illustration, and show that a BH–NS merger with a rapidly spinning black hole and a large neutron star radius is favored.

Neutron production and ion beam generation in plasma focus devices

International Nuclear Information System (INIS)

Steinmetz, K.

1980-01-01

Concerning the physical processes leading to neutron emission, a clearer situation has been achieved compared to the state at the start of this work. The general discussion will realize that the whole experimental data cannot be described consistently by the predictions of either the beam-target model or the quasi-thermonuclear fusion model, although many questions about the neutron production properties have been solved. In particular the neutron fluence anisotropy is found to be a property basically related to the existence of fast ions escaping axially out of the pinch region. The requirements to explain broad radial neutron energy spectra, long emission times, and energetic but not spatial emission anisotropies suggest a kind of particle trapping in the main source region. (orig./HT)

Enhancing neutron beam production with a convoluted moderator

Energy Technology Data Exchange (ETDEWEB)

Iverson, E.B., E-mail: iversoneb@ornl.gov [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Baxter, D.V. [Center for the Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408 (United States); Muhrer, G. [Lujan Neutron Scattering Center, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States); Ansell, S.; Dalgliesh, R. [ISIS Facility, Rutherford Appleton Laboratory, Chilton (United Kingdom); Gallmeier, F.X. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Kaiser, H. [Center for the Exploration of Energy and Matter, Indiana University, Bloomington, IN 47408 (United States); Lu, W. [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2014-10-21

We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally enhanced neutron beam source, improving beam emission over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.

Pre-equilibrium emission and nuclear level densities in neutron induced reactions on Fe, Cr and Ni isotopes

International Nuclear Information System (INIS)

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

1989-01-01

The experimentally well known (n,p), (n,α) and (n,2n) reaction excitation functions, from threshold to 20 MeV incident energy, and neutron, proton and alpha-particle emission spectra at 14.8 MeV from Fe, Cr and Ni isotopes are calculated in the frame of a generalized Geometry-Dependent-Hybrid pre-equilibrium emission model, including angular momentum and parity conservation and alpha-particle emission, 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 incident orbital momenta, has been evidenced. Higher orbital momenta involved also in the emergent channels of this process are suggested by calculations of the residual nuclei level populations. Finally, the unitary account of the (n, p) and (n, 2n) reaction excitation functions for Fe, Cr and Ni isotopes has allowed the proper establishment of the limits of the transition excitation range between the two different nuclear level density models used at medium and higher excitation energies, respectively. (author). 83 refs, 15 figs

Neutron generator (HIRRAC) and dosimetry study.

Science.gov (United States)

Endo, S; Hoshi, M; Takada, J; Tauchi, H; Matsuura, S; Takeoka, S; Kitagawa, K; Suga, S; Komatsu, K

1999-12-01

Dosimetry studies have been made for neutrons from a neutron generator at Hiroshima University (HIRRAC) which is designed for radiobiological research. Neutrons in an energy range from 0.07 to 2.7 MeV are available for biological irradiations. The produced neutron energies were measured and evaluated by a 3He-gas proportional counter. Energy spread was made certain to be small enough for radiobiological studies. Dose evaluations were performed by two different methods, namely use of tissue equivalent paired ionization chambers and activation of method with indium foils. Moreover, energy deposition spectra in small targets of tissue equivalent materials, so-called lineal energy spectrum, were also measured and are discussed. Specifications for biological irradiation are presented in terms of monoenergetic beam conditions, dose rates and deposited energy spectra.

In vitro and in vivo studies in boron neutron capture therapy of malignant melanoma

International Nuclear Information System (INIS)

Allen, B.J.

1982-01-01

A multidisciplinary research project in boron neutron capture therapy of malignant melanoma is under consideration by the Australian Atomic Energy Commission. This paper reviews the biochemistry of melanoma and the properties of some melanoma-affined radiopharmaceuticals and their boron analogues. Human cell lines are being used for in vitro tests of uptake and incorporation of some of these compounds, and selected lines will then be implanted in nude mice for in vivo distribution studies. The fidelity of human melanoma xenografts in nude mice has been well studied, and results are reviewed in this paper. Boron concentration will be measured directly by plasma arc emission spectroscopy or liquid scintillation counting with 14 C-labelled boron analogues. Track-etch techniques will be used for the microscopic determination of boron in tumor sections. Neutron irradiation and radiobiology experiments are outlined

20070607 NATO Advanced Study Institute on the Electromagnetic Spectrum of Neutron Stars Marmaris, Turkey 07 - 18 Jun 2004 2004 marmaris20040607 TR 20040618

CERN Document Server

Baykal, Altan; Inam, Sitki C; Grebenev, Sergei

2005-01-01

Neutron stars hold a central place in astrophysics, not only because they are made up of the most extreme states of the condensed matter, but also because they are, along with white dwarfs and black holes, one of the stable configurations that stars reach at the end of stellar evolution. Neutron stars posses the highest rotation rates and strongest magnetic fields among all stars. They radiate prolifically, in high energy electromagnetic radiation and in the radio band. This book is devoted to the selected lectures presented in the 6th NATO-ASI series entitled "The Electromagnetic Spectrum of Neutron Stars" in Marmaris, Turkey, on 7-18 June 2004. This ASI is devoted to the spectral properties of neutron stars. Spectral observations of neutron stars help us to understand the magnetospheric emission processes of isolated radio pulsars and the emission processes of accreting neutron stars. This volume includes spectral information from the neutron stars in broadest sense, namely neutrino and gravitational radiat...

Improved Fission Neutron Data Base for Active Interrogation of Actinides

Energy Technology Data Exchange (ETDEWEB)

Pozzi, Sara; Czirr, J. Bart; Haight, Robert; Kovash, Michael; Tsvetkov, Pavel

2013-11-06

This project will develop an innovative neutron detection system for active interrogation measurements. Many active interrogation methods to detect fissionable material are based on the detection of neutrons from fission induced by fast neutrons or high-energy gamma rays. The energy spectrum of the fission neutrons provides data to identify the fissionable isotopes and materials such as shielding between the fissionable material and the detector. The proposed path for the project is as follows. First, the team will develop new neutron detection systems and algorithms by Monte Carlo simulations and bench-top experiments. Next, They will characterize and calibrate detection systems both with monoenergetic and white neutron sources. Finally, high-fidelity measurements of neutron emission from fissions induced by fast neutrons will be performed. Several existing fission chambers containing U-235, Pu-239, U-238, or Th-232 will be used to measure the neutron-induced fission neutron emission spectra. The challenge for making confident measurements is the detection of neutrons in the energy ranges of 0.01 – 1 MeV and above 8 MeV, regions where the basic data on the neutron energy spectrum emitted from fission is least well known. In addition, improvements in the specificity of neutron detectors are required throughout the complete energy range: they must be able to clearly distinguish neutrons from other radiations, in particular gamma rays and cosmic rays. The team believes that all of these challenges can be addressed successfully with emerging technologies under development by this collaboration. In particular, the collaboration will address the area of fission neutron emission spectra for isotopes of interest in the advanced fuel cycle initiative (AFCI).

Hydrogen content in Zircaloy-IV by neutron emissions

International Nuclear Information System (INIS)

Granada, J.R.

1991-01-01

The feasibility of using thermal neutron transmission techniques to determine the initial hydrogen content in Zry-IV is discussed in this work. The usual conditions of very low H concentration (∼ 10-20 ppm in weight) in the alloy, require a high degree of accuracy in the relevant cross sections in order to obtain reliable values of that concentration from the measured transmission spectra. Total cross sections corresponding to the metallic alloy and to hydrogen in that matrix were evaluated using interaction models developed in this Laboratory, for neutrons covering the range from subthermal up to epithermal energies. The sensitivity of this method as a function of neutron energy is discussed, and an optimized and self consistent procedure for data analysis after a transmission experiment is proposed. (Author) [es

RE-EVALUATION OF THE NEUTRON EMISSION FROM THE SOLAR FLARE OF 2005 SEPTEMBER 7, DETECTED BY THE SOLAR NEUTRON TELESCOPE AT SIERRA NEGRA

Energy Technology Data Exchange (ETDEWEB)

González, L. X. [SCiESMEX, Instituto de Geofísica Unidad Michoacán, Universidad Nacional Autónoma de México, 58190, Morelia, Michoacán (Mexico); Valdés-Galicia, J. F.; Musalem, O.; Hurtado, A. [Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, 04510, D. F. Mexico (Mexico); Sánchez, F. [Instituto de Tecnologías en Detección de Astropartículas, Comisión Nacional de Energía Atómica, 1429, Buenos Aires (Argentina); Muraki, Y.; Sako, T.; Matsubara, Y.; Nagai, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Watanabe, K. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai, chuo-ku, Sagamihara 252-5210 (Japan); Shibata, S. [College of Engineering, Chubu University, Kasugai, Aichi 487-8501 (Japan); Sakai, T. [College of Industrial Technologies, Nihon University, Narashino 275-0005 (Japan)

2015-12-01

The X17.0 solar flare of 2005 September 7 released high-energy neutrons that were detected by the Solar Neutron Telescope (SNT) at Sierra Negra, Mexico. In three separate and independent studies of this solar neutron event, several of its unique characteristics were studied; in particular, a power-law energy spectra was estimated. In this paper, we present an alternative analysis, based on improved numerical simulations of the detector using GEANT4, and a different technique for processing the SNT data. The results indicate that the spectral index that best fits the neutron flux is around 3, in agreement with previous works. Based on the numerically calculated neutron energy deposition on the SNT, we confirm that the detected neutrons might have reached an energy of 1 GeV, which implies that 10 GeV protons were probably produced; these could not be observed at Earth, as their parent flare was an east limb event.

Neutron spectroscopy for confinement studies

International Nuclear Information System (INIS)

Zorn, R.

2010-01-01

Neutron spectroscopy is an important method for the study of microscopic dynamics because it captures the spatial as well as the temporal aspects of the atomic or molecular motion. In this article techniques will be presented which are of special importance for the study of confined systems. Many of these are based on the fact that neutron scattering is isotope-dependent. Possible sources of systematic errors in measurements of confined systems will be pointed out. (author)

Inversion methods for analysis of neutron brightness measurements in tokamaks

International Nuclear Information System (INIS)

Gorini, G.; Gottardi, N.

1990-02-01

The problem of determining neutron emissivity from neutron brightness measurements in magnetic fusion plasmas is addressed. In the case of two-dimensional measurements with two orthogonal cameras, a complete, tomographic analysis of the data can in principle be performed. The results depend critically on the accuracy of the measurements and alternative solutions can be sought under the assumption of a known emissivity topology (Generalized Abel Inversion). In this work, neutron brightness data from the JET tokamak have been studied with both methods. We find that with the present experimental uncertainty (levels 10-20%) the Abel inversion method works best, while two-dimensional information cannot in general be deduced. This is confirmed by studies of the error propagation in the inversion using artificial data, which are also presented here. An important application of emissivity profile information is the determination of the plasma deuterium temperature profile, T D (R). Results are presented here from the analysis of JET data and the errors in T D (R) are discussed in some detail. It is found that, for typical JET plasma conditions, the dominant source of uncertainty arises from the high plasma impurity level and the fact that it is poorly known; these problems can be expected to be remedied and neutron brightness measurements would be expected to be very effective (especially in high density plasmas) as a T D (R) diagnostics. (author)

Neutron stimulated emission computed tomography applied to the assessment of calcium deposition due to the presence of microcalcifications associated with breast cancer; Tomografia computadorizada de emissao estimulada por neutrons aplicada para avaliar a deposicao de calcio devido a presenca de microcalcificacoes associadas ao cancer de mama

Energy Technology Data Exchange (ETDEWEB)

Viana, Rodrigo S.S.; Yoriyaz, Helio [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, (SP) (Brazil)

2011-07-01

In this paper we presented an application of the Neutron Stimulated Emission Computed Tomography (NSECT), which uses a thin beam of fast neutrons to stimulate stable nuclei in a sample, emitting characteristic gamma radiation. The photon energy is unique and it is used to identify the emitting nuclei. This technique was applied for evaluating the calcium isotopic composition changing due to the development of breast microcalcifications. A particular situation was simulated in which clustered microcalcifications were modeled with diameters less than 1.40 mm. In this case, neutron beam breast spectroscopy was successful in detecting the counting changes in the photon emission spectra for energies, which are characteristics of 4{sup 0C}a isotope in a low deposited dose rate. (author)

Study of a transportable neutron radiography system

International Nuclear Information System (INIS)

Souza, S.N.A. de.

1991-05-01

This work presents a study a transportable neutron radiography system for a 185 GBq 241 Am-Be (α, η) source with a neutron yield roughly 1,25 x 10 7 n/s. Studies about moderation, collimation and shielding are showed. In these studies, a calculation using Transport Theory was carried out by means of transport codes ANISN and DOT (3.5). Objectives were: to obtain a maximum and more homogeneous thermal neutron flux in the collimator outlet to the image plain, and an adequate radiation shielding to attend radiological protection rules. With the presented collimator, it was possible to obtain for the thermal neutron flux, at the collimator outlet and next to the image plain, a L/D ratio of 14, for neutron fluxes up to 4,09 x 10 2 n.cm -2 .s -1 . Considering the low intensity of the source, it is a good value. Studies have also been carried out for L/D ratios of 22 and 30, giving thermal neutron fluxes at the image plain of 1,27 x 10 2 n.cm -2 .s -1 and 2,65 x 10 2 n.cm -2 .s -1 , respectively. (author). 30 refs, 39 figs, 9 tabs

Investigation of the neutron production phases of a large plasma focus device

International Nuclear Information System (INIS)

Hayd, A.; Maurer, M.; Meinke, P.; Herold, H.; Bertalot, L.; Deutsch, R.; Grauf, W.; Jaeger, U.; Kaeppeler, H.J.; Lepper, F.; Oppenlaender, T.; Schmidt, H.; Schmidt, R.; Schwarz, J.; Schwoerer, K.; Shakhatre, M.

1982-09-01

Plasma dynamic behavior and neutron production in large focus devices with pinch currents of approximately 1 MA have been studied with theoretical as well as experimental methods. For treating turbulent plasma motion, a hybrid code based on the analytical computer algorithm REDUCE was developed. Experimental diagnostics include schlieren photographs, reaction proton localization with pinhole cameras and neutron measurements with Ag-counters and scintillators. Calculated and measured data concern the 280 kJ, 60 kV operational mode of the POSEIDON plasma focus. It is shown that for large pinch currents ( > 500 kA), neutron emission also appears before m = 0 onset in the intermediate phase. This part of the neutron production becomes predominant for very large currents. The lifetime of this intermediate phase strongly increases with increasing current. According to theory, the late phase of the focus is governed by strong turbulence phenomena. The lifetime of the turbulence packets is approximately 150 ns and seems to explain the long lasting neutron emission in this phase. (orig.)

Summary Report of 1st Research Coordination Meeting on Development of Reference Database for Beta-delayed Neutron Emission

International Nuclear Information System (INIS)

Dillmann, Iris; Dimitriou, Paraskevi; Singh, Balraj

2014-03-01

A summary is given of the 1st Research Coordination Meeting of the new IAEA Coordinated Research Project (CRP) on Development of a Reference Database for Beta-delayed neutron emission data. Participants presented their work, reviewed the current status of the field with regards to individual precursors and aggregate data, and discussed the scope of the work to be undertaken. A list of priorities and task assignments was produced. (author)

Filtered epithermal quasi-monoenergetic neutron beams at research reactor facilities.

Science.gov (United States)

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

2015-03-01

Filtered neutron techniques were applied to produce quasi-monoenergetic neutron beams in the energy range of 1.5-133keV at research reactors. A simulation study was performed to characterize the filter components and transmitted beam lines. The filtered beams were characterized in terms of the optimal thickness of the main and additive components. The filtered neutron beams had high purity and intensity, with low contamination from the accompanying thermal emission, fast neutrons and γ-rays. A computer code named "QMNB" was developed in the "MATLAB" programming language to perform the required calculations. Copyright © 2014 Elsevier Ltd. All rights reserved.

Neutron emission in peripheral heavy ion collisions in the system Ho + Ne

International Nuclear Information System (INIS)

Orf, H.

1983-01-01

In the present thesis peripheral collision processes in the system 165 Ho + 20 Ne were studied. The measurement of the neutrons in coincidence with projectile-like fragments should answer the central question whether at incident energies of approx.=15 respectively 20 MeV/nucleon a thermal equilibrium is reached yet during the interaction time. The analysis of the neutron spectra resulted that the largest part of the neutrons was evaporated just after reaching the thermal equilibrium from the fragments fully accelerated in the Coulomb field. About 10% of the neutrons however were emitted during the interaction time and showed the same spectral shape as the pre-equilibrium neutrons in central collisions. A further hint for pre-equilibrium effects yielded the result that the temperatures of the projectile-like fragments were larger than those of the target-like. This could be explained for quasi-elastic processes by assuming a fluctuation in the partition of the excitation energy. For deep inelastic processes such explanation wasn't possible. At neon fragment with low energy loss furthermore direct processes could be observed in which the projectile has picked up a neutron from the target nucleus without excitation of it. From the known width of the observed state in 21 Ne the reaction time could be fixed to values lower than 6x10 -21 s. (HSI) [de

Neutron measurements from beam-target reactions at the ELISE neutral beam test facility

International Nuclear Information System (INIS)

Xufei, X.; Fan, T.; Nocente, M.; Gorini, G.; Bonomo, F.; Franzen, P.; Fröschle, M.; Grosso, G.; Tardocchi, M.; Grünauer, F.; Pasqualotto, R.

2014-01-01

Measurements of 2.5 MeV neutron emission from beam-target reactions performed at the ELISE neutral beam test facility are presented in this paper. The measurements are used to study the penetration of a deuterium beam in a copper dump, based on the observation of the time evolution of the neutron counting rate from beam-target reactions with a liquid scintillation detector. A calculation based on a local mixing model of deuterium deposition in the target up to a concentration of 20% at saturation is used to evaluate the expected neutron yield for comparison with data. The results are of relevance to understand neutron emission associated to beam penetration in a solid target, with applications to diagnostic systems for the SPIDER and MITICA Neutral Beam Injection prototypes

Energy dependence of the asymmetry-violated space parity of fragment emission from the 239PU fission by slow polarized neutrons

International Nuclear Information System (INIS)

Val'skij, G.V.; Zvezdkina, T.K.; Nikolaev, D.V.; Petrova, V.I.; Petrov, G.A.; Petukhov, A.K.; Pleva, Yu.S.; Tyukavin, V.A.

1982-01-01

Asymmetry violating parity in the fragment emission from fission of 239 Pu induced by polarized neutrons at six energy points in the interval 0.01 <= E <0.3 eV was measured. The results providing with an evidence in favour of the hypothesis that the asymmetry is independent on energy are discussed in view of the existing theoretical picture

Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

International Nuclear Information System (INIS)

Overbury, Steven H.; Coates, Leighton; Herwig, Kenneth W.; Kidder, Michelle

2011-01-01

This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

Energy Technology Data Exchange (ETDEWEB)

Overbury, Steven {Steve} H [ORNL; Coates, Leighton [ORNL; Herwig, Kenneth W [ORNL; Kidder, Michelle [ORNL

2011-10-01

This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

Conditional probability distribution associated to the E-M image reconstruction algorithm for neutron stimulated emission tomography

International Nuclear Information System (INIS)

Viana, R.S.; Yoriyaz, H.; Santos, A.

2011-01-01

The Expectation-Maximization (E-M) algorithm is an iterative computational method for maximum likelihood (M-L) estimates, useful in a variety of incomplete-data problems. Due to its stochastic nature, one of the most relevant applications of E-M algorithm is the reconstruction of emission tomography images. In this paper, the statistical formulation of the E-M algorithm was applied to the in vivo spectrographic imaging of stable isotopes called Neutron Stimulated Emission Computed Tomography (NSECT). In the process of E-M algorithm iteration, the conditional probability distribution plays a very important role to achieve high quality image. This present work proposes an alternative methodology for the generation of the conditional probability distribution associated to the E-M reconstruction algorithm, using the Monte Carlo code MCNP5 and with the application of the reciprocity theorem. (author)

Conditional probability distribution associated to the E-M image reconstruction algorithm for neutron stimulated emission tomography

Energy Technology Data Exchange (ETDEWEB)

Viana, R.S.; Yoriyaz, H.; Santos, A., E-mail: rodrigossviana@gmail.com, E-mail: hyoriyaz@ipen.br, E-mail: asantos@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2011-07-01

The Expectation-Maximization (E-M) algorithm is an iterative computational method for maximum likelihood (M-L) estimates, useful in a variety of incomplete-data problems. Due to its stochastic nature, one of the most relevant applications of E-M algorithm is the reconstruction of emission tomography images. In this paper, the statistical formulation of the E-M algorithm was applied to the in vivo spectrographic imaging of stable isotopes called Neutron Stimulated Emission Computed Tomography (NSECT). In the process of E-M algorithm iteration, the conditional probability distribution plays a very important role to achieve high quality image. This present work proposes an alternative methodology for the generation of the conditional probability distribution associated to the E-M reconstruction algorithm, using the Monte Carlo code MCNP5 and with the application of the reciprocity theorem. (author)

Recent development in magnetic neutron scattering studies

International Nuclear Information System (INIS)

Endoh, Yasuo

1993-01-01

Neutron scattering results contain many new concepts in modern magnetism. We review here the most recent neutron magnetic scattering studies from so called '214' copper oxide lamellar materials, because a number of important developments in magnetism are condensed in this novel subject. We show that neutron scattering has played crucial role in our understanding of modern magnetism. (author)

Conceptual design, neutronic and radioprotection study of a fast neutron irradiation station at SINQ

International Nuclear Information System (INIS)

Zanini, L.; Baluc, N.; Simone, A. De; Eichler, R.; Joray, S.; Manfrin, E.; Pouchon, M.; Rabaioli, S.; Schumann, D.; Welte, J.; Zhernosekov, K.

2011-12-01

This comprehensive, illustrated report by the Paul Scherrer Institute PSI in Switzerland documents the proposals concerning the conceptual design, neutronic and radioprotection study of a fast neutron irradiation station at the PSI's Swiss Spallation Neutron Source SINQ facility. The need for fast neutron irradiation is discussed and the possibility of using SINQ as a fast neutron irradiation facility is considered. The production of isotopes, tracers and medical isotopes is discussed, as are fission and fusion reactor technologies. The characteristics of the neutron spectrum in SINQ are discussed. The neutronic and radioprotection calculations for an irradiation station at SINQ are looked at in detail and extensive examples of work done and results obtained are presented and discussed. Radioprotection issues are also looked at. Further contributions in the report cover the hot/cold irradiation station in the SINQ target. An appendix provides detailed drawings of the facility's pneumatic delivery system

Comparison study on in-core neutron detector for online neutron flux mapping of research and power reactor

International Nuclear Information System (INIS)

Zareen Khan Abdul Jalil Khan; Mohd Idris Taib; Izhar Abu Husin; Nurfarhana Ayuni

2010-01-01

This paper presents the comparison study on In-Core neutron detector using for online flux mapping of Research and Power reactor. Technical description of in-core neutron also taken into consideration to identify the different characterization of neutron detector and describe on Self Power neutron detector (SPND) for online neutron flux mapping. Able to provide information on the neutron flux distribution and understand how in-core neutron detector are being used in nuclear power plant including to enable to state the principles of neutron detector. (author)

International key comparison of measurements of neutron source emission rate (1999-2005): CCRI(III)-K9.AmBe

Energy Technology Data Exchange (ETDEWEB)

Roberts, N.J.; Jones, L.N. [National Physical Laboratory (NPL), Teddington, (United Kingdom); Wang, Z.; Liu, Y.; Wang, Q.; Chen, X.; Luo, H.; Rong, C. [China Institute of Atomic Energy (CIAE), Beijing (China); Kralik, M. [Czech Metrology Institute (CMI), Praha, (Czech Republic); Park, H.; Choi, K.O. [Korea Research Institute of Standards and Science (KRISS), Daejeon, (Korea, Republic of); Pereira, W.W.; Da Fonseca, E.S. [National Laboratory of Metrology of Ionizing Radiation (LNMRI), Rio de Janeiro, (Brazil); Cassette, P. [Laboratoire National Henri Becquerel (LNE-LNHB), Paris, (France); Dewey, M.S. [National Institute of Standards and Technology (NIST), Gaithersburg, MD, (United States); Moiseev, N.N.; Kharitonov, I.A. [D I Mendeleyev Institute for Metrology (VNIIM), St Petersburg, (Russian Federation)

2011-07-01

Section III (neutron measurements) of the Comite Consultatif des Rayonnements Ionisants, CCRI, conducted a key comparison of primary measurements of the neutron emission rate of an {sup 241}Am-Be({alpha},n) radionuclide source. A single {sup 241}Am-Be({alpha},n) source was circulated to all the participants between 1999 and 2005. Eight laboratories participated - the CIAE (China), CMI (Czech Republic), KRISS (Republic of Korea), LNMRI (Brazil), LNE-LNHB (France), NIST (USA), NPL (UK) and the VNIIM (Russian Federation) - with the NPL making their measurements at the start and repeating them near the end of the exercise to verify the stability of the source. Each laboratory reported the emission rate into 4{pi} sr together with a detailed uncertainty budget. All participants used the manganese bath technique, with the VNIIM also making measurements using an associated particle technique. The CMI, KRISS, VNIIM, and later the NPL, also measured the anisotropy of the source although this was not a formal part of the comparison. The first draft report was released in May 2006 and having been discussed and modified by the participants and subsequently reviewed by the CCRI(III), the present paper is now the final report of the comparison. (authors)

Statistical effects in beta-delayed neutron emission from fission product nuclides

International Nuclear Information System (INIS)

McElroy, R.D. Jr.

1986-01-01

The delayed neutron spectra for the precursors Rb-93, 94, 95, 96, 97 and Cs-145 were measured by use of the on-line isotope separator facility TRISTAN and a time-of-flight (TOF) spectrometer. Flight paths were used that provided, for energies below 70 keV, a FWHM energy resolution between 2 and 4 percent. Each spectrum showed discrete neutron peaks below 156 keV, with as many as 26 in the Rb-95 spectra. Level densities near the neutron binding energy in the neutron-emitting nuclide were deduced using a missing-level indicator based on a Porter-Thomas distribution of neutron peak intensities. The resulting level density data were compared to the predictions of the Gilbert and Cameron formulism and to those of Dilg, Schantl, Vonach and Uhl. Comparisons were made between the empirically-based level parameter a and the values predicted by each model for Sr-93, 94, 95, 97 and Ba-145. The two models appear, within the uncertainties, to be equally capable of describing these neutron-rich nuclides and equally as capable for them as they are for nuclides in the valley of beta stability. Measurements of the neutron strength function are sometimes possible with the present TOF system for neutron decays with competing neutron branches to levels in the grandchild nucleus. A value for the d-wave strength function of Sr-96 is found to be (4.2 +- 1.1)/10 4 . Improvements in the TOF system, allowing the measurement of the neutron strength function for the more general case, are discussed. 72 refs., 56 figs., 16 tabs

Neutron activation analysis: Modelling studies to improve the neutron flux of Americium–Beryllium source

Directory of Open Access Journals (Sweden)

Abdessamad Didi

2017-06-01

Full Text Available Americium–beryllium (Am-Be; n, γ is a neutron emitting source used in various research fields such as chemistry, physics, geology, archaeology, medicine, and environmental monitoring, as well as in the forensic sciences. It is a mobile source of neutron activity (20 Ci, yielding a small thermal neutron flux that is water moderated. The aim of this study is to develop a model to increase the neutron thermal flux of a source such as Am-Be. This study achieved multiple advantageous results: primarily, it will help us perform neutron activation analysis. Next, it will give us the opportunity to produce radio-elements with short half-lives. Am-Be single and multisource (5 sources experiments were performed within an irradiation facility with a paraffin moderator. The resulting models mainly increase the thermal neutron flux compared to the traditional method with water moderator.

New Beta-delayed Neutron Measurements in the Light-mass Fission Group

Energy Technology Data Exchange (ETDEWEB)

Agramunt, J. [Instituto de Física Corpuscular, CSIC-Univ. Valencia, Apdo. Correos 22085, E-46071 Valencia (Spain); García, A.R. [Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, E-28040 Madrid (Spain); Algora, A. [Instituto de Física Corpuscular, CSIC-Univ. Valencia, Apdo. Correos 22085, E-46071 Valencia (Spain); Äystö, J. [University of Jyväskylä, FI-40014 Jyväskyä (Finland); Caballero-Folch, R.; Calviño, F. [Secció d' Enginyeria Nuclear, Universitat Politécnica de Catalunya, E-08028 Barcelona (Spain); Cano-Ott, D. [Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, E-28040 Madrid (Spain); Cortés, G. [Secció d' Enginyeria Nuclear, Universitat Politécnica de Catalunya, E-08028 Barcelona (Spain); Domingo-Pardo, C. [Instituto de Física Corpuscular, CSIC-Univ. Valencia, Apdo. Correos 22085, E-46071 Valencia (Spain); Eronen, T. [University of Jyväskylä, FI-40014 Jyväskyä (Finland); Gelletly, W. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Gómez-Hornillos, M.B. [Secció d' Enginyeria Nuclear, Universitat Politécnica de Catalunya, E-08028 Barcelona (Spain); and others

2014-06-15

A new accurate determination of beta-delayed neutron emission probabilities from nuclei in the low mass region of the light fission group has been performed. The measurements were carried out using the BELEN 4π neutron counter at the IGISOL-JYFL mass separator in combination with a Penning trap. The new results significantly improve the uncertainties of neutron emission probabilities for {sup 91}Br, {sup 86}As, {sup 85}As, and {sup 85}Ge nuclei.

Introduction to neutron stars

Energy Technology Data Exchange (ETDEWEB)

Lattimer, James M. [Dept. of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)

2015-02-24

Neutron stars contain the densest form of matter in the present universe. General relativity and causality set important constraints to their compactness. In addition, analytic GR solutions are useful in understanding the relationships that exist among the maximum mass, radii, moments of inertia, and tidal Love numbers of neutron stars, all of which are accessible to observation. Some of these relations are independent of the underlying dense matter equation of state, while others are very sensitive to the equation of state. Recent observations of neutron stars from pulsar timing, quiescent X-ray emission from binaries, and Type I X-ray bursts can set important constraints on the structure of neutron stars and the underlying equation of state. In addition, measurements of thermal radiation from neutron stars has uncovered the possible existence of neutron and proton superfluidity/superconductivity in the core of a neutron star, as well as offering powerful evidence that typical neutron stars have significant crusts. These observations impose constraints on the existence of strange quark matter stars, and limit the possibility that abundant deconfined quark matter or hyperons exist in the cores of neutron stars.

Anisotropy of neutron sources of Neutron Metrology Laboratory, IRD, Brazil

International Nuclear Information System (INIS)

Silva, A.C.F.; Silva, F.S.; Leite, S.P.; Creazolla, P.G; Patrão, K.C.S.; Fonseca, E.S. da; Fernandes, S.S.; Pereira, W.W.

2017-01-01

The anisotropy measurements have as main objective to define the emission of the radiation by different angles of an encapsulated neutron source. The measurements were performed using a Long Accuracy Counter (PLC) Detector in the Low Dispersion Room of the LNMRI / IRD with different neutron sources. Each measurement was made using a support for the source, emulated through an arduino system to rotate it. The carrier is marked with a variation of 5 °, ranging from 0 ° to 360 °, for the work in question only half, 0 ° to 180 ° is used for a total of nineteen steps. In this paper three sources of "2"4"1AmBe (α, n) 5.92 GBq (16 Ci) were used, neutron sources having the following dimensions: 105 mm in height and 31 mm in diameter. The PLC was positioned at a distance of 2 meters from the neutron source and has a radius of 15 cm for the detection area. The anisotropy factor of the "2"4"1AmBe source was 17%. The results in this work will focus mainly on the area of radioprotection and studies that will improve the process of routine measurements in laboratories and instrument calibrations. (author)

The thin-foil magnetic proton recoil neutron spectrometer MPRu at JET

International Nuclear Information System (INIS)

Andersson Sunden, E.; Sjoestrand, H.; Conroy, S.; Ericsson, G.; Gatu Johnson, M.; Giacomelli, L.; Hellesen, C.; Hjalmarsson, A.; Ronchi, E.; Weiszflog, M.; Kaellne, J.; Gorini, G.; Tardocchi, M.; Combo, A.; Cruz, N.; Batista, A.; Pereira, R.; Fortuna, R.; Sousa, J.; Popovichev, S.

2009-01-01

Neutrons are produced in fusion energy experiments with both deuterium (D) and deuterium-tritium (DT) plasmas. Neutron spectroscopy is a valuable tool in the study of the underlying fuel ion populations. The magnetic proton recoil neutron spectrometer, originally installed at JET in 1996 for 14-MeV neutron measurements, has been upgraded, with the main aim of improving its signal-to-background ratio (S/B), making measurements of the 2.5-MeV neutron emission in D plasmas possible. The upgrade includes a new focal-plane detector, based on the phoswich technique and consequently less sensitive to background, and a new custom-designed digital data acquisition system based on transient recorder cards. Results from JET show that the upgraded MPRu can measure 2.5-MeV neutrons with S/B=5, an improvement by a factor of 50 compared with the original MPR. S/B of 2.8x10 4 in future DT experiments is estimated. The performance of the MPRu is exemplified with results from recent D plasma operations at JET, concerning both measurements with Ohmic, ion cyclotron resonance (ICRH) and neutral beam injection (NBI) plasma heating, as well as measurements of tritium burn-up neutrons. The upgraded instrument allows for 2.5-MeV neutron emission and deuterium ion temperature measurements in plasmas with low levels of tritium, a feature necessary for the ITER experiment.

Neutron stars, magnetic fields, and gravitational waves

International Nuclear Information System (INIS)

Lamb, F.K.

2001-01-01

The r-modes of rapidly spinning young neutron stars have recently attracted attention as a promising source of detectable gravitational radiation. These neutron stars are expected to have magnetic fields ∼ 10 12 G. The r-mode velocity perturbation causes differential motion of the fluid in the star; this is a kinematic effect. In addition, the radiation-reaction associated with emission of gravitational radiation by r-waves drives additional differential fluid motions; this is a dynamic effect. These differential fluid motions distort the magnetic fields of neutron stars and may therefore play an important role in determining the structure of neutron star magnetic fields. If the stellar field is ∼ 10 16 (Ω/Ω B ) G or stronger, the usual r-modes are no longer normal modes of the star; here Ω and Ω B are the angular velocities of the star and at which mass shedding occurs. Much weaker magnetic fields can prevent gravitational radiation from amplifying the r-modes or damp existing r-mode oscillations on a relatively short timescale by extracting energy from the modes faster than gravitational wave emission can pump energy into them. The onset of proton superconductivity in the cores of newly formed magnetic neutron stars typically increases the effect on the r-modes of the magnetic field in the core by many orders of magnitude. Once the core has become superconducting, magnetic fields of the order of 10 12 G or greater are usually sufficient to damp r-modes that have been excited by emission of gravitational radiation and to suppress any further emission. A rapid drop in the strength of r-mode gravitational radiation from young neutron stars may therefore signal the onset of superconductivity in the core and provide a lower bound on the strength of the magnetic field there. Hence, measurements of r-mode gravitational waves from newly formed neutron stars may provide valuable diagnostic information about magnetic field strengths, cooling processes, and the

Preclinical studies on gadolinium neutron capture therapy

International Nuclear Information System (INIS)

Akine, Yasuyuki

1994-01-01

Gadolinium neutron capture therapy is based on radiations (photons and electrons) produced in the tumor by a nuclear reaction between gadolinium and lower-energy neutrons. Studies with Chinese hamster cells have shown that the radiation effect resulting from gadolinium neutron capture reactions is mostly of low LET and that released electrons are the significant component in the over-all dose. Biological dosimetry revealed that the dose does not seem to increase in proportion to the gadolinium concentration, leading to a conclusion that there is a range of gadolinium concentrations most efficient for gadolinium neutron capture therapy. The in vivo studies with transplantable tumors in mice and rabbits have revealed that close contact between gadolinium and the cell is not necessarily required for cell inactivation and that gadolinium delivery selective to tumors is crucial. The results show that the potential of gadolinium neutron capture therapy as a therapeutic modality appears very promising. (author)

Neutron scattering studies of solid electrolytes

International Nuclear Information System (INIS)

Shapiro, S.M.

1976-01-01

The role which neutron scattering can play in determining the nature of the disorder and the conducting mechanism in the solid electrolytes is discussed. First, some of the general formalism for elastic and inelastic neutron scattering is reviewed, and the quantities which can be measured are pointed out. Then the application of neutron scattering to the studies of three different problems is examined; the anion disorder in the fluorite system, the dynamical behavior in beta-alumina, and the cation diffusion in αAgI are discussed. 8 figures

A study of television imaging system for fast neutron radiography

International Nuclear Information System (INIS)

Yoshii, Koji

1992-01-01

The neutron radiography with fast neutron beam is a very useful imaging technique for thicker objects, especially those composed of hydrogen-rich materials which are sometimes difficult to image by thermal neutron radiography. The fast neutron radiography has not been studied so much as the thermal neutron radiography. The fast neutron radiography has been studied at the fast neutron source reactor 'Yayoi' of the University of Tokyo built in Tokai-mura. The average neutron energy of the Yayoi is about 1 MeV, and the peak neutron flux at the core center is 0.8 x 10 12 at the maximum operating power of 2 kW. In the experiment on fast neutron radiography, a CR39 nuclear track detector has been used successfully. But in the Yayoi radiography procedure, about 24 hours were required for obtaining an imaging result. To get a prompt imaging result and a real-time imaging result, it is necessary to develop a fast neutron television system, and in this paper, a new fast neutron TV system is proposed. The main difference is the converter material sensitive to fast neutrons. The study on the fast neutron TV system was carried out by using the Baby Cyclotron of Japan Steel Works, and the good images were realized. (K.I.)

Neutron scattering studies on frustrated magnets

International Nuclear Information System (INIS)

Arima, Taka-hisa

2013-01-01

A lot of frustrated magnetic systems exhibit a nontrivial magnetic order, such as long-wavelength modulation, noncollinear, or noncoplanar order. The nontrivial order may pave the way for the novel magnetic function of matter. Neutron studies are necessary to determine the magnetic structures in the frustrated magnetic systems. In particular, spin-polarized neutron scattering is a useful technique for the investigation of the novel physical properties relevant to the nontrivial spin arrangement. Here some neutron studies on a multiferroic perovskite manganese oxide system are demonstrated as a typical case. The frustrated magnetic systems may also a playground of novel types of local magnetic excitations, which behave like particles in contrast to the magnetic waves. It is becoming a good challenge to study such particle-type magnetic excitations relevant to the magnetic frustration. (author)

New data on prefission neutrons

International Nuclear Information System (INIS)

Boikov, G.S.; Dmitriev, V.D.; Kudyaev, G.A.; Ostapenko, Yu.B.; Svirin, M.I.; Smirenkin, G.N.

1991-01-01

The spectra of neutrons emitted in fission of 232 Th, 235 U and 238 U induced by 2.9 and 14.7 MeV neutrons (below and above the chance fission threshold, respectively) were measured by the time-of-flight method. Two effects were observed in the prefission neutron spectra: the high-energy wing is related to the nonequilibrium mechanism of emission up to the well pronounced upper boundary of ε max = 8.5 MeV; in the lower-energy wing ε < 2 MeV, neutron yield exceeds conventional statistical model description. The latter effect was attributed to the fission process dynamics. (author). 18 refs, 3 figs, 2 tabs

Neutron angular distribution in a plasma focus obtained using nuclear track detectors.

Science.gov (United States)

Castillo-Mejía, F; Herrera, J J E; Rangel, J; Golzarri, J I; Espinosa, G

2002-01-01

The dense plasma focus (DPF) is a coaxial plasma gun in which a high-density, high-temperature plasma is obtained in a focused column for a few nanoseconds. When the filling gas is deuterium, neutrons can be obtained from fusion reactions. These are partially due to a beam of deuterons which are accelerated against the background hot plasma by large electric fields originating from plasma instabilities. Due to a beam-target effect, the angular distribution of the neutron emission is anisotropic, peaked in the forward direction along the axis of the gun. The purpose of this work is to illustrate the use of CR-39 nuclear track detectors as a diagnostic tool in the determination of the time-integrated neutron angular distribution. For the case studied in this work, neutron emission is found to have a 70% contribution from isotropic radiation and a 30% contribution from anisotropic radiation.

Neutron diffraction studies of glasses

International Nuclear Information System (INIS)

Wright, A.C.

1987-01-01

A survey is given of the application of neutron diffraction to structural studies of oxide and halide glasses. As with crystalline materials, neutron and X-ray diffraction are the major structural probes for glasses and other amorphous solids, particularly in respect of intermediate range order. The glasses discussed mostly have structures which are dominated by a network in which the bonding is predominantly covalent. The examples discussed demonstrate the power of the neutron diffraction technique in the investigation of the structures of inorganic glasses. The best modern diffraction experiments are capable of providing accurate data with high real space resolution, which if used correctly, are an extremely fine filter for the various structural models proposed in the literature. 42 refs

Studies on biological macromolecules by neutron inelastic scattering

International Nuclear Information System (INIS)

Fujiwara, Satoru; Nakagawa, Hiroshi

2013-01-01

Neutron inelastic scattering techniques, including quasielastic and elastic incoherent neutron scattering, provide unique tools to directly measure the protein dynamics at a picosecond time scale. Since the protein dynamics at this time scale is indispensable to the protein functions, elucidation of the protein dynamics is indispensable for ultimate understanding of the protein functions. There are two complementary directions of the protein dynamics studies: one is to explore the physical basis of the protein dynamics using 'model' proteins, and the other is more biology-oriented. Examples of the studies on the protein dynamics with neutron inelastic scattering are described. The examples of the studies in the former direction include the studies on the dynamical transitions of the proteins, the relationship between the protein dynamics and the hydration water dynamics, and combined analysis of the protein dynamics with molecular dynamics simulation. The examples of the studies in the latter direction include the elastic incoherent and quasielastic neutrons scattering studies of actin. Future prospects of the studies on the protein dynamics with neutron scattering are briefly described. (author)

Determination of hydrogen/deuterium ratio with neutron measurements on MAST

Energy Technology Data Exchange (ETDEWEB)

Klimek, I., E-mail: iwona.klimek@physics.uu.se; Cecconello, M.; Ericsson, G. [Department of Physics and Astronomy, Uppsala University, Uppsala (Sweden); Sharapov, S. E.; Harrison, J. [CCFE, Culham Science Centre, Abingdon (United Kingdom)

2014-11-15

On MAST, compressional Alfvén eigenmodes can be destabilized by the presence of a sufficiently large population of energetic particles in the plasma. This dependence was studied in a series of very similar discharges in which increasing amounts of hydrogen were puffed into a deuterium plasma. A simple method to estimate the isotopic ratio n{sub H}/n{sub D} using neutron emission measurements is here described. The inferred isotopic ratio ranged from 0.0 to 0.6 and no experimental indication of changes in radial profile of n{sub H}/n{sub D} were observed. These findings are confirmed by TRANSP/NUBEAM simulations of the neutron emission.

Neutron activation studies on JET

International Nuclear Information System (INIS)

Loughlin, M.J.; Forrest, R.A.; Edwards, J.E.G.

2001-01-01

Extensive neutron transport calculations have been performed to determine the neutron spectrum at a number of points throughout the JET torus hall. The model has been bench-marked against a set of foil activation measurements which were activated during an experimental campaign with deuterium/tritium plasmas. The model can predict the neutron activation of the foils on the torus hall walls to within a factor of three for reactions with little sensitivity to thermal neutrons. The use of scandium foils with and without a cadmium thermal neutron absorber was a useful monitor of the thermal neutron flux. Conclusions regarding the usefulness of other foils for benchmarking the calculations are also given

Neutron measurements in search of cold fusion

International Nuclear Information System (INIS)

Anderson, R.E.; Goulding, C.A.; Johnson, M.W.; Butterfield, K.B.; Gottesfeld, S.; Baker, D.A.; Springer, T.E.; Garzon, F.H.; Bolton, R.D.; Leonard, E.M.; Chancellor, T.

1990-01-01

We have conducted a research for neutron emission from cold fusion systems of the electrochemical type and, to a lesser extent, the high-pressure gas cell type. Using a high-efficiency well counter and an NE 213 scintillator, the experiments were conducted on the earth's surface and in a shielded cave approximately 50 ft underground. After approximately 6500 h of counting time, we have obtained no evidence for cold fusion processes leading to neutron production. However, we have observed all three types of neutron data that have been presented as evidence for cold fusion: large positive fluctuations in the neutron counting rate, weak peaks near 2.5 MeV in the neutron energy spectrum, and bursts of up to 145 neutrons in 500-μs intervals. The data were obtained under circumstances that clearly show our results to be data encountered as a part of naturally occurring neutron background, which is due primarily to cosmic rays. Thus, observing these types of data does not, of itself, provide evidence for the existence of cold fusion processes. Artifacts in the data that were due to counter misbehavior were also to lead to long-term ''neutron bursts'' whose time duration varied from several hours to several days. We conclude that any experiments which attempt to observe neutron emission must include strong steps to ensure that the experiments deal adequately with both cosmic-ray processes and counter misbehavior. 13 refs., 14 figs

Filtered epithermal quasi-monoenergetic neutron beams at research reactor facilities

International Nuclear Information System (INIS)

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

2015-01-01

Filtered neutron techniques were applied to produce quasi-monoenergetic neutron beams in the energy range of 1.5–133 keV at research reactors. A simulation study was performed to characterize the filter components and transmitted beam lines. The filtered beams were characterized in terms of the optimal thickness of the main and additive components. The filtered neutron beams had high purity and intensity, with low contamination from the accompanying thermal emission, fast neutrons and γ-rays. A computer code named “QMNB” was developed in the “MATLAB” programming language to perform the required calculations. - Highlights: • Quasi-monoenergetic neutron beams in energy range from (1.5–133) keV. • Interference between the resonance and potential scattering amplitudes. • Epithermal neutron beams used in BNCT

Feasibility study on using imaging plates to estimate thermal neutron fluence in neutron-gamma mixed fields

International Nuclear Information System (INIS)

Fujibuchi, T.; Tanabe, Y.; Sakae, T.; Terunuma, T.; Isobe, T.; Kawamura, H.; Yasuoka, K.; Matsumoto, T.; Harano, H.; Nishiyama, J.; Masuda, A.; Nohtomi, A.

2011-01-01

In current radiotherapy, neutrons are produced in a photonuclear reaction when incident photon energy is higher than the threshold. In the present study, a method of discriminating the neutron component was investigated using an imaging plate (IP) in the neutron-gamma-ray mixed field. Two types of IP were used: a conventional IP for beta- and gamma rays, and an IP doped with Gd for detecting neutrons. IPs were irradiated in the mixed field, and the photo-stimulated luminescence (PSL) intensity of the thermal neutron component was discriminated using an expression proposed herein. The PSL intensity of the thermal neutron component was proportional to thermal neutron fluence. When additional irradiation of photons was added to constant neutron irradiation, the PSL intensity of the thermal neutron component was not affected. The uncertainty of PSL intensities was approximately 11.4 %. This method provides a simple and effective means of discriminating the neutron component in a mixed field. (authors)

Kartini Research Reactor prospective studies for neutron scattering application

International Nuclear Information System (INIS)

Widarto

1999-01-01

The Kartini Research Reactor (KRR) is located in Yogyakarta Nuclear Research Center, Yogyakarta - Indonesia. The reactor is operated for 100 kW thermal power used for research, experiments and training of nuclear technology. There are 4 beam ports and 1 column thermal are available at the reactor. Those beam ports have thermal neutron flux around 10 7 n/cm 2 s each other and used for sub critical assembly, neutron radiography studies and Neutron Activation Analysis (NAA). Design of neutron collimator has been done for piercing radial beam port and the calculation result of collimated neutron flux is around 10 9 n/cm 2 s. This paper describes experiment facilities and parameters of the Kartini research reactor, and further more the prospective studies for neutron scattering application. The purpose of this paper is to optimize in utilization of the beam ports facilities and enhance the manpower specialty. The special characteristic of the beam ports and preliminary studies, pre activities regarding with neutron scattering studies for KKR is presented. (author)

Neutron production with mixture of deuterium and krypton in Sahand Filippov type plasma focus facility

International Nuclear Information System (INIS)

Mohammadi, M.A.; Sobhanian, S.; Rawat, R.S.

2011-01-01

This Letter reports the order of magnitude enhancement in neutron yield from Sahand plasma focus device with krypton seeded deuterium operation. The highest average neutron yield of 2.2x10 9 neutrons per shot was achieved at 1.00 Torr deuterium with 3% krypton which is higher than the best average neutron yield of 3.18x10 8 neutrons per shot for pure deuterium operation. Estimation of average neutron energy showed that the maximum and minimum average energies are 2.98±0.6 MeV at 16 kV in 0.25 Torr deuterium with 3% Kr and 2.07±0.2 MeV at 18 kV operation in 0.5 Torr deuterium with 3% Kr, respectively. The anisotropy of neutron emission from Sahand DPF showed that the neutrons are produced mainly by beam-target mechanisms. -- Highlights: → The highest average neutron yield of 2.2x10 9 neutrons per shot was achieved at mixture of deuterium and krypton. → In the krypton seeding of deuterium also anisotropy of neutron emission deuterium is found. → The krypton seeding of deuterium made the neutron emission more reliable over wider operating pressure ranges.

Studies in precise neutron optics at JAERI

International Nuclear Information System (INIS)

Tomimitsu, Hiroshi

1994-01-01

Studies in the field of so-called 'Precise Neutron Optics' at JAERI were reported, since the beginning of 1970. It started with the photographic detection of the 'Pendellusung Fringes' in a wedge-shaped Si crystal, promoted by Prof.K.Kohra. Neutron diffraction topography was also tried and used for the 'direct' observation of the substructure in a Cu-5%Ge single crystal, carried out by the present author. So-called 'VSANS' (Very Small Angle Neutron Scattering) was also tried, with the angular resolution better than 0.1 sec. of arc, for the structural observation of several kinds of 'amorphous' materials, such as neutron-irradiated silica glasses, Pb-containing glasses and several ribbon-shaped amorphous alloys, carried out by Dr.K.Doi. Recently with the co-operation with Prof.S.Kikuta's group, some interferometric experiments were tried, such as the detection of the double-refraction phenomenon of the neutron in the magnetic materials, carried out by Dr.S.Nakatani. The apparatus for precise neutron optics and topography (PNO) was constructed at the JRR-3M in JAERI in 1992, which was just properly made for the studies in the present thema. With the PNO, the characterization of Ni-Ti multilayer mirror for the interferometer with the cold/ ultra-cold neutrons was carried out, the results being reported in the other article of this symposium by Dr.H.Funahashi. Through the test use of the PNO with the neutron interferometry, carried out by Dr.Y.Hasegawa, it was revealed that the PNO is the best facility in the world for the neutron interferometry; with the datas of the count ratio upto 20 cps and the contrast more than 40%. Dr.K.Aizawa is now refining the VSANS-technique on the PNO, for the precise observation of the precipitation behaviour of high density small particles such as metatic alloy-system. (author)

Neutron ion temperature measurement

International Nuclear Information System (INIS)

Strachan, J.D.; Hendel, H.W.; Lovberg, J.; Nieschmidt, E.B.

1986-11-01

One important use of fusion product diagnostics is in the determination of the deuterium ion temperature from the magnitude of the 2.5 MeV d(d,n) 3 He neutron emission. The detectors, calibration methods, and limitations of this technique are reviewed here with emphasis on procedures used at PPPL. In most tokamaks, the ion temperature deduced from neutrons is in reasonable agreement with the ion temperature deduced by other techniques

The intense neutron generator study

Energy Technology Data Exchange (ETDEWEB)

Lewis, W B

1966-07-01

The study has confirmed that a beam of 65 mA of protons at 1000 MeV, striking a molten lead-bismuth target surrounded by heavy water moderator, would give the desired flux of 10{sup 16} thermal neutrons per cm{sup 2} per second to provide intense beams of neutrons and also to produce radioisotopes. The proton beam passing through a thin auxiliary target would also produce beams of mesons. The design and construction of the ion source, injector, accelerator, target and auxiliaries present challenging technical problems. Moreover, continued development for improved life and economy promises to be rewarding. The high neutron intensity is sought for research in solid and liquid state physics and also for nuclear physics. Participation by universities and industry, both in development and use, is expected to be extensive. (author)

The intense neutron generator study

International Nuclear Information System (INIS)

Lewis, W.B.

1966-01-01

The study has confirmed that a beam of 65 mA of protons at 1000 MeV, striking a molten lead-bismuth target surrounded by heavy water moderator, would give the desired flux of 10 16 thermal neutrons per cm 2 per second to provide intense beams of neutrons and also to produce radioisotopes. The proton beam passing through a thin auxiliary target would also produce beams of mesons. The design and construction of the ion source, injector, accelerator, target and auxiliaries present challenging technical problems. Moreover, continued development for improved life and economy promises to be rewarding. The high neutron intensity is sought for research in solid and liquid state physics and also for nuclear physics. Participation by universities and industry, both in development and use, is expected to be extensive. (author)

Studies for improvement of WWER-440 neutron fluence determination

International Nuclear Information System (INIS)

Ilieva, Kr.; Belousov, S.; Apostolov, T.

2001-01-01

For assessment of radiation embrittlement and prediction of reactor vessel lifetime with reasonable conservatism a 'best estimated' neutron fluence is necessary. New studies purposed to improve the fluence determination are presented: 1) study on the reliability of multigroup presentation of the neutron cross sections, and 2) impact of negative gradient of reactor power in the periphery assemblies on the neutron fluence evaluation. The results of these studies are base for improvement of neutron fluence determination methodology applied by the INRNE, BAS at Kozloduy NPP. (author)

Synthesis and study of neutron-rich nuclides

International Nuclear Information System (INIS)

Luo Yixiao

1995-01-01

During the past few years our understanding of the decay properties and nuclear structure has been extended in a systematic fashion for the neutron-rich nuclei. This review will first sketch the production and identification of the neutron-rich nuclei throughout the whole mass region, and will then discuss the impressive progress in the studies of the exotic decay properties and nuclear structure of neutron-rich nuclei. Their astrophysical implications will also be outlined

Neutronic study of the two french heavy water reactors

International Nuclear Information System (INIS)

Horowitz, J.

1955-01-01

The two french reactors - the reactor of Chatillon, named Zoe, and the reactor of Saclay - P2 - were the object of detailed neutronic studies which the main ideas are exposed in this report. These studies were mostly done by the Department of the Reactor Studies (D.E.P.). We have thus studied the distribution of neutronic fluxes; the factors influencing reactivity; the link between reactivity and divergence with the formula of Nordheim; the mean time life of neutrons; neutron spectra s of P2; the xenon effect; or the effect of the different adjustments of the plates and controls bar. (M.B.) [fr

Measuring the energies and multiplicities of prompt gamma-ray emissions from neutron-induced fission of $^{235}$U using the STEFF spectrometer

CERN Document Server

AUTHOR|(CDS)2093036; Smith, Alastair Gavin; Wright, Tobias James

Following a NEA high priority nuclear data request, an experimental campaign to measure the prompt $\\gamma$-ray emissions from $^{235}$U has been performed. This has used the STEFF spectrometer at the new Experimental Area 2 (EAR2) within the neutron timeof-flight facility (n_TOF), a white neutron source facility at CERN with energies from thermal to approximately 1 GeV. Prior to the experimental campaign, STEFF has been optimised for the environment of EAR2. The experimental hall features a high background $\\gamma$-ray rate, due to the nature of the spallation neutron source. Thus an investigation into reduction of the background $\\gamma$-ray rate, encountered by the NaI(Tl) detector array of STEFF, has been carried out. This has been via simulations using the simulation package FLUKA. Various materials and shielding geometries have been investigated but the effects determined to be insufficient in reducing the background rate by a meaningful amount. The NaI(Tl) detectors have been modified to improve their ...

Gamma–neutron imaging system utilizing pulse shape discrimination with CLYC

International Nuclear Information System (INIS)

Whitney, Chad M.; Soundara-Pandian, Lakshmi; Johnson, Erik B.; Vogel, Sam; Vinci, Bob; Squillante, Michael; Glodo, Jarek; Christian, James F.

2015-01-01

Recently, RMD has investigated the use of CLYC (Cs 2 LiYCl 6 :Ce), a new and emerging scintillation material, in a gamma–neutron coded aperture imaging system based on RMD's commercial RadCam TM instrument. CLYC offers efficient thermal neutron detection, fast neutron detection capabilities, excellent pulse shape discrimination (PSD), and gamma-ray energy resolution as good as 4% at 662 keV. PSD improves the isolation of higher energy gammas from thermal neutron interactions (>3 MeV electron equivalent peak), compared to conventional pulse height techniques. The scintillation emission time in CLYC provides the basis for PSD; where neutron interactions result in a slower emission rise and decay components while gamma interactions result in a faster emission components. By creating a population plot based on the ratio of the decay tail compared to the total integral amplitude (PSD ratio), discrimination of gammas, thermal neutrons, and fast neutrons is possible. Previously, we characterized the CLYC-based RadCam system for imaging gammas and neutrons using a layered W-Cd coded aperture mask and employing only pulse height discrimination. In this paper, we present the latest results which investigate gamma-neutron imaging capabilities using PSD. An FPGA system is used to acquire the CLYC–PSPMT last dynode signals, determine a PSD ratio for each event, and compare it to a calibrated PSD cutoff. Each event is assigned either a gamma (low) or neutron (high) flag signal which is then correlated with the imaging information for each event. - Highlights: • The latest results are presented for our CLYC RadCam-2 system which investigate gamma–neutron imaging using pulse shape discrimination. • CLYC RadCam-2 system successfully discriminates gammas, thermal neutrons, and fast neutrons by employing a fully integrated, FPGA-based PSD system. • Imaging of our 252 Cf source was possible using both pulse height and pulse shape discrimination with CLYC. • Imaging

A design study on hyper-thermal neutron irradiation field for neutron capture therapy at Kyoto University Reactor

International Nuclear Information System (INIS)

Sakurai, Y.; Kobayashi, T.

2000-01-01

A study about the installation of a hyper-thermal neutron converter to a clinical collimator was performed, as a series of the design study on a hyper-thermal neutron irradiation field at the Heavy Water Neutron Irradiation Facility of Kyoto University Reactor. From the parametric-surveys by Monte Carlo calculation, it was confirmed that the practical irradiation field of hyper-thermal neutrons would be feasible by the modifications of the clinical collimator and the bismuth-layer structure. (author)

Study of neutron radiation effects on MOS structures

International Nuclear Information System (INIS)

Vaidya, Sangeeta J.

2003-01-01

We have studied charge trapping in the oxide and generation of interface states due to neutrons. It is observed that neutrons, though uncharged, are capable of causing ionization and interface damage and it is significant under biased irradiation conditions. One of the important features of this work is that neutron irradiation was carried out in a nuclear reactor (swimming pool type) itself in contrast to the earlier reported work which used separate neutron sources for similar studies. To simulate real life situations, all our devices were biased during irradiation. In our belief, both of these facts gave credence to our observed experimental results. (author)

Photo-induced current transient spectroscopy for high-resistivity neutron-transmutation-doped silicon

International Nuclear Information System (INIS)

Tokuda, Yutaka; Inoue, Yajiro; Usami, Akira

1987-01-01

Defects in high-resistivity neutron-transmutation-doped (NTD) silicon prior to annealing were studied by photo-induced current transient spectroscopy (PICTS). The thermal-neutron fluence was 9.5 x 10 17 cm -2 to give a resistivity of about 30 Ω after annealing, and the fast-neutron fluence was 9.5 x 10 16 cm -2 . Four traps with thermal emission activation energies of 0.15, 0.41. 0.47 and 0.50 eV were observed in NTD silicon. A trap with the thermal emission activation energy of 0.15 eV was considered to correspond to the divacancy. Although the clustered nature of the defects was observed, PICTS measurements suggest that the material state of high-resistivity NTD silicon is still crystalline and not amorphous. (author)

Observation of repetitive bursts in emission of fast ions and neutrons in sub-nanosecond laser-solid experiments

Czech Academy of Sciences Publication Activity Database

Krása, Josef; Klír, D.; Velyhan, Andriy; Margarone, Daniele; Krouský, Eduard; Jungwirth, Karel; Skála, Jiří; Pfeifer, Miroslav; Kravárik, J.; Kubeš, P.; Řezáč, K.; Ullschmied, Jiří

2013-01-01

Roč. 31, č. 3 (2013), s. 395-401 ISSN 0263-0346 R&D Projects: GA MŠk EE2.3.20.0279; GA ČR GAP205/12/0454; GA MŠk LM2010014 Grant - others:OPVK 3 Laser Zdroj(XE) CZ.1.07/2.3.00/20.0279 Program:EE Institutional support: RVO:68378271 ; RVO:61389021 Keywords : laser-plasma interactions * neutron yield scaling * bursts in ion emission Subject RIV: BH - Optics, Masers, Lasers; BL - Plasma and Gas Discharge Physics (UFP-V) Impact factor: 1.701, year: 2013

Delayed neutron detection in canning burst detection studies (1961); Etude sur la detection des neutrons differes en vue de la detection des ruptures de gaines (1961)

Energy Technology Data Exchange (ETDEWEB)

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

1961-07-01

This paper describes a theoretical and experimental study on the detection of neutrons present in the primary cooling circuit of a reactor cooled by heavy or light water, with a view to the installation of a canning burst detection unit. The concentration of background neutrons is first calculated, taking into account the neutrons from nitrogen 17 decay, and the photoneutrons produced by the decay of nitrogen 16 and sodium 24. The emission of delayed fission neutrons, originating at a given crack in the canning, has been estimated. Using the D{sub 2}O circuit of the pile EL-3, three units have been developed by means of which the following three types of detector may be compared: 1) BF{sub 3} proportional counter 2) Boron scintillator 3) Fission chamber Under the present experimental conditions the BF{sub 3} counter gave the best results. The influence on these detectors of the {gamma} flux, which in certain cases reaches 200 R/h, is analysed. Finally a calibration is carried out with an experimental crack of 30 mm{sup 2} of uranium exposed to a flux of 5.8 x 10{sup 13} n.cm{sup -2}.s{sup -1}. The sensitivity obtained with the BF{sub 3} counter during this test is 2 counts/s per mm{sup 2} of exposed uranium. (author) [French] Le present rapport est une etude theorique et experimentale sur la detection des neutrons presents dans le circuit primaire de refroidissement d'un reacteur refrigere par l'eau lourde ou l'eau legere, en vue d'une installation de detection de ruptures de gaines. On fait d'abord un calcul sur la concentration des neutrons de bruit de fond en tenant compte: des neutrons de decroissance de l'azote 17 et des photoneutrons produits par les decroissances de l'azote 16 et du sodium 24. L'emission des neutrons differes de fission, qui ont pour origine une fissure de gaine donnee, a ete evaluee. Utilisant le circuit D{sub 2}O de la pile EL3, trois installations ont ete mises au point permettant de comparer les trois types de detecteurs suivants: 1

Neutron-fragment angular correlations in /sup 235/U(n/sub th/,f)

International Nuclear Information System (INIS)

Franklyn, C.B.

1985-01-01

Neutron-fragment angular correlations in /sup 235/U(n/sub th/,f) as a function of neutron energy and fragment mass are presented. The results obtained in this experiment, together with data for neutron-neutron angular correlations, are compared with a Monte Carlo simulation of the fission process incorporating both a scission neutron component and an anisotropic neutron emission component

X-Ray Measurements Of A Thermo Scientific P385 DD Neutron Generator

International Nuclear Information System (INIS)

Wharton, C. J.; Seabury, E. H.; Chichester, D. L.; Caffrey, A. J.; Simpson, J.; Lemchak, M.

2011-01-01

Idaho National Laboratory is experimenting with electrical neutron generators, as potential replacements for californium-252 radioisotopic neutron sources in its PINS prompt gamma-ray neutron activation analysis (PGNAA) system for the identification of military chemical warfare agents and explosives. In addition to neutron output, we have recently measured the x-ray output of the Thermo Scientific P385 deuterium-deuterium neutron generator. X rays are a normal byproduct from neutron generators, but depending on their intensity and energy, x rays can interfere with gamma rays from the object under test, increase gamma-spectrometer dead time, and reduce PGNAA system throughput. The P385 x-ray energy spectrum was measured with a high-purity germanium (HPGe) detector, and a broad peak is evident at about 70 keV. To identify the source of the x rays within the neutron generator assembly, it was scanned by collimated scintillation detectors along its long axis. At the strongest x-ray emission points, the generator also was rotated 60 deg. between measurements. The scans show the primary source of x-ray emission from the P385 neutron generator is an area 60 mm from the neutron production target, in the vicinity of the ion source. Rotation of the neutron generator did not significantly alter the x-ray count rate, and its x-ray emission appears to be axially symmetric. A thin lead shield, 3.2 mm (1/8 inch) thick, reduced the 70-keV generator x rays to negligible levels.

Calibration Of A 14 MeV Neutron Generator With Reference To NBS-1

International Nuclear Information System (INIS)

Heimbach, Craig R.

2011-01-01

NBS-1 is the US national neutron reference source. It has a neutron emission rate (June 1961) of 1.257x10 6 n/s 1,2,3 with an uncertainty of 0.85%(k = 1). Neutron emission-rate calibrations performed at the National Institute of Standards and Technology (NIST) are made in comparison to this source, either directly or indirectly. To calibrate a commercial 14 MeV neutron generator, NIST performed a set of comparison measurements to evaluate the neutron output relative to NBS-1. The neutron output of the generator was determined with an uncertainty of about 7%(k = 1). The 15-hour half-life of one of the reactions used also makes possible off-site measurements. Consideration is given to similar calibrations for a 2.5 MeV neutron generator.

Dispersion of the Neutron Emission in U{sup 235} Fission

Science.gov (United States)

Feynman, R. P.; de Hoffmann, F.; Serber, R.

1955-01-01

Equations are developed which allow the calculation of the average number of neutrons per U{sup235} fission from experimental measurements. Experimental methods are described, the results of which give a value of (7.8 + 0.6){sup ½} neutrons per U{sup 235} thermal fission.

Systematics in delayed neutron yields

Energy Technology Data Exchange (ETDEWEB)

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

1998-03-01

An attempt was made to reproduce the systematic trend observed in the delayed neutron yields for actinides on the basis of the five-Gaussian representation of the fission yield together with available data sets for delayed neutron emission probability. It was found that systematic decrease in DNY for heavier actinides is mainly due to decrease of fission yields of precursors in the lighter side of the light fragment region. (author)

Calculation of Spectra of Neutrons and Charged Particles Produced in a Target of a Neutron Generator

Science.gov (United States)

Gaganov, V. V.

2017-12-01

An algorithm for calculating the spectra of neutrons and associated charged particles produced in the target of a neutron generator is detailed. The products of four nuclear reactions 3H( d, n)4He, 2H( d, n)3He, 2H( d, p)3H, and 3He( d, p)4He are analyzed. The results of calculations are presented in the form of neutron spectra for several emission angles and spectra of associated charged particles emitted at an angle of 180° for a deuteron initial energy of 0.13 MeV.

The new JET 2.5-MeV neutron time-of-flight spectrometer

International Nuclear Information System (INIS)

Elevant, T.; Belle, P.v.; Grosshoeg, G.; Hoek, M.; Jarvis, O.N.; Olsson, M.; Sadler, G.

1992-01-01

A major upgrade of the JET 2.5-MeV neutron time-of-flight spectrometer has been completed. The improvement has permitted ion temperature measurements for Maxwellian deuterium plasmas with T i >4 keV to be obtained in 0.5-s intervals. By combining observations of neutron and x-ray energy spectra with studies of γ-ray emission from reactions between fast deuterons and impurities, the effects of ICRF heating on the deuterium energy distribution have been studied. The time evolution of neutron energy spectra from deuterium-beam heated deuterium plasmas is illustrated and a method for evaluating the ion temperature from such sequences is indicated. Furthermore, the spectrometer has shown stable performance during high neutron fluxes

Non-destructive studies of fuel pellets by neutron resonance absorption radiography and thermal neutron radiography

Energy Technology Data Exchange (ETDEWEB)

Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [University of California, Berkeley, CA 94720 (United States); Vogel, S.C.; Mocko, M.; Bourke, M.A.M.; Yuan, V.; Nelson, R.O.; Brown, D.W. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Rd., Sturbridge, MA 01566 (United States)

2013-09-15

Many isotopes in nuclear materials exhibit strong peaks in neutron absorption cross sections in the epithermal energy range (1–1000 eV). These peaks (often referred to as resonances) occur at energies specific to particular isotopes, providing a means of isotope identification and concentration measurements. The high penetration of epithermal neutrons through most materials is very useful for studies where samples consist of heavy-Z elements opaque to X-rays and sometimes to thermal neutrons as well. The characterization of nuclear fuel elements in their cladding can benefit from the development of high resolution neutron resonance absorption imaging (NRAI), enabled by recently developed spatially-resolved neutron time-of-flight detectors. In this technique the neutron transmission of the sample is measured as a function of spatial location and of neutron energy. In the region of the spectra that borders the resonance energy for a particular isotope, the reduction in transmission can be used to acquire an image revealing the 2-dimensional distribution of that isotope within the sample. Provided that the energy of each transmitted neutron is measured by the neutron detector used and the irradiated sample possesses neutron absorption resonances, then isotope-specific location maps can be acquired simultaneously for several isotopes. This can be done even in the case where samples are opaque or have very similar transmission for thermal neutrons and X-rays or where only low concentrations of particular isotopes are present (<0.1 atom% in some cases). Ultimately, such radiographs of isotope location can be utilized to measure isotope concentration, and can even be combined to produce three-dimensional distributions using tomographic methods. In this paper we present the proof-of-principle of NRAI and transmission Bragg edge imaging performed at Flight Path 5 (FP5) at the LANSCE pulsed, moderated neutron source of Los Alamos National Laboratory. A set of urania mockup

ROLE OF NUCLEONIC FERMI SURFACE DEPLETION IN NEUTRON STAR COOLING

Energy Technology Data Exchange (ETDEWEB)

Dong, J. M.; Zuo, W. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Lombardo, U. [Universita di Catania and Laboratori Nazionali del Sud (INFN), Catania I-95123 (Italy); Zhang, H. F. [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)

2016-01-20

The Fermi surface depletion of beta-stable nuclear matter is calculated to study its effects on several physical properties that determine the neutron star (NS) thermal evolution. The neutron and proton Z factors measuring the corresponding Fermi surface depletions are calculated within the Brueckner–Hartree–Fock approach, employing the AV18 two-body force supplemented by a microscopic three-body force. Neutrino emissivity, heat capacity, and in particular neutron {sup 3}PF{sub 2} superfluidity, turn out to be reduced, especially at high baryonic density, to such an extent that the cooling rates of young NSs are significantly slowed.

Gamma-ray emission profile measurements during JET ICRH discharges

Energy Technology Data Exchange (ETDEWEB)

Howarth, P.J.A. [Birmingham Univ. (United Kingdom); Adams, J.M.; Bond, D.S.; Watkins, N. [AEA Technology, Harwell (United Kingdom); Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Belle, P. van [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking

1994-12-31

Ion Cyclotron Resonant Heating (ICRH) that is tuned to minority fuel ions can induce an energy diffusion of the heated species and create high energy tail temperatures of {approx} 1 MeV. The most energetic of these accelerated minority ions can undergo nuclear reactions with impurity Be and C that produces {gamma}-ray emission from the decay of the excited product nuclei. This RF-induced {gamma}-ray emission has been recorded using the JET neutron emission profile diagnostic which is capable of distinguishing neutrons and {gamma}-rays. Appropriate data processing has enabled the RF-induced {gamma}-ray emission signals to be isolated from the {gamma}-ray emission signals associated with neutron interactions in the material surrounding the profile monitor. The 2-d {gamma}-ray emission profiles show that virtually all the radiation originates from the low field side of the RF resonance layer, as expected from RF-induced pitch angle diffusion. The emission profiles indicate the presence of a small population of resonant {sup 3}He ions that possess orbits lying near the passing-trapped boundary. (author) 6 refs., 4 figs.

Study on the dose distribution of the mixed field with thermal and epi-thermal neutrons for neutron capture therapy

International Nuclear Information System (INIS)

Kobayashi, Tooru; Sakurai, Yoshinori; Kanda, Keiji

1994-01-01

Simulation calculations using DOT 3.5 were carried out in order to confirm the characteristics of depth-dependent dose distribution in water phantom dependent on incident neutron energy. The epithermal neutrons mixed to thermal neutron field is effective improving the thermal neutron depth-dose distribution for neutron capture therapy. A feasibility study on the neutron energy spectrum shifter was performed using ANISN-JR for the KUR Heavy Water Facility. The design of the neutron spectrum shifter is feasible, without reducing the performance as a thermal neutron irradiation field. (author)

Neutron radiation damage studies on silicon detectors

International Nuclear Information System (INIS)

Li, Zheng; Chen, W.; Kraner, H.W.

1990-10-01

Effects of neutron radiation on electrical properties of Si detectors have been studied. At high neutron fluence (Φ n ≥ 10 12 n/cm 2 ), C-V characteristics of detectors with high resistivities (ρ ≥ 1 kΩ-cm) become frequency dependent. A two-trap level model describing this frequency dependent effect is proposed. Room temperature anneal of neutron damaged (at LN 2 temperature) detectors shows three anneal stages, while only two anneal stages were observed in elevated temperature anneal. 19 refs., 14 figs

High resolution measurements and study of the neutron inelastic scattering reaction on 56Fe

International Nuclear Information System (INIS)

Dupont, E.

1998-01-01

High resolution measures of neutrons inelastic scattering cross section, have been performed on 56 Fe from 862 KeV to 3 MeV. The time of flight method has been used on the GELINA source of the IRMM in Geel (Belgium). Four barium fluoride scintillators, placed around the samples, recorded the gamma rays emissions coming from the iron and the boron. A study of the correlations between the partial elastic and inelastic lengths has been performed taking into account first transmission measures realized at Geel. (A.L.B.)

Study of material science by neutron scattering

International Nuclear Information System (INIS)

Kim, H.J.; Yoon, B.K.; Cheon, B.C.; Lee, C.Y.; Kim, C.S.

1980-01-01

To develop accurate methods of texture measurement in metallic materials by neutron diffraction, (100),(200),(111) and (310) pole figures have been measured for the oriented silicon steel sheet, and currently study of correction methods for neutron absorption and extinction effects are in progress. For quantitative analysis of texture of polycrystalline material with a cubic structure, a software has been developed to calculate inverse pole figures for arbitrary direction specified in the speciman as well as pole figures for arbitrary chosen crystallographic planes from three experimental pole figures. This work is to be extended for the calculation of three dimensional orientation distribution function and for the evaluation of errors in the quantitative analysis of texture. Work is also for the study of N-H...O hydrogen bond in amino acid by observing molecular motions using neutron inelastic scattering. Measurement of neutron inelastic scattering spectrum of L-Serine is completed at 100 0 K and over the energy transfer range of 20-150 meV. (KAERI INIS Section)

Rapid Cooling of the Neutron Star in Cassiopeia A Triggered by Neutron Superfluidity in Dense Matter

International Nuclear Information System (INIS)

Page, Dany; Prakash, Madappa; Lattimer, James M.; Steiner, Andrew W.

2011-01-01

We propose that the observed cooling of the neutron star in Cassiopeia A is due to enhanced neutrino emission from the recent onset of the breaking and formation of neutron Cooper pairs in the 3 P 2 channel. We find that the critical temperature for this superfluid transition is ≅0.5x10 9 K. The observed rapidity of the cooling implies that protons were already in a superconducting state with a larger critical temperature. This is the first direct evidence that superfluidity and superconductivity occur at supranuclear densities within neutron stars. Our prediction that this cooling will continue for several decades at the present rate can be tested by continuous monitoring of this neutron star.

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

Directory of Open Access Journals (Sweden)

Neudecker D.

2016-01-01

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

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

Science.gov (United States)

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

2015-12-01

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

A possible island of beta-delayed neutron precursors in heavy nucleus region

International Nuclear Information System (INIS)

Zhang Li

1991-01-01

The possible Beta-Delayed neutron precursors in the elements Tl, Hg, and Au were predicted following a systematic research on the known Beta-Delayed neutron precursors. The masses of the unknown nuclei and neutron emission probabilities were calculated

Investigation of capture reactions far off stability by β-delayed neutron emission

International Nuclear Information System (INIS)

Wiescher, M.; Leist, B.; Ziegert, W.; Gabelmann, H.; Steinmueller, B.; Ohm, H.; Kratz, K.h.; Thielemann, F.h.; Hillebrandt, W.

1985-01-01

Beta-delayed neutron spectroscopy is applied to determine reaction rates of neutron capture on several neutron rich nuclei. The results of these experiments are presented and discussed in the light of their astrophysical implications. Furthermore, the experimental possibilities and limits of planned measurements are advertised

Study of the surrogate-reaction method applied to neutron-induced capture cross sections

International Nuclear Information System (INIS)

Boutoux, G.; Jurado, B.; Méot, V.; Roig, O.; Mathieu, L.; Aïche, M.; Barreau, G.; Capellan, N.; Companis, I.; Czajkowski, S.; Schmidt, K.-H.; Burke, J.T.; Bail, A.; Daugas, J.M.; Faul, T.; Morel, P.; Pillet, N.; Théroine, C.; Derkx, X.; Sérot, O.

2012-01-01

Gamma-decay probabilities of 173 Yb and 176 Lu have been measured using the surrogate reactions 174 Yb( 3 He,αγ) 173 Yb* and 174 Yb( 3 He,pγ) 176 Lu*, respectively. For the first time, the gamma-decay probabilities have been obtained with two independent experimental methods based on the use of C 6 D 6 scintillators and Germanium detectors. Our results for the radiative-capture cross sections are several times higher than the corresponding neutron-induced data. To explain these differences, we have used our gamma-decay probabilities to extract rather direct information on the spin distributions populated in the transfer reactions used. They are about two times wider and the mean values are 3 to 4 ℏ higher than the ones populated in the neutron-induced reactions. As a consequence, in the transfer reactions neutron emission to the ground and first excited states of the residual nucleus is strongly suppressed and gamma-decay is considerably enhanced.

Utilization of low voltage D-T neutron generators in neutron physics studies

International Nuclear Information System (INIS)

Singkarat, S.

1995-01-01

In a small nuclear laboratory of a developing country a low voltage D-T neutron generator can be a very useful scientific apparatus. Such machines have been used successfully for more than 40 years in teaching and scientific research. The original continuous mode 150-kV D-T neutron generator has been modified to have also a capability of producing 2-ns pulsed neutrons. Together with a carefully designed 10 m long flight path collimator and shielding of a 25 cm diameter · 10 cm thick BC-501 neutron detector, the pulsing system was successfully used for measuring the double differential cross-section (DDX) of natural iron for 14.1-MeV neutron from the angle of 30 deg to 150 deg in 10 deg steps. In order to extend the utility of the generator, two methods for converting the almost monoenergetic 14-MeV neutrons to monoenergetic neutrons of lower energy were proposed and tested. Both designs used the neutron-proton interaction at a circular surface-of-revolution made of hydrocarbon materials. The first design is for a pulsed neutron generator and the second design is for an ordinary continuous mode generator. The latter method was successfully used to measure the scintillation light output of a 1.4 cm diameter spherical NE-213 scintillation detector. The neutron generator has also been used in the continuous search for improved neutron detection techniques. There is a proposal, based on Monte Carlo calculations, of using a scintillation fiber for a fast neutron spectrometer. Due to the slender shape of the fiber, the pattern of produced light gives a peak in the pulse height spectrum instead of the well-known rectangular-like distribution, when the fiber is bombarded end-on by a beam of 14-MeV neutrons. Experimental investigations were undertaken. Detailed investigations on the light transportation property of a short fiber were performed. The predicted peak has not yet been found but the fiber detector may be developed as a directional discrimination fast neutron

Neutron diffraction studies of thin film multilayer structures

International Nuclear Information System (INIS)

Majkrzak, C.F.

1985-01-01

The application of neutron diffraction methods to the study of the microscopic chemical and magnetic structures of thin film multilayers is reviewed. Multilayer diffraction phenomena are described in general and in particular for the case in which one of the materials of a bilayer is ferromagnetic and the neutron beam polarized. Recent neutron diffraction measurements performed on some interesting multilayer systems are discussed. 70 refs., 5 figs

Studies of neutron irradiation effects at IPNS-REF

International Nuclear Information System (INIS)

Kirk, M.A.

1983-09-01

Neutron irradiation effects studies at the Radiation Effects Facility (REF) at the Intense Pulsed Neutron Source (IPNS) located at Argonne National Laboratory (ANL) are reviewed. A brief history of the development of this user facility is followed by an overview of the scientific program. Experiments unique to a spallation neutron source are covered in more detail. Future direction of research at this facility is suggested

Search for low lying dipole strength in the neutron rich nucleus Ne{sup 26}

Energy Technology Data Exchange (ETDEWEB)

Gibelin, J

2005-11-15

We carried out the Coulomb excitation, on a lead target, of an exotic beam of neutron-rich nucleus Ne{sup 26} at 58 MeV/n, in order to study the possible existence of a pygmy dipole resonance above the neutron emission threshold. The experiment was performed at the Riken Research Facility, in Tokyo (Japan) and included a gamma-ray detector, a charged fragment hodoscope and a neutron detector. Using the invariant mass method in the Ne{sup 25} + n decay channel, and by comparing the reaction cross section on the lead target and a light target of aluminum, we observe a sizable amount of E1 strength between the one neutron and the two neutron emission thresholds. The corresponding Ne{sup 26} angular distribution confirms its nature and we deduce its reduced dipole transition probability value of B(E1) = 0.54 {+-} 0.18 e{sup 2}fm{sup 2}. Our method also enables us to extract for the first time the decay pattern of a pygmy resonance. By detecting the decay photons from the excited states below the neutron emission threshold and by analyzing the angular distribution of the inelastically scattered Ne{sup 26} we deduce the reduced transition probability of the first 2{sup +} state, from the ground state. The value obtained of B(E2) = 87 {+-} 13 e{sup 2}fm{sup 4} being in disagreement with a previous result. (author)

$\\beta$-delayed neutron spectroscopy of $^{130-132}$ Cd isotopes with the ISOLDE decay station and the VANDLE array

CERN Multimedia

We propose to use the new ISOLDE decay station and the neutron detector VANDLE to measure the $\\beta$-delayed neutron emission of N=82-84 $^{130-132}$Cd isotopes. The large delayed neutron emission probability observed in a previous ISOLDE measurement is indicative of the Gamow-Teller transitions due to the decay of deep core neutrons. Core Gamow-Teller decay has been experimentally proven in the $^{78}$Ni region for the N>50 nuclei using the VANDLE array. The spectroscopic measurement of delayed neutron emission along the cadmium isotopic chain will allow us to track the evolution of the single particle states and the shell gap.

Parallel theoretical study of the two components of the prompt fission neutrons: Dynamically released at scission and evaporated from fully accelerated fragments

Directory of Open Access Journals (Sweden)

Carjan Nicolae

2017-01-01

Full Text Available Prompt fission neutrons (PFN angular and energy distributions for the reaction 235U(nth,f are calculated as a function of the mass asymmetry of the fission fragments using two extreme assumptions: 1 PFN are released during the neck rupture due to the diabatic coupling between the neutron degree of freedom and the rapidly changing neutron-nucleus potential. These unbound neutrons are faster than the separation of the nascent fragments and most of them leave the fissioning system in few 10−21 sec. i.e., at the begining of the acceleration phase. Surrounding the fissioning nucleus by a sphere one can calculate the radial component of the neutron current density. Its time integral gives the angular distribution with respect to the fission axis. The average energy of each emitted neutron is also calculated using the unbound part of each neutron wave packet. The distribution of these average energies gives the general trends of the PFN spectrum: the slope, the range and the average value. 2 PFN are evaporated from fully accelerated, fully equilibrated fission fragments. To follow the de-excitation of these fragments via neutron and γ-ray sequential emissions, a Monte Carlo sampling of the initial conditions and a Hauser-Feshbach statistical approach is used. Recording at each step the emission probability, the energy and the angle of each evaporated neutron one can construct the PFN energy and the PFN angular distribution in the laboratory system. The predictions of these two methods are finally compared with recent experimental results obtained for a given fragment mass ratio.

Simulation and prototyping of 2 m long resistive plate chambers for detection of fast neutrons and multi-neutron event identification

Energy Technology Data Exchange (ETDEWEB)

Elekes, Z., E-mail: z.elekes@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Aumann, T. [GSI Helmholtzzentrumfür Schwerionenforschung, Darmstadt (Germany); Technische Universität Darmstadt, Darmstadt (Germany); Bemmerer, D. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Boretzky, K. [GSI Helmholtzzentrumfür Schwerionenforschung, Darmstadt (Germany); Caesar, C. [GSI Helmholtzzentrumfür Schwerionenforschung, Darmstadt (Germany); Technische Universität Darmstadt, Darmstadt (Germany); Cowan, T.C. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Technische Universität Dresden, Dresden (Germany); Hehner, J.; Heil, M. [GSI Helmholtzzentrumfür Schwerionenforschung, Darmstadt (Germany); Kempe, M. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Rossi, D. [GSI Helmholtzzentrumfür Schwerionenforschung, Darmstadt (Germany); Röder, M. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Technische Universität Dresden, Dresden (Germany); Simon, H. [GSI Helmholtzzentrumfür Schwerionenforschung, Darmstadt (Germany); Sobiella, M.; Stach, D. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Reinhardt, T. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Technische Universität Dresden, Dresden (Germany); Wagner, A.; Yakorev, D. [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Zilges, A. [Universität zu Köln, Köln (Germany); Zuber, K. [Technische Universität Dresden, Dresden (Germany)

2013-02-11

Resistive plate chamber (RPC) prototypes of 2 m length were simulated and built. The experimental tests using a 31 MeV electron beam, discussed in details, showed an efficiency higher than 90% and an excellent time resolution of around σ=100ps. Furthermore, comprehensive simulations were performed by GEANT4 toolkit in order to study the possible use of these RPCs for fast neutron (200 MeV–1 GeV) detection and multi-neutron event identification. The validation of simulation parameters was carried out via a comparison to experimental data. A possible setup for invariant mass spectroscopy of multi-neutron emission is presented and the characteristics are discussed. The results show that the setup has a high detection efficiency. Its capability of determining the momentum of the outgoing neutrons and reconstructing the relative energy between the fragments from nuclear reactions is demonstrated for different scenarios.

Pulsar kicks from majoron emission

International Nuclear Information System (INIS)

Farzan, Yasaman; Gelmini, Graciela; Kusenko, Alexander

2005-01-01

We show that majoron emission from a hot nascent neutron star can be anisotropic in the presence of a strong magnetic field. If majorons carry a non-negligible fraction of the supernova energy, the resulting recoil velocity of a neutron star can explain the observed velocities of pulsars

Study of scattering in bi-dimensional neutron radiographic images

International Nuclear Information System (INIS)

Oliveira, K.A.M. de; Crispim, V.R.; Silva, F.C.

2009-01-01

The effect of neutron scattering frequently causes distortions in neutron radiographic images and, thus, reduces the quality. In this project, a type of filter, comprised of cadmium (a neutron absorber), was used in the form of a grid to correct this effect. This device generated image data in the discrete shadow bands of the absorber, components relative to neutron scattering on the test object and surroundings. Scattering image data processing, together with the original neutron radiographic image, resulted in a corrected image with improved edge delineation and, thus, greater definition in the neutron radiographic image of the test object. The objective of this study is to propose a theoretical/experimental methodology that is capable of eliminating the components relative to neutron scattering in neutron radiographic images, coming from the material that composes the test object and the materials that compose the surrounding area. (author)

Plastic fiber scintillator response to fast neutrons

Energy Technology Data Exchange (ETDEWEB)

Danly, C. R.; Sjue, S.; Wilde, C. H.; Merrill, F. E.; Haight, R. C. [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)

2014-11-15

The Neutron Imaging System at NIF uses an array of plastic scintillator fibers in conjunction with a time-gated imaging system to form an image of the neutron emission from the imploded capsule. By gating on neutrons that have scattered from the 14.1 MeV DT energy to lower energy ranges, an image of the dense, cold fuel around the hotspot is also obtained. An unmoderated spallation neutron beamline at the Weapons Neutron Research facility at Los Alamos was used in conjunction with a time-gated imaging system to measure the yield of a scintillating fiber array over several energy bands ranging from 1 to 15 MeV. The results and comparison to simulation are presented.

Solar flare pion and neutron production

International Nuclear Information System (INIS)

Forrest, D.J.; Vestrand, W.T.

1992-01-01

During cycle 21, the Gamma Ray Spectrometer on SMM observed three large flares with clear evidence for pion decay gamma rays and high energy neutrons. Two of these had an extended emission phase. The emission observed in these extended phases were clearly different from those observed in the impulsive phase. Compared to the impulsive phase, the extended phase emissions were strongly deficient in electron bremsstrahlung relative to the nuclear line emission in the 1.0-7.0 MeV band and appeared to have a reduced energetic neutron to pion gamma ray emission in the >10 MeV band. These changes can be produced either by a strong hardening of the accelerated ion spectrum together with a relative decrease in the energetic electron spectrum, or by a pronounced change in the geometry of the particle spectrum downwards towards the photosphere. The authors review the observational evidence in terms of these two possibilities. A dramatic change in the energetic particle geometry appears to offer the simplest explanation. If true these two flares represent the first clear evidence of strong particle geometry effects within individual flares

Thermal neutron source study

International Nuclear Information System (INIS)

Holden, T.M.

1983-05-01

The value of intense neutron beams for condensed matter research is discussed with emphasis on the complementary nature of steady state and pulsed neutron sources. A large body of information on neutron sources, both existing and planned, is then summarized under four major headings: fission reactors, electron accelerators with heavy metal targets, pulsed spallation sources and 'steady state' spallation sources. Although the cost of a spallation source is expected to exceed that of a fission reactor of the same flux by a factor of two, there are significant advantages for a spallation device such as the proposed Electronuclear Materials Test Facility (EMTF)

Study of neutron-deficient Sn isotopes

International Nuclear Information System (INIS)

Auger, G.

1982-05-01

The formation of neutron deficient nuclei by heavy ion reactions is investigated. The experimental technique is presented, and the results obtained concerning Sn et In isotopes reported: first excited states of 106 Sn, high spin states in 107 Sn and 107 In; Yrast levels of 106 Sn, 107 Sn, 108 Sn; study of neutron deficient Sn and In isotopes formed by the desintegration of the compound nucleus 112 Xe. All these results are discussed [fr

90 deg.Neutron emission from high energy protons and lead ions on a thin lead target

CERN Document Server

Agosteo, S; Foglio-Para, A; Mitaroff, W A; Silari, Marco; Ulrici, L

2002-01-01

The neutron emission from a relatively thin lead target bombarded by beams of high energy protons/pions and lead ions was measured at CERN in one of the secondary beam lines of the Super Proton Synchrotron for radiation protection and shielding calculations. Measurements were performed with three different beams: sup 2 sup 0 sup 8 Pb sup 8 sup 2 sup + lead ions at 40 GeV/c per nucleon and 158 GeV/c per nucleon, and 40 GeV/c mixed protons/pions. The neutron yield and spectral fluence per incident ion on target were measured at 90 deg.with respect to beam direction. Monte-Carlo simulations with the FLUKA code were performed for the case of protons and pions and the results found in good agreement with the experimental data. A comparison between simulations and experiment for protons, pions and lead ions have shown that--for such high energy heavy ion beams--a reasonable estimate can be carried out by scaling the result of a Monte-Carlo calculation for protons by the projectile mass number to the power of 0.80-0...

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-05-28

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

Utilization of low voltage D-T neutron generators in neutron physics studies

Energy Technology Data Exchange (ETDEWEB)

Singkarat, S.

1995-08-01

In a small nuclear laboratory of a developing country a low voltage D-T neutron generator can be a very useful scientific apparatus. Such machines have been used successfully for more than 40 years in teaching and scientific research. The original continuous mode 150-kV D-T neutron generator has been modified to have also a capability of producing 2-ns pulsed neutrons. Together with a carefully designed 10 m long flight path collimator and shielding of a 25 cm diameter {center_dot} 10 cm thick BC-501 neutron detector, the pulsing system was successfully used for measuring the double differential cross-section (DDX) of natural iron for 14.1-MeV neutron from the angle of 30 deg to 150 deg in 10 deg steps. In order to extend the utility of the generator, two methods for converting the almost monoenergetic 14-MeV neutrons to monoenergetic neutrons of lower energy were proposed and tested. The first method uses a pulsed neutron generator and the second method uses an ordinary continuous mode generator. The latter method was successfully used to measure the scintillation light output of a 1.4 cm diameter spherical NE-213 scintillation detector. The neutron generator has also been used in the continuous search for improved neutron detection techniques. There is a proposal, based on Monte Carlo calculations, of using a scintillation fiber for a fast neutron spectrometer. Due to the slender shape of the fiber, the pattern of produced light gives a peak in the pulse height spectrum instead of the well-known rectangular-like distribution, when the fiber is bombarded end-on by a beam of 14-MeV neutrons. Experimental investigations were undertaken. Detailed investigations on the light transportation property of a short fiber were performed. The predicted peak has not yet been found but the fiber detector may be developed as a directional discrimination fast neutron detector. 18 refs.

Linear stochastic neutron transport theory

International Nuclear Information System (INIS)

Lewins, J.

1978-01-01

A new and direct derivation of the Bell-Pal fundamental equation for (low power) neutron stochastic behaviour in the Boltzmann continuum model is given. The development includes correlation of particle emission direction in induced and spontaneous fission. This leads to generalizations of the backward and forward equations for the mean and variance of neutron behaviour. The stochastic importance for neutron transport theory is introduced and related to the conventional deterministic importance. Defining equations and moment equations are derived and shown to be related to the backward fundamental equation with the detector distribution of the operational definition of stochastic importance playing the role of an adjoint source. (author)

Study on Neutron Generation by Using Modified Prototype D-D Neutron Generator

International Nuclear Information System (INIS)

Kim, In-Jung; Kim, Suk-Kwon; Park, Chang-Su; Jung, Nam-Suk; Jung, Hwa-Dong; Chung, Kyoung-Jae; Hwang, Yong-Seok; Choi, H. D.

2006-01-01

The effects of Ti target thickness and deuteron beam energy on neutron generation in the modified prototype DD neutron generator were studied. Three kinds of Ti targets with the thickness of 10 μm, 40 μm and 1 mm were used. Deuteron beam energy was varied from 45 keV to 65 keV. The effects of target thickness and deuteron beam energy were evaluated for every set of experimental run and the results were discussed

Neutron emission during lithium deuteride hydration in heavy water

International Nuclear Information System (INIS)

Arzhannikov, A.V.; Kezerashvili, G.Ya.; Muratov, V.V.; Sinitskij, S.L.

1989-01-01

An experiment on neutron detection during lithium deuteride hydration in heavy water using a system of SNM-17 or SNM-18 gas counters was set up. Signals were simultaneously detected by 6 counters and the data were stored in a computer. At the same time the temperature of the reaction ampule external surface was measured. It was found that the neutron number per 1 gram of lithium deuteride reacted with water in the ampule was equal to several dozens if their initial energy was about 2.5 MeV. 4 refs.; 2 figs

Study of the neutron slowing-down in graphite; Etude du ralentissement des neutrons dans le graphite

Energy Technology Data Exchange (ETDEWEB)

Martelly, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Duggal, V P [Commission a l' Energie atomique indienne (India)

1955-07-01

Study of the slowing-down age of neutrons in graphite. In the aim to eliminate the effect of resonance neutrons on the detector, neutrons captured by cadmium are studied with a classic method consisting of calculating the difference between the activity measured with and without screens. This method is described and screening properties of cadmium and gadolinium are compared. The experimental parameters and detectors details are described. The radioactive source is Ra-{alpha}-Be. The experimental results are given and the experimental distribution is compared with theoretical formula. In a second part, the spatial distribution of resonance neutrons in indium is discussed. Finally, the neutron slowing-down between the indium resonance and the thermal equilibrium is discussed as well as the research for the effective value of slowing-down age. The slowing-down age definition is given before calculating its effective value. It compared the slowing-down law with the experiment and the Gurney theory. (M.P.)

Exciton luminescence characteristic of ZnO. Ga scintillator for neutron detection

International Nuclear Information System (INIS)

Kinoshita, A.; Fujiwara, A.; Koyama, S.; Takei, Y.; Nanto, H.; Katagiri, Masaki

2008-01-01

ZnO family phosphors as novel phosphor materials for neutron detector have prepared using Spark Plasma Sintering method. The optical properties of ZnO phosphor prepared are investigated. The following results were obtained. Two dominant PL emission peaks at 395 nm and 495 nm were observed. The lifetime of the PL emission peak at 395 nm (UV emission band) is about 20 ns, which is suitable for neutron detection. The Ga (30 mol%)-doped ZnO phosphor exhibited an intense UV emission band without the visible emission band. The Ga-doped ZnO phosphor can be prepared at the atmospheric pressure of about 8 Pa using SPS method. It was found that the PL intensity of UV emission band is increased with improving the crystallinity of the ZnO phosphor. (author)

First Measurement of Several β-Delayed Neutron Emitting Isotopes Beyond N=126.

Science.gov (United States)

Caballero-Folch, R; Domingo-Pardo, C; Agramunt, J; Algora, A; Ameil, F; Arcones, A; Ayyad, Y; Benlliure, J; Borzov, I N; Bowry, M; Calviño, F; Cano-Ott, D; Cortés, G; Davinson, T; Dillmann, I; Estrade, A; Evdokimov, A; Faestermann, T; Farinon, F; Galaviz, D; García, A R; Geissel, H; Gelletly, W; Gernhäuser, R; Gómez-Hornillos, M B; Guerrero, C; Heil, M; Hinke, C; Knöbel, R; Kojouharov, I; Kurcewicz, J; Kurz, N; Litvinov, Yu A; Maier, L; Marganiec, J; Marketin, T; Marta, M; Martínez, T; Martínez-Pinedo, G; Montes, F; Mukha, I; Napoli, D R; Nociforo, C; Paradela, C; Pietri, S; Podolyák, Zs; Prochazka, A; Rice, S; Riego, A; Rubio, B; Schaffner, H; Scheidenberger, Ch; Smith, K; Sokol, E; Steiger, K; Sun, B; Taín, J L; Takechi, M; Testov, D; Weick, H; Wilson, E; Winfield, J S; Wood, R; Woods, P; Yeremin, A

2016-07-01

The β-delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with β-decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N≳126. These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the β-decay strength distribution. This provides important constraints on global theoretical models currently used in r-process nucleosynthesis.

Cross section for inelastic neutron acceleration by 178Hfm2

International Nuclear Information System (INIS)

Karamyan, S.A.; Carroll, J.J.

2009-01-01

The scattering of thermal neutrons from isomeric nuclei may include events in which the outgoing neutrons have increased kinetic energy. This process has been called Inelastic Neutron Acceleration (INNA) and occurs when the final nucleus after emission of the neutron is left in a state with lower energy than that of the isomer. The result, therefore, is an induced depletion of the isomeric population to the ground state. A cascade of several gammas must accompany the neutron emission to release the high angular momentum of the initial isomeric state. INNA was previously observed in a few cases and the associated cross sections were only in modest agreement with theoretical estimates. The most recent measurement of an INNA cross section was σ INNA = (258 ± 58) b for neutron scattering by 177 Lu m . In the present work, an INNA cross section of σ INNA = 152 -36 +51 b was deduced from measurements of the total burn-up of the high-spin, four-quasiparticle isomer 178 Hf m2 during irradiation by thermal neutrons. Statistical estimates for the probability of different reaction channels past neutron absorption were used in the analysis, and the deduced σ INNA is compared to the theoretically predicted cross section

Studies of neutron measurement methods for fusion plasma diagnostics

International Nuclear Information System (INIS)

Beimer, K.H.

1986-03-01

This thesis comprises several studies mainly devoted to neutron measurement systems for plasma diagnostics at JET (Joint European Torus). An in situ calibration of the U-235 fission chamber detectors located at JET is presented. These detectors are used for measuring the neutron yield from the thermonuclear reactions in the plasma. The energy spectrum of the neutrons from the reactions D(d,n) 3 He has been studied by means of a 3 He spectrometer. Especially, it was found that by measuring the width of the full energy peak in the response spectrum of the 3 He-spectrometer, the deuterium distribution in the deuterium targets used can be estimated. In order to measure different neutron energies it is necessary to obtain a detailed knowledge of the response of the spectrometer. Therefore, the response function to monoenergetic neutrons in the energy range 130-3030 keV was experimentally determined. Some work has been related to a design study of a 14 MeV spectrometer for neutron diagnostics. It is a combined proton-recoil and time-of-flight spectrometer for high resolution measurements. The main parts of it are the collimator, the scattering foil, and the detectors for the recoil protons and the scattered neutrons. The influence of proton straggling in the foil on the resolution and efficiency of the spectrometer has been studied. Furthermore, a three dimensional Monte Carlo code has been written and used for the design of the collimator. (author)

Annual report on neutron scattering studies in JAERI

International Nuclear Information System (INIS)

Sato, Masatoshi; Nishi, Masakazu; Fujishita, Hideshi; Iizumi, Masashi

1982-07-01

Neutron scattering studies carried out from September 1979 to August 1981 by Division of Physics, JAERI, and universities with JRR-2 and -3 neutron beam facilities are described: 61 summary reports, and a list of publications. (author)

Neutron emission in fission of highly excited californium nuclei (E*=76 MeV)

International Nuclear Information System (INIS)

Blinov, M.V.; Bordyug, V.M.; Kozulin, Eh.M.; Mozhaev, A.N.; Levitovich, M.; Muzychka, Yu.A.; Penionzhkevich, Yu.Eh.; Pustyl'nik, B.I.

1990-01-01

The differential cross sections for neutron production in the fission of highly excited californium nuclei formed in the 238 U+ 12 C (105 MeV) reaction have been measured. From the analysis of the experimental data is follows that the number of pre-fission neutrons substantially exceeds the value obtained in the framework of the standard statistical model. The saddle-to-scission time of the excited nucleus is estimated on the basis of the neutron multiplicity. The dependences of the neutron number and neutron average energies upon the fragment mass are determined

Study of a Loop Heat Pipe Using Neutron Radiography

International Nuclear Information System (INIS)

C. Thomas Conroy; A. A. El-Ganayni; David R. Riley; John M. Cimbala; Jack S. Brenizer, Jr.; Abel Po-Ya Chuang; Shane Hanna

2001-01-01

An explanation is given of what a loop heat pipe (LHP) is, and how it works. It is then shown that neutron imaging (both real time neutron radioscopy and single exposure neutron radiography) is an effective experimental tool for the study of LHPs. Specifically, neutron imaging has helped to identify and correct a cooling water distribution problem in the condenser, and has enabled visualization of two-phase flow (liquid and vapor) in various components of the LHP. In addition, partial wick dry-out, a phenomenon of great importance in the effective operation of LHPs, has been identified with neutron imaging. It is anticipated that neutron radioscopy and radiography will greatly contribute to our understanding of LHP operation, and will lead to improvement of LHP modeling and design

Neutron data evaluation of {sup 238}U

Energy Technology Data Exchange (ETDEWEB)

Maslov, V.M.; Porodzinskij, Y.V.; Hasegawa, Akira; Shibata, Keiichi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1998-08-01

Cross sections for neutron-induced reactions on {sup 238}U are calculated by using the Hauser-Feshbach-Moldauer theory, the coupled channel model and the double-humped fission barrier model. The direct excitation of ground state band levels is calculated with a rigid-rotator model. The direct excitation of vibrational octupole and K = 2{sup +} quadrupole bands is included using a soft (deformable) rotator model. The competition of inelastic scattering to fission reaction is shown to be sensitive to the target nucleus level density at excitations above the pairing gap. As for fission, (n,2n), (n,3n), and (n,4n) reactions, secondary neutron spectra data are consistently reproduced. Pre-equilibrium emission of first neutron is included. Shell effects in the level densities are shown to be important for estimation of energy dependence of non-emissive fission cross section. (author). 105 refs.

Measurement of the ROT effect in the neutron induced fission of 235U in the 0.3 eV resonance at a hot source of polarized neutrons

Science.gov (United States)

Kopatch, Yuri; Novitsky, Vadim; Ahmadov, Gadir; Gagarsky, Alexei; Berikov, Daniyar; Danilyan, Gevorg; Hutanu, Vladimir; Klenke, Jens; Masalovich, Sergey

2018-03-01

The TRI and ROT asymmetries in fission of heavy nuclei have been extensively studied during more than a decade. The effects were first discovered in the ternary fission in a series of experiments performed at the ILL reactor (Grenoble) by a collaboration of Russian and European institutes, and were carefully measured for a number of fissioning nuclei. Later on, the ROT effect has been observed in the emission of prompt gamma rays and neutrons in fission of 235U and 233U, although its value was an order of magnitude smaller than in the α-particle emission from ternary fission. All experiments performed so far are done with cold polarized neutrons, what assumes a mixture of several spin states, the weights of these states being not well known. The present paper describes the first attempt to get "clean" data by performing the measurement of gamma and neutron asymmetries in an isolated resonance of 235U at the POLI instrument of the FRM2 reactor in Garching.

Recent research on nuclear reaction using high-energy proton and neutron

Energy Technology Data Exchange (ETDEWEB)

Shibata, Tokushi [Tokyo Univ., Tanashi (Japan). Inst. for Nuclear Study

1997-11-01

The presently available high-energy neutron beam facilities are introduced. Then some interesting research on nuclear reaction using high-energy protons are reported such as the intermediate mass fragments emission and neutron spectrum measurements on various targets. As the important research using high-energy neutron, the (p,n) reactions on Mn, Fe, and Ni, the elastic scattering of neutrons, and the shielding experiments are discussed. (author)

Neutron-irradiation facilities at the Intense Pulsed Neutron Source-I for fusion magnet materials studies

International Nuclear Information System (INIS)

Brown, B.S.; Blewitt, T.H.

1982-01-01

The decommissioning of reactor-based neutron sources in the USA has led to the development of a new generation of neutron sources that employ high-energy accelerators. Among the accelerator-based neutron sources presently in operation, the highest-flux source is the Intense Pulsed Neutron Source (IPNS), a user facility at Argonne National Laboratory. Neutrons in this source are produced by the interaction of 400 to 500 MeV protons with either of two 238 U target systems. In the Radiation Effects Facility (REF), the 238 U target is surrounded by Pb for neutron generatjion and reflection. The REF has three separate irradiation thimbles. Two thimbles provide irradiation temperatures between that of liquid He and several hundred degrees centigrade. The third thimble operates at ambient temperature. The large irradiation volume, the neutron spectrum and flux, the ability to transfer samples without warm up, and the dedication of the facilities during the irradiation make this ideally suited for radiation damage studies on components for superconducting fusion magnets. Possible experiments for fusion magnet materials are discussed on cyclic irradiation and annealing of stabilizers in a high magnetic field, mechanical tests on organic insulation irradiated at 4 K, and superconductors measured in high fields after irradiation

A Preliminary Study on Detecting Fake Gold Bars Using Prompt Gamma Activation Analysis: Simulation of Neutron Transmission in Gold Bar

Energy Technology Data Exchange (ETDEWEB)

Lee, K. M.; Sun, G. M. [KAERI, Daejeon (Korea, Republic of)

2016-05-15

The purpose of this study is to develop fake gold bar detecting method by using Prompt-gamma activation analysis (PGAA) facility at the Korea Atomic Energy Research Institute (KAERI). PGAA is an established nuclear analytical technique for non-destructive determination of elemental and isotopic compositions. For a preliminary study on detecting fake gold bar, Monte Carlo simulation of neutron transmission in gold bar was conducted and the possibility for detecting fake gold bar was confirmed. Under the gold bullion standard, it guaranteed the government would redeem any amount of currency for its value in gold. After the gold bullion standard ended, gold bars have been the target for investment as ever. But it is well known that fake gold bar exist in the gold market. This cannot be identified easily without performing a testing as it has the same appearance as the pure gold bar. In order to avoid the trading of fake gold bar in the market, they should be monitored thoroughly. Although the transmissivity of cold neutrons are low comparing that of thermal neutrons, the slower neutrons are more apt to be absorbed in a target, and can increase the prompt gamma emission rate. Also the flux of both thermal and cold neutron beam is high enough to activate thick target. If the neutron beam is irradiated on the front and the reverse side of gold bar, all insides of it can be detected.

A Preliminary Study on Detecting Fake Gold Bars Using Prompt Gamma Activation Analysis: Simulation of Neutron Transmission in Gold Bar

International Nuclear Information System (INIS)

Lee, K. M.; Sun, G. M.

2016-01-01

The purpose of this study is to develop fake gold bar detecting method by using Prompt-gamma activation analysis (PGAA) facility at the Korea Atomic Energy Research Institute (KAERI). PGAA is an established nuclear analytical technique for non-destructive determination of elemental and isotopic compositions. For a preliminary study on detecting fake gold bar, Monte Carlo simulation of neutron transmission in gold bar was conducted and the possibility for detecting fake gold bar was confirmed. Under the gold bullion standard, it guaranteed the government would redeem any amount of currency for its value in gold. After the gold bullion standard ended, gold bars have been the target for investment as ever. But it is well known that fake gold bar exist in the gold market. This cannot be identified easily without performing a testing as it has the same appearance as the pure gold bar. In order to avoid the trading of fake gold bar in the market, they should be monitored thoroughly. Although the transmissivity of cold neutrons are low comparing that of thermal neutrons, the slower neutrons are more apt to be absorbed in a target, and can increase the prompt gamma emission rate. Also the flux of both thermal and cold neutron beam is high enough to activate thick target. If the neutron beam is irradiated on the front and the reverse side of gold bar, all insides of it can be detected

Procedure for measurement of anisotropy factor for neutron sources; Procedimentos para medição do fator de anisotropia de fontes de nêutrons

Energy Technology Data Exchange (ETDEWEB)

Creazolla, Prycylla Gomes

2017-07-01

Radioisotope neutron sources allow the production of reference fields for calibration of neutron detectors for radiation protection and analysis purposes. When the emission rate of these sources is isotropic, no correction is necessary. However, variations in source encapsulation and in the radioactive material concentration produce differences in its neutron emission rate, relative to the source axis, this effect is called anisotropy. In this study, is describe a procedure for measuring the anisotropy factor of neutron sources performed in the Laboratório de Metrologia de Neutrons (LN) using a Precision Long Counter (PLC) detector. A measurement procedure that takes into account the anisotropy factor of neutron sources contributes to solve some issues, particularly with respect to the high uncertainties associated with neutron dosimetry. Thus, a bibliographical review was carried out based on international standards and technical regulations specific to the area of neutron fields, and were later reproduced in practice by means of the procedure for measuring the anisotropy factor in neutron sources of the LN. The anisotropy factor is determined as a function of the angle of 90° in relation to the cylindrical axis of the source. This angle is more important due to its high use in measurements and also of its higher neutron emission rate if compared with other angles. (author)

Preliminary neutron shielding calculations of the electronics in the EAST BES systems focusing on neutron induced displacement damage

Energy Technology Data Exchange (ETDEWEB)

Náfrádi, Gábor, E-mail: nafradi@reak.bme.hu [Institute of Nuclear Techniques (NTI), Budapest University of Technology and Economics (BME), H-1111 Budapest (Hungary); Kovácsik, Ákos, E-mail: kovacsik.akos@reak.bme.hu [Institute of Nuclear Techniques (NTI), Budapest University of Technology and Economics (BME), H-1111 Budapest (Hungary); Németh, József, E-mail: nemeth.jozsef@wigner.mta.hu [Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics (Wigner RCP), Hungarian Academy of Sciences (HAS), POB 49, 1525 Budapest (Hungary); Pór, Gábor, E-mail: por@reak.bme.hu [Institute of Nuclear Techniques (NTI), Budapest University of Technology and Economics (BME), H-1111 Budapest (Hungary); Zoletnik, Sándor, E-mail: zoletnik.sandor@wigner.mta.hu [Institute for Particle and Nuclear Physics, Wigner Research Centre for Physics (Wigner RCP), Hungarian Academy of Sciences (HAS), POB 49, 1525 Budapest (Hungary)