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1

Leading neutron spectra  

E-print Network

It is shown that the observation of the spectra of leading neutrons from proton beams can be a good probe of absorptive and migration effects. We quantify how these effects modify the Reggeized pion-exchange description of the measurements of leading neutrons at HERA. We are able to obtain a satisfactory description of all the features of these data. We also briefly discuss the corresponding data for leading baryons produced in hadron-hadron collisions.

A. B. Kaidalov; V. A. Khoze; A. D. Martin; M. G. Ryskin

2006-05-27

2

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

3

Mechanical approach to the neutrons spectra collimation and detection  

SciTech Connect

Neutrons spectra from most of known sources require being collimated for numerous applications; among them one is the Neutron Activation Analysis. High energy neutrons are collimated through a mechanical procedure as one of the most promising methods. The output energy of the neutron beam depends on the velocity of the rotating Polyethylene disks. The collimated neutrons are then measured by an innovative detection technique with high accuracy.

Sadeghi, H.; Roshan, M. V. [Energy Engineering and Physics Department, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

2014-11-15

4

FIGARO : measuring neutron emission spectra with a white neutron source /.  

SciTech Connect

Neutron emission spectra from reactions induced by fast neutrons are of importance in basic physics and applications. Very few data are available in the literature over a wide range of incident neutron energies such as produced with a white neutron source. The FIGARO facility at the WNR/LANSCE neutron source has been established to measure such neutron emission over a range of incident neutron energies from 1 to over 100 MeV. Using the time-of-flight technique twice (once to determine the incident neutron energy and again to determine the outgoing neutron energy), we are measuring neutron emission spectra for several reactions such as (n,n') and (n,f). Neutron emission from inelastic scattering gives information on the level density of excited states of the target nucleus. Our first measurements are on structural materials such as iron.

Haight, Robert C.; O'Donnell, J. M.; Zanini, L.; Devlin, M.; Rochman, D. (Dimitri)

2002-01-01

5

Neutron leakage spectra from beryllium shells  

SciTech Connect

First results on neutron leakage spectra measurements for eight beryllium spheres with wall thickness from 3.2cm to 19.8cm with 14MeV neutron point source in the center are reported. Brief description of experimental arrangement, time of flight spectrometer, measurements and data reduction procedures are given. Preliminary experimental results are compared with the transport calculations, using the latest versions of evaluated data libraries.

Devkin, B.V.; Kobozev, M.G.; Kuzminov, B.D.; Simakov, S.P.; Sinitsa, V.V. [Institute of Physics and Power Engineering, Obninsk (Russian Federation); Chuvilin, D.Yu.; Zagryadsky, V.A. [Kurchatov Institute of Atomic Energy, Moscow (Russian Federation); Fischer, U.; Wiegner, E. [Kernforschungszentrum, Karlsruhe (Russian Federation)

1994-12-31

6

Dose spectra from energetic particles and neutrons  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

7

Activity: Graphing Spectra  

NSDL National Science Digital Library

This activity introduces two different representations of spectra: the photographic representation, such as the rainbow, and the graphical representation used more often by astronomers. A rainbow is often given as an everyday example of a spectrum. Most students have seen a rainbow, so this example is used to help make the unfamiliar more familiar. However, the spectra that scientists use, which students will see in this lesson plan, appear very different than a rainbow. In this activity, students will explore for themselves two different representations of the same spectrum, noting advantages and disadvantages of each. They will explore the differences and similarities of both these representations, and will develop a more intuitive feel for a graphical representation, which may not yet be familiar to them.

2007-02-03

8

Microdosimetric spectra measurements of JANUS neutrons  

SciTech Connect

Neutron radiation from the JANUS reactor at Argonne National Laboratory is being used with increasing frequency for major biological experiments. The fast neutron spectrum has a Kerma-weighted mean energy of 0.8 MeV and low gamma-ray contamination. In 1984 the JANUS fission converter plate of highly enriched uranium was replaced by one made of low-enriched uranium. We recorded microdosimetric spectra at several different positions in the high-flux irradiation room of JANUS before the change of the converter plate. Each set of measurements consisted of spectra taken at three different site diameters (0.5, 1.0, and 5.0 ..mu..m) and in both ''attenuator up'' and ''attenuator down'' configurations. At two conventional dosimetry reference positions, two sets of measurements were recorded. At three biological reference positions, measurements simulating several biological irradiation conditions, were taken. The dose rate at each position was estimated and compared with dose rates obtained previously by conventional dosimetry. Comparison of the different measurements showed no major change in spectra as a function of position or irradiation condition. First results from similar sets of measurements recorded after the installment of the new converter plate indicate no major change in the spectra. 11 refs., 4 figs., 5 tabs.

Marshall, I.R.; Williamson, F.S.

1985-01-01

9

Arsenic activation neutron detector  

DOEpatents

A detector of bursts of neutrons from a deuterium-deuteron reaction includes a quantity of arsenic adjacent a gamma detector such as a scintillator and photomultiplier tube. The arsenic is activated by the 2.5 Mev neutrons to release gamma radiation which is detected to give a quantitative representation of detected neutrons.

Jacobs, Eddy L. (Albuquerque, NM)

1981-01-01

10

Arsenic activation neutron detector  

DOEpatents

A detector of bursts of neutrons from a deuterium-deuteron reaction includes a quantity of arsenic adjacent a gamma detector such as a scintillator and photomultiplier tube. The arsenic is activated by the 2.5-MeV neutrons to release gamma radiation which is detected to give a quantitative representation of detected neutrons.

Jacobs, E.L.

1980-01-28

11

Neutron Irradiation Experiments: Automated Processing and Analysis of ?-spectra  

NASA Astrophysics Data System (ADS)

Adequate prediction of the activation and transmutation response of materials under fusion neutron irradiation is heavily reliant on the quality of the nuclear data used in inventory calculations. Foil irradiation experiments have been conducted using a 14 MeV DT neutron source hosted at AWE Aldermaston in the UK as part of an effort to improve and increase the integral data available for input to the nuclear cross section database. An automated processing system has been developed to handle the huge number of ?-spectra generated from these experiments. As well as providing a framework in which to process a large number of separate experiments automatically and in a consistent manner, the system also allows for the time-dependent ?-spectra available for an individual experiment to be considered as a whole, thereby improving the accuracy of measurements in comparison to those based on a single time-integrated spectrum.

Gilbert, M. R.; Packer, L. W.; Lilley, S.

2014-05-01

12

Evaluation of fission neutron spectra for minor actinides  

SciTech Connect

A method of evaluation of fission neutron spectra was developed and applied to minor actinides. The method is based on the Madland-Nix model of fission neutron emission, combined with the Ignatyuk model of the level density, the Moriyama-Ohnishi model of fission fragment mass distribution and the mass formula of Tachibana et al. It was found that the neutron spectra tend to be harder with increasing fissility of the compound nucleus.

Ohsawa, Takaaki; Shibata, Toshikazu [Kinki Univ., Osaka (Japan)

1994-12-31

13

Eigenvalue-dependent neutron energy spectra: Definitions, analyses, and applications  

Microsoft Academic Search

A general qualitative analysis of spectral effects that arise from solving the kappa-, ..cap alpha..-, ..gamma..-, and sigma-eigenvalue formulations of the neutron transport equation for nuclear systems that deviate (to first order) from criticality is presented. Hierarchies of neutron spectra softness are established and expressed concisely in terms of the newly introduced spatialdependent local spectral indices for the core and

D. G. Cacuci; Y. Ronen; Z. Shayer; J. J. Wagschal; Y. Yeivin

1982-01-01

14

Neutron Spectra and Dose Equivalent Inside Nuclear Power Reactor Containment  

SciTech Connect

This study was conducted to determine absorbed dose, dose-equivalent rates, and neutron spectra inside containment at nuclear power plants. We gratefully acknowledge funding support by the Nuclear Regulatory Commission. The purpose of this study is: 1) measure dose-equivalent rates with various commercial types of rem meters, such as the Snoopy and Rascal, and neutron absorbed dose rates with a tissue-equivalent proportional counter 2) determine neutron spectra using the multi sphere or Bonner sphere technique and a helium-3 spectrometer 3) compare several types of personnel neutron dosimeter responses such as NTA film, polycarbonates, TLD albedo, and a recently introduced proton recoil track etch dosimeter, and CR-39. These measurements were made inside containments of pressurized water reactors (PWRs) and outside containment penetrations of boiling water reactors (BWRs) operating at full power. The neutron spectral information, absorbed dose. and dose-equivalent measurements are needed for proper interpretation of instrument and personnel dosimeter responses.

Aldrich, J. M.

1981-08-01

15

Calculated Neutron and Gamma-ray Spectra across the Prismatic Very High Temperature Reactor Core  

SciTech Connect

Neutron and gamma-ray flux spectra are calculated using the MCNP5 computer code and a one-sixth core model of a prismatic Very High Temperature Reactor based on the General Atomics Gas Turbine-Modular Helium Reactor. Spectra are calculated in the five inner reflector graphite block rings, three annular active core fuel rings, three outer graphite reflector block rings, and the core barrel. The neutron spectra are block and fuel pin averages and are calculated as a function of temperature and burnup. Also provided are the total, fast, and thermal radial profile fluxes and core barrel dpa rates.

James W. Sterbentz

2008-05-01

16

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

PubMed Central

Neutrons are a by-product of high-energy x-ray radiation therapy (threshold for [?,n] reactions in high-Z material ?7 MeV). Neutron production varies depending on photon beam energy as well as on the manufacturer of the accelerator. Neutron production from modern linear accelerators (linacs) has not been extensively compared, particularly in terms of the differences in the strategies that various manufacturers have used to implement multileaf collimators (MLCs) into their linac designs. However, such information is necessary to determine neutron dose equivalents for different linacs and to calculate vault shielding requirements. The purpose of the current study, therefore, was to measure the neutron spectra from the most up-to-date linacs from three manufacturers: Varian 21EX operating at 15, 18, and 20 MV, Siemens ONCOR operating at 15 and 18 MV, and Elekta Precise operating at 15 and 18 MV. Neutron production was measured by means of gold foil activation in Bonner spheres. Based on the measurements, the authors determined neutron spectra and calculated the average energy, total neutron fluence, ambient dose equivalent, and neutron source strength. The shapes of the neutron spectra did not change significantly between accelerators or even as a function of treatment energy. However, the neutron fluence, and therefore the ambient dose equivalent, did vary, increasing with increasing treatment energy. For a given nominal treatment energy, these values were always highest for the Varian linac. The current study thus offers medical physicists extensive information about the neutron production of MLC-equipped linacs currently in operation and provides them information vital for accurate comparison and prediction of neutron dose equivalents and calculation of vault shielding requirements. PMID:19810475

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

2009-01-01

17

Neutron spectra due (13)N production in a PET cyclotron.  

PubMed

Monte Carlo and experimental methods have been used to characterize the neutron radiation field around PET (Positron Emission Tomography) cyclotrons. In this work, the Monte Carlo code MCNPX was used to estimate the neutron spectra, the neutron fluence rates and the ambient dose equivalent (H*(10)) in seven locations around a PET cyclotron during (13)N production. In order to validate these calculations, H*(10) was measured in three sites and were compared with the calculated doses. All the spectra have two peaks, one above 0.1MeV due to the evaporation neutrons and another in the thermal region due to the room-return effects. Despite the relatively large difference between the measured and calculated H*(10) for one point, the agreement was considered good, compared with that obtained for (18)F production in a previous work. PMID:25699664

Benavente, J A; Vega-Carrillo, H R; Lacerda, M A S; Fonseca, T C F; Faria, F P; da Silva, T A

2015-05-01

18

A study of neutron spectra from medical linear accelerators.  

PubMed

Medical accelerators with photon energies over 10 MeV generate an undesired fast neutron contamination in the therapeutic beam. In this work, the Monte Carlo code MCNP was used to simulate the transport of these photoneutrons across the head of various medical accelerators of high energy. The average and most probable neutron energies were obtained from these spectra, before and after crossing the accelerator shielding. The degradation of these spectra, when they cross concrete barriers with thickness which vary between 25 and 100 cm, was also studied. PMID:15498687

Facure, A; Falcão, R C; Silva, A X; Crispim, V R; Vitorelli, J C

2005-01-01

19

Neutron activation for ITER  

SciTech Connect

There are three primary goals for the Neutron Activation system for ITER: maintain a robust relative measure of fusion power with stability and high dynamic range (7 orders of magnitude); allow an absolute calibration of fusion power (energy); and provide a flexible and reliable system for materials testing. The nature of the activation technique is such that stability and high dynamic range can be intrinsic properties of the system. It has also been the technique that demonstrated (on JET and TFTR) the highest accuracy neutron measurements in DT operation. Since the gamma-ray detectors are not located on the tokamak and are therefore amenable to accurate characterization, and if material foils are placed very close to the ITER plasma with minimum scattering or attenuation, high overall accuracy in the fusion energy production (7--10%) should be achievable on ITER. In the paper, a conceptual design is presented. A system is shown to be capable of meeting these three goals, also detailed design issues remain to be solved.

Barnes, C.W. [Los Alamos National Lab., NM (United States); Loughlin, M.J. [JET Joint Undertaking, Abingdon (United Kingdom); Nishitani, Takeo [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

1996-04-29

20

Neutron emission profiles and energy spectra measurements at JET  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

21

Neutron emission profiles and energy spectra measurements at JET  

SciTech Connect

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

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

2014-08-21

22

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

PubMed

This paper aims to measure the spectra of HB11 (high flux reactor, HFR) and the Tsing Hua open-pool reactor (THOR) boron neutron capture therapy (BNCT) beams by multiple activation foils. The self-shielding corrections were made with the aid of MCNP calculations. The initial spectra were adjusted by a sophisticated process named coarse-scaling adjustment using SAND-EX, which can adjust a given coarse-group spectrum into a fine-group structure, i.e. 640 groups, with excellent continuity. The epithermal neutron flux of the THOR beam is about three times of HB11. The thermal neutron flux, boron and gold reaction rates along the central axis of a PMMA phantom are calculated for both adjusted spectra for comparison. PMID:19409798

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

2009-07-01

23

Measurements of the neutron spectra from the 7Li(p,n) accelerator based neutron source: Position and angular dependences  

NASA Astrophysics Data System (ADS)

Thick target 7Li(p,n) neutron spectra were measured using a 3He ion chamber in the proton energy range of 1.95 to 2.30 MeV. The fast neutron spectra were collected for various distances from the lithium target as well as for various neutron emission angles. By unfolding the 3He raw data with the iterative van Cittert algorithm, the neutron fluence spectra were obtained. The 3He measured neutron spectra were compared with both analytically computed and Monte Carlo simulated spectra to account for neutron scatterings in the lithium target assembly and in the experimental area. To verify the accuracy of the neutron dose computation, the fast neutron kerma was obtained for each neutron spectrum using the fluence to kerma conversion coefficients and was compared with the measured neutron dose using tissue-equivalent proportional counters. In the position dependence investigation at the 0° emission angle, the analytically computed neutron kerma overestimates the experimental kerma by a factor of two mainly due to neutron moderation. The corresponding neutron kerma from the 3He measured spectra were in agreement with the neutron doses measured using tissue-equivalent proportional counters within 20% for lower proton energies, but the discrepancy increased to ˜50% for higher proton energies. In the angular distribution investigation, a notable discrepancy between measured and computed neutron spectra were observed due to the neutron scattering effects in the target assembly and experimental room.

Matysiak, W.; Prestwich, W. V.; Byun, S. H.

2012-11-01

24

Neutron dose and energy spectra measurements at Savannah River Plant  

SciTech Connect

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

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

1987-08-01

25

Neutron Activation Data for Neutron Interrogation  

NASA Astrophysics Data System (ADS)

Various schemes have been proposed for neutron interrogation of packages, luggage, or containers with the intent of locating concealed contraband items such as conventional explosives, drugs, or restricted special nuclear materials. Relatively intense and energetic neutron sources are usually required in these applications in order to penetrate the scanned objects and to provide unambiguous characteristic signals that are well above background, thereby minimizing both false positives and negatives. Consequently, neutron irradiation of the materials in tested objects during the interrogation process could lead to the production of significant residual radioactivity. This, in turn, might either limit or prevent the application of these methods in those situations where there is a potential for unacceptable public exposure to the induced secondary radiations. The present study aims to identify those particular neutron-induced reactions that might generate significant activation. This is accomplished by conducting a thorough survey of the current status of the pertinent cross section data available from the major general purpose and special purpose data files for neutron energies up to 15 MeV. This conference paper provides an overview of this ongoing project and discusses the status of some of the more prominent candidate reactions that have been identified to date.

Smith, Donald L.; Micklich, Bradley J.

2005-05-01

26

Calculation of Prompt Neutron Multiplicities and Spectra for Several Actinides  

SciTech Connect

The prompt fission neutron multiplicity and spectra of actinides are nuclear data of crucial importance. Based on experimental fission yield and total kinetic energy data, new calculations for the prompt neutron multiplicity and spectra for 238U(n,f), 237Np(n,f) in the incident neutron energy range up to the second chance fission threshold, for 238U(n,f), up to 50 MeV, and for 252Cf(SF) have been performed.For the first time the multi-modality of the fission process was taken into account up to the second fission chance (about 6 MeV). Additionally, for some isotopes a more realistic fission fragment residual temperature distribution as well as an anisotropy of the prompt neutron emission led to improved agreement between the calculation and experimental results. Also, the range of fission fragment pairs entering in the multiplicity and spectrum model was extended over the entire experimental fission-fragment mass range. This led to an improved version of the Los Alamos (LA) model and especially to an improved determination of the input model parameters. In addition the LA model is extended towards higher incident neutron energy, where the fission of compound nuclei formed by charged particle emission occurs.

Hambsch, Franz-Josef; Oberstedt, Stephan [EC-JRC-Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium); Tudora, Anabella; Vladuca, Gheorghita [Faculty of Physics, Bucharest University, RO-76900 Bucharest (Romania)

2005-05-24

27

X-ray spectra from convective photospheres of neutron stars  

SciTech Connect

We present first results of modeling convective photospheres of neutron stars. We show that in photospheres composed of the light elements convection arises only at relatively low effective temperatures ({le}3 - 5 x 10{sup 4} K), whereas in the case of iron composition it arises at T{sub eff}{le} 3 x 10{sup 5}K. Convection changes the depth dependence of the photosphere temperature and the shapes of the emergent spectra. Thus, it should be taken into account for the proper interpretation of EUV/soft-X-ray observations of the thermal radiation from neutron stars.

Zavlin, V.E. [Max-Planck-Institut fuer Extraterrestrische Physik, Garching (Germany); Pavlov, G.G. [Pennsylvania State Univ., PA (United States)]|[Ioffe Institute of Physics and Technology, St. Petersburg, RU (United States); Shibanov, Yu.A. [Ioffe Institute of Physics and Technology, St. Petersburg (Russian Federation); Rogers, F.J.; Iglesias, C.A. [Lawrence Livermore National Lab., CA (United States)

1996-01-17

28

Neutron Activation Analysis: Techniques and Applications  

SciTech Connect

The role of neutron activation analysis in low-energy low-background experimentsis discussed in terms of comparible methods. Radiochemical neutron activation analysis is introduce. The procedure of instrumental neutron activation analysis is detailed especially with respect to the measurement of trace amounts of natural radioactivity. The determination of reactor neutron spectrum parameters required for neutron activation analysis is also presented.

MacLellan, Ryan [University of Alabama, Department of Physics and Astronomy, Tuscaloosa, AL, 35487-0324 (United States)

2011-04-27

29

PUBLISHED VERSION Neutron emission profiles and energy spectra measurements at JET  

E-print Network

.1063/1.35052 Nuclear Emulsions and the Measurement of Low Energy Neutron Spectra Rev. Sci. Instrum. 21, 534 (1950); 10PUBLISHED VERSION Neutron emission profiles and energy spectra measurements at JET Giacomelli L be found at : http://dx.doi.org/10.1063/1.4894035 #12;Neutron emission profiles and energy spectra

30

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

E-print Network

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

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

2014-09-05

31

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

32

Improved Fission Neutron Data Base for Active Interrogation of Actinides  

SciTech Connect

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).

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

2013-11-06

33

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

34

Pulsed neutron generator for use with pulsed neutron activation techniques  

SciTech Connect

A high-output, transportable, pulsed neutron generator has been developed by Sandia National Laboratories for use with Pulsed Neutron Activation (PNA) techniques. The PNA neutron generator generates > 10/sup 10/ 14 MeV D-T neutrons in a 1.2 millisecond pulse. Each operation of the unit will produce a nominal total neutron output of 1.2 x 10/sup 10/ neutrons. The generator has been designed to be easily repaired and modified. The unit requires no additional equipment for operation or measurement of output.

Rochau, G.E.

1980-01-01

35

Calculated proton-induced thick-target radionuclide activation yields and neutron yield spectra for E/sub p/ less than or equal to 50 MeV, with comparisons to other calculations and measured data  

SciTech Connect

Radionuclide production cross sections have been calculated with the GNASH code for protons below 50 MeV incident of on the stable nuclides of a range of elements common to accelerator materials. These elements include C, O, Ne, Al, Si, Fe, Co, Ni, Cu, and W. These data, augmented with limited measured data, have been used with the proton stopping cross-section data of Anderson and Ziegler to calculate thick-target yield values for the formation of a range of radionuclides in accelerator materials. Illustrative results are presented. GNASH calculations have also been made on a grid of proton energies below 50 MeV to produce differential cross sections describing angle-integrated neutron production spectra. The angular distribution systematics of Kalbach and Mann have been used to produce double-differential cross-section, which were used with the proton stopping data to produce anisotropic thick-target neutron yield spectra. Results are presented for 52-MeV protons on a thick target of Cu. Comparisons are made with results of HETC calculations, using cross sections from the intranuclear cascade plus evaporation model, and with thick-target neutron yield spectra measured by Nakamura, Fijii, and Shin. 15 refs., 3 figs., 1 tab.

Wilson, W.B.; Arthur, E.D.; LaBauve, R.J.; Perry, R.T.

1988-01-01

36

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

SciTech Connect

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

Kroc, T.K.; /Fermilab

2009-10-01

37

Neutron Spectra from Intermediate-Energy Nucleus-Nucleus Reactions  

NASA Astrophysics Data System (ADS)

Double-differential cross sections of neutron production at angles from 0 to 110 degrees from many reactions induced by light and medium nuclei on targets from 12C to 208Pb, at several incident energies from 95 to 600 MeV/nucleon have been measured recently at the Institute of Physical and Chemical Research (RIKEN) Ring Cyclotron in Japan and at the Heavy-Ion Medical Accelerator of the National Institute of Radiological Science in Chiba, Japan using the time-of-flight technique. We have analyzed all these new measurements using the Quantum Molecular Dynamics (QMD) model, the Oak Ridge intranuclear cascade model HIC, the ISABEL intranuclear cascade model from LAHET, and the Los Alamos version of the Quark-Gluon String Model code LAQGSM03. On the whole, all four models used here describe reasonably well most of the measured neutron spectra, although different models agree differently with data from specific reactions and some serious discrepances are observed for some reactions. We present here some illustrative results from our study, discuss possible reasons for some of the observed discrepancies and try to outline ways to further improve the tested codes in order to address these problems.

Iwase, Hiroshi; Iwata, Yoshiyuki; Nakamura, Takashi; Gudima, Konstantin; Mashnik, Stepan; Sierk, Arnold; Prael, Richard

2005-05-01

38

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

SciTech Connect

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

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

2008-01-01

39

Realistic neutron spectra for radiation protection and other applications at AERI, Budapest  

Microsoft Academic Search

The reconstruction of the Budapest Research Reactor (BRR) gave a good possibility to develop mixed neutron-gamma radiation fields for different applications like: simulation of operational spectra at power reactors, dosimeter development, neutron radiography, biological experiments. Recently, there are 3 horizontal channels available. In addition, isotopic neutron sources are in use in a separate laboratory. In a rotatable holder 4 different

J. Pálfalvi; L. Sajó-Bohus; M. Balaskó

2002-01-01

40

Neutron Activation Diagnostics for FRCHX at AFRL  

Microsoft Academic Search

Neutron diagnostics have been developed for MTF on the field reversed configuration heating experiment (FRCHX) to detect both DD and DT neutrons. We are working with time-integrated activation counting systems for absolute measurements of neutron yields, in the range of 10^6-10^13 neutrons\\/shot. We are using multiple diagnostics due to different activation thresholds and need for diagnostic redundancy. The first system

D. A. Sutherland; G. A. Wurden; T. P. Intrator

2009-01-01

41

Measurement of free beam neutron spectra at eight BNCT facilities worldwide.  

PubMed

Eight epithermal neutron beams, constructed for clinical or preclinical studies of NCT, have been dosimetrically characterized by in-air measurements with a set of activation foils for the determination of the neutron energy spectra in free beam. Measurements have been made on the already closed epithermal BNCT facility at the BMRR of the Brookhaven National Laboratory, on the HFR at JRC in Petten, The Netherlands, on the epithermal mode beam at KURRI, Japan, on the fission converter beam at MIT, USA, on the epithermal beam of the RA-6 facility in Bariloche, Argentina, on the epithermal beam at WSU, USA, on the mixed mode beam at JRR-4 at JAERI, Japan, as well as on the epithermal beam at FiR 1 at VTT, Espoo, Finland. PMID:15308186

Auterinen, I; Serén, T; Anttila, K; Kosunen, A; Savolainen, S

2004-11-01

42

Differential neutron energy spectra measured on spacecraft low Earth orbit  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

43

Spectra  

NSDL National Science Digital Library

Learners construct a spectroscope out of a shoe box or mailing tube, diffraction grating, and other simple materials. They then use their spectroscope to observe spectra, the colors that make up light. Learners compare the spectra of various light sources. Use this activity to introduce learners to basic principles of light and color. Also, look at a related page about auroras to understand how distinguishing spectra of different atoms helps scientists understand the universe.

The Exploratorium

2012-06-26

44

Investigation of elemental analysis using neutron-capture gamma ray spectra  

E-print Network

This thesis evaluated the potential of neutron-capture gamma rays in elemental analysis. A large portion of the work was devoted to the development of a method for the analysis of weak peaks in gamma ray spectra. This was ...

Hamawi, John Nicholas

1969-01-01

45

Measurements of energy spectra and doses in liquid air of neutrons from a californium-252 source  

Microsoft Academic Search

To provide data for testing nitrogen and oxygen cross-section sets, transport of neutrons from a ²⁵²Cf source was investigated in a large volume of liquid air. Neutron energy spectra and doses were measured at distances between 30 and 230 cm from the source. Proton recoil proportional counters and NE-213 scintillation detectors were used to obtain energy spectra from 40 keV

K. Clausen; U. Roose; P. Schneider-Kuehnle; F. W. Buchholz; L. Schaenzler; S. Stueker; G. Tumbraegel; M. Weinert

1977-01-01

46

MAGNETIC ENERGY SPECTRA IN SOLAR ACTIVE REGIONS  

SciTech Connect

Line-of-sight magnetograms for 217 active regions (ARs) with different flare rates observed at the solar disk center from 1997 January until 2006 December are utilized to study the turbulence regime and its relationship to flare productivity. Data from the SOHO/MDI instrument recorded in the high-resolution mode and data from the BBSO magnetograph were used. The turbulence regime was probed via magnetic energy spectra and magnetic dissipation spectra. We found steeper energy spectra for ARs with higher flare productivity. We also report that both the power index, {alpha}, of the energy spectrum, E(k) {approx} k{sup -}{alpha}, and the total spectral energy, W = {integral}E(k)dk, are comparably correlated with the flare index, A, of an AR. The correlations are found to be stronger than those found between the flare index and the total unsigned flux. The flare index for an AR can be estimated based on measurements of {alpha} and W as A = 10{sup b}({alpha}W){sup c}, with b = -7.92 {+-} 0.58 and c = 1.85 {+-} 0.13. We found that the regime of the fully developed turbulence occurs in decaying ARs and in emerging ARs (at the very early stage of emergence). Well-developed ARs display underdeveloped turbulence with strong magnetic dissipation at all scales.

Abramenko, Valentyna; Yurchyshyn, Vasyl [Big Bear Solar Observatory, 40386 N. Shore Lane, Big Bear City, CA 92314 (United States)

2010-09-01

47

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

NASA Astrophysics Data System (ADS)

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

Ján, Mil?ák; Michal, Koš?ál; Marie, Švadlenková; Michal, Koleška; Vojt?ch, Rypar

2014-11-01

48

Assessing neutron generator output using neutron activation of silicon  

NASA Astrophysics Data System (ADS)

D-T neutron generators are used for elemental composition analysis and medical applications. Often composition is determined by examining elemental ratios in which the knowledge of the neutron flux is unnecessary. However, the absolute value of the neutron flux is required when the generator is used for neutron activation analysis, to study radiation damage to materials, to monitor the operation of the generator, and to measure radiation exposure. We describe a method for absolute neutron output and flux measurements of low output D-T neutron generators using delayed activation of silicon. We irradiated a series of silicon oxide samples with 14.1 MeV neutrons and counted the resulting gamma rays of the 28Al nucleus with an efficiency-calibrated detector. To minimize the photon self-absorption effects within the samples, we used a zero-thickness extrapolation technique by repeating the measurement with samples of different thicknesses. The neutron flux measured 26 cm away from the tritium target of a Thermo Electron A-325 D-T generator (Thermo Electron Corporation, Colorado Springs, CO) was 6.2 × 10 3 n/s/cm 2 ± 5%, which is consistent with the manufacturer's specifications.

Kehayias, Pauli M.; Kehayias, Joseph J.

2007-08-01

49

Measured neutron and gamma spectra from californium-252 in a tissue-equivalent medium  

Microsoft Academic Search

A method of experimentally obtaining both neutron and gamma-ray spectra in a scattering medium is described. The method utilizes a liquid-organic scintillator (NE-213) coupled with a pulse-shape discrimination circuit. This allows the separation of the neutron-induced pulse-height data from the gamma-ray pulse-height data. Using mathematical unfolding techniques, the two sets of pulse-height data were transformed to obtain the neutron and

Howard R. Elson; Terry A. Stupar; Alvin Shapiro; James G. Kereiakes

1979-01-01

50

Measurement of the MACS of Ta181(n,?) at kT=30 keV as a test of a method for Maxwellian neutron spectra generation  

NASA Astrophysics Data System (ADS)

Measurement of the Maxwellian-Averaged Cross-Section (MACS) of the Ta(n,?)181 reaction at kT=30 keV by the activation technique using an innovative method for the generation of Maxwellian neutron spectra is presented. The method is based on the shaping of the proton beam to produce a desired neutron spectrum using the 7Li(p,n) reaction as a neutron source. The characterization of neutron spectra has been performed by combining measured proton distributions, an analytical description of the differential neutron yield in angle and energy of the 7Li(p,n) reaction, and with Monte Carlo simulations of the neutron transport. A measured value equal to 815±73 mbarn is reported for the MACS of the reaction Ta(n,?)181 at kT=30 keV. The MACS of the reaction Au(n,?)197 provided by KADoNiS has been used as a reference.

Praena, J.; Mastinu, P. F.; Pignatari, M.; Quesada, J. M.; García-López, J.; Lozano, M.; Dzysiuk, N.; Capote, R.; Martín-Hernández, G.

2013-11-01

51

Measurement of spectra and neutron fluxes on artificial earth satellites from the Cosmos series  

NASA Technical Reports Server (NTRS)

In 1966-1967 measurements were carried out at the altitudes of 200 to 400 km to determine the spectra and fluxes of fast neutrons inside the hermetically sealed artificial earth satellites of the Cosmos series. The detectors used were nuclear emulsions of the B9 and BR types and an emulsion of the P9 type, filled with Li and P. Spectra and fluxes of neutrons in the range of energies from thermal energies to 10 MeV are presented. Neutron doses are also estimated.

Dudkin, V. Y.; Kovalev, Y. Y.; Novikova, M. R.; Potapov, Y. V.; Skvortsov, S. S.; Smirennyy, L. N.

1975-01-01

52

Analysis of primary damage in silicon carbide under fusion and fission neutron spectra  

NASA Astrophysics Data System (ADS)

Irradiation parameters on primary damage states of SiC are evaluated and compared for the first wall of ITER under deuterium-deuterium (DD) and deuterium-tritium (DT) operation, the high temperature gas-cooled reactor (HTGR) and high flux isotope reactor (HFIR). With the same neutron fluence, the studied fusion spectra produce more damage and much higher gas production than the fission spectra. Due to comparable gas production and similar weighted primary recoil spectra, HFIR is considered suitable to simulate the neutron irradiation in an HTGR. In contrast to the significant differences between the weighted primary recoil spectra of the fission and the fusion spectra, the weighted secondary recoil spectra of HFIR and HTGR match those of DD and DT, indicating that displacement cascades by the fission and the fusion irradiation are similar when the damage distribution among damaged regions by secondary recoils is taken into account.

Guo, Daxi; Zang, Hang; Zhang, Peng; Xi, Jianqi; Li, Tao; Ma, Li; He, Chaohui

2014-12-01

53

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

NASA Astrophysics Data System (ADS)

We report on irradiation tests of InSb based Hall sensors at two irradiation facilities with two distinct types of neutron spectra. One was a fission reactor neutron spectrum with a significant presence of thermal neutrons, while another one was purely fast neutron field. Total neutron fluence of the order of 1016 cm-2 was accumulated in both cases, leading to significant drop of Hall sensor sensitivity in case of fission reactor spectrum, while stable performance was observed at purely fast neutron spectrum. This finding suggests that performance of this particular type of Hall sensors is governed dominantly by transmutation. Additionally, it further stresses the need to test ITER candidate Hall sensors under neutron flux with ITER relevant spectrum.

?uran, I.; Bolshakova, I.; Viererbl, L.; Sentkerestiová, J.; Holyaka, R.; Lahodová, Z.; Bém, P.

2010-10-01

54

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

SciTech Connect

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

Duran, I. [Institute of Plasma Physics AS CR, v. v. i., Association EURATOM/IPP.CR, 182 00 Prague 8 (Czech Republic); Bolshakova, I.; Holyaka, R. [Magnetic Sensor Laboratory, Lviv Polytechnic National University, 790 31 Lviv (Ukraine); Viererbl, L.; Lahodova, Z. [Nuclear Research Institute plc., 250 68 Husinec-Rez (Czech Republic); Sentkerestiova, J. [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, 115 19 Prague 1 (Czech Republic); Bem, P. [Nuclear Physics Institute AS CR, v. v. i., 250 68 Husinec-Rez (Czech Republic)

2010-10-15

55

Neutron dose equivalent and neutron spectra in tissue for clinical linacs operating at 15, 18 and 20 MV.  

PubMed

In this work, the dose equivalent due to photoneutrons and the neutron spectra in tissue was calculated for various linacs (Varian Clinac 2100C, Elekta Inor, Elekta SL25 and Siemens Mevatron KDS) operating at energies between 15 and 20 MV, using the Monte Carlo code MCNPX (v. 2.5). The dose equivalent in an ICRU tissue phantom has been calculated for anteroposterior treatments with a detailed simulation of the geometry of the linac head and the coupled electron-photon-neutron transport. Neutron spectra at the phantom entrance and at 1-cm depth in the phantom, depth distribution of the neutron fluence in the beam axis and dose distributions outside the beam axis at various depths have also been calculated and compared with previously published results. The differences between the neutron production of the various linacs considered has been analysed. Varian linacs show a larger neutron production than the Elekta and Siemens linacs at the same operating energy. The dose equivalent due to neutrons produced by medical linacs operating at energies >15 MeV is relevant and should not be neglected because of the additional doses that patients can receive. PMID:21233098

Martínez-Ovalle, S A; Barquero, R; Gómez-Ros, J M; Lallena, A M

2011-11-01

56

Testing of the IRDF-90 cross-section library in benchmark neutron spectra  

SciTech Connect

The new version of the International Reactor Dosimetry File IRDF-90 (called Version April 1993) has been tested by calculation of average cross-sections and their uncertainties in a coarse three energy group structure and by neutron spectrum adjustments in reference neutron spectra. This paper presents the results and compares them with the corresponding ones for the old Reactor Dosimetry File IRDF-85 and with the data of the Nuclear Data Guide for Reactor Neutron Metrology. Finally, the applicability of the new library in the field of neutron metrology is discussed.

Nolthenius, H.J. [Energy Research Foundation ECN, Petten (Netherlands); Zsolnay, E.M.; Szondi, E.J. [Technical Univ. of Budapest (Hungary). Inst. of Nuclear Techniques

1994-12-31

57

Calculations of neutron flux spectra induced in the earth's atmosphere by galactic cosmic rays  

NASA Technical Reports Server (NTRS)

Calculations have been carried out to determine the neutron flux induced in the earth's atmosphere by galactic protons and alpha particles at solar minimum for a geomagnetic latitude of 42 N. Neutron flux spectra were calculated using Monte Carlo and discrete ordinates methods, and various comparisons with experimental data are presented. The magnitude and shape of the calculated neutron-leakage spectrum at the particular latitude considered support the theory that the cosmic-ray-albedo-neutron-decay mechanism is the source of the protons and electrons trapped in the Van Allen belts.

Armstrong, T. W.; Chandler, K. C.; Barish, J.

1972-01-01

58

What should neutron spectra from boron carbide devices look like?  

Microsoft Academic Search

GEANT4 (Geometry ANd Tracking) monte carlo modeling was performed on boron based neutron detectors [1]. Two different detector geometries were used. Geometry 1 consisted of a boron carbide (BC) layer placed on a Silicon (Si) layer in a cylindrical design with thermal neutrons of energy 0.025eV incident on the BC face. Geometry 2 was a rudimentary calorimeter made by sandwiching

Carl Lundstedt; Ellen Day; Shireen Adenwalla

2006-01-01

59

Experimental arrangements suitable for the acquisition of inelastic neutron scattering spectra of heterogeneous catalysts.  

PubMed

Inelastic neutron scattering (INS) is increasingly being used for the characterization of heterogeneous catalysts. As the technique is uniquely sensitive to hydrogen atoms, vibrational spectra can be obtained that emphasize a hydrogenous component or hydrogen-containing moieties adsorbed on to an inorganic support. However, due to sensitivity constraints, the technique typically requires large sample masses (?10 g catalyst). A reaction system is hereby described that enables suitable quantities of heterogeneous catalysts to be appropriately activated and operated under steady-state conditions for extended periods of time prior to acquisition of the INS spectrum. In addition to ex situ studies, a cell is described which negates the need for a sample transfer stage between reaction testing and INS measurement. This cell can operate up to temperatures of 823 K and pressures up to 20 bar. The apparatus is also amenable to adsorption experiments at the gas-solid interface. PMID:21456765

Silverwood, Ian P; Hamilton, Neil G; McFarlane, Andrew; Ormerod, R Mark; Guidi, Tatiana; Bones, Jonathan; Dudman, Michael P; Goodway, Christopher M; Kibble, Mark; Parker, Stewart F; Lennon, David

2011-03-01

60

Measurement of Leakage Neutron Spectra for Tungsten with D-T Neutrons and Validation of Evaluated Nuclear Data  

E-print Network

Integral neutronics experiments have been investigated at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS) in order to validate evaluated nuclear data related to the design of Chinese Initiative Accelerator Driven Systems (CIADS). In present paper, the accuracy of evaluated nuclear data for Tungsten has been examined by comparing measured leakage neutron spectra with calculated ones. Leakage neutron spectra from the irradiation of D-T neutrons on Tungsten slab sample were experimentally measured at 60$^{\\circ}$ and 120$^{\\circ}$ by using a time-of-flight method. Theoretical calculations are carried out by Monte Carlo neutron transport code MCNP-4C with evaluated nuclear data of the ADS-2.0, ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0 and CENDL-3.1 libraries. From the comparisons, it is found that the calculations with ADS-2.0 and ENDF/B-VII.1 give good agreements with the experiments in the whole energy regions at 60$^{\\circ}$, while a large discrepancy is observed at 120$^{\\circ}$ in the elastic scattering peak, caused by a slight difference in the oscillation pattern of the elastic angular distribution at angles larger than 20$^{\\circ}$. However, the calculated spectra using data from ENDF/B-VII.0, JENDL-4.0 and CENDL-3.1 libraries showed larger discrepancies with the measured ones, especially around 8.5-13.5 MeV. Further studies are presented for these disagreements.

S. Zhanga; Z. Chen; Y. Nie; R. Wada; X. Ruan; R. Han; X. Liu; W. Lin; J. Liu; F. Shi; P. Ren; G. Tian; F. Luo; J. Ren; J. Bao

2014-11-20

61

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

NASA Astrophysics Data System (ADS)

A large set of nuclear data are investigated to improve the calculation predictions of the new neutron transport simulation codes. With the next generation of nuclear power plants (GEN IV projects), one expects to reduce the calculated uncertainties which are mainly coming from nuclear data and are still very important, before taking into account integral information in the adjustment process. In France, future nuclear power plant concepts will probably use MOX fuel, either in Sodium Fast Reactors or in Gas Cooled Fast Reactors. Consequently, the knowledge of 239Pu cross sections and other nuclear data is crucial issue in order to reduce these sources of uncertainty. The Prompt Fission Neutron Spectra (PFNS) for 239Pu are part of these relevant data (an IAEA working group is even dedicated to PFNS) and the work presented here deals with this particular topic. The main international data files (i.e. JEFF-3.1.1, ENDF/B-VII.0, JENDL-4.0, BRC-2009) have been considered and compared with two different spectra, coming from the works of Maslov and Kornilov respectively. The spectra are first compared by calculating their mathematical moments in order to characterize them. Then, a reference calculation using the whole JEFF-3.1.1 evaluation file is performed and compared with another calculation performed with a new evaluation file, in which the data block containing the fission spectra (MF=5, MT=18) is replaced by the investigated spectra (one for each evaluation). A set of benchmarks is used to analyze the effects of PFNS, covering criticality cases and mock-up cases in various neutron flux spectra (thermal, intermediate, and fast flux spectra). Data coming from many ICSBEP experiments are used (PU-SOL-THERM, PU-MET-FAST, PU-MET-INTER and PU-MET-MIXED) and French mock-up experiments are also investigated (EOLE for thermal neutron flux spectrum and MASURCA for fast neutron flux spectrum). This study shows that many experiments and neutron parameters are very sensitive to the PFNS, in particular for high leakage thermal criticality cases for which the discrepancy between international evaluation files spectra and Kornilov spectra can reach 800 pcm. A neutronic analysis is proposed to explain this large discrepancy. For fast spectrum cases, Maslov's and Kornilov's spectra have a negative effect, between some dozens of pcm to around 300 pcm.

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

2014-04-01

62

Measurements of the Martian Gamma/Neutron Spectra with MSL/RAD  

NASA Astrophysics Data System (ADS)

The Radiation Assessment Detector (RAD) onboard Mars Science Laboratory's rover curiosity measures the energetic charged and neutral particle spectra and the radiation dose rate on the Martian surface. An important factor for determining the biological impact of the Martian surface radiation is the specific contribution of neutrons, which possess a high biological effectiveness. In contrast to charged particles, neutrons and gamma rays are generally only measured indirectly. Their measurement is the result of a complex convolution of the incident particle spectrum with the measurement process. We apply an inversion method to calculate the gamma/neutron spectra from the RAD neutral particle measurements. Here we show first measurements of the Martian gamma/neutron spectra and compare them to theoretical predictions. We find that the shape of the gamma spectrum is very similar to the predicted one, but with a ~50% higher intensity. The measured neutron spectrum agrees well with prediction up to ~100 MeV, but shows a considerably increased intensity for higher energies. The measured neutron spectrum translates into a radiation dose rate of 25 ?Gy/day and a dose equivalent rate of 106 ?Sv/day. This corresponds to 10% of the total surface dose rate, and 15% of the biological relevant surface dose equivalent rate on Mars. Measuring the Martian neutron spectra is an essential step for determining the mutagenic influences to past or present life at or beneath the Martian surface as well as the radiation hazard for future human exploration, including the shielding design of a potential habitat. The contribution of neutrons to the dose equivalent increases considerably with shielding thickness, so our measurements provide an important figure to mitigate cancer risk.

Kohler, J.; Zeitlin, C. J.; Ehresmann, B.; Wimmer-Schweingruber, R. F.; Hassler, D.; Reitz, G.; Brinza, D.; Weigle, E.; Boettcher, S.; Burmeister, S.; Guo, J.; Martin-Garcia, C.; Boehm, E.; Posner, A.; Rafkin, S. C.; Kortmann, O.

2013-12-01

63

NONDESTRUCTIVE MULTIELEMENT INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS  

EPA Science Inventory

A nondestructive instrumental neutron activation analysis procedure permitted accurate and sensitive measurement of most elements with atomic numbers between 11 and 92. The sensitivity of the procedure was dependent on each element's intrinsic characteristics and the sample matri...

64

A laser-induced repetitive fast neutron source applied for gold activation analysis  

SciTech Connect

A laser-induced repetitively operated fast neutron source was developed for applications in laser-driven nuclear physics research. The developed neutron source, which has a neutron yield of approximately 4 Multiplication-Sign 10{sup 5} n/pulse and can be operated up to a pulse repetition rate of 10 Hz, was applied for a gold activation analysis. Relatively strong delayed gamma spectra of the activated gold were measured at 333 keV and 355 keV, and proved the possibility of the neutron source for activation analyses. In addition, the nuclear reactions responsible for the measured gamma spectra of gold were elucidated by the 14 MeV fast neutrons resulting from the D(t,n)He{sup 4} nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T{sup 3}.

Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki [Quantum Optics Division, Korea Atomic Energy Research Institute, Daejeon 305-600 (Korea, Republic of)

2012-12-15

65

Diagnostic neutron activation system for KSTAR  

NASA Astrophysics Data System (ADS)

The Korea Superconducting Tokamak Advanced Research (KSTAR) device has begun deuterium plasma operation and increased neutron generation from D-D fusion reaction in the plasma is expected as the heating power of the plasma increases. A neutron activation system utilizing the pneumatic transfer of encapsulated metal samples has been implemented to monitor the fusion neutron source strength and the total fusion power from the KSTAR plasma. The prototype pneumatic transfer system for the ITER neutron activation system was slightly modified to be used for KSTAR, and a High Purity Germanium (HPGe) detection system was used to count gamma photons from the activated samples. The Monte Carlo code MCNP and the inventory code FISPACT were also used for the calculations to evaluate the total number of neutrons emitted from the D-D fusion reactions in the KSTAR plasma. The analysis of data from an activation measurement obtained from the 2011 KSTAR campaign shows the neutron flux at the irradiation station was 2.2 × 108 cm-2s-1, and the total neutron yield was 4.7 × 1013 n/s for a typical NBI-heated, H-mode KSTAR plasma shot.

Cheon, M. S.; Lee, Y. S.; England, A. C.; Kim, H. S.; Pak, S.; Seon, C. R.; Lee, H. G.

2012-05-01

66

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

SciTech Connect

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

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

2009-04-15

67

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

PubMed

Neutrons are by-products of high-energy radiation therapy and a source of dose to normal tissues. Thus, the presence of neutrons increases a patient's risk of radiation-induced secondary cancer. Although neutrons have been thoroughly studied in air, little research has been focused on neutrons at depths in the patient where radiosensitive structures may exist, resulting in wide variations in neutron dose equivalents between studies. In this study, we characterized properties of neutrons produced during high-energy radiation therapy as a function of their depth in tissue and for different field sizes and different source-to-surface distances (SSD). We used a previously developed Monte Carlo model of an accelerator operated at 18 MV to calculate the neutron fluences, energy spectra, quality factors, and dose equivalents in air and in tissue at depths ranging from 0.1 to 25 cm. In conjunction with the sharply decreasing dose equivalent with increased depth in tissue, the authors found that the neutron energy spectrum changed drastically as a function of depth in tissue. The neutron fluence decreased gradually as the depth increased, while the average neutron energy decreased sharply with increasing depth until a depth of approximately 7.5 cm in tissue, after which it remained nearly constant. There was minimal variation in the quality factor as a function of depth. At a given depth in tissue, the neutron dose equivalent increased slightly with increasing field size and decreasing SSD; however, the percentage depth-dose equivalent curve remained constant outside the primary photon field. Because the neutron dose equivalent, fluence, and energy spectrum changed substantially with depth in tissue, we concluded that when the neutron dose equivalent is being determined at a depth within a patient, the spectrum and quality factor used should be appropriate for depth rather than for in-air conditions. Alternately, an appropriate percent depth-dose equivalent curve should be used to correct the dose equivalent at the patient surface. PMID:19472632

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

2009-04-01

68

Measurement of Leakage Neutron Spectra for Tungsten with D-T Neutrons and Validation of Evaluated Nuclear Data  

E-print Network

Integral neutronics experiments have been investigated at Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS) in order to validate evaluated nuclear data related to the design of Chinese Initiative Accelerator Driven Systems (CIADS). In present paper, the accuracy of evaluated nuclear data for Tungsten has been examined by comparing measured leakage neutron spectra with calculated ones. Leakage neutron spectra from the irradiation of D-T neutrons on Tungsten slab sample were experimentally measured at 60$^{\\circ}$ and 120$^{\\circ}$ by using a time-of-flight method. Theoretical calculations are carried out by Monte Carlo neutron transport code MCNP-4C with evaluated nuclear data of the ADS-2.0, ENDF/B-VII.0, ENDF/B-VII.1, JENDL-4.0 and CENDL-3.1 libraries. From the comparisons, it is found that the calculations with ADS-2.0 and ENDF/B-VII.1 give good agreements with the experiments in the whole energy regions at 60$^{\\circ}$, while a large discrepancy is observed at 120$^{\\circ}$ in the elastic...

Zhanga, S; Nie, Y; Wada, R; Ruan, X; Han, R; Liu, X; Lin, W; Liu, J; Shi, F; Ren, P; Tian, G; Luo, F; Ren, J; Bao, J

2014-01-01

69

High-Resolution Measurements of Neutron Energy Spectra from Americium-Beryllium and Americium-Boron Neutron Sources  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. A Helium-3 sandwich spectrometer incorporating two semiconductor detectors was designed and constructed to enable the measurement of high resolution neutron energy spectra in the energy range from 100 keV to 15 MeV. The instrument is novel in respect of the inclusion of an anode wire which enables the gas chamber to function as a gas proportional counter. Few similar instruments have been constructed and no similar instrument is known to be currently (1990) in use in the UK. The efficiency of the spectrometer was determined experimentally, using a Californium-252 spontaneous fission source, in the low-scatter facility of the National physical Laboratory. A Monte Carlo code has been written to determine the absolute efficiency over an energy range from 81 keV to 20 MeV. The calculated values were used to extrapolate the measured efficiency to higher energies. Furthermore the Monte Carlo code was used to determine certain operating parameters to optimise the efficiency of the spectrometer. The neutron energy spectra from two different size standard Am-Be neutron sources and a standard Am-B neutron source available at NPL were measured. Although these types of neutron sources have been subject to energy spectra measurements elsewhere, the present work improves considerably on the previous poorer energy resolution and energy range. The new data indicates for the three neutron sources studied that the ambient dose equivalent, H*(10) per unit fluence, for each, were identical, being within 2% of 3.70 E-10 Sv cm^2.

Marsh, James W.

70

Neutron counter based on beryllium activation  

SciTech Connect

The fusion reaction occurring in DD plasma is followed by emission of 2.45 MeV neutrons, which carry out information about fusion reaction rate and plasma parameters and properties as well. Neutron activation of beryllium has been chosen for detection of DD fusion neutrons. The cross-section for reaction {sup 9}Be(n, ?){sup 6}He has a useful threshold near 1 MeV, which means that undesirable multiple-scattered neutrons do not undergo that reaction and therefore are not recorded. The product of the reaction, {sup 6}He, decays with half-life T{sub 1/2} = 0.807 s emitting ?{sup ?} particles which are easy to detect. Large area gas sealed proportional detector has been chosen as a counter of ?–particles leaving activated beryllium plate. The plate with optimized dimensions adjoins the proportional counter entrance window. Such set-up is also equipped with appropriate electronic components and forms beryllium neutron activation counter. The neutron flux density on beryllium plate can be determined from the number of counts. The proper calibration procedure needs to be performed, therefore, to establish such relation. The measurements with the use of known ?–source have been done. In order to determine the detector response function such experiment have been modeled by means of MCNP5–the Monte Carlo transport code. It allowed proper application of the results of transport calculations of ?{sup ?} particles emitted from radioactive {sup 6}He and reaching proportional detector active volume. In order to test the counter system and measuring procedure a number of experiments have been performed on PF devices. The experimental conditions have been simulated by means of MCNP5. The correctness of simulation outcome have been proved by measurements with known radioactive neutron source. The results of the DD fusion neutron measurements have been compared with other neutron diagnostics.

Bienkowska, B.; Prokopowicz, R.; Kaczmarczyk, J.; Paducha, M. [Institute of Plasma Physics and Laser Microfusion (IPPLM), Hery 23, 01-497 Warsaw (Poland); Scholz, M.; Igielski, A. [Institute of Nuclear Physics PAS (IFJPAN), Radzikowskiego 152, 31-342 Krakow (Poland); Karpinski, L. [Faculty of Electrical Engineering, Rzeszow University of Technology, Pola 2, 35-959 Rzeszow (Poland); Pytel, K. [National Centre for Nuclear Research (NCBJ), Soltana 7, 05-400 Otwock - Swierk (Poland)

2014-08-21

71

Neutron counter based on beryllium activation  

NASA Astrophysics Data System (ADS)

The fusion reaction occurring in DD plasma is followed by emission of 2.45 MeV neutrons, which carry out information about fusion reaction rate and plasma parameters and properties as well. Neutron activation of beryllium has been chosen for detection of DD fusion neutrons. The cross-section for reaction 9Be(n, ?)6He has a useful threshold near 1 MeV, which means that undesirable multiple-scattered neutrons do not undergo that reaction and therefore are not recorded. The product of the reaction, 6He, decays with half-life T1/2 = 0.807 s emitting ?- particles which are easy to detect. Large area gas sealed proportional detector has been chosen as a counter of ?-particles leaving activated beryllium plate. The plate with optimized dimensions adjoins the proportional counter entrance window. Such set-up is also equipped with appropriate electronic components and forms beryllium neutron activation counter. The neutron flux density on beryllium plate can be determined from the number of counts. The proper calibration procedure needs to be performed, therefore, to establish such relation. The measurements with the use of known ?-source have been done. In order to determine the detector response function such experiment have been modeled by means of MCNP5-the Monte Carlo transport code. It allowed proper application of the results of transport calculations of ?- particles emitted from radioactive 6He and reaching proportional detector active volume. In order to test the counter system and measuring procedure a number of experiments have been performed on PF devices. The experimental conditions have been simulated by means of MCNP5. The correctness of simulation outcome have been proved by measurements with known radioactive neutron source. The results of the DD fusion neutron measurements have been compared with other neutron diagnostics.

Bienkowska, B.; Prokopowicz, R.; Scholz, M.; Kaczmarczyk, J.; Igielski, A.; Karpinski, L.; Paducha, M.; Pytel, K.

2014-08-01

72

Theoretical description of prompt fission neutron multiplicity and spectra  

E-print Network

The present work concerns two successful models used today: Point by Point (PbP) and the Monte Carlo approaches. The description of the PbP model and of the extended Los Alamos model for higher energies that takes into account the secondary chains and ways is given in Chapter II. In this chapter are given also examples of PbP and most probable fragmentation approach calculations for various quantities which characterize prompt emission: multi-parametric matrices, quantities as a function of fragment mass, quantities as a function of the TKE and total average quantities, for different spontaneous and neutron induced fissioning systems. Special care was given to the TXE partition between the fully accelerated fission fragments, two partition methods used in the PbP model being discussed in details. In Chapter III is given the description of the Monte Carlo treatment included in the FIFRELIN code. Only those aspects that differ from the PbP treatment are emphasized. A special attention is given to the latest developments of the code concerning the inclusion of the energy dependent compound nucleus cross section of the inverse process of neutron evaporation from fragments. In this chapter examples of calculation with the FIFRELIN code for the case of the standard fissioning system 252Cf(SF) are given. Original results for several plutonium spontaneous fissioning systems (236,238,240,242,244Pu) and one neutron induced fissioning system (239Pu(nth,f)) obtained with both PbP and Monte Carlo treatments are given in Chapter IV. The last chapter includes an overview of the most important conclusions resulting from the intercomparison of the results obtained with both treatments in chapter IV.

Cristian Manailescu

2014-10-16

73

Calibration of the TFTR neutron activation system  

NASA Astrophysics Data System (ADS)

Neutron generators, both D-D and D-T, have been used to calibrate the TFTR neutron activation (NA) system for point sources located within the tokamak. The foils used were In for D-D neutrons and Cu, Al, and 238U for D-T neutrons. Delayed neutrons following fission were counted when using 238U foils, 336-keV ? rays from 115In(n,n')115m In reactions, annihilation radiation from 62Cu following the 63Cu(n,2n)62Cu reaction, and 1368- and 2754-keV ? rays from the 27Al(n,?)24Na reaction. Large effects caused by source anisotropy and local machine structure were observed. These effects and the attempts to accommodate them in the data analysis will be described.

Nieschmidt, E. B.; Saito, T.; Barnes, C. W.; Bosch, H.-S.; Murphy, T. J.

1988-08-01

74

Prompt fission neutron spectra and anti. nu. p  

SciTech Connect

Methods used to obtain the evaluated prompt fisson neutron spectrum N(E) and the average prompt neutron multiplicity anti ..nu../sub p/ are reviewed. The relative influence of experimental data; interpolated, extrapolated, and fitted experimental data; systematics; and nuclear theory are considered for the cases where (a) abundant experimental data exist, (b) some experimental data exist, and (c) no experimental data exist. The Maxwellian and Watt distributions, and the determination of the parameters of these distributions by data fitting, are described and compared to recent new theoretical work on the calculation of N(E). Similarly, various expressions for anti ..gamma../sub p/ that have been obtained by data fitting and systematics are described and compared to recent new theoretical work. Complications in the evaluation of N(E) and anti ..gamma../sub p/ due to the onset of multiple-chance fission and the interrelationships between N(E), anti ..gamma delta../sub p/ and the multiple-chance fission cross section are discussed using the example of the fission of /sup 235/U. Some statistics and comments are given on the evaluations of N(E) and anti ..gamma../sub p/ contained in ENDF/B-V, and a number of concluding recommendations are made for future evaluation work.

Madland, D.G.

1980-09-22

75

Dynamics of Myoglobin: Comparison of Simulation Results with Neutron Scattering Spectra  

Microsoft Academic Search

Molecular dynamics simulations are used to calculate the incoherent neutron scattering spectra of myoglobin between 80 K and 325 K and compared with experimental data. There is good agreement over the entire temperature range for the elastic, quasi-elastic, and inelastic components of the scattering. This provides support for the accuracy of the simulations of the internal motions that make the

Jeremy Smith; Krzysztof Kuczera; Martin Karplus

1990-01-01

76

Solar flare proton rigidity spectra deduced from cosmic ray neutron monitor observations  

Microsoft Academic Search

The solar flare proton rigidity spectra for several flares occurring between 1967 and 1972 have been deduced from the ground level cosmic ray neutron monitor observations. To obtain consistent agreement for all the ground level events (GLE's) analyzed, the specific yield functions of Lockwood and Webber (1967) must be reduced slightly below P = 1.6 GV. The typical spectral indices

J. A. Lockwood; W. R. Webber; L. Hsieh

1974-01-01

77

Monte Carlo calculations of neutron and gamma-ray energy spectra for fusion-reactor shield design: Comparison with experiment  

NASA Astrophysics Data System (ADS)

Neutron and gamma-ray spectra resulting from the interactions of approx. 14-MeV neutrons in laminated slabs of stainless steel type-304 and borated polyethylene were calculated using the Monte Carlo code MCNP. The calculated spectra are compared with measured data as a function of slab thickness and material composition and as a function of detector location behind the slabs. Comparisons of the differential energy spectra are made for neutrons with energies above 850 keV and for gamma rays with energies above 750 keV. The measured neutron spectra and those calculated using Monte Carlo methods agree within 5% to 50% depending on the slab thickness and composition and neutron energy. The agreement between the measured and calculated gamma-ray energy spectra is also within this range. The MCNP data are also in favorable agreement with attenuated data calculated previously by discrete ordinates transport methods and the Monte Carlo code SAM-CE.

Santoro, R. T.; Barnes, J. M.

1983-08-01

78

Dynamically Comptonized Spectra from Near Critical Accretion onto Neutron Stars  

E-print Network

We investigate the effects of dynamical Comptonization on the emergent radiation spectrum produced by near critical accretion onto a neutron star. The flow dynamics and the transfer of radiation are self--consistently solved in the case of a spherically symmetric, ``cold'', pure scattering flow, including general relativity. A sequence of models, each characterized by the value of the total observed luminosity, was obtained assuming that the spectrum at the star surface is black body in shape. It is found that when the luminosity approaches the Eddington limit dynamical effects become important shifting the spectrum to the blue and producing a power--law, high--energy tail. The relevance of these results in connection with the observed spectral properties of LMXBs, and of Cyg X--2 in particular, are discussed.

Luca Zampieri; Roberto Turolla; Aldo Treves

1993-08-27

79

Analysis of neutron noise spectra using neural networks  

SciTech Connect

Neural network architectures based on the back-propagation paradigm have been developed to recognize the features, and detect resonance shifts in, power spectral density (PSD) data. Our goal is to advance the state of the art in the application of noise analysis techniques to monitor nuclear reactor internals. The initial objectives have been to use PSD data, acquired over a period of about 2 years by PSDREC (power spectral density recognition system), to develop neural networks that are able to differentiate between normal neutron power spectral density data and anomalous spectral data, and detect significant shifts in the positions of spectral resonances while reducing the effect of small shifts. Neural network systems referred to in this paper as spectral feature detectors (SFDs) and integral network filters have been developed to meet these objectives. The performance of the SFDs is the subject of this paper. 2 refs., 2 figs.

Korsah, K. (Oak Ridge National Lab., TN (USA)); Uhrig, R.E. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA))

1991-01-01

80

Neutron activation measurements on natural tellurium  

NASA Astrophysics Data System (ADS)

Natural tellurium has been activated with thermal neutrons (kT=22 meV) and with quasistellar neutrons (kT=25 keV). By analyzing the ground state decay of the odd isotopes as a function of time, information on the partial capture cross sections to the isomeric states could be determined with systematic uncertainties of 3-8 %. Additionally, the decay parameters of some isomers could be significantly improved. These results are of relevance for s-process nucleosynthesis.

Reifarth, R.; Käppeler, F.

2002-11-01

81

Neutron spectra and dose-rate measurements around a transport cask for spent reactor fuel  

NASA Astrophysics Data System (ADS)

A storage facility with a capacity of 420 containers is available for the interim storage of spent fuel from power reactors at the village of Gorleben in Germany. During transportation and storage of spent fuel casks radiation exposure of the personnel is dominated by neutrons. The routine control of the dose rate limits according to the transport regulations and the licence of the storage facility is performed with conventional neutron survey meters. These monitors, calibrated for fast neutrons at radionuclide neutron sources, usually overestimate the real dose rate in unknown neutron fields. In this paper, a series of measurements with several monitoring instruments near a transport cask of the CASTOR type is presented. The results are compared with reference data for the does equivalents calculated from the measured fluence spectra using a Bonner multisphere spectrometer. Besides reliable information about neutron spectra and dose rates at the container, it was found that some of the rem counters overestimate the true dose rate by a factor of 2 or more.

Rimpler, Arndt

1997-02-01

82

Rotational Corrections to Neutron-star Radius Measurements from Thermal Spectra  

NASA Astrophysics Data System (ADS)

We calculate the rotational broadening in the observed thermal spectra of neutron stars spinning at moderate rates in the Hartle-Thorne approximation. These calculations accurately account for the effects of the second-order Doppler boosts as well as for the oblate shapes and the quadrupole moments of the neutron stars. We find that fitting the spectra and inferring the bolometric fluxes under the assumption that a star is not rotating causes an underestimate of the inferred fluxes and, thus, radii. The correction depends on the stellar spin, mass, radius, and the observer's inclination. For a 10 km, 1.4 M ? neutron star spinning at 600 Hz, the rotational correction to the flux is ~1%-4%, while for a 15 km neutron star with the same spin period, the correction ranges from 2% for pole-on sources to 12% for edge-on sources. We calculate the inclination-averaged corrections to inferred radii as a function of the neutron-star radius and mass and provide an empirical formula for the corrections. For realistic neutron-star parameters (1.4 M ?, 12 km, 600 Hz), the stellar radius is on the order of 4% larger than the radius inferred under the assumption that the star is not spinning.

Bauböck, Michi; Özel, Feryal; Psaltis, Dimitrios; Morsink, Sharon M.

2015-01-01

83

Neutron detection efficiency and capture product energy spectra of all-semiconducting-boron carbide and conversion-layer detectors  

Microsoft Academic Search

Solid-state neutron detectors based only on boron-rich semiconductor are of interest for their potential to provide the highest thermal neutron detection efficiencies of any solid-state neutron detectors. A simplified physical model is shown to generate capture product spectra that agree quantitatively with full-physics GEANT4 simulation. Using this model, comparisons are made between the ideal capture-product energy spectra of planar conversion

A. D. Harken; C. N. Lundstedt; E. E. Day; B. W. Robertson

2004-01-01

84

Vibrational spectra of light and heavy water with application to neutron cross section calculations  

NASA Astrophysics Data System (ADS)

The design of nuclear reactors and neutron moderators require a good representation of the interaction of low energy (E < 1 eV) neutrons with hydrogen and deuterium containing materials. These models are based on the dynamics of the material, represented by its vibrational spectrum. In this paper, we show calculations of the frequency spectrum for light and heavy water at room temperature using two flexible point charge potentials: SPC-MPG and TIP4P/2005f. The results are compared with experimental measurements, with emphasis on inelastic neutron scattering data. Finally, the resulting spectra are applied to calculation of neutron scattering cross sections for these materials, which were found to be a significant improvement over library data.

Damian, J. I. Marquez; Malaspina, D. C.; Granada, J. R.

2013-07-01

85

Vibrational spectra of light and heavy water with application to neutron cross section calculations.  

PubMed

The design of nuclear reactors and neutron moderators require a good representation of the interaction of low energy (E < 1 eV) neutrons with hydrogen and deuterium containing materials. These models are based on the dynamics of the material, represented by its vibrational spectrum. In this paper, we show calculations of the frequency spectrum for light and heavy water at room temperature using two flexible point charge potentials: SPC-MPG and TIP4P/2005f. The results are compared with experimental measurements, with emphasis on inelastic neutron scattering data. Finally, the resulting spectra are applied to calculation of neutron scattering cross sections for these materials, which were found to be a significant improvement over library data. PMID:23862950

Marquez Damian, J I; Malaspina, D C; Granada, J R

2013-07-14

86

Moderated 252Cf neutron energy spectra in brain tissue and calculated boron neutron capture dose.  

PubMed

While there is significant clinical experience using both low- and high-dose (252)Cf brachytherapy, combination therapy using (10)B for neutron capture therapy-enhanced (252)Cf brachytherapy has not been performed. Monte Carlo calculations were performed in a brain phantom (ICRU 44 brain tissue) to evaluate the dose enhancement predicted for a range of (10)B concentrations over a range of distances from a clinical (252)Cf source. These results were compared to experimental measurements and calculations published in the literature. For (10)B concentrations neutron capture dose enhancement was small in comparison to the (252)Cf fast neutron dose. PMID:15308139

Rivard, Mark J; Zamenhof, Robert G

2004-11-01

87

Relativistic neutrons in active galactic nuclei  

NASA Technical Reports Server (NTRS)

The acceleration of protons to relativistic energies in active galactic nuclei leads to the creation of relativistic neutrons which escape from the central engine. The neutrons decay at distances of up to 1-100 pc, depositing their energies and momenta in situ. Energy deposition by decaying neutrons may inhibit spherical accretion and drive a wind, which could be responsible for the velocity fields in emission-line regions and the outflow of broad absorption line systems. Enhanced pressure in the neutron decay region may also help to confine emission line clouds. A fraction of the relativistic proton energy is radiated in gamma-rays with energies which may be as large as about 100,000 GeV.

Sikora, Marek; Begelman, Mitchell C.; Rudak, Bronislaw

1989-01-01

88

Neutron activation analysis of arsenic species  

SciTech Connect

Recently, the authors reported that on neutron irradiation, mono- and dimethyl arsenic compounds (MMA, DMA) were mainly degraded to [sup 76]As labeled inorganic arsenic, but that sufficient [sup 76]As labeled MMA and DMA was retained or reformed to be useful as a radiotracer for calibrating chromatographic separations. In this study, this work was enlarged and extended to the environmentally important trimethyl arsenic compound, arsenobetaine (As[beta]). Organoarsenicals were separated by cation and anion chromatography, followed by neutron irradiation. Two complementary approaches were used. First authentic arsenicals, singly or in combination, were separated and instrumental neutron activation analysis (INAA) of the fractions used as an element specific detection method. Second, the neutron irradiated compounds were chromographed. Then the [sup 76]As labeled species were used to further collaborate, develop, and improve the column separations. Speciation of arsenic was then performed in a real samples using the separations developed, followed by the INAA of the fractions.

Slejkovec, Z.; Byrne, A.R. (Institu Jozef Stefan, Ljubljana (Slovenia))

1993-01-01

89

An integral test of the inelastic cross sections of Pb and Mo using measured neutron spectra  

NASA Technical Reports Server (NTRS)

Comparison of measurements and calculations of fast neutron spectra from a radioactive neutron source inside spheres of Mo or Pb and from a cylindrical reactor containing a thick Pb or Mo reflector are used as a test of ENDF cross sections. The sphere leakage spectra were measured at a sphere-to-spectrometer distance of 2 meters using a 54 Ci spherical Am-Be neutron source. Reactor leakage spectrum measurements were made at the surface of the ZP-1 reactor when bare, with a Pb radial reflector 21 cm thick, and with a metallic Mo radial reflector 10 cm thick. In the case of the thin Mo sphere there is agreement between the calculation and measurement. The Pb calculation is much lower than the measurement except at the highest neutron energy. Two-dimensional calculations of reactor spectra result indicate that the reactor source is reasonably well known. Significant differences in leakage spectrum shape for both Mo and Pb reflectors suggest that there are large uncertainties in the inelastic cross sections for Pb and some for Mo.

Shook, D. F.; Fieno, D.; Ford, C. H.; Wrights, G. N.

1972-01-01

90

Measurement of prompt neutron spectra from the 239Pu(n,f) fission reaction for incident neutron energies from 1 to 200 MeV  

NASA Astrophysics Data System (ADS)

Prompt fission neutron spectra in the neutron-induced fission of 239Pu have been measured for incident neutron energies from 1 to 200 MeV at the Los Alamos Neutron Science Center. Mean energies deduced from the prompt fission neutron spectra (PFNS) lead to the observation of the opening of the second chance fission at 7 MeV and to indications for the openings of fission channels of third and fourth chances. Moreover, the general trend of the measured PFNS is well reproduced by the different models. The comparison between data and models presents, however, two discrepancies. First, the prompt neutron mean energy seems constant for neutron energy, at least up to 7 MeV, whereas in the theoretical calculations it is continuously increasing. Second, data disagree with models on the shape of the high energy part of the PFNS, where our data suggest a softer spectrum than the predictions.

Chatillon, A.; Bélier, G.; Granier, T.; Laurent, B.; Morillon, B.; Taieb, J.; Haight, R. C.; Devlin, M.; Nelson, R. O.; Noda, S.; O'Donnell, J. M.

2014-01-01

91

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

PubMed Central

Neutrons are by-products of high-energy radiation therapy and a source of dose to normal tissues. Thus, the presence of neutrons increases a patient’s risk of radiation-induced secondary cancer. Although neutrons have been thoroughly studied in air, little research has been focused on neutrons at depths in the patient where radiosensitive structures may exist, resulting in wide variations in neutron dose equivalents between studies. In this study, we characterized properties of neutrons produced during high-energy radiation therapy as a function of their depth in tissue and for different field sizes and different source-to-surface distances (SSD). We used a previously developed Monte Carlo model of an accelerator operated at 18 MV to calculate the neutron fluences, energy spectra, quality factors, and dose equivalents in air and in tissue at depths ranging from 0.1 to 25 cm. In conjunction with the sharply decreasing dose equivalent with increased depth in tissue, the authors found that the neutron energy spectrum changed drastically as a function of depth in tissue. The neutron fluence decreased gradually as the depth increased, while the average neutron energy decreased sharply with increasing depth until a depth of approximately 7.5 cm in tissue, after which it remained nearly constant. There was minimal variation in the quality factor as a function of depth. At a given depth in tissue, the neutron dose equivalent increased slightly with increasing field size and decreasing SSD; however, the percentage depth-dose equivalent curve remained constant outside the primary photon field. Because the neutron dose equivalent, fluence, and energy spectrum changed substantially with depth in tissue, we concluded that when the neutron dose equivalent is being determined at a depth within a patient, the spectrum and quality factor used should be appropriate for depth rather than for in-air conditions. Alternately, an appropriate percent depth-dose equivalent curve should be used to correct the dose equivalent at the patient surface. PMID:19472632

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

2009-01-01

92

Comparison between experimental and numerical determination of neutron-induced activation in low-activation materials  

NASA Astrophysics Data System (ADS)

The need for studies of the activation of materials in the neutron fluxes encountered in D-T fusion devices has long been recognized as a key area of fusion technology programs. In this paper a comparison between experimental and numerical results of the induced radioactivity in a low activation material, the SiC/SiC fiber ceramic composite, is presented. The SiC/SiC fiber ceramic composite is a candidate material for the DEMO phase of a commercial fusion power station. This material was exposed to the neutron flux produced by a D-T neutron generator and the induced activity was carefully measured using the Low Background Counting Facility in the Gran Sasso laboratory. The neutron flux and spectra at the irradiation position have been determined using foil activation and numerical calculations with the Monte Carlo Code MCNP. These quantities have been used as input values for the activation code FISPACT and the cross section library EAF 4.1, to calculate the induced activity. The material composition and its impurities have been taken from existing data. The results of the comparison are discussed, focusing on the validation of the cross sections and the activity coming from the impurities.

Pillon, Mario; Angelone, M.; Arpesella, C.; Forrest, R. A.; Sublet, J.-Ch.

1997-02-01

93

Fitting Prompt Fission Neutron Spectra Using Kalman Filter Integrated with Empire Code  

NASA Astrophysics Data System (ADS)

Prompt fission neutron spectra (PFNS) have proven to have a significant effect on criticality of selected benchmarks, in some cases as important as cross-sections. Therefore, a precise determination of uncertainties in PFNS is desired. Existing PFNS evaluations in nuclear data libraries relied so far almost exclusively on the Los Alamos model. However, deviations of evaluated data from available experiments have been noticed at both low and high neutron emission energies. New experimental measurements of PFNS have been recently published, thus demanding new evaluations. The present work describes the effort of integrating Kalman and EMPIRE codes in such a way to allow for parameter fitting of PFNS models. The first results are shown for the major actinides for two different PFNS models (Kornilov and Los Alamos). This represents the first step towards reevaluation of both cross-section and fission spectra data considering both microscopic and integral experimental data for major actinides.

Nobre, G. P. A.; Herman, M.; Hoblit, S.; Palumbo, A.; Capote, R.; Trkov, A.

2014-04-01

94

Nondestructive examination using neutron activated positron annihilation  

DOEpatents

A method is provided for performing nondestructive examination of a metal specimen using neutron activated positron annihilation wherein the positron emitter source is formed within the metal specimen. The method permits in situ nondestructive examination and has the advantage of being capable of performing bulk analysis to determine embrittlement, fatigue and dislocation within a metal specimen.

Akers, Douglas W. (Idaho Falls, ID); Denison, Arthur B. (Idaho Falls, ID)

2001-01-01

95

Calculated neutron-source spectra from selected irradiated PWR fuel assemblies  

SciTech Connect

The energy spectra of neutrons emitted from a pressurized-water-reactor fuel assembly have been calculated for a variety of exposures and cooling times. They are presented in graphical form. Some effects of initial enrichment are also included. Neutrons from spontaneous fissions were given either a Maxwellian temperature of 1.2 or 1.5 MeV, depending on whether they were due to plutonium and uranium nuclides or curium nuclides. A single (..cap alpha..,n) spectrum was deemed sufficient to represent the neutrons from all the alpha-emitting nuclides. The proportions of the nuclides undergoing spontaneous fission and those emitting alpha particles were determined from calculated atom densities. The particular pressurized-water-reactor fuel assembly assumed for this purpose was of the type used in the H.B. Robinson Unit-2 power plant (740 MWe).

Rinard, P.M.; Bosler, G.E.; Phillips, J.R.

1981-12-01

96

High-resolution spectroscopy used to measure inertial confinement fusion neutron spectra on Omega (invited)  

SciTech Connect

The areal density ({rho}R) of cryogenic DT implosions on Omega is inferred by measuring the spectrum of neutrons that elastically scatter off the dense deuterium (D) and tritium (T) fuel. Neutron time-of-flight (nTOF) techniques are used to measure the energy spectrum with high resolution. High signal-to-background data has been recorded on cryogenic DT implosions using a well-collimated 13.4-m line of sight and an nTOF detector with an advanced liquid scintillator compound. An innovative method to analyze the elastically scattered neutron spectra was developed using well-known cross sections of the DT nuclear reactions. The estimated areal densities are consistent with alternative {rho}R measurements and 1-D simulations.

Forrest, C. J.; Radha, P. B.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Pruyne, A.; Romanofsky, M.; Sangster, T. C.; Shoup, M. J. III; Stoeckl, C. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299 (United States); Casey, D. T.; Gatu-Johnson, M. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States); Gardner, S. [Constellation Energy Nuclear Group, Ontario, New York 14519 (United States)

2012-10-15

97

Iron Filtered Neutron Spectra: Measurement and Comparison with Calculations Using Different Libraries  

NASA Astrophysics Data System (ADS)

Iron filtered neutron spectra were measured for benchmark assemblies of three types: Fe spheres of 30, 50 and 100 cm diameter with a 252Cf neutron source placed in the center; WWER-1000 reactor pressure vessel mock-up (Fe slab 20 cm); and Fe slabs 67 and 120 cm thick in the reactor beam. Monte Carlo simulations with the MCNP-4c code using different evaluated data libraries ENDF/B-VII.1, BROND-3, JENDL-4.0, JEFF-3.2T2, CENDL-3.1 and TENDL-2012 were performed for spherical assemblies focusing on the neutron energy range of 0.06 to 1.3 MeV. Considerable discrepancies with experimental data were observed for all libraries.

Jansky, B.; Turzik, Z.; Novak, E.; Kostal, M.; Rejchrt, J.; Blokhin, A. I.

2014-04-01

98

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

NASA Astrophysics Data System (ADS)

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

Yücel, Haluk; Budak, Mustafa Guray; Karadag, Mustafa; Yüksel, Alptu? Özer

2014-11-01

99

Neutron Yield Measurements via Aluminum Activation  

SciTech Connect

Neutron activation of aluminum may occur by several neutron capture reactions. Four such reactions are described here: {sup 27}Al + n = {sup 28}Al, {sup 27}Al(n,{alpha}){sup 24}Na, {sup 27}Al(n, 2n){sup 26}Al and {sup 27}Al(n,p){sup 27}Mg. The radioactive nuclei {sup 28}Al, {sup 24}Na, and {sup 27}Mg, which are produced via the {sup 27}Al + n = {sup 28}Al, {sup 27}Al(n,{alpha}){sup 24}Na and {sup 27}Al(n,p){sup 27}Mg neutron reactions, beta decay to excited states of {sup 28}Si, {sup 24}Mg and {sup 27}Al respectively. These excited states then emit gamma rays as the nuclei de-excite to their respective ground states.

None

1999-12-08

100

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

PubMed

The fundamental properties of neutron stars provide a direct test of the equation of state of cold nuclear matter, a relationship between pressure and density that is determined by the physics of the strong interactions between the particles that constitute the star. The most straightforward method of determining these properties is by measuring the gravitational redshift of spectral lines produced in the neutron star photosphere. The equation of state implies a mass-radius relation, while a measurement of the gravitational redshift at the surface of a neutron star provides a direct constraint on the mass-to-radius ratio. Here we report the discovery of significant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO0748-676. We identify the most significant features with the Fe XXVI and XXV n = 2-3 and O VIII n = 1-2 transitions, all with a redshift of z = 0.35, identical within small uncertainties for the respective transitions. For an astrophysically plausible range of masses (M approximately 1.3-2.0 solar masses; refs 2-5), this value is completely consistent with models of neutron stars composed of normal nuclear matter, while it excludes some models in which the neutron stars are made of more exotic matter. PMID:12422210

Cottam, J; Paerels, F; Mendez, M

2002-11-01

101

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

102

Measurements of fast and intermediate neutron energy spectra on MIR space station in the second half of 1991  

Microsoft Academic Search

This paper describes the neutron energy spectra measured inside and outside the Mir space station. The measurements were made during the second half of 1991 with nuclear emulsions and a neutron and recoil proton spectrometer, whose output data was telemetry-transmitted. In the fast-neutron (En > 1.0 MeV) range, the measurements were carried out using the method of recoil protons in

V. E. Dudkin; Yu. V. Potapov; A. B. Akopova; L. V. Melkumyan; V. G. Bogdanov; V. I. Zacharov; V. A. Plyuschev; A. P. Lobakov; V. I. Lyagyshin

1996-01-01

103

A simple method for the analysis of neutron resonance capture spectra  

SciTech Connect

Neutron resonance capture analysis (NRCA) is a method used to determine the bulk composition of various kinds of objects and materials. It is based on analyzing direct capture resonance peaks. However, the analysis is complicated by scattering followed by capture effects in the object itself. These effects depend on the object's shape and size. In this paper the new Delft elemental analysis program (DEAP) is presented which can automatically and quickly analyze multiple NRCA spectra in a practical and simple way, yielding the elemental bulk composition of an object, largely independent of its shape and size. The DEAP method is demonstrated with data obtained with a Roman bronze water tap excavated in Nijmegen (The Netherlands). DEAP will also be used in the framework of the Ancient Charm project as data analysis program for neutron resonance capture imaging (NRCI) experiments. NRCI provides three-dimensional visualization and quantification of the internal structure of archaeological objects by performing scanning measurements with narrowly collimated neutron beams on archaeological objects in computed tomography based experimental setups. The large amounts (hundreds to thousands) of spectra produced during a NRCI experiment can automatically and quickly be analyzed by DEAP.

Clarijs, Martijn C.; Bom, Victor R.; Eijk, Carel W. E. van [Radiation, Detection and Medical Imaging, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)

2009-03-15

104

Measured microdosimetric spectra and therapeutic potential of boron neutron capture enhancement of 252Cf brachytherapy.  

PubMed

Californium-252 is a neutron-emitting radioisotope used as a brachytherapy source for radioresistant tumors. Presented here are microdosimetric spectra measured as a function of simulated site diameter and distance from applicator tube 252Cf sources. These spectra were measured using miniature tissue-equivalent proportional counters (TEPCs). An investigation of the clinical potential of boron neutron capture (BNC) enhancement of 252Cf brachytherapy is also provided. The absorbed dose from the BNC reaction was measured using a boron-loaded miniature TEPC. Measured neutron, photon and BNC absorbed dose components are provided as a function of distance from the source. In general, the absorbed dose results show good agreement with results from other measurement techniques. A concomitant boost to 252Cf brachytherapy may be provided through the use of the BNC reaction. The potential magnitude of this BNC enhancement increases with increasing distance from the source and is capable of providing a therapeutic gain greater than 30% at a distance of 5 cm from the source, assuming currently achievable boron concentrations. PMID:16137204

Burmeister, J; Kota, C; Maughan, R L

2005-09-01

105

Neutron capture prompt-? activation analysis of foods  

Microsoft Academic Search

The suitability of neutron capture prompt-? activation analysis (PGAA) for multielement analysis of foods was investigated.\\u000a A total of 22 elements was observed in 40 food and mineral supplements. Hydrogen, B, C, N, Na, S, Cl, and K concentrations\\u000a were determined in NIST RM 8431a Mixed Diet and in a wet diet composite made from FDA Total Diet Study collections.

D. L. Anderson; W. C. CUNNINGHAM; E. A. Mackey

1990-01-01

106

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

108

Theoretical and Experimental Research in Neutron Spectra and Nuclear Waste Transmutation on Fast Subcritical Assembly with MOX Fuel  

NASA Astrophysics Data System (ADS)

The paper deals with theoretical and experimental investigation of transmutation rates for a number of long-lived fission products and minor actinides, as well as with neutron spectra formed in a subcritical assembly driven with the following monodirectional beams: 660-MeV protons and 14-MeV neutrons. In this work, the main objective is the comparison of neutron spectra in the MOX assembly for different external driving sources: a 660-MeV proton accelerator and a 14-MeV neutron generator. The SAD project (JINR, Russia) has being discussed. In the context of this project, a subcritical assembly consisting of a cylindrical lead target surrounded by a cylindrical MOX fuel layer will be constructed. Present conceptual design of the subcritical assembly is based on the core with a nominal unit capacity of 15 kW (thermal). This corresponds to a multiplication coefficient, keff= 0.945, and an accelerator beam power of 0.5 kW. The results of theoretical investigations on the possibility of incinerating long-lived fission products and minor actinides in fast neutron spectrum and formation of neutron spectra with different hardness in subcritical systems based on the MOX subcritical assembly are discussed. Calculated neutron spectra emitted from a lead target irradiated by a 660-MeV protons are also presented.

Arkhipkin, D. A.; Buttsev, V. S.; Chigrinov, S. E.; Kutuev, R. Kh.; Polanski, A.; Rakhno, I. L.; Sissakian, A.; Zulkarneev, R. Ya.; Zulkarneeva, Yu. R.

2003-07-01

109

Systematic Measurements of keV-NEUTRON Capture Cross Sections and Capture Gamma-Ray Spectra of pd Isotopes  

NASA Astrophysics Data System (ADS)

The capture cross sections and capture ?-ray spectra of 104,105Pd were measured in the neutron energy region of 15-100 keV as a part of systematic series of measurements. A neutron time-of-flight method was adopted, using a ns pulsed neutron source via the 7Li(p, n)7Be reaction. The capture ?-rays from the samples were measured with an anti-Compton NaI(Tl) spectrometer. The capture yields were obtained by applying a pulse-height weighting technique to the net capture ?-ray pulse-height spectra. The capture cross sections of 104,105Pd were derived with errors less than 5%, using the standard capture cross sections of 197Au. The capture ?-ray spectra of 104,105Pd were also derived by un-folding the respective observed capture ?-ray pulse-height spectra.

Terada, K.; Igashira, M.; Matsuhashi, T.; Katabuchi, T.; Anh, T. T.

2013-03-01

110

Validation of a method for neutron dosimetry and spectrometry using neutron activation of metal discs.  

PubMed

A technique for neutron dosimetry and spectrometry based on neutron activation of different metal discs has been studied. After exposure to a neutron field, the radionuclides produced in the discs are detected using low-level gamma-ray spectrometry and the neutron spectrum is obtained using a spectrum unfolding technique. In order to validate the method, irradiation was performed in a well-characterised (252)Cf neutron reference field. Furthermore, the detector was used to determine the neutron fluence rate and spectrum at a storage place for MOX nuclear fuel. The results of the two measurements are reported and discussed. PMID:19897859

Wieslander, J S Elisabeth; Lövestam, Göran; Hult, Mikael; Fessler, Andreas; Gasparro, Joël; Kockerols, Pierre

2010-03-01

111

Moisture measurement for radioactive wastes using neutron activation of copper  

Microsoft Academic Search

Laboratory tests have demonstrated the use of neutron activation of copper to measure the moisture in radioactive wastes. Neutrons from a source scatter and return to activate the copper in the probe, the amount of activation varying with moisture content. A low-background spectrometer counts the gamma rays from activated 64Cu. The calibration of count rate vs moisture was measured with

P. L. Reeder; D. C. Stromswold; R. L. Brodzinski; J. H. Reeves; W. E. Wilson

1997-01-01

112

Eulogy for a neutron activation analysis facility  

SciTech Connect

A relatively inexpensive facility for neutron activation analysis (NAA) was developed in the early 1970s at Pacific Northwest National Laboratory (PNNL). With the availability of large {sup 252}Cf sources, a subcritical facility was designed that could contain up to 100 mg of {sup 252}Cf (T{sub 1/2} = 2.645 yr and a spontaneous fission yield of 2.34 x 10{sup 9} n/s{center_dot}mg{sup {minus}1}). The {sup 252}Cf source was surrounded by a hexagonal array of {sup 235}U enriched fuel rods, which provided a 10- to 20-fold multiplication of the neutrons emitted from the {sup 252}Cf source. This assembly was located near the bottom of a 1.52-m-diam x 6.10-m-deep water-filled pool. The Neutron Multiplier Facility (NMF) was operational from November 1977 to April 1998--a period of 20.4 yr. The NMF began operation with {approximately}100 mg of {sup 252}Cf, and because of decay of the {sup 252}Cf, it had decreased to 0.34 mg at the time of shutdown. Decommissioning of the NMF began April 1998 and was completed in October 1999.

Lepel, E.A.

2000-07-01

113

OPACITIES AND SPECTRA OF THE r-PROCESS EJECTA FROM NEUTRON STAR MERGERS  

SciTech Connect

Material ejected during (or immediately following) the merger of two neutron stars may assemble into heavy elements through the r-process. The subsequent radioactive decay of the nuclei can power transient electromagnetic emission similar to, but significantly dimmer than, an ordinary supernova. Identifying such events is an important goal of future optical surveys, offering new perspectives on the origin of r-process nuclei and the astrophysical sources of gravitational waves. Predictions of the transient light curves and spectra, however, have suffered from the uncertain optical properties of heavy ions. Here we argue that the opacity of an expanding r-process material is dominated by bound-bound transitions from those ions with the most complex valence electron structure, namely the lanthanides. For a few representative ions, we run atomic structure models to calculate the radiative transition rates for tens of millions of lines. The resulting r-process opacities are orders of magnitude larger than that of ordinary (e.g., iron-rich) supernova ejecta. Radiative transport calculations using these new opacities suggest that the light curves should be longer, dimmer, and redder than previously thought. The spectra appear to be pseudo-blackbody, with broad absorption features, and peak in the infrared ({approx}1 {mu}m). We discuss uncertainties in the opacities and attempt to quantify their impact on the spectral predictions. The results have important implications for observational strategies to find and study the radioactively powered electromagnetic counterparts to neutron star mergers.

Kasen, Daniel; Barnes, Jennifer [Department of Physics and Astronomy, University of California, Berkeley, CA 94720 (United States); Badnell, N. R. [Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

2013-09-01

114

Experimental and MCNP simulated gamma-ray spectra for the UNCOSS neutron-based explosive detector  

NASA Astrophysics Data System (ADS)

In the frame of the FP7 UNCOSS project (Underwater Coastal Sea Surveyor), whose aim is to develop a neutron-based explosive detection system to identify unexploded ordnance (UXO) lying on the sea bottom, the choice of the gamma-ray detector is essential to reach the optimal performances. This paper presents comparative tests between the two candidates: NaI(Tl) and LaBr 3(Ce) detectors, in favour to the 3 in.×3 in. LaBr 3(Ce); thus, confirming the choice previously performed by numerical simulation because of its higher fast timing properties, spectral resolution, and efficiency per volume unit. The gamma-ray spectra produced by 14 MeV tagged neutron beams on the elements of interest (C, O, N, Al, Fe, Si, and Ca) have also been recorded with this detector in order to unfold the spectrum of the interrogated object into elementary contributions. A qualitative comparison with the gamma-ray spectra simulated with the MCNPX computer code and the ENDFB/VII.0 nuclear library has also been performed to validate the numerical model. An additional quantitative validation has been performed with an explosive-like material (ammonium acetate).

Eleon, C.; Perot, B.; Carasco, C.; Sudac, D.; Obhodas, J.; Valkovic, V.

2011-02-01

115

Total body nitrogen analysis. [neutron activation analysis  

NASA Technical Reports Server (NTRS)

Studies of two potential in vivo neutron activation methods for determining total and partial body nitrogen in animals and humans are described. A method using the CO-11 in the expired air as a measure of nitrogen content was found to be adequate for small animals such as rats, but inadequate for human measurements due to a slow excretion rate. Studies on the method of measuring the induced N-13 in the body show that with further development, this method should be adequate for measuring muscle mass changes occurring in animals or humans during space flight.

Palmer, H. E.

1975-01-01

116

Neutron activation analysis of Etruscan pottery  

SciTech Connect

Neutron activation analysis (NAA) has been widely used in archaeology for compositional analysis of pottery samples taken from sites of archaeological importance. Elemental profiles can determine the place of manufacture. At Cornell, samples from an Etruscan site near Siena, Italy, are being studied. The goal of this study is to compile a trace element concentration profile for a large number of samples. These profiles will be matched with an existing data bank in an attempt to understand the place of origin for these samples. The 500 kW TRIGA reactor at the Ward Laboratory is used to collect NAA data for these samples. Experiments were done to set a procedure for the neutron activation analysis with respect to sample preparation, selection of irradiation container, definition of activation and counting parameters and data reduction. Currently, we are able to analyze some 27 elements in samples of mass 500 mg with a single irradiation of 4 hours and two sequences of counting. Our sensitivity for many of the trace elements is better than 1 ppm by weight under the conditions chosen. In this talk, details of our procedure, including quality assurance as measured by NIST standard reference materials, will be discussed. In addition, preliminary results from data treatment using cluster analysis will be presented. (author)

Whitehead, J.; Silverman, A.; Ouellet, C.G.; Clark, D.D.; Hossain, T.Z

1992-07-01

117

COMPUTER GRAPHICS TO SEPARATE neutron from gamma-ray spectra, applied to the measurement of neutron attenuation coefficients using an NE213 scintillator  

Microsoft Academic Search

A new approach is described in the use of NE-213 detectors to perform neutron spectra measurements, which have been developed jointly by the U.S. Naval Academy and the Naval Surface Weapons Center. The approach is based on collecting a three-dimensional matrix of neutron and gamma-ray data. The dimensional plots of the collected data, which are computer generated, are used to

M. E. Nelson; D. A. Miller; G. Riel; T. D. Strickler; P. F. Wiggins

1985-01-01

118

Active Neutron Shielding R&D for Dark Matter Searches  

NASA Astrophysics Data System (ADS)

Neutrons are a dangerous background to direct dark matter detection searches because they can mimic exactly the signal signature. For this reason, it is desirable to measure the neutron flux directly at underground sites where dark matter experiments are active. We have developed a liquid scintillator-based neutron detector for this purpose, which is currently underground and taking data at the Waste Isolation Pilot Plant (WIPP) in NM. Before being commissioned underground, the response of this detector to neutrons with kinetic energies from 50 MeV to 800 MeV was determined in a beam test at the Los Alamos Neutron Science Center (LANSCE) in NM. The goal of this R&D is to (i) demonstrate the feasibility of a large scale active and passive neutron shield for dark matter searches and (ii) to measure the neutron energy spectrum underground at WIPP above 50 MeV neutron kinetic energies.

Henderson, Shawn; Monroe, Jocelyn; Fisher, Peter

2011-04-01

119

Nuclear-level densities around Z = 50 from neutron evaporation spectra in (p, n) reactions  

SciTech Connect

Neutron excitation functions, spectra, and angular distributions in the (p, n) reactions on the isotopes {sup 116}Sn, {sup 118}Sn, {sup 122}Sn, and {sup 124}Sn were measured in the proton-energy range 7-11 MeV. The measurements were performed by the time-of-flight method with the aid of a fast-neutron spectrometer at the EGP-15 pulsed tandem accelerator of the Institute of Physics and Power Engineering (Obninsk). A high resolution (about 0.6 ns/m) and a high stability of the time-of-flight spectrometer made it possible to identify reliably low-lying levels along with the continuous section of the neutron spectra. The data obtained in this way were analyzed on the basis of the statistical equilibrium and preequilibrium models of nuclear reactions. The respective calculations were performed with the aid of the precise Hauser-Feshbach formalism of statistical theory. The nuclear-level densities in the isotopes {sup 116}Sb, {sup 118}Sb, {sup 122}Sb, and {sup 124}Sb were determined, along with their energy dependences and model parameters. In the excitation-energy range 0-2 MeV, the energy dependence of the nuclear-level densities exhibits a structure that is associated with the shell inhomogeneities of the spectrum of single-particle states near filled shells. The isotopic dependence of the nuclear-level density is discovered and explained. It is also shown that the data obtained here for the nuclear-level density differ markedly from the predictions of model systematics of nuclear-level densities.

Zhuravlev, B. V.; Lychagin, A. A.; Titarenko, N. N. [Institute for Physics and Power Engineering (Russian Federation)

2006-03-15

120

Active and sterile neutrino mass effects on beta decay spectra  

SciTech Connect

We study the spectra of the emitted charged leptons in charge current weak nuclear processes to analyze the effect of neutrino masses. Standard active neutrinos are studied here, with masses of the order of 1 eV or lower, as well as sterile neutrinos with masses of a few keV. The latter are warm dark matter (WDM) candidates hypothetically produced or captured as small mixtures with the active neutrinos. We compute differential decay or capture rates spectra in weak charged processes of different nuclei ({sup 3}H, {sup 187}Re, {sup 107}Pd, {sup 163}Ho, etc) using different masses of both active and sterile neutrinos and different values of the mixing parameter.

Boillos, Juan Manuel; Moya de Guerra, Elvira [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, U. Complutense de Madrid, Av. Complutense s/n, E-28040, Madrid (Spain); Moreno, Oscar [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, U. Complutense de Madrid, Av. Complutense s/n, E-28040, Madrid (Spain)

2013-06-10

121

Measurements of keV-NEUTRON Capture Cross Section and Gamma-Ray Spectra of 142Nd  

NASA Astrophysics Data System (ADS)

The neutron capture cross section and capture ?-ray spectra of 142Nd in the neutron energy ranges from 15 to 95 keV, and around 550 keV have been measured by the time-of-flight method. Capture ?-rays were detected with an anti-Compton NaI(Tl) spectrometer, and the pulse-height weighting technique was applied to derive the neutron capture cross section. The capture ?-ray spectra were obtained by unfolding the detector pulse-height spectra with the detector response matrix. The results were compared with previous measurements and cross section data in the evaluated nuclear data libraries, JENDL-4.0 and ENDF/B-VII.0.

Katabuchi, T.; Igashira, M.; Tajika, M.; Nakamura, Y.; Kamada, S.; Terada, K.

2013-03-01

122

Modeling and small-angle neutron scattering spectra of chromatin supernucleosomal structures at genome scale  

NASA Astrophysics Data System (ADS)

Eukaryotic genome is a highly compacted nucleoprotein complex organized in a hierarchical structure based on nucleosomes. Detailed organization of this structure remains unknown. In the present work we developed algorithms for geometry modeling of the supernucleosomal chromatin structure and for computing distance distribution functions and small-angle neutron scattering (SANS) spectra of the genome-scale (˜106 nucleosomes) chromatin structure at residue resolution. Our physical nucleosome model was based on the mononucleosome crystal structure. A nucleosome was assumed to be rigid within a local coordinate system. Interface parameters between nucleosomes can be set for each nucleosome independently. Pair distance distributions were computed with Monte Carlo simulation. SANS spectra were calculated with Fourier transformation of weighted distance distribution; the concentration of heavy water in solvent and probability of H/D exchange were taken into account. Two main modes of supernucleosomal structure generation were used. In a free generation mode all interface parameters were chosen randomly, whereas nucleosome self-intersections were not allowed. The second generation mode (generation in volume) enabled spherical or cubical wall restrictions. It was shown that calculated SANS spectra for a number of our models were in general agreement with available experimental data.

Ilatovskiy, Andrey V.; Lebedev, Dmitry V.; Filatov, Michael V.; Grigoriev, Mikhail; Petukhov, Michael G.; Isaev-Ivanov, Vladimir V.

2011-11-01

123

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

PubMed

Neutron spectrometry measurements were carried out at the McMaster Accelerator Laboratory (MAL), which is equipped with a 3-MV Van de Graaff-type accelerator. Protons were accelerated onto a thick natural lithium target inducing the (7)Li(p,n)(7)Be threshold reaction. Depending on the proton energy, slightly different poly-energetic neutron fields were produced. Neutron spectra were measured at two incident proton energies: 2.15 and 2.24 MeV, which produced poly-energetic neutrons with maximum kinetic energies of 401 and 511 keV, respectively. Measurements were performed at a distance of 1.5 m from the target in the forward direction with three different instruments: Bonner sphere spectrometer, Nested Neutron Spectrometer and ROtational proton recoil SPECtrometer. PMID:24298169

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

2014-10-01

124

Neutron activation of NIF Final Optics Assemblies  

NASA Astrophysics Data System (ADS)

Analyses were performed to characterize the radiation field in the vicinity of the Final Optics Assemblies (FOAs) at the National Ignition Facility (NIF) due to neutron activation following Deuterium-Deuterium (DD), Tritium-Hydrogen-Deuterium (THD), and Deuterium-Tritium (DT) shots associated with different phases of the NIF operations. The activation of the structural components of the FOAs produces one of the larger sources of gamma radiation and is a key factor in determining the stay out time between shots to ensure worker protection. This study provides estimates of effective dose rates in the vicinity of a single FOA and concludes that the DD and THD targets produce acceptable dose rates within10 minutes following a shot while about 6-days of stay out time is suggested following DT shots. Studies are ongoing to determine the combined effects of multiple FOAs and other components present in the Target Bay on stay-out time and worker dose.

Sitaraman, S.; Dauffy, L.; Khater, H.; Brereton, S.

2010-08-01

125

Neutron Activation of NIF Final Optics Assemblies  

SciTech Connect

Analyses were performed to characterize the radiation field in the vicinity of the Final Optics Assemblies (FOAs) at the National Ignition Facility (NIF) due to neutron activation following Deuterium-Deuterium (DD), Tritium-Hydrogen-Deuterium (THD), and Deuterium-Tritium (DT) shots associated with different phases of the NIF operations. The activation of the structural components of the FOAs produces one of the larger sources of gamma radiation and is a key factor in determining the stay out time between shots to ensure worker protection. This study provides estimates of effective dose rates in the vicinity of a single FOA and concludes that the DD and THD targets produce acceptable dose rates within 10 minutes following a shot while about 6-days of stay out time is suggested following DT shots. Studies are ongoing to determine the combined effects of multiple FOAs and other components present in the Target Bay on stay-out time and worker dose.

Sitaraman, S; Dauffy, L; Khater, H; Brereton, S

2009-09-29

126

A CORRELATION BETWEEN STELLAR ACTIVITY AND HOT JUPITER EMISSION SPECTRA  

SciTech Connect

We present evidence for a correlation between the observed properties of hot Jupiter emission spectra and the activity levels of the host stars measured using Ca II H and K emission lines. We find that planets with dayside emission spectra that are well-described by standard one-dimensional atmosphere models with water in absorption (HD 189733, TrES-1, TrES-3, WASP-4) orbit chromospherically active stars, while planets with emission spectra that are consistent with the presence of a strong high-altitude temperature inversion and water in emission orbit quieter stars. We estimate that active G and K stars have Lyman {alpha} fluxes that are typically a factor of 4-7 times higher than quiet stars with analogous spectral types and propose that the increased UV flux received by planets orbiting active stars destroys the compounds responsible for the formation of the observed temperature inversions. In this paper, we also derive a model-independent method for differentiating between these two atmosphere types using the secondary eclipse depths measured in the 3.6 and 4.5 {mu}m bands on the Spitzer Space Telescope and argue that the observed correlation is independent of the inverted/non-inverted paradigm for classifying hot Jupiter atmospheres.

Knutson, Heather A.; Howard, Andrew W.; Isaacson, Howard, E-mail: hknutson@berkeley.ed [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)

2010-09-10

127

A Correlation Between Stellar Activity and Hot Jupiter Emission Spectra  

NASA Astrophysics Data System (ADS)

We present evidence for a correlation between the observed properties of hot Jupiter emission spectra and the activity levels of the host stars measured using Ca II H & K emission lines. We find that planets with dayside emission spectra that are well-described by standard one-dimensional atmosphere models with water in absorption (HD 189733, TrES-1, TrES-3, WASP-4) orbit chromospherically active stars, while planets with emission spectra that are consistent with the presence of a strong high-altitude temperature inversion and water in emission orbit quieter stars. We estimate that active G and K stars have Lyman ? fluxes that are typically a factor of 4-7 times higher than quiet stars with analogous spectral types and propose that the increased UV flux received by planets orbiting active stars destroys the compounds responsible for the formation of the observed temperature inversions. In this paper, we also derive a model-independent method for differentiating between these two atmosphere types using the secondary eclipse depths measured in the 3.6 and 4.5 ?m bands on the Spitzer Space Telescope and argue that the observed correlation is independent of the inverted/non-inverted paradigm for classifying hot Jupiter atmospheres. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time has been granted by both NASA and the University of California.

Knutson, Heather A.; Howard, Andrew W.; Isaacson, Howard

2010-09-01

128

The dependence of build-up 233 U, 232 U, 233 Pa and fission products from ThO 2 irradiated in HFETR on integral thermal neutron fluxes and neutron spectra  

Microsoft Academic Search

In this paper the dependence of build-up233U,232U,233Pa and fission products from ThO2 irradiated in HFETR on integral thermal neutron fluxes and neutron spectra have been investigated. The yields of all above nuclides in ThO2 increase with the increase of integral thermal neutron fluxes at different neutron spectra. The values of233U\\/232Th increase with the increases of th and decreases with the

J. H. Zhang; B. R. Bao; Y. X. Xia; J. B. Zhu

1987-01-01

129

Determination of neutron spectra in a MOX plant for the qualification of the BD-PND bubble detector.  

PubMed

As a result of the introduction of the ICRP 60 recommendations and the increasing contribution of the neutron dose to the total dose of the personnel at the Belgonucleaire Mox fuel fabrication plant, the BD-PND bubble detector manufactured by Bubble Technology industries was introduced as a new, reliable personal neutron dosimeter. In the framework of the evaluation program of the bubble detector, measurements and calculations of the neutron spectra in the installations of the fuel fabrication plant were performed. The measurements were carried out with a ROSPEC neutron spectrometer, and the calculations were performed by means of the Monte Carlo code MCNP 4A. Comparison between measurements and calculations revealed good agreement. On the basis of the obtained neutron spectra, a correction factor was determined to take into account the new ICRP 60 recommendations and the difference between the calibration spectrum of the bubble detectors and the observed neutron spectra at the plant. This correction factor was applied to the calibration factor provided by Bubble Technology Industries. PMID:12877343

Olaerts, R; Kockerols, P; Renard, A; Rosenstock, W; Köble, T; Vanhavere, F

1999-08-01

130

Passive and Active Neutron Matrix Correction for Heterogeneous Distributions Utilizing the Neutron Imaging Technique  

Microsoft Academic Search

Classical Non-Destructive Assay (NDA) Passive Neutron Coincidence Counting (PNCC) and Differential Die-Away (DDA) active neutron interrogation techniques [1, 2] are well suited for determining the gross matrix correction factors for homogenous mass distributions of Special Nuclear Material (SNM) within an interfering waste drum matrix. These measured passive and active matrix correction factors are crucial in quantifying the SNM mass, associated

Marcel F. Villani; Stephen Croft; Eloisa Alvarez; Colin G. Wilkins; Dave Stamp; John Fisher; Alessandro Ambrifi; Gianluca Simone; Ludovic C. Bourva

2008-01-01

131

Neutron spectra as a function of angle at two meters from the Little Boy assembly  

SciTech Connect

Measurements of neutron spectra produced by the Los Alamos National Laboratory (LANL) Little Boy replica assembly (Comet) were made with a combined multisphere and liquid scintillator system, that has been widely used at the Lawrence Livermore National Laboratory. The combined system was used for measurements at the side (90/sup 0/) and nose (0/sup 0/) of the assembly; additional measurements were made at 45/sup 0/ using only the liquid scintillator. Data were obtained at two meters from the center of the reactive region of the assembly, with good agreement between the multisphere and scintillator results. Comparison with liquid scintillator measurements performed by experimenters from the Canadian Defence Research Establishment, Ottawa (DREO) and calculations from LANL depended on the specific angle, obtaining the best agreement at 90/sup 0/. 32 references, 11 figures, 4 tables.

Griffith, R.V.; Huntzinger, C.J.; Thorngate, J.H.

1984-07-02

132

Effect of hydrogenous shields on the average energy of neutron spectra  

SciTech Connect

In a previous work, the authors and colleagues studied problems of photoneutron transport in concrete rooms using the Monte Carlo transport program, MORSE and supporting experimental measurements. From this work, an empirical method of calculation was developed based on the average energy, anti E, of the neutron spectrum. Using this method, it is possible to calculate the effect of metal shielding and also scattering inside a concrete room based on anti E, and to provide a suitable conversion factor for converting fluence to either dose equivalent or to absorbed dose. For subsequent shielding, TVL's for polyethylene or concrete were given for two different geometries, one from the accelerator moderated by a heavy metal (sphere geometry) and the other from these same spectra modified by room scattering (long geometry). 3 refs., 4 figs.

McCall, R.C.; Jenkins, T.M.

1987-11-01

133

NEWSPEC: A computer code to unfold neutron spectra from Bonner sphere data  

SciTech Connect

A new computer code, NEWSPEC, is in development at the University of Arkansas. The NEWSPEC code allows a user to unfold, fold, rebin, display, and manipulate neutron spectra as applied to Bonner sphere measurements. The SPUNIT unfolding algorithm, a new rebinning algorithm, and the graphical capabilities of Microsoft (MS) Windows and MS Excel are utilized to perform these operations. The computer platform for NEWSPEC is a personal computer (PC) running MS Windows 3.x or Win95, while the code is written in MS Visual Basic (VB) and MS VB for Applications (VBA) under Excel. One of the most useful attributes of the NEWSPEC software is the link to Excel allowing additional manipulation of program output or creation of program input.

Lemley, E.C.; West, L. [Univ. of Arkansas, Fayetteville, AR (United States)

1996-12-31

134

Neutron activation system for spectral measurements of pulsed ion diode neutron production  

SciTech Connect

A neutron energy spectrometer has been developed to study intense ion beam-target interactions in the harsh radiation environment of a relativistic electron beam source. The main component is a neutron threshold activation system employing two multiplexed high efficiency Ge(Li) detectors, an annihilation gamma coincidence system, and a pneumatic sample transport. Additional constraints on the neutron spectrum are provided by total neutron yield and time-of-flight measurements. A practical lower limit on the total neutron yield into 4..pi.. required for a spectral measurement with this system is approx. 10/sup 10/ n where the neutron yield is predominantly below 4 MeV and approx. 10/sup 8/ n when a significant fraction of the yield is above 4 MeV. Applications of this system to pulsed ion diode neutron production experiments on Hermes II are described.

Hanson, D.L.; Kruse, L.W.

1980-02-01

135

X-ray spectra and atmospheric structures of bursting neutron stars  

NASA Technical Reports Server (NTRS)

Atmospheric structures and emitted X-ray spectra of bursting neutron stars are investigated. Theoretical curves are fitted to observational ones on the color temperature vs. luminosity diagram and two relations among mass, radius, and distance of the bursters are obtained. The fit of the theoretical curve to observations is statistically acceptable. Two possible sets of mass, radius, and distance to the X-ray bursts source MXB 1636-536 are derived, taking into account absorption lines at 4.1 keV, theoretical mass-radius relations of neutron star models, and the distance to the Galactic center. If the absorption line is due to Cr XX III, then M = 1.7-2.0 solar masses, R = 11-12 km, and d = 6.3-6.7 kpc, and if it is due to Fe XXV, then M = 1.8-2.1 solar masses, R = 8-10 km, and d = 5.8-6,4 kpc. The distance to the Galactic center is almost the same as that to MXB 1636-536.

Ebisuzaki, Toshikazu

1987-01-01

136

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

SciTech Connect

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

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

2002-01-01

137

SOURCES 4A: A Code for Calculating (alpha,n), Spontaneous Fission, and Delayed Neutron Sources and Spectra  

SciTech Connect

SOURCES 4A is a computer code that determines neutron production rates and spectra from ({alpha},n) reactions, spontaneous fission, and delayed neutron emission due to the decay of radionuclides. The code is capable of calculating ({alpha},n) source rates and spectra in four types of problems: homogeneous media (i.e., a mixture of {alpha}-emitting source material and low-Z target material), two-region interface problems (i.e., a slab of {alpha}-emitting source material in contact with a slab of low-Z target material), three-region interface problems (i.e., a thin slab of low-Z target material sandwiched between {alpha}-emitting source material and low-Z target material), and ({alpha},n) reactions induced by a monoenergetic beam of {alpha}-particles incident on a slab of target material. Spontaneous fission spectra are calculated with evaluated half-life, spontaneous fission branching, and Watt spectrum parameters for 43 actinides. The ({alpha},n) spectra are calculated using an assumed isotropic angular distribution in the center-of-mass system with a library of 89 nuclide decay {alpha}-particle spectra, 24 sets of measured and/or evaluated ({alpha},n) cross sections and product nuclide level branching fractions, and functional {alpha}-particle stopping cross sections for Z < 106. The delayed neutron spectra are taken from an evaluated library of 105 precursors. The code outputs the magnitude and spectra of the resultant neutron source. It also provides an analysis of the contributions to that source by each nuclide in the problem.

Madland, D.G.; Arthur, E.D.; Estes, G.P.; Stewart, J.E.; Bozoian, M.; Perry, R.T.; Parish, T.A.; Brown, T.H.; England, T.R.; Wilson, W.B.; Charlton, W.S.

1999-09-01

138

Mineral exploration and soil analysis using in situ neutron activation  

USGS Publications Warehouse

A feasibility study has been made to operate by remote control an unshielded portable positive-ion accelerator type neutron source to induce activities in the ground or rock by "in situ" neutron irradiation. Selective activation techniques make it possible to detect some thirty or more elements by irradiating the ground for periods of a few minutes with either 3-MeV or 14-MeV neutrons. The depth of penetration of neutrons, the effect of water content of the soil on neutron moderation, gamma ray attenuation in the soil and other problems are considered. The analysis shows that, when exploring for most elements of economic interest, the reaction 2H(d,n)3He yielding ??? 3-MeV neutrons is most practical to produce a relatively uniform flux of neutrons of less than 1 keV to a depth of 19???-20???. Irradiation with high energy neutrons (??? 14 MeV) can also be used and may be better suited for certain problems. However, due to higher background and lower sensitivity for the heavy minerals, it is not a recommended neutron source for general exploration use. Preliminary experiments have been made which indicate that neutron activation in situ is feasible for a mineral exploration or qualititative soil analysis. ?? 1976.

Senftle, F.E.; Hoyte, A.F.

1966-01-01

139

Nuclear Instruments and Methods in Physics Research A 526 (2004) 359375 Computation and inversion of ion spectra for neutron  

E-print Network

Nuclear Instruments and Methods in Physics Research A 526 (2004) 359­375 Computation and inversion of ion spectra for neutron depth profiling of curved surfaces J. Kenneth Shultis* Department of Mechanical and Nuclear Engineering, Kansas State University, 137B Ward Hall, Manhattan, KS 66506, USA

Shultis, J. Kenneth

140

Experimental neutronics tests for a neutron activation system for the European ITER TBM  

SciTech Connect

We are investigating methods for neutron flux measurement in the ITER TBM. In particular we have tested sets of activation materials leading to induced gamma activities with short half-lives of the order of tens of seconds up to minutes and standard activation materials. Packages of activation foils have been irradiated with the intense neutron generator of Technical University of Dresden in a pure DT neutron field as well as in a neutronics mock-up of the European ITER HCLL TBM. An important aim was to check whether the gamma activity induced in the activation foils in these packages could be measured simultaneously. It was indeed possible to identify gamma lines of interest in gamma-ray measurements immediately after extraction from the irradiation.

Klix, A.; Fischer, U. [Karlsruhe Institute of Technology (KIT), INR, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Gehre, D. [Technical University of Dresden, IKTP, Zellescher Weg 19, 01062 Dresden (Germany); Kleizer, G. [Karlsruhe Institute of Technology (KIT), INR, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany and Budapest University of Technology and Economics, M?egyetem rkp. 3-9. H-1111 Budapest (Hungary); Raj, P. [Karlsruhe Institute of Technology (KIT), INR, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany and Université Paris-Sud, 15 rue Georges Clemenceau, F-91405 Paris (France); Rovni, I. [Budapest University of Technology and Economics, M?egyetem rkp. 3-9. H-1111 Budapest (Hungary); Ruecker, Tom [Karlsruhe Institute of Technology (KIT), INR, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany and University of Applied Sciences Zittau-Goerlitz, Theodor-Körner-Allee 16, D-02754 Zittau (Germany)

2014-08-21

141

Experimental neutronics tests for a neutron activation system for the European ITER TBM  

NASA Astrophysics Data System (ADS)

We are investigating methods for neutron flux measurement in the ITER TBM. In particular we have tested sets of activation materials leading to induced gamma activities with short half-lives of the order of tens of seconds up to minutes and standard activation materials. Packages of activation foils have been irradiated with the intense neutron generator of Technical University of Dresden in a pure DT neutron field as well as in a neutronics mock-up of the European ITER HCLL TBM. An important aim was to check whether the gamma activity induced in the activation foils in these packages could be measured simultaneously. It was indeed possible to identify gamma lines of interest in gamma-ray measurements immediately after extraction from the irradiation.

Klix, A.; Fischer, U.; Gehre, D.; Kleizer, G.; Raj, P.; Rovni, I.; Ruecker, Tom

2014-08-01

142

An Interpretation of the Anomalous Bump in keV-NEUTRON Capture ?-RAY Spectra of Lanthanide Nuclides  

NASA Astrophysics Data System (ADS)

To investigate the origin of the anomalous bump or shoulder observed in the ?-ray energy region from 1.5 to 3.5 MeV in the keV-neutron capture ?-ray spectra of lanthanide nuclides, the spectra of 145Nd, 161Dy, and 167Er were analyzed with the statistical model calculation from the viewpoint of the M1 scissors mode excitation, assuming the Brink hypothesis for the excitation. The values of B(M1) for the excitation were derived from the analysis, and the derived values were in good agreement with those derived from the (?, ?') reactions. From this agreement, the anomalous bump or shoulder in the keV-neutron capture ?-ray spectra of lanthanide nuclides may be ascribed to the M1 scissors mode excitation if we can assume the Brink hypothesis for the M1 scissors mode excitation.

Igashira, M.; Kawasaki, M.; Ohsaki, T.

2003-06-01

143

Neutron activation analysis of some building materials  

NASA Astrophysics Data System (ADS)

Concentrations of As, Au, Ba, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Mo, Na, Nd, Rb, Sb, Sc, Sr, Ta, Tb, Th, U. Yb, W and Zn in seven Romanian building materials were determined by the Instrumental Neutron Activation Analysis (INAA) method using the VVR-S Reactor of NIPNE- Bucharest. Raw matarials used in cement obtaining ? 75% of limestone and ? 25% of clay, cement samples from three different factories, furnace slag, phosphogypsum, and a type of brick have been analyzed. The brick was compacted from furnace slay, fly coal ash, phosphogypsum, lime and cement. The U, Th and K concentrations determined in the brick are in agreement with the natural radioactivity measurements of226Ra,232Th and40K. These specific activities were found about twice and 1.5 higher than the accepted levels in the case of226Ra and232Th, as well as40K, respectively. By consequence, the investigated brick is considered a radioactive waste. The rather high content of Co, Cr, K, Th, and Zh in the brick is especially due to the slag and fly ash, the main componets. The presence of U, Th and K in slag is mainly correlated with the limestone and dolomite as fluxes in matallurgy.

Salagean, M. N.; Pantelica, A. I.; Georgescu, I. I.; Muntean, M. I.

1999-01-01

144

Neutron activation analysis of arsenic in Greece  

SciTech Connect

Arsenic is considered a toxic trace element for plant, animal, and human organisms. Arsenic and certain arsenic compounds have been listed as carcinogens by the U.S. Environmental Protection Agency. Arsenic is emitted in appreciable quantities into the atmosphere by coal combustion and the production of cement. Arsenic enters the aquatic environment through industrial activities such as smelting of metallic ores, metallurgical glassware, and ceramics as well as insecticide production and use. Neutron activation analysis (NAA) is a very sensitive, precise, and accurate method for determining arsenic. This paper is a review of research studies of arsenic in the Greek environment by NAA performed at our radioanalytical laboratory. The objectives of these studies were (a) to determine levels of arsenic concentrations in environmental materials, (b) to pinpoint arsenic pollution sources and estimate the extent of arsenic pollution, and (c) to find out whether edible marine organisms from the gulfs of Greece receiving domestic, industrial, and agricultural wastes have elevated concentrations of arsenic in their tissues that could render them dangerous for human consumption.

Grimanis, A.P.

1989-11-01

145

Neutron induced prompt gamma-ray and instrumental neutron activation analyses of urban estuarine sediments  

Microsoft Academic Search

Neutron induced prompt -ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Tama River estuary in Tokyo, Japan. The vertical distribution of 24 elements in the sediments was determined and the factors goveming the vertical profiles have been discussed. Major elements are distributed depending on weathering that proceeds much with increasing

A. Kuno; M. Matsuo; B. Takano; C. Yonezawa; H. Matsue; H. Sawahata

1997-01-01

146

Fast neutron activation analysis of high energy materials and polymers  

Microsoft Academic Search

Fast neutron activation analysis (FNAA) technique using 14 MeV neutrons has been applied to estimate nitrogen, chlorine, oxygen and aluminium in explosives and propellants. FNAA also has been employed to determine nitrogen, oxygen, chlorine and fluorine in various polymers. The technique is fast, accurate, nondestructive and non-hazardous in analysing elements in explosives and propellants compared to a number of chemical

S. P. Panda; S. G. Kulkarni; S. K. Sahu; V. N. Bhoraskar; P. A. Dokhale

1998-01-01

147

SIGNATURES OF PHOTON-AXION CONVERSION IN THE THERMAL SPECTRA AND POLARIZATION OF NEUTRON STARS  

SciTech Connect

Conversion of photons into axions under the presence of a strong magnetic field can dim the radiation from magnetized astrophysical objects. Here we perform a detailed calculation aimed at quantifying the signatures of photon-axion conversion in the spectra, light curves, and polarization of neutron stars (NSs). We take into account the energy and angle dependence of the conversion probability and the surface thermal emission from NSs. The latter is computed from magnetized atmosphere models that include the effect of photon polarization mode conversion due to vacuum polarization. The resulting spectral models, inclusive of the general-relativistic effects of gravitational redshift and light deflection, allow us to make realistic predictions for the effects of photon to axion conversion on observed NS spectra, light curves, and polarization signals. We identify unique signatures of the conversion, such as an increase of the effective area of a hot spot as it rotates away from the observer line of sight. For a star emitting from the entire surface, the conversion produces apparent radii that are either larger or smaller (depending on axion mass and coupling strength) than the limits set by NS equations of state. For an emission region that is observed phase-on, photon-axion conversion results in an inversion of the plane of polarization with respect to the no-conversion case. While the quantitative details of the features that we identify depend on NS properties (magnetic field strength and temperature) and axion parameters, the spectral and polarization signatures induced by photon-axion conversion are distinctive enough to make NSs very interesting and promising probes of axion physics.

Perna, Rosalba [JILA and Department of Astrophysical and Planetary Science, University of Colorado at Boulder, 440 UCB, Boulder, CO 80304 (United States); Ho, Wynn C. G. [School of Mathematics, University of Southampton, Southampton, SO17 1BJ (United Kingdom); Verde, Licia; Jimenez, Raul [ICREA and ICC, University of Barcelona (IEEC-UB) (Spain); Van Adelsberg, Matthew [Center for Relativistic Astrophysics and School of Physics Georgia Institute of Technology, Atlanta, GA 30332 (United States)

2012-04-01

148

Active Neutron Interrogation to Detect Shielded Fissionable Material  

SciTech Connect

Portable electronic neutron generators (ENGs) may be used to interrogate suspicious items to detect, characterize, and quantify the presence fissionable material based upon the measurement of prompt and/or delayed emissions of neutrons and/or photons resulting from fission. The small size (<0.2 m3), light weight (<12 kg), and low power consumption (<50 W) of modern ENGs makes them ideally suited for use in field situations, incorporated into systems carried by 2-3 individuals under rugged conditions. At Idaho National Laboratory we are investigating techniques and portable equipment for performing active neutron interrogation of moderate sized objects less than ~2-4 m3 to detect shielded fissionable material. Our research in this area relies upon the use of pulsed deuterium-tritium ENGs and the measurement of die-away prompt fission neutrons and other neutron signatures in-between neutron pulses from the ENG and after the ENG is turned off.

D. L. Chichester; E. H. Seabury

2009-05-01

149

Measurement and calculation of fast-neutron spectra in water, graphite and lithium fluoride assemblies with a D-T neutron source  

NASA Astrophysics Data System (ADS)

Scalar neutron spectra were measured with a miniature NE213 spectrometer at several positions in water, graphite and lithium fluoride assemblies, which were irradiated with D-T neutrons. The n-? discrimination was executed at each pulse height. The pulse height spectrum was unfolded to an energy spectrum with a modified FERDOR code. The measured spectrum was compared with a calculated spectrum using the MORSE-GG Monte Carlo code with the GICXFNS group cross-section set processed from the ENDF/B-IV and -V libraries. The measured spectrum in the graphite assembly showed fine structure, and each peak and valley corresponds to a level-inelastic scattering and total cross-section resonance peak. The measured spectrum in the lithium-fluoride assembly was rather smooth. In general, all the measured spectra agreed with the calculated ones in measurement and calculation error, though the error and oscillation of the unfolding were substantial.

Sekimoto, H.; Lee, D.; Hojo, K.; Hojo, T.; Oishi, K.; Noura, T.; Ohtsuka, M.; Yamamuro, N.

1985-08-01

150

Fast neutron spectra produced by a 49 MeV deuteron-beryllium reaction and its modification by selected absorbers  

E-print Network

for the Straight Bore Collimator after Passage Through 23 9 cm of Steel . . . . . . . . 47 25. Neutron Spectrum at 0 for the Straight Bore Collimator 0 26 27. after Passage Through 31. 8 cm of Steel o Neutron Spectrum at 0 in Air for the P Collimator 0... measured after passage through 0, 4, 8, 'l2, 16, and 20 cm of TE liquid. Spectra were then measured after passage through 3. 95, 7. 9, 15. 9, 23. 9, and 31. 8 cm of steel which also was adjacent to the collimator. After the 3. 95 cm steel measurement...

Hertel, Nolan Elmer

1975-01-01

151

Measurement of neutron spectra for determining dose equivalent rates at the Texas A&M University Nuclear Science Center  

E-print Network

, the instruments can best be evaluated by a relative comparison of the data. MULTISPHERES Analysis of the Multisphere spectrometer data illustrates problems in determining spectra using this method. The neutron energy spectrum determined through the program.... Piesch, B. Burgkhardt, 1985, "Albedo Neutron D I t y", R di I P t' 0~It 10:175 ? 188. Po85 Ro55 Ro68 Poston, J. W. , 1985, Personal Communication H. H. Rossi, W. Rosenzweig, 1955, "A Device for the Measurement of Dose as a Function of Specif ic I...

Sanza, Bruce Jerome

1986-01-01

152

Active neutron multiplicity counting of bulk uranium  

SciTech Connect

This paper describes a new nondestructive assay technique being developed to assay bulk uranium containing kilogram quantities of {sup 235}U. The new technique uses neutron multiplicity analysis of data collected with a coincidence counter outfitted with AmLi neutron sources. We have calculated the expected neutron multiplicity count rate and assay precision for this technique and will report on its expected performance as a function of detector design characteristics, {sup 235 }U sample mass, AmLi source strength, and source-to-sample coupling. 11 refs., 2 figs., 2 tabs.

Ensslin, N.; Krick, M.S.; Langner, D.G.; Miller, M.C.

1991-01-01

153

Active neutron multiplicity counting of bulk uranium  

SciTech Connect

This paper describes a new nondestructive assay technique being developed to assay bulk uranium containing kilogram quantities of {sup 235}U. The new technique uses neutron multiplicity analysis of data collected with a coincidence counter outfitted with AmLi neutron sources. The authors have calculated the expected neutron multiplicity count rate and assay precision for this technique and will report on its expected performance as a function of detector design characteristics, {sup 235}U sample mass, AmLi source strength, and source-to-sample coupling.

Ensslin, N.; Krick, M.S.; Langner, D.G.; Miller, M.C. (Los Alamos National Lab., NM (United States))

1991-01-01

154

Uncertainty Quantification of Prompt Fission Neutron Spectra Using the Unified Monte Carlo Method  

NASA Astrophysics Data System (ADS)

In the ENDF/B-VII.1 nuclear data library, the existing covariance evaluations of the prompt fission neutron spectra (PFNS) were computed by combining the available experimental differential data with theoretical model calculations, relying on the use of a first-order linear Bayesan approach, the Kalman filter. This approach assumes that the theoretical model response to changes in input model parameters be linear about the a priori central values. While the Unified Monte Carlo (UMC) method remains a Bayesian approach, like the Kalman filter, this method does not make any assumption about the linearity of the model response or shape of the a posteriori distribution of the parameters. By sampling from a distribution centered about the a priori model parameters, the UMC method computes the moments of the a posteriori parameter distribution. As the number of samples increases, the statistical noise in the computed a posteriori moments decrease and an appropriately converged solution corresponding to the true mean of the a posteriori PDF results. The UMC method has been successfully implemented using both a uniform and Gaussian sampling distribution and has been used for the evaluation of the PFNS and its associated uncertainties. While many of the UMC results are similar to the first-order Kalman filter results, significant differences are shown when experimental data are excluded from the evaluation process. When experimental data are included a few small nonlinearities are present in the high outgoing energy tail of the PFNS.

Rising, M. E.; Talou, P.; Prinja, A. K.

2014-04-01

155

Herschel/SPIRE Submillimeter Spectra of Local Active Galaxies  

NASA Astrophysics Data System (ADS)

We present the submillimeter spectra from 450 to 1550 GHz of 11 nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) on board Herschel. We detect CO transitions from J up = 4 to 12, as well as the two [C I] fine structure lines at 492 and 809 GHz and the [N II]1461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions. The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n_H_2 \\sim 103.2-103.9 cm-3 and T kin ~ 300-800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H2 emission. We could not determine the specific heating mechanism of the warm gas, however, it is possibly related to the star formation activity in these galaxies. Our modeling of the [C I] emission suggests that it is produced in cold (T kin < 30 K) and dense (n_H_2 \\gt 10^3 cm-3) molecular gas. Transitions of other molecules are often detected in our SPIRE/FTS spectra. The HF J = 1-0 transition at 1232 GHz is detected in absorption in UGC 05101 and in emission in NGC 7130. In the latter, near-infrared pumping, chemical pumping, or collisional excitation with electrons are plausible excitation mechanisms likely related to the active galactic nucleus of this galaxy. In some galaxies, few H2O emission lines are present. Additionally, three OH+ lines at 909, 971, and 1033 GHz are identified in NGC 7130.

Pereira-Santaella, Miguel; Spinoglio, Luigi; Busquet, Gemma; Wilson, Christine D.; Glenn, Jason; Isaak, Kate G.; Kamenetzky, Julia; Rangwala, Naseem; Schirm, Maximilien R. P.; Baes, Maarten; Barlow, Michael J.; Boselli, Alessandro; Cooray, Asantha; Cormier, Diane

2013-05-01

156

HERSCHEL/SPIRE SUBMILLIMETER SPECTRA OF LOCAL ACTIVE GALAXIES {sup ,}  

SciTech Connect

We present the submillimeter spectra from 450 to 1550 GHz of 11 nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) on board Herschel. We detect CO transitions from J{sub up} = 4 to 12, as well as the two [C I] fine structure lines at 492 and 809 GHz and the [N II]1461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions. The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n{sub H{sub 2}}{approx} 10{sup 3.2}-10{sup 3.9} cm{sup -3} and T{sub kin} {approx} 300-800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H{sub 2} emission. We could not determine the specific heating mechanism of the warm gas, however, it is possibly related to the star formation activity in these galaxies. Our modeling of the [C I] emission suggests that it is produced in cold (T{sub kin} < 30 K) and dense (n{sub H{sub 2}}>10{sup 3} cm{sup -3}) molecular gas. Transitions of other molecules are often detected in our SPIRE/FTS spectra. The HF J = 1-0 transition at 1232 GHz is detected in absorption in UGC 05101 and in emission in NGC 7130. In the latter, near-infrared pumping, chemical pumping, or collisional excitation with electrons are plausible excitation mechanisms likely related to the active galactic nucleus of this galaxy. In some galaxies, few H{sub 2}O emission lines are present. Additionally, three OH{sup +} lines at 909, 971, and 1033 GHz are identified in NGC 7130.

Pereira-Santaella, Miguel; Spinoglio, Luigi; Busquet, Gemma [Istituto di Astrofisica e Planetologia Spaziali, INAF, Via Fosso del Cavaliere 100, I-00133 Roma (Italy); Wilson, Christine D.; Schirm, Maximilien R. P. [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada); Glenn, Jason; Kamenetzky, Julia; Rangwala, Naseem [Center for Astrophysics and Space Astronomy, 389-UCB, University of Colorado, Boulder, CO 80303 (United States); Isaak, Kate G. [ESA Astrophysics Missions Division, ESTEC, P.O. Box 299, 2200 AG Noordwijk (Netherlands); Baes, Maarten [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Barlow, Michael J. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Boselli, Alessandro [Laboratoire d'Astrophysique de Marseille (LAM), Universite d'Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France); Cooray, Asantha [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Cormier, Diane, E-mail: miguel.pereira@ifsi-roma.inaf.it [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d'Astrophysique, CEA Saclay, F-91191 Gif-sur-Yvette (France)

2013-05-01

157

Neutron activation studies and the effect of exercise on osteoporosis  

SciTech Connect

A technique is described to measure calcium content by in vivo neutron activation analysis of the trunk and upper thighs. In postmenopausal women, estrogen and calcium or fluoride reversed osteoporosis.

Harrison, J.E.

1984-01-01

158

Thermal Neutron Imaging in an Active Interrogation Environment  

NASA Astrophysics Data System (ADS)

We have developed a thermal-neutron coded-aperture imager that reveals the locations of hydrogenous materials from which thermal neutrons are being emitted. This imaging detector can be combined with an accelerator to form an active interrogation system in which fast neutrons are produced in a heavy metal target by means of excitation by high energy photons. The photo-induced neutrons can be either prompt or delayed, depending on whether neutron-emitting fission products are generated. Provided that there are hydrogenous materials close to the target, some of the photo-induced neutrons slow down and emerge from the surface at thermal energies. These neutrons can be used to create images that show the location and shape of the thermalizing materials. Analysis of the temporal response of the neutron flux provides information about delayed neutrons from induced fission if there are fissionable materials in the target. The combination of imaging and time-of-flight discrimination helps to improve the signal-to-background ratio. It is also possible to interrogate the target with neutrons, for example using a D-T generator. In this case, an image can be obtained from hydrogenous material in a target without the presence of heavy metal. In addition, if fissionable material is present in the target, probing with fast neutrons can stimulate delayed neutrons from fission, and the imager can detect and locate the object of interest, using appropriate time gating. Operation of this sensitive detection equipment in the vicinity of an accelerator presents a number of challenges, because the accelerator emits electromagnetic interference as well as stray ionizing radiation, which can mask the signals of interest.

Vanier, Peter E.; Forman, Leon; Norman, Daren R.

2009-03-01

159

Measurements and analysis of transmitted spectra from LOTUS fission-suppressed hybrid blanket driven by D-T neutrons  

NASA Astrophysics Data System (ADS)

The neutron spectra transmitted across a fission-suppressed hybrid blanket and its components, driven by a low intensity 14 MeV Haefely neutron generator, were measured with a 2?×2? NE213 detector at LOTUS facility. These experiments have been analyzed with 2D and 3D codes DOT3.5 and MCNP, respectively. The spectral integrals between 15 to 1 MeV show good agreement among the 2D, the 3D, and the NE213 for 15 cm lead, 18 cm beryllium, and 25 cm graphite slabs. However, there are large discrepancies for 6.2 cm stainless steel and 15 cm lithium carbonate slabs. The assemblies involving two or more of these slabs reflect these tendencies. We observe also considerable disagreement over pointwise spectra for a number of assemblies.

Kumar, Anil; Leo, William R.; Green, Lawrence; Woodruff, Gene L.

1989-06-01

160

Alterations in dose and lineal energy spectra under different shieldings in the Los Alamos high-energy neutron field  

NASA Technical Reports Server (NTRS)

Nuclear interactions of space radiation with shielding materials result in alterations in dose and lineal energy spectra that depend on the specific elemental composition, density and thickness of the material. The shielding characteristics of materials have been studied using charged-particle beams and radiation transport models by examining the risk reduction using the conventional dose-equivalent approach. Secondary neutrons contribute a significant fraction of the total radiation exposure in space. An experiment to study the changes in dose and lineal energy spectra by shielding materials was carried out at the Los Alamos Nuclear Science Center neutron facility. In the energy range of about 2 to 200 MeV, this neutron spectrum is similar in shape within a factor of about 2 to the spectrum expected in the International Space Station habitable modules. It is shown that with a shielding thickness of about 5 g cm(-2), the conventional radiation risk increases, in some cases by as much as a factor of 2, but decreases with thicknesses of about of 20 g cm(-2). This suggests that care must be taken in evaluating the shielding effectiveness of a given material by including both the charged-particle and neutron components of space radiation.

Badhwar, G. D.; Huff, H.; Wilkins, R.

2000-01-01

161

In vivo neutron activation facility at Brookhaven National Laboratory  

SciTech Connect

Seven important body elements, C, N, Ca, P, K, Na, and Cl, can be measured with great precision and accuracy in the in vivo neutron activation facilities at Brookhaven National Laboratory. The facilities include the delayed-gamma neutron activation, the prompt-gamma neutron activation, and the inelastic neutron scattering systems. In conjunction with measurements of total body water by the tritiated-water dilution method several body compartments can be defined from the contents of these elements, also with high precision. In particular, body fat mass is derived from total body carbon together with total body calcium and nitrogen; body protein mass is derived from total body nitrogen; extracellular fluid volume is derived from total body sodium and chlorine; lean body mass and body cell mass are derived from total body potassium; and, skeletal mass is derived from total body calcium. Thus, we suggest that neutron activation analysis may be valuable for calibrating some of the instruments routinely used in clinical studies of body composition. The instruments that would benefit from absolute calibration against neutron activation analysis are bioelectric impedance analysis, infrared interactance, transmission ultrasound, and dual energy x-ray/photon absorptiometry.

Ma, R.; Yasumura, Seiichi; Dilmanian, F.A.

1997-11-01

162

Planetary Geochemistry Using Active Neutron and Gamma Ray Instrumentation  

NASA Technical Reports Server (NTRS)

The Pulsed Neutron Generator-Gamma Ray And Neutron Detector (PNG-GRAND) experiment is an innovative application of the active neutron-gamma ray technology so successfully used in oil field well logging and mineral exploration on Earth, The objective of our active neutron-gamma ray technology program at NASA Goddard Space Flight Center (NASA/GSFC) is to bring the PNG-GRAND instrument to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Venus, asterOIds, comets and the satellites of the outer planets, Gamma-Ray Spectrometers have been incorporated into numerous orbital planetary science missions and, especially in the case of Mars Odyssey, have contributed detailed maps of the elemental composition over the entire surface of Mars, Neutron detectors have also been placed onboard orbital missions such as the Lunar Reconnaissance Orbiter and Lunar Prospector to measure the hydrogen content of the surface of the moon, The DAN in situ experiment on the Mars Science Laboratory not only includes neutron detectors, but also has its own neutron generator, However, no one has ever combined the three into one instrument PNG-GRAND combines a pulsed neutron generator (PNG) with gamma ray and neutron detectors to produce a landed instrument that can determine subsurface elemental composition without drilling. We are testing PNG-GRAND at a unique outdoor neutron instrumentation test facility recently constructed at NASA/GSFC that consists of a 2 m x 2 m x 1 m granite structure in an empty field, We will present data from the operation of PNG-GRAND in various experimental configurations on a known sample in a geometry that is identical to that which can be achieved on a planetary surface. We will also compare the material composition results inferred from our experiments to both an independent laboratory elemental composition analysis and MCNPX computer modeling results,

Parsons, A.; Bodnarik, J.; Evans, L.; Floyd, S.; Lim, L.; McClanahan, T.; Namkung, M.; Schweitzer, J.; Starr, R.; Trombka, J.

2010-01-01

163

Atmospheres and spectra of strongly magnetized neutron stars - II. The effect of vacuum polarization  

NASA Astrophysics Data System (ADS)

We study the effect of vacuum polarization on the atmosphere structure and radiation spectra of neutron stars with surface magnetic fields B= 1014-1015 G, as appropriate for magnetars. Vacuum polarization modifies the dielectric property of the medium and gives rise to a resonance feature in the opacity; this feature is narrow and occurs at a photon energy that depends on the plasma density. Vacuum polarization can also induce resonant conversion of photon modes via a mechanism analogous to the Mikheyev-Smirnov-Wolfenstein (MSW) mechanism for neutrino oscillation. We construct atmosphere models in radiative equilibrium with an effective temperature of a few ×106 K by solving the full radiative transfer equations for both polarization modes in a fully ionized hydrogen plasma. We discuss the subtleties in treating the vacuum polarization effects in the atmosphere models and present approximate solutions to the radiative transfer problem which bracket the true answer. We show from both analytic considerations and numerical calculations that vacuum polarization produces a broad depression in the X-ray flux at high energies (a few keV <~E<~ a few tens of keV) as compared to models without vacuum polarization; this arises from the density dependence of the vacuum resonance feature and the large density gradient present in the atmosphere. Thus the vacuum polarization effect softens the high-energy tail of the thermal spectrum, although the atmospheric emission is still harder than the blackbody spectrum because of the non-grey opacities. We also show that the depression of continuum flux strongly suppresses the equivalent width of the ion cyclotron line and therefore makes the line more difficult to observe.

Ho, Wynn C. G.; Lai, Dong

2003-01-01

164

CTOF measurements and Monte Carlo analyses of neutron spectra for the backward direction from a lead target irradiated with 200-1000 MeV protons  

NASA Astrophysics Data System (ADS)

A calorimetric-time-of-flight technique was used for real-time, high-precision measurement of neutron spectra at an angle of 175 o from the initial proton beam direction, which hits a face plane of a cylindrical lead target of 20 cm in diameter and 25 cm thick. A comparison was performed between the neutron spectra predicted by the MARS, RTS&T, MCNP6, and the MCNPX 2.6.0 transport codes and that measured for 200, 400, 600, 800, and 1000 MeV protons. Neutron spectra were measured within the energy range from 0.7 to 250 MeV almost continuously. The transport codes tested here describe with different success the measured spectra, depending on the energy of the detected neutrons and on the incident proton energy, but all the models agree reasonably well with our data.

Azhgirey, I. L.; Belyakov-Bodin, V. I.; Degtyarev, I. I.; Sherstnev, V. A.; Mashnik, S. G.; Gallmeier, F. X.; Lu, W.

2010-11-01

165

The cross-section data from neutron activation experiments on niobium in the NPI p-7Li quasi-monoenergetic neutron field  

NASA Astrophysics Data System (ADS)

The reaction of protons on 7Li target produces the high-energy quasi- monoenergetic neutron spectrum with the tail to lower energies. Proton energies of 19.8, 25.1, 27.6, 30.1, 32.6, 35.0 and 37.4 MeV were used to obtain quasi-monoenergetic neutrons with energies of 18, 21.6, 24.8, 27.6, 30.3, 32.9 and 35.6 MeV, respectively. Nb cross-section data for neutron energies higher than 22.5 MeV do not exist in the literature. Nb is the important material for fusion applications (IFMIF) as well. The variable-energy proton beam of NPI cyclotron is utilized for the production of neutron field using thin lithium target. The carbon backing serves as the beam stopper. The system permits to produce neutron flux density about 109 n/cm2/s in peak at 30 MeV neutron energy. The niobium foils of 15 mm in diameter and approx. 0.75 g weight were activated. The nuclear spectroscopy methods with HPGe detector technique were used to obtain the activities of produced isotopes. The large set of neutron energies used in the experiment allows us to make the complex study of the cross-section values. The reactions (n,2n), (n,3n), (n,4n), (n,He3), (n,?) and (n,2n?) are studied. The cross-sections data of the (n,4n) and (n,2n?) are obtained for the first time. The cross-sections of (n,2n) and (n,?) reactions for higher neutron energies are strongly influenced by low energy tail of neutron spectra. This effect is discussed. The results are compared with the EAF-2007 library.

Honusek, M.; Bém, P.; Fischer, U.; Götz, M.; Novák, J.; Simakov, S. P.; Šime?ková, E.

2010-10-01

166

CTOF measurements and Monte Carlo analyses of neutron spectra for the backward direction from a lead target irradiated with 200–1000 MeV protons  

Microsoft Academic Search

A calorimetric-time-of-flight technique was used for real-time, high-precision measurement of neutron spectra at an angle of 175o from the initial proton beam direction, which hits a face plane of a cylindrical lead target of 20cm in diameter and 25cm thick. A comparison was performed between the neutron spectra predicted by the MARS, RTS&T, MCNP6, and the MCNPX 2.6.0 transport codes

I. L. Azhgirey; V. I. Belyakov-Bodin; I. I. Degtyarev; V. A. Sherstnev; S. G. Mashnik; F. X. Gallmeier; W. Lu

2010-01-01

167

Active Neutron-Based Interrogation System with D-D Neutron Source for Detection of Special Nuclear Materials  

NASA Astrophysics Data System (ADS)

The detection of special nuclear materials (SNM) is an important issue for nuclear security. The interrogation systems used in a sea port and an airport are developed in the world. The active neutron-based interrogation system is the one of the candidates. We are developing the active neutron-based interrogation system with a D-D fusion neutron source for the nuclear security application. The D-D neutron source is a compact discharge-type fusion neutron source called IEC (Inertial-Electrostatic Confinement fusion) device which provides 2.45 MeV neutrons. The nuclear materials emit the highenergy neutrons by fission reaction. High-energy neutrons with energies over 2.45 MeV amount to 30% of all the fission neutrons. By using the D-D neutron source, the detection of SNMs is considered to be possible with the attention of fast neutrons if there is over 2.45 MeV. Ideally, neutrons at En>2.45 MeV do not exist if there is no nuclear materials. The detection of fission neutrons over 2.45 MeV are hopeful prospect for the detection of SNM with a high S/N ratio. In the future, the experiments combined with nuclear materials and a D-D neutron source will be conducted. Furthermore, the interrogation system will be numerically investigated by using nuclear materials, a D-D neutron source, and a steel container.

Takahashi, Y.; Misawa, T.; Yagi, T.; Pyeon, C. H.; Kimura, M.; Masuda, K.; Ohgaki, H.

2015-10-01

168

Calibration of the JET neutron activation system for DT operation  

NASA Astrophysics Data System (ADS)

The neutron activation system at JET is a pneumatic transfer system capable of positioning activation samples close to the plasma. Its primary purpose is to provide a calibration for the time-dependent neutron yield monitors (fission chambers and solid state detectors). Various activation reactions with different high energy thresholds were used including 56Fe(n,p) 56Mn, 27Al(n,?) 24Na, 93Nb(n,2n) 92mNb, and 28Si(n,p) 28Al reactions. The silicon reaction, with its short half life (2.25 min), provides a prompt determination of the 14 MeV DT yield. The neutron induced ?-ray activity of the Si samples was measured using three sodium iodide scintillators, while two high purity germanium detectors were used for other foils. It was necessary to use a range of sample masses and different counting geometries in order to cover the wide range of neutron yields (1015-1019 neutrons) while avoiding excessive count rates in the detectors. The absolute full energy peak efficiency calibration of the detectors was measured taking into account the source-detector geometry, the self-attenuation of the samples and cross-talk effects. An error analysis of the neutron yield measurement was performed including uncertainties in efficiency calibration, neutron transport calculations, cross sections, and counting statistics. Cross calibrations between the different irradiation ends were carried out in DD and DT (with 1% and 10% tritium content) discharges. The effect of the plasma vertical displacement was also experimentally studied. An agreement within 10% was found between the 14 MeV neutron yields measured from Si, Fe, Al, Nb samples in DT discharges.

Bertalot, L.; Roquemore, A. L.; Loughlin, M.; Esposito, B.

1999-01-01

169

Reactor neutron activation analysis by a triple comparator method  

Microsoft Academic Search

The single comparator method has been extended to a triple comparator method, using60Co,114m\\u000a In and198Au. In this technique, thek-ratios of the elements to be analyzed, now determined against the three comparators, are corrected for each new ratio of\\u000a thermal to epithermal reactor neutron flux. These flux ratios are calculated from the absolute activities of the three comparators.\\u000a The thermal neutron

F. De Corte; A. Speecke; J. Hoste

1969-01-01

170

Characterization of a nuclear reactor for neutron activation analysis  

Microsoft Academic Search

\\u000a Résumé  Ouelques caractéristiques du réacteur nucléaire NBSR utilisé pour l'analyse par activation neutronique ont été évaluées; les\\u000a techniques de mesure développées sont décrites. La discussion porte sur les caractéristiques suivantes: (1) le flux de neutrons\\u000a thermiques absorbés par le cadmium, (2) la distribution énergétique des neutrons mesurée grâce aux rapports cadmium et à des\\u000a détecteurs à seuil. L'excès de pression dans

D. A. Becker; P. D. LaFleur

1974-01-01

171

Analysis of carbon soil content by using tagged neutron activation  

NASA Astrophysics Data System (ADS)

Here we describe a prototype for non-destructive, in-situ, accurate and cost-effectively measurement procedure of carbon in soil based on neutron activation analysis using 14 MeV tagged neutron beam. This technology can be used for carbon baseline assessment on regional scale and for monitoring of its surface and depth storage due to the changes in agricultural practices undertaken in order to mitigate global climate change.

Obhodas, Jasmina; Sudac, Davorin; Matjacic, Lidija; Valkovic, Vladivoj

2012-06-01

172

Spectra of fast neutrons using a lithiated glass film on silicon  

NASA Astrophysics Data System (ADS)

Experimental results of a neutron detector manufactured by coating a silicon charged particle detector with a film of lithiated glass are presented. The silicon surface barrier detector (SBD) responds to the 6Li(n, alpha)triton reaction products generated in the thin film of lithiated glass entering the SBD. Neutron spectral information is present in the pulse height spectrum. An energy response is seen that clearly shows that neutrons from a Pu-Be source and from a deuterium-tritium (D-T) pulsed neutron generator can be differentiated and counted above a gamma background. The significant result is that the fissile content within a container can be measured using a pulsed D-T neutron generator using the neutrons that are counted in the interval between the pulses.

Wallace, Steven; Stephan, Andrew C.; Womble, Phillip C.; Begtrup, Gavi; Dai, Sheng

2003-06-01

173

Addressing Different Active Neutron Interrogation Signatures from Fissionable Material  

SciTech Connect

In a continuing effort to examine portable methods for implementing active neutron interrogation for detecting shielded fissionable material research is underway to investigate the utility of analyzing multiple time-correlated signatures. Time correlation refers here to the existence of unique characteristics of the fission interrogation signature related to the start and end of an irradiation, as well as signatures present in between individual pulses of an irradiating source. Traditional measurement approaches in this area have typically worked to detect die-away neutrons after the end of each pulse, neutrons in between pulses related to the decay of neutron emitting fission products, or neutrons or gamma rays related to the decay of neutron emitting fission products after the end of an irradiation exposure. In this paper we discus the potential weaknesses of assessing only one signature versus multiple signatures and make the assertion that multiple complimentary and orthogonal measurements should be used to bolster the performance of active interrogation systems, helping to minimize susceptibility to the weaknesses of individual signatures on their own. Recognizing that the problem of detection is a problem of low count rates, we are exploring methods to integrate commonly used signatures with rarely used signatures to improve detection capabilities for these measurements. In this paper we will discuss initial activity in this area with this approach together with observations of some of the strengths and weaknesses of using these different signatures.

D. L. Chichester; E. H. Seabury

2009-10-01

174

Measurement of neutron spectra generated from bombardment of 4 to 24 MeV protons on a thick ?Be target and estimation of neutron yields.  

PubMed

A systematic study on the measurement of neutron spectra emitted from the interaction of protons of various energies with a thick beryllium target has been carried out. The measurements were carried out in the forward direction (at 0° with respect to the direction of protons) using CR-39 detectors. The doses were estimated using the in-house image analyzing program autoTRAK_n, which works on the principle of luminosity variation in and around the track boundaries. A total of six different proton energies starting from 4 MeV to 24 MeV with an energy gap of 4 MeV were chosen for the study of the neutron yields and the estimation of doses. Nearly, 92% of the recoil tracks developed after chemical etching were circular in nature, but the size distributions of the recoil tracks were not found to be linearly dependent on the projectile energy. The neutron yield and dose values were found to be increasing linearly with increasing projectile energies. The response of CR-39 detector was also investigated at different beam currents at two different proton energies. A linear increase of neutron yield with beam current was observed. PMID:24985813

Paul, Sabyasachi; Sahoo, G S; Tripathy, S P; Sharma, S C; Ramjilal; Ninawe, N G; Sunil, C; Gupta, A K; Bandyopadhyay, T

2014-06-01

175

Measurement of neutron spectra generated from bombardment of 4 to 24 MeV protons on a thick {sup 9}Be target and estimation of neutron yields  

SciTech Connect

A systematic study on the measurement of neutron spectra emitted from the interaction of protons of various energies with a thick beryllium target has been carried out. The measurements were carried out in the forward direction (at 0° with respect to the direction of protons) using CR-39 detectors. The doses were estimated using the in-house image analyzing program autoTRAK-n, which works on the principle of luminosity variation in and around the track boundaries. A total of six different proton energies starting from 4 MeV to 24 MeV with an energy gap of 4 MeV were chosen for the study of the neutron yields and the estimation of doses. Nearly, 92% of the recoil tracks developed after chemical etching were circular in nature, but the size distributions of the recoil tracks were not found to be linearly dependent on the projectile energy. The neutron yield and dose values were found to be increasing linearly with increasing projectile energies. The response of CR-39 detector was also investigated at different beam currents at two different proton energies. A linear increase of neutron yield with beam current was observed.

Paul, Sabyasachi; Sahoo, G. S.; Tripathy, S. P., E-mail: sam.tripathy@gmail.com, E-mail: tripathy@barc.gov.in; Sunil, C.; Bandyopadhyay, T. [Health Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Sharma, S. C.; Ramjilal,; Ninawe, N. G.; Gupta, A. K. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

2014-06-15

176

Magnetic helicity and energy spectra of a solar active region  

E-print Network

We compute magnetic helicity and energy spectra of the solar active region NOAA 11158 during 11-15 February 2011 at 20 degr southern heliographic latitude using observational photospheric vector magnetograms. We adopt the isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field. The sign of magnetic helicity turns out to be predominantly positive at all wavenumbers. This sign is consistent with what is theoretically expected for the southern hemisphere. The relative magnetic helicity is around 8% and strongest at intermediate wavenumbers of k ~ 0.4 Mm^{-1}, corresponding to a scale of 2 pi/k ~ 16 Mm. The same sign and a somewhat smaller value is also found for the relative current helicity evaluated in real space based on the vertical components of magnetic field and current density. The current helicity spectrum is estimated from the magnetic helicity spectrum and its modulus shows a k^{-5/3} spectrum at large wavenumbers. A similar power law is also obtained for...

Zhang, Hongqi; Sokoloff, D D

2013-01-01

177

Raw Materials for Low-Activation Concrete Neutron Shields  

Microsoft Academic Search

Concrete surrounding a nuclear reactor accumulates radioisotopes induced by neutron reactions during operation, and this concrete still remains to an enormous degree as radioactive waste after decommissioning. The disposal of such activated concrete is very costly and requires strict supervision. Hence, there has been a strong desire to develop a concrete that retains little residual radioactivity, that is, “low-activation” concrete.

Masaharu KINNO; Ken-ichi KIMURA; Takashi NAKAMURA

2002-01-01

178

Nuclear level densities in 47V, 48V, 49V, 53Mn, and 54Mn from neutron evaporation spectra  

NASA Astrophysics Data System (ADS)

The spectra of neutrons from the ( p, n) reactions on 47Ti, 48Ti, 49Ti, 53Cr, and 54Cr nuclei were measured in the proton-energy range 7-11 MeV. The measurements were performed with the aid of a fast-neutron spectrometer by the time-of-flight method over the base of the EGP-15 tandem accelerator of the Institute for Physics and Power Engineering (IPPE, Obninsk). Owing to a high resolution and a high stability of the time-of-flight spectrometer used, low-lying discrete levels could be identified reliably along with a continuum section of neutron spectra. An analysis of measured data was performed within the statistical equilibrium and preequilibrium models of nuclear reactions. The relevant calculations were performed by using the exact formalism of Hauser-Feshbach statistical theory supplemented with the generalized model of a superfluid nucleus, the back-shifted Fermi gas model, and the Gilbert-Cameron composite formula for the nuclear level density. The nuclear level densities for 47V, 48V, 49V, 53Mn, and 54Mn were determined along with their energy dependences and model parameters. The results are discussed together with available experimental data and recommendations of model systematics.

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

2011-03-01

179

Active Neutron Veto Shield Design for SuperCDMS-SNOLAB  

NASA Astrophysics Data System (ADS)

Protection against neutron backgrounds is one of the key issues for the next generation SuperCDMS direct dark matter detection experiment that aims at exploring the 10-46 cm^2 cross section region for spin-independent interactions of Weakly Interacting Massive Particles (WIMPs) with nucleons. Estimation of the background from radioactive processes is a crucial task for the current experiment stage and for designing future large-scale detectors. An active neutron veto would make the next generation of dark matter experiment more robust, improving the credibility of a dark matter detection claim based on the observation of a few recoil events. SuperCDMS is investigating the feasibility of adding a liquid scintillator active neutron veto, loaded with high neutron capture cross section isotopes, to the SuperCDMS SNOLAB shield design. This system not only will allow us to reject neutron-induced backgrounds, but also will provide an in-situ measurement of the neutron flux near the detector. I will report the status of ongoing studies related to the design and construction of such a veto.

Qiu, Hang

2013-04-01

180

Bonner sphere measurements of 241Am-B and 241Am-F neutron energy spectra unfolded using high-resolution a priori data.  

PubMed

High-resolution neutron energy spectra, covering the entire energy range of interest, for two standard radionuclide neutron sources ((241)Am-B and (241)Am-F) have been derived from Bonner sphere measurements by using high-resolution a priori data in the unfolding process. In each case, two a priori spectra were used, one from a two-stage calculation and also one from a combination of the calculated spectrum with a high-resolution measured spectrum. The unfolded spectra are compared with those published elsewhere and show significant differences from the ISO- and IAEA-recommended spectra for (241)Am-B and (241)Am-F, respectively. Values for the fluence-average energy and fluence-to-dose-equivalent conversion coefficients are presented for the new spectra, and the implications of the new spectra for the emission rates of the sources when measured by the manganese bath technique are also determined. PMID:24126487

Roberts, N J; Jones, L N; Liu, Z Z; Tagziria, H; Thomas, D J

2014-10-01

181

Possible differentiation of natal areas of North American waterfowl by neutron activation analysis  

USGS Publications Warehouse

The possibility of using neutron activation analyses to differentiate sources of North American waterfowl was investigated by irradiating rectrices and wing bones of birds collected in several localities, and comparing the characteristic gamma-ray spectra. Canada goose rectrices from Oregon specimens could be distinguished from those taken in Wisconsin and Colorado based on higher levels of Mn. Mallard, black duck, and blue-winged teal wing bones from Wisconsin, Colorado, and New Brunswick could not be clearly identified as to locality from levels of Ca, Al, Na, Mn, and Cl.

Devine, T.; Peterle, T.J.

1968-01-01

182

Neutron activation analysis for antimetabolites. [in food samples  

NASA Technical Reports Server (NTRS)

Determination of metal ion contaminants in food samples is studied. A weighed quantity of each sample was digested in a concentrated mixture of nitric, hydrochloric and perchloric acids to affect complete solution of the food products. The samples were diluted with water and the pH adjusted according to the specific analysis performed. The samples were analyzed by neutron activation analysis, polarography, and atomic absorption spectrophotometry. The solid food samples were also analyzed by neutron activation analysis for increased sensitivity and lower levels of detectability. The results are presented in tabular form.

1973-01-01

183

Simulation of neutron emission spectra from neutral beam-heated plasmas in the EAST tokamak  

NASA Astrophysics Data System (ADS)

The neutron emission spectrum from neutral beam-heated plasmas of the Experimental Advanced Superconducting Tokamak (EAST) is investigated based on first-principles simulations of the fast deuteron energy distribution. Parametrized plasma profiles are used to determine the beam deposition and fast deuteron distribution function using the NUBEAM code. The deuteron distribution is also interpreted with the help of empirical models and the components in the neutron energy spectrum are computed for different viewing lines using a Monte Carlo method. The resulting observational possibilities are discussed for the case of a time-of-flight neutron emission spectrometer optimized for EAST.

Chen, Z.; Nocente, M.; Tardocchi, M.; Fan, T.; Gorini, G.

2013-06-01

184

Magnetospheric Birefringence Induces Unique Polarization Signatures in Neutron-Star Spectra  

E-print Network

We study the propagation of polarization light through the magnetosphere of neutron stars. At intermediate frequencies (the optical through the infrared), both the birefringence induced by the plasma and by quantumelectrodynamics influence the observation polarization of radiation from the surface of the neutron star. Because these two processes compete in this regime, we find that polarization observations can constrain the properties of the neutron-star magnetosphere, specifically the total charge density. We calculate both the phase-resolved and the phase-averaged polarization signatures induced by magnetospheric birefringence.

R. M. Shannon; Jeremy S. Heyl

2006-02-18

185

The effect of turbulent kinetic energy on inferred ion temperature from neutron spectra  

SciTech Connect

Measuring the width of the energy spectrum of fusion-produced neutrons from deuterium (DD) or deuterium-tritium (DT) plasmas is a commonly used method for determining the ion temperature in inertial confinement fusion (ICF) implosions. In a plasma with a Maxwellian distribution of ion energies, the spread in neutron energy arises from the thermal spread in the center-of-mass velocities of reacting pairs of ions. Fluid velocities in ICF are of a similar magnitude as the center-of-mass velocities and can lead to further broadening of the neutron spectrum, leading to erroneous inference of ion temperature. Motion of the reacting plasma will affect DD and DT neutrons differently, leading to disagreement between ion temperatures inferred from the two reactions. This effect may be a contributor to observations over the past decades of ion temperatures higher than expected from simulations, ion temperatures in disagreement with observed yields, and different temperatures measured in the same implosion from DD and DT neutrons. This difference in broadening of DD and DT neutrons also provides a measure of turbulent motion in a fusion plasma.

Murphy, T. J., E-mail: tjmurphy@lanl.gov [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2014-07-15

186

Extending neutron activation analysis to materials with high concentrations of neutron absorbing elements  

NASA Astrophysics Data System (ADS)

The purpose of this study was to investigate epithermal neutron self-shielding for all nuclides used in Neutron Activation Analysis, NAA. The study started with testing the theory and measuring the nuclear factors characterizing thermal and epithermal self-shielding for 1 mL cylindrical samples containing the halogens Cl, Br and I irradiated in a mixed thermal and epithermal neutron spectrum. For mono-element samples, both thermal and epithermal experimental self-shielding factors were well fitted by sigmoid functions. As a result, to correct thermal neutron self-shielding, the sigmoid uses a single parameter, mth, which can be directly calculated for any element from the sample size, the weighted sum of the thermal absorption cross-sections, sigmaabs, of the elements in the sample and a constant kth characteristic of the irradiation site. However, to correct epithermal self-shielding, the parameter mep, a function of sample geometry and composition, irradiation conditions and nuclear characteristics, needs to be measured for each activated nuclide. Since the preliminary tests were positive and showed that self-shielding, as high as 30%, could be corrected with an accuracy of about 1%, except in cases with significant epithermal shielding of one element by another, we pursued the study with the verification of two additional aspects. First, the dependency of the self-shielding parameters mth, and mep, on the properties of the irradiation site was evaluated using three different irradiation sites of a SLOWPOKE reactor, and it was concluded that the amount of both thermal and epithermal self-shielding varied by less than 10% from one site to another. Second, the variation of the self-shielding parameters, mth, and mep, with the size of the cylinder, as r( r+h), was tested for h/r ratios from 0.02 to 6.0, and this geometry dependence was confirmed even in slightly non-isotropic neutron fields. These results allowed separating from the mep parameter the amount of chemical element and the sample geometrical factor. Therefore, the remaining nuclear factor, considered as a product of nuclide composite nuclear characteristics and irradiation site characteristics, led to the introduction of a so-called epithermal neutron absorption cross-sections, sigmaabs,ep. This new nuclear parameter will allow the calculation of the epithermal self-shielding for all cylindrical samples activated in all types of irradiation sites. For the 13 cases studied, the epithermal self-shielding factor, Gep, was obtained from the experimental effective self-shielding factor, Geff, by extracting the thermal neutron self-shielding factor, calculated with the sigmoid formulation. A least-squares fit of the experimental Gep values as a function of the mass of element yielded sigmaabs,ep for each activated nuclide. In addition, for all nuclides commonly used in neutron activation analysis, sigmaabs,ep was calculated with the Martinho, Salgado and Goncalves sigmoid formulation, which uses the total cross-section values at the peaks of the resonances. A comparison of the calculated sigmaabs,ep with the 13 measured values reveals that the calculated values are accurate to about 20%. Finally, for all 76 nuclides commonly used in NAA, a spreadsheet program was written to use experimental or calculated sigmaabs,ep nuclear parameters to perform iterative self-shielding corrections of concentrations measured by neutron activation analysis. The user provides the parameters f and alpha of the neutron spectrum, the sample mass and dimensions, and the measured concentrations. In a typical case with 10% thermal self-shielding and 30% epithermal self-shielding, the corrected concentrations had uncertainties varying from 2% to 3%. Keywords. Instrumental Neutron Activation Analysis, epithermal, thermal, self-shielding factors. (Abstract shortened by UMI.)

Chilian, Cornelia

187

BOREHOLE NEUTRON ACTIVATION: THE RARE EARTHS.  

USGS Publications Warehouse

Neutron-induced borehole gamma-ray spectroscopy has been widely used as a geophysical exploration technique by the petroleum industry, but its use for mineral exploration is not as common. Nuclear methods can be applied to mineral exploration, for determining stratigraphy and bed correlations, for mapping ore deposits, and for studying mineral concentration gradients. High-resolution detectors are essential for mineral exploration, and by using them an analysis of the major element concentrations in a borehole can usually be made. A number of economically important elements can be detected at typical ore-grade concentrations using this method. Because of the application of the rare-earth elements to high-temperature superconductors, these elements are examined in detail as an example of how nuclear techniques can be applied to mineral exploration.

Mikesell, J.L.; Senftle, F.E.

1987-01-01

188

Measurement of the neutron capture cross-section of 232 Th using the neutron activation technique  

Microsoft Academic Search

.  The 232Th(n,) reaction cross-section at average neutron energies of 3.7±0.3 MeV and 9.85±0.38 MeV from the 7Li(p, n) reaction has been determined for the first time using activation and off-line -ray spectrometric technique. The 232Th(n, 2n) reaction cross-section at the average neutron energy of 9.85±0.38 MeV has been also determined using the same technique.\\u000a The experimentally determined 232Th(n,) and 232Th(n,

H. Naik; P. M. Prajapati; S. V. Surayanarayana; K. C. Jagadeesan; S. V. Thakare; D. Raj; V. K. Mulik; B. S. Sivashankar; B. K. Nayak; S. C. Sharma; S. Mukherjee; Sarbjit Singh; A. Goswami; S. Ganesan; V. K. Manchanda

2011-01-01

189

NEUTRON ACTIVATION ANALYSIS OF COLONIAL CERAMICS FROM SOUTHERN HIGHLAND ECUADOR  

Microsoft Academic Search

Sixty-one ceramic samples collected in Cuenca, Ecuador, were analysed by neutron activation analysis in an attempt to establish their elemental compositions. The bulk of the samples were manufactured in the region of Cuenca, with others imported from Quito in the northern highlands of Ecuador, from Panama Vieja in Panama, and from Seville in Spain. Relative to the Cuenca ceramics, the

R. W. JAMIESON; R. G. V. HANCOCK

2004-01-01

190

Neutron-Activation Soil Analysis in Ecological Investigations  

Microsoft Academic Search

The scientific-technical base and instrumentation for neutron-activation analysis has reached a level such that today such an analysis can be used to find more than 70 chemical elements in soil and other biological objects. The method is widely used in various fields of science and industry. At the same time, as noted in [1], unsolved methodological and metrological problems are

Sh. Khatamov; A. Zhumamuratov; B. Ibragimov; T. Tillaev

2000-01-01

191

Instrumental neutron activation analysis for bromine in pig tissues  

Microsoft Academic Search

Bromine was determined by instrumental neutron activation analysis in ; tissues and organs of pigs as an indicator of brominated vegetable oil residues. ; The bromine content was found to be dose-related. An advantage of this technique ; is that the sample was not treated chemically. The analyses were done with the ; aid of an automatic sample changer and

Melvin H. Friedman; Theodore M. Farber; James T. Tanner

1973-01-01

192

Raw Materials for Low-Activation Concrete Neutron Shields  

Microsoft Academic Search

Concrete surrounding a nuclear reactor accumulates radioisotopes induced by neutron reactions during operation, and this concrete still remains to an enormous degree as radioactive waste after decommissioning. The disposal of such activated concrete is very costly and requires strict supervision. Hence, there has been a strong desire to develop a concrete that retains little residual radioactivity, that is, \\

Masaharu KINNO; Ken-ichi KIMURA; Takashi NAKAMURA

2002-01-01

193

Quantitative neutron capture resonance analysis verified with instrumental neutron activation analysis  

NASA Astrophysics Data System (ADS)

The newly developed elemental analysis technique Neutron Resonance Capture Analysis (NRCA) was verified by analyzing a prehistoric bronze arrowhead with both NRCA and Instrumental Activation Analysis (INAA). In NRCA, elements are identified through their neutron resonance capture energies as determined through detection of prompt capture gamma-rays as a function of time of flight. The quantification is obtained from the resonance peak areas. Corrections are required for neutron-energy-dependent dead time and self-shielding, the latter also depending on Doppler broadening. The analysis program REFIT, of which the intended use is the determination of the resonance parameters, was used to this end. The agreement observed between INAA and NRCA results indicates that the NRCA results obtained are accurate.

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

2003-06-01

194

Hard X-ray spectra of neutron stars and black hole candidates  

NASA Technical Reports Server (NTRS)

The hard X-ray behavior of several X-ray binary systems containing a neutron star or a black hole candidate is analyzed in an attempt to determine the specific signature of these categories of compact objects. Limiting the consideration to two subclasses of neutron stars, Atoll sources and non-pulsating Z sources, it appears that only the Atoll sources have a spectral behavior similar to black holes. It is proposed that Atoll sources are weakly magnetized neutron stars, whereas Z sources are small radius moderate magnetized neutron stars. Large magnetic fields funnel the accreting matter, thus preventing spherical accretion and free fall if the neutron star radius is smaller than the last stable accreting orbit. Weak magnetic fields do not have this effect, and blackbody soft photons from the stellar surface are upscattered on the relativistic infalling matter, leading to excess hard X-rays. This excess is visible in two of the observed Atoll sources and in the spectrum of a black hole candidate. In the case of a Z source, a lack of photons was remarked, providing a possible signature to distinguish between these classes of objects.

Durouchoux, P.; Mahoney, W.; Clenet, Y.; Ling, J.; Wallyn, P.; Wheaton, W.; Corbet, S.; Chapuis, C.

1997-01-01

195

In-vessel design of ITER diagnostic neutron activation system.  

PubMed

A neutron activation system utilizing an encapsulated metal sample technique will be implemented to evaluate total fusion power from ITER plasma. The positions of seven irradiation ends for each poloidal section are determined to optimize the measurements from asymmetric, elongated plasma with minimum uncertainty. To determine the exact location of the irradiation end, some physical and technical aspects for each location are investigated. Monte Carlo neutronic calculations are performed to assess the physical characteristics and optimize the design of each irradiation end. PMID:19044490

Cheon, M S; Pak, S; Lee, H G; Bertalot, L; Walker, C

2008-10-01

196

Active neutron multiplicity analysis and Monte Carlo calculations  

SciTech Connect

Active neutron multiplicity measurements of high-enrichment uranium metal and oxide samples have been made at Los Alamos and Y-12. The data from the measurements of standards at Los Alamos were analyzed to obtain values for neutron multiplication and source-sample coupling. These results are compared to equivalent results obtained from Monte Carlo calculations. An approximate relationship between coupling and multiplication is derived and used to correct doubles rates for multiplication and coupling. The utility of singles counting for uranium samples is also examined.

Krick, M.S.; Ensslin, N.; Langner, D.G.; Miller, M.C.; Siebelist, R.; Stewart, J.E. [Los Alamos National Lab., NM (United States); Ceo, R.N.; May, P.K.; Collins, L.L. Jr [Oak Ridge Y-12 Plant, TN (United States)

1994-08-01

197

Multielement trace analysis of coals, ashes and related materials from coal-treatment facilities by instrumental neutron activation analysis  

Microsoft Academic Search

Concentration of trace elements found in coal, ash, and materials used in a fluidizedbed combustion process have been determined\\u000a by thermal neutron activation and absolute Ge(Li) gamma-ray spectrometry. Described are the calibration of detectors and corrections\\u000a associated with the method along with estimated uncertainties. A brief description of the computer code used in the processing\\u000a of the Ge(Li) spectra is

E. T. Kucera; R. R. Heinrich

1976-01-01

198

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

199

Determination of the internal structure of neutron stars from gravitational wave spectra  

E-print Network

In this paper the internal structure of a neutron star is shown to be inferrable from its gravitational-wave spectrum. Iteratively applying the inverse scheme of the scaled coordinate logarithmic perturbation method for neutron stars proposed by Tsui and Leung [Astrophys. J. {\\bf 631}, 495 (2005)], we are able to determine the mass, the radius and the mass distribution of a star from its quasi-normal mode frequencies of stellar pulsation. In addition, accurate equation of state of nuclear matter can be obtained from such inversion scheme. Explicit formulas for the case of axial $w$-mode oscillation are derived here and numerical results for neutron stars characterized by different equations of state are shown.

L. K. Tsui; P. T. Leung; J. Wu

2006-10-20

200

Active Interrogation Using Electronic Neutron Generators for Nuclear Safeguards Applications  

SciTech Connect

Active interrogation, a measurement technique which uses a radiation source to probe materials and generate unique signatures useful for characterizing those materials, is a powerful tool for assaying special nuclear material. The most commonly used technique for performing active interrogation is to use an electronic neutron generator as the probe radiation source. Exploiting the unique operating characteristics of these devices, including their monoenergetic neutron emissions and their ability to operate in pulsed modes, presents a number of options for performing prompt and delayed signature analyses using both photon and neutron sensors. A review of literature in this area shows multiple applications of the active neutron interrogation technique for performing nuclear nonproliferation measurements. Some examples include measuring the plutonium content of spent fuel, assaying plutonium residue in spent fuel hull claddings, assaying plutonium in aqueous fuel reprocessing process streams, and assaying nuclear fuel reprocessing facility waste streams to detect and quantify fissile material. This paper discusses the historical use of this technique and examines its context within the scope and challenges of next-generation nuclear fuel cycles and advanced concept nuclear fuel cycle facilities.

David L. Chichester; Edward H. Seabury

2008-08-01

201

Neutron activation analysis; A sensitive test for trace elements  

SciTech Connect

This paper discusses neutron activation analysis (NAA), an extremely sensitive technique for determining the elemental constituents of an unknown specimen. Currently, there are some twenty-five moderate-power TRIGA reactors scattered across the United States (fourteen of them at universities), and one of their principal uses is for NAA. NAA is procedurally simple. A small amount of the material to be tested (typically between one and one hundred milligrams) is irradiated for a period that varies from a few minutes to several hours in a neutron flux of around 10{sup 12} neutrons per square centimeter per second. A tiny fraction of the nuclei present (about 10{sup {minus}8}) is transmuted by nuclear reactions into radioactive forms. Subsequently, the nuclei decay, and the energy and intensity of the gamma rays that they emit can be measured in a gamma-ray spectrometer.

Hossain, T.Z. (Cornell Univ., Ithaca, NY (United States). Ward Lab.)

1992-01-01

202

Measurement of Residual 60Co Activity Induced by Atomic-bomb Neutrons in Nagasaki and Background Contribution by Environmental Neutrons  

Microsoft Academic Search

60 Co \\/ Specific activity \\/ Atomic bomb \\/ DS86 \\/ Neutrons Residual 60 Co activity in five steel samples induced by neutrons from the Nagasaki atomic bomb has been measured within about 1000 m from the hypocenter. The chemical separation of cobalt and nickel from steel samples was performed, and cobalt-enriched samples were prepared for all samples. Gamma-ray measurements

KIYOSHI SHIZUMA; SATORU ENDO; MASAHARU HOSHI; JUN TAKADA; KAZUO IWATANI; HIROMI HASAI; TAKAMITSU OKA; TATSUYA SHIMAZAKI; YUTAKA OKUMURA; SHOICHIRO FUJITA; TADAAKI WATANABE; TETSUJI IMANAKA

2002-01-01

203

BNL ACTIVITIES IN ADVANCED NEUTRON SOURCE DEVELOPMENT: PAST AND PRESENT  

SciTech Connect

Brookhaven National Laboratory has been involved in advanced neutron sources almost from its inception in 1947. These efforts have mainly focused on steady state reactors beginning with the construction of the first research reactor for neutron beams, the Brookhaven Graphite Research Reactor. This was followed by the High Flux Beam Reactor that has served as the design standard for all the subsequent high flux reactors constructed worldwide. In parallel with the reactor developments BNL has focused on the construction and use of high energy proton accelerators. The first machine to operate over 1 GeV in the world was the Cosmotron. The machine that followed this, the AGS, is still operating and is the highest intensity proton machine in the world and has nucleated an international collaboration investigating liquid metal targets for next generation pulsed spallation sources. Early work using the Cosmotron focused on spallation product studies for both light and heavy elements into the several GeV proton energy region. These original studies are still important today. In the sections below the authors discuss the facilities and activities at BNL focused on advanced neutron sources. BNL is involved in the proton source for the Spallation Neutron source, spectrometer development at LANSCE, target studies using the AGS and state-of-the-art neutron detector development.

HASTINGS,J.B.; LUDEWIG,H.; MONTANEZ,P.; TODOSOW,M.; SMITH,G.C.; LARESE,J.Z.

1998-06-14

204

Consistent analysis and evaluation of prompt fission neutron and gamma-ray spectra and multiplicities  

SciTech Connect

A simple, approach for consistent analysis and evaluation of prompt fission emission characteristics is presented. The approach is mainly based on Madland-Nix model for neutrons and empiric systematic for gamma rays. The comparison with experimental and evaluated data is given. To use this approach for minor actinides prompt fission emission data evaluation is proposed.

Klepatskij, A.B. [Radiation Physics and Chemistry Problems Institute, Minsk-Sosny (Belarus)

1994-12-31

205

Combined texture and structure analysis of deformed limestone from time-of-flight neutron diffraction spectra  

Microsoft Academic Search

The orientation distribution of a textured polycrystalline material has been traditionally determined from a few individual pole figures of lattice planes hkl, measured by x-ray or neutron diffraction. A new method is demonstrated that uses the whole diffraction spectrum, rather than extracted peak intensities, by combining the orientation distribution calculation with the crystallographic Rietveld method. The feasibility of the method

L. Lutterotti; S. Matthies; H.-R. Wenk; A. S. Schultz; J. W. Richardson Jr.

1997-01-01

206

Neutron Production Measurements Relevant to Shielding forSpace-Related Activities  

SciTech Connect

Neutron production cross sections have been measured from290 MeV/nucleon C and 600 MeV/nucleon Ne interacting in a slab ofsimulated Martian regolith/polyethylene composite, and from 400MeV/nucleon Ne interacting in a section of wall materials from theInternational Space Station. Neutron spectra were measured at 7 anglesbetween 5 degrees and 80 degrees, and for neutron energies 5 MeV andgreater. Spectra at forward angles are dominated by the breakup of theprojectile, whereas spectra at back angles show the typical exponentialfalloff with energy that is indicative of decay from the overlap regionand the target remnant. The measured total neutron production crosssections indicate that the regolith/polyethylene composite may be a moreeffective shielding material than the ISS wall materials, in terms of thenumber of neutrons produced.

Heilbronn, Lawrence; Iwata, Yoshiyuki; Murakami, Takeshi; Iwase,Hiroshi; Nakamura, Takashi; Sato, Hisaki; Ronningen, Reginald

2002-04-09

207

Measured and Calculated Neutron Spectra and Dose Equivalent Rates at High Altitudes; Relevance to SST Operations and Space Research  

NASA Technical Reports Server (NTRS)

Results of the NASA Langley-New York University high-altitude radiation study are presented. Measurements of the absorbed dose rate and of secondary fast neutrons (1 to 10 MeV energy) during the years 1965 to 1971 are used to determine the maximum radiation exposure from galactic and solar cosmic rays of supersonic transport (SST) and subsonic jet occupants. The maximum dose equivalent rates that the SST crews might receive turn out to be 13 to 20 percent of the maximum permissible dose rate (MPD) for radiation workers (5 rem/yr). The exposure of passengers encountering an intense giant-energy solar particle event could exceed the MPD for the general population (0.5 rem/yr), but would be within these permissible limits if in such rare cases the transport descends to subsonic altitude; it is in general less than 12 percent of the MPD. By Monte Carlo calculations of the transport and buildup of nucleons in air for incident proton energies E of 0.02 to 10 GeV, the measured neutron spectra were extrapolated to lower and higher energies and for galactic cosmic rays were found to continue with a relatively high intensity to energies greater than 400 MeV, in a wide altitude range. This condition, together with the measured intensity profiles of fast neutrons, revealed that the biologically important fast and energetic neutrons penetrate deep into the atmosphere and contribute approximately 50 percent of the dose equivalant rates at SST and present subsonic jet altitudes.

Foelsche, T.; Mendell, R. B.; Wilson, J. W.; Adams, R. R.

1974-01-01

208

MEASUREMENTS OF NEUTRON SPECTRA IN 0.8-GEV AND 1.6-GEV PROTON-IRRADIATED<2 OF 2>NA THICK TARGETS  

SciTech Connect

Measurements of neutron spectra in W, and Na targets irradiated by 0.8 GeV and 1.6 GeV protons are presented. Measurements were made by the TOF techniques using the proton beam from ITEP U-10 synchrotron. Neutrons were detected with BICRON-511 liquid scintillator-based detectors. The neutron detection efficiency was calculated via the SCINFUL and CECIL codes. The W results are compared with the similar data obtained elsewhere. The measured neutron spectra are compared with the LAHET and CEM2k code simulations results. Attempt is made to explain some observed disagreements between experiments and simulations. The presented results are of interest both in terms of nuclear data buildup and as a benchmark of the up-to-date predictive power of the simulation codes used in designing the hybrid accelerator-driven system (ADS) facilities with sodium-cooled tungsten targets.

Titarenko, Y. E. (Yury E.); Batyaev, V. F. (Vyacheslav F.); Zhivun, V. M. (Valery M.); Koldobsky, A. B. (Aleksander B.); Mulambetov, R. D. (Ruslan D.); Fischenko, D. V. (Dmitry V.); Smirnov, G. N. (Gennady N.); Mashnik, S. G. (Stepan G.); Prael, R. E. (Richard E.); Yasuda, H.; Sierk, A. J. (Arnold J.)

2001-01-01

209

Neutron activation analysis of arsenic in Greece  

Microsoft Academic Search

Arsenic is considered a toxic trace element for plant, animal, and human organisms. Arsenic and certain arsenic compounds have been listed as carcinogens by the U.S. Environmental Protection Agency. Arsenic is emitted in appreciable quantities into the atmosphere by coal combustion and the production of cement. Arsenic enters the aquatic environment through industrial activities such as smelting of metallic ores,

Grimanis

1989-01-01

210

ter, electrical conductivity, activity of sac-charase, amount of proline and sugar spectra.  

E-print Network

ter, electrical conductivity, activity of sac- charase, amount of proline and sugar spectra. A short time after intake of sugar solu- tions there are changes of sugar spectra, which can be explained by the effect of the enzyme invertase/saccharase. But, in addi- tion, there are sugar types in the honey sac

Boyer, Edmond

211

Rainbow-Like Spectra with a CD: An Active-Learning  

E-print Network

Rainbow-Like Spectra with a CD: An Active-Learning Exercise G. Planins v ic v , University and transmission, and rainbow-like spectra to a large lecture hall of 200­300 students. He also described how rainbow-like spec- tra; and 2. a qualitative explanation of surprising results of those explorations

Planin�iè, Gorazd

212

Passive and Active Neutron Matrix Correction for Heterogeneous Distributions Utilizing the Neutron Imaging Technique  

SciTech Connect

Classical Non-Destructive Assay (NDA) Passive Neutron Coincidence Counting (PNCC) and Differential Die-Away (DDA) active neutron interrogation techniques [1, 2] are well suited for determining the gross matrix correction factors for homogenous mass distributions of Special Nuclear Material (SNM) within an interfering waste drum matrix. These measured passive and active matrix correction factors are crucial in quantifying the SNM mass, associated Total Measurement Uncertainty (TMU), and Minimum Detectable Activity (MDA) within the drum. When heterogeneous SNM mass distributions are encountered, the measured SNM mass, TMU and MDA biases introduced may be 100%, or greater, especially for dense hydrogenous matrices. The standard matrix correction factors can be adjusted if a coarse spatial image of the SNM mass, relative to the matrix, is available. The image can then be analyzed to determine the spatially-adjusted, matrix correction factors case by case. This image analysis approach was accomplished by modifying the standard Passive-Active Neutron (PAN) counter design [3] to accommodate a unique data acquisition architecture that supports a newly developed image acquisition and analysis application called the Neutron Imaging Technique (NIT). The NIT functionality supports both PNCC and DDA acquisition and analysis modes and exploits the symmetry between a stored set of factory acquired NIT images with those from the unknown PAN assay. The NIT result is then an adjustment to the classical correction factor reducing, if not removing, the SNM mass bias and revealing the true TMU and MDA values. In this paper we describe the NIT for the PAN design from the software and algorithmic perspectives and how this technique accommodates waste matrix drums that are difficult, from the classical standpoint, if not impossible, to extract meaningful SNM mass, TMU and MDA results. (authors)

Villani, M.F.; Croft, St. [Canberra Industries, Inc., Meriden, CT (United States); Alvarez, E.; Wilkins, C.G.; Stamp, D.; Fisher, J. [Canberra Harwell, Ltd., Didcot (United Kingdom); Ambrifi, A.; Simone, G. [Nucleco SpA, Casaccia (Italy); Bourva, L.C. [International Atomic Energy Agency, Dept. of Safeguards, Vienna (Australia)

2008-07-01

213

Determinations of the radii, redshifts, and atmospheric compositions of neutron stars from modeling their Chandra X-ray spectra  

NASA Astrophysics Data System (ADS)

Fitting the X-ray spectra of thermal radiation from neutron stars with realistic atmosphere models provides a way to place constraints on their radii, surface gravities and compositions, and to test general relativity in the strong field limit. Such determinations allow us to constrain the equation of state of nuclear matter. I present fits which constrain the radii and surface compositions of two neutron stars, using high quality Chandra X-ray Observatory observations of the point source in the Cassiopeia A supernova remnant (Cas A XPS), and the isolated neutron star RX J1856.5-3754. I apply models calculated with advanced versions of the ATM model atmosphere code developed by Madej and Joss for neutron- star atmospheres composed of hydrogen, hydrogen-helium, iron, or a silicon to iron mixture. The results, taken assuming a typical value of 1.4 solar masses, show that the X-ray emission is generated from hot spot regions of scale size ˜3 4 km, on stars of intrinsic radius 9 and 12.5 km. This implies a relatively stiff equation of state. For the Cas A XPS, I fit the most source photons to date with spectra extracted from three Chandra Advanced CCD Imaging Spectrometer observations (ObsIds 114, 1952, 1046), with a total effective exposure of approximately 110,000 seconds. With these data, I am able to show that atmosphere models fit significantly better than blackbody models, although a wide range of radii are permitted. I also present evidence of an absorption feature in the XPS spectrum caused by silicon present in the supernova remnant, and discuss efforts to fit CCD pileup of the spectrum. For the RX J1856.5-3754, I fit a 450,000 second Chandra Low Energy Transmission Grating/High Resolution Camera observation. My findings agree with previous results that a blackbody model provides the best fit, and reject hydrogen and iron atmospheres. While previous attempts to fit the spectrum with rotationally-blurred iron or solar abundance atmospheres have failed, I successfully fit the spectrum to a rotationally Doppler blurred silicon-ash model, a surface composition which might exist following a supernova. The fit implies a rotational period of approximately 2 ms. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Stage, Michael D.

2003-12-01

214

Inherent Protection of Plutonium by Doping Minor Actinide in Thermal Neutron Spectra  

Microsoft Academic Search

The present study focuses on the exploration of the effect of minor actinide (MA) addition into uranium oxide fuels of different enrichment (5% U and 20% U) as ways of increasing fraction of even-mass-number plutonium isotopes. Among plutonium isotopes, Pu, Pu and Pu have the characteristics of relatively high decay heat and spontaneous fission neutron rate that can improve proliferation-resistant

Yoga PERYOGA; Hiroshi SAGARA; Masaki SAITO; Alexey EZOUBTCHENKO

2005-01-01

215

Development of a new deuterium-deuterium (D-D) neutron generator for prompt gamma-ray neutron activation analysis.  

PubMed

A new deuterium-deuterium (D-D) neutron generator has been developed by Adelphi Technology for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA), and fast neutron radiography. The generator makes an excellent fast, intermediate, and thermal neutron source for laboratories and industrial applications that require the safe production of neutrons, a small footprint, low cost, and small regulatory burden. The generator has three major components: a Radio Frequency Induction Ion Source, a Secondary Electron Shroud, and a Diode Accelerator Structure and Target. Monoenergetic neutrons (2.5MeV) are produced with a yield of 10(10)n/s using 25-50mA of deuterium ion beam current and 125kV of acceleration voltage. The present study characterizes the performance of the neutron generator with respect to neutron yield, neutron production efficiency, and the ionic current as a function of the acceleration voltage at various RF powers. In addition the Monte Carlo N-Particle Transport (MCNP) simulation code was used to optimize the setup with respect to thermal flux and radiation protection. PMID:25305524

Bergaoui, K; Reguigui, N; Gary, C K; Brown, C; Cremer, J T; Vainionpaa, J H; Piestrup, M A

2014-12-01

216

The epithermal neutron flux distribution in a nuclear reactor and its effect on epithermal neutron activation analysis  

Microsoft Academic Search

The shape of the epithermal neutron energy distribution has been determined in two irradiation positions of the University\\u000a of London CONSORT II reactor. The method applied involves cadmium ratio measurements using a series of resonance detectors.\\u000a Principles of the method and some considerations relative to epithermal neutron activation analysis in connection with the\\u000a deviation of the epithermal neutron flux distribution

T. Bereznai; T. D. Mac Mahon

1978-01-01

217

Dose equivalents to neutron therapy facility staff due to induced activation.  

PubMed

The sources of the induced activity from the d(48.5)+Be fast neutron therapy beam of the Harper Hospital superconducting cyclotron have been investigated. The distribution of activity in the treatment room was measured, and the levels of dose equivalent to the staff were established. Activation spectra were measured with a high purity RE-Ge detector. Peaks corresponding to 28Al, 56Mn, 24Na, 64Cu, 66Cu, and 187W were present in the spectra. The dose equivalents due to the induced activation were measured by means of an ionization chamber type survey meter at six locations in the room. Irradiations of 120 monitor units were given at 15-min intervals, thus simulating the clinical situation. The measurements were made between the irradiations. The highest levels were registered around the treatment head. Two patterns are clearly distinguishable in these measurements. A fast decaying component with approximately 2 min half-life can be ascribed predominantly to 28Al and a slow growing component reaching saturation after about 4-5 treatments is associated with the presence of 56Mn. For uniform treatment load the activation build-up in each location was similar every day of the week with minimal values measured after the week end shut down. Personnel monitoring is achieved with dosimeters capable of detecting an extended range of neutron energies as well as beta rays and photons. Correlation between the number of fields treated and the doses to the radiation therapy technologists was shown. The mean dose equivalent received by the therapists is 7.1 +/- 0.2 microSv per treatment field. Means of reducing personnel dose equivalent levels are proposed. PMID:9030837

Yudelev, M; Maughan, R L; Jordan, L E; Saxena, R

1997-03-01

218

Areawide Trace Metal Concentrations Measured by Multielement Neutron Activation Analysis  

Microsoft Academic Search

A suite of 24 hour high volume air particulate samples, collected June 11–12,1969, at 25 locations in the Northwest Indiana area, has been analyzed by nondestructive neutron activation analysis for 30 trace elements. The use of Ge(Li) gamma-ray spectrometry and computer assisted data reduction, combined with 2-4 replications of each analysis, yielded precise results which allowed a study of the

P. R. Harrison; K. A. Rahn; R. Dams; J. A. Robbins; J. W. Winchester; S. S. Brar; D. M. Nelson

1971-01-01

219

Neutron-activation analysis of trace elements in thyroids  

Microsoft Academic Search

Neutron activation analysis was used for routine measurement of trace elements in thyroids of inhabitants of Belarus as well\\u000a as in thyroids of people operated for thyroid cancer. The method chosen allowed the analysis of 28 elements, among them essential\\u000a and toxic ones, with a good accuracy. The results obtained showed significant differences in the elemental composition of\\u000a thyroid from

S. F. Boulyga; H. Petri; I. V. Zhuk; N. V. Kanash; A. F. Malenchenko

1999-01-01

220

Instrumental neutron activation analysis of fly ashes and emissions  

Microsoft Academic Search

Instrumental neutron activation analysis (INAA) has been utilized for the analysis of 19 different fly ashes, 1 sample of\\u000a coal and 3 samples of industrial emissions. Both short and long irradiations in a nuclear reactor have been used. The irradiated\\u000a samples have been measured by means of a computer-based Ge(Li) gamma-ray spectrometer. The concentrations of 27 elements have\\u000a been determined

I. Obrusník; B. Stárková; J. Blažek

1976-01-01

221

Instrumental neutron activation analysis of fly ash, aerosols and hair  

Microsoft Academic Search

Samples of coal, slag, emissions retained on the separating devices, fly ash, aerosols and hair taken in the area of coal-fired\\u000a power plant were analyzed by means of instrumental neutron activation analysis. 13 to 23 elements were determined in the samples.\\u000a The data obtained for emissions and aerosols were further evaluated by calculation of enrichment factors, correlation coefficients\\u000a and by

I. Obrusník; B. Stárková; J. Blažek; V. Bencko

1979-01-01

222

Determination of indium in standard rocks by neutron activation analysis.  

PubMed

A rapid neutron activation method for the determination of indium in rocks, based on 54 min (116m)In, is described. The method has been applied to a series of geochemical standards including granite G-1 and diabase W-1. The precision is better than +/- 5% for samples containing more than 5 x 10(-10)g indium. Good agreement with previously published values for G-1 and W-1 has been obtained. PMID:18959988

Johansen, O; Steinnes, E

1966-08-01

223

A study of aliphatic amino acids using simulated vibrational circular dichroism and Raman optical activity spectra  

E-print Network

Vibrational optical activity (VOA) spectra, such as vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra, of aliphatic amino acids are simulated using density functional theory (DFT) methods in both gas phase (neutral form) and solution (zwitterionic form), together with their respective infrared (IR) and Raman spectra of the amino acids. The DFT models, which are validated by excellent agreements with the available experimental Raman and ROA spectra of alanine in solution, are employed to study other aliphatic amino acids. The inferred (IR) intensive region (below 2000 cm-1) reveals the signature of alkyl side chains, whereas the Raman intensive region (above 3000 cm-1) contains the information of the functional groups in the amino acids. Furthermore, the chiral carbons of the amino acids (except for glycine) dominate the VCD and ROA spectra in the gas phase, but the methyl group vibrations produce stronger VCD and ROA signals in solution. The C-H related asymmetric vibrations domina...

Ganesan, Aravindhan; Wang, Feng

2013-01-01

224

BARYON LOADING OF ACTIVE GALACTIC NUCLEUS JETS MEDIATED BY NEUTRONS  

SciTech Connect

Plasmas of geometrically thick, black hole (BH) accretion flows in active galactic nuclei (AGNs) are generally collisionless for protons, and involve magnetic field turbulence. Under such conditions a fraction of protons can be accelerated stochastically and create relativistic neutrons via nuclear collisions. These neutrons can freely escape from the accretion flow and decay into protons in the dilute polar region above the rotating BH to form relativistic jets. We calculate geometric efficiencies of the neutron energy and mass injections into the polar region, and show that this process can deposit luminosity as high as L{sub j}{approx}2 Multiplication-Sign 10{sup -3} M-dot c{sup 2} and mass loading M-dot{sub j}{approx}6 Multiplication-Sign 10{sup -4} M-dot for the case of the BH mass M {approx} 10{sup 8} M{sub Sun }, where M-dot is the mass accretion rate. The terminal Lorentz factors of the jets are {Gamma} {approx} 3, and they may explain the AGN jets having low luminosities. For higher luminosity jets, which can be produced by additional energy inputs such as Poynting flux, the neutron decay still can be a dominant mass loading process, leading to, e.g., {Gamma} {approx} 50 for L{sub j,tot}{approx}3 Multiplication-Sign 10{sup -2} M-dot c{sup 2}.

Toma, K.; Takahara, F., E-mail: toma@vega.ess.sci.osaka-u.ac.jp [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka 560-0043 (Japan)

2012-08-01

225

Design of active-neutron fuel rod scanner  

NASA Astrophysics Data System (ADS)

An active-neutron fuel rod scanner has been designed for the assay of fissile materials in mixed oxide fuel rods. A 252Cf source is located at the center of the scanner very near the through hole for the fuel rods. Spontaneous fission neutrons from the californium are moderated and induce fissions within the passing fuel rod. The rod continues past a combined gamma-ray and neutron shield where delayed gamma rays above 1 MeV are detected. We used the Monte Carlo code MCNP to design the scanner and review optimum materials and geometries. An inhomogeneous beryllium, graphite, and polyethylene moderator has been designed that uses source neutrons much more efficiently than assay systems using polyethylene moderators. Layers of borated polyethylene and tungsten are used to shield the detectors. Large NaI(Tl) detectors were selected to measure the delayed gamma rays. The enrichment zones of a thermal reactor fuel pin could be measured to within 1% counting statistics for practical rod speeds. Applications of the rod scanner include accountability of fissile material for safeguards applications, quality control of the fissile content in a fuel rod, and the verification of reactivity potential for mixed oxide fuels.

Griffith, G. W.; Menlove, H. O.

1996-02-01

226

Magnetar activity mediated by plastic deformations of neutron star crust  

NASA Astrophysics Data System (ADS)

We advance a `solar flare' model of magnetar activity, whereas a slow evolution of the magnetic field in the upper crust, driven by electron magnetohydrodynamic flows, twists the external magnetic flux tubes, producing persistent emission, bursts, and flares. At the same time, the neutron star crust plastically relieves the imposed magnetic field stress, limiting the strain ?t to values well below the critical strain ?crit of a brittle fracture, ?t ˜ 10-2?crit. Magnetar-like behaviour, occurring near the magnetic equator, takes place in all neutron stars, but to a different extent. The persistent luminosity is proportional to cubic power of the magnetic field (at a given age), and hence is hardly observable in most rotationally powered neutron stars. Giant flares can occur only if the magnetic field exceeds some threshold value, while smaller bursts and flares may take place in relatively small magnetic fields. Bursts and flares are magnetospheric reconnection events that launch Alfvén shocks which convert into high-frequency whistlers upon hitting the neutron star surface. The resulting whistler pulse induces a strain that increases with depth both due to the increasing electron density (and the resulting slowing of the waves), and due to the increasing coherence of a whistler pulse with depth. The whistler pulse is dissipated on a time-scale of approximately a day at shallow depths corresponding to ? ˜ 1010 g cm-3; this energy is detected as enhanced post-flare surface emission.

Lyutikov, Maxim

2015-02-01

227

Monte Carlo determined self-shielded groupwise cross-sections for the activation foil stack applied in the epithermal neutron spectrum adjustment  

NASA Astrophysics Data System (ADS)

Activation foils, stacked in a package, together with a spectrum adjustment code are generally the means to characterize the neutron spectrum of a BNCT epithermal neutron beam. When using foil stacks, the phenomenon of neutron scattering is appreciably enhanced, especially in an epithermal neutron beam, as compared to a thermal neutron field. Contrary to the conventional idea of the self-shielding effect, self-shielding correction factors in most of the foils in the stack are larger than one. This paper demonstrates a way to correct the complex self-shielding effect using groupwise cross-sections modified for self-shielding, as calculated by the Monte Carlo neutron transport code, MCNP. This methodology can solve the perturbation problems caused by the foil stack applied in an epithermal neutron beam. In this study, the adjusted spectrum of the HB11 epithermal neutron beam, dedicated for BNCT research in Petten, The Netherlands, is utilized and two adjusted spectra are presented with and without the self-shielding correction. The difference between the spectra is highly significant and demonstrates that the self-shielding correction cannot be ignored.

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

2009-04-01

228

Measurement of action spectra of light-activated processes  

NASA Astrophysics Data System (ADS)

We report on a new experimental technique suitable for measurement of light-activated processes, such as fluorophore transport. The usefulness of this technique is derived from its capacity to decouple the imaging and activation processes, allowing fluorescent imaging of fluorophore transport at a convenient activation wavelength. We demonstrate the efficiency of this new technique in determination of the action spectrum of the light mediated transport of rhodamine 123 into the parasitic protozoan Giardia duodenalis.

Ross, Justin; Zvyagin, Andrei V.; Heckenberg, Norman R.; Upcroft, Jacqui; Upcroft, Peter; Rubinsztein-Dunlop, Halina H.

2006-01-01

229

[Spectra and thermal analysis of the arc in activating flux plasma arc welding].  

PubMed

In activating flux plasma arc welding the welding arc was analyzed by spectra analysis technique, and the welding arc temperature field was measured by the infrared sensing and computer image technique. The distribution models of welding arc heat flow density of activating flux PAW welding were developed. The composition of welding arc affected by activated flux was studied, and the welding arc temperature field was studied. The results show that the spectral lines of argon atom and ionized argon atom of primary ionization are the main spectra lines of the conventional plasma welding arc. The spectra lines of weld metal are inappreciable in the spectra lines of the conventional plasma welding arc. The gas particle is the main in the conventional plasma welding arc. The conventional plasma welding arc is gas welding arc. The spectra lines of argon atom and ionized argon atom of primary ionization are intensified in the activating flux plasma welding arc, and the spectra lines of Ti, Cr and Fe elements are found in the activating flux plasma welding arc. The welding arc temperature distribution in activating flux plasma arc welding is compact, the outline of the welding arc temperature field is narrow, the range of the welding arc temperature distribution is concentrated, the welding arc radial temperature gradient is large, and the welding arc radial temperature gradient shows normal Gauss distribution. PMID:20545181

Chai, Guo-Ming; Zhu, Yi-Feng

2010-04-01

230

Analysis of initial in-plant active neutron multiplicity measurements  

SciTech Connect

This paper analyzes initial in-plant measurements made by active neutron multiplicity counting, a new technique currently under development for the assay of bulk uranium containing kilograms of {sup 235}U. The measurements were made at Savannah River and Y-12 using active well coincidence counters and prototype multiplicity electronics and software from Los Alamos. For one of the sets of highly enriched uranium samples measured to data, we improved the assay accuracy by an order-of-magnitude by adding the multiplicity analysis to the conventional coincidence analysis. This paper summarizes our results and describes areas where further work is needed.

Ensslin, N.; Krick, M.S.; Harker, W.C. [and others

1993-08-01

231

NSVA-3:. a Computer Code for Least-Squares Adjustment of Neutron Spectra and Measured Dosimeter Responses  

NASA Astrophysics Data System (ADS)

A new spectrum adjustment code, NSVA-3, has been developed and is being made available to the community. The name refers to Neutron Spectrum Validation and Adjustment. The designation NSVA-3 is a version of the code that simultaneously adjusts spectra for multiple environments. The code is written in MATLAB®, a high-level script language. The main advantage of the NSVA code is its use of graphic user interfaces (GUIs) to assist the user with the data input and in interactive execution of adjustment cases. Items of data may be easily swapped in or out of the calculation. As with previous least-squares adjustment codes, the data input requires the preparation of files for fluence spectra, dosimetry measurements, the standard deviations of each of these, and correlation matrices of each. In the case of multiple environments, the cross correlations between environments of the input fluence and dosimetry measurements can also be included. The GUI assists the user in keeping track of all of these files. An 89-group cross section library including covariance matrices is incorporated in the code package. The paper presents the basic theory used in the code, the limitations and assumptions that are built into this implementation, and will describe the operation of the code by means of an example problem.

Williams, J. G.; Ribaric, A. P.; Schnauber, T.

2009-08-01

232

Calculation of effective dose from measurements of secondary neutron spectra and scattered photon dose from dynamic MLC IMRT for 6 MV, 15 MV, and 18 MV beam energies  

Microsoft Academic Search

Effective doses were calculated from the delivery of 6 MV, 15 MV, and 18 MV conventional and intensity-modulated radiation therapy (IMRT) prostate treatment plans. ICRP-60 tissue weighting factors were used for the calculations. Photon doses were measured in phantom for all beam energies. Neutron spectra were measured for 15 MV and 18 MV and ICRP-74 quality conversion factors used to

Rebecca M. Howell; Nolan E. Hertel; Wang Zhonglu; Jesson Hutchinson; Gary D. Fullerton

2006-01-01

233

A study of aliphatic amino acids using simulated vibrational circular dichroism and Raman optical activity spectra*  

NASA Astrophysics Data System (ADS)

Vibrational optical activity (VOA) spectra, such as vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra, of aliphatic amino acids are simulated using density functional theory (DFT) methods in both gas phase (neutral form) and solution (zwitterionic form), together with their respective infrared (IR) and Raman spectra of the amino acids. The DFT models, which are validated by excellent agreements with the available experimental Raman and ROA spectra of alanine in solution, are employed to study other aliphatic amino acids. The inferred (IR) intensive region (below 2000 cm-1) reveals the signature of alkyl side chains, whereas the Raman intensive region (above 3000 cm-1) contains the information of the functional groups in the amino acids. Furthermore, the chiral carbons of the amino acids (except for glycine) dominate the VCD and ROA spectra in the gas phase, but the methyl group vibrations produce stronger VCD and ROA signals in solution. The C-H related asymmetric vibrations dominate the VOA spectra (i.e., VCD and ROA) > 3000 cm-1 reflecting the side chain structures of the amino acids. Finally the carboxyl and the C(2)H modes of aliphatic amino acids, together with the side chain vibrations, are very active in the VCD/IR and ROA/Raman spectra, which makes such the vibrational spectroscopic methods a very attractive means to study biomolecules.

Ganesan, Aravindhan; Brunger, Michael J.; Wang, Feng

2013-11-01

234

One-group fission cross sections for plutonium and minor actinides inserted in calculated neutron spectra of fast reactor cooled with lead-208 or lead-bismuth eutectic  

SciTech Connect

The paper is dedicated to one-group fission cross sections of Pu and MA in LFRs spectra with the aim to increase these values by choosing a coolant which hardens neutron spectra. It is shown that replacement of coolant from Pb-Bi with Pb-208 in the fast reactor RBEC-M, designed in Russia, leads to increasing the core mean neutron energy. As concerns fuel Pu isotopes, their one-group fission cross sections become slightly changed, while more dramatically Am-241 one-group fission cross section is changed. Another situation occurs in the lateral blanket containing small quantities of minor actinides. It is shown that as a result of lateral blanket mean neutron energy hardening the one-group fission cross sections of Np-237, Am-241 and Am-243 increases up to 8-11%. This result allows reducing the time of minor actinides burning in FRs. (authors)

Khorasanov, G. L.; Blokhin, A. I. [State Scientific Center of the Russian Federation, Inst. for Physics and Power Engineering Named after A.I. Leypunsky, Bondarenko Square 1, Obninsk, 249033 (Russian Federation)

2012-07-01

235

CTOF Measurements and Monte Carlo Analyses of Neutron Spectra for the Backward Direction from a Copper Target Irradiated with 800, 1000, and 1200 MeV Protons  

E-print Network

A calorimetric-time-of-flight (CTOF) technique was used for real-time, high-precision measurement of the neutron spectrum at an angle of 175 deg from the initial proton beam direction, which hits a face plane of a cylindrical copper target of 20 cm in diameter and 25 cm thick. A comparison was performed between the neutron spectra predicted by the MARS, RTS&T, GEANT4, and the MCNP6 codes and that measured for 800, 1000, and 1200 MeV protons. The transport codes tested here describe with different success the measured spectra, depending on the energy of the detected neutrons and on the incident proton energy, but all the models agree reasonably well with our data.

Azhgirey, I L; Degtyarev, I I; Smirnov, N P; Mashnik, S G

2012-01-01

236

CTOF Measurements and Monte Carlo Analyses of Neutron Spectra for the Backward Direction from a Copper Target Irradiated with 800, 1000, and 1200 MeV Protons  

E-print Network

A calorimetric-time-of-flight (CTOF) technique was used for real-time, high-precision measurement of the neutron spectrum at an angle of 175 deg from the initial proton beam direction, which hits a face plane of a cylindrical copper target of 20 cm in diameter and 25 cm thick. A comparison was performed between the neutron spectra predicted by the MARS, RTS&T, GEANT4, and the MCNP6 codes and that measured for 800, 1000, and 1200 MeV protons. The transport codes tested here describe with different success the measured spectra, depending on the energy of the detected neutrons and on the incident proton energy, but all the models agree reasonably well with our data.

I. L. Azhgirey; V. I. Belyakov-Bodin; I. I. Degtyarev; N. P. Smirnov; S. G. Mashnik

2012-11-13

237

Verification of Monte Carlo Calculations by Means of Neutron and Gamma Fluence Spectra Measurements behind and inside of Iron-Water Configurations  

SciTech Connect

Neutron and gamma spectra were measured behind and inside of modules consisting of variable iron and water slabs that were installed in radial beams of the zero-power training and research reactors AKR of the Technical University Dresden and ZLFR of the University of Applied Sciences Zittau/Goerlitz. The applied NE-213 scintillation spectrometer did allow the measurement of gamma and neutron fluence spectra in the energy regions 0.3-10 MeV for photons and 1.0-20 MeV for neutrons. The paper describes the experiments and presents important results of the measurements. They are compared with the results of Monte Carlo transport calculations made by means of the codes MCNP and TRAMO on an absolute scale of fluences.

Boehmer, Bertram; Konheiser, Joerg; Noack, Klaus; Rogov, Anatoli [FZ Rossendorf, Institut fuer Sicherheitsforschung, PF 510119, D-01314 Dresden (Germany); Grantz, Martin; Mehner, Hans-Christoph [HS Zittau/Goerlitz, FB Maschinenwesen, Theodor-Koerner-Allee 16, D-02763 Zittau (Germany); Hansen, Wolfgang; Stephan, Ingrid [Technische Universitaet Dresden, Institut fuer Energietechnik, D-01062 Dresden (Germany); Hinke, Dietmar; Unholzer, Siegfried [Technische Universitaet Dresden, Institut fuer Kern- und Teilchenphysik, D-01062 Dresden (Germany)

2005-05-24

238

Diagnosing suprathermal ion populations in Z-pinch plasmas using fusion neutron spectra  

SciTech Connect

The existence of suprathermal ion populations gives rise to significant broadening of and modifications to the fusion neutron spectrum. We show that when this population takes the form of a power-law at high energies, specific changes occur to the spectrum which are diagnosable. In particular, the usual Gaussian spectral shape produced by a thermal plasma is replaced by a Lorentz-like spectrum with broad wings extending far from the spectral peak. Additionally, it is found that the full width at half maximum of the spectrum depends on both the ion temperature and the power-law exponent. This causes the use of the spectral width for determination of the ion temperature to be unreliable. We show that these changes are distinguishable from other broadening mechanisms, such as temporal and motional broadening, and that detailed fitting of the spectral shape is a promising method for extracting information about the state of the ions.

Knapp, P. F.; Sinars, D. B.; Hahn, K. D. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2013-06-15

239

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

PubMed Central

The effect of the jaw configuration and the presence and configuration of the tertiary multileaf collimator (MLC) on the secondary neutron spectra for an 18 MV Varian 21EX linear accelerator (linac) is investigated in detail. The authors report the measured spectra for four collimator (jaw-and-MLC) configurations. These configurations represent the extreme settings of the jaws and MLC and should therefore describe the range of possible fluence and spectra that may be encountered during use of this linac. In addition to measurements, a Monte Carlo model was used to simulate the four collimator configurations and calculate the energy spectra and fluence at the same location as it was measured. The Monte Carlo model was also used to calculate the sources of neutron production in the linac head for each collimator configuration. They found that photoneutron production in the linac treatment head is dominated by the order in which the primary photon beam intercepts the high-Z material. The primary collimator, which has the highest position in the linac head (in a fixed location), is the largest source of secondary neutrons. Thereafter, the collimator configuration plays a role in where the neutrons originate. For instance, if the jaws are closed, they intercept the beam and contribute substantially to the secondary neutron production. Conversely, if the jaws are open, the MLC plays a larger role in neutron production (assuming, of course, that it intercepts the beam). They found that different collimator configurations make up to a factor of 2 difference in the ambient dose equivalent. PMID:19810476

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

2009-01-01

240

Activation energies and temperature effects from electrical spectra of soil  

Technology Transfer Automated Retrieval System (TEKTRAN)

Apparent permittivity often has soil-specific temperature responses as well as soil water responses. Variations of permittivity as a function of frequency and temperature can be used to calculate activation energies. The purpose of this study was to examine permittivity-temperature responses for six...

241

Neutron spectral and angular distribution measurements for 113 and 256 MeV protons on range-thick Al and sup 238 U targets using the foil activation techniques  

SciTech Connect

Second neutron yields, energy spectra, and angular distributions have been measured at seven angles from 0 to 150{degree} for 113 and 256 MeV protons stopped in range-thick targets of aluminum and depleted uranium ({sup 238}U). Thin foil stacks of ten different materials were activated by secondary neutrons at distances of 20--30 cm from the targets. Following each irradiation, 30--40 different activation products were measured by gamma-ray spectroscopy. These activation rates were then used to adjust neutron energy spectra calculated by the HETC computer code. Activation cross sections were taken from ENDF/BV below 20 MeV, from literature values tested in Be(d,n) fields up to 50 MeV, and from proton spallation data and calculations from 50--250 MeV. Spectral adjustments were made with the STAY'SL computer code using a least-squares technique to minimize {chi}{sup 2} for a covariance matrix determined from uncertainties in the measured activities, cross sections, and calculated flux spectra. Neutron scattering effects were estimated from foil packets irradiated at different distances from the target. Proton effects were measured with (p,n) reactions. Systematic differences were found between the adjusted and calculated neutron spectra, namely, that HETC underpredicts the neutron flux at back angles by a factor of 2--3 and slightly overpredicts the flux at forward angles. 19 refs., 23 figs., 13 tabs.

Greenwood, L.R.; Intasorn, A.

1989-07-01

242

NEUTRON ACTIVATION ANALYSIS APPLICATIONS AT THE SAVANNAH RIVER SITE USING AN ISOTOPIC NEUTRON SOURCE  

SciTech Connect

NAA using {sup 252}Cf is used to address important areas of applied interest at SRS. Sensitivity needs for many of the applications are not severe; analyses are accomplished using a 21 mg {sup 252}Cf NAA facility. Because NAA allows analysis of bulk samples, it offers strong advantages for samples in difficult-to-digest matrices when its sensitivity is sufficient. Following radiochemical separation with stable carrier addition, chemical yields for a number methods are determined by neutron activation of the stable carrier. In some of the cases where no suitable stable carriers exist, the source has been used to generate radioactive tracers to yield separations.

Diprete, D; C Diprete, C; Raymond Sigg, R

2006-08-14

243

RADSAT Benchmarks for Prompt Gamma Neutron Activation Analysis Measurements  

SciTech Connect

The accurate and efficient simulation of coupled neutron-photon problems is necessary for several important radiation detection applications. Examples include the detection of nuclear threats concealed in cargo containers and prompt gamma neutron activation analysis for nondestructive determination of elemental composition of unknown samples. High-resolution gamma-ray spectrometers are used in these applications to measure the spectrum of the emitted photon flux, which consists of both continuum and characteristic gamma rays with discrete energies. Monte Carlo transport is the most commonly used simulation tool for this type of problem, but computational times can be prohibitively long. This work explores the use of multi-group deterministic methods for the simulation of coupled neutron-photon problems. The main purpose of this work is to benchmark several problems modeled with RADSAT and MCNP to experimental data. Additionally, the cross section libraries for RADSAT are updated to include ENDF/B-VII cross sections. Preliminary findings show promising results when compared to MCNP and experimental data, but also areas where additional inquiry and testing are needed. The potential benefits and shortcomings of the multi-group-based approach are discussed in terms of accuracy and computational efficiency.

Burns, Kimberly A.; Gesh, Christopher J.

2011-07-01

244

A Hybrid Model for the Spectra of Neutron Star Accretion Columns Including Comptonization and Cyclotron Lines  

NASA Astrophysics Data System (ADS)

A physical model for the radiation emitted from accretion columns of neutron stars with magnetic fields on the order of 1012 G has to reflect the large-scale dynamical structure of the inflowing matter as well as the quantum mechanical scattering processes leading to the formation of cyclotron resonant scattering features (CRSFs). Becker & Wolff (B&W) developed an analytic model for the broadband continuum while the CRSFs have been investigated by Schönherr & Schwarm (S&S). While both models describe the separate trends seen in observational data very well, a fully self-consistent fitting approach to determine the physical parameters (e.g., accretion rate, magnetic field strength) of the accretion column in accreting X-ray pulsars requires accounting for both processes in one unified model. We present our first approach towards such an unified hybrid model covering both the macro- and the microphysics of the accreting plasma. We assume a cylinder symmetrical dual layer structure of the accretion column. The inner layer reflects the dynamical structure described by the B&W model while the optical thin outer layer acts as a CRSF forming region similar to a photosphere. We adopt the parameters from a fit of the B&W model to Her X-1 and calculate the emergent radiation as well as the dynamical properties such as bulk velocity within the core of the accretion column. Radiation escaping the optical thick core region is further altered by the outer shell, a thin layer with an optical depth on the order of 10-4-10-2 Thomson optical depth, adding cyclotron lines by processing it through the S&S model. This hybrid model is only a first step towards an unified model for accreting neutron stars with strong magnetic fields. In the future we will investigate the insertion of a third layer in the middle as a transition region, parameter boundaries, and also incorporate general relativity with the ultimate goal to use this new tool to model phase-resolved spectroscopy of accreting X-ray pulsars. We would like to thank the ISSI, Bern, for hosting inspiring and productive international team meetings such as the one resulting in the ideas presented here.

Schwarm, Fritz-Walter; Schönherr, G.; Becker, P. A.; Wolff, M. T.; Wilms, J.; Ferrigno, C.; West, B.

2013-04-01

245

Spectrum evaluation at the filter-modified neutron irradiation field for neutron capture therapy in Kyoto University Research Reactor  

Microsoft Academic Search

The Heavy Water Neutron Irradiation Facility of the Kyoto University Research Reactor (KUR-HWNIF) was updated in March 1996, mainly to improve the facility for neutron capture therapy (NCT). In this facility, neutron beams with various energy spectra, from almost pure thermal to epithermal, are available. The evaluation of the neutron energy spectra by multi-activation-foil method was performed as a series

Yoshinori Sakurai; Tooru Kobayashi

2004-01-01

246

Magnetic spectra in the tridiminished-icosahedron {Fe9} nanocluster by inelastic neutron scattering  

SciTech Connect

Inelastic neutron scattering (INS) experiments under applied magnetic field at low temperatures show detailed low-lying magnetic excitations in the so-called tridiminshed iron icosahedron magnetic molecule. The magnetic molecule consists of nine iron Fe3+ (s=5/2) and three phosphorous atoms that are situated on the 12 vertices of a nearly perfect icosahedron. The three phosphorous atoms form a plane that separates the iron cluster into two weakly coupled three- and six-ion fragments, {Fe3} and {Fe6}, respectively. The magnetic field INS results exhibit an S=1/2 ground state expected from a perfect equilateral triangle of the {Fe3} triad with a powder averaged g value =2.00. Two sets of triplet excitations whose temperature and magnetic field dependence indicate an S=0 ground state with two nondegenerate S=1 states are attributed to the {Fe6} fragment. The splitting may result from a finite coupling between the two fragments, single-ion anisotropy, antisymmetric exchange couplings, or from magnetic frustration of its triangular building blocks.

Vaknin, David [Ames Laboratory; Demmel, Franz [Rutherford Appleton Laboratory

2014-05-01

247

Determination of thorium concentration in seawater by neutron activation analysis  

SciTech Connect

A sensitive neutron activation analysis method has been successfully developed to determine /sup 232/Th concentration in seawater. The method involves both preirradiation and postirradiation radiochemical separations. The isotopes were separated from the samples and purified during the preirradiation chemistry. /sup 233/Pa was extracted and counted after the irradiation. Yields were monitored with /sup 230/Th and /sup 231/Pa tracers. The separation and purification schemes include ion exchange chromatography and solvent extraction. By this method the authors have measured /sup 232/Th concentrations in some seawater samples that are 1 order of magnitude lower than most previously reported values. 21 references, 3 figures, 2 tables.

Huh, C.A.; Bacon, M.P.

1985-09-01

248

Analysis of k 0 neutron activation analysis at the University of Missouri Research Reactor  

Microsoft Academic Search

k0 Instrumental Neutron Activation Analysis (k0 INAA) was evaluated at the University of Missouri Research Reactor (MURR). The MURR, unlike many other research reactors that employ k0 INAA, is refueled on a weekly basis. To determine if the neutron spectrum is stable enough for routine k0 INAA analysis, the neutron spectrum parameters ? and f were measured over a 9

J. D. Brockman; J. D. Robertson

2009-01-01

249

Activation of cobalt by neutrons from the Hiroshima bomb  

SciTech Connect

A study has been completed of cobalt activation in samples from two new locations in Hiroshima. The samples consisted of a piece of steel from a bridge located at a distance of about 1300 m from the hypocenter and pieces of both steel and concrete from a building located at approximately 700 m. The concrete was analyzed to obtain information needed to calculate the cobalt activation in the two steel samples. Close agreement was found between calculated and measured values for cobalt activation of the steel sample from the building at 700 m. It was found, however, that the measured values for the bridge sample at 1300 m were approximately twice the calculated values. Thus, the new results confirm the existence of a systematic error in the transport calculations for neutrons from the Hiroshima bomb. 52 refs., 32 figs., 16 tabs.

Kerr, G.D.; Dyer, F.F.; Emery, J.F.; Pace, J.V. III (Oak Ridge National Lab., TN (USA)); Brodzinski, R.L. (Pacific Northwest Lab., Richland, WA (USA)); Marcum, J. (R and D Associates, Marina del Rey, CA (USA))

1990-02-01

250

A simple and fast method for the determination of active ingredient in antiperspirant cosmetics by neutron activation analysis  

Microsoft Academic Search

Antiperspirant cosmetics are tested for their active ingredient (aluminium chlorohydroxide) by conventional analytical techniques. Aluminium has been determined by instrumental neutron activation analysis in all antiperspirant products and package forms available in the Greek market in order to develop a simple and fast method for its quantitation. Our results show that neutron activation analysis could be established as an official

G. D. Kanias

1984-01-01

251

Determination of boron in water using neutron scattering and transmission, and prompt gamma ray neutron activation analysis methods: A comparative study  

NASA Astrophysics Data System (ADS)

The boron concentration in water was determined using neutron scattering and transmission, and prompt gamma ray neutron activation analysis methods. The experimental setup is based on a Pu-Be neutron source, 3He neutron detectors and an NaI(Tl) gamma-ray detector. Water samples of different volumes and known amounts of boron were prepared. Transmitted and scattered neutrons and prompt gamma rays resulting from neutron capture reactions within the samples were simultaneously measured. The sensitivities of the neutron scattering and transmission measurements were determined to be better than those of the prompt gamma ray neutron activation analysis. The neutron scattering measurements were determined to be more sensitive than those of the neutron transmission measurements.

El Abd, A.

2014-10-01

252

Evolution of Magnetic Helicity and Energy Spectra of Solar Active Regions  

E-print Network

We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field for estimating magnetic energy and helicity spectra as well as current helicity spectra of individual active regions and the change of their spectral indices with the solar cycle. The departure of the spectral index of current helicity from 5/3 is analyzed, and it is found that it is lower than that of magnetic energy. There is no obvious relationship between the change of the normalized magnetic helicity and the integral scale of the magnetic field for individual active regions. The evolution of the spectral index reflects the development and distribution of various scales of magnetic structures in active regions. It is found that around solar maximum the magnetic energy and helicity spectra are steeper.

Zhang, Hongqi; Sokoloff, D D

2015-01-01

253

Symmetry adapted cluster-configuration interaction calculation of the photoelectron spectra of famous biological active steroids  

NASA Astrophysics Data System (ADS)

The photoelectron spectra of some famous steroids, important in biology, were calculated in the gas phase. The selected steroids were 5?-androstane-3,11,17-trione, 4-androstane-3,11,17-trione, cortisol, cortisone, corticosterone, dexamethasone, estradiol and cholesterol. The calculations were performed employing symmetry-adapted cluster/configuration interaction (SAC-CI) method using the 6-311++G(2df,pd) basis set. The population ratios of conformers of each steroid were calculated and used for simulating the photoelectron spectrum of steroid. It was found that more than one conformer contribute to the photoelectron spectra of some steroids. To confirm the calculated photoelectron spectra, they compared with their corresponding experimental spectra. There were no experimental gas phase Hesbnd I photoelectron spectra for some of the steroids of this work in the literature and their calculated spectra can show a part of intrinsic characteristics of this molecules in the gas phase. The canonical molecular orbitals involved in the ionization of each steroid were calculated at the HF/6-311++g(d,p) level of theory. The spectral bands of each steroid were assigned by natural bonding orbital (NBO) calculations. Knowing the electronic structures of steroids helps us to understand their biological activities and find which sites of steroid become active when a modification is performing under a biological pathway.

Abyar, Fatemeh; Farrokhpour, Hossein

2014-11-01

254

CTOF measurements and Monte Carlo analyses of neutron spectra for the backward direction from a lead target irradiated with 200 to 1000 MeV proton  

E-print Network

A calorimetric-time-of-flight (CTOF) technique was used for real-time, high-precision measurement of neutron spectrum at an angle of 175 degrees from the initial proton beam direction, which hits a face plane of a cylindrical lead target of 20 cm in diameter and 25 cm thick. A comparison was performed between the neutron spectra predicted by the MARS, RTS&T, MCNP6, and the MCNPX 2.6.0 transport codes and that measured for 200, 400, 600, 800, and 1000 MeV protons

Azhgirey, I L; Degtyarev, I I; Sherstnev, V A; Mashnik, S G; Gallmeier, F X; Lu, W

2010-01-01

255

CTOF measurements and Monte Carlo analyses of neutron spectra for the backward direction from a lead target irradiated with 200 to 1000 MeV proton  

E-print Network

A calorimetric-time-of-flight (CTOF) technique was used for real-time, high-precision measurement of neutron spectrum at an angle of 175 degrees from the initial proton beam direction, which hits a face plane of a cylindrical lead target of 20 cm in diameter and 25 cm thick. A comparison was performed between the neutron spectra predicted by the MARS, RTS&T, MCNP6, and the MCNPX 2.6.0 transport codes and that measured for 200, 400, 600, 800, and 1000 MeV protons

I. L. Azhgirey; V. I. Belyakov-Bodin; I. I. Degtyarev; V. A. Sherstnev; S. G. Mashnik; F. X. Gallmeier; W. Lu

2010-06-25

256

Measurement of energy spectra and spatial distributions of neutron beams provided by the ANNRI beamline for capture cross-section measurements at the J-PARC/MLF  

NASA Astrophysics Data System (ADS)

We measured the energy spectra and spatial distributions of the neutron beam of Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) at the Japan Proton Accelerator Research Complex/Materials and Life Science Experimental Facility (J-PARC/MLF). Our research team designed and built ANNRI to measure nuclear data with high precision. The measurements of the neutron beam were performed on three types of beams provided by ANNRI in the neutron energy range from 1.5 meV to 10 keV. The energy spectra show a typical feature of para-hydrogen moderator, and the absolute intensities almost agree with predictions based on both a simulation calculation of the Japan Spallation Neutron Source (JSNS) and a neutron transmission calculation of the beamline. The available neutron intensities at 21.5 m are 7.5×10 5, 1.6×10 4, and 1.1×10 5 n/cm 2/s in the energy ranges 1.5-25 meV, 0.9-1.1 eV, and 0.9-1.1 keV, respectively, under the 17.5 kW JSNS operation. The measured spatial distributions of the beams formed by three different collimators are consistent with those expected from the collimator-system design of the beamline. The beam sizes in FWHM are about 29, 14, and 11 mm for the three different beam collimators. The edges of the spatial distributions are relatively sharp, enabling us to measure the nuclear data successfully.

Kino, K.; Furusaka, M.; Hiraga, F.; Kamiyama, T.; Kiyanagi, Y.; Furutaka, K.; Goko, S.; Harada, H.; Harada, M.; Kai, T.; Kimura, A.; Kin, T.; Kitatani, F.; Koizumi, M.; Maekawa, F.; Meigo, S.; Nakamura, S.; Ooi, M.; Ohta, M.; Oshima, M.; Toh, Y.; Igashira, M.; Katabuchi, T.; Mizumoto, M.

2011-01-01

257

Neutron activation analysis of ceramic tiles and its component and radon exhalation rate.  

PubMed

The concentrations of 20 trace elements in several ceramics tiles and ceramic composites used in Egypt were elementally analyzed by neutron activation analysis(NAA) technique. The samples and standard were irradiated with reactor for 4 h (in the Second Research Egyptian Reactor(Et-RR-2)) with thermal neutron flux 5.9 x 10(13) n/(cm2 x s). The gamma-ray spectra obtained were measured for several times by means of the hyper pure germanium detection system(HPGe). Also a solid state nuclear track detector(SSNTD) CR-39, was used to measure the emanation rate of radon for these samples. The radium concentrations were found to vary from 0.39-3.59 ppm and the emanation rates were found to vary from (0.728-5.688) x 10(-4) kg/(m2 x s). The elemental analysis of the ceramic tiles and ceramic composites have a great importance in assigning the physical properties and in turn the quality of the material. PMID:14971460

El-Shershaby, A; Sroor, A; Ahmed, F; Abdel-Haleem, A S; Abdel, Z

2004-01-01

258

Epithermal Neutron Activation Analysis of the Asian Herbal Plants  

SciTech Connect

Asian medicinal herbs Chrysanthemum (Spiraea aquilegifolia Pall.) and Red Sandalwood (Pterocarpus Santalinus) are widely used in folk and Ayurvedic medicine for healing and preventing some diseases. The modern medical science has proved that the Chrysanthemum (Spiraea aquilegifolia Pall.) possesses the following functions: reducing blood press, dispelling cancer cell, coronary artery's expanding and bacteriostating and Red Sandalwood (Pterocarpus Santalinus) is recommended against headache, toothache, skin diseases, vomiting and sometimes it is taken for treatment of diabetes. Species of Chrysanthemums were collected in the north-eastern and central Mongolia, and the Red Sandalwood powder was imported from India. Samples of Chrysanthemums (branches, flowers and leaves)(0.5 g) and red sandalwood powder (0.5 g) were subjected to the multi-element instrumental neutron activation analysis using epithermal neutrons (ENAA) at the IBR-2 reactor, Frank Laboratory of Neutron Physics (FLNP) JINR, Dubna. A total of 41 elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Br, Rb, Sr, Zr, Mo, Cd, Cs, Ba, La, Hf, Ta, W, Sb, Au, Hg, Ce, Nd, Sm, Eu, Tb, Dy, Yb, Th, U, Lu) were determined. For the first time such a large group of elements was determined in the herbal plants used in Mongolia. The quality control of the analytical results was provided by using certified reference material Bowen Cabbage. The results obtained are compared to the ''Reference plant? data (B. Markert, 1992) and interpreted in terms of excess of such elements as Se, Cr, Ca, Fe, Ni, Mo, and rare earth elements.

Baljinnyam, N.; Frontasyeva, M. V.; Ostrovnaya, T. M.; Pavlov, S. S. [Frank Laboratory of Neutron Physics, JINR, Dubna (Russian Federation); Jugder, B. [Medical college 'Monos', Ulaanbaatar (Mongolia); Norov, N. [Centre of Nuclear Research, NUM, Ulaanbaatar (Mongolia)

2011-06-28

259

Epithermal Neutron Activation Analysis of the Asian Herbal Plants  

NASA Astrophysics Data System (ADS)

Asian medicinal herbs Chrysanthemum (Spiraea aquilegifolia Pall.) and Red Sandalwood (Pterocarpus Santalinus) are widely used in folk and Ayurvedic medicine for healing and preventing some diseases. The modern medical science has proved that the Chrysanthemum (Spiraea aquilegifolia Pall.) possesses the following functions: reducing blood press, dispelling cancer cell, coronary artery's expanding and bacteriostating and Red Sandalwood (Pterocarpus Santalinus) is recommended against headache, toothache, skin diseases, vomiting and sometimes it is taken for treatment of diabetes. Species of Chrysanthemums were collected in the north-eastern and central Mongolia, and the Red Sandalwood powder was imported from India. Samples of Chrysanthemums (branches, flowers and leaves) (0.5 g) and red sandalwood powder (0.5 g) were subjected to the multi-element instrumental neutron activation analysis using epithermal neutrons (ENAA) at the IBR-2 reactor, Frank Laboratory of Neutron Physics (FLNP) JINR, Dubna. A total of 41 elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Br, Rb, Sr, Zr, Mo, Cd, Cs, Ba, La, Hf, Ta, W, Sb, Au, Hg, Ce, Nd, Sm, Eu, Tb, Dy, Yb, Th, U, Lu) were determined. For the first time such a large group of elements was determined in the herbal plants used in Mongolia. The quality control of the analytical results was provided by using certified reference material Bowen Cabbage. The results obtained are compared to the "Reference plant» data (B. Markert, 1992) and interpreted in terms of excess of such elements as Se, Cr, Ca, Fe, Ni, Mo, and rare earth elements.

Baljinnyam, N.; Jugder, B.; Norov, N.; Frontasyeva, M. V.; Ostrovnaya, T. M.; Pavlov, S. S.

2011-06-01

260

Determination of 30 elements in coal and fly ash by thermal and epithermal neutron-activation analysis  

USGS Publications Warehouse

Thirty elements are determined in coal and fly ash by instrumental neutron-activation analysis using both thermal and epithermal irradiation. Gamma-ray spectra were recorded 7 and 20 days after the irradiations. The procedure is applicable to the routine analysis of coals and fly ash. Epithermal irradiation was found preferable for the determination of Ni, Zn, As, Se, Br, Rb, Sr, Mo, Sb, Cs, Ba, Sm, Tb, Hf, Ta, W, Th and U, whereas thermal irradiation was best for Sc, Cr, Fe, Co, La, Ce, Nd, Eu, Yb and Lu. Results for SRM 1632 (coal) and SRM 1633 (fly ash) agree with those of other investigators. ?? 1977.

Rowe, J.J.; Steinnes, E.

1977-01-01

261

Low-Flux Neutron Activation Analysis Applications at the Savannah River Site  

SciTech Connect

Neutron activation analysis using low-flux isotopic neutron sources is put to use in addressing areas of applied interest in managing the Savannah River Site. Some of the applications are unique due the site's operating history and its chemical processing facilities. Because sensitivity needs for many of the applications are not severe, they can be accomplished using approximately 6 mg 252Cf neutron activation analysis facility. Overviews of the facility and several example applications are presented.

Sigg, R.A.

1999-04-13

262

COLLISIONAL ACTIVATION MASS SPECTRA OF M-. IONS OF AZO DYES CONTAINING 2-NAPHTHOL  

EPA Science Inventory

Collisionally activated decomposition mass spectra of M- ions of azo dyes are presented. he compounds are of general structure Ar(l)-N=N-Ar(2), where Ar(l) is substituted phenyl and Ar(2) is 2-naphthol. Characteristic fragment ions observed include m/z 157, which corresponds to t...

263

Assessing Neutron Generator Output Using Delayed Activation of Silicon  

Technology Transfer Automated Retrieval System (TEKTRAN)

Deuterium-tritium (D-T) neutron generators are used for elemental composition analysis and medical applications. Often composition is determined by examining elemental ratios in which the knowledge of the neutron flux is unnecessary. However, the absolute value of the neutron flux is required when t...

264

Tables for simplifying calculations of activities produced by thermal neutrons  

USGS Publications Warehouse

The method of calculation described is useful for the types of work of which examples are given. It is also useful in making rapid comparison of the activities that might be expected from several different elements. For instance, suppose it is desired to know which of the three elements, cobalt, nickel, or vanadium is, under similar conditions, activated to the greatest extent by thermal neutrons. If reference is made to a cross-section table only, the values may be misleading unless properly interpreted by a suitable comparison of half-lives and abundances. In this table all the variables have been combined and the desired information can be obtained directly from the values of A 3??, the activity produced per gram per second of irradiation, under the stated conditions. Hence, it is easily seen that, under similar circumstances of irradiation, vanadium is most easily activated even though the cross section of one of the cobalt isotopes is nearly five times that of vanadium and the cross section of one of the nickel isotopes is three times that of vanadium. ?? 1954 Societa?? Italiana di Fisica.

Senftle, F.E.; Champion, W.R.

1954-01-01

265

Determination of arsenic in hair using neutron activation.  

PubMed

Arsenic concentrations were measured in scalp hair of three groups of people of a village in west of Iran. One group consisted of healthy subjects, the second of subjects with suspected arsenic poisoning and the third with people infected with arsenic poisoning. The measurements were carried out using neutron activation analysis at Tehran Research Reactor. Along with these measurements, the arsenic content of water sources used by the inhabitants were also measured. The measurements revealed that the average arsenic concentration in the healthy group was 0.2 +/- 0.07 ppm, in the suspected group was 4.9 +/- 0.5 ppm, in the infected group was 5.6 +/- 0.5 ppm and in water samples varied between 0.03 +/- 0.01 and 1.04 +/- 0.10 ppm. PMID:9570092

Pazirandeh, A; Brati, A H; Marageh, M G

1998-07-01

266

Clinical applications of in vivo neutron-activation analysis  

SciTech Connect

In vivo neutron activation has opened a new era of both clinical diagnosis and therapy evaluation, and investigation into and modelling of body composition. The techniques are new, but it is already clear that considerable strides can be made in increasing accuracy and precision, increasing the number of elements susceptible to measurement, enhancing uniformity, and reducing the dose required for the measurement. The work presently underway will yield significant data on a variety of environmental contaminants such as Cd. Compositional studies are determining the level of vital constituents such as nitrogen and potassium in both normal subjects and in patients with a variety of metabolic disorders. Therapeutic programs can be assessed while in progress.

Cohn, S.H.

1982-01-01

267

In-vivo neutron activation analysis: principles and clinical applications  

SciTech Connect

In vivo neutron activation has opened a new era of both clinical diagnosis and therapy evaluation, and investigation into and modelling of body composition. The techniques are new, but it is already clear that considerable strides can be made in increasing accuracy and precision, increasing the number of elements susceptible to measurement, enhancing uniformity, and reducing the dose required for the measurement. The work presently underway will yield significant data on a variety of environmental contaminants such as Cd. Compositional studies are determining the level of vital constituents such as nitrogen and potassium in both normal subjects and in patients with a variety of metabolic disorders. Therapeutic programs can be assessed while in progress. It seems likely that by the end of this century there will have been significant progress with this research tool, and exciting insights obtained into the nature and dynamics of human body composition.

Cohn, S.H.

1982-01-01

268

Neutron activation analysis of sea-, lake-, and evaporated salt  

NASA Astrophysics Data System (ADS)

Salt is essential for human nutrition. Recently, it has become popular in Europe to rather use exotic sea salt or lake salt instead of purified evaporated salt, because of an alleged higher content of trace elements. In this study the content of trace elements and their bioavailability of 19 samples of different types of salt and 1 sample of brine purification sludge were investigated using instrumental neutron activation analysis. In general, sea-, lake-, and evaporated salt are quite pure. Trace elements determined in salt were Al, Br, Co, Cr, Cs, Fe, Rb, Sc, Sr, and Zn; some of them only in individual cases. It was found that, in general, the content of trace elements in sea- or lake salt was higher than in purified salt. Nevertheless, the use of sea- or lake salt does not contribute significantly to the human needs of essential trace elements, because their concentration in salt is too low or their compounds are not bioavailable.

Steinhauser, G.; Sterba, J. H.; Poljanc, K.; Bichler, M.; Buchtela, K.

2006-01-01

269

Standardization of process parameters for a chemical reaction using neutron activation analysis technique  

Microsoft Academic Search

The chemical process to convert polyepichlorohydrin (PECH) into a glycidyl azide polymer (GAP) has been standardized by measuring the relative concentrations of nitrogen, chlorine and oxygen with the fast neutron activation analysis technique. For comparison PECH and GAP samples were also analysed by IR spectroscopy. The results indicate that, for standardization of the present chemical process, the fast neutron activation

P. A. Dokhale; V. N. Bhoraskar

1996-01-01

270

Copper activation deuterium-tritium neutron yield measurements at the National Ignition Facility  

E-print Network

Copper activation deuterium-tritium neutron yield measurements at the National Ignition Facility G://rsi.aip.org/about/rights_and_permissions #12;REVIEW OF SCIENTIFIC INSTRUMENTS 83, 10D918 (2012) Copper activation deuterium-tritium neutron(+ ) and 65 Cu(n,2n) 64 Cu(+ ), has been fielded at the National Ignition Facility (NIF). The induced copper

271

Study of Neutron Induced Activity in Low-Background Gamma Spectroscopy Systems  

SciTech Connect

Cosmic-rays induced neutrons can produce measurable activity in carefully selected materials used for construction of low-background gamma spectroscopy systems. In order to improve shielding of low-background systems, flux of neutrons inside the shield and level of induced activity should be measured.

Jovancevic, N.; Krmar, M.; Bikit, I.; Mrda, D.; Veskovic, M.; Slivka, J.; Todorovic, N.; Forkapic, S.; Soti, G.; Papuga, J. [Department of Physics, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 4, 21 000 Novi Sad (Serbia)

2009-08-26

272

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

PubMed

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

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

2014-10-01

273

Evaluation of the /sup 63/Cu activation foil for determining the neutron dose in the energy range of 1 eV to 1 MeV  

SciTech Connect

The appropriateness of the /sup 63/Cu activation foil for determining the neutron dose in the energy region from 1 eV to 1 MeV has been investigated for spectra of seven different criticality accident configurations. A program was written for folding the published spectra with the /sup 63/Cu activation cross sections and with the fluence-to-dose or kerma conversion factors. It is shown that for these spectra the neutron dose and kerma result primarily from the energy region above 15 keV whereas the measured /sup 64/Cu activity is mainly determined by the fluence in the region between 1 eV and 15 keV. Uncertainties in the fluence spectrum in the low-energy region between 1 eV and 15 keV, which in reality do not affect the dose contribution, might lead to large deviations in the measured /sup 64/Cu activity and hence to the derived dose in the 1 eV to 1 MeV range. Use of /sup 10/B shielding for attenuating the fluence in the 1-eV to 15-keV region was evaluated, leading to the conclusion that the necessary amount of boron material is unacceptably large and would appreciably increase the cost of the dosimeter currently used at Los Alamos. The lower limit of neutron detectability would also be increased.

Eisen, Y.; Vasilik, D.G.; Brake, R.J.

1984-08-01

274

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

E-print Network

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

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

2015-01-01

275

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

E-print Network

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

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

2015-01-01

276

Photon-photon absorption and the uniqueness of the spectra of active galactic nuclei  

NASA Technical Reports Server (NTRS)

The effects of the feedback of e(+)-e(-) pair reinjection in a plasma due to photon-photon absorption of its own radiation was examined. Under the assumption of continuous electron injection with a power law spectrum E to the minus gamma power and Compton losses only, it is shown that for gamma 2 the steady state electron distribution function has a unique form independent of the primary injection spectrum. This electron distribution function can, by synchrotron emission, reproduce the general characteristics of the observed radio to optical active galactic nuclei spectra. Inverse Compton scattering of the synchrotron photons by the same electron distribution can account for their X-ray spectra, and also implies gamma ray emission from these objects. This result is invoked to account for the similarity of these spectra, and it is consistent with observations of the diffuse gamma ray background.

Kazanas, D.

1984-01-01

277

Empirical comparison of neutron activation sample analysis methods  

NASA Astrophysics Data System (ADS)

The U.S. Geological Survey (USGS) operates a research reactor used mainly for neutron activation of samples, which are then shipped to industrial customers. Accurate nuclide identification and activity determination are crucial to remain in compliance with Code of Federal Regulations guidelines. This facility utilized a Canberra high purity germanium detector (HPGe) coupled with Canberra Genie(TM) 2000 (G2K) software for gamma spectroscopy. This study analyzed the current method of nuclide identification and activity determination of neutron activated materials utilized by the USGS reactor staff and made recommendations to improve the method. Additionally, analysis of attenuators, effect of detector dead time on nuclide identification, and validity of activity determination assumptions were investigated. The current method of activity determination utilized the G2K software to obtain ratio of activity per nuclide identified. This determination was performed without the use of geometrically appropriate efficiency calibration curves. The ratio of activity per nuclide was used in conjunction with an overall exposure rate in mR/h obtained via a Fluke Biomedical hand-held ion chamber. The overall exposure rate was divided into individual nuclide amounts based on the G2K nuclide ratios. A gamma energy of 1 MeV and a gamma yield of 100% was assumed for all samples. Utilizing the gamma assumption and nuclide ratios, a calculation was performed to determine total sample activity in muCi (microCuries). An alternative method was proposed, which would eliminate the use of exposure rate and rely solely on the G2K software capabilities. The G2K software was energy and efficiency calibrated with efficiency curves developed for multiple geometries. The USGS reactor staff were trained to load appropriate calibration data into the G2K software prior to sample analysis. Comparison of the current method and proposed method demonstrated that the activity value calculated with the 1 MeV assumption could be as much as 3-4 orders of magnitude higher than the activity value established with the G2K software. The exposure rate calculation was also performed for each sample using actual gamma energies and yields to verify accuracy of the G2K software calibration. Facility specifications for detector dead time during sample analysis were stated to be 10% or less. Investigation of the effect of detector dead time on nuclide identification was performed. It was demonstrated that accurate nuclide identification could be performed with a detector dead time as high as 86.08% and a keV tolerance range of 1.5. A shielded lead cave was created to allow for greater source-to-detector distance. Additionally, an attenuator system was developed to aid in the reduction of detector dead time to meet facility specifications of less than 10%.

Gillenwalters, Elizabeth

278

The role of neutron activation analysis in nutritional biomonitoring programs  

SciTech Connect

Nutritional biomonitoring is a multidisciplinary task and an integral part of a more general bioenvironmental surveillance. In its comprehensive form, it is a combination of biological, environmental, and nutrient monitoring activities. Nutrient monitoring evaluates the input of essential nutrients required to maintain vital bodily functions; this includes vigilance over extreme fluctuations of nutrient intake in relation to the recommended dietary allowances and estimated safe and adequate daily dietary intakes and adherence to the goals of provisional tolerance limits. Environmental monitoring assesses the external human exposure via ambient pathways, namely, air, water, soil, food, etc. Biological monitoring quantifies a toxic agent and its metabolites in representative biologic specimens of an exposed organ to identify health effects. In practice, coordinating all three components of a nutritional biomonitoring program is complex, expensive, and tedious. Experience gained from the US National Health and Nutrition Examination Surveys demonstrates the problems involved. By far the most critical challenge faced here is the question of analytical quality control, particularly when trace element determinations are involved. Yet, measures to ensure reliability of analytical data are mandatory, and there are no short-cuts to this requirement. The purpose of this presentation is to elucidate the potential of neutron activation analysis (NAA) in nutritional biomonitoring activities.

Iyengar, V.

1988-01-01

279

Health physics aspects of neutron activated components in a linear accelerator.  

PubMed

The purpose of this study was to investigate the residual radioactivity in the therapy accessories of a medical x ray linear accelerator. The residual radioactivity mainly originated from nuclear activation reactions by neutrons, which are present as a contamination radiation in the x-ray beam. The radiation used in this study was the 25 MV x-ray beam produced by a CGR Saturne III linear accelerator. The five treatment aids include four wedges of various angles and one cerrobend block. The decrease in dose rates with time was followed for 60 min for each of the five treatment aids immediately after 999 monitor units of irradiation. The integral doses from the surface of each of four activated therapy accessories following three different radiation doses were measured by using thermoluminescent dosimeters (CaF2). In the TLD measurement, polyethylene filters were used to differentiate beta or beta particles from the mixed decay radiation. A high-purity germanium detection system was utilized to collect and to analyze the gamma spectra from the activated therapy accessories. The residual radioisotopes found in the 15 degree wedge and 30 degree wedge included V, Cr, Cr, Mn, Fe, Co, and Ni. In the 45 degree and 60 degree wedges, the radionuclides identified were Co, Ni, Cu, and W. The principal nuclides identified in the irradiated cerrobend block were In, Sn, Cd, Pb. The corresponding nuclear reactions from which the residual radionuclides produced were confirmed by consulting the current literature. PMID:15069298

Guo, Shuntong; Ziemer, Paul L

2004-05-01

280

Active detection of shielded SNM with 60-keV neutrons  

SciTech Connect

Fissile materials, e.g. {sup 235}U and {sup 239}Pu, can be detected non-invasively by active neutron interrogation. A unique characteristic of fissile material exposed to neutrons is the prompt emission of high-energy (fast) fission neutrons. One promising mode of operation subjects the object to a beam of medium-energy (epithermal) neutrons, generated by a proton beam impinging on a Li target. The emergence of fast secondary neutrons then clearly indicates the presence of fissile material. Our interrogation system comprises a low-dose 60-keV neutron generator (5 x 10{sup 6}/s), and a 1 m{sup 2} array of scintillators for fast neutron detection. Preliminary experimental results demonstrate the detectability of small quantities (370 g) of HEU shielded by steel (200 g/cm{sup 2}) or plywood (30 g/cm{sup 2}), with a typical measurement time of 1 min.

Hagmann, C; Dietrich, D; Hall, J; Kerr, P; Nakae, L; Newby, R; Rowland, M; Snyderman, N; Stoeffl, W

2008-07-08

281

Neutron-capture prompt. gamma. -ray activation analysis for multielement determination in complex samples  

Microsoft Academic Search

Gamma-ray spectra were taken up to 11 MeV from a wide range of samples and elemental standards while under neutron irradiation to determine the elements whose prompt ..gamma.. rays are observable and can be used for analytical measurement. Up to 17 elements from among the set H, B, C, N, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti,

M. P. Failey; D. L. Anderson; W. H. Zoller; G. E. Gordon; R. M. Lindstrom

1979-01-01

282

Prompt-gamma neutron activation analysis system design: effects of D-T versus D-D neutron generator source selection  

Technology Transfer Automated Retrieval System (TEKTRAN)

Prompt-gamma neutron activation analysis (PGNAA) is used for the non-invasive measurement of human body composition. Advancements in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators are available: D-D with 2.5 MeV, and D-T wi...

283

Prompt-gamma neutron activation analysis system design: Effects of D-T versus D-D neutron generator source selection  

Technology Transfer Automated Retrieval System (TEKTRAN)

Prompt-gamma neutron activation (PGNA) analysis is used for the non-invasive measurement of human body composition. Advancements in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators are available: D-D with 2.5 MeV and D-T with...

284

Fusion-neutron-yield, activation measurements at the Z accelerator: Design, analysis, and sensitivity  

SciTech Connect

We present a general methodology to determine the diagnostic sensitivity that is directly applicable to neutron-activation diagnostics fielded on a wide variety of neutron-producing experiments, which include inertial-confinement fusion (ICF), dense plasma focus, and ion beam-driven concepts. This approach includes a combination of several effects: (1) non-isotropic neutron emission; (2) the 1/r{sup 2} decrease in neutron fluence in the activation material; (3) the spatially distributed neutron scattering, attenuation, and energy losses due to the fielding environment and activation material itself; and (4) temporally varying neutron emission. As an example, we describe the copper-activation diagnostic used to measure secondary deuterium-tritium fusion-neutron yields on ICF experiments conducted on the pulsed-power Z Accelerator at Sandia National Laboratories. Using this methodology along with results from absolute calibrations and Monte Carlo simulations, we find that for the diagnostic configuration on Z, the diagnostic sensitivity is 0.037% ± 17% counts/neutron per cm{sup 2} and is ? 40% less sensitive than it would be in an ideal geometry due to neutron attenuation, scattering, and energy-loss effects.

Hahn, K. D., E-mail: kdhahn@sandia.gov; Ruiz, C. L.; Fehl, D. L.; Chandler, G. A.; Knapp, P. F.; Smelser, R. M.; Torres, J. A. [Sandia National Laboratories, Diagnostics and Target Physics, Albuquerque, New Mexico 87123 (United States)] [Sandia National Laboratories, Diagnostics and Target Physics, Albuquerque, New Mexico 87123 (United States); Cooper, G. W.; Nelson, A. J. [Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States); Leeper, R. J. [Los Alamos National Laboratories, Plasma Physics Group, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratories, Plasma Physics Group, Los Alamos, New Mexico 87545 (United States)

2014-04-15

285

Neutronic reactor  

DOEpatents

A nuclear reactor includes an active portion with fissionable fuel and neutron moderating material surrounded by neutron reflecting material. A control element in the active portion includes a group of movable rods constructed of neutron-absorbing material. Each rod is movable with respect to the other rods to vary the absorption of neutrons and effect control over neutron flux.

Wende, Charles W. J. (Augusta, GA); Babcock, Dale F. (Wilmington, DE); Menegus, Robert L. (Wilmington, DE)

1983-01-01

286

Neutron dosimetry and activation on the tokamak Tore-Supra  

SciTech Connect

In Tore-Supra, neutron productions up to 10{sup 20} neutrons/year are expected. Calculations based on 1-D and 3-D codes have been made before the assembly phase. A strategy has been established to reconcile high neutron levels with the needs of an experimental device, i.e. access to the tokamak. Operation at low power (8.5 10{sup 16} neutrons) has allowed an initial set of measurements, which has been compared to the calculations. Quite good agreement is observed, especially for fast neutrons. A difference for slow neutrons is attributed to a small quantity of boron added in the concrete wall surrounding the experiment and to safety factors in the computations.

Joyer, P.; Martin, G. [Association Euratom-CEA, Saint-Paul-Lez-Durance (France)

1994-12-31

287

Measurement of the assay precision of the active neutron multiplicity technique  

SciTech Connect

This paper describes a measurement of the precision of the new active-neutron-multiplicity assay technique, which is currently under development for bulk uranium containing kilogram quantities of {sup 235}U. The new technique analyzes neutron multiplicity data collected with a coincidence counter outfitted with AmLi neutron sources. We report on the observed assay precision and the implications for field use of the technique.

Ensslin, N.; Krick, M.S.; Langner, D.G.; Miller, D.W.; Miller, M.C.

1992-08-01

288

Measurement of the assay precision of the active neutron multiplicity technique  

SciTech Connect

This paper describes a measurement of the precision of the new active-neutron-multiplicity assay technique, which is currently under development for bulk uranium containing kilogram quantities of {sup 235}U. The new technique analyzes neutron multiplicity data collected with a coincidence counter outfitted with AmLi neutron sources. We report on the observed assay precision and the implications for field use of the technique.

Ensslin, N.; Krick, M.S.; Langner, D.G.; Miller, D.W.; Miller, M.C.

1992-01-01

289

The spectral classification of chromospherically active binary stars with composite spectra  

NASA Technical Reports Server (NTRS)

This paper presents and analyzes blue and red-wavelength high-resolution spectra of twelve chromospherically active binary or triple systems with composite spectra. Spectral classifications for the individual stellar components are derived by means of the 'spectrum-synthesis' technique and are compared to stellar evolutionary models and observed masses and/or mass ratios. Also presented is a carefully selected set of MK reference stars of luminosity class III, IV, and V, and spectral type A9-K5, and v sin i less than 10 km/s, to cover the spectral range of the components of chromospherically active binary systems of the RS CVn-type. New values of v sin i are determined for some of the reference and program stars. Two spectroscopic binaries have been discovered.

Strassmeier, K. G.; Fekel, F. C.

1990-01-01

290

X-ray spectra and the rotation-activity connection of RS Canum Venaticorum binaries  

NASA Astrophysics Data System (ADS)

Results are presented from a survey of RS CVn binaries which were observed with the imaging proportional counter (IPC) on board the Einstein Observatory. Spectral analyses of the IPC pulse height spectra show that the coronae of RS CVn binaries always contain hot gas with temperatures in excess of 10 to the 7th K, similar to active late-type main-sequence stars, and that at least two temperature components are necessary to account for the higher quality IPC spectra (when absorption is unimportant). It is argued that these bimodal temperature distributions found by the IPC are indicative of true distributions of emission measure versus temperature that are continuous (just as is the case of magnetically confined coronal plasma loops observed on the sun). It is further shown that none of the derivable X-ray characteristics of RS CVn binaries depend on rotation period, implying that previous claims of period-activity relationships in RS CVn binaries were unfounded.

Majer, P.; Schmitt, J. H. M. M.; Golub, L.; Harnden, F. R., Jr.; Rosner, R.

1986-01-01

291

Nuclear level densities in {sup 47}V, {sup 48}V, {sup 49}V, {sup 53}Mn, and {sup 54}Mn from neutron evaporation spectra  

SciTech Connect

The spectra of neutrons from the (p, n) reactions on {sup 47}Ti, {sup 48}Ti, {sup 49}Ti, {sup 53}Cr, and {sup 54}Cr nuclei were measured in the proton-energy range 7-11 MeV. The measurements were performed with the aid of a fast-neutron spectrometer by the time-of-flight method over the base of the EGP-15 tandem accelerator of the Institute for Physics and Power Engineering (IPPE, Obninsk). Owing to a high resolution and a high stability of the time-of-flight spectrometer used, low-lying discrete levels could be identified reliably along with a continuum section of neutron spectra. An analysis of measured data was performed within the statistical equilibrium and preequilibrium models of nuclear reactions. The relevant calculations were performed by using the exact formalism of Hauser-Feshbach statistical theory supplemented with the generalized model of a superfluid nucleus, the back-shifted Fermi gas model, and the Gilbert-Cameron composite formula for the nuclear level density. The nuclear level densities for {sup 47}V, {sup 48}V, {sup 49}V, {sup 53}Mn, and {sup 54}Mn were determined along with their energy dependences and model parameters. The results are discussed together with available experimental data and recommendations of model systematics.

Zhuravlev, B. V., E-mail: zhurav@ippe.ru; Lychagin, A. A.; Titarenko, N. N.; Demenkov, V. G.; Trykova, V. I. [Institute for Physics and Power Engineering (Russian Federation)

2011-03-15

292

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

293

Real-Time Active Cosmic Neutron Background Reduction Methods  

SciTech Connect

Neutron counting using large arrays of pressurized 3He proportional counters from an aerial system or in a maritime environment suffers from the background counts from the primary cosmic neutrons and secondary neutrons caused by cosmic ray?induced mechanisms like spallation and charge-exchange reaction. This paper reports the work performed at the Remote Sensing Laboratory–Andrews (RSL-A) and results obtained when using two different methods to reduce the cosmic neutron background in real time. Both methods used shielding materials with a high concentration (up to 30% by weight) of neutron-absorbing materials, such as natural boron, to remove the low-energy neutron flux from the cosmic background as the first step of the background reduction process. Our first method was to design, prototype, and test an up-looking plastic scintillator (BC-400, manufactured by Saint Gobain Corporation) to tag the cosmic neutrons and then create a logic pulse of a fixed time duration (~120 ?s) to block the data taken by the neutron counter (pressurized 3He tubes running in a proportional counter mode). The second method examined the time correlation between the arrival of two successive neutron signals to the counting array and calculated the excess of variance (Feynman variance Y2F)1 in the neutron count distribution from Poisson distribution. The dilution of this variance from cosmic background values ideally would signal the presence of man-made neutrons.2 The first method has been technically successful in tagging the neutrons in the cosmic-ray flux and preventing them from being counted in the 3He tube array by electronic veto—field measurement work shows the efficiency of the electronic veto counter to be about 87%. The second method has successfully derived an empirical relationship between the percentile non-cosmic component in a neutron flux and the Y2F of the measured neutron count distribution. By using shielding materials alone, approximately 55% of the neutron flux from man-made sources like 252Cf or Am-Be was removed.

Mukhopadhyay, Sanjoy; Maurer, Richard; Wolff, Ronald; Mitchell, Stephen; Guss, Paul

2013-09-01

294

Determination of Long-Lived Neutron Activation Products in Reactor Shielding Concrete Samples  

Microsoft Academic Search

The results of activation studies of TRIGA research reactor concrete shielding are given. Samples made of ordinary and barytes concrete were irradiated in the reactor to simulate neutron activation in the shielding concrete. Long-lived neutron-induced gamma-ray-emitting radioactive nuclides were measured in the samples with a high-purity germanium detector. The most active long-lived radioactive nuclides in the ordinary concrete samples were

Tomaz Zagar; Matjaz Ravnik

2002-01-01

295

Potassium-Argon Dating by Activation with Fast Neutrons  

Microsoft Academic Search

When a potassium-bearing mineral is irradiated by a neutron flux containing a significant fraction of fast neutrons, 270-year Ar  is produced by the K 3 (n, p) reaction, and this may be used as a basis for measuring the potassium-argon age of the mineral. WSnke and Konig [1959] described such a method in which counting techniques were used to

Craig Merrihue; Grenville Turner

1966-01-01

296

CWB, 6/25/00 High-Yield Neutron Activation System for the  

E-print Network

CWB, 6/25/00 High-Yield Neutron Activation System for the National Ignition Facility Cris W. Barnes and precise determination of the total neutron yield over extreme dynamic range comes from radioactivity six-orders-of-magnitude.2 The high-yield system for NIF uses thin elemental samples ("foils

Barnes, Cris W.

297

Neutron activation analysis for determination of induced radioactivity in concrete of nuclear reactor shielding  

Microsoft Academic Search

The content of binding agent components and aggregates of shielding concrete (portland cement, gabbro, silicate, granite, hematite, magnetite, limestone) has been studied to identify nuclides contributing to the long-lived radioactivity of concretes used in nuclear reactor shielding. Elemental content was determined by neutron activation analysis at the IBR-2 reactor of the Laboratory of Neutron Physics (JINR). It is shown that

P. A. Lavdanskij; V. M. Nazarov; N. I. Stefanov; M. V. Frontasyeva

1989-01-01

298

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

SciTech Connect

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

Williams, R.E.

1981-10-12

299

New thermal neutron prompt ?-ray activation analysis instrument at the National Institute of Standards and Technology Center for Neutron Research  

NASA Astrophysics Data System (ADS)

A new thermal neutron prompt ?-ray activation analysis (PGAA) instrument was designed and built to replace the original PGAA system at the NIST Center for Neutron Research. By placing a sapphire filter in the neutron beam shutter assembly, the fast neutron fluence rate was reduced by a factor of 5 and low-energy (50-200 keV) ?-ray intensities were reduced by factors of 5-10. The thermal neutron fluence rate was reduced by only a factor of 1.13. A new external beam tube, sample chamber, beam stop, and support structure were built and a new detection system installed. The new beam tube is made of two cylindrical aluminum sections lined with a lithiated polymer. Both sections are kept under vacuum to reduce the number of neutrons scattered by air into the beam tube walls. The sample chamber is also fabricated from aluminum and lined with lithiated polymer, and may be evacuated to minimize the number of neutrons scattered and absorbed by air. The beam tube and sample chamber assembly is suspended from the aluminum support structure. The detection system consists of a 40% efficient (relative) germanium detector (resolution 2.0 at 1332.5 keV) and a bismuth germanate Compton suppressor. The detection system is shielded by lead, surrounded by borated and lithiated polyethylene, and placed on a table attached to the support structure. The new, more compact beam stop is welded to the support structure. Capture ?-ray photopeaks from H, B, C, N, Na, Al, Fe, Ge, I and Pb in the background spectrum were either of lower intensity or eliminated with the new PGAA instrument. The more efficient detection system, positioned closer to the sample, yielded element sensitivity increases of 5-50%. Limits of detection have been greatly reduced compared with those of the original instrument due to reduced Compton and scattered ?-ray backgrounds (especially in the low-energy region), increased sensitivities, and reduction of background ?-ray photopeak intensities.

Mackey, E. A.; Anderson, D. L.; Liposky, P. J.; Lindstrom, R. M.; Chen-Mayer, H.; Lamaze, G. P.

2004-11-01

300

Flow speed measurement and rheometry by pulsed neutron activation  

SciTech Connect

Pulsed Neutron Activation (PNA) is a means of non-invasive flow velocity measurement based on tagging the flowing medium with a short-lived radioactivity. Previous work with salt or dye-tagging showed poor accuracy in turbulent and failed in laminar flow when conventional data processing was used. However, use of a data acquisition and processing scheme that is based on tag dispersion modelling can produce absolute values over a wide range of flow speeds and regimes with high accuracy. For non-Newtonian/laminar flow, rheological information can also be obtained. The inherently non-intrusive nature of PNA tagging makes this scheme available for slurry measurements. The performance of PNA in slurry flow at up to 60 percent solid content was compared to full-flow diversion and weighing. Errors ranged from less than 0.2% at high Reynolds' numbers to about 2% for paste flow. Rheological parameters (yield shear stress or flow behaviour index) could be determined with an accuracy that compared to that of a spindle viscometer with grab-samples. The PNA scheme thus offers a unique means of studying slurry flow in a dedicated laboratory facility, or of providing calibration for other flowmeters in an industrial plant through temporary installation by a team of expert consultants. 27 refs., 8 figs.

Porges, K.G.A.; Cox, S.A.; Herzenberg, C.; Kampschoer, C.

1988-01-01

301

Fast-neutron activation of long-lived nuclides in natural Pb  

NASA Astrophysics Data System (ADS)

We measured the production of the long-lived nuclides 207 Bi, 202 Pb, and 194 Hg in a sample of natural Pb due to high-energy neutron interactions using a neutron beam at the Los Alamos Neutron Science Center. The activated sample was counted by a HPGe detector to measure the amount of radioactive nuclides present. These nuclides are critical in understanding potential backgrounds in low background experiments utilizing large amounts of Pb shielding due to cosmogenic neutron interactions in the Pb while residing on the Earth's surface. By scaling the LANSCE neutron flux to a cosmic neutron flux, we measure the sea level cosmic ray production rates of 8.0 ± 1.3 atoms/kg/day of 194 Hg, 120 ± 25 atoms/kg/day 202 Pb, and <0.17 ± 0.04 atoms/kg/day 207 Bi.

Guiseppe, V. E.; Elliott, S. R.; Fields, N. E.; Hixon, D.

2015-04-01

302

Threshold Reaction Rates and Energy Spectra of Neutrons in the 0.8-1.6 GeV Proton-Irradiated W, Na Targets  

E-print Network

Considering the prospects of using the W-Na target assemblies in ADS facilities, the experiments were made to study the nuclear-physics characteristics of W and Na, and the composite structures thereof in their interactions with 0.8-GeV and 1.6-GeV protons. The neutron and proton-induced reaction rates were measured inside, and on the surface of, a cylinder-shaped heterogeneous W-Na assembly together with the double-differential spectra of secondary neutrons emitted from different-depth W and Na discs. The measurement results were simulated by the LAHET, CEM2k, and KASKAD-S codes in terms of the latest versions of nuclear databases.

Yury E. Titarenko; Vyacheslav F. Batyaev; Evgeny I. Karpikhin; Valery M. Zhivun; Svetlana V. Kvasova; Ruslan D. Mulambetov; Dmitry V. Fischenko; Aleksander B. Koldobsky; Yury V. Trebukhovsky; Vladimir A. Korolev; Gennady N. Smirnov; Andrey M. Voloshenko; Vladimir Yu. Belov; Nikolay I. Kachalin Stepan G. Mashnik; Richard E. Prael; Arnold J. Sierk; Hideshi Yasuda

2002-08-30

303

Nuclear Level Densities of 56Co, 57Co, 90Nb, and 94Nb from Neutron Evaporation Spectra in the (p,n) Reaction  

NASA Astrophysics Data System (ADS)

Excitation functions, neutron spectra, and angular distributions in the (p,n) reaction on isotopes of 56Fe, 57Fe, 90Zr, and 94Zr have been measured in the proton energy range of (7-11) MeV. The measurements were performed on the pulsed tandem accelerator EGP-15 of IPPE by time-of-flight fast neutron spectrometer. Analyses of the measured data have been carried out in the framework of statistical equilibrium and pre-equilibrium models of nuclear reactions. The contribution of non-equilibrium emission has been studied. The nuclear level densities of 56Co, 57Co 90Nb, 94Nb, and their energy dependences have been determined.

Zhuravlev, Boris V.; Kornilov, Nikolai V.; Lychagin, Anatoliy A.; Titarenko, Nikolai N.; Trykova, Valentina I.

2005-05-01

304

Nuclear Level Densities of 56Co, 57Co, 90Nb, and 94Nb from Neutron Evaporation Spectra in the (p,n) Reaction  

SciTech Connect

Excitation functions, neutron spectra, and angular distributions in the (p,n) reaction on isotopes of 56Fe, 57Fe, 90Zr, and 94Zr have been measured in the proton energy range of (7-11) MeV. The measurements were performed on the pulsed tandem accelerator EGP-15 of IPPE by time-of-flight fast neutron spectrometer. Analyses of the measured data have been carried out in the framework of statistical equilibrium and pre-equilibrium models of nuclear reactions. The contribution of non-equilibrium emission has been studied. The nuclear level densities of 56Co, 57Co 90Nb, 94Nb, and their energy dependences have been determined.

Zhuravlev, Boris V.; Kornilov, Nikolai V.; Lychagin, Anatoliy A.; Titarenko, Nikolai N.; Trykova, Valentina I. [Institute for Physics and Power Engineering, 249033 Obninsk, Kaluga Region (Russian Federation)

2005-05-24

305

Electron-positron pairs, Compton reflection, and the X-ray spectra of active galactic nuclei  

NASA Technical Reports Server (NTRS)

It is shown here that reprocessing of radiation fron nonthermal pair cascades by cold material in the central parts of active galactic nuclei (AGN) gives rise to X-ray and gamma-ray spectra that satisfy current observational constraints. An average 1-30 keV X-ray spectral index alpha(x) of about 0.7 in the compact range 30-300 is obtained for a wide range of Lorentz factors of the injected electrons. The gamma-ray spectra are steep, with alpha(gamma) about two, and satisfy the observational constraints. Radiation from pair cascades exhibits steep power law decreases in soft X-rays similar to those observed in AGN. The overall picture is consistent with AGN having an accretion disk which intercepts and reprocesses a substantial fraction of the nonthermal continuum incident upon it from above and below.

Zdziarski, Andrzej A.; Ghisellini, Gabriele; George, Ian M.; Fabian, A. C.; Svensson, Roland; Done, Chris

1990-01-01

306

Analysis of body calcium (regional changes in body calcium by in vivo neutron activation analysis)  

NASA Technical Reports Server (NTRS)

The effect of space flight on urine and fecal calcium loss was documented during the three long-term Skylab flights. Neutron activation analysis was used to determine regional calcium loss. Various designs for regional analysis were investigated.

Suki, W.; Johnson, P. C.; Leblanc, A.; Evans, H. J.

1981-01-01

307

An Analysis Technique for Active Neutron Multiplicity Measurements Based on First Principles  

SciTech Connect

Passive neutron multiplicity counting is commonly used to quantify the total mass of plutonium in a sample, without prior knowledge of the sample geometry. However, passive neutron counting is less applicable to uranium measurements due to the low spontaneous fission rates of uranium. Active neutron multiplicity measurements are therefore used to determine the {sup 235}U mass in a sample. Unfortunately, there are still additional challenges to overcome for uranium measurements, such as the coupling of the active source and the uranium sample. Techniques, such as the coupling method, have been developed to help reduce the dependence of calibration curves for active measurements on uranium samples; although, they still require similar geometry known standards. An advanced active neutron multiplicity measurement method is being developed by Texas A&M University, in collaboration with Los Alamos National Laboratory (LANL) in an attempt to overcome the calibration curve requirements. This method can be used to quantify the {sup 235}U mass in a sample containing uranium without using calibration curves. Furthermore, this method is based on existing detectors and nondestructive assay (NDA) systems, such as the LANL Epithermal Neutron Multiplicity Counter (ENMC). This method uses an inexpensive boron carbide liner to shield the uranium sample from thermal and epithermal neutrons while allowing fast neutrons to reach the sample. Due to the relatively low and constant fission and absorption energy dependent cross-sections at high neutron energies for uranium isotopes, fast neutrons can penetrate the sample without significant attenuation. Fast neutron interrogation therefore creates a homogeneous fission rate in the sample, allowing for first principle methods to be used to determine the {sup 235}U mass in the sample. This paper discusses the measurement method concept and development, including measurements and simulations performed to date, as well as the potential limitations.

Evans, Louise G [Los Alamos National Laboratory; Goddard, Braden [Los Alamos National Laboratory; Charlton, William S [Los Alamos National Laboratory; Peerani, Paolo [European Commission, EC-JRC-IPSC

2012-08-13

308

A Neutron Activation Gamma Ray spectrometer for Planetary Surface Analysis  

NASA Technical Reports Server (NTRS)

A pulsed DT neutron generator system, similar to that used in commercial well logging, offers the possibility of performing accurate elemental analyses to depths of tens of centimeters in a few seconds with the probe on the body's surface.

Bradley, J. G.; Schweitzer, J. S.; Truax, J. A.; Rice, A.; Tombrello, T. A.

1994-01-01

309

Inelastic neutron scattering spectra of a hydrogen molecule in a nanocavity: Methodology for quantum calculations incorporating the coupled five-dimensional translation-rotation eigenstates  

NASA Astrophysics Data System (ADS)

We present an in-depth description of the methodology for accurate quantum calculation of the inelastic neutron scattering (INS) spectra of an H2 molecule confined inside a nanosize cavity of an arbitrary shape. This methodology was introduced in a recent work [M. Xu, L. Ulivi, M. Celli, D. Colognesi, and Z. Ba?i?, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.83.241403 83, 241403(R) (2011)], where the INS spectra of para- and ortho-H2 in the small cage of the structure II clathrate hydrate were simulated and compared with the measured spectra. The key distinctive feature of our approach, and its main strength and advantage, is the use of the coupled quantum 5D translation-rotation (TR) energy levels and wave functions of the entrapped H2 molecule, rigorously calculated on the 5D intermolecular potential energy surface (PES), as the initial and the final states of the INS transitions. In this work, we describe the implementation of the 5D TR wave functions within the quantum INS formalism, and obtain the working expressions for the matrix elements required to compute the INS spectra of the nanoconfined H2 molecule. The computational approach devised for efficient calculation of the 5D TR eigenstates in the compact contracted basis, indispensable for our quantum simulation of the INS spectra, is presented as well. Since the TR coupling is fully taken into account, the computed INS spectra exhibit a uniquely high degree of realism and faithfully reflect the quantum dynamics of H2 on the PES of the host environment.

Xu, Minzhong; Ba?i?, Zlatko

2011-11-01

310

Geomagnetic activity and diurnal variation of cosmic ray neutron intensity  

Microsoft Academic Search

A study of the geomagnetic relationship of the daily variation of Cosmic ray neutron intensity, corrected for barometric pressure\\u000a variation, at Uppsala, Sulphur Mountain, Climax, Huancayo, Buenos Aires and Mawson has been undertaken. The neutron data of\\u000a the year 1961 are divided into four groups depending upon the value of the daily geomagnetic planetary index, C\\u000a p\\u000a . The results

D. S. R. Murty; Y. Nagabhushanam; K. Ramanuja Rao

1965-01-01

311

Bayesian calibration of reactor neutron flux spectrum using activation detectors measurements: Application to CALIBAN reactor  

SciTech Connect

In this paper, we present calibration methods in order to estimate reactor neutron flux spectrum and its uncertainties by using integral activation measurements. These techniques are performed using Bayesian and MCMC framework. These methods are applied to integral activation experiments in the cavity of the CALIBAN reactor. We estimate the neutron flux and its related uncertainties. The originality of this work is that these uncertainties take into account measurements uncertainties, cross-sections uncertainties and model error. In particular, our results give a very good approximation of the total flux and indicate that neutron flux from MCNP simulation for energies above about 5 MeV seems to overestimate the 'real flux'. (authors)

Cartier, J. [Commissariat a l'Energie Atomique et aux Energies Alternatives CEA, DAM, DIF, F-91297 Arpajon (France); Casoli, P. [Commissariat a l'Energie Atomique et aux Energies Alternatives CEA, DAM, Valduc, F-21120 Is sur Tille (France); Chappert, F. [Commissariat a l'Energie Atomique et aux Energies Alternatives CEA, DAM, DIF, F-91297 Arpajon (France)

2013-07-01

312

Preparation of Neutron-activated Xenon for Liquid Xenon Detector Calibration  

E-print Network

We report the preparation of neutron-activated xenon for the calibration of liquid xenon (LXe) detectors. Gamma rays from the decay of xenon metastable states, produced by fast neutron activation, were detected and their activities measured in a LXe scintillation detector. Following a five-day activation of natural xenon gas with a Cf-252 (4 x 10^5 n/s) source, the activities of two gamma ray lines at 164 keV and 236 keV, from Xe-131m and Xe-129m metastable states, were measured at about 95 and 130 Bq/kg, respectively. We also observed three additional lines at 35 keV, 100 keV and 275 keV, which decay away within a few days. No long-lifetime activity was observed after the neutron activation.

K. Ni; R. Hasty; T. M. Wongjirad; L. Kastens; A. Manzur; D. N. McKinsey

2007-09-27

313

Determination of trace elements by instrumental neutron activation analysis in Anatolian bentonitic clays  

NASA Astrophysics Data System (ADS)

Instrumental Neutron Activation Analysis (INAA) was carried out for the determination of trace elements in non-swelling type bentonitic clays. Samples were irradiated in Triga Mark II type of reactor at the Nuclear Institute of Technical University of Istanbul. Irradiation was performed in two steps for "short and long lived" isotopes. The ? spectra of short lived isotopes were interpreted with respect to Al, Ca, Mg, Na, K, Ti, Mn, V qualitatively and that of long lived isotopes with respect to Sc, Cr, Br, Sb, Cs, La, Ce, Sm, Yb, Hf quantitatively. The relative richness of the trace elements (Al, Ti, Ca, Mg, Na, K) observed in the Sampo 90 program was obtained using Atomic Absorption technique by normalizing its value to that of sodium. The silicon content of samples was determined by gravimetry. The results indicated that Sample I contained relatively higher amount of REE, Sb, Ca and Na than Sample II. The amount of Sc, Cr and Br were about similar in both samples. Concentrations of La, Ce, Sm and Yb are higher than REE abundances found in all natural waters. These results suggest that Ca-bentonite samples are representative of primary deposition environment. In addition, the Sc content of both the samples indicates that Ca-bentonite deposits originated from continental crust. The relatively high amount of REE might bring about porosity problems in the use of Ca-bentonite in cement and concrete production.

Güngör, N.; Tulun, T.; Alemdar, A.

1998-08-01

314

A SEARCH FOR IRON EMISSION LINES IN THE CHANDRA X-RAY SPECTRA OF NEUTRON STAR LOW-MASS X-RAY BINARIES  

E-print Network

While iron emission lines are well studied in black hole systems, both in X-ray binaries and active galactic nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, ...

Cackett, E. M.

315

Comparison of Impurities in Charcoal Sorbents Found by Neutron Activation Analysis  

SciTech Connect

Abstract: Neutron activation of gas samples in a reactor often requires a medium to retain sufficient amounts of the gas for analysis. Charcoal is commonly used to adsorb gas and hold it for activation; however, the amount of activated sodium in the charcoal after irradiation swamps most signals of interest. Neutron activation analysis (NAA) was performed on several commonly available charcoal samples in an effort to determine the activation background. The results for several elements, including the dominant sodium element, are reported. It was found that ECN charcoal had the lowest elemental background, containing sodium at 2.65 ± 0.05 ppm, as well as trace levels of copper and tungsten.

Doll, Charles G.; Finn, Erin C.; Cantaloub, Michael G.; Greenwood, Lawrence R.; Kephart, Jeremy; Kephart, Rosara F.

2013-01-01

316

Seasonal variations of gravity wave activity and spectra derived from sodium temperature lidar  

NASA Astrophysics Data System (ADS)

Gravity wave measurements were carried out by a newly developed sodium temperature lidar at São José dos Campos (23 S, 46 W). The temperature lidar was first put into operation in a March, 2007, and 51 nights observation data were obtained, until April 2008. The seasonal variations of gravity wave activity and spectra derived from temperature data are investigated. The total temperature perturbation, and temperature vertical power spectra, Ft(m) at 2/(8km), 2/(4km), and 2/(2km) all show that the semiannual maxima occur near the equinoxes, which agrees with our earlier study [Yang et al., 2006] using only sodium concentration data. Large nightly variability of the temperature perturbation spectral slope was also found, in common with other sodium concentration lidar studies. The comparison between temperature and den-sity perturbations induced by quasi-random waves was investigated, and the agreement was found to be good on most nights. The comparisons between their vertical power spectra are also approached. Good agreement between monochromatic wave-induced temperature pertur-bations and sodium concentration perturbations has also been found, and the wave parameters derived from temperature data and sodium concentration data are comparable. The good com-parison obtained in this paper not only validates the fundamental assumptions of gravity wave measurements from sodium concentration data, but also indicates our previous method and steps for gravity wave measurements from sodium concentration data are effective.

Yang, Guotao; Clemesha, Barclay; Batista, Paulo; Simonich, Dale

317

Use of the MCNPX to calculate the neutron spectra around the GE-PETtrace 8 cyclotron of the CDTN/CNEN, Brazil.  

PubMed

The Monte Carlo code MCNPX was used to calculate the neutron spectra in 4 points around the targets of the CDTN/CNEN cyclotron, Belo Horizonte, Brazil, during the production of the (18)FDG. Simulated data were compared with experimental data obtained with a Bonner multisphere spectrometry system (BSS) using TLD-600 and TLD-700 and the unfolding codes BUNKIUT, BUMS and NSDUAZ. In general, simulated spectra disagreed with those obtained by experimental means by a factor as high as 14. Measurements performed with a doserate meter in other 3 more shielded points, showed also an overestimation of the ambient dose equivalent rate by a factor as high as 20 in comparison with simulated results. Results are not conclusive and a more refined study is necessary. However, neutron emission rate of the source-term of radiation must be investigated and an special caution must be taken in the experimental measurements, by discriminating of the target selected for the irradiations and utilizing a matrix response suitable for the passive detectors (e.g. TLD) utilized in the experiments, instead of a matrix response (e.g. UTA4) developed for scintillation detectors. PMID:23958629

Lacerda, M A S; Campolina, D A M; Guimarães, A M; Benavente, J A; da Silva, T A

2014-01-01

318

A method to predict electric field spectra from empirically modeled geomagnetic ULF activity  

NASA Astrophysics Data System (ADS)

A model for prediction of the Earth background electromagnetic field spectra in the ULF range (1 mHz to 10 Hz) is developed. The possibility to model the hourly integrated magnetic wave power spectra with two different mathematical models, a power law or a fourth?order polynomial, is investigated. Spectral properties of 3 months of ground magnetic data show that the temporal evolution of the power law parameters can be modeled based on the hourly planetary magnetic activity, the Kp index. Furthermore, the parameters of the polynomial model are related to the magnetic wave power in two spectral bands within the Pc3 and Pc1 pulsation bands. Empirical models of the magnetic wave power in these bands are developed based on the diurnal variation and the correlation with solar wind velocity of geomagnetic pulsations. Comparison with observations shows that the power law model represents the spectra well for low frequencies. However, the polynomial model based on solar wind velocity provides a better representation for the bulk of the ULF domain with mean errors between 2 and 7 dB, increasing with decreasing frequency. The modeled magnetic wave spectrum and knowledge of the underlying electrical conductivity profile can be used to predict the induced ground electric field spectra. An apparent electric conductivity profile was found via model?based inversion, and the predicted electric wave power is compared to observations from an electrode systems offshore of the test site. The mean error between the observed and predicted electric field amplitudes is 2-7 dB and is consistently lower than the 95% central range of the data set.

Rosenqvist, L.

2013-08-01

319

Radiolabeling of intact dosage forms by neutron activation: effects on in vitro performance  

SciTech Connect

Compressed tablets containing various quantities of stable isotopes of Ba, Er, and Sm for use in neutron activation studies were evaluated for the effect of stable isotope incorporation on tablet hardness and disintegration times. At concentrations likely to be used in scintigraphic studies employing neutron activation as a radiolabeling method, no significant effect on in vitro parameters were observed. While the incorporation of stable isotopes influenced tablet hardness to a greater degree than disintegration time, irradiation of tablets in a neutron flux of 4.4 x 10(13) n/cm2 sec had a direct effect on tablet disintegration time. Thus, future neutron activation studies should focus on minimizing the amount of stable isotope to be incorporated with the formulation while using the shortest feasible irradiation time.

Parr, A.; Jay, M.

1987-12-01

320

Neutron and photon fluence-to-dose conversion factors for active marrow of the skeleton  

SciTech Connect

Calculation of the absorbed dose to active marrow is a complex problem because charged particle equilibrium may not exist near a soft tissue-bone interface and it is difficult to model the intricate intermixture of soft tissue and bone in the skeleton. This study provides the first definitive calculations for a variety of bones and a wide range of neutron and photon energies. We avoid the assumption of a special geometry by using measured chord-length distributions to represent the microstructure of trabecular bone which contains the active marrow. Results of our calculations for neutrons and photons with energies up to 20 MeV are presented as dose response factors. The response factors can be applied in radiation transport calculations of absorbed dose in active marrow from photons and neutrons externally incident on the body and photons produced by neutrons interactions within the body. 34 references, 6 figures, 2 tables.

Kerr, G.D.; Eckerman, K.F.

1984-01-01

321

PROMETHEE: An Alpha Low Level Waste Assay System Using Passive and Active Neutron Measurement Methods  

SciTech Connect

The development of a passive-active neutron assay system for alpha low level waste characterization at the French Atomic Energy Commission is discussed. Less than 50 Bq[{alpha}] (about 50 {mu}g Pu) per gram of crude waste must be measured in 118-l 'European' drums in order to reach the requirements for incinerating wastes. Detection limits of about 0.12 mg of effective {sup 239}Pu in total active neutron counting, and 0.08 mg of effective {sup 239}Pu coincident active neutron counting, may currently be detected (empty cavity, measurement time of 15 min, neutron generator emission of 1.6 x 10{sup 8} s{sup -1} [4{pi}]). The most limiting parameters in terms of performances are the matrix of the drum - its composition (H, Cl...), its density, and its heterogeneity degree - and the localization and self-shielding properties of the contaminant.

Passard, Christian [French Atomic Energy Commission, C.E.A. Cadarache (France); Mariani, Alain [French Atomic Energy Commission, C.E.A. Cadarache (France); Jallu, Fanny [French Atomic Energy Commission, C.E.A. Cadarache (France); Romeyer-Dherbey, Jacques [French Atomic Energy Commission, C.E.A. Cadarache (France); Recroix, Herve [French Atomic Energy Commission, C.E.A. Cadarache (France); Rodriguez, Michel [French Atomic Energy Commission, C.E.A. Cadarache (France); Loridon, Joel [French Atomic Energy Commission, C.E.A. Cadarache (France); Denis, Caroline [French Atomic Energy Commission, C.E.A. Cadarache (France); Toubon, Herve [COGEMA (France)

2002-12-15

322

Calculated gamma-ray and\\/or neutron attenuation coefficients in 14 MeV neutron activation analysis  

Microsoft Academic Search

A program of theoretical and experimental work was performed to develop a mathematical model which can represent all the parameters\\u000a of the neutron activation analysis operation. However, we avoid absolute technique by using a sample containing the same element\\u000a as the reference but having a different geometry and weight. In the present work we apply this model to determine the

A. G. Elayi

1983-01-01

323

Studies of neutron cross-sections important for spallation experiments using the activation method  

NASA Astrophysics Data System (ADS)

A series of experiments devoted to studies of neutron cross-sections by activation method was carried out. The cross-sections of various threshold reactions were studied by means of different quasi-monoenergetic neutron sources with energies from 14 MeV up to 100 MeV. Threshold reactions in various materials are among other used to measure fast neutron fields produced during accelerator driven system studies. For this reason our measurements of neutron cross-sections are crucial. At present, neither experimental nor evaluated data above 30 MeV are available for neutron threshold reactions in Au, I and In published in this proceedings. We studied materials in the form of thin foils and compared our data with the calculations preformed using the deterministic code TALYS 1.4.

Vrzalová, J.; Chudoba, P.; Krása, A.; Majerle, M.; Suchopár, M.; Svoboda, O.; Wagner, V.

2014-09-01

324

Determination of boron in materials by cold neutron prompt gamma-ray activation analysis.  

PubMed

An instrument for cold neutron prompt gamma-ray activation analysis (PGAA), located at the NIST Center for Neutron Research (NCNR), has proven useful for the measurement of boron in a variety of materials. Neutrons, moderated by passage through liquid hydrogen at 20 K, pass through a (58)Ni coated guide to the PGAA station in the cold neutron guide hall of the NCNR. The thermal equivalent neutron fluence rate at the sample position is 9 x 10(8) cm(-2) s(-1). Prompt gamma rays are measured by a cadmium- and lead-shielded high-purity germanium detector. The instrument has been used to measure boron mass fractions in minerals, in NIST SRM 2175 (Refractory Alloy MP-35-N) for certification of boron, and most recently in semiconductor-grade silicon. The limit of detection for boron in many materials is <10 ng g(-1). PMID:15614360

Paul, Rick L

2005-01-01

325

Dosimetric considerations in neutron activation analysis in vivo  

SciTech Connect

The use of filtered low energy neutron beams from reactors and isotopic sources opens new possibilities for detection of trace elements, particularly in the brain. The low values of kerma/neutron in 24 and 2 KeV beams, together with a relatively small value of quality factor made it possible to utilize these for detection of Ca in skull with a negligible dose administered to the patient. Furthermore, for an acceptable radiation dose to the brain and satisfactory eye sparing the levels of mercury in brain can be determined using prompt gamma ray technique at much lower concentrations than in the past. The tailoring of neutron spectrum is finding applications in the detection of calcium in parts of the skeleton, close to the skin. For this and similar applications filtered beams offer better detectability i.e. less dose to the patient. Dose sparing is also achieved if /sup 252/Cf replaces Am-Be and Pu-Be sources.

Ettinger, K.V.; Fairchild, R.G.; Cohn, S.H.

1981-01-01

326

The determination of phosphorus by fast neutron activation analysis  

E-print Network

and Properties of Nuclei Formed by Bombarding Phosphorus with Neutrons uclide p31 p31 Relative abund. (7o) 100 100 Energy of Neutron . 025 ev 14. 5 Mev Cross Section (mb) 190 146 Product Nuclide p3 2 A128 Half Life 14 2 d. 2 3 min... Mode of Decay beta beta Type and Energy of Radiation for Detection Mev) 1. 70 y 1. 78 Nuclear Reaction (n, v) (n, u) p31 100 14. 5 Mev 86 8. 31 2. 6 hr'. beta (n, p) p31 100 14 5 Mev p30 2. 5 min. positron 3 01 (n, 2n) RESULTS...

To-On, Maen

1964-01-01

327

Using Electronic Neutron Generators in Active Interrogation to Detect Shielded Fissionable Material  

SciTech Connect

Experiments have been performed at Idaho National Laboratory to study methodology and instrumentation for performing neutron active interrogation die-away analyses for the purpose of detecting shielded fissionable material. Here we report initial work using a portable DT electronic neutron generator with a He-3 fast neutron detector to detect shielded fissionable material including >2 kg quantities of enriched uranium and plutonium. Measurements have been taken of bare material as well as of material hidden within a large plywood cube. Results from this work have demonstrated the efficacy of the die-away neutron measurement technique for quickly detecting the presence of special nuclear material hidden within plywood shields by analyzing the time dependent neutron signals in-between neutron generator pulses. Using a DT electronic neutron generator operating at 300 Hz with a yield of approximately 0.36 x 10**8 neutrons per second, 2.2 kg of enriched uranium hidden within a 0.60 m x 0.60 m x 0.70 m volume of plywood was positively detected with a measurement signal 2-sigma above the passive background within 1 second. Similarly, for a 500 second measurement period a lower detection limit of approaching the gram level could be expected with the same simple set-up.

D. L. Chichester; E. H. Seabury

2008-10-01

328

Determination of (n,?) Cross Sections of 241Am by Cold Neutron Activation  

NASA Astrophysics Data System (ADS)

Accurate cross section data of actinides are crucial for criticality calculations of GEN IV reactors and transmutation but also for analytical purposes such as nuclear waste characterization, decommissioning of nuclear installations and safeguard applications. Tabulated data are inconsistent and sometimes associated with large uncertainties. Neutron activation with external cold neutron beams from high flux reactors offers a chance for determination of accurate capture cross sections scalable to the whole 1/?{E}-region even for isotopes with low-lying resonances like 241Am. Preparation of 241Am samples for irradiation at the PGAA station of the FRM II in Garching has been optimized together with PTB in Braunschweig. Two samples were irradiated together with gold flux monitors to extract the thermal neutron capture cross section after appropriate corrections for attenuation of neutrons and photons in the sample. For one sample, the thermal ground state neutron capture cross section was measured as 663.0 ± 28.8 b. The thermal neutron capture cross section was calculated to 725.4 ± 34.4 b. For the other sample, a ground state neutron capture cross section of 649.9 ± 28.2 b was measured and a thermal neutron capture cross section of 711.1 ± 33.9 b was derived.

Genreith, C.; Rossbach, M.; Révay, Zs.; Kudejova, P.

2014-05-01

329

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

330

Nondestructive assay of spent boiling-water-reactor fuel by active neutron interrogation  

SciTech Connect

Spent boiling water reactor (BWR) fuel from Dresden I was assayed for total fissile mass, using the active neutron interrogation method. The nondestructive assay (NDA) system used has four Sb-Be sources for interrogation of the fuels; the induced fission neutrons from the fuel are counted by four lead-shielded methane-filled proportional counters biased above the energy of the source neutrons. Results agreed with results from the chemical analyses to within 2 to 3%. Similar agreement was obtained when two combinations of canned spent fuel were used as standards for the nondestructive assays.

Blakeman, E.D.; Ricker, C.W.; Ragan, G.L.; Difilippo, F.C.; Slaughter, G.G.

1981-01-01

331

Active-Interrogation Measurements of Induced-Fission Neutrons from Low-Enriched Uranium  

SciTech Connect

Protection and control of nuclear fuels is paramount for nuclear security and safeguards; therefore, it is important to develop fast and robust controlling mechanisms to ensure the safety of nuclear fuels. Through both passive- and active-interrogation methods we can use fast-neutron detection to perform real-time measurements of fission neutrons for process monitoring. Active interrogation allows us to use different ranges of incident neutron energy to probe for different isotopes of uranium. With fast-neutron detectors, such as organic liquid scintillation detectors, we can detect the induced-fission neutrons and photons and work towards quantifying a sample’s mass and enrichment. Using MCNPX-PoliMi, a system was designed to measure induced-fission neutrons from U-235 and U-238. Measurements were then performed in the summer of 2010 at the Joint Research Centre in Ispra, Italy. Fissions were induced with an associated particle D-T generator and an isotopic Am-Li source. The fission neutrons, as well as neutrons from (n, 2n) and (n, 3n) reactions, were measured with five 5” by 5” EJ-309 organic liquid scintillators. The D-T neutron generator was available as part of a measurement campaign in place by Padova University. The measurement and data-acquisition systems were developed at the University of Michigan utilizing a CAEN V1720 digitizer and pulse-shape discrimination algorithms to differentiate neutron and photon detections. Low-enriched uranium samples of varying mass and enrichment were interrogated. Acquired time-of-flight curves and cross-correlation curves are currently analyzed to draw relationships between detected neutrons and sample mass and enrichment. In the full paper, the promise of active-interrogation measurements and fast-neutron detection will be assessed through the example of this proof-of-concept measurement campaign. Additionally, MCNPX-PoliMi simulation results will be compared to the measured data to validate the MCNPX-PoliMi code when used for active-interrogation simulations.

J. L. Dolan; M. J. Marcath; M. Flaska; S. A. Pozzi; D. L. Chichester; A. Tomanin; P. Peerani; G. Nebbia

2012-07-01

332

Prompt gamma ray neutron activation analysis of cadmium in municipal solid waste  

E-print Network

as well as to other elements such as Fe, Al, and Cl. Californium-252 neutrons are commonly used and the resultant gamma-ray photopeaks are measured by a high resolution germanium detector. For borehole logging, the source and detector are housed within...PROMPT GAMMA RAY NEUTRON ACTIVATION ANALYSIS OF CADMIUM IN MUNICIPAL SOLID WASTE A Thesis by KATHERINE HOGE DENDAHL Submitted to the Office of Graduate Studies of Texas ASM University in partial fulfillment of the requirements for the degree...

Dendahl, Katherine Hoge

1991-01-01

333

Determination of europium in minerals and rocks by neutron activation and gammagamma-coincidence spectrometry.  

PubMed

Neutron activation followed by gammagamma-coincidence measurements of 9-3 hr (152)Eu is shown to be a convenient method for routine determination of europium in minerals and rocks. In the concentration range 10-150 ppm the method is free of interference from other elements, and neutron shielding effects do not interfere seriously in the analysis. The precision of the method is about 5%. PMID:18960651

Michelsen, O B; Steinnes, E

1969-10-01

334

Neutron dosimetry in poly-vinyl-chloride by activation foil technique  

NASA Astrophysics Data System (ADS)

Fast, intermediate and thermal neutrons were investigated inside slabs of poly-vinyl-chloride as a tissue equivalent medium in addition to poly-ethylene by using the activation foil technique. Neutrons are originally emitted from D-T generator with energy 14.5 MeV. The dose equivalent rate as well as the backscattering factors were measured. The presence of chloride atoms within the poly-vinyl-chloride affects its absorption characteristics.

El-Khatib, A. M.; Abou Taleb, W. M.; Fawzy, M. A.; Gad, K. E.

1995-03-01

335

Absolute calibration method for laser megajoule neutron yield measurement by activation diagnostics  

SciTech Connect

The laser megajoule (LMJ) and the National Ignition Facility (NIF) plan to demonstrate thermonuclear ignition using inertial confinement fusion (ICF). The neutron yield is one of the most important parameters to characterize ICF experiment performance. For decades, the activation diagnostic was chosen as a reference at ICF facilities and is now planned to be the first nuclear diagnostic on LMJ, measuring both 2.45 MeV and 14.1 MeV neutron yields. Challenges for the activation diagnostic development are absolute calibration, accuracy, range requirement, and harsh environment. At this time, copper and zirconium material are identified for 14.1 MeV neutron yield measurement and indium material for 2.45 MeV neutrons. A series of calibrations were performed at Commissariat a l'Energie Atomique (CEA) on a Van de Graff facility to determine activation diagnostics efficiencies and to compare them with results from calculations. The CEA copper activation diagnostic was tested on the OMEGA facility during DT implosion. Experiments showed that CEA and Laboratory for Laser Energetics (LLE) diagnostics agree to better than 1% on the neutron yield measurement, with an independent calibration for each system. Also, experimental sensitivities are in good agreement with simulations and allow us to scale activation diagnostics for the LMJ measurement range.

Landoas, Olivier; Rosse, Bertrand; Briat, Michelle; Marmouget, Jean Gabriel; Varignon, Cyril; Ledoux, Xavier; Caillaud, Tony; Thfoin, Isabelle; Bourgade, Jean-Luc [CEA, DAM, DIF, F-91297 Arpajon (France); Glebov, Vladimir Yu; Sangster, Thomas C.; Duffy, Tim [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623 (United States); Disdier, Laurent [CEA, LIST, F-91191 Gif-sur-Yvette (France)

2011-07-15

336

Signs of antimetastatic activity of palladium complexes of methylenediphosphonic acid in IR spectra  

NASA Astrophysics Data System (ADS)

We have used Fourier transform IR spectroscopy methods to study normal mouse lung tissue and also after subcutaneous transplantation of a B-16 melanoma tumor in the tissue. We also studied tissues with B-16 melanoma after they were treated with coordination compounds based on palladium complexes of methylenediphosphonic acid. The IR spectra of the lung tissues with metastases in the region of the C = O stretching vibrations are different from the IR spectra of normal tissue. We identified spectroscopic signs of the presence of metastases in the lung. We show that when a cancerous tumor is treated with a preparation of palladium complexes of methylenediphosphonic acid, the spectroscopic signs of the presence of metastases in the lung are missing. After treatment with the optimal dose of this drug, the IR spectrum of the lung tissue in which multiple metastases were present before treatment corresponds to the spectrum of normal tissue. We have determined the efficacy of the antitumor activity of coordination compounds based on palladium complexes of methylenediphosphonic acid.

Tolstorozhev, G. B.; Skornyakov, I. V.; Pekhnio, V. I.; Kozachkova, A. N.; Sharykina, N. I.

2012-07-01

337

Fission and activation of uranium by fusion-plasma neutrons  

NASA Technical Reports Server (NTRS)

Fusion-fission hybrid reactors are discussed in terms of two main purposes: to breed fissile materials (Pu 233 and Th 233 from U 238 or Th 232) for use in low-reactivity breeders, and to produce tritium from lithium to refuel fusion plasma cores. Neutron flux generation is critical for both processes. Various methods for generating the flux are described, with attention to new geometries for multiple plasma focus arrays, e.g., hypocycloidal pinch and staged plasma focus devices. These methods are evaluated with reference to their applicability to D-D fusion reactors, which will ensure a virtually unlimited energy supply. Accurate observations of the neutron flux from such schemes are obtained by using different target materials in the plasma focus.

Lee, J. H.; Hohl, F.; Mcfarland, D. R.

1978-01-01

338

Metabolic activity of sodium, measured by neutron activation, in the hands of patients suffering from bone diseases: concise communication  

SciTech Connect

Turnover of sodium in the human hand was studied by neutron activation. Patients suffering from various metabolic abnormalities affecting the skeleton, who were undergoing routine neutron activation for the measurement of calcium, were investigated along with a group of healthy volunteers. Neutron activation labels the sodium atoms simultaneously and with equal probability regardless of the turnover time of individual body compartments. The loss of sodium can be described either by a sum of two exponentials or by a single power function. Distinctions between patients and normal subjects were not apparent from the exponential model but were brought out by the power function. The exponent of time in the latter is a measure of clearance rate. The mean values of this parameter in (a) a group of patients suffering from acromegaly; (b) a group including Paget's disease, osteoporosis, Cushing's disease, and hyperparathyroidism; and (c) a group of healthy subjects, were found to be significantly different from each other.

Spinks, T.J.; Bewley, D.K.; Paolillo, M.; Vlotides, J.; Joplin, G.F.; Ranicar, A.S.O.

1980-01-01

339

Estimated neutron-activation data for TFTR. Part II. Biological dose rate from sample-materials activation  

SciTech Connect

The neutron induced material activation dose rate data are summarized for the TFTR operation. This report marks the completion of the second phase of the systematic study of the activation problem on the TFTR. The estimations of the neutron induced activation dose rates were made for spherical and slab objects, based on a point kernel method, for a wide range of materials. The dose rates as a function of cooling time for standard samples are presented for a number of typical neutron spectrum expected during TFTR DD and DT operations. The factors which account for the variations of the pulsing history, the characteristic size of the object and the distance of observation relative to the standard samples are also presented.

Ku, L.; Kolibal, J.G.

1982-06-01

340

Active Neutron and Gamma-Ray Instrumentation for In Situ Planetary Science Applications  

NASA Technical Reports Server (NTRS)

We describe the development of an instrument capable of detailed in situ bulk geochemical analysis of the surface of planets, moons, asteroids, and comets. This instrument technology uses a pulsed neutron generator to excite the solid materials of a planet and measures the resulting neutron and gamma-ray emission with its detector system. These time-resolved neutron and gamma-ray data provide detailed information about the bulk elemental composition, chemical context, and density distribution of the soil within 50 cm of the surface. While active neutron scattering and neutron-induced gamma-ray techniques have been used extensively for terrestrial nuclear well logging applications, our goal is to apply these techniques to surface instruments for use on any solid solar system body. As described, experiments at NASA Goddard Space Flight Center use a prototype neutron-induced gamma-ray instrument and the resulting data presented show the promise of this technique for becoming a versatile, robust, workhorse technology for planetary science, and exploration of any of the solid bodies in the solar system. The detection of neutrons at the surface also provides useful information about the material. This paper focuses on the data provided by the gamma-ray detector.

Parsons, A.; Bodnarik, J.; Evans, L.; Floyd, A.; Lim, L.; McClanahan, T.; Namkung, M.; Nowicki, S.; Schweitzer, J.; Starr, R.; Trombka, J.

2011-01-01

341

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

E-print Network

While iron emission lines are well studied in black hole systems, both in X-ray binaries and Active Galactic Nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, recent observations with Suzaku and XMM-Newton have revealed broad asymmetric iron line profiles in 4 neutron star LMXBs, confirming an inner disk origin for these lines in neutron star systems. Here, we present a search for iron lines in 6 neutron star LMXBs. For each object we have simultaneous Chandra and RXTE observations at 2 separate epochs, allowing for both a high resolution spectrum, as well as broadband spectral coverage. Out of the six objects in the survey, we only find significant iron lines in two of the objects, GX 17+2 and GX 349+2. However, we cannot rule out that there are weak, broad lines present in the other sources. The equivalent width of the line in GX 17+2 is consistent between the 2 epochs, while in GX 349+2 the line equivalent width increases by a factor of ~3 between epochs as the source flux decreases by a factor of 1.3. This suggests that the disk is highly ionized, and the line is dominated by recombination emission. We find that there appears to be no specific locations in the long-term hardness-intensity diagrams where iron emission lines are formed, though more sources and further observations are required.

E. M. Cackett; J. M. Miller; J. Homan; M. van der Klis; W. H. G. Lewin; M. Mendez; J. Raymond; D. Steeghs; R. Wijnands

2008-09-18

342

DT neutron generator as a source for a thermal neutron activation system for confirmatory land mine detection  

NASA Astrophysics Data System (ADS)

A DT neutron generator has been integrated into the Canadian Improved Landmine Detection Program's Thermal Neutron Activation sensor. The generator has been redesigned from a commercial version, and the moderator structure around the generator has been completely redesigned. These developments allow the DT generator and its moderator structure to be placed interchangeably into the location currently occupied by a 252Cf source and its moderator structure. Experimental and calculational studies have helped to define the optimal operating parameters for the neutron generator in this application. Performance comparisons between the old californium-based system and the new DT-generator-based system have demonstrated that the new system out-performs the old in all tested scenarios, particularly when the mine is deeply buried or when the source is not directly over the explosive. This is in excellent agreement with calculations performed in the design phase of this system. Combined with the myriad other benefits associated with DT generators over isotopic sources, these results demonstrate the desirability of using a DT generator in a TNA land mine detection system.

Haslip, Dean S.; Cousins, Thomas; Andrews, H. Robert; Chen, Jing; Clifford, Edward T. H.; Ing, Harry; McFee, John E.

2001-12-01

343

Medical applications of in vivo neutron inelastic scattering and neutron activation analysis: Technical similarities to detection of explosives and contraband  

NASA Astrophysics Data System (ADS)

Nutritional status of patients can be evaluated by monitoring changes in elemental body composition. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used in vivo to assess elements characteristic of specific body compartments. There are similarities between the body composition techniques and the detection of hidden explosives and narcotics. All samples have to be examined in depth and the ratio of elements provides a "signature" of the chemical of interest. The N/H and C/O ratios measure protein and fat content in the body. Similarly, a high C/O ratio is characteristic of narcotics and a low C/O together with a strong presence of N is a signature of some explosives. The available time for medical applications is about 20 min—compared to a few seconds for the detection of explosives—but the permitted radiation exposure is limited. In vivo neutron analysis is used to measure H, O, C, N, P, Na, Cl, and Ca for the study of the mechanisms of lean tissue depletion with aging and wasting diseases, and to investigate methods of preserving function and quality of life in the elderly.

Kehayias, J. J.

2001-07-01

344

Analysis of EMG Signals in Aggressive and Normal Activities by Using Higher-Order Spectra  

PubMed Central

The analysis and classification of electromyography (EMG) signals are very important in order to detect some symptoms of diseases, prosthetic arm/leg control, and so on. In this study, an EMG signal was analyzed using bispectrum, which belongs to a family of higher-order spectra. An EMG signal is the electrical potential difference of muscle cells. The EMG signals used in the present study are aggressive or normal actions. The EMG dataset was obtained from the machine learning repository. First, the aggressive and normal EMG activities were analyzed using bispectrum and the quadratic phase coupling of each EMG episode was determined. Next, the features of the analyzed EMG signals were fed into learning machines to separate the aggressive and normal actions. The best classification result was 99.75%, which is sufficient to significantly classify the aggressive and normal actions. PMID:23193379

Sezgin, Necmettin

2012-01-01

345

INTERMITTENCY AND MULTIFRACTALITY SPECTRA OF THE MAGNETIC FIELD IN SOLAR ACTIVE REGIONS  

SciTech Connect

We present the results of a study of intermittency and multifractality of magnetic structures in solar active regions (ARs). Line-of-sight magnetograms for 214 ARs of different flare productivity observed at the center of the solar disk from 1997 January until 2006 December are utilized. Data from the Michelson Doppler Imager (MDI) instrument on board the Solar and Heliospheric Observatory operating in the high resolution mode, the Big Bear Solar Observatory digital magnetograph, and the Hinode SOT/SP instrument were used. Intermittency spectra were derived from high-order structure functions and flatness functions. The flatness function exponent is a measure of the degree of intermittency. We found that the flatness function exponent at scales below approximately 10 Mm is correlated with flare productivity (the correlation coefficient is -0.63). The Hinode data show that the intermittency regime is extended toward small scales (below 2 Mm) as compared to the MDI data. The spectra of multifractality, derived from the structure functions and flatness functions, are found to be broader for ARs of higher flare productivity as compared to those of low flare productivity. The magnetic structure of high-flaring ARs consists of a voluminous set of monofractals, and this set is much richer than that for low-flaring ARs. The results indicate the relevance of the multifractal organization of the photospheric magnetic fields to the flaring activity. The strong intermittency observed in complex and high-flaring ARs is a hint that we observe a photospheric imprint of enhanced sub-photospheric dynamics.

Abramenko, Valentyna; Yurchyshyn, Vasyl [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)

2010-10-10

346

The feasibility of measuring manganese concentrations in human liver using neutron activation analysis.  

PubMed

Manganese is an element which is required by the human body. However, as with most metals, in large amounts manganese can be toxic. People who suffer from severe manganese intoxication have symptoms similar to those of Parkinson's disease. Preclinical symptoms of manganese intoxication have recently been detected in individuals working in industries which have manganese dioxide dust in the air. The concentration of many toxic elements can be measured in vivo using neutron activation. A small dose of neutrons is delivered to the organ of interest, the neutrons are readily captured by the target nuclei, and the gamma rays given off can be detected outside of the body. A neutron activation analysis system is being developed to measure manganese concentrations in humans. The McMaster KN-accelerator supplies the neutron beam and the thermal neutron capture reaction 55Mn(n,gamma)56Mn is used. The half-life of 56Mn is 2.58 hr and thus counting can occur after irradiation. The 847 keV gamma ray given off when 56Mn decays is detected using a Nal detector. Calibration curves are made using phantoms with known concentrations of Mn. This system will be used to monitor manganese levels in individuals who have occupational exposure to the element. Preliminary measurements, using liver phantoms, give a minimum detectable limit for Mn in the liver of less than one part per million, which is well below normal levels. PMID:10385900

Arnold, M L; McNeill, F E; Chettle, D R

1999-01-01

347

DIVERSE ACTIVE WELL NEUTRON COINCIDENCE COUNTER UTILITY AT THE SAVANNAH RIVER NATIONAL LABORATORY  

SciTech Connect

In this paper we describe use of the Aquila active well neutron coincidence counter for nuclear material assays of {sup 235}U in multiple analytical techniques at Savannah River Site (SRS), at the Savannah River National Laboratory (SRNL), and at Argonne West National Laboratory (AWNL). The uses include as a portable passive neutron counter for field measurements searching for evidence of {sup 252}Cf deposits and storage; as a portable active neutron counter using an external activation source for field measurements searching for trace {sup 235}U deposits and holdup; for verification measurements of U-Al reactor fuel elements; for verification measurements of uranium metal; and for verification measurements of process waste of impure uranium in a challenging cement matrix. The wide variety of uses described demonstrate utility of the technique for neutron coincidence verification measurements over the dynamic ranges of 100 g-5000 g for U metal, 200 g-1300 g for U-Al, and 8 g-35 g for process waste. In addition to demonstrating use of the instrument in both the passive and active modes, we also demonstrate its use in both the fast and thermal neutron modes.

Dewberry, R; Saleem Salaymeh, S

2007-01-08

348

Development of advanced neutron/gamma generators for imaging and active interrogation applications  

NASA Astrophysics Data System (ADS)

We report here on the development of neutron and photon sources for use in imaging and active interrogation applications, where there is a growing urgency for more advanced interrogation tools. These devices include high yield D-D, D-T and T-T fusion reaction based neutron generators and also low energy nuclear reaction based high-energy gamma generators. One common feature in these various devices is the use of a high-efficiency, RF-induction discharge ion source. This discharge method provides high plasma density for high output current, high atomic species from molecular gases for high efficiency neutron or gamma generation and long lifetime. Predictable discharge characteristics of these plasma generators allow accurate modeling for both the beam dynamics and for the heat loads at the target spot. Current status of the neutron and gamma generator development with experimental data will be presented.

Reijonen, J.; Andresen, N.; Gicquel, F.; Gough, R.; King, M.; Kalvas, T.; Leung, K.-N.; Lou, T.-P.; Vainionpaa, H.; Antolak, A.; Morse, D.; Doyle, B.; Miller, G.; Piestrup, M.

2007-04-01

349

The feasibility of accelerator-based in vivo neutron activation analysis of nitrogen.  

PubMed

The feasibility of accelerator-based in vivo neutron activation analysis of nitrogen has been investigated. It was found that a moderated neutron flux from approximately 10 microA of 2.5 MeV protons on a 9Be target performed as well as, and possibly slightly better than the existing isotope-based approach in terms of net counts per unit subject dose. Such a system may be an attractive alternative to the widespread use of (238,239)Pu/Be or 252Cf neutron sources, since there is more flexibility in the energy spectrum generated by accelerator-based neutron sources. From a radiation safety standpoint, accelerators have the advantage in that they only produce radiation when in operation. Furthermore, an accelerator beam can be pulsed, to reduce background detected in the prompt-gamma measurement, and such a device has a wide range of additional biological and medical applications. PMID:11761098

O'Meara, J M; Blackburn, B W; Chichester, D L; Gierga, D P; Yanch, J C

2001-12-01

350

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

PubMed

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

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

2011-07-01

351

Device and software used to carry out Cyclic Neutron Activation Analysis  

NASA Astrophysics Data System (ADS)

This paper discusses the device and software used to carry out Cyclic Neutron Activation Analysis (CNAA). The aim of this investigation is defining through this device the fluorite content present on different samples from fluorspar concentration plant through the DGNAA (Delayed Gamma Neutron Activation Analysis) method. This device is made of americium-beryllium neutron source, NaI (2"×2") and BGO (2"×2") gamma rays detectors, multichannel and an automatic mechanism which moves the samples from activation and reading position. This mechanism is controlled by a software which allows moving the samples precisely and in a safe way (~ms), which it is very useful when the radioactive isotopes have to be detected with a half time less than 8s.

Castro-García, M. P.; Rey-Ronco, M. A.; Alonso-Sánchez, T.

2014-11-01

352

Prediction of mutagenic activity of nitrophenanthrene and nitroanthracene isomers by simulated IR and Raman spectra.  

PubMed

This paper expands upon our original work on nitroanthracenes in (Alparone, A., Librando, V., 2012. Spectrochim. Acta A 89, 129-136) on the series of nitrophenanthrene isomers. Geometries, electric properties, IR and Raman spectra of 1-, 2-, 3-, 4- and 9-nitrophenanthrene (1-NP, 2-NP, 3-NP, 4-NP and 9-NP) were obtained and analyzed using Density Functional Theory calculations. The balance between steric and ?-conjugative interactions determines the order of stability 4-NP<1-NP~9-NP<2-NP?3-NP. IR and Raman spectral zones between 1000 and 1600 cm(-1) show intense bands noticeably affected by the position of the substituent, being potentially useful to discriminate and monitor the investigated isomers. Dipole moments, summations of IR intensity (?I(IR)) and Raman activity (?A(Raman)) over the 3N-6 vibrational modes are sensitive to the structure, increasing steadily from the non-planar to the planar isomers. Good linear relationships between the ?I(IR) (r=0.90) and ?A(Raman) (r=0.99) against the Salmonella typhimurium strain TA98 mutagenic activity of nitrophenanthrenes and isomeric nitroanthracenes are found. On the basis of the structural and vibrational properties, 4-NP seems to have not mutagenic activity, while the unknown TA98 mutagenic potency of 1-nitroanthracene is predicted to be between that of 9-NP and 3-NP. Calculated ?I(IR) and ?A(Raman) values could be used as molecular descriptors for QSARs applications of series of isomers. PMID:22809700

Alparone, Andrea; Librando, Vito

2013-01-01

353

NEUTRON ACTIVATION COOLDOWN OF THE TOKAMAK FUSION TEST REACTOR  

E-print Network

activation decay, exploring low activation issues, and investigating options for future radioactive waste management. II. EXPERIMENTAL CONDITIONS Extensive simulations of TFTR radioactivation have been performed

354

The fast neutron fluence and the activation detector activity calculations using the effective source method and the adjoint function  

SciTech Connect

This paper describes the application of effective source in forward calculations and the adjoint method to the solution of fast neutron fluence and activation detector activities in the reactor pressure vessel (RPV) and RPV cavity of a VVER-440 reactor. Its objective is the demonstration of both methods on a practical task. The effective source method applies the Boltzmann transport operator to time integrated source data in order to obtain neutron fluence and detector activities. By weighting the source data by time dependent decay of the detector activity, the result of the calculation is the detector activity. Alternatively, if the weighting is uniform with respect to time, the result is the fluence. The approach works because of the inherent linearity of radiation transport in non-multiplying time-invariant media. Integrated in this way, the source data are referred to as the effective source. The effective source in the forward calculations method thereby enables the analyst to replace numerous intensive transport calculations with a single transport calculation in which the time dependence and magnitude of the source are correctly represented. In this work, the effective source method has been expanded slightly in the following way: neutron source data were performed with few group method calculation using the active core calculation code MOBY-DICK. The follow-up neutron transport calculation was performed using the neutron transport code TORT to perform multigroup calculations. For comparison, an alternative method of calculation has been used based upon adjoint functions of the Boltzmann transport equation. Calculation of the three-dimensional (3-D) adjoint function for each required computational outcome has been obtained using the deterministic code TORT and the cross section library BGL440. Adjoint functions appropriate to the required fast neutron flux density and neutron reaction rates have been calculated for several significant points within the RPV and RPV cavity of the VVER-440 reacto rand located axially at the position of maximum power and at the position of the weld. Both of these methods (the effective source and the adjoint function) are briefly described in the present paper. The paper also describes their application to the solution of fast neutron fluence and detectors activities for the VVER-440 reactor. (authors)

Hep, J.; Konecna, A.; Krysl, V.; Smutny, V. [Calculation Dept., Skoda JS plc, Orlik 266, 31606 Plzen (Czech Republic)

2011-07-01

355

Investigation of the neutron activation of endohedral rare earth metallofullerenes  

SciTech Connect

Endohedral lanthanide metallofullerenes and their water-soluble biocompatible derivatives have been synthesized. The effect that fast-neutron irradiation has on the stability and nuclear physical properties of endohedral metallofullerenes that are used as magnetocontrast materials ({sup 46}Sc, {sup 140}La, {sup 141}Nd, {sup 153}Sm, {sup 152}Eu, {sup 154}Eu, {sup 153}Sm, {sup 160}Tb, {sup 169}Yb, {sup 170}Tm (isomers I and III), and {sup 177}Lu) is studied. Our hypothesis, according to which carbon-shell relaxation is based on the fast nonradiative processes of an electron shake-off type, is confirmed.

Shilin, V. A., E-mail: shilin@pnpi.spb.ru; Lebedev, V. T.; Kolesnik, S. G.; Kozlov, V. S.; Grushko, Yu. S.; Sedov, V. P.; Kukorenko, V. V. [Russian Academy of Sciences, St. Petersburg Nuclear Physics Institute (Russian Federation)

2011-12-15

356

Active-Interrogation Measurements of Fast Neutrons from Induced Fission in Low-Enriched Uranium  

SciTech Connect

A detection system was designed with MCNPX-PoliMi to measure induced-fission neutrons from U-235 and U-238 using active interrogation. Measurements were then performed with this system at the Joint Research Centre (JRC) in Ispra, Italy on low-enriched uranium samples. Liquid scintillators measured induced fission neutron to characterize the samples in terms of their uranium mass and enrichment. Results are presented to investigate and support the use of organic liquid scintillators with active interrogation techniques to characterize uranium containing materials.

J. L. Dolan; M. J. Marcath; M. Flaska; S. A. Pozzi; D. L. Chichester; A. Tomanin; P. Peerani

2014-02-01

357

Neutron activation analysis of the rare earth elements in Nasu hot springs.  

PubMed

Eleven rare earth elements (lanthanum, cerium, neodymium, samarium, europium, gadolinium, terbium, holmium, thulium, ytterbium and lutetium) in hot spring waters and sinter deposits in the Nasu area were determined by the neutron activation method. The rare earth elements in hot spring water were pre-concentrated in ferric hydroxide precipitate and neutron-irradiated. The rare earth elements were chemically separated into lighter and heavier groups and the activity of each group was measured with a Ge(Li) detector. Distribution of the rare earth elements between the hot spring water and the sinter deposit was also discussed. PMID:684229

Ikeda, N; Takahashi, N

1978-06-01

358

Standardization of process parameters for a chemical reaction using neutron activation analysis technique  

NASA Astrophysics Data System (ADS)

The chemical process to convert polyepichlorohydrin (PECH) into a glycidyl azide polymer (GAP) has been standardized by measuring the relative concentrations of nitrogen, chlorine and oxygen with the fast neutron activation analysis technique. For comparison PECH and GAP samples were also analysed by IR spectroscopy. The results indicate that, for standardization of the present chemical process, the fast neutron activation analysis technique is superior to IR spectroscopy. In this paper the techniques used to analyse the samples are described in detail but the information on the actual chemical process adopted is provided in brief.

Dokhale, P. A.; Bhoraskar, V. N.

1996-08-01

359

Large sample neutron activation analysis: a challenge in cultural heritage studies.  

PubMed

Large sample neutron activation analysis compliments and significantly extends the analytical tools available for cultural heritage and authentication studies providing unique applications of non-destructive, multi-element analysis of materials that are too precious to damage for sampling purposes, representative sampling of heterogeneous materials or even analysis of whole objects. In this work, correction factors for neutron self-shielding, gamma-ray attenuation and volume distribution of the activity in large volume samples composed of iron and ceramic material were derived. Moreover, the effect of inhomogeneity on the accuracy of the technique was examined. PMID:17867535

Stamatelatos, Ion E; Tzika, Faidra

2007-07-01

360

Analysis of active neutron multiplicity data for Y-12 skull oxide samples  

SciTech Connect

Previous work on active neutron multiplicity measurements and analyses is summarized. New active multiplicity measurements are described for samples of Y-12 skull oxide using an Active Well Coincidence Counter and MSR4 multiplicity electronics. Neutron multiplication values for the samples were determined from triples/doubles ratios. Neutron multiplication values were also obtained from Monte Carlo calculations using the MCNP code and the results compared with the experimental values. A calibration curve of AmLi source-sample coupling vs neutron multiplication was determined and used for active multiplicity assay of the skull oxides. The results are compared with those obtained from assay with the conventional calibration-curve technique, where the doubles rate is calibrated vs the {sup 235}U mass. The coupling-multiplication relationship determined for the skull oxides is compared with that determined earlier for pure high-enrichment uranium metal and pure uranium oxide. Conclusions are drawn about the application of active multiplicity techniques to uranium assay. Additional active multiplicity measurements and calculations are recommended.

Krick, M.S.; Ensslin, N. [Los Alamos National Lab., NM (United States); Ceo, R.N.; May, P.K. [Oak Ridge Y-12 Plant, TN (United States)

1996-09-01

361

Studies of neutron and proton nuclear activation in low-Earth orbit  

NASA Technical Reports Server (NTRS)

The expected induced radioactivity of experimental material in low Earth orbit was studied for characteristics of activating particles such as cosmic rays, high energy Earth albedo neutrons, trapped protons, and secondary protons and neutrons. The activation cross sections for the production of long lived radioisotopes and other existing nuclear data appropriate to the study of these reactions were compiled. Computer codes which are required to calculate the expected activation of orbited materials were developed. The decreased computer code used to predict the activation of trapped protons of materials placed in the expected orbits of LDEF and Spacelab II. Techniques for unfolding the fluxes of activating particles from the measured activation of orbited materials are examined.

Laird, C. E.

1982-01-01

362

First principle active neutron coincidence counting measurements of uranium oxide  

NASA Astrophysics Data System (ADS)

Uranium is present in most nuclear fuel cycle facilities ranging from uranium mines, enrichment plants, fuel fabrication facilities, nuclear reactors, and reprocessing plants. The isotopic, chemical, and geometric composition of uranium can vary significantly between these facilities, depending on the application and type of facility. Examples of this variation are: enrichments varying from depleted (~0.2 wt% 235U) to high enriched (>20 wt% 235U); compositions consisting of U3O8, UO2, UF6, metallic, and ceramic forms; geometries ranging from plates, cans, and rods; and masses which can range from a 500 kg fuel assembly down to a few grams fuel pellet. Since 235U is a fissile material, it is routinely safeguarded in these facilities. Current techniques for quantifying the 235U mass in a sample include neutron coincidence counting. One of the main disadvantages of this technique is that it requires a known standard of representative geometry and composition for calibration, which opens up a pathway for potential erroneous declarations by the State and reduces the effectiveness of safeguards. In order to address this weakness, the authors have developed a neutron coincidence counting technique which uses the first principle point-model developed by Boehnel instead of the "known standard" method. This technique was primarily tested through simulations of 1000 g U3O8 samples using the Monte Carlo N-Particle eXtended (MCNPX) code. The results of these simulations showed good agreement between the simulated and exact 235U sample masses.

Goddard, Braden; Charlton, William; Peerani, Paolo

2014-03-01

363

Determination of fluorine in glasses by cyclic activation analysis using a californium-252 neutron source  

Microsoft Academic Search

A cyclic activation analysis method with a 100 ?g252Cf source was developed for the determination of low concentrations of fluorine in glasses containing high concentrations\\u000a of oxygen. Factors influencing errors in the analysis were investigated quantitatively. The activation cross-section of19F(n, ?)16N for252Cf fission neutrons was determined. A brief description is given of the cyclic activation, analysis apparatus, and also the

H. Tominaga; T. Imahashi; S. Enomoto; N. Tachikawa; H. Maeda; K. Itakura

1979-01-01

364

Residual 152Eu and 60Co activities induced by neutrons from the Hiroshima atomic bomb  

Microsoft Academic Search

Specific activities of 152Eu:Eu in stone samples exposed to the Hiroshima atomic bomb were determined for 70 samples up to a 1,500-m slant range from the epicenter. The specific activities of 60Co:Co were also determined for six samples near the Hiroshima hypocenter. First, the 152Eu data were investigated to find out the directional dependence of neutron activation. Directional anisotropy was

Kiyoshi Shizuma; Kazuo Iwatani; Hiromi Hasai; Masaharu Hoshi; Takamitsu Oka; Hiroshige Morishima

1993-01-01

365

A passive-active neutron device for assaying remote-handled transuranic waste  

SciTech Connect

A combined passive-active neutron assay device was constructed for assaying remote-handled transuranic waste. A study of matrix and source position effects in active assays showed that a knowledge of the source position alone is not sufficient to correct for position-related errors in highly moderating or absorbing matrices. An alternate function for the active assay of solid fuel pellets was derived, although the efficacy of this approach remains to be established. 4 refs., 7 figs., 1 tab.

Estep, R.J.; Coop, K.L.; Deane, T.M.; Lujan, J.E.

1989-01-01

366

A bismuth activation counter for high sensitivity pulsed 14 MeV neutrons  

NASA Astrophysics Data System (ADS)

We have built a fast neutron bismuth activation counter that measures activation counts from pulsed 14-MeV neutron generators for incident neutron fluences between 30 and 300 neutrons/cm2 at 15.2 cm (6 in.). The activation counter consists of a large bismuth germanate (BGO) detector surrounded by a bismuth metal shield in front of and concentric with the cylindrical detector housing. The 14 MeV neutrons activate the 2.6-millisecond (ms) isomer in the shield and the detector by the reaction 209Bi (n,2n?) 208mBi. The use of millisecond isomers and activation counting times minimizes the background from other activated materials and the environment. In addition to activation, the bismuth metal shields against other outside radiation sources. We have tested the bismuth activation counter, simultaneously, with two data acquisition systems (DASs) and both give similar results. The two-dimensional (2D) DAS and three dimensional (3D) DAS both consist of pulse height analysis (PHA) systems that can be used to discriminate against gamma radiations below 300 keV photon energy, so that the detector can be used strictly as a counter. If the counting time is restricted to less than 25 ms after the neutron pulse, there are less than 10 counts of background for single pulse operation in all our operational environments tested so far. High-fluence neutron generator operations are restricted by large dead times and pulse height saturation. When we operate our 3D DAS PHA system in list mode acquisition (LIST), real-time corrections to dead time or live time can be made on the scale of 1 ms time windows or dwell times. The live time correction is consistent with nonparalyzable models for dead time of 1.0±0.2 ?s for our 3D DAS and 1.5±0.3 ?s for our 2D DAS dominated by our fixed time width analog to digital converters (ADCs). With the same solid angle, we have shown that the bismuth activation counter has a factor of 4 increase in sensitivity over our lead activation counter, because of higher counts and negligible backgrounds.

Burns, E. J. T.; Thacher, P. D.; Hassig, G. J.; Decker, R. D.; Romero, J. A.; Barrett, K. P.

2011-08-01

367

Analysis of the Rotationally-Resolved Spectra of the Vibronically-Active Molecules  

NASA Astrophysics Data System (ADS)

Rotational structure of the vibronically coupled, and specifically, Jahn-Teller active molecules in isolated vibronic states has been studied for the decades, and the corresponding Hamiltonian and relationship of its parameters to the molecular properties are well-established, at least for the e vibronic states. However, in many cases an isolated state approach, both for the ground and vibronically excited levels, does not produce satisfactory results either because the experimentally obtained parameters of such model are not physically transparent, or the model fails to predict the observed spectrum to the experimental accuracy. To circumvent these problems, we develop, from the molecular symmetry standpoint, an effective coupled state rotational Hamiltonian directly accounting for the interactions within the appropriate subset of the interacting vibronic states. This approach is expected to be useful for the analysis of the rotational level structure of the closely-spaced vibronic levels such as those occurring in the vibrationally excited manifolds of the open-shell molecules. The application of this approach to the spectra of the nitrate radical, NO_3, in the Jahn-Teller active ˜{A}^2E'' state, will be discussed. D. G. Melnik, T. A. Miller and J. Liu, TI15, 67^th Molecular Spectroscopy Symposium, Columbus, 2012 M. Roudjane, T. J. Codd and T. A. Miller, TI03, 67^th Molecular Spectroscopy Symposium, Columbus, 2012

Melnik, Dmitry G.; Miller, Terry A.

2013-06-01

368

FUV Spectra of Evolved Late-K and M Stars: Mass Loss Revisited and Stellar Activity  

NASA Technical Reports Server (NTRS)

This is the final report for the FUSE Cycle 1 program A100: FUV Spectra of Evolved Late-K and M Stars: Mass Loss revisited and Stellar Activity. Targets alpha TrA (K3 II) and gamma Cru (M3 III) were originally assigned 25 ksec each, to be observed in the medium aperture. Once the in-flight performance and telescope alignment problems were known, the observations were reprogrammed to optimized the scientific return of the program. Alpha TrA was scheduled for 25 ksec observations in both the medium and large apertures. The principle aim of this program was to measure the stellar FUV line and continuum emission, in order to estimate the photoionization radiation field and to determine the level of stellar activity through the fluxes in the collisionally excited high temperature diagnostics: C III 977Angstroms and O VI 1032,1038Angstrom doublet. The medium aperture observations were obtained successfully while the large aperture observations were thought by Johns Hopkins University (JHU)to be lost to satellite problems. There was insufficient signal-to- noise in the medium aperture short wavelength Sic channels to do quantitative science.

Harper, Graham M.

2002-01-01

369

Improvement of the prompt-gamma neutron activation facility at Brookhaven National Laboratory.  

PubMed

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient. The gamma detectors have been relocated from positions close to the upward-emerging collimated neutron beam to positions close to and at the sides of the patient. These modifications substantially reduced spurious counts resulting from the capture of small-angle scattered neutrons in the NaI detectors. The pile-up background under the 10.8 MeV 14N(n, gamma)15N spectral peak has been reduced so that the nitrogen peak-to-background ratio has been increased by a factor of 2.8. The resulting reduction in the coefficient of variation of the total body nitrogen measurements from 3% to 2.2% has improved the statistical significance of the results possible for any given number of patient measurements. The new system also has a more uniform composite sensitivity. PMID:9509530

Dilmanian, F A; Lidofsky, L J; Stamatelatos, I; Kamen, Y; Yasumura, S; Vartsky, D; Pierson, R N; Weber, D A; Moore, R I; Ma, R

1998-02-01

370

Delayed neutron spectra by decay group for fissioning systems from /sup 227/Th through /sup 255/Fm  

SciTech Connect

The quality and quantity of delayed neutron precursor data has greatly improved over the past approximately 15 years. Supplementation of the data with model calculations and the use of models to extend the number of precursors to 271 is now practical. These data, along with improved fission-product parameters, permit direct calculations of aggregate behavior for many fissioning nuclides. The results can even be approximated using a few (usually six) temporal groups. This paper summarizes an extensive four-year effort to provide a complete set of evaluated data and emphasizes its use to generate the temporal approximations; precursor data and group values are intended for inclusion in ENDF/B-VI. 19 refs., 8 figs., 1 tab.

England, T.R.; Brady, M.C.

1988-01-01

371

Measurement and analysis of induced activities in concrete irradiated using high-energy neutrons at KENS Neutron Spallation Source Facility.  

PubMed

Precise estimation of induced activities in concrete shields for high-energy accelerator facilities is one of the most important issues that need to be solved, not only for the reduction of exposure for workers, but also for the reduction of radioactive wastes. Irradiation experiments have been performed by using the 500 MeV Neutron Spallation Source Facility in KEK. The large concrete assembly was placed in the direction of 0 degrees to the beamline. Two kinds of samples were placed at several positions in the assembly. The irradiation period was about 1 week and induced activities in the samples were measured until approximately 1.5 y after irradiation. From the comparison between the experiment and the available Monte Carlo calculation code system, good agreement was obtained for 24Na, 47Sc, 47Ca and 54Mn within a factor 2; however, large discrepancies were observed for some other nuclides. PMID:16381795

Oishi, Koji; Nakao, Noriaki; Kosako, Kazuaki; Yamakawa, Hiroshi; Nakashima, Hiroshi; Kawai, Masayoshi; Yashima, Hiroshi; Sanami, Toshiya; Numajiri, Masaharu; Shibata, Tokushi; Hirayama, Hideo; Nakamura, Takashi

2005-01-01

372

Characteristics of low energy accelerator neutron sources  

SciTech Connect

Energy and fluence monitors are recommended for D-D and D-T neutrons. Neutron flux density spectra were determined for extended samples using the foil activation and physical integration methods. The unfolding method was checked by TOF and pulse height response spectrometers. Signal-to-background ratio was optimized for D-D gas cell neutron sources. Results show that the contribution of Coulomb breakup neutrons from the beam stop materials to the background is dominant at incident deuteron energies below 10 MeV.

Csikai, J.; Grallert, A.; Olah, L. [Kossuth Univ., Debrecen (Hungary); Qaim, S.M. [Institut fuer Nuklearchemie, Juelich (Germany)

1994-12-31

373

Measurement and analysis of activation induced in titanium with fusion peak neutrons  

NASA Astrophysics Data System (ADS)

The intense neutron flux densities in fusion reactor blankets produce activation in the blanket materials relevant to operational safety, decommissioning, etc. The aim of the present work is to check the European Activation System EASY-2007 for its capability to predict important gamma activities induced in titanium in a fusion neutron field. Many advanced low-activation materials for fusion applications contain titanium, most notably in the breeder material Li 2TiO 3. In the present work, a small sample of Ti was irradiated with the intense DT neutron generator of Technical University of Dresden. The gamma-radioactivity following irradiation was measured and nuclide activities were derived. For each of the measured gamma activities, the corresponding value was calculated with EASY, and calculation-to-experiment ratios ( C/ E) were determined. EASY predicted the induced gamma activities, isotopes of scandium, well with some overestimation for 47Sc. The results of this measurement together with available EXFOR and validated state-of-the-art activation libraries are discussed.

Klix, A.; Domula, A.; Forrest, R.; Zuber, K.

2011-10-01

374

Minimum activation martensitic alloys for surface disposal after exposure to neutron flux  

DOEpatents

Steel alloys for long-term exposure to neutron flux have a martensitic microstructure and contain chromium, carbon, tungsten, vanadium and preferably titanium. Activation of the steel is held to within acceptable limits for eventual surface disposal by stringently controlling the impurity levels of Ni, Mo, Cu, N, Co, Nb, Al and Mn.

Lechtenberg, Thomas (San Diego, CA)

1985-01-01

375

Applications of Prompt Gamma Ray Neutron Activation Analysis: Detection of Illicit Materials  

Microsoft Academic Search

Prompt gamma ray neutron activation analysis (PGNAA) is an efficient nondestructive multi-elemental detection technique for samples such as metals, coal (mineral), cement, and radioactive materials as well as for explosives, chemical warfare agents, various narcotics, land mines, etc. The technique can be used in the laboratory or for on-site analysis for various samples. In addition, the PGNAA technique in elemental

Hee-Jung Im; Kyuseok Song

2009-01-01

376

Multielemental analysis of vegetarian human diets and dietary components by neutron activation  

Microsoft Academic Search

Two vegetarian diet samples representative of the Indian sub-continent were prepared (in raw form) by the proportionate blending method for adolescent and adult age groups. These along with its components, viz. wheat, rice flours and pulses, were analyzed for 12 minor and trace elements by instrumental neutron activation analysis (INAA) and high resolution ?-ray spectrometry. Bowen's kale was also analyzed

Dhananjay L. Samudralwar; Amar N. Garg

1994-01-01

377

Neutron activation analysis of fluid inclusions for copper, manganese, and zinc  

USGS Publications Warehouse

Microgram quantities of copper, manganese, and zinc, corresponding to concentrations greater than 100 parts per million, were found in milligram quantities of primary inclusion fluid extracted from samples of quartz and fluorite from two types of ore deposits. The results indicate that neutron activation is a useful analytical method for studying the content of heavy metal in fluid inclusions.

Czamanske, G.K.; Roedder, E.; Burns, F.C.

1963-01-01

378

Neutron Activation Analysis of Single Grains Recovered by the Hayabusa Spacecraft  

NASA Astrophysics Data System (ADS)

Single grain samples returned by the Hayabusa spacecraft are analyzed by neutron activation for characterizing the material in terms of chemical composition. Gamma ray counting is performed by using a well-type Ge detector at the heavily shielded counting facility.

Ebihara, M.; Sekimoto, S.; Hamajima, Y.; Yamamoto, M.; Kumagai, K.; Oura, Y.; Shirai, N.; Ireland, T. R.; Kitajima, F.; Nagao, K.; Nakamura, T.; Naraoka, H.; Noguchi, T.; Okazaki, R.; Tsuchiyama, A.; Uesugi, M.; Yurimoto, H.; Zolensky, M. E.; Abe, M.; Fujimura, A.; Mukai, T.; Yada, T.

2011-03-01

379

Neutron activation analysis of the ashes of some medicinally used tropical woods  

Microsoft Academic Search

Ashes of medicinally used tropical plant woods collected in the southern part of Nigeria were analyzed for up to 24 elements using Instrumental Neutron Activation Analysis techniques (INAA). The plants are:Azadirachta indica, Astonia congensis, Chlorophora excelsa, Antiaris africana andBrachystegia euricoma. Concentrations of 24 major, minor and trace lements were determined. The result of elemental contents were discussed with reference to

O. A. Fakankun; E. A. Oluyemi; O. A. Akanle

1993-01-01

380

Neutron-activation determination of iridium in sedimentary rocks after sorption preconcentration  

SciTech Connect

A sorption-neutron-activation technique has been developed for iridium determination in sedimentary rocks with a detection limit of 4 x 10/sup -10/% and a relative standard deviation of 0.35. A polymeric tertiary amine was used as sorbent.

Barsukova, L.D.; Kolesov, G.M.; Malofeeva, G.I.; Nazarov, M.A.; Marcheva, E.V.

1986-11-10

381

Calcium sensitivity determinations by neutron activation analysis as applied to bone  

E-print Network

crystal. As mentioned in the theory section, the neutrons activate calcium mo'L effectively at: t?ermal energies& therefoxe a thermelizer was cousLxucted. Paraffin was selected because of its ease of handling and availability. It was formed...

Blasdel, Michael John

1971-01-01

382

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

SciTech Connect

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

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

2013-03-01

383

Neutron Spectrum Determination of the p(35 MeV)-Be Source Reaction by the Dosimetry Foils Method  

NASA Astrophysics Data System (ADS)

The thick target neutron field of source reaction p + Be was investigated for a proton energy of 35 MeV. The spectral neutron flux at 0? for two target-to-sample distances was determined by using the dosimetry foils activation method. The present p(35)-Be white neutron spectra provide the suitable basis for irradiation experiments and integral tests of nuclear data.

Štefánik, M.; Bém, P.; Götz, M.; Katovský, K.; Majerle, M.; Novák, J.; Šime?ková, E.

2014-05-01

384

X-ray spectra and time variability of active galactic nuclei  

NASA Technical Reports Server (NTRS)

The X-ray spectra of broad line active galactic nuclei (AGN) of all types (Seyfert I's, NELG's, broadline radio galaxies) are well fit by a power law in the .5 to 100 keV band of man energy slope alpha = .68 + or - .15. There is, as yet, no strong evidence for time variability of this slope in a given object. The constraints that this places on simple models of the central energy source are discussed. BL Lac objects have quite different X-ray spectral properties and show pronounced X-ray spectral variability. On time scales longer than 12 hours most radio quiet AGN do not show strong, delta I/I .5, variability. The probability of variability of these AGN seems to be inversely related to their luminosity. However characteristics timescales for variability have not been measured for many objects. This general lack of variability may imply that most AGN are well below the Eddington limit. Radio bright AGN tend to be more variable than radio quiet AGN on long, tau approx 6 month, timescales.

Mushotzky, R. F.

1984-01-01

385

On the hard X-ray spectra of radio-loud active galaxies  

NASA Astrophysics Data System (ADS)

Over the last few years X-ray observations of broad-line radio galaxies (BLRGs) by ASCA , RXTE and BeppoSAX have shown that these objects seem to exhibit weaker X-ray reflection features (such as the iron K? line) than radio-quiet Seyferts. This has lead to speculation that the optically thick accretion disc in radio-loud active galactic nuclei (AGN) may be truncated to an optically thin flow in the inner regions of the source. Here, we propose that the weak reflection features are a result of reprocessing in an ionized accretion disc. This would alleviate the need for a change in accretion geometry in these sources. Calculations of reflection spectra from an ionized disc for situations expected in radio-loud AGN (high accretion rate, moderate-to-high black hole mass) predict weak reprocessing features. This idea was tested by fitting the ASCA spectrum of the bright BLRG 3C 120 with the constant density ionized disc models of Ross & Fabian. A good fit was found with an ionization parameter of ? ~4000ergcms-1 and the reflection fraction fixed at unity. If observations of BLRGs by XMM-Newton show evidence for ionized reflection then this would support the idea that a high accretion rate is likely required to launch powerful radio jets.

Ballantyne, D. R.; Ross, R. R.; Fabian, A. C.

2002-05-01

386

A new automated sample transfer system for instrumental neutron activation analysis.  

PubMed

A fully automated and fast pneumatic transport system for short-time activation analysis was recently developed. It is suitable for small nuclear research reactors or laboratories that are using neutron generators and other neutron sources. It is equipped with a programmable logic controller, software package, and 12 devices to facilitate optimal analytical procedures. 550 ms were only necessary to transfer the irradiated capsule (diameter: 15 mm, length: 50 mm, weight: 4 gram) to the counting chamber at a distance of 20 meters using pressurized air (4 bars) as a transport gas. PMID:20369063

Ismail, S S

2010-01-01

387

Neutron field for activation experiments in horizontal channel of training reactor VR-1  

NASA Astrophysics Data System (ADS)

The experimental channels of nuclear reactors often serve for nuclear data measurement and validation. The dosimetry-foils activation technique was employed to measure neutron field parameters in the horizontal radial channel of the training reactor VR-1, and to test the possibility of using the reactor for scientific purposes. The reaction rates, energy spectral indexes, and neutron spectrum at several irradiation positions of the experimental channel were determined. The experimental results show the feasibility of the radial channel for irradiating experiments and open new possibilities for data validation by using this nuclear facility.

Stefanik, Milan; Katovsky, Karel; Vins, Miroslav; Soltes, Jaroslav; Zavorka, Lukas

2014-11-01

388

A New Automated Sample Transfer System for Instrumental Neutron Activation Analysis  

PubMed Central

A fully automated and fast pneumatic transport system for short-time activation analysis was recently developed. It is suitable for small nuclear research reactors or laboratories that are using neutron generators and other neutron sources. It is equipped with a programmable logic controller, software package, and 12 devices to facilitate optimal analytical procedures. 550?ms were only necessary to transfer the irradiated capsule (diameter: 15?mm, length: 50?mm, weight: 4 gram) to the counting chamber at a distance of 20 meters using pressurized air (4 bars) as a transport gas. PMID:20369063

Ismail, S. S.

2010-01-01

389

Innovative high pressure gas MEM's based neutron detector for ICF and active SNM detection.  

SciTech Connect

An innovative helium3 high pressure gas detection system, made possible by utilizing Sandia's expertise in Micro-electrical Mechanical fluidic systems, is proposed which appears to have many beneficial performance characteristics with regards to making these neutron measurements in the high bremsstrahlung and electrical noise environments found in High Energy Density Physics experiments and especially on the very high noise environment generated on the fast pulsed power experiments performed here at Sandia. This same system may dramatically improve active WMD and contraband detection as well when employed with ultrafast (10-50 ns) pulsed neutron sources.

Martin, Shawn Bryan; Derzon, Mark Steven; Renzi, Ronald F.; Chandler, Gordon Andrew

2007-12-01

390

Feasibility study: In vivo neutron activation for regional measurement of calcium using Californium 252  

Microsoft Academic Search

The feasibility of using a collimated ²⁵²Cf neutron source to measure regional changes in skeletal calcium was tested because in vivo regional activation of diseased bone should offer advantages over the more widely reported total-body calcium measuring techniques. Regional activation allows examination of discrete regions where the greatest changes in calcium content occur. Additionally, a simpler radiation facility is required

Harlan J. Evans; A. D. LeBlanc; P. C. Johnson

1976-01-01

391

Neutron-activation analysis of vanadium in oils with californium-252  

Microsoft Academic Search

Results are given which have been obtained by the application of relatively small252Cf sources for the neutron-activation analysis of vanadium in oils. It could be shown that by optimization the geometrical\\u000a conditions for activation and counting with a 24 ?g252Cf source detection limits down to the order of 1 ppm vanadium are attainable; the absolute error, e.g., at 1.3 ppm

H. Meier; G. Zeitler; P. Menge

1977-01-01

392

Predicting long-lived, neutron-induced activation of concrete in a cyclotron vault  

Microsoft Academic Search

Many elements in concrete can become activated by neutrons in a cyclotron vault, but only a few of the activation products are long-lived. The most prominent of these are Eu-152, Eu-154, Co-60, and Cs-134 which build up over time from (n, gamma) reactions in trace amounts of stable Europium, Cobalt, and Cesium that are normally present in concrete in concentrations

L. R. Carroll

2001-01-01

393

Predicting long-lived, neutron-induced activation of concrete in a cyclotron vault  

Microsoft Academic Search

Many elements in concrete can become activated by neutrons in a cyclotron vault, but only a few of the activation products are long-lived. The most prominent of these are Eu-152, Eu-154, Co-60, and Cs-134 which build up over time from (n, ?) reactions in trace amounts of stable Europium, Cobalt, and Cesium that are normally present in concrete in concentrations

L. R. Carroll

2001-01-01

394

TFT-Based Active Pixel Sensors for Large Area Thermal Neutron Detection  

NASA Astrophysics Data System (ADS)

Due to diminishing availability of 3He, which is the critical component of neutron detecting proportional counters, large area flexible arrays are being considered as a potential replacement for neutron detection. A large area flexible array, utilizing semiconductors for both charged particle detection and pixel readout, ensures a large detection surface area in a light weight rugged form. Such a neutron detector could be suitable for deployment at ports of entry. The specific approach used in this research, uses a neutron converter layer which captures incident thermal neutrons, and then emits ionizing charged particles. These ionizing particles cause electron-hole pair generation within a single pixel's integrated sensing diode. The resulting charge is then amplified via a low-noise amplifier. This document begins by discussing the current state of the art in neutron detection and the associated challenges. Then, for the purpose of resolving some of these issues, recent design and modeling efforts towards developing an improved neutron detection system are described. Also presented is a low-noise active pixel sensor (APS) design capable of being implemented in low temperature indium gallium zinc oxide (InGaZnO) or amorphous silicon (a-Si:H) thin film transistor process compatible with plastic substrates. The low gain and limited scalability of this design are improved upon by implementing a new multi-stage self-resetting APS. For each APS design, successful radiation measurements are also presented using PiN diodes for charged particle detection. Next, detection array readout methodologies are modeled and analyzed, and use of a matched filter readout circuit is described as well. Finally, this document discusses detection diode integration with the designed TFT-based APSs.

Kunnen, George

395

Recent upgrade of the in vivo neutron activation facility at Brookhaven National Laboratory  

SciTech Connect

The in vivo neutron activation facility at Brookhaven National Laboratory consists of a delayed- and a prompt-gamma neutron activation (DGNA and PGNA) system and an inelastic neutron scattering (INS) system. The total body contents of several basic elements, including potassium, calcium, chlorine, sodium, and phosphorus are measured at the DGNA system; total body carbon is measured at the INS system; and the nitrogen-tohydrogen ratio is measured at the PGNA system. Based on the elemental composition, body compartments, such as total body fat and total body protein can be computed with additional independently measured parameters, such as total body water, body size, and body weight. Information on elemental and compartmental body composition obtained through neutron activation analysis is useful, if not essential, for research on growth, malnutrition, aging diseases, such as osteoporosis and acquired immunodeficiency syndrome in which the progression of the illness is closely related to changes in major body compartments, such as bone, adipose tissue, and muscle. The DGNA system has been modified and upgraded several times since it was first built. Recently, all three systems underwent major upgrades. This upgrading and some preliminary studies carried out with the modified facilities are reported here.

Ma, R.; Dilmanian, F.A..; Rarback, H.; Meron, M.; Kamen, Y.; Yasumura, S.; Weber, D.A. [Brookhaven National Lab., Upton, NY (United States); Stamatelatos, I.E. [Ioannina Univ. (Greece). Dept. of Medical Physics; Lidofsky, L.J. [Columbia Univ., New York, NY (United States). Dept. of Applied Physics and Nuclear Engineering; Pierson, R.N. Jr. [Saint Luke`s-Roosevelt Body Composition Unit, New York, NY (United States)

1993-10-01

396

Low-temperature thermally-activated deformation and irradiation softening in neutron-irradiated molybdenum  

NASA Astrophysics Data System (ADS)

The effect of neutron irradiation on low-temperature deformation of Mo in two heat treatments, i.e. annealed and stress-relieved, was investigated. Specimens were irradiated at reactor coolant temperature (˜80 °C) to doses ranging from 7.2 × 10 -5 to 0.28 dpa in the High Flux Isotope Reactor. Tensile tests were carried out between -50 and 100 °C at strain rates of 1 × 10 -5-1 × 10 -2 s -1. Thermal activation analysis based on tensile data was performed to understand the low-temperature deformation mechanism. Irradiation softening and reduced dependence on test temperature and strain rate of the yield stress was observed in the annealed Mo after low-dose neutron irradiation (<˜0.003 dpa). Higher dose neutron irradiation caused athermal hardening only. The stress-relieved Mo showed a weaker dependence on test temperature and strain rate of the yield stress than the annealed Mo, and the dependence of the yield stress of the stress-relieved Mo was nearly unchanged after irradiation. Comparison of the experimental values of activation parameters with the theoretical predictions of dislocation models indicates that the Fleischer model of interactions of dislocations with tetragonal strains gave a better description of the activation process than the double-kink model, which implies a scavenging effect. The reduced test temperature and strain rate dependence following irradiation may be explained by the decreased effective stress due to trapping of interstitial solute species by neutron-produced defects.

Li, Meimei; Byun, T. S.; Snead, L. L.; Zinkle, S. J.

2008-07-01

397

Secondary standards (non-activation) for neutron data measurements above 20 MeV  

SciTech Connect

In addition to H(n,p) scattering and {sup 235,238}U(n,f) reactions, secondary standards for neutron flux determination may be useful for neutron energies above 20 MeV. For experiments where gamma rays are detected, reference gamma-ray production cross sections are relevant. For neutron-induced charged particle production, standard (n,p) and (n,alpha) cross sections would be helpful. Total cross section standards would serve to check the accuracy of these measurements. These secondary standards are desirable because they can be used with the same detector systems employed in measuring the quantities of interest. Uncertainties due to detector efficiency, geometrical effects, timing and length of flight paths can therefore be significantly reduced. Several secondary standards that do not depend on activation techniques are proposed. 14 refs.

Haight, R.C.

1991-01-01

398

Importance of neutron energy distribution in borehole activation analysis in relatively dry, low-porosity rocks  

USGS Publications Warehouse

To evaluate the importance of variations in the neutron energy distribution in borehole activation analysis, capture gamma-ray measurements were made in relatively dry, low-porosity gabbro of the Duluth Complex. Although sections of over a meter of solid rock were encountered in the borehole, there was significant fracturing with interstitial water leading to a substantial variation of water with depth in the borehole. The linear-correlation coefficients calculated for the peak intensities of several elements compared to the chemical core analyses were generally poor throughout the depth investigated. The data suggest and arguments are given which indicate that the variation of the thermal-to-intermediate-to-fast neutron flux density as a function of borehole depth is a serious source of error and is a major cause of the changes observed in the capture gamma-ray peak intensities. These variations in neutron energy may also cause a shift in the observed capture gamma-ray energy.

Senftle, F.E.; Moxham, R.M.; Tanner, A.B.; Philbin, P.W.; Boynton, G.R.; Wager, R.E.

1977-01-01

399

Apparatus for the measurement of total body nitrogen using prompt neutron activation analysis with californium-252.  

PubMed

Details of clinical apparatus designed for the measurement of total body nitrogen (as an indicator of body protein), suitable for the critically ill, intensive-care patient are presented. Californium-252 radio-isotopic neutron sources are used, enabling a nitrogen measurement by prompt neutron activation analysis to be made in 40 min with a precision of +/- 3.2% for a whole body dose equivalent of 0.145 mSv. The advantages of Californium-252 over alternative neutron sources are discussed. A comparison between two irradiation/detection geometries is made, leading to an explanation of the geometry adopted for the apparatus. The choice of construction and shielding materials to reduce the count rate at the detectors and consequently to reduce the pile-up contribution to the nitrogen background is discussed. Salient features of the gamma ray spectroscopy system to reduce spectral distortion from pulse pile-up are presented. PMID:3057210

Mackie, A; Hannan, W J; Smith, M A; Tothill, P

1988-01-01

400

Prompt gamma activation analysis and time of flight neutron diffraction on ‘black boxes’ in the ‘Ancient Charm’ project  

Microsoft Academic Search

The aim of the ‘Ancient Charm’ project is combining neutron tomography, prompt gamma activation analysis, time of flight neutron\\u000a diffraction and neutron resonance transmission to generate elemental, and phase compositions of complex museum objects in\\u000a 3D. To develop a protocol for such investigations, complex test samples were constructed and then analyzed by each method.\\u000a The ‘black boxes’ are sealed iron

Zs. Kasztovszky; Z. Kis; T. Belgya; W. Kockelmann; S. Imberti; G. Festa; A. Filabozzi; C. Andreani; A. Kirfel; K. T. Biró; K. Dúzs; Zs. Hajnal; P. Kudejova; M. Tardocchi

2008-01-01

401

New models for carrying out cyclic neutron activation. Discussion of the theoretical response  

NASA Astrophysics Data System (ADS)

This paper studies two specific procedures for analyzing mining samples through a neutron activation technique called DGNAA (Delayed Gamma Neutron Activation Analysis). This particular study is part of a broader line of research, whose overall objective is to find the optimal procedure for analyzing the fluorite content of samples taken from different parts of a fluorite concentration plant, using the DGNAA method [1-2]. The mining sample is fluorspar, which contains other minerals in addition to fluorite, such as silica, barite, iron oxides and silicates. The main contribution of the article is the development of a new method for determining the fluorite content in minerals and the increase of sensitivity in respect to the symmetrical method and single-cycle activation.

Castro-García, M. P.; Rey-Ronco, M. A.; Alonso-Sánchez, T.

2014-11-01

402

Gamma exposure rates due to neutron activation of soil: site of Hood detonation, Operation Plumbbob  

SciTech Connect

This paper is the result of some recent discussions of exposure rates within the first few hours of the Hood detonation of the Plumbbob series due to neutron activation of soil. We estimated the exposure rates from 1/2 to 3 h after the detonation from ground zero to 1000 yards from ground zero. The area was assumed to be uncontaminated by fallout. Soil samples from the area of the Nevada Test Site at which the Hood device was detonated were sent to ORNL by Dr. John Malik of Los Alamos and by Mr. Gordon Jacks of the Nevada Test Site. These samples were irradiated at the DOSAR facility and the resulting activity analyzed. Calculations of exposure rates were then made based on the analyzed activity and the measured thermal neutron fluences at DOSAR and at the Hood Site.

Auxier, J.A.; Ohnesorge, W.F.

1980-06-01

403

Neutron field characteristics of Ciemat's Neutron Standards Laboratory.  

PubMed

Monte Carlo calculations were carried out to characterize the neutron field produced by the calibration neutron sources of the Neutron Standards Laboratory at the Research Center for Energy, Environment, and Technology (CIEMAT) in Spain. For (241)AmBe and (252)Cf neutron sources, the neutron spectra, the ambient dose equivalent rates and the total neutron fluence rates were estimated. In the calibration hall, there are several items that modify the neutron field. To evaluate their effects different cases were used, from point-like source in vacuum up to the full model. Additionally, using the full model, the neutron spectra were estimated to different distances along the bench; with these spectra, the total neutron fluence and the ambient dose equivalent rates were calculated. The hall walls induce the largest changes in the neutron spectra and the respective integral quantities. The free-field neutron spectrum is modified due the room return effect. PMID:25468287

Guzman-Garcia, Karen A; Mendez-Villafañe, Roberto; Vega-Carrillo, Hector Rene

2014-11-01

404

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

NASA Astrophysics Data System (ADS)

Beta-delayed neutron (?n) 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 ?-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 ?n-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 ?-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 ?-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 ?-delayed neutron emitters and help to ensure a reliable database for the future discoveries of new isotopes and help to constrain astrophysical and theoretical models.

Dillmann, Iris; Abriola, Daniel; Singh, Balraj

2014-05-01

405

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

SciTech Connect

Beta-delayed neutron (?n) 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 ?-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 ?n-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 ?-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 ?-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 ?-delayed neutron emitters and help to ensure a reliable database for the future discoveries of new isotopes and help to constrain astrophysical and theoretical models.

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

406

Spatially Resolved Spectra of the "Teacup" Active Galactic Nucleus: Tracing the History of a Dying Quasar  

NASA Astrophysics Data System (ADS)

The Sloan Digital Sky Survey (SDSS) Galaxy Zoo project has revealed a number of spectacular galaxies possessing extended emission-line regions (EELRs), the most famous being Hanny's Voorwerp galaxy. We present another EELR object discovered in the SDSS endeavor: the Teacup active galactic nucleus (AGN). Nicknamed for its EELR, which has a "handle"-like structure protruding 15 kpc into the northeast quadrant of the galaxy. We analyze the physical conditions of this galaxy with long-slit, ground-based spectroscopy from the Lowell, Lick, and KPNO observatories. With the Lowell 1.8 m Perkin's telescope we took multiple observations at different offset positions, allowing us to recover spatially resolved spectra across the galaxy. Line diagnostics indicate the ionized gas is photoionized primarily by the AGN. Additionally we are able to derive the hydrogen density from the [S II] ?6716/?6731 ratio. We generated two-component photoionization models for each spatially resolved Lowell spectrum. These models allow us to calculate the AGN bolometric luminosity seen by the gas at different radii from the nuclear center of the Teacup. Our results show a drop in bolometric luminosity by more than two orders of magnitude from the EELR to the nucleus, suggesting that the AGN has decreased in luminosity by this amount in a continuous fashion over 46,000 yr, supporting the case for a dying AGN in this galaxy independent of any IR based evidence. We demonstrate that spatially resolved photoionization modeling could be applied to EELRs to investigate long timescale variability.

Gagne, J. P.; Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.; Keel, W. C.; Rafter, S.; Fischer, T. C.; Bennert, V. N.; Schawinski, K.

2014-09-01

407

Active Neutron and Gamma Ray Instrumentation for In Situ Planetary Science Applications  

NASA Technical Reports Server (NTRS)

The Pulsed Neutron Generator-Gamma Ray And Neutron Detectors (PNG-GRAND) experiment is an innovative application of the active neutron-gamma ray technology so successfully used in oil field well logging and mineral exploration on Earth. The objective of our active neutron-gamma ray technology program at NASA Goddard Space Flight Center (NASA-GSFC) is to bring the PNG-GRAND instrument to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Menus, asteroids, comets and the satellites of the outer planets. Gamma-Ray Spectrometers (GRS) have been incorporated into numerous orbital planetary science missions and, especially its the case of the Mars Odyssey GRS, have contributed detailed maps of the elemental composition over the entire surface of Mars. However, orbital gamma ray measurements have low spatial sensitivity (100's of km) due to their low surface emission rates from cosmic rays and subsequent need to be averaged over large surface areas. PNG-GRAND overcomes this impediment by incorporating a powerful neutron excitation source that permits high sensitivity surface and subsurface measurements of bulk elemental compositions. PNG-GRAND combines a pulsed neutron generator (PNG) with gamma ray and neutron detectors to produce a landed instrument to determine subsurface elemental composition without needing to drill into a planet's surface a great advantage in mission design. We are currently testing PNG-GRAND prototypes at a unique outdoor neutron instrumentation test facility recently constructed at NASA/GSFC that consists of a 2 m x 2 in x 1 m granite structure placed outdoors in an empty field. Because an independent trace elemental analysis has been performed on the material, this granite sample is a known standard with which to compare both Monte Carlo simulations and our experimentally measured elemental composition data. We will present data from operating PNG-GRAND in various experimental configurations on a known sample in a geometry that is identical to that on a planetary surface. We will also illustrate the use of gamma ray timing techniques to improve sensitivity and will compare the material composition results from our experiments to both an independent laboratory elemental composition analysis and MCNPX computer modeling results.

Parsons, A.; Bodnarik, J.; Evans, L.; Floyd, S.; Lim, L.; McClanahan, T.; Namkung, M.; Schweitzer, J.; Starr, R.; Trombka, J.

2010-01-01

408

Optimal conditions for identifying 80Br and 128I in health food Angelica keiskei using rapid epithermal neutron activation analysis  

Microsoft Academic Search

This study presents an optimal rapid epithermal neutron activation analysis (ENAA) technique, using a 1mm Cd filter in reactor neutron flux, to analyze 80Br and 128I in the roots, stems, and leaves of health food Angelica keiskei (AK). Various sample weights of lichen (IAEA-336) for each portion of AK, under various periods of irradiation and counting, were used to optimize

Chien-Yi Chen

2003-01-01

409

Measurement of highly enriched uranium metal buttons with the high-level neutron coincidence counter operating in the active mode  

SciTech Connect

The portable High-Level Neutron Coincidence Counter is used in the active mode with the addition of AmLi neutron sources to assay the /sup 235/U content of highly enriched metal pieces or buttons. It is concluded that the portable instrument is a practical instrument for assaying uranium metal buttons with masses in the range 1.5 to 4 kg.

Foley, J.E.

1980-10-01

410

High-fidelity MCNP modeling of a D-T neutron generator for active interrogation of special nuclear material  

NASA Astrophysics Data System (ADS)

Fast and robust methods for interrogation of special nuclear material (SNM) are of interest to many agencies and institutions in the United States. It is well known that passive interrogation methods are typically sufficient for plutonium identification because of a relatively high neutron production rate from 240Pu [1]. On the other hand, identification of shielded uranium requires active methods using neutron or photon sources [2]. Deuterium-deuterium (2.45 MeV) and deuterium-tritium (14.1 MeV) neutron-generator sources have been previously tested and proven to be relatively reliable instruments for active interrogation of nuclear materials [3,4]. In addition, the newest generators of this type are small enough for applications requiring portable interrogation systems. Active interrogation techniques using high-energy neutrons are being investigated as a method to detect hidden SNM in shielded containers [4,5]. Due to the thickness of some containers, penetrating radiation such as high-energy neutrons can provide a potential means of probing shielded SNM. In an effort to develop the capability to assess the signal seen from various forms of shielded nuclear materials, the University of Michigan Neutron Science Laboratory's D-T neutron generator and its shielding were accurately modeled in MCNP. The generator, while operating at nominal power, produces approximately 1×10 10 neutrons/s, a source intensity which requires a large amount of shielding to minimize the dose rates around the generator. For this reason, the existing shielding completely encompasses the generator and does not include beam ports. Therefore, several MCNP simulations were performed to estimate the yield of uncollided 14.1-MeV neutrons from the generator for active interrogation experiments. Beam port diameters of 5, 10, 15, 20, and 25 cm were modeled to assess the resulting neutron fluxes. The neutron flux outside the beam ports was estimated to be approximately 2×10 4 n/cm 2 s.

Katalenich, Jeff; Flaska, Marek; Pozzi, Sara A.; Hartman, Michael R.

2011-10-01

411

Irradiation and penetration tests of boron-doped low activation concrete using 2.45 and 14 MeV neutron sources  

Microsoft Academic Search

The neutron penetration and the activation characteristics of the boron-doped low activation concrete were investigated for irradiation of 2.45 and 14 MeV neutrons. The shielding property of the 2 wt% boron-doped low activation concrete is superior to that of the 1 wt% boron for the thermal neutron, on the contrary to no clear difference for the fast neutron. The total

Atsuhiko Morioka; Satoshi Sato; Masaharu Kinno; Akira Sakasai; Junichi Hori; Kentaro Ochiai; Michinori Yamauchi; Takeo Nishitani; Atsushi Kaminaga; Kei Masaki; Shinji Sakurai; Takao Hayashi; Makoto Matsukawa; Hiroshi Tamai; Shinichi Ishida

2004-01-01

412

Neutron activation analysis method and apparatus for determining sodium and sodium compounds in liquid samples  

SciTech Connect

Sodium is determined, virtually without known interferences, based on neutron activation of liquid sample to produce radioactive 23Ne activation product from 23Na, sparging of the sample whereby a headspace gas mixture comprising 23Ne in an inert sparging gas is collected, and remote analysis of the headspace gas mixture to determine total parent sodium based on monitoring radiation emissions of 23Ne. As an illustration of utility, the analysis is demonstrated as applicable to determinations of sodium in aqueous or organic matrices at concentrations of 1 part per thousand and greater using preferred forms of 241Am/Be radioactive isotope as the activation source.

Kamp, A.J.; Kelly, K.J.

1981-10-06

413

A neutron activation analysis procedure for the determination of uranium, thorium and potassium in geologic samples  

USGS Publications Warehouse

A neutron activation analysis procedure was developed for the determination of uranium, thorium and potassium in basic and ultrabasic rocks. The three elements are determined in the same 0.5-g sample following a 30-min irradiation in a thermal neutron flux of 2??1012 n??cm-2??sec-1. Following radiochemical separation, the nuclides239U (T=23.5 m),233Th (T=22.2 m) and42K (T=12.36 h) are measured by ??-counting. A computer program is used to resolve the decay curves which are complex owing to contamination and the growth of daughter activities. The method was used to determine uranium, throium and potassium in the U. S. Geological Survey standard rocks DTS-1, PCC-1 and BCR-1. For 0.5-g samples the limits of detection for uranium, throium and potassium are 0.7, 1.0 and 10 ppb, respectively. ?? 1972 Akade??miai Kiado??.

Aruscavage, P. J.; Millard, H.T., Jr.

1972-01-01

414

Non-destructive examination of roman silver coins by neutron activation analysis  

Microsoft Academic Search

The detection of “plated” specimens (ancient falsifications consisting of a copper core with a silver outer layer) amidst\\u000a a great collection of silver coins was performed by non-destructive neutron analysis. The “plating” can be detected by measuring\\u000a the Ag\\/Cu ratio. In practice it is more convenient to determine the Au\\/Cu ratio which is proportional to it, A short activation\\u000a in

A. van Dalen; H. A. Das; J. Zonderhuis

1973-01-01

415

k o -measurements and related nuclear data compilation for (n, ?) reactor neutron activation analysis  

Microsoft Academic Search

ko-factors of 35 isotopes used in reactor neutron activation analysis were measured with a high degree of accuracy (1–2%). To\\u000a minimize systematic errors, measurements were carried out using different reactor types, irradiation conditions (18 s\\/?e), Ge(Li) detectors, sample detector geometry, etc. Analyst-oriented tabulations including all necessary nuclear data, “best\\u000a values”, as well as recommended ko-values are given to facilitate analytical

A. Simonits; L. Moens; F. De Corte; A. De Wispelaere; A. Elek; J. Hoste

1980-01-01

416

Survey of trace elements in coals and coal-related materials by neutron activation analysis  

USGS Publications Warehouse

Utilizing primarily instrumental neutron activation analysis (INAA) and other analytical methods as many as 61 elements were quantitatively surveyed in 170 U.S. whole coals, 70 washed coals, and 40 bench samples. Data on areal and vertical distributions in various regions were obtained along with extensive information on the mode of occurrence of various elements in the coal matrix itself. ?? 1977 Akade??miai Kiado??.

Ruch, R.R.; Cahill, R.A.; Frost, J.K.; Camp, L.R.; Gluskoter, H.J.

1977-01-01

417

A well-tested procedure for instrumental neutron activation analysis of silicate rocks and minerals  

Microsoft Academic Search

Procedures for instrumental neutron activation analysis (INAA) have been developed and used on more than a thousand small\\u000a samples of terrestrial and lunar silicate rocks and minerals for determination of Co, Cr, Fe, Hf, Na, Ni, Sc, Ta, Th, and\\u000a the rare earths La, Ce, Sm, Eu, Tb, Yb, and Lu. Precision has been determined by repeated analysis of Knippa

J. W. Jacobs; R. L. Korotev; D. P. Blanchard; L. A. Haskin

1977-01-01

418

Determination of selenium in Libyan food items using pseudocyclic instrumental neutron activation analysis  

Microsoft Academic Search

Cyclic and pseudocyclic instrumental neutron activation analysis (INAA) has been used to determine the Se content of 40 Libyan\\u000a food items. The selected samples include different varieties of local and imported foods such as wheat and barley products\\u000a (bran and flours), rice, bread, almond, peanuts, vegetables as bean and peas, tea, coffee, sugar, and commonly used spices\\u000a such as red

U. M. El-Ghawi; A. A. Al-Sadeq; M. M. Bejey; M. B. Alamin

2005-01-01

419

PROMETHEE: An Alpha Low Level Waste Assay System Using Passive and Active Neutron Measurement Methods  

Microsoft Academic Search

The development of a passive-active neutron assay system for alpha low level waste characterization at the French Atomic Energy Commission is discussed. Less than 50 Bq[α] (about 50 μg Pu) per gram of crude waste must be measured in 118-l 'European' drums in order to reach the requirements for incinerating wastes. Detection limits of about 0.12 mg of effective ²³⁹Pu

Christian Passard; Alain Mariani; Fanny Jallu; Jacques Romeyer-Dherbey; Herve Recroix; Michel Rodriguez; Joel Loridon; Caroline Denis; Herve Toubon

2002-01-01

420

Performance report for a small package counter that uses active neutron interrogation  

SciTech Connect

An active neutron interrogation system utilizing the differential die-away technique (DDT), was built to assay fissile material in small waste packages for a variety of matrices. Within minutes the system can make a ``go/no-go`` decision for sorting low-level waste (LLW) from transuranic waste (TRUW). It can also provide gram-level accountability of weapons-grade (WG) Pu in TRUW providing lumps of self-shielding fissile material are absent.

Harlan, R.A.; Wishard, B.E.; Santopietro, R.D.; Anderson, B.P.

1993-07-07

421

Epithermal Neutron Activation Analysis of Some Geological Samples of Different Origin  

SciTech Connect

Instrumental Epithermal Neutron Activation Analysis was used to investigate the distribution of six major elements and 34 trace elements in a set of eight igneous and metamorphic rocks collected from Carpathian and Macin Mountainsas well as unconsolidated sediments collected from anoxic zone of the Black Sea. All experimental data were interpreted within the Upper Continental Core and Mid Ocean Ridge Basalt model system that allowed getting more information concerning samples origin as well as the environmental peculiarities.

Duliu, O. G. [University of Bucharest, Department of Atomic and Nuclear Physics, P.O. Box MG-11, 077125, Magurele (Ilfov) (Romania); Cristache, C. I. [National Institute of Research and Development for Physics and Nuclear Engineering Horia-Hulubei, P.O. Box MG-6, 077125, Magurele (Ilfov) (Romania); Oaie, G. [National Institute of Research and Development for Geology and Marine Geoecologylogy, 34 Dimitrie Onciul str., 024504 Bucharest (Romania); Ricman, C. [Geological Institute of Romania, 1 Caransebes Street, 012271 Bucharest (Romania); Culicov, O. A.; Frontasyeva, M. V. [Joint Institute for Nuclear Research, 6, Joliot-Curie str. 141980 Dubna (Russian Federation)

2010-01-21

422

Chemical composition of T-21 silica tubing and implications for neutron activation analysis  

Microsoft Academic Search

T-21 silica, a commonly used encapsulation material in neutron activation analysis of small samples, was analyzed by INAA to determine trace levels of the following impurities: Na, Sc, Cr, Fe, Co, Ni, Zn, Br, Sb, La, Ce, Sm, Tb, Hf and Au. In the unprocessed form supplied by the manufacturer, pieces of T-21 weighing 50 mg contain 6·10–2 g Na;

X.-Y. Mao; B. J. Ward; L. Grossman; B. D. Keck

1991-01-01

423

Neutron activation analysis for reference determination of the implantation dose of cobalt ions  

SciTech Connect

The authors prepared depth profilling reference materials by cobalt ion implantation at an ion energy of 300 keV into n-type silicon. The implanted Co dose was then determined by instrumental neutron activation analysis (INAA) giving an analytical dynamic range of almost 5 decades and uncertainty of 1.5%. This form of analysis allows sources of error (beam spreading, misalignment) to be corrected. 70 refs., 3 tabs.

Garten, R.P.H. [Max-Planck-Institut fuer Metallforschung, Dortmund (Germany); Bubert, H. [Institut fuer Spektrochemie und angewandte Spektrokopie, Dortmund (Germany); Palmetshofer, L. [Johannes-Kepler-Universitaet, Linz (Australia)

1992-05-15

424

Analysis of infrared spectra of a stellar occultation by the active Centaur (2060) Chiron  

NASA Astrophysics Data System (ADS)

Chiron, the first known Centaur, orbits primarily between Saturn and Uranus. It was originally thought to be an asteroid, but has since exhibited cometary-like behavior [e.g., 1,2]. This behavior is unusual given Chiron's relatively large distance from the Sun and its nucleus being larger than that of other comets. Previous stellar occultation data suggested that Chiron is greater than approximately 180 km in diameter and detected narrow jets as well as a gravitationally-bound dust coma [3,4]. More recent measurements from Herschel place the size at 218 ± 20 km [5]. On 29 November 2011, Chiron occulted a fairly bright star (R=14.8) as seen from Hawai'i. We observed the event from the 3-m NASA Infrared Telescope Facility (IRTF) on Mauna Kea and the 2-m Faulkes Telescope North at Haleakala (run by the Las Cumbres Observatory Global Telescope network, LCOGT). Data were taken as visible wavelength images at the Faulkes, using an Andor iXon 888 camera, and at the IRTF, using the MIT Optical Rapid Imaging System (MORIS [6]). Simultaneously, low-resolution, near-infrared, 0.9--2.4 micron spectra were taken using SpeX [7] on the IRTF. The MORIS lightcurve contains an occultation by Chiron's nucleus, with a chord corresponding to a minimum radius of 158 ± 14 km [8,9]. The Faulkes lightcurve, a station located 97 km to the north, contains deep, symmetric dips before and after the predicted midtime and no solid-body occultation. The extinction features are located roughly 300 km from Chiron's center, and are approximately 3 and 7 km in extent separated by 10--14 km [8,9]. The MORIS data were taken at ten times slower cadence (2 s) and show shallow dips at roughly the same distance from Chiron's center. These lightcurve features indicate optically thick material in a roughly circular distribution, suggesting the presence of a near-circular ring or shell of material. Here, we present an analysis of the IRTF SpeX data of the occultation. Although the cadence was relatively slow (at 9.6 s), we investigate the flux versus wavelength dependence of the data in order to characterize the dust coma and shell/ring particles. This work is placed in context with other active Centaurs, given the recent discovery of rings around (10199) Chariklo [10] and the dust/gas coma observed on 174P/Echeclus [e.g. 11].

Gulbis, A.; Emery, J.; Ruprecht, J.; Bosh, A.; Person, M.; Bianco, F.; Bus, S.; Zangari, A.

2014-07-01

425

Radiography apparatus using gamma rays emitted by water activated by fusion neutrons  

DOEpatents

Radiography apparatus includes an arrangement for circulating pure water continuously between a location adjacent a source of energetic neutrons, such as a tritium target irradiated by a deuteron beam, and a remote location where radiographic analysis is conducted. Oxygen in the pure water is activated via the .sup.16 O(n,p).sup.16 N reaction using .sup.14 -MeV neutrons produced at the neutron source via the .sup.3 H(d,n).sup.4 He reaction. Essentially monoenergetic gamma rays at 6.129 (predominantly) and 7.115 MeV are produced by the 7.13-second .sup.16 N decay for use in radiographic analysis. The gamma rays have substantial penetrating power and are useful in determining the thickness of materials and elemental compositions, particularly for metals and high-atomic number materials. The characteristic decay half life of 7.13 seconds of the activated oxygen is sufficient to permit gamma ray generation at a remote location where the activated water is transported, while not presenting a chemical or radioactivity hazard because the radioactivity falls to negligible levels after 1-2 minutes.

Smith, Donald L. (Plainfield, IL); Ikeda, Yujiro (Ibaraki, JP); Uno, Yoshitomo (Ibaraki, JP)

1996-01-01

426

Radiography apparatus using gamma rays emitted by water activated by fusion neutrons  

DOEpatents

Radiography apparatus includes an arrangement for circulating pure water continuously between a location adjacent a source of energetic neutrons, such as a tritium target irradiated by a deuteron beam, and a remote location where radiographic analysis is conducted. Oxygen in the pure water is activated via the {sup 16}O(n,p){sup 16}N reaction using {sup 14}N-MeV neutrons produced at the neutron source via the {sup 3}H(d,n){sup 4}He reaction. Essentially monoenergetic gamma rays at 6.129 (predominantly) and 7.115 MeV are produced by the 7.13-second {sup 16}N decay for use in radiographic analysis. The gamma rays have substantial penetrating power and are useful in determining the thickness of materials and elemental compositions, particularly for metals and high-atomic number materials. The characteristic decay half life of 7.13 seconds of the activated oxygen is sufficient to permit gamma ray generation at a remote location where the activated water is transported, while not presenting a chemical or radioactivity hazard because the radioactivity falls to negligible levels after 1--2 minutes. 15 figs.

Smith, D.L.; Ikeda, Yujiro; Uno, Yoshitomo

1996-11-05

427

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

PubMed

The paper presents the results of calculating the equivalent dose from and energy spectrum of neutrons in the right-hand crewquarters in module Zvezda of the ISS Russian segment. Dose measurements were made in the period between July, 2010 and November, 2012 (ISS Missions 24-34) by research equipment including the bubble dosimeter as part of experiment "Matryoshka-R". Neutron energy spectra in the crewquarters are in good agreement with what has been calculated for the ISS USOS and, earlier, for the MIR orbital station. The neutron dose rate has been found to amount to 196 +/- 23 microSv/d on Zvezda panel-443 (crewquarters) and 179 +/- 16 microSv/d on the "Shielding shutter" surface in the crewquarters. PMID:25089327

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

2014-01-01

428

Neutron activation analysis of airborne thorium liberated during welding operations  

SciTech Connect

Typically, reactive metals such as aluminum are welded using a thoriated tungsten welding electrode which is attached to a source of argon gas such that the local atmosphere around the weld is inert. The metal is heated by the arc formed between the electrode and the grounded component to be welded. During this process, some of the electrode is vaporized in the arc and is potentially liberated to the surrounding air. This situation may result in a hazardous airborne thorium level. Because the electrode is consumed during welding, the electrode tip must be repeatedly dressed by grinding the tip to a fine point so that the optimal welding conditions are maintained. These grinding activities may also release thorium to the air. Data generated in the 1950s suggested that these electrodes posed no significant health hazard and seemed to justify their exemption from licensing requirements for source material. Since that time, other studies have been performed and present conflicting results as to the level of risk. Values both above and below the health protection limit in use in the United States, have been reported in the literature recently. This study is being undertaken to provide additional data which may be useful in evaluating both the chemical toxicity risk and radiological dose assessment criteria associated with thoriated tungsten welding operations.

Glasgow, D.C.; Robinson, L.; Janjovic, J.T.

1996-02-01

429

Neutron activation analysis of airborne thorium liberated during welding operations  

SciTech Connect

Typically, reactive metals such as aluminum are welded using a thoriated tungsten welding electrode that is attached to a source of argon gas such that the local atmosphere around the weld is inert. The metal is heated by the arc formed between the electrode and the grounded component to be welded. During this process, some of the electrode is vaporized in the arc and may be liberated to the surrounding air. This situation may result in a hazardous airborne thorium level. Because the electrode is consumed during welding, the electrode tip must be repeatedly dressed by grinding the tip to a fine point so that the optimal welding conditions are maintained. These grinding activities may also release thorium to the air. Data generated in the 1950s suggested that these electrodes posed no significant health hazard and seemed to justify their exemption from licensing requirements for source material. Since that time, other studies have been performed and present conflicting results as to the level of risk. Values both above and below the health protection limit in use in the United States have been reported in the literature recently. This study is being undertaken to provide additional data that may be useful in evaluating both the chemical toxicity risk and radiological dose assessment criteria associated with thoriated tungsten welding operations.

Glasgow, D.C.; Robinson, L.; Jankovic, J.T. [Oak Ridge National Laboratory, TN (United States)

1996-12-31

430

Cosmogenic-neutron activation of TeO2 and implications for neutrinoless double-beta decay experiments  

E-print Network

Flux-averaged cross sections for cosmogenic-neutron activation of natural tellurium were measured using a neutron beam containing neutrons of kinetic energies up to $\\sim$800 MeV, and having an energy spectrum similar to that of cosmic-ray neutrons at sea-level. Analysis of the radioisotopes produced reveals that 110mAg will be a dominant contributor to the cosmogenic-activation background in experiments searching for neutrinoless double-beta decay of 130Te, such as CUORE and SNO+. An estimate of the cosmogenic-activation background in the CUORE experiment has been obtained using the results of this measurement and cross-section measurements of proton activation of tellurium. Additionally, the measured cross sections in this work are also compared with results from semi-empirical cross-section calculations.

Wang, Barbara S; Scielzo, Nicholas D; Smith, Alan R; Thomas, Keenan J; Wender, Stephen A

2015-01-01

431

The Role of Neutron Activation Analysis in the Pathological Evaluation of Silver-Eluting Biomedical Devices in Biological Matrices  

E-print Network

The purpose of this research was to determine the viability of using instrumental neutron activation analysis (INAA) to quantify silver nanoparticle (AgNP) content in biological matrices in the context of pathology evaluations of silver...

Lancon, Trevor

2014-08-14

432

Rainbow-Like Spectra with a CD: An Active-Learning Exercise  

ERIC Educational Resources Information Center

Rainbow-like spectra, produced by reflexive diffraction of white light on a CD, offer a spectacular visual effect as well as an excellent classroom opportunity for students to learn how physics works. In this paper we show that building a coherent qualitative explanation can be a challenging task that requires students to combine gained knowledge…

Planinsic, G.

2008-01-01

433

Four new active galaxies with steep soft X-ray spectra  

E-print Network

We have discovered four AGN in the ROSAT all-sky-survey data with very steep X-ray spectra. We apply several models to these X-ray spectra with emphasis on warm absorber models which give an adequate description of the data. We report on the follow-up optical and radio observations which allow the identification of three of these objects as Narrow Line Seyfert 1 galaxies, and the fourth as BL Lac object. We have measured small-FWHM Hbeta lines, strong FeII emission and weak [OIII] emission in the three Narrow Line Seyfert 1 galaxies, in line with known correlations with respect to the steepness of the X-ray spectra. We have discovered strong optical variability in the BL Lac object and two of the Seyfert galaxies using photographic plates of the Sonneberg Observatory field patrol. We finally discuss the statistical implications of our search algorithm on the expected number density of soft X-ray selected AGN and conclude that up to 30% of X-ray selected AGN might have supersoft X-ray spectra.

J. Greiner; R. Danner; N. Bade; G. A. Richter; P. Kroll; S. Komossa

1995-12-04

434

Resonant Absorption in the Active Galactic Nucleus Spectra Emerging from Photoionized Gas: Differences between Steep and Flat Ionizing Continua  

NASA Astrophysics Data System (ADS)

We present photoionization models accounting for both photoelectric and resonant absorption. Resonance absorption lines from C, O, Ne, Mg, Si, S, and Fe between 0.1 and 10 keV are treated. In particular we consider the complex of almost 60 strong Fe L absorption lines around 1 keV. We calculate profiles, intensities, and equivalent widths of each line, considering both Doppler and natural broadening mechanisms. Doppler broadening includes a term accounting for turbulence of the gas along the line of sight. We computed spectra transmitted by gas illuminated by drastically different ionizing continua and compared them to spectra observed in flat X-ray spectrum, broad optical emission-line type 1 active galactic nuclei (AGNs), and steep X-ray spectrum, narrow optical emission